Deprecated: Function get_magic_quotes_gpc() is deprecated in /home/isthin5/public_html/addon-domains/speleogenesis.info/template/toolbar_right.php on line 7
Search KARSTBASE:
Search in KarstBase
|
|
Kartchner Caverns, located near Benson, Arizona, USA, is an active carbonate cave that serves as the major attraction for Kartchner Caverns State Park. Low-impact development and maintenance have preserved prediscovery macroscopic cavern features and minimized disturbances to biological communities within the cave.. The goal of this study was to examine fungal diversity in Kartchner Caverns on actively-forming speleothem surfaces. Fifteen formations were sampled from five sites across the cave. Richness was assessed using standard culture-based fungal isolation techniques. A culture-independent analysis using denaturing gradient gel electrophoresis (DGGE) was used to assay evidence of community homogeneity across the cave through the separation of 18S rDNA amplicons from speleothem community DNA. The culturing effort recovered 53 distinct morphological taxonomic units (MTUs), corresponding to 43 genetic taxonomic units (GTUs) that represented 21 genera. From the observed MTU accumulation curve and the projected total MTU richness curve, it is estimated that 51 percent of the actual MTU richness was recovered. The most commonly isolated fungi belonged to the genera Penicillium, Paecilomyces, Phialophora, and Aspergillus. This culturebased analysis did not reveal significant differences in fungal richness or number of fungi recovered across sites. Cluster analysis using DGGE band profiles did not reveal distinctive groupings of speleothems by sample site. However, canonical correspondence analysis (CCA) analysis of culture-independent DGGE profiles showed a significant effect of sampling site and formation type on fungal community structure. Taken together, these results reveal that diverse fungal communities exist on speleothem surfaces in Kartchner Caverns, and that these communities are not uniformly distributed spatially. Analysis of sample saturation indicated that more sampling depth is required to uncover the full scale of mycological richness across spelothem surfaces.
Kitava is the most easterly island of the Trobriand group. It is an uplifted coral atoll, oval in plan, with a maximum diameter of 4 1/2 miles. The centre of the island is swampy and surrounded by a rim that reaches a height of 142 m. Caves occur in various parts of the rim and several have been described in a previous article (Ollier and Holdsworth, 1970). One of the caves, Inakebu, is especially important as it contains the first recorded cave drawings from the Trobriand Islands. Inakebu is situated on the inner edge of the island rim at the north-eastern end of the island. Map 1 shows the location of the cave on Kitava Island. Map 2 is a plan of the cave, surveyed by C.D. Ollier and G. Heers. The location of the cave drawings is shown on the plan. Inakebu is a "bwala", that is a place where the original ancestor of a sub-clan or dala is thought to have emerged from the ground. The bwala tradition is common throughout the Trobriands and neighbouring islands. It has been described by many writers on the anthropology of the area, and was summarised in Ollier and Holdsworth (1969). The people believe that if they enter such places they will become sick and die. Until November, 1968, no member of the present native population had been in the cave, though there is a rumour that a European had entered it about 20 years before, but turned back owing to lack of kerosene. It must be admitted that this tale sounds rather like the stories one hears in Australia that Aborigines were afraid of the dark caves and therefore did not go into them. In fact, the many discoveries in the Nullarbor Plain caves show that they did, and the cave drawings in Inakebu show that someone has been in this cave. The point is that it does not seem to be the present generations who entered the caves but earlier ones; people from "time before" as they say in New Guinea. The first known European to enter the cave was Gilbert Heers, a trader in copra and shell who lived on the nearby island of Vakuta. He went into the cave on 8 November 1968 accompanied by Meiwada, head of the sub-clan associated with Inakebu, who had never been inside before. Heers and Meiwada investigated the two outer chambers but then turned back because they had only poor lights. They returned with better light on 15 November. Since they had not become sick or died, they then found seven other men willing to accompany them. They found the narrow opening leading to the final chamber, and discovered the drawings. None of the men, many of whom were quite old, had ever seen the drawings or heard any mention of them before. The drawings are the only indication that people had previously been in this deep chamber. There are no ashes or soot marks, no footprints, and no pottery, bones or shells such as are commonly found in other Trobriand caves, though bones and shells occur in the chamber near the entrance. With one exception, the drawings are all on the same sort of surface, a clean bedrock surface on cream coloured, fairly dense and uniform limestone, with a suitably rough texture. Generally the surface has a slight overhang, and so is protected from flows or dripping water. On surfaces with dripstone shawls or stalactites, the drawings were always placed between the trickles, on the dry rock. We have found no examples that have been covered by a film of flow stone. The one drawing on a flow stone column is also still on the surface and not covered by later deposition. A film of later deposit would be good to show the age of the drawings, but since the drawings appear to have been deliberately located on dry sites the lack of cover does not indicate that they are necessarily young. There are stencil outlines of three hands, a few small patches of ochre which do not seem to have any form, numerous drawings in black line, and one small engraving.
