Disentangling Eocene/Oligocene ocean changes on the Western North Atlantic margin using three different micropaleontological groups and foraminiferal stable isotopes (DSDP site 612)

• Main Authors: Legarda Lisarri A., Bordiga M., Coxall H., Henderks J., Arenillas I., Molina E., MANCIN, NICOLETTA
• Other Authors: Legarda Lisarri, A., Bordiga, M., Mancin, Nicoletta, Coxall, H., Henderks, J., Arenillas, I., Molina, E.
• Format: Conference Object
• Language: English
• Published: country:NLD 2016
• Subjects: North Atlantic; Eocene-Oligocene climate transition; microfossil assemblages; planktonic foraminifera; calcareous nannofossils; benthic foraminifera; stable isotopes; Antarc*; Antarctica; Planktonic foraminifera
• Online Access: http://hdl.handle.net/11571/1131443

The Eocene-Oligocene climate transition (EOT) is associated with pronounced ocean cooling and changes in ocean circulation that culminated in the onset of glaciation on Antarctica. Much of the cooling and ocean restructuring has been linked to southern high latitude processes while details of North Atlantic (NA) circulation remain uncertain. This study contributes new insights into the ocean environment on the western NA margin during the EOT using 3 micropaleontological groups (calcareous nannofossils, planktonic and benthic foraminifera) and foraminiferal stable isotopes from DSDP Site 612. Located on the New Jersey Continental Slope (1404 m), this site today has potential to feel oceanic changes from high (Labrador Current) and low latitudes (Gulf Stream). Isotopic and biostratigraphic data imply that the first phase of the EOT (EOT-1 and the Eocene/Oligocene boundary, EOB) is captured and that the rest is truncated by a hiatus. Based on microfossil assemblages we identify three paleoenvironmental phases: pre -EOT (~34.7-34.46 Ma), high primary productivity/high organic matter flux to the sea floor, evidenced by abundant ‘euthrophic’ planktonic taxa and deep-infaunal benthic taxa indicative of high food supply; Latest Eocene to EOT-1 event (~34.46-33.9 Ma), oxygen minimum zone expanding to the sea floor, evidenced by hypoxic benthic indices; and EOB (~33.9-33.85 Ma), lower productivity and increased seasonality, inferred by abundant opportunistic benthic taxa suggestive of seasonally fluctuating organic input. These observations imply changes in nutrient supply and mixing in the NA prior to the EOT.