G T Cook
Dados Biográficos
| ID | 3642002 |
|---|---|
| NOME | G T Cook |
| PRENOMES | G T |
| SOBRENOME | Cook |
| ASSINATURA | COOK G T |
| AFILIAÇÕES | SUERC, UK |
| VERIFICADO | Não |
| TOTAL DE OBRAS | 61 |
| TOTAL DE CITAÇÕES | 639 |
| TOTAL COMO AUTOR | 61 |
| TOTAL COMO EDITOR | 0 |
| PRIMEIRO ANO DE PUBLICAÇÃO | 1989 |
| ANO MAIS RECENTE DE PUBLICAÇÃO | 2019 |
| ÍNDICE H | 15 |
Learning from the Wood Samples in ICS, Tiri, Firi, Viri, and Siri
Each of the laboratory intercomparisons (from ICS onwards) has included wood samples, many of them dendrochronologically dated. In the early years, as a result of the majority of laboratories being radiometric, these samples were typically blocks of 20–40 rings, but more recently (SIRI), they have been single ring samples. The sample ages have spanned background through to modern. In some intercomparisons, we have examined different wood pretreat…
Should Archaeologists Care about 14 C Intercomparisons? Why? A Summary Report on Siri
Radiocarbon ( 14 C) dating is used widely in many projects as a basis for the creation and testing of chronological constructs. 14 C measurements are by their nature complex and the degree of sample pretreatment varies considerably depending on the material. Within the United Kingdom and Europe, there are a number of well-established laboratories and increasingly, archaeologists are not just commissioning new dates, but also using statistical mod…
Preliminary Results for Estimating the Bone Background Uncertainties at Suerc Using Statistical Analysis
Bone is frequently dated in archaeological studies and, especially for very old bones (more than 40,000 years old), it is critical to have an accurate and precise measure of the material-specific background value and its associated uncertainty. The SUERC Radiocarbon Laboratory has obtained a mammoth bone as a background bone standard and an appropriate number are now routinely prepared and measured in each AMS batch, resulting in the accumulation…
Investigation of the Analytical F 14 C Bone Background Value at Suerc
The SUERC Radiocarbon Laboratory employs a one-step “background subtraction” method when calculating 14 C ages. An interglacial wood (VIRI Sample K) is employed as the non-bone organic background standard, while a mammoth bone (LQH12) from Latton Quarry is used as the bone background standard. Results over several years demonstrate that the bone background is consistently around a factor of two higher and more variable than the wood background. A…
AMS 14 C Dating at the Scottish Universities Environmental Research Centre (Suerc) Radiocarbon Dating Laboratory
This paper describes all the major procedures adopted by the Scottish Universities Environmental Research Centre (SUERC) Radiocarbon Dating Laboratory. This includes sample pretreatment, graphite production, accelerator mass spectrometry (AMS) measurement, associated stable isotope measurements, data handling, and age calculations, but with the main emphasis being on the chemical pretreatment methods. All of the above enable the laboratory to pro…
Holocene climate change and prehistoric settlement in the lower Danube valley
Radiocarbon Analysis of Modern Skeletal Remains to Determine Year of Birth and Death—A Case Study
To aid in the development of a biological profile for human remains found in Collyhurst (Manchester, England), we undertook radiocarbon analysis of tooth enamel, tooth collagen, and bone collagen on behalf of the Greater Manchester Police. On the basis of the analyses of the teeth, we concluded that the person was born between 1950 and 1954, while on the basis of our analyses of cortical and trabecular bone we estimated the year of death to be be…
Bogs, Bodies and Burnt Mounds
The recording and analysis of a burnt mound and adjacent palaeochannel deposits on the floodplain of the River Soar in Leicestershire revealed that the burnt mound was in use, possibly for a number of different purposes, at the transition from the Neolithic to the Bronze Age. An extensive radiocarbon dating programme indicated that the site was revisited. Human remains from the palaeochannel comprised the remains of three individuals, two of whom…
Assessment of Infinite-Age Bones from the Upper Thames Valley, UK, as 14C Background Standards
It is becoming increasingly clear that in order to generate accurate radiocarbon dates for bone collagen samples it is important to determine a sample-specific background correction to account for the greater complexity and higher number of steps in the pretreatment chemistry of this material. To provide suitable samples for the 14 C community, 7 bone samples were obtained from contexts within British gravel quarries, which according to other dat…
