The C14 measurements reported here were made in this laboratory between November 1, 1963 and November 15, 1965. Sample descriptions are classified as follows:

1. I. Geochemical Samples

2. II. Geologic-Paleoclimatic Samples

3. III. Early Man-Alluvial Stratigraphy Samples

4. IV. Archaeologic Samples

This list includes about half of the samples measured during the last year. Many studies need further investigation and the results will be published later when additional information will make better interpretations possible.

The equipment and the technique is essentially the same as described earlier (Bern IV).

Reliable results on CO2 samples extracted out of ice are obtained with the small counter mentioned in Bern IV.

Our laboratory is financed by the Schweizerischer Nationalfonds. The authors wish to thank H. Loosli and P. Horisberger for their assistance in the measurements of part of the samples. They also thank M. Welten and H.-G. Bandi for their help in selecting and discussing the samples.

This date list covers age measurements carried out at the Radiocarbon Dating Laboratory of the German Academy of Sciences of Berlin (DAW) since 1963 and is a continuation of our first date list (Berlin I). Procedures and methods of preparing the samples are essentially the same. We completed our laboratory with a second electronic counting apparatus. Two further proportional counters with internal anticoincidence (Houtermann-Oeschger counters) are made from an old railway-car axle. The total volume of these counters is 4 L, the effective volume 2.2 L, the background 2.0 counts/min at 700 Torr (acetylene filling), and the contemporary standard value (0.95 NBS oxalic acid) is 20 counts/min. Each sample is measured twice, first for 48 hr and after 8 days for another 24 hr. Data have been calculated on the basis of a C14 half-life of 5570 yr (Godwin, 1962). Errors listed include the standard deviations (1σ) of the counting rates of the contemporary samples, the background and the unknown samples. Calculated errors less than 100 yr have been increased to that figure as a minimum.

Corrections have not been made for C13 content. Mass spectrometrics C13 measurements of some samples indicate that errors resulting from fractionation are minimal.

Laboratory construction was begun in December 1964 and routine dating was in progress by late February 1965. The primary purpose of this facility is to assist in marine geological studies and the archaeological chronologies of the region. Dating is carried out by utilizing the techniques of liquid scintillation described by Noakes et al. (1965), wherein the carbon of the sample to be dated is converted to benzene and the natural radioactivity detected in a liquid scintillation spectrometer.

This list includes many of the datings done from September 1964 to October 1965. The instruments and techniques used for this work are essentially the same as those used previously (Gakushuin III). Bone samples were dated on the organic materials obtained by the following procedure. After washing with distilled water the powdered bone samples were boiled with 10% H2SO4 solution 10 to 40 hours. The extract, a clear solution, was exaporated to almost dryness, and, after concentrated H2SO4 was added, heating was continued until most of the organic compounds became insoluble carbonized or polymerized material. The black residue was washed in water and treated as the usual charcoal sample for dating.

The C14 dating laboratories of Saclay (Saclay I, 1964 and Saclay II, 1965) and Gif (Gif-sur-Yvette, 1966) have joined together under the name of Gif C14 Dating Laboratory. The first series of dating results appears here with code designation Gif, Sa now being obsolete.

Both the 2-L counter, described in GSC I, and the 5-L counter (GSC IV) were operated routinely during the past year. Approximately one-half of the determinations reported here were obtained from each counter. The 5-L counter was operated mainly at 1 atm.

For more than a year, age calculations have been carried out monthly by an I.B.M. 1620 computer. If the background, standard, and sample counts during a month conform to statistical laws, they are entered on sheets together with their respective counting times and sample identifications and sent to the computing center for processing.

The following list shows the age measurements carried out from 1958 to March 1963 at the Radiocarbon Laboratory at Gif-sur-Yvette, This laboratory has been replaced by a new one whose first measurements are also given in this volume.

It was equipped with 2 proportional counters similar to those used in Saclay laboratory and operating with 1 atm of pure CO2. These counters were shielded by 15 cm lead, 5 cm iron and 1.5 cm of mercury.

