Tectonics and stratigraphic relationships in the Pernambuco Sub-basin, NE Brazil: contribution to the knowledge of the South Atlantic Rift

Abstract

The Pernambuco-Paraíba Basin is related to the final
stages of the breakup between South America and
Africa during the early Cretaceous. The southern segment of this basin (the Pernambuco Sub-basin, SBPE) extends from the Pernambuco Lineament to the
Maragogi High, at the border with the Sergipe-Alagoas Basin. 
The stratigraphy of the SBPE comprises a basal
volcanosedimentary rift sequence (siliciclastics of the
Cabo Formation interlayered and intruded by the
Ipojuca Magmatic Suite) of Mesoaptian-Mesoalbian
age, which overlies the precambrian basement through non-conformity or fault contacts. The onset of the drift stage is marked by the carbonates and siliciclastics of the Estiva Formation, which define a transgressive sequence of Cenomanian-Santonian age. In most cases, the rift sequence is directly overlain by the siliciclastics of the Algodoais Formation, a regressive sequence which reworked sources internal to the basin. In the continent, the youngest units of the regressive sequence correspond to the Barreiras Formation and quaternary covers.
At least three deformation events were recognized in the SBPE. The oldest one defines the structural framework of the basin, being related to the rift stage, controled by a NW extension kinematics. This event comprises NE-trending, high or low-angle normal faults connected through NW-trending transfer faults. This style is also mapped in the offshore basin using gravity and seismic data, allowing to recognize half-graben systems separated by a major tectonic high trending paralell to the coast. Besides the Cabo Formation alluvial fans that follow the border faults, the emplacement of the igneous bodies of the Ipojuca Suite was also controled by this event, implying that rift fault activity was still active during Mesoalbian times.
Two younger events overprint the drift sequences,
generating new faults or reactivating the rift stage
structures; the Barreiras Formation is affected by the
youngest one.