GEIKIE GORGE #8

GEIKIE GORGE #8

“During the wet season, the Fitzroy River rises about 16.5 metres, scouring the walls of the gorge and flooding the national park with seven metres of water.

In the dry, between April and November, the river transforms itself into a quiet stream strung out beneath the towering cliffs of the Devonian reef.
Unlike modern reefs, which are built by corals, algae and a group of now extinct lime-secreting organisms built the bulk of this reef.

Ranging from atolls of a few hectares to hundreds of square kilometres, the reef platforms grew close to sea level, rising 200 metres or more above the sea floor.

As the ocean floor slowly subsided over the 50 million years of the Devonian period, the reef-building organisms were able to keep pace, building up and up until, in places, the reef became more than two kilometres thick.
The limestone ranges, formed from the ancient barrier reef, wind across the country between 50 and 100 metres above the surrounding plains, in much the same way that the reef would have reared above the Devonian sea floor. From the air, it's easy to imagine that the sea has just withdrawn, leaving the reefs uncovered.

Here, layers of fossils and the limestone strata of an ancient reef are exposed in cross section, showing glimpses of life in the Devonian period before reptiles or mammals evolved.” (http://www.dec.wa.gov.au/component/option,com_hotproperty/task,view/id,43/Itemid,755/)