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

该项目的目标是建立北美东部最南端的三叠纪裂谷盆地的高分辨率年代学、地层学和古地理框架，特别是深河和丹河盆地，以及较小程度的里士满和泰勒斯维尔盆地。这些盆地构成了被限制在三叠纪联合古陆赤道带的唯一露头大陆层序。这些盆地出人意料地发现了出人意料的丰富、看似特有的四足动物组合，这对晚三叠世动物群演化模式提出了新的解释，推动了精确时空框架的发展。这些动物群含有数量惊人的突触体(双齿类、穿越类和高级类)，这些突触体将这些古赤道组合与更北部的三叠纪裂谷的同时代组合以及美国西南部经典的钦勒群的突触区分开来。此外，这些动物群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方法，将这些新发现的和以前发现的组合置于一个严格限制的古地理和时间框架中，该框架与通过先前NSF资助的工作开发的明确定义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地动物群变化的速率、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.