Navegando por Autor "PEREIRA, Ana Paula Linhares"

Agora exibindo 1 - 2 de 2

Acesso aberto (Open Access)
Ostracodes da Formação Solimões, Neógeno do estado do Amazonas, Brasil: taxonomia, paleoecologia e bioestratigrafia
(Universidade Federal do Pará, 2011-08-16) PEREIRA, Ana Paula Linhares; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936
The analysis of 123 samples from 1AS-31-AM and 1AS-34-AM cores from the southwest of Amazonas State, Brazil allowed to recognize the abundance and diversity of ostracodes with register of five families: Cytherideidae, Limnocytheridae, Cyclocyprididae, Darwinulidae and Candonidae, distributed in six genera (Candona, Cypria, Cytheridella, Darwinula, Perissocytheridea e Cyprideis) and 23 species, 15 of them previously recorded to adjacent areas. The family Cytherideidae is the most representative with two genera and 19 species. The Cyprideis genera, as recorded in previous studies, is the most abundant representing 96% of ostracofauna and most diverse with 18 species. The ostracod stratigraphic distribution and the associated microfauna allowed the reconstruction the paleoenviromental evolution, The paleoenvironmental interpretation reveal an evolution of the depositional system in the Amazonia, which grades from continental (lacustrine) environments, at the base to a sporadically marine influenced settings into fluvial conditions at the top of the core sequence. This vertical variation might be better observed in 1AS-31-AM core. Probably, the radiation of Cyprideis is associated with sudden changes (mainly related to salinity change), supported by the presence of nodules in its shell. The biostratigraphic distribution of the Cyprideis species possibilited the determination of three biozones (OS1, OS2 e OS3), aged between the later Early Miocene/earlier Middle Miocene to later Middle Miocene/early Late Miocene. In the 1AS-34-AM core the analyzed range possibly corresponds to Middle Miocene/Late Miocene. The short-lived marine ingression reached the central part of Amazonia, probably in the Early-Middle Miocene based on the biostratigraphic model proposed here and supported by ostracod, palinological and mollusk biozonations.
Acesso aberto (Open Access)
Ostracofauna da Formação Solimões (Atalaia do Norte, Amazonas, Brasil): taxonomia, implicações paleoambientais e bioestratigráficas.
(Universidade Federal do Pará, 2017-09-12) PEREIRA, Ana Paula Linhares; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936; 4546620118003936
The study of the ostracods from the boreholes 1AS-7D-AM, 1AS-8-AM and 1AS-31- AM, drilled at the locality of Atalaia do Norte, in Amazonas State, Brazil, allowed to recognized 9 genera and 30 species; the eurialyne genera Cyprideis is the most abundant and diverse, with 19 known species and two new species described herein: C. atalaiensis sp. nov. and C. diction sp. nov. Other marine and/or transitional (Paracypris, Perissocytheridea, Rhadinocytherura, Pellucistoma and Skopaeocythere) and non-marine (Cypria, Cytheridella and Penthesilenula) genera have been found, as well as other microfossils (foraminifera, fishs, mollusks and palinomorphs) which have been used for the paleoenvironmental interpretations and biostratigraphy of the Solimões Formation. The integrated stratigraphic analisys of ostracods and palinomorphs in the boreholes 1AS-8-AM and 1AS-7D-AM allowed to date the sequence from Early Miocene to Late Miocene. Through the index fossils, were identified five palinological zones already proposed from the Neogene of western Amazon: Verrutricolporites, Early Miocene; Psiladiporites-Crototricolpites, Late Early Miocene to Early Middle Miocene; Crassoretitriletes, Middle Miocene; Grimsdalea, Late Middle Miocene to Early Late Miocene; and Astaraceae, Late Miocene. The distribution of the Cyprideis species allowed to recognize five zones corresponding to the palynological zones, four of which previously established, although its age limits have been changed in this study: C. aulakos, renamed as C. sulcosigmoidalis, from late Early Miocene to early Middle Miocene, C. caraione, Middle Miocene to early Late Miocene, C. minipunctata, late Late Miocene and C. cyrtoma Late Miocene. Furthermore, is proposed here a new ostracod zone: C. paralela, from Late Miocene. The biostratigraphic analysis, based on palinology and ostracods, as well as other microfossils reveals a sequence which starts at the Early Miocene, with influence of coastal environments attested by the presence of palinomorphs and foraminifera typically from mangrove. At the Middle Miocene, the paleoenvironments are characterized as fluvio-lacustrine with marine influence. Finally, in the Late Miocene although still marked by marine influence, predominate fluvio-lacustrine environment upward to the section.