Middle Pleistocene Ostracoda from a large freshwater lake in the presently dry Qaidam Basin (NW China)

Abstract. Ostracods of Middle Pleistocene age were recovered from an escarpment at the northeastern margin of the large Qarhan playa surface in the Qaidam Basin (NW China). The Middle Pleistocene age of the sampled Quan Ji section was determined by means of Optically Stimulated Luminescence (OSL) dating of seven sediment samples. Among the 31 ostracod taxa identified in total, only Eucypris gyirongensis, Leucocythere dorsotuberosa and Prionocypris gansenensis seem to be restricted to high-altitude sites in Central Asia whereas most taxa are known from a number of European and Siberian (Palaeoarctic) or even Holarctic sites. Laterally widespread sediments and the ostracods from the Quan Ji section suggest the formation of a large freshwater to oligohaline lake of at least several metres in depth in the Qaidam Basin, which is presently dry apart from a few shallow salt lakes.