Bipolar Atlantic deepwater circulation in the middle-late Eocene; effects of Southern Ocean gateway openings

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doi: 10.1002/2012PA002444
Author(s): Borrelli, Chiara; Cramer, Benjamin S.; Katz, Miriam E.
Author Affiliation(s): Primary:
Rensselaer Polytechnic Institute, Department of Earth and Environmental Sciences, Troy, NY, United States
Other:
Theiss Research, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 29(4), p.308-327. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 106 refs.; illus., incl. 2 tables
Summary: We present evidence for Antarctic Circumpolar Current (ACC)-like effects on Atlantic deepwater circulation beginning in the late-middle Eocene. Modern ocean circulation is characterized by a thermal differentiation between Southern Ocean and North Atlantic deepwater formation regions. In order to better constrain the timing and nature of the initial thermal differentiation between Northern Component Water (NCW) and Southern Component Water (SCW), we analyze benthic foraminiferal stable isotope (δ18Obf and δ13Cbf) records from Ocean Drilling Program Site 1053 (upper deep water, western North Atlantic). Our data, compared with published records and interpreted in the context of ocean circulation models, indicate that progressive opening of Southern Ocean gateways and initiation of a circum-Antarctic current caused a transition to a modern-like deep ocean circulation characterized by thermal differentiation between SCW and NCW beginning ∼38.5 Ma, in the initial stages of Drake Passage opening. In addition, the relatively low δ18Obf values recorded at Site 1053 show that the cooling trend of the middle-late Eocene was not global, because it was not recorded in the North Atlantic. The timing of thermal differentiation shows that NCW contributed to ocean circulation by the late-middle Eocene, ∼1-4 Myr earlier than previously thought. We propose that early NCW originated in the Labrador Sea, based on tectonic reconstructions and changes in foraminiferal assemblages in this basin. Finally, we link further development of meridional isotopic gradients in the Atlantic and Pacific in the late Eocene with the Tasman Gateway deepening (∼34 Ma) and the consequent development of a circumpolar proto-ACC. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2014
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctic Circumpolar Current; Assemblages; Atlantic Ocean; Blake Nose; Blake Plateau; Bottom water; C-13/C-12; Carbon; Cenozoic; Correlation; Currents; Demerara Rise; Differentiation; Drake Passage; East Pacific; Eocene; Equatorial Atlantic; Equatorial Pacific; Foraminifera; Invertebrata; Isotope ratios; Isotopes; Leg 113; Leg 171B; Leg 199; Leg 207; Maud Rise; Microfossils; Nannoplankton; North Atlantic; North Pacific; Northeast Pacific; Northwest Atlantic; O-18/O-16; ODP Site 1053; ODP Site 1218; ODP Site 1260; ODP Site 689; Ocean Drilling Program; Ocean circulation; Ocean currents; Oxygen; Pacific Ocean; Paleo-oceanography; Paleobathymetry; Paleocirculation; Paleogene; Plankton; Protista; Sea water; South Pacific; Southern Ocean; Southwest Pacific; Stable isotopes; Tasman Basin; Tertiary; Weddell Sea; West Atlantic; West Pacific
Coordinates: S643101 S643100 E0030600 E0030559
N091600 N091600 W0543300 W0543300
N295932 N295932 W0763125 W0763125
Record ID: 2014071401
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom