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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 formation of the Oligocene « calcaires à Astéries » in the region of « Entre-deux-Mers » is affected by a karstification with subhorizontal caves that drained rivers from swallow-holes to resurgences. Observations in quarries show that ghost-rock alterites are present. This paper describes the ghost-rocks in the quarry of Piquepoche exploiting the Frontenac stone. We have studied horizontally developed ghost-rocks with vertical extensions still containing the residual alterite. They can be badly consolidated calcarenites up to soft material which has been sampled. Speleogenesis is reviewed in the frame of the mechanical erosion of the alterite of a horizontal ghost-rock followed by an incision by free-flowing waters which form a passage with promontories and potholes. Finally, we show that ceiling anastomoses can form by ghost-rock karstification.
The Cliefden Caves have developed in the Late Ordovician Cliefden Caves Limestone mainly by solution in the phreatic zone. Speleogenesis has been inhibited in steeply dipping thinly bedded limestone and shows a high degree of structural control. Collapse has been significant in late stage development of the caves. Much sediment has been deposited in the four caves studied in detail - Main Cliefden, Murder, Boonderoo and Transmission. Formed in the phreatic zone, layered clay fill is the earliest sediment deposited and occurs in all but Transmission Cave. The phosphate mineral heterosite is found in these sediments. Subaqueous precipitation deposits deposited in the phreas or vadose pools are distinguished from speleothems by their texture. Aragonite is inferred to have been deposited in these sediments and to have since inverted to calcite. Friable loam and porous cavity fill are the most common vadose deposits in the caves. Vadose cementation has converted friable loam to porous cavity fill. Speleothem deposits are prolific in Main Cliefden, Murder and Boonderoo Caves. Helictites are related to porous wall surfaces, spar crystals result from flooding of caves in the vadose zone and blue stalactites are composed of aragonite. Cliefden Caves belong to that class proposed by Frank (1972) in which deposition has been more important than downcutting late in their developmental history.
Isaacs Creek Caves are situated in the Hunter Valley of New South Wales and form a distinct unit within the Timor karst region. The larger caves such as Man, Helictite and Belfry all show evidence of early development under sluggish phreatic conditions. Nevertheless later phases of dynamic phreatic and vadose development occurred in Belfry and Helictite caves. In the case of Helictite Cave sluggish phreatic, dynamic phreatic and vadose action may have operated simultaneously in different parts of the same cave. After each cave was drained through further valley incision by Isaacs Creek, extensive clay fills derived from surface soil were deposited in it. There has been considerable re-excavation of the fills; in Main Cave younger clay loams have partially filled the resulting cavities and thus underlie the older clays. The earliest speleogenesis took place in Main Cave which pre-dates the valley of Isaacs Creek. This cave now lies in the summit of Caves Ridge about 100m above the modern valley floor. Helictite and Shaft Caves formed when the valley had been cut down to within 30m of its present level and some early phreatic development also took place in the Belfry Cave at this time. Later phases of dynamic phreatic and vadose development in Belfry Cave occurred when the valley floor lay about 12m above its present level and can be correlated with river terraces at this height. Evidence from cave morphology, isotopic basalt dates and surfaces geomorphology indicates that Main Cave formed in the Cretaceous and that Helictite Cave, Shaft Cave and the early development in Belfry Cave date from the Palaeogene. Although the dynamic phreatic and vadose action in Belfry Cave is more recent, it may still range back into the Miocene. This is a much more ancient and extended chronology than has hitherto been proposed for limestone caves and is in conflict with widely accepted ideas about cave longevity. Nevertheless evidence from Isaacs Creek and other parts of the Hunter Valley indicates that the caves and landforms are ancient features and thus notions of cave longevity developed in younger geological environments of the northern hemisphere do not apply in the present context.
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