A description is given of the use of a Tandetron accelerator mass spectrometer system for measuring the isotopes 10Be and 26Al.

The following list contains samples of geologic interest that were processed from June 1980 through March 1983 at the Illinois State Geological Survey (ISGS) Radiocarbon Dating Laboratory. The benzene liquid scintillation technique was used following laboratory procedures previously reported by Coleman (1973, 1974).

The advent of accelerator-based mass spectrometry (AMS) radiocarbon dating has reduced the minimum sample size required to ca 1 mg from the 1 g of traditional beta counting techniques (cf Wölfli, Polach & Andersen, 1984). However, it is clear that even smaller samples will be necessary for some fields of endeavor, particularly environmental work where the absolute quantities are small, perhaps of the order of a few micrograms (Currie et al, 1985). This raises serious problems in the handling and measurement of such small amounts, so that dilution will sometimes be required. Normally, sample dilution is accomplished by adding “dead” CO2 to the combusted sample CO2, which requires very careful measurement of two gas pressures for the calculation of a dilution ratio. By forming a chemical derivative of a sample before combustion, gas pressure measurement is not necessary and an exact dilution ratio can be selected by judicous choice of the dilution reagent. This paper demonstrates that such a technique is possible for the AMS 14C dating of derivatized amino acids.

Precision 14C analyses have been performed on samples comprising 1 to 4 annual rings from the south-central European dendrochronologic sequence of sub-fossil oak wood covering the period 1930 to 3100 bc. Apart from a major deviation in the 29th century bc, the 14C fluctuations have amplitudes of ca 10‰ and a possible periodicity of 90 years. A 14C peak at 2190 bc has a rise- and decay-time of <20 years indicating rather abrupt changes in the production rate of 14C. The 14C calibration curve derived from these data can be used for precise dating of the Early Bronze Age in the Near East.

This paper contains 14C results obtained by the special high-precision proportional gas counter, designed by Tans and Mook (1978), on tree rings from the South German oak chronologies: Donau 7, 3, 10, and 12, originating from the Danube River basin (48° 24’ N, 10° 5’ E).

A description of accelerator mass spectrometry (AMS) measurements with the long-lived radioisotope 36Cl is given. All measurements were made at the Munich tandem accelerator laboratory. Results are presented for 36Cl measurements in ground waters, in the meteorite Bjurböle, in ice-core samples of the Vernagtferner, Austria, and in granite samples from Hiroshima, Japan, irradiated by the atomic bomb explosion in 1945.

The prehistoric settlement of Abu Hureyra in Syria was occupied in both the Epipaleolithic and Neolithic periods. It has provided significant evidence for changes in economy at the time of the inception of agriculture in southwest Asia. Twenty accelerator mass spectrometry (AMS) dates have been obtained to determine the duration of occupation of the Epipaleolithic settlement there and the precise age of samples of cereal grains and animal bones found within it. The results have demonstrated that the AMS technique can answer such questions because it dates exceedingly small samples with high precision. The dates indicate that the Epipaleolithic settlement was inhabited for about a millennium, from before 11,000 to nearly 10,000 bp, significantly longer than had been anticipated from study of the artifacts.

The present list contains 14G dates from archaeologic samples attributed to the European Mesolithic period from the typology of associated finds, especially microliths. Of these samples, 14 are from Germany and 6 from France.

It was T Higashimura of Kyoto University who did the first liquid scintillation measurement for 14C in Japan. The External Standard Method (Higashimura et al, 1962) has been accepted the world over as an efficient method of measuring low-level radiation.

New results of radiocarbon dating of ca 100 decadal bristlecone pine samples from 6554 BC to 6084 BC and from 5820 to 5350 BC are presented. Using 3 new 2.5L counters filled to ca 3atm with carbon dioxide, high-precision dating has been performed by this laboratory for more than two years. Demonstration of the precision and accuracy of these counters is presented using ±2‰ measurements from the Spörer minimum period. For the older samples, ±3‰ measurements were made using ca 12-day counting times. Results are presented both as C age bp vs dendro-year BC, particularly for calibration purposes, and as Δ14C vs time.

