Laterite Karst - Medium scale features

Medium scale Laterite Karst features in Deep Weathering profiles (DWPs) include solution and subsidence dolines at various scale (see also the page on Large-scale features), subsoil cutters and vertical solution pipes, pinnacles, and polygonal walls associated with very large scale mottled patterns. There are also some special features that do not have good karst analogues, such as core stones and large nodules.
Caves are described on a separate page.

Selected photographs and diagrams

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

Dolines etc.

Solution dolines (pits & pipes) in a mottled DWP. The original soft soil cover has been removed.
Mystery Craters, Bundaberg, Qld.
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A small soil subsidence doline. The surface soil is subsiding into cavities beneath a ferricrete band.
Doomadgee Plain, NW Qld.
In this case the nearest, shallow, stream channel was 4 km away, so piping is unlikely - the cavity beneath the ferricrete must be due to solution alone.
Stereopair - view cross-eyed.
S74-G00x.jpg and S74-G01x.jpg
Hummocky surface resulting from broad-scale subsidence of a ferricrete duricrust that has been undermined by extensive solution and piping. Piping is possible here as there is an incised stream only 100m away. Tobeys Waterhole, NW Qld.
Stereopair - view cross-eyed.
S830302.jpg and S830303.jpg

Solution Pipes and Pinnacles

Solution pipes are vertical cylinders, possibly formed by focussed downward vadose flow.
They grade in size down to smaller tubelets (which can run in all directions) and up to pits and dolines (shown above). Some may be large mottles that have had the soft core removed.
Solution pipes and pinnacles in laterite are best compared to those in the syngenetic karsts, rather than to classic hard-rock karst. Laterites have in common with syngenetic karsts the similtaneous occurrence of solution and cementation.

Left: vertical solution pipes in a lateritised duricrust - used as waterholes by the Aboriginal people. Yulba area, southern Queensland
Right: A field of solution pipes in dune limestone. Canunda NP, SA
Both forms appear to form by solution by focussed vertical water flow through the crust as it is forming.

PandP3.jpg
Left: Pinnacles in a laterite profile, Denna Plain, Queensland
Right: Similar Pinnacles in dune limestone at Nambung, WA
Both forms appear to form by cementation by focussed vertical water flow through the sediment. They have been left upstanding after erosion of the softer surrounding material.

PandP1.jpg
Left: Hollow Pinnacle in a laterite profile, Denna Plain, Queensland
Right: Similar Pinnacle in dune calcarenite at Nambung, WA
Both forms might have commenced as solution pipes, and the rim was later cemented - possibly by material that had been removed from the adjoining pipe.

PandP2.jpg
Stereopair of laterite pinnacles. Dissected edge of the Denna Plain, Hughenden, Queensland
Stereopair - view cross-eyed.
S780515.jpg and S780516.jpg
Sterepair of a laterite pinnacle with a hollow core
Dissected edge of the Denna Plain, Hughenden, Queensland
Stereopair - view cross-eyed.
KG083189s.JPG and KG083188s.JPG
Pinnacles in a siliceous duricrust.
Glendower area, Hughenden, Queensland

S780316.jpg

Cutters

Cutters in a DWP, infilled by a younger(?) surface soil.
Exposed in a mine cut, Mt. Coolon region, Qld.
Cutters are subsoil fissures (enlarged joints), They are not commonly seen, but large-scale sets may be responsible for the "stone cities" of tropical Australia (see Large-scale features).


S890128.jpg

Other features - these do not have an obvious karst analog.

Residual corestone of fresh granite (behind hammer) floating in a soft mottled DWP (foreground). Einasleigh region, N. Qld.
Erosion could expose such cores to form tors and possible boulder caves.
S841521.jpg
Large nodules of silcrete embedded in a DWP. The host rock is a siltstone - these are NOT transported cobbles.
Lake Buchanan, Qld.
Stereopair - view cross-eyed.
S841414.jpg and S841415.jpg

Polygonal ground and walls

Polygonal walls on a lateritic DWP. Lake Buchanan, Qld.
S841404.jpg
Large mottles in a lateritic DWP at Mt. Coolon, Qld.
The dark areas are ferruginised and hard, the white areas are softer leached material. The white areas could become pipes or pits, and the ferruginised areas around them could become indurated walls.
S850404.jpg
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