800 million years ago a shallow sea covered central Australia.
The tides and currents deposited a deep layer of quartz sand coated
in iron oxide dust. This sand was buried by later deposits and
later compressed into a very hard rock called quartzite.
Millions of years later mountain building forces and erosion,
exposed this hard layer of quartzite at the surface. This is part
of the Heavitree Range.
Since that time,rain water has entered cracks and fissures and
dissolved the softer materials making up this range. Redbank Creek
contributed to this weathering by continuing to scour away the
weaker rock. Eventually carving a path through the range. This is
Redbank Gorge.
The gorge consists of up to 13 pools, which are left behind
after the creek floods, during periods of heavy rain. These
permanent pools shrink during the summer months leaving behind
large exposed sand banks which are deposited by the creek
itself.
The gorge is very narrow, indicating that erosion is occurring
at a faster pace vertically than it is horizontally. The sides of
the gorge consisting of much harder rock than that found in the
creek bed.
Why is the rock red?
The original quartz grains were coated in iron oxide dust. When
the rainwater stated to seep into the cracks it dissolved these
iron minerals. This dissolved iron is brought back to the surface
by capillary action, where it evaporates, forming a hard red
crust.
To log this cache, go to the listed coordinates and email me
the answers to these questions:
1.What other method causes this hard red crust to
occur?
Then go to: S 23 33.993 E 132 31.179. Estimate the length of
the first pool.
2.Estimate the width of the gorge at the end of the first
pool.
3. Take a photo of yourself with your GPS standing on one of
the many highly polished rocks, that is no longer coated in this
hard red crust.Include this photo in your log.
This cache was set on Day 18 of our Larapinta trail
walk.