D D HARKNESS
Dados Biográficos
| ID | 5215428 |
|---|---|
| NOME | D D HARKNESS |
| PRENOMES | D D |
| SOBRENOME | HARKNESS |
| ASSINATURA | HARKNESS D D |
| AFILIAÇÕES | Scottish Universities Environmental Research Centre |
| VERIFICADO | Não |
| TOTAL DE OBRAS | 43 |
| TOTAL DE CITAÇÕES | 203 |
| TOTAL COMO AUTOR | 43 |
| TOTAL COMO EDITOR | 0 |
| PRIMEIRO ANO DE PUBLICAÇÃO | 1970 |
| ANO MAIS RECENTE DE PUBLICAÇÃO | 2010 |
| ÍNDICE H | 8 |
Nerc Radiocarbon Age Measurements Determined By Radiometric Counting 1996–2005
We describe a new compilation of radiocarbon age measurements performed by the NERC Radiocarbon Laboratory that is freely available to access over the World Wide Web. The database contains 1000 14 C measurements performed using the liquid scintillation counting method between 1996 and 2005, and further results will be added as the information is compiled. Contextual information including sampling location and the nature of sample material is prov…
Precision and accuracy in applied 14C dating
How reliable are radiocarbon laboratories? A report on the Fourth International Radiocarbon Inter-comparison (Firi) (1998-2001)
Radiocarbon laboratories undertake rigorous programmes of internal quality control (QC) and overall quality assurance (QA). In a laboratory "inter-comparison" samples of the same age are dated at different laboratories using a range of techniques and the results are then compared. The authors summarise the results of the fourth of these scientific audits
Is Comparability of 14 C Dates an Issue
For more than 15 years, the radiocarbon community has participated in a series of laboratory intercomparisons in response to the issue of comparability of measurements as perceived within the wider user communities (Scott et al. 1990; Rozanski et al. 1992; Gulliksen and Scott 1995; Scott et al. 1997). In this report, we provide an update on the current 14 C laboratory intercomparison and reflect on future issues linked to the laboratory intercomp…
Towards a Radiocarbon Chronology of the Late-Glacial
This paper outlines a dating program designed to test the reproducibility of radiocarbon dates on different materials of Late-Glacial age (plant macrofossils, fossil beetle remains, and the “humic” and “humin” chemical fractions of limnic sediments) using a combination of radiometric (beta counting) and accelerator mass spectrometry (AMS) techniques. The results have implications for the design of sampling strategies and for the development of im…
Drought and dust deposition in the West African Sahel
A high-resolution, multiproxy palaeolimnological record from the Manga Grasslands, northeastern Nigeria, spanning the last 5500 calendar years, reveals the episodic deterioration in Sahelian climate as significant biogeophysical thresholds were crossed. Desert-dust deposition began to increase 4700 cal. BP. Rainfall during the summer-monsoon season declined permanently after 4100 cal. BP. A further significant change in atmospheric circulation, g…
MacBride's Brigade
Received
What Future for Radiocarbon
In this short article, we summarize some milestones in the 50-yr-long development of natural 14 C measurement. In the light of this appraisal we presume to hazard some personal opinions and forecasts as to where best opportunities might lie for future gains from the continued investment in applied 14 C science. The technique and the journal are one and the same in this regard
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…
Mid- and late-Holocene vegetation, surface weathering and glaciation, Fjallsjökull, southeast Iceland
A natural section at the southern margin of Fjallsjökull in southeastern Iceland provides evidence of a mid-Holocene land-surface that has been deformed by 'Little Ice Age' glaciation. Deformation is inter preted as compression around coarse gravel core and extension along deformable silts. Restoration of the original sedimentary units reveals a succession of lake sediments and fan gravels, with pollen and wood macro fossil remains preserved in t…
Radiocarbon dating of a recent high latitude peat profile
The value of both high-precision (HP) and AMS 14 C determinations in the fine-resolution dating of recent peat at Stor Åmyrân, near Umeå, northern Sweden has been explored. A detailed chronology of accumu lation, based on 14 C, an occurrence of the Askja AD 1875 tephra and 241 Am measurements has been derived for the last 700 years. This shows significant changes in the mass balance of the peat profile, with minimum rates of net carbon sequestrat…
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…
C Dating of Laminated Sediments from Loch Ness, Scotland
Radiometric and AMS radiocarbon dating of a 6-m sediment core from Loch Ness, Scotland, indicates that it represents perhaps the very end of the Late Pleistocene, and the first ca. 7500 yr of the Holocene. Counts of laminations observed in the Holocene section of the core suggest that they are present in sufficient number to constitute annual laminations (varves), an hypothesis consistent with the pollen record, which contains a sequence of zones…
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…
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…
Problems associated with correlating calibrated radiocarbon-dated pollen diagrams with historical events