Data have been calculated on the basis of a C14 half-life of 5570 yr, in agreement with the decision of the Fifth Radiocarbon Dating Conference. As a modern carbon standard, wood taken from old furniture was used. This standard was found equivalent to 95% of the activity of the NBS oxalic acid, if a 2% Suess-effect is adopted for this wood.

The following list presents dates on a small fraction of the total number of measurements made during 1964 and 1965 as well as data on some samples previously dated but not published. Results not appearing have not been released by our clients.

This list presents dates on samples measured at Isotopes, Inc., during the years 1963 to 1965 and measurements made previously for which sample data has been recently received. The many results which do not appear are withheld pending additional information or at the request of our clients.

The dates reported in this list were measured from December, 1964 to November, 1965. The laboratory continues to employ liquid scintillation techniques with synthesized benzene; however, the chemical yield has been improved to the point where it is now between 80 and 100%. For most of the measurements listed here, a 4 cc counting vial was used with 3 cc benzene and 1 cc commercial toluene containing PPO and dimethyl-POPOP scintillators. The counting efficiency is 72%, which gives a net modern count of 23.5 cpm, and the background is 8.2 cpm. The detection limit (48 hours counting, 2σ statistics) with ordinary size samples is 43,000 yr using the 4 cc vial and 52,000 yr with a 20 cc vial. Errors introduced by the laboratory procedure are less than ½% (Tamers and Pearson, 1965a). A detailed review of the methods being used has been published recently (Tamers, 1965b).

The following list comprises a selected number of measurements made up to November, 1965. Age calculations are based on a contemporary value equal to 95% of the activity of the NBS oxalic-acid standard, and on a half life for C14 of 5570 yr. Results are reported in years before 1950, and in the A.D./B.C. scale. Errors quoted include the standard deviations of the count rates for the unknown sample, the contemporary value, and the background. Because possible errors arising from isotopic fractionation in the plants, or from the de Vries effect, have not been included, calculated errors smaller than 100 yr have been increased by rounding to that figure as a minimum.

The C14 Laboratory at Kiel University was established in 1963. It continues measurements, which were made at the Institut für Kernphysik, Kiel, on age determination with Chlorine 36, which is produced by cosmic ray neutrons (Bagge and Willkomm, 1963, 1966). The first C14-counting apparatus was completed in 1964 and dating work started at the end of 1964 after extensive general tests of counter working conditions (Erlenkeuser, 1965). The data reported here have been obtained during the first half of 1965. During this period the dating measurements were interrupted on numerous occasions by measurements of background and the oxalic standard in order to check long-time variations of the apparatus.

After publication of the occurrence of C14 in nature and the first successful datings made by the radiocarbon method (Anderson et al., 1947; Arnold and Libby, 1949), a fair number of physicists as well as geologists, paleobotanists, and prehistorians in Germany became interested (e.g., Harteck, 1951; Zeuner, 1951; Firbas, 1953; Schwabedissen, 1949) in studying the applicability of the new method. So, one of us (H.S.) together with F. Firbas tried to stimulate plans by F. Houtermans (later at Bern, Switzerland) to organize a dating laboratory at Göttingen, before 1950. When the Heidelberg laboratory was founded, close contact was kept with O. Haxel and K. O. Münnich by providing them with carefully selected samples covering a variety of prehistoric ages (partly published in Heidelberg I). Samples were also submitted to Washington, D. C. (see USGS III, I, II), Yale (see Yale III), and Copenhagen (unpub.).

The following list covers most of the samples measured at the Louvain C14 laboratory since the last list (Louvain III).

The method is essentially the same as the one used for the work described in the previous lists. A CH4 proportional counter, 0.6 L volume, operating at 3 atm pressure, is used. Equipment and counting techniques have been described in Louvain I. Dates are computed on the basis of the Libby half-life, 5570 yr, and the zero of the age scale is A.D. 1950. Ages are quoted with 1σ experimental error, which includes the counting variations of the sample as well as that of the background and the contemporary standard. As modern standard we now use NBS oxalic-acid standard or wood taken from A.D. 1870 to A.D. 1900 tree rings. No differences between the two standards have been observed.

