Unearthing Fraser Island’s Natural History

Dr Errol Stock is a fount of knowledge about Fraser Island and its fascinating sandscapes. Having devoted most of his geosciences efforts in understanding dune terrain in Australia and elsewhere in the world, particularly along coastal western USA, Dr Stock has also consulted to the Australian Heritage Commission and has generated a substantial knowledge base about dune landscapes and processes, across a range of climatic conditions including Fraser Island.

On my last visit to Fraser Island earlier this year, I had the privilege and great fun to test-run the latest way to learn about its natural history and access sites close to Kingfisher Bay Resort. I’m speaking about using a Segway Personal Transporter from the resort fleet and travelling along the western beach. After essential instructions from a guide, our small party headed south, making sure we didn’t get into sand that was too soft or boggy and avoided the stingray feeding holes. A Segway allows you to cover the distance in a shorter time but not at such speed that you miss the sights; if you see something of interest it’s easy to stop, park the platform and check it out.

Dune bedding can be seen as fine lines running at an angle from upper right to lower left.

Dune bedding can be seen as fine lines running at an angle from upper right to lower left.

While most of those in my party were interested in the vegetation and wildlife along the shore I looked for what old and new things could be found since I was on this stretch a year ago.

There had been some undercutting of the higher dunes and sand slumping down the escarpment as this western coast slowly but surely erodes.

Along most of the way towards McKenzies Jetty, the lower part of the escarpment is black/brown ‘coffee’ rock several metres thick. Because the coffee rock (also known has humicrete and sandy beachrock) was formed in the past by penetrating organic chemicals from tannin-rich groundwater seeping through old sand dunes it’s still possible to see traces of the layers of sand in the dune.

In other places along this shore, where the coffee rock is exposed right on the beach, some of the bedding layers are visible as fin-like surfaces.  The bedding surfaces in the photo below can be explained as the products of differential erosion. In the past, as the groundwater chemicals turned the buried sand into soft ‘rock’, different parts of the dunes were better cemented than others.

Differential Erosion on the western beach.

Differential Erosion on the western beach.

Now, on the beach and pounded by the waves, these slightly harder layers proved a little more resistant to erosion. The preserved layers in this

Just how much of the coffee rock and ‘frozen’ dune bedding you can actually see your particular Segway exploring trip will depend on how much sand has been is built up to form a full-width beach. Because coffee rock is so easy to crush, follow the Ranger’s directions and avoid driving your Segway over any coffee rock exposures, large or small. Many other visitors can then continue to enjoy the local geology and geomorphology.

Enjoy the Island! I certainly intend to do so when I return in a couple of months.

Errol Stock
Geoscientist Presenter

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