GCG - Artigos em revistas internacionais
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Browsing GCG - Artigos em revistas internacionais by Field of Science and Technology (FOS) "Ciências Naturais::Ciências da Terra e do Ambiente"
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- Depositional environment and redox conditions of the Moncorvo Ironstone: Unveiling the evolution of ironstones under Rheic Ocean influencePublication . Urbano, Emilio Evo Magro Correa; Preto Gomes, Maria Elisa; Pinto de Meireles, Carlos Augusto; Brandão, Paulo Roberto Gomes; Hippertt, Joa Pedro T.M.; Scholz, Ricardo; Lana, CristianoABSTRACT: Ironstones, as key archives of past marine environments, provide invaluable insights into Paleozoic history. Their mineralogy may reflect the physical-chemical conditions of the environment and the nature of available sediments. This study focuses on the Moncorvo Ironstone, a Lower-Middle Ordovician deposit formed during the opening of the Rheic Ocean. Here, we use an integrated approach combining sedimentology, petrology, and geochemistry to constrain the depositional settings and the redox landscape associated with the ironstone deposition. The Moncorvo Ironstone present some unusual characteristics, such as the lack of ooids, an uncommon mineralogy, and a stratigraphic thickness that can reach over >45 m, a remarkable feature for an ironstone. Our investigation reveals that this iron-rich sequence is distributed in two distinct marine environments: an inner shelf and a middle to distal shelf. Each environment has a unique mineral assemblage. Despite the influence of metamorphism and deformation, evidence suggests that much of the mineralogy and texture of this deposit still preserve characteristics of the original sediments. Finally, our findings, alongside a careful assessment of the mineralogy of other ironstones of similar age, suggest a strong stratification of the Rheic Ocean throughout the Early and Middle Ordovician.
- Evaluating the role of physical mechanisms as possible triggers for turbidity currents in a deep ocean seamountPublication . Lebreiro, Susana M.; Peliz, Álvaro; Antón, Laura; Nave, Silvia; Reguera, M. Isabel; Lozano-Luz, Rocío; Waelbroeck, Claire; Crowhurst, Simon; Martrat, Belen; Lopez, Jordi F.; Hebert, Raphael; Lopez-Rodriguez, AlejandraABSTRACT: Turbidity currents on continental margins are often attributed to cyclic climate variability and sea-level change, while the causes of deep ocean turbidites are as yet to be tested. The Atlantic Iberian margin provides a unique setting to contrast deep ocean and continental environments, including depression features that further protect from resuspension and erosion by along-slope bottom currents. We present records of low-frequency, non-periodic, climate-independent turbidites from three deep cores covering up to 426,000 years in the Tore seamounts area. By evaluating a range of physical oceanographic mechanisms, the breaking of internal waves and mesoscale Mediterranean-eddies against unstable slopes in the seamounts area arises as the most likely triggers that precondition the recurrence pattern of the observed deep ocean turbidites.
