NYSGA 2009
New York Geological Association
81st Annual Meeting
Field Trip Guidebook
Hosted by
SUNY New Paltz
New Paltz, New York
Edited by
Frederick W. Vollmer
Published by the
New York State Geological Society
www.nysga.net
For additional copies contact
William Kelly
New York State Museum
3140 Cultural Education Center
wkelly@mail.nysed.gov
Dedicated to
Russell H. Waines
1927 - 2009
Ph.D. Paleontology, UC Berkley 1965
Professor of Geology, SUNY New Paltz
1963 – 2006, Retired Emeritus
Editor of 1967 and 1987 NYSGA Guidebooks

1: STRUCTURES OF THE HUDSON-VALLEY FOLD-THRUST BELT IN THE APPALACHIAN FORELAND OF EASTERN NEW YORK
Stephen Marshak and Pragnyadipta Sen,
Department of Geology
University of Illinois
Urbana, Illinois 61801
Kurtis C. Burmeister
Department of Geosciences
University of the Pacific
Stockton, California 95211
Petr V. Yakovlev and Yvette D. Kuiper
Department of Geology and Geophysics
Boston College
Chestnut Hill, MA 02467
TRIP OVERVIEW
Exposures of a thin-skinned, foreland fold-thrust belt crop out west of the Hudson River in the central Hudson Valley of New York State (Figure 1a, b). This Hudson Valley fold-thrust belt (HVB), which involves Middle Ordovician through lower Middle Devonian strata, is generally less than 4 km wide. Thus, first-order structures (e.g., fault-related folds, detachment faults and duplexes) of the belt are small enough to be seen in their entirety within individual outcrops. The small size of the belt also makes it possible to examine along-strike variations in fold-thrust belt structural architecture that reflect variations in the thickness and mechanical properties of pre-deformational strata and/or in the amount of shortening (Marshak, 1983; 1986a; Burmeister and Marshak, 2003; Burmeister, 2005). This field trip will visit selected exposures of structures in the HVB to examine the structures of the belt at all scales. The stops illustrate the relationships between deformation style and stratigraphy.
In addition to examples of fold-thrust belt structural architecture, stops on the trip will also provide: (1) exposures of the Taconic angular unconformity (Rodgers, 1971); (2) examples of tectonic cleavage, veins, and slip fibers (Marshak and Engelder, 1985); (3) classic Lower Devonian North American faunas (Chadwick, 1944; Goldring, 1943); (4) examples of shallow-marine carbonate facies (Rickard, 1962; LaPorte, 1969); (5) an example of an orocline (Marshak and Tabor, 1989; Marshak, 2004); and (6) a context for considering continuing debates concerning the timing (Alleghanian vs. Acadian) of regional orogeny in the New England Appalachians, and the nature of the transition between the central Appalachians and the northern Appalachians (Marshak, 1986a; Marshak and Tabor, 1989; Marshak and Bosworth, 1991).
This trip proceeds from north to south along the belt. Highlights include the Route 23 roadcuts near Catskill, evidence for overprinting of deformation features near Kingston, and structural complexities of the Helderberg escarpment. This guidebook is a modification of a one that the lead authors have prepared for earlier field trips sponsored by the Geological Society of America and NYSGA.

STOP A. (Optional) Abandoned quarry near Fuerra Bush
This quarry is now owned by the South Bethlehem Police, and is used for firearms training. It cannot be entered without permission. The high walls are very unstable and dangerous, and should only be observed from a distance. The best exposure of the duplex is at the base of the north high wall. To reach the quarry, take the Selkirk Exit (Exit 22) off the NYS Thruway. After the tollgates, turn right onto Route 144. Proceed southwest on 144 for about 0.4 miles, then turn right and head west on Rte 396 through Selkirk, to South Bethlehem (about 2 miles). Continue on Rte 396 for another 0.5 miles west of South Bethlehem to the junction with Old Quarry Road (County Rte. 102). Turn right and head north on Old Quarry Road for about 1.5 miles. There will be a highway department shed on the left, and a parking lot. The quarry is up the hill behind the shed, and can be reached by walking about 10 minutes along a trail.
Exposure of a duplex along the Rondout Detachment, and a large Ramp anticline. This stop provides excellent exposures of an impressive 10 m-high duplex involving the Rondout Formation and the Manlius Limestone along the Rondout Detachment. Within the duplex, there are numerous ramps spaced at 0.5 to 2 m. The duplex has a flat roof. The quarry also exposes of a first-order ramp anticline involving the Manlius Limestone, Coeymans Limestone, and Kalkberg Formation. The quarry has been cut into the Helderberg Escarpment, a 10 to 50 m-high cliff that marks the eastern limit of Siluro-Devonian strata in the HVB west of the Hudson River.

STOP 1. Route 23 Roadcuts, northwest of Catskill
To reach the Roadcuts, take the Catskill Exit (Exit 21) off the NYS Thruway. At the end of the tollgate access road, turn left (southeast) onto State Route 23B heading toward Jefferson Heights and Catskill. Continue on State Route 23B for 0.2 mi (0.3 km) to the junction with State Route 23. Park here. To reach outcrops 1A and 1B, park on the west shoulder of 23B just north of the entrance ramp that leads onto State Route 23 heading northwest. Depending on logistics, it may be easiest to walk the length of the highway to Catskill Creek. Drivers can pick up participants on the shoulder of Route 23 near Catskill Creek. WARNING! These highways are very busy, and vehicles are traveling very fast. Outcrop 1A is along the exit ramp from State Route 23 northwest leading to 23B, and outcrop 1B is along the entrance ramp from 23B onto 23 northwest. To reach outcrops 1CN-1EN and 1CS1ES, drive onto State Route 23 heading northwest toward Cairo.
A cross section of the entire HVB. Stop 1 includes several roadcut exposures along State Route 23, approximately 2 km northwest of Catskill. The outcrops are numbered in succession from west to east (Figure 7); those containing the letter N border the north side of the road, and those containing the letter S border the south side. For logistic reasons, we start the trip at the east end of the fold-thrust belt and work our way westwards, toward the foreland. These exposures show the following:
Roadcut 1A exposes the post-Taconic angular unconformity and the Rondout detachment. The unconformity dips moderately westward, parallel to the strata above, and cuts across steeply dipping beds of Austin Glen Formation. Displacement on the detachment resulted in formation of west-verging (i.e., down-dip verging, in this outcrop) folds, and in cleavage that has rotated counterclockwise, relative to bedding (Marshak, 1986a, b). A homoclinally dipping sequence of the lower Helderberg Group (Manlius, Coemans, and Kalkberg Formations) lies over the Rondout Formation. The Manlius contains small black ostracods, the top of the Manlius is a layer of thinly laminated micrite, the Coeymans contains the white, beaked brachiopod Gypidula coeymanensis, and the base of the Kalkberg is marked by a distinctive black chert layer.
Here, as throughout the Hudson Valley fold-thrust belt, development of cleavage is lithologically controlled; cleavage occurs primarily in rocks containing greater than 10 percent clay (Marshak, 1983). Also, slip fibers develop on bedding planes due to both detachment faulting and flexural slip. On the west limb of folds, slip due to flexural slip can be distinguished from that due to detachment faulting by the sense of slip indicated by imbrication of fiber sheets and by shear rotation of cleavage adjacent to slip surfaces. Flexural slip displacement is always "top-up." Slip on a west-verging, but now west dipping detachment, is "top-down" in its present (post-folding orientation).
Outcrop 1B provides another exposure of the lower Helderberg Group in the western limb of the Tollgate Syncline, a first-order fold that underlies State Route 23B between 1A and 1B. In this outcrop, the section was thickened as a result of movement on two well-exposed, out-of-the-syncline forethrusts (see Dahlstrom, 1970). The lower fault brings the Manlius Formation over the Kalkberg Formation.
Outcrops 1CN and 1CS provide additional exposures of the Taconic Unconformity and of the Helderberg Group (through the Becraft Formation). Of particular note in these outcrops are the complex faults and folds in the Rondout and lower Manlius Formations, manifestations of movement on the Rondout detachment. Many bedding-plane slip surfaces, which developed during flexural-slip folding and are coated with sheets of calcite slip fibers, occur in outcrops 1CN and S3. In the Kalkberg Formation, some of these slip surfaces are bounded by zones of nearly slaty cleavage. At the northwest end of outcrop 1DN, numerous mesoscopic folds, as well as two back-thrusts, occur within the Becraft Limestone.
Outcrops 1DN and 1DS are the most spectacular of the State Route 23 outrcrops. Together, these exposures (which include rocks of the Manlius Formation through Becraft Limestone) display, from southeast to northwest, ramp faults with hanging wall anticlines (Rip van Winkle anticline), out-of-the-syncline forethrusts and backthrusts, folded ramps and flats (in the Central anticline), and zones of tectonic cleavage intensification (on the northwest limb of the Central anticline). Of particular note are the examples of fault bends (Suppe, 1983) at which bedding-parallel flats join cross-strata ramps. The Central anticline appears to be composed of a stack of fault-bounded horses (see Boyer and Elliott, 1982), one of which is internally deformed throughout by mesoscopic folds. Structures of outcrops 1DN and 1DS do not directly correlate across the highway, illustrating how rapidly structural geometry can change along strike in the HVB. The contrast in structural geometry between outcrops on opposite sides of the road may reflect the occurrence of a lateral ramp in the interval that was excavated during construction of the highway. We can also see variations in strain magnitude, indicated by cleavage intensity, as well as lithologic control on the degree of cleavage development. Studies of these rocks provide interesting constraints on the volume-constant vs. volume-loss models of cleavage development (Bhagat and Marshak, 1990).
Outcrops 1EN and 1ES expose the Esopus and Schoharie Formations, and the base of the Onondaga Limestone. These units are arched around the Mill Falls anticline. Nearly slaty cleavage occurs within the lower Esopus Shale. The upper few meters of the Esopus Shale are composed of beds of finely laminated mudstone and siltstone that have been crinkled into tiny folds. A sub-horizontal fault is present at the top of outcrop 1DS. Time permitting, we will visit the deformation front of the fold-thrust belt as it is exposed along Catskill Creek in the village of Leeds, approximately 1 km north of State Route 23.

STOP 2. The Esopus Detachment, along Route 23A.
These outcrops can be reached by continuing west from 1EN/1ES on State Route 23. Turn left (south) on State Route 47. Turn right (west) at the intersection with Old Kings Road and continue to the intersection with State Route 23A. Turn left (east) on State Route 23A and pull off the road to the right (south) after 0.1 miles onto the abandoned Thruway ramp. The exposure is a roadcut along the abandoned ramp.
STOP 2 exposes disharmonic folds that formed in association with movement on a detachment fault between the Esopus and Glenerie Formations. This outcrop inspires considerable debate about the origin of the deformation. Is the structure tectonic, or is it a consequence of slumping that was penecontemporaneous with deposition? The association of fractures, cleavages, and shear zones with the folds suggests that the deformation is tectonic. Deformation likely occurred at this horizon because of the viscosity contrast between the Esopus and Glenerie Formations. The lowermost Esopus Shale is composed of alternating beds of siltstone and shale, and such a sequence is susceptible to buckling. The overlying Esopus Shale is more homogeneous and contains closely spaced to slaty cleavage. The detachment at the contact may reflect differential shortening between the Esopus and Glenerie Formations.

STOP B. (Optional) Bakoven Shale Exposures, City View Terrace Road, Kingston
Take the Kingston Exit (Exit 19) from the NYS Thruway. Follow the roundabout to Route 28. Head west on Route 28 across the Thruway, and then across Route 209. At 0.3 miles west of the Route 28 bridge over Route 209, turn right off of Route 28 onto Forest Hills Drive. Head north on Forest Hills Drive for about 50 m, and turn right to head east on City View Terrace Road. Pull off on the shoulder. The exposures at Optional Stop B are along the north side of City View Terrace Road.
Cleavage duplexes in the Bakoven Member of the Union Springs Formation. This stop exposes the Bakoven and Stony Hollow Members of the Union Springs Formation, the basal unit of the Hamilton Group, in the steep escarpment and road cut along City View Terrace, beneath the Skytop Motel. Mesoscopic-scale duplexes and shear zones in the upper 10 m of the Bakoven Member provides an opportunity to examine deformation associated with the stratigraphically highest detachment of the HVB (Bosworth, 1984; Nickelsen, 1986; Ver Straeten and Brett, 1995). Nickelsen referred to the structures in this outcrop as "cleavage duplexes," implying that the planar laminations within the shear zone is slaty cleavage not bedding. An alternative view is that the laminations are bedding planes that have rotated almost 90°, due to shear. The kinematics of these zones remains unclear.

STOP 3. Route 209/199 roadcuts, north of Kingston.
To reach these outcrops, take NYS Thruway Exit 19. Leave the Thruway and pass through the tollgate. At the end of the tollgate access road, bear right (west) onto State Route 28. Proceed west on Rte 28 for 0.3 miles and bear right to take the entrance ramp onto Route 209 north. Proceed north on Rte 209 (toward the Rhinebeck Bridge) for about 3.7 miles. The road curves and heads east. When it crosses Route 9W, it becomes Route 199. Park along the south shoulder of Rte. 199/209 about 0.7 miles east of the State Route 9W underpass. [Note: If you are heading to Stop 3 after Optional Stop B, simply backtrack from B back to the junction with Route 209 to pick up the route described above.]
Exposures of large anticlines and synclines. Stop 3 exposes large, slightly asymmetric open folds with no visible thrust faulting or mesoscopic folding. Five major, map-scale fold hinges cross State Route 209 between Routes 9W and 32 (McEachran, 1985; Marshak and Tabor, 1989; Marshak, 1990). The most prominent of the folds at Stop 3 is a large anticline involving the upper Becraft Limestone, the Alsen Formation, and the Port Ewen Formation (Figure 8). Note the differential development of cleavage in these units. The Becraft Limestone contains little to no cleavage, whereas a strong, southeast-dipping cleavage is developed in the Alsen and Port Ewen Formations. These folds are characteristic of structural styles in the northern arm of the Kingston Orocline, in that they trend roughly N015°E and lack structural complexity (Marshak and Tabor, 1989).

STOP 4. Roadcuts exposing lateral ramps in the Rondout
To reach these outcrops from Stop 3, continue east on Rte 199 to the exit for Route 32 (the last exit before the KingstonRhinecliff Bridge over the Hudson River). At the end of the ramp, turn left and head south on Rte 32 (= Flatbush Avenue). Proceed about 0.5 miles south on Route 32 and pull off on the shoulder to the right. The exposures are road-cuts on the west side of the road.
Lateral ramping in the Rondout Formation. Stop 4 is along the west side of State Route 32 (Flatbush Ave.), 0.3 miles south of US 199 overpass (Figure 9). Stop 4 exposes four major thrust faults duplicating the Rondout and Manlius Formations in a series of imbricate thrust sheets along the west side of State Route 32 (Figure 7; Waines and Hoar, 1967; McEachran, 1985; Marshak, 1990). Thrust faults in this outcrop strike roughly N040E. Calcite slip fibers on the fault surfaces suggest a transport direction of N060E-N070E. In places, these faults have a flat-on-flat geometry (i.e., thrust faults are bedding parallel in both the hanging wall and footwall), suggesting large displacements. These thrusts occasionally appear to cut down-section due to the obliquity of the road cut face to the orientation of the structures and the transport direction (hanging walls are thrust westward into the outcrop). These faults are untraceable west of the road cut, but may ramp laterally up-section and die out to the north.

Optional Stop C. Cross-Cutting Cleavage in the Onondoga Limestone, Kingston.
To reach this stop from Stop 4, proceed drive south to southwest along Rte 32 (Flatbush Road) for about 2.2 miles. You will go 0.2 miles past the entrance to Route 9W south (part of a divided highway), to the junction with non-divided Route 9W north (East Chester Street). There is a convenience store at the corner. Park where convenient, then walk north along the east side of Route 9W (East Chester Street) to the first roadcut. Climb to the top of the roadcut and look for bedding planes.
Cross-cutting cleavage. At this exposure, in the center of the Kingstone orocline, a bedding surface of Onondagaga limestone at the top of a roadcut on the east side of the Highway, appears to contain two distinct cleavage trends (Figure 10). This relationship is evidence that two distinct segments of the fold-thrust belt cross cut in the Kingston area.

STOP 5 - Hasbrouck Park, Kingston
Turn south off of Route 32 and proceed south for 1.1 miles on Route 9W south (part of a divided highway). Take the Delaware Avenue Exit. At the end of the exit ramp, turn left and proceed east on Delaware Avenue, on a bridge across Route 9w. You need to take the right turn immediately after the bridge to stay on Delaware Avenue. Proceed for 0.4 miles on Delaware Avenue to Hasbrouck Park Road. (The park entrance road is small and not well marked; it occurs before Delaware Avenue goes over the Helderberg Escarpment.) For the first part of this stop, proceed south on Hasbrouck Park Road for 100 m, and turn left into the small parking lot. Follow the trail from the parking lot to the outcrop in the woods, about 100 m to the east of the lot. For the second part of this stop, drive to the viewpoint at the south end of the park. First, look at the view to the south. Then, walk back north following the trail through the woods to where there is an access trail over the escarpment. The exposures are old roof and pillar quarries. WARNING! The trails are steep and slippery, and the cliffs have loose rock.
The foreland edge of an antiformal stack along the Helderberg Escaprment. Stop 5 at Hasbrouck Park provides a cross-sectional view through the leading edge of a duplex structure involving horses from the Rondout through Kalkberg Formations (Figure 11; Marshak and Tabor, 1989; Marshak, 1990). The basal thrust fault in this duplex, the Hasbrouck thrust, cuts laterally up-section along the sloping footpath between the parking lot and Stop 5. The Hasbrouck thrust fault reappears north of Delaware Avenue, where it places the Manlius Formation over the Alsen Formation. A tear fault with a trace roughly coincident with Delaware Avenue may extend to the west of the lateral ramp. The complexity of the structural relationships at Hasbrouck Park is characteristic of the geology along the Helderberg Escarpment near Kingston.

STOP D (Optional) Exit Ramp from Route 9W to Delaware Avenue
Backtrack from Hasbrouck Park toward Route 9W. Park on Delaware Avenue before the bridge over 9W, and walk to a viewpoint where you can see the roadcuts along 9W and the exit ramp from 9W to Delaware Avenue.
Fly Mountain Thrust. At this locality, we see an exposure of a thrust fault that places Esopus Shale against Onondaga Limestone. The fault surface is decorated with calcite fiber slip lineations. This fault changes trend, south of Kingston

STOP E. (Optional) Callanan Quarry
Connelly (south of Kingston)
This stop can be reached by driving south on US 9W from Kingston, crossing Rondout Creek, and continue into Port Ewen (about 0.7 miles south of the bridge). In Port Ewen, turn right (west) onto Salem Street (County Road 25). Continue on Salem Street across railroad tracks and around a sharp bend to the right. The entrance to Callanan Quarry is approximately 2.2 miles west of the intersection of Salem Road and US 9W. The Quarry cannot be entered without permission, hardhats, etc.
Backthrusts along the Helderberg Escarpment. The northwest wall of the quarry (the high wall below the railroad line) is a spectacular exposure of complex structural relationships, including backthrusts, out-of-the-syncline faults, and duplex structures that are characteristic of the Helderberg Escarpment near Kingston (Fig 12). The Upper Becraft Limestone provides a distinctive marker horizon.

STOP G. (Optional) Rail Trail exposure near Fourth Lake
This stop can be reached by walking 350 south along the Wallkill rail trail from the dirt parking lot on Hickory Bush Road. Warning! The exposure is an abandoned roof and pillar mine. There are steep drop offs and obscured openings.
Limb of Hickory Bush anticline. Walk southwest along the rail trail from the parking lot along Hickory Bush Road for roughly 350 m until you encounter a cut exposing northwest dipping strata. The exposed sequence includes High Falls, Binnewater, Rondout, and Manlius Formations (Figure 13). Along the northwest side of the trail, the High Falls Shale is difficult to distinguish, but it is overlain by a complete thickness of the Binnewater Sandstone. The Rosendale and Whiteport members of the Rondout Formation were quarried at this location. Climb onto the embankment on the south side of the rail trail using the small path through the trees located just north of the northernmost quarry opening. The embankment was once a tramway that serviced the cement quarries in this area. Watch your step and be careful to stay away from the large openings atop the cement kilns that are hidden in the underbrush.

STOP H. (Optional) Former Williams Lake Hotel property
Exposures of an asymmetric anticline in an abandoned room-and-pillar mine. Abandoned cement mines at Stop G provide unique exposures of a series of large, asymmetric folds in the High Falls, Binnewater, Rondout, and Manlius Formations on the property of the former Williams Lake Resort. Watch your step-abandoned cement kilns and sunken shed foundations are scattered along this tramway and are often difficult to see. The floor of the "Chop Shop" mine in the Rosendale Member of the Rondout Formation is formed by the contact with the underlying Binnewater Sandstone, whereas the contact with the overlying Glasco Member forms the ceiling. Because of a recent change in ownership, it is not clear if permission can be obtained to visit this property.

STOP 6. Snyder Estate
This stop can be reached by driving south on Hickory Bush Road for roughly 0.8 miles and turn right (west) onto Breezy Hill Road. At the first stop sign, turn left (south) onto Binnewater Road/County Route 7. Turn right (west) at the intersection with State Route 213 in the Town of Rosendale. Continue east on State Route 213 for 0.2 miles before turning right (north) into the driveway of the Snyder Estate. Proceed up the driveway and across the bridge before parking in the gravel lot on the right.
Historic mine in the footwall of the laterally ramping Century thrust fault. This outcrop is an extensively mined exposure of the Rondout Formation in the footwall of the Century thrust fault. As units in the mechanically rigid Siluro-Devonian strut thin along strike to the north, the Century thrust ramps laterally up section. South of Rondout Creek, the Century thrust juxtaposes Ordovician and Late Silurian strata, but ramps up section into Middle Devonian strata north of Rondout Creek. The abandoned mine at this stop is one of the oldest in the Rosendale natural cement region and is an example of a classic, two-tiered Rosendale cement mine. Dolostone was extracted for the production of natural cement from the Rosendale and Whiteport members of the Rondout Formation, which were historically referred to as the upper and lower cements, respectively. The Glasco Member, historically referred to as the middle ledge, is left un-quarried between the dolomitic layers. There are many remnants of the cement industry on the historic Snyder Estate property, including the ruins of cement kilns, a screening house, and many tramway roadbeds. Use caution when exploring these ruins and be careful to stay away from the large openings atop the cement kilns.

STOP I. (Optional) Rondout Creek Exposures, Lawrenceville
Optional Stop I can be reached by continuing west 0.7 miles on State Route 213 from the entrance to the Snyder Estate. Pull into the public parking lot along the left (south) side of the road for longer stays at this location. This stop affords a good view of the Kalkberg and New Scotland Formations in the Lawrenceville anticline. This anticline is the westernmost major, map-scale fold exposed in the Rosendale region and appears in numerous historical photographs taken of the Delaware & Hudson Canal in this region. This exposure is often obscured by vegetation during the spring and summer months.

STOP J. (Optional) Roadcuts in Schwangunk, Old Route 213
Exposures at Stop J are along both north and south sides of State Route 213, 1.8 miles west of the Snyder Estate. Turn right onto Old Route 213 or Bruceville Road to park, because the road shoulders at the stop are low and generally muddy.
Exposure of a bedding-parallel slip surface in Shawangunk Conglomerate. Optional Stop J provides an excellent exposure of the Shawangunk Conglomerate. The contact with the overlying High Falls Shale lies near the top of the road cuts.
Rocks exposed at the eastern end of this road cuts lie in the footwall of a thrust fault that strikes roughly perpendicular to the trend of State Route 213.
The hanging wall of this fault is exposed in the next set of road cuts east of R8 along State Route 213. A distinct, beddingparallel slip surface exposed along the north side of State Route 213 at this stop contains a cleavage duplex composed of powdered quartz. This duplex suggests a top-to-the-west sense of shear. However, the lack of piercing points prevents a quantification of the amount of slip that has occurred on this surface. For this reason, it is unclear if the slip on this surface was the result of flexural-slip folding (suggesting little lateral displacement between bedding layers) or if it is a segment of a thrust fault exhibiting a flat-on-flat geometry (suggesting large lateral displacement).

STOP 7. Waterfall in the High Falls Shale, High Falls
To reach this outcrop, take Route 213 to High Falls. The outcrop is a stream cut in Rondout Creek, viewed from a state historic site, on the north side of Route 213, about 0.4 miles northwest of the village of High Falls, and about 1.4 miles southeast of the junction between Route 213 and Route 209.
Exposure of an east-verging asymmetric anticline at High Falls. Stop 7 can be reached by continuing west on State Route 213 for 0.4 miles before turning right (north) into High Falls Park/Central Hudson Power Station. Follow paths north down the hill to the bank of the Rondout Creek. Stop 7 exposes an asymmetric anticline in the Binnewater Sandstone and High Falls Shale along the Rondout Creek, northwest of High Falls (Figure 14). To the southwest of High Falls, Rondout Creek flows north, roughly parallel to the strike of gently west-dipping strata. At High Falls, Rondout Creek bends sharply to the east and begins cutting perpendicular to strike, down-section towards Rosendale. The highest waterfall is over an outcrop of the Rondout Formation. Downstream, smaller waterfalls occur in the Binnewater Sandstone and High Falls Shale, and are followed by minor rapids in shallowly east-dipping Shawangunk Conglomerate. The asymmetric anticline in the Binnewater Sandstone and High Falls shale at Stop 7 is the westernmost mesoscopic structure in the fold-thrust belt near Rosendale, and is best exposed along the north bank of the creek. Note that the axial surface of the fold dips to the west, which is a vergence opposite to the regional trend. The geometry and scale of this fold suggest that it is a fault-propagation fold above a blind thrust fault. The fault underlying this structure is most likely a west-dipping back thrust associated with detachment horizons in the Ordovician strata at depth.

