“…7). To the western of the Araripe Basin, Varejão et al 90 described microbialites and stromatolites associated to rocky-protected lagoon, that corroborates our interpretation of a low-gradient ramp, deeper to the east of the basin where Sítio Sobradinho Section is located. The lower studied interval corresponds to the mid-ramp shoal facies association, which groups the glauconite-bearing calcareous quartz arenite and the siltstone to claystone overlaid strata.…”
Section: Discussionsupporting
confidence: 89%
“… Figure 7 Schematic palaeoenvironmental reconstitution of the Romualdo Formation deposits: ( a ) Glauconite-bearing sandstone shoal; ( b – d ) Shale interbedded with ostracode and foraminifera wackestone and calcisphere mudstone: ( b ) calcispheres; ( c ) planktic foraminifera; ( d ) benthic foraminifera and ostracode Pattersoncypris crepata . The interpretation of the west portion of the Araripe Basin is based on Varejão et al 90 data. The complete figure was composed by Robbyson Melo on CorelDRAW version 22.0 ( https://www.coreldraw.com ).…”
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.
“…7). To the western of the Araripe Basin, Varejão et al 90 described microbialites and stromatolites associated to rocky-protected lagoon, that corroborates our interpretation of a low-gradient ramp, deeper to the east of the basin where Sítio Sobradinho Section is located. The lower studied interval corresponds to the mid-ramp shoal facies association, which groups the glauconite-bearing calcareous quartz arenite and the siltstone to claystone overlaid strata.…”
Section: Discussionsupporting
confidence: 89%
“… Figure 7 Schematic palaeoenvironmental reconstitution of the Romualdo Formation deposits: ( a ) Glauconite-bearing sandstone shoal; ( b – d ) Shale interbedded with ostracode and foraminifera wackestone and calcisphere mudstone: ( b ) calcispheres; ( c ) planktic foraminifera; ( d ) benthic foraminifera and ostracode Pattersoncypris crepata . The interpretation of the west portion of the Araripe Basin is based on Varejão et al 90 data. The complete figure was composed by Robbyson Melo on CorelDRAW version 22.0 ( https://www.coreldraw.com ).…”
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.
“…In this basin, the Barbalha, Crato, Ipubi and Romualdo formations, Santana Group, comprise three Aptian depositional sequences that are bounded by internal unconformities (Assine et al ., 2014). All depositional sequences record transgressive–regressive successions (Assine et al ., 2014), although only the latter (Romualdo Formation) is demonstrably linked to marine ingressions (see Beurlen, 1963; Custódio et al ., 2017; Fürsich et al ., 2019; Varejão et al ., 2019a; Rodrigues et al ., 2020; Melo et al ., 2020).…”
The Aptian evaporitic transitional sequence (sag phase) of the Brazilian marginal basins records the first connection between the Central and South Atlantic oceans in the equatorial area. During this phase, lacustrine carbonate reservoirs and giant salt deposits developed in the southern basins of Santos and Campos, forming world-class petroleum reservoirs. The sag succession is also well-preserved in the interior rift basins of north-eastern Brazil, where upper Aptian strata are represented by a continuous section. This contribution presents an interpretation of the evolution of a third-order depositional sequence comprising lacustrine limestones, marine siliciclastic facies and evaporite deposits of the intracontinental Araripe Basin. The Lowstand Systems Tract is characterized by fluvial deposits filling accommodation generated during the syn-rift phase. The overlying deposits comprise marine facies with preservation of dinoflagellates and marine ichnotaxa, evidencing marine deposition in bayhead delta settings. The transgressive surface is represented by limestones, including the Konservat-Lagerst€ atte laminites, onlapping the basement rocks. Above, tide-dominated bay deposits with distinct subtidal, intertidal and supratidal portions are recorded. The Maximum Flooding Surface is a dark shale below foreshore to shoreface facies, marking the beginning of the Highstand Systems Tract, culminating with deposition of evaporites (gypsum and anhydrite). The stratigraphic architecture and palaeocurrents measured in different facies associations suggest that marine waters reached the basin from the south. The data unequivocally records late Aptian marine ingressions of an incipient South Atlantic Ocean over the interior basins of north-eastern Brazil, while lacustrine conditions were still prevailing in the Pre-Salt sag units of the Santos and Campos basins.
“…However, Catto et al (2016) hypothesize that around 90% of that carbonate came from organic activity that reduced sulfates, which promoted an atypical concentration of sulfides by biological induction. Varejão et al (2019), in a study on crustacean taphonomy, called attention to the role of microbial mats in improving the extremely fine fossilization. These laminated carbonates are a Konservat-Lagerstätte that holds astonishingly well-preserved and diverse fossil assemblages with plants, palynomorphs, vertebrates, invertebrates and ichnofossils.…”
A robust biostratigraphic zonation based on microfossils supports the stratigraphic framework and correlation of the interior basins of the Lower Cretaceous of NE Brazil. This zonation has also allowed correlations with coeval sections in the Brazilian marginal basins and in the Gabon and Congo basins (central-west Africa). These records, consisting mainly of non-marine sediments, were a great challenge with regard to the correlation with the International Chronostratigraphic Chart. Therefore, local stages were used, the most recent being the Alagoas local Brazilian Stage, with which the Post-rift Sequence I of the Araripe Basin is related. Regarding lithostratigraphy, this sequence includes the Rio da Batateira (Barbalha for some authors) and Santana formations, the last one with the famous Crato, Ipubi, and Romualdo members, from the base to the top. Although currently there is a consensus on the age of the Alagoas local Brazilian Stage in the Araripe Basin, recently a new age for at least part of the Post-rift Sequence I was proposed. This new proposal, based on isotopic analysis of Re-Os, arose as a panacea to correlate the Rio da Batateira Formation and the Crato and Ipubi members with the international stages. Surprisingly, their authors, although on the one hand, they seem to underestimate biostratigraphic results, on the other they seek to support their proposal from microfossils studied by previous authors, but they do so in an inappropriate way, leading readers to misinterpret their results. Therefore, this paper presents a critical review on the age of the Alagoas local Brazilian Stage in the Araripe Basin and nearby basins, refuting a Barremian age for part of the Post-rift Sequence I. Keywords: Alagoas local Brazilian Stage, biostratigraphy, ostracods, palynomorphs, radiometric ages.
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