VICTORIAN CAVES AND KARST - A SUMMARY
Victorian caves are not particularly notable in the ways that people often think of such things. That is the caves do not rank amongst the longest, deepest, largest cavern size type of ratings. Other areas may also have beautifully decorated caves. However, there is great variety of caves in Victoria, both in type of host rock and in cave form. There are five major types of cave and karst landscape; only two of these are in limestone.
1. Palaeozoic limestone - Eastern Victoria.
The rock types are Silurian Marbles and Devonian limestones and tend to be pure (high CaCO3 content), massive, well jointed and in areas of relatively high relief and annual rainfall. Most of them are karst barriers where limestone is completely surrounded by non-karstic rocks. These conditions give good conditions for the formation of karst landforms. The caves in these areas fall into three main types:
- Stream Passage Caves: formed by perennial and intermittent streams, some examples showing older abandoned high levels. Many are well decorated but some are not e.g. Tourist system, Buchan.
- Vertical Potholes: varying from blind shafts e.g. Jampot (M-48) to complex examples with both vertical and horizontal development e.g. Exponential Pot (M-125). Again there is a great variety of decoration. These caves form as a result of solution along the intersection of joint planes.
- Collapse caves: caves formed due to the collapse of roof material e.g. Anticline M-11.
These karst areas include the Buchan valley, Limestone Creek, New Guinea Ridge etc in East Gippsland.
2. Cainozoic limestones - Western Victoria & S.E. South Australia
There are large areas of limestone but not necessarily a great deal of cave formation in this western province. The reasons for this are not very well understood. There is sufficient rainfall but there are more impurities in the limestones, lower relief and very few joints compared with the above type. Examples include Glenelg, Bats Ridge, Warrnambool, and Naracoorte. These caves tend to be more horizontal, have more collapse features, are often multi-entrance and may or may not have much decoration. The most common decoration is moonmilk.
3. Basalt
The Western District lava plains extend from Melbourne to about Mt Gambier and were formed in periods of volcanic activity in the last Tertiary and early Quaternary. Fluid lava erupted from fissures and shield cones and spread across large areas. One theory is that as the lava cooled tubes of less cooled lava within the flow drained away leaving lava tubes and caves. They vary from simple tubes to complex ones and other forms as well e.g. Mt Eccles, Byaduk.
4. Acid igneous rocks
These have never been thought to be important but are now shown to be more common and extensive. The main rocks are granite and granite-like rocks and examples of caves are found at Labertouche, near Warburton, Tynong and Nerrim South. Some very interesting small and rare decoration is found in some.
5. Miscellaneous
These include sea caves in basalt (C. Bridgewater), sometimes with limestone overlying the basalt; mudstones (C. Liptrap), sandstones (C. Patton, C. Otway area, Mt Speculation) and caves behind waterfalls such as Den of Nargun in Glenaladale National Park.
The conclusion that one has about Victorian and S.E. South Australian caves is the immense variety of types and forms.