干旱区生态环境知识资源中心

Quaternary sediments in the northern part of the Thar desert in India show fluvial, fluvio-lacustrine and aeolian lithe-successions, affected by episodic neotectonism. Near-surface Quaternary geological studies reveal three distinct generations of aeolian deposits. These are, (1) the youngest active aeolian dunes, (2) semistable pedogenized dunes of post-Kalibangan cultural period (3000 to 2000 years B.C.) and, (3) consolidated older aeolian deposits (dating to c. 14 ka B.P.), and overlie gypcrete/calcrete and lacustrine deposits. Analyses of the deeper Quaternary formations in the area reveal that the Ghaggar sedimentation basin is much deeper than the surroundings, and hosts more than 350 m thick sediment infill. The basin is bound by distinctive boundary faults. Quaternary fluvial and fluvio-lacustrine deposits constitute the bulk of the total sedimentation package that shows a gradually increasing thickness towards north and northeast. The northward deepening basin was aggraded with inflow of clastics from the south, either pari passu, or in episodic pulses with neotectonic activities in the region. Two or three more aeolian sedimentation units which are older than the exposed stable dunes, are also inferred within the stratigraphic column, suggesting phases of aridity during the mid-Pleistocene. (C) 1996 Academic Press Limited