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Mullamullang Cave N37 is the longest and most complex cave on the Nullarbor Plain, Southern Australia. Unlike the other caves, it possesses extensive levels of phreatic solution tube passages which permit stronger inferences to be made on the development of the collapse passages constituting the bulk of Mullamullang Cave and other deep Nullarbor caves. These passages have been formed by collapse through overlying belts of solution tube networks along an elongated zone of cavitation in the limestone. Massive breakdown was probably initiated at depth within the zone, at least 50 feet below the present watertable level. Upward stoping of the collapse would have been facilitated by the higher network levels in the zone, such as the Ezam and Easter Extension. Channelling of groundwater flow under the Plain is suggested by the belt-like nature of the networks. An epiphreatic origin is proposed for the network levels though convincing morphological evidence is wanting. Eustatic changes in sea level have been of fundamental importance in the development of the multiple levels. Wetter periods in the past were probably important as little development is taking place under present-day dry conditions. Correlation of wetter periods with Pleistocene glacials would help explain the development of huge collapse passages, but such correlatien cannot be assumed on present evidence. Massive collapse and doline formation were followed by subaerial weathering and vadose activity which modified the cave - especially near the entrance. Correlation of levels in Mullamullang with those in other Nullarbor deep caves is attempted. However, Mullamullang Cave is unique probably due to the lithology of the Abrakurrie Limestone in which it is developed.
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.
The 200,000 square kilometre Nullarbor Plain is a largely and relatively inhospitable tract of semi-arid land on the southern coast of Australia. It is also one of the world's largest and probably oldest karst landscapes. It contains a substantial number of caves, some of them very large. The sheer size of the plain together with its lack of surface water have made it a powerful ecological, physical and psychological barrier to the dispersal of evolving plants and animals and to human trade, settlement and communications. Because the plain is otherwise easily perceived as featureless, the more obvious of the caves have played an unusually prominent part in human exploration and occupation of the region. Aboriginal prehistory of cave exploration and use extends over many millenia. Two themes are especially interesting: quarrying underground as one of the earliest, and the role of water and shade in an inhospitable environment as the most persistent. The advent of European, Afghan and other cultures on this part of the southern coastline during the last four centuries has diversified the relevant historic themes. Victorian British discovery and exploration is the first stage in modern recognition of the caves, although long after the region was first discovered. The next and perhaps most remarkable phase brings together developments in Australian aviation and the adaptation of a grounded mariner to the land and air. Eventually the action moves on to the development of organised speleology. Other sub-themes in human interactions with the caves in this large waterless area include what may turn out to be either art or vandalism. They also include attempted grand solutions to the problem of water, by improbable engineering, as well as adventures of tourism, recreation and science.
In Australia, the karst land referred to as the Nullarbor covers an area in excess of 200,000 km2, although in proportion to its area the karst is poor in known caves. Despite being referred to by their collective name, the Nullarbor Caves, many of the individual caves are world class in their own right. In the world of caves, where in most cases biogenic carbon dioxide and surface waters provide the essential ingredients for the solution of limestone and the precipitation of decorations, the more of both, the bigger and more spectacular the caves. The Nullarbor Caves provide an example of how caves can originate, enlarge, and become decorated with speleothems at times when there is a shortage of both.