The C14 measurements reported here were carried out by the Radiocarbon Laboratory, Dept. of Geophysics and Geochemistry, A.N.U., between Jan. and Aug. 1967. Laboratory equipment consists of a Beckman methane gas-proportional unit (ANU I) supplemented in Dec. 1966 by an automatic 3-channel Beckman model LS-200 liquid scintillation spectrometer. Synthesis of methane and benzene is the same as used in ANU I and described by Polach and Stipp (1967). Treatment of samples remains a 2N hot acid (HCl) wash unless otherwise specified. Where applicable, fractional separation follows procedures reported by Olson (1963), Berger et al. (1964), Tamers and Pearson (1965), and Krueger (1966). In the treatment of bone samples, physical or mechanical cleaning could not completely remove sedimentary material often filling the structural pores. This material, if present, was retained with the fraction referred to as “collagen”. Since we are not dealing with pure collagen, we prefer to call it “acid-insoluble” bone fraction, a name describing the treatment. These dates are reported as equal to or greater than given age. Table 1 summarizes all dated fractions.

Measurements have continued with the 6 L counter which has proved reliable at pressures as high as 2.6 atm and as low as 0.3 atm. It has now been enclosed in a double ring of 27 geiger tubes which has reduced the background count to 10 cpm at 2 atm. So far, we have had no success with the 1.5 L Oeschger-type proportional counter. Failure to obtain steady readings is probably due to continued outgassing from the teflon insulation. All insulating parts have now been remanufactured from the same source of teflon as was used in the 6 L counter, and the Oeschger counter is being reassembled.

Results are still given without correction for δC13. Errors quoted refer only to the standard deviation calculated from a statistical analysis of count rates and the Libby half-life of 5570 ± 30 yr.

The 2-L counter (GSC I) and the 5-L counter (GSC IV) were operated routinely during the past year. The 5-L counter was operated at 1 atm, except for February-March 1967, when it was operated at 4 atm. Approximately half the determinations reported were obtained from each counter.

This list presents dates on a portion of the samples measured at ISOTOPES since publication of Isotopes V, and for previously analyzed samples for which complete sample data are now available.

Samples were analyzed by gas proportional counting of carbon dioxide at 3 atm pressure in counters of 1 1. volume. Each sample was assayed twice, in different counters and on different days.

Procedures employed in sample preparation and age calculations have been described previously (Isotopes V).

The following list comprises a selected number of measurements made up to October, 1967. Age calculations are based on 95% of the activity of the NBS oxalic-acid standard, and on a half-life for C14 of 5570 yr. Results are reported in yr before 1950, and in the A.D./B.C. scale.

Errors quoted include standard deviations of the count rates for the unknown sample, contemporary value, and 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.

Sample descriptions have been prepared in collaboration with collectors and submitters.

Most of the measurements have been obtained with a 4.5-L CO2 counter (Kiel I). Dates given are not corrected for C13/C12 except Ulmus series. Error corresponds to 1σ of statistical variations of sample net counting rate including variance of reference and background, but does not include the uncertainty in C14 half-life and in secular C14 variations. Half-life is 5570 yr and a.d. 1950 is zero point of b.p. scale.

The C14 dates given below are a continuation of the work presented in our previous list (RIKEN III), and have been obtained by counting CO2 at ca. 2 atm pressure in a 2.7 L stainless steel counter. Results obtained mainly during 1967 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.

Dates were calculated on the basis of the C14 half-life of 5568 yr and 95% NBS oxalic acid as modern standard. No correction was applied even for fresh water shell samples.

The Radiocarbon Dating Laboratories of the Oak Ridge Associated Universities (ORAU) has previously published radiocarbon dates under the Oak Ridge Institute of Nuclear Studies (ORINS) name. ORINS has recently changed its name to ORAU and its laboratories and programs have accordingly assumed this new name. The ORINS prefix, which previously designated the published radiocarbon dates of this laboratory, will be continued to minimize confusion in the literature.

The radiocarbon dating program carried out at this laboratory is primarily concerned with assisting the ORAU Special Training Program in its teaching and research activities. Radiocarbon dates which appear in this paper represent samples submitted from research groups associated with the 41 universities which make up ORAU and by other college and university personnel who do not have access to radiocarbon dating facilities.

Carbon samples are chemically synthesized to liquid benzene and their C14 activity determined by liquid scintillation spectroscopy. Samples are first converted to lithium carbide and then to acetylene gas as described by Barker (1953). The acetylene is catalytically trimerized to benzene by a method described by Noakes et al. (1965). Chemical yields for the synthesized benzene routinely approach 90% with no evidence of chemical impurities or carbon isotope fractionation occurring in the chemistry.

A Packard Tricarb Model 314 D.C. liquid scintillation spectrometer, which has been modified for low level counting, is used to count the benzene samples. Counting efficiency is 50% when operating at a voltage of 800 with discriminator setting of 100-800-1000. Background count rate is 1.7 c/m with a 5 cc benzene sample. Shielding consists of 4 in. of lead with coincidence and anticoincidence systems.

The modern reference standard is 0.95% activity of NBS oxalic acid standard which is 6.82 c/m/g carbon. Ages are calculated on a C14 half-life of 5570 yr as suggested by Godwin (1962). The statistics quoted are compiled as one standard deviation (1σ) of the uncertainty involved in counting background, standard, and sample.

The list includes age measurements carried out from December 1966 and November 1967. All samples both of archaeologic and geologic interest are drawn from Italian territory.

