ABSTRACT
Pedocalcified and stabilized complex parabolic dune clusters occurring typically in the northeasterly oriented central tract of the Thar Desert in India are presently deciphered to constitute patterns of crescentic megadunes of higher magnitude aeolian bedform hierarchy. These en-echelon parabolics also show complex multitiered evolutionary morphologies owing to morphologic integration, successive super imposition of transverse/barchanoid and linear dunes of meso-scale. Four dune morphometric categories were inferred and arranged in a bedform hierarchy. Current geological and morphostratigraphic studies suggested earliest aeolian accumulations under fluctuating wet and dry periods in semiarid environment, resting disconformably over polymictic continental deposits of prolonged fluvial aggradation belonging to early/mid-Pleistocene. The successive episodes of increased aeolian activity in the area have been assigned the ages of ca 35–40 ka, 14–16 ka and 4–5 ka BP and the recent mildly active sand mobilization. It is ascertained that the nature of substrata has been an important determinant for the dune type and pattern of spatial disposition. Similar orientation patterns of linear dune-elements in older stabilized clustered parabolic megadunes in the area indicate long continued growth conditions of abundant sand supply, under intense aeolian dynamism, dominantly persistent from the southwest to the northeast.
