A deeper understanding of hyperthermal events in the Earth’s history can provide an important scientific basis for understanding and coping with global warming in the Anthropocene. Two types of hyperthermal events ar...A deeper understanding of hyperthermal events in the Earth’s history can provide an important scientific basis for understanding and coping with global warming in the Anthropocene. Two types of hyperthermal events are classified based on the characteristics of the carbon isotope excursion(CIE) of the five representative hyperthermal events in the Mesozoic and Cenozoic. The first type is overall characterized by negative CIEs(NCHE) and represented by the Permian-Triassic boundary event(PTB, ~252 Ma), the early Toarcian oceanic anoxic event(TOAE, ~183 Ma), and the Paleocene-Eocene Thermal Maximum event(PETM, ~56 Ma). The second type is overall characterized by positive CIEs(PCHE) and represented by the early Aptian oceanic anoxic event(OAE1 a, ~120 Ma) and the latest Cenomanian oceanic anoxic event(OAE2, ~94 Ma).Hyperthermal events of negative CIEs(NCHE), lead to dramatic changes in temperature, sedimentation, and biodiversity. These events caused frequent occurrence of terrestrial wildfires, extreme droughts, acid rain, destruction of ozone layer, metal poisoning(such as mercury), changes in terrestrial water system, and carbonate platform demise, ocean acidification, ocean anoxia in marine settings, and various degree extinction of terrestrial and marine life, especially in shallow marine. In contrast,hyperthermal events of positive CIEs(PCHE), result in rapid warming of seawater and widespread oceanic anoxia, large-scale burial of organic matter and associated black shale deposition, which exerted more significant impacts on deep-water marine life,but little impacts on shallow sea and terrestrial life. While PCHEs were triggered by volcanism associated with LIPs in deep-sea environment, the released heat and nutrient were buffered by seawater due to their eruption in the deep sea, thus exerted more significant impacts on deep-marine biota than on shallow marine and terrestrial biota. This work enriches the study of hyperthermal events in geological history, not only for the understanding of hyperthermal events themselves, large igneous provinces, marine and terrestrial environment changes, mass extinctions, but also for providing a new method to identify the types of hyperthermal events and the inference of their driving mechanism based on the characteristics of carbon isotopic excursions and geological records.展开更多
Although Paleogene warm climatic intervals have received considerable attention for atmospheric and oceanographic changes,the authigenic mineralization associated with these time spans remains overlooked.An extensive ...Although Paleogene warm climatic intervals have received considerable attention for atmospheric and oceanographic changes,the authigenic mineralization associated with these time spans remains overlooked.An extensive review of the literature reveals a close correspondence between the high abundance of glauconite and warm climatic intervals during the Paleogene period.The abundance of phosphorite,ironstone,lignite and black shale deposits reveals similar trends.Although investigated thoroughly,the origin of these authigenic deposits is never understood in the background of Paleogene warming climatic intervals.A combination of factors like warm seawater,hypoxic shelf,low rate of sedimentation,and enhanced rate of continental weathering facilitated the glauconitization.The last factor caused the excess supply of nutrients,including Fe,Si,K,Mg and Al through the rivers,the cations needed for the formation of glauconite.The excessive inflow of nutrient-rich freshwater into the shallow seas further ensured high organic productivity and stratification in shallow shelves,causing hypoxia.The consequent rapid rise in sea-level during the warm periods created extensive low-relief shallow marine shelves starved in sediments.Oxygen-deficiency in the shallow marine environment facilitated the fixation of Fe into the glauconite structure.The inflow of nutrient-rich water during the warm climatic intervals facilitated the formation of phosphorite,ironstone,and organic-matter-rich sedimentary deposits as well.Although global factors primarily controlled the formation of these authigenic deposits,local factors played significant roles in some of the deposits.Therefore,phosphorites formed in marine conditions with open circulation within the tropical zone.While lush growth of rainforest covers in the tropical belt facilitated the formation of coastal lignite.展开更多
