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Storm Deposited Fish Debris in the Cretaceous Mowry Shale Near Vernal, Utah
Utah Geological Association Publication (2005)
  • Alvin D Anderson
  • Bart J Kowallis, Brigham Young University - Provo

Isolated, lens-shaped accumulations of fi sh bones, scales, teeth, and coprolites in a sandy matrix occur along a few bedding planes within the Cretaceous Mowry Shale in an outcrop along Highway 191 north of Vernal, Utah. These accumulations have previously been interpreted to be large coprolites or regurgitate material, but are actually storm lag deposits in a sediment-starved basin. Accumulations (lenses) vary in size: the largest measured is 15 x 10 cm in plan view and 2 cm thick. Matrix in these lenses consist of fine-grained, well-rounded quartz grains that are absent in the surrounding shale layers. The disarticulated fossil material is the size of coarse sand, with some bone fragments and fish scales over 1 cm. The material is compacted, but poorly cemented. Jaw fragments, teeth, and vertebrae found within the lenses are mostly from teleost fish, commonly from the genus Enchodus, an alepisauroid. Teeth from Carcharias amonensis, a lamniform shark, are also present. Phosphatic pebbles (1-5 mm), which are likely teleost microcoprolites, are also found in these lenses. The lenses were deposited by bottom, winnowing storm currents and trapped in bottom scours in an area of limited coarse sediment supply on a gently sloping shelf.

  • Mowry Shale,
  • fish,
  • storm deposits,
  • Uinta Mountains
Publication Date
Citation Information
Alvin D Anderson and Bart J Kowallis. "Storm Deposited Fish Debris in the Cretaceous Mowry Shale Near Vernal, Utah" Utah Geological Association Publication Vol. 33 (2005)
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