NYSGA 2004
FieldTrip Guidebook
Field Trip Guidebook for the 76th Annual Meeting of the New York State Geological Association
Potsdam, New York
THE STATE UNIVERSITY OF NEW YORK
Potsdam
Edited by
Robert L. Badger
This guidebook was published by the New York State Geological Association.
Additional copies may be obtained from the Publications Manager of the NYSGA:
William Kelly
New York State Museum/Geological Survey
3140 Cultural Education Center
Albany, NY 12230
wkelly@mail.nysed.gov

F1: STROMATOLITES AND ASSOCIATED BIOGENIC STRUCTURES IN CAMBRIAN AND ORDOVICIAN STRATA IN AND NEAR OTTAWA, ONTARIO
J. Allan Donaldson
Department of Earth Sciences
Carleton University
Ottawa, Ontario, Canada K1S 5B6
Jeffrey R. Chiarenzelli
Department of Geology
State University of New York
Potsdam, New York 13676
chiarejr@potsdam.edu
INTRODUCTION
This trip will provide an overview of some interesting sedimentary and biosedimentary structures in Cambrian and Ordovician strata of the National Capital Region (Figure 1); stratigraphic relationships (Brand and Rust, 1977; Williams, 1991; Wilson, 1946) will receive only cursory attention (Figures 2 and 3). The main thrust of the trip is to bring attention to the abundance and variety of shallow water environments throughout early Paleozoic time in this part of eastern Canada. Most outcrops to be visited are within the fault-controlled Ottawa-Bonnechere Graben.
During the drives between several stops, the uplifted northern block of the Gatineau Hills is clearly visible. While driving along Carp Road, we will be following a parallel fault along which Precambrian basement of the Carp Ridge has been uplifted relative to the Paleozoic strata to the south. Most of the rich farmland underlain by Paleozoic strata was inundated by the Champlain Sea, which receded from the region less than 12,000 years ago. Some of these clay-rich areas (including substantial volumes of the landslide-prone Leda clay), were buried by sand and gravel initially deposited as outwash during deglaciation, and subsequently by the paleo-Ottawa River.
Although several outcrops containing fossils will be visited, the unusual abundance of stromatolites in strata of eastern Ontario will be emphasized. In places these stromatolites are so abundant that they provide views reminiscent of large tracts of Proterozoic terranes in northern Canada with which both trip leaders are familiar. Such abundance of biofilm-mediated structures, in strata deposited well after the time during which many browsers and grazers had evolved, seems paradoxical. Yet environments suitable for abundant biofilm growth essentially free of predators exist in several parts of the world today. Where such active ecoscapes currently exist, hypersalinity sufficiently high to inhibit proliferation of browsers and grazers is the primary environmental condition that allows biofilm structures to grow in abundance. Such environments are postulated for growth of most of the stromatolitic units to be viewed in Paleozoic strata during this excursion. Although commonly abundant in beds above and below, shelly and trace fossils are essentially absent from the stromatolitic strata; another line of evidence is the common occurrence of associated evaporite pseudomorphs.
A highlight of the trip will be visits to two occurrences of stromatolites and associated biofilm structures in quartz arenite beds. Similar biosedimentary structures have been observed on the other side of theFrontenac Axis (Dalrymple, pers. com.), and we have seen similar biosedimentary structures in a few localities in New York State. Because such structures can be readily mistaken for dewatering structures when seen in vertical section, re-examination of well-know localities elsewhere is warranted. Because of the prevailing view that stromatolites occur only in carbonate strata, quartz sand stromatolites may well have been overlooked in other areas of correlative strata (especially in unmetamorphosed Precambrian siliciclastic strata, where such biosedimentary structures should have been abundant under conditions of normal as well as elevated salinity).

F1: STROMATOLITES AND ASSOCIATED BIOGENIC STRUCTURES IN CAMBRIAN AND ORDOVICIAN STRATA IN AND NEAR OTTAWA, ONTARIO

STOP 1. Limestone, Ottawa Group (Ordovician)
AT KITCHISSIPPI LOOKOUT, OTTAWA
(Caution: cyclists and skateboarders use the paved path near the river, and patches of poison ivy occur sporadically along the shore beyond it).
The top of a two-metre cliff section along this part of the shore reveals a 20 cm bed of limestone containing laterally linked domal stromatolites with a synoptic relief of 10 cm. The recessively weathered underlying flaggy to slabby beds of limestone contain rare shale interlayers, and are sporadically rich in fossils, including orthocone cephalopods, brachiopods and bryozoa. Some bedding surfaces display desiccation cracks and ripple marks.

STOP 2. Limestone, Ottawa Group (Ordovician)
PARC BREBEUF, GATINEAU, QUEBEC
Those arriving early at STOP 2 may wish to check out the tapered base of the Brebeuf statue, which contains at least 500 cobble stones representative of the many rock types within the Grenville Province, sampled during Pleistocene glaciation, and rounded during subglacial transport and fluvial transport during deglaciation <12000 years ago). Their clean polished surfaces, reflecting derivation from a gravel pit in Pleistocene outwash, provide an opportunity to study the mineralogy, textures and structures (foliation, lineation, intrusive contacts, folding) typical of Precambrian terrane to the north. Around the base of the statue, metre-square pavement panels have been inset with uniformly sized clasts -- some with well rounded equi-size pebbles of white limestone; others with angular fragments of black basalt.
From the base of the statue, walk directly to the shore of the Ottawa River where gently dipping bedrock platforms of limestone display a variety of fossils: corals, stromatoporoids, cephalopods, gastropods, mollusks, brachiopods, crinoids, bryozoa, trace fossils, and fragments of trilobites. The artistically arranged limestone blocks in the retaining walls display a wide range in grain size, as well as primary structures such as bedding, ripple marks and crossbedding. Secondary structures include joints and stylolites. Note how features are accentuated on weathered surfaces.
To the east, a large boulder of Precambrian gneiss marking the Voyageurs Portage shows excellent folded foliation in three-dimensions. Immediately north, Rue Bourget has a curb along the south side consisting of two rows of stone paving blocks. Most are Nepean sandstone (set both on edge and parallel to bedding), but a few are granite. Some of the sandstone blocks display Liesegang banding. From the east end of Rue Bourget, walk east along the bike path (look out for speeding cyclists and roller-bladers). In rounding the curve below the transformer station on the left, note the variety of bedding-surface structures in limestone slabs set in the sloping base of the fenced-in transformer area. At its northeast fenced corner, take the last gravel footpath to the east (just before the T- junction in the bike path) out to the south shore of an inlet on the Ottawa River. Excellent views of folds in limestone beds can be seen along the northeastern shore of this inlet.

STOP 3. Ottawa Group Limestone (Ordovician)
VICTORIA ISLAND, OTTAWA RIVER
In this exposure of Ottawa Group limestone, megaripples are recurring bedforms topping coarse clastic flat-lying beds that are intercalated with carbonate mudstones containing abundant trace fossils both perpendicular and parallel to bedding. Fossils in the megarippled units include bryozoa, brachiopods, crinoids and orthocone cephalopods (cf. Wilson, 1956). A distinct alternation is evident between these calcarenite beds rich in shelly fossils (mainly fragmented) and the shaly calcilutite beds rich in trace fossils. This probably represents alternation between quiet-water conditions and episodic storms. This interpretation fits well with the abundance of fine-grained intraclasts in the coarse grained interbeds. Rare carbonate mudstone surfaces displaying desiccation cracks, reflecting intermittent exposure. The symmetrical megaripples are superposed on cross bedded units, suggesting storm reactivation of originally asymmetric current-deposited subaqueous dunes.

STOP 4. Stromatolites in Pamelia Formation
(ORDOVICIAN), FABLEWOOD
Glaciation has cut a near bedding-parallel section (Figure 4) through a single bed less than 40 cm thick that contains a continuous display of closely packed domal stromatolites. Successive degraded biofilm sheets separated by storm-deposited fine-grained carbonate sediments are marked by concentric rings of carbonaceous matter. In some areas, freeze-thaw action has exhumed the original morphologies over many square metres of laterally linked, domal stromatolites. Mapping at 1:25 scale has revealed strong local north-south trends of elongation for the stromatolite heads (Donaldson et al., 2002). In many places two or more are coalesced in parallel strings oriented in the same (north-south) direction. By analogy with modern stromatolites in Hamelin Pool, Shark Bay, Western Australia, these trends are readily attributed to the action of tides and onshore-wind-driven waves (Playford, pers. com.). Some small stromatolites are elongate perpendicular to the prominent north-south trend; because several inter-stromatolite patches of small-scale asymmetric ripples indicate easterly currents, elongation of the orthogonally oriented small stromatolites is attributed to longshore currents. Intermittent exposure is reflected by micro-desiccation patterns on the tops of a few large stromatolites. Also by analogy with the modern stromatolites of Shark Bay, a hypersaline environment in which biofilm predators (Garrett, 1970) could not survive is inferred. This is supported by the observation that, whereas the underlying stromatolite-free beds of carbonate are fossiliferous (with gastropods and vermiform trace fossils particularly abundant), the stromatolite unit is free of megafossils. Only conodonts have been observed, and those extracted from the stromatolite unit are compatible with a hypersaline environment (Von Bitter, pers. com.).

STOP 5. March Formation
DOLOSTONE AND DOLOMITIC QUARTZ ARENITE (ORDOVICIAN), TIMM DRIVE
This section is only a few metres above the top of the Nepean formation. The carbonate beds contain abundant burrows, including several varieties that are bedding-parallel. Despite the extensive bioturbation, wispy biofilm structures and a few possible dewatering structures can be seen at several stratigraphic levels. Both the siliciclastic and carbonate beds display abundant crossbedding, and carbonate intraclasts are evident in some of the siliciclastic beds. Scattered patches of white to pale pink calcite are inferred to be replacements after evaporite minerals. The strata exposed here are similar to some outcrops showing the Potsdam-Theresa transition in New York State, as described by Selleck (1984).

STOP 6. Nepean Formation Quartz Arenite
(CAMBRO-ORDOVICIAN; POTSDAM EQUIVALENT), CENTURM SHOPPING PLAZA
This 3 m section (Figure 5), recently studied in detail (Anderson, 2004; Anderson et al., 2004), has provided significant information about the complex history of cementation in relation to sea level changes for this uppermost part of the Nepean. Additional information for the study was obtained from a longer exposure of equivalent strata (Dobie, 2004), but unfortunately, much of her longer section to the south (subparallel to the Queensway, north side), has been significantly degraded by construction now underway (a reflection of the lack of respect/protection afforded significant geological features not only in Ontario, but in most parts of the world).
The strata exposed in this section have been divided into facies on the basis of bedding thickness and sedimentary structures such as crossbedding and inferred biofilm structures. The diversity of these interdigitated facies is considerably more complex than as described for the principal reference section (Greggs and Bond, 1972). The prominent thick-bedded dune facies consists mainly of subaqueous dune cross-stratified quartz arenite, in places infilling erosionally-based tidal channels. The thin-bedded laminated facies is characterized by biofilm-mediated crenulate laminations (cryptalgal laminations), heavy mineral streaks, cross-laminated asymmetric ripple marks and granule-rich single-grain layers suggestive of lag accumulation. Soft-sediment deformation (convolute lamination) is locally evident at the top of the section, locally capped by a thin layer of domal quartz-sand stromatolites.
Frameworks grains consist almost entirely of fine- to very coarse-grained quartz; minor components are microcline, plagioclase and chert. Extremely well-rounded zircon, tourmaline and opaque iron oxides form the heavy mineral streaks, but some opaque patches are of post-depositional origin, having clearly been deposited interstitially. Biofilms, now degraded, are inferred to have played a role in accumulation of these trace components (rare semi-opaque brownish-stained patches visible in thin section may be degraded pyrobitumen). Interstitial clay minerals occur as thin discontinuous films around some framework grains in the least-cemented zones. Quartz alone is the cement for well-indurated beds up to 3 cm thick in all facies, and for most crossbedded sandstones in the dune facies; a few beds that stand out as glassy markers display abrupt truncations (Figure 6), suggesting that they may have been penecontemporaneously cemented, and then locally disrupted by erosional undercutting of unconsolidated substrate, localized upward pressure associated with dewatering, or dissolution of patchy zones of intercalated evaporites. Subspherical clusters of quartz sand (almost exclusive to the dune facies) show a distinctive blade-like external morphology comparable to modern desert rose structures, suggesting that they are pseudomorphs after evaporite cemented rosettes which grew interstitially within the quartz sand before cementation by silica. Some of these subspherical structures, locally coalesced in clusters (as are modern 'desert roses' of gypsum), contain cores of calcite-cemented quartz sand.
Different cementation styles in the dune facies compared to the bounding thin-bedded facies are attributed to contrasts in permeability and differences in the flux of silica-bearing solutions related to water-table variations. Rosettes in the dune facies probably grew soon after emergence above sea level of the highly permeable dune facies; subsequent precipitation of quartz cement in pore spaces between framework components of this facies resulted in widespread preservation of original grains within overgrowths. Having escaped this early cementation, the beds above and below were more subject to grain-contact solution during subsequent burial compaction, leading to the development of pervasive mosaic textures and abundant stylolites. Grenville basement rocks form a hill a few hundred m to the northeast, immediately beyond Castlefrank Road, (just past the top of the section). Such Precambrian highs may have been islands adjacent to, and ultimately over which, the Paleozoic strata were deposited. If time permits, an extra stop will be made at segments of outcrop not yet covered by concrete along the vertical section south of Earl Grey Drive, parallel to the east side of Terry Fox Drive (marking the western boundary of the Centrum Shopping Centre). Impressive cross-sections of metre deep channels (Figure 7) filled with dune facies sandstone are exposed behind the Texas Chop House (at N45 18.476' W075 54.255'). Crossbed inclinations indicate that these represent tidal channels.

STOP 7. Nepean Formation Quartz Arenite
(CAMBRO-ORDOVICIAN), QUEENSWAY CLOVERLEAF
In the top 30 cm of this 2-m section, and in correlative outcrops on the south side of the Queensway, plus the median strip between them, various aspects of distinctive domal stromatolites in quartz arenite are remarkably well displayed. Since their discovery a few years ago, more have been recognized in other Nepean and Potsdam outcrops, but none to compare with these. This locality has been designated as an Ontario ANSI (Area of Natural Scientific Interest) Site, which is supposed to afford protection for significant geoscientific features. The fact that currently planned expansion of the Queensway will mean destruction of a good part of this world-class site clearly indicates the low priority allotted to significant geofeatures in relation highway construction and commercial development.
The glacially polished top of this outcrop of quartz arenite provides numerous cross sections through distinctly laminated domal stromatolites, many showing elaborate crenulate to colloform ornamentation of their laminae (Donaldson et al., 2000). To account for the random tilted arrangement of stromatolites displayed so well here in a flat-lying succession, the model proposed requires early cementation of the stromatolite unit above a still-unlithified substrate of water-charged sand. As a result of a seismic disturbance, the rigid unit of laterally linked silica-cemented stromatolites snapped apart along the thin inter-stromatolite links, allowing the now-separated heads to rotate and founder in random directions into the overpressured sand. Subsequent burial and completion of cementation of the entire unit allowed preservation of the distinctive array that has been so well displayed as a result of fortuitous bedding-parallel slicing through this stromatolite unit during Wisconsinan glaciation.
Local patches displaying overturning of thin sandstone laminae are attributed to synsedimentary rupture of flexible sand-charged biofilm sheets that were subsequently flipped or rolled back (Figure 8) by waves and/or currents (cf. Donaldson, 1967). Dubiofossils described from Potsdam sandstone of New York State (Erickson, 1993) may have had a similar biofilm-mediated origin. The section east of the entry cloverleaf road displays a distinct channel cut into biofilm laminated strata. Thin recessively weathered chips in the lower part of this massive channel-fill unit are inferred to be flakes torn from the truncated biofilm sheets. The base of the channel shows a few load-like protuberances, suggesting rapid deposition, perhaps as a result of bank collapse.
A few small bedding-surface exposures display intact horizontal layers of small, low-amplitude domal stromatolites, some superposed on, or laterally grading to, asymmetric ripple marks. Other bedding surfaces display very small-scale wrinkle patterns capping laminae of quartz sand, similar to interference ripple marks, but significantly under-scaled relative to grain size. These appear to be analogous to small scale ripples mediated by thin biofilm coatings on siliciclastic tidal flats in modern peritidal sediments (De Boer, 1981; Gerdes et al., 2000; Noffke, 2000.), as well as in other ancient siliciclastic deposits (Hagadorn and Bottjer, 2002; Noffke et al., 2002; Schieber, 1999). In well-sorted layers of silica cemented sandstone, hemispherical hollows are inferred to represent the molds of gypsum rosettes. Although no evaporite minerals have yet been directly detected, blade-like impressions in the hemispherical cavities suggest early silica cementation of the enclosing sands, followed by subsequent dissolution of the evaporites responsible for the 'sand rose' morphology (Figure 9). In addition, some stromatolites display upward pointed crystal pseudomorphs of probable evaporite minerals (Figure 10). This suggestion of hypersalinity provides an explanation for this rare occurrence of stromatolites in a Phanerozoic setting (Donaldson and Hilowle, 2002) -- just as for the earlier observed lack of gastropods in stromatolite-rich Ordovician carbonates. Probable stromatolites in the Potsdam sandstone on the southwestern side of the Frontenac Axis have also been noted by Dalrymple (pers. com.).
Thin-section and geochemical analysis (Table 1) indicate that the rock composed predominantly of quartz framework grains cemented by silica overgrowths (Figure 11). Geochemical analyses from this location indicate the rock is composed of 98% silica (Table 1) and relatively little else. Locally copper oxide and yellow carnotite(?) staining is evident. Some zones weather recessively indicating carbonate cement. The relative abundance of zirconium indicates that zircon is likely the dominant heavy mineral.

STOP 8. Nepean Formation (Cambro-Ordovician)
OLD QUARRY TRAIL
This siliciclastic outcrop is correlative with the outcrop at STOP 7. Convolute folds in a 1 m-thick unit below a thin unit of foundered 'half-moons and bananas' formed by disruption of an early cemented layer of stromatolites above still-unconsolidated sand. Overpressure by interstitial water due to closer packing of well-rounded framework grains, aided by an almost complete lack of matrix, resulted in the creation of convolute folds (note lack of deformation in the underlying quartz arenite beds, and progressive attenuation in the upper limbs of antiforms in the metre-thick unit showing convolute lamination). Side views show several foundered 'half-moon' stromatolites within the synformal cores (Figure 12). The three-dimensional morphology of the apparent 'folds' is envisioned as linked bowls (somewhat like half an egg carton, with the egg-pocket openings facing concave-up). Subparallel alignment of the foundered and rotated stromatolites, as seen on the upper surface, suggests possible slope control, with probable condensation of the discrete stromatolite 'clasts' due to downslope sliding. Areas in the Nepean/Potsdam succession elsewhere showing evidence of synsedimentary brecciation (e.g. Selleck, 1978), suggesting that such areas warrant re-examination for evidence of early cementation of beachrock-like carapaces developed over unconsolidated sand layers due to biofilm mediation -- an association likely to rupture easily during seismic disturbances.
OHM 2019: Latitude in Guidebook is off by six minutes.

A1: PRECAMBRIAN BASEMENT AND CAMBRIAN-ORDOVICIAN STRATA, AS DISPLAYED IN THREE PROVINCIAL PARKS OF CANADA
J. Allan Donaldson
Department of Earth Sciences
Carleton University
Ottawa, Ontario, Canada K 1 S 5B6
Jeffrey R. Chiarenzelli
Department of Geology
State University of New York
Potsdam, New York 13676
INTRODUCTION
General overviews of the region covered by this excursion are provided by Wilson (1946) and by Williams (1991). A regional sedimentological study of the Nepean formation was carried out by Wolf and Dalrymple (1984). The relationship of Paleozoic strata of eastern Ontario to the Frontenac Axis remains a problem not yet resolved: Was the arch a positive structure during sedimentation, or did it become so as a result of elevation through faulting/subsequent crustal upwarp/compactional draping or some combination of these processes? This question will be considered during the trip, which was designed to provide an overview of Paleozoic strata and the underlying Grenvillian basement along a traverse from the Ottawa River to the St. Lawrence River.
One highlight will be a visit to a shallow underground mica-apatite mine at Murphys Point Provincial Park to view workings abandoned in 1920. Another will be a visit in Charleston Lake Provincial Park to view a giant cylindrical structure in Nepean quartz arenite, which appears to represent the outline of an exhumed dewatering structure. The Paleozoic-over-Grenville unconformity will be viewed at two localities, both showing evidence of paleo weathering of the Precambrian basement. Stops will be made to view a variety of abundant trace fossils, including Skolithos and Diplocraterion, as well as several Cambrian and Ordovician stromatolite localities (complementary to those seen during Trip F-1). Local sedimentary units have been used extensively as building stone, as will be seen in several historic examples. Teachers and other educators are particularly encouraged to attend this trip, as an introduction to the geoheritage potential of Ontario's Provincial Parks.
This trip has been modified from a series of three guided geoheritage hikes in Ontario Provincial Parks (July 10th, 17th, 24th, 2004), organized by Friends of Canadian Geoheritage, a group founded in 2003 to encourage greater public appreciation and understanding of Canada's geological diversity. The first of these hikes attracted 35 participants, the second drew 40 and the final one drew 80 participants, ranging in age from 3 to 90. The educational aspects of geology and geography provided by visits to these three parks, which offer different slants on the varied geoheritage of this part of North America, should be of particular interest to teachers. The geological heritage of eastern Ontario spans over 1 billion years of Earth history. Ontario's provincial parks provide significant examples of this heritage, ranging from bedrock that shows evidence of billion year-old mountains and ancient sea-floor deposits, to more recent signs of glaciation, succeeded by development of postglacial lakes and river systems that were initially much larger.

A1: PRECAMBRIAN BASEMENT AND CAMBRIAN-ORDOVICIAN STRATA, AS DISPLAYED IN THREE PROVINCIAL PARKS OF CANADA

STOP 1 - TERRACES TRAIL, FITZROY PROVINCIAL PARK
OXFORD AND ROCKCLIFFE FORMATION (ORDOVICIAN)
Park entrance kiosk
From the Terraces Trailhead, a one-hour hike provides a snapshot view of the principal Paleozoic strata comprising the bedrock beneath this park (Figures 2 and 3). A succession of carbonates, sandstone, and shale record a succession of changing environments marginal to and within a sea that episodically covered the area from about 500 million years ago. Low-angle crossbeds in sandstones of the Rockliffe Formation indicate unimodal southward transport, consistent with fluvial accumulation in a system feeding into a basin to the south. Low dispersion about the mean suggests deposition as sandbars in a braided river system. Overlying green shale in the upper part of the Rockliffe Formation gives way upwards to dull red shale. Both varieties contain abundant bedding-parallel vermiform trace fossils, as well as rare desiccation cracks, suggesting transition to relatively quiet-water deposition on tidal flats or in a delta.
The present landscape is largely the product of modification by ice and meltwaters related to the Wisconsinan ice sheet that retreated from the Ottawa Valley less than 12,000 years ago. As the ice sheet melted, it left deposits of glacial drift containing boulders of Precambrian rock derived from the Canadian Shield (mainly from the adjacent Grenville Province, but a few from the more remote Superior Province). In addition, many large angular slabs were ripped up from nearby stromatolitic limestone and dolostone. As the once much larger post-glacial ancestor of the Ottawa River cut its way through the Ottawa Valley, it carved increasingly narrower channels in the Paleozoic rock, exposing a succession of bedrock cliffs along Terraces Trail.
On completion of the Trail loop, we will visit the shore of the Ottawa River, just north of the most northerly bathing beach, where a few small outcrops of Oxford dolostone that underlie the Rockliffe Formation display domal stromatolites. These stromatolites, near the top of the Oxford, are laterally linked (Figure 4), generally with smooth, gently domed calcilutitic laminae (some of the smaller stromatolites show incipient branching). The best bedrock exposures occur in shoals and along the shores of several nearby offshore islands in the Ottawa River, where individual stromatolite domes commonly exceed one metre in diameter, have a synoptic relief of up to 40 cm, and display a distinct north-south elongation trend. Discontinuous patches of silicification commonly accentuate the laminae. Locally derived stromatolitic blocks have been placed throughout the park along interior roads, and on both sides of the road at the park entrance. These large blocks provide opportunities to observe three-dimensional morphologies of the stromatolites.

