Geologica Belgica https://popups.uliege.be/1374-8505 fr JONGERENDAG - JOURNEE DES JEUNES – 10.09.2025 https://popups.uliege.be/1374-8505/index.php?id=7339 Sun, 28 Dec 2025 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7339 Lithofacies and depositional settings of the Coniacian–Campanian Chalks in the Mons Basin (Belgium) https://popups.uliege.be/1374-8505/index.php?id=7327 Three drill holes in the Mons Basin yield together 350 m of Coniacian to Campanian chalk cores. Detailed geological logging was conducted on the well-known Trivières Chalk, Saint-Vaast Chalk, and Maisières Chalk formations. A thorough sedimentological characterization was performed, from macrofacies to SEM microtexture. Petrographic observations and geochemical analysis indicate eogenetic calcite cementation and phosphatization in two benchmark levels, already known for their high glaucony content, namely in the Trivières Chalk Formation and the Maisières Chalk Formation. Upwelling currents, prevalent during the Late Cretaceous, are likely the source of the phosphates, and the cause of reduced sedimentation rates. Strong anoxic currents resulted in the formation of hardgrounds, the development of glaucony pellets and pyrite formation within shallow subtidal sediments. Multiple conglomeratic chalk intervals were identified in the Trivières Chalk Formation. They likely result from local sediment destabilization due to extensional tectonic activity. Moreover, the identification of deformation bands attests to synsedimentary tectonic activity within the basin. Overall, this research unravels various phenomena, including marine currents, sea-level fluctuations, and tectonic activity, that influenced chalk deposition in the Mons Basin. This research enables enhanced comprehension and forecasting of the heterogeneities in chalk and its spatial variability. Tue, 23 Dec 2025 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7327 Predator-prey dynamics in a latest Cretaceous marine ecosystem: mosasaur and shark attacks on the echinoid Hemipneustes striatoradiatus from the Maastrichtian type area (the Netherlands, Belgium) https://popups.uliege.be/1374-8505/index.php?id=7317 Three tests of the holasteroid echinoid Hemipneustes striatoradiatus from the Belgian-Dutch type area of the Maastrichtian Stage preserving evidence of vertebrate-invertebrate interactions are documented and analysed. One specimen exhibits adoral pentagonal puncture marks and a large aboral scar from a mosasaur attack, with Mosasaurus hoffmannii as the presumed predator. A second test preserves evidence of two separate attacks, the first by a mosasaur, presumably Plioplatecarpus marshi, leaving both a pentagonal adoral scar and a large aboral one, and the second by a shark, leaving non-penetrating small, deep triangular pits with tapering tails. A similar pitting is seen on the third test, arranged in clusters and here interpreted as a shark bite from above followed by a second bite subsequent to a 90° rotation of the echinoid. These finds provide the first unambiguous evidence of mosasaur predation on Hemipneustes and add to the sparse record of shark-echinoid interactions, suggesting that predation on large holasteroids by vertebrates was more frequent than previously recognised. All three tests also exhibit syn vivo and post-mortem invertebrate interactions, including also an undescribed serpulid. Fri, 19 Dec 2025 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7317 Taxonomic revision and new elasmobranch records from the Wemmel Sand and Asse Clay members, base of the Maldegem Formation (middle Lutetian, southern North Sea Basin) https://popups.uliege.be/1374-8505/index.php?id=7310 The elasmobranch fauna of the middle Lutetian Asse Clay Member (the lower part of the Maldegem Formation) has been updated and complemented with new material from a temporary outcrop at Papenboskant (Wolvertem), about 20 km north of Brussels. This faunal assemblage, which exclusively comes from its coarse-grained glauconitic base, traditionally known as the bande noire, comprises 22 taxa. Fourteen are mentioned for the first time in this horizon, including Abdounia lapierrei, which has never been recorded in Belgium before, and Casierabatis spp. The latter comprises dental morphologies deviating from these of the two nominal Casierabatis species known to date, although it is currently unclear if these reflect intraspecific variability or represent taxonomic novelties. The new records from Papenboskant consist predominantly of small-toothed taxa, mainly batoids, which are absent from the historical handpicked museum collections of the Wemmel Sand and Asse Clay members reviewed in this study. The composition of the elasmobranch fauna indicates that during the middle Lutetian, the area north of Brussels was covered by a tropical to warm-temperate shallow