Browsing by Author "Fernandes, Paulo"
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- The age and depositional environments of the lower Karoo Moatize Coalfield of Mozambique: insights into the postglacial history of central GondwanaPublication . Fernandes, Paulo; Hancox, Philip John; Mendes, Márcia; Pereira, Zélia; Rodrigues Lopes, Gilda Maria; Marques, João; Jorge, Raul Carlos Godinho Santos; Albardeiro, LuísThe Moatize Coalfield belongs to a network of continental Karoo basins of central Mozambique, known as the Zambezi Basin. Palynological and sedimentological studies were performed on four coal exploration boreholes to determine the age, depositional settings, and overall geological evolution of its extensive coal deposits. Clastic formations recognised in this coalfield, in ascending order, are the Vu´zi, Moatize and Matinde formations. Palynomorph assemblages indicate that the Moatize Coalfield succession ranges from Roadian (lower Guadalupian) to Changhsingian (upper Lopingian) in age. Two main depositional phases are identified, whose initiation and development are attributed to regional tectonic events and climate amelioration. The first phase formed towards the end of the deglacial period, characterised initially by fan deltas, represented by the upper Vu´zi Formation, and the shift to lake–delta environments, represented by the lower part of the Moatize Formation. This phase took place from Roadian to the Wordian times. The lake–delta settings indicate a sediment aggradation trend with high subsidence rates in the lake basin, which, together with the associated post-glacial climate amelioration, led to the accumulation of coal deposits in swamps of the delta top and lake margins. The second depositional phase took place from Capitanian to Changhsingian times and related to fluvial environments initiated by uplift that reorganised the depocenter into alluvial plains characterised by bedload dominated rivers (braided) and overbank floodplains. Results obtained in this study provide critical information for the onset of the deglaciation events and the age of coal deposits in this part of Gondwana, important for wider stratigraphic correlation of these events in Africa and throughout the Gondwana.
- Análise de proveniência dos sedimentos siliciclásticos do Grupo do Flysch do Baixo Alentejo, Zona Sul PortuguesaPublication . Fernandes, Paulo; Jorge, R. C. G. S.; Oliveira, José Tomás; Pereira, Zélia; Rodrigues, B.Os estudos de análise de proveniência dos sedimentos siliciclásticos do Grupo do Flysch do Baixo Alentejo sugerem mudanças na natureza das áreas fonte ao longo da sua história deposicional. Petrograficamente regista-se uma mudança de áreas iniciais caracterizadas por rochas magmáticas para áreas representadas por rochas (meta)sedimentares recicladas. Os indicadores geoquímicos de proveniência sugerem mistura de fontes, envolvendo quer rochas ígneas félsicas, quer litologias máficas para a Fm. Mértola, evoluindo para um predomínio de rochas (meta)félsicas associada à área fonte dos sedimentos siliciclásticas da Fm. Brejeira.
- Assessing thermal maturity through a multi-proxy approach: a case study from the Permian Faraghan Formation (Zagros Basin, Southwest Iran)Publication . Spina, Amalia; Cirilli, Simonetta; Sorci, Andrea; Schito, Andrea; Clayton, Geoff; Corrado, Sveva; Fernandes, Paulo; Galasso, Francesca; Montesi, Giovanni; Pereira, Zelia; Rashidi, Mehrab; Rettori, RobertoThis study focuses on the thermal maturity of Permian deposits from the Zagros Basin, Southwest Iran, employing both optical methods (Thermal Alteration Index, Palynomorph Darkness Index, Vitrinite Reflectance, UV Fluorescence) and geochemical analyses of organic matter (Rock Eval Pyrolysis and MicroRaman spectroscopy) applied to the Faraghan Formation along two investigated Darreh Yas and Kuh e Faraghan surface sections. Furthermore, an integrated palynofacies and lithofacies analysis was carried out in order to integrate the few studies on the depositional environment. The Faraghan Formation, which is widely distributed in the Zagros area, generally consists of shale intercalated with sandstones and pebble conglomerates in the lower part, followed by a succession of sandstone, siltstone and shaly intercalations and with carbonate levels at the top. The integrated palynofacies and lithofacies data confirm a coastal depositional setting evolving upwards to a shallow marine carbonate environment upwards. Rock Eval Pyrolysis and Vitrinite Reflectance analysis showed that the organic matter from samples of the Darreh Yas and Kuh e Faraghan sections fall in the mature to postmature range with respect to the oil to gas generation window, restricting the thermal maturity range proposed by previous authors. Similar results were obtained with MicroRaman spectroscopy and optical analysis such as Thermal Alteration Index and UV Fluorescence. Palynomorph Darkness Index values were compared with Rock Eval Pyrolysis and vitrinite reflectance values and discussed for the first time in the late stage of oil generation.
