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The majority of South Australian caves occur in the Tertiary and Quaternary limestones of the coastal areas. Their distribution is discussed here on a geological rather than a geographical basis. The most significant caves are briefly described and illustrated to indicate different types and related developments in the coastal limestones. The most notable feature of the limestones is their soft, porous nature. Caves also occur in South Australia in hard, massively bedded Cambrian and Pre-Cambrian limestones and dolomites. These are not discussed in the present paper. To facilitate recording, South Australia has been divided into six zones as shown in Figure 1, and the caves numbered in order of discovery in each area. In general, both the name and the number of the cave have been given, but unnamed caves are specified by number only. The cave maps have been chosen to give as wide a coverage as possible of the various types, or to illustrate points of particular interest. The arrows on the section lines show the direction of viewing, and the sections are numbered to relate them to the plans. Where a cross-section and longitudinal section intersect, the common line has been drawn to relate the sections. The same scale has been used throughout for ease of comparison.
Holy Jump Lava Cave consists of portions of lava tubes in two superimposed flows. The upper tube probably connected with the downflow section of the lower tube via a lavafall. A small upflow part of the lower tube is also preserved, and shows the original wall and roof structures. Elsewhere the cave has suffered extensive breakdown, and only small sections of the original walls are still present. The cave has been further modified by secondary silica mineralisation, fine sediment deposition, and guano accumulation. The enclosing lava flows are early Miocene basalts of the Main Range Volcanics, making Holy Jump Lava Cave one of the oldest lava tube caves known.
The appearance and relationships of Brucker Breakdown and adjacent area, a portion ofthe Mammoth Cave System,implythatcomplex structural and hydrogeological factors affectected and/or controlled passage development. Detailed surveys include geographic, cartographic, lithologic, morphologic, stratigraphic, and paleoflow indicators. The five proposed scenarios were the following. Case 1: All (or most) of the passages were once continuous across the Brucker Breakdown void, which is a subsequent feature. Case Ia: The Brucker Breakdown void is a subsequentfeature whose development caused morphological changes in the pre-existing passages adjacent to it (traditional hypothesis). Case II: The passages converge toward or diverge from the Brucker Breakdown void, which acted as either a source or target of flow and is a primary feature. Case Ila: Several passages converge on the Brucker Breakdown void and fewer components depart from it, indicating that the Brucker Breakdown void is a primary feature and represented a local potentiometric low. Case lIb: Several passages diverge from the Brucker Breakdown void, and fewer components converge on it, indicating that the Brucker Breakdown void is a primary feature and represented a local potentiometric high. Of these, Case lib was found to most closely represent the situation presented by the data.
To perform this study, a detailed procedure was developed that, until this time, had not been established nor outlined in the literature. Once the area of study was chosen and defined, an extremely detailed cartographic and morphologic survey was performed that established both horizontal and vertical data points throughout the area. These data points were tied to existing transit surveys of the surface that linked the subsurface area to U.S. Geological Survey bench marks. The cartographic, geographic, and morphologic data were converted with computer aid to map form. The maps were then field-checked for accuracy. Comprehensive geological mapping surveys were executed. Multiple stratigraphic sections were described and measured in each passage segment, and these were tied to the vertical data points. Correlations were made between sections and were physically traced whenever conditions permitted. Speleothem dating information from prior research was obtained and correlated throughout the study area. Finally, important features and passage morphologies were documented photographically.
This work, based on the study of several underground alpine networks, aims to propose some milestone in the history of these karstic regions.
The first part of the work is made up of three regional studies.
The Tennengebirge mountains are a massif of the limestone High Alps in the region of Salzburg in Austria. A cone karst close to the base level developed in the Neogene. Streams from the Alps fed the karst, resulting in the huge horizontal networks of which the Eisriesenwelt provides evidence. During the successive phases of upthrust, the levels of karstification, whether on the surface or deeper down, settled into a tier pattern, thus descending in stages from the base level. From the Pliocene era onwards, thanks to an increase in potential, alpine shafts replace the horizontal networks. The formation of these shafts is more pronounced during glaciation. The study of the Cosa Nostra - Bergerhöhle system developing 30 km of conduits on a gradient reaching almost 1 500 m provides a fairly full view of the karstification of this massif. It includes the horizontal levels developed in the Miocene and the Plio-Pleistocene, joined together by vertical sections. The most noteworthy features of the Tennengebirge, as in the neighboring massifs, lie first and foremost in the extreme thickness of the limestone which has recorded and immunized the differents steps of karstification. Secondly, the size of the networks can be, for the most part, accounted for by the contribution of allogenous waters from the streams of the Neogene and the glaciers of the Pleistocene. Generally sudden and unexpected, these flows of water engendered heavy loads (up to 600 m), simultaneously flooding several levels. To a lesser extent, the situation is similar today.
