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Carnets Geol., vol. 25, no. 07 David J. Jutson, Michael D. Bidgood & Ben Johnson.- Microfossil and nannofossil analysis of the Upper Cretaceous to Lower Paleogene interval from two wells in the locality of the U.K. North Sea 'Silverpit Crater'.- Micropaleontological and nannopaleontological analyses have been carried out on ditch cuttings samples from two wells (Arco British 43/24-3 and British Gas 43/25-1), which penetrated the 'Silverpit Crater' structure in the Southern North Sea Basin (UK Sector). A stratigraphic gap (within the limits of resolution imposed by sampling constraints) has been identified between chalky limestones of Maastrichtian age, which are overlain by sediments of latest Paleocene age or younger. Accepting an impact-origin for the structure, the gap represents an impact-event, which occurred almost certainly post Cretaceous and Early Paleocene times and thus probably within the Late Paleocene, close to the Paleocene-Eocene boundary, ruling out an association with the K/P extinction impact. In well 43/25-1 a short interval of mixed microfaunas and nannofloras was observed, which is suggested as being related to 'resurgence deposits' entering the crater immediately after the impact-event. Geologia Acta, vol. 23, no. 9, 18 p. DomĂnguez-Carretero D., Villanova-de-Benavent C., TorrĂł L., Pujol-SolĂ N., Bover-Arnal T., Mestre Ă., Aiglsperger T., RamĂrez A., RodrĂguez J., Espaillat J. & Proenza J.A. (2025).- Mineralogy, geochemistry and origin of karst bauxite deposits from the Reserva Fiscal Ăvila, SW Dominican Republic.- The energy transition, which aims to reduce carbon emissions and to slow down climate change, demands an ever-increasing supply of the so-called "critical metals". Rare-earth Elements and Yttrium (REY) are among the most critical metals, as they are indispensable in most technologies associated with the generation and storage of renewable energy. In recent years there has been a growing interest in the potential of karst bauxites as non-conventional sources of REY and other critical metals such as Sc and Ga. The Sierra de Bahoruco (SW Dominican Republic) contains the most REY-enriched karst bauxites globally. In view of the high potential for hosting important REY contents, the Dominican Republic government has declared the Reserva Fiscal Ăvila (RFA), a state-owned area within the Sierra de Bahoruco for assessment and exploration of its REY resources. In this study, we present the first data on the mineralogy and composition of bauxitic rocks from the RFA. The bauxitic deposits comprise clayey bauxites and Fe-rich bauxites that are composed predominantly of Al-oxyhydroxides (gibbsite, boehmite and nordstrandite), kaolinite and Fe-oxyhydroxides. The bauxites are enriched in REY, with a median value of 1,310ppm and up to 2,542ppm, with a consistent enrichment in Light REE (LREE) and Y compared to Middle REE (MREE) and Heavy REE (HREE). The positive correlation between the contents of REY and Th, and negative correlation with K, makes gamma-ray spectrometry an appropriate tool for the exploration. In addition, bauxitic rocks from the RFA contain significant Sc (up to 105ppm) and Ga (up to 54ppm) contents, and their extraction could potentially represent a substantial economic surplus to the revenue generated solely from the aluminum production. BoletĂn de la Sociedad GeolĂłgica Mexicana, vol. 77, no. 01, A031024 AndrĂ©s Michael Vite Galindo, Ana MarĂa Soler Arechalde & VerĂłnica Ortega Cabrera.- Aportaciones a la cronologĂa de la plaza de la PirĂĄmide de la Luna, TeotihuacĂĄn, MĂ©xico - Contributions to the chronology of the Moon Pyramid square, TeotihuacĂĄn, Mexico.