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The name refers to the municipality of Terhagen (at present part of the municipality of Rumst; Antwerp province) in the Rupel area.

General characteristics

The Terhagen Member is the middle part of the Boom Clay in the outcrop area. The base of clay layer 5 (sensu Vandenberghe, 1978) forms the basis of the Terhagen Member. The Member consists of pale grey clay, it is the least silty part of the Boom Clay Formation and it only contains two outspoken black organic rich layers. In its lower part it is calcareous but its upper part, starting with the R-bed is free of carbonates and it displays a pink to brownish hue.The boundary with the overlying Putte Member is situated between the layers 31 and 32 (sensu Vandenberghe, 1978). Its thickness in the outcrop area is about 20 m.


The Terhagen Member occurs everywhere in the outcrop area above the Belsele-Waas Member. In the Leuven area, where the latter Members is absent the Terhagen Member overlies the Berg Sand. The Terhagen Member is overlain by the Putte Member.

In East-Limburg the lower part of the Boom Clay overlying the Kerniel Sand (Van-denberghe et al., 2001) ( Fig. 1).


The lower part of the active clay exploitation front along the cuesta between Rumst and Boom (VANDENBERGHE, 1978, photo 2, p. 25) ; map sheet 23/3-4 (Boom-Mechelen).

Coordinates: X = 154.000; Y = 197.500; Z = + 30 m.

Previous designations

Geological map 1/40.000: R2c p.p.

Stratigraphical Register (1929, 1932): R2b p.p.

New Geological Map 1/50.000: BmTe

A twofold subdivision of the Boom Clay in a lower grey clay and an upper black clay, respectively named Waasland Clay and Putte Clay, was proposed earlier by VAN-DENBERGHE (1974, fig. 8.1. and p. 186; 1978). The present name of Terhagen Member replaces the Waasland clay in which originally also the Belsele-Waas Mem-ber was included.