South Australia’s Pink Sands: Beaches Born from Ancient Antarctic Mountains

It’s amazing what we can learn from something as simple as sand. In this blog, we’ll be discussing the pink sands that wash up in an area of South Australia, and we’ll discuss the link between it and an ancient mountain range in Antarctica.

At first glance, the soft, pale pink sands that stretch along certain South Australian beaches seem like nothing more than a picturesque curiosity. However, beneath these delicate grains lies a geological saga that stretches across hundreds of millions of years. This is a story of colliding continents, towering mountain ranges, massive ice sheets, and the unrelenting forces of erosion and transport. To understand how these sands came to rest in South Australia, we must travel deep into the past, to a time when the Earth was an entirely different world.

The Birth of Gondwana: A Supercontinent Forms (~650–600 Million Years Ago)

Our story begins in the Ediacaran Period, around 650–600 million years ago, when the Earth was experiencing dramatic shifts in its continental arrangement. During this time, individual landmasses were coming together to form a vast supercontinent known as Gondwana. This supercontinent would eventually include present-day South America, Africa, India, Australia, and Antarctica. However, the birth of such a massive landmass was anything but peaceful.

Along what is now East Antarctica, crustal thickening and high-grade metamorphism occurred around 590 million years ago, leading to the formation of an ancient mountain range. This event, known as the Ediacaran Orogeny, represents a significant but previously unknown tectonic episode in the region. While the precise cause of this orogeny is still debated, evidence suggests it was a result of regional compression and crustal deformation, rather than a clear subduction-driven event. This mountain-building event helped shape the continental crust of East Antarctica, forming metamorphic rocks rich in garnet, which would later play a crucial role in the story of South Australia’s pink sands.

The Ross Orogeny: Further Mountain Building (520–480 Million Years Ago)

Fast forward to around 520–480 million years ago, and a second major tectonic event reshaped East Antarctica: the Ross Orogeny. This event intensified the formation of mountains, deforming and reworking the already garnet-rich rocks that had formed during the Ediacaran Orogeny. It was during this time that Antarctica's ancient mountain ranges became part of an extensive Andean-style continental arc system, where volcanoes and high-grade metamorphism occurred along the edge of the supercontinent.

Meanwhile, southern Australia was experiencing a completely different fate. While Antarctica was being subjected to intense mountain-building, South Australia was instead experiencing a passive margin phase, meaning it lay relatively stable while sediments were deposited over time. This would become an important distinction, as the events in Antarctica would later play a significant role in shaping the sands of South Australia.

Geochemical analysis of detrital zircon and garnet grains from modern South Australian beach sands has shown a clear correlation with the ages of these orogenic events in Antarctica. This means that the sedimentary record in South Australia preserves evidence of mountain-building processes that occurred in Antarctica, offering valuable insights into the past dynamics of supercontinents and the deep-time geological evolution of the region.

By the time Gondwana was fully assembled, around 300 million years ago, the stage was set for the next major event in our story—one that would transport the ancient garnet grains from Antarctica all the way to Australia.

The Permo-Carboniferous Glaciation: Ice Transports the Garnets (~300 Million Years Ago)

One of the most extreme ice ages in Earth’s history occurred during the Permo-Carboniferous Period (~300 million years ago). During this time, Gondwana drifted over the South Pole, causing vast ice sheets to form across much of its landmass. These glaciers would eventually shape the landscapes of Antarctica and Australia in profound ways.

Glaciers act as some of the most powerful natural forces on Earth. As they grow and move, they scrape away at the landscape, eroding massive amounts of rock and sediment in the process. The garnet-rich metamorphic rocks of East Antarctica were no exception. As the glaciers carved their way through the ancient mountain ranges, they eroded and entrained garnet-bearing material into the ice.

Geological evidence from glacial sedimentary rocks in South Australia suggests that ice-flow indicators align with an Antarctic origin for these garnet deposits. Researchers traced the northwest movement of glaciers during the Late Palaeozoic Ice Age, confirming that the garnet sands now seen on South Australian beaches were once part of a glacial transport system that moved sediment from Antarctica to Australia.

But glaciers do more than just erode—they transport. Over thousands of years, the ice sheets moved northward, carrying their mineral cargo toward what is now southern Australia. As these glaciers eventually melted, they deposited the garnet-rich sediments, forming what is today known as the Cape Jervis Formation within the Troubridge Basin in South Australia.

Deposition in South Australia: The Cape Jervis Formation (~280 Million Years Ago)

As the glaciers retreated, they left behind a vast expanse of glacial sediments, many of which contained the garnet-rich materials transported from East Antarctica. These deposits formed what we now call the Cape Jervis Formation, a geological unit rich in Permo-Carboniferous glaciogenic sediments. These glacial sediments settled within the Troubridge Basin, covering vast areas of South Australia.

At this stage, the pink garnet sands were still buried within layers of sediment. Over millions of years, these sediments became compressed and buried, lying dormant beneath the surface. However, Earth’s geological processes were not finished with them yet.

Exhumation and Coastal Transport: The Sands Reach the Beach (~Present Day)

Over the next 280 million years, a combination of erosion, uplift, and weathering slowly exhumed the garnet-bearing sediments from the Cape Jervis Formation. Rivers and streams carried them toward the coast, where they were finally deposited onto modern beaches.

Today, beaches such as Myponga Beach, Petrel Cove Beach, Port Moorowie Beach, and Port Vincent Beach showcase these pink sands, a visible reminder of Earth’s deep geological history. The unique chemistry of these garnet grains has provided geologists with a direct connection between the sands of modern South Australia and a hidden mountain range buried beneath the Antarctic ice.

So next time you walk along a pink sand beach in South Australia, take a moment to consider what you’re really seeing. Each grain of sand has traveled an epic journey across land and time—from an ancient, buried mountain range in Antarctica, through glacial transport, deposition, and erosion, to finally rest on a modern shoreline. It’s a silent witness to the extraordinary and interconnected history of our planet.

Here's the video we made on South Australia's Pink Sand Beaches on the OzGeology YouTube channel: