Proposals and discussions
New formation
Hemptinne Formation (meeting 06/2016)
Description : The formation comprises pluridecimetre-thick bedded, pale to white, limestones of peritidal facies. They are lime mudstones with fenestrae, stromatolitic boundstones, peloidal and oolitic grainstones. There are typically numerous levels of pluricentimetre oncolites. Fossils are uncommon. The formation ressembles the Terwagne Formation, but is very pale while the other is very dark, and it is devoid of silica and argillaceous layers, except for an argillaceous layer in its upper part (cinerite M). Therefore the Hemptinne limestone is very pure and was often confounded with the overlying Neffe Formation and with the underlying Avins Member of the Longpré Formation.
Stratotype : The section in the eastern bank of the small valley of the Hubièssau rivulet, between Robièpont and the Ferme de la Bataille, 500 m northwest of Hemptinne, 4 km north of Philippeville, Dinant sedimentation area (DSA).
Area : northern and southern borders of the DSA. The formation marks the transition between the Salet Formation of the DSA and the Terwagne Formation of the Condroz sedimentation area (CSA) and of the Southern Avesnois sedimentation area (ASA).
Thickness : about 80 m in the type section. In fact, because the formation has a pale colour and some oolitic facies similar to those of the Avins Mbr and the Neffe Fm, its boundaries are usually not easy to recognize.
Age : Moliniacian (early Viséan), MFZ11 Mississippian Foraminifer Zone. The cinerite M is present in its upper part, as in the Terwagne Formation. Until now, no corals were found in it. The formation corresponds to the transgressive systeme tract of the Dinantian third-order sequence 6.
Changes in the lithostratigraphy
Ourthe Fm : Thickness : About 35 m in the type area, 20 m in the Hoyoux valley.
Martinrive Fm : There was a mistake in the description of the lithology : « Most of the formation consists of dark limestones (mudstones to wackestones)… » (and not « packstones to wackestones »)
Accepted
Dinantian in the Campine Basin; date : 25/01/2013; by : VITO - David Lagrou; accepted 10/06/2014