The Sunshine Coast has roughly 4 different sandstone groups which include the Woogaroo Subgroup, Landsborough Sandstone, Myrtle Creek Sandstone and Tiaro Coal Measures. The Woogaroo Subgroup has an array of coarser sandstones and conglomerate and can be found in quite thick layers, while the Landsborough and Myrtle Creek Sandstones sandstones and in particular the Landsborough Sandstone is generally in quite thin beds. Most of these beds are generally still well bedded, however there are some local variations where past earth movements have affected their current bedding directions. The Woogaroo Subgroup are generally of lower fertility and therefore will display different vegetation composition to perhaps slightly more fertile Myrtle Creek Sandstone.
A great place to see the Myrtle Creek Sandstone is along the coastline at Point Arkwright around Coolum. The Woogaroo Subgroup is around the Nambour area and the Landsborough Sandstone to the south. Geological History The uplifting of the metamorphic rock (Rock that changes, through the process of heat and pressure), was followed by one or more major volcanic episodes resulting in extensive areas of the land surfaces covered by lavas and fragmental rock.
These lavas were viscous (sticky), slow moving rich in gases. Since that time, erosion has removed a large part of these rocks and what remains is a complex sequence of overlapping sheets that is difficult to decipher. These remnants, named the North Arm Volcanics are now exposed between Maleny and Eumundi.
The sands and gravel formed by the erosion of the older rocks were deposited over broad plains to the south, east and north east of the Maleny Plateau. Great thicknesses of sediment accumulated in sedimentary basins which subsequently consolidated and hardened to form the sedimentary rock known as the Landsborough Sandstone. It comprises of variable late Triassic (245 – 210 Million years ago) to early Jurassic (210 – 65 Million years ago) sedimentary rock including Sandstone, Siltstone, Shale, and Conglomerate. In the middle Tertiary period (25 Million years ago), numerous dome-like plugs of Rhyolite and Trachytes magma intruded into the higher rocks as volcanic vents or subsurface bulges.
The erosion of enormous volumes of the softer sedimentary rock (sandstone, Landsborough Sandstone), has revealed the Glasshouse Mountains in the South. Below the Myrtle Creek Sandstones is a distinct layer if Igneous rocks, indicating this is older than the Sandstones above the original bedrock. This layer of igneous rocks include Rhyolite, Trachytes and Basalts. Here is a wonderful place to spend the whole day on the beach and learn something great.
Here is a wonderful place to spend the whole day on the beach and learn something great. Bring Geofamily and enjoy this wonder.
This cache should be attempted at low tide, however high tide won’t make it too difficult. Come and enjoy this experience and take photo of yourself with GPS at GZ [don't post pic that shows rocks with log as it will spoil experience - feel free to post other pics with log] and answer the following questions:
1. What are the main two colours seen here?
2. Name the rock types associated with the above mention colours?
3. What dominant feature is seen along the cliff face, and what effect did it have on the surrounding rock below it?
4. At GZ there is a very distinct feature running along the floor, that differentiates itself of the surrounding rocks, What do you think it is, and do you think its older or younger than the rocks mentioned in Q1 and Q2.
To log find - Please mail answers and log the find, you may snap a pic if you like aswell