Long-range transport of aeolian deposits during the last 32 kyr inferred from rare earth elements and grain-size analysis of sediments from Lake Lugu, Southwestern China

Abstract

Accumulations of aeolian deposits in a range of sedimentary environments provide evidence for past changes in atmospheric circulation patterns over a range of spatiotemporal scales. As yet, there have been relatively few studies of aeolian records in Southwestern (SW) China, and thus there is hitherto untapped potential of using such records to reveal regional atmospheric circulation. Rare earth element (REE) and grain-size analyses were carried out on a well-dated sediment core from Lake Lugu, SW China, to establish the provenance of aeolian deposits preserved within the lake during the last 32 kyr. The core sediments (LGH2) possess high δEuN values (0.73–0.87) and exhibit a moderate REE abundance (156–274 ppm). The δEuN-∑REE pattern of the Lake Lugu sediments are distinct from those of adjacent geographical areas, but are shown to overlap with the sediments from the Kashmir Valley and northwestern (NW) Deccan Plateau indicating a long-distance dust source. The grain-size endmember for the aeolian deposits shows a gradually increasing trend from 32 kyr B.P. to the onset of the Holocene, followed by a sharp decrease around 9 kyr B.P., with very low values observed during the Holocene optimum (8.3–2 kyr B.P.). Aeolian deposition resumed from 2 kyr B.P. and has continued to the present day. Comparisons with both local and regional palaeoclimate records show that both the local climate and East Asian monsoon (EAM) have not influenced aeolian deposition in Lake Lugu. Rather, changing vegetation cover in the north India and NW Deccan Plateau provided the sediment supply, with entrainment governed by variations in the Southern Winter Westerlies in the dry season (north India), and the South Asian summer monsoon (SASM) in the rainy season (NW Deccan Plateau).