Late Neogene marine Ostracoda from Tjörnes, Iceland

Abstract

On the western side of the Tjörnes Peninsula in northern Iceland exposures of fossiliferous marine sediments, basalts, and glacial tills record the climatic history of this region of the North Atlantic Ocean. Seventy-five marine ostracode species were recovered from the Pliocene Tjörnes sediments and Quaternary sediments known as the Breidavik beds. The ostracode assemblages contain many warm-water genera that do not inhabit Iceland today and indicate early to middle Pliocene (4.5–3.0 Ma) winter and summer bottom-water temperatures that averaged 5–6°C and 14–16°C, respectively (maximum 20°C in summer, rarely below 3°C in winter except during a brief cooling 3.5–3.2 Ma). An intensified North Atlantic Drift and a diminished or absent East Greenland Current account for warm-water oceanographic conditions at 66°N. Late Pliocene marine climates were cooler with winter and summer averages of about 9°C and 8°C. Early Pleistocene ostracode assemblages dated at 1.7–1.3 Ma contain extant arctic–subarctic species that indicate winter and summer temperatures of about − 1.5°C and 4–5°C. New speciesBensonocythere eirikssoni, Robertsonites williamsi, Hemicythere rekaensis, Thaerocythere mayburyae, Thaerocythere whatleyi, Leptocythere tjornesensis, Tetracytherura bardarsoni, andCytheromorpha einarssoniare described.