Multi‐scale transgressive–regressive cycles from the mid‐Jurassic were recognised in the Central Lusitanian Basin, Portugal. These cycles allow the depositional evolution of the basin to be better understood and aid in the construction of stratigraphic sequences composed of three hierarchies. The stacking pattern of high‐frequency transgressive–regressive sequences forms larger clusters that define medium‐frequency transgressive–regressive sequences. Likewise, the stacking pattern of medium‐frequency transgressive–regressive sequences generates two Bathonian–early Callovian low‐frequency transgressive–regressive sequences. Integration of several methods supported the interpretation of facies associations representing clastic deposition in offshore to shoreface environments and carbonate sediments in outer to inner ramp settings. New data from calcareous nannofossils and dinoflagellate assemblages constrained the interval's Bathonian–early Callovian age, thus unveiling the Middle–Upper Jurassic disconformity and filling the Middle Jurassic stratigraphic record gap in the Central Lusitanian Basin. This study may be helpful for similar successions in Tethyan domains and comparable depositional settings elsewhere.

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Five 3rd-order depositional sequences are interpreted from the early Albian to late Campanian interval in the Potiguar Basin. An integrated analysis of seismic interpretations, well logs, cores and biostratigraphic data provides a stratigraphic framework composed by stratigraphic surfaces, systems tracts and sequences. Depositional Sequence 1 and 2 are, respectively, Albian and early to mid-Cenomanian aged and are composed by the falling stage, low stand, transgressive and high stand systems tracts. Depositional Sequence 3 is late Cenomanian to mid-Turonian aged and is composed by the transgressive and high stand systems tracts. Depositional sequences 4 and 5 are, respectively, late Turonian to mid-Santonian and late Santonian to mid-Campanian aged and are composed only by transgressive and high stand systems tracts. The lack of falling stage and low stand systems tracts in depositional sequences 3, 4 and 5, as well the increasing in transgressive and highstand systems tracts thickness as depositional sequences get younger, are reflection of an overall transgressive trend of a 2nd-order sequence. The interpretation proposed in this paper correlates onshore with offshore deposits within a seismic scale (3rd-order) sequence stratigraphy framework. This approach allows a better understanding of the Açu Formation, the primary oil-bearing formation of the Potiguar Basin. The Açu Formation is part of depositional sequences 1, 2 and 3 and is characterized by lateral and vertical variations of depositional systems instead of being associated to a specific depositional system. This sequence stratigraphy analysis can be used as a low-resolution framework for future high-resolution (4th-order scale) studies.

Palavras-chave: Formação Barreiras, sistemas deposicionais, caracterização faciológica. RESUMOAo longo da costa brasileira são encontrados depósitos sedimentares atribuídos à Formação Barreiras. No Rio Grande do Norte, estes depósitos ocorrem principalmente na linha de costa, tendo como melhor exemplo a Barreira do Inferno, um afloramento com mais de 1 km de extensão e até 20 m de espessura, situado no município de Parnamirim (RN). As associações de fácies descritas foram interpretadas como indicativas da deposição em um contexto fluvial, sendo as de granulação mais grossa relacionadas a depósitos de preenchimento de canais e as de textura mais fina, atribuídas a depósitos de planície de inundação. Estes depósitos mostram lateralmente uma clara diminuição da proporção entre arenitos e conglomerados versus lamitos. Na região que foi interpretada como a porção mais central de um suposto cinturão fluvial, a sucessão apresenta quase 80% de arenitos e conglomerados, ao passo que, lateralmente, a menos de 200 m, chega a ter 40% de rochas de granulação mais fina, o que sugere a proximidade da planície de inundação. Apesar de o sistema fluvial interpretado apresentar algumas características de um sistema entrelaçado, a abundância de fácies pelíticas, bem como a ocorrência freqüente de estratos com geometria de preenchimento de canais, permite estabelecer uma maior aproximação a um sistema fluvial meandrante. Considerando esses aspectos, o modelo "Meandrante de Granulometria Grossa" é o que melhor representa estes depósitos.Keywords: Barreiras Formation, fluvial systems, facies analysis. ABSTRACTThe Barreiras Formation is composed of sedimentary siliciclastic rocks that crop out at the continental scale along the Brazilian coastline from the State of Rio de Janeiro to the State of Amapá. In the State of Rio Grande do Norte, this formation is well exposed in cliffs along the coastline, best represented by the Barreira do Inferno cliff, which is 1 km long and 20 m high. Facies characterization and interpretation of depositional systems of the Barreiras Formation in this cliff were based on stratigraphic columnar sections and digital photomosaics. The Barreira do Inferno cliff comprises a large area affording continuous exposure of bed geometries, generally tabular in shape with secondary channels filled by mudstones, indicative of a fluvial context. Coarse facies characterize channel environments, whereas fine facies represent flood plains. This interpretation is supported by a lateral decrease in the ration of sandstone/conglomerates versus mudstones along the outcrop. In the central portion of the fluvial belt, sands and conglomerates comprise up to 80% of the deposits. Laterally, in the flood plain, up to 40% of the deposits are mudstones, fine sands, and very fine sands. This system is similar to braided fluvial systems, but the facies association (with pelites) and layer geometries (abandoned channels filled by mudstones) are characteristic of meandering rivers. The model that best explains these deposits is the "coar...

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