Australia’s vast beaches seem a world away from the towering glaciers of Antarctica, and yet clues found in the antipodean sands have led to a dazzling discovery on the frozen continent.
The incredible discovery was made when scientists started noticing pink streaks washing up on the remote southern beach of Petrel Cove, about 90km from Adelaide.
They quickly discovered that the colored sand was composed of the mineral garnet, but were stunned to learn about its age and origin.
“This journey started with the question of why there was so much garnet on the beach at Petrel Cove,” University of Adelaide geologist Jacob Mulder said in a statement.
They soon realized that the grains were small pink flags, indicating the existence of an ancient mountain thousands of miles away.
“It’s fascinating to think that we have been able to trace tiny grains of sand on a beach in Australia to a previously undiscovered mountain range beneath the Antarctic ice,” Mulder added.
The pink sands of Petrel Cove reveal a secret that has been hidden for thousands of years (University of Adelaide)
Garnet, a deep red colored mineral, is quite common; it crystallizes at high temperatures, usually where large mountain areas emerge from colliding tectonic plates.
The crystals serve as records of the pressure and temperature histories of the metamorphic rocks in which they form, making them immensely valuable for deducing how and when mountains formed.
When the University of Adelaide team dated the garnet at Petrel Cove and in nearby rock formations, they found it formed about 590 million years ago – some 76 to 100 million years before the local mountain range the Adelaide Fold Belt took shape. and billions of shells years after Gawler Craton’s crystalline basement formed.
“The garnet is too young to come from the Gawler Craton and too old to come from the eroding Adelaide Fold Belt,” explains Sharmaine Verhaert from the University of Adelaide who led the research.
Instead, the mineral most likely formed at a time when the South Australian crust was “relatively cool and non-mountainous”, Verhaert added.
The Transantarctic Mountains divide the continent’s ice sheet into two parts. The larger, eastern part is on land that is largely above sea level; the smaller, western part is largely below sea level(US National Science Foundation)
Garnet is typically destroyed by long-term exposure to waves and currents, so the researchers also concluded that it was originally formed millions of miles away, millions of years ago, before surfacing locally. Science alertreports.
Their research revealed a link between the pink sand at Petrel Cove and layers of nearby glacial sedimentary rock and distant garnet deposits previously found in a spur of the Transantarctic Mountains in East Antarctica.
These rock formations protrude from a thick ice sheet that otherwise covers the area, making it impossible to sample the geology of a mountain range thought to lie beneath.
The buried mountain belt is believed to be 590 million years old, as is the garnet analyzed in Verhaert’s study, but she and her colleagues have not been able to get a good look at it.
The researchers believe that the garnet-rich glacial sand from the Antarctic mountains – which remain hidden beneath the ice – was ground down by an ice sheet that moved northwest during the Late Paleozoic Ice Age.
At the time, Australia and Antarctica were connected by the supercontinent Gondwana.
“The garnet deposits were then stored locally in glacial deposits along the southern Australian margin,” explains fellow geologist Stijn Glorie of the University of Adelaide, “until erosion occurred. [once again] freed them and the waves and tides concentrated them on the South Australian beaches.
It’s amazing how something as seemingly innocuous as a sand deposit can bridge such enormous gaps between space and time.
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