2: HYDROTHERMAL ALTERATION, MASS TRANSFER AND MAGNETITE MINERALIZATION IN DEXTRAL SHEAR ZONES, WESTERN HUDSON HIGHLANDS, NY
Michael J. Kalczynski and Alexander E. Gates
Department of Earth & Environmental Sciences
Rutgers University
Newark, NJ 07102
Matthew L Gorring
Department of Earth & Environmental Studies
Montclair State University
Montclair, NJ 07043
Marian V Lupulescu
New York State Museum
Division of Research and Collections
Albany, NY 12230
INTRODUCTION
The Reading Prong is a Grenville basement massif that forms part of the spine of the Appalachians, connecting the Blue Ridge and Green Mountain provinces, in Pennsylvania, New Jersey, New York, and into Connecticut (Figure 1). Known as the New Jersey Highlands and the Hudson Highlands in New York, it hosts thousands of iron deposits, the first discovery of which was as early as 1730 (Lenik, 1996). These deposits were extensively mined throughout the 18 th and 19 th centuries (Lupulescu and Gates, 2006).
Earliest investigations of the iron districts in the Highlands focused on the ore deposits (e.g. Kitchell, 1857; Cook, 1868; Wendt, 1885; Ruttman, 1887), and generally accepted an origin from metamorphosed sediments. Rodgers (1840), however, proposed that the magnetite deposits were of igneous genesis. Colony (1923) later proposed that the ore deposits were the result of magmatic replacement of country rocks. More recent investigators found that the deposits were either the result of magma driven replacement or hydrothermal processes (e.g. Sims and Leonard, 1952; Hotz, 1953, 1954; Sims, 1958; Hagner et al., 1963; Buddington, 1966; Collins, 1969; Baker and Buddington, 1970; Foose and McLelland, 1995; Martinko and Gates, 2000). Gundersen (1984, 1985, 2000) proposed that they formed in a back arc setting, but Volkert (2001) proposed that the magnetite deposits were formed in an extensional setting, prior to metamorphism. It is evident that there are multiple modes of emplacement for the magnetite bodies of the Hudson Highlands (Lupulescu and Gates, 2006), as there are multiple types. Gundersen (2000) and Puffer (2001) acknowledge several types, including vein deposits created by remobilization of magnetite into faults and fractures, as well as deposits that are related to plutonic rocks and hydrothermal activity (Gundersen, 2004).
This guide will focus on two, kilometer scale shear zones that host several hydrothermally mineralized veins containing massive magnetite bodies. The NE trending dextral shear zones formed in crystalline rocks of the western Hudson Highlands late in the Grenville orogenic cycle. The veins are exposed at several abandoned magnetite mines within Harriman State Park. New modeling for the mode of formation of these deposits is discussed, following an overview of the bedrock geology, and brief description of each of the veins. New geochemical evidence from the wall rock-vein contact will also be explored. This guide will then conclude with an overview of the current working model for the formation of these iron oxide deposits.

2: HYDROTHERMAL ALTERATION, MASS TRANSFER AND MAGNETITE MINERALIZATION IN DEXTRAL SHEAR ZONES, WESTERN HUDSON HIGHLANDS, NY

STOP 1. Unsheared Metavolcanic Gneiss
Strongly interlayered intermediate and mafic gneisses with migmatitic bodies, just outside of the SE shear zone (Figure 11). Mafic layers are characterized by assemblages of clinopyroxene and amphibole with minor plagioclase, magnetite, sphene, and apatite. Intermediate layers are mainly plagioclase with minor quartz, apatite, amphibole, and biotite. The felsic leucosome is composed of coarse plagioclase, quartz, and K-feldspar, which form veins and clots including classic "net veining". Minerals exhibit preferred orientations in the gneiss and appear granular in the leucosome. Late stage K-feldspar pegmatites can also be observed in this outcrop, containing mafic gneiss xenoliths.
Gneisses exhibit a strongly banded, intermediately dipping, foliation that strikes N-NE. Isoclinal intrafolial folds can also be observed, with axis following similar orientation. This deformation is indicative of main stage Grenville tectonism, and was unaffected during the later tectonic event, associated with the formation of the ore deposits. Contrast these rocks with Stop 2.

STOP 2. Southeastern Shear Zone Boundary
Several meter scale lozenge and cigar shaped boudins of mafic gneiss are contained within mylonitic quartzofeldspathic gneiss, with folded biotite and local amphibole-rich layers (Figure 12). The layers appear contorted and wrap around the mafic bodies. The encased mafic gneiss is similar to that of Stop 1, however it also contains contorted folds and veins of magnetite. The long axis of the bodies and fold axis appear sub-parallel, and shallowly plunge to the northeast.
Both Stops 1 and 2 are similar in composition and therefore grouped within the same metavolcanic sequence. Long axis and fold axes roughly parallel shear zone boundaries and fabrics within. This location is at the edge of the southeastern dextral, strike-slip shear zone. Deformation steadily increases to the northwest, into the central shear zone, characterized by a steepening of planar fabric and increase in intensity of linear fabric. The contrast of the features at Stop 1 with Stop 2 shows the difference between the first main Grenville and second strike-slip events.

STOP 3. Hogencamp Mine
Locate the gated path directly on the opposite side of route 106. Walk this path heading north for a quarter mile, to the intersection with Dunning Trail (E-W trending). Head roughly northeast on Dunning Trail for about a half mile until you reach several large holes in the ground, and the path crosses a small stream. Hike upstream for roughly 100 feet until you are almost cliff side. A linear open pit mine should be visible to the southwest and a large mine shaft to the northeast into the cliff, beneath Cape Horn (Stop 3, Figure 13).
Hogencamp Mine lies in the southern part of the SE mineralized zone. Here the sheared wall rock is dominated by quartzofeldspathic and amphibole-pyroxene (metavolcanic) gneisses with interlayered calc-silicate gneiss and marble locally. Hogencamp Mine was active from the earliest to latest 18 th century. It is characterized by a series of meter to several meter scale horizontal and vertical mine shafts and open pit mines. The mines can be traced along strike for up to a kilometer. The mineralized zone that hosts Hogencamp Mine is roughly 6 kilometers long and extends into Pine Swamp Mine (Stop 4). The vein ranges in thickness from 3-15 meters at the mine locations to as little as one meter in the narrow zones connecting the deposits. The Hogencamp Mines can be followed to the southwest from this location for up to a kilometer.
The vein-wall rock contact is sharp and semi-concordant to mylonitic foliation. On the small-scale it appears slightly discordant, crosses foliation and erodes into the wall rock. This is best observed in the open pit mine, directly in front of the northeastern most mine shaft, below Cape Horn (Figure 13). Here, the bleached zone is characterized by the deposition of calcite and scapolite, and retrogression pyroxene to amphibole, also containing phlogopite, calcite, and minor apatite locally. Earliest vein deposit is characterized by layered amphibole, orthopyroxene, and clinopyroxene, later by massive clinopyroxene and magnetite, cemented by late stage, interstitial calcite in the ore zone. Clinopyroxene and localized magnetite are euhedral, forming doubly terminated crystals, thought to have crystallized in cavities. The veins are also intruded by very coarse grained pegmatites which contain xenoliths of the mafic vein material.

STOP 4. Pine Swamp Mine
Back on Dunning Trail, walk east than north-northeast, another half mile until you reach a large swamp to the east, and a large, steep hillside to the west, littered with dark-colored mine tailings. Locate the makeshift path on the hillside. Take this path uphill for about two hundred feet, until your reach the entrance to the mine (Stop 4, Figure 13).
Pine Swamp Mine lies in the northern part of the SE shear zone within the same mineralized vein which hosts Hogencamp Mine, roughly one kilometer alone strike (NE). Pine Swamp is also characterized by a 3-12 meter horizontal mine openings and several, meter scale open pit mines (Figure 13). The mines that compromise the Pine Swamp deposit can be traced along strike for several hundred meters, with minor semi-concordant offshoots in the northern extent of the deposit. This portion of the hydrothermal vein lies dominantly within sulfide-bearing quartzofeldspathic gneiss country rock, which contains interlayered metavolcanic gneisses. The bleached zone is primarily defined by retrogression of pyroxene to amphibole, also containing minor amounts of scapolite, and apatite locally. Orthopyroxene and amphibole dominate the narrow layered vein and thick massive sequences followed by the magnetite deposits. Massive minerals are locally cemented by late stage sulfide minerals, mainly pyrite and pyrrhotite. The flat wall adjacent to the mine proper is yellow to rust colored, due to the weathering of the sulfide-rich country rock. Massive minerals orthopyroxene, amphibole, and substantial magnetite can also be observed.

STOP 5. Bradley Mine
Mine is the northern deposit in the northwestern shear zone, located a few hundred meters north of Arden Valley Road (Figure 13). Bradley Mine was active through the latest 19 th century, when it closed permanently in 1874. Wall rock is primarily calc-silicate gneiss, containing salite, K-feldspar, apatite, sphene, scapolite, and amphibole. Bradley Mine also hosts a several meter thick discontinuous body of diopside marble, composed of medium-coarse grained calcite, fine-medium diopside, and minor amounts of garnet locally. Diopside is generally dispersed, though locally forms cm-scale aggregates.
The vein deposit at this location appears only a few hundred meters in length and varies in thickness from 2-10 meters. The bleached zone here is characterized by scapolite, diopside, and sericite, followed by narrow zone of layered clinopyroxene, calcite and very fine grained micas. Massive intergrowths of clinopyroxene cemented by calcite, than magnetite, appear in the center of the deposit. Both types of pegmatites can also be observed here. The earliest, white-colored pegmatite appears slightly deformed; containing minor internal fabrics, whereas the latest stage, pink pegmatites appear very coarse grained, and shows no deformational fabrics. A much more recent brittle fault also cross cuts the entrance to the mine proper.

3: STRATIGRAPHIC AND STRUCTURAL RELATIONSHIPS OF THE ORDOVICIAN FLYSCH AND MOLASSE ALONG THE WESTERN BOUNDARY OF THE TACONIC ALLOCHTHON NEAR KINGSTON NY
Gerald Pratt
New York State Department of Environmental Conservation
Overview
This trip will visit recently described exposures of the allochthonous Ordovician Normanskill Group juxtaposed against autochthonous Quassaic and Martinsburg sedimentary rocks. Exposures in the Kingston and Esopus Townships demonstrate through stratigraphic position, sedimentary structures and fossils, the collapse of a foredeep basin and subsequent down warping of a foreland basin during the latest stages of the Taconic Orogeny. The trip includes several stops at outcroppings of the allochthon strata, Taconic Unconformity and the later arenites of the Quassaic, which contain an unusual molasse facies.
Introduction
Sandstone petrology of compositions of the strata in the field trip area indicate Ordovician formations originate from a volcanic terrain and are classified as recycled orogen blocks directly or indirectly. It is likely that these formations were formed proximal to one another. A structural inlier consisting of fossiliferous thin shale and siltstone is identified and delineated within unfossiliferous massive arenites. Structural geometry, biostratigraphy and sedimentology were analyzed to constrain the inlier stratigraphic boundaries to the Martinsburg Formation. Massive Ordovician arenites in the study area are uncharacteristic of those of the Normanskill Group, lacking fauna and allocyclic characteristic. Bedding is massive, exceeding 5 meters containing laminate sets and contained greater amounts of quart and lesser amounts of calcite and lithic fragments as well. Sedimentology of the massive arenites suggests this formation is an alluvial or olistostrome deposit and its structural position would place it above the Normanskill Group. However, analysis distinguishing structural domains potentially places the arenites within the Normanskill Group. Thus, the arenite strata are proposed as a new formation for the uppermost position of the Normanskill Group. The stratigraphic sequence of the Ordovician strata within the study area represents a transgressive progression from an older flysch to a younger molasse facies. This is interpreted as a tectonic depositional loading to a flexural extension of underlying continental blocks.

3: STRATIGRAPHIC AND STRUCTURAL RELATIONSHIPS OF THE ORDOVICIAN FLYSCH AND MOLASSE ALONG THE WESTERN BOUNDARY OF THE TACONIC ALLOCHTHON NEAR KINGSTON NY

STOP 1. Rotary Park at Kingston Point.
Enter Park through iron gate. Outcrop immediately along dirt path on right just after entering park. Cleavage face of Austin Glen formation. Continue south along dirt path to outcrop. Crossection of angular beds of Austin Glen formation consisting of alternating shales and siltstones. Siltstones substantially bioturbated. Continue along path to southern peninsula of park. Large outcrop of sandstones, siltstones and shales.
Within the park are several outcrops of Austin Glen lithology, which generally dip 55 degrees east. Thin to thick beds of alternating sequences of laminated and cross-stratified thin grey phyllarenites, calcareous grey to dark-grey siltstones interspersed with thin argillaceous dark-grey siltstones and bluegrey and black shales. Arenite and siltstone beds are typically less than 1 meter thick but can range from several cen timeters to two meters. Shale is often lenticular and varies in thickness from a few centimeters to less than a meter. Erosive contacts of the hummocky cross-stratified beds with underlying dark gray shales are common. Shale and siltstone cleavage is common on two planes orientations are NNE in shales exhibiting penciling and NE in siltstones in a few outcrops at the park. Orthogonal jointing and plumose structures are common in arenite beds. Limited detrital fauna deposits are found in the shale and siltstone layers due to bioturbation.

STOP 2. Hasbrouck Park.
A path off the parking area continues along the base of an escarpment of Helderberg limestones. The path continues along the southwest side of a large vertical adit runs northeast southwest. The escarpment was extensively mined in the past for the dolostones of the Rondout Formation to make cement. Carefully continue past the adit and scramble down off the path to a cut in the slope. Here the Austin Glen is juxtaposed against the remnants of the Wilbur Limestone member of the Rondout Formation in angular unconformity.

STOP 3. Trolley Museum.
The Trolley Museum is part of and adjacent to an active railroad switchyard and permission is needed to access this location. The outcrop is located behind the museum buildings along the base of North Hill. This is the northern extents of North Hill and is truncated by Rondout Creek. The outcrop consists of massive arenites and thin lenticular conglomerated of the proposed upper formation of the Normanskill formation.
Take a few minutes and peruse the museum. Follow the railroad cut west along base of Hasbrouck Park, Outcrop is exposed along its entire length. Massive sandstone layers include some lenticular conglomerates of chert and limestone. Clasts of semi-angular large and small pebble-sized black and green chert, grey shale and weathered laminated light to dark grey limestone. Approximately 100' along the railroad bed from the museum the rock face gives way to a slope. Scramble up the slope to an abandoned road. Walk east along the road to the end of the chain link fence approximately 75'. Scramble up the slope toward a large rock fall. A section is cut out of the slope perpendicular to the mine adit. Here the upper Normanskill is in contact with Silurian or Devonian Limestone. The orientation of the unconformity has changed from a NNE strike to NE. This sight is also accessible from Hasbrouck Park. Beginning at the pavilion in the park, walk north along a sidewalk path toward an abandoned block building, continue though a break in the fence behind the building and scramble down a steep path through the talus. The ground levels and the contact is on the left approximately 50 feet from the base of the slope.

STOP 4. West Strand Street.
Extensive exposure approximately 250 long at base of Wurts Ave Bridge exhibits large amounts of deformation and a few folds plunging northeast. Beds are both upright and overturned, generally striking N40W and dipping 50E. A number of low to high angle faults strike NE throughout the section. Orthogonal joints exhibiting plumose structures are common. Turbidite structures are used to determine overturned or upright sections of the outcrop. Pock marks eroded from joint faces generally run along bedding planes and are thought to be of soft mudstone pockets within the otherwise massive sandstone.

STOP 5. Slaughterhouse.
Just West of Stop 4 this outcrop was recently uncovered after demolition of a large abandoned structure once used as a slaughterhouse. Massive quartz arenite in most of the exposure, thickness of beds exceeds 5 meters. Minor dark shale and siltstone beds vary in thickness from several centimeters to two meters. Cleavage planes orientations in shales is NNE. Color of arenites range from light to buff in fresh exposures to orange brown to black in weathered exposures. Beds are often graded or cross-stratified, faint laminae sets are also present and vary from 5 mm to a centimeter in thickness. A high angle normal fault occurs in the exposure, strike of this fault is approximately 060. Faulting bounds the upper and lower contacts of Street boarders the upper part of the exposure on the South side. Bordering the north side of Abeel Street is an outcrop of Devonian limestone outcrop in apparent unconconformity. Arenite beds near contact are nearly devoid of shales as opposed to more frequent layers away from contacts seen to the east. It is likely that there is an increase in shear stress as beds near the contact thus during deformation and less competent shales were squeezed out leaving behind arenites.

STOP 6. Apparent Taconic Unconformity.
Top side of the Stop 5 outcrop, this part of the exposure demonstrates an apparent contact with the Devonian beds of the Coeyman limestone formation directly across the street.

STOP 7. Old 9W Roadcut.
The proposed Ulster Park formation in the extensive road cut is exposed. Massive quartz arenites dominate the cut. Bedding displays graded and cross bedding and is overturned. The few thin shales exposed are cleaved in at least two directions. At least two major faults cut through the outcrop and is traceable across the highway. A high angle fault dominates the outcrop, its displacement effectively dissects the exposure into two distinguishable and different parts. Some shale and limestone pebble conglomerates are evident. Several lode casts are evident on bedding planes.

STOP 8. Connelly Road residence.
Permission is needed to enter location.
Large outcrop behind residence exhibits plunging fold oriented N75W. This orientation is not typical of Taconian deformations that follow a NNE trend.

STOP 9.Outcrop at back of lot.
Facing east and up gradient along Salem St. a contact of Martinsburg with upper Normanskill strata is evident. Facing north, the outcrop continues for 0.76 miles along Millbrook Rd and within the stream gully that runs beside the road. The Martinsburg strata continues until it is truncated by the Rondout Creek. Facing west across the stream gully a steep slope rises, where outcrop of upper Normanskill is found. Leave lot north on Millbrook Dr.
Locally fault-bounded above and below by upper massive quartz arenites and composed of low-to moderately-eastward dipping, 020 to 040 degrees, faulted and folded, medium to dark-grey sandstone and interbedded shale. Total section represented in this exposure is approximately 40 m. Dominate dark-grey to black mudstone with a few lenticular fine-grained, medium grey, sandstone turbidites, calcareous with mudstone clasts. Many of the turbidites observed are arranged in small-scale (1-2 m) fining-upward sequences demonstrating bedding is upright in position. Calcareous shelly fossils preserved primarily as molds and casts. Shelly fossils occur throughout the shale and sandstone with locally dense concentrations. There were several fossil localities along Millbrook Rd. Fossil localities chiefly contained disarticulated brachiopods, ostracods, crinoids, bryozoans, and trilobites. Genera and limited species of brachiopods found were identified as Dalmanella sp., Paucicrura rogata sp., Sowerbyella spp. and Rhynchonella sp. articulate brachiopods, Dilobella spp. ostracod, trepostomate bryozoa zoaria, and a pygitium belonging to a trilobite tentatively identified as Decoroproetus spp. was found.

STOP 10. Outcrop is on northeast stream bank.
This outcrop contains calcareous thin-bedded siltstones and shales. Bedding is dark grey to black, and is moderately dipping east 50 degrees. These strata are similar in composition to Stop 9, though the fossils are absent.

STOP 11. Walk behind mobile home to the right along ATV path about 200 feet.
Outcrop is low lying and may be difficult to locate in high vegetation.
East side of railroad cut is massive sandstone bedding overlooking extensive sand cover to the southeast.

STOP 12. Old quarry.
This quarry lies the opposite side of the railroad cut west of Stop11. Here the Esopus Fault is presumed to lie within the railroad cut and plunges under the Silurian and Devonian limestone immediately north of the stop. The fault extends to the south with rocks of the upper Ordovician Quassaic Group sitting to the west of the railroad. Thin bedded sandstones are truncated by massive conglomerates of red clay clasts of pebble to cobble size. The bedding generally strikes N30 degrees dip east moderately 40 degrees. Slumping of bedding at the location indicates a molasse facies. An upslope outcrop to the south and west exposes bedding as thin sands oriented 30 degrees west dipping, similar to that found on the east side of the slump indicating a defined block of red clasts slumped into the sands.

STOP 13. Railroad cut at County Route 25 and West Shore Railroad line.
Here again lies the presumed exposure of the Esopus fault. Rocks on the west side of the railroad cut are massive steeply dipping and medium to thick quartz arenites and conglomerates. Conglomerates contain of rounded or subangular pink or grey (rarely banded) limestone and black or green chert and shale pebbles. In the railroad cut, the basal Shaupeneak Formation of the Quassaic group is exposed. To the east of this extend the proposed Ulster Park rocks of the upper Normanskill Group. They are seen in numerous outcrops along the backstreets of Port Ewen and form low-lying ridges extending north to south.

STOP 14. Hussey Hill.
A moderate climb up a steep slope is required to access this stop. Along the slope path are exposures of red clasts of the Shaupeneak. At the top are exposures of the Slabsides Formation of the Quassaic Group are found. They mostly occur as vertical beds of thin to medium quartz arenites. The Quassaic Group makes up the Hussey Hill at its northern point and extends south from the north to the Marlboro Mountains.

4: DEGLACIATION IN THE SOUTHEASTERN LAURENTIDE SECTOR AND THE HUDSON VALLEY – 15,000 YEARS OF VEGETATIONAL AND CLIMATE HISTORY
Dorothy Peteet
NASA/GISS and Lamont Doherty Earth Observatory
Palisades, NY 10964
John Rayburn
SUNY New Paltz
New Paltz, New York 12561
Kirsten Menking
Vassar College
Poughkeepsie, New York 12604
Guy Robinson
Fordham College
Fordham, New York 10458
Byron Stone
United States Geological Survey
Connecticut 06340
Introduction
In this field trip, we provide a review of the significant controversy concerning the timing of deglaciation in the Hudson and Wallkill Valleys. We outline the differences in methodology and chronology with a circular route throughout the Hudson and Wallkill valleys. We begin the trip at Lake Mohonk near New Paltz led by Kirsten Men-king and Dorothy Peteet, then continue to the "black dirt" region of the Wallkill Valley where John Rayburn has contributed a new GIS model of deglaciation in the Wallkill Valley and Guy Robinson will review the history of fossil mammals, including mammoths. From this point we travel southeast to a rare exposure of glaciolacustrine beds on the west side of the Huson River, described by Byron Stone and John Rayburn, and on to Croton Marsh at Croton Point, New York where Dorothy Peteet will review the marsh histories of the region.
A recent review of literature relating to the last glacial recession in the Hudson Valley indicates that the timing of deglaciation is very controversial (Peteet et al., 2006; Peteet, in review; Balco et al., 2006; Balco et al., 2009; Schaefer, 2007). Some questions to consider:
1) How does timing of new lake basal dates at the margin of the ice (Staten Island) compare with sites to the north and inland (ie. Mohonk)?
2) What is the vegetational history of the region and how does it compare with Deevey's classical southern New England stratigraphy?
3) What is the latest model of the deglaciation of the Wallkill Valley?
4) What have the Hudson marshes added to our understanding of the vegetation and landscape history, particularly in the last few millennia?

4: DEGLACIATION IN THE SOUTHEASTERN LAURENTIDE SECTOR AND THE HUDSON VALLEY – 15,000 YEARS OF VEGETATIONAL AND CLIMATE HISTORY

STOP 1. Mohonk Lake
We begin our trip with a walk around the shores of Mohonk Lake, guided by Paul Huth, director of research for Mohonk Preserve. Starting in front of Mohonk Mountain House, a Victorian era hotel built in 1869 and operated continuously by several generations of the Smiley family, we will climb onto the quartz pebble conglomerate cliffs of the Silurian Shawangunk formation that surrounds the lake. Glacial striations and crescentic gouges are evident at several points along the trail, and Mohonk Lake itself is thought to have been formed by glacial plucking of tectonically fractured bedrock. The sediment core described earlier in this guide was taken at the northern end of the lake near the Mountain House and spans most of the Holocene (see Figures 1-3). The first appearance of organic matter in the core dates to approximately 11.6 14 C kyr b.p., in keeping with young AMS dates found at other sites in southern New York and New Jersey. In addition, the core appears to record a mid-Holocene drought episode that might have caused the decline of hemlocks previously attributed to a pathogen.
Continuing along the trail affords a view of Rhododendron Swamp from above. A paleoindian rock shelter adjacent to the swamp contains evidence of human habitation as early as 10 kyrs b.p. and possibly as early as 11.5 kyrs b.p. (Eisenberg, 1991). Ongoing paleoecological stratigraphy attempts to link the Swamp record to the archeological record..

STOP 2. Dutchess Quarry Caves
Paleoindian culture and Pleistocene Megafauna . Perhaps the most significant early human site in the northeast is at Dutchess Quarry, in a group of small caves formed in Paleozoic limestone on the northwest side of Mount Lookout in southern Orange County, NY. One complete and four partial Paleoindian fluted projectile points have been recovered from cave numbers 1 and 8 (Funk et al., 1969; Funk et al., 1970; Kopper et al., 1980; Funk and Steadman 1994) Bones of caribou, (Rangifer tarandus), extinct flat-headed peccary (Platygonus compressus) and the extinct giant beaver (Castoriodes ohioensis) have been among the 71 species of vertebrates discovered, although there is no clear association between any of the Pleistocene fauna and the cultural material (Steadman, Stafford and Funk 1997).
At an elevation of 177m Mount Lookout offers a view from 80m above the Black Dirt agricultural region, itself lying over the largest accumulation of terrestrial peat in eastern United States after the Florida Everglades. A succession of proglacial lakes occupying the Wallkill River Valley left a large, poorly drained area that was to become an immense peat deposit continuing to build throughout the Holocene. By the early 20 th Century, these mucklands were being artificially drained for agriculture. Occasionally, maintenance of drainage ditches exposed the remains of the extinct Pleistocene megafauna. In this way, numerous mastodons (Mammut americanum) and at least three stag moose skeletons (Cervalces scotti) have been discovered in and around this vast wetland. The two most recent of the stag moose have been AMS dated to 12,180+/-60 and 11,040+/- 110 the latest known occurrence of this species in North America.

STOP 3. Newburgh Terrace
The only available exposure of glaciolacustrine deposits on the west side of the Hudson River is in this pit at the mouth of Moodna Creek on the south side of Newburg. The pit is in the south side of the excavated terrace that has a surface altitude of over 49 m (160 ft). A small inset plain at the top of the exposure had a surface altitude of just above 33 m (100 ft). The pit exposes: 1) cobble gravel at the surface, 2) glaciolacustrine beds that extend to the bottom of the cut. The gravel, 1-2 m thick, underlies the inset terrace surfacecut into the southern part of the original higher glacial terrace landform. The gravel rests on a sharp, horizontal disconformity with the underlying sand. The surface of the gravel plain is correlated with nonspecific levels of glacial Lake Albany, projected from deltas surfaces and topset-fore-set contacts from deposits east and north of this site. The gravel in this exposure is a thin, postglacial fluvial terrace deposit, probably graded to lowering lake levels in the valley.
The glaciolacustrine sand deposit consists of alternating, laterally continuous beds of fine to coarse sand, pebbly sand, and very fine sand and silt. Basal bedding contacts are sharp; bedding forms are chiefly flat thin beds and laminations, with few ripples and hummucky forms. Color of beds is related to their composition and, therefore, their particle size: coarser beds are lighter colored and contain quartz, some feldspar, minor carbonates, and scattered pebbles of carbonate and sandstone. Darker beds are finer grained and contain platey rock fragments of shale and some carbonate. The lake beds have a gentle southerly slope of <1o reflecting their subaqueous origin as bottomset beds of an ice-marginal delta deposited in glacial Lake Albany.
The excavation exposed on this trip affords us an opportunity to determine the local vertical successions of delta bottomset underflow deposits, their cross-cutting relationships, and paleocurrent flow directions.

STOP 4. Croton Marsh.
Archeological evidence indicates that the Croton region was populated by the Kitchawanc tribe as early as 5000 BC. The marsh was called Senasqua, Croton itself is believed to be named for the local Indian Chief, meaning "wild wind". A 1718 census of the area counted 91 inhabitants in the Manor estate of Cortland, including Dutch settlers and English Quakers (http://www.crotononhudson-ny.gov). An overview of the Croton Marsh remaining from the landfill road to the south of the entrance to Croton Park. Today, one can only see the invasive Phragmites communis covering the site, but prior to European impact it was comprised of a diverse sedge mixture. Peteet et al. extracted a 10 m marsh core and pollen/macrofossil work on the core is in progress.

