The Global Boundary Stratotype Section and Point （GSSP） for the Katian Stage of the Upper Ordovician Series is defined as the 4.0 m-level above the base of the Bigfork Chert in the Black Knob Ridge section, southeas...The Global Boundary Stratotype Section and Point （GSSP） for the Katian Stage of the Upper Ordovician Series is defined as the 4.0 m-level above the base of the Bigfork Chert in the Black Knob Ridge section, southeastern Oklahoma. This point in this section is coincident with the first appearance of the graptolite Diplacanthograptus caudatus, which has proved to be a reliable datum for precise worldwide correlation. The FAD ofD. caudatus occurs very near the first occurrences of the graptolites D. lanceolatus, Co.rynoides americanus, Orthograptus pageanus, O. quadrimucronatus, Dicranograptus hians, and Neurograptus margaritatus. This rapid succession of fossil species appearance events provides a secure basis for identification of the base of the Katian Stage of the Upper Ordovician Series and for its global chronostratigraphic correlation.展开更多
The Wandashan accretionary complex(AC),consisting of the Raohe and Yuejinshan complexes,is located on the continental margin of Northeast Asia and represents an excellent source of information about Paleo-Pacific subd...The Wandashan accretionary complex(AC),consisting of the Raohe and Yuejinshan complexes,is located on the continental margin of Northeast Asia and represents an excellent source of information about Paleo-Pacific subduction and accretion.However,the protolith nature and tectonic evolution of the Wandashan AC are under debate.This contribution reports new geochronological,geochemical,and Sr-Nd-Pb-Hf isotopic data for ophiolitic rocks from the Wandashan AC.The 169–166 Ma plagioclasites and homogeneous gabbros from the Raohe complex are OIBs while 228–214 Ma homogeneous gabbros are continental VABs.Cumulate gabbros from the Yuejinshan complex formed at 280–278 Ma and~220 Ma and have similar characteristics with E-MORB and N-MORB,respectively.They are BABBs and their primary magma was derived from a source region between EMI and EMII that was affected by continental crustal contamination as well as subduction-zone metasomatism.Combined with previous studies,we suggest that the onset of subduction of the Paleo-Pacific Plate was in the Early Permian.Subsequently,a back-arc basin,whose present suture is on the eastern margin of the Jiamusi Massif,formed and widened during 280–232 Ma,after which the basin closed and BABBs were emplaced to form the Yuejinshan complex during 210–180 Ma.The formation of VABs of the Raohe complex is coincident with the closure of the back-arc basin,and together with the 169–166 Ma OIBs,they constitute a major part of the Raohe complex.The accretionary process was completed during 133–131 Ma.Taken together,the ophiolitic rocks indicating multistage magmatism in the Paleo-Wandashan region recorded the formation-closure process of back-arc basin and the accretionary process of the Wandashan AC,during the westward subduction of the Paleo-Pacific plate.The back-arc basin identified in our study sheds new lights on geodynamic evolution model of subduction and accretion of the Paleo-Pacific Plate on the continental margin of NE Asia.展开更多
Early oceans （〉520 Ma） were characterized by widespread water-column anoxia, stratification, and limited oxidant availability which are comparable to the chemical characteristics of modern marine sedimentary pore-w...Early oceans （〉520 Ma） were characterized by widespread water-column anoxia, stratification, and limited oxidant availability which are comparable to the chemical characteristics of modern marine sedimentary pore-waters in productive continental margins. Based on this similarity and our current understanding of the formation mechanism of early Earth ocean chemistry, we propose an idealized chemical zonation model for early oceans that includes the following redox zones （from shallow nearshore to deep offshore regions）： oxic, nitrogenous （NO3^-NO2^-enriched）, manganous-ferruginous （Mn^2＋ or Fe^2＋-enriched）, sulfidic （H2S-enriched）, methanic （CH4-enriched）, and ferruginous （Fe^2＋-enriched）. These zones were dynamically maintained by a combination of processes including surface-water oxygenation by atmospheric free oxygen, nitrate reduction beneath the chemocline, nearshore manganese-iron reduction, sulfate reduction, methanogenesis, and hydrothennal Fe^2＋ inputs from the deep ocean. Our modified ＂euxinic wedge＂ model expands on previous versions of this model, providing a more complete theoretical framework for the chemical zonation of early Earth oceans that helps to explain observations of unusual Mo-S-C isotope patterns. This model may provide a useful foundation for future studies of ocean chemistry evolution and elemental biogeochemical cycles in early Earth history.展开更多
