Mostrando recursos 1 - 20 de 63

  1. Mudança do nível do mar no golfo de Cádiz durante o Plistocénico tardio e Holocénico

    Boski, T.; Moura, Delminda; Sousa, Carlos; Gomes, Ana; Pereira, Laura; Oliveira, Sónia; Santana, Paulo
    The multiproxy information data set obtained from borehole sequences permitted to establish a robust chronology of events, which led to the post glacial infilling of the terminal stretches of regional river palleovaleys. The paleoecological reconstructions combined with 14C age model of Guadiana Estuary sedimentary record revealed the fast sea level rise period since ca 13.5 kyr cal BP, halted during the Younger Dryas and resuming at ca 11500 yr cal BP. The Holocene history of coastal evolution is also well documented in the Estuary of Arade and in Ria Formoza, pointing to the sea level stabilization at ca 7500 cal BP...

  2. Moving sands along a headland-embayed beach system (Algarve, Southern Portugal)

    Oliveira, Sónia; Horta, João; Nascimento, Ana; Gomes, Ana; Veiga-Pires, C.; Moura, Delminda
    Resilience of embayed and pocket beaches located at the southernmost coast of Portugal is currently a major question to coastal management of this region. In fact, several among those beaches have been artificially fed aiming to increase the width of the beach allowing people to maintain a safe distance to the unstable rocky cliffs.

  3. Modelling the hydrodynamic and morphosedimentary response of an beach-headland system (Algarve, Southern Portugal)

    Horta, João; Oliveira, Sónia; Moura, Delminda
    Future behaviour of beaches within a headland-beach system is of fundamental interest on coastal evolution since they act as a buffer between the waves’ attack and the cliffs backing them. The beaches at the cliffs’ foot anchored between headlands are space-limited environments to morphosedimentary processes.

  4. O registo de diatomáceas e foraminiferos da Ria Formosa (Sul da Península Ibérica): uma contribuição para a compreensão da evolução Holocénica do sistema lagunar.

    Gomes, Ana; Pereira, Laura; Boski, T.; Connor, Simon; Sousa, Carlos; Oliveira, Sónia; Santana, Paulo
    As part of a multi-proxy study to reconstruct the Holocene evolution of the Ria Formosa Lagoon, diatom and foraminifera assemblages were analyzed in a ca. 24.6-m-deep borehole, which crossed the entire infill sequence of the local paleovalley. Except in a few samples, diatom assemblages were generally poorly preserved, whereas foraminiferal assemblages were mostly well preserved. In the core depths interval from 23.5 and 3.2 m, both proxies indicate a marine environment installed during the progressive flooding of the fluvial valley during the Holocene. Above 3.2-m, both proxies

  5. Holocene history of Ria Formosa coastal lagoon system (Southern Portugal): borehole evidence and threedimensional paleotopography

    Sousa, Carlos; Boski, T.; Gomes, Ana; Pereira, Laura; Lampreia, João; Oliveira, Sónia
    A paleotopographic model of Ria Formosa is presented based on two borehole campaigns and a systematic comparison with previous works, revealing the existence of a complex network of fluvial valleys. Vertical sediment profiles showed a mosaic of changing depositional environments, resulting from local hydrodynamics, sedimentary sources and, to an extent, by the structurally inherited accommodation space. Sedimentological, geochemical and micropaleontological data were put in the context of an age model obtained from 14C datings, pointing to the existence of an estuarine environment subjected to a rapid coastal flooding from ca. 10000 to 7500 cal. years B.P., followed by a period...

  6. Aplicação multimédia sobre a Ria Formosa e seus fins educacionais (ForDid)

    Oliveira, Sónia; Boski, T.; Moura, Delminda; Sousa, Carlos; Gomes, Ana; Pereira, Laura
    Na atualidade torna-se inquestionável a necessidade de integrar a aprendizagem com as novas tecnologias de modo a cativar e facilitar a compreensão dos temas abordados através de aplicações didáticas. Durante a última década o Centro de Investigação Marinha e Ambiental (CIMA) assumiu a responsabilidade de criar meios eficazes de comunicação entre o público em geral e a comunidade científica, através de plataformas multimédia interativas. Foram objecto destas aplicações didáticas as várias vertentes do património natural do Algarve. Após o sucesso das primeiras aplicações GuaDid e MonDid visando o Estuário do Rio Guadiana e a Serra de Monchique respectivamente, o desafio de criar e inovar foi acrescido, resultando numa...

  7. Hydro-sedimentary processes in a beach-headland system

    Moura, Delminda; Veiga-Pires, C.; Oliveira, Sónia; Horta, João; Nascimento, Ana; Gomes, Ana; Guerra, Liliana
    Understanding hydro-sedimentary processes in space-limited environments as embayed beaches is a key question to reconstruct preterit and predict future coastal evolution forced by the mean sea level rise. Moreover, such knowledge is a fundamental management tool in areas where coastal erosion is currently a worrying fact. This work aims thus to assess the sedimentary contribute, provided by the alongshore transport, to feed embayed beaches. At the southernmost rocky coast of Portugal (Algarve), beaches occurring at the cliffs’ foot are separated by headlands connected to shore platforms forming littoral cells as a consequence of the extremely karstified carbonate landscape. The survival of those beaches depends almost exclusively on the...