STOP 5. Croton Moraine and Varves.
A summary of Croton Point Pleistocene glacial history is provided by Sanders and Mergurian (l994). It is as follows:
1) Several tills starting with gray-tan, then red-brown, then, after red outwash was deposited, another red-brown till, followed by the yellow-brown till. The red-brown tills contain erratics from the west side of the Hudson River whereas the youngest and oldest tills contain only rocks found on the east side of the Hudson River.
2) After the youngest of the tills had been deposited and the glacier responsible for it had melted away, the region was flooded. All the drainage from the Great Lakes flowed eastward through the Mohawk Valley and down the Hudson. Proglacial Lake Albany was backed up behind the natural dam of till at the Narrows. Deltaic sediments from the ancestral Croton River and possibly drainages to the north were deposited along the east shore of this lake. The water plane presumably stood at about elevation +70 feet (level of the flat terrace underlain by topset beds of the delta that coincide with the uppermost water level). To the west, the depth of water where the clay was deposited away from influence of the delta was 70 feet. The coarse browner clays probably represent the dark suspended load of the river(s). The light clays are winter deposits when river(s) experienced low- flow conditions and/or were shut down altogether because their waters froze solid.

6: ECONOMIC GEOLOGY OF THE CENTRAL HUDSON VALLEY, NEW YORK
Paul H. Griggs
Mining Geologist
Griggs-Lang Consulting Geologists, Inc.
Troy, New York 12180
pgriggs@griggs-lang.com
Jeffrey T. Lang
Hydrogeologist
jlang@griggs-lang.com
INTRODUCTION
This trip provides an overview of the Portland cement and aggregate mining industry, past and present, in the central Hudson Valley. We will visit the Holcim US Catskill Quarry, as well as the Colarusso and Holcim US quarries on Becraft Mountain in the Town of Greenport, Columbia County. We will review the classic Tristates and Helderberg stratigraphy, see how geologic principles are applied, examine complex structural settings and see how various professions—e.g. geologist, mining engineer, chemist—work together to make viable products in as efficient, economical and environmentally friendly a manner as possible.

6: ECONOMIC GEOLOGY OF THE CENTRAL HUDSON VALLEY, NEW YORK

STOP 1. Tracey's Landing Quarry.
Historically, the quarry operators gave numerical names to their quarries. This practice became difficult at the Catskill Quarry as the property was an amalgamation of at least three different quarries and each company often had the same name on different quarries. Beginning in the early 1990's quarry nomenclature reached an art form under the guidance of Richard Playle and Dave Blasko, mining engineers, Jim Sucke, Murray Craft and Floyd Mower, quarry managers and Paul Griggs, consulting geologist. We became frustrated at trying to use everchanging landmarks in planning discussions so a systematic nomenclature system based on geologic structure was devised (see Figure 8).
The Tracey's Landing Quarry was named after Bart Tracey, a mining engineer and quarry manager who worked at the quarry in the early 1990's. He had done some of the original chip sampling exploration in this area and was one of the first people to suggest this area as a viable source of cement stone.
Overall, the geologic structure in the Tracey's Landing Quarry is a rolling, doublyplunging asymmetrical, thrustfaulted syncline. The east limb of the syncline is nearly vertical and continues east down the slope overlooking U.S. Route 9W. The center of the syncline was typically capped by siliceous limestones of the Glenerie and Port Ewen Formations overlying the cementfriendly Alsen Limestone and the cement mother lode, the Becraft Limestone. The west limb of the syncline contains the argillaceous limestones of the New Scotland Formation.
This quarry was worked by removing the argillaceous limestones from the underlying Alsen and Becraft. The "overburden" rock was used by Peckham Materials as high friction aggregate. This quarry served as the main source of cement stone for about 10 years.

STOP 2. Mower's Lake.
This quarry is part of the Apple Orchard and was named for Floyd Mower who worked his way up from an equipment operator in 1970 to Quarry Manager in 2003. The quarry serves as a sump for the Apple Orchard which has been a major source of cement stone since the early 1990's.
A series of pumps discharge water from the quarry so that it can be worked dry. The water is used in the cement plant for thermal cooling. Overall, the structure in this area consists of a southwardplunging asymmetrical, heavily faulted synclineanticline pair.

STOP 3. Floyd's Folly.
The aforementioned Floyd Mower contributed greatly to the economic viability of this quarry which is in the final developmental stages for full cement stone production. In the 1980's the quarry manager was considering plans for filling this area with overburden rock (this was prior to the involvement of the aggregate producer, Peckham Materials). Floyd, who often operated the bulldozer and was a pretty good amateur geologist, pointed out the presence of near vertical beds of Becraft Limestone in the floor and convinced the powers that be to not cover this area.

STOP 4 Apple Orchard.
The Apple Orchard Quarry was developed in the early 1990's and has been a major supplier of cement stone since that time. The cement stone reserves were first evaluated by George Chadwick in the late1940's but were not mined due to the thickness of overburden rock overlying the faultrepeated thick section of cement stone.
In 1988, a geology student named Bill Reinhart worked as an intern at the quarry and researched the prior studies, Figure 10. Photo of the north face of the Tracey's Landing Quarry showing the did some field mapping and made some center of the syncline. The dark colored argillaceous limestones of the Port logical conclusions based on his work. Ewen Formation cap the face. The middle of the face contains the Alsen Lime
There is an infamous memo in the quarry stone and the light–colored stone in the lower third of the face is the Becraft files from a bemused high level manager Formation. that questioned how a geology student could find such a large reserve of cement stone so close to the primary crusher when everyone else had been searching all over the quarry. The answer is, like the quarry geology, fairly complex: (1) the other searchers did not have the requisite geologic expertise; (2) until the authors' involvement at the quarry, geologic investigation had largely been confined to specific areas with little or no formal correlation between individual studies; (3) the task of map making was more time consuming in past days and there were few landmarks that could be used to accurately determine the locations of individual study areas; (4) the text and large scale plans in the geologic reports had gotten separated over the course of the numerous quarry sales and land swaps; and (5) the geology is insanely complex.
The development of the Apple Orchard was a turning point in the history of the quarry. This quarry led to the involvement of Peckham Materials, starting in 1991, to remove the aggregate stone and led to the ultimate geologic investigation and mine planning of the entire quarry.
Overall, the structure in this quarry consists of an asymmetrical, doubly plunging, rolling, highly faulted anticlinesyncline pair. The west limb is nearly vertical and the east limb in bounded by the most prominent fault in the quarry, the Sucke's Bluff (or "Sucke's") Fault. This fault has been traced the entire length of the quarry and onto the Lehigh Northeast Cement quarry to the south. The dark colored stone to the left (east) is New Scotland argillaceous limestone and the stone underlying the fault is mainly Alsen and Becraft limestone.
Note in driving to the next stop that the main haul road parallels the path of Sucke's Fault and is mainly underlain by thick repeat sections of aggregate grade rock.

STOP 5. Golf Club.
The Golf Club Quarry was last mined more than 50 years ago. At that time, a public road ran through the middle of the quarry. The northward advancing face containing high grade Becraft Limestone at the surface neared the road so the quarry operators started moving in a westerly direction, giving the quarry its distinctive shape. Using much more primitive blasting methods than employed today, they opened up large fractures in the rock that allowed a steady stream of water to flow into the quarry, effectively ending excavation operations at that time.
Overall, this quarry is part of the east limb of a faulted, fairly symmetrical syncline bounded on the east by Sucke's Fault.

STOP 6. Streekie Lake.
The Streekie Lake Quarry is a current and future major source of cement stone. Named for a prior owner and its tendency to hold water during periods of wet weather, the quarry structure consists of the west limb of a faulted anticline and a complexly faulted anticlinesyncline pair. In general, the top of the face contains Port Ewen siliceous limestone that is removed for use as aggregate overlying repeated sections of Alsen and Becraft limestone to great depth.
The hydrogeology in this area is interesting. The upland areas to the west are underlain by tillcovered Devonian shales and a large drainage basin feeds to a sinkhole just west of this quarry. During dry weather, the sinkhole may be dry or is surrounded by a small pond a few feet across. This pond grows dramatically during wet weather (see Figure 14).

STOP 7. Ace in the Hole Quarry.
Most of the aggregate stone used by Peckham Materials is blasted, excavated and hauled to their surge pile by Holcim US. Peckham started the Ace in the Hole Quarry in the early 1990's to cover times when the cement company could not haul enough stone or the needed quality of stone to meet the aggregate demand.
This quarry consists of a highly faulted, westward dipping west limb of an anticline primarily containing repeated sections of New Scotland and Kalkberg argillaceous and siliceous limestone. Holcim US has removed Coeymans and Manlius Limestone from the east wall. The west side of this quarry is bounded by Sucke's Fault (see Figure 15).
The northsouth trending Sucke's Fault typically dips to the west at about 60 to 80 degrees. However, the fault plane tends to wander at times and varies from slightly overturned to as low as 20 degrees. The two sides of the fault tend to widen in areas where the fault begins to rotate and larger fault slivers are common. The fault acts as a barrier to eastwest flow of water and locally promotes northsouth flow. Large doublyterminated, internally flawed quartz crystals (nicknamed "Catskill" diamonds) are periodically found near this fault (see Figure 16).
We will stop for lunch at this location before returning to the parking lot and proceeding to the Greenport Quarry.

STOP 8. Overview of Aggregate Processing and Blacktop Plants.
Like the Catskill Quarry, mining activities at Becraft Mountain have included both cement stone mining and mining for the production of construction aggregates. The differing end products actually result in beneficial production logistics, as the rock formations suitable for construction aggregates are generally not suitable for cement manufacturing and vice versa.
Crushed stone aggregate [any of several hard, inert materials, such as sand, gravel, slag, or crushed stone, used for mixing with a cementing or bituminous material to form concrete, mortar, or plaster; or used alone, as in railroad ballast or graded fill] is a finite, nonrenewable natural resource which is essential in the construction and maintenance of roads, industrial development, building structures, airports, railways and dams and should be recognized as an important component of any comprehensive landuse or resource management program.
The New York State Department of Environmental Conservation Division of Mineral Resources website states that each person in New York consumes about 50 pounds of mineral products per day [NYSDEC Division of Mineral Resources http://www.dec.state.ny.us/website/dmn/rocktalk.htm]. This amounts to approximately 175,000,000 tons of mineral products consumed per year in New York State. Most of this consumption comes in the form of construction materials such as those being produced at the A. Colarusso & Son, Inc. (Colarusso) quarry on Becraft Mountain.
Construction aggregates are mechanically processed by a combination of crushers (primary, secondary and, often, tertiary), screens and conveyor systems. These mechanisms serve to reduce, separate and stockpile rock materials that have previously been removed from the quarry by blasting.
A high percentage of blacktop and Portland cement concrete is composed of aggregate: approximately 94 percent of asphalt pavement is aggregate and 80 percent of concrete is aggregate. Due to the high percentage of aggregates in asphalt and concrete every mile of interstate highway contains 38,000 tons of aggregates and about 400 tons of aggregates are used in construction of the average home [National Stone, Sand and Gravel Association website: http://www.nssga.org/].
Note that approximately 25 percent of cement used on the east coast is imported.
The properties that make a particular rock unit attractive for use as a construction aggregate can make it undesirable for use in cement production. Cement stone manufacturing generally targets pure or relatively pure limestones limestones with high calcium oxide (CaO) contents. Extensive mapping, core drilling, sampling and chemical analysis is performed to confirm a rock unit's suitability for use in cement manufacturing.
Although CaO is the most important component of limestone Figure 18. Construction Aggregate Uses. used in Portland cement, other oxides such as iron, silicon and aluminum among other components must be present in the correct proportions. The raw materials (limestone, shale, iron ore, flyash, bauxite, etc.) are crushed and ground to a fine powder and fed to a kiln that heats the powder to about 2700 degrees F, breaking down the chemical bonds. As the material cools, the resulting chemical reaction forms an intermediate product called "clinker". The clinker is finely ground along with gypsum to make the finished cement.
By contrast, construction aggregate producers in limestone terrains target rock units with high acid insoluble residues (AIR). The geologic formations on Becraft Mountain consist of interbedded high and low residue limestones. Colarusso preferentially removes some of the high residue limestones, leaving the lower residue limestones for Holcim. In general, Colarusso mines the geologic units (New Scotland and Kalkberg Formations) containing high acid insoluble residue (AIR, usually in the form of SiO2 , Fe2O3 and Al2O 3 ) for high friction aggregates. Example oxide analyses for sampled rock units are shown in Figure 21.

STOP 9. Thrust Faulting on East Side of Becraft Mountain.
The geologic structure of Becraft Mountain is a doubly plunging, asymmetrical, faulted, north-­northeast trending syncline. As a whole, the structure in the eastern portion of the syncline is more complex, owing to the orientation of the stresses impart by continental collisions (i.e. the Acadian Orogeny). The east limb dips at high angles to the west and is highly contorted and thrust faulted. The center of the syncline is contorted and thrust faulted. The west limb of the syncline dips to the east at a few degrees. A strong basal, or sole, fault separates the carbonates from the Ordovician shales they overrode. Numerous thrust faults in the eastern portion of the syncline result in an imbricate arrangement of sheets and repeated sections of rock units.

STOP 10. Overview of Mine Impoundment and Description of Past Mine Plans
Universal Atlas Cement (UAC) and their predecessors mined the Holcim property, primarily on the west side of Newman Road, for cement stone until 1976. This portion of Becraft Mountain contains the gently easterly dipping western flank of the asymmetrical syncline and includes Helderberg Group units from the Alsen-Becraft down to the Rondout Formation. This area represented some of the thickest exposures of cement stone (Alsen, Becraft and Becraft-Contact) on Becraft Mountain and was the logical area for cement stone quarrying operations to be concentrated. The initial quarrying occurred down to an elevation of approximately 285 to 295 feet above sea level (asl).
UAC developed a dropcut down to an elevation of about 245 feet (75 m) starting in the late 1950's in order to mine out a wedge of cement stone (Becraft and Becraft Contact) left in the floor. The cut began in the northern end of the property and proceeded southward. Excavation for cement stone (Becraft and Becraft contact) was limited from advancing to the full width of the first cut owing to the easterly dip of the western flank of the syncline. This resulted in a pinching out of the cement stone (Becraft and Becraft Contact) to the west. Mining by Universal Atlas ceased in 1976 and the excavated dropcut slowly filled with water.
The upper–lift quarry faces westerly of the water-filled drop cut (mine impoundment) include Becraft Contact over the New Scotland Formation. The uppermost quarry lift has been advanced to the west in recent years to prepare the area for deeper excavation.

STOP 11. Overview of Mine Impoundment and North Quarry.
Presently, Colarusso is advancing a cut south from the North Quarry towards the area to the west of the mine impoundment. Colarusso is quarrying the New Scotland Formation and upper part of the Kalkberg Formation for use as construction aggregate. Ultimately, the underlying Kalkberg Formation will be removed as another lift, exposing the Coeymans and Manlius Formations for future cement-stone quarrying.
The North Quarry is being advanced toward the south with a floor elevation of approximately 235 to 245 feet asl. This is some 15 to 25 feet below the elevation of the water surface in the mine impoundment (260 feet asl). The aggregate-grade stone (the New Scotland and the Kalkberg formations) extends down to an elevation of approximately 150 or 160 feet asl in the area immediately west of the impoundment. The underlying cement stone (the Coeymans and Manlius Formations) extend down further to an elevation of approximately 90 or 100 feet asl. The ability to mine to these depths is predicated upon the hydraulic connection (or lack thereof) between the impoundment and the excavated cuts, unless the impoundment is first drained. The North Quarry is not pumped, and the elevation difference between the North Quarry floor and the water level in the adjacent mine impoundment indicates that the intervening rock is comparatively tight (see Figure 24).

STOP 12. Angular Unconformity and Old West Quarry.
The angular unconformity (Taconic Orogeny) between the Ordovician shales and the overlying Silurian Rondout Formation is evident on the west side of Becraft Mountain in an outcrop south of the old West Quarry. The West Quarry was mined for cement stone (Manlius Formation) during the early and middle parts of the past century.
During the Late Silurian and Early Devonian, warm, shallow seas bordered by lands of relatively low relief largely covered New York State. In the Greenport area, the first sediments were deposited in very shallow, quiet (lagoonal), highly saline waters. These sediments formed the relatively fossil poor, thinly bedded, impure dolomites and calcareous shales typical of the Rondout Formation. In the Greenport area, sandy portions of the Rondout likely represent near shore sand bar deposits in the generally lagoonal environment.
The Early Devonian seas advanced and covered previous landmasses due to a rise in water level or a downwarping of the land. Water circulation within the deeper oceans gradually increased and living conditions generally improved. Examples of the numerous invertebrates (including brachiopods, trilobites, crinoids, gastropods and bryozoans) that lived in the Early Devonian seas are preserved in the numerous fossils and fossil fragments in the quarry stone.
The Manlius Formation was deposited in slightly deeper water than the Rondout. The Manlius sediments were deposited in very shallow, generally quiet, somewhat saline (lagoonal) water and lithified into typically fine-grained, uniformly bedded limestones. Small reefs called biostromes occur scattered throughout the Manlius. The reefy parts of the Manlius were deposited in shallow, clear, agitated waters and typically consist of medium-grained, irregularly bedded limestones. Ripple marks in the Manlius Formation are evident on the sloping floor of the West quarry (see Figure 26).
Cement stone was crushed on site and transported by train and trestle over U.S. Route 9 to the Universal Atlas Cement Plant (see Figure 6). The railroad grade and crusher foundation is still evident in the area west of the notch (see Figure 27).

STOP 13. South End of Mine Impoundment.
Large reserves of aggregate and cement stone remain on Becraft Mountain. Excavation will largely be done below the surface elevation of the water in the impoundment. Future quarrying will eventually necessitate dewatering of the quarry as excavation proceeds to depth. Proper planning necessitates that operators gain a handle on what quantities of water will necessarily be pumped from the quarry to maintain dry operating conditions.
The Greenport Quarry is located within a comparatively small drainage basin. Precipitation, where not falling within the internally draining quarries, tends to run off the site in a focused, but radially outward manner. Water budgets have been performed to assess what fractions of incident precipitation will be lost to evapotranspiration, surface runoff and infiltration. The constantly changing quarry configuration(s) result in altered hydrologic boundaries. The infiltration (always) and runoff (sometimes) components of the incident precipitation must be managed by the operator, in the most environmentally sound and economically viable manner possible, in concert with the geology (and chemistry) of the desired excavation sequence.
Walls and floors of quarries excavated below the water table will only yield groundwater as fast as the host rock permits. Accurate mapping of joints (see Figure 28) and other discontinuities, in relation to the position of recharge areas (and the mine impoundment), is of critical importance, as are the hydraulic conductivities of the excavated units. Hydraulic conductivities can be estimated via pump tests, slug tests, packer tests and flow net construction, combined with proper geologic interpretation.

STOP 14. Blasting Overview.
We will stop at a drilled shot if time allows to describe drilling and blasting procedures, current best management practices, view videos of recent blast and discuss and review vibration standards and results.

7: THE CLASSIC DEVONIAN OF THE CATSKILL FRONT: A FORELAND BASIN RECORD OF ACADIAN OROGENESIS
Charles A. Ver Straeten
New York State Museum
The State Education Department
Albany, NY 12230
cverstra@mail.nysed.gov
INTRODUCTION
Foreland basins sedimentary rocks preserve a record of the evolution of a mountain belt. Indeed, adjacent to ancient, deeply eroded orogens like the Devonian Acadian mountain belt, the foreland basin sedimentary succession is a key source of data on the timing and character of orogenic events and processes long since eroded away.
Making viable interpretations of orogenesis from foreland basin sedimentary rocks is, of course, not simple and straightforward. For example, look at the evolving understanding of Devonian volcanic ash beds ("tephras", "tuffs", "K-bentonites") and their implications for explosive Acadian volcanism, one of the author's primary research interests (Ver Straeten, 2004a, 2008; Ver Straeten et al., 2005).
Prior to the mid-1970s, only a few thin volcanic tephras were known from Devonian strata across eastern North America. Now approximately 100 beds are known from the Devonian of the Appalachian basin. Older perspectives interpreted each bed to represent a single explosive volcanic eruption. Microstratigraphic and geochemical study of the beds, however, indicate that many are multi-event layers, with a history of amalgamation of multiple eruptions, resedimentation on the sea floor, and/or mixing with detrital sediments. Furthermore, it is unknown how many tephra layers, erupted over ca. 60 million years, were not preserved in the sedimentary rock record. The question then arises, does the existing record of foreland basin tephras yield a viable proxy of Acadian volcanism through time, despite biased and incomplete preservation of individual eruptions?
This field trip and paper examine the Devonian (± Upper Silurian) sedimentary rock succession in the Catskill Front of eastern New York, with additional perspectives from across New York and the Appalachian basin. Through a review of the existing literature, and presentation of new data, the author hope to produce a detailed, yet broad perspective of the implications of data from the foreland basin on the Acadian orogeny in the northeastern U.S. It is, of course, a progress report on the subject, a single author's perspective on what is known at this time, and resulting interpretations. Much more and varied work is needed.
This paper and field trip will present an overview of the Acadian orogeny and its foreland basin. It will then focus on a set of sedimentary rock characters that potentially provide regional perspectives on Acadian orogenesis. These include: 1) sedimentation and sea level history; 2) clastic rock composition; 3) volcanic tephra beds; and 4) soft sediment deformation. These four types of information may, and generally indeed do, permit interpretation of the developmental history of the Acadian orogen and the evolution of the Acadian foreland basin.

Outcrops of Martinsburg Formation. Interbedded turbidites and shales.

Catskills visible ahead.

Cross over Wallkill River.

Cross over Rondout Creek. Begin climb up onto Devonian bedrock.

Lower Devonian Glenerie Formation.

Lower Devonian New Scotland Formation?

Lower Devonian, upper part of New Scotland to Becraft formations.

New Scotland Formation.

New Scotland to Becraft formations.

Lower Devonian Schoharie Formation

Middle Devonian Onondaga Limestone (Edgecliff Member).

Onondaga Limestone (Nedrow to Moorehouse members).

Cross over Esopus Creek.

Middle Devonian Union Springs Formation (Stony Hollow Member).

Esopus Creek on right.

Cross under Rte. 209, with a classic set of Lower to Middle Devonian road cuts along it.

Cross over Sawkill Creek.

Middle Devonian Mount Marion Formation (East Berne Member).

Mount Marion ahead on left. Type section of Mount Marion Formation.

Cross over Plattekill Creek.

Stony Hollow Member again.

Mount Marion to left.

Note large quarry on north flank of Mount Marion.
East Berne and Otsego members, Mount Marion Formation.

Bypass Saugerties exit.
Most complete section of Onondaga Limestone in eastern New York, visible along Thruway and northbound entrance; Schoharie Formation visible at far end, right side.

Excellent section of Lower Devonian Becraft, Alsen, Port Ewen, and Glenerie fms.

Schoharie Formation (Aquetuck & Saugerties members).

Schoharie Formation.

Extensive limestone quarries
Extensive limestone quarries in Lower Devonian Helderberg Group beyond ridge to right.

Becraft Formation (?).

Schoharie Formation ± uppermost underlying Esopus Formation.

South end of long exposure along abandoned Thruway exit
South end of long exposure along abandoned Thruway exit, ending at Stop 2 of this trip. Strata visible from Thruway include Schoharie and Esopus formations. Complete section of Esopus exposed.

Onondaga to Schoharie formations.

Schoharie exposed on southbound side of Thruway.

Cross over Kaaterskill Creek.

Schoharie Formation on west side, Onondaga Formation on east side.

Esopus Formation (mostly Quarry Hill Member, in middle of formation).

Cross over Catskill Creek.

Becraft to New Scotland formations

New Scotland Formation along exit ramp.

New Scotland Formation on left.

New Scotland Formation on left, Kalkberg Formation on right.

Pull over and park on shoulder.
Cross and continue ahead on Rte. 23b, then walk up exit ramp off of Rte. 23 to prominent angular Taconic unconformity.

STOP 1. Taconic Unconformity and Helderberg Group Limestones, Catskill.
This classic locality has been the subject of many field trips. For this trip, we will visit two road cuts along Rte. 23: a) exit ramp to Leeds/Rte. 23b, off of Rte. 23 westbound; and b) the succession on the north side of Rte. 23 west of Rte. 23b. We will largely focus on various features with implications for Acadian orogenesis, as interpreted from the sedimentary rock record. These include the Taconic unconformity and Manlius-Coeymans contact, carbonate deposition in a back-bulge basin of the foreland basin system, volcanic tephra beds (K-bentonites), and possible Devonian deformation of the "Little Mountains Fold-Thrust Belt" here.
Near the base of the succession, the prominent angular unconformity (Taconic unconformity) places supratidal dolostones and sandstones (Upper Silurian (?) Rondout Formation) over deep water turbidite sandstones and shales (Middle Ordovician Austin Glen Formation). The hiatus represents approximately 30 million years of time, and marks a series of events associated with the Taconian orogeny. This history begins with deep water deposition of synorogenic clastics, overthrusting of the rocks from western Massachusetts into eastern New York, and later uplift of the area due to erosional unroofing and rebound of the Taconian orogen through the latest Ordovician to Late Silurian. The latter resulted in the elevation of eastern New York above sea level throughout most of the Silurian, and restriction of the sea to western ± central New York during most of the Silurian. Transgression of marine waters over eastern New York in the latest Silurian to earliest Devonian is at least in part due to tectonic-induced subsidence and migration of the foreland basin to the east. This was associated with collision and crustal loading during Late Silurian, with the onset of the Acadian orogeny on the far margin of eastern North America.
The limestones, dolostones and minor shales of the Rondout Formation and Helderberg Group along Rte. 23 here comprise a carbonate ramp succession. They were deposited in the back-bulge basin of the greater Acadian foreland basin, at a time when the orogen and the main body of the foreland basin were still far to the east. The strata examined on this trip (Rondout, Manlius, Coeymans, Kalkberg, New Scotland, and Becraft formations) record an overall deepening- to shallowing up succession through supratidal, tidal, shoal, and shallow to deep ramp facies (Rondout to lower New Scotland fms.), followed by a gradational shallowing up to shoal to tidal facies (middle New Scotland to lower Becraft formations). In sequence stratigraphic terms, the succession comprises comprise a single "third order" depositional sequence, and the lowstand base of a second sequence. In total, the Rondout-Helderberg succession represents two major "third order" sea level cycles/depositional sequences.
The Manlius-Coeymans contact in the Catskill area was interpreted by Chadwick (1944) to represent an erosional hiatus. However, the wider distribution and implications of this break has only been recently documented by Ebert and Matteson (2003). Their detailed work through the two formations has documented at least two significant unconformities, including the formational contact. Noting a subtle but documented angularity to the unconformity, Ebert and Matteson (2003) interpret its formation to be associated with the orogen-ward migration of a bulge-like feature, associated with early stages of the Acadian orogen on the distant margin of North America near the SilurianDevonian boundary.
Ancient volcanic airfall tephra beds, altered to clay-rich K-bentonites, occur in the Kalkberg and New Scotland formations along Rte. 23. This cluster of approximately 15 beds, termed the Bald Hill K-bentonites, are widely reported across the Appalachian basin, from eastern New York to Virginia and West Virginia. They preserve a record of explosive, plinian-type volcanism in the Acadian orogen. Additional K-bentonites have been noted in the Manlius Formation at other localities (Ebert and Matteson, 2003; P. Rubin, pers. commun. 2007).
The age of deformation of the strata along Rte. 23 is the subject of debate. Some workers (e.g., Marshak, 1986; Mar shak and Tabor, 1989; Zadins, 1989) interpreted the folding and faulting to be Devonian, at least in part. In contrast, Geiser and Engelder (1983) interpret the structures to have formed later, during the Late Carboniferous-Permian Alleghanian orogeny. It is possible that both orogenic events led to the deformation. At present, the timing of deformation is unclear.

