Overview of Australian Karst areas

A recent overview the caves and karst of Australia by Webb & others (2003) forms the first chapter of the book Beneath the Surface: A Natural History of Australian Caves by Finlayson & Hamilton-Smith (2003).

[KGG: NB cut in segments of geol etc text from Webb etc 2003,
also mine the Reference list in myPDF versionof webb etc]
also add links to the various pages on this CD-ROM.

Click the map for a larger view.

Soft-rock Karsts

The Tertiary limestones are extensive areas of soft, porous, horizontal-bedded limestone with some jointing. Examples include the Cape Range (Allen, 1993), the Nullarbor (Jennings, 1967, Lowry & Jennings, 1974; Smith, 1988, Gillieson & Spate, 1992; Contos & others, 2001), the Murray Basin (Pilkington & others 1982; Smith, 1988), and the Gambier Karst (Grimes & others, 1999, Emmit & Telfer 1994; Stadter, 1999; Thurgate, 1996, 1999). With the exception of the Murray Basin, they are connected to the sea and their water-table history was influenced by Quaternary sea level changes coupled with local uplift and warping. These limestones form major aquifers. Water flow is by both porous and conduit movement with some joint influence. Storage is large because of the large areas and the high matrix porosity

The arid Nullarbor karst is the broadest of these areas (Gillieson & Spate, 1992). A low gradient watertable underlies the plain and its depth ranges from 30m in the north to 120m in the south. The ground water is brackish to saline - which complicates the cave genesis. The cave systems of the Nullarbor may have originated in a more humid climate phase in the late Miocene. Alternatively, they may have formed more recently by a combination of solution by saline waters, and mixing corrosion (James & Spate, 1993). Cave diving has demonstrated the existence of extensive flooded conduits, with an unusual biota that could be damaged by diver activities (Contos & others, 2001).

The Quaternary dune limestones are soft syngenetic karsts (Jennings, 1968; Grimes, 2002, 2003). They mostly form linear ridges parallel to the coast. See Bastian (1964, 1991, 2003a,b) and Williamson & Bell (1980) for West Australia; for southeastern Australia see White (1994, 2000) and Grimes & others (1999). Smaller areas occur on some of the islands of Bass Strait, and on Lord Howe Island.

The calcareous dune sands are porous, but as the sand becomes cemented in the older dunes the importance of solutional conduits increases. There is considerable storage available in the dune sands, and they can form significant, but shallow, aquifers in places (e.g. Davidson, 1995 (WA); Martin & Clarke, 2000 (SA)). Major through-caves can bypass this matrix storage in places. In the Gambier Karst the dune limestones sit on the Tertiary limestone and the two form a single connected aquifer (see Stadter, 1999, Love & others, 1993). In West Australia some of the dune limestone is perched on an impermeable basement which channels flows into underground streams (Williamson, 1980, Williamson & Bell, 1980) whereas other areas overlie porous non-limestone aquifers with which they exchange water and the hydrology is more complex (Bastian, 1991, 2003a,b). Eberhard (2003) has published a detailed study of the hydrology and groundwater ecology of the Jewel Cave region, documenting a complex history of water table changes. In that area recent drops in the water table are thought to be due to a change in the fire frequency.

Hard-rock Karsts

East Australian Karsts

Paleokarsts: Stating in the late Palaeozoic, the limestones were exposed near the surface several times prior to the present erosional cycle which produced the modern caves. These earlier events formed paleokarsts which are seen as sediment and speleothem-filled cavities in the walls of modern caves or in surface outcrops (see ++Osborne ...). At Chillagoe it has been argued that early versions of the towers were already well formed at the time of their burial during the early Cretaceous transgression. Their present form evolved subsequent to exhumation in the late Cretaceous and early Tertiary. first apeared in the Cretaceous (++Robinson 1978, Jennings, 1982, ++Webb, 1996, ++Gillieson etc 2003)

The climate varies from tropical monsoon in the north to cool temperate in the south; and one could argue for a climatic subdivision of this group with a boundary line north of Brisbane delineating the distinctive tropical karsts from the temporate karsts to the south.

