Braquiópodes do Sinemuriano superior da região de S. Pedro
de Moel e de Peniche (Bacia Lusitânica, Portugal)
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2013
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Instituto Geológico e Mineiro (Lisboa)
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Abstract
Neste estudo analisam-se as associações de braquiópodes e a sua distribuição estratigráfica no Sinemuriano superior da região de S. Pedro de Moel e Peniche (Bacia Lusitânica). Estão representadas 9 famílias, 11 géneros e 21 espécies desde as subcronozonas Oxynotum até Aplanatum na primeira secção, e entre a parte superior da Subcronozona Aplanatum e a parte inferior da Subcronozona Taylori na segunda. As famílias Rhynchonellidae (39%), Tetrarhynchiidae (28%) e Zeilleriidae (16%) revelam-se como as de maior abundância. A maior diversidade e abundância é reconhecida na Subcronozona Oxynotum em S. Pedro de Moel, observando-se uma rápida diminuição até à parte inferior da Subcronozona Aplanatum. Desde esse momento poderá ter tido lugar um acontecimento local que condicionou a ocorrência destas faunas, devido a causas relacionadas com um aprofundamento do ambiente marinho e/ou um défice de oxigénio. Em Peniche as associações presentes apontam para condições mais proximais e menos profundas. A maioria dos taxa presentes permitem estabelecer relações com a província noroeste europeia.
The stratigraphical distribution of Upper Sinemurian brachiopods at S. Pedro de Moel and Peniche (Lusitanian Basin) is presented here. They are represented by 9 families, 11 genera and 21 recognized species, spanning from the Oxynotum to the lower part of Aplanatum subchronozones at S. Pedro de Moel and from the upper part of Aplanatum to lower part of Taylori subchronozones in the Peniche area. The most common families are Rhynchonellidae (39%), Tetrarhynchiidae (28%) and Zeilleriidae (16%). The highest abundance and diversity of brachiopods is recognized in the Oxynotum Subchronozone at S. Pedro de Moel. A rapid decrease in brachiopods is observed until the lower part of the Aplanatum Subchronozone, interpreted as the result of specific local conditions, most probably related to a deepening episode and/or oxygen depleted conditions. Shallower water conditions are inferred by the represented associations at Peniche. Most of the recorded taxa are related with the NW European Province.
The stratigraphical distribution of Upper Sinemurian brachiopods at S. Pedro de Moel and Peniche (Lusitanian Basin) is presented here. They are represented by 9 families, 11 genera and 21 recognized species, spanning from the Oxynotum to the lower part of Aplanatum subchronozones at S. Pedro de Moel and from the upper part of Aplanatum to lower part of Taylori subchronozones in the Peniche area. The most common families are Rhynchonellidae (39%), Tetrarhynchiidae (28%) and Zeilleriidae (16%). The highest abundance and diversity of brachiopods is recognized in the Oxynotum Subchronozone at S. Pedro de Moel. A rapid decrease in brachiopods is observed until the lower part of the Aplanatum Subchronozone, interpreted as the result of specific local conditions, most probably related to a deepening episode and/or oxygen depleted conditions. Shallower water conditions are inferred by the represented associations at Peniche. Most of the recorded taxa are related with the NW European Province.