Fine-grained silicate fractions (< 2-mu-m and 2-16-mu-m) of Holocene and Late Glacial sediments in a deep-sea core from the northeast Atlantic Ocean (47-degrees-30'N- 19-degrees-30'W) have been analysed by X-ray diffraction, K-Ar and Sr isotopic methods. During the Holocene, the K-Ar apparent ages and the Sr-87/Sr-86 ratios of the clay size minerals averaged 436(-22)+13 Ma and 0.72638 +/- 0.00051, respectively. The K-Ar values essentially reflect the high Ar-40 contribution from the detrital mica in binary smectite-mica mixtures, where smectite is a low potassium and Tertiary-Quaternary component. Higher K Ar age values, up to 569(-124)+112 Ma are determined for the coarser 2-16-mu-m fractions which contain, in addition to mica, other detrital K-bearing phases (amphibole, K-feldspar and plagioclase). An important change in the mineralogical composition and the K-Ar ages is displayed by the silicate fractions of a thin layer of ice-rafted detritus, located at the termination of the last glaciation. Their K-Ar apparent ages increase to 773-933 Ma and correspond to an increase of the detrital supply (amphibole, mica and feldspar) from the Precambrian terrains of North America or Greenland and a dilution or a decrease of the input of basaltic material (smectite, oligoclase) from the region of Iceland.
