Revised marine reservoir offset (ΔR) values for molluscs and marine mammals from Arctic North America. (3rd November 2022) - Pieńkowski, Anna J.
Abstract : Appropriate marine–terrestrial reservoir offset (ΔR) values are essential for accurate calibration of marine radiocarbon dates. However, ΔR values are only valid for the specific calibration curve that their calculation is based on. Here, we present revised ΔR values for the Marine20 calibration curve from Arctic North America, based on previously published 14 C dates on pre‐bomb live‐collected marine molluscs ( n = 124) and cetaceans (beluga whales; tooth dentine; n = 12), and bowhead whale–driftwood age comparisons from the same glacio‐isostatically uplifted shorelines ( n = 18). Molluscan‐based ΔR are: Chukchi/Beaufort sea coasts, 265±116 14 C years; NW Canadian Arctic Archipelago, 188±91 14 C years; NE Baffin Island, 81±18 14 C years; SE Baffin Island, 14±58 14 C years; Hudson Strait, −73±64 14 C years; Ungava Bay, 0±86 14 C years; Foxe Basin, 175±89 14 C years; Hudson Bay, −21±72 14 C years; James Bay, 209±114 14 C years; West Greenland, −93±111 14 C years. Species‐specific marine mammal ΔR terms are 107±59 14 C years for beluga and 24±58 14 C years for bowheads. Our revised ΔR values are applicable for as long as the same broad oceanographic conditions (circulation, ventilation) have persisted, i.e. through the Holocene. While molluscan values are applicable to other marine carbonate (e.g. foraminifera), cetacean ΔR are valid only for the species they were calculated for and should not be applied to other marine mammals. Importantly, the ΔR terms calculated here are only valid for Marine20 and should not be used with earlier or later calibration curves. Abstract : Marine reservoir offset values (?R) are calculated for the Marine20 calibration curve for molluscs and cetaceans from Arctic North America. These new terms are essential for accurate chronologies necessary for comparisons between environments, regions, and across different geochronological methods.