西藏南部中生代海相地层钙质超微化石的发现及意义

THE DISCOVERY OF CALCAREOUS NANNOFOSSILS IN MESOZOIC MARINE STRATA AT GYANGZE,SOUTHERN TIBET AND ITS SIGNIFICANCE

西藏南部有出露良好的海相侏罗—白垩纪地层,对采集自藏南江孜甲不拉沟口剖面甲不拉组的样品进行了高倍显微观察和照相,首次发现了具有地层标志意义的钙质超微化石。通过对化石的进一步鉴定,发现了保存较为完好的早白垩世贝利阿斯期和凡兰吟期的标准分子,还鉴定出了一些具有区域性对比意义的全球性分子和洲际分子。化石整体呈现早白垩世钙质超微生物的组合特征。研究区中生代海相地层钙质超微化石的发现,为藏南海相侏罗—白垩纪界线的厘定提供了新的古生物学证据。

The marine strata around the Jurassic-Cretaceous boundary crop out well in southern Tibet. The samples collected from the Jiabula Formation in the Jiabula- Gokou section of Gyangze area were analyzed by the authors under high-resolution microscope. The calcareous zonal nannofossils of Berriasian-Valanginian stages of early Cretaceous were found for the first time in the section. Some global or intercontinental species with regional significance for correlation were also discovered. In general, the nannofossils discovered have the same features of the Early Cretaceous assemblage. The discovery provides new paleontological evidence for delineation of the Jurassic--Cretaceous boundary in southern Tibet.