British Museum Natural Radiocarbon Measurements VII
Nigel Meeks1971, Radiocarbon
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Abstract
Dates listed below are based on measurements made from June 1968 to May 1970 by the liquid scintillation technique using benzene. In general, the experimental procedure is as described previously (Barker, Burleigh, and Meeks, 1969a) with a few changes in detail. Data are now processed by computer using a comprehensive Algol program written by Andrew Barker, King's College, Univ. of London. There is no need to standardize on any particular sample weight and, as the benzene synthesizer can also deal with samples in the range up to the equivalent of 9 gm of carbon in a single synthesis, the amount of sample available is now less critical. However, for older material, a minimum of 1 gm of carbon is required. Another factor contributing to efficiency of operation is the "bomb" technique for sample combustion (Barker, Burleigh, and Meeks, 1969b), also mentioned in the previous date list. Finally, during 1969, an MS20 double collection mass spectrometer was acquired and all dates (but not all those in this list) are now corrected for isotopic fractionation. Samples were pretreated for removal of contaminants, with dilute hydrochloric acid and, where appropriate, with dilute alkali also. Bone and antler samples were demineralized in low vacuum with 0.75 N hydrochloric acid at ambient temperature, leaving only the protein fractiori (collagen) which was washed and dried before combustion. Dates were calculated using the Libby half-life for C14 of 5568 years. Descripdons, comments, and references to publications are based on information supplied by the persons who contributed the samples. ACKNOWLEDGMENT Thanks are due to Miss G. I. Hassall, National Physical Laboratory, for isotopic fractionation measurements made in connection with the investigation of C14 age discrepancies using well-dated Egyptian materials.
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British Museum Natural Radiocarbon Measurements VIII
Radiocarbon: An International Journal of Cosmogenic Isotope Research, 1976
The following list consists entirely of dates for archaeologic samples from the British Isles measured since about mid-1970 up to June 1974*. The dates were obtained by liquid scintillation counting of benzene using a Model 3315 Packard Tricarb Liquid Scintillation Spectrometer. In general, procedures are as described in the previous date list (R, 1971, v 13, p 157; see also Burleigh, 1972). However, data processing was improved by means of a real-time link with a Hewlett Packard 2100A computer having 32K of core, which accepts readings from the counter at the end of each individual counting period. The computer monitors the accumulated sample counts and reports when the statistical error terms of these have reached previously chosen limits; final dates are then obtained on supplying the appropriate benzene sample weights and isotopic fractionation values. The system maintains a permanent record of all the data obtained from measurement of samples and reference standards and gives warning of any serious changes in counter performance. A full description of the capabilities of this system is given elsewhere (Hall and Hewson, in press). Finally, improvements were made to the bomb used for initial combustion of sample materials (Burleigh, 1974) and a new, stainless-steel, lithium reaction furnace (similar to that described by Polach and Stipp, 1967) was recently installed. Raw sample materials are systematically pretreated with dilute acid and alkali; but only collagen is used for antler and bone. The dates, relative to AD 1950, are based on the Libby half-life 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 gratefully acknowledge the continued guidance and helpful criticism and advice of H Barker. SAMPLE DESCRIPTIONS ARCHAEOLOGIC SAMPLES A. British Isles 5730 ± 150 BM-91. High Rocks, Kent 3780 BC Charcoal from Layer 2 (Period III) of Site F at High Rocks, Tunbridge Wells, Kent, England (51° 07' N, 0° 14' E, Nail Grid Ref TQ * Dates obtained over the same period for samples from other geographic regions form the next list, British Museum IX.
Oak Ridge Institute of Nuclear Studies radiocarbon dates I.
