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Grain size of surface sediments in Selin Co (central Tibet) linked to water depth and offshore distance
- Wang, Can, Wang, Hailei, Song, Gao, Zheng, Mianping
- Journal of paleolimnology 2019 v.61 no.2 pp. 217-229
- atmospheric precipitation, cobalt, frequency distribution, lakes, limnology, paleontology, rivers, runoff, sediments, wind, China
- 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)].