Chinese expedition discovers the deepest, largest and oldest whale cemetery in the Indian Ocean

The discovery

A team led by Xiaotong Peng from the Chinese Academy of Sciences in Sanya has uncovered a vast whale necropolis in the southeastern Indian Ocean. The site, roughly 1,000 kilometres west of Perth, Australia, was first explored in February 2023 by the Chinese submersible "Fendouzhe". During an initial dive near the Dordrecht Deep, the researchers spotted bones protruding from the sediment at a depth of around 7,000 metres, coated in a black layer of iron-manganese oxides.

Scale of the necropolis

Over 32 subsequent dives, the full extent of the site became clear. The so-called "whale-fall super-corridor" stretches for 1,200 kilometres along the Diamantina Fracture Zone, lying at depths between 4,200 and 7,000 metres. The team documented 476 fossilised whale remains, making it the deepest, largest and oldest known whale cemetery. The previous depth record was a site in the southwestern Atlantic off southern Brazil, reported in 2016 at 4,204 metres. The new site lies up to 2,800 metres deeper.

I was amazed by the many carcasses, some of which are millions of years old.

Ancient species and living ecosystems

The fossils include both extant species, such as Andrew's beaked whale and Layard's beaked whale, and long-extinct groups like the beaked whale genera Pterocetus and Izikoziphius. Some specimens date back 5.3 million years. The bones support a highly specialised ecosystem dominated by jellyfish, brittle stars, mussels and beard worms of the genus Osedax.

The living ecosystems we saw there offered a completely new perspective on this otherwise dark and cold seafloor.

Why here?

Several factors explain the concentration of remains. The V-shaped topography of the deeply incised fracture zone helps carcasses accumulate. Beaked whales have very high bone density, so their skeletons decompose especially slowly. An additional protective layer of iron-manganese oxide coats the fossils. The researchers estimate that more than ten million carcasses could lie in this area, with densities reaching up to 750 whales per square kilometre. The site also acts as a carbon sink, binding millions of tonnes of carbon.

The large number of documented fossil whale carcasses — including a new species of beaked whale — is truly astonishing and of great importance for understanding the evolution and distribution of whales.

Global context

While whale falls are common, only slightly more than 70 such areas have been documented worldwide to date. The team, publishing in the journal Nature, expects many more whale cemeteries exist globally. Fossil finds from trawl fishing suggest similar sites off the coasts of South Africa and the Iberian Peninsula.