SEDIMENTOLOGY AND STRATIGRAPHIC PALEONTOLOGY OF THE PLEISTOCENE DHOK GANGAAL HILLS, UPPER SIWALIKS OF PAKISTAN: A BIOSTRATIGRAPHIC REVISION

More than a century after their first discovery, the Plio-Pleistocene faunas of northern Pakistan remain poorly understood. The Dhok Gangaal village is located south of Islamabad in northern Pakistan. The hills around the village are composed of fluvial deposits characterized by clay beds interbedded with gravel lenses. The presence of fluvial deposits and the vertebrate paleofauna indicate that these are not Holocene glacial deposits as mapped by the Geological Survey of Pakistan. The incorrect lithologic identification and consequent incorrect mapping of these and similar deposits has led to a bias against Pleistocene-aged fossils and towards Miocene and Eocene fossils in museum collections from Pakistan.

The biostratigraphy of the Upper Siwaliks is revised. The vertebrate paleofauna of these hills represents the Pinjor Zone of the Upper Siwaliks that was first recognized by Dr. Guy E. Pilgrim of the Geological Survey of India in 1913. New collections of suid (Potamochoerus theobaldi and Sus falconeri) and equid (Equus sivalensis) specimens indicate that the Dhok Gangaal hills are Pleistocene in age. Revised geologic maps which distinguish between Plio-Pleistocene fluvial deposits and Holocene glacial deposits are currently being compiled, and the Plio-Pleistocene deposits are placed in the Tatrot and Pinjor Zones of the Upper Siwalik Group. Radiometric dating of ash fall tuffs will provide a geochronologic framework for the Upper Siwaliks.