基金financially supported by the National Natural Science Foundation of China (Grant No. 41888101)National Natural Science Fund for Distinguished Young Scholars (Grant No. 41525007)。
文摘A deeper understanding of hyperthermal events in the Earth’s history can provide an important scientific basis for understanding and coping with global warming in the Anthropocene. Two types of hyperthermal events are classified based on the characteristics of the carbon isotope excursion(CIE) of the five representative hyperthermal events in the Mesozoic and Cenozoic. The first type is overall characterized by negative CIEs(NCHE) and represented by the Permian-Triassic boundary event(PTB, ~252 Ma), the early Toarcian oceanic anoxic event(TOAE, ~183 Ma), and the Paleocene-Eocene Thermal Maximum event(PETM, ~56 Ma). The second type is overall characterized by positive CIEs(PCHE) and represented by the early Aptian oceanic anoxic event(OAE1 a, ~120 Ma) and the latest Cenomanian oceanic anoxic event(OAE2, ~94 Ma).Hyperthermal events of negative CIEs(NCHE), lead to dramatic changes in temperature, sedimentation, and biodiversity. These events caused frequent occurrence of terrestrial wildfires, extreme droughts, acid rain, destruction of ozone layer, metal poisoning(such as mercury), changes in terrestrial water system, and carbonate platform demise, ocean acidification, ocean anoxia in marine settings, and various degree extinction of terrestrial and marine life, especially in shallow marine. In contrast,hyperthermal events of positive CIEs(PCHE), result in rapid warming of seawater and widespread oceanic anoxia, large-scale burial of organic matter and associated black shale deposition, which exerted more significant impacts on deep-water marine life,but little impacts on shallow sea and terrestrial life. While PCHEs were triggered by volcanism associated with LIPs in deep-sea environment, the released heat and nutrient were buffered by seawater due to their eruption in the deep sea, thus exerted more significant impacts on deep-marine biota than on shallow marine and terrestrial biota. This work enriches the study of hyperthermal events in geological history, not only for the understanding of hyperthermal events themselves, large igneous provinces, marine and terrestrial environment changes, mass extinctions, but also for providing a new method to identify the types of hyperthermal events and the inference of their driving mechanism based on the characteristics of carbon isotopic excursions and geological records.
基金SB is thankful to Ministry of Mines,Government of India for financial support through grant F No.14/77/2015-MetIV.TRC is thankful to Council of Scientific and Industrial Research,India for the financial support.
文摘Although Paleogene warm climatic intervals have received considerable attention for atmospheric and oceanographic changes,the authigenic mineralization associated with these time spans remains overlooked.An extensive review of the literature reveals a close correspondence between the high abundance of glauconite and warm climatic intervals during the Paleogene period.The abundance of phosphorite,ironstone,lignite and black shale deposits reveals similar trends.Although investigated thoroughly,the origin of these authigenic deposits is never understood in the background of Paleogene warming climatic intervals.A combination of factors like warm seawater,hypoxic shelf,low rate of sedimentation,and enhanced rate of continental weathering facilitated the glauconitization.The last factor caused the excess supply of nutrients,including Fe,Si,K,Mg and Al through the rivers,the cations needed for the formation of glauconite.The excessive inflow of nutrient-rich freshwater into the shallow seas further ensured high organic productivity and stratification in shallow shelves,causing hypoxia.The consequent rapid rise in sea-level during the warm periods created extensive low-relief shallow marine shelves starved in sediments.Oxygen-deficiency in the shallow marine environment facilitated the fixation of Fe into the glauconite structure.The inflow of nutrient-rich water during the warm climatic intervals facilitated the formation of phosphorite,ironstone,and organic-matter-rich sedimentary deposits as well.Although global factors primarily controlled the formation of these authigenic deposits,local factors played significant roles in some of the deposits.Therefore,phosphorites formed in marine conditions with open circulation within the tropical zone.While lush growth of rainforest covers in the tropical belt facilitated the formation of coastal lignite.