The following is a list of dates obtained since the time of the compilation of List X in December 1964. The method is essentially the same as that used for the work described in the previous list. Two CO2-CS2 Geiger counter systems are used. The equipment and counting techniques have been described elsewhere (Crane, 1961). The dates and estimates of error in this list follow the practice recommended by the International Radiocarbon Dating Conferences of 1962 and 1965, in that (a) dates are computed on the basis of the Libby half-life, 5570 yr, (b) A.D. 1950 is used as the zero of the age scale, and (c) the errors quoted are the standard deviations obtained from the numbers of counts only. In previous Michigan date lists up to and including VII we have quoted errors at least twice as great as the statistical errors of counting, in order to take account of other errors in the over-all process. If the reader wishes to obtain a standard deviation figure which will allow ample room for the many sources of error in the dating process, we suggest he double the figures that are given in this list.

This series reports some of the measurements made since publication of the previous list. Chemical preparation of samples is basically the same as described in Monaco I.

The counting electronics of the proportional counter has been entirely rebuilt by J. Galliot and P. Albertinoli of C.S.M. The new device is transistorized and battery-operated. At regular intervals of time, usually 10 min, the count (anti-coincidence channel) is printed in tape. Large deviations from the mean are easily visible and can lead to rejection of the measurement if the distribution is not normal, i.e. does not fit a straight line on Gaussian paper.

Results of absolute age determination by the radiocarbon method, obtained in the Radiocarbon Laboratory of the Vernadsky Institute are given in this article. The counting of natural C14 activity was realized by measuring the gaseous carbon compounds—CO2 and C2H6—with the aid of a proportional counter. Investigation objects were wood, peat, coal, plant and animal remains and other organic material. All samples were preliminarily treated with hot 2% NaOH and 5% HCl to remove foreign humic acid and carbonate. Carbon dioxide, which was obtained after burning, was freed of electronegative admixtures by purification with the aid of CaO. Ethane was synthesized from the sample carbon through the following stages: natural sample→CO2→CaCO3→CaC2→C2H2→C2H6. The counting gas was let into the counter up to a pressure of 2 atm. Counters of stainless steel or copper of different volumes from 0.5 to 2 litres were used. The screening of the counters was effected by steel (24 cm thick) and mercury (2.5 cm thick) shields; the counter together with the mercury shield was enclosed in a circle of Geiger counters of the GS-60 type arranged in anti-coincidence. A detailed description of the methods, the constructions and the apparatus has been published (Vinogradov, Devirts, Dobkina, Markova, Martishchenko, 1961).

The C14 dates given below are a continuation of the work presented in our first list (RIKEN I), and have been obtained by counting CO2 at about 2 atm pressure in a 2.7-L stainless steel counter. In this article, results obtained during 1964-65 are described.

Shell samples were treated with 1% HCl to remove the outer 10%. Calcareous deposits on the surface, when observed, were removed by mechanical means.

The following list comprises measurements made since those reported in NPL III and is complete to the end of November 1965.

Ages are relative to A.D. 1950 and are calculated using a half-life of 5568 yr. The measurements, corrected for fractionation (quoted δC13 values are relative to the P.D.B. standard), are referred to 0.950 times the activity of the NBS oxalic acid as contemporary reference standard. The quoted uncertainty is one standard deviation derived from a proper combination of the parameter variances as described in detail in NPL III. These variances are those of the standard and background measurements over a rolling twenty week period, of the sample δC14 and δC13 measurements and of the de Vries effect (assumed to add an additional uncertainty equivalent to a standard deviation of 80 yr). Any uncertainty in the half-life has been excluded so that relative C14 ages may be correctly compared. Absolute age assessments, however, should be made using the accepted best value for the half-life and the appropriate uncertainty then included. If the net sample count rate is less than 4 times the standard error of the difference between the sample and background count rates, a lower limit to the age is reported corresponding to a net sample count rate of 4 times the standard error of this difference.