Radiocarbon chronology of depositional regimes in the western Arctic Ocean

Abstract

The foraminiferal abundance and percentage of coarse ice-rafted detritus (IRD) define glacial, deglacial, and interglacial depositional regimes in AMS radiocarbon-dated box cores from the western Arctic Ocean. Sediment deposition rates are generally less than 0.5 cm/ka for glacial regimes, greater than this for deglacial regimes and greater than 1–2 cm/ka for interglacial regimes. These differences in deposition rates might account for the much lower average sedimentation rates for the last 780 ka of 1–3 mm/ka in cores from the central Arctic Ocean if glacial regimes dominated this interval. Foraminiferal abundances are less than 500/g during glacial maxima and mostly higher than 2000/g during deglacial and interglacial regimes. Slightly higher coarse IRD percentages occur in deglacial intervals (> 5–10% up to 30%) compared with interglacial intervals (mostly ≤5%), which characterize the last 10–12 ka in the western Arctic Ocean. Glacial regimes occurred from about 40 to 11 ka except for a brief interglacial or deglacial interval around 24–28 ka in the central Arctic Ocean. The coarsest deglacial events occurred prior to 45 ka. The Late Wisconsin deglaciation sediments (approximately 9–16 ka) are difficult to detect in the central Arctic Ocean sediments because they are only slightly coarser than the Holocene and, in some box cores, less coarse than the Holocene. A previously unrecognized coarse IRD event occurred near the core tops (0–3 cm) between 1500 and 3500 radiocarbon years ago in the western Arctic Ocean. Only sediment older than 40 ka is coarser than this recent IRD event, which might correspond to a Neoglaciation recognized in the North Atlantic and elsewhere.