Paleoclimatic evolution since the Late Pleistocene in western Central Asia and its response to mid-latitude westerlies and low-latitude high pressure: insights from aeolian loess-paleosol sections in the Surkhandarya River Basin

Abstract

The aeolian loess-paleosol sections in Central Asia (CA) are a valuable archive of paleoclimatic information due to their geographic location. Based on detailed field investigations in the Surkhandarya River Basin of southern Uzbekistan, western CA, two Late Pleistocene-Holocene aeolian loess-paleosol sections were identified. A multi-proxy approach was applied, incorporating magnetic susceptibility (MS), grain size, colorimetry, total organic carbon (TOC), and geochemical elements to reconstruct wind strength and humidity variations since the Late Pleistocene. The results indicate that: (i) humidity variations can be inferred from proxy indicators, including colorimetric indices, TOC content, clay fraction, Na/K, and Rb/Sr value. Given the weak pedogenesis in this region, MS is primarily governed by wind strength rather than pedogenesis and can thus serve as an indicator of wind activity. The strong correlation between MS variations and Zr/Rb value further supports this interpretation; (ii) prior to ca. 14 ka, the region experienced arid conditions with strong wind activity and weak pedogenesis, likely dominated by cold-dry air masses from Siberia; (iii) during ca. 14–5 ka, the combined influence of the negative phase of the North Atlantic Oscillation and El Niño events likely enhanced moisture transport by modulating westerly circulation and low-latitude high pressure anomalies, intensifying pedogenesis and paleosol development, which provided favorable conditions for oasis formation and human settlement. This study contributes to a deeper understanding of paleoclimate evolution and its driving mechanisms in western CA while also providing a climatic context for investigating human-environment interactions in the Surkhandarya River Basin.