D J Donahue
Datos Biográficos
| ID | 248763 |
|---|---|
| NOMBRE | D J Donahue |
| NOMBRES | D J |
| APELLIDO | Donahue |
| FIRMA | DONAHUE D J |
| AFILIACIONES | University of Arizona |
| VERIFICADO | No |
| TOTAL DE OBRAS | 27 |
| TOTAL DE CITAS | 231 |
| TOTAL COMO AUTOR | 27 |
| TOTAL COMO EDITOR | 0 |
| PRIMER AÑO DE PUBLICACIÓN | 1982 |
| AÑO MÁS RECIENTE DE PUBLICACIÓN | 2009 |
| ÍNDICE H | 9 |
Modern and Pleistocene Reservoir Ages Inferred from South Pacific Corals
This paper presents radiocarbon results from modern South Pacific corals from the Marquesas Islands, Vanuatu, Papua New Guinea (PNG), and Easter Island. All of the measurements are from pre-bomb Porites corals that lived during the 1940s and 1950s. The data reflect subannual to multiannual surface ocean 14 C variability and allow for precise, unambiguous reservoir age determinations. The results are compared with published values from other coral…
Environmental variability within the Chinese desert-loess transition zone over the last 20000 years
The desert/loess transition zone in northern China is sensitive to climate variability, which is controlled mainly by the relative strengths of the East Asian summer and winter monsoons. Sandy loess layers found in the Loess Plateau and palaeosol sequences found in the sandy desert demonstrate latitudinal shifts of the southern desert margin over the last 20000 years. Stratigraphic investigations together with radiocarbon and some thermoluminesce…
Determination of the Radiocarbon Age of Parchment of the Vinland Map
The Vinland Map, drawn on a 27.8 × 41.0 cm parchment bifolium, is housed in the Beinecke Rare Book and Manuscript Library at Yale University. In the northwest Atlantic Ocean, it shows “the Island of Vinland, discovered by Bjarni and Leif in company.” Skelton, Marston, and Painter (Skelton et al. 1965, 1995) firmly argued the map's authenticity, associating it with the Council of Basle (AD 1431–1449), that is, half a century before Columbus's voya…
Radiocarbon Measurements of Tree Rings from 14 ka Huon Pine
We have measured the radiocarbon content of tree rings from a section of Huon pine retrieved from Tasmania. The sample was divided into 39 five-ring sub-samples covering a period of 194 years. Radiocarbon ages of each of these sub-samples was determined by making four measurements of each sub-sample at the Arizona AMS laboratory (Table 1). The resulting 1σ precisions are about 0.5%. A comparison of our data with the appropriate curve in INTCAL98 …
AMS Dating Mammoth Bones
Fossilized Siberian mammoth remains are important indicators of environmental change in the Late Pleistocene. The NSF-Arizona AMS Laboratory radiocarbon results on amino acid separations compare well with mammoth bone collagen from the same specimens treated by HCl and dated by beta counting (the Russian Academy Geological Institute Radiocarbon Laboratory). Neither laboratory was aware of the other's dates for these comparisons. The results coinc…
The Reliability of AMS Radiocarbon Dating of Shells from China
We tested the feasibility of dating freshwater and terrestrial molluscs from the semiarid and arid zone in China, since these types of shell material deposit only aragonite to form their shell structure, and shell integrity can be easily observed using X-ray diffraction. We also tested the possibility of estimating microenvironmental changes from shell δ 13 C values, but variations within shell populations preclude the use of these values as a re…
A High-Resolution Radiocarbon Calibration Between 11,700 and 12,400 Calendar Years Bp Derived from 230 Th Ages of Corals from Espiritu Santo Island, Vanuatu
This paper presents radiocarbon results from a single Diploastrea heliopora coral from Vanuatu that lived during the Younger Dryas climatic episode, between ca. 11,700 and 12,400 calendar yr bp. The specimen has been independently dated with multiple 230 Th measurements to permit calibration of the 14 C time scale. Growth bands in the coral were used to identify individual years of growth. 14 C measurements were made on each year. These values we…
Reappraisal of Chinese Loess Plateau Stratigraphic Sequences Over the Last 30,000 Years
Through the establishment of radiocarbon chronozones relating common geological events within lacustrine and eolian sediments from five profiles representative of loess yuan (tablelands), river valley and northwest margin features of the Loess Plateau, we propose a series of stratigraphic divisions within the last 30 ka. The focus of this detailed study involves stratigraphic relationships contributing to evidence of Younger Dryas events, with th…
