Collaborative Research: Permian-Triassic Mass Extinction in Antarctica

该奖项由极地计划办公室的南极地质和地球物理计划提供，支持对南极洲河流沉积物的跨学科研究，以寻找是什么导致了二叠纪-三叠纪界线生命历史上最大的大规模灭绝的证据。直到最近，这条界线还很难定位，而且在南极洲被认为是明确不整合的。新的研究，特别是碳同位素化学地层学和作为古生态系统指示的古土壤和根迹的研究，以及改进的植物化石、爬行动物和花粉生物地层学，现在表明可以确定边界的准确位置，并导致局部发现具有外星惰性气体的Ir异常、震荡石英和富勒烯。这些异常与一种独特的粘土角砾岩层有关，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。南极洲和其他地方已经有很多证据表明，陆地上的大规模灭绝是突然的，并且与海洋中的灭绝同步。现在的问题是，是什么导致了这种死亡和破坏。这些和其他二叠系-三叠系界线段的碳同位素值如此之低，很可能对甲烷笼状化合物的灾难性不稳定起到了一定作用。要从可能的储集层中提取出模拟的甲烷数量，需要发生像火流星撞击、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规模灭绝有关，而且有独立的证据。梳理这些不同的假设需要仔细地重新检查似乎代表二叠系-三叠系界线的地层，并寻找更有信息的层序，就像白垩纪-第三系界线的情况一样。这项关于边界层和古土壤的地球化学和岩石学(由Retallack进行)、碳同位素在边界区间的变化(由Jahren进行)以及富勒烯、Ir和He(由Becker进行)的合作研究旨在检验有关南极洲二叠纪-三叠纪边界的这些想法，并阐明导致地球上这一最大规模物种灭绝的过程。这项研究的实地工作将在横贯北极的中部山脉和维多利亚州南部进行，初步目标是检查跨越边界的地层层序的连续性。地层连续性是这项工作取得成功所必须存在的一个关键因素。如果实地调查表明切片足够连续，则完整的分析程序将在实地调查之后进行。

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.