四川南部布拖地区志留系的新研究  

NEW STUDY OF THE SILURIAN SYSTEM IN THE BUTUO DISTRICT,SOUTHERN SICHUAN,SW CHINA

作　　者：王怿[1,2] 戎嘉余[1,2] 詹仁斌[1,2] 黄冰[1,2] 吴荣昌[2] 栾晓聪 

机构地区：[1]现代古生物学和地层学国家重点实验室,江苏南京210008 [2]中国科学院南京地质古生物研究所,江苏南京210008 [3]中国科学院大学,北京100049

出　　处：《地层学杂志》2014年第3期257-267,共11页Journal of Stratigraphy

基　　金：国家基础发展规划项目(973项目)(2012CB821901);国家自然科学基金(No.41221001;41290260;41172013);中国地质调查局(12100122332项目)资助;IGCP 591(早;中古生代重大事件)项目成果之一

摘　　要：四川南部布拖地区位于扬子块体周缘盆地构造的西南缘,属于楚雄前陆盆地与小江断裂系的北部,其地层古生物研究,可为华南古陆构造演化提供可靠的基础地质资料和证据。根据布拖地区志留系3条剖面的生物地层研究,认为本地区志留系主要发育Llandovery世,缺失Wenlock、Ludlow和Pridoli世的地层,其地层序列自下而上为:龙马溪组、布拖组(新名)、石门坎组(厘定)、乌科组(新名)、大路寨组和莱地湾组,在志留纪Llandovery晚期,该地区抬升为陆地,直至二叠纪早期再次接受沉积。通过与扬子块体其他地区志留系的对比研究,提出布拖地区与扬子块体的志留纪具有相同和类似地质发展史,表明整个扬子块体为稳定的、以浅海沉积为主的沉积区;在扬子块体上,下红层底、顶界是穿时的;初步分析布拖地区志留系的沉积环境,认为从康滇古陆到布拖沉积区,是一个从陆地到浅海的古地理格局,扬子地块西缘不存在较深或深海的环境。The Butuo district is located geographically in southern Sichuan Province, SW China, and paleo- geographically in the southwestern margin of the Yangtze Platform. Detailed paleontological and stratigra- phical investigation in this area could provide some reliable basic geological data to understand the regional tectonic evolution of the South China plate. On the basis of biostratigraphical data from three Silurian sec- tions in the Butuo district, we are able to draw the following conclusions. 1） Only Llandovery rocks were developed in the study area, including the Lunmachi, the Butuo（new name）, the Shimenkan （emend.）, the Wuke （new name）, the Daluzhai and the Caidiwan formations, in an ascending order. 2） No Wenlock, Ludlow and Pridoli strata have been observed in this area, indicating that this part of the Yangtze Block was uplifted above the sea level since the late Llandovery, and received no marine deposits untill the Early Permian when it was flooded again by sea water. 3） The geologic history of Butuo district is similar to that of other districts or areas of the Yangtze Block, suggesting that the Yangtze Block was a stable tectonic u- nit dominated by shallow marine depositional environments. 4） The so-called Silurian ＂Lower Red Beds＂ are diachronous in its lower and upper boundaries, both of which become older eastward. 5） Preliminary investigation reveals that the Silurian sedimentological facies of the Butuo district indicate a dominance by shallow marine environments. Thus, there may have been a paleogeographical setting from oldland to shal- low marine between the Kangdian Oldland and the Butuo district, and there were no deep or deep marine environments in the western margin of the Yangtze Block.

关 键 词：岩石地层 生物地层 布拖组 石门坎组 乌科组 志留系 扬子块体 康滇古陆 四川南部 

分 类 号：P534.43[天文地球—古生物学与地层学]