NYSGA 1996.kmz

NYSGA 1996.kml
Field Trip Guide for the 68th Annual Meeting of
the New York State Geological Association
edited by
Alan I. Benimoff
Anderson A. Ohan
Hosted by:
Department of Applied Sciences
The College of Staten Island/CUNY
Staten Island, NY 10314
This guidebook was published by the New York State Geological Association. Additional copies may be obtained from the Executive Secretary of the NYSGA:
Dr. William Kelly
Executive Secretary
New York State Geologic Survey
Room 3140 Cultural Educational Center
Albany, NY 12230

A1: EARLY JURASSIC DIABASE SHEETS AND BASALT FLOWS, NEWARK BASIN, NEW JERSEY: AN UPDATED GEOLOGICAL SUMMARY AND FIELD GUIDE1996 A1
JOHN H. PUFFER
Geology Department
Rutgers University
Newark, NJ 07102
JONATHAN HUSCH
Department of Geological and Marine Sciences
Rider University
Lawrenceville, NJ 08648-3099
INTRODUCTION
Many important features of the early Jurassic igneous rocks exposed in the northern and central Newark Basin can be examined at the stops detailed below and located in Figures 1 and 2. The narrative preceding the road log and site descriptions is an update of one presented by Puffer and others (1992) and focuses on two aspects of the igneous activity that are the subject of considerable ongoing research. Part One - The PRHL and Other Diabase Sheets reviews the petrogenetic processes responsible for producing the rock compositions found within the sheets. In particular, evidence is presented that low density, late-stage granophyric magmas, produced by the olivine-absent crystal fractionation of an Eastern North America (ENA) quartz-normative high-titanium tholeiite (HTQ) magma, migrated laterally and vertically to the highest structural levels within any given sheet. In addition, each sheet apparently differentiated as a relatively closed system with little, if any, of the residual magmas reaching the surface flows of the Watchung Basalts. Part Two - The Watchung Basalts is a review and discussion of the geochemical data showing that the youngest of the three basalts formations, the Orange Mountain Basalt, is part of a huge chemically uniform HTQ igneous province and appears to be largely unchanged by fractionation from its mantle source, either an undepleted subcontinental lithosphere or a slightly enriched lithosphere produced by previous subduction events throughout the Paleozoic. The overlying basalt formations, the Preakness and Hook Mountain Basalts, are much more chemically diverse and contain high-iron (HFQ) and low-titanium (L TQ) quartz-normative ENA magma types derived from mantle sources chemically modified or distinct from the HTQ source.

A1: EARLY JURASSIC DIABASE SHEETS AND BASALT FLOWS, NEWARK BASIN, NEW JERSEY: AN UPDATED GEOLOGICAL SUMMARY AND FIELD GUIDE1996 A1

View Site: Laurel Hill
Due to the realities of traffic congestion and aggressively enforced trespassing laws throughout the New York City area, Laurel Hill is one of several excellent sites that we will not be able to stop at. But this exposure is at least clear enough to see through the bus windows.
Laurel Hill is an almost completely exposed early Jurassic volcanic neck, consisting of three concentric zones (Puffer and Benimoff, in press). The diverse chemical composition of Laurel Hill diabase overlaps each of the major eastern North American (ENA) Jurassic diabase types. Zone 1 is an irregular, heterogeneous, border-zone characterized by chemistry resembling the low-Ti-quartz-normative type (LTQ) ENA diabase but is interpreted as an alteration product of high-Ti-quartz-normative type (HTQ) diabase. Dilution of HTQ magma with hydrothermal sericite, and with plagioclase and pyroxene that accumulated during fractionation, has reduced the TiO2 content of Zone 1 from HTQ (1.1 percent) to LTQ levels (<0.9 percent). Localized assimilation of Passaic Formation siltstone is recognized by an enrichment of Zr in some Zone 1 samples. Zone 2, the intermediate zone, is characterized by chemistry typical of HTQ-type diabase. Zone 3, the interior zone, resembles the HFQ-type (High-Fe-quartz-normative) ENA diabase and is interpreted as an HTQ fractionation product.

Observe the Palisades sill on the east
Observe the Palisades sill on the east exposed as the north-south ridge in the background.

Observe upper portions of the Palisades sill on the left.
The upper contact is hidden behind vegetation and retaining walls.

Observe the vertical leucocratic dikes
Observe the vertical leucocratic dikes cutting through black Palisades diabase. The relatively thick dikes are composed of trondhjemite while the relatively thin dikes are albatite and calcite. They are described by Benimoff and others (1989) and are interpreted as fusion products of sodic Lockatong argillite host rock. They have a chemical composition similar to the host rock.

Observe olivine zone of Palisades Sill
Follow park road to the north; observe olivine zone of Palisades Sill on left recognized as an eroded out deeply altered cut at the base of the diabase slope. Stopping on the park road is strictly forbidden, but if you park at the entrance to the park the olivine zone is only a short walk.

Observe irregular lower contact of the Palisades Sill.
Observe irregular lower contact of the Palisades Sill with the Lockatong Formation.

Observe additional exposures of the conformable Lockatong/Palisades contact on the left

STOP 1. Lower Contact Of Palisades Sill With Lockatong Hornfels
Permission From The Palisades Interstate Park Commission To Stop And Collect Along The Road Is Required.
After admiring the view of the Hudson River and Manhattan Island, walk south from the parking lot along the road to the boat launch, then up the stone steps, through the tunnel under the road, and out onto road level. Walk north along the contact of the lower chilled zone with hornfels of the Lockatong Formation. According to Gorring and Naslund (1995), the fine-grained diabase chilled zone in the Fort Lee area consists of about 1-2 percent olivine (Fo68-78), 35-55 percent augite, 1-2 percent orthopyroxene (En75-80), and 35-55 percent plagioclase (An65-70; Walker, 1969). The pyroxene-dominated (along with plagioclase), tholeiitic-trend fractionation of this HTQ-type parental magma culminated in the development of a 33 m-thick granophyre layer, or sandwich horizon (Shirley, 1987), 50-100 m below the upper contact of the 330 m-thick sheet. Because this section of the PRHL megasheet is quite conformable, there appears to be little in the way of density driven lateral migrations of residual magmas and nearby sections through the Palisades contain very similar distributions of rock types (Husch, 1990). Some thin leucocratic veins and dikes of quartzofeldspathic material cut the diabase along the road at this locality. As discussed in Part I, these may have multiple origins.
The 3-4 m-thick OZ is exposed approximately 15 m above the road level and is exposed at road level 0.1 mile east of the entrance to the park (mile 30.8). At this locality the lower contact of the OZ is somewhat gradational, although the upper contact is quite abrupt, with olivine modes falling from over 20 percent to zero within less than one meter (Gorring and Naslund, 1995). At other localities along the Hudson river, both the upper and lower contacts of the OZ can be equally sharp (Walker, 1940; Gorring and Naslund, 1995).
Although originally thought by Walker (1969) to be the result of in situ gravitational crystal settling from a second pulse of Palisades magma that produced most (if not all) of the residual, granophyric compositions found higher up in the sheet, recent studies by Rusch (1990, 1992) and Gorring and Naslund (1995) indicate that this interpretation is incorrect. Rusch (1990, 1992) showed that olivine removal is inconsistent with the geochemical fractionation trends observed for the PRHL megasheet (see Part I) and that there are large-scale features of the OZ that suggest it was a separate olivine-rich intrusion into an already formed, although still largely molten, PRHL sheet. Gorring and Naslund (1995), on the other hand, believe the OZ to have formed as part of the initial injection of the RTQ parent (or at least within 5 years of that event) and that the olivine accumulation took place prior to or during the injection sequence. Based upon the distribution of olivine within the OZ and its composition (Fig. 13), Gorring and Naslund (1995) propose a mechanical sorting of olivine by a flow differentiation mechanism, a process also suggested by Rusch (1990).
Beneath the lower contact of the Palisades are contact metamorphosed buff-colored arkoses and platy and laminated siltstones. These metasediments have been described by Olsen (1980) and correlate with other Lockatong Formation exposures to the south. The pelitic layers, in particular, have been affected by thermal metamorphism and have been converted into black hornfels consisting of biotite and albite with minor analcime, diopside, and calcite, or to green hornfels consisting of green diopside, grossularite, chlorite, and calcite with minor biotite, feldspar, amphibole, and prehnite (Van Routen, 1969).
Porphyroblasts of pinite after cordierite commonly occur as small green spots in the black biotite-albite hornfels (Miller and Puffer, 1972). Large tourmaline porphyroblasts and even larger green spherical structures, up to 4 cm across, composed largely of clinozoisite, are less common in the hornfels, but are known from several other hornfels localities in the Newark and Culpeper Basins.

STOP 1A (Optional). Upper Contact Of Palisades Sill
Along Westbound Interstate 95 (Local Lanes). Stopping Along The Highway Other Than For Emergencies Is Illegal In New Jersey. The Police Will Ask You To Leave Immediately (If You Haven't Been Arrested Already).
This rare exposure of the upper contact of the Palisades is visible on both sides of the highway. The chilled margin is almost identical in composition, mineralogy, and texture to that found at the lower contact (Stop 1). Of course, no upper analog to the OZ is seen. Overlying the upper contact are hornfels of the Lockatong Formation, again similar to those found beneath the lower contact. The contact is highly conformable at this locality with only minor cross cutting "steps" visible; a few minor faults also have offset the contact. In at least one instance, apparent cooling cracks have been filled in with overlying sediments, producing a sedimentary dike structure. Other fractures in the upper contact zone contain copper mineralization and calcite fillings.
As one walks east towards the viaduct, more interior portions of the sheet are exposed and grain size increases, as does the amount of granophyric material. Eventually, pods of pegmatitic granophyre are found within a finer-grained, less differentiated diabase. Looking south across the highway at the opposite cliff (now sheathed in metal netting to keep loose boulders from faIling onto the highway) it is possible to see a number of leucocratic dikes running vertically across the face. Benimoff and others (1989) described these dikes as being trondhjemitic in character and concluded, on the basis of geochemical data, that they represented the late-stage injection of anatectic melts, derived from country rock xenoliths, into cooling fractures.

Exposure of Orange Mountain Basalt is on the left
Continue west across valley underlain by Jurassic red-beds of the Passaic Formation. Exposure of Orange Mountain Basalt is on the left with a well defined flow contact identified by an undulating erosion surface, and the contrasting textures of the vesicular upper entablature of the lower flow and the relatively massive lower colonnade of the upper flow.

Lower contact of Preakness Basalt on the right.
Most of the actual contact has been recently hidden by a new retaining wall and some landscaping but Feltville Formation siltstones exposed here have been thermally metamorphosed by the extrusion of one of the thickest flows of flood basalt anywhere on earth. The contact metamorphism has converted the otherwise consistently red siltstone into a gray layer within 5 meter of the contact and a dark gray hornfels within 1 meter of the contact. The thickness of the lower flow is about 150 m, comparable to the thickness of the Grand Ronde flow of the Columbia River Basalt and thicker than almost any flood basalt.

Note vertical strike-slip faults through the Preakness Basalt
Note vertical strike-slip faults through the Preakness Basalt defined by eroded fault gouge. The fault planes curve below the Preakness flow and do not seem to penetrate into the underlying Feltville Formation. Apparently shearing stresses were absorbed by plastic flow of unlithified Feltville sediments. Similar strike-slip faults are exposed at each of the several trap-rock quarries cut into Orange Mt., Preakness and Hook Mt. basalts in New Jersey.

Vertical jointing of the lowest of the five Preakness flows
Note the very closely spaced vertical jointing of the lowest of the five Preakness flows. A set of tectonically generated vertical platy-prismatic joints have been superimposed onto the vertical polygonal cooling joints, probably along incipient planes of weakness opened during cooling. The joint patterns have been described and their origin has been discussed by Puffer and Student (1992) and by Faust (1978).

The discontinuous exposure of the lower flow of the Preakness Basalt on the right
The discontinuous exposure of the lower flow of the Preakness Basalt on the right was a virtually uninterrupted exposure 6 miles long during highway construction in 1987, and afforded close inspection and sampling (Puffer, 1992). The chemistry and texture is uniform although there is a slight change in composition across the lower colonnade / entablature contact. The upper contact of the flow is clearly define d by a layer of ferruginous siltstone. The chemistry of the lower flow is the most highly fractionated of the 5 Preakness flows. The least fractionated flows are the thin upper flows (flows 3,4 and 5) which have typical LTQ compositions.

Observe the variations in jointing of Preakness basalt
Observe the variations in jointing of Preakness basalt exposures on the right and the strike slip fault planes.

STOP 2. Preakness Basalt
The view to the south includes the Orange Mountain basalt of the First Watchung Mountain in the background and the valley eroded into Early Jurassic Feltville Formation red beds in the foreground. While examining the Preakness note:
1. The very uniform medium grained texture consisting largely of plagioclase and pyroxene with only minor glass or mesostasis.
2. The large flat widely spaced joint plains in strong contrast to the very closely spaced platy prismatic joints exposed along 1-78.
3. The long curved but subhorizontal step-like parallel structure on the joint surfaces. They are interpreted as the kind of boundaries that join crack segments described by DeGraff and Aydin (1987). The cracks propagate downward through layers of freshly hardened basalt in the entablature as the upper crystallization front of the flow advances down into the largely liquid crystal mush below.
4. The strike-slip fault plain eroded into the Preakness. Note the horizontal striations on the slickenside surfaces.
5. The occurrence of a few rare and small shapeless basaltic pegmatites located between crack segment boundaries, and the occurrence of discontinuous, very thin, vesicular, basaltic pegmatite layers at the crack segment boundaries as described by Puffer and Horter (1993). Although the crack segment boundaries are well defined at this exposure, the pegmatites are not particularly well developed. The size and occurrence of basaltic pegmatite is rather unpredictable but seems to be restricted to unusually thick lava flows. Probably the largest pegmatite layer found in any ENA basalt, as of 1996, was recently mapped by Richard Volkert of the New Jersey Geological Survey at a construction site in the Preakness basalt located near the Chimney Rock quarry. The pegmatite in addition to being huge is highly fractionated with only 2% MgO and as much as 3% TiO2. It also contains considerable glass, but for more details we will wait for Volkert's report.

The Weldon Trap Rock Quarry
The Weldon Trap Rock Quarry cut into Orange Mountain basalt is on the left. The basalt here is mineralized with zeolites and prehnite that lines huge vugs over 2 m across. The quality of the zeolites and prehnite is easily of museum grade but access to the quarry was denied. Chemical analyses of several basalt samples collected here are reported by Puffer (1992). Each of the three Orange Mountain flows are exposed in the quarry.

