Westerly aridity in the western Tarim Basin driven by global cooling since the mid-Pleistocene transition

To explore the relationship between the global change, westerlies, and central Asian aridity, we report ~1.1 Ma local sedimentary environment changes according tohigh-resolution gammaray (GR) from downhole logging, Grain size, magnetic susceptibility (MS), rubidium/strontium (Rb/Sr) ratiosand total organic carbon (TOC)ofan 800-m core (KT11) from the Kashgar region in the western Tarim Basin, arid zone of China. Four dominant sedimentation types, including lacustrine facies, delta facies, fluvial facies, and aeolian dunes, were identified through lithology and grain size frequency curves. The 1.1 Ma sedimentary successions experienced delta deposits with fluvial and aeolian deposits and lacustrines (1.1-0.6 Ma), alternating fluvial and aeolian facies with the occurrence of deltas and lacustrines (0.6-0.15 Ma), and aeolian facies interbedded with deltas and fluvial facies (0.15 Ma-present). Spectral analyses of the GR, MS, and Rb/Sr data reveal cycles with ~70 m, ~30 m and ~14 m wavelengths.These cycles represent ~100-kyr short-eccentricity, ~40-kyr obliquity and ~20-kyr precession frequencies, respectivelyandmainly are driven by orbitally forced climate change. Stepwise drying sedimentary conditionsandenhanced desertification indicated by increasing Rb/Sr ratios and proportion of aeolian sands, and decreasing TOCsince the past 1.1 Ma, implied intensified westerlies, likely resulted from ice volume expansion and ongoing global cooling according to geological record comparison and simulations during the Last Glacial Maximum compared to preindustrial conditions, which may have controlled the expansion of the permanent deserts in inland Asia. These persistent drying trends and intensified westerly circulation in arid regionsduring glacial periodsafter the mid-Pleistocene Transition indicated by larger amplitudes of aeolian sand proportion than prior to 0.6 Maare similarto those in the interior monsoonal Asia, where the larger-amplitude of median grain sizeindicated enhanced East Asian Winter monsoon intensityand drier glacials.