Comparative AMS radiocarbon dating of pretreated versus non-pretreated tropical wood samples

NASA Astrophysics Data System (ADS)

Patrut, Adrian; von Reden, Karl F.; Lowy, Daniel A.; Mayne, Diana H.; Elder, Kathryn E.; Roberts, Mark L.; McNichol, Ann P.

2010-04-01

Several wood samples collected from Dorslandboom, a large iconic African baobab ( Adansonia digitata L.) from Namibia, were investigated by AMS radiocarbon dating subsequent to pretreatment and, alternatively, without pretreatment. The comparative statistical evaluation of results showed that there were no significant differences between fraction modern values and radiocarbon dates of the samples analyzed after pretreatment and without pretreatment, respectively. The radiocarbon date of the oldest sample was 993 ± 20 BP. Dating results also revealed that Dorslandboom is a multi-generation tree, with several stems showing different ages.

Dating of the Basal Aurignacian Sandwich at Abric Romanı́ (Catalunya, Spain) by Radiocarbon and Uranium-Series

USGS Publications Warehouse

Bischoff, James L.; Ludwig, Kenneth R.; Garcia, Jose Francisco; Carbonell, E.; Vaquero, Manola; Stafford, Thomas W.; Jull, A.J.T.

1994-01-01

Abric Romani{dotless}??, a rock shelter located near Barcelona, Spain, contains a charcoal-bearing basal Aurignacian occupation level sandwiched between beds of moss-generated carbonate. The Aurignacian culture is the oldest artefact industry in Europe with which anatomically modern human remains have been associated. Radiocarbon analysis of charcoal fragments by accelerator mass spectrometry (AMS) dates the basal Aurignacian to about 37 ?? 2 ka bp. U-series analyses by alpha spectrometry (AS) and mass spectrometry (MS) date the enclosing carbonate to 43 ?? 1 ka bp. These results confirm the great antiquity of the Aurignacian in northern Spain and support the similar AMS dates from El Castillo and l'Arbreda caves. They also show that radiocarbon dates are significantly younger than U-series at 40 ka bp, as predicted by theory. ?? 1994 Academic Press. All rights reserved.

Radiocarbon dating of twentieth century works of art

NASA Astrophysics Data System (ADS)

Petrucci, F.; Caforio, L.; Fedi, M.; Mandò, P. A.; Peccenini, E.; Pellicori, V.; Rylands, P.; Schwartzbaum, P.; Taccetti, F.

2016-11-01

The atmospheric tests of nuclear weapons caused a sudden increase in the radiocarbon concentration in the atmosphere from 1955, reaching its maximum value in 1963-1965. Once the nuclear tests in the atmosphere were halted, the 14C concentration started to decrease. This behavior of the radiocarbon concentration is called the "Bomb Peak", and it has successfully been used as a tool for high-precision radiocarbon measurements, in forensic sciences and biology. In the art field, the possibility of dating canvas, wood and paper, widely used as supports for paintings, may be an invaluable tool in modern art studies.

Radiocarbon dating of terrestrial carbonates

USGS Publications Warehouse

Pigati, Jeffrey S.; Rink, W. Jack; Thompson, Jeroen

2014-01-01

Terrestrial carbonates encompass a wide range of materials that potentially could be used for radiocarbon (14C) dating. Biogenic carbonates, including shells and tests of terrestrial and aquatic gastropods, bivalves, ostracodes, and foraminifera, are preserved in a variety of late Quaternary deposits and may be suitable for 14C dating. Primary calcareous deposits (marls, tufa, speleothems) and secondary carbonates (rhizoliths, fracture fill, soil carbonate) may also be targeted for dating when conditions are favorable. This chapter discusses issues that are commonly encountered in 14C dating of terrestrial carbonates, including isotopic disequilibrium and open-system behavior, as well as methods used to determine the reliability of ages derived from these materials. Recent methodological advancements that may improve the accuracy and precision of 14C ages of terrestrial carbonates are also highlighted.

A reevaluation of the Pallett Creek earthquake chronology based on new AMS radiocarbon dates, San Andreas fault, California

NASA Astrophysics Data System (ADS)

Scharer, Katherine M.; Biasi, Glenn P.; Weldon, Ray J., II

2011-12-01

The Pallett Creek paleoseismic record occupies a keystone position in most attempts to develop rupture histories for the southern San Andreas fault. Previous estimates of earthquake ages at Pallett Creek were determined by decay counting radiocarbon methods. That method requires large samples which can lead to unaccounted sources of uncertainty in radiocarbon ages because of the heterogeneous composition of organic layers. In contrast, accelerator mass spectrometry (AMS) radiocarbon dates may be obtained from small samples that have known carbon sources and also allow for a more complete sampling of the section. We present 65 new AMS radiocarbon dates that span nine ground-rupturing earthquakes at Pallett Creek. Overall, the AMS dates are similar to and reveal no dramatic bias in the conventional dates. For many layers, however, individual charcoal samples were younger than the conventional dates, leading to earthquake ages that are overall slightly younger than previously reported. New earthquake ages are determined by Bayesian refinement of the layer ages based on stratigraphic ordering and sedimentological constraints. The new chronology is more regular than previously published records in large part due to new samples constraining the age of event R. The closed interval from event C to 1857 has a mean recurrence of 135 years (σ = 83.2 years) and a quasiperiodic coefficient of variation (COV) of 0.61. We show that the new dates and resultant earthquake chronology have a stronger effect on COV than the specific membership of this long series and dating precision improvements from sedimentation rates.

Vulcanism and Radiocarbon Dates

DOE R&D Accomplishments Database

Libby, L. M.; Libby, W. F.

1972-10-01

We consider whether the long term perturbation of radiocarbon dates, which is known to be approximately a sin function of period about 8000 years and amplitude of about 8% peak-to-peak, could have been caused in any major part by vulcanism. We conclude that this is not the case. On the contrary, present day volcanoes are a far less important source of inert CO{sub 2} (about 100 fold less) than is man's burning of fossil fuels which has caused the Suess dilution of about 2%. (auth)

Chemical Principles Revisited: Archaeological Dating.

ERIC Educational Resources Information Center

Rowe, M. W.

1986-01-01

Discusses methods used to date archaeological artifacts and other remains. They include: (1) nuclear dating techniques (radiocarbon dating, accelerator radiocarbon dating, thermoluminescence, and others); (2) chemical dating techniques (amino acid racemization, obsidian hydration dating, elemental content changes, and thermal analysis dating); and…

A combined method for DNA analysis and radiocarbon dating from a single sample.

PubMed

Korlević, Petra; Talamo, Sahra; Meyer, Matthias

2018-03-07

Current protocols for ancient DNA and radiocarbon analysis of ancient bones and teeth call for multiple destructive samplings of a given specimen, thereby increasing the extent of undesirable damage to precious archaeological material. Here we present a method that makes it possible to obtain both ancient DNA sequences and radiocarbon dates from the same sample material. This is achieved by releasing DNA from the bone matrix through incubation with either EDTA or phosphate buffer prior to complete demineralization and collagen extraction utilizing the acid-base-acid-gelatinization and ultrafiltration procedure established in most radiocarbon dating laboratories. Using a set of 12 bones of different ages and preservation conditions we demonstrate that on average 89% of the DNA can be released from sample powder with minimal, or 38% without any, detectable collagen loss. We also detect no skews in radiocarbon dates compared to untreated samples. Given the different material demands for radiocarbon dating (500 mg of bone/dentine) and DNA analysis (10-100 mg), combined DNA and collagen extraction not only streamlines the sampling process but also drastically increases the amount of DNA that can be recovered from limited sample material.

Collagen Fingerprinting: A New Screening Technique for Radiocarbon Dating Ancient Bone.

PubMed

Harvey, Virginia L; Egerton, Victoria M; Chamberlain, Andrew T; Manning, Phillip L; Buckley, Michael

2016-01-01

Collagen is the dominant organic component of bone and is intimately locked within the hydroxyapatite structure of this ubiquitous biomaterial that dominates archaeological and palaeontological assemblages. Radiocarbon analysis of extracted collagen is one of the most common approaches to dating bone from late Pleistocene or Holocene deposits, but dating is relatively expensive compared to other biochemical techniques. Numerous analytical methods have previously been investigated for the purpose of screening out samples that are unlikely to yield reliable dates including histological analysis, UV-stimulated fluorescence and, most commonly, the measurement of percentage nitrogen (%N) and ratio of carbon to nitrogen (C:N). Here we propose the use of collagen fingerprinting (also known as Zooarchaeology by Mass Spectrometry, or ZooMS, when applied to species identification) as an alternative screening method for radiocarbon dating, due to its ability to provide information on collagen presence and quality, alongside species identification. The method was tested on a series of sub-fossil bone specimens from cave systems on Cayman Brac (Cayman Islands), chosen due to the observable range in diagenetic alteration, and in particular, the extent of mineralisation. Six (14)C dates, of 18 initial attempts, were obtained from remains of extinct hutia, Capromys sp. (Rodentia; Capromyidae), recovered from five distinct caves on Cayman Brac, and ranging from 393 ± 25 to 1588 ± 26 radiocarbon years before present (yr BP). All of the bone samples that yielded radiocarbon dates generated excellent collagen fingerprints, and conversely those that gave poor fingerprints also failed dating. Additionally, two successfully fingerprinted bone samples were screened out from a set of 81. Both subsequently generated (14)C dates, demonstrating successful utilisation of ZooMS as an alternative screening mechanism to identify bone samples that are suitable for 1(4)C analysis.

Collagen Fingerprinting: A New Screening Technique for Radiocarbon Dating Ancient Bone

PubMed Central

Harvey, Virginia L.; Egerton, Victoria M.; Chamberlain, Andrew T.; Manning, Phillip L.; Buckley, Michael

2016-01-01

Collagen is the dominant organic component of bone and is intimately locked within the hydroxyapatite structure of this ubiquitous biomaterial that dominates archaeological and palaeontological assemblages. Radiocarbon analysis of extracted collagen is one of the most common approaches to dating bone from late Pleistocene or Holocene deposits, but dating is relatively expensive compared to other biochemical techniques. Numerous analytical methods have previously been investigated for the purpose of screening out samples that are unlikely to yield reliable dates including histological analysis, UV-stimulated fluorescence and, most commonly, the measurement of percentage nitrogen (%N) and ratio of carbon to nitrogen (C:N). Here we propose the use of collagen fingerprinting (also known as Zooarchaeology by Mass Spectrometry, or ZooMS, when applied to species identification) as an alternative screening method for radiocarbon dating, due to its ability to provide information on collagen presence and quality, alongside species identification. The method was tested on a series of sub-fossil bone specimens from cave systems on Cayman Brac (Cayman Islands), chosen due to the observable range in diagenetic alteration, and in particular, the extent of mineralisation. Six 14C dates, of 18 initial attempts, were obtained from remains of extinct hutia, Capromys sp. (Rodentia; Capromyidae), recovered from five distinct caves on Cayman Brac, and ranging from 393 ± 25 to 1588 ± 26 radiocarbon years before present (yr BP). All of the bone samples that yielded radiocarbon dates generated excellent collagen fingerprints, and conversely those that gave poor fingerprints also failed dating. Additionally, two successfully fingerprinted bone samples were screened out from a set of 81. Both subsequently generated 14C dates, demonstrating successful utilisation of ZooMS as an alternative screening mechanism to identify bone samples that are suitable for 14C analysis. PMID:26938469

New Hydroxyproline Radiocarbon Dates from Sungir, Russia, Confirm Early Mid Upper Palaeolithic Burials in Eurasia

PubMed Central

Nalawade-Chavan, Shweta; McCullagh, James; Hedges, Robert

2014-01-01

Sungir (Russia) is a key Mid-Upper Palaeolithic site in Eurasia, containing several spectacular burials that disclose early evidence for complex burial rites in the form of a range of grave goods deposited along with the dead. Dating has been particularly challenging, with multiple radiocarbon dates ranging from 19,160±270 to 28,800±240 BP for burials that are believed to be closely similar in age. There are disparities in the radiocarbon dates of human bones, faunal remains and charcoal found on the floor of burials [1], [2], [3]. Our approach has been to develop compound-specific methods using High Performance Liquid Chromatography (HPLC) to separate single amino acids, such as hydroxyproline, and thereby avoid the known human contamination on the bones themselves. Previously, we applied this technique to obtain radiocarbon dates of ∼30,000 BP for Sungir 2, Sungir 3 and a mammoth bone from the occupation levels of the site [4]. The single amino acid radiocarbon dates were in good agreement with each other compared to all the dates previously reported, supporting their reliability. Here we report new hydroxyproline dates for two more human burials from the same site, Sungir 1 and Sungir 4. All five hydroxyproline dates reported are statistically indistinguishable and support an identical age for the group. The results suggest that compound-specific radiocarbon analysis should be considered seriously as the method of choice when precious archaeological remains are to be dated because they give a demonstrably contaminant-free radiocarbon age. The new ages are, together with the previously dated ‘Red Lady of Paviland’ human in the British Isles, the earliest for Mid Upper Palaeolithic burial behaviour in Eurasia, and point to the precocious appearance of this form of rite in Europe Russia. PMID:24416120

New hydroxyproline radiocarbon dates from Sungir, Russia, confirm early Mid Upper Palaeolithic burials in Eurasia.

PubMed

Nalawade-Chavan, Shweta; McCullagh, James; Hedges, Robert

2014-01-01

Sungir (Russia) is a key Mid-Upper Palaeolithic site in Eurasia, containing several spectacular burials that disclose early evidence for complex burial rites in the form of a range of grave goods deposited along with the dead. Dating has been particularly challenging, with multiple radiocarbon dates ranging from 19,160±270 to 28,800±240 BP for burials that are believed to be closely similar in age. There are disparities in the radiocarbon dates of human bones, faunal remains and charcoal found on the floor of burials. Our approach has been to develop compound-specific methods using High Performance Liquid Chromatography (HPLC) to separate single amino acids, such as hydroxyproline, and thereby avoid the known human contamination on the bones themselves. Previously, we applied this technique to obtain radiocarbon dates of ∼30,000 BP for Sungir 2, Sungir 3 and a mammoth bone from the occupation levels of the site. The single amino acid radiocarbon dates were in good agreement with each other compared to all the dates previously reported, supporting their reliability. Here we report new hydroxyproline dates for two more human burials from the same site, Sungir 1 and Sungir 4. All five hydroxyproline dates reported are statistically indistinguishable and support an identical age for the group. The results suggest that compound-specific radiocarbon analysis should be considered seriously as the method of choice when precious archaeological remains are to be dated because they give a demonstrably contaminant-free radiocarbon age. The new ages are, together with the previously dated 'Red Lady of Paviland' human in the British Isles, the earliest for Mid Upper Palaeolithic burial behaviour in Eurasia, and point to the precocious appearance of this form of rite in Europe Russia.

Microflora distributions in paleosols: a method for calculating the validity of radiocarbon-dated surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mahaney, W.C.; Boyer, M.G.

1986-08-01

Microflora (bacteria and fungi) distributions in several paleosols from Mount Kenya, East Africa, provide important information about contamination of buried soil horizons dated by radiocarbon. High counts of bacteria and fungi in buried soils provide evidence for contamination by plant root effects or ground water movement. Profiles with decreasing counts versus depth appear to produce internally consistent and accurate radiocarbon dates. Profiles with disjunct or bimodal distributions of microflora at various depths produce internally inconsistent chronological sequences of radiocarbon-dated buried surfaces. Preliminary results suggest that numbers up to 5 x 10/sup 2/ g/sup -1/ for bacteria in buried A horizonsmore » do not appear to affect the validity of /sup 14/C dates. Beyond this threshold value, contamination appears to produce younger dates, the difference between true age and /sup 14/C age increasing with the amount of microflora contamination.« less

Results of Radiocarbon Dating of Holocene Deposits from the Sea of Azov

NASA Astrophysics Data System (ADS)

Matishov, G. G.; Kovaleva, G. V.; Arslanov, Kh. A.; Dyuzhova, K. V.; Polshin, V. V.; Zolotareva, A. E.

2018-04-01

New data on the absolute age of Quaternary bottom deposits from the Sea of Azov based on the results of radiocarbon analysis (14C) are presented. Overall, 67 radiocarbon dating of bottom deposits of New and Ancient Azov Ages were obtained. The thickness of sediments of the New Azov Age and their distribution over different areas of the Sea of Azov was determined during the study; the results obtained were compared with the reference data available. An integrated approach to the study of deposits, based on the combination of the biostratigraphy methods and the results of absolute age dating, was applied.

Santorini eruption radiocarbon dated to 1627-1600 B.C.

PubMed

Friedrich, Walter L; Kromer, Bernd; Friedrich, Michael; Heinemeier, Jan; Pfeiffer, Tom; Talamo, Sahra

2006-04-28

Precise and direct dating of the Minoan eruption of Santorini (Thera) in Greece, a global Bronze Age time marker, has been made possible by the unique find of an olive tree, buried alive in life position by the tephra (pumice and ashes) on Santorini. We applied so-called radiocarbon wiggle-matching to a carbon-14 sequence of tree-ring segments to constrain the eruption date to the range 1627-1600 B.C. with 95.4% probability. Our result is in the range of previous, less precise, and less direct results of several scientific dating methods, but it is a century earlier than the date derived from traditional Egyptian chronologies.

New Radiocarbon Dates on Upper Mid-West Proboscideans: Determining Date Robustness

NASA Astrophysics Data System (ADS)

Hodgins, G.; Widga, C.; Lengyel, S. N.; Saunders, J.; Walker, J. D.

2013-12-01

With the objective of refining the picture of Megafaunal extinction patterns in the upper Midwest in the terminal Pleistocene, we have assembled for radiocarbon dating specimens from more than 80 distinct Mammut and Mammuthus remains from potentially late sites. So far, we have measurements for 65 bones, tusks and teeth, nearly double the extant number of published dates . These new specimens were all from museums rather than excavation sites, and 60% were known to be coated with a consolidant. The predominant consolidant was Butvar B-76, however shellac, Elmer's Glue, Glyptol were also noted in the conservation records, or deduced from knowledge of a particular museum's practices. Given the objective of the project is to identify extinction patterns, coupled with the wide prevalence of consolidants amongst the specimen set, it was imperative that testing be carried out to confirm that radiocarbon laboratory protocols removed the consolidants, so that ultimately the dates can be considered robust. To this end, key specimens were dated three times using different sample preparation protocols. These were 1) a solvent extraction followed by a modified Longin-plus -Base continuous flow collagen extraction method used in the NSF-Arizona AMS facility, 2) the solvent/modified Longin method plus ultrafiltration, and 3) solvent/modified Longin method plus hydroxyproline single amino acid dating. Among the specimens subjected to triplicate testing were some of the youngest late Wisconsin proboscidean specimens from the Upper Midwest Region. The data reveal general agreement between the different protocols, and suggested either limited penetration of consolidants into the specimens, or that the standard laboratory cleaning protocols were sufficient to remove traces from deep within bone, tooth or tusk tissue. The preservation of each specimen, recorded in terms of collagen content, C/N ratio and stable isotope values, indicated that most were actually well preserved, implying

Radiocarbon dating casts doubt on the late chronology of the Middle to Upper Palaeolithic transition in southern Iberia.

PubMed

Wood, Rachel E; Barroso-Ruíz, Cecilio; Caparrós, Miguel; Jordá Pardo, Jesús F; Galván Santos, Bertila; Higham, Thomas F G

2013-02-19

It is commonly accepted that some of the latest dates for Neanderthal fossils and Mousterian industries are found south of the Ebro valley in Iberia at ca. 36 ka calBP (calibrated radiocarbon date ranges). In contrast, to the north of the valley the Mousterian disappears shortly before the Proto-Aurignacian appears at ca. 42 ka calBP. The latter is most likely produced by anatomically modern humans. However, two-thirds of dates from the south are radiocarbon dates, a technique that is particularly sensitive to carbon contaminants of a younger age that can be difficult to remove using routine pretreatment protocols. We have attempted to test the reliability of chronologies of 11 southern Iberian Middle and early Upper Paleolithic sites. Only two, Jarama VI and Zafarraya, were found to contain material that could be reliably dated. In both sites, Middle Paleolithic contexts were previously dated by radiocarbon to less than 42 ka calBP. Using ultrafiltration to purify faunal bone collagen before radiocarbon dating, we obtain ages at least 10 ka (14)C years older, close to or beyond the limit of the radiocarbon method for the Mousterian at Jarama VI and Neanderthal fossils at Zafarraya. Unless rigorous pretreatment protocols have been used, radiocarbon dates should be assumed to be inaccurate until proven otherwise in this region. Evidence for the late survival of Neanderthals in southern Iberia is limited to one possible site, Cueva Antón, and alternative models of human occupation of the region should be considered.

Radiocarbon dating casts doubt on the late chronology of the Middle to Upper Palaeolithic transition in southern Iberia

PubMed Central

Wood, Rachel E.; Barroso-Ruíz, Cecilio; Caparrós, Miguel; Jordá Pardo, Jesús F.; Galván Santos, Bertila; Higham, Thomas F. G.

2013-01-01

It is commonly accepted that some of the latest dates for Neanderthal fossils and Mousterian industries are found south of the Ebro valley in Iberia at ca. 36 ka calBP (calibrated radiocarbon date ranges). In contrast, to the north of the valley the Mousterian disappears shortly before the Proto-Aurignacian appears at ca. 42 ka calBP. The latter is most likely produced by anatomically modern humans. However, two-thirds of dates from the south are radiocarbon dates, a technique that is particularly sensitive to carbon contaminants of a younger age that can be difficult to remove using routine pretreatment protocols. We have attempted to test the reliability of chronologies of 11 southern Iberian Middle and early Upper Paleolithic sites. Only two, Jarama VI and Zafarraya, were found to contain material that could be reliably dated. In both sites, Middle Paleolithic contexts were previously dated by radiocarbon to less than 42 ka calBP. Using ultrafiltration to purify faunal bone collagen before radiocarbon dating, we obtain ages at least 10 ka 14C years older, close to or beyond the limit of the radiocarbon method for the Mousterian at Jarama VI and Neanderthal fossils at Zafarraya. Unless rigorous pretreatment protocols have been used, radiocarbon dates should be assumed to be inaccurate until proven otherwise in this region. Evidence for the late survival of Neanderthals in southern Iberia is limited to one possible site, Cueva Antón, and alternative models of human occupation of the region should be considered. PMID:23382220

Analysis of Artificial Radiocarbon in Different Skeletal and Dental Tissue Types to Evaluate Date of Death

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ubelaker, D H; Buchholz, B A; Stewart, J

Radiocarbon dating, with special reference to the modern bomb-curve, can provide useful information to elucidate the date of death of skeletonized human remains. Interpretation can be enhanced with analysis of different types of tissues within a single skeleton because of the known variability of formation times and remodeling rates. Analysis of radiocarbon content of teeth, especially the enamel in tooth crowns provides information about the date of formation in the childhood years and in consideration of the known timing of tooth formation can be used to estimate the birth date after 1950 A.D. Radiocarbon analysis of modern cortical and trabecularmore » bone samples from the same skeleton may allow proper placement on the pre-1963 or post-1963 sides of the bomb-curve since most trabecular bone generally undergoes more rapid remodeling than does most cortical bone. Pre-1963 bone formation would produce higher radiocarbon values for most trabecular bone than for most cortical bone. This relationship is reversed for formation after 1963. Radiocarbon analysis was conducted in this study on dental, cortical and trabecular bone samples from two adult individuals of known birth (1925 and 1926) and death dates (1995 and 1959). As expected, the dental results correspond to pre-bomb bomb-curve values reflecting conditions during the childhoods of the individuals. The curve radiocarbon content of most bone samples reflected the higher modern bomb-curve values. Within the bone sample analyses, the values of the trabecular bone were higher than those of cortical bone and supported the known placement on the pre-1963 side of the bomb-curve.« less

Dating of palaeomagnetic secular variation in Swedish varved lake sediments using radiocarbon wiggle-matching

NASA Astrophysics Data System (ADS)

Mellström, Anette; Nilsson, Andreas; Stanton, Tania; Muscheler, Raimund; Snowball, Ian

2013-04-01

Well-dated natural archives are crucial when investigating the timing between climate change and climate forcing. Annually laminated (varved) lake sediments, in particular, can provide valuable knowledge about past climatic and environmental conditions as the annual nature of the sediments enables the establishment of high-resolution archives. In addition, lake sediments can record variations in the Earth's magnetic field, which has the potential to be used as a dating validation technique if the palaeo-secular and -intensity curves are dated correctly. If individual and well-defined geomagnetic events can be dated accurately, they can then be used as isochrones, thereby allowing the synchronisation of different records. We therefore aim to date the "f" event, a late Holocene secular variation change, which is recorded in many sites in the northern hemisphere. Varved sites in Sweden have dated the "f" event to ~2700 cal. yrs BP. In order to constrain this date further, we have used the radiocarbon wiggle-matching method on a lake in central west Sweden, Kälksjön (Stanton et al., 2010), whose chronology has previously been validated using a number of complimentary dating methods. With the radiocarbon wiggle-matching technique, closely spaced samples are measured and matched to distinct wiggles in the radiocarbon calibration curve. The advantage of using varve-dated sediments is that it is possible to know the exact number of years between each sample, and therefore improve the initial age model. We compare the wiggle-match results of Kälksjön with results from a newly discovered varved lake sediment sequence in southern Sweden, Gyltigesjön. This comparison can provide information about magnetisation processes in sediments, such as the length of the palaeomagnetic lock-in delay. Stanton, T., Snowball, I., Zillén, L., Wastegård, S., 2010. Validating a Swedish varve chronology using radiocarbon, palaeomagnetic secular variation, lead pollution history and

Comparison of sampling methods for radiocarbon dating of carbonyls in air samples via accelerator mass spectrometry

NASA Astrophysics Data System (ADS)

Schindler, Matthias; Kretschmer, Wolfgang; Scharf, Andreas; Tschekalinskij, Alexander

2016-05-01

Three new methods to sample and prepare various carbonyl compounds for radiocarbon measurements were developed and tested. Two of these procedures utilized the Strecker synthetic method to form amino acids from carbonyl compounds with either sodium cyanide or trimethylsilyl cyanide. The third procedure used semicarbazide to form crystalline carbazones with the carbonyl compounds. The resulting amino acids and semicarbazones were then separated and purified using thin layer chromatography. The separated compounds were then combusted to CO2 and reduced to graphite to determine 14C content by accelerator mass spectrometry (AMS). All of these methods were also compared with the standard carbonyl compound sampling method wherein a compound is derivatized with 2,4-dinitrophenylhydrazine and then separated by high-performance liquid chromatography (HPLC).

High-precision radiocarbon dating and historical biblical archaeology in southern Jordan

PubMed Central

Levy, Thomas E.; Higham, Thomas; Bronk Ramsey, Christopher; Smith, Neil G.; Ben-Yosef, Erez; Robinson, Mark; Münger, Stefan; Knabb, Kyle; Schulze, Jürgen P.; Najjar, Mohammad; Tauxe, Lisa

2008-01-01

Recent excavations and high-precision radiocarbon dating from the largest Iron Age (IA, ca. 1200–500 BCE) copper production center in the southern Levant demonstrate major smelting activities in the region of biblical Edom (southern Jordan) during the 10th and 9th centuries BCE. Stratified radiocarbon samples and artifacts were recorded with precise digital surveying tools linked to a geographic information system developed to control on-site spatial analyses of archaeological finds and model data with innovative visualization tools. The new radiocarbon dates push back by 2 centuries the accepted IA chronology of Edom. Data from Khirbat en-Nahas, and the nearby site of Rujm Hamra Ifdan, demonstrate the centrality of industrial-scale metal production during those centuries traditionally linked closely to political events in Edom's 10th century BCE neighbor ancient Israel. Consequently, the rise of IA Edom is linked to the power vacuum created by the collapse of Late Bronze Age (LB, ca. 1300 BCE) civilizations and the disintegration of the LB Cypriot copper monopoly that dominated the eastern Mediterranean. The methodologies applied to the historical IA archaeology of the Levant have implications for other parts of the world where sacred and historical texts interface with the material record. PMID:18955702

Radiocarbon dating late Quaternary loess deposits using small terrestrial gastropod shells

USGS Publications Warehouse

Pigati, Jeff S.; McGeehin, John P.; Muhs, Daniel R.; Bettis, E. Arthur

2013-01-01

Constraining the ages and mass accumulation rates of late Quaternary loess deposits is often difficult because of the paucity of organic material typically available for 14C dating and the inherent limitations of luminescence techniques. Radiocarbon dating of small terrestrial gastropod shells may provide an alternative to these methods as fossil shells are common in loess and contain ∼12% carbon by weight. Terrestrial gastropod assemblages in loess have been used extensively to reconstruct past environmental conditions but have been largely ignored for dating purposes. Here, we present the results of a multi-faceted approach to understanding the potential for using small terrestrial gastropod shells to date loess deposits in North America. First, we compare highly resolved 14C ages of well-preserved wood and gastropod shells (Succineidae) recovered from a Holocene loess section in Alaska. Radiocarbon ages derived from the shells are nearly identical to wood and plant macrofossil ages throughout the section, which suggests that the shells behaved as closed systems with respect to carbon for at least the last 10 ka (thousands of calibrated 14C years before present). Second, we apply 14C dating of gastropod shells to late Pleistocene loess deposits in the Great Plains using stratigraphy and independent chronologies for comparison. The new shell ages require less interpretation than humic acid radiocarbon ages that are commonly used in loess studies, provide additional stratigraphic coverage to previous dating efforts, and are in correct stratigraphic order more often than their luminescence counterparts. Third, we show that Succineidae shells recovered from historic loess in the Matanuska River Valley, Alaska captured the 20th century 14C bomb spike, which suggests that the shells can be used to date late Holocene and historic-aged loess. Finally, results from Nebraska and western Iowa suggest that, similar to other materials, shell ages approaching ∼40 ka should

A Chronology of Late-Glacial and Holocene Advances of Quelccaya Ice Cap, Peru, Based on 10Be and Radiocarbon Dating

NASA Astrophysics Data System (ADS)

Kelly, M. A.; Lowell, T. V.; Schaefer, J. M.

2007-12-01

The Quelccaya Ice Cap region in the southeastern Peruvian Andes (~13-14°S latitude) is a key location for the development of late-glacial and Holocene terrestrial paleoclimate records in the tropics. We present a chronology of past extents of Quelccaya Ice Cap based on ~thirty internally consistent 10Be dates of boulders on moraines and bedrock as well as twenty radiocarbon dates of organic material associated with moraines. Based on results from both dating methods, we suggest that significant advances of Quelccaya Ice Cap occurred during late-glacial time, at ~12,700-11,400 yr BP, and during Late Holocene time ~400-300 yr BP. Radiocarbon dating of organic material associated with moraines provides maximum and minimum ages for ice advances and recessions, respectively, thus providing an independent check on 10Be dates of boulders on moraines. The opportunity to use both 10Be and radiocarbon dating makes the Quelccaya Ice Cap region a potentially important low-latitude calibration site for production rates of cosmogenic nuclides. Our radiocarbon chronology provides a tighter constraint on maximum ages of late-glacial and Late Holocene ice advances. Upcoming field research will obtain organic material for radiocarbon dating to improve minimum age constrains for late-glacial and Late Holocene ice recessions.

Collection of radiocarbon dates on the mammoths ( Mammuthus primigenius) and other genera of Wrangel Island, northeast Siberia, Russia

NASA Astrophysics Data System (ADS)

Vartanyan, Sergey L.; Arslanov, Khikmat A.; Karhu, Juha A.; Possnert, Göran; Sulerzhitsky, Leopold D.

2008-07-01

We present and discuss a full list of radiocarbon dates for woolly mammoth and other species of the Mammoth fauna available from Wrangel Island, northeast Siberia, Russia. Most of the radiocarbon dates are published here for the first time. Of the124 radiocarbon dates on mammoth bone, 106 fall between 3700 and 9000 yr ago. We believe these dates bracket the period of mammoth isolation on Wrangel Island and their ultimate extinction, which we attribute to natural causes. The absence of dates between 9-12 ka probably indicates a period when mammoths were absent from Wrangel Island. Long bone dimensions of Holocene mammoths from Wrangel Island indicate that these animals were comparable in size to those on the mainland; although they were not large animals, neither can they be classified as dwarfs. Occurrence of mammoth Holocene refugia on the mainland is suggested. Based on other species of the Mammoth fauna that have also been radiocarbon on Wrangel Island, including horse, bison, musk ox and woolly rhinoceros, it appears that the mammoth was the only species of that fauna that inhabited Wrangel Island in the mid-Holocene.

AMS radiocarbon dating of very large Grandidier's baobabs (Adansonia grandidieri)

NASA Astrophysics Data System (ADS)

Patrut, Adrian; von Reden, Karl F.; Danthu, Pascal; Leong Pock-Tsy, Jean-Michel; Rakosy, Laszlo; Patrut, Roxana T.; Lowy, Daniel A.; Margineanu, Dragos

2015-10-01

The article reports the AMS radiocarbon investigation of the two largest known Adansonia grandidieri specimens. The two baobabs, which are named Tsitakakoike and Pregnant baobab, are located in Southwestern Madagascar, near Andombiro. A third specimen from this area, the House baobab, was also investigated. According to measurements, Tsitakakoike is the biggest individual above ground level of all Adansonia species. The House baobab was selected for its exposed structure, which is identical to the closed ring-shaped structure with false cavities identified by us in large and old Adansonia digitata specimens. According to our research, Tsitakakoike and the Pregnant baobab have multi-stemmed cylindrical trunks which are mainly hollow; the two very large baobabs also possess a ring-shaped structure. The radiocarbon dates of the oldest wood samples collected from the large trunks were 1274 ± 20 BP for Tsitakakoike and 930 ± 20 BP for the Pregnant baobab. According to their original positions and to the architectures of the two A. grandidieri, the ages of Tsitakakoike and Pregnant baobab would be between 1300 and 1500 years. Therefore, A. grandidieri becomes the third Adansonia species with individuals that can live over 1000 years, according to accurate dating results.

Radiocarbon dating the late Middle Paleolithic and the Aurignacian of the Swabian Jura.

PubMed

Conard, Nicholas J; Bolus, Michael

2008-11-01

Many lines of evidence point to the period between roughly 40 and 30 ka BP as the period in which modern humans arrived in Europe and displaced the indigenous Neandertal populations. At the same time, many innovations associated with the Upper Paleolithic--including new stone and organic technologies, use of personal ornaments, figurative art, and musical instruments--are first documented in the European archaeological record. Dating the events of this period is challenging for several reasons. In the period about six to seven radiocarbon half-lives ago, variable preservation, pre-treatment, and sample preparation can easily lead to a lack of reproducibility between samples and laboratories. A range of biological, cultural, and geological processes can lead to mixing of archaeological strata and their contents. Additionally, some data sets point to this period as a time of significant spikes in levels of atmospheric radiocarbon. This paper assesses these questions in the context of the well-excavated and intensively studied caves of Geissenklösterle and Hohle Fels in the Swabian Jura of southwestern Germany. We conclude that variable atmospheric radiocarbon production contributes to the problems of dating the late Middle Paleolithic and the early Upper Paleolithic. To help establish a reliable chronology for the Swabian Aurignacian, we are beginning to focus our dating program on short-lived, stratigraphically secure features to see if they yield reproducible results. This approach may help to test competing explanations for the noisy and often non-reproducible results that arise when trying to date the transition from the Middle to the Upper Paleolithic.

Study of a metallurgical site in Tuscany (Italy) by radiocarbon dating

NASA Astrophysics Data System (ADS)

Cartocci, A.; Fedi, M. E.; Taccetti, F.; Benvenuti, M.; Chiarantini, L.; Guideri, S.

2007-06-01

Tuscany represents one of the most important ancient mining districts of Italy. Metalworking activities have been present in the area since ancient times and several mining centres have been active in the region since the Etruscan period. Two of the more notable mining locations are the island of Elba and the towns of Populonia and Massa Marittima. In order to reconstruct the development of metallurgical techniques in the past, a multi-disciplinary approach is required, involving both archaeological study and archaeometric analysis of the sites of interest. One of the most complex problems is establishing the chronological history of metallurgical exploitation in ancient sites: archaeological remains are sometimes incomplete and the stratigraphy of archaeological horizons might have been deeply altered. Thus, direct dating of metallurgical slags and other remains of mining and metalworking activities using radiocarbon measurements is particularly useful for developing site chronologies. Charcoal samples from a recent excavation in Populonia were dated by AMS radiocarbon in order to reconstruct the chronological evolution of ancient metallurgical production; results reported here are consistent with archaeological observations.

Single amino acid radiocarbon dating of Upper Paleolithic modern humans

PubMed Central

Marom, Anat; McCullagh, James S. O.; Higham, Thomas F. G.; Sinitsyn, Andrey A.; Hedges, Robert E. M.

2012-01-01

Archaeological bones are usually dated by radiocarbon measurement of extracted collagen. However, low collagen content, contamination from the burial environment, or museum conservation work, such as addition of glues, preservatives, and fumigants to “protect” archaeological materials, have previously led to inaccurate dates. These inaccuracies in turn frustrate the development of archaeological chronologies and, in the Paleolithic, blur the dating of such key events as the dispersal of anatomically modern humans. Here we describe a method to date hydroxyproline found in collagen (∼10% of collagen carbon) as a bone-specific biomarker that removes impurities, thereby improving dating accuracy and confidence. This method is applied to two important sites in Russia and allows us to report the earliest direct ages for the presence of anatomically modern humans on the Russian Plain. These dates contribute considerably to our understanding of the emergence of the Mid-Upper Paleolithic and the complex suite of burial behaviors that begin to appear during this period. PMID:22517758

Single amino acid radiocarbon dating of Upper Paleolithic modern humans.

PubMed

Marom, Anat; McCullagh, James S O; Higham, Thomas F G; Sinitsyn, Andrey A; Hedges, Robert E M

2012-05-01

Archaeological bones are usually dated by radiocarbon measurement of extracted collagen. However, low collagen content, contamination from the burial environment, or museum conservation work, such as addition of glues, preservatives, and fumigants to "protect" archaeological materials, have previously led to inaccurate dates. These inaccuracies in turn frustrate the development of archaeological chronologies and, in the Paleolithic, blur the dating of such key events as the dispersal of anatomically modern humans. Here we describe a method to date hydroxyproline found in collagen (~10% of collagen carbon) as a bone-specific biomarker that removes impurities, thereby improving dating accuracy and confidence. This method is applied to two important sites in Russia and allows us to report the earliest direct ages for the presence of anatomically modern humans on the Russian Plain. These dates contribute considerably to our understanding of the emergence of the Mid-Upper Paleolithic and the complex suite of burial behaviors that begin to appear during this period.

The Remarkable Metrological History of Radiocarbon Dating [II].

PubMed

Currie, Lloyd A

2004-01-01

This article traces the metrological history of radiocarbon, from the initial breakthrough devised by Libby, to minor (evolutionary) and major (revolutionary) advances that have brought (14)C measurement from a crude, bulk [8 g carbon] dating tool, to a refined probe for dating tiny amounts of precious artifacts, and for "molecular dating" at the 10 µg to 100 µg level. The metrological advances led to opportunities and surprises, such as the non-monotonic dendrochronological calibration curve and the "bomb effect," that gave rise to new multidisciplinary areas of application, ranging from archaeology and anthropology to cosmic ray physics to oceanography to apportionment of anthropogenic pollutants to the reconstruction of environmental history. Beyond the specific topic of natural (14)C, it is hoped that this account may serve as a metaphor for young scientists, illustrating that just when a scientific discipline may appear to be approaching maturity, unanticipated metrological advances in their own chosen fields, and unanticipated anthropogenic or natural chemical events in the environment, can spawn new areas of research having exciting theoretical and practical implications.

Direct radiocarbon dating and DNA analysis of the Darra-i-Kur (Afghanistan) human temporal bone.

PubMed

Douka, Katerina; Slon, Viviane; Stringer, Chris; Potts, Richard; Hübner, Alexander; Meyer, Matthias; Spoor, Fred; Pääbo, Svante; Higham, Tom

2017-06-01

The temporal bone discovered in the 1960s from the Darra-i-Kur cave in Afghanistan is often cited as one of the very few Pleistocene human fossils from Central Asia. Here we report the first direct radiocarbon date for the specimen and the genetic analyses of DNA extracted and sequenced from two areas of the bone. The new radiocarbon determination places the find to ∼4500 cal BP (∼2500 BCE) contradicting an assumed Palaeolithic age of ∼30,000 years, as originally suggested. The DNA retrieved from the specimen originates from a male individual who carried mitochondrial DNA of the modern human type. The petrous part yielded more endogenous ancient DNA molecules than the squamous part of the same bone. Molecular dating of the Darra-i-Kur mitochondrial DNA sequence corroborates the radiocarbon date and suggests that the specimen is younger than previously thought. Taken together, the results consolidate the fact that the human bone is not associated with the Pleistocene-age deposits of Darra-i-Kur; instead it is intrusive, possibly re-deposited from upper levels dating to much later periods (Neolithic). Despite its Holocene age, the Darra-i-Kur specimen is, so far, the first and only ancient human from Afghanistan whose DNA has been sequenced. Copyright © 2017 Elsevier Ltd. All rights reserved.

Rewriting the Central European Early Bronze Age Chronology: Evidence from Large-Scale Radiocarbon Dating

PubMed Central

Knipper, Corina; Friedrich, Ronny; Kromer, Bernd; Lindauer, Susanne; Radosavljević, Jelena; Wittenborn, Fabian; Krause, Johannes

2015-01-01

The transition from the Neolithic to the Early Bronze Age in Central Europe has often been considered as a supra-regional uniform process, which led to the growing mastery of the new bronze technology. Since the 1920s, archaeologists have divided the Early Bronze Age into two chronological phases (Bronze A1 and A2), which were also seen as stages of technical progress. On the basis of the early radiocarbon dates from the cemetery of Singen, southern Germany, the beginning of the Early Bronze Age in Central Europe was originally dated around 2300/2200 BC and the transition to more complex casting techniques (i.e., Bronze A2) around 2000 BC. On the basis of 140 newly radiocarbon dated human remains from Final Neolithic, Early and Middle Bronze Age cemeteries south of Augsburg (Bavaria) and a re-dating of ten graves from the cemetery of Singen, we propose a significantly different dating range, which forces us to re-think the traditional relative and absolute chronologies as well as the narrative of technical development. We are now able to date the beginning of the Early Bronze Age to around 2150 BC and its end to around 1700 BC. Moreover, there is no transition between Bronze (Bz) A1 and Bronze (Bz) A2, but a complete overlap between the type objects of the two phases from 1900–1700 BC. We thus present a revised chronology of the assumed diagnostic type objects of the Early Bronze Age and recommend a radiocarbon-based view on the development of the material culture. Finally, we propose that the traditional phases Bz A1 and Bz A2 do not represent a chronological sequence, but regionally different social phenomena connected to the willingness of local actors to appropriate the new bronze technology. PMID:26488413

Radiocarbon dates from the Grotte du Renne and Saint-Césaire support a Neandertal origin for the Châtelperronian

PubMed Central

Hublin, Jean-Jacques; Talamo, Sahra; Julien, Michèle; David, Francine; Connet, Nelly; Bodu, Pierre; Vandermeersch, Bernard; Richards, Michael P.

2012-01-01

The transition from the Middle Paleolithic (MP) to Upper Paleolithic (UP) is marked by the replacement of late Neandertals by modern humans in Europe between 50,000 and 40,000 y ago. Châtelperronian (CP) artifact assemblages found in central France and northern Spain date to this time period. So far, it is the only such assemblage type that has yielded Neandertal remains directly associated with UP style artifacts. CP assemblages also include body ornaments, otherwise virtually unknown in the Neandertal world. However, it has been argued that instead of the CP being manufactured by Neandertals, site formation processes and layer admixture resulted in the chance association of Neanderthal remains, CP assemblages, and body ornaments. Here, we report a series of accelerator mass spectrometry radiocarbon dates on ultrafiltered bone collagen extracted from 40 well-preserved bone fragments from the late Mousterian, CP, and Protoaurignacian layers at the Grotte du Renne site (at Arcy-sur-Cure, France). Our radiocarbon results are inconsistent with the admixture hypothesis. Further, we report a direct date on the Neandertal CP skeleton from Saint-Césaire (France). This date corroborates the assignment of CP assemblages to the latest Neandertals of western Europe. Importantly, our results establish that the production of body ornaments in the CP postdates the arrival of modern humans in neighboring regions of Europe. This new behavior could therefore have been the result of cultural diffusion from modern to Neandertal groups. PMID:23112183

New radiocarbon dates for terminal Pleistocene and early Holocene settlements in West Turkana, northern Kenya

NASA Astrophysics Data System (ADS)

Beyin, Amanuel; Prendergast, Mary E.; Grillo, Katherine M.; Wang, Hong

2017-07-01

The Turkana Basin in northern Kenya is located in an environmentally sensitive region along the eastern African Rift system. Lake Turkana's sensitivity to fluctuations in precipitation makes this an ideal place to study prehistoric human adaptations during key climatic transitions. Here we present eleven radiocarbon dates from two recently excavated sites in West Turkana, Kokito 01 and Kokito 02. The sites span the Pleistocene-Holocene transition, a time of fluctuating lake levels and novel cultural responses within the region. Several scenarios are laid out for the interpretation of site chronologies, and these are discussed with reference to the terminal Pleistocene and early Holocene chronological record for the region. Given the paucity of well-dated sites from this timespan in the Turkana Basin, the new radiocarbon dates are an important step toward establishing human settlement history and associated cultural developments in the region.

Quantity of dates trumps quality of dates for dense Bayesian radiocarbon sediment chronologies - Gas ion source 14C dating instructed by simultaneous Bayesian accumulation rate modeling

NASA Astrophysics Data System (ADS)

Rosenheim, B. E.; Firesinger, D.; Roberts, M. L.; Burton, J. R.; Khan, N.; Moyer, R. P.

2016-12-01

Radiocarbon (14C) sediment core chronologies benefit from a high density of dates, even when precision of individual dates is sacrificed. This is demonstrated by a combined approach of rapid 14C analysis of CO2 gas generated from carbonates and organic material coupled with Bayesian statistical modeling. Analysis of 14C is facilitated by the gas ion source on the Continuous Flow Accelerator Mass Spectrometry (CFAMS) system at the Woods Hole Oceanographic Institution's National Ocean Sciences Accelerator Mass Spectrometry facility. This instrument is capable of producing a 14C determination of +/- 100 14C y precision every 4-5 minutes, with limited sample handling (dissolution of carbonates and/or combustion of organic carbon in evacuated containers). Rapid analysis allows over-preparation of samples to include replicates at each depth and/or comparison of different sample types at particular depths in a sediment or peat core. Analysis priority is given to depths that have the least chronologic precision as determined by Bayesian modeling of the chronology of calibrated ages. Use of such a statistical approach to determine the order in which samples are run ensures that the chronology constantly improves so long as material is available for the analysis of chronologic weak points. Ultimately, accuracy of the chronology is determined by the material that is actually being dated, and our combined approach allows testing of different constituents of the organic carbon pool and the carbonate minerals within a core. We will present preliminary results from a deep-sea sediment core abundant in deep-sea foraminifera as well as coastal wetland peat cores to demonstrate statistical improvements in sediment- and peat-core chronologies obtained by increasing the quantity and decreasing the quality of individual dates.

Performance report for the low energy compact radiocarbon accelerator mass spectrometer at Uppsala University

NASA Astrophysics Data System (ADS)

Salehpour, M.; Håkansson, K.; Possnert, G.; Wacker, L.; Synal, H.-A.

2016-03-01

A range of ion beam analysis activities are ongoing at Uppsala University, including Accelerator Mass Spectrometry (AMS). Various isotopes are used for AMS but the isotope with the widest variety of applications is radiocarbon. Up until recently, only the 5 MV Pelletron tandem accelerator had been used at our site for radiocarbon AMS, ordinarily using 12 MeV 14,13,12C3+ ions. Recently a new radiocarbon AMS system, the Green-MICADAS, developed at the ion physics group at ETH Zurich, was installed. The system has a number of outstanding features which will be described. The system operates at a terminal voltage of 175 kV and uses helium stripper gas, extracting singly charged carbon ions. The low- and high energy mass spectrometers in the system are stigmatic dipole permanent magnets (0.42 and 0.97 T) requiring no electrical power nor cooling water. The system measures both the 14C/12C and the 13C/12C ratios on-line. Performance of the system is presented for both standard mg samples as well as μg-sized samples.

New radiocarbon dates for Columbian mammoth and Mexican horse from southern Alberta and the Lateglacial regional fauna

NASA Astrophysics Data System (ADS)

Hills, Leonard V.; Harington, C. Richard

2003-06-01

New radiocarbon dates on Columbian mammoth ( Mammuthus columbi) and Mexican horse ( Equus conversidens) specimens from southern Alberta are 10,930±100 BP and 10,870±45 years BP, respectively—older than originally thought. These specimens are reviewed in the light of 10 other sites in southern Alberta that have yielded large mammal remains radiocarbon dated to about 11,000 BP. Thus, the regional fauna includes at least 11 mammalian species. This fauna was not restricted to the foothills, but extended well onto the plains and may prove useful in correlating foothills terraces with those of the plains.

Co-Development of Conceptual Understanding and Critical Attitude: Analyzing Texts on Radiocarbon Dating

ERIC Educational Resources Information Center

Décamp, N.; Viennot, L.

2015-01-01

This research documents the impact of a teaching interview aimed at developing a critical attitude in students, and focused on a particular topic: radiocarbon dating. This teaching interview is designed to observe students' reaction to limited written explanations of the phenomenon under study, and their possible frustration or intellectual…

Radiocarbon dating of American pika fecal pellets provides insights into population extirpations and climate refugia.

PubMed

Millar, Constance I; Heckman, Katherine; Swanston, Christopher; Schmidt, Karena; Westfall, Robert D; Delany, Diane L

The American pika (Ochotona princeps) has become a species of concern for its sensitivity to warm temperatures and potential vulnerability to global warming. We explored the value of radiocarbon dating of fecal pellets to address questions of population persistence and timing of site extirpation. Carbon was extracted from pellets collected at 43 locations in the western Great Basin, USA, including three known occupied sites and 40 sites of uncertain status at range margins or where previous studies indicated the species is vulnerable. We resolved calibrated dates with high precision (within several years), most of which fell in the period of the mid-late 20th century bomb curve. The two-sided nature of the bomb curve renders far- and near-side dates of equal probability, which are separated by one to four decades. We document methods for narrowing resolution to one age range, including stratigraphic analysis of vegetation collected from pika haypiles. No evidence was found for biases in atmospheric 14C levels due to fossil-derived or industrial CO2 contamination. Radiocarbon dating indicated that pellets can persist for >59 years; known occupied sites resolved contemporary dates. Using combined evidence from field observations and radiocarbon dating, and the Bodie Mountains as an example, we propose a historical biogeographic scenario for pikas in minor Great Basin mountain ranges adjacent to major cordillera, wherein historical climate variability led to cycles of extirpation and recolonization during alternating cool and warm centuries. Using this model to inform future dynamics for small ranges in biogeographic settings similar to the Bodie Mountains in California, extirpation of pikas appears highly likely under directional warming trends projected for the next century, even while populations in extensive cordillera (e.g., Sierra Nevada, Rocky Mountains, Cascade Range) are likely to remain viable due to extensive, diverse habitat and high connectivity.

Test of Martin's overkill hypothesis using radiocarbon dates on extinct megafauna.

PubMed

Surovell, Todd A; Pelton, Spencer R; Anderson-Sprecher, Richard; Myers, Adam D

2016-01-26

Following Martin [Martin PS (1973) Science 179:969-974], we propose the hypothesis that the timing of human arrival to the New World can be assessed by examining the ecological impacts of a small population of people on extinct Pleistocene megafauna. To that end, we compiled lists of direct radiocarbon dates on paleontological specimens of extinct genera from North and South America with the expectation that the initial decline of extinct megafauna should correspond in time with the initial evidence for human colonization and that those declines should occur first in eastern Beringia, next in the contiguous United States, and last in South America. Analyses of spacings and frequency distributions of radiocarbon dates for each region support the idea that the extinction event first commenced in Beringia, roughly 13,300-15,000 BP. For the United States and South America, extinctions commenced considerably later but were closely spaced in time. For the contiguous United States, extinction began at ca. 12,900-13,200 BP, and at ca. 12,600-13,900 BP in South America. For areas south of Beringia, these estimates correspond well with the first significant evidence for human presence and are consistent with the predictions of the overkill hypothesis.

Closed tubes preparation of graphite for high-precision AMS radiocarbon analysis

NASA Astrophysics Data System (ADS)

Hajdas, I.; Michczynska, D.; Bonani, G.; Maurer, M.; Wacker, L.

2009-04-01

Radiocarbon dating is an established tool applied in Geochronology. Technical developments of Accelerator Mass Spectrometry AMS, which allow measurements of samples containing less than 1 mg of carbon, opened opportunities for new applications. Moreover, high resolution records of the past changes require high-resolution chronologies i.e. sampling for 14C dating. In result, the field of applications is rapidly expanding and number of radiocarbon analysis is growing rapidly. Nowadays dedicated 14C AMS machines have great capacity for analysis but in order to keep up with the demand for analysis and provide the results as fast as possible a very efficient way of sample preparation is required. Sample preparation for 14C AMS analysis consists of two steps: separation of relevant carbon from the sample material (removing contamination) and preparation of graphite for AMS analysis. The last step usually involves reaction of CO2 with H2, in the presence of metal catalyst (Fe or Co) of specific mesh size heated to 550-625°C, as originally suggested by Vogel et al. (1984). Various graphitization systems have been built in order to fulfil the requirement of sample quality needed for high-precision radiocarbon data. In the early 90ties another method has been proposed (Vogel 1992) and applied by few laboratories mainly for environmental or biomedical samples. This method uses TiH2 as a source of H2 and can be easily and flexibly applied to produce graphite. Sample of CO2 is frozen in to the tube containing pre-conditioned Zn/TiH2 and Fe catalyst. Torch sealed tubes are then placed in the stepwise heated oven at 500/550°C and left to react for several hours. The greatest problem is the lack of control of the reaction completeness and considerable fractionation. However, recently reported results (Xu et al. 2007) suggest that high precision dating using graphite produced in closed tubes might be possible. We will present results of radiocarbon dating of the set of standards

The Remarkable Metrological History of Radiocarbon Dating [II

PubMed Central

Currie, Lloyd A.

2004-01-01

This article traces the metrological history of radiocarbon, from the initial breakthrough devised by Libby, to minor (evolutionary) and major (revolutionary) advances that have brought 14C measurement from a crude, bulk [8 g carbon] dating tool, to a refined probe for dating tiny amounts of precious artifacts, and for “molecular dating” at the 10 µg to 100 µg level. The metrological advances led to opportunities and surprises, such as the non-monotonic dendrochronological calibration curve and the “bomb effect,” that gave rise to new multidisciplinary areas of application, ranging from archaeology and anthropology to cosmic ray physics to oceanography to apportionment of anthropogenic pollutants to the reconstruction of environmental history. Beyond the specific topic of natural 14C, it is hoped that this account may serve as a metaphor for young scientists, illustrating that just when a scientific discipline may appear to be approaching maturity, unanticipated metrological advances in their own chosen fields, and unanticipated anthropogenic or natural chemical events in the environment, can spawn new areas of research having exciting theoretical and practical implications. PMID:27366605

Database of Alluvial Radiocarbon Dates in European Russia and Siberia and its Palaeohydrological Interpretation

NASA Astrophysics Data System (ADS)

Matlakhova, Ekaterina; Panin, Andrei

2017-04-01

We collected and analyzed published radiocarbon dates from East European Plain (EEP) and Siberia to pick absolute dates on alluvial and associated deposits. After filtering unreliable dates, 1000 radiocarbon dates from EEP and 500 from Siberia were included into the database. Each date was supplied with information on geographic location and coordinates, catchment area, geomorphological position, characteristics of geological section and dated materials. Also the information about published sources was given. Documented sections refer to fluvial forms in a wide range of catchment sizes. To extract palaeohydrological signal we used two kinds of proxies: sedimentological and geomorphological. We used the following indicators of low activity: organic horizons (soil, peat) in overbank alluvium, balka bottoms and gully fans, small river palaeochannels; and the following indicators of high activity: active sedimentation on river floodplains (burial of organic horizons), balka bottoms and gully fans, erosion by flood flows on floodplains, in bottoms of balkas and gullies, river incision, big palaeochannels, channel avulsions and chute cutoffs. 
 Each date that received palaeohydrological interpretation was regarded as the indicator of a particular Local Palaeohydrological Event. Combined probability density functions of high- and low-activity dates were used to detect time intervals of different palaeohydrological status. For EEP after low fluvial activity during LGM two palaeohydrological epochs were designated: extremely high activity in the end of MIS 2 (ca. 18-11.7 ka b2k), and much lower activity in the Holocene. Within the Holocene two hierarchical levels of hydroclimatic variability were designated according to their duration and magnitude - regional palaeohydrological phases (centuries to few millennia) and regional palaeofluvial episodes (decades to few centuries). Tendency is rather clear of activity lowering in the first half and rise in the second half of

Preparation of bone samples in the Gliwice Radiocarbon Laboratory for AMS radiocarbon dating.

