High Resolution Chronostratigraphic Constraints on Terminal Paleozoic Crises and Recovery in the Circum-Tethys Region

roland Mundil, Kenneth R. Ludwig, Paul R. renne本研究项目旨在通过三叠纪生物地层和磁地层时间尺度来改进晚二叠世的定标，以加强对古生代末期环境和生物危机以及随后的中生代复苏的认识。改进的时间尺度对于现实地评估这种转变特征的各种观测到的生物和古环境异常的原因和相互关系至关重要。我们最初的放射性同位素年龄数据（U/Pb和Ar/Ar）与最近的研究结果不一致，其中许多研究都认为是由核爆撞击引起的快速灭绝。尽管不能先验地排除在P-T边界或其附近的影响，但必须考虑二叠纪末中国南方和二叠纪-三叠纪边界的西伯利亚的大规模大陆玄武岩火山活动（可能结合其他因素）与生物危机之间更为渐进的情景和因果关系。尽管可获得的晚二叠世至早三叠世的地质年代学数据急剧增加，但仍有一些关键问题有待解决：1)二叠-三叠纪界线上的全球生物地层对比有多同步？生物地层、地球化学、岩石地层和其他记录的对比有多精确？2)二叠纪-三叠纪界线上陆地记录与海洋记录的时间关系如何？3)早三叠纪生物恢复的速率是多少？4)二叠纪-三叠纪边界高精度U/Pb锆石年龄之间的实验室间差异（物理差异或解释差异）是否破坏了推断出的极快灭绝事件年表？事实上，U/Pb锆石年代学作为显生宙时间尺度方法的可靠性如何？

ABSTRACTHigh Resolution Chronostratigraphic Constraints on Terminal Paleozoic Crises and Recovery in the Circum-Tethys RegionRoland Mundil, Kenneth R. Ludwig, Paul R. RenneThis research program is intended to improve the calibration of late Permian through Triassic biostratigraphic and magnetostratigraphic time scales towards an enhanced understanding of the terminal Paleozoic environmental and biotic crisis and subsequent Mesozoic recovery. Improved time scales are critical to realistic evaluation of the causes of, and interrelationships between, the various observed biotic and paleoenvironmental anomalies that characterize this transition. Our initial radio-isotopic age data (both U/Pb and Ar/Ar) are at variance with recent studies, many of which favor a rapid extinction caused by a bolide impact. Although an impact at or near the P-T boundary cannot be excluded a priori, a more gradual scenario and a causal relation between the massive continental basalt volcanism in South China at the end of the Permian and Siberia at the Permian-Triassic boundary - possibly in combination with other factors - and the biotic crisis must be considered. Despite the dramatic increase in available geochronologic data for the Late Permian through Early Triassic interval, crucial questions remain unanswered and will be addressed: 1) How synchronous are global biostratigraphic correlations across the Permo-Triassic boundary, and how precisely can biostratigraphic, geochemical, lithostratigraphic, and other records be correlated? 2) What are the temporal relations between terrestrial and marine records across the Permo-Triassic boundary? 3) What was the rate of the biotic recovery in the Early Triassic? 4) Do interlaboratory discrepancies (either physical or by interpretation) between high-precision U/Pb zircon ages for the Permo-Triassic boundary undermine the inferred extremely rapid chronology of extinction events? Indeed, how reliable is U/Pb zircon geochronology as a Phanerozoic time scale method?