Beyond The Ice Preview

Welcome to the first site of your Hallett Cove mobile adventure – Black Cliff!

Check out the aerial view of Black Cliff as it appears now. Look for the purple layers of sedimentary rock which were originally deposited as horizontal layers of sand and silt in a deep ocean around 600 million years ago. Over time and with heat and pressure these layers were turned into siltstones and sandstones in what is called formally, the Brachina Formation. Click the link to inspect a 3D model of the siltstone in this formation. Spin it around and pinch and stretch to see the detail in the rock.

Later on, tremendous pressures of the earth movements buckled the originally flat lying beds into the complicated fold patterns you see at Black Cliff today. The information pages below to learn more about these fantastic folds and amazing arches.

The interactive panorama of the Black Cliff lookout gives an almost birds-eye view of the folded rocks on the shore platform below. Zoom in/out and turn on the annotation feature to see the detail.

The purple layers of sedimentary rock exposed on the shore were deposited as horizontal beds of sand and silt in the deep ocean around 600 million years ago, in a long north-south depression that now follows the Mount Lofty and Flinders Ranges. Geologists call this time the Neoproterozoic.

We can now see these rocks exposed at Earth’s surface because of a mountain building event that occurred around 500 million years ago during the Cambrian. This event is called the Delamerian Orogeny. It uplifted the rock layers and in the process folded and tilted them into the orientation you see today. This was the start of the Mt Lofty and Flinders Ranges, which are still growing today!

Play the animation above - there's an important clue here for you to find out why Hallett Cove became world famous!

280 million years ago, Australia was part of the supercontinent Gondwana, which was located near the South Pole. Imagine that – Australia being located at the South Pole! This was 320 million years after the rocks at Black Cliff were deposited, and 220 million years after they were folded during the Delamerian Orogeny.

At this time, southern Australia was covered in thick ice sheets, much like what we observe in Antarctica today. This means that Hallett Cove was underneath a glacier! As the glacier moved, this smooth pavement at the top of Black Cliff became pitted by lots of grooves that form straight lines. These grooves are known as striations. They were created by rock fragments being dragged across the surface by the glacier.

This very special location, is where you can observe evidence of all four seasons in one rock!

The rocks here are glacial sediments mostly made up of fine sand and clay deposited 280 million years ago. The formal name for this rock type is the Cape Jervis Formation.

Sedimentary rocks like these are often layered, with each layer defined by changes in colour or composition. These variations help geologists understand how the environmental conditions changed while the rock was being deposited.

Welcome to wonderful Waterfall Creek!

Look at the image above and the interactive panorama of Waterfall Creek. Be sure to turn animation on.

The different layers of rock seen in the image above were deposited between 3 and 600 million years ago. The dark brown folded rocks are the
siltstones and sandstones of the Brachina Formation you observed at Black Cliff. They were deposited 600 million years ago during a time known as the Neoproterozoic, before complex life evolved on Earth. The light-coloured glacial sediments above belong to the Cape Jervis Formation that you observed at the glacial varves site. They were deposited about 280 million years ago during a time known as the Permian. The thin white layer above it is the Hallett Cove Sandstone and is only 3 million years old.

Waves and wind have eroded the rocks here for millions of years to reveal many impressive folds arching upwards to form an antiform. The interactive panorama of the shore platform will make it much easier for you to see to the folds as will the3D model of the shore platform.

Turn annotation on in the panorama and spin the 3D model around and zoom in/out to view the spectacularly exposed plunging folds.

Welcome to the Amphitheatre, the site of one of the best views at Hallett Cove.

Check out the interactive 360 fly-by video of the amphitheatre above using the gyroscope functionality in your phone to control where you look. The rock layers you can see in the distance record some of the youngest events to affect this area.

The white layer that sticks out from the hillside here is the Hallett Cove Sandstone. It forms this shape because it is made up of well cemented quartz grains that are very hard and resistant to weathering. Beneath this rock is the Cape Jervis Formation made up of soft silt and fine sand, so it erodes more easily. The top layer are the red alluvial sediments that also erode easily making the Hallett Cove Sandstone stick out like a ledge.

Looking at the image above follow the white Hallett Cove Sandstone layer along the hillside left to right in the photo. You are tracing the contact between two rocks of very different types. This is an extension of the unconformity you discovered at Waterfall Creek!

But wait - there's more!

There is an additional unconformity above the upper boundary of the thin Hallett Cove Sandstone layer though it's clearer to see in the interactive panorama of this site. Be sure to turn annotation on to see the details of the unconformities.

Welcome to the spectacular Sugarloaf!

This very colourful cone-shaped hill is one of the most famous sites at Hallett Cove.

Checkout the video above. You can see many of the rock types we’ve discovered at previous sites. The sediments exposed in the Sugarloaf are of glacial origin and Permian in age.

View the 3D virtual tour and the panorama of Sugarloaf. Zoom in/out and turn annotation on to see the details of this unique landscape.

Check out the video and image above (slide to view image).

The Hallett Cove beach is covered in multi-coloured stones of all shapes and sizes. Every single one of these was originally encased in the glacial sediments. They are now deposited on the beach because the soft sediment holding them in place eroded away. Some of them are boulders the size of a car!

They are called erratics.