Abstract
Calcareous nannofossils of the Lower Tejo Basin Miocene, Portugal. This study presents the taxonomy, biostratigraphy, and paleoecology of calcareous nannofossils from an outcrop on the border of Foz da Fonte beach, geologically setting in the Neogene of the Lower Tejo Basin, Portugal. The taxonomic description allowed us to identify 19 calcareous nannofossils species belonging to ten genera (Helicosphaera, Pontosphaera, Reticulofenestra, Cyclicargolithus, Coccolithus, Discoaster, Sphenolithus, Umbilicosphaera, Calcidiscus, and Thoracosphaera). Based on the stratigraphic range of Discoaster druggii, Reticulofenestra lockeri, and Helicosphaera ampliaperta the section was defined in the NN2 and CN1 biozones, within the Burdigalian (lower Miocene). Quantitative analysis showed a significant variation in species diversity as a function of depth, as well as a relationship between species richness and the calcium carbonate content present in these rocks. According to these data, mainly due to the abundance of Reticulofenestra spp., Coccolithus spp. and Helicosphaera spp., it is possible to infer that this was a nutrient-rich nearshore marine environment (eutrophic) influenced by warm water conditions. Keywords: calcareous nannofossils, taxonomy, biostratigraphy, paleoecology, Neogene, Lower Tejo Basin.
Highlights
RESUMO – Este estudo apresenta a taxonomia, bioestratigrafia e paleoecologia dos nanofósseis calcários presentes nas rochas que afloram às margens da praia da Foz da Fonte, geologicamente pertencentes ao Neógeno da Bacia do Baixo Tejo, Portugal
As informações referentes às associações de nanofósseis calcários na Bacia do Baixo Tejo (BBT), Portugal, ainda são pouco documentadas na literatura
O presente trabalho objetiva apresentar e discutir os resultados obtidos com a investigação de quatro amostras pertencentes ao Mioceno da Bacia do Baixo Tejo, Portugal
Summary
A área de estudo (Figura 1) é localmente conhecida como praia da Foz da Fonte e situa-se geograficamente a centro-oeste de Lisboa, Portugal, compreendendo parte da Península de Setúbal. O acesso até o local de estudo, partindo de Lisboa, pode ser feito através da autoestrada A5, no sentido Lisboa-Setúbal, acessando posteriormente a autoestrada do Sul, pela ponte 25 de Abril e, finalmente, através das estradas nacionais N378 e N379, respectivamente, chega-se à praia da Fonte da Foz
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