PubMed

Piotrowska, N; Goslar, T

2002-12-01

In the Gliwice Radiocarbon Laboratory, a system for preparation of samples for AMS dating has been built. At first it was used to produce graphite targets from plant macrofossils and sediments. In this study we extended its capabilities with the preparation of bones. We dealt with 3 methods; the first was the classical Longin method of collagen extraction, the second one included additional treatment of powdered bone in alkali solution, while in the third one carboxyl carbon was separated from amino acids obtained after hydrolysis of protein. The suitability of the methods was tested on 2 bone samples. Most of our samples gave ages > 40 kyr BP, suggesting good performance of the adapted methods, except for one sample prepared with simple Longin method. For routine preparation of bones we chose the Longin method with additional alkali treatment.

Forgery at the Snite Museum of Art? Improving AMS Radiocarbon Dating at the University of Notre Dame

NASA Astrophysics Data System (ADS)

Troyer, Laura; Bagwell, Connor; Anderson, Tyler; Clark, Adam; Nelson, Austin; Skulski, Michael; Collon, Philippe

2017-09-01

The Snite Museum of Art recently obtained several donations of artifacts. Five of the pieces lack sufficient background information to prove authenticity and require further analysis to positively determine the artwork's age. One method to determine the artwork's age is radiocarbon dating via Accelerator Mass Spectrometry (AMS) performed at the University of Notre Dame's Nuclear Science Laboratory. Samples are prepared by combustion of a small amount of material and subsequent reduction to carbon into an iron powder matrix (graphitization). The graphitization procedure affects the maximum measurement rate, and a poor graphitization can be detrimental to the AMS measurement of the sample. Previous graphitization procedures resulted in a particle current too low or inconsistent to optimize AMS measurements. Thus, there was a desire to design and refine the graphitization system. The finalized process yielded physically darker samples and increased sample currents by two orders of magnitude. Additionally, the first testing of the samples was successful, yet analysis of the dates proved inconclusive. AMS measurements will be performed again to obtain better sampling statistics in the hopes of narrowing the reported date ranges. NSF and JINA-CEE.

Radiocarbon dating with annual-resolution of subfossil trees from the Younger Dryas event in the southern French Alps

NASA Astrophysics Data System (ADS)

Capano, Manuela; Miramont, Cécile; Guibal, Frédéric; Kromer, Bernd; Tuna, Thibaut; Fagault, Yoann; Bard, Edouard

2017-04-01

Tree rings are an important archive for the calibration of radiocarbon data. The younger part of the IntCal curve is based essentially on tree-ring chronologies, absolutely dated by dendrochronological analysis. For the Northern Hemisphere (NH), a gap still exists between the absolutely dated sequences and a floating chronology. Based on the Southern Hemisphere (SH) tree-ring chronologies a link has been previously proposed (Reimer et al. 2013, Radiocarbon; see also update in Hogg et al. 2016, Radiocarbon). By measuring radiocarbon at annual resolution in French subfossil pines (Pinus sylvestris L.) we propose to improve the connection between the absolute chronology and the floating chronology. Several subfossil pines have been found in the Southern French Alps; they were buried by flood deposits, allowing their preservation. Some trees discovered in the Barbier riverbed were dated to the Younger Dryas periods by previous decadal radiocarbon measurements, performed in Heidelberg and Mannheim. The trees selected for our new study are Barb12 and Barb17 (analyzed sequences of 163 and 152 rings, respectively). These sequences were sampled at annual resolution when permitted by the ring width. As a first step, every third ring was pretreated for radiocarbon analysis. These samples were sliced in small pieces and pretreated by using the ABA-B method before being combusted, graphitized with the AGE system and measured with AixMICADAS (Bard et al. 2015, Nucl. Instr. Meth. B). From the comparison with the kauri sequence, the Barb12-17 sequence can be dated from about 12835 to 12606 cal. BP. It can also be used to calculate the interhemispheric gradient (IHG) over the overlapping period. In order to reduce the inter-annual variability, the Barb12-17 record was smoothed, grouped and averaged over the same decades as in the Kauri record. On the basis of twenty values, a mean IHG value of ca. 60 years was calculated. Quantification of the IHG around 50 yr is particularly

Radiocarbon dating of the Late Cycladic building and destruction phases at Akrotiri, Thera: New evidence

NASA Astrophysics Data System (ADS)

Maniatis, Yannis

2012-01-01

Akrotiri was a flourishing prehistoric settlement on the Cycladic island of Santorini (Thera) until its life was ended by a huge volcanic eruption in the LCI period. There is much debate as to when this final destruction occurred. Based on the Egyptian historical dating this happened around 1540-1530 BC, while, based on radiocarbon and other scientific data, around 1640-1600 BC. This work is an attempt to date with radiocarbon the whole settlement's life starting from the earlier phases of occupation but focusing in the sequence of the latest events. The samples, coming from the deep shafts dug in the site for the pillars of the new shelter, are pieces of wood and charcoal from house architectural elements and other constructions, including the final earthquake victims temporary camps. Therefore, the dates obtained represent the beginning of the different cultural phases plus the latest events. The results provide novel absolute dates for the commencement of the LMC and LCI Phases at Akrotiri, giving mean ranges around 1820-1790 BC and 1775-1722 BC, respectively, while the final destruction is dated around 1622-1548 BC. These results show that the LCI phase started about 100 years earlier than estimated with the Egyptian Historical chronology while the final destruction around 60 years or less earlier.

High-precision radiocarbon dating shows recent and rapid initial human colonization of East Polynesia.

PubMed

Wilmshurst, Janet M; Hunt, Terry L; Lipo, Carl P; Anderson, Atholl J

2011-02-01

The 15 archipelagos of East Polynesia, including New Zealand, Hawaii, and Rapa Nui, were the last habitable places on earth colonized by prehistoric humans. The timing and pattern of this colonization event has been poorly resolved, with chronologies varying by >1000 y, precluding understanding of cultural change and ecological impacts on these pristine ecosystems. In a meta-analysis of 1,434 radiocarbon dates from the region, reliable short-lived samples reveal that the colonization of East Polynesia occurred in two distinct phases: earliest in the Society Islands A.D. ∼1025-1120, four centuries later than previously assumed; then after 70-265 y, dispersal continued in one major pulse to all remaining islands A.D. ∼1190-1290. We show that previously supported longer chronologies have relied upon radiocarbon-dated materials with large sources of error, making them unsuitable for precise dating of recent events. Our empirically based and dramatically shortened chronology for the colonization of East Polynesia resolves longstanding paradoxes and offers a robust explanation for the remarkable uniformity of East Polynesian culture, human biology, and language. Models of human colonization, ecological change and historical linguistics for the region now require substantial revision.

High-precision radiocarbon dating shows recent and rapid initial human colonization of East Polynesia

PubMed Central

Wilmshurst, Janet M.; Hunt, Terry L.; Lipo, Carl P.; Anderson, Atholl J.

2011-01-01

The 15 archipelagos of East Polynesia, including New Zealand, Hawaii, and Rapa Nui, were the last habitable places on earth colonized by prehistoric humans. The timing and pattern of this colonization event has been poorly resolved, with chronologies varying by >1000 y, precluding understanding of cultural change and ecological impacts on these pristine ecosystems. In a meta-analysis of 1,434 radiocarbon dates from the region, reliable short-lived samples reveal that the colonization of East Polynesia occurred in two distinct phases: earliest in the Society Islands A.D. ∼1025–1120, four centuries later than previously assumed; then after 70–265 y, dispersal continued in one major pulse to all remaining islands A.D. ∼1190–1290. We show that previously supported longer chronologies have relied upon radiocarbon-dated materials with large sources of error, making them unsuitable for precise dating of recent events. Our empirically based and dramatically shortened chronology for the colonization of East Polynesia resolves longstanding paradoxes and offers a robust explanation for the remarkable uniformity of East Polynesian culture, human biology, and language. Models of human colonization, ecological change and historical linguistics for the region now require substantial revision. PMID:21187404

Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radiocarbon Dates from Bluefish Caves, Canada.

PubMed

Bourgeon, Lauriane; Burke, Ariane; Higham, Thomas

2017-01-01

The timing of the first entry of humans into North America is still hotly debated within the scientific community. Excavations conducted at Bluefish Caves (Yukon Territory) from 1977 to 1987 yielded a series of radiocarbon dates that led archaeologists to propose that the initial dispersal of human groups into Eastern Beringia (Alaska and the Yukon Territory) occurred during the Last Glacial Maximum (LGM). This hypothesis proved highly controversial in the absence of other sites of similar age and concerns about the stratigraphy and anthropogenic signature of the bone assemblages that yielded the dates. The weight of the available archaeological evidence suggests that the first peopling of North America occurred ca. 14,000 cal BP (calibrated years Before Present), i.e., well after the LGM. Here, we report new AMS radiocarbon dates obtained on cut-marked bone samples identified during a comprehensive taphonomic analysis of the Bluefish Caves fauna. Our results demonstrate that humans occupied the site as early as 24,000 cal BP (19,650 ± 130 14C BP). In addition to proving that Bluefish Caves is the oldest known archaeological site in North America, the results offer archaeological support for the "Beringian standstill hypothesis", which proposes that a genetically isolated human population persisted in Beringia during the LGM and dispersed from there to North and South America during the post-LGM period.

Earliest Human Presence in North America Dated to the Last Glacial Maximum: New Radiocarbon Dates from Bluefish Caves, Canada

PubMed Central

Bourgeon, Lauriane; Burke, Ariane; Higham, Thomas

2017-01-01

The timing of the first entry of humans into North America is still hotly debated within the scientific community. Excavations conducted at Bluefish Caves (Yukon Territory) from 1977 to 1987 yielded a series of radiocarbon dates that led archaeologists to propose that the initial dispersal of human groups into Eastern Beringia (Alaska and the Yukon Territory) occurred during the Last Glacial Maximum (LGM). This hypothesis proved highly controversial in the absence of other sites of similar age and concerns about the stratigraphy and anthropogenic signature of the bone assemblages that yielded the dates. The weight of the available archaeological evidence suggests that the first peopling of North America occurred ca. 14,000 cal BP (calibrated years Before Present), i.e., well after the LGM. Here, we report new AMS radiocarbon dates obtained on cut-marked bone samples identified during a comprehensive taphonomic analysis of the Bluefish Caves fauna. Our results demonstrate that humans occupied the site as early as 24,000 cal BP (19,650 ± 130 14C BP). In addition to proving that Bluefish Caves is the oldest known archaeological site in North America, the results offer archaeological support for the “Beringian standstill hypothesis”, which proposes that a genetically isolated human population persisted in Beringia during the LGM and dispersed from there to North and South America during the post-LGM period. PMID:28060931

Si-Traceable Scale for Measurements of Radiocarbon Concentration

NASA Astrophysics Data System (ADS)

Hodges, Joseph T.; Fleisher, Adam J.; Liu, Qingnan; Long, David A.

2017-06-01

Radiocarbon (^{14}C) dating of organic materials is based on measuring the ^{14}C/^{12}C atomic fraction relative to the nascent value that existed when the material was formed by photosynthetic conversion of carbon dioxide present in the atmosphere. This field of measurement has numerous applications including source apportionment of anthropogenic and biogenic fuels and combustion emissions, carbon cycle dynamics, archaeology, and forensics. Accelerator mass spectrometry (AMS) is the most widely used method for radiocarbon detection because it can measure extremely small amounts of radiocarbon (background of nominally 1.2 parts-per-trillion) with high relative precision (0.4 %). AMS measurements of radiocarbon are typically calibrated by reference to standard oxalic-acid (C_2H_2O_4) samples of known radiocativity that are derived from plant matter. Specifically, the internationally accepted absolute dating reference for so-called "modern-equivalent" radiocarbon is 95 % of the specific radioactivity in AD 1950 of the National Bureau of Standards (NBS) oxalic acid standard reference material and normalized to δ^{13}C_{VPDB} = 19 per mil. With this definition, a "modern-equivalent" corresponds to 1.176(70) parts-per-trillion of ^{14}C relative to total carbon content. As an alternative radiocarbon scale, we propose an SI-traceable method to determine ^{14}C absolute concentration which is based on linear Beer-Lambert-law absorption measurements of selected ^{14}C^{16}O_2 ν_3-band line areas. This approach is attractive because line intensities of chosen radiocarbon dioxide transitions can be determined by ab initio calculations with relative uncertainties below 0.5 %. This assumption is justified by the excellent agreement between theoretical values of line intensities and measurements for stable isotopologues of CO_2. In the case of cavity ring-down spectroscopy (CRDS) measurements of ^{14}C^{16}O_2 peak areas, we show that absolute, SI-traceable concentrations of

Revised direct radiocarbon dating of the Vindija G1 Upper Paleolithic Neandertals.

PubMed

Higham, Tom; Ramsey, Christopher Bronk; Karavanić, Ivor; Smith, Fred H; Trinkaus, Erik

2006-01-17

The 1998/1999 direct dating of two Neandertal specimens from level G(1) of Vindija Cave in Croatia to approximately 28,000 and approximately 29,000 radiocarbon ((14)C) years ago has led to interpretations concerning the late survival of Neandertals in south-central Europe, patterns of interaction between Neandertals and in-dispersing early modern humans in Europe, and complex biocultural scenarios for the earlier phases of the Upper Paleolithic. Given improvements, particularly in sample pretreatment techniques for bone radiocarbon samples, especially ultrafiltration of collagen samples, these Vindija G(1) Neandertal fossils are redated to approximately 32,000-33,000 (14)C years ago and possibly earlier. These results and the recent redating of a number of purportedly old modern human skeletal remains in Europe to younger time periods highlight the importance of fine chronological control when studying this biocultural time period and the tenuous nature of monolithic scenarios for the establishment of modern humans and earlier phases of the Upper Paleolithic in Europe.

Radiocarbon dating of individual lignin phenols: a new approach for establishing chronology of late quaternary lake sediments.

PubMed

Hou, Juzhi; Huang, Yongsong; Brodsky, Corynn; Alexandre, Marcelo R; McNichol, Ann P; King, John W; Hu, Feng Sheng; Shen, Ji

2010-09-01

The reliability of chronology is a prerequisite for meaningful paleoclimate reconstructions from sedimentary archives. The conventional approach of radiocarbon dating bulk organic carbon in lake sediments is often hampered by the old carbon effect, i.e., the assimilation of ancient dissolved inorganic carbon (DIC) derived from carbonate bedrocks or other sources. Therefore, radiocarbon dating is ideally performed on organic compounds derived from land plants that use atmospheric CO(2) and rapidly delivered to sediments. We demonstrate that lignin phenols isolated from lake sediments using reversed phase high performance liquid chromatography (HPLC) can serve as effective (14)C dating materials for establishing chronology during the late Quaternary. We developed a procedure to purify lignin phenols, building upon a published method. By isolating lignin from standard wood reference substances, we show that our method yields pure lignin phenols and consistent ages as the consensus ages and that our procedure does not introduce radiocarbon contamination. We further demonstrate that lignin phenol ages are compatible with varve counted and macrofossil dated sediment horizons in Steel Lake and Fayetteville Green Lake. Applying the new method to lake sediment cores from Lake Qinghai demonstrates that lignin phenol ages in Lake Qinghai are consistently younger than bulk total organic carbon (TOC) ages which are contaminated by old carbon effect. We also show that the age offset between lignin and bulk organic carbon differs at different Lake Qinghai sedimentary horizons, suggesting a variable hard water effect at different times and that a uniform age correction throughout the core is inappropriate.

The Worldwide Marine Radiocarbon Reservoir Effect: Definitions, Mechanisms, and Prospects

NASA Astrophysics Data System (ADS)

Alves, Eduardo Q.; Macario, Kita; Ascough, Philippa; Bronk Ramsey, Christopher

2018-03-01

When a carbon reservoir has a lower radiocarbon content than the atmosphere, this is referred to as a reservoir effect. This is expressed as an offset between the radiocarbon ages of samples from the two reservoirs at a single point in time. The marine reservoir effect (MRE) has been a major concern in the radiocarbon community, as it introduces an additional source of error that is often difficult to accurately quantify. For this reason, researchers are often reluctant to date marine material where they have another option. The influence of this phenomenon makes the study of the MRE important for a broad range of applications. The advent of Accelerator Mass Spectrometry (AMS) has reduced sample size requirements and increased measurement precision, in turn increasing the number of studies seeking to measure marine samples. These studies rely on overcoming the influence of the MRE on marine radiocarbon dates through the worldwide quantification of the local parameter ΔR, that is, the local variation from the global average MRE. Furthermore, the strong dependence on ocean dynamics makes the MRE a useful indicator for changes in oceanic circulation, carbon exchange between reservoirs, and the fate of atmospheric CO2, all of which impact Earth's climate. This article explores data from the Marine Reservoir Database and reviews the place of natural radiocarbon in oceanic records, focusing on key questions (e.g., changes in ocean dynamics) that have been answered by MRE studies and on their application to different subjects.

Holocene age of the Yuha burial: Direct radiocarbon determinations by accelerator mass spectrometry

USGS Publications Warehouse

Stafford, Thomas W.; Jull, A.J.T.; Zabel, T.H.; Donahue, D.J.; Duhamel, R.C.; Brendel, K.; Haynes, C.V.; Bischoff, J.L.; Payen, L.A.; Taylor, R.E.

1984-01-01

The view that human populations may not have arrived in the Western Hemisphere before about 12,000 radiocarbon yr BP1,2 has been challenged by claims of much greater antiquity for a small number of archaeological sites and human skeleton samples. One such site is the Homo sapiens sapiens cairn burial excavated in 1971 from the Yuha desert, Imperial County, California3-5. Radiocarbon analysis of caliche coating one of the bones of the skeleton yielded a radiocarbon age of 21,500??1,000 yr BP4, while radiocarbon and uranium series analyses of caliche coating a cairn boulder yielded ages of 22,125??400 and 19,000??3,000 yr BP, respectively5. The late Pleistocene age assignment to the Yuha burial has been challenged by comparing the cultural context of the burial with other cairn burials in the same region6, on the basis of the site's geomorphological context and from radiocarbon analyses of soil caliches. 7,8 In rebuttal, arguments in defence of the original age assignment have been presented9,10 as well as an amino acid racemization analysis on the Yuha skeleton indicating an age of 23,600??2,600 yr BP11. The tandem accelerator mass spectrometer at the University of Arizona has now been used to measure the ratio of 14C/13C in several organic and inorganic fractions of post-cranial bone from the Yuha H. sapiens sapiens skeleton. Isotope ratios from six chemical fractions all yielded radiocarbon ages for the skeleton of less than 4,000 yr BP. These results indicate that the Yuha skeleton is of Holocene age, in agreement with the cultural context of the burial, and in disagreement with the previously assigned Pleistocene age of 19,000-23,000 yr. ?? 1984 Nature Publishing Group.

The impact of Last Glacial climate variability in west-European loess revealed by radiocarbon dating of fossil earthworm granules.

PubMed

Moine, Olivier; Antoine, Pierre; Hatté, Christine; Landais, Amaëlle; Mathieu, Jérôme; Prud'homme, Charlotte; Rousseau, Denis-Didier

2017-06-13

The characterization of Last Glacial millennial-timescale warming phases, known as interstadials or Dansgaard-Oeschger events, requires precise chronologies for the study of paleoclimate records. On the European continent, such chronologies are only available for several Last Glacial pollen and rare speleothem archives principally located in the Mediterranean domain. Farther north, in continental lowlands, numerous high-resolution records of loess and paleosols sequences show a consistent environmental response to stadial-interstadial cycles. However, the limited precision and accuracy of luminescence dating methods commonly used in loess deposits preclude exact correlations of paleosol horizons with Greenland interstadials. To overcome this problem, a radiocarbon dating protocol has been developed to date earthworm calcite granules from the reference loess sequence of Nussloch (Germany). Its application yields a consistent radiocarbon chronology of all soil horizons formed between 47 and 20 ka and unambiguously shows the correlation of every Greenland interstadial identified in isotope records with specific soil horizons. Furthermore, eight additional minor soil horizons dated between 27.5 and 21 ka only correlate with minor decreases in Greenland dust records. This dating strategy reveals the high sensitivity of loess paleoenvironments to Northern Hemisphere climate changes. A connection between loess sedimentation rate, Fennoscandian ice sheet dynamics, and sea level changes is proposed. The chronological improvements enabled by the radiocarbon "earthworm clock" thus strongly enhance our understanding of loess records to a better perception of the impact of Last Glacial climate changes on European paleoenvironments.

Radiocarbon dating the appearance of modern humans and timing of cultural innovations in Europe: new results and new challenges.

PubMed

Conard, Nicholas J; Bolus, Michael

2003-03-01

New radiocarbon dates from the sites of Bockstein-Törle, Geissenklösterle, Hohle Fels, Hohlenstein-Stadel, Sirgenstein, and Vogelherd in the Swabian Jura of southwestern Germany indicate that the Aurignacian of the region spans the period from ca. 40-30ka BP. If the situation at Vogelherd, in which skeletal remains from modern humans underlie an entire Aurignacian sequence, is viewed as representative for the region, the dates from the Swabian Jura support the hypothesis that populations of modern humans entered the region by way of the "Danube Corridor." The lithic technology from the lower Aurignacian of Geissenklösterle III is fully developed, and classic Aurignacian forms are well represented. During the course of the Aurignacian, numerous assemblages rich in art works, jewelry, and musical instruments are documented. By no later than 29ka BP the Gravettian was well established in the region. These dates are consistent with the "Kulturpumpe" hypothesis that important cultural innovations of the Aurignacian and Gravettian in Swabia predate similar developments in other regions of Europe. The radiocarbon dates from Geissenklösterle corroborate observations from other non-archaeological data sets indicating large global fluctuations in the atmospheric concentrations of radiocarbon between 30 and 50ka calendar years ago. These fluctuations lead to complications in building reliable chronologies during this period and cause the "Middle Paleolithic Dating Anomaly" and the "Coexistence Effect," which tend to exaggerate the temporal overlap between Neanderthals and modern humans.

The impact of Last Glacial climate variability in west-European loess revealed by radiocarbon dating of fossil earthworm granules

PubMed Central

Moine, Olivier; Antoine, Pierre; Hatté, Christine; Landais, Amaëlle; Mathieu, Jérôme; Prud’homme, Charlotte

2017-01-01

The characterization of Last Glacial millennial-timescale warming phases, known as interstadials or Dansgaard–Oeschger events, requires precise chronologies for the study of paleoclimate records. On the European continent, such chronologies are only available for several Last Glacial pollen and rare speleothem archives principally located in the Mediterranean domain. Farther north, in continental lowlands, numerous high-resolution records of loess and paleosols sequences show a consistent environmental response to stadial–interstadial cycles. However, the limited precision and accuracy of luminescence dating methods commonly used in loess deposits preclude exact correlations of paleosol horizons with Greenland interstadials. To overcome this problem, a radiocarbon dating protocol has been developed to date earthworm calcite granules from the reference loess sequence of Nussloch (Germany). Its application yields a consistent radiocarbon chronology of all soil horizons formed between 47 and 20 ka and unambiguously shows the correlation of every Greenland interstadial identified in isotope records with specific soil horizons. Furthermore, eight additional minor soil horizons dated between 27.5 and 21 ka only correlate with minor decreases in Greenland dust records. This dating strategy reveals the high sensitivity of loess paleoenvironments to Northern Hemisphere climate changes. A connection between loess sedimentation rate, Fennoscandian ice sheet dynamics, and sea level changes is proposed. The chronological improvements enabled by the radiocarbon “earthworm clock” thus strongly enhance our understanding of loess records to a better perception of the impact of Last Glacial climate changes on European paleoenvironments. PMID:28559353

Radiocarbon dating of American pika fecal pellets provides insights into population extirpations and climate refugia

Treesearch

Constance I. Millar; Katherine Heckman; Christopher Swanston; Karena Schmidt; Robert D. Westfall; Diane L. Delany

2014-01-01

The American pika (Ochotona princeps) has become a species of concern for its sensitivity to warm temperatures and potential vulnerability to global warming. We explored the value of radiocarbon dating of fecal pellets to address questions of population persistence and timing of site extirpation. Carbon was extracted from pellets collected at 43...

Radiocarbon dating of prehistoric phytoliths: a preliminary study of archaeological sites in China

NASA Astrophysics Data System (ADS)

Zuo, Xinxin; Lu, Houyuan; Zhang, Jianping; Wang, Can; Sun, Guoping; Zheng, Yunfei

2016-05-01

Phytoliths can occlude some organic carbon during their deposition in plants. This carbon fraction is recognised as an ideal dating material because of its high resistance to decomposition and post-deposition contamination at the time of phytolith formation. However, the reliability of phytolith radiocarbon dating has recently been questioned. The development of a new extraction protocol for phytoliths, with paired dating between phytoliths and other materials from the same sediment, may provide further evidence for the reliability of phytolith dating. We present an improved method for extracting phytoliths from soils. We compared the dating of phytoliths and other materials (e.g., charcoal and plant seeds) recovered at the same depth from seven pits at six archaeological sites in China. The estimated ages of the phytoliths and other materials were generally consistent, except for one outlier. We attribute this inconsistency to the post-depositional processes of phytoliths in soil, rather than to the uptake of old carbon from the soil. Our results clearly show the potential for phytolith carbon dating at archaeological sites in the absence of other dating materials.

Towards an Absolute Chronology for the Aegean Iron Age: New Radiocarbon Dates from Lefkandi, Kalapodi and Corinth

PubMed Central

Toffolo, Michael B.; Fantalkin, Alexander; Lemos, Irene S.; Felsch, Rainer C. S.; Niemeier, Wolf-Dietrich; Sanders, Guy D. R.; Finkelstein, Israel; Boaretto, Elisabetta

2013-01-01

The relative chronology of the Aegean Iron Age is robust. It is based on minute stylistic changes in the Submycenaean, Protogeometric and Geometric styles and their sub-phases. Yet, the absolute chronology of the time-span between the final stages of Late Helladic IIIC in the late second millennium BCE and the archaic colonization of Italy and Sicily toward the end of the 8th century BCE lacks archaeological contexts that can be directly related to events carrying absolute dates mentioned in Egyptian/Near Eastern historical sources, or to well-dated Egyptian/Near Eastern rulers. The small number of radiocarbon dates available for this time span is not sufficient to establish an absolute chronological sequence. Here we present a new set of short-lived radiocarbon dates from the sites of Lefkandi, Kalapodi and Corinth in Greece. We focus on the crucial transition from the Submycenaean to the Protogeometric periods. This transition is placed in the late 11th century BCE according to the Conventional Aegean Chronology and in the late 12th century BCE according to the High Aegean Chronology. Our results place it in the second half of the 11th century BCE. PMID:24386150

Annually resolved atmospheric radiocarbon records reconstructed from tree-rings

NASA Astrophysics Data System (ADS)

Wacker, Lukas; Bleicher, Niels; Büntgen, Ulf; Friedrich, Michael; Friedrich, Ronny; Diego Galván, Juan; Hajdas, Irka; Jull, Anthony John; Kromer, Bernd; Miyake, Fusa; Nievergelt, Daniel; Reinig, Frederick; Sookdeo, Adam; Synal, Hans-Arno; Tegel, Willy; Wesphal, Torsten

2017-04-01

The IntCal13 calibration curve is mainly based on data measured by decay counting with a resolution of 10 years. Thus high frequency changes like the 11-year solar cycles or cosmic ray events [1] are not visible, or at least not to their full extent. New accelerator mass spectrometry (AMS) systems today are capable of measuring at least as precisely as decay counters [2], with the advantage of using 1000 times less material. The low amount of material required enables more efficient sample preparation. Thus, an annually resolved re-measurement of the tree-ring based calibration curve can now be envisioned. We will demonstrate with several examples the multitude of benefits resulting from annually resolved radiocarbon records from tree-rings. They will not only allow for more precise radiocarbon dating but also contain valuable new astrophysical information. The examples shown will additionally indicate that it can be critical to compare AMS measurements with a calibration curve that is mainly based on decay counting. We often see small offsets between the two measurement techniques, while the reason is yet unknown. [1] Miyake F, Nagaya K, Masuda K, Nakamura T. 2012. A signature of cosmic-ray increase in AD 774-775 from tree rings in Japan. Nature 486(7402):240-2. [2] Wacker L, Bonani G, Friedrich M, Hajdas I, Kromer B, Nemec M, Ruff M, Suter M, Synal H-A, Vockenhuber C. 2010. MICADAS: Routine and high-precision radiocarbon dating. Radiocarbon 52(2):252-62.

An absolute chronology for early Egypt using radiocarbon dating and Bayesian statistical modelling

PubMed Central

Dee, Michael; Wengrow, David; Shortland, Andrew; Stevenson, Alice; Brock, Fiona; Girdland Flink, Linus; Bronk Ramsey, Christopher

2013-01-01

The Egyptian state was formed prior to the existence of verifiable historical records. Conventional dates for its formation are based on the relative ordering of artefacts. This approach is no longer considered sufficient for cogent historical analysis. Here, we produce an absolute chronology for Early Egypt by combining radiocarbon and archaeological evidence within a Bayesian paradigm. Our data cover the full trajectory of Egyptian state formation and indicate that the process occurred more rapidly than previously thought. We provide a timeline for the First Dynasty of Egypt of generational-scale resolution that concurs with prevailing archaeological analysis and produce a chronometric date for the foundation of Egypt that distinguishes between historical estimates. PMID:24204188

Preparative separation of underivatized amino acids for compound-specific stable isotope analysis and radiocarbon dating of hydrolyzed bone collagen.

PubMed

Tripp, Jennifer A; McCullagh, James S O; Hedges, Robert E M

2006-01-01

Analysis of stable and radioactive isotopes from bone collagen provides useful information to archaeologists about the origin and age of bone artifacts. Isolation and analysis of single amino acids from the proteins can provide additional and more accurate information by removing contamination and separating a bulk isotope signal into its constituent parts. In this paper, we report a new method for the separation and isolation of underivatized amino acids from bone collagen, and their analysis by isotope ratio MS and accelerator MS. RP chromatography is used to separate the amino acids with nonpolar side chains, followed by an ion pair separation to isolate the remaining amino acids. The method produces single amino acids with little or no contamination from the separation process and allows for the measurement of accurate stable isotope ratios and pure samples for radiocarbon dating.

Radiocarbon Dating of an Olive Tree Cross-Section: New Insights on Growth Patterns and Implications for Age Estimation of Olive Trees.

PubMed

Ehrlich, Yael; Regev, Lior; Kerem, Zohar; Boaretto, Elisabetta

2017-01-01

The age of living massive olive trees is often assumed to be between hundreds and even thousands of years. These estimations are usually based on the girth of the trunk and an extrapolation based on a theoretical annual growth rate. It is difficult to objectively verify these claims, as a monumental tree may not be cut down for analysis of its cross-section. In addition, the inner and oldest part of the trunk in olive trees usually rots, precluding the possibility of carting out radiocarbon analysis of material from the first years of life of the tree. In this work we present a cross-section of an olive tree, previously estimated to be hundreds of years old, which was cut down post-mortem in 2013. The cross-section was radiocarbon dated at numerous points following the natural growth pattern, which was made possible to observe by viewing the entire cross-section. Annual growth rate values were calculated and compared between different radii. The cross-section also revealed a nearly independent segment of growth, which would clearly offset any estimations based solely on girth calculations. Multiple piths were identified, indicating the beginning of branching within the trunk. Different radii were found to have comparable growth rates, resulting in similar estimates dating the piths to the 19th century. The estimated age of the piths represent a terminus ante quem for the age of the tree, as these are piths of separate branches. However, the tree is likely not many years older than the dated piths, and certainly not centuries older. The oldest radiocarbon-datable material in this cross-section was less than 200 years old, which is in agreement with most other radiocarbon dates of internal wood from living olive trees, rarely older than 300 years.

Radiocarbon dating of silica sinter deposits in shallow drill cores from the Upper Geyser Basin, Yellowstone National Park

USGS Publications Warehouse

Lowenstern, Jacob B.; Hurwitz, Shaul; McGeehin, John

2016-01-01

To explore the timing of hydrothermal activity at the Upper Geyser Basin (UGB) in Yellowstone National Park, we obtained seven new accelerator mass spectrometry (AMS) radiocarbon 14C ages of carbonaceous material trapped within siliceous sinter. Five samples came from depths of 15–152 cm within the Y-1 well, and two samples were from well Y-7 (depths of 24 cm and 122 cm). These two wells, at Black Sand and Biscuit Basins, respectively, were drilled in 1967 as part of a scientific drilling program by the U.S. Geological Survey (White et al., 1975). Even with samples as small as 15 g, we obtained sufficient carbonaceous material (a mixture of thermophilic mats, pollen, and charcoal) for the 14C analyses. Apparent time of deposition ranged from 3775 ± 25 and 2910 ± 30 14C years BP at the top of the cores to about 8000 years BP at the bottom. The dates are consistent with variable rates of sinter formation at individual sites within the UGB over the Holocene. On a basin-wide scale, though, these and other existing 14C dates hint that hydrothermal activity at the UGB may have been continuous throughout the Holocene.

Radiocarbon Dating and Wood Density Chronologies of Mangrove Trees in Arid Western Australia

PubMed Central

Santini, Nadia S.; Hua, Quan; Schmitz, Nele; Lovelock, Catherine E.

2013-01-01

Mangrove trees tend to be larger and mangrove communities more diverse in tropical latitudes, particularly where there is high rainfall. Variation in the structure, growth and productivity of mangrove forests over climatic gradients suggests they are sensitive to variations in climate, but evidence of changes in the structure and growth of mangrove trees in response to climatic variation is scarce. Bomb-pulse radiocarbon dating provides accurate dates of recent wood formation and tree age of tropical and subtropical tree species. Here, we used radiocarbon techniques combined with X-ray densitometry to develop a wood density chronology for the mangrove Avicennia marina in the Exmouth Gulf, Western Australia (WA). We tested whether wood density chronologies of A. marina were sensitive to variation in the Pacific Decadal Oscillation Index, which reflects temperature fluctuations in the Pacific Ocean and is linked to the instrumental rainfall record in north WA. We also determined growth rates in mangrove trees from the Exmouth Gulf, WA. We found that seaward fringing A. marina trees (∼10 cm diameter) were 48±1 to 89±23 years old (mean ± 1σ) and that their growth rates ranged from 4.08±2.36 to 5.30±3.33 mm/yr (mean ±1σ). The wood density of our studied mangrove trees decreased with increases in the Pacific Decadal Oscillation Index. Future predicted drying of the region will likely lead to further reductions in wood density and their associated growth rates in mangrove forests in the region. PMID:24265797

Radiocarbon dating and wood density chronologies of mangrove trees in arid Western Australia.

PubMed

Santini, Nadia S; Hua, Quan; Schmitz, Nele; Lovelock, Catherine E

2013-01-01

Mangrove trees tend to be larger and mangrove communities more diverse in tropical latitudes, particularly where there is high rainfall. Variation in the structure, growth and productivity of mangrove forests over climatic gradients suggests they are sensitive to variations in climate, but evidence of changes in the structure and growth of mangrove trees in response to climatic variation is scarce. Bomb-pulse radiocarbon dating provides accurate dates of recent wood formation and tree age of tropical and subtropical tree species. Here, we used radiocarbon techniques combined with X-ray densitometry to develop a wood density chronology for the mangrove Avicennia marina in the Exmouth Gulf, Western Australia (WA). We tested whether wood density chronologies of A. marina were sensitive to variation in the Pacific Decadal Oscillation Index, which reflects temperature fluctuations in the Pacific Ocean and is linked to the instrumental rainfall record in north WA. We also determined growth rates in mangrove trees from the Exmouth Gulf, WA. We found that seaward fringing A. marina trees (~10 cm diameter) were 48 ± 1 to 89 ± 23 years old (mean ± 1 σ) and that their growth rates ranged from 4.08 ± 2.36 to 5.30 ± 3.33 mm/yr (mean ± 1 σ). The wood density of our studied mangrove trees decreased with increases in the Pacific Decadal Oscillation Index. Future predicted drying of the region will likely lead to further reductions in wood density and their associated growth rates in mangrove forests in the region.

Radiocarbon dates for lava flows and pyroclastic deposits on Sao Miguel, Azores

USGS Publications Warehouse

Moore, R.B.; Rubin, M.

1991-01-01

We report 63 new radiocarbon analyses of samples from Sao Miguel, the largest island in the Azores archipelago. The samples are mainly carbonized tree roots and other plant material collected from beneath 20 mafic lava flows and spatter deposits and from within and beneath 42 trachytic pyroclastic flow, pyroclastic surge, mudflow, pumice-fall and lacustrine deposits and lava flows. One calcite date is reported. These dates establish ages for 48 previously undated lava flows and pyroclastic deposits, and revise three ages previously reported. These data are critical to deciphering the Holocene and late Pleistocene eruptive history of Sao Miguel and evaluating its potential volcanic hazards. Average dormant intervals during the past 3000 years are about 400 years for Sete Cidades volcano, 145 years for volcanic Zone 2, 1150 years for Agua de Pau volcano and 320 years for Furnas volcano. No known eruptions have occurred in volcanic Zone 4 during the past 3000 years. -from Authors

A New Accelerator-Based Mass Spectrometry.

ERIC Educational Resources Information Center

Gove, H. E.

1983-01-01

Tandem electrostatic accelerators produce beams of positive ions which are used to penetrate atomic nuclei in a target, inducing nuclear reactions whose study elucidates varied properties of the nucleus. Uses of the system, which acts like a mass spectrometer, are discussed. These include radiocarbon dating measurements. (JN)

Dating Studies of Elephant Tusks Using Accelerator Mass Spectrometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sideras-Haddad, E; Brown, T A

A new method for determining the year of birth, the year of death, and hence, the age at death, of post-bomb and recently deceased elephants has been developed. The technique is based on Accelerator Mass Spectrometry radiocarbon analyses of small-sized samples extracted from along the length of a ge-line of an elephant tusk. The measured radiocarbon concentrations in the samples from a tusk can be compared to the {sup 14}C atmospheric bomb-pulse curve to derive the growth years of the initial and final samples from the tusk. Initial data from the application of this method to two tusks will bemore » presented. Potentially, the method may play a significant role in wildlife management practices of African national parks. Additionally, the method may contribute to the underpinnings of efforts to define new international trade regulations, which could, in effect, decrease poaching and the killing of very young animals.« less

Numerical dating of a Late Quaternary spit-shoreline complex at the northern end of Silver Lake playa, Mojave Desert, California: A comparison of the applicability of radiocarbon, luminescence, terrestrial cosmogenic nuclide, electron spin resonance, U-series and amino acid racemization methods

USGS Publications Warehouse

Owen, L.A.; Bright, Jordon; Finkel, R.C.; Jaiswal, M.K.; Kaufman, D.S.; Mahan, S.; Radtke, U.; Schneider, J.S.; Sharp, W.; Singhvi, A.K.; Warren, C.N.

2007-01-01

A Late Quaternary spit-shoreline complex on the northern shore of Pleistocene Lake Mojave of southeastern California, USA was studied with the goal of comparing accelerator mass spectrometry (AMS) radiocarbon, luminescence, electron spin resonance (ESR), terrestrial cosmogenic radionuclide (TCN) surface exposure, amino acid racemization (AAR) and U-series dating methods. The pattern of ages obtained by the different methods illustrates the complexity of processes acting in the lakeshore environment and highlights the utility of a multi-method approach. TCN surface exposure ages (mostly ???20-30 ka) record the initial erosion of shoreline benches, whereas radiocarbon ages on shells (determined in this and previous studies) within the spit, supported by AAR data, record its construction at fluctuating lake levels from ???16 to 10 ka. Luminescence ages on spit sediment (???6-7 ka) and ESR ages on spit shells (???4 ka) are anomalously young relative to radiocarbon ages of shells within the same deposits. The significance of the surprisingly young luminescence ages is not clear. The younger ESR ages could be a consequence of post-mortem enrichment of U in the shells. High concentrations of detrital thorium in tufa coating spit gravels inhibited the use of single-sample U-series dating. Detailed comparisons such as this provide one of the few means of assessing the accuracy of Quaternary dating techniques. More such comparisons are needed. ?? 2007 Elsevier Ltd and INQUA.

Radiocarbon dating uncertainty and the reliability of the PEWMA method of time-series analysis for research on long-term human-environment interaction.

PubMed

Carleton, W Christopher; Campbell, David; Collard, Mark

2018-01-01

Statistical time-series analysis has the potential to improve our understanding of human-environment interaction in deep time. However, radiocarbon dating-the most common chronometric technique in archaeological and palaeoenvironmental research-creates challenges for established statistical methods. The methods assume that observations in a time-series are precisely dated, but this assumption is often violated when calibrated radiocarbon dates are used because they usually have highly irregular uncertainties. As a result, it is unclear whether the methods can be reliably used on radiocarbon-dated time-series. With this in mind, we conducted a large simulation study to investigate the impact of chronological uncertainty on a potentially useful time-series method. The method is a type of regression involving a prediction algorithm called the Poisson Exponentially Weighted Moving Average (PEMWA). It is designed for use with count time-series data, which makes it applicable to a wide range of questions about human-environment interaction in deep time. Our simulations suggest that the PEWMA method can often correctly identify relationships between time-series despite chronological uncertainty. When two time-series are correlated with a coefficient of 0.25, the method is able to identify that relationship correctly 20-30% of the time, providing the time-series contain low noise levels. With correlations of around 0.5, it is capable of correctly identifying correlations despite chronological uncertainty more than 90% of the time. While further testing is desirable, these findings indicate that the method can be used to test hypotheses about long-term human-environment interaction with a reasonable degree of confidence.

A new graphite preparation line for AMS 14C dating in the Zagreb Radiocarbon Laboratory

NASA Astrophysics Data System (ADS)

Krajcar Bronić, I.; Horvatinčić, N.; Sironić, A.; Obelić, B.; Barešić, J.; Felja, I.

2010-04-01

The new line for preparation of graphite samples for 14C dating by AMS has been constructed in the Zagreb Radiocarbon Laboratory. The performance of the rig and sample preparation procedure has been validated by preparing graphites from various reference materials of known 14C activity. The yield of the graphitization was good and the measured fraction of modern carbon ( Fm) values have not significantly deviated from the expected ones. Detailed analysis of measured Fm values indicates a slight bias to more positive values and should be carefully investigated.

Radiocarbon dating of planktonic foraminifer shells: A cautionary tale

NASA Astrophysics Data System (ADS)

Mekik, Figen

2014-01-01

rate, bioturbation, winnowing, and calcite dissolution produce significant radiocarbon age offsets among multiple species of coexisting planktonic foraminifers and pteropod fragments. We compare the radiocarbon age of foraminifer species and pteropod fragments with estimates of percent calcite dissolved made with a sedimentary proxy (Globorotalia menardii fragmentation index—MFI) to delineate the effect of dissolution on radiocarbon age of foraminifers. Data from two core top transects on the Rio Grande Rise (RIO) and Ontong Java Plateau (OJP) and from down core sediments of varying sedimentation rates in the tropical Pacific (ME-27, MD98 2177, and MW91-9 56GGC) reveal that sediments with the greatest accumulation rates produce the least age offsets among coexisting species. Age offsets among coexisting foraminifers are about 3500 years on RIO, and 1000 years on OJP. Two core tops from RIO yield an age of the Last Glacial Maximum possibly due to mass displacement of younger sediments downslope. Foraminifer age increases with increasing dissolution and there is a consistent pattern of older foraminifer fragments coexisting with younger whole shells of the same species. The only exception is sediments which have experienced high dissolution where fragments are younger than whole shells. The age offset between fragments of G. menardii and its coexisting whole shells does not exceed the age offset among other coexisting foraminifer species in the same core tops.

Concordance of Collagen-Based Radiocarbon and Aspartic-Acid Racemization Ages

PubMed Central

Bada, Jeffrey L.; Schroeder, Roy A.; Protsch, Reiner; Berger, Rainer

1974-01-01

By determining the extent of racemization of aspartic acid in a well-dated bone, it is possible to calculate the in situ first-order rate constant for the interconversion of the L and D enantiomers of aspartic acid. Collagen-based radiocarbon-dated bones are shown to be suitable samples for use in “calibrating” the racemization reaction. Once the aspartic-acid racemization reaction has been “calibrated” for a site, the reaction can be used to date other bones from the deposit. Ages deduced by this method are in good agreement with radiocarbon ages. These results provide evidence that the aspartic-acid racemization reaction is an important chronological tool for dating bones either too old or too small for radiocarbon dating. As an example of the potential application of the technique for dating fossil man, a piece of Rhodesian Man from Broken Hill, Zambia, was analyzed and tentatively assigned an age of about 110,000 years. PMID:4522802

Evolution of size-specific foraminiferal assemblages and the consequences for radiocarbon dating in bioturbated sediment

NASA Astrophysics Data System (ADS)

Costa, K.; Faith, E. S.; McManus, J. F.

2017-12-01

Deep-sea sediment mixing by bioturbation is ubiquitous on the seafloor, and it can be an important influence on the fidelity of paleoceanographic records. Bioturbation can be difficult to quantify, especially in the past, but diffusive models based on radioactive tracer profiles have provided a relatively successful approach. Stable isotope and radiocarbon data from five different foraminiferal species from sediment on the Juan de Fuca Ridge, Northeast Pacific, have previously identified age plateaus that correspond to peak foraminiferal abundances, related to assemblage shifts and carbonate preservation changes since the last glacial period. Here we present size-specific foraminiferal assemblages and over 100 radiocarbon dates to better constrain the effects of bioturbation on fossil chronometers. N. pachyderma is the dominant species in the 150-212µm while G. bulloides is the dominant species in all other size fractions (212-250 µm, 250-300 µm, 300-355 µm). The foraminiferal assemblage of 212-300 µm is found to be representative of the entire adult foraminiferal population >150 µm. Size-specific radiocarbon analyses on G. bulloides demonstrate that larger specimens are generally younger than smaller specimens, but all sizes are susceptible to abundance peak age plateaus. The young bias towards larger specimens may reflect their greater susceptibility to fragmentation during prolonged bioturbation, so that the influence of abundance peaks is shorter-lived in these size fractions. When foraminiferal abundance peaks are unavoidable, e.g. due to large shifts in carbonate preservation, we suggest that larger foraminiferal may provide a more accurate chronometer for sediment age.

Mortar radiocarbon dating: preliminary accuracy evaluation of a novel methodology.

PubMed

Marzaioli, Fabio; Lubritto, Carmine; Nonni, Sara; Passariello, Isabella; Capano, Manuela; Terrasi, Filippo

2011-03-15

Mortars represent a class of building and art materials that are widespread at archeological sites from the Neolithic period on. After about 50 years of experimentation, the possibility to evaluate their absolute chronology by means of radiocarbon ((14)C) remains still uncertain. With the use of a simplified mortar production process in the laboratory environment, this study shows the overall feasibility of a novel physical pretreatment for the isolation of the atmospheric (14)CO(2) (i.e., binder) signal absorbed by the mortars during their setting. This methodology is based on the assumption that an ultrasonic attack in liquid phase isolates a suspension of binder carbonates from bulk mortars. Isotopic ((13)C and (14)C), % C, X-ray diffractometry (XRD), and scanning electron microscopy (SEM) analyses were performed to characterize the proposed methodology. The applied protocol allows suppression of the fossil carbon (C) contamination originating from the incomplete burning of the limestone during the quick lime production, providing unbiased dating for "laboratory" mortars produced operating at historically adopted burning temperatures.

Bomb-curve radiocarbon measurement of recent biologic tissues and applications to wildlife forensics and stable isotope (paleo)ecology

NASA Astrophysics Data System (ADS)

Uno, Kevin T.; Quade, Jay; Fisher, Daniel C.; Wittemyer, George; Douglas-Hamilton, Iain; Andanje, Samuel; Omondi, Patrick; Litoroh, Moses; Cerling, Thure E.

2013-07-01

Above-ground thermonuclear weapons testing from 1952 through 1962 nearly doubled the concentration of radiocarbon (14C) in the atmosphere. As a result, organic material formed during or after this period may be radiocarbon-dated using the abrupt rise and steady fall of the atmospheric 14C concentration known as the bomb-curve. We test the accuracy of accelerator mass spectrometry radiocarbon dating of 29 herbivore and plant tissues collected on known dates between 1905 and 2008 in East Africa. Herbivore samples include teeth, tusks, soft tissue, hair, and horn. Tissues formed after 1955 are dated to within 0.3-1.3 y of formation, depending on the tissue type, whereas tissues older than ca. 1955 have high age uncertainties (>17 y) due to the Suess effect. 14C dating of tissues has applications to stable isotope (paleo)ecology and wildlife forensics. We use data from 41 additional samples to determine growth rates of tusks, molars, and hair, which improve interpretations of serial stable isotope data for (paleo)ecological studies. 14C dating can also be used to calculate the time interval represented in periodic histological structures in dental tissues (i.e., perikymata), which in turn may be used as chronometers in fossil teeth. Bomb-curve 14C dating of confiscated animal tissues (e.g., ivory statues) can be used to determine whether trade of the item is legal, because many Convention of International Trade of Endangered Species restrictions are based on the age of the tissue, and thus can serve as a powerful forensic tool to combat illegal trade in animal parts.

Bomb-curve radiocarbon measurement of recent biologic tissues and applications to wildlife forensics and stable isotope (paleo)ecology.

PubMed

Uno, Kevin T; Quade, Jay; Fisher, Daniel C; Wittemyer, George; Douglas-Hamilton, Iain; Andanje, Samuel; Omondi, Patrick; Litoroh, Moses; Cerling, Thure E

2013-07-16

Above-ground thermonuclear weapons testing from 1952 through 1962 nearly doubled the concentration of radiocarbon ((14)C) in the atmosphere. As a result, organic material formed during or after this period may be radiocarbon-dated using the abrupt rise and steady fall of the atmospheric (14)C concentration known as the bomb-curve. We test the accuracy of accelerator mass spectrometry radiocarbon dating of 29 herbivore and plant tissues collected on known dates between 1905 and 2008 in East Africa. Herbivore samples include teeth, tusks, soft tissue, hair, and horn. Tissues formed after 1955 are dated to within 0.3-1.3 y of formation, depending on the tissue type, whereas tissues older than ca. 1955 have high age uncertainties (>17 y) due to the Suess effect. (14)C dating of tissues has applications to stable isotope (paleo)ecology and wildlife forensics. We use data from 41 additional samples to determine growth rates of tusks, molars, and hair, which improve interpretations of serial stable isotope data for (paleo)ecological studies. (14)C dating can also be used to calculate the time interval represented in periodic histological structures in dental tissues (i.e., perikymata), which in turn may be used as chronometers in fossil teeth. Bomb-curve (14)C dating of confiscated animal tissues (e.g., ivory statues) can be used to determine whether trade of the item is legal, because many Convention of International Trade of Endangered Species restrictions are based on the age of the tissue, and thus can serve as a powerful forensic tool to combat illegal trade in animal parts.

Radiocarbon dating uncertainty and the reliability of the PEWMA method of time-series analysis for research on long-term human-environment interaction

PubMed Central

Carleton, W. Christopher; Campbell, David

2018-01-01

Statistical time-series analysis has the potential to improve our understanding of human-environment interaction in deep time. However, radiocarbon dating—the most common chronometric technique in archaeological and palaeoenvironmental research—creates challenges for established statistical methods. The methods assume that observations in a time-series are precisely dated, but this assumption is often violated when calibrated radiocarbon dates are used because they usually have highly irregular uncertainties. As a result, it is unclear whether the methods can be reliably used on radiocarbon-dated time-series. With this in mind, we conducted a large simulation study to investigate the impact of chronological uncertainty on a potentially useful time-series method. The method is a type of regression involving a prediction algorithm called the Poisson Exponentially Weighted Moving Average (PEMWA). It is designed for use with count time-series data, which makes it applicable to a wide range of questions about human-environment interaction in deep time. Our simulations suggest that the PEWMA method can often correctly identify relationships between time-series despite chronological uncertainty. When two time-series are correlated with a coefficient of 0.25, the method is able to identify that relationship correctly 20–30% of the time, providing the time-series contain low noise levels. With correlations of around 0.5, it is capable of correctly identifying correlations despite chronological uncertainty more than 90% of the time. While further testing is desirable, these findings indicate that the method can be used to test hypotheses about long-term human-environment interaction with a reasonable degree of confidence. PMID:29351329

Bomb-curve radiocarbon measurement of recent biologic tissues and applications to wildlife forensics and stable isotope (paleo)ecology

PubMed Central

Uno, Kevin T.; Quade, Jay; Fisher, Daniel C.; Wittemyer, George; Douglas-Hamilton, Iain; Andanje, Samuel; Omondi, Patrick; Litoroh, Moses; Cerling, Thure E.

2013-01-01

Above-ground thermonuclear weapons testing from 1952 through 1962 nearly doubled the concentration of radiocarbon (14C) in the atmosphere. As a result, organic material formed during or after this period may be radiocarbon-dated using the abrupt rise and steady fall of the atmospheric 14C concentration known as the bomb-curve. We test the accuracy of accelerator mass spectrometry radiocarbon dating of 29 herbivore and plant tissues collected on known dates between 1905 and 2008 in East Africa. Herbivore samples include teeth, tusks, soft tissue, hair, and horn. Tissues formed after 1955 are dated to within 0.3–1.3 y of formation, depending on the tissue type, whereas tissues older than ca. 1955 have high age uncertainties (>17 y) due to the Suess effect. 14C dating of tissues has applications to stable isotope (paleo)ecology and wildlife forensics. We use data from 41 additional samples to determine growth rates of tusks, molars, and hair, which improve interpretations of serial stable isotope data for (paleo)ecological studies. 14C dating can also be used to calculate the time interval represented in periodic histological structures in dental tissues (i.e., perikymata), which in turn may be used as chronometers in fossil teeth. Bomb-curve 14C dating of confiscated animal tissues (e.g., ivory statues) can be used to determine whether trade of the item is legal, because many Convention of International Trade of Endangered Species restrictions are based on the age of the tissue, and thus can serve as a powerful forensic tool to combat illegal trade in animal parts. PMID:23818577

Revised age of deglaciation of Lake Emma based on new radiocarbon and macrofossil analyses

USGS Publications Warehouse

Elias, S.A.; Carrara, P.E.; Toolin, L.J.; Jull, A.J.T.

1991-01-01

Previous radiocarbon ages of detrital moss fragments in basal organic sediments of Lake Emma indicated that extensive deglaciation of the San Juan Mountains occurred prior to 14,900 yr B.P. (Carrara et al., 1984). Paleoecological analyses of insect and plant macrofossils from these basal sediments cast doubt on the reliability of the radiocarbon ages. Subsequent accelerator radiocarbon dates of insect fossils and wood fragments indicate an early Holocene age, rather than a late Pleistocene age, for the basal sediments of Lake Emma. These new radiocarbon ages suggest that by at least 10,000 yr B.P. deglaciation of the San Juan Mountains was complete. The insect and plant macrofossils from the basal organic sediments indicate a higher-than-present treeline during the early Holocene. The insect assemblages consisted of about 30% bark beetles, which contrasts markedly with the composition of insects from modern lake sediments and modern specimens collected in the Lake Emma cirque, in which bark beetles comprise only about 3% of the assemblages. In addition, in the fossil assemblages there were a number of flightless insect species (not subject to upslope transport by wind) indicative of coniferous forest environments. These insects were likewise absent in the modern assemblage. ?? 1991.

New and revised 14C dates for Hawaiian surface lava flows: Paleomagnetic and geomagnetic implications

USGS Publications Warehouse

Pressline, N.; Trusdell, F.A.; Gubbins, David

2009-01-01

Radiocarbon dates have been obtained for 30 charcoal samples corresponding to 27 surface lava flows from the Mauna Loa and Kilauea volcanoes on the Island of Hawaii. The submitted charcoal was a mixture of fresh and archived material. Preparation and analysis was undertaken at the NERC Radiocarbon Laboratory in Glasgow, Scotland, and the associated SUERC Accelerator Mass Spectrometry facility. The resulting dates range from 390 years B.P. to 12,910 years B.P. with corresponding error bars an order of magnitude smaller than previously obtained using the gas-counting method. The new and revised 14C data set can aid hazard and risk assessment on the island. The data presented here also have implications for geomagnetic modelling, which at present is limited by large dating errors. Copyright 2009 by the American Geophysical Union.