Look to the north to see the Ottawa-Bonnechere Graben.
As we leave the park, look to the north to see the Gatineau region of Quebec, where Precambrian Grenville gneisses have been uplifted along a series of faults that form the Ottawa-Bonnechere Graben. This ancient tectonic feature controls the course of the Ottawa River for more than 600 kilometers to the northwest.

STOP 3. Oxford Formation Stromatolites (Ordovician)
STOP 3 - OXFORD FORMATION STROMATOLITES (ORDOVICIAN), ALMONTE
Victoria Woolen Mill
This stop will allow an opportunity to see some of the various stones used to construct the many historic buildings in this village of approximately 4500 inhabitants. Depending on the water level we will observe several units of laterally linked stromatolites in Ordovician carbonate strata (Oxford Formation), right beneath the centre-town dam on the Mississippi River, in downtown Almonte. These stromatolite beds are best viewed from the observation deck behind the Victoria Woolen Mill on Mill St., immediately east of Slide Bridge (Main Street/Hwy 49).
Lunch may be obtained in any of several restaurants along Mill St. Information pamphlets are available from the Visitor Centre, immediately east of the Victoria Woolen Mill (note the stromatolite-bearing block near the entrance).

Murphys Point Provincial Park - Check In

STOP 4. Murphys Point Provincial Park
SILVER QUEEN APATITE-MICA-FELDSPAR MINE, LALLY HOMESTEAD
Murphys Point Provincial Park lies within the Grenville Province, on the eastern side of the Frontenac axis. A wide variety of both igneous and metamorphic rocks are exposed within the park. Some of the metamorphic rocks show evidence of multiple stages of folding, best seen in exposures of the several belts of crystalline limestone that traverse the park. We will park at the Lally Homestead, where an outcrop of marble displays folding, foliation, possible relic bedding and a variety of positive-weathering inclusions (Figure 7).
Closed in 1920, the Silver Queen Mine was an important source of phosphorous for munitions during World War I. A part of this mine has been restored to allow safe underground entry, where large crystals of mica and apatite stand out on the partially mined rock walls.

STOP 5. Trace Fossils in Nepean Sandstone
Old Stone Mill, Delta
Built in 1810 of Nepean (Potsdam) sandstone, this is the only stone gristmill in Canada designated as a National Historic Site. The quartz arenite blocks used to construct this building are remarkable for their almost universal abundance of the trace fossils, Skolithos and Diplocraterion. (Figure 8). We are currently unaware of the provenance of this building stone, but are attempting to track down where it was quarried. Some Nepean/Potsdam and March/Theresa beds have such traces in abundance (cf. Bjerstedt and Erikson, 1989).

Charleston Lake Provincial Park Check in

STOP 6. Giant Cylinder in Nepean Formation
We will drive to Sandstone Island Trailhead, and follow Sandstone Island Trail (Figure 9) to view basal conglomerate and sandstone of the nearly 500-million-year-old Nepean Formation in unconformable contact with billion-year-old Precambrian metamorphic and igneous rocks of the Grenville Province (Figure 10). This contact, representing more than half a billion years of elapsed time, is best displayed at Post 2, where weathered granite at the top of the Grenville basement may well represent a paleosol. Isoclinally folded units of crystalline limestone and intercalated siliciclastic metasediments are abundant within the park (see map of Hewitt, 1961).
Many of the well-rounded conglomerate clasts (readily seen on the undersides of undercut bedding surfaces, as well as in vertical sections at Posts 3 and 4) consist almost exclusively of vein quartz and Precambrian quartzite, but a few clasts are identical to the Nepean, indicating early cementation and cannibalism of basal Paleozoic units (some Covey Hill reworking?). Crossbedding shows a preferential southerly trend, but herringbone patterns (well-exposed at Posts 6 and 7) are locally abundant, suggesting alternation between fluvial and marine depositional environments. A few cross-sections of probable tidal channels are visible in close proximity to packages of strata displaying herringbone crossbedding. Similar successions, as well as facies containing spectacular aeolian dunes, occur on the west side of the Frontenac Axis (cf. Dalrymple and Wolf, 1988).
A particularly fascinating structure occurs at the site described as 'The Waterfall' (Post 8). Initially thought to have been formed by rapidly flowing meltwater cascading over a cliff during Wisconsinan deglaciation, it now is apparent that this hollowed segment of almost half a cylindrical structure (Figure 11), extending vertically through 5 m of well-indurated Nepean strata, is an exhumed dewatering structure (cf. Gruhman and Pederson, 1992). This interpretation, first presented here to account for 'The Waterfall', is provided by two lines of evidence: 1. A patch of sandstone on one side of the structure shows lamination parallel to the cylindrical surface; and 2. Below the level at which a conglomerate bed within the stratigraphic section intersects the cylindrical surface, pebbles and cobbles are cemented to the inner surface of this columnar structure by sand identical to sand in the horizontal source bed (Figure 11).
While still unconsolidated, forceful upward hydraulic overpressure could create such a structure, with streaming parallel to the walls accounting for creation of an annulus of nested concentric laminations in sand along the margin of the vertical dewatering column. During waning stages of dewatering, individual pebbles and cobbles from the intersected gravel bed could have readily sunk along the periphery of the dewatering cylinder, to then be concentrated along the cylinder's margin, and held in place by a matrix of sand until the walls and interior of the structure were completely cemented. Similar structures elsewhere within the Nepean/Potsdam have long been recognized and debated (Baker, 1916; Hawley and Hart, 1934; Hawley, 1935; Miser, 1935; and Deitrich, 1953).
We probably will return back along the path from this point, but if time permits, we will follow the trail forward to Post 11, where glacially polished surfaces on uppermost exposures of Nepean quartz arenite display high polish, parallel grooves and striae, and abundant chattermark clusters, all showing consistent facings of concave chattermark curvatures in a down-ice (southwestward) direction.

STOP 7. Unconformity
ORDOVICIAN LIMESTONE AND SANDSTONE UNCONFORMABLY OVERLYING GRENVILLE BASEMENT
Corestones in a variety of mafic and felsic basement rocks are preserved below the unconformity on the north side of the road. The overlying sandy carbonates, probably in the lower part of the March Formation, contain abundant trace fossils, as well as a few nodular zones that may represent soil profiles (Figure 12). The lowermost beds contain quartz sand and silt, and shaly beds become locally abundant upwards in the section. The lack of Covey Hill or Nepean beds suggests that this may have been a paleo high during early Ordovician time.

A2: SOME CLASSIC TEACHING LOCALITIES IN ST. LAWRENCE COUNTY, NEW YORK
John T. Bursnall and Catherine H. Shrady
Department of Geology
St.Lawrence University
Canton, New York 13617
INTRODUCTION
Western St.Lawrence County, within the central section of the St.Lawrence Lowlands in New York, contains a wonderful variety of outcrops that lend themselves to illustrating a wide range of geological processes and principles for all levels. The purpose of this trip is to visit a limited number of these - 'tried and true' localities - those that have proven to be excellent ones for introducing students to a variety of geological problems in addition to the regional geology of the North Country. The stops on this field trip have been chosen for ease of accessibility in addition to their outstanding teaching possibilities. All have been used in introductory to advanced field labs in the Geology Department at St.Lawrence. They are, therefore, suitable for moderately large groups (say, a maximum of 20 or so). Our choice clearly had to be constrained by logistical limitations such as accessibility in the time available, and the number of stops appropriate for a single day field trip, but we may prove to have been over-ambitious (!) and so it should be anticipated that we might not be able to cover all the stops described in this field guide. What we offer here is, by necessity, far from comprehensive (and certainly not complete), but is a subjectively biased attempt to provide an introduction to some of the teaching possibilities in what is a geologically quite complex and varied terrain. Five of the ten stops are featured in Van Diver's (1976) highly recommended Rocks and Routes of the North Country. A BRIEF BACKGROUND
The St. Lawrence Valley was an important area for mineral exploration in the early nineteenth century and a number of mines were developed in the western part of the region. Lead, zinc, and iron ore were important products. Most are now defunct but a few still remain in operation, notably the zinc and talc mines in Balmat, just south of Gouverneur (Fig. 1).
In part in response to this early exploration and also to subsequent research of the complex geology, the region has become an important collecting and study area for a wide variety of minerals (see MATRIX: a Journal of the History of Minerals, Fall 1998; also, field trips A7 and B4, this volume). The geology of this area is now generally well understood and this, coupled with some magnificent outcrop coverage, has resulted in the area becoming an important one for teaching at all levels, and has been a venue for many traveling field parties.
The geology of the St.Lawrence Valley, including St.Lawrence County, is essentially made up of three major rock groups. A ca. 1.35-1.0 Ga Precambrian basement (Stops 2-5) comprised of medium- to high-grade gneisses is overlain by sedimentary cover rocks, which may be divided into three age-defined packages. The oldest of these is somewhat enigmatic since these sediments (quartzarenites and breccias) likely represent a latest Precambrian to Cambrian phase of deposition, and infill depressions on an undulating (in part karstic) Precambrian erosion surface. There is clear evidence for dissolution of marble and subsequent infill at many localities, as well as some interesting possible cave collapse structures (see Stops 6, 7 and 8). Clearly separating this 'transitional' sequence from the overlying Potsdam Sandstone, sensu stricto, has proven to be very difficult, and is still one of the outstanding problems in the region.
The Potsdam Sandstone represents the base of an east to west Lower Paleozoic marine transgression sequence. Overlying limestones and shaley limestones (Theresa and Ogdensburg formations) indicate a progressive deepening and distance from terrigenous sources. The age of the Potsdam is likely uppermost Cambrian to Ordovician.
Pleistocene glacial and related fluvial and lacustrine deposits (Stop 1) make up the third depositional package and these, together with glacial erosional features, provide the most significant control on the North Country landscape.

A2: SOME CLASSIC TEACHING LOCALITIES IN ST. LAWRENCE COUNTY, NEW YORK

Notice small marble outcrop on right

Small amphibolite outcrop

Remains of pyrite mine on left

Large outcrop of marble on left

Notice outcrops of sand/gravel
Notice outcrops of sand/gravel and horizontal surfaces indicating glacial meltwater deposits (delta top?). Adjacent outcrops of gneiss indicate significant relief on the postglacial surface.

Drive through a broad valley in Marshville
Drive through a broad valley in Marshville and follow CR 21 noticing numerous roadcuts of basement gneiss. The valley is rejoined in a few miles.

STOP 1. opposite one of these knolls
This stop is a 'puzzler,' and may be only appropriate for those students who have taken an advanced glacial geomorphology class - although it was regularly, and quite successfully, used in a summer session introductory course for many years. Notice that the four hillocks visible from this vantage point are comprised of poorly sorted boulder-rich sandy till (i.e., they do not have the characteristics of the agricultural boulder piles common elsewhere in the North Country). Jim Street (long time geomorphologist at St. Lawrence University until his untimely death in 1993) persuaded us that these are the remains of subglacial or englacial debris piles that collected at the base of glacial 'sinkholes'. [The term 'moulin' (mill) refers to the noise of moving pebbles and boulders at the base of the waterfalls producing these deposits, which is reminiscent of the noise of a mill.] What do you think of Jim's hypothesis?

Notice the hummocky terrain to the right (moraine?) and the large gravel pit to the left

STOP 2. MINERAL IDENTIFICATION AND METAMORPHIC REACTIONS
Turn right at T-junction with Route 58 and park on verge beyond barrier. STOP 2 is a short walk behind on Route 58.
A classic collecting site, now suffering from 'field party erosion'! (PLEASE DO NOT SAMPLE FROM THE OUTCROP). Superb samples of diopside occur in the contact zone between pink calcite veins and the granular textured diopside-rich gneiss. In our experience, a relatively large number of students will misidentify the salmon pink calcite as K-feldspar (providing an almost guaranteed teachable moment!) Other minerals present are actinolitic amphibole, phlogopite (a mica), pyrite, and rare molybdenite and blue apatite. Some genuine potassium feldspar has been collected from a pit just to the north. It is likely that the protolith for this rock was a siliceous dolomitic limestone with the abundant diopside in the outcrop being produced in part by the simple reaction:
2(Ca,Mg)CO3 + SiO2 → 2(CaMg)SiO3 + CO2
dolomite + quartz → diopside

Notice tailings and stockpiles from Gouverneur Talc mine on left.

STOP 3. STROMATOLITIC FORMS IN MARBLE.
One of the most significant outcrops in the Grenville geology of New York. The stromatolites are not only important as vestiges of past life (as old as 1.3 Ga) but, since they are upside down, gives credence to the existence of postulated large-scale folds (nappes) in the St.Lawrence Valley. AGAIN, PLEASE, NO HAMMERS.

STOP 4. MIGMATITIC GNEISS COMPLEX (POPLAR HILL GNEISS)
Gray paragneiss invaded by a variety of moderate to steeply dipping granitic veins and dikes, most of which have suffered (or enjoyed) significant extension (stretching). Rare veins that have low dip may be quite strongly folded. A very fine example of this occurs on a grass ledge at the top of the southern end of the western outcrop, and at least one structural geology text has featured these as 'ptygmatic' folds (see Fig. 4). The varied response of the veins to the deformation is systematic within small areas of these outcrops and can give a fairly crude assessment of the principal axes of finite strain - moderately steep extension and shallow shortening.

Pass the turn-off for Hailsboro and the 'steers head' on the right
Pass the turn-off for Hailsboro and the 'steers head' on the right (marble injection into in gray gneiss, Figure 5).

STOP 5. DISRUPTED AND METAMORPHOSED MAFIC DIKE IN GNEISSIC MARBLE
PLEASE WATCH FOR SPEEDING TRAFFIC!
The marble in this magnificent roadcut is a compositionally layered variety with alternating graphite-rich and graphite-poor layers. It is uncertain if the layers are original layering or are deformational in origin. Careful observation of the train of boudinaged dike fragments will indicate a complex relationship to the layers. Note also that the attitude of the layering along the outcrop suggests the existence of a large recumbent fold with the lower limb below road level in the southern part of the cut. More than one phase of folding is necessary to accommodate the complex geometry, even if the 'dike' was originally non-planar. Our introductory geology field lab exercise for this outcrop require students to make a sketch of the whole section on the east side of the road as well as to identify the principal minerals present in both the marble and the mafic dike remnants.

Marble on both sides of the road with a basaltic dike
Small low outcrops of marble on both sides of the road with a basaltic dike (short stop, if time permits).

STOP 6: ROCK ISLAND ROAD CUT.
This outcrop is perhaps one of the most intriguing road sections in the North Country and is a common stopping point for field parties visiting the region. It is appropriate for all levels - introductory physical geology to advanced courses (senior level structural geology, for example). Our main interest here is to characterize the relationship of the presumed Potsdam Sandstone to Grenville gneisses, which at the upper part of the roadcut are calcitic marbles. This deep roadcut provides magnificent exposure and is one of the better outcrops in illustrating the variety of marble-sandstone relationships present in the region. Evidence for significant post-arenite deposition deformation is present at many localities.
At the southeast end of the cut, a well-bedded quartz-arenite illustrates the attractiveness of an interpretation that these represent the lowermost Potsdam Sandstone. However, the very complex relationships of these sandstones with the "underlying" marbles invite alternative explanations to a simple erosional unconformity. Moderate dips (∼30°), angular marble clasts in quartzarenite, thin sandstone dikes extending outwards and upwards from contacts, and changes in composition of the sandstones close to the marble have all contributed to a karst surface depression infill (see Van Diver, 1976). Some of the contact relationships in this section have been used as evidence for structural control of deposition and basement remobilization (Bannerman in Carl and Van Diver, 1971) - similar to that of Barber and Bursnall (1978) for outcrops in the area around Theresa, some twelve miles to the west.
For introductory students, clear evidence of faulting and a basaltic dike at approximately half-distance down the outcrop are additional important features.
Contact zones need to be carefully examined and advanced students should be directed to iron oxide and iron pyrite that armor many of the surfaces, and the potential significance of angular marble fragments. Subtle brecciation features particularly in the northern sections (perhaps, autobrecciation), matrix supported conglomerates (upper west side of northern section), etc., may be easily overlooked, and a spectacular tourmaline-rich breccia in the latter area further suggest a protracted and complex history for the section.

STOP 7. SANDSTONE WITHIN MARBLE AND THE RICHVILLE BRECCIA
(a) If time permits, an outcrop of marble on the northwest side of Route 11, a few hundred yards to the south should be visited (see Fig. 6, above). It contains narrow subvertical veinlets of arenite at the northeast end, which provide good evidence for solution cavity infill (Bursnall and Elberty, 1993).
PLEASE CROSS WITH CARE (DUAL LANES IN THE UPHILL DIRECTION).
(b) Return to Welch Road and continue along a large outcrop on the north side of Route 11. Karboski et al. (1983) describe this outcrop as containing a "flow breccia" at its base. This is overlain by a densely consolidated breccia with an overlying highly deformed metaquartzite, overlain by an "orthoquartzite," which contains pebble-sized quartz clasts - possibly derived from the underlying metaquartzite. The breccias contain quartz clasts set in a hematite stained, medium-grained arenite. Large (0.5m) phacoidal blocks of the breccia are enveloped by thin shaley borders, the whole giving the impression of a shear zone.
This outcrop certainly inhibits any notion that the unconformity between Precambrian basement and overlying arenaceous cover rocks is a simple one! Points of interest are:
i) possible shear fabrics in the lower part of the outcrop, in part defining the borders of coherent blocks of breccia;
ii) compositional variation of clasts in the breccias; and,
iii) the relationship between and the textural character of each of these identified rock types.
If the upper part of this outcrop is indeed comprised of rocks which are parts of the Grenville basement, as supposed by Karboski (1976) and Karboski et al. (1983), then the current disposition of lithologies seems not to be satisfied by a model that involves karst infill alone. It is possible, however, that the wall collapse of a large solution depression may have allowed a slab of basement to slide into a sediment filled basin. The presence of shear fabrics within the breccia may be accommodated by this model, provided that these rocks were only partially lithified at the time. Another possibility, since there is evidence of folding and brittle faults in Lower Paleozoic rocks elsewhere in the St.Lawrence Valley (Barber and Bursnall, 1978), is that these shear fabrics are a remote product of Alleghenian deformation.
Cross over Route 11 to return the vehicles and investigate the southern end of the outcrop on the southeast side of the road. Here, a narrow zone of sandstone breccia dips steeply through marble. One of the contacts is sheared indicating high angle faulting. Is there evidence for displacement sense?

STOP 8. SANDSTONE/MARBLE CONTACT, EAST DEKALB.
This series of outcrops (Figure 7), known as the 'Red and White' by St.Lawrence introductory geology students illustrates some of the complexities of the unconformity between the Grenville metamorphic rocks and overlying quartzarenite sediments, which may, or may not, be Potsdam Sandstone. The stop has a number of interesting features that will test students' abilities in assessing field relationships and has similarities to the Rock Island Road outcrops (solution pockets, sulfide mineralization close to gneiss-sediment contact, etc.). A number of small sandstone breccia wedges (see below) penetrate downwards into the underlying marble close to its steep contact with a rusty sulfidic quartzarenite in the central section of outcrops on the northwestern side of the road.
A poorly defined cylindrical structure (supposed solution pocket collapse structure, Bursnall and Elberty, 1993; see Figure 8, below) may be seen on the top of a low outcrop of compact, rusty weathered, quartzarenite in the southernmost outcrop on the northwest side of Route 11. Bedding in the sandstone is irregular and breccia/conglomerates are present low in this section and in the outcrop on the southeast side of the road a short distance to the south.
Also of interest is well-layered marble at the north end of this long outcrop showing excellent recumbent folds and calcite fiber slickenlines.

STOP 9. THE DEKALB ANTIFORM (if time and interest permits)
The Dekalb antiform occurs in garnetiferous gneiss. Layering changes from a relatively shallow dip at the northern section of the outcrop to steep to vertical at the southern end. The change in dip and "S" and "Z" parasitic folds suggest an antiformal structure with a few complications including a fault near the large granitic vein toward the northern end of the outcrop and a change of parasitic fold plunge direction. A lab exercise for structural geology students includes sketching the change in orientation of layering, measuring strike and dip of layering across the outcrop, measuring the trend and plunge of the parasitic fold axes and then interpreting the structure taking into account the afore-mentioned "complications".

STOP 10. THE 'SNAKE' (if time and interest permits)
This classic outcrop is well described by Van Diver in Rocks and Routes of the North Country. It is appropriate for introductory and advanced students. A thin band of feldspar-rich rock, thought to be a metamorphosed volcanic ash layer, snakes across the outcrop displaying at least two phases of folding on the outcrop face on the east side of the road. Interference patterns on the top of the east side outcrop and at the far northern edge of the west side outcrop show two and possibly three phases of folding.

A3: THE 1993 LEMIEUX LANDSLIDE AND MER BLEUE BOG, SOUTHEASTERN ONTARIO, CANADA
Stephen Robinson
Department of Geology, St. Lawrence University
Canton, New York 13617
srobinson@stlawu.edu
Marine silts and clays were deposited through much of the St. Lawrence and Ottawa Valleys during the incursion of the Champlain Sea. These clays, known in Canada as Leda clay and in the U.S. as Massena clay, are sensitive to disturbance and prone to low-angle slope failure despite the muted topography of the area. Landslides have been occurring in the Ottawa Valley (Figure 1) since the recession of the Champlain Sea at about 10 ka (Aylsworth et at., 2000). Several of these landslides have resulted in significant loss of life and property damage. Geotechnical testing for slope stability and landslide potential led to the abandonment of the 28 homes making up the community of Lemieux in 1991. Only 2 years later, on June 20, 1993, a large (17 ha) retrogressive landslide occurred near the former townsite. The landslide occurred within the scar of an earlier rotational failure, and widened through lateral spreading and subsidence, translation, and rotation of blocks separated from the side walls. About 2.8 million cubic meters of debris flowed into the South Nation River valley, extending for several kilometers up and downstream. Since the landslide, the site has changed considerably owing to erosion of the sides of the crater, erosion and revegetation of spoil piles, and the incision of the river into the debris. This field trip (Figure 2) visits the landslide scar and will discuss the conditions that led to these low angled failures. An additional stop will be made at Mer Bleue, one of the largest ombrotrophic peatlands in southern Canada. This bog has developed in a former channel of the Ottawa River, and in places is underlain by Champlain Sea sediments.

