Anasibirites Bed Study

    A 5.25 square meter area on top of the Anasibirites Bed in the Triassic Thaynes Formation of West Central Utah was uncovered, photographed, and mapped.  Just the cephalopods that were fully exposed, and complete enough for orientation determination were mapped.  The area was excavated and photographed in October, 1997.  It was collected by me in September, 1998, and by others, both known, and unknown, since.  A small outcrop about 200m north of the mapped area provided samples for the cross section, the two units are easily correlated with the 20-50mm shale bed below the top section.


The top of the Anasibirites Bed during mapping

    The Anasibirites Beds are about 200 to 305 millimeters thick, and are packed with cephalopods.  Studies that could be done on the beds to find out why they accumulated include:
    The graphs on the stats page, come from the map, and show mostly information pertaining to the composition of the fauna and prefered orientation of the shells.  The cross section gives information on the faunal composition and thickness of the strata.

Map        Charts        Cross Section       Discussion   


Anasibirites Beds  Inyoites Beds  Meekoceras Beds

Studies that have been done trying to answer all the questions.  No end in sight?

Brayard, A., Bylund, K. G., Jenks, J., Stephen, D. A., Olivier, N., Escarguel, G., Fara, E. & Vennin, E., 2013. Smithian ammonoid faunas from Utah: implications for Early Triassic biostratigraphy, correlations and basinal paleogeography. Swiss Journal of Paleontology 132:141-219.

Daniel A. Stephen, Kevin G. Bylund, Paul J. Bybee and Wesley J. Ream, 2010, Ammonoid Beds in the Lower Triassic Thaynes Formation of western Utah, USA, in: Cephalopods Present and Past, edited by K. Tanabe, Y. Shigeta  and T. Sasaki & H. Hirano. Tokai UniversityPress, Tokyo, p. 243-252

Natural Outcrop

a natural outcrop showing ammonoids on top of the Anasibirites beds

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