A Grand Geological Unroofing
The Oxley Wild Rivers National Park is one of Australia's largest and most dramatic gorge systems. Rivers like the Macleay and Apsley have sliced deep into the New England Tablelands, creating chasms that reach depths of up to 600 meters. This process measures the slow, relentless erosion of the Great Dividing Range, the continental spine of Eastern Australia. The range itself was formed over 300 million years ago during the Carboniferous period when the Australian continent collided with parts of what are now South America and New Zealand.
The gorges owe their impressive depth and steepness to the underlying geology. The rivers carve through Paleozoic-era meta-sedimentary rocks, primarily slate, which were deposited on an ancient seafloor around 400 million years ago. These rocks were later buckled, folded, and tilted to a near-vertical orientation during a major mountain-building event 250 million years ago. This vertical alignment of the rock layers makes them more susceptible to erosion by the rivers, allowing for rapid down-cutting and the formation of sheer gorge walls. The process is river incision, where the vertical erosion rate outpaces the weathering and widening of the valley sides.