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Abstract The objectives of this study were the biostratigraphic and paleobiogeographic interpretations of the calcareous nannofossil records of the Romualdo Formation (Aptian-Albian) in the south-central portion of the Araripe Basin. The methods used to process the samples were decanting, smear slide, centrifugation, and ultra-thin section confection. The taxonomic and biostratigraphic interpretations were carried out through qualitative and quantitative investigations. A total of 11 genera and 17 species of calcareous nannofossils, namely, Biscutum constans, Biscutum sp., Braarudosphaera africana, Braarudosphaera sp., Calculites sp., Discorhabdus ignotus, Hayesites albiensis, Hayesites sp., Nannoconus bucheri, Nannoconus sp., Retecapsa surirella, Rhagodiscus sp., Thoracosphaera sp., Watznaueria barnesiae, Watznaueria sp., Zeughrabdotus erectus, and Zeughrabdotus noeliae were identified. The integrated analysis of three outcrops suggests two distinct marine phases: the first in the Aptian, recognized in two outcrops, and during the Albian age. The genera Hayesites and Nannoconus suggest a strong Tethyan affinity. Differently, other calcareous nannofossils such as Watznaueria, Thoracosphaera, and Braarudosphaera recorded here are considered more resistant, cosmopolitan, and/or opportunistic species. Biscutum and Zeughrabdotus are sensitive calcareous nannofossils because they are more susceptible to dissolution and cannot be surely used to define this paleobiogeography and biostratigraphic range.

Este trabalho foi desenvolvido após o cadastramento de 570 poços tubulares da porção norte da região metropolitana do Recife, abrangendo os municípios de Paulista, Abreu e Lima, Araçoiaba, Igarassú, Itamaracá, Itaquitinga e Goiana, como parte integrante do Projeto intitulado Estudo Hidrogeológico da porção Norte da Região Metropolitana do Recife financiado pela Companhia Pernambucana do Meio Ambiente (CPRH). A partir das informações obtidas dos perfis litológicos-construtivos dos poços, foram elaborados oito perfis geológicos. Os resultados obtidos são de grande importância para a caracterização da geologia regional e demonstra alguns aspectos relevantes quanto à geometria dos aqüiferos. Ressalta- se ainda algumas considerações feitas sobre as dificuldades em utilizar os dados das descrições das amostras de calha feitas pelos profissionais que acompanham a perfuração dos poços, sendo que nem sempre se trata de pessoal devidamente treinado. Contudo, os resultados obtidos foram satisfatórios e apresentam-se coerentes com a bibliografia, tendo sido definidos três sistemas aqüiferos assim denominados: Aqüífero intergranular principal (Formação Beberibe e Itamaracá), Aquifero cárstico (Formação Gramame/Maria Farinha) e Aqüífero Barreiras (Formação Barreiras). ABSTRACT This work was developed after the cadastre of 570 tubular wells of the portion north of the region metropolitan of Recife, having enclosed the cities of Paulista, Abreu eLima, Araçoiaba, Igarassú, Itamaracá, Itaquitinga and Goiana, as integrant part of the intitled Project Estudo Hidrogeológico of the portion North of the Region Metropolitan of Recife financed for the Companhia Pernambucan do Meio Ambiente (CPRH). From the gotten information of the constructive profiles litológicos- of the wells, had been elaborated eight geologic profiles. The gotten results are of great importance for the characterization of regional geology and demonstrate some excellent aspects how much to the geometry of the aqüiferos. One still standes out some considerations made on difficulties in using the data of the descriptions of the samples made by the professionals who follow the perforation of the wells, being that nor always one is about staff duly trained. However, the gotten results had been satisfactory and are presented coherent with the bibliography, having been defined three thus called aqüiferos systems: intergranular main aquifer (Formation Beberibe and Itamaracá), Karst aquifer (Gramame/Maria Farinha) and Barreiras aquifer (Formation Barreiras).