Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch (or, in chronostratigraphy: the fifth of six stages in the Upper Cretaceous series). The Campanian spans the time from 83.6 ± 0.7 Ma to 72.1 ± 0.6 Ma (million years ago). It is preceded by the Santonian and it is followed by the Maastrichtian.
La Colonia Formation
Originally thought to be Campanian in age or earlier, studies of underlying formations have made a Maastrichtian (70–66 million years ago) age more likely.
It is divided up into three distinct facies, the first is up to 16 metres thick and consists of conglomerate, the second is by far the thickest at over 100 metres, consists of siltstone/claystone, with interbeds of claystone/shale and sandstone, the third is less than 10 metres thick and consists of clay, and probably represents a nearshore marine environment.