5 research outputs found
Early Palaeozoic orogenic events north of the Rheic suture (Brabant, Ardenne): a review
Get PDFThe Lower Palaeozoic rocks exposed in the Brabant-Ardenne region (Belgium, France) recorded the Early Palaeozoic history on the southern margin of the perigondwanan microcontinent of Avalonia, north of the Rheic suture. These rocks crop out in the Brabant basement and in the Ardenne basement inliers within the Variscan Ardenne allochthon. The two main unconformities are classically associated with distinct orogenic episodes, the Late Ordovician "Ardennian" event and the Early Devonian "Brabantian" event. A review of the current state-of-knowledge with respect to the reconstruction of Early Palaeozoic geodynamics in the Brabant-Ardenne region is presented. It is demonstrated that an unconformity does not necessarily represent an orogenic event, and that the hiatus related to an unconformity does not necessarily coincide with tectonic activity, especially when tectonism is diachronous in nature. The former applies to the Ardennian unconformity, while the latter applies to the Brabantian unconformity. Finally, the well-constrained Brabantian orogeny, as well as the Ardenne-Eifel basin development, is tentatively framed within the Early Palaeozoic geodynamic context of the northern margin of the Rheic realm. By doing so, it is shown that the Brabant-Ardenne region links, both in space and time, the Rheic and Rhenohercynian ocean. © 2008 Académie des sciences.sponsorship: [
"This research is sponsored by the Fonds voor Wetenschappelijk Onderzoek - Vlaanderen (FWO - Vlaanderen). The work is part of the research projects 6.0271.05 and KAN1.5.128.05. Manuel Sintubin is Research Professor of the Bijzonder Onderzoeksfonds at the K.U.Leuven. Timothy N. Debacker is Postdoctoral Fellow of the FWO - Vlaanderen. Herve Van Baelen is Research Assistant of the Institute for Promotion of Innovation through Science and Technology (IWT - Vlaanderen). Jacques Verniers is thanked to provide a photograph of the Fepin outcrop.",
"Brian Windley and Stanislaw Mazur are greatly acknowledged for their comments. Karel Schulmann, Jean-Marc Lardeaux and Richard Scriveners are thanked to edit this special issue of the Comptes Rendus Geoscience."
] (Fonds voor Wetenschappelijk Onderzoek - Vlaanderen (FWO - Vlaanderen), 6.0271.05, KAN1.5.128.05)status: Publishe
A new geological map of the outcrop areas of the Brabant Massif (Belgium)
No full textAs a result of the “new geological map of Wallonia” program undertaken by the Walloon Government since 1990, all the maps at 1/25 000 scale covering the outcrop areas of the Brabant Massif have been finalised. During the long period of mapping (1993-2017) our understanding of the stratigraphy and tectonics of the Brabant Massif has evolved significantly and this led to several inconsistencies between different maps. We present here an overarching geological map of the outcrop areas of the Brabant Massif, resulting from the merging of these 21 maps, updated according to the most recent findings and insights. The resulting map, at a scale of ~1/200 000, shows a coherent image of the outcrop areas of the Brabant Massif. This map better illustrates the geological history and structural architecture of the Brabant Massif compared to previous maps (e.g. Fourmarier, 1921; Legrand, 1968) and allows for a better understanding of the geology of the Brabant Massif. Also, it fully complements the subcrop map of the Brabant Massif of Piessens et al. (2005, in prep.).SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Révision stratigraphique du sondage de Lessines (Massif du Brabant, Belgique)
No full textIn this short communication we provide an overview of the new and recently published data on the Lessines borehole since its original description in 1991 and integrate these into the new stratigraphy and the current ideas on the evolution and structure of the Brabant Massif. Although these data are mainly of a stratigraphical kind, they have considerable implications for the overall basin evolution. Unit I belongs to the middle Katian (uppermost Caradocian to lower Ashgillian) Fauquez Formation and Unit II belongs to the upper Sandbian to the lowest Katian (middle Caradocian) Ittre Formation. A previously non-identified, probably normal fault separates both units. As initially proposed, Unit III clearly belongs to the lower Tremadocian Chevlipont Formation. A fault breccia, also probably belonging to a normal fault, separates units II and III. Unit IV corresponds to the Asquempont Member of the Early to lower Middle Cambrian Oisquercq Formation. A pre-cleavage fault breccia, initially interpreted as a microconglomerate, separates units III and IV. This fault, responsible for the removal of at least 4500 m of sediments is interpreted as a low-angle extensional detachment belonging to the Asquempont Detachment System.SCOPUS: re.jinfo:eu-repo/semantics/publishe
