Abstract: The study on grain size in the sediments from the large lake basins is helpful to interpret global exploration of tight oil-gas
and shale oil-gas as well as their recorded paleoclimate information. In this paper, the spatial and temporal distribution of grain size in
the Qinghai Lake, the largest lake in China, was studied in detail. Twenty seven cores covering almost the whole lake area spanning the
last 60 years were drilled, and the three typical cores were dated by 210Pb and 137Cs. Based on the magnetic susceptibility age model, the
age framework of sedimentary cores in the whole lake area was established. Results show that sediments in the Qinghai Lake have
multimodal distribution in the grain size and mainly consist of fine grains (< 63 μm). The silt content ranges from 60% to 70%, the clay
component ranges from 10% to 35%, and the sand component is less than 20%. Therefore, the variation of grain size in the Qinghai
Lake sediments is relatively complex on the spatial scale. The median grain size is high in the areas around the Sand Island, the western
and southwestern lakes, while it is low in other lake areas. In the temporal scale, the grain size is roughly coarse, the sand component
increased and the clay component decreased from 1960 AD to 2017AD. The temporal and spatial variations of grain size may be caused
by the combined action of wind and sand activities, soil erosion in the basin, and the changes of river runoff and lake levels.

Key words: grain size, spatial-temporal variation, Qinghai Lake, 1960 AD；2010 AD