Oorderen Member

The information on this page is a summary description.
The full formal description is available here: Oorderen Member

Abbreviation LiOo
Parent unit Lillo Formation
Child units
Lithological description The Oorderen Member as introduced by De Meuter & Laga (1976) is a greyish fine-grained, shelly unit containing numerous shells and shell grit, both dispersed in a glauconiferous quartz sand matrix as well as arranged into a number of cm to dm thick shell beds. The basal shell layer is generally several dm thick, contains also gravel with large pebbles, reworked shells and cetacean bones. Major shell beds show load casting, and generally, three of these can be followed over adjacent outcrops several kilometres apart. Three intervals characterized by different sedimentary structures (respectively: throughs and storm beds, predominantly homogenized sand, predominantly bioturbated clayey sand) and mollusc fauna composition (respectively frequent occurrence of: Atrina fragilis kalloensis (previously Pinna pectinata), Cultellus cultellatus, Angulus (or Tellina) benedeni benedeni), and separated by shell beds that experienced load coasting, can be recognized all over the Port of Antwerp area, namely the Atrina (previously Pinna) level, the Cultellus level and the benedeni level (previously Angulus or Tellina benedeni level, or clayey Oorderen) (see Vervoenen, 1995; Marquet, 1998; Marquet & Herman, 2009 and others).
Age Early late Pliocene. See Louwye et al. (2020) and references therein.
Thickness In the Port of Antwerp area, the member has a maximum thickness of up to 7 m (Van Haren et al., 2021). It is truncated in southern direction by the Kruisschans Member, so that it becomes absent in the City of Antwerp area. Further east, in the Grobbendonk outcrop (DOV TO-19970101), the member is thought to be lacking in between the Luchtbal and Kruisschans members (Vandenberghe et al., 2000). Further north in the Campine area, the member seems to have a rather uniform thickness (between 5 to 10 m; Deckers et al., 2019).
Area of occurrence From the Waasland area in the west (Laga, 1971), across the City of Antwerp and Port of Antwerp areas into the western Campine area. It presumably covers the western Campine area up to roughly the SW-NE line between Beerse and Weelde in the east. Here, the transition towards the time-equivalent Poederlee Member is proposed (Louwye et al., 2020).
Type locality De Meuter & Laga (1976) named Oorderen, a former village to the north of the city of Antwerp as type locality. These authors also selected the temporary outcrop of the Boudewijnsluis (DOV kb7d15w-B282) described by De Heinzelin de Braucourt (1955) and where the member occurs between -10.5 and -13.5 m TAW as type section. In the Tunnel Kanaaldok section of Laga (1972) (now named Tijsmanstunnel) (GSB 015W0304; DOV BGD015W0304), the stratotype-section of the Lillo Formation, the member corresponds to the interval between 15 and 21 m depth, translating to -13.5 m TAW to -19.5 m TAW (Figure 58 1). On the nearby CPT (DOV GEO-20/034-S5), the Oorderen Member is characterised by relatively uniform friction ratios (between 1 and 2%) and cone resistance values of on average around 30 MPa. In the Verrebroekdok section of Goolaerts (2000) (DOV TO-19990901), the member outcropped between -5.8 and -11.2 m TAW (fide Deckers et al., 2020; Figure 58 2). Type geophysical borehole is borehole Stabroek (GSB: 015W0216; DOV kb7d15w-B296) with the Oorderen Member from 26 m to 36 m depth (Laga, 1979; Figure 58 3).
Alternative names “Sables à Trophon antiquum”; “Sables à Fusus contrarius”; “Sables à Neptunea contraria”; “Sables de Kallo” (see De Meuter & Laga (1976) and Louwye et al. (2020) for references and more historical details)
Authors Deckers, J., Louwye, S. & Goolaerts, S.
Date 01/09/2023
Cite as Deckers, J., Louwye, S. & Goolaerts, S., 2023. The Oorderen Member, 01/09/2023. National Commission for Stratigraphy Belgium. http://ncs.naturalsciences.be/lithostratigraphy/Oorderen-Member
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