Modern Sedimentary Environment and Sedimentary Facies Characteristics in Qinghai Lake

Key words: 
• Qinghai Lake /
• modern deposition /
• sedimentary facies /
• sedimentary enviroment /
• rift-subsidence lake /
• tectonic-sedimentary system

Abstract: Qinghai lake is a plateau inland intermountain rift-subsidence Iake basin developped since quaternary. The development andevolution of the lake basin have experienced four stages, that is, the rift period, the lake and river coexistence period, the mostflourishing development period and the shrivel period. The distribution of the sedimentary facies is controlled by climate, sedimentsource, rivers, topography and tectonic evolution histories, which is charactered by intermountain rift-subsidence and near sedi-ment source deposition. Along the long axis direction of the basin, the sedimentary deposit system of braided river, meanderingriver, delta, subaqueous channel and deep water lacustrine facies are developed at the west end, whereas at the east end of thebasin mainly distributed the aeolian and lagoon deposits. In the areas along the short axis direction of the basin, the systems of in-termontain fluvial, braided river, diluvial fan, fan-delta and shallow lake shore facies are deposited. The south bank is relativelysteeper, where mainly formed several large and small alluvial fan or aprons. In shallow lake shore areas, sedimentary deposits oflongshore bar, sand spit, shingle beach, sand beach, mudflat, swamp and lakebay facies are well developed. Compared with otherlakes in China and abroad, the deposits in Qinghai lake are featured by their better developed aeolian, subaqueous fluvial and long-shore bar facies. Based on field survey, sampling anisys and comprehensive research the paper discusses its development, regional tectonics mi-lieu, lake environment, sedimentation, sedimentary facies, and structure-sediment evolution of lake basin.