Siwalik sediments and fossils are continental deposits derived from the southern margin of the Himalayas and associated mountain ranges bounding the contact between the Indian and Asian tectonic plates. Outcrops of the Siwalik Group extend from western Pakistan to Myanmar. The most detailed studies of sediments, faunas, geochronology, and environmental history have focused on sequences in Pakistan, ranging from Oligocene through Quaternary in age. My work has occurred in Siwalik deposits of the Potwar Plateau, a low plateau of Quaternary silts covered with villages and farms southwest of Islamabad. The edges of the plateau are eroded into badland exposures of the Neogene Siwalik sequence.
The Siwalik record of the Potwar Plateau occurs in fluvial deposits that accumulated in a foreland basin over much of the Neogene. Boundary faults between the Indian and Asian plates now underlie the Potwar Plateau, which has been uplifted and deformed into a shallow syncline with thousands of meters of sediments exposed along modern river valleys. The Neogene deposits represent the channels and floodplains of major and minor tributaries of the ancient Indo-Gangetic fluvial system and are continuous between 18.0 and 5.0 Ma. Over 300 species in 50 families of mammals have been documented from this sequence, recording both notable endemic groups and notable absences. The large-mammal record is dominated by ungulates, proboscideans, and carnivorous mammals, and the small-mammal record is dominated by cricetids, murids, and rhizomyine spalacids.
