This dissertation is a collection of five calcareous nannofossil and one stable isotope studies on materials from Ocean Drilling Program (ODP) Legs 183 (Site 1135), 206 (Site 1256), and 207 (Site 1259) that target two important paleo-oceanographic events: (1) the middle/late Miocene carbonate crash, and (2) the Paleocene/Eocene Thermal Maximum (PETM). Site 1256 nannofossil biostratigraphy refined the author's shore-based shipboard Quaternary-middle-Miocene nannofossil biostratigraphy with 16 zones/combined zones recognized based on 28 nannofossil datums. The detailed examination of the Site 1256 material also yielded well-preserved Discoaster stellulus. A redescription and re-illustration of both sides of this asterolith is provided. A stable oxygen and carbon isotopes were used to explore the late/middle Miocene "carbonate crash". A quantitative study of the response of nannoplankton to the PETM at Demerara Rise, equatorial Atlantic (Site 1259) is presented. Results presented from Site 1135 on the Kerguelen Plateau, Southern Ocean suggest that nannoplankton responded differently to the PETM at southern high latitudes. The different responses of nannoplankton to the PETM and the constrasts evident in previous work from the open ocean vs the continental margins further demonstrate that the response to the PETM can be influenced by local differences in geologic setting the oceanographic conditions. (mod. auth. abst.)