A simple radiocarbon dating method for determining the age and growth rate of deep-sea sponges

NASA Astrophysics Data System (ADS)

Fallon, S. J.; James, K.; Norman, R.; Kelly, M.; Ellwood, M. J.

2010-04-01

The ability to reliably age siliceous sponges is explored using radiocarbon dating of several hexactinellid sponge specimens including Rossella racovitzaeracovitzae Topsent, 1901 ( C. Hexactinellida: O. Lyssacinosida: F. Rossellidae), collected from the Ross Sea, Antarctica. The optimal pretreatment was found to consist of both sequential acid digestion and pre-roasting at temperatures >400 °C. Subsequent combustion at 900 °C liberated the proteinaceous material within the spicule matrix and once the reservoir age of the surrounding water was accounted for, a linear extension rate was calculated to be around 2.9 mm yr -1, aging the sponge at ˜440 years old.

High-precision radiocarbon dating of political collapse and dynastic origins at the Maya site of Ceibal, Guatemala

PubMed Central

Inomata, Takeshi; Triadan, Daniela; MacLellan, Jessica; Burham, Melissa; Aoyama, Kazuo; Palomo, Juan Manuel; Yonenobu, Hitoshi; Pinzón, Flory; Nasu, Hiroo

2017-01-01

The lowland Maya site of Ceibal, Guatemala, had a long history of occupation, spanning from the Middle Preclassic Period through the Terminal Classic (1000 BC to AD 950). The Ceibal-Petexbatun Archaeological Project has been conducting archaeological investigations at this site since 2005 and has obtained 154 radiocarbon dates, which represent the largest collection of radiocarbon assays from a single Maya site. The Bayesian analysis of these dates, combined with a detailed study of ceramics, allowed us to develop a high-precision chronology for Ceibal. Through this chronology, we traced the trajectories of the Preclassic collapse around AD 150–300 and the Classic collapse around AD 800–950, revealing similar patterns in the two cases. Social instability started with the intensification of warfare around 75 BC and AD 735, respectively, followed by the fall of multiple centers across the Maya lowlands around AD 150 and 810. The population of Ceibal persisted for some time in both cases, but the center eventually experienced major decline around AD 300 and 900. Despite these similarities in their diachronic trajectories, the outcomes of these collapses were different, with the former associated with the development of dynasties centered on divine rulership and the latter leading to their downfalls. The Ceibal dynasty emerged during the period of low population after the Preclassic collapse, suggesting that this dynasty was placed under the influence from, or by the direct intervention of, an external power. PMID:28115691

High-precision radiocarbon dating of political collapse and dynastic origins at the Maya site of Ceibal, Guatemala.

PubMed

Inomata, Takeshi; Triadan, Daniela; MacLellan, Jessica; Burham, Melissa; Aoyama, Kazuo; Palomo, Juan Manuel; Yonenobu, Hitoshi; Pinzón, Flory; Nasu, Hiroo

2017-02-07

The lowland Maya site of Ceibal, Guatemala, had a long history of occupation, spanning from the Middle Preclassic Period through the Terminal Classic (1000 BC to AD 950). The Ceibal-Petexbatun Archaeological Project has been conducting archaeological investigations at this site since 2005 and has obtained 154 radiocarbon dates, which represent the largest collection of radiocarbon assays from a single Maya site. The Bayesian analysis of these dates, combined with a detailed study of ceramics, allowed us to develop a high-precision chronology for Ceibal. Through this chronology, we traced the trajectories of the Preclassic collapse around AD 150-300 and the Classic collapse around AD 800-950, revealing similar patterns in the two cases. Social instability started with the intensification of warfare around 75 BC and AD 735, respectively, followed by the fall of multiple centers across the Maya lowlands around AD 150 and 810. The population of Ceibal persisted for some time in both cases, but the center eventually experienced major decline around AD 300 and 900. Despite these similarities in their diachronic trajectories, the outcomes of these collapses were different, with the former associated with the development of dynasties centered on divine rulership and the latter leading to their downfalls. The Ceibal dynasty emerged during the period of low population after the Preclassic collapse, suggesting that this dynasty was placed under the influence from, or by the direct intervention of, an external power.

Sun, Ocean, Nuclear Bombs, and Fossil Fuels: Radiocarbon Variations and Implications for High-Resolution Dating

NASA Astrophysics Data System (ADS)

Dutta, Koushik

2016-06-01

Radiocarbon, or 14C, is a radiometric dating method ideally suited for providing a chronological framework in archaeology and geosciences for timescales spanning the last 50,000 years. 14C is easily detectable in most common natural organic materials and has a half-life (5,730±40 years) relevant to these timescales. 14C produced from large-scale detonations of nuclear bombs between the 1950s and the early 1960s can be used for dating modern organic materials formed after the 1950s. Often these studies demand high-resolution chronology to resolve ages within a few decades to less than a few years. Despite developments in modern, high-precision 14C analytical methods, the applicability of 14C in high-resolution chronology is limited by short-term variations in atmospheric 14C in the past. This article reviews the roles of the principal natural drivers (e.g., solar magnetic activity and ocean circulation) and the anthropogenic perturbations (e.g., fossil fuel CO2 and 14C from nuclear and thermonuclear bombs) that are responsible for short-term 14C variations in the environment. Methods and challenges of high-resolution 14C dating are discussed.

Optical Measurement of Radiocarbon below Unity Fraction Modern by Linear Absorption Spectroscopy.

PubMed

Fleisher, Adam J; Long, David A; Liu, Qingnan; Gameson, Lyn; Hodges, Joseph T

2017-09-21

High-precision measurements of radiocarbon ( 14 C) near or below a fraction modern 14 C of 1 (F 14 C ≤ 1) are challenging and costly. An accurate, ultrasensitive linear absorption approach to detecting 14 C would provide a simple and robust benchtop alternative to off-site accelerator mass spectrometry facilities. Here we report the quantitative measurement of 14 C in gas-phase samples of CO 2 with F 14 C < 1 using cavity ring-down spectroscopy in the linear absorption regime. Repeated analysis of CO 2 derived from the combustion of either biogenic or petrogenic sources revealed a robust ability to differentiate samples with F 14 C < 1. With a combined uncertainty of 14 C/ 12 C = 130 fmol/mol (F 14 C = 0.11), initial performance of the calibration-free instrument is sufficient to investigate a variety of applications in radiocarbon measurement science including the study of biofuels and bioplastics, illicitly traded specimens, bomb dating, and atmospheric transport.

Radiocarbon application in environmental science and archaeology in Croatia

NASA Astrophysics Data System (ADS)

Krajcar Bronić, I.; Obelić, B.; Horvatinčić, N.; Barešić, J.; Sironić, A.; Minichreiter, K.

2010-07-01

Radiocarbon is a cosmogenic radioisotope equally distributed throughout the troposphere and biosphere. This fact enables its most common application—radiocarbon dating. Natural equilibrium of radiocarbon has been disturbed by diverse anthropogenic activities during the last ˜150 years, enabling also the use of 14C in various environmental applications. Here we present three types of studies by using 14C that were performed in the Zagreb Radiocarbon Laboratory. 14C in atmospheric CO 2 has been monitored at several sites with various anthropogenic influences and the difference between the clean-air sites, the industrial city and the vicinity of a nuclear power plant has been established. 14C has been applied in geochronology of karst areas, especially in dating of tufa, speleothems and lake sediments, as well as in studies of geochemical carbon cycle. 14C has been used in various archaeological studies, among which the dating of the early Neolithic settlements in Croatia is presented. In these studies 14C was measured by radiometric techniques, i.e., by gas proportional counting and more recently by liquid scintillation counting (LSC). Two sample preparation techniques for LSC measurement were used: benzene synthesis for archaeological dating and other applications that require better precision, and direct absorption of CO 2 for monitoring purposes. The presented results show that various studies by using 14C can be successfully performed by the LSC technique, providing a large enough sample (>1 g of carbon).

THE ABSOLUTE AGE OF THE UPPER PALEOLITHIC PERIOD (SOLUTREAN, GRAVETTIAN TYPE) IN THE REGION ADJOINING THE DNESTER RIVER, DETERMINED BY RADIOCARBON DATING (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanova, I.K.; Chernysh, A.P.

1963-01-11

Determination of the age of the dwellings of primitive man is of interest both from the point of view of the stratigraphy of quaternary deposits and for solving anthropogenetic problems. For this reason, radiocarbon dating techniques were used for layers containing paleolithic residue of Molodova V, located in a 200-m deep canyon at the right bank of the Dnester River in the Chernowith region. The measurements were carried out at a depth of 3.1 to 3.25 m from the surface. The age of layer VI was calculated at 23,000 plus or minus 800 years which is close to the agemore » reported for the Czechoslovak gravette and from samples from the French Abri plateau. Thus, radiocarbon dating results confirmed earlier findings obtained by topological means concerning the age of the region near the Dnester River. (TTT)« less

Pre- and post-bomb radiocarbon in fish otoliths

NASA Astrophysics Data System (ADS)

Kalish, John M.

1993-02-01

Measurements of radiocarbon in seawater dissolved inorganic carbon (DIC), or suitable proxies such as hermatypic corals, are a valuable source of information on carbon flux and ocean circulation. However, knowledge of the global distribution of both pre- and post-bomb radiocarbon is limited due to the sources of these data. Suitable hermatypic corals are restricted to shallow tropical and subtropical waters and oceanographic collections of seawater are prohibitively expensive. What is needed is a proxy for ocean radiocarbon that can be collected at most latitudes and depths, and which can be reliably aged. Here I report accelerator mass spectrometry analyses of radiocarbon from selected regions of fish otoliths and show that such measurements are suitable for determining both pre- and post-bomb radiocarbon in all oceans and at most depths. Radiocarbon data obtained from otoliths can extend our knowledge of carbon flux in the oceans and atmosphere and help to develop further understanding of the fate of atmospheric CO 2 and ocean circulation. The data presented here represent the first pre- and post-bomb time series of radiocarbon levels from temperate waters. Furthermore, I demonstrate that the dramatic increase in radiocarbon in the atmosphere and oceans, attributable to the atmospheric testing of thermonuclear bombs during the 1950's and 1960's, provides a chemical mark on fish otoliths that is suitable for the validation of age in fishes.

Difference in radiocarbon ages of carbonized material from the inner and outer surfaces of pottery from a wetland archaeological site.

PubMed

Miyata, Yoshiki; Minami, Masayo; Onbe, Shin; Sakamoto, Minoru; Matsuzaki, Hiroyuki; Nakamura, Toshio; Imamura, Mineo

2011-01-01

AMS (Accelerator Mass Spectrometry) radiocarbon dates for eight potsherds from a single piece of pottery from a wetland archaeological site indicated that charred material from the inner pottery surfaces (5052 ± 12 BP; N = 5) is about 90 (14)C years older than that from the outer surfaces (4961 ± 22 BP; N = 7). We considered three possible causes of this difference: the old wood effect, reservoir effects, and diagenesis. We concluded that differences in the radiocarbon ages between materials from the inner and outer surfaces of the same pot were caused either by the freshwater reservoir effect or by diagenesis. Moreover, we found that the radiocarbon ages of carbonized material on outer surfaces (soot) of pottery from other wetland archaeological sites were the same as the ages of material on inner surfaces (charred food) of the same pot within error, suggesting absence of freshwater reservoir effect or diagenesis.

The Naples University 3 MV tandem accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campajola, L.; Brondi, A.

2013-07-18

The 3 MV tandem accelerator of the Naples University is used for research activities and applications in many fields. At the beginning of operation (1977) the main utilization was in the field of nuclear physics. Later, the realization of new beam lines allowed the development of applied activities as radiocarbon dating, ion beam analysis, biophysics, ion implantation etc. At present, the availability of different ion sources and many improvements on the accelerator allow to run experiments in a wide range of subjects. An overview of the characteristics and major activities of the laboratory is presented.

Youngest radiocarbon age for Jefferson's ground sloth, Megalonyx jeffersonii (Xenarthra, Megalonychidae)

NASA Astrophysics Data System (ADS)

Gregory McDonald, H.; Stafford, Thomas W.; Gnidovec, Dale M.

2015-03-01

A partial skeleton of the extinct ground sloth, Megalonyx jeffersonii, recovered from a farm near Millersburg, Ohio in 1890, was radiocarbon dated for the first time. The ungual dated is part of a skeleton mounted for exhibit at the Orton Geological Museum at Ohio State University and was the first mounted skeleton of this animal. From its initial discovery the bones were treated with multiple organic compounds that had the potential to compromise the radiocarbon age and the specimen required special treatments in order to obtain a valid radiocarbon age. The 14C measurement on the ungual from this skeleton (11,235 ± 40 14C yr BP = 13,180-13,034 cal yr BP) is the youngest 14C age presently determined for M. jeffersonii.

AMS radiocarbon analyses from Lake Baikal, Siberia: Challenges of dating sediments from a large, oligotrophic lake

USGS Publications Warehouse

Colman, Steven M.; Jones, Glenn A.; Rubin, M.; King, J.W.; Peck, J.A.; Orem, W.H.

1996-01-01

A suite of 146 new accelerator-mass spectrometer (AMS) radiocarbon ages provides the first reliable chronology for late Quaternary sediments in Lake Baikal. In this large, highly oligotrophic lake, biogenic and authigenic carbonate are absent, and plant macrofossils are extremely rare. Total organic carbon is therefore the primary material available for dating. Several problems are associated with the TOC ages. One is the mixture of carbon sources in TOC, not all of which are syndepositional in age. This problem manifests itself in apparent ages for the sediment surface that are greater than zero. However, because most of the organic carbon in Lake Baikal sediments is algal (autochthonous) in origin, this effect is limited to about 1000+500 years, which can be corrected, at least for young deposits. The other major problem with dating Lake Baikal sediments is the very low carbon contents of glacial-age deposits, which makes them extremely susceptible to contamination with modern carbon. This problem can be minimized by careful sampling and handling procedures. The ages show almost an order of magnitude difference in sediment-accumulation rates among different sedimentary environments in Lake Baikal, from about 0.04 mm/year on isolated banks such as Academician Ridge, to nearly 0.3 mm/year in the turbidite depositional areas beneath the deep basin floors, such as the Central Basin. The new AMS ages clearly indicate that the dramatic increase in diatom productivity in the lake, as evidenced by increases in biogenic silica and organic carbon, began about 13 ka, in contrast to previous estimates of 7 ka for the age of this transition. Holocene net sedimentation rates may be less than, equal to, or greater than those in the late Pleistocene, depending on the site. This variability reflects the balance between variable terrigenous sedimentation and increased biogenic sedimentation during interglaciations. The ages reported here, and the temporal and spatial variation in

The scientific dating of standing buildings.

PubMed

Alcock, Nathaniel W

2017-11-17

The techniques of dendrochronology (tree-ring dating) and radiocarbon (14C) dating are described, as they are applied to historic buildings. Both rely on determining the felling dates of the trees used in their construction. For dendrochronology, the construction of master chronologies and the matching of individual ring-width sequences to them is described and, for radiocarbon dating, the use of tree-ring results in calibration. Results of dating are discussed, ranging from the cathedrals of Peterborough and Beauvais and the development of crown-post roof structures, to the dating and identification of standing medieval peasant houses, particularly those built using cruck construction.

Studies of industrial emissions by accelerator-based techniques: A review of applications at CEDAD

NASA Astrophysics Data System (ADS)

Calcagnile, L.; Quarta, G.

2012-04-01

Different research activities are in progress at the Centre for Dating and Diagnostics (CEDAD), University of Salento, in the field of environmental monitoring by exploiting the potentialities given by the different experimental beam lines implemented on the 3 MV Tande-tron accelerator and dedicated to AMS (Accelerator Mass Spectrome-try) radiocarbon dating and IB A (Ion Beam Analysis). An overview of these activities is presented by showing how accelerator-based analytical techniques can be a powerful tool for monitoring the anthropogenic carbon dioxide emissions from industrial sources and for the assessment of the biogenic content in SRF (Solid Recovered Fuel) burned in WTE (Waste to Energy) plants.

AMS radiocarbon investigation of the African baobab: Searching for the oldest tree

NASA Astrophysics Data System (ADS)

Patrut, Adrian; von Reden, Karl F.; Mayne, Diana H.; Lowy, Daniel A.; Patrut, Roxana T.

2013-01-01

The Glencoe baobab, a very large specimen from South Africa, split twice in 2009. Several wood samples were collected from the eastern cavity, from the outer part of the main section and also from the largest broken segment which was connected to this section. These wood samples were processed and investigated by AMS radiocarbon dating. The radiocarbon date of the oldest sample was found to be 1838 ± 21 BP, which corresponds to a calibrated age of 1835 ± 40 years. Thus, the Glencoe baobab becomes the oldest dated baobab and also the oldest angiosperm tree with accurate dating results. The distribution of dating results revealed that the Glencoe baobab is a multi-generation tree, with several standing or collapsed and partially fused stems, showing different ages.

Radiocarbon dating of charcoal and bone collagen associated with early pottery at Yuchanyan Cave, Hunan Province, China

PubMed Central

Boaretto, Elisabetta; Wu, Xiaohong; Yuan, Jiarong; Bar-Yosef, Ofer; Chu, Vikki; Pan, Yan; Liu, Kexin; Cohen, David; Jiao, Tianlong; Li, Shuicheng; Gu, Haibin; Goldberg, Paul; Weiner, Steve

2009-01-01

Yuchanyan Cave in Daoxian County, Hunan Province (People's Republic of China), yielded fragmentary remains of 2 or more ceramic vessels, in addition to large amounts of ash, a rich animal bone assemblage, cobble and flake artifacts, bone tools, and shell tools. The artifacts indicate that the cave was a Late Paleolithic foragers' camp. Here we report on the radiocarbon ages of the sediments based on analyses of charcoal and bone collagen. The best-preserved charcoal and bone samples were identified by prescreening in the field and laboratory. The dates range from around 21,000 to 13,800 cal BP. We show that the age of the ancient pottery ranges between 18,300 and 15,430 cal BP. Charcoal and bone collagen samples located above and below one of the fragments produced dates of around 18,000. These ceramic potsherds therefore provide some of the earliest evidence for pottery making in China. PMID:19487667

Summary findings of the fourth international radiocarbon intercomparison (FIRI)(1998-2001)

NASA Astrophysics Data System (ADS)

Boaretto, Elisabetta; Bryant, Charlotte; Carmi, Israel; Cook, Gordon; Gulliksen, Steinar; Harkness, Doug; Heinemeier, Jan; McClure, John; McGee, Edward; Naysmith, Philip; Possnert, Goran; Scott, Marian; van der Plicht, Hans; van Strydonck, Mark

2002-10-01

Interlaboratory comparisons have been widely used in applied radiocarbon science. These are an important part of ongoing quality assurance (QA) programmes, which are vital to the appropriate interpretation of the evidence provided by the 14C record in Quaternary applications (including climate change and environmental reconstruction). International comparisons of laboratory performance are an essential component of the quality assurance process in radiocarbon dating. If the user community is to have confidence in radiocarbon results, it needs to be assured that laboratories world wide are producing measurements that are reliable and in accordance with good practice. The findings from the most recent (completed in 2001) and extensive (more than 90 participating laboratories) radiocarbon intercomparison (FIRI) are reported here. This study was designed (i) to assess comparability, or otherwise, of the results from different laboratories and (ii) to quantify the extent and possible causes of any interlaboratory variation. The results demonstrate that there are no significant differences amongst the main measurement techniques (gas proportional counting, liquid scintillation counting and accelerator mass spectrometry (AMS)) but there is evidence of small laboratory offsets relative to known age samples for some laboratories. There is also evidence in some cases of underestimation of measurement precision. Approximately 10% of all results were classified as extreme (outliers) and these results were generated by 14% of the laboratories. Overall, the evidence supports the fact that radiocarbon laboratories are generally accurate and precise but that, notwithstanding internal QA procedures, some problems still occur, which can best be detected by participation in independent intercomparisons such as FIRI, where the results allow individual laboratories to assess their performance and to take remedial measures where necessary. The results from FIRI are significant in that

A complete terrestrial radiocarbon record for 11.2 to 52.8 kyr B.P.

PubMed

Bronk Ramsey, Christopher; Staff, Richard A; Bryant, Charlotte L; Brock, Fiona; Kitagawa, Hiroyuki; van der Plicht, Johannes; Schlolaut, Gordon; Marshall, Michael H; Brauer, Achim; Lamb, Henry F; Payne, Rebecca L; Tarasov, Pavel E; Haraguchi, Tsuyoshi; Gotanda, Katsuya; Yonenobu, Hitoshi; Yokoyama, Yusuke; Tada, Ryuji; Nakagawa, Takeshi

2012-10-19

Radiocarbon ((14)C) provides a way to date material that contains carbon with an age up to ~50,000 years and is also an important tracer of the global carbon cycle. However, the lack of a comprehensive record reflecting atmospheric (14)C prior to 12.5 thousand years before the present (kyr B.P.) has limited the application of radiocarbon dating of samples from the Last Glacial period. Here, we report (14)C results from Lake Suigetsu, Japan (35°35'N, 135°53'E), which provide a comprehensive record of terrestrial radiocarbon to the present limit of the (14)C method. The time scale we present in this work allows direct comparison of Lake Suigetsu paleoclimatic data with other terrestrial climatic records and gives information on the connection between global atmospheric and regional marine radiocarbon levels.

Origin of PCDDs in ball clay assessed with compound-specific chlorine isotope analysis and radiocarbon dating.

PubMed

Holmstrand, Henry; Gadomski, Damien; Mandalakis, Manolis; Tysklind, Mats; Irvine, Robert; Andersson, Per; Gustafsson, Orjan

2006-06-15

Polychlorinated dibenzo-p-dioxins (PCDDs) of high concentrations in a ball clay deposit from the Mississippi Embayment were found to be consistent with a natural abiotic and non-pyrogenic origin by investigation with bulk radiocarbon analysis, compound-specific chlorine isotope analysis (CSIA-delta37Cl) of octachlorodibenzo-p-dioxin (OCDD), and black carbon (BC) analysis. The conventional radiocarbon date of total organic carbon from a depth of approximately 10 m in three parallel cores ranged from 14 700 years to >48 000 years, indicating that the strata with elevated levels of PCDDs have remained isolated from recent anthropogenic input in these >40 Ma old clay sediments. The CSIA-delta37Cl of OCDD yielded a delta37Cl of -0.2 per thousandth, which is significantly higher than the postulated range for biotic chlorination by chloroperoxidase enzymes, -11 to -10 per thousandth, and falls within the known range for abiotic organochlorines, -6 to +3 per thousandth. The absence of correlations between concentrations of PCDDs and corresponding pyrogenic black carbon (BC), together with estimations of BC sorptive loadings and the absence of polychlorinated dibenzofurans (PCDFs), suggest that vegetation fires did not form these ball-clay PCDDs. Results from this study indicate that the high levels of the toxic and carcinogenic PCDDs found in kaolinite-bearing clays may result from natural abiotic formation via in situ surface-promoted reactions on the clay mineral, including a so-far unknown organic precursor, rather than being the result of anthropogenic contamination.

Reassessment of the 13C/12C and 14C/12C isotopic fractionation ratio and its impact on high-precision radiocarbon dating

NASA Astrophysics Data System (ADS)

Fahrni, Simon M.; Southon, John R.; Santos, Guaciara M.; Palstra, Sanne W. L.; Meijer, Harro A. J.; Xu, Xiaomei

2017-09-01

("unknowns") would be shifted by 2‰ (16 radiocarbon years) or more due to this effect: for example, for b = 1.882, between 16.8% and 25.9% of almost 60,000 radiocarbon values measured at the Keck Carbon Cycle AMS facility between 2002 and 2012 would be affected. The implications for radiocarbon dating and its accuracy are discussed.

A graphical method to evaluate predominant geochemical processes occurring in groundwater systems for radiocarbon dating

USGS Publications Warehouse

Han, Liang-Feng; Plummer, Niel; Aggarwal, Pradeep

2012-01-01

A graphical method is described for identifying geochemical reactions needed in the interpretation of radiocarbon age in groundwater systems. Graphs are constructed by plotting the measured 14C, δ13C, and concentration of dissolved inorganic carbon and are interpreted according to specific criteria to recognize water samples that are consistent with a wide range of processes, including geochemical reactions, carbon isotopic exchange, 14C decay, and mixing of waters. The graphs are used to provide a qualitative estimate of radiocarbon age, to deduce the hydrochemical complexity of a groundwater system, and to compare samples from different groundwater systems. Graphs of chemical and isotopic data from a series of previously-published groundwater studies are used to demonstrate the utility of the approach. Ultimately, the information derived from the graphs is used to improve geochemical models for adjustment of radiocarbon ages in groundwater systems.

Mass spectrometry with accelerators.

PubMed

Litherland, A E; Zhao, X-L; Kieser, W E

2011-01-01

As one in a series of articles on Canadian contributions to mass spectrometry, this review begins with an outline of the history of accelerator mass spectrometry (AMS), noting roles played by researchers at three Canadian AMS laboratories. After a description of the unique features of AMS, three examples, (14)C, (10)Be, and (129)I are given to illustrate the methods. The capabilities of mass spectrometry have been extended by the addition of atomic isobar selection, molecular isobar attenuation, further ion acceleration, followed by ion detection and ion identification at essentially zero dark current or ion flux. This has been accomplished by exploiting the techniques and accelerators of atomic and nuclear physics. In 1939, the first principles of AMS were established using a cyclotron. In 1977 the selection of isobars in the ion source was established when it was shown that the (14)N(-) ion was very unstable, or extremely difficult to create, making a tandem electrostatic accelerator highly suitable for assisting the mass spectrometric measurement of the rare long-lived radioactive isotope (14)C in the environment. This observation, together with the large attenuation of the molecular isobars (13)CH(-) and (12)CH 2(-) during tandem acceleration and the observed very low background contamination from the ion source, was found to facilitate the mass spectrometry of (14)C to at least a level of (14)C/C ~ 6 × 10(-16), the equivalent of a radiocarbon age of 60,000 years. Tandem Accelerator Mass Spectrometry, or AMS, has now made possible the accurate radiocarbon dating of milligram-sized carbon samples by ion counting as well as dating and tracing with many other long-lived radioactive isotopes such as (10)Be, (26)Al, (36)Cl, and (129)I. The difficulty of obtaining large anion currents with low electron affinities and the difficulties of isobar separation, especially for the heavier mass ions, has prompted the use of molecular anions and the search for alternative

Marine radiocarbon reservoir age simulations for the past 50,000 years

NASA Astrophysics Data System (ADS)

Butzin, M.; Köhler, P.; Lohmann, G.

2017-08-01

Radiocarbon (14C) dating calibration for the last glacial period largely relies on cross-dated marine 14C records. However, marine reservoirs are isotopically depleted with respect to the atmosphere and therefore have to be corrected by the Marine Radiocarbon Ages of surface waters (MRAs), whose temporal variabilities are largely unknown. Here we present simulations of the spatial and temporal variability in MRAs using a three-dimensional ocean circulation model covering the past 50,000 years. Our simulations are compared to reconstructions of past surface ocean Δ14C. Running the model with different climatic boundary conditions, we find that low-latitude to midlatitude MRAs have varied between 400 and 1200 14C years, with values of about 780 14C years at the Last Glacial Maximum. Reservoir ages exceeding 2000 14C years are simulated in the polar oceans. Our simulation results can be used as first-order approximation of the MRA variability in future radiocarbon calibration efforts.

Chronometric investigations of the Middle to Upper Paleolithic transition in the Zagros Mountains using AMS radiocarbon dating and Bayesian age modelling.

PubMed

Becerra-Valdivia, Lorena; Douka, Katerina; Comeskey, Daniel; Bazgir, Behrouz; Conard, Nicholas J; Marean, Curtis W; Ollé, Andreu; Otte, Marcel; Tumung, Laxmi; Zeidi, Mohsen; Higham, Thomas F G

2017-08-01

The Middle to Upper Paleolithic transition is often linked with a bio-cultural shift involving the dispersal of modern humans outside of Africa, the concomitant replacement of Neanderthals across Eurasia, and the emergence of new technological traditions. The Zagros Mountains region assumes importance in discussions concerning this period as its geographic location is central to all pertinent hominin migration areas, pointing to both east and west. As such, establishing a reliable chronology in the Zagros Mountains is crucial to our understanding of these biological and cultural developments. Political circumstance, coupled with the poor preservation of organic material, has meant that a clear chronological definition of the Middle to Upper Paleolithic transition for the Zagros Mountains region has not yet been achieved. To improve this situation, we have obtained new archaeological samples for AMS radiocarbon dating from three sites: Kobeh Cave, Kaldar Cave, and Ghār-e Boof (Iran). In addition, we have statistically modelled previously published radiocarbon determinations for Yafteh Cave (Iran) and Shanidar Cave (Iraqi Kurdistan), to improve their chronological resolution and enable us to compare the results with the new dataset. Bayesian modelling results suggest that the onset of the Upper Paleolithic in the Zagros Mountains dates to 45,000-40,250 cal BP (68.2% probability). Further chronometric data are required to improve the precision of this age range. Copyright © 2017 Elsevier Ltd. All rights reserved.

Radiocarbon dating Arctic deep marine sediment to refine the usage of Mn pattern as a stratigraphic tool

NASA Astrophysics Data System (ADS)

Chiu, Pin-Yao Bernie; Löwemark, Ludvig

2016-04-01

The distinctive pattern of Mn content in Arctic deep marine sediment has been used as a proxy to indicate glacial-interglacial cyclicity (Löwemark et al., 2014). As has been observed in many sediment cores, Mn peaks correspond to warm interglacial periods. In order to improve the preciseness of Mn pattern as a proxy, we collected the foraminifera Neogloboquadrina pachyderma (sinistral) from brownish, Mn-rich layers, and performed radiocarbon dating on selected cores collected during the LOMROG07, LOMROG09 and LOMROG12 expeditions. Additional cores form the YMER and AO96 expeditions are also included. Based on our general understanding of the Mn system in the Arctic Ocean, we predicted a Mn pattern with a high peak in the uppermost core top, representing the Holocene. This Holocene peak in Mn is separated from the underlying warm period MIS 3 by a Mn-poor interval also characterized by a drop in Ca. This Mn and Ca poor interval reperesents MIS 2 and the LGM. Older warm periods, such as MIS 3, 5, 7 etc will display a similar pattern with distinct Mn peaks, separated by Mn minima representing cold iperiods For example, the MIS 5 sometimes shown a distinct pattern with three Mn peaks representing MIS 5a, 5c and 5e. However, there are still some limitations in the applicability of Mn stratigraphy, such as the remobilization of the Mn layer and the core-top loss during coring. We performed AMS carbon 14 dating on more than 10 cores, and the result revealed several cases of lost core tops, leading to depletion or complete loss of the Holocene interval. In several cores, our AMS dating revealed a hiatus in the MIS2 interval. The complete lack of MIS2 sediment likely is the result of extremely slow sedimentation rate due to severe sea ice conditions, while places with records of LGM may be the result of polynyas within the sea ice, or certain circulation pattern. Consequently, although Mn pattern can be used as a preliminary tool to identify glacial-interglacial cycles

Status report on the Zagreb Radiocarbon Laboratory - AMS and LSC results of VIRI intercomparison samples

NASA Astrophysics Data System (ADS)

Sironić, Andreja; Krajcar Bronić, Ines; Horvatinčić, Nada; Barešić, Jadranka; Obelić, Bogomil; Felja, Igor

2013-01-01

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

Changes in the radiocarbon reservoir age in Lake Xingyun, Southwestern China during the Holocene.

PubMed

Zhou, Aifeng; He, Yuxin; Wu, Duo; Zhang, Xiaonan; Zhang, Can; Liu, Zhonghui; Yu, Junqing

2015-01-01

Chronology is a necessary component of paleoclimatology. Radiocarbon dating plays a central role in determining the ages of geological samples younger than ca. 50 ka BP. However, there are many limitations for its application, including radiocarbon reservoir effects, which may cause incorrect chronology in many lakes. Here we demonstrate temporal changes in the radiocarbon reservoir age of Lake Xingyun, Southwestern China, where radiocarbon ages based on bulk organic matter have been reported in previous studies. Our new radiocarbon ages, determined from terrestrial plant macrofossils suggest that the radiocarbon reservoir age changed from 960 to 2200 years during the last 8500 cal a BP years. These changes to the reservoir effect were associated with inputs from either pre-aged organic carbon or 14C-depleted hard water in Lake Xingyun caused by hydrological change in the lake system. The radiocarbon reservoir age may in return be a good indicator for the carbon source in lake ecosystems and depositional environment.

Radiocarbon analysis of halophilic microbial lipids from an Australian salt lake

NASA Astrophysics Data System (ADS)

Bray, P. Sargent; Jones, Claudia M.; Fallon, Stewart J.; Brocks, Jochen J.; George, Simon C.

2012-01-01

Assigning accurate dates to hypersaline sediments opens important terrestrial records of local and regional paleoecologies and paleoclimatology. However, as of yet no conventional method of dating hypersaline systems has been widely adopted. Biomarker, mineralogical, and radiocarbon analyses of sediments and organic extracts from a shallow (13 cm) core from a hypersaline playa, Lake Tyrrell, southeastern Australia, produce a coherent age-depth curve beginning with modern microbial mats and extending to ~ 7500 cal yr BP. These analyses are furthermore used to identify and constrain the timing of the most recent change in hydrological regime at Lake Tyrrell, a shift from a clay deposit to the precipitation of evaporitic sands occurring at some time between ~ 4500 and 7000 yr. These analyses show the potential for widespread dating of hypersaline systems integrating the biomarker approach, reinforce the value of the radiocarbon content of biomarkers in understanding the flow of carbon in modern ecologies, and validate the temporal dimension of data provided by biomarkers when dating late Quaternary sediments.

Impact of fossil fuel emissions on atmospheric radiocarbon and various applications of radiocarbon over this century.

PubMed

Graven, Heather D

2015-08-04

Radiocarbon analyses are commonly used in a broad range of fields, including earth science, archaeology, forgery detection, isotope forensics, and physiology. Many applications are sensitive to the radiocarbon ((14)C) content of atmospheric CO2, which has varied since 1890 as a result of nuclear weapons testing, fossil fuel emissions, and CO2 cycling between atmospheric, oceanic, and terrestrial carbon reservoirs. Over this century, the ratio (14)C/C in atmospheric CO2 (Δ(14)CO2) will be determined by the amount of fossil fuel combustion, which decreases Δ(14)CO2 because fossil fuels have lost all (14)C from radioactive decay. Simulations of Δ(14)CO2 using the emission scenarios from the Intergovernmental Panel on Climate Change Fifth Assessment Report, the Representative Concentration Pathways, indicate that ambitious emission reductions could sustain Δ(14)CO2 near the preindustrial level of 0‰ through 2100, whereas "business-as-usual" emissions will reduce Δ(14)CO2 to -250‰, equivalent to the depletion expected from over 2,000 y of radioactive decay. Given current emissions trends, fossil fuel emission-driven artificial "aging" of the atmosphere is likely to occur much faster and with a larger magnitude than previously expected. This finding has strong and as yet unrecognized implications for many applications of radiocarbon in various fields, and it implies that radiocarbon dating may no longer provide definitive ages for samples up to 2,000 y old.

Impact of fossil fuel emissions on atmospheric radiocarbon and various applications of radiocarbon over this century

PubMed Central

Graven, Heather D.

2015-01-01

Radiocarbon analyses are commonly used in a broad range of fields, including earth science, archaeology, forgery detection, isotope forensics, and physiology. Many applications are sensitive to the radiocarbon (14C) content of atmospheric CO2, which has varied since 1890 as a result of nuclear weapons testing, fossil fuel emissions, and CO2 cycling between atmospheric, oceanic, and terrestrial carbon reservoirs. Over this century, the ratio 14C/C in atmospheric CO2 (Δ14CO2) will be determined by the amount of fossil fuel combustion, which decreases Δ14CO2 because fossil fuels have lost all 14C from radioactive decay. Simulations of Δ14CO2 using the emission scenarios from the Intergovernmental Panel on Climate Change Fifth Assessment Report, the Representative Concentration Pathways, indicate that ambitious emission reductions could sustain Δ14CO2 near the preindustrial level of 0‰ through 2100, whereas “business-as-usual” emissions will reduce Δ14CO2 to −250‰, equivalent to the depletion expected from over 2,000 y of radioactive decay. Given current emissions trends, fossil fuel emission-driven artificial “aging” of the atmosphere is likely to occur much faster and with a larger magnitude than previously expected. This finding has strong and as yet unrecognized implications for many applications of radiocarbon in various fields, and it implies that radiocarbon dating may no longer provide definitive ages for samples up to 2,000 y old. PMID:26195757

Extraneous carbon assessment in ultra-microscale radiocarbon analysis using benzene polycarboxylic acids (BPCA)

NASA Astrophysics Data System (ADS)

Hanke, Ulrich M.; McIntyre, Cameron P.; Schmidt, Michael W. I.; Wacker, Lukas; Eglinton, Timothy I.

2016-04-01

Measurements of the natural abundance of radiocarbon (14C) concentrations in inorganic and organic carbon-containing materials can be used to investigate their date of origin. Particularly, the biogeochemical cycling of specific compounds in the environment may be investigated applying molecular marker analyses. However, the isolation of specific molecules from environmental matrices requires a complex processing procedure resulting in small sample sizes that often contain less than 30 μg C. Such small samples are sensitive to extraneous carbon (Cex) that is introduced during the purification of the compounds (Shah and Pearson, 2007). We present a thorough radiocarbon blank assessment for benzene polycarboxylic acids (BPCA), a proxy for combustion products that are formed during the oxidative degradation of condensed polyaromatic structures (Wiedemeier et al, in press). The extraneous carbon assessment includes reference material for (1) chemical extraction, (2) preparative liquid chromatography (3) wet chemical oxidation which are subsequently measured with gas ion source AMS (Accelerator Mass Spectrometer, 5-100 μg C). We always use pairs of reference materials, radiocarbon depleted (14Cfossil) and modern (14Cmodern) to determine the fraction modern (F14C) of Cex.Our results include detailed information about the quantification of Cex in radiocarbon molecular marker analysis using BPCA. Error propagation calculations indicate that ultra-microscale samples (20-30 μg) are feasible with uncertainties of less than 10 %. Calculations of the constant contamination reveal important information about the source (F14C) and mass (μg) of Cex (Wacker and Christl, 2011) for each sub procedure. An external correction of compound specific radiocarbon data is essential for robust results that allow for a high degree of confidence in the 14C results. References Shah and Pearson, 2007. Ultra-microscale (5-25μg C) analysis of individual lipids by 14C AMS: Assessment and

Direct dating of human fossils.

PubMed

Grün, Rainer

2006-01-01

The methods that can be used for the direct dating of human remains comprise of radiocarbon, U-series, electron spin resonance (ESR), and amino acid racemization (AAR). This review gives an introduction to these methods in the context of dating human bones and teeth. Recent advances in ultrafiltration techniques have expanded the dating range of radiocarbon. It now seems feasible to reliably date bones up to 55,000 years. New developments in laser ablation mass spectrometry permit the in situ analysis of U-series isotopes, thus providing a rapid and virtually non-destructive dating method back to about 300,000 years. This is of particular importance when used in conjunction with non-destructive ESR analysis. New approaches in AAR analysis may lead to a renaissance of this method. The potential and present limitations of these direct dating techniques are discussed for sites relevant to the reconstruction of modern human evolution, including Florisbad, Border Cave, Tabun, Skhul, Qafzeh, Vindija, Banyoles, and Lake Mungo. (c) 2006 Wiley-Liss, Inc.

Radiocarbon dating of dissolved inorganic carbon in groundwater from confined parts of the Upper Floridan aquifer, Florida, USA

USGS Publications Warehouse

Plummer, Niel; Sprinkle, C.L.

2001-01-01

Geochemical reaction models were evaluated to improve radiocarbon dating of dissolved inorganic carbon (DIC) in groundwater from confined parts of the Upper Floridan aquifer in central and northeastern Florida, USA. The predominant geochemical reactions affecting the 14C activity of DIC include (1) dissolution of dolomite and anhydrite with calcite precipitation (dedolomitization), (2) sulfate reduction accompanying microbial degradation of organic carbon, (3) recrystallization of calcite (isotopic exchange), and (4) mixing of fresh water with as much as 7% saline water in some coastal areas. The calculated cumulative net mineral transfers are negligibly small in upgradient parts of the aquifer and increase significantly in downgradient parts of the aquifer, reflecting, at least in part, upward leakage from the Lower Floridan aquifer and circulation that contacted middle confining units in the Floridan aquifer system. The adjusted radiocarbon ages are independent of flow path and represent travel times of water from the recharge area to the sample point in the aquifer. Downgradient from Polk City (adjusted age 1.7 ka) and Keystone Heights (adjusted age 0.4 ka), 14 of the 22 waters have adjusted 14C ages of 20-30 ka, indicating that most of the fresh-water resource in the Upper Floridan aquifer today was recharged during the last glacial period. All of the paleowaters are enriched in 18O and 2H relative to modern infiltration, with maximum enrichment in ??18O of approximately 2.0%o.

Opportunities in low-level radiocarbon microtracing: applications and new technology

PubMed Central

Vuong, Le Thuy; Song, Qi; Lee, Hee Joo; Roffel, Ad F; Shin, Seok-Ho; Shin, Young G; Dueker, Stephen R

2016-01-01

14C-radiolabeled (radiocarbon) drug studies are central to defining the disposition of therapeutics in clinical development. Concerns over radiation, however, have dissuaded investigators from conducting these studies as often as their utility may merit. Accelerator mass spectrometry (AMS), originally designed for carbon dating and geochronology, has changed the outlook for in-human radiolabeled testing. The high sensitivity of AMS affords human clinical testing with vastly reduced radiative (microtracing) and chemical exposures (microdosing). Early iterations of AMS were unsuitable for routine biomedical use due to the instruments’ large size and associated per sample costs. The situation is changing with advances in the core and peripheral instrumentation. We review the important milestones in applied AMS research and recent advances in the core technology platform. We also look ahead to an entirely new class of 14C detection systems that use lasers to measure carbon dioxide in small gas cells. PMID:28031933

A coherent high-precision radiocarbon chronology for the Late-glacial sequence at Sluggan Bog, Co. Antrim, Northern Ireland

NASA Astrophysics Data System (ADS)

Lowe, J. J.; Walker, M. J. C.; Scott, E. M.; Harkness, D. D.; Bryant, C. L.; Davies, S. M.

2004-02-01

Seventy-five radiocarbon dates are presented from Sluggan Bog in Co. Antrim, Northern Ireland. The Holocene peats are underlain by Late-glacial sediments, which also appear to have accumulated largely in a mire environment. The radiocarbon dates, from the Late-glacial and early Holocene part of the profile, were obtained from the humic and humin fractions of the sedimentary matrix, and from plant macrofossils. The last-named were dated by AMS and the sediment samples by radiometric (beta counting) methods. Age-depth models for the three dating series show a very high level of agreement between the two fractions and the macrofossils. No statistically significant difference is found between the beta counting and AMS results. Three tephras were located in the profile, the uppermost of which is in a stratigraphical position suggestive of the Vedde Ash, but the geochemical and radiocarbon evidence do not support this interpretation. The lower ashes are in the correct stratigraphical position for the Laacher See and Borrobol tephras, attributions substantiated by the radiocarbon evidence, but not by the geochemical data. The Sluggan sequence has generated one of the most internally consistent radiocarbon chronologies for any Late-glacial site in the British Isles, and it is suggested that in future more effort should be devoted to the search for, and analysis of, Late-glacial mire sequences, rather than the limnic records that have formed the principal focus of Late-glacial investigations hitherto. Copyright

An effective method of UV-oxidation of dissolved organic carbon in natural waters for radiocarbon analysis by accelerator mass spectrometry

NASA Astrophysics Data System (ADS)

Xue, Yuejun; Ge, Tiantian; Wang, Xuchen

2015-12-01

Radiocarbon (14C) measurement of dissolved organic carbon (DOC) is a very powerful tool to study the sources, transformation and cycling of carbon in the ocean. The technique, however, remains great challenges for complete and successful oxidation of sufficient DOC with low blanks for high precision carbon isotopic ratio analysis, largely due to the overwhelming proportion of salts and low DOC concentrations in the ocean. In this paper, we report an effective UV-Oxidation method for oxidizing DOC in natural waters for radiocarbon analysis by accelerator mass spectrometry (AMS). The UV-oxidation system and method show 95%±4% oxidation efficiency and high reproducibility for DOC in both river and seawater samples. The blanks associated with the method was also low (about 3 µg C) that is critical for 14C analysis. As a great advantage of the method, multiple water samples can be oxidized at the same time so it reduces the sample processing time substantially compared with other UV-oxidation method currently being used in other laboratories. We have used the system and method for 14C studies of DOC in rivers, estuaries, and oceanic environments and have received promise results.

Radiocarbon dating, chronologic framework, and changes in accumulation rates of holocene estuarine sediments from Chesapeake Bay

USGS Publications Warehouse

Colman, Steven M.; Baucom, P.C.; Bratton, J.F.; Cronin, T. M.; McGeehin, J.P.; Willard, D.; Zimmerman, A.R.; Vogt, P.R.

2002-01-01

Rapidly accumulating Holocene sediments in estuaries commonly are difficult to sample and date. In Chesapeake Bay, we obtained sediment cores as much as 20 m in length and used numerous radiocarbon ages measured by accelarator mass spectrometry methods to provide the first detailed chronologies of Holocene sediment accumulation in the bay. Carbon in these sediments is a complex mixture of materials from a variety of sources. Analyses of different components of the sediments show that total organic carbon ages are largely unreliable, because much of the carbon (including coal) has been transported to the bay from upstream sources and is older than sediments in which it was deposited. Mollusk shells (clams, oysters) and foraminifera appear to give reliable results, although reworking and burrowing are potential problems. Analyses of museum specimens collected alive before atmospheric nuclear testing suggest that the standard reservoir correction for marine samples is appropriate for middle to lower Chesapeake Bay. The biogenic carbonate radiocarbon ages are compatible with 210 Pb and 137 Cs data and pollen stratigraphy from the same sites. Post-settlement changes in sediment transport and accumulation is an important environmental issue in many estuaries, including the Chesapeake. Our data show that large variations in sediment mass accumulation rates occur among sites. At shallow water sites, local factors seem to control changes in accumulation rates with time. Our two relatively deep-water sites in the axial channel of the bay have different long-term average accumulation rates, but the history of sediment accumulation at these sites appears to reflect overall conditions in the bay. Mass accumulation rates at the two deep-water sites rapidly increased by about fourfold coincident with widespread land clearance for agriculture in the Chesapeake watershed.

The Middle to Upper Paleolithic transition: dating, stratigraphy, and isochronous markers.

PubMed

Blockley, S P E; Ramsey, C Bronk; Higham, T F G

2008-11-01

Accurate and precise dating is vital to our understanding of the Middle to Upper Paleolithic transition. There are, however, a number of uncertainties in the chronologies currently available for this period. We attempt to examine these uncertainties by utilizing a number of recent developments in the field. These include: the precise dating of the Campanian Ignimbrite (CI) tephra by 40Ar/39Ar; the tracing of this tephra to a number of deposits that are radiocarbon dated; the publication of revised radiocarbon calibration data for the period, showing a much better convergence with other available data than during the recent IntCal comparison; and a layer-counted ice-core chronology extending beyond 40,000cal BP. Our data comparisons suggest that a reasonable overall convergence between calibrated radiocarbon ages and calendar dates is possible using the new curves. Additionally, we suggest that charcoal-based radiocarbon ages, as well as bone-based radiocarbon determinations, require cautious interpretation in this period. Potentially, these issues extend far beyond the sites in this study and should be of serious concern to archaeologists studying the Middle to Upper Paleolithic. We conclude by outlining a strategy for moving the science forward by a closer integration of archaeology, chronology, and stratigraphy.

Radiocarbon content in the annual tree rings during last 150 years and time variation of cosmic rays

NASA Technical Reports Server (NTRS)

Kocharov, G. E.; Metskvarishvili, R. Y.; Tsereteli, S. L.

1985-01-01

The results of the high accuracy measurements of radiocarbon abundance in precisely dated tree rings in the interval 1800 to 1950 yrs are discussed. Radiocarbon content caused by solar activity is established. The temporal dependence of cosmic rays is constructed, by use of radio abundance data.

Radiocarbon chronology of Black Sea sediments

NASA Astrophysics Data System (ADS)

Jones, Glenn A.; Gagnon, Alan R.

1994-03-01

Accelerator Mass Spectrometer (AMS) radiocarbon analyses have been made on 102 samples from 12 sediment cores and 23 samples from two water column profiles. These materials, collected during the first leg of the 1988 joint U.S.-Turkish Black Sea Expedition, provide the most comprehensive radiocarbon chronology of Black Sea sediments yet attempted. Radiocarbon analyses from carefully collected box cores and a mollusc shell collected live in 1931 suggest the prebomb surface waters had a Δ 14C value of -55% (460 years) and that the maximum detrital correction for radiocarbon ages of Unit I sediments is 580 years for the organic carbon and 260 years for the carbonate fractions. Evidence does not support the 1430-2000 years pre-bomb surface water and/or detrital corrections argued for in past studies. The best estimates for the age of the beginning of the final invasion of the coccolithophore Emiliania huxleyi (Unit 1/2 boundary of Ross and DEGENS, 1974, The Black Sea—geology, chemistry and biology, pp. 183-199) and the age of the first invasion of E. huxeleyi (Unit I/II boundary of HAYet al., 1991, Deep-Sea Research, 38, S1211-S1235) are 1635 ± 60 and 2720 ± 160 years BP, respectively. Sapropel formation began at approximately 7540 ± 130 years BP at all depths in the basin, a pattern in disagreement with those predicted by existing time-evolution models of sapropel formation for this basin. Our data suggest that the oxic-anoxic interface has remained relatively stable throughout the Holocene, is controlled largely by the physical oceanography of the basin, and has not evolved as assumed by previous workers.

New radiocarbon measurement methods in the Hertelendi Laboratory, Hungary

NASA Astrophysics Data System (ADS)

Janovics, Róbert; Major, István; Rinyu, László; Veres, Mihály; Molnár, Mihály

2013-04-01

In this paper we present two very different and novel methods for C-14 measurement from dissolved inorganic carbonate (DIC) of water samples. A new LSC sample preparation method for liquid scintillation C-14 measurements was implemented in the ATOMKI. The first method uses direct absorption into a special absorbent (Carbosorb E®) and a following liquid scintillation measurement. Typical sample size is 20-40 litre of water. The developed CO2 absorption method is fast, and simple. The C-14 activities is measured by an ultra low background LSC (TRI-CARB 3170 TR/SL, Perkin Elmer) including quenching parameter (tSIE).The corresponding limit of C-14 dating is 31200 year. Several tests were executed with old borehole CO2 gas without significant content of C-14 and also performed on samples of known C-14 activities between 29 and 7000 pMC, previously measured by GPC. The combined uncertainty of the described determination is about 2 % in the case of recent carbon. It is a very cost-effective and easy to use method based on a novel and simple static absorption process for the CO2 extracted from groundwater. The other very sensitive method is based on accelerator mass spectrometry (AMS) using gas ion source. This method does not require graphite generation and a small volume of water sample (1-20mL) is enough for the radiocarbon measurement. The procedure is very similar to pre-treatment of carbonate contained sample preparation for stable isotope measurement with gasbench technique. We applied a MICADAS type accelerator mass spectrometry (AMS) with gas ion source for C-14 analysis. The radiocarbon content of water was sat free with phosphoric acid and then the headspace gas was rinsed vials. The whole measurement needs only 20 min of each sample. The precision of measurement is better than 1% for modern samples. The preparation is vastly reduced compared to the other AMS methods and principally allows fully automated measurements of groundwater samples with an auto

Age estimation in forensic sciences: application of combined aspartic acid racemization and radiocarbon analysis.

PubMed

Alkass, Kanar; Buchholz, Bruce A; Ohtani, Susumu; Yamamoto, Toshiharu; Druid, Henrik; Spalding, Kirsty L

2010-05-01

Age determination of unknown human bodies is important in the setting of a crime investigation or a mass disaster because the age at death, birth date, and year of death as well as gender can guide investigators to the correct identity among a large number of possible matches. Traditional morphological methods used by anthropologists to determine age are often imprecise, whereas chemical analysis of tooth dentin, such as aspartic acid racemization, has shown reproducible and more precise results. In this study, we analyzed teeth from Swedish individuals using both aspartic acid racemization and radiocarbon methodologies. The rationale behind using radiocarbon analysis is that aboveground testing of nuclear weapons during the cold war (1955-1963) caused an extreme increase in global levels of carbon-14 ((14)C), which has been carefully recorded over time. Forty-four teeth from 41 individuals were analyzed using aspartic acid racemization analysis of tooth crown dentin or radiocarbon analysis of enamel, and 10 of these were split and subjected to both radiocarbon and racemization analysis. Combined analysis showed that the two methods correlated well (R(2) = 0.66, p < 0.05). Radiocarbon analysis showed an excellent precision with an overall absolute error of 1.0 +/- 0.6 years. Aspartic acid racemization also showed a good precision with an overall absolute error of 5.4 +/- 4.2 years. Whereas radiocarbon analysis gives an estimated year of birth, racemization analysis indicates the chronological age of the individual at the time of death. We show how these methods in combination can also assist in the estimation of date of death of an unidentified victim. This strategy can be of significant assistance in forensic casework involving dead victim identification.

The role of inter-comparisons in radiocarbon quality assurance

NASA Astrophysics Data System (ADS)

Scott, Marian; Cook, Gordon; Naysmith, Philip

2016-04-01

Radiocarbon dating is used widely in many geochronology projects as a basis for the creation and testing of chronological constructs. Radiocarbon measurements are by their nature complex and the degree of sample pre-treatment varies considerably depending on the material. Within the UK and Europe, there are a number of well-established laboratories and increasingly, scientists are not just commissioning new dates, but also using statistical modelling of assemblages of dates, perhaps measured in different laboratories, to provide formal date estimates for their investigations. The issue of comparability of measurements (and thus bias, accuracy and precision of measurement) from the diverse laboratories is one which has been the focus of some attention both within the 14C community and the wider user communities for some time. As a result of this but also as part of laboratory benchmarking and quality assurance, the 14C community has undertaken a wide-scale, far-reaching and evolving programme of inter-comparisons, to the benefit of laboratories and users alike. This paper presents the results from the most recent exercise SIRI. The objectives of SIRI included, through choice of material, to contribute to the discussion concerning laboratory offsets and error multipliers in the context of IntCal (the International Calibration Programme) and to gain a better understanding of differences in background derived from a range of infinite age material types.

Age validation of canary rockfish (Sebastes pinniger) using two independent otolith techniques: lead-radium and bomb radiocarbon dating.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andrews, A H; Kerr, L A; Cailliet, G M

2007-11-04

Canary rockfish (Sebastes pinniger) have long been an important part of recreational and commercial rockfish fishing from southeast Alaska to southern California, but localized stock abundances have declined considerably. Based on age estimates from otoliths and other structures, lifespan estimates vary from about 20 years to over 80 years. For the purpose of monitoring stocks, age composition is routinely estimated by counting growth zones in otoliths; however, age estimation procedures and lifespan estimates remain largely unvalidated. Typical age validation techniques have limited application for canary rockfish because they are deep dwelling and may be long lived. In this study, themore » unaged otolith of the pair from fish aged at the Department of Fisheries and Oceans Canada was used in one of two age validation techniques: (1) lead-radium dating and (2) bomb radiocarbon ({sup 14}C) dating. Age estimate accuracy and the validity of age estimation procedures were validated based on the results from each technique. Lead-radium dating proved successful in determining a minimum estimate of lifespan was 53 years and provided support for age estimation procedures up to about 50-60 years. These findings were further supported by {Delta}{sup 14}C data, which indicated a minimum estimate of lifespan was 44 {+-} 3 years. Both techniques validate, to differing degrees, age estimation procedures and provide support for inferring that canary rockfish can live more than 80 years.« less

African Baobabs with False Inner Cavities: The Radiocarbon Investigation of the Lebombo Eco Trail Baobab

PubMed Central

Patrut, Adrian; Woodborne, Stephan; von Reden, Karl F.; Hall, Grant; Hofmeyr, Michele; Lowy, Daniel A.; Patrut, Roxana T.