STOP 3. Orange Mountain Basalt
Walk to the monument to General George Washington at the flag pole. The view to the south-east is largely a valley eroded into Triassic red-beds. This entire view area was once occupied by Orange Mountain flood basalt. The Atlantic Ocean (Raritan Bay) is 15 miles to the south/east and can be seen on a clear day. Picnic tables and drinking fountains are available but the rest-room facilities have been closed as a cost cutting measure in defiance of the laws of nature.
The Orange Mountain Basalt exposed near the flag pole is much finer-grained than typical of the Preakness. The basalt here contains common amygdules composed of chlorite and less commonly by quartz. The columnar joint pattern is reasonably clear but lacks the sharp flat surfaces typical of Preakness exposures or the greater degree of clarity at greater depths into Orange Mountain entablatures. The irregular columnar joint pattern and amygdule content are evidence of close proximity to a flow top.

Chimney Rock Quarry in OMB on right.
This is probably the largest active trap-rock quarry in the Watchung basalts. In addition to a spectacular array of beautiful prehnite and zeolites, particularly heulandite and some of the best natrolite anywhere on earth, there is abundant native copper mineralization in the first Orange Mountain basalt flow and in the Passaic red-beds within a meter of the contact. Sheets of native copper measuring as much as a foot across are easily collected; however, permission for us to collect today was denied. Basalt flow contacts are clearly displayed with very thin layers of red-bed rock between the flows. A description of the mineral collecting here was written by Sassen (l978).

Cross North Branch of the Raritan River.

View to SW of the Cushetunk Mountain diabase (CMD).
Good view to the southwest (left) of the forested ridge, rising approximately 500 feet above the surrounding plain of the Newark Basin, formed by the northeastern arm of the Cushetunk Mountain diabase (CMD).

STOP 4. Fault Zone In Granophyric Rock
Fault Zone In Granophyric Rock of the Cushetunk Mountain Diabase West End of Round Valley North Dam, Lebanon, NJ.
Round Valley Reservoir was filled in the late 1960's and is an important source of water for many municipalities in northern and central New Jersey. It is surrounded on three sides by the arcuate ridge of the CMD. The northwest quadrant of the reservoir is bounded by Precambrian metamorphic rocks, presumably of Grenville age.
Initial geochemical data by Puffer and Lecher (1979) indicated that the CMD chilled margin composition was a quartz normative, high-iron (HFQ) ENA type. However, more recent analyses by Keely and Husch (1993) show that the CMD chilled margin composition is very similar to all other Newark Basin HTQ chills and flows. Keely and Husch (1993) also show that the composition of the interior of the CMD generally becomes more fractionated and granophyre rich as one progresses northward along the intrusion's northeastern arm (Fig. 14). This arm cross-cuts over 5000 feet of the Triassic sedimentary section, rising to within 3000 feet of the OMB, the presumed Early Jurassic paleosurface (Houghton and others, 1992). Reversals in the general fractionation trend, as is found for this stop location (Fig. 14), are believed to be due to post-intrusion normal faulting exposing deeper, less fractionated structural levels of the CMD within the footwall block (Keely and Husch, 1993).
The diabase at this locality is quite granophyric, although less so than the diabase found at the east end of the dam, and contains abundant pink alkali feldspar. Equally obvious at this exposure are numerous fracture surfaces on which well-developed slickensides are observed. Most surfaces indicate a nearly horizontal right-lateral motion, although a few surfaces suggest a normal oblique, right-lateral motion. Houghton and others (1992) map this fault zone as a normal oblique splay fault of the Flemington Fault Zone (Fig. 2). Based upon the geochemical data of Keely and Husch (1993), as much as 5000 ft of vertical offset may have occurred along the fault zone seen here between the footwall block to the west and the headwall block exposed on the opposite side of the dam to the east (see sample CMl, Fig. 14). Jakubicki and Husch (1995), utilizing two-dimensional Bouguer Anomaly modeling, confirmed the normal sense of the vertical offset, but suggested the throw was less, on the order of 1500-2000 feet. The gravity modeling of Jakubicki and Husch (1995) also confirmed the initial findings of Wofford (1962) that the CMD dips outward (Fig. 15) and has the general shape of a ring dike.

Crossing Prescott Brook. Round Valley South Dam on left.

STOP 4A (optional). Outcrops of Granophyre
At Northern End Of The Prescott Brook Diabase, Stanton, NJ.
Park along side of road immediately across from white house. Climb to top of hill on right.
The diabase at this locality is quite coarse grained and granophyre rich, with MgO concentrations as low as 1.5 weight percent (Keely and Husch, 1993). Approximately 1 km farther south (and structurally lower by approximately 1500 ft) the diabase composition is not quite as fractionated with an MgO content of approximately 3.0 weight percent (Houghton and others, 1992). Again, the chilled margin (not exposed here) composition for the Prescott Brook diabase (PBD) is typical ENA-HTQ type (Houghton and others, 1992). Keely and Husch (1993) proposed that the PBD was connected at depth to the adjacent CMD to the east, based upon their similar relationships between stratigraphic level of emplacement and composition (Fig. 14). This however, could neither be confirmed nor refuted by the Bouguer Anomaly modeling of Jakubicki and Husch (1995).
Running diagonally across the north-facing slope of the hill is an enigmatic 3 to 5 ft-thick layer that weathers more readily than the surrounding rocks, forming a prominent recess in the hillside. Two of the layer's more noticeable features are its broken, brecciated character and the presence of chevron-like fractures or folds across it. A number of origins have been suggested for this unit, none with any great conviction or certainty. Thus, its origins are unknown at this time and any and all suggestions or ideas, no matter how far-fetched, will be entertained.

Hill to left is western slope of the Round Mountain diabase (RMD
Hill to left is western slope of the Round Mountain diabase (RMD), a HTQ-derived, granophyre-rich intrusion located approximately one mile to the south of the CMD and PBD (Houghton and others, 1992). Gravity data suggests that it is connected at depth to the CMD (Jakubicki and Husch, 1995).

Cross over South Branch of the Raritan River.

Family Golf Center on right.
A fairly complete cross section of the Flemington dike (FD)was exposed for a few weeks in the foundation pit during the construction of the center's main building. Samples collected at that time were analyzed by Crohe (1996) for major and trace-element compositions. Significant contamination affects (see Part I), particularly adjacent to the eastern contact zone of the dike, were found.

Road crosses over the FD (now on left)
Road crosses over the FD (now on left) which continues to strike almost due south towards the upper contact zone of the Lambertville sill.

STOP 5. Float Boulders of Flemington Dike, Ringoes, NJ.
All Boulders At This Location Are On Private Property. Many Are In Yards Or Gardens. Please Ask For and Get Permission Before Examining Or Collecting.
Walk across road (west side) to wooded area just to the left of the gray house (Janet and George Holt, 39 Back Brook Road, Ringoes, NJ 08552). There are numerous pieces of FD float lying along the road; there are no known outcrops of the dike exposed at the present time. Please disturb the pieces on the property as little as possible and leave those in the yard and garden alone. Hand samples may be collected from float in the bushes on the east side of the road opposite the house.
All float pieces contain the same fine-grained diabase found along the entire strike length (approximately 7 miles) of the FD. The dike, which is approximately 50-100 feet wide, exhibits little textural or mineralogic variation. Although all samples of the FD have compositions very typical of the ENA-HTQ type (Crohe, 1996), probable wall rock contamination affects, such as elevated concentrations of Na2O, K2O, and Ba, and decreased concentrations of CaO, generally become more pronounced as the dike strikes northward towards shallower structural levels. This is not surprising given the fact that the FD traverses over 9000 feet of the Triassic sedimentary section between the Lambertville sill (the dike's source; Stop 6) and the Flemington basalt (Houghton and others, 1992), the OMB equivalent flow that the FD presumably feeds. According to Houghton and others (1992), the Flemington Basalt exhibits striking geochemical signs of contamination, with as much as 5 weight percent Na2O and 300 ppm Ba.

Cross over Flemington Dike.
Small pieces of float have been collected from south side of road. Dike strikes south up the hill to the right and intersects the stope-like structure of the Lambertville sill at crest.

Float from intersection of Flemington dike and Lambertville sill
Just beyond gray ranch house (23 Losey Road) on right a dirt road heads west along the crest of the hill. Approximately 0.3 miles up from Losey Road, float from the approximate intersection of the Flemington dike and the Lambertville sill contact zone can be collected. Compositions and textures are very similar to what can be found at Stop 5.

STOP 6. Diabase With Pegmatitic Granophyre
In The Stope-Like Structure Of The Lambertville Sill, Rocktown, NJ.
This stop is located along the eastern limb of the stope-like structure found in the central portion of the Lambertville sill (Fig. 2). The top of this structure is emplaced approximately 3000 feet higher in the stratigraphy than the adjoining northeastward striking arm of the sill. Consistent with the dynamic fractionation model where residual, fractionated magmas migrate to the highest structural levels within a sheet, Szemple (1996) found that all diabase samples collected from the stop-like structure are differentiated to some degree, containing between 2.9 and 5.6 weight percent MgO; no MgO-rich samples with elevated pyroxene modes are known. This makes the stope-like structure compositions complimentary to the mafic- (and pyroxene-) rich compositions found in sections at the Lambertville sill's southwestern and northeastern ends by Eliason (1986) and Roth (1988), respectively (Fig. 16). By combining these sections, a regional or sheet-wide mass balance is attained, although at any individual section a local mass balance is lacking.
At this particular locality, the diabase is fairly feldspathic with as much as 19 weight percent Al2O3 (Crohe, 1996). However, pods of pegmatitic granophyre, reminiscent of those seen at Stop 1A, are quite common within the host diabase. A more granophyric diabase can be seen in some of the float pieces located across the road and in float located on the other side of Route 31, approximately one mile to the west.
Finally, it should be reiterated here, that it does not appear that any of the residual, granophyric material, so common in this section of the Lambertville sill, was transported into the immediately adjoining Flemington dike or erupted onto the surface as part of the Flemington basalt. This indicates that the emplacement of the HTQ magma into the Flemington dike and its eruption as the Flemington basalt was completed prior to the internal differentiation of the PRHL sheet (as represented locally by the Lambertville sill). Otherwise, granophyric compositions resulting from that differentiation would be more common within the dike and flow.

A2: STRATIGRAPHY, STRUCTURAL GEOLOGY, AND DUCTILE- AND BRITTLE FAULTS OF NEW YORK CITY
Charles Merguerian
Geology Department
114 Hofstra University
Hempstead, NY 11550-1090
E-Mail: geocmm@hofstra.edu
INTRODUCTION
Long the center of commerce and culture in the United States, Manhattan is an island around which many geologic units and structural features coalesce. Manhattan's underlying lithology and durable crystalline structure have enabled the construction of enormous towering skyscrapers rooted into glacially-sculpted Paleozoic and older crystalline rock. First studied by naturalists in the 1700's, and by geologists in the 1800's and 1900's, the bedrock geology of the New York City area was mapped in systematic detail beginning in the mid- to late 1800's by L. D. Gale, W. W. Mather and F. J. H. Merrill. Merrill, the senior author of the United States Geological Survey New York City Folio (#83) published in 1902, outlined the basic stratigraphic and structural framework that all succeeding geologists would test, promote, and expound upon.
Today's trip examines the Paleozoic bedrock geology and the ductile- and brittle faults of New York City. The trip consists of seven easily accessible localities ("stops") in Manhattan and the Bronx (Figure 1). All of the outcrop areas are located in public parks or road cuts which may be easily reached by car, bus, or subway. The seven localities are plotted on segments of the Central Park 7-1/2 minute quadrangle (Figure 2) and UTM grid coordinates are supplied with the stop descriptions. Thus, no detailed road log has been made for this trip. The field-trip stops have been chosen to best identify outcrops critical to my new interpretations of the bedrock geology of New York City, including the results of joint studies with J. E. Sanders that have provided evidence for post-Pleistocene uplift along the footwall of the Mosholu Parkway fault in the Bronx.
No road log. UTM coordinates are probably NAD27, so were not used. Instead, locations were taken from little insert maps.

STOP 1 - HARTLAND FORMATION IN RIVERSIDE PARK
UTM Coordinates: 585.95EI4515.35N northward to 586.35EI4516.10N, Central Park 7-112 minute quadrangle.
The Hartland Formation or upper schist unit (G - Oh) crops out in Riverside Park from West 75th Street northward to West 116 Street. Described here are exposures near West 90-91 Streets and West 82-85 Streets.
The northernmost outcrops consist of gray-weathering, well-layered and slab by to laminated, lustrous muscovitic schist containing interlayers of quartz-muscovite biotite granofels. Locally, 1 cm thick glassy quartzite interlayers and elliptical pods of recrystallized dark quartz occur. The prominent 2-3 cm scale layering results from original compositional variations and subparallel S1 + S2 metamorphic recrystallization. The metamorphic layering is parallel to N48°E, 65°SE axial surfaces of long-limbed F2 isoclinal folds plunging 60° into S28°E. A strong down-dip stretching lineation (L2) composed of quartz ribs and streaked mica lies within S2 and is deformed by F3 folds. The F3 folds are tight, south-plunging "s" folds with abundant shearing along their axial surfaces (S3 = N37°E, 78°SE). L3 intersection lineations and stretching lineations are parallel to F3 hinge lines which plunge 22° into S29°W and deform the L2 lineations. S3 is typically a transposition foliation with oriented mica and migmatite overprinting the older folds and related fabrics. Pre-, syn-, and post-D3 pegmatites are found throughout the area.
The southern outcrops of the upper schist unit are lithologically identical to the above except the layering is thicker (6-8 cm) and a laminated black-weathering, greenish-black biotite-amphibolite layer (1 m thick) occurs near West 82 Street. Together these outcrops illustrate the penetrative nature of F3 isoclinal folds with their shallow southward plunges. Apparently the NW-trending, shallow SW-dipping enveloping S2 metamorphic layering exerted a strong control on the orientation of F3 hinge lines despite the fact that significant transposition occurred during D3. The average orientation of S3 is N55°E, 75°SE with F3 hinge lines and sub-parallel L3 lineations plunging 20° into S40°W. (See Figure 6.) Late, open folds with axial surfaces trending N47°E, 90° are locally developed.
Several glacial features of interest are present here. The overall shape of the surface of the bedrock defines several roches moutonnees. Not only are the rock surfaces rounded and smoothed on a large scale, but grooves and striae are present as well. The trends of these show that the ice flowed across the Hudson River, from NW to SE, consistent with a multi-glacier model proposed recently by Sanders and Merguerian (1991, 1992, 1994a, b) and Merguerian and Sanders (1996c).

