西藏申扎和改则地区早石炭世地层及腕足类研究

EARLY CARBONIFEROUS BIOSTRATIGRAPHY AND BRACHIO-PODS OF GERZE AND XAINZA, NORTH TIBET

西藏申扎和改则地区早石炭世地层发育,腕足类及珊瑚类化石丰富。腕足类化石计有34属45种,共建立3个组合;申扎大塘阶下部巴日阿郎寨组Ovatia-Unispirifer组合;大塘阶上部永珠组Balakhonia-Productus组合;改则大塘阶上部Latiproductus-Striatifera组合。本文系统讨论了各腕足类组合的时代及与国内外同期地层的对比,将西藏境内早石炭世的沉积物及生物群划分为3个类型。根据生物群及沉积物在空间上的分布特点,笔者认为在早石炭世时,班公湖至怒江断裂南北生物群及沉积物具有明显的差异,即南部申扎和珠峰地区生物群及沉积物特征与冈瓦纳大陆相似,而北部改则地区与扬子地台的生物群及沉积物特征相同,其间可能有宽阔的海域隔离。

: The marine Lower Carboniferous of North Tibet is well-developed and abounds with bra-chiopods, which consist of 45 species and 24 genera recognized and described here, Among these three brachiopod assemblages have been set up in ascending order, all within the Upper Visean : (1) Ovatia-Unispirifer assemblage; (2) Balakhonia-Productus assemblage; (3) Latiproductus-Striatifera assemblage. The Lower Carboniferous of Xainza in North Tibet is divided into the Duonageli Formation (Lower Tournasian), Pongka Formation (Upper Tournasian); Barialangzhai Formation (Lower Visean) and Yongzhu Formation (Upper Visean) . The Lower Carboniferous of Gerze in North Tibet is only represented by the Riwanzhaka Formation (Upper Visean), the Yanguanian and Lower Datangian being absent. The Lower Carboniferous biostratigraphic correlation and the faunal characteristics of Xainsa and Gerze are also discussed. Based on the analysis of materials available, it is concluded that during Early Carboniferous Xainza formed a part of the Gondwana, wheres Gerze lay on the Yangtze plate.