The Ile de Cremieu is a low limestone plateau on the western edge of the Jura. Due to its location in the foothills, the lobes of the Rhône glacier have covered it up, obliterating the surface karst. However, widespread evidence of anteglacial morphologies remains : paleokarst, cone karst, polygenic surface. Because of glacial plugging, access to the underground karst is limited. The main cavity is the cave of La Balme. Its initial development dates back to an early period. The morphological study has permitted the identification of several phases which go back to the Pleistocene and which are related to the Rhône glacier. The latter brought about modifications in the base level by supplying its merging waters as well as moraine material. These variations in the base level shaped the drainage structure. The underground glacial polishes are one of the noteworthy aspects recorded.
The massives of the Moucherotte and dent de Crolles belong to the northern French Prealps. They conceal large networks, respectively the Vallier cave and the Dent de Crolles. They were formed in the early Pliocene after the final orogenic phase and are in the form of horizontal conduits. The upthrust, which brought about the embanking of the Isère valley, left them in a perched position by taking away the basin which fed them. They were later, however, able to take advantage of waters from the Isère glacier during a part of the Pleistocene. The Vallier cave contains particularly glacio-karstic sediments of the lower Pleistocene, representing unique evidence of glaciation during this period. The vertical networks were put in place at the end of the Pliocene with the increase in karstification potential ; they underwent changes in the Pleistocene due to the effect of autochton and allogenous glaciers.
The second part of the work deals in general with the various forms and processes of karstification, sometimes going beyond the Alps. The study of cave deposits is a privileged tool in the understanding and reconstruction not only of the history of the networks but also the regional environment. The dating of speleothems by the U / Th method has very ofen given an age of over 350 000 years. The age of the networks is confirmed by the use of paleomagnetism which has yielded evidence of speleothems and glacio-karstic sediments anterior to 780 000 years. Anisotropic measurements of magnetic susceptibility have been used to distinguish the putting into place of glacio-karstic deposits by decantation.
Measurements of calcite rates lead to a typology of sediments based on their nature and carbonate content (rehandled weathered rocks, fluvial sands, carbonated varves, decantation clays). Granulometry confirms this differenciation by supplying precise details of transport and sedimentation modes : suspension and abrupt precipitation of clay, suspension and slow decantation of carbonated varves, suspension and rolling together with a variable sorting of sand and gravel. Mineralogical analyses oppose two types of detrital deposits. On the one hand, the rehandling of antequaternary weathered rocks extracted by the karst as a result of scouring during environmental destabilization and on the other hand, sediments characteristic of the ice age of the Pleistocene. The latter are not highly developed and their arrival in the karst is always later. Examination of heavy minerals, the morphoscopy of quartz grains and study of micromorphologies on thin blades provide precise details of conditions of evolution. The use of these methods of investigation allows for an accurate definition of the features of the evolution of the differents types of fillings, particularly speleothems, rehandled weathered rocks as well as carbonated varves. This wealth and complexity are emphasized by a detailed study of the sedimentary sequences of the Vallier cave and of the Bergerhöhle.
Speleogenesis is approached last of all in the light of above study. Emphasis is placed on the major part played by corrosion in the temporarily phreatic zone and on its many consequences (multi-level concept, simultaneous evolution of levels, origin of deep waterlogged karsts…).
Varia tions in the base level have induced karstification in contexts in which the potential was weak. These were followed by periods of increased potential to which were added the effects of glaciation. Perched horizontal levels belong to the first stages which ended in the early Pliocene, whereas alpine shafts developed in the second context. The role of structure and the parameters governing the shape of conduits (pits, meanders, canyons) are also dealt with. The different parts of the karst are borne in mind when dealing with the strength of karstic erosion during the ice age. It notably appears that it is weak on the crests and more or less non-existent in the deep parts of the karst which are liable to flooding. Finally, a preliminary analysis of an observation of neotectonic traces is presented.
This thesis aims to provide a better knowledge of karst flow systems, from a functional point of view (behaviour with time), as well as from a structural one (behaviour in space). The first part of the thesis deals with the hydrodynamic behaviour of karst systems, and the second part with the geometry of karstic networks, which is a strong conditioning factor for the hydrodynamic behaviour.
