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

该项目的目标是为北美东部最南端暴露的三叠纪裂谷盆地，特别是深河和丹河盆地，以及较小程度上的里士满和泰勒斯维尔盆地，开发一个高分辨率的年代学、地层学和古地理框架。这些盆地构成了三叠纪泛大陆赤道带唯一的露头大陆层序。精确时空框架的发展是由这些盆地中意想不到的丰富的、看似地方性的四足动物组合的令人兴奋的发现推动的，这些发现为晚三叠纪动物进化模式提供了新的解释。这些断裂群包含了数量惊人的下齿目动物（双齿目、横齿目和先进的犬齿目），它们将这些古赤道组合与同期三叠纪北部裂谷的组合以及美国西南部经典的Chinle群区分开来。此外，这些断裂的元素提供了相互矛盾的生物地层信息，需要独立的机制来评估它们的年龄和相关性。我们建议使用古地磁和旋回地层学的方法，将这些新的和以前发现的组合放置到一个严格限制的古地理和时间框架中，该框架与通过以前nsf资助的工作开发的明确的纽瓦克盆地时间尺度相关。我们预计该项目将对三叠纪陆生动物变化的速率、分类学和地理格局以及三叠纪-侏罗纪大灭绝的特征和后果产生重大影响。

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.