Variations in felsic- versus mafic-sources in the Western Nordic Seas during MIS 1 to MIS 4

Abstract The goal of this paper is to employ quantitative methods to: first, describe the spatial variations in the quantitative non-clay and clay mineral composition of seafloor (surface) sediments; secondly, use those data to describe the temporal variations in mineral compositions of nine cores that extend (variously) between the present-day and ~85 ka BP; and thirdly, describe regional variations in the transport of felsic- versus mafic-rich glacial marine sediments at four sites close to Denmark Strait. K-mean clusters of recent seafloor samples (n = 156) distinguished four mineral facies, which characterize a range of mafic to felsic compositions. These samples serve as a training set to identify the down-core mineral facies in eight cores (n = 1053); the degree of provenance mixing is measured by fuzzy clustering on an unsupervised cluster analysis. Classification Decision Trees validate the mineral facies (only 6% misclassified) and indicate that variations in the weight % of pyroxene are of primary importance in defining cluster membership. Mineral compositions identify two end member core sites JM07–174GC (Greenland Sea) and LO9–18 (Reykjanes Ridge), while the cores north and south of the Greenland-Faroes Ridge (cores PS2644, MD99–2274, −2280, and − 2323) are a mixture of mafic-rich and felsic-rich mineral facies. Variations in magnetic susceptibility and quartz wt% exhibit coherent runs of values above or below their medians in three of the cores occurred, indicating that these cannot be ascribed to random variations (p