Mid-Pleistocene Climatic Transition (MPT) As Evidenced By A Sediment Record From Lake Gas Hure, Northwestern Qaidam Basin

In the middle Pleistocene, Earth's climate gradually descends from high-frequency, low-amplitude 41-kyr obliquity band into the low-frequency, high-amplitude quasi-periodic (～100-kyr) glacial-interglacial cycles in the late Pleistocene. Because this prominent transition occurs in the absence of any significant changes in orbital forcing configuration, the origin of the ～100-kyr cycles and the associated mid-Pleistocene climatic transition (MPT) remains a fundamental mystery in climatic evolutions during the Quaternary period. Episodic tectonic uplifts of Qinghai-Tibetan Plateau represent one of the most significant geologic events in the late Cenozoic, strongly imprinted on regional climate changes in and around the Plateau, and even on a global scale. As a huge intermountane basin in the Plateau, Qaidam Basin develops nearly continuous, integrative and ultra-thick Quaternary sediment sequences in response to the rapid uplifts, of the Plateau. High-resolution paleoclimatic researches on lake sediments from the Basin are of great importance to the understanding of climatic change history in the interior of the Plateau, and also to the comprehension of the role played by Tibetan uplifts in the progress of the MPT. Toward this end, a 222-meter-long sediment core (labeled GSK0305) was retrieved from Lake Gas Hure in the northwestern margin of Qaidam Basin, providing such a unique opportunity.On the basis of tie points derived by matching the observed magnetostratigraphy to the geomagnetic polarity timescale (GPTS), an orbitally tuned timescale for core GSK0305 was developed, which assigns an age of 1320 kyr for the base of the core. This provides a robust chronological basis for subsequent regional and global climate correlations. The magnetic susceptibility (MS) record is highly consistent with deep-sea δ¹⁸O record on glacial-interglacial timescale. In general, high peaks of MS correspond to interglacial periods with less ice volume and low peaks to glacials with more ice volume. Moreover, the MS record displays certain asymmetric sawtoothed patterns, especially during the late Pleistocene, comparable to δ¹⁸O record, i.e. rather rapid transitions from glacials to interglacials and much slower changes from interglacials to glacial periods. We interpret the pattern of changes in the MS record as a reflection of changes in stream carrying capacity. In glacials, dropped river discharges are simply unable to transport a large amount of clastic...