2.2.8. Trois Fontaines Formation - TRF
Authors: Gosselet, 1876; Bonte & Ricour, 1949; Errera, Mamet & Sartenaer, 1972; Preat & Tourneur, 1991b.
Description: The lowest part, only a few meters thick consists of bedded argillaceous crinoidal limestones. The overlaying part consists of thick biostromal beds with locally coquinoid beds with stringocephalids. The major, upper part of the formation, consists of micritic, occasionally laminated limestones.
Stratotype: Quarry at Les Trois Fontaines on the north-west bank of the Meuse, about 1.5 km south-west of Givet.
Area: Southern and south-eastern flank of the Dinant Synclinorium, west of the Xhoris Fault.
Thickness: In the Couvin-Givet area the thickness is about 80m and about 100m between Wellin and Resteigne. From Hotton on the thickness decreases in north-eastern direction.
Age: Early Givetian. Based on conodont data, the base of the Trois Fontaines Fm is a few dozens of meters above te Eifelian-Givetian boundary and belongs entirely to the hemiansatus Zone (Bultynck, 1987).
Remarks: On the south-eastern flank of the Dinant Synclinorium, west of the Xhoris Fault, there is an increasing influx, of terrigeneous material.