- Callovian (Middle Jurassic) dinoflagellate cysts from the Algarve Basin, southern PortugalPublication . Borges, Marisa; Riding, James B.; Fernandes, Paulo; Matos, Vasco; Pereira, ZéliaThe palynology of three Callovian (Middle Jurassic) limestone-marl successions from the Algarve Basin in southern Portugal was studied. These localities are Baleeira Harbour, Mareta Beach and Telheiro Quarry; they provide a composite. succession, tied to ammonite zones, through the Lower, Middle and Upper Callovian from the western and eastern subbasins of the Algarve Basin. The three sections generally yielded relatively abundant marine and continental palynofloras. Diversity is low to moderate and the dinoflagellate cyst associations are dominated by Ctenidodinium spp., the Ellipsoidictyum/Valensiella group, Gonyaulacysta jurassica subsp. adecta, Korystocysta spp., Meiourogonyaulax spp., Pareodinia ceratophora, Sentusidinium spp., Surculosphaeridium? vestitum and Systematophora spp. Some intra-Callovian marker bioevents were recorded; these include the range bases of Ctenidodinium ornatum, Gonyaulacysta eisenackii, Korystocysta pachyderma, Mendicodinium groenlandicum, Rigaudella spp. and Surculosphaeridium? vestitum. The occurrences of Endoscrinium acroferum and Impletosphaeridium varispinosum in the Early to Middle Callovian of Mareta Beach and Telheiro Quarry are also characteristic of this interval. At Baleeira Harbour, the presence of Ctenidodinium continuum and Gonyaulacysta centriconnata in the Peltoceras athleta Zone confirms the Late Callovian age of this section. The successions studied were deposited in restricted infralittoral neritic marine environments which lack deep water circulation, and possibly represent restricted embayments. The relatively low diversity nature of the dinoflagellate cyst assemblages appears to be largely due to the highly enclosed nature of this depocentre. Many Callovian index dinoflagellate cyst taxa which are found in northwest Europe are absent in the Algarve Basin. These forms may have been intolerant of enclosed palaeoenvironments which have restricted or no deep circulation. The Callovian marine palynofloras from the Algarve Basin compare well to the few other published records from the Iberian Peninsula of this age. However they are significantly less diverse than coeval floras from elsewhere in the extensive Mid Latitude Callovian phytoprovince. Many typically Callovian dinoflagellate cysts are cosmopolitan, however some provincialism is clearly manifested. The Arctic and Austral Callovian phytoprovinces are characterised by key endemic taxa such as Paragonyaulacysta retiphragmata and Ternia balmei, which are not present in the Algarve Basin and are assumed to have been polar forms.
- Caracterização da evolução do perfil longitudinal das ribeiras do oeste do Algarve - dados preliminaresPublication . Rodrigues, Bruno; Veiga-Pires, C.; Moura, Delminda; Fernandes, Paulo; Boski, T.A actual rede hidrográfica na região do Algarve, devido à proximidade do mar e ao seu contexto tectónico, teve ao longo da sua formação uma forte influência dos efeitos eustáticos, tendo também o clima regional um papel fulcral na incisão do vales actuais a diferentes escalas temporais.
