Luminescence chronology of aeolian deposition during the Late Quaternary on the southern margin of Thar Desert, India
摘要
Aeolian deposits constitute the uppermost lithostratigraphic unit in the southern margin of the Thar desert. They occur as poorly organized dunes resting on the upper part of a major fluvial sequence. Considerable evidence exists to show that the southern margin witnessed fluvial aggradation before the onset of dune accretion. Transition from a dominantly fluvial phase to aeolian deposition was gradational. Blue-green light stimulated luminescence chronometry of six fossil dunes indicates that the dune building activity started around 26ka and continued episodically until around 5ka. Evidence of a phase of landscape stability is seen corresponding to the interval 11–9ka. This is also reflected by the presence of Stone Age artifacts (microliths) and fluvially reworked aeolian sand, and corresponds to the strengthening of the southwest monsoon in the region. A progressive northward shift through time in the parameters controlling dune building activity is seen. Aeolian accretion in the southern part (Mahi basin) ended around 10ka, whereas in the northern Sabarmati it continued until around 5ka and in the case of core regions of Thar, it continued until 0.6ka. The southern margins of the Thar Desert thus have not experienced any major aeolian deposition since 5ka.