Charco Azul FormationCharco Azul Formation is a geologic formation of the Charco Azul Group in western Panama and southeastern Costa Rica. It preserves gastropod fossils dating back to the Pliocene period.DescriptionThe Charco Azul Formation comprises tuffaceous shales deposited in a deep marine environment The formation unconformably underlies the Armuelles Formation. The formation is correlated to the Jama and Canoa Formations of Ecuador.Fossil contentThese fossils have been reported from the formation: Strombina penita, Strombina recurva Distorsio decussata Marsupina bufo, ''M. nana''