220-7 Stratigraphy and Depositional Environments of the Mesaverde Formation in Central Wyoming: A Preliminary Review of Marine and Nonmarine Fossil Occurrences and Paleobiogeographic Affinities

Session: Life and Environments Through Time and Space: Multi-Record Approaches to Stratigraphic Paleobiology (Posters)

Poster Booth No.: 133

Presenting Author:

Blake Mautz

Authors:

Mautz, Blake Weston¹, Tenney, Zachary David², Currano, Ellen³, McElroy, Brandon⁴, Slattery, Joshua S.⁵

(1) University of Wyoming, Geology & Geophysics, Laramie, Wyoming, USA, (2) University of Wyoming, Department of Geology & Geophysics, Laramie, WY, USA, (3) University of Wyoming, Laramie, WY, USA, (4) University of Wyoming, Geology & Geophysics, Laramie, WY, USA, (5) University of Wyoming, Cheyenne, WY, USA,

Abstract:

Upper Cretaceous nonmarine faunas from the Western Interior of North America contain numerous extremely fossiliferous deposits which are commonly divided into northern (Montana/Alberta) and southern (Utah/New Mexico) regions based on their distinct and diverse taxonomic compositions. The Mesaverde Formation in central Wyoming preserves a diverse array of both marine and nonmarine fossil assemblages, providing a valuable opportunity to examine nonmarine fossil occurrences and test paleobiogeographic hypotheses of faunal mixing and/or ecological and physiographic barriers. However, improved geochronologic and lithostratigraphic correlation with other middle to late Campanian formations to the north (e.g., Foremost Formation, Judith River Formation) and south (e.g., Wahweap Formation) is required to conduct paleobiogeographic analyses. To accomplish this goal, we measured six lithostratigraphic sections through the Mesaverde Formation in the eastern Wind River and southwestern Powder River basins, examined the stratigraphic distribution of fossil localities, and conducted a preliminary faunal taxonomic review. 

In our study area, we identify three middle to late Campanian transgressive/regressive cycles of the Western Interior Seaway resulting in the deposition of six stratigraphic members of the Mesaverde Formation; the Fales Sandstone, Wallace Creek tongue, Parkman Sandstone, middle member, North Platte tongue, and Teapot Sandstone. New marine mollusk collections were sampled from the Parkman Sandstone, North Platte tongue, and overlying Lewis Shale, allowing for an improved chronostratigraphic framework to be developed based on the standard U.S. Western Interior ammonite biozonation. Nonmarine fossil localities are typically characterized by mixed taxonomically diverse microvertebrate and freshwater mollusk assemblages (e.g., Fales Rock/Barwin Quarry). These vertebrate assemblages contain an assortment of aquatic (Chondrichthyes, Osteichthyes, Crocodylia, Testudines) and terrestrial taxa (Dinosauria, Squamates, Lissamphibia, Mammalia). Based on our chronostratigraphic framework, the richest nonmarine fossil horizons are stratigraphically projected to be of similar age allowing for future research comparing coastal proximal-to-distal faunal gradients. Our preliminary faunal review suggests a mixed assemblage, with species exhibiting both northern and southern affinities. Continued paleontological prospecting and taxonomic refinement within the Mesaverde Formation is essential for a more comprehensive understanding of Campanian paleobiogeographic patterns and faunal provinces in the Western Interior.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9849

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