Preliminary report on the geology and vertebrate fauna of the Miocene Manchar Formation, Sind, Pakistan

The Manchar Formation, a middle and upper Miocene fluvial sequence of sandstones, silts, and conglomerates, is exposed in a narrow north-south belt in the Lower Indus Basin of Sind Province, Pakistan. The formation, as measured in geological sections near Lake Manchar, can be divided into three parts differing in the proportions of the sandstones and silts. The contact with the underlying marine Gaj Formation is gradational; when the base of the Manchar Formation is taken as the lowest thick sandstone of fluvial origin, it lies above the highest marine or estuarine beds. Fossil localities cluster into three stratigraphie groups which correspond to the three horizons previously recognized. New additions to the Manchar faunas include a large hominoid and another small primate, two creodonts, three amphicyonids, a shovel-tusked amebelodontine, a chalicothere, species of Orycteropus, Zygolophodon, Stegolophodon, and Brachyodus, a species comparable to Tetraconodon minor, two small species of Dorcatherium, and a palaeomerycid. Although stratigraphie ranges are incomplete, there is a clear pattern of faunal change from a rhinoceros-anthracothere dominated assemblage to one rich in proboscideans, suids, and ruminants. Hipparion (s.l.) appears only in the youngest levels. As defined here, both the basal and middle Manchar levels are probably older than the fauna from the Chinji Formation in its type area, and younger than the Dera Bugti fauna.