A3: THE 1993 LEMIEUX LANDSLIDE AND MER BLEUE BOG, SOUTHEASTERN ONTARIO, CANADA

STOP 1. The Lemieux Townsite
The small village of Lemieux (28 homes, 50 km east of Ottawa) was a predominantly French-speaking farming community started in the 1850's as a mill town to service the local lumber industry. The Roman Catholic church was the focal point of the small community that became known as La Paroisse Saint Joseph de Lemieux. The villagers had always known about the local landslides, as a significant failure occurred nearby in 1895 and there are numerous older landslide scars in the area.
Engineering studies were conducted in the area following the large landslide on the South Nation River in 1971 (Eden et al., 1971) (Figure 7). In 1989, the South Nation Conservation Authority (SNCA) engineers discovered that soil conditions underlying the community were unstable. Mindful of the landslide that had killed 33 people under similar conditions in NotreDame-de-la-Salette, and the loss of 31 lives in 1971 at St. Jean Vianny, Quebec, government authorities decided that the community of Lemieux would have to be abandoned. Homes were purchased by the SNCA as part of a landslide mitigation program.
Some homes were moved and others were bulldozed. All that remains of the community is the cemetery and a plaque reading
" ... The village was located over an area of sensitive clay soils, known as the Champlain Sea clays or Leda clays. These soils are unique to eastern Ontario and western Quebec and exhibit the characteristic that, when disturbed, they can liquefy. River banks and slopes composed of Leda clay, when left unprotected, have a tendency to fail and can cause large and small scale landslides.
After consultation with residents, the South Nation Conservation Authority, in conjunction with the Ministry of Natural Resources and the Township of South Plantagenet, purchased the residences in 1989 to eliminate the possible threat to life and property. Some houses were relocated while others were destroyed. With the closing of the church, the parish of Lemieux ceased to exist on August 4, 1991."
Several homesites are still easily seen as small clearings in the forest with obviously recent vegetation, and several sections of driveway tarmac.

STOP 2. The Lemieux Landslide
Late on the afternoon of June 20, 1993, a 17 ha area of sensitive marine silt and clay close to the Lemieux townsite failed with flow proceeding rapidly into the South Nation River (Figure 8). The first eyewitnesses noted a water displacement of up to 2 m high moving along the river both up- and downstream. Trees and spoil accumulation were soon noted at the bridge crossing Regional Road 8. It took over half an hour for the retrogressive failure to reach and sever Regional Road 16, with portions of the road surface being rafted up to 200 m down into the crater. One motorist on Regional Road 16 ended up in the crater, and was rescued by a Canadian Forces helicopter. In all, Brooks et al. (1994) estimate that the entire failure event probably lasted less than one hour. The debris from the landslide eventually buried 3.3 km of valley bottom and caused flooding 18 km upstream. Costs relating to the failure event have been estimated at $12.5 million Canadian dollars.
Three boreholes had been drilled in 1986 and 1987 as a part of the geotechnical investigation. Three coarse units are delineated from these boreholes by Evans and Brooks (1994) (Figure 10; Table 1). An upper cap of loose brown silty sand forms the upper 3-7 m. The middle unit is composed of laminated interbedded silts and sands ranging in thickness from 5 to 10 m and depth below the pre-failure surface of 3 to 17 m. These are the sediments that make up the majority of the blocks and sharp crests in the landslide crater. One of the boreholes indicated that the strength of this unit decreased with depth.
The lowest unit is composed of marine clay below about 8 to 17 m depth (Figure 10). During drilling the auger rods of the drill descended into the hole under their own weight (Evans and Brooks, 1994); a testament to the low strength inherent in this layer. Below 19 m the liquidity index (a measure of the sensitivity to remolding and failure, with values greater than 1.0 indicating extreme sensitivity) is measured to be up to 1.6, and shear strength testing also indicate low strengths when remolded (Figure 10; Table 1). This lower layer of soft marine clay is thought to be the failure plane that caused the failure owing to liquefaction, with the overlying sediments remaining somewhat intact but transported into the crater (Evans and Brooks, 1994).
There was no obvious trigger for the landslide (Evans and Brooks, 1994), although an elevated water table appears to have been an important factor (Aylsworth et at., 1997). The first 6 months of 1993 were the wettest on record for the first half of the year since 1947 (Brooks et at., 1994). The region had above average snowfall, a rapid spring melt and heavy spring rainfall, resulting in a water table that was at or near the ground surface in many areas. Ongoing erosion from the South Nation River played an important role in providing an initial scarp for failure along its banks.
The field trip vans park along a road that represents the original path of Regional Road 16. From here the headwall and landslide crater are easily visible. Failure of the landslide occurred in blocks, and intact tilted blocks of the original stiffer surface cap are visible. Several trees survived the rafting into the crater and have continued to grow on the ridge and furrow topography. It is unclear why the landslide terminated at this point, although the bedrock rise noted towards the headwall (Figure 10) may have contributed to stabilization. Sections of the headwall have been regraded and flattened to prevent further retrogressive retreat.
In walking thorough the bowl eleven years after the event, it is obvious that previously sharp-edged blocks and topography have been muted through ongoing erosion (Figure 11). Several of the ridges contain trees that survived the rafting event, while the general vegetation is of more recent succession. Several sections of impounded drainage contain cattails.
The failure occurred at depths of greater than 10 m (Evans and Brooks, 1994), so the majority of the surficial material in the failure bowl is reworked sand that provided the stiff cap sediments. Transported Leda clay is not noticed until the banks of the South Nation River are reached (Figure 12). Tilted rhythmic bedding is noticed on both banks of the river. Groundwater piping at the edge of the crater, noted shortly after failure (Aylsworth et at., 1997), is no longer visible. The river has entrenched 5-6 m into the spoil pile and river flow has essentially been restored (Aylsworth et at., 1997), with striated limestone bedrock exposed to the north of the failure.

Stop 3. The South Nation Bridge.
Landslide spoil up to 12 m deep is visible at this site upstream of the landslide (Aylesworth et al., 1997). The debris at this location consisted of the liquefied clay and silt, intact silt and sand blocks, and rafts of sod with some intact trees (Evans and Brooks, 1994). Several of the trees hit the bridge, although no damage was reported. Fishermen near the bridge report running for their lives to avoid an "8ft. high wall of water" (Ottawa Citizen, June 21, 1993 reported in Evans and Brooks, 1994). The landslide dam was overtopped by the South Nation River late on June 22, two days after the failure, with a strong current flowing over the debris by June 23. Incision into the spoil pile has been ongoing since then, with bedrock reached in several areas.
A Water Survey of Canada hydrographic station at Plantagenet Springs, 28.4 km downstream, recorded the abrupt increase in water level in response to the displacement wave (Figure 13), followed by a dramatic drop in stage as upstream flow was disrupted by the dam at the failure site.

Stop 4. The 1895 Landslide.
This brief stop is at the headwall of the 1895 landslide (Figure 14) that covered 24.4 ha and retrogressed a total of 600 m from the South Nation River. Notice that the landslide scar is now well vegetated and is used by the owner as a pasture.

STOP 5. Mer Bleue Bog
Mer Bleue Bog is a Provincial Conservation Area in the eastern portion of the National Capital Region, and less than 10 km from the city of Ottawa. The bog covers approximately 3500 hectares (Figure 15), and has formed in an abandoned channel of the Ottawa River. The western section of the bog has three distinct arms, separated by sand ridges that were formed by the anastomosing river channel.
The majority of the central portions (Figure 16) of the bog are composed of a raised carpet of Sphagnum mosses, representing an ecological community usually found further north in the boreal forest of Canada. Other vegetation dominating the raised central portions includes Labrador tea (Ledum groenlandicum), bog laurel (Kalmia polifolia), Leatherleaf (Chamaedaphne calyculata), and various sedges. The majority of trees in the central portions are tamarack (Larix laricina), with some black spruce (Picea mariana) in more acidic areas. The dominance of Sphagnum species and a lack of contact with mineralized groundwater leads to acidic conditions within the bog.
Raised bogs such as Mer Bleue obtain all of their nutrients through rainwater, and are termed ombrotrophic peatlands. Drainage from the raised portions flows laterally to the marginal channels. These channels, or lagg areas, provide the slow continual lateral drainage for the central portions of the peatland. Marginal areas of the bog are actually marsh (Figure 17), composed of open water lagg and vegetated primarily by cattails (Typha sp.), Salix sp., and various sedges. Drainage of the wetland downwards is impeded by the presence of fine-grained material, including Leda clay. Lagg areas generally have greater contact with mineralized groundwater and their less acidic waters are able to support more luxurious vegetation.
Peat deposits in Mer Bleue are up to 6 m thick, but are most commonly about 3 m in thickness, and are underlain by up to 40 m of Champlain Sea sediments (Fraser et al., 2001). This peatland has been forming for approximately 8,500 years. The ecosystem here is unique as the vegetation assemblages are more typical of northern boreal forest, found over 1000 km to the north.

A4: WORKING ACROSS THE DISCIPLINES: BIOLOGY, ART, AND GEOLOGY MEET AT THE ADIRONDACK HIGHLAND-LOWLAND BOUNDARY
William L. Romey
Department of Biology, SUNY Potsdam, NY 13676
romeywl@potsdam.edu
Lucretia L. Romey
P.O. Box 294, East Orleans, MA 02643
William D. Romey
ashladpress@earthlink.net
The purpose of this field trip is to explore the kinds of interactions the biologist, artist, and geologist can bring to bear on a location geologists might tend to think of as "their own." We have selected Stone Valley in Colton New York as a place where an interdisciplinary approach to the locality is particularly fruitful. Too often, the geologist's eye is so fixed on the bedrock or the geomorphology of an area that he or she scarcely notices the animals and plants of the area. Although we all probably recognize the importance of being able to sketch the landscape, geological, and biological features of places as a way of recording what we see, we rarely sit down really to devote full attention to recording in sketches the esthetic dimensions of field sites. Drawing is also a fantastic tool for seeing. The act of drawing forces us to look more carefully at the scene we are observing.
NOTE: PLEASE BRlNG A DRAWING PAD OR NOTEBOOK AND DRAWING PENCILS. YOU MAY WANT TO BRlNG ALONG A FEW COLORED PENCILS AS WELL.

A4: WORKING ACROSS THE DISCIPLINES: BIOLOGY, ART, AND GEOLOGY MEET AT THE ADIRONDACK HIGHLAND-LOWLAND BOUNDARY

Note gravel pits to the left (east) filled in with water.

Note bridge over Raquette River with a Dam to the right
Note bridge over Raquette River with a Dam to the right (village of Hannawa Falls). For those interested, there is a newly laid foot trail to an old Potsdam Sandstone quarry. If you take a right directly after this bridge and park near the new sign there is a nice walk along river which ends at the quarry.

Adirondack Highland granitic gneiss crops out on the right (west) below the school.

Hepburn Library on the right is made of blocks of Precambrian Gneiss

On the left is the Episcopal church, made of Potsdam Sandstone.

STOP 1. EXPLORING STONE VALLEY
The Raquette River flows north from the Adirondack Highlands from Tupper Lake. It is the most dammed river in the Adirondacks, with 8 major dams. South of Colton it flows through Potsdam, Norwood, Norfolk, and passes just south of Massena before flowing into the St. Lawrence River at St. Regis Village. The reservoir behind the dam at Colton extends some 6 km south to the next dam up the line, at South Colton.
The West Side of the Valley We begin our descent to Stone Valley along the gravel road leading north from the parking lot on River Road. We will first see the power plant at the dam. It is one of several such plants such as the ones at Hannawa Falls and Norfolk. The photos below show the dam at Colton (left) and the penstock that leads water from the Colton reservoir 5 km south to the power plant just south of Brown's Bridge. This generating plant produces 30 megawatts of power and is one of 8 generation stations on the upper Raquette River that produce a total of approximately 100 megawatts of power (owned by Reliant Energy). Cross over the penstock via a small brown-painted metal foot-bridge onto the main path which then follows the river downstream past some spectacular falls. A short distance down the trail is the stone foundation of a tanner's mill. During the expansion to the western states, bison pelts were shipped east by rail and tanned wherever tanners could find the raw materials for the tannin, such as in the Adirondacks. Huge piles of bison fur accumulated outside tanneries such as this and remain today (hair is not easily degraded by microorganisms). Right past the foundation there is a 15 foot section of trail where the "buffalo fur mountain" can be seen underfoot. The ground sounds hollow here when you stamp on it. A look at the ground reveals clumps of matted buffalo fur that remain here to this day.
The Dam and Penstock at Colton The gorge of the Raquette River as it tumbles down Stone Valley from below the dam at Colton is steep, narrow, and scenic. Vast numbers of logs were floated down the north-flowing Adirondack rivers to the St. Lawrence. Many towns were established along the "fall line," the escarpment where the hard Precambrian rocks of the Adirondacks are in contact with the flat-lying Lower Paleozoic sedimentary rocks of the St. Lawrence Valley. This contact is marked by relatively sharp topographic drops between the harder metamorphic rocks to the south and the flat-lying sediments to the north. The crystalline rocks form steps over which the river tumbles in waterfalls that provided hydropower to operate saws and other equipment. The falls at Colton represent such a place. In these days of extreme sports kayak races are now popular, as daring boatmen test themselves through the roaring falls in times of high water. A caution: Depending on the water level (which in turn depends on the time of year and the amount of water being released at the dam), various platforms of bedrock can be visited along the river. Signs warn of the possibility of being caught by rapidly rising water levels, but the power company provides no advance warning. The excellent hiking trails along both sides of the river make it possible to examine many of the excellent bedrock exposures.
Carthage-Colton mylonite zone Once down along Stone Valley we will assemble on one or another set of stream-polished outcrops of rocks of the Carthage-Colton mylonite zone, the boundary zone between the Adirondack Highlands and Northwest Adirondack Lowlands. First we will look around at the gneisses and the general topography and geomorphology of the area, with commentary from Bill D. ("older Bill"). Then we will explore the area for its biological dimensions with Bill L. ("tall Bill"). We invite you to do some sketching so that you will have things to show to Lucretia when we return to the cars and things to discuss on the outcrops as well. Throughout, the group leaders will interact with each other and with the trip participants to consider the connections among the geological, biological, and artistic attractions of the area. What can the geologist, biologist, and artist contribute to each other and take from each other in exploring an area such as Stone Valley? What kinds of new insights can emerge from cross disciplinary action and an earth-systems approach to an area?

A5: THE NATURE AND TECTONIC SIGNIFICANCE OF THE CARTHAGE COLTON SHEAR ZONE: ADIRONDACK MOUNTAINS, NEW YORK STATE.
Eric Lee Johnson
Hartwick College
Department of Geology and Environmental Science
Oneonta, NY 13820
Johnsone@hartwick.edu
ABSTRACT
This trip will examine the nature and geologic significance of the Carthage-Colton Shear Zone (CCSZ) and late to post-Ottawan intrusive activity along this zone. The CCSZ marks the boundary between the Central Metasedimentary Belt and the Central Granulite Terrane (Frontenac-Adirondack Belt). The significance of this shear zone and the bounding terranes has been a matter of continued debate. This trip will analyze field, geothermometric, and geochronologic relationships along several transects across the CCSZ with the goal of better elucidating the nature and timing of this complex and enigmatic structure.

A5: THE NATURE AND TECTONIC SIGNIFICANCE OF THE CARTHAGE COLTON SHEAR ZONE: ADIRONDACK MOUNTAINS, NEW YORK STATE.

STOP 1. Valentine Wollastonite Mine
Discuss field relationships between the Diana Syenite Body and lowland marbles. Basic goal here is to demonstrate that the Diana Syenite intrudes into lowlands marbles and contact metamorphism drove formation of the Wollastonite.
Note that much of the wollastonite body is at best weakly deformed and so lacks Ottawan deformation.

STOP 2. Big Crop Diana Syenite
Look at pegmatites and shear zones that cut the body. These shear zones vary to greenschist facies formed during the end of CCSZ deformation.

STOP 3. Contact Metamorphism of marble at the Diana Contact (route 813).
OHM 2019: There is no route 813, perhaps the author means route 812... Also no location is given so I put this on the place identified in NYSGA trip 1998 A2, stop 3.
Once again show a lack of a strong Ottawan deformation. Note that this type of grain coarsened marble can be found in many locations at or near to Diana Syenite contacts.

STOP 4. Jayville Road
STOP 4. Jayville Road Here we will cross into the Adirondack Highlands for the first time. Variations in the orientation of stretching lineation will mark our passage across the CCSZ. In the Lowlands, stretching lineations are more steeply dipping and oriented to the NW, but once we cross the CCSZ, stretching lineations rotate to near strike parallel orientation (NNW).
OHM 2019: Guesses were made for most of stops A-E, as only A had any mileage given.

STOP 4A. Fault Zone in Diana Syenite.
This zone shows both strong ductile and brittle deformational fabrics. The Diana Syenite Body is vertically stacked by several small thrust faults. (Lowlands)

STOP 4B. Contact between Diana Syenite and the Border Granite
(Lyon Mountain?) Along RR tracks near Topa-da-Hill Road. Is this the Highlands-Lowlands Boundary?

STOP 4C. Long Lake Fault Zone (look up the lake at this major lineament).
This structure is a brittle normal fault that offsets the CCSZ detachment (SEE FIGURE 1). We will encounter this fault once again at STOP 10. At this location, the Long Lake Fault vertically truncates the CCSZ detachment.

STOP 4D. Road south of Jayville Road (ROD and TODD outcrop)
Note that while to the North of Jayville Road we have passed into the Granite, but here to the south and east, we are still in the Diana Syenite Body. A small east-west trending (strike-slip?) fault offsets the CCSZ (Highlands-lowlands boundary) at this location. This fault passes directly through the Jayville Mine (STOP 4E) and continues (at least in topographic expression) to the east passing through the Benson Mine.

STOP 4E. Jayville Mine (stop to look for vonsenite ore)
Here we can visit the mine shaft and discuss the amphibolite matrix for the vonsenite (Fe2+Fe3+2BO5) ore and the origin of the boron. Discuss the Lyon Mountain Granite at this local and the presence of felsic quartz-albite facies dikes. Examine the location of the mine in terms of known brittle and ductile features.

STOP 5. Faulting in the Diana Syenite Body.
Classic mixture of rock types that characterize the faulted contact between the Diana Syenite Body and lowlands paragneisses including the feldspathic quartzite, marble and diopsidite. Note the strong ductile fabric of these rocks that is overprinted by later brittle faulting.

Greenwood Falls Picnic Area. Look at the Diana Syenite Body

STOP 6. Outcrop of diopsidite skarn.
Contact skarn between the Diana Syenite Body and the Balmat Edwards (?) marble. This friable green colored rock is primarily made up of green diopside and grey calcite. (mapped as Tia)
OHM 2019: Because lunch will be one mile down this road, it is apparent that we must no longer be on Route 3. This stop was located by coming back one mile from the picnic area, which was found on the DEC map of Greenwood Creek State Forest.

STOP 7. Diopsidite contact rock (Dia/Tia).
Note on the map that these diopsidic contact skarns are found in the middle of the Diana Syenite Body and along its eastern edge, at the CCSZ detachment. This unit is associated with the contact between the Diana Syenite and the Balmat Edwards Marble.

STOP 8.
Once we pass the last outcrop of green diopsidite, we have left the Adirondack Lowlands and entered the Adirondack Highlands Terrane. Pink leucogranite and hornblende granite outcrops underpin the ridge. Our stop is near the intersection of Route 3 and Sykes Road. The contact between the Leucogranitic gneiss and the Irish Hill Gneiss is well exposed in this outcrop. The Irish HilI Gneiss (Whippoorwill Corners Gneiss of Hall, 1981) consists of calc-silicate gneiss (containing calcite + diopside ± tourmaline) and quartzite with abundant concordant and crosscutting pegmatites.

STOP 9. Hornblende granite.
This stranded small body of granite differs from those that we have seen on Jayville road. Larger exposures of a similar granite can be found to the north in the South Edwards Quadrangle (Eastern Granite Gneiss of Hall 1981). The granite is moderately deformed at this location.

STOP 10. Faulted Block of the Lowlands and Granite Gneiss
STOP 10A. Faulted Block of the Lowlands
Intersection of NY Routes 58 and 3. Park in the small lot at the intersection of Routes 58 and 3. Directly to the north of the parking lot is a small mine adit. We will start by heading north to the old bridge over the Oswegatchie River. Outcrops to the west (down the slope) are of green Irish Hill Gneiss. The outcrops along the road show a strong brittle deformation and a mixture of rock types. This outcrop contains marble (looks very much like Balmat Edwards Type), bleached syenite-granite, and even some diopsidite. Fluorite crystals have been found in vugs and tension gashes in the marble. This outcrop lies on the trace of the Long Lake Lineament (Fault) and movements on this lineament are the logical cause for the strong brittle overprint observed in these rocks. The intriguing thing about this series of outcrops is that the rock types are more like those of the Lowlands Terrane even though we have crossed the CCSZ and are well into the Highlands at this location. Just 100 m west one can find outcrops of Irish Hill Gneiss (Highlands) and to the east (on Route 3) we find pink granite (Highlands Rock) with a strong brittle overprint. This outcrop may represent a block belonging to the Adirondack Lowlands that has been down faulted along the Long Lake Fault (see figure 2).
STOP 10B. Route 3 Granite gneiss and breccia (Long Lake Fault)
Calcite filled breccia in highlands granite gneiss and Irish Hill Gneiss. Both sides of the road.

STOP 11. IHG/Lg contact
Two large road cuts expose (or nearly expose) the contact between the pink leucogranitic gneiss and the calc-silicate Irish Hill Gneiss. Here the Irish Hill Gneiss is cut by many coarse pegmatite bodies. Stop 11a: Irish Hill Gneiss. Stop 11b: Leuco-granitic gneiss. We are now nearly due north of STOP 8 (IHG/Lg contact on Route 3).

STOP 12. Outcrops of strongly deformed leuco-granitic gneiss
(Highlands).

STOP 13 Roadcut into Diana Syenite.
The Diana Syenite (granitic phase) shows strong ductile deformation with well developed c/s fabric. Note also the strong brittle overprint as marked by the abundant and closely spaced joints sets. We have once again crossed the Highlands/Lowlands boundary. Here we will look for kinematic indicators.

STOP 14. Shear Zones in the Diana Syenite Complex
The outcrop on the north side of the road show numerous anastomosing shear zones. Sheared Diana contains Hornblende (Cl-rich) + biotite + plagioclase (An) + perthite + quartz + titanite ± Fe-Ti oxide minerals. Relict clinopyroxene rimmed by amphibole and amphibole + chlorite is common as is scapolite replacement of some plagioclase crystals.
Samples SE-TF-8 and SE TF-11 have been dated by the author using U/Pb titanite and 39Ar/40Ar for hornblende. The intrusion age for the Diana Syenite Complex has been dated to 1155 ± 4 Ma (Grant et al. 1986).
In shear zones, titanite replaces Fe-Ti oxides probably via a reaction involving plagioclase feldspar, and calcic amphibole. Titanite is also found in the syenite outside of these shear zones but it is rare. Away from the shear zones, Fe-Ti oxides are common while they are nearly absent in the shear zones. These observations suggest that sphene growth accompanied recrystallization during shearing, and since the recrystallization conditions during shear zone formation range only to the lower amphibolite facies and probably well below the 600-650°C closure temperature for lead in titanite, U/Pb ages are interpreted to represent growth ages and hence the time of shearing.
The U/Pb age for titanite are concordant and constrain the time of titanite growth during shearing to ∼1041 Ma (see figure 5). 39Ar/40Ar data for amphibole from this sample yield a flat spectrum with a plateau age of 979.8 ± 8.6 Ma. The closure temperature for hornblende (Ar) is 500-550°C, and these ages are interpreted to represent cooling ages.
Sample SE-TF 11: (Same outcrop as SE-TF-8) Geochronology data for the SETF-II is shown in figure 6. Three fractions prepared from this sample all yield concordant ages that range from 1054 to 1034 Ma. These ages are interpreted to represent multiple generations of titanite (sphene) growth in the shear zone.