- The chronology of the Pyramid of the Moon square in TeotihuacĂĄn was determined through relative dating of the ceramic remains present in the different strata sampled, during archaeological excavations carried out since the 1960s, so establishing dating through archaeomagnetism will allow having a database that complements those obtained in different urban sectors such as La Ciudadela, Xalla and Teopancazco, thus generating greater certainty in the chronology and understanding of the phenomena of urban growth and renewal of the ancient city. In this work, the results of the first archaeomagnetic dating carried out in the Plaza de la Luna are presented, based on the sampling of three floors of gravel and a tamped floor, corresponding to the different construction moments of this space, with the aim of establishing a sequence chronological base, with which to compare future dating, both for the square and for other public spaces in the city. Mineralogia, vol. 56, no. 1, p. 34-43 Walczak K.A., Wlodek A., Cuthbert S., Carter I.S.M. & Ziemniak G.- Long story encrypted in a small grain â zircon from meta-andesite in the Lower Köli Nappes reveals a complex history of the Virisen Arc Terrane, Scandinavian Caledonides, Sweden.- This short report presents the investigation results on the zircon from meta-andesitic rock from the Ankarede Volcanite Formation of the Lower Köli Nappe Complex in Scandinavian Caledonides. Previous U-Pb dating revealed a wide span of dates ranging from ca. 520 to ca. 480 Ma, with a mean age of 491 ± 3 Ma for the zircon cores. Using cathodoluminescence and back-scattered electron imaging, along with chemical mapping, we identified distinct zones within the zircon grains; 1) cores of clear magmatic provenance, 2) mantles also of magmatic origin but with a slightly different chemical composition and 3) zircon rims that suffered metamictisation and fluid-induced alterations. These findings highlight a complex growth history and alteration of studied zircon that affect the interpretation of zircon dating results. This research underscores the importance of detailed zircon studies for understanding the intricate processes involved in the magmatic and metamorphic evolution of Virisen terrain in Scandinavian Caledonides. Mineralogia, vol. 56, no. 1, p. 34-43 Walczak K.A., Wlodek A., Cuthbert S., Carter I.S.M.. & Ziemniak G. (2025).- Long story encrypted in a small grain â zircon from meta-andesite in the Lower Köli Nappes reveals a complex history of the Virisen Arc Terrane, Scandinavian Caledonides, Sweden.- Long story encrypted in a small grain â zircon from meta-andesite in the Lower Köli Nappes reveals a complex history of the Virisen Arc Terrane, Scandinavian Caledonides, Sweden. This short report presents the investigation results on the zircon from meta-andesitic rock from the Ankarede Volcanite Formation of the Lower Köli Nappe Complex in Scandinavian Caledonides. Previous U-Pb dating revealed a wide span of dates ranging from ca. 520 to ca. 480 Ma, with a mean age of 491 ± 3 Ma for the zircon cores. Using cathodoluminescence and back-scattered electron imaging, along with chemical mapping, we identified distinct zones within the zircon grains; 1) cores of clear magmatic provenance, 2) mantles also of magmatic origin but with a slightly different chemical composition and 3) zircon rims that suffered metamictisation and fluid-induced alterations. These findings highlight a complex growth history and alteration of studied zircon that affect the interpretation of zircon dating results. This research underscores the importance of detailed zircon studies for understanding the intricate processes involved in the magmatic and metamorphic evolution of Virisen terrain in Scandinavian Caledonides. Geologia Acta, vol. 23, no. 8, 13 p. RoquĂ©-Rosell J., Ibåñez-Insa J., Granado P., MartĂn-MartĂn J.D., Ălvarez-Pousa S., CerdĂ -DomĂšnech M. & JimĂ©nez-Franco A. (2025).- Major-element analysis of the La Alquimia CompañĂa AnĂłnimarock collection: Establishing a geochemical repository for the systematic classification of Iberian karstic bauxite and kaolin deposits.