Dear Editor,

Professor R. E. Taylor, in his review for R adiocarbon of my book Relic, Icon or Hoax? Carbon Dating the Turin Shroud (Taylor 1997) noted that I had incorrectly used the word “invent” and its derivatives in connection with the origins of accelerator mass spectrometry (AMS). A more accurate description of the development of AMS is to be found in the papers that I co-authored (Gove, Litherland and Purser 1987) and authored (Gove 1992) prior to publication of my book. Who actually “invented” AMS is not clear. Certainly, strong contenders are L. W. Alvarez and R. Cornog (Alvarez and Cornog 1939) and K. H. Purser (Purser 1977). The contributions made by Purser, A. E. Litherland and me to the development of AMS were recognized by Pergamon Press in 1980 when the Board of Editors of the International Journal of Applied Radiation and Isotopes (JARI) voted to give us the first JARI award. I should note that neither of my two colleagues with whom I was involved in the development of AMS, Professor Litherland nor Dr. Purser, saw a copy of my book before publication. If they had, this unintended contretemps would not have occurred.

Yours sincerely,

The following list presents results of dating of 55 paleoenvironmental and archaeological samples from Argentina, processed between 1984 and 1986 by M. A. Albero and F. Angiolini. Procedures for sample pretreatment, counting, statistical analysis and age calculation were essentially the same as previously described by Albero and Angiolini (1985). Results are reported as conventional 14C dates in years before ad 1950. They are corrected for isotopic fractionation.

Based on the study of DNA adduction with nicotine, we have measured the mouse hepatic histone adduction with 14C-labeled nicotine in vivo by bio-accelerator mass spectrometry (bio-AMS). In the exposure of mice to nicotine, the dose range administered was from 0.2 μg to 6.0 μg kg b.w.-1, which was equivalent to a very low level of human exposure to cigarette smoke. The adducts of either histone 1 (H1) or histone 3 (H3) with nicotine in mouse liver increased markedly with increasing nicotine dose. Our results have demonstrated that in the study of protein adduction with toxic xenobiotics as a biomarker, the AMS method achieves the highest sensitivity, 4.6 × 10-17 mol (46 amol) adducts per mg H1 protein, compared to all the other methods used previously.

This paper includes determinations of archaeological, geological and palaeobotanical samples from Spain and Portugal, measured at the University of Granada Radiocarbon Dating Laboratory, from 1990 to 1991. Pretreatment of charcoal and wood samples is a standard acid-basic procedure using 8% HCl and 2% NaOH at boiling temperature. The collagen of bone samples is obtained by the Longin (1971) method. The method of dating is benzene synthesis and liquid scintillation counting.

This paper includes determinations of archaeological, geological and paleobotanical samples from Spain and Brazil, measured at the University of Granada Radiocarbon Dating Laboratory, mainly from 1991 to 1992. As previously reported (González-Gómez 1992), pretreatment of charcoal and wood samples is a standard acid-basic procedure using 8% HCl and 2% NaOH at boiling temperature. The collagen of bone samples was extracted by the Longin (1971) method. The method of dating is liquid scintillation counting of synthesized benzene.

The radiocarbon dating laboratory has been in operation since 1984 at the Radiation Center of Osaka Prefecture (OR), predecessor of the Research Center of Radioisotopes, University of Osaka Prefecture. We use liquid scintillation counting (LSC), following sample conversion to methanol through combustion and LiAlH4 reduction. This method was developed by Yamada et al. (Yamada, Higashimura and Shidei 1966; Yamada and Kobashigawa 1986). In cooperation with Yamada, we somewhat modified their procedure: 1) sample charcoal is burned at 700° in the presence of CuO needles and Sulfix grains to remove sulfur and halogen compounds produced during the combustion; 2) the combustion is carried out by using N2-O2 mixed gas of minimized O2 content and stopped when a small amount of the charcoal still remains unchanged, because precise investigation of methanol preparation revealed that O2 gas stimulates byproduct formation during LiAlH4 reduction (Shibata et al. 1985; Shibata et al. 1993). Usually, methanol is prepared directly from sample charcoal in a reaction apparatus (“direct method”). When the sample quantity is insufficient, generated CO2 is isolated as CaCO3 and diluted with inactive commercial CaCO3 if necessary (< 40 g of CaCO3 yield). Then CaCO3 is hydrolyzed with HCl to CO2 for methanol preparation in the usual way (“separate method”). We use standard oxalic acid SRM 4990C (HOxII) for determination of modern 14C (Stuiver 1983). The acid is oxidized to CO2 using the wet method of Valastro, Land and Valera (1977) followed by methanol preparation in the same manner as for unknown samples.

This paper presents a compilation of the >520 radiocarbon and oxidizable carbon ratio dates obtained since the early 1950s from archaeological sites in East Texas. Many of the dates are from difficult-to-obtain sources, such as archaeological sites investigated during the course of cultural resource management projects. An analysis of the age ranges in the dates indicate that most pertain to prehistoric and protohistoric Caddoan Indian occupations, particularly the Early (ad 1000–1200) and Middle Caddoan (ad 1200–1400) periods when prehistoric Caddoan settlements were widely distributed throughout the region.

This date list mainly reports on samples processed from 1982 to 1991. Each sample is converted to methanol. Radiocarbon is measured in a Teflon™ vial containing a mixture of 40 g of methanol and 50 cc of xylene, 1% Butyl PBD and 0.1% PBBO using low-background scintillation counters Aloka LSC-800, LB-I and LB-III. The background of LB-III is ca. 8 cpm and counting efficiency is ca. 70%. The recent 14C standard used is 95% of NBS oxalic acid; 5568 yr is used as the half-life of 14C.

The lithium reagent used in the synthesis of benzene for 14C dating contributes insignificant 14C in high-precision measurements on 7 g benzene samples. Blank experiments on three different batches of lithium yielded small amounts of carbon, most of which probably originated as “memory” in the reaction vessel.

We present a proposal for a further intercomparison exercise following discussions at the 16th International Radiocarbon Conference in Groningen in 1997. This new intercomparison will build on previous exercises by making use of both reference materials already characterized and additional known-age material. For this comparison, we describe two separate but essentially related protocols that are meant to satisfy the different priorities of radiometric and AMS laboratories. The new intercomparison is planned to begin in mid-1998.

This note describes point and interval estimation of a settlement time from a collection of radiocarbon dates. An application concerning the settlement time of New Zealand is presented.