Sedimentary Dynamics and Biostratinomy of a Middle Cambrian Rusophycus Lagerstätte, Gros Ventre Formation, Wyoming, USA
Published:January 01, 2012
Jayme D. Csonka, Danita S. Brandt, 2012. "Sedimentary Dynamics and Biostratinomy of a Middle Cambrian Rusophycus Lagerstätte, Gros Ventre Formation, Wyoming, USA", Microbial Mats in Siliciclastic Depositional Systems Through Time, Nora Noffke, Henry Chafetz
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The Middle Cambrian Gros Ventre Formation (north-central Wyoming, USA) contains a lagerstätte of Rusophycus (arthropod ichnofossils) preserved in convex hyporelief on the base of sandstone beds or as sand lenses within beds of silty mudstone. Rusophycus was produced by typical trilobite behavior but was preserved only under the particular confluence of conditions that were common during the deposition of the Gros Ventre Formation. These conditions include the background deposition of firm, cohesive muds bound by bacterial mats, which allowed the burrows to maintain their shape until cast by episodic sand deposition. The absence of spreiten and presence of storm event bedding within sectioned Rusophycus specimens support this scenario and contradict previous assertions that Rusophycus was formed within the substrate. Chondrites were also present, extending its range into the Middle Cambrian. Bacterial mats and microbially induced sedimentary structures were present before, during, and after the deposition of the Gros Ventre Formation. Bioturbation indices are comparable to other Middle Cambrian sites, supporting a gradual increase of bioturbation intensity during the Agronomic and Cambrian Substrate Revolutions.
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Microbial Mats in Siliciclastic Depositional Systems Through Time
The research field on microbial mats in siliciclastic environmental settings has greatly developed since its establishment by studies of pioneering scientists such as Gisela Gerdes, Wolfgang Krumbein, Jürgen Scheiber, David Bottjer and others. This SEPM Special Publication is the result of the SEPM Research Conference on Sandy Microbial Mats (modern and ancient), which was held in May 21-23, 2010 at Dinosaur Ridge, Denver, Colorado, USA. This volume presents peer reviewed individual case studies on microbial mats and on sedimentary structures (often called “microbially induced sedimentary structures-MISS”) that occur in modern and ancient marine and terrestrial environments. The conference brought together sedimentologists, microbiologists, and paleontologists from 30 countries and all five continents.