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Many lava tunnels are found in the Western District of Victoria, associated with volcanic eruptions of Pleistocene to Recent age, and some are probably only a few thousand years old. All Australian volcanoes are now extinct, but the most recently active were probably erupting up to 5,000 years ago, that is after the arrival of the Australian aboriginal. The newness of the Victorian caves results in original features being preserved in fine detail. All known lava caves have now been surveyed, mainly by members of the Victorian Cave Exploration Society.
Although research has been unable to establish a definite date of discovery for the limestone caves at Wellington, New South Wales, documentary evidence has placed it as 1828. The actual discovery could have been made earlier by soldiers or convicts from the Wellington Settlement, which dated from 1823. Whether the aborigines knew of the cave's existence before 1828 is uncertain, but likely, as in 1830 they referred to them as "Mulwang". A number of very small limestone caves were also discovered about the same time in the nearby Molong area. The Bungonia Caves, in the Marulan district near Goulburn, were first written about a short time later. On all the evidence available at present, the Wellington Caves can be considered to be the first of any size discovered on the mainland of Australia. The Wellington Caves are situated in a low, limestone outcrop about six miles south by road from the present town of Wellington, and approximately 190 miles west-north-west of Sydney. They are at an altitude of 1000 feet, about half a mile from the present bed of the Bell River, a tributary of the Macquarie River. One large cave and several small caves exist in the outcrop, and range in size from simple shafts to passages 200 to 300 feet long. Mining for phosphate has been carried out, resulting in extensive galleries, often unstable, at several levels. Two caves have been lit by electricity for the tourist trades; the Cathedral Cave, 400 feet long, maximum width 100 feet, and up to 50 feet high; and the smaller Gaden Cave. The Cathedral Cave contains what is believed to be the largest stalagmite in the world, "The Altar", which stands on a flat floor, is 100 feet round the base and almost touches the roof about 40 feet above. It appears that the name Cathedral was not applied to the cave until this century. The original names were "The Great Cave", "The Large Cave" or "The Main Cave". The Altar was named by Thomas Mitchell in 1830. See map of cave and Plate. Extensive Pleistocene bone deposits - a veritable mine of bone fragments - were found in 1830, and have been studied by palaeontologists almost continually ever since. These bone deposits introduced to the world the extinct marsupials of Australia, and have a special importance in view of the peculiar features of the living fauna of the continent. The names of many famous explorers and scientists are associated with this history, among the most prominent being Sir Thomas Mitchell and Sir Richard Owen. Anderson (1933) gives a brief outline of why the Wellington Caves fossil bone beds so rapidly attracted world-wide interest. During the 18th and early 19th Century, the great palaeontologist, Baron Georges Cuvier, and others, supposed that the earth had suffered a series of catastrophic changes in prehistoric times. As a result of each of these, the animals living in a certain area were destroyed, the area being repopulated from isolated portions of the earth that had escaped the catastrophe. The Bilical Deluge was believed to have been the most recent. Darwin, during the voyage of the Beagle around the world (1832-37), was struck by the abundance of Pleistocene mammalian fossils in South America, and also by the fact that, while these differed from living forms, and were in part of gigantic dimensions, they were closely related to present-day forms in that continent. Darwin's theory of descent with modification did not reconcile with the ideas of Cuvier and others. As the living mammalian fauna of Australia was even more distinctive than that of South America, it was a matter of importance and excitement to discover the nature of the mammals which had lived in Australia in the late Tertiary and Pleistocene.
Murray Cave is an almost horizontal former outflow cave, which is now on the brink of inactivity. A heavily decorated upper branch functioned during the first outflow phase and the present inactive entrance succeeded it as the outlet point. Both are at the level of a low aggradational terrace of the North Branch of Cave Creek outside the cave; this probably belongs to a Pleistocene cold period. An undecorated lower branch provided the third phase outlet, which still functions occasionally when water rises up a water trap at the inner end of the main passage and flows along that passage into it. The entrance chamber has angular gravel fill due to frost shattering, which post-dates the development of the lower branch passage and belongs to a late Pleistocene cold period. Evidence of free surface stream action predominates in the cave but shallow phreatic conditions must have contributed to its development.
Ten species of Australian cockroaches are recorded from Australian caves and mines. Most are troglophiles or guanobia. Only one troglobitic species is known. The distribution of these species is given, and attention is drawn to their absence from south-eastern Australia and Tasmania. It is suggested that climatic changes in the Pleistocene and early Recent may have been responsible for this, and that the fauna found in many cave areas may be of comparatively recent origin.
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