At the crest
Outcrops of a reef can be found at this location, belonging to the oldest fossil carbonate reefs in the world. Sites such as the Arkaroola Reef is one of the few places on Earth where the geology and palaeontology of Precambrian and earlier periods of the Earth's crust formation can be seen and researched.
These reefs were once a giant underwater reef – with an escarpment of 1100m, ten times higher than the Great Barrier Reef. The reef is about 650 million years old and is the only known reef complex of this age anywhere in the world. It existed for 5-10 million years during a period of tropical climate squeezed between two major ice age events (the so-called ‘Snowball Earth’ events) where ice was present even at equatorial latitudes. This extreme climate change from ice age to tropical conditions and back to ice age occurred approximately 750-550 million years ago (hundreds of millions of years before dinosaurs roamed the Earth) and is one of the most tumultuous climatic periods of Earth’s history. It is a particularly intriguing period because it also coincided with the sudden and widespread appearance of very early primitive lifeforms.
(Free after Malcolm William Wallace et alii, University of Melbourne)