AncientWorldArtifacts: Smithsonian scientists solve "Cerro Ballena" mystery

It is one of the most astonishing fossil discoveries of recent years - a graveyard of whales found beside the Pan-American Highway in Chile. And now scientists think they can explain how so many of the animals came to be preserved in one location more than five million years ago.

It was the result of not one but four separate mass strandings, they report in a Royal Society journal.

The site was first discovered during an expansion project of the Pan-American Highway in 2010. The following year, paleontologists from the Smithsonian and Chile examined the fossils, dating 6-9 million years ago, and recorded what remained before the site was paved over.

The team documented the remains of 10 kinds of marine vertebrates from the site, named Cerro Ballena—Spanish for "whale hill." In addition to the skeletons of the more than 40 large baleen whales that dominated the site, the team documented the remains of a species of sperm whale and a walrus-like whale, both of which are now extinct. They also found skeletons of billfishes, seals and aquatic sloths.

The skeletons were preserved in four separate levels, pointing to a repeated and similar underlying cause. The skeletons' orientation and condition indicated that the animals died at sea, prior to burial on a tidal flat. Today, toxins from harmful algal blooms, such as red tides, are one of the prevalent causes for repeated mass strandings that include a wide variety of large marine animals.

From their research, the scientists conclude that toxins generated by harmful algal blooms most likely poisoned many ocean-going vertebrates near Cerro Ballena in the late Miocene (5-11 million years ago) through ingestion of contaminated prey or inhalation, causing relatively rapid death at sea. Their carcasses then floated toward the coast, where they were washed into a tidal flat by waves.