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British Museum Natural Radiocarbon Measurements VI
Radiocarbon, 1969
Dates listed below are based on measurements made up to May 1968, and cover a period during which the technique of gas proportional counting using CO2 was gradually replaced by liquid scintillation counting using benzene. The gas counting measurements were carried out by the method and techniques previously described (Barker and Mackey, 1968) the only modifications being the replacement of some old electronic units by more stable solid-state equipment; proportional counting results are indicated in the text by (P) at the end of the relevant sample descriptions. Liquid scintillation counting, which is now the preferred method in this laboratory, is carried out using a Packard Tri-Carb liquid scintillation spectrometer model 3315/AES fitted with selected low-noise quartz-faced photomultipliers. Normally 3 ml of benzene is prepared from each sample. This is dissolved in 12 ml of scintillation grade toluene containing 5 gm/liter of scintillator (PPO) and the solution is measured in a standard low-potassium glass vial at a temperature of 0°C. Photomultiplier E.H.T., amplifier, and channel width settings are optimized for C14, and measurements are carried out at ca. 65% efficiency of detection for C14 to eliminate interference from any tritium which may be present in the benzene. Under these circumstances the background is approx. 8.6 cpm and the modern (95% A0X) is approx. 24.0 cpm. Samples are counted in groups of 3 to 5 together with background and modern reference samples and are measured for at least one week, the instrument being set to cycle at 100 min intervals. In this period, the counts accumulated are such that the background is always measured to a statistical accuracy of better than 1% and most other samples to a higher accuracy than this. Background and modern counts used in the calculation of each result are only those relevant to the period of measurement of that particular sample. Statistical analysis of groups of replicate measurements made under these conditions over a very long period of time has demonstrated the excellent long-term stability of the equipment and indicates that the technique is quite capable of achieving results of very high statistical accuracy when required. SAMPLE DESCRIPTIONS ARCHAEOLOGIC SAMPLES A. Crete Knossos series Five samples from Neolithic settlement of Knossos, Crete (35° 31' N Lat, 25 ° 20' E Long), from sounding below central court of Minoan Palace (Evans, 1964a,b). Coll. 1960 and subm. by J. D. Evans, Inst. of Archaeol., Univ. of London, for comparison with unexpectedly early dates previously obtained for Knossos Neolithic, BM-124, 8050 ± 180 and BM-126, 7000 + 180 (Radiocarbon, 1963, v. 5, p. 104). 7570 ± 150 BM-272. Knossos 2 5620 B.C. Sample 2, ref. Area AC, Level 24. Charcoal from Occupation layer assoc. with 1st brick houses and immediately overlying earliest camp occupation above bedrock (Stratum IX, Evans, 1964b). Expected age early 6th millennium B.C. based on BM-124 and BM-126. (P) 6210 ± 150 BM-273. Knossos 3 4260 B.C. Sample 3, ref. Area AC, Level 17. Charcoal from habitation deposit in Stratum VI (Evans, 1964b). Expected age late 6th millennium B.C. based on BM-124 and BM-126. (P) 6140 ± 150 BM-274. Knossos 4 4190 B.C. Sample 4, ref. Area A, Level 15. Charcoal from habitation level in Stratum V (Evans, 1964b). Expected age end of 6th millennium B.C. based on BM-124 and BM-126. (P)
Radiocarbon dating and its applications in Quaternary studies
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.
A Secondary Standard for Radiocarbon Dating
Radiocarbon, 1983
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Ingeis radiocarbon laboratory dates IV
Radiocarbon 44(1): 181-193. , 2002
"We present here the results of dating of 80 archaeological and paleoenvironmental samples from Argentina and Uruguay, processed between 1986 and 1988 by M A Albero and M A Gonzalez. Series of samples and single samples are grouped by province and then by locality or archeological site, from north to south. See sample location maps for details. 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. 14C contents of some paleoenvironmental samples are expressed in percent modern carbon (pMC)."
INGEIS Radiocarbon Laboratory Dates II
Radiocarbon, 1985
The following list consists of archaeologic and geologic dates from Argentina processed in the 14C laboratory of INGEIS. The ages presented were obtained by liquid scintillation counting of benzene, using the techniques outlined in a previous paper (Albero & Angiolini, 1983). The results are expressed in 14C years relative to 1950, using the Libby half-life of 5570 yr.
