The information on this page is a summary description.
The full formal description is available here: Opgrimbie Facies
| Abbreviation | BbOg |
| Parent unit | Genk Member |
| Child units | |
| Lithological description | A medium-grained, white sandy unit holding a lignite seam (Kikbeek Lignite) and a quartzite layer (a silcrete cemented by originally opal bioliths) (Gullentops, 1963, 1972-1973; Matthijs, 1999). The white sand of the Opgrimbie Facies has in the type locality (Opgrimbie quarry) a modal grain size of approximately 215 µm. A sample from this facies in the Wijshagen borehole has a modal grain size of 296 µm, a clay content of only 0.7 % and a D90 of 433 µm. (Gullentops, 1963, 1973; see also Adriaens, 2015). |
| Age | No precise absolute or relative dating of the Opgrimbie Facies is available. The Genk Member has been relatively dated through biostratigraphy as Langhian to early Serravallian (Louwye et al., 2020). |
| Thickness | The thickness of the Opgrimbie Facies ranges between 10 and 15 m. The lignite seam has a thickness of about 3 m. The precise lateral and vertical limits of this facies remain to be determined (Louwye et al., 2020). |
| Area of occurrence | The Opgrimbie Facies occurs in the eastern part of the Limburg province. |
| Type locality | Sibelco sand pit at Opgrimbie in eastern part of the Limburg province (Gulinck, 1961; Wouters & Vandenberghe, 1994; Van Loon, 2009). |
| Alternative names | Miocene glass sand of Maasmechelen (Gullentops, 1972-1973); Maasmechelen Silver Sands (Sels et al., 2001; Buffel et al., 2001), ‘Mechelen aan de Maas sand’ (Laga, 1973). This unit includes the Terlamen gravel at its base. It is topped by the Opgrimbie gravel. |
| Authors | Louwye, S., Adriaens, R., Deckers, J. Vandenberghe, N. & Verhaegen, J. |
| Date | 01/09/2023 |
| Cite as | Louwye, S., Adriaens, R., Deckers, J. Vandenberghe, N. & Verhaegen, J., 2023. The Opgrimbie Facies, 01/09/2023. National Commission for Stratigraphy Belgium. http://ncs.naturalsciences.be/lithostratigraphy/Opgrimbie-Facies |
