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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.
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.
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 general objective of this work was to develop a basic understanding of the karst hydrology, the nature and origin of the caves, the water chemistry, the surface geomorphology, and relationships among these aspects for a high relief tropical karst region having a thick section of limestone. The Valles-San Luis Potosí region of northeastern México, and in particular, the Sierra de El Abra, was selected for the study. A Cretaceous Platform approximately 200 km wide and 300 km long (N-S) delimits the region of interest. A thick Lower Cretaceous deposit of gypsum and anydrite, and probably surrounded by Lower Cretaceous limestone facies, is overlain by more than 1000 m of the thick-bedded middle Cretaceous El Abra limestone, which has a thick platform-margin reef. The Sierra de El Abra is a greatly elongated range along the eastern margin of the Platform. During the late Cretaceous, the region was covered by thick deposits of impermeable rocks. During the early Tertiary, the area was folded, uplifted, and subjected to erosion. A high relief karst having a wide variety of geomorphic forms controlled by climate and structure has developed. Rainfall in the region varies from 250-2500 mm and is strongly concentrated in the months June-October, when very large rainfalls often occur.
A number of specific investigations were made to meet the general objective given above, with special emphasis on those that provide information concerning the nature of ground-water flow systems in the region. Most of the runoff from the region passes through the karstic subsurface. Large portions of the region have no surface runoff whatsoever. The El Abra Formation is continuous over nearly the whole Platform, and it defines a region of very active ground-water circulation. Discharge from the aquifer occurs at a number of large and many small springs. Two of them, the Coy and the Frío springs group, are among the largest springs in the world with average discharges of approximately 24 m³/sec and 28 m³/sec respectively. Most of the dry season regional discharge is from a few large springs at low elevations along the eastern margin of the Platform. The flow systems give extremely dynamic responses to large precipitation events; floods at springs usually crest roughly one day after the causal rainfall and most springs have discharge variations (0max/0min) of 25-100 times. These facts indicate well-developed conduit flow systems.
The hydrochemical and hydrologic evidence in combination with the hydrogeologic setting demonstrate the existence of regional ground-water flow to several of the large eastern springs. Hydrochemical mixing-model calculations show that the amount of regional flow is at least 12 m³/sec, that it has an approximately constant flux, and that the local flow systems provide the extremely variable component of spring discharge. The chemical and physical properties of the springs are explained in terms of local and regional flow systems.
Local studies carried out in the Sierra de El Abra show that large conduits have developed, and that large fluctuations of the water table occur. The large fossil caves in the range were part of great deep phreatic flow systems which circulated at least 300 m below ancient water tables and which discharged onto ancient coastal plains much higher than the present one. The western margin swallet caves are of the floodwater type. The cave are structurally controlled.
Knowledge gained in this study should provide a basis for planning future research, and in particular for water resource development. The aquifer has great potential for water supply, but little of that potential is presently used.
A brief description of the geology and drainage of the Northern limestone at Jenolan Caves is introduced. Approaches to karst geochemistry are given. The reasons are given for the choice of complete chemical analyses followed by calculations of the thermochemical parameters (saturation indices with respect to calcite and dolomite, SIc and SId, and the partial pressure of carbon dioxide PCO2) for the Jenolan groundwaters. The methods of chemical analysis and thermochemical calculations are reported. The results of the groundwater survey are presented both as the raw chemical data and the derived thermochemical data. The raw data give more useful information than the calculated parameters. The results obtained by this survey are consistent with observations and the previous knowledge of the underground drainage of the Northern limestone. The water chemistry reflected the rock type and the residence time of the water in bedrock and gravels. It is concluded that the Jenolan underground River and Central River have different types of source and that Central River is not a braid of the Jenolan Underground River.
27 caves were examined on Misima Island. Most are sea caves, but some have clear phreatic origins and some result from vadose solution along joints. One cave is formed by washing out of fragments in fault-shattered gneiss. Karst development in the raised coral appears to have been limited by the absence of streams flowing through the limestone. This results from the geomorphic development of the area, which has isolated the coral into discontinuous patches. Many caves have human burials, with associated pottery and one cave contains at least 100 skulls.
Trials of the method of estimating the aggressiveness of karst water by artificial saturation (Stenner, 1969) were made on stream and spring waters in limestone country at Buchan, Victoria. Saturation was brought about with both laboratory reagent grade calcium carbonate and also with powdered local limestone. Resulting estimates of the initial degree of saturation varied considerably. The differences amounted to an average 5.6% (maximum 8.0%) in aggressiveness estimated from change in total hardness, 8.8% (maximum 14.0%) using calcium hardness, and 9.4% (maximum 31.0%) using magnesium hardness. Whilst the average difference between the two sets of results are not great, and certainly do not prohibit the use of the original Stenner method, they do serve to indicate that in particular individual cases misleading results can be obtained if local limestone is not used. Possible reasons for the differing behaviour of the two materials is suggested.
The Nam Lang - Nam Khong Karst Region, located in a thinly populated, remote part of Mae Hong Son Province, north-west Thailand, comprises about 1,000km2 of massive Permian limestone. Over much of the area is developed a characteristic polygonal karst dominated by over 3,000 depressions, with an assemblage of forms including dolines, uvalas, poljes, streamsinks, through caves, springs and blind valleys. Speleological exploration commenced only in 1983 and the major discovery is the Tham Nam Lang, the longest cave reported on the mainland of south-east Asia with nearly 7km of passages. Cave development is strongly influenced by regional strike and fault orientation and by base level incision into impermeable sediments underlying the limestone. The largest caves are formed where aggressive water collects on impervious rocks before entering the limestone. Elsewhere cave development is limited. Several caves are important archaeological sites, and a number have tourist potential.
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