Parakarst

Parakarst refers to karst landforms produced by solution of non-carbonate rocks. As distinct from pseudokarst which is karst landforms produced by processes other than solution.

Parakarst includes gypsum karst and salt (halite) karst, but neither of those types occurs in Australia.

Silicate karst is, however, quite common, especially (but not only) in tropical Australia. This mainly forms sandstone caves (e.g. Whalemouth Cave, WA (Jennings, 1983)) and surface karst landforms (rock cities and pinnacles) in tropical areas (Jennings, 1979), but it also can occur in laterite duricrusts and other silicate rocks in a variety of climates. Extensive boulder maze caves in jointed granite are transitional between this category and piping caves (e.g. Black Mountain, near Cooktown, Qld, and Labertouche Cave, Vic.).

Sandstone terrains in tropical Australia commonly have large-scale fissured forms which can break up into "stone cities" (Jennings, 1979) have have visual similarities to karst towers, pinnacles and giant grikes. Some of these areas also have caves that appear to be at least partly solutional in origin. However many are borderline cases in which the main processes are other forms of chemical and mechanical weathering and erosion.

It is not always easy to determine if a particular sandstone (or other, non-limestone) cave is true silicate karst, or whether it has formed by a combination of several process, e.g. solution, other chemical weathering processes (e.g. hydration), and piping and other forms of mechanical erosion of the soft weathering products. For example, tafoni are included in silicate karst by some people, but the processes probably involve more than straight solution.

Some Australian examples:

  • Laterite Karst: A type of silicate karst formed in tropical deep weathering profiles.
  • Whalemouth Cave: Western Australia. A poster on this large sandstone stream cave in tropical WA.
  • Sandstone karst at Lawn Hill Gorge: - NW Queensland. Dolines, streamsink & spring, small caves, small stone cities.
  • Silicate karren Small scale solutional sculpturing.

    • Further Reading

    Jennings, JN., 1979: Arnhem Land city that never was. Geogr. Mag., 60: 822-827.
    Jennings, JN., 1983: Sandstone pseudokarst or karst? in RW Young & GC Nanson (eds), Aspects of Australian Sandstone Landscapes. Australian and New Zealand Geomorphology Group, Special Publication, 1: 21-30.
    McFarlane, M.J., Ringrose, S., Giusti, L. & Shaw, P.A.,1995: The origin and age of karstic depressions in the Darwin - Koolpinyah area of the Northern Territory of Australia. in Brown, A.G. (editor) Geomorphology and Groundwater, Wiley, pp.93-120.
    McFarlane, M.J. & Twidale, C.R., 1987: Karstic features associated with tropical weathering profiles. Zeitschrift fur Geomorphology(NF), Suppl-Bd. 64: 73-95.
    Wray, RAL., 1997: A global review of solutional weathering forms on quartz sandstones. Earth Science reviews, 42: 137-160.

    Selected photographs and diagrams

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

    Sandstone stone cities

    Across much of tropical Australia, strongly jointed sandstones form fissured plateau that may break up into "stone cities". The degree of analogy to pinnacle karst varies - this aerial view is of a borderline case.
    Robinson R., Georgetown region, Qld.
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    Ground view of the surface of a sandstone plateau. Note the "giant grike" in foreground. Georgetown region, Qld.
    S690805.jpg
    Pinnacles in Cretaceous sandstone, west of Chillagoe, N. Qld.
    Although there is a physical similarity to limestone pinnacles, the processes of weathering are probably quite different, and it is doubtfull if they should even be called "pseudokarst" .
    S711220.jpg
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