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.

The Tombador Formation exhibits depositional sequence boundaries placed at the base of extensive amalgamated fluvial sand sheets or at the base of alluvial fan conglomeratic successions that indicate basinward shifts of facies. The hierarchy system that applies to the Tombador Formation includes sequences of different orders, which are defined as follows: sequences associated with a particular tectonic setting are designated as ‘first order’ and are separated by first‐order sequence boundaries where changes in the tectonic setting are recorded; second‐order sequences represent the major subdivisions of a first‐order sequence and reflect cycles of change in stratal stacking pattern observed at 102 m scales (i.e., 200–300 m); changes in stratal stacking pattern at 101 m scales indicate third‐order sequences (i.e., 40–70 m); and changes in stratal stacking pattern at 100 m scales are assigned to the fourth order (i.e., 8–12 m). Changes in palaeogeography due to relative sea level changes are recorded at all hierarchical levels, with a magnitude that increases with the hierarchical rank. Thus, the Tombador Formation corresponds to one‐first‐order sequence, representing a distinct intracratonic sag basin fill in the polycyclic history of the Espinhaço Supergroup in Chapada Diamantina Basin. An angular unconformity separates fluvial‐estuarine to alluvial fan deposits and marks the second‐order boundary. Below the angular unconformity the third‐order sequences record fluvial to estuarine deposition. In contrast, above the angular unconformity these sequences exhibit continental alluvial successions composed conglomerates overlain by fluvial and eolian strata. Fourth‐order sequences are recognized within third‐order transgressive systems tract, and they exhibit distinct facies associations depending on their occurrence at estuarine or fluvial domains. At the estuarine domain, they are composed of tidal channel, tidal bar and overlying shoreface heterolithic strata. At the fluvial domain the sequences are formed of fluvial deposits bounded by fine‐grained or tidal influenced intervals. Fine grained intervals are the most reliable to map in fourth‐order sequences because of their broad laterally extensive sheet‐like external geometry. Therefore, they constitute fourth‐order sequence boundaries that, at the reservoir approach, constitute the most important horizontal heterogeneity and, hence, the preferable boundaries of production zones. The criteria applied to assign sequence hierarchies in the Tombador Formation are based on rock attributes, are easy to apply, and can be used as a baseline for the study of sequence stratigraphy in Precambrian and Phanerozoic basins placed in similar tectonic settings.

With standardized methodology and nomenclature, the sequence stratigraphy aims to characterize multi-scale cyclical units of genetically related rocks into a hierarchical chronostratigraphic framework. From facies to basin scale, the stacking patterns and stratigraphic surfaces are recognized as sequence elements. In parallel, Earth sciences have developed a sophisticated understanding of geological processes (tectonic, climatic, and eustatic) that produce the main cyclicity observed in the sedimentary rock record. This review paper discusses how the elaboration of hierarchical stratigraphic frameworks that incorporate the knowledge of these periodic geological processes -from high-to low-frequencies -as the control of generation and preservation of sequences -from high-to low-resolutions -guarantees objective results in predicting vertical recurrence and the lateral correlation of genetic stratigraphic units. This interpretive approach of cyclic stratigraphic analysis supports the development of effective observable criteria to identify and rank sequences in multiple scales, based on cycle anatomy, recurrence, vertical trends, and mappability. This methodological improvement reduces the inaccuracies and contradictions of traditional conceptual models based on fully preserved three-dimensional depositional systems.

No abstract

Microbialitos gerados em ambiente deposicional lacustre apresentam grande diversidade de estruturas e texturas internas. A organização e a caracterização do arranjo formado por esses atributos correspondem ao que se denomina intrabioarquitetura. Este trabalho tem o objetivo de identificar os principais tipos de intrabioarquiteturas nos microbialitos da Sequência Balbuena IV (Daniano, Bacia de Salta, Argentina) em escala mesoscópica (100 – 10-2 m) e a interpretação cíclica da recorrência dos componentes que formam estas intrabioarquiteturas, em escala microscópica. Foram reconhecidos sete padrões intrabioarquiteturais, assim denominados: Microbialito Aglutinante de grão grosso (MA-gg); Microbialito Bandeado Fasciculado/Aglutinante de grão fino (MBFA-gf); Microbialito Pseudo-microcolunar Aglutinante de micrita (MPMA-m); Microbialito Arbustiforme Microgrumoso Aglutinante de grão fino (MArbMA-gf); Microbialito Dendriforme Microgrumoso Aglutinante de grão fino (MDMA-gf); Microbialito Bandeado Fasciculado/Aglutinante de grão fino com esferulito (MBFA-gf,esf) e Estromatólito Microgrumoso/Aglutinante de grão grosso (EMA-gg). Essas intrabioarquiteturas foram agrupadas e relacionadas a três tipos de microciclos deposicionais. Os microciclos possibilitam organizar o registro microbial em escala meso- e microscópica. Essa organização cíclica está relacionada às variações climáticas, que afetam o nível de base, o aporte sedimentar e os processos biológicos e geoquímicos do sistema lacustre. Portanto, foi possível associar a formação dos microbialitos a períodos de maior ou de menor aridez no ambiente deposicional.