Assessment of Infinite-Age Bones from the Upper Thames Valley, UK, as 14 C Background Standards
It is becoming increasingly clear that in order to generate accurate radiocarbon dates for bone collagen samples it is important to determine a sample-specific background correction to account for the greater complexity and higher number of steps in the pretreatment chemistry of this material. To provide suitable samples for the 14 C community, 7 bone samples were obtained from contexts within British gravel quarries, which according to other dat…
An Icelandic freshwater radiocarbon reservoir effect
A freshwater radiocarbon ( 14 C) reservoir effect (FRE) is a 14 C age offset between the atmospheric and freshwater carbon reservoirs. FREs can be on the order of 10 000 14 C yr in extreme examples and are a crucial consideration for 14 C dating of palaeoenvironmental and archaeological samples. Correction for a FRE may be possible, provided the FRE and the proportion of FRE-affected carbon within a sample can be accurately quantified. However, a…
Examining the Inherent Variability in ΔR
Currently, there is significant ongoing research into the temporal and spatial variability of marine radiocarbon reservoir effects (MREs) through quantification of ΔR values. In turn, MRE studies often use large changes in ΔR values as proxies for changes in ocean circulation. ΔR values are published in a variety of formats with variations in how the errors on these values are calculated, making it difficult to identify trends or to compare value…
Species specific marine radiocarbon reservoir effect
Update on the Performance of the Suerc In Situ Cosmogenic 14 C Extraction Line
In this paper, we describe improvements to the in situ cosmogenic radiocarbon extraction system at SUERC made since 2004, highlighting the factors that potentially control the reduction of analytical variability. We also present new results on system blanks and of measurements of in situ 14 C in shielded quartz and a surface quartz sample used at the University of Arizona as an in situ 14 C standard (PP-4). The SUERC in situ 14 C extraction syste…
New Dating Evidence for North Sea Trade Between England, Scotland, and Norway in the 11th Century AD
This study follows on from previous research at Perth, Scotland, in which we dated carbonized food residues removed from the external surface of rim sherds of cooking pots of London Sandy Shellyware pottery (Museum of London Pottery Fabric Code SSW). The 15 residues that were dated produced 14 C ages between 910 ± 35 and 1085 ± 40 BP. We have now carried out radiocarbon measurements on similar residues from the same fabric obtained from the Billi…
C AMS at Suerc
In 2003, a National Electrostatics Corporation (NEC) 5MV tandem accelerator mass spectrometer was installed at SUERC, providing the radiocarbon laboratory with 14 C measurements to 4–5‰ repeatability. In 2007, a 250kV single-stage accelerator mass spectrometer (SSAMS) was added to provide additional 14 C capability and is now the preferred system for 14 C analysis. Changes to the technology and to our operations are evident in our copious quality…
Temporal and Spatial Variations in Freshwater 14 C Reservoir Effects
Lake Mývatn is an interior highland lake in northern Iceland that forms a unique ecosystem of international scientific importance and is surrounded by a landscape rich in archaeological and paleoenvironmental sites. A significant freshwater reservoir effect (FRE) has been identified in carbon from the lake at some Viking (about AD 870–1000) archaeological sites in the wider region (Mývatnssveit). Previous accelerator mass spectrometry (AMS) measu…
High-Precision Radiocarbon Dating of the Construction Phase of Oakbank Crannog, Loch Tay, Perthshire
Many of the Loch Tay crannogs were built in the Early Iron Age and so calibration of the radiocarbon ages produces very broad calendar age ranges due to the well-documented Hallstatt plateau in the calibration curve. However, the large oak timbers that were used in the construction of some of the crannogs potentially provide a means of improving the precision of the dating through subdividing them into decadal or subdecadal increments, dating the…
Spatial Variation in the Marine Radiocarbon Reservoir Effect Throughout the Scottish Post-Roman to Late Medieval Period
The marine radiocarbon reservoir effect (MRE) occurs as a spatially and temporally dependent variable owing to localized changes in oceanic water composition. This study investigates ΔR values (deviations from the global average MRE whose ΔR = 0) during the period 500–1350 BP for the east coast of Scotland, where a complex estuarine system exists that drains into the semi-enclosed North Sea basin. Due to the availability of suitable archaeologica…
