The La Colonia Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation. Originally thought to be Campanian (c.73-72 million years ago) in age or earlier, studies of underlying formations have made a Maastrichtian (72–66 million years ago) age more likely.

Description

It is divided up into three distinct facies, the first is up to 16 m thick and consists of conglomerate, the second is by far the thickest at over 100 m, consists of siltstone and claystone, with interbeds of claystone/shale and sandstone, the third is less than 10 m thick and consists of clay, and probably represents a nearshore marine environment. The paleoflora was known for its aquatic components, Paleoazolla and Regnellidium. However, recent paleobotanical discoveries at the Cañadón del Irupé locality have revealed the presence of a more diverse range of plants associated with these water bodies, including pteridophytes, gymnosperms, and various angiosperms. Among these are fossil leaves and fruits assignable to Nelumbonaceae.

Fossil content

Turtles

Fish

Plesiosaurs

Dinosaurs

Ornithiscians

Sauropods

Theropods

Mammals

Over 300 mammal specimens have been found in the La Colonia Formation.

Snakes

Fossils of madtsoiids, and perhaps boids, have been found in the formation.