二叠纪-三叠纪生物演化重大转折时期华南-西藏高精度地层对比

Owing to natural factors, global biotic mass extinctions had appeared for five times since Cambrian biotic explosion. One of the most mass extinctions event happened in the end of Permian. The research on the Permian-Triassic biotic mass extinctions and recovery has become one of the important problem in the global paleontological research. Because South China (Tethys) and Tibet (Gondwanaland marginal) were situated in different geographical position during Permian and Triassic, we don't know whether or not the time of the biotic mass extinctions and recovery were identical between South China and Tibet; and biotic extinctions in the world happened at the same time, or passed with the lapse of time to move from South China to Tibet. For solving these important problems，the basis of the sitratigraphic correlation of high precision is very important. Therefore, the Permian-Triassic regional sitratigraphic correlations of high precision between South China and Tibet have become one of the heart of the matter in research on the major turning period of the biotic evolution. According to the Global Stratotype Section and Point(GSSP) and Unit-Stratotype of China, this project will establish the standards of the Late Permian-Middle Triassic regional stratigraphic division and correlation in South China and Tibet, and make stratigraphic correlation of high precision between South China and Tibet, by comprehensive study of different stratigraphic methods. These researches will bring about a great development in the study on the Permian -Triassic biotic mass extinctions and recovery as well as environmental change, and realize the aim from regional correlation to global correlation.

自寒武纪生物大爆发以来，地球上的生物经历了五次生物大灭绝事件，发生在晚二叠纪末期的是其中最大的一次。二叠纪-三叠纪之交生物大灭绝与复苏已成为当前国际古生物学研究的热点问题之一。由于当时中国华南（特提斯域）和西藏（冈瓦纳边缘）处在不同地理位置，两地之间生物灭绝和复苏延续的时间是否一致？全球生物灭绝是同时的还是随时间的推移存在地理上的迁移？这些问题都需要高精度区域地层对比研究来提供解决依据。因此，华南-西藏二叠纪-三叠纪高精度区域地层对比已经成为研究这一生物演化重大转折的关键问题之一。在全球层型剖面和点位(GSSP)和中国地层建阶标准的统一框架下，本项目通过多种地层学方法综合研究，建立与完善华南和西藏地区晚二叠世-中三叠世区域地层划分标准，进行相关地层单位之间的高精度对比，可有效推动二叠纪-三叠纪时期生物的灭绝与复苏以及环境的变化研究的深入开展，实现地层从区域对比发展到全球对比的目标。

二叠纪-三叠纪之交生物演化重大转折时期，华南地区位于靠近赤道的特提斯域，西藏地区位于冈瓦纳大陆边缘高纬度区。该时期两地的生态环境不同，生物大灭绝与复苏是否同步是当前广泛关注的热点问题之一。建立起不同地区地层划分标准及相关地层单位的对比关系是解决该问题的关键基础之一。本项目以全球层型剖面和点位和中国地层建阶剖面为标准，通过生物地层、岩石地层、年代地层、化学地层以及沉积环境等的研究，在西藏的班戈县保吉纳木错湖西岸原归为下白垩统“郎山组”中发现早三叠世牙形石；在仲巴县仁多原归为中二叠统“下拉组”白云岩地层中获得早三叠世印度期牙形石；在申扎县格仁错北面原划为中、上泥盆统“查果罗玛组”中发现中-晚二叠世珊瑚动物群；在南羌塘盆地改则县古姆乡座倾错原划为上三叠统“日干配错群”的硅质岩地层中发现中三叠世放射虫动物群；并将西藏措勤和南羌塘盆地的晚二叠世－早三叠世地层和沉积环境与华南四川地区的普光气田进行了对比。这些新发现修正了所研究地层的时代，弥补了研究区二叠纪和三叠纪地层研究的不足。通过详细的综合地层研究，本项目在华南的四川东部和重庆地区初步揭示了三叠纪海相红层的沉积特征、对比关系和分布规律；在贵州和云南地区建立了中三叠统坡段组及相关地层的区域对比关系；在湖北西部地区确定了上二叠统大隆组有机质富集的主控因素。在对资料进行综合分析的基础上，建立了华南和西藏重要地区中-晚三叠世珊瑚动物群特征、生态环境和对比关系；在Yao Jianxin(2016)文章中展示了中国地层表（2014）中国际年代地层与中国年代地层的对比关系、以及华南、华北和青藏高原三大区域岩石地层和生物地层的详细对比关系。上述研究成果修正和完善了华南和西藏地区晚二叠世-中三叠世区域地层划分标准、建立了相关地层之间对比关系，为在不同地层区深入开展二叠纪-三叠纪时期生物的灭绝与复苏的对比性研究提供了重要依据。