SOURCE AND GRAIN-SIZE INFLUENCES UPON THE CLAY MINERAL DISTRIBUTION IN THE SKAGERRAK AND NORTHERN KATTEGAT

Bottom sediments from 78 sites in the Skagerrak-Kattegat area have bee n used to determine the semi-quantitative distribution of clay mineral s, and to interpret sediment provenance and the transport pathways. Th e sediment reflects incorporation of four sources, affected both by ea rlier glacial processes and on-going marine mixing. The southern North Sea, characterized by dioctaheadral illite, kaolinite and smectite, i s the dominating source. The central North Sea provides a limited, but significant, source for chlorite. The sediment from the Swedish west coast has an unweathered character, containing trioctaheadral illite, vermiculite, illite-vermiculite mixed-layer minerals and chlorite. The contribution from the southern Kattegat (southern Sweden and Denmark) is dominated by kaolinite and smectite. Correlation between clay cont ent and the contents of smectite, kaolinite and chlorite in the Skager rak indicate that the clay mineral distribution is influenced by sorti ng. This grain-size dependency must be considered when interpreting so urces.