Shelly sand with a clayey admixture in the central part and with several distinct shell layers. The colour is grey, grey-brown to light grey-brown. A gradual decrease of the clay and shells occurs in the upper part of the formation. Locally, the uppermost part can be decalcified. Glauconite content is fairly constant and varies between 6 and 12% with locally some higher content up to 20% in the basal part (Luchtbal Member; Laga, 1972). The formation was subdivided by De Meuter & Laga (1976), from base to top, into the Luchtbal Member, the Oorderen Member, the Kruisschans Member, the Merksem Member and the Zandvliet Member. Now, the Poederlee Member (former formation) and the Broechem Bed (new) are also included in the Lillo Formation. De Meuter & Laga (1976) stressed the fact that whereas only the lower Luchtbal Member has distinct boundaries, a gradual change is observed between all other members.
Age
Early to Late Pliocene. See Louwye et al. (2020) and references therein.
Thickness
Maximum around 30 m (Deckers et al., 2019).
Area of occurrence
From the Waasland area in the west, across the City of Antwerp and Port of Antwerp areas into the western Campine area. East of the city of Turnhout, it transitions into the time equivalent white sands of the Mol Formation.
Type locality
The type locality is to the north of the city of Antwerp in the Lillo district, where the former eponymous village disappeared during the construction works of two docks. The type section was visible in a temporary outcrop during the digging of the Tunnel Kanaaldok, later called the Tijsmanstunnel (GSB 015W0304; DOV BGD015W0304), at between 3 m and 23.5 m depth (Fig. 1). This section can be correlated to the nearby type CPT (DOV GEO-20/034-S5) which shows high cone resistance (20-40 MPa) and low friction ratio (1%) at the sandy units and low cone resistance (10 MPa) and higher friction ratio (> 2%) at the clayey central unit of the Lillo Formation. Type geophysical borehole is borehole Stabroek (GSB: 015W0216; DOV kb7d15w-B296) with the Lillo Formation between 4 to 36 m depth (modified after Laga, 1979; Fig. 2).
Alternative names
Authors
Deckers, J., Louwye, S. & Goolaerts, S.
Date
01/09/2023
Cite as
Deckers, J., Louwye, S. & Goolaerts, S., 2023. The Lillo Formation, 01/09/2023. National Commission for Stratigraphy Belgium. http://ncs.naturalsciences.be/lithostratigraphy/Lillo-Formation
