RADIOLARIAN FAUNAL PROVINCES IN SURFACE SEDIMENTS OF THE GREENLAND, ICELAND AND NORWEGIAN (GIN) SEAS

The overall abundance and species composition of the polycystine and p haeodarian radiolaria have been determined in 63 surface sediment samp les from the GIN Seas. These results are compared to chemical and phys ical properties of the overlying water masses. There are three abundan ce maxima in the distribution of radiolarian skeletal debris preserved in these surface sediments, centered on the Iceland Plateau, southern Norwegian Basin and northern Norwegian Basin. The most commonly encou ntered species were: (a) Spumellarida -Actinomma boreale, A. leptoderm a, Larcospira minor, and Phorticium clevei, (b) Nassellarida -Amphimel issa setosa, Artobotrys boreale, Lithomelissa setosa, Lithocampe platy cephala, Pseudodictyophimus gracilipes, Cycladophora davisiana, and Li thomitra lineata. Based on factor analysis of the core-top assemblages , the radiolarian species were grouped into three associations: Factor 1 -a polar- and arctic water association dominated by Amphimelissa se tosa (varimax factor score 5.269), high factor component values are fo und in the Iceland Plateau area and in a wedge just north of the Icela nd-Faeroe Ridge; Factor 2 -an Atlantic water association dominated by Pseudodictyophimus gracilipes (3.247), Lithomelissa setosa (2.731), an d Actinomma boreale (1.851), high factor component values are found in the eastern part of the Norwegian Sea, particularly in the area under the influence of the Norwegian Current; and Factor 3 -an Atlantic and arctic water mixed association dominated by Lithocampe platycephala ( 3.251), Lithomelissa setosa (-2.176), Actinomma leptoderma (1.994) and Artobotrys boreale (1.504), high factor component values are found im mediately to the east of the Iceland Plateau in correspondence to the deepest part of the Norwegian Basin. The correlation coefficients obta ined between seasonal sea surface temperature and Factors I (R-2 = 0.8 35), and 2 (R-2 = 0.891) show a good fit, whilst for Factor 3 there wa s a less marked (R-2 = 0.497), but still significant at the 5% confide nce level, correlation for fifth-degree polynomial regression function s. The factors correlated better with the summer than the winter sea s urface temperatures. However, at 20, 50, 100 and 200 m depth, the corr elation became increasingly better, particularly so for the winter sit uation. The highest species richness for polycystine radiolarians (>28 species) was found in the warm Atlantic domain, the lowest (<24 speci es) was found in the colder arctic and polar domains, whilst an area a pproximating the position of the Arctic front had between 24 and 28 sp ecies. (C) 1998 Elsevier Science B.V. All rights reserved.