Quaternary primary productivity in Porcupine Seabight, NE North Atlantic

Biogenic opal and calcium carbonate contents in the Quaternary fine-grained sediments in the deep sea coral mound area (Hole U1317E and Hole U1318B drilled by IODP Expedition 307) in Porcupine Seabight, southwest off Ireland, were measured to estimate the primary productivity (P p) of the surface seawater in NE Atlantic. The results from the two holes commonly show relatively high P p values of 10–30 g cm−2 ky−1, having stratigraphic cyclicity reversely correlated with the δ 13C profile. The high P p could be attributed to the oceanic setting controlled by the Eastern North Atlantic (Central) Water and Shelf Edge Current, which have been strongly influenced by the obliquity forcing of the Milankovitch cycle. A positive covariance was observed between high P p and the mound development in U1317E, implying that the organic matter was the principal food source for the mound coral community. It is proposed that the pelagic marl matrix of the mound sediments provides information of the surface water productivity that is useful for reconstructing the paleoceanography and the paleoclimate in the NW Atlantic.