Four sedimentary units, with a total thickness of 377 m, overlie basaltic crust at Site 1179 (Kanazawa, Sager, Escutia, et al., 2001). Unit I, at the top of the section, consists of clay- and radiolarian-bearing diatom ooze. It extends from the seafloor to a depth of 223.5 meters below seafloor (mbsf), where it is late Miocene in age. Sediments from 0.01 to 35.0 mbsf were used in this study. The uppermost sediment samples from 0.01 to 1.81 mbsf were recovered from Core 191-1179C-1H. Samples at greater depths were recovered from Cores 191-1179B-1H through 4H, which cover depths between 0.60 and 35.00 mbsf. The precise depth of each sample examined in this study is shown in Table T1, along with the major element composition.
The core recovered at Site 1179 is of a typical abyssal sediment overlying chert (Kanazawa, Sager, Escutia, et al., 2001). Brief sample descriptions are given in Table T1. Diatoms predominate over the collected depth range, and radiolarians are common. Sponge spicules and silicoflagellates also contribute to the siliceous nature of the sediment. The sediment can be regarded as a precursor of chert or siliceous shale. In addition to the biogenic silica component, the sediment includes clay and ash.