The Devonian Scherr Formation is a mapped bedrock unit in Pennsylvania, Maryland, Virginia and West Virginia.
| Scherr Formation | |
|---|---|
| Stratigraphic range: Late Devonian | |
| Type | sedimentary |
| Unit of | Greenland Gap Group |
| Sub-units | Minnehaha Springs Member |
| Underlies | Foreknobs Formation |
| Overlies | Brallier Formation |
| Thickness | 1,004 ft (306 m) at type section |
| Lithology | |
| Primary | Shale |
| Other | Siltstone |
| Location | |
| Region | Appalachian Mountains |
| Extent | Pennsylvania, Maryland, Virginia, West Virginia |
| Type section | |
| Named for | Scherr, West Virginia |
| Named by | J. M. Dennison, 1970 |
Description
editThe 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
editDennison (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]
Notable outcrops
edit- Type section: along West Virginia Route 42, Grant County 39°11′45″N 79°10′48″W / 39.19583°N 79.18000°W
Age
editRelative age dating places the Scherr in the late Devonian.
Paleontology
editThe 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
edit- ^ 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.
- ^ 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
- ^ 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.
- ^ 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.
- ^ 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.
- ^ Lucas, Spencer G. (2015). "Thinopus and a critical review of Devonian tetrapod footprints". Ichnos. 22 (3–4): 136–154. Bibcode:2015Ichno..22..136L. doi:10.1080/10420940.2015.1063491. S2CID 130053031.
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