# Eastern Equatorial Pacific Isotopic Ratios of Sr, Nd, and Pb and Nd Concentration Data over last 25,000 Years #----------------------------------------------------------------------- # World Data Center for Paleoclimatology, Boulder # and # NOAA Paleoclimatology Program #----------------------------------------------------------------------- # NOTE: Please cite original publication, online resource and date accessed when using this data. # If there is no publication information, please cite Investigator, title, online resource and date accessed. # # Online_Resource: http://www.ncdc.noaa.gov/paleo/study/17371 # Online_Resource: ftp://ftp.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/xie2012-epsl/xie2012-epsl-odp849.txt # # Archive: Paleoceanography # #-------------------------------- # Contribution_Date # Date: 2014-10-27 #-------------------------------- # Title: Eastern Equatorial Pacific Isotopic Ratios of Sr, Nd, and Pb and Nd Concentration Data over last 25,000 Years #-------------------------------- # Investigators: Xie, Ruifang C.; Marcantonio, Franco #-------------------- # Description and Notes: # The provenance of eolian dust supplied to deep-sea sediments has the potential to offer insights into changes in past atmospheric circulation. Specifically, measuring temporal changes in dust provenance can shed light on changes in the mean position of the Intertropical Convergence Zone (ITCZ), a region acting as a barrier separating wind-blown material derived from northern versus southern hemisphere sources. Here we have analyzed Nd, Sr, and Pb isotope ratios in the operationally-defined detrital component extracted from deep-sea sediments in the eastern equatorial Pacific (EEP) along a meridional transect at 110°W from 3°S to 7°N (ODP Leg 138, sites 848 – 853). Sr isotope results show that barite Sr has a significant influence on 87Sr/86Sr isotope ratios of samples in the upwelling zone of the EEP. However, sites located >3° or more away from the equator (sites 852 and 853) are believed to not be affected by barite Sr and provide useful detrital Sr signals. 208Pb/206Pb and 207Pb/206Pb ratios in all cores fall into the Pb-isotope space of five potential dust sources (Asia, North and Central/South America, Sahara, and Australia), with no distinct isotopic fingerprinting of the dominant source(s). εNd values were most valuable for discerning detrital source provenance, and their values at all sites, ranging from -5.46 to -3.25, were more unradiogenic for sediments deposited during the last glacial than for those deposited during the Holocene. There are distinct latitudinal trends in the εNd values, with more radiogenic values further south and less radiogenic values further north, excluding site 848. This distinction hold s true for both Holocene and last glacial periods. For the most southerly site, 848, we invoke, for the first time, a distinct southern hemisphere Australian source as being responsible for the unradiogenic Nd isotope ratios. Both average last glacial and Holocene εNd values show similar sharp gradients along the transect between 5.29°N and 2.77°N, suggesting little movement of the glacial ITCZ in the EEP. However, during the deglacial, this gradient is stronger and shifted further north between 5.29°N to 7.21°N, suggesting a more northerly, possibly stronger, deglacial ITCZ. # There are 6 cores in total in our study. # Provided keywords: Radiogenic isotopes, Intertropical Convergence Zone, dust provenance #-------------------- # Publication # Authors: Xie, R.C. and F. Marcantonio # Journal_Name: Earth Planetary Science Letters # Published_Title: Deglacial dust provenance changes in the Eastern Equatorial Pacific and implications for ITCZ movement during Last Glaciation # Published_Date_or_Year: 2012 # Volume: 317 # Pages: 386-395 # DOI: 10.1016/j.epsl.2011.11.014 # Abstract: The provenance of eolian dust supplied to deep-sea sediments has the potential to offer insights into changes in past atmospheric circulation. Specifically, measuring temporal changes in dust provenance can shed light on changes in the mean position of the Intertropical Convergence Zone (ITCZ), a region acting as a barrier separating wind-blown material derived from northern versus southern hemisphere sources. Here we have analyzed Nd, Sr, and Pb isotope ratios in the operationally-defined detrital component extracted from deep-sea sediments in the eastern equatorial Pacific (EEP) along a meridional transect at 110°W from 3°S to 7°N (ODP Leg 138, sites 848 – 853). Sr isotope results show that barite Sr has a significant influence on 87Sr/86Sr isotope ratios of samples in the upwelling zone of the EEP. However, sites located >3° or more away from the equator (sites 852 and 853) are believed to not be affected by barite Sr and provide useful detrital Sr signals. 