Genesis of the flint eluvium and related beds in South Limburg, The Netherlands

Abstract

The flint eluvium in South Limburg and Belgium is a dissolution residue of Upper Cretaceous chalk which may occur either at the present surface or below a cover of Early Oligocene sand. Eluvia with sand cover contain weathered glauconite and iron accumulations but no birefringent, oriented clay. Similar eluvia without sand cover show strong orientation of clay throughout the residue. Such orientation of residual clay immediately follows dissolution of the chalk and is not derived from overlying deposits. As eluviation and orientation of clay are strictly bound to subaerial weathering, eluvia with this property must have formed after erosion of the Early Oligocene sands. Eluvia that are covered by sand do not represent a pre-Oligocene soil formation, but have formed below the sand cover. The kleefaarde, a weathering residue without flints, but with properties similar to those of the eluvia without sand cover, is probably a lateral equivalent of the latter and much older than presumed. Accumulation at the base of the beds continues to this day, but weathering at the soil surface is different from that during the Tertiary. The paper presents a dynamic model of the formation of such eluvia.