Factors Affecting the Apparent Radiocarbon Age of Textiles
A Large Drop in Atmospheric 14 C/ 12 C and Reduced Melting in the Younger Dryas, Documented with 230 Th Ages of Corals
Paired carbon-14 ( 14 C) and thorium-230( 230 Th) ages were determined on fossil corals from the Huon Peninsula, Papua New Guinea. The ages were used to calibrate part of the 14 C time scale and to estimate rates of sea-level rise during the last deglaciation. An abrupt offset between the 14 C and 230 Th ages suggests that the atmospheric 14 C/ 12 C ratio dropped by 15 percent during the latter part of and after the Younger Dryas (YD). This promi…
AMS Radiocarbon Dating of Ice
In the “sublimation technique,” carbon dioxide entrapped in ice is recovered by sublimation, converted to graphite and ratio of 14 C/ 13 C in the CO 2 determined by AMS measurements. We describe here several experiments performed to check the validity of such measurements and to study the effect of cosmogenically produced in-situ 14 C on the measurements
Mass Spectrometric 14 C and U-Th Measurements in Coral
We discuss U-Th and 14 C measurements in coral. Samples with U-Th dates in excess of 50 ka BP were chosen for study. Some bulk samples from this group have measurable 14 C dates, which range from 30 ka to 43 ka bp. These can be explained by 0.5–2.5% contamination by modern carbon. This small amount of contamination can produce significant offsets in 14 C dates of coral samples older than ≃10 ka. It may be undetectable in X-ray powder diffraction …
Chronology of the Baxie Loess Profile and the History of Monsoon Climates in China Between 17,000 and 6000 Years BP
The valley of the Baxie River, situated in the western region of the Loess Plateau in central China, contains a loess profile 15 m thick, which can be considered representative of loess-paleosol sequences formed over the last 17 ka. Both thermoluminescence (TL) determinations on fine-grained sediment (4–11 μm) and 14 C determinations on various organic fractions of paleosols from the profile have provided an extremely useful chronological framewo…
Anomalous 11-Year Δ 14 C Cycle at High Latitudes
We find no evidence for an anomalously intense 11-yr cycle in Δ 14 C at high latitudes during the period, AD 1870–1885, as reported by Fan et al . (1983, 1986). However, there does appear to be a regional effect within the MacKenzie River region (67°N, 130°W), with atmospheric 14 C depressed by relative to the Olympic Peninsula. Such an effect would require only 5% of CO 2 in the air mass to have been derived from 5% 14 C-depleted soil gas CO 2 .…
C Profiles in the Norwegian and Greenland Seas by Conventional and AMS Measurements
CO 2 in the atmosphere is an important climate gas because of its absorption of infrared radiation. More knowledge about CO 2 uptake in the ocean is of critical significance in predicting future climate development. For a period of approximately 30 years, radioactive carbon from nuclear tests has been a very useful tracer in CO 2 exchange studies. Up to now, the measurements have been based mainly on the conventional counting technique with large…
Accelerator mass spectrometry
The Recovery and Dating of Carbon Dioxide in Polar Ice Cores
A new method is described for recovering trapped CO 2 from polar ice cores. The ice is sublimed under vacuum, and H 2 O vapor and CO 2 are collected at appropriate cold traps. The application of this method to obtain CO 2 from a specific ice core, the conversion of that CO 2 to graphite, and the measurement of radiocarbon in the CO 2 are described in detail. The potentialities and problems of the method are discussed
Spallogenic 14C in High-Altitude Rocks and in Antarctic Meteorites
14 C in high-altitude rocks and in Antarctic meteorites of long terrestrial age has been found at levels consistent with in-situ production by cosmic rays. Levels of 0.2–0.59 dpm/kg (or 1.0–2.6 × 10 6 14 C/g) are found in high-altitude samples ranging from 3300 to 5460m. Similar values are observed in Antarctic meteorites that have been dated by 81 Kr by Freundel, Schultz & Reedy (1986) as over 100 kyr old
First Direct AMS Dates on Early Maize From Tehuacán, Mexico
