Quartary geological profile type chart (1/200.000)

The intention was not to touch the contents of the existing maps, only where difficulties were encountered at the edges with connection. Initially, it was examined where the boreholes were located in those specific problem border strips. The interpretations of the respective boreholes were carefully examined and, if necessary, reinterpreted to make it possible to connect the different map sheets. The resulting card eventually distinguishes 25 karting units. Each karting unit is genetically and chronostratigraphically defined. The karting units form the building blocks of the different profile types. A profile type is thus defined by a specific sequence of the karting units. However, in order to keep a profile type card readable, it is desirable to limit the number of units per profile type to eight (mixing & Vinken, 1975). That maximum number of units has not been reached in any profile type. The original carting units were defined differently, depending on the contractor who carried out the mapping (1/50.000), or even from card sheet to card sheet drawn up by the same contractor. Some karting units were lithostratigraphically appointed, others were lithologically defined. In addition, the various contractors generally used different lithostratigraphic names for the same karting unit. With the objective that this overview map is initially intended for a non-geologist, it has been opted for a simple definition of the karting units. The karting units are therefore defined by the genesis and age of the deposits. On the basis of the genesis, four groups are distinguished, namely fluvatory deposits (F), aeolian deposits (E), tidal deposits (G) and slope deposits (H). With regard to quartary chronostratigraphy, two classifications are followed in Flanders. A first group follows the international classification as defined by the International Union of Geological Sciences (IUGS, 2000). The Quartair started 1.81 million years ago. However, that provision is based only on the study of marine sediments originating from southern Italy (Aguirre & Pasini, 1985). The maps drawn up by the Catholic University of Leuven follow this classification. A second group follows the Northwest European classification. The Quartair, in particular the Pleistocene, was originally defined in Northwestern Europe as the period in which cold influences have clearly left their mark on the deposits (Lyell, 1839). The Quartair started a cold phase about 2.6 million years ago. This phase is characterised, among other things, by the disappearance of subtropical plants, by changes in mammals and by the presence of shells and other organisms in the North Sea that are present only in colder regions. All these changes coincide almost with the reversal of the Earth’s magnetic field, called the Gauss — Matuyama boundary. Based on these elements, the author of this quartary geological map, as well as geologists in Belgium, the Netherlands, Great Britain and other countries, uses the original definition of the Quartair. The “plenary session of the ICS in Kyoto (1992)” showed that the strong flow within the group of quartary geologists to redefine the lower boundary of the Quartair to the former border of about 2.6 million years has achieved results. A joint group of specialists from the Quartair and Neogen re-examines the problem. Since both classifications are used in Flanders, a chronostratigraphic overview table has been drawn up in the layout of this map on which both classifications have been proposed so that the user always has a guide to place the information over time.