Completing the Devonian Reef

Today saw us travelling down the old Devonian Reef, from Windjana, through Tunnel Creek and into Giekie Gorge. We stopped first at Lillimooloora for a brief history lesson – see associated post.

The first major stop was Tunnel Creek. A fascinating piece of geology, it flows underground through a range between two plains of nearly equal level. The Devonian Reef, being of aquatic coral origin, is limestone. It is believe a small fracture in the limestone allowed a stream to work its way through the rock through the ages. Limestone being soluble in the right conditions,  allowed the creek to work its way down through the rock, and the resulting fissure was closed up behind (above) the stream by more fill from above.

The rock itself is white limestone, with rich red veins flowing through it. I have read no explanation for this colouring.

Tunnel creek as we know it today runs for about 750m, about 100m below the range above. Near the middle the roof has fallen in, effectively creating two tunnels each of the order of 350m long. In general the tunnels are 10-15m wide, and up to 12m high in the middle. There are some features of typical limestone caves in places. The walk involves some wading, for us sometimes over our knees. Once out the other side the creek continues as normal.

Don’t be fooled by my camera which can take photos in the dark. It was dark in there! It’s amazing what can be achieved with a long shutter opening and waving a torch around.

On our way out to the Great Northern Highway (and bitumen – yay!), we passed an old mine.  It was notable mostly for the bizzarre alien landscape it occupied, but also for the two-up toilet left behind. I’m sure Louis will fill you in with the details at some stage.

 

Fitzroy Crossing seems to be a town under construction. Perhaps we will discover more tomorrow, but the impression I have is of a large indigenous population, and a recent injection of huge amounts of government money for services. I suspect it will be good when it is finished…

Giekie Gorge is the main attraction just 20km out of town, and the last stop on our Devonian Reef tour. Had it been our first stop on this trip it would have been impressive, but coming as it does when we have already done the Katherine Gorge cruise and after 12 days away from civilisation, the hot walk impressed us mostly for how tired we all were.