Terrigenous grain-size record of the Newfoundland ridge contourite drift, IODP Site U1411; the first physical proxy record of North Atlantic abyssal current intensity during the Eocene-Oligocene transition

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http://abstractsearch.agu.org/meetings/2016/FM/PP53A-2373.html
Author(s): Chilton, Kristin; Romans, Brian W.; Spray, James; Wilson, Paul A.; Bohaty, Steven M.; Sanchez, Taylor
Author Affiliation(s): Primary:
Virginia Polytechnic Institute and State University, Blacksburg, VA, United States
Other:
University of Southampton, United Kingdom
Volume Title: AGU 2016 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2016; American Geophysical Union 2016 fall meeting, San Francisco, CA, Dec. 12-16, 2016. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Atlantic Meridional Ocean Circulation (AMOC) is a vital process that helps to regulate global climate and support marine ecosystems. The timing and nature of the shift to modern AMOC, and especially to deep-water formation in the North Atlantic, has been a topic of ongoing study, with the Eocene-Oligocene Transition (EOT, ∼34 Ma) being a potential focal point of this shift. However, the role played by abrupt EOT cooling in North Atlantic circulation remains unclear. Improved constraints on Paleogene circulation will provide insight into the sensitivity of AMOC to perturbations in global climate. We obtained grain-size data from the terrigenous fraction of the mud-dominated sediments of the Southeast Newfoundland Ridge contourite drift complex at IODP Site U1411, which is interpreted to have formed under the influence of the Deep Western Boundary Current. We analyzed 195 samples that span 150 m of stratigraphy from 36-26 Ma. The main objective was to use the 'sortable silt' fraction (10-63 µm) to generate a record of relative change in bottom-current velocity. These data are complemented with a record of the abundance and size of lithogenic sand (>63 µm). Here we present U1411 sortable silt data as the first physical proxy record of abyssal current intensity in the North Atlantic, from late Eocene to mid Oligocene. Invigoration of North Atlantic deep circulation occurred gradually (over Myr timescales). We infer that deep circulation in the North Atlantic was not sensitive to the abrupt global cooling and Antarctic glaciation associated with the EOT. Rather, our data suggest that changes in North Atlantic circulation were likely governed by longer-term processes related to the opening of key tectonic gateways (i.e., the Greenland-Scotland-Faeroes Ridge in the North Atlantic, and the Drake and Tasman Passages in the Southern Ocean). Lithogenic sand is nearly absent in the Eocene and then systematically increases in abundance from the earliest Oligocene through the mid Oligocene, which could represent bottom-current transport of an additional supply of terrigenous sediment during the Oligocene. Our findings have important implications for debate over the mechanisms responsible for carbon cycle perturbation associated with the Cenozoic initiation of sustained Antarctic glaciation.
Year of Publication: 2016
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Atlantic Ocean; Cenozoic; Contourite; Eocene; Expedition 342; IODP Site U1411; Integrated Ocean Drilling Program; Marine sediments; North Atlantic; Oligocene; Paleogene; Sediments; Tertiary
Coordinates: N413705 N413706 W0485959 W0490000
Record ID: 2018008366
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