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This list contains the results of 14C determinations that we obtained in 1988 and 1989. δ13C was measured by the Free University, Brussels. Our dating techniques have been described previously (Dauchot-Dehon & Heylen 1971; Dauchot-Dehon, Van Strydonck & Heylen 1986).
This list contains the results of 14C determinations obtained at the laboratory in 1986 and 1987. δ13C was measured by the British Museum Research Laboratory or the Free University of Brussels: *δ13C is estimated (Stuiver & Polach, 1977).
This list contains the results of 14C determinations obtained at the laboratory in 1984. Our laboratory measures 14C activity in the form of methane with a proportional counter built by Heidelberg University and an electronic unit built by Berthold, Benelux Analytical Instruments. The sample counting time is 4000 minutes with printouts at 100 minute intervals. Sample error is reported as one standard deviation. δ13C for mortar is measured by the University of Lyon Laboratory, δ13C was not measured or estimated for other samples.
Recent studies comparing dates from the carbon content of mortars with dendrochronologic dates for the same material have shown considerable inconsistencies related to mortar type (Van Strydonck et al, 1985). Even after the best possible removal of “dead” calcite, some mortars are unsuitable for dating. We describe here our experimental study of carbon isotope fractionation during the manufacture and hardening of mortars. Preliminary experiments established overall uptake of CO2 from the air. We then measured isotopic ratios in identical mortars at different hardening times.
The influence of the aggregate in mortar dating is examined. Sample activity as well as isotopic fractionation approach the expected values at lower yields of the preparation reaction of the counting gas. Good results are obtained at low fossil carbonate concentration. δ13C cannot give information about this concentration but preliminary visual and chemical analysis of the mortar makes prediction of sample validity possible.
This list contains the results of 14C age determinations obtained at the laboratory in 1981–1982. Samples are analyzed in three new proportional counters which are described in R, 1980, v 22, p 442. Our installation differs from that of Heidelberg in that our filling gas is methane.
This list contains most of the measurements made during 1979, since our last list (R, 1979, v 21, p 180–185). The laboratory procedures were outlined previously (R, 1968, v 10, p 29–34; R, 1971, v 13, p 29–31). The collagen extraction follows Longin (1970).
This list contains most of the measurements made during 1980, since our last list (R, 1981, v 23, p 33-37). A second methane synthesis unit became operational (Dauchot-Dehon and Van Strydonck, 1979) at the end of 1979. Basically, this unit is the same as the one built earlier (Klebert and Heylen, 1966).
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