青藏高原北部茅口晚期地层缺失研究

青藏高原北部二叠纪地层分布广泛,化石丰富,尤其是早—中二叠世地层层序完整,且产丰富的、珊瑚、腕足类等化石,晚二叠世地层分布较为零星,仅局部地区有保存。通过对1999年以来在青藏高原北部空白区开展的1/25万区域地质调查成果等资料的分析,结合大量的野外观察,发现中、晚二叠世之间普遍存在着沉积间断,表现为地层之间的不整合或假整合以及晚二叠世地层的大量缺失。与华南区对比,普遍缺失中二叠统茅口阶顶部的Yabeina生物化石带,相当于本带所代表的茅口晚期地层是缺失的,这对于建立青藏高原北部地层序列,探讨沉积—构造演化史均具有重要意义。

STUDY OF THE LATE MAOKOUAN (PERMIAN) HIATUS IN NORTHERN QINGHAI-TIBET PLATEAU

There are abundant Early-Middle Permian fossils in northern Qinghai-Tibet Plateau, including mainly fusulinids, corals, and brachiopods, but Late Permian fossils are sparse and uncommon. Based on geological mapping and field observations, we conclude that there occurs a sedimentary interruption between the Middle and Upper Permian in the northern Qinghai-Tibet Plateau, which is represented by disconformity and angular unconformity. In contrast to South China, this region lacks the uppermost Mao- kouan Yabeina Biozone, consistent with the presence of a sedimentary hiatus around the Middle-Upper Permian boundary. This conlcusion has implications for the sedimentary sequence and sedimentary-tectonic evolution of this northern Qinghai-Tibet Plateau.