Many models have been developed in the past for describing the hydrodynamic behaviour of karst hydrogeological systems. They usually aim to provide a tool to extrapolate, in time and/or space, some characteristics of the flow fields, which can only be measured at a few points. Such models often provide a new understanding of the systems, beyond what can be observed directly in the field. Only special field measurements can verify such hypotheses based on numerical models. This is an significant part of this work. For this purpose, two experimental sites have been equipped and measured: Bure site or Milandrine, Ajoie, Switzerland, and Holloch site, Muotathal, Schwyz, Switzerland. These sites gave us this opportunity of simultaneously observe hydrodynamic parameters within the conduit network and, in drillholes, the "low permeability volumes" (LPV) surrounding the conduits.
These observations clearly show the existence of a flow circulation across the low permeability volumes. This flow may represent about 50% of the infiltrated water in the Bure test-field. The epikarst appears to play an important role into the allotment of the infiltrated waters: Part of the infiltrated water is stored at the bottom of the epikarst and slowly flows through the low permeability volumes (LPV) contributing to base flow. When infiltration is significant enough the other part of the water exceeds the storage capacity and flows quickly into the conduit network (quick flow).
For the phreatic zone, observations and models show that the following scheme is adequate to describe the flow behaviour: a network of high permeability conduits, of tow volume, leading to the spring, is surrounded by a large volume of low permeability fissured rock (LPV), which is hydraulically connected to the conduits. Due to the strong difference in hydraulic conductivity between conduits and LPV, hydraulic heads and their variations in time and space are strongly heterogeneous. This makes the use of piezometric maps in karst very questionable.
Flow in LPV can be considered as similar to flow in fractured rocks (laminar flow within joints and joints intersections). At a catchment scale, they can be effectively considered as an equivalent porous media with a hydraulic conductivity of about 10-6 to 10-7 m/s.
Flow in conduits is turbulent and loss of head has to be calculated with appropriate formulas, if wanting any quantitative results. Our observations permitted us to determine the turbulent hydraulic conductivity of some simple karst conduits (k', turbulent flow), which ranges from 0.2 to 11 m/s. Examples also show that the structure of the conduit network plays a significant role on the spatial distribution of hydraulic heads. Particularity hydraulic transmissivity of the aquifer varies with respect to hydrological conditions, because of the presence of overflow conduits located within the epiphreatic zone. This makes the relation between head and discharge not quadratic as would be expected from a (too) simple model (with only one single conduit). The model applied to the downstream part of Holloch is a good illustration of this phenomena.
The flow velocity strongly varies along the length of karst conduits, as shown by tracer experiments. Also, changes in the conduit cross-section produce changes in the (tow velocity profile. Such heterogeneous flow-field plays a significant role in the shape of the breakthrough curves of tracer experiments. It is empirically demonstrated that conduit enlargements induce retardation of the breakthrough curve. If there are several enlargements one after the other, an increase of the apparent dispersivity will result, although no diffusion with the rock matrix or immobile water is present. This produces a scale effect (increase of the apparent dispersivity with observation scale). Such observations can easily be simulated by deterministic and/or black box models.
The structure of karst conduit networks, especially within the phreatic zone, plays an important role not only on the spatial distribution of the hydraulic heads in the conduits themselves, but in the LPV as well. Study of the network geometry is therefore useful for assessing the shape of the flow systems. We further suggest that any hydrogeological study aiming to assess the major characteristics of a flow system should start with a preliminary estimation of the conduit network geometry. Theories and examples presented show that the geometry of karst conduits mainly depends on boundary conditions and the permeability field at the initial stage of the karst genesis. The most significant boundary conditions are: the geometry of the impervious boundaries, infiltration and exfiltration conditions (spring). The initial permeability field is mainly determined by discontinuities (fractures and bedding planes). Today's knowledge allows us to approximate the geometry of a karst network by studying these parameters (impervious boundaries, infiltration, exfiltration, discontinuity field). Analogs and recently developed numerical models help to qualitatively evaluate the sensitivity of the geometry to these parameters. Within the near future, new numerical tools will be developed and will help more closely to address this difficult problem. This development will only be possible if speleological networks can be sufficiently explored and used to calibrate models. Images provided by speleologists to date are and will for a long time be the only data which can adequately portray the conduit networks in karst systems. This is helpful to hydrogeologists. The reason that we present the example of the Lake Thun karst system is that it illustrates the geometry of such conduits networks. Unfortunately, these networks are three-dimensional and their visualisation on paper (2 dimensions) is very restrictive, when compared to more effective 3-D views we can create with computers. As an alternative to deterministic models of speleogenesis, fractal and/or random walk models could be employed.
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