ABSTRACT

The sediments and soils constitute an erosion-sedimentation cycle composed of: Solid carbonate rock Soil Fluviatile sediment Estuarine sediment Marine sediment Salt marsh. Determinations were made of the total carbonate and dolomite contents of the sediments as well as the strontium and carbon-14 content of the carbonates and their stable carbon and oxygen isotopic composition. In soils the isotopic composition of the carbonates was studied. The soils analysed are from the Netherlands and France. The sediments are from the r vers Rhine, Meuse, Ems, Seine, Somme and Rhone, from the estuaries of the Rhine, Meuse and the Ems and from the coastal areas of Belgium, the Netherlands and Western Germany.

The isotopic composition of the carbonates in soils is different from that of the parent material. This difference is due to the presence of newly formed carbonates. The amount varies between 10 and 50% of the carbonates present. The rivers Rhine, Meuse and Seine contain both soil-derived carbonates and carbonates from eroded carbonate rocks. The carbonates in the river Somme originate mainly from carbonate rocks. The carbonates in the estuaries of the Rhine, Meuse and Ems are predominantly derived from the marine environment. The carbonates are transported up to the freshwater boundary in these estuaries. The carbonates in marine sediments from the Wadden area are derived for about one fifth from the rivers Rhine and Meuse.