西藏吉隆白垩纪末期浮游有孔虫的发现及其年代意义  

DISCOVERY OF THE LATEST CRETACEOUS PLANKTONIC FORAMINIFERA FROM GYIRONG OF SOUTHERN TIBET AND ITS CHRONOSTRATIGRAPHIC SIGNIFICANCE

作　　者：万晓樵[1] 丁林[2] 

机构地区：[1]中国地质大学,北京100083 [2]中国科学院地质与地球物理研究所,北京100029

出　　处：《古生物学报》2002年第1期89-95,共7页Acta Palaeontologica Sinica

基　　金：国家重点基础研究发展规划项目 (G19980 40 80 0 );国家自然科学基金 (No .49872 0 0 3)资助课题

摘　　要：西藏吉隆县宗卓组顶部发现了丰富的浮游有孔虫动物群 ,其时代为晚白垩世马斯特里赫特期G .gansseri带的上部至A .mayaroensis带的下部 ,年龄值在 6 8— 70Ma之间。据江孜至吉隆一带地层和古生物学的研究与对比 ,认为特提斯 喜马拉雅北亚带的半深水至远洋环境是在康潘晚期至白垩纪末期由东向西逐步结束的 。Marine Cretaceous is widespread in the Tethys Himalaya region. It has been accepted that the Himalayas was formed by collision of the Indian Plate with the south Asian margin. The northward shifting of the Indian Plate closed the Neothethys Ocean which lay to the north of the former. Suturing is thought to have occurred scissor like, with first contact in the western Himalayas as early as perhaps the latest Cretaceous (Beck et al ., 1995), and afterwards prograding eastwards. The collision in southern Tibet, by the recent study, started around the Cretaceous Tertiary boundary time (Wan et al ., in press). Prior to the collision, a pelagic ocean existed along the Yarlung Zangbo suture. The north margin of the Indian Plate was in continental slop and shelf positions. That part of sea in Cretaceous is called the Tethys Himalaya. This region is sedimentologically subdivided into the south Tethys Himalaya sub belt and north Tethys Himalaya sub belt. During the Latest Cretaceous, the south sub belt was a carbonate platform sedimentary belt that has been studied by many authors (Wen Shixuan, 1974; Wang Yigang, 1980; Wan Xiaoqiao, 1985,1991; Hao Yichun et al ., 1985; Willems, 1993). The north sub belt, however, was a semi pelagic to pelagic sedimentary belt. Due to the tectonic deformation and rare fossil preservation in the north sub belt, the stratigraphic sequence and dating were obscure. Recently, the authors found a rich planktonic foraminiferal fauna from the Gyirong region. The discovery of the fauna give an age to the stratigraphy of the northern sub belt, and also make a better understanding to the shifting progress of the Indian Plate to the north. The Cretaceous is distributed along the south sside of the Yarlung Zangbo suture zone and represented by a set of sandy and pelagic sediments intercalated with volcanic rocks and silicalites. The entire sequence of strata has been strongly deformed, especially near the Yarlung Zangbo opiolites. Tectonic mélanges and high pressure/low tempera

关 键 词：浮游有孔虫 白垩纪末期 西藏吉隆 时代 

分 类 号：Q915[天文地球—古生物学与地层学]