B5: AN OVERVIEW OF THE EARLY PALEOZOIC STRATIGRAPHY OF THE CHAMPLAIN VALLEY OF NEW YORK STATE
James C. Dawson
Earth & Environmental Science
State University of New York,
Plattsburgh, NY, 12901
TRIP ABSTRACT
This, Sunday only, trip provides participants with an opportunity to visit some of the well-exposed, classic Early/Medial Cambrian to Medial Ordovician clastic and carbonate shelf sequences and the Medial Ordovician foreland basin carbonates and calcareous shales. Stops include the Potsdam Group (Lower/Middle and Upper Cambrian), the Theresa Formation and the Beekmantown Group (Lower Ordovician), the Chazy Group (Middle Ordovician) and the Trenton Group (Middle Ordovician). The trip essentially repeats the author’s 2002 Joint New England Intercollegiate Geological Conference/New York Geological Association trip (Dawson, 2002) and is ideal for high school teachers and undergraduates seeking an introduction to these rocks.
INTRODUCTION
The field trip begins at the Comfort Inn, near Exit 37, I-87 ‘the Northway’, Plattsburgh, NY at 8:30 AM and will end about 4:00 PM at the Comfort Inn, Plattsburgh, NY. This trip visits many of the localities that are commonly visited in the undergraduate classes at SUNY Plattsburgh. The field trip description is largely based on the work of Fisher (1968) and Isachsen, et al. (2000) and is not based on any significant research by this author.

B5: AN OVERVIEW OF THE EARLY PALEOZOIC STRATIGRAPHY OF THE CHAMPLAIN VALLEY OF NEW YORK STATE

Note the 'old base' stone buildings
On your right you will note three stone buildings constructed by the U. S. Army before the area became Plattsburgh Air Force Base (PAFB). The oldest building, the Old Stone Barracks, is the one furthest from the road. Construction on this started in 1839, but due to construction and funding issues, the building was not occupied until 1843. The two younger replica barracks date from the 1930s. All three buildings are constructed of local Keeseville Sandstone.

STOP 1. Montreal Member of the Glens Falls Limestone and Dike
Montreal Member of the Glens Falls Limestone of the Trenton Group and Lamprophyre (Monchiquite Dike) at the former PAFB Marina.
From the parking area walk down the obvious roadway to the lake shore where the former PAFB marina and warf can be seen on Marina Point. To reach the outcrop, hike, approximately 700 or so paces north along the cobble beach shore of Lake Champlain. The Pleistocene sediments forming the bluff between the railroad track and Lake Champlain along the way include a contact between earlier Lake Vermont varved and later Champlain Sea sediments. The Montreal Member and a cross cutting Lampophyre Dike are exposed to varying degrees depending on the water level of Lake Champlain. The Montreal Member is a medium-bedded limestone with some shale partings that weather to medium dark gray. Thin laminations within the medium-thickness beds have been interpreted as turbidity current deposits. Crab Island (the smaller island that can be seen in Lake Champlain two miles/3.2 km southeast of this stop) takes its name from the trilobite, Isotelus, that is commonly found in exposures of the Montreal Member on the island. Fisher (1968) mapped the Lamprophyre Dike as a monchiquite dike, containing phenocrysts of titanaugite with some biotite and barkevikite (a monoclinic amphibole), phenocrysts of olivine and titanomagnetite. After visiting the outcrop return to the vehicles.

Parking for Stop 1A

STOP 1A. (Alternate) Montreal Member
After parking, walk north along the paved pedestrian walkway for 0.3 miles/0.5 km to a pedestrian bridge on your right/east. Cross over the Canadian Pacific mainline railroad tracks on the pedestrian bridge and follow the path down to the lake shore. This will bring you to Sailor’s Point, the former PAFB beach and picnic area. The Montreal Limestone is exposed at the south end of the cobble beach. From the outcrop you can see Crab Island to the southeast and Marina Point to the south.

