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Boyle, Patrick R.; Romans, Brian W.; Tucholke, Brian E.; Norris, Richard D.; Swift, Stephen A. and Sexton, Philip F.
(2016).
DOI: https://doi.org/10.1016/j.margeo.2016.12.014
Abstract
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 region- al 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 ~47 Ma, near the Early-Middle Eocene boundary, well developed contourite drifts began to accrete in paleo-water depths of ~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 AC) 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 AU along the margin of eastern North America about Early Oligocene time. Beginning in the Late Oligocene (~25 Ma) a thick drift exhibiting seismically laminated mudwaves was deposited in a distinct belt at ~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 (~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.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)
