Terrestrial shell

Biogenic carbonates may be derived from ostracode and aquatic mollusk shells, or terrestrial mollusk shells. Terrestrial mollusks obviously do not carry any record of lake water and must be removed. The of biogenic fractions is typically offset from thermodynamic... 

Zinc normally aids wound healing in terrestrial invertebrates. Wounding of the optic tentacle, foot tissue, and partial shell removal in Helix aspersa, a terrestrial gastropod, resulted in deposition of zinc in the wound area after 2 to 5 days. Increased zinc in Helix wound areas may be necessary to promote protein synthesis, collagen formation, and mitotic cell division (Ireland 1986). 

The calcium carbonate shells of marine microfauna are a large repository of terrestrial calcium and constitute a potential record of changes in the cycling of calcium at and near the earth s surface (Zhu and MacDougall 1998 De La Rocha and DePaolo 2000 Schmitt et al. 2003a,b). To understand the record held in deep sea carbonate sediments, it is necessary to document any Ca isotopic fractionation that occurs between dissolved seawater Ca and carbonate shell material. 

It is essential to understand the isotopic variability within authigenic minerals that form the basis of terrestrial paleoclimate records and between such samples that are isochronous within an outcrop of a stratigraphic formation. Except for variability studies in biogenic materials (teeth, bone, shells) (e.g., Kohn et al. 2002), we know of no paleoaltimetry studies that have examined this natural variability in authigenic or pedogenic proxy materials. Such variability studies should be conducted before any quantitative estimates of paleoelevation can be made. 

Mollusca Clams, snails, slugs, cephalopods, chitons Soft body, most with hard outer shell marine, freshwater and terrestrial... 

The shells of terrestrial tortoises and freshwater turtles have also been used in some of the same ways as the larger marine turtles. Whole turtle bodies, with the soft tissue and most of the skeleton removed, have been made into pouches and specialized containers for personal and ceremonial use. 

With improved possibilities for infrared spectroscopy, broad extinction bands around 9.7 pm and 18 pm have been detected, which were ascribed to the stretching (Woolf Ney 1969) and bending (Treffers Cohen 1974) modes in the SiC>4 tetrahedron forming the building block of silicates, because they correspond to known absorption bands seen in all terrestrial silicates. These bands are also seen in the emission from dust shells around O-rich stars. This gave the first observational hints on the mineralogy of the silicate dust. The smooth, structureless nature of the bands indicated that the silicates in the ISM and in circumstellar dust shells are amorphous. 

Table I. Paired Terrestrial Organics/Marine Shell Samples from the West Coast of North America...

It is important to emphasize that a discussion of the problems associated with marine shell could be repeated for any sample type/geo-chemical environment where the contemporary radiocarbon values may not be in equilibrium with the atmosphere. In such cases, a specific contemporary standard must be used for each sample type or geochemical environment which can be related to the terrestrial biological radiocarbon standard. Special standards and/or correction values would, for example, be required for specifically defined oceanographic regions in the case of marine shell, standards for specific fresh water shell or gastropod geochemical environments, standards for Arctic and Antarctic specimens, and specific soil carbonate environments (75). 

Recent converter hardware development has concentrated on flame heated devices for terrestrial topping cycle applications. Significant progress has been made with chemical vapor deposited silicon carbide as the oxidation protection hot shell. Flame heated converters have now been operated by Thermo Electron Corporation with emitter temperatures over 1700 K for 7000+ hours ( ). 

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