By Joel Achenbach

The Washington Post

The whales were found more than 120 feet above sea level, about a mile from the ocean, in ancient sandstones in the Atacama region of northern Chile.

It has turned out to be one of most extraordinary marine mammal fossil sites on the planet. Scientists discovered more than 40 skeletons, most of them baleen whales, strewn across a small area in four distinct levels, suggesting four separate mass strandings over a period of more than 10,000 years. In one spot, the skeletons of two adult whales lay on top of the skeleton of a juvenile whale.

The site includes two seals, an extinct species of sperm whale, a walrus-like toothed whale, and an aquatic sloth. Most of the animals were belly-up, suggesting they died at sea or shortly after washing ashore, said Nick Pyenson, curator of fossil marine mammals at the Smithsonian’s National Museum of Natural History.

Pyenson is the lead author of a paper describing the assemblage of cetacean fossils, published Tuesday evening in the journal Proceedings of the Royal Society B.

The likely cause of the mass strandings were harmful algal blooms, sometimes known as red tides.

The scientists estimate the age of the rock formation, and thus of the skeletons, at 6 million to 9 million years. In the time since, the tidal cove where the whales and other animals washed ashore has been lifted high above sea level by the immense tectonic forces that also created the Andes.