Magmatism and sedimentation in an area in the Continental Shelf of Cabo Frio, Rio de Janeiro, Brazil, in the Upper Cretaceous - Tertiary interval

Abstract

The Continental Shelf of the Cabo Frio Area shows unique features in its tectono-sedimentary evolution when compared to the other areas of the Campos and Santos basins. The presence of a regular pattern of antithetic faults in the basement and in the sin-rift and post-rift sedimentary sections, are some of these fea-tures. In addition, the area shows important magmatic events in the Upper Cretaceous and Tertiary sequences, which climax took place in the earliest por-tion of the Middle Eocene. The description of these magmatic events and their influence in the post-rift sedimentation is the main objective of this paper.
The analyses of seismic reflection and well log data, in the work area, points to a set of diagnostic features that can lead to the identification of mag-matic events and the distinction of intrusive from extrusive rocks, as well as their intercalations with epiclastic sedimentary sequences. 
Volcanic edifices have preserved their conical shapes when they were formed under submarine conditions; under subaereal conditions, they show irregular shapes due to erosion. In this way, these observations indicate the palaeobathymetry for the time of the formation of these edifices. In the case of the work area, the integration of the analyzed data indicates that extrusive events are more widespread than intrusive events. 
The sedimentary pattern of the work area is similar to that of the Campos Basin. The sedimentary sequences that overlap this volcano-sedimentary sec-tion are not directly related to the magmatic pulses in the area; however, they affected the palaeo-relief of the seafloor, which controlled turbiditic deposition.