A7:THE CHAMPLAIN THRUST SYSTEM IN THE WHITEHALL-SHOREHAM AREA -- INFLUENCE OF PRE- AND POST-THRUST NORMAL FAULTS ON THE PRESENT THRUST GEOMETRY AND LITHOFACIES DISTRIBUTION.
Nicholas W. Hayman
Department of Earth and Space Sciences
Box 351310
University of Washington
Seattle,WA 98195
nickh@u.washington.edu
W.S.F. Kidd
Department of Earth and Atmospheric Sciences
University at Albany
Albany, NY, 12222
Introduction
The Taconic foreland is an exemplar of collisional tectonics and the Champlain Valley of West-Central Vermont is a pivotal region for mapping and reconstructing this system (figure 1). This is because between the latitudes of Middlebury, VT and Whitehall, NY, the shelf sequence gives way to the fore-deep and rise sequences along the strike of the eastward dipping range (Stanley, 1987; Kidd et al., 1995) (figure 2). Although many significant contacts between the sequences have been recognized as faults, the accrued transport on these faults, and the relationship between them in time and space, is ambiguous. This is partly due to the difficulty in determining the map trace of significant faults across regions of poor outcrop and sharp contrasts in stratigraphic units and sedimentary facies.
This field trip visits outcrops along the Champlain thrust system (CTS). including the Mettawee (River) fault, a late normal fault that significantly truncates thrusts of the CTS. These outcrops are from the areas discussed in Hayman and Kidd (2002), a synthesis of our work in the region. Our mapping focused on the CTS, which was responsible for large (>80 km) transport of the shelf section (Rowley, 1982). A cornerstone of our interpretation is that many abrupt changes in map units along-strike, and problems in restoration of cross-sections across the map area, are the consequence of reactivation of preexisting faults. The early (pre-thrust) faulting occurred in response to extension along the synconvergent flexural forebulge. Other significant lithic changes are the result of late (post-thrust) normal faulting associated with one of the several phases of extension that affected the region. The thrust system projects to depth and thus is dynamical1y related to the overlying Taconic thrusts, and collectively forms a decollement beneath the Green Mountain crystalline core of the Taconic orogen (Rowley, 1982).

A7:THE CHAMPLAIN THRUST SYSTEM IN THE WHITEHALL-SHOREHAM AREA -- INFLUENCE OF PRE- AND POST-THRUST NORMAL FAULTS ON THE PRESENT THRUST GEOMETRY AND LITHOFACIES DISTRIBUTION.7

STOP 1. Orwell/Main Champlain Thrust at Shoreham
ASK PERMISSION AT THE FARMHOUSE to visit this outcrop. Unplanned encounters with an unfriendly bull may result if you ignore this instruction.
From Slateledge Farm house, walk east along the road passing the track to the barn nearest the house, and take the next track which heads toward the low ridge extending north from the second barn. About 100 meters from the road, small exposures of dark grey shales/slates occur at the side of the track. After passing a fence line (and maybe crossing an electric fence across the track) small exposures of steeply east-dipping calcareous dark shale, and more extensive loose material occur on the western slope of the ridge [43°: 53.740'N, 73° 19.723'W). Based on lithic correlation, these are mid-Ordovician in age, termed Stony Point Formation in this region. They represent the transition to deep-water deposition from the previous shallow passive margin carbonate sedimentation as the Laurentian margin subsided rapidly on entering the Taconic subduction system. On top of the ridge here are outcrops of pale tan-weathering, grey quartzite, gently east-dipping at this position, becoming flat and then moderately west-dipping in a small ramp anticline on going north along the ridge. This quartzite is identified as Potsdam Fm., of mid-Cambrian age. The westernmost major thrust of the Champlain Thrust System at this latitude is located between the quartzite and the dark shale. This fault to the north of the Shoreham area is termed the Champlain Thrust; in the area of Shoreham, where several major splays occur, this one has been called the Orwell Thrust, although we have placed the name "Main Champlain Thrust" on it. The fault surface itself is not exposed here, although the position can be constrained to an interval less than 10 meters wide.
Looking east from the ridge towards Shoreham village, no outcrops occur in the lowlands, but extrapolation from outcrops along strike imply that this belt is underlain by Cambrian-early Ordovician Beekmantown carbonates, largely dolostones, which are stratigraphically above the Potsdam. In Shoreham Village, and farther east, imbricate slices of the Shoreham and Pinnacle Thrusts occur, which are examined in subsequent stops. To the west, the Champlain lowlands, under the blanket of Quaternary lake clays, contain a few outcrops of mid-Ordovician shaly strata which are the Taconic trench/foredeep sediments. Walk back to the road, and slates, siltstones and fine-grained greywacke arenites of these mid-Ordovician flysch sediments can be seen in outcrops by the road opposite the farmhouse, and in the small quarry adjacent [43° 53.639'N, 73° 19.832'W]. A well-developed moderately east-dipping slaty cleavage cuts moderately NW-dipping bedding, and excellent slate pencils formed by this oblique intersection weather out. The bedding strikes obliquely towards the N-S trace of the Main Champlain Thrust. We infer from the strong cleavage and down-plunge lineation that this is probably an imbricate thrust slice attached to and considerably transported by the Main Champlain Thrust; more autochthonous flysch west of the Champlain Thrust in this region tends not to have prominent cleavage.