2015-01-01

The article reports the radiocarbon investigation results of the Lebombo Eco Trail tree, a representative African baobab from Mozambique. Several wood samples collected from the large inner cavity and from the outer part of the tree were investigated by AMS radiocarbon dating. According to dating results, the age values of all samples increase from the sampling point with the distance into the wood. For samples collected from the cavity walls, the increase of age values with the distance into the wood (up to a point of maximum age) represents a major anomaly. The only realistic explanation for this anomaly is that such inner cavities are, in fact, natural empty spaces between several fused stems disposed in a ring-shaped structure. We named them false cavities. Several important differences between normal cavities and false cavities are presented. Eventually, we dated other African baobabs with false inner cavities. We found that this new architecture enables baobabs to reach large sizes and old ages. The radiocarbon date of the oldest sample was 1425 ± 24 BP, which corresponds to a calibrated age of 1355 ± 15 yr. The dating results also show that the Lebombo baobab consists of five fused stems, with ages between 900 and 1400 years; these five stems build the complete ring. The ring and the false cavity closed 800–900 years ago. The results also indicate that the stems stopped growing toward the false cavity over the past 500 years. PMID:25621989

Improved radiocarbon dating for contaminated archaeological bone collagen, silk, wool and hair samples via cross-flow nanofiltrated amino acids.

PubMed

Boudin, Mathieu; Boeckx, Pascal; Vandenabeele, Peter; Van Strydonck, Mark

2013-09-30

Radiocarbon dating and stable isotope analyses of bone collagen, wool, hair and silk contaminated with extraneous carbon (e.g. humic substances) does not yield reliable results if these materials are pre-treated using conventional methods. A cross-flow nanofiltration method was developed that can be applied to various protein materials like collagen, hair, silk, wool and leather, and should be able to remove low-molecular and high-molecular weight contaminants. To avoid extraneous carbon contamination via the filter a ceramic filter (molecular weight cut-off of 200 Da) was used. The amino acids, released by hot acid hydrolysis of the protein material, were collected in the permeate and contaminants in the retentate (>200 Da). (14)C-dating results for various contaminated archaeological samples were compared for bulk material (pre-treated with the conventional methods) and for cross-flow nanofiltrated amino acids (permeate) originating from the same samples. Contamination and quality control of (14)C dates of bulk and permeate samples were obtained by measuring C:N ratios, fluorescence spectra, and δ(13)C and δ(15)N values of the samples. Cross-flow nanofiltration decreases the C:N ratio which means that contaminants have been removed. Cross-flow nanofiltration clearly improved sample quality and (14)C results. It is a quick and non-labor-intensive technique and can easily be implemented in any (14)C and stable isotope laboratory for routine sample pre-treatment analyses. Copyright © 2013 John Wiley & Sons, Ltd.

Optical Dating of Holocene Dune Sands in the Ferris Dune Field, Wyoming

NASA Astrophysics Data System (ADS)

Stokes, Stephen; Gaylord, David R.

1993-05-01

Optical dating of late Quaternary quartz dune sands from the Clear Creek portion of Ferris dune field, Wyoming, demonstrates the considerable potential of the technique as a chronostratigraphic tool. A sequence of radiocarbon-dated Holocene interdune strata permit optical dating of the intercalated dune sand to be tested; the concordance is good. The optical dates for the aeolian deposits not datable by radiocarbon suggest that aeolian sedimentation at Clear Creek peaked during two relatively short phases at ca. 8500 and 4000 yr B.P. The dates indicate that aeolian accumulation maxima (at least in the Clear Creek area) may not be synchronous with previously defined phases of marked aridity.

Investigations on alluvial deposits through borehole stratigraphy, radiocarbon dating and passive seismic technique (Carnic Alps, NE Italy)

NASA Astrophysics Data System (ADS)

Viero, Alessia; Marchi, Lorenzo; Cavalli, Marco; Crema, Stefano; Fontana, Alessandro; Mozzi, Paolo; Venturini, Corrado

2016-04-01

Alluvial sediment investigations provide fundamental tools to infer the processes that control geomorphological evolution of mountain environments. By analyzing sediment stratigraphy in depth, it is possible to retrieve the source, the geology, the time of deposition, the relative distance travelled by material as well as to distinguish among different type of transport (i.e., gravitational, fluvial or glacial). In this work, we present a combination of log stratigraphy, radiocarbon dating and geophysical surveys carried out on the valley floor of the But River (Carnic Alps, North East Italy). The But River basin drains an area of 326 km2 with a range in elevation from 2769 to 323 m a.s.l.; the bedrock mainly consists of carbonates and quartz arenites with minor inclusions of effusive rocks. After Pleistocene the gravitational deposits from mountain slopes have impounded the But River several times. In particular, we analyzed a sector of the upper portion of the But valley close to the confluence of the Moscardo Torrent, frequently affected by debris flows. A borehole was drilled in the But River floodplain, at the intersection with the Moscardo Torrent alluvial fan, down to a depth of 80 m. The analysis of the core samples allowed discerning three sedimentary levels rich in clay and organic materials, which testify the presence of small dam lakes, originated from the Moscardo debris-flow deposits. Three samples of wood and plant debris were collected from 13, 14 and 23 m of depth, respectively. They were analyzed through radiocarbon dating in order to determine the age of the lakes and, thus, to infer the activity of the debris flows building the Moscardo cone. The calibrated ages of the 3 samples are close to the younger limit of the radiocarbon method indicating a fast aggradation of the valley floor, starting from a period ranging between 1450 - 1632 AD. Historical maps and documents confirm the presence of the lakes until 19th century and they permit to assess

Direct radiocarbon dating and genetic analyses on the purported Neanderthal mandible from the Monti Lessini (Italy).

PubMed

Talamo, Sahra; Hajdinjak, Mateja; Mannino, Marcello A; Fasani, Leone; Welker, Frido; Martini, Fabio; Romagnoli, Francesca; Zorzin, Roberto; Meyer, Matthias; Hublin, Jean-Jacques

2016-07-08

Anatomically modern humans replaced Neanderthals in Europe around 40,000 years ago. The demise of the Neanderthals and the nature of the possible relationship with anatomically modern humans has captured our imagination and stimulated research for more than a century now. Recent chronological studies suggest a possible overlap between Neanderthals and anatomically modern humans of more than 5,000 years. Analyses of ancient genome sequences from both groups have shown that they interbred multiple times, including in Europe. A potential place of interbreeding is the notable Palaeolithic site of Riparo Mezzena in Northern Italy. In order to improve our understanding of prehistoric occupation at Mezzena, we analysed the human mandible and several cranial fragments from the site using radiocarbon dating, ancient DNA, ZooMS and isotope analyses. We also performed a more detailed investigation of the lithic assemblage of layer I. Surprisingly we found that the Riparo Mezzena mandible is not from a Neanderthal but belonged to an anatomically modern human. Furthermore, we found no evidence for the presence of Neanderthal remains among 11 of the 13 cranial and post-cranial fragments re-investigated in this study.

Direct radiocarbon dating and genetic analyses on the purported Neanderthal mandible from the Monti Lessini (Italy)

PubMed Central

Talamo, Sahra; Hajdinjak, Mateja; Mannino, Marcello A.; Fasani, Leone; Welker, Frido; Martini, Fabio; Romagnoli, Francesca; Zorzin, Roberto; Meyer, Matthias; Hublin, Jean-Jacques

2016-01-01

Anatomically modern humans replaced Neanderthals in Europe around 40,000 years ago. The demise of the Neanderthals and the nature of the possible relationship with anatomically modern humans has captured our imagination and stimulated research for more than a century now. Recent chronological studies suggest a possible overlap between Neanderthals and anatomically modern humans of more than 5,000 years. Analyses of ancient genome sequences from both groups have shown that they interbred multiple times, including in Europe. A potential place of interbreeding is the notable Palaeolithic site of Riparo Mezzena in Northern Italy. In order to improve our understanding of prehistoric occupation at Mezzena, we analysed the human mandible and several cranial fragments from the site using radiocarbon dating, ancient DNA, ZooMS and isotope analyses. We also performed a more detailed investigation of the lithic assemblage of layer I. Surprisingly we found that the Riparo Mezzena mandible is not from a Neanderthal but belonged to an anatomically modern human. Furthermore, we found no evidence for the presence of Neanderthal remains among 11 of the 13 cranial and post-cranial fragments re-investigated in this study. PMID:27389305

Blank corrections for ramped pyrolysis radiocarbon dating of sedimentary and soil organic carbon.

PubMed

Fernandez, Alvaro; Santos, Guaciara M; Williams, Elizabeth K; Pendergraft, Matthew A; Vetter, Lael; Rosenheim, Brad E

2014-12-16

Ramped pyrolysis (RP) targets distinct components of soil and sedimentary organic carbon based on their thermochemical stabilities and allows the determination of the full spectrum of radiocarbon ((14)C) ages present in a soil or sediment sample. Extending the method into realms where more precise ages are needed or where smaller samples need to be measured involves better understanding of the blank contamination associated with the method. Here, we use a compiled data set of RP measurements of samples of known age to evaluate the mass of the carbon blank and its associated (14)C signature, and to assess the performance of the RP system. We estimate blank contamination during RP using two methods, the modern-dead and the isotope dilution method. Our results indicate that during one complete RP run samples are contaminated by 8.8 ± 4.4 μg (time-dependent) of modern carbon (MC, fM ∼ 1) and 4.1 ± 5.5 μg (time-independent) of dead carbon (DC, fM ∼ 0). We find that the modern-dead method provides more accurate estimates of uncertainties in blank contamination; therefore, the isotope dilution method should be used with caution when the variability of the blank is high. Additionally, we show that RP can routinely produce accurate (14)C dates with precisions ∼100 (14)C years for materials deposited in the last 10,000 years and ∼300 (14)C years for carbon with (14)C ages of up to 20,000 years.

Co-development of Conceptual Understanding and Critical Attitude: Analyzing texts on radiocarbon dating

NASA Astrophysics Data System (ADS)

Décamp, N.; Viennot, L.

2015-08-01

This research documents the impact of a teaching interview aimed at developing a critical attitude in students, and focused on a particular topic: radiocarbon dating. This teaching interview is designed to observe students' reaction to limited written explanations of the phenomenon under study, and their possible frustration or intellectual satisfaction in relation to these texts. We aim to document the possible link between students' developing conceptual understanding of a topic and their ability to express their frustration when presented with very incomplete explanations, or their intellectual satisfaction when presented with complete explanation. As a side product, we intend to observe some of their a priori ideas concerning this topic. Ten teaching interviews conducted with fourth-year University students were recorded, transcribed and coded. Beyond a series of results concerning students' a priori understanding of the domain, the analysis of the interviews suggests that, when students are presented with texts of increasing completeness and discuss these with the interviewer, their critical reactions evolve in time in a very specific way. We propose a tentative model for this co-evolution of student conceptual command and critical stance. The discussion bears on possible interpretations for the 'anesthesia of judgment' observed in most students at the beginning of the interview, and for a few of them throughout the discussion. Keeping in mind the 'competence vs concepts' current alternative, the conditions that seem to free students' critical potential are analyzed in relation to their evolving command of the topic and their degree of intellectual satisfaction.

The AD 1300 1700 eruptive periods at Tungurahua volcano, Ecuador, revealed by historical narratives, stratigraphy and radiocarbon dating

NASA Astrophysics Data System (ADS)

Le Pennec, J.-L.; Jaya, D.; Samaniego, P.; Ramón, P.; Moreno Yánez, S.; Egred, J.; van der Plicht, J.

2008-09-01

Tungurahua is a frequently active and hazardous volcano of the Ecuadorian Andes that has experienced pyroclastic flow-forming eruption in 1773, 1886, 1916-18 and 2006-08. Earlier eruptions in Late Pre-Hispanic and Early Colonial times have remained poorly known and are debated in the literature. To reconstruct the eruptive chronology in that time interval we examine relevant historical narratives recently found in Sevilla, Spain, and Rome, Italy, and we combine stratigraphic field constraints with 22 new radiocarbon age determinations. Results show that pyroclastic flow-forming eruptions and tephra falls took place repeatedly since ~ 700 14C yr BP, when the Tungurahua region was already populated. Radiocarbon ages averaging around 625 yr BP reveal a period of notable eruptive activity in the 14th century (Late Integration cultural period). The associated andesitic eruptions produced ash and scoria falls of regional extent and left scoria flow deposits on the western flanks of the edifice. The fact that Tungurahua was known by the Puruhás Indians as a volcano at the time of the Spanish Conquest in 1533 perhaps refers to these eruptions. A group of ages ranging from 380 to 270 yr BP is attributed to younger periods of activity that also predates the 1773 event, and calibration results yield eruption dates from late 15th to late 17th centuries (i.e. Inca and Early Colonial Periods). The historical narratives mention an Early Colonial eruption between the Spanish Conquest and the end of the 16th century, followed by a distinct eruptive period in the 1640s. The descriptions are vague but point to destructive eruptions likely accompanied by pyroclastic flows. The dated tephras consist of andesitic scoria flow deposits and the contemporaneous fallout layers occur to the west. These findings reveal that the eruption recurrence rate at Tungurahua is at least one pyroclastic flow-forming event per century since the 13th century and the occurrence of such eruptions in 2006

Agriculture, population growth, and statistical analysis of the radiocarbon record.

PubMed

Zahid, H Jabran; Robinson, Erick; Kelly, Robert L

2016-01-26

The human population has grown significantly since the onset of the Holocene about 12,000 y ago. Despite decades of research, the factors determining prehistoric population growth remain uncertain. Here, we examine measurements of the rate of growth of the prehistoric human population based on statistical analysis of the radiocarbon record. We find that, during most of the Holocene, human populations worldwide grew at a long-term annual rate of 0.04%. Statistical analysis of the radiocarbon record shows that transitioning farming societies experienced the same rate of growth as contemporaneous foraging societies. The same rate of growth measured for populations dwelling in a range of environments and practicing a variety of subsistence strategies suggests that the global climate and/or endogenous biological factors, not adaptability to local environment or subsistence practices, regulated the long-term growth of the human population during most of the Holocene. Our results demonstrate that statistical analyses of large ensembles of radiocarbon dates are robust and valuable for quantitatively investigating the demography of prehistoric human populations worldwide.

Estimation of past intermittent methane seep activity using radiocarbon dating of Calyptogena shells in the eastern Nankai subduction zone

NASA Astrophysics Data System (ADS)

Yagasaki, K.; Ashi, J.; Yokoyama, Y.; Miyairi, Y.; Kuramoto, S.

2013-12-01

alive shell age away from the fossilsed shell age. Preliminary results of radiocarbon dating indicate a distinct age gap of several hundred years between the formerly alive shells (~ 1126calAD -1276calAD) and the fossil shells (~ 671calAD - 797calAD).

Age estimation in forensic sciences: Application of combined aspartic acid racemization and radiocarbon analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alkass, K; Buchholz, B A; Ohtani, S

Age determination of unknown human bodies is important in the setting of a crime investigation or a mass disaster, since the age at death, birth date and year of death, as well as gender, can guide investigators to the correct identity among a large number of possible matches. Traditional morphological methods used by anthropologists to determine age are often imprecise, whereas chemical analysis of tooth dentin, such as aspartic acid racemization has shown reproducible and more precise results. In this paper we analyze teeth from Swedish individuals using both aspartic acid racemization and radiocarbon methodologies. The rationale behind using radiocarbonmore » analysis is that above-ground testing of nuclear weapons during the cold war (1955-1963) caused an extreme increase in global levels of carbon-14 ({sup 14}C) which have been carefully recorded over time. Forty-four teeth from 41 individuals were analyzed using aspartic acid racemization analysis of tooth crown dentin or radiocarbon analysis of enamel and ten of these were split and subjected to both radiocarbon and racemization analysis. Combined analysis showed that the two methods correlated well (R2=0.66, p < 0.05). Radiocarbon analysis showed an excellent precision with an overall absolute error of 0.6 {+-} 04 years. Aspartic acid racemization also showed a good precision with an overall absolute error of 5.4 {+-} 4.2 years. Whereas radiocarbon analysis gives an estimated year of birth, racemization analysis indicates the chronological age of the individual at the time of death. We show how these methods in combination can also assist in the estimation of date of death of an unidentified victim. This strategy can be of significant assistance in forensic casework involving dead victim identification.« less

Grass material as process standard for compound-specific radiocarbon analysis

NASA Astrophysics Data System (ADS)

Cisneros-Dozal, Malu; Xu, Xiaomei; Bryant, Charlotte; Pearson, Emma; Dungait, Jennifer

2015-04-01

Compound-specific radiocarbon analysis (CSRA) is a powerful tool to study the carbon cycle and/or as a dating technique in paleoclimate reconstructions. The radiocarbon value of individual compounds can provide insight into turnover times, organic matter sources and in specific cases can be used to establish chronologies when traditional dating materials (e.g. macrofossils, pollen, charcoal) are not available. The isolation of compounds (or group of compounds) from parent material (e.g. soil, plant) for radiocarbon analysis can, however, introduce carbon contamination through chemical separation steps and preparative capillary gas chromatography (PCGC). In addition, the compounds of interest are often in low abundance which amplifies the contamination effect. The extraneous carbon can be of modern 14C age and/or 14C -free and its amount and 14C value must be determined for a given system/isolation procedure in order to report accurate 14C values. This can be achieved by using adequate standard materials but, by contrast with traditional radiocarbon dating, there are not established reference standards for CSRA work, in part because the type of standard material depends on the compounds of interest and the isolation procedure. Here we evaluate the use of n-alkanes extracted from single-year growth grass as modern process standard material for CSRA using PCGC isolation. The grass material has a known 14C value of 1.224 ± 0.006 fraction modern (FM) and the individual n-alkanes are expected to have a similar 14C value. In order to correct for the addition of extraneous carbon during PCGC isolation of the n-alkanes, we used commercially available compounds of modern 14C content and 14C -free (adipic acid, FM= 0.0015 ± 0.0001 and docosane, FM=1.059 ± 0.003) to evaluate our PCGC procedure. The corrected 14C values of the isolated n-alkanes extracted from the modern grass are within one sigma of the grass bulk 14C value for n-C29 and within two sigma for n-C23-C27, C31

Accelerator mass spectrometry for measurement of long-lived radioisotopes.

PubMed

Elmore, D; Phillips, F M

1987-05-01

Particle accelerators, such as those built for research in nuclear physics, can also be used together with magnetic and electrostatic mass analyzers to measure rare isotopes at very low abundance ratios. All molecular ions can be eliminated when accelerated to energies of millions of electron volts. Some atomic isobars can be eliminated with the use of negative ions; others can be separated at high energies by measuring their rate of energy loss in a detector. The long-lived radioisotopes (10)Be, (14)C,(26)A1, 36Cl, and (129)1 can now be measured in small natural samples having isotopic abundances in the range 10(-12) to 10(- 5) and as few as 10(5) atoms. In the past few years, research applications of accelerator mass spectrometry have been concentrated in the earth sciences (climatology, cosmochemistry, environmental chemistry, geochronology, glaciology, hydrology, igneous petrogenesis, minerals exploration, sedimentology, and volcanology), in anthropology and archeology (radiocarbon dating), and in physics (searches for exotic particles and measurement of halflives). In addition, accelerator mass spectrometry may become an important tool for the materials and biological sciences.

Accelerator Mass Spectrometry for Measurement of Long-Lived Radioisotopes

NASA Astrophysics Data System (ADS)

Elmore, David; Phillips, Fred M.

1987-05-01

Particle accelerators, such as those built for research in nuclear physics, can also be used together with magnetic and electrostatic mass analyzers to measure rare isotopes at very low abundance ratios. All molecular ions can be eliminated when accelerated to energies of millions of electron volts. Some atomic isobars can be eliminated with the use of negative ions; others can be separated at high energies by measuring their rate of energy loss in a detector. The long-lived radioisotopes 10Be, 14C, 26Al, 36Cl, and 129I can now be measured in small natural samples having isotopic abundances in the range 10-12 to 10-15 and as few as 105 atoms. In the past few years, research applications of accelerator mass spectrometry have been concentrated in the earth sciences (climatology, cosmochemistry, environmental chemistry, geochronology, glaciology, hydrology, igneous petrogenesis, minerals exploration, sedimentology, and volcanology), in anthropology and archeology (radiocarbon dating), and in physics (searches for exotic particles and measurement of half-lives). In addition, accelerator mass spectrometry may become an important tool for the materials and biological sciences.

Rate estimates for lateral bedrock erosion based on radiocarbon ages, Duck River, Tennessee

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brakenridge, G.R.

Rates of bedrock erosion in ingrown meandering rivers can be inferred from the location of buried relict flood-plain and river-bank surfaces, associated paleosols, and radiocarbon dates. Two independent methods are used to evaluate the long-term rates of limestone bedrock erosion by the Duck River. Radiocarbon dates on samples retrieved from buried Holocene flood-plain and bank surfaces indicate lateral migration of the river bank at average rates of 0.6-1.9 m/100 yr. Such rates agree with lateral bedrock cliff erosion rates of 0.5-1.4 m/100 yr, as determined from a comparison of late Pleistocene and modern bedrock cliff and terrace scarp positions. Thesemore » results show that lateral bedrock erosion by this river could have occurred coevally with flood-plain and terrace formation and that the resulting evolution of valley meander bends carved into bedrock is similar in many respects to that of channel meanders cut into alluvium. 11 references, 5 figures.« less

Complexities in the Use of Bomb-Curve Radiocarbon to Determine Time Since Death of Human Skeletal Remains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ubelaker, D H; Buchholz, B A

2005-04-26

Atmospheric testing of nuclear weapons during the 1950s and early 1960s doubled the level of radiocarbon ({sup 14}C) in the atmosphere. From the peak in 1963, the level of {sup 14}CO{sub 2} has decreased exponentially with a mean life of about 16 years, not due to radioactive decay, but due to mixing with large marine and terrestrial carbon reservoirs. Since radiocarbon is incorporated into all living things, the bomb-pulse is an isotopic chronometer of the past half century. The absence of bomb radiocarbon in skeletonized human remains generally indicates a date of death before 1950. Comparison of the radiocarbon valuesmore » with the post 1950 bomb-curve may also help elucidate when in the post 1950 era, the individual was still alive. Such interpretation however, must consider the age at death of the individual and the type of tissue sampled.« less

Radiocarbon and stable isotope investigations at the Central Rhineland sites of Gönnersdorf and Andernach-Martinsberg, Germany.

PubMed

Stevens, Rhiannon E; O'Connell, Tamsin C; Hedges, Robert E M; Street, Martin

2009-08-01

The late glacial open-air sites of Gönnersdorf and Andernach-Martinsberg in the German Central Rhineland are well known for their Magdalenian occupation and activities. The latter site also produced evidence for a younger, Final Palaeolithic occupation of the locality by people of the Federmessergruppen. Both sites are particularly well preserved, largely due to their burial beneath volcanic deposits of the late glacial Laacher See eruption. We conducted a program of AMS radiocarbon dating and stable isotope analyses with the aim of improving understanding of the chronological history and ecological setting of the two sites. Previously published radiocarbon dates appeared to indicate that the earliest Magdalenian occupation at Gönnersdorf fell around 12,900 uncalibrated (14)C yr BP, while the earliest occupation at Andernach may have been more than 500 radiocarbon years earlier. The AMS determinations presented here revise this impression and suggest that the onset of occupation at the two sites was in fact simultaneous and prior to the warming of Greenland Interstadial GI 1e. At Gönnersdorf, a chronological hiatus exists between the main Magdalenian faunal assemblage and mega-faunal remains interpreted as collected sub-fossil material. At Andernach-Martinsberg, there is a clear chronological hiatus between the Magdalenian occupation and subsequent Federmessergruppen activities at the site. However, an intermediate radiocarbon date on an atypically preserved horse bone is suggestive of ephemeral human visits to the site between these well demonstrated phases. A date of similar age on an elk bone from Gönnersdorf may indicate broadly contemporaneous human presence at Gönnersdorf too. Stable isotope analysis of faunal remains from Gönnersdorf and Andernach-Martinsberg was conducted with the aim of both reconstructing and comparing local environmental conditions at the two sites, and also potentially identifying subtle variations in the chronological development

Radiocarbon dating of the human eye lens crystallines reveal proteins without carbon turnover throughout life.

PubMed

Lynnerup, Niels; Kjeldsen, Henrik; Heegaard, Steffen; Jacobsen, Christina; Heinemeier, Jan

2008-01-30

Lens crystallines are special proteins in the eye lens. Because the epithelial basement membrane (lens capsule) completely encloses the lens, desquamation of aging cells is impossible, and due to the complete absence of blood vessels or transport of metabolites in this area, there is no subsequent remodelling of these fibers, nor removal of degraded lens fibers. Human tissue ultimately derives its (14)C content from the atmospheric carbon dioxide. The (14)C content of the lens proteins thus reflects the atmospheric content of (14)C when the lens crystallines were formed. Precise radiocarbon dating is made possible by comparing the (14)C content of the lens crystallines to the so-called bomb pulse, i.e. a plot of the atmospheric (14)C content since the Second World War, when there was a significant increase due to nuclear-bomb testing. Since the change in concentration is significant even on a yearly basis this allows very accurate dating. Our results allow us to conclude that the crystalline formation in the lens nucleus almost entirely takes place around the time of birth, with a very small, and decreasing, continuous formation throughout life. The close relationship may be further expressed as a mathematical model, which takes into account the timing of the crystalline formation. Such a life-long permanence of human tissue has hitherto only been described for dental enamel. In confront to dental enamel it must be held in mind that the eye lens is a soft structure, subjected to almost continuous deformation, due to lens accommodation, yet its most important constituent, the lens crystalline, is never subject to turnover or remodelling once formed. The determination of the (14)C content of various tissues may be used to assess turnover rates and degree of substitution (for example for brain cell DNA). Potential targets may be nervous tissues in terms of senile or pre-senile degradation, as well as other highly specialised structures of the eyes. The precision with

Between a rock and a soft place: Using optical ages to date ancient clam gardens on the Pacific Northwest

PubMed Central

Neudorf, Christina M.; Smith, Nicole; Lepofsky, Dana; Toniello, Ginevra; Lian, Olav B.

2017-01-01

Rock-walled archaeological features are notoriously hard to date, largely because of the absence of suitable organic material for radiocarbon dating. This study demonstrates the efficacy of dating clam garden wall construction using optical dating, and uses optical ages to determine how sedimentation rates in the intertidal zone are affected by clam garden construction. Clam gardens are rock-walled, intertidal terraces that were constructed and maintained by coastal First Nation peoples to increase bivalve habitat and productivity. These features are evidence of ancient shellfish mariculture on the Pacific Northwest and, based on radiocarbon dating, date to at least the late Holocene. Optical dating exploits the luminescence signals of quartz or feldspar minerals to determine the last time the minerals were exposed to sunlight (i.e., their burial age), and thus does not require the presence of organic material. Optical ages were obtained from three clam garden sites on northern Quadra Island, British Columbia, and their reliability was assessed by comparing them to radiocarbon ages derived from shells underneath the clam garden walls, as well as below the terrace sediments. Our optical and radiocarbon ages suggest that construction of these clam garden walls commenced between ~1000 and ~1700 years ago, and our optical ages suggest that construction of the walls was likely incremental and increased sedimentation rates in the intertidal zone by up to fourfold. Results of this study show that when site characteristics are not amenable to radiocarbon dating, optical dating may be the only viable geochronometer. Furthermore, dating rock-walled marine management features and their geomorphic impact can lead to significant advances in our understanding of the intimate relationships that Indigenous peoples worldwide developed with their seascapes. PMID:28182645

Accelerator mass spectrometry.

PubMed

Hellborg, Ragnar; Skog, Göran

2008-01-01

In this overview the technique of accelerator mass spectrometry (AMS) and its use are described. AMS is a highly sensitive method of counting atoms. It is used to detect very low concentrations of natural isotopic abundances (typically in the range between 10(-12) and 10(-16)) of both radionuclides and stable nuclides. The main advantages of AMS compared to conventional radiometric methods are the use of smaller samples (mg and even sub-mg size) and shorter measuring times (less than 1 hr). The equipment used for AMS is almost exclusively based on the electrostatic tandem accelerator, although some of the newest systems are based on a slightly different principle. Dedicated accelerators as well as older "nuclear physics machines" can be found in the 80 or so AMS laboratories in existence today. The most widely used isotope studied with AMS is 14C. Besides radiocarbon dating this isotope is used in climate studies, biomedicine applications and many other fields. More than 100,000 14C samples are measured per year. Other isotopes studied include 10Be, 26Al, 36Cl, 41Ca, 59Ni, 129I, U, and Pu. Although these measurements are important, the number of samples of these other isotopes measured each year is estimated to be less than 10% of the number of 14C samples. Copyright 2008 Wiley Periodicals, Inc.

14C dates from Tel Rehov: Iron-Age chronology, pharaohs, and Hebrew kings.

PubMed

Bruins, Hendrik J; van der Plicht, Johannes; Mazar, Amihai

2003-04-11

Stratified radiocarbon dates provide an independent chronological link between archaeological layers and historical data. The invasion by Pharaoh Shoshenq I (Shishak) is a key historical synchronism, approximately 925 B.C.E., mentioned in both Egyptian inscriptions and the Hebrew Bible. The list of places raided by Shoshenq, mentioned at Karnak (Egypt), includes Rehov (Israel). The site yielded a consistent series of radiocarbon dates from the 12th to 9th century B.C.E. Our results (i) suggest a revised Iron-Age chronology; (ii) date an archaeological stratum to Shoshenq's campaign; (iii) indicate the similarity of "Solomonic" and "Omride" pottery; and (iv) provide correlation with Greece and Cyprus.

The radiocarbon reservoir age of the Chukchi Sea, Arctic Ocean

NASA Astrophysics Data System (ADS)

Pearce, C.; Gyllencreutz, R.; West, G.; O'Regan, M.; Jakobsson, M.

2017-12-01

Radiocarbon (14C) dating is the standard method for obtaining the age of marine sediments of Holocene and late Pleistocene age. For accurate calibrations, however, this tool relies on precise knowledge of the local radiocarbon reservoir age of the surface ocean, i.e. the regional difference (ΔR) from the average global marine calibration dataset. This parameter has become impossible to measure from modern mollusk samples because of 14C contamination from extensive testing of thermo-nuclear bombs in the second half of the twentieth century. The local reservoir age can thus only be calculated from the radiocarbon age of samples collected before AD 1950 or from sediment records containing absolute age markers, derived from e.g. tephrochronology or paleomagnetism. Knowledge of the marine reservoir age in the Arctic Ocean is extremely sparse, and relies on work by only a few studies. No information exists for the entire East Siberian Sea, and the Chukchi Sea is represented solely by sites along the Alaskan coast. Here we present new radiocarbon measurements on historical mollusk collections from the East Siberian and Chukchi margins. Our results show a clear and consistent signal of "old" Pacific Water in the Chukchi Sea with ΔR values around 450 years. Towards the East Siberian Sea the values drop as Pacific Water has decreased influence further away from the Bering Strait. Complementing the modern data, we also provide constraints on the reservoir age during the late Holocene. These are based on tephrochronology and high resolution analyses of paleomagnetic secular variation from a sediment archive from Herald Canyon, Chukchi Sea.

U-Th Burial Dates on Ostrich Eggshell

NASA Astrophysics Data System (ADS)

Sharp, W. D.; Fylstra, N. D.; Tryon, C. A.; Faith, J. T.; Peppe, D. J.

2015-12-01

Obtaining precise and accurate dates at archaeological sites beyond the range of radiocarbon dating is challenging but essential for understanding human origins. Eggshells of ratites (large flightless birds including ostrich, emu and others) are common in many archaeological sequences in Africa, Australia and elsewhere. Ancient eggshells are geochemically suitable for the U-Th technique (1), which has about ten times the range of radiocarbon dating (>500 rather than 50 ka), making eggshells attractive dating targets. Moreover, C and N isotopic studies of eggshell provide insights into paleovegetation and paleoprecipitation central to assessing past human-environment interactions (2,3). But until now, U-Th dates on ratite eggshell have not accounted for the secondary origin of essentially all of their U. We report a novel approach to U-Th dating of eggshell that explicitly accounts for secondary U uptake that begins with burial. Using ostrich eggshell (OES) from Pleistocene-Holocene east African sites, we have measured U and 232Th concentration profiles across OES by laser ablation ICP-MS. U commonly peaks at 10s to 100s of ppb and varies 10-fold or more across the ~2 mm thickness of OES, with gradients modulated by the layered structure of the eggshell. Common Th is high near the shell surfaces, but low in the middle "pallisade" layer of OES, making it optimal for U-Th dating. We determine U-Th ages along the U concentration gradient by solution ICP-MS analyses of two or more fractions of the pallisade layer. We then estimate OES burial dates using a simple model for diffusive uptake of uranium. Comparing such "U-Th burial dates" with radiocarbon dates for OES calcite from the same shells, we find good agreement in 7 out of 9 cases, consistent with rapid burial and confirming the accuracy of the approach. The remaining 2 eggshells have anomalous patterns of apparent ages that reveal they are unsuitable for U-Th dating, thereby providing reliability criteria innate

Surface Ocean Radiocarbon Reservoir Ages From Land-Sea Tephra Correlation Constrains Deglacial Chronology and Ocean Circulation in the Southeast Bering Sea

NASA Astrophysics Data System (ADS)

Cook, M. S.; Miller, R.; White-Nockleby, C.; Chapman, A.; Mix, A. C.

2017-12-01

Radiocarbon estimates of the past ocean are valuable because unlike passive tracers, radiocarbon has the potential to trace both the distribution and rate of transport of water masses. Most studies using paired radiocarbon measurements on planktonic and benthic foraminifera assume that the surface reservoir age was constant at the preindustrial value, which if incorrect, can strongly bias radiocarbon reconstructions. The subarctic Pacific is ringed by volcanic arcs, and there is great potential to use tephrochronology as a stratigraphic tool in sediments from the last glacial and deglaciation, and assign calendar ages to the marine sediment without relying on calibrated planktonic radiocarbon ages. In this study, we use major and trace element analysis of volcanic glass to match tephras between radiocarbon-dated lake cores from Sanak Island in the eastern Aleutians to marine cores from Umnak Plateau in the southeast Bering Sea. There are numerous thin tephras preserved in laminated sediments from the Bolling-Allerod and early Holocene in marine cores from depths (1000-1500 m) within the modern oxygen minimum zone. We find that trace elements are crucial in distinguishing tephras from individual eruptions. Our preliminary radiocarbon measurements suggest that the benthic-atmosphere radiocarbon differences and marine surface reservoir ages in the Bolling-Allerod are similar to pre-industrial values, supporting previously published radiocarbon reconstructions from the region.

Accelerator mass spectrometer with ion selection in high-voltage terminal

NASA Astrophysics Data System (ADS)

Rastigeev, S. A.; Goncharov, A. D.; Klyuev, V. F.; Konstantinov, E. S.; Kutnyakova, L. A.; Parkhomchuk, V. V.; Petrozhitskii, A. V.; Frolov, A. R.

2016-12-01

The folded electrostatic tandem accelerator with ion selection in a high-voltage terminal is the basis of accelerator mass spectrometry (AMS) at the BINP. Additional features of the BINP AMS are the target based on magnesium vapors as a stripper without vacuum deterioration and a time-of-flight telescope with thin films for reliable ion identification. The acceleration complex demonstrates reliable operation in a mode of 1 MV with 50 Hz counting rate of 14C+3 radiocarbon for modern samples (14C/12C 1.2 × 10-12). The current state of the AMS has been considered and the experimental results of the radiocarbon concentration measurements in test samples have been presented.

RADIOCARBON DATING: A CASE AGAINST THE PROPOSED LINK BETWEEN RIVER MOLLUSKS AND SOIL HUMUS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Broecker, W.

The C/sup 14/ link between river mollusks and soil humus is discussed. It is stated that the explanation that the C/sup 13/ deficiency should be attributed to the uptake of soil CO/sub 2/ by ground water (oxidation of humus in the soil, rather than after it has been transported into streams) and the C/sup 14/ deficiency to the solution of limestone is far more plausible. It was concluded that any relation between the radiocarbon concentrations in soil humus and fresh water mollusks is almost certainly coincidental. (P.C.H.)

Development of a Process Based Paleomagnetic Secular Variation Dating Curve for the Northern Hemisphere Through the Radiocarbon Interval

NASA Astrophysics Data System (ADS)

Stoner, J. S.; Reilly, B. T.; Walczak, M. H.; Mix, A. C.; Lavoie, N.; Velle, J. H.; St-Onge, G.; Xuan, C.

2017-12-01

Paleomagnetic secular variation is a well-known centennial to millennial stratigraphic dating tool, but is generally considered to be regionally limited. Recent observations from the Holocene suggest that such spatial limitations may result from our incomplete understanding of field dynamics, rather than actual geomagnetic limitations. Comparisons of independently well-dated, high-resolution paleomagnetic secular variation records from the mid-latitudes of the Northern Hemisphere—including Asia, Northwest Pacific, Northeast Pacific, North America, North Atlantic, and Europe—reveal the existence of a primary (there may be others) coherent millennial scale oscillation of the geomagnetic field. This oscillation is observed using different geomagnetic parameters (e.g., inclination, declination, intensity) and signs depending on the site's location relative to the region of primary geomagnetic flux. This distinct spatial and temporal pattern is consistent with oscillations of geomagnetic flux recurring at just a few locations. The recurring persistence of this pattern, through the Holocene and possibly much longer, implicates lower mantle heterogeneity as a likely driver of field morphology. As with any paleo reconstructions, data coverage is far from perfect and as a result the geomagnetic details are just coming into focus. Yet, the stratigraphic potential is readily apparent and, if iteratively used, could significantly enhance our geomagnetic understanding as well as facilitate chronological control in a variety of settings. Here we explore the nature, uncertainties, and implications; including our initial attempt to extend the oscillation beyond the Holocene and through the radiocarbon interval starting from a Northeast Pacific perspective. Our intent is to develop a type curve with constrained uncertainties that can be used for stratigraphic correlation around the Northern Hemisphere as we move toward a process based dynamic magnetostratigraphic understanding.

Thermal history of the Acoculco geothermal system, eastern Mexico: Insights from numerical modeling and radiocarbon dating

NASA Astrophysics Data System (ADS)

Canet, Carles; Trillaud, Frederic; Prol-Ledesma, Rosa María; González-Hernández, Galia; Peláez, Berenice; Hernández-Cruz, Berenice; Sánchez-Córdova, María M.

2015-10-01

Acoculco is a geothermal prospective area hosted by a volcanic caldera complex in the eastern Trans-Mexican Volcanic Belt. Surface manifestations are scarce and consist of gas discharges (CO2-rich) and acid-sulfate springs of low temperature, whereas hydrothermal explosive activity is profusely manifested by meter-scale craters and mounds of hydrothermal debris and breccias. Silicic alteration extends for several square kilometers around the zone with gas manifestations and explosive features, affecting surficial volcanic rocks, primarily tuffs and breccias. In the subsurface, an argillic alteration zone (ammonium illite) extends down to a depth of ∼ 600 m, and underneath it a propylitic zone (epidote-calcite-chlorite) occurs down to ∼ 1000 m. Thermal logs from an exploratory borehole (EAC-1, drilled in 1995 down to 1810 m) showed a conductive heat transfer regime under high geothermal gradient (∼ 140 °C/1000 m). In contrast, the thermal profile established from temperatures of homogenization of fluid inclusions-measured on core samples from the same drill hole-suggests that convection occurred in the past through the upper ~ 1400 m of the geothermal system. A drop in permeability due to the precipitation of alteration minerals would have triggered the cessation of the convective heat transfer regime to give place to a conductive one. With the purpose of determining when the transition of heat transfer regime occurred, we developed a 1D model that simulates the time-depth distribution of temperature. According to our numerical simulations, this transition happened ca. 7000 years ago; this date is very recent compared to the lifespan of the geothermal system. In addition, radiocarbon chronology indicates that the hydrothermal explosive activity postdates the end of the convective heat transfer regime, having dated at least three explosive events, at 4867-5295, 1049-1417 and 543-709 y cal. BP. Therefore, hydrothermal explosions arise from the self-sealing of

Radiocarbon Dating of the Human Eye Lens Crystallines Reveal Proteins without Carbon Turnover throughout Life

PubMed Central

Lynnerup, Niels; Kjeldsen, Henrik; Heegaard, Steffen; Jacobsen, Christina; Heinemeier, Jan

2008-01-01

Background Lens crystallines are special proteins in the eye lens. Because the epithelial basement membrane (lens capsule) completely encloses the lens, desquamation of aging cells is impossible, and due to the complete absence of blood vessels or transport of metabolites in this area, there is no subsequent remodelling of these fibers, nor removal of degraded lens fibers. Human tissue ultimately derives its 14C content from the atmospheric carbon dioxide. The 14C content of the lens proteins thus reflects the atmospheric content of 14C when the lens crystallines were formed. Precise radiocarbon dating is made possible by comparing the 14C content of the lens crystallines to the so-called bomb pulse, i.e. a plot of the atmospheric 14C content since the Second World War, when there was a significant increase due to nuclear-bomb testing. Since the change in concentration is significant even on a yearly basis this allows very accurate dating. Methodology/Principal Findings Our results allow us to conclude that the crystalline formation in the lens nucleus almost entirely takes place around the time of birth, with a very small, and decreasing, continuous formation throughout life. The close relationship may be further expressed as a mathematical model, which takes into account the timing of the crystalline formation. Conclusions/Significance Such a life-long permanence of human tissue has hitherto only been described for dental enamel. In confront to dental enamel it must be held in mind that the eye lens is a soft structure, subjected to almost continuous deformation, due to lens accommodation, yet its most important constituent, the lens crystalline, is never subject to turnover or remodelling once formed. The determination of the 14C content of various tissues may be used to assess turnover rates and degree of substitution (for example for brain cell DNA). Potential targets may be nervous tissues in terms of senile or pre-senile degradation, as well as other highly

10Be dating of late-glacial moraines near the Cordillera Vilcanota and the Quelccaya Ice Cap, Peru

NASA Astrophysics Data System (ADS)

Kelly, M. A.; Thompson, L. G.

2004-12-01

The surface exposure method, based on the measurement of cosmogenic 10Be produced in quartz, is applied to determine the age of deposition of glacial moraines near the Cordillera Vilcanota and the Quelccaya Ice Cap (about 13° S, 70° W) in southeastern Peru. These data are useful for examining the timing of past glaciation in the tropical Andes and for comparison with chronologies of glaciation at higher latitudes. The preliminary data set consists of more than ten surface exposure ages. Samples used for dating are from the surfaces of boulders on a set of prominent moraines about four kilometers away from the present ice margins. The age of the moraine set was previously bracketed by radiocarbon dating of peat associated with the glacial deposits. Based on radiocarbon ages, these moraines were formed during the late-glacial period, just prior to the last glacial-interglacial transition. The surface exposure dating method enables the direct dating of the moraines. Surface exposure dates are cross-checked with the previously existing radiocarbon dates and provide a means to improve the chronology of past glaciation in the tropical Andes.

Mauna Loa eruptive history—The preliminary radiocarbon record

NASA Astrophysics Data System (ADS)

Lockwood, John P.

Radiocarbon dating of charcoal from beneath lava flows of Mauna Loa has provided the most detailed prehistoric eruptive chronology of any volcano on Earth. Three hundred and fifty-five 14C dates have been reviewed, stratigraphically contradictory dates have been rejected, and multiple dates on single flows averaged to give "reliable" ages on 170 separate lava flows (about 35% of the total number of prehistoric Mauna Loa flows mapped to date). The distribution of these ages has revealed fundamental variations in the time and place of Mauna Loa eruptive activity, particularly for Holocene time. As lava flow activity from Mauna Loa's summit waxes, activity on the rift zones wanes. A cyclic model is proposed which involves a period of concentrated summit shield-building activity associated with long-lived lava lakes and frequent overflows of pahoehoe lavas on the north and southeast flanks. At this time, compressive stresses across Mauna Loa's rift zones are relatively high, inhibiting eruptions in these areas. This period is then followed by a relaxation of stresses across Mauna Loa's rift zones and a long period of frequent rift zone eruptions as magma migrates downrift. This change of eruptive style is marked by summit caldera collapse (possibly associated with massive eruptions of picritic lavas low on the rift zones). Concurrent with this increased rift zone activity, the summit caldera is gradually filled by repeated summit eruptions, stress across the rift zones increases, magma rises more easily to the summit, rift activity wanes, and the cycle repeats itself. Two such cycles are suggested within the late Holocene, each lasting 1,500-2,000 years. Earlier evidence for such cycles is obscure. Mauna Loa appears to have been quiescent between 6-7 ka, for unknown reasons. A period of increased eruptive activity marked the period 8-11 ka, coincident with the Pleistocene-Holocene boundary. Other volcanoes on the Island of Hawaii for which (limited) radiocarbon dating

Radiocarbon evidence for a smaller oceanic carbon dioxide sink than previously believed

NASA Astrophysics Data System (ADS)

Hesshaimer, Vago; Heimann, Martin; Levin, Ingeborg

1994-07-01

RADIOCARBON produced naturally in the upper atmosphere or arti-ficially during nuclear weapons testing is the main tracer used to validate models of oceanic carbon cycling, in particular the exchange of carbon dioxide with the atmosphere1-3 and the mixing parameters within the ocean itself4-7. Here we test the overall consistency of exchange fluxes between all relevant compartments in a simple model of the global carbon cycle, using measurements of the long-term tropospheric CO2 concentration8 and radiocarbon composition9-12, the bomb 14C inventory in the stratosphere13,14 and a compilation of bomb detonation dates and strengths15. We find that to balance the budget, we must invoke an extra source to account for 25% of the generally accepted uptake of bomb 14C by the oceans3. The strength of this source decreases from 1970 onwards, with a characteristic timescale similar to that of the ocean uptake. Significant radiocarbon transport from the remote high stratosphere and significantly reduced uptake of bomb 14C by the biosphere can both be ruled out by observational constraints. We therefore conclude that the global oceanic bomb 14C inventory should be revised downwards. A smaller oceanic bomb 14C inventory also implies a smaller oceanic radiocarbon penetration depth16, which in turn implies that the oceans take up 25% less anthropogenic CO2 than had previously been believed.

Decadally resolved Lateglacial radiocarbon evidence from New Zealand kauri

NASA Astrophysics Data System (ADS)

Hogg, Alan; Southon, John; Turney, Chris; Palmer, Jonathan; Bronk Ramsey, Christopher; Fenwick, Pavla; Boswijk, Gretel; Büntgen, Ulf; Friedrich, Michael; Helle, Gerhard; Hughen, Konrad; Jones, Richard; Kromer, Bernd; Noronha, Alexandra; Reinig, Frederick; Reynard, Linda; Staff, Richard; Wacker, Lukas

2017-04-01

The Last Glacial-Interglacial Transition (LGIT; 15,000 - 11,000 cal BP) was characterised by complex spatiotemporal patterns of climate change, with numerous studies requiring accurate chronological control to decipher leads from lags in global palaeoclimatic, -environmental and archaeological records. However, close scrutiny of the few available tree-ring chronologies and radiocarbon-dated sequences composing the IntCal13 radiocarbon (14C) calibration curve, indicates significant weakness in 14C calibration across key periods of the LGIT. Here, we present a decadally-resolved atmospheric 14C record derived from New Zealand kauri spanning Greenland Stadial 1 (GS-1; 12,900 - 11,650 cal BP). Two floating kauri 14C time series, curve-matched to IntCal13, serve as a radiocarbon backbone through GS-1. Floating Northern Hemisphere (NH) 14C datasets are matched against the new kauri data, forming a robust NH 14C time series to 14,200 cal BP. Our results show that IntCal13 is questionable from 12,200 - 11,900 cal BP and the 10,400 BP 14C plateau is approximately five decades too short. By precisely aligning Southern and Northern Hemisphere tree-ring 14C records with marine 14C sequences, we document two relatively short periods of North Atlantic Meridional Overturning Circulation (AMOC) collapse during GS-1. Hence, sustained North Atlantic cooling across GS-1 was not driven by a prolonged AMOC reduction but was probably due to an equatorward migration of the Polar Front.

Re-dating Zhoukoudian Upper Cave, northern China and its regional significance.

PubMed

Li, Feng; Bae, Christopher J; Ramsey, Christopher B; Chen, Fuyou; Gao, Xing

2018-05-31

Due to the presence of multiple partial modern human skeletons thought to have been interred along with a diversity of evidence of symbolic behavior, Zhoukoudian Upper Cave (ZKD UC; formally "Choukoutien") from northern China has long been a critical site for understanding Late Quaternary human evolution and particularly the role eastern Asia played. Unfortunately, uncertainty regarding ZKD UC's chronology has long hindered determination of its importance in the debate over modern human origins. This situation has been particularly problematic because dates from the primary archaeological layers of ZKD UC have ranged from the Late Pleistocene to the Early Holocene (∼34-10 ka), with clearly different implications depending on which age is used. Here, we present a new set of accelerator mass spectrometry radiocarbon dating results from ZKD UC. Based on this new set of dates and further re-evaluations of the previous dating analyses, archaeological materials, published excavation reports and stratigraphy, we conclude that the ZKD UC archaeological layers minimally date to 35.1-33.5 ka. Given the similarities between the human fossils and archaeology between ZKD UC and western Eurasia, it is likely that the ZKD UC human foragers were part of dispersal events across northern Eurasia toward Siberia and eventually reaching into northern China. Copyright © 2018 Elsevier Ltd. All rights reserved.

The Oldest Anatomically Modern Humans from Far Southeast Europe: Direct Dating, Culture and Behavior

PubMed Central

Prat, Sandrine; Péan, Stéphane C.; Crépin, Laurent; Drucker, Dorothée G.; Puaud, Simon J.; Valladas, Hélène; Lázničková-Galetová, Martina; van der Plicht, Johannes; Yanevich, Alexander

2011-01-01

Background Anatomically Modern Humans (AMHs) are known to have spread across Europe during the period coinciding with the Middle to Upper Paleolithic transition. Whereas their dispersal into Western Europe is relatively well established, evidence of an early settlement of Eastern Europe by modern humans are comparatively scarce. Methodology/Principal Finding Based on a multidisciplinary approach for the study of human and faunal remains, we describe here the oldest AMH remains from the extreme southeast Europe, in conjunction with their associated cultural and paleoecological background. We applied taxonomy, paleoecology, and taphonomy combined with geomorphology, stratigraphy, archeology and radiocarbon dating. More than 160 human bone remains have been discovered. They originate from a well documented Upper Paleolithic archeological layer (Gravettian cultural tradition) from the site of Buran-Kaya III located in Crimea (Ukraine). The combination of non-metric dental traits and the morphology of the occipital bones allow us to attribute the human remains to Anatomically Modern Humans. A set of human and faunal remains from this layer has been radiocarbon dated by Accelerator Mass Spectrometry. The direct-dating results of human bone establish a secure presence of AMHs at 31,900+240/−220 BP in this region. They are the oldest direct evidence of the presence of AMHs in a well documented archeological context. Based on taphonomical observations (cut marks and distribution of skeletal elements), they represent the oldest Upper Paleolithic modern humans from Eastern Europe, showing post-mortem treatment of the dead as well. Conclusion/Significance These findings are essential for the debate on the spread of modern humans in Europe during the Upper Paleolithic, as well as their cultural behaviors. PMID:21698105

The oldest anatomically modern humans from far southeast Europe: direct dating, culture and behavior.

PubMed

Prat, Sandrine; Péan, Stéphane C; Crépin, Laurent; Drucker, Dorothée G; Puaud, Simon J; Valladas, Hélène; Lázničková-Galetová, Martina; van der Plicht, Johannes; Yanevich, Alexander

2011-01-01

Anatomically Modern Humans (AMHs) are known to have spread across Europe during the period coinciding with the Middle to Upper Paleolithic transition. Whereas their dispersal into Western Europe is relatively well established, evidence of an early settlement of Eastern Europe by modern humans are comparatively scarce. Based on a multidisciplinary approach for the study of human and faunal remains, we describe here the oldest AMH remains from the extreme southeast Europe, in conjunction with their associated cultural and paleoecological background. We applied taxonomy, paleoecology, and taphonomy combined with geomorphology, stratigraphy, archeology and radiocarbon dating. More than 160 human bone remains have been discovered. They originate from a well documented Upper Paleolithic archeological layer (Gravettian cultural tradition) from the site of Buran-Kaya III located in Crimea (Ukraine). The combination of non-metric dental traits and the morphology of the occipital bones allow us to attribute the human remains to Anatomically Modern Humans. A set of human and faunal remains from this layer has been radiocarbon dated by Accelerator Mass Spectrometry. The direct-dating results of human bone establish a secure presence of AMHs at 31,900+240/-220 BP in this region. They are the oldest direct evidence of the presence of AMHs in a well documented archeological context. Based on taphonomical observations (cut marks and distribution of skeletal elements), they represent the oldest Upper Paleolithic modern humans from Eastern Europe, showing post-mortem treatment of the dead as well. These findings are essential for the debate on the spread of modern humans in Europe during the Upper Paleolithic, as well as their cultural behaviors.

Coral radiocarbon constraints on the source of the Indonesian throughflow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moore, M.D.; Schrag, D.P.; Kashgarian, M.

1997-06-01

Radiocarbon variability in {ital Porites} spp. corals from Guam and the Makassar Strait (Indonesian Seaway) was used to identify the source waters contributing to the Indonesian throughflow. Time series with bimonthly resolution were constructed using accelerator mass spectrometry. The seasonal variability ranges from 15 to 60{per_thousand}, with large interannual variability. {Delta}{sup 14}C values from Indonesia and Guam have a nearly identical range. Annual mean {Delta}{sup 14}C values from Indonesia are 50 to 60{per_thousand} higher than in corals from Canton in the South Equatorial Current [{ital Druffel}, 1987]. These observations support a year-round North Pacific source for the Indonesian throughflow andmore » imply negligible contribution by South Equatorial Current water. The large seasonality in {Delta}{sup 14}C values from both sites emphasizes the dynamic behavior of radiocarbon in the surface ocean and suggests that {Delta}{sup 14}C time series of similar resolution can help constrain seasonal and interannual changes in ocean circulation in the Pacific over the last several decades.{copyright} 1997 American Geophysical Union« less

Recent sediment remolding on a deep shelf, Ross Sea: implications for radiocarbon dating of Antarctic marine sediments

NASA Astrophysics Data System (ADS)

Domack, Eugene W.; Taviani, Marco; Rodriguez, Anthonio

1999-11-01

Coarse, bioclastic rich sands have been widely reported from the banks of the Antarctic continental shelf but their origin is still poorly known. We report on a suite of coarse sediments recovered from the top of the Mawson Bank in the northwestern Ross Sea. Radiocarbon ages of biogenic calcite, for modern and apparently late Pleistocene deposits, range from 1085±45 to 20,895±250 yr B.P.. Discovery of soft tissue (Ascidian) preserved as an incrustation on a pebble at 2 m depth indicates aggregation of the sediment within several months or a year of core recovery. Radiocarbon ages of acid insoluble organic matter (aiom) are less than those of the foraminifera calcite. The aiom ages are also reversed in sequence, indicating reworking of the sediment during deposition. These observations and a review of recently published literature suggest that much of the bank top sediment in Antarctica is presently undergoing remobilization, under the influence of strong currents and/or icebergs even under interglacical (high-stand) sea levels. These observations point out the need for careful, integrated studies on high latitude marine sediment cores before resultant "ages" alone are used as the foundation for paleoglacial reconstructions.

Direct dating of archaeological pottery by compound-specific 14C analysis of preserved lipids.

PubMed

Stott, Andrew W; Berstan, Robert; Evershed, Richard P; Bronk-Ramsey, Christopher; Hedges, Robert E M; Humm, Martin J

2003-10-01

A methodology is described demonstrating the utility of the compound-specific 14C technique as a direct means of dating archaeological pottery. The method uses automated preparative capillary gas chromatography employing wide-bore capillary columns to isolate individual compounds from lipid extracts of archaeological potsherds in high purity (>95%) and amounts (>200 microg) sufficient for radiocarbon dating using accelerator mass spectrometry (AMS). A protocol was developed and tested on n-alkanes and n-carboxylic acids possessing a broad range of 14C ages. Analytical blanks and controls allowed background 14C measurements to be assessed and potential sources of errors to be detected, i.e., contamination with modern or dead 14C, isotopic fraction effects, etc. A "Russian doll" method was developed to transfer isolated target compounds onto tin powder/capsules prior to combustion and AMS analyses. The major advantage of the compound-specific technique is that 14C dates obtained for individual compounds can be directly linked to the commodities processed in the vessels during their use, e.g., animal fats. The compound-specific 14C dating protocol was validated on a suite of ancient pottery whose predicted ages spanned a 5000-year date range. Initial results indicate that meaningful correlations can be obtained between the predicted date of pottery and that of the preserved lipids. These findings constitute an important step forward to the direct dating of archaeological pottery.

