The massive outcrops of Wilkawillina Limestone in this area contain fossil Archaeocyatha in a state of remarkable preservation on a scale rarely found in other parts of the world.
This type of fossiliferous limestone is unique in Earth history. The mineral was only formed during the Early Cambrian. The classic localities for these unusual Early Cambrian fossils are Siberia and Australia.
The local stone was formed 530MYA when this area was covered by a shallow sea. Abundant animal life lived in the warm, clean, shallow seas. The fossil remains of the life are preserved in the rocks surrounding this area.
Archaeocyathans were sessile, benthic filter-feeding invertebrates that made a double-walled, calcareous skeleton. They are now considered to be an odd group of sponges. They formed bioherms (reefs) and are significant guide fossils in Lower Cambrian rocks.
Caves are formed by the dissolution of limestone. Rainwater picks up carbon dioxide from the air and as it percolates through the soil, which turns into a weak acid. This slowly dissolves out the limestone along the joints, bedding planes and fractures, some of which become enlarged enough to form caves.
Earthcache Tasks. Please submit answers for the following questions to the cache owner.
- Describe the condition of the local stone? Can you see any fossils.
- Looking north what feature can be seen on the cliff face? What has caused this feature?