STOP 2 - Potsdam/Ticonderoga quartzites/arenites at base of Shoreham Thrust Duplex
This stop has DANGEROUS TRAFFIC CONDITIONS (high speeds and limited sight distance) - please park as far off the paved road as possible, be extremely careful crossing the road. and do not stand on or step into the pavement when contemplating the outcrop.
From the parking place specified, cross the road and walk north to the roadcut [43° 55.241'N, 73° 18.743'W]. Pale tan-weathering, grey, well-indurated quartzites and local dolomitic arenites dip gently east. These can be identified as either the upper part of the Potsdam and/or the arenite-rich part of the overlying unit, the Ticonderoga Fm. Small-scale cross-bedding occurs locally. Mapping shows that they form an imbricate slice on the Shoreham Thrust. In this area near Shoreham. the Shoreham Thrust Slice is a complex imbricated stack of slices, forming the Shoreham Duplex.

STOP 3 - Middlebury Limestone in the Shoreham Duplex
ASK PERMISSION to park and view this outcrop AT THE GARAGE, OR AT THE HOUSE ON THE CORNER OF THE 74/22A INTERSECTION.
From the east side of the parking area, walk to the north-east corner, then go east to the nearest outcrop. This is massive limestone, showing a fairly well-developed steep east-dipping cleavage in places. About 50 meters east of the first outcrop, another ridge of limestone [43° 54. 144'N. 73° 18.377W] contains locally prominent large coiled gastropod fossils, probably Maclurites, which is common in autochthonous sections of Chazy Group mid-Ordovician limestones. In these transported rocks this limestone is usually termed Middlebury Limestone. These outcrops map as imbricate slices within the Shoreham Duplex. Recent expansion of the parking area has unfortunately resulted in the best outcrop being buried by bulldozed trees, soil and trash. If time is short, or permission is refused. a smaller roadcut outcrop of this limestone can be viewed just east of the Mobil Station parking lot on Route 74 east, but the gastropods are not clearly seen there.

STOP 4A. Potsdam quartzites of the Pinnacle Thrust slice adjacent to the Lemon Fair Fault
From the parking place, cross the road, and view tan-weathering, grey indurated quartzites, locally dolomitic, of the Potsdam Fm. East of the intersection [43° 52.386'N, 73° 16.321'W] they dip steeply southwest; in the outcrop west of the intersection, they dip gently southwest. The monoclinal fold outlined by this dip change, and the oblique strike, we interpret as due to proximity to the Lemon Fair Fault, and the lateral ramp it defines in the thrust geometry. These quartzites are regionally part of the Pinnacle Thrust Slice; this thrust is not exposed here, but its position can be constrained by mapping to the south. The Lemon Fair Fault runs here along the river; looking across from the parking place, limestones on the other side of the fault can be seen at the base of the old bridge abutment.

