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Aquia Formation

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Aquia Formation
Stratigraphic range: Late Paleocene
~59.0–55.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Boulder of Aquia Formation along Chester River. Contains casts of large mollusks. (c. 1917)
TypeGeological formation
Unit ofPamunkey Group
Sub-unitsPaspotansa & Piscataway Members
UnderliesNanjemoy Formation
OverliesBrightseat Formation
Thicknessup to 100 feet (30 m)
Lithology
PrimarySandstone
Location
LocationHopewell, Virginia
Coordinates38°18′N 77°18′W / 38.3°N 77.3°W / 38.3; -77.3
Approximate paleocoordinates39°00′N 58°54′W / 39.0°N 58.9°W / 39.0; -58.9
RegionMaryland, New Jersey, Virginia
Country United States
ExtentUpper Chesapeake Bay-James River
Type section
Named forAquia Creek
Thecachampsa crocodile coprolite from Aquia Formation, King George County, Virginia)

The Aquia Formation is a geologic sandstone formation that extends from the upper Chesapeake Bay to the James River near Hopewell, Virginia. It consists of clayey, silty, very shelly, glauconitic sand. Fossil records indicate that this stratigraphic unit was created during the Paleocene.

The Aquia formation was named for Aquia Creek where it is exposed in cliff faces along the banks.

Geology

Lithology

When uncovered, it appears dark green to gray-green, argillaceous, with well sorted fine- to medium-grained sand and locally indurated shell beds. It is between 0 and 100 feet thick in Maryland. Quartz and phosphatic pebbles and/or very coarse glauconitic quartz sand mark the base of the unit. A few hard streaks of shells or thin "rock" layers are often reported but appear to be more abundant in the sections south of the James River.

Stratigraphy

The Aquia formation is overlain by the Nanjemoy Formation and overlies the Brightseat Formation.

The Aquia formation is broken down into two members: the lower Piscataway member and upper Paspotansa member.

Age

The Aquia Formation is thought to be 59.0-55.5 million years old. The Piscataway member is 59–56.25 million years old, and the Paspotansa member is 56–55.5 million years old. This is the Paleocene period.

Older publications describe the Aquia as being of Eocene age.

Fossils

Vertebrates

Bony fish

Chondrichthyes

Sharks
Rays

Reptiles

Crocodylians
Turtles

Mammals

Mammal fossils are extremely rare.

Birds

Bird fossils are extremely rare.

Molluscs

Gastropods

  • Turritella is very common.
  • Pleurotoma potomacensis

Bivalves

Cephalopods

  • Cimomia marylandensis is present but uncommon.

See also

References

  1. ^ Geology of the National Capital Region - Field Trip Guidebook. Reston, Virginia: U.S. Geological Survey, Department of the Interior. 2004. p. 270.
  2. ^ Phatfossils Aquia Formation in Maryland and Virginia
  3. ^ "Coastal Plain Rocks and Sediments". Geological Maps of Maryland. Maryland Geological Survey. 1968. Retrieved 21 January 2015.
  4. ^ Powars, D.S.; Bruce, T.S. (2000). The Effects Of The Chesapeake Bay Impact Crater On The Geological Framework And Correlation Of Hydrogeologic Units Of The Lower York-James Peninsula, Virginia. United States Geological Survey. Retrieved 22 January 2015.
  5. Page, Richard A (1959). "The Questionable Age of the Aquia Formation". Journal of Paleontology. 33 (2): 347–350. JSTOR 1300764.
  6. Tolchester folio, Maryland, Folios of the Geologic Atlas 204, by B. L. Miller, E. B. Mathews, A. B. Bibbins, and H. P. Little, 1917.
  7. Elasmo.com, The Life and Times of Long Dead Sharks, Abdounia, Jim Bourdon, author.
  8. ^ "Fossil Identification for the Potomac River".
  9. ^ "Potomac - Aquia Formation 3/15/18".
  10. "Paleohypotodus?".
  11. "Physogaleus secundus".
  12. "Myliobatis".
  13. "Thecachampsa".
  14. "Trionyx".
  15. "Turritella sp".
  16. ^ Virginia Division of Mineral Resources (1912). Bulletin. p. 200. fossils of the aquia formation.
  17. "Cucullaea Gigantea". 15 May 2010.
  18. "Views of the Mahantango: Cucullaea gigantea pelecypod from the Aquia Formation". 11 August 2014.
  19. ^ "Ostrea compressirostra".
  20. "Sanity check: It's a Nautilus, right?".
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