Chemical techniques have remained unchanged (Bella and Cortesi, 1960). Two counters have been used for dating: the 1st, of 1.5 L, already described (Bella and Cortesi, 1960; Alessio, Bella, and Cortesi, 1964), the 2nd, of 1 L, recently assembled, is identical to the previous 1 L counter (Alessio, Bella, and Cortesi, 1964), its anticoincidence system was realized by a plastic scintillator and photomultipliers. Background 6.15 ± 0.08 counts/min, counting rate for modern carbon 24.49 ±0.15 counts/min. Higher efficiency of electronic recording was obtained by reducing pulse length and by a few other changes. All samples are usually measured by both counters.

The errors quoted, as in previous measurements, are 1σ statistical error. Age has been calculated using Libby's half-life of 5568 ± 30 yr, with 1950 as the standard year of reference. As in all previous measurements, the same modern wood, grown near Rome between 1949 and 1953, has been taken as modern standard: its activity has once again been carefully checked and judged satisfactory.

This series reports some of the measurements made since publication of the previous list. Equipment and methods are described in Saskatchewan II.

In dating the samples reported here as well as in calculating their ages, the same equipment and method of processing and counting were used which were previously described in Tartu I and II.

This laboratory is now a part of the Bureau of Economic Geology, The University of Texas at Austin. The present list reports C14 measurements made in dating projects completed in the year ending November, 1967, and some measurements for projects still in progress. Age calculations are based on C14 half-life of 5568 yr and a modern standard of 95% of NBS oxalic acid. The deviations reported are based on the counting statistics of the sample, background, and modern, and are ± 1σ except that when the sample count approaches either the modern or the background, 2σ limits are reported. The laboratory continues to use liquid scintillation counting of benzene, using Li2C2 and vanadium activated catalyst in preparation, as described in Texas IV and earlier lists. Chemical yields now average 85%.

Rightmire's caliche dating (done for an M.A. thesis in the Dept. of Geol.) is the principal project reported in this list; in addition to the research he prepared the samples in our laboratory and wrote the statements which accompany the list. Valastro is in charge of all technical operations in the laboratory, and he and Davis share the administrative responsibilities. Davis, who handles sample screening (with the aid of an Advisory Committee) and archaeological appraisal, compiled the list.

The measurements reported were made during the 2nd half of 1967 in the Isotope Lab. of the Inst. of Geophysics and Planetary Physics as a continuation of the UCLA date lists I through VII. Samples were analyzed as CO2-gas at close to one atm in a 7.5 L proportional counter with 3 energy channels described earlier. Radiocarbon ages were calculated for uniformity on the basis of a 5568 yr half-life as was recommended by the Sixth International C14 and H3 Dating Conference, June 1965, in Pullman, Washington. The standard for the contemporary biosphere remains as 95% of the count rate of NBS oxalic acid for radiocarbon labs. Background determinations have been based on CO2 obtained from marble. The error listed is always at least a 1σ statistical counting error. In critical cases C13/C12 isotope ratio measurements were made to correct the dates for fractionation. All samples were subjected to accepted NaOH and/or HCl pretreatments depending on the individual case as a minimum to exclude contamination.

We used the scintillation variant of the radiocarbon method. The scintillator is prepared on the basis of ethylbenzol [benzene], synthesized from acetylene according to the method of Kuchkarev and Kondratenko (1955). For radiocarbon dating we used materials both rich in carbon: wood and charcoal, and [those] poorer: also peat, buried soils, and fossil bones. In the first instance, the initial material for synthesis was [char] coal, which was treated as follows:

Charcoal. Pavlov campsite [48° 50′ N Lat, 16° 25′ E Long], Czechoslovakia. Archaeologic [sic] age is beginning of Wörm III. Other determinations of charcoal from same campsite are: 24,800 ± 150 yr (GRO-1325, de Vries, 1958) and 26,400 ± 230 yr (GRO-1242, ibid.), which agree with our date. Subm. by A. N. Rogachev; [no date given (E.M.S.)].

Charcoal from campsite hearth from Zozov village, Rovno Oblast [Rovno city: 50° 30′ N Lat, 26° 12′ E Long], Ukrainian SSR. Kut hamlet, semi-subterranean Dwellings VII and VIII. Corded pottery culture; (cf. Gimbutas, 1956 [D.B.S.]). Subm, by I. K. Sveshnikov, Inst. of Social Studies, L'vov.

Lime (grouting) from old structures near city of Khar'khov [50° 00′ N Lat, 36° 10′ E Long]. Subm. [n.d.] by L. P. Papkova.

For determining age scintillation variant was used. Measurement of a large quantity of benzol [benzene] permitted reaching a limit of 62,000 yr without isotope enrichment. Precautions against contamination of the samples with contemporary carbon and tritium were taken in laboratory handling. Dating began only after it had been established that contamination had not taken place during chemical treatment. Benzol which displayed no radioactivity was synthesized from anthracite. Special measures were taken to remove humic acids from the sample by boiling the powdered sample for three days with three fresh lots of 2% solution of NaOH (Arslanov et al., 1966a, p. 134).

Peat, at depth 3.5 m, from upper of 2 layers, at village of Timoshkovichi [53° 35′ N Lat, 26° 05° E Long], Korelichi Raion, Grodno Oblast, Belorussian SSR. Timoshkovichi is located on Novogrudok upland, beyond limits of region of Valday [Wurm] Glaciation. Cross section synchronous with ancient ravine of Neman R. basin where 2 horizons of peat can be detected: the lower, according to pollen data, accumulated at time of Mikulino [Eem] Interglacial; the upper believed accumulated at time of 2nd climatic optimum of Mikulino Interglacial, or at time of early Interstadial of Valday [Wurm] Glaciation (Tsapenko and Makhnach, 1959). Coll. 1962 by N. S. Chebotareva, Geog. Inst., Acad. of Sci., USSR.