Evidence for SCW circulation in the eastern South Atlantic as a consequence of southern gateway openings during the middle to late Eocene

Author(s): Langton, Samantha; Cramer, Benjamin S.; Katz, Miriam E.
Author Affiliation(s): Primary:
RPI, 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.122; 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: The opening of the Drake and Tasman passages initiated proto-Antarctic Circumpolar Current (ACC) flow during the late Eocene to early Oligocene, which contributed to the isolation and glaciation of Antarctica and greatly impacted global thermohaline circulation. Even at its early stages of development, the proto-ACC hindered the Weddell Sea surface waters from mixing with warm equatorial surface waters of the subtropical gyre. The isolated Weddell Sea surface waters then cooled and became a source of the cold, dense Southern Component Water (SCW) that flowed north as a deepwater mass from Antarctica. We present new benthic foraminiferal δ18O and δ13C records from the Walvis Ridge, ODP Site 1263, with comparisons to published records from other ocean basins in the late middle Eocene to early Oligocene (40-33 Ma). Comparison of Site 1263 to Site 689 on the Maud Rise reveals the paleocirculation history of the SCW and its effect at the Walvis Ridge. The δ18O record from Site 1263 correlates to equatorial Pacific Site 1218 and Site 689 from 40 to ∼38.5Ma. At 38.5Ma, the Weddell Sea deepwater continued to cool, while deep water at the Walvis Ridge and Site 1218 was warmer until 37.5Ma. At this time, the Site 1263 δ18O diverged from Site 1218 and began to cool and track Site 689 through 33Ma. The correlation between these records shows that SCW was the primary deepwater mass at the Walvis Ridge after 37.5Ma, while more northern locations (e.g., Site 1218, North Atlantic Site 1053) maintained warmer deepwater as indicated by their published δ18O records. This implies that the early stages of the development of the Drake Passage and proto-ACC impacted South Atlantic deepwater circulation in the late middle to late Eocene, prior to the large isotopic shift of the early Oligocene associated with continent-scale Antarctic glaciation and the deepening of the Tasman Gateway.
Year of Publication: 2012
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctica; Atlantic Ocean; C-13/C-12; Carbon; Cenozoic; Drake Passage; East Pacific; Eocene; Equatorial Pacific; Foraminifera; Glaciation; Invertebrata; Isotope ratios; Isotopes; Leg 199; Leg 208; Microfossils; North Pacific; Northeast Pacific; O-18/O-16; ODP Site 1218; ODP Site 1263; Ocean Drilling Program; Oxygen; Pacific Ocean; Paleo-oceanography; Paleocirculation; Paleoclimatology; Paleoenvironment; Paleogene; Protista; South Atlantic; Stable isotopes; Tertiary; Walvis Ridge
Coordinates: N085300 N085300 W1352200 W1352200
S283200 S283200 E0024700 E0024700
Record ID: 2013047183
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States