https://popups.uliege.be/1374-8505 fr https://popups.uliege.be/1374-8505/index.php?id=7157 Species of the odontopleurine trilobites Leonaspis Richter & Richter, 1917 and Kettneraspis Prantl & Přibyl, 1949 from the Silurian and the Devonian have been studied. Dorsal tubercle and spine patterns are highly variable and deemed of restricted use. The pygidial segmentation of Leonaspis is consistent among species in the development of a rudimentary inner pleural ridge or wide space between the pleural ridge and the axis. In Kettneraspis, an inner pleural ridge is never developed but the primitive condition is to have a space here. The formation of this ridge and an auxiliary interior border spine pair was arrested prematurely during ontogeny in species assigned to Kettneraspis at present. The type species of the monotypic Rupbachella Alberti, 2021 is regarded as a juvenile Leonaspis. Bruthansovaspis gen. nov. (type species: Acidaspis roemeri Barrande, 1852) is proposed for a Silurian clade of former Kettneraspis species from peri-Gondwana, that are principally distinct in lacking the combination of stunted anterior and macropleural posterior, thoracic segments synapomorphic of Kettneraspis and Leonaspis. The types of Bruthansovaspis roemeri, Bruthansovaspis dormitzeri (Hawle & Corda, 1847), Bruthansovaspis dumortieri (Hawle & Corda, 1847), Kettneraspis propinqua (Barrande, 1852), Kettneraspis lindackeri (Hawle & Corda, 1847) and Bruthansovaspis zenkeri (Hawle & Corda, 1847) (= B. dormitzeri) from the Silurian of the Barrandian, all of which had previously been lumped as dormitzeri, are figured and their classifications revisited. Exceptionally well-preserved odontopleurine material from the Devonian in the Tafilalt (southern Morocco) is described as Kettneraspis freitagi sp. nov. Leonaspis? strix Lütke, 1965 from the Devonian of the Harz Mountains is in need of revision; a previously tentatively assigned pygidium does not belong in that genus. Mon, 15 Apr 2024 00:00:00 +0200 https://popups.uliege.be/1374-8505/index.php?id=7157 https://popups.uliege.be/1374-8505/index.php?id=7149 The Mesoproterozoic Karagwe-Ankole belt (KAB) in Central Africa hosts important mineralized lithium-cesium-tantalum pegmatites enriched in Sn, Nb, Ta and W. Microscopic techniques are required to further refine the paragenetic history of mineralized pegmatites in the KAB and to understand the pegmatite-forming processes leading to an enrichment of economically important minerals. Using a combination of scanning electron microscopy (SEM)-based automated mineralogy systems with X-ray computed tomography (µCT), we investigated the mineral relationships in a three-dimensional (3D) space. This paper presents new insights into the crystallization sequence of mineralized pegmatites in the KAB. A stage of albitization followed the primary crystallization, where muscovite probably plays a role in the fluid migration and the subsequent precipitation of ore minerals. Primary saccharoidal albitization was followed by tourmaline crystallization, but before the secondary cleavelandite-type albitization. The ‘Cornish Type’ cassiterite originating from greisen pockets confirms the suggested hydrothermal formation conditions. A first-time description of oriented zircon and the association with flat tabular columbite-tantalite points to the importance of local magmatic-hydrothermal conditions. This study emphasizes the possibilities of using 3D automated mineralogy for the identification of minerals and their position in the paragenetic history of mineralized pegmatites and by extension of microscopically complex and diverse ore deposits. Wed, 17 Jan 2024 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7149 https://popups.uliege.be/1374-8505/index.php?id=7134 The Mousty Formation has unique and particularly interesting lithological, mineralogical, sedimentological, metamorphic and tectonic characteristics which have been the subject of much research in connection with the new geological map of Wallonia, but also within the framework of a large amount of academic research, sometimes unpublished. An effort to synthesise and upgrade it in an updated framework seemed necessary. After a history of its definition, mapping and outcrop areas, the following topics are successively addressed in detail and illustrated with diagrams and photos: its lithostratigraphy with the probable discovery of its base near the Court-St-Etienne anticline, its well-constrained biostratigraphy and chronostratigraphy, a new estimate of its minimum thickness, its sedimentology—a subject little addressed until now—, and the resulting depositional