东特提斯二叠–三叠纪古地理解析：滇藏地区的古生物学、沉积学和古地磁学证据

The evolution of Tethys is one of the most significant events of the Phanerozoic. It fundamentally reformed the tectonics and geological environment of Eurasia. The evolution of Tethys is highly complicated and even today there is no a single model/hypothesis can satisfactorily explain comprehensively the field observations and lab data of different disciplines. Each model/hypothesis may explain one or several phenomena in a region, but cannot explain and may even contradict some other phenomena or data. .Due to differences in viewpoints, amount of geological data possessed, and understandings of these data, people have varied opinions on many important issues, such as, time and manner of Gondwana-derived blocks rifting from the northern margin of Gondwana, the way they drifted across the Paleo-Tethys, and the process of final collision with the southern margin of Laurasia..This project aims to find out more paleobiogeographical, sedimentological, paleomagnetic and other geological constraints on the evolution of the eastern Tethyan realm during the Permo-Triassic times. Our investigations will be mainly conducted on the Gondwana-derived blocks and the remnants (sutures) of Paleotethys in Yunann and Tibet. The key objectives of the project are 1) fossil content and paleobiogeographic property change; 2) check whether there is any sedimentological and other geological evidence for a Permian rift of the Lhasa block from the northern margin of Gondwana; 3) explore the tectono-sedimentary environment of stratigraphic successions in the Changning-Menglian Belt; and 4) acquire new paleomagnetic data from the these Gondwana-derived blocks.

特提斯的地质演化是显生宙最为重大的事件之一，深刻影响了欧亚地区的构造格局和地质环境。同时，其演化过程也高度复杂，迄今仍无一个模型/假说可以较为圆满地综合解释不同学科的野外地质观测资料和实验室数据。人们仍在涉及冈瓦纳派生地块裂解、飘移过程等一些重大问题上，争论颇多，亟待深入研究。.本项目将从我们近年来研究积累的实际情况出发，选择二叠-三叠纪这一古特提斯演化的重要时期，以滇藏地区冈瓦纳派生地块的裂解和向劳亚大陆南缘增生过程为主要对象，从进一步查找古生物地理学、沉积学、古地磁学等证据入手，探讨冈瓦纳派生地块上化石组成与古生物地理属性的变化、核查拉萨地块有无二叠纪从冈瓦纳北缘裂解的沉积学和其它证据、了解在昌宁-孟连带中几种地层序列的构造-沉积环境、获取冈瓦纳派生地块二叠-三叠纪的古地磁数据，对东特提斯域二叠-三叠纪的演化过程进行深入探讨，以获取更多的约束条件，减少在古地理重建方面的不确定性。

特提斯的演化是显生宙的一个重大事件，其演化过程高度复杂。在涉及瓦纳派生地块裂解、飘移过程等一些关键问题上，仍争论颇多，亟待深入研究。本项目选择二叠-三叠纪这一古特提斯演化的重要时期，以滇藏地区冈瓦纳派生地块的裂解和向劳亚大陆南缘的增生为主要对象，从进一步查找古生物地理学、沉积学、古地磁学等证据入手，对东特提斯域二叠-三叠纪的演化过程进行深入探讨。围绕这一主题，我们采取了以下研究思路，即研究该地区冈瓦纳派生地块上的沉积序列和所含化石，获取古环境、生物古地理和古气候变化的信息，结合不同地区古地磁数据，分析判断这些地块相对的古地理格局；通过对特提斯缝合带中混杂出现的诸地层单元的辨析和研究，提取有关特提斯的发育和消亡过程的信息。经过大量的野外工作和实验室分析测试工作，在以下几个方面取得了新的进展：（1）腾冲地块早二叠世含䗴鲕粒灰岩对气候环境变暖的指示、保山地块与缅甸掸邦䗴类Rugososchwagerina的生物古地理和中二叠世基默里陆块代表分子的确定、拉萨地块中二叠世䗴类分布特征及其对该地块古地理环境的指示意义；（2）昌宁-孟连带不同碎屑岩序列的区分及其沉积和构造环境分析、碳酸盐生物地层学和沉积环境分析；（3）保山地块、拉萨地块和特提斯喜马拉雅以及华南不同时代的古地磁数据的获取及其相应的古地理意义探讨。这些成果的取得，为深入了解东特提斯的演化过程提供了新的证据和有效的约束。