Doswell Formation

Doswell Formation
Stratigraphic range: Upper Triassic, early Carnian
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TypeFormation
Unit ofChatham Group
Sub-unitsStagg Creek Member, Vinita Member, Irishtown Member, Lahaska Creek Member
UnderliesStockton Formation
OverliesPetersburg Granite, Evangeline Formation
Thickness2,000 ft (610 m)
Location
RegionVirginia, Pennsylvania
Type section
Named forDoswell, Virginia
Named byRobert E. Weems

The Doswell Formation (also known as the Doswell Group) is a geologic unit of Upper Triassic age, part of the Newark Supergroup. The Doswell Formation was originally named to refer to a geological sequence which forms the lower part of the sedimentary fill of the Taylorsville Basin in Virginia and Maryland. This sequence was deposited by lakes and rivers in the developing rift basin.[1] A 2016 study argued that several geological layers in Pennsylvania as well as the neighboring Richmond Basin of Virginia also qualified as components of the Doswell Formation.[2]

The most diverse and fossiliferous component of the Doswell formation is the Vinita member, also sometimes known as the Turkey Branch, Tuckahoe, or Falling Creek Formations in earlier publications, and frequently referred to as the Vinita Formation by many authors. The Doswell formation is biostratigraphically characterized by a fauna including the fish Dictyopyge macrurus[3] and the conchostracan Laxitextella multireticulata.[4] The Richmond Basin has several notable fossil sites, such as the Tomahawk site which has hundreds of fossils from the cynodont Boreogomphodon,[5] and the Winterpock site which has an extraordinarily diverse assortment of plants.[3] The Taylorsville Basin is much more restricted in terms of fossil locales, but it was home to the unusual armored reptile Doswellia.[6]

The Doswell Formation is among the oldest Triassic formations on the east coast of the United States. It is believed to belong to the early Carnian (Cordevolian) age of the Triassic based on its fauna and flora,[4][2] which is distinctly dominated by tetrapods similar to gondwanan groups, as well as a high diversity of humidity-loving plants such as ferns and cycads. This gives it a distinct disconnect from the younger formations of the Newark Supergroup, which typically have a fauna similar to the Triassic formations of the western United States and a flora including elements such as conifer trees, which are better adapted for drier conditions.[3]

  1. ^ LeTourneau, P.M. (2003). "Stratigraphic Architecture and Paleomagnetic Reversal Stratigraphy of the Late Triassic Taylorsville Basin, Virginia and Maryland". In LeTourneau P.M. & Olsen P.E. (ed.). The Great Rift Valleys of Pangea in Eastern North America: Volume 2. Edinburgh University Press. ISBN 978-0-231-12676-2. Retrieved 24 November 2012.
  2. ^ a b Cite error: The named reference :2 was invoked but never defined (see the help page).
  3. ^ a b c Cite error: The named reference :1 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference Concho was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Tet1994 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference WRE80 was invoked but never defined (see the help page).