Carbon isotope ratios for

Figure 3.2. Average carbon isotopic ratios for all human, herbivore, carnivore, and omnivore bone samples from the European Holocene in the data base A Uncorrected ratios (Cu) B climate-corrected ratios (Cc). Only countries with more than 10 samples are included. For a description of the climatic correction procedure see text. 

TabU IV. Carbon Isotope Ratios for Martinsburg Anthraxolite and Calcite"... 

Harper DB, Kalin RM, Hamilton JTG, Lamb C (2001) Carbon Isotope Ratios for Chloromethane of Biological Origin Potential Tool in Determining Biological Emissions. Environ Sci Technol 35 3616... 

Variability in Carbon Isotope Ratios. For the radiocarbon method, the basic physical measurement used to index time is the ratio. 

Harper D. B., Kalin R. M., Hamilton J. T. G., and Lamb C. (2001) Carbon isotope ratios for chloromethane of biological origin potential tool in determining biological emissions. Environ. Sci. Technol. 35, 3616-3619. 

A plot of carbon isotope ratios for each of the oil fractions, known as a Galimov plot, is shown... 

Fig. 4. Seasonal changes in (a) the concentrations of total carbon (TC) and total organic carbon (TOC) and (b) stable carbon isotopic ratios for TC and TOC in aerosol samples. TOC is defined as total carbon that remained after HCl fume treatment.

Stable carbon isotope ratios for the saturated and aromatic hydrocarbon fractions of the Algerian oil samples support a genetic relationship between the Silurian Hassi Messaoud and Zemlet oil samples, which differ from the Devonian Assekaifaf, Dome, Zarzaitine, and Oued Zenani samples (Table 4). However, these isotopic differences are small (< l%o) and cannot be generally applied because of larger differences that might be imposed by secondary processes, such as thermal maturity. The calculated canonical variables (Sofer, 1984) for the six oil samples indicate marine source-rock organic matter (CV < 0.47), but lack systematic differences between the Silurian and Devonian samples. 

Table 4. Stable carbon isotope ratios for saturated and aromatic hydrocarbons and the calculated canonical variable...

The isotopic composition and the pattern of isotopic compositions among certain n-alkanes and isoprenoids (Table 6) and gasoline-range branched and cyclic hydrocarbons (Table 7) measured by CSIA differ from the Silurian-sourced Hassi Messaoud and Zemlet oil samples compared to the four Devonian samples. Except at mC and wCg, the Zemlet oil sample has more negative stable carbon isotope ratios for the Ce-Cig w-alkanes than the other Algerian oil samples (Fig. 7). The isotopic compositions of w-alkanes in Hassi Messaoud oil sample more closely resemble the other samples than the Zemlet sample, except at nCe and possibly nCf. Devonian source rock input may affect the heavier components in the Hassi Messaoud oil sample or their isotopic compositions may simply not be diagnostic of Silurian versus Devonian oil. The nCe in Hassi Messaoud and Zemlet oil samples is substantially depleted in (l.l-2.3%o) compared to the other samples. 

Hassi Messaoud and Zemlet oil samples have more negative CSIA stable carbon isotope ratios for several gasoline-range cyclic hydrocarbons (Fig. 8), especially methylcyclopentane, cyclohexane, and methylcyclohexane sO.6, 1.9, and 0.2%o, respectively) compared to the other Algerian oil samples. The pattern of isotopic ratios among these three compounds also systematically varies. Unlike the other oil samples, cyclohexane is more depleted in than methylcyclopentane and methylcyclohexane in the Hassi Messaoud and Zemlet oil samples. 

Fig. 7. Zemlet oil has generally more negative stable carbon isotope ratios for C6-C19 u-alkanes than the other Algerian oil samples (Table 6). The largest isotopic difference between Hassi Messaoud and Zemlet (Silurian) oil samples and the Devonian samples occurs at nC. ...

Fig. 8. Hassi Messaoud and Zemlet oil samples have more negative stable carbon isotope ratios for methylcyclopentane (MCyC5), cyclohexane (CyC6), methylcyclohexane (MCyC6), and several other light hydrocarbons compared to the Devonian oil samples (Table 7). The nC and nCj alkanes show similar results (Fig. 7). Unlike the other samples, the Hassi Messaoud and Zemlet oil samples have cyclohexane that is isotopically more negative than methylcyclopentane and methylcyclohexane.

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