STOP 15. Ultramylonite zone in the Diana Complex.
The small shear zone exposed here shows extremely sharp strain gradients. The core of this shear zone is ultramylonitic and yet within 2-3 meters, the host Diana Syenite retains some igneous texture. It is interesting to note that strain recorded throughout the Diana Syenite Body is highly variable. The DSC is everywhere deformed ranging from coarse-grained augen gneisses with distinct igneous textures preserved (most common) to ultramlyonite. Against this deformational backdrop, the Diana Syenite is cut by sub-meter width shear zones that record low recrystallization temperatures (greenschist-amphibolite facies). In many locations, a strong brittle deformational event is also evident.

STOP 16. Famous Green Diopside skarn outcrop.
This skarn body marks the contact between the granitic gneiss, which exhibits a strong lineation, and the marble. It is interesting to note that the skarn does not show a deformational overprint.

Leucogranitic Gneiss (Lowlands)

STOP 17. Freshly blasted small outcrop of leucogranitic gneiss.
This granite gneiss body outcrops along the eastern margin of the Diana Syenite Body. This granite body is, therefore, a part of the Adirondack Lowlands. Just around the next corner, we will encounter the Diana Syenite.
DANA HILL METAGABBRO
The Dana Hill Metagabbro preserves multiple deformation and veining events ranging from granulite facies ductile to sub-greenschist facies brittle events (see appendix). In many cases, cross-cutting relationships allow for the determination of a sequence of events. To date, six major deformational/veining events have been identified (Johnson et al., 2004; Streepey et al., 2001). At STOP 18 we will examine EVENT 4 shearing. Events 1 through 6 will be examined at stop 20.

STOP 18. The "Zebra" rock outcrop of Dana Hill Metagabbro
(Adirondack Highlands).
The gabbro is cut by multiple cm to sub meter wide EVENT 4 (see appendix) shear zones. The zones typically dip steeply and shear sense, which varies from shear to shear, can be determined by rotation of a preexisting foliation into the zone (see appendix and figure 8).
The typical assemblage consists of amphibole ± clinopyroxene + scapolite + plagioclase + Fe-Ti oxides. Plagioclase compositions are consistent within individual shear zones but range from An05 to An32 between shear zones. Polygonal scapolite forms distinct halos about amphibole and original ilmenite is replaced by titanite in the shear zones. Geochronologic data for this outcrop are presented in Figure 9.
Sphene (titanite) growth is constrained to occur during shearing and U/Pb ages are considered to be cooling ages off of peak Ottawan temperatures of 680-720°C (Streepey et al., 2001). These shear zones are similar in size and type with those found in the Diana Syenite Body (STOP 14) but shearing in these zones takes place at considerably higher temperatures. Sphene (titanite) U/Pb ages for shear zones in the Diana Syenite are considered to be growth ages marking the time of shear zone formation at ∼ 1054-1034 Ma. Shear zones in the Dana Hill Metagabbro at this location record cooling temperatures at 1020 Ma so it is not unreasonable to suggest that the shear zones found in Dana Hill Metagabbro were active at the same time but at very different temperatures. 39Ar/40Ar cooling ages for these shear zones and similar style shear zones in the Dianan Syenite Body overlap indicating that both units cooled through 550°C closure temperature for hornblende at the same time.

STOP 19. Shear zones in the Lyon Mountain Granite Gneiss.
Sillimanite + quartz + magnetite is a common assemblage in the Lyon Mountain Gneiss (McLelland et al., 2001). At this location, one can see the formation of this assemblage as a consequence of deformation and post deformational fluid flow through the shear zones. In the shear zones, sillimanite needles are both aligned along the developing folia and as radial splays that clearly cross-cut the foliation. In the shear zones, plagioclase feldspar is only present as albite lamellae in exsolved perthite. Bulk and trace element chemistries of this rock both in and outside of the shear zones show some interesting variations (see table 1 RL).
Samples from sheared sillimanite-bearing Lyon Mountain samples (SRCHI and SRCH2) show marked depletions in Ca, Na, and enrichments in K, Rb, and Ba. The proposed mechanism for quartz-sillimanite formation is via the incongruent dissolution of plagioclase feldspar via the reaction:
CaAl2Si2O8 +H2O = Al2SiO5 +SiO2 +Ca(OH)2aq
2NaAlSi3O8 + H2O = Al2SiO5 +5SiO2 + 2Na(OH)aq
REACTIONS 1 AND 2
Slight enrichments in SiO2 Al2O3 can be accommodated by these reactions and the simple removal of Na2O and CaO , but K2O enrichments cannot be caused in this fashion. It appears that potassium was indeed introduced to these samples during and after shearing.
The timing of this fluid infiltration event is constrained to post date emplacement of the granite during syn to late-Ottawan time (∼1050 Ma).

Note the large outcrop of Irish Hill (Whippoorwill Corners) Gneiss.

Roadcut of pink granitic gneiss

Roadcut into pink granitic gneiss (hornblende granite protolith)

STOP 20. DANA HILL METAGABBRO
Park the vans and climb the hill on the north side of the road. On the trail up the hill we will pass several sub-meter width EVENT 4 shear zones.
We return to the Dana Hill Metagabbro to examine the complex deformation of the body. This outcrop along with the outcrops at the top of the hill across the road, exhibit all 6 deformational events (see appendix and fig. 10). We will start at the far end of the outcrop and examine the deformational sequence of events recorded. From the oldest to the youngest, this outcrop preserves EVENT 1 mega-shearing, EVENT 3 hornblende veining, EVENT 4 sub-meter shearing, and EVENT 6 folding and brecciation. EVENTS 2 and 4 can be observed at the top of the hill across the road. Events 3 through 5 take place in the presence of a fluid or fluids that drive scapolite replacement of original plagioclase feldspar in the host metagabbro. In the Diana Syenite Body (Lowlands Terrain), sub meter wide shear zones (dated to 1052-1034 Ma) also exhibit scapolite replacement of plagioclase feldspar. This scapolitization event is widespread in and around the CCSZ from just north of Harrisville to Colton and is present in both the Highlands and Lowlands Terranes. It therefore marks a common event for both terranes.
The goal of this stop is to demonstrate that the Dana Hill Metagabbro Body acted as a rigid block during deformation. In some instances, cumulate igneous textures have been completely preserved while in others the gabbro ranges to ultramylonitic in texture. The resistance to deformation in the Dana Hill Metagabbro resulted in an episodic response to the applied stress leading to discrete pulses of deformation. This body preserves individual and distinct events that record the entire deformational history of the region. The earliest shear zones are massive (30 m wide) and mylonitic to ultramylonitic. These shear zones record recrystallization temperatures in excess of 700°C. Subsequent shearing events are dramatically different, forming sub-meter wide anastomosing shear zones at recrystallization temperatures at or below 700°C. The last deformation events to affect the Dana Hill Metagabbro transition to brittle failure at low to sub greenschist facies conditions. The deformational history is one of an exhuming footwall with deformation beginning in the granulite facies and eventually passing through the brittle-ductile transition at greenshist to sub greenschist facies conditions. We will examine these events and the available geochronologic data for this complex outcrop.

A6: CORDIERITE-BEARING GNEISSES IN THE WEST -CENTRAL ADIRONDACK HIGHLANDS
Frank P. Florence
Science Division, Jefferson Community College, Watertown, NY, USA 13601
fflorence@sunyjefferson.edu
Robert S. Darling
Department of Geology, SUNY College at Cortland, Cortland, NY, USA 13045
Phillip R. Whitney
New York State Geological Survey (ret.), New York State Museum, Albany, NY, USA 12230
Gregory W. Lester
Department of Geological Sciences and Geological Engineering, Queen's University, Kingston,
Ontario, CANADA K7L 3N6
Cordierite-bearing gneiss is uncommon in the Adirondack Highlands. To date, it is has been described from three locations, one near the village of Inlet (Seal, 1986; Whitney et al. 2002) and two along the Moose River further to the west (Darling et al. 2004). All of these cordierite occurrences are located in the west-central Adirondacks, a region characterized by somewhat lower metamorphic pressures as compared to the rest of the Adirondack Highlands (Florence et al., 1995; Darling et al., 2004).
In the Fulton Chain of Lakes area of the west-central Adirondack Highlands, a heterogeneous unit of metasedimentary rocks, including cordierite-bearing gneisses, forms the core of a major NE to ENE trending synform. Cordierite appears in an assortment of mineral assemblages, including one containing the uncommon borosilicate, prismatine, the boron-rich end-member of kornerupine (Grew et al., 1996). The assemblage cordierite + orthopyroxene is also present, the first recognized occurrence of this mineral pair in the Adirondack Highlands (Darling et al., 2004).
This field trip includes stops at four outcrops containing cordierite in mineral assemblages that are characteristic of granulite facies metamorphism in aluminous rocks. Stops 1, 3 and 4 are from those previous described (Seal, 1986; Whitney et al., 2002; Darling et al., 2004) whereas Stop 2 is described here for the first time. Our intention is to consider the different parageneses in cordierite gneisses, and to consider the metamorphic pressure-temperature controls, as well as compositional controls, on the formation of these assemblages. We will also discuss the utility of these low variance assemblages for characterizing the pressure-temperature path of metamorphism (as well as formation conditions for prismatine) and the implications of their moderate pressure conditions of metamorphism for our understanding of the geologic history of this portion of the Adirondacks.

A6: CORDIERITE-BEARING GNEISSES IN THE WEST -CENTRAL ADIRONDACK HIGHLANDS

STOP 1. Biotite Gneiss With Cordierite
A long series of roadcuts is exposed along this section of road. The rocks immediately to the right are light gray outcrops of calcsilicates. Begin walking in the same direction as you were driving (to the N along this section of Route 28.) The next outcrops are garnet-biotite-quartz-feldspar gneisses containing abundant K-feldspar. Notice the color of these iron-rich garnets.
Proceed to the next outcrop to the north, containing darker gray quartzite and layers of biotite-quartz-plagioclase gneiss. Coarse sillimanite and lavender grains of garnet are found associated with biotite-rich layers. Bluish cordierite, ca. 1 cm in size, can be observed on fresh surfaces on the face of the outcrop or on top, towards the south end. Deformed leucosomes and pegmatite veining is also seen in outcrop.

STOP 2. Cordierite-Bearing Outcrop
Pink and gray two-feldspar gneisses outcrop along both sides of the road and exhibit steeply NW dipping to nearly vertical layers. Coarse grains of bluish cordierite are visible within a deformed pegmatite vein at the southern end of the exposure.
These gneisses show strong evidence migmatization. There are numerous K-Feldspar-, biotite-, quartz- rich pegmatite veins parallel to foliation, some of which are deformed into isoclinal or ptygmatic folds. Cm long, thin, discontinuous lenses of biotite and sillimanite (restite?) are abundant on the south end of the outcrop on the west side of Route 28, where it can be seen that the long axis of sillimanite blades are randomly oriented within the plane of foliation. The association of cordierite with the pegmatite veins suggests that its formation was the result of a melt-producing reaction.
These outcrops contain abundant oxides and the coloration of garnet implies a relatively high Fe content. Overall, the mineral abundances suggests that these rocks have a different bulk composition than the cordierite gneiss seen at Stop 1 and those that will be shown at Stops 3 and 4.

Parking for stops 3 and 4. Mg-rich Metapelites
The next two stops are along the Moose River and require a little more than a kilometer of walking to visit them both. The outcrops are exposed along the river's edge. Caution is advised during periods of high water. Please DO NOT USE HAMMERS at these outcrops. We request that sampling be restricted to collecting loose material.
From the parking area, follow an unimproved fishing trail that leads left out of the parking area and walk downstream on the bank above the south side of the river. Continue for approximately 100- 200 m, past NW dipping quartzite beds containing tremolite needles, diopside, and other calcsilicate minerals. The trail passes through the old foundation of a former tannery. After another few 100 m, the river then bends to the north and the trail drops down to the river's waters edge. Stop 3 consists of the first outcrops along the riverbank that are exposed downstream from the bend.

STOP 3. Mg-Rich Metapelites
This stop consists of a continuous bedrock exposure along the south side of the Moose River. The first exposures past the bend in the river contain large greenish-gray blades of prismatine that have formed in a biotite-quartz-K-feldspar gneiss containing massive, cm scale "lumps" of garnet. Cordierite was recognized in thin sections taken from these outcrops.
Continuing downstream, biotite-quartz-feldspar gneiss outcrops show elongate segregations of cordierite, sillimanite, and spinel in the layers adjacent to spectacular splays of prismatine. Prismatine is also well displayed in an isoclinal fold that can be seen on a 2 m high vertical face. Notice that prismatine needles grow both parallel to and across the plane of foliation. A little further downstream, outcrops contain zones with abundant small, black tourmaline crystals. Prismatine is also present here, immediately rimmed by tourmaline-free halos. Cordierite is present in this portion of the outcrop as well, sometimes as dark, pinitized (altered) grains and in lumpy-looking symplectite intergrowths with quartz.

STOP 4. Metapelites Containing Cordierite + Orthopyroxene
The western end of the exposures at Stop 3 rises directly above the Moose River. To continue further west from here, walk directly upslope and return to the fishing trail. Continue in the downstream direction another 400 m to where quartz-rich outcrops are exposed along the river. Follow these outcrops for another 30-50 m. This is Stop 4.
The first exposures along this section of outcrop contain occasional euhedral grains of prismatine in quartz-biotite-feldspar lenses in quartzite. Just downstream (ca. 10 m) from these are layers locally displaying large blue knots of cordierite and lavender garnets.
Another 10-15 m of downstream travel brings one to a few south dipping rocks that extend a little into the river. Here, cm long, dark green prismatine blades form radiating splays on surfaces of biotite-quartz-feldspar lenses within quartzite. Most grains lie within the plane of foliation but individual crystals are in fact arranged in random orientations with respect to foliation in what appear to be leucosomes. Sillimanite occurs in this assemblage only as anhedral grains included in prismatine, leading Darling et al., (2204) to suggest that sillimanite abundance was the limiting reactant in the melt-forming reaction leading to prismatine formation.
Other feldspathic gneiss lenses within these outcrops contain orthopyroxene, garnet, K-feldspar, and plagioclase in melt zones. In thin section, grains of orthopyroxene and plagioclase moderate to well-developed ophitic texture. As with the prismatine-bearing lenses, these mineral assemblages are considered to be the result of partial melting.
Adjacent biotite-rich layers contain bronze colored, weathered orthopyroxene megacrysts and cordierite knots. Grains of unaltered orthopyroxene were seen in thin section, where they appear in textural equilibrium with cordierite, biotite, quartz, and K-feldspar. Some grains of cordierite are rimmed by biotite and quartz symplectites. Presumably, the alteration and replacement of orthopyroxene and cordierite proceeded according to the reaction
orthopyroxene + cordierite + K-feldspar + (hydrous melt or H2O) → biotite + quartz
It is not clear whether this reaction operated during the subsolidus portion of the retrograde path, presumably by the introduction of an aqueous phase, or it was brought on by melt-formation at or near the peak of metamorphic conditions.

A7: THE POWERS FARM UVITE LOCALITY: A DAY IN THE FIELD AT THIS CLASSIC MINERAL OCCURRENCE
Parishville Central School
P.O. Box 137
Nicholville, New York, 12965
gdesires@slic.com
Once named pierrepontite (discredited name) the tourmalines from the Power's Farm occurrence in Pierrepont, New York can be found in private collections and museums worldwide. Amazingly this site can still be accessed by collectors looking for well crystallized uvites and other minerals.
Introduced to the mineral collecting world of the 1800's as pierrepontite, the tourmaline crystals from the Bower Power's Farm, Pierrepont, St. Lawrence County, New York, USA, have achieved world-wide notoriety. Dana (1877) notes the occurrence of these unusual tourmaline specimens while Kunz (1892) describes the locality in his text Precious Stones of North America. To this day Pierrepont tourmalines are still noted and photographed in current editions (now in its 22nd edition) of the Manual of Mineral Science (Klein, 2002). Specimens of this aluminum-poor uvitic dravite (Dalton, 2003) and its accessory minerals can be found in many of the world's top museums and private collections. Though universally recognized as a classic tourmaline locale, the name of this mineral has been intensely debated. Based on recent chemical and x-ray analysis, the author believes the proper species name for this so called uvite may actually be in question. Henceforth, this tourmaline will be referred to as uvite, as it has been locally for many decades.
This field trip description will attempt to present an overview of what many have considered to be one of the world's classic tourmaline localities. Due to extensive coverage of the area's bedrock by Pleistocene glacial deposits, many aspects of the site's geology will remain speculative. Its minerals, however, are available for study and documentation, and the site remains open to collectors at the time of this writing.

A7: THE POWERS FARM UVITE LOCALITY: A DAY IN THE FIELD AT THIS CLASSIC MINERAL OCCURRENCE

Parking Area

STOP 1. Historic Dig Site

STOP 2. DuFoe's Dig Site

STOP 3. Hillside Dig Site

STOP 4. Power's House

A8: A TOUR OF DAMAGE SITES AND A PROPOSED EPICENTER FOR THE CORNWALL-MASSENA EARTHQUAKE OF 1944
(This afternoon trip will follow Workshop W-2)
G.N.Nottis
1605 W. Market St.
Lewisburg, PA 17837
gnottis@yahoo.com
September 5, 1944. It was a warm late summer night in Massena, New York. World War II still raged. The local ALCOA plant was involved in the war effort with the manufacture of aluminum structural parts for the wings of American war planes. During the previous year, Nazi saboteurs had been caught near Long Island, New York with plans for the ALCOA plant. Many residents knew that. At 12:38 Eastern War Time (04:38 UTC), an ominous rumbling and hard shaking of the ground and buildings shocked the residents of Massena. The shaking lasted for what seemed like an eternity. Some had no idea what was happening. Others thought the Nazis had succeeded in landing a V-I bomb on the ALCOA plant. Still others knew it was an earthquake. When the shaking was over, numerous homes, businesses, and other buildings along with their contents had been considerably damaged in the vicinity of Massena and Cornwall, Ontario. Many would never forget that night, and many, after more than 50 years, would call it the most upsetting night they had ever known, even those who fought in the war. During this fieldtrip we will visit some of the damage sites, recall what happened on that night in 1944, and consider a proposal for where the epicenter of the 1944 earthquake might have been.

A8: A TOUR OF DAMAGE SITES AND A PROPOSED EPICENTER FOR THE CORNWALL-MASSENA EARTHQUAKE OF 1944

STOP 1. Former Site of New York Telephone Company Office
Discussion of communication disruption in the earthquake.

STOP 2. Home at 16 Danforth Place
Former home of Mr. and Mrs. Charles Stubbs. Discussion of residential damages.

STOP 3. Old Cemetery on West Orvis Street.
Search for rotated cemetery monuments.

STOP 4. Home at 2 Ransom Avenue.
Former home of Mr. Herbert Hatch. House has chimney repaired from the 1944 main shock.

STOP 5. Home at 61 Bridges Avenue.
Former home of Mr. and Mrs. Leonard Prince. Discussions of residential building contents damage and psychological trauma.

STOP 6. Former site of Massena High School
Discussion of damage to the school, and other schools in Massena and Cornwall.

STOP 7. St. John's Episcopal Church
The chimney at this church appears to have repaired cracks from the earthquake. Marble alter was also damaged.

STOP 8. United States Post Office,
Discussion of earthquake damage to the building and about unreinforced masonry buildings in general.

STOP 9. First Baptist Church
Church exhibits repaired cracks in exterior brick work from the earthquake. Discussion of church damage in Cornwall and Massena.
OHM 2019: Church was demolished on 12/12/12...

STOP 10. Massena Town Hall, Main Street
Discussion of damage to this building.

STOP 11. C-M Building, 60 Main Street
Examination of north wall which was torn-out and replaced because of earthquake damage.

STOP 12. Former Site of the Sunshine Store, 10 Main Street
Discussion of damage to the former business here and the earthquake's impact on small business in the Massena and Cornwall area.

STOP 13. Overview of the Alcoa Plant.
This plant suffered minor cracking to brick walls and interior plaster damage. Five large chimneys ranging in height from 80' to 220' were cracked by the earthquake. The chimneys were cracked at points ranging from 8' to 30' down from the tops. It was on the plant grounds that 3 large water lines were broken by the earthquake due to apparent lateral spreading of the ground. One ALCOA employee was severely burned at the plant when a power surge damaged equipment after power was restored following an earthquake caused power outage.

STOP 14. Massena Center Cemetery
Many of the monuments in this cemetery were rotated, shifted, or knocked-down by the earthquake. At this stop please take some time to find some of the damaged grave stones. Just across the stream to the east of the cemetery is Massena Center. All of the chimneys in this area were up-bumped. The old Massena School, once located across the stream and north of the road was severely damaged in the earthquake and had to be demolished.

STOP 15. Former Site of the William Hooper Farm
This is the site of the liquefactions or "sand boils" that occurred during the 1944 earthquake. The farm well also went dry here. A discussion of work done on the site, liquefaction, and the earthquake's impact on local water wells will be conducted here.

STOP 16. Eisenhower Lock
This stop is near the location of the H.R. Horton Farm where the majority of the Cornwall/Massena earthquake aftershocks were felt. The aftershocks will be discussed here as well as the evidence for the proposed epicenter.

