The Patuxent Formation is a Cretaceous geologic formation of the Atlantic coastal plain.
| Patuxent Formation | |
|---|---|
| Stratigraphic range: | |
 . View at School House Hill, Baltimore County, Maryland showing the Patuxent Formation overlain by the Arundel Formation | |
| Type | Sedimentary |
| Unit of | Potomac Group |
| Underlies | Arundel Formation |
| Overlies | Basement |
| Thickness | up to 250 feet (80 m) |
| Lithology | |
| Primary | Sand, Gravel |
| Other | Clay |
| Location | |
| Region | Atlantic coastal plain |
| Country | U.S.A. |
| Extent | Maryland, Washington D. C., Delaware, Virginia |
| Type section | |
| Named for | Patuxent River |
| Named by | W. B. Clark, 1897[1] |
Description
editThe Patuxent formation was first described by William Bullock Clark in 1897.[1] The formation is primarily unconsolidated white-grey or orange-brown sand and gravel, with minor clay and silt. The sand often contains kaolinized feldspar, making it an arkose. Clay lumps are common, and sand beds gradually transition to clay. Sandy beds may be crossbedded, which is evidence of shallow water origin.
The Patuxent is the basal unit of the Coastal Plain sedimentary formations and unconformably overlies the crystalline basement rocks. This underlying unconformity is the subsurface equivalent of the Atlantic Seaboard Fall Line.
Fossils
editPropanoplosaurus, a nodosaurid known from a single natural cast and mold of a hatchling, was found recovered from rocks belonging to the Patuxent Formation in Maryland.[2]
Fossil stegosaur tracks have been reported from the formation.[3]
E. Dorf (1952)[4] compared the flora identified in the Patuxent to that of the Wealden Flora in England studied by Albert Seward.[5]
Pollen spores have been identified in the formation by G. J. Brenner (1963).[6][7]
Notable exposures
editThe type locality is the upper and lower valleys of the Little Patuxent River and Big Patuxent River in Maryland.
Economic value
editAge
editBiostratigraphic dating by Dorf (1952) confirmed Early Cretaceous (Neocomian) age.[4]
See also
edit
Footnotes
edit- ^ a b Clark, W.B. (1897). Outline of present knowledge of the physical features of Maryland (Report). Volume Series. Vol. 1. Maryland Geological Survey. pp. 172–188.
- ^ Stanford, Ray; Weishampel, David B.; Deleon, Valerie B. (2011). "The First Hatchling Dinosaur Reported from the Eastern United States: Propanoplosaurus marylandicus (Dinosauria: Ankylosauria) from the Early Cretaceous of Maryland, U.S.A." Journal of Paleontology. 85 (5): 916–924. doi:10.1666/10-113.1.
- ^ Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
- ^ a b Dorf, Erling (1952-11-01). "Critical Analysis of Cretaceous Stratigraphy and Paleobotany of Atlantic Coastal Plain". American Association of Petroleum Geologists Bulletin. 36 (11): 2161–2184. doi:10.1306/5CEADBC6-16BB-11D7-8645000102C1865D.
- ^ Seward, A. C., The Wealden Flora, 2 vols, 1894-95.
- ^ Brenner, Gilbert J. (1963). "The spores and pollen of the Potomac Group of Maryland" (PDF). Maryland Geological Survey Bulletin. 27: 215.
- ^ Brenner, Gilbert J. (1963-02-21). The Spores and Pollen of the Potomac Group of Maryland. Science. Vol. 143, no. 3608. p. 795. doi:10.1126/science.143.3608.795.a.
- ^ Curtin, Stephen E.; Andreasen, David C.; Staley, Andrew W. (2009). Potentiometric surface of the Patuxent aquifer in Southern Maryland, September 2007 (Map). U.S. Geological Survey Open-File Report. U.S. Geological Survey.
References
edit- Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.
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