The formation of rattle stones and the climatological factors which limited their distribution in the Dutch Pleistocene, 2. The climatological factors

Abstract

The geographical distribution of rattle stones (Fig.1) and allochthonous siderite concretions (Fig.2) in the Dutch pre-Riss Pleistocene suggests that in the upper layers of the soil, north of the ice-frontline of the Riss glaciers, the concretions were oxidised to rattle stones, whereas south of it they disappeared by dissolution in percolating CO 2-containing rainwater. It is postulated that this difference in the fate of the concretions resulted from differences in the subterranean atmosphere. To the north of the ice-frontline the subterranean atmosphere was oxidative in nature during and some time after the Riss Glacial due to the absence of a plant cover. South of it a reducing subterranean atmosphere existed which was maintained by the vegetative growth on the surface. In south Limburg the originally high CaCO 3 content of the sediments may have tended to prevent dissolution and to promote oxidation of the concretions. The fact that a number of the FeCO 3 concretions and rattle stones show deformations typical for rolled soft bodies suggests that the former were formed just before transport started. Hence it is believed that formation took place during the warmer interglacial and interstadial epochs of the pre-Riss Pleistocene. Periods of enhanced erosion in the catchment area of the Rhine and Meuse, caused by a fall in sea level during recurrent extensions of the polar ice-sheets is thought to be responsible for the degradation of the siderite-containing layers and the final deposition of the concretions in the deltaic beds.