The close-space luminescence dated loess record from SW Junggar Basin indicates persistent aridity during the last glacial-interglacial cycle in lowlands of Central Asia

Abstract

Our understanding of how Central Asia evolves in response to climate change remains poorly constrained primarily due to the lack of sufficient paleoclimate records across different altitudinal zones with the adequate resolution for reconstructions. Using a 23.8 m thick loess sequence in the SW Junggar Basin, we establishe a robust chronology over the past ~150 kyr based on K-feldspar pIRIR techniques and Bacon age-depth modelling. To further track the paleoclimatic evolution of this part of Central Asia, this study documents changes in grain size, magnetic susceptibility, CaCO3 content, and sediment color. Together with previously reported loess records from the slopes and intermontane basins of the Tianshan Mountains, altitudinal and spatial variability in moisture changes during the last glacial-interglacial cycle are clarified in Central Asia. Our results indicate that loess in the SW Junggar Basin and northern slopes of Tianshan Mountains was mainly deposited during the Penultimate Glacial and Last Glacial periods. However, the deposition rates were relatively very slow deposition and/or deposited loess records have been entirely eroded possibly due to the deflation in the last interglacial and Holocene. The enhancement of the winter monsoon plays an important role in the rapid deposition of loess in Central Asia during glacial periods. Findings support that the continuous aridity prevailed in the lowlands of the Junggar Basin and the northern slope of Tianshan mountains during the last glacial-interglacial cycle, which is in opposition to the moist interglacial and dry glacial changes recorded in the higher altitude intermontane and mountain areas of the Tianshan Mountains. Limited Westerlies precipitation and high evaporation in lowland areas of Central Asia are responsible for prevailing aridity in these regions during interglacial periods.