A systematic crosschecking of the NBS oxalic acid standard, the ANU Sucrose secondary standard, and the RB oak tree rings grown in 1858 ± 5 and 1890 ± 5 has been performed using the proportional counter technique. Details on the counter gas (methane) purification are given. Corrections of count rates due to changes of barometric pressure and ambient temperature are applied and discussed. Results of measurements are presented and the ratios between mean activities of the NBS oxalic, ANU sucrose and RB oak samples are given.

The thermal diffusion enrichment system of the Quaternary Isotope Laboratory consists of 23 hot wire columns of 3m effective length combined to 2 separate systems of 3 and 3 separate systems of 4 columns at the top, each system in series with 1 bottom column. From ≈ 130 L NTP of CO (∼ 65g of carbon) it produces ≈ 8 L NTP of CO (~ 4g of carbon) enriched in 12C18O by a factor 6 to 7 and in 14C16O by a factor 7 to 8 in about 5 weeks. For 12C18O the system has a theoretical equilibrium separation factor of about 250 and a theoretical equilibrium enrichment of about 15. For 14C16O these values are 1300 and 16, respectively. The dependence of thermal diffusion transport on gas exchange between top and bottom section and between columns and reservoirs and on wire temperature is given. Forced gas exchange and a higher wire temperature gave a more rapidly increasing enrichment without substantially increasing its final value of 6 to 7 for 12C18O. A comparison with the Groningen enrichment system shows that the two systems behave very similarly and that not the system geometry but individual column parameters and the ratio total sample mass/enriched sample mass are the dominant factors determining the enrichment.

Radiocarbon dating involves a comparison of the count rate of sample carbon with that of modern reference standard material. To calculate a date the ratio Z must be determined where

Along SE coast of Australia a variety of Holocene barriers composed of siliceous sand and shell detritus occur within bedrock-confined embayments. On basis of morphostratigraphy 4 barrier types are recognized: prograded, stationary, receded and episodic transgressive dunes. Several subtypes are also distinguished. Composite bay barriers involving partial eolian reworking of a prograded barrier constitute most complex examples of Holocene depositional sequences on this coast. The present list is a preliminary attempt at defining the age structure of a group of such barriers (excepting receded type). Ages are reported in conventional years bp. Text references to ages and age ranges are environmental effect corrected ages bp* and yr* (as recommended by Stuiver and Polach, 1977), using 450 ± 35 yr as postulated by Gillespie and Polach (in press) in order to relate Australian oceanic environment shells to terrestrial environment wood. δ13C errors, where based on measurement, are always ± 0.2% and are not shown in the text; when based on estimated values (Est) the error is given.

Most of the dates reported in this list were obtained between November 1975 and December 1976. All samples were subjected to standard de Vries pretreatment. Age calculations are based on a contemporary value equal to 0.95 of the activity of NBS oxalic acid standard and on the Libby value for the half-life of radiocarbon. Results are reported as conventional radiocarbon dates in years before ad 1950. All measurements were made with our L1 counter (Mościcki & Zastawny, 1976). Counting rates of all samples were normalized to the standard value of CO2 pressure and corrected for the counting efficiency (Pazdur et al, 1978). Errors quoted (±1σ) include estimated overall standard deviations of count rates for the unknown sample, contemporary standard and background (Pazdur, & Walanus, in press). No corrections for 13C/12C ratio were made for measurements reported in this list. The value of δ13C for our NBS oxalic acid standard is equal to — 19.41% relative to the PDB standard. The descriptions of the samples are based on information provided by the submitters.

The construction and performance of a proportional CO2 counter system is described by which an over-all accuracy is obtained of 1.3‰ after a two-day counting period.

The following date list presents results obtained during 1975-1977. The facilities at Glasgow have been further developed and include a gas counting system utilizing CO2 as counting material and two liquid scintillation counting laboratories based on synthesis of benzene. The results presented here were obtained using the liquid scintillation system only. Sample pretreatment varied according to individual sample type, whether wood or charcoal. The majority of samples were of preserved wood. After manual removal of gross contamination, samples of wood were finely chopped and digested in boiling, 2M KOH solution. The dehumified wood was then separated by filtration, thoroughly washed with distilled water and dilute hydrochloric acid, and then bleached in a solution of NaClO2/HCl at 80°C for 48 hours. Pure, white wood cellulose was obtained by filtration and washed with a large volume of distilled water. The cellulose, typically 40% by weight of the original material, was then dried overnight in an oven at 80°C. Samples of charcoal were closely examined for non-contemporaneous contamination and then subjected to successive treatments with hot, dilute (1M) KOH and HCL, respectively. The remaining charcoal was then dried overnight at 80°C.

