Author(s)

Resti Samyati Jatiningrum¹, Tokiyuki Sato²

¹Department of Geosciences, Geotechnology and Materials Engineering for Resources, Akita University, Akita, Japan.
²Faculty of International Resources Sciences, Akita University, Akita, Japan.

Calcareous nannofossils were observed to reconstruct the surface water conditions during late Pliocene climate transition (2.55 to 2.88 Ma) from the southern Gardar Drift, in the subpolar North Atlantic IODP Site U1314 (56°21.9’1N, 27°53.3’W). A total of 24 species from 14 genera were identified by polarizing microscope observation. The coccolith assemblages are dominated by species belonging to genus Reticulofenestra with different (size-defined) morphotype. Hence, changes in paleoceanographic condition are shown by the size variation of Reticulofenstraspecimens. Before ~2.76 Ma, the studied interval is characterized by the presence of an abundant larger Reticulofenstra group. It indicates warm oligotrophic and stable surface waters. At ~2.76 Ma the abundance of large Reticulofenstra decreased abruptly and alternated with small Reticulofenstra, suggesting collapse of sea surface stability with strong mixing condition. This event coeval with the final closure of the Central American Seaway (CAS) and the onset of intensified North Hemisphere Glaciation (NHG). Subsequently, the size variation of Reticulofenestra specimens exhibits a sequential pattern that is somewhere consistent with the interglacial-glacial cycle. The pattern begins with a gradual increase in size upward during interglacial suggesting warm oligotrophic and stable condition, and ends with an abrupt decrease in coccolith size during glacial suggesting eutrophic or strong mixing condition and destabilized sea surface waters.

Late Pliocene, Sea-Surface Waters Conditions, Calcareous Nannofossil, Subpolar North Atlantic

Jatiningrum, R. and Sato, T. (2017) Sea-Surface Dynamics Changes in the Subpolar North Atlantic Ocean (IODP Site U1314) during Late Pliocene Climate Transition Based on Calcareous Nannofossil Observation. Open Journal of Geology, 7, 1538-1551. doi: 10.4236/ojg.2017.710103.