SUMMARY

1. Because the Site 1148 locality now lies between the modern lysocline and CCD in the northern SCS, Oligocene and Miocene planktonic foraminifers from Site 1148 are found to have been affected to a varying extent by dissolution. The biofacies is dominated by dissolution-resistant species, especially S. seminulina and Globoquadrina spp.
2. More than 30 planktonic foraminifer datum levels are found between 170 and 700 mcd, enabling the recognition of Oligocene Zones P18–P22 and Miocene Zones N4–N18. By correlation, most bioevents are considered synchronous with their open-ocean records. Three of them, however, appear to represent local events: the LO of G. dehiscens at ~9.5 Ma, the LO of G. fohsi s.l. at ~13.0 Ma, and the FO of G. insueta at ~18.0 Ma.
3. At least four major unconformities occurred in the late Oligocene, respectively, at ~488 mcd (OHS1), ~478 mcd (OHS2), 472 mcd (OHS3), and 457 mcd (OHS4 = MHS1). The last two are in the slump deposit between 458 and 472 mcd that marks the transition from rifting to spreading of the SCS.
4. Miocene unconformities MHS1–MHS12 are mainly caused by dissolution because of an elevated CCD during third-order glaciations or Mi events. This positive relationship indicates that a similar or related driving mechanism was responsible for deepwater circulation changes concomitantly in world oceans and the marginal SCS during the Miocene.