The Tehuacán region in Central Mexico is thought to be the locale of origin of Zea mays , or maize, a cultivated plant pivotal in the development of agriculture in the Americas (MacNeish, 1981, 1985). The age of the earliest maize, and its rate of dispersal are thus important components of cultural development in the New World. We have secured permission from the Federal Government of Mexico to date critical specimens from Tehuacán, which represe…
Radiocarbon Dating of Deep-Sea Sediments
Radiocarbon dating (Libby, 1955) has been an important tool in the marine sciences since the early 1950s (eg, Arrhenius, Kjellberg & Libby, 1951; Ericson et al , 1956; Broecker, Ewing & Heezen, 1960; Emery & Bray, 1962) and the basic principles and analytic procedures of the method have changed little. In the late 1970s, the Accelerator Mass Spectrometer (AMS) method of 14 C dating was developed (Bennett et al , 1977, 1978), the major advantages …
New radiocarbon dates and Late Palaeolithic diet at Wadi Kubbaniya, Egypt
Vegetable remains are a rarity in Palueolithic contexts. These new determinations on material from southern Egypt establish securely the date of an intensive grass-tuber and fish economy in the Nile Valley towards 20,000 years ago
Operation of the NSF-Arizona Accelerator Facility for Radioisotope Analysis and Results from Selected Collaborative Research Projects
Radiocarbon dating at the Arizona accelerator facility has improved substantially in the last three years. Since starting to use graphite targets (see Jull et al , 1986), we have been able to obtain routinely a precision of ca ± 1% (ca 80 yr) for relatively modern material. Our routine technique of tuning and operating the tandem accelerator mass spectrometer (TAMS) and our method of calculating 14 C results are discussed in detail. Data on activ…
Urban Atmospheric 14 CO and 14 CH 4 Measurements by Accelerator Mass Spectrometry
Atmospheric gas samples (0.1m 3 ) were collected at ground level during January/February 1984 in Las Vegas, Nevada for 14 C/ 13 C accelerator mass spectrometry and total abundance measurements of CO and CH 4 . During winter months in this locale, CO concentrations can occur at 10 to 100 times background, occasionally exceeding the National Ambient Air Quality Standard (NAAQS). Methane concentrations show a slight enhancement (∼24%) above the back…
Production of Graphite Targets by Deposition from CO/H 2 for Precision Accelerator 14 C Measurements
A method has been developed at the Arizona AMS facility for production of graphite directly from CO 2 by catalytic reduction of CO/H 2 mixtures. The method is a modification of procedures discussed by Vogel et al (1984). Currents of 12 C − from these targets vary considerably, but have a median value which is 70% of that achieved from spectroscopic graphite. Precisions of ±60 to 100 yr are routinely achieved for 14 C ages of 5000-yr-old samples c…
Major Revisions in the Pleistocene Age Assignments for North American Human Skeletons by C-14 Accelerator Mass Spectrometry
Radiocarbon analyses by accelerator mass spectrometric (AMS) techniques on organic fractions of human bone from various North American localities previously assigned ages ranging from about 70,000 to 15,000 years B.P. now suggest that none of these skeletons is older than 11,000 C-14 years B.P
First Direct AMS Dates on Early Maize From Tehuacán, Mexico
The Tehuacán region in Central Mexico is thought to be the locale of origin of Zea mays , or maize, a cultivated plant pivotal in the development of agriculture in the Americas (MacNeish, 1981, 1985). The age of the earliest maize, and its rate of dispersal are thus important components of cultural development in the New World. We have secured permission from the Federal Government of Mexico to date critical specimens from Tehuacán, which represe…
A High-Resolution Radiocarbon Calibration Between 11,700 and 12,400 Calendar Years Bp Derived from 230 Th Ages of Corals from Espiritu Santo Island, Vanuatu
This paper presents radiocarbon results from a single Diploastrea heliopora coral from Vanuatu that lived during the Younger Dryas climatic episode, between ca. 11,700 and 12,400 calendar yr bp. The specimen has been independently dated with multiple 230 Th measurements to permit calibration of the 14 C time scale. Growth bands in the coral were used to identify individual years of growth. 14 C measurements were made on each year. These values we…
