Biostratigraphy and surface-water reconstruction for the Oligocene of the North Atlantic based on organic-walled dinoflagellate cysts

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The Oligocene epoch (33.9-23.03 Ma) represents a critical interval of the Cenozoic because it allows to study the processes underlying the transition from a world free of large-scale continental ice shields and rapid eustatic sea-level change to one dominated by these factors. To contribute to a better understanding of Oligocene climate dynamics in the higher-latitude North Atlantic, we propose a two-step approach based on the complete, magnetostratigraphically dated Oligocene sequence recovered during IODP Expedition 342 off Newfoundland using dinoflagellate cysts as biostratigraphic and paleoenvironmental indicators. While the main focus of the first project phase was on establishing the first chronostratigraphically calibrated dinocyst biostratigraphy for the Oligocene of the higher-latitude North Atlantic, the second project phase will be dedicated to elucidating surface-water conditions during key intervals of the Oligocene using dinocysts. Much of the sample processing and microscope analyses necessary for the second project phase have already been carried out. The key intervals to be studied in high (c. 15 kyr) resolution, are (i) the Eocene/Oligocene transition (34.9-33.2 Ma; comprising the paleoceanographic change connected to the onset of large-scale Antarctic glaciation), (ii) the "mid"-Oligocene (28.3-25.9 Ma; Oi-2b glacial maximum with surface-water cooling extending into the mid-latitudes), and (iii) the Oligocene/Miocene transition (23.3-22.6 Ma; Mi-1 glacial maximum). The results will be integrated with other SST data that are currently being generated within the Expedition 342 consortium. Besides providing unprecedented insights into Oligocene surface-water dynamics in the higher-latitude North Atlantic, this study will also contribute towards a better understanding of the Oligocene climate system as a whole.