西藏南部江孜地区早白垩世甲不拉组底栖有孔虫动物群的发现

DISCOVERY OF THE EARLY CRETACEOUS BENTHIC FORAMINIFERA FROM THE GYABULA FORMATION IN GYANGZE,SOUTHERN XIZANG(TIBET),CHINA

根据最新的国际年代地层表,侏罗/白垩系界线是显生宇系一级唯一没有GSSP(全球界线层型与点位)的界线。位于特提斯喜马拉雅北亚带的江孜地区,发育了连续的侏罗/白垩系界线地层,是目前国内海相侏罗/白垩纪界线生物地层学研究最具潜在竞争力的地区之一。本文在西藏南部江孜地区甲不热北沟剖面甲不拉组底部往上3.9米处及19.3米处首次发现了胶结壳底栖有孔虫动物群,共计4属11种:Ammobaculites agglutinans,Ammobaculites sp.1,Ammobaculites sp.2,Ammobaculites sp.3,Ammobaculites sp.4,Ammobaculites sp.5,Glomospira charoides,Haplophragmoides gigas minor,Haplophragmoides sp.1,Haplophragmoides sp.2,Reophax texanus。根据该动物群重要分子的地质时限推测,甲不拉组底部往上3.9米处就已经属于白垩系地层。因此甲不拉组底部胶结壳有孔虫动物群的发现支持了将甲不拉组划归白垩系的意见。

A diverse agglutinated foraminiferal fauna has been recovered for the first time from the basal Gyabula For- mation at the Gyabura Section in Gyangze, southern Xizang （Tibet）, China. This fauna consists of eleven species in four genera （including species in open nomenclature）：Ammobaculites agglutinans （d＇Orbigny）, Ammobaculites sp. 1, Ammobaculites sp. 2, Ammobaculites sp. 3, Ammobaculites sp. 4, Ammobaculites sp. 5, Glomospira charoides （Jones et Parker）, HaDlophragmoides gigas minor Nauss, Haplophragmoides sp. 1, HaDlophragmoides sp. 2 and Reophax texanus Cushman et Waters. According to the global stratigraphic distribution of the above-mentioned spe- cies, the foraminiferal fauna may be of the Early Cretaceous.