Modern Radiocarbon Dating
2015
The ICR (Institute for Creation Research) recently spent eight years on a project known as RATE (Radioisotopes and the Age of The Earth). The RATE team claims the results have yielded convincing and irrefutable scientific evidence of a young earth. John Baumgardner, a geophysicist with expertise in tectonic modeling, presents experimental data claiming to show that all biological material contains intrinsic radiocarbon, no matter how old that material may be thought to be [1, 2]. He makes additional claims that even non-biological carbonaceous material contains intrinsic radiocarbon. He suggests that this radiocarbon is residual from the material's creation. If true, his claims would have far-reaching implications for the ages of these materials. Baumgardner presents two classes of data. The first is a set of 90 previously published radiocarbon AMS dates of old samples (most >100k years) that he has re-analyzed. The second is a set of new samples that the RATE team collected and sent to a leading radiocarbon AMS laboratory to be dated. In both cases, I am convinced that the "intrinsic radiocarbon" is nothing more than contamination and instrument background. Modern Radiocarbon Dating New Methods Allow Smaller Samples Willard Libby discovered radiocarbon dating in the late 1940s. He received the Nobel Prize in Chemistry for this discovery in 1960. The technique arises from radiocarbon being continually produced in the upper atmosphere by cosmic rays while it is continually decaying, so the atmospheric concentration has reached a fairly steady equilibrium. Plants are in equilibrium with atmospheric radiocarbon through respiration. This equilibrium continues through plants to herbivores and through them to carnivores. Once an organism dies, its carbon ceases exchanging with atmospheric carbon but continues decaying with a half-life of about 5730 years. Thus, measurement of the radiocarbon concentration can give the time that the organism died. Early measurements were done by counting the beta particles (high energy electrons) liberated in radiocarbon decay. The age limit was roughly 30k years, due both to poor statistics from low decay count rates and to cosmic ray backgrounds. Richard Muller proposed a new measurement technique, called "accelerator mass spectrometry" (AMS), in 1976 [3]. Muller suggested that particle accelerators be used to separate the atoms, allowing the radiocarbon atoms to be counted directly instead of waiting for them to decay. It was hoped that this would enable dating of much smaller and perhaps much older samples. This technique has indeed allowed use of much smaller samples and has become the dominant method of radiocarbon dating. However, the original anticipation of 100,000-year background levels has been "unrealized due to a variety of sample processing and instrument-based experimental constraints" [4].
IFAN Radiocarbon Laboratory Measurements I
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.
British Museum Natural Radiocarbon Measurements IX
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.
Microchemical and molecular dating
…, 2006
The depth and reliability of archaeological and environmental information on ages, sources and pathways of carbon are being greatly enhanced through a new synergism between advances in "micro 14C dating" and advances in micro-organic analytical chemistry and individual particle characterization. Recent activities at the National Institute of Standards and Technology (NIST, formerly NBS) involving this linkage include dating individual amino acids isolated from bone collagen and the apportionment or tracing of individual carbon compounds derived from anthropogenic sources. Important knowledge has been gained through "direct" (sequential) and "indirect" (parallel) links between microchemistry and 14C measurement. The former is illustrated by 14C measurements on specific amino acids and on the polycyclic aromatic hydrocarbon (PAH) class of compounds. Isolation of the respective molecular fractions from far greater quantities of extraneous carbon held the key to valid dating and source apportionment respectively. Parallel data on 14C and molecular patterns promises new knowledge about the identity of sources of environmental carbon at the nanogram level through multivariate techniques such as principal component analysis and multiple linear regression. Examples are given for atmospheric particulate carbon, using PAM molecular patterns and laser microprobe mass spectral patterns.
Reassessment of the 13 C/ 12 C and 14 C/ 12 C isotopic fractionation ratio and its impact on high-precision radiocarbon dating ScienceDirect
Geochimica et Cosmochimica Acta, 2017
The vast majority of radiocarbon measurement results (14 C/ 12 C isotopic ratios or sample activities) are corrected for isotopic fractionation processes (measured as 13 C/ 12 C isotopic ratios) that occur in nature, in sample preparation and measurement. In 1954 Harmon Craig suggested a value of 2.0 for the fractionation ratio b that is used to correct 14 C/ 12 C ratios for shifts in the 13 C/ 12 C ratios and this value has been applied by the radiocarbon community ever since. While theoretical considerations suggest moderate deviations of b from 2.0, some measurements have suggested larger differences (e.g. b = 2.3, measured by Saliège and Fontes in 1984). With the high precision attained in radiocarbon measurements today (±2‰), even a relatively small deviation of b from 2.0 can impact the accuracy of radiocarbon data, and it is, therefore, of interest to re-evaluate the fractionation corrections. In the present study, the fractionation ratio b was determined by independent experiments on the chemical reduction of carbon dioxide (CO 2) to elemental carbon (graphitization reaction) and on the photo-synthetic uptake of CO 2 by C 3 and C 4 plants. The results yielded b = 1.882 ± 0.019 for the reduction of CO 2 to solid graphite and b = 1.953 ± 0.025 for the weighted mean of measurements involving C 3 and C 4 photosynthesis pathways. In addition, the analysis of over 9600 full-sized OX-I and OX-II normalizing standards measured between 2002 and 2012 confirms b values lower than 2.0. The obtained values are in good agreement with quantum mechanical estimates of the equilibrium fractionation and classic kinetic fractionation as well as with results from other light three-isotope systems (oxygen, magnesium, silicon and sulfur). While the value of the fractionation ratio varies with the relative importance of kinetic and equilibrium fractionation, the values obtained in the present study cluster around b = 1.9. Our findings suggest that a significant fraction of all samples (''unknowns") would be shifted by 2‰ (16 radiocarbon years) or more due to this effect: for example, for b = 1.882, between 16.8% and 25.9% of almost 60,000 radiocarbon values measured at the Keck Carbon Cycle AMS facility between 2002 and 2012 would be affected. The implications for radiocarbon dating and its accuracy are discussed.
