Gradual intensification of North Atlantic deep circulation from middle Eocene through late Oligocene; terrigenous grain size data from IODP sites U1406 and U1411, Newfoundland ridges

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Author(s): Parent, Andrew; Chilton, Kristin; Romans, Brian
Author Affiliation(s): Primary:
Virginia Polytechnic Institute and State University, Blacksburg, VA, United States
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Major climatic perturbations can have profound effects on and be affected by thermohaline circulation. Constraining the history of past ocean circulation is key to reconstructing paleoclimatic events and understanding the response of water mass transfer to modern climate change. Onset of modern Atlantic Meridional Overturning Circulation (AMOC) has been interpreted to have occurred at the Eocene-Oligocene Transition (EOT; 33.7 Ma), a global cooldown coincident with Antarctic continental ice sheet build-up. The relationship of North Atlantic circulation to change in the Southern Hemisphere has major implications for understanding hemispheric feedback in global climate systems but is poorly understood. Widespread erosional hiatuses that span the late Eocene through middle Oligocene in the North Atlantic suggest a global deep-circulation response; however, a lack of continuous sedimentary archives makes studying bottom current behavior through this transition difficult. Contourite drift deposits, drilled during IODP Exp 342, offshore Newfoundland, provide continuous and relatively expanded sedimentary records across the EOT. Here, we investigate the response of deep ocean circulation to the EOT through terrigenous grain-size (sortable silt, silt:clay ratio, etc.) records generated from two sites (U1406, U1411) drilled during Exp 342. Integration of seismic stratigraphy with core data from the J-Anomaly and Southeast Newfoundland Ridges suggests onset of contourite drift sedimentation at ∼47 Ma, but post-Middle Eocene depositional history remains poorly constrained. Grain-size records from U1411, ∼250 km northeast of U1406, reveal a gradual upward coarsening with no notable change at the EOT. Instead, a sudden coarsening is observed at 29.5 Ma, which may correspond to recent interpretations of the opening of the Greenland-Scotland Ridge in the North Atlantic. This record suggests that regional tectonics had a strong influence on ocean circulation changes, where cooling initiated in the Southern Hemisphere played a marginal role. This scenario may also support a pre-EOT onset of North Atlantic Deep Water export. Data from U1406, complimentary to U1411, will provide insight to regional changes in deep ocean invigoration, extending the record to deeper water and into the Middle Eocene.
Year of Publication: 2018
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Canada; Cenozoic; Eastern Canada; Eocene; Expedition 342; IODP Site U1406; IODP Site U1411; Integrated Ocean Drilling Program; Marine sediments; Middle Eocene; Newfoundland; Newfoundland and Labrador; North Atlantic; North Atlantic Deep Water; Oligocene; Paleogene; Sediments; Tertiary; Upper Oligocene
Coordinates: N402059 N402100 W0513859 W0513900
N413705 N413706 W0485959 W0490000
Record ID: 2019046520
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