Karstification

The dissolution of carbonates can create spectacular features like those found in many caves. The process is termed karstification. Some reservoirs are related to Karst. Examples are the Bohai Bay Field in China or the Nang Nuan oil field in the Gulf of Thailand. These reservoirs are characterised by high initial production from the large open pore system. However, since the Karst features are connected downdip to the waterleg this is usually followed by rapid and substantial water breakthrough. ... 

In 1968 a previous neutralizing process was stopped, and the waste was injected with a pH of 3, resulting in a sharp increase in dissolved calcium in the monitoring well (Fig. 16.8). This indicated that limestone was dissolved at a high rate. The resulting karstification probably enhanced the movement of the waste in the aquifer. 

Talking about karstification often the question arises why karst phenomena do not only occur at the surface but in greater depths as well. The reason is that the carbonate dissolution is a comparatively fast process, but still takes some time, while water may cover quite a long distance along a fracture. 

Glacial ice may have been responsible for removing some of the rock that overlies the Leadville Limestone, exposing the limestone to karstification. As discussed previously, glacial ice also transported igneous and metamorphic material from exposed Precambrian bedrock westward, onto the limestone. Glacial effects on cave sedimentation and karst development vary throughout Lime Creek. 

Gustavson, T.C., Simpkins, W.W., Alhades, A. and Hoadley, A., 1981. Karstification of the Rolling Plains of the Texas Panhandle. J. Earth Surf. Process, (in press). 

Frumkin A. and Raz E. (2001) Collapse and subsidence associated with salt karstification along the Dead Sea. 

The developing law of water transmissibility is affected by many factors. The medium characteristics are internal factors influencing the water transmissibility of Ordovician top strata. However, geological structure, buried depth, karstification, filling and cementation are the main external factors influencing the water transmissibility of top strata. If there are the undeveloped structure texture, weak karstification and dense filling, Ordovician top strata can be considered as impermeable key layer. 

There are three varieties of rocky layers subjected to karstification (figures la, b, and c) ... 

Below the procedure for calculation of the slabs and strap footings taking into account the risk of the karstification is explained. 

Zhang, J.G. 2004a. Variation of mechanic property of marlite in process of karstification and weathering in Three Gorges region. Chinese Journal of Rock Mechanics and Engineering 23(7) 1073-1077. 

As a pilot in this research were served karst massifs of Permsky kray (Russia), which localized within the town of Kungur, urban settlement of Polazna, settlement of Oktyabrsky and a site of pipeline route near the settlement of Krasny Yasil (Fig. 1). These territories located within the areas of development of carbonate-sulfate karst. Natural conditions of karstification at this site were active studied over the last 50-60 years. During this period accumulated extensive material, which was partially analyzed and systematized in the course of 5-year research program Monitoring of karstic areas of Permsky krai (2006-2010). 

Estimation of impact of factors of natural conditions on the activity and scales of karstification can be obtained by the way of its comparison with karst forms and their morphometric parameters. 

Parameters of defined theoretical distributions (average values and standard deviations) of karst forms within studied areas are shown in Table 2. These parameters can be used to prognosis the karstification in areas of karst development where natural conditions of its evolution are similar with pilot territories, for which were defined theoretical distributions. 

On the areas with different hthologic types of karst are generated specific kinds of karst form. For the reliable investigations it s necessary the sufficient quantity of karst forms. Natural conditions of karstification were collected in the course of 5-year research program Monitoring of karst areas of Permskiy krai (2006 2010). 

Under visual comparison of distribution of lineament linear density zones and units of an intensive karst occurrence the connection of the latter to zones of lineament linear density zones in the range of their average values can be clearly traced. This situation is confirmed by experience of an assessment of a spatial ratio of disjunctive dissociation to karstification within various regions of classical development of both sulphatic, and carbonate karst. 

Confined aquifer formed by Cretaceous limestone of the Fm. Oviedo with calcareous conglomerates (both show karstification processes). 

The results of these studies revealed the existence, within the gypsiuns, a network of well-developed karstification, sometimes linked to tectonics accidents, and manifested by the presence of cavities whose dimensions surpass, in some cases, 4.5 m in the vertical (Pulgar et al., 1999, p. 297). 

The Table 7 shows the values of karstification calculated from cores from several of these boreholes... 

Figura 21. Isopach of gypsum layer and percentage of karstification around Ventanielles Oviedo.

Karstic landforms vary enormously in character, shape and size and are formed in wet climatic conditions at present or in the geological past. When developed in the past, surface features may be buried and hidden by more recent sediments deposited in a changed climatic environment e.g., in the Middle East, currently known for its hyper-arid conditions, widespread karstification has occurred during the wet Middle Pleistocene period (325,000-560,000 years ago) affecting the Eocene limestones (Sadiq et al, 2002). The presence of dissolution cavities and other karst-related hazards may not always be visible at the ground surface, but may have to be identified by site investigations specifically aimed at karstic features. 

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