sea with sandy to muddy bottoms and an open connection to deeper waters. The pronounced similarities between the assemblages of the Belgian, Hampshire, and Paris basins indicate that, during the middle and late Lutetian, these three subareas of the southern North Sea remained interconnected and maintained marine exchange with the Atlantic Ocean, not only through the northern seaway but also via the southwestern English Channel. Virtually all of the newly recovered elasmobranch taxa existed over a considerable period of time and were reported from several Ypresian and/or Lutetian deposits across the North Sea Basin. Abdounia lapierrei appears to possess biostratigraphic significance, being so far confined to Lutetian strata. This may also apply to certain representatives of the Casierabatis species group, although this remains to be confirmed. The single tooth of Notorynchus figured in Leriche (1905) and recovered from the Wemmel Sand Member at Neder-Over-Heembeek is re-examined and refigured. This specimen represents the first occurrence of Notorynchus kempi in Belgium. Thu, 18 Dec 2025 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7310 Two cases of sclerobionts including foraminifers on Lower Devonian asteropygine trilobites from Germany and Luxembourg https://popups.uliege.be/1374-8505/index.php?id=7298 Two Devonian asteropygine trilobite specimens exhibiting rare cases of encrustation are recorded. An almost fully articulated exoskeleton of Rhenops australocustos from the lower Emsian in Luxembourg carries hederelloid colonies on its cephalon and thorax. The colonies are interpreted to have attached syn vivo (i.e. to the living trilobite) and the relation with their host was likely commensal. A cephalon of Philonyx philonyx from the upper Emsian in Germany exhibits five putative morphotype encrusters identified as hederelloids, auloporid corals, cornulitids, bryozoans and foraminifers. This is the first documented evidence of a foraminifer on a trilobite host. This cephalon is either a moult or a carcass. Fri, 28 Nov 2025 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7298 First report on the occurrence of the echinoderm classes Soluta and Stylophora in a new Lower Devonian (Pragian) Konservat-Lagerstätte from southern Belgium https://popups.uliege.be/1374-8505/index.php?id=7287 In the Neufchâteau–Eifel Synclinorium (southern Belgium), remnants of the spoil heap of the disused and now flooded underground Sainte-Barbe Quarry (Warmifontaine) yielded an invertebrate Pragian assemblage occurring in the dark monotonous slates of the La Roche Formation (Martelange Member). This locality is considered as a new Belgian Konservat-Lagerstätte (fossil conservation deposit) due to the presence of both biomineralised and soft-bodied organisms. Two specimens from the Sainte-Barbe Quarry Biota are described and assigned to two distinct classes of extinct echinoderms. The first one corresponds to an almost complete, flattened and distorted dendrocystitid solutan, which is tentatively identified as Dehmicystis? sp., based on similarities with D. globulus from the Hunsrück Slate (Emsian) of Germany. The second echinoderm specimen is a well-preserved, flattened, fully articulated and almost complete mitrate stylophoran, morphologically close to Mitrocystites? styloideus-like peltocystidans from the Lower and Middle Devonian of Germany. Taphonomic attributes of the two echinoderms from Warmifontaine (e.g. both fully articulated; mitrate with its aulacophore preserved in feeding position) suggest they were probably killed and entombed by obrution deposits in an otherwise quiet and deep setting. Other echinoderms (asteroids, crinoids, blastoids, cyclocystoids, ophiuroids) reported from the Lower Devonian of Belgium are also briefly discussed and illustrated (e.g. holotypes). Wed, 12 Nov 2025 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7287 A tiny dolphin (Cetacea, Odontoceti, Kentriodontidae) cranium from the Middle Miocene of the southern North Sea with a rare osteological malformation https://popups.uliege.be/1374-8505/index.php?id=7277 Though the Neogene deposits of northern Belgium yielded many marine vertebrate remains, including cetaceans, the fossil record of several clades remains scarce. Among echolocating toothed whales (Odontoceti), cranial fossils of early delphinidans generally referred to the family Kentriodontidae are surprisingly rare in the Miocene units of the Antwerp area. Recently, a large construction pit excavated in the city centre of Antwerp allowed for the lithostratigraphic description of a section in the Kiel and Antwerpen members of the Berchem Formation. In addition to an elasmobranch assemblage of 13 species, a well-preserved, tiny odontocete cranium was discovered in the lower part of the Antwerpen Member (Middle Miocene, lower Langhian). Representing