Grain size of surface sediments in Selin Co (central Tibet) linked to water depth and offshore distance

Abstract

Grain size of lake sediments is often measured in paleolimnological studies, especially investigations of past lake-level changes. The paleohydrologic implications of such measures, however, remain unclear. We explored the relationship between grain-size characteristics of surface sediments in Selin Co, central Tibet (Median Diameter (Md), fine component percentage, and the grain-size frequency distribution curve), and both water depth and offshore distance. Under the same river/runoff transport and wind conditions, the Md value of grain size displays a significant negative correlation with water depth (r = − 0.767, N = 22, P < 0.001) and offshore distance (r = − 0.633, N = 22, P = 0.002), whereas the percentage of grains < 10 μm has a significant positive correlation with water depth (r = 0.689, N = 22, P < 0.001) and offshore distance (r = 0.673, N = 22, P < 0.001). The percentage of grains < 4 μm was also positively correlated with water depth and offshore distance (r = 0.549, N = 22, P < 0.01 for both). We recommend that the grain sizes transported by river/runoff or wind be identified and eliminated from consideration before employing the Md value and < 10-μm component of grain size for lake level reconstruction. The modal size of ~ 10 μm in the grain-size distribution curve is not affected by river/runoff or wind transportation, and is a reliable proxy for past lake level reconstruction, with smaller modal sizes associated with larger offshore distance [r = − 0.577, N = 22, P = 0.006), larger lake area (r = − 0.786, N = 7, P = 0.036) and higher annual precipitation (r = − 0.784, N = 8, P = 0.021 for Bange (station 55279) and r = − 0.769, N = 8, P = 0.026 for Shenzha (station 55472)].