  8. Modern diatom assemblages as tools for paleoenvironmental reconstruction: a case study from estuarine intertidal zones in southern Iberia

    Gomes, Ana; Boski, T.; Moura, Delminda; Szkornik, Katie; Witkowski, Andrzej; Connor, Simon; Laut, Lazaro; Sobrinho, Frederico; Oliveira, Sónia
    Diatoms are unicellular algae that live in saline, brackish and freshwater environments, either floating in the water column or associated with various substrates (e.g., muddy and sandy sediments). Diatoms are sensitive to changes in environmental variables such as salinity, sediment texture, nutrient availability, light and temperature. This characteristic, along with their short lifespan, allows diatoms to quickly respond to environmental changes. Since the beginning of the 20th century, diatoms have been widely used to study the Holocene evolution of estuaries worldwide, particularly to reconstruct ecological responses to sea-level and climate changes. However, diatoms have been poorly studied in estuarine intertidal zones, due to the complexity of...

  9. Potencial gerador de hidrocarbonetos dos argilitos carbonosos do Karoo Inferior (Pérmico) da Bacia de Moatize – Minjova, Província de Tete, Moçambique

    Fernandes, Paulo; Rodrigues, Bruno; Jorge, R. C. G. S.; Marques, João
    A Formação Moatize na Bacia de Moatize – Minjova é uma unidade importante do Karoo de Moçambique, consistindo em argilitos carbonosos, arenitos e camadas de carvão. Os argilitos carbonosos possuem um importante potencial como rochas geradoras de gás, podendo ser considerados como unidades importante de ‘gás de xisto’. Os valores de %Rr medidos indicam um grau de maturação orgânica compatível com o final da janela do petróleo (ca, 1,35 – 1,4 %Rr). A Formação Moatize é caracterizada por possuir querogénio do tipo II-III e do tipo III, com elevados valores de COT e valores de HI médios a elevados, sendo...

  10. The Middle Jurassic palynology of the Sagres region, southern Portugal.

    Borges, Marisa; Fernandes, Paulo; Pereira, Zélia; Riding, Jim
    The Algarve Basin corresponds to the southernmost geological province of mainland Portugal. It has an E-W strike and is represented onshore from Cap São Vicente to the Guadiana River on the Portuguese-Spanish border. More than 3000 m of essentially marine sediments accumulated during Mesozoic-Cenozoic times in the Algarve Basin.

  11. Palynostratigraphy study of the Caveira Mine (NW sector of the Iberian Pyrite Belt, Portugal)

    Pereira, Zélia; Fernandes, Paulo; Oliveira, José Tomás; Matos, João Xavier
    In the NW sector of Iberian Pyrite Belt, the geology is dominated by complex antiformal structures, as we can observe in the Lousal and Caveira old massive sulphide mines, both located at the Azinheira de Barros region. The age of the lithostratigraphic units of these structures is still poorly constrained and subsequently palynostratigraphy revisions are being undertaken.

  12. Organic maturation levels and thermal history of the Carboniferous rocks of the Dublin Basin

    Fernandes, Paulo; Clayton, Geoff
    The Dublin Basin sucession comprises sediments in age from Mississippian (Courceyan) to Pennsylvanian (Langsettian). The Viséan part of. the succession is dominated by turbiditic calcarenites interbedded with grey-black shales. Namurian and earliest Westphalian rocks preserved in the Kingscourt Outlier in the north of the basin are dominated by sandstones interbedded with silstones and shales.

  13. História térmica do grupo do Flysch do Baixo Alentejo, Zona Sul Portuguesa

    Rodrigues, Bruno; Chew, Dave; Jorge, R. C. G. S.; Fernandes, Paulo
    Com objectivo de reconstruir a história térmica do Grupo Flysch Baixo Alentejo foi realizado um estudo sistemático com o auxílio de duas metodologias complementares: medição do poder reflector da vitrine e datações de traços de fissão de apatites contidas em grauvaques das formações de Mértola, Mira e Brejeira.

  14. Geochemistry of the Baixo Alentejo Flysch Group, South Portuguese Zone: implications for provenance and palaeoweathering

    Fernandes, Paulo; Jorge, R. C. G. S.; Pereira, Zélia; Oliveira, José Tomás
    The Baixo Alentejo Flysch Group (BAFG) is one of the domains of the South Portuguese Zone, consisting of deepwater tubiditic sediments, with more than 5 km in thickness. Stratigraphically the BAFG is subdivided into three formations, from the bottom to the top: Mértola Formation, Mira Formation and Brejeira Formation, with ages ranging from Middle to Upper Carboniferous.

