Abstract

The Attock-Cherat Range forms the southern boundary of the Peshawar basin and includes rocks transitional between metasediments of the Lesser Himalaya and foreland-basin strata to the south. The Attock-Cherat Range comprises three fault-bounded structural blocks which are, from north to south, (1) Precambrian metaclastic strata overlain by unfossiliferous limestone which is itself apparently overlain by Paleozoic strata with the contact not exposed; (2) unfossiliferous flysch of Precambrian(?) age overlain by Cretaceous and Paleogene marine strata and Murree red beds at least in part of early Miocene age; and (3) unfossiliferous limestone, argillite, and quartzite correlated in part to Paleozoic strata in the Peshawar basin, overlain by a Tertiary sequence generally similar to that in block 2. Farther south, in the Kala Chitta Range, strata of Triassic to Eocene age occur in south-verging folds and thin thrust sheets. The similarity of the Tertiary sequences in the Kala Chitta Range and in blocks 2 and 3 demonstrates that the pre-Tertiary sequences were juxtaposed by faults prior to deposition of the Paleocene Lockhart Limestone. This may coincide with initial contact of the west-northwest–facing passive margin of India with Eurasia or nearby microplates. Major late Tertiary imbricate thrusting and folding took place prior to uplift of the Attock-Cherat Range and to deposition of Peshawar intermontane basin fill of Pliocene-Pleistocene age. The Peshawar basin formed as the Kala Chitta Range was faulted south on the Main Boundary thrust (MBT), forcing Siwalik foreland basins still farther south. Late Quaternary deformation in the southern Peshawar basin occurred along a seismically active zone of en echelon, stepped-left faulted pressure ridges that may reflect a subsurface ramp on the older MBT.

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