This list includes the results of measurements made during 1972–73.

The following list of dates contains the majority of measurements made during 1974, ie, since our last list (R, 1974, v 16, p 285–303).

This date list was compiled by the Institute of Geological Sciences (UK) incorporating data supplied under contract by E Welin, Radioactive Dating Laboratory, Stockholm. Unless otherwise stated, age figures are in 14C years before AD 1950. The half-life of 14C is taken as 5568 years and the error, based on counting statistics of sample, background, and modern, is given as one standard deviation. Correction for 13C/12C fractionation has been made.

The measurements presented in this list are part of the joint research program “Sonderforschungsbereich 95” of Kiel University for interdisciplinary research on problems of “Interaction Sea-Sea Bottom”, sponsored by the Deutsche Forschungsgemeinschaft. They are directed 1) to the study of the path of 14C from the atmosphere into argillaceous sediments, and 2) to date stratigraphic records within sediment. Associated problems are to identify sources of different 14C activity that contribute to recent deposits, and to learn about effects of morphologic and hydrographic factors, especially of bottom currents, on sedimentation sequence. Even short term processes can be successfully studied by analyses of bomb produced radiocarbon in the marine environment.

This list includes most of the samples measured from June 1972 to December 1973 and some other results as yet unpublished.

All samples processed from February 1973 through January 1974 at the Illinois State Geological Survey Radiocarbon Dating Laboratory are reported here. The benzene liquid scintillation technique was used. Laboratory procedures used were the same as those previously reported by Coleman (1973, 1974).

Most of the 14C measurements reported here were made between October 1973 and October 1974. Equipment, measurement, and treatment of samples are the same as reported previously (R, 1968, v 10, p 36–37; 1970, v 12, p 534).

The dates presented here were calculated from measurements made at the University Radiocarbon Dating Research Laboratory mostly during 1973–74. The radioactivity of the samples was counted in gas proportional detectors, either silica lined (de Vries et al, 1959) or of pure copper, filled to 2 atmospheres pressure with pure carbon dioxide. The detectors were fixed in, and completely surrounded by, a plastic scintillator anticoincidence shield mounted inside a massive lead shield to protect against environmental radiation (Switsur, Hall and West, 1970). Modern sample gas was obtained from the combustion of ad 1845 to 1855 rings of an oak tree grown near Cambridge and felled in 1950. Background samples were prepared from Welsh anthracite. The contemporary sample was frequently compared with the activity of the NBS oxalic acid international standard. Age calculations were based on the 14C half-life of 5568 years and the uncertainty stated as one standard deviation calculated from the statistical analyses of sample and standards counting rates.

The dates presented in this paper comprise results of determinations made at the University Radiocarbon Dating Research Laboratory, mostly during the latter half of 1974. Radioactivity was measured with proportional counters using pure carbon dioxide at 2 atmospheres pressure as filling gas. Effects of cosmic and local environmental radiation on the counters were reduced by surrounding them completely with 1) a plastic scintillator anticoincidence shield, 7.5cm thick, viewed by 2 photomultiplier tubes operating in coincidence mode, the output pulses of which were in anticoincidence with the proportional counters signals, and 2) by a 17.5 ton lead castle.

This list reports 14C measurements completed between August 1971 and November 1973. Other projects completed in that period will be reported later. Age calculations are based on 14C half-life of 5568 yr and modern standard of 95% NBS oxalic acid, supplemented by tree rings of pre-industrial wood from a log cut in the 1850's (Tx-540; R, 1970, v 12, p 249). Deviations reported are based on counting statistics of sample, background, and modern, and are ± 1σ, except when sample count approaches either modern or background, 2σ limits are reported. Unless noted, 12C/13C measurements were not made and results are not corrected for 13C fractionation. The laboratory uses liquid scintillation counting of benzene, with Li2C2 and vanadium-activated catalyst in preparation; chemical yields average 90%. Three counters are employed: a Packard Tri-Carb Model 3002, and 2 Beckman LS-230 spectrometers obtained through a grant from the National Science Foundation.

