Carbonates caves

Despite the potential problems, two recent studies provide positive results. Matthews et al. (2000) analyzed the 5D of fluid inclusions in present-day cave carbonates from Soreq cave (Israel) using the method of thermal vacuum extraction and standard techniques on cave pool water from the same cave to estimate isotopic fractionation during measurement (Aex = 5Dextracted water - 8Dcave water). After subtracting Aex from 5D... 

Two features in caves facilitate the use of stable isotopes as a palaeoarchive (1) cave air temperatures remain relatively constant throughout the year and are similar to the mean annual temperature above the cave. (2) In cool temperate climate regions, cave air is characterized by very high humidity that minimizes evaporation effects. Interest in speleothems as recorders of continental palaeoenvironments has increased considerably in recent years. The potential of speleothems as climate indicators was first discussed by Hendy and Wilson (1968) followed by Thompson et al. (1974). These early investigators already recognized the complexity of cave carbonate iso-... 

Since that time the process has been acquired by the 3 M Company, the technology developed, and given the additional name of the CAVE (Carbon Anode Vapor phase Electrochemical fluorination) Process [54]. 

Stalactites (top) and stalagmites (bottom) consist of calcium carbonate. They form when a water solution containing Ca and HCO3 ions enters a cave. Carbon dioxide is released, and calcium carbonate precipitates Ca (aq) + 2 HCOi (aq) —> CaC03(s) + H2O + C02(g). 

When the solution reaches a cave, carbon dioxide slowly escapes from the solution, and the subsequent shift in the equilibrium causes CaC03 to be precipitated. Deposits of CaC03 produce the attractive cave formations. 

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. ... 

The solubility of the carbonate in water containing carbon dioxide causes the formation of caves with stalagtites and stalagmites and is responsible for hardness in water. Other important compounds are the carbide, chloride, cyanamide, hypochlorite, nitrate, and sulfide. 

Carbon Blacks. Carbon black is one of the oldest pigments known. It was used by prehistoric peoples for painting pictures on cave walls, and commercially produced by the Chinese as early as 3000 BC. 

During the 1950s, Professor W. F. Libby (1908-1980) of the University of Chicago and others worked out a method for determining the age of organic material It is based on the decay rate of carbon-14. The method can be applied to objects from a few hundred up to 50,000 years old. It has been used to determine the authenticity of canvases of Renaissance painters and to check the ages of relics left by prehistoric cave dwellers. 

The remains of an ancient cave were unearthed. Analysis from charcoal in the cave gave 12.0 disintegrations/min/g of carbon. The half-life of C-14 is 5730 years. Analysis of a tree cut down when the cave was unearthed showed 15.3 disintegrations/min/g of carbon. How old are the remains in the cave ... 

FIGURE 10.2 Stalactites hang from the roof of a cave and stalagmites grow from the floor. Both are made of insoluble calcium carbonate formed from the soluble hydrogen carbonate ions in groundwater. 

A current 1.00-g sample of carbon shows 921 disintegrations per hour. If 1.00 g of charcoal from an archaeological dig in a limestone cave in Slovenia shows 5.50 X 103 disintegrations in 24.0 h, what is the age of the charcoal sample ... 

The results for all sites are given in Table 5.1, and are best considered by dividing sites into three groups according to isotopic nature of the matrix (i) sites with most isotopically emiched matrix carbonates (Die Kelders and Swartkrans), (ii) sites with rather less enriched carbonates (Klasies River Mouth and Makapansgat), and finally (iii) a site with depleted deposit values (Border Cave). This is summarized in Fig. 5.5. The division also fortuitously provides a range of age depths in two categories. As indicated in Table 5.1, many of these data have been published elsewhere, but the purpose for which they are considered in combination here has not been previously attempted. 

Sealy, J.C. 1996 Seasonality of rainfall around the Last Glacial Maximum as reconstructed from carbon isotope analyses of animal bones from Nelson Bay Cave. South African Journal of Science 92 441 144. 

C06-0134. The reaction that forms calcium carbonate deposits in caves is as follows ... 

Limestone caverns are among nature s most spectacular displays. These caves occur in many parts of the world. Examples are Carlsbad Caverns In New Mexico, Jeita Caves in Lebanon, the Blue Grotto in Italy, and the Jenolan Caves In Australia. Wherever they occur, the chemistry of their formation involves the aqueous equilibria of limestone, which Is calcium carbonate. Three such equilibria, linked to one another by Le Chatelier s principle, play essential roles In cave dynamics. 

Organic acid fluorescence. In a similar manner to trace constituents, such as Mg, Sr and P, concentrations of organic acids present in speleothem calcite are sufficient to observe variation at temporal scales of less than annual in some cases (e.g.. Baker et al. 1993, Shopov et al. 1994). Organic acids (humic and fulvic) are formed in the soil by humification, and transported to the cave void by percolating waters where they are entrapped in precipitating carbonates. Under certain circumstances, where precipitation patterns are strongly seasonal and the nature of vadose percolation is such that seasonal mixing is incomplete, bands with different luminescent intensities can be differentiated after excitation with UV radiation. In other cases, bands are not observable but secular... 

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