(Table 2) Maximum values of relative abundances of radiolarian species in samples of surface layer sediments from the North Atlantic

Distribution of twelve Radiolaria species in the surface layer of sediments was analyzed from the author's data for the North Atlantic and from published materials for the Norwegian-Greenland Basin. Presumably, the groups of species are distinguished with respect to their relation and not related to water masses participating in formation of the North Atlantic Deep Water. They are as follows: (a) the group of species (A. tumudulum, L. arachnea) from surface and subsurface water masses of the Labrador Sea, which is relatively independent of the mechanism of North Atlantic Deep Water formation; (b) the group of species (Ph. clevei, S. osculosus, S. glacialis) from regions of generation (Norwegian-Greenland Basin, ? Labrador Sea) and transport to the North Atlantic (Denmark Strait, Labrador Sea) of transformed North Atlantic water involved into formation of the North Atlantic Deep Water; and (c) the group of species (A. setosa, Cr. borealis, C. davisiana, Ps. gracilipes) from areas of intensive transformation of North Atlantic water masses (Norwegian-Greenland Basin). An analysis of distribution of these Radiolaria species from sediments of Core MK-340 collected on the Reykjanes Ridge allows to suppose that no long hiatuses (with duration of few hundreds of years) in the generation of water masses forming the North Atlantic Deep Water occurred during the period from 12.3 to 8 ky ago.