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Quantitative Evaluation of the Sea-level Drop at the End-Permian:Based on Reefs

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Quantitative Evaluation of the Sea-level Drop at the End-Per...

中国科学院地质与地球物理研究所2003学术年会

作者： wu yasheng and fan jiasong institute of geology and geophysics,chinese academy of sciences,beijing 100029

The amplitude of pre-Quaternary sea level drop,H,can be calculated by using the formula H = D + To. where To is the original thickness from the top of the tidal deposits on the reef core to the bottom of the tidal deposits on the reef front,or to the bottom of the ancient meteoric vadose zone,or to the edge of the mixed-water dolostone zone. The identity and similarity between the sea-level drop amplitudes calculated from different reefs far away from each other indicates that such sea-level changes are eustatic rather than relative *** of an end-Permian sea-level drop has been found on the Changxingian(*** end of the Palaeofusulina zone) reefs at Ziyun in South China,including algal laminated deposits,sabkha-related *** cracks,dissolution collapse breccia. According to calculation based on the meteoric dissolution zone of the reef-core sequence at Ziyun,Guizhou province, the amplitude of the sea-level drop at the end-Permian is about 89.3 *** via the dolomitized upper part of the Changxingian reef in Lichuan,Hubei Province,yields an 88.9 m amplitude of the sea-level drop at the end-Permian. Comparison shows that the sea-level drop recorded in the two distantly located reefs may be of eustatic *** the amplitude of the sea level drop of the Tethys Sea at the end-Permian might be at least 89.3 m.

关键词： sea-level drop eustatic reef Permian Changxingian

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川东二叠纪生物礁的再认识

石油与天然气地质 2002年第1期23卷 12-18页

作者：范嘉松吴亚生中国科学院地质与地球物理研究所北京100029

通过川东 8口二叠纪长兴期钻井岩芯剖面的详细研究 ,铁山 5井、天东 10井代表典型的礁相剖面 ;板东 4井、双 15井既有礁相沉积 ,且有棘屑滩沉积 ;卧 117井、黄龙 1井以及云安 14井基本上由碳酸盐台地沉积组成 ;池 2 4井出现两种类型的礁... 详细信息

通过川东 8口二叠纪长兴期钻井岩芯剖面的详细研究 ,铁山 5井、天东 10井代表典型的礁相剖面 ;板东 4井、双 15井既有礁相沉积 ,且有棘屑滩沉积 ;卧 117井、黄龙 1井以及云安 14井基本上由碳酸盐台地沉积组成 ;池 2 4井出现两种类型的礁相 :海绵骨架礁和海绵障积礁。川东礁相剖面中的白云岩以海水与淡水混合作用而成的白云石化为主导因素 ,但它们在深埋阶段以后 ,又遭受后期白云石化的叠加 ,因此表现出许多深埋白云石化的地化特征。白云岩的原始沉积既可能是礁骨架岩 ,也可能是棘屑滩 ,甚至是碳酸盐台地沉积。因此在寻找礁型白云岩储层时。

关键词：油气地质生物礁二叠纪川东钻井岩芯

Extinction pattern of reef ecosystems in latest Permian

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chinese Science Bulletin 2007年第4期52卷 512-520页

作者： wu yasheng fan jiasong JIANG HongXia YANG Wan institute of geology and geophysics Chinese Academy of Sciences Beijing 100029 China Department of geology Wichita State University 1845 Fairmount Wichita KS 67260 USA

Studies of two Permian-Triassic boundary (PTB) sections on top of a Changhsingian reef in Ziyun, Guizhou Province, southwestern China indicate that the end-Permian mass extinction of reef ecosystems occurred in two steps. The first step is the extinction of all stenotropic organisms such as calcisponges and fusulinids in the latest Permian (in the Clarkina yini conodont zone). The biota after the first extinction is simple, comprising eurytropic organisms including microgastropods, ostracods, and some small burrowing organisms, or only algal mats. At the beginning of the Early Triassic (i.e. the beginning of the Hindeodus parvus zone), the environments became anoxic, and the microgastropod dominated biota or algal mats disappeared, which constituted the second episode of the mass extinction. The biota after the second extinction comprises small spherical microproblematica, some kinds of specialized organisms tolerant of anoxic or oxygen-poor conditions. As the environments became oxygenated, the specialized biota was replaced by a microgastropod-dominated simple biota. When the environmental conditions improved further, the simple biota was replaced by a diverse biota with normal-sized ammonoids, bivalves, and gastropods, representing restoration of normal oceanic condi- tions. Comparison with PTB sections in Dolomites, Italy and Meishan, Zhejiang Province shows that non-reef ecosystems had a similar first episode of mass extinction in the latest Permian. In the case that oceanic anoxia happened, non-reef ecosystems had a second extinction episode similar to that of reef ecosystems.

关键词：贵州晚二叠纪珊瑚礁生态系统生物灭绝灭绝类型

Microbialite of anoxic condition from Permian-Triassic transition in Guizhou,China

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Microbialite of anoxic condition from Permian-Triassic trans...