Beginning of another classic cut through the "Little Mountains" fold-thrust belt.

Cross over Catskill Creek.
Downstream the creek passes for approximately 1 mile through the gorge of Austin Glen, descending stratigraphically through Lower Devonian to uppermost Silurian strata of the Esopus through Rondout formations, and into the Ordovician Austin Glen Formation. Classic, beautiful site.

Esopus through basal Onondaga Formations (Stop 1B of Ver Straeten and Brett, 1995).

Onondaga Formation.

Cross over Kaaterskill Creek.
Ordovician Austin Glen Formation exposed in creek bed to left.

Kaaterskill Creek will follow road for some distance.

Onondaga Limestone.
Section between 46.5-.6 exposes Edgecliff, Nedrow and lower Moorehouse members.

STOP 2. Lower Devonian Ramp Carbonates etc.
Lower Devonian Ramp Carbonates and the Initial Acadian Clastic Wedge, the Sprout Brook K-Bentonites, and the Wallbridge Unconformity.
This is another classic Devonian locality, chiefly noted for its prominent structural folds. However, several additional characters of the outcrop provide a record Acadian Lower Devonian activity in the Acadian mountain belt. These include the Wallbridge unconformity; a carbonate-quartz arenite suite of rocks succeeded by the first major influx of Acadian synorogenic sediments; migration of the foreland basin foredeep into the Catskill Front; and a second major cluster of altered volcanic tephra beds. The Glenerie-Esopus contact at this outcrop lies approximately 90 m stratigraphically above the Taconic unconformity, seen at Stop 1.
The units visible at Stop 2, from low to high include the top of the Port Ewen Formation, the Wallbridge unconformity, local chert facies of the Glenerie, and a rare, complete section of the overlying Esopus Formation. At the far end of the outcrop, along the NYS Thruway, lower strata of the Schoharie Formation are visible.
The top of the Port Ewen Formation, a shaly limestone analogous to the New Scotland formation, directly underlies the Wallbridge unconformity here. The Wallbridge, which marks one of the major Phanerozoic sea level lowstands in North America (Sloss, 1963), is of relatively short duration in the Hudson Valley. Deposition across the interval is continuous in the Port Jervis area, where New York, New Jersey, and Pennsylvania meet.
Immediately overlying the Wallbridge unconformity is a conglomeratic lag bed at the base of the Glenerie Formation. The conglomerate in the area of Catskill is largely composed of phosphatic pebbles with scattered milky quartz. To the south, beginning near Kingston, a conglomerate unit of milky quartz wedges in below the Glenerie. This unit, termed the Connelly Conglomerate, is the oldest conglomerate found in the New York Devonian (Table 2). Its quartz composition (>99% milky quartz) contrasts with younger pebbly to conglomeratic strata in the Catskill front, which feature a more diverse composition (Table 2). The conglomeratic base of the Glenerie locally near Catskill is dominated by chert; to the south, it transitions into silica-rich limestones, and to the north to the quartz sand-rich Oriskany Sandstone.
Glenerie-Esopus contact is relatively gradational at Stop 2 and in the eastern New York region. Elsewhere across the central to southern part of the basin, the contact is generally more sharp (Ver Straeten, 2007a). It marks a time of foundering of widespread shallow marine ramp conditions, and progressive subsidence and migration of the foreland basin foredeep into eastern New York, during the onset of the first Acadian Tectophase recognized by Ettensohn (1985). In reality, at least one previous tectonically active to quiescent "tectophase" likely occurred during the Late Silurian to Early Devonian parts of the Acadian orogeny.
The mudstones, shales, siltstones and sandstones of the Esopus Formation mark the first significant influx of Acadian synorogenic clastics into the Catskill Front and the Appalachian basin. Migration of the orogenic front across New England has by the Emsian Stage moved far enough craton-ward for the foredeep segment of the foreland basin system to migrate west of the present day Hudson River. Petrologic data from Rehmer (1976) indicates that fine sandstones to siltstones of the Esopus are rich in quartz (∼33-55%), with a high concentration of matrix (∼19-49%), and minor amounts of fragmentary mica and chlorite, detrital and diagenetic chert, and pyrite.
Detailed work by the author on Emsian-age (upper Lower Devonian) strata of the Esopus and Schoharie formations and equivalent strata across the Appalachian basin (Ver Straeten, 2007a), along with geochronologic age dating (Tucker et al., 1998; Kaufmann, 2006), outline a longer, more complex history to the Emsian stage in the eastern U.S. than has been appreciated. U-Pb dating indicates a duration on the order of 15-18 million years for the Emsian (Tucker et al., 1998; Kaufmann, 2006), and that its global sea level history comprises five major third order cycles (Ver Straeten, in press), not one as previously interpreted by Johnson et al. (1985).
To the author, one of the key stories linking the foreland and orogenic belt is tied a series of thin, tan-colored clay beds in the lower part of the Esopus Formation here (Spawn Hollow Member). These are the Sprout Brook K-bentonites, 15 altered volcanic tephras dated at 408.1 ± 1.5 Ma (Tucker et al., 1998). In contrast with other Devonian clusters of K-bentonites in the Appalachian basin, these are geographically restricted to eastern New York (Ver Straeten, 2004a, b). The age of the Sprout Brook K-bentonites cluster overlaps with dates of numerous volcanic and plutonic rocks in the northern Appalachians, predominantly in Maine (e.g., Bradley et al., 2000; and additional references in main body of this paper). This includes the Katahdin Granite and co-magmatic Traveler Rhyolite of central Maine; the Traveler alone, from only one of many volcanic centers of lower Emsian age, is conservatively estimated to have a volume on the order of the largest Cenozoic-age tuffs in the western U.S. (Rankin and Hon, 1987; Ver Straeten, 2004b). It is plausible that explosive, plinian-type volcanoes in northern New England were the source of the tephra deposited in eastern New York.
As at Stop 1, the age of deformation of the strata here is unknown. An interesting point here is the relationship of deformation to the Sprout Brook K-bentonites. The soft, unlithified clay beds form a sharp rheological contrast with their interbedded thin chert and shale beds. Slippage largely appears to follow the clay beds, which in places appear to have been squeezed through the folds ("like toothpaste"). This is well seen in the uppermost K-bentonite, which varies in thickness from zero to over 1.5 meters along the outcrop over the central anticline. The K-bentonites probably helped concentrate deformation along this zone in the Catskill Front and into the subsurface, the position of a major decollement in the Catskill Front/Little Mountains fold-thrust belt according to Marshak (1986).

Prominent exposures of Lower Devonian Schoharie Formation.

Pass Old Kings Highway on left.
Topmost Schoharie and Edgecliff Member of Middle Devonian Onondaga Limestone exposed along beginning of Road (Stop 3B of Ver Straeten and Brett, 1995).

Folded Nedrow and Moorehouse members
Folded Nedrow and Moorehouse members (Onondaga Limestone) exposed on left. To proceed from here to Stop 3, carefully walk 0.3 miles ahead to east (proximal) side of bridge over Kaaterskill Creek. Walk down steep slope on south (left) side of bridge to exposure along creek.

STOP 3. Middle Devonian Ramp Carbonates etc.
Middle Devonian Ramp Carbonates and the Second Acadian Clastic Wedge, and Tephras.
Note: No hammers or collecting from the Onondaga-Bakoven contact – it is a rare exposure. The creek exposure is on private property - ask permission for access.
Strata exposed at Stop 3 include the uppermost limestones of the Middle Devonian Onondaga Formation and overlying black shales of the Bakoven Member of the Union Springs Formation (lower part of the Marcellus subgroup of Ver Straeten and Brett, 2006). At least one K-bentonite of the Tioga A-G K-bentonite cluster is exposed here. The first part of the outcrop is along Kings Highway and Rte. 23a, where the lower to middle Onondaga Formation is exposed (Edgecliff, Nedrow and Moorehouse members). Walk westward down the hill to the south side of the bridge over Kaaterskill Creek, where the top Onondaga (Seneca Member?) and lower Bakoven Shale are exposed along the creek. This outcrop lies approximately 270 m stratigraphically above the Taconic unconformity, seen at Stop 1.
Above the Esopus Formation at the previous stop, the Schoharie Formation is transitional from extra-basinal clastics to intra-basinal carbonates. This shift culminates in deposition of the Middle Devonian Onondaga Limestone. Onondaga-equivalent carbonate-rich facies occur widely across eastern North America; they mark a shutdown of clastic sedimentation in the northern Appalachian basin, although to the south in deeper parts of the basin (PA through VA-WV), the interval marks more of a decline in % clastic content, and deposition of mixed carbonate-clastic facies.
Base of Onondaga is a lowstand of sea level. In the Schunnemunk outlier north of NYC, and in the area of Palmerton, eastern PA, lower Onondaga ± upper Schoharie strata are represented by shallow marine quartz sandstones conglomerates. Exclusively quartz pebbles also occur scattered through strata at two positions within the Schoharie Formation. Furthermore, rare quartz pebbles have also been found in the same position in the Moorehouse Member and equivalent strata in central New York and central Pennsylvania. Curiously, widespread occurrence of quartz-rich strata are a contrast with the synorogenic sediments of the Esopus Shale below. Conditions that permitted progradation of Esopus extrabasinal clastics no longer existed.
Here at Stop 3 we stand at a major depositional shift, where relatively shallow marine carbonates are succeeded by basinal organic-rich black shales (by some estimates representative of ca. 100-200 m depth). A prominent bone-rich phosphatic lag interval at the formational contact marks a period of sediment starvation across the transition. A similar lag bed occurs along the Onondaga-Bakoven contact into western New York, overlying progressively younger uppermost Onondaga strata in that direction. The top of the Onondaga progressively youngs to the west, indicated but by the progressive upward appearance of the Tioga B, B', C, D, E, and F K-bentonites with the thickening of upper Onondaga (Seneca Member) strata to the west. This younging is associated with earlier foundering and subsidence of the foredeep of the foreland basin in eastern New York; subsequently, the shallow Onondaga ramp progressively subsided to the west, due to loading and uplift during the onset of Acadian Tectophase II of Ettensohn (1985).
The Onondaga to lower Union Springs Formation and equivalent strata across eastern North America are well known for the occurrence of the Tioga K-bentonites. Actually, the so-called "Tioga" interval comprises two major clusters of volcanic tephras (Ver Straeten, 2004a, 2007a). In the northern and central part of the Appalachian basin, an upper cluster of eight beds (Tioga A-G K-bentonites) occurs widely in upper Onondaga and Union Springs-equivalent strata. A lower cluster of up to 32 beds, previously correlated with the Tioga A-G K-bentonites, is found only in middle Onondaga-equivalent strata in the southern part of the Appalachian basin (Virginia and West Virginia; Ver Straeten, 2004a, 2007a). The lower cluster has been dated at 391.4±1.8 Ma (Tucker et al., 1998), the upper one at 390± 0.5 Ma (Roden et al., 1990). They appear to be sourced from volcanic centers in northern Virginia and southeast of the Stroudsburg, PA area, respectively (Dennison and Textoris, 1970, 1978; Ver Straeten, 2004a). At Stop 3, some of the long bedding planes exposed along Rte. 23a may represent thin K-bentonites. Along the creek exposure, a thin centimeter-thick clay bed 35 cm below the contact is a K-bentonite. Another thicker bed, possibly the widely known Tioga B K-bentonite bed from the base of the Seneca Member in New York, is covered just above the base of a small gully closer to the bridge.

Kaaterskill creek visible along road again, on left.

Exposures of upper part of the Mount Marion Formation on left.

STOP 4. Nearshore Marine Clastics, Upper Mount Marion Fm.
This stop examines shallow marine clastics (upper part, Middle Devonian Mount Marion Fm.), not far below the transition into terrestrial strata (Ashokan Fm. and higher strata). Exposed along Rte. 23 are approximately 12.3 m of sandstone-dominated strata. Well defined hummocky cross beds, indicative of storm processes low in the outcrop are replaced above by mega-ripples (dunes), suggesting an overall shallowing up succession. Intraformational conglomerates and soft sediment deformation zones are also visible in the upper part of the outcrop. The strata at Stop 4 are approximately 750 m stratigraphically above the Taconic unconformity at Stop 1.
Two sandstone beds with reworked, intraformational pebbles and brachiopods are visible in the upper part of the outcrop. Along Catskill Creek, approximately 0.8 km to the north-northwest, a conglomerate with abundant macro-crystalline milky quartz and chert, with lesser numbers of sandstone and other clasts, was reported by Wolff (1967) and exposed in the late 1980s. It is presently covered in the creek bed. The author has noted multiple thin, sometimes lensing conglomerate beds in the upper Mount Marion Formation along and in the forest off of Rtes. 28 and 28a northwest of Kingston. They also mark the progradation of gravels into the Catskill Front at approximately 388 Ma, possibly concentrated into beds during the lowstand or basal transgressions of small scale (fifth to sixth order) cycles (e.g., Bergman and Walker, 1987; Smith and Jacobi, 1998).
Compositionally (Table 2), these conglomerates contrast sharply with the only white quartz pebble compositions of conglomerates and scattered pebbles in older strata (Connelly Formation; Schoharie Formation; Kanouse, Palmerton and Onondaga/upper Needmore formations) in New York and Pennsylvania. The relatively high concentration of various-colored cherts in the conglomerates also contrast with relatively chert poor compositions of overlying conglomerates in the Devonian succession. This indicates a relatively significant source of chert in rocks exposed in the Acadian orogen at this time. The upper Mount Marion conglomerates
Smith's (1970) petrographic studies of upper Mount Marion sandstones in the Catskill front found that the sands were composed of a mix of mono- and polycrystalline quartz, chert, metamorphic and sedimentary rock fragments with less abundant chlorite, other micas, and plagioclase feldspars. His reported average compositions for the upper Mount Marion strata ("Solsville" and overlying "Pecksport" equivalents, 5 and 8 samples, respectively) are: Quartz + chert = 50.0 & 37.4%; matrix = 9.1 & 13.2%; rock fragments = 37.6 & 41.1%; and carbonate = 1.6 & 8.3%. The presence of slate and phyllite fragments, along with recycled sandstone and limestone grains indicated erosion of low grade metamorphic and sedimentary rocks in the Acadian orogen by approximately 388 Ma.
On the south side of the outcrop, along Vedder Road, two zones of soft sediment deformation can be seen in the upper part of the outcrops (Figure 15b). These potentially represent "seismite" beds, formed when severe seismic shocks from the Acadian orogen triggered liquifaction of the loosely packed sands, and their subsequent, more condensed repacking, and expulsion of excess water.
The first outcrop west of Five Mile Woods Road, on the south side of Rte. 23, exposes roughly five meters of interbedded sandstone and dark gray mudstones. Two sandstone bodies (ca. 1.5 and 3 m-thick) are not notably cross-bedded or erosively based; small delicate traces in the intervening mudstones may represent small plant root traces. The outcrop may be the lowest terrestrial deposits exposed along Rte. 23. If so, it could represent a thin tongue of terrestrial facies within the upper Mount Marion Formation, as seen near Kingston (Stop 8 of Ver Straeten and Brett, 1995), or deposits low in the overlying Ashokan Formation.
Strata from the lowest redbeds to the top of Slide Mountain, the highest peak of the Catskills, comprise approximately 1.9 km thickness of Middle to Upper Devonian strata (lower Givetian to upper Frasnian stages, Rickard, 1975). They were almost exclusively deposited in fluvial-dominated, terrestrial environments. These strata will be seen at subsequent Stops 5-7, and in road cuts along the route.

Interbedded sandstones and shales on south side of Rte. 23.

Lowest exposure of terrestrial "redbeds"
Lowest exposure of terrestrial "redbeds" of Plattekill Formation along Rte. 23. Lower red and green mudrocks (including paleosols) deposited on floodplain, overlain further along road by channel sandstones. Outcrops for next ∼10 miles (to ∼66.1 miles) are in the Plattekill Formation.

Good exposure of Plattekill Formation along Silver Spur Road to left.

STOP 5. Middle Devonian Fluvial Channel and Floodplain Deposits
This outcrop of the Middle Devonian Plattekill Formation exposes typical terrestrial facies of the Catskill delta complex, as developed in the Catskill front. The strata at Stop 5 are roughly a little less than one kilometer stratigraphically above the Taconic unconformity (Stop 1).
Along the outcrop (ca. 11.6 m-thick), two channel sandstone bodies and two sandy to muddy floodplain deposits, including ancient soils (paleosols) are visible. Fining up pairs of channel sandstones to floodplain deposits in the Catskills are interpreted to represent thousands to tens of thousands of years (Bridge, 2000).
The lower "mudrock" unit (ca. 2.0 m-thick) is characterized by dark gray to gray shales that grade upward into inter bedded thin sandstones and green mudstones. The upper 40 cm have a blocky texture and feature small-scale slickensided surfaces (pedogenic slickensides), associated with soil development.
Lower strata of the overlying sandstone body (ca. 4.2 m-thick) grade laterally between gray sandstones, dark gray shaly sandstones, and intraformational conglomerates, of which at least one is dominated by calcareous nodules, eroded and reworked from erosion of paleosols upstream, Cross-bedded sandstones above feature more than one channel (multi-storied) up through the succession.
The top of the channel is marked by a 0.7 m-thick interval of more tabular sandstone beds, which grade upward into ca. 1.2 m of red mudrock-dominated strata, deposited across a floodplain after migration of the channel. Centimeter scale vertical traces, often green in color represent root traces of Eospermatopteris-type cladoxylopsid trees, similar to the famous tree stumps found near Gilboa, higher in the Catskills. In places, the roots have extensively bioturbated the sediments. In addition, the upper 40-60 centimeters feature multiple "dish/gilgai/pseudoanticline" soil deformation structures, and pedogenic slickensides occur through the strata. These features form by wetting and drying of expandable smectite (montmorillonite) clay rich, fine-grained sediments, and indicate the development of vertic paleosols.
The upper unit (ca. 3.5 m exposed) is another multi-storied channel sandstone body. Mudrock lenses occur locally along the outcrop, and prominent, down-cutting erosional surfaces are overlain by additional channel deposits. The sandstone bodies are interpreted to be deposited in single channel, sinuous ("meandering") rivers, which migrated across vegetated alluvial plains (Bridge, 2000).
Sandstone petrologic studies by Gale (1985) through the Plattekill to Slide Mountain formations in the Catskills found that composition of the sandstones is relatively consistent. Mono- and polycrystalline quartz, foliated metamorphic rock fragments and sedimentary rock fragments comprise 80% or more of the sandstones (Gale, 1985). Low in the succession (e.g., Plattekill Formation), sandstones contain a greater percentage of foliated metamorphic rock fragments and a correlative lower concentration of quartz. The sandstones are relatively clay poor, and are best defined as lithic to sub-lithic arenites (Gale, 1985). Overall, the sand-size fraction increases in grain-size upward through the succession, as environments change from lowland to transitional lowland-upland alluvial plain environments.
Plattekill Formation sandstones analyzed by Gale (1985; 10 samples) feature concentrations of foliated metamorphic rock fragments between 19-47%, in sharp contrast with the Slide Mountain Formation (3-17%; 5 samples); total macrocrystalline quartz (mono- + polycrystalline) in the Plattekill comprises 25-50 % of the rock, compared with 47-62% in the Slide Mountain Formation. In addition to quartz, metamorphic rock fragments and sedimentary rock fragments (10-23%), lesser amounts of chert (0.4-3.6%), plagioclase and orthoclase feldspars (0.2-1.9%), along with chlorite and micas, illite and kaolinite are found in Plattekill Formation sandstones (Gale, 1985).
Analysis of the clay minerals in the Catskill succession, and marine strata beyond, indicate a dominance of illite with lesser amounts of chlorite and minor kaolinite (e.g., Friend, 1966; Hosterman and Whitlow, 1983). However, vertic paleosols, as relatively well developed in the upper floodplain deposit, form in smectite-rich sediments. These clays, which swell and shrink with wetting and drying, are derived from igneous sources. The abundance of vertic paleosols in the Catskill succession appear to represent an otherwise hidden component of sediments derived from igneous sources. The sources could be derived from weathering of plutonic or volcanic rocks in the source area, or from volcanic ash erupted from explosive volcanic eruption in the Acadian orogenic belt.
At this time, only intraformational conglomerates/breccias are known by the author in the Plattekill Formation (Figure 9d). The clasts in these beds consist of reworked calcareous nodules ("peds") reworked from paleosols, or chips of mud. They commonly occur in the base of channel sandstone deposits.

Exposures of Plattekill Formation are visible along Catskill Creek, 1.4 miles north.
Rte. 32 turns to right (North). More excellent exposures of Plattekill Formation are visible along Catskill Creek, 1.4 miles north. Outcrops include well exposed bedding plane and cross-sectional exposures of fluvial channel sandstones and floodplain mudstones. Also found (some distance upstream of abandoned dam) is a ∼1.5 m-thick interval of carbonate-rich facies, capped by a thin (ca. 20 cm-thick) limestone bed indicative of lacustrine facies in floodplain environments. NOTE: Exposures along the creek are on private property. And pay attention to extensive No Parking signs along Rte. 32 near Catskill Creek.

Exposures of Plattekill Formation along Rte. 23.

Peaks of Acra Point, Burnt Knob, and beyond, Windham High Peak (3524')
Peaks of Acra Point, Burnt Knob, and beyond, Windham High Peak (3524') visible in distance. Cairo-Durham town line. Approximate position of Plattekill-Manorkill ("Moscow") formational boundary, according to Fisher et al., (1970).

Cairo-Durham town line.
Approximate position of Plattekill-Manorkill ("Moscow") formational boundary, according to Fisher et al., (1970).

Good exposures of Manorkill Formation along south side of road
Good exposures of Manorkill Formation along south side of road, near interesting and unusual buildings. Additional exposures of the Manorkill along highway ahead.

STOP 6. Floodplain and Channel Sandstone Deposits, East Windham.
Over 60 m of mudrocks, sandstones and a thin limestone bed in the Manorkill Formation at Stop 6 represent deposition in floodplain, fluvial channel, and lacustrine environments on the subaerial delta plain of the Catskill delta complex. It is possible that a part of the section may represent some brackish water conditions however. This outcrop is roughly 1.25 km stratigraphically above the Taconic unconformity at Stop 1.
Low in the part of the outcrop facing the parking area, another red paleosol zone with green, cm-scale diameter root traces of cladoxylopsid trees is visible, more easily seen than those at the last stop. Additional paleosols along the outcrop show varying development (Mintz et al., 2006). Along the outcrop, floodplain deposits vary between red, green, yellow-tan and dark gray/black mudstones and lesser fine-grained sandstones. Several sandstone bodies occur along the outcrop also, though few are thicker than 1-2 m.
Around the bend and uphill from the parking area, a prominent sloping-to-the-right interval of yellowish-green strata is succeeded by a zone of thin sandstones and dark gray mudrocks, at a distinctly different angle to the underlying beds. A number of isolated soft sediment deformation pillows occur along the outcrop within the lower approximately 1-3 m of the upper unit.
Higher in the section, downhill from the first driveway uphill of the bend, a prominent, thin ledge of limestone sticks out from the outcrop. Fallen slabs of the bed can be seen in the talus. Light gray to brown-gray, varyingly smooth to knobby in appearance, the fauna noted in the bed consists of ostracodes. Mintz et al. (2006) state that the bed appears to have been pedogenically modified and brecciated. It is over and underlain by red to green paleosols.
Apparent lacustrine (lake) and palustrine (wetland) facies, including similar thin limestones, are not often discussed but not unknown in Upper Devonian Catskill magnafacies (DeMicco et al., 1987; Dunagan and Driese, 1999). Similar limestones are documented from Devonian terrestrial facies in Canada, Great Britain and Australia (e.g., Donovan, 1975). They are generally interpreted to have formed toward the center of ponds and lakes, beyond the transport of fine-grained clastics. Carbonate is derived from calcareous, photosynthetic algae (e.g., charophytes). The author has found multiple apparent freshwater limestones in the Plattekill and Manorkill formations along the Catskill Front. Lacustrine and palustrine/wetland environments comprise an interesting and relatively overlooked facies in the Catskill Front, which deserves more attention.
A short distance above the limestone, along the lower part of a driveway, an interval of olive-colored, mudrock-dominated strata above the limestone, best seen along the lowest part of a driveway, features common fish bone material, ostracodes and desiccation cracks. Also found in the interval are Spirophyton trace fossils, which have been interpreted by some to have lived in freshwater setting (Bridge and Gordon, 1985; DeMicco et al., 1987), but by others (Gordon, 1988; Miller, 1991) to indicate brackish water conditions. Miller (1991) proposed that the animals producing Spirophyton lived in ephemeral ponds on the coastal floodplain, with fluctuating fresh- to brackish water salinities, perhaps tied to floods of brackish water that flowed upstream and spread across floodplains during major storms.
As in other fluvial-dominated strata of the Catskills, Manorkill Formation sandstones analyzed by Gale (1985; 3 samples) feature common mono- and polycrystalline quartz (29.6-60.0%), and foliated metamorphic and sedimentary rock fragments (30.4-41.8% and 9.3 to 22.0%, respectively). lesser amounts of chert (0.2-0.7%), plagioclase and orthoclase feldspars (1.6-4.3%), along with chlorite and micas, illite and kaolinite are found in Manorkill sandstones (Gale, 1985). This represents a subtle shift toward increased quartz content from the underlying Plattekill Formation. With the exception of a single bed at or near the base of the Manorkill Formation, conglomerates known to the author at this point are intra-basinal ones, with reworked mud or pedogenic carbonate nodules.

Peak of Burnt Knob and/or Acra Point ahead.

Channel sandstones of Plattekill Formation.
All exposures along Rte. 32 ahead are in the Plattekill Formation.

Area between here and turn at Rte. 23a are called the Kiskatom Flats, which we'll see from above at Stop 7.

Note rise of the highway, ascending up alluvial fan out front of Kaaterskill Clove.

Enter Kaaterskill Clove.

Lower bridge in Kaaterskill Clove.
Cross over Kaaterskill Creek. Excellent exposures of Plattekill Formation upstream, including channel sandstones, floodplain deposits, and at least one more apparent freshwater limestone.

