Using 210Pb and related proxies to decode event-driven sedimentation in shelf environments: The Laptev Sea case study.

The reliability of 210Pb dating relies on the assumption of continuous sediment accumulation, which may not hold in dynamic environments. This study assesses its applicability in sediment cores from the Laptev Sea shelf and compares the results with cores from the East/Japan Sea under more stable conditions, using literature data. Laptev Sea cores exhibit irregular unsupported 210Pb profiles, with plateaus and uniform and/or anomalous values of independent proxies (sand content, bulk density, 226Ra and 137Cs). These features indicate short-term sedimentation events, frequently accompanied by abrupt changes in sediment provenance. Such episodes are here collectively termed event-driven sedimentation (EDS). In contrast, East/Japan Sea cores display profiles consistent with continuous accretion. The application of the TERESA model in its basic formulation, with the truncation of the 210Pbexc profiles to remove homogenites, and with its multimodal (multi-transect) version, proves useful for full and semi-quantitative analyses in these complex sedimentary scenarios. The major sedimentary events in the Laptev Sea were dated in the 1990s, consistent with the intensification of global warming. In EDS environments, consistency across multiple proxies is required to constrain physically plausible interpretations, and 210Pb data are better suited to infer sedimentary processes than for establishing precise chronologies.