黄河三角洲细粒物质搬运和沉积动力学研究

黄河以细粒物质含量高为特征.经研究发现,细粒物质搬运和沉积的动力有物理、化学和生物三种.物理作用是最主要的动力,主要表现为河水、潮水、风和柯氏力等过程的作用.主河道中的物理因素最活跃,又可细分为高水位、中等水位、低水位、涨—落水流、浪成水流、反向水流、裂流及“冲积扇”水流等状况.黄河下游河水显微碱性,且富含CaCo_3,故形成同生碳酸盐胶结物和柱状结核.另外,一定量的细粒物质还以胶体的形式搬运、沉积.黄河三角洲上的动物主要形成潜穴、球粒和爬迹等;而植物的作用较为重要,以直接和间接的方式影响细粒物质的沉积.

TRANSPORT AND DEPOSITION OF THE FINE-GRAINED SEDIMENTS IN THE YELLOW RIVER DELTA

The Yellow River is characterised by a high content of fine-grained materials dispersed in the water. There are three processes operating on transport and deposition of the fine sediments, i. e, physical, chemical and biological factors. Current is the most important of the physical processes. A number of currents have been distinguished. Floods can transport most of the sediments from the Loess plateau-the major source area, and form a thin layer of muds which extends laterally to a long distance. Winds play an unignorable part by reworking original deposits, making them well-sorted and generating ripples, laminations, rolling and saltating populations, scours, mud-clast microlevee and hard ground. Inverse currents, which flow in opposite directions, are found to work where there is a concave bank or where the channel broadens suddenly. Sedimentary records can also be produced by rip-flow and "alluvial fan flow" which are perpendicular to the channel strike, and by ice in winters. Animals only form burrows, pellets and track ways. But plants (mainly grass) are much more important, because they can (1) block and deposit suspended materials: (2) destroy primary structures and form seatearths; (3) act as nuclei for concretions. This research has provided a comparable model for understanding subsurface hydrocarbon generation, reservoir and sealing in non-marine fine-grained deposits.