Signs of ancient life at Z-bend

While we were on holiday we discovered this Z-bend of the Murchison River

How gorges are formed

A gorge is a steep-sided, narrow valley with a river or stream running along the bottom. Gorges are formed by the interplay of several geological processes, including erosion, tectonic processes such as vertical uplift and cavern collapse. Erosion by the resident body of water is usually the primary contributor to gorge formation.

A River Cuts Through It

Rivers carve gorges as they pass over the land by carrying rocks and soil away. The continuous flow of water and abrasion by debris in the water eventually cuts a deep trench through the landscape that exposes many layers of rock. Glaciers can also dig gorges into the land as they advance and retreat. These glacial gorges fill with water and become rivers, which in turn remove more rock and soil to form even deeper gorges.

Land Motion

Gorge formation is accelerated by certain geological processes. Vertical uplift is when the edges of tectonic plates rise as they crash into one another to form steep, rocky features, such as mountains and gorges. When the roofs of underground caverns collapse, they can also form or deepen a gorge.

Z-bend
The gorge below you forms the middle part of the "Z-bend" - a distinctive zig-zag section of the Murchison River. This unusual shape is formed by joints (fractures) whitin the red Tumblagooda Sandstone.
These straight, vertical joints allowed the Murchison River to deeply incise the rock layers and form straight river segments. Where the joints intersect each other, the river's course changed to create a zig-zag pattern - the 'Z Bend' shape.
Signs of life
Western Australia is well known for its very old rocks, but it also has many significant localities of younger rocks (Phanerozoic, less than 541 million years). Geologists working on trace fossils in the Tumblagooda Sandstone have described what may be some of the earliest steps of life on land. The following describes the Tumblagooda Sandstone and its formation and landscape, as well as the aquatic and terrestrial traces of life it preserves.
Only one body fossil has been found so far in the Tumblagooda Sandstone — an impression of a strange arthropod called Kalbarria, which belongs to a now-extinct group called the euthycarcinoids. Body fossils are rare in the sandstone because the depositional environment was not favourable for the preservation of organic material. This is because the active, high-energy river system would have quickly broken down any carcasses, and the water’s high oxygen level would have rapidly decayed flesh. Despite this, the sandstones are rich in signs of life, preserving abundant tracks, traces and burrows of organisms that lived while the sandstone was being deposited. These ichnofossils give us an insight into not only what organisms were present while the sandstone was forming, but also what the environment was like

source: www.sciencing.com, www.dmp.wa.gov.au

To log this earthcache: 

1. At the front of the look-out deck on the right you can find a flat rock with terrestrial traces. What do you think what kind of ancient animal made this?
2. Measure the lenght and width of the terrestrial traces.
3. About the Z-bend: What is the reason that the river is following a zig-zag shape?
4. At certain moments the water of the river is unclear. How does this come?
5. (Optional) Post a photo with you and/or your team with the Z-bend in the background.

You are welcome to log your answers straight away to keep your TB's and Stats in order but please message us with your answers within 1 week of your log. Cacher’s who do not fulfil the Earth Cache requirement will have their logs deleted.

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