Area of "High Rocks" of Chadwick (1944, Fig. 47).

Middle bridge in Kaaterskill Clove.
Excellent exposures of red mudstone/paleosol facies of Manorkill Formation at and above bridge.

Upper bridge in Kaaterskill Clove.
Excellent exposures of Oneonta Formation upstream, along trail to base of Kaaterskill Falls.

Parking area for trail to Kaaterskill Falls.

Classic exposures of Oneonta Formation along road, with well developed paleosols.

Top of Kaaterskill Clove

STOP 7. Upper Devonian Clastics, North-South Lake
Note: No hammers or collecting at this stop (a Catskill Park campground, run by NYS-DEC).
At this stop, we will walk north along the Catskill escarpment to Artists Rock and Sunset Rock. The rocks exposed comprise lower strata of the Upper Devonian Oneonta Formation, and will include the Twilight Park Conglomerate Member (at Sunset Rock). The latter outcrop is approximately 1.5 km stratigraphically above the Taconic unconformity at Stop 1. Another ∼1.2 km of strata overlie the Twilight Park Conglomerate, to the top of Slide Mountain, the highest peak in the Catskills.
The Escarpment trail going north from the parking area at North Lake slowly rises upward through a major sandstone ledge that caps the Catskill escarpment here. Termed the "Kaaterskill Sandstones" by Chadwick (1944), they form the lower part of the Upper Devonian Oneonta Formation. Sandstones dominate the strata along the trail to Artists Rock. An abandoned trail a short distance beyond Artists Rock exposes red mudstones that lie between major sandstone packages.
Partway along the trail to Artists Rock, shortly after a several-meter rise up through the lower Oneonta sandstones, an odd set of sedimentary structures occur in the sandstones in the trail. At first glance, they appear to be trough cross beds. On closer observation, however, the edges of the troughs are vertical to near vertical, well beyond the angle of repose. The vertical edges are water-escape structures, along the margins of foundered bowls of sandstone. This represents another soft sediment deformation zone, developed in sand-only facies (as found at Stop 4). The author has not examined their correlatability, although previous workers have noted disturbed soft sediments elsewhere in the area, in the lower part of the Oneonta Formation. If the feature is relatively widespread, it could possibly represent a "seismite", triggered by a significant seismic shock during the Acadian orogeny. Without more evidence (e.g., correlatability across a broad area), this is only conjecture.
Mono- and polycrystalline quartz comprise approximately 37.9-59.1% of the rock in petrographically analyzed sandstones of the Oneonta Formation (Gale, 1985). The concentration of foliated metamorphic and sedimentary rock fragments (15.7-33.4% and 8.7 to 21.1%, respectively) have decreased relative to underlying strata, while the concentration of quartz has increased. The concentration of other components (e.g., chert, feldspars, chlorite and micas, etc.) remain about the same as in the underlying Manorkill and Plattekill formations.
There is a rise of approximately 530 m (1750') from the Kiskatom Flats below. In the distance to the east, the Taconic Mountains are visible along the New York-Massachusetts border; high peaks of the Berkshire Mountains (including Mount Greylock) locally project above the Taconics. Farther to the north/left, the Green Mountains are visible in Vermont. These highlands today expose low grade metamorphic rocks (e.g., slates and phyllites in the Taconics; some schist in the higher Berkshires and Greens). However, those rocks would have been deeply buried under younger rocks during the Devonian Acadian orogeny.
At Sunset Rock, up the trail beyond Artists Rock, a 23 m-thick outcrop of the Twilight Park Conglomerate (member of the Oneonta Formation) is very well exposed. The unit marks the first major progradation of clastics into the Catskill front from the Acadian orogen. Bridge and Nickelsen (1985) hypothesized that the progradation was due to increased slope due to tectonic changes, stating that climate did not appear to vary through the interval. In this case, a base-level drop associated with a significant sea level fall was not discussed. Bridge and students generally dismiss eustatic sea level controls over processes active in the terrestrial settings of the Catskill magnafacies. However, Devonian workers (e.g., House and Kirchgasser, 1993; Brett and Baird, 1996; Bartholomew, 2006; Ver Straeten, 2007a, in press) have now established significant eustatic control over sea level changes in New York's marine succession. And that tectonic patterns of flexure are superposed over the record of third order sea level cycles/stratigraphic sequences (Figure 8).
The author proposes a counter hypothesis, that Twilight Park gravels may have prograded basin-ward during one of the major sea level falls near the Middle-Upper Devonian boundary. As there is no tight control over where the Middle-Upper Devonian boundary actually occurs in the Catskill front, that sea level drop could be one of a few near the boundary.
Petrologically, clastic rocks of the Catskill front indicate that rocks exposed in the Acadian orogen consisted of dominantly low grade (up to greenschist) metamorphic and sedimentary rocks. Rare igneous- or high grade metamorphic-derived sediments indicate only very minor exposure of such rocks. A hidden source of more igneous than previously thought seems to be indicated by common vertic paleosols, which form in smectite clay-rich sediments (smectite clays are derived from the weathering of igneous rocks, including volcanic ash).
A number of previous authors hypothesized that Cambrian and Ordovician rocks in the Taconics region were the source of the Devonian Catskill delta sediments. However, beginning in the Late Silurian, the Acadian orogen and the associated foreland basin developed on the far margin of eastern North America. Through the Lower Devonian, massive volumes of Acadian-derived sediments were deposited in the foredeep basin in New England, while the Hudson Valley was positioned in the back bulge basin to craton-ward edge of the foredeep of the foreland basin system. As the orogen progressively migrated craton-ward toward eastern New York, Devonian sediments in that early Acadian foredeep basin (e.g., Littleton Formation of New England) were caught up in the deformational front of the orogen (e.g., wedge-top of the foreland basin system). Some of the Lower Devonian foredeep sediments were metamorphosed; metamorphosed or not, the foreland basin strata were thrust up, eroded and transported into the Catskill front. The clastic wedge, of which 2.7 kilometers thickness is preserved in the Catskills, by the latest Devonian apparently distributed muds as far west as northern Iowa (B. Witzke, pers. commun., 1999). Possibly by the Late Devonian, folding and thrusting of the foreland basin wedge-top may have migrated west of the Hudson River.

8: FLUVIAL GEOMORPHOLOGY OF THE UPPER ESOPUS CREEK WATERSHED AND IMPLICATIONS FOR STREAM MANAGEMENT
Dan Davis
Mark Vian
Stream Management Program
New York City Department of Environmental Protection
71 Smith Avenue, Kingston, NY 12401
Peter L.K. Knuepfer
Department of Geological Sciences and Environmental Studies
Binghamton University, Binghamton, NY 13902-6000
Nicolas Miller
Binghamton University and Field Geology Services
P.O. Box 985, Farmington, ME 04938
The New York City water supply system depends on the maintenance of natural high water quality in the watersheds that drain into the reservoirs that store water for the system. Accordingly, concentrations of suspended sediment in both streams and reservoirs are major concerns, and the identification and remediation of sites that are concentrated sources of high suspended load/turbidity are essential to water quality management.
The concern about water quality by New York City's Department of Environmental Protection (DEP) is further motivated by a Filtration Avoidance Determination (FAD), which was renewed by the U.S. Environmental Protection Agency in 2007 and currently runs through 2017. This determination allows New York City to avoid the high capital cost that would be associated with building and maintaining a filtration system to treat the New York City water supply originating west of the Hudson River (∼90% of the total supply). The FAD requires DEP to maintain high water quality through, among other practices, the development of stream management protocols and funding additional stream restoration projects (US EPA, 2007).
The DEP established a Stream Management Program to oversee the assessment of stream corridor condition and the development of management strategies for the watersheds that comprise the West-of-Hudson water supply system (Figure 1), including the Ashokan Reservoir/Upper Esopus Creek watershed (Figure 2). The DEP has worked with municipal, county, state and federal partners to develop Stream Management Plans (SMP) for many of the principal streams supplying the Ashokan, Schoharie, Cannonsville, and Pepacton Reservoirs. The work in the Upper Esopus Creek watershed that will be summarized in this field trip has been part of this overall effort (see www.catskillstreams.org).
The purpose of this field trip, then, is to explore the Upper Esopus Creek watershed, highlighting historic changes to the creek channel (Miller, 2009) and strategies that have been implemented or are being considered to alleviate or manage suspended sediment yield. We will examine sites where lateral migration or change in base elevation of the channel is degrading water quality or threatening property damage, where bank erosion has created a source of turbidity, and where stream restoration/remediation strategies have been applied and will be applied in the future in efforts to remediate "hotspots" of erosion and sources of high suspended sediment loading.

8: FLUVIAL GEOMORPHOLOGY OF THE UPPER ESOPUS CREEK WATERSHED AND IMPLICATIONS FOR STREAM MANAGEMENT

Cross Wallkill River, incised into Ordovician shales and siltstones

Cross Rondout Creek, also incised into Ordovician shales.
Lefever Falls on the left.

Cross Esopus Creek

Kings Town Stone Quarry on right into Middle Devonian Mt. Marion Formation.

Kenozia Lake on right.
Drained in 2008 for repairs, the lake has refilled quickly in 2009 due to the heavy spring meltoff and rains.

Weir that divides West and East basins of Ashokan Reservoir.

STOP 1. Ashokan Reservoir and Esopus Creek Watershed.
Ashokan Reservoir was the first of the New York City water-­supply reservoirs to be constructed in the Catskills. The dam across Esopus Creek was completed in 1913 and the reservoir was impounded by 1914 (Schneiderman, 2000; New York City Department of Environmental Protection, 2009). Water is carried to New York City through the Catskill Aqueduct, completed in 1915. Because of concerns about the influx of suspended sediment from Esopus Creek, the reservoir is managed in two basins. The West Basin receives input from Esopus Creek (and the Shandaken Tunnel from Schoharie Reservoir), and is designed to act as a settling basin. It is separated from the East Basin, from which water is withdrawn into the Catskill Aqueduct, by the weir across which we have just driven (Figure 9). This overview provides a dramatic view into the mountainous upper Esopus Creek watershed. Also, an automated suspended sediment sampling site is located just east of the weir, visible from this overview site.

Descend into Esopus Creek valley bottom.

Bridge across Esopus Creek
Stony Clove enters from left just downstream (right) of bridge. Stony Clove is a significant source of suspended sediment load/turbidity during high flow events and will be the location of Stops 6 and 7.

STOP 2. Esopus Creek at Woodland Valley Restoration Demonstration Site.
This stop in Esopus Creek Reach 7 will provide an introduction to the challenges in stream management of the Esopus Creek watershed and an illustration of the application of channel stabilization/stream restoration techniques. There is an informational kiosk at the site documenting the project history. The site is at the confluence of Woodland Creek with Esopus Creek – a setting that is inherently dynamic given the variability in magnitude of water and sediment discharge from the two mountain streams (Figure 10). Anecdotal and aerial photo evidence suggests that the channel and bar formation have undergone dramatic shifts in response to large flood events. The setting's inherent "instability" is compounded by a double-span bridge located just downstream of the confluence that produces a clear constriction in channel dimensions. Following the January 1996 flood, a headcut into underlying glacial lake clay propagated through a secondary channel along the left bank and eventually captured most of the Esopus Creek flow (Figure 10). The altered alignment of the channel, the stratified composition of the 32 foot (9.8 meter) high terrace (from bottom to top: glacial lake clay, glacial till, prehistoric stream deposits; Figure 11) and subsequent floods resulted in a rapidly retreating eroding bank (approximately 3 feet or 0.9 m per year).
Risks associated with continuing erosion included increasing potential for exhuming several residential septic systems, causing additional property damage, producing a continuing source of turbidity and creating a hazard to recreational users of the stream (Figures 10 and 11).
In 2000, DEP hired FIScH Engineering (principal engineer Dr. Craig Fischenich) to complete an assessment and conceptual design for remediating this reach (Fischenich, 2001). The hydraulic and stability analyses, sediment transport calculations, and geomorphic assessment resulted in recommendations for an approach that incorporated several technical techniques including a channel relocation based upon natural channel design principles, bioengineering and traditional bank revetment, and habitat and recreational enhancement features. DEP selected this project to be the demonstration stream restoration project for Esopus Creek required by the US EPA as part of the FAD schedule of compliance (US EPA, 2007). The project was constructed in 2003 in two stages: the channel work, bank revetment, and flood plain reconstruction were completed by Oct. 1, 2003 and the vegetation (trees and willow fascines) and bioengineering (VRSS) were completed in early Dec., 2003. Figure 12 is an aerial view of the site taken approximately one year after construction (Aug., 2004).

Office of Ashokan Watershed Stream Management Program on left
(which will be lunch stop)

Bridge across Broadstreet Hollow (location of Stops 5a and 5b)

Shandaken Tunnel (location of Stop 4b) emerges on right side of highway

Esopus Creek bridge

Start of bridge across Birch Creek

STOP 3. Esopus Creek Bank Failure on Reach 16.
Note: This is Private Property. Get permission from owner across road before crossing property to creek.
Esopus Creek has been actively changing its channel configuration through an anabranching reach from near Hatchery Hollow about 3 km upstream from this site. This has included a number of avulsions and meander-bend migrations (Miller, 2009). At this site, a very tight meander bend has been expanding westward at least since 1959 (Figure 13). This expansion has resulted in undermining and rapid headward growth of propagating failures in an elevated terrace that forms the left descending stream bank. Fluvial gravels overlie interbedded glacio-lacustrine clays and silts and glacial till. Stormwater runoff and groundwater flow off the adjacent mountainside has limited infiltration potential due to the impermeable glacial deposits and emerges as springs on the creek bank. Water does infiltrate into rotational slip surfaces in the underlying lacustrine unit resulting in very active collapse of the bank (Figures 14 and 15). This reach is often the upstream source of suspended sediment into Esopus Creek following high water events. This reach is part of DEP's longterm geomorphic monitoring program with 6 monumented cross sections, repeated longitudinal profile surveys, sediment sampling, and GPS-based mapping of channel feature alignment.
Risks associated with continuing erosion included increasing potential for exhuming several residential septic systems, causing additional property damage, producing a continuing source of turbidity and creating a hazard to recreational users of the stream (Figures 10 and 11).
In 2000, DEP hired FIScH Engineering (principal engineer Dr. Craig Fischenich) to complete an assessment and conceptual design for remediating this reach (Fischenich, 2001). The hydraulic and stability analyses, sediment transport calculations, and geomorphic assessment resulted in recommendations for an approach that incorporated several technical techniques including a channel relocation based upon natural channel design principles, bioengineering and traditional bank revetment, and habitat and recreational enhancement features. DEP selected this project to be the demonstration stream restoration project for Esopus Creek required by the US EPA as part of the FAD schedule of compliance (US EPA, 2007). The project was constructed in 2003 in two stages: the channel work, bank revetment, and flood plain reconstruction were completed by Oct. 1, 2003 and the vegetation (trees and willow fascines) and bioengineering (VRSS) were completed in early Dec., 2003. Figure 12 is an aerial view of the site taken approximately one year after construction (Aug., 2004).

Junction Hwy. 42 on left at Shandaken.
The highway climbs up Bushnellsville Creek through Deep Notch and into the Schoharie Creek watershed.

STOP 4A. Esopus Creek Gage at Allaben (Reach 11/12).
A USGS gaging station, maintained in cooperation with the DEP, has been operating at this site since 1988; from 1963 to 1988 a gage was located about 0.8 km upstream. Bankfull discharge is ∼3000 cfs (85 cumecs) has been exceeded numerous times during the period of record, and the site has recorded peak discharges of at least 15,000 cfs (425 cumecs) 4 times.
The estimated 100year flood at this site is around 26000 cfs (∼740 cumecs) (NYCDEP et al., 2007), whereas the largest flood of record — April 2, 2005 — was 21,700 cfs (∼615 cumecs). This site also has been used as a location to measure the hydraulic geometry of the bankfull channel. Miller and Davis (2003) used this as one of their calibration sites in developing regional bankfull discharge and hydraulic geometry curves for the Catskills region.
Realignment of Hwy. 28 in the 1960s was accompanied by cutoff of a natural meander downstream of the bridge (Figure 16; Miller, 2009). Miller (2009) describes the changes in this way: In 1959 the stream bifurcated around a large island (I11-1) upon entering the meander bend. But with road construction and cutoff of this meander, a new island (I11-3) formed just upstream of the old meander bend, as seen on the 1980 aerial photograph (Figure 16). The stream impinged on the road 200 meters farther upstream (20.2 km). By 2001, this island was attached to the left bank and no longer part of the channel. A new island (I11-5) has formed 140 meters farther downstream due to a channel avulsion across the floodplain leaving the old thalweg between the newly formed island I11-5 and the road.

STOP 4B. Shandaken Tunnel Portal.
The Shandaken Tunnel brings water from Schoharie Reservoir to Esopus Creek to contribute to the New York City water supply system. This 18­mile (29­km) long underground tunnel, built by hand between 1917 and 1924, was the longest handmade aqueduct in the world when it was completed. Both minimum and max­imum discharge from the tunnel as well as turbidity limits are regulated by the New York State Department of Environmental Conservation in order to balance recreational (and ecological) uses of Esopus Creek downstream of the tunnel with water­supply needs of New York City.

STOP 5A. Broadstreet Hollow Restoration Project: Reference Reach.
Severe flooding in 1996 resulted in destabilization of a section of the right bank of the Broadstreet Hollow stream, with bank widening that threatened some houses on the left bank. An emergency response team relocated the channel and used extensive rock riprap to harden the banks and stream bed, but in doing so further destabilized the channel (Greene County Soil and Water Conservation District, 2008). Rapid incision of the channel into underlying glacial lake sediment was exacerbated by a high flow in 1999, resulting in destabilization of the left bank and development of a migrating artesian mud boil within the channel. This produced high turbidity levels, with Broadstreet Hollow becoming a significant source of turbidity for Esopus Creek. By 2000, the Broadstreet Hollow Restoration Project was initiated cooperatively among the Greene County and Ulster County Soil and Water Conservation Districts and the DEP Stream Management Program. The project was designed according to Natural Channel Design guidelines, using a reference reach upstream of the project area to define "natural" step-pool conditions and a construction program that attempted to recreate such conditions in the project reach.
The Broadstreet Hollow creek here displays a typical step-pool pattern with large cobble and boulder bedload. This reach is classified as a Rosgen B3 channel (Rosgen, 1996). Sediment size and distribution as well as channel morphology (hydraulic geometry and slope) provide the targets for design of the restoration reach using Rosgen's natural channel design methodology. This site also has been monitored since project initiation; repeated crosssection measurements have been coupled with monitoring transport of large marked boulders to document changes in this "natural" channel reach.

STOP 5B. Broadstreet Hollow Restoration Site: Restoration Reach.
Complex glacio-lacustrine and post­glacial geology along with residential development have contributed to the challenges in restoring and stabilizing this reach of the Broadstreet Hollow stream. As reported by GCSWCD (2008), slumping of glacio-lacustrine clays on the right bank has been fostered by artesian pressure in an interlayered sand deposit that has resulted in an artesian boil within the stream channel. Dewatering wells were installed; they have since been decommissioned. However, mud boils have continued to propagate upstream within the channel, still present in June 2009. Channel restoration was designed using the step-pool bedform and hydraulic geometry of the reference reach. Large quarried rocks were used to construct "cross vanes" to function as boulder-­dominated steps in a constructed B3 channel (Figure 17). Several high flow events through this reach have caused some of the rock structures to be flanked or to need repair. Also, some of the struc­tures have caused excess scour in the pool below the constructed step resulting in impaired fish passage at low flow. Willows and other riparian trees also were planted along the bank to add to bank stabilization.

Left side of road undergoes routine repairs
Left side of road undergoes routine repairs due to collapse of underlying glaciolacustrine clays. Note bedrock exposure across creek.

Bridge over Stony Clove; Stony Clove gaging station.

STOP 6. Lanesville Demonstration Restoration Project Site on Stony Clove Creek.
A long history of channel modification and response has led to severe bank erosion and undermining of the right bank of Stony Clove just downstream of the hamlet of Lanesville. This reach was chosen for remediation because the development of a landslide on the left bank (Figure 18) was a significant source of fine sediment and turbidity into Stony Clove, Esopus Creek, and Ashokan Reservoir. This reach also had become increasingly confined by channel modifications, exacerbating the tendency to undermine the unstable left bank. Bank stabilization was promoted through construction of a bankfull bench at the toe of the slope, designed to re-establish a floodplain and minimize the interaction of most flows with the unstable bank (DuBois, 2003). Natural channel design principles were followed, including the construction of rock vanes and cross vanes within the channel and planting of a riparian buffer along the right bank and on the constructed bench (DuBois, 2003). The project was begun in 2003 but not completed until 2005 because of high water levels in the creek. Since construction this project has received several flow events around or greater than the bankfull discharge and has functioned quite well in stabilizing the reach and reducing turbidity downstream.
OHM 2019: Error in UTM, it should be 560227E not 566227E .

Meteorological station on right.

STOP 7. Landslide Along Stony Clove Creek.
Get permission from landowner before walking down to creek.
The Ashokan Watershed Stream Management Program Action Plan (http://www.catskillstreams.org/majorstreams_ec.html) identifies this reach of the stream between the Silver Hollow Bridge and the Route 214 crossing 1 km downstream as the highest priority restoration target for improving water quality in the Esopus Creek watershed. This area has a long history of modification, including development and construction of a railroad line (Figure 19) and various efforts to control the creek channel alignment. Today there are three distinct streambank/hillslope failures into glacial lake sediment and glacial till that are quite active. During spring snow melt and after rainfall runoff events this reach of stream is the most significant "point source" of turbidity for days and sometimes weeks after high water events (Figures 20 and 21). This stop is located at the largest and most problematic of the failures. It is a large active landslide initiated sometime prior to 1995. Upslope propagation of the slope failure resulted in collapse of a railroad right-of-way as well as increased groundwater and sediment discharge. The scale of this landslide presents especially great challenges for channel restoration and suspended sediment management. We will discuss restoration and management strategies being considered here. Given what we have seen elsewhere in the basin, how might the stream be managed through this reach to preserve/restore water quality?
OHM 2019: Error in UTM, it should be 557436E not 567436E.

STOP BK1. Exposed Willow Moraine.
This cutbank exposes a complex sequence of interbedded till and lacustrine sediments currently being studied by Andrew Kozlowski and colleagues from the New York State Museum as part of surficial geologic mapping of the quadrangles in this area. A lower, consolidated till is overlain by some 18 till units interbedded with lacustrine sediments. This exposure illustrates the complexity of glacial deposits in the Upper Esopus watershed and highlights the difficulties in mapping stratigraphy — and identifying possible sources of suspended sediment turbidity into Esopus Creek and its tributaries.

STOP BK2. Landslide in Glacial Deposits.
A landslide along the right bank of Beaver Kill has propagated as much as 70 m upslope and at least 70 m along the channel downstream of the Hwy. 212 bridge (Figure 22). This site is a dramatic representation of several similar stream bank erosion/hillslope mass failures in the confined portions of the Beaver Kill watershed that seem to be significant sources of bedload sediment supply resulting in numerous gravel/cobble bars that induce further lateral erosion of the channel. An assessment of this stream corridor is planned for late summer 2009.

STOP 8. Meander Bend Migration on Esopus Creek at Beechford.
The meander of Esopus Creek just upstream of this location has been migrating eastward and downstream, as recognized from comparison of aerial photographs from 1959, 1980, and 2001 (Miller, 2009; Figure 23). The channel here appears to have been left (east) of the island on the 1903 topographic map. By 1959, the channel had avulsed to the right (west) side of the floodplain, though the original channel was still occupied (at least in part) as a secondary channel, creating a mid-­channel island. We do not know exactly when this occurred, nor whether this was a natural avulsion or was induced to protect the Hwy. 28 alignment. However, the main channel has been migrating eastward since 1959, eroding the island and creating a point bar on the right (west) bank. This continuing meander migration likely will result in reoccupation of the original channel and could threaten the Hwy. 28 alignment in the future.

9: PRE-OTTAWAN (1.09 GA) INFRASTRUCTURE AND TECTONICS OF THE HUDSON HIGHLANDS, NEW YORK
Nicholas M. Ratcliffe
U.S. Geological Survey
Reston VA 20192
ratclif@usgs.gov
John N. Aleinikoff
Denver, CO 80225
jaleinikoff@usgs.gov
This trip focuses on some of the oldest Mesoproterozic rocks in the Appalachians and the nature of the pre-Ottawan (pre-1.09 Ga) infrastructure of the Hudson Highlands and Manhattan Prong. Zircon geochronology by Aleinikoff (Table 1) is revised from that given in Table 1 of Ratcliffe and Aleinikoff (2008) and is still preliminary. Ongoing geologic mapping east of the Hudson River in the Peekskill, West Point, Lake Carmel, Mohegan Lake, Brewster and Peach Lake quadrangles continues to lead to a reinterpretation and clarification of our former views (Ratcliffe and Aleinikoff, 2001, 2008) as well a new synthesis for the Hudson Highlands east of the Hudson River. After publishing the detailed geology of the Poughquag quadrangle (Ratcliffe and Burton, 1990) and the Oscawana Lake quadrangle (Ratcliffe, 1992), investigations were resumed in 2000 to prepare the previously mapped but unpublished quadrangles for publication.
This trip presents, in preliminary form, much of the recent, (post-2000) information, which helps clarify the age and distribution of Mesoproterozoic basement rocks of the Hudson Highlands and Manhattan Prong and is an abbreviated version of our 2008 NEIGC trip. Please note that stops have been changed and that the route is different.
A remarkable newly recognized aspect of Hudson Highlands geology covered in this trip is the widespread presence of orthogneisses and metavolcanic rocks belonging to the time period between 1400 Ma and 1200 Ma, or during Geochrons 14 and 13 of Rivers (1997). These rocks formed before the Grenville orogeny, defined by Rivers (1997), as ranging from 1.09 Ga to 0.98 Ga, and are coeval with crustal convergence in the Elzevir belt in Ontario and Quebec, at the western margin of the Grenville orogenic belt. We know little about the nature of the deformation that may have affected rocks of the Hudson Highlands during the Elzevirian orogeny except that some were transformed into gneissic rocks prior to about 1230 Ma and multiply deformed after that.
Igneous activity and deformation in the time period of about 1170 to 1145 my ago, at or near the time of the Shawinigan pulse of the Grenville orogeny of Rivers (1997) affected many the rocks of the Hudson Highlands and presumably of the Manhattan Prong although data there are sparse. Penetrative, regionally developed, Y F2 folds of the Hudson Highlands have been mapped in northern New Jersey (Dallmeyer, 1972) and West Point area of the Hudson River (Helenek, 1971; Helenek and Mose, 1984) eastward through the Hudson Highlands (Ratcliffe and Burton, 1990; Ratcliffe, 1992). This deformation resulted in redeformation of older rocks as well as deformation of hornblende granites of the Storm King type, which have an intrusive age of 1174 ± 8 Ma (Table 1). Folds of this generation are folded by the sigmiodal deformation zones associated with the intrusion of the Canopus pluton, and crosscut by mafic dike swarms. Acceptance of an intrusive age of 1143 ± 12 Ma for the Canopus pluton (Table 1) and for the associated mafic dikes, requires that the regional Y F2 dynamothermal event be older than the Ottawan phase of the Grenville orogeny. This is important because many workers think that Ottawan or the terminal phase of the Grenville orogeny was responsible for the major deformational features in Mesoproterozoic rocks of the Appalachians. This view is being revaluated in the Appalachian outliers of the Grenville and in the Adirondacks, as the recognition of rocks and deformational events at about 1230 Ma and 1150-1134 Ma that are older than the Ottawan are discovered (Ratcliffe and others, 1991; Ratcliffe and Aleinikoff, 2001, 2008). In the Adirondack Highlands evidence for Shawingan migmatite in the age range of 1180-1160 Ma is widespread (Heumann and others, 2006; Bickford and others, 2007) Throughout the Hudson Highlands and in northern Appalachians, there is a relative scarcity of Ottawan igneous rocks, although ages of metamorphic overgrowths on zircon and of migmatization of older rocks attest to widespread Ottawan remetamorphism.
Rocks intruded between 1134 ± 8 Ma and 1045 Ma, are foliated, as in adjacent areas, such as the New Milford massif (Walsh and others, 2004) and as seen on this trip. However there are abundant data which suggest that the deformational effects in the Hudson Highlands and elsewhere in the northern Appalachains are the result of multiple orogenic events, some predating the Ottawan. On this trip we will visit and summarize information concerning recently dated rocks that are critical to defining the pre-Ottawan history of the Grenville orogen here and elsewhere in the Appalachians of New York and New England.
In addition newly determined SHRIMP U-Pb zircon data, and Ar 40 /Ar 39 hornblende ages support late Ordovician to Silurian Taconian overprinting of the basement and cover rocks between 450 to about 443 my ago and suggest that Acadian effects were minimal by comparison.

