青海可可西里盆地雅西措组介形类动物群及其地层意义

OSTRACOD FAUNA FROM THE YAXICUO FORMATION IN THE HOH XIL BASIN, QINGHAI PROVINCE AND ITS STRATIGRAPHIC SIGNIFICANCE

青海可可西里盆地是青藏高原腹地最大的沉积盆地。然而对于该盆地新生代地层的沉积时代目前仍然存在争议。可可西里盆地南侧雁石坪地区雅西措组中含丰富的介形类化石,该介形类动物群对青藏高原腹地新生代生物地层对比具有重要意义。文中通过对可可西里盆地南侧雁石坪地区通天河剖面进行系统的采样和室内分析,共获得652枚介形类壳体,共鉴定识别出14属48种,自下而上建立了2个介形类组合带,即Austrocypris cf. posticaudata-Candoniella albicans-Leucocythere tropis组合带和Ilyocypris errabundis- Darwinula stenimpudica组合带。通过与柴达木盆地、伦坡拉盆地、江汉盆地以及渤海湾沿岸等地区的介形类生物地层进行区域对比研究,推测可可西里盆地通天河剖面雅西措组的沉积时代为晚始新世—早渐新世。

The Hoh Xil Basin is the largest continental Cenozoic basin in the plateau’s interior. However, the stratigraphic age of the Cenozoic sediments of the Hoh Xil Basin remain debated. The Yaxicuo Formation from the Yanshiping area, southern Hoh Xil Basin contains abundant ostracod fossils. The research on this ostracod fauna is important for the study of Cenozoic biostratigraphic correlation for the hinterland of the Tibetan Plateau. In this study, 48 ostracod species belonging to 14 genera are described from the Yaxicuo Formation of the Tongtianhe section. The ostracod fauna can be subdivided into two assemblage zones: Austrocypris cf. posticaudata-Candoniella albicans-Leucocythere tropis assemblage and Ilyocypris errabundis-Darwinula stenimpudica assemblage. Through comparing these ostracod fossils with other ostracod records in the Qaidam Baisn, Luopola Basin, Jianghan Basin and Bohai area etc., we bracket the depositional age of the Yaxicuo Formation of the studied Tongtianhe section as the late Eocene?early Oligocene.