The information on this page is a summary description.
The full formal description is available here: Lichtaart Member
| Abbreviation | KlLi |
| Parent unit | Kasterlee Formation |
| Child units | Oud-Turnhout Facies, Hoge Berg Facies |
| Lithological description | The Lichtaart Member consists of pale green fine sand with a moderate glauconite content. Reported modal grain size varies between 125 and 170 µm and a <62 µm fraction of about 10 to 15% is present. The sand fraction is very well sorted. The colour varies from pale to darker green depending on the glauconite content; sparse glauconite grains can give the sand a speckled outlook. Glauconite pellet content can range from around 4% in the Lichtaart –Kasterlee hill outcrops, called the Hoge Berg Facies, up to 30% in boreholes north of the hill ridge, called the Oud-Turnhout Facies. Muscovite flakes are common. An exceptionally high content of hornblende in the heavy mineral fraction (55%) is reported in Lichtaart (TO-19990101B). The Lichtaart Sand Member contains neither calcareous fossils nor carbonates in general. |
| Age | Dinoflagellate cyst biozone DN10 was identified in the Lichtaart Member (Rees borehole, 017E0399; kb8d17e-B495), attributing a late Tortonian to Messinian Miocene age to this member. |
| Thickness | In the type area Herentals-Lichtaart-Kasterlee a thickness of about 15 m is interpreted in sections drafted by Laga and Gulinck (Laga, 1976) and confirmed by a CPT log interpretation (10-CPTE-138). In the boreholes of the Turnhout area, Gierle (017W0158/kb8d17w-B14), Rees (017E0399/kb8d17e-B495), Oud-Turnhout (017E 0401;kb817e-B497) and Turnhout (017E0398; kb8d17e-B294), the Lichtaart Member occurs underneath the Poederlee Sand and thickness is reduced to 8 to 11 m. Towards the border with the Netherlands in the north of the Antwerp province, the Kasterlee Formation, probably the Lichtaart Member, is suggested to thicken in the profiles drafted by Laga (1976). |
| Area of occurrence | The Lichtaart Member occurs west of an approximate line Olen–Kasterlee. Due to the northwards dip of the Kasterlee Formation, south of Olen only the Hallaar, Beerzel and Heist-op-den-Berg members occur. East of this Olen-Kasterlee line the Lichtaart Member is geometrically replaced by the Retie Member of the Mol Formation (Schiltz, 2020; Vandenberghe et al., 2020; Verhaegen et al., 2020). West and northwest of an approximate Grobbendonk–Merksplas-Weelde zone, the Lichtaart Member wedges out, probably as a consequence of end-Miocene to earliest Pliocene erosion. |
| Type locality | The occasional outcrops in the flanks of the hills between Herentals, Lichtaart and Kasterlee on the right bank of the Kleine Nete valley always expose the top part of the Kasterlee Formation. Therefore these outcrops are always part of the Lichtaart Member. They were selected as the type section for the Kasterlee Formation in the Lithostratigraphic scale of Belgium (2001) although the lower part of the formation was never exposed in the hill ridge. These outcrops in fact show the southern glauconite-poor Hoge Berg Facies. Several boreholes in the Turnhout area contain reference data on the Lichtaart Member, where the northern glauconite-rich Oud-Turnhout Facies is present. The reference section selected for the Lichtaart Member is in the Rees borehole (017E0399; kb8d17e-B495). The full section described as Kasterlee Formation between 25 and 33,5 m is interpreted as the Lichtaart Member. Cores, sediment analyses and dinoflagellate cyst analyses are available in this interval (Buffel et al., 2001; Vandenberghe et al., 2020). The Kasterlee Formation in the Gierle borehole (017W0158 ; Kb8d17w-B14) between 26 and 34 m is also identified as the Lichtaart Member and has detailed grain-size analyses (Gullentops and Huyghebaert, 1999). Although the base of the Lichtaart Member is not reached in the Oud-Turnhout borehole (017E 0401;kb817e-B497), a section of about 11 m of the Lichtaart Member between 39 and 50 m with sediment analyses is juxtaposed to a gamma-ray log of the similar interval in the nearby Turnhout borehole (017E0398; kb8d17e-B294) in Louwye et al. (2020 fig. 4). |
| Alternative names | Type Kasterlee Sand (Vandenberghe et al., 2020), formerly part of the at the time not yet subdivided Kasterlee Formation sensu De Meuter and Laga (1976) and Laga et al. (2001). |
| Authors | Verhaegen, J. & Vandenberghe, N. |
| Date | 01/09/2023 |
| Cite as | Verhaegen, J. & Vandenberghe, N., 2023. The Lichtaart Member, 01/09/2023. National Commission for Stratigraphy Belgium. http://ncs.naturalsciences.be/lithostratigraphy/Lichtaart-Member |
