Global warmth, ice volume and ocean acidity change across the late Eocene - early Oligocene transition

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Author(s): Sghibartz, C.; Wilson, Paul A.; Foster, Gavin L.; Palike, H.; Edgar, K. M.
Author Affiliation(s): Primary:
University of Southampton, Ocean and Earth Science, Southampton, United Kingdom
Universität Bremen, Germany
Cardiff University, United Kingdom
Volume Title: AGU 2012 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2012; American Geophysical Union 2012 fall meeting, San Francisco, CA, Dec. 3-7, 2012. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The Eocene Oligocene Transition (EOT, 34 - 33.5 Ma) represents a fundamental shift in the evolution of Cenozoic climate from the "greenhouse" of the early Paleogene to the "icehouse" of the present day. The onset of major Antarctic Cenozoic glaciation across the EOT took place rapidly, likely as a threshold response to a slow decline in atmospheric CO2, with superimposed orbital forcing. Although it is well known that this event was associated with a pronounced perturbation in the global carbon cycle, the stability of Earth's climate in the late Eocene and carbon cycling across the EOT remain poorly understood. In this study, new records of δ13C and δ18O in benthic foraminiferal calcite (mono-specific samples of C. grimsdalei and C. havanensis), biogenic opal and organic carbon accumulation rates are reported from deep-sea sediments from the eastern equatorial Pacific (EEP), recovered during Integrated Ocean Drilling Program (IODP) Expedition (Exp) 320 "Pacific Equatorial Age Transect" (PEAT). IODP Exp 320 improves upon published records as carbonate is present throughout the EOT interval, and the sedimentary section extends further back into the Eocene than previously drilled material. The records presented here are broadly consistent with the previously documented two-step onset of Antarctic glaciation across the EOT and simultaneous ocean deacidification, as shown by the deepening of the calcite compensation depth (CCD). However, Site U1333 benthic δ18O Eocene data show a greater amplitude of variability than the concurrent ODP Site 1218 record. Furthermore, while δ13C and δ18O vary coherently across the EOT at Site U1333, they exhibit markedly different behavior prior to the transition. An opal mass accumulation rate record from Site U1333 and a benthic assemblage study from Site 552 in the South Atlantic are also presented to assess changes in local and global palaeoproductivity.
Year of Publication: 2012
Research Program: IODP Integrated Ocean Drilling Program
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; East Pacific; Eocene; Equatorial Pacific; Expedition 320; Expeditions 320/321; IODP Site U1333; Integrated Ocean Drilling Program; Leg 199; Lower Oligocene; North Pacific; Northeast Pacific; ODP Site 1218; Ocean Drilling Program; Oligocene; PH; Pacific Ocean; Paleo-oceanography; Paleoclimatology; Paleogene; Tertiary; Upper Eocene
Coordinates: N103100 N103100 W1382510 W1382510
N085300 N085300 W1352200 W1352200
Record ID: 2014044744
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