Sampling strategies and mitigation of natural and anthropogenic effects in detrital zircon provenance analysis of fluvial strata

Detrital zircon ages are widely used in sediment provenance investigations. However, given the preponderance of studies, relatively few have focused on enhancing the fidelity of data interpretations through the improvement of sampling strategies. Anthropogenic modification to sedimentary systems, like the damming of rivers and construction-related hillslope erosion, generally decreases the confidence that can be placed on detrital zircon-based provenance interpretations. In response to this issue, we sampled fluvial sediments from the Yangtze and Yellow Rivers, and their tributaries, focusing on the anthropogenic effects of sediment mixing between higher- and lower-order streams. The results from our study show that (1) the inflow of lower-order streams has a meaningful impact on the provenance signal of higher-order channels, but the impact distances are quite limited. (2) Lakes have significant hydraulic sorting effects on different-sized particles, and thus, complicate provenance signals, but trapping of zircon by lakes might be more limited. (3) The construction of dams would have a limited long-term impact on the detrital zircon provenance of rivers downstream if sediment could be discharged from the sediment pathway through the dam. (4) Anthropogenic erosion creates provenance signal enrichments of more easily eroded strata and can interfere with natural sediment sourcing. Our results indicate modifications to detrital mineral sampling strategies are needed in modern and paleo fluvial deposits.