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It is revealed that the lowest 1010 m of the Saint-Ghislain borehole (-4393 to -5403 m), of which cuttings are available, constitutes a crucial source of information to investigate, amongst others, the deep geothermal potential within the Brabant Parautochthon, underlying the Mons Basin, Hainaut. The lithological succession of this interval was reconstructed based mainly on visual analysis and calcimetry of 852 cutting samples as well as four cored sections. Additionally, palynological, magnetic susceptibility and X-ray diffraction analyses were conducted in order to complement the dataset. The lower section of the investigated borehole sequence mainly consists of grey calcareous shale while the middle section is dominated by blue-grey shaly limestone and the upper section is mainly composed of green shale. Palynomorphs found at -5261 m suggest a latest Givetian-Early Frasnian age. A new lithostratigraphical interpretation of the deepest part of the Saint-Ghislain borehole is proposed. The lower calcareous shale from -5403 to -5100 m is interpreted as the Bovesse Formation (Lower Frasnian) and at its base possibly uppermost Givetian. The overlying limestones from -5100 to -4790 m can be attributed to the Rhisnes Formation (Upper Frasnian), and the green shale between ca. -4393 and -4790 m, to the Bois de la Rocq Member (Famennian). These results open new insights regarding the geological interpretation of the basement underlying the Mons Basin. They also present a promising approach and example regarding interpretations based on cuttings. [ABSTRACT FROM AUTHOR]

The Mons Basin (Province of Hainaut, western Belgium) is a geologically rich region, particularly from the point of view of Upper Cretaceous sedimentary deposits, conducive to an important flint gathering activity during the whole regional Prehistory. Focusing on the Neolithic period, indications of flint procurement as early as the end of the 6th millennium have been recorded, but there are concrete evidences of mining sites in the region since the second half of the 5th millennium. Flint extraction activities have lasted at least until the second half of the 3rd millennium. According to literature and recent researches, eleven sites could be extraction sites, including the World Heritage site of Spiennes. This paper critically assesses the accuracy of the data available and focuses on the issue of the unequal function of these extraction sites and their socio-economic function for Neolithic communities. Is it really possible to establish a hierarchy between the extraction sites? Can different acquisition-production strategies be highlighted? These questions are dealt with by synthesizing the data concerning the methods of flint exploitation in the Mons Basin, the qualitative and quantitative characteristics of the products relative to the production intentions but also by addressing the issue of their importance in exchange networks.

The geothermal reservoir of Hainaut mainly consists in a fissured and karstic carbonate aquifer. It is composed of thick Lower Carboniferous limestone and dolostone formations with an E-W direction and a 10-15° south dip. In the Saint-Ghislain area, several layers of massive anhydrite are interbedded in the Upper and Middle Visean carbonate. Coeval formations in other areas consist of a collapse breccia suggesting that the entire anhydrite/carbonate sequence has been subjected to karstification. The existence of a deep karst in the Visean of Hainaut is supported by several indications, as, for example, the occurrence of abundant karstic pipes observed in the whole Upper Carboniferous formations. The overlying Mons Basin is also thought to be (at least partly) the result of karstic subsidence in the Visean basement. Anomalies in temperature and/or chemical and isotopic signatures in springs and water catchment wells of the Dinantian outcrop suggest moderate uprising flow of geothermal deep groundwater and mixing with shallow groundwater. Flow and heat transfers have been simulated using simplified models. Results corroborate the existence of large thermal-induced convection loops within the Dinantian reservoir. Karst development in the deep Lower Carboniferous strata of Hainaut is related to an increase of permeability due to tectonic activity that initiated at least at the end of Jurassic, that allowed the initiation of thermal convection. This time estimation is consolidated by sedimentologic data on Cretaceous deposits in the Mons Basin. [ABSTRACT FROM AUTHOR]