Physical Research Laboratory (Chemistry) radiocarbon date list I
Radiocarbon, 2006
Growth year 1960. and soaked in 30% H2O2 for 2 days to remove organic matter. We report 14C ages of the samples below. CH-96. Chikasa Gosa Reef Oyster Collected from Chikasa, Saurashtra (21°45'N, 70°30'E) at 1 m asl. CH-97. Chikasa Gosa Reef Oyster Collected from Chikasa at 1 m asl. CH-98. Chikhli Oyster Collected from Chikhli (20°48'N, 70°52'E) at 4 m asl. CH-99. Patan Bridge Oyster Collected from Patan Bridge over the Hiren River (20°55'N, 70°30'E) at 12 m asl. CH-101. Babarkot Oyster Collected from Babarkot (20°52'N, 71°25'E) at 8 m asl. CH-102. Diu Oyster Collected from Diu (20°44'N, 70°55'E) at 2 m asl. CH-103. Jafarabad Oyster Collected from Jafarabad (20°52'N, 71°25'E) at 3 m asl. CH-108. Rohisa Oyster Collected from Rohisa (20°50'N, 71°15'E) at 2 m asl.
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The world recreated: redating Silbury Hill in its monumental landscape
Antiquity, 2007
A classic exposition of the difficulties of dating a major monument and why it matters. Silbury Hill, one of the world's largest prehistoric earth mounds, is too valuable to take apart, so we are reliant on samples taken from tunnels and chance exposures. Presenting a new edition of thirty radiocarbon dates, the authors offer models of short-or long-term construction, and their implications for the ritual landscape of Silbury and Stonehenge. The sequence in which monuments, and bits of monuments, were built gives us the kind and history of societies doing the building. So nothing matters more than the dates . . .
British Museum Natural Radiocarbon Measurements VIII
Radiocarbon: An International Journal of Cosmogenic Isotope Research, 1976
The following list consists entirely of dates for archaeologic samples from the British Isles measured since about mid-1970 up to June 1974*. The dates were obtained by liquid scintillation counting of benzene using a Model 3315 Packard Tricarb Liquid Scintillation Spectrometer. In general, procedures are as described in the previous date list (R, 1971, v 13, p 157; see also Burleigh, 1972). However, data processing was improved by means of a real-time link with a Hewlett Packard 2100A computer having 32K of core, which accepts readings from the counter at the end of each individual counting period. The computer monitors the accumulated sample counts and reports when the statistical error terms of these have reached previously chosen limits; final dates are then obtained on supplying the appropriate benzene sample weights and isotopic fractionation values. The system maintains a permanent record of all the data obtained from measurement of samples and reference standards and gives warning of any serious changes in counter performance. A full description of the capabilities of this system is given elsewhere (Hall and Hewson, in press). Finally, improvements were made to the bomb used for initial combustion of sample materials (Burleigh, 1974) and a new, stainless-steel, lithium reaction furnace (similar to that described by Polach and Stipp, 1967) was recently installed. Raw sample materials are systematically pretreated with dilute acid and alkali; but only collagen is used for antler and bone. The dates, relative to AD 1950, are based on the Libby half-life 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 gratefully acknowledge the continued guidance and helpful criticism and advice of H Barker. SAMPLE DESCRIPTIONS ARCHAEOLOGIC SAMPLES A. British Isles 5730 ± 150 BM-91. High Rocks, Kent 3780 BC Charcoal from Layer 2 (Period III) of Site F at High Rocks, Tunbridge Wells, Kent, England (51° 07' N, 0° 14' E, Nail Grid Ref TQ * Dates obtained over the same period for samples from other geographic regions form the next list, British Museum IX.
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