The Early Medieval Origin of Perth, Scotland
The radiocarbon results (and Bayesian modeling) of 15 samples of carbonized food residues removed from the external surface of rim sherds of cooking pots indicate that shellyware pottery first appeared in Perth, Scotland, around cal AD 910–1020 (95% probability) and that it had disappeared by cal AD 1020–1140 (95% probability). Previously, it had been suggested that this pottery could not date to before AD 1150. These data, together with 14 C ana…
Radiocarbon Dating of the Crannogs of Loch Tay, Perthshire (Scotland)
Crannogs are ancient artificial islands found in Scotland and Ireland, which typically had some sort of dwelling place constructed on them that served variously as farmers' homesteads, status symbols, refuges in times of trouble, hunting and fishing stations, etc. Substantial research has been carried out for similar sites in mainland Europe, which has demonstrated that they were lakeside settlements, mostly dating to the Neolithic period and not…
Radiocarbon and Blue Optically Stimulated Luminescence Chronologies of the Oitavos Consolidated Dune (Western Portugal)
The dune of Oitavos, the underlying paleosol, and Helix sp. gastropod shells found within the paleosol were dated using a combination of radiocarbon and blue optically stimulated luminescence (OSL). The organic component of the paleosol produced a significantly older age (∼20,000 cal BP) than the OSL age measurement (∼15,000 yr), while 14 C age measurements on the inorganic component and the gastropods produced ages of ∼35,000 yr and ∼34,000 yr, …
Chronology of Holocene Climate and Vegetation Changes and their Connection to Cultural Dynamics in Southern Siberia
Two sediment sequences from Big Kyzykul Lake and the Shushenskoe paleolake in the Minusinsk depression, Southern Siberia, were studied by pollen, microfossil, and geochemical analyses, as well as radiocarbon dating. The records indicate the persistence of an arid period between ∼11.7–7.6 cal kyr BP, increased effective moisture since ∼7.6 cal kyr BP, 2 humid impulses at ∼5.1 and 2.8 cal kyr BP separated by a dry interval, and the return to genera…
Charcoal Production During the Norse and Early Medieval Periods in Eyjafjallahreppur, Southern Iceland
Timber procurement and the use of woodlands are key issues in understanding the open landscapes of the Norse and Medieval periods in the North Atlantic islands. This paper outlines evidence for the timing and mechanisms of woodland use and deforestation in an area of southern Iceland, which is tracked through the mapping and analysis of charcoal production pits. Precise dating of the use of these charcoal production pits within a Bayesian framewo…
Chronological and Dietary Aspects of the Human Burials from Ajdovska Cave, Slovenia
Ajdovska Jama (The Pagan's Cave) in southeast Slovenia lies within the catchment of the River Sava, a major tributary of the Danube. The site is well known for its Neolithic burials and has been excavated to a high standard on various occasions since 1884. The human remains at the site occurred as distinct clusters of mainly disarticulated bones belonging to at least 31 individuals. Hitherto, dating of the burials has been based on the associated…
A Freshwater Diet-Derived 14 C Reservoir Effect at the Stone Age Sites in the Iron Gates Gorge
Human bones from single inhumation burials and artifacts made from terrestrial mammal (ungulate) bone found in direct association with the skeletons were obtained from the Stone Age site of Schela Cladovei situated just below the Iron Gates Gorge of the River Danube. The results of stable isotope analyses of the human bone collagen are consistent with a heavy dependence on aquatic protein while radiocarbon dating of the samples reveals an offset …
Is there a Fifth International Radiocarbon Intercomparison (Viri)
The issue of comparability of measurements (and thus bias, accuracy, and precision of measurement) from diverse laboratories is one which has been the focus of some attention both within the radiocarbon community and the wider user communities. As a result, the 14 C community has undertaken a widescale, far-reaching, and evolving program of intercomparisons, to the benefit of laboratories and users alike. The benefit to the users is, however, ind…
AMS 14 C Dating at the Scottish Universities Environmental Research Centre (Suerc) Radiocarbon Dating Laboratory
