In parts of South Australia, there are long stretches of beach covered in patches of pink sand. These pink sands are due to the presence of garnet crystals, which are quite rare in beach sand. Garnet forms deep in the Earth’s crust, similar to how diamonds are created. One way garnet can reach the surface is through erosion of mountain ranges where it is typically found in large amounts.
Geologists have been trying to determine the source of the pink sand in South Australia. One possible origin could be the Adelaide Fold Belt, a mountain range that developed between 514 million and 490 million years ago. Another potential source is the Gawler Craton, an ancient rock formation beneath South Australia. By analyzing the age of the garnets found in the beach sand, researchers discovered that they were around 590 million years old, which did not match the expected sources.
The study ruled out a local source for the garnets, leading researchers to believe that the garnets must have traveled a long distance without being damaged. One possible explanation is that the garnets were stored in sedimentary glacial deposits during the Late Palaeozoic Ice Age around 280 million years ago. This was a time when Australia was connected to Antarctica in a landmass called Gondwana, covered by a massive ice sheet.
Ice flow from what is now East Antarctica towards Australia during the Late Palaeozoic Ice Age could have transported the garnets to the South Australian coast. Although garnets of the right age have been found in East Antarctica near the Skelton Glacier, the volume of garnets found on Australian shores suggests a much larger source beneath the thick ice sheet. This hidden treasure of garnets may have been eroded by millions of years of ice transport and eventually released into the sea, making its way to the beaches of South Australia.
While it is currently not feasible to sample the rock under the ice sheet to confirm this theory, the research provides a compelling explanation for the origins of South Australia’s pink sand. By tracing the journey of these garnets from an ancient mountain range in East Antarctica to the coastlines of Australia, scientists have uncovered a fascinating geological mystery that adds to the rich tapestry of Earth’s history.