Pass the Fort Brown historic site markers on your left/west.
Pass the Fort Brown historic site markers on your left/west. Fort Brown was the left/west flank of the American defense during the land portion of the Battle of Plattsburgh on September 6 - 11th, 1814.

City Hall and Macdonough monument
Continue north on City Hall Place past the Plattsburgh City Hall on your left and the Macdonough (American naval commander during the Battle of Plattsburgh) Monument on your right.

STOP 2. Cumberland Head Argillite of the Trenton Group.
The Cumberland Head Argillite is exposed in this road cut on both sides of Route 9, although the exposures are better on the left/west side. The roadcut (Fisher, 1968 - Figure 27) is typical of the Cumberland Head Argillite. The thin bedding (it looks like varves) of fairly distal turbidite deposition can clearly be seen as more calcareous layers alternate with the thinner, pale buff-colored quartz-silt bearing layers being slightly more resistant to erosion. Fresh surfaces of the rock are uniformly black; however, the thin layers can still be distinguished. The rocks in the vicinity are folded; but, the strike is generally N35E with a dip of 23 degrees N. Be sure to look north along Route 9 and see the slight dip that the highway makes north of the road cut. STOP 3 is just beyond the dip.

STOP 3. Providence Island Dolostone of the Beekmantown Group.
The Providence Island Dolostone is exposed in this road cut on both sides of Route 9, although the exposures are better on the right/east side (Fisher, 1968 - Figure 17). Before examining the outcrop, be sure to look south along Route 9 and recognize that you can see Stop 2. The Rocks at STOP 3 are nearly horizontal, compared to the steeper dips at STOP 2 and the entire Chazy Group and lower portion of the Trenton Group (some 400' or more of rock section) are missing. Fisher (1968) has mapped the edge of the Cumberland Head Allochthon, a Taconic thrust fault, as passing between these two trip stops on the basis of missing section at both the surface and in a 200' deep water well on Cumberland Head.
The Providence Island Dolostone is a thick bedded, massive unit that weathers to the buff color characteristic of dolostones. With careful examination, horizons that display significant soft sediment rip ups and other features characteristic of supra-tidal environments. The dolostone is sometime vuggy and fracture zones that have been filled with secondary crystalline calcite are common.

STOP 4. Cumberland Head Argillite at Point au Roche State Park.
Walk the short distance from the parking lot to Lake Champlain and examine the large outcrop of Cumberland Head Argillite along the shore. The folding and jointing associated with the Taconic thrusting is very obvious. The rock is essentially the same as that seen at Stop 2 and again the thinning bedding of the fairly distal turbidite deposition can be seen as the more calcareous layers alternate with the thinner, pale buff-colored, quartz silt bearing layers being more resistant to erosion.

A hump in the road will indicate that you are crossing the Ingraham Esker (Denny. 1972).

A series of sand pits can be seen to the right/east
A series of sand pits can be seen to the right/east after you first cross the Esker. Route 9 crosses the Ingraham Esker again, just before the hamlet of Ingraham on the left/west.

STOP 5. Day Point Limestone of the Chazy Group.
(THIS IS NOT A HAMMER STOP.)
This road cut is part of the upper part of The Day Point Limeston, probably the Fleury Member of Oxley and Kay (1959). It is a medium gray calcarenite that is both cross bedded and regular bedded in this small exposure. Fisher (1968) mentions this outcrop as containing pelmatozoan debris. Note the nicely developed stylolites.

STOP 6. Valcour Limestone of the Chazy Group at Sheldon Lane.
(THIS IS NOT A HAMMER STOP.)
This is the first of two opportunities that we will have to see the bioherms in the Valcour Limestone.
See the Stop 10 description for the details of what to see at this stop.

Road to old Quarry
Just past a faded red barn on the right/east there is an amateurish ‘stonehenge’ and an unpaved road. The road leads to the abandoned International Lime and Stone quarry where the Pamelia Dolostone, the Lowville Limestone and the Isle La Motte Limestone formations of the Black River Group (Fisher, 1968 – Figure 25) were once exposed. A few years ago much of the remainder of this outcrop and the quarry floor today consists of Valcour Limestone. Some of the Black River Group remains on the north side of the quarry on private property; but, this exposure is only accessible when the water in the quarry is frozen.

