Abstract
Mineral dust particles from different source regions typically have distinct Pb isotope ratios. Theoretically, Pb isotopic composition of terrigenous minerals isolated from open-ocean sediments should allow for dust provenance reconstructions. However, Pb isotopes of terrigenous fractions of sediments have frequently been inconsistent with expected source region signatures. This study investigates the reason(s) for offsets between the Pb isotope values of the dust component in sediment cores and those expected from source regions with focus on changes in sediment composition, sediment age, and sediment processing for analysis. Pb isotope ratios from Pacific Ocean core-top sediments show a general delineation of the Intertropical Convergence Zone (ITCZ). Isotope mixing models support these general trends, though similarity in Pb isotope ratios of disparate source regions makes constraining specific sources challenging. Pb isotope ratios in downcore samples varied on glacial/interglacial time scales, being less radiogenic during the last glacial maximum, suggesting either a weakened ITCZ or the addition of a new, less radiogenic, source to the system. Finally, Pb isotope ratios in some source region samples yielded different Pb isotope signatures in bulk source sample than in the insoluble terrigenous fraction of the source sample, indicating that differential mineral preservation within the terrigenous component in sediments may cause offsets from source signatures. Overall, while Pb isotopes show distinct basin-scale variations, high-resolution spatial reconstructions require tight age controls and consistency in analytical treatment if used to define ocean sediment source regions.
| Original language | English (US) |
|---|---|
| Article number | e2020PA004144 |
| Journal | Paleoceanography and Paleoclimatology |
| Volume | 36 |
| Issue number | 4 |
| DOIs | |
| State | Published - Apr 2021 |
Funding
Daniel R. Muhs and Jeffrey S. Pigati provided source region samples for North America and the Atacama Desert, respectively, along with enlightening comments on the manuscript. Christopher Moy collected samples from the New Zealand region. The Oregon State and Scripps Institute of Oceanography core repositories provided ocean sediment samples for this study. Rob Franks provided critical assistance with both the ICP-MS and MC-ICP-MS at the University of California at Santa Cruz. Cheryl Zubrick was a wonderful resource for instrument troubleshooting on the MC-ICP-MS. Funding for this work was in part provided by NSF CAREER Grant OCE-0449732 and NSF-OCE Grant 0850467 to Adina Paytan and a Schlanger Ocean Drilling Fellowship to Andrea M. Erhardt. We thank R. Xie, an anonymous reviewer, and editor U. Röhl for the constructive feedback. Daniel R. Muhs and Jeffrey S. Pigati provided source region samples for North America and the Atacama Desert, respectively, along with enlightening comments on the manuscript. Christopher Moy collected samples from the New Zealand region. The Oregon State and Scripps Institute of Oceanography core repositories provided ocean sediment samples for this study. Rob Franks provided critical assistance with both the ICP‐MS and MC‐ICP‐MS at the University of California at Santa Cruz. Cheryl Zubrick was a wonderful resource for instrument troubleshooting on the MC‐ICP‐MS. Funding for this work was in part provided by NSF CAREER Grant OCE‐0449732 and NSF‐OCE Grant 0850467 to Adina Paytan and a Schlanger Ocean Drilling Fellowship to Andrea M. Erhardt. We thank R. Xie, an anonymous reviewer, and editor U. Röhl for the constructive feedback.
Keywords
- Eastern Equatorial Pacific
- Intertropical Convergence Zone
- Pb isotopes
ASJC Scopus subject areas
- Oceanography
- Atmospheric Science
- Palaeontology