STOP 4B - Carbonates adjacent to the Lemon Fair Fault, and just beneath the Pinnacle Thrust
Roadcut outcrop [43° 52.398'N, 73° 16.280'W] of limestones, dolomitic limestones, and minor dolostones which are adjacent to the Lemon Fair Fault. The generally rather fractured appearance, and the common presence of calcite veins, are indicative of this proximity. The dominant fractures and veins strike NW, dipping steeply north to vertical, subparallel with the Lemon Fair Fault. One vein shows prominent steeply pitching slickensides. These rocks are part of a slice of early-mid Ordovician limestone-dominated carbonates localized immediately under the Pinnacle Thrust in the area north of the Lemon Fair Fault, but not present to the south. This and other substantial changes in structural geometry that occur across the Lemon Fair Fault show that it was used as a major lateral ramp structure by the thrusts of the Champlain System. Because facies and stratigraphic thickness variations only occur in mid-Ordovician units across this structure, we infer that it was generated as a mid-Ordovician cross-strike "flexural" normal fault, and then converted to use as a lateral ramp in the Champlain Thrust System.

STOP 5 - Champlain/Orwell Thrust at Stevens Orchard
Walk up the road from the parking place by the house and barn/garage. On the east side, an outcrop of calcareous dark shale/slate, with a local phacoidally cleaved fault zone, is mid-Ordovician Stony Point Formation. Farther up on the same side just above a driveway there is a smaller outcrop and loose material of the same unit. About 20 feet above this, seen in the roadcut and the ridge going south from it, are dolostones of the Beekmantown Group forming the base of the Main Champlain (or Orwell) Thrust here. A little farther up on the north side of the road [43° 47.077'N, 73° 20.586'W], similar dolostones, showing not very prominent medium to thick-bedding and homogeneous brown-weathering, are exposed. This outcrop also shows the characteristic "fretted" weathering pattern produced by differential removal of abundant narrow calcite veins that are ubiquitously and abundantly developed in these transported dolostones, but are not usually seen in autochthonous dolostone sections in areas to the south. Dolostones like these form all of the body of both the Main Champlain (Orwell) and Shoreham Thrust Slices at this latitude; the Potsdam quartzites are absent because the thrusts have ramped up laterally to within the late Cambrian-early Ordovician carbonate section. Rocks like these are conventionally termed "Providence Island Formation", but we have little confidence that this is stratigraphically meaningful in the sense of strict correlation to the type section on Providence Island. The map pattern of the Main Champlain Thrust in this local area shows that it is very gently east-dipping, or almost flat.

STOP 6 - Shoreham Thrust near Orwell
On the corner with the roadcut outcrop [43° 47.439'N. 73° 19.236'W], east of the parking spot specified, deformed calcareous shales ("Stony Point Fm") make up most of the exposure, although at the western end a contact can be observed with fractured tan-weathering Beekmantown (late Cambrian/early Ordovician) dolostone above the shales. This dolostone forms a low ridge in the woods that parallels the road westwards to beyond the Bascom Road junction and, back along the road in this direction, smaller outcrops of both calcareous and non-calcareous deformed shales can be found locally, with dolostones near or in contact above the shales. The thrust fault defined by this contact is the Shoreham Thrust; the local map pattern demonstrates that this fault also is near flat-lying here. As for the Main Champlain Thrust, the absence here of Potsdam Fm is due to the thrust climbing section southwards, in part across the lateral ramp structure of the Lemon Fair Fault. A much better, even excellent outcrop of this fault exists 20 meters west into the woods near the end of Wilcox Road, about 1.0 mile SW of this outcrop, but the current landowner is most unwelcoming and is quick to display a gun.