STOP 1B. Northern Limit of Stop 1

STOP 2 - CAMERON'S LINE AND THE HARTLAND AND MANHATTAN Fms
NEAR WEST 165 STREET. UTM Coordinates: 588.90E / 4521.41N, Central Park 7.5 minute quadrangle.
The Manhattan formation (G - Om) is exposed here in a large outcrop west of Riverside Drive. The Manhattan formation dominates, consisting of rusty- to gray-weathering, coarse-grained gneiss and schist with 2-15 cm interlayers of quartz-biotite-garnet-kyanite-sillimanite granofels. The rock contains porphyroblasts of kyanite +/- sillimanite and garnet (up to 1 cm). Outcrops 350 m to the north show more typical rusty-weathering colors and abundant aluminosilicates of G - Om, yet in November 1985, subsurface construction exposures to the east of Riverside Drive exposed muscovite-rich Hartland lithologies (G - Oh) cut by brittle faults. These exposures are typical of Cameron's Line, with intercalated lithologies of both bounding units found in close proximity and clear distinction blurred by D2 tectonic intercalation.
Structurally, at the south end of the outcrop, there is a clear example of a long-limbed intrafolial F2 reclined fold refolded by F3 "z" folds. Here, F2 folds an S1 biotite foliation and granitoid pods developed parallel to S2 (and/or S1) are folded by F3. S2 trends N54°E, 44°SE with F2 plunging 40° into S19°E and S4 trends N20°E, 75°SE with F3 axes plunging 42° into S10°W. Excellent examples of type-3 interference patterns (Ramsay, 1962) are found on the sloping north-facing portion of the outcrop. Cameron's Line passes above our heads as we stand in the core of a south-plunging F3 fold, exposing G -Om at street level. Hartland rocks crop out to the south and east.
Several glacial features of interest are present here. The overall shape of the surface of the bedrock defines several roches moutonnees. This particular rock knoll probably was a splendid example of a roche moutonee many years ago, but cannot be considered as such any longer. The diamond-drill holes along the rock face by the sidewalk indicate that the SE side of this knoll was blasted away to make way for the street and the sidewalk. Not only has the rock surface been rounded and smoothed on a large scale, but grooves and striae are present as well. The trends of these show that the ice flowed across the Hudson River, from NW to SE.

STOP 3 - ST. NICHOLAS THRUST AND CAMERON'S LINE
INWOOD HILL AND ISHAM PARKS UTM Coordinates centered on: 590.50E / 4525.00N, Central Park 7.5 minute quadrangle.
Inwood Hill Park is located in the extreme northwest corner of Manhattan Island. The park is bordered by Dyckman Street on the south, the Hudson River on the west, Spuyten Duyvil (Harlem Ship Canal) on the north, and Payson and Seaman Avenues on the east. Isham Park occupies the flat area northeast of Inwood Hill Park extending eastward to Broadway between Isham and West 214 Streets.
The area of Manhattan north of Dyckman Street is known as the Inwood section. Except for Inwood Hill Park, the region is underlain by the Inwood Marble marking the name-locality (originally called the Inwood Limestone by Merrill 1890). Isham Park contains near continuous exposure of the Inwood Marble (G - Oi). Several lithologies occur such as coarse-grained dolomitic marble, fine-grained calcite marble, foliated calc-schist, and marble containing siliceous layers and calc-silicate aggregates that stand in relief as knots on the weathered surface. The marble ranges from white- to blue-white to gray-white. Depending on the amount of impurities, it weathers gray or tan and produces a sugary-textured surface on outcrops which ultimately develops into a residual calcareous sand. In addition, the outcrops illustrate differential weathering with dolomite-silicate units standing in high relief and calcite marble forming depressions.
The Inwood trends N45°E, 73°SE and forms the eastern overturned limb of a large F3 synform which is cored to the west by the middle schist unit (G - Om) of Inwood Hill Park. Tight south-plunging F3 folds are locally developed. Older structures are not obvious but can be found (especially after, or during, a rain) as long-limbed F2 isoclinal folds. Abundant examples of boudinage of the siliceous and calc-silicate layers into lenses occur due to the marked ductility contrast between them and the surrounding marble.
Enter Inwood Hill Park following the path past the playground. The first (of two) prominent ridges is composed of kyanite-garnet gneiss and schist of the middle schist unit (G-Om) which is structurally separated from the Inwood Marble by the St. Nicholas thrust (not exposed here). Follow the path to where it curves around to the west side of the ridge and enters a valley underlain by a south-plunging F3 antiform which exposes tan weathering, gray-white Inwood Marble striking N40°E, and dipping 58°NW.
Along the path going north (up-slope) along the westernmost ridge, massive, brown-weathering, blackish amphibolite of the middle schist unit crops out. Rocks exposed on the ridge (G - Om) are massive muscovite-biotite-plagioclase-quartz-garnet-kyanite gneiss and schist with weathered kyanite+quartz+sillimanite nodules. The structure of the ridge is a south-plunging F3 synform overturned toward the northwest. The S3 foliation in the middle schist unit is related to F3 folds with axial surfaces oriented N41°E, 75°SE and south-plunging hinge lines. The F3 structures are superimposed on an older S2 metamorphic layering which trends N50°W, 25°SW. Atop the ridge, a few exposures of muscovitic schists that are strikingly "Hartland-ish" occur. If they are indeed Hartland rocks and not minor muscovite-rich zones in the Manhattan (which do occur, locally), a case may be made for skirting the top of the ridge with a klippe underlain by Cameron's Line.
Along the N-facing backslope of the western ridge, the contact between the middle (G-Om) and lower (Om) schist units (the St. Nicholas thrust) is exposed in a 20 m zone from beneath the Henry Hudson Bridge abutment to river level. Structurally beneath the middle schist unit a 0.5 m layer of mylonitic amphibolite is deformed by F3 folds. Unlike the amphibolite in the middle schist unit above, which contains subidiobastic hornblende, this amphibolite has been retrograded by intense shearing parallel to the S2 foliation. Green hornblende porphyroclasts are set in an anastomosing S2 foliation consisting of colorless clinoamphibole, biotite, and quartzose ribbons.
Directly beneath the bridge, where a dirt trail leads down to the river, a coarse-grained gray-white calcite marble with differentially eroded calc-silicate nodules is exposed at low tide. It is unknown whether the marble exposed at the low-tide mark is a "Balmville" interlayer in the lower schist unit (Om) or a faulted part of the Inwood Marble.
Physically above the marble exposure, the lower schist unit consists of biotite-quartz-plagioclase and kyanite with abundant garnet porphyroblasts. Here the lower schist unit contains an S2 mylonitic foliation composed of mm-scale ribboned and polygonized quartz with recrystallized reddish pleochroic biotite. Produced in the axial planes of F2 reclined folds, the S2 foliation strikes N45°E and dips 55°SE with a strong down-dip lineation plunging 50° in a S34°E direction. The thrust zone is structurally complex consisting of intercalated lithologies of the lower- and middle schist units together with mylonitic amphibolite.

STOP 4 - ST. NICHOLAS THRUST AND MANHATTAN Fm
IN ST. NICHOLAS PARK UTM Coordinates: 588.45E / 4518.28N northward to 588.75E / 4519.15N, Central Park 7.5 minute quadrangle.
The St. Nicholas thrust separates the middle schist unit (G - am) from the Inwood Marble (G- Oi) along the east edge of St. Nicholas Park situated west of St. Nicholas Avenue between West 129 and West 141 Streets. Excellent outcrops of the schist form the steep ridge of the park. The southernmost outcrops consist of rusty-weathering biotite- and muscovite-rich gneiss and schist with abundant alumino silicate nodules, interlayered biotite-quartz-garnet granofels, and thin amphibolite. The Inwood Marble is not exposed but, based on drill core data and geomorphology, underlies the lowland immediately east of the park.
Outcrops atop the ridge on St. Nicholas Terrace contain flattened alumino silicate layers folded by F3 folds. Northward, F2 isoclinal folds with subhorizontal axial surfaces are also deformed by F3 folds. S3 trends N30°E, dipping 70° SE and is locally warped by several generations of late crenulate and open folds.
A penetrative S2 mylonitic layering occurs at the northeastern most exposures in the park. Tight- to isoclinal F3 folds deform and locally transpose the S2 mylonitic foliation into parallelism with S3. In addition, the F3 folds deform pegmatite sills injected sub-parallel to S2 + S1, thin lit-par-lit foliated syn-D2 granitoids, alumino silicate layers, and quartz veins. Because of the combined effects of D2 and D3 the rocks are highly recrystallized and locally migmatitic.
The contact between the middle schist unit and the Inwood Marble is never observed but the presence of unusually penetrative S2 fabrics in the schist at the eastern edge of the park and the apparent absence of the lower schist unit together suggest that the St. Nicholas thrust may be marked by the abrupt break in slope to the east.

STOP 5 - ST. NICHOLAS THRUST AND THE MOUNT MORRIS PARK OUTLIER
UTM Coordinates centered on: 589.13E / 4517.25, Central Park 7-1/2 minute quadrangle.
The Mount Morris Park Outlier, a hill protruding above the Harlem Valley centered at West 122 Street and Fifth Avenue, consists of an erosional remnant of the middle schist unit (G-Om). The Inwood Marble (G - Oi) crops out on the Madison Avenue (east) side of the park. The marble is gray- to tan-weathering and contains schistose zones with layers and nodules of diopside+tremolite+quartz. The middle schist unit is composed of rusty- and locally, maroon-weathering, gray, gneiss and schist with kyanite layers, zones of porphyroblastic kyanite+garnet, and layers of biotite-quartz-plagioclase+ garnet granofels.
The overall structure of the park is a south-plunging klippe of the middle schist unit produced by the superposition of an F3 synform and a late, NW-trending synform. The klippe of G - am is terminated along its southern margin by a brittle fault (splay of the 125th Street fault?) exposed at street level trending N69°W, dipping 84°SW. Slickensides in the fault surface are oriented N70°W @ 22° clearly indicating a strike-slip movement sense although a component of reverse motion is suggested by faint dip-slip slicks and the presence of Inwood Marble to the south. Along the east-face of the exposure, the St. Nicholas thrust is found between the Manhattan schist and Inwood Marble and is marked by 10° truncation of lithologic layering and an early S1 foliation in the marble, extreme flattening, 2-3 cm scale annealed mylonitic layering, shearing and imbrication of lithologic units (including small tectonic slivers and interlayers of schist unit Om?), and quartz veins.
Developed during thrusting and deformed by F3 folds, the S2 enveloping surface is variable but on average trends N30°W, 20°SW and marks the axial surface of reclined and isoclinal folds found both above and beneath the St. Nicholas thrust contact. Disharmonic F3 folds of mylonite developed at the thrust contact are exposed at the northern edge of the klippe. They trend N32°E, 80°NW to 70°SE and plunge 23° into S25°W.

STOP 6 -BALMVILLE MARBLE AND LOWER MANHATTAN SCHIST UNIT
GRAND CONCOURSE AND THE CROSS BRONX EXPRESSWAY, BRONX.
UTM Coordinates: 591.65E / 4521.95N, Central Park 7.5 minute quadrangle.
An excellent exposure of the lower schist unit (Om) occurs west of the Grand Concourse in an overpass above the Cross Bronx Expressway (1-95). Here, fine- to medium-grained, massive but locally friable, tan- to brown-weathering schist and granofels is found interlayered on the scale of 3-4 m with calcite and dolomite marble containing 2-3 cm diopside+tremolite calc-silicate and siliceous layers. Massive Inwood Marble (G - Oi) occurs in the roadcut forming the south wall of 1-95 beneath the overpass. This locality, together with exposures described earlier in Inwood Hill Park (Stop 3) and a few other outcrops south of I-95 paralleling the Grand Concourse (C. A. Baskerville, personal communication), are interpreted as the autochthonous portions of the "Tippecanoe" Manhattan Schist.

STOP 7 - CAMERON'S LINE - BORO HALL AND CROTONA PARKS
, CROSS BRONX EXPRESSWAY. UTM Coordinates centered on: 593.00E / 4521.80N, Central Park 7-1/2 minute quadrangle.
Boro Hall Park in the Bronx is surrounded by East Tremont A venue on the north, Third Avenue on the west, Arthur Avenue on the east, and East 175th Street on the south. The last named also serves as the westbound service road for the Cross Bronx Expressway (I-95). This park is situated on an important subdivision of the metamorphic schistose rocks of the Bronx. On the 1971 edition of the Geologic Map of New York (New York State Museum and Science Service) places a queried dashed line through the center of the park as the contact between the New York City Group on the west from the Hutchinson River Group on the east. Seyfert and Leveson (1969) discuss the contact as a thrust fault and argue that it is on strike with Cameron's Line. Based on lithologic correlations, Baskerville (1982a, b, 1992) first identified the contact as Cameron's Line; Merguerian and Baskerville (1987) defined the structural relationships discussed below.
Along East 175th Street the outcrop nearest Third Avenue is a brown- to rusty-weathering, medium-textured, gray, biotite-muscovite schist of the middle schist unit (G - Om) containing several pegmatite dikes. The foliation strikes N40°E, and dips 70°SE. Test borings for the I-95 overpass near this locality indicate that marble occupies the Third A venue valley to the west. East of the middle schist unit is a soil-covered shallow swale, 30- to 40 m wide, that trends N40°E. The Hartland Formation (G - Oh) crops out to the east of the swale and also south of the expressway in Crotona Park (described below). The Hartland rocks are brown- to tan-weathering, gray muscovite-biotite-quartz-plagioclase-garnet schist and gneiss with granitoid sills and thick layers of greenish amphibolite.
The contact between the middle schist unit (G - Om) on the west and the Hartland Formation (G - Oh) is never exposed but presumably occupies the swale between the outcrops. Rocks on either side of the contact are highly flattened; as a result of recrystallization during D3, the microscope shows little evidence for mylonitization. Microscopically, brittle fractures are well developed in the minerals, suggesting the contact may be a brittle fault reactivating an older ductile contact. The contact between these units is known as Cameron's Line, a ductile fault separating allochthonous sequences of the Taconian Hartland and Manhattan formations.
Dr. Patrick W. G. Brock of Queens College, who took a class to this stop, collected specimens, and examined the rocks petrographically, detected a corroded grain of corundum that had been highly retrograded by higher-crustal-level metamorphic overprinting. Although it was not in contact with quartz and clearly had undergone retrograde reactions, the corundum discovery suggests that the rocks in this region had initially experienced metamorphism at least up to K-feldspar- sillimanite grade.
To the south of the Cross Bronx Expressway, in Crotona Park, Cameron's Line again separates schist, gneiss, and amphibolite of the Hartland Formation (G - Oh) on the east from westerly exposures of schist and gneiss of the middle unit of the Manhattan Schist Formation (Gam). The rocks are not found in direct contact but, similar to exposures to the north, are separated by a soil-covered interval. The Manhattan exposures are mylonitized, however, with shear folds and laminated textures well displayed.

