Precise dating of deglacial Laptev Sea sediments via ¹⁴C and authigenic ¹⁰Be/⁹Be – assessing local ¹⁴C reservoir ages

Abstract. Establishing accurate chronological frameworks is imperative for reliably identifying lead-lag dynamics within the climate system and enabling meaningful inter-comparisons across diverse paleoclimate proxy records over long time periods. Robust age models provide a solid temporal foundation for establishing correlations between paleoclimate records. One of the primary challenges in constructing reliable radiocarbon-based chronologies in the marine environment is to determine the regional marine radiocarbon reservoir age correction. Calculations of the local marine reservoir effect (ΔR) can be acquired using ¹⁴C-independent dating methods, such as synchronization with other well-dated archives. The cosmogenic radionuclide ¹⁰Be offers such a synchronization tool. Its atmospheric production rate is controlled by the global changes in the cosmic ray influx, caused by variations in solar activity and geomagnetic field strength. The resulting fluctuations in the meteoric deposition of ¹⁰Be are preserved in sediments and ice cores and can thus be utilized for their synchronization. In this study, for the first time, we use the authigenic ¹⁰Be/⁹Be record of a Laptev Sea sediment core for the period 8–14 kyr BP and synchronize it with the ¹⁰Be records from absolutely dated ice cores. Based on the resulting absolute chronology, a benthic ΔR value of +345 ± 60 ¹⁴C years was estimated for the Laptev Sea, which corresponds to a marine reservoir age of 848 ± 90 ¹⁴C years. The ΔR value was used to refine the age-depth model for core PS2458-4, establishing it as a potential reference chronology for the Laptev Sea. We also compare the calculated ΔR value with modern estimates from the literature and discuss its implications for the age-depth model.