Browsing by Author "Pereira, H. J. R."
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- Late Barremian–early Aptian charophytes from the Arrifes section (Algarve). Biostratigraphy and correlation with marine domainPublication . Pérez-Cano, J.; Pereira, H. J. R.; Mendes, Márcia; Pereira, Zélia; Callapez, Pedro M.; Fernandes, PauloSUMÁRIO: A secção estratigráfica dos Arrifes (Albufeira, Algarve) foi estudada, em detalhe, para biostratigrafia de carofitas. Este estudo permitiu-nos reconhecer duas associaçõoes distintas: i) A primeira, composta por Echinochara lazarii, Atopochara trivolvis triquetra, A. trivolvis trivolvis, Clavator grovesii jiuquanensis, Clavator harrisii harrisii e C. harrisii zavialensis, pertenece à biozona de Calvator grovesii var. jiuquanensis do Barremiano superior–Aptiano inferior da Eurásia; ii) A segunda, com A. trivolvis trivolvis, Clavator grovesii corrugatus e C. harrisii zavialensis, é atribuída à biozona de Clavator grovesii var. corrugatus do Aptiano superior–Albiano médio. Estas biozonas de carofitas correlacionam-se com dados de palinomorfos publicados recentemente. Com base nessa correlação, a base da Zona Corrugatus é atribuída ao Aptiano inferior, considerando a sua ocorrência em estratos que contêm quistos do dinoflagelado Odontochinia operculata, pelo que é um pouco mais antiga do que se pensava previamente.
- The Arrifes geosite: a fascinating glimpse into an Early Cretaceous ecosystem within the Algarvensis aspiring UNESCO Global Geopark (Portugal) [Resumo]Publication . Pereira, H. J. R.; Lopes, Francisco; Pérez-Cano, J.; Santos, Vanda Faria dos; Malafaia, Elisabete; Mendes, Márcia; Pereira, Zélia; Sweetman, Steven C.; Fernandes, Paulo; Callapez, Pedro M.ABSTRACT: Over a century after Paul Choffat's initial description of the Arrifes section, a pioneering figure in Portuguese geology who highlighted the vertical arrangement of the strata and the occurrence of a limestone bed containing a copious quantity of orbitolinid tests, this upper Barremian–lower Aptian stratigraphic succession, which is fully exposed along a coastal cliff section located 2.5 km west-southwest of Albufeira (Algarve, southern Portugal), has become one of the most outstanding geosites within the Algarvensis aspiring UNESCO Global Geopark.
- Upper Barremian-lower Aptian charophyte biostratigraphy from Arrifes section (Algarve Basin, Southern Portugal): correlation with dinoflagellate cyst biostratigraphyPublication . Pérez-Cano, J.; Pereira, H. J. R.; Mendes, Márcia; Pereira, Zélia; Callapez, Pedro M.; Fernandes, PauloABSTRACT: The Arrifes section (Algarve Basin, Southern Portugal) has been studied from the viewpoint of char-ophyte biostratigraphy. The previous sedimentological studies in this section showed that it is built of the interbedding of continental and marine facies that contain both marine and continental palynomorphs (pollen, spores, and dinoflagellates), providing an excellent sedimentary context to perform direct cor-relations between marine and continental domains. In the present work, the identified charophyte biozones have been correlated with dinoflagellate biozones previously recognized in the Arrifes section, being the first time that these two biochronologies can be directly correlated. From the charophyte biostratigraphy viewpoint, two assemblages are distinguished. The older one is found between 65 and 135 m of the stratigraphic section, and it is composed of the species Echinochara lazarii, Atopochara trivolvis var. triquetra, A. trivolvis var. trivolvis, Clavator grovesii var. jiuquanensis, Clavator harrisii var. harrisii, C. harrisii var. reyi, and C. harrisii var. zavialensis. This assemblage belongs to the upper Barremian -lower Aptian Clavator grovesii var. jiuquanensis Eurasian biozone and also to the Ascidiella cruciata-Pseudoglobator paucibracteatus European biozone and it is described in beds with the dinoflagellate cyst Subtilisphaera scabrata (lower to lowermost upper Barremian) and Odontochitina operculata (from upper Barremian upwards). The younger charophyte assemblage is found between 135 and 155 m of the stratigraphic section, and it is composed of the species A. trivolvis var. trivolvis, Clavator grovesii var. corrugatus, Clavator harrisii var. harrisii, C. harrisii var. reyi, and C. harrisii var. zavialensis. This assemblage belongs to Clavator grovesii var. corrugatus biozone, previously assigned to upper Aptian (Clavator grovesii var. lusitanicus biozone). However, in the Arrifes section, this assemblage is found in beds assigned to the dinoflagellate cyst Odontochitina operculata (from upper Barremian-lower Aptian). The direct correlation of the base of the C. grovesii var. corrugatus biozone with the dinoflagellate cyst O. operculata, indicates that the base of the Clavator grovesii var. corrugatus biozone is in the upper lower Aptian, which is slightly older than was previously suggested, and it is extended until the middle Albian.