The ion chemistry of lakes and late Holocene desiccation in the Badain Jaran Desert, Inner Mongolia, China

Abstract

In the markedly arid Badain Jaran Desert, one of the least-studied areas in the world, over a hundred permanent lakes exist among the dunes. The geochemistry of water samples from nine lakes and from the groundwater in the desert and on its periphery was investigated. Ion chemistry of the water from these desert lakes changes considerably on a regional scale. We argue that there is a positive correlation between the ages of these lakes and their totally dissolved solids (TDS) varying between 1.2 and 398.2 g/l. Tritium analysis of groundwater in wells gives an age generally older than four decades and younger than 100 years. The lacustrine deposits, freshwater fauna and shorelines indicate the existence of large water bodies with low salinities in the inter-dune hollows of this desert during the early and middle Holocene. The precipitation in this desert during the early and middle Holocene was estimated to be ca. 200 mm/year on average, at least twice as high as at present. On the basis of paleoecology, TL and radiocarbon ages, it was concluded that the huge enrichment of ions in the lakes and decrease of water availability originated from climatic desiccation during the last 4000 years. The paleoclimate of the Badain Jaran Desert reported here was remarkably consistent with the late Quaternary climatic histories of the regions to the immediate north, west, east and south of the study area.