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A numerical model was built using FEFLOW® to simulate groundwater flow and heat transport in a confined aquifer in Brussels where two Aquifer Thermal Energy Storage (ATES) systems were installed. These systems are operating in adjacent buildings and exploit the same aquifer made up of mixed sandy and silty sublayers. The model was calibrated for groundwater flow and partially for heat transport. Several scenarios were considered to determine if the two ATES systems were interfering. The results showed that a significant imbalance between the injection of warm and cold water in the first installed ATES system led to the occurrence of a heat plume spreading more and more over the years. This plume eventually reached the cold wells of the same installation. The temperature, therefore, increased in warm and cold wells and the efficiency of the building’s cooling system decreased. When the second ATES system began to be operational, the simulated results showed that, even if the heat plumes of the two systems had come into contact, the influence of the second system on the first one was negligible during the first two years of joint operation. For a longer modeled period, simulated results pointed out that the joint operation of the two ATES systems was not adapted to balance, in the long term, the quantity of warm and cold water injected in the aquifer. The groundwater temperature would rise inexorably in the warm and cold wells of both systems. The heat plumes would spread more and more over the years at the expense of the efficiency of both systems, especially concerning building’s cooling with stored cold groundwater.

Ostracods from the Sourd d'Ave section have been collected in the Moulin Boreux and Fort Hulobiet Members (Fromelennes Fm., Givet Group) and in the Pont d'Avignon Member (Nismes Fm., Frasnes Group). Ostracods collected in the Fromelennes Fm. by Milhau (1983a) and in the Nismes Fm. by Casier (1987a) have been also reviewed. Forty-four ostracod species are identified in the Fromelennes Fm. and 25 in the Nismes Fm. They belong exclusively to the Eifelian Mega-Assemblage, and several assemblages indicative of restricted and shallow marine, sometimes agitated, environments are recognized in the Fromelennes Fm. The great rarity of ostracods in the upper part of this formation provides evidence for less favourable lagoonal conditions probably related to increasing aridity at the end of the Givetian. In the Frasnes Group, assemblages are exclusively open marine and indicative of increasing water depth. The majority of ostracod species recognized in the Givet Group are missing in the base of the Frasnes Group as a consequence of the Frasnes Event. A systematic list of ostracods identified in the Fromelennes Fm. at Sourd d'Ave is published as an annex. Systematic sampling has been carried out in order to establish the sedimentological evolution of the environments and to detail the Givetian-Frasnian (G/F) transition. This allowed recognition of 13 microfacies types that replicate the standard sequence of Préat & Mamet (1989) from open marine shallow subtidal to restricted supratidal near emersion. The Boreux Member and the Fort Hulobiet Member display restricted facies (Amphipora, spongiostromid and algal bafflestones and bindstones, loferites with desiccation lumps) with poorly fossiliferous beds interbedded with higher energy peloidal and sometimes oolitic grainstone facies. Laminite horizons, sometimes with small-sized lateral linked hemispheroid stromatolites are uncommon, and are associated with dolomicrites showing pseudomorphs of evaporite minerals. These evaporitic facies become common in the upper part of the Fort Hulobiet Member suggesting the palaeoclimate became more arid at the G/F transition. Metre-scale cyclicity is pervasive throughout the Givetian part of the section. The boundary between the Givet Group and the Frasnes Group is very distinctive in the field, and is characterized by a transition from restricted evaporative lagoonal facies to open marine interbedded marly shales and nodular limestones. The upper part of the Fort Hulobiet Member consists of interbedded biostromes (semi-restricted stromatoporoid boundstones) followed by Amphipora floatstones, then fossil-poor units and restricted supratidal laminites with well-developed fenestral fabrics. The Frasnian Pont d'Avignon Member contains a rich faunal assemblage (bryozoans brachiopods, molluscs, nautiloids, tentaculitids) suggesting an abrupt drowning from the marginal Givetian carbonate platform into a Frasnian distal ramp or deep basinal environment below or near storm wave base.•

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Limestones at the Puech de la Suque Global Boundary Stratotype Section and Point (GSSP) of the Givetian–Frasnian boundary show a drastic change towards much higher magnetic susceptibility values in the Givetian rocks. Different rock magnetic parameters indicate that ferromagnetic minerals are the main controlling factor. The ferromagnetic fraction is composed of low- (magnetite-type) and high-coercivity (hematite and goethite) phases. Confirmed by the spectral reflectance, high coercivity minerals are fluctuating along the section with a higher abundance in the basal Frasnian. These phases may be of secondary origin and produced during burial stage. The magnetite-type phase contains two different grain-size populations. The identified that Stable Single-domain/Superparamagnetic (SSD/SP) particles are of diagenetic origin and their amount decreases slightly upwards. A second group of magnetite grains correspond to coarse-grained particles identified using the squareness v. coercive force plot. It is tentatively suggested here that these particles present throughout the section are of primary origin. On the contrary, the paramagnetic minerals underwent a clear diagenetic overprinting and may represent secondary minerals. The presence of a primary ferromagnetic carrier allowed the use of spectral analyses, leading to the detection of spectral peaks at 1.25 and 4 cycles/m, which can be interpreted as the result of 405-kyr and 100-kyr eccentricity forcing, respectively.