Production of Graphite Targets by Deposition from CO/H 2 for Precision Accelerator 14 C Measurements
A method has been developed at the Arizona AMS facility for production of graphite directly from CO 2 by catalytic reduction of CO/H 2 mixtures. The method is a modification of procedures discussed by Vogel et al (1984). Currents of 12 C − from these targets vary considerably, but have a median value which is 70% of that achieved from spectroscopic graphite. Precisions of ±60 to 100 yr are routinely achieved for 14 C ages of 5000-yr-old samples c…
Mass Spectrometric 14 C and U-Th Measurements in Coral
We discuss U-Th and 14 C measurements in coral. Samples with U-Th dates in excess of 50 ka BP were chosen for study. Some bulk samples from this group have measurable 14 C dates, which range from 30 ka to 43 ka bp. These can be explained by 0.5–2.5% contamination by modern carbon. This small amount of contamination can produce significant offsets in 14 C dates of coral samples older than ≃10 ka. It may be undetectable in X-ray powder diffraction …
Major Revisions in the Pleistocene Age Assignments for North American Human Skeletons by C-14 Accelerator Mass Spectrometry
Radiocarbon analyses by accelerator mass spectrometric (AMS) techniques on organic fractions of human bone from various North American localities previously assigned ages ranging from about 70,000 to 15,000 years B.P. now suggest that none of these skeletons is older than 11,000 C-14 years B.P
Operation of the NSF-Arizona Accelerator Facility for Radioisotope Analysis and Results from Selected Collaborative Research Projects
Radiocarbon dating at the Arizona accelerator facility has improved substantially in the last three years. Since starting to use graphite targets (see Jull et al , 1986), we have been able to obtain routinely a precision of ca ± 1% (ca 80 yr) for relatively modern material. Our routine technique of tuning and operating the tandem accelerator mass spectrometer (TAMS) and our method of calculating 14 C results are discussed in detail. Data on activ…
The Reliability of AMS Radiocarbon Dating of Shells from China
We tested the feasibility of dating freshwater and terrestrial molluscs from the semiarid and arid zone in China, since these types of shell material deposit only aragonite to form their shell structure, and shell integrity can be easily observed using X-ray diffraction. We also tested the possibility of estimating microenvironmental changes from shell δ 13 C values, but variations within shell populations preclude the use of these values as a re…
Determination of the Radiocarbon Age of Parchment of the Vinland Map
The Vinland Map, drawn on a 27.8 × 41.0 cm parchment bifolium, is housed in the Beinecke Rare Book and Manuscript Library at Yale University. In the northwest Atlantic Ocean, it shows “the Island of Vinland, discovered by Bjarni and Leif in company.” Skelton, Marston, and Painter (Skelton et al. 1965, 1995) firmly argued the map's authenticity, associating it with the Council of Basle (AD 1431–1449), that is, half a century before Columbus's voya…
Chronology of the Baxie Loess Profile and the History of Monsoon Climates in China Between 17,000 and 6000 Years BP
The valley of the Baxie River, situated in the western region of the Loess Plateau in central China, contains a loess profile 15 m thick, which can be considered representative of loess-paleosol sequences formed over the last 17 ka. Both thermoluminescence (TL) determinations on fine-grained sediment (4–11 μm) and 14 C determinations on various organic fractions of paleosols from the profile have provided an extremely useful chronological framewo…
Anomalous 11-Year Δ 14 C Cycle at High Latitudes
We find no evidence for an anomalously intense 11-yr cycle in Δ 14 C at high latitudes during the period, AD 1870–1885, as reported by Fan et al . (1983, 1986). However, there does appear to be a regional effect within the MacKenzie River region (67°N, 130°W), with atmospheric 14 C depressed by relative to the Olympic Peninsula. Such an effect would require only 5% of CO 2 in the air mass to have been derived from 5% 14 C-depleted soil gas CO 2 .…
Modern and Pleistocene Reservoir Ages Inferred from South Pacific Corals
This paper presents radiocarbon results from modern South Pacific corals from the Marquesas Islands, Vanuatu, Papua New Guinea (PNG), and Easter Island. All of the measurements are from pre-bomb Porites corals that lived during the 1940s and 1950s. The data reflect subannual to multiannual surface ocean 14 C variability and allow for precise, unambiguous reservoir age determinations. The results are compared with published values from other coral…
