西藏措勤打加错地区上三叠统江让组的发现及其地质意义

摘要

在西藏措勤打加错地区新发现上三叠统江让组，其为一套海相碎屑岩及碳酸盐岩沉积建造，岩性主要为不等厚层状石英质砾岩、深灰色薄层状-块状生物碎屑微晶灰岩、含砂粉砂质微晶灰岩、含石英砾质生物碎屑灰岩、砂屑灰岩夹钙质细砂岩，产珊瑚 Distichophyllia sp.，Volzeia sp.，Montlivaltia sp.，M. cf . xainzaensis 、海绵：Hartmanina sp.和双壳类 Xenocardita ？sp.，时代为晚三叠世卡尼期-诺利期，与下二叠统昂杰组呈角度不整合接触。江让组在该地区的发现，完善了冈底斯西部三叠纪的地层系统，为研究印支运动对冈底斯西部的影响和古特提斯洋的演化提供了依据。%The Upper Triassic Jiangrang Formation newly discovered in the Daggyai Lake area,Coqen,Xizang is built up of a succession of sedimentary formation composed of mixed marine clastic rocks and carbonate rocks. Lithologically,these rocks include bedded quartzose conglomerates,dark grey thin-bedded to massive bioclastic micritic limestones,sand-bearing silty micritic limestones,quartz-bearing gravelly bioclastic limestones and sandy limestones intercalated with calcareous fine-grained sandstones,in which there occur the Carnian-Norian( Late Triassic)organic fossils such as the corals Distichophyllia sp. ,Volzeia sp. ,Montlivaltia sp. and M. cf. xainzaensis ,the sponges Hartmanina sp. ,and the bivalves Xenocardita?sp. . The Jiangrang Formation displays an angular unconformable contact with the Lower Permian Angjie Formation. The discovery of the Jiangrang Formation will improve the Triassic stratigraphic systems in western Gangdise,and may provide the new evidence for the better understanding of the Indosinian movements in western Gangdise and the evolution of the Palaeo-Tethys.