Astronomical Cyclicity in Loess Magnetic Proxy Records from Western Arid Central Asia During the Early Pleistocene
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The Earth orbital precession cycle is expected to have a sustained impact on global climate. However, most Early Pleistocene terrestrial records from mid-latitude Asia are dominated by 41-kyr obliquity cycles, with little or no evidence of strong 21-kyr precessional signals. Here, we present new evidence of dominant ~21-kyr precession cycles in terrestrial climate proxy records from arid Central Asia (ACA) during the Early Pleistocene. We show that the ratio of anhysteretic remanent magnetization susceptibility (χ<sub>ARM</sub>) to low-frequency magnetic susceptibility (χ<sub>lf</sub>) in loess sediments is a robust proxy for paleoprecipitation. A ~600 ka χ<sub>ARM</sub>/χ<sub>lf</sub> record from loess deposits in western ACA exhibits clear 21-kyr cycles between ~2.24 and 2.05 Ma, when the regional climate was dry and the pedogenic intensity was weak. These findings provide evidence for precession forcing during the Early Pleistocene in mid-latitude Asia, and highlight the complementary roles of high- and low-latitude forcing in shaping climate variability.
