Stratigraphie sequentielle du Dinantien type (Belgique) et correlation avec le Nord de la France (Boulonnais, Avesnois)

Abstract

The relative influences of local tectonics and global eustasy in the architecture of the sedimentary units of the Namur-Dinant Basin (southern Belgium) are determined. Nine third-order sequences are recognised. During the Lower Tournaisian (Hastarian and lower Ivorian) a homoclinal ramp extended from southern Belgium through southern England (Mendips) and into southern Ireland. From the upper Ivorian to the lower Visean rapid facies changes occurred due to progradation and increasing prominence of Waulsortian mudmounds. Progradation gradually produced a situation in which inner shelf facies covered the Namur (NSA), Condroz (CSA) and southern Avesnes (ASA) sedimentation areas, whereas outer shelf facies were restricted to the Dinant sedimentation area (DSA). During the middle and late Visean a broad shelf was established from western Germany to southern Ireland. Because the shelf built up mainly by aggradation, parasequences can be followed over a large area. An early phase of Variscan shortening is perceptible during the Livian. The stratigraphic gap between the first Namurian sediments (E2 Goniatite Zone) and the underlying Visean varies from place to place, but is more important in the north.

The Kulm Facies of the Montagne Noire (Mississippian, southern France)

“…Hance et al, 2001;Poty et al, 2014). Thus, this sea-level drop opened for a short time the window for carbonate production and deposition, and it could be equivalent to the lowstand system tracts and beginning transgressive system tracts of sequence 5 of Hance et al (2001). Then, the general transgressive trend of the early Viséan time closed the window for carbonate production again.…”

“…Minor facies changes reflect slight differences in the position to sediment sources and small-scale sea-level fluctuations, common at least from the Middle Viséan onwards, as seen in the Belgian platform successions (Hance et al, 2001;Poty et al 2014). During most of the Mississippian, deposition in the areas of the Para-Autochthone and the Faugères-Compartment took place in distal basinal environments.…”

“…The onset of carbonate sedimentation (nodular limestones of the Faugères Fm) in the Mont Peyroux Succession started slightly later, and corresponds to an important sea-level drop just below the Tournaisian/Viséan Boundary, which resulted in a hiatus of the earliest Viséan in the platform successions (e.g. Hance et al, 2001;Poty et al, 2014). Thus, this sea-level drop opened for a short time the window for carbonate production and deposition, and it could be equivalent to the lowstand system tracts and beginning transgressive system tracts of sequence 5 of Hance et al (2001).…”

Upper and uppermost Famennian (Devonian) brachiopods from north-western France (Avesnois) and southern Belgium

“…It was considered by Conil et al (1986) as a lateral equivalent of the mostly Tournaisian-aged Hastière Formation that is well-known in southern Belgium. Hance et al (2001) correlated the Avesnelles Formation with the two first members (α and β) of the Hastière Formation and thus, according to E. Poty (pers. com., October 2015), only its base (the equivalent of the bed 159 of the Hastière Formation in the Anseremme section (see Poty et al, 2014)), could be correlated with the Upper praesulcata Zone.…”

“…The uppermost Famennian succession (see sequential interpretation in Hance et al, 2001) is markedly different from the upper Famennian formations, notably with the occurrence of limestones and that of the first post-Upper Frasnian development of stromatoporoid boundstones within the Comblain-au-Pont and Dolhain formations (e.g. Conil et al, 1964;Aretz & Chevalier, 2007).…”