Miocene to Pleistocene dinoflagellate cysts in ODP Sites 133-815 and 133-823

Well-preserved and diverse dinoflagellate cyst assemblages were recovered from Ocean Drilling Program (ODP) Sites 815 and 823. The late middle Miocene is indicated by the presence of Sumatradinium spp. up to Core 133-823C-10R at Site 823 and up to Core 133-815B-47X at Site 815. Melitasphaeridium choanophorum appeared in the late Miocene (Cores 133-823C-19R and 133-815B-45X) and disappeared during the late Pliocene (Cores 133-823C-56X and 133-815 B-4H). Other significant biostratigraphic datums include the disappearances of Hystrichokolpoma rigaudiae (Cores 133-823B-22X and 133-815A-5H) and Dapsilidiniumpasteilsii (Cores 133-823B-23X and 133-815A-5H) at the end of the Pliocene; the first appearance of Blysmatodinium argoi during the late Miocene (Core 133-815B-43X) and subsequent disappearance during the early Pliocene (Cores 133-823B-47X and -815B-27X); and the disappearance of Operculodinium longispinigerum (Sections 133-823A-3H-4 and -815A-1H-3) during the Pleistocene. These results are consistent with the ages determined by nannoplankton and foraminifers at these sites and also with the dinoflagellate biostratigraphy from Leg 123 (McMinn, 1992, doi:10.2973/odp.proc.sr.123.120.1992).
The Neogene assemblages of both sites are characterized by abundant Spinife rites spp., Impagidinium spp., and Operculodinium spp. Both Tuberculodinium vancampoae and Lingulodinium machaerophorum are consistently present and sometimes abundant but most other species occur only sporadically. Peridiniaceae, which is often associated with nutrient enrichment, is rare in all samples. This suggests that the environment has always been oligotrophic. Imp?gidinium spp., taxa typically associated with oceanic environments, are present throughout both cores, but are more abundant in post-Pliocene sediments.