9: PRE-OTTAWAN (1.09 GA) INFRASTRUCTURE AND TECTONICS OF THE HUDSON HIGHLANDS, NEW YORK

STOP 1. Reservoir Gneiss--amphibolite inclusions
I-84 Exit 17 Luddingtonville Rd. Poughquag quadrangle STAY OFF THE INTERSTATE PLEASE. Park by the overpass and walk along west entrance lane.
This belt of trondhjemitic gneiss forms the eastern end of a wide belt of Reservoir Gneiss (of Ratcliffe and Burton, 1990) that extends from near Cat Hill Stop 7 through alternate Stop 5b into the Poughquag quadrangle and the contiguous Brewster quadrangle (Figure ). A SHRIMP zircon age of 1333±6 Ma has been obtained from this outcrop. Ages of overgrowths on the zircon are 1.2 and 1.0 Ga indicative of Elzeviran and Ottawan zircon growth. Sweat outs of more granitic composition are common and are shown by coarser grain size in indefinite irregular pockets in which and older gneissosity is overprinted. Abundant mafic inclusions choke this rock in most exposures. Reaction rims around the mafic inclusions contain pyroxene, hornblende, and biotite and are gradational with the host rock. It is likely that these reaction zones and the pegmatitc sweat outs are the result of Ottawa metamorphism.
Normative An-Ab-Or compositions of some the felsic rocks belonging to Geon 14 and those of Geon 13 are plotted in Figure 8 and range from trondhjemite to granite. Fields for the Reservoir Gneiss at Peekskill (stop 9), at Cat Hill (Stop 8), in the Oscawana Lake area (Stop 5b) and here at Luddingtonville (Stop 1) show the range of compositions in the Reservoir Gneiss in the westernmost belt closest to the Canopus deformation zone.
These trondhjemites and granites all have distinctively high La/Ybcn values, steep middle to light rare earth slopes, and flat, negative to positive HREE slopes comparable to that shown for the Cat Hill Gneiss (Figure 10). The samples of the dated Fordham Gneiss have very similar patterns. Plots of Rb vs Nb+Y (Figure 9) show the similarities among the dated rocks as well. The filled dots are samples of Yrg in the Brewster area that are correlated with the main Reservoir Gneiss belt on the basis of continuity on the ground between the two areas. We can not be certain that all rocks shown as Reservoir Gneiss in the Brewster area are in fact the same as these rocks are not dated.
Mafic inclusions in this outcrop and in all stops in the rocks of Geon 14 may be inclusions and or dikes as will be discuss further at Stop 2. The amphibolites here show no clear indications of having been dikes but that cannot be ruled out. Note the felsic sweat outs and pegmatites near the wall of the "inclusions" as well as the pyroxene- hornblende reaction zones, which grade into the bordering rocks.

STOP 2. Snake Hill - Granitic gneiss typical of Brewster belt and mafic dikes
Steeply dipping biotite granite gneiss typical of the vast majority of granititic gneiss and associated migmatitic lit par lit contact zone on Joes Hill. Gneissic granite like this is crosscut at the west end of Joe Hill by a monzonite dike that has a zircon Pb207/206 SHRIMP age of 1240±7 Ma. The granite gneiss here is tentatively assigned to the old gneiss belt and is judged to be 1330 Ma or older. Fine-grained foliated mafic dikes cross cut the gneissic structure and are fairly abundant on this hill and in areas to the east. Locally coarser grained diorite to gabbroic masses also cross cut the older gneisses and these rocks pass into finer grained rocks like the dikes seen here.
Figure 12 shows one of a series of meter-wide dikes petrographically like the small ones above. On Joes Hill these dikes cross cut high-grade gneissosity and intrude across mylonite zones. Although apparently straight walled, they are redeformed by isoclinal folding. Both the dikes and the older gneissosity are cut by foliated granitic pegmatite of probable Mesoproterozoic age. Based on these observations, the mafic dikes, like that figured below must be Grenvillian and perhaps older than the Ottawan phase of the Grenville orogeny. In this regard these dikes resemble the dikes of the Canopus pluton (stop 6), which also cross cut an older gneissosity.
Chemically, the dikes in question are somewhat like those of the Canopus pluton as illustrated in Figure 13, and to dioritic rocks at stop 3. The diagram shows a similarity in chondrite LREE enrichment trends (but not in absolute values) and similar range in Ta -Yb ratios. The plots do not establish identity of the various rocks only suggest that possibility.
The dike in Figure 12 is a typical example. It cross cuts migmatitic gneiss that at this locality is intruded by a monzonitic granite that has a SHRIMP zircon age of 1240±7 Ma (Table 1). The age of these dikes is younger than 1240 Ma. They could be the same age as the diorites associated with the dated hornblende granite (1134±8 Ma) at stop 3 and with dikes of the Canopus pluton (Stop 6A, B) that are probably approximated by the Canopus monzonite zircon Figure 11. Two fine-grained mafic dikes cross the coarse ropy gneissosity of SHRIMP age of 1143±12 Ma. The mafic dikes of the Canopus and else-where in the Brewster area cross cut coarse gneissosity in the 1340-1330 Ma rocks; both are intruded by foliated pegmatite.
Alternately these dikes could be Neoproterozoic. However major and trace element characteristic differ from Neoproterozoic dikes found in the Hudson Highlands (Ratcliffe, 1978), which are typical transitional rift basalts.
The clearly cross cutting mafic dikes and mafic and isoclinally folded "inclusions" in the granitic gneisses of the Brewster area are indistinguishable chemically and petrographically from one another. This observation plus the fact that individual dikes like that in Figure 12, which cross cut a gneissosity can be traced within outcrops into isoclinally and cross foliated zones suggests that many of the inclusions or indefinite dikes like those at stop 1 may all be the same age. If so, there is a widespread mafic dike event at about 1143 to 1134 Ma. that post dates an earlier Shawinagan deformation.

STOP 3. Unnamed 1134±8 Ma hornblende granite gneiss
Dioritic gneiss and sulfidic schist screen, Brewster, N.Y.
Hornblende-biotite granite gneiss 140 feet wide, on the southeast end of this NW-SE vertical cut becomes very hornblende rich and passes into a 15-ft-wide pyroxene hornblende pegmatite near the small screen of sulfidic paragneiss. The hornblende granite has a 1134±8 Ma SHRIMP age. North of that dioritic gneiss about 35 ft thick passes northward into a hornblende-rich margin that grades into a second 40 ft-thick zone of granite gneiss. That granite gneiss grades upwards into diorite gneiss at northwest end of the exposure. The felsic and mafic components grade into each other at the margins and appear to be coeval. In this characteristic these rocks resemble rocks of the Canopus pluton (Stop 6A, B) and have essentially the same age as the felsic component of the Canopus which has a concordant zircon SHRIMP age of 1143±12 Ma.
We regard the felsic and more mafic rocks as part of the same igneous suite. Near contacts with sulfidic schists and calc-silicate rocks hornblende-pyroxene pegmatite and a white hornblende-spotted aplite carrying magnetite is common. This is the common association for the Brewster magnetic deposits, which are developed on strike to the southwest at the borders of xenoliths included in the hornblende granite and along the wall of this intrusion. All the rocks are foliated but tend not to be gneissic like the older rocks. Similar dioritic intrusives occur to the north in Brewster and preserve coarse diabasic texture and relict coarse - plagioclase flow structure. The mafic dikes we have seen may also be the same age.

Tilly Foster mines
Calc-silcate rock, marble and magnetite are developed here at the contact with the same hornblende granite gneiss dated at Stop 3.

STOP 4. Hornblende Granite gneiss like that at Stop 3
NOTE: on Figure 4 this location does not correctly show the hornblende granite which was discovered after the figure was published. See Figure 2 for a more accurate map. This illustrates an important point namely that telling the old 1340-1300 Ma granite gneisses from the 1134 Ma ones is not easy. I expect to complete mapping in the Lake Carmel quadrangle this Fall and undoubtedly contacts will shift.
Well lineated and foliated hornblende granite gneiss and aplite cuts gneissosity in older well layered biotite and hornblende-quartz-plagioclase gneisses. Both rocks are folded into tight folds containing axial surfaces of N 65 W 45 NE and a strong lineation plunging to the east and northeast. These relationships support the idea that the 1135 Ma hornblende granites cross cut older structure just as the Canopus pluton Stop 6A, B does.
Excellent exposures in the Croton Reservoir (Stop '08-4 of Ratcliffe and Aleinikoff, 2008) are no longer available as the reservoir has now been refilled and the exposures covered. Observations there showed that:
1. The hornblende granite is foliated but does not have the same coarse ropy- textured gneissosity of the older 1340 Ma gneisses seen at Stop 2.
2. Xenoliths of foliated gneisses occur within the younger hornblende granite gneisses and aplite
3. The coarse and fine grained variants of the hornblende granite and hornblende pegmatite occur at contacts with the country rocks and an older gneissosity is truncated by the younger granites.
4. Contacts with rusty sulfidic paragneisses developed abundant magnetite and sulfides just as the wall rocks of the larger bodies of hornblende granite do in the Brewster magnetite district do.

General geology.
We are in the center of the Lake Carmel quadrangle headed west across a particularly well developed sequence of Mesoproterozoic paragneiss, calc-silicate rock, marble, thin quartzites and schist. We will cross two of the thickest belts of amphibolite in the Hudson Highlands that are mappable into the Poughquagh quadrangle to the north. These amphibolites are true amphibolites, unlike so many of the rocks mapped as amphibolites by myself and others in the Highlands. These are composed of >70% hornblende rather that the more common type of "dioritic" amphibolites which commonly contain equal amounts of plagioclase and hornblende. This belt of coarse to fine amphibolite is associated with pods of serpentinite, anthophyllite schist and gabbroic to dioritic igneous rocks. The serpentinites are in contact with paragneisses, diopside bearing quartzites, and carbonate containing ovoidal pods of what probably are serpentinized fosterite knots.

STOP 5A. Coarsest amphibolite
Coarsest amphibolite perhaps related to the Wiccopee pluton of the Oscawana Lake quadrangle (Ratcliffe, 1992) discussion of amphibolite chemistry

STOP 5B. (Optional) Reservoir Gneiss at its type locality
Discussion of regional tectonic of the Oscawana Lake-right lateral deformation zone (see Stops 1 and 7 for chemistry discussion)
These road cuts in the Reservoir Gneiss represent the type locality of the gneiss and were visited on Stop 6 of Ratcliffe and others (1985) and is in part reproduced from Figure 23 of Ratcliffe (1992). Aside from illustrating the type Reservoir Granite of Berkey and Rice (1921), these crops contain mylonite zones typical of the Paleozoic fabrics found to mark the larger shear zones at biotite and higher grades. Here evidence for reactivation as Mesozoic normal faults may be seen. A similar observation will be made at Stop 8.

General geology
We are traveling down the Peekskill Hollow-Nuclear Lake-shear zone that marks the eastern side of the large right-lateral sigmoidal deformation zone in the center of the Oscawana Lake quadrangle. Although the sigmoid is Mesoproterozoic (Ratcliffe, 1992), the California Hill and this shear zone are Paleozoic based on the retrogressive phyllonite there and offsets of Paleozoic rocks along their lengths and from dating of syntectonic biotite in the mylonite of the California Hill shear zone that has a 436 ± 3 Ma Ar/Ar age (see Figure 0 in Ratcliffe, 1992). The sigmoidal deformation of the gneisses however is Mesoproterozic based on the mapping of non rotated metadiabase dikes that have the chemistry of Neoproterozoic rift basalt. (Ratcliffe, 1992). Based on this reasoning, the California Hill shear zone has both a Mesoproterozoic and a Paleozoic history, as do the faults bordering the Canopus Valley to the west.

At Adams Corner we will turn west and cross the end of the Annsville syncline
At Adams Corner we will turn west and cross the end of the Annsville syncline which probably has a Mesozoic fault long its northwestern flank. See discussion Stop 7.

General geology
Two miles south on Rt. 20, in front of the Putnam Valley Elementary School, there are superb outcrops of Mesoproterozoic shear zone rocks invaded by aplites that are also highly deformed and crossed by Mesoproterozoic pegmatites supporting intense Mesoproterozoic deformation east of and parallel to the main Canopus shear zones. This is approximately on the California Hill fault zone and supports Mesoproterozoic inheritance here.

Canopus Valley
Continue on Cimmaron Rd. down the hill into the Canopus Valley that is underlain by coarse phlogopitic- felsdspathic-scapolite dolomite marble, quartzite and retrograde diopside calc- silicate rock. This is the thickest belt of Mesoproterozoic marble and calc-silicate rocks in the Hudson Highlands of NY.

Old magnetite mine developed in marble and calc-silcate rock
Immediately above and on the south side of Indian Hill Road is an old magnetite mine developed in marble and calc-silcate rock just off the north end of the Canopus pluton. Here aplite and pegmatite that makes the border phase of the Canopus , contain large 1-2 cm clots of magnetite where it intrudes hornblende granite gneiss like the Storm King Granite. This lit par lit border zone will be seen at Stop 6b where it is caught in the retrogressive shear zone along the west side of the Canopus Valley at the east edge of the pluton.

STOP 6A. Canopus pluton diorite, dikes and screen of Mesoproterozoic gneiss
At the end of the driveway are excellent new exposures of the dioritic rocks of the pluton on the right and left sides of the cut. Note the well defined areas of monzodiorite in diorite in the block to the left (S), the diorite - a screen of isoclinaly folded country rocks exhibiting the YF2 structure and the flow layered diorite on the right (N). Two mafic dikes cross cut both the gneiss inclusion and the flow layered diorite. The observations here point to composite intrusion of the dioritic phases of the pluton. Dike swarms in the vicinity of the pluton cross cut YF2 structures in the gneisses. Some dikes are as much a 0.5 km long and are present as many as 2 km west of the pluton.These dikes are chemically and petrographically like the dikes in the Brewster area seen at Stop 2.

STOP 6B. Canopus pluton 1143 ± 12 Ma
Biotite monzonite and hypersthene biotite diorite composite intrusive.
This spectacular and demonstrative new driveway cut exposes the transition from the Canopus shear zone into the Canopus pluton. The Canopus pluton is intruded between two Mesoproterozoic right lateral shear zones. The eastern one has been reactivated at greenschist grade and is exposed here. The western one is not reactivated and contains stringers of monzodiorite- monzonite and cross cutting composite diorite- monzonite dikes of the main pluton and abundant pegmatite, all of which crosscut the mylonitic host rocks, or as much as 2 km north of the pluton. Internal structure in the pluton consists of mutually crystallizing igneous phases and a well developed and folded igneous flow layering that defines right lateral deformation of the pluton during crystallization. At the walls igneous rocks of the pluton cross cut the bordering mylonite zones of the faults and fill internal shears within the pluton. Isoclinal folds in the mylonitic country rocks plunge nearly vertically down the mylonite structure, as do the axes of the internal and folded igneous flow structure in the pluton. This has been interpreted to mean intrusion of the igneous rocks into a subvertical active shear zone in the Mesoproterozoic. Early attempts to date the igneous rocks using Rb/Sr whole rock techniques by Dick Armstrong (Ratcliffe and others, 1972) and using multigrain zircon techniques by Aleinikoff gave ages of about 1.0 Ga and were erroneous. Subsequent SHRIMP zircon dating by Aleinikoff gives a more precise concordant age of 1143±12 Ma with overgrowth ages of about 1 Ga. That is, during the end stages of the Shawinigan pulse of the Grenville orogeny (Rivers, 1997) as well as Ottawan overgrowths.
Starting from the road level some of the significant features to be seen are:
1. Mylonite, consisting of lit par lit veins of aplite , isoclinal steeply plunging folds in the mylonite.
2. Zones of pegmatite saturating and postdating the mylonite structure
3. The wall of the monzonite with fine grained monzonite in the mylonite
4. Tabular K-spar defining an igneous flow structure cut by aplite dikes and by intermediate diorite dikes
5. A pillowed zone consisting of monzodiorite ellipsoidal segregations in the monzonite and turbulent flow structure in the monzonite around the "pillows"
6. Ductile shear zones in the monzonite which deform the flow layering into lineated tectonites and undeformed granitic segregations which saturate the lineated zones
Some features described above are shown in Figure 19.
These features and other similar observations made during mapping of the shear zones and the igneous rock (Ratcliffe, 1971; Ratcliffe and others, 1972) support the concept of syntectonic intrusion and document right-slip faulting at about 1143 Ma. To the east the right sigmoidal deformation in the area of Wiccopee diorite pluton indicates this type of tectonism in a zone as much as 10 km wide (Ratcliffe, 1992). Mafic dioritic to hornblendic dikes are common within this sheared zone cutting the fault fabrics and folds associated with the strike-slip events. This is very similar to the dikes and igneous rocks associated with stops 2 and 3 today in the Brewster area where a similar age for intrusion of 1134±8 Ma has been established for comagmatic granitic and mafic rocks.
Mafic dikes commonly less than several meters thick, crosscut high grade shear zones on both sides of the Canopus shear zone and have compositions similar to the dioritic and most mafic part of the pluton. Locally ultramafic hornblendite plugs and radiating dikes are found near Fort Hill. Importantly, dioritic dikes and segregations within the pluton crosscut the igneous flow structure (Figure 6), and all rocks of the pluton lack a strong Mesoproterozoic deformational structure that is present in the country rocks. This is also true of the granites and dioritic rocks of the same age at Stops 3 and 4 and of the mafic dikes and gabbro-diorite plutons in the Brewster area. We may speculate that the deformed dikes seen in the tonalite –trondhjemite and at Stop 1 today might also be dikes of the same age.

The dated monzonite
The dated monzonite came from just north of this intersection on the west side of the road.

STOP 7. Cat Hill Gneiss 1333 ±7 Ma trondhjemite gneiss
And Mesozoic cataclastic structure on the north limb of the Annsville syncline
On the south side of the road are limestone crops of the Cambrian and Ordovician Wappinger Group here barely at biotite grade. North of the road before the Cat Hill Gneiss are crops of the Lower Cambrian Poughquag Quartzite then cataclastic gneiss of the Cat Hill Gneiss. In the 1970's, I mapped an unconformity between Paleozoic rocks of the Annsville syncline and the basement as Walter Bucher had. New cuts and reexamination of the cover rocks along the Annsville syncline to the east now support high angle normal faulting and brecciation of the kind associated with Mesozoic tectonics and the Newark basin.
The Cat Hill Gneiss is less cataclastic in the outcrops behind the house but even these are not typical because of the extensive fracturing. A few hand samples from the dated locality less tan 0.5 miles to the northeast demonstrate the difference. To get to the sample locality follow the directions to Stop 11 in Ratcliffe and Aleinikoff (2008)
The Cat Hill Gneiss is a white-weathering biotite-oligoclase-quartz gneiss of trondhjemititic and tonalitic composition. It is typical of a series of similar massive biotite poor garnet bearing gneisses that occur in the Reservoir Gneiss of Berkey and Rice (1923) and which closely resemble parts of the Losee gneiss of the New Jersey Highlands. It also is very similar to tonalitic gneisses of the Green Mountains of Vermont, which formed as calc-alkaline intrusives between about 1390 Ma to about 1320 Ma (Ratcliffe and others, 1991). The rock is very massive, contains almost no inclusions. It does pass into a more garnet-rich phase and also hosts abundant white aplitic granites at its contacts with amphibolites and has brown weathering spots suggestive of hypersthene but none has been found here. These bordering aplites produce a spectacular intrusive breccia with inclusions of hornblende gneisses, amphibolites. Because the Cat Hill Gneiss contains migmatitic zones of similar aplite and granite it may be that the breccia is a product of mobilization and intrusion along the walls resulting from secondary mobilization in an event younger than 1337 Ma. The purple brittle fracture zones contain minute riebeckite and are very similar to fracture zones along the Ramapo and other faults along the Newark basin in New Jersey
Figure 20 summarizes the axial traces of Mesoproterozoic folds in the Hudson Highlands of NewYork. Folds related to the Canopus- California hill deformation zone document a wide area of right sigmoidal folding here interpreted to be of Pre-Ottawan at approximately 1142 Ma and contemporaneous with intrusion of the Canopus pluton and its ferrodiorite dikes. Folds west of the shear zone, identified as Yf3 folds are Ottawan and folds identified as Yf2? to the east may be also be.In the Brewster quadrangle (Stop 2) and on Joes Hill similar dioritic dikes cross cut the granitic gneisses and intrude along steeply dipping high-grade shear zones. I tentatively correlate the igneous rocks of the Canopus area with the dikes in the Brewster area and with the dated granite - and diorite at stops 3 and 4. If this is correct, there may be evidence for a broad zone of right lateral shearing and igneous activity in the northern Hudson Highlands near the end of the Shawinigan phase of the Grenville orogeny. This raises the possibility that some of the amphibolite inclusions in these older rocks (Stops 1, 8 and 10) could be dikes, masking as xenoliths in the older granitic to tonalitic rocks! The more I learn about these rocks the more that interpretation seems likely to me.

Sprout Brook valley
Sprout Brook valley is a continuation of the Canopus Valley that extend south to the Hudson River and which is floored by highly mylonite sillimanite containing garnet gneisses, as well as and calc- silicate rocks. Biotite grade phyllites of Ordovician age correlative with the Wallomsac Formation occur along the east side of the valley where they rest on Mesoproterozoic rocks along the east dipping Annsvile fault which I originally interpreted was an Ordovician thrust fault but which I now regard as a Mesozoic normal fault traceable to branches of the main Ramapo fault to the south.

Exposures of Wallomsac Formation
Exposures of Wallomsac Formation in contact with Mesoproterozoic gneiss along the extension of the Annsville fault. At these outcrops Walter Bucher documented a conglomeratic fine grained dolomite with clasts of gneiss which he interpreted as a basal units of the Wappinger Group resting unconformably on the basement. However, the large pebble- to cobble- size inclusions within the dolomite are all fragments of retrograded calc-silicate rock in an ultrafine grained mylonite or foliated dolomitic cataclasite that derived from Mesoproterozoic rock.

Poughquag Quartzite to the left are unconformable on Reservoir Gneiss
Crops facing consist of Cambrian Poughquag Quartzite to the left are unconformable on Reservoir Gneiss. Large continuous crops of the Reservoir Gneiss continue for a mile to the south in high road cuts.

STOP 8. Reservoir granite of Berkey and Rice (1921) at Peekskill
The exposures sampled for dating of zircon are at the east end of the large road cut on Rt. 9 and 202 below the Peekskill Inn. The exposures extend about 1000 feet to the north in high road cuts. Numerous thin to thick amphibolite gneisses and more biotitic gneisses form septae in the granodioritic gneiss. The rock is remarkably homogeneous and is interpreted as an intrusive rock. At one locality near the middle of the cut a pod of amphibolite is included in the granodiorite. A concordant SHRIMP zircon age of 1338 ± 6 Ma has been determined for the granodiorite. Zircon overgrowth ages are about 1.26 and 0.98 Ga.

STOP 9. Cortlandt complex monzonorite and contact with the Walloomsac Formation
We are at the southeastern margin of the Cortlandt complex that consists of igneous norite, diorite, pyroxenite that cross cuts Taconic deformed metasediments of the Manhattan prong as well as the Laurentian basement. It was intruded following Taconic deformation and metamorphism and is one of the key observations in determining the timing of the Taconian orogeny. The igneous rocks are folded and intruded by the Devonian Peekskill Granite. A discussion of the contact relations, chemistry, and petrogenesis of the complex is beyond the scope of the present trip. Several papers and guidebooks provide that information (Bender, 1982; Ratcliffe and others, 1982, 1983).
The central basin of the complex consists of inward dipping sheets of biotite norite, hornblende and biotite poikilitic norite and locally at the very border a monzodiorite that contains zircon. Pockets of interstial k-feldspar- quartz and radiating biotite define slightly pinkish areas in the norite adjacent to the contact with the Walloomsac Formation. Zircon from this rock yielded a concordant SHRIMP age of 444±3 Ma almost identical to the concordant SHRIMP zircon age from monzodiorite of the Peach Lake pluton (447±5 Ma).
Near the contact igneous rocks and mobilized schist form an intrusive breccia In the breccia are rotated fragments of foliated and folded calc- silicate rock, and calc- schist characteristic of the basal part of the Walloomsac Formation (formerly termed Manhattan A of Hall, 1968). A breccia zone like this was previously recognized along this contact but none of the exposures are as spectacular as this one. Just west of this location and in the cuts for the exit ramp from Rt. 9W dikelets of mobilized schist containing garnet sillimanite-spinel- and corundum back intrude the chill norite and cut across the intrusive flow layering in the igneous rocks (see Stop 6 of Ratcliffe and others, 1983). Evidently the schists of the contact aureole were mobilized not as melts but as volatile-rich pneumatic injections, driven by contact-induced decarbonization and dehydration reactions along the walls.
Thin sections of the contact schist here contain garnet- biotite- staurolite- plagioclase and quartz and lack either kyanite or sillimanite both of which are present in contact rocks not far from here. Schist outside the aureole to the south on Torment Hill also contains abundant staurolite and lacks either kyanite or fibrolite.

