There is a long-standing controversy of what triggered the extinction at the Permian-Triassic boundary, the most severe mass extinction in the geologic record, including flood basaltic volcanism and/or bolide impact h...There is a long-standing controversy of what triggered the extinction at the Permian-Triassic boundary, the most severe mass extinction in the geologic record, including flood basaltic volcanism and/or bolide impact hypothesis. In order to clarify various pieces of evidence for the mass extinction event at the Permian-Triassic boundary, some researchers from some laboratories throughout the world have made a comprehensive study on a group of samples from the Meishan area of China. Some fresh core samples from the Permian-Triassic boundary in the Meishan area were analyzed in this study. The results showed that there is no Ir anomaly. Moreover, the PGEs patterns of those samples show obvious differentiation characteristics, that is different from the case encountered in meteorites. So no evidence supports the hypothesis of extraterrestrial impact. In contrast, the PGEs patterns are similar to those of Siberian and Emeishan basalts, which indicates that those PGEs are derived mainly from the basalts, lending a support to the correlation between mass extinction at the Permian-Triassic boundary and flood basaltic volcanism. This study has also confirmed the results for samples from section C prior to the analysis of the samples.展开更多
When gigantic meteorite impact sites in Southern Africa are plotted on the geological map of the region, they overlap with the SW-NE fault lines and it indicates that meteorite impacts have contributed to the geologic...When gigantic meteorite impact sites in Southern Africa are plotted on the geological map of the region, they overlap with the SW-NE fault lines and it indicates that meteorite impacts have contributed to the geological structure of the region. The Morokweng Meteorite Impact of 145 Ma （Million years ago）, at the J/K （Jurassic/Cretaceous） boundary, seems to have broken up the Gondwanaland. It is plausible that, at the time of continental break-up, seawater poured into Morokweng crater and ignited a gigantic volcanic eruption which delivered low viscose magma into the outer space to form the Moon. An extremely flat surface of the Megakalahari extending 3,800,000 sq. km at 800-1,200 m above sea level in the central and southern Africa seems to be the terrestrial residue of fluid magma at the end of the volcanic event.展开更多
Section Z of Meishan in Changxing of Zhejiang, known as the stratotype section of the Permain-Triassic boundary in South China, is also one of the candidate stratotype sections of the same boundary in the world. Here ...Section Z of Meishan in Changxing of Zhejiang, known as the stratotype section of the Permain-Triassic boundary in South China, is also one of the candidate stratotype sections of the same boundary in the world. Here the strata crossing the Permian-Triassic boundary are well exposed. The Upper Permian Changhsingian is展开更多
Ocean anoxia has been widely implicated in the Permian-Triassic extinction. However, the duration and distribution of the ocean anoxia remains controversial. In this study, the detailed redox changes across the Permia...Ocean anoxia has been widely implicated in the Permian-Triassic extinction. However, the duration and distribution of the ocean anoxia remains controversial. In this study, the detailed redox changes across the Permian-Triassic boundary （PTB） in the shallow platform interior at Great Bank of Guizhou （GBG） has been reconstructed based on the high-resolution microfossil composition and multiple paleo-redox proxies. The shallow platform is characterized by low sulfur （total sulfur （TS） and pyrite sulfur （Spy）） concentrations, low Spy/TOC ratios, and low DOP values before the mass extinction, representing oxic conditions well. Following the mass extinction, the shift of multiple geochemical proxies, including high Spy/TOC ratios and DOP values, indicates dysoxic-anoxic conditions in shallow ocean. Furthermore, we reconstruct the transition of the redox conditions of Nanpanjiang Basin： the intense volcanic eruptions, which release huge COz and SO2 before the mass extinction, provoke the temperature rising and the collapse of terrestrial ecosystem. As a result, the increased weathering influx causes the carbon iso- topic negative excursion and the expansion of the ocean oxygen minimum zone （OMZ）. When the OMZ expanded into the photic zone, the episodic H2S release events enhance the pyrite burial at Dajiang section. Thus, intense volcanic eruptions, temperature increase, and oceanic hypoxia together lead to the PTB extinction. Recent studies show high temperature might be the key mechanism of the PTB extinction. In addition, this study confirms that the microbialites were formed in the dysoxic- anoxic shallow water.展开更多
基金financially supported by the National Natural Science Foundation of China (No. 41073053)
文摘There is a long-standing controversy of what triggered the extinction at the Permian-Triassic boundary, the most severe mass extinction in the geologic record, including flood basaltic volcanism and/or bolide impact hypothesis. In order to clarify various pieces of evidence for the mass extinction event at the Permian-Triassic boundary, some researchers from some laboratories throughout the world have made a comprehensive study on a group of samples from the Meishan area of China. Some fresh core samples from the Permian-Triassic boundary in the Meishan area were analyzed in this study. The results showed that there is no Ir anomaly. Moreover, the PGEs patterns of those samples show obvious differentiation characteristics, that is different from the case encountered in meteorites. So no evidence supports the hypothesis of extraterrestrial impact. In contrast, the PGEs patterns are similar to those of Siberian and Emeishan basalts, which indicates that those PGEs are derived mainly from the basalts, lending a support to the correlation between mass extinction at the Permian-Triassic boundary and flood basaltic volcanism. This study has also confirmed the results for samples from section C prior to the analysis of the samples.
