2.2. Bolderberg Formation - Bb

Authors: De Meuter & Laga (1976), after Dumont (1850); age corrected by J. Verhaegen & S. Louwye (26/09/2019)

Description: lateral succession from marine to continental sandy deposits; dark-green, medium fine, slightly clayey, often very micaceous, very slightly ligniferous, glauconiferous sand, fossiliferous in the lower part, passing into white, fairly coarse sand with lignite layers and glassy quartzite banks; basal gravel well developed with dark rounded flint pebbles and shark teeth.

Stratotype: outcrops of the road cuttings on the Bolderberg hill.

Area: exposures and deep borings of the western edge of the Limburg province; exposures on the hills around and to the south of Diest, Brabant province.

Thickness: 50 m, 285 m in the Roer valley Graben.

Members: the formation is divided into the Houthalen Sands Mbr and the Genk Sands Mbr.

Age: Burdigalian (Houthalen Sands Mbr) and late Burdigalian-early Serravallian (Genk Sands Mbr).

Remarks: the formation is also discussed by de Heinzelin & Glibert (1957), Glibert (1945, 1952), Gulinck (1956, 1959, 1963), Hinsch (1952), Le Hon (1862), Leriche (1934), Mourlon (1898), Tavernier & de Heinzelin (1963), Vanden Broeck (1880).