B1: L-VERSES S-TECTONITE FABRIC VARIATIONS WITHIN THE SOUTHERN ADIRONDACK SHEAR ZONE SYSTEM: PROGRESSIVE DEFORMATION ASSOCIATED WITH A SINISTRAL CONJUGATE TO A GRENVILLE SYNTAXIS
David W. Valentino, Dept. of Earth Sciences, SUNY Oswego, Oswego, NY 13126
Gary S. Solar, Dept. of Earth Sciences, SUNY Buffalo, Buffalo, NY 14222
Jeffrey R. Chiarenzelli, Dept. of Geology, SUNY Potsdam, Potsdam, NY 13676
Alexander E. Gates, Dept. of Geological Sciences, Rutgers University, Newark, NJ 07102
Paul Freyer, Dept. of Earth Sciences, SUNY Oswego, Oswego, NY 13126
Rachel E. Price, Dept. of Geological Sciences, Rutgers University, Newark, NJ 07102
This field guide was prepared in tandem with a field guide for the 73th and 75th NYSGA field conferences, and synchronously with an article written for the Memorial Volume to Nicholas Rast, recently published in the Journal of Geodynamics (Gates et al., 2004). Therefore, some parts of this guide are directly related to work presented in the earlier field guides and some parts were prepared for multiple projects; however, the emphasis here is exclusively on new findings in the Adirondacks. We encourage the reader to examine our data presented in the earlier field guides (Gates et al., 2001; Gorring et al., 2003) and summarized in Gates et al. (2004) for further details.
Transpressional strain is found to be related to a variety of tectonic environments. Transcurrent faults with restraining bends produce structures such as thrusts and conjugate faults (Woodcock, 1986). Oblique motion vectors between two tectonic plates result in oblique collision that produces zones of transpressional strike-slip deformation in the hinterland, and belts of thrusting in the foreland (e.g., Woodcock, 1986; Tappionier and Molnar, 1976). As well, zones of transcurrent strain can develop syntaxes in regions of the crust experiencing horizontal escape as the result of rigid indentors in the colliding lithosphere (Tappionier and Molnar, 1977). These structures have been almost exclusively described for rocks that were exhumed from intermediate to shallow levels of the crust. The distribution of strain and the location of faults can be controlled by the presence of pre-existing structures (Dewey and Burke, 1973), or by the juxtaposition of rock bodies with ductility contrasts such as decoupling of cover rocks over deforming crystalline basement (Gates et al., 1999; Valentino et al., 2004).
Dewey and Burke (1973) and Windley (1986) proposed a model for tectonism recorded in the Grenville Province rocks based upon the deep structure of Himalayas and the intensity of tectonism recorded there. Tapponnier and Molnar (1977) proposed that the rigid indentation of India formed a syntaxis (abrupt bend in the general attitude of the orogen) containing conjugate strike-slip faults in the Eurasian continent during the Himalayan Orogeny. Northeast-striking sinistral, transcurrent shear systems accommodate tectonic escape (Tapponnier et al., 1982) in China and southeast Asia, and these fault systems record hundreds to thousands of kilometers of offset over tens of millions of years. There are also smaller, northwest-striking, dextral systems that have been synchronously active with the sinistral zones that form the conjugate pairs to the larger sinistral zones of tectonic escape within the Himalayan syntaxis.
The Grenville Province forms one of the longest and most deeply exhumed areas of continental crust on Earth, extending from Scandinavia, through eastern Canada and inliers in the Appalachian chain, to Texas and Mexico, and perhaps beyond. Grenvillian basement massifs in the northeastern United States form a series of unconnected inliers along the Appalachian orogen (Figure 1). Because of the great spacing and high degree of tectonism associated with the Appalachian tectonic events, correlation of Grenvillian rocks among the massifs are difficult. In addition to widespread granulite-facies metamorphic conditions at about 1.0 Ga, these basement massifs all contain vast volumes of 'A-type' granite bodies whose magma had intruded (ca. 1150 Ma) into older supracrustal rocks (ca. 1250 Ma) of varied character prior to Ottawan deformation (ca. 1040 Ma; e.g., McLelland and Isachsen, 1986). The Grenville Province exposes the deep crustal roots of an ancient mountain range of immense portions, and records the assembly of one of the Earth's few recognized supercontinents, Rodinia. Consequently the Ottawan Orogeny (ca. 1070-1000 Ma) is often cited as a classic example of continent-continent collision and compressive thickening of the crust, with invocation of the Himalayas as a modern tectonic reference frame (Dewey and Burke, 1973; Windley, 1986; McLelland et al. 2001). However, refinement and testing of such a model must address many important components of the orogeny. One of the most significant components in the Himalayas is the massive amount of strike-slip faulting expressed in tectonic escape and the syntaxis (Tapponnier and Molnar, 1977). Whereas compressive tectonics is universally documented in the Grenville orogen, few workers have recognized analogous, large-scale, orogen-parallel deformation (cf. Baer, 1977). Some of the evidence for strike-parallel deformation is described herein, and is much of the basis for the sequence of outcrops listed in this guide.

B1: L-VERSES S-TECTONITE FABRIC VARIATIONS WITHIN THE SOUTHERN ADIRONDACK SHEAR ZONE SYSTEM: PROGRESSIVE DEFORMATION ASSOCIATED WITH A SINISTRAL CONJUGATE TO A GRENVILLE SYNTAXIS
D.W.Valentino, G.S.Solar, J.R.Chiarenzelli, A.E.Gates, P.Freyer, R.E.Price

STOP 1. Calc-silicate gneiss on the north side of the Snowy Mountain Dome (SMD).
Turn left into the overlook parking lot, and walk south on Rt. 30 approximately 0.2 miles to the first roadcut on the west (right) side of the road.
Calc-silicate gneiss with penetrative foliation and folds occurs in outcrops on the west side of Route 30. The foliation is defined by planar aggregates of recrystallized plagioclase, quartz and diopside (Figure 13). Locally the calc-silicate gneiss contains quartzofeldspathic layers that define isoclinal folds, and locally there are recrystallized masses of diopside (some 10 cm in diameter).
The dominant foliation in the outcrop in most places is structurally continuous with penetrative foliation (S2) in the Snowy Mountain dome, and dips moderately northward at this location. Portions of the exposure reveal an earlier foliation (S1) preserved mostly in the hinges of the isoclinal folds (F2) (Figure 13). The S1 foliation does not occur in the rocks of the Snowy Mountain suite, and the S2 foliation dies out away from the Snowy Mountain dome. In a relative sense, the S1 foliation either predates or is synchronous with the intrusion of the Snowy Mountain suite, and the S2 foliation is superimposed on the suite.
D.W.Valentino, G.S.Solar, J.R.Chiarenzelli, A.E.Gates, P.Freyer, R.E.Price

Roadcuts of charnockitic gneiss.
D.W.Valentino, G.S.Solar, J.R.Chiarenzelli, A.E.Gates, P.Freyer, R.E.Price

STOP 2: Charnockitic gneiss on the north side of the SMD.
Park on the right side of Rt. 30 and cross the road to the roadcut on the east (left) side (at the "Southwinds" sign).
The contact between the calc-silicate gneiss of STOP 1 and charnockitic gneiss of the Snowy Mountain suite occurs approximately 1 km northeast of this location, and is concordant with the S2 foliation. Here there is exposure of highly deformed charnockitic gneiss on both sides of the road. The foliation (S2) is defined by planar aggregates of dynamically recrystallized plagioclase and broken grains of hypersthene and augite. The foliation dips moderately northeastward and weak mineral lineations trend shallowly toward the east. Many of the outcrop surfaces reveal augen of plagioclase with core-mantle structure. Dynamically recrystallized tails developed on porphyroclasts of plagioclase merge with the penetrative foliation. The plagioclase augen are interpreted to be relict igneous crystals, possibly original megacrysts. When viewed on outcrop surfaces that are parallel to the lineation and perpendicular to the foliation, the augen appear to be asymmetric defining both σ- and β-porphyroclasts. Additionally, domino structures and Type I S-C fabrics can be viewed on some optimum surfaces. The kinematic indicators are consistent with top toward to the west ductile shearing, or low-angle sinistral considering the shallow plunge of the lineations.
Proceeding south across the Snowy Mountain dome, the penetrative foliation in the charnockitic gneiss progressively dips toward the east and then toward the southeast. There are numerous outcrops along Route 30 that can easily be viewed. Where the southeastern spur of Squaw Mountain intersects Route 30, there is exposure of gabbroic gneiss and megacrystic anorthosite. We will not be stopping at this outcrop during this trip due to time constraints. However, this is a good place to view the transitional compositions and deformation fabrics. The megacrystic anorthosite lacks penetrative deformation at this location, but some parts of the outcrop contain dynamically recrystallized anorthosite with well developed S2 foliation. The gabbroic gneiss contains penetrative foliation and well developed lineations at this location.
The transition from gabbroic- to charnockitic-gneiss occurs approximately 1000 meters northeast along the Squaw Mountain spur. This transition was documented by DeWaard and Romey (1969). Within the charnockitic gneiss branching high-strain zones can be seen (Figure 14). In places, the high-strain zones merge and have tapered terminations, and close inspection will reveal the penetrative foliation. Compositionally, the rocks in the high-strain zones are identical to the bounding charnockitic gneiss, except for the occurrence of minor quartz veins. The high-strain zones have the same general strike as the location foliation, but typically dip steeper northward in this area. Mineral lineations are better developed in the high-strain zones. Shear sense indicators are consistent with the shear sense indicators observed in the charnockitic gneiss with top toward the west ductile flow, or low-angle sinistral. The high-strain zones contain the same metamorphic minerals as the lower-strain charnockitic gneiss.

Roadcuts of metanorthosite.
Roadcuts of gabbroic metanorthosite and megacrystic metanorthosite.

STOP 3: "Underview" of the Snowy Mountain Dome
From this location, the entire structure of the Snowy Mountain dome can be viewed. Numerous slide faces expose the shallowly dipping foliation that occurs at the top of the dome (Figure 15). The exposures at the top of Snowy Mountain can be accessed by a popular hiking trail that occurs about 2 km north of this location. The top of Snowy Mountain is underlain by gabbroic gneiss with penetrative S2 foliation. The foliation dips shallowly toward the north and sub-horizontal mineral lineations trend nearly due east. A near vertical outcrop near the top of the mountain reveals abundant shear sense fabrics. Detailed kinematic analysis using porphyroclasts, S-C fabrics and shear bands resulted in dominant shear of top toward the west. However, some domains upward of a few meters thick showed conflicting shear sense of top toward the east. These exposures are the structurally highest part of the dome.

STOP 4: Charnockitic gneiss on the SE side of the Snowy Mountain Dome.
Turn right onto access road for campsites. Drive this road until just into the woods, and park in the wide flat area just before the bridge over Falls Brook. Walk across the bridge and past the metal gate, then plunge into the woods on the right of the access road about 10 meters to the outcrops in the brook that form the falls.
Stop 4 is of highly deformed charnockitic gneiss, the same lithology as Stop 2. However, the penetrative foliation dips moderately toward the southeast due to the position on the Snowy Mountain dome. At this location, and as before, the foliation (S2) is defined by planar aggregates of dynamically recrystallized plagioclase and broken grains of hypersthene and augite, and weak mineral lineations trend shallowly toward the east. Augen of plagioclase have dynamically recrystallized tails, often forming asymmetric kinematic indicators. As well, Type I S-C fabrics are well developed in some domains (Figure 16). Unlike Stop 2, the shear sense determined at this location is top toward the east. But, considering the dip is southerly, and mineral lineations trend easterly, the shear sense can be considered low-angle sinistral.

Jessup River

Roadcuts of quartzo-feldspathic gneiss with granite dikes
Roadcuts of quartzo-feldspathic gneiss with granite dikes on both sides of the road.

Calcite-garnet rock on right, rock painted as a pig on the left.
Roadcut of calcite-garnet rock on the right, with a rock painted as a pig on the left.

Roadcut of steeply-dipping dextrally sheared rocks on the right.

STOP 5A. Garnet amphibolite, calc-silicate rock and quartzo-feldspathic gneiss.
Here, these three rock types and their contacts are seen. The northern portion of the outcrop consists of garnet amphibolite, the next section of the outcrop is calc-silicate rock and the southern portion is fine-grained quartzofeldspathic gneiss. Complex sheath folds with sub-horizontal tight, isoclinal and sheath folds of foliation and compositional layers dominate the rock, particularly in the gneiss (trend to 110°) (Figure 17). Excellent views of the folds are seen on top of the southern part of the outcrop. The contacts between the rock types are also folded in similar fashion. Matrix minerals define lineations that are E-W and subhorizontal, but are variable in orientation due to folding.

STOP 5B. Garnet amphibolite and quartzo-feldspathic gneiss.
Park on the right, just after the guard rail, as you ascend the north slope of Burgess Hill (see location map). The outcrop is a roadcut on the east (opposite) side ofRt. 30 just north of the sign for Lake Pleasant.
Here the garnet amphibolite and garnet-bearing quartzo-feldspathic rock are in sheared contact. The amphibolite has a distinct foliation and lineation that is folded into shallowly inclined tight folds (N dipping axial planes) whose axes are shallowly E-W plunging. The lineation in the amphibolite is shallowly plunging to 112°. The fabric in the quartzo-feldspathic rock is distinct in contrast to the amphibolite, showing a penetrative L>>S tectonite fabric whose lineation plunges shallowly to 112°. The L>>S fabric is defined by both rods of quartz and quartz aggregates, and by tails around garnet. The highly fractured nature of the outcrop offers excellent views of this fabric. The contact between the rock types is distinct due to the color difference, but also because the amphibolite is boudinaged (foliation boudinage) due to apparent contact-parallel shear. The interboudin partitions are in-filled by plagioclase and amphibole (Figure 17).

Top of the hill (garnet amphibolite roadcuts on both sides).

STOP 5C: Overlook of Speculator Mountain, and the PLSZ.
Park on the right side of the road just south of the intersection, and walk to the top of the large roadcut for southerly views of Lake Pleasant and Speculator Mountain, and the PLSZ.
The rock here is sub-horizontally stratified, with the rock at the top of the hill to the north (garnet amphibolite) the lowest stratum, and the base of the outcrop is interlayered amphibolite and granitic gneiss, followed by granitic gneiss with mica 'mats' at the top (at the viewing area). Foliation is subhorizontal here, but, again, the mineral lineation is shallowly E- and W-plunging. The view to Speculator Mountain illustrates the structure of the late history of the PLSZ. The bench on the east side of the mountain is the top of the hanging wall block of a moderately W -dipping normal fault, and the peak of Speculator Mountain is the hanging wall block. This normal fault is defined by fabric with a distinct top-down fabric trajectory (see Figure 10), and defines the zone to be about 100 m thick. This is one of many normal shear zones that cut the E-W fabric that defines the PLSZ, but this one is perhaps the thickest. Most identified are a few centimeters thick (as in Figure 10).

STOP 6: L-S and L>S fabrics in the PLSZ.
The Piseco Lake shear zone is developed in rocks of granitic composition. Dynamically recrystallized feldspars and quartz form spectacular ribbon- and rod-shaped mineral lineations (McLelland, 1984), in addition to mafic phases such as biotite, chlorite and accessory magnetite. In many places, the alignment of ribbons forms the foliation in this outcrop (Figure 18). Individual quartz ribbons have aspect ratios upward of 60: 1. The foliation dips gently southward and the lineations trend about 110°(Figure 18). This location occurs on the southern flank of the map-scale antiform defined by the foliation in the Piseco Lake shear zone. At the western end of the outcrop there are rods of amphibolite (10-30 cm diameter) within the granitic gneiss. In the granitic gneiss, both biotite and chlorite blades form microscopic lineations and foliation parallel to the macroscopic structure. Rare grains of hypersthene have been found, but they always have well developed overgrowth textures that include biotite and chlorite. The biotite and chlorite are the most abundant index minerals in the granitic gneiss, and suggest the deformation was last active under low-grade metamorphic conditions, although probably began at much higher conditions to account for the relict grains of hypersthene.

TOP 7: Shear fabrics of the southern PLSZ.
Park as far off the road as possible. The outcrop for Stop 7 is pavement exposures located within the bed and the gutter on the east side of the road.
This stop consists of a sub-continuous series of pavement exposures located in the road bed, and in the gutter on the east (northeast-bound) side of the road. Due to the nature of this location, the extent of the exposed rock at this stop changes daily, so some or all of the rock described here may be viewable depending upon the time of the season in which the stop is visited (best later in the season).
Here, quartzo-feldspathic gneiss has intense shallowly WSW-plunging lineation and steeply S dipping foliation, both defined by ribbons (generally 1-5 cm long depending upon grain size). Locally, the gneiss has layers (up to 50 cm wide) of coarser-grained fabrics (grains up to 1 cm in diameter). Within the gneiss is lens- to block-shaped, and blunt-ended amphibolite bodies, also with a distinct mineral fabric that is sub-parallel to that of the gneiss. In general, the long dimension of lens-shaped amphibolite bodies are sub-parallel to the host gneiss fabric. The lengths of these bodies are not quantified due to the fact that the outcrop is composed of meter-scale windows through road gravel, but short dimensions are usually exposed showing bodies 10 to 30 cm wide. Fabric in the amphibolite is generally terminated at the boundary of the body, whereas the fabric in the quartzo-feldspathic gneiss drape the amphibolite bodies, showing fabric tails at the blunt ends of the bodies, sub-parallel to the mineral lineation (as porphyroclasts draped by matrix minerals; Figure 19).

STOP 8: Variations of L-S, L>S and L»S fabrics of the PLSZ.
Park along the side of the road in "the notch" between East and West Notch Mountains (see location map). The notch is Stop 8, featuring 0.2 miles of continuous exposure on both sides of Powley Road. The exposure on the northwest side (left) is the subject of the stop.
Due to the continuous nature of the exposure in an across-strike direction, the fabrics within the quartzo-feldspathic gneiss may be examined for their variations at about the meter scale. In general, the rock fabrics vary between L-S to L»S tectonite. Foliation intensity is variable, but mostly weak here. Foliation dip varies greatly across strike (moderately to steeply south-dipping), whereas the intensity and orientation of the lineation is consistently sub-horizontally E- and ESE-plunging. Of particular note in this outcrop, in addition to the matrix fabrics, is the pervasive feldspar porphyroclasts. Fabrics drape the porphyroclasts to form tails that are elongate sub-parallel to the matrix mineral lineation (sub-horizontal). Perhaps the cleanest views of the fabrics along the lineation may be seen at the very end (northeast end) of the exposure. We suggest that it is best to leave this spot for last in order to best appreciate the nature of the fabric in these rocks.

STOP 9: Fabric variations in gneiss in the PLSZ
Park along the side of the road avoiding the blind curve. The outcrops for Stop 9 are along the side and gutter of the northwest side of the road just before and at the left-hand curve in the road.
Fabric variations in garnet-bearing quartzo-feldspathic gneiss in the PLSZ. Here the quartzo-feldspathic gneiss fabrics vary from LS to L»S tectonite, whose lineation is shallowly E- to ESE-plunging, and the relatively weak foliation is moderately to steeply S-dipping. Feldspar porphyroclasts are present as at Stop 8. The southwest end of the exposure shows a high density of garnet porphyroclasts within foliation. Locally, garnet is concentrated into 2-3 cm-wide bladed bands, or is apparently flattened. Also locally, garnet occurs in patches or 'clots' 3-5 cm wide and up to 20 cm long.

STOP 10: Mylonitic augen gneiss of the PLSZ.
Park on the side of the road for a set of small low pavement exposures on the left (northwest) side of the road as the top of the hill is approached.
Best views of the fabrics in the quartzo-feldspathic gneiss are seen in the approximately 1.5 meter-long, beautifully polished pavement at the top of the hill. Here the rock has meter-scale mineralogical layers where the northern part is relatively more leucocratic, dominated by feldspar (up to 1 cm wide) and quartz ribbons (up to 3 mm wide). The fabric is intensely strong L-S tectonite throughout the exposure, with a steeply S-dipping foliation, and a sub-horizontal shallowly E-plunging lineation. The fabric may be considered 'textbook' mylonite, with spectacularly grain-size reduced texture in the less leucocratic layer. The mylonitic fabric transects the sharp contact between mineralogical layers at a low angle where it transitions into a more ribbon texture in the leucocratic layer. Of particular note here, besides the intense matrix fabrics, is the penetrative augen (generally 1 to 4 cm long) composed exclusively of aggregates of millimeter-grain-size quartz + feldspar, not single crystals. In every case, augen are draped by the matrix fabric, elongate sub-parallel to the lineation. There are a few much larger of these augen in this rock composed of rounded single feldspar crystals (up to 4 cm long) that are surrounded by aggregate quartz and feldspar (Figure 20).

STOP 11. Ultramylonite of the PLSZ.
Park on the side of the road to view the two small pavement exposures in the bed of the road for Stop 11.
These outcrops are very small (about 1 m or so long each) and isolated, so whether or not these rocks are viewable depends upon many factors including whether or not the road has been re-graded recently. As with STOP 7, the exposure of these rocks is better later in the season. The quartzo-feldspathic gneiss here shows spectacular mylonitic fabrics, as at Stop 10, where foliation and lineation are penetratively parallel across the small exposures (E-W fabrics with steep south dips and sub-horizontal E-plunges). Centimeter-scale textural layers are the highlight of this exposure where 1 to 5 cm wide bands of quartz + feldspar aggregate. Relatively thin layers of these aggregates are seen 'pinched and swelled' lenses. Individual augen of the aggregate are in the less leucocratic layers. We envision these textural variations to illustrate a progression of mylonitization where larger bands progressively become augen. Further, we suggest that the augen are seen kinematically combined, and as they interfered, they may form new aggregate bands. In a manner of speaking, one could say that the fabrics in this rock are snapshots of the progression, and that this rock is mylonite that has been multiply reworked as deformation continued.

STOP 12: L-S tectonite of the PLSZ.
Park on the right side of the road for the road cuts just over the top of the hill.
The quartzo-feldspathic gneiss here is spectacular L-S tectonite, whose foliation is moderately SSW-dipping, and whose lineation is shallowly W-plunging. As at Stop 10, augens are aggregates of fine-grained feldspar + quartz, and some here have asymmetric delta tails that show sinistral offset (see Figure 9B). Pavement outcrop at the top of the western roadcut show excellent three-dimensional views of the fabric.

STOP 13A: East of the gorge.
Turn left onto Gray Wilmurt Road just after a sharp right-hand curve in Rt. 8. Cross a bridge over the West Canada Creek and park at the intersection with Jones Road. Walk back toward the bridge over West Canada Creek and down the hill to the outcrop just east (upstream) of the bridge (see location map). The outcrop forms a small water fall on the creek.
The Piseco Lake shear zone traces westward through the West Canada Creek basin. Some of the best continuous exposures occur in the Ohio Gorge near Wulmurt. The last stops for this field trip are in highly deformed granitic gneiss in the gorge. During periods of high water, the exposures at the eastern and western end of the gorge may be covered or not easily accessed. Permission is needed from the landowner at Stop 13A.
The West Canada Creek forms a small waterfall at the upstream part of this outcrop. Pavement exposures reveal the L-S and LS deformation fabric in granitic gneiss (Figure 21). Foliation is gently dipping and the lineations are subhorizontal. In the region immediately down-stream of the falls, the foliation is defined by planar aggregates of recrystallized K-feldspar and quartz that alternate with dark layers containing abundant chlorite and minor biotite. The dominant fabrics are cross cut by at least three small high-strain zones. Two are steeply dipping and strike about east-west, and the third strikes south and dips moderately westward. One of the steeply dipping high-strain zones occurs in the vertical face at the southern side of the outcrop. Another occurs at the western limit of the outcrop close to the water. The north-south striking zone occurs in the low ledge near the falls. This small shear zone contains deformed pegmatite, and cross cuts the PLSZ foliation and lineation (Figure 10). Shear sense is top down to the west or normal. The other high strain zones both contain evidence for oblique sinistral shear.

STOP 13B: Western limit of the outcrop belt in the Ohio Gorge.
Park on the right shoulder just after a steep downhill drive. Walk upstream along West Canada Creek to the first bedrock exposures for the westernmost outcrops in the Ohio Gorge, and Stop 13B.
At this location the north dipping foliation of the Piseco antiform can be viewed in addition to the typical variation in L-S and LS fabrics at the outcrop scale. Again, the foliation is defined by planar aggregates of dynamically recrystallized feldspars and quartz. Quartz also occurs in greatly attenuated ribbons, as seen at other locations during this field trip. Of particular interest at this location, are abundant kinematic indicators that are easily observed. Outcrop surfaces that are perpendicular to the foliation and parallel to the lineation reveal asymmetric augen of K-feldspar and plagioclase forming both σ- and β-type shear sense indicators with most showing top toward the west displacement (Figure 9A). Since the mineral lineations are subhorizontal, the shear sense is considered to be low-angle sinistral at this location. The abundant large (cm-size) porphyroclasts of feldspar provide some information about the protolith for the PLSZ rocks in this region. The relict grains are most likely the remains of megacrysts from an original granite.

