Stratigraphic evolution from the early Albian to late Campanian of the Potiguar Basin, Northeast Brazil: An approach in seismic scale

Abstract

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.

Cyclicity and hierarchy in sequence stratigraphy: an integrated approach

“…Characterizing and understanding the multi-scale cyclical behavior of the sedimentary record has been one of the most critical aspects of stratigraphic analysis (Schwarzacher 1993(Schwarzacher , 2000. In the context of sequence stratigraphy, the stratigraphic cyclicity observed at different scales can be described as sequences from different hierarchical levels, in which the stacking pattern of a higher order is composed of an organized amalgamation of lower rankings sequences (Catuneanu 2006, 2019a, Magalhães et al 2020Fig. 18).…”

“…Its frequency allows the interpreter to speculate what could be that mechanism (long or shortterm -e.g., Pittet and Strasser 1998). Also, the frequency is inversely proportional to the hierarchy (e.g., Magalhães et al 2016, Melo et al 2020. Thus, the higher the frequency of a cycle candidate to be a sequence, the lower its hierarchy and the duration of its generating mechanisms (e.g., Pedrinha et al 2015).…”

“…The change in any deposition trend is always marked by a stratigraphic surface (e.g., Catuneanu 2006). According to Magalhães et al (2020), stratigraphic surfaces of any hierarchy are always anchored to the lowest rank. Lower rank surfaces may be a candidate to belong to a higher hierarchy.…”

“…23. 3 -e.g., Embry 2009, Magalhães et al 2016, Melo et al 2020. This criterion is based on the analysis related to time and the evolution of depositional topography.…”

“…Its modern application offers powerful tools for describing the observable record from facies cycle to basin scale, through the definition of sequences within a hierarchical chronostratigraphic framework (e.g., Catuneanu 2019a). Notably, the sequential analysis on the outcrop scale has received special attention from the scientific community, increasingly improving what is known as high-resolution stratigraphy (e.g., Magalhães et al 2020).…”