Statistical self-similarity of detrital zircon U-Pb ages reveals sedimentary provenance: A case study from the Chinese Loess Plateau

Abstract

A major concern of the geoscience community is often where sediments originally come from — this is a material's provenance. Tracing provenance allows us to determine how a material moved from its source to its sink, and thereby to evaluate the tectonic and paleoclimatic history. Detrital zircon UPb geochronology has long been used for this purpose. However, current approaches to measuring (dis)similarity in zircon age distributions may lead to erroneous geologic interpretations. Here we propose an Age-Number fractal model to characterize zircon age densities and perform intersample comparisons using multidimensional scaling. The advantage of the new method is that compared to such traditional methods as Kolmogorov-Smirnov test, it accentuates holistic rather than partial differences between two age distributions and is less-affected by data biases related to grain-size sorting and uneven sample sizes. We then use this model to unravel the debatable provenance of the Chinese Loess Plateau (CLP) by comparing the zircon ages of Quaternary loess on the CLP with that of loose sediments from potential source regions. The model divides the CLP into four distinct provenance zones, receiving materials primarily from the northeastern Tibetan Plateau, upper Yellow River, and/or Mu Us Desert. Our observations corroborate that the aeolian (East Asian monsoon and Westerlies) and fluvial (Yellow River) processes play a joint role in the dust deposition. A new pattern of spatial heterogeneity in the loess provenance is established and can be interpreted as a combined effect of atmospheric circulation patterns, availability of riverine sediments, and such factors as aridification, implying a more dynamically-evolved CLP than previous thought. Our results will aid future development and interpretation of the dust-based paleoclimatic proxies.