STOP 7. Crown Point Limestone of the Chazy Group at the Northway in Chazy
Maclurites magnus Le Sueur, Death Assemblage
(THIS IS NOT A HAMMER STOP.)
To reach the outcrop cross the open area to the north and enter the woods on a vague trail behind and to the right of the obvious transmission pole. The vague trail heads north a few yards in a white cedar forest and then bends left/west toward the Northway. The outcrop is close to the Northway, a short distance north of the Fiske Road Bridge and is illustrated in Fisher, 1968 (Figure 20). The Crown Point Limestone is mainly a medium to dark gray calcilutite. This locality exhibits an unusually large assemblage of the planispiral gastropod Maclurites magnus along with trilobite and brachiopod fragments. Be sure to note the insipient karst development.

STOP 8. Lacolle Melange at the Chazy Railroad Bridge.
The road cut is located along the west side of Route 9 as you walk toward the railroad bridge and is figured in Fisher, 1968 (Figure 30). Fisher, 1968 maps this locality and the STOP 9 locality as part of the Tracy Brook (normal) Fault. The wide range of angular clasts are composed of angular sandstone fragments in a sandstone matrix, presumably a tectonically crushed portion of the Keeseville Sandstone.

Cross Corbeau Creek.
Corbeau Creek was studied, as a monitored watershed, by a succession of students at SUNY Plattsburgh in the 1970s and early 1980s. In recent years SUNY Plattsburgh students have been engaged in watershed studies on the Altona 'Flat Rock' lands owned by the William H. Miner Institute and some of this work is described in Field Trip A6 of this field conference.

STOP 9. Lacolle Melange at Coopersville.
The small outcrop is located adjacent to the south side of Route 9B and is figured in Fisher, 1968 (Figure 29). The breccia clasts include a wide range of sizes and the lithology of the clasts is predominately carbonate fragments, likely of Black River Group and Trenton Group origin. Also refer to the Stop 8 description.

STOP 10. Valcour Limestone at the Bechard Quarry, Near Kings Bay.
To reach the quarry walk across the open pasture to the higher vegetated area that is visible to the west. Once you reach the top of the vegetated mound the quarry can be seen as illustrated in Fisher, 1968 (Figure 22). The bioherms consist of intertidal stromatolites (algae), stromatoporoids, and bryozoans with the various colonies being completely compatible (Pitcher, 1964b) and building their colonies on top of one another. Nautiloid cephalopods have been found.

STOP 11. Keeseville ss of the Potsdam ss at the Clinton Farm Supply, Champlain.
The outcrop is exposed along the north side of the northernmost of the two driveways and in the flat area behind the Farm Supply building. In a series of articles (Erickson, 1993a. Erickson, 1993b. Erickson and Bjerstdt, 1993. Erickson. Connett, and Fetterman, 1993) the stratigraphy and trace fossils of the Keeseville Sandstone and Theresa Dolostone/Sandstone have been described. STOP 11 (Erickson, 19938, and Erickson, Connett and Fetterman, 1993) consists of medium bedded, cream colored Keeseville Sandstone. At this locality large scale ripple marks, and an unusual abundance of trace fossils can be seen.

STOP 12. Theresa Dolostone/Sandstone at Champlain.
The Theresa Dolostone/Sandstone consists of an inter-layered, medium and thick bedded, quartz dolostone. Bjerstedt and Erickson (1989) and Erickson and Bjerstedt (1993) have described the trace fossils of the Theresa in detail and Skolithos can be located on the south wall of this quarry.

STOP 13. Keeseville ss of the Potsdam ss at the Gadway Preserve.
This stop requires driving in to the Gadway Preserve of the Adirondack Nature Conservancy and consists of three short STOPS within the STOP. Vehicles with low clearance should not attempt this and we will consolidate riders at the entrance.

