The Paja Formation is a Mesozoic geologic formation from the Hauterivian - Aptian stages of the Early Cretaceous of central Colombia, extending in the Eastern Cordillera of the Colombian Andes in the departments of Cundinamarca, Santander and Boyaca. It mainly composed of mudrocks with nodules of sandstones and limestones, that are interpreted as part of a marginal marine deposit, with anoxic zones, in the warm and shallow sea that covered most of the Colombian territory during the Cretaceous. Plesiosaur, ichthyosaur, sea turtles, teleostean fishes and ammonites remains are among the main fossils that have been recovered from its strata, mainly near to the modern town of Villa de Leiva in Boyaca.