Oxygen isotopic compositions of quartz in the sand seas and sandy lands of northern China and their implications for understanding the provenances of aeolian sands

Abstract

A better understanding of aeolian sand provenance in deserts would be useful for studying interactions between various Earth surface processes occurring in arid and semiarid regions. In this study we examined oxygen isotopic compositions of quartz in sand samples taken from Taklamakan and Badain Jaran deserts of northwestern China and from the Hunshandake and Hulunbeier sandy lands in northeastern China. Typical fractions of grain sizes were chosen for examination. Sample preparation followed the chemical principals described in geochemistry and final measurements were performed with mass spectrometers. In the sands from the Badain Jaran Desert the δ 18O value is generally low, with a mean of 12.1‰ in the coarse fraction (0.200–0.250 mm) and a mean of 13.2‰ in the fine fraction (0.125–0.154 mm). The sands of the Taklamakan Desert show a mean δ 18O value of 15.4‰ in the main grain size fraction 0.064–0.150 mm. In contrast, the mean δ 18O values in all grain size fractions of sand samples from the Hunshandake Sandy Land and from the Hulunbeier Sandy Land are much lower, varying between 6.8‰ and 9.9‰. The outcome established a preliminary database about δ 18O distributions in quartz sands throughout China's large deserts and sandy lands. The results show regional differences between each of the sand seas and sandy lands, indicating different provenances of the aeolian sands. Further detailed comparison of the δ 18O values between the deserts and loess stratigraphy in the Loess Plateau would provide information about changes in areas of loess sources and evidence of palaeocirculation.