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Foraminíferos miocénicos de Porto Santo (Madeira, Portugal)
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São estudados foraminíferos miocénicos de afloramentos na região nordeste da ilha de Porto Santo (Madeira, Portugal), entre a Serra de Dentro e o Pico Branco. Foram analisados quatro afloramentos correspondentes a "depósitos pararecifais e conglomerados", intercalados com hialoclastitos, da fase submarina da construção do edifício vulcânico que viria a dar origem à ilha. Colheram-se e trataram-se 24 amostras. Identificaram-se 20 espécies planctónicas e 22 géneros bentónicos. A presença de Praeorbulina glomerosa e Orbulina suturalis e a ausência de Orbulina universa nas associações permitiu enquadrar biostratigraficamente os níveis fos-silíferos no Miocénico Médio (biozona N9 de Blow; Langhiano; 15.1-14.74 Ma). As associações bentónicas são constituídas maioritariamente pelos géneros Cibicides e Cibicidoides, incluindo Heterolepa, Lenticulina, Asterigerinata, Quinqueloculina, Bolivina, Amphistegina, Textularia, Nonion e Ammonia, e mais raramente Elphidium, Uvigerina, Bulimina, Rotalidium, Parafissu-rina, Cancris, Lagena, Melonis, Reussella, Operculina, Orthomorphina e Astacolus, permitindo inferir paleoambientes do infralitoral a circalitoral. O índice de oceanidade sugere profundida-des entre 15 e 70 m. O corte de Pico Branco (SDPB) apresenta maior abundância e diversidade de foraminíferos, com alguns níveis muito ricos de Amphistegina, relacionados com águas quentes, pouco profundas e agitadas pela ondulação. A sedimentação ocorreu durante o má-ximo eustático do ciclo 2.4 seguindo-se a emersão da ilha e vulcanismo subaéreo a partir dos 14 Ma.
Foraminifera from Miocene outcrops located in the northeast region of Porto Santo island (Madeira, Portugal), between Serra de Dentro and Pico Branco hills, are studied. Four outcrops with exposed "parareef deposits and conglomerates" corresponding to the underwater phase of the volcanic edifice construction which gave rise to the island were analysed. 24 samples were collected and treated. Within the obtained collection of foraminifera 20 planktonic spe-cies and 22 benthic genera were identified. The presence of Praeorbulina glomerosa and Or-bulina suturalis and the absence of Orbulina universa in the analysed assemblages allows as-signation of the fossiliferous levels to Blow's N9 biozone, corresponding to Langhian (Middle Miocene, 15.1-14.74 My). The bentonhic foraminifera are mainly represented by Cibicides and Cibicidoides, common Heterolepa, Lenticulina, Asterigerinata, Quinqueloculina, Bolivina, Amphistegina, Textularia, Nonion e Ammonia, and rarely Elphidium, Uvigerina, Rotalidium, Pa-rafissurina, Cancris, Lagena, Melonis, Reussella, Operculina, Orthomorphina e Astacolus. The mentioned assemblages indicate infralitoral to circalitoral paleoenvironments. The oceanity in-dex suggests depths between 15 and 70 m. Pico Branco's geological log (SDPB) indicates larger abundance and taxonomic diversity of foraminifera, with some strata containing large amounts of Amphistegina, which is related to the shallow, warm marine environment often affected by turbulent flows. The sedimentation occured at the eustatic maximum of 2.4, followed by the island's upwelling and surface volcanism, commencing 14 Ma.
Foraminifera from Miocene outcrops located in the northeast region of Porto Santo island (Madeira, Portugal), between Serra de Dentro and Pico Branco hills, are studied. Four outcrops with exposed "parareef deposits and conglomerates" corresponding to the underwater phase of the volcanic edifice construction which gave rise to the island were analysed. 24 samples were collected and treated. Within the obtained collection of foraminifera 20 planktonic spe-cies and 22 benthic genera were identified. The presence of Praeorbulina glomerosa and Or-bulina suturalis and the absence of Orbulina universa in the analysed assemblages allows as-signation of the fossiliferous levels to Blow's N9 biozone, corresponding to Langhian (Middle Miocene, 15.1-14.74 My). The bentonhic foraminifera are mainly represented by Cibicides and Cibicidoides, common Heterolepa, Lenticulina, Asterigerinata, Quinqueloculina, Bolivina, Amphistegina, Textularia, Nonion e Ammonia, and rarely Elphidium, Uvigerina, Rotalidium, Pa-rafissurina, Cancris, Lagena, Melonis, Reussella, Operculina, Orthomorphina e Astacolus. The mentioned assemblages indicate infralitoral to circalitoral paleoenvironments. The oceanity in-dex suggests depths between 15 and 70 m. Pico Branco's geological log (SDPB) indicates larger abundance and taxonomic diversity of foraminifera, with some strata containing large amounts of Amphistegina, which is related to the shallow, warm marine environment often affected by turbulent flows. The sedimentation occured at the eustatic maximum of 2.4, followed by the island's upwelling and surface volcanism, commencing 14 Ma.
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Foraminíferos Miocénico Porto Santo Paleoambientes