STOP 7. Orwell/Main Champlain thrust sheet at Benson Bay/Blue Ledge
STOP 7. Orwell/Main Champlain thrust sheet at Benson Bay/Blue Ledge ASK PERMISSION AT THE HOUSE.
The main part of the outcrop visible from the parking area is now only accessible through the pig mud wallow, unfortunately. We recommend viewing it from the road, from where the nearly flat-lying well-defined planar bedding in the dolostones is clearly seen. To see rocks closer up, walk east along the road, to a large oak tree on the corner [43° 45.889'N, 73° 20.399'W], and then go into the bushes a short distance where the same well-bedded sugary-textured dolostones continue to outcrop. Here the existence of common dark chert as nodules and patches in the dolostones can be seen, both in the outcrop and in the talus fragments. This unit is clearly identifiable in the Beekmantown stratigraphy of Fisher (1985) as the Whitehall Formation. Nearby, on White Ledge, the cliff visible to the east of the road, more Whitehall Formation is exposed; above it one can find in the woods good outcrop that shows overlying Beekmantown units matching those of Fisher (1985), including the unmistakeable Winchell Creek cross-bedded arenites. Structurally, we are back down in the Main Champlain Thrust slice (the fault is well~ constrained by outcrop on Blue Ledge a few hundred meters to the northwest of this outcrop), yet the whole section carried by the Thrust here is utterly different from the homogeneous, poorly-bedded, veined dolostones at and just south of Stop 5, no more than 1-2 km. away. We identify this change to occur across a NW-trending valley just to the northeast of this stop location, and interpret this to be a lateral ramp in the thrust system inherited from a flexural Ordovician normal fault. The change in the shelf facies that occurs in the "Main Champlain" Thrust sheet here is by far the most pronounced anywhere, and it must represent a very substantial relative distance (we think many tens of kilometers) between the sites of detachment of the stratigraphic sequences north and south of this change. Because the sequence in the MCT slice from here south so closely matches the autochthonous stratigraphic sequence defined by Fisher (1985), we think it is unlikely to have been displaced very far <10 km?). Because it is likely the MCT to the north has significantly larger displacement (at least several tens, and perhaps 80 km - Rowley, 1982) we think there must be a large displacement transfer here from the MCT north of this site, along the lateral ramp fault up to the next thrust, the Shoreham Thrust. Not only is there a substantial change in the MCT hanging wall here, but the footwall also contains a similar (and we think closely related) feature about 1 km SW of this stop. There is an abrupt change, from mid-Ordovician shales and calcareous shales of the Stony Point Fm as the footwall strata, to an autochthonous shelf carbonate/clastic section of the "Whitehall" sequence. This change takes place across a mapped cross-fault which affects the MCT as a small-offset lateral ramp/tear fault, but which has a much larger stratigraphically-defined offset in the footwall. We think this is also a mid-Ordovician normal fault used soon after to localise a ramp in the lowest part of the thrust system.

STOP 8 - Shoreham Thrust and end of Orwell/Main Champlain Thrust near Benson Landing
GET PERMISSION AT FARM ON N. LAKE ROAD 0.4 MILES WEST OF FRAZIER HILL ROAD JUNCTION
This stop may be omitted if time becomes short.
Enter field on south side of road [43° 43.781'N, 73° 20.562'W] through gate [OPEN AND CLOSE IT BEHIND YOU - PLEASE DON'T CLIMB OVER IT]
About 50 meters from gate [43° 43.751 'N, 73° 20.599'W] dark calcareous shales of Stony Point Fm. Follow the track on the east side of the valley for another 50 meters or so; small outcrops of calcareous shales occur at the foot of the ridge to the east, while massive fractured dolostones occur up the slope and at the crest of the ridge. This defines the Shoreham Thrust here (to the south this has been called the Shaw Mountain Thrust). On the hillsides and tableland to the west of this valley, on a longer walk than we have time for, flat-lying shelf strata of "Whitehall facies" that map in the MCT slice are sparingly exposed; there has to be a normal fault bounding these against the Stony Point Fm. shales which continue down this valley in and near the stream. The Main Champlain Thrust terminates against this normal fault, and is not present farther south. We think that this normal fault originated as an Ordovician "flexural" normal fault, and was subsequently reactivated with reverse displacement sense and used by the Champlain Thrust System as a "terminal ramp" including the transfer of the residual displacement on this southernmost part of the MCT up to the Shoreham Thrust.
If desired by those on independent schedules, continue walking down the valley until the stream enters a continuous section exposing dark calcareous shales [43° 43.575'N. 73° 20.934'W]. Outcrops of near flat-lying dolostones (Fort Edward) or cross-bedded arenites (Winchell Creek) are found on the northwestern slope of the valley. e.g. dolostones at [43° 43.636'N. 73° 20.895'W], at an elevation significantly above the shales in the stream bed.

