Aquia Formation
Stratigraphic range: Late Paleocene
~
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.[1] It consists of clayey, silty, very shelly, glauconitic sand.[1] Fossil records indicate that this stratigraphic unit was created during the Paleocene.[1]

The Aquia formation was named for Aquia Creek where it is exposed in cliff faces along the banks.[2]

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.[3] It is between 0 and 100 feet thick in Maryland.[3] Quartz and phosphatic pebbles and/or very coarse glauconitic quartz sand mark the base of the unit.[4] 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.[4]

Stratigraphy

The Aquia formation is overlain by the Nanjemoy Formation and overlies the Brightseat Formation.[5]

The Aquia formation is broken down into two members: the lower Piscataway member and upper Paspotansa member.[2]

Age

The Aquia Formation is thought to be 59.0-55.5 million years old.[2] The Piscataway member is 59–56.25 million years old, and the Paspotansa member is 56–55.5 million years old.[2] This is the Paleocene period.

Older publications describe the Aquia as being of Eocene age.[6]

Fossils

Vertebrates

Bony fish

Chondrichthyes

Sharks
Rays

Reptiles

Crocodylians
Turtles

Mammals

Mammal fossils are extremely rare.[2]

Birds

Bird fossils are extremely rare.[2]

Molluscs

Gastropods

Bivalves

Cephalopods

  • Cimomia marylandensis is present but uncommon.[20]

See also

References

  1. 1 2 3 Geology of the National Capital Region - Field Trip Guidebook. Reston, Virginia: U.S. Geological Survey, Department of the Interior. 2004. p. 270.
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 Phatfossils Aquia Formation in Maryland and Virginia
  3. 1 2 "Coastal Plain Rocks and Sediments". Geological Maps of Maryland. Maryland Geological Survey. 1968. Retrieved 21 January 2015.
  4. 1 2 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. 1 2 3 4 5 6 7 8 9 10 11 "Fossil Identification for the Potomac River".
  9. 1 2 "Potomac - Aquia Formation 3/15/18".
  10. ↑ "Paleohypotodus?".
  11. ↑ "Physogaleus secundus".
  12. ↑ "Myliobatis".
  13. ↑ "Thecachampsa".
  14. ↑ "Trionyx".
  15. ↑ "Turritella sp".
  16. 1 2 3 4 5 6 7 8 9 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. 1 2 "Ostrea compressirostra".
  20. ↑ "Sanity check: It's a Nautilus, right?".
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