华南地区拉丁期大海退的生物地层限定

South China has developed extensive Triassic strata of marine origin and is an ideal location for studies of biostratigraphy and event stratigraphy. Amongst these Triassic sediments, the Early Triassic attracted most research attentions whereas the Middle Triassic, especially the Ladinian stage, was less systematically studied. This may be an artefact ascribed to rare Ladinian sediments in South China, which was postulated as in response to the Great Ladinian Regression (Yin, 1992). Many advances have been made on the Middle Triassic stratigraphy in recent years but not on the Great Ladinian Regression. The timing, magnitude and impact on marine ecosystem of this sea-level low stand is not fully understood. This proposal is based on the superb Triassic record of South China. We plan to carry out detailed biostratigraphic, chemostratigraphic and sedimentological investigations on the Ladinian strata in western Guizhou, eastern Yunnan and Qinling Trough areas. A better understanding of manifestations of the Great Ladinian Regression within the South China Plate can be achieved with aids of our combined approaches using high-resolution biostratigraphy, chemostratigraphy and sedimentology. We aim to archive and compare Ladinian faunas and palaeoenvironmental settings in the Yangtze and Qinling regions.

华南发育广泛的海相三叠纪地层，是研究生物地层和事件地层的理想地区。其中，下三叠统的地层研究十分充分；而中三叠统的地层，特别是拉丁阶地层，研究相对薄弱。这可能是由于拉丁期大海退（殷鸿福，1982）导致的海相地层偏少所致。近年来中三叠世的研究得到了一定的发展，而对拉丁期大海退这一事件的理解却停滞不前：拉丁期大海退的时限，范围和造成的生态环境影响均没有得到很好的理解。本项目依托华南良好的海相三叠系记录，拟在黔西-滇东及南秦岭两个地区深入开展拉定期的岩石地层、生物地层、化学地层及沉积学的研究，力争通过扎实的野外和室内沉积学观察，高分辨牙形石生物地层的建立和碳同位素化学地层的辅助全面理解拉丁期大海退在华南不同相区的表现，进而对比扬子地区与秦岭地区拉丁期生物与环境的异同。

我国华南的三叠系地层广发发育，但碳酸盐岩台地自中三叠起不断萎缩，至晚三叠卡尼晚期，扬子台地碳酸盐岩生产完全关闭。一直以来我国西南地区中-上三叠统地层研究相对薄弱。这可能是由于拉丁期大海退导致的海相地层偏少所致；而华南地区安尼期之后的化石面貌独具特色，国际对比困难。近年来，中-晚三叠世的研究得到了一定的发展，拉丁-卡尼期逐渐成为国际研究热点。本项目依托华南良好的海相三叠系记录，在黔西-滇东及南秦岭两个地区深入开展拉定期的岩石地层、生物地层、化学地层及沉积学的研究，建立了适用于华南的牙形石生物地层框架、碳同位素化学地层曲线和国际对比方案。经过三年努力，本项目顺利完成既定研究目标，资助发表SCI论文6篇，对我国华南地区拉丁-卡尼期生物地层的国际对比提供了大量化石证据。