Central Pacific ODP865 d18O measurements covering the Early Paleogene Kozdon, R.; Kelly, D.C.; Kita, N.T.; Fournelle, J.H.; Valley, J.W. Kozdon, R. Kelly, D.C. Kita, N.T. Fournelle, J.H. Valley, J.W. earth science/paleoclimate/paleoceanography (depth,null,null,meter,null,paleoceanography,null,null,N,meters below sea floor) earth science/paleoclimate/paleoceanography (delta 18O,planktic foraminifer,null,per mil PDB,null,paleoceanography,averaged,secondary ion mass spectrometry,N,Morozovella allisonensis and diagenetic carbonate; in situ measurements) earth science/paleoclimate/paleoceanography (notes,null,null,null,null,paleoceanography,null,null,C,null) earth science/paleoclimate/paleoceanography (delta 18O,planktic foraminifer,null,per mil PDB,null,paleoceanography,averaged,secondary ion mass spectrometry,N,Morozovella subbotinae and diagenetic carbonate; in situ measurements) earth science/paleoclimate/paleoceanography (delta 18O,planktic foraminifer,null,per mil PDB,null,paleoceanography,null,secondary ion mass spectrometry,N,Morozovella subbotinae and diagenetic carbonate; in situ measurements) earth science/paleoclimate/paleoceanography (delta 18O,planktic foraminifer,null,per mil PDB,null,paleoceanography,null,secondary ion mass spectrometry,N,Morozovella allisonensis and diagenetic carbonate; in situ measurements) earth science/paleoclimate/paleoceanography (age,null,null,million years ago,null,paleoceanography,null,null,N,null) earth science/paleoclimate/paleoceanography (delta 18O,planktic foraminifer,null,per mil PDB,null,paleoceanography,null,secondary ion mass spectrometry,N,Morozovella aragonensis and diagenetic carbonate; in situ measurements) earth science/paleoclimate/paleoceanography (delta 18O,planktic foraminifer,null,per mil PDB,null,paleoceanography,null,secondary ion mass spectrometry,N,Morozovella velascoensis and diagenetic carbonate; in situ measurements) earth science/paleoclimate/paleoceanography (delta 18O,planktic foraminifer,null,per mil PDB,null,paleoceanography,averaged,secondary ion mass spectrometry,N,Morozovella velascoensis and diagenetic carbonate; in situ measurements) earth science/paleoclimate/paleoceanography (delta 18O,planktic foraminifer,null,per mil PDB,null,paleoceanography,averaged,secondary ion mass spectrometry,N,Morozovella aragonensis and diagenetic carbonate; in situ measurements) earth science/paleoclimate/paleocean (ODP 865>LATITUDE 18.440167>LONGITUDE -179.555667) Cool tropical sea surface temperatures (SSTs) are reported for warm Paleogene greenhouse climates based on the d18O of planktonic foraminiferal tests. These results are difficult to reconcile with models of greenhouse gas–forced climate. It has been suggested that this “cool tropics paradox” arises from postdepositional alteration of foraminiferal calcite, yielding erroneously high d18O values. Recrystallization of foraminiferal tests is cryptic and difficult to quantify, and the compilation of robust d18O records from moderately altered material remains challenging. Scanning electron microscopy of planktonic foraminiferal chamber-wall cross sections reveals that the basal area of muricae, pustular outgrowths on the chamber walls of species belonging to the genus Morozovella, contain no mural pores and may be less susceptible to postdepositional alteration. We analyzed the d18O in muricae bases of morozovellids from the central Pacific (Ocean Drilling Program Site 865) by ion microprobe using 10 µm pits with an analytical reproducibility of ±0.34‰ (2 standard deviations). In situ measurements of d18O in these domains yield consistently lower values than those published for conventional multispecimen analyses. Assuming that the original d18O is largely preserved in the basal areas of muricae, this new d18O record indicates Early Paleogene (~49–56 Ma) tropical SSTs in the central Pacific were 4°–8°C higher than inferred from the previously published d18O record and that SSTs reached at least ~33°C during the Paleocene-Eocene thermal maximum. This study demonstrates the utility of ion microprobe analysis for generating more reliable paleoclimate records from moderately altered foraminiferal tests preserved in deep-sea sediments. STUDY NOTES: In situ oxygen isotope data were acquired between 2009 and 2011 in the WiscSIMS Laboratory at UW-Madison by a CAMECA ims-1280 large radius ion microprobe. A 133Cs+ primary ion beam with an intensity of ~1.8 nA was focused to a diameter of ~10 µm. The typical secondary 16O- ion intensity was 3.0 x 10^9 cps, and 18O- and 16O- ions were simultaneously collected by two Faraday Cup detectors. Charging of the sample surface was compensated by Au-coating and an electron flood gun. Grains of UWC-3 calcite standard (d18O = 12.49 per mill V-SMOW, Kozdon et al. 2009) were cast in the center of each epoxy mount. Four to five consecutive measurements of UWC-3 calcite standard were performed before and after every set of 9-15 sample analyses. The average precision (reproducibility) for a set of bracketing standard analyses is ±0.34 per mil (2 SD). Detailed analytical protocols are described by Kita et al. 2009. A total of 283 measurements were performed, including 95 bracketing standard analyses. NCDC-Paleoclimatology https://www.ncdc.noaa.gov/data-access/paleoclimatology-data - Bauer Bruce Investigator : Kozdon, R. Investigator : Kelly, D.C. Investigator : Kita, N.T. Investigator : Fournelle, J.H. Investigator : Valley, J.W. 2014-11-04 ONLINE Files online, ASCII https://www.ncdc.noaa.gov/paleo/study/17396 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/kozdon2011/kozdon2011-865.txt https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/kozdon2011/kozdon2011-865.txt English https://www.ncdc.noaa.gov/paleo/study/17396 https://www1.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/kozdon2011/kozdon2011-865.txt Kozdon, R., D.C. Kelly, N.T. Kita, J.H. Fournelle, and J.W. Valley2011Planktonic foraminiferal oxygen isotope analysis by ion microprobe technique suggests warm tropical sea surface temperatures during the Early PaleogenePaleoceanography26PA320610.1029/2010PA002056 START YEAR: 55200000 cal yr BP * END YEAR: 48800000 cal yr BP -179.555667 18.440167 -179.555667 18.440167