The rapid diversification of early animals during the Ediacaran(635–541 Ma) and early Cambrian(ca.541–509 Ma) has frequently been attributed to increasing oceanic oxygenation. However, the pattern of oceanic oxygena...The rapid diversification of early animals during the Ediacaran(635–541 Ma) and early Cambrian(ca.541–509 Ma) has frequently been attributed to increasing oceanic oxygenation. However, the pattern of oceanic oxygenation and its relationship to early animal evolution remain in debate. In this review,we examine the redox structure of Ediacaran and early Cambrian oceans and its controls, offering new insights into contemporaneous oceanic oxygenation patterns and their role in the coevolution of environments and early animals. We review the development of marine redox models which, in combination with independent distal deep-ocean redox proxies, supports a highly redox-stratified shelf and an anoxia-dominated deep ocean during the Ediacaran and early Cambrian. Geochemical and modeling evidence indicates that the marine redox structure was likely controlled by low atmospheric O2 levels and low seawater vertical mixing rates on shelves at that time. Furthermore, theoretical analysis and increasing geochemical evidence, particularly from South China, show that limited sulfate availability was a primary control on the attenuation of mid-depth euxinia offshore, in contrast to the existing paradigm invoking decreased organic carbon fluxes distally. In light of our review, we infer that if oceanic oxygenation indeed triggered the rise of early animals, it must have done so through a shelf oxygenation which was probably driven by elevated oxidant availability. Our review calls for further studies on EdiacaranCambrian marine redox structure and its controls, particularly from regions outside of South China, in order to better understand the coevolutionary relationship between oceanic redox and early animals.展开更多
The Doushantuo negative carbon isotope excursion(DOUNCE) is the largest known marine inorganic carbon isotope anomaly. The origin of this pronounced negative excursion is still an enigmatic issue that attracts geologi...The Doushantuo negative carbon isotope excursion(DOUNCE) is the largest known marine inorganic carbon isotope anomaly. The origin of this pronounced negative excursion is still an enigmatic issue that attracts geologists. Time constraints on the excursion are the critical information that would provide insight into its genesis. In previous decades, the timing of its termination has been constrained by the widely cited zircon U-Pb age of 550.5 ± 0.8 Ma for the tuff at the top of the Miaohe Member at the Jiuqunao section in the Yangtze Gorges area, South China. However, results of recent studies indicate that the reliability of this time constraint needs to be re-evaluated. Here, a geochronological study was carried out using two K-bentonites from Fanglong in South China. A K-bentonite in the lower Dengying Formation yielded a U-Pb age of 557 ± 3 Ma, while a K-bentonite in the basal Liuchapo Formation yielded an age of 550 ± 3 Ma. Based on regional correlations between the Ediacaran successions in South China,the age(557 ± 3 Ma) for the K-bentonite in the lower Dengying Formation may serve as a second critical timing constraint for the ending of the DOUNCE. Combined with available estimates of the DOUNCE duration, our new data indicate that the DOUNCE has a maximum onset age ～570 Ma.展开更多
The largest global carbon-cycle perturbation in Earth history was recorded in the Ediacaran—a persistent negative shift in the global marine dissolved inorganic carbon(DIC) reservoir that lasted for ~25–50 million y...The largest global carbon-cycle perturbation in Earth history was recorded in the Ediacaran—a persistent negative shift in the global marine dissolved inorganic carbon(DIC) reservoir that lasted for ~25–50 million years, with a nadir of –12‰(i.e.,the Shuram Excursion, or SE). This event is considered to have been a result of full or partial oxidation of a large dissolved organic carbon(DOC) reservoir, which, if correct, provides evidence for massive DOC storage in the Ediacaran ocean owing to an intensive microbial carbon pump(MCP). However, this scenario was recently challenged by new hypotheses that relate the SE to oxidization of recycled continentally derived organic carbon or hydrocarbons from marine seeps. In order to test these competing hypotheses,this paper numerically simulates changes in global carbon cycle fluxes and isotopic compositions during the SE, revealing that:(1) given oxygen levels in the Ediacaran atmosphere-ocean of ≤40% PAL, the recycled continental organic carbon hypothesis and the full oxidation of oceanic DOC reservoir hypothesis are challenged by the atmospheric oxygen availability which would have been depleted in 4 and 6 million years, respectively;(2) the marine-seep hydrocarbon oxidation hypothesis is challenged by the exceedingly large hydrocarbon fluxes required to sustain the SE for >25 Myr; and(3) the heterogeneous(partial) DOC oxidation hypothesis is quantitatively able to account for the SE because the total amount of oxidants needed for partial oxidation(<50%)of the global DOC reservoir could have been met.展开更多
