Facies volcanoclásticas y procesos deposicionales de la formación cayo (cretácico), al sureste del cerro azul, Guayaquil – Ecuador

Topic: FORMACIÓN CAYO
FACIES
TOBA LAPILLI
IGNIMBRITA
FLUJOS PIROCLÁSTICOS
The Cayo Formation represents an important part in the geology of the ecuadorian coast, it can be located lying in the Calentura Formation and underlying the Guayaquil Formation in the Piñón Block. The present study focused on the facies characterization and association as well as the depositional processes of the Late Cretaceous Cayo Formation, at the southeast of Cerro Azul in the city of Guayaquil. The massive lithofacies of thick lapilli tuffs and massive lithic breccias were found interbedded with thin to medium bedded tuffaceous shales and lapilli tuffs facies. These lithofacies consist of high concentrations of highly vesicular juvenile fragments and plagioclase crystals that have been altered to chlorite, while the most common textures of the vitric fragments vary from perlitic to axiolitic. The facies analysis and their respective associations suggest a subaqueous explosive volcanism environment dominated by high temperature pyroclastic flows that because of the high pumice fragment content can be described as ignimbrites. The sedimentary processes involved different sediment gravity flows that deposited the lapilli tuffs, tuffaceous shales, and ashfall tuffs, which in turn built the thick volcanic apron sequences.