This paper describes all the major procedures adopted by the Scottish Universities Environmental Research Centre (SUERC) Radiocarbon Dating Laboratory. This includes sample pretreatment, graphite production, accelerator mass spectrometry (AMS) measurement, associated stable isotope measurements, data handling, and age calculations, but with the main emphasis being on the chemical pretreatment methods. All of the above enable the laboratory to pro…
Radiocarbon and Stable Isotope Evidence of Dietary Change from the Mesolithic to the Middle Ages in the Iron Gates
A previous radiocarbon dating and stable isotope study of directly associated ungulate and human bone samples from Late Mesolithic burials at Schela Cladovei in Romania established that there is a freshwater reservoir effect of approximately 500 yr in the Iron Gates reach of the Danube River valley in southeast Europe. Using the δ 15 N values as an indicator of the percentage of freshwater protein in the human diet, the 14 C data for 24 skeletons…
Problems of dating human bones from the Iron Gates
It is widely recognized that when marine resources form a significant proportion of the human diet, this results in radiocarbon ages for human remains that are significantly older than the contemporary atmosphere. While there has been widespread assessment of marine14C reservoir ages, there has been little study of the freshwater equivalent. However, recent analyses of human bone from archaeological sites in the Danube Valley have confirmed the e…
The potential significance of dietary offsets for the interpretation of radiocarbon dates
Temporal and Spatial Variations in Freshwater 14 C Reservoir Effects
Lake Mývatn is an interior highland lake in northern Iceland that forms a unique ecosystem of international scientific importance and is surrounded by a landscape rich in archaeological and paleoenvironmental sites. A significant freshwater reservoir effect (FRE) has been identified in carbon from the lake at some Viking (about AD 870–1000) archaeological sites in the wider region (Mývatnssveit). Previous accelerator mass spectrometry (AMS) measu…
Should Archaeologists Care about 14 C Intercomparisons? Why? A Summary Report on Siri
Radiocarbon ( 14 C) dating is used widely in many projects as a basis for the creation and testing of chronological constructs. 14 C measurements are by their nature complex and the degree of sample pretreatment varies considerably depending on the material. Within the United Kingdom and Europe, there are a number of well-established laboratories and increasingly, archaeologists are not just commissioning new dates, but also using statistical mod…
Capabilities of the New Suerc 5MV AMS Facility for 14 C Dating
A new National Electrostatic Corporation (NEC) 5MV accelerator mass spectrometer became operational at the Scottish Universities Environmental Research Centre (SUERC) in July 2002. It has 2 Cs sputter negative ion sources: a 134-sample source (S1) for the routine measurement of all species, and a hybrid source (S2) with 40 spaces for radiocarbon measurements with either graphite or CO 2 samples. A number of performance tests on graphite samples h…
An Overview of All Three Stages of the International Radiocarbon Intercomparison
The International Collaborative Study involved a wide range of sample materials and ages and, on completion, assessed each stage independently (Scott et al 1989; Aitchison et al 1990). We combine here the three stages of the study and provide an overview of the uncertainties in the dating procedure as a whole and in its component processes. Three key optimal performance indices, related to internal and external precision and to bias, have been de…
Examining the Inherent Variability in ΔR
Currently, there is significant ongoing research into the temporal and spatial variability of marine radiocarbon reservoir effects (MREs) through quantification of ΔR values. In turn, MRE studies often use large changes in ΔR values as proxies for changes in ocean circulation. ΔR values are published in a variety of formats with variations in how the errors on these values are calculated, making it difficult to identify trends or to compare value…
An Icelandic freshwater radiocarbon reservoir effect
A freshwater radiocarbon ( 14 C) reservoir effect (FRE) is a 14 C age offset between the atmospheric and freshwater carbon reservoirs. FREs can be on the order of 10 000 14 C yr in extreme examples and are a crucial consideration for 14 C dating of palaeoenvironmental and archaeological samples. Correction for a FRE may be possible, provided the FRE and the proportion of FRE-affected carbon within a sample can be accurately quantified. However, a…
Variability in North Atlantic marine radiocarbon reservoir effects at c. AD 1000
