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Scherr Formation
Stratigraphic range: Late Devonian
Typesedimentary
Unit ofGreenland Gap Group
Sub-unitsMinnehaha Springs Member
Underlies Foreknobs Formation
Overlies Brallier Formation
Thickness1,004 ft (306 m) at type section
Lithology
Primary Shale
Other Siltstone
Location
Region Appalachian Mountains
ExtentPennsylvania, Maryland, Virginia, West Virginia
Type section
Named for Scherr, West Virginia
Named byJ. M. Dennison, 1970

The Devonian Scherr Formation is a mapped bedrock unit in Pennsylvania, Maryland, Virginia and West Virginia.

Description

The Scherr Formation consists predominantly of siltstone and shale. Lower part of unit includes considerable fine-grained sandstone, while upper two thirds contains almost no sandstone. It weathers light olive gray. [1]

Stratigraphy

Dennison (1970) renamed the old Chemung Formation the Greenland Gap Group and divided it into the lower Scherr Formation and the upper Foreknobs Formation. De Witt (1974) extended the Scherr and Foreknobs into Pennsylvania but did not use the term Greenland Gap Group. [2]

Boswell et al. (1987), does not recognize the Scherr and Foreknobs Formations in the subsurface of West Virginia, and thus, these formations are reduced from "group" to "formation" as the Greenland Gap Formation. [3]

The Minnehaha Springs Member is a " clastic bundle" consisting of interbedded medium gray siltstone and olive-gray shale with some grayish-red siltstone and shale and some sandstone. It is interpreted as turbidites. [4] This same member is proposed to exist at the base of the Scherr's lateral equivalent, the Lock Haven Formation. [5]

Scherr Formation within a geological cross section of the United States

Notable outcrops

Age

Relative age dating places the Scherr in the late Devonian.

Paleontology

The Scherr Formation is the likely origin of the trace fossil Thinopus, which was described in 1896 by Othniel Charles Marsh as the earliest known tetrapod (land vertebrate). Later research, however, identified this fossil as coprolites (fossilized feces) of fishes. [6]

References

  1. ^ Dennison, J.M., 1970, Stratigraphic divisions of Upper Devonian Greenland Gap Group ("Chemung Formation") along Allegheny Front in West Virginia, Maryland, and Highland County, Virginia: Southeastern Geology, v. 12, no. 1, p. 53-82.
  2. ^ de Witt, Wallace, Jr., 1974, Geologic map of the Beans Cove and Hyndman quadrangles and part of the Fairhope quadrangle, Bedford County, Pennsylvania: U.S. Geological Survey Miscellaneous Investigations Series Map, I-801, 6 p., 1 sheet, scale 1:24,000
  3. ^ Boswell, R.M., Donaldson, A.C., and Lewis, J.S., 1987, Subsurface stratigraphy of the Upper Devonian and Lower Mississippian of northern West Virginia: Southeastern Geology, v. 28, no. 2, p. 105-131.
  4. ^ Lyke, W.L., 1986, The stratigraphy, paleogeography, depositional environment, faunal communities, and general petrology of the Minnehaha Springs Member of the Scherr Formation: Southeastern Geology, v. 26, no. 3, p. 173-192.
  5. ^ Warne, A.G., and McGhee, G.R., Jr., 1991, Stratigraphic subdivisions of the Upper Devonian Scherr, Foreknobs, and Lock Haven Formations near the Allegheny Front of central Pennsylvania: Northeastern Geology, v. 13, no. 2, p. 96-109.
  6. ^ Lucas, Spencer G. (2015). "Thinopus and a critical review of Devonian tetrapod footprints". Ichnos. 22 (3–4): 136–154. doi: 10.1080/10420940.2015.1063491. S2CID  130053031.



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