STOP 13a. Large scale ripples
Continue west on the Gadway Road and stop and park at a bare rock rock wash. Carefully cross over a barbed wire fence to examine a pavement of large scale ripples in the Keeseville Sandstone.

STOP 13b.
Continue west on the Gadway Road and park at the next significant open area on the right/north. At the north end of the open area near a red posted sign there is a 4 meter long (10 cm wide) Protichnites track. Yochelson and Fedonkin (1993) illustrate several similar examples of this trace fossil in the Keeseville Sandstone of northern New York. Additional trace fossils can be seen near the Adirondack Nature Conservancy sign. Recent literature suggests that the trace fossil Protichnites may be the track of a eurypterid-like stem arthropod (Seilacher, 2007; Hagadorn and Seilacher, 2009) or by euthycarcinoid arthropods travelling in pairs (Collette and Hagadorn, 2010; Collette, et. al, 2012).

STOP 13c.
Park at the turn around loop. Walk about 100 paces beyond the turn-around loop and pass an arrow sign. On the left/south side of the road you can locate additional Protichnites tracks. One track is 1.4 meters long (11 cm wide) and some partial tracks cross over one another.

Bridge across Great Chazy River
Continue south on the Devil Den Road as it crosses the Great Chazy River. Just upstream from the bridge to the right/west is the McGregor Powerhouse, in Spanish architectural style, and the LaSalle Dam that were constructed by William H. Miner in 1923. Excellent exposures of the Keeseville Sandstone can be found on both sides of the river between the road bridge and the powerhouse.

STOP 14. Trough Cross Stratification in the Keeseville ss of the Potsdam ss
The trough cross stratification is located on the east side of the road, within what goes for a right of way. It is a small outcrop of well exposed cross stratification in the Keeseville Sandstone

Route 190, ‘the Military Turnpike’.
You will soon see one of the local wind farms set back on both sides of the road. These units feed their power to the nearby Power Authority of New York’s Duley, Altona, NY, substation.

Pass the historic Robinson Tavern on the left/east.
On the left/east side of the road you pass the overgrown ruins of Lewis Sage Robinson’s Tavern, erected in 1837. The opposite/west side of the road is the site of the Original Log Tavern erected in 1810. This 1810 tavern was visited by President James Madison in 1817.

STOP 15. Ausable Arkose of the Potsdam ss on the Military Turnpike.
Examples of the Altona Member of the Potsdam Sandstone can be found in and along the ditch from near the ‘Truck 0.5 Mile’ sign south to the near the bottom of the hill. The best exposures are toward the top of the hill. Grenville meta-anorthosite can be found just across the small drainage at the bottom of the hill.
The prominent hard reddish rock is a hematitic, micaceous quartzose dolostone. When highway crews clear the ditch it is also possible to see interbedded red shales; but, these tend to get grassed over in between ditch clearings.
About 2 miles/3.2 km east of here, SUNY Plattsburgh has a series of research hydrology wells on the William H. Miner Agricultural Research Institute’s Altona Flat Rock. One of these wells penetrated 235 feet of Altona Dolostone/Shale before entering the underlying Grenville meta-anorthosites and basalt dikes.

Pass the Rand Hill dikes on both sides of the road
Pass the Murtagh Hill Road on the right/west. Just south of the Murtagh Hill Road on both sides of Route 190 there are good exposures of Grenville meta-anorthosites that have been intruded by a series of diabase dikes, also of Grenville age, and locally known as the Rand Hill Dikes.

STOP 16. Crown Point ls with Lamprophyre Dikes
This extensive road cut along both sides of Route 374/Cadyville expressway contains two lamprophyre dikes on the south side of the road that intrude the Crown point Limestone with a strike of N70W and a dip 85 degrees N. Only the easternmost of the two dikes appears on the north side of the road. Interesting features, including baked zones, xenoliths and partial xenoliths, can be seen associated with the intrusions. The Crown Point Limestone is mainly a medium to dark gray calcilutite. Some of the large planispiral gastropod, Maculurites magnus Le Sueur are present along with trilobite and brachiopod fragments.