208Pb/206Pb and 207Pb/206Pb ratios in all cores fall into the Pb-isotope space of five potential dust sources (Asia, North and Central/South America, Sahara, and Australia), with no distinct isotopic fingerprinting of the dominant source(s). εNd values were most valuable for discerning detrital source provenance, and their values at all sites, ranging from -5.46 to -3.25, were more unradiogenic for sediments deposited during the last glacial than for those deposited during the Holocene. There are distinct latitudinal trends in the εNd values, with more radiogenic values further south and less radiogenic values further north, excluding site 848. This distinction holds true for both Holocene and last glacial periods. For the most southerly site, 848, we invoke, for the first time, a distinct southern hemisphere Australian source as being responsible for the unradiogenic Nd isotope ratios. Both average last glacial and Holocene εNd values show similar sharp gradients along the transect between 5.29°N and 2.77°N, suggesting little movement of the glacial ITCZ in the EEP. However, during the deglacial, this gradient is stronger and shifted further north between 5.29°N to 7.21°N, suggesting a more northerly, possibly stronger, deglacial ITCZ. #-------------------------------- # Funding_Agency: # Funding_Agency_Name: # Grant: #-------------------------------- # Site Information: # Site_Name: ODP849 # Location: Eastern Pacific Ocean # Northernmost_Latitude: 0.18333 # Southernmost_Latitude: 0.18333 # Easternmost_Longitude: -110.51833 # Westernmost_Longitude: -110.51833 # Elevation: -3839 #-------------------------------- # Data Collection # Collection_Name: ODP849 Isotopes X12 # Oldest_Year: 23400 # Most_Recent_Year: 900 # Time_Unit: cal yr BP # Core_Length # Notes: #-------------------------------- # Chronology #-------------------------------- # Variables # # Data variables follow (have double marker- "##") # Data line variables format: Variables list, one per line, shortname-tab-nine components: what, material, error, units, seasonality, archive, detail, method, C or N for Character or Numeric data) ## age_calkaBP Age,,,calendar kiloyears before present,,,,,N ## 87Sr/86Sr-DT Strontium 87/Strontium 86 ratio,,, ,,paleoceanography,with DTPA,Thermal Ionization Mass Spectrometry (TIMS),N ## 87Sr/86Sr-DT_err Strontium 87/Strontium 86 ratio,,standard error, ,,paleoceanography,with DTPA,Thermal Ionization Mass Spectrometry (TIMS),N ## 87Sr/86Sr-noDT Strontium 87/Strontium 86 ratio,,, ,,paleoceanography,without DTPA,Thermal Ionization Mass Spectrometry (TIMS),N ## 87Sr/86Sr-noDT_err Strontium 87/Strontium 86 ratio,,standard error, ,,paleoceanography,without DTPA,Thermal Ionization Mass Spectrometry (TIMS),N ## e-Nd epsilon-Neodymium,,, ,,paleoceanography,,Thermal Ionization Mass Spectrometry (TIMS),N ## 206Pb/204Pb Lead 206/Lead 204 ratio,,, ,,paleoceanography,,Thermal Ionization Mass Spectrometry (TIMS),N ## 207Pb/204Pb Lead 207/Lead 204 ratio,,, ,,paleoceanography,,Thermal Ionization Mass Spectrometry (TIMS),N ## 208Pb/204Pb Lead 208/Lead 204 ratio,,, ,,paleoceanography,,Thermal Ionization Mass Spectrometry (TIMS),N ## 207Pb/206Pb Lead 207/Lead 206 ratio,,, ,,paleoceanography,,Thermal Ionization Mass Spectrometry (TIMS),N ## 208Pb/206Pb Lead 208/Lead 206 ratio,,, ,,paleoceanography,,Thermal Ionization Mass Spectrometry (TIMS),N ## Nd Neodymium,,,mg/kg,,paleoceanography,bulk,Inductively coupled plasma - mass spectrometry,N ## Nd%-crst Neodymium,in crust,,percent,,paleoceanography,,,N ## Residual% Residual,,,percent,,paleoceanography,,,N ## notes notes,,, ,, ,,,C # Data: # Missing Value: NaN age_calkaBP 87Sr/86Sr-DT 87Sr/86Sr-DT_err 87Sr/86Sr-noDT 87Sr/86Sr-noDT_err e-Nd 206Pb/204Pb 207Pb/204Pb 208Pb/204Pb 207Pb/206Pb 208Pb/206Pb Nd Nd%-crst Residual% notes 0.9 NaN NaN NaN NaN -3.31 18.7856 15.6393 38.5981 0.8325 2.0547 NaN NaN NaN EEP849-1 Samples analyzed during the second time period during the course of study. 3 NaN NaN NaN NaN -3.36 18.7550 15.6491 38.7054 0.8347 2.0649 0.3429 1.32 1.61 EEP849-2 Samples analyzed during the second time period during the course of study. 7 0.708997 3.70E-06 0.709042 1.58E-05 -3.25 18.8159 15.7385 38.9814 0.8364 2.0717 0.7234 2.78 1.69 EEP849-3 10 0.709015 4.44E-06 0.709089 1.58E-05 -3.41 18.7296 15.6381 38.6464 0.8349 2.0634 NaN NaN NaN EEP849-4 13.4 0.709023 4.19E-06 0.709042 1.58E-05 -3.75 18.7045 15.6667 38.7367 0.8376 2.0710 NaN NaN NaN EEP849-5 17 0.708969 1.13E-05 0.709045 1.58E-05 -4.15 18.8125 15.7375 38.9446 0.8365 2.0701 0.7879 3.03 1.99 EEP849-6 20.3 0.709024 6.99E-06 0.709056 1.58E-05 -4.02 18.9876 15.8903 39.2491 0.8391 2.0732 0.8452 3.25 1.74 EEP849-7 23.4 0.709038 3.74E-06 0.709060 1.58E-05 -3.99 18.6920 15.6323 38.6643 0.8363 2.0685 1.0092 3.88 2.93 EEP849-8