Provenance of the late Neogene aeolian Baode Red Clay in northern Chinese Loess Plateau by combined rutile geochemical and zircon U-Pb analysis

Understanding the provenance of aeolian dust deposits is essential for identifying past atmospheric circulation patterns and sediment generation. Knowledge of dust provenance not only reveals variations in the dust transportation paths and dust availability, but also increases our understanding of the climatic and/or tectonic controls on dust emission, allowing analysis of potential climate feedbacks. A globally exceptional terrestrial archive of atmospheric dust and paleoclimate can be found in North China on the Chinese Loess Plateau (CLP), where mineral dust deposits cover ca. 440 000 km² and can reach thicknesses of hundreds of meters.

The late Neogene (ca. 11–2.6 Ma) dust on the CLP is known as the Red Clay. The Red Clay deposits are the products of inland Asian aridification driven by global cooling, increasing continentality, and uplift phases of Tibetan Plateau (e.g. Lu et al., 2019). Previous Red Clay provenance studies have shown that the dust originated mostly from different sources in the areas west and northwest of the CLP (e.g. Nie et al., 2018; Shang et al., 2016), and was transported by the East Asian winter monsoon and westerly winds (all winds deriving from the west of the CLP). These studies focused on bulk sediment geochemistry, heavy mineral and detrital zircon U-Pb age analyses, which to date have not allowed detailed understanding of metamorphic source regions, source region variations, and indeed leave open ambiguities over differentiating between certain potential source areas.

Here we present combined detrital rutile trace element and detrital zircon U-Pb data from the late Neogene-early Quaternary Baode Red Clay-loess section (depositional ages of 6.91–2.41 Ma) in northern CLP, as well as detrital rutile data from 14 potential sedimentary source areas. Our study aims at testing the use of rutile geochemistry in multi-proxy sourcing the CLP sediments. Rutile, a common mineral in metamorphic rocks, has the potential of testing between potential source regions that cannot be distinguished by zircon U-Pb dating, the most commonly used single-grain provenance proxy. In Baode Red Clay, some samples show very similar zircon age spectra but have notable differences in their rutile geochemistry, which verifies the need of multi-proxy single-grain provenance work. The preliminary Baode rutile data also imply that the dominant source(s) of the dust changed at least at the Neogene-Quaternary transition, a suggestion which has not always been supported by previous provenance studies and is lacking consensus.

References

Lu, H. et al., 2019. Formation and evolution of Gobi Desert in central and eastern Asia. Earth-Science Reviews, 194: 251-263.

Nie, J. et al., 2018. Pre-Quaternary decoupling between Asian aridification and high dust accumulation rates. Science Advances, 4(2).

Shang, Y. et al., 2016. Variations in the provenance of the late Neogene Red Clay deposits in northern China. Earth and Planetary Science Letters, 439: 88-100.