The origin of the rocks that make up the landscape of the Kimberley is very complex.
Volcanic activity with outpourings of lava has formed basalt, while intrusions of magma (molten rock) beneath the land’s surface have formed granites and dolerites – now exposed in places by erosion.
Sediments weathered from rocks have accumulated in immense basins producing sedimentary rocks such as sandstone, conglomerate and siltstone.
El Questro Wilderness Park is part of the Kimberley Plateau, which consists of a vast area of comparatively flat high country, interrupted by sandstone escarpments that may stretch for tens of kilometres. Some of the most spectacular form the Cockburn Ranges along the Gibb River road.
Extensive rugged tablelands and mesas rise up to nearly 800 metres in the central part of the plateau and dip gently north and west towards the sea. They are fringed by steep escarpments up to 300 metres high, through which large rivers have cut steep-sided gorges. El Questro, Chamberlain and Emma Gorge are prime examples of these activities. Broad valleys between the escarpments contain low, boulder-strewn hills.
The most common rocks on El Questro are sandstones of the Bastion and Kimberley Group. El Questro Gorge, the Zebedee escarpment and Chamberlain Gorge are made of Warton sandstone, Elgee siltstone and Carson volcanic, which also includes quartzite.
The subsequent retreat of the sea and the uplifting of the land now belie their origins. Movements within the earth’s crust have buried volcanic and sedimentary rocks at depths of up to 20 kilometres in the Earth’s crust and the resultant heat and pressure have produced metamorphic rocks such as schist and gneiss.
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