Occurrence of Limestones

Many other terms are used in describing limestone. The more common ones, including those already mentioned, are listed in the Glossary of Terms (Annex 1). 

Limestone deposits cover about 10 % of the earth s land surface [2.4,2.7] and are found in the majority of countries. Three major inter-related factors have had a major influence on the occurrence of limestones around the world, namely climate, geotechnics and sea level. 

Because the original ancient continents formed in relatively high southerly latitudes, those parts of the continental plates which have remained south of 30 °S generally have little limestone. Conversely, those continents which 

Conversely, regional up-lift, coupled with lowering sea levels, raised the deposits above sea level and into the positions in which they are now found. 

As a result of the above factors, every deposit of limestone has a unique history in terms of the carbonate-producing organisms/mechanisms, the sedimentary environment, the diagenetic mechanism, and geotechnics involved. 

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Clay intercalations, sand inclusions or soft moist limestone strata are forced aside by the rotary percussive drill bit and remain sticking to the wall of the borehole, so that a proper sample of such material is not obtained. Nor is it possible to get information on the presence of any cavities in the rock. The most serious drawback of rotary percussive drilling, however, is that it offers no possibility of sampling the rock as such and thus forming a reliable picture of the occurrence of limestone in the deposit under investigation. 

Argentite, natural occurrence of, 22 668 Argentium Sterling, 12 562 Argentothiosulfate complexes, 19 215 Argillaceous limestone, 15 26 Argillic alteration zones, gallium in,... 

Cinnabar occurs in veins or may be in masses in shales, slates, limestones and similar rocks due to the impregnation by mineral-bearing solutions or as replacements. The former U.S.S.R., former Czechoslovakia, Bohemia, Bavaria, Italy and Spain have furnished excellent specimens. The most important of the world s mercury deposits is at Almaden in Spain. Italy, Peru, Surinam. China and Mexico have commercially valuable occurrences of cinnabar. In the Uniled Slates this mineral is found in California (most important deposit), Nevada, Utah. Texas and Oregon. Cinnabar is the chief ore of mercury. Its name is supposed to be of Hindu origin. 

Coal is Interspersed as individual beds within other types of sedimentary rock beds, including sandstones, limestones, clays, shales, and mixtures of these materials. The plant material that ultimately became coal deposits was accumulated in upland bogs, coastal or near-coastal swamps, or della plains. It is envisioned that the conditions were somewhat similar to the conditions existing today in the Okefenokce Swamp in Georgia or the Everglades of Florida. These areas may have varied from a few acres in several hundreds of square miles (hectares/square kilometers). Hence, the variation in ihe occurrence of coal as we find it today. 

Figure 10.18. Number of occurrences of Phanerozoic ironstones (upper diagram, data from Van Houten and Bhattacharyya, 1982) and odlitic limestones (lower diagram, data from Wilkinson et al., 1985) as a function of geologic age. The relative sea level curve is that of Hallam (1984). Minima in occurrences appear to correlate with times of sea level withdrawal from the continents and major cycles of orogenesis (Caledonian, Hercynian, and Alpine).

Composite cements may contain mineral additions other than, or as well as, ones with pozzolanic or latent hydraulic properties. Regourd (R34) reviewed the use of ground limestone, which is widely used in France in proportions of up to 27%. The limestones used consist substantially of calcite, with smaller proportions of quartz or amorphous silica and sometimes of dolomite. They must be low in clay minerals and organic matter because of the effects these have on water demand and setting, respectively. The XRD peaks of the calcite are somewhat broadened, indicating either small crystallite size or disorder or both IR spectra confirm the occurrence of disorder. 

Despite the wide occurrence of calcareous glacial, aqueous and deluvial deposits, most soils of the region do not contain carbonates in the soil profiles. Rendzinas formed on moraines rich in limestones or directly on the eluvium of limestones, found in the lacustrine northern part of the region, are an exception. The deep migration of carbonates is associated with intense leaching of the soils and the absence of any period of drying or freezing. 

Research-Cottrell has demonstrated the commercial availability of limestone flue gas desulfurization on a 115 MW installation. Certain chemistry and process considerations were taken into account in designing and operating these systems. Methods have been developed to minimize the occurrence of potential problems. 

R. Hermann reported the occurrence of a basic lead chromate in the limestone of Beresowsk, Urals, and he called it melaoochroite— from jiieAa , black and xpoa, colour—but since the colour of the mineral is red, not black, E. F. Glocker changed the name to pkoenicochroite—-from otw/ceo , deep-red and colour—and... 

In addition to the irregular or highly pinnacled bedrock profile and solution cavities, the occurrence of very weak slumped materials immediately above the limestone bedrock is yet another geological feature of great concern to the foundation engineers. These weak slumped materials are characterised by their very low Standard Penetration Test (SPT), N values ofFigure 14.4. Their origin or formation plus additional characteristics have been discussed previously (Tan 1988,... 

Tan, B.K. 1988. A short note on the occurrence of a soft soil zone above limestone bedrock. Proc. Int. Conf. 

The Tertiary basin of Asturias (see Figure 1) was partially occupied by small lakes and ponds of muddy water (bogs), in which borders developed a rich vegetation of algae. This lake system, well characterized by limestone, marly limestone ancl white and green marl with some of charophyte oogonia, is done locally evaporitic with occurrence of gypsiferous sedimentation. 

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