The Gatún Formation (Tg) is a geologic formation in the Colón and Panamá Provinces of central Panama. The formation crops out in and around the Panama Canal Zone. The coastal to marginally marine sandstone, siltstone, claystone, tuff and conglomerate formation dates to the latest Serravallian to Tortonian (Clarendonian to Hemphillian in the NALMA classification), from 12 to 8.5 Ma. It preserves many fossils, among others, megalodon teeth have been found in the formation.