Microkarren - Barkly Karst Region

The Barkly Karst Region is developed on flat-lying Cambrian dolomites and lesser limestones. Its climate ranges from semi-arid BShw to arid BWhw (Koppen classes). At the northern (wetter) edge it is strongly dissected and there is well-developed large karren (grikefields, rillenkarren and spitzkarren). Microkarren have not been recorded from that part, but are probably present.

Moving south the larger karren forms become weaker and we find mainly grikes and etched bedding planes, with "rainpits" replacing the rillenkarren. Microkarren have been recently reported by the 2003 cave expedition to the O'Shannassy River (north of Undilla). These are illustrated in the photos below and include microrills, networks and rasp-like teeth, as well as fine pitting.

There is also fine etching of cracks and other structures (see also separate page for Etchings at Camooweal).

Selected photographs and diagrams

To view full size images, click on the displayed thumbnail image.

O'Shannassy River area

Deep etched cracks (micro-grikes?) and micro-rills.
Stereopair - view cross-eyed.
File: D031637.jpg

Micro-rills and shallow pits (Micro-pans?); with small micro-pits within the larger pits.
Stereopair - view cross-eyed.
File: D031633.jpg

Deep conical micro-pits.
Note that they are not circular but elongated.
Stereopair - view cross-eyed.
File: D031636.jpg

Boulia area

Further south, in the dryer area near Boulia, some very well developed microkarren were seen on loose cobbles of limestone (see photos). The upper, horizontal, surface had radiating micro-rills, and linear micro-rills also ran down the vertical sides, but became less pronounced downward. The underside of a loose specimen had fine pits (0.5 - 2 mm) where it had been in contact with the soil.

Radiating micro-rills on top of a cobble.
East of Boulia.
File: D031628.jpg

Decantation micro-rills running down the side of the same cobble.
East of Boulia.
File: D030003.jpg

Fine pits on underside of the same cobble as in photo 628.
This surface was in contact with the soil.
File: D031631.jpg

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