The information on this page is a summary description.
The full formal description is available here: Houthalen Member
| Abbreviation | BbHo |
| Parent unit | Bolderberg Formation |
| Child units | |
| Lithological description | The Houthalen Member is a dark green, often clayey, medium fine-grained sandy unit, micaceous, slightly ligniferous and glauconitic. Dispersed and concentrated mollusks occur which are also reworked in the basal gravel of the superjacent Diest Formation (De Meuter & Laga, 1976). The Houthalen Member has an average glauconite content of 17% (Adriaens, 2015). The Elsloo gravel at the base of the Houthalen Member consists of reworked Oligocene components, dark blue, egg-shaped, indented phosphate pebbles and shark teeth (Vandenberghe et al., 1998). |
| Age | The benthic foraminifers from the Houthalen Member were extensively studied by De Meuter (1980), De Meuter & Laga (1976) and Willems et al. (1988) and indicated deposition during early Miocene times. The analysis of the planktonic foraminifera (Hooyberghs & De Meuter, 1972; Hooyberghs, 1983; Hooyberghs & Moorkens, 1988) indicates deposition during the Burdigalian. Nannoplankton studies (Martini & Müller, 1973; Verbeek et al., 1988) point towards a lower Miocene age. Wouters (1978) recognised the lower Miocene U2 Ostracoda Zone, while Gaemers (1988) reports the presence of the late Burdigalian to Langhian otolith Zones 12/13. |
| Thickness | 11 m in the Houthalen borehole (DOV kb25d62e-B274; GSB 062E0270), 16 m in the Wijshagen borehole (DOV kb18d48w-B181; GSB 048W0180) and reaches a maximum of 30 m in the Molenbeersel boreholes (DOV kb18d49w-B225 and kb18d49w-B226; GSB 049W0225 and 049W0226) in the differentially subsiding Roer Valley Graben. |
| Area of occurrence | The Houthalen Member occurs in the subsoil of the type area and outcrops in the hills near Bolderberg, Waanrode (south of the city of Diest) and Lubbeek (De Meuter & Laga, 1976). |
| Type locality | The type locality is Houthalen (north of Hasselt). The type section is the mine shaft “Puits no. 1)” of the Houthalen coal mine (De Meuter & Laga, 1976; after Glibert, 1945). The Houthalen Member in the Wijshagen borehole (DOV kb18d48w-B181; GSB 048W0180; depth 162 m to probably 178 m) is an alternative type section. The Houthalen borehole (DOV kb25d62e-B274; GSB 062E0270) is a type geophysical borehole with the Houthalen Member expressed by high gamma-ray and low resistivity values between 90 m and 101 m depth. |
| Alternative names | This unit includes the Elsloo gravel at its base. |
| 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 Houthalen Member, 01/09/2023. National Commission for Stratigraphy Belgium. http://ncs.naturalsciences.be/lithostratigraphy/Houthalen-Member |