14 C age measurements made on samples from three archaeological sites located on North Atlantic coasts were used to investigate the marine reservoir effect (MRE) at c.AD 1000. This is an important period within human cultural and palaeoenvironmental research as it is a time when Norse expansion to the North Atlantic islands occurred, during what appears to be a period of ameliorating climatic conditions. This makes improved chronological precisio…
An Interim Progress Report on Stages 1 and 2 of the International Collaborative Program
We report in this paper on a preliminary analysis of Stages 1 and 2 of the International Collaborative program. We have chosen to concentrate on the internal and external consistencies of the participating laboratories. The two stages so far completed have dealt only with the processes of sample synthesis and counting, and results indicate that the major component of variability lies in the counting process. Outlying laboratories are observed at …
Species specific marine radiocarbon reservoir effect
C AMS at Suerc
In 2003, a National Electrostatics Corporation (NEC) 5MV tandem accelerator mass spectrometer was installed at SUERC, providing the radiocarbon laboratory with 14 C measurements to 4–5‰ repeatability. In 2007, a 250kV single-stage accelerator mass spectrometer (SSAMS) was added to provide additional 14 C capability and is now the preferred system for 14 C analysis. Changes to the technology and to our operations are evident in our copious quality…
Spatial Variation in the Marine Radiocarbon Reservoir Effect Throughout the Scottish Post-Roman to Late Medieval Period
The marine radiocarbon reservoir effect (MRE) occurs as a spatially and temporally dependent variable owing to localized changes in oceanic water composition. This study investigates ΔR values (deviations from the global average MRE whose ΔR = 0) during the period 500–1350 BP for the east coast of Scotland, where a complex estuarine system exists that drains into the semi-enclosed North Sea basin. Due to the availability of suitable archaeologica…
Sellafield-Derived Anthropogenic 14 C in the Marine Intertidal Environment of the NE Irish Sea
The intertidal biota from Parton beach, close to the Sellafield nuclear fuel reprocessing plant, were all found to be enriched in radiocarbon relative to ambient background. The degree of enrichment appears to reflect the positions of the biota in the food chain once the dilution in seaweed from atmospheric uptake is taken into account. Close to the low-water mark, the order was mussels > limpets > anemones winkles > seaweed. The same order was o…
Report on Stage 3 of the International Collaborative Program
This report on the third and final stage of the International Collaborative Program concentrates on the analysis of internal and external variability of 14 C dates obtained from samples involved in the full 14 C dating process. Thirty-eight laboratories took part in this stage with most producing 8 14 C dates from 3 sets of duplicate material (eg, wood, shell and peat) and 2 single samples of wood of known ages 190 yr BP apart. From the 3 sets of…
Learning from the Wood Samples in ICS, Tiri, Firi, Viri, and Siri
Each of the laboratory intercomparisons (from ICS onwards) has included wood samples, many of them dendrochronologically dated. In the early years, as a result of the majority of laboratories being radiometric, these samples were typically blocks of 20–40 rings, but more recently (SIRI), they have been single ring samples. The sample ages have spanned background through to modern. In some intercomparisons, we have examined different wood pretreat…
Anthropogenic Radiocarbon in the Eastern Irish Sea and Scottish Coastal Waters
14 C is produced as an activation product in nuclear reactors, and may be discharged to both the atmosphere and the marine environment during nuclear fuel reprocessing. In the UK, 14 C is discharged, under license, into the Eastern Irish Sea by the British Nuclear Fuels plc (BNFL) reprocessing plant at Sellafield, Cumbria, northwest England, and is then transported into Scottish coastal waters. We analyzed intertidal biota samples to determine th…
The 14 C Content of Modern Vegetation Samples from the Flanks of the Katla Volcano, Southern Iceland
Samples of living terrestrial plants comprising a moss ( Calliergon sp.), Carex spp. and Alchemilla spp. were collected from the surface of the mire at Engimýri in Mýrdalur, southern Iceland, 10 km from the crater rim of the central complex of the Katla volcano. This area is 16 km from the fissures active in ad 1918 and was directly affected by the tephra fall. Although there is no hot-spring or fumerole activity in the area, sufficient volcanic …
International Collaborative Study
