Uppsala Natural Radiocarbon Measurements IX

Quaternary Geochronology, 2009

The past few hundred years have seen large fluctuations in atmospheric 14 C concentration. In part, these have been the result of natural factors, including the climatic changes of the Little Ice Age, and the Spö rer and Maunder solar activity minima. In addition, however, changes in human activity since the middle of the 19th century have released 14 C-free CO 2 to the atmosphere. Moreover, between c. 1955 and c. 1963, atmospheric nuclear weapon testing resulted in a dramatic increase in the concentration of 14 C in the atmosphere. This was followed by a significant decrease in atmospheric 14 C as restrictions on nuclear weapon testing began to take effect and as rapid exchange occurred between the atmosphere and other carbon reservoirs. The large fluctuations in atmospheric 14 C that occurred prior to 1955 mean that a single radiocarbon date may yield an imprecise calibrated age consisting of several possible age ranges. This difficulty may be overcome by obtaining a series of 14 C dates from a sequence and either wigglematching these dates to a radiocarbon calibration curve or using additional information on dated materials and their surrounding environment to narrow the calibrated age ranges associated with each 14 C date. For the period since 1955 (the bomb-pulse period), significant differences in atmospheric 14 C levels between consecutive years offer the possibility of dating recent samples with a resolution of from one to a few years. These approaches to dating the recent past are illustrated using examples from peats, lake and salt marsh sediments, tree rings, marine organisms and speleothems.

uni-koeln.de

Contains a description of technical procedures used for radiocarbon dating at the University of Cologne Radiocarbpn Laboratory.

Memoirs of the Society for American Archaeology, 1951

The Preceding discussions have considered the radiocarbon dates in relation to a number of archaeological, geological, and palynological problems. It remains to consider the endeavor as a whole, and to reach some conclusions concerning its present and future value and usefulness. Of primary importance is a consideration of what the dates mean. Basic to this is an understanding of the statistics involved. At the request of the Committee, Arnold, who has been intimately associated with the project, has kindly contributed the following explanatory paragraphs:It seems worth while to review briefly the physical…

2013

All in-text references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.

Radiocarbon, 1983

The preparation and calibration of a secondary standard for the INGEIS Radiocarbon Dating Laboratory are presented. This standard is barium carbonate with a specific activity almost twice that of NBS oxalic acid. It was prepared from BaCO3 with high specific activity and commercial potassium carbonate by an isotopic dilution technique. The advantages of this standard are: 1) the preparation is simple and can be achieved with ordinary labware; 2) the production of CO2 by acid attack from this carbonate shows minimum isotopic fractionation. At least, it has less fractionation than wet oxidation of oxalic acid, the problems of which are described in the literature. This standard ensures better reproducibility in activity measurements; 3) despite some problems of activity exchange with atmospheric CO2 concerning carbonates, measurements of activity over a period of about two years have shown no significant deviation from the mean value. A tentative explanation of this phenomenon is also...

Radiocarbon, 2022

The European Spallation Source (ESS) is a neutron-based research facility under construction in Lund in southern Sweden. The spallation reactions will generate not only the desired neutrons, but also many radioactive byproducts, including 14 C. As part of the licensing process, and as recommended by the IAEA, various preoperational studies are being carried out, including mapping the "zero-point" radiation environment around the site. As the city of Lund hosts several facilities using 14 C-labeled substances, and since temporary and local 14 C contamination have been observed in the past, 14 C mapping is an important part of these baseline assessments. We here present a summary of 14 C levels in various terrestrial environmental samples in Lund and in southern Sweden during the years 2012 to 2020. These environmental F 14 C do not display significantly elevated levels compared to sites located remote from Lund. We also describe a local 14 C contamination event that was detected at the Lund Radiocarbon Dating Laboratory in 2009. Horse-chestnut leaves collected close to the laboratory exhibited F 14 C values of up to ∼25% above the clean air background. Elevated values of F 14 C were also found in a short tree-ring series, especially in 2007. The source of this contamination was identified and successfully removed.

Radiocarbon, 1994

We present here radiocarbon dates obtained using a liquid scintillation system installed at the Physical Research Laboratory (PRL), which has been in operation for the past three years for14C measurements of oceanographic and geochemical samples from India.