STOP 9A. Shoreham Thrust at West Haven
From the parking place [430 38.727'N, 73° 20.888'W] walk about 120 meters south along Book Road [43° 38.663'N. 73° 20.929'W] to roadcut on east side. In the center portion of this exposure. black non-calcareous shale (mid-Ordovician) up to 1 meter thick, with a pronounced phacoidal cleavage indicative of large shear strain. occurs below a sharp contact with highly fractured massive dolostones ("Providence Island" lithology). This is the Shoreham Thrust, and mapping of the surrounding area shows unequivocally that it is here the westernmost thrust in the Champlain System - in other words that the "Main Champlain Thrust" farther north has disappeared. To the south across the Vermont-New York border at the Poultney River, the Shoreham Thrust too disappears as a discrete mappable structure, although minor folding and incipient ramps can be detected in shelf rocks at its expected position as far south as the latitude of Whitehall. A major WSW-ENE cross-fault passing north of this outcrop cuts and displaces the autochthonous shelf section and the Champlain Thrust System stack, crossing Book Road at the parking spot. The Shoreham Thrust is offset by this structure with an apparent left lateral displacement of about 2 kilometers. Two other faults like this one pass through the next valley north near West Haven hamlet. These cross faults are discussed in the description of Stop 9B below.

STOP 9B.Mettawee River Fault at WestHaven
ASK PERMISSION AT BOOK FARM BEFORE ENYERING - FIND BOOK FARM ALONG BOOK ROAD 1.1 MILES SOUTH OF STOP
From parking place [43° 38.727'N. 73° 20.888'W]. enter field on east by walking between the two fences, opening the gate if necessary. Follow the grassed-over track into the edge of the woods (about 100 meters), then along the edge of the woods (about another 200 meters), then angle down the crest of a low ridge in the meadow (about another 100 meters) to the edge of the woods crossing the low ridge [43° 38.850'N. 73° 20.513'W]. Outcrop of fractured tan-weathering dolostone ("Providence Island" lithology) is found just inside the woods at this point. Use the sketch map below to navigate and understand the geology from. this point on. About 200 feet east of the first dolostone outcrop. in the bed of the stream near the south end of the small ravine, dark slates ("Hortonville"), of presumed mid-Ordovician age, are exposed in contact with the dolostones [43° 38.853'N, 73° 20.473'W]. This contact is clearly a steep (60°) east-dipping fault, truncating the moderately east-dipping thick bedding in the dolostones, and the cleavage in the slates. Given the regional context, with no thick dark slates occurring west of this point, but rather the carbonates of the Shoreham Thrust slice, then the underlying autochthonous Cambro-Ordovician "Whitehall facies" sequence, with Potsdam sandstone/quartzite at its base lying unconformably on Grenville Basement, this fault must be a normal fault, and is in fact the Mettawee River Fault first proposed by Fisher (1985) in New York. It is the only complete exposure of this fault, although our mapping demonstrates that it runs continuously from the Mettawee River (to be seen at stop 12) north through this locality at least as far north as the latitude of Shoreham, and all along this length it regionally truncates the thrust stack of the Champlain Thrust System. We suspect that it extends significantly farther north and south than this, but this falls outside our mapping area, and there is a lack of clear truncation of components of the Champlain Thrust System beyond these extents. One reason for suspecting a larger along-strike extent is the minimum displacement, which can be constrained from accurately drawn cross-sections, and which demand at least 1000 meters of throw, and perhaps more than 1500 meters. This fault cuts out very significant parts of the Champlain Thrust stack, and is one of the main reasons why previous attempts to trace the major thrust faults of the System failed. What age is this normal fault? We have no direct younger age limit in the mapped area, other than the observation that it is cut and displaced by the WSW-ENE faults which also cut the Shoreham Thrust. In fact this set of local outcrops (see sketch map) shows that relationship directly, with a smaller splay of the larger WSW -ENE fault displacing in an apparent left-lateral sense the dolostone-slate contact (the Mettawee River Fault). Despite the prominence of the WSW -ENE faults, we have seen no direct evidence in outcrops near the fault valley indicating whether they are really left-lateral strike slip faults or whether the displacements are created by dip slip movement (in this case, it would require north side down) working on consistently east-dipping strata and faults. Thus these ENE-WSW faults, and the Mettawee River Fault, could be Taconic in age, although they might be younger, e.g. Acadian, or even Mesozoic, and they do not necessarily have to belong to the same orogenic episode.

