engleski

Rudjer Bošković Institute radiocarbon measurements V

The following list contains dates of samples measured since our previous list (R, 1977, v 19, p 465-475). As before, age calculations are based on the Libby half-life, 5570 ± 30 years, and reported in years before 1950. The modern standard is 0.95 of the activity of NBS oxalic acid. Solid sample pretreatment, combustion and counting technique are essentially the same as described in R, 1971, v 13, p 135-140. Groundwater samples were prepared following the procedure adopted by the IAEA (IAEA, 1977). Carbonates and hydrocarbonates from water samples were precipitated by adding saturated barium chloride solution while the alkalinity was adjusted to pH = 8 by adding carbonate-free saturated solution of sodium hydroxide. The precipitation was enhanced by adding iron salts and Praestol as coagulating medium. Carbon dioxide was evolved by acidification of the precipitate and converted to methane. Statistical processing of data has been computerized (Obelic and Planinic, 1975). Sample descriptions were prepared with collectors and submitters. The errors quoted correspond to lo- variation of sample net counting rate and do not include the uncertainty in 14C half-life. Results were corrected for isotopic fractionation using measured 13C/12C ratios for groundwater samples and estimated values (Stuiver & Polach, 1977) for all other samples. Calculations of ages or percent of modern of speleothems and groundwaters are based on the initial activity of reservoirs equal to 65% or 85% of modern standard (i.e. 95% activity of NBS oxalic acid) depending on the geology of the catchment area (Munnich & Vogel, 1959 ; Geyh, 1972 ; Job et al, 1975 ; Sonntag et al, 1976).

Radiocarbon dating; Archaeology

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