Synchronous Changes in Sediment Transport and Provenance at the Iceland-Faroe Ridge Linked to Millennial Climate Variability From 55 to 6 ka BP

Abstract

Unique marine sediment cores retrieved from the southwestern slope of the Iceland-Faroe Ridge (IFR), close to the main axis of the Iceland-Scotland Overflow Water (ISOW), revealed prominent sedimentary cycles reflecting near-bottom current dynamics, sediment transport, and deposition, coincident with Dansgaard-Oeschger cycles and deglacial perturbations of the Atlantic Meridional Overturning Circulation. The transition between Greenland Stadials (GSs) and Greenland Interstadials (GIs) follows a distinct, recurring sedimentation pattern. Basaltic (Ti-rich) silts were transported from local volcanic sources by strong bottom currents and deposited during GIs comparable to modern ocean circulation. Finer-grained felsic (K-rich) sediments were deposited during GSs, when Iceland-Scotland Overflow was weak. Possible felsic source areas include British-Ireland and/or Fennoscandian shelf areas. A cyclic sawtooth pattern of bottom current strength is characterized by gradual intensification during GIs followed by a sharp decline toward GSs as is documented at core sites along the flank of Reykjanes Ridge. The cores north of the Faroe Channel instead document the opposite pattern. This suggests that the near-bottom currents along the Reykjanes Ridge are strongly controlled by the flow cascading over the IFR. Heinrich-(like) HS-1 and HS-2, are characterized by the deposition of very fine felsic sediments pointing to weakened bottom currents. Distinct coarse-grained intervals of ice-rafted debris are absent from the sediment records, although pebble- and gravel-sized ice-rafted debris is irregularly distributed throughout the fine sediment matrix. Near-bottom currents are considered to have a major control on the lithogenic sediment deposition southwest of the IFR and further downstream.