COLLISION-INDUCED TECTONISM ALONG THE NORTHWESTERN MARGIN OF THE INDIAN SUBCONTINENT AS RECORDED IN THE UPPER PALEOCENE TO MIDDLE EOCENE STRATA OF CENTRAL PAKISTAN (KIRTHAR AND SULAIMAN RANGES)

Outcrop data from the Upper Paleocene to Middle Eocene Ghazij Formatio n of central Pakistan provide information about the depositional envir onments, source areas, and paleogeographic and tectonic settings along the northwestern margin of the Indian subcontinent during the closing of the Tethys Ocean. In this region, in the lower part of the exposed stratigraphic sequence, are various marine carbonate-shelf deposits ( Jurassic to Upper Paleocene). Overlying these strata is the Ghazij, wh ich consists of marine mudstone (lower part), paralic sandstone and mu dstone (middle part), and terrestrial mudstone and conglomerate (upper part). Petrographic examination of sandstone samples from the middle and upper parts reveals that rock fragments of the underlying carbonat e-shelf deposits are dominant; also present are volcanic rock fragment s and chromite grains. Paleocurrent measurements from the middle and u pper parts suggest that source areas were located northwest of the stu dy area. We postulate that the source areas were uplifted by the colli sion of the subcontinent with a landmass during the final stages of th e closing of the Tethys Ocean. Middle Eocene carbonate-shelf deposits that overlie the Ghazij record a return to marine conditions pries to the Miocene to Pleistocene sediment influx denoting the main collision with Eurasia. (C) 1998 Elsevier Science B.V. All rights reserved.