TITLE:
Sea-Surface Dynamics Changes in the Subpolar North Atlantic Ocean (IODP Site U1314) during Late Pliocene Climate Transition Based on Calcareous Nannofossil Observation
AUTHORS:
Resti Samyati Jatiningrum, Tokiyuki Sato
KEYWORDS:
Late Pliocene, Sea-Surface Waters Conditions, Calcareous Nannofossil, Subpolar North Atlantic
JOURNAL NAME:
Open Journal of Geology,
Vol.7 No.10,
October
27,
2017
ABSTRACT: 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.