The Thal interfluve, Pakistan. Geomorphology and depositional history

Abstract

Landforms and depositional history of the semi-arid and arid Thal desert and the adjoining Indus floodplain in Pakistan are described and discussed. Climate and sand relief are controlled by three wind regimes: southern monsoon from the Arabian Sea and eastern monsoon from the Bay of Bengal in summer, and northern winds in winter. Present vegetation ranges from wooded steppe to (arid) desert steppe. The sands deposited by the Pleistocene Indus river were reworked into longitudinal and transverse ridges, alveolar (honeycomb-pattern) sands and locally barchan dunes, depending upon wind directions and forces. Abandoned Pleistocene Indus channels containing narrow clayey strips occur in this area, the eastern ones mostly obscured by wind resorting. The Holocene Indus floodplain shows four depositional stages: the sandy base of a braided river system; two stages of a thin finetextured cover; and recent moderately coarse sediments