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Percorrer GCG - Artigos em revistas internacionais por Domínios Científicos e Tecnológicos (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.
- Ediacaran and early-palaeozoic bimodal volcanism in the Ossa-Morena Zone, SW Iberian Massif: New clues for intraplate rifting shortly after the Cadomian OrogenyPublication . Cachapuz, P.; Chichorro, Martim Afonso; Bento dos Santos, Telmo; Carvalho, D.; Linnemann, Ulf; Zieger-Hofmann, M.; Zieger, J.; Dantas, E.; Santos, R. V.; Moita, Patrícia; Beltrame, M.; Solá, A. Rita; Díaz-Azpíroz, M.; Fernández, C.ABSTRACT: This study focuses on bimodal meta-volcanic rocks present in the Iberian Massif, in the Evora-Aracena Metamorphic Belt of the Ossa-Morena Zone (OMZ), near the boundary with the South Portuguese Zone. New petrological, geochemical (whole-rock and Sr-Nd isotopes) and LA-ICP-MS U-Pb zircon geochronology data are presented to track the magmatic evolution of both felsic and mafic rocks and their respective geodynamic setting during the transition between the Cadomian Orogeny and subsequent Palaeozoic rifting events. Our research shows that the Evora-Aracena Metamorphic Belt (EAMB) in the southwestern OMZ possesses a significant record of the transition between the Cadomian and Variscan cycles. U-Pb geochronological data confirm the existence of both felsic and mafic Ediacaran igneous rocks (546 and 556 Ma, respectively), a novelty in the region. The Cadomian-related felsic rocks show geochemical similarities to meta-felsic rocks formed during the initial phases of the Cambrian rifting event, namely very negative epsilon Nd values (-10.1 to -11.8), depleted HREE patterns and orogenic signatures. Such similarities imply that meta-felsic rocks formed in the earliest stages of the Cambrian Rift-to-Drift event resulted from a shallower melting. Moreover, meta-felsic rocks formed in the early stages of the Cambrian rifting (525 Ma) present a significant amount of Ediacaran aged zircons, whereas the Cadomian-related counterparts display a few discordant Cambrian ages, likely a consequence of Pb-loss. This indicates that the convergent, subduction-related regime that prevailed during most of the Cryogenian-Ediacaran times along the boundaries of NW Gondwana was swiftly supplanted by a rift-dominated regime during the Cambrian, with no substantial gap between these two thermal events. Meanwhile, meta-felsic rocks formed during the Rift-to-Drift (525-480 Ma) event exhibit progressively higher epsilon Nd values (-5.0 to +3.0), HREE-enrichment, as well as anorogenic signatures, denoting an increasing contribution of mantle-derived melts. This increasing mantle contribution eventually led to the occurrence of bimodal magmatism in the Middle Cambrian Main Rift event. Such Cambrian mafic rocks, unlike the Ediacaran mafic rocks that present flat REE patterns and continental arc signatures, display varying degrees of LREE enrichment and N-MORB to E-MORB signatures.
- 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.
- Follow that blade!- Petroarchaeological proxies as indicators of human mobility during the Copper age of the SW of the Iberian Peninsula: Vila Nova de Sao Pedro case study (Portugal)Publication . Jordão, Patrícia; Neves, César; Mesquita Soares, Sofia; Morgado-Rodríguez, Antonio; Diniz, Mariana; Arnaud, José M.ABSTRACT: Petroarchaeological proxies of blades are a powerful tool for the study of mobility in prehistoric populations to deliver more information on the network relationships of exchange, particularly during the Copper age. However, it is only recently that the first petroarchaeological studies have begun in the SW of the Iberian Peninsula, concerning Recent Prehistory. A sampling of blades from Vila Nova de Sao Pedro, one of the main fortified settlements in Portuguese Estremadura, was used for petrographic and geochemical study. Following the same protocol, geological samples of flint and also igneous rocks were analysed. Additionally, a techno-typological approach was combined in order to characterize the blades types in circulation. This preliminary study traced the diverse and complex dynamics of blade production, which involved the collection of the most readily available Rio Maior flint and the regionally selected Caxarias flint. There were no significant differences in knapping techniques for these two types of flint. The most distant oolitic varieties from Subbetic Cordillera (within 500 km) and the igneous rocks from the Iberian Piryte Belt (within 250 km), particularly for large blades, were not debitated at the site. Due to the high numbers of those types of materials at the site, Vila Nova de Sao Pedro most likely played a significant role in the complex mobility networks of large blades, establishing itself as an aggregating site and possibly a distributor of these artefacts to the Southwest of the Iberian Peninsula. Considering the proximity and the quality of Rio Maior flint sources but also to the amount of raw materials at the site sourced from a long distance, this study shows that mobility is more influenced by cultural motivations than by the availability or quality of raw materials.