A3: A SURVEY OF THE NATURAL AND URBANIZED SHORELINES ON LONG ISLAND, NEW YORK - A DILEMMA IN COASTAL MANAGEMENT
Manfred P. Wolff(l), Nicholas K. Coch(2), Robert W. Johnson(3)
(1) Geology Department, Hofstra University
(2) Department of Geology, Queens College, CUNY
(3) Biology Department, Hofstra University
INTRODUCTION
This trip will examine six stops on the barrier island beaches along the south shore of Long Island (Figure 1). Such beaches were probably first formed during the Pleistocene glaciation from eroded and reworked continental Cretaceous-Tertiary strata 100 Km. seaward of their present location. They were then gradually submerged and modified into shoals, lagoons, barrier islands and inlets by the current marine transgression. During the past 25,000 years of glacial melting and deposition the rising sea reached the outer edge of the glacial outwash and moraine deposits, perhaps 3-5 Km. seaward of their present location (Wolff, 1982). It is this newer source of Pleistocene glacial sediments that continue to undergo the transitory processes that modify them into the current coastal features. Ultimately, they will be eroded and deposited offshore, on the shoreface, and below wave base on the inner continental shelf--as the Holocene transgression continues.
We accept the concept of "barrier island migration" with the rising sea, and will provide evidence for it. This emphasizes the idea that the barrier islands have not been "drowned" but instead, continue to be preserved by progressive landward sand migration. This migration occurs during the shoaling associated inlet formation, and during the flooding and over wash deposition associated with the wave surge from major storms (Wolff, 1989).
Anthropogenic changes brought on by coastal habitation during this century have seriously curtailed the influence of these natural processes in maintaining the sporadic pattern of inlet formation and landward barrier island migration. Management philosophy has instead substituted a policy that now emphasizes mechanisms that attempt preservation of all the natural environments through coastal stabilization. While most of our field stops are on urban beaches, they are maintained by different levels of government (state, county, city and town) and the management policies may also differ. We will review the history of development (natural and urban) at each of these stops, examine the methods used for the artifIcial (and temporary) stabilization of the dunes and beaches, and discuss the impact of storms in promoting either the destruction or the preservation of these natural features in the future.
Most field trips at this meeting will examine outcrops visited by geologists for over 100 years; the road cuts remain the same-- but the interpretation changes. For our trip, the interpretation has remained the same, but the "outcrops" continuously change (in shape, form or position). As this is written the authors realize that the effects of a nor'easter or hurricane before October could signifIcantly change the form or location of our "outcrops". Most of our stops were within the "zone of breaking waves" within the past few years but all of them have been recently "restored" by beach nourishment. Coastal inhabitants-- particularly park managers and home owners on or near beaches demand a permanent position for their beaches, and have in place a powerful political lobby (at all levels of government) that will fight "beach erosion" and promote coastal maintenance and stabilization (which we realize only promotes more beach erosion).
But nature still remains a powerful influence for coastal change. The most obvious one is the coastal storm that erodes barrier island beaches, breaches dunes, overwashes barrier terraces and marshes, creates inlets, and floods mainland beaches. It floods or destroys all the "permanent" anthropogenic infrastructure, but only temporarily disturbs the habitats of the natural flora and fauna. As with a forest fire, after the initial devastation, the habitats are frequently extended and improved as the cycle of biological and physical evolution is renewed.
The less obvious change is the influence of the rate of sea level rise. It is now 0.6 m./1OO years and is estimated to be increasing to 1.5 m./100 years because of the global warming. Yet coastal management policies still reflect the "status quo"--the demands of the coastal managers and the communities. Because of the intense coastal development, they remain oblivious to the benefits of the storms, (which provide the natural sand migration) and because we haven't had a major hurricane crossing over this region in more than fifty years. There is never a discussion for the initiation of a policy that would emphasize the relocation or abandonment of destroyed structures after a major storm--only renourishment and renewed stabilization of the beach, and the return of larger (and more expensive) structures. In the meantime, the storms and sea level rise will continue. Thus, the dilemma!

A3: A Survey of the Natural and Urbanized Shorelines on Long Island, New York - A Dilemma in Coastal Management

New York skyline in view for camera shot.

Park near Captree Cove Restaurant
Park near Captree Cove Restaurant for last-minute
preparations and a pit stop

Robert Moses Causeway Bridge
Robert Moses Causeway Bridge that crosses Fire Island Inlet (see map) - one of the few parallel inlets on the East coast. Note Fire Island Lighthouse in distance on left; enter Fire Island.

STOP 1A. North side of Robert Moses State Park
The use of hard stabilization for erosion protection on the bayside of Fire Island.
Here we will examine the concrete "rubble" and and a gabion ramp that is being used as revetment to curtail bayside erosion at the end of the Loop Parkway. The reason for the initial loss of 75 meters of this beach and marsh relates to the curved spit seen at the western end of Fire Island (Democrat Point) in the distance. This was a coast-perpendicular inlet in the 1860's, but the extensive westward growth of the island from the lighthouse (over 6 Km.) has now produced a coast-parallel inlet (Figure 2). By the 1940's, it was in deep-enough water off Oak Beach to enable the flood-tidal currents and wave refraction to form a series of recurved spits at Democrat Pt. that began to constrict the inlet (Wolff, 1975a,b).
As the tidal channel narrowed and deepened, its velocity increased, and it began forming a curved "meander" shape as it impinged on the Jones Beach barrier at Oak Beach. The resulting erosion required the construction of a jetty at Democrat point (to trap the littoral drift) and the dredging and by-passing of the accumulated sand across the inlet. But during the early 1950's, sand was already passing around the jetty, and by 1959 it was again constricting the inlet (Figure 2.) causing erosion near Oak Beach.
This led to the construction of a reveted sand dike by the U.S. Army Corps of Engineers west of Oak Beach. But this produced deposition and shoaling behind the dike (near Oak Beach) - which again increased the extent of the "meander" curve of the tidal channel. Acting as a "point-bar" in a meandering river, the shoals diverted the tidal currents against the bayside of Fire Island, resulting in the loss of the beach. The rubble and gabion ramp were added in 1986 to curtail the erosion.
The effect of hurricane track near this area would have particularly disastrous regional consequences since there could be a breach anywhere along Oak Beach, as there was in 1901 and 1923 (Wolff, 1975b). Depending on the extent of spit development in front of the Federal jetty, (Figure 2) this could lead to the closure of the present inlet and a deepening and widening of the new one. Such an opening recently occurred at Westhampton Beach, but was soon closed by offshore dredging (Wolff,1994).

STOP 1B. Water tower at Robert Moses St. Park.
Use of soft stabilization for erosion protection on the oceanside of Fire Island.
This elongate mound is composed of gravelly sand trucked-in from the mainland under emergency conditions by the N.Y.S. Department of Transportation during the winter of 1990-'91 and again in 1992-'93 when an additional 20,000 cubic yards of sand were added. It is meant to augment the eroded dunes that once protected this traffic circle along the Loop Parkway. The history of beach erosion here dates from the 1940's, but dune erosion did not occur until the 1960's. Wave surge reached the oceanside parking lots east of here by 1973, and this zone of erosion has continued to migrate westward. Using slat fencing with periodic beach scraping, the dunes in front of the parking areas were restored in the 1980's, but erosion here, at this circle continues, necessitating the mainland trucking of gravel against the roadway.
A hurricane path near this area would not breach the barrier island, but it could create extensive damage to the parkway road, and to the water tower. The bridge is unlikely to be affected.

Views to Oak Island (right) and Oak Beach
(mouth of Fire Island Inlet) on left.

Note region of high dunes on left.

STOP 2. Gilgo Beach (Town of Babylon)
Use of soft stabilization for erosion protection of Ocean Parkway.
This stop was used by Wolff (1975b) to indicate the process of "ravinement" as described by Swift (1968) in which the active surf zone on a beach, during major storms, will expose old bayside marsh and lagoonal sediments. Such deposits were exposed on this beach during the nor'easters of 1972-73. Here is an area where over 400 meters of beach were eroded in 75 years--it was also used to demonstrate the effects of the process of barrier island "rollover" or landward migration. Once back-bay marsh sediments are buried beneath sands deposited as sand spits (by longshore currents) or overwash (from storm surges) they will later be overlain by sand from the terraces and dunes. As sea level rises, they will ultimately appear beneath the beach--were they can be re-exposed and excavated by the ocean waves (Figure 3). This beach has been renourished periodically since then (Buttner, 1989).
The wide beach at present is a result of several renourishment projects, initiated in 1988, that continue at present. Gilgo is the "feeder beach" for the cubic meters (or yards) of sand dredged and then pumped here from Fire Island Inlet. This sand will naturally feed the western town beaches and Jones Beach through the influence of the littoral drift.
The replenishment volume is as follows (Hanse, 1996):
1988 - 1 million cubic yards spread across 10,000 feet of beach
1990 - 1 million cubic yards spread across the same area
1992 - 1.7 mill. cubic yards spread across 18,000 feet of beach
1994 - 1.9 mill. cubic yards spread across 18,000 feet of beach
1994-'96 - an emergency stockpile of20,000 cubic yards.
Note also the elongate ridge of gravelly sand used to replace the dunes along the edge of the Ocean Parkway. During the 1950's N.Y. State had constructed a pavilion near this location. It was being undermined and eroded by the 1970's and was abandoned and dismantled by 1975. The foundation was broken into "rip-rap" to armor the beach, and acted as a 'stubby' groin that trapped sand east of this location. But this resulted in a loss of beach at this location that, by 1986 was extensive enough to erode the dunes and nearly reach the Ocean Parkway. As at Stop 1B. N.Y.S.D.O.T., using emergency funds, was able to truck-in the gravelly sand from the mainland to save this vital roadway. The roadway is built on sand-clay fill dredged from the bay during its construction in the late 1920's and will erode even more quickly if it is ever undermined by the ocean waves. The replenishment of sand at Gilgo Beach (Stop 1B.) has kept the waves from returning.
The effect of a hurricane path passing near this area could also be quite profound since it was already near the site of a former inlet. While tidal marshes are extensive, the adjacent dredged channel for the boat moorings and the intra-coastal waterway leave this portion of the island quite narrow and susceptible to inlet breaching (Figure 3). There is not enough sand left for overwash. In fact, one of the ironies is that the sand that has been pushed by wind or water onto the Ocean Parkway over the past 30 years is rapidly collected and returned to the beach. Undermining of the south side of the roadway is imminent--but only if the trucking-in of sand and gravel is eliminated.

STOP 3A. Tobay Beach (Town of Oyster Bay)
Use of soft stabilization for erosion protection of Tobay Beach and the beach pavilion.
Note the location of the Tobay Beach Pavilion and the line of the eroded natural dunes. Note also the size and "storm-proof' construction of pavilion #4. This site for a pavilion goes back to the 1940's - when the dunes were in front of this location and the beach extended seaward another 115 meters. The construction of the Federal jetty at Democrat Pt. on Fire Island (Stop 1A.) blocked the sand from crossing the inlet, causing erosion along all the beaches of the Jones Beach barrier island during the 1950's. Without inlet bypassing, this pattern will persist. Once the beach and dunes were eroded, various storms undermined and partially destroyed the older pavilion. It was rebuilt, refurbished (and re-destroyed) several times before being completely torn down in 1986. Yet, instead of being rebuilt on the north side of Ocean Parkway, it was rebuilt (because of a need for convenient public access) at the same site in 1987. It has been "embraced" by waves from various storms, but the deep, sturdy concrete pilings assure its preservation - as long as periodic beach nourishment remains available. This one, and all the pavilions and bath houses to the west (ie. at Jones Beach State Park) now occupy sites in front of the natural dune line. Even the huge ocean-side parking lots are now in front of the dunes. This again demonstrates the subtle but continuous pattern of natural sand migration that, without continual stabilization, will ultimately cause all the barrier environments to migrate landward (Figure 4).

STOP 3B. Tobay Beach - Wildlife Sanctuary
Return of pre-historic inlets into ecologically productive barrier island forests, ponds, and marshes.
This is the site of a pre-historic inlet that retained a large volume of sand and relatively wide dunes and marshes for a long period of time. The result is (on a small scale) the development of freshwater ecosystem in a mature forest - something more characteristic of the mainland. While relatively rare, they demonstrate that certain areas on barrier islands do not rapidly undergo landward migration if enough overwash sand was deposited during prior storms; such areas may remain stable for long periods, and unaffected by the rising sea (Buttner, 1987).
The effect of a hurricane across this region, as before, has more regional than local consequences. Because of the prior overwash and inlet-filling sand, the extensive terraces and secondary dunes, and the wide expanse of salt marsh, a breach through here remains unlikely.

Note the location of the dunes
Note the location of the dunes versus the location of the parking lot and pavilion.