Microbes not only show sensitive responses to environmental changes but also play important roles in geochemical and geophysical systems. It is well known that microbes have caused major changes in surface environment...Microbes not only show sensitive responses to environmental changes but also play important roles in geochemical and geophysical systems. It is well known that microbes have caused major changes in surface environments and biogeochemical cycles through Earth history. Microbial processes can also induce the synthesis of certain minerals under Earth-surface conditions that previously were believed to form only under high temperatures and pressures in the deep Earth. For example, microbes can promote the conversion of smectite to illite, synthesis of authigenic plagioclase, precipitation of dolomite, and biotransformation of geolipids. These effects of microbes are due to their large surface/volume ratios, enzyme production, and abundant functional groups. Microbial catalyzation of chemical reactions proceeds through reaction-specific enzymes, a decrease in Gibbs' s free energy, and/or break through the dynamics reaction thresholds via their metabolisms and physiology. Microbes can lower the surface free energy of mineral nuclei via biophysical adsorption due to their large surface/volume ratios and abundant functional groups. The mineral precipitation and transformation processes induced by microbes are functionally equivalent to geological processes operating at high temperatures and pressures in the deep Earth, suggesting that microbial processes can serve as analogs to deep abiotic processes that are difficult to observe.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
The Ediacaran Period(~635–539 Ma)was a critical time in Earth history due to large increases in atmospheric and oceanic oxygen levels and rapid evolution of early animals[1].It was also an interval of major climatic ...The Ediacaran Period(~635–539 Ma)was a critical time in Earth history due to large increases in atmospheric and oceanic oxygen levels and rapid evolution of early animals[1].It was also an interval of major climatic and geochemical perturbations,such as the~580-Ma Gaskiers Glaciation[2](Fig.S1 online)and the late Ediacaran Shuram Excursion(SE;also known as DOUNCE or EN3 in South China,see Fig.S2 online),which was the largest negative carbonate carbon isotope(δ13Ccarb)excursion in Earth history[3,4].In contrast to established redox,biological,and C-cycling records for the Ediacaran,however,no secular,high-resolution paleotemperature record with climatic significance has been reported to date,impeding our understanding of the relationships among major environmental,biological,geochemical,and climatic processes and milestones.展开更多
A SHRIMP U-Pb zircon age of 1437±21 Ma was obtained for a recently discovered K-bentonite bed in the Tieling Formation,situated northeast of Beijing at the boundary between Liaoning and Hebei provinces,on the nor...A SHRIMP U-Pb zircon age of 1437±21 Ma was obtained for a recently discovered K-bentonite bed in the Tieling Formation,situated northeast of Beijing at the boundary between Liaoning and Hebei provinces,on the northern margin of the North China Craton(NCC).The SHRIMP U-Pb age places Tieling Formation near the end of the Calymmian Period of the early Mesoproterozoic Era.In addition,a SHRIMP U-Pb zircon date of 1372±18 Ma was acquired for K-bentonite beds in the overlying,dark-shale-dominated Xiamaling Formation from the same location northeast of Beijing.This date assigns a similar Mid-Mesoproterozoic(Ectasian Period) age for the Xiamaling Formation,as have previously determined dates from other sections northwest of Beijing.These dates indicate that the Tieling and Xiamaling formations,as well as the related succession in the eastern part of the Yanshan Mountains,represented by the well-known Meso-to Neoproterozoic standard section in Jixian,can be correlated well with sections northwest of Beijing in the western part of the Yanshan Mountains.In other words,the boundary between the Calymmian and Ectasian periods in the northern parts of the NCC is marked by the unconformity between the Tieling and Xiamaling formations in the northern NCC.This boundary was previously ascribed to the "Qinyu Orogeny" and thought to be of Grenville age.In this regard,the conventional "Qinyu Orogeny" should now be regarded as a short-lived regional uplift during Early Mesoproterozoic time,rather than a result from the Grenvillian assembly of the NCC to the Rodinia Supercontinent(～1.0 Ga).展开更多
