Australia’s Famous Caves Are 500,000 Years Older Than Previously Thought

According To A New Study, The Naracoorte Caves In South Australia, Which Contain Valuable Fossil Remains, Are 500,000 Years Older Than Previously Thought.

The Naracoorte Caves in South Australia are one of the best fossil sites, with a history of more than half a million years. Among the remains obtained from the sand layers, bones of Australian megafauna (giant animals) can be seen, which became extinct between 48,000 and 37,000 years ago.

The reason for the destruction of these megafauna species is still not completely clear. Until today, it was difficult to determine the exact age of the caves. Still, we will better understand species’ evolution and extinction with the discovery of older fossils.

The findings confirm the age of these important places. However, new research shows for the first time that the age of the Narakurt caves is 500,000 years older than expected. The researchers hope that this finding will help to understand the impact of biodiversity on climate change.


Artist’s rendering of Pleistocene megafauna in Australia

A moment in geological time

Caves can be fantastic time capsules because they often contain the remains of plants and animals that went extinct years ago. The Naracoorte Caves in South Australia are a prime example of such pills. South Australia’s cave complex is the only World Heritage Site. Among the complete and diverse fossil records, the following megafauna remains can be observed:

  • Thylacoleo carnifex (marsupial hunter)
  • Zygomaturus tribolus (large herbivore)
  • Wonambi naracoortensis (a giant snake)
  • Procoptadon goliah (giant kangaroo)

Paleontologists excavated and dated many fossil remains and reconstructed the skeletons of several megafauna species. Caves were formed when underground water seeped into the crevices of limestone and dissolved, creating cavities.

Their age in the past was between 0.8 and 1.1 million years. This estimate is based on a sand groove located in a cave complex.

But the methods used to date the sand groove were not entirely suitable for this project. For this reason, no exact age has been obtained for the caves. This complex project took five years, but it was worth the wait.

Flowstone layers

Flagstone layers on sand layers with fossil bone material at Naracoorte

Actions taken

The dating method includes examining the beautiful calcite formations inside the caves. These structures are called “gravestones” and include stalagmites, stalactites, and flagstones. When rocks are formed, a small amount of uranium (a radioactive element) is trapped inside them.

Over time, uranium slowly decays into its original element. It happens constantly, so the uranium in the rocks can be used as a natural clock to date them.

The dating of cave rocks includes steps such as extracting uranium and the main element from the cave rock in the laboratory. In the next step, each piece will be measured, and the sample’s age will be calculated precisely.

Will Boone Cave

Will Bon Cave, one of the oldest caves in the Naracoorte region

Gravestones begin to grow only when an aqueduct is formed, and the age of the oldest monument indicates the minimum age of the cave. Based on this evidence, we conclude that the formation of the caves began at least 1.34 million years ago, and based on estimates, their age is 250 to 500 thousand years older than previous estimates.

The second part of the research showed when the caves were opened to the surface for the first time and air and animals penetrated inside them. The researchers did this by examining the microscopic particles of coal and pollen trapped in the calcite structures.

They found that coal and pollen in the caves first appeared 600,000 years ago. This finding shows that the caves probably host new fossil materials of vertebrates up to 600 thousand years old. This estimate is 100,000 years older than the oldest known fossil remains in a cave complex.

Wedge rink digging

Rink Wage, lead author of the study Descending from a Cave in Naracoorte

The reason is important

There is a hot debate about whether the Australian megafauna’s extinction resulted from the presence of humans or the climate. With a proper chronology, can we understand when and at what speed natural processes occurred over time? Without exact age, it is impossible to realize the speed of change in landscapes, climate, and biological diversity.

Therefore, although the Naracoorte caves were formed at least 1.34 million years ago, they were not exposed to the surface until 600,000 years ago. This finding provides new insight into the vast temporal separation between Earth’s evolution and the accumulation of fossils. The results also help paleontologists target new dig sites for older fossils.

The researchers’ new method also helps to solve the mystery of the age of fossil deposits in other cave complexes in Australia and around the world. In these caves, cave stones and vertebrate fossils were discovered.

Australia’s animal and plant species diversity is facing an uncertain future due to climate change and other human works. Investigating essential sites like the Naracoorte Caves helps us understand the impact of climate change on biodiversity in the past but also allows us to predict the future.