georefid:2013-035821SEDIS Publication Catalogue

ana.macario@awi.de

http://sedis.iodp.org/pub-catalogue/informationpointOfContact2013-07-08T00:00:00Zhttp://sedis.iodp.org/pub-catalogue/index.php?id=10.1029/2010PA0020372011-01-01publicationgeorefid:2013-035821doi:10.1029/2010PA002037Dawber, Caroline F.University of Cambridge, Department of Earth Sciences, Cambridge, United KingdomauthorTripati, Aradhna K.authorAmerican Geophysical Union, Washington, DC, United StatespublisherdocumentHardcopyPaleoceanography26 (2)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 delta (super 18) O reconstructions are less clear, and there are few high-resolution delta (super 18) O records. We present a new detailed record of benthic foraminiferal delta (super 18) O from Site 1209 that exhibits variations (Delta delta (super 18) O (sub benthic) ) of 0.6ppm-1.3ppm. Different approaches have previously been used to interpret Delta delta (super 18) O (sub 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 Delta delta (super 18) O (sub benthic) ; or (3) assuming temperature and seawater delta (super 18) O contributions can be partitioned through comparison with benthic Mg/Ca. Using assumption 1, the record from Site 1209 indicates changes in seawater delta (super 18) O of 0.3ppm-0.7ppm, equivalent to approximately 33-72 m (m) of ASL (assuming mean ice delta (super 18) O of approximately -45ppm). Using assumption 2 and two different end-member calibrations, the delta (super 18) O (sub benthic) record implies changes in ASL of 23-50 m or 50-108 m. The third approach yields changes in seawater delta (super 18) O of up to 0.6ppm to 1.4 ppm. 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.completedStratigraphyalkaline earth metalscalciumCenozoicchemostratigraphycoresEoceneForaminiferaglaciationInvertebrataisotope ratiosisotopesLeg 198magnesiummarine sedimentsmetalsMg/Camicrofossilsmiddle EoceneNorth PacificNorthwest PacificO-18/O-16Ocean Drilling ProgramODP Site 1209oxygenPacific Oceanpaleo-oceanographypaleoclimatologyPaleogenepaleotemperatureProtistareconstructionsedimentsShatsky Risestable isotopesTertiaryWest Pacificurn:org.iodp:exp:198urnlargerWorkCitationcampaignurn:org.iodp:exp:198:site:1209urnlargerWorkCitationstudyurn:org.iodp:exp:198urnlargerWorkCitationcampaignEnglishgeoscientificInformation158.3000158.310032.390032.4000