THE APPLICATION OF DIATOM BIOSTRATIGRAPHY AND PALEOECOLOGY TO RESOLVE EARLY MIOCENE PALEOCLIMATIC EVENTS

The Early Miocene was a time of large global climate fluctuations making it ideal for paleoclimatic reconstructions and future climate analogues. The reconstruction of high-latitude climatic changes are critical for assessing global temperature and ice-volume changes during the Early Miocene. Stratigraphic drillcores from southern high-latitude sites that would reveal this history of Early Miocene paleoenvironmental changes are fairly limited. Low core recovery, poor microfossil preservation, and uncertainty in age models prevent a clear view of paleoceanographic changes in the Southern Ocean and linked climatic changes on the Antarctic continent for this time period. A history of glacial-interglacial cyclicity and dynamic-to-stable ice sheet behavior is evident from the ANDRILL Program's Southern McMurdo Sound Project (SMS) drillcore AND-2A, although diatom occurrence in the core is sparse and sporadic. In order to extend the reach of this proximal Antarctic record and correlate paleoenvironmental events from this Antarctic shelf site into the deep-sea, we investigate the diatom biostratigraphical and paleoecological history of several Southern Ocean sites spanning the time interval from 22.3 to 16.4 Ma. Early Miocene climatic and glacial fluctuations in the Southern Ocean are documented through a qualitative study of fossil marine diatoms recovered from Ocean Drilling Program (ODP) Legs 119 and 188. Specifically, we develop fossil diatom distributions in terms of abundance, preservation changes, and assemblage composition variation in Holes 744A & 744B on the southern Kerguelen Plateau (Leg 119) and Hole 1165B on the continental rise near Prydz Bay (Leg 188). Our study encompasses the stratigraphic interval from the highest occurrence of the diatom Rocella gelida (~22.3 Ma) up to the lowest occurrence of Denticulopsis maccollumii (~16.4 Ma). Building on previous work, this study provides new paleobiological records of paleoceanographic changes from the southern high-latitudes during the Early Miocene and helps constrain the nature of Early Miocene paleoclimatic and glacial events recognized from deep-sea (ODP) and Antarctic shelf (ANDRILL) sites.