A ~200 ka record of climatic change and dune activity in the Thar Desert, India

Abstract

An 18.4 m excavated dune section in the Thar Desert of India with a chronology based on 12 TL ages and a basal age of ~190 ka has preserved 12 cycles of dune accretion, soil formation, calcrete development, and subsequent erosion, together with the presence of stone artefacts ranging in age from Lower Palaeolithic to Mesolithic, coeval with more humid climatic interludes. Phases of soil development and carbonate precipitation were relatively wet and phases of dune accretion relatively dry, so that there were 12 significant moist intervals separated by 11 drier intervals during the past ~190 ka. The calculated time interval between successive phases of dune sand accumulation ranged from 22.2 ka to 15.8 ka, with a mean of 19.0 ka. These values are consistent with a precessional influence on dune activity and on the associated onset of early monsoonal activity in this region. Carbon isotopes measured on organic matter within the sand profiles show consistent values close to −21.6±1‰, pointing to deposition during a transitional climatic regime characterized by a change from open C3 grassland to C4 woodland or forest.