The present date list contains only details of C14 measurements on sites selected for archaeomagnetic study. Except where otherwise stated in the text, all samples were collected in 1970 or 1971 during fieldwork by one of the authors (M.B.), and were pretreated with hot 2N HCl to remove any possible contamination by pedogenic carbonate. Benzene samples were prepared using updated synthesis techniques (Polach et al., 1972) and measurements of C14 activity were made on two Beckman LS-200 liquid scintillation spectrometers following automatic cycling procedures described previously (Polach, 1969). Samples ANU-677-697 were counted on the spectrometer which has been in use since 1968 (LS-1).

The Radiocarbon Dating Laboratory was established in 1967 at the Department of Nuclear Physics, Comenius University, as part of a program of low level counting research of the department and as a contribution to geophysical, geologic, archaeologic and hydrologie research.

The following list comprises results obtained during 1971 from both the 1 L and 6 L proportional gas counters at pressures of 1 to 3 atm of methane. Age calculations are based on 95% activity of NBS oxalic acid standard and computed from the Libby half-life of 5570 ± 30 yr. Background samples are synthesized from Welsh anthracite. Errors quoted refer only to the standard deviation (1σ) calculated from a statistical analysis of sample, background, and standard count rates. Recently a Micromass 6 mass spectrometer was installed in the Radiocarbon Dating Laboratory which will enable C13 measurements on future samples. Pretreatment is continued as described previously (R., 1969, v. 11, p. 263) but in cases where sample size was insufficient for full pretreatment, details are described.

Continuation of radiocarbon measurements, mainly on ground water, soil, and subhydric sediment samples. Sample preparation was described earlier (Scharpenseel and Pietig, 1969).

The following list of dates contains all measurements made during 1972, i.e., since our last list. Counting equipment, operating procedures and sample pretreatment are the same as previously described (R., 1969, v. 11, p. 263). Age calculations are based on 95% activity of the NBS oxalic acid standard computed from the Libby half-life of 5570 ± 30 yr. Background samples are synthesized from Welsh anthracite. Errors quoted refer only to the standard deviation (1σ) calculated from a statistical analysis of sample, background and standard count rates.

Radiocarbon measurements, mainly on soil and water samples are being continued. Benzene samples are prepared as described earlier (Scharpenseel and Pietig, 1969). By adding another counting unit, the lab. now uses 3 liquid scintillation spectrometers and 4 benzene synthesis lines.

The U.S. Geological Survey, at the Denver Federal Center, Lakewood, Colorado assays C14 concentration of water samples using liquid scintillation techniques. The laboratory synthesizes benzene from precipitated barium carbonate using techniques described by Noakes, Kim, and Akers (1967). Three ml of the synthesized benzene is pipetted into a tared, low potassium-40 glass vial. The sample is weighed and 1ml of a scintillation solution is added to the vial. The scintillation solution used is a mixture of 10g PPO and 0.025g dimethyl-POPOP scintillators in 250ml toluene. Calculations of dates are made with the radiocarbon half-life of 5568 years; plus or minus numbers quoted herein are the standard error for the counting of radioactive disintegrations.

This list continues Gakushuin VII (R., 1969, v. 11, p. 295–362); the same instruments and techniques were employed. Age calculations are based on the Libby half-life of C14, 5570 ± 30 years, and the modern activity given by 95% of the activity of NBS oxalic acid standard. Errors quoted are the standard deviation obtained from the number of counts only. When observed activity is less than 2σ above background, infinite date is given with a limit corresponding to the activity of 3σ. For shell samples, dates are computed without any correction for environmental and biological isotopic fractionation. The description and comments are essentially those of the submitters.

The measurements presented below were made during 1970–71 by techniques described in R., 1968, v. 10, p. 246, and 1970, v. 12, p. 87. Errors associated with the de Vries effect and the uncertainty of the half-life are not included. In November 1971 a new low level, quartz-lined 1/2L counter designed by M. Stuiver was put into operation. It has allowed routine measurements with the samples representing 500mg to 1g pure carbon.

The Florence Radiocarbon Dating Laboratory was built in 1970 under the direction of Consiglio Nazionale delle Ricerche at the Istituto di Antropologia, Università di Firenze.

This date list was compiled by the Institute of Geological Sciences (U.K.) incorporating data supplied under contract by E. Welin, Radioactive Dating Laboratory, Stockholm. Unless otherwise stated, age figures are in C14 years before a.d. 1950. The half-life of C14 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 C13/C12 fractionation has not been made.

The radiocarbon dating laboratory of the University of Hawaii was established with joint support of the Hawaii Institute of Geophysics, the Water Resources Research Center, the Department of Chemistry, and the Graduate Division. The laboratory is located in the Hawaii Institute of Geophysics, on the ground floor of a four-story concrete building, and contains two separate radiocarbon counting systems.

This list includes the results of datings made during 1970–71. The methods of measurements are the same as described in R., 1971, v. 13, p. 29–31.

This list presents results obtained during 1971-1972 and is a continuation of research evaluating natural C14 levels for which data have been published previously (Baxter et al., 1969; Baxter and Walton, 1970; Farmer et al., 1972). The results of these studies are presented as δC14 and Δ values based on age-corrected activities, although this correction is very small. Errors quoted are lσ counting uncertainties only. Pretreatment procedures are outlined in the text and analytical methods are essentially unchanged. Gas proportional counting of CH4 in a 0.5L detector is employed (Baxter et al., 1969). Mass spectrometric analyses are performed to a precision of 0.1‰ (± 2σ) on a V.G. Micromass 602B stable isotope mass spectrometer.

This date list includes all samples processed from December 1970 through November 1971 at the Illinois State Geological Survey Radiocarbon Dating Laboratory. The benzene liquid scintillation method of Noakes, Kim, and Stipp (1965), and Noakes, Kim, and Akers (1967) was used. A new benzene synthesis system has been completed, and several changes in the sample preparation procedure have been made since the last date list report (Coleman, 1972). A brief summary of the benzene synthesis and sample pretreatment techniques used to determine the dates reported here follows.

Most of the C14 measurements reported here were made between October 1971 and October 1972. 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 samples reported in this date list were processed during 1970. Alter preliminary sample treatments including carbonates and rootlet removal, a complete benzene synthesis was made. This liquid serves as the solvent in a liquid scintillation spectrometer, using a modified 4cc: counting vessel; 2.42g of carbon are counted with a 64% efficiency. The background is constant at 6.8 cpm.

The following list comprises a selected number of measurements made on archaeologic samples from 1959 to December 1971. Measurements of geologic samples will be given in a later date list. A survey of the radiocarbon chronology for the Danish Mesolithic and Neolithic, ensuing from these and previously published dates from the laboratory, has recently been compiled (Tauber, 1972).

The following list of dates includes most of the samples processed from 1968 to 1972. Proportional counting is used and the counting gas is CO2 at constant filling pressure of 740mmHg at 22°C (Thommeret et al., 1969). Samples are counted at least twice on two different counters and errors quoted are averages of standard deviations obtained on each counting.

This list contains data obtained during 1971. Unless otherwise stated, all organic samples or organic fractions are carefully washed with dil. HCl and dil. NaOH to remove all carbonates. Age calculations are based on 95% of NBS oxalic acid standard activity with modern value A.D. 1950. Results are calculated using the Libby half-life and are given in the B.P. scale. Also ages of shells are calculated with the NBS oxalic acid standard. Ages are not corrected for δC13 variations. Errors correspond to Iσ variation of sample net counting rate including statistics of modern standard and background. Sample activities, if given in per cent refer to 0.95 NBS oxalic acid standard activity.