Late Quaternary geomorphology, palynology and magnetic susceptibility of playas in western margin of the Indian Thar Desert

Abstract

Multidisciplinary studies of Bap-Malar and Kanod playas in the arid western margin of the Thar desert have been carried out to understand past climate changes in this region. These studies are well supported by AMS 14 C dates and archaeological material preserved on dunes and pediments surrounding the playas. Present investigations show that the playas originated during the Last Glacial Maximum (>15 ka) and survived with fluctuating hydrology till 5 ka. The lake full stage is suggested by rarity of gypsum, increased proportion of paramagnetic minerals and relative increase in organic material in playa sediments. On the other hand, predominance of gypsum, decrease in paramagnetic minerals and organic material indicate ephemeral stage of these playas. Though lake full stage was between 8 ka and 6 ka, these playas remained brackish to saline throughout their existence. Biomass was predominantly C4 type and overall vegetation was grass dominated. Peak of aridity affected human life in the area, as indicated by rarity of upper Palaeolithic sites. On the other hand, there is prolific development of human occupation during the Mesolithic cultural stage between 8 ka and 6 ka when the climate was relatively wet. Even after drying of playas around 5 ka, pastoral human activity continued in the Thar till about 1.5 ka in favourable ecological niches in otherwise water starved western margin of the Thar.