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- Silurian to Lower Devonian Palynomorphs from the Barrancos region, Ossa Morena Zone, PortugalPublication . Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Piçarra, J. M.; Oliveira, José TomásNew 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 present. This new preliminary data allow correlation with the graptolite biozonation already established in this region (Piçarra, et al., 1995, 1998; Piçarra, 2000) and completes previous palynological studies (Pereira et al., 1999). Even so, detailed palynostratigraphic research is needed and is currently being undertaken to better understand the complex geology of the region.
- A late Fammenian age storm-dominated succession at Berrocal (Iberian Pyrite Belt - Spain)Publication . Fernandes, Paulo; Pereira, Zélia; Oliveira, José Tomás; Jorge, R. C. G. S.; Relvas, J.The Berrocal area is situated in the northern limb of Valverde del Camino anticlinal in the Spanish sector the Iberian Belt and exposes the upper part of the Phyllite-Quartzite Group. Recent studies on palynostratigraphy and sedimentology of the Berocal section indicates that the stratigraphic succession is late Famennian age (VH miospore biozone) and was accumulated on the offshore zone of a siliciclastic shelf dominated by storm events.
- 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).
- The significance of reworked palynomorphs (middle Cambrian to Tournaisian) in the Visean Toca da Moura Complex (South Portugal). Implications for the geodynamic evolution of Ossa Morena ZonePublication . Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Wicander, Reed; Matos, João Xavier; Rosa, Diogo; Oliveira, José TomásThe 404.5 m deep SDJ1 borehole is located in the Jongeis mining sector of the Santa Susana Basin (SSB), and has been palynostratigraphically studied. The SSB is a Carboniferous coal-bearing basin developed along the suture contact between the Ossa Morena Zone (OMZ) and the South Portuguese Zone (SPZ).
- The age of the first pulse of continental rifting associated with the breakup of Pangea in Southwest Iberia: new palynological evidencePublication . Vilas Boas, Margarida; Paterson, Niall W.; Pereira, Zélia; Fernandes, Paulo; Cirilli, SimonettaIn this work, we report the first palynological age for the base strata of the Silves Sandstones of the Silves Group in the Algarve Basin, located in Southern Portugal. The group is the oldest sedimentary unit of the Algarve Basin and was deposited unconformably over late Pennsylvanian turbidites of the Mira Formation, which were folded and faulted during the Variscan Orogeny. The Silves Group comprises a detrital red bed succession, representing the earliest phase of sedimentation associated with the initial rifting of Pangaea. Macrofossils are rare, occurring predominantly in the top layers of this group, and do not accurately constrain the age of the entire group's deposition. From an outcrop exposed in the central Algarve, a grey mudstone bed positioned 2.5 m above the Variscan unconformity plane yielded palynomorphs that date the beginning of sedimentation in this basin to the early Carnian age (Late Triassic). The moderately well preserved and low-diversity palynological association comprises Aulisporites astigmosus, Enzonalasporites densus, Ovalipollis pseudoalatus, Samaropollenites speciosus, Tulesporites briscoensis and Vallasporites ignacii, among others, and is indicative of an early Carnian age.
- Resultados preliminares do registo isotópico de carbono orgânico (d13C org) do Silúrico da região de Barrancos, Zona de Ossa Morena, PortugalPublication . Lopes, Gilda; Fernandes, Paulo; Goodhue, R.; Pereira, Zélia; Piçarra, J. M.A região de Barrancos apresenta uma das sessões mais complexas de Silúrico na zona da Ossa Morena.
- 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.
- Middle-Upper Jurassic palynology of the Sagres region and the Carrapateira outlier: southern PortugalPublication . Borges, Marisa; Fernandes, Paulo; Pereira, Zélia; Riding, JimThe palynology of the Middle-Upper Jurassic fill of the Sagres region (Algarve Basin) and the Carrapateira outlier, southern Portugal was investigated. Samples were collected from Mareta beach, Cilheta beach and the Carrapateira outlier. Dinoflagellate cysts are confined to the Upper Bajocian to Upper Callovian sedimentary rocks exposed at Mareta and Cilheta beaches and the Lower Kimmeridgian strata of the Carrapateira outlier. The palynostratigraphical study of the Jurassic successions has yielded new biostratigraphical data based on dinoflagellate cysts and miospores. The results confirm, and in some cases refine, the existing macrofaunal age determinations of these successions.
- A importância dos palinomorfos remobilizados no Complexo Vulcano-Sedimentar da Toca da Moura - Implicações para a evolução geodinâmica da Zona de Ossa Morena, PortugalPublication . Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Wicander, Reed; Matos, João Xavier; Rosa, Diogo; Oliveira, José TomásO estudo palinostratigráfico da sondagem SDJ11 permitiu a recuperação de associações in situ de palinomorfos do Carbónico assim como associações de palinomorfos remobilizados do Câmbrico médio ao Devónico inferior e Câmbrico médio ao Tournaisiano.
- 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.