The success of any intercomparison exercise depends largely on participation and cooperation of a sufficient number of laboratories and the selection of a suitable suite of samples. Unless the latter is satisfactorily devised, the former cannot be guaranteed. The hierarchical nature of this study has necessarily resulted in a far more comprehensive set of sample types than has previously been employed. The exercise was structured to satisfy the f…
Design and Preparation of Samples for the International Collaborative Study
Sample materials issued to participants in the interlaboratory calibration exercise are defined and in context of their intended interpretational significance. Preparation of the benzene and calcium carbonate standards as issued for stage 1 is described in detail; likewise, the source and pretreatment/extraction of the environmental samples dispatched for stages 2 and 3
Assessment of Infinite-Age Bones from the Upper Thames Valley, UK, as 14 C Background Standards
It is becoming increasingly clear that in order to generate accurate radiocarbon dates for bone collagen samples it is important to determine a sample-specific background correction to account for the greater complexity and higher number of steps in the pretreatment chemistry of this material. To provide suitable samples for the 14 C community, 7 bone samples were obtained from contexts within British gravel quarries, which according to other dat…
Design and Preparation of Samples for the International Collaborative Study
Sample materials issued to participants in the interlaboratory calibration exercise are defined and in context of their intended interpretational significance. Preparation of the benzene and calcium carbonate standards as issued for stage 1 is described in detail; likewise, the source and pretreatment/extraction of the environmental samples dispatched for stages 2 and 3
Performance of the Packard 2000 CA/LL and 2250 CA/XL Liquid Scintillation Counters for 14C Dating
Results are presented on the comparative characteristics of the Packard 2000 CA/LL liquid scintillation counter with and without the low-level option on line. An initial performance assessment using 14 C labeled benzene with butyl-PBD as the scintillant revealed that although the background count rate decreased by approximately a factor of 3 using the low-level option, a substantial decrease in efficiency was also observed. However, subsequent in…
An Interim Progress Report on Stages 1 and 2 of the International Collaborative Program
We report in this paper on a preliminary analysis of Stages 1 and 2 of the International Collaborative program. We have chosen to concentrate on the internal and external consistencies of the participating laboratories. The two stages so far completed have dealt only with the processes of sample synthesis and counting, and results indicate that the major component of variability lies in the counting process. Outlying laboratories are observed at …
Applicability of ‘New Technology’ Scintillation Counters (Packard 2000 CA/LL and 2260 XL) for 14 C Dating
The results of this study indicate that scintillation counters employing burst-counting circuitry are capable of producing accurate age measurements. Replicate analyses confirm the validity of the minimum error of 50-60 years quoted on routine age measurements carried out at this laboratory
An Overview of Some Interlaboratory Studies
Many interlaboratory studies have been made in the 14 C community at irregular intervals over the past ten years. At times, the results from these studies have been contentious, mostly because of the lack of consistency in their findings. The importance of regular exercises has become particularly acute due to the large number of operating laboratories and the diversity of their methodologies. Hence, we briefly review the studies that have been m…
Report on Stage 3 of the International Collaborative Program
This report on the third and final stage of the International Collaborative Program concentrates on the analysis of internal and external variability of 14 C dates obtained from samples involved in the full 14 C dating process. Thirty-eight laboratories took part in this stage with most producing 8 14 C dates from 3 sets of duplicate material (eg, wood, shell and peat) and 2 single samples of wood of known ages 190 yr BP apart. From the 3 sets of…
International Collaborative Study
The success of any intercomparison exercise depends largely on participation and cooperation of a sufficient number of laboratories and the selection of a suitable suite of samples. Unless the latter is satisfactorily devised, the former cannot be guaranteed. The hierarchical nature of this study has necessarily resulted in a far more comprehensive set of sample types than has previously been employed. The exercise was structured to satisfy the f…
