Provenance of eolian deposits in the Xorkol Basin: Implications for Eocene dust-transport pattern in western China

Abstract

Atmospheric circulation in western China significantly affects the inland climate of Asia. Constraining the provenance of eolian sequences can provide robust evidence for dust-transport pathways, and thus the evolution of paleo-atmospheric circulation. Western China has been dominated by the westerly wind regime since the late Oligocene, as demonstrated by provenance studies of eolian deposits. However, the wind regime responsible for the accumulation of eolian deposits during the Eocene is unclear due to a lack of corresponding provenance studies. Here, we present the first provenance analysis for an Eocene (ca. 51−40 Ma) eolian Red Clay sequence in the Xishuigou Formation of the Xorkol Basin in western China, based on multiproxy geochemical and geochronological data. Comparison of zircon U−Pb ages from the Xishuigou sequence with ages from potential source regions reveals that the northern piedmont of the West Kunlun Range was a persistent source, although sediments from the nearby Altun-Xorkol region were an important dust source for the lower part of the Xishuigou sequence which were deposited between ca. 51 Ma and 46.5 Ma. These results reveal that the westerly dust-transport pattern has been dominant in western China since at least ca. 51 Ma. The similarity of provenance between the Eocene Red Clay of the Xishuigou Formation and the Neogene eolian sequence of the overlying Caihonggou Formation in the same area implies that this dust-transport pattern was stable from the Eocene to the Neogene, despite dramatic changes in paleogeography, paleotopography, and global climate.