Factors Affecting the Apparent Radiocarbon Age of Textiles
Radiocarbon Dating of Deep-Sea Sediments
Radiocarbon dating (Libby, 1955) has been an important tool in the marine sciences since the early 1950s (eg, Arrhenius, Kjellberg & Libby, 1951; Ericson et al , 1956; Broecker, Ewing & Heezen, 1960; Emery & Bray, 1962) and the basic principles and analytic procedures of the method have changed little. In the late 1970s, the Accelerator Mass Spectrometer (AMS) method of 14 C dating was developed (Bennett et al , 1977, 1978), the major advantages …
Environmental variability within the Chinese desert-loess transition zone over the last 20000 years
The desert/loess transition zone in northern China is sensitive to climate variability, which is controlled mainly by the relative strengths of the East Asian summer and winter monsoons. Sandy loess layers found in the Loess Plateau and palaeosol sequences found in the sandy desert demonstrate latitudinal shifts of the southern desert margin over the last 20000 years. Stratigraphic investigations together with radiocarbon and some thermoluminesce…
C Profiles in the Norwegian and Greenland Seas by Conventional and AMS Measurements
CO 2 in the atmosphere is an important climate gas because of its absorption of infrared radiation. More knowledge about CO 2 uptake in the ocean is of critical significance in predicting future climate development. For a period of approximately 30 years, radioactive carbon from nuclear tests has been a very useful tracer in CO 2 exchange studies. Up to now, the measurements have been based mainly on the conventional counting technique with large…
Spallogenic 14C in High-Altitude Rocks and in Antarctic Meteorites
14 C in high-altitude rocks and in Antarctic meteorites of long terrestrial age has been found at levels consistent with in-situ production by cosmic rays. Levels of 0.2–0.59 dpm/kg (or 1.0–2.6 × 10 6 14 C/g) are found in high-altitude samples ranging from 3300 to 5460m. Similar values are observed in Antarctic meteorites that have been dated by 81 Kr by Freundel, Schultz & Reedy (1986) as over 100 kyr old
New radiocarbon dates and Late Palaeolithic diet at Wadi Kubbaniya, Egypt
Vegetable remains are a rarity in Palueolithic contexts. These new determinations on material from southern Egypt establish securely the date of an intensive grass-tuber and fish economy in the Nile Valley towards 20,000 years ago
Radiocarbon Measurements of Tree Rings from 14 ka Huon Pine
We have measured the radiocarbon content of tree rings from a section of Huon pine retrieved from Tasmania. The sample was divided into 39 five-ring sub-samples covering a period of 194 years. Radiocarbon ages of each of these sub-samples was determined by making four measurements of each sub-sample at the Arizona AMS laboratory (Table 1). The resulting 1σ precisions are about 0.5%. A comparison of our data with the appropriate curve in INTCAL98 …
AMS Radiocarbon Dating of Ice
In the “sublimation technique,” carbon dioxide entrapped in ice is recovered by sublimation, converted to graphite and ratio of 14 C/ 13 C in the CO 2 determined by AMS measurements. We describe here several experiments performed to check the validity of such measurements and to study the effect of cosmogenically produced in-situ 14 C on the measurements
Results of Tests and Measurements from the Nsf Regional Accelerator Facility for Radioisotope Dating
Tests of performance of the tandem accelerator mass spectrometer at the NSF Regional Facility at the University of Arizona are discussed. Results of measurements on some tree rings and on some archaeologic samples are presented
Charcoal production from wood and cellulose
Radiocarbon dating with accelerators requires the manufacture of suitable carbon targets. Carbon yield and 13 C fractionation were investigated for the simple and direct pyrolysis of wood and cellulose to charcoal. Under continuous vacuum removal of evolved volatiles, carbon yields of 35 to 40% and δ 13 C fractionation of −2.5‰ were observed in the pyrolysis of wood to charcoal, whereas yields of 30% and fractionation of −0.8‰ were obtained in th…
AMS Dating Mammoth Bones
