【作者】 徐桂荣； 罗新民； 黄世骥； 王永标； 林启祥； 陈林洲； 肖诗宇；

【Author】 Xu Guirong;Lao Xinmin;Huang Shiji;Wang Yongbiao;Lin Qixiang;Chen Linzhou;Xiao Shiyu;China University of Geosciences;

【机构】 中国地质大学；

【摘要】 长江中游地区江南古陆的两侧(尤其是北侧)晚二叠世生物碳酸盐岩岩隆发育。慈利、辰澳和清水岩等地出露海一藻礁和珊瑚礁。本文论述了生物碳酸盐岩岩隆和生物礁在该地区出露的地质条件、地层层序和沉积体系、生物面貌、生物一微相等实际资料,分析了成岩作用和孔隙度的变化。通过原始沉积厚度恢复估算了海平面变化和基底沉降的相对值。最后讨论了它们生成的控制条件。更多还原

【Abstract】 Late Permian carbonate building- up developed at both,north and south,sides of Jiangnan old- land in the Middle Yangtze river Area.There are two types of reefs,Spongealga reef and compound coral reef,exposed in Cili county,Chenxi county of Hunan Province,Chongyang county of Hubei province and Xiushuicounty of Jiangxi province.Sponge-alga reefs exist in the lower Daluockeng Formation(of the lower Changxingian stage),and compound coral reefs occur in the upper part of the Xiamidong Formation(Wujiaping stage).In sponge-alga reefs there are abundant reef builders and dwellers,builders including calcisponges(identified more 15 genera of sphinctozoans and inozoahs),tabulozoans,hydrozoans,calcareous algae and bryozoans,and dwellers including braehiopbds,bivalves,gastropods,foraminifers and crinoids.On the basis of the bio- microfacies analyses and shallowing- up sequences,a stratigraphic sequence franework isrestored taking Gaofeng area as a representative.The Xiamidong Formation is composed of a highstand sysems tract(HST) and a lower systems tract(LST).A type 1 sequence boundary distinguished the Daluokeng Formation from the Xiamidong Formation.Two shelf margin wedge systems tracts(SMW),sponge- alga reef and oolite band,exist in the Daluokeng Formation,and with a HST between them.The upper boundary of each SMW is the type 2 sequence boundary(Fig.3).Diageneses of carbonatte building up in the Middle Yangtze area are complicated with various processes.Diagenetic recorders of rocks display that marine phreatic and vadoset,freshwater phreatic and vadose,mixing and deep burial environment all exist in Late Permian carbonate rocks of the area.Porosity of rocks has regular change in stratigraphic sections.In Daluokeng section,for example,reef framestones and calcirudites usually have higher porosities.Oolites and oncolites have lower porosity but higher thav algal or foraminifer limestones.By restoring the original sediment thickmess we estimate the sea level change and subsidence of substrata.As showing in table 1,there are high values of relative subsidence of substrata in each cycle from transgression to regression.Finally,oribinal control conditions of Late Permian carbonate builking up and reefs are reefs are discussed in the paper.更多还原