STOP 4. Hempstead Beach Town Park
Use of hard stabilization for erosion protection at Jones Inlet.
Note the distance (over 350 meters) between the major roadway and the dunes. Though an urban park, there is a large "buffer zone" between the community and the beach - all urban development on barrier islands should have a management plan that will lead to this zonation. Once on the beach, view the shoreline from the last groin. Observe the wide beach and extensive dune field on the east (Jones Inlet) side of the groin. Note the large beach "re-entrant" and lack of dunes on the west side. This area was under water at various times during the 1970's and '80's, threatening the Town Pavilion (seen in the distance). Only the periodic sand bypassing from the inlet has prevented its annihilation. The last nourishment program ended in the spring of '96. You can already see the development of a beach scarp and the lowered profile as the swash undercutting continues to undermine the beach. Dune rebuilding through the use of slat fencing and Ammophila (beach grass) has been quite successful here, but only for a limited period.
This beach, near Jones Inlet, has a history similar to that of Oak Beach at Fire Island Inlet (Stop 1A.) The westward littoral drift from Jones Beach, as it moved into the deeper water in the inlet, created a series of recurved spits. By the 1950's the narrowing of the inlet forced the channel against the beach near the community of Pt. Lookout at the eastern end of Long Beach. Erosion also prevailed along much of Jones Beach. A jetty was now constructed at the western tip of Jones Beach. This led to the restoration of the state park beaches behind the jetty, but it increased the erosion at Pt. Lookout. This later required the construction of three groins east of this park, which trapped the sand supplied by the tidal currents in the inlet. But this also increased the rate of erosion beyond the most westerly groin - resulting in the need for periodic inlet sand bypassing for beach renourishment.
A description of the regional effects of wave surge from a hurricane passing near this inlet towards Freeport (Figure 5) was detailed by Coch and Wolff (l990). This was based on their observations of inland flooding and destruction of mainland communities behind tidal marshes after Hurricane Hugo in 1989. Less serious mainland inundation was noted along Long Island, opposite the recent opening of Little Pike's Inlet (Wolff, 1994). The extent of the enlarged tidal prism that must enter and exit an inlet during a hurricane are profound! The areal extent of the flood surge for hurricanes of different intensity has been depicted on N.Y. State SLOSH maps, and these depict inundations over hundreds of square kilometers that would affect thousands of houses.
Many beachfront homeowners have some low-level protection from bulkheads and retaining walls. But the ebb surge that follows will have some unexpected consequences. Besides opening barrier breaches into new inlets, it will also scour and erode the areas behind the bulkheads. These structures trap the ebb flood, preventing its return to the ocean. This "wall of water" will cause the houses or bulkheads to be overtopped or undermined as the surge seeks its way back to the ocean (Coch and Wolff, 1990).

STOP 5. Lido Beach Town Park
Use of soft stabilization for erosion protection.
The western edge of this park occurs at the boundary between an area with proper urban coastal management and an area that sees the return of community development directly behind the dunes. This region has also experienced periods of extensive dune breaching and beach erosion, but the periodic beach nourishment and the extensive care given toward dune development have made it a "healthy" beach. This is the last area within the next 50 Km. where one can see dunes in front of coastal structures. In fact, if we continued across the Hudson River into Staten Island, and then across the Arthur Kill into New Jersey, other than a few short stretches along Sandy Hook, we would travel past the 50 Km. of seawalls in N.J. and all the way to Pt. Pleasant before again encountering dunes of this magnitude in front of houses. What was a coastal dilemma becomes a coastal crisis!
In descending the dune boardwalk "overpass," note the location of the dunes with regard to the gold-painted twin spires of the Lido Beach Towers in the distance - their position aligns itself with the mid section of this building. Dune restoration has been frequently attempted across this section of the "New York Bight" from Long Beach to Sea Girt, but it will always fail because the position of the natural dune line is now well within the first block of houses on the urban streets. Without beach nourishment, all the "beachfront" houses would have been removed by erosion during the 1950's, and development has since increased 3-fold. The rebuilding of the dunes west of this area is an "effort in futility". As described at stops 2 and 3, the original dunes were trapped between the rising sea and the most shoreward anthropogenic structures--boardwalk, roadways, or houses (Figure 6). Other than this local area, any new dune restoration will rapidly be eroded. Not until the relocation or abandonment of the first 1-4 rows of houses can the shoreline adapt an equilibrium position that would retain natural dunes for storm protection.
The effect of a hurricane path anywhere in the New York Bight, with its large coastal population density, would be overwhelming Wolff,( 1992) and Coch,( 1995). Though the erosion problems persist, the area cannot be abandoned, and at any expense, beach nourishment (without dunes) must continue--therefore, the coastal dilemma!

STOP 6- Edgemere Section of Rockaway Beach
Beach dynamics and inlet sedimentation along a highly urbanized shoreline, Rockaway Peninsula, Queens County, New York.
Historical records show that the Rockaway Peninsula was largely pristine until the 1850's. In 1835, large areas were covered by cedar trees and sand ridges rising in places to altitudes of 25-30 feet above sea level. Urbanization, starting in the 1850's, was largely in the form of summer home developments. With the coming of the railroad in 1893, permanent communities became established. The increasing urbanization was to result in drastic changes in the morphology and hydrography of this area.
The Rockaway Peninsula, and the Coney Island barrier island to the east (Figure 7) are the most heavily urbanized and eroded hurricane - prone shorelines in the United States (Coch, 1995). The original dunes covering the Peninsula are long gone and the beaches have receded to such a degree that there is no longer any natural storm surge protection for the high-density structures along this shoreline. The major cause for this continual erosion has been the removal of sand from the longshore drift system by engineering structures and stabilized inlets in the areas to the east. This has deprived the beaches of Western Long Island of a sand supply sufficient to replace that lost to storms. In order to maintain this recreational area and protect the structures, the Army Corps of Engineers must replenish this stretch every 3-5 years.
Our stop will cover the shoreline area from Beach 37th to Beach 25th Streets. We hope to answer the following questions:: 1) how does beach morphology and sediment dynamics differ from that along more pristine shorelines?; 2) how has this shoreline evolved and what does this imply for the future?; 3) What accounts for the exceptional rate of erosion along this coastal segment? and; 4) how have engineering structures affected sediment dynamics in the vicinity of East Rockaway Inlet.
The area we will be examining today has a history of severe erosion. It was replenished in 1995, when it was built out 140 feet from the boardwalk. By March of 1996 it had eroded back nearly to the boardwalk. Replenishment in June 1996 built the beach out 240 feet from the boardwalk. High waves associated with the passage of Hurricane Bertha in mid-July, 1996, has already caused a beach recession of 40 feet.
The Eastern Rockaway Peninsula has been the subject of a continuing investigation by Queens College students since March of 1996. Examination of the beach section in March of 1966 showed a most unusual stratigraphic section. Sedimentary structures included upper flow regime plane beds, well defined channels oriented in a number of directions and avalanche bedding. The sediments consisted of sand, gravel and whole shells as well as shell fragments. However, as much as 5-30% of the section consisted of solid waste dating from the 19th Century. The debris included numerous rounded bricks, pieces of drainage pipe, pottery, plates bottles, personal items, animal bones and a few pieces of silverware and coins (Liogys et al., 1996).
We considered two working hypotheses to explain this deposit. The dredging could have uncovered an old borrow pit into which solid waste was dumped in the 19th Century. Another possibility is that the debris was washed offshore in the ebb surge of a past hurricane.
Historical records synthesized by Fuqua (1996) indicate that a barrier island (Hog Island) existed 1,000 feet offshore of the Rockaway Peninsula in 1879. A number of recreational facilities existed on Hog Island at that time and they were reached by ferry and causeway from the Rockaway Peninsula. The New York Times of August 21, 1893 reported that a major storm completely inundated Hog Island and it was "the beginning of the end for the island". Later newspaper reports indicate that Hog Island disappeared completely in nor'easter storms in 1893-4. The major storm was probably the "Jamaica Bay Hurricane" of 1893. The eye of that Category 3 storm probably did not pass over Jamaica Bay but crossed the coast in what is now the western part of Nassau County (B. Jarvinen, 1996, personal communication). This would have put the Rockaway area on the weaker, or left side, of that hurricane, so how can we explain the extraordinary coastal damage that was reported? The wave and surge levels reported were much higher than expected, because of the unique shoreline orientation and offshore bathymetry that occur in this region (Coch. 1994). The obliteration of structures on Hog Island would have provided debris that was washed onto the adjacent sea floor and covered by sand in the following decades. Dredging operations by the Army Corps of Engineers in 1995 (just south of the inferred position of Hog Island) returned this material to the land as part of the hydraulic fill used for beach replenishment. As you look around at the high rise buildings right on the boardwalk, think about the consequences of a major hurricane making landfall again in this highly urbanized area in the future.
Beach sedimentation in this area today consists of swash buildup of the beach face between storms as well as deflation of surface sands by southerly winds. The sand accumulates as drifts against the boardwalk. Some of the sand is blown under the boardwalk to form drifts against eroded vegetated dune remnants with incipient soil profiles. We will examine some of these dune remnants and discuss the inevitable consequence of "barrier rollover" in this area.
There are two sets of groins in the area (Figure 8). The older wooden groins were poorly maintained and are now largely destroyed. The newer stone groins function as effective sediment traps. The most easterly stone groin is at Beach 35th Street at our field trip stop.
A number of factors are responsible for the severe erosion in this area. Observations over several years suggest the following scenario for the water and sediment dynamics in the East Rockaway Inlet area. These dynamics are shown in generalized fashion in Figure 3. Sand moves in the predominant east to west drift toward the jetty at Atlantic Beach. Most of this sand is trapped against the jetty, but a portion is swept across the inlet area toward the Rockaways. Bathymetric contours (Figure 8) indicate shoals that suggest the presence of an ebb tidal delta on the north side of East Rockaway Inlet. Some of the sand moved across East Rockaway Inlet is transported by waves refracted around that ebb tidal delta, and moved towards the inlet. The last stone groin at Beach 35th Street traps some of that sand, but most moves past the area towards the inlet. This sand is deposited in the vicinity of the "light" (Figure 8) where the ebb currents block further penetration into the inlet. This scenario accounts for the presence of a sand-starved section from Beach 35th to Beach 25th Streets and the severe erosion that occurs continually along that coastal segment.

A4: STRATIGRAPHY AND HYDROGEOLOGY OF THE UPPER CRETACEOUS RARITAN, MAGOTHY, AND CHEESEQUAKE FORMATIONS, N.J. COASTAL PLAIN
PETER J. SUGARMAN
New Jersey Geological Survey
CN-427
Trenton, New Jersey 08625
This field trip (Figure 1) examines some of the remaining pits exposing Cretaceous rocks in Middlesex County. Continuing rapid development of Middlesex County has led to the closure of many of the best geological exposures of the Cretaceous Raritan and Magothy Formations. Fortunately, many of these exposures have been documented and described in previous field guides including Owens and Sohl (1969), Owens et al. (1977), and Olsson (1987), and in geologic maps (Owens et al., 1995; Sugarman et al., 1995).
The stratigraphy of Cretaceous rocks in Middlesex County, New Jersey has been studied for well over a century. Early economic studies concentrated on the use of clay deposits for making earthen and stoneware pottery, and fire brick (e.g., Ries et al., 1904). Because small beds or lenses of clay were economically important, a stratigraphic terminology developed which often had local significance, but lacked criteria for regional correlation.
Later studies focused on the growing importance of these deposits as sources of ground-water (e.g., Barksdale et al., 1943). Ground-water supply and contamination studies continue to be the major focus of recent geologic and geohydrologic studies in the northern New Jersey Coastal Plain, in large part due to increasing ground-water withdrawals, declining water levels, and saltwater intrusion.
This trip will examine outcropping geology of the Cretaceous Raritan and Magothy Formations (Figure 2) to: 1) develop familiarity with the prominent members (or facies) within these formations; and 2) place these facies into a hydrostratigraphic framework. We will also examine the newly named Cheesequake Formation (Litwin et al., 1993).

A4: STRATIGRAPHY AND HYDROGEOLOGY OF THE UPPER CRETACEOUS RARITAN, MAGOTHY, AND CHEESEQUAKE FORMATIONS, N.J. COASTAL PLAIN

STOP 1: Raritan Center, Edison
Owner: Federal Business Centers.
In the drainage ditch on the Federal Business Centers, ∼30 feet of the Raritan Formation are exposed. This formation is capped (at ∼100 feet) by 5 feet of surficial material consisting of cross bedded sand and gravel. At this stop, the Raritan Formation consists of (from top down):
10 feet of interbedded black laminated to thin bedded clay.
10-15 feet of pale yellowish orange to grayish orange cross-bedded fine to coarse sand, occasionally micaceous.
10 feet massive black clay-silt; very lignitic, with pyrite, occasional 2 inch diameter siderite concretions, and interbedded fine sand.
1 foot of white, very clayey sand with possible burrows or roots. Contact of this white clayey sand and black clay above is irregular.
No marine fossils have been collected at this site. Pollen collected from black clays has been assigned to Pollen Zone IV of Sirkin (1974). This zone is equivalent with the Complexiopollis-Atlantopollis Assemblage Zone of Christopher (1979) which is predominantly middle to upper (?) Cenomanian.
Prior to recent industrial development, the Farrington Sand Member of the Raritan Formation was exposed across the road at lower elevations.
5-10 feet of an interbedded crossbedded, medium micaceous sand and dark gray, very woody claysilt, which can be both massive and bedded. Interpreted as meandering stream deposit. Also assigned to Pollen Zone IV. At the base of the pit (∼20-30 feet elevation), the Farrington was in contact with a red shale and clay.

STOP 2: Abandoned Pit of the Sayre & Fisher Brick Co.
Owner: K-Land Corporation #5
The Sayre & Fischer brick pit offers the best exposure of the Woodbridge Clay Member in New Jersey. It also contains the contact of the Raritan and Magothy Formations in the southeastern part of the pit. This stop has been previously described by Owens and Sohl (1969), Owens et al. (1977) and Olsson (1987, 1980). The Woodbridge Clay at the pit contains:
30-40 feet of black laminated silts and clays containing many layers of siderite- and iron-oxide- cemented sand. Laminations destroyed by burrowing in the top section. Fossil imprints occur near the middle and top of the Woodbridge Clay in micaceous siderite sandstone concretions (Owens et al., 1977). Pyrite and lignite are scattered throughout the Woodbridge.
5-6 feet of sand and clay containing wood (often in an upright position) were previously exposed at the base of the pit and are now below the upper level of the pond. Richards (1943) and Stephenson (1954) describe a diverse assemblage of bivalves and gastropods. Stephenson (1954) correlates this fossiliferous layer with the Cenomanian Woodbine Formation of Texas. Sohl (in Owens et al., 1977) interprets this fossil bed to be the result of a winnowed storm deposit, placing an infaunal-dominated molluscan assemblage into a marginal marine environment Recently, the upper Cenomanian ammonites Metoicoceras bergquisti and Metengonoceras sp. were collected from the Woodbridge Clay at this pit (Cobban and Kennedy, 1990). The Woodbridge Clay is also the type for the Cenomanian Complexipollis-Atlantopollis assemblage Zone (Christopher, 1979).

