The India-Asia collision led to the demise of the Tethys Ocean, and the subsequent uplift of the Qinghai-Tibet Plateau had a profound impact on Cenozoic topography, oceanography, and climate. However, collision ages vary depending on collision definition and methodology, with the cessation of marine deposition constraining the minimum/youngest collision age. The Enba and Zhaguo formations of the Qumiba Section (southern Tibet) represent the youngest marine strata in the eastern Tethys Ocean. Previous studies have suggested a middle-late Eocene or early Eocene closure time, however, our nannofossil data indicate an age of 53.67–52.64 Ma (nannofossil zone CNE3, which closely corresponds to Zone NP11). Nannofossil relative abundances can explain the early Eocene tectonic evolution of southern Tibet, with the increasing number of reworked Cretaceous nannofossils over time reflecting the degree of erosion of previously deposited sediments as the plateau uplift progressed. Our data suggest that Cretaceous and Paleocene calcareous nannofossils were an important sediment source to the Qumiba Section.

印亚碰撞导致特提斯洋消亡，随后青藏高原隆升对新生代地貌、海洋和气候产生了深远的影响。然而，碰撞年龄因碰撞定义和方法而异，海洋沉积的停止限制了最小/最年轻的碰撞年龄。曲米巴剖面（藏南）的恩巴组和扎果组代表了特提斯洋东部最年轻的海相地层。先前的研究表明始新世中晚期或始新世早期闭合时间，然而，我们的纳米化石数据表明年龄为 53.67-52.64 Ma（纳米化石区 CNE3，与 NP11 区密切对应）。纳米化石相对丰度可以解释藏南早始新世构造演化，随着时间的推移，重新加工的白垩纪纳米化石的数量不断增加，这反映了随着高原隆起的进展，先前沉积的沉积物的侵蚀程度。我们的数据表明，白垩纪和古新世钙质纳米化石是 Qumiba 剖面的重要沉积物来源。