The geodynamic importance of the Late Cambrian to Late Devonian reworked palynomorphs from borehole SDJ1, Santa Susana region, Ossa Morena Zone, Portugal

G Lopes, Z Pereira, P Fernandes, JX Matos, D. Rosa, JT Oliveira

Publikation: Bidrag til bog/rapport/konferenceproceedingsAbstract i proceedings

Abstrakt

The detailed 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 Viséan (NM Biozone) i.e.,
they belong to the Toca da Moura Volcano Sedimentary Complex (TMC). The deepest few meters of the drill core have shales of mid Moscovian (Biozona SL) (see Pereira et al., 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, interpreted as reworked into the Carboniferous rocks. Four
ages of reworked associations were identified: 1 - Late Cambrian acritarchs: Acanthodiacrodium ?petrovii, Cristallinium randomense, Eliasum sp., Timofeevia phosphoritica; 2 - Ordovician acritarchs: Navifusa punctata, Stelliferidium
striatulum, Striatotheca rarirrugulata; 3 - Mid Late Silurian to Lower Devonian, spore taxa: Ambitisporites sp., Archaeozonotriletes chulus, Brochotriletes sp., Dictyotriletes subgranifer; Emphanisporites sp. and Synorisporites labeonis, cryptospores taxa Laevolancis sp., Tetrahedraletes medinensis and Quadritisporites variabilis, acritarch taxa such as Duvernaysphaera aranaides, Micrhystridium stellatum, Multiplicisphaeridium ramusculosum; 4 - Late Devonian miospore taxa: Retispora lepidophyta and Rugospora flexuosa and acritarch taxa Craterosphaeridium ?sprucegrovense, Gorgonisphaeridium ohioense, Stellinium comptum, S. micropolygonale, Villosacapsula colemanii, Pterospmella sp.. Detailed 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 by the first pulses 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 Phyllodocites
Shales (Piçarra et al., 2011); the Raiados and Nódulos Shales Fm. and the Terena Fm. of Mid Late Silurian to Lower Devonian, age (Pereira et al., 1999; Lopes et al., 2009). The Late Devonian association could have come from the South Portuguese Zone, were late Famennian palynomorphs are very well documented. Lastly, there are no proved units of Late Cambrian age in the OMZ. The occurrence of reworked Late Cambrian palynomorphs in the Santa Susana
region indicate that elsewhere in the OMZ, sedimentation of this age must have existed.
OriginalsprogEngelsk
Titel44th Annual Meeting of the American Association of Stratigraphic Palynogists, Abstract volume
UdgivelsesstedSouthampton
ForlagAmerican Association of Stratigraphic Palynologists
Sider22
StatusUdgivet - 2011
Begivenhed44th Annual Meeting of the American Association of Stratigraphic Palynologists - Southampton, United Kingdom
Varighed: 1 sep. 2011 → …

Konference

Konference44th Annual Meeting of the American Association of Stratigraphic Palynologists
BySouthampton, United Kingdom
Periode1/09/11 → …

Programområde

  • Programområde 4: Mineralske råstoffer

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