- How was the site discovered?
- What was discovered?
- How did all of these fossils arrive at the site?
- How old is the site?
- Why is this important?
- What is happening to the site now?
Cerro Ballena is along the Pan-American Highway, just north of the town of Caldera, in Atacama Region, Chile. The site is at the southern edge of the Atacama Desert; it is about a 30-minute drive north of the Copiapó Airport, and about an hour north of Copiapó, where the famed 33 miners were rescued from underground in 2010.
How was the site discovered?
The roadcut locality had long been known as a fossil locality. The site earned its name, Cerro Ballena, from one or two whale bones noted along the walls of the roadcut. Starting in 2010, Sacyr Chile S.A., a construction company, expanded the roadcut to build another lane of highway, slowly revealing the extent of the fossils at Cerro Ballena. In late 2011, a team of paleontologists from Chile and the Smithsonian, along with 3D digitization staff members from the Smithsonian, rushed to the site to document what remained. In 2012, Smithsonian magazine published a brief article about how 3D technology provided a critical solution to the scientific problems at Cerro Ballena.
What was discovered?
Our team documented the remains of ten (10) different kinds of marine vertebrates from Cerro Ballena, including billfishes, seals, aquatic sloths, and several different species of whales. The skeletons of over 40 individual large baleen whales dominate the site. We also documented the remains of an extinct sperm whale and a walrus-like whale (Odobenocetops), both of which were previously only known from Peru. One of the three fossil seals discovered is also new to science, and will be fully described in a future work.
Our team also discovered that all of these marine vertebrates are preserved in four different layers at the site. Cerro Ballena was a tidal flat-like environment, and we estimate that the total amount of sediment (about 9 meters thick) at the site accumulated between 10-16,000 years.
How did all of these fossils arrive at the site?
The skeletons of the fossil whales and other marine vertebrates were preserved in four discrete horizons, indicating a repeated, but similar underlying cause. The orientation and condition of their skeletons point to death at sea, prior to burial on a tidal flat. In today’s world, toxins from harmful algal blooms (HABs) are the most prevalent explanation for repeated mass strandings that include a wide variety of large marine animals. HABs are common along the coasts of continents, and they are enhanced by vital nutrients, such as iron, released during erosion and carried by rivers flowing into the ocean. Because the Andes of South America are iron-rich, the runoff that has occurred along the west coast of South America for over the past 20 million years has long provided the ideal conditions for HABs to form.
We argue that, in the late Miocene, toxins generated by HABs poisoned many ocean-going vertebrates near Cerro Ballena through ingestion of contaminated prey and/or inhalation, causing relatively rapid death at sea. Their carcasses then floated towards the coast, where they washed into a tidal flat by waves. Once stranded on the tidal flat, the dead or drying animals were protected from marine scavengers and there were no large land scavengers in South America at this time. Eventually, the carcasses were buried by sand. Because there are four layers at Cerro Ballena, this pathway from sea to land happened four different times over the course of 10-16,000 years in the same area.
How old is the site?
The sediments at Cerro Ballena are broadly similar to others near Caldera that belong to the Bahía Inglesa Formation. These sediments were once on the seafloor, and over the course of millions of years of geologic activity, they were pushed up into the arid coastal desert. We estimate an age of the site as between 6-9 million years old by correlating key marker fossils (specific species of fossil shark teeth and extinct aquatic sloths) with sites in southern Peru that preserve identical species within rocks with known geologic ages. This age, between 6-9 million years old, places it in the late Miocene, which was millions of years before humans arrived in South America.
Why is this important?
- Cerro Ballena is the densest site for individual fossil whales and other extinct marine mammals in entire world. In this way, it is similar to the La Brea Tar Pits or Dinosaur National Monument in the United States.
- This is the first definitive example of repeated mass strandings of marine mammals in the fossil record.
- Cerro Ballena preserves marine predators that are familiar to modern eyes, including large whales, seals, and billfishes. However, it also preserves completely extinct and bizarre marine mammals, including walrus-like whales and aquatic sloths. In this way, the site is an amazing window into ancient marine ecosystems along the coast of South America.
- Catastrophic mass death assemblages are rare in the fossil record, and it is very hard to find a ‘smoking gun’ for their cause. We argue that toxins from harmful algal blooms killed the marine animals at Cerro Ballena. This argument comes from several lines of evidence at the site, and modern examples of such mass strandings, with similar causes.
- 3D technology provided a time-sensitive solution to documented fossils at the site before key data were lost. Now, anyone with a web connection can return to the site digitally, and see what kinds of information paleontologists in Chile and from the Smithsonian collected.
What is happening at the site now?
Expansion of the road is now complete, and northbound lane where many of these fossils were documented is now paved over. All of the fossils found between 2010-2013 have been moved to museums in either Caldera or Santiago, although many await careful preparation. This enormous wealth of fossils, however, represents only a fraction of the potential at Cerro Ballena, which remains unexcavated. We conservatively estimate that the entire area preserves several hundred fossil marine mammal skeletons, awaiting discovery.