This is an approximately circular intrusion of about 5 km2 cutting Precambrian gneisses, but overlapped on the northern side by Tertiary sedimentary rocks.
This is an area of alkaline rocks which includes much of the island of Cabo Frio (6.3 km2) together with the smaller intrusions of Morro do Forno and Atalaia on the adjacent mainland; there is an abundant dyke suite.
A lava flow with a maximum thickness of 20 m outcrops over a semicircular area less than 1 km in diameter, 4.5 km southeast of Volta Redonda. It is associated with sediments of the Resenda Formation.
Scratchpads developed and conceived by (alphabetical):
Ed Baker,
Katherine Bouton
Alice Heaton
Dimitris Koureas,
Laurence Livermore,
Dave Roberts,
Simon Rycroft,
Ben Scott,
Vince Smith