Bagaces formation: characterization of units for identification of deposits and lithofacies

Abstract

The base of Guanacaste Volcanic Range is formed predominantly by an interesting sequence of pyroclastic deposits with ages ranging between Miocene and Pleistocene, which correspond with the Bagaces and Liberia formations. In this stratigraphic proposal, the units of the Bagaces Formation have been identified based on their composition and vertical variations. The unit’s lithofacies was characterized through the analysis of fifteen borehole cores, stratigraphic field sections and the compilation of thin section analysis. The Potrerillos, Limbo I, Sandillal, Pan de Azúcar, Limbo II (Upper deposit), Poza Salada, Santa Rosa, La Casona (Upper deposit), Monte del Barco, Río Colorado y Montenegro Tuffs correspond to complex deposits which present vertical variations. While the Alto Mirador, Rama de Nance, Limbo II (Lower deposit), Mata de Caña, La Casona (Lower deposit), Cuajiniquil and Cañas Tuffs are simple deposits. The eruptive centers that originated the tuffs Mata de Caña and La Casona must have been located close to the town of Curubandé. The magmatic evolution shows a cyclicity behavior between slightly more acidic or basic magmas.