Constraints on glaciation in the middle Eocene (46–37 Ma) from Ocean Drilling Program (ODP) Site 1209 in the tropical Pacific Ocean

Dawber, Caroline F. and Tripati, Aradhna K. (2011) Constraints on glaciation in the middle Eocene (46–37 Ma) from Ocean Drilling Program (ODP) Site 1209 in the tropical Pacific Ocean. Paleoceanography, 26. 17 PP.. DOI 10.1029/2010PA002037

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Abstract

The presence of glacial ice in the late middle Eocene has been vigorously debated. Recently published sedimentary data from the high latitudes is suggestive of episodic cooling events and near-freezing sea surface temperatures during parts of the late middle Eocene. Constraints on ice volumes and the significance of excursions in open ocean foraminifera and seawater δ 18O reconstructions are less clear, and there are few high-resolution δ 18O records. We present a new detailed record of benthic foraminiferal δ 18O from Site 1209 that exhibits variations (Δ δ 18O benthic) of 0.6‰–1.3‰. Different approaches have previously been used to interpret Δ δ 18O benthic, including (1) an a priori assumption of a 50% contribution of temperature, similar to what is reconstructed for the Last Glacial Maximum–recent change; (2) applying Oligocene calibrations between apparent sea level (ASL) and Δ δ 18O benthic; or (3) assuming temperature and seawater δ 18O contributions can be partitioned through comparison with benthic Mg/Ca. Using assumption 1, the record from Site 1209 indicates changes in seawater δ 18O of 0.3‰–0.7‰, equivalent to ∼33–72 m (m) of ASL (assuming mean ice δ 18O of ∼−45‰). Using assumption 2 and two different end-member calibrations, the δ 18O benthic record implies changes in ASL of 23–50 m or 50–108 m. The third approach yields changes in seawater δ 18O of up to 0.6‰ to 1.4‰. We explore the compatibility of the results of each of these approaches with other studies that discuss evidence for ephemeral glaciations during the middle Eocene with variable ice storage at one or both poles.

Item Type: Article
Uncontrolled Keywords: 2010AREP; IA61;
Subjects: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Divisions: 01 - Climate Change and Earth-Ocean Atmosphere Systems
Journal or Publication Title: Paleoceanography
Volume: 26
Page Range: 17 PP.
Identification Number: 10.1029/2010PA002037
Depositing User: Sarah Humbert
Date Deposited: 01 Sep 2011 08:09
Last Modified: 23 Jul 2013 10:02
URI: http://eprints.esc.cam.ac.uk/id/eprint/2173

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