Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.1/5116
Título: The geodynamic importance of the Late Cambrian to Late Devonian reworked palynomorphs from the borehole SDJ1, Santa Susana region, Ossa Morena Zone (OMZ), Portugal
Autor: Lopes, Gilda
Pereira, Zélia
Fernandes, Paulo
Matos, João Xavier
Rosa, Diogo
Oliveira, José Tomás
Palavras-chave: Ossa Morena Zone
Data: 2011
Citação: Lopes, Gilda; Pereira, Zélia; Fernandes, Paulo; Matos, João Xavier; Rosa, Diogo; Oliveira, José Tomás. The geodynamic importance of the Late Cambrian to Late Devonian reworked palynomorphs from the borehole SDJ1, Santa Susana region, Ossa Morena Zone (OMZ), Portugal, Trabalho apresentado em 44th annual meeting AASP Southampton 2011, In 44th annual meeting AASP Southampton 2011 - Abstracts, Southampton, 2011.
Resumo: 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 Carboniferous ocks. Four ages of reworked associations were identified: 1 - Late Cambrian acritarchs: Aeanthodiaerodium ?petrovii, Cristallinium randomense, Eliasum sp., Timofeevia phosphoritica; 2 - Ordovician acritarchs: Navifusa punctata, Stelliferidium striatulum, Striatotheea rarirrugulata; 3 - Mid Late Silurian to Lower Devonian, spore taxa: Ambitisporites sp., Arehaeozonotriletes ehulus, Brochotriletes sp., Dietyotriletes subgranifer; Emphanisporites sp. and Synorisporites Jabeonis, cryptospores taxa aevolaneis sp., Tetrahedraletes medinensis and Quadritisporites variabilis, acritarch taxa such as Ouvernaysphaera aranaides, Micrhystridium stellatum, Multiplicisphaeridium ramusculosum; 4 - Late Devonian miospore taxa: Retispora lepidophyta and Rugospora f1exuosa and acritarch taxa Craterosphaeridium ?sprueegrovense, Gorgonisphaeridium ohioense, Stellinium eomptum, S. mieropolygonale, Vil/osaeapsula eolemanii, Pterospermella sp.. Detail examination of the reworked assemblages, still in progress, indicates that these are clearly dominated by Late Cambrian, Early Ordovician and Late Devonian acritarchs. In minor amount are Mid Silurian to Lower Devonian palynomorphs and the typical Middle Devonian species are very scarce. The TMC sediments are interpreted as had been deposited in an intra-arc basin in close association with the igneous rocks of the Beja Massif, a magmatic arc installed at the south border of the OMZ (Oliveira et al. 2006). The ages of the reworked palynomorphs suggest that considerable erosion of exposed Lower Palaeozoic OMZ basement occurred during Carboniferous times. The exposure of these rocks may have occurred during the first phases of the Variscan Orogeny in the OMZ. Within the OMZ the rock formations that may constitute the sources for the reworked palynomorphs are: the Early Ordovician Phyllodoeites Shales (Pigarra et aI., 2011); the Raiados and Nodulos Shales Fm. and the Terena Fm. of Mid ate Silurian to Early Devonian, age (Pereira et aL, 1999; Lopes et ai., 2009). The Late Devonian association could have come from the South Portuguese Zone, where late amennian palynomorphs are very well documented. Lastly, there are no units of proven late Cambrian age in the OMZ. The occurrence of reworked Late Cambrian palynomorphs in the Santa Susana region indicates that elsewhere in the OMZ, sedimentation of this age must have existed.
Peer review: yes
URI: http://hdl.handle.net/10400.1/5116
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