Early Oligocene glaciation and productivity in the eastern Equatorial Pacific; insights into global carbon cycling

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doi: 10.1029/2010PA002021
Author(s): Coxall, Helen K.; Wilson, Paul A.
Author Affiliation(s): Primary:
Cardiff University, School of Earth and Ocean Sciences, Cardiff, United Kingdom
University of Southampton, United Kingdom
Volume Title: Paleoceanography
Source: Paleoceanography, 26(2). Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. 139 refs.; illus., incl. 2 tables, sketch map
Summary: The onset of sustained Antarctic glaciation across the Eocene-Oligocene transition (EOT) marks a pivotal change in Earth's climate, but our understanding of this event, particularly the role of the carbon cycle, is limited. To help address this gap we present the following paleoceanographic proxy records from Ocean Drilling Program Site 1218 in the eastern equatorial Pacific (EEP): (1) stable isotope (δ18O and δ13C) records generated in epifaunal benthic foraminifera (Cibicidoides spp.) to improve (double the resolution) the previously published records; (2) δ18O and δ13C records measured on Oridorsalis umbonatus, a shallow infaunal species; and (3) a record of benthic foraminifera accumulation rate (BFAR). Our new isotope data sets confirm the existence at Site 1218 of a two-step δ18O increase. They also lend support to the hypothesized existence of a late Eocene transient δ18O increase and early Oligocene Oi-1a and Oi-1b glacial maxima. Our record of BFAR indicates a transient (∼500 kyr) twofold to threefold peak relative to baseline Oligocene values associated with the onset of Antarctic glaciation that we attribute to enhanced biological export production in the EEP. This takes the same general form as the history of opal accumulation in the Southern Ocean, suggesting strong high-to-low-latitude oceanic coupling. These findings appear to lend support to the idea that the EOT δ13C excursion is traceable to increased organic carbon (Corg) burial. Paradoxically, early Oligocene sediments in the EEP are extremely Corg-poor, and proxy records of atmospheric pCO2 indicate a transient increase associated with the EOT.
Year of Publication: 2011
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; C-13/C-12; Calcium carbonate; Carbon; Carbon dioxide; Cenozoic; Chemostratigraphy; Cores; Crosscorrelation; East Pacific; Eocene; Equatorial Pacific; Foraminifera; Glaciation; Invertebrata; Isotope ratios; Isotopes; Leg 199; Lower Oligocene; Marine sediments; Microfossils; North Pacific; Northeast Pacific; O-18/O-16; ODP Site 1218; Ocean Drilling Program; Oligocene; Oxygen; Pacific Ocean; Paleo-oceanography; Paleogene; Productivity; Protista; Sediments; Stable isotopes; Statistical analysis; Tertiary; Upper Eocene
Coordinates: N085300 N085300 W1352200 W1352200
Record ID: 2013035833
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