sedimentary environment. Its geochemistry, never addressed, is comparable to black shale international standards, except for abnormally high manganese and very low calcium contents; high radon levels in buildings are related to the black slate presence in outcrops. Its mineralogy is rich in manganese-bearing metamorphic minerals, its metamorphism in which we go beyond the strict framework of the formation to deal with the entire southern outcropping rim of the Brabant Massif. Finally, the relationship between the Mousty Formation and the tectonic is discussed, with additional field data, in the context of the innovative and unifying concept of a low-angle extensional detachment called the Asquempont Detachment System. All these observations, some old and some very recent, discussed in the updated framework of the geology of the Caledonian basement of Brabant and in the global stratigraphy and palaeogeography of the lower Palaeozoic, allow us to renew in depth the vision we had of the Mousty Formation and of its place in the Brabant Massif. Fri, 29 Dec 2023 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7134 https://popups.uliege.be/1374-8505/index.php?id=7139 Fri, 29 Dec 2023 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7139 https://popups.uliege.be/1374-8505/index.php?id=7124 The Great Lakes area in Central Africa forms a large metallogenic province that hosts important deposits of gold mineralization. We present a petrographic, mineralogical and geochemical study of unique borehole samples from the Imonga-Saramabila gold deposit, a historical mine site located in the Maniema Province (DR Congo) in the Karagwe-Ankole belt (KAB) in the Great Lakes area and one of the only places in the Maniema province with accessible boreholes allowing to study the mineralization. The samples are metasedimentary rocks belonging to the Mesoproterozoic Kivu Supergroup, with bedding-parallel meta-igneous rocks. These rocks have undergone upper greenschist to lower amphibolite facies metamorphism, based on the presence of andalusite and chiastolite porphyroblasts, and are affected by hydrothermal alteration. The porphyroblasts formed during peak metamorphism and posterior to a first vein generation. Three additional vein generations were identified at Imonga based on crosscutting relationships, with the second and third events overprinting the porphyroblasts by intense chloritization, and associated with sulfide mineralization. The fourth vein generation is again barren. The first veining event formed pre-folding and the three subsequent generations postdate folding, as concluded based on the relationship of the veins with the cleavage. Only one important folding event is proposed based on the development of only one cleavage. Gold occurs as free gold or is included in pyrite in the second (and maybe third) vein generation. Based on the paragenesis, structural characteristics, and the link between veining and metamorphic minerals, the gold mineralization at Imonga is interpreted to be linked to the early Neoproterozoic (~980 Ma) compressional deformation event, associated with the amalgamation of the Rodinia supercontinent. Fri, 17 Nov 2023 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7124 https://popups.uliege.be/1374-8505/index.php?id=7115 Granulometric, carbonate and glauconite analyses were performed on samples of the Kiel and Antwerpen members (Berchem Formation) in temporary exposures and boreholes in the area of the City of Antwerp. Since the upper part of the Antwerpen Member is only locally preserved from post-depositional erosion, this study focuses on the much more frequently sampled lower part of the Antwerpen Member. The granulometric results show that the Kiel Member and lower part of the Antwerpen Member are both dominated by the fine sand fraction, with an overall finer grain size for the lower Antwerpen Member compared to the Kiel Member. The Kiel Member is relatively enriched in the fine and medium sand fractions, whereas the lower Antwerpen Member is relatively enriched in the very fine sand to silt fraction. Both members show a similar, low clay content. Measurements of clay content are higher in boreholes (on average 3.9–5.2%) than in temporary exposures (less than 1%), which might be explained by the crushing of the glauconite into the clay fraction during drilling. In borehole samples, especially those analysed by sieving, the Antwerpen Member often shows a higher amount of coarse grains than the Kiel Member, which represent shell fragments present in the Antwerpen Member and nearly absent in the Kiel Member. Like the amounts of shells, also the measured