Nanofósseis calcários do Mioceno da Bacia do Baixo Tejo, Portugal

IF 0.7 4区地球科学 Q4 PALEONTOLOGY

Revista Brasileira De Paleontologia Pub Date : 2021-01-30 DOI:10.4072/RBP.2021.1.04

João da Fonseca Gomes de Lemos, Geize Carolinne Correia Andrade Oliveira

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引用次数: 0

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. RESUMO – Este estudo apresenta a taxonomia, bioestratigrafia e paleoecologia dos nanofosseis calcarios presentes nas rochas que afloram as margens da praia da Foz da Fonte, geologicamente pertencentes ao Neogeno da Bacia do Baixo Tejo, Portugal. A descricao taxonomica permitiu identificar 19 especies de nanofosseis calcarios pertencentes a dez generos (Helicosphaera, Pontosphaera, Reticulofenestra, Cyclicargolithus, Coccolithus, Discoaster, Sphenolithus, Umbilicosphaera, Calcidiscus e Thoracosphaera). Com base na distribuicao bioestratigrafica de Discoaster druggii, Reticulofenestra lockeri e Helicosphaera ampliaperta a secao foi definida pertencendo as biozonas NN2 e CN1, dentro do Burdigaliano (Mioceno inferior). A analise quantitativa mostrou significativa variacao na diversidade de especies em funcao da profundidade e, tambem, uma relacao entre a riqueza especifica e abundância com o teor de carbonato de calcio presente nas rochas. De acordo com esses dados, principalmente pela abundância de Reticulofenestra spp., Coccolithus spp. e Helicosphaera spp. e possivel inferir que tratava de um ambiente marinho proximo a costa, rico em nutrientes (eutrofico), influenciado por massas de aguas quentes. Palavras-chave: nanofosseis calcarios, taxonomia, bioestratigrafia, paleoecologia, Neogeno, Bacia do Baixo Tejo.

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葡萄牙Baixo-Tejo盆地中新世的石灰岩纳米化石

葡萄牙下特茹盆地中新世的钙质超微化石。本研究介绍了葡萄牙下特霍盆地新近系Foz da Fonte海滩边界露头的钙质超微化石的分类学、生物地层学和古生态学。分类描述使我们能够鉴定出19种钙质超微化石，隶属于10个属（Helicosphaera、Ponthopaera、Reticulfenestra、Cycicargolithus、Coccolithus、Discoaster、Sphenolithus、Umbilicophaera、Calcidesis和Thoracophaera）。根据Discoaster drugii、Reticulfenestra lockeri和Helicosphaera magnifaperta的地层范围，该剖面被定义在Burdigalian（下中新世）内的NN2和CN1生物带中。定量分析显示，物种多样性随着深度的变化而发生显著变化，物种丰富度与这些岩石中碳酸钙含量之间也存在关系。根据这些数据，主要由于网织开窗菌属、Coccolithus属和Helicosphaera属的丰度，可以推断这是一个受温水条件影响的营养丰富的近岸海洋环境（富营养化）。关键词：钙质纳米化石，分类学，生物地层学，古生态学，新近纪，下特茹盆地摘要——本研究介绍了在Foz da Fonte海滩海岸露头的岩石中存在的钙质纳米化石的分类学、生物地层学和古生态学，在地质学上属于葡萄牙Baixo-Tejo盆地的新近纪。分类描述允许鉴定出19种钙质纳米化石，属于10个大类（Helicosphaera、Pontosphaera，Reticulfenestra，Cycicargolithus，Coccolithus，Discoaster，Sphenolithus，Umbilichosphaera）。根据Discoaster drugii、Reticulfenestra lockeri和Helicosphaera amplifaperta的生物地层学分布，该剖面被定义为属于Burdigalian（下Myocene）内的NN2和CN1生物带。定量分析显示，物种多样性随着深度的变化而发生显著变化，特定丰富度和丰度与岩石中碳酸钙含量之间也存在关系。根据这些数据，主要是由于网状开窗菌属、Coccolithus属和Helicosphaera属的丰度，可以推断这是一个靠近海岸的海洋环境，富含营养物质（富营养化），受到热水团的影响。关键词：钙质纳米化石，分类学，生物地层学，古生态学，新近纪，拜克索特霍盆地。

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来源期刊

Revista Brasileira De Paleontologia PALEONTOLOGY-

CiteScore

1.60

自引率

14.30%

发文量

审稿时长

>12 weeks

期刊介绍： It publishes original contributions on all aspects of Paleontology. Papers are written in English, Spanish, or Portuguese and are reviewed by international experts.