Late Quaternary palaeoclimatic reconstruction from the lacustrine sediments of the Sambhar playa core, Thar Desert margin, India

Abstract

The Sambhar playa in Rajasthan, India, located at the eastern fringe of the Thar Desert, records multiple phases of clastic- and evaporite-dominated deposition as revealed from a ∼ 23 m deep core drilled in the center of the playa. Seven evaporite facies, identified from the mineralogical data, reflect variable brine chemistry throughout the history of the playa. The complete absence of gypsum-rich facies in the upper 5 m and dominance of carbonate- and gypsum-rich facies in the lower parts of the core reflect fluctuations in salinity level induced by climate change. Stable isotope data on carbonates ( δ 18O values) correlate with the [MgO/(MgO + CaO)] ratio, geochemical ratios (Na/Al, Na/Ti, Na/K) and the evaporite mineralogy. These data, coupled with AMS chronology of the organic fraction of the core sediments, have been integrated to interpret evaporation/inflow ratios which reflect humid and arid climatic conditions. Our data reconstruct the palaeoclimatic fluctuations in the Thar Desert margin for the last 30 ka and show significant spatial variation from the available lacustrine records from the Thar Desert. The Sambhar playa does not show any evidence of complete desiccation throughout its history although we record arid phases during the LGM and between ca. 7500 and 6800 years.