Fossilized Siberian mammoth remains are important indicators of environmental change in the Late Pleistocene. The NSF-Arizona AMS Laboratory radiocarbon results on amino acid separations compare well with mammoth bone collagen from the same specimens treated by HCl and dated by beta counting (the Russian Academy Geological Institute Radiocarbon Laboratory). Neither laboratory was aware of the other's dates for these comparisons. The results coinc…
The Recovery and Dating of Carbon Dioxide in Polar Ice Cores
A new method is described for recovering trapped CO 2 from polar ice cores. The ice is sublimed under vacuum, and H 2 O vapor and CO 2 are collected at appropriate cold traps. The application of this method to obtain CO 2 from a specific ice core, the conversion of that CO 2 to graphite, and the measurement of radiocarbon in the CO 2 are described in detail. The potentialities and problems of the method are discussed
Urban Atmospheric 14 CO and 14 CH 4 Measurements by Accelerator Mass Spectrometry
Atmospheric gas samples (0.1m 3 ) were collected at ground level during January/February 1984 in Las Vegas, Nevada for 14 C/ 13 C accelerator mass spectrometry and total abundance measurements of CO and CH 4 . During winter months in this locale, CO concentrations can occur at 10 to 100 times background, occasionally exceeding the National Ambient Air Quality Standard (NAAQS). Methane concentrations show a slight enhancement (∼24%) above the back…
Charcoal production from wood and cellulose
Radiocarbon dating with accelerators requires the manufacture of suitable carbon targets. Carbon yield and 13 C fractionation were investigated for the simple and direct pyrolysis of wood and cellulose to charcoal. Under continuous vacuum removal of evolved volatiles, carbon yields of 35 to 40% and δ 13 C fractionation of −2.5‰ were observed in the pyrolysis of wood to charcoal, whereas yields of 30% and fractionation of −0.8‰ were obtained in th…
Results of Tests and Measurements from the Nsf Regional Accelerator Facility for Radioisotope Dating
Tests of performance of the tandem accelerator mass spectrometer at the NSF Regional Facility at the University of Arizona are discussed. Results of measurements on some tree rings and on some archaeologic samples are presented
Major Revisions in the Pleistocene Age Assignments for North American Human Skeletons by C-14 Accelerator Mass Spectrometry
Radiocarbon analyses by accelerator mass spectrometric (AMS) techniques on organic fractions of human bone from various North American localities previously assigned ages ranging from about 70,000 to 15,000 years B.P. now suggest that none of these skeletons is older than 11,000 C-14 years B.P
Operation of the NSF-Arizona Accelerator Facility for Radioisotope Analysis and Results from Selected Collaborative Research Projects
Radiocarbon dating at the Arizona accelerator facility has improved substantially in the last three years. Since starting to use graphite targets (see Jull et al , 1986), we have been able to obtain routinely a precision of ca ± 1% (ca 80 yr) for relatively modern material. Our routine technique of tuning and operating the tandem accelerator mass spectrometer (TAMS) and our method of calculating 14 C results are discussed in detail. Data on activ…
Urban Atmospheric 14 CO and 14 CH 4 Measurements by Accelerator Mass Spectrometry
Atmospheric gas samples (0.1m 3 ) were collected at ground level during January/February 1984 in Las Vegas, Nevada for 14 C/ 13 C accelerator mass spectrometry and total abundance measurements of CO and CH 4 . During winter months in this locale, CO concentrations can occur at 10 to 100 times background, occasionally exceeding the National Ambient Air Quality Standard (NAAQS). Methane concentrations show a slight enhancement (∼24%) above the back…
Production of Graphite Targets by Deposition from CO/H 2 for Precision Accelerator 14 C Measurements
A method has been developed at the Arizona AMS facility for production of graphite directly from CO 2 by catalytic reduction of CO/H 2 mixtures. The method is a modification of procedures discussed by Vogel et al (1984). Currents of 12 C − from these targets vary considerably, but have a median value which is 70% of that achieved from spectroscopic graphite. Precisions of ±60 to 100 yr are routinely achieved for 14 C ages of 5000-yr-old samples c…
New radiocarbon dates and Late Palaeolithic diet at Wadi Kubbaniya, Egypt
