Holocene palaeo‐oceanography of the northern Iceland Sea, indicated by Radiolaria and sponge spicules

Abstract The micropalaeontological analysis of 49 samples, from three box cores collected from the northern Iceland Plateau, indicates that radiolarian and sponge remains are rare in glacial sediments but are common after deglaciation; mostly during the first half of the Holocene. The record trend of the abundance of Oxycalthrop sponge spicules is regional in character. Fluctuations in radiolarian abundance, and the first occurrence of each of the species inhabiting the Iceland Sea at present, coincide with changes in oceanographic conditions that occurred during the Holocene. At the Younger Dryas chronozone, the downcore record of Cycladophora davisiana (Ehrenberg) depicts a maximum peak, because the sea surface was colder than it has been recently; though still seasonally free of ice‐cover. During the Preboreal, Boreal and Atlantic chronozones, Amphimelissa setosa (Cleve) was highly abundant, as a consequence of the increase in mixing between the Arctic Water and the North Atlantic Water. During the Subboreal chronozone, the East Icelandic Current became better developed, and initiated the onset of the ‘Arctic Front’ in the Iceland Sea; as is suggested by the Lithomitra lineata (Ehrenberg) record. This ‘cooled’ environment also allowed an increase in the occurrence of Artobotrys borealis (Cleve). The reappearance of Stylodictya validispina (Jörgensen) in the Iceland Sea, during the Sub Atlantic chronozone, indicates a larger input of Atlantic Water, via the Norwegian Current.