Welcome to the Australia Rock Earth Cache
I hope you enjoy this beautiful location and the geology.
Australia Rock is located on the NSW coast in Narooma at the end of Bar Rock Road, 350kms south of Sydney.
Australia Rock is an impressive location with rock folds and weathering that has created what you see here today. There are various explanations for how the rock formed into this continental likeness, including that it is simply a natural result of thousands of years of erosion of the ancient chert and shale headland. One of the more interesting tales is that the hole was created inadvertently when a ship was moored to the heads with large chains. In heavy seas the chains wore away the rock to create the familiar shape you see today.
Australia Rock consists of Narooma Chert deposited on the Pacific Ocean floor over a period of 50 million years (from Late Cambrian to Ordovician period) and moved westward to its present location when the Pacific plate collided with Gondwana. The terrane (a fault-bounded area or region with a distinctive stratigraphy or structure) gradually approached the continental margin and began to include sediments derived from the continent, such as sandstone, siltstone, argillite and shale as well as chert bands.
Chert
Chert is a fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline silica. Depending on its origin, it can contain either microfossils, small macrofossils, or both. It varies greatly in color (from white to black), but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements present in the rock, and both red and green are most often related to traces of iron (in its oxidized and reduced forms respectively).
Macrofossils, also known as megafossils, are preserved organic remains large enough to be visible without a microscope. The term macrofossil stands in opposition to the term microfossil. Microfossils, by contrast, require substantial magnification for evaluation by fossil-hunters or professional paleontologists. As a result, most fossils observed in the field and most "museum-quality" specimens are macrofossils.
Plant macrofossils include leaf, needle, cone and stem debris and will be used to identify types of plants formerly growing in the area. Such botanical macrofossil data provide a valuable complement to pollen and faunal data that can be used to reconstruct the prehistoric terrestrial environment. Algal macrofossils (for instance, brown kelp, sea lettuce and large stromatolites) are increasingly used to analyze prehistoric marine and aquatic ecosystems. Animal macrofossils include the teeth, skulls, and bones of vertebrates, as well as such invertebrate remains as shells, tests, faunal armor, and exoskeletons. Fossilized dung (that is, coprolites) are also macrofossils.
Example of macrofossils
Today you will be exploring the rocks for answers to the Earth Cache
Questions
The posted co-ords will have you at the base of Australia Rock
Q1 Can you find any plant or animal Macrofossils in the rock?
Q2 Describe the chert that you see here in the rocks. What colour is it, how does it feel to touch and describe any folds in the rock you can see.
Once you complete the EarthCache requirements you can post your find without delay, as per the EarthCache guidelines. You will also need to verify your find by sending me a message and provide your answers to the questions.
For a link to my profile, click here - Na'wal
Thanks for visiting this Earth Cache. I hope you enjoy exploring the area.
Feel free to attach photos to your log (optional) but please don't post any spoliers.
References ~ geomaps.com.au & wikipedia