文摘When gigantic meteorite impact sites in Southern Africa are plotted on the geological map of the region, they overlap with the SW-NE fault lines and it indicates that meteorite impacts have contributed to the geological structure of the region. The Morokweng Meteorite Impact of 145 Ma （Million years ago）, at the J/K （Jurassic/Cretaceous） boundary, seems to have broken up the Gondwanaland. It is plausible that, at the time of continental break-up, seawater poured into Morokweng crater and ignited a gigantic volcanic eruption which delivered low viscose magma into the outer space to form the Moon. An extremely flat surface of the Megakalahari extending 3,800,000 sq. km at 800-1,200 m above sea level in the central and southern Africa seems to be the terrestrial residue of fluid magma at the end of the volcanic event.
基金Project partly supported by the National Natural Science Foundation of China.
文摘Section Z of Meishan in Changxing of Zhejiang, known as the stratotype section of the Permain-Triassic boundary in South China, is also one of the candidate stratotype sections of the same boundary in the world. Here the strata crossing the Permian-Triassic boundary are well exposed. The Upper Permian Changhsingian is
基金supported by National Basic Research Program of China (Grant No. 2011CB808800)National Natural Science Foundation of China (Grant Nos. 41172312, 41272372, 41172036, 41240016, 41302271)+1 种基金Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan)Fund of State Key Laboratory of Biogeology and Environmental Geology (Grant No. BGEG1016)
文摘Ocean anoxia has been widely implicated in the Permian-Triassic extinction. However, the duration and distribution of the ocean anoxia remains controversial. In this study, the detailed redox changes across the Permian-Triassic boundary （PTB） in the shallow platform interior at Great Bank of Guizhou （GBG） has been reconstructed based on the high-resolution microfossil composition and multiple paleo-redox proxies. The shallow platform is characterized by low sulfur （total sulfur （TS） and pyrite sulfur （Spy）） concentrations, low Spy/TOC ratios, and low DOP values before the mass extinction, representing oxic conditions well. Following the mass extinction, the shift of multiple geochemical proxies, including high Spy/TOC ratios and DOP values, indicates dysoxic-anoxic conditions in shallow ocean. Furthermore, we reconstruct the transition of the redox conditions of Nanpanjiang Basin： the intense volcanic eruptions, which release huge COz and SO2 before the mass extinction, provoke the temperature rising and the collapse of terrestrial ecosystem. As a result, the increased weathering influx causes the carbon iso- topic negative excursion and the expansion of the ocean oxygen minimum zone （OMZ）. When the OMZ expanded into the photic zone, the episodic H2S release events enhance the pyrite burial at Dajiang section. Thus, intense volcanic eruptions, temperature increase, and oceanic hypoxia together lead to the PTB extinction. Recent studies show high temperature might be the key mechanism of the PTB extinction. In addition, this study confirms that the microbialites were formed in the dysoxic- anoxic shallow water.
