Abstract:
The Neogene Pliocene-Quaternary lower Pleistocene strata in the Zanda basin, Ngari area, Tibet, may be divided into the lower Pleistocene Qangzü (Q
p1x) Formation and the Neogene upper Pliocene Guge Group (N
2gg) and the latter may be further divided into the Pliocene Zanda Formation (N
22z) and the Pliocene Toling Formation (N
21t).The strata belong to graben-type lake-basin deposits and consist predominantly of alluvial-proluvial, paraglacial, glaciolacustrine, lacustrine and fluvial facies.The tectonic evolution of the basin went through five stages, i.e.:the early-rifting stage (N
21t), sustained rifting (N
22z), lake basin outflow (Q
p1x), steady uplift (Q
p2f) and rapid strong uplift (Q
p3-Qh).The activities of several normal faults on the southern and northern sides of the basin control the distribution pattern of the sedimentary facies:when fault activities were strong, the water bodies of the lake basin enlarged, the water became deep and mainly deep-and semi-deep lake deposits occurred; when fault activities weakened, the water bodies became shallow or dried up, the lake basin was filled up and there mainly occurred fluvial and alluvial-proluvial deposits.Since the beginning of the Quaternary, alpine glacial activities around the Zanda basin have intensified with the rapid uplift of Qinghai-Tibet Plateau, and then paraglacial and glaciolacustrine deposits have developed.