  15. Geochemical signatures in detrital tourmalines as indicators for sediment provenance: the Baixo Alentejo Flysch Group, South Portuguese Zone

    Rodrigues, B.; Dias, Patrícia; Jorge, R. C. G. S.; Fernandes, Paulo
    Microprobe analyses were made to infer the source of detrital tourmalines from the Mid to Late Carboniferous turbiditic deposits of the Baixo Alentejo Flysch Group (BAFG) of the South Portuguese Zone.

  16. Poder reflector da vitrinite, mineralogia das argilas e cristalinidade da ilite na Zona Sul Portuguesa

    McCormack, Niall; Clayton, Geoff; Fernandes, Paulo
    O Poder Reflector Aleatório da Vitrinite (PRAV) na Zona Sul Portuguesa (ZST) varia entre 2,1% e 5,3%. O PRAV não aumenta com o aumento da idade estratigráfica e o processo de maturação é portanto, considerado como pós-deformação (pós-Vestefaliano D inferior). Amostras do Triásico e do Jurássico do Outlier da Carrapateira têm PRAV de 1,1% e 0,9% respectivamente. Isto implica que temperaturas máximas relacionadas com a maturação da ZSP foram alcançadas entre o Vestefaliano D inferior e o Triásico médio. A caulinite é o mineral das argilas dominante nas regiões ocidentais da ZSP, enquanto que as regiões localizadas a este e...

  17. Geologia Sul Portuguesa, com ênfase na estratigrafia, vulcanologia física, geoquímica e mineralizações da faixa piritosa

    Oliveira, José Tomás; Relvas, J.; Pereira, Zélia; Munhá, José; Rosa, Carlos; Rosa, Diogo; Fernandes, Paulo; Jorge, R. C. G. S.; Pinto, Álvaro
    O presente trabalho resulta da adaptação e actualização do artigo «O Complexo Vulcano--Sedimentar da Faixa Piritosa: Estratigrafia, Vulcanismo e Mineralizações Associadas no Contexto da Zona Sul Portuguesa» de autoria de Oliveira et al., inserido no Livro Geologia de Portugal no Contexto da Ibéria, editado por Rui Dias, Alexandre Araújo, Pedro Terrinha e Carlos Kulberg e publicado pela Universidade de Évora, em 2006, durante o VII Congresso Nacional de Geologia.

  18. The thermal history of the Mesozoic Algarve Basin (South Portugal) and its implications for hydrocarbon exploration

    Rodrigues, Bruno; Fernandes, Paulo; Matos, Vasco; Borges, Marisa; Clayton, Geoff
    The Algarve Basin is the southernmost geological province of mainland Portugal, outcropping along the entire south coast area and extending offshore, where it is recognised on seismic lines and in hydrocarbon exploration wells. It mainly comprises Jurassic and Lower Cretaceous limestones and marls making a succession over 3 km thick. This sedimentary basin belongs to a series of basins that were initiated by rifting associated with the opening of the North and Central Atlantic Ocean, following the breakup of Pangaea.

  19. The geodynamic importance of the Late Cambrian to Late Devonian reworked palynomorphs from the borehole SDJ1, Santa Susana region, Ossa Morena Zone (OMZ), Portugal

    Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Matos, João Xavier; Rosa, Diogo; Oliveira, José Tomás
    The detail study of the borehole SDJ1 from the Santa Susana coal basin western border of the OMZ, Portugal, proved that most of the volcano sedimentary lithologic sequence yielded palynomorphs of mid late Visean age (NM Biozone) i.e., they belong to the Toea da Moura Volcano Sedimentary Complex (TMC). The deepest few meters of the drill core have shales of mid Moscovian (Biozona SL) (see Pereira et ai., in this volume).Together with the miospore assemblages that provide the age of the SDJ1 strata, mid late Visean and Moscovian age, associations of exceptional well preserved Lower Palaeozoic acritarchs and spores were identified and interpreted as reworked into the...

  20. Silurian to Lower Devonian Palynomorphs from the Barrancos region, Ossa Morena Zone, Portugal

    Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Piçarra, J. M.; Oliveira, José Tomás
    New miospore results were obtained from the Palaeozoic stratigraphic succession present in the Barrancos region, Portugal. The studied formations comprise the Silurian carbonaceous shales intercalated with cherts and rare lenticular carbonates of the Xistos com Nódulos Formation, as well as, the dark shales that alternates with thin psammit beds of Late Silurian to Early Devonian age from the Xistos Raiados Formation. Two miospore biozones were identified: the cf. protophanus verrucatus Miospore Biozone, of the Lower Wenlock (Homerian) (Richardson &McGregor, 1986) and the Verrucosisporites polygonalis (Po)Miospore Biozone of the Lower Pragian (Streel et al., 1987). For the first time cryptospores are reported. Rare acritarchs and chitinozoans are also...

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