A fossil site in the Atacama Desert of Chile, containing the remains of at least 40 whales, has been confirmed as one of the most significant marine mammal graveyards ever discovered. The deposit, known as Cerro Ballena, dates from the late Miocene epoch, approximately five million years ago. British paleontologists from the University of Oxford and the Natural History Museum in London have led the international team that has spent the last decade excavating and analysing the site.
The discovery, published in the journal Proceedings of the Royal Society B, provides an unprecedented window into a series of mass stranding events. The skeletons, primarily of baleen whales, were preserved in exceptional condition. Researchers identified four distinct layers of whale fossils, each separated by sedimentary deposits, indicating that the strandings occurred repeatedly over a period of 16,000 years.
The cause of these ancient mass deaths has been a subject of intense debate. The team’s analysis points to toxic algal blooms, known as harmful algal blooms (HABs). Modern HABs, often referred to as red tides, produce potent neurotoxins that can paralyse marine mammals, leading to stranding and death. The geological evidence at Cerro Ballena, including the presence of iron-rich minerals associated with algal blooms, supports this hypothesis.
Professor Nicholas Pyenson, a paleontologist at the Smithsonian Institution who was not involved in the study, described the finding as a key to understanding ancient marine ecosystems. The British-led team used advanced imaging techniques and geochemical analysis to reconstruct the environmental conditions at the time of each stranding event.
The site also yielded remains of other marine animals, including seals, dolphins, and an extinct species of aquatic sloth. This diversity suggests that the blooms affected a broad swath of the marine food web. The findings have implications for modern conservation, as HABs are increasing in frequency and intensity due to climate change and nutrient runoff.
Dr. Nicholas Higgs, a paleontologist at the University of Oxford and a lead author of the study, emphasised the importance of the discovery. The repeated nature of these events indicates that the region was a hotspot for harmful algal blooms over millennia. Understanding the triggers and patterns of these ancient blooms can help predict and mitigate future events.
The Chilean government has designated Cerro Ballena a protected archaeological site. The fossils will remain in situ, with replicas displayed in local museums. The research was funded by the UK’s Natural Environment Research Council and the Chilean National Commission for Scientific and Technological Research.
