Late Cenozoic magnetostratigraphy and paleoenvironmental change in the northeastern Tibetan Plateau: Evidence from a drill core in the Wuwei Basin, NW China

Abstract

• Late Cenozoic sediments sampled by the WW-01 drillhole in the Wuwei basin were depoisted since ca. 11.15 Ma. • The northeastern Tibetan Plateau experienced rapid uplift at 8.25 and 2.58 Ma. • The aridification in NW China was controlled by the tectonic uplift at ca. 8.25 Ma. Basin deposits of the northeastern Tibetan Plateau provide an ideal record for understanding the uplift of the plateau and the history of aridification in NW China. In this study, we present sedimentology, magnetostratigraphy, and paleoenvironmental indexes from the drill core WW-01 in the Wuwei Basin in the northeastern Tibetan Plateau to reconstruct a long depositional–paleoenvironmental history spanning from ca. 11.15 Ma to the present. Firstly, ages of the Fengle Formation, Guoyuan Formation, and Quaternary sediments are precisely defined through the magnetostratigraphy study of the drill core WW-01. Our results show that the upper age limit of Fengle Formation is 8.25 Ma, Guoyuan Fromation ranges from 8.25 to 2.58 Ma, and the Quaternary sediments span the interval from 2.58 Ma to the present. Secondly, detailed analysis of the sedimentology of the drill core reveals that marked changes in sedimentary environment and accumulation rate occurred at ca. 8.25 and 2.58 Ma, respectively. Our results, combined with regional research, indicate that the initial uplift of the northeastern Tibetan Plateau started at ca. 8.25 Ma and that the latest phase of rapid uplift occurred at ca. 2.58 Ma. In addition, the changes of grain size and magnetic susceptibility in the sediments of the drill core combined with knowledge of the regional paleoenvironment evolution show that NW China underwent gradual aridification from the late Miocene (ca. 8.25 Ma), which is consistent with global cooling at that time. However, tectonic uplift of the northeastern Tibetan Plateau may have been the primary driving force of the aridification between ca. 8.25 and 7.14 Ma.