Burial conditions

Materials that have been buried underwater cause a special problem. Waterlogged woods and leathers (139), although quite stable under such burial conditions, are ia danger of irreversible damage through drying out upon recovery. Indeed, after excavations from bogs or upon recovery from underwater sites, these items need to be stored underwater until laboratory treatment. 

A large number of archaeological artifacts are found in burial conditions. Water acting as a solvent, as well as a carrier of ionic species coming from the soil, is responsible for the migration of the latter—the acid/alkaline attack on the object material and further lixiviation of materials and ionic species from the object. Thus, determination of physical and chemical properties of the soil (pH, conductivity, chemical composition, etc.) is of great importance. 

While it is often stated that few textiles survive from archaeological sites in eastern North America, some examples with preserved features have been uncovered. These materials have survived burial conditions because of the peculiarities of the burial context or due to some feature of their composition that made them less susceptible to microbial degradation. These preserved materials often are very fragile handling them results in the loss of small particulate material. Rather than discarding this particulate, collection and analysis may provide some clues to the content and condition of the artifact. 

Even Ca, the element we used to normalize all our other measures, may be subject to post-depositional alteration. Moreover, such alteration may vaiy depending on local environmental conditions. Such a factor may account for some of the overlap or blurring we see between regional elemental signatures in our prehistoric samples. Without knowing exactly how much change may have taken place in Ca concentrations in different burial conditions, it is difficult in such sourcing studies to account for this possibility. 

In the course of time it has been unambiguously demonstrated that humic- and fulvic acids interact with metal cations by forming rather stable, and often soluble complexes(1 2). The increasing awareness of a possible pollution of the environment, e.g. in connection with the disposal of nuclear waste, emphasizes the need for additional knowledge about the interaction between relevant metal ions, e.g. radionuclides commonly present in nuclear waste, and humic substances. The possible presence of soluble and rather stable complexes may play an important role in determining the migration behavior of the metal ions under shallow land burial conditions. The influence of humic- and fulvic acids on the migration behavior of metal ions has been discussed previously (2-6),... 

Figure 8.5. The influence of dissolved NaCl on pK Sp (-logarithm of stoichiometric solubility constant for calcite) under typical burial conditions. (After Nagy and Morse, 1990.)...

The two most common natural textile fibers encountered in modern fabrics have contrasting responses to soil burial. Under most soil burial conditions cellulose will degrade rapidly whereas wool will decay at a slower rate. These phenomena are demonstrated by the degradation of textile fibers from the Experimental Earthworks Project (Janaway 1996a). Figures 7.9 and 7.10 compare wool and linen buried in the chalk environments at Overton Down for 32 years. The linen is denatured to the point that there is little surviving morphology, whereas the wool retained some fiber structure. 

The excavation of a clandestine grave had revealed the largely skeletonized remains of a young man who had been buried for 5 years in a biologically active soil. The subsoil was clay, with the grave cut being water-filled at the time of the excavation due to a fractured field drain. It was covered by a stack of horse manure used as agricultural fertilizer that had considerably modified the burial conditions. The body had been buried clothed, and items of textile were recovered with the human remains. These included cloth, metal, and leather that had been subject to considerable differential preservation. 

The stability of buried metals largely depends on a combination of pH and redox (Edwards 1996). Under high redox values (oxidizing conditions) most metals will easily corrode, whereas under low redox values (reducing conditions) they will tend to remain as uncorroded metal. In addition, acidic conditions (low pH) will assist corrosion, whereas alkaline conditions will tend result in the formation of a stable corrosion matrix in most metals. Thus, in a well-drained, acidic sand or gravel site, all metals except the most inert (e.g., gold) will corrode rapidly and extensively. However, under most other burial conditions, most metal will be capable of recovery, albeit in a corroded state even after many centuries. 

Additional Methods of Analysis. Racemization studies (11,12,13) hold considerable promise for the dating of ancient bone samples. If the diflBculties of shorter time span compared with those already studied, limited sample universe, and nonuniform burial conditions can be overcome, the application of this procedure to Ancient Near Eastern ivory specimens would be useful. Also of interest is the possibility (19,20,21,... 

Today, basin-scale mass transfer of some materials (e.g., helium, water, and petroleum) is unquestioned (e.g.. Hunt, 1996). OAer materials (e.g., titanium and the REEs) are sufficiently mobile to appear within authigenic precipitates, but are likely to be immobile on the scale of a hand specimen. Mobilities of the major elements that make up sandstones and shales (silicon, aluminum, calcium, sodium, potassium) remain controversial. Conflicting notions about processes in rock suites across the wide range of burial conditions and alteration show that fundamental questions remain unanswered about the nature of the volumetrically significant processes within a major segment of the rock cycle. It is very likely that something is wrong, or at least inadequate. 

Berthierines having experienced diagenetic burial conditions contain about one-third as much aluminum as iron their average alumina content is, therefore, comparable to that of other chlorites (Velde, 1973). 

In general, the minerals now identified as chamosite are found in iron ore bodies of sedimentary origin (e.g., Maynard, 1986 Fernandez and Moro, 1998 Wiewora et al, 1998 Kim and Lee, 2000). Chamosite associated with iron oxides appears to follow a compositional trend from iron oxides plus kaolinite to chlorite, as indicated in Figure 8, using the data of Velde (1989). The recombination of iron oxide in the presence of kaolinite gives an aluminous, ferrous mineral, chamosite. This mineral is formed under burial conditions where ferric iron oxide is reduced to feiTous iron which is rapidly incorporated into a 7 A chlorite mineral. Both chamosite and berthierine result from the reduction of ferric iron to ferrous iron. 

Starch and cellulosic materials are frequently used as fillers in degradable materials. The addition of starch to LDPE in combination with a pro-oxidant increases the photooxidation rate and the formation of hydroperoxides and carbonyl groups. Starch alone does not increase the photooxidation rate. The addition of starch to LDPE increases its stability in 80°C water. Slower degradation in water is due to leaching out of the pro-oxidant. The addition of starch causes biodegradation process under soil burial conditions. Further increase in the degradation rate can be achieved by preheating polyethylene filled with starch. ... 

In the Furado area there was no interruption in burial conditions caused by post-rift uplift, and the reservoirs remained at similar depths during this phase. Therefore, it is uncertain whether or not the mesogenetic constituents were precipitated during syn-rift or post-rift phases. Some C2 calcite, which engulfed and thus post-dated albite, chlorite, illite, quartz and trace amounts of pyrite, barite and sphalerite, is interpreted to have precipitated during this time interval. This C2 calcite is characterized by a chemical and isotopic composition similar to the carbonate cements formed during the syn-rift subsidence phase. 

Another similarity between Monterey and Stevens dolomites is their excess Ca, typical of Tertiary dolomite compositions. Apparently these non-stoichiometric compositions are retained in San Joaquin dolomites at temperatures at least as high as 100°C (their present burial condition). Stevens dolomites are generally much richer in Fe than Monterey dolomites, possibly owing to the alteration of Fe-bearing minerals in the Stevens sandstones. 

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