- Geochemical and Sr-Nd isotope constraints on the provenance of Permian deposits from Mozambique's Lower Karoo Zambezi BasinPublication . Jorge, Raul C. G. Santos; Fernandes, Paulo; Pereira, Zélia; Santos, José Francisco; Lopes, Gilda; Marques, JoãoABSTRACT: Whole-rock geochemistry and Sr-Nd isotopic compositions of Permian mudrocks from the Moatize and Matinde formations were analysed to constrain the sediment provenance, weathering history and palaeogeographic setting of the Moatize - Minjova Sub-Basin in the Karoo Zambezi Basin of Mozambique. The geochemical signatures of both formations suggest minimal effects of recycling and sorting, and point to rapid sediment deposition within an active tectonic setting. Trace element systematics and key provenance ratios (Th/Sc, La/Sc, Cr/Th, La-N/Sm-N,Sm- Eu/Eu & lowast;) indicate heterogeneous source areas dominated by felsic rocks with a minor mafic contribution. The mudrocks of the Moatize and Matinde formations exhibit similar isotopic signatures, with epsilon Nd (t) values of -9.32 +/- 0.74 and -7.99 +/- 1.10, and Nd T-DM model ages of 1.68 +/- 0.08 and 1.51 +/- 0.12 Ga, respectively. These isotopic signatures indicate that both formations were derived from mixed sources, including late Mesoproterozoic and Neoproterozoic rocks from southern Malawi, the Nampula Block (a subdomain of southernmost Malawi), the Guro Suite and the Macossa-Chimoio Nappe. Both Moatize and Matinde mudrocks exhibit high Chemical Index of Alteration (>85) and Chemical Index of Weathering (>90) values, along with low Index of Compositional Variability and low K/Cs ratios. The Al2O3-(CaO + Na2O)-K2O (A-CN-K) relationships indicate that the Moatize and Matinde mudrocks have not undergone post-depositional K-metasomatism. The data collectively indicate intense palaeoweathering conditions in the source areas. Furthermore, the weathering indices suggest warm and humid palaeoclimate during the deposition of the Moatize and Matinde formations. These formations were deposited in a confined continental basin between the Guadalupian (middle Permian) and the Lopingian (late Permian).
- Maps of Industrial Rocks and Minerals of Angola: CARMINA Project. Products obtained and main resultsPublication . Fernández, J.; Lisboa, Jose; Iglesias-Martínez, Mario; Gumiel, J.C.; Feria, María Carmen; Francés, Alain Pascal; Merino-Martinez, Enrique; Manuel, José; Garcia-Lobon, Jose LuisABSTRACT: Recognizing the pivotal role of the sector in the socioeconomic development of the nation, the Government of the Republic of Angola has actively endorsed the establishment of a geological-mining cartography. This initiative, employing modern methodologies, is a fundamental tool for strategically planning mineral resource exploitation. The outcomes of this initiative underscore the remarkable diversity of substances and the considerable significance of the studied deposits. In the domain of Industrial Rocks and Minerals, specifically within the CARMINA subprogram, a comprehensive compilation of 30 geological-mining maps has been generated. These maps delineate Areas of Mining Potential, and are accompanied by corresponding reports that encapsulate the research findings and technical-analytical outcomes of the investigated regions. The undertaken efforts have unveiled the substantial potential for Natural Stone, featuring novel varieties of granites, marbles, and “exotic” rocks such as amazonites, sodalites, pegmatites, and carbonatites. The last refered rock types are particulary interesting since they serve as sources for industrial rocks and minerals, encompassing valuable resources like lithium and Rare Earths. Thus, these resources exhibit promising prospects in the context of the energy transition. Additionally, noteworthy deposits include high-purity quartz in Equimina region, feldspars in Giraúl area, kaolins and clays within the Cunene Anorthositic Complex. The systematic creation of mineral resource maps, along with the associated research, contributes to the provision of up-to-date information regarding the geological-mining potential of the studied territory.