Viruses are the most diverse and abundant type of biological entity on Earth,infecting species from all of life’s domains and being found in almost all types of environments.They are gaining increasing attention from...Viruses are the most diverse and abundant type of biological entity on Earth,infecting species from all of life’s domains and being found in almost all types of environments.They are gaining increasing attention from scientists,officials and the public due to recent major outbreaks with human health consequences(e.g.,AIDS,SARS,COVID-19)and a growing appreciation of the impact viruses have had on the long-term development of both the biosphere and geosphere.The ability to identify viruses in ancient times is of importance in promoting our understanding of viral evolution and the relationships of viruses to their hosts and to paleoclimate conditions,enabling predictions of present and future impacts of the virosphere on life and the climate system.展开更多
基金Acknowledgments This work was supported by National Science Foundation grant EAR - 0106844 to D. Goldman and Estonian Science Foundation grant ETF - 5922 to J. Nōlvak. We would like to thank S.C. Finney for showing us the Black Knob Ridge section, suggesting its potential as a GSSP, and critically reviewing previous versions of the manuscript.
文摘The Global Boundary Stratotype Section and Point （GSSP） for the Katian Stage of the Upper Ordovician Series is defined as the 4.0 m-level above the base of the Bigfork Chert in the Black Knob Ridge section, southeastern Oklahoma. This point in this section is coincident with the first appearance of the graptolite Diplacanthograptus caudatus, which has proved to be a reliable datum for precise worldwide correlation. The FAD ofD. caudatus occurs very near the first occurrences of the graptolites D. lanceolatus, Co.rynoides americanus, Orthograptus pageanus, O. quadrimucronatus, Dicranograptus hians, and Neurograptus margaritatus. This rapid succession of fossil species appearance events provides a secure basis for identification of the base of the Katian Stage of the Upper Ordovician Series and for its global chronostratigraphic correlation.
基金This work was financially supported by the National Natural Science Foundation of China(Grants 42002223 and 41790453).
文摘The Wandashan accretionary complex(AC),consisting of the Raohe and Yuejinshan complexes,is located on the continental margin of Northeast Asia and represents an excellent source of information about Paleo-Pacific subduction and accretion.However,the protolith nature and tectonic evolution of the Wandashan AC are under debate.This contribution reports new geochronological,geochemical,and Sr-Nd-Pb-Hf isotopic data for ophiolitic rocks from the Wandashan AC.The 169–166 Ma plagioclasites and homogeneous gabbros from the Raohe complex are OIBs while 228–214 Ma homogeneous gabbros are continental VABs.Cumulate gabbros from the Yuejinshan complex formed at 280–278 Ma and~220 Ma and have similar characteristics with E-MORB and N-MORB,respectively.They are BABBs and their primary magma was derived from a source region between EMI and EMII that was affected by continental crustal contamination as well as subduction-zone metasomatism.Combined with previous studies,we suggest that the onset of subduction of the Paleo-Pacific Plate was in the Early Permian.Subsequently,a back-arc basin,whose present suture is on the eastern margin of the Jiamusi Massif,formed and widened during 280–232 Ma,after which the basin closed and BABBs were emplaced to form the Yuejinshan complex during 210–180 Ma.The formation of VABs of the Raohe complex is coincident with the closure of the back-arc basin,and together with the 169–166 Ma OIBs,they constitute a major part of the Raohe complex.The accretionary process was completed during 133–131 Ma.Taken together,the ophiolitic rocks indicating multistage magmatism in the Paleo-Wandashan region recorded the formation-closure process of back-arc basin and the accretionary process of the Wandashan AC,during the westward subduction of the Paleo-Pacific plate.The back-arc basin identified in our study sheds new lights on geodynamic evolution model of subduction and accretion of the Paleo-Pacific Plate on the continental margin of NE Asia.