STOP 10. Pinnacle/Comstock Thrust, and Mettawee River Fault, at Fish Hill
OBTAIN PERMISSION FROM HARMONY HILL FARM [0.5 MILE DOWN BUCKLEY ROAD FROM JUNCTION]
Enter field to north of parking point through gateway/over electric fence. Go round pond on western side, loop round north end, crossing dry bouldery bed of stream, and head NE up slope toward outcrops just into the woods. [Cross electric fence at edge of woods]. Find contact between grey indurated quartzites above and tan-weathering crudely bedded dolostones below [43° 33.942'N, 73° 21.398'W]. all dipping gently east. About 1 meter below the base of the quartzites, there is a projecting ledge exposing a bedding-parallel surface of fractured and veined dolostones, smears of limestone, and loose fragments of dark shale coming from the 10-30 cm unexposed interval between the dolostone above and the ledge with limestone smears below. This is the Comstock Thrust, which we maintain corresponds with the Pinnacle Thrust to the north of Orwell (or more precisely here it is the lowest fault surface in a zone which places imbricated Potsdam and Ticonderoga/Whitehall quartzites and dolostones over Fort Ann and Providence Island dolostones). Walk east along the base of the hillside outcrop; an ∼10 meter section mostly of quartzites is conformably overlain by dolostones which extend to near the west end of the barn, where there are some dark cherty patches in the dolostones. Climb up on the outcrop to avoid the manure piles and to find another imbricate fault contact placing the quartzites back on top of the dolostones, with truncation of the dolostone bedding in the footwall as a thrust ramp. Near the east end of the barn [43° 33.920'N, 73° 21.305'W], the quartzite outcrop ends, with locally steep and folded bedding probably reflecting accommodation to the ramp/imbricate geometry underneath. Walk north up into the field over quartzite outcrop, then curve to the east across exposure gap of about 40 meters to outcrop of dark and strongly deformed, melangy mid-Ordovician shales [43° 33.957'N. 73° 21.281'W]. You have just crossed the Mettawee River Fault. which again must have substantial normal, down to east displacement. You may find the evidence here for the existence of the Comstock/Pinnacle Thrust not wholly compelling, but raise your eyes to the view towards the southwest, where, in the hills south of Whitehall, the map of Fisher (1985) unquestionably demonstrates a) the existence of the Pinnacle/Comstock Thrust duplicating most of the Cambrian-Ordovician shelf stratigraphy from the Potsdam upward, and b) the unquestionable fact that this thrust is truncated on a large scale by the Mettawee River Fault.
To the east of the shale outcrop, up the slope of Fish Hill, limestones and dolostones of early-mid Ordovician age form another of several thrust slices involving only the upper part of the outer Laurentian shelf and the overlying mid-Ordovician dark shales. These slices rest below the westernmost fault bounding the Taconic Allochthon, which outcrops only about a kilometer to the east.

