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Primeiros dados litoestratigráficos e paleontológicos do Carbonífero de Águeda (Aveiro, Portugal)
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Abstract(s)
RESUMO: O Paleozoico da região de Águeda, pertencente à Zona Centro-Ibérica, está localizado na zona de cisalhamento Porto-Tomar-Ferreira do Alentejo e permanece amplamente desconhecido. Neste trabalho são documentados os primeiros dados litoestratigráficos e paleontológicos do Carbonífero da região, o qual representa o limite setentrional da Bacia Carbonífera do Buçaco. A secção estudada, localizada em Souralvo (Bolfiar), corresponde à Formação Vale da Mó, estando representada por duas sequências granodecrescentes de argilitos siltíticos vermelhos, massivos, que passam gradualmente a pelitos laminados cinzentos no topo, às quais se sobrepõem arenitos finos com intercalações silto-argilosas. A associação de fácies indica um ambiente essencialmente lacustre. A associação fossilífera é quase exclusivamente composta por fósseis de vegetais, incluindo representantes de Cordaitopsida (folhas de Cordaites e sementes do tipo Cardiocarpus e Carpolithes), Trigonocarpales (Neuropteris zeilleri e Callipteridium gigas), Marattiales (Pecopteris cyathea e P. cf. arborescens) e Equisetales (Annularia spinulosa e A. sphenophylloides). Embora raros, foram também recolhidos fósseis de bivalves límnicos (Anthraconaia sp.) e identificadas marcas de oviposição endofítica de insetos em folhas de Cordaites, o primeiro registo deste tipo de icnofósseis no Carbonífero de Portugal. A associação está composta inteiramente por espécies conhecidas nos restantes setores da Bacia Carbonífera do Buçaco, indicando uma idade Estefaniano C tardio (ca. Ghzeliano, Pensilvaniano Superior). A raridade e baixa diversidade de pteridopsídeos, bem como a abundância de representantes de flora mesófila (Cordaites e Neuropteris), sugerem adaptação a condições secas, uma tendência reconhecida no final do Estefaniano C.
ABSTRACT: The Palaeozoic of the Águeda region, within the Central Iberian Zone, is located in the Porto-Tomar-Ferreira do Alentejo shear zone and remains largely unknown. This work documents the first lithostratigraphical and palaeontological data from the Carboniferous of Águeda, which represents the northernmost limit of the Buçaco Carboniferous Basin. The section studied, located in Souralvo (Bolfiar), is recognized as the Vale da Mó Formation and is represented by two coarsening upwards sequences of massive red silty mudstones, which gradually change to grey shales at the top, overlain by fine sandstones with silty and mudstones fine intercalations. The association of facies essentially indicates a lake system. The fossil assemblage is mainly composed of fossil plants, including representatives of Cordaitopsida (Cordaites-type leaves and Cardiocarpus and Carpolithes-type seeds), Trigonocarpales (Neuropteris zeilleri and Callipteridium gigas), Marattiales (Pecopteris cyathea and P. cf. arborescens) and Equisetales (Annularia spinulosa and A. sphenophylloides). Although rare, fossils of limnic bivalves (Anthraconaia sp.) were also collected and insect endophytic oviposition traces were identified on Cordaites leaves, being the first record of this type of ichnofossils in the Carboniferous of Portugal. The assemblage is composed entirely of species known from the other sectors of the Buçaco Carboniferous Basin, indicating a late Stephanian C age (ca. Ghzelian, Late Pennsylvanian). The rarity and low diversity of pteridopsids, as well as the abundance of representatives of mesophilous flora (Cordaites and Neuropteris), suggest adaptation to dry conditions, a trend recognised at the end of the Stephanian C.
ABSTRACT: The Palaeozoic of the Águeda region, within the Central Iberian Zone, is located in the Porto-Tomar-Ferreira do Alentejo shear zone and remains largely unknown. This work documents the first lithostratigraphical and palaeontological data from the Carboniferous of Águeda, which represents the northernmost limit of the Buçaco Carboniferous Basin. The section studied, located in Souralvo (Bolfiar), is recognized as the Vale da Mó Formation and is represented by two coarsening upwards sequences of massive red silty mudstones, which gradually change to grey shales at the top, overlain by fine sandstones with silty and mudstones fine intercalations. The association of facies essentially indicates a lake system. The fossil assemblage is mainly composed of fossil plants, including representatives of Cordaitopsida (Cordaites-type leaves and Cardiocarpus and Carpolithes-type seeds), Trigonocarpales (Neuropteris zeilleri and Callipteridium gigas), Marattiales (Pecopteris cyathea and P. cf. arborescens) and Equisetales (Annularia spinulosa and A. sphenophylloides). Although rare, fossils of limnic bivalves (Anthraconaia sp.) were also collected and insect endophytic oviposition traces were identified on Cordaites leaves, being the first record of this type of ichnofossils in the Carboniferous of Portugal. The assemblage is composed entirely of species known from the other sectors of the Buçaco Carboniferous Basin, indicating a late Stephanian C age (ca. Ghzelian, Late Pennsylvanian). The rarity and low diversity of pteridopsids, as well as the abundance of representatives of mesophilous flora (Cordaites and Neuropteris), suggest adaptation to dry conditions, a trend recognised at the end of the Stephanian C.
Description
Keywords
Bacia Carbonífera do Buçaco Estefaniano C Oviposição Cordaites Buçaco Carboniferous Basin Stephanian C Oviposition
Citation
Pereira, S. & Correia, P. (2025). Primeiros dados litoestratigráficos e paleontológicos do Carbonífero de Águeda (Aveiro, Portugal). In: Comunicações Geológicas, 2025, vol. 112, Fascículo Especial I, pp. 97-101
Publisher
LNEG - Laboratório Nacional de Energia e Geologia