Sedimentary Characteristics and Microfacies of Shore Zone in Qinghai Lake

Key words: 
• modern deposition /
• shore zone /
• sedimentary microfacies /
• Qinghai lake

Abstract: The shore zone in Qinghai Lake is divided into six sedimentary microfacies:longshore bar，mudflat,sand beach,shingle beach,lagoon and subagueous aeolian.Compared with othe lakes in China and abroad,the deposits in the shore zone of Qinghai Lake are featured by their better developed longshore bar and subaqueous aeolian;A large scale of longshore bar and sand beach are distributed in the shore zone of small slope(slope 10°±)and strong wave,longshore current and wind action.There are characteristics of main traction and saltation parts (two parts of saltation) and little suspended load in their grain－size probability curve.The vertical sequences are reversed rhythmite of poorly sorted (δ₁＞1) overlying coarse-grained clastics and well-sorted (δ₁＜1) underlying fine－grained clastics;The shingle beach distributes mainly in the erosion coast and the areas from alluvial fan or fan delta into the lake.The gravels are homogenous size and well-psephicity,the long-axis of most gravels parallel the lake strandline,the maximam flat surface tend to lake and the dip angle is about 8°±;The mudflats mainly distribute in the lakebay,level lakeshore and stagnant area behind longshore bar;The characteristics of subagueous aeolian have well-sorted (δ1＜1),well-psephicity,deflation hollows of quartz surface,Sk=-0.15-0.21, Kg=0.75-1.13,Md=0.22～0.023 mm,convex-upward and two parts of saltation in the grain-size probability curve.