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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.
The Nullarbor Plain, Australia's most extensive limestone region, consists of about 65,000 square miles of almost horizontal beds of Tertiary limestone. The Plain extends from near Fowlers Bay, South Australia, approximately 600 miles west across the head of the Great Australian Bight into Western Australia. However, for its size, the Nullarbor appears to be deficient in caves compared with other Australian cavernous limestones. The vastness of the area, isolation, and complete lack of surface water, makes speleological investigation difficult. Some of the most important caves are more than 100 miles apart. The 1963-4 Nullarbor Expedition was organised by members of the Sydney University Speleological Society (SUSS). Two major caves, as well as a number of smaller features were discovered in the western part of the Plain. One cave contains what is believed to be the longest single cave passage in Australia.
The majority of South Australian caves occur in the Tertiary and Quaternary limestones of the coastal areas. Their distribution is discussed here on a geological rather than a geographical basis. The most significant caves are briefly described and illustrated to indicate different types and related developments in the coastal limestones. The most notable feature of the limestones is their soft, porous nature. Caves also occur in South Australia in hard, massively bedded Cambrian and Pre-Cambrian limestones and dolomites. These are not discussed in the present paper. To facilitate recording, South Australia has been divided into six zones as shown in Figure 1, and the caves numbered in order of discovery in each area. In general, both the name and the number of the cave have been given, but unnamed caves are specified by number only. The cave maps have been chosen to give as wide a coverage as possible of the various types, or to illustrate points of particular interest. The arrows on the section lines show the direction of viewing, and the sections are numbered to relate them to the plans. Where a cross-section and longitudinal section intersect, the common line has been drawn to relate the sections. The same scale has been used throughout for ease of comparison.
The clustering areas of bent-winged bats in limestone caves are frequently stained and etched. This staining is very intense, and covers large areas at breeding caves present in Palaeozoic limestones. Erosion of limestone is very conspicuous in these caves. Staining is not intense at breeding caves in Tertiary limestones, but a combination of chemical and mechanical erosion may, in part, account for the depth of dome pits in which the bats cluster. Certain caves that are characterised by extensive guano deposits and by conspicuously eroded and/or stained limestone, but which are currently without large colonies of bats, may represent ancestral breeding caves.
River Cave is a Zwischenhohle (between-cave) in which the active river passage is reached through a former tributary stream passage from a dry valley. Now vadose in character, it is of gentle gradient, with some normally and some temporarily water-filled reaches of shallow phreatic nature. There is only a single level of development. Water tracing has confirmed previous inferences that it is mainly fed from the South Branch watersink, that its normal flow goes to the Blue Waterholes, the main rising of the Plain, and that there is flood overflow to Murray Cave, which is shown to have been formerly the normal outflow cave of the system. In the changeover from one outflow point (Vorfluter) to another, a shorter, steeper cave and longer surface course has been replaced by a longer cave of shorter gradient. Ev's Cave, a flood inflow cave of the South Branch, may also feed River Cave and Keith's Faint Cave is inferred to be part of the link between South Branch Sink and River Cave. It has the aspect of an early stage of vadose development from phreatic conditions. Previous interpretation of Glop Pot as a true phreatic relic is maintained in the light of new facts. Evidence is lacking with which to date the caves at all reliably. Glop Pot possibly belongs to a phase of surface planation of Tertiary age whereas the other caves are likely to be consequent on Pleistocene dissection. The tributary passage of River Cave and its associated dry valley may have lost their stream in the Holocene when Murray Cave became intermittent in action also. The Murray Cave event is due to subterranean piracy associated with rejuvenation whereas the loss of the tributary stream is probably in part due to increasing warmth and less effective precipitation.
The existence of a small cave in Tertiary basalt in the Bunya Mountains, Queensland, has been known for some time, but has only recently come to the attention of speleologists. The origin of the cave is uncertain, although multi-process formation or modification of an original lava tube is suggested. The cave contains a small colony of Miniopterus schreibersii.
The Nullarbor Plain is a low plateau of Tertiary limestone covering an area of 194,175 km2 in southern Australia. It has a semi-arid climate and supports a stunted vegetation. Ninety-five species of arthropods have been recorded from 47 Nullarbor caves, and many of these species are widely distributed across the Plain. Two possible explanations for their distribution are discussed. Subterranean migration may occur through the widespread zone of small interconnecting cavities in the Nullarbor Limestone, but this has not yet been confirmed. While cave arthropods are confined to the cool, moist cave environment during the day, they have been observed at night in cave entrances, in dolines and on the surface of the Plain. Cave "breathing", similarity in cave and epigean climate at night, strong winds, occasional heavy rain and numerous animal burrows all contribute towards favourable conditions for surface migration.
Wellington Caves, New South Wales (figure 1), have attracted scientific attention for more than a century, largely through discoveries in the cave sediments of bones from extinct animals. These bone discoveries provided impetus for a number of early speculations about the geomorphology of the caves area and its relationship to the caves. Notable among these was the conjecture of Mitchell (1839) that the valley floor sediments of the Bell River and the cave fills had been deposited during a marine transgression about one million years ago. The first systematic geomorphological work was carried out by Colditz (1943), who argued for two distinct relict erosion levels in the Bell Valley; the older level was assigned to the Lower Pliocene and the younger to the Upper Pliocene. Colditz considered that these levels provided evidence for two phases of uplift in late Tertiary times. More recently Frank (1971) made detailed studies of the cave sediments, and devoted some attention to landscape evolution. He believed that the Bell River had been captured by Catombal Creek, during the late Pliocene or early Pleistocene.
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