The “Sunshine Coast” conjures up images of golden beaches, rocky islands and green mountains of the hinterland, and we could assume that this peaceful landscape results from a stable geological framework. 

Yet if we look at the outcropping rock formations, we have to accept that this has not always been the case, as they reveal a complex and often violent geological history, spanning more than 300 million years. Even in the last 800,000 years, sea levels have fluctuated dramatically, resulting in major changes to the shoreline and coastal scenery.

The oldest rocks exposed on the Sunshine Coast reveal origins dating back to the active growth of the eastern side of the Australian continent, from about 375 to 210 million years ago.

'Rocks and Landscapes of the Sunshine Coast', written by Warwick Willmott.

Landsborough Sandstone.

At Ground Zero you will find a strange yet beautiful rock formation which at first glance is unimposing. A study of this formation will reveal a strange history.

This Early Jurassic formation forms the bedrock for most of the coastal plain stretching from the northern suburbs of Brisbane to Coolum in an area geologists call the Nambour Basin.

The Landsborough Sandstone is the bedrock through which the Glasshouse Mountains volcanoes forced their magma 25 million years ago. It is the Landsborough Sandstone that crops out to form the majestic promontories of the Sunshine Coast such as Caloundra, Point Cartwright, Alexandra Headland, Mudjimba, and Point Arkwright. These headlands not only refract the waves and uplift the sea breezes for the benefit of surfers and paragliders, but provide local windows into the geology underpinning the Sunshine Coast and shed light on the biota that lived in the region nearly 200 million years ago.

The sediments that now form the Landsborough Sandstone were deposited mainly in the channels and associated floodplains of large, north-easterly flowing, braided river systems around 200–175 million years ago. The rocks are mostly thick-bedded sandstones (hence the name of the formation), but siltstones, conglomerates (consolidated gravels) and a few coal beds are also preserved.

Story by Dr Stephen Mcloughlin

Now some definitions.

Conglomerate is a coarse-grained clastic sedimentary rock that is composed of a substantial fraction of rounded to sub angular gravel-size clasts, e.g., granules, pebbles, cobbles, and boulders, larger than 2 mm (0.079 in) in diameter.

Sandstone is a clastic sedimentary rock composed of sand-sized grains of mineral, rock or organic material.

Siltstone is a sedimentary rock composed mainly of silt-sized particles. It forms where water, wind, or ice deposit silt, and the silt is then compacted and cemented into a rock.

Here are some questions to help you understand the rock formation in front of you. It is very important to take the time to answer questions and send them to the CO. Any logs that don’t have answers sent will be deleted.

1. The rock at Ground Zero is 2 different types, describe them.

2. There is a formation that looks like cement, is this man made? If not what type of rock is it.

3. What colours do you see, describe them?

4. Feel free to add pics as long as the features at GZ are not in the image.