豫西宜阳地区晚二叠世晚期—早三叠世沉积记录及其对古气候变化的响应

Palaeoclimate Changes Revealed by Sedimentary Records of the Upper Permian-Lower Triassic Strata in Yiyang Area,Western Henan Province, China

晚二叠世早三叠世宜阳地区位于东特提斯低纬度地区的华北板块南缘,发育一套连续且沉积特征显著的陆相碎屑岩相沉积,是研究陆相晚二叠世早三叠世古环境与古气候变化的理想地层。本文在前人研究与野外实测的基础上,采用岩石学、沉积学、古生物学方法综合分析研究区的沉积记录,识别出宜阳地区在该时期由陆源近海的滨湖沉积环境向河流沉积环境过渡的古环境,重建了晚二叠世晚期早三叠世宜阳地区的古地理面貌。沉积特征显示,此期整体气候条件为炎热半干旱,并且在长兴期末期与奥伦尼克期早期出现了极端干旱气候,可能是受到当时全球性巨型季风环流的影响。这一时期的古气候与古环境的变化可能对二叠纪末陆地大灭绝事件起到了推动作用,并抑制了早三叠世生物复苏的进展。

The Yiyang area during the late Permian-early Triassic Boundary(PTB) was located in the southern margin of the North China Craton in the lower latitudes of eastern Tethys. A set of continental clastic lithofacies was developed in this area and is ideal for studying the paleoenvironment and paleoclimatic changes of the late Permain-early Triassic. This paper is based on previous research and field observations to study the sedimentary characteristics in Yiyang area by investigating the lithology, sedimentology and paleobiology. A lacustrine-fluvial sedimentary environment is identified and the paleogeography of Yiyang area is reconstructed. The overall climate conditions during this period were hot-semiarid and extreme drought occurred at the end of the Changsingian and the early Olenekian. The periodic(seasonal) climate could be controlled by Pangean Megamonsoon. The evolution of paleoclimate and paleoenvironment may have played an important role in the end-Permian massive extinction and inhibited Triassic biotic recovery.