Problems of reconciling events registered in radiocarbon-dated pollen diagrams with calendar- dated archaeological events have been encountered when interpreting pollen diagrams constructed from a number of mire sites in the Hadrianic-Antonine frontier zone of Roman Britain. Only at Fozy Moss, Northumbria, is it possible to relate a substantial clearance in the radiocarbon-dated pollen diagram to a particular event in the calendar-dated archaeolo…
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 …
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…
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…
Some Radiocarbon Dates for Tufas of the Craven District of Yorkshire
14 C dates of relict tufa deposits at Gordale indicated a Subboreal age when the carbonate age was corrected with empirical bedrock dilution factors ‘q’ of 0.79 or 0.85. Estimates of ‘apparent age,’ based on extrapolated δ 13 C values were about twice those obtained with q, and the 1 σ error was large. The δ 13 C values of tufa samples were not correlated with carbonate age and were close to −10. Application of q values in this district requires …
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
An abstract is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content
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
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 dating of a recent high latitude peat profile
The value of both high-precision (HP) and AMS 14 C determinations in the fine-resolution dating of recent peat at Stor Åmyrân, near Umeå, northern Sweden has been explored. A detailed chronology of accumu lation, based on 14 C, an occurrence of the Askja AD 1875 tephra and 241 Am measurements has been derived for the last 700 years. This shows significant changes in the mass balance of the peat profile, with minimum rates of net carbon sequestrat…
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 …
The Stones of Stenness, Orkney
HY 307125. Report of excavations on the Class I henge together with discussion (by E W Marwick) of the folklore surrounding an outlying standing stone, the Stone of Odin, and a catalogue of important 18th and 19th century illustrations of both sites. Excavation of the henge revealed that a ring of twelve stones was originally planned and that a complex stone and timber setting occupied the centre, grooved ware was found in both the central featur…
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…
Anthropogenic Soil Erosion around Lake Patzcuaro, Michoacan, Mexico, during the Preclassic and Late Postclassic-Hispanic Periods
Lake Pátzcuaro (2,035 m asl), situated in the temperate highland-forest region of central Mexico, was the focus of Postclassic Tarascan civilization. Today, the lake is bordered by wide, swampy flats, which can be interpreted as low-angle fans of colluvial material derived from the deeply eroded, lower-valley side slopes. A gully near the northwest shore exposed two colluvial units: The lower one was dated at 2,300 years B.P. (350 B.C.) at the ba…
The Temporal Distribution of ‘Bomb’ 14 C in a Forest Soil
Patterns of 14 C enrichment in the superficial plant debris and mineral soil horizons of an established woodland have been monitored at regular intervals during the past 15 years. These data are compared with a model evaluation of carbon turnover based on the recorded changes in atmospheric 14 C concentration since AD 1900. Leaf litter and decomposing plant debris are characterized by steady-state turnover values of ca 2 and ca 8 years, respectiv…
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
Glasgow University Radiocarbon Measurements II
A third radiocarbon counting system has been established in the Chemistry Department, University of Glasgow, since April, 1968. Operating conditions for the previous systems have remained essentially as described by Baxter et al. (1969)
Radiocarbon
An abstract is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content
Drought and dust deposition in the West African Sahel
A high-resolution, multiproxy palaeolimnological record from the Manga Grasslands, northeastern Nigeria, spanning the last 5500 calendar years, reveals the episodic deterioration in Sahelian climate as significant biogeophysical thresholds were crossed. Desert-dust deposition began to increase 4700 cal. BP. Rainfall during the summer-monsoon season declined permanently after 4100 cal. BP. A further significant change in atmospheric circulation, g…
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…
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…
Problems associated with correlating calibrated radiocarbon-dated pollen diagrams with historical events
Problems of reconciling events registered in radiocarbon-dated pollen diagrams with calendar- dated archaeological events have been encountered when interpreting pollen diagrams constructed from a number of mire sites in the Hadrianic-Antonine frontier zone of Roman Britain. Only at Fozy Moss, Northumbria, is it possible to relate a substantial clearance in the radiocarbon-dated pollen diagram to a particular event in the calendar-dated archaeolo…
Is Comparability of 14 C Dates an Issue
For more than 15 years, the radiocarbon community has participated in a series of laboratory intercomparisons in response to the issue of comparability of measurements as perceived within the wider user communities (Scott et al. 1990; Rozanski et al. 1992; Gulliksen and Scott 1995; Scott et al. 1997). In this report, we provide an update on the current 14 C laboratory intercomparison and reflect on future issues linked to the laboratory intercomp…