Luminescence and Radiocarbon dating of roman time harbour sediments from Cologne - A comparison of different methods

NASA Astrophysics Data System (ADS)

Lauer, Tobias; Frechen, Manfred; Fuchs, Magret C.; Trier, Marcus; Tsukamoto, Sumiko

2010-05-01

Optically stimulated luminescence (OSL) dating was applied to fluvial and colluvial deposits which were taken from a roman time harbour basin in Cologne. Hence, independent age control was given by roman artefacts (coins, bricks) of known age and by three radiocarbon data. For one sample (well sorted fluvial sand), a single aliquot regenerative (SAR) protocol was applied to coarse grain quartz. A large number of equivalent doses (80) were collected and after De-measurements, different statistical approaches were tested. The results show, that calculating the age by using the Mean or Median of all accepted De-values yields OSL ages of 3.5 ± 0.3 ka and 2.8 ± 0.3 ka, respectively, what would be significantly too old. The application of the Leading Edge Method (Lepper & McKeever 2002), the statistical approach after Fuchs & Lang (2001) or the Minimum Age Method (MAM3) after Galbraith et al. (1999) yield OSL age estimates of 2.0 ± 0.1 ka, 2.1 ± 0.1 ka and 1.7 ± 0.6 ka, respectively. Those ages fit very well to the 14C-ages and are in better agreement with the known archaeological background. For the colluvial sample, the quartz OSL signal was effected by feldspar impurities. For this sample, different methodological approaches were tested to see which one has the best potential to minimize the feldspar contribution. Therefore the post-IR blue stimulated quartz luminescence was recorded. The quartz signal was measured using continuous wave (CW) and pulsed OSL (POSL). For the CW measurements, it was tested if a prior IR-bleach @ 50°C or @ 225°C has better potential for minimizing the feldspar signal. In this case, an IR-bleach @ 225°C (Buylaert et al. in press) was the most effective way to obtain a higher purity of the quartz OSL signal. Buylaert, J.P., Murray, A.S., Thomsen, K.J., Jain, M.: The effect of preheating on the IRSL signal from feldspar. In press. - Radiat. Meas., special issue, LED08. Fuchs, M. & Lang, A. (2001): OSL dating of coarse-grain fluvial

Marine04 Marine radiocarbon age calibration, 26 ? 0 ka BP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hughen, K; Baille, M; Bard, E

2004-11-01

New radiocarbon calibration curves, IntCal04 and Marine04, have been constructed and internationally ratified to replace the terrestrial and marine components of IntCal98. The new calibration datasets extend an additional 2000 years, from 0-26 ka cal BP (Before Present, 0 cal BP = AD 1950), and provide much higher resolution, greater precision and more detailed structure than IntCal98. For the Marine04 curve, dendrochronologically dated tree-ring samples, converted with a box-diffusion model to marine mixed-layer ages, cover the period from 0-10.5 ka cal BP. Beyond 10.5 ka cal BP, high-resolution marine data become available from foraminifera in varved sediments and U/Th-dated corals.more » The marine records are corrected with site-specific {sup 14}C reservoir age information to provide a single global marine mixed-layer calibration from 10.5-26.0 ka cal BP. A substantial enhancement relative to IntCal98 is the introduction of a random walk model, which takes into account the uncertainty in both the calendar age and the radiocarbon age to calculate the underlying calibration curve. The marine datasets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed here. The tree-ring datasets, sources of uncertainty, and regional offsets are presented in detail in a companion paper by Reimer et al.« less

Global Peak in Atmospheric Radiocarbon Provides a Potential Definition for the Onset of the Anthropocene Epoch in 1965.

PubMed

Turney, Chris S M; Palmer, Jonathan; Maslin, Mark A; Hogg, Alan; Fogwill, Christopher J; Southon, John; Fenwick, Pavla; Helle, Gerhard; Wilmshurst, Janet M; McGlone, Matt; Bronk Ramsey, Christopher; Thomas, Zoë; Lipson, Mathew; Beaven, Brent; Jones, Richard T; Andrews, Oliver; Hua, Quan

2018-02-19

Anthropogenic activity is now recognised as having profoundly and permanently altered the Earth system, suggesting we have entered a human-dominated geological epoch, the 'Anthropocene'. To formally define the onset of the Anthropocene, a synchronous global signature within geological-forming materials is required. Here we report a series of precisely-dated tree-ring records from Campbell Island (Southern Ocean) that capture peak atmospheric radiocarbon ( 14 C) resulting from Northern Hemisphere-dominated thermonuclear bomb tests during the 1950s and 1960s. The only alien tree on the island, a Sitka spruce (Picea sitchensis), allows us to seasonally-resolve Southern Hemisphere atmospheric 14 C, demonstrating the 'bomb peak' in this remote and pristine location occurred in the last-quarter of 1965 (October-December), coincident with the broader changes associated with the post-World War II 'Great Acceleration' in industrial capacity and consumption. Our findings provide a precisely-resolved potential Global Stratotype Section and Point (GSSP) or 'golden spike', marking the onset of the Anthropocene Epoch.

Intercomparison of radiocarbon bomb pulse and 210Pb age models. A study in a peat bog core from North Poland

NASA Astrophysics Data System (ADS)

Piotrowska, Natalia; De Vleeschouwer, François; Sikorski, Jarosław; Pawlyta, Jacek; Fagel, Nathalie; Le Roux, Gaël; Pazdur, Anna

2010-04-01

Radiocarbon and 210Pb were measured on the uppermost 40 cm of a Wardenaar peat core retrieved from a Baltic raised bog at Słowińskie Błota (Pomerania, North Poland). This site is the subject of ongoing multiproxy studies covering the last 1300 years. Radiocarbon age model was constructed on the basis of 14 AMS dates obtained on selected Sphagnum spp. fragments, with use of P_Sequence tool. We present here a comparison of this model with the age model obtained using CRS model classically applied to 210Pb measurements.

A case of early Wisconsinan ;over-chill;: New radiocarbon evidence for early extirpation of western camel (Camelops hesternus) in eastern Beringia

NASA Astrophysics Data System (ADS)

Zazula, Grant D.; MacPhee, Ross D. E.; Southon, John; Nalawade-Chavan, Shweta; Reyes, Alberto V.; Hewitson, Susan; Hall, Elizabeth

2017-09-01

There are comparatively few fossils that document the presence of the Pleistocene western camel (Camelops hesternus) in the unglaciated regions of Alaska and Yukon, northwestern North America (eastern Beringia). It has been previously reported on the basis of stratigraphic and radiocarbon data that this species was present within this region from the Sangamonian interglaciation (Marine Isotope Stage (MIS) 5) through the Last Glacial Maximum (LGM, MIS 2). However, the continued presence of western camel through the LGM is at odds with its ecological preferences as inferred from more southerly parts of the continent. Here we report 43 new radiocarbon dates on 34 western camel fossils from Alaska and Yukon, including specimens that have been dated previously. To minimize exogenous carbon contamination, we utilized either ultrafiltered collagen or single amino acid (hydroxyproline) methodologies in conducting the analyses. All samples, including previously reported specimens with finite ages, yielded ages that were either non-finite or close to the effective limit of radiocarbon dating. These results indicate that dates implying local presence of western camels in Alaska and Yukon during full-glacial conditions of MIS 2 are erroneous by as much as several tens of millennia, probably because of carbon contamination from glue or varnish used in fossil preparation and conservation. The revised radiocarbon chronology, together with other evidence, indicates that western camels were only able to occupy eastern Beringia only during Pleistocene interglaciations such as MIS 5, when forests and shrublands became the dominant regional biomes. The subsequent transition to cold, arid full-glacial conditions during the early Wisconsinan glaciation (MIS 4) around 75 000 years ago created unfavorable environmental conditions, eliminated browse, and led to their local extirpation in eastern Beringia. After their complete population loss in the Arctic and Subarctic, the range of

Searching for the oldest baobab of Madagascar: radiocarbon investigation of large Adansonia rubrostipa trees.

PubMed

Patrut, Adrian; von Reden, Karl F; Danthu, Pascal; Pock-Tsy, Jean-Michel Leong; Patrut, Roxana T; Lowy, Daniel A

2015-01-01

We extended our research on the architecture, growth and age of trees belonging to the genus Adansonia, by starting to investigate large individuals of the most widespread Malagasy species. Our research also intends to identify the oldest baobabs of Madagascar. Here we present results of the radiocarbon investigation of the two most representative Adansonia rubrostipa (fony baobab) specimens, which are located in south-western Madagascar, in the Tsimanampetsotse National Park. We found that the fony baobab called "Grandmother" consists of 3 perfectly fused stems of different ages. The radiocarbon date of the oldest sample was found to be 1136 ± 16 BP. We estimated that the oldest part of this tree, which is mainly hollow, has an age close to 1,600 yr. This value is comparable to the age of the oldest Adansonia digitata (African baobab) specimens. By its age, the Grandmother is a major candidate for the oldest baobab of Madagascar. The second investigated specimen, called the "polygamous baobab", consists of 6 partially fused stems of different ages. According to dating results, this fony baobab is 1,000 yr old. This research is the first investigation of the structure and age of Malagasy baobabs.

Millennial-scale variability in the local radiocarbon reservoir age of the Florida Keys reef tract during the Holocene

NASA Astrophysics Data System (ADS)

Ashe, E.; Toth, L. T.; Cheng, H.; Edwards, R. L.; Richey, J. N.

2016-12-01

The oceanic passage between the Florida Keys and Cuba, known as the Straits of Florida, provides a critical connection between the tropics and northern Atlantic. Changes in the character of water masses transported through this region may ultimately have important impacts on high-latitude climate variability. Although recent studies have documented significant changes in the density of regional surface waters over millennial timescales, little is known about the contribution of local- to regional-scale changes in circulation to surface-water variability. Local variability in the radiocarbon age, ΔR, of surface waters can be used to trace changes in local water-column mixing and/or changes in regional source water over a variety of spatial and temporal scales. We reconstructed "snapshots" of ΔR variability across the Florida Keys reef tract during the last 10,000 years by dating 68 unaltered corals collected from Holocene reef cores with both U-series and radiocarbon techniques. We combined the snapshots of ΔR into a semi-empirical model to develop a robust statistical reconstruction of millennial-scale variability in ΔR on the Florida Keys reef tract. Our model demonstrates that ΔR varied significantly during the Holocene, with relatively high values during the early Holocene and around 3000 years BP and relatively low values around 7000 years BP and at present. We compare the trends in ΔR to existing paleoceanographic reconstructions to evaluate the relative contribution of local upwelling versus changes in source water to the region as a whole in driving local radiocarbon variability, and discuss the importance of these results to our understanding of regional-scale oceanographic and climatic variability during the Holocene. We also discuss the implications of our results for radiocarbon dating of marine samples from south Florida and present a model of ΔR versus 14C age that can be used to improve the accuracy of radiocarbon calibrations from this region.

Rapid isolation of biomarkers for compound specific radiocarbon dating using high-performance liquid chromatography and flow injection analysis-atmospheric pressure chemical ionisation mass spectrometry.

PubMed

Smittenberg, Rienk H; Hopmans, Ellen C; Schouten, Stefan; Sinninghe Damsté, Jaap S

2002-11-29

Repeated semi-preparative normal-phase HPLC was performed to isolate selected biomarkers from sediment extracts for radiocarbon analysis. Flow injection analysis-mass spectrometry was used for rapid analysis of collected fractions to evaluate the separation procedure, taking only 1 min per fraction. In this way 100-1000 microg of glycerol dialkyl glycerol tetraethers, sterol fractions and chlorophyll-derived phytol were isolated from typically 100 g of marine sediment, i.e., in sufficient quantities for radiocarbon analysis, without significant carbon isotopic fractionation or contamination.

Soil organic matter stability as indicated by compound-specific radiocarbon analyses

NASA Astrophysics Data System (ADS)

van der Voort, Tessa Sophia; Zell, Claudia; Hagedorn, Frank; McIntyre, Cameron; Eglinton, Timothy Ian

2017-04-01

Carbon storage in soils is increasingly recognized as a key ecosystem function, and molecular-level analyses could be a valuable potential indicator of this storage potential. In this framework, radiocarbon constitutes a powerful tool for unraveling soil carbon dynamics on both decadal as well as centennial and millennial timescales. In this study, we look at the radiocarbon signature of specific compounds (fatty acids and n-alkanes) in two forested ecosystems (temperate and pre-alpine) with the aim of attaining a better understanding of soil organic carbon stability on a molecular level. Radiocarbon dating of the fatty acids and n-alkanes has been coupled to abundance data of these compounds and additionally lignin phenols. We hypothesize that potentially, these long-chain apolar compounds could be a representative indicator of the mineral-bound soil organic carbon pool. These well-studied sites are part of the Long-Term Forest Ecosystem Research (LWF) program of the Swiss Federal Institute for Forest, Snow and Landscape research (WSL). Therefore, a wide suite of ancillary climatic and textural data is available for these sites. Initial results show a wide range of ages in the specific compounds which constitute a much larger range than the ages indicated by the density fractions done on the same samples. Overall, this study explores the use of molecular-level indicators to study soil organic matter dynamics, which could help assess the overall potential vulnerability of soil carbon in various ecosystems.

Germination, genetics, and growth of an ancient date seed.

PubMed

Sallon, Sarah; Solowey, Elaine; Cohen, Yuval; Korchinsky, Raia; Egli, Markus; Woodhatch, Ivan; Simchoni, Orit; Kislev, Mordechai

2008-06-13

An ancient date seed (Phoenix dactylifera L.) excavated from Masada and radiocarbon-dated to the first century Common Era was germinated. Climatic conditions at the Dead Sea may have contributed to the longevity of this oldest, directly dated, viable seed. Growth and development of the seedling over 26 months was compatible with normal date seedlings propagated from modern seeds. Preliminary molecular characterization demonstrated high levels of genetic variation in comparison to modern, elite date cultivars currently growing in Israel. As a representative of an extinct date palm population, this seedling can provide insights into the historic date culture of the Dead Sea region. It also has importance for seed banking and conservation and may be of relevance to modern date palm cultivation.

RADIOCARBON SOURCE APPORTIONMENT IN A BIOFUELS ERA

EPA Science Inventory

Biofuels (gasohol and biodiesel) introduce radiocarbon into the U.S. mobile source fuel supply where it was previously absent. Initial measurements of radiocarbon in the PM_2.5 combustion emissions from engines using gasohol indicate that this may have less effect on r...

Paired dating of pith and outer edge (terminus) samples from prehispanic Caribbean wooden sculptures

Treesearch

Fiona Brock; Joanna Ostapkowicz; Christopher Bronk Ramsey; Alex Wiedenhoeft; Caroline Cartwright

2012-01-01

Radiocarbon dating of historical and archaeological wood can be complicated, sometimes involving issues of “inbuilt” age in slow-growing woods, and/or the possibility of reuse or long delays between felling and use of the wood. Terminus dates can be provided by dating the sapwood, or the outermost edge of heartwood, while a date from the pith can give an indication of...

Eye lens radiocarbon reveals centuries of longevity in the Greenland shark (Somniosus microcephalus).

PubMed

Nielsen, Julius; Hedeholm, Rasmus B; Heinemeier, Jan; Bushnell, Peter G; Christiansen, Jørgen S; Olsen, Jesper; Ramsey, Christopher Bronk; Brill, Richard W; Simon, Malene; Steffensen, Kirstine F; Steffensen, John F

2016-08-12

The Greenland shark (Somniosus microcephalus), an iconic species of the Arctic Seas, grows slowly and reaches >500 centimeters (cm) in total length, suggesting a life span well beyond those of other vertebrates. Radiocarbon dating of eye lens nuclei from 28 female Greenland sharks (81 to 502 cm in total length) revealed a life span of at least 272 years. Only the smallest sharks (220 cm or less) showed signs of the radiocarbon bomb pulse, a time marker of the early 1960s. The age ranges of prebomb sharks (reported as midpoint and extent of the 95.4% probability range) revealed the age at sexual maturity to be at least 156 ± 22 years, and the largest animal (502 cm) to be 392 ± 120 years old. Our results show that the Greenland shark is the longest-lived vertebrate known, and they raise concerns about species conservation. Copyright © 2016, American Association for the Advancement of Science.

Searching for the Oldest Baobab of Madagascar: Radiocarbon Investigation of Large Adansonia rubrostipa Trees

PubMed Central

Patrut, Adrian; von Reden, Karl F.; Danthu, Pascal; Leong Pock-Tsy, Jean-Michel; Patrut, Roxana T.; Lowy, Daniel A.

2015-01-01

We extended our research on the architecture, growth and age of trees belonging to the genus Adansonia, by starting to investigate large individuals of the most widespread Malagasy species. Our research also intends to identify the oldest baobabs of Madagascar. Here we present results of the radiocarbon investigation of the two most representative Adansonia rubrostipa (fony baobab) specimens, which are located in south-western Madagascar, in the Tsimanampetsotse National Park. We found that the fony baobab called “Grandmother” consists of 3 perfectly fused stems of different ages. The radiocarbon date of the oldest sample was found to be 1136 ± 16 BP. We estimated that the oldest part of this tree, which is mainly hollow, has an age close to 1,600 yr. This value is comparable to the age of the oldest Adansonia digitata (African baobab) specimens. By its age, the Grandmother is a major candidate for the oldest baobab of Madagascar. The second investigated specimen, called the “polygamous baobab”, consists of 6 partially fused stems of different ages. According to dating results, this fony baobab is 1,000 yr old. This research is the first investigation of the structure and age of Malagasy baobabs. PMID:25806967

Radiocarbon dating of magnetic and non magnetic soil fractions as a method to estimate the heterotrophic component of soil respiration in a primary forest of Ghana.

NASA Astrophysics Data System (ADS)

Chiti, T.; Certini, G.; Marzaioli, F.; Valentini, R.

2012-04-01

We estimated the heterotrophic component (Rh) of soil respiration in a primary forest of Ghana by radiocarbon dating, a method we already successfully applied in temperate and Mediterranean forests. In this case, given the advanced stage of alteration of tropical soils, which are thus rich in oxides, we implemented the method on soil fractions obtained by High Gradient Magnetic Separation (HGMS), hence based on different degrees of magnetic susceptibility. In particular, we separated an organic pool associated with magnetic minerals (e.g iron oxides) from an organic pool engaged with non-magnetic minerals. This non destructive method of fractionation, often applied to the finest fraction of soil (clay), is here attempted on the bulk fine earth (< 2 mm). We sampled the soil at 0-5, 5-15, 15-10, and 30-50 cm depth intervals, since a previous study in the same site suggested that only the first 50 cm of soil was enriched in bomb carbon (C younger than 1950). The samples of each layer were sieved at 2 mm and further at 0.5 mm ,so as to have two size fractions: 2 to 0.5 mm and <0.5 mm, and both of them were separated into a magnetic and non magnetic fraction. All the specimens were then investigated in terms of mineralogical assemblage (by X-Ray diffrattometry), chemical structure of the organic component (13C NMR spectroscopy), and 14C concentration (AMS) for inferring the mean residence time (MRT) of the organic component in the soil. Radiocarbon concentration was always higher in the finest SOC fractions (<0.5 mm), with the magnetic fraction always showing an higher 14C concentration than the non magnetic one. The magnetic and non magnetic materials of the coarser fraction (0.5-2 mm) showed quite similar 14C concentrations in all of the soil layers investigated. The composition of the organic matter is different in the different fractions and partly explains the differences in MRT, although a major role in preserving the organics from decomposition is probably played

Chronostratigraphy of a salt marsh sediment core from North Cinder Island in the Town of Hempstead, Long Island, NY, using radiocarbon and pollen

NASA Astrophysics Data System (ADS)

Farmer, E. C.; Browne, J.; Peteet, D. M.; Cochran, K. K.; Heilbrun, C.; Chery, N.; LongJohn, T.; Mayo, J.; Ricigliano, V.

2016-12-01

A 122 cm long sediment core was collected from the salt marsh of North Cinder Island (73.6092W, 40.6097N), a small uninhabited island in Middle Bay between Oceanside and Point Lookout, in the Town of Hempstead, NY, on 2 July 2013, in order to investigate the age of the marsh and the history of trace metal pollution in the area. First, to determine the chronostratigraphy of the core, pollen counts were compared to radiocarbon measurements. Sediment samples at several depths in the core were analyzed for Pine, Oak, Hickory, Birch, Grass (S. alterniflora and S. patens), and Ragweed pollen. The concentration of Ragweed was below 3% in samples below 80cm, and greater than 7% in samples above 80cm. This proliferation of a disturbance species suggests that layers deeper than 81cm were deposited prior to widespread European settlement, sometime in the 1600s AD. Paired radiocarbon measurements on sieved fine sediment at 42-43 cm depth, however, match well with each other (their 1-sigma confidence intervals overlap), but suggest a calendar age between 932 and 997 years before present. Paired radiocarbon measurements from the 60-61 cm depth also match well with each other, but represent an age that is approximately 200 years younger. Additional paired radiocarbon measurements at 78-79 cm and 96-97 cm depths give older ages, as expected stratigraphically. Perhaps the reversal between 43 and 60 cm represents reworking of sediments in the marsh by tidal currents. Interestingly, root matter extracted from the sediment at the same depths gives radiocarbon ages that range from 600-1200 years younger. Perhaps the roots penetrate down through older sediment, or perhaps the fine sediment is comprised of recaptured sediment with lignin or other residual organic matter that is older because it is difficult to break down. This would explain the apparent contradiction between the radiocarbon dates on fine sediment and the younger pollen date at a deeper depth.

Radiocarbon ages of pre-bomb clams and the hard-water effect in Lakes Michigan and Huron

USGS Publications Warehouse

Rea, David K.; Colman, Steven M.

1995-01-01

Five radiocarbon ages, all determined by accelerator mass spectrometry, have been obtained for two pre-bomb bivalves from Lake Michigan and one from Lake Huron. After correcting those ages for the fractionation of14C in calcite and for the radioactively inert CO2 in the atmosphere, we find residual ages, caused by the hard water effect, of about 250 years for Lake Michigan and 440 years for Lake Huron.

Southern Appalachian hillslope erosion rates measured by soil and detrital radiocarbon in hollows

USGS Publications Warehouse

Hales, T.C.; Scharer, K.M.; Wooten, R.M.

2012-01-01

Understanding the dynamics of sediment generation and transport on hillslopes provides important constraints on the rate of sediment output from orogenic systems. Hillslope sediment fluxes are recorded by organic material found in the deposits infilling unchanneled convergent topographic features called hollows. This study describes the first hollow infilling rates measured in the southern Appalachian Mountains. Infilling rates (and bedrock erosion rates) were calculated from the vertical distribution of radiocarbon ages at two sites in the Coweeta drainage basin, western North Carolina. At each site we dated paired charcoal and silt soil organic matter samples from five different horizons. Paired radiocarbon samples were used to bracket the age of the soil material in order to capture the range of complex soil forming processes and deposition within the hollows. These dates constrain hillslope erosion rates of between 0.051 and 0.111mmyr-1. These rates are up to 4 times higher than spatially-averaged rates for the Southern Appalachian Mountains making creep processes one of the most efficient erosional mechanisms in this mountain range. Our hillslope erosion rates are consistent with those of forested mountain ranges in the western United States, suggesting that the mechanisms (dominantly tree throw) driving creep erosion in both the western United States and the Southern Appalachian Mountains are equally effective. ?? 2011 Elsevier B.V.

Diet and mobility in a late Neolithic population of coastal Oman inferred from radiocarbon dating and stable isotope analysis.

PubMed

Zazzo, Antoine; Munoz, Olivia; Saliège, Jean-François

2014-03-01

In Oman, the presence of highly productive marine environments, coupled with relatively limited land resources, have led to intense exploitation of coastal resources, but the question of the seasonality of occupation of coastal sites remains open. Our aim is to evaluate the contribution of marine resources to the diet of the Neolithic population of Ra's al-Hamra 5 (RH-5) to shed new light on its mobility, using stable isotopes and radiocarbon ((14)C) dating as dietary tracers. Charcoal, shell, human bone and enamel apatite from eight contemporary graves were sampled. Graves are thought to provide the best chance to obtain marine and terrestrial remains that were contemporary with the human remains in order to calculate the marine reservoir effect (MRE) for this period. Inter-individual variation in human bone apatite δ(13)C value is small, suggesting a homogenous diet. Bone apatite (14)C ages are very close to the shell ages while enamel is significantly younger and plots near the charcoal ages. Older enamel ages were obtained when a stronger acetic treatment was used, demonstrating that the young ages are due to diagenetic alteration rather than a diachronic change in diet and that only bone apatite retained in vivo dietary signals. Bone ages indicate a heavy reliance on marine resources and it is therefore unlikely that the individuals analyzed here were leaving the coast seasonally, although mobility along the coast cannot be excluded. Copyright © 2013 Wiley Periodicals, Inc.

Radioisotope Dating with Accelerators.

ERIC Educational Resources Information Center

Muller, Richard A.

1979-01-01

Explains a new method of detecting radioactive isotopes by counting their accelerated ions rather than the atoms that decay during the counting period. This method increases the sensitivity by several orders of magnitude, and allows one to find the ages of much older and smaller samples. (GA)

Associated terrestrial and marine fossils in the late-glacial Presumpscot Formation, southern Maine, USA, and the marine reservoir effect on radiocarbon ages

USGS Publications Warehouse

Thompson, W.B.; Griggs, C.B.; Miller, N.G.; Nelson, R.E.; Weddle, T.K.; Kilian, T.M.

2011-01-01

Excavations in the late-glacial Presumpscot Formation at Portland, Maine, uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit. Buds of Populus balsamifera (balsam poplar) occurred with twigs of Picea glauca (white spruce) in the Presumpscot clay. Tree rings in Picea logs indicate that the trees all died during winter dormancy in the same year. Ring widths show patterns of variation indicating responses to environmental changes. Fossil mosses and insects represent a variety of species and wet to dry microsites. The late-glacial environment at the site was similar to that of today's Maine coast. Radiocarbon ages of 14 tree samples are 11,907??31 to 11,650??5014C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at ca. 13,520+95/??20calyr BP. Ages of shells juxtaposed with the logs are 12,850??6514C yr BP (Mytilus edulis) and 12,800??5514C yr BP (Balanus sp.), indicating a marine reservoir age of about 1000yr. Using this value to correct previously published radiocarbon ages reduces the discrepancy between the Maine deglaciation chronology and the varve-based chronology elsewhere in New England. ?? 2011 University of Washington.

Associated terrestrial and marine fossils in the late-glacial Presumpscot Formation, southern Maine, USA, and the marine reservoir effect on radiocarbon ages

NASA Astrophysics Data System (ADS)

Thompson, Woodrow B.; Griggs, Carol B.; Miller, Norton G.; Nelson, Robert E.; Weddle, Thomas K.; Kilian, Taylor M.

2011-05-01

Excavations in the late-glacial Presumpscot Formation at Portland, Maine, uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit. Buds of Populus balsamifera (balsam poplar) occurred with twigs of Picea glauca (white spruce) in the Presumpscot clay. Tree rings in Picea logs indicate that the trees all died during winter dormancy in the same year. Ring widths show patterns of variation indicating responses to environmental changes. Fossil mosses and insects represent a variety of species and wet to dry microsites. The late-glacial environment at the site was similar to that of today's Maine coast. Radiocarbon ages of 14 tree samples are 11,907 ± 31 to 11,650 ± 50 14C yr BP. Wiggle matching of dated tree-ring segments to radiocarbon calibration data sets dates the landslide occurrence at ca. 13,520 + 95/-20 cal yr BP. Ages of shells juxtaposed with the logs are 12,850 ± 65 14C yr BP ( Mytilus edulis) and 12,800 ± 55 14C yr BP ( Balanus sp.), indicating a marine reservoir age of about 1000 yr. Using this value to correct previously published radiocarbon ages reduces the discrepancy between the Maine deglaciation chronology and the varve-based chronology elsewhere in New England.

Holocene history of deep-seated landsliding in the North Fork Stillaguamish River valley from surface roughness analysis, radiocarbon dating, and numerical landscape evolution modeling

NASA Astrophysics Data System (ADS)

Booth, Adam M.; LaHusen, Sean R.; Duvall, Alison R.; Montgomery, David R.

2017-02-01

Documenting spatial and temporal patterns of past landsliding is a challenging step in quantifying the effect of landslides on landscape evolution. While landslide inventories can map spatial distributions, lack of dateable material, landslide reactivations, or time, access, and cost constraints generally limit dating large numbers of landslides to analyze temporal patterns. Here we quantify the record of the Holocene history of deep-seated landsliding along a 25 km stretch of the North Fork Stillaguamish River valley, Washington State, USA, including the 2014 Oso landslide, which killed 43 people. We estimate the ages of more than 200 deep-seated landslides in glacial sediment by defining an empirical relationship between landslide deposit age from radiocarbon dating and landslide deposit surface roughness. We show that roughness systematically decreases with age as a function of topographic wavelength, consistent with models of disturbance-driven soil transport. The age-roughness model predicts a peak in landslide frequency at 1000 calibrated (cal) years B.P., with very few landslide deposits older than 7000 cal years B.P. or younger than 100 cal years B.P., likely reflecting a combination of preservation bias and a complex history of changing climate, base level, and seismic shaking in the study area. Most recent landslides have occurred where channels actively interact with the toes of hillslopes composed of glacial sediments, suggesting that lateral channel migration is a primary control on the location of large deep-seated landslides in the valley.

Determination of radiocarbon reservoir age of Lake Van by mineral magnetic and geochemical analysis

NASA Astrophysics Data System (ADS)

Makaroglu, Ozlem; Namik Cagatay, M.; Pesonen, Lauri J.; Orbay, Naci

2017-04-01

Lake Van is the largest soda lake in the world, located on the east Anatolian Plateau in Turkey. Its varved sediments provide an excellent archive of high-resolution paleoclimate record for the Near East. Varve counting and radiocarbon methods are therefore important dating techniques for investigating the Lake Van sedimentary paleoclimate record. In here we present detailed magnetic and geochemical record of Lake Van. We have studied 4.56 m (core VP0801) and 4.70 m (core VP0807) long cores recovered from 80 m and 65 m water depths located in SE and SW of Lake Van, respectively. Here, we have benefited from magnetic properties with associated remanent magnetization of the sediments from Lake Van to correlate the cores which contain of tephra layers. The cores cover the last 8.4 ka and lithologically include three laminated sedimentary units. From top to the bottom, the units were dated 4.2 ka BP-present, 5.4-4.2 ka BP and older than 5.4 ka BP. We identified tephra layers previously dated by varve counting, and used the varve ages to obtain age models for the cores. We also obtained a total of eight Accelerator Mass Spectrometry (AMS) 14C dates from total organic carbon (TOC) in the two cores, close to the tephra layers. Comparison of the varve ages of the AMS 14C dated samples with their corresponding AMS 14C dates indicates large differences, suggesting significant reservoir ages that range from 2.8 to 2.5 ka for 3.0-2.4 varve ka BP and from 2.8 to 3.3 ka for 8.0-5.9 varve ka BP. The results suggest that the reservoir age of the organic matter increases with the varve age of the sediments. This increase is mainly related to the rate of supply of "dead" carbon from the old carbonate rocks in the watershed of Lake Van, which was relatively higher during 8.4-5.9 ka than during 3.0-2.4 ka BP because of the higher atmospheric precipitation and higher rate of biochemical weathering during the former period.

A new procedure for extraction of collagen from modern and archaeological bones for 14C dating.

PubMed

Maspero, F; Sala, S; Fedi, M E; Martini, M; Papagni, A

2011-10-01

Bones are potentially the best age indicators in a stratigraphic study, because they are closely related to the layer in which they are found. Collagen is the most suitable fraction and is the material normally used in radiocarbon dating. Bone contaminants can strongly alter the carbon isotopic fraction values of the samples, so chemical pretreatment for (14)C dating by accelerator mass spectrometry (AMS) is essential. The most widespread method for collagen extraction is based on the Longin procedure, which consists in HCl demineralization to dissolve the inorganic phase of the samples, followed by dissolution of collagen in a weak acid solution. In this work the possible side effects of this procedure on a modern bone are presented; the extracted collagen was analyzed by ATR-IR spectroscopy. An alternative procedure, based on use of HF instead of HCl, to minimize unwanted degradation of the organic fraction, is also given. A study by ATR-IR spectroscopic analysis of collagen collected after different demineralization times and with different acid volumes, and a study of an archaeological sample, are also presented.

A review of single-sample-based models and other approaches for radiocarbon dating of dissolved inorganic carbon in groundwater

USGS Publications Warehouse

Han, L. F; Plummer, Niel

2016-01-01

underlying assumptions on which the various models and approaches are based can result in a wide range of estimates of 14C0 and limit the usefulness of radiocarbon as a dating tool for groundwater. In each of the three generalized approaches (single-sample-based models, statistical approach, and geochemical mass-balance approach), successful application depends on scrutiny of the isotopic (14C and 13C) and chemical data to conceptualize the reactions and processes that affect the 14C content of DIC in aquifers. The recently developed graphical analysis method is shown to aid in determining which approach is most appropriate for the isotopic and chemical data from a groundwater system.

The remarkable metrological history of 14C dating: From ancient Egyptian artifacts to particles of soot and grains of pollen

NASA Astrophysics Data System (ADS)

Currie, L. A.

2003-01-01

Radiocarbon dating would not have been possible if 14C had not had the “wrong” half-life—a fact that delayed its discovery [1]. Following the discovery of this 5730 year radionuclide in laboratory experiments by Ruben and Kamen, it became clear to W. F. Libby that 14C should exist in nature, and that it could serve as a quantitative means for dating artifacts and events marking the history of civilization. The search for natural radiocarbon was a metrological challenge; the level in the living biosphere [ca. 230 Bq/kg] lay far beyond the then current state of the measurement art. This article traces the metrological history of radiocarbon, from the initial breakthrough devised by Libby, to minor (evolutionary) and major (revolutionary) advances that have brought 14C measurement from a crude, bulk [8 g carbon] dating tool, to a refined probe for dating tiny amounts of precious artifacts, and for “molecular dating” at the 10 μg to 100 μg level. The metrological advances led to opportunities and surprises, such as the non-monotonic dendrochronological calibration curve and the “bomb effect,” that spawned new multidisciplinary areas of application, ranging from cosmic ray physics to oceanography to the reconstruction of environmental history.

Analysis of past recurrent methane seep activity using radiocarbon dating of Calyptogena spp. shells in the eastern Nankai subduction zone, Japan

NASA Astrophysics Data System (ADS)

Yagasaki, Kazuhiro; Ashi, Juichiro; Yokoyama, Yusuke; Miyairi, Yosuke; Kuramoto, Shin'ichi

2016-04-01

analysis that show multiple shallow faults and chaotic sediment structure below the colony site, the Calyptogena spp. shells have a strong connection to the coseismic faulting activity and could show potential for radiocarbon dating to be applied on marine samples providing the necessary calibration tools are available.

The radiocarbon hydroxyl technique

NASA Technical Reports Server (NTRS)

Campbell, Malcolm J.; Sheppard, John C.

1994-01-01

The Radiocarbon Technique depends upon measuring the rate of oxidation of CO in an essentially unperturbed sample of air. The airborne technique is slightly different. Hydroxyl concentrations can be calculated directly; peroxyl concentrations can be obtained by NO doping.

Fire and Fish: Using Radiocarbon And Stratigraphy To Discern The Impact Of Wildfire On Fish Metapopulations

NASA Astrophysics Data System (ADS)

Schaffrath, K. R.; Finch, C.; Belmont, P.; Budy, P.

2015-12-01

Wildfires have profound and variable impacts on erosion, channel morphology, and aquatic habitat. Previous research has quantified post-fire geomorphic response on event and millennial timescales. While these studies have informed our understanding of post-fire geomorphic response during the Holocene, we have yet to fully understand the variability of post-wildfire geomorphic response and how it might change in response to changing climate. Response of aquatic biota is just as variable as post-wildfire response yet we know very little about effects on metapopulations and how management decisions affect aquatic populations. Barriers to movement are installed to isolate native fish populations and prescribed fire and thinning are used to try to reduce future wildfire severity and extent. In order to improve understanding of the implications of management decisions, we evaluated geomorphic response and synchronicity of wildfires over the Holocene relative to the impact to the metapopulation of Bonneville cutthroat trout from a recent wildfire. The Twitchell Canyon fire burned 45,000 acres near Beaver, UT in July 2010. Over 30% of the area burned at high severity, which included two major headwater streams that sustained a trout population. In summer 2011, monsoonal thunderstorms caused massive debris flows and sheetflow erosion that altered channel morphology and aquatic habitat in the burned area. A previously robust, non-native trout fishery was nearly extirpated as a result of the geomorphic response to the wildfire. We used radiocarbon dating of burned material to determine how often headwater streams burned synchronously over the Holocene. Radiocarbon dates are associated with field observations of stratigraphy in order to infer geomorphic response to historic wildfires. Thirty samples were collected from sediment layers in 10 alluvial fans distributed among three watersheds (two burned and one unburned in the 2010 fire). Preliminary results suggest that we

Time since death and decay rate constants of Norway spruce and European larch deadwood in subalpine forests determined using dendrochronology and radiocarbon dating

NASA Astrophysics Data System (ADS)

Petrillo, M.; Cherubini, P.; Fravolini, G.; Ascher, J.; Schärer, M.; Synal, H.-A.; Bertoldi, D.; Camin, F.; Larcher, R.; Egli, M.

2015-09-01

Due to the large size and highly heterogeneous spatial distribution of deadwood, the time scales involved in the coarse woody debris (CWD) decay of Picea abies (L.) Karst. and Larix decidua Mill. in Alpine forests have been poorly investigated and are largely unknown. We investigated the CWD decay dynamics in an Alpine valley in Italy using the five-decay class system commonly employed for forest surveys, based on a macromorphological and visual assessment. For the decay classes 1 to 3, most of the dendrochronological samples were cross-dated to assess the time that had elapsed since tree death, but for decay classes 4 and 5 (poorly preserved tree rings) and some others not having enough tree rings, radiocarbon dating was used. In addition, density, cellulose and lignin data were measured for the dated CWD. The decay rate constants for spruce and larch were estimated on the basis of the density loss using a single negative exponential model. In the decay classes 1 to 3, the ages of the CWD were similar varying between 1 and 54 years for spruce and 3 and 40 years for larch with no significant differences between the classes; classes 1-3 are therefore not indicative for deadwood age. We found, however, distinct tree species-specific differences in decay classes 4 and 5, with larch CWD reaching an average age of 210 years in class 5 and spruce only 77 years. The mean CWD rate constants were 0.012 to 0.018 yr-1 for spruce and 0.005 to 0.012 yr-1 for larch. Cellulose and lignin time trends half-lives (using a multiple-exponential model) could be derived on the basis of the ages of the CWD. The half-lives for cellulose were 21 yr for spruce and 50 yr for larch. The half-life of lignin is considerably higher and may be more than 100 years in larch CWD.

New radiocarbon dating and demographic insights into San Juan ante Portam Latinam, a possible Late Neolithic war grave in North-Central Iberia.

PubMed

Fernández-Crespo, Teresa; Schulting, Rick J; Ordoño, Javier; Duering, Andreas; Etxeberria, Francisco; Herrasti, Lourdes; Armendariz, Ángel; Vegas, José I; Bronk Ramsey, Christopher

2018-03-15

San Juan ante Portam Latinam is one of a small number of European Neolithic sites meeting many of the archaeological criteria expected for a mass grave, and furthermore presents evidence for violent conflict. This study aims to differentiate between what is potentially a single episode of deposition, versus deposition over some centuries, or, alternatively, that resulting from a combination of catastrophic and attritional mortality. The criteria developed are intended to have wider applicability to other such proposed events. Ten new AMS 14 C determinations on human bone from the site, together with previously available dates, are analyzed through Bayesian modeling to refine the site's chronology. This is used together with the population's demographic profile as the basis for agent-based demographic modeling. The new radiocarbon results, while improving the site's chronology, fail to resolve the question whether the burial represents a single event, or deposition over decades or centuries-primarily because the dates fall within the late fourth millennium BC plateau in the calibration curve. The demographic modeling indicates that the population's age and sex distribution fits neither a single catastrophic event nor a fully attritional mortality profile, but instead may partake of elements of both. It is proposed that San Juan ante Portam Latinam was used as burial place for the mainly adolescent and adult male dead of a particular or multiple violent engagements (e.g., battles), while previously or subsequently seeing use for attritional burial by other members of one or more surrounding communities dead over the course of a few generations. The overall bias towards males, particularly to the extent that many may represent conflict mortality, has implications for the structure of the surviving community, the members of which may have experienced increased vulnerability in the face of neighboring aggressors. © 2018 Wiley Periodicals, Inc.

Reconciling radiocarbon and ice core timescales over the Holocene - Cosmogenic radionuclides as synchronization tools

NASA Astrophysics Data System (ADS)

Muscheler, R.; Adolphi, F.; Mekhaldi, F.

2015-12-01

The atmospheric production rates of cosmogenic radionuclides, such as 14C and 10Be, vary globally due to external processes, namely the solar and geomagnetic modulation of the galactic cosmic ray flux as well as solar proton events. This signature is recorded in various archives such as ice cores (10Be) and tree-rings (14C). Hence, cosmogenic radionuclides offer a means to continuously assess timescale differences between two of the most widely used timescales in paleoclimatology - the radiocarbon and the ice core timescales. Short lived solar proton events additionally provide distinct marker horizons that allow synchronization of discrete horizons at annual precision. We will present a cosmogenic radionuclide based synchronization of the Greenland ice core timescale (GICC05, Svensson et al., 2008) and the radiocarbon timescale (IntCal13, Reimer et al., 2013) over the Holocene. This synchronization allows radiocarbon dated and ice core paleoclimate records to be compared on a common timescale at down to sub-decadal precision. We will compare these results to independent discrete isochrones obtained from tephrochronology and solar proton events. In addition, we will discuss implications for the accuracy and uncertainty estimates of GICC05 over the Holocene. Reimer, P. J., Bard, E., Bayliss, A., Beck, J. W., Blackwell, P. G., Bronk Ramsey, C., Buck, C. E., Cheng, H., Edwards, R. L., Friedrich, M., Grootes, P. M., Guilderson, T. P., Haflidason, H., Hajdas, I., Hatté, C., Heaton, T. J., Hoffmann, D. L., Hogg, A. G., Hughen, K. A., Kaiser, K. F., Kromer, B., Manning, S. W., Niu, M., Reimer, R. W., Richards, D. A., Scott, E. M., Southon, J. R., Staff, R. A., Turney, C. S. M., and van der Plicht, J.: IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0-50,000 Years cal BP, Radiocarbon, 55, 1869-1887, 10.2458/azu_js_rc.55.16947, 2013. Svensson, A., Andersen, K. K., Bigler, M., Clausen, H. B., Dahl-Jensen, D., Davies, S. M., Johnsen, S. J., Muscheler, R., Parrenin

Radiocarbon ages on late pleistocene loess stratigraphy of Nebraska and Kansas, Central Great Plains, U.S.A.

NASA Astrophysics Data System (ADS)

Martin, Charles W.

In the central Great Plains of the United States, radiocarbon dating of loess and buried soils is clarifying the late Quaternary loess chronology for the period 25,000 to 10,000 BP. Along Harland Lake, Nebraska, a soil developed in the Gilman Canyon Formation and overlain by Peoria Loess has radiocarbon ages on soil humates of 30,700 to 21,500 BP. At one site, two Picea charcoal bands in the lower meter of Peoria Loess have radiocarbon ages of 21,250 and 19,730 BP. Therefore, in the vicinity of Harlan Lake, deposition of Peoria Loess apparently began around 21,000 BP. Peoria Loess deposition appears to have been interrupted by an episode of river entrenchment prior to 12,600 BP. Spring activity shortly thereafter suggests that incision was coeval to an increase in effective moisture. The termination of Peoria Loess deposition is marked by the Brady Soil, which in the Harlan Lake area has radiocarbon ages on soil humates of 11,800 to 10,200 BP. Comparison of the Harlan Lake chronology with chronologies completed elsewhere in the central Great Plains reveals general synchrony among periods of pedogenesis and Peoria Loess deposition. Little is known, however, about vegetation conditions in the region when loess was accumulating. Charcoal has been noted chiefly in the basal Peoria Loess, suggesting that some trees were present during initial Peoria Loess deposition. The extent of this tree cover is unknown, however. Charcoal is rare in the middle and upper Peoria Loess.

Optimization of simultaneous tritium–radiocarbon internal gas proportional counting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonicalzi, R. M.; Aalseth, C. E.; Day, A. R.

Specific environmental applications can benefit from dual tritium and radiocarbon measurements in a single compound. Assuming typical environmental levels, it is often the low tritium activity relative to the higher radiocarbon activity that limits the dual measurement. In this paper, we explore the parameter space for a combined tritium and radiocarbon measurement using a methane sample mixed with an argon fill gas in low-background proportional counters of a specific design. We present an optimized methane percentage, detector fill pressure, and analysis energy windows to maximize measurement sensitivity while minimizing count time. The final optimized method uses a 9-atm fill ofmore » P35 (35% methane, 65% argon), and a tritium analysis window from 1.5 to 10.3 keV, which stops short of the tritium beta decay endpoint energy of 18.6 keV. This method optimizes tritium counting efficiency while minimizing radiocarbon beta decay interference.« less

Palaeoecological caracterisation of the mammoth steppe at Final Pleistocene in Central Ukraine from zooarchaeology, stable isotope analyses and direct radiocarbon dating

NASA Astrophysics Data System (ADS)

Péan, Stéphane; Drucker, Dorothée.; Bocherens, Hervé; Haesaerts, Paul; Valladas, Hélène; Stupak, Dmytro; Nuzhnyi, Dmytro

2010-05-01

that a modification of the regional plant and climatic context may have inferred a change of food resource for mammoths, which could have been put into food competition with horses. Mammoths from Central Ukraine at late OIS 2 may have formed an isolated local population, under the pressure of modified ecological conditions, compared to the period of maximal extension of the mammoth steppe. Thus, thanks to a combined approach of zooarchaeology, stable isotopes and radiocarbon dating, in the stratigraphic context, a better knowledge of the palaeoecological context of the last mammoths at late Pleniglacial in Central Ukraine is expected.

Directly dated starch residues document early formative maize (Zea mays L.) in tropical Ecuador

PubMed Central

Zarrillo, Sonia; Pearsall, Deborah M.; Raymond, J. Scott; Tisdale, Mary Ann; Quon, Dugane J.

2008-01-01

The study of maize (Zea mays L.) domestication has advanced from questions of its origins to the study—and debate—of its dietary role and the timing of its dispersal from Mexico. Because the investigation of maize's spread is hampered by poor preservation of macrobotanical remains in the Neotropics, research has focused on microbotanical remains whose contexts are often dated by association, leading some to question the dates assigned. Furthermore, some scholars have argued that maize was not introduced to southwestern Ecuador until ≈4150–3850 calendar years before the present (cal B.P.), that it was used first and foremost as a fermented beverage in ceremonial contexts, and that it was not important in everyday subsistence, challenging previous studies based on maize starch and phytoliths. To further investigate these questions, we analyzed every-day cooking vessels, food-processing implements, and sediments for starch and phytoliths from an archaeological site in southwestern Ecuador constituting a small Early Formative village. Employing a new technique to recover starch granules from charred cooking-pot residues we show that maize was present, cultivated, and consumed here in domestic contexts by at least 5300–4950 cal B.P. Directly dating the residues by accelerator mass spectrometry (AMS) radiocarbon measurement, our results represent the earliest direct dates for maize in Early Formative Ecuadorian sites and provide further support that, once domesticated ≈9000 calendar years ago, maize spread rapidly from southwestern Mexico to northwestern South America. PMID:18362336

Ocean science: Radiocarbon variability in the western North Atlantic during the last deglaciation

USGS Publications Warehouse

Robinson, L.F.; Adkins, J.F.; Keigwin, L.D.; Southon, J.; Fernandez, D.P.; Wang, S.-L.; Scheirer, D.S.

2005-01-01

We present a detailed history of glacial to Holocene radiocarbon in the deep western North Atlantic from deep-sea corals and paired benthic-planktonic foraminifera. The deglaciation is marked by switches between radiocarbon-enriched and -depleted waters, leading to large radiocarbon gradients in the water column. These changes played an important role in modulating atmospheric radiocarbon. The deep-ocean record supports the notion of a bipolar seesaw with increased Northern-source deep-water formation linked to Northern Hemisphere warming and the reverse. In contrast, the more frequent radiocarbon variations in the intermediate/deep ocean are associated with roughly synchronous changes at the poles.

AMS 14C analysis of teeth from archaeological sites showing anomalous esr dating results

NASA Astrophysics Data System (ADS)

Grün, Rainer; Abeyratne, Mohan; Head, John; Tuniz, Claudio; Hedges, Robert E. M.

We have carried out AMS radiocarbon analysis on two groups of samples: the first one gave reasonable ESR age estimates and the second one yielded serious age underestinations. All samples were supposedly older than 35 ka, the oldest being around 160 ka. Two pretreatment techniques were used for radiocarbon dating: acid evolution and thermal release. Heating to 600, 750 and 900°C combined with total de-gassing at these temperatures was chosen to obtain age estimates on the organic fraction, secondary carbonates and original carbonate present in the hydroxyapatite mineral phase, respectively. All radiocarbon results present serious age underestimations. The secondary carbonate fraction gives almost modern results indicating an extremely rapid exchange of this component. Owing to this very rapid carbonate exchange it is not likely that the ESR signals used for dating are associated with the secondary carbonates. One tooth from Tabun with independent age estimates of >150 ka was further investigated by the Oxford AMS laboratory, yielding an age estimate of 1930±100 BP on the residual collagen from dentine and 18,000±160 BP on the carbonate component of the enamel bioapatite. We did not, however, find an explanation of why some samples give serious ESR underestimatioils whilst many others provide reasonable results.

Radiometric dating of the Siloam Tunnel, Jerusalem.

PubMed

Frumkin, Amos; Shimron, Aryeh; Rosenbaum, Jeff

2003-09-11

The historical credibility of texts from the Bible is often debated when compared with Iron Age archaeological finds (refs. 1, 2 and references therein). Modern scientific methods may, in principle, be used to independently date structures that seem to be mentioned in the biblical text, to evaluate its historical authenticity. In reality, however, this approach is extremely difficult because of poor archaeological preservation, uncertainty in identification, scarcity of datable materials, and restricted scientific access into well-identified worship sites. Because of these problems, no well-identified Biblical structure has been radiometrically dated until now. Here we report radiocarbon and U-Th dating of the Siloam Tunnel, proving its Iron Age II date; we conclude that the Biblical text presents an accurate historic record of the Siloam Tunnel's construction. Being one of the longest ancient water tunnels lacking intermediate shafts, dating the Siloam Tunnel is a key to determining where and when this technological breakthrough took place. Siloam Tunnel dating also refutes a claim that the tunnel was constructed in the second century bc.

preparation of microgram samples on iron wool for radiocarbon analysis via accelerator mass spectrometry: A closed-system approach

NASA Astrophysics Data System (ADS)

Verkouteren, R. Michael; Klouda, George A.; Currie, Lloyd A.; Donahue, Douglas J.; Jull, A. J. Timothy; Linick, T. W.

1987-11-01

A technique has been developed at NBS for the production of high quality targets for radiocarbon analysis by accelerator mass spectrometry (AMS). Our process optimizes chemical yields, ion currents and characterizes the chemical blank. The approach encompasses sample combustion to CO 2, catalytic reduction of CO 2 by Zn to CO, reduction to graphitic carbon on high-purity iron wool and in situ formation of a homogeneous iron-carbon bead; all steps are performed in a closed system. The total measurement system blank and variability are considered in the light of contributions from combustion, iron wool, reduction, bead formation and instrument blank. Additionally, use of this approach provides an increase in throughput, i.e. the effective management of large numbers of samples. Chemical yields for 50-800 μg C samples deposited on 15 mg iron wool were greater than 90%. Integrated 12C - ion currents observed were significant, being 4-64% of those observed in pure graphite. These currents are about an order of magnitude greater than those expected from dilution of graphite with an inert substrate. Isotopic accuracy, precision and blank were assessed by measuring the {14C }/{13C } ratios of a series of targets prepared from dead carbon and oxalic acid (SRM 4990C). Each target was typically measured for one hour; bead consumption was estimated at 5% to 10%. System blank subsequent to combustion was equivalent to (2.2 ± 0.5) μg modern carbon (chemistry + instrument); combustion blank currently stands at (0.4 ± 0.1) (SE, n = 6) μg C.

Map of Western Copper River Basin, Alaska, Showing Lake Sediments and Shorelines, Glacial Moraines, and Location of Stratigraphic Sections and Radiocarbon-Dated Samples

USGS Publications Warehouse

Williams, John R.; Galloway, John P.

1986-01-01

The purpose of this report is to make available basic data on radiocarbon dating of 61 organic samples from 40 locations in the western Copper River Basin and adjacent uplands and in the uppermost Matanuska River Valley. The former distribution of late Quaternary glacial lakes and of glaciers as mapped from field work and photo interpretation is provided as background for interpretation of the radiocarbon dates and are the basic data needed for construction of the late Quaternary chronology. The glacial boundaries, formed and expressed by moraines, ice-contact margins, marginal channels, deltas, and other features, are obscured by a drape of glaciolacustrine deposits in a series of glacial lakes. The highest lake, represented by bottom sediments as high as 914 m to 975 m above sea level, extends from Fog Lakes lowland on Susitna River upstream into the northwestern part of the Copper River Basin (the part now draining to Susitna River) where it apparently was held in by an ice border. It was apparently dammed by ice from the Mt. McKinley area, by Talkeetna G1acier, and may have had a temporary drainage threshold at the headwaters of Chunilna Creek. No shorelines have been noted within the map area, although Nichols and Yehle (1961) reported shorelines within the 914-975 m range in the Denali area to the north of that mapped. Recent work by geologic consultants for the Susitna Hydroelectric Project has confirmed the early inferences (Karlstrom, 1964) about the existence of a lake in the Susitna canyon, based originally on drilling by the Bureau of Reclamation about 35 years ago. According to dating of deposits at Tyone Bluff (map locations 0, P), Thorson and others (1981) concluded that a late Wisconsin advance of the glaciers between 11,535 and 21,730 years ago was followed by a brief interval of lacustrine sedimentation, and was preceded by a long period of lake deposition broken by a lowering of the lake between 32,000 and about 25,000 years ago. An alternate

Atmosphere-ocean gas exchange based on radiocarbon data

NASA Astrophysics Data System (ADS)

Byalko, Alexey

2014-05-01

In recent decades, the intensity of global atmospheric convection has accelerated faster than climate warming; it is possible to judge this process from indirect data. Increasing ocean salinity contrasts provide evidence that evaporation has intensified [1]; sea surface wind velocities and wave heights have increased [2]. The CO2 gas exchange between the atmosphere and ocean must also simultaneously increase. Monthly measurements of atmospheric CO2 concentration have been published since 1958 [3], but directly measuring its fluxes from the atmosphere to the ocean and back is hardly possible. We show they can be reconstructed from 14C isotope concentration data. In the past century, two processes influenced the atmospheric 14C concentration in opposite directions: burning fossil fuels and testing nuclear weapons in the atmosphere. We compare the gas exchange theory with measurements of radiocarbon content in the atmosphere [4—6], which allows assessing the gas exchange quantitatively for the ocean to atmosphere and atmosphere to ocean fluxes separately for period 1960—2010 [7]. References 1. Durack P. J. and Wijffels S. E., J. Climate 23, 4342 (2010). 2. Young I. R., Sieger S., and Babanin A.V., Science 332, 451 (2011). 3. NOAA Earth System Research Laboratory Data: ftp://ftp.cmdl.noaa.gov/ccg/co2/trends/co2_mm_mlo.txt. 4. Nydal R., Lövseth K. // J. Geophys. Res. 1983. V. 88. P. 3579. 5. Levin I., Kromer B. // Radiocarbon. 1997. V. 39. P. 205. 6. Miller J.B., Lehman S.J., Montzka S.A., et al. // J. Geophys. Res. 2012. V. 117. D08302. 7. Byalko A.V. Doklady Physics, 2013. V. 58, 267-271.

10Be inventories in Alpine soils and their potentiality for dating land surfaces

NASA Astrophysics Data System (ADS)

Egli, Markus; Brandová, Dagmar; Böhlert, Ralph; Favilli, Filippo; Kubik, Peter W.

