The Middle Triassic records the return of diverse marine communities after the severe effects of the end-Permian mass extinction.This diversification leads to the Mesozoic/modern adaptive radiation resulting in substantial changes in marine communities in comparison to their Paleozoic predecessors.This analysis focuses on the faunal abundance,ecological patterns,and environmental interpretation of a Middle Triassic section in Central Nevada.Twelve bulk samples were collected.Visible fossils were identified and tallied from hand samples and thin-sections were used to aid in environmental interpretation.Beginning in the Late Anisian,we observed an ammonoid dominated to flat-clam,epifaunal dominated benthic community within a muddy,quiet,inner shelf depositional environment.Through time,epifaunal bivalves dominate within a middle shelf environment followed by an increase in infaunalization and shell-thickness.During this time the presence of oncoids and the reported finding of corals suggest the middle shelf environment gave way to a higher energy patch reef shelf edge environment.Finally,we observe epifaunal brachiopods communities at the top of our section deposited in a middle shelf environment.In sum,we observe the dominance of modern taxa(i.e.,bivalves)with Paleozoic ecologies(i.e.,epifaunal),followed by the dominance of modern taxa with Modern ecologies(i.e.,infaunal,thick shells)and then a return to Paleozoic taxa(i.e.,brachiopods)and Paleozoic ecologies within an overall transgressive environment.
展开▼
