古新世-始新世极热事件（PETM）对藏南浅水碳酸盐岩沉积环境的影响

The Paleocene-Eocene Thermal Maximum event (PETM) is the latest and rare extreme warming event in geological history, which can help us to understand the global climate and environment change under extreme greenhouse condition, and the international academic community take it as a typical example of today's global warming. In the past decades, our knowledge about PETM has been greatly improved by investigating this event. However, previous studies, on the one hand, are mainly focused on western Tethys or North Atlantic area, and less about eastern Tethys, on the other hand, are commonly focused on the deep sea, shallow continental shelf or continental sediments, and less about the shallow water carbonates. .It is reported that the continuous Paleocene-early Eocene shallow-marine carbonate were outcropped from Gamba to Tingri area in Tethyan Himalaya, Southern Tibet. In this program, an integrated studies of stratigraphic, sedimentologic, petrologic, mineralogical and geochemical will be carried out to identify the detailed PETM process in the shallow marine carbonates successions, the Origin of the conglomerates and hydrological changes during the PETM. On the basis of these studies, we will discuss the hydrological changes associated with the PETM and its effects on sedimentary environment of shallow water carbonate in Southern Tibet. We believe that this program will improve our knowledge about the PETM in Southern Tibet, and will also help us understanding the impact of the PETM event on the global climate and environment.

古新世-始新世极热事件（PETM）作为距今最近、最为剧烈的全球增温事件，对了解极端温室气候条件下，全球气候环境变化有重要意义，国际学术界将其视作现今全球变暖的对比实例。过去的几十年中，PETM的研究取得了大量成果。然而，前人的研究一方面多集中于西特提斯和北大西洋地区，对东特提斯研究少；另一方面，多集中于深海、陆相沉积物，对浅海碳酸盐岩研究少。.区域地质研究发现，东特提斯藏南特提斯喜马拉雅定日-岗巴一带，发育完整的古新统-早始新统浅海相碳酸盐岩，本项目拟以这套浅水碳酸盐岩为研究对象，通过系统的地层学、沉积学、岩石学和地球化学研究，精细刻画PETM事件在地层中的作用过程，查明PETM时期水循环变化、碳酸盐砾岩成因等。在此基础上，探讨PETM对东特提斯浅水碳酸盐岩沉积环境的影响，以提高PETM在浅水碳酸盐岩台地上的研究现状，为区域对比、全面了解PETM对全球气候环境造成的影响提供依据。

藏南特提斯喜马拉雅地区晚古新世-早始新世浅水碳酸盐岩做了详细的沉积学、古生物学和地球化学工作。研究发现在PETM事件起始段（onset）、负偏段（core），沉积环境、底栖大有孔虫生物组合与PETM事件之前相比并无变化，即SBZ4/SBZ5界线，生物组合以Nummulitids底栖大有孔虫为主，沉积环境为碳酸盐岩中缓坡，且水深向上逐渐变深，但是在PETM事件恢复段（recovery），即SBZ5/SBZ6界线，底栖大有孔虫生物组合更替为Alveolina-Orbitolites，沉积环境突变为局限潟湖，二者之间存在一次明显的古水深变浅事件，而此次变浅对应于岗巴地区瘤状灰岩与块状灰岩之间的砾岩沉积。在PETM恢复段，相对海平面突然变浅，形成一系列深切谷，在随后的海侵过程中形成岗巴地区的砾岩层。至于此次水深变浅的原因，目前仍存在争议，可能为构造引起的隆升，也可能是海平面变化引起的。PETM事件期间，赤道地区海水表层温度从PETM起始段开始迅速上升，在PETM core阶段达到最高，但是有趣的是，底栖大有孔虫在温度最高的core段，没发生改变，却在PETM恢复段，发生改变，因此，认为，温度并非底栖大有孔虫发生变化的原因，提出可能是海平面突然下降，改变了底栖大有孔虫的生活环境（水深、盐度等），从而引起了底栖大有孔虫的更替。藏南定日地区PETM事件碳同位素CIE幅度达7‰，可能亦与海平面变化相关。共发表SCI论文3篇，其中第一作者2篇。