The combined use of newly interpreted well data and reprocessed 2D seismic data provides new insights in the Early to Middle Paleocene tectonic evolution of the south-eastern part of the Campine Basin. A late Danian fundamental change in the intra-plate stress-field of Europe changed the deformation style in several southern North Sea basins, including the Campine Basin and neighboring Roer Valley Graben. In the south-eastern part of the Campine Basin, this stress change ended an early to middle Danian tectonic quiet phase with calcarenite deposition and started a late Danian to middle Selandian phase of differential subsidence and restricted deposition of continental to shallow marine siliciclastics. Onlap patterns and associated thickness variations in the siliciclastics indicate that the south-eastern part of the Campine Basin experienced flexural subsidence in the direction of the downthrown Roer Valley Graben. Simultaneously, in the footwall to the Roer Valley Graben border fault system, the Bree Uplift was deformed by subtle (re)activation of faults, possibly in strike-slip mode. After the middle Selandian, former dynamics diminished throughout the region.
Research conducted since the 1960s on the upper Miocene Diest Formation in NE Belgium is reviewed and integrated. Their lithology unites the deposits of the glauconiferous Diest Sand in one formation, though biozones and internal sedimentary structures strongly suggest the formation may agglomerate the deposits of two separate, successive sedimentary cycles. The lowermost cycle is thought to have deposited the "Hageland Diest sand" during the early or middle Tortonian. It contains the Diest Sand in the main outcrop area in Hageland, Zuiderkempen and central Limburg, and probably also the Deurne Member near the city of Antwerpen. It furthermore includes the lower part of the Dessel Member in the central Kempen and in the Belgian part of the Roer Valley Graben (RVG). The Hageland Diest cycle represents the infill of a large tidal inlet tributary to the southern North Sea bight, then situated over the southern Netherlands and the Lower Rhine embayment. The Hageland Diest sand has the composition of a marine deposit, yet the confined area of occurrence and the presence of tens of metres deep incisions at the base, set it apart. The confinement of the embayment, strong tides and a steady supply of coastal‐marine sand are invoked as the main driving forces that resulted in the distinctive geometry and internal architecture of the unit. The upper cycle is associated with the "Kempen Diest sand", which is found in the subsurface of the RVG and the Noorderkempen. It has a late Tortonian to earliest Messinian age with progressively younger ages occurring to the NW. It encompasses the upper part of the Dessel Member and the overlying, coarser Diest Sand, and correlates to most or all of the thickly developed Diessen Formation in The Netherlands. It is the deposit of a prograding marine delta, containing both marine components and continental components fed by the palaeo‐Meuse/Rhine river mouths. Accommodation space kept increasing during deposition, due to subsidence of the deposition area, especially inside the RVG but also in the Noorderkempen. Although there is a fair consensus on the above, many concrete points about the geometry and depositional history of the Diest Formation and even a definitive decision on its single or dual character remain to be sorted out. In addition, this review excludes the Flemish Hills sand and the Gruitrode Member from the Diest Formation.
Abstract The late Maastrichtian to Late Paleocene seismostratigraphic record of the Roer Valley Graben provides new data on the timing and dynamics of stress changes related to the intra-plate deformation of northwestern Europe. During the deposition of late Maastrichtian to middle Danian limestones, no severe tectonic movements occurred in the southern part of the Roer Valley Graben. Around the late Danian, a known fundamental change in the European intra-plate stress field initiated an increase in subsidence of the southern part of the Roer Valley Graben. Subsidence along the graben border zone enabled relatively thick accumulations of the latest Danian to mid-Selandian siliciclastics in the intra-graben zone. Subsidence was not bounded by large offsets along faults, but rather by flexuring within and along the borders of the Roer Valley Graben. The intensity of these dynamics diminished after the middle Selandian. Most likely due to inherited intra-basinal structural differences, the northern and southern part of the Roer Valley Graben experienced distinctly different late Maastrichtian to Late Paleocene tectonics.
