This list includes most of the samples measured from June 1970 to June 1972 and some other results not yet published in previous date lists.

The following list comprises selected measurements made in the Louvain 14C Dating Laboratory with the 0.6 L CH4 proportional counter. Details of procedure are given in previous lists. Dates are reported in terms of the Libby half-life, 5570 ± 30 years and quoted with 1σ experimental error.

The C14 dates given below have been obtained by counting CO2 at 2 atm pressure in a 1 L proportional counter. Details of procedure are given in our previous list (R., 1970, v. 12, p. 187–192). Radiocarbon dates in this list are based on 95% of activity of NBS oxalic acid as the modern standard and were calculated using 5570 yr as the half-life of C14. Errors quoted with the dates are standard deviation originating from the statistical nature of radioactive disintegration process. Results obtained during 1970 and 1971 are described here.

The dates presented here comprise results obtained since our last list (R., 1973, v. 15, p. 156-164). Pure carbon dioxide prepared from the samples is used to fill copper proportional counters at two atmospheres pressure. The detectors are protected from environmental radiation by a massive lead shield inside which, and completely surrounding the proportional counters, is a high efficiency plastic scintillation anticoincidence screen (Switsur, Hall, and West, 1970). Modern sample gas is obtained from combustion of a.d. 1845 to 1855 rings of an oak tree grown near Cambridge, felled in 1950. Background samples are prepared from Welsh anthracite or Connemara limestone. The contemporary standard is compared frequently with the activity of NBS oxalic acid international standard. Age calculations are based on the 14C half-life of 5568 years and the uncertainty stated as one standard deviation calculated from the statistical analysis of sample and standard counting rates.

The following list of determinations is compiled from samples prepared since publication of our last date list (R., 1969, v. 11, p. 137–149) and includes sample measurements through July, 1970. The Radiocarbon Laboratory was dismantled and transported to Halifax, Nova Scotia, where it will resume operation as the Dalhousie University Radiocarbon Dating Laboratory.

The following list of dates was compiled since 1971, (R., 1971, v. 13, p. 420-431). Procedures of measurements are essentially unchanged from those reported previously (R., 1964, v. 6, p. 31-36; 1966, v. 8, p. 423-429; 1971, v. 13, p. 420-431).

The present list includes most of the samples measured since the establishment of the laboratory in 1965 and not yet published in the two previous dates lists.

The measurements presented in this paper were carried out at the University Radiocarbon Dating Research Laboratory during the second half of 1971 using carbon dioxide counting. The counting equipment used was substantially that described by Switsur, Hall, and West (1970). Oxidation of samples of sufficiently high carbon content was performed in a stainless steel high pressure combustion bomb, developed at this laboratory, otherwise by ‘wet’ oxidation using acidified permanganate solutions for lake mud and samples of low organic content.

The Radiocarbon Laboratory at the Scottish Universities Research and Reactor Centre was established in August 1971. The laboratory is funded by the Natural Environment Research Council and its main function is geochemical investigations in collaboration with the component bodies of the Council and with grant-aided associations. A dating service is also provided to others.

This date list includes most of the archaeologic and geologic samples dated in this laboratory since publication of our last date list (R., v. 12, p. 577–589), as well as some samples which had previously been dated, but lacked the sample information necessary for publication. Known-age samples, completed in this time period, will be reported elsewhere. The b.p. ages are based upon a.d. 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 minutes each. Errors quoted for each sample are derived from the measurement of the sample, the background, and of several counts of our mid-19th century standard 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 list includes age measurements made from November 1970 to December 1971. All archaeologic and geologic samples come from Italian territory. Laboratory equipment, largely unchanged but expanded and technically improved, was previously described (Alessio et al., 1970a). Charcoal and wood samples underwent standard pretreatment by boiling with 5 to 10% HCl; α-labeled samples were given additional leaching with 6% NH4OH or 0.2N NaOH.

During the last few years, we have set up the benzene scintillation method in our laboratory. C14 activity measurements are now carried out with both liquid scintillation and CO2-proportional counters. Chemical apparatus for benzene synthesis and a liquid scintillation spectrometer for low-level counting were built and are described below.

This list describes samples dated in this laboratory from January to November, 1972. Operating principles are as previously reported (Gillespie et al. 1972) using synthesized benzene for liquid scintillation counting. Ages are calculated using 0.95 NBS oxalic acid standard with reference to a.d. 1950 using Libby 5570 year half-life.

This list contains results obtained since July 1970. They are mainly hydrologic and geologic samples prepared and counted as described in our previous date list, (Carmi et al., 1971). The coordinate system used to describe sampling locations is the local one.

This list includes samples completed to July, 1972. All samples are counted for at least 2500 min., and X2 analyses are made on 100-min. print-outs. Errors quoted are 1σ, derived from sample, background, and NBS oxalic acid standard measurements, adjusted where appropriate for small-sample dilution.

In this date list we present dates from some very important archaeologic and Quaternary sites. For the first time the temporal spread of the Neolithic cultures of Bihar and the transformation of the Harappa culture in Gujarat has been dated. Some of the sites of controversial antiquity in Pakistan and India also have now been unambiguously dated.

The radiocarbon dating laboratory at Rice University first became operative in the fall of 1970. A workable technique has been developed although operations are still in a state of flux. The benzene liquid scintillation counting method is used, the benzene being prepared as outlined by Noakes, Kim, and Akers (1967) with the following modifications. The CO2 is further purified prior to storage and measuring by passing it through 3 gas bubblers containing potassium permanganate solution, silver nitrate solution, and a sulfuric acid-sodium dichromate solution (S. Valastro, pers. commun., 1970). Since no C12 C13 analyses are available at present, to insure a complete reaction, both the CO2 generation and the C2H2 generation are continued for ½ hr after all visible signs of reaction have disappeared.

Preparations for determining absolute age by the radiocarbon method were started at the Institute of Geology, Academy of Sciences of the Estonian SSR in 1971. Dating of samples has been carried out since 1972.

Measurements have continued with the same proportional counter system, the same procedure in sample pretreatment, methane preparation and measurement, and the same age calculation using a half-life of 5568 ± 30 yr as described previously (R., 1970, v. 12, p. 298–318).

Ages reported in this date list are calculated using the Libby half life of 5568 ± 30 years with 1950 as the standard year of reference; results are quoted in years b.p. and on the a.d./b.c. time scale.