Evolução tectono-estratigráfica da porção central da Bacia do Rio do Peixe, NE do Brasil

Abstract

The Rio do Peixe Basin is part of a set of aborted rifts with NE-SW trend along the NE region of Brazil installed on Borborema Province pre-cambrian basement. This axis originated in response to the stress caused by the fragmentation of Pangea during the Mesozoic, and effectively installed during the Cretaceous event that has provided the opening of the South Atlantic Ocean and defined the Brazilian equatorial margin. The Brejo das Freiras Half-Graben is one of the main BRP depocentres and presents a tectonostratigraphic evolution, developed under a NW-SE distension regime, controlled by the fragile reactivation of pre-Cambrian structures. The interpretation of 2D 3D seismic data from the SE portion of this half-graben, which was preceded by a data treatment step using filtering techniques and seismic attributes analysis, allowed a more detailed characterization of the structural and stratigraphic framework of the region. Further seismic structural interpretation allowed the recognition of the structures indicative of the structural style of the basin as well as deformational mechanisms responsible for affecting the sedimentary layers. The Brejo das Freiras fault zone, which presents NE-SW trend and locally ENE-WSW, strongly influenced by the basement fabric, deforms the layers and originates folds essentially formed by bending mechanisms, such as drag folds, fault-bending folds, and fault-propagation. The rift tectonosequence, which corresponds to the Rio do Peixe Group, has been compartmentalized in nine depositional sequences and arranged five tectonic systems tracts. Those sequences are bounded by flooding surfaces and are responsible for registering shallowing upwards cycles encompassing conglomerates, sandstones, siltstones, shales, claystones, and calcilutites lithofacies. Tectonic systems tracts related to the initial stages of installation of the rift, succeeded by moments of high and low tectonic activity, have been designate as: Rift Initiation Tectonic Systems Tract, HalfGraben Development, High Tectonic Activity (phase 1), Low Tectonic Activity and High Tectonic Activity (phase 2). A set of reflections corresponding to the pre-rift section with occurrence restrict to the depocenter was additionally interpreted. The expected result for the present study, which integrates structural and stratigraphic analysis, is a contribution to the understanding of the tectonic influence on spatial and temporal distribution of depositional systems responsible for filling the basin, allowing the prediction of potential petroleum systems, either directly or by the interpretation of analogs.