Deep-burial environment

Although cementation is a process that can occur throughout the life of a sedimentary carbonate body, the dominant processes and types of cements produced generally differ substantially between those formed in the shallow-meteoric and deep-burial environments. Mineralogic stabilization (i.e., dissolution of magnesian calcites and aragonite, see Chapter 7) commonly drives cement formation during the early shallow-burial period, whereas the previously discussed processes of pressure solution and neomorphism are more important in the deep-burial environment. The pore waters in which cementation takes place also tend to differ substantially between the two environments. In shallow subsurface environments, cementation usually takes place in dilute meteoric waters that are oxic to only... 

Choquette P.W. and James N.P. (1987) Diagenesis 12. Diagenesis in limestones-3. The deep burial environment. Geoscience Canada 14,3-35. 

The other major factor that considerably retards decomposition of buried bodies is the surrounding soil environment. A body buried in soil is protected from the temperature fluctuations usually experienced in an ambient environment (Galloway, Walsh-Haney, and Byrd 2001). The extent of protection is also dependent on the depth of burial, as temperature will decrease with soil depth. In a deep burial environment, the temperature will be relatively cool, thus slowing the rate of decomposition (Rodriguez and Bass 1985). Shallow burials of less than 1 ft. will experience temperature fluctuations similar to the ambient temperature. Hence, decomposition in a shallow grave will proceed more rapidly than in a deep burial but still at a slower rate than a body decomposing on the soil surface (Rodriguez 1997 Weitzel 2005). 

Sur cia.1 Deposits. Uraniferous surficial deposits maybe broadly defined as uraniferous sediments, usually of Tertiary to recent age which have not been subjected to deep burial and may or may not have been calcified to some degree. The uranium deposits associated with calcrete, which occur in Australia, Namibia, and Somaha in semiarid areas where water movement is chiefly subterranean, are included in this type. Additional environments for uranium deposition include peat and bog, karst caverns, as well as pedogenic and stmctural fills (15). 

In a study of chlorite in sedimentary rocks, Hayes (1970) concluded that type-I chlorite most likely represents authigenic chlorite (because of its relative instability) the lib stable poly type, in most cases, would indicate that the chlorite is detrital and reflects formation by igneous or metamorphic processes. Hayes points out that a few of his samples of lib chlorite appear to be authigenic, probably formed in a higher-temperature environment caused by deep-burial or hydrothermal activity. 

The processes of livor, rigor, and algor mortis can be useful indicators of a recently deceased person, but the processes may have expired by the time a body is placed in a shallow or deep grave site. Once these changes have passed, soft-tissue decomposition proceeds through the processes of autolysis and putrefaction (Fiedler and Craw 2003). In a burial environment, it is these processes that are likely to result in the disintegration of soft tissue and skeletonization. 

Carbon is the twelfth most abundant element in the Earths crust, although it accounts for only c.0.08% of the combined lithosphere (see Box 1.2), hydrosphere and atmosphere. Carbon-rich deposits are of great importance to humans, and comprise diamond and graphite (the native forms of carbon), calcium and magnesium carbonates (calcite, limestone, dolomite, marble and chalk) and fossil fuels (gas, oil and coal). Most of these deposits are formed in sedimentary environments, although the native forms of C require high temperature and pressure, associated with deep burial and metamorphism. 

At all over the entire history of the earth the sum of all (non-radioactive) elements is constant despite exhausting of hydrogen and helium into space. The loss of hydrogen to space (and later its deep burial in hydrocarbons) is the reason for the changing redox state from a low oxygen to a more oxidized environment. This happens with photolysis of water (2.1) and hydrides such as CH4, NH3 and H2S (2.2) and later with marine photosynthesis (2.3)... 

The geological environments for these assemblages are those of weather ing, deep-sea floor sediments and continental shelf sediments, or shallow burial of these materials as sedimentary or tuffaceous rocks. 

Vanden Heuvel, 1966 Paquet, 1970), continental lakes (Millot, 1964 McLean, et al., 1972 Parry and Reeves, 1968) and they appear in shallow seas, continental slope and deep-sea sediments (Latouche, 1971 Bonatti and Joenesu, 1968 Hathaway and Sachs, 1965 MUller, 1967 Chamley, et al... 1962 Millot, 1964 Bowles, et al., 1971 Blanc-Vernet and Chamley, 1971 Fleischer, 1972). They are present in carbonates and salt deposits (Bartholome, 1966b Braitsch, 1971 Millot, 1964 Peters and von Salis, 1965). There seems to be no exclusion of either species from any of these environments. There is little conclusive evidence for their diagenetic formation during burial and lithification processes but the possibility should be considered (Millot, 1964). 

Many chalks undergoing burial diagenesis in the present oceanic realm and those exposed on land were originally pelagic foram-nannofossil calcite oozes. However, calcareous oozes deposited in the periplatform environment are compositionally more complex. These oozes represent transitional carbonate deposits found between carbonate banks and the deep sea (Schlager and James,... 

The available literature clearly shows that fungi are present in even the deepest sediments of the sea, and therefore could potentially be buried with sediments. Little is known about marine filamentous fungi and yeasts, and almost nothing about their life-cycles or metabolism under deep-sea and sub-sea-floor conditions. If they survive burial, they will eventually become part of the sub-sea-floor biosphere. No direct data describe how long fungi can survive in subsurface environments. Data from dried soil specimens indicate that fungi survive fewer than 50-100 years separated from their autochthonous surface environment (Sneath, 1962). However, sub-sea-floor conditions may very well be more favourable for preservation than are soil conditions. 

In January, 1976, the Environmental Protection Agency (17, 18) reported that radioactive material migrated from a surface burial facility and extended to the surrounding environment for several hundred feet from its original site. Radioactive material was detected in surface soil samples, in soil cores, in sediments from deep monitoring wells, and in sediments from intermittent streams which drained the burial sites. Again, whenever possible, if carcinogenic material cannot be rendered harmless, it should be disposed of by incineration. 

The transformation of opal-A to opal-CT generally begins at 35-50 °C, corresponding to burial depths of hundred of meters. In some environments this temperature may be as low as 17-21 °C (Matheney and Knauth, 1993 Monterey Formation) or even 0-4 °C (Botz and Bohrmann, 1991 Antarctic deep sea). The acoustic properties of the sediment are altered during the transformation to opal-CT, typically providing an acoustic reflector of the diagenetic front (Calvert, 1983 Tribble et al., 1992). Opal-CT, also known as porcelanite, exhibits X-ray characteristics of low cristobalite and tridymite (Figure 4). This mineral exists as... 

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