The present geological map of the Flemish Region shows a small lens-shaped isolated outcrop of the Miocene Bolderberg, Diest and Kasterlee Formations, surrounded by younger formations, in an area that coincides with the tectonic Bree Uplift segment, on the southwestern border of the Roer Valley Graben in NE Limburg. The fault, bordering the segment at its SW side, had been interpreted to be tectonically active throughout the Neogene. Now, it is argued that an erroneous lithostratigraphic interpretation of the outcropping strata supported that view. Field observations of some of the outcrops and sampled drill holes show that the sediments do not belong to an Opitter member of the Bolderberg Formation, a Gruitrode Mill member of the Diest Formation and a Dorperberg member of the Kasterlee Formation, but most probably to the lower, latest Miocene or early Pliocene part of the Mol Formation and an unknown Pliocene marginal marine deposit not unlike and at about the stratigraphic position of the Poederlee Formation. That glauconiferous sand deposit, which has always been interpreted as consisting of two successive sedimentary cycles, is now accommodated in a single cycle, using the sedimentary model of deposition in a confined, backbarrier tidal basin subject to marine sand input and local stages of flow constriction and intraformational incision. Like already proposed by Rossa (1986) and Demyttenaere (1989), reprocessed seismic sections show only minor movements along the southwestern fault of the Bree Uplift since the Paleocene, and no inverse tectonic movements at all since the Middle Miocene.
Abstract During the middle Paleocene Laramide phase, several basins in Europe experienced subsidence, while others experienced uplift. Previous studies have shown that during the Laramide phase some basins surrounding the Brabant Massif experienced subsidence into shallow depocentres. This study discusses how the Brabant Massif simultaneously experienced uplift along its WNW–ESE Caledonian structural axis from central Belgium in the east up to the southeast coast of England (Ipswich) in the west. Uplift resulted in erosion of the formerly deposited Chalk Group on top of the axis of the Brabant Massif. The erosion products of the Chalk Group were reworked in the latest Danian to earliest Thanetian deposits that filled the surrounding depocentres. Early to middle Thanetian pulsed marine transgressions caused flooding and deposition across the entire region, including the previously uplifted axis of the Brabant Massif. The depositional thicknesses, however, indicate that the axis of the Brabant Massif remained a relative high up to the middle Thanetian. Both the geometry and timing of the middle Paleocene vertical surface movements of the Brabant Massif and surrounding areas are very similar to those described for other structural entities in central and northern Europe, despite their often strongly differing Mesozoic tectonic evolutions. We discuss several mechanisms that might have triggered these vertical surface movements, of which lithospheric folding seems the most likely.
1. IntroductionSeveral cored boreholes have recently been drilled in strategic areas in order to generate and update the geological maps of Belgium. Most of these wells were designed to elucidate regional stratigraphic problems. The Zemst borehole (BGD 73E359; x = 155.444, y = 187.591; GPS-coordinates 50°59’54.52”N, 4°26’46.50”E; Fig. 1) was executed in 2001 to evaluate the presence of the P1n clay in the area between Aalst and Mechelen. This P1n clay, which figures on the old geological maps of Belgium (Anonymous, 1893; Fig. 2), was introduced by Rutot (1890) as part of the Paniselian Stage (now upper part of Ypresian Stage; Steurbaut, 2006a,b) and termed P1(d) or the grey plastic clay (“argile grise plastique”), positioned in between the sandstone bearing P1d sands (“lower Paniselian”) and the overlying Aalter Sands (P2 or “upper Paniselian”). It clearly postdates the P1m clay (Anonymous, 1893), before known as the basal grey plastic clay (“argile grise plastique schistoide de base”) or P1(a) (Rutot, 1890; Fig. 2), and today as Merelbeke Clay.Figure 1. Location of the Zemst borehole and additional borehole and outcrop sections mentioned in the text.Figure 2. Subdivision of the obsolete Paniselian Stage, used until the mid-1950 (e.g. Gulinck & Hacquaert, 1954) (grey shading = not identified).The present study aims at elucidating the stratigraphy of the upper Ypresian and the lower Lutetian in the Zemst area (Fig. 3), with special attention to the Ypresian-Lutetian transition
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