First investigated on the ground in June 1972, the Nahanni karst of northern Canada is the most complex karst terrain yet reported from high latitudes. It is centered at 61°28' N, longitude 124°05' W and lies within the zone of discontinuous permafrost. Mean annual temperature is 24°F and mean total precipitation 22.3 inches. Principal karst forms are fracture-located karst streets and irregularly-shaped closed depression called karst platea which may be up to 600 feet in depth. Platea often contain karst towers which are residuals of wall recession. Vertical-walled pond dolines up to 120 feet deep are common in bare karst areas while subjacent karst collapse, subsidence and suffosion depressions occur on marginal shale- and drift-mantled surfaces. Three small poljes have been identified, two produced entirely by solution, the other a structural form. These are periodically inundated. There are several peripheral fluvial canyons up to 3,000 feet deep that are blocked by glacial drift and which presently drain underground. Similarity in the hydrogeological properties of Nahanni Formation limestones at a variety of scales has led to the development of morphologically-identical karst forms which range in size from inches up to hundreds of feet. Furthermore, many of these landforms are part of a developmental sequence that at one scale links vertical-walled dolines, karst streets, platea and poljes; and at another links solution pits, grikes and joint hollows on limestone pavements. The evidence suggests that poljes form by the coalescence of dolines and uvalas just as Cvijic suggested in 1918. In attempting to explain the almost "tropical" nature of the sub-arctic Nahanni karst landform assemblage, a number of facts are of importance.
(a) The Nahanni Formation limestones have been highly warped and intensively fractures during the past one million years. Open fractures have encouraged karstification by allowing easy movement of water underground. Warping has provided the relief necessary for the development of solutional forms with a distinct vertical component.
(b) The karst can not be considered relict because it was glaciated during the Pleistocene. In addition the hydrological activity in it today is comparable with that in many humid tropical karst areas.
(c) Solutional denudation rates governed by aspects of surficial and bedrock geology may in some localized areas be equivalent to rates in humid tropical carbonate regions.
(d) At present rates, the most highly developed forms could have been produced within the last 200,000 years and because there is evidence to indicate that the karst may not have been glaciated for up to 250,000 years, such a period has been available for solutional development.
Because the Nahanni region has not been glaciated for an extremely long period, it may be one of only a few high-latitude carbonate terrains that have had time to develop fully. Its very existence questions the validity of the concept that the intensity and direction of karst development is climate-controlled. In the Nahanni at least, the structural and lithological properties of the host limestone appear to have been of greater importance. The labyrinth karst type present in regions of humid-tropical to sub-arctic climate, is an outstanding example of a structurally-controlled karst landscape. It may well be that the same controls also influence the distributions of other karst types.
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.
The microstructure of the surfaces of quartz and grains can reveal their history prior to their deposition in a cave. The scanning electron microscope is the ideal tool for such studies. This paper presents examples of the sort of information obtainable from such a study, drawing examples from caves in Australia, Papua New Guinea and Norway.
|
|
|