STOP 11. Mettawee River Fault at the type locality
NO HAMMERS OR SAMPUNG PLEASE - NY DEC REGULATIONS
From parking area [43° 28.259'N. 73° 22.153'W], walk from northeast corner along path which quickly descends to a bouldery small stream bed. If wet, the path down can be slippery since it passes through well-rounded fluvial pebble gravel and underlying lake clays; the sloping bedding surfaces of the carbonate outcrops can also be treacherous in places. Cross the stream bed near/at the Mettawee River bank and get onto the outcrop along the west· bank of the River [43° 28.283'N. 73° 22.103'W]. These carbonates are mapped by Fisher as Providence Island Formation, and dip about 10-20 degrees east. The lowest part of the section here consists of dolostones; the upper 4 meters contains substantial limestones; we think it is possible that the part of the section containing limestones is either basal Chazy or Black River. This shows some bedding surfaces with well-developed ripples, and small mudcracks, and selectively dolomitized burrows. Local meter-scale folding of periclinal type affects these beds near this end of the section. Walk north along the west bank on the outcrop; mostly dolostones are exposed farther north. About 70 meters north, dark highly deformed mid-Ordovician shales extend from the east bank across the river to an almost complete section at the small rapids. Depending on the streamflow, it may or may not not be possible to examine the shale closely. The contact of the deformed shale with the dolostone beds at the west side of the stream is not quite fully exposed (even at the lowest water we have seen, there is a gap of 10 cm or so), but is clearly sharp, and parallel with bedding in the dolostones. This is somewhat surprising, for a contact which maps out a short distance to the north as a sharp fault that unquestionably truncates strata of the carbonate shelf stratigraphy, as well as the major thrust fault which duplicates this sequence (see the map of Fisher, 1985). Also surprising, for a fault that must have substantial normal sense displacement, is the fact that most or all quartz fiber slickensides in the shale here give thrust sense of displacement!
We infer either that the normal fault mapped to the north passes east of this outcrop within the shale belt, or that the motion is confined to a surprisingly narrow zone along the contact; the full exposure at Stop 9B suggests the latter possibility is more likely than one might be inclined to think based on this outcrop at Stop 11 alone.

STOP 12 - Pre-thrust normal fault in Comstock/Pinnacle Thrust slice at Tyler Farm
ASK PERMISSION at Tyler Farm house [43° 26.849'N, 73° 24.432'W] before going into fields to north of road. If visiting the western part of the ridge, also ask at the old stone house about 0.2 mi west of Tyler farmhouse.
This stop may be skipped if time runs short.
Refer to the outcrop map to navigate. Outcrops on the slope above the Tyler farmhouse, and above the old stone house 0.2 miles west of this, begin with mid-Ordovician limestones of Black River and/or Trenton age; the thin-bedded shaly ones are termed Glens Falls Fm, the more massive ones stratigraphically below are Orwell Fm. They strike about E-W and dip steeply south. Units of the upper Beekmantown (Providence Island, Sciota Limestone, and Ward Siltstone) are found on and near the crest of the first ridge, with decreasing dips towards the valley to the north in which a fault is located. The zone of steep dips is interpreted as a bend fold ["drag fold"] against the hanging wall of (inferred from its straight trace, and the limestone maximum dips) a steeply south-dipping normal fault, and perhaps also is partly an accommodation to the lateral ramp this fault has provided to the Comstock Thrust. North of this ∼E-W striking fault, various units of the older parts of the Beekmantown are found forming mostly a moderately east-dipping panel truncated at the normal fault. These strata are in the hanging wall of the Comstock Thrust (=Pinnacle Thrust), which here is the last and only thrust fault in the exposed part of the Laurentian shelf sequence between the autochthonous Grenville basement and mid-Ordovician shales of the Taconic foredeep. The Comstock Thrust is included on the map of Fisher (1985), although he shows its continuation by joining it to the E-W fault referred to above, which we think is geometrically and kinematically unlikely. Our map (based on mapping by Y. Pan and W. Kidd), instead interprets the E-W norma1 fault to intersect the Comstock thrust and to be truncated by it. In addition, we interpret the Comstock Thrust to continue south across the point of this truncation, and the map pattern requires that it abruptly climb stratigraphic level from the Ticonderoga or Potsdam sandstone to near the base of the mid-Ordovician limestones despite no change in its structural level. This requires the thrust to have truncated an existing normal fault that had a throw of several hundred meters, nearly the full thickness of the shelf sequence. Since there is no indication approaching the E-W fault of any thickness or facies change in the pre-Black River section, we infer that this normal fault too is a mid-Ordovician age structure, generated during flexure of the Laurentian continental margin as it approached the Taconic trench and subduction system. (As a additional note on the structure of the loca1 faults, we find no evidence of the existence of the rootless klippen of Potsdam-Whitehall Fm strata shown not far southwest of this locality on Fisher's 1985 map. We think he confused gently dipping autochthonous Winchell Creek and stratigraphically conformable dolostones with the lower units here; there is in our view no stratigraphic or structural evidence requiring this peculiar object to exist).