2010-05-01

To exploit natural archives and geomorphic objects it is necessary to date them first. Landscape evolution of Alpine areas is often strongly related to the activities of glaciers in the Pleistocene and Holocene. At sites where no organic matter for radiocarbon dating exists and where suitable boulders for surface exposure dating (using in situ produced cosmogenic nuclides) are absent, dating of soils could give information about the timing of landscape evolution. We explored the applicability of soil dating using the inventory of meteoric Be-10 in Alpine soils. For this purpose, a set of 6 soil profiles in the Swiss and Italian Alps was investigated. The surface at these sites had already been dated (using the radiocarbon technique or surface exposure dating using in situ produced Be-10). Consequently, a direct comparison of the ages of the soils using meteoric Be-10 and other dating techniques was made possible. The estimation of Be-10 deposition rates is subject to severe limitations and strongly influences the obtained results. We tested three scenarios using a) the meteoric Be-10 deposition rates as a function of the annual precipitation rate, b) a constant Be-10 input for the Central Alps and c) as b) but assuming a pre-exposure of the parent material. The obtained ages that are based on the Be-10 inventory in soils and on scenario a) for the Be-10 input agreed reasonably well with the expected age (obtained from surface exposure or radiocarbon dating). The ages obtained from soils using scenario b) produced mostly ages that were too old whereas the approach using scenario c) seemed to yield better results than scenario b). Erosion calculations can, in theory, be performed using the Be-10 inventory and Be-10 deposition rates. An erosion estimation was possible using scenario a) and c), but not using b). The estimated erosion rates are in a reasonable range. The dating of soils using Be-10 has several potential error sources. Analytical errors as well as errors

Differential extraction of radiocarbon associated with soil biomass and humus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsao, C.W.; Bartha, R.

To detect the humification of organic compounds in soil that bypasses biomass incorporation, selective extraction procedures for radiocarbon from soil biomass and humus were evaluated. Following the incubation of [sup 14]C-glucose and [sup 14]C-benzoate in soil, fumigation--0.5 M K[sub 2]SO[sub 4] extraction and 0.15 M Na[sub 4]P[sub 2]O[sub 7] extraction selectively removed biomass-associated and humus-associated radiocarbon, respectively. Applying the recovery correction of 3.4[times] to biomass and 3.5[times] to humus, radiocarbon balances of 95 to 107% were obtained during a time window following the degradation of these substrates. Negligible overlap between the extractions renders the technique suitable for investigating the fatemore » of organics that, through cometabolism, attain unusual radiocarbon distributions in soil.« less

10Be inventories in Alpine soils and their potential for dating land surfaces

NASA Astrophysics Data System (ADS)

Egli, Markus; Brandová, Dagmar; Böhlert, Ralph; Favilli, Filippo; Kubik, Peter W.

2010-07-01

To exploit natural sedimentary archives and geomorphic landforms it is necessary to date them first. Landscape evolution of Alpine areas is often strongly related to the activities of glaciers in the Pleistocene and Holocene. At sites where no organic matter for radiocarbon dating exists and where suitable boulders for surface exposure dating (using in situ produced cosmogenic nuclides) are absent, dating of soils could give information about the timing of landscape evolution. This paper explores the applicability of soil dating using the inventory of meteoric 10Be in Alpine soils. For this purpose, a set of 6 soil profiles in the Swiss and Italian Alps was investigated. The surface at these sites had already been dated (using the radiocarbon technique or the surface exposure determination using in situ produced 10Be). Consequently, a direct comparison of the ages of the soils using meteoric 10Be and other dating techniques was made possible. The estimation of 10Be deposition rates is subject to severe limitations and strongly influences the obtained results. We tested three scenarios using a) the meteoric 10Be deposition rates as a function of the annual precipitation rate, b) a constant 10Be input for the Central Alps, and c) as b) but assuming a pre-exposure of the parent material. The obtained ages that are based on the 10Be inventory in soils and on scenario a) for the 10Be input agreed reasonably well with the age using surface exposure or radiocarbon dating. The ages obtained from soils using scenario b) produced ages that were mostly too old whereas the approach using scenario c) seemed to yield better results than scenario b). Erosion calculations can, in theory, be performed using the 10Be inventory and 10Be deposition rates. An erosion estimation was possible using scenario a) and c), but not using b). The calculated erosion rates using these scenarios seemed to be plausible with values in the range of 0-57 mm/ky. The dating of soils using 10Be has

Ion beam analysis and AMS dating of the silver coin hoard of Preuschdorf (Alsace, France)

NASA Astrophysics Data System (ADS)

Beck, Lucile; Alloin, Elise; Vigneron, Anaïs; Caffy, Ingrid; Klein, Ulrich

2017-09-01

The hoard of Preuschdorf is a monetary deposit discovered in Alsace (France) in 2005. This find was composed of 7327 silver-copper coins. They seem to have been struck over more than one century, between the end of the 15th and the beginning of the 17th century. This hoard is an exceptional find composed of a large quantity of coins from various periods, areas and contexts. It is also remarkable by the presence of counterfeit coins. IBA was used to analyze the silver content of the official coins by combining PIXE and RBS. The fineness was found to be between 20 and 42% according to the mint place and an unexpected subdivision of the values has been revealed. For the counterfeit coins, the analyses were able to bring to light different elaboration processes: amalgam silvering with two various contents of mercury and application of a thin layer of pure silver. Finally, linen fibers attached to the coins have been dated by AMS radiocarbon dating. The radiocarbon calibrated dates perfectly match with the chronological range given by the coins.

Forensic applications of 14C bomb-pulse dating

NASA Astrophysics Data System (ADS)

Zoppi, U.; Skopec, Z.; Skopec, J.; Jones, G.; Fink, D.; Hua, Q.; Jacobsen, G.; Tuniz, C.; Williams, A.

2004-08-01

After a brief review of the basics of 14C bomb-pulse dating, this paper presents two unique forensic applications. Particular attention is dedicated to the use of the 14C bomb-pulse to establish the time of harvest of illicit drugs such as heroin and opium. Preliminary measurements of 14C concentrations in milligram samples taken from seized drugs are presented. 14C bomb-pulse dating can determine whether drug distribution originates from stockpiles or recent manufacture, and support the action of law enforcement authorities against criminal organisations involved in drug trafficking. In addition, we describe the dating of wine vintages for a number of authenticated single label vintage red wines from the Barossa Valley - South Australia. Our results show that radiocarbon dating can be used to accurately determine wine vintages and therefore reveal the addition of unrelated materials of natural and synthetic origin.

Development and application of a method for ivory dating by analyzing radioisotopes to distinguish legal from illegal ivory.

PubMed

Schmidberger, Andreas; Durner, Bernhard; Gehrmeyer, David; Schupfner, Robert

2018-06-19

The age determination of elephant ivory provides necessary and crucial information for all criminal prosecution authorities enforcing the Convention on International Trade in Endangered Species of Wild Fauna and Flora. The knowledge of the age of ivory allows to distinguish between pre-convention, hence legal material and ivory deriving from recent, illegal poaching incidents. The commonly applied method to determine the age of ivory is radiocarbon dating in the form of bomb pulse dating, which however will fade out soon. This work provides an enhancement of the radiocarbon dating method by supplementary determination of the isotope profile of 90-Sr and the two thorium isotopes 228-Th and 232-Th. This combined analysis allows for a precise and unambiguous age determination of ivory. We provided calibration curves for all involved radionuclides by analyzing ivory samples with known age and investigated a new method for the extraction of strontium from ivory. Copyright © 2018 Elsevier B.V. All rights reserved.

Extension of the Southern Hemisphere Atmospheric Radiocarbon Curve, 2120-850 years BP: Results from Tasmanian Huon Pine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zimmerman, S R; P.Guilderson, T; Buckley, B M

2010-02-12

Decadal samples of dendrochronologically-dated pine (Lagorostrobos franklinii) from the Stanley River basin, Tasmania have been radiocarbon dated between 2120-850 yr BP. This data set overlaps and extends the current Southern Hemisphere record, which currently covers the period 110-995 yr BP. There is good agreement between the two records between 995-850 yr BP, between sample replicates and with consensus values for standards. As in the younger dataset, we find evidence for a distinct but variable offset between the southern hemisphere data and IntCal04; although this is likely due to real temporal variability in the interhemispheric offset, further work is planned tomore » rule out possible laboratory or sample preparation differences.« less

A novel tertiary prep-HPLC method for the isolation of single amino acids for AMS-radiocarbon measurement.

PubMed

Fernandes, Ricardo; Koudelka, Tomas; Tholey, Andreas; Dreves, Alexander

2017-07-15

AMS-radiocarbon measurements of amino acids can potentially provide more reliable radiocarbon dates than bulk collagen analysis. Nonetheless, the applicability of such an approach is often limited by the low-throughput of existing isolation methods and difficulties in determining the contamination introduced during the separation process. A novel tertiary prep-HPLC amino acid isolation method was developed that relies on the combustion of eluted material without requiring any additional chemical steps. Amino acid separation was carried out using a gradient mix of pure water and phosphoric acid with an acetonitrile step in-between runs to remove hydrophobic molecules from the separation column. The amount of contaminant carbon and its 14 C content were determined from two-point measurements of collagen samples of known 14 C content. The amount of foreign carbon due to the isolation process was estimated at 4±1μg and its 14 C content was 0.43±0.01 F 14 C. Radiocarbon values corrected for carbon contamination have only a minor increase in uncertainties. For Holocene samples, this corresponds to an added uncertainty typically smaller than 10 14 Cyears. The developed method can be added to routine AMS measurements without implying significant operational changes and offers a level of measurement uncertainty that is suitable for many archaeological, ecological, environmental, and biological applications. Copyright © 2017. Published by Elsevier B.V.

Xenocrysts and antecrysts and their effect on the precision of 40Ar/39Ar dates of explosive volcanic eruption

NASA Astrophysics Data System (ADS)

Smith, V.; Mark, D.; Blockley, S.; Weh, A.

2010-12-01

Evolved melts that fuel large explosive eruptions encounter, and are often generated through melting, crystal-rich parts of the magmatic system that fed previous eruptions. This results in many antecrysts being incorporated into the magma prior to eruption. In addition, many xenocrysts are entrained during eruption through conduit excavation. Combining all these crystal populations produces 40Ar/39Ar dates with wide-ranges, such as those that are often reported in the literature. In order to gain very precise dates of volcanic events it is thus necessary to assess whether antecrysts and xenocrysts effect the precision of the dates, and establish ways to reduce these components. Here we use the deposits of the ~11 ka Ulleung-Oki eruption from the alkaline volcanic island of Ulleung, situated 130 km east of the Korean peninsula. The eruption deposits are widely dispersed and found in the Suigetsu lake sequence from central Japan. A precise date of the tephra would help with construction of the terrestrial radiocarbon calibration curve that spans back to the limit of radiocarbon dating (~50 ka). The new calibration model is currently being constructed using varve chronology (annual layer counting) and >600 14C determinations of terrestrial macrofossils*. However, the annual layers stop shortly after the 2 cm-thick Ulleung-Oki tephra. Precise dates of this volcanic event using a method that is independent of radiocarbon dating, would help validate the chronology of the core, and test the validity of the radiocarbon calibration curve. The tephra in the core has been correlated to proximal deposits using major and trace element composition (determined using an electron microprobe and LA-ICPMS) of the glass shards that comprise the distal ash. The proximal Ulleung-Oki eruption deposits are sandine-rich with crystals that range from ~80 microns to a few millimetres in size. These are likely to be a mixture of phenocrysts, antecrysts and xenocrysts. In order to get a very

Radiocarbon chronology of Manot Cave, Israel and Upper Paleolithic dispersals

PubMed Central

Alex, Bridget; Barzilai, Omry; Hershkovitz, Israel; Marder, Ofer; Berna, Francesco; Caracuta, Valentina; Abulafia, Talia; Davis, Lauren; Goder-Goldberger, Mae; Lavi, Ron; Mintz, Eugenia; Regev, Lior; Bar-Yosef Mayer, Daniella; Tejero, José-Miguel; Yeshurun, Reuven; Ayalon, Avner; Bar-Matthews, Mira; Yasur, Gal; Frumkin, Amos; Latimer, Bruce; Hans, Mark G.; Boaretto, Elisabetta

2017-01-01

The timing of archeological industries in the Levant is central for understanding the spread of modern humans with Upper Paleolithic traditions. We report a high-resolution radiocarbon chronology for Early Upper Paleolithic industries (Early Ahmarian and Levantine Aurignacian) from the newly excavated site of Manot Cave, Israel. The dates confirm that the Early Ahmarian industry was present by 46,000 calibrated years before the present (cal BP), and the Levantine Aurignacian occurred at least between 38,000 and 34,000 cal BP. This timing is consistent with proposed migrations or technological diffusions between the Near East and Europe. Specifically, the Ahmarian could have led to the development of the Protoaurignacian in Europe, and the Aurignacian in Europe could have spread back to the Near East as the Levantine Aurignacian. PMID:29152566

Radiocarbon chronology of Manot Cave, Israel and Upper Paleolithic dispersals.

PubMed

Alex, Bridget; Barzilai, Omry; Hershkovitz, Israel; Marder, Ofer; Berna, Francesco; Caracuta, Valentina; Abulafia, Talia; Davis, Lauren; Goder-Goldberger, Mae; Lavi, Ron; Mintz, Eugenia; Regev, Lior; Bar-Yosef Mayer, Daniella; Tejero, José-Miguel; Yeshurun, Reuven; Ayalon, Avner; Bar-Matthews, Mira; Yasur, Gal; Frumkin, Amos; Latimer, Bruce; Hans, Mark G; Boaretto, Elisabetta

2017-11-01

The timing of archeological industries in the Levant is central for understanding the spread of modern humans with Upper Paleolithic traditions. We report a high-resolution radiocarbon chronology for Early Upper Paleolithic industries (Early Ahmarian and Levantine Aurignacian) from the newly excavated site of Manot Cave, Israel. The dates confirm that the Early Ahmarian industry was present by 46,000 calibrated years before the present (cal BP), and the Levantine Aurignacian occurred at least between 38,000 and 34,000 cal BP. This timing is consistent with proposed migrations or technological diffusions between the Near East and Europe. Specifically, the Ahmarian could have led to the development of the Protoaurignacian in Europe, and the Aurignacian in Europe could have spread back to the Near East as the Levantine Aurignacian.

Radiocarbon and DNA evidence for a pre-Columbian introduction of Polynesian chickens to Chile

PubMed Central

Storey, Alice A.; Ramírez, José Miguel; Quiroz, Daniel; Burley, David V.; Addison, David J.; Walter, Richard; Anderson, Atholl J.; Hunt, Terry L.; Athens, J. Stephen; Huynen, Leon; Matisoo-Smith, Elizabeth A.

2007-01-01

Two issues long debated among Pacific and American prehistorians are (i) whether there was a pre-Columbian introduction of chicken (Gallus gallus) to the Americas and (ii) whether Polynesian contact with South America might be identified archaeologically, through the recovery of remains of unquestionable Polynesian origin. We present a radiocarbon date and an ancient DNA sequence from a single chicken bone recovered from the archaeological site of El Arenal-1, on the Arauco Peninsula, Chile. These results not only provide firm evidence for the pre-Columbian introduction of chickens to the Americas, but strongly suggest that it was a Polynesian introduction. PMID:17556540

Radiocarbon and DNA evidence for a pre-Columbian introduction of Polynesian chickens to Chile.

PubMed

Storey, Alice A; Ramírez, José Miguel; Quiroz, Daniel; Burley, David V; Addison, David J; Walter, Richard; Anderson, Atholl J; Hunt, Terry L; Athens, J Stephen; Huynen, Leon; Matisoo-Smith, Elizabeth A

2007-06-19

Two issues long debated among Pacific and American prehistorians are (i) whether there was a pre-Columbian introduction of chicken (Gallus gallus) to the Americas and (ii) whether Polynesian contact with South America might be identified archaeologically, through the recovery of remains of unquestionable Polynesian origin. We present a radiocarbon date and an ancient DNA sequence from a single chicken bone recovered from the archaeological site of El Arenal-1, on the Arauco Peninsula, Chile. These results not only provide firm evidence for the pre-Columbian introduction of chickens to the Americas, but strongly suggest that it was a Polynesian introduction.

Comparison of Radiocarbon Ages of Sediments, Plants, and Shells From Coastal Lakes in North Florida

NASA Astrophysics Data System (ADS)

Wang, Y.; Das, O.; Liu, J.; Xu, X.; Roy, R.; Donoghue, J. F.; Means, G. H.

2017-12-01

Coastal lakes sediments are valuable archives of paleo-hurricanes and environmental changes during the late Quaternary provided that they can be accurately dated. Here, we report new radiocarbon (14C) dates derived from various organic and inorganic substrates, including bulk sediment organic matter, plants, shells, particulate organic matter (POM) and dissolved organic matter (DOM), from three coastal lakes in Florida, and compare these ages to evaluate the "reservoir effect" on 14C dating of both organic and inorganic carbon in these lakes. Bulk sediment organic matter yielded consistently older 14C ages than contemporaneous plants and shell fragments, indicating significant radiocarbon deficiencies in sedimentary organic matter in these coastal lakes, caused by influx of old organic carbon from terrestrial sources (such as soils and ancient peat deposits) in the watershed. Several reversals are observed in the 14C ages of bulk sediment organic matter in sediment cores from these lakes, indicating that input of aged organic matter from terrestrial sources into these lakes can vary considerably over time. DOM and POM samples collected at different times also yielded variable 14C signatures, further confirming the temporal variability in the contribution of old organic carbon from terrestrial sources to the lakes. The 14C age discrepancy between bulk sediment organic matter and co-occurring plant fragments or shells varies from less than one hundred years to nearly three thousand years in sediment cores examined in this study. The results show that 14C ages obtained from bulk sediment organic matter in these coastal lakes are unreliable. Analyses of both modern and fossil shells from one of the lakes suggest that the 14C reservoir effect on inorganic carbon in the lake is small and thus freshwater shells (if preserved in the sediment cores) may serve as a good substrate for 14C dating in the absence of plant fragments. However, unidentifiable shell fragments

Predicted net efflux of radiocarbon from the ocean and increase in atmospheric radiocarbon content

NASA Astrophysics Data System (ADS)

Caldeira, Ken; Rau, Greg H.; Duffy, Philip B.

Prior to changes introduced by man, production of radiocarbon (14C) in the stratosphere nearly balanced the flux of 14C from the atmosphere to the ocean and land biosphere, which in turn nearly balanced radioactive decay in these 14C reservoirs. This balance has been altered by land-use changes, fossil-fuel burning, and atmospheric nuclear detonations. Here, we use a model of the global carbon cycle to quantify these radiocarbon fluxes and make predictions about their magnitude in the future. Atmospheric nuclear detonations increased atmospheric 14C content by about 80% by the mid-1960's. Since that time, the 14C content of the atmosphere has been diminishing as this bomb radiocarbon has been entering the oceans and terrestrial biosphere. However, we predict that atmospheric 14C content will reach a minimum and start to increase within the next few years if fossil-fuel burning continues according to a “business-as-usual” scenario, even though fossil fuels are devoid of 14C. This will happen because fossil-fuel carbon diminishes the net flux of 14C from the atmosphere to the oceans and land biosphere, forcing 14C to accumulate in the atmosphere. Furthermore, the net flux of both bomb and natural 14C into the ocean are predicted to continue to slow and then, in the middle of the next century, to reverse, so that there will be a net flux of 14C from the ocean to the atmosphere. The predicted reversal of net 14C fluxes into the ocean is a further example of human impacts on the global carbon cycle.

Radiocarbon dating of dissolved inorganic carbon in groundwater from confined parts of the Upper Floridan aquifer, Florida, USA

NASA Astrophysics Data System (ADS)

Plummer, Niel; Sprinkle, Craig

2001-03-01

Geochemical reaction models were evaluated to improve radiocarbon dating of dissolved inorganic carbon (DIC) in groundwater from confined parts of the Upper Floridan aquifer in central and northeastern Florida, USA. The predominant geochemical reactions affecting the 14C activity of DIC include (1) dissolution of dolomite and anhydrite with calcite precipitation (dedolomitization), (2) sulfate reduction accompanying microbial degradation of organic carbon, (3) recrystallization of calcite (isotopic exchange), and (4) mixing of fresh water with as much as 7% saline water in some coastal areas. The calculated cumulative net mineral transfers are negligibly small in upgradient parts of the aquifer and increase significantly in downgradient parts of the aquifer, reflecting, at least in part, upward leakage from the Lower Floridan aquifer and circulation that contacted middle confining units in the Floridan aquifer system. The adjusted radiocarbon ages are independent of flow path and represent travel times of water from the recharge area to the sample point in the aquifer. Downgradient from Polk City (adjusted age 1.7 ka) and Keystone Heights (adjusted age 0.4 ka), 14 of the 22 waters have adjusted 14C ages of 20-30 ka, indicating that most of the fresh-water resource in the Upper Floridan aquifer today was recharged during the last glacial period. All of the paleowaters are enriched in 18O and 2H relative to modern infiltration, with maximum enrichment in δ18O of approximately 2.0‰. Résumé. Les modèles de réactions géochimiques ont été évalués afin de tester la datation par le radiocarbone du carbone minéral dissous (CMD) des eaux souterraines dans les parties captives de la nappe supérieure de Floride, en Floride centrale et nord-orientale (États-Unis). Les réactions géochimiques prédominantes affectant l'activité en 14C du CMD comprennent (1) la dissolution de la dolomite et de l'anhydrite accompagnée de la précipitation de la calcite (d

Evolution of chemical and isotopic composition of inorganic carbon in a complex semi-arid zone environment: Consequences for groundwater dating using radiocarbon

NASA Astrophysics Data System (ADS)

Meredith, K. T.; Han, L. F.; Hollins, S. E.; Cendón, D. I.; Jacobsen, G. E.; Baker, A.

2016-09-01

Estimating groundwater age is important for any groundwater resource assessment and radiocarbon (14C) dating of dissolved inorganic carbon (DIC) can provide this information. In semi-arid zone (i.e. water-limited environments), there are a multitude of reasons why 14C dating of groundwater and traditional correction models may not be directly transferable. Some include; (1) the complex hydrological responses of these systems that lead to a mixture of different ages in the aquifer(s), (2) the varied sources, origins and ages of organic matter in the unsaturated zone and (3) high evaporation rates. These all influence the evolution of DIC and are not easily accounted for in traditional correction models. In this study, we determined carbon isotope data for; DIC in water, carbonate minerals in the sediments, sediment organic matter, soil gas CO2 from the unsaturated zone, and vegetation samples. The samples were collected after an extended drought, and again after a flood event, to capture the evolution of DIC after varying hydrological regimes. A graphical method (Han et al., 2012) was applied for interpretation of the carbon geochemical and isotopic data. Simple forward mass-balance modelling was carried out on key geochemical processes involving carbon and agreed well with observed data. High values of DIC and δ13CDIC, and low 14CDIC could not be explained by a simple carbonate mineral-CO2 gas dissolution process. Instead it is suggested that during extended drought, water-sediment interaction leads to ion exchange processes within the top ∼10-20 m of the aquifer which promotes greater calcite dissolution in saline groundwater. This process was found to contribute more than half of the DIC, which is from a mostly 'dead' carbon source. DIC is also influenced by carbon exchange between DIC in water and carbonate minerals found in the top 2 m of the unsaturated zone. This process occurs because of repeated dissolution/precipitation of carbonate that is dependent on

Quartz OSL Dating of the loess deposit in the eastern Tibetan Plateau and its environment implications since the Last Glaciation

NASA Astrophysics Data System (ADS)

Yang, S.; Cheng, T.; Liu, W.; Fang, X.

2017-12-01

Loess deposit is widespread in the Chuanxi Plateau, the eastern Tibetan Plateau, which is a critical archive for understanding the aeolian process, the evolution of the westerly and the environment changes on the Plateau. Previous studies have shown its aeolian origin, and mainly transported by wind from the western part of the Tibetan Plateau. However, the aeolian processes of the loess and its environment implications are not well understood mainly due to lack of detailed age controls. We carry out a combined quartz optically stimulated luminescence (OSL) dating and accelerator mass spectrometry radiocarbon dating (AMS 14-C) for the loess deposits in Garzê and Jinchuan. The results indicate that the quartz OSL dating can provide reliable age controls for the loess-paleosol sequences from the Chuanxi Plateau, showing the potential of OSL to date loess in the high altitude region. The results indicate that the OSL ages are in agreement with the observed stratigraphy in the field. The constructed OSL and AMS 14-C chronology of the Garzê loess reveals that the widespread loess in Ganzi Region deposited since the Last Glacial. The dust accumulation is rapid during marine isotope stage (MIS) 3 and 2, and a relative low accumulation rate in the Holocene, which may related with the desertification processes of the inner Tibetan Plateau.

Application of Bomb Radiocarbon Chronologies to Shortfin Mako (Isurus oxyrinchus)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ardizzone, D; Cailliet, G M; Natanson, L J

performed and the number of samples for MIA analysis was insufficient for some months. Hence, unequivocal validation of shortfin mako age estimates has yet to be accomplished. Atmospheric testing of thermonuclear devices in the 1950s and 1960s effectively doubled the natural atmospheric radiocarbon ({sup 14}C). The elevated {sup 14}C levels were first recorded in 1957-58, with a peak around 1963. As a consequence, {sup 14}C entered the ocean through gas exchange with the atmosphere at the ocean surface and in terrestrial runoff. Despite variable oceanographic conditions, a worldwide rise of the bomb {sup 14}C signal entered the ocean mixed layer as dissolved inorganic carbon (DIC) in 1957-58. The large amounts of {sup 14}C released from the bomb tests produced a signature that can be followed through time, throughout the marine food web, and into deeper waters. The marked increase of radiocarbon levels was first measured in the DIC of seawater and in biogenic marine carbonates of hermatypic corals in Florida. Subsequently, this record was documented in corals from other regions and in the thallus of rhodoliths. The accumulation of radiocarbon in the hard parts of most marine organisms in the mixed layer (such as fish otoliths and bivalves) was synchronous with the coral time-series. This technique has been used to validate age estimates and longevity of numerous bony fishes to date, as well as to establish bomb radiocarbon chronologies from different oceans. In the first application of this technique to lamnoid sharks, validated annual band-pair deposition in vertebral growth bands for the porbeagle (Lamna nasus) aged up to 26 years. Radiocarbon values from samples obtained from 15 porbeagle caught in the western North Atlantic Ocean (some of which were known-age) produced a chronology similar in magnitude to the reference carbonate chronology for that region. The observed phase shift of about 3 years was attributed to different sources of carbon between vertebrae and those

Time since death and decay rate constants of Norway spruce and European larch deadwood in subalpine forests determined using dendrochronology and radiocarbon dating

NASA Astrophysics Data System (ADS)

Petrillo, Marta; Cherubini, Paolo; Fravolini, Giulia; Marchetti, Marco; Ascher-Jenull, Judith; Schärer, Michael; Synal, Hans-Arno; Bertoldi, Daniela; Camin, Federica; Larcher, Roberto; Egli, Markus

2016-03-01

Due to the large size (e.g. sections of tree trunks) and highly heterogeneous spatial distribution of deadwood, the timescales involved in the coarse woody debris (CWD) decay of Picea abies (L.) Karst. and Larix decidua Mill. in Alpine forests are largely unknown. We investigated the CWD decay dynamics in an Alpine valley in Italy using the chronosequence approach and the five-decay class system that is based on a macromorphological assessment. For the decay classes 1-3, most of the dendrochronological samples were cross-dated to assess the time that had elapsed since tree death, but for decay classes 4 and 5 (poorly preserved tree rings) radiocarbon dating was used. In addition, density, cellulose, and lignin data were measured for the dated CWD. The decay rate constants for spruce and larch were estimated on the basis of the density loss using a single negative exponential model, a regression approach, and the stage-based matrix model. In the decay classes 1-3, the ages of the CWD were similar and varied between 1 and 54 years for spruce and 3 and 40 years for larch, with no significant differences between the classes; classes 1-3 are therefore not indicative of deadwood age. This seems to be due to a time lag between the death of a standing tree and its contact with the soil. We found distinct tree-species-specific differences in decay classes 4 and 5, with larch CWD reaching an average age of 210 years in class 5 and spruce only 77 years. The mean CWD rate constants were estimated to be in the range 0.018 to 0.022 y-1 for spruce and to about 0.012 y-1 for larch. Snapshot sampling (chronosequences) may overestimate the age and mean residence time of CWD. No sampling bias was, however, detectable using the stage-based matrix model. Cellulose and lignin time trends could be derived on the basis of the ages of the CWD. The half-lives for cellulose were 21 years for spruce and 50 years for larch. The half-life of lignin is considerably higher and may be more than

Time in tortoiseshell: a bomb radiocarbon-validated chronology in sea turtle scutes.

PubMed

Van Houtan, Kyle S; Andrews, Allen H; Jones, T Todd; Murakawa, Shawn K K; Hagemann, Molly E

2016-01-13

Some of the most basic questions of sea turtle life history are also the most elusive. Many uncertainties surround lifespan, growth rates, maturity and spatial structure, yet these are critical factors in assessing population status. Here we examine the keratinized hard tissues of the hawksbill (Eretmochelys imbricata) carapace and use bomb radiocarbon dating to estimate growth and maturity. Scutes have an established dietary record, yet the large keratin deposits of hawksbills evoke a reliable chronology. We sectioned, polished and imaged posterior marginal scutes from 36 individual hawksbills representing all life stages, several Pacific populations and spanning eight decades. We counted the apparent growth lines, microsampled along growth contours and calibrated Δ(14)C values to reference coral series. We fit von Bertalanffy growth function (VBGF) models to the results, producing a range of age estimates for each turtle. We find Hawaii hawksbills deposit eight growth lines annually (range 5-14), with model ensembles producing a somatic growth parameter (k) of 0.13 (range 0.1-0.2) and first breeding at 29 years (range 23-36). Recent bomb radiocarbon values also suggest declining trophic status. Together, our results may reflect long-term changes in the benthic community structure of Hawaii reefs, and possibly shed light on the critical population status for Hawaii hawksbills. © 2016 The Author(s).

Time in tortoiseshell: a bomb radiocarbon-validated chronology in sea turtle scutes

PubMed Central

Van Houtan, Kyle S.; Andrews, Allen H.; Jones, T. Todd; Murakawa, Shawn K. K.; Hagemann, Molly E.

2016-01-01

Some of the most basic questions of sea turtle life history are also the most elusive. Many uncertainties surround lifespan, growth rates, maturity and spatial structure, yet these are critical factors in assessing population status. Here we examine the keratinized hard tissues of the hawksbill (Eretmochelys imbricata) carapace and use bomb radiocarbon dating to estimate growth and maturity. Scutes have an established dietary record, yet the large keratin deposits of hawksbills evoke a reliable chronology. We sectioned, polished and imaged posterior marginal scutes from 36 individual hawksbills representing all life stages, several Pacific populations and spanning eight decades. We counted the apparent growth lines, microsampled along growth contours and calibrated Δ14C values to reference coral series. We fit von Bertalanffy growth function (VBGF) models to the results, producing a range of age estimates for each turtle. We find Hawaii hawksbills deposit eight growth lines annually (range 5–14), with model ensembles producing a somatic growth parameter (k) of 0.13 (range 0.1–0.2) and first breeding at 29 years (range 23–36). Recent bomb radiocarbon values also suggest declining trophic status. Together, our results may reflect long-term changes in the benthic community structure of Hawaii reefs, and possibly shed light on the critical population status for Hawaii hawksbills. PMID:26740617

Geographic and temporal trends in proboscidean and human radiocarbon histories during the late Pleistocene

NASA Astrophysics Data System (ADS)

Ugan, Andrew; Byers, David

2007-12-01

The causes of large animal extinctions at the end of the Pleistocene remain a hotly debated topic focused primarily on the effects of human over hunting and climate change. Here we examine multiple, large radiocarbon data sets for humans and extinct proboscideans and explore how variation in their temporal and geographic distributions were related prior to proboscidean extinction. These data include 4532 archaeological determinations from Europe and Siberia and 1177 mammoth and mastodont determinations from Europe, Siberia, and North America. All span the period from 45,000 to 12,000 calendar years BP. We show that while the geographic ranges of dated human occupations and proboscidean remains overlap across the terminal Pleistocene of the Old World, the two groups remain largely segregated and increases in the frequency of human occupations do not coincide with declines in proboscidean remains. Prior to the Last Glacial Maximum (LGM; ca 21,000 years BP), archaeological 14C determinations increase slightly in frequency worldwide while the frequency of dated proboscidean remains varies depending on taxon and location. After the LGM, both sympatric and allopatric groups of humans and proboscideans increase sharply as climatic conditions ameliorate. Post-LGM radiocarbon frequencies among proboscideans peak at different times, also depending upon taxon and location. Woolly mammoths in Beringia reach a maximum and then decline beginning between 16,000 and 15,500 years BP, woolly mammoths in Europe and Siberia ca 14,500 and 13,500 BP, and Columbian mammoth and American mastodont only after 13,000 BP. Declines among woolly mammoths appear to coincide with the restructuring of biotic communities following the Pleistocene-Holocene transition.

Performance of the rebuilt SUERC single-stage accelerator mass spectrometer

NASA Astrophysics Data System (ADS)

Shanks, Richard P.; Ascough, Philippa L.; Dougans, Andrew; Gallacher, Paul; Gulliver, Pauline; Rood, Dylan H.; Xu, Sheng; Freeman, Stewart P. H. T.

2015-10-01

The SUERC bipolar single-stage accelerator mass spectrometer (SSAMS) has been dismantled and rebuilt to accommodate an additional rotatable pre-accelerator electrostatic spherical analyser (ESA) and a second ion source injector. This is for the attachment of an experimental positive-ion electron cyclotron resonance (ECR) ion source in addition to a Cs-sputter source. The ESA significantly suppresses oxygen interference to radiocarbon detection, and remaining measurement interference is now thought to be from 13C injected as 13CH molecule scattering off the plates of a second original pre-detector ESA.

Determination of 14C/ 12C of acetaldehyde in indoor air by compound specific radiocarbon analysis

NASA Astrophysics Data System (ADS)

Kato, Yoshimi; Shinohara, Naohide; Yoshinaga, Jun; Uchida, Masao; Matsuda, Ayuri; Yoneda, Minoru; Shibata, Yasuyuki

A method of compound-specific radiocarbon analysis (CSRA) for acetaldehyde in indoor air was established for the source apportionment purpose and the methodology was applied to indoor air samples. Acetaldehyde in indoor air samples was collected using the conventional 2,4-dinitrophenylhydrazine (DNPH) derivatization method. Typically 24-h air sampling at 5-10 L min -1 allowed collection of adequate amount of acetaldehyde for radiocarbon analysis by accelerator mass spectrometry (AMS). The 14C abundance of acetaldehyde in indoor air was measured by AMS after solvent extraction of derivatized acetaldehyde and sequential purification by a preparative liquid chromatography system and a preparative capillary gas chromatography system. The recovery and purity of the derivatized acetaldehyde was satisfactory for 14C analysis by AMS. 14C abundance of acetaldehyde was calculated by considering that of derivatizing agent DNPH. Our preliminary survey showed that percent modern carbon (pMC) values of acetaldehyde isolated from indoor air sampled in newly built, unoccupied housings ( n=5) in the suburb of Tokyo ranged from 49.4 to 67.0. This result indicated that contribution of anthropogenic source was greater than previously expected.

The Sea Peoples, from Cuneiform Tablets to Carbon Dating

PubMed Central

Kaniewski, David; Van Campo, Elise; Van Lerberghe, Karel; Boiy, Tom; Vansteenhuyse, Klaas; Jans, Greta; Nys, Karin; Weiss, Harvey; Morhange, Christophe; Otto, Thierry; Bretschneider, Joachim

2011-01-01

The 13th century BC witnessed the zenith of the Aegean and Eastern Mediterranean civilizations which declined at the end of the Bronze Age, ∼3200 years ago. Weakening of this ancient flourishing Mediterranean world shifted the political and economic centres of gravity away from the Levant towards Classical Greece and Rome, and led, in the long term, to the emergence of the modern western civilizations. Textual evidence from cuneiform tablets and Egyptian reliefs from the New Kingdom relate that seafaring tribes, the Sea Peoples, were the final catalyst that put the fall of cities and states in motion. However, the lack of a stratified radiocarbon-based archaeology for the Sea People event has led to a floating historical chronology derived from a variety of sources spanning dispersed areas. Here, we report a stratified radiocarbon-based archaeology with anchor points in ancient epigraphic-literary sources, Hittite-Levantine-Egyptian kings and astronomical observations to precisely date the Sea People event. By confronting historical and science-based archaeology, we establish an absolute age range of 1192–1190 BC for terminal destructions and cultural collapse in the northern Levant. This radiocarbon-based archaeology has far-reaching implications for the wider Mediterranean, where an elaborate network of international relations and commercial activities are intertwined with the history of civilizations. PMID:21687714

Oldest Directly Dated Remains of Sheep in China

NASA Astrophysics Data System (ADS)

Dodson, John; Dodson, Eoin; Banati, Richard; Li, Xiaoqiang; Atahan, Pia; Hu, Songmei; Middleton, Ryan J.; Zhou, Xinying; Nan, Sun

2014-11-01

The origins of domesticated sheep (Ovis sp.) in China remain unknown. Previous workers have speculated that sheep may have been present in China up to 7000 years ago, however many claims are based on associations with archaeological material rather than independent dates on sheep material. Here we present 7 radiocarbon dates on sheep bone from Inner Mongolia, Ningxia and Shaanxi provinces. DNA analysis on one of the bones confirms it is Ovis sp. The oldest ages are about 4700 to 4400 BCE and are thus the oldest objectively dated Ovis material in eastern Asia. The graphitisised bone collagen had δ13C values indicating some millet was represented in the diet. This probably indicates sheep were in a domestic setting where millet was grown. The younger samples had δ13C values indicating that even more millet was in the diet, and this was likely related to changes in foddering practices

Oldest directly dated remains of sheep in China.

PubMed

Dodson, John; Dodson, Eoin; Banati, Richard; Li, Xiaoqiang; Atahan, Pia; Hu, Songmei; Middleton, Ryan J; Zhou, Xinying; Nan, Sun

2014-11-24

The origins of domesticated sheep (Ovis sp.) in China remain unknown. Previous workers have speculated that sheep may have been present in China up to 7000 years ago, however many claims are based on associations with archaeological material rather than independent dates on sheep material. Here we present 7 radiocarbon dates on sheep bone from Inner Mongolia, Ningxia and Shaanxi provinces. DNA analysis on one of the bones confirms it is Ovis sp. The oldest ages are about 4700 to 4400 BCE and are thus the oldest objectively dated Ovis material in eastern Asia. The graphitisised bone collagen had δ(13)C values indicating some millet was represented in the diet. This probably indicates sheep were in a domestic setting where millet was grown. The younger samples had δ(13)C values indicating that even more millet was in the diet, and this was likely related to changes in foddering practices.

Mt. Fuji Holocene eruption history reconstructed from proximal lake sediments and high-density radiocarbon dating

NASA Astrophysics Data System (ADS)

Obrochta, S.; Yokoyama, Y.; Yoshimoto, M.; Yamamoto, S.; Miyairi, Y.; Nagano, G.; Nakamura, A.; Tsunematsu, K.; Lamair, L.; Hubert-Ferrari, A.; Heyvaert, V.; De Batist, M. A. O.; Fujiwara, O.

2017-12-01

Understanding the eruption history of volcanos located near large population centers is of direct societal relevance. Here we present a 8,000-year lacustrine record that includes previously unreported eruptions of the active Mt. Fuji volcano, which receives approximately 47 million annual visitors with another 40 million living in the adjacent Kanto Plain. A high-fidelity age model is constructed from a number of terrestrial macrofossil and bulk organic radiocarbon measurements and is extremely consistent with the independently determined age of diagnostic tephra layers. In addition to reporting new eruptions, we also present more accurate ages for known eruptions and detect a wider distribution of ejecta for the most recent summit eruption, that latter of which will alter modeled prevailing wind vector during eruption. Furthermore, closely spaced fall-scoria layers, unlikely to be differentiated as separate events in land-based surveys, will lower the estimated mass of ejecta erupted and in turn reduce calculated magnitude. These results, the first of their kind from a highly populated region, demonstrate the utility of lacustrine sediments as powerful tools for understanding characteristics of volcanic eruptions and will improve disaster mitigation plans for the region.

Acceptance Tests for AMS Radiocarbon Measurements at iThemba LABS, Gauteng, South Africa

NASA Astrophysics Data System (ADS)

Mbele, Vela L.; Mullins, Simon M.; Winkler, Stephan R.; Woodborne, Stephan

The accelerator mass spectrometer was commissioned recently at the iThemba LABS 6 MV tandem accelerator. Improvements in the vacuum system, requiring procurement of cryo-pumps and the reducing the tank pressure of the N2 + CO2 insulation gas mixture below the level used for IBA measurements, were necessary. This resulted in the reduction of the nitrogen background and improved the resolution of 14C from 14N background in the ionisation chamber. The nitrogen was leaking to the stripping canal because of inadequate sealing. The analysing magnet was scaled to detect C3+ ions, at 3 MV terminal potential. The first sensible spectra allowed for the pin-pointing of many persistent issues. This resulted in measurements with a precision better than 1 pMC, and current blank levels correspond to 12 half-lives of 14C or ∼68000 years. The radiocarbon sample preparation laboratory has reached production status. A brief outlook of the work towards the implementation of the measurement and chemical preparation protocols for radionuclides 10Be and 26Al is also summarised in the conclusion

Palaeomagnetic dating method accounting for post-depositional remanence and its application to geomagnetic field modelling

NASA Astrophysics Data System (ADS)

Nilsson, A.; Suttie, N.

2016-12-01

Sedimentary palaeomagnetic data may exhibit some degree of smoothing of the recorded field due to the gradual processes by which the magnetic signal is `locked-in' over time. Here we present a new Bayesian method to construct age-depth models based on palaeomagnetic data, taking into account and correcting for potential lock-in delay. The age-depth model is built on the widely used "Bacon" dating software by Blaauw and Christen (2011, Bayesian Analysis 6, 457-474) and is designed to combine both radiocarbon and palaeomagnetic measurements. To our knowledge, this is the first palaeomagnetic dating method that addresses the potential problems related post-depositional remanent magnetisation acquisition in age-depth modelling. Age-depth models, including site specific lock-in depth and lock-in filter function, produced with this method are shown to be consistent with independent results based on radiocarbon wiggle match dated sediment sections. Besides its primary use as a dating tool, our new method can also be used specifically to identify the most likely lock-in parameters for a specific record. We explore the potential to use these results to construct high-resolution geomagnetic field models based on sedimentary palaeomagnetic data, adjusting for smoothing induced by post-depositional remanent magnetisation acquisition. Potentially, this technique could enable reconstructions of Holocene geomagnetic field with the same amplitude of variability observed in archaeomagnetic field models for the past three millennia.

Forensic applications of 14C at CIRCE

NASA Astrophysics Data System (ADS)

Marzaioli, F.; Fiumano, V.; Capano, M.; Passariello, I.; Cesare, N. De.; Terrasi, F.

2011-12-01

The decreasing trend of the radiocarbon pulse produced during the atmospheric tests of nuclear weapons (bomb-carbon) coupled with high sensitivity accelerator mass spectrometry (AMS) measurements, drastically increased the precision of radiocarbon age determinations since the second part of the sixties, allowing the application of radiocarbon AMS to a wide range of studies previously not directly involving conventional radiocarbon dating (i.e. food authenticity, forensic, biochemistry). In the framework of authenticity evaluation of artworks, high precision radiocarbon ( 14C) AMS measurements (Δ R/ R < 0.3%) reduce the conventional uncertainty of the dating to few decades, allowing precise age estimation of materials containing carbon (C). The Centre for Isotopic Research on Cultural and Environmental heritage (CIRCE) during its activity on AMS 14C dating achieved high precision measurements opening the opportunity to these kinds of applications. This paper presents the main results obtained from radiocarbon measurements on a set of bone samples analyzed for the determination of the post-mortem interval in the framework of an unsolved case investigated by the Rome prosecutor office. The chronological characterization of the wooden support of the "Acerenza portrait" is also presented with the aim to evaluate its age and to further investigate the possibility to attribute this artwork to Leonardo da Vinci. Bomb- 14C dating on the lipid and collagen fractions of bones allows the evaluation of the year of the death of the individuals by means of ad hoc calibration data sheet with the typical few years precision and difference between collagen apparent age and the year of death appeared in agreement with the age of one individual estimated by dating of tooth collagen. Conventional radiocarbon dating on both wood and wood extracted cellulose leads to an estimation of the portrait wood board age (2σ) of 1459-1524 AD (57% relative probability), 1571-1631 AD interval (42

Radiocarbon Dates from Volcanic Deposits of the Chaos Crags and Cinder Cone Eruptive Sequences and Other Deposits, Lassen Volcanic National Park and Vicinity, California

USGS Publications Warehouse

Clynne, Michael A.; Christiansen, Robert L.; Trimble, Deborah A.; McGeehin, John P.

2008-01-01

This contribution reports radiocarbon ages obtained from charcoal, wood and other samples collected between 1979 and 2001 in Lassen Volcanic National Park and vicinity and a few samples from other nearby localities. Most of the samples are from the Chaos Crags and Cinder Cone eruptive sequences. Brief summaries are given of the Chaos Crags and Cinder Cone eruptive sequences.

Luminescence dating of the lacustrine record of Vršac (Carpathian Basin, Serbia) - implications for a palaeoenvironmetal reconstruction

NASA Astrophysics Data System (ADS)

Klasen, N.; Zeeden, C.; Markovic, S.; Fischer, P.; Lehmkuhl, F.; Schulte, P.; Bösken, J.; Hambach, U.; Vött, A.

2017-12-01

The Carpathian Basin is one of the key areas to investigate the influence of the continental, Mediterranean and Atlantic climate interaction over Europe. The available Upper Pleistocene and Holocene geoarchives in the region are mainly loess-paleosol records. Long lacustrine records are sparse and do not always span the whole last glacial cycle. In the area around Vršac, we drilled a 10 m core to contribute to the palaeoenvironmental reconstruction of the Carpathian Basin. Electrical Resistivity Tomography (ERT) was used to find the best-suited drilling location. We applied luminescence and radiocarbon dating, because a robust chronology is important for the interpretation of the sedimentary record. Pulsed OSL measurements were carried out to identify the best sampling positions. We expect runoff from the catchment being the main source of the lacustrine sediments, because coarse fluvial input is absent. Knowledge about the depositional conditions is important in luminescence dating to evaluate partial bleaching prior to deposition, which may cause age overestimation. Therefore, we compared infrared stimulated luminescence (IRSL) signals with post infrared infrared stimulated luminescence (pIRIR) signals, which bleach at different rates. Estimation of a representative water content has major influence on the age estimate, but remains challenging in luminescence dating. We measured the present day water content as well as the saturation water content, to account for variations over time. Luminescence and radiocarbon ages differ greatly from each other. According to the laboratory experiments, luminescence dating was reliable and we conclude that radiocarbon ages were underestimated because of an intrusion of younger organic material. The initial results demonstrated the potential of the drill core. Integrating more proxy data will be useful to enhance the importance of the geoarchive at Vršac for a better understanding of the last glacial cycle in the Carpathian

Luminescence dating of paleolake deltas and glacial deposits in Garwood Valley, Antarctica: Implications for climate, Ross ice sheet dynamics, and paleolake duration

USGS Publications Warehouse

Levy, Joseph S.; Rittenour, Tammy M.; Fountain, Andrew G.; O'Connor, Jim E.

2017-01-01

The formation of perched deltas and other lacustrine deposits in the McMurdo Dry Valleys of Antarctica is widely considered to be evidence of valley-filling lakes dammed by the grounded Ross Sea ice sheet during the local Last Glacial Maximum, with lake drainage interpreted as a record of grounding line retreat. We used luminescence dating to determine the age of paleolake deltas and glacial tills in Garwood Valley, a coastal dry valley that opens to the Ross Sea. Luminescence ages are stratigraphically consistent with radiocarbon results from algal mats within the same delta deposits but suggest radiocarbon dates from lacustrine carbonates may overestimate deposit ages by thousands of years. Results suggest that late Holocene delta deposition into paleolake Howard in Garwood Valley persisted until ca. 3.5 ka. This is significantly younger than the date when grounded ice is thought to have retreated from the Ross Sea. Our evidence suggests that the local, stranded ice-cored till topography in Garwood Valley, rather than regional ice-sheet dynamics, may have controlled lake levels for some McMurdo Dry Valleys paleolakes. Age control from the supraglacial Ross Sea drift suggests grounding and up-valley advance of the Ross Sea ice sheet into Garwood valley during marine oxygen isotope stage (MIS) 4 (71–78 ka) and the local Last Glacial Maximum (9–10 ka). This work demonstrates the power of combining luminescence dating with existing radiocarbon data sets to improve understanding of the relationships among paleolake formation, glacial position, and stream discharge in response to climate change.

Oldest Directly Dated Remains of Sheep in China

PubMed Central

Dodson, John; Dodson, Eoin; Banati, Richard; Li, Xiaoqiang; Atahan, Pia; Hu, Songmei; Middleton, Ryan J.; Zhou, Xinying; Nan, Sun

2014-01-01

The origins of domesticated sheep (Ovis sp.) in China remain unknown. Previous workers have speculated that sheep may have been present in China up to 7000 years ago, however many claims are based on associations with archaeological material rather than independent dates on sheep material. Here we present 7 radiocarbon dates on sheep bone from Inner Mongolia, Ningxia and Shaanxi provinces. DNA analysis on one of the bones confirms it is Ovis sp. The oldest ages are about 4700 to 4400 BCE and are thus the oldest objectively dated Ovis material in eastern Asia. The graphitisised bone collagen had δ13C values indicating some millet was represented in the diet. This probably indicates sheep were in a domestic setting where millet was grown. The younger samples had δ13C values indicating that even more millet was in the diet, and this was likely related to changes in foddering practices PMID:25417648

Turnover of Grassland Roots in Mountain Ecosystems Revealed by Their Radiocarbon Signature: Role of Temperature and Management

PubMed Central

Leifeld, Jens; Meyer, Stefanie; Budge, Karen; Sebastia, Maria Teresa; Zimmermann, Michael; Fuhrer, Juerg

2015-01-01

Root turnover is an important carbon flux component in grassland ecosystems because it replenishes substantial parts of carbon lost from soil via heterotrophic respiration and leaching. Among the various methods to estimate root turnover, the root’s radiocarbon signature has rarely been applied to grassland soils previously, although the value of this approach is known from studies in forest soils. In this paper, we utilize the root’s radiocarbon signatures, at 25 plots, in mountain grasslands of the montane to alpine zone of Europe. We place the results in context of a global data base on root turnover and discuss driving factors. Root turnover rates were similar to those of a subsample of the global data, comprising a similar temperature range, but measured with different approaches, indicating that the radiocarbon method gives reliable, plausible and comparable results. Root turnover rates (0.06–1.0 y-1) scaled significantly and exponentially with mean annual temperatures. Root turnover rates indicated no trend with soil depth. The temperature sensitivity was significantly higher in mountain grassland, compared to the global data set, suggesting additional factors influencing root turnover. Information on management intensity from the 25 plots reveals that root turnover may be accelerated under intensive and moderate management compared to low intensity or semi-natural conditions. Because management intensity, in the studied ecosystems, co-varied with temperature, estimates on root turnover, based on mean annual temperature alone, may be biased. A greater recognition of management as a driver for root dynamics is warranted when effects of climatic change on belowground carbon dynamics are studied in mountain grasslands. PMID:25734640

Biogenic contribution to PM-2.5 ambient aerosol from radiocarbon measurements

NASA Astrophysics Data System (ADS)

Lewis, C.; Klouda, G.; Ellenson, W.

2003-04-01

Knowledge of the relative contributions of biogenic versus anthropogenic sources to ambient aerosol is of great interest in the formulation of strategies to achieve nationally mandated air quality standards. Radiocarbon (14C) measurements provide a means to quantify the biogenic fraction of any carbon-containing sample of ambient aerosol. In the absence of an impact from biomass burning (e.g., during summertime) such measurements can provide an estimate of the contribution of biogenic secondary organic aerosol, from biogenic volatile organic compound precursors. Radiocarbon results for 11.5-h PM-2.5 samples collected near Nashville, Tennessee, USA, during summer 1999 will be presented. On average the measured biogenic fraction was surprisingly large (more than half), with the average biogenic fraction for night samples being only slightly smaller than for day samples. Discussion will include (a) description of the radiocarbon methodology, (b) use of radiocarbon measurements on local vegetation and fuel samples as calibration data, (c) concurrent measurements of organic carbon and elemental carbon ambient concentrations, (d) assessment of organic aerosol sampling artifact through use of organic vapor denuders, variable face velocities, and filter extraction, and (e) comparison with published radiocarbon results obtained in Houston, Texas in a similar study. Disclaimer: This work has been funded wholly or in part by the United States Environmental Protection Agency under Interagency Agreement No. 13937923 to the National Institute of Standards and Technology, and Contract No. 68-D5-0049 to ManTech Environmental Tecnology, Inc. It has been subjected to Agency review and approved for publication.

Environmental tritium and radiocarbon studies in the Vedavati River basin, Karnataka and Andhra Pradesh, India

NASA Astrophysics Data System (ADS)

Sukhija, B. S.; Achutha Rao, A.

1983-01-01

Environmental tritium and radiocarbon studies were undertaken in the Vedavati river basin situated partly in Karnataka and partly in Andhra Pradesh, India, aimed at the determination of the general recharge condition of the water-bearing zones in the gneissic complex, granites and the Dharwar Group of metamorphic rocks, where groundwater occurs under semi-unconfined to semi-confined conditions and at places under the water-table condition. The groundwater movement is controlled by fractures, fissures, a weathered zone and surficial mantle. An attempt was also made to find out whether substantial recharge occurs along fractured lineaments; whether the water-bearing zones can be considered as interconnected or isolated, and whether the recharge and discharge areas identified by geohydrological considerations can be confirmed. Environmental tritium and radiocarbon contents, measured in ˜ 45 groundwater samples, show that a large number of samples are very young, containing water from post-thermonuclear-era rain, thus indicating an age less than 25 yr. In some other samples, despite radiocarbon ages found to be older, some component of recent precipitation is found to be present as indicated by bomb tritium. Groundwater dating in the area shows an excellent correlation between hydro-isochrons of minimum age with the recharge contour of maximum magnitude. This study has clearly resulted in the demarcation of the recharge areas. However, the discharge areas as such cannot be clearly delineated because of lack of a pattern indicating increase of ages in any particular direction. This, however, also reflects somewhat discontinuous groundwater bodies, which may also be expected from the general structure and hydrogeology of the region. Along a major lineament the groundwater is found to be very young thus confirming that substantial recharge occurs along lineaments.

Age depth model construction of the upper section of ICDP Dead Sea Deep Drilling Project based on the high-resolution 14C dating

NASA Astrophysics Data System (ADS)

Kitagawa, H.; Nakamura, T.; Neugebauer, I.; Schwab, M. J.; Brauer, A.; Goldstein, S. L.; Stein, M.

2014-12-01

To reconstruct environmental, climatic and tectonic histories of the Levant, a deep drilling has been accomplished in the northern basin of the Dead Sea during the fall winter of 2010-2011 by the Dead Sea Deep Drilling Project (DSDDP) in the framework of the ICDP program. The sediment cores from site 5017-1 (water depth of ~300 m) recorded the paleoenvironmental and paleohydrological changes in the Dead Sea and the Levant during the last two glacial-interglacial cycles (Neugebauer et al., QSR in press). To provide precise timing of sedimentological - limnological events in the lake and its watershed, and more critically the relative timing of these events, radiocarbon dating of >70 well-preserved terrestrial plants and some carbonate deposits from the upper 150 m long section of the sediment core were performed. Based on the high-resolution radiocarbon dating, a statistical age-depth model was constructed with assumptions on the deposition condition and the radiocarbon age offset of carbonate samples. We discuss the practicality and the limitation of the age-depth model toward interpreting the high-resolution records of environmental, climatic and tectonic events recorded in the long sediment cores from site 5017-1.

Centuries of marine radiocarbon reservoir age variation within archaeological Mesodesma Donacium shells from Southern Peru

USGS Publications Warehouse

Jones, K.B.; Hodgins, G.W.L.; Etayo-Cadavid, M. F.; Andrus, C.F.T.; Sandweiss, D.H.

2010-01-01

Mollusk shells provide brief (<5 yr per shell) records of past marine conditions, including marine radiocarbon reservoir age (R) and upwelling. We report 21 14C ages and R calculations on small (~2 mg) samples from 2 Mesodesma donacium (surf clam) shells. These shells were excavated from a semi-subterranean house floor stratum 14C dated to 7625 ?? 35 BP at site QJ-280, Quebrada Jaguay, southern Peru. The ranges in marine 14C ages (and thus R) from the 2 shells are 530 and 170 14C yr; R from individual aragonite samples spans 130 ?? 60 to 730 ?? 170 14C yr. This intrashell 14C variability suggests that 14C dating of small (time-slice much less than 1 yr) marine samples from a variable-R (i.e. variable-upwelling) environment may introduce centuries of chronometric uncertainty. ?? 2010 by the Arizona Board of Regents on behalf of the University of Arizona.

