Opening of circum-Antarctic gateways and the evolution of deepwater circulation at eastern Equatorial Atlantic DSDP Site 366 (40-33 Ma)

Author(s): Rabideaux, Nathan; Cramer, Benjamin S.; Katz, Miriam E.
Author Affiliation(s): Primary:
Rensselaer Polytechnic Institute, Earth and Environmental Science, Troy, NY, United States
Other:
Theiss Research, United States
Volume Title: Geological Society of America, 2012 annual meeting
Source: Abstracts with Programs - Geological Society of America, 44(7), p.123; Geological Society of America, 2012 annual meeting, Charlotte, NC, Nov. 4-7, 2012. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: We attribute the evolution of deepwater circulation during the late middle Eocene and Oligocene to the opening of circum-Antarctic gateways at the Drake Passage and Tasman Rise. These gateways allowed the development of a proto-Antarctic Circumpolar Current (proto-ACC) by the late Eocene, and the subsequent thermal differentiation of Southern relative to Northern Component Water (SCW vs. NCW). The timing and influence of the tectonic events are important in understanding their significance for deepwater flow during this time period. Shallow flow through the Drake Passage began by ∼41 Ma; the Tasman Rise experienced an initial minor deepening from ∼39-36 Ma, possibly allowing the formation of a shallow proto-ACC. Further deepening of these gateways during the early Oligocene resulted in intensification of flow, with a full depth ACC established in the late Oligocene. We compare benthic foraminiferal stable isotope records from Deep Sea Drilling Project (DSDP) Site 366 with published records from other sites to reconstruct deepwater circulation in the eastern equatorial Atlantic from the late middle Eocene to earliest Oligocene (∼40-33 Ma). Comparison of Site 366 δ18O values to Southern Ocean Site 689 during the late middle Eocene indicates that SCW was the dominant water mass in the eastern equatorial Atlantic at the time of initial flow through the Drake Passage. In the early late Eocene, δ18O records from Site 366 and equatorial Pacific Site 1218 indicate that, in place of SCW, a warmer deepwater mass was dominant in the equatorial ocean in both basins. Site 366 δ18O values indicate a shift back to SCW in the middle late Eocene, likely as a result of enhanced SCW production. During the latest Eocene, Site 366 δ18O values diverged from Site 689, indicating a return of warmer deepwater during this time, possibly due to deepening of the proto-ACC and resultant reduction in SCW export.
Year of Publication: 2012
Research Program: DSDP Deep Sea Drilling Project
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctic Circumpolar Current; Atlantic Ocean; Cenozoic; DSDP Site 366; Deep Sea Drilling Project; Drake Passage; Equatorial Atlantic; Isotope ratios; Isotopes; Leg 113; Leg 41; Maud Rise; North Atlantic; O-18/O-16; ODP Site 689; Ocean Drilling Program; Oligocene; Oxygen; Paleo-oceanography; Paleocirculation; Paleoclimatology; Paleogene; Sierra Leone Rise; Southern Ocean; Stable isotopes; Tertiary; Weddell Sea
Coordinates: S643101 S643100 E0030600 E0030559
N054040 N054041 W0195104 W0195105
Record ID: 2013047185
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