Preface (volume I): Quaternary paleoclimate and paleoenvironmental changes in Central Asia

The core area of Central Asia (CA), an arid Westerlies-dominated area, is crucial for analysis of interregional atmospheric circulation interactions along the Eurasian mid-latitude belt. However, it remains unclear how climate and environment in this region evolved during the Quaternary Period. Based on the articles in this special issue, this review recapitulates the spatio-temporal distribution of Quaternary sediments in CA, discusses paleoclimate and paleoenvironmental implications of various physicochemical and palaeontological proxies, and finally summarizes the paleoclimate and paleoenvironmental history since the middle Pleistocene. Field investigation and previous studies indicate that loess sediments are mainly distributed on the river terraces and windward piedmonts of Central Asian high mountains since the late Pliocene (mainly late Pleistocene). Multiple proxies analysis, e.g., grain size, geochemistry, sporopollen and magnetism, for the loess and fluvial deposits in this region reveal that the paleoclimate and paleoenvironment manifest a long-term stepwise drying or desertification trend of CA over the past 1 Myr, with at least one major drying event occurring at about similar to 0.5-0.6 Ma. One of the consequences is the development of the modern deserts in the Junggar Basin and the Tarim Basin. Despite the overall drying trend since the last interglacial period, the Holocene is characterized by a persistent wetting trend with millennial-scale oscillation. This special issue provides a useful glimpse into multi-scale climate and environmental changes in CA, facilitating climatic prediction in the future and climate modeling