西藏定日县贡扎上白垩统浮游有孔虫与桑顿阶/坎潘阶界线的厘定

UPPER CRETACEOUS PLANKTIC FORAMINIFERAL BIOSTRATIGRAPHY AND DETERMINATION OF THE SANTONIAN/CAMPANIAN BOUNDARY IN GONGZA, TINGRI,TIBET

白垩纪是大洋缺氧及生物灭绝等重大地质事件频发的一个时期,也是全球气候变暖的重要时期。因此,白垩纪研究对于探讨地质历史时期地球的系统演化,尤其是生物与环境之间的协同演化关系,具有十分重要的意义。西藏定日贡扎剖面保存着上白垩统较为完整的地层序列,文中对上白垩统岗巴村口组和宗山组剖面岩石样品中获得的有孔虫化石进行研究,鉴定出有孔虫化石8属22种,识别出Dicarinella asymetrica、Globotruncanita elevata、Globotruncana ventricosa、Radotruncana calcarata等4个有孔虫化石带。根据有孔虫化石确定贡扎剖面的地层时代为晚白垩世桑顿期(Santonian)至坎潘期(Campanian),桑顿阶/坎潘阶界线位于Dicarinella asymetrica带与Globotruncanita elevata带之间。

The Cretaceous is a period of frequent occurrence of major geological events such as oceanic anoxia and biological extinction, and also an important period of global warming. Therefore, the study of the Cretaceous is of great significance to the study of the systematic evolution of the earth in geological history, especially the co-evolution relationship between organisms and environment. The complete stratigraphic sequence of the Upper Cretaceous is preserved in Gongza, Tingri, Tibet. In this paper, well-preserved planktic foraminiferal fossils obtained from the samples of the Gangba Cunkou Formation and Zongshan Formation of the Upper Cretaceous are studied, and 22 species of 8 planktic foraminiferal genera are identified. Four foraminiferal zones are recognized as follows, from bottom to top: Dicarinella asymetrica, Globotruncanita elevata, Globotruncana ventricosa, and Radotruncana calcarata. According to foraminifera fossils, the age of Upper Cretaceous strata of Gongza section should be from the late Cretaceous Santonian-Campanian, and the Santonian/Campanian boundary should be located at the boundary between the Dicarinella asymetrica Zone and the Globotruncanita elevata Zone.