西藏中南部雄马—措麦以南地区早、中二叠世地层及其意义
Early and Middle Permian strata in the area south of Xungma-Comai in south-central Tibet and their significance
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摘要: 在西藏中南部雄马—措麦以南地区前人所定的属于中—晚侏罗世达雄群中采获了古生物化石，地层时代重新厘定为早—中二叠世。早二叠世早期拉嘎组中赋含重力滑塌块体和冰川漂砾，早二叠世晚期昂杰组碎屑岩中夹大量火山岩，中二叠世下拉组含大量火山岩碎屑等，与冈底斯—腾冲地层区广泛出露的早—中二叠世地层比较，岩性组合特征、沉积类型、沉积相、生物富集程度和属种组分及所处地质背景等诸方面均存在显著差异。该套地层的确定，对研究西藏早、中二叠世地层沉积相，重塑古地理环境，以及研究青藏高原和邻区特提斯构造发展阶段的地层演化、盆地构造背景等都有重要意义。Abstract: Fossils were collected from the strata assigned previously to the Mid-Late Jurassic Xungma Group in the area south of Xungma-Comai in south-central Tibet.Now the age of the strata has been determined to be Early-Mid Permian.The early Early Permian Laga Formation contains olistostromes and glacial boulders;clastic rocks in the late Early Permian Angji Formation contains large amounts of volcanic rocks;the Middle Permian Xiala Forma tion contains large amounts of fragments of volcanic rocks.In comparison with the Early-Mid Permian strata exposed widely in the Gangdise-Tengchong,there are ap-preciable differences in features of the lithologic association,sediment type,fossil concentration and generic and species components,as well as the geological setting.The determination of this sequence of strata has great significance for the study of the sedimentary facies of the Early-Mid Permian strata and reconstruc-tion of the paleogeographic environment in Tibet and the study of the stratigraphic evolution in the Tethyan tectonic development stage and tectonic setting of the basin in the Qinghai-Tibet Plateau and its adjacent areas.
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Keywords:
- Tibet /
- area south of Xungma-Comai /
- Early-Mid Permian /
- new sedimentary type
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