摘要:
青海湖系第四纪以来形成的一个高原内陆断陷湖盆。湖盆的形成与演化经历了断陷期、河湖共存期、全盛时期和萎缩时期四个阶段,目前处于萎缩期。沉积体系展布受气候、物源、河流、地形、构造演化和断裂系统等多种因素的控制,具有山间断陷近物源沉积的特点。沿盆地长轴方向,西部发育有辫状河、曲流河、三角洲、水下河、深湖相沉积体系;东部有风成堆积相、泻湖相。湖盆南北短轴方向,北岸较缓,形成山间河道、辫状河、洪积扇、扇三角洲和滨浅湖沉积体系;南岸较陡,形成几个大大小小的冲积扇裙和水下扇沉积。滨浅湖地带,沿岸砂坝、沙嘴、砾石滩、沙滩、泥坪、沼泽、湖湾相当发育。与国内外其它湖泊相比,风成堆积、水下河流相和滨岸砂坝较为发育是其特点。本文是在野外考察、采样分析和综合研究的基础上,对青海湖的形成及其区域构造背景、湖泊环境、沉积作用和沉积相,以及湖盆的构造与沉积演化进行了一些探讨。
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.
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