Surface sediments of Lake Sugan and dust storm in the Northern Qaidam Basin,China:preliminary results of elemental tracers

Abstract

To understand the role of atmospheric dust in the global climate system further, it is necessary that a longer sequence of dust storm history should be established using geological archives in dust provenance area. Hydrologically closed lakes in the arid regions of China could be ideal objectives to trace dust storm evolution since the most of Northwest China has been recognized as an important source area for global dust loading. Lake Sugan, a closed lake located at the northern margin of the Qinghai-Tibetan Plateau, would be employed to study on the dust storm history in the Qaidam Basin. Here, 8 elements and 11 rare-earth elements were analyzed for three different sediments/deposits in the Sugan Lake region, namely, the surface sediments of Lake Sugan, the settled sand dust including materials collected during dust storm durations, and the surface deposits of the region. The results show the element of Al has been enriched by 11% relative to the surface ground deposits. The composition of the element in lake sediments is nearly half of the settled dust, which may be diluted by the carbonate accounting for about 50% of the lake sediment. Two of Al, Fe and Sc exhibit apparent positive correlations in the lake sediments. Also, for one of the three elements positive correlation was found between the settled sand dust and the lake sediments. However, there are negative correlations between the catchment deposits and the settled sand dust, and between the catchment deposits and the lake sediment for Al and Sc. Variations in Fe and Sc compositions exhibit an apparent positive correlation not only with intensity of dust storm events, but also with frequency of the events. The Fe and Sc compositions seem to be changeless for the three kinds of sediments/ deposits. In addition, the results of rare-earth elements analyses show that the lake sediments, the settled sand dust and the surface ground deposits may derive from a homologous source. The elements of Al, Fe, Sc are most likely to be transported into lake through strong wind and dust storm processes. Therefore, sediments of Lake Sugan could he used to trace dust storm in this region, and the elements of Al, Fe, So could be applied in reconstruction of dust storm history.