STOP 3: Sayreville Recreational Complex.
Owner: The Borough of Sayreville
The closing of the South River Sand and Gravel Pit (see Owens et al. 1977 for a description) several years ago eliminated the finest exposure of the Old Bridge Sand in New Jersey. This exposure of the Old Bridge Sand member of the Magothy Formation is a good (but slumped) outcrop showing a major sand channel in the Old Bridge Sand. To the east of this exposure is a graded, seeded bank which offers a partial view of the very carbonaceous, laminated clay-silt and fine sand which was better exposed at the South River Sand and Gravel Pit, and is a common facies of the Old Bridge. The Old Bridge Sand (and thin surficial cap) at this site consist of:
0-5 feet of light brown surficial sand and gravel. At the contact of the surficial unit and the Old Bridge Sand (∼90 feet elevation) is an ironstone layer.
25 feet of medium (occasionally coarse) micaceous cross bedded sand. Cross-beds consist of small 2-3 inch troughs, sometimes with thin clay stringers, and occasional thin lignitic cross-lamina

STOP 4: John F. Kennedy Park - Lunch
The park is the site of an old pit where there used to an excellent exposure of the South Amboy Fire Clay Member of the Magothy Formation. This member was described at this location by Owens et al. (1977; p. 96) as:
" ... a tough, White, light -blue to gray or red-mottled clay. Locally it may be quite dark and contain some lignite ... ". "Sulfur-balls" (round, ball-like aggregates of pyrite, 1 to 4 inches in diameter) are found in many places, and disseminated pyrite is common throughout the unit. At some localities, small pieces of amber occur near the base of the South Amboy".
On the other side of Washington Avenue we passed the DuPont plant on the way to Kennedy Park. A split spoon well from the site, described below, gives thickness and description of strata outcropping at the park, as well as in the shallow subsurface.
DuPont Parlin FW-5 (Ground Elevation 107 ft; depths reported below land surface).
Pennsauken Formation (∼40 feet thick)
5-7': Yellowish red poorly sorted fine -very coarse sand, some rock fragments, trace granules and clear mica, 1 % opaques.
10-12': Reddish yellow (7.5 YR 6/6) gravel (maximum 3/4"), gravely sand, some silt, poorly sorted, with rock fragments and feldspar, 2% opaques.
15-17': Light brown (7.5 YR 6/4) gravel (maximum 1.25"), gravely sand, and some rock fragments, with more large gravel.
20-22' Light gray (10YR 712) sand, well sorted, mixed with sandy gravel.
25-27': Very pale brown (10YR 7/3) moderately sorted sand, mostly fine with some medium, trace mica.
30-32': Light reddish brown (5YR 6/3) sand, poorly sorted, mostly medium, trace of clear and green mica
35-37': Reddish yellow (5YR 6/6) clayey gravely sand; gravel to 1" maximum.
Magothy Formation - Old Bridge Sand (∼55 feet thick)==========
40-42': Light gray (10YR 7/2) sand, well sorted, fine, clear quartz, trace medium, some fine opaques.
45-47': Same as above.
50-52': Light gray sand, medium.
60-62': Light gray sand, medium, some fine and coarse, minor mica and carbonaceous material ..
65-67': As above, medium to coarse, trace gravel to 1/4".
70-72': Light gray to light brownish gray coarse to very coarse sand, trace mica
75-77': Sand, clayey, medium to -very coarse, with some 1/2" gravel, becoming light yellowish brown.
80-82': Sand, light gray, coarse, with occasional gravel.
85-87': Yellowish gray (5Y 7/2) to light brown (5YR 5/6) interbedded clay and fine to medium sand.
90-92': Light gray sand, medium to coarse, poorly sorted, with some mica
Magothy Formation - South Amboy Fire Clay (∼32 feet thick)=========
95-97': White (N9) - pinkish gray (5YR 8/1) sand, very fine to fine, trace silt.
100-102': Yellow gray to light brown sand, very fine to fine, laminated, trace silt.
105-107': Yellowish gray (5Y 7/2) silty fine sand, with mica.
110-112': Sand, silty, fine to medium, with some coarse to very coarse.
115-117': As above, various shades of orange (10YR 8/2, 8/6, 7/4).
120-122': Light gray (N7) silty sand, very fine, well sorted, 1 % clear mica, trace lignite.
125-127': Medium dark gray laminated clay-silt, 5% fine sand, 1% pyrite, mica, trace lignite.
Raritan Formation - Woodbridge Clay (∼100 feet thick)==============
130-132': Light to medium light gray clay-silt, some very fine to fine sand, with some elongated lignite pieces.
135-137': Medium-dark (N6-N3) gray, as above, with more clay, carbonaceous material, and mica
140-142': Light gray (N7) silt, 1-2% very fine sand, 2% mica (White).
145-147': Light olive gray (5Y 611) very fine to fine sand, some silt, white mica, and trace of fine carbonaceous matter.
150-152': Light olive gray (5Y 611) laminated silt, with abundant finely disseminated mica and carbonaceous material, some siderite.
160-162': Grayish orange (10YR 7/4) sand, very fine -fine, with white mica and some carbonaceous material.
165-167': Light gray silty fine sand, mica and trace wood.
170-172': Dusky yellowish brown (10YR 212) clay with some very fine sand laminae, trace mica, with occasional thin siderite lenses.
175-177': Moderate brown weathered siderite stained clay-silt
180-182': Dark to moderate yellowish brown (10YR 4/2 to 5/4) laminated clay/silt with very fine sand, 2-3% finely disseminated mica and carbonaceous material.
185-187': Light gray (N7) clayey silt, laminated (?), with finely disseminated mica and carbonaceous material.
195-197': Light gray silt, as above, less mica
205-207': Light olive gray to olive gray (5Y 611-411) clay, some silt, trace mica; massive.
215-217': Medium dark gray (N4) carbonaceous clay, slightly micaceous.
220-222': Medium dark gray (N4) silty clay with some very fine to fine sand, 2% clear mica. 1 % fine carbonaceous material.
Raritan Formation - Farrington Sand (minimum 13 feet thick)=========
227-240': Light gray sand, medium to very coarse, tr.lignite.

STOP 5: Gully by Cheesequake Creek and Garden State Parkway
Owner: Kaplan Companies
The gully contains a complicated arrangement of facies generalized by Olsson (1987) as:
0-29 feet of "...dark gray sands and carbonaceous-rich clays, uniformly cross-bedded sands, intermixed flaser bedding, and layers of rip-up clasts." Sands are very micaceous.
16 feet of "...dark gray laminated clay, dark gray alternating sands and clays, and carbonaceous-rich layers".

STOP 6 Route 34 - Northwest tributary to Lake Leffert
Owner: Russ Weber
When initially entering the creek, the Merchantville and Woodbury Formations are exposed. They are gradational units, with no clear contact between them. Exposed in the northern part of the creek is:
0-5 feet of surficial gravel.
5 feet of massive to laminated slightly glauconitic clay-silt (Woodbury Formation).
2-3 feet of massive, burrowed clayey glauconite sand (Merchantville Formation).
Further down the creek, the contact of the Merchantville and Cheesequake Formations are exposed. The contact is irregular and burrowed with a 3 to 4 foot reworked zone, and siderite concretions along contact. Along the contact is a burrowed brown clay with dark green medium-to-course glauconite sand of the Merchantville Formation in the burrows.
The Cheesequake Formation is exposed in the southern part of the creek (tributary to Lake Leffert). Its total thickness is -30 - 35 feet; descriptions are developed from composite sections. We will see the upper beds of the Cheesequake at this locality.
4 feet of pale to moderate to dark brown fine sand (lighter colors reflects more weathered sands), laminated with yellowish brown clay-silt, finely burrowed, with much fine dispersed mica (mostly clear) and lignite.
6 feet of massive olive-gray clay-silt with very fine sand, very micaceous and lignitic.
The lower beds down the creek and in gullies just to the north off Morristown Road are more fine grained and glauconitic:
10 feet of massive, dark greenish-gray clay-silt with very fine to fine sand, very lignitic and micaceous (clear, white, green, and brown - very fine to very coarse plates), and glauconitic (4-5%, mostly coarse and immature). Some delicate sand filled burrows are present.
1 foot of olive gray clay-silt, glauconitic (20%, fine to medium, botryoidal and accordion forms), with some very fine sand, very micaceous (mostly clear), and slightly lignitic. Contains 0.25-1 foot in diameter pale to grayish brown siderite concretions. At the base of the unit are clay filled burrows (0.5" diameter), occasional molds of gastropods, and siderite concretions (at basal contact with the Cliffwood Beds).

A5: DEGLACIATION OF CENTRAL LONG ISLAND
LES SIRKIN
Earth Science
Adelphi University
Garden City, NY 11530
ABSTRACT
The moraines of Long Island were deposited during the late Wisconsinan Stage of the Pleistocene Epoch by the lobate margin of the Laurentide Glacier. This glacier advanced into the Long Island region twenty-two thousand years ago (22ka) and deposited the terminal moraine and the outwash plain to the south. Between 22ka and 20ka, the ice receded northward across Long Island, establishing at least two recessional positions. During each stand of the ice, recessional moraines were deposited, proglacial lakes developed between the ice and the moraines, and meltwater carved drainage channels southward across the outwash plain and laterally along the ice front. In central Long Island, these features, which can be identified by tracing the recession of the Connecticut Lobe of the glacier northward from the Ronkonkoma Moraine, the terminal moraine of this lobe, include the Connetquot-Nissequogue meltwater channel that drained north to south through outwash plains and proglacial lake basins, the Stony Brook Recessional Moraine, and finally the last recessional moraine, the Roanoke Point Recessional Moraine, along what is now the northeastern coast of Long Island, and draining of the proglacial lakes in the Long Island Sound basin. The glacial history of the region is the subject of Dr. Sirkin's books "Eastern Long Island Geology" and "Western Long Island Geology.
In the context of geologic time-- over four and one half billion years-- the formation of Long Island is barely a footnote. It took only about two thousand years, between twenty-two thousand and twenty thousand years ago for glacial advance and deposition of the terminal moraine and deglaciation and deposition of the recessional moraines. From twelve thousand years ago to the present, sea level rise and coastal erosion have shaped the moraines and created the characteristic, fish-shaped Island geography. Consequently, the variety of glacial and postglacial features, ranging from ice-contact deposits to relict landforms is readily available for study. This geology is well represented and readily accessible in coastal bluffs and on the surface, and is easily seen from roadways, beaches and trails.

A5: DEGLACIATION OF CENTRAL LONG ISLAND

STOP 1. Heckscher State Park
The trip starts at the entrance to Heckscher State Park (Bay Shore East Quadrangle). Follow the roadway loop through the park for four and one-quarter miles.

The late Wisconsinan outwash plain underlies the park
The late Wisconsinan outwash plain underlies the park, salt marshes and the bay to the south. A filled-in, crescent beach forms the south shore of the park. The Connetquot River estuary drains into Nicoll Bay over one mile to the northeast, but prior to Holocene submergence the river probably meandered to the southwest against the Heckscher shore. A few miles to the south, Fire Island forms the barrier beach that encloses Great South Bay.

Great River Road follows the west bank
Great River Road follows the west bank on the outside curve of the southernmost meander of the river, beginning south of Sunrise Highway. The west bank is the steep side (outside) of the meander loop, and it rises about fifteen feet above the river. The topography of the river valley is somewhat obscured by development.

Rt 27A essentially follows the meander curve
Rt 27A essentially follows the meander curve but well above the cut bank. Note: the field trip follows the meanders of the meltwater channel valley in the direction of glacial recession and against the direction of late-glacial meltwater discharge. North of the terminal moraine, the meltwater channel meandered and lengthened as the ice front receded and tributary channels drained proglacial lakes.

Cross the Connetquot River valley near Lower Pond.
The river has been dammed here to form Lower Pond and East Pond. The river bottom is partially hidden by development and highway ramps to the south. To the north, stands of trees and shrubs mask the ponds and the channel.

STOP 2a. Western margin of the Connetquot valley
Stop where convenient to become oriented to the terrain. Note that while the river meanders are easily followed on the topographic map, extensive housing development hides the valley. The road follows the western margin of the Connetquot valley, passing the Bayard Cutting Arboretum and the Connetquot State Preserve (Central Islip Quadrangle). The Connetquot River, while gently meandering on its flood plain, has been dammed for mill ponds and a fish hatchery. A well defined, west-trending valley meander forms the river's reach and a low eroded bank in the outwash between the Long Island Railroad tracks and the village of North Great River. But it is against the easterly bend of the valley, located in the State Preserve to the south, that meltwater carved a twenty foot escarpment. The breadth of the valley meanders compared with the width of the Connetquot channel shows the river to be decidedly underfit in this segment. Evidently, a much more robust, meltwater-laden river established the meander pattern and shaped this much broader valley (Figure 1b). The fifty-foot contour line and the adjacent contour lines outline the valley morphology from meander to meander northward from the State Preserve to the Ronkonkoma Moraine.

STOP 2b. "Headwaters of Connetquot River."
The valley can be entered from a gate east of the sign with permission from the State Park Preserve, as indicated.

Nichols Road crosses the outwash plain
Nichols Road crosses the outwash plain between the Ronkonkoma Moraine to the north and the rapidly narrowing river valley to the east.

STOP 3. Sand pit in the Ronkonkoma Moraine.
Walk to the west to the remnant exposure in the extensively mined and once two hundred foot high segment of the Ronkonkoma Moraine. Here about twenty feet of outwash is capped by a thin (two to four foot) layer of brown sandy and gravelly till. Erratics are scarce. The thin soil horizon (A?) at the top is formed on loess (Figure 4).

STOP 4. The headwaters are buried here
The headwaters of the Connetquot River drainage are now buried under the roadways. The watershed begins in a significant gap in the Ronkonkoma Moraine. Stop, if traffic allows, as near the gap as possible, even though roads and residential development obscure the view. The late-glacial meltwater channel was incised through the moraine as meltwater carved an easterly meander sixty feet above present sea level (Figure 1b). In a short excursion to the east, Vanderbilt Motor Parkway ascends the Ronkonkoma Moraine (Figure 3a and b). To the west, the Parkway crosses the gap and climbs the meander-scarred moraine--although not easily seen due to the highly suburbanized character of the terrain.

The road follows the meander scar
The road goes up a hill that follows the meander scar. The evidence of meander erosion shows that meltwater flowed at this higher elevation during the interval of valley widening. Upstream, the valley turns sharply from the northwest against the steep proximal slope of the moraine, incised by a seventy foot-high meander scar.
The northern half of this meltwater-formed meander has become, in the context of the modem drainage, the headwaters of the north-flowing Nissequogue River drainage, a region of wetlands and ponds within the fifty-foot contour line. The river valley casts two broad meanders over the relatively flat basin enclosed by the Ronkonkoma Moraine to the south and the recessional moraines of the last glaciation to the north--the Stony Brook Moraine to the northeast and the Northport Moraine to the northwest). These moraines may be recessional moraines of the Connecticut and Hudson lobes of the glacier, respectively, or segments of the moraine of a sublobe of the ice front that formed between the main lobes at this stage of glacial recession (Figure 3c and d). This lowland, characterized by meanders incised into a plain of low relief, wetlands and pitted outwash, is underlain by lake clays deposited on the floor of a proglacial lake formed between the terminal moraine and the ice front during deglaciation.