Towards a Radiocarbon Chronology of the Late-Glacial
This paper outlines a dating program designed to test the reproducibility of radiocarbon dates on different materials of Late-Glacial age (plant macrofossils, fossil beetle remains, and the “humic” and “humin” chemical fractions of limnic sediments) using a combination of radiometric (beta counting) and accelerator mass spectrometry (AMS) techniques. The results have implications for the design of sampling strategies and for the development of im…
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 …
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…
Scottish Universities Research and Reactor Centre Radiocarbon Measurements III
Results reported here are for samples of geologic context. Throughout the period of these analyses, viz , 1973 through 1975, the preparation of samples and operation of counting systems remained essentially as described in Radiocarbon, 1973, v 15, p 554 to 565
Precision and accuracy in applied 14C dating
Scottish Universities Research and Reactor Centre Radiocarbon Measurements IV
Results reported here are for samples of geologic or geographic context completed during the period 1975 to 1978
Excavation of two Orcadian burnt mounds at Liddle and Beaquoy
ND 464841; HY 301219. Extensive excavation of two 'burnt mounds' suggests that, in Orkney at least, they are the remains of permanent farming settlements. Both mounds covered traces of substantial stone buildings associated with flat-rimmed ware, hammerstones, stone ard-shares, quernstones and flint implements. Radiocarbon and thermoluminescence analyses gave dates in the range 1300-100 BC. The discussion includes a detailed survey of the evidenc…
Possible Carbon‐14 Enrichment in High Altitude Wood
S It has been suggested that utilization of the bristlecone pine calibration for 14 C age correction can result in dates which are up to several hundred years too early in comparison with archaeological evidence. Among other possible causes in situ production of 14 C due to the high altitude growth region of the bristlecone pine has been proposed to explain this effect. Although theoretical evaluation indicates that a significant amount of 14 C c…
Scottish Universities Research and Reactor Centre Radiocarbon Measurements I
The Radiocarbon Laboratory at the Scottish Universities Research and Reactor Centre was established in August 1971. The laboratory is funded by the Natural Environment Research Council and its main function is geochemical investigations in collaboration with the component bodies of the Council and with grant-aided associations. A dating service is also provided to others
Glasgow University Radiocarbon Measurements II
A third radiocarbon counting system has been established in the Chemistry Department, University of Glasgow, since April, 1968. Operating conditions for the previous systems have remained essentially as described by Baxter et al. (1969)
Glasgow University Radiocarbon Measurements V
Operation of counting systems and preparation of results remain as described previously by Baxter et al. (1969), and Ergin et al. (1970)
Glasgow University Radiocarbon Measurements IV
The following list and data presented previously (R., 1970, v. 12, p. 494–495) were obtained to investigate the transport of carbon between man and his environment (Harkness, 1970). These data constitute a study of contemporary variations of C 14 concentrations viz. , Suess effect and bomb effect, as reflected in the tissues and food chain of the population of the United Kingdom (Harkness and Walton, 1969)
Scottish Universities Research and Reactor Centre Radiocarbon Measurements I
The Radiocarbon Laboratory at the Scottish Universities Research and Reactor Centre was established in August 1971. The laboratory is funded by the Natural Environment Research Council and its main function is geochemical investigations in collaboration with the component bodies of the Council and with grant-aided associations. A dating service is also provided to others
Scottish Universities Research and Reactor Centre Radiocarbon Measurements II
Preparation of samples, operation of counting systems, and calculation of results remain as described previously (Harkness and Wilson, 1973)
Possible Carbon‐14 Enrichment in High Altitude Wood
S It has been suggested that utilization of the bristlecone pine calibration for 14 C age correction can result in dates which are up to several hundred years too early in comparison with archaeological evidence. Among other possible causes in situ production of 14 C due to the high altitude growth region of the bristlecone pine has been proposed to explain this effect. Although theoretical evaluation indicates that a significant amount of 14 C c…
Excavation of two Orcadian burnt mounds at Liddle and Beaquoy
ND 464841; HY 301219. Extensive excavation of two 'burnt mounds' suggests that, in Orkney at least, they are the remains of permanent farming settlements. Both mounds covered traces of substantial stone buildings associated with flat-rimmed ware, hammerstones, stone ard-shares, quernstones and flint implements. Radiocarbon and thermoluminescence analyses gave dates in the range 1300-100 BC. The discussion includes a detailed survey of the evidenc…
