Pseudokarst

Most caves and karst form by solution of limestone/dolomite, but caves also form in a variety of non-carbonate rocks, both by solution and other mechanisms. A large variety of non-carbonate rocks can host caves, but here we will discuss only those that are most common in Australia. Pseudokarst in tropical Australia is poorly documented but appears to be more widespread than previously supposed.

Australian pseudokarsts are described briefly in Webb & others (2003) and include:

  • Volcanic caves: mainly lava tubes from which the molten material has drained, but some other types, e.g. open volcanic vents, can also occur (see the Mt. Eccles* site, Victoria and Undara* Qld.).
  • Parakarst: Also known as Silicate Karst. Parakarst" refers to karst landforms formed by solution of non-carbonate rocks, as against pseudokarst (processes other than solution). Parakarst mainly forms sandstone caves (e.g. Whalemouth Cave, WA) and surface karst landforms (rock cities and pinnacles) in tropical areas, but 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.).
  • Piping caves formed by water seeping through certain types of soils (e.g. Flagstone Ck, Qld.) and beneath duricrust layers (e.g. Chittering, WA, and see photo of Mt Gravatt cave below).
  • Sea caves formed by wave action. Some sea caves (in limestone) may be breached karst caves and the distinction is not always easy to make. Examples occur on most of our rocky coasts (e.g. Tasman Arch, Tas. - see photos below)
  • Tectonic or fissure caves form by gravitational sliding and toppling movements, e.g. cambering, to form open fissures that may sometimes become roofed to form caves (e.g. Pilchers Mountain, NSW).
  • Mixed or uncertain origin: Many caves and karst features are formed by a number of processes in conjunction, and so are hard to classify. e.g. some caves appear to be formed by a combination of solution (parakarst)and other processes of chemical weathering, but with the soft product removed by piping etc.
    An example of caves of uncertain origin in rhyolitic ignimbrite (solution or piping) is at Turtle Rock,Qld.
  • Homokarst: What do we call "caves"made by humans? These include mines, dwellings, city drains, etc... See photo below.

    • Readings

    Grimes, KG., 1975: Pseudokarst: definition and types. Proceedings of the 10th Biennial Conference of the Australian Speleological Federation (ASF), 1975, 6-10.
    Grimes, KG., 1997: "Redefining the boundary between karst and pseudokarst: a discussion", Cave and Karst Science, 24(2): 87-90
    Jennings, JN, 1983: Sandstone pseudokarst or karst? in YOUNG, RW & NANSON, GC (eds) Aspects of Australian Sandstone Landscapes, Australian & New Zealand Geomorphology Group, Special Pub. No 1. pp.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.
    Webb, J.A., Joyce, E.B., & Stevens, N.C., 1982: Lava caves of Australia. Proceedings, Third International Symposium on Vulcanospeleology, Oregon, USA. pp 74-85.
    Webb, J., Grimes, K. & Osborne, A., 2003: Black Holes: caves in the Australian landscape. pp. 1-52 in B. Finlayson & E. Hamilton-Smith (editors), Beneath the Surface: a natural history of Australian caves. University of New South Wales Press, Sydney.
    Wray, R.A.L., 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.

    Piping Caves

    The main,downstream, entrance to Mt. Gravatt cave (4MG-1), in a suburb of Brisbane, Qld
    The cave is in a poorly consolidated fanglomerate. There are several upstream entrances where surface water enters, to flow through the cave and exit from this entrance.
    IMG00209.jpg

    Sea caves

    An example from Torres Strait, at the northern end of Australia
    This one hosts a large bat colony
    IMG00007.jpg
    And one from the southern end of Australia.
    Tasman Arch, Tasmania
    S740111s.jpg

    Homokarst ??

    And what is this? Some people like to call it "Homokarst".
    The Creek Street Drain, Brisbane, Qld.
    Photo by Simon Jolly, c.1970s
    SJ.CreekSt.jpg
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