Resolving eolian, volcanogenic, and authigenic components in pelagic sediment from the Pacific Ocean

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 similar to 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 similar to 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 alummosilicate component of pelagic sediment allows resolution, respectively, of the climatic, geologic, and chemical processes contributing to the paleoceanographic archive in this critical oceanic region. (c) 2006 Elsevier B.V. All rights reserved.