High-resolution reconstruction of historical flood events in the Changjiang River catchment based on geochemical and biomarker records

摘要

Extreme hydrologic events such as floods have caused catastrophic losses to modern human society, especially in highly developed coastal areas. However, high-resolution reconstructions of extreme flood events are scarce due to a paucity of suitable proxies in marginal seas. Here we present a high-resolution record of extreme flood events in the Changjiang River catchment during the last 110 years using samples from the subaqueous delta of Changjiang River estuary. We used a multi-proxy approach including Sr-Nd isotopes, Zr/Rb ratio and biomarkers (branched GDGTs, i.e. brGDGTs, and crenarchaeol, and the ratio of the two as calculated by the BIT index) as proxies for the evolution of extreme floods in the Changjiang River catchment. Rapid shifts in these proxies agreed with the timing of floods on the Changjiang River. We also tested the reliability of biomarker indices to reconstruct paleoflood events in this area. The results indicated that the abundances of GDGTs fluctuated in concert with historical floods. Cross-spectral analyses revealed that historical floods in the Changjiang River catchment were consistent with ENSO variance.