The pink sand found on the beaches of South Australia has long been a geological enigma. While garnet is a rare mineral in beach sand due to its susceptibility to destruction by ocean waves and currents, the presence of these colorful crystals indicates a local source of garnet-bearing rock. The origin of this rock has puzzled geologists for some time.
Recent research published in Communications Earth & Environment sheds light on the mystery of South Australia’s pink sand. The study took researchers on a journey thousands of kilometers and half a billion years back in time to uncover the source of the beach garnets. While kimberlite pipes and erosion of mountain belts were considered as possible sources, the dating of the garnets revealed a different story.
Analysis of coastal garnet grains indicated that the majority of them formed around 590 million years ago. This finding ruled out local sources such as the Gawler Craton and the Adelaide Fold Belt, leading researchers to explore alternative explanations for the origin of the beach garnets.
It was discovered that the garnets likely traveled from a distant location without being ground to pieces. The Hallet Cove Conservation Park, located south of Adelaide, provided a clue with its sedimentary rocks formed around 280 million years ago during an icy phase in Earth’s history. Glaciers and icebergs from the Late Palaeozoic Ice Age could have transported the garnets from East Antarctica to the South Australian coast.
During the Late Palaeozoic Ice Age, Australia was connected to Antarctica as part of the Gondwana supercontinent. Glaciers from what is now East Antarctica may have carried the garnets northwest to Australia. The Transantarctic Mountains were considered as a potential source, but the timing did not match up with the age of the garnets found in the pink sands.
Further research pointed to an area near the Skelton Glacier in East Antarctica as a possible location where garnets of the right age were discovered. This area, buried beneath a thick ice sheet, could contain abundant garnet that was transported to the South Australian coast over millions of years.
While sampling the rock under the Antarctic ice sheet is currently impossible, the theory suggests that erosion and ice transport could have brought the garnet-bearing rocks to the Australian shores. The pink sand of South Australia, once a geological mystery, now tells a story of ancient mountain belts, icy glaciers, and long-distance journeys across the vast expanses of time and space.
