Etching structures in the Barkly Karst Region

These photos are mainly from Camooweal, which lies at the boundary between the semi-arid BShw and arid BWhw climates. Here, the dolomite strata are horizontal and thick to medium and occasionally thin bedded. They have well developed vertical joints that result in a blocky to slabby outcrop with thin grikes and clints. Karren are restricted to "rain pits" and fine etching of joints, bedding, fine cracks and other structures.

The etching can be quite detailed, following nets of very fine cracks, and forming deeper v-notches in larger cracks or the bedding planes (Photo B770705 and ..06). Colour variations in the cream-coloured dolomite indicate that weathering has penetrated a few mm into the rock from the major cracks (photo B770707). Microkarren also occur and include microrills, networks and rasp-like teeth, as well as fine pitting.

The final (colour) photo is from further south, in the dryer area near Boulia, some very well developed microkarren were seen on loose cobbles of limestone (see Microkarren page). The underside of a loose specimen had fine pits (0.5 - 2 mm) where it had been in contact with the soil.


Selected photographs and diagrams

To view full size images, click on the displayed thumbnail image.
B770708.jpg Etched joints and bedding in flat-lying dolomite.
At Camooweal.
File: B770708.jpg
B770710.jpg Etched joints in dolomite
File: B770710.jpg
B770707.jpg Etched joints, with weathered halos.
In dolomite.
File: B770707.jpg
B770705s.tif B770706s.tif Two levels of etched joints:
Large joints form deep v-notches, and there is a finer mesh of small etched cracks.
Stereo-pair: view cross-eyed.
File: B770705s.tif
B770714.jpg B770713.jpg Etched pits and angular (polygonal?) branching cracks.
In dolomite.
Stereopair: View cross-eyed.
File: B770714.jpg
B770716.jpg Etched grooves and pits.
File: B770716.jpg

At Boulia

D031631.jpg Fine pitting on the underside of a cobble.
These were in contact with the soil.
The upper surface had fine micro-rills (see page on microkarren).
On limestone near Boulia.
File: D031631.jpg

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