Directional trends in Dutch coversands

Abstract

The article presents a general survey of the coversands in The Netherlands and northern Belgium. About 50 samples were taken mainly in a N-S run and in 15 localities oriented cores were taken with plexiglas tubes. Of all the samples a grain-size analysis was made by sieving and all the sieve fractions were tested for rollability, a functional shape parameter. After impregnation, the cores were inspected with X-rays and the directions of the oblique bedding planes measured. Of selected parts thin-sections were cut and the grain orientation was measured under a microscope. The directional features of foreset dips and fabric anisotropy both pointed towards transport from mainly northern directions. Also the grain-size and shape-sorting studies revealed a N-S trend. This trend, however, was not continuous but showed a repetition south of the rivers Rhine and Meuse. The coversands showed strong receiving shape characteristics and the coarser grains are of low sphericity. Although the infiuence of local sources is probable, the impression was gained that the main source of the Dutch coversands must be looked for in the region north and northwest to Holland, in the present North Sea. This fits well with the former observation of the pronounced sphericity of the sands in this area, which is explained as a lag characteristic obtained during the blowing out of the coversands.