- Caracterização geoquímica da formação brejeira (grupo do Flysch do Baixo Alentejo): resultados preliminaresPublication . Fernandes, Paulo; Jorge, R. C. G. S.; Rodrigues, B.; Pereira, Zélia; Oliveira, José TomásA Formação Brejeira é a unidade litoestratigráfica mais recente do Grupo do Flysch do Baixo Alentejo consistindo, essencialmente, de grauvaques e quartzovaques de natureza turbidítica intercalados com xistos argilosos. A idade da Fm. Brejeira distribui-se entre o Bashkiriano e o Moscoviano superior (Carbonífero Superior). O estudo petrográfico e mineralógico dos grauvaques da Fm. Brejeira relevou a seguinte composição Qt81,6F0,9Lt17,5, resultados que sugerem uma proveniência dos sedimentos de áreas caracterizadas predominantemente por rochas (meta)sedimentares recicladas. Do ponto de vista geoquímico os grauvaques são enriquecidos em SiO2 (>75%) reflectindo uma mineralogia dominada pelo quartzo. Os xistos argilosos apresentam Índices de Variabilidade Composicional (IVC) inferiores a 1 e baixas razões K2O/Al2O3 (0,2±0,02) e Na2O/K2O (0,15±0,06). As litologias da Fm. Brejeira exibem padrões normalizados das Terras Raras caracterizados por enriquecimento em Terras Raras Leves, anomalia de Eu negativa e reduzido fraccionamento das Terras Raras Pesadas. Quer os grauvaques quer os xistos argilosos possuem valores similares das razões Lan/Smn, Gdn/Ybn e Eu/Eu*. O Índice de Meteorização Química (CIW) das litologias da Fm. Brejeira é elevado (>80,93) e o Índice de Alteração da Plagioclase (PIA) apesar de mais variável, é na maioria das amostras elevado (PIA 67,24 – 96,14). Os valores de CIW e PIA sugerem condições de meteorização química de moderada a intensa. Os dados petrográficos e geoquímicos sugerem áreas-fonte dos sedimentos da Fm. Berjeira caracterizadas por rochas félsicas e (meta)sedimentares recicladas
- Caracterização geoquímica do Grupo do Flysch do Baixo Alentejo (Zona Sul Portuguesa): resultados preliminaresPublication . Fernandes, Paulo; Jorge, R. C. G. S.; Pereira, Zélia; Oliveira, José TomásO Grupo do Flysch do Baixo Alentejo (GFBA) é um dos domínios da Zona Sul Portuguesa (ZSP), sendo constituído por sedimentos turbidíticos profundos, com uma espessura superior a 5 km (Oliveira, 1990).
- Carbon isotope record (d13Ccarbonate) of the Middle to Late Jurassic (Callovian - Oxfordian) from the Algarve Basin, PortugalPublication . Borges, Marisa; Fernandes, Paulo; Rodrigues, Bruno; Goodhue, R.The Algarve Basin is an important Mesozoic depocentre located in southern Portugal which formed during the succesive phases of the North Atlantic rifting following the break-up of Pangea [1]. Several unconformities related to compressive episodes are observed in the stratigraphic record of the Algarve Basin. One of these episodes ocurred in the transition from Middle to Upper Jurassic times and is marked by an important tectonic episode, observed throughout Iberia [1], that caused the tilting and folding of the Middle Jurassic strata. This situation can be observed at Benaçoitão, where Oxfordian limestones rest unconformably over tilted Middle Callovian marly limestones. In this work we present !13Ccarbonate data across the Middle and Upper Jurassic rocks from the Algarve Basin at Benaçoitão.
- Carboniferous palynostratigraphy of the borehole SDJ1 from the Santa Susana region, Ossa Morena Zone, PortugalPublication . Pereira, Zélia; Lopes, Gilda; Fernandes, Paulo; Matos, João Xavier; Rosa, Diogo; Oliveira, José TomásThe borehole SDJ1, with a total depth of 404.5 meters, was drilled in 1991 by the Serviço de Fomento Mineiro to investigate an Electromagnetic TEM conductor (Oliveira & Matos 1991). This hole is located in the eastern sector of the Santa Susana/Moinho da Ordem coal mine (1927-1944), in the Jongeis mine sector. The borehole log indicates that it cuts lithologies of the Carboniferous Toca da Moura Complex (TMC) and the Santa Susana Formation (SSF).
- Contribuição para o estudo da estrutura da mina de Aljustrel (Faixa Piritosa Ibérica) com base em novos dados palinoestratigráficos do Complexo Vulcano-Sedimentar e da Fm. MértolaPublication . Matos, João Xavier; Pereira, Zélia; Fernandes, Paulo; Rosa, Diogo; Oliveira, José TomásA cartografia geológica de detalhe e a análise palinoestratigráfica de sedimentos do Complexo Vulcano-Sedimentar da Faixa Piritosa e da Fm. Mértola, na região da mina de Aljustrel, permite uma melhor compreensão da estrutura local. A Fm. Paraíso apresenta uma idade Tournaisiano sup. - Viseano inf. (biozonas CM e Pu). A Fm. Gavião tem uma idade semelhante, contendo associações de miosporos da biozona CM, do Tournaisiano sup. Propõe-se uma nova unidade sedimentar correspdente à base da Fm. Mértola, a Unidade Canal da BAI, de idade Viseano médio-sup. (biozona NM).