Palaeohydrology of the Sambhar Playa, Thar Desert, India, using geomorphological and sedimentological evidences

Abstract

The Sambhar Playa in western Rajasthan, India has been studied to understand its tectono-geomorphologic evolution and palaeohydrological reconstruction. The playa basin originated due to tectonic movements during the Quaternary, and was deepened by large scale deflation during arid periods. A dense network of relict drainage reflects abundant supply of water and sediments during wetter phases. A deep core (∼23 m) raised from the center of the playa indicates an alternation of clastic and evaporitic sediments. Mineralogical assemblages and the geochemical characteristics have been used to decipher the palaeohydrological conditions in the region for a period extending over 25 ka. Evaporite mineralogy shows a major change in brine chemistry at ∼5 m depth, the lower part being rich in gypsum and the upper part completely devoid in gypsum. The vertical profile shows a correlation between Na/Al fatio, δ18O values of carbonates. MgO /(MgO+CaO) ratio of insoluble fraction and dolomite content. We interpret these trends as changes in evaporation/inflow fatio which in turn would reflect low/high stands of the lake.