Hydrodynamic evolution from quartz microtextures of a beach ridge in Qinghai Lake, China

Beach ridges are landforms that exist on beach shorelines and can supply abundant information regarding palaeoenvironments. To better understand the hydrodynamic processes of beach ridges, a quartz microtexture analysis was carried out. In this study, the microtextural features of a total of 1063 quartz grains from seven beach ridge samples and eight reference samples from rivers, a dune, and a nearby beach were observed and analysed by scanning electron microscopy. The qualitative and quantitative results suggest that the quartz microtextures of the beach ridge samples present more fresh surfaces and percussion marks than the river samples but less angularity. The upper sequence samples from the beach ridge present higher values of fresh surfaces and percussion marks and lower dissolution than the lower sequence samples. A cluster analysis shows that the hydrodynamic conditions of Qinghai Lake underwent pronounced changes from weak to strong and then to weak at the present time. Furthermore, quantitative analyses indicate that the beach ridge and river sedimentary environments can be distinguished through the microtextural features of the 250–125 μm size fraction. However, more grain size fractions should be observed and analysed to interpret the hydrodynamic conditions. The quartz microtextural analysis of beach ridges may be an effective method reflecting the palaeohydrodynamic conditions.