1. Diatom productivity can be estimated roughly by means of abundance and lithology: at the offshore site (Site 1021), it is poorest probably because of its location in a subtropical gyre; at the coastal site (Site 1018), it is richest.
2. Diatoms are abundant during interglacial periods and are rare during glacial periods.
3. Marine conditions changed from oceanic to more coastal and productive ~400 ka.
4. The fluctuation pattern of freshwater diatoms at Site 1020 is different from the pattern at Site 1018; patterns in the former suggest shorter cycles such as precession or obliquity, and those in the latter suggest eccentricity-related 100-k.y. cycles. There seem to be several causes for increased transportation of freshwater diatoms.
5. Four diatom datum levels (LO of N. kamtschatica, LO of N. koizumii, and FO and LO of R. matuyamai) are recognized since 3.0 Ma at Site 1018.