Evidence for sea-level falls in the Permian-Triassic transition in the Ziyun area,South China
会议名称：《中国科学院地质与地球物理研究所第十届(2010年度)学术年会》
会议日期：2011年
学科分类：0709[理学-地质学] 081803[工学-地质工程] 07[理学] 08[工学] 0818[工学-地质资源与地质工程]
基 金：funded by the National Natural Science Foundation of China(Project Nos40802001 and 40472015) the Science Foundation of China Postdoctors (Grant No20070420523) the State Key Laboratory of Modern Paleontology and stratigraphy(Grant No083113)
关 键 词：Permian-Triassic boundary P-T transition subaerial exposure sea-level fall end-Permian Ziyun reef
摘 要：The sedimentology of three sections showing the Permian-Triassic(P-T) transition on an Upper Permian reef in Ziyun,Guizhou Province, southwest China provides evidence of sea-level fall in this *** P-T transition in the Gendan section,which covers a reef-front sequence, contains a subaerial exposure surface and various desiccation cracks(including rolled-up chips,in-chip cracks,pyramid cracks,vertical cracks and sheet cracks),indicating sea-level *** P-T transition in the Shitouzhai section,which covers a reef-core sequence,contains three micritic beds with abundant pseudomorphs of tabular gypsum crystals replaced by *** underlying centimetres of deposits are composed of fine-crystalline dolostone,and have a sharp contact with the underlying reef-core *** association of gypsum pseudomorphs and fine-crystalline dolostone suggests an origin related to a supratidal evaporative *** P-T transition in the Tanluzhai section,which covers a back-reef sequence,is fine-crystalline dolostone,and shows a laminated algal structure indicating tidal-flat *** middle part of the dolostone interval has become a collapse breccia composed of dolostone fragments and a matrix of micrites or crustose multi-generation calcite *** formation of the collapse breccia is interpreted to be related to the dissolution of the evaporite interbeds originally present between the thin dolostone *** formation of the evaporite deposits requires a supratidal condition.