PALYNOLOGY AND CARBON ISOTOPE STRATIGRAPHY OF THE ORDOVICIAN - SILURIAN ROCKS OF PORTUGAL: PALAEOGEOGRAPHIC AND PALAEOCLIMATIC IMPLICATIONS

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

Publication . 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 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.

2009Conference object

Open access

A importância dos palinomorfos remobilizados no Complexo Vulcano-Sedimentar da Toca da Moura - Implicações para a evolução geodinâmica da Zona de Ossa Morena, Portugal

Publication . Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Wicander, Reed; Matos, João Xavier; Rosa, Diogo; Oliveira, José Tomás

O 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.

2013Conference object

Open access

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 Zone

Publication . Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Wicander, Reed; Matos, João Xavier; Rosa, Diogo; Oliveira, José Tomás

The 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).

2014Journal article

Open access

Superimposed thermal histories in the southern limit of the Ossa Morena Zone - Portugal

Publication . Fernandes, Paulo Manuel Carvalho; Lopes, Gilda; Machado, G.; Pereira, Z.; Rodrigues, B.

The Mississippian volcano-sedimentary complex in the Toca da Moura - Cabrela areas represents remnants of intra-volcanic marine sedimentary basins, formed during the collision between the Ossa Morena Zone with the South Portuguese Zone. These rock units are unconformably overlain by the Pennsylvanian intramontane coal-bearing Santa Susana Basin. Vitrinite reflectance determinations from rocks of these two basins indicate two episodes of thermal maturation. During the first episode, the Toca da Moura - Cabrela volcano-sedimentary complexes attained high maturation levels, equivalent to anthracite coal rank (3.0-3.5% R-oran ), which pre-dates the middle Moscovian Santa Susana Basin. The Santa Susana Basin attained moderate maturation levels equivalent to bituminous coal rank (1.35-1.5% R-oran ) recording a second episode of thermal maturation. Here, peak thermal conditions did not overprint the first maturation episode. The observed effects of magmatic intrusion on the thermal maturity and the lack of any increase in vitrinite reflectance with depth through c. 400 m of section in borehole SDJ-1 indicate high geothermal gradients during the first maturation episode. A contemporaneous magmatic event associated with the c. 335-320 Ma Cuba-Alvito Gabbros/Diorites of the Beja Massif was the possible cause for the high geothermal gradients postulated for the first maturation episode. Burial under a post-upper Moscovian sedimentary cover was the most likely process to account for the maturation levels determined for the Santa Susana Basin and for the second episode of thermal maturation.

2017-05Journal article

Restricted access

Palynomorphs from the Gorstian (Silurian) of the Sazes Formation (Buçaco Syncline), Central Iberian Zone, Portugal - preliminary results

Publication . Lopes, Gilda; Vaz, Nuno; Sequeira, A. J. D.; Piçarra, J. M.; Fernandes, Paulo; Pereira, Zélia

Occuring in a complex syncline that extends from Buçaco to Penedo de Góis, the studied area is located in the Central Iberian Zone of the Iberian Massif. In this region outcrops a well-preserved and complete stratigraphic succession of Lower Paleozoic age. At the top of the Buçaco Syncline stratigraphic succession, the Silurian Sazes Formation (Paris, 1981), is currently being studied at a palynological (miospores and chitinozoans) and macrofossil (graptolites) level, allowing a preliminary revision and completion of the initial biostratigraphy of this area. This studies will also provide information to support the undergoing surveying mapping project (1:50 000) that is being undertaken by the “Laboratório Nacional de Energia e Geologia” (Portuguese Geological Survey) (Sequeira, in prep).

2010Conference object

Open access