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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 new data from the Big Hole and its vicinity give some further support to the view maintained previously as to its origin, though an approach through water chemistry proved non-committal. Difficulties attaching to an origin by true phreatic solution of underlying limestone through circulations of groundwater of meteoric provenance remain however. Nevertheless, the possibility, not considered previously, that the Big Hole is due to hydrothermal solution in the manner of many collapse structures associated with uranium ore bodies in southwestern U.S.A. finds no support in the regional geology of the Shoalhaven valley, though it could produce features of the right dimensions. Previous lack of a complete parallel to the Big Hole has been removed by reference to the furnas of southern Brazil where a similar origin to the one proposed here is also inferred.
The Appalachian fold belt system in Newfoundland is divided into three tectonic divisions: Western Platform; Central Mobile Belt; Avalon Platform Rocks of the Western Platform range in age from Precambrian to Carboniferous. Major karst areas are found there is Ordovician and Carboniferous rocks. Karst features of the study area (Goose Arm to Bonne Bay Big Pond) are in the Ordovician carbonates of the undivided St. George and Table Head Formations, covering a few hundred square kilometers. Features include karren, sinkholes, sinking streams, and karst springs, caves and other solutional and collapse features.
In the study area multiple fold and faulting episodes complicate the geology. Extensive and probably repeated glaciations have produced rugged terrane with U-shaped valleys and as much as 300m relief on the carbonates. There is variable but thick till cover. A class or classes of ice-scoured closed depressions with internal drainage are recognized. Postglacial karst forms are limited to varieties of karren (mainly littoral), small sinkholes, and cave systems that are inaccessively small in most instances. Distribution of all karst features is highly irregular.
Hydrologic patterns follow fluvial, fluviokarstic and holokarstic drainage. Large number of sinking ponds have seasonal overflow channels. The ground water drainage routes are generally short and shallow, with varied hydraulic gradients. Few instances of ground water route integration to regional springs is found.
The water chemistry of the area displays a tight normal distribution of hardness. This is attributed to the ponding effect. Seasonal trends show an overall increase in total hardness and other parameters, with some ponds showing linear increases and others cyclic variations.
Karst type and distribution is complex and irregular, but both glaciokarstic and karstiglacial development is present. The majority of karst forms point to karstiglacial development where previous karst forms have been modified by ice. Karstification is controlled by geology, rock lithology, hydraulic gradients and glacial scour and infill. Karstic processes continue to operate today, modifying the scoured basins and creating new karst forms.
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