LATE MIOCENE (10.4-7.8 MA) PALEOCEANOGRAPHIC CHANGES ON THE CONTINENT OF ZEALANDIA USING STABLE ISOTOPE RECORDS FROM IODP SITE U1508

The IODP Expedition 371 drilled 6 sites on and near the mainly submerged, newly named continent Zealandia. Zealandia is located in the Tasman Sea off the east coast of Australia, with New Zealand being the largest part of the continent above sea level. The third drill site, Site U1508, was drilled in 1,609 meters water depth, and is located off the northwestern coast of New Zealand. This site recovered an exceptional archive of late Miocene (10.4-7.8 Ma) paleoceanographic history, as the strata are overlain by less than 180 meters of sediment, resulting in excellent preservation of calcareous microfossils. Until recently, only low-resolution stable isotopes records have been collected from Zealandia for this time interval, which hindered our understanding of the paleoceanographic history of this area during the late Miocene. This study is developing stable isotopic (δ¹⁸O and δ¹³C) records, which are higher resolution than previous studies from Zealandia during this time interval. Preliminary results show that both the δ¹⁸O and δ¹³C records register global signals (e.g., ice-volume events) and trends. Our isotopic records also contain significant differences from the global records implying regional changes in bottom water masses in Zealandia during the late Miocene. The stable isotope records were obtained using species specific foraminifers, Cibicidoides mundulus from over 90 samples. In addition, downhole logs and XRF data will enable the development of a high-resolution record that can be correlated to Milankovitch cycles. The ultimate goal is to create a detailed chronology of regional paleoceanographic and paleoclimatic changes and events in the late Miocene on and around Zealandia.