Cenozoic North Atlantic deep circulation history recorded in contourite drifts, offshore Newfoundland, Canada

Boyle, PR, Romans BW, Tucholke BE, Norris RD, Swift SA, Sexton PF.  2017.  Cenozoic North Atlantic deep circulation history recorded in contourite drifts, offshore Newfoundland, Canada. Marine Geology. 385:185-203.

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abyssal circulation, continental rise, contourite drifts, eocene climatic optimum, hemisphere glaciation, J-Anomaly, j-anomaly ridge, middle Eocene, North Atlantic Ocean, ocean circulation, ridge, seismic stratigraphy, Southeast Newfoundland Ridge, southern-ocean, thermohaline circulation, water circulation, western boundary current


In the North Atlantic Ocean, contour-following deep currents have created regional erosional unconformities and deposited contourite drifts that exceed 2 km in thickness and extend for 100 s of km. The stratigraphic records in the drifts have been used to reconstruct variations in North Atlantic deep-water circulation throughout the Cenozoic; however, uncertainties remain about certain aspects of the timing, intensity, depth distribution, and regional impact of these currents. Here, we use an integrated dataset of seismic-reflection profiles and IODP core data (lithology, biostratigraphy, and magnetostratigraphy) to document sedimentation history and the development of current effects in the Cretaceous to present sedimentary record on the J-Anomaly Ridge and Southeast Newfoundland Ridge, offshore Newfoundland, Canada. The Newfoundland ridges are in a key location, lying between well-studied areas in the northern and western North Atlantic and under the path of both the modern Deep Western Boundary Current and the Gulf Stream. Late Cretaceous through Early Eocene sedimentation on the ridges was dominated by biogenic pelagic sedimentation, but at similar to 47 Ma, near the Early-Middle Eocene boundary, well developed contourite drifts began to accrete in paleo-water depths of similar to 4000-4500 m, accompanied by an order-of-magnitude increase in terrigenous sediment mass accumulation rates. From this time forward, drift deposition, interrupted by brief episodes of erosion, continued unabated. This timing for the onset of persistent deep currents is coincident with reorganization of Atlantic circulation inferred from a change from biosiliceous to non-biosiliceous sedimentation in the western North Atlantic (Horizon A(C)) and with the current-eroded Intra-Eocene Unconformity (IEU) in the northern North Atlantic A change in sedimentation style occurred within the Middle Eocene to upper Oligocene drift sequence, and it likely was related to a shift to deeper, more intense currents that eroded the widespread Horizon A(U) along the margin of eastern North America about Early Oligocene time. Beginning in the Late Oligocene (similar to 25 Ma) a thick drift exhibiting seismically laminated mudwaves was deposited in a distinct belt at similar to 3500-4500 m paleodepth on the Southeast Newfoundland Ridge. This development correlates with widespread Late Oligocene through Miocene-Pliocene drift accumulation throughout the North Atlantic. The most recent phase of drift deposition, since Late Pliocene time (similar to 3 Ma), occurred after a shift to the 'modern' circulation system of deeper, swifter currents, and it includes mixed pelagic-hemipelagic sediments and ice-rafted debris that reflect glacial-interglacial influences on sedimentation. (C) 2017 Elsevier B.V. All rights reserved.