Abstract

During three Pleistocene glaciations, large valley glaciers originating at altitudes of 12,000 ft or more occupied the northern part of the Swat River drainage basin and terminated at altitudes as low as 5800 ft. Discrimination and subdivision of the three principal drift sheets is based on various relative-age criteria, including moraine and terrace morphology, weathering characteristics of surface stones, and degree of soil development. The areal and altitudinal distribution of the three drifts, which are designated Laikot (oldest), Gabral, and Kalam, indicates a less extensive glacier cover during each successive glacial age (510 mi2, 473 mi2, and 430 mi2, respectively). Laikot Drift is poorly preserved, strongly weathered, and retains little or no depositional morphology. Moraines and outwash terraces built during the Gabral and Kalam advances are well preserved in two intermont valleys at Kalam and Utrot and permit subdivision of the two younger drifts into two and three units, respectively, of lesser stratigraphic rank. Moraines of Gabral age tend to be broad and smooth and have few surface stones, whereas those of Kalam age are bouldery and sharp-crested.

The altitude of the equilibrium-line (ELA) for existing glaciers in Swat Kohistan ranges from 13,000 to 14,000 ft. Assuming accumulation-area ratios of 0.6 ± 0.1 for Pleistocene glaciers in this region, steady-state ELA's during former glaciations are estimated to have been some 3000 to 3600 ft below their present levels.

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