The Tropical areas: Spate & Little (1995) provide a broad discussion of North Australia in general. The Chillagoe ang Mitchell River karsts have spectacular towers developed on steep dipping limestone. (Jennings, 1982; .......). Karren development is strong, with extensive jagged spitzkarren fields, giant grikes, and towers (?? Dunkerley, ?????). ... Broken River... ... Fanning River ... Mt Etna, just north of the Tropic of Capricorn, is the southernmost of the strongly developed spitzkarren hills, and also has extensive caves (Shannon, 1970). Karren are found fureth south, but with some exceptions (e.g. at Kempsey, NSW.) are not as strongly developed.

[re-arrange this - list by area, with brief descr, and a list of refs;]

The Temperate areas: The numerous small impounded karsts and cave areas of NSW have been described in general by Jennings 1977; Osborne & Branagan, 1988; Dunkley & Dykes, 2000; Crabb, 2000. Many of the caves are now thought to be quite old .... (++Osborne ...)

The five most cavernous karsts, with more than 100 recorded caves, are Bungonia, Jenolan, Wee Jasper, Wombeyan and Yarrangobilly. The Borders Rivers Karst, which straddles the Queensland-NSW border, has many small lenses of limestone, but only a few contain caves or even significant karren. Best known were the Texas Caves, which are now floded by an irrigation dam (++Grimes, 1976, 1978). Moving south ... Kempsey etc... (no useful pubs ?) Timor Wellington Jenolan Womeyan Bungonia, Wee Jasper Wyanbeen, Big Hole, Londen bridge, Cooeman Plain Yag'by Buchan etc Tasi ......... Jennings, 1967 (several NSW & Tas areas - SPILT THIS UP) Osborne, 2001 (Wellington); Welch, 1976 (Jenolan); Osborne, 1999 (Jenolan); Kiernan, 1988 (Jenolan); Shannon, 2001 (Jenolan); Lucas, 2001 (Cliefden); Dyson & others, 1982 (Wombeyan); Ellis, 2004 (Wombeyan); James & others 1982, 2004 (Wombeyan); Dennis, 1993, 2004 (Wombeyan); Osborne, 2004 (Wombeyan); McDonald & Drysdale, 2004 (Wombeyan); ????????.... [1st Bungonia Book .]; Bauer & Bauer, 1998 (Bungonia); Spate & others, 1976 (Yarrangobilly); Webb & others, 1992 (Buchan); Kiernan, 1995 (Tasmania in general); Kiernan, 1989 (Mole Ck), Kiernan, 1990 (Mole Ck), Parks and Wildlife Service, 2004 (Mle Creek); Kiernan, 1993 (Exit Cave) and Eberhard, 1994 (Junee - Florentine). Evolution of these areas is influenced by uplift & stream incision so that older, drained, high-level conduits are common; e.g. Osborne,1993 (Bungonia); Webb & others, 1992 (Buchan).

++ Timor (++James & others, 1976, ++Connolly & Francis, 1979) In South Australia the Flinders Ranges & Adelaide Hills are broadly similar in structure to the east coast areas, but have a drier climate (Pilkington & others 1982; Lawrence, 1997). In the Yorke Peninsula Corra Lynn cave is a distinctive multi-level horizontal maze caves developed in jointed flat-lying Cambrian dolomite (Pilkington & others 1982). It has over 13 km of passage in four levels within an area of 450 x 250m x 40m depth.

A few small caves are also present in Proterozoic dolomites in Western Australia, for example, at Moora and in the East Pilbara (++ ..... = Helictite notes?).

