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2.8.2. Brussel Formation - Br

Authors: Dumont (1839), Houthuys & Fobe (1988).

Description: this rather heterogeneous formation consists of an alternation of strongly and poorly calcareous sets. The non calcareous sands (silica facies) are homogeneous or crossbedded with thin clay layers. They show a lot of silicified borings, spherical or platy concretions. Locally silicified marl layers may occur. The calcareous facies consists of finer sands. Subhorizontal laminations are frequently disturbed by bioturbation. Limestone layers occur frequently, together with silicified concretions. The formation has been deposited in a marine environment with strong tidal currents. The calcareous sands were deposited in quiet, protected areas.

Stratotype: a lectostratotype is defined in Jodoigne (Zétrud - Lumay area). Sheet 32/7-8 (Meldert - Tienen). Co-ordinates: x = 185.375, y = 161.2, z = +90 m.

Area: Brabant and the north of Hainaut and Namur. The most important outcrops are between the Zenne and the Gete Valleys.

Thickness: 20 to 40 m, exceptionally 70 m.

Members: the formation is subdivided into the Archennes Mbr, the Bois de la Hous-sière Mbr, the Chaumont - Gistoux Mbr, the Diegem Mbr and the Neerijse Mbr.

Age: Early Lutetian.

Remarks: see Lede Fm.