The information on this page is a summary description.
The full formal description is available here: Vlierzele Member
| Abbreviation | GeVl |
| Parent unit | Gentbrugge Formation |
| Child units | |
| Lithological description | In the recent literature, based on outcrop observations, the Vlierzele Member is described as consisting of a lower part of mostly bioturbated, slightly clayey, glauconitic sand and an upper section of alternating units of tidal cross‐bedding with mud drapes and structureless intercalations; the upper section may contain lignite lumps (Houthuys, 1990). In the recent literature, based on outcrops, the Vlierzele Member is described as consisting of fine glauconitic green‐grey mostly bioturbated sand, finely laminated horizontally and in cross stratification. Towards the base the sands becomes clayey and more homogeneous. Towards the top individualised clay layers occur together with humic intercalations. Macrofossils are very rare. Thin cemented siliceous sandstone beds commonly occur (Geets et al., 2000); irregularly shaped siliceous sandstone concretions are also common. The maximal thickness is about 20 m; in the type locality the cross bedded sand above is 7m thick and the lower homogeneous sand at least 5 m (see sections in Houthuys & Gullentops, 1988 p 142). Fobe (1995), after reviewing information available from more than 25 localities, considers the ‘traditional Vlierzele sand sensu stricto’ as only one of 5 members in a formation between the Pittem Member and the Aalter Sand in the Zenne Group. Steurbaut (2006) reports erroneous correlations in Fobe’s (op.cit.) subdivisions ; the Beernem sand, traditionally a member of the Aalter Formation of the Zenne Group (Maréchal & Laga,1988 p 120‐121; Geets et al., 2000), is included in the Vlierzele unit by Fobe and the existence of a distinct Aalterbrugge unit is refuted by this author. Therefore the present review is not following the interpretations by Fobe (1995, 1997) but recognizes that the clayey basis, a 3‐10m very fine clayey sand with mm‐thick clay layers, (Lochristi layer sensu Fobe) and locally a thin coarser basal layer (Hijfte layer sensu Fobe) merit a separate mention aside the traditional Vlierzele sand sensu stricto (which according to Fobe 1995,1997 could be named Oosterzele unit). |
| Age | |
| Thickness | |
| Area of occurrence | The Vlierzele Member outcrops in the northern and central parts of the provinces East and West Flanders and in the western part of the Flemish Brabant province. It also occurs as outliers in the top zones of the South‐ Flemish hills. On a regional scale the base of the Vlierzele is erosive into underlying strata (see also Fobe, 1989b, 1995). In northern Flanders the grainsize properties of the Vlierzele Member seem to be more variable (Laga & Vandenberghe, 1990 p 1; Fobe, 1993, 1995). The boundary between the clayey sediment of the Pittem Member and the overlying Vlierzele Sand can mostly be traced with reasonable confidence in the geophysical log correlation profiles by Welkenhuysen and De Ceukelaire (2009). On the legend of the 1:40 000 maps the Vlierzele Member is coded P1d and P1n for the upper clayey facies. In the stratigraphic register (1929, 1932) the Vlierzele Member is included in the Y2 division. The P1n‐clay, defined by Rutot (1890) and described as a local top clay in the Vlierzele Sand (Gulinck & Hacqaert, 1954) is believed to correspond in fact to the Merelbeke Clay (Fobe, 1995; Buffel et al., 2009). |
| Type locality | The Vlierzele locality is part of the Sint‐Lievens‐Houtem municipality in the East Flanders province where several extractions have been active in the past. The sand pit, formerly known as the Verlee or Balegem sand pit (at present Balegro sand pit)– 070E0050, is the stratotype; it is located on topographic map sheet 22/7‐8, Oordegem‐Aalst (X = 116.650, Y = 181.725, Z = + 45 m) (Geets et al., 2000). However this stratotype is limited to the Vlierzele sand sensu stricto. Following Fobe (1995), as far as the Vlierzele sensu stricto, the Lochristi and Hijfte layers are concerned, the Ursel borehole (039W0212 x= 87.910, y= 204.260, z= + 29 m TAW) shows the Vlierzele Member between 58 and 69,3 m with the Vlierzele sand sensu stricto between 58‐63 m, Lochristi layerbetween 63‐66 m and the Hijfte layer between 66‐69,3 m. |
| Alternative names | |
| Authors | Steurbaut, E., De Ceukelaire, M., Lanckacker, T., Matthijs, J., Stassen, P., Van Baelen, H. & Vandenberghe, N. |
| Date | 09/01/2017 |
| Cite as | Steurbaut, E., De Ceukelaire, M., Lanckacker, T., Matthijs, J., Stassen, P., Van Baelen, H. & Vandenberghe, N., 2017. The Vlierzele Member, 09/01/2017. National Commission for Stratigraphy Belgium. http://ncs.naturalsciences.be/lithostratigraphy/Vlierzele-Member |
