The information on this page is a summary description.
The full formal description is available here: Op-den-Berg Facies
| Abbreviation | KzOp |
| Parent unit | Kieseloolite Formation |
| Child units | |
| Lithological description | A medium to coarse-grained even gravelly, poorly-sorted, grey to white quartz-enriched sand; quartz grains have angular outlines. Gully structures and oblique stratification occur in the sand. Among the gravels, which are mainly of Ardennes origin, a few ooliths occur. |
| Age | No biostratigraphic data are available. |
| Thickness | A minimal thickness of 19 m, figured in the reference sandpit (Gullentops, 1963). |
| Area of occurrence | The reference sand pit is located just east of the fault zone bordering the deeper subsidence area of the Roer Valley Graben in east Belgium, in between the Feldbiss/Geleen and Heerlerheide Faults (Op den Berg fault block by Langenaeker, 1999). Therefore the Op-den-Berg Facies is included in the Kieseloolite Formation rather than in the Mol Formation. |
| Type locality | Tavernier & de Heinzelin (1962) define the Op-den-Berg, formerly Neeroeteren, sand as analogous to the Mol sand but situated at about + 80 m topographic height at the border of the Campine Plateau. They indicate on the geological map attached to their paper the sand pit Magge close to Neeroeteren-Berg. The Magge sand pit was first described by Hacquaert & Tavernier (1946). The Op-den-Berg Facies is described, formerly as Neeroeteren facies, from the former sand quarry Neeroeteren-Berg (064W0211, kb26d64w-B217), by Gulinck (1962) and by Gullentops (1963) who made a sedimentological and mineralogical analysis of the sand pit, and by Sels et al. (2001, Stop 4 & Photo 2) who ranked the sand in the Waubach sand and Gravel unit. Geys (1972) has analysed in detail the grain size of the Magge sand pit in Neeroeteren and interpreted a fluviatile depositional environment with some beach horizons. |
| Alternative names | Neeroeteren sand |
| Authors | Vandenberghe, N., & Dusar, M. |
| Date | 01/09/2023 |
| Cite as | Vandenberghe, N., & Dusar, M., 2023. The Op-den-Berg Facies, 01/09/2023. National Commission for Stratigraphy Belgium. http://ncs.naturalsciences.be/lithostratigraphy/Op-den-Berg-Facies |
