The approximately 640 metres (2,100 ft) thick formation was deposited in the Pisco Basin, spanning an age from the Late Miocene up to the Early Pliocene, roughly from 9.6 to 4.5 Ma.

Several specialists consider the Pisco Formation one of the most important Lagerstätten,[2][3] based on the large amount of exceptionally preserved marine fossils, including sharks (most notably megalodon), penguins, whales, dolphins, birds, marine crocodiles and aquatic giant sloths.

[10] It is also one of the richest sites in the world for fossil cetaceans, with close to 500 examples being found in the formation.

[11] The oldest fossils of the aquatic sloth Thalassocnus (T. antiquus) come from the Aguada de Lomas horizon of the Pisco Formation and were dated at roughly 7 Ma.

The youngest specimen (T. carolomartini) was found in the Sacaco horizon and dated to approximately 3 Ma.