Sediment flux patterns in the northeastern Atlantic: variability since the last interglacial

Abstract

The distribution of terrigenous and carbonate absolute accumulation rates in the northeastern Atlantic during the last climatic cycle shows that climate and sediment accumulation are closely coupled, either directly or through oceanic circulation and eustatic variation. The strong contrast between the glacial and Holocene flux distribution is related to oceanic circulation changes: either surface circulation which governs both the ice-rafting supply and the planktonic biogenic production, or, more particularly, deep circulations via the reinitiation of the Iceland-Scotland overflow. Glacial erosion and the low sea-level stand enhance the terrigenous supply, but the Holocene deep circulation reinforcement leads to important material reworking. As a consequence, an almost constant average sediment flux is obtained (4g· −2·ky −1 during the Holocene, compared to 4.7 g·cm −2·ky −1 during the glacial period). During the Holocene period, the notable increase in mean carbonate flux (from 1.5 to 3 g·cm −2·ky −1) is associated with carbonate biogenic production, but the carbonate flux distribution shows the influence of redistributive agents. On margins, fluxes do not simply decrease from continental sources to the oceanic basin. Eustatic drops leads to a shift in the areas of preferential accumulation from the upper to the lower slope. During the deglacial warming period, the fluxes are respectively an average of two and three times higher than during the Holocene and the glacial periods. Their importance highlights the major impact of rapid climatic changes. Finally, local conditions — the location of terrigenous sources and the presence of contour currents — are among the many factors which will modify the trends observed on a global scale.