Stratigraphie sequentielle du Dinantien type (Belgique) et correlation avec le Nord de la France (Boulonnais, Avesnois)
(2001) Bulletin de la société géologique de France — Vol. 172, n° 4, p. 411-426 (2001)
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- 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 Viscan 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. Sequence 1 straddles the Devonian-Carboniferous boundary. It starts with a transgressive system tract (TST) corresponding to the Etroeungt Formation (Fm.) and its lateral equivalent (the upper part of the Comb lain-au-Pont Fin.), and to the lower member of the Hastiere Fin. The highstand system tract (HST) is represented by the middle member of the Hastiere Fin. which directly overlies Famennian silicielastics in the northern part of the NSA. Sequence 2 starts abruptly, in the DSA and CSA, with the upper member of the Hastiere Fin. as the TST. The maximum flooding surface (MFS) lies within the shales of the Pont d'Arcole Fin., whereas the thick-bedded crinoidal limestones of the Landelies Fm. form the HST. Sequence 3 can clearly be recognised in the DSA and CSA. Its TST is formed by the Maurenne Fm. and the Yvoir Fm. in the northern part of the DSA and by the Maurenne Fm. and the Bayard Fin. in the southern part of the DSA. The Ourthe Fin. represents the HST. Growth of the Waulsortian mudmounds started during the TST. Sequence 4 shows a significant change of architecture. The TST is represented by the Martinrive Fm. in the CSA and the lower part of the Leffe Fin. in the DSA. The HST is marked by the crinoidal rudstones of the Flemalle Member (Mbr.) and the overlying oolitic limestones of the Avins Mbr. (respectively lower and upper parts of the Longpre Fin.). These latter units prograded far southwards, producing a clinoform profile. Sequence 5 is only present in the DSA and in the Vise sedimentation area (VSA). The TST and the HST form most of the Sovet Fm. and its equivalents to the south, namely, the upper part of the Leffe Fm. and the overlying Molignee Fm. In the VSA, the HST is locally represented by massive grainstones. Sequence 6 filled the topographic irregularities inherited from previous sedimentation. In the CSA, NSA and ASA the TST is formed by the peritidal limestones of the Terwagne Fm. which rests abruptly on the underlying Avins Nibr. (sequence 4) with local karst development. In the DSA, the TST corresponds to the Salet Fin. and, further south, to the black limestones of the strongly diachronous Molignee Fin. Over the whole Namur-Dinant Basin, the sequence ends with the thick-bedded packstones and grainstones of the Neffe Frn. as the HST. Sequence 7 includes the Lives Fm. and the lower part of the Grands-Malades Fm. (Seilles Mbr. and its lateral equivalents), corresponding respectively to the TST and HST. Sequence 8 corresponds to the Bay-Bonnet Mbr. (TST), characterised by stromatolitic limestones. The HST corresponds to the Thon-Samson Mbr. Sequence 9 is the youngest sequence of the Belgian Dinantian in the CSA and DSA. It includes the Poilvache Nibr. (TST, Bonne Fm.) and the Anhee Fm. (HST). These units are composed of shallowing-upward parasequences. The uppermost Visean and basal Namurian are lacking in southern Belgium where sequence 9 is directly capped by Namurian E2 silicielastics. In the VSA, sequence 9 is well developed.
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Hance, L., Poty, E., & Devuyst, F. (2001). Stratigraphie sequentielle du Dinantien type (Belgique) et correlation avec le Nord de la France (Boulonnais, Avesnois). Bulletin de la société géologique de France, 172(4), 411-426. https://doi.org/10.2113/172.4.411 (Original work published 2001)