Collaborative Research: Permian-Triassic Mass Extinction in Antarctica

该奖项由极地方案办公室南极地质和地球物理方案提供，支持对南极洲河流沉积物进行跨学科研究，以证明是什么导致了二叠纪-三叠纪边界生命史上最大的大规模灭绝。直到最近，这一边界还很难确定，而且在南极洲被认为是明显不整合的。新的研究，特别是碳同位素化学地层学和古土壤和根痕迹作为古生态系统的指标，加上改进的植物化石，爬行动物和花粉生物地层学，现在表明，边界的精确位置可能被确定，并导致当地发现铱异常，冲击石英和富勒烯与外星惰性气体。这些异常与一个独特的粘土岩角砾岩层有关，类似于南非和澳大利亚已知的地层，并被视为森林砍伐的证据。来自南极洲和其他地方的大量证据表明，陆地上的大规模灭绝是突然的，与海洋中的灭绝同步。现在的问题是什么导致了这样的死亡和破坏。碳同位素值是如此之低，在这些和其他二叠纪-三叠纪的边界部分，有可能是一些灾难性的甲烷笼形物的不稳定的作用。要从可能的储层中获得模拟的甲烷量，需要像火流星撞击、洪水玄武岩喷发或大陆架坍塌这样的灾难性事件，这些事件都独立地与大灭绝有关，并且有独立的证据。要把这些不同的假设分开，就需要仔细地重新检查那些似乎代表着二叠纪-三叠纪界线的岩层，并寻找更多的信息序列，就像寻找白垩纪-第三纪界线的情况一样。这一关于边界层和古土壤的地球化学和岩相学（Retallack）、边界层间的碳同位素变化（Jahren）以及富勒烯、铱和氦（Becker）的合作研究旨在检验这些关于南极洲二叠纪-三叠纪边界的想法，并阐明促成地球上这一最大规模沉积的过程。本研究的野外工作将在中部跨南极山脉和南部维多利亚地进行，其初步目标是检查跨边界地层序列的连续性。地层连续性是工作取得成功必须具备的一个关键要素。如果现场工作表明有足够连续的剖面，则将在现场工作之后进行完整的分析程序。

This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports an interdisciplinary study of fluvial sediments in Antarctica for evidence of what caused the greatest of all mass extinctions in the history of life at the Permian-Triassic boundary. This boundary was, until recently, difficult to locate and thought to be unequivocally disconformable in Antarctica. New studies, particularly of carbon isotopic chemostratigraphy and of paleosols and root traces as paleoecosystem indicators, together with improved fossil plant, reptile and pollen biostratigraphy, now suggest that the precise location of the boundary might be identified and have led to local discovery of iridium anomalies, shocked quartz, and fullerenes with extraterrestrial noble gases. These anomalies are associated with a distinctive claystone breccia bed, similar to strata known in South Africa and Australia, and taken as evidence of deforestation. There is already much evidence from Antarctica and elsewhere that the mass extinction on land was abrupt and synchronous with extinction in the ocean. The problem now is what led to such death and destruction. Carbon isotopic values are so low in these and other Permian-Triassic boundary sections that there was likely to have been some role for catastrophic destabilization of methane clathrates. Getting the modeled amount of methane out of likely reservoirs would require such catastrophic events as bolide impact, flood-basalt eruption or continental-shelf collapse, which have all independently been implicated in the mass extinction and for which there is independent evidence. Teasing apart these various hypotheses requires careful re-examination of beds that appear to represent the Permian-Triassic boundary, and search for more informative sequences, as was the case for the Cretaceous-Tertiary boundary. This collaborative research on geochemistry and petrography of boundary beds and paleosols (by Retallack), on carbon isotopic variation through the boundary interval (by Jahren), and on fullerenes, iridium and helium (by Becker) is designed to test these ideas about the Permian-Triassic boundary in Antarctica and to shed light on processes which contributed to this largest of mass extinctions on Earth. Fieldwork for this research will be conducted in the central Transantarctic Mountains and in Southern Victoria Land with an initial objective of examining the stratigraphic sequences for continuity across the boundary. Stratigraphic continuity is a critical element that must exist for the work to be successful. If fieldwork indicates sufficiently continuous sections, the full analytical program will follow fieldwork.