中国二叠纪岩石地层划分和对比

LITHOSTRATIGRAPHIC SUBDIVISION AND CORRELATION OF THE PERMIAN IN CHINA

二叠系是古生界最后一个系,自下而上包括乌拉尔统、瓜德鲁普统和乐平统,进一步划分为9个阶。中国各块体都发育有很好的二叠纪地层,本文依据最新研究成果与已有地层资料,系统整理了中国二叠纪岩石地层区划、主要剖面地层划分和对比框架,包括5个地层区、22个地层分区和59条综合岩石地层剖面。以生物地层学和地质年代学为约束因素,本文厘定并更新了中国二叠纪不同块体间岩石地层的划分和对比方案。北部边缘地层区二叠系发育不完整,地层层序和各岩石地层单位的时代缺乏系统研究,整体为陆相碎屑岩夹火山岩沉积,海相地层主要发育在乌拉尔统—瓜德鲁普统,从西向东海水逐渐退出。塔里木地层区二叠系海相地层主要发育乌拉尔统,瓜德鲁普统—乐平统则为陆相地层且不完整。华北地层区的二叠系层序相对清楚,但最新研究表明很可能缺失瓜德鲁普统,海相地层主要在乌拉尔统底部发育,并含有重要煤层,乌拉尔统上部至乐平统则发育陆相地层,并随着气候逐渐干旱化出现越来越多的红层。喜马拉雅地层区二叠系在各个块体差异明显,其中藏南分区的喜马拉雅特提斯带缺乏瓜德鲁普统沉积,含冈瓦纳冷水型生物群,而拉萨地块和南羌塘地块的二叠系均发育有较为完整的碎屑岩和碳酸盐岩,在乌拉尔统上部生物群逐渐向暖水型过渡。华南地层区的二叠系最为完整,整体为海相碳酸盐岩沉积,层序清晰,所含各门类化石丰富,是重要的国际对比标准。中国二叠系是煤炭、油气、铝土矿等重要矿产资源的富集层位。精细的岩石地层划分和时代对比对于阐明重要矿产资源的形成机制和分布规律,以及指导资源勘探具有重要的科学意义和实际意义。

The Permian System is the uppermost system in the Paleozoic and consists of three series(i.e.,Cisuralian,Guadalupian and Lopingian in ascending order)and nine component stages.The Permian System is well-developed and widely distributed in all blocks of China.Based on the latest research and available stratigraphic data,this study summarized and updated the Permian lithostratigraphic subdivisions,correlations and distributions of the different stratigraphic provinces of China,including 5 stratigraphic provinces,22 stratigraphic subprovinces and 59 composite lithostratigraphic columns.The Permian strata,which are mainly composed of terrestrial clastic rocks with volcanic rocks,in the North Marginal Stratigraphic Province is incompletely developed,their ages and lithostratigraphic successions are unclear and need to be further investigated.Marine deposits are only developed in the Cisuralian-Guadalupian.The marine Permian strata in the Tarim Stratigraphic Province is only developed in the Cisuralian Series,while the terrestrial strata are incompletely developed in the Guadalupian-Lopingian.The Permian strata in the North China Stratigraphic Province is characterized by marine and marine-non-mmarine transitional deposits in the lowest part,succeeded by the terrestrial clastic deposits under relatively arid climate condition.A recent high-precision geochronologic study suggested that a ca 20 Myr long gap is probably present between the Upper Shihhotse Formation and the overlying Sunjiagou Formation.The upper part of the Cisuralian and the Guadalupian are missing.Permian strata are mostly not complete in the Himalaya stratigraphic province.The lower Cisuralian Series is characterized by well-developed glacial deposits with typical Gondwanan faunas;whereas,the upper Cisuralian,Guadalupian and Lopingian series are characterized by carbonates and clastic deposits with mixed and warm-water faunas after the Cimmerian blocks rifted away from the peri-Gondwanan margin.The South China Stratigraphic Province develops the most complete Permian sequences,which are mainly composed of marine carbonate rocks and contain abundant fossils.In particular,the conodonts and fusulines have been well studied.Permian strata in China and their biostratigraphical and chronostratigraphical frameworks can be used as standards for global correlation.The Permian deposits in China is rich in natural resources including coal,oil,gas and bauxite.High-resolution biostratigraphical and lithostratigraphic subdivisions and correlations are essential to illuminate the formation process and explore the spatial and temporal patterns of natural resources in the Permian System.