Excess 230Th and 231Pa records from Arctic Ocean Sediments: Implications for Chronology and Sedimentation

Abstract

Developing consensual chronostratigraphy in Arctic sediments is hampered by multiple problems due to low sedimentation rates and poor preservation of biogenic components, and the existing tentative age models are mostly based on core stratigraphic correlation. More recently, excess 230Th and 231Pa (230Thxs and 231Paxs) are emerging as important tracers for reconstructing past oceanic sedimentation and circulation changes in Arctic sediments. In order to further understand Th/Pa behaviour and attempt at setting time constraints, we have investigated 230Thxs and 231Paxs profiling data of core ARC5-MA01 from the Mendeleev Ridge in the Arctic Ocean. Based on the decrease and final contents of 230Thxs and 231Paxs in the core, an average sedimentation rate of ~3.5 mm/ka has been estimated, which is similar to those calculated by 230Thxs or 10Be methods in the Mendeleev-Alpha and Lomonosov Ridges. Sedimentation rates of the order of a few mm/ka suggest that a ‘sediment-starved’ environment exists over ridges in the central Arctic Ocean. Combining the 230Thxs and 231Paxs records available in the Arctic Ocean allow us to highlight the similarity of 230Thxs profiles from the Mendeleev-Alpha Ridge during the late Quaternary, indicating regional correlation of 230Thxs may be of significance. Profiles from the Gakkel Ridge cores are highly variable and show higher values, highlighting more complex sedimentary environment in the Eastern Arctic Ocean.