Vegetable remains are a rarity in Palueolithic contexts. These new determinations on material from southern Egypt establish securely the date of an intensive grass-tuber and fish economy in the Nile Valley towards 20,000 years ago
Accelerator mass spectrometry
The Recovery and Dating of Carbon Dioxide in Polar Ice Cores
A new method is described for recovering trapped CO 2 from polar ice cores. The ice is sublimed under vacuum, and H 2 O vapor and CO 2 are collected at appropriate cold traps. The application of this method to obtain CO 2 from a specific ice core, the conversion of that CO 2 to graphite, and the measurement of radiocarbon in the CO 2 are described in detail. The potentialities and problems of the method are discussed
Spallogenic 14C in High-Altitude Rocks and in Antarctic Meteorites
14 C in high-altitude rocks and in Antarctic meteorites of long terrestrial age has been found at levels consistent with in-situ production by cosmic rays. Levels of 0.2–0.59 dpm/kg (or 1.0–2.6 × 10 6 14 C/g) are found in high-altitude samples ranging from 3300 to 5460m. Similar values are observed in Antarctic meteorites that have been dated by 81 Kr by Freundel, Schultz & Reedy (1986) as over 100 kyr old
First Direct AMS Dates on Early Maize From Tehuacán, Mexico
The Tehuacán region in Central Mexico is thought to be the locale of origin of Zea mays , or maize, a cultivated plant pivotal in the development of agriculture in the Americas (MacNeish, 1981, 1985). The age of the earliest maize, and its rate of dispersal are thus important components of cultural development in the New World. We have secured permission from the Federal Government of Mexico to date critical specimens from Tehuacán, which represe…
Radiocarbon Dating of Deep-Sea Sediments
Radiocarbon dating (Libby, 1955) has been an important tool in the marine sciences since the early 1950s (eg, Arrhenius, Kjellberg & Libby, 1951; Ericson et al , 1956; Broecker, Ewing & Heezen, 1960; Emery & Bray, 1962) and the basic principles and analytic procedures of the method have changed little. In the late 1970s, the Accelerator Mass Spectrometer (AMS) method of 14 C dating was developed (Bennett et al , 1977, 1978), the major advantages …
AMS Radiocarbon Dating of Ice
In the “sublimation technique,” carbon dioxide entrapped in ice is recovered by sublimation, converted to graphite and ratio of 14 C/ 13 C in the CO 2 determined by AMS measurements. We describe here several experiments performed to check the validity of such measurements and to study the effect of cosmogenically produced in-situ 14 C on the measurements
Mass Spectrometric 14 C and U-Th Measurements in Coral
We discuss U-Th and 14 C measurements in coral. Samples with U-Th dates in excess of 50 ka BP were chosen for study. Some bulk samples from this group have measurable 14 C dates, which range from 30 ka to 43 ka bp. These can be explained by 0.5–2.5% contamination by modern carbon. This small amount of contamination can produce significant offsets in 14 C dates of coral samples older than ≃10 ka. It may be undetectable in X-ray powder diffraction …
Chronology of the Baxie Loess Profile and the History of Monsoon Climates in China Between 17,000 and 6000 Years BP
The valley of the Baxie River, situated in the western region of the Loess Plateau in central China, contains a loess profile 15 m thick, which can be considered representative of loess-paleosol sequences formed over the last 17 ka. Both thermoluminescence (TL) determinations on fine-grained sediment (4–11 μm) and 14 C determinations on various organic fractions of paleosols from the profile have provided an extremely useful chronological framewo…
Anomalous 11-Year Δ 14 C Cycle at High Latitudes
We find no evidence for an anomalously intense 11-yr cycle in Δ 14 C at high latitudes during the period, AD 1870–1885, as reported by Fan et al . (1983, 1986). However, there does appear to be a regional effect within the MacKenzie River region (67°N, 130°W), with atmospheric 14 C depressed by relative to the Olympic Peninsula. Such an effect would require only 5% of CO 2 in the air mass to have been derived from 5% 14 C-depleted soil gas CO 2 .…
C Profiles in the Norwegian and Greenland Seas by Conventional and AMS Measurements
