Effects of proto-Antarctic Circumpolar Current circulation in the middle to late Eocene

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Author(s): Katz, M.; Cramer, B. S.; Toggweiler, J. Robbie
Author Affiliation(s): Primary:
Rensselaer Polytechnic Institute, Department of Earth & Environmental Sciences, Troy, NY, United States
Theiss Research, United States
NOAA, Geophysical Fluid Dynamics Laboratory, United States
Volume Title: AGU 2011 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2011; American Geophysical Union 2011 fall meeting, San Francisco, CA, Dec. 5-9, 2011. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Progressive development of the Antarctic Circumpolar Current (ACC) and reorganization of global ocean circulation accompanied the critical climate transition from the late middle Eocene to mid-Oligocene (∼38-28 Ma), marked by global cooling and development of continental-scale Antarctic ice sheets. The ACC began to develop in the middle Eocene through a shallow Drake Passage, with deepwater flow likely established by 29 Ma (Livermore et al. 2004). Rapid deepening of the Tasman gateway occurred in the late Eocene to early Oligocene). The timing of the earliest impact of the (proto-) ACC on global circulation and climate has been debated for decades. Here, we present new middle to late Eocene (∼36-40 Ma) benthic foraminiferal stable isotopic (δ18O, δ13C) records and %CaCO3 data from ODP Site 1090 that extend published late Eocene-early Oligocene records (Pusz et al. 2011). Comparisons with published isotopic records (Cramer et al. 2009) highlight the development of a significant carbon isotopic (δ13C) offset between Site 1090 (values ∼0.7ppm lower) and other sites from ∼37.5 to 34 Ma, reminiscent of similar low δ13C values in this region during the Plio-Pleistocene (Hodell & Venz-Curtis, 2006). The low δ13C interval coincides with elevated opaline silica deposition at Site 1090 (Diekmann et al. 2004), and with the development of small, but significant, meridional δ18O gradients within the deep Atlantic basin. We interpret these observations as indicative of enhanced primary production at the northern edge of the polar front accompanied by increased thermal differentiation of northern- and southern-sourced deepwaters. These records are consistent with model predictions for the effects of proto-ACC development in the late Eocene (Heinze and Crowley, 1997; Toggweiler and Bjornsson, 2000).
Year of Publication: 2011
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctic Circumpolar Current; Atlantic Ocean; C-13/C-12; Carbon; Cenozoic; Eocene; Isotope ratios; Isotopes; Leg 177; Middle Eocene; Middle Oligocene; O-18/O-16; ODP Site 1090; Ocean Drilling Program; Oligocene; Oxygen; Paleo-oceanography; Paleocirculation; Paleocurrents; Paleogene; Paleogeography; South Atlantic; Stable isotopes; Tertiary; Upper Eocene
Coordinates: S425449 S425449 E0085359 E0085359
Record ID: 2018030581
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