E&G Quaternary Science Journal, 2008

This paper gives an overview of the origin of 14 C, the global carbon cycle, anthropogenic impacts on the atmospheric 14 C content and the background of the radiocarbon dating method. For radiocarbon dating, important aspects are sample preparation and measurement of the 14 C content. Recent advances in sample preparation allow better understanding of long-standing problems (e.g., contamination of bones), which helps to improve chronologies. In this review, various preparation techniques applied to typical sample types are described. Calibration of radiocarbon ages is the fi nal step in establishing chronologies. The present tree ring chronology-based calibration curve is being constantly pushed back in time beyond the Holocene and the Late Glacial. A reliable calibration curve covering the last 50,000-55,000 yr is of great importance for both archaeology as well as geosciences. In recent years, numerous studies have focused on the extension of the radiocarbon calibration curve (INTCAL working group) and on the reconstruction of palaeo-reservoir ages for marine records. [Die Radiokohlenstoffmethode und ihre Anwendung in der Quartärforschung] Kurzfassung: Dieser Beitrag gibt einen Überblick über die Herkunft von Radiokohlenstoff, den globalen Kohlenstoffkreislauf, anthropogene Einfl üsse auf das atmosphärische 14 C und die Grundlagen der Radiokohlenstoffmethode. Probenaufbereitung und das Messen der 14 C Konzentration sind wichtige Aspekte im Zusammenhang mit der Radiokohlenstoffdatierung. Gegenwärtige Fortschritte in der Probenaufbereitung erlauben ein besseres Verstehen lang bekannter Probleme (z.B. die Kontamination von Knochen) und haben zu verbesserten Chronologien geführt. In diesem Überblick werden verschiedene Aufbereitungstechniken für typische Probengattungen beschrieben. Der letzte Schritt beim Erstellen einer Chronologie ist die Kalibration der Radiokohlenstoffalter. Die gegenwärtige auf Baumringzeitreihen basierende Kalibrationskurve wird stetig über das Holozän und Spätglazial hinaus erweitert. Eine zuverlässige Kalibrationkurve für die letzten 50.000-55.000 Jahre ist von herausragender Bedeutung sowohl für die Archäologie als auch die Geowissenschaften. In den letzten Jahren haben zahlreiche Studien an der Erweiterung der Radiokohlenstoff-Kalibrationskurve (INTCAL working group) und an der Rekonstruktion des Paläo-Reservoireffekts in marinen Archiven gearbeitet.

Radiocarbon, 1977

The following list contains measurements made during the period 1972-5 which have not been previously published and which form part of a research project on marine shell dating (Gillespie, 1975). These sets of samples were measured to determine 1) “apparent age” of marine shells coll alive from Australian coastal waters before the advent of large-scale nuclear weapons testing, 2) the possibility of using post 1950 Australian marine shells as a modern reference, 3) “apparent age” of Australian marine shells in the past as shown by comparisons between stratigraphically equivalent charcoal and marine shell samples.

Radiocarbon, 2011

Results obtained from a liquid scintillation counter using BGO (Bi 4 Ge 3 0 12) tubes have produced more precise radiocarbon dates in our laboratory. Duplicate analyses confirm the electronic stability of the counter with a background of 0.1 cpm. Our 14 C dates agree well with those from another laboratory (Paris 6-LOCEAN). Most of the 14 C dates in this study were obtained on samples taken from different archaeological sites. Calibration of the various dates with the appropriate software (CALIB 5.0 in our case) allows better interpretation of the results and their importance in this understudied region. In this paper, we investigate the performance of the counter by analyzing samples from archaeological and marine sites in Senegal and Mauritania, and report the results in our first laboratory date list.

Radiocarbon, 2006

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2013

A new line for preparation of the graphite samples for 14 C dating by Accelerator Mass Spectrometry (AMS) in the Zagreb Radiocarbon Laboratory has been validated by preparing graphite from various materials distributed within the Fifth International Radiocarbon Intercomparison (VIRI) study. 14 C activity of prepared graphite was measured at the SUERC AMS facility. The results are statistically evaluated by means of the z-score and u-score values. The mean z-score value of 28 prepared VIRI samples is (0.06 ± 0.23) showing excellent agreement with the consensus VIRI values. Only one sample resulted in the u-score value above the limit of acceptability (defined for the confidence interval of 99%) and this was probably caused by a random contamination of the graphitization rig. After the rig had been moved to the new adapted and isolated room, all u-score values laid within the acceptable limits. Our LSC results of VIRI intercomparison samples are also presented and they are all accepted according to the u-score values.

