Heavy minerals as a stratigraphical tool for the Eemian and Post-Eemian deposits in the lower Lys valley (Belgium)

Abstract

The lithostratigraphic units in the Upper-Pleistocene Lys valley may be subdivided into two distinct populations, each with its own characteristic heavy mineral assemblage. The Eemian and Early Weichselian sediments, which belong to the Formations of Oostwinkel/Templeuve, Dendermonde and Oostakker, are characterized by a very high opaque grains and ubiquists content and by rather low proportions of epidote, garnet and hornblende. These sediments originate mainly from the erosion of the Eocene deposits in the studied area. The overlying deposits, which make up the Formations of Oeselgem/Wevelgem, Eke, Gottem, St.-Baafs-Vijve and the youngest alluvial sediments, show a duplication in the number of garnets, epidotes and amphiboles and hence a considerable reduction in the amount of ubiquists. This heavy mineral association was influenced by an eolian supply from the north, in this case from the bottom of the then aerially exposed North Sea.