[2] The terrain around the caldera is formed by a Paleozoic basement, Mesozoic sedimentary rocks and also Mesozoic volcanic rocks; the latter are separated from the first two units by branches of the Domeyko fault system;[3] this fault system and its branches have controlled the emplacement of a large number of copper deposits.
[1] The Paleocene volcanism is characterized by trachyandesite and trachybasalt, which define a potassium-rich calc-alkaline suite.
[6] El Salvador during the Paleocene collapsed and erupted the Cerros Contreras-La Antena ignimbrites.
[3] The history of the volcanic complex was at first considered to be continuous, but later it was found that it involved a Paleocene and an Eocene phase,[7] with caldera formation occurring about 63-61 million years ago.
[8] The Eocene volcanic episode appears to be unrelated to the Paleocene one and gave rise to ore deposits.