Radiocarbon, 1977

The following list consists of dates for archaeologic samples from countries other than the British Isles measured with a few exceptions over the period of mid-1970 to June 1974.' The dates were obtained by liquid scintillation counting of benzene using a Model 3315 Packard Tricarb Liquid Scintillation Spectrometer. The laboratory procedures used were those outlined in the previous date list (R, 1976, v 18, p 16). As before, the dates, relative to AD 1950, are based on the Libby half-life for '4C of 5570 years, are corrected for isotopic fractionation (relative to the PDB standard) and are expressed in radiocarbon years uncorrected for natural 14C variations. NBS oxalic acid is used as the modern reference standard. Descriptions, comments, and references to publications are based on information supplied by the persons who submitted the samples. ACKNOWLEDGMENTS We wish to thank H Barker for helpful criticism and advice. SAMPLE DESCRIPTIONS ARCHAEOLOGIC SAMPLES 559 ± 40 BM-760. Lake Varna boat, Bulgaria AD 1391 Wood (Quercus f rainetto Ten) from structure of boat taken from L Varna, Stalin, Black Sea coast, Bulgaria (43° 20' N, 27° 75' E). Coll 1970 and subm by A Michailov, Nail Inst Cult Properties, Sofia, Bulgaria. Comment: when 1st recovered boat considered prehistoric; actual date is clearly much more recent. 12,984 ± 76 BM-728. Mylodon Cave, Chile 11,034 BC Collagen from femur of mylodon (giant sloth, Grypotherium listai) from Cueva del Milodon Grande, Puerto Consuelo, Ultima Esperanza, Chile (51° 36' S, 72° 36' W). Coll ca 1900 from cave floor deposits beneath fallen roof debris (British Mus [Nat Hist] ref M8748; purchased from G A Milward, 1904). Subm by A J Sutcliffe, British Mus (Nat Hist) to * Dates obtained over the same period for samples from the British Isles formed the previous list, British Museum VIII. troversy because of surviving flesh and hair. Comment: date confirms Pleistocene age of remains and agrees with C-484: 10,832 ± 400, for giant sloth droppings from same site (Libby, 1952, p 94). Carrizal series, Colombia Charcoal from protohist Carrizal phase occupation levels overlying Antigua levels at Carrizal, Municipio Barichava, Santander, Colombia (6° 40' N, 73° 14' W). Coil 1970 and subm by W Bray, Inst Archaeol, Univ London. 603 ± 63 BM-802. Carrizal AD 1347 Carrizal stratigraphic trench, Levels 4 and 5, 30 to 50 cm below surface. Dates middle part of Carizal phase occupation. 682 ± 66 BM-803. Carrizal AD 1268 Carrizal stratigraphic trench, Level 7, 60 to 70 cm below surface. Comment: samples should date transition from underlying Antigua phase (see BM-804-806, below) but appear contemporaneous with BM-802 from middle of Carrizal phase. Cueva la Antigua series, Colombia Charcoal from Antigua phase levels at Cueva la Antigua, Municipio of San Gil, Santander, Colombia (6° 35' N, 73° 10' W). Coil 1970 and subm by W Bray. Samples date newly defined Antigua phase pottery styles, earliest so far discovered in northern part of highland Colombia. 1368 ± 103 BM804. Cueva la Antigua AD 582 Trench 1/2, Spit 1 of Antigua phase. Dates transition from Antigua phase to subsequent protohist Carrizal phase.

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2010

Radiocarbon is a cosmogenic radioisotope equally distributed throughout the troposphere and biosphere. This fact enables its most common application-radiocarbon dating. Natural equilibrium of radiocarbon has been disturbed by diverse anthropogenic activities during the last $ 150 years, enabling also the use of 14 C in various environmental applications. Here we present three types of studies by using 14 C that were performed in the Zagreb Radiocarbon Laboratory. 14 C in atmospheric CO 2 has been monitored at several sites with various anthropogenic influences and the difference between the clean-air sites, the industrial city and the vicinity of a nuclear power plant has been established. 14 C has been applied in geochronology of karst areas, especially in dating of tufa, speleothems and lake sediments, as well as in studies of geochemical carbon cycle. 14 C has been used in various archaeological studies, among which the dating of the early Neolithic settlements in Croatia is presented. In these studies 14 C was measured by radiometric techniques, i.e., by gas proportional counting and more recently by liquid scintillation counting (LSC). Two sample preparation techniques for LSC measurement were used: benzene synthesis for archaeological dating and other applications that require better precision, and direct absorption of CO 2 for monitoring purposes. The presented results show that various studies by using 14 C can be successfully performed by the LSC technique, providing a large enough sample (41 g of carbon).