南盘江坳陷晚古生代隆林孤立台地沉积特征与演化阶段

Sedimentary characteristics and evolutionary stages of Late Paleozoic Longlin isolated platform in Nanpanjiang depression

南盘江坳陷隆林孤立碳酸盐台地在中泥盆世至晚二叠世的大部分时间内属于四周被深水海槽围绕的、受南盘江海演化拉张断裂而形成的一个孤立碳酸盐台地环境(其中早石炭世晚期-晚石炭世为连陆台地阶段)。通过对隆林地区晚古生代野外地层踏勘成果表明,孤台-台间海槽相区共识别出碳酸盐潮坪、台地边缘浅滩、台地边缘礁、台缘斜坡、台棚及台盆相等6种沉积相类型,并建立了其独具特色的孤立台地沉积模式。研究表明,它的演化经历了边缘碳酸盐台地(D1-D2)、孤立碳酸盐台地(D3-C11)、连陆台地(C12-C2)、孤立-淹没碳酸盐台地(P)4个发展阶段,反映了南盘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。

During most time of Middle Devonian-Late Permian period,the Nanpanjiang depression was in an environment of isolated carbonate platform surrounded by a deep sea trough and formed by extensional faulting during the evolution of the Nanpanjiang Ocean.The platform was a land platform during the period from late Early Carboniferous to Late Carboniferous.The field exploration of Late Paleozoic strata in Longlin area revealed six kinds of sedimentary facies types in the isolated platform-trough facies region,i.e.,carbonate tidal flat,restricted platform,platform margin beach,platform margin reef,shelf between platforms,and basin between platforms,and established a sedimentary model for the unique isolated platform.The current study shows that its evolution experienced four stages of development,namely,marginal carbonate platform（D1-D2）,isolated carbonate platform（D3-C11）,land platform（C21-C2） and isolated-drowned carbonate platform（P）,implying that during the Late Paleozoic period,the Nanpanjiang basin evolved from rifting to a small oceanic basin with intense expansion and subsidence,while the southern margin of the Yangtze Platform experienced extension and breaking splitting.