This list includes the second group of age measurements made from September 1972 to July 1974 using the benzene scintillation method. All archaeologic and geologic samples come from Italian territory. Chemical apparatus for benzene synthesis and the liquid scintillation spectrometer are unchanged (Alessio et al, 1970a, 1973). Charcoal and wood samples underwent standard pretreatment by boiling with 5 to 10% HCl; α-labeled samples were given additional leaching with .2N NaOH. The counting rate of approx half the samples was corrected based on the 13C/12C ratio, mass-spectrometrically measured on CO2 obtained in combustion line set up after Broecker et al (1959), according to previously described procedure (Alessio et al, 1969).

This date list includes most of the archaeologic samples dated in this laboratory since publication of our last date list (R, 1974, v 16, p 219–237), as well as some samples dated previously, which lacked adequate sample information. The BP ages are based on AD 1950, and have been calculated with the half-life value of 5568 yr. All samples were counted at least twice for periods of not less than 1000 min each. Errors quoted for each sample are derived from the measurement of the sample, the background, and several counts of our mid-19th century Oak sample, but do not include the half-life error. All samples were pretreated with 3N HCl and some, where noted, were given additional pretreatment with 2% NaOH for the removal of possible humic acid contaminants.

This series reports some of the measurements made since the previous list. Methods essentially remain as described in Saskatchewan II (R, 1960, v 2, p 73) with expanded facilities and new electronic equipment since 1973. The laboratory operates commercially, administered by the Saskatchewan Research Council under the direction of A A Rutherford.

The following list of dates is compiled from samples prepared since publication of our last date list (R, 1974, v 16, p 131–141). The counting equipment and operating procedures are the same. Ages are quoted with a 1σ counting error which includes statistical variation of the sample count as well as for background and standard, using ad 1950 as the reference year and 95% NBS oxalic acid for 14C dating as the standard. The half-life value used is 5570 years.

This date list is composed of the ages of tests of fossil populations of the foraminiferal species, Amphistegina gibbosa, and algal nodules collected from submerged banks in the N Gulf of Mexico. A Shipek grab sampler was used to collect the Amphistegina gibbosa and a few of the algal nodule samples. Algal nodules from the West Flower Garden Bank were obtained from cores at various intervals as indicated in Sec III.

This is the last installment of 14C dates done at the Tata Institute; the lab has now shifted to the Physical Research Laboratory, Navarangpura, Ahmedabad-380 009, India.

The following list of dates are selected from geologic and archaeologic samples measured in late 1973. The laboratory procedures and techniques are the same as indicated in R, 1974, v 16, p 402–408, where sample is synthesized to benzene and counted for 24 hours in either a Beckman LS-100-C or Packard 2311 liquid scintillation spectrometer. Ages are calculated relative to 0.95 x NBS oxalic acid using a 14C half-life of 5568 years. The quoted error is 1σ, which includes only the counting uncertainties of the background, modern standard, and sample. Sample descriptions and comments were written in collaboration with collectors and submitters.

All samples described in this date list have been dated from November 1973 to January 1975. Only the benzene liquid scintillation installation was used during this time. For the combustion of soil and fossil bone samples containing a high content of sulfur (ie, in the form of pyrite), a new CO2 extraction and cleaning system was built. The gases released by the combustion are dried in ice and dry ice traps, passed through hot copper oxide and bubbled through KOH solution. Following the combustion, the K2CO3 precipitate is acidified in the same vessel where it formed and the released CO2 is again dried in a dry ice trap and by passing it through ascarite. This CO2 gas is quite clean and can be brought to the original system where the gas volume is measured. Further processing is as previously described (Haynes and Haas, 1974).

Most dates in this list were obtained in the period 1970 to 1972. Treatment of samples and counting equipment have remained essentially the same as described previously (R, 1972, v 14, p 418–419).

Procedures of measurements and calculation remain as previously described. All samples are pretreated according to the methods described in R, 1971, v 13, p 103 and p 123 unless specified under the sample descriptions. Unless stated samples are from Ireland.