Miocene stratigraphy and mammal fauna from the Sulaiman Range, Southwestern Himalayas, Pakistan

The thick (> 4000 m) coarsening-upward terrestrial Neogene sequence of the Sulaiman Range (Middle Indus Basin, central Pakistan) is the western extension of the Siwalik outcrop belt of the Sub-Himalayas. The near-shore to terrestrial sedimentation in the Sulaiman Range, represented by the Chitarwata Formation, began by the late Oligocene to basal Miocene when the main Himalayan foreland was primarily a non-depositional region. The fluvial system of channel-floodplain deposits was fully established in the late early Miocene, marking the beginning of the Vihowa Formation. There is a sudden increase in the proportion of sandstones to mudstones, and change in the geometry of the sandbodies, at the conformable contact of the Vihowa with the overlying Litra Formation. The trend of coarsening and increased complexity of sandbodies with more conglomerate interbeds continued upward from the Litra to the Chaudhwan Formation, which in the upper reaches becomes a conglomerate-dominant sequence. Our mammalian faunal collections from the Vihowa and Litra formations, though small, are definitive, providing a temporal framework for interpreting the Sulaiman depositional regimes in the context of Himalayan orogeny. The Vihowa and Litra mammalian faunas are strikingly similar to the Middle to Late Miocene Siwalik faunas from the Potwar Plateau. Fauna from the lower Vihowa records diversification in the small boselaphine bovid Eotragus around 17 Ma. The three-toed hipparionine horses appear in the lower Litra Formation, giving a Late Miocene age to those strata. The middle Litra Formation has entirely different species of bovids, suids, and giraffids suggesting a more open country habitat. Similar community restructuring with substantial faunal turnover occurred about 7.5-7.0 Ma on the Potwar Plateau. The Chaudhwan Formation is probably of Pliocene age. Paleocurrent data suggest a southerly flowing river system, which perhaps was part of a much larger river system, analogous to the modern Indus River, draining southwestern Himalayas since Miocene. The Chitarwata through Chaudhwan sequence in the Sulaiman Range contains an almost continuous terrestrial record of the Neogene, perhaps more complete than anywhere else in the Himalayan foreland. (C) 2002 Elsevier Science B.V. All rights reserved.