滇西南昌宁—孟连构造带西带研究初探——以耿马弄巴剖面为例

Research on the Western Belt of Changning-Menglian Tectonic Belt:Exampled by the Nongba Section in Gengma,Southwest of Yunnan,China

昌宁—孟连构造带的地层层序、地层时代归属和构造背景一直是热点争议问题。在1∶25万临沧幅区域地质调查和系统总结前人研究的基础上,对该区弄巴剖面进行了细致的地层学、古生物学、沉积学、岩石地球化学等方面的研究,重新厘定了该区的地层层序,更正了其地质时代,在恢复该区的构造背景和古地理格架等方面取得了突破性进展。研究表明,滇西南耿马弄巴剖面是由不同时代、不同岩性的7个地层断片组成的断片型地层体,其地层序列为:上覆新近系南林组,下伏大陆斜坡相碎屑岩沉积和代表洋盆沉积环境的两套地层。在此基础上,重新对岩石地层单位进行了划分,厘定了温泉组、曼信组、平掌组和南皮河组,并恢复了该区被动大陆边缘至洋盆构造背景,进而探讨了其古地理格架的演化历史。

The stratigraphic sequence, age, and geotectonic background of Changning-Menglian tectonic belt have long been disputed. In this paper, the Nongba Section was measured in Lincang sheet 1 ： 25000 regional geological surveying and studied in stratigraphy, palaeontology, sedimentology and geochemisty. There is the significant progress made in stratigraphic sequence subdivision, age, geotectonic background and paleogeographic evolution. It indicated that the Nongba section was a fragment stratum system composed of seven different lithologic stratum fragments. The stratigraphic sequence was subdivided by tertiary Nanlin Formation, clastic rock represented continental slope facies and strata deposited in oceanic basin. Each of thrust slices is on the basis of the correation of those slices, the sequences of the passive continental margin to oceanic basin are reconstructed and the lithology stratum units are redefined to Wenquan Formation, Manxin Formation, Pingzhang Formation, Nanpihe Formation. Lastly the evolvemental history of paleogeography frame is explored in detail.