Tongeren Formation

NMTO

Formal (Kuyl 1975).

From bottom to top three successions can be distinguished: 

• Sand, very fine to moderately coarse (105-300 µm), weakly to moderately silty, predominantly glauconite-bearing, sometimes containing mica. Green grey to grey green;
• Clay, slightly, moderately to strongly sandy, glauconite and mica-bearing. Dark green to grey;
• Clay with shells and with thin intercalations of very fine sand (105-150 µm) and lignites at the top. Grey to green grey.

Shallow-marine environment (sands), and lagoonal to coastal-plain environment (clays).

Unconformably overlies the Dongen Formation or older deposits.

Sharp, when the top contains a layer of flat and rounded flint pebbles. Sharp, when overlain by fluvial sands and gravels or aeolian sediments of the Upper North Sea Group, but gradual when these consist of the sands and clays of the Walcheren Member (Naaldwijk Formation) in Zeeland. Sharp, when overlain by the clays of the Boom Member. Gradual when the overlying unit consists of the sands and clays of the Rupel Formation.

Up to 125 m, thickness increases in a northwesterly direction.

Restricted to the southern part of the province of Limburg and the southern part of the province of Zeeland.

UK: Solent Group; GER: Tongeren Formation; BEL: classified as the Sint Huibrechts-Hern Formation and the Borgloon Formation (Marechal & Laga 1988).

Priabonian - early Rupelian.

Named after the Belgian town of Tongeren.

Dumont (1839) introduced the name Tongerian for equivalent deposits in Belgium. The Kallo complex and Berg Sands. The Vessem Member in the southwestern part of the Netherlands.

Dirk Munsterman (2018).

Dumont, A. 1839. Rapport sur les travaux de la carte Géologique pendant l'année 1839. Bulletins de l'Académie royale des sciences, des lettres et des beaux-arts de Belgique (1), 6, 2e partie, 464-485.

Kuyl, O.S. 1975. Lithostratigrafie van de Mio-Oligocene afzettingen in Zuid-Limburg. In: Zagwijn, W.H., Van Staalduinen, C.J. (eds.), Toelichting bij geologische overzichtskaarten van Nederland. Rijks Geologische Dienst, Haarlem, 56-63.

Maréchal, R., Laga, P. (eds.) 1988. Voorstel lithostratigrafische indeling van het Paleogeen - Nationale Commissies voor Stratigrafie. Commissie: Tertiair, Belgische Geologische Dienst, Brussel, 208 p.