Cenozoic calcareous nannofossils in DSDP Leg 77 holes

Hiatuses are prominent in each of these continuously cored intervals. A prominent upper Oligocene hiatus, observed at each of these three sites, can be correlated to a large-scale "global" regression event.

Other disconformable horizons present in the study area cannot be positively related to sealevel fluctuations and may be caused by a number of factors including local tectonic activity. Paleogene sections are generally marked by thick accumulations within the upper Oligocene Sphenolithus ciperoensis Zone and by a pronounced braarudosphaerid-holococcolith bloom recorded in the lower Oligocene and upper Eocene. This bloom is particularly well developed at Site 540.