De jongste geologische geschiedenis van de Belgische Zeepolders

The lay-out of the soil map of the Belgian maritime plain (1947-1953) has made it possible to correct our present-day ideas about the formation of our maritime polders. The main fact in this formation is the Dunkirk transgression, which comprises three phases: the Dunkirk 1 transgression (2nd century B.C. to 1st century A.D.), the Dunkirk 2 transgression (4th to 8th century) and the Dunkirk 3 transgression, subdivised in two subsidiary phases : the Dunkirk 3A transgressive phase (11th century) and the Dunkirk 3B transgressive phase (12th century). In the course of each of these transgressive phases sediment layers have been deposited, which constitute the present surface of the polder plain. According to their geological constitution, five typical geographical areas in the polder plain can be distinguished: the ancient area, the intermediate area, the recent area, the historical Ostend polders and the drained marshes

Amélioration de sols polderiens à mauvaise structure par labour profond

In the Belgian marsh-area many soils have a bad surface-structure. Their top soil is non-calcareous, while the subsoil presents a considerable amount of lime. In many cases an impermeable claylayer is found at a depth of 30-40 cm. After heavy rainfalls these soils show a strong degradation of the structure. The topsoil is muddy, with a typical shiny appearance and the seeds do not run out or only partially. These soils can be improved by deep- ploughing to 50-100 cm, given that the calcareous subsoil is brought to the surface. After this process had been successfully applied in 1952 as a field experiment, there was no decrease of yield. In 1955 the yield had increased with 8 %. The soil had become more productive and the new topsoil needed no more liming