Magnetostratigraphy of the Neogene Chaka basin and its implications for mountain building processes in the north-eastern Tibetan Plateau

摘要: ABSTRACT Magnetostratigraphy of sedimentary rock deposited in the Chaka basin (north‐eastern Tibetan Plateau) indicates a late Miocene onset formation and subsequent development adjacent Qinghai Nan Shan. Sedimentation initiated at ∼11 Ma. In lower part fill, coarsening‐upward sequence starting ∼9 Ma, as well rapid sedimentation rates, northward paleocurrents, are consistent with continued growth Ela Shan to south. upper section, several lines evidence suggest that thrust faulting topographic began ∼6.1 Paleocurrent indicators, preserved proximal footwall Shan, show change from southward flow between 6.5 3.8 At same location, sediment derived appears 6.1 Finally, initiation progressively shallowing dips observed deformed strata pebbly, fluvial deposits Ma provide minimum age for slip on fault north‐east beneath We interpret decrease accumulation rates since ∼6 indicate reduction accommodation space due active folding along incorporation into wedge‐top depozone. Declination anomalies beginning counter‐clockwise rotation which we associate local deformation, not regional block rotation. The emergence near end Epoch partitioned once contiguous Chaka‐Gonghe complex. framework, our study adds growing body points widespread and/or reactivation networks during across north‐eastern Plateau.