『Abstract
We measured major and trace element concentrations in the operationally
defined, chemically extracted, residual aluminosilicate component
of sediment from Ocean Drilling Program Sites 1215 and 1256 in
the central and eastern equatorial Pacific Ocean and found that
this residual component contains volcanogenic and authigenic aluminosilicates
in addition to inferred eolian material. While the residual component
younger than 20 Ma from the central Pacific (ODP Site 1215) is
similar compositionally to upper continental crust and suggests
an increase in the delivery of Asian dust material since 20 Ma,
the residual in sediment older than 20 Ma indicates significant
amounts of volcanogenic and authigenic materials. Volcanogenic
debris comprises as much as 〜40% of the residual between 23-40
Ma, which coincides with the mid-Tertiary “ignimbrite flare-up”
that occurred in much of western North America. The residual component
extracted from the 50 Ma biogenic sediment reflects authigenic
signatures (seawater-like negative cerium anomalies and elevated
Fe/Si ratios). The previously interpreted increase in an andesitic
detrital source in North Pacific locations may instead be authigenic
material, presenting significant challenges for many paleoclimate
proxies. Additionally, in the eastern Pacific (ODP Site 1256),
the residual component contains 〜70% of volcanogenic material,
most likely originating from Central America, and also includes
refractory barite. The ability to separately identify eolian,
volcanogenic, and authigenic materials in the aluminosilicate
component of pelagic sediment allows resolution, respectively,
of the climatic, geologic, and chemical processes contributing
to the paleoceanographic archive in this critical oceanic region.
Keywords: Eolian; Authigenic; Volcanogenic; Sequential extractions;
ODP Site 1215; ODP Site 1256; Pacific; Dust』
1. Introduction
2. Site description and sampling
2.1. ODP Site 1215: Central North Pacific (0-58 Ma)
2.2. ODP Site 1256: Eastern Equatorial Pacific (0-8 Ma)
3. Analytical procedures and multivariate statistics
3.1. Sequential extraction
3.2. Sediment digestion and chemical analyses
3.3. Grain-size analysis
3.4. Multivariate statistics
3.4.1. Q-mode factor analysis
3.4.2. Multiple linear regression
4. Chemical composition of the residual component
4.1. Central Pacific (ODP Site 1215)
4.2. Eastern Pacific (ODP Site 1256)
5. Discriminating eolian, volcanogenic debris, and authigenic
clay
5.1. Central Pacific (Site 1215): extracting from young (<20
Ma) and old (>20 Ma) red clay
5.2. Central Pacific (Site 1215): extracting from 50 Ma nannofossil
ooze
5.3. Eastern Pacific (Site 1256): extracting from young (0-8
Ma) biogenic sediment
6. Significance for central Pacific eolian records
6.1. Detrital contribution
6.2. Volcanogenic and authigenic contributions
7. Summary and conclusions
Acknowledgements
Appendix A. Supplementary data
References