Discovery and significance of Quaternary aqueously deposited aeolian sandstones in the Sanhu area, Qaidam Basin, China

Abstract

Influenced by neo-tectonic movement, the Sanhu area of China’s Qaidam Basin formed in the Quaternary in response to migration of its depocentre. A study of core material from the Qijia 1 Well reveals novel Quaternary aqueously deposited aeolian sandstones in the Qigequan Formation of the Sanhu area. Here we report the sedimentary petrology and geochemistry data of these deposits that constrain their depositional history. Evidence for aeolian influence during deposition includes: sorting and roundness, pure quartz sand with single mode grain size distribution and few suspension materials, very fine sand grain size distribution indicating sorting by saltation and suspension transport, dish-shaped and crescent-shaped pits in grain surfaces indicating aeolian transport and chemical composition similar to that observed in active or recent dune deposits, namely enrichment in SiO2, Na2O, and MgO relative to the sand dam sediment in the lakeshore. Identification of these aqueously deposited aeolian sandstones expands the range of sedimentary deposit types found in the Sanhu area and improves understanding of its paleoclimatic history.