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Most concepts of conduit development have focused on telogenetic karst aquifers, where low matrix permeability focuses flow and dissolution along joints, fractures, and bedding planes. However, conduits also exist in eogenetic karst aquifers, despite high matrix permeability which accounts for a significant component of flow. This study investigates dissolution within a 6-km long conduit system in the eogenetic Upper Floridan aquifer of north-central Florida that begins with a continuous source of allogenic recharge at the Santa Fe River Sink and discharges from a first-magnitude spring at the Santa Fe River Rise. Three sources of water to the conduit include the allogenic recharge, diffuse recharge through epikarst, and mineralized water upwelling from depth. Results of sampling and inverse modeling using PHREEQC suggest that dissolution within the conduit is episodic, occurring only during 30% of 16 sampling times between March 2003 and April 2007. During low flow conditions, carbonate saturated water flows from the matrix to the conduit, restricting contact between undersaturated allogenic water with the conduit wall. When gradients reverse during high flow conditions, undersaturated allogenic recharge enters the matrix. During these limited periods, estimates of dissolution within the conduit suggest wall retreat averages about 4 × 10−6 m/day, in agreement with upper estimates of maximum wall retreat for telogenetic karst. Because dissolution is episodic, time-averaged dissolution rates in the sink-rise system results in a wall retreat rate of about 7 × 10−7 m/day, which is at the lower end of wall retreat for telogenetic karst. Because of the high permeability matrix, conduits in eogenetic karst thus enlarge not just at the walls of fractures or pre-existing conduits such as those in telogenetic karst, but also may produce a friable halo surrounding the conduits that may be removed by additional mechanical processes. These observations stress the importance of matrix permeability in eogenetic karst and suggest new concepts may be necessary to describe how conduits develop within these porous rocks.
An integrated geophysical study was performed over a known cave in Colorado Bend State Park (CBSP), Texas, where shallow karst features are common within the Ellenberger Limestone. Geophysical survey such as microgravity, ground penetrating radar (GPR), direct current (DC) resistivity, capacitively coupled (CC) resistivity, induced polarization (IP) and ground conductivity (GC) measurements were performed in an effort to distinguish which geophysical method worked most effectively and efficiently in detecting the presence of subsurface voids, caves and collapsed features. Horseshoe Chimney Cave (HCC), which is part of a larger network of cave systems, provides a good control environment for this research. A 50 x 50 meter grid, with 5 m spaced traverses was positioned around the entrance to HCC. Geophysical techniques listed above were used to collect geophysical data which were processed with the aid of commercial software packages. A traditional cave survey was conducted after geophysical data collection, to avoid any bias in initial data collection. The survey of the cave also provided ground truthing. Results indicate the microgravity followed by CC resistivity techniques worked most efficiently and were most cost effective, while the other methods showed varying levels of effectiveness.
Karst aquifers represent dual flow systems consisting of a highly conductive conduit system embedded in a less permeable rock matrix. Hybrid models iteratively coupling both flow systems generally consume much time, especially because of the nonlinearity of turbulent conduit flow. To reduce calculation times compared to those of existing approaches, a new iterative equation solver for the conduit system is developed based on an approximated Newton–Raphson expression and a Gauß–Seidel or successive over-relaxation scheme with a single iteration step at the innermost level. It is implemented and tested in the research code CAVE but should be easily adaptable to similar models such as the Conduit Flow Process for MODFLOW-2005. It substantially reduces the computational effort as demonstrated by steady-state benchmark scenarios as well as by transient karst genesis simulations. Water balance errors are found to be acceptable in most of the test cases. However, the performance and accuracy may deteriorate under unfavorable conditions such as sudden, strong changes of the flow field at some stages of the karst genesis simulations.
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The historical study of Australian caves and caving areas is fascinating although involving the expenditure of vast amounts of time. Australia's early days are unusually well-documented, but in the case of caves the early history is usually wrapped up in rumour, hearsay and clouded by lack of written record. Most research work means long hours poring over old newspaper files, mine reports, land department records and so on, little of which is catalogued. A small number of exploration journals and scientific studies have extensive material on special cave areas, and of these, the volume by Rev. Julian Edmund Woods, F.G.S., F.R.S.V., F.P.S., etc., and is one of the most interesting. This book gives the ideas and beliefs of 100 years ago concerning the origin, development and bone contents of caves and makes interesting reading in the light of more recent studies of cave origins. Wood's study "Geological Observations in South Australia : Principally in the District South-East of Adelaide" was published in 1862 by Longman, Green, Roberts and Green, London. In a preface dated November 15, 1861, Rev. Woods points out that the book was written while he was serving as a missionary in a 22,000 square mile district, and "without the benefit of reference, museum, library, or scientific men closer than England". Up to the time of writing, almost no scientific or geological work had been done in South Australia and much of the area was completely unexplored. The book, also, contained the first detailed description of caves in the south-east of the state. Father Woods writes about many different types of caves in South Australia, for instance, the "native wells" in the Mt. Gambier/Mt. Shanck area. These are caves, rounded like pipes, and generally leading to water level. Woods points out their likeness to artificial wells. He also writes of sea cliff caves, particularly in the Guichen Bay area, and blow holes caused by the action of the waves on the limestone cliffs. Woods discusses many other types of caves found further inland, particularly bone caves. Father Woods discusses cave origins under two sub-heads: 1. Trap rock caves generally resulting from violent igneous action, and 2. Limestone caves resulting from infiltration of some kind. He is mainly concerned with limestone caves which he sub-divides into (a) crevice caves - caves which have arisen from fissures in the rock and are therefore wedge-shaped crevices, widest at the opening, (b) sea-beach caves, caves which face the seashore and are merely holes that have been worn by the dashing of the sea on the face of the cliff, (c) egress caves, or passages to give egress to subterranean streams, (d) ingress caves, or passages caused by water flowing into the holes of rocks and disappearing underground. These caves would have entrance holes in the ground, opening very wide underneath, and having the appearance of water having entered from above, (e) finally a group of caves which he lists by use as "dens of animals".
Limestone caves in New Zealand can be divided into two distinct groups : those developed in the nearby flat-lying limestone of Oligocene age, and those formed in the strongly folded Mt. Arthur Marble of Upper Ordovician age. Caves formed in Oligocene limestone are typically horizontal in development, often having passages at several levels, and are frequently of considerable length. Those formed in Mt. Arthur Marble have mainly vertical development, some reaching a depth of several hundred feet. Previous research into the formation and geological history of New Zealand cave systems is discussed briefly, and the need for further work is emphasised.
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.
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