a young individual, this rare fossil displays strong anatomical similarities with the small kentriodontid Kentriodon pernix, originally found in upper Lower to Middle Miocene deposits of the Atlantic Coastal Plain (USA). It is referred here to Kentriodon cf. K. pernix, contributing to the improvement of the scant fossil record of early delphinidans in the North Sea. Associated to a degree of tooth wear that is unexpected in such a young individual, highly unusual anatomical traits, especially in the orbit region, are interpreted as resulting from a malformation that occurred relatively early during cranial development. Wed, 29 Oct 2025 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7277 New records of the homalonotid trilobite Burmeisterella delattrei (Pillet & Waterlot, 1983) from the Lower Devonian in Belgium and Luxemburg https://popups.uliege.be/1374-8505/index.php?id=7272 The homalonotid trilobite Burmeisterella delattrei is recorded from the early Emsian Ruisseau de la Forge Formation in Belgium (southern limb of the Dinant Synclinorium), somewhat lower than its previously recorded first occurrence in the overlying Vireux Formation. The species may be considered an index fossil for the German Singhofen and Vallendar groups along with the homalonotids Burmeisterella armata and Digonus ornatus ornatus. A pygidium of B. delattrei from the Clervaux Formation in Luxemburg with one of the dorsal spines in place on the first pleural rib, allows a minor modification of current reconstructions of the dorsal exoskeleton to be proposed. The holotype and two paratypes (pygidia) of B. delattrei from the Vireux Formation in northern France are refigured. In total, four species of Burmeisterella, namely B. aculeata, B. armata, B. delattrei (= B. vixarmata) and B. quadrispinosa, are now recognised in the upper Pragian to lower Emsian of Belgium. Tue, 17 Jun 2025 00:00:00 +0200 https://popups.uliege.be/1374-8505/index.php?id=7272 Description of some Middle Devonian rugose corals from the Ma’der (eastern Anti-Atlas, Morocco) https://popups.uliege.be/1374-8505/index.php?id=7268 Twelve species and four forms of Middle Devonian rugose corals from Morocco are described and illustrated. The material comes from four localities of the Ma’der Basin whose age from the Late Eifelian to the base of the middle Givetian is based on conodonts. Three taxa are new: Marennophyllum kaufmanni n. sp., Stringophyllum pedderi n. sp. and Siphonophrentis subaequalis n. sp. Heliophyllum moghrabiense Le Maître, 1947 is the only taxon common to the four outcrops and it suggests an Eastern North American influence at the level of the genus. Siphonophrentis cantabrica Birenheide, 1978, first described from Spain, is also a North Gondwanan species whereas Stringophyllum acanthicum (Frech, 1885), Acanthophyllum heterophyllum (Milne-Edwards & Haime, 1851), A. vermiculare (Goldfuss, 1826) and Spinophyllum blacourti (Rohart, 1988) are interesting for correlations with Western Europe and sometimes with Eastern Europe. Enallophrentis corniformis (Gürich, 1896) was defined in Poland, also in the Old World Realm. Farther to the east, there is a link with China where Siphonophrentis cantabrica is present. Finally, it must be mentioned that Australophyllum Stumm, 1949 is observed for the first time in Morocco. Tue, 27 May 2025 00:00:00 +0200 https://popups.uliege.be/1374-8505/index.php?id=7268 Early Quaternary channel incisions at the base of the Merksplas Formation at the southern margin of the North Sea Basin https://popups.uliege.be/1374-8505/index.php?id=7260 Borehole log correlations provide the first evidence for >15 m deep channel incision in the base of the Quaternary at the southern margin of the North Sea Basin. The coarse sand of the lower Quaternary Merksplas Formation fills up the channels that were cut into the top of the subjacent fine, glauconite-bearing shelly sand of the upper Pliocene Lillo Formation. Channel erosion was locally able to remove the entire upper sandy unit (Merksem Member) of the Lillo Formation. The interpretation of a seismic line in the area shows that the channel erosion reached even deeper at some locations. The very coarse, poorly sorted infill of the channels, with plenty of reworked material, testifies to deposition under tidal or tidally enhanced currents. The channel incisions probably cut into the Lillo Formation during the earliest Quaternary sea-level lowstands. During a subsequent sea-level rise, tides entered the paleo-valleys and widened them. Channel lag deposits were formed with abraded shells and other intraclasts. The latter are overlain by a thicker fining-upward sequence, which is indicative of channel fills and mainly composed of coastal environment-sourced quartz sand. Thu, 15 May 2025 00:00:00 +0200 https://popups.uliege.be/1374-8505/index.php?id=7260