B2: METAMORPHIC PETROGRAPHY BETWEEN TUPPER LAKE AND BLUE MOUNTAIN LAKE
Robert Badger and James Carl
Department of Geology, SUNY Potsdam
Potsdam, NY 13676
badgerrl@potsdam.edu
This trip examines the petrography and petrology of roadside outcrops along Route 30 between Tupper Lake and Blue Mountain Lake. As with most Adirondack rocks, these have been intensely metamorphosed. Lost during the metamorphism are the features which distinguish sedimentary rocks from extrusive and intrusive igneous rocks. Their intrusive igneous textures and/or content of fossils, clay minerals, layers of volcanic lava and ash, have long since been transformed. We will visit outcrops of marble and quartzite that clearly represent metamorphosed limestone and sandstone, and amphibolites that most likely were basaltic dikes. Most rocks, however, are gneisses with varying proportions of feldspars, quartz, amphibole, pyroxene and garnet. Without geochemical analysis, it is sometimes difficult to determine if their protolith was an igneous or sedimentary rock. We draw your attention to features at the outcrop that support our interpretations; color microphotographs will be provided at most stops. We anticipate lively discussion of interpretations about the outcrops.
Our understanding of the geologic history of the Adirondacks is an ever-evolving project that involves the work of hundreds of researchers. We offer a brief summary, and refer you to more detailed studies by Isachsen et al. (1991), Chiarenzelli and McLelland (1991), McLelland et al. (1996), Hamilton et al. (2004), and the summary by Kirchgasser in this volume (Trip B-3). The oldest rocks in the Adirondacks are 1.2 to 1.3 billion year old metasedimentary rocks that include marbles and gneisses seen on this trip. Included are gneisses that carry a geochemical signature of island-arc complexes, suggesting that northern New York consisted of a marine environment fed with materials from a nearby island arc. These rocks were metamorphosed during the Elzevirian Orogeny about 1210 to 1160 million years ago (Hamilton et al., 2004). Intruded into this sequence were the anorthosites, mangerites, charnockites and granites comprising the AMCG suite of McLelland et al. (1996). The ages of many of these plutonic rocks cluster around 1155 million years; the rocks at stop 1 are younger. A second orogenic event, the Ottawan, occurred between 1090 and 1030 million years ago (Hamilton et al., 2004). It was associated with the supercontinent of Rodinia and the formation of the Grenville Mountain range, whose heights were similar in magnitude to the present-day Himalayas. By the time Rodinia broke up, between 600 and 550 million years ago, the Grenville Mountains had been eroded to a gently rolling landscape, not unlike the present-day Adirondack lowlands, except barren of vegetation. Detailed apatite fission track thermochronology by Mary Roden-Tice (Roden-Tice et al., 2000) at SUNY Plattsburgh indicates that uplift and unroofing of the central Adirondacks began during the late Jurassic.

B2: METAMORPHIC PETROGRAPHY BETWEEN TUPPER LAKE AND BLUE MOUNTAIN LAKE

Meeting Spot. Public boat launch
The boat launch, with restrooms, was renovated in 2002 with $610,000 provided by the Department of Environmental Conservation and the Environmental Protection Fund. Access to the lake is considered essential to the region's enjoyment and economy, and the launch is a very busy place in summer.

STOP 1. Metamorphosed, fractured and mineralized meta-syenite.
A long roadcut of reddish-colored rock on the right (west) side of Route 30. This outcrop was the focus of a senior research project by SUNY Potsdam student Scott McDonald, whose data are presented here.
Meta-syenite
This dark reddish-brown stained rock contains abundant red to tan K-feldspar, albite, and quartz (Fig. 1-1). The dark minerals are hornblende, but locally have been altered to chlorite. The K-feldspar shows marvelous perthitic textures. The minerals display pronounced parallel alignment. We believe the protolith was an igneous syenite and classify the rock as a meta-syenite or hornblende-alkali feldspar gneiss.
Microprobe data for albite are listed in Appendix 1, for potassium feldspar in Appendix 2, and for calcite and chlorite in Appendix 3. Data was obtained on the microprobe at SUNY Binghamton, with the help of probe guru Bill Blackburn. The data show that the plagioclase was almost completely altered to albite during metamorphism, and that the potassium feldspar contains very little sodium.
The rock probably was coarse grained to begin with. What once were randomly oriented, tabular crystals of alkali feldspar were later transformed by shearing into small, parallel-aligned grains. Some chunky feldspar crystals were deformed into lens-shaped grains or augen, (German for "eye"). On the east side of the road, the gneiss is brown and finer grained, but it grades into reddish meta-syenite and probably is the same rock. Zircon crystals, ZrSiO4, were separated from similar rock at a nearby outcrop. They have a uranium-lead age of 1098±4 million years, which is the age of crystallization of the syenite magma (McLelland et al., 1988, p. 921, their rock sample #10). The meta-syenite is typical of younger granitic rocks of the Adirondack Highlands which have not been studied in detail.
Joint planes and rockfalls
This outcrop has many prominent joint planes. Note the geometric shapes of the large blocks at the south end on the west side. Produced by breakage along sets of intersecting joints, they resemble children's play blocks perched precariously on edge (Fig. 1-2). A small rockfall occurred by breakage along joints on the east side of the road (Fig. 1-3). In July, 2000, crushed green plants beneath the rubble indicated that the fall had occurred a few days prior to our visit.
Mineral deposition in breccia zones
Pace off about one hundred feet from the north end of the outcrop, west side, and locate the zones of crushed, broken and angular rock fragments (Fig. 1-4). The breccia formed long after cooling of syenite magma and long after the period of Adirondack metamorphism, perhaps during uplift of the Adirondack dome.The breccia zones are shown by the presence of irregular patches and stringers of low magnesium, Mn-bearing calcite, CaCO3 (see microprobe data in Appendix 3).
The calcite was deposited as cement in open spaces in the breccia. However, the calcite hides a sprinkling of tiny, brassy-yellow crystals of pyrite (FeS2). The crystals occur as a coating on brecciated meta-syenite rock fragments (Fig. 1-5). Magnified under a hand lens, the pyrite consists of millimeter-sized crystals of two types: (1) cubes with six square-shaped sides, and (2) pentagonal dodecahedrons, a geometric form consisting of twelve faces, each with the five sides of a pentagon.
The calcite could have originated in one of two ways. It could have precipitated from fluids that dissolved minerals from overlying rocks, or, less likely, it could be igneous calcite (carbonatite) with CO2 derived by mantle degassing. To test these hypotheses, a sample of the calcite was sent to Steve Howe, stable isotope magician at the mass spectrometer lab at SUNY Albany. His analysis shows a delta 18O value of-14.927 per mil (compared to PDB) or +15.474 per mil (compared to SMOW), and a delta 13C value of -4.303 per mil (compared to PDB). These stable isotope numbers indicate a meteoric origin of the water and a bedrock source for the carbonate (Steve Howe, personal communication).
The carbon and oxygen isotope data therefore indicate that the calcite came from the dissolution of overlying layers of marble, the dominant carbonate rock in the Adirondacks. Calcite was dissolved in water to produce ions of calcium (Ca+2), bicarbonate (HCO3-1), carbonate (CO3-2) and molecules of carbonic acid (H2CO3). The ions and molecules were transported downward by groundwater, perhaps traveling a considerable distance before crystallizing as calcite in the breccia. The marble source of these components, probably hundreds to perhaps thousands of feet above your head, was long ago removed by erosion.
The sulphur-bearing mineral, pyrite, is virtually insoluble in oxygenated groundwater. Reducing conditions are required for transport and deposition of iron sulfide. Such groundwater is generally deep-seated, oxygen-depleted and full of dissolved material. The point being made is that the kind of groundwater required to transport calcite is incompatible with water that transported the iron and sulphur. Separate solutions from different sources must have formed the minerals, the pyrite was first and the calcite later on.

STOP 2. Calc-silicate metasediments
Park in the large, paved pullover on the right (west) side of Route 30. We are located on South Bay at the south end of Tupper Lake. Examine the roadcut opposite the middle of the parking area (Fig. 2-1). This outcrop was discussed by Jim McLelland in the 1992 NYSGA Guidebook.
We have left metamorphosed igneous rocks and entered a domain of metamorphosed sedimentary rocks. This outcrop is a slice through the steep west side of a bedrock hill, and the steeply inclined rocks include pale green gneisses with abundant diopside, CaMgSi2O6 (Fig. 2-2). These metasediments must be older than the meta-syenite and other igneous rocks that intruded them.
The mineral assemblage of diopside, quartz, K-feldspar, plagioclase feldspar and sphene formed during the metamorphism of impure limestone. A chemical reaction occurred among minerals that commonly occur in limestone--calcite, CaCO3, dolomite, CaMg(CO3)2, and the so-called impurity - a little quartz sand, SiO2. Note that the formula of diopside, CaMgSi2O6, contains elements derived from each of them.
A difficulty with the presence of diopside at this outcrop is the scarcity of carbonate minerals, calcite and dolomite, that were needed to make it. Note the presence of light colored seams and veins that help to define the gneissic banding. At first glance, they might be mistaken for calcite, but the minerals do not fizzle in acid and cannot be scratched with a knife. The light-colored mineral is potassium feldspar, not calcite. We suspect that calcite and dolomite of the impure limestone protolith were completely used up in metamorphic reactions to produce diopside.
Before leaving, examine the outcrop from a distance and note the color change where green, diopside-bearing gneiss gives way to gray hornblende-biotite-feldspar gneiss as you look from right (south) to left (north). The gray gneiss was interpreted by McLelland (1992, p. 40-41) as an igneous intrusive rock, even though its contact with the diopside-bearing gneiss appears gradational over a distance of a few feet. McLelland's interpretation is that this is a highly sheared contact between two very different rock types, one igneous and one sedimentary. Another interpretation is that both are sedimentary and that the gray gneiss represents a facies change in the original sedimentary protolith, an impure limestone, to perhaps to a shale or mudstone that was metamorphosed to a hornblende-biotite gneiss. A few tens of feet north of the contact between diopside gneiss and the gray hornblende gneiss is another much smaller zone of diopside gneiss, interpreted as either a sheared fragment of the diopsidic gneiss or another facies change. You may form your own opinion.

The William C. Whitney Wilderness Area
Called the "most significant Forest Preserve acquisition in twenty five years," the estate of Mary Lou Whitney was purchased by the State of New York in December, 1997. The purchase consisted of 14,700 acres surrounding Little Tupper Lake, once the largest privately owned lake in the northeast. The eight mile-long lake is relatively shallow (less than twenty five feet deep), drains into the Bog River and is home to a native strain of fish called the Little Tupper brook trout. Canoeists were pleased with a land purchase that connected major canoe routes throughout a vast region of wetlands, lakes, bogs and cut-over timberland. In March, 2000, the area was classified as wilderness.
The road leads to an eighty acre site on the lake's north shore, once used as the headquarters for Whitney Industries. Now classified for "administrative use," the site includes a ranger station in a grove of tall pine trees, a parking area and a canoe launch. The lake has become one of the most widely used, flat water canoe routes in the East, and several tens of primitive camping sites have been constructed around its perimeter.

STOP 3. Marble and other metasediments
Drive beyond the outcrop and park beyond the guard rail at the south end. Walk north and examine three outcrops on the west side. These outcrops were studied by SUNY Potsdam student Aaron Fiaschetti for his senior research.
Here's a good example of diopside-bearing marble, an easily recognized metamorphic rock that once was a limestone (Fig. 3-1). The marble lies between gneissic layers of debatable origin. Separated by intervals of soil, the three parts of the outcrop include (1) garnetiferous biotite gneiss with quartzite layers at the south end, (2) marble outcrops in the middle, and (3) garnet-bearing gneiss at the north end.
South outcrop
The dark gneiss contains alkali feldspar, quartz, hornblende, seams of biotite and locally garnet (Fig. 3-2). The mica seams are close together and locally give the gneiss a schistose appearance. Some of the biotite appears to have been altered to bronze colored phlogopite. Non-geologists have misidentified such grains as flakes of gold. Thin layers of quartzite that broke away from weathered mica seams give the rock a slab-like appearance. The hornblende gneiss contains pods of quartz with small grains of garnet (Fig. 3-3) whose lavender color indicates a small spessartine (i.e. manganese, Mn) component.
Middle outcrop
The white marble and calc-silicate rock are easily recognized in the center outcrop (and across the road) (Fig. 3-1). They consist of coarse calcite grains that were recrystallized from limestone during metamorphism. Most likely, the marble is much lighter in color than the original limestone. Finely dispersed coloring agents such as organic matter, clay minerals and iron oxides, were either expelled from the limestone or incorporated into the crystal structure of another mineral during metamorphism.
Glassy grains of green diopside are present, but there are fewer of them than at Stop 2. Also present are muscovite, brown sphene, shiny black flakes of graphite (pure carbon), tiny grains of pyrite, smoky to clear grains of quartz, and light colored seams of chunky alkali feldspar that, at first glance, can be mistaken for calcite. Look for veins of milky quartz. The graphite is probably the recrystallized remains of primitive algae that once lived in the warm marine environment in which the original limestone was deposited. A breccia zone at the south end of the outcrop may have formed at the same time as the breccia zone at stop 1.
North outcrop
This hornblende-biotite-garnet gneiss has more hornblende and less biotite than gneiss at the south outcrop. There are layers and lenses of pink alkali feldspar, as well as quartz veins that parallel the gneissic layering. Some layers were deformed into ragged and elongate stringers, whereas others were pulled apart into sausage-like boudins. Garnets in the boudins are iron-rich and reddish in color.
Layers of quartzite in the south outcrop and the proximity of the intervening marble lead us to interpret the gneisses at both ends of this outcrop as shales or mudstones prior to deep burial and metamorphism. There's a certain chemical "richness" to shale, thanks to the presence of sheet-structured clay minerals such as illite, chlorite, kaolinite and montmorillonite. They became unstable and decomposed during high temperature metamorphism, and their elements were re-combined to form a variety of high-grade metamorphic minerals. Imagine the conversion of compact and drab mud into an attractive crystalline aggregate of garnet, hornblende, biotite mica and feldspars (Fig. 3-3). Hence, the well known saying, "There's nothing wrong with a sedimentary rock that 10 kilobars can't cure."

STOP 4. Multiple igneous intrusive rocks?
Park beyond the guard rail and examine the rocks on the opposite (east) side of the road.
Description
This outcrop contains a variety of metamorphic rock types, from pink, garnetiferous gneiss to gray garnet-poor gneiss to pegmatite with coarse, black hornblende crystals. Clearly, multiple protoliths are called for.
The massive, pink and gray gneisses that predominate at the south end of the outcrop (Fig. 4-1) contain abundant quartz and potassium feldspar with lesser amounts of plagioclase feldspar, biotite and a few small garnets scattered here and there. In thin section, the potassium feldspar contains a wide range of excellent examples of perthitic textures, which clearly suggest an igneous origin. The rock has a fairly uniform grain size. It lacks the pronounced banding and segregation of minerals that we observed at Stop 3. It also lacks dark colored minerals, but chemical reactions that produced the garnet may have used them up. Most likely this rock was originally a granite.
Present in the light colored granitic gneiss is a distinctive 10-15 inch wide layer of amphibolite (Fig. 4-1), composed predominantly of black hornblende and plagioclase feldspar. This rock probably was a basaltic dike that intruded the granite prior to metamorphism.
The mafic content of the gneiss increases towards the north end of the outcrop, and the rock becomes an orthopyroxene-bearing granitic gneiss, or "charnockite" (see discussion of charnockites at Stop 9). Much of the opx has been altered to chlorite and other alteration minerals, but the persistence of relict cleavage indicates that the mafic grains were originally pyroxenes. Other portions of the rock contain significant amounts of hornblende. Again, an igneous protolith is called for, but the high mafic content suggests this intrusive rock unit differs from the mafic-poor granite gneiss at the south end of the outcrop.
A coarse grained pegmatite occurs near the north end of the outcrop (Fig. 4-2). It contains coarse grains of potassium and plagioclase feldspar, hornblende and two varieties of pyroxene-one a pale green with second order interference colors of clinopyroxene, the other a pale pink with first order interference colors of orthopyroxene. The opx shows more alteration than cpx, which is typical in Adirondacks rocks with co-existing pyroxenes. Apatite is also a significant component. The coarse minerals are randomly oriented as though crystallized from a silicate melt in the presence of a watery fluid. The pegmatite appears to be a late igneous intrusion that post-dates metamorphism. Or, given the compositional similarity to the surrounding rock, it could be recrystallized gneiss in the presence of hot, watery fluids of late stage metamorphism.

STOP 5. The granite quarry outcrop.
Park at the south end of this long roadcut, beyond the guard rail, and examine the outcrop on the right (west) side (Fig. 5-1).
Quarries
No, they don't quarry the granite for building stone here. In a sense, however, all road cuts are quarries because rock was removed to make room for the roadbed. The Department of Transportation blasted through the massive rock, and much breakage occurred along the natural fractures (joints). Breakage along prominent near-horizontal sheeting joints has provided some flat and narrow surfaces that resemble crude stair steps in the face of the outcrop, similar to the working face of an active stone quarry.
Metamorphosed granite
The finely foliated meta-granite or alkali feldspar-quartz-hornblende gneiss, has small grains of dark hornblende aligned as parallel stringers (Fig. 5-2). Some of the hornblende has altered to chlorite, but most is intact. A little plagioclase feldspar is present, along with apatite and a few grains of zircon. Cutting diagonally across the outcrop is a dark amphibolite layer (Fig. 5-1) that once was a tabular dike of basalt that intruded the granite. A small fault extends from the granite into the dike about midway up. See if you can find it. The top part of the dike was displaced a few inches to the right of the bottom part. Also note whether the dike lies parallel to, or cuts across the gneissic layering in meta-granite.
Small faults in meta-granite are often coated with fault gouge. Slickenlines in the gouge indicate the direction of fault movement (Fig. 5-3). The fractures are coated with green hydrous alteration minerals, probably chlorite and serpentine.

STOP 6. The marble cake outcrop (that isn't marble).
Evidence for igneous intrusive origin.
Examine the outcrop on the left (east) side of Route 30. The rock is cream and black mottled gneiss that reminds us of a marble cake. The light portions are composed primarily of plagioclase (An36, optically determined) and alkali feldspar, with very little quartz, while the dark zones are predominantly composed of clumps of hornblende and diopside, with minor garnet, magnetite and scattered apatite. At the south end of the outcrop and on the west side of the road is a different type of rock. Thus, our "marble cake" rock may be of small volume and confined to this outcrop, but we think it is the most unusual rock on this field trip.
To make a marble cake, one takes a yellow cake batter and divides it into two parts. Chocolate is added and thoroughly blended in one part. Spoonfuls of the chocolate batter are then dropped into the remaining yellow batter, and a spatula is used to swirl the blobs about. This outcrop is the result. Or so it seems. The dark, steeply inclined layers contain abundant hornblende and pyroxene (Fig. 6-1). The "free form" pattern of layers, ribbons, loops and swirls, however, was not produced by stirring. The pattern results from the intersection of the viewing surface with the plane of gneissic banding, whether parallel to it, perpendicular, or somewhere in between. Marble cakes and rocks that resemble them have beautifully convolute patterns, but the anticipation of eating is absent here.
An early effect of metamorphism was to segregate a coarse-grained igneous rock into light and dark layers. The rock then became "mobile" and began to flow. Some of the dark layers behaved rather stiffly. They were ruptured and shredded while the light-colored, feldspar-rich layers flowed plastically around them (Fig. 6-2).
Evidence that the swirled gneiss was an igneous rock includes a large fragment of diopside-bearing marble in the gneiss (Fig. 6-3). The fragment is a xenolith whose presence is a powerful argument that the gneiss was once magma and that the fragment was caught up in it. Another xenolith is composed of green diopside and red garnet (Fig. 6-4). Note that the gneissic layering is deflected around it. The swirled gneiss also contains large feldspar crystals up to eight inches across (Fig. 6-5). Minerals of that size generally have crystallized from low viscosity silicate melts, often in the presence of watery fluid. The question is how such large crystals survived the metamorphism, especially the shearing that produced the gneissic banding.
Our explanation is not very profound. A wide range in grain size is expected if the shearing had been a hit and miss operation. Some parts of the rock were reduced in grain size, whereas other parts were left undisturbed. Primary igneous textures are preserved elsewhere in the Adirondacks, including anorthosite outcrops near Saranac Lake which contain single plagioclase feldspar grains more than 12 inches long.
We note that angular fragments make up a breccia zone parallel to the gneissic banding (Fig. 6-6). This post-metamorphic breccia zone may be synchronous with the one seen at Stop 1.
A change in rock type occurs at the south end of the outcrop. The banded rock gives way to a pinkish and green, faintly foliated gneiss whose minerals include pink alkali feldspar, quartz, biotite, a little hornblende, and locally significant amounts of red brown garnet (Fig. 6-7).

STOP 7. Layered "gray gneiss," a common metamorphic rock.
Examine the left (east) side of the road.
Welcome to the "gray gneisses," a common and widespread rock type in Precambrian age rocks throughout the eastern United States and Canada. This medium grained example has fewer surprises than the last outcrop. It, too, contains plagioclase and alkali feldspar, hornblende, pyroxene, garnet, quartz and a little biotite mica. The gneissic banding consists of stringers and seams of cream-colored alkali feldspar. Some bands are convoluted and pinch out, and all are vertical or steeply inclined (Fig. 7-1). The gneiss is peppered with garnets, and the large ones are prominently displayed in the light colored seams. The rocks at this outcrop lack the large feldspar crystals and marble xenoliths seen at the previous stop and may not be intrusive in origin.
This gray gneiss may have been volcanic ash, an extrusive igneous rock. Similar-looking rock underlies a belt more than seventy miles across in the Adirondack Lowlands to the northwest. Published geological studies suggested that the original rock was sedimentary in origin, a shale or an arkose, but the chemical data were a good match for dacite volcanic rocks (Carl, 1988). We have not analyzed the rock at this outcrop but it, too, could represent a thick pile of volcanic ash.
Note the presence of a fifteen inch-thick pegmatite vein that cuts across the gneiss (Fig. 7-2). It consists of smoky quartz and coarse, chunky grains of alkali feldspar, cream to gray in color. The vein also contains dark and tabular hornblende crystals about three quarters of an inch wide and up to four inches long (Fig. 7-3). The crystals are randomly oriented as expected from growth within a low viscosity, water-bearing silicate magma. Such magma would promote the growth of large crystals, as well as the crystallization of the hydrous minerals hornblende and biotite observed along the vein margins.

