New marine data and age accuracy of the Romualdo Formation, Araripe Basin, Brazil

Abstract

A combined biostratigraphic and palaeoecological study of foraminifera, ostracodes and microfacies was carried out on the Aptian in the Sítio Sobradinho section of the Araripe Basin, northeast Brazil. The analysed section represents a deepening-upward sequence with mid-ramp shoal and outer ramp to basin facies associations on a mixed siliciclastic-carbonate marine ramp. The analysed rocks are dominated by Early Cretaceous planktic foraminifera (Hedbergella aptiana, H. praelippa, H. sigali, Blesfucuiana cf. cumulus, Microhedbergella miniglobularis, Gorbachikella cf. kugleri, Pseudoguembelitria blakenosensis, Globigerinelloides clavatus, Globigerinelloides aff. aptiensis, Gubkinella sp. and Loeblichella sp.). Ostracoda fauna is composed mainly of Pattersoncypris crepata and Pattersoncypris micropapillosa. The occurrence of P. crepata associated with the Aptian planktic foraminifera demonstrates the potential of this ostracode species to date this interval. The planktic foraminifera from the upper Aptian (Microhedbergella miniglobularis Zone) of the Araripe Basin show characteristical Tethyan affinities.

Age of the Post-rift Sequence I from the Araripe Basin, Lower Cretaceous, NE Brazil: implications for spatio-temporal correlation

“…The first concluded that there are no Albian palynomorphs in the Post-rift Sequence I, which corresponds entirely to the Sergipea variverrucata palynozone. Melo et al (2020), studying ostracods and foraminifers, came to the same conclusion, that is, the sequence in question corresponds to the upper part of the Aptian. In view of this, the present work aims to contribute to this debate, considering biostratigraphic and geochronological analyses, having as a case study the Post-rift Sequence I of the Araripe Basin.…”

“…Regali, 1987. However, the very recent works by Arai & Assine (2020) and Melo et al (2020) are the ones that present the most in-depth studies on the age and paleoenvironments of this lithostratigraphic unit.…”

“…Consequently, the entire Post-rift Sequence I of the Araripe Basin corresponds to the palynozone Sergipea variverrucata (= P-270 for Petrobras), which determines the upper part of the Aptian in Brazilian basins. Melo et al (2020) analyzed the calcareous microfossils of the same outcrop studied by Arai & Assine (2020), recording the Cytheridea spp. 201-218 ostracode biozone (RT-011 for Petrobras).…”

“…Considering that the works of Arai & Assine (2020) and Melo et al (2020) were published after that of Lúcio et al (2020), the present discussion focuses only on the works on microfossils and biostratigraphy available to the last authors.…”

“…published, one by Arai & Assine (2020) and the other by Melo et al (2020). The first concluded that there are no Albian palynomorphs in the Post-rift Sequence I, which corresponds entirely to the Sergipea variverrucata palynozone.…”