Copenhagen Radiocarbon Dates IV

The following list includes samples from sites or sections described in archaeologic or geologic publications. Several others, already dated, will be published when the archaeologic and geologic investigations are concluded.

Variations in the Atmospheric Radiocarbon Concentration over the Past 1300 Years

Considerable attention has been focussed in recent years upon the validity of the radiocarbon dating method by papers whose authors have considered that one or other of the fundamental principles might either be in error or require serious modification (Crowe, 1958; Milojčić, 1957; Elsasser, Ney, and Winkler, 1957; Daniel, 1959). It has even been suggested that errors as great as 800 years might arise between datings on the same sample made in different laboratories (Crowe, 1958). In the light of such criticism, it is clearly of the utmost importance to investigate, and, if possible, justify the basic assumptions on which the validity of the method rests.

University of Michigan Radiocarbon Dates V

The following is a list of radiocarbon dates obtained since the time of the preparation of Michigan list IV. The method of measurement and treatment of data are the same as those described in the introductions to lists III and IV.

British Museum Natural Radiocarbon Measurements II

The second series of radiocarbon measurements made at the British Museum Research Laboratory are reported in the following list. The equipment and method used remain the same as described in our first date list (Barker and Mackey, 1959) and, as stated there, the error terms are not based solely on counting statistics but are widened to include contributions of ±80 years for possible isotopic fractionation effects and ±100 years for the de Vries-effect. Ages are calculated on a half-life of 5568 ± 30 years.

U. S. Geological Survey Radiocarbon Dates V

The dates listed herein have been determined at the U. S. Geological Survey radiocarbon laboratory at Washington since our last date list (USGS IV) and up to the end of 1959. Acetylene continues to be the gas of our choice. Each sample is run for a period of two days in two separate counters with separate electronics. The modern standard used is wood grown in the 19th century, and the ages and errors have been computed in the same manner as before. Pretreatment of wood, charcoal, and peat samples by boiling in acid, alkali, and acid again, is standard procedure.

University of Saskatchewan Radiocarbon Dates II

This paper is a list of radiocarbon dates obtained at the University of Saskatchewan since the last report was issued (McCallum, 1955). The method used is essentially that of Suess (1954), in which the sample is counted as acetylene gas. The proportional counter has a sensitive volume of one liter and is filled with acetylene to a pressure of one atmosphere. Each sample is counted for at least two 20-hour periods. The modern standards used were obtained from softwood logs grown in Northern Saskatchewan and were either 50 or 100 years old as obtained from ring counts.

Trondheim Natural Radiocarbon Measurements II

This date list covers the period from September 1958 to December 1959 and a few earlier dates omitted from our first list (Nydal, 1959). As regards the geologic samples, the accordance between the C14age and the age predicted from geologic considerations is generally very good, and most of the discrepancies can be reconciled in favor of the C14result.

Stockholm Natural Radiocarbon Measurements III

This paper is a direct continuation of the second date list released from this laboratory (Östlund, 1959), and the technique of preparation and the characteristics of our two 3-atmospheres carbon dioxide counters are substantially unchanged (Östlund 1957a, b). As in previous lists, our standard is oak wood, grown, A. D. 1845–1855 in Stockholm. corrected for radioactive decay to 1960. As usual, the counting rates have been corrected according to the massspectrometrically measured C13/C12ratio in each sample of purified carbon dioxide. In this scale the U. S. National Bureau of Standards Natural Radiocarbon Standard (NBS standard) gives a counting rate which is 104.5 ± 0.4% of our age-corrected oak standard. Taking into account that our oak has a C13/C12ratio of 25 per mil lower than the Chicago PDB-C13standard, our age figures can, by subtracting 55 years, be converted to the new, international radiocarbon age scale proposed by Broecker and Olson (1959).