- 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.
- Palynological insights into the Eocene-Oligocene biostratigraphy , palaeoenvironment, and palaeoclimates of the Kwanza Basin, AngolaPublication . Pereira, Zélia; Silva Mendes, Márcia Cristina; Rodrigues, Cristina F.A.; Nsungani, P.C.ABSTRACT: New biostratigraphic and palaeoenvironmental data from Cabo de Sao Bras in the Kwanza Basin reveal over 40 m of marine sediments (Cunga and Quifangondo formations) spanning the Eocene-Oligocene transition. Wellpreserved dinoflagellate cysts within these sediments provide precise age determinations and palaeoenvironmental insights. The Cunga Formation, ranging from the late Eocene to the Oligocene, is characterized by sporadic occurrences of Diphyes colligerum, Glaphyrocysta semitecta, Schematophora cf. speciosa, Deflandrea heterophlycta, Rhombodinium draco, and Rhombodinium porosum. The overlying interval reveals a Rupelian assemblage, including Achomosphaera alcicornu and Hystrichokolpoma cf. Pseudooceanicum. The uppermost part of the Cunga Formation is marked by the lowest occurrence of Tuberculodinium vancampoae and the highest occurrence of Achomosphaera alcicornu during the Chattian. In contrast to existing geological maps, the transition to the Quifangondo Formation reveals a continuous sequence from the uppermost Chattian, based on the cooccurrence of Distatodinium paradoxum and Phelodinium africanum, along with a significant acme of Hystrichokolpoma spp. Palaeoenvironmental analysis suggests a marine setting with periods of both low and high productivity. Significant environmental transitions are observed, ranging from outer neritic to oceanic conditions at the base of the Cunga Formation (late Eocene-Oligocene, late Rupelian-early Chattian). In the late Oligocene, despite considerable terrigenous input, palynological data suggest predominantly inner to outer neritic conditions at the top of the Cunga Formation and the base of the Quifangondo Formation. Fluctuations in dinoflagellate cyst influxes reflect changes in water temperatures, providing insights into past climate shifts, during the EoceneOligocene transition, and offering a valuable framework for future palaeoclimatic investigations.
- The palynology of the Upper Triassic-Lower Jurassic in the Algarve and Lusitanian basins, PortugalPublication . Vilas Boas, Margarida; Cirilli, Simonetta; Pereira, Zélia; Duarte, Luis; Fernandes, PauloABSTRACT: High-resolution palynological analyses from the Algarve and Lusitanian basins (Portugal) provide a refined biostratigraphical framework and palaeoenvironmental reconstruction for the Late Triassic-Early Jurassic transition. In the Algarve Basin, three new palynozones (AT, SC, and CP) characterise the Silves Group from the early Carnian to early Hettangian, documenting the first Iberian occurrence of Tulesporites briscoensis and precisely delineating the Triassic-Jurassic Boundary (TJB). In the Lusitanian Basin, three palynozones (CG, IK, and Pm) constrain the Conraria and Pereiros formations to the Norian-Hettangian, with the TJB located at the base of the Pereiros Formation. Palaeoenvironmental reconstructions reveal distinct basin-specific evolutions. The Algarve Basin records an early transition from fluvial (Silves Sandstones) to marginal-marine (lagoonal and pond) settings, evidenced by abundant upper Carnian algal elements and reworked Neoproterozoic algae. Conversely, the Lusitanian Basin reflects a Norian-Hettangian marginal-marine, river-dominated setting, with microforaminiferal linings at the base of the Pereiros Formation marking the earliest marine transgression in the Lusitanian Basin. Quantitatively, both basins show a persistent dominance of xerophytic taxa, indicating a shift toward warmer, seasonally dry conditions across the TJB. Malformed sporomorphs in both records suggest environmental stress potentially linked to Central Atlantic Magmatic Province (CAMP) activity. Comparative analysis reveals that sedimentation initiated earlier in the Algarve (early Carnian) than in the Lusitanian Basin (Norian), suggesting diachronous development during Pangaea breakup. The assemblages show strong affinities with the Onslow Microflora, highlighting the Portuguese margin as a key archive for western Tethyan floral and climatic evolution.