- Megaglomerospora lealiae nov. gen., nov. sp. from the upper Carboniferous of Portugal: the largest glomeromycotan fungal sporesPublication . Correia, Pedro; Sá, Artur A.; Pereira, ZéliaABSTRACT: A new genus and species of fossil fungus, Megaglomerospora lealiae, is described from the Bu & ccedil;aco Carboniferous Basin (upper Stephanian C, Upper Pennsylvanian, upper Carboniferous), in central western Portugal. The new fossil fungus consists of a dense cluster of silicified large spores. These new fungal spores are oblong, subelliptical to subspherical-shaped, with a glabrous surface characterized by having a lipid-filled lumen, and display a strong septate-like hypha attached. The presence of lobe-shaped germination shields suggests close affinities to Diversisporales (Glomeromycota). Megaglomerospora lealiae nov. gen., nov. sp. is remarkably distinctive because it is by far the largest fossil fungal spore (similar to 1.6 mm long) documented for the phylum Glomeromycota. This is the first report of an endomycorrhizal-like fungus from the Carboniferous of Iberia. (c) 2025 Elsevier Masson SAS. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
- The old central igneous complexes of Sal, Boa Vista and Maio islands: Implications for 17 Ma of isotopic evolution of the Cape Verde archipelagoPublication . Villaseca, Carlos; Orejana, David; Huertas, Maria J.; Ancochea, Eumenio; Ignacio, Cristina; Mata, João; Caldeira, Rita; Garcia-Rodriguez, Maria; Moreno, Juan A.; Perez-Soba, CeciliaABSTRACT: The central igneous complexes of the easternmost islands (Sal, Boa Vista and Maio) preserve some of the most ancient outcropping rocks of the Cape Verde (CV) archipelago. These Early to Middle Miocene (about 25 to 12 Ma) complexes show marked isotopic differences between mafic rocks from the northern (Sal and Boa Vista) and the southern Maio Island, the latter showing lower 143Nd/144Nd, 206Pb/204Pb, 207Pb/204Pb, and higher 87Sr/86Sr ratios. The main mantle plume composition beneath Cape Verde is here considered to be dominated by the FOZO component. Our data supports previous models suggesting the incorporation to plume components of minor DMM mantle sources in the northern CV island alignment, whereas mixing with the EM1 pole is prevalent on the southern CV islands. These isotopic differences are evident since the early stages of Cape Verde magmatism. The Late Miocene to Holocene time period (7 to 1.7 Ma) is characterized by the irruption of silica-undersaturated and carbonatite magmas with a relatively homogeneous isotopic composition and highly radiogenic Pb signatures (206Pb/204Pb up to 20.6 in carbonatitic rocks and 20.2 in silicate rocks) throughout most of the Cape Verde archipelago. During this transitional stage, the input of this new HIMU mantle component overprinted the previous mixing of the main FOZO plume component with shallow mantle members (DMM, EM1) of minor contribution.
- The UTE-PLANAGEO Project (National Geology Plan of Angola). Objectives, methods, and resultsPublication . Garcia-Lobon, Jose Luis; Merino-Martinez, Enrique; Fernández, J.; Carvalho, João; Batista, Maria Joao; Escuder, Javier; Lisboa, Jose; Martín-Banda, Raquel; Francés, Alain Pascal; Ramalho, Elsa; Martín-Méndez, I.; Rey-Moral, Carmen; Feria, María Carmen; Mochales, Tania; Ferreira, Ezequiel; Cuervo, I.; Manuel, José; Victorino, Américo da MataABSTRACT: The National Geology Plan of Angola (PLANAGEO) has been one of the most important Angolan infrastructure projects throughout the past twenty years. The objectives of PLANAGEO were: (a) to enhance Angola's geological and mineral resources knowledge; (b) to foster diversification of the national economy; and, (c) to attract foreign investment and promote the country development. The project integrated regional interdisciplinary geological surveys, including geological/aerogeophysical/geochemical mapping, raw materials and mineral resources prospecting, as well as specific studies in target areas. The project was launched by the Angolan government (Presidential Resolution 52/09), and implemented by the Geological Survey of Angola (IGEO), under the oversight of the Angolan Ministry of Mineral Resources, Oil and Gas (MIREMPET). In 2011, UTE consortium, a joint venture of IGME, the National Laboratory of Energy and Geology of Portugal (LNEG) and the Spanish company Impulso Industrial Alternativo (IIA) bid the call for tenders. In 2013 IGEO awarded UTE a contract to undertake PLANAGEO´s activities in the southwestern region of Angola, covering roughly 480.000 km2. From July of 2014 to the end of 2022, the UTE consortium conducted interdisciplinary studies and investigations that resulted in a comprehensive collection of maps and scientific reports and documents, comprising: Airborne geophysical mag/rad mapping. Geological mapping at 1:250.000 scale (and 1:500.000 and 1:1.000.000 synthesis). Geological mapping at 1:100.000 scale in selected areas. Geochemical mapping at 1:250.000 scale. Raw materials and Mineral resources mapping in target areas, at 1:50.000 scale.