A set of 11 abstracts and short papers (extended abstracts) of presentations given at a meeting organized by the "Groupe Français du Crétacé (GFC)", held on November 27-28, 2007 at the "École des Mines" in Paris, France. These contributions are available only in English or in French. 1- Les bioévénements de la limite Albien (Vraconnien) - Cénomanien aux marges nord et sud de la Téthys (S.E. de la France et Tunisie centrale) - Bioevents at the Albian (Vraconnian) - Cenomanian boundary at the North and South margins of the Tethyan Ocean (SE France and Central Tunisia) 2- Échanges et colonisations fauniques (Ammonitina) entre Téthys et Atlantique sud au Crétacé supérieur : voies atlantiques ou sahariennes ? - Late Cretaceous faunal exchange and colonization (Ammonitina) between the Tethys and the South Atlantic: Atlantic or Saharan routes? 3- Phosphorus and trace-metal records during Cretaceous oceanic anoxic events: Example of the Early Aptian OAE in the western Tethys - Évolution de la concentration du phosphore et des métaux-traces durant les événements anoxiques du Crétacé inférieur : exemple de l'événement de l'Aptien inférieur (OAE 1a) dans la Téthys occidentale 4- L'évolution tectono-sédimentaire du système "Golfe de Gascogne-Pyrénées Occidentales" au Crétacé inférieur : un nouveau regard - The tectonic and sedimentary evolution of the Bay of Biscay-Western Pyrenees during the Early Cretaceous : a new point of view 5- The marine squamates (reptiles) from the Cenomanian-Turonian of the Tethys: a noteworthy radiation - Les squamates (reptiles) marins du Cénomanien-Turonien de la Téthys : une radiation remarquable 6- Influences boréales dans le bassin de Mons (Belgique) à l'Albien - Boreal influences in the Mons basin (Belgium) during the Albian 7- On the track of a major trans-Tethyan discontinuity - Sur la piste d'une discontinuité majeure trans-Téthys 8- The Cretaceous of Lebanon in the Middle East (Levant) context - Le Crétacé du Liban dans le cadre du Moyen-Orient (Levant) 9- Le Cénomanien-Turonien de l'Atlas saharien (Algérie) 10- Endémisme et cosmopolitisme des faunes d'ammonites de la plaque arabique au Cr&#233 ;tacé moyen (Aptien - Turonien) - Endemism vs. cosmopolitanism of the ammonite faunas from the Arabian plate during mid-Cretaceous times (Aptian – Turonian 11- La discontinuité albienne à l'échelle globale et ses implications paléobiogéographiques et biostratigraphiques - The Albian unconformity at a global scale and its palaeobiogeographic and biostratigraphic implications

Abstract: Pedogenic nodules, calcitic shells, dispersed organic carbon and bulk rocks affected by low diagenesis are judged to be reliable tools for carbon-isotope chemostratigraphy. Up to now no systematic study has been carried out to check the reliability of fossil wood material for carbon-isotope chemostratigraphy in terrestrial settings. The 235-m thick Wealden facies sediments of the Danube-Bouchon quarry at Hautrage (Hautrage Clays Formation, Mons Basin, Belgium) encompass dark to grey clays and sands, rich in organic matter and coalified–charcoalified fragments of fossil wood, deposited in an alluvial plain during middle Barremian to earliest Aptian. We measured and compared the carbon-isotope ratios of 110 levels of the stratigraphic succession for dispersed organic carbon (δ 13CDOC), and fossil wood (δ 13CWOOD) collected in the same geological level. In the whole succession, the averages of δ 13CDOC and δ 13CWOOD have a significant difference of about 0.9‰. The δ 13CWOOD is usually heavier than the δ 13CDOC, which is consistent with measurements on different constituents of modern trees (branches versus leaves and tissues). In one single stratigraphic level, the variability of δ 13CWOOD is much higher (up to 7.3‰) than that of δ 13CDOC (0.4‰). Four main causes may explain these results. Firstly, the δ 13CDOC averages the isotopic signal of different compounds and tissues (such as leaves, seeds, cuticles) as they become mixed and dispersed. The δ 13CWOOD reflects the carbon-isotope ratio of a small part only of one single tree, which is a complex system with δ 13C variations over a range of 4‰. Secondly, there is strong δ 13C variability between different species of plants. In Hautrage, several gymnosperm genera were collected (including Podocarpoxylon, Taxodioxylon, Brachyoxylon, and Thujoxylon) and numerous fern taxa. Thirdly, coalification and charcoalification can affect the δ 13C of the DOC and the various kinds of woods in a different way. Fourthly, the wood fragments may be reworked several times from more ancient geological levels, especially in the alluvial plain environment of Hautrage where thick levels of fluviatile coarse sand deposits are observed. However, in the whole succession, both δ 13CWOOD and δ 13CDOC curves show similar trends. This suggests that carbon-isotope curves on fossil wood can be matched to carbon-isotope curves on DOC. For the whole trend fossil wood is a relatively good chemostratigraphic tool when sufficient samples are measured in the succession. Whenever possible both control of the wood taxa, and estimation of degree of (char)coalification are however recommended. In one single level, charcoal has more stable δ 13CWOOD values than δ 13CWOOD of coalified fragments. The δ 13C positive trend can be due to several causes, including global pCO2 variations and/or regional changes and/or local environmental conditions in the alluvial plain. If global, the dating of the Hautrage succession may be refined to the late Early Barremian–early Late Barremian by matching palynological and carbon-isotope chemostratigraphical data. [Copyright &y& Elsevier]

