| Cerro Ballena | |
|---|---|
| Stratigraphic range: Late Miocene, ~ | |
 Adult and juvenile balaenopterid whale mass mortality nicknamed "La Familia" | |
| Type | Locality |
| Unit of | Cerro Ballena Member (Bahía Inglesa Formation) |
| Thickness | ~9 m (30 ft) |
| Lithology | |
| Primary | Sandstone |
| Other | Sand, silt |
| Location | |
| Coordinates | 27°02′33″S 70°47′43″W / 27.042385°S 70.795255°W |
| Region | Caldera Basin |
| Country | Chile |
Cerro Ballena (meaning "Whale Hill") is a fossiliferous locality of the Bahía Inglesa Formation, located in the Atacama Desert along the Pan-American Highway a few kilometers north of the port of Caldera, Chile. It has been dated back to the Late Miocene epoch, during the Neogene period. The locality was first noted in 1965 during military work and fully excavated and studied between 2011 and 2012, and is protected by law since the latter year.
Cerro Ballena is extremely abundant in cetacean fossil skeletons, including over 40 individuals of adult and juvenile ages. This high concentration of cetacean skeletons has made Cerro Ballena well known, now considered a national treasure of Chile. Besides cetaceans the site does also contains fossils of pinnipeds (seals), sailfish, sharks, swordfish, aquatic sloths (not a group as such, but rather the genus Thalassocnus) and invertebrate trace fossils.
The unusual concentration of cetacean remains and other marine vertebrates is explained to have occurred due to poisoning by toxins secreted by algae (events also known as harmful algal bloom). Geological and paleontological evidence indicates that high levels of iron in the sea saturated the growth of algae. Cetaceans and other vertebrates became poisoned, and their carcasses then floated towards the coastline, where they were later transported by strong waves into a flattened berm/shore, and finally becoming buried. This sequence of events happened four times during the deposition of sediments at Cerro Ballena.