CO 2 in the atmosphere is an important climate gas because of its absorption of infrared radiation. More knowledge about CO 2 uptake in the ocean is of critical significance in predicting future climate development. For a period of approximately 30 years, radioactive carbon from nuclear tests has been a very useful tracer in CO 2 exchange studies. Up to now, the measurements have been based mainly on the conventional counting technique with large…
A Large Drop in Atmospheric 14 C/ 12 C and Reduced Melting in the Younger Dryas, Documented with 230 Th Ages of Corals
Paired carbon-14 ( 14 C) and thorium-230( 230 Th) ages were determined on fossil corals from the Huon Peninsula, Papua New Guinea. The ages were used to calibrate part of the 14 C time scale and to estimate rates of sea-level rise during the last deglaciation. An abrupt offset between the 14 C and 230 Th ages suggests that the atmospheric 14 C/ 12 C ratio dropped by 15 percent during the latter part of and after the Younger Dryas (YD). This promi…
Factors Affecting the Apparent Radiocarbon Age of Textiles
Reappraisal of Chinese Loess Plateau Stratigraphic Sequences Over the Last 30,000 Years
Through the establishment of radiocarbon chronozones relating common geological events within lacustrine and eolian sediments from five profiles representative of loess yuan (tablelands), river valley and northwest margin features of the Loess Plateau, we propose a series of stratigraphic divisions within the last 30 ka. The focus of this detailed study involves stratigraphic relationships contributing to evidence of Younger Dryas events, with th…
A High-Resolution Radiocarbon Calibration Between 11,700 and 12,400 Calendar Years Bp Derived from 230 Th Ages of Corals from Espiritu Santo Island, Vanuatu
This paper presents radiocarbon results from a single Diploastrea heliopora coral from Vanuatu that lived during the Younger Dryas climatic episode, between ca. 11,700 and 12,400 calendar yr bp. The specimen has been independently dated with multiple 230 Th measurements to permit calibration of the 14 C time scale. Growth bands in the coral were used to identify individual years of growth. 14 C measurements were made on each year. These values we…
The Reliability of AMS Radiocarbon Dating of Shells from China
We tested the feasibility of dating freshwater and terrestrial molluscs from the semiarid and arid zone in China, since these types of shell material deposit only aragonite to form their shell structure, and shell integrity can be easily observed using X-ray diffraction. We also tested the possibility of estimating microenvironmental changes from shell δ 13 C values, but variations within shell populations preclude the use of these values as a re…
AMS Dating Mammoth Bones
Fossilized Siberian mammoth remains are important indicators of environmental change in the Late Pleistocene. The NSF-Arizona AMS Laboratory radiocarbon results on amino acid separations compare well with mammoth bone collagen from the same specimens treated by HCl and dated by beta counting (the Russian Academy Geological Institute Radiocarbon Laboratory). Neither laboratory was aware of the other's dates for these comparisons. The results coinc…
Radiocarbon Measurements of Tree Rings from 14 ka Huon Pine
We have measured the radiocarbon content of tree rings from a section of Huon pine retrieved from Tasmania. The sample was divided into 39 five-ring sub-samples covering a period of 194 years. Radiocarbon ages of each of these sub-samples was determined by making four measurements of each sub-sample at the Arizona AMS laboratory (Table 1). The resulting 1σ precisions are about 0.5%. A comparison of our data with the appropriate curve in INTCAL98 …
Environmental variability within the Chinese desert-loess transition zone over the last 20000 years
The desert/loess transition zone in northern China is sensitive to climate variability, which is controlled mainly by the relative strengths of the East Asian summer and winter monsoons. Sandy loess layers found in the Loess Plateau and palaeosol sequences found in the sandy desert demonstrate latitudinal shifts of the southern desert margin over the last 20000 years. Stratigraphic investigations together with radiocarbon and some thermoluminesce…
Radiocarbon dating (25 obras) · Geology (21 obras) · Archaeology and ancient environmental studies (14 obras) · Geography (14 obras) · Paleontology (14 obras) · Geology and Paleoclimatology Research (13 obras) · Chemistry (11 obras) · Accelerator mass spectrometry (10 obras) · Archaeology (9 obras) · Pleistocene-Era Hominins and Archaeology (9 obras)