STOP 10. Granitic Fordham Gneiss 1351±6 Ma and amphibolitic gneisses
The first exposures by the RR tracks are dark-gray biotitic gneisses, amphibolite gneisses and some sulphidic schists of the Fordham gneiss, which are in contact with the granite gneiss from the dated locality westward to this point. The biotite- hornblende gneiss resembles the inclusions we will see in the granite gneiss on Oscawana Island. The amphibolitic gneiss is layered and grades into schists near the south end of the RR exposure. This suggests that the Fordham Gneiss contains paragneisses that are older than 1351 Ma. Hornblende from these exposures yielded a 40Ar/39Ar cooling age of 450 Ma (Dietsch and others, 2004).
Walk northwest to the island. Take bridge over tracks and follow trail to end of island. Walking south then west along the shore we will see excellent exposures of the dated gneiss and inclusions in it. Some of the tabular to irregular-shaped inclusions are layered, but the gneissosity seems to be shared by the granite. Note this is unlike the relations of the 1134 Ma intrusive rocks at Stops 3 and 4. I have not seen evidence that the 1350-1330 Ma rocks cross cut an older gneissosity.
Here we might consider how the zircon age and intrusive relationships should be interpreted. Does the zircon age date the time of the intrusion of granite, or could the intrusive relations we deduce been produced by migmatization of a pile of felsic and mafic volcanic rocks? This is a difficult question not easily answered, either from the zircon zoning patterns or the field observations. I think we can conclude safely however that the granitic gneiss and the inclusions were present at 1351 Ma, but in what exact form is left undetermined. We have chosen to interpret the zircon age as the emplacement and crystallization age. If this is correct then the biotite hornblende gneisses in the RR cut might be older than the granite and some of the Fordham Gneiss older than 1351 Ma. Summary diagrams of dike chemistry Figures 22 and 23 give a summary of some of the chemical characteristics of the mafic dikes and amphibolites we have seen on this trip. The data are consistent with the mysterious dikes of the Brewster area being correlative with 1143 Ma Canopus plutonism rather than Ordovician, as the field observations indicate. The data also allow for some of the amphibolite "inclusions" in the ∼ 1340 Ma granitoids to be deformed dikes, as field observations do indicate for some, perhaps in the same 1143-1134 Ma Shawinigan event. Notable are the coarse amphibolites (Stop 5) of the Nimham belt which are distinct outliers of low TiO2 mafic rocks. Ta/Yb of the Brewster dikes overlap those of the Canopus dikes although the centroid of the former suggests a more depleted mantle source rather than more MORB-like source for the latter. The quite alkaline nature of the Cortlandt-age dike swarm suggests an enriched mantle source at about 450 Ma., and the high-TiO2 – low MgO metadiabase dikes of probable Neoproterozoic age (Ratcliffe, 1987) suggest low degrees of partial melting in a rift event at about 570 to 600 Ma, although the age of these dikes has not been determined.

10: REFINING THE TIMING OF FAUNAL TURNOVER IN THE MIDDLE DEVONIAN APPALACHIAN BASIN: PALEOECOLOGICAL ANALYSIS OF THE EARLIEST HAMILTON FAUNA AND A REVISION OF THE BASE OF THE GIVETIAN STAGE IN EASTERN NORTH AMERICA
Alex Bartholomew
Thomas Schramm
State University of New York at New Paltz
Charles Ver Straeten
Jeffery Over
State University of New York at Geneseo
The Middle Devonian of the Appalachian Basin has long been a testing ground for various evolutionary and paleoecological hypotheses (Eldredge and Gould, 1972; Brett and Baird, 1995; etc.). Units such as the Onondaga Limestone and Hamilton Group contain an excellently preserved invertebrate fauna spanning a wide array of marine facies ranging from shallow, reefal environments with diverse faunas to deep-water, dysoxic settings typified by nearly monospecific assemblages. The well-documented nature of the stratigraphy of the Middle Devonian rocks of New York State in particular makes this interval the perfect area in which to investigate the spatial and temporal nature of paleoecology and faunal turnover during this critical interval in Earth history.
Workers such as Cleland (1903) recognized early on the presence of patterns of extended intervals of faunal stability within the Middle Devonian of New York State, patterns that lead Brett and Baird (1995) to the formation of the hypothesis of Coordinated Stasis. Their hypothesis states that there are extended intervals of compositional faunal stability, termed evolutionary-ecological subunits (EE subunits), within various environments throughout geologic time, that are bounded by relatively rapid pulses of faunal turnover with very low amounts of taxonomic hold-over between stable intervals.
More recent investigations on the topic of Coordinate Stasis have focused on gaining a better understanding of the type interval from which Brett and Baird formed their hypothesis within the Middle Devonian of the Appalachian Basin. Bonnelli et al. (2006) documented the nature of abundance patterns within the Hamilton EE subunit, noting that faunas from similar paleoecological settings had high levels of compositional stability but low levels of stability when taking abundance of the taxa into consideration; although the composition of the top ten taxa changed little from bed to bed, the abundance ordering between beds was quite different. A more recent study by Brett et al. (2007) focused on patterns of biofacies tracking within the Hamilton EE subunit, noting high levels of similarity of taxonomic relative abundance within biofaces through depositional cycles. While these studies have documented the nature of the intervals of faunal stability, the intervening periods of faunal turnover remain as yet poorly understood. The present study aims to shed light on the details of the faunal turnover between two of the EE subunits with the Middle Devonian of the Appalachian Basin, the Stony Hollow and Hamilton EE subunits, specifically examining how rapid was that turnover and how quickly were the previously documented suit of biofaces from the Hamilton interval established within the basin.

10: REFINING THE TIMING OF FAUNAL TURNOVER IN THE MIDDLE DEVONIAN APPALACHIAN BASIN: PALEOECOLOGICAL ANALYSIS OF THE EARLIEST HAMILTON FAUNA AND A REVISION OF THE BASE OF THE GIVETIAN STAGE IN EASTERN NORTH AMERICA

Upper Ordovician Martinsburg Shale outcrops

Cross Rondout Creek

Lower Devonian Port Ewen Fm. outcrops

Lower Devonian Port Ewen, Alsen, and Becraft Fm.'s

Lower Devonian Schoharie Fm.

Lower-Middle Devonian Onondaga Fm.

Onondaga Fm

STOP 1. City View Terrace.
Our first stop this morning will be used to set up the stratigraphic and faunal story that will be the focus of today's trip. The outcrop along City View Terrace consists of shales and siltstones of the middle Union Springs Fm. and is the type locality for the base of the Stony Hollow Member with the upper-most portion of the underlying Bakover Member also being exposed (Figure 5). The contact between the two formations is marked by a layer of carbonate concretions as well as a discrete color change from dark-gray to black shales below to lighter-gray shales above; the concretions contain rare goniatites (Cabrieroceras) (Figure 18). This outcrop is a good example of the sediments that were deposited during the initial phases of the second tectophase of the Acadian Orogeny (Ettensohn, 1985). The downwarping of the edge of the craton due to back thrusting of the magmatic arc to the east created an over-deepened basin containing dysoxic to anoxic bottom waters allowing little to no benthic faunas to exist. Associated with this initial tectonic deepening is an eustatic sea level rise that brought warm, equatorial waters and associated faunas down to the south into the Appalachian Basin during this time; this is the local manifestation of the Kacak Bioevent. We see the first influx of warm-water adapted taxa in the upper Union Springs with the appearance of pelagic cephalopods previously unknown in much of the basin, such as Cabrieroceras. Additional taxa invade into the basin, displacing the preexisting cold-water adapted taxa, with a moderately diverse benthic fauna being present in the overlying Stony Hollow Member; this fauna has been termed the Stony Hollow Fauna (Figure 2). Today we will be primarily examining the interval that records a return to more 'normal' conditions for the Appalachian Basin near the end of the Kacak Bioevent showing a return of cold-water adapted taxa into the basin (Figure 4) associated with basin shallowing and associated sea level fall within the overlying East Berne Member of the Mt. Marion Fm.

Middle Devonian Stony Hollow Member of Union Springs Fm.

Middle Devonian Otsego Member of Mt. Marion Fm.

STOP 2. Route 209.
Halihan Hill Bed in outcrop to right marking boundary between the East Berne Member (below) and Otsego Member (above) of Mt. Marion Fm.
At this stop we will be dropped off at the southern end of the outcrop and walk upwards through the section from the upper Stony Hollow Member, through boundary of the Union Springs and Mt. Marion Fm. at the base of the Cherry Valley Member, then into the overlying East Berne Member with a fine exposure of the Dave Elliot Bed, finishing up at the Halihan Hill Bed at the base of the Otsego Member where we will reboard the vehicles (Figure 5). Starting at the southern end of the outcrop we are in the upper siltstones and sandstones of the Stony Hollow Member (Figure 19). The unit is bioturbated and contains several shelly horizons including the lower and upper Proëtid beds containing a diverse example of the Stony Hollow Fauna (Figure 2). In the interval between the upper Proëtid Bed and the base of the Cherry Valley Member is the Hurley Member of Ver Straeten et al. (1994). This interval contains the distinctive goniatite Agoniatites nodiferans. Only the lower ∼2 m of the Cherry Valley Member is exposed here consisting of thick-bedded sandstone with a depauperate fauna of dominantly leiorhynchid brachiopods (Cherryvalleyrostrum).
Sadly, the contact between the Cherry Valley Member and the overlying East Berne Member is covered here, but only for ∼10 m or so. The lowest portions of the East Berne Member are medium-gray, fine-grained, very fissile shales that grade upwards with more and more silts. Near the middle of the member, we see the entrance of thicker-bedded siltstones and fine-grained sandstones. These beds are very homogenous inside and show little to no burrowing in nearly every instance at this outcrop. We interpret these beds to be storm-derived sediments that were most likely deposited nearly instantaneously into deep, dysoxic waters. Continuing up section we first come to a distinct rusty horizon that contains an incredible abundance of infaunal nuculid bivalves (Nuculoidea) (Figure 20). Approximately 2 m above this bed is a distinctive horizon of vertically-oriented concretions formed around tubular pyritic burrows. This bed is ∼1 m below the Dave Elliot Bed, another rusty horizon with abundant nuculid bivalves and rare leiorhynchid brahiopods and cephalopods. This bed represents a 'dirtier' water version of the leiorhynchid biofacies of Brett et al. (2007) (Figure 15). Continuing upwards we see thicker and thicker siltstone and sandstone beds until near the northern end of the outcrop we encounter the diverse Halihan Hill Bed that contains abundant spiriferid brachiopods and common small rugosan corals.

Stony Hollow Member

Cross Sawkill Creek

East Berne Member

Cross Plattekill Creek

Otsego Member

Mt. Marion to west of Thruway

Big Quarry in East Berne Member on north end of Mt. Marion

REST STOP at Stewart's/MacDonald's

Onondaga Fm.

Kaatsban Stone Church (Kaatsban is Dutch for tennis court)

STOP 3. Dave Elliot Quarry.
Stop 3 is the type locality of the Dave Elliot Bed along Dave Elliot Road (Figure 5, 21). This small quarry exposes ∼10 m of the upper East Berne Member and dip markedly to the west. The Dave Elliot Bed consisting of a ∼20 cm siltstone bed containing an abundance of chonetid brachiopods exposed near the eastern end of the quarry, holding up a small terrace; many of the brachiopods in the bed are distinctly white in color at this locality. Also present in the fauna of the bed here are rare to common spirifers and common emmanuellid brachiopods. The biofacies preserve here would be consistent with the chonetid biofaces of Brett et al. (2007) (Figure 15).

Cross Kaaterskill Creek just above High Falls

Stony Hollow and Cherry Valley members
Base of Cherry Valley Member marks the base of the Mt. Marion Fm.

Upper Proetid Bed of Stony Hollow Member

STOP 4. Sandy Plains Road.
The Dave Elliot Bed at Sandy Plains Road (Figure 5) is exposed at the top of a ∼1.5 m sandstone bed and is dominated by crinoidal debris, abundant spiriferid brachiopods along with with rare bryozoans. It is interesting to note that the upper portion of the East Berne Member has coarsened considerable in this area, with the sandstone containing the Dave Elliot Bed thickening by almost an order of magnitude (Figure 22). The biofacies preserved in the bed here most closely resemble a moderately diverse brachiopod assemblage of the Hamilton Group (Figure 15).

LUNCH STOP - Butter Milk Falls.
Our lunch stop today is a picturesque spot at the Buttermilk Falls preserve just north of Leeds (Figure 5, 23). Exposed in the stream is the uppermost portion of the Stony Hollow Member and the overlying Cherry Valley Member. Continuing upstream the East Berne is exposed on private property and consists of silty shales with numerous thin-bedded sandstones. The main face of the falls where we will eat lunch is the upper Proëtid Bed and the distinctive brachiopods Variatrypa arctica and Pentamerella cf. wintereri have been found here representing the Stony Hollow Fauna. The smaller falls just upstream from the main falls is the Cherry Valley sandstone and is distinctly cleaved at this locality. The Dave Elliot Bed is present upstream and forms another ∼4 m waterfalls and very closely resembles that seen at Sandy Plains Road just to the south (Figure 24).

Onondaga Fm. outcrops all along this road

Quarry on left, Albany Co. line

STOP 5. Gedney Hill Road.
Stop 5 today is an exposure of the middle portion of the East Berne Member along Gedney Hill Road (Figure 5). We have skipped what are perhaps some of the most interesting exposures of the Dave Elliot Bed in the intervening area between Buttermilk Falls and here, however access to these exposures is limited at this time. We will walk up through the entirety of the exposure of the East Berne Member here as parking is limited. The Dave Elliot Bed is here represented by a ∼1 m very hard quartz-rich sandstone bed (Figure 25) and contains an abundant fauna of brachiopods (Athyris, Mediospirifer, Mucrospirifer, Tropidoleptus) and rare corals and conulariids and would sit somewhere between the diverse brachiopod biofacies and the coral bed biofacies in the parlance of Brett et al. (2007) (Figure 15). In between here at Butter Milk Falls are the Earlton and Stanton Hill Ravine sections. The Dave Elliot Bed at Earlton contains the most diverse fauna yet discovered including rare tabulate corals, moderately-common rugosan corals, and abundant spiriferid and athyrid brachiopods. This biofacies is the closest we get within the interval to the coral bed biofacies of Brett et al. (2007) (Figure 15). The outcrop of the Dave Elliot Bed at Stanton Hill Ravine is similar in lithology to the exposure at Gedney Hill Road, however the fauna is less diverse (entirely lacking in corals) and almost entirely dominated by Tropidoleptus. This association would sit on the 'dirtier' side somewhere between the diverse brachiopod and Athyris-Mediospirifer biofacies of Brett et al. (2007) (Figure 15).

End of Gulch Cave to right

Onesquethaw Cave to left

Cross Onequethaw Creek;
Nice fold in creek in upper Onondaga Fm.

Clarksville Cave

Cross Onesquethaw Creek

REST STOP

STOP 6. Hannacroix Ravine.
The last stop today will be at Hannacroix Ravine (Figure 5). We consider this locality is somewhat of a 'Rosetta Stone' of sorts for the East Berne Member as it contains numerous individual fossiliferous horizons in addition to a number of well-developed small-scale cycles throughout the member. The abundance of thin, shelly horizons within this exposure confused us at first as to the proper identification of the true Dave Elliot interval, however this led to the discovery of some very important fossils that might have otherwise gone unnoticed. The actual Dave Elliot Bed consists of a ∼0.75 m thick silty sandstone with Zoophycus burrows and a fauna dominated by spirifered brachiopods and conulariids and is underlain by the distinctive vertically-oriented concretions; the bed itself caps a small falls within the creek (Figure 25).
We have, to date, found nine distinct fossiliferous horizons within the middle to upper East Berne Member at this locality (Figure 27, 28). Besides the Dave Elliot Bed, the horizon with the most well-developed fauna forms a ∼30 cm interval with dispersed abundant nuculid bivalves, rare leiorhynchid brachiopods, and common nautiloid and goniatite cephalopods. This interval is underlain by two distinct 'gummy' clay horizons (possible bentonites, see discussion in main body of text). We have provisionally named this interval the Hannacroix Ravine Bed. Of great importance was the discovery at this site of the zonally important goniatite Tornoceras aff. mesopleuron (Figure 29, graciously identified for us by Dr. R. Thomas Becker of Muenster, Germany). At the standard section for the base of the Givetian in Morocco, this taxa first appears just above the base of the P. hemiansatus conodont zone that marks the base of the Givetian Stage and the occurrence of this taxa in the Dave Elliot Bed here marks its lowest record in eastern North America to date and helps to establish the base of the Givetian Stage as occurring somewhere below this bed and above the top of the Cherry Valley Member which contains conodonts indicative of the upper Eifelian (T. kockelianus Zone) and puts the lower East Berne in the P. ensensis Zone (Figure 30).
Between the Dave Elliot Bed and the Halihan Hill Bed at the top of the East Berne, there are at least four distinct fossiliferous horizons, each becoming progressively more diverse as you proceed up-section. Between the Hannacroix Ravine Bed and the Dave Elliot Bed are two, thin fossiliferous horizons dominated by scattered nuculid bivalves. There are also two nuclulid-dominated horizons below the Hannacroix Ravine Bed that can be traced through the ravine and out onto the road where the lowest forms a ∼2 m falls in a side gully entering from a ditch to the south of the main ravine; the upper of the two beds is visible further up the ditch to the south. A more detailed investigation of the entire East Berne Member is planned for this section. To date no fossiliferous horizons have been found downstream of the road culvert, although a picturesque waterfall is present about 100 yards downstream providing an accessible lower section that needs more work.

11: THE CLASSIC BARROVIAN METAMORPHIC SEQUENCE OF DUTCHESS COUNTY AND ITS STRUCTURAL AND STRATIGRAPHIC CONTEXT IN THE TACONIC OROGENY
Frederick W. Vollmer
Department of Geological Sciences
State University of New York at New Paltz
New Paltz, New York
Jeffrey Walker
Department of Earth Science and Geography
Vassar College
Poughkeepsie, New York
Introduction
etamorphism in Dutchess County, NY has been considered a classic example of Barrovian-type metamorphism since early mapping of the region (Knopf, 1927; Balk, 1936; Barth, 1936). Interestingly enough, few workers have extended the work that Balk and Barth began. People have been willing to accept it as classic without further testing (notable exceptions are the work of Bence, Vidale, Whitney and their coworkers). In his 1998 NYSGA field guide to Dutchess County, Donnelly remarks that "The area remains one of the clearest Barrovian sequences in the world." And yet, there are unanswered questions about the metamorphism. Some questions arise because of the complexities of the stratigraphy and the timing of episodes of deformation, metamorphism, and fluid flow. Others arise because of new analytical techniques that can be brought to bear to help elucidate the complex metamorphic history of the rocks.
The metamorphic sequence in Dutchess County begins with chlorite grade rocks at the Hudson River (Figure 1; Stop 1 in this guide; all pelitic rocks east of the Shawangunk Ridge in Ulster County contain chlorite, although whether detrital or authigenic/metamorphic is not always clear) and progresses beyond the second sillimanite (sillimanite-orthoclase) isograd near the Connecticut border (Stop 8). Rocks now exposed over a distance of about 30 km were tectonically buried as much as 25 km (Bence and McLelland, 1976; Whitney et al., 1996b) during the Taconic Orogeny. The sequence was subsequently tilted to its present orientation during uplift to the east associated with the Acadian Orogeny. In addition to isograd mineral growth, the prograde sequence also demonstrates fabric development from phacoidal cleavage at the Hudson River, through phyllites and schists in the middle of the county, to gneissic fabric near the Connecticut border.
Balk (1936) and Barth (1936) believed that metamorphism in Dutchess County was due to "steeping" of the pelitic rocks in igneous fluids emanating from magmas deeper within the crust. They cited as evidence the fact that granitoid intrusions are found to the east and south (in Connecticut and Westchester County, NY, respectively), on strike with the increasing metamorphic gradient mapped in the county. Some of these granites, however, contain muscovite suggesting that they are peraluminous S-type granitoids formed by partial melting of a source dominated by sedimentary material (Winter, 2001, p. 350). Some outcrops in the sillimanite zone of Dutchess County contain qtz-fsp-mica veins which Barth (1936) interpreted as apophyses from the granitoid intrusions. These veins have also been interpreted as leucosomes from anatectic melting of the sediments (Bence and McLelland, 1976; Whitney, personal communication, 2009). Most workers now believe that the heat for metamorphism was generated by tectonic burial of the rocks during the Taconic Orogeny although fluid flow was probably an important heat-transfer mechanism (Whitney et al., 1996b).
The classic nature of the metamorphic sequence in Dutchess County, and its excellence for teaching, mean that a number of very good field guides are available for the area (Bence and McLelland, 1976; Donnelly, 1998; Whitney and Peck, 2004). Bence and McLelland's 1976 NYSGA field guide provided a thorough discussion of the sequence, and identified many of the outcrops that have since become almost mandatory on local field trips (Stops 2, 4, 6, 7 and 9 in this guide). They also included whole rock chemical analyses, and microprobe analyses of individual miner - als that are very helpful for understanding metamorphic conditions. Additional sources of whole rock analyses are Vidale (1974b), Whitney et al. (1996b) and Donnelly (1998). Whitney et al. (1996b) also published microprobe analyses of individual mineral grains. This field trip will follow Bence and McLelland (1976) and Whitney and Peck (2004) for the higher grade (chlorite grade and higher) outcrops. To this, we add several additional topics:
We will make stops in the lower part of the chlorite zone at which we discuss the evidence for low grade metamorphism and the difficulties in distinguishing metamorphic from detrital chlorite
We stop at exposures of the Taconic melange and discuss it's significance.
We comment on some recent proposals relevant to the sometimes confusing stratigraphic nomenclature.
We comment on the development of metamorphic fabrics across the county.
We provide photomicrographs for discussion of relationships that are difficult to examine in outcrop.
We include additional equations and AFM projections to illustrate possible reactions.

11: THE CLASSIC BARROVIAN METAMORPHIC SEQUENCE OF DUTCHESS COUNTY AND ITS STRUCTURAL AND STRATIGRAPHIC CONTEXT IN THE TACONIC OROGENY

STOP A. (Optional) Austin Glen Formation
Graywacke beds here show sedimentary structures indicative of deep marine turbidity deposits, including ripple marks, graded beds, and sole marks. Although these sedimentary structures show that the beds are upright, cleavage dips more gently than the upright bedding indicating downward facing structures (Figure 5). This illustrates the complex structural relationships found in this belt due to refolding and probable post-cleavage block rotation in front of the Taconic Allochthon.

STOP B. (Optional) Austin Glen Fm. at Johnson Iorio Park
Outcrops of Middle Ordovician Austin Glen Formation thick bedded graywacke and shale show sedimentary structures typical of these deep marine turbidity current deposits that were shed to the west off the rising Taconic Mountains (Figure 6). These deposits were subsequently deformed as the Taconic Allochthon overrode them from the east. Across the Hudson River can be seen outcrops of the Taconic melange, the main Taconic thrust zone (Stop 1), and the Taconic Range to the east. The rock in these cuts is particularly well exposed because of the high percentage of sandstone, more common shale rich exposures may be more representative of a protolith for metapelite outcrops visited at subsequent stops.

Excellent exposures of the Middle Ordovician Austin Glen Fm.
Road cuts from here to the Mid-Hudson Bridge show excellent exposures of the Middle Ordovician Austin Glen Formation thick bedded graywacke and shale. The outcrop shows the variation in bed thickness and shale content, as well as numerous faults. See the descriptions above for similar exposures at Optional Stops A and B.

STOP 1. Taconic Melange at Kaal Park
Taconic melange at Kaal Park is the type locality of the Poughkeepsie Melange of Fisher. The Taconic melange is well exposed here, although large sections are covered with poison ivy. The phacoidal, or scaly, cleavage is typical of melange fabric world-wide. The shale breaks into centimeter-scale lens-like phacoids whose surfaces are polished and striated. Blocks within the melange are mainly graywacke here, and probably represent a disrupted bedded sequence similar to exposures of Austin Glen on the west side of the river at Optional Stop A. Locally, however, limestone blocks occur within the melange suggesting a sedimentary olistostromal component. The Taconic melange is a thick (kilometer-scale) tectonostratigraphic unit that occurs along the western margin of the Taconic Allochthons in the northern Appalachians, and represents a complex syn-sedimentary fault zone associated with allochthon emplacement. To the north, the Taconic melange is unconformably overlain by the Silurian Helderberg Group (Vollmer,1981), establishing it's Taconian age.
Many exposures of "Normanskill" or "Snake Hill" shale in the Poughkeepsie area show clasts suggestive of melange, and the Taconic melange is suggested to be a potential protolith for some of the metapelites (such as Walloomsac) examined at subsequent stops.

STOP C. (Optional) Wappinger Group Carbonates
For optional stop C, park on Henmond Road to the right just past the outcrop and return on foot.
Outcrop of Wappinger Group carbonates, possible protolith for metacarbonates to be examined at Stop 9.

Cross Wappinger Creek

Cross Sprout Creek

STOP 2. Chlorite Zone at Noxon Road
These outcrops are within the Taconic Allochthon, and show considerable structural complexity. The rock here is chlorite grade, and exhibits slaty cleavage, abundant chevron folds, and crenulation cleavage that folds an earlier foliation subparallel to bedding. Thin sections show that cleavage formation is dominated by pressure solution, a likely source of quartz veins (Figure 8 and 9). Witney et al. (1996) suggest that the chlorite forms from clay minerals. These reactions release silica that may also contribute SiO2 to the formation of quartz veins. Four distinct lithologic units are present within these outcrops: graywacke and dark shale, green slates, red slates, and slate with interbedded micrite. The contacts do not trace directly across the road, and are either part of steeply plunging structures or are discontinuous. Fisher and Warthin (1976) and Bence and McLelland (1976) assign the graywacke unit to Mount Merino (at the far west end), and the other three to the Indian River Formation. Structurally this outcrop lies within the Giddings Brook Slice, the the structurally lowest slice of the Taconic Allochthon (Stanley and Ratcliffe, 1985).
On the south side of the road, west of the main outcrops, are dark crenulated slates and folded graywacke beds. Bottom structures exposed in a meter-scale synform indicate the folds are upward facing. This unit is in contact with green slates further east on the north side of the outcrop, where quartz veining indicate faulting along the contact. It seems likely that this unit is equivalent to the Austin Glen/Pawlet, and represents flysch deposited on the continental rise and subsequently carried with the allochthon (see main text).
The bulk of the main outcrop consists of highly folded and crenulated green slate with some interbedded chert and siltstone, however on the south side of the road is a large section of red slates of typical Indian River aspect. Bence and McLelland (1976) report hematite is present in the red slates, and absent in the green slates. The presence of hematite in Indian River has been attributed to both primary and secondary origins (e.g., Bird and Dewey, 1970; Bence and McLelland, 1976), and may represent erosion of a weathered horizon exposed as a foreland bulge during the Taconic Orogeny. If the graywacke unit is Austin Glen/Pawlet, then the Mount Merino may be represented by the green slates with cherty interlayers.
At the eastern end of the outcrop on the north side, a unit of banded gray micrites and interlayered slate is in contact with the green slate. The contact between the two units is complex, and disruption of the micrite beds is suggestive of soft sediment deformation with a strong tectonic overprint. This unit is remarkably similar to thinly bedded to brecciated micrites at Schodack Landing, also within the Giddings Brook slice, which have been interpreted as slump deposits on the continental slope (Bird and Dewey, 1975; Friedman, 1979). This unit likely has a similar origin.
As we drive east from this stop we will leave the Giddings Brook slice, and shortly enter the structurally higher Everett slice. The remaining metapelite stops, except possibly Stop 5, are below the Everett slice (Stanley and Ratcliffe, 1985).

