Significance and genetic interpretation of the sequential organization of the aptian-albian lacustrine system of the Araripe basin

Abstract

The Passa Dois Group is divided into formations and members, representing variations of lithofacies separated by unconformities or correlative conformities.The contact between the Passa Dois and Tubarão Groups is represented by a paraconformity, and the contact between the Passa Dois and São Bento Groups corresponds to a regional unconformity or correlative conformity.Intracratonic basins differ physiographically from passive margin basins, for which the concepts of Sequence Stratigraphy were originally developed; so some adjustment has to be done for the application of the theory.The 3rd order chronostratigraphic framework for the Passa Dois Group begins by offshore marine sedimentation of the Taquaral Member upon the coastal marine regressive sediments of the upper part of the Palermo Formation, through a conformable contact representing a transgressive surface. After this, a highstand phase prevails, bounded at its top by the maximum flooding surface, that is coincident with the lower conformable contact of the Assistência Member, which represents a new lowstand phase. Sea level rises again, through transgression, depositing the offshore sediments of the Serra Alta Formation. Deposition of the sediments of the Teresina Formation follows, suggesting a new lowstand phase with wave and tidal structures, than passes to the Serrinha Member of deeper waters with hummocky structures indicating a new highstand phase. A new lowstand phase occurs with well-sorted sandstones showing cross-stratification with medium to high angles, with clay drapes, suggesting the recurrence of tidal conditions, corresponding to the base of the Morro Pelado Member, that passes, by transition, to continental deposits, bounded at their top by a regional unconformity or a correlative conformity considered between the Passa Dois and the São Bento Groups, corresponding to a 2nd order sequence.The thicknesses of each pair of units, deposited in shallower waters at its base and by deeper waters at its top, do not exceed 500 m. Considering a rate of deposition of the order of 1 m per each 10,000 years, they correspond to 3rd order sequences. The bounding surfaces that separate the sequences are of conformable type 2. Depositional systems characteristic of steeper slopes, or of floor basin fans or slope fans, that are common in sequences of type 1 are not observed. The duration of deposition of the related pairs varied from 1 to 10 M.a., well within the known duration of stages, which strengthens the hypothesis that they represent 3rd order sequences. - ( December 10, 1999 ) .

Definição Estratigráfica Da Formação Missão Velha, Bacia Do Araripe

“…Com base na revisão apresentada, partimos da definição de Formação Missão Velha de Ponte & Appi (1990), seguida por Assine (1990Assine ( , 1992, Neumann (1999), Neumann & Cabrera (2000) e revisada por Arai (2006), na qual esta unidade é constituída predominantemente por corpos arenosos amalgamados, lateralmente contínuos e portadores de abundantes troncos fósseis, onde os pelitos subordinam-se (Fambrini et al 2011). Esta foi a tônica de Fambrini et al (2011de Fambrini et al ( , 2017 no qual são discutidos os elementos arquiteturais e as fácies para a elaboração dos sistemas deposicionais e do arcabouço estratigráfico de sequências da unidade.…”

“…(iv) Sequência pós-rifte, separada em duas, Pós-Rifte I, de idade aptiano-albiana, constituída pelas formações Barbalha, Crato, Ipubi e Romualdo, e Pós-Rifte II, de idade albiano-cenomaniana, achase caracterizada por sedimentos aluviais das formações Araripina e Exu. A Bacia do Araripe, sendo amplamente conhecida por sua grande variedade de ocorrências fósseisespecificamente de peixes, insetos, e pterossauros no Grupo Santana (sensu Neumann, 1999;Assine et al, 2014;Fambrini et al, 2017Fambrini et al, , 2019, vem sendo objeto de numerosas publicações na última metade de século (Chagas, 2006). A Formação Missão Velha (Ponte & Appi, 1990) destaca-se na bacia sobretudo pela ocorrência de uma assembleia fossilífera de troncos silicificados de coníferas.…”

Facies architecture of the fluvial Missão Velha Formation (Late Jurassic–Early Cretaceous), Araripe Basin, Northeast Brazil: paleogeographic and tectonic implications

“…3). Several significant lacustrine depositional episodes have been recognized in the Araripe Basin Neumann and Cabrera 2000;Fambrini et al 2007Fambrini et al , 2008Fambrini et al , 2012aFambrini et al , b, 2013. A first episode took place during the Late Jurassic (Dom João Stage) and led to deposition of the fine-grained siliciclastic, shallow lacustrine successions of the Brejo Santo Formation, richly fossiliferous (ostracodes, conchostraceans, fish bones and teeth, dypnoids, Carvalho and Viana 1993;Brito et al 1994;Viana et al 2002;Barros et al 2011;Fambrini et al 2007Fambrini et al , 2008Fambrini et al , 2012bFambrini et al , 2013, which have been reported from the subsurface and from extensive outcrops.…”