Sedimentological thickness variations within Silurian mudstone-dominated turbidite deposits and the effects on cleavage fanning (Anglo-Brabant Deformation Belt, Belgium)
No full textThe effect of vertical changes in lithology on cleavage refraction and cleavage fanning is relatively well understood. In contrast, the control that lateral changes in bed thickness and related multilayer characteristics have on cleavage fanning has not been widely documented. Mudstone-dominated Wenlock-age turbidites of the Anglo-Brabant Deformation Belt, Belgium, exhibit pronounced lateral thickness changes, which we attribute to intraslope flow ponding during foreland basin development. The mudstone-dominated nature of the turbidites is considered to reflect a particularly fine-grained source area, rather than a distal origin. Formation boundaries and lateral changes in lithofacies unit thickness are reflected in the amount of cleavage fanning. The degree of convergent cleavage fanning increases with an increase in thickness of the less competent units and with a decrease in thickness and number of the more competent units. As such, a detailed analysis of changes in cleavage-bedding angle aids in the distinction of different lithostratigraphic units of similar appearance, the location of their boundaries and identification of subtle lateral sedimentological changes. The utilization of cleavage and bedding data to recognize and describe vertical and lateral changes in a semi-quantitative way allows the linkage of subtle changes in multilayer rheology to finite strain trajectories
The Cambrian to mid Devonian basin development and deformation history of Eastern Avalonia, east of the Midlands Microcraton: new data and a review.
No full textA review is given of recently published and new data on Avalonia east of the Midlands Microcraton. The three megasequences from Cambrian to mid Devonian described in Wales and Welsh Borderland are also present east of the Midlands Microcraton (Brabant Massif, Condroz, Ardennes, Remscheid and Ebbe inliers, Krefeld high). The three mega-sequences are caused by a tectonic driving mechanism and are explained by three different geodynamic contexts: an earlier phase with extensional basins or rifting and rather thick sequences, when Avalonia was still attached to Gondwana; a second phase with a shelf basin with moderately thin sequences when Avalonia was a separate continent and a later phase with a shelf or foreland basin development and thick sequences. Deformation of the megasequences 1 and 2 or 1 to 3 varies between areas. In Wales and the Lake District the Acadian phase is long-lived and active from early to mid Devonian. In the Ardennes inliers a deformation is active between the late Ordovician and the Silurian (Ardennian Phase), with a similar intensity as the core of the Brabant Massif, when present erosion levels are compared. The Brabant Massif is partly deformed by the long-lived Brabantian Phase from late Silurian till early mid Devonian. Both the Ardennes inliers and the Brabant Massif are not classic orogenic belts, only slate belts where no more than the epizone is reached at present erosion levels. Areas supposedly close to the microcraton or basement are nearly undeformed (SW Brabant Massif and central Condroz). A model of anticlockwise rotation of Avalonia of about 55° from Caradoc to Emsian is proposed to explain the deposition setting of megasequence 3 and the subsequent Acadian and Brabantian deformation. Immediately after the Avalonian microcontinent touched Baltica in Caradoc times it created a short-lived subduction magmatic event from The Wash to the Brabant Massif and soon after the magmatism ended a foreland basin developed. Possibly during and after that development a long-lived and slow compressional event occurred, leading to the deformation of the Anglo-Brabant Deformation Belt. In the early Devonian, contemporaneous with the shortening of the Anglo-Brabant Deformation Belt, extension occurred in the Rheno-Hercynian Zone, possibly caused by the same slow rotation of Avalonia. More evidence emerges that Avalonia cast of the Midlands Microcraton comprises not one but probably two terranes: the remnant of the palaeocontinent Avalonia, and what is called the palaeocontinent Far Eastern Avalonia; the latter is only occasionally observed in the few deep boreholes into the Heligoland-Pomerania Deformation Belt, in southern Denmark, NE Germany and NW Poland, with scant available indirect data in between indicating only Proterozoic basement and no Caledonian deformation. For Far Eastern Avalonia a similar palaeogeographical history is postulated as Avalonia, with rifting from Gondwana in Arenig or earlier times, collision with Baltica before the mid-Ashgill and deformation between the late Ordovician and latest Silurian. The Avalonia concept might need to be expanded to an 'Avalonian Terrane Assemblage' with cratonic cores and small short-lived oceans as in the Armorican Terrane Assemblage.SCOPUS: ar.kinfo:eu-repo/semantics/publishe