基金supported by the National Basic Research Program of China(Grant No.2013CB955704)National Natural Science Foundation of China(Grant No.41172030)support from the U.S.National Science Foundation,the NASA Exobiology Program,and the China University of Geosciences(Wuhan)(SKL-GPMR program GPMR201301,and SKL-BGEG program BGL21407)
文摘Early oceans （〉520 Ma） were characterized by widespread water-column anoxia, stratification, and limited oxidant availability which are comparable to the chemical characteristics of modern marine sedimentary pore-waters in productive continental margins. Based on this similarity and our current understanding of the formation mechanism of early Earth ocean chemistry, we propose an idealized chemical zonation model for early oceans that includes the following redox zones （from shallow nearshore to deep offshore regions）： oxic, nitrogenous （NO3^-NO2^-enriched）, manganous-ferruginous （Mn^2＋ or Fe^2＋-enriched）, sulfidic （H2S-enriched）, methanic （CH4-enriched）, and ferruginous （Fe^2＋-enriched）. These zones were dynamically maintained by a combination of processes including surface-water oxygenation by atmospheric free oxygen, nitrate reduction beneath the chemocline, nearshore manganese-iron reduction, sulfate reduction, methanogenesis, and hydrothennal Fe^2＋ inputs from the deep ocean. Our modified ＂euxinic wedge＂ model expands on previous versions of this model, providing a more complete theoretical framework for the chemical zonation of early Earth oceans that helps to explain observations of unusual Mo-S-C isotope patterns. This model may provide a useful foundation for future studies of ocean chemistry evolution and elemental biogeochemical cycles in early Earth history.
基金supported by the National Natural Science Foundation of China-Research Councils United Kingdom_Natural Environment Research Council Program (41661134048)the National Natural Science Foundation of China (41825019, 41821001), the National Key Research & Development Program of China (2016YFA0601100)+1 种基金111 Project of China (BP0820004) to Chao Li. Meng Chengsupport from the National Natural Science Foundation of China (41703008, 41902027)。
文摘The rapid diversification of early animals during the Ediacaran(635–541 Ma) and early Cambrian(ca.541–509 Ma) has frequently been attributed to increasing oceanic oxygenation. However, the pattern of oceanic oxygenation and its relationship to early animal evolution remain in debate. In this review,we examine the redox structure of Ediacaran and early Cambrian oceans and its controls, offering new insights into contemporaneous oceanic oxygenation patterns and their role in the coevolution of environments and early animals. We review the development of marine redox models which, in combination with independent distal deep-ocean redox proxies, supports a highly redox-stratified shelf and an anoxia-dominated deep ocean during the Ediacaran and early Cambrian. Geochemical and modeling evidence indicates that the marine redox structure was likely controlled by low atmospheric O2 levels and low seawater vertical mixing rates on shelves at that time. Furthermore, theoretical analysis and increasing geochemical evidence, particularly from South China, show that limited sulfate availability was a primary control on the attenuation of mid-depth euxinia offshore, in contrast to the existing paradigm invoking decreased organic carbon fluxes distally. In light of our review, we infer that if oceanic oxygenation indeed triggered the rise of early animals, it must have done so through a shelf oxygenation which was probably driven by elevated oxidant availability. Our review calls for further studies on EdiacaranCambrian marine redox structure and its controls, particularly from regions outside of South China, in order to better understand the coevolutionary relationship between oceanic redox and early animals.