Extinction pattern of reef ecosystems in latest Permian

中国科学院地质与地球物理研究所2007学术年会

作者： wu yasheng~(1+),JIANG HongXia~1,YANG Wan~2 & fan jiasong~1 1 institute of geology and geophysics,chinese academy of sciences,beijing 100029,China 2 Department of geology,Wichita State University,1845 Fairmount,Wichita,KS 67260,USA

Spherical microfossils are present in the Hindeodus parvus zone of the Lower Triassic in Ziyun, Guizhou *** generally range from 0.15 to 0.30 mm across,with micritic wall and filled by micro-sparry calcites,and are evenly scattered in micritic *** abundance makes the rock assigned to *** accompanied organisms include ostracods and algal mat,but no gastropods or *** of small(<7μm) pyrite framboids indicates that this bed formed in anoxic *** some sections,this bed is overlain and underlain by tidal-flat micritic limestone with microgastropods and small *** only in deposits on reef top indicates that the microbial organism was benthic,and needed sunlight in *** size of the microbial fossil exceeds that of any bacteria or ***,it does not belong to these two *** may belong to lower green algae,and is assigned to a new species in a new genus,Ziyunosphaeridium sinensis *** ***. Up to now,the rocks described as microbialites from the Permian-Triassic transition include six types: (1) porous micritic limestone such as that descried from Japan by Sano and Nakashima(1997),(2) limestone with rich globular microfossils such as that described from the Nanpanjiang Basin in China by Lehrmann(1999),(3) dendroidal limestone such as that described from the vicinity of Chongqing by Kershaw et al.(1999),(4) spherical microbial limestone adapted to anoxic environments described from Ziyun,Guizhou reported in this paper,(5) limestone with cyanobacterial fossils such as that described by Wang et al.(2005),and(6) *** these microbialites are not reefs in the proper sense, and the argument that Permian reef ecosystems extended into the Mesozoic is incorrect.

关键词： Microbialites reefs Permian-Triassic boundary mass extinction end-Permian

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Extinction pattern of reef ecosystems in latest Permian

Microbialite of anoxic condition from Permian-Triassic transition in Guizhou,China

中国科学院地质与地球物理研究所2007学术年会

作者： wu yasheng~(1+),fan jiasong~1,JIANG HongXia~1 & YANG Wan~2 1 institute of geology and geophysics,chinese academy of sciences,beijing 100029,China 2 Department of geology,Wichita State University,1845 Fairmount,Wichita,KS 67260,USA

Studies of two Permian-Triasslc boundary(PTB) sections on top of a Changhsingian reef in Ziyun, Guizhou Province,southwestern China indicate that the end-Permian mass extinction of reef ecosystems occurred in two *** first step is the extinction of all stenotropic organisms such as calcisponges and fusulinids in the latest Permian(in the Clarkina yini conodont zone).The biota after the first extinction is simple,comprising eurytropic organisms including microgastropods,ostracods,and some small burrowing organisms,or only algal *** the beginning of the Early Triassic(*** beginning of the Hindeodus parvus zone),the environments became anoxic,and the microgastropod dominated biota or algal mats disappeared,which constituted the second episode of the mass extinction. The biota after the second extinction comprises small spherical microproblematica,some kinds of specialized organisms tolerant of anoxic or oxygen-poor *** the environments became oxygenated,the specialized biota was replaced by a microgastropod-dominated simple *** the environmental conditions improved further,the simple biota was replaced by a diverse biota with normal -sized ammonoids,bivalves,and gastropods,representing restoration of normal oceanic conditions. Comparison with PTB sections in Dolomites,Italy and Meishan,Zhejiang Province shows that non-reef ecosystems had a similar first episode of mass extinction in the latest *** the case that oceanic anoxia happened,non-reef ecosystems had a second extinction episode similar to that of reef ecosystems.

关键词： end-Permian reef mass extinction Guizhou Permian-Triassic boundary

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Science China Earth sciences 2007年第7期50卷 1040-1051页

作者： wu yasheng JIANG HongXia YANG Wan fan jiasong institute of geology and geophysics Chinese Academy of SciencesBeijing 100029China Department of geology Wichita State University1845 FairmountWichitaKS 67260USA

Spherical microfossils are present in the Hindeodus parvus zone of the Lower Triassic in Ziyun,Guizhou Province. They generally range from 0.15 to 0.30 mm across,with micritic wall and filled by micro-sparry calcites,and are evenly scattered in micritic matrix. Their abundance makes the rock as-signed to microbialites. The accompanied organisms include ostracods and algal mat,but no gastro-pods or bivalves. Presence of small (<7 μm) pyrite framboids indicates that this bed formed in anoxic conditions. In some sections,this bed is overlain and underlain by tidal-flat micritic limestone with microgastropods and small burrows. Occurrence only in deposits on reef top indicates that the micro-bial organism was benthic,and needed sunlight in life. The size of the microbial fossil exceeds that of any bacteria or cyanobacteria. Thus,it does not belong to these two phyla. It may belong to lower green algae,and is assigned to a new species in a new genus,Ziyunosphaeridium sinensis gen. et sp. nov. Up to now,the rocks described as microbialites from the Permian-Triassic transition include six types: (1) porous micritic limestone such as that descried from Japan by Sano and Nakashima (1997),(2) limestone with rich globular microfossils such as that described from the Nanpanjiang Basin in China by Lehrmann (1999),(3) dendroidal limestone such as that described from the vicinity of Chongqing by Kershaw et al. (1999),(4) spherical microbial limestone adapted to anoxic environments described from Ziyun,Guizhou reported in this paper,(5) limestone with cyanobacterial fossils such as that described by Wang et al. (2005),and (6) stromatolites. All these microbialites are not reefs in the proper sense,and the argument that Permian reef ecosystems extended into the Mesozoic is incorrect.

关键词： Microbialites reefs Permian-Triassic boundary mass extinction end-Permian