- The La Alquimia CompañĂa AnĂłnimarock collection comprises a diverse range of rock samples collected across the Iberian Peninsula to identify bauxites suitable for aluminum oxide production. In this study, the major-element compositions of the rock samples were analysed using non-destructive portable X-Ray Fluorescence (XRF). The data were processed through Principal Component Analysis (PCA), calibrated and used to calculate the Index of Laterisation/Index of Bauxitisation (IOL/IOB) and the Chemical Index of Alteration (CIA). The PCA results revealed SiO#8322;, Al#8322;O#8323; and Fe#8322;#8322;O#8323; as the key components explaining most of the rock samples compositional variance. The calibrated data provided the major-element compositions, confirming that the rock samples predominantly correspond to karstic bauxites and kaolin deposits. For the karstic bauxite samples, the calculated IOL/IOB values, combined with theSiO#8322;--AlâOâ--FeâOâ ternary diagram, facilitated their classification. The samples were categorised into bauxitic types associated with regions of moderate uplift and karst development and near-lateritic types indicative of advanced weathering processes typical of more stable continental terrains under warm and humid climates. Besides, the calculated CIA values and the Al#8322;O#8323;-CaO*+Na#8322;O-K#8322;O ternary diagram were applied to classify the kaolin deposits. This approach also identified compositional variations among the kaolin rock samples, reflecting differences in their formation. The rock collection serves as a repository for advancing the regional understanding of the formation, distribution and geochemical trends of Iberian karstic bauxite and kaolin deposits. Moreover, these deposits hold significance as potential sources of Al, Li and REE, emphasising the value of the La AlquĂmia CompañĂa AnĂłnima collection as a geochemical repository, particularly considering the growing demand for these critical resources. Carnets Geol., vol. 25, no. 06 Olev Vinn, Andrej Ernst, Mark A. Wilson & Ursula Toom.- Symbiosis between bryozoans with erect cribrate colonies and rugose corals from the lower Katian (Upper Ordovician) of Estonia.- Specimens of the rugose coral Streptelasma? sp. are found intergrown with a host bryozoan Oanduellina bella in the lower Katian of Estonia. Rugosa also occur in the bryozoan Proavella proava. This is the earliest and only known record of endobiotic rugose symbionts in cryptostome bryozoans from the Late Ordovician of Baltica. The erect bryozoan colonies provided symbiotic Rugosa with both a higher and more advantageous tier for feeding in the water column and a hard substrate that these encrusting Rugosa required. The rugose corals may have protected the bryozoans with their stinging cells against predators. The lack of malformations in the bryozoan zooid architecture and their normal dimensions around the Rugosa show that the relationship between the Rugosa and bryozoans could have been mutualistic, which is similar to many other Rugosa-bryozoan associations in the Late Ordovician of Baltica, although the exact nature of this association remains uncertain. Geologia Acta, vol. 23, no. 7, 17 p. MartĂn-Closas C., Lozano-FernĂĄndez I., PĂ©rez-Cano J. & Bover-Arnal T. (2025).- The non-marine Lower Cretaceous of El Montsec thrust sheet (South-Central Pyrenees).- The aim of this study is resolving uncertainties on the lithostratigraphy and chronostratigraphy of the non-marine Lower Cretaceous of El Montsec thrust sheet, which contains the most developed record of such facies in the central Pyrenees (Catalonia, Spain). The materials, traditionally known as "El Montsec Charophyte Limestones", overlie upper Berriasian marine limestones and belong in fact to two different stratigraphic units, separated by an angular unconformity, which is represented by an irregular karstic surface. The lower unit, newly defined as the Cova dels Lladres Intraclastic Limestone Formation, is composed by metric-scale fining-upward parasequences with black intraclast conglomerates at the base covered by charophyte limestones at the top. This first non-marine unit is attributed to the lower Barremian Eurasian charophyte biozone Atopochara trivolvis triquetra. The upper non-marine unit, (revisited El Montsec Charophyte Limestone), is made of metric-scale fining-upward parasequences of charophyte limestones. Ferruginous marls at the base of the upper unit have yielded charophytes of the Hemiclavator neimongolensis neimongolensis Eurasian charophyte biozone, corresponding