Abstract: Upper Cretaceous-Eocene strata are typically absent in northern Qilian Mountain and Jiuxi Basin,at the northeastern margin of the Tibetan Plateau,The Basin contains a succession of Neogene(Oligocene)-Quatemary fluvial strata that unconformably overlie the Lower Cretaceous rocks.The Oligocene Huoshaogou Formation is exposed only at the northern part of the basin and balking southward. On the basis of pa1eocurrent data and seismic profiles we suggest that its source area is from north.The Oligocene Baiyanghe Formation is popularly exposed in the basin and between some thrust sheets in the mountain.The formation in the mountain consists of coarse elastic alluvial piedmont deposits that are different from the fluvial-lacustrine sediments in the basin.The sedimentation characteristics and paleocurent measurements show that the sediments are from the northern Qilian Mountain in south.We suggest that uplifting ofthe northern Qilian Mountain occurred no later than late Oligocene.Rock samples from Mesozoic-Cenozoic strata show that the representative heavy minerals increase abruptly in the Baiyanghe Formation.The relative contents and modal proportions of heavy minerals,the heavy minaral ratios(ATi and GZi)and the parameter ZTR all suggest that the mineral maturity is low and tectonic activity is strong in Oligocene.We interpret that the Oligocene heavy mineral pulses are important record of initial uplift and exhumation of the northern Qilian Mountain.