New constraints on the source of loess from U/Th-Pb geochronology of detrital multi-minerals

Abstract

Abstract The origin and provenance of eolian sediments such as loess can potentially reveal paleo-air circulation directions that drive temporal changes in climate. The provenance of these deposits has been mostly assessed by detrital zircon U-Pb geochronology and remains debated. Recent studies reveal that constraining sediment provenance using only detrital zircon yields a restricted view of the overall sediment sources, because zircon commonly records high-temperature tectonothermal events and thus only represents a portion of provenance lithologies. We applied a new strategy for constraining the provenance of eolian sediments from the Chinese Loess Plateau—Earth's most extensive loess deposit—by using a multi-proxy (i.e., zircon, monazite and rutile) U/Th-Pb geochronology approach. We show that while zircon U-Pb-Lu-Hf isotopic data cannot conclusively discriminate the potential sources, monazite and rutile grains display dominant U/Th-Pb age peaks in the early Paleozoic, early Mesozoic, and late Cenozoic, mirroring the orogenic episodes of the northeast Tibetan Plateau. Monazite and rutile records also reveal spatial variability in sediment provenance between the western and central parts of the Chinese Loess Plateau, which is potentially affected by dust transport from westerly/northwesterly winds. Our integrated data set provides diagnostic constraints on the dust source, provenance variability, and transportation trajectory of the Chinese Loess Plateau, and highlights the importance of this new approach to provenance study of eolian deposits worldwide.