An Overview of All Three Stages of the International Radiocarbon Intercomparison
The International Collaborative Study involved a wide range of sample materials and ages and, on completion, assessed each stage independently (Scott et al 1989; Aitchison et al 1990). We combine here the three stages of the study and provide an overview of the uncertainties in the dating procedure as a whole and in its component processes. Three key optimal performance indices, related to internal and external precision and to bias, have been de…
Radiocarbon
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Scintillation Cocktail Optimization for 14 C Dating Using the Packard 2000CA/LL and 2260XL
In terms of both quenching and, in particular, counting efficiency, scintillation counters employing burst counting circuitry are sensitive to changes in scintillant concentration. Our research demonstrates that there are plateau regions where neither parameter is significantly influenced by moderate changes in a cocktail containing butyl - PBD and bis - MSB. One of these, consisting of butyl - PBD 2.8mg.g -1 and bis - MSB 3mg.g -1 of benzene is …
Further Analysis of the International Intercomparison Study (ICS)
The major findings of the Intercomparison Study (ICS) have already been published (Scott, Long & Kra 1990), but a number of questions remain unresolved. We address here some issues of user and technical relevance, which include: 1) further investigation of the quoted errors and their relation to the perceived precision and accuracy, which is of interest to users of 14 C dates; 2) the analysis of the known-age wood samples provided in Stages 2 and…
The Statistics of Low-Level Counting Using the New Generation of Packard Liquid Scintillation Counters
We consider the suitability of commonly used Poisson counting statistics applied to background count rates measured in the new generation of low-background Packard liquid scintillation spectrometers. We also investigate the stability of these systems over long time intervals. Undetected instability will result in an underestimation of the precision of any result ( i.e., the calculated error will be too small), and, in the presence of a systematic…
A Radiocarbon Dating Protocol for use with Packard Scintillation Counters Employing Burst-Counting Circuitry
Considerable research has been carried out in this laboratory on the use of Packard scintillation counters employing burst-counting circuitry. The nature of the pulse-shape discrimination circuit has led to redefining our sample vialing philosophy and scintillation cocktail optimization. Results presented here demonstrate: 1) the enhancements in efficiency that are achievable using a two-component cocktail compared with the use of a primary fluor…
Anthropogenic Radiocarbon in the Eastern Irish Sea and Scottish Coastal Waters
14 C is produced as an activation product in nuclear reactors, and may be discharged to both the atmosphere and the marine environment during nuclear fuel reprocessing. In the UK, 14 C is discharged, under license, into the Eastern Irish Sea by the British Nuclear Fuels plc (BNFL) reprocessing plant at Sellafield, Cumbria, northwest England, and is then transported into Scottish coastal waters. We analyzed intertidal biota samples to determine th…
The 14 C Content of Modern Vegetation Samples from the Flanks of the Katla Volcano, Southern Iceland
Samples of living terrestrial plants comprising a moss ( Calliergon sp.), Carex spp. and Alchemilla spp. were collected from the surface of the mire at Engimýri in Mýrdalur, southern Iceland, 10 km from the crater rim of the central complex of the Katla volcano. This area is 16 km from the fissures active in ad 1918 and was directly affected by the tephra fall. Although there is no hot-spring or fumerole activity in the area, sufficient volcanic …
Radiocarbon Age Offsets in Different-Sized Carbonate Components of Deep-Sea Sediments
We compared accelerator mass spectrometry (AMS) 14 C ages of large (>150 μm) pelagic foraminifera with radiometric bulk carbonate 14 C ages in two northeastern Atlantic cores. The foraminiferal ages are consistently older than those of the bulk sediment (by + 0.76 ka in Core 11881 and by + 1.1 ka in Core 11886), whereas corresponding fine ( −1 in Core 11881 and 5.9 cm ka −1 in Core 11886). Consideration of various factors that might produce such …
Anthropogenic 14 C Marine Geochemistry in the Vicinity of a Nuclear Fuel Reprocessing Plant
