A total of 53 nannofossil events were recognized in the lower Oligocene to Pleistocene sediments studied. The sediments at the base of Site 1148 are in the lowermost lower Oligocene Zone NP22 with an age younger than 32.8 Ma.
Based on these events, the lower Oligocene to Pleistocene sequences recovered at Sites 1146 and 1148 were subdivided into the 4 Paleogene zones and 21 Neogene to Quaternary zones of Martini (1971), in correlation with the 3 Paleogene zones and 15 Neogene to Quaternary zones of Okada and Bukry (1980).
A significant unconformity was recognized in the Oligocene–Miocene transition, in which the upper part of Oligocene Zone NP25 and the lower part of Miocene Zone NN1 were missing. The time span of the unconformity was estimated to be ~1 m.y.
Very high sedimentation rates were seen in the Oligocene, along with relatively low values in the Miocene and the highest in the Pleistocene; these rates were seen as the result of tectonic and sedimentation history of the SCS.