Biostratigraphy of the Equatorial North Pacific DOMES Sites A, B, and C
Radiolarians from box cores and gravity cores indicate that Quaternary sediment covers the sea floor at DOMES Sites A, B, and C; however, at Sites A and B dissolution-resistant, reworked Tertiary species (predominantly middle and late Eocene and early Miocene) generally outnumber the fragile Quaternary forms. In contrast, at Site C an early Miocene calcareous nannofossil flora underlies the Quaternary layer in three cores, and specimens of different ages are not mixed; barren sediment generally underlies the Quaternary in the remainder of cores from Site C. The abundant admixture of Tertiary radiolarians in Quaternary sediment at Sites A and B is most likely caused by an increase ill bottom current activity during the Pleistocene, resulting in several cycles of erosion and redeposition of Tertiary sediment. This physical process of erosion, aided by selective dissolution of fragile radiolarians, explains the dominance of dissolution-resistant forms in the mixtures.
KeywordsHydrogen Peroxide Manganese Sedimentation Geochemistry Drilling
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