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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.
Clastic sedimentary rocks are generally considered non-karstifiable and thus less vulnerable to pathogen contamination than karst aquifers. However, dissolution phenomena have been observed in clastic carbonate conglomerates of the Subalpine Molasse zone of the northern Alps and other regions of Europe, indicating karstification and high vulnerability, which is currently not considered for source protection zoning. Therefore, a research program was established at the Hochgrat site (Austria/Germany), as a demonstration that karst-like characteristics, flow behavior and high vulnerability to microbial contamination are possible in this type of aquifer. The study included geomorphologic mapping, comparative multi-tracer tests with fluorescent dyes and bacteria-sized fluorescent microspheres, and analyses of fecal indicator bacteria (FIB) in spring waters during different seasons. Results demonstrate that (i) flow velocities in carbonate conglomerates are similar as in typical karst aquifers, often exceeding 100 m/h; (ii) microbial contaminants are rapidly transported towards springs; and (iii) the magnitude and seasonal pattern of FIB variability depends on the land use in the spring catchment and its altitude. Different ground water protection strategies than currently applied are consequently required in regions formed by karstified carbonatic clastic rocks, taking into account their high degree of heterogeneity and vulnerability.
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Various geomorphologists such as Bögli, Corbel and Lehmann have in recent years demonstrated the interest that certain simple chemical analyses of natural waters can have for the comparison of rates of limestone solution in different in different climatic conditions. They can also have their relevance for the tracing of underground water connections as Oertli (1953) has shown in the example of the Slovenian part of the classical Yugoslavian karst. Since 1957, the writer has therefore been making such analyses of waters from Australian limestone areas. The chief significance of these measurements comes when one caving area is compared with another. M.M. Sweeting (1960) has already commented briefly on observations from Mole Creek, Tasmania, Buchan, Victoria and the Fitzroy Basin, Western Australia, made in 1958-59 by herself and the writer; further discussion will appear in a forthcoming publication of ours on the Limestone Ranges of the Fitzroy Basin. Nevertheless measurements of this kind can have a certain intrinsic interest as it is hoped to show in the following notes on the few observations I made at Yarrangobilly. These observations are set out in tabular and Trombe graph forms; the locations of the collecting points are shown on the map.
The geology and nature of the caves is discussed. Cave development has been affected by glacial outwash and periglacial conditions which must be taken into account when considering the development and distribution of cave fauna. The food supply in the caves is limited by the absence of cave-inhabiting bats. Floods while adding to the food supply must be destructive to some forms of terrestrial cave life. The cave fauna consists entirely of invertebrates. The carab genus Idacarabus Lea contains the only troglobites found in Tasmania. A common troglophile throughout the island is Hickmania troglodytes (Higgins and Petterd) which belongs to a very small group of relict spiders. Five species of cave crickets are known from Tasmania and Flinders Island. Three species belong to the genus Micropathus Richards and show an interesting distribution pattern. A single species of glow-worm, Arachnocampa (Arachnocampa) tasmaniensis Ferguson occurs in a number of Tasmanian caves. It is more closely related to the New Zealand species than to glow worms found on the Australian mainland. Other terrestrial cave life is briefly discussed. Aquatic cave life is poorly known. The syncarid Anaspides tasmaniae (Thomson) has been recorded from several caves. It differs from epigean forms in reduction of pigment.
The Trobriand group of coral islands is situated 100 miles off the northeast coast of Papua and north of the D'Entrecasteaux Islands. The largest island, Kiriwina, is 30 miles long and 12 miles across at its widest point. The authors visited Kiriwina for two separate periods of one week in 1967 and 1968 to undertake a phytochemical survey and a reconnaissance exploration of the caves. They believe that they explored all the sizeable caves from Wawela north. A DC-3 aircraft of Papuan Airlines operates a weekly flight between Port Moresby and Losuia, the Administration centre. Accommodation is provided on the island at the Trobriand Hotel, conducted by Mr. T. Ward, whose two trucks are used for local transportation on roads engineered by the US Army during World War II.
After brief descriptions of the geomorphology of the Cooleman Plain karst and in particular of the Blue Waterholes, the methods adopted to analyse the functioning of these major risings are detailed. The discharge regime of Cave Creek below them is oceanic pluvial in type perturbed by drought and snow. There is much annual variation both in seasonal incidence and total amount, with catchment efficiency correspondingly variable. Suspended sediment concentration is even more erratic and monthly determinations are inadequate for calculating corrasional denudation rates. Mean concentrations of suspended solids are about 1/18th of solute load. Total dissolved salts have a strong inverse relationship with discharge, and mean values are high compared with those for other catchments in eastern Australia but none of these determinations are from limestone catchments. Sodium, potassium, and chlorine contents are low compared with the same catchments but silica is relatively high. The ratio of alkaline earths to alkalis indicate that Cave Creek carries carbonate waters and there is an inverse regression of the ratio on discharge. There is inverse correlation of total hardness on discharge likewise due to concentration of surface waters by evaporation in dry periods, together with reduced underground solution rate at times of large, rapid flow. The spring waters remain aggressive. Close regressions of hardness on specific conductivity now permit the latter to be determined in the place of the former. Much evidence converges to indicate that all the springs at the Blue Waterholes are fed from the same conduit. The intermittent flow which comes down the North Branch on the surface to the Blue Waterholes differs significantly in many characters from the spring waters. Rates of Ca + M carbonate equivalent removal vary directly with discharge since hardness varies much less than does water volume. These gross rates have to be adjusted for (a) atmospheric salts entering the karst directly, (b) peripheral solute inputs from the non-karst two-thirds of the catchment and (c) subjacent karst solution before they can be taken as a measure of exposed karst denudation. The methods for achieving this are set out. The total corrections amount to about one third of the total hardness, though the correction for subjacent karst on its own lies within the experimental error of the investigation. The residual rate of limestone removal from the exposed karst also shows a winter/spring high rate and a summer/autumn low rate but the seasonal incidence and annual total varied very much from year to year. In comparison with results from karsts in broadly similar climate, the seasonal rhythm conforms and so does the high proportion (78%) of the solution taking place at or close to the surface. This reduces the importance of the impounded condition of this small karst but supports the use of karst denudation rate as a measure of surface lowering. Cave passage solution may however be more important in impounded karst than its absolute contribution might suggest, by promoting rapid development of underground circulation. The mean value of limestone removal is low for the climatic type and this is probably due to high evapotranspirational loss as well as to the process of eliminating atmospheric, peripheral non-karst and subjacent karst contributions. The difficulties of applying modern solution removal rate to the historical geomorphology of this karst are made evident; at the same time even crude extrapolations are shown to isolate problems valuably.
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