Patuxent Formation

The Patuxent Formation is a Cretaceous geologic formation of the Atlantic coastal plain.

Patuxent Formation Stratigraphic range: Aptian PreꞒ Ꞓ O S D C P T J K Pg N
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

The Patuxent formation was first described by W. B. 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

Propanoplosaurus, 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 Charles Seward.[5]

Pollen spores have been identified in the formation by G. J. Brenner (1963).[6]

Notable exposures

The type locality is the upper and lower valleys of the Little Patuxent River and Big Patuxent River in Maryland.

Economic value

The Patuxent is a notable aquifer in southern Maryland.[7]

Age

Biostratigraphic dating by Dorf (1952) confirmed Early Cretaceous (Neocomian) age.[4]

See also

• List of dinosaur-bearing rock formations
  • List of stratigraphic units with ornithischian tracks
    • Stegosaur tracks

Footnotes

1. Clark, W.B., 1897, Outline of present knowledge of the physical features of Maryland: Maryland Geological Survey Volume Series, v. 1, pt. 3, p. 172-188.
2. Ray Stanford, David B. Weishampel and Valerie B. Deleon (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. http://www.bioone.org/doi/abs/10.1666/10-113.1
3. Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607.
4. Dorf, Erling, 1952, Critical analysis of Cretaceous stratigraphy and paleobotany of the Atlantic Coastal Plain: American Association of Petroleum Geologists Bulletin, v. 36, no. 11, p. 2162-2184.
5. Seward, A. C., The Wealden Flora, 2 vols, 1894-95.
6. Brenner, Gilbert J., 1963, The spores and pollen of the Potomac Group of Maryland: Maryland Geological Survey Bulletin, no. 27, 215 p.
7. http://pubs.usgs.gov/of/2009/1088/ Curtin, S.E., Andreasen, D.C., and Staley, A.W., 2009, Potentiometric surface of the Patuxent aquifer in Southern Maryland, September 2007: U.S. Geological Survey Open-File Report 2009–1088, 1 map sheet.

References

• Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. 861 pp. ISBN 0-520-24209-2.