Bridge, beach and floatplane dock at Long Lake

STOP 8. Buttermilk Falls on the Raquette River.
Park near a small sign on the right (north) side of North Point Road. Walk the short distance to the waterfall. We are located upstream less than a mile from Long Lake.
This relatively steep stretch of the Raquette River lies east of Forked Lake and southwest of Long Lake. The river drops 116 feet in five miles, and Buttermilk Falls is the third of three canoe carries from Forked Lake. Rapids here extend for about one hundred yards before ending in a waterfall, and the total drop in elevation is about forty feet.
The bedrock at the falls is a highly weathered, dark brown, metamorphosed granite. One can see pods and veins of milky quartz that crop out near the shore. The bedrock is covered with pine needles and shallow soil. Trees are shallow-rooted and unstable in high winds.
Unless many rock hammers improve the quality of fresh outcrop exposures, this is a structure stop, and the petrography of the rock is best examined at Stop 9. Two prominent directions of jointing are present here (Fig. 8-1), with one extending across the river. The joint planes had little influence in creating the stream channel, in contrast to joints that lie parallel to stream courses. But "cross joints" like these are partly responsible for the presence of rapids. Blocks were removed from the downstream side of a joint, resulting in stair steps that decline in the downstream direction. The river spills over them. People who sit in spaces where the blocks once sat will either enjoy a shower or a bouncing ride downstream (Fig. 8-2).
The same joint spacing, often outlined by pine needles caught in the grooves, can be observed in the bedrock surrounding the falls. The origin of jointing is unclear. Is it due to isostatic rebound following glacial retreat? Or is it much older, related to uplift of the Adirondacks and erosion of the overlying bedrock? Or is it older still, caused by tectonic forces shortly after metamorphism?
The falls and spray sparkle in the sunlight, and our geology field trips get bogged down when the college students disperse among the rocks. They sit at the falls and perch with the demeanor of poised herons, legs crossed, patiently waiting for a stray fish. They relax, get wet and cannot hear their professor's voice over the roar of the falls. If the timing is right, this is a good place for lunch.

STOP 9. Dark brown meta-granite with pegmatite.
Park on the shoulder of Route 30, before the curve and near the center of a long outcrop on the right side.
The dark brown colored meta-granite (Fig. 9-1) is similar to the bedrock at Buttermilk Falls. This type of rock was quarried and used as a building stone in handsome but very dark-walled churches in Saranac Lake, Lake Placid, Tupper Lake and elsewhere. The major minerals are alkali feldspar, hornblende and orthopyroxene with lesser amounts of quartz, plagioclase feldspar, clinopyroxene, garnet, magnetite and apatite. Gneissic banding is faint, steeply inclined and hard to see when the outcrop is wet.
The presence of pyroxene is unusual for granite, and geologists have a special name for orthopyroxene-bearing granite: charnockite. The name honors Job Charnock, the founder of Calcutta, India, who died in 1693. Charnock was not a geologist and may not have appreciated this particular rock, but his memory is preserved among geologists because the first described example of charnockite was his tombstone.
Charnockites are igneous rocks that were subjected to high grade metamorphism. The presence of hypersthene pyroxene, (Mg,Fe)SiO3, raises a question. Did the mineral crystallize in the magma and, therefore, is of igneous origin? Or did it form much later during metamorphism when water-bearing silicate minerals, such as biotite and hornblende, dehydrated and converted into hypersthene? If so, hypersthene would be a metamorphic mineral. Adirondack charnockites are widespread igneous rocks that make up the "C" part of the AMCG suite of intrusive rocks.
Look closely along the outcrop, before the right bend in the road, for a pegmatite vein consisting of quartz and alkali feldspar (Fig. 9-1). Also of interest are mottled patches of light colored, slightly coarser grained rock that lack hypersthene (Fig. 9-2). The patches are best seen on dry surfaces around the bend towards the south end of the outcrop. The pegmatite and mottled patches are generally interpreted as having formed by partial melting of the charnockite.
During metamorphism, the temperatures were hot enough to melt some of the biotite, hornblende, quartz and feldspar. Most likely, the break-down of biotite and hornblende supplied enough water to lower the melting temperatures of the other minerals. Where appreciable quantities formed, the melt migrated into fractures to form pegmatite veins, like the one seen here, that may have migrated several tens or even hundreds of feet. The patches, on the other hand, appear to be small quantities of melt that did not migrate very far. The patches are sometimes called "sweats," a reminder of efforts by the human body to cool itself. The sweats at this outcrop solidified near where they formed.

Adirondack Museum at Blue Mountain Lake
The Museum honors the people of the Adirondacks. There are exhibits about the lives of Native Americans, early settlers, wealthy tourists who joined them in summertime, the unique architecture of Adirondack camps, and the intricate transportation networks that brought people into the woods. One learns about farmers, hunters, miners, loggers, guides, artists, writers, furniture makers and, most of all, tourists like you, drawn here for more than 150 years by the natural beauty of the mountains, lakes and forests.
The museum itself is a mountainside courtyard of large and small buildings, some serving to house a collection of artifacts, and others to illustrate a distinctive style of Adirondack architecture. All are clustered on a mountain side, the site of a former hotel and resort. The center of the grounds is a courtyard with an artificial pond and the steam engine from the Marion River Railroad. People climb on the engine, sit on Adirondack chairs, and leisurely stroll about, enjoying a spectacular view of mountains that overlook Blue Mountain Lake. The lake and its inflowing streams are the source of the Raquette River that we encountered at Tupper Lake, Long Lake and Buttermilk Falls.
As geologists, we call attention to the building and exhibits entitled "Mining in the Adirondacks" with an emphasis on iron mining. Note the diorama of the 1847 McIntyre iron works, as well as the wall-size photograph of the main arch of the 1854 charcoal-fueled blast furnace. Also on display are Adirondack industrial products that include graphite, garnet, talc and zinc. Be sure to visit the log cabin of the Buck Lake Club and examine the mineral specimens mounted in the stone fireplace that include agate, garnet, rose quartz, flint, obsidian, feldspar, tourmaline and magnetite.

B3: EXCURSION TO CLIMB MT. ARAB IN THE ADIRONDACK MOUNTAINS NEAR TUPPER LAKE
W.Kirchgasser,
Department of Geology, SUNY Potsdam
kirchgwt@potsdam.edu
The easily reached summit of Arab Mountain (Mt. Arab of trail guides), near Tupper Lake in southern St. Lawrence County, with its Fire Tower and open overlooks, offers spectacular panoramic views of the Adirondack Mountains. For geologists, naturalists and tourists of all ages and experiences, it is an accessible observatory for contemplating the geologic, biologic and cultural history of this vast wilderness exposure of the ancient crust of the North American continent.
My connection to Mt. Arab began in the 1980s on the first of several hikes to the summit in the fall season with Elizabeth (Betsy) Northrop's third grade classes from Heuvelton Central School. Although the highways and waterways in these mountains can offer breathtaking vistas, to truly experience the expanse and quiet grandure of the Adirondacks, one must climb to a summit. At two miles roundtrip on a well-maintained trail and only 760 ft. (232 m) elevation change, Mt. Arab is ranked among the easiest of the fire tower trails in New York State (Freeman, 2001); at a leisurely pace the summit at 2545 ft (176m) elevation can be reached in thirty to forty-five minutes. Mt. Arab is included in many trail guides, among them one with many useful tips on hiking with children in the Adirondacks (Rivezzi and Trithart, 1997). Through the efforts of the Friends of Mt. Arab, the Fire Tower and Observer's Cabin have been restored and there are trail guides available at the trailhead. In recent years naturalist guides are on duty during summer weekdays.

B3: EXCURSION TO CLIMB MT. ARAB IN THE ADIRONDACK MOUNTAINS NEAR TUPPER LAKE

Athletic fields: proglacial lake bottom plain (clays and silts).

Glacial-till plain (ground moraine) on left

North-facing front of proglacial-lake delta
Slope of Rte. 72 hill is north-facing front of proglacial-lake delta, the lowest of a series marking stages in the lowering of Lake Iroquois.

On right: Meander cutoff (oxbow) in Stafford Brook.

On left: Large active sand and gravel quarry
On left: Large active sand and gravel quarry in kame-moraine-delta complex. Greymont- Potsdam Stone & Concrete.

Village of Hannawa Falls.
Clean sands at top of pro glacial-lake delta (about 550 ft. elevation), marking a static level stage of Lake Iroquois.

Rte. 56 Bridge, Hannawa Falls
(Hannawa Falls Pond on left, hydroelectric dam and canal on right).

STOP 1. Potsdam Sandstone at Hannawa Falls Dam (Fig. 2)
Turn right onto Mill Street and park across the road from the Hannawa Falls Firestation Walk about 100 yards along side of road to dirt track* and follow footpath down and back towards the base of the dam.
The section here is close to the great unconformity, the boundary between the Grenville basement metamorphic gneisses of the Proterozoic Era (1.3-1.0 billion years old) and the covering sedimentary rocks of the Paleozoic Era, here in the form of the Potsdam Sandstone of Lower Cambrian (?) age. This is the type area of the the famous red Potsdam Sandstone whose age is problematic as there are no fossils (not even trace fossils) here or farther downstream in the exposures in the river and mostly abandoned stone quarries; if Lower Cambrian in age, the "time gap" at the unconformity is in the order of half a billion years. In his correlation chart, Fisher (1977) placed the lower or red Potsdam in the Lower Cambrian and assigned the underlying intermittent occurrences of arkosic conglomerates (Allens Falls/Nicholville) at the unconformity to the Late Proterozoic.
The gneisses hereabouts are typical Lowland Adirondack metamorphosed sedimentary (metasedimentary) rocks, gneisses with light-colored bands of quartz and pink orthoclase feldspar with minor dark bands of hornblende, mica and pyroxene minerals. Good exposures of these rocks may be seen in the rapids just below the dams in the Raquette River at Potsdam.
The Potsdam Sandstone exposed here, and in the rapids and side quarries downstream, display large-scale cross-bedding which indicate deposition in either a deltaic or sand dune environment (Fig. 2). Near the base of the dam on the Mill Street side, is a cylindrical structure of Potsdam Sandstone. These structures, known elsewhere in the lower Potsdam in the region, are believed to have formed from unconsolidated sands sinking into cavities lower down in the Potsdam or in the underlying Grenville basement (marbles?) (Dietrich, 1953).
The Potsdam here is a medium-bedded, fine to medium grained, silica-cemented orthoquartzite, with hematite-stained quartz grains giving the rock its distinctive red color. Its flat bedding surfaces, durability, and sets of vertical joints made the rock a valuable dimension stone and flagstone for use throughout the region in the 19th and early 20th centuries. Its limited use today is primarily as a red gravel for landscaping. In place samples of the Potsdam Sandstone can be readily obtained from exposures in the embankment on the Mill Street side of the river near the base of the dam.
The hydroelectric dam at Hannawa Falls is the 9th of 19 hydro-dams in the 167 mile length of the Raquette River between its headwaters in the Adirondacks at Blue Mountain Lake and its entry into the St. Lawrence River. The Raquette River drops some 82 feet from the dam to the powerhouse, a half-mile downstream on the east side of the river. The water at the dam is channelled to the powerhouse in a forty-foot wide, open canal, the only hydroelectric canal in the country. The Hannawa Falls powerstation, maintained by Reliant Power Corporation, generates about 50,000 mwh on average through the year.
(*Dirt track is at the south end of the 3.5 mile Red Sandstone Trail, a nature trail which leads to excellent exposures of the Potsdam Sandsone in quarries and rapids along the Raquette River).

Hannawa Pond or Flow on left.

Far left across pond: Postwood Park Town Beach.

Road climbs to flat surface at top of a delta
Road climbs to flat surface at top of a delta at about 650 ft. elevation marking another static level in proglacial Lake Iroquois.
Dunes on right are wind-blown delta sands.

County Road 24 (Brown's Bridge Road
County Road 24 (Brown's Bridge Road): left turn leads to bridge over Raquette River and trailhead parking for northern access to Stone Valley Recreational Area (see below).
Road begins climb to upper Hannawa Delta at about 680 ft. elev.

At crest of hill, view south of St. Lawrence Valley and Adk Lowlands.

Dune sands on left.

Outcrop of Grenville gneiss
Outcrop of Grenville gneiss in front of Colton-Pierrepont Central School.

Turn left to go to Stone Valley Recreational Area
Main Street Colton. Left turn and follow signs to Stone Valley Recreational Area, a 7 mile-long trail along the Raquette River which gives access to rocks of the Colton-Carthage Mylonite Zone (CCMZ).

Bridge over Raquette River: Higley Flow Reservoir.

Bog on left

Bog on right.

On left: large exposure of pink alaskitic-leucogranitic gneiss.

South Colton; dune sands on left.

STOP 2: SUNDAY ROCK, SOUTH COLTON (FIG. 3)
This huge glacial erratic boulder of Grenville gneiss was dropped by the ice-sheet that covered the North Country during Pleistocene Epoch sometime between 14,000 and 10,000 years ago. It is a legendary trail marker at the cultural boundary between the "civilized" life in the St. Lawrence Valley to the north and the rough and ready workday and recreational life in the great South Woods of the Adirondack Mountains to the south, the area where in the old days there was no Sunday. Through the efforts of the Sunday Rock Association, the boulder was moved from the center to the opposite side of the road in 1925 when Rte. 56 was first built and again to its present park location on the south side of the road in 1965 when the highway was widened. The inscription on the tablet next to the monument reads in part:
"THE TOWN OF COLTON STRADDLES THE NORTHERN BOUNDARY OF THE ADIRONDACK FOREST PRESERVE. ONE END OF THE TOWN TOUCHES ON THE NEAT HOMES OF ST. LAWRENCE COUNTY; THE OTHER REACHES INTO THE WOODS. IN THE MIDDLE IS SUNDAY ROCK.
PREVIOUS TO SETTLEMENT IN THIS AREA, THE INDIAN TRAIL INTO THE MOUNTAINS RAN BY HERE. IN THAT LONG TIME AGO THIS 64,000 POUND GLACIAL BOULDER WAS USED AS A LANDMARK BY THE INDIANS AND WHEN THE WHITE SETTLERS CAME, THEY USED IT FOR THE SAME PURPOSE. THE ROCK WAS A NATURAL LANDMARK AND TRAVELERS WERE GUIDED BY THE BIG ROCK IN THE MIDDLE OF THE ROAD, AND THE ROCK SEPARATED THE WOODS FROM THE WORLD.
THERE WAS NO LAW FOR DEER NOR TROUT, AND ALL OF THE WOODS WAS ONE GRAND HUNTING GROUND. IN THOSE DAYS, IT WAS SAID THAT BEYOND THE ROCK THERE WAS NO SUNDAY. CAMP LIFE WENT ON FROM DAY TO DAY WITH NO CHANGE. IT WAS ONE GLORIOUS HOLIDAY WHEN TUESDAY MIGHT JUST AS WELL AS BEEN SATURDAY, AND THURSDAY AND WEDNESDAY COULD CHANGE PLACES AND FRIDAY MIGHT BEGIN THE WEEK FOR ALL ANYBODY KNEW OR CARED. THE RIVERS, THE BROOKS, THE PONDS, THE MOUNTAINS, THE TREES, THE FLEET DEER, THE RUSHING TROUT, THE WILD CAT, THE BLACK BEAR RULED SUPREME. IT WAS THEIR LAND AND THERE WAS NO SUNDAY. THE ROAD PAST THE ROCK ALSO SERVED AS THE WAY FOR SCORES OF LOGGERS AND FOR THEM, THERE THE ROUGH AND TUMBLE FELLOWSHIP OF THE WINTER CAMP BEGAN. THUS THE BIG ROCK BEGAN TO BE CALLED SUNDAY ROCK. BY WHOM NOBODY KNOWS BUT THE REASON IS EVIDENT.
AFTER A WHILE, THE ROCK CAME TO STAND FOR SOMETHING ELSE. WHEN PEOPLE FROM THE VALLEY PASSED IT ON THEIR WAY TO THE MOUNTAINS, THEY FELT A SENSE OF ARRIVAL, OF HAVING CROSSED A DIVIDING LINE. ON THE OTHER SIDE OF THE ROCK WERE THE WOODS AND MOUNTAINS, LIFE WAS FREER AND EASIER. SALUTING THE ROCK BECOME A KIND OF JOYFUL RITUAL TO BE OBSERVED. ELDERS MIGHT UNCORK A BOTTLE AT IT AND CHILDREN COULD CUT UP WITHOUT FEAR OF A SCOLDING. HUNTERS AND FISHERMEN HAD THE FEELING OF EAGER ANTICIPATION AS THE CARES OF EVEYDAY LIFE WERE LEFT BEHIND ...
FOR MANY WHO PASS BY HERE, THE ADIRONDACKS STILL EXERT THEIR MYSTICAL APPEAL. VACATIONISTS WHO RETURN TO THESE HILLS YEAR AFTER YEAR, PROBABLY HAVE THEIR OWN SUNDAY ROCK: A RIVER CROSSING, A TURN IN THE ROAD THAT REVEALS A FIRST GLIMPSE OF THE MOUNTAINS, SOME SIGN THAT YOU HAVE CROSSED INTO A PLACE WHERE THE CALENDAR CAN BE FORGOTTEN, WHERE THERE IS BEAUTY TO LOVE AND THE EVERLASTING HILLS TO SAVOR.
THE MEANING OF THE ROCK HAS NOT BEEN FORGOTTEN ...IT HAS BEEN THE CONTINUED AFFECTION OF MANY GENERATIONS WHICH HAS PRESERVED THE OLD LANDMARK AND LEGEND SURROUNDING IT. SUNDAY ROCK STILL SEPARATES THE WOODS FROM THE WORLD, AND THE MESSAGE FROM THOSE WHO PRESERVED IT IS STILL CLEAR. THE WOODS ARE BETTER."
Allan Pospisil (1968) Colton Story of a Town. The New York Times. [extracted in part from an article by Potsdam Town Historian C. H. Leete in Potsdam Herald Recorder, September 11, 1925 (Sunday Rock-Its history and the story of its preservation-1929, Herald Recorder Press, Potsdam, N.Y.,55p.)]

STOP 3. GRENVILLE GNEISS BELOW SOUTH COLTON DAM
Warning: Take care not to be trapped on the outcrop by water released from the dam upstream.
These well-exposed rocks display many of the structural and textual features typical of the Grenville basement rock of the northern part of the Adirondack Highlands. The variety of gneisses and minerals, and the predominantly banded fabric, suggest an original sedimentary sequence that was metamorphosed deep within the roots of a mountain belt under the extreme conditions (granulite facies) associated with continental collision and consequent tectonic burial. Included are pyroxene and hornblende granitic gneisses with subordinate leucogranitic gneisses, amphibolites (dark colored hornblende-rich gneisses) and migmatites (mixed igneous and metamorphic rock) in which coarse pods of pegmatitic crystals of pink K-feldspar indicate partial melting during metamorphism.
Notable are the complex ductile folds and broken layers isolated as fragments or 'tectonic' xenoliths. The fold patterns and the predominant NE-SW strike of the foliation or banding are typical of the basement rocks of the region.
At low discharge, the rivelets of water flowing across the surface of the outcrop and the orientation (facing) of the waterfall is a fine example of local structural control of drainage, a microcosm of patterns seen in the Adirondacks as a whole. The broadly radial stream courses (outward from the center of the Adirondack Dome) are locally controlled by differential erosion of the banding, foliation and folding in the various metamorphic facies and the intersections of faults, joints or fractures. Other notable erosion features include potholes at various stages of development.
A hundred yards or so upstream on the west bank of the river, a tabular basalt (diabase) dike (2.3 m across) is well exposed along the shore. The dike is nearly parallel to the steeply inclined foliation or banding of the gneisses. Its dark color and uniform mineralogical texture and higher resistance to weathering contrasts with the lighter colored and banded gneisses. The dike is clearly younger than the host rock and was intruded after the gneisses were metamorphosed but before the tectonic development of the joints. The dike is probably late Proterozoic in age (around 570 Ma.), based on its similarity to pre-Potsdam dikes elsewhere in the region. At high water the dike can be reached by the dirt tract that parallels the edge of the river upstream from the waterfall.
The rock forming the hill to the south of the outcrop, which can be reached along the Allen Hill Road, is a quartz-rich granite-gneiss with prominent pink orthoclase and minor dark mineral (leucogranitic gneiss) that retains its igneous (pluton) texture, and although the contact is not exposed, it probably cross-cuts the banded gneisses at the waterfall and is thus younger than the gneisses and older than the basalt dike.

Cold Brook Drive-right turn to Higley Flow State Park.

Allen Hills Road on left: granite-gneiss outcrops at top of hill.

Caution: entering "zig-zag" in highway
Caution: entering "zig-zag" in highway (watergap cut through glacial-delta sediments by Cold Brook).

"Blue Line" Sign on right marking boundary of 6 million acre Adirondack Park.

"The Plains"-top of pro glacial-lake delta at about 1210 ft.

Joe Indian Pond Road-on left.

Bog pond on right.

"Fraternity Rock"-huge, painted glacial erratic on left.

Large bog on right.

Outcrops of Grenville gneiss on left.

Massawepie Lake-Scout Camp

Sand pit on left

Mt. Arab Fire Tower visible-straight ahead

Park on right side of road opposite signs at trailhead.

