The Helderberg Group at Schoharie, NY

     The strata of the Lower Devonian are exposed in New York State in a narrow band extending from Port Jervis to the Helderberg Mountains southwest of Albany and then westward to Syracuse.  The carbonate-rich sediments that became these rocks were deposited in shallow warms seas.  The limestones and calcareous shales of the Helderberg Group are especially accessible for study at a roadcut on Rickard Hill Road east of Schoharie, Schoharie County, NY.   The formations of the Helderberg Group exposed at this location are the Coeymans, Kalkberg, and Becraft Formations.

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Stratigraphy of the lower Helderberg Group in eastern and central New York (modified from Ebert and Matteson, 2003).  OF, Oriskany Falls; CV, Cherry Valley; Sch, Schoharie; C, Catskill; K, Kingston.  HCU, Howe Cave Unconformity; PKU, Punch Kill Unconformity.

   The lowest and oldest layer, the Coeymans Formation, is exposed in a short roadcut near the base of the hill.  It is a medium to coarse grained massively bedded limestone thought to represent deposition in shallow water above the normal wave base.  While fossils are relatively abundant, the roadcut is relatively fresh and the stone very resistant, making collecting difficult.

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Rickard Hill Road, upper roadcut (south side).  The lighter colored layer in this fresh cut, B, is the Becraft Formation; the lower darker layer, K, the Kalkberg Formation.

    The younger Kalkberg and Becraft Formations are exposed in the longer cut higher up Rickard Hill Road.  The roadcut on the south side of the road is quite new, and offers few collecting opportunities.  However, the cut on the north side of the road is older, and numerous fossils can be found weathered out in the talus and scree. 

    The Becraft Formation is exposed in the top half of the site in both the rock wall and in the weathered talus.  It is a coarse-grained massively bedded limestone that presumably represents a depositional environment similar to that of the Coeymans Formation.  The Becraft is a highly resistant layer that forms the prominent cliffs on the hill surrounding Schoharie.   Grabau (1906) lists the following fauna from the Becraft at Schoharie: 2 crinoid species, 11 brachiopods, 1 pteropod, 1 pelecypod, and 9 gastropods.  The Becraft rests unconformably above the Kalkberg, separated by a thin layer of bentonite, an altered volcanic ash.  This contact is evident in sections where the less resistant bentonite is weatthered away to form a rentrant in the cliff face. 

    The Kalkberg is a thin to medium bedded, fine to medium grained limestone with shaley layers.  It is thought to represent deposition in well agitated deeper waters at or near the normal wave base.  The Kalkberg is highly fossiliferous.  Grabau (1906) lists 115 species in the "New Scotland beds" at Schoharie. These include 4 coral species, 2 conularia, 6 bryozoa, 8 crinoids, 38 brachiopods, 28 gastropods, 15 pelecypods, 4 cephalopods, and 9 trilobites. [Grabau did not differentiate the Kalberg and New Scotland Formations, considering both as the "New Scotland beds".  Ebert and Matteson (2003) have recently shown that the New Scotland Formation is absent at Schoharie (see stratigraphic diagram above).]

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Rickard Hill Road, upper roadcut (north side).  Looking at the right side of this picture, the cliff is composed primarily of the Becraft, while the Kalkberg is exposed in the shallow slope.

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Contact between the Kalkberg Formation (K) and the Becraft Formation (B) at Rickard Hill Road.  The arrow indicates the position of the thin bentonite layer (altered volcanic ash) separating B and K.

Representative fossils from the Becraft and Kalkberg Formations can be seen by clicking on the links below:

Fossils of the Becraft Formation
Fossils of the Kalkberg Formation

Acknowledgement:  My special thanks to Erich Rose, Field Guide Editor of the New York Paleontological Society, for telling me about this site, and serving as a guide on one visit there.

References:
Ebert, J.R., & Matteson, D.K. (2003) Grabau's "Transition Beds" - Key Elements in a Radical Revision of Helderberg Stratigraphy".  New York State Geological Association, 2003 Meeting, Field Trip Guidebook.

Goldring, W. (1935) Geology of the Berne Quadrangle.

Grabau, A.W. (1906) Geology and Paleontology of the Schoharie Valley.  New York State Department (NYS Museum) Bulletin No. 92, Albany, NY.

Rose, Erich (2002) "Schoharie" Geology and Paleontology of the Lower Devonian.  NY Plaeontological Society Fall Field Trip Guide, Oct. 26, 2002.


Web Resources:

Rickard Hill Road, Schoharie Lab Project - From Dr. James Ebert at SUNY at Oneonta

 

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Page last revised Feb. 4, 2009