The following is a list of dates obtained since the time of the compilation of List VIII in December 1962. 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, 1961a, 1961b). The dates and the estimates of error in this list follow the practice recommended by the International Radiocarbon Dating Conference of 1962, in that (a) dates are computed on the basis of the Libby half life, 5570 years, (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 other sources of error in the dating process, we suggest he double the figures that are given in this list. Where there is no comment, it is because the submitter of the sample had none to make.

We wish to acknowledge the help of Patricia Dahlstrom in preparing chemical samples and Roscoe Wilmeth in preparing the descriptions. The descriptions and comments are essentially those of persons submitting the samples.

The following list comprises measurements made since those reported in NPL I and is complete to the end of November 1963.

Ages are relative to a.d. 1950 and are calculated using a half-life of 5568 yr. The measurements have been corrected for fractionation and referred to 0.950 times the activity of the NBS oxalic acid as a contemporary reference standard. The quoted uncertainty is one standard deviation derived from a proper combination of the parameter variances, viz. those of the standard and background measurements over a rolling twenty-week period, of the sample measurements from at least three independent fillings, of the 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 included. If the net sample activity is less than 4 times the standard error of the difference between the sample and background activities, a lower limit to the age is reported equivalent to a sample activity of 4 times the standard error of this difference.

The description of each sample is based on information provided by the person submitting the sample to the Laboratory.

The work reported forms part of the research programme of the Laboratory and is published by permission of the Director.

The first series of C14 dating measurements made in the Gulbenkian Radiocarbon Dating Laboratory, which came into operation in October 1962, are reported in the following list.

This date list contains the results of measurements made during 1961, 1962 and 1963. The method of counting, utilizing acetylene gas, remains essentially unchanged, except for the addition of some solid state electronics. The method of computation, using the Libby half-life of 5568 ± 30 yr, is continued. The error listed is always larger than the one-sigma statistical counting error commonly used, and takes into account known uncertainty laboratory factors, and does not include external (field or atmospheric) variations.

Unless otherwise stated, collectors of all samples are members of the U. S. Geological Survey.

A first list of datings by our laboratory was published in 1957 (Bella and Cortesi, 1957). The measurements were performed with a solid Carbon counter (Ballario et al., 1955). Between the beginning of 1958 and December 1961 laboratory apparatus was completely renewed and proportional gas-counters were introduced. At present four counters are available. Measurements are carried out with CO2 at 3 atm pressure.

With few exceptions the C14 measurements reported here were made in this laboratory between October 1, 1962 and November 1, 1963.

Radiocarbon measurements were begun at Sharp Laboratories in the spring of 1962 with the construction of a complete C14 dating laboratory. This first system used the method described by Fairhall, Schell, and Takashima (1961) for the conversion of CO2 to methane via ruthenium catalyst. This system proved to be fast and reliable, giving overall yields of solid sample to counting gas of better than 90% for the total conversion and purification (the conversion yield of CO2 to methane is quantitative). The detector in present use is 2 L, with construction materials consisting solely of O.F.H.C. copper, teflon, and epoxy resin. The shield consists of 4 in. of high purity lead (specially prepared), 4 in. of borated hydrogenous neutron moderator, a guard counter (cosmic ray detector), and 1 in. of ultra pure mercury. The gross to net ratio obtained with this system averages about 53. The background, for P in cm methane pressure, is:

Background = 3.95 ± .008 + .00705P

The following results represent measurements carried out since our second date list was prepared. The pretreatment of the samples and the production of pure CO2 followed the method described in Finland I.

Natural C14 measurements at the Institute of Physical and Chemical Research (RIKEN) became routine in 1962. The counters presently used are made of stainless steel with a volume of about 2.7 L. They are surrounded by 2.5 cm of pure lead, a ring of 22 propane gas-flow anticoincidence counters, about 10 cm of boric acid and 20 cm of iron. When filled with dead CO2 up to 2 atm, they gave a background counting rate of about 9 cpm (Hamada, 1960).

In this article, results obtained for geologic and archaeologic samples since 1962 are described. Dates have been calculated on the basis of the C14 half-life of 5568 yr, and 95% of NBS oxalic acid as modern standard. Correction for isotopic fractionation was not applied.

The dates and activity measurements given below have been obtained during 1962 and 1963, and have been made with CO2 at 3 atm pressure in a proportional gas-counter very little modified from those described in previous contributions from this laboratory.

