Santa Lucía Formation, Geological formation near Cochabamba, Bolivia.

The Santa Lucía Formation is a roughly 100-metre-thick geological formation in southern Bolivia's Potosí Basin, divided into three sections. The lower and upper sections consist of red-brown mudstones, with white to pink tuff beds in the lower part and green bands in the upper. The middle section is mudstone intercalated with turbidites and slumped blocks, and most vertebrate fossils come from conglomerate sandstones at the basin edges.

This formation developed during the transition from the Cretaceous to the Paleogene period, spanning the Maastrichtian and Danian stages. This timeframe marks when dinosaurs disappeared and early mammals began to flourish in South America.

Scientists from multiple countries conduct research at this formation to study the evolution of early mammals following the extinction of dinosaurs.

The mammal fossils come from a single site of about 100 m² near Tiupampa, 95 km southeast of Cochabamba, where 95% of the specimens were found. The fossil beds lie in the middle section of the formation, in sandstone lenses at the basin margin. The site is a research locality, so fieldwork and collecting require arrangements with the scientists working there.

This site holds some of the oldest known mammal fossils from South America following the dinosaur extinction. Specimens found here reveal how early mammals adapted and survived in the period after dinosaurs vanished.