Cross Jackson Creek

STOP 3. Biotite Zone at Perkins Lane
Black slates in biotite zone, although biotite is not visible in hand sample. These rocks are assigned to the Walloomsac Formation and are believed to be deposited on Wappinger Group shelf carbonates, which underlie Clove Valley just to the east. Thus, tectonically, these are exposed in a window and represent flysch overridden by the allochthon, or are brought up with basement by late reverse faults.
The main cleavage in the outcrop is relatively low angle, suggestive of high shear strains associated with allochthon emplacement. Numerous folded veins are related to shortening across the cleavage (Figure 10). Whitney, et al. (1996b) propose that biotite could form by the reaction:
phengite + chlorite = biotite + muscovite + quartz + H2O
An AFM projection for the upper biotite zone shows that at this grade biotite is stable for a wide range of pelitic compositions (Figure 11A).

Lunch Stop - Tymor Park.
South of the picnic area a dirt road runs through a spectacular gorge in the Wappingers Group dolostones to Furnace Pond. The pond was named either for a lime mill that stood on its shore (on Lime Mill Road), or for the Clove Springs Ironworks whose furnaces processed up to 700 tons of iron ore from Union Vale mines during the 19th century. Remains of the ironworks can be seen south of the park on Furnace Road.

STOP 4. Garnet Zone at Wingdale Mountain Road
Garnet zone with chloritoid. At this point we have crossed the garnet isograd, and garnets are now present in hand sample, although not always easy to find. Downhill from the parking area are biotite-bearing dark schists and metagraywackes (Figure 12). Garnet is found in the more fine-grained beds, which are presumably more aluminous than the graywackes. Whitney et al. (1996b) propose the reaction:
chlorite + muscovite = biotite + quartz + H2O
Across from the pull out, near a gated entrance, are chloritoid-bearing schists (Figures 13 and 14), suggesting the reaction:
chloritoid + biotite + quartz = garnet + muscovite + H2O
Bence and McLelland (1976) attribute the mineralogical difference between these two outcrops to a more aluminous protolith, and the separation of the two bulk compositions by the garnet-chlorite tie line in an AKFM projection (Figure 11B). Note that the tie line switch in the biotite (Stop 3) to garnet (Stop 4) zone transition (Figures 11A and 11B) allows garnet to occur in typical pelitic compositions.
In thin sections from the lower outcrop, biotite is found growing across a crenulation cleavage, suggesting post-tectonic growth (Figure 12). Thin sections from the chloritoid-bearing outcrop show clear rotation of chloritoid and garnet porphyroblasts associated with shear strain (Figures 13 and 14). These porphyroblasts have overgrown an early foliation which has then been rotated during continued or later deformation.

STOP 5a. Staurolite Zone (Alternate stop with better parking)
Alternate stop location with better parking than Stop 5 without requiring permission. Pull out is on left at hair pin turn. It is suggested that cars turn around below and return to park on right, facing up hill. Outcrops are across from pull out and up hill on right.

STOP 5. Staurolite Zone at Beebe Hill Road
Coarse biotite-muscovite schists with garnet and stauroite porphyroblasts. Rocks here are now well within the staurolite zone, and contain centimeter scale garnet and staurolite porphyroblasts in the muscovite schist. This is the upper staurolite zone of Whitney, et al. (1996b), and because there is no chlorite in the rocks, the likely reaction is:
chlorite + muscovite = staurolite + biotite + quartz + H2O
A tie line switch from garnet-chlorite to staurolite-biotite occurs at this grade, making staurolite stable over a wide range of pelitic compositions (Figure 11D).

STOP D. (Optional) Lower Staurolite Zone at Still Road
Please DO NOT HAMMER on outcrop. Chloritoid is partially replaced by staurolite, and prophyroblasts are difficult to see in hand sample. As noted by Bence and McLelland (1976), five coexisting ferromagnesian phases, garnet-chloritoid-staurolite-biotite- chlorite, can be identified in thin section, a disequilibrium assemblage violating the mineralogical phase rule (Figures 11C and 15). Three different reactions are possible here (Whitney et al., 1996b):
chloritoid + quartz = staurolite + garnet + H2O
chlorite + garnet + muscovite = staurolite + biotite + quartz + H2O
garnet + chloritoid + chlorite + muscovite + ilmenite = biotite + staurolite
Careful study is needed to determine which reaction(s) are most likely because garnet may be either a product and a reactant. Figure 11C shows the chloritoid-out reaction, and the phase stability triangles for the five phases.

STOP E. (Optional) Poughquag Quartzite
The Poughquag Quartzite is the basal unit overlying Precambrian gneisses here, and is correlative with the Potsdam sandstone and similar Cambrian basal units. On NY 55 to the left (east) the unconformity of the Poughquag Quartzite with underlying Precambrian gneisses is crossed proceeding uphill. These basement rocks were carried up on reverse faults, presumably later in the orogeny, and along steeper faults, when the continental basement eventually became involved in the collisional event.

STOP 6. Kyanite Zone
Kyanite is present as small 1-2 centimeter blue blades, but is difficult to find. It appears on weathered surfaces as white sprays or rosettes on foliation planes (Figure 16), apparently with no preferred linear alignment. DO NOT HAMMER WEATHERED SURFACES, samples may easily be obtained from fresh surfaces on existing road outcrops.
In thin section the assemblage kyanite-sillimanite-staurolite-garnet has been observed (Figures 17 and 18). The kyanite appears resorbed (Figure 17), and the presence of sillimanite as fibrolite (Figure 18) in the rocks suggests a captured divarient reaction, or disequilibrium (see Figures 3, 11E and 11F). Fibrolite has been observed in close proximity (millimeters) to the kyanite. One possibility is that linked reactions are occurring in adjacent local domains separated by a chemical potential gradient as proposed by Carmichael (see Blatt et al., 2006):
kyanite + quartz + K+ + H2O = muscovite + H+
muscovite + H+ = sillimanite + quartz + K+ + H2O
This allows the reaction to proceed without direct contact of the polymorphs. However, in the sample described here, this requires chemical potential gradients at a millimeter scale. Another possible reaction to explain the presence of fibrolite (Whitney et al., 1996b) is:
staurolite + muscovite + quartz = biotite + sillimanite + H2O
Again, this seems to require a strong chemical potential gradient and extremely limited fluid mobility.
Whitney et al. (1996) noted that fibrolite first occurs in the kyanite zone. They discuss this in detail, and present several hypotheses to explain this. Variation in Mg content between layers and a reaction involving staurolite is ruled out by them, as they did not find evidence of staurolite in fibrolitic sillimanite-bearing layers. They suggest instead that the fibrolite may have grown at a later time (later Taconic or possibly Acadian), and that the reaction may be related to fluid infiltration, with fibrolite growth controlled by differences in local permeability and possible metasomatic Al-enrichment.
As discussed in the main text, two metamorphic events have been identified in Dutchess County (Sutter et al., 1985), and may be related to these perplexing apparent disequilibrium assemblages.

STOP 7. Sillimanite Zone at Quaker Hill Road
Park on right using CAUTION DUE TO NARROW SHOULDER. Hazard blinkers and flag person recommended. Alternate parking is just below hairpin curve at bottom of hill (UTM 18T 0619799 4602388).
Prismatic sillimanite crystals are evident in thin section (Figure 19), but not visible in outcrop. Small pegmatite dikes containing tourmaline-muscovite- potassium feldspar-quartz intrude the sillimanite-garnet-muscovite schists, and provide evidence of anatectic melting (as opposed to quartz veins formed by lower temperature pressure solution dissolution and precipitation). In thin section (Figure 19) there is evidence for the reaction:
muscovite + quartz = sillimanite + potassium feldspar
Note that the sillimanite between the muscovite and potassium feldspar has a coarser prismatic form than that between the quartz and potassium feldspar. A possible explanation is that ion mobility was greater along the muscovite- potassium feldspar interface than the quartz-potassium feldspar interface due to easier fluid migration, so growth was favored over nucleation.

Alternate parking for Stop 7.

STOP 8. Sillimanite-Potassium Feldspar Zone at Burgess Road
Manhattan schist here displays more pronounced gneissic banding, and tourmaline-muscovite-potassium feldspar-quartz pegmatite dikes. Whitney and Peck (2004) assign this outcrop to the Sillimanite-Potassium Feldspar zone.

STOP 9. Metacarbonates of the Briarcliff Dolostone
Outcrops of diopside-tromolite- phlogopite marble that represent the metamorphism of carbonates to metamorphic grades approaching the sillimanite zone. One layer in particular contains a high concentration of diopside tablets and sprays (Figures 9 and 10). The diopsidic composition of these unusual forms was confirmed by thin section and X-ray diffraction analysis. Remnants of the less ductile silica-bearing beds within the marble record extreme ductile folding and boudinage, testifying to the high temperature deformation they enjoyed.

12: THE SHAWANGUNK AND MARTINSBURG FORMATIONS REVISITED: SEDIMENTOLOGY, STRATIGRAPHY, MINERALOGY, GEOCHEMISTRY, STRUCTURE AND PALEONTOLOGY
Howard R. Feldman
Division of Paleontology (Invertebrates)
Museum of Natural History
Street at Central Park West
New York, NY 10024
Jack B. Epstein
Geologist Emeritus, MS926A
US Geological Survey
12201 Sunrise Valley Drive
Reston, VA 20192
John A. Smoliga
Senior Principal Scientist
Solid-State Characterization
Analytical Sciences,
Boehringer Ingelheim Pharmaceuticals, Inc.
In southeastern New York Middle Silurian Shawangunk Formation (Figure 1), containing gray conglomerate, sandstone and shale, lies unconformably above the Ordovician Martinsburg Formation, consisting of shales and graywackes. In southwestern New York, near the Port Jervis area, The Shawangunk Formation is overlain by the Bloomsburg Red Beds, the same stratigraphic sequence that occurs in Pennsylvania and New Jersey to the southwest. The Shawangunk Formation thins gradually from Port Jervis to its pinchout near Hidden Valley and Binnewater, New York. Two tongues of the upper part of the Shawangunk are: the Ellenville Tongue that extends from the Ellenville-Accord area to its feather edge just southwest of the New York-New Jersey border and, the High View Tongue that is restricted to the Wurtsboro area (Epstein and Lyttle, 1987; Epstein, 1993).
Early in the Paleozoic carbonate banks lay along the east coast of the ancient North American continent. During the Ordovician plate convergence commenced in the closing of the Iapetus Sea and a deep basin developed into which thick muds and dirty sands were deposited. These were later lithified into the Martinsburg Formation. Eventually, with continued compression, these sediments were folded and faulted during the complex deformation of the Taconic Orogeny. The trend of these folds in southeastern New York is approximately N20E. As one proceeds westward across the Wallkill Valley these structures become less intense. Subsequent to the Taconic Orogeny mountains rose to the east and coarse sediments were transported westward and deposited as the conglomerates and sandstones of the Shawangunk Formation across the beveled folds of the Martinsburg. Deposition occurred on a plain of alluviation and in a marine basin to the northwest. Erosion of the source area was intense, and the climate, based on the mineralogy of the rocks, was warm and at least semiarid. The source was composed predominately of sedimentary and low-grade metamorphic rocks with exceptionally abundant quartz veins and small local areas of gneiss and granite. As the source highlands were eroded, the steep braided streams of the Shawangunk gave way to more gentle-gradient streams of the Bloomsburg Red Beds.

12: THE SHAWANGUNK AND MARTINSBURG FORMATIONS REVISITED: SEDIMENTOLOGY, STRATIGRAPHY, MINERALOGY, GEOCHEMISTRY, STRUCTURE AND PALEONTOLOGY

Leave parking lot at SUNY New Paltz.
This locality is on blacktop of Holocene age, conformably overlying fill of unknown age brought in by contractors.

Cross bridge over Wallkill River.

Continue straight up steep hill.
Several sharp curves will signal approach to the top of hill. Note outcrops of Martinsburg Formation on right, consisting of thin-bedded shale, minor siltstone, and very rusty weathering with fine-grained graywacke. Cleavage is poorly developed.

Stop at gatehouse and check in.

STOP 1. We Will Be Spending About 2 Hours Here Examining Various Outcrops on the Mohonk Mountain House Grounds.
Please, no hammers, only cameras! The Shawangunk (pronounced Shongum) Formation (Figure 1) was deposited during the Silurian Period, approximately 438-418 million years ago. At that time a shallow sea covered the southeastern part of New York State into which drained rivers and streams. The bottoms of these streams were layered with pieces of abraded quartz. Constant motion of the water eroded the chunks of quartz into sub-rounded 'pebbles' that were eventually "glued" together by silica-rich cement carried by percolating ground water. The name of the sedimentary rock formed by this process is conglomerate (Figure 2). The exact source of the quartz that makes up the conglomerate is not clear. It may have formed by braided streams or alluvial fan deposition. A braided stream divides into an interlacing network of several small branching and reuniting shallow channels. An alluvial fan is a low outspread flat to gently sloping mass of rock material shaped like an open fan, deposited by a stream at the place where it issues from a narrow mountain valley upon a plain (Jackson, 1997). The Shawangunk Mountains (Figure 3) extend to the southwest into New Jersey where they are called the Kittatinny Mountains. The Shawangunk Formation ranges in thickness from 733 m (2,200 ft) near Ellenville, to the southwest, to <1 m (about 1 ft) near Hidden Valley, to the northeast, finally 'pinching out' and disappearing. Stratigraphically below the Shawangunk lies the Middle to Late Ordovician age (489-439 million years old) Martinsburg Formation, consisting mostly of shale, up to a thickness of almost 3333 m (10,000 ft).
Glacial Geology
Note the beautiful glacially paved surface with striations and chattermarks. Chattermarks are small, closely spaced curved scars or cracks made by chipping a brittle bedrock surface, in this case the conglomerate, by rock fragments carried in the base of a glacier. Each chattermark is roughly transverse to the direction of ice movement and its 'horns' point in the direction the glacier moved. Compare the direction of the striations here (about 10 degrees to the northeast) with the direction of the striations at the top of the crevice (about 20 degrees to the northwest). As the glacier moved down through the valley a small lobe moved around the ridge changing direction slightly resulting in a change in strike.
Mineralization within the Shawangunk Formation
The sulfide mineralization observed within the Shawangunk Formation along Eagle cliff consists of predominately marcasite and pyrite with small amounts of chalcopyrite (Figure 4). The sulfides are disseminated within the conglomerate. Emplacement appears to be associated with fault structures. SEM/EDS analysis of the sulfides also shows trace amounts of lead and zinc. Gossan in the form of goethite, hematite and jarosite has formed in places as a result of sulfide weathering. In some areas the water soluble sulfate minerals melanterite Fe(SO4)·7H2O) and rozenite Fe(SO4)·4H2O) are observed as a white to yellowish encrustation on the surface of sulfide containing exposures, when weather conditions permit (Figure 5). One from Eagle Cliff (valley side) sample contained two hydrated Fe-sulfate phases: melanterite Fe(SO4)·7H2O) and rozenite Fe(SO4)·4H2O). Rozenite is a lower hydrate containing 4 moles of water, as compared to melanterite which contains 7 moles of water. Rozenite can be formed in one of two ways: 1. Dehydration of melanterite or, 2. during lower relative humidity conditions; at room temperature rozenite is the stable phase below 70-80% RH. Examination by polarized light microscopy of the sample shows euhedral (well formed) crystals of rozenite encased in melanterite. This relationship indicates that the rozenite crystallized first, followed by the melanterite. Additionally, no alteration/dehydration textures were observed in the melanterite. From this we conclude that the rozenite crystallized during lower RH conditions, followed by melanterite which crystallized during increased RH conditions (i.e., above 70-80% RH depending on ambient temperature).
The Sky Lakes
Looking toward the southwest observe the ridge forming the "backbone" of the Shawangunks. Continuing along the ridge, located at its highest point about 30km (10 mi) away, is Sam's Point and the Ice Caves, so called because of the cold air trapped at the bottom of open vertical joints. Within the deep recesses of the caves one can find ice that lasts all summer long. Along the top of the Shawangunk Ridge are located four "Sky Lakes" in addition to Mohonk Lake (Figure 6), that are so-called because they receive their water supply solely from rainwater. These lakes are Minnewaska (closest to Mohonk), Awosting, Mud Pond and Maratanza. The lakes most likely overlie faults that weakened the bedrock, which was then scooped up by the passing glaciers. Interestingly, Mohonk Lake (Figure 6) is the only one of the five sky lakes that has greenish water; the others have clear blue water. The reason for this is that the acidic pH of the water of the four sky lakes (4.0) precludes algae and fish from living in them. However, Mohonk Lake's water is buffered by the alkaline rocks of the underlying Martinsburg Formation that floors the southeastern portion of the lake and has a pH of 7-7.5. This raises the pH level such that the conditions are more conducive to life. Between the Shawangunks and the Catskill Front is a broad valley known as the Port Jervis trough. The trough was formed by erosion and glacial scouring of the relatively weak sediments beneath the Catskill Formation. The floor of the valley is fairly flat due to the deposition of glacial debris (till) and lake sediments. Looking toward the southeast one can see the Hudson Valley (the Hudson River is about 18km [6 mi] to the east). Continue to the Huntington Lookout summer cottage. The view here is spectacular. Toward the southwest we see the Shawangunk Ridge and the Trapps (famous among technical rock climbers). To the northwest one can see the Catskill Mountains, also known as the Catskill Front, rising in the distance to a height of 700 m (2,100 ft) above the Hudson River. The highest peak in the Catskill Mountains is Slide Mountain which rises 1,282 m (3,846 ft) above sea level. These mountains began to rise in New England and the Canadian Maritime Provinces during the Devonian Period (due to a collision of tectonic plates known as the Acadian Orogeny). Throughout the Middle and Late Devonian Period the mountains were eroded by streams and rivers that flowed toward the west, carrying vast quantities of mud and sand that were deposited on the floor of a great inland sea as the rivers lost velocity. Closer to the ancient shoreline the heavier particles settled out first, leaving mostly sands and some shale, whereas farther from the shoreline the deposits consisted of mainly shales with some sand and, farthest from the shoreline we find only shale. Thus, as the rivers and streams lost velocity, the heaviest particles (larger sand-size grains) settled out first and the smallest, finer particles settled out last forming the fine-grained shales.

Contact between the Shawangunk and Martinsburg
On right observe the (covered) contact between the Shawangunk and Martinsburg at Woodland Bridge. Note the relatively shallow dip of the shales typical of the proximity to the contact with the Shawangunk.

STOP 2. Shale Pit.
In this shale pit (Figure 7) the Martinsburg contains fault-related structures interpreted to be of two different ages. A mélange, or broken formation, is part of a mélange zone that is Taconic in age that has been carried westward over the Silurian Shawangunk in the hanging wall of the younger Kleine Kill thrust. Most of the small faults and slickensided surfaces that are common in this locality are probably related to this younger thrust fault. The trace of the Kleine Kill thrust nearby has a strike of N15E and is interpreted to be Alleghanian in age. The fault zones in the Martinsburg which clearly do not cut Silurian and younger rocks generally have: (1) a trend more northerly than the northeast-trending folds and faults in the Silurian rock, (2) a diagnostic scaly cleavage, (3) tightly folded "floating" knockers of graywacke whose axes plunge predominantly to the northeast with variable azimuth, and (4) very little, if any, vein quartz. The faults that definitely cut both the Ordovician Martinsburg and the Silurian Shawangunk, and which we interpret to be Alleghanian in age, generally have: (1) a slightly more easterly strike, (2) well-developed "pencils" in the shale formed by the intersection of bedding and cleavage, and (3) vein quartz parallel to bedding and/or cleavage that commonly contains shale fragments.
The exposure here consists of predominantly dark gray shales and siltstones interbedded with fine grained graywacke beds, occasional prominent pyrite layers and disseminated sphalerite, chalcopyrite and galena. Oscillation ripples (Figure 8) occur on some bedding surfaces. Carbonaceous material occurs mostly as fine-grained patches throughout the matrix. The studied section is tectonically stressed with shiny quartz slickensided surfaces, parallel cross-laminated strata and ripple marks. Crinoid stems, some disarticulated, and free columnals occur on different bedding surfaces, indicating a possible change in current regime. Scattered linear to sinusoidal horizontal burrow structures ranging in diameter from .5-3 cm are found on the silty beds. Some of the burrows are infilled with coarse quartz grains. The faunal constituents include brachiopods (93%), crinoids (Ectenocrinus; 3%), bivalves (3%), ostracodes (<1%), corals (<1%), trilobites (Cryptolithus, <1%) (Figure ), conulariids (<1%) and unidentified burrowers (<1%). The brachiopods are represented by a low diversity assemblage of dalmanellids and what may be a new species of Sowerbyella. The fauna can be classified into distinct trophic groups: (1) high-level suspensions feeders (crinoids, corals); (2) low-level suspension feeders (brachiopods, bivalves); (3) animals that collect food from the sediment surface (ostracodes, trilobites); and (4) animals that feed within the sediment (burrowers). This partition of feeding niches leads to a reduced competitive trophic structure and therefore increased community stability.
Mineralization within the Martinsburg Formation
Within the Martinsburg Formation at the Mohonk shale pit sulfide mineralization has also been observed. The sulfides include pyrite, chalcopyrite, galena and sphalerite. The sulfides are found associated with calcite veins and as disseminations throughout the shale. Carbonaceous material has also been observed in thin section (Figure 9).

Observe cliffs of the extremely resistant Shawangunk Fm
As we progress in a southerly direction on Butterville Road observe cliffs of the extremely resistant Shawangunk Formation on the right. The lowland and hills in the foreground are underlain by the shales and graywackes of the Martinsburg Formation, striking toward the northeast. Note Sky Top (tower) from which one can see six states (New York, New Jersey, Pennsylvania, Connecticut, Vermont, and Massachusetts). Sky Top sits atop a rock scramble and steep climb through the "Crevice" and ending with an egress called the "Lemon Squeeze." This is the signature hike of Mohonk Mountain House that is adjacent to the 6,400 acre Mohonk Preserve.

Overturned Martinsburg Formation on right
On the right note the overturned shales and thin graywackes of the Martinsburg Formation. Here there are several narrow fault zones with vein quartz.

Ahead view the "Trapps"
On the right note the steeply dipping and overturned Martinsburg shales and thin graywackes.
Ahead view the "Trapps" a world famous site for rock technical climbers located on the Mohonk Preserve. The Mohonk Preserve, founded in 1963, was established to protect the northern Shawangunk Ridge. Its mission is to protect the ecology of the area and to provide for public environmental education and recreation.

Steeply dipping and overturned Martinsburg on right.
Steeply dipping and overturned Martinsburg shales and thin graywackes on right. View of the Shawangunk cliffs at the Trapps straight ahead.

Note Martinsburg with graywackes on right.
The bedding appears to be right-side-up however, the poorly developed cleavage in the shales dips steeply to the west suggesting that both bedding and cleavage have been rotated by faulting.

We will be climbing to the top of the Shawangunk Mountains for the next mile or so.

Visitor's Center, Mohonk Preserve on right.
Shortly we will be making a sharp left turn with the Martinsburg (on the right) and shale interbedded with thin-bedded (up to 5 in), cross-bedded to planar laminated siltstone, and minor fine-grained sandstone. Soft-sediment slump folds are common in the siltstones. Cleavage is absent or very poorly developed, except near tight folds and narrow fault zones. Most of these faults and folds do not affect the overlying Shawangunk Formation and must be Taconic in age. They trend from N5E to N20E, whereas structures in the overlying Shawangunk trend in a more easterly direction.

On the left is a scenic overview of the Wallkill Valley.

The contact between the Shawangunk and Martinsburg
The contact between the Shawangunk and Martinsburg formations is exposed at two spots approximately 400 feet southwest of the road at the base of the cliffs. Fairly regular and linear mullions can be observed in the basal Shawangunk at the contact.

Conglomerates and quartzites of the Shawangunk
As we pass under the Trapps Bridge note the conglomerates and quartzites of the Shawangunk dipping to the northwest (31NW).

Cross Coxing Kill.
As we cross Coxing Kill note that the Coxing Kill Valley coincides with the trough of a broad, open syncline that plunges gently to the northeast. This is also a favorite site for skinny dipping. For the next 0.5 mile we will begin to cross a broad open anticline that exposes a window of Martinsburg that is about 2 miles long. To the right note an outcrop of basal Shawangunk with unconformably underlying shales of the Martinsburg exposed about 40 feet away. Dips in both units are very gentle and the angle of unconformity is as little as 2⁰. The divergence in strike, however, is as much as 38⁰, with the strike in the Martinsburg being more northerly. The Martinsburg here is in the broad open-fold Taconic tectonic zone (zone 3 of Epstein and Lyttle, 1987).

Peters Kill parking area on right.

Entrance to Minnewaska State Park on the left.

Trailhead leading to Lake Awosting on left.

Cross Sanders Kill.

Scenic overview of the Rondout Valley
Turn into small parking area with scenic overview of the Rondout Valley underlain by Upper Silurian through Middle Devonian rocks that are buried by a variety of glacial sediments. In the distance note the Middle and Upper Devonian clastics forming the Catskill Mountains. There is a thrust fault with nice slickensides across the road from the parking area. BE CAREFUL OF ONCOMING CARS!

STOP 3. Mysterious 'Pods'.
Walk back along NY 44/55 (north side of road) and observe the mysterious 'pods' of Feldman et al., (2009) that follow the beds (N20E; 38NW) in the upper part of the Shawangunk Formation. The pods (Figures 10, 11) are often conical with flat bottoms and associated with quartz pebbles. Note that the quartzite is recrystallized. The matrix filling the pods is often dark gray and seems to follow the bedding and/or crossbedding. WHAT ARE THEY? The pods range from 0.2 to 7 cm across (at the base) and 0.2 to 6 cm in height. Internally, the 'pods' are mostly non-recrystallized quartz grains with interstitial mica and possibly clays (Figure 12). In contrast, the areas outside the 'pods' consist of pressure solution welded quartz grains consistent with the quartzitic nature of the formation. The pods are restricted to a relatively narrow stratigraphic interval and show no evidence of internal bedding. The pods may be: (1) microbial mounds/algal mats, (2) sponges, (3) mud balls or SOMETHING ELSE! They are similar in general outline to some thrombolites in that the internal texture is non-laminated but there is no indication of microbial activity such as clotting. The possibility that they are sponges or algal mats is somewhat doubtful because the braided stream depositional environment was one of relatively fast-moving fresh water draining mountains to the southeast; in addition, most sponges live in a marine environment. The conical shape does not favor a mud ball origin. Hint: note that the gray matrix follows the cleavage. PLEASE DO NOT COLLECT SAMPLES; ACTIVE RESEARCH SITE!)