Influences of Norwegian Sea overflow water on sedimentation in the northern North Atlantic and Labrador Sea

Abstract

Reflection profiles and hydrographic data indicate that sedimentation in parts of the northernmost Atlantic and in the Labrador basin has been largely governed by the movement of bottom water derived from the Norwegian Sea. Three areas are considered in detail. The first is the channel separating Rockall bank from the Irish continental shelf, where a ridge, nearly 600 km long, composed of sediment deposited on a gently dipping reflector of early Tertiary age, has been found. Hydrographic observations suggest that the feature, for which the name Feni ridge is proposed, is the result of deposition close to the boundary of a component of the Iceland‐Scotland overflow water from the Norwegian Sea, which enters the channel from the north and in flowing southward is constrained by Coriolis force to the Rockall scarp. Farther north, reflection profiles show a marked asymmetry of sediment distribution across the volcanic Faeroe‐Iceland ridge, the sediment cover being much thicker and more continuous on the north‐facing slope than on the crest and southern flank. This difference is attributed to fast bottom currents in the south, caused by sinking of the Norwegian Sea overflow, and the persistence of tranquil bottom conditions in the north. Seismic profiles from the Labrador basin reveal a well‐defined body of thick sediments trending NNW on a portion of the continental rise of southern Greenland where turbidity currents cannot reach. The thick sediments lie in a region in which the flow of deep water is weak and in which rapid deposition from sediment‐laden bottom waters is allowed. Appreciably stronger bottom currents associated with the counterclockwise circulation of dense water derived from the Norwegian Sea appear to have greatly inhibited deposition of pelagic material in the area surrounding the sediment body. Sedimentation under the influence of bottom currents in this region, in the Rockall area, and on the Blake‐Bahama outer ridge took place throughout a large part of Tertiary time but did not occur in the Upper Cretaceous. This is attributed to a major alteration in the circulation pattern of the North Atlantic caused by continental drift, polar wandering, and climatic deterioration between late Cretaceous and late Eocene times.

Late Neogene and Quaternary sedimentation on the continental slope and upper rise offshore southeast Greenland: interplay of contour and turbidity processes

“…Their observations are largely confirmed by the present study. Considerable deposition by contour-currents was previously thought to take place only south of Cape Farewell on the Eirik Ridge (Johnson and Schneider, 1969;Jones et al, 1970;Ruddiman, 1972;Egloff and Johnson, 1975). However, both erosion and deposition by contour-currents were believed by Larsen (1990, fig.…”

Studies of deep-sea sedimentary microtopography in the North Atlantic Ocean

“…North Atlantic (Jones et al, 1970;Johnson et al, 1971;Davies and Laughton, 1972); the lower continental rise of eastern North America (Ballard, 1966;Fox et al, 1968;Rona, 1969);…”

High Resolution Records of Benthic foraminifers in the Late Neogene of the Northeastern Atlantic

“…1). Hatton Drift is one of several elongate bodies of sediment in the northern North Atlantic whose genesis is thought to be closely related to the activities of deep bottom currents (Jones et al, 1970;Ruddiman, 1972;Roberts, 1975) and which date back to at least the middle or early Miocene (Shor and Poore, 1979). The deep bottom currents flowing clock-…”