All microfossil groups are clearly dominated by cool, high-latitude elements throughout the late Neogene. Site 1018 is sufficiently far north in the California Current to exclude most to all subtropical elements even during interglacial episodes. Radiolarians are entirely represented by subarctic forms. Diatoms are dominated by subarctic forms with the addition of much less abundant temperate elements. Planktonic foraminifer assemblages are dominated by subarctic to cool temperate forms, and subtropical elements are absent, except during warmest interglacial episodes.
Planktonic foraminifers exhibit glacial to interglacial oscillations throughout.
Radiolarians, however, do not exhibit such changes, almost certainly because they largely live at greater water depths. Changes in microfossil assemblages provide evidence of progressive cooling during the late Neogene. The first consistent occurrence of mostly common to abundant populations of sinistrally coiled Neogloboquadrina pachyderma marks a distinct cooling step at about 1.3 Ma. Likewise, changes in radiolarian assemblages indicate a further step towards cooler conditions at about 1.0 Ma. Diatoms are dominated by oceanic forms, but during the Quaternary include a small but distinct littoral assemblage that typically lives on sea grass.