carbonate content—measured outside the shell beds—is lower for the Kiel Member than for the lower Antwerpen Member (3% vs 4.2%). The average glauconite content—based on the >63 µm fraction—displays similar, strong fluctuations between 35% and 60% for both members. On top of these fluctuations, a general downward decrease in glauconite content is noticed in the Kiel Member. Mon, 30 Oct 2023 00:00:00 +0100 https://popups.uliege.be/1374-8505/index.php?id=7115 https://popups.uliege.be/1374-8505/index.php?id=7109 Extant beaked whales (family Ziphiidae) are deep diving suction feeders and none of them can be considered as a permanent resident of the shallow southern North Sea. The rich fossil record of ziphiids from Neogene deposits of this area is thus surprising. However, chronostratigraphic intervals of most recorded taxa remain poorly constrained, preventing from assessing the evolution of their local diversity. In this work, we describe a new ziphiid cranium from the Neogene of Antwerp (north of Belgium), which is attributed to Caviziphius aff. C. altirostris. Sediment samples were extracted from 15 fossil ziphiid cranial remains from this area (including the one described herein), referred to eight species. The samples were analysed for their palynological content, leading to improved chronostratigraphic ranges for several species. Seven to eight ziphiid species from the southern North Sea, all from the Messapicetus clade, are proposed to originate from a Serravallian to Tortonian (late Middle to early Late Miocene) interval, and three to six more precisely from the mid- to late Tortonian. Added to the fossil record of other regions, these results point to a Late Miocene radiation of members of the Messapicetus clade, possibly related to the synchronous worldwide decline of several hyper-longirostrine dolphin clades. Thu, 12 Oct 2023 00:00:00 +0200 https://popups.uliege.be/1374-8505/index.php?id=7109 https://popups.uliege.be/1374-8505/index.php?id=7098 Newly recognised material of the Late Cretaceous nautilid Angulithes westphalicus is described from the subsurface of the eastern part of the Campine in north-east Belgium. This constitutes the first formal documentation of this genus and species from the Cretaceous of Belgium, having been identified amongst a large suite of fossils collected from the Voort Shafts I & II of the Zolder colliery during the first half of the twentieth century. The specimens originate from an interval of marine calcareous sand with a marly glauconiferous base, dated as late middle Santonian (Gonioteuthis westfalicagranulata belemnite Zone) and for which a deepening of the depositional environment is documented. Lithostratigraphically, the specimens occur within the Vaals Formation, within the upper part of the Asdonk Member or alternatively within the lower part of the Sonnisheide Member. The early Campanian age of the Asdonk Member suggested previously is refuted, the age of the Sonnisheide Member needs further study. The position of the siphuncle in A. westphalicus is illustrated for the first time; it is positioned closer to the venter than the dorsum, which confirms the close evolutionary relationship with Angulithes galea, which ranges from the upper Turonian to middle Coniacian in central Europe. Thu, 07 Sep 2023 00:00:00 +0200 https://popups.uliege.be/1374-8505/index.php?id=7098 https://popups.uliege.be/1374-8505/index.php?id=7105 Thu, 07 Sep 2023 00:00:00 +0200 https://popups.uliege.be/1374-8505/index.php?id=7105 https://popups.uliege.be/1374-8505/index.php?id=7090 Ammonoid cephalopods are extremely rare in the Lower and Middle Devonian sedimentary rocks of Belgium, which contrasts with the neighboring sedimentary basins. However, searches in old collections and recent collecting efforts show that ammonoids do occur in these beds in Belgium, which allows to enlarge our knowledge of Lower and Middle Devonian ammonoid occurrences. Here, a record of the Eifelian (Middle Devonian) anarcestid ammonoid genus Subanarcestes is described for the first time from Belgium based on a specimen from the Jemelle Formation (Chavées Member). This specimen was collected more than a century ago by Eugène Maillieux at Trou Bodet near Couvin. It laid unrecognized as an ammonoid cephalopod for many decades in the collections of the Royal Belgian Institute of Natural Sciences, while being previously identified as Cryptoceras or ‘Nautilus’ fossil, which if correct, constituted Belgium’s oldest Nautilida fossil. Micro-CT imaging greatly helped in the taxonomic assignment of the specimen. Thu, 31 Aug 2023 00:00:00 +0200 https://popups.uliege.be/1374-8505/index.php?id=7090