La Colonia Formation
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 in age or earlier, studies of underlying formations have made a Maastrichtian age more likely. A further study in 2021 utilizing magnetostratigraphy and palynological data provided an age of 69 to 64 million years ago.
Description
It is divided up into three distinct facies, the first is up to thick and consists of conglomerate, the second is by far the thickest at over, consists of siltstone and claystone, with interbeds of claystone/shale and sandstone, the third is less than 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.
During the Maastrichtian, Patagonia was flooded by the Transgression of the Kawas Sea. This would have likely rendered much of Patagonia, including the region represented by what is now the La Colonia Formation, scattered faunal Islands.