High-resolution record of export production in the eastern Equatorial Pacific across the Eocene-Oligocene transition and relationships to larger climatic records

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Author(s): Erhardt, A. M.; Pälike, H.; Paytan, A.
Author Affiliation(s): Primary:
Stanford University, Department of Geology & Environmental Science, Stanford, CA, United States
University of Southampton, School of Ocean and Earth Science, Southampton, United Kingdom
University of California Santa Cruz, Institute of Marine Sciences, Santa Cruz, CA, United States
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: Understanding changes in export production through time provides insight into the response of the biological pump, particularly during periods of rapid climate change. In this study, we report changes in export production in the Eastern Equatorial Pacific (EEP) from Site U1333 across The Eocene-Oligocene transition (EOT) reconstructed from a high-resolution record of marine barite accumulation rates (BAR). The EOT marked a global shift from a greenhouse to an icehouse climate, possibly triggered by a rapid decline in pCO2, leading to the onset of Antarctic glaciation. This transition is characterized by changes in the carbon cycle as evident by deepening of the carbonate compensation depth. The causes for the pCO2 decline are still unclear, with enhanced silicate weathering, changes in circulation patterns, and increased export production proposed as possible mechanisms. BAR fluctuations suggest synchronous declines in export production associated with the two-step increases in oxygen isotopes that define the transition. BAR decline over 50% during the first step of the EOT, and 95% across the second step, translating to an overall decline in export production from ≈16 mgC m-2 day-1 to ≈13 mgC m-2 day-1 based on modern day BAR/export production relationships. These declines are in step with the changes recorded in the oxygen and carbon benthic isotopic records from nearby Site 1218, indicative of strong direct and indirect climatic controls on export production in the EEP. In addition, we show a previously undocumented peak in export productivity in the EEP before the onset of the EOT. This peak is consistent with proxies of export production from the Southern Ocean, namely reactive P and opal accumulation rates, potentially implying a global driver for this precursor event. We propose that this enhanced export production and the associated carbon sequestration may have contributed to the pCO2 drawdown at the onset of Antarctic glaciation.
Year of Publication: 2012
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; Climate change; East Pacific; Eocene; Equatorial Pacific; Expedition 320; Expeditions 320/321; IODP Site U1333; Integrated Ocean Drilling Program; Marine sediments; North Pacific; Northeast Pacific; Oligocene; Pacific Ocean; Paleoclimatology; Paleogene; Sediments; Tertiary
Coordinates: N103100 N103100 W1382510 W1382510
Record ID: 2014054460
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