Eocene cooling linked to early flow across the Tasmanian Gateway

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doi: 10.1073/pnas.1220872110
Author(s): Bijl, Peter K.; Bendle, James A. P.; Bohaty, Steven M.; Pross, Jörg; Schouten, Stefan; Tauxe, Lisa; Stickley, Catherine E.; McKay, Robert M.; Röhl, Ursula; Olney, Matthew; Sluijs, Appy; Escutia, Carlota; Brinkhuis, Henk
Integrated Ocean Drilling Program, Expedition 318 Scientists
Author Affiliation(s): Primary:
Utrecht University, Department of Earth Sciences, Utrecht, Netherlands
University of Glasgow, United Kingdom
University of Southampton, United Kingdom
University of Frankfurt, Germany
Royal Netherlands Institute for Sea Research, Netherlands
Scripps Institution of Oceanography, United States
University of Troms, Norway
Victoria University of Wellington, New Zealand
University of Bremen, Germany
University of South Florida, United States
CSIC-Universite de Granada, Spain
Volume Title: Proceedings of the National Academy of Sciences of the United States of America
Source: Proceedings of the National Academy of Sciences of the United States of America, 110(24), p.9645-9650. Publisher: National Academy of Sciences, Washington, DC, United States. ISSN: 0027-8424 CODEN: PNASA6
Note: In English. 45 refs.; illus., incl. sketch map
Summary: The warmest global temperatures of the past 85 million years occurred during a prolonged greenhouse episode known as the Early Eocene Climatic Optimum (52-50 Ma). The Early Eocene Climatic Optimum terminated with a long-term cooling trend that culminated in continental-scale glaciation of Antarctica from 34 Ma onward. Whereas early studies attributed the Eocene transition from greenhouse to icehouse climates to the tectonic opening of Southern Ocean gateways, more recent investigations invoked a dominant role of declining atmospheric greenhouse gas concentrations (e.g., CO2). However, the scarcity of field data has prevented empirical evaluation of these hypotheses. We present marine microfossil and organic geochemical records spanning the early-to-middle Eocene transition from the Wilkes Land Margin, East Antarctica. Dinoflagellate biogeography and sea surface temperature paleothermometry reveal that the earliest throughflow of a westbound Antarctic Counter Current began ?49-50 Ma through a southern opening of the Tasmanian Gateway. This early opening occurs in conjunction with the simultaneous onset of regional surface water and continental cooling (2-4°C), evidenced by biomarker- and pollen-based paleothermometry. We interpret that the westbound flowing current flow across the Tasmanian Gateway resulted in cooling of Antarctic surface waters and coasts, which was conveyed to global intermediate waters through invigorated deep convection in southern high latitudes. Although atmospheric CO2 forcing alone would provide a more uniform middle Eocene cooling, the opening of the Tasmanian Gateway better explains Southern Ocean surface water and global deep ocean cooling in the apparent absence of (sub-) equatorial cooling.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Antarctica; Apectodinium; Australasia; Australia; Bathymetry; Benthic taxa; Cenozoic; Cooling; Dinoflagellata; Early Eocene Climatic Optimum; East Tasman Plateau; Endemic taxa; Eocene; Expedition 318; Foraminifera; Great Australian Bight; Greenhouse effect; IODP Site U1356; Indian Ocean; Integrated Ocean Drilling Program; Invertebrata; Leg 182; Leg 189; Lower Eocene; Microfossils; Middle Eocene; Morphology; ODP Site 1128; ODP Site 1171; ODP Site 1172; Ocean Drilling Program; Otway Basin; Pacific Ocean; Paleo-oceanography; Paleocirculation; Paleoclimatology; Paleogene; Paleogeography; Palynomorphs; Protista; South Pacific; South Tasman Rise; Southern Ocean; Southwest Pacific; Subtropical environment; TEX86; Tasman Sea; Tasmanian Gateway; Tertiary; West Pacific; Wilkes Land
Coordinates: S435800 S435700 E1495600 E1495500
S483000 S482900 E1490700 E1490600
S342328 S342328 E1273527 E1273527
S631837 S631837 E1355956 E1355956
Record ID: 2015070727
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