The following list consists of dates for archaeologic samples measured over the period from June 1974 to July 1976. The dates were obtained by liquid scintillation counting of benzene using a Model 3315 Packard Tricarb Liquid Scintillation Spectrometer linked to a Hewlett Packard 2100A computer system for on-line processing of counting data (Hall & Hewson, 1977). The laboratory procedures used were essentially those outlined in previous lists (see, eg, BM-VIII, R, 1976, v 18, p 16).

The following list consists entirely of dates for archaeologic samples from the prehistoric flint mining site of Grime's Graves, Weeting, Thetford, Norfolk, England (52° 30' N, 0° 40' E, Natl Grid Ref TL 816898), measured over the period from August 1973 to December 1977,* all the samples having been excavated between 1972 and 1976. The dates were obtained by liquid scintillation counting of benzene using a Model 3315 Packard Tricarb Liquid Scintillation Spectrometer linked to a Hewlett Packard 2100A computer system for on-line processing of counting data (Hall & Hewson, 1977). The laboratory procedures used were those outlined in the two previous lists (R, 1976, v 18, p 16; 1977, v 19, p 143).

This series reports some of the measurements made since publication of the previous list. Methods essentially remain as described in Saskatchewan II (R, 1960, v 2, p 73). The laboratory now joins operation with the National Museum of Canada, Ottawa. The prime purpose is to provide radiocarbon dating service for Canadian archaeologists through the National Museum, although commercial services are available to others as analytical capacity permits.

This list comprises age measurements carried out from May 1977 to July 1978. Nearly all the samples are of prehistoric and archaeologic interest. All samples are from Italian territory.

This list includes results of measurements made during 1974-1978. When requested, MASCA corrected dates (Ralph et al, 1973) are reported.

The following date list covers certain samples dated by this laboratory from Nov 1975 through December 1977. All archaeological, all geological, and some of the geochemical samples measured during that period are included here. Measurements of tree-ring samples analyzed through Sept 1977 have been published previously (Suess, 1978); later measurements of wood samples will be included in the next list. Data and interpretation of 14C in the CaCO3 of annual coral growth have been published (Druffel & Linick, 1978) with further coral data to be published in the future.

Experimental procedures and methods of age calculation are as previously described (Gillespie Sc Temple, 1976), except that bc/ad ages are not reported (resolution of 9th Radiocarbon Conference, 1976).

The dates in this list follow on, approximately chronologically, from Harwell II (R, 1977, v 19, p 400-423) and refer principally to measurements carried out in the period 1975-6. Laboratory techniques have remained essentially unchanged from earlier reports but a full description of the setting-up philosophy and operating procedure of the liquid scintillation counting systems has now been published separately (Otlet and Warchal, 1977).

Results reported here are for samples of geologic context. Throughout the period of these analyses, viz, 1973 through 1975, the preparation of samples and operation of counting systems remained essentially as described in Radiocarbon, 1973, v 15, p 554 to 565.

The following radiocarbon dates are a partial list of samples measured since January 1978. The chemical, counting and calculation procedures are the same as indicated in R, v 20, p 000-000.

Most of the 14C measurements reported here were made between October 1977 and October 1978. Equipment, measurement, and treatment of samples are as reported previously (R, 1968, v 10, p 36-37; 1976, v 18, p 290) except for some minor improvements of the electronic equipment.

This list reports certain 14C measurements completed by November 1978; other projects completed by this time will be reported later. Age calculations are based on 14C half-life of 5568yr and modern standard of 95% NBS oxalic acid, supplemented by tree rings of pre-industrial wood from a log cut in the 1850's (Tx-540; R, 1970, v 12, p 249). Deviations reported are based on counting statistics of sample, background and modern, and are ± 1σ, except that when sample count approaches either modern or background, 2σ limits are reported. Unless noted, 12C/13C measurements were not made and results are not corrected for 13C fractionation (assumed ratio = −25‰ WRT PDB). Our laboratory uses liquid scintillation counting of benzene, with Li2C2 and vanadium-activated catalyst in preparation; chemical yields range between 95% and 99%. Three counters are employed; a Packard Tri-Carb Model 3002 and 2 Beckman LS320 spectrometers obtained through a grant from the National Science Foundation.

Measurements have continued with the same proportional counter system, pretreatment procedure, methane preparation and measurement, and calculation, as described previously (R, 1970, v 12, p 298-318). Uncertainties quoted are single standard deviations originating from standard, sample, background counting rates and half-life. No 13C/12C ratios were measured.