Identifying sources of dissolved organic carbon in agriculturally dominated rivers using radiocarbon age dating: Sacramento-San Joaquin River Basin, California

USGS Publications Warehouse

Sickman, James O.; DiGiorgio, Carol L.; Davisson, M. Lee; Lucero, Delores M.; Bergamaschi, Brian A.

2010-01-01

We used radiocarbon measurements of dissolved organic carbon (DOC) to resolve sources of riverine carbon within agriculturally dominated landscapes in California. During 2003 and 2004, average Δ14C for DOC was −254‰ in agricultural drains in the Sacramento–San Joaquin Delta, −218‰ in the San Joaquin River, −175‰ in the California State Water Project and −152‰ in the Sacramento River. The age of bulk DOC transiting the rivers of California’s Central Valley is the oldest reported for large rivers and suggests wide-spread loss of soil organic matter caused by agriculture and urbanization. Using DAX 8 adsorbent, we isolated and measured 14C concentrations in hydrophobic acid fractions (HPOA); river samples showed evidence of bomb-pulse carbon with average Δ14C of 91 and 76‰ for the San Joaquin and Sacramento Rivers, respectively, with older HPOA, −204‰, observed in agricultural drains. An operationally defined non-HPOA fraction of DOC was observed in the San Joaquin River with seasonally computed Δ14C values of between −275 and −687‰; the source of this aged material was hypothesized to be physically protected organic-matter in high clay-content soils and agrochemicals (i.e., radiocarbon-dead material) applied to farmlands. Mixing models suggest that the Sacramento River contributes about 50% of the DOC load in the California State Water Project, and agricultural drains contribute approximately one-third of the load. In contrast to studies showing stabilization of soil carbon pools within one or two decades following land conversion, sustained loss of soil organic matter, occurring many decades after the initial agricultural-land conversion, was observed in California’s Central Valley.

YALE NATURAL RADIOCARBON MEASUREMENTS. PART VI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stuiver, M.; Deevey, E.S.

1961-01-01

Most of the measurements made since publication of Yale V are included; some measurements, such as a series collected in Greenland, are withneld pending additional information or field work that will make better interpretations possible. In addition to radiocarbon dates of geologic and/or archaeologic interest, recent assays are given of C/sup 14/ in lake waters and other lacustrine materials, now normalized for C/sup 13/ content. The newly accepted convention is followed in expressing normalized C/sup 14/ values as DELTA = delta C/sup 14/ (2 delta C/sup 13/ + 50)STAl + ( delta C/sup 14//1000)! where DELTA is the per milmore » deviation of the C/sup 14/ if the sample from any contemporary standard (whether organic or a carbonate) after correction of sample and/or standard for real age, for the Suess effect, for normal isotopic fractionation, and for deviations of C/sup 14/ content of the age- and pollution- corrected l9th-century wood standard from that of 95% of the NBS oxalic acid standard; delta C/sup 14/ is the measured deviation from 95% of the NBS standard, and delta C/sup 13/ is the deviation from the NBS limestone standard, both in per mil. These assays are variously affected by artificial C/sup 14/ resulting from nuclear tests. (auth)« less

Guide to luminescence dating techniques and their application for paleoseismic research

USGS Publications Warehouse

Gray, Harrison J.; Mahan, Shannon; Rittenour, Tammy M.; Nelson, Michelle Summa; Lund, William R.

2015-01-01

Over the past 25 years, luminescence dating has become a key tool for dating sediments of interest in paleoseismic research. The data obtained from luminescence dating has been used to determine timing of fault displacement, calculate slip rates, and estimate earthquake recurrence intervals. The flexibility of luminescence is a key complement to other chronometers such as radiocarbon or cosmogenic nuclides. Careful sampling and correct selection of sample sites exert two of the strongest controls on obtaining an accurate luminescence age. Factors such as partial bleaching and post-depositional mixing should be avoided during sampling and special measures may be needed to help correct for associated problems. Like all geochronologic techniques, context is necessary for interpreting and calculating luminescence results and this can be achieved by supplying participating labs with associated trench logs, photos, and stratigraphic locations of sample sites.

A non-destructive method for dating human remains

USGS Publications Warehouse

Lail, Warren K.; Sammeth, David; Mahan, Shannon; Nevins, Jason

2013-01-01

The skeletal remains of several Native Americans were recovered in an eroded state from a creek bank in northeastern New Mexico. Subsequently stored in a nearby museum, the remains became lost for almost 36 years. In a recent effort to repatriate the remains, it was necessary to fit them into a cultural chronology in order to determine the appropriate tribe(s) for consultation pursuant to the Native American Grave Protection and Repatriation Act (NAGPRA). Because the remains were found in an eroded context with no artifacts or funerary objects, their age was unknown. Having been asked to avoid destructive dating methods such as radiocarbon dating, the authors used Optically Stimulated Luminescence (OSL) to date the sediments embedded in the cranium. The OSL analyses yielded reliable dates between A.D. 1415 and A.D. 1495. Accordingly, we conclude that the remains were interred somewhat earlier than A.D. 1415, but no later than A.D. 1495. We believe the remains are from individuals ancestral to the Ute Mouache Band, which is now being contacted for repatriation efforts. Not only do our methods contribute to the immediate repatriation efforts, they provide archaeologists with a versatile, non-destructive, numerical dating method that can be used in many burial contexts.

Cold Reversal on Kodiak Island, Alaska, Correlated with the European Younger Dryas by Using Variations of Atmospheric C-14 Content

NASA Technical Reports Server (NTRS)

Hajdas, Irka; Bonani, Georges; Boden, Per; Peteet, Dorothy M.; Mann, Daniel H.

1999-01-01

High-resolution AMS (accelerator-mass-spectrometer) radiocarbon dating was performed on late-glacial macrofossils in lake sediments from Kodiak Island, Alaska, and on shells in marine sediments from southwest Sweden. In both records, a dramatic drop in radiocarbon ages equivalent to a rise in the atmospheric C-14 by approximately 70%. coincides with the beginning of the cold period at 11000 yr B.P. (C-14 age). Thus our results show that a close correlation between climatic records around the globe is possible by using a global signature of changes in atmospheric C-14 content.

Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses.

PubMed

Boyd, Thomas J; Montgomery, Michael T; Cuenca, Richard H; Hagimoto, Yutaka

2016-10-21

A method is described which uses the absence of radiocarbon in industrial chemicals and fuels made from petroleum feedstocks which frequently contaminate the environment. This radiocarbon signal - or rather the absence of signal - is evenly distributed throughout a contaminant source pool (unlike an added tracer) and is not impacted by biological, chemical or physical processes (e.g., the 14 C radioactive decay rate is immutable). If the fossil-derived contaminant is fully degraded to CO2, a harmless end-product, that CO2 will contain no radiocarbon. CO2 derived from natural organic matter (NOM) degradation will reflect the NOM radiocarbon content (usually <30,000 years old). Given a known radiocarbon content for NOM (a site background), a two end-member mixing model can be used to determine the CO2 derived from a fossil source in a given soil gas or groundwater sample. Coupling the percent CO2 derived from the contaminant with the CO2 respiration rate provides an estimate for the total amount of contaminant degraded per unit time. Finally, determining a zone of influence (ZOI) representing the volume from which site CO2 is collected allows determining the contaminant degradation per unit time and volume. Along with estimates for total contaminant mass, this can ultimately be used to calculate time-to-remediate or otherwise used by site managers for decision-making.

Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses

PubMed Central

Boyd, Thomas J.; Montgomery, Michael T.; Cuenca, Richard H.; Hagimoto, Yutaka

2016-01-01

A method is described which uses the absence of radiocarbon in industrial chemicals and fuels made from petroleum feedstocks which frequently contaminate the environment. This radiocarbon signal — or rather the absence of signal — is evenly distributed throughout a contaminant source pool (unlike an added tracer) and is not impacted by biological, chemical or physical processes (e.g., the 14C radioactive decay rate is immutable). If the fossil-derived contaminant is fully degraded to CO2, a harmless end-product, that CO2 will contain no radiocarbon. CO2 derived from natural organic matter (NOM) degradation will reflect the NOM radiocarbon content (usually <30,000 years old). Given a known radiocarbon content for NOM (a site background), a two end-member mixing model can be used to determine the CO2 derived from a fossil source in a given soil gas or groundwater sample. Coupling the percent CO2 derived from the contaminant with the CO2 respiration rate provides an estimate for the total amount of contaminant degraded per unit time. Finally, determining a zone of influence (ZOI) representing the volume from which site CO2 is collected allows determining the contaminant degradation per unit time and volume. Along with estimates for total contaminant mass, this can ultimately be used to calculate time-to-remediate or otherwise used by site managers for decision-making. PMID:27805601

Millennial-scale variability in the local radiocarbon reservoir age of south Florida during the Holocene

USGS Publications Warehouse

Toth, Lauren T.; Cheng, Hai; Edwards, R. Lawrence; Ashe, Erica; Richey, Julie N.

2017-01-01

-scale changes in western Atlantic circulation associated with an increase in the supply of equatorial South Atlantic water to the Caribbean and shifts in the character of South Atlantic waters resulting from variation in the intensity of upwelling off the southwest coast of Africa. Because accurate estimates of ΔR are critical to precise calibrations of radiocarbon dates from marine samples, we also developed models of nearshore and open-ocean ΔR versus conventional 14C ages that can be used for regional radiocarbon calibrations for the Holocene. Our study provides new insights into the patterns and drivers of oceanographic and hydrologic variability in the Straits of Florida and highlights the value of the paleoceanographic records from south Florida to our understanding of Holocene changes in climate and ocean circulation throughout the Atlantic.

Effect of artificial accelerated aging on the optical properties and monomeric conversion of composites used after expiration date.

PubMed

Garcia, Lucas da Fonseca Roberti; Mundim, Fabricio Mariano; Pires-de-Souza, Fernanda de Carvalho Panzeri; Puppin Rontani, Regina Maria; Consani, Simonides

2013-01-01

This study sought to evaluate how artificial accelerated aging (AAA) affected color stability (ΔE), opacity (ΔOP), and degree of conversion (DOC) for 3 composite materials (Tetric Ceram, Tetric Ceram HB, and Tetric Flow) used both 180 days before and 180 days after their expiration dates. To evaluate the materials' optical properties, 10 specimens of each composite-5 prior to expiration and 5 after the materials' expiration date-were made in a teflon matrix. After polishing, the specimens were submitted to initial color and opacity readings and submitted to AAA for 384 hours; at that point, new readings were taken to determine ΔE and ΔOP. To evaluate monomeric conversion evaluation, 6 specimens from each composite and expiration date-3 prior to AAA and 3 after-were submitted to DOC analysis. Results of the 2-way ANOVA and Bonferroni's tests (P < 0.05) demonstrated that all composites had ΔE values above the clinically acceptable level (ΔE ≥ 3.3). When expiration dates were compared, only Tetric Flow showed a statistically significant difference (P < 0.05). Regardless of the expiration date, ΔOP values for all composites increased after AAA, but not significantly (P > 0.05). The expired Tetric Flow had the highest DOC values (71.42% ± 4.21) before AAA, significantly different than that of the other composites (P > 0.05). It was concluded that both expiration date and AAA affected the properties of the composites tested.

Constraining the Stratosphere-Troposphere Exchange of Radiocarbon using AirCore 14CO2 Measurements

NASA Astrophysics Data System (ADS)

Chen, H.

2016-12-01

Radiocarbon (14C) plays an important role in the carbon cycle studies to understand both natural and anthropogenic carbon fluxes, but also in atmospheric chemistry to constrain hydroxyl radical (OH) concentrations in the atmosphere. Apart from the enormous 14C emissions from nuclear bomb testing in the 1950s and 1960s, radiocarbon is primarily produced in the upper atmosphere due to reactions of nitrogen nuclei with thermal neutrons that are induced by cosmic rays. 14C is quickly oxidized to 14CO, which is then further oxidized to 14CO2 by OH. To this end, better understanding the radiocarbon source is very useful to advance the use of radiocarbon for these applications. However, upper atmospheric 14C observations have been very sparse to constrain the magnitude and the location of the 14C production as well as the transport of radiocarbon from the stratosphere to the troposphere. Recently we have successfully made stratospheric 14CO2 measurements using AirCore samples from Sodankylä, Northern Finland, along with regular AirCore profiles of CO2, CH4, and CO since 2013. In this study, we calculate the stratosphere-troposphere exchange of 14C using the correlation between 14CO2 and N2O, and the estimated N2O loss rate. Besides this, we assess the impact of the mean age of air on 14CO2 profiles. Furthermore, we will evaluate the influence of different cosmogenic 14C production scenarios and the uncertainties in the OH field on the seasonal cycles of radiocarbon and on the stratosphere-troposphere exchange.

Carbonates in leaching reactions in context of 14C dating

NASA Astrophysics Data System (ADS)

Michalska, Danuta; Czernik, Justyna

2015-10-01

Lime mortars as a mixture of binder and aggregate may contain carbon of various origins. If the mortars are made of totally burnt lime, radiocarbon dating of binder yields the real age of building construction. The presence of carbonaceous aggregate has a significant influence on the 14C measurements results and depending on the type of aggregate and fraction they may cause overaging. Another problem, especially in case of hydraulic mortars that continue to be chemically active for a very long time, is the recrystallization usually connected with rejuvenation of the results but also, depending on local geological structures, with so called reservoir effect yielding apparent ages. An attempt in separating the binder from other carbonaceous components successfully was made for samples from Israel by Nawrocka-Michalska et al. (2007). The same preparation procedure, after taking into account the petrographic composition, was used for samples coming from Poland, Nawrocka et al. (2009). To verify the procedure used previously for non-hydraulic samples determination an experimental tests on carbonaceous mortars with crushed bricks from Novae in Bulgaria were made. Additionally, to identify different carbonaceous structures and their morphology, a cathodoluminescence and scanning electron microscope with electron dispersive spectrometer were applied. The crushed bricks and brick dust used in mortars production process have been interpreted as an alternative use to other pozzolanic materials. The reaction between lime and pozzolanic additives take place easily and affects the rate and course of carbonates decomposition in orthophosphric acid, during the samples pretreatment for dating. The composition of the Bulgarian samples together with influence of climate conditions on mortar carbonates do not allow for making straightforward conclusions in chronology context, but gives some new guidelines in terms of hydraulic mortars application for dating. This work has mainly

Comment on "Radiocarbon Calibration Curve Spanning 0 to 50,000 Years B.P. Based on Paired 230Th/234U/238U and 14C Dates on Pristine Corals" by R.G. Fairbanks, R. A. Mortlock, T.-C. Chiu, L. Cao, A. Kaplan, T. P. Guilderson, T. W. Fairbanks, A. L. Bloom, P

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reimer, P J; Baillie, M L; Bard, E

2005-10-02

Radiocarbon calibration curves are essential for converting radiocarbon dated chronologies to the calendar timescale. Prior to the 1980's numerous differently derived calibration curves based on radiocarbon ages of known age material were in use, resulting in ''apples and oranges'' comparisons between various records (Klein et al., 1982), further complicated by until then unappreciated inter-laboratory variations (International Study Group, 1982). The solution was to produce an internationally-agreed calibration curve based on carefully screened data with updates at 4-6 year intervals (Klein et al., 1982; Stuiver and Reimer, 1986; Stuiver and Reimer, 1993; Stuiver et al., 1998). The IntCal working group hasmore » continued this tradition with the active participation of researchers who produced the records that were considered for incorporation into the current, internationally-ratified calibration curves, IntCal04, SHCal04, and Marine04, for Northern Hemisphere terrestrial, Southern Hemisphere terrestrial, and marine samples, respectively (Reimer et al., 2004; Hughen et al., 2004; McCormac et al., 2004). Fairbanks et al. (2005), accompanied by a more technical paper, Chiu et al. (2005), and an introductory comment, Adkins (2005), recently published a ''calibration curve spanning 0-50,000 years''. Fairbanks et al. (2005) and Chiu et al. (2005) have made a significant contribution to the database on which the IntCal04 and Marine04 calibration curves are based. These authors have now taken the further step to derive their own radiocarbon calibration extending to 50,000 cal BP, which they claim is superior to that generated by the IntCal working group. In their papers, these authors are strongly critical of the IntCal calibration efforts for what they claim to be inadequate screening and sample pretreatment methods. While these criticisms may ultimately be helpful in identifying a better set of protocols, we feel that there are also several erroneous and misleading

New radiocarbon ages from cirques in Colorado Front Range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davis, P.T.; Birkeland, P.W.; Caine, N.

The authors recovered sediment cores 3.1 m long from Blue Lake ([approximately]37m water depth, [approximately]3,445m a.s.l., 40[degree]5 minutes 20 seconds N, 105[degree]37 minutes 08 seconds W) and 2.7m long from Lake Dorothy ([approximately]35m water depth, [approximately]3,675m a.s.l., 40[degree]00 minutes 46 seconds N, 105[degree]41 minutes 11 seconds W). A light-weight percussion coring system suspended from perlon ropes was used because of sediment thicknesses, water depths, and ski-backpacking requirements. Lake ice provided a stable coring platform. One purpose of the project is provision of a high-resolution record of environmental change in the subalpine/alpine ecotone during the Holocene, under the auspices of themore » Niwot Ridge Long-Term Ecological Research program. The sediment cores also provide minimum-limiting radiocarbon ages for deglaciation of cirques and the deposits that impound their tarns. Here the authors report on this second purpose. The Blue Lake core bottomed in sandy, gray, inorganic sediment, presumably glacial diamict. A bulk sample from 2.8--2.9m depth yielded a conventional radiocarbon age of 12,275[+-]345 yrs BP. Thus, ice retreated from the site by 12 ka. Since 12 ka both glacial and rock-glacial sediments have been deposited upvalley; some of these events may be recognized in the core. In contrast, the Lake Dorothy core did not penetrate gray inorganic diamict and is entirely organic-rich. A bulk sample from 2.65--2.7m depth yielded a conventional radiocarbon age of 10,910 [+-] 320 yrs BP. Thus, the moraines impounding the lake are 2--3 times older than suggested by a combination of relative-age methods and one radiocarbon age from surface sediments.« less

Reconnaissance dating: a new radiocarbon method applied to assessing the temporal distribution of Southern Ocean deep-sea corals

USGS Publications Warehouse

Burke, Andrea; Robinson, Laura F.; McNichol, Ann P.; Jenkins, William J.; Scanlon, Kathryn M.; Gerlach, Dana S.

2010-01-01

We have developed a rapid 'reconnaissance' method of preparing graphite for 14C/12C analysis. Carbonate (~15 mg) is combusted using an elemental analyzer and the resulting CO2 is converted to graphite using a sealed tube zinc reduction method. Over 85% (n=45 replicates on twenty-one individual corals) of reconnaissance ages measured on corals ranging in age from 500 to 33,000 radiocarbon years (Ryr) are within two standard deviations of ages generated using standard hydrolysis methods on the same corals, and all reconnaissance ages are within 300 Ryr of the standard hydrolysis ages. Replicate measurements on three individual aragonitic corals yielded ages of 1076±35 Ryr (standard deviation; n=5), 10,739±47 Ryr (n=8), and 40,146±3500 Ryr (n=9). No systematic biases were found using different cleaning methods or variable sample sizes. Analysis of 13C/12C was made concurrently with the 14C/12C measurement to correct for natural fractionation and for fractionation during sample processing and analysis. This technique provides a new, rapid method for making accurate, percent-level 14C/12C analyses that may be used to establish the rates and chronology of earth system processes where survey-type modes of age estimation are desirable. For example, applications may include creation of sediment core-top maps, preliminary age models for sediment cores, and growth rate studies of marine organisms such as corals or mollusks. We applied the reconnaissance method to more than 100 solitary deep-sea corals collected in the Drake Passage in the Southern Ocean to investigate their temporal and spatial distribution. The corals used in this study are part of a larger sample set, and the subset that was dated was chosen based on species as opposed to preservation state, so as to exclude obvious temporal biases. Similar to studies in other regions, the distribution of deep-sea corals is not constant through time across the Drake Passage. Most of the corals from the Burdwood Bank

Radiocarbon and stable isotopes in Palmyra corals during the past century

NASA Astrophysics Data System (ADS)

Druffel-Rodriguez, Kevin C.; Vetter, Desiree; Griffin, Sheila; Druffel, Ellen R. M.; Dunbar, Robert B.; Mucciarone, David A.; Ziolkowski, Lori A.; Sanchez-Cabeza, Joan-Albert

2012-04-01

Annual samples from two Palmyra Atoll corals (Porites lutea) that lived during the past 110 years were analyzed for radiocarbon (Δ14C) and δ18O. The Δ14C values decreased 7.6‰ from 1896 to 1953, similar to other coral records from the tropical and subtropical Pacific. Δ14C values rose from ˜-60‰ to ˜+110‰ by 1980 due to the input of bomb radiocarbon from the atmosphere. Elevated Δ14C values were observed for the mid- to late-1950s, suggesting early input of bomb radiocarbon, possibly from the largest Marshall Islands bomb tests in 1954. Secondary aragonite precipitation was identified in a portion of one core using scanning electron microscopy and X-radiography, and was responsible for high δ18O and δ13C values and a correlation between them. The Δ14C results were more resistant to alteration, except when contamination was from the bomb era (>1956).

Pyrolysis-combustion 14C dating of soil organic matter

USGS Publications Warehouse

Wang, Hongfang; Hackley, Keith C.; Panno, S.V.; Coleman, D.D.; Liu, J.C.-L.; Brown, J.

2003-01-01

Radiocarbon (14C) dating of total soil organic matter (SOM) often yields results inconsistent with the stratigraphic sequence. The onerous chemical extractions for SOM fractions do not always produce satisfactory 14C dates. In an effort to develop an alternative method, the pyrolysis-combustion technique was investigated to partition SOM into pyrolysis volatile (Py-V) and pyrolysis residue (Py-R) fractions. The Py-V fractions obtained from a thick glacigenic loess succession in Illinois yielded 14C dates much younger but more reasonable than the counterpart Py-R fractions for the soil residence time. Carbon isotopic composition (??13C) was heavier in the Py-V fractions, suggesting a greater abundance of carbohydrate- and protein-related constituents, and ??13C was lighter in the Py-R fractions, suggesting more lignin- and lipid-related constituents. The combination of 14C dates and ??13C values indicates that the Py-V fractions are less biodegradation resistant and the Py-R fractions are more biodegradation resistant. The pyrolysis-combustion method provides a less cumbersome approach for 14C dating of SOM fractions. With further study, this method may become a useful tool for analyzing unlithified terrestrial sediments when macrofossils are absent. ?? 2003 University of Washington. Published by Elsevier Inc. All rights reserved.

Increase of radiocarbon concentration in tree rings from Kujawy (SE Poland) around AD 774-775

NASA Astrophysics Data System (ADS)

Rakowski, Andrzej Z.; Krąpiec, Marek; Huels, Mathias; Pawlyta, Jacek; Dreves, Alexander; Meadows, John

2015-10-01

Evidence of a rapid increase in atmospheric radiocarbon (14C) content in AD 774-775 was presented by Miyake et al. (2012), who observed an increase of about 12‰ in the 14C content in annual tree rings from Japanese cedar. Usoskin et al. (2013) report a similar 14C spike in German oak, and attribute it to exceptional solar activity. If this phenomenon is global in character, such rapid changes in 14C concentration may affect the accuracy of calibrated dates, as the existing calibration curve is composed mainly of decadal samples. Single-year samples of dendro-chronologically dated tree rings of deciduous oak (Quercus robur) from Kujawy, a village near Krakow (SE Poland), spanning the years AD 765-796, were collected and their 14C content was measured using the AMS system in the Leibniz Laboratory. The results clearly show a rapid increase of 9.2 ± 2.1‰ in the 14C concentration in tree rings between AD 774 and AD 775, with maximum Δ14C = 4.1 ± 2.3‰ noted in AD 776.

Radiocarbon Analysis to Calculate New End-Member Values for Biomass Burning Source Samples Specific to the Bay Area

NASA Astrophysics Data System (ADS)

Yoon, S.; Kirchstetter, T.; Fairley, D.; Sheesley, R. J.; Tang, X.

2017-12-01

Elemental carbon (EC), also known as black carbon or soot, is an important particulate air pollutant that contributes to climate forcing through absorption of solar radiation and to adverse human health impacts through inhalation. Both fossil fuel combustion and biomass burning, via residential firewood burning, agricultural burning, wild fires, and controlled burns, are significant sources of EC. Our ability to successfully control ambient EC concentrations requires understanding the contribution of these different emission sources. Radiocarbon (14C) analysis has been increasingly used as an apportionment tool to distinguish between EC from fossil fuel and biomass combustion sources. However, there are uncertainties associated with this method including: 1) uncertainty associated with the isolation of EC to be used for radiocarbon analysis (e.g., inclusion of organic carbon, blank contamination, recovery of EC, etc.) 2) uncertainty associated with the radiocarbon signature of the end member. The objective of this research project is to utilize laboratory experiments to evaluate some of these uncertainties, particularly for EC sources that significantly impact the San Francisco Bay Area. Source samples of EC only and a mix of EC and organic carbon (OC) were produced for this study to represent known emission sources and to approximate the mixing of EC and OC that would be present in the atmosphere. These samples include a combination of methane flame soot, various wood smoke samples (i.e. cedar, oak, sugar pine, pine at various ages, etc.), meat cooking, and smoldering cellulose smoke. EC fractions were isolated using a Sunset Laboratory's thermal optical transmittance carbon analyzer. For 14C analysis, samples were sent to Woods Hole Oceanographic Institution for isotope analysis using an accelerated mass spectrometry. End member values and uncertainties for the EC isolation utilizing this method will be reported.

The Holocene Minimum of the West Antarctic Ice Sheet: Radiocarbon Model Ages for Subglacial Sediments

NASA Astrophysics Data System (ADS)

Tulaczyk, S. M.; Stansell, N.; Scherer, R. P.; Powell, R. D.

2017-12-01

It is commonly assumed that the West Antarctic Ice Sheet (WAIS) is at the present time as small as it has been since at least the last interglacial period about 125,000 years ago. Yet, our recent analyses of subglacial sediments recovered from beneath the ice sheet indicate regionally widespread presence of radiocarbon. This unstable isotope with half life of 5,730 years should decay to nil if the analyzed subglacial sediment samples have been isolated beneath the ice sheet from the atmosphere and the ocean for 125,000 years (over 20 half lives). However, the apparent radiocarbon ages for these samples are in the range of about 20,000-30,000 years BP, based on radiocarbon Fraction Modern (FM) of a few to several percent. The apparent sediment ages cannot be taken at face value because: (1) they overlap with the Last Glacial Maximum (LGM) when WAIS is known to have extended over 1,000 km past the sediment sampling locations, and (2) Antarctic glacigenic sediments commonly contain significant admixture of old, radiocarbon-dead organic matter. The latter biases apparent radiocarbon ages because it violates the assumption that the initial radiocarbon fraction in a sample was equal to FM. To mitigate the problem with apparent ages, we assume that initial radiocarbon fraction in subglacial sediments was equal to that determined by us independently in J-9 sediments from beneath the Ross Ice Shelf (RIS) and calculate radiocarbon 'model ages' between 1,000 and 6,000 years BP. This period of time overlaps with a regional climatic optimum and with late phases of post-LGM glacioisostatic adjustment in the region (e.g., Kingslake et al., this session). We propose that the grounding line of WAIS, at least on the RIS side, retreated in mid/late Holocene more than 300 km beyond its current position and then re-advanced to reach its modern geometry. This implies that the main body of WAIS was significantly smaller than today in mid/late Holocene and that the ice sheet is capable of

Dating of Modern Human Evolution

NASA Astrophysics Data System (ADS)

Grun, R.

Dating studies on palaoeanthropological sites is usually carried out on material associ- ated with the human remains, such as the sediment, charcoal or other fauna rather than the human specimen itself. The reason lies in the fact that most dating techniques are destructive and because the hominid remains are too rare to be sacrificed for dating. This indirect dating approach is in many cases not satisfactory, because: (i) the human remains are often buried into the sediments and the association with other materials is uncertain (e.g. Skhul, Qafzeh, etc.); (ii) faunal remains or minerals from the sediment are re-worked from older deposits (see e.g. present discussion of the age of the Homo erectus remains in Indonesia; (iii) the hominid fossils were discovered at a time when no careful excavations were carried out and it is impossible to correlate the specimen with other datable material (which applies tonearly 90% of all palaeoanthropological specimens). For example, the hominid burial site of Qafzeh in Israel has been dated by several independent dating laboratories with a multitude of methods. However, the data are still not accepted by some because the dating has not been carried out on the hominid specimen. Until recently, hominid fossils could only be dated by radiocarbon. This method reaches back to about 40,000 years. As a consequence, all the older fossils could not be analysed and many important questions in our understanding of human evolution could not be addressed. Human remains are scarce and extremely valuable, therefore any sort of destruction has to be kept to an absolute minimum. This is of particular importance in Australia where any human fossils are sacred. Thus, for the analysis of hominid material it was necessary to develop a more or less non-destructive techniques. This has been ac- complished in recent years by the application of ESR dating of tooth enamel and a combination of gamma spectrometric and TIMS U-series dating of bones. The exam

Extinction of Harrington's mountain goat

PubMed Central

Mead, Jim I.; Martin, Paul S.; Euler, Robert C.; Long, Austin; Jull, A. J. T.; Toolin, Laurence J.; Donahue, Douglas J.; Linick, T. W.

1986-01-01

Keratinous horn sheaths of the extinct Harrington's mountain goat, Oreamnos harringtoni, were recovered at or near the surface of dry caves of the Grand Canyon, Arizona. Twenty-three separate specimens from two caves were dated nondestructively by the tandem accelerator mass spectrometer (TAMS). Both the TAMS and the conventional dates indicate that Harrington's mountain goat occupied the Grand Canyon for at least 19,000 years prior to becoming extinct by 11,160 ± 125 radiocarbon years before present. The youngest average radiocarbon dates on Shasta ground sloths, Nothrotheriops shastensis, from the region are not significantly younger than those on extinct mountain goats. Rather than sequential extinction with Harrington's mountain goat disappearing from the Grand Canyon before the ground sloths, as one might predict in view of evidence of climatic warming at the time, the losses were concurrent. Both extinctions coincide with the regional arrival of Clovis hunters. Images PMID:16593655

Ancient human mitochondrial DNA and radiocarbon analysis of archived quids from the Mule Spring Rockshelter, Nevada, USA.

PubMed

Hamilton-Brehm, Scott D; Hristova, Lidia T; Edwards, Susan R; Wedding, Jeffrey R; Snow, Meradeth; Kruger, Brittany R; Moser, Duane P

2018-01-01

Chewed and expectorated quids, indigestible stringy fibers from the roasted inner pulp of agave or yucca root, have proven resilient over long periods of time in dry cave environments and correspondingly, although little studied, are common in archaeological archives. In the late 1960s, thousands of quids were recovered from Mule Spring Rockshelter (Nevada, USA) deposits and stored without consideration to DNA preservation in a museum collection, remaining unstudied for over fifty years. To assess the utility of these materials as repositories for genetic information about past inhabitants of the region and their movements, twenty-one quids were selected from arbitrary excavation depths for detailed analysis. Human mitochondrial DNA sequences from the quids were amplified by PCR and screened for diagnostic single nucleotide polymorphisms. Most detected single nucleotide polymorphisms were consistent with recognized Native American haplogroup subclades B2a5, B2i1, C1, C1c, C1c2, and D1; with the majority of the sample set consistent with subclades C1, C1c, and C1c2. In parallel with the DNA analysis, each quid was radiocarbon dated, revealing a time-resolved pattern of occupancy from 347 to 977 calibrated years before present. In particular, this dataset reveals strong evidence for the presence of haplogroup C1/C1c at the Southwestern edge of the US Great Basin from ~670 to 980 cal YBP, which may temporally correspond with the beginnings of the so-called Numic Spread into the region. The research described here demonstrates an approach which combines targeted DNA analysis with radiocarbon age dating; thus enabling the genetic analysis of archaeological materials of uncertain stratigraphic context. Here we present a survey of the maternal genetic profiles from people who used the Mule Spring Rockshelter and the historic timing of their utilization of a key natural resource.

Late Holocene Radiocarbon Variability in Northwest Atlantic Slope Waters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sherwood, O; Edinger, E; Guilderson, T P

2008-08-15

Deep-sea gorgonian corals secrete a 2-part skeleton of calcite, derived from dissolved inorganic carbon at depth, and gorgonin, derived from recently fixed and exported particulate organic matter. Radiocarbon contents of the calcite and gorgonin provide direct measures of seawater radiocarbon at depth and in the overlying surface waters, respectively. Using specimens collected from Northwest Atlantic slope waters, we generated radiocarbon records for surface and upper intermediate water layers spanning the pre- and post bomb-{sup 14}C eras. In Labrador Slope Water (LSW), convective mixing homogenizes the pre-bomb {Delta}{sup 14}C signature (-67 {+-} 4{per_thousand}) to at least 1000 m depth. Surface watermore » bomb-{sup 14}C signals were lagged and damped (peaking at {approx} +45{per_thousand} in the early 1980s) relative to other regions of the northwest Atlantic, and intermediate water signals were damped further. Off southwest Nova Scotia, the vertical gradient in {Delta}{sup 14}C is much stronger. In surface water, pre-bomb {Delta}{sup 14}C averaged -75 {+-} 5{per_thousand}. At 250-475 m depth, prebomb {Delta}{sup 14}C oscillated quasi-decadally between -80 and -100{per_thousand}, likely reflecting interannual variability in the presence of Labrador Slope Water vs. Warm Slope Water (WSW). Finally, subfossil corals reveal no systematic changes in vertical {Delta}{sup 14}C gradients over the last 1200 years.« less

Detection of Adriamycin–DNA adducts by accelerator mass spectrometry at clinically relevant Adriamycin concentrations

PubMed Central

Coldwell, Kate E.; Cutts, Suzanne M.; Ognibene, Ted J.; Henderson, Paul T.; Phillips, Don R.

2008-01-01

Limited sensitivity of existing assays has prevented investigation of whether Adriamycin–DNA adducts are involved in the anti-tumour potential of Adriamycin. Previous detection has achieved a sensitivity of a few Adriamycin–DNA adducts/104 bp DNA, but has required the use of supra-clinical drug concentrations. This work sought to measure Adriamycin–DNA adducts at sub-micromolar doses using accelerator mass spectrometry (AMS), a technique with origins in geochemistry for radiocarbon dating. We have used conditions previously validated (by less sensitive decay counting) to extract [14C]Adriamycin–DNA adducts from cells and adapted the methodology to AMS detection. Here we show the first direct evidence of Adriamycin–DNA adducts at clinically-relevant Adriamycin concentrations. [14C]Adriamycin treatment (25 nM) resulted in 4.4 ± 1.0 adducts/107 bp (∼1300 adducts/cell) in MCF-7 breast cancer cells, representing the best sensitivity and precision reported to date for the covalent binding of Adriamycin to DNA. The exceedingly sensitive nature of AMS has enabled over three orders of magnitude increased sensitivity of Adriamycin–DNA adduct detection and revealed adduct formation within an hour of drug treatment. This method has been shown to be highly reproducible for the measurement of Adriamycin–DNA adducts in tumour cells in culture and can now be applied to the detection of these adducts in human tissues. PMID:18632763

RADIOCARBON ANALYSIS OF PM 2.5 AMBIENT AEROSOL

EPA Science Inventory

The radiocarbon (14C) content of an ambient aerosol sample can be directly related to the fraction of the sample's total carbon mass contributed by natural (biogenic) sources. Such knowledge is difficult to determine by other means, and important for devising ambient PM contro...

RADIOCARBON MEASUREMENTS ON PM-2.5 AMBIENT AEROSOL

EPA Science Inventory

Radiocarbon (14C) measurements provide an estimate of the fraction of carbon in a sample that is biogenic. The methodology has been extensively used in past wintertime studies to quantify the contribution of wood smoke to ambient aerosol. In summertime such measurements can p...

AMS Radiocarbon Dating Individual Taxa and Individual Specimens: Implications for Small Mammal Paleoecology.

NASA Astrophysics Data System (ADS)

Graham, Russell; Stafford, Thomas, Jr.; Semken, Holmes, Jr.

2010-05-01

Advances in AMS physics and organic geochemistry have revolutionized our ability to establish absolute chronologies on vertebrate fossils. Highly purified collagen, which provides extremely accurate 14C ages, can be extracted from single bones and teeth as small as 50 mg. Combined with measurement precisions of ±15 to 25 years for ages of < 20,000 yr, the direct AMS 14C technique enables fossil deposits to be chronologically dissected at the level of single animals. Analysis of data from a variety of sites in the United States indicates that most excavation levels (analysis units) as small as 10 cm can be time averaged by several thousand years at a minimum, even with the greatest care in excavation and processing of sediments. Time averaging of this magnitude has important implications for fine-scale paleoecological analysis of faunas, especially when compared to high-resolution climate records like those derived from speleothems, ice cores, or marine cores. To this end, we propose saturation dating of indicative taxa and plotting dates of individual specimens against high-resolution climate records rather than analysis of complete faunas or faunules. This technique provides even higher resolution of paleoenvironments than pollen spectra.

Independently dated paleomagnetic secular variation records from the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Haberzettl, Torsten; Henkel, Karoline; Kasper, Thomas; Ahlborn, Marieke; Su, Youliang; Wang, Junbo; Appel, Erwin; St-Onge, Guillaume; Stoner, Joseph; Daut, Gerhard; Zhu, Liping; Mäusbacher, Roland

2015-04-01

Magnetostratigraphy has been serving as a valuable tool for dating and confirming chronologies of lacustrine sediments in many parts of the world. Suitable paleomagnetic records on the Tibetan Plateau (TP) and adjacent areas are, however, extremely scarce. Here, we derive paleomagnetic records from independently radiocarbon-dated sediments from two lakes separated by 250 km on the southern central TP, Tangra Yumco and Taro Co. Studied through alternating field demagnetization of u-channel samples, characteristic remanent magnetization (ChRM) directions document similar inclination patterns in multiple sediment cores for the past 4000 years. Comparisons to an existing record from Nam Co, a lake 350 km east of Tangra Yumco, a varve-dated record from the Makran Accretionary Wedge, records from Lakes Issyk-Kul and Baikal, and a stack record from East Asia reveal many similarities in inclination. This regional similarity demonstrates the high potential of inclination to compare records over the Tibetan Plateau and eventually date other Tibetan records stratigraphically. PSV similarities over such a large area (>3000 km) suggest a large-scale core dynamic origin rather than small scale processes like drift of the non-dipole field often associated with PSV records.

Radiocarbon reservoir between charred seeds and fish bone in Neolithic sites, northeastern Qinghai-Tibetan Plateau

NASA Astrophysics Data System (ADS)

Zhou, A.; Dong, G.; Ren, L.

2017-12-01

Many efforts have been done to understand the reservoir effect of Qinghai Lake, yet no agreement has been reached. Five archaeological sites, located around the junction between the estuary of Rivers and Qinghai Lake, are the earliest Neolithic Age sites in the Qinghai- Tibetan Plateau (QTP), which is critical for understanding patterns of prehistoric human inhabitation in the high plateau extreme environments. This study compares radiocarbon dates of fish bones and terrestrial plant remains uncovered from the same archaeological strata to see whether there was reservoir effect reference to reliable data. Results demonstrate that there were reservoir effects ranging from 300 to 600 years back to 3600 years ago, nevertheless, no reservoir was observed of the modern fish. Besides, stable isotopic analysis illustrated that modern fish consumed similar food to those of millennias ago.

Challenging developments in three decades of accelerator mass spectrometry at ETH: from large particle accelerators to table size instruments.

PubMed

Suter, Martin

2010-01-01

Accelerator mass spectrometry (AMS) was invented for the detection of radiocarbon at natural isotopic concentrations (10(-12) to 10(-15)) more than 30 years ago. Meanwhile this method has also been applied for the analysis of many other long-lived radioisotopes, which are found at very low concentrations. The first investigations were made at large tandem accelerators originally built for nuclear physics research and operating at voltages of 6-12 MV. Today dedicated instruments are mostly used for AMS, which are optimized for associated applications. In the past 15 years, a new generation of much smaller instruments has been developed. For many years it was believed that accelerators with voltages of 2 MV or higher are needed to eliminate the molecular interferences. At these energies the ions are predominantly stripped to charge state 3+, thereby removing the binding electrons of the molecules. In contrast, the new compact facilities use 1+ or 2+ ions. In this case the molecular destruction process is based on molecule-atom collisions in the gas cell. The cross sections for this destruction are sufficiently large that the intensity of molecular components such as (12)CH(2) and (13)CH can be reduced by 10 orders of magnitude. These new facilities can be built much smaller due to the lower energies. Universal instruments providing analysis for many isotopes over the whole range of periodic table have a space requirement of about 4 x 6 m(2); dedicated radiocarbon facilities based on a 200 kV accelerator have a footprint of about 2.5 x 3 m(2). This smallest category of instruments use special technologies: The high voltage terminal with the gas stripper canal is vacuum insulated and the gas is pumped to ground potential through a ceramic pipe. A conventional 200 kV power supply provides the terminal voltage from outside. A review of this new generation of compact AMS facilities is given. Design considerations and performance of these new instruments will be presented

Towards constraining the stratosphere-troposphere exchange of radiocarbon: strategies of stratospheric 14CO2 measurements using AirCore

NASA Astrophysics Data System (ADS)

Chen, Huilin; Paul, Dipayan; Meijer, Harro; Miller, John; Kivi, Rigel; Krol, Maarten

2016-04-01

Radiocarbon (14C) plays an important role in the carbon cycle studies to understand both natural and anthropogenic carbon fluxes, but also in atmospheric chemistry to constrain hydroxyl radical (OH) concentrations in the atmosphere. Apart from the enormous 14C emissions from nuclear bomb testing in the 1950s and 1960s, radiocarbon is primarily produced in the stratosphere due to the cosmogenic production. To this end, better understanding the stratospheric radiocarbon source is very useful to advance the use of radiocarbon for these applications. However, stratospheric 14C observations have been very limited so that there are large uncertainties on the magnitude and the location of the 14C production as well as the transport of radiocarbon from the stratosphere to the troposphere. Recently we have successfully made stratospheric 14C measurements using AirCore samples from Sodankylä, Northern Finland. AirCore is an innovative atmospheric sampling system, which passively collects atmospheric air samples into a long piece of coiled stainless steel tubing during the descent of a balloon flight. Due to the relatively low cost of the consumables, there is a potential to make such AirCore profiling in other parts of the world on a regular basis. In this study, we simulate the 14C in the atmosphere and assess the stratosphere-troposphere exchange of radiocarbon using the TM5 model. The Sodankylä radiocarbon measurements will be used to verify the performance of the model at high latitude. Besides this, we will also evaluate the influence of different cosmogenic 14C production scenarios and the uncertainties in the OH field on the seasonal cycles of radiocarbon and on the stratosphere-troposphere exchange, and based on the results design a strategy to set up a 14C measurement program using AirCore.

Late Quaternary sedimentological and climate changes at Lake Bosumtwi Ghana: new constraints from laminae analysis and radiocarbon age modeling

USGS Publications Warehouse

Shanahan, Timothy M.; Beck, J. Warren; Overpeck, Jonathan T.; McKay, Nicholas P.; Pigati, Jeffrey S.; Peck, John A.; Scholz, Christopher A.; Heil, Clifford W.; King, John W.

2012-01-01

The Lake Bosumtwi sediment record represents one of the longest and highest-resolution terrestrial records of paleoclimate change available from sub-Saharan Africa. Here we report a new sediment age model framework for the last ~ 45 cal kyr of sedimentation using a combination of high-resolution radiocarbon dating, Bayesian age-depth modeling and lamination counting. Our results highlight the practical limits of these methods for reducing age model uncertainties and suggest that even with very high sampling densities, radiocarbon uncertainties of at least a few hundred years are unavoidable. Age model uncertainties are smallest during the Holocene (205 yr) and the glacial (360 yr) but are large at the base of the record (1660 yr), due to a combination of decreasing sample density, larger calibration uncertainties and increases in radiocarbon age scatter. For portions of the chronology older than ~ 35 cal kyr, additional considerations, such as the use of a low-blank graphitization system and more rigorous sample pretreatment were necessary to generate a reliable age depth model because of the incorporation of small amounts of younger carbon. A comparison of radiocarbon age model results and lamination counts over the time interval ~ 15–30 cal kyr agree with an overall discrepancy of ~ 10% and display similar changes in sedimentation rate, supporting the annual nature of sediment laminations in the early part of the record. Changes in sedimentation rates reconstructed from the age-depth model indicate that intervals of enhanced sediment delivery occurred at 16–19, 24 and 29–31 cal kyr, broadly synchronous with reconstructed drought episodes elsewhere in northern West Africa and potentially, with changes in Atlantic meridional heat transport during North Atlantic Heinrich events. These data suggest that millennial-scale drought events in the West African monsoon region were latitudinally extensive, reaching within several hundred kilometers of the Guinea coast

Dating the Late Archaic occupation of the Norte Chico region in Peru.

PubMed

Haas, Jonathan; Creamer, Winifred; Ruiz, Alvaro

2004-12-23

The Norte Chico region on the coast of Peru north of Lima consists of four adjacent river valleys--Huaura, Supe, Pativilca and Fortaleza--in which archaeologists have been aware of a number of apparently early sites for more than 40 years (refs 1- 3). To clarify the early chronology in this region, we undertook fieldwork in 2002 and 2003 to determine the dates of occupation of sites in the Fortaleza and Pativilca valleys. Here we present 95 new radiocarbon dates from a sample of 13 of more than 20 large, early sites. These sites share certain basic characteristics, including large-scale monumental architecture, extensive residential architecture and a lack of ceramics. The 95 new dates confirm the emergence and development of a major cultural complex in this region during the Late Archaic period between 3000 and 1800 calibrated calendar years bc. The results help to redefine a broader understanding of the respective roles of agricultural and fishing economies in the beginnings of civilization in South America.

The radiocarbon budget for Mono Lake: an unsolved mystery

USGS Publications Warehouse

Broecker, W.S.; Wanninkhof, R.; Mathieu, G.; Peng, T.-H.; Stine, S.; Robinson, S.; Herczeg, A.; Stuiver, M.

1988-01-01

Since 1957 the 14C C ratio of the dissolved inorganic carbon in Mono Lake has risen by about 60???. The magnitude of this increase is about four times larger than that expected from the invasion of bomb-produced 14C from the atmosphere. We have eliminated the following explanations: (1) measurement error, (2) an unusually high physical exchange rate for non-reactive gases, (3) inorganic enhancement of the CO2 exchange rate, and (4) biological enhancement of the CO2 exchange rate. Clandestine disposal of waste radiocarbon remains a dark-horse explanation. In the course of our investigations we have uncovered evidence for at least one episodic input of radiocarbon-free carbon to the lake over the last 1000 years. We speculate that this injection was related to a hydrothermal event resulting from sublacustrine volcanic activity. ?? 1988.

Radiocarbon dating and Dendrochronology for Statigraphic Units near Tebano, Senio Northern Apennines - Time frame of Climatic Fluctuation at the onset of the Younger Dryas

NASA Astrophysics Data System (ADS)

Eggenschwiler, Loren; Hajdas, Irka; Cherubini, Paolo; Picotti, Vincenzo; Saurer, Matthias

2017-04-01

The presence of Pinus [sylvestris] provides an insight into dramatic events due to climatic changes. Several major and minor climatic fluctuations have had a strong impact on terrestrial and marine environments since the last glacial period to present day (Ravazzi et al. 2006). This study aims to describe the response of a fluvial environment through the use of dendrochronology and stratigraphy. Here, we intend to get a better understanding of how these climatic fluctuations affect the behavior of the Senio River (Lotter et al. 1992). In Tebano, Italy, several Pinus sylvestris subfossil trunks were discovered during excavation for an irrigation pool. Subfossil samples were collected to analyze the climate during the Younger Dryas (11,000 years BP) in detail. Charcoal samples from the Bubano clay quarry extend our research to further to 35,500 cal. years BP. The combination of dendrochronology along with stratigraphy allowed us to examine the climate at a detailed local and apply it to a broader spectrum. Tree-ring measurements and cross dating provided a better understanding and verification of extreme events that occurred during the lifespans of the trees. The use of stable isotopes indicates the extreme conditions that occurred. Radiocarbon dating validates the age of the samples and what geological period they come from. Along with stratigraphy, we were able to compile depth data to create a sediment curve. Using various methods throughout this study, we discovered the climatic situation of Pinus 11,000 years BP and are able to compare them with samples from today. These present day samples mark two of the southernmost extents of the Pinus population. We were then able to comprehend the magnitude of sediment supply and precipitation. Through this collection of methods and data, we are able to understand the influence of climate change in the past and the potential changes of the future. REFERENCES Lotter, A. F.; Eicher, U.; Siegenthaler, U.; Birks, H. J. B

Simultaneous measurement of tritium and radiocarbon by ultra-low-background proportional counting.

PubMed

Mace, Emily; Aalseth, Craig; Alexander, Tom; Back, Henning; Day, Anthony; Hoppe, Eric; Keillor, Martin; Moran, Jim; Overman, Cory; Panisko, Mark; Seifert, Allen

2017-08-01

Use of ultra-low-background capabilities at Pacific Northwest National Laboratory provide enhanced sensitivity for measurement of low-activity sources of tritium and radiocarbon using proportional counters. Tritium levels are nearly back to pre-nuclear test backgrounds (~2-8 TU in rainwater), which can complicate their dual measurement with radiocarbon due to overlap in the beta decay spectra. We present results of single-isotope proportional counter measurements used to analyze a dual-isotope methane sample synthesized from ~120mg of H 2 O and present sensitivity results. Copyright © 2017 Elsevier Ltd. All rights reserved.

Simultaneous measurement of tritium and radiocarbon by ultra-low-background proportional counting

DOE PAGES

Mace, Emily; Aalseth, Craig; Alexander, Tom; ...

2016-12-21

Use of ultra-low-background capabilities at Pacific Northwest National Laboratory provide enhanced sensitivity for measurement of low-activity sources of tritium and radiocarbon using proportional counters. Tritium levels are nearly back to pre-nuclear test backgrounds (~2-8 TU in rainwater), which can complicate their dual measurement with radiocarbon due to overlap in the beta decay spectra. In this paper, we present results of single-isotope proportional counter measurements used to analyze a dual-isotope methane sample synthesized from ~120 mg of H 2O and present sensitivity results.

An analysis of carbon and radiocarbon profiles across a range ecosystems types

NASA Astrophysics Data System (ADS)

Heckman, K. A.; Gallo, A.; Hatten, J. A.; Swanston, C.; Strahm, B. D.; Sanclements, M.

2016-12-01

Soil carbon stocks have become recognized as increasingly important in the context of climate change and global C cycle modeling. As modelers seek to identify key parameters affecting the size and stability of belowground C stocks, attention has been drawn to the mineral matrix and the soil physiochemical factors influenced by it. Though clay content has often been utilized as a convenient and key explanatory variable for soil C dynamics, its utility has recently come under scrutiny as new paradigms of soil organic matter stabilization have been developed. We utilized soil cores from a range of National Ecological Observatory Network (NEON) experimental plots to examine the influence of mineralogical parameters on soil C stocks and turnover and their relative importance in comparison to climatic variables. Results are presented for a total of 11 NEON sites, spanning Alfisols, Entisols, Mollisols and Spodosols. Soils were sampled by genetic horizon, density separated according to density fractionation: light fractions (particulate organics neither occluded within aggregates nor associated with mineral surfaces), occluded fractions (particulate organics occluded within aggregates), and heavy fractions (organics associated with mineral surfaces). Bulk soils and density fractions were measured for % C and radiocarbon abundance (as a measure of C stability). Carbon and radiocarbon abundances were examined among fractions and in the context of climatic variables (temperature, precipitation, elevation) and soil physiochemical variables (% clay and pH). No direct relationships between temperature and soil C or radiocarbon abundances were found. As a whole, soil radiocarbon abundance in density fractions decreased in the order of light>heavy>occluded, highlighting the importance of both surface sorption and aggregation to the preservation of organics. Radiocarbon concentrations of the heavy fraction (mineral adsorbed) were significantly, though weakly, correlated with pH (r

Dating the Middle Paleolithic deposits of La Quina Amont (Charente, France) using luminescence methods.

PubMed

Frouin, Marine; Lahaye, Christelle; Valladas, Hélène; Higham, Thomas; Debénath, André; Delagnes, Anne; Mercier, Norbert

2017-08-01

The site of La Quina Amont, located in the Charente region, is one of the most important sites in southwestern France for studying major changes in human behaviors from the Middle Paleolithic (MP) to the Early Upper Paleolithic (EUP). Extensively excavated over the past 50 years, numerous dating studies have been focused on the Upper Paleolithic deposits using radiocarbon on bone collagen and thermoluminescence (TL) on heated flints; however, the Mousterian levels remain undated due to the scarcity of suitable materials. Our investigations aimed to provide for the first time a chronological framework for the site using luminescence dating methods on different minerals contained in the sediments. Coarse grains of quartz were dated using the optically stimulated luminescence (OSL) technique, and polymineral fine grains were dated using both infrared (IRSL) and post-infrared (pIR-IRSL) stimulated luminescence signals. OSL, IRSL and pIR-IRSL results were combined with available TL and radiocarbon data sets to propose a chronology for the site. The agreement between these methods provides key insights into the sedimentological processes involved in the site formation and into the chronology of the human occupations. In particular, it shows that the sequence spans almost ∼20,000 years (20 ka). Moreover, the new chronological framework suggests that the makers of the Quina lithic technocomplex (LTC), who were reindeer hunters, inhabited the site from the end of marine isotope stage (MIS) 4 to the beginning of MIS 3. We also show that Levallois and Discoidal industries occurred successively under temperate paleoclimatic conditions, during MIS 3 but not after ∼40 ka. Finally, we compare the Quina LTC dataset with other sites in southern France in order to shed light upon the variability in Mousterian industries of this region. Copyright © 2017 Elsevier Ltd. All rights reserved.

RADIOCARBON MEASUREMENT OF THE BIOGENIC CONTRIBUTION TO SUMMERTIME PM 2.5 AMBIENT AEROSOL IN NASHVILLE, TN

EPA Science Inventory

Radiocarbon (14C) measurements performed on PM-2.5 samples collected near Nashville, TN from June 21 to July 13, 1999, showed high levels of modern carbon, ranging from 56 to 80% of the total carbon in the samples. Radiocarbon measurements performed on dichloromethane extracts of...

Paleoseismic event dating and the conditional probability of large earthquakes on the southern San Andreas fault, California

USGS Publications Warehouse

Biasi, G.P.; Weldon, R.J.; Fumal, T.E.; Seitz, G.G.

2002-01-01

We introduce a quantitative approach to paleoearthquake dating and apply it to paleoseismic data from the Wrightwood and Pallett Creek sites on the southern San Andreas fault. We illustrate how stratigraphic ordering, sedimentological, and historical data can be used quantitatively in the process of estimating earthquake ages. Calibrated radiocarbon age distributions are used directly from layer dating through recurrence intervals and recurrence probability estimation. The method does not eliminate subjective judgements in event dating, but it does provide a means of systematically and objectively approaching the dating process. Date distributions for the most recent 14 events at Wrightwood are based on sample and contextual evidence in Fumal et al. (2002) and site context and slip history in Weldon et al. (2002). Pallett Creek event and dating descriptions are from published sources. For the five most recent events at Wrightwood, our results are consistent with previously published estimates, with generally comparable or narrower uncertainties. For Pallett Creek, our earthquake date estimates generally overlap with previous results but typically have broader uncertainties. Some event date estimates are very sensitive to details of data interpretation. The historical earthquake in 1857 ruptured the ground at both sites but is not constrained by radiocarbon data. Radiocarbon ages, peat accumulation rates, and historical constraints at Pallett Creek for event X yield a date estimate in the earliest 1800s and preclude a date in the late 1600s. This event is almost certainly the historical 1812 earthquake, as previously concluded by Sieh et al. (1989). This earthquake also produced ground deformation at Wrightwood. All events at Pallett Creek, except for event T, about A.D. 1360, and possibly event I, about A.D. 960, have corresponding events at Wrightwood with some overlap in age ranges. Event T falls during a period of low sedimentation at Wrightwood when conditions

Annual variability in the radiocarbon age and source of dissolved CO2 in a peatland stream.