The Radiocarbon Dating Laboratory of the University of Texas was reorganized in late 1962. The dates reported in this list were obtained from February to November, 1963. The laboratory uses liquid scintillation counting with benzene solutions (Tamers, Stipp, and Collier, 1961; Noakes et al., 1963). The chemical synthesis has been modified and improved in several ways in order to permit one worker to produce a sample per day.

The measurements reported in this list were made in the Louvain C14 dating laboratory from July 1962 to October 1963.

All C14 measurements in this date list were made with the 2 L counter described in our first date list (GSC I). Ages were calculated on a C14 half life of 5570 ± 30 yr and 0.95 of the activity of the NBS oxalic-acid standard, and are quoted in years before 1950.

The radiocarbon dating laboratory at the Smithsonian Institution, Division of Radiation and Organisms, was established in September 1962. After careful calibration with known samples and refinements in the methane synthesis system, routine analysis of samples was begun in the spring of 1963.

The Radiocarbon Dating Laboratory of Texas A & M University was initiated as a research facility in the Oceanography and Meteorology Department. The facilities are available to graduate study programs and to other research groups associated with the University.

Research was begun in June 1960, towards development of a carbon dating method utilizing liquid scintillation counting. Benzene was chosen as the counting solvent because of its high energy transmitting properties and the high carbon content of benzene which could be totally derived from the sample to be dated. A catalytic method of synthesis of C6H6 at low temperature, as first reported by Shapiro and Weiss (1957), was further developed and modified by Noakes and others (1963) to a procedure suitable for carbon dating. A combined effort of this laboratory and the University of Texas Radiocarbon Dating Laboratory has resulted in a routine procedure for carbon dating, as reported earlier (Texas I).

In the dates reported here the sample preparation and the method of conversion of carbon samples to the counting solvent, benzene, was the same as reported in the earlier papers cited. The problem, reported then, of variation in background count rate between counting vials was eliminated by prior determination of the background for each vial used. With the exception of samples TAM 1 and TAM 2, all dates reported here were calculated according to this procedure.

Created in 1961, the C14 dating laboratory of the Centre Scientifique de Monaco (founded by H. S. H. Prince Rainier III in 1960) made its first dating measurements in 1962.

This date list covers many of the datings done from November 1962 to October 1963. The instruments and technique used for this work are essentially the same as those used for the previous work (Gakushuin II). Age calculations are based on the Libby half life of C14, 5570 ± 30 yr. The errors quoted are the standard deviations obtained from the number of counts only. When observed activities are less than 2a above background, infinite dates are given with a limit corresponding to the activity of 3σ, and when they are greater than the activity of 95% of NBS oxalic-acid standard minus 2a, modern dates are given with the limit equal to 3a below the 95% of NBS standard.

The list of dates grouped below is a continuation of work reported in our earlier lists. In one case (Core A 254-BR-C), an extensive sequence of dates is reported which, for completeness, includes some data presented in an earlier report (Miami II, 1963).

We continue to use a 1.0-L CO2 proportional counter operating a 3 atm pressure (see Stockholm V for details). Except for the early incorporation of a counter for tritium analyses within our present shielding house and switching over to transistorized electronics, we do not anticipate changes in our set-up.

Wherever possible we have entered the δC13 corrected date as well as the δC13 value determined from that sample. An apparent 400-yr sea-surface carbonate age is subtracted from the calculated age of marine carbonate materials, but not for organic material (Miami I and Miami II).

The following list comprises a selected number of measurements made up to November 1963. 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 ± 30 yr.

Results are expressed in years before 1950 and in the b.c.-a.d. scales. Errors quoted include the standard deviations of the count rates for the unknown sample, the contemporary value, and the background. Calculated errors smaller than 100 yr have been increased by rounding to that figure as a minimum. Sample descriptions have been prepared in collaboration with collectors and submitters.

The C14 dates presented here have been obtained by counting acetylene, synthesised from the sample, in an Oeschger-Houtermans’ gas proportional counter. The chemical and counting procedures have been described in some detail (Kusumgar et al., 1963a).

Dates are based on the C14 half-life value of 5568 yr. For conversion of b.p. dates to a.d./b.c. scale, a.d. 1950 has been taken as the reference yr. Ninety-five % activity of NBS oxalic acid has been adopted as the value for the pre-1900 age-corrected wood.

All samples were treated with dilute HCl. Whenever NaOH pretreatment was possible, it has been mentioned in the date list. In the case of bones, only the inorganic fraction has been dated.