to the early-late Barremian boundary. El Montsec Charophyte Limestone Formation transitions laterally to La Pedrera de RĂșbies Lithographic Limestones Formation, which includes the two famous fossil Konservat LagerstĂ€tten of La Pedrera de MeiĂ and La Cabroa. In sum, the non-marine Lower Cretaceous succession of El Montsec thrust sheet shows at its base a stratigraphic gap ranging from the upper Berriasian to the early Barremian. Furthermore, the angular unconformity separating the Cova dels Lladres Formation and El Montsec Formation clearly reflects the strong tectonic activity associated with the Barremian Iberian rift, which has been linked with the opening of the Bay of Biscay. Mineralogia, vol. 56, no. 1, p. 23-33 Bal S., Nejbert K., Michalski K., Domanska-Siuda J., Manby G., Holda-Michalska A. & SlĂĄma J. (2025).- Petrographic and mineralogical characteristics of diagenetic overprinting in Neoproterozoic diamictites from Murchisonfjorden, Nordaustlandet, Svalbard.- Petrographic and mineralogical characteristics of diagenetic overprinting in Neoproterozoic diamictites from Murchisonfjorden, Nordaustlandet, Svalbard. The diagenetic processes exhibited by the Neoproterozoic diamictites from Murchisonfjorden (Nordaustlandet, NE Svalbard) are presented. Diamictite samples from the Cryogene Polarisbreen Group - the Petrovbreen Member of the Elbobreen Formation and the Wilsonbreen Formation were analysed. The mineralogical associations composed of chlorite group minerals (chamosite), albite, calcite, Fe-dolomite, clay minerals (illite) and quartz, recognized by integrated optical microscopy, scanning electron microscopy (SEM) and Raman spectroscopy techniques are typical for an advanced stage of mesogenetic diagenesis. Low-grade burial mineral associations were not identified. Our investigations indicate that during diagenesis increased heat flux accompanied fluid migration and remineralization. Identified Fe-Ti â oxides, anatase in thin sections and magnetite identified by rock-magnetic experiments are the products of the secondary diagenetic mineralization. The ferromagnetic carriers representing primary depositional remanence magnetization (DRM) were not preserved. Geologia Acta, vol. 23, no. 6, 23 p. Alçiçek H., Bouchal J.M. & Alçiçek M.C. (2025).- Sedimentology and isotope geochemistry of Early Pliocene shallow lacustrine dolomitic succession in the Baklan Basin, Southwestern TĂŒrkiye.- A multiproxy study of the Lower Pliocene (Zanclean) shallow lacustrine succession in the southwestern margin of the Baklan Basin (southwestern Anatolia, TĂŒrkiye) provides new insights into the paleoclimatic and paleohydrologic evolution of an extensional basin located at the top of the western Taurides mountain range in the southeastern Mediterranean region. Detailed petrographic, sedimentological, palynological and stable isotope analyses on Mg-rich carbonates were carried out on the dolomitic succession in the Sapaca locality in the basin, indicating a vegetated, quiet to slow-moving, low-gradient, perennial, alkaline shallow lake environment under warm and arid climate conditions. The stable isotopic analysis of the dolomitic carbonates exhibits a narrow range of values (-1.31<ÎŽ18O<+5.82â° and -7.10<ÎŽ13C<-2.10â°) and the ÎŽ18O-ÎŽ13C correlation (r=0.70) indicates a hydrologically closed lake. Two types of dolomite are identified in the studied section. Type-1 crystals formed mainly as a result of primary precipitation of dolomite in the shallow lake, whereas type-2 crystals probably indicate microbially controlled dolomite precipitation. The palynological record from Sapaca reveals that the Early Pliocene paleoenvironment was dominated by steppe and open vegetation with some isolated shrubs. Similar paleoclimatic and paleovegetational conditions are observed in other Anatolian basins and in the southern Mediterranean region. Therefore, the results of this study demonstrate that the shallow lacustrine system of the Baklan Basin serves as a good analogue for understanding Early Pliocene warmth and aridity in this region. | |
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