基金supported by the National Natural Science Foundation of China (41462001, 41072054)the Project of National Key Research and Development Program of China (2016YFC0502601)
文摘The Doushantuo negative carbon isotope excursion(DOUNCE) is the largest known marine inorganic carbon isotope anomaly. The origin of this pronounced negative excursion is still an enigmatic issue that attracts geologists. Time constraints on the excursion are the critical information that would provide insight into its genesis. In previous decades, the timing of its termination has been constrained by the widely cited zircon U-Pb age of 550.5 ± 0.8 Ma for the tuff at the top of the Miaohe Member at the Jiuqunao section in the Yangtze Gorges area, South China. However, results of recent studies indicate that the reliability of this time constraint needs to be re-evaluated. Here, a geochronological study was carried out using two K-bentonites from Fanglong in South China. A K-bentonite in the lower Dengying Formation yielded a U-Pb age of 557 ± 3 Ma, while a K-bentonite in the basal Liuchapo Formation yielded an age of 550 ± 3 Ma. Based on regional correlations between the Ediacaran successions in South China,the age(557 ± 3 Ma) for the K-bentonite in the lower Dengying Formation may serve as a second critical timing constraint for the ending of the DOUNCE. Combined with available estimates of the DOUNCE duration, our new data indicate that the DOUNCE has a maximum onset age ～570 Ma.
基金supported by the National Program on Key Basic Research Project(Grant No.2013CB955704)the National Key Research and Development Program of China(Grant No.2016YFA0601100)+2 种基金the NSFC-RCUK_NERC Program(Grant No.41661134048)the Fundamental Research Funds for Central Universities(Grant Nos.CUG-Wuhan,grants 1610491T01 and G1323531767)the NASA Exobiology Program(TJA)
文摘The largest global carbon-cycle perturbation in Earth history was recorded in the Ediacaran—a persistent negative shift in the global marine dissolved inorganic carbon(DIC) reservoir that lasted for ~25–50 million years, with a nadir of –12‰(i.e.,the Shuram Excursion, or SE). This event is considered to have been a result of full or partial oxidation of a large dissolved organic carbon(DOC) reservoir, which, if correct, provides evidence for massive DOC storage in the Ediacaran ocean owing to an intensive microbial carbon pump(MCP). However, this scenario was recently challenged by new hypotheses that relate the SE to oxidization of recycled continentally derived organic carbon or hydrocarbons from marine seeps. In order to test these competing hypotheses,this paper numerically simulates changes in global carbon cycle fluxes and isotopic compositions during the SE, revealing that:(1) given oxygen levels in the Ediacaran atmosphere-ocean of ≤40% PAL, the recycled continental organic carbon hypothesis and the full oxidation of oceanic DOC reservoir hypothesis are challenged by the atmospheric oxygen availability which would have been depleted in 4 and 6 million years, respectively;(2) the marine-seep hydrocarbon oxidation hypothesis is challenged by the exceedingly large hydrocarbon fluxes required to sustain the SE for >25 Myr; and(3) the heterogeneous(partial) DOC oxidation hypothesis is quantitatively able to account for the SE because the total amount of oxidants needed for partial oxidation(<50%)of the global DOC reservoir could have been met.
基金supported by National Natural Science Foundation of China (Grant No. 41330103)the "111 Project" (Grant No. B08030)
文摘Microbes not only show sensitive responses to environmental changes but also play important roles in geochemical and geophysical systems. It is well known that microbes have caused major changes in surface environments and biogeochemical cycles through Earth history. Microbial processes can also induce the synthesis of certain minerals under Earth-surface conditions that previously were believed to form only under high temperatures and pressures in the deep Earth. For example, microbes can promote the conversion of smectite to illite, synthesis of authigenic plagioclase, precipitation of dolomite, and biotransformation of geolipids. These effects of microbes are due to their large surface/volume ratios, enzyme production, and abundant functional groups. Microbial catalyzation of chemical reactions proceeds through reaction-specific enzymes, a decrease in Gibbs' s free energy, and/or break through the dynamics reaction thresholds via their metabolisms and physiology. Microbes can lower the surface free energy of mineral nuclei via biophysical adsorption due to their large surface/volume ratios and abundant functional groups. The mineral precipitation and transformation processes induced by microbes are functionally equivalent to geological processes operating at high temperatures and pressures in the deep Earth, suggesting that microbial processes can serve as analogs to deep abiotic processes that are difficult to observe.
