PLEISTOCENE TO MIOCENE CALCAREOUS NANNOFOSSIL BIOSTRATIGRAPHY FROM IODP EXPEDITION 334 HOLE U1381A AND EXPEDITION 352 HOLE 1439A
Calcareous nannofossil biostratigraphy has now provided zonations for the samples taken from IODP Expedition 334 cores. Samples from core 6R are assigned to the Pleistocene nannofossil Zone NN19 due to the presence of Pseudoemiliania lacunosa and the absence of Emiliania huxleyi. Using the zonal scheme by de Kaenel (1999), this can further be broken down into Event 18 due to the presence of Gephyrocapsa oceanica larger than 4 µm but less than 5 µm, the presence of Calcidiscus macintyrei smaller than 11 µm, and the absence of Gephyrocapsa caribbeanica larger than 4 µm. De Kaenel (1999) has assigned this event datum an age of 1.718 Ma using orbital time scales and oxygen isotope data. Below these samples, an extensive hiatus ranges from the Pleistocene to the early Miocene. Samples from cores 7R through 10R are assigned to nannofossil zone NN5; however, it is impossible to constrain the top of this zone due to the hiatus. The presence of Sphenolithus heteromorphus and other restrictive species, and the absence of Helicosphaera ampliaperta and Sphenolithus belemnos help constrain these samples to Zone NN5 (13.2Ma to 14.66Ma).
Further work as above will be conducted to analyze Miocene samples from IODP Expedition 352.