运用鱼牙化石氧同位素估算西藏特提斯喜马拉雅带白垩纪海水古温度

白垩纪气候状态被认为是预测未来全球变化的重要参照，然而东特提斯地区海水古温度数据十分缺乏，严重制约了白垩纪全球古气候研究。特提斯喜马拉雅带是研究东特提斯白垩纪古气候的理想场所，但由于后期改造强烈，导致诸多古温度指标无法适用。项目组前期在该区白垩系中发现多枚鱼牙化石，初步研究结果表明它们保存了水温原始信息，未受明显后期改造。基于此，项目拟在特提斯喜马拉雅带浅海沉积物中进一步系统采集鱼牙化石，以鱼牙氧同位素为指标，定量估算研究区白垩纪海水温度，通过阴极发光观察和地球化学手段剔除受成岩改造的数据。通过沉积学、微体生物地层学和碳同位素地层学研究，获得化石的形成环境和年代学信息。在此基础上，重建研究区白垩纪海水温度演化历史，将其与全球古气候记录及其它地质事件对比，探讨区域气候演化的机制。项目研究有望填补该区域定量古水温数据的空白，为白垩纪全球古气候研究提供新的资料。

Typical greenhouse climate of Cretaceous is regarded as a best analogy to the future global change. Tempo and spatial distribution of seawater temperature is the fundament to investigate the evolution of Cretaceous climate. At present, there are very scarce data obtained from the eastern Tethys area, which is the second largest ocean during the Cretaceous period according to the paleogeographic reconstructions. As a consequence, the climate modeling results can not be testified in this area. Shortage of data in eastern Tethys also limits our understanding to the global climate state and change process during Cretaceous. Tethyan Himalayas is the unique place to study the paleoclimate of eastern Tethys. Because the carbonates and organic carbon were altered significantly by orogenesis, many paleothermometers can not be used to estimate the sea water temperatures. The applicant of this proposal found abundant fossil fish teeth in the Cretaceous shallow marine sediment of the area in last year. Theoretically, the bio-apatite are less prone to diagenetic alteration than carbonates and organic carbon. We did experiments on some fossils and the results indicate that they probably recorded the primary seawater temperature signals. So we plan to collect more fossils in the Cretaceous strata of Tethyan Himalayas. The seawater temperature will be estimated with the δ18O values of fish teeth. The CL image and REE geochemistry will be used to diagnose diagenetically overprinted data. Based on studies of lithostratigraphy, microfossil biostratigraphy and δ13C chemostratigraphy, the ages of the fossils will be analyzed. Thus the history of the seawater temperature during Cretaceous can be obtained. By comparison with global paleoclimate and geological event archives , we will investigate the mechanisms controlling the paleotemperature evolution of eastern Tethys. This study will provide the first quantitative paleotemperature data for the Cretaceous eastern Tethys Ocean and enable a better understanding to the global climate changes during the Cretaceous greenhouse world.