The Stones of Stenness, Orkney
HY 307125. Report of excavations on the Class I henge together with discussion (by E W Marwick) of the folklore surrounding an outlying standing stone, the Stone of Odin, and a catalogue of important 18th and 19th century illustrations of both sites. Excavation of the henge revealed that a ring of twelve stones was originally planned and that a complex stone and timber setting occupied the centre, grooved ware was found in both the central featur…
Radiocarbon Measurements on a Floating Tree‐ring Chronology From North‐east Scotland
Radiocarbon measurements have been performed on a 250 year ‘floating’ tree‐ring section recovered from an archaeological site in north‐east Scotland. Short term fluctuations in atmospheric concentration appear to be superimposed on a general trend of decreasing ambient 14 Cparallel with tree growth. The most significant finding is the range of dates obtained from the sequence, namely 400 years, since it implies that the error on a single radiocar…
Scottish Universities Research and Reactor Centre Radiocarbon Measurements III
Results reported here are for samples of geologic context. Throughout the period of these analyses, viz , 1973 through 1975, the preparation of samples and operation of counting systems remained essentially as described in Radiocarbon, 1973, v 15, p 554 to 565
Carbon Isotope Measurement as An Index of Soil Development
14 C and 13 C enrichment values are reported for a series of surface soil profiles which represent the progressive transition from mor to mull humus induced by birch ( Betula pendula ) colonization. Variations in Δ and δ 13 C, which range between 85 to 154‰ modern and −28.1 to −25.3‰ (PDB), respectively, reflect changes in the rate and mode of organic decomposition. The most marked alterations in soil character occur over the first few decades fo…
Possibility of Climatically Induced Variations in the 14 C and 13 C Enrichment Patterns as Recorded by a 300-Year-Old Norwegian Pine
The secular patterns of Δ and δ 13 C measured in wood cellulose are compared with a palaeotemperature index published for the immediate growth region. 14 C enrichment shows an overall decrease of ca 20% (Δ) during the 18th and 19th centuries with shorter term (decade) variations superimposed on the general trend. Measured Δ values correlate significantly with the average mean summer temperatures and indicate a linear coefficient of ca − 10.2% °C …
Scottish Universities Research and Reactor Centre Radiocarbon Measurements IV
Results reported here are for samples of geologic or geographic context completed during the period 1975 to 1978
The Temporal Distribution of ‘Bomb’ 14 C in a Forest Soil
Patterns of 14 C enrichment in the superficial plant debris and mineral soil horizons of an established woodland have been monitored at regular intervals during the past 15 years. These data are compared with a model evaluation of carbon turnover based on the recorded changes in atmospheric 14 C concentration since AD 1900. Leaf litter and decomposing plant debris are characterized by steady-state turnover values of ca 2 and ca 8 years, respectiv…
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 …
The Influence of Afforestation on Upland Soils
A series of soil samples were collected in November 1984 from five stands of Sitka spruce planted at recorded times between 1951 and 1968. Within a comprehensive program of ecologic and biogeochemical analyses, natural 14 C measurements on selected organic components of the 0 to 5cm soil horizons serve to quantify progressive changes induced in the organic carbon inventory and relative to that of the original grassland. Points of particular inter…
Anthropogenic Soil Erosion around Lake Patzcuaro, Michoacan, Mexico, during the Preclassic and Late Postclassic-Hispanic Periods
Lake Pátzcuaro (2,035 m asl), situated in the temperate highland-forest region of central Mexico, was the focus of Postclassic Tarascan civilization. Today, the lake is bordered by wide, swampy flats, which can be interpreted as low-angle fans of colluvial material derived from the deeply eroded, lower-valley side slopes. A gully near the northwest shore exposed two colluvial units: The lower one was dated at 2,300 years B.P. (350 B.C.) at the ba…
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…
Some Radiocarbon Dates for Tufas of the Craven District of Yorkshire
14 C dates of relict tufa deposits at Gordale indicated a Subboreal age when the carbonate age was corrected with empirical bedrock dilution factors ‘q’ of 0.79 or 0.85. Estimates of ‘apparent age,’ based on extrapolated δ 13 C values were about twice those obtained with q, and the 1 σ error was large. The δ 13 C values of tufa samples were not correlated with carbonate age and were close to −10. Application of q values in this district requires …
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
An abstract is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content
Radiocarbon dating (33 obras) · Geology (31 obras) · Archaeology (30 obras) · Archaeology and ancient environmental studies (28 obras) · Geography (26 obras) · Geology and Paleoclimatology Research (19 obras) · Chemistry (16 obras) · Environmental Science (15 obras) · Computer Science (12 obras) · Paleontology (12 obras)