Central North Atlantic paleoceanography during the Late Early Pleistocene (spanning Marine Isotope Stage 21) based on a high-resolution dinoflagellate cyst record
A high-resolution dinoflagellate cyst record from Integrated Ocean Drilling Program Site U1313, constrained by an ultra-high resolution δ 18O record from the same sample set, is established to enhance our understanding of the paleoceanography and structure of Marine Isotope Stage (MIS) 21 in the central North Atlantic. Changes in cyst abundance, composition of cyst assemblages, and their diversity reflect major regional shifts in climate and ocean circulation for this time interval (866–814 ka). The following paleoenvironmental indicators are used: Operculodinium centrocarpum sensu Wall & Dale (North Atlantic Current), Nematosphaeropsis labyrinthus and Impagidinium pallidum (subpolar gyre), total Impagidinium species (subtropical gyre), and protoperidiniacean cysts (biological productivity). The integration of stable isotope and the generated dinoflagellate cyst data shows MIS 21 to have been climatically unstable and interrupted between 830 and 840 ka by two significant cool episodes. These are resolved using the relative abundance of cooler-water species and by tracking the abundance of O. centrocarpum. During MIS 21, Site U1313 was predominantly under the influence of the subtopical gyre until after 835 ka when the NAC was re-established until the end of MIS 21. This study also extends the stratigraphic range of Fibrocysta? fusiforma from its previously documented range top in the Lower Pleistocene at 2.3 Ma to ~812 ka in the present study. An unnamed Spiniferites species (Spiniferites sp. 1) is confined to the latest phase of MIS 22. Two unidentified acritarchs (Acritarch spp. 1 and 2) occur throughout MIS 21 and merit further investigation.