桂西北晚古生代乐业孤立碳酸盐岩台地沉积特征与演化阶段  

Sedimentary characteristics and evolution of the Late Paleozoic Leye isolated carbonate platform in northwest Guangxi

作　　者：王新强[1] 史晓颖[1] 

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《古地理学报》2008年第4期329-340,共12页Journal of Palaeogeography：Chinese Edition

基　　金：国家自然科学基金(编号:40272018);国家创新群体项目(编号:40621002);教育部创新团队项目(编号:IRT00546)成果

摘　　要：桂西北乐业台地是右江盆地北部典型的晚古生代孤立碳酸盐岩台地。从中泥盆统唐家湾组至上二叠统合山组均由碳酸盐岩构成,与北侧陆棚区多样的沉积类型及台地周边泥质—硅质岩深水沉积形成鲜明对比。台地内上古生界主要由台缘生物礁组合和礁后澙湖组合两种浅水碳酸盐沉积类型构成。地层发育与沉积特征主要受基底沉降、海平面波动、气候变化和盆地内生碳酸盐沉积速率控制。研究表明,乐业台地是在右江盆地强烈扩张、沉降过程中由扬子地台南缘破裂的微地块向盆地滑移而形成的孤立台地。它的演化经历了边缘台地(D1-D2)、孤立台地(D3-P2)和淹没台地(P3-T1)3个发展阶段。孤立台地是其最重要的主体特征,反映了右江盆地在晚古生代强烈扩张、沉降,扬子地台边缘拉伸、破裂,微地块向盆地滑移的构造背景。乐业孤立台地的形成及演化模式可能具有普遍性,也适用于右江盆地西北部其他晚古生代孤立碳酸盐岩台地。The Leye carbonate platform in northwest Guangxi is a typical Paleozoic isolated carbonate platform in the northern part of the Youjiang Basin. The Upper Paleozoic in this platform consists almost completely of shallow water carbonates with a thickness of up to 3 000 m, without significant terrestrial influx, and is in sharp contrast with the contemporary diversified facies of sediments on the shallow shelf in the north and with the deep-water chert-argillaceous sediment assemblages in the surrounding areas. In this platform, two major facies types, the reef-related grainstone-packstone assemblage along the margins and the wackestone-mudstone assemblage in the back-reef lagoon, can be recognized for the Upper Paleozoic. The architectures of the depositional sequences and the sedimentary characteristics of the Upper Paleozoic are mainly controlled by the base subsidence, sea-level eustacy and climate changes, along with the change of the carbonate production rate in the basin. The current study shows that the Leye platform was initially formed as a micro-terrane that was split from the southern margin of the Yangtze Platform and gradually slipped into the basin as intensive expansion and subsidence occurred in the Youjiang Basin in the Late Devonian, The Leye platform had experienced three stages in evolution during the Late Paleozoic： 1 ） a marginal carbonate platform （Early to Middle Devonian） ; 2） an isolated carbonate platform （Late Devonian to Middle Permian） ; and 3） a drowned carbonate platform （Late Permian to Early Triassic）, with the second stage being most prominent. This probably implies that during the Late Paleozoic, the Youjiang Basin had evolved from rifting to a small oceanic basin with intensive expansion and subsidence, while the southern margin of the Yangtze Platform experienced extension and breaking splitting. The formation and evolution of the Leye platform may have general significance and the suggested model may also be used for other isolated carbonate platforms in th

关 键 词：桂西北 右江盆地 晚古生代 孤立碳酸盐岩台地 沉积相 盆地演化 

分 类 号：P512.2[天文地球—地质学]