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- Organic Maturation and Source-Rock Potential of the Mesozoic Algarve Basin: southern PortugalPublication . Fernandes, Paulo; Borges, Marisa; Rodrigues, B.; Matos, VascoThe Algarve Basin is an important Mesozoic depocentre in southern Portugal.
- História térmica da bacia carbonífera de Moatize-MinjovaPublication . Fernandes, Paulo; Cogné, N.; Marques, J. M.; Rodrigues, B.; Jorge, R. C. G. S.; Jamal, D.Duas sondagens de prospecção de carvão executadas na Bacia Carbonífera de Moatize-Minjova, foram estudadas usando as técnicas do poder reflector da vitrinite e dos traços de fissão da apatite para avaliar a sua história térmica.
- Idades U-Pb de zircões detríticos do Grupo do Flysch do Baixo Alentejo, Zona Sul PortuguesaPublication . Rodrigues, B.; Chew, Dave; Jorge, R. C. G. S.; Fernandes, Paulo; Veiga-Pires, C.; Oliveira, J. T.Foram obtidas idades U-Pb através de ablação a lazer de zircões detríticos das formações do Grupo do Flysch do Baixo Alentejo. As idades obtidas sugerem uma proveniência sedimentar, no caso das formações de Mértola e Mira, com o envolvimento de uma componente detrítica intrabasinal (Zona Sul Portuguesa) e de áreas fontes associadas ao bordo sul da Zona da Ossa Morena. No caso da Formação de Brejeira as idades sugerem um envolvimento de áreas fontes correlacionáveis com o terreno Avalonia/Meguma assim como de sedimentos reciclados oriundos do Domínio Sul Português.
- Reply to Discussion on 'Detrital zircon geochronology of the Carboniferous Baixo Alentejo Flysch Group (South Portugal); constraints on the provenance and geodynamic evolution of the South Portuguese Zone', Journal of the Geological Society, 172, 294-308Publication . Rodrigues, B.; Chew, D. M.; Jorge, R. C. G. S.; Fernandes, Paulo; Veiga-Pires, C.; Oliveira, J. T.We would like to thank Pereira (2015) for his interest in our work and appreciate the opportunity to clarify some aspects of the Rodrigues et al. (2015) study. Here we dispute several fundamental assertions made in the discussion of our original paper. (1) Pereira (2015) states, based on the U–Pb detrital zircon data of Pereira et al. (2012a, 2014), that the turbidites of the Mértola (late Visean) and the Mira (Serpukhovian to early Bashkirian) formations of the Baixo Alentejo Flysch Group of the South Portuguese Zone (Fig. 1b), were ‘mainly derived from a source terrane dominated by zircon populations of Middle–Late Devonian ages (c. 393–359 Ma) that are absent in the Ossa–Morena Zone’ and that this detrital zircon population forms 37.7% of all detrital zircons of these two formations. However, a large population of zircons of Middle–Late Devonian age was not found in the Rodrigues et al. (2015) study. The Mértola Formation (sample FM1; table 1 of Rodrigues et al. 2015) is clearly dominated by one population whose zircon ages range between 388 and 326 Ma, with this group representing 68% of all ages obtained. This population shows a peak at 336 Ma (middle Visean).
- Geochemistry and provenance of the Carboniferous Baixo Alentejo Flysch Group, South Portuguese ZonePublication . Jorge, R. C. G. S.; Fernandes, Paulo; Rodrigues, B.; Pereira, Zélia; Oliveira, José TomásThis work is focused on the turbiditic sediments from the Carboniferous Baixo Alentejo Flysch Group (BAFG) in the South Portuguese Zone, an external zone of the Iberian Variscides. The aim of this work is to constrain the provenance and tectonic setting of these sediments in a context of a complex evolution of SW Iberian Variscides. For this purpose, we performed a systematic study of petrographical and geochemical signatures of greywackes and shales from the three BAFG formations: Mértola, Mira and Brejeira. Major and trace element composition and ratios suggest heterogeneous source area composition for BAFG shales and greywackes. For the oldest Mértola Formation greywackes, source area is dominated by granitoid rocks with minor mafic input. The latter becomes residual in the Mira Formation. The youngest Brejeira Formation greywackes show clear felsic affiliation associated with an increase in recycled components. The shales of all three BAFG formations denote a granodioritic affiliation. Chemical Index of Alteration (CIA) and Plagioclase Index of Alteration (PIA) values suggest moderate weathering in the source areas of Mértola and Mira formations. These indices, together with A–CN–K relations, point out to steady-state weathering conditions in the source areas of both formations. In contrast, both CIA and PIA values for the Brejeira Formation indicate variable conditions of palaeoweathering, from moderate to intense, as a consequence of non-steady-state conditions probably triggered by tectonic instability in the provenance area. Compared to the greywackes, the shales of all three BAFG formations exhibit higher CIA and PIA values, as well as low K2O/Al2O3 (~0.2) and index of compositional variability (b1), reflecting the cumulative effect of multiple cycles of sedimentary recycling and prolonged chemical weathering history. Major and trace element distribution and upper continental crust-normalized multi-element plots suggest that the sediments of BAFG were derived mainly from a continental arc/active margin with minor contribution from old continental crust. Together, our geochemical data are compatible with BAFG sediments derived mainly from SW border of the Ossa Morena Zone (Gondwanan affinity), with possible contribution from an external (Avalonian) source.