Abstract: A detailed study of normal faults in the calcarenites and chalks of the Mons Basin reveals that pressure-solution processes play a significant role in fault zones, which affects the determination of the amounts of extension. Drag folding associated with normal simple shear and rock dissolution concurred to produce layer flexuring in the hanging wall of the normal faults, whereas the footwall remained almost intact. Analysing the distribution of fossil belemnite rostra in and away from fault zones enabled us to evaluate these effects. The sense and amount of belemnite tilt constrain the minimum thickness of dissolved hanging wall fringe, revealing significant pressure-solution in addition to drag folding. We developed 2-D and 3-D analytical models of along-fault belemnite rotations induced by drag folding and dissolution, and we applied these models to our data from the Mons Basin. The results show that the pressure-solution effect is significant, implying a smaller ratio between horizontal and vertical components of motion than expected. It follows that the across-fault amount of extension is smaller than that predicted from the single fault geometry, suggesting that although the existence of Campanian–Maastrichtian–Danian extension in the Mons Basin area is beyond doubt, its amplitude should not be overestimated. [Copyright &y& Elsevier]

Abstract: In the Mons basin (Belgium), the long-term trend of both δ 13C and Sr/Ca reflects stable high and then falling relative sea levels in the Boreal realm through the Campanian. The transition between the stable high and the falling sea levels coincides with the Early Campanian–Late Campanian boundary. Two short-term sea-level changes were also recognised: a major transgressive period at the Early Campanian–Late Campanian boundary associated with an important hydrothermal activity of sub-marine ridges and a regressive period at the mid-Late Campanian characterised by a negative shift in the δ 13C profile. The transgressive period at the Early Campanian–Late Campanian boundary is marked by a positive Mn anomaly, a negative anomaly in the δ 13C and Sr/Ca curves and lithological evidence (a simple hardground with mineralized intraclasts above and below its surface, bioclastic concentrations with coarse debris). The δ 18O curve characterised by a depth-related depletion could support a Campanian long-term cooling trend. These chemostratigraphic data were interpreted in the light of the diagenetic history of the investigated section. The SEM and macroscopic observations do not show any evidence of burial diagenesis. On the other hand, a simple hardground allowed to clarify the impact of the early diagenesis on chalk. The geochemical signature of the hardground is characterised by a depletion in Sr (≈350 ppm) and δ 13C (≈0.5‰) values and an increase in Mn (≈210 ppm), Mg (≈500 ppm) and δ 18O (≈0.5‰) values. The lithification is associated with important modifications of the pore-space network: a total porosity depletion from 31.9–38.5% to 18.9–27.6% and a decrease in pore aperture from 0.25–0.38 to 0.14–0.15 μm. The diagenetic evolution of the pore-space is mostly controlled by an overgrowth of calcitic particles. The lack of oriented particles (SEM observations) suggests that the lithification requires a sediment stability. [Copyright &y& Elsevier]

Abstract: Palaeontological and geodynamical implications of the palynological dating of the wealden facies sediments of Bernissart (Mons Basin, Belgium). The para-taxon biorecord Superret-croton, characterized in 1979 by Hughes et al. in the Wessex sub-basin (England), is for the first time recognized in the Wealden facies sediments of Bernissart (Sainte-Barbe Formation, Mons Basin, Belgium). This morphotype demonstrates the presence of angiosperms. It is equivalent to the morphographic taxon Stellatopollis hughesii Penny, 1986. By using its stratigraphic distribution in the well-dated reference sections of the Weald and Wessex sub-basins (England), we suggest that the wealden facies sediments at 322 m deep in the natural pit of Bernissart are Middle Barremian to Earliest Aptian in age. This dating confirms the hypothetic Barremian age previously suggested on the basis of the morphologic evolution of the Iguanodontidae. It also clarifies the beginning of the subsidence in the Mons Basin, coeval with an eustatic drop (second order) and probably related to the dissolution of deep anhydrites. To cite this article: J. Yans et al., C. R. Palevol 4 (2005) . [Copyright &y& Elsevier]