志留纪晚期小溪组在湖北宜昌纱帽山的发现  

DISCOVERY OF THE LATE SILURIAN XIAOXI FORMATION AT THE SHAMAOSHAN SECTION, YICHANG, HUBEI, SOUTH CHINA

作　　者：王怿[1] 唐鹏[1] 张小乐[2] 张雨晨 黄冰[1] 戎嘉余[1] Wang Yi;Tang Peng;Zhang Xiao-le;Zhang Yu-heng;Huang Bing(State Key Laboratory of Palaeobiology and Stratigraphy,Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment,Chinese Academy of Sciences,Nanjing 210008;School of Earth and Space Seienees of Peking University,Beijing 100871)

机构地区：[1]中国科学院南京地质古生物研究所和生物演化与环境卓越中心现代古生物学和地层学国家重点实验室,江苏南京210008 [2]北京大学地球与空间科学学院,北京100871

出　　处：《地层学杂志》2018年第4期371-380,共10页Journal of Stratigraphy

基　　金：国家自然科学基金委(Nos.41530103;41521061;41290260);中国科学院B类先导专项培育项目(XDPB05)资助

摘　　要：湖北宜昌纱帽山出露了中国志留纪地层研究最早的一个经典地质剖面。近三十年来该处志留系上部的纱帽组一直被归于兰多维列统。在研究遗迹化石和植物类表皮后发现,纱帽组最上部(第4段)与第1、2、3三段,除岩性存在区别外,生物面貌也有重要差别。联系到上扬子区其他剖面志留纪晚期地层的发育情况,第4段与小溪组的特征相同,宜单独分出,称小溪组,时代归于Ludlow晚期到Pridoli早期,而纱帽组其余部分仍归于Llandovery世Telychian早期。小溪组与厘定后的纱帽组之间为假整合接触。研究表明,扬子区于Llandovery世晚期海水退尽,上升成陆后,部分地区(包括宜昌)到志留纪晚期一度又被海水淹没,沉积了一定厚度的地层,之后又上升成陆,直到中泥盆世。The Shamaoshan section in Yichang, Hubei, South China is a classical geological section of Silurian in China. The Shamao Formation in the upper part of this section has been considered Llandovery in age for nearly 30 years. This paper reports tubular trace fossils and cuticle-like plant fossils from Member four of the Shamao Formation as originally defined. We found that there are distinct differences in lithology and paleon- tology between Member four and members one to three of the Shamao Formation as originally defined. In consideration of recent developments in late Silurian stratigraphy in the Upper Yangtze Platform, we propose that Member four of the original Shamao Formation is the same as the Xiaoxi Formation. Thus, it is removed from the Shamao Formation and regarded as the Xiaoxi Formation. The age of the Xiaoxi Formation is late Ludlow to early Pridoli. The rest of the original Shamao Formation is early Telychian, Llandovery in age. The contact between the Xiaoxi Formation and the redefined Shamao Formation is a parallel unconformity. The study also shows that, in the Yangtze Platform may have been exposed subaerially in the late Llandovery and was then flooded in the late Silurian. After the late Silurian, this area rose again and was exposed subaerially until the Middle Devonian.

关 键 词：岩石地层 生物地层 纱帽组 小溪组 志留纪晚期 宜昌 湖北 

分 类 号：P534.43[天文地球—古生物学与地层学]