A record of coccolith Sr/Ca over the Eocene/Oligocene transition from the Equatorial Pacific

Author(s): Prentice, K. C.; Dunkley Jones, T.; Stoll, H. M.; Bolton, C. T.; Lees, J. A.; Bown, P. R.; Young, Jeremy R.; Langer, G.; Fearn, S.
Author Affiliation(s): Primary:
Imperial College London, London, United Kingdom
Other:
University of Birmingham, United Kingdom
University of Oviedo, Spain
University of Cambridge, United Kingdom
Volume Title: AGU 2014 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2014; American Geophysical Union 2014 fall meeting, San Francisco, CA, Dec. 15-19, 2014. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: Using the Sr/Ca proxy, we have produced direct records of coccolithophore growth rates from the equatorial Pacific (IODP site U1334) across the Eocene/Oligocene transition (E/OT), ∼34 to 33.5 Ma, from both individual coccoliths and bulk coccolith calcite. The E/OT is the most extreme period of climate change in the Cenozoic. The world changes from a "Greenhouse" to an "Ice House" within ∼400 ky. The environmental changes are accompanied by extinctions amongst tropical taxa and a shift from coccolithophore to mixed coccolithophore - diatom primary productivity. The data reveals a significant shift in coccolithophore Sr/Ca (growth rate) over the E/OT, linked with changes in both (partial differential) 13C and (partial differential) 18O. This shift may be associated with changes in nutrient cycling and/or ocean thermal structure due to changes in ocean circulation. Due to their small size, coccoliths are often perceived to preserve poorly compared with the much larger foraminifera. Coupled with this, until recently, it has been difficult to obtain species-specific geochemical data for individual specimens. Historically this has proved a limiting factor in the use and interpretation of coccolithophore geochemical proxies. We demonstrate the preservation of primary coccolithophore calcite from the U1334 sediments. This supports the further use and interpretation of both coccolith trace element and stable isotope data as proxies for past environmental change. Using SIMS and TOF-SIMS (Time of Flight-Secondary Ion Mass Spectrometry) it is possible to demonstrate that the Sr/Ca values from fossil coccoliths are comparable to those collected from their modern counterparts. It has also been possible to examine the distributions of different ions within individual coccoliths, demonstrating the presence of primary biogenic calcite, and identifying that the effects of diagenesis can often be overcome. The proportion of abiogenic to biogenic calcite further suggests that reliable results of coccolith geometry can be obtained from bulk samples. ICP-AES (inductively coupled plasma-atomic emission spectrometry) has been used to examine elemental ratios and DI-IRMS (dual-inlet isotope ratio mass spectrometer) used to examine oxygen and carbon isotopes.
Year of Publication: 2014
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Cenozoic; Cores; East Pacific; Eocene; Equatorial Pacific; Expedition 320; Expeditions 320/321; IODP Site U1334; Integrated Ocean Drilling Program; Marine sediments; North Pacific; Northeast Pacific; Oligocene; Pacific Ocean; Paleogene; Sediments; Tertiary
Coordinates: N080000 N080000 W1315824 W1315824
Record ID: 2015092862
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