2.2.6 Neeroeteren Formation

Authors: Renier, 1944; Van Leckwijck, 1957; Delmer, 1958; Paproth et al., 1983.

Description: The formation starts with the onset of massive, partly coarse-grained to conglomeratic, kaolinitic white sandstones, characterised by high porosities and permeability. Interbedded with variegated mudstones, which tend to become predominant upwards, and rare coal seams. Deposited in braided alluvial channels of large extension and associated floodplain.

The Neeroeteren Formation is succeeding to the Flénu Formation. Locally, contacts may seem regular, taking into account the geometry of the sandstone bodies. On regional scale, however, a slight unconformity may be present.

The top of the formation coincides with the top of the Belgian Coal Measures Group and is always eroded.

Stratotype: Borehole KB113 (Neeroeteren-Neerheide).

Area: The unmined northeastern Campine basin (Neeroeteren-Rotem area). An extension in the neighbouring part of the Roer Valley Graben is probable (no borehole reconnaissance yet).

Thickness: Maximum thickness traversed in exploration boreholes is 300 m. Based on seismic evidence, preserved thickness attains 500 m (Dusar, 1989).

Age: Upper Moscovian; practically coinciding with the Westphalian D, according to traditional subdivision. The Westphalian C-D boundary, recognised by means of microflora, lies about 30 m below the base of the Neeroeteren Formation (Paproth et al., 1983).

Remark: First described by Renier (1944) as ‘Grès de Neeroeteren’ and defined at formation level by Van Leckwijck (1957) and Delmer (1958) but restricted as a member of the Belgian Coal Measures Formation in Paproth et al. (1983).