The British Nuclear Fuels plc reprocessing plant at Sellafield in Cumbria, Northwest England, discharges between 1 and 3 TBq of 14 C per annum as low-level waste via a pipeline into the Eastern Irish Sea. Our results demonstrate 14 C activities in excess of the current ambient level ( i.e., ca. 260 Bq kg −1 carbon) in a range of both biotic and abiotic samples with evidence that a significant percentage of the discharges are in the form of dissol…
Radiocarbon Dating Tephra Layers in Britain and Iceland
Layers of volcanic ash, or tephra form widespread chronostratigraphic marker horizons which are important because of their distinctive characteristics and rapid deposition over large areas. Absolute dating of prehistoric layers effectively depends upon 14 C analysis. We focus here on Icelandic tephra layers at both proximal and distal sites and consider three strategies to obtain age estimates: 1) the conventional dating of individual profiles; 2…
Consensus Dating of Mammoth Remains from Wrangel Island
Previous results from remains of tusks, teeth and bones collected from Wrangel Island (Vartanyan et al . 1995) had given results in the range 3730 bp to 20,000 bp and the authors had concluded that “mammoths inhabited Wrangel Island for as long as 6000 yr after the estimated extinction on the Siberian continent”. There still remained the question of the earliest date for such remains. Further, the authors had noted such samples may present some d…
The Behavior of Sellafield-Derived 14 C in the Northeast Irish Sea
Radiocarbon is an important constituent of the low level, liquid, radioactive effluent discharged from the Sellafield nuclear fuel reprocessing plant in northwest England, but despite the fact that it gives the highest collective dose commitment of all the nuclides in the waste, its behavior in the Irish Sea is poorly defined. There is therefore a clear requirement for an improved understanding of 14 C behavior in the Irish Sea, to assist with do…
Performance of the Packard Tri-Carb ® 2770TR/SL Liquid Scintillation Analyzer for 14 C Dating
We present results that demonstrate the potential of the Packard Tri-Carb ® Model 2770TR/SL for radiocarbon dating. For 2 g of sample benzene, a stable background count rate of 0.307 cpm and a stable counting efficiency of 64.78% were determined using a 13–75 keV counting window. Changes to the mathematical routines for t-SIE (quench indicating parameter) calculation and a reduction in the activity of the external standard have enabled stability …
Interlaboratory Comparisons
Interlaboratory comparisons have been widely used in analytical chemistry and radiochemistry as an important part of ongoing quality assurance programs. The 14 C community has been no exception in this respect, and in just under 20 years, there have been a number of significant and very extensive interlaboratory trials organized by individual laboratories and the International Atomic Energy Agency (IAEA) to the benefit of the 14 C community (both…
The Influence of Pretreatment on Humic Acid Yield and 14 C Age of Carex Peat
The object of the study was to assess the effects of a range of pretreatment/extraction schemes on the yields of humic acid and humin obtained from peat and the subsequent radiocarbon ages. We analyzed peat from Flókadalur in northern Iceland, collecting material from a profile containing seven visible tephra horizons in the upper 3 m, whose form and extent indicated little disturbance to the section over the last 4000 yr. The results of a range …
Analytical Protocol and Quality Assurance for 14 C Analyses
We present a proposal for a further intercomparison exercise following discussions at the 16th International Radiocarbon Conference in Groningen in 1997. This new intercomparison will build on previous exercises by making use of both reference materials already characterized and additional known-age material. For this comparison, we describe two separate but essentially related protocols that are meant to satisfy the different priorities of radio…
A Radiocarbon Database for Scottish Archaeological Samples
For the majority of dating laboratories and their respective user communities, the journal Radiocarbon is no longer regarded as the medium for primary publication of radiocarbon measurements. In compliance with editorial policy, the emphasis has long since moved towards the publication of research papers on technological enhancements and applications of 14 C as well as other cosmogenic isotopes and this has left a requirement for an alternative m…
Radiocarbon dating (49 obras) · Archaeology and ancient environmental studies (42 obras) · Geology (42 obras) · Geography (38 obras) · Archaeology (37 obras) · Chemistry (31 obras) · Isotope Analysis in Ecology (24 obras) · Paleontology (24 obras) · Geology and Paleoclimatology Research (21 obras) · Physical geography (18 obras)