Recent experimental work has suggested that the relative fractionation of 14C to 13C may differ from the accepted value of b = 2. In order to explore the implications of this possibility, the standard formulae for correcting radiocarbon dates for fractionation effects are rederived, but without making any of the usual assumptions or approximations. A generalized dating equation is derived (where ASN and AON are normalized sample and standard activities, β is a factor which reflects changes in atmospheric 13C and 14C content, {RST(o)/RST}b accounts for post-depositional changes in sample 13C ratio, and tcal is calendar age in years before ad 1950. The errors in calculated ages which might arise from different b values are estimated and shown to be small relative to other dating uncertainties. The effect of b ≠ 2 may be important in the calibration of radiocarbon dates using tree-ring samples of known age. A theoretical analysis suggests that b ≠ 2 effects may result in a correlation between age anomaly (ie, the difference between radiocarbon age and calendar age) and sample 13C data. However, an analysis of published data reveals no meaningful correlation. This result, while not eliminating the possibility that b ≠ 2, highlights its unimportance even in this high-precision application of radiocarbon dating.

The aims of the 1973 Great Barrier Reef Expedition's radiocarbon dating programs were: 1) to collect live specimens from various reef environments to serve as modern reference standards, 2) to evaluate suitability of materials from drilling, geomorphic, and sediment programs for dating purposes, and 3) to date appropriate samples related to those programs. Radiometric ages provide a time scale for evolution of reefs and reef islands, and the history of sea level in the area.

The following list consists entirely of dates for archaeologic samples from the British Isles, mainly measured over the period from May 1979 to June 19801. The dates were obtained by liquid scintillation counting of benzene using the laboratory procedures outlined in previous lists (see, eg, BM-VIII, R, 1976, v 18, p 16).

This date list reports samples completed before 1979. Methods, equipment, and techniques were reported previously (R, 1968, v 10, p 246; R, 1970, v 12, p 87). Age calculations are based on the conventional 14C half-life of 5568 years. The working laboratory standard is 95% of the NBS oxalic acid standard (SRM 4990). Results are reported in years before 1950 and the standard deviation is based on counting statistics of sample, background, and modern standard. Corrections for δ13C are not included.

Routine radiocarbon analyses were last reported for the Laboratory of Isotope Geochemistry at the University of Arizona in 1971 (Haynes, Grey, and Long, 1971), and a special date list on packrat middens appeared in 1978 (Mead, Thompson, and Long, 1978). This list presents results obtained from our gas proportional counting facility before its major renovation and before the addition of a liquid scintillation counting system. The characteristics of these new systems will be described in the next date list.

This list contains the results of measurements made during 1978 and 1979. Ages were computed on the radiocarbon half-life of 5568 ± 30 years. Statistical errors quoted herein are 1σ counting errors which include sample, background, and standard. The age limit reported is calculated on the basis of 3σ activity. The σ13C values in table 1 were measured by Krueger Enterprises, Inc, Geochron Laboratories Division1 and calculated based on Craig's Peedee Belemnite (PDB) limestone standard (Craig, 1957). The total alkalinity as bicarbonate values reported in table 1 was determined using techniques described by Brown, Skougstad, and Fishman (1970). Unless otherwise stated, all samples were collected and submitted by personnel of the US Geological Survey.

This list contains most of the measurements made during 1980, since our last list (R, 1981, v 23, p 33-37). A second methane synthesis unit became operational (Dauchot-Dehon and Van Strydonck, 1979) at the end of 1979. Basically, this unit is the same as the one built earlier (Klebert and Heylen, 1966).

Samples in this paper are a continuation of the Florida geologic samples, reported earlier (R, 1978, v 20, p 436–440). Each specimen analyzed in this list was a carbonate shell. All dates are from single shells as opposed to means of multiple shell samples.

This list contains most of the measurements made during 1979, since our last list (R, 1979, v 21, p 180–185). The laboratory procedures were outlined previously (R, 1968, v 10, p 29–34; R, 1971, v 13, p 29–31). The collagen extraction follows Longin (1970).

The results presented in this date list are from the same sampling program previously reported (R, 1978, v 20, p 436–440). Each sample reported herein was geologic in origin and, in most instances, represents a single shell date.

This date list includes most of the archaeologic and geologic samples dated in this laboratory since publication of our last date list (R, 1978, v 20, p 210–233), as well as some samples dated previously which lacked adequate sample information.

The following list contains samples of geologic interest that were processed from February 1974 through May 1980 at the Illinois State Geological Survey (ISGS) Radiocarbon Dating Laboratory. The archaeologic samples processed during the same period will be published in our next date list. The benzene liquid scintillation technique was used following laboratory procedures previously reported by Coleman (1973; 1974).

The dates presented below are from some important archaeologic and Quaternary sites. All the dates are in years bp, based on τ½ = 5568 years. When converting archaeologic dates into the ad/bc scale, 1950 should be used as the base year. The dates are not corrected for 13C fractionation. All the dates older than 10,000 years have been given with 2σ errors.

Most of the 14C measurements reported here were made between October 1979 and October 1980. Equipment, measurement, and treatment of samples are as reported previously (R, 1968, v 10, p 36-37; 1976, v 18, p 290; 1980, v 22, p 1045).

This list contains 227 radiocarbon dates pertaining to the western part of southern Africa, between Luanda (9°S) in the north and the Orange R (29°S) in the south.

The results presented in this list have been obtained by benzene synthesis and liquid scintillation counting: ages are calculated using the 14C half-life of 5570 yr with 0.95 activity of NBS oxalic acid as modern standard, with no correction. The given precision is obtained from a one-standard-deviation criterion.

The following radiocarbon dates are a partial list of samples measured for a variety of projects and materials since August 1980. Chemical and counting procedures remain the same as indicated in R, v 20, p 274-282.

Results reported here are for samples of geologic or geographic context completed during the period 1975 to 1978.