Paleoecology of post-extinction fossil assemblages of the lower Triassic virgin limestone member in the Muddy Mountains, Southern Nevada : new insights into silicification of recovery faunas

Abstract

The Virgin Limestone of the Moenkopi Formation in the southwestern United States has proven key in understanding the marine invertebrate recovery during the latest Early Triassic (e.g., Schubert and Bottjer, 1995; Pruss and Bottjer, 2004; Marenco et al., 2012), but to date no studies have focused on its silicified fossils. A major goal of this work is to analyze the paleoecology of these silicified faunas through samples from Virgin Limestone exposures at two localities in Muddy Mountains, Nevada. A second goal is to gain insight into preservation biases associated with silicification by comparing the silicified fossil assemblages with results of point-count analyses of thin sections of the same samples, which show both silicified and non-silicified fossils. A third part of the study compares !13Ccarb isotope profiles from Muddy Mountains with !13Ccarb profiles of dated Lower Triassic carbonates from the Great Bank of Guizhou, China, from Payne et al. (2004), and estimates the age of the Virgin Limestone at Ute and Overton exposures to be around ~247.95 Ma to ~246.11 Ma