An excellent record of siliceous microfossils is present in Hole 1165B, allowing the application of the Neogene high-latitude zonal schemes for both diatoms and radiolarians. Twenty-one diatom and 12 radiolarian biostratigraphic datums were identified to approximately 600 mbsf where dissolution became extensive. Below this level, age assignments are inferred from occasional calcareous nannofossil occurrences. Nannofossils are generally rare and sporadic at Site 1165 with only a few discrete intervals of higher abundance and moderate to good preservation of assemblages that have low diversity, like previously found in this region. Nannofossils yield Pleistocene to lowermost Miocene ages.
Benthic foraminifers are more common than planktonic ones, which are rare.
Foraminfers indicate several intervals of redeposited material. Measurements of rock magnetic properties in the interval 114-370 mbsf indicate that magnetic mineral concentrations drop significantly with near complete loss of magnetic intensity. Preliminary analysis suggests that this is due to diagenesis of magnetite, the primary magnetic-signal carrier. Interstitial water profiles document downhole sediment diagenesis. Concentrations of dissolved silica increase from 522 uM at the sea floor to a maximum of 1000 uM at 200 mbsf, reflecting dissolution of abundant silicious microfossils.