Delayed sedimentary response of the Huanghe alluvial plain to climate change inferred from source variations of the Xiashu loess since-1 Ma

Large river systems are reactive or buffered to large climate oscillations on orbital timescales, depending on whether their sedimentary response time is shorter or longer than the period of these climate oscillations. Estimating the sedimentary response time of large river systems is essential for understanding their sensitivity to climate change and their corresponding ability to reshape themselves, but few studies have estimated the sedimentary response time of real large river systems by geologic records. Provenance analysis of the Xiashu loess in China since -1 Ma provides the opportunity to estimate the sedimentary response time of the adjacent Huanghe (Yellow River). Here, we conducted the first provenance analysis of such a Xiashu loess section, using measured data of element contents, Nd isotopes, and grain-size compositions. The results reveal changes in loess provenance at -0.3 Ma and -0.07 Ma. The provenance changes were caused by the expansion of the Huanghe alluvial plain at -0.3 Ma and its contraction at -0.07 Ma. The expansion and contraction can be attributed to the delayed sedimentary response of the Huanghe alluvial plain to the Mid-Pleistocene Transition and the MidBrunhes Transition, respectively. Therefore, the sedimentary response time of the Huanghe alluvial plain is estimated to be -0.4 Ma, which is much longer than the duration of the high-amplitude Quaternary climate oscillations on orbital timescales. Our findings support that the Huanghe and similar large rivers are buffered to these climate oscillations. The alluvial plains of the Huanghe and similar rivers may play a key role in delaying and reducing the impacts of future climate change on the land surface.