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 in 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.

The sediment was first washed over a 62-micrometer sieve, the residues boiled in hydrogen peroxide, sieved again, and dried. Strewn microslides were prepared from a portion of the residues.

Supplement to: Quinterno, Paula J; Theyer, Fritz (1979): Biostratigraphy of the Equatorial North Pacific DOMES Sites A, B, and C. In: Bischoff, J L, Piper, D Z (Eds) Marine Geology and Oceanography of the Pacific Manganese Nodule Province, Marine Science. Plenum Publishing Corporation, New York, U.S.A., 349-364