Terry Road enters hummocky topography
Terry Road enters hummocky, stream-dissected and kamic topography north of the Ronkonkoma Moraine.

Dissected kame or outwash fan
Note the exposure of a dissected kame or outwash fan on the east side of Terry Road.

Another possible dissected kame or outwash fan
Another possible dissected kame or outwash fan can be seen on the north side of the junction of Terry Road and Rt 25, Middle Country Road. Eroding sand and gravel forms the slopes.

STOP 5. Proglacial lake basin
Stop where convenient to consult the topographic map (Central Islip Quadrangle), get your bearings, and consider these features. Terry Road and this segment of Rt 25 follow the edge of a proglacial lake basin that formed between the Ronkonkoma Moraine and the receding ice front during the late Wisconsinan. The roads curve against the meander-cut valley wall. The underfit channel of the Northeast Branch of the Nissequogue River first wanders northward through (former) wetlands before making a broad northward curve.
The channel is divided into several small ponds formed from dammed-up stream segments. It then heads westward, south of Smithtown, to New Mill Pond, also the result of a dam, and then turns northward across the flat channel bottom and flood plain deposits where the valley narrows significantly. While clearly seen on the topographic map, the channel is obscured on the east side by housing, office buildings and a shopping center. The poor drainage on the proglacial lake-bottom clay beds, cf. the Smithtown Clay, of late Wisconsinan age, serves as a reminder of the geologic history of this lowland. Emerging from the lake basin southwest of Smithtown, the valley turns northeastward. The narrow river channel is incised into the outwash with high banks on either side. The river can be seen south of and parallel to Rt 25, west of the Rt 25-Rt 25A fork, west of Smithtown, where it flows northeastward through a young hardwood forest established on the flood plain. It then crosses Rt 25 just east of the Rt 25-Rt 25A fork, about one mile west of the Rt 111 intersection.
The narrow valley persists through a broad eastward meander north of Smithtown where the meltwater channel cut through the recessional moraine. The modern Nissequogue River actually meanders in a confined belt on its own marsh-covered flood plain, but through steep valley walls of the meltwater channel up to one hundred feet high. The river becomes tidal near Mill Creek, and tidal flats cover channel deposits northward to the river mouth. Where the Nissequogue River enters Smithtown Bay, it is restricted by sand bars from both the east and west sides. On the east side, a northwest-hooking spit, Short Beach, indicates the dominant direction of littoral drift. The spit has forced the river outlet to bend further westward; the west sand spit has, in turn, confined the westward discharge.
A proglacial lake basin extends to the northeast and underlies much of the Saint James region. This basin drained, in part, to the southwest via narrow channels into the Nissequogue meltwater channel in the Village of the Branch and Smithtown, and eroded the interfluves into narrow ridges. One such ridge was described by Fuller (1914) as an esker which bordered a drift-less area [i.e. the proglacial lake bed of the current model] and was somehow seen as evidence of the greater age of that terrain.

Road rises onto the Stony Brook Moraine.
The road rises onto the distal slope of the recessional moraine, the Stony Brook Moraine. The river lies near the interlobate angle, but Nissequogue River Road and adjoining roadways cut through successive, washboard ridges and swales of the Stony Brook Moraine for over three miles between here and the north shore. This segment of the Stony Brook Moraine is typically hummocky and has a number of kettles. The east-west washboard texture is probably the result of stillstands of the ice front during recession and postglacial channel deepening.

A good view of the river and moraine
A good view of the river to the west (left) and the eroding roadcut in the moraine on the east (right) side.

Views of Nissequogue tidal estuary to west.

The road descends the kame moraine
The road descends the kame moraine to the level of the salt marsh, and then enters Smithtown Short Beach.

STOP 6a. Consider the variety of coastal landforms.
Park and walk to the beach. Consider the variety of coastal landforms. To the southwest, a bluff has been cut into the moraine by coastal processes. To the northeast, you can see the topography of the Roanoke Point Recessional Moraine forming distant bluffs on the Old Field headland. The successive ridges of this eroded westernmost extension of the moraine are apparent from this perspective. Try to imagine the confluence of the Roanoke Point and Sands Point moraines to the north in what is now Smithtown Bay in late-glacial time before the deposits were erased by meltwater streams and later by coastal currents. To the east, large erratics in the Bay are a reminder of the continuing erosion of the moraine and recent increments of sea level rise. Today, bay currents are dominantly east to west along this beach.

Meanders of the meltwater channel valley
Here you can observe the estuary and the meanders of the meltwater channel valley south of the Short Beach spit. The Nissequogue River estuary, the drowned and silting mouth of the north-flowing river, is confined by two sand bars. Short Beach trends east to west and then northwest on the east side and forces the river to the northwest; the opposing Sunken Meadow Beach on the west side channels Sunken Meadow Creek eastward parallel to the bar and into the estuary.

Last prominent ridge of the Stony Brook Moraine.
Long Beach Road cuts northeasterly across the last prominent ridge of the Stony Brook Moraine.

The eroded edge of the moraine
The eroded edge of the moraine, at the base of Long Beach, reveals a 100' high bluff with an exposure of thin (2-4 ft), sandy melt-out till over outwash, capped by 5-10 ft high sand dunes (Figure 4).

STOP 6b. Long Beach. Stony Brook Harbor
Stop 6b. Long Beach. Stony Brook Harbor, the mouth of a north-trending stream valley cut into the Stony Brook Moraine, is diverted eastward through Porpoise Channel by. the one and one half mile long, Long Beach sand bar. This estuary is also silting in. On the east side of Smithtown Bay, Long Beach forms a narrow inlet along with West Meadow Beach, a spit that trends southward along the Setauket coast from the distal margin of the Roanoke Point Moraine at Old Field to the northeast. The Roanoke Point Moraine forms the headland in a series of washboard ridges. As mentioned, the geographic extension of the trends of the Roanoke Point Moraine from the east and the Sands Point Moraine from the west meets in an interlobate angle near the north-central margin of Smithtown Bay (Figure 3d-f).

A6: HIGHLIGHTS OF STATEN ISLAND GEOLOGY
Alan I. Benimoff and Anderson A. Ohan
Department of Applied Sciences
The College of Staten Island
Staten Island, NY 10314
Introduction
Since the 1975 NYSGA field trip on Staten Island (see Ohan et al. 1975) there have been many contributions to the geology of Staten Island. Staten Island geology(see figures I and 2) is very diverse, consisting of Cambro-Ordovician serpentinite, Jurassic diabase, Newark Group sedimentary rocks, Cretaceous and Pleistocene sediments. In addition, there are numerous wetlands, stream drainage basins and the world's largest landfill. Staten Island has an interesting plate tectonic history as John McPhee notes in his 1993 book entitled Assembling California "Southeastern Staten Island is a piece of Europe glued to an ophiolite from the northwest Iapetus floor". The aim of this trip is to give highlights of the geology of Staten Island.

A6: Highlights of Staten Island Geology

Outcrops of Staten Island Serpentinite on right and left

STOP 1. The Staten Island Serpentinite
This outcrop represents the largest continuous exposure of the Central-Zone Serpentinite on Staten Island, and is a foliated serpentinized Harzburgite, composed essentially of Lizardite (48-71%), chrysotile (15-30%), and olivine (10-15%). Antigorite, anthophyllite, talc and magnetite are present in minor concentration (Puffer & Gennine 1994). Numerous veins are filled with carbonates, chrysotile or talc. A number of folds exist displaying a N40°E - N 45°E trend and a NE plunge. Several folds have western limbs that are overturned and are cut by high angle NE-SW trending faults. At this locality, the trend of one hundred and twenty-five fractures were measured and statistically plotted, in an attempt to determine the relationship between the joint patterns and the existing structure. The fractures can be categorized into 3 types based on their orientation to the folds. Type (1) longitudinal joints subparallel to the axial planes of folds, and may be release joints. Cross Joints This joint set is oriented normal to the fold axis and commonly develop in the hinge zone of folding by stretching parallel to the fold axis. Oblique Joints may be conjugate shear sets produced by a shortening normal to the axis of folding (Davis & Reynolds 1996).The fracture pattern relationship with the folds indicates a common origin. It is suggested that the folding, faulting and fracture patterns were produced by a SE-NW oriented compressional stress and may be related to the Mid Ordovician Taconic event.

STOP 2. The Graniteville Quarry.
At this locality, we see an extraordinary example of two coexisting magmatic liquids, now represented by the diabase of the Palisades Sill and a pyroxene Trondhjemite derived by fusion of the the margins of a xenolith of sodium rich Lockatong Argillite (Benimoff and Sclar, 1978, 1980, 1984, 1988, 1992, 1996; Sclar and Benimoff,1993). The diabase is composed dominantly of plagioclase (An61Ab38.8Or0.2) and augite (En34-44Fs17-31 Wo35-42). The trondhjemite is composed dominantly of quartz-albite granophyre in which are enclosed large discrete crystals of albite(Ab99An0.52Or0.44) and Ca-rich pyroxene. Minor constituents include interstitial calcite, titanite, ilmenite, optically homogeneous titanomagnetite, nickelian and cobaltian pyrrhotites, apatite, and sphalerite. The modal mineral percentages are clinopyroxene 38, albite 38, quartz 18, titanite 2.7, calcite 1.3, and opaques 2.0. The xenolith is now a hornfels and exhibits a granoblastic texture. The hornfels is composed dominantly of albite and quartz and subordinately of calcite, titanite, apatite, ilmenite, and actinolite. The modal mineral percentages are albite 66, quartz 30, titanite 2.3, calcite 0.9, apatite 0.5, and actinolite 0.3. Normative albite ranges from 56.4 to 80.2 wt.%, whereas normative quartz ranges from 7.0 to 35.4 wt.%. Chemical analyses(Table 1) reveal that diffusion of calcium, magnesium, iron, and sodium ions occurred across the liquid-liquid interface.
On the surface of the bedrock in the quarry area, numerous ice-sculpted features are present. These include shallow trough-like grooves, striae, and crescentic marks.

View Landfill

Arthur Kill Correctional Facility on Right

STOP 3. AKR TRUCKING COMPANY, 4288 Arthur Kill Road
The owner is Mr. Frank Agugliaro.
Prolific Pleistocene till overlies most of the older units on Staten Island and the age of these deposits are believed to be late Wisconsin (Roberts-Dolgin 1989). This exposure is approximately 1 mile north of the Terminal Moraine, which exists on the eastern part of Staten Island, extending from the Narrows to Tottenville. Sanders and Merguerian (1994) report red-brown till overlying decayed-pebble outwash, which rests on white, charcoal-bearing Cretaceous micaceous sands and gray clays. At this exposure, glacial outwash is present at the northern section of the driveway. The unit is a tan to red-brown sand, alternating with sandy gravel. The entire outcrop displays abundant trough cross-stratification, and existing rock fragments have an origin from the following sources:
1) Diabase and clastic sedimentary rocks from the Triassic-Jurassic Newark Super Group
2) Ironstone clastics of Cretaceous Age.
3) Granite-Gneiss Precambrian N.Y.-N.] . Highlands.
4) Lowerre or Poughquag Quartzite.
The source of these clastics may have been from the north or west.
The rock fragments show advanced stages of chemical weathering. Sanders and Merguerian (1994) believe that and the trough cross-bedding and the extensive chemical alteration indicates this unit was formed in a braided stream during the Early Pleistocene (Nebraskan).
Roberts-Dolgin (1989) concludes this unit is the Pensauken formation which represents a stream deposit formed during an interglacial period. It is suggested that the existing glacio-fluvial deposit is part of a delta that entered Lake Bayonne, a glacial lake that existed between the glacier and the Terminal Moraine. (Stanford and Harper, 1991).

STOP 4. The Conference House Park
Proceed past the conference house to the beach. The late Wisconsin aged Harbor Hill terminal moraine(see figures 2 and 5) is present in the cliffs facing the Raritan Bay. The typical unsorted, unstratified character of glacial till is exposed at this locality. The till is red-brown, with many large boulders intermixed with finer sediments in the moraine, as well as on the beach. The existing erratics display a wide variety in rock type, reflecting a source from the North or Northwest. They are examples of glacial outwash in several areas along the cliff. Merguerian & Sanders (1994) believe The Terminal moraine is Mid-Wisconsinan, (Sangamonian?) These authors believe that overlying the terminal moraine is a Paleosol, with downward extending zones of discoloration. They interpret these zones as tree roots.

B1: SEDIMENTARY ENVIRONMENTS IN THE NEWARK BASIN IN NEW JERSEY AND CONTIGUOUS
NY
GERALD M. FRIEDMAN
Brooklyn College and Graduate School of the City University of New York
Brooklyn, New York 11210
and Northeastern Science Foundation affiliated with Brooklyn College of the City of New York
P.O. Box 746
Troy,
As Manspeizer (1988) noted "these are extraordinary times for Triassic-Jurassic researchers of the Atlantic passive margins. Extensive field studies on the African and North American plates during this past decade have yielded a wealth of new data and ideas about rift basins and the origin of passive margins, that but a few years ago would have seemed like childish speculation.
New surface and subsurface basins have been identified, fossils abound in strata that only recently were considered barren, oil exploration is being pursued actively in continental strata of the Richmond - Taylorsville, Sanford and Newark basins, Late Triassic marine strata have been identified in Georges Bank off the coast of Massachusetts, and the roles of wrench tectonics, successor basins and listric normal faults have challenged the classical view that these are simple extensional basins. Geologic data from the Atlantic passive margins record that continental rifting of central Pangaea occurred during the Late Triassic - Early Jurassic (Liassic), and that sea-floor spreading probably began no later than the Middle Jurassic.
The Newark Supergroup is composed of Late Triassic to Early Jurassic continental sedimentary rocks and interbedded basalts that crop out in a series of elongated basins along the eastern margin of North America (Froelich and Olsen, 1985).

