青藏高原东缘古近纪粗碎屑岩沉积学及其构造意义  

Sedimentology and Tectonic Significance of Paleogene Coarse Clastic Rocks in Eastern Tibet

作　　者：周江羽[1] 王江海[2] An YIN BK HORTON MS SPURLIN 

机构地区：[1]中国地质大学资源学院 [2]中国科学院广州地球化学研究所 [3]Department of Earth and Space Sciences,University of California,Los Angeles,CA90095,USA

出　　处：《地质学报》2003年第2期262-271,T008,共11页Acta Geologica Sinica

基　　金：国家重点基础研究发展规划项目(编号G1998040800);国家自然科学基金(编号49972026;39972026);中国科学院重点知识创新项目(编号KZCXZ-SW-117)和美国国家自然科学基金项目联合资助的成果

摘　　要：青藏高原东缘古近纪盆地的填图和沉积学研究表明,在青藏高原东缘区域性走滑-挤压构造背景下形成的古近纪盆地内广泛发育厚层—巨厚层状的紫红色粗碎屑岩系。其沉积特征指示为一种近源快速堆积的泥石流和辫状河道沉积体,形成于干旱炎热气候条件下的典型陆内冲积扇环境。盆地充填序列、粗碎屑岩层序、动植物化石和盆地内岩浆岩^(40)Ar-^(39)Ar年代学等综合研究结果表明,古近纪盆地内粗碎屑岩大约形成于38～29 Ma。该时期与青藏高原东缘北段(横断山地区)古近纪盆地的形成和南段(兰坪—思茅地区)大盆地的裂解时间基本一致,这很可能预示着青藏高原在晚始新世—早渐新世期间曾发生过整体的快速构造隆升。Field mapping and sedimentologic investigations of Paleogene basins in eastern Tibet suggest that the depositional characteristics of widespread thick-bedded, purplish red, coarse-grained clastic series of Paleogene basins in the setting of regional strike-slipping and thrusting indicate that the series is a proximal and rapid-accumulating sediment body in debris flows and a fan-surface braided river in a typical dry and hot subaerial alluvial fan environment. The sequences of basin filling and coarse clastic rocks, fauna and sporopollen associations and 40Ar/39Ar dating confirm that the coarse clastic rocks formed in Paleogene basins in the period of 38 ~ 29 Ma, nearly coeval with the formation of the Paleogene basins in the northern segment (Hengduanshan area) and the disintegration of large basins in the southern segment (Lanping - Simao area). The sedimentologic characteristics of the Paleogene coarse-grained clastic rocks, basin tectonics and magmatic activity indicate that a rapid wholesale tectonic uplift may have occurred in the Tibetan Plateau from the Late Eocene to Early Oligocene.

关 键 词：青藏高原 古近纪 粗碎屑岩 沉积学 构造隆升 氩同位素年代学 

分 类 号：P512.2[天文地球—地质学]