Introduction

This list includes dates of geological samples measured using a single-channel liquid scintillation 14C counter at the Geochemical and Statistical Laboratory, Tartu, Estonia. Our modern standard is made of benzene enriched in 14C, and its activity is checked with NBS oxalic acid standard sample. Dates are given in conventional radiocarbon years, based on the Libby half-life of 5570 ± 30 years. A.D. 1950 is the reference year. Errors refer only to 1σ standard deviation calculated from count rates involved.

The results in this list come from our earlier years of operation and form part of the special series of lists being prepared to clear the backlog of unpublished dates from this laboratory, in this case 49 samples coming from sites in and around Northampton, UK. They originate from excavations directed by John Williams and Helen M Bamford of the Northampton Development Corporation between 1973 and 1982, and all were submitted for measurement and paid for by the Ancient Monuments Laboratory of the Historic Buildings and Monuments Commission for England and Wales.

This is the third of the series of lists of English archaeologic dates submitted to Harwell for measurement by the Historic Buildings and Monuments Commission for England and Wales within a prescribed contractual period. This list of 155 dates covers the period April 1987 to March 1988 and results are reported whether the associated projects are completed or on-going.

The Radiocarbon Laboratory at the University of Barcelona began its serial measurements in 1985. The following list contains dates obtained between 1985 and 1987. Both archaeological and geological samples were dated.

The measurement technique we use is liquid scintillation counting of benzene. A previous paper (Mestres, García & Rauret 1991) describes sample pretreatment, synthesis and counting protocols and equipment.

This paper includes some determinations of archaeological, art and palaeobotanical samples from Spain and Portugal, obtained at the University of Granada Radiocarbon Dating Laboratory, mostly from 1986 to 1988. Pretreatment of charcoal and wood samples is a standard acid-basic procedure using 8% HC1 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 as previously reported (González-Gómez, López-González & Domingo-García 1982; González-Gómez, Sánchez-Sánchez and Domingo-García 1985; González-Gómez, Sánchez-Sánchez and Villafranca-Sánchez 1986, 1987).14C activity was measured in a Packard Tri-Carb Mod 4640 liquid scintillation spectrometer, using 20 ml low 40K counting vials with 5 ml benzene and 10 ml PPO-toluene as scintillator with a background of ca. 9 cpm. Efficiency was approximately 70% using the part of spectrum above the end point of tritium.

The results presented in this list were obtained from 1986 to 1989. Equipment, measurement and treatment of samples are as reported previously (Kanwiszer & Trzeciak 1984: 111). Age calculations are based on a contemporary value equal to 95% of the activity of NBS oxalic acid standard and on the conventional half-life for 14C of 5568 ± 30 years. Results are reported in years before 1950 (years BP). Errors quoted (± 1σ) include standard deviations of count rates for the unknown sample, contemporary standard and background. The dates are not corrected for 13C fractionation. Descriptions and comments are based on information supplied by submitters of samples.

This list includes dates from Italy, Libyan Sahara, Niger and the Dahlak Islands, obtained from 1976 to 1980, using the benzene scintillation method.

Chemical processing from sample to benzene follows procedures of Alessio et al (1978a). Standard pretreatment for wood and charcoal included boiling with 5–10% HCL.

This list includes some significant measurements carried out by CRAD Radiocarbon Laboratory from 1979 to 1985. The dates were obtained by liquid scintillation counting of benzene using the laboratory procedures described in previous lists (Barbina et al 1982: 214-216; Barbina, Calligaris & Ciuti 1979). Samples were pretreated according to generally applied methods, depending on type of material and particular archaeologic and geologic features.

We report 63 new radiocarbon analyses of samples from São Miguel, the largest (ca 62 × 13km) and most populous (ca 150,000 inhabitants) island in the Azores archipelago (Fig 1). The samples are mainly carbonized tree roots and other plant material collected from beneath 20 mafic lava flows and spatter deposits and from within and beneath 42 trachytic pyroclastic flow, pyroclastic surge, mudflow, pumice-fall, and lacustrine deposits and lava flows. One calcite date is reported. The samples were collected during geologic mapping of the entire island (Moore, in press A; sample locations are shown on this map). Nine 1:25,000-scale topographic maps, published in 1983 by the Portuguese Army Cartographic Service, cover the island; samples and locations described below refer to these named sheets.