B1: SEDIMENTARY ENVIRONMENTS IN THE NEWARK BASIN IN NEW JERSEY AND CONTIGUOUS
NY

STOP 1. Feltville Formation of the Newark Supergroup
On north side of Blue Brook are exposed interbedded micaceous red and gray siltstones and shales with sporadic lenticular channels of quartz sandstones. These exposed strata are part of the type section of the Feltville Formation of the Newark Supergroup. Similar exposures are present an estimated 1/4 to 1/2 mile farther east on south side of the brook, where a tributary meets Blue Brook. In the creek bottom are numerous blocks of quartz-pebble conglomerate.
According to Paul Olsen (personal communication, 1985) the strata at this site carry abundant spores and pollen.
For stratigraphic section see Table I. Figure 4 shows type section of the Feltville Formation exposed along ravine near Blue Lake; Table 2 provides the key for individual units.

Note exposures of Watchung Basalt, especially spectacular columnar jointing.

Note exposures of Watchung Basalt.

Ascend road to Scenic Overlook and return to Interstate 78.

STOP 2. Anthony Ferranti Quarry.
(Permission is needed to enter this quarry. _ Contact Linda Kimler, Public Relations, Anthony Ferranti Quarry, 908-647-8273).
Spectacular outcrops of sandstone, siltstone, and shale of the Feltville Formation occur beneath the Preakness Basalt (see Table I). Crossbedded sandstones show local channeling. Find sandstones with dinosaur footprints and plant fossils as well as raindrop impressions on mudcracked surfaces. Note small strike-slip faults in quarry.

Cuts on L side are in Palisades dolerite.

Cuts in dolerite, both sides of road.

End of cuts in dolerite.

Small dolerite cut on R.

Wooded hill in distance on R is Palisades sill
Wooded hill in distance on R is dip slope on W side of Palisades sill (strike NS, dip 150 W).

Exposure of dolerite of sill on R; overlain by sill.

Exposure of dolerite of sill in slope at R.

Barricade; passage for "Official Cars Only".
Park vehicles at barrier.

STOP 3. Nyack Landing, Upper Nyack
(SE part of Haverstraw 7.5 minute quadrangle, along W shore of Hudson River at Long. 73°54'W, from Lat. 41°08'15" to Lat. 41°07'30"N).
Walk southward on gravel road, along floor of old quarry in Palisades dolerite. Take trail toward Hudson River from S end of quarry. Walk down to lower level and study exposures along lower trail. The level of the old quarry floor lies at an altitude of about 60 ft; the top of the cliff facing the quarry is at an altitude of 510 ft. Thus the face is about 450 ft high. The face extends downward nearly to the contact with the underlying basal Newark sandstones. The contact is not exposed but lies near altitude +50 ft. The descriptions at this stop follow Friedman, Sanders and Martini (1982).
The continuous exposure of dolerite in the face is a noteworthy display of cooling joints, which are inclined off the vertical about the same amount as the base of the sill dips westward, i.e., 12 to 15°. At this locality, no olivine zone is exposed. Farther south the olivine zone, 10 to 15 ft thick, is located about 50 ft above the base of the Palisades sill. The absence of the olivine zone here could mean one of several things: (1) This exposure includes the lower 450 ft of the sill but no such zone ever formed here; (2) This exposure does not include the lowermost 450 ft of the sill, but that much of some part of the interior of the sill lying above the lowermost 60 to 70 ft, hence the olivine zone may be present but is not exposed in the old quarry face. Alternative 2 implies that a fault follows close along the base of the face and throws down on the west by at least 70 ft.
The large institution directly opposite us on the east side of the Hudson River is Sing Sing, the notorious destination of prisoners "sent up the river" (from New York City). The wide expanse of wooded countryside between Ossining and Tarrytown is the Rockefeller family preserve, an area so large that it has been incorporated as a separate town (Pocantico Hills). Nobody levies local taxes on the Rockefellers but other Rockefellers!
The Croton River enters the Hudson just S of Croton Point, to the NE of us. The till exposed on the tip of Croton Point itself has been interpreted by some as a lateral moraine, but we think this till is part of a drumlin having a N-S axis. Between the till and the mainland is a sandy deltaic deposit which formed when lake water occupied the Hudson Valley to altitude about +60 ft.
The sandstones exposed in a long strike section are situated about 1000 ft above the base of the Newark Group (Upper Triassic to Lower Jurassic)(based on projection from the section at the Tappan Zee Bridge). These sandstones probably belong to the Stockton Arkose (Upper Triassic to Lower Jurassic). The strata strike N20°W and dip 12°SW (determined on base of ledge overhanging the siltstone toward the S end of the exposure). Typical Stockton Arkose is a light gray pebbly coarse rock that contains large-scale cross strata indicating water flow toward the west. Such gray rock interfingers with red siltstones and sandstones containing less feldspar (or even zero feldspar), which form the Brunswick Formation. Farther SW the Newark sequence from base upward is Stockton, Lockatong, Brunswick. Lockatong, typically a tough black argillite deposit of a former lake, is not exposed north of the George Washington Bridge; the argillite disappears by interfingering with the sandstones and siltstones of the Stockton and Brunswick.
The bluff west of the trail exposes about 20 ft of strata, of which the thickest and most persistent unit is a maroon siltstone 6 to 8 ft thick. This unit is overlain and underlain by various sandstones. At the N end of the exposure only the overlying sandstones are present. These include (upward) a coarse pebbly laminated sandstone about 1 ft thick, a laminated, reddish medium-grained sandstone, 2 to 3 ft thick, and 6 to 8 ft of coarse-grained pebbly sandstone having prominent cross strata dipping (now) 28° toward the direction of S45°W (225° true on a 360° scale). The original dip of the cross strata is about 16°. Hence these are considered to be accretion-type cross strata (in the sense of Imbrie and Buchanan, 1965), of the kind that form by the advance of "washed-out sand waves" (features transitional between the "regular" sand waves of the lower flow regime and the plane-bed condition of the lower part of the upper flow regime).
Below the siltstone unit is a bed, 1 to 1.5 ft thick, composed of greenish, poorly sorted conglomeratic arkose, almost a "pebbly mudstone." Next below is a lenticular arkose having a maximum thickness of about 2 ft.
The interbedding of the siltstones and sandstones probably resulted from the action of a floodplain meandering river. One usually tends to expect such rivers to deposit the coarse sediments in channels and the fine sediment on the floodplain. As the channels migrate, a sheet of sediment is deposited consisting of what has been termed a point-bar sequence. This sequence begins with a channel-floor lag at the base and passes upward through various deep-channel and shallow-channel deposits whose thickness equals the depth of flow in the former channel. Such sequences have been much discussed under the heading of "fining-upwards cycles" (Allen, 1965b; also Friedman, Sanders, and Kopaska-Merkel, 1992).
Closely associated with this typical channel-migration succession are deposits of natural levees and fan-like bodies of coarse sediment that spread over the floodplain from crevasses in the levees where floodwaters erode a gap through the levees. These fans have been termed splay deposits (or crevasse splays). (See summary paper dealing with alluvial sediments by Allen, 1965a).
The upper sandstones west of the trail do not seem to be part of a typical fining-upward cycle deposited by a migrating channel. The laminated, medium-grained sandstone just above the siltstone may be a natural-levee deposit and the coarse, cross-bedded sandstone next above may be a crevasse-splay (idea suggested by John Connolly). The coarse sandstone forms a series of imbricate, overlapping lenses, the upper ones of which extend farther southward than the lower ones. Thus, instead of being incised into the siltstone as in a channel, these sands prograde over the siltstone as would the sediments of a growing fan (or the foreset beds of a delta lobe).
The sandstones underlying the siltstone are not exposed enough to be analyzed in detail. The lenticular sandstone, previously interpreted as a "double-channel" are here considered to be a depositional bedform having positive relief, a sort of longitudinal sandbar with the long axis parallel to the main direction of current flow. At the S end of the exposure sandstone and dolerite are in close juxtaposition. The sandstone lacks evidence of contact metamorphism and the dolerite is much too coarse grained for this contact relationship to be explained as intrusive. Accordingly, J.E. Sanders interprets this contact as a normal fault which strikes about NW, is nearly vertical, and throws down on the west by at least 70 ft; this much displacement is inferred in order to drop the olivine zone out of sight. Thus, J.E. Sanders presumes that the olivine zone is present, but is not exposed.

B2: SERPENTINITES OF NEW YORK CITY AND VICINITY
John H. Puffer
Dept of Geology
Rutgers Univ.
Newark, New Jersey, 07102
ABSTRACT
A discontinuous chain of early Paleozoic serpentinites are exposed along the Appalachian Mountains from Quebec Canada, through the New York City area, and into the southeastern states. The Geologic Map of New York, 1970, (Lower Hudson Sheet) shows five serpentinite bodies in the New York City Area: Staten Island, Hoboken, Manhattan, New Rochelle, and Port Chester that are part of this chain. The Staten Island and Hoboken serpentinites are the largest of the five bodies and are known to contain considerable asbestos (Puffer and Germine, 1994). The serpentinites of Staten Island and Hoboken consist of about 95 percent serpentine with minor but highly variable olivine, anthophyllite, talc, magnetite, and trace amounts of several additional minerals.
The chemical range is typical of metamorphosed harzburgite and dunite suites although some unusually low CaO and Al2O3 values may be due to hydrothermal leaching and re-precipitation as a network of amphibole and carbonate veins in shear zones.
The mode of emplacement of the New York area serpentinites is controversial but most evidence tends to favor the Taconic obduction of the base of a Iapetus ophiolite sequence. This would force the placement of the New York area serpentinites into the Taconic suture zone (Cameron's Line) between Hartland terrain (C-Oh) and Manhattan-C terrain (C-Om).
The chrysotile content of New York area serpentinites, as determined using a combination of polarized light and transmission electron microscopy and XRD techniques, is highly variable but is typically about 15 to 40 volume percent of the rock (Puffer and Germine, 1994). The widespread distribution of asbestos minerals in the serpentinites may lead to contamination of water and air supplies wherever exposures are being eroded.

B2: SERPENTINITES OF NEW YORK CITY AND VICINITY

STOP 1. STATEN ISLAND SERPENTINITE
Caution!! At the outcrop, stay on the unused roadway, do not go near I-278; watch out for falling rocks and do not attempt to climb loose rock faces.
This is the most extensive exposure of serpentinite in the New York City area. The serpentinite here contains variable amounts of relic olivine and minor amounts of anthophyllite schist. Both the highly foliated and the massive types of serpentinite are exposed here. The serpentinite exposed within a few cm of any of the closely spaced anastomosing shear planes visible on both walls of the road cut, tends to be green, highly foliated, and includes megascopically fibrous minerals. The rock furthest removed from the shear-planes is relatively dark-green to black and is massive.
An average mode based on 12 thin sections cut from the I-278 exposure is 88 % serpentine, (mostly lizardite and chrysotile), 3 % olivine, 2 % talc, 2 % anthophyllite, 3 % opaque oxide (mostly fine grained magnetite but also including coarse magnetite, chromite, and picotite), and 2 % carbonate (including dolomite and magnesite). About 1/2 of the serpentine is lizardite with highly variable concentrations of chrysotile ranging from absent to 70 % but averaging about 50 %. Minor antigorite is also present including the fibrous variety (picrolite, Benimoff and others, in prep). Olivine is commonly found in the massive, black rock typically as relic micro islands surrounded by serpentine that has replaced most of the individual grains. Talc and anthophyllite are typically found together as a coarse fibrous schist or less commonly as individual grains disseminated within the rock or in veins. The opaque oxides consist largely of the kind of finely disseminated magnetite that is typically expelled from olivine during hydration to serpentine. Olivine can hold more iron than serpentine so the excess iron is typically left as an intergrowth of magnetite and serpentine.
Chrysotile is not readily recognizable in most hand specimens or thin-sections of samples from this exposure. In thin section, only lizardite was recognized in one sample, but using transmitting electron microscopic (TEM) techniques (Puffer and Germine, 1994) abundant chrysotile was found.
Ten samples collected on the south side of the I-278 outcrop, spaced approximately 50 feet apart, were ground in a rock grinder, mixed, split and prepared on an EM grid. TEM point count data indicate a total chrysotile content of approximately 54 volume percent. Germine and Puffer (1994) also performed selected area electron diffraction analyses (SAED) and energy dispersive x-ray spectroscopy (EDEX) on several particles, confirming chrysotile as the major component and lizardite as comprising most of the remainder, with a minor talc component.
The same kind of analyses was conducted on another sample of serpentine from this roadcut (Sample 8p, Figure 4). It contains 38 percent chrysotile as confirmed by SAED and EDXS. The results were within the error range of the Puffer and Germine (1994) XRD estimate.
At least two varieties of massive chrysotile were recognized in samples of serpentine at the roadcut using TEM techniques (Germine, 1981). One variety is light to medium green and has a smooth fracture. It occurs in irregular masses and in veins ranging up to a centimeter in width. This type is composed of cross-fiber and randomly oriented fiber, and is often associated with abundant olivine. The second variety is a light green to white substance with pearly luster and platy to fine-grained meerschaum-like texture. This type of motive chrysotile occurs in veins, fracture fillings, and pore fillings. TEM examination indicates that it is composed of tubules with a diameter of 300 to 400 angstroms. Fiber lengths are generally less than 1 micron but also occur up to 5 microns (Germine, 1981).
Chrysotile with a megascopic fibrous appearance is much less common than massive varieties at this outcrop but occurs in veinlets typically less than 1 mm to 3 mm wide. The fibers are white to light green and silky. The veins readily fiberize and poses the flexibility that is a characteristic of all asbestos (Germine and Puffer, 1989). Asbestiform anthophyllite from this roadcut consists of straw-colored aggregates on anthophyllite fiber in association with gray to yellow-brown talc. The anthophyllite fibers range up to 18 cm in length in silky and splintery aggregates that are fairly rigid.
Slip-fiber veins of picrolite from this outcrop measuring 1 to 3 mm thick are also described by Germine (1981) and Benimoff and others (in prep.).

STOP 2. CASTLE POINT SERPENTINITE
This is probably the second most extensive exposure of serpentinite in the New York City area. The rock here is chemically (Table 2) and mineralogically indistinguishable from the 1-278 exposure but is more highly foliated. Most rock surfaces are bright green. Close inspection reveals common grains of chromite. The network of thin white veins are composed largely of magnesite. Minor quantities of talc is visible on freshly broken rock surfaces.
Some of the bright green serpentinite has a glassy gem-like appearance that is a variety called Williamsite. The Williamsite is composed of very fine-grained chrysotile.
Chemical analysis of four typical bright green samples from this exposure are consistent with meta-dunite although a two dark samples containing pseudomorphs of orthopyroxene are slightly richer in alumina and calcium and are interpreted as meta-harzburgite.