In detail, we find less consistency. For example, in New South Wales the western areas are in a more subdued topography and the folding is less pronounced so the caves tend to be more horizontal and shallow (Osborne & Branagan, 1988). However, generally speaking water flow in these impounded karsts is dominantly through conduits with some bedding or joint influence, and water inputs are dominantly external from the adjoining non-limestone areas. Storage is limited by the small size of the area, so springs tend to be flashy - although less so than non-karstic streams. The underground plumbing is variable and of limited extent in the smaller areas (e.g. Jennings, 1967, 1977), though a few larger areas such as Mole Creek in Tasmania with 150 km² of exposed limestone have a more complex plumbing (Kiernan, 1990, Kiernan & others, 1994).

The North Australian Karsts

We can distinguish two main subdivisions: Smaller but better-exposed areas include the Limestone Ranges of the Kimberley Karst ( ++Jennings & Sweeting, 1963a; Jennings, 1967, Williams, 1978) or the Gregory Karst (Bannink & others, 1995) which has Australia's two longest caves (100 and 50 km). These areas also have well developed surface karst - in particular deeply dissected karrenfields (++ Refs ????). In the Kimberley there are major through-flowing external streams that have either cut superimposed gorges across the karst (Jennings, 1967; Williams, 1978) or been csptured to underground courses (++Jennimgs & Sweeting, 1963b).

The larger areas are mainly of Cambrian carbonates in the Northern Territory and north-west Queensland: the Georgina, Wiso and Daly River Basins (Randal, 1967, 1973, 1978; Smith, 1988; Drysdale & others, 1998). These large Cambrian aquifers are largely buried under a cover of Mesozoic and Cainozoic sediments (shown as horizontal hatching on the map) but limestone and dolomite crops out at the northern and eastern margins and has well-developed surface karst (karren and collapse dolines) and caves that extend down to the regional water table (Grimes, 1988; Eberhard, 2001; ??Ellis, ??1979a,b; Lauretzen & Karp, 1993; Karp, 2002). Much of the drainage in these basins is deep and possibly in paleokarst conduits that could date back to the Mesozoic or even earlier. The water supplies in the Darwin region are drawn partly from a karst aquifer in Proterozoic dolomite and a shallow "laterite karst" aquifer also occurs in the region (Doyle, 2001).

Many of the tropical karsts have extensive tufa deposits associated with the springs (e.g. Dunkerley, 1981 (Mt. Etna), 1987 (Chillagoe); Drysdale & Gale, 1997 (Barkly Karst); Drysdale & others, 1998 (Barkly Karst); Viles & Goudie, 1990 (Kimberley).

Miscellaneous karsts

Coastal & Island Karst: This grouping overlaps with the soft-rock karsts described above, most of which are close to the sea. In addition, present and past Australian territories include harder, Tertiary, reef limestones at Christmas Island (Grimes, 2001) and Nauru Island (Jacobson & Hill, 1993), and in Papua New Guinea (Gillieson & Spate, 1998). Blue holes have been reported in the Great Barrier Reef (Backshall & others, 1979). These island and coastal karst areas have fresh-water lenses floating over salt water. Cave development shows a strong influence from sea-level controlled water table changes (complicated by uplift in some cases) and of mixing corrosion at the salt-fresh water interface.

Pseudokarst

...... Mass-mvmt caves & fissures in NSW (++Smith, 2003) ......

Silicate parakarst ... ++Wray 1997 ...... Whalemouth cave ...... Yulirienji cave, in Arnhem Land = ++Jennings 1979 ...South of Katherine, on the Sturt Plateau, recent collapse dolines have been reported in lateritised Mesozoic sandstones (McFarlane & Twidale, 1987[=Karstic features associated with tropical weathering profiles. Z.Geomorph, Suppl-Bd 64: 73-95]).

Annotated References

......... ???????? ............... MARKER, ME., 1976: A geomorphological assessment of the Chillagoe Karst Belt, Queensland. Helictite 14(1): 31_49. FORD, T.D., 1978: Chillagoe - a tower karst in decay. Trans British Cave Research Assoc. 5: 61-84. ROBINSON, TR., 1978: A Question of Age. Tower Karst (Chillagoe Caving Club, occasional paper) 2: 18-36.