Using the shipboard chronologies, time intervals of the mid-Pliocene were chosen from just above the top of the Gauss normal-polarity Chron (2.6 Ma) down through the Mammoth reversed-polarity Subchron (basal age, 3.33 Ma). From Site 1016, samples were collected every 20 cm (roughly every 3 k.y.) from Cores 167-1016B-16H through 17H with additional fill-in samples taken from 167-1016D-16H-3 and 16H-4 (106 total samples taken). At Site 1021, samples were taken every 15 cm (roughly every 4 k.y.) from Cores 167-1021C-10H and 167-1021D-11H (78 samples total). From Site 1022, samples were collected (one per section, or roughly every 20 k.y.) from Cores 167-1022A-1H through 13H (21 samples taken).
Diatom samples (0.5-1.0 cm3 in size) were processed in hydrogen peroxide and hydrochloric acid. Strewn slides of the residues were initially examined under the light microscope at 500x. Except where preservation was poor, at least 300 diatoms per slide were counted at 1250x from Site 1022 using the techniques of Schrader and Gersonde (1978).