Abstract

A 4000 metre thick fining-up succession of conglomerates, sandstones and mudstones on the northwestern edge of the Golfo de Penas, southern Chile, is defined as the Puerto Barroso Formation. It probably formed in a forearc basin where a fan delta built across a narrow coastal plain into a shallow marine environment during the Barremian to Aptian. The basin is situated to the west of contemporaneous arc, back are and epicratonic basins and is the only documented forearc basin of this age in southern South America.