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.
基金supported by the National Natural Science Foundation of China(41825019,42130208,41821001,and 42102343)the Programme of Introducing Talents of Discipline to Universities(BP0820004)+1 种基金China Postdoctoral Science Foundation(2020M682515)an award from “Laboratoire Excellence”LabexMER(ANR-10-LABX-19)。
文摘The Ediacaran Period(~635–539 Ma)was a critical time in Earth history due to large increases in atmospheric and oceanic oxygen levels and rapid evolution of early animals[1].It was also an interval of major climatic and geochemical perturbations,such as the~580-Ma Gaskiers Glaciation[2](Fig.S1 online)and the late Ediacaran Shuram Excursion(SE;also known as DOUNCE or EN3 in South China,see Fig.S2 online),which was the largest negative carbonate carbon isotope(δ13Ccarb)excursion in Earth history[3,4].In contrast to established redox,biological,and C-cycling records for the Ediacaran,however,no secular,high-resolution paleotemperature record with climatic significance has been reported to date,impeding our understanding of the relationships among major environmental,biological,geochemical,and climatic processes and milestones.
基金supported by the National Natural Science Foundation of China (40372057 and 40772076)the SINOPEC Project (G0800-06-ZS-319)the China Geological Survey (CGS) project (1212010611802)
文摘A SHRIMP U-Pb zircon age of 1437±21 Ma was obtained for a recently discovered K-bentonite bed in the Tieling Formation,situated northeast of Beijing at the boundary between Liaoning and Hebei provinces,on the northern margin of the North China Craton(NCC).The SHRIMP U-Pb age places Tieling Formation near the end of the Calymmian Period of the early Mesoproterozoic Era.In addition,a SHRIMP U-Pb zircon date of 1372±18 Ma was acquired for K-bentonite beds in the overlying,dark-shale-dominated Xiamaling Formation from the same location northeast of Beijing.This date assigns a similar Mid-Mesoproterozoic(Ectasian Period) age for the Xiamaling Formation,as have previously determined dates from other sections northwest of Beijing.These dates indicate that the Tieling and Xiamaling formations,as well as the related succession in the eastern part of the Yanshan Mountains,represented by the well-known Meso-to Neoproterozoic standard section in Jixian,can be correlated well with sections northwest of Beijing in the western part of the Yanshan Mountains.In other words,the boundary between the Calymmian and Ectasian periods in the northern parts of the NCC is marked by the unconformity between the Tieling and Xiamaling formations in the northern NCC.This boundary was previously ascribed to the "Qinyu Orogeny" and thought to be of Grenville age.In this regard,the conventional "Qinyu Orogeny" should now be regarded as a short-lived regional uplift during Early Mesoproterozoic time,rather than a result from the Grenvillian assembly of the NCC to the Rodinia Supercontinent(～1.0 Ga).
基金supported by the National Natural Science Foundation of China(41821001,41830319,42072336,and 42293294)the Program of Introducing Talents of Discipline to Universities(111 Program)(BP0820004)。
文摘Viruses are the most diverse and abundant type of biological entity on Earth,infecting species from all of life’s domains and being found in almost all types of environments.They are gaining increasing attention from scientists,officials and the public due to recent major outbreaks with human health consequences(e.g.,AIDS,SARS,COVID-19)and a growing appreciation of the impact viruses have had on the long-term development of both the biosphere and geosphere.The ability to identify viruses in ancient times is of importance in promoting our understanding of viral evolution and the relationships of viruses to their hosts and to paleoclimate conditions,enabling predictions of present and future impacts of the virosphere on life and the climate system.
