Saturday, September 28, 2013

Lawn Hill National Park

My second camping trip in northern Queensland was to Lawn Hill National Park. Lawn Hill is essentially a gorge cut through Precambrian sandstone by a spring-fed river. You can walk along the cliff tops, or kayak up the gorge. I absolutely loved it!


Geology: Science before safety

These ripples are about 1.5 billion years old!

 Rows of termite mounds

The cliffs of Lawn Hill Station.

I camped at Adel's Grove, about 8km from Lawn Hill NP. The camping area is under huge, shady trees, and it has a restaurant, bar and kayak hire so that you can paddle up the river. It has a general store and fuel bowser, and they run tours through the Park and to nearby, privately owned scenic spots. In contrast, the National Park campground was open, sunny and dusty. My recommendation is definitely to stay down the road.

About 50km south of Lawn Hill is the world-famous Riversleigh fossil deposit. It contains fossils of many of Australia's land-based animals, and charts the evolution of Australia's famous marsupials and megafauna. 

For the geologists: above the Precambrian sandstone is a Cambrian limestone. Rainwater seeps through the limestone and becomes saturated with carbonate. The various spring-fed rivers (Lawn Hill Stream included) are carbonate-saturated. At various times through the Tertiary, the climate has been wet enough to produce small lakes across the plains. In warm weather these would partially evaporate,and the water would become super-saturated. Animals trapped in mud along the banks, or walking onto rafts of crystallised carbonate would get trapped and preserved in the redeposited limestones. The region's now dotted with hard, elevated limestone outcrops, each one a window onto a specific period.

Riversleigh locality 'D', the only portion of the fossil reserve open to the public. Leave your geo-pick in the car!

The Cambrian limestone, with silica nodules. 

Closeup of the silica nodules. These have nothing to do with the fossil story, they just look cool!

 A turtle in the redeposited, Tertiary limestone.
A crocodile 


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