Most of the 14C measurements reported here were made between October 1983 and October 1984. 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).

Tests have been carried out on the measurement of 14C directly from CO2, using a source designed by Middleton, and a Tandetron accelerator mass spectrometer system. These tests were very promising from the point of view of minimum quantity of carbon necessary (<50μg), but suffered from a background (apparently not memory effect) giving an equivalent age of ∼25,000 years. As a demonstration of the technique, a single thread from the mummy wrapping of the Egyptian king Ramses II was dated.

The Simon Fraser University accelerator mass spectrometry (AMS) facility has now been in semi-routine use since the beginning of 1985. The advantages and limitations for 14C dating are described.

The following list consists of dates of archaeologic and geologic samples measured from January 1981 to December 1982. Measurements were continued with the same proportional counter system, pretreatment procedure, methane preparation, measurement, and calculation, as described previously (Kanwiszer & Trzeciak, 1984). Ages were computed on the 14C half-life of 5568 ± 30 years. Precision is reported as one standard deviation based only on statistical counting uncertainties in the measurement of the background, NBS modern standard, and sample activities. The dates are not corrected for 13C fractionation. Descriptions and comments are based on information supplied by submitters of samples.

Glassy microspherules, typically 200μm or less in diameter, are well documented from a variety of terrestrial and extraterrestrial sources (Baker, 1959, p 192–198; Glass, 1969; Rost, 1969; McKay, Greenwood & Morrison, 1970; Mueller & Hinsch, 1970; Cross, 1971; O'Keefe, 1980). To these we would add the formation of microspherules of similar habit when wood charcoal is burned in a combustion bomb (Barker, Burleigh & Meeks, 1969; Burleigh, 1973, 1974; Switsur, 1973; Switsur et al, 1974) as a first step in the chemical synthesis of samples for 14C age measurement. The glassy material of these spherules originates from fusion at the high temperatures reached during the combustion, of traces of alkali-metal minerals in the charcoal and silica bodies (phytoliths) within its microstructure. Other materials commonly burned, such as bone collagen, do not yield microspherules. The age and source of the charcoal are immaterial, though different species (and perhaps other woody plant materials) may be more-or-less productive of spherules. Here we give a brief summary of the characteristics of these glassy microspherules, based on optical and scanning electron microscopy and energy-dispersive x-ray analysis.

14C calibration curves derived from South German oak tree-ring series are presented. They cover the interval between 4400 and 7200 BC complementing existing data sets and extending them to older periods. The atmospheric 14C level before 6200 BC no longer follows the long-term sinusoidal trend fitted to the bristlecone data. This observation is supported by a tentative match of the Main 9 series.

A proposal for an international collaborative study to investigate and assess the existence of inter-laboratory variability is discussed. The proposed study would be conducted over two years and would investigate each stage of the dating process in turn.

A new laser-based analytical technique is described for isotope selective noble gas atom counting. The method has been used to detect 81Kr atoms in a groundwater sample.

Holocene tree-ring chronologies have been established for south-central Europe covering the past 11,000 years. The Hohenheim absolute oak chronology extends to 4089 bc. The C-calibrated mid-Holocene floating oak master covers a 3181-year period from ca 4045 to 7225 bc. The earliest well-replicated floating oak master (estimated calendar age 7215 to 7825 bc) extends the European oak dendrochronology back to Boreal times.

Further extension of the Holocene dendrochronology has been achieved by subfossil oak and pine trees from the Rhine, Main, and Danube Rivers. A 774-year floating series of Preboreal pine has been established. 14C ages range (from younger to older end) from 9200 to 9800 BP. Within this series a major atmospheric 14C variation is indicated, resulting in nearly constant 14C ages (9600 BP) over a period of 370 tree-rings.

The European oak and pine tree-ring chronologies cover without major gaps the entire Holocene epoch. Based on the length of the dendro-records, an approximate solar year age of 11,280 years is calculated for the Holocene/Pleistocene boundary.

The Preboreal pine forests along the rivers were replaced by mixed oak forests between 9200 and 8800 BP. By linking the earliest oak masters and the Preboreal pine series, the European dendrochronology can be extended up to the end of Late Glacial times.