High resolution stratigraphy of channelized deposits on a continental slope setting with sea-floor topography controlled by halokinetics, uppermost cretaceous, Espirito Santo offshore basin, Brazil

摘要

All published chronostratigraphic charts of the Espirito Santo basin, Brazil, show stratigraphic frameworks based on second-order depositional sequences. The absence of published high-resolution biostratigraphic analyses precludes the proposition of a higher order stratigraphic framework. This work breaks down the second-order depositional sequences, from Campanian to Maastrichtian succession in the drift phase of Espirito Santo offshore basin, in three third-order depositional sequences based upon seismic interpretation of a hierarchical scheme of channel on continental slope setting coupled with a correlation to a global sea-level curve. The resolution of the 2D seismic data analyzed allowed the identification of three levels of erosional surfaces and their subsequent filling, from smaller to higher: composite channels, channel complexes and channel complexes set. Channel complexes development is related to lowstand deposits on the continental slope. Also, the aspect ratio of the channel complexes analyzed are reverse to the expected for channel development on continental slope settings. Usually, the further down-dip the channels are located, the higher their aspect ratio, however, it does not happen in the study case. Most of down-dip channels show a lower aspect ratio. It is ascribed to the control of the seafloor topography by the halokinetics. The identification of the geometric pattern of the channels on seismic data allowed a proposition of an exportable depositional model to predict possible sandy deposits on the continental slope regarding the intensity of salt tectonics.