STOP 4. Mt. Arab
Introduction
The trail to Arab Mountain is approximately 1 mile (1.6 km.) long and rises 760 ft. (232 m.) to a summit elevation of 2545 ft. (776 m.). The summit is about 2115 ft. (645 meters) above the elevation of downtown Potsdam 430 ft. (131 meters).
Follow the red Department of Conservation (DEC) markers and stay on the designated trail. The restoration and maintenance of Mt. Arab is under the care of Friends of Mt. Arab, Inc. with the cooperation of the Laurentian Chapter of the Adirondack Mountain Club (ADK). Please register for your safety and help the Friends of Mt. Arab determine the frequency of trail use; the Interpretive Information Brochure in the registration box is a guide to sixteen locations of features of biological interest.
Basement rock
The gravel covering the lower part of the trail is crushed anorthosite, the blue-gray feldspar-rich rock that underlies the region of high mountainous terrane to the east, including Whiteface Mountain and the Marcy Massif of the High Peaks region. At about midway, the trail surface is mainly on mangerite, the principal bedrock of Mt. Arab. Mangerite is an intrusive or plutonic igneous rock, like a granite, but with less quartz and containing the mineral pyroxene. A few hundred yards from the summit, the mangerite bedrock is exposed in a large outcrop. The broad, subhorizontal fractures seen here and at the summit are sheeting or exfoliation structures, formed by the release of pressure on the rock by the tectonic unroofing, and uplift and erosion of overburden rock during the Proterozoic and later times, and most recently following the final melting of the mile-thick Pleistocene glacier. These fractures and the glacial scour are what account for the smooth and broadly rounded shape of many Adirondack summits.
The mangerite exposed here and at the summit is a metamorphosed igneous intrusive (plutonic) rock whose color, composition and texture contrast strongly with the variety of banded metasedimentary gneisses seen at South Colton and the intrusive anorthosites of Whiteface Mountain and the Marcy Massif to the northeast, east and southeast (Fig. I-C). The mangerite, which contains only minor quartz, consists of cream colored intergrowths of feldspars (mainly potassium feldspar) with dark mafic minerals (pyroxene) oriented subparallel to the long axes of the feldspar crystals (anastomosing, perthitic texture), giving the rock a strongly planar foliation. The contrast with banded hornblende gneisses seen at South Colton is striking. On the outcrop surfaces (west of the Observer's Cabin) sheared quartz veins (Fig. 6) give evidence of plastic (ductile) deformation and the high intensity of metamorphism (granulite facies with temperatures of 675-800 degrees C and pressures of 7-8 kilobars) in the roots of a mountain range, comparable to some 25-30 km. (17-20 miles) depth below the surface.
A Uranium (U)-lead (Pb) radiometric date on the mangerite of 1134 ± 4 million years at Tupper Lake (McLelland and Chiarenzelli, 1990) gives the time of crystallization of the magma intrusion. The mangerite in the Tupper Lake region shows a spatial relationship with the anorthosite, the great mass of plutonic rock that underlies the Whiteface Mountain region and Marcy Massif of the High Peaks region; the contact between these units is just east of Tupper Lake. The anorthosite is composed predominantly of the blue-green-gray crystals of the plagioclase feldspar andesine and the small fragments of the anorthosite can occasionally be seen "floating" in the mangerite at Mt. Arab. The age of emplacement of the anorthosite plutons is around 1155 Ma., which is close to the time of emplacement of the mangerites.
Fire Tower
The 35 foot high steel Fire Observation Tower at the summit, installed in 1918, replaced wooden structures dating from 1911 and 1912. This "survivor that still stands guard" (Laskey, 2003) is one of only two remaining fire towers in St. Lawrence County; the other is on Cathedral Rock in Wanakena (Freeman, 2001, p. 44). The network of observation towers was established after the disastrous fires in the Adirondacks in 1903 and 1908; at one time there were 57 towers in the Adirondacks. No longer in service, the Mt. Arab Tower and Observer's Cabin were last staffed in the 1980s in the final stages (accelerated during and after WWII) of the systematic dismantling of the fire tower observation system in Adirondack and Catskill Mountains. After decommission, the Mt. Arab Tower deteriorated and was condemned for public use in 1993.
The restoration of the tower and access trail dates from 1997 and the founding of the citizens's group Friends of Mt. Arab (FOMA), an organization that has coordinated endorsements and financial support from state, county and local government agencies as well as several Adirondack Mountain Club (ADK) chapters, school groups, camp owners and local residents. The Observer's Cabin has been restored as a small museum and base for a summer interpreter, thus completing the functional evolution of the tower and cabin from fire observation to education and recreation. Supported by the Adirondack Architectural Heritage (AARCH), the Friends of Mt. Arab can be contacted at P.O. Box 185, Piercefield, NY, 12973.
Adirondack Landscapes (Figs. 5-6)
Among the features that can be seen from the top of the the Fire Tower: north- northeast, Mt. Matumbla (2700 ft.; 823 m.), the highest point in St. Lawrence County; northeast, in far the distance beyond Tupper Lake and Tupper Lake Village, Whiteface Mountain (4867 ft.; 1483 m.) with its distinctive white landslide scars; southeast Mt. Morris (3163ft.; 964 m.) with its Big Tupper ski-trail clearings, and in the distance, the rounded profile of Blue Mountain (3759 ft.; 1146 m.) near the center the Adirondack Dome and the headwaters of the Raquette River; far to the east-southeast, the High Peaks, which include Algonquin Peak (5114 ft.; 1559 m.), Mount Colden (4714ft.; 1437 m.) and Mount Marcy (5344 ft.; 1629 m.), the highest point in New York State. Nearby to the southwest, Mt. Arab and Eagle Crag Lakes; and south-southeast, the south end of Tupper Lake.
With modern technology, changes in elevation and geographic position of features on the surface of the earth can be monitored remotely by satellite and laser. Attached to the bedrock on the summit are three small metal disks, the United States Geological Survey bench marks that were used in surface surveys to determine the geographic position and elevation of Arab Mountain.

B4: MINERAL COLLECTING AT J & L STEEL CORPORATION, BENSON MINES, STAR LAKE, NY
M.Whitton
Herkimer Central School
Herkimer, N.Y.
mwhitton@herk-high.moric.org
HISTORY OF THE MINES
The ores were first discovered in 1812 when a military road was being built in the region. It became known as the Chaumont Ore Bed. In 1883, the Magnetic Iron Ore Co. was formed. Byron C. Benson, a large land owner in southern St. Lawrence County sold the company the mineral rights on 2,201 acres of the Brodie Tract in the Town of Pitcairn. In 1886, a railroad was started from Carthage to Jayville in the Town of Pitcairn and additional mineral rights on 40,000 acres in the southern part of the county were obtained by the Magnetic Iron Ore Co.
In 1887 and 1888, the company purchased mineral rights for magnetite iron ore on Vrooman Ridge in the Town of Fine and all the mineral rights (9185 acres) in the southeast comer of Chaumont Township (later part of Clifton Township) including the Chaumont Ore Bed. In 1888-89, work was done on the Jayville mines in the Town of Pitcairn. From 1889-93, the Magnetic Iron are Co. shipped 150,000 tons of high grade concentrates (magnetic iron ore) to Pennsylvania.
In 1906, Benson Mines Company formed and leased Benson Mines (Chaumont Ore Bed). From 1907-1919, sporadic mining occurred at Benson Mines and in 1922 the Benson Mines Co. gave up its lease and sold its plant to the Magnetic Iron are Co., owner of the mineral rights.
Later in 1922, the Benson Iron Co. Inc. was formed, but did not do much mining. In 1941, Jones and Laughlin Ore Co. leased Benson Mines and built a $7,000,000 mill and upgrade of the mine. In 1946, the Benson Iron Co. Inc. and Magnetite Iron Ore Co. (both belonged to the Benson Family) consolidated to form Benson Iron are Corporation and by 1950, it was the largest open pit magnetite iron ore mine in the world.
In 1978 Benson Mines shut down. The St. Lawrence Development Corporation tried to find a buyer or lessee without success. Lumbering is the only thing going on in the mine area now that is bringing in any money, but just barely enough to pay the taxes. Of the 3,200 acres now owned by the company, only 1,200 are cut in a 15 year cycle to allow for replenishment. There is some sale of waste rock, but the income from this is negligible. The mine used to employ 1,000 people and pump 2,000,000 gallons of water a day.

B4: MINERAL COLLECTING AT J & L STEEL CORPORATION, BENSON MINES, STAR LAKE, NY

STOP 1. Benson Mines, Star Lake
Turn left just before the large blue buildings and across the road from the St. Lawrence County Solid Waste Disposal Authority's Waste Transfer Site. This is the mine entrance. We will proceed through the gate, pass the mill buildings and toward the flooded open pit mine. We will let our tour guide lead us around the mine for some history and then head for the mine dumps to do some mineral collecting. The trip after here is toward home. There are no plans to return to Potsdam.

B5: INITIAL DEGLACIATION OF THE ADIRONDACK MOUNTAINS AND DEVELOPMENT OF THE FULTON CHAIN LAKES
G. Gordon Connally and Donald H. Cadwell
New York State Museum
Albany, New York
The Adirondack Mountains, located in northern New York State, offer a textbook example of radial drainage. The Black River and its tributaries drain the west and southwest region of the Adirondacks (Figure 1). The Moose River is the largest tributary of the Black River and drains most of the southwest Adirondacks. The Fulton Chain is a series of eight lakes that lie along the Middle Branch of the Moose River.
One purpose of this paper is to describe five proglacial lakes that preceded the present day Fulton Chain, and neighboring Raquette Lake. A second purpose is to relate the formation of those glacier-dammed lakes to the inception of ice withdrawal from the Adirondack Mountains. The third purpose is to correct misrepresentations on the Surficial Geologic Map of New York, Adirondack Sheet (Cadwell and Pair, 1991) for which the senior author of this paper was responsible.
Fieldwork for this study was completed during the 1989 through 1992 field seasons. Fieldwork in the Adirondacks always has been frustrating because of 1) the large area, 2) the great topographic relief, 3) the limited road access, and 4) the paucity of exposures. During 1989 and 1990, under the aegis of the New York State Geological Survey, the existing road networks were covered and all major accessible exposures were examined. Most time was spent packing into wilderness areas during 2-day and 3-day trips - often finding no surficial materials exposed. Under those conditions, an implicit response model was adapted from nearby areas of New York State where almost all level features adjacent to ice-contact deposits are observed to be outwash.
It was not until preparation for oral presentations summarizing the field mapping (Connally and Cadwell, 1991; Fleisher et al., 1991) that Connally began to suspect a consistent error. Fieldwork later in 1991 confirmed the error. In the few places where Connally had observed exposures beneath horizontal topographic features, he had mapped lacustrine deposits. Yet, he inferred outwash beneath similar landforms lacking visible exposures. Each new exposure confirmed lacustrine deposition. When he realized that it was likely that he had systematically misinterpreted those features, the Adirondack Sheet was in final production. It was too late to revise the submitted work.

B5: INITIAL DEGLACIATION OF THE ADIRONDACK MOUNTAINS AND DEVELOPMENT OF THE FULTON CHAIN LAKES

1840 ft Blue Mountain delta in the woods at left.
Blue Mt. Lake is on the right; 1840 ft Blue Mountain delta in the woods at left.

Look for an arete on the right.

Delta terrace sediments exposed.

Raquette Lake is on the right
4.5 x 3.4 mi (7.3 x 5.6 km), present elevation of 1,762 ft.

STOP 1. Burke's Cabins are on the right; Burke's Marina on the left
Park where you can but, NOT in the restaurant parking lot. We will look at the sediment behind the marina buildings and then find an open space to discuss Glacial Lakes Raquette and Fulton.
Glacial Lake Raquette
The initial high level lake, at ±1840 ft, straddled the divide between upper Moose River and upper Raquette River drainage. It was centered on the present day Raquette Lake depression and is here named Glacial Lake Raquette (hereafter GLR). GLR spread southwest, up the Sucker Brook valley to beyond Shallow Lake; south into northern Eighth Lake, via Browns Tract Creek; and eastward up the Marion River to the Utowana Lake basin, as illustrated in Figure 4. The ±1840 ft delta at Blue Mountain suggests a long extension of GLR to the east, down the Rock River valley, where it must have been dammed by Hudson River ice.
Glacier ice in the northern Adirondack drainage basins became the northern border of GLR. South-graded outwash near Grass Pond, above Sargent Ponds, documents the former ice margin. The Forked Lake depression shows no evidence of GLR. Inversion ridges between Outlet Bay of Raquette Lake and western Forked Lake might have resulted from the drainage of GLR northward through or under the ice into Raquette River drainage. The ice margin probably remained banked against the eastern mountains north of the Marion River, anchored to the east at Blue Mountain. At least initially, ice remained along Blue Ridge, south of the Marion River valley.
There is sedimentary evidence of a small lake at ±1920 ft between Blue Ridge and Eighth Lake Mountain in the vicinity of Sagamore Lake. That lake might have been contemporary, but probably developed after GLR and its successor had drained. Moose River ice evidently established a margin at the south end of Eighth Lake and in the North Branch between present day Big Moose Lake and GLR. The Hudson-Champlain Lobe ice remained in the upper Hudson River drainage basin at Lake Durant, immediately east of Blue Mountain. Thus, GLR must have been completely surrounded by thick glacier ice.
Although it had a very irregular shoreline, and was barely 0.6 km wide in the Marion River valley, GLR had maximum dimensions of 28 km east-to-west and 12 km north-to-south. The eastward extension is documented by the hanging delta on Blue Mountain northeast of the hamlet of Blue Mountain Lake (Figure 2). Other deposits were observed along Sucker Brook to the west and south of Eighth Lake Mountain from Eighth Lake to the Raquette Lake Reservoir. More are concentrated near Inlet Creek, south of the Marion River, and along Boulder Brook, a second eastern tributary to Raquette Lake. Esker ridges (?) near Eldon Lake, at the east side of Raquette Lake, and ice-contact structures in the Blue Mountain Lake delta, suggest that remnant ice remained in GLR, at least initially.
Where was the outlet for GLR? Ice stood in the Lake Durant depression blocking eastern drainage and in the Forked Lake depression blocking northern drainage. Ice probably remained in Inlet Creek, up to the elevation of Sagamore Pond at 1904 ft. Inversion ridges suggest that this ice did not melt until GLR and its successor had drained. And there are no GLR features south of Eighth Lake. This leaves northward or eastward drainage into the ice; or southwestward drainage via either Eagle Creek or Sucker Brook.
Ice-contact stratified drift appears to have filled Eagle Creek up to ±1900 ft along Uncas Road. Indeed, the drift may mark the edge of Moose River ice that dammed GLR Although there may have been an early level of ±1960 ft in upper Sucker Brook, that may have drained southwest via the Cascade Lake channel, the thresholds are well above 1840 ft. Thus, it is not now possible to pinpoint a drainage threshold responsible for the level of GLR. The most likely possibility is somewhere eastward within the blocking Hudson River basin ice. It is proposed here that GLR drained eastward into or under leaky Hudson-Champlain Lobe ice where a topographic barrier served as an 1840 ft threshold. The most likely candidate is the channel south of the Stark Hills, 3 km east of Lake Durant. There is a possible threshold at ±1840 ft on Ledge Mountain south of the Stark Hills that overlooks what may be an abandoned plunge pool. Perhaps GLR waters were on their way to the subglacial Indian River channel.
Glacial Lake Fulton
Glacial Lake Raquette was succeeded by a more extensive lake at ±1805 ft. The release of 35 ft of water caused lake waters to withdraw almost entirely from Sucker Brook in the northwest. A dense concentration of boulders at Eagles Nest, north of Eagle Lake, probably represents a lag deposit formed during drainage of GLR. The new lake, here named Glacial Lake Fulton (hereafter GLF), spread eastward in the valley of Lake Durant, in the Rock River drainage basin. Inversion ridges west of Stark Hills, near Rock Lake on the Rock River, and between Ledge Mountain and Sawyer Mountain, suggest that this lake drained east like its predecessor into or beneath ice of the withdrawing Hudson-Champlain Lobe. To the south, the lake extended into the Fulton Chain, for which it is named, as far as Sixth Lake. The maximum extent is illustrated in Figure 5.
The dimensions for GLF shrank from 28 to 22 km east-to-west, but increased from 12 to 17.5 km north-to-south, compared to GLR. Stratified sand and silt deposits surround Raquette Lake at ±1805 ft. Those deposits extend eastward to the head of Utowana Lake and were observed adjacent to eastern Blue Mountain Lake. In the Fulton Chain, 1805 ft terraces were mapped between Eighth and Seventh Lakes and immediately south of Sixth Lake. They extend to the ice margin deposits in Eagle Creek that probably bounded GLR. Similar deposits at Lake Durant Camp and surrounding O'Neil Flow east of Blue Mountain document extension into the Rock River valley and upper Hudson drainage.
The northern ice border for GLF probably remained unchanged. Outwash south of Forked Lake is graded to ±1800 and ±1780 ft. Evidently it was deposited by active northern ice still in place after the demise of GLF. Ice-contact structures in deltas at "Burke's Cabins" and at the former landfill for the village of Inlet document the presence of remnant ice during establishment of this lake. To the east, Hudson-Champlain ice was beginning to withdraw and probably to disintegrate at its western margin. The withdrawal probably initiated the drawdown of 1840 ft GLR to 1805 ft resulting in GLF. To the west, ice still occupied the North Branch of the Moose River in the vicinity of Big Moose Lake. However, in the Middle Branch the ice margin withdrew southwestward through Eighth, Seventh, and Sixth Lakes. A small terrace remnant south of Fifth Lake also may represent this level. GLF waters may have been present in northern Fourth Lake, but we conclude that Fourth Lake deposits near 1805 ft probably represent southwest-flowing drainage that ended GLF. Late in the history ofGLF it probably drained into stagnant ice in the Fourth Lake basin.

Delta foreset beds may be exposed on the left.

Historic Sagamore is to the left
Historic Sagamore is to the left; to the right is the hamlet of Raquette Lake.

Eighth Lake
Eighth Lake, the highest of the Fulton chain, is on the right; 1.8 mi (2.6 km) long, present elevation 1,791 ft.

Cross an inlet to Seventh Lake
Cross an inlet to Seventh Lake; 3.1 mi (5.0 km) long, present elevation 1,789 ft.

Pryor's Sea Plane rides on right are on Seventh Lake.
Sixth Lake is the next lake seen through the trees; 0.9 mi (1.5 km) long, present elevation 1,789 ft.

Sixth Lake Road is on the right.

Fifth Lake is on the left
Fifth Lake is on the left, only 0.3 mi (0.5 km) long, present elevation 1,707 ft.

Inlet public parking lot on the left at the head of Fourth Lake.

Fourth Lake is on the left
6.0 mi (8.6 km) long, present elevation 1,707 ft.

Fourth Lake still is on the left.

Third Lake is now on the left, but is not visible
1.0 mi (1.6 km) long, present elevation 1,707 ft.

Second Lake now is on the left, but it also is not visible
0.8 (1.4 km) long, present elevation 1,707 ft.

First Lake is visible on the left
2.7 mi (4.4 km) long, present elevation 1,707 ft.

STOP 2. Present day Fulton chain and their predecessors
Here we will discuss the present day Fulton chain and their predecessors Glacial Lakes Inlet, Old Forge, and Thendara.
Glacial Lake Inlet
A ±1760 ft level is documented in the northern part of Fourth Lake and south of Fifth Lake. It is here named Glacial Lake Inlet (hereafter GLI) for the hamlet of Inlet just north of Fourth Lake. Although GLI was a relatively minor lake at 6 km by 10 km, it was an important step in the overall sequence.
East of the Raquette River/Hudson River drainage divide, the Hudson-Champlain ice withdrew farther eastward. GLF waters fell to a new threshold elevation at ±1790 ft and then drained altogether down the Rock River. No distinct features were observed at that elevation surrounding Raquette Lake. Thus, northern drainage of GLF to the Raquette River probably followed immediately via the Outlet Bay inversion ridge channels. That would have lowered the water level in the Raquette Lake depression to its present level of 1762 ft. South of the Raquette River/Moose River drainage divide, southwestward drainage must have commenced into or onto Moose River ice. The north portion of the Middle Branch became ice-free enabling Eighth Lake to reach its stable level at 1791 ft, Seventh Lake to reach 1786 ft, and Sixth Lake to reach ±1773 ft. Miller (1917, p. 70) stated that "From ... Raquette Lake ... preglacial drainage was almost certainly southwestward by way of ... the Fulton Chain ... ". Evidently, just the reverse was true. Seventh and Eighth Lakes, without Lake Fulton lacustrine deposits at ±1805 ft at their northern ends, probably were tributaries to the Raquette River, via the Raquette Lake depression.
In the Moose River basin, ice evidently remained in the South Branch. But a lake developed at ±1800 ft across the Dart Lake and Moss Lake depressions in the upper North Branch. It is marked by very thick deposits of lacustrine sand. The lake extended to the vicinity of Safford Pond and we here name that lake Glacial Lake Safford. The northern margin of Fourth Lake ice must have been just west of Bubb Lake, then north of Lake Rondaxe to southeast of Safford Pond. It acted as a dam for both Lake Safford in the North Branch and GLI in the Middle Branch as illustrated in Figure 6. We posit that Lake Safford gradually emptied into the Middle Branch at the hamlet of Thendara, either into the ice or over it, bypassing GLI.
Above Glacial Lake Safford another lake developed at ±1900 ft from Lake Big Moose northeastward to the drainage divide. That lake, here named Glacial Lake Big Moose, might have developed prior to Lake Safford or contemporaneously. But because overflow deposits from Big Moose Lake appear to be graded to previously deposited Lake Safford sands, we infer that it was subsequent. In any case, the combined waters of Lakes Big Moose and Safford eventually extended Lake Safford down the North Branch to a threshold at Thendara. Drainage into Moose River ice probably caused retreat of the Fourth Lake ice margin to the North Branch/Middle Branch confluence, initiating the succeeding lake.
Because of the lack of sediment downstream in the Moose River, we conclude that superglacial drainage sluiced water and sediment from the central Adirondacks into the Black River Valley. The draining of Glacial Lake Safford and Glacial Lake Inlet initiated large scale sediment bypassing as a process in the Moose River drainage basin. Bypassing was previously proposed by Connally and Cadwell (1991).
Glacial Lake Old Forge
The retreat of Moose River ice to Thendara was accompanied by a lowering water level along the Middle Branch from ±1760 to ±1740 ft. Lake Safford and Lake Inlet drained completely. The 1740 ft level is here named Glacial Lake Old Forge (hereafter GLO) for the former Browns Tract Forge and the village of Old Forge. GLO extended 20 km from Fifth Lake to the ice dam at Thendara as illustrated in Figure 7. GLO and it successor were only ±1 km wide in the Middle Branch of the Moose River and even narrower in the North Branch. Boulder deposits immediately above GLO deposits south of Fourth Lake suggest that the lowering from GLI to GLO was accomplished by strong current action. It might have been catastrophic.
Ice must have remained in the valley of Nicks Creek, to the southeast, because no 1740 ft features were observed there. However, GLO did extend up the North Branch to the vicinity of Rondaxe Lake. GLO terraces are the dominant features surrounding all of the lower lakes of the Fulton Chain. They were particularly well exposed in 1990 at the Old Forge airport. Again, drainage must have escaped southward, sluicing water and sediment through superglacial channels to the Black River Valley.
Glacial Lake Thendara
Evidence for the final pre-Fulton Chain lake is preserved at ±1720 ft. The Moose River ice margin retreated 1 km southwest and later another 6 km to Flatrock Mountain. The lowest level is here named Glacial Lake Thendara (hereafter GLT) for the hamlet of Thendara. It was ±27 km long from Fifth Lake to the ice dam as illustrated in Figure 8. GLT left low terraces from 10 to 14 ft high at many points along the lower Fulton Chain. However, GLT deposits are much more prominent along the Moose River southwest of Old Forge and in the valley of Nicks Creek. At the mouth of the North Branch, west of Old Forge, the Thendara Flats were deposited.
Drainage from GLT, like its predecessors, must have been southwest over decaying Moose River ice. Connally was able to identify the probable outlet channel, at least for GLT, in a gravel pit southwest of Thendara. A linear concentration of huge boulders that strongly suggests catastrophic drainage by very swift currents was uncovered in the autumn of 2002. These boulders are illustrated in Figure 9.
The relationship between the five proglacial lakes of the Fulton Chain, and Raquette Lake, and the natural elevations of the nine lakes are illustrated in Figure 10. The elevations, dimensions, and boundaries for those lakes are summarized in Table 2.

1740 ft lake terrace of Glacial Lake Old Forge
Rise up the scarp to the 1740 ft lake terrace of Glacial Lake Old Forge lacustrine sand.

STOP 3. Sands of Lake Thendara
STOP 3. Park where you can, then cross the bridge over the Moose River to view the sands of Lake Thendara.

1740 ft terrace deposited in Lake Old Forge.
The hamlet of Old Forge is constructed on the 1740 ft terrace deposited in Lake Old Forge.

Descend to the 1720 ft terrace deposited in Lake Thendara.

Exposure of channel deposit of boulders on the left

STOP 4. Park where you can.
We will look at ice-contact lacustrine sediments, and extremely coarse channel deposits. Then we will discuss the history recorded here. On the way out, visit the outlet channel deposits for Glacial Lake Thendara (and perhaps Lake Old Forge, and even Lake Inlet before it) in the original sand pit on the left. Note the size of the "sediment" and speculate on the rate of flow as the lake(s) drained.