Chronological and rock magnetic constraints on the transition of the Quaternary paleoclimate in the western Qaidam Basin, NE Tibetan Plateau

Abstract

AbstractA closed Quaternary saline paleolake, currently still a lake and named Dalangtan after one of its largest sub-basins, has widely distributed sediments in the western Qaidam Basin, NE Tibetan Plateau. Lacustrine salt minerals and fine sediments from this paleolake provide an environmental record for investigating paleoclimatic evolution in the Asian interior. However, detailed continuous Pliocene–Quaternary paleoclimatic records are broadly lacking from the NE Tibetan Plateau owing to poor exposure of the outcrops in section. For this study, we performed a detailed magnetostratigraphic dating and rock magnetic analysis on a 590-m-long core from the SG-5 borehole in the western Qaidam Basin. The results demonstrate that the lacustrine sediments in the SG-5 borehole were deposited more than ~3.0 Ma. Saline minerals began to increase at 1.2 Ma, and the magnetic susceptibility (χ) also changed at that time; the percentage frequency-dependent magnetic susceptibility was relatively low and uniform throughout the whole core. These observations, combined with the χ, pollen, salt ion, and grain-size records from other boreholes, indicate that the western Qaidam Basin and the greater Asian interior had a significant climate transition at 1.2 Ma during an extreme drought.