Diagnostic features of volcanic and volcaniclastic rocks in seismic sections on the Continental Shelf of Cabo Frio Area, SE Brazil

The Continental Shelf of Cabo Frio Area, located in between Campos and Santos basins, has been affected by an important magmatic episode in the Upper Cretaceous and Lower Tertiary Sequences. The analysis of seismic reflections, in the work area, pointed to a set of diagnostic features that can lead to the identification of magmatic events and the distinction of intrusive from extrusive igneous rocks, as well as their intercalations with epiclastic sedimentary sequences. The volcano-sedimentary section in the Cabo Frio Area is characterized by sets of strong and discontinuous reflections, usually with a well defined top and poorly defined base, and by the presence of volcanic edifices (cones). Intrusive rock bodies, like sills and dikes, are less common and have a seismic response characterized by strong positive reflections with abrupt lateral limits associated to their tops. The sedimentary sequences that overlap this volcano-sedimentary section are not directly related to the magmatic pulses in the area, however the pulses affected the paleorelief of the seafloor, which controlled the turbiditic deposition.