The information on this page is a summary description.
The full formal description is available here: Dessel Member
| Abbreviation | DiDe |
| Parent unit | Diest Formation |
| Child units | |
| Lithological description | The member contains the fine-grained, glauconiferous, greyish green sand that is found near the base of the Diest Formation only in subcrop in boreholes in the central and northern part of the Kempen and in northern Limburg (Houthuys et al., 2020). Glauconite content averages 25%. In the vertical direction, grain size is either constant or coarsening upwards. The sand is most often homogenized by bioturbation. In cores, white burrow traces devoid of glauconite can be seen. No primary lamination is found in this member. The member was originally defined as the lowest part of the Diest Formation in the Kempen containing foraminifera and organic-walled microfossils (Laga & De Meuter, 1972). In practice however, the member has primarily been identified based on the grain-size criterion “modal grain size smaller than 200 µm”. This implies that also overlying fine-grained sand without carbonates is included in the member. The lowest, carbonaceous part is referred to as “lower Dessel Member” and the overlying, fine-grained sand without carbonates as “upper Dessel Member” (see annex 2 to Diest Formation sheet). The lower Dessel Member is not found systematically over the area of the Dessel Member. |
| Age | Late Miocene: last part of the early to middle Tortonian biochron DN8 for the lower, often calcareous, part of the Dessel Member (Vandenberghe & Louwye, 2020; Goolaerts et al., 2020); late Tortonian to earliest Messinian, biochron DN9 for the upper, often non-calcareous, part of the Dessel Member (Vandenberghe & Louwye, 2020). |
| Thickness | The thickness is difficult to establish as the upper boundary is not well defined. The thickness is often between 10 and 30 m. If there is a lower calciferous part, it is only about 10 m thick. In the Veerle borehole, the “Hageland Dessel sand” is 45 m thick. |
| Area of occurrence | The member occurs in the Kempen region below the Kempen Diest Member. The western border is a few km east of the city of Antwerpen and the southern border is approximately along a line Lier – Veerle – southwest border fault of the Roer Valley Graben. Both borders are poorly defined. |
| Type locality | To be defined. A preferred candidate would be one of the cored boreholes from Dessel or Mol preserved in the collections of the Royal Belgian Institute of Natural Sciences. |
| Alternative names | sables fins du Diestien (Gulinck et al., 1963) |
| Authors | Houthuys, R., Adriaens, R., Goolaerts, S., Laga, P., Louwye, S., Matthijs, J., Vandenberghe, N. & Verhaegen, J. |
| Date | 01/09/2023 |
| Cite as | Houthuys, R., Adriaens, R., Goolaerts, S., Laga, P., Louwye, S., Matthijs, J., Vandenberghe, N. & Verhaegen, J., 2023. The Dessel Member, 01/09/2023. National Commission for Stratigraphy Belgium. http://ncs.naturalsciences.be/lithostratigraphy/Dessel-Member |
