西藏聂拉木晚奥陶世的介形类

LATE ORDOVICIAN OSTRACODS IN NYALAM, SOUTHERN TIBET

文中首次报道西藏聂拉木地区亚来水厂剖面上奥陶统甲曲组介形类16属30种,介形类以古足介目类和圆足介目类为主,少量速足介目类。根据该剖面介形类时代特征,可以推断甲曲组应属于晚奥陶世早期,大致为Sandbian期—Katian期。该介形类生态组合为艾菲尔生态型,指示甲曲组在沉积时为近岸浅水环境。晚奥陶世喜马拉雅地层区与华南扬子区及塔里木介形类面貌相似,应属于相同的生物地理分区。

Ostracods are described for the first time from the Late Ordovician in Nyalam, southern Xizang (Tibet), China. Thirty species belonging to sixteen genera are described and figured from the Jiaqu Formation in the Yalai Waterworks section. The ostracod fauna suggests a probable Sandbian-Katian Age for the Jiaqu Formation. The ecological assemblage of ostracods fauna belongs to the Eifelian Ecotype, which implies a nearshore depositional environment for the Jiaqu Formation. In the diverse ostracod fauna of the Jiaqu Formation, many cosmopolitan or provincial genera are shared in Himalaya, Tarim and South China, suggesting a close biogeographic relationship for the blocks.