- Detrital zircon geochronology of the Carboniferous Baixo Alentejo Flysch Group (South Portugal); constraints on the provenance and geodynamic evolution of the South Portuguese ZonePublication . Rodrigues, B.; Chew, Dave; Jorge, R. C. G. S.; Fernandes, Paulo; Veiga-Pires, C.; Oliveira, J. T.U–Pb detrital zircon data from the Baixo Alentejo Flysch Group in the South Portuguese Zone show significant age differences between formations. The Visean Mértola Formation and Serpukhovian to early Bashkirian Mira Formation are dominated by zircons in the 316–388Ma age range, whereas the late Bashkirian to late Moscovian Brejeira Formation is dominated by zircons with an age range of 498–687Ma. Detrital zircons spanning an age range of 0.9–1.1Ga are present in the Brejeira Formation but are absent in the Mértola and Mira formations. Detrital zircon ages of the Mértola and Mira formations indicate provenance from an extra-basinal source (Ossa–Morena Zone) with a minor intra-basinal contribution (South Portuguese Zone). The abundant presence of detrital zircon with age ranges of 500–750 and 0.9–1.1Ga in the Brejeira Formation suggests a sediment source from the Avalon–Meguma terranes with limited recycling from the SW Portugal Domain. The different inferred source areas for the Baixo Alentejo Flysch Group formations are attributed to the presence of a forebulge that was formed in Mid-Visean times during the foreland phase of the South Portuguese Zone. The forebulge acted as a physical barrier separating sub-basins that accumulated the Mértola–Mira and Brejeira sediments respectively.
- Integrated thermochronology and organic maturation studies in the South Portuguese Zone and Algarve Basin (South Portugal)Publication . Rodrigues, B.; Chew, Dave; Fernandes, Paulo; Jorge, R. C. G. S.This PhD research project started in February this year. Its main goal is to combine apatite fission track analysis (AFTA) with other low-temperature thermochronometers (zircon fission track, (U-Th)/He apatite) to construct temperature-time paths for the South Portuguese Zone and the Algarve Basin.
- d13Ccarbonate chemostratigraphy of the Carrapateira Outlier (Lower Kimmeridgian), Southern PortugalPublication . Borges, Marisa; Goodhue, R.; Fernandes, Paulo; Pereira, Zélia; Matos, Vasco; Rodrigues, B.The Carrapateira Outlier (CO) located 20 km north of Sagres is formed by Upper Triassic to Kimmeridgian sediments. The studied section is located at Três Angras bay and consists of approximately 50 m of limestones interbedded with marls, assigned to the Early Kimmeridgian based on corals, foraminifera and dinoflagellate cysts. The uppermost limestone beds are rich in macrofossils with well-preserved corals in life position. To compile 13C chemostratigraphy for this section, sixty five bulk carbonate samples were studied.
- 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.
- Maturação orgânica e palinoestratigrafia da Sondagem RUIVO-1, região imersa da Bacia Algarvia. Contribuições para a prospecção de hidrocarbonetosPublication . Borges, Marisa; Fernandes, Paulo; Rodrigues, B.; Matos, VascoA sondagem RUIVO-1, localizada na região imersa da Bacia Algarvia, foi estudada com a finalidade de se caracterizar o grau de maturação e conhecer as idades das unidades litológicas com base na bioestratigrafia dos dinoflagelados.