High-Resolution Chronostratigraphic Constraints on the Biogeography of New Tetrapod Assemblages from Triassic Paleoequatorial Rift Basins of Southeastern North America

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The objective of this project is to develop a high-resolution chronologic, stratigraphic, and paleogeographic framework for the southernmost exposed Triassic rift basins in eastern North America, specifically the Deep River and Dan River basins and to a lesser extent, the Richmond, and Taylorsville basins. These basins comprise the only outcropping continental sequences constrained to have been in the equatorial zone of Triassic Pangea. The development of a precise spatiotemporal framework is prompted by the exciting discovery of unexpectedly rich, seemingly endemic tetrapod assemblages from these basins that suggest new interpretations of the pattern of Late Triassic faunal evolution. These faunules contain surprisingly large numbers of synapsids (dicynodonts, traversodonts, and advanced cynodonts) that differentiate these paleoequatorial assemblages from coeval ones of the more northern Triassic rifts, as well as those from the classic Chinle Group of the American Southwest. In addition, elements of these faunules provide conflicting biostratigraphic information requiring independent mechanisms for assessing their age and correlation. We propose to use paleomagnetic and cyclostratigraphic means to place these new and previously discovered assemblages into a tightly constrained paleogeographic and temporal framework correlated to the well-defined Newark Basin time scale developed through previous NSF-funded work. We anticipate that this project will have major implications for the rates and taxonomic and geographic patterns of Triassic terrestrial faunal change, as well as the character and consequences of the Triassic-Jurassic mass extinction.