An Oligocene-Miocene intermontane narrow lowland in the central Tibetan Plateau: Insights from provenance analysis and palynological record of a Cenozoic sedimentary succession

•The Niubao Formation in the Avengco Basin, the western part of the BNSZ, was deposited during Oligocene-Miocene with bidirectional sources.•The Oligocene-Miocene paleoelevation of the Avengco Basin was 3090–3290 m.•A 3 km high intermontane lowland on the BNSZ were formed during the Oligo-Miocene.•This intermontane lowland was probably formed by the reactivation of thrust belts and cloud extend westward to the Avengco Basin.