青海湖水动力特征对滨湖沉积体系的控制

Hydrodynamic Control of Sedimentary Systems in Shore Zone of Qinghai Lake

青海湖盆地是我国西北内陆干旱区典型的山间断陷湖盆,与我国西北一些含油气盆地沉积特征十分相似,发育有一系列有利于油气储集的沉积体系。对青海湖沉积体系的研究,可以为陆相古含油气盆地沉积原貌的恢复提供借鉴。通过对比总结前人研究资料、实地考察以及对湖区近40年(1972~2010)来8张遥感图像的判读,分析了青海湖滨湖区域沉积体系演变特征。同时,在青海湖水动力特征研究的基础上,通过沉积物输运模拟,结合每一区域沉积演变特征,分析该区域沉积体系形成演变的水动力成因机制,并预测未来一段时间内环青海湖滨湖区域沉积体系演变趋势。研究结果表明:青海湖水动力特征主要表现出三个顺时针主旋回和湖湾和河流入湖口等处的次级旋回,沉积物输运和堆积趋势与水动力湖流特征对应一致,水动力特征控制着沉积体系的形成及演变;河流入湖口、沙岛—海晏湾、郎剑沙嘴以及东南湖湾等区域,是青海湖滨湖区域沉积演变最明显的区域;今后较长时期内,沉积物输运、堆积趋势将不会发生大的改变。

Qinghai Lake is a typical intermontane downfaulted lake in the arid region of northwest China. It is very similar to some continental petroliferous basins,and developed a series of sedimentary facies which are favorable for hydrocarbon accumulation. Thus,researching the sedimentary systems of Qinghai Lake could provide us a good example of paleogeographic recovery in the similar ancient lacustrine basin. In order to analyze the evolution of coastline and sedimentary system of Qinghai Lake,field trip are taken,large amounts of previous data are summed up and 10 pieces of remote sensing images over the past 40 years are interpreted in this study. Meanwhile,on basis of detailed study of hydrodynamics of Qinghai Lake,computer numerical simulation method is used to reveal the sediment transport patterns of Qinghai Lake. There are mainly three clockwise currents in Qinghai Lake; the hydrodynamic characteristics in the beach area are more complicated,sediment transport patterns are consistent with regional hydrodynamic features. It indicates that hydrodynamic condition is the most important factor to affect the sedimentary system of Qinghai Lake. Furthermore,the area including,river estuary,sand island- Haiyan bay,Langjian spit and eastern bay,have the most obvious evolutionary characteristics in Qinghai Lake. It is inferred that the evolution pattern of sedimentary system will keep unchanging under the condition of dry climate in a short time.