PubMed

Garnett, Mark H; Dinsmore, Kerry J; Billett, Michael F

2012-06-15

Radiocarbon dating has the capacity to significantly improve our understanding of the aquatic carbon cycle. In this study we used a new passive sampler to measure the radiocarbon ((14)C) and stable carbon (δ(13)C) isotopic composition of dissolved CO(2) for the first time in a peatland stream throughout a complete year (May 2010-June 2011). The in-stream sampling system collected time-integrated samples of CO(2) continuously over approximately 1 month periods. The rate of CO(2) trapping was proportional to independently measured streamwater CO(2) concentrations, demonstrating that passive samplers can be used to estimate the time-averaged dissolved CO(2) concentration of streamwater. While there was little variation and no clear trend in δ(13)CO(2) values (suggesting a consistent CO(2) source), we found a clear temporal pattern in the (14)C concentration of dissolved CO(2). The (14)C age of CO(2) varied from 707±35 to 1210±39 years BP, with the youngest CO(2) in the autumn and oldest in spring/early summer. Mean stream discharge and (14)C content of dissolved CO(2) were positively correlated. We suggest that the observed pattern in the (14)C content of dissolved CO(2) reflects changes in its origin, with older carbon derived from deeper parts of the peat profile contributing proportionally more gaseous carbon during periods of low stream flow. Copyright © 2012 Elsevier B.V. All rights reserved.

Épisodes majeurs de la podzolisation en forêt de Fontainebleau (France). Essai de synthèse à l'aide du radiocarbone naturel

NASA Astrophysics Data System (ADS)

Robin, Anne-Marie

2005-04-01

The sandy materials underlying the Fontainebleau Forest (Paris Basin) are often podzolised. Several radiocarbon datings reveal different periods of podzolisation: during the first millenary before Christ (aliotic podzols, often humic, over Stampian sands, very quartzic and acid - certainly under heather and pines); from 10th to 12th centuries AD (humoferruginous podzols with Bh and Bs partially indurated, over blown sands, poor in fine particles - probably under heather); from 16th to 17th centuries AD (ochrepodzolic soils on blown sands, richer in fine particles than precedent, and humic podzols upon eroded Stampian sands); more recently, not precisely dated (ochrepodzolic soils or podzols with loose Bh over blown sands, relatively rich in fine particles, sometimes under leafed trees). To cite this article: A.-M. Robin, C. R. Geoscience 337 (2005).

Radiocarbon datings of Yamato meteorites

NASA Technical Reports Server (NTRS)

Kigoshi, K.; Matsuda, E.

1986-01-01

The terrestrial ages of five Yamato Meteorites were measured by the content of cosmic-ray-produced carbon-14. Three Yamato Meteorites Y-74013, Y-74097, and Y-74136, which are all diogenites, were found at sites from one to two kilometers apart from each other. Evidence is presented for these three meteorites being a single meteorite. Also presented is a method adopted in the experimental procedure which includes a check for modern carbon contamination in the meteorites.

Marine radiocarbon reservoir corrections (∆R) for Chesapeake Bay and the Middle Atlantic Coast of North America

NASA Astrophysics Data System (ADS)

Rick, Torben C.; Henkes, Gregory A.; Lowery, Darrin L.; Colman, Steven M.; Culleton, Brendan J.

2012-01-01

Radiocarbon dates from known age, pre-bomb eastern oyster (Crassostrea virginica) shells provide local marine reservoir corrections (∆R) for Chesapeake Bay and the Middle Atlantic coastal area of eastern North America. These data suggest subregional variability in ∆R, ranging from 148 ± 46 14C yr on the Potomac River to - 109 ± 38 14C yr at Swan Point, Maryland. The ∆R weighted mean for the Chesapeake's Western Shore (129 ± 22 14C yr) is substantially higher than the Eastern Shore (- 88 ± 23 14C yr), with outer Atlantic Coast samples falling between these values (106 ± 46 and 2 ± 46 14C yr). These differences may result from a combination of factors, including 14C-depleted freshwater that enters the bay from some if its drainages, 14C-depleted seawater that enters the bay at its mouth, and/or biological carbon recycling. We advocate using different subregional ∆R corrections when calibrating 14C dates on aquatic specimens from the Chesapeake Bay and coastal Middle Atlantic region of North America.

Correlating the Ancient Maya and Modern European Calendars with High-Precision AMS 14C Dating

PubMed Central

Kennett, Douglas J.; Hajdas, Irka; Culleton, Brendan J.; Belmecheri, Soumaya; Martin, Simon; Neff, Hector; Awe, Jaime; Graham, Heather V.; Freeman, Katherine H.; Newsom, Lee; Lentz, David L.; Anselmetti, Flavio S.; Robinson, Mark; Marwan, Norbert; Southon, John; Hodell, David A.; Haug, Gerald H.

2013-01-01

The reasons for the development and collapse of Maya civilization remain controversial and historical events carved on stone monuments throughout this region provide a remarkable source of data about the rise and fall of these complex polities. Use of these records depends on correlating the Maya and European calendars so that they can be compared with climate and environmental datasets. Correlation constants can vary up to 1000 years and remain controversial. We report a series of high-resolution AMS 14C dates on a wooden lintel collected from the Classic Period city of Tikal bearing Maya calendar dates. The radiocarbon dates were calibrated using a Bayesian statistical model and indicate that the dates were carved on the lintel between AD 658-696. This strongly supports the Goodman-Martínez-Thompson (GMT) correlation and the hypothesis that climate change played an important role in the development and demise of this complex civilization. PMID:23579869

Radiocarbon as a Novel Tracer of Extra-Antarctic Feeding in Southern Hemisphere Humpback Whales.

PubMed

Eisenmann, Pascale; Fry, Brian; Mazumder, Debashish; Jacobsen, Geraldine; Holyoake, Carlysle Sian; Coughran, Douglas; Bengtson Nash, Susan

2017-06-29

Bulk stable isotope analysis provides information regarding food web interactions, and has been applied to several cetacean species for the study of migration ecology. One limitation in bulk stable isotope analysis arises when a species, such as Southern hemisphere humpback whales, utilises geographically distinct food webs with differing isotopic baselines. Migrations to areas with different baselines can result in isotopic changes that mimic changes in feeding relations, leading to ambiguous food web interpretations. Here, we demonstrate the novel application of radiocarbon measurement for the resolution of such ambiguities. Radiocarbon was measured in baleen plates from humpback whales stranded in Australia between 2007 and 2013, and in skin samples collected in Australia and Antarctica from stranded and free-ranging animals. Radiocarbon measurements showed lower values for Southern Ocean feeding than for extra-Antarctic feeding in Australian waters. While the whales mostly relied on Antarctic-derived energy stores during their annual migration, there was some evidence of feeding within temperate zone waters in some individuals. This work, to our knowledge, provides the first definitive biochemical evidence for supplementary feeding by southern hemisphere humpback whales within temperate waters during migration. Further, the work contributes a powerful new tool (radiocarbon) for tracing source regions and geographical feeding.

Radiocarbon Depression in Aquatic Foodwebs of the Colorado River, USA: Coupling Between Carbonate Weathering and the Biosphere

NASA Astrophysics Data System (ADS)

Sickman, J. O.; Huang, W.; Lucero, D.; Anderson, M.

2012-12-01

The 14C isotopic composition of living organisms is generally considered to be in isotopic equilibrium with atmosphere CO2. During the course of investigations of aquatic foodwebs of the Colorado River, we measured substantial radiocarbon depression of organisms within planktonic and benthic foodwebs of Copper Basin Reservoir, a short residence-time water body at the intake to the Colorado River Aqueduct. All trophic levels had depressed radiocarbon content with inferred "age" of ca. 1,200 radiocarbon years (range: 0.85 to 0.87 fraction modern carbon (fmc)). Additional measurements of the radiocarbon content of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) were made in other major rivers in California (New (near Salton Sea), Santa Ana (near Riverside), San Joaquin (near Fresno) and Salinas (near San Luis Obispo)). In the New River (which is composed primarily of irrigation tailwater derived from the Colorado River), the radiocarbon values for DIC closely matched those found in biota of the Copper Basin Reservoir (0.85 to 0.87 fmc), but radiocarbon values for DOC were slightly higher (0.91 to 0.95 fmc). In the other California rivers, radiocarbon concentrations in DIC were generally below modern and lower than corresponding levels in DOC; in the case of the Santa Ana River, DOC was older than DIC as a result of wastewater inputs from upstream treatment plants. Together these data suggest that the carbonate equilibrium of California rivers is influenced by weathering of carbonate minerals which produces HCO3- with no 14C. We hypothesize that this dead carbon can move into aquatic foodwebs via algae and phytoplankton uptake during photosynthesis, depressing the 14C content of aquatic foodwebs below that of the atmosphere. Based on a simple two-component mixing model incorporating carbonate weathering and atmospheric CO2, we estimate that 15-17% of the carbon in the aquatic foodweb of Copper Basin is derived directly from mineral weathering of

Antiquity of man in America indicated by radiometric dates on the Yuha burial site

USGS Publications Warehouse

Bischoff, J.L.; Merriam, R.; Childers, W.M.; Protsch, R.

1976-01-01

MUCH evidence suggests that man was present in the Western Hemisphere before 12,000 yr ago, but the case has remained less than conclusive 1. In some situations, the geological age of the site is reasonably well established but the association or nature of the artefacts is questionable2,3. In other cases, museum specimens of human bones dated by radiocarbon analysis of collagen lack desirable information concerning site location, geology, and stratigraphy even though the accuracy of their absolute ages seems valid4-6. We report here the results of radiometric dates of the Yuha burial site from Imperial County, California, for which the geology and stratigraphy have been documented and reported in detail7. ?? 1976 Nature Publishing Group.

The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea

NASA Astrophysics Data System (ADS)

Pearce, Christof; Varhelyi, Aron; Wastegård, Stefan; Muschitiello, Francesco; Barrientos, Natalia; O'Regan, Matt; Cronin, Thomas M.; Gemery, Laura; Semiletov, Igor; Backman, Jan; Jakobsson, Martin

2017-04-01

The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution, combined with the fact that the eruption is relatively well constrained in time using radiocarbon dating of lake sediments and annual layer counts in ice cores, makes it an excellent stratigraphic marker for dating and correlating mid-late Holocene sediment and paleoclimate records. This study presents the outcome of a targeted search for the Aniakchak tephra in a marine sediment core from the Arctic Ocean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 57 m water depth in Herald Canyon, western Chukchi Sea. High concentrations of tephra shards, with a geochemical signature matching that of Aniakchak ash, were observed across a more than 1.5 m long sediment sequence. Since the primary input of volcanic ash is through atmospheric transport, and assuming that bioturbation can account for mixing up to ca. 10 cm of the marine sediment deposited at the coring site, the broad signal is interpreted as sustained reworking at the sediment source input. The isochron is therefore placed at the base of the sudden increase in tephra concentrations rather than at the maximum concentration. This interpretation of major reworking is strengthened by analysis of grain size distribution which points to ice rafting as an important secondary transport mechanism of volcanic ash. Combined with radiocarbon dates on mollusks in the same sediment core, the volcanic marker is used to calculate a marine radiocarbon reservoir age offset ΔR = 477 ± 60 years. This relatively high value may be explained by the major influence of typically carbon-old Pacific waters, and it agrees well with recent estimates of ΔR along the northwest Alaskan coast

Radiocarbon dating of archaeological samples (sambaqui) using CO(2) absorption and liquid scintillation spectrometry of low background radiation.

PubMed

Mendonça, Maria Lúcia T G; Godoy, José M; da Cruz, Rosana P; Perez, Rhoneds A R

2006-01-01

Sambaqui means, in the Tupi language, a hill of shells. The sambaquis are archaeological sites with remains of pre-historical Brazilian occupation. Since the sambaqui sites in the Rio de Janeiro state region are older than 10,000 years, the applicability of CO(2) absorption on Carbo-sorb and (14)C determination by counting on a low background liquid scintillation counter was tested. In the present work, sambaqui shells were treated with H(3)PO(4) in a closed vessel in order to generate CO(2). The produced CO(2) was absorbed on Carbo-sorb. On saturation about 0.6g of carbon, as CO(2), was mixed with commercial liquid scintillation cocktail (Permafluor), and the (14)C activity determined by counting on a low background counter, Packard Tricarb 3170 TR/SL, for a period of 1000 mins to enable detection of a radiocarbon age of 22,400 BP. But only samples with ages up to 3500 BP were submitted to the method because the samples had been collected in the municipality of Guapimirim, in archaeological sambaqui-type sites belonging to this age range. The same samples were sent to the (14)C Laboratory of the Centro de Energia Nuclear na Agricultura (CENA/USP) where similar results were obtained.

Suitability of biogenic carbonate of Lithospermum fruits for 14C dating

NASA Astrophysics Data System (ADS)

Pustovoytov, Konstantin; Riehl, Simone

2006-05-01

Lithospermum (Boraginaceae) belongs to a small group of plant taxa that accumulate biogenic carbonate in their fruits. In this genus, carbonate incrustations form in the cells of the epidermis and sclerenchyma of the pericarp. Fossil Lithospermum fruits (nutlets) with well-preserved calcified tissues commonly occur in Quaternary sediments and cultural layers. We tested the suitability of biogenic carbonate of Lithospermum fruits for radiocarbon dating using a total of 15 AMS measurement results from four modern and 11 fossil samples. The 14C data from modern samples suggest that Lithospermum utilises only atmospheric carbon to synthesise calcite in the nutlets. In general, the ages determined through 14C dating of fossil fruitscorresponded well with the absolute-age intervals for archaeological sites over the last 5000 yr. Biogenic carbonate of Lithospermum fruits, like that of Celtis, represents a new source of chronological information for late Quaternary studies.

The potential of using thermoluminescence to date buried soils developed on colluvial and fluvial sediments from Utah and Colorado, U.S.A.: Preliminary results

NASA Astrophysics Data System (ADS)

Forman, S. L.; Jackson, M. E.; McCalpin, J.; Maat, P.

The natural TL intensity for surface and buried Holocene and Pleistocene A horizons developed on flood-plain silts, near Denver, Colorado exponentially decreases with time. This signal is approaching saturation by ca. 130 ka. The A horizon of the modern flood-plain soil is not fully light bleached. The TL properties and age estimates are presented for radiocarbon dated, eolian-enriched buried-A horizons developed on fault-derived colluvium from the American Fork segment of the Wasatch fault zone, Utah. Dating of these buried soils provide a close age estimate on paleoearthquake events. Mean TL age estimates by regeneration and total bleach techniques for buried A horizons are 0.5 ± 0.1 ka and 2.7 ± 0.4 ka which are in agreement with corresponding radiocarbon dates of 980 ± 70 years BP and 2620 ± 70 years BP. A surface sag pond mud formed within an antithetic grabben is well light bleached and yielded a TL age estimate by the total bleach method of 240 ± 60 years BP, in agreement with its known age of <300 years BP. This study indicates that relatively brief periods of pedogenesis are not sufficient to light-bleach sediment and that eolian additions enhance the reduction of TL in soils.

Using age of colonizing douglas-fir for the dating of young geomorphic surfaces: a case study

USGS Publications Warehouse

Pierson, Thomas C.

2013-01-01

Dating of many types of young (<500 year), dynamic, geomorphic landforms (e.g. mass-movement erosional tracks and deposits, alluvial terraces, flood plains, etc.) for purposes of hazard assessment and mitigation commonly requires greater dating precision than is available through radiocarbon dating or other methods. Ages of trees growing on landform surfaces have been used in a number of studies to estimate the time of landform creation or surface clearing, but the time lag between surface formation or disturbance and the reestablishment of trees can vary from 1 to more than 200 years (Desloges and Ryder 1990; Frenzen et al. 1988, 2005; Larsen and Bliss 1998; McCarthy and Luckman 1993; Sigafoos and Hendricks 1969; Winter et al. 2002). Appropriate lag times for selected tree species and for particular climatic and altitudinal ranges must be determined for the method to be useful.

Resin composite characterizations following a simplified protocol of accelerated aging as a function of the expiration date.

PubMed

D'Alpino, Paulo Henrique Perlatti; Vismara, Marcus Vinícius Gonçalves; Mello, Luciano Marcelo de Medeiros; Di Hipólito, Vinicius; González, Alejandra Hortencia Miranda; Graeff, Carlos Frederico de Oliveira

2014-07-01

This study evaluated the mechanical, thermal, and morphological characteristics of different classifications of dental composites as a function of the material condition (new, aged and expired). Specimens were obtained according to these factors: Composites: Filtek P60, Filtek Z250, Filtek Z350XT, and Filtek Silorane; and Material conditions: new, aged, and expired. The syringe composites underwent an accelerated aging protocol (Arrhenius model). The flexural strength (FS) and flexural modulus (E) were obtained. The thermogravimetric analysis (TGA) and differential thermal analysis (DTA) were also performed and the glass transition temperature (Tg) and the weight loss calculated. Topographic analysis of the composites was performed under SEM. The material conditions influenced the mechanical properties of the composites. The silorane composite exhibited a characteristic thermal behavior different from that of the methacrylates. In general, the Tg increased after the accelerated aging protocol and decreased for expired ones, compared to the new composites. A significant increase in FS of Filtek Z350XT after aging was accompanied by an increase in the Tg. The filler packings were in accordance with the manufacture׳s information. The topographic aspects of the composites were modified as a function of the material condition. The mechanical properties of the composites following a simplified protocol of accelerated aging varied as a function of the expiration date. The silorane composite presented a characteristic thermal behavior. Although the dental manufacturers may not be able to control variables as storage temperature and transportation conditions, these effects on the composite clinical performance can be minimized if properly considered. Copyright © 2014 Elsevier Ltd. All rights reserved.

The 3.6 ka Aniakchak tephra in the Arctic Ocean: A constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea

USGS Publications Warehouse

Pearce, Christof; Varhelyi, Aron; Wastegård, Stefan; Muschitiello, Francesco; Barrientos Macho, Natalia; O'Regan, Matt; Cronin, Thomas M.; Gemery, Laura; Semiletov, Igor; Backman, Jan; Jakobsson, Martin

2017-01-01

The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution, combined with the fact that the eruption is relatively well constrained in time using radiocarbon dating of lake sediments and annual layer counts in ice cores, makes it an excellent stratigraphic marker for dating and correlating mid–late Holocene sediment and paleoclimate records. This study presents the outcome of a targeted search for the Aniakchak tephra in a marine sediment core from the Arctic Ocean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 57 m water depth in Herald Canyon, western Chukchi Sea. High concentrations of tephra shards, with a geochemical signature matching that of Aniakchak ash, were observed across a more than 1.5 m long sediment sequence. Since the primary input of volcanic ash is through atmospheric transport, and assuming that bioturbation can account for mixing up to ca. 10 cm of the marine sediment deposited at the coring site, the broad signal is interpreted as sustained reworking at the sediment source input. The isochron is therefore placed at the base of the sudden increase in tephra concentrations rather than at the maximum concentration. This interpretation of major reworking is strengthened by analysis of grain size distribution which points to ice rafting as an important secondary transport mechanism of volcanic ash. Combined with radiocarbon dates on mollusks in the same sediment core, the volcanic marker is used to calculate a marine radiocarbon reservoir age offset ΔR = 477 ± 60 years. This relatively high value may be explained by the major influence of typically "carbon-old" Pacific waters, and it agrees well with recent estimates of ΔR along the northwest

Ramped PyrOx 14C With a Twist: Improving Radiocarbon Chronologies on Highly Detrital Marginal Antarctic Sediments

NASA Astrophysics Data System (ADS)

Subt, C.; Yoon, H.; Yoo, K. C.; Lee, J. I.; Domack, E. W.; Rosenheim, B. E.

2016-02-01

Highly detrital sediments can be difficult to date when the detritus includes material similar to that from which dates are sought. For radiocarbon dating, samples with a high degree of pre-aged detrital carbon contamination necessitate measurement of a very small portion of the sample to remove that contamination from the targeted component, even when using advanced techniques such as Ramped PyrOx (RP) 14C dating. Here we present three case studies of alternative RP approaches, producing accurate and precise chronologies for highly detrital sediments near the Larsen C ice shelf, near the Drygalski Ice Tongue in Ross Sea, and in Lapeyrère Bay, Anvers Island. For sediments where the proportion of organic carbon that was modern at the time of deposition is too small for a traditional AMS analysis after RP treatment, we have developed an innovative multiple RP analyses approach to minimize the cost in precision from using smaller temperature intervals, while maximizing the benefit in accuracy. Resulting sub ice-shelf chronologies show vastly improved dates down-core, significantly younger than the equivalent 14C chronology from the bulk acid insoluble organic (AIO) carbon with increasing ages down-core. By comparison, bulk AIO 14C dates in the study areas are not only older, but are subject to age reversals and nearly constant ages that make sedimentation rates impossible to resolve. Using our new approaches, we can reduce pre-aged carbon contamination in Lapeyrère Bay, and date sediments within layers of siliceous mud and ooze in the Ross Sea, and near the Larsen C ice shelf. Improved accuracy for 14C dates of highly detrital sediments can sometimes require the incorporation of a larger blank correction to account for multiple analyses, decreasing the precision. Application of this method refines ages of hard-to-date sediments, removing limits on what to include in a regional approach to chronicle ice shelf collapse.

The Younger Dryas phase of Great Salt Lake, Utah, USA

USGS Publications Warehouse

Oviatt, Charles G.; Miller, D.M.; McGeehin, J.P.; Zachary, C.; Mahan, S.

2005-01-01

Field investigations at the Public Shooting Grounds (a wildlife-management area on the northeastern shore of Great Salt Lake) and radiocarbon dating show that the Great Salt Lake rose to the Gilbert shoreline sometime between 12.9 and 11.2 cal ka. We interpret a ripple-laminated sand unit exposed at the Public Shooting Grounds, and dated to this time interval, as the nearshore sediments of Great Salt Lake deposited during the formation of the Gilbert shoreline. The ripple-laminated sand is overlain by channel-fill deposits that overlap in age (11.9-11.2 cal ka) with the sand, and by wetland deposits (11.1 to 10.5 cal ka). Consistent accelerator mass spectrometry radiocarbon ages were obtained from samples of plant fragments, including those of emergent aquatic plants, but mollusk shells from spring and marsh deposits yielded anomalously old ages, probably because of a variable radiocarbon reservoir effect. The Bonneville basin was effectively wet during at least part of the Younger Dryas global-cooling interval, however, conflicting results from some Great Basin locations and proxy records indicate that the regional effects of Younger Dryas cooling are still not well understood. ?? 2005 Elsevier B.V. All rights reserved.

A multi-centennial time series of well-constrained ΔR values for the Irish Sea derived using absolutely-dated shell samples from the mollusc Arctica islandica

NASA Astrophysics Data System (ADS)

Butler, P. G.; Scourse, J. D.; Richardson, C. A.; Wanamaker, A. D., Jr.

2009-04-01

Determinations of the local correction (ΔR) to the globally averaged marine radiocarbon reservoir age are often isolated in space and time, derived from heterogeneous sources and constrained by significant uncertainties. Although time series of ΔR at single sites can be obtained from sediment cores, these are subject to multiple uncertainties related to sedimentation rates, bioturbation and interspecific variations in the source of radiocarbon in the analysed samples. Coral records provide better resolution, but these are available only for tropical locations. It is shown here that it is possible to use the shell of the long-lived bivalve mollusc Arctica islandica as a source of high resolution time series of absolutely-dated marine radiocarbon determinations for the shelf seas surrounding the North Atlantic ocean. Annual growth increments in the shell can be crossdated and chronologies can be constructed in a precise analogue with the use of tree-rings. Because the calendar dates of the samples are known, ΔR can be determined with high precision and accuracy and because all the samples are from the same species, the time series of ΔR values possesses a high degree of internal consistency. Presented here is a multi-centennial (AD 1593 - AD 1933) time series of 31 ΔR values for a site in the Irish Sea close to the Isle of Man. The mean value of ΔR (-62 14C yrs) does not change significantly during this period but increased variability is apparent before AD 1750.

Insights into soil carbon dynamics across climatic and geologic gradients from temporally-resolved radiocarbon measurements

NASA Astrophysics Data System (ADS)

van der Voort, T. S.; Hagedorn, F.; Mannu, U.; Walthert, L.; McIntyre, C.; Eglinton, T. I.

2016-12-01

Soil carbon constitutes the largest terrestrial reservoir of organic carbon, and therefore quantifying soil organic matter dynamics (carbon turnover, stocks and fluxes) across spatial gradients is essential for an understanding of the carbon cycle and the impacts of global change. In particular, links between soil carbon dynamics and different climatic and compositional factors remains poorly understood. Radiocarbon constitutes a powerful tool for unraveling soil carbon dynamics. Temporally-resolved radiocarbon measurements, which take advantage of "bomb-radiocarbon"-driven changes in atmospheric 14C, enable further constraints to be placed on C turnover times. These in turn can yield more precise flux estimates for both upper and deeper soil horizons. This project combines bulk radiocarbon measurements on a suite of soil profiles spanning strong climatic (MAT 1.3-9.2°C, MAP 600 to 2100 mm m-2y-1) and geologic gradients with a more in-depth approach for a subset of locations. For this subset, temporal and carbon-fraction specific radiocarbon data has been acquired for both topsoil and deeper soils. These well-studied sites are part of the Long-Term Forest Ecosystem Research (LWF) program of the Swiss Federal Institute for Forest, Snow and Landscape research (WSL). Resulting temporally-resolved turnover estimates are coupled to carbon stocks, fluxes across this wide range of forest ecosystems and are examined in the context of environmental drivers (temperature, precipitation, primary production and soil moisture) as well as composition (sand, silt and clay content). Statistical analysis on the region-scale - correlating radiocarbon signature with climatic variables such as temperature, precipitation, primary production and elevation - indicates that composition rather than climate is a key driver of ­­Δ14C signatures. Estimates of carbon turnover, stocks and fluxes derived from temporally-resolved measurements highlight the pivotal role of soil moisture as a

Dating Caral, a preceramic site in the Supe Valley on the central coast of Peru.

PubMed

Solis, R S; Haas, J; Creamer, W

2001-04-27

Radiocarbon dates from the site of Caral in the Supe Valley of Peru indicate that monumental corporate architecture, urban settlement, and irrigation agriculture began in the Americas by 4090 years before the present (2627 calibrated years B.C.) to 3640 years before the present (1977 calibrated years B.C.). Caral is located 23 kilometers inland from the Pacific coast and contains a central zone of monumental, residential, and nonresidential architecture covering an area of 65 hectares. Caral is one of 18 large preceramic sites in the Supe Valley.

Measurements and modeling of contemporary radiocarbon in the stratosphere

NASA Astrophysics Data System (ADS)

Kanu, A. M.; Comfort, L. L.; Guilderson, T. P.; Cameron-Smith, P. J.; Bergmann, D. J.; Atlas, E. L.; Schauffler, S.; Boering, K. A.

2016-02-01

Measurements of the 14C content of carbon dioxide in air collected by high-altitude balloon flights in 2003-2005 reveal the contemporary radiocarbon distribution in the northern midlatitude stratosphere, four decades after the Limited Test Ban Treaty restricted atmospheric testing of nuclear weapons. Comparisons with results from a 3-D chemical-transport model show that the 14CO2 distribution is now largely governed by the altitude/latitude dependence of the natural cosmogenic production rate, stratospheric transport, and propagation into the stratosphere of the decreasing radiocarbon trend in tropospheric CO2 due to fossil fuel combustion. From the observed correlation of 14CO2 with N2O mixing ratios, an annual global mean net flux of 14CO2 to the troposphere of 1.6(±0.4) × 1017‰ mol CO2 yr-1 and a global production rate of 2.2(±0.6) × 1026 atoms 14C yr-1 are empirically derived. The results also indicate that contemporary 14CO2 observations provide highly sensitive diagnostics for stratospheric transport and residence times in models.

Vertebral bomb radiocarbon suggests extreme longevity in white sharks.

PubMed

Hamady, Li Ling; Natanson, Lisa J; Skomal, Gregory B; Thorrold, Simon R

2014-01-01

Conservation and management efforts for white sharks (Carcharodon carcharias) remain hampered by a lack of basic demographic information including age and growth rates. Sharks are typically aged by counting growth bands sequentially deposited in their vertebrae, but the assumption of annual deposition of these band pairs requires testing. We compared radiocarbon (Δ(14)C) values in vertebrae from four female and four male white sharks from the northwestern Atlantic Ocean (NWA) with reference chronologies documenting the marine uptake of (14)C produced by atmospheric testing of thermonuclear devices to generate the first radiocarbon age estimates for adult white sharks. Age estimates were up to 40 years old for the largest female (fork length [FL]: 526 cm) and 73 years old for the largest male (FL: 493 cm). Our results dramatically extend the maximum age and longevity of white sharks compared to earlier studies, hint at possible sexual dimorphism in growth rates, and raise concerns that white shark populations are considerably more sensitive to human-induced mortality than previously thought.

Vertebral Bomb Radiocarbon Suggests Extreme Longevity in White Sharks

PubMed Central

Hamady, Li Ling; Natanson, Lisa J.; Skomal, Gregory B.; Thorrold, Simon R.

2014-01-01

Conservation and management efforts for white sharks (Carcharodon carcharias) remain hampered by a lack of basic demographic information including age and growth rates. Sharks are typically aged by counting growth bands sequentially deposited in their vertebrae, but the assumption of annual deposition of these band pairs requires testing. We compared radiocarbon (Δ14C) values in vertebrae from four female and four male white sharks from the northwestern Atlantic Ocean (NWA) with reference chronologies documenting the marine uptake of 14C produced by atmospheric testing of thermonuclear devices to generate the first radiocarbon age estimates for adult white sharks. Age estimates were up to 40 years old for the largest female (fork length [FL]: 526 cm) and 73 years old for the largest male (FL: 493 cm). Our results dramatically extend the maximum age and longevity of white sharks compared to earlier studies, hint at possible sexual dimorphism in growth rates, and raise concerns that white shark populations are considerably more sensitive to human-induced mortality than previously thought. PMID:24416189

Radiocarbon constraints on the glacial ocean circulation and its impact on atmospheric CO2

PubMed Central

Skinner, L. C.; Primeau, F.; Freeman, E.; de la Fuente, M.; Goodwin, P. A.; Gottschalk, J.; Huang, E.; McCave, I. N.; Noble, T. L.; Scrivner, A. E.

2017-01-01

While the ocean’s large-scale overturning circulation is thought to have been significantly different under the climatic conditions of the Last Glacial Maximum (LGM), the exact nature of the glacial circulation and its implications for global carbon cycling continue to be debated. Here we use a global array of ocean–atmosphere radiocarbon disequilibrium estimates to demonstrate a ∼689±53 14C-yr increase in the average residence time of carbon in the deep ocean at the LGM. A predominantly southern-sourced abyssal overturning limb that was more isolated from its shallower northern counterparts is interpreted to have extended from the Southern Ocean, producing a widespread radiocarbon age maximum at mid-depths and depriving the deep ocean of a fast escape route for accumulating respired carbon. While the exact magnitude of the resulting carbon cycle impacts remains to be confirmed, the radiocarbon data suggest an increase in the efficiency of the biological carbon pump that could have accounted for as much as half of the glacial–interglacial CO2 change. PMID:28703126

Radiocarbon constraints on the glacial ocean circulation and its impact on atmospheric CO2

NASA Astrophysics Data System (ADS)

Skinner, L. C.; Primeau, F.; Freeman, E.; de La Fuente, M.; Goodwin, P. A.; Gottschalk, J.; Huang, E.; McCave, I. N.; Noble, T. L.; Scrivner, A. E.

2017-07-01

While the ocean's large-scale overturning circulation is thought to have been significantly different under the climatic conditions of the Last Glacial Maximum (LGM), the exact nature of the glacial circulation and its implications for global carbon cycling continue to be debated. Here we use a global array of ocean-atmosphere radiocarbon disequilibrium estimates to demonstrate a ~689+/-53 14C-yr increase in the average residence time of carbon in the deep ocean at the LGM. A predominantly southern-sourced abyssal overturning limb that was more isolated from its shallower northern counterparts is interpreted to have extended from the Southern Ocean, producing a widespread radiocarbon age maximum at mid-depths and depriving the deep ocean of a fast escape route for accumulating respired carbon. While the exact magnitude of the resulting carbon cycle impacts remains to be confirmed, the radiocarbon data suggest an increase in the efficiency of the biological carbon pump that could have accounted for as much as half of the glacial-interglacial CO2 change.

Dilemma posed by uranium-series dates on archaeologically significant bones from Valsequillo, Puebla, Mexico

USGS Publications Warehouse

Szabo, B. J.; Malde, H.E.; Irwin-Williams, C.

1969-01-01

In an attempt to date stone artifacts of Early Man excavated from several sites at the Valsequillo Reservoir, a few kilometers south of Puebla, Mexico, Szabo applied the uranium-series method on bone samples known to be either from the same geologic formation as the sites or in direct association with the artifacts. The geologic context of the bones was studied by Malde, and the archaeological sites were excavated by Irwin-Williams. A date determined for bone associated with an artifact (Caulapan sample M-B-6, see below) agrees with a radiocarbon date for fossil mollusks in the same bed and indicates man's presence more than 20 000 years ago. However, some of these bone dates exceed 200 000 years. Because such dates for man in North America conflict with all prior archaeological evidence here and abroad, we are confronted by a dilemna - either to defend the dates against an onslaught of archaeological thought, or to abandon the uranium method in this application as being so much wasted effort. Faced with these equally undesirable alternatives, and unable to decide where the onus fairly lies (if a choice must be made), we give the uranium-series dates as a possible stimulus for further mutual work in isotopic dating of archaeological material. A sample from the Lindenmeier archaeological site north of Fort Collins and another from a Pleistocene terrace along the Arkansas River, both in Colorado, were also dated. ?? 1969.

Dating the End of the Greek Bronze Age: A Robust Radiocarbon-Based Chronology from Assiros Toumba

PubMed Central

Wardle, Kenneth; Higham, Thomas; Kromer, Bernd

2014-01-01

Over 60 recent analyses of animal bones, plant remains, and building timbers from Assiros in northern Greece form an unique series from the 14th to the 10th century BC. With the exception of Thera, the number of 14C determinations from other Late Bronze Age sites in Greece has been small and their contribution to chronologies minimal. The absolute dates determined for Assiros through Bayesian modelling are both consistent and unexpected, since they are systematically earlier than the conventional chronologies of southern Greece by between 70 and 100 years. They have not been skewed by reference to assumed historical dates used as priors. They support high rather than low Iron Age chronologies from Spain to Israel where the merits of each are fiercely debated but remain unresolved. PMID:25222862

Dating High Arctic Holocene relative sea level changes using juvenile articulated marine shells in raised beaches

NASA Astrophysics Data System (ADS)

Long, Antony J.; Strzelecki, Mateusz C.; Lloyd, Jerry M.; Bryant, Charlotte L.

2012-08-01

High Arctic raised beaches provide evidence for changes in relative sea-level (RSL), sea-ice extent, storminess, and variations in sediment supply. In many High Arctic areas, driftwood and whale bone are usually the preferred targets for radiocarbon dating, with marine shells a third choice because of their often large age and height uncertainties with respect to former sea level. Here we detail a new approach to sampling marine shells that reduces these problems by targeting juvenile, articulated specimens of Astarte borealis that are washed onto the beach under storm conditions and become incorporated into the beach crest. Radiocarbon dates from articulated valves of A. borealis from eight raised beaches from Billefjorden, Svalbard, provide a chronology for Holocene beach ridge formation and RSL change that compares favourably to the most precise records developed from elsewhere in Svalbard using driftwood or whale bone. We demonstrate the value of this new approach by comparing our record with previously published RSL data from eastern Svalbard to test different models of Late Weichselian ice load in this region. We find support for a major ice dome centred south and east of Kong Karls Land but no evidence for a significant ice dome located over easternmost Spitsbergen or southern Hinlopen Strait as proposed from recent marine geophysical survey. The approach is potentially applicable elsewhere in Svalbard and the High Arctic to address questions of RSL change and beach ridge chronology, and hence wider questions regarding palaeoclimate and ice load history.

Are Icelandic rock-slope failures paraglacial? Age evaluation of seventeen rock-slope failures in the Skagafjörður area, based on geomorphological stacking, radiocarbon dating and tephrochronology

NASA Astrophysics Data System (ADS)

Mercier, Denis; Coquin, Julien; Feuillet, Thierry; Decaulne, Armelle; Cossart, Etienne; Jónsson, Helgi Pall; Sæmundsson, Þorstein

2017-11-01

In Iceland there are numerous rock-slope failures, especially in the Tertiary basaltic formations of the northern, eastern and northwestern regions. The temporal pattern of rock-slope failures is fundamental for understanding post-glacial events. In the Skagafjörður district, central northern Iceland, 17 rock-slope failures were investigated to determine the age of their occurrence. A geomorphic survey was carried out to identify and characterize landform units, both on the rock-slope failures and in their immediate vicinity. In this coastal area, we used geomorphological stacking which included the relationship between rock-slope failures and raised beaches caused by glacial isostatic rebounds, the chronology of which was established in previous studies. We searched for depressions on the rock-slope failures to then excavate a series of pits and map the stratigraphy. The resulting stratigraphic framework was then validated using (i) radiocarbon dating of wood remains, and (ii) tephrochronology, both of which were complemented by age-depth model calibration. The results confirm that all the rock-slope failures potentially occurred before the Boreal (8 ka), while 94% occurred before the Preboreal (10 ka). They all potentially occurred after the glacial retreat following the maximal ice extent and the Preboreal. More precisely, 11 of them potentially occurred between the Preboreal and the first half of the Holocene. This study demonstrates the relationship between the deglaciation and destabilization of slopes during the paraglacial phase (debuttressing, decompression, glacial isostatic rebound, seismic activity, etc.), which are also controlling factors favouring landsliding, but are difficult to identify for each individual rock-slope failure.

Radiocarbon evidence for extensive plate-boundary rupture about 300 years ago at the Cascadia subduction zone

USGS Publications Warehouse

Nelson, A.R.; Atwater, B.F.; Bobrowsky, P.T.; Bradley, L.A.; Clague, J.J.; Carver, G.A.; Darienzo, M.E.; Grant, W.C.; Krueger, H.W.; Sparks, R.; Stafford, Thomas W.; Stuiver, M.

1995-01-01

THE Cascadia subduction zone, a region of converging tectonic plates along the Pacific coast of North America, has a geological history of very large plate-boundary earthquakes1,2, but no such earthquakes have struck this region since Euro-American settlement about 150 years ago. Geophysical estimates of the moment magnitudes (Mw) of the largest such earthquakes range from 8 (ref. 3).to 91/2 (ref. 4). Radiocarbon dating of earthquake-killed vegetation can set upper bounds on earthquake size by constraining the length of plate boundary that ruptured in individual earthquakes. Such dating has shown that the most recent rupture, or series of ruptures, extended at least 55 km along the Washington coast within a period of a few decades about 300 years ago5. Here we report 85 new 14C ages, which suggest that this most recent rupture (or series) extended at least 900 km between southern British Columbia and northern California. By comparing the 14C ages with written records of the past 150 years, we conclude that a single magnitude 9 earthquake, or a series of lesser earthquakes, ruptured most of the length of the Cascadia subduction zone between the late 1600s and early 1800s, and probably in the early 1700s.

BIOGENIC CONTRIBUTION TO PM-2.5 AMBIENT AEROSOL FROM RADIOCARBON MEASUREMENTS

EPA Science Inventory

Knowledge of the relative contributions of biogenic versus anthropogenic sources to ambient aerosol is of great interest in the formulation of strategies to achieve nationally mandated air quality standards. Radiocarbon (Carbon-14) measurements provide a means to quantify the ...

The quest for an absolute chronology in human prehistory: anthropologists, chemists and the fluorine dating method in palaeoanthropology.

PubMed

Goodrum, Matthew R; Olson, Cora

2009-03-01

By the early twentieth century there was a growing need within palaeoanthropology and prehistoric archaeology to find a way of dating fossils and artefacts in order to know the age of specific specimens, but more importantly to establish an absolute chronology for human prehistory. The radiocarbon and potassium-argon dating methods revolutionized palaeoanthropology during the last half of the twentieth century. However, prior to the invention of these methods there were attempts to devise chemical means of dating fossil bone. Collaborations between Emile Rivière and Adolphe Carnot in the 1890s led to the development of the fluorine dating method, but it was not until the 1940s that this method was improved and widely implemented by Kenneth Oakley to resolve a number of problems in palaeoanthropology, including the Piltdown Man controversy. The invention of the fluorine dating method marked a significant advance in the quest for absolute dating in palaeoanthropology, but it also highlights interesting problems and issues relating to the ability of palaeoanthropologists and chemists to bring together different skills and bodies of knowledge in order successfully to develop and apply the fluorine dating method.

7 CFR 1436.13 - Loan installments, delinquency, and acceleration of maturity date.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 10 2010-01-01 2010-01-01 false Loan installments, delinquency, and acceleration of... FACILITY LOAN PROGRAM REGULATIONS § 1436.13 Loan installments, delinquency, and acceleration of maturity... delinquency, CCC may permit a rescheduling of the debt or other measures consistent with the collection of...

The earliest archaeological maize (Zea mays L.) from highland Mexico: New accelerator mass spectrometry dates and their implications

PubMed Central

Piperno, D. R.; Flannery, K. V.

2001-01-01

Accelerator mass spectrometry age determinations of maize cobs (Zea mays L.) from Guilá Naquitz Cave in Oaxaca, Mexico, produced dates of 5,400 carbon-14 years before the present (about 6,250 calendar years ago), making those cobs the oldest in the Americas. Macrofossils and phytoliths characteristic of wild and domesticated Zea fruits are absent from older strata from the site, although Zea pollen has previously been identified from those levels. These results, together with the modern geographical distribution of wild Zea mays, suggest that the cultural practices that led to Zea domestication probably occurred elsewhere in Mexico. Guilá Naquitz Cave has now yielded the earliest macrofossil evidence for the domestication of two major American crop plants, squash (Cucurbita pepo) and maize. PMID:11172082

The earliest archaeological maize (Zea mays L.) from highland Mexico: new accelerator mass spectrometry dates and their implications.

PubMed

Piperno, D R; Flannery, K V

2001-02-13

Accelerator mass spectrometry age determinations of maize cobs (Zea mays L.) from Guilá Naquitz Cave in Oaxaca, Mexico, produced dates of 5,400 carbon-14 years before the present (about 6,250 calendar years ago), making those cobs the oldest in the Americas. Macrofossils and phytoliths characteristic of wild and domesticated Zea fruits are absent from older strata from the site, although Zea pollen has previously been identified from those levels. These results, together with the modern geographical distribution of wild Zea mays, suggest that the cultural practices that led to Zea domestication probably occurred elsewhere in Mexico. Guilá Naquitz Cave has now yielded the earliest macrofossil evidence for the domestication of two major American crop plants, squash (Cucurbita pepo) and maize.

Dating rice remains through phytolith carbon-14 study reveals domestication at the beginning of the Holocene

PubMed Central

Lu, Houyuan; Jiang, Leping; Zhang, Jianping; Huan, Xiujia; He, Keyang; Wang, Can; Wu, Naiqin

2017-01-01

Phytolith remains of rice (Oryza sativa L.) recovered from the Shangshan site in the Lower Yangtze of China have previously been recognized as the earliest examples of rice cultivation. However, because of the poor preservation of macroplant fossils, many radiocarbon dates were derived from undifferentiated organic materials in pottery sherds. These materials remain a source of debate because of potential contamination by old carbon. Direct dating of the rice remains might serve to clarify their age. Here, we first validate the reliability of phytolith dating in the study region through a comparison with dates obtained from other material from the same layer or context. Our phytolith data indicate that rice remains retrieved from early stages of the Shangshan and Hehuashan sites have ages of approximately 9,400 and 9,000 calibrated years before the present, respectively. The morphology of rice bulliform phytoliths indicates they are closer to modern domesticated species than to wild species, suggesting that rice domestication may have begun at Shangshan during the beginning of the Holocene. PMID:28559349

Dating rice remains through phytolith carbon-14 study reveals domestication at the beginning of the Holocene.

PubMed

Zuo, Xinxin; Lu, Houyuan; Jiang, Leping; Zhang, Jianping; Yang, Xiaoyan; Huan, Xiujia; He, Keyang; Wang, Can; Wu, Naiqin

2017-06-20

Phytolith remains of rice ( Oryza sativa L.) recovered from the Shangshan site in the Lower Yangtze of China have previously been recognized as the earliest examples of rice cultivation. However, because of the poor preservation of macroplant fossils, many radiocarbon dates were derived from undifferentiated organic materials in pottery sherds. These materials remain a source of debate because of potential contamination by old carbon. Direct dating of the rice remains might serve to clarify their age. Here, we first validate the reliability of phytolith dating in the study region through a comparison with dates obtained from other material from the same layer or context. Our phytolith data indicate that rice remains retrieved from early stages of the Shangshan and Hehuashan sites have ages of approximately 9,400 and 9,000 calibrated years before the present, respectively. The morphology of rice bulliform phytoliths indicates they are closer to modern domesticated species than to wild species, suggesting that rice domestication may have begun at Shangshan during the beginning of the Holocene.

Investigating the Impact of Past and Future CO2 Emissions on the Distribution of Radiocarbon in the Ocean

NASA Astrophysics Data System (ADS)

Khatiwala, S.; Payne, S.; Graven, H. D.; Heimbach, P.

2015-12-01

The ocean is a significant sink for carbon dioxide from fossil fuel burning, absorbing roughly a third of human CO2 emitted over the industrial period. This has implications not only for climate but also for the chemical and isotopic composition of the ocean. Human activities have increased the ocean radiocarbon content through nuclear bomb tests in the 1950s-60s, which released a large amount of radiocarbon (14C) into the atmosphere, but fossil fuel emissions are decreasing the radiocarbon content through the release of 14C-depleted CO2. Here, we use the ECCO-v4 ocean state estimate to examine the changing nature of the air-sea flux of radiocarbon and its spatial distribution in the ocean in response to past and future CO2 emissions, the latter taken from the the Representative Concentration Pathway (RCP) database used in IPCC simulations. In line with previous studies we find that the large air-sea gradient of 14C induced by nuclear bomb testing led to rapid accumulation of radiocarbon in the surface ocean. Surface fluxes of 14C have considerably weakened over the past several decades and in some areas 14C is being returned to the atmosphere. As fossil fuel emissions continue to reduce the atmospheric 14C/C ratio (Δ14C), in most RCP scenarios the total ocean 14C inventory starts decreasing by 2030. With strong emissions, the Δ14C of surface waters is driven to increasingly negative values and in RCP 8.5 by 2100 much of the surface ocean has apparent radiocarbon ages in excess of 2000 years, with subtropical gyres more depleted in 14C than the Southern Ocean. Surface waters become significantly more negative in Δ14C than underlying waters. As a result, turning conventional tracer oceanography on its head, recently ventilated waters are characterized by more negative Δ14C values. Similar patterns can be expected for CFCs in the ocean as atmospheric concentrations decrease over the next several decades. Our results have a number of implications, notably for

Regional benthic δ18O stacks with radiocarbon age models show Termination I onset differences of up to 4,000 years

NASA Astrophysics Data System (ADS)

Stern, J.; Lisiecki, L. E.

2013-12-01

The assumption of globally synchronous benthic foraminiferal δ18O changes is central to the development of global stacks (averages) and many other types of paleoclimate studies. However, a few well-dated individual benthic δ18O records have suggested the possibility of regional differences in the timing of Termination I (e.g., Skinner and Shackleton, 2005; Waelbroeck et al., 2011). These previous studies often used single core locations to describe vast areas of the ocean, so it has remained unclear whether the observed diachroneities are truly regional in scale or merely local. Here, we bridge the gap between global benthic δ18O stacks and individual records by presenting eight regional benthic δ18O stacks from 252 cores with age models based on a total of 776 planktonic foraminiferal radiocarbon dates from 61 of those cores. The earliest termination onset (beginning of deglacial benthic δ18O decrease) occurs in the intermediate South Atlantic stack at 18.5 kyr BP, shortly after the initial deglacial melting of Northern Hemisphere ice sheets. The latest termination onset occurs in the deep Indian stack at 14.5 kyr BP, coeval with the Bølling-Allerød warming. We find synchronous termination onsets at 17.5 kyr BP in the intermediate North Atlantic, deep North Atlantic, and deep South Atlantic, contrary to Waelbroeck et al. (2011). The deglacial benthic δ18O decrease in the deep Pacific lagged that of the deep Atlantic by an average of 1000 yr, with a maximum lag of ~1700 yr during the middle of the termination. The intermediate Pacific termination onset at 16.5 kyr BP happens 1000 yr after the deep Pacific termination onset at 17.5 kyr BP. The stacks extend beyond Termination I to ~40 kyr BP, allowing us to clarify and update certain aspects of millennial-scale benthic δ18O chronostratigraphy surrounding Heinrich events 2-3 and the transition into the Last Glacial Maximum. Our radiocarbon-dated regional benthic δ18O stacks demonstrate some of the

Amino acid racemization analysis (AAR) as a successful tool for dating Holocene coastal sediments: Stratigraphy of a barrier island spit (Southern Sylt/North Sea)

NASA Astrophysics Data System (ADS)

Tillmann, Tanja; Ziehe, Daniel

2014-05-01

Dating of Holocene sediments in shallow coastal areas of the German North Sea by conventional techniques is commonly problematic. In particular the marine reservoir effect of radiocarbon means that radiocarbon dating cannot be applied to sediments younger than about 400 years. Amino acid racemization dating (AAR) is a viable alternative for dating young sediments. The method is based on the determination of ratios of D and L amino acid enantiomers in organic matrices of biogenic carbonates. In this study we use AAR as a tool for dating Holocene barrier islands sediments. Based on an AAR derived chronological framework we develop a model of barrier spit accretion which describes the interaction between extreme events, fair weather coastal processes and sedimentary development that constrains the major episodes of barrier island evolution. The stratigraphy was defined using ground-penetrating radar (GPR) surveys complemented by sedimentological coring data. The stratigraphy is then conceptualised in a AAR chronostratigraphic framework to define a chronological order and allow the development of a stratigraphic model of the evolution of Southern Sylt. The AAR data provide high temporal resolution and have been used for dating stages of barrier spit accretion. The time lines are marked as storm surge generated erosion unconformities in the stratigraphic profile. Individual shells and shell fragments of Cerastoderma edule, Mya arenaria, Mytilus edulis and Scrobicularia plana have been accumulated by short-term storm events as shell layers associated with the erosion unconformities and have been dated by AAR. Time lines reveal that the barrier spit accretion occurred episodically, and is dependant on the provided rate of sand delivery. The general trend is that sequences young to the. South. The AAR derived time lines have been verified and correlated by historic maps and sea charts. It is apparent that spit enlargement at this site increased significantly during the

Strong Paleoearthquakes along the Aksuu Border Fault according to the Results of Dating the Offset Terrace Complex of the Chon-Aksuu River, Northern Tien Shan

NASA Astrophysics Data System (ADS)

Korzhenkov, A. M.; Arrowsmith, J. R.; Crosby, C. J.; Guralnik, B.; Rogozhin, E. A.; Sorokin, A. A.; Abdieva, S. V.; Fortuna, A. B.; Yudakhin, A. S.; Agatova, A. R.; Deev, E. V.; Mazeika, J. V.; Rodkin, M. V.; Shen, J.

2018-03-01

The study and radiocarbon dating of the low alluvial terraces of the Chon-Aksuu River, in the Northern Issyk-Kul region, which were broken by the Kebin (Kemin) earthquake of 1911 (Ms = 8.2, Io = 10 to 11), are carried out. The obtained radiocarbon dated ages refer to the second half of the Holocene. Since that time, at least eight strong earthquakes took place along this (Chon-Aksuu) segment of the Aksuu border fault. Three seismic events, including the earthquake of 1911 occurred in the second millennium A.D. This outburst of seismic energy was preceded by two millennia of seismic quiescence, which set in after another pulse of seismic activation. The latter lasted for 1.5 millennia and included five strong earthquakes. The recurrence period of seismic events during the activations is 300-600 years. Hence, the seismic regime along the Chon-Aksuu segment of the Aksuu border fault in the second half of the Holocene was a succession of two seismic activations, each with a duration of 1.0-1.5 ka, which were separated by a 2-ka interval of seismic quiescence. Therefore, the absolute datings of the river terraces of different ages which have been broken by a seismogenic rupture can serve as a reliable source of information about the age of the strong earthquakes that occurred along the seismogenic fault.

RADIOCARBON MEASUREMENTS ON PM 2.5 AMBIENT AEROSOL FROM NASHVILLE, TN

EPA Science Inventory

Radiocarbon (Carbon-14) measurements provide an estimate of the fraction of carbon in a sample that is biogenic. The methodology has been extensively used in past wintertime studies to quantify the contribution of wood smoke to ambient aerosol. In summertime such measurements...

Multi-proxy dating the 'Millennium Eruption' of Changbaishan to late 946 CE

NASA Astrophysics Data System (ADS)

Oppenheimer, Clive; Wacker, Lukas; Xu, Jiandong; Galván, Juan Diego; Stoffel, Markus; Guillet, Sébastien; Corona, Christophe; Sigl, Michael; Di Cosmo, Nicola; Hajdas, Irka; Pan, Bo; Breuker, Remco; Schneider, Lea; Esper, Jan; Fei, Jie; Hammond, James O. S.; Büntgen, Ulf

2017-02-01

Ranking among the largest volcanic eruptions of the Common Era (CE), the 'Millennium Eruption' of Changbaishan produced a widely-dispersed tephra layer (known as the B-Tm ash), which represents an important tie point for palaeoenvironmental studies in East Asia. Hitherto, there has been no consensus on its age, with estimates spanning at least the tenth century CE. Here, we identify the cosmogenic radiocarbon signal of 775 CE in a subfossil larch engulfed and killed by pyroclastic currents emplaced during the initial rhyolitic phase of the explosive eruption. Combined with glaciochemical evidence from Greenland, this enables us to date the eruption to late 946 CE. This secure date rules out the possibility that the Millennium Eruption contributed to the collapse of the Bohai Kingdom (Manchuria/Korea) in 926 CE, as has previously been hypothesised. Further, despite the magnitude of the eruption, we do not see a consequent cooling signal in tree-ring-based reconstructions of Northern Hemisphere summer temperatures. A tightly-constrained date for the Millennium Eruption improves the prospect for further investigations of historical sources that may shed light on the eruption's impacts, and enhances the value of the B-Tm ash as a chronostratigraphic marker.

Measurements and modeling of contemporary radiocarbon in the stratosphere

DOE PAGES

Kanu, A. M.; Comfort, L. L.; Guilderson, T. P.; ...

2016-01-29

Measurements of the 14C content of carbon dioxide in air collected by high-altitude balloon flights in 2003–2005 reveal the contemporary radiocarbon distribution in the northern midlatitude stratosphere, four decades after the Limited Test Ban Treaty restricted atmospheric testing of nuclear weapons. Comparisons with results from a 3-D chemical-transport model show that the 14CO 2 distribution is now largely governed by the altitude/latitude dependence of the natural cosmogenic production rate, stratospheric transport, and propagation into the stratosphere of the decreasing radiocarbon trend in tropospheric CO 2 due to fossil fuel combustion. From the observed correlation of 14CO 2 with N 2Omore » mixing ratios, an annual global mean net flux of 14CO 2 to the troposphere of 1.6(±0.4) × 10 17‰ mol CO 2 yr –1 and a global production rate of 2.2(±0.6) × 10 26 atoms 14C yr –1 are empirically derived. Furthermore, the results also indicate that contemporary 14CO 2 observations provide highly sensitive diagnostics for stratospheric transport and residence times in models.« less

C-14 content of ten meteorites measured by tandem accelerator mass spectrometry

NASA Technical Reports Server (NTRS)

Brown, R. M.; Andrews, H. R.; Ball, G. C.; Burn, N.; Imahori, Y.; Milton, J. C. D.; Fireman, E. L.

1984-01-01

Measurements of C-14 in three North American and seven Antarctic meteorites show in most cases that this cosmogenic isotope, which is tightly bound, was separated from absorbed atmospheric radiocarbon by stepwise heating extractions. The present upper limit to age determination by the accelerator method varies from 50,000 to 70,000 years, depending on the mass and carbon content of the sample. The natural limit caused by cosmic ray production of C-14 in silicate rocks at 2000 m elevation is estimated to be 55,000 + or - 5000 years. An estimation is also made of the 'weathering ages' of the Antarctic meteorites from the specific activity of loosely bound CO2 which is thought to be absorbed from the terrestrial atmosphere. Accelerator measurements are found to agree with previous low level counting measurements, but are more sensitive and precise.

Radiocarbon dating loess deposits in the Mississippi Valley using terrestrial gastropod shells (Polygyridae, Helicinidae, and Discidae)

USGS Publications Warehouse

Pigati, Jeffery S.; McGeehin, John P.; Muhs, Daniel; Grimley, David A.; Nekola, Jeffery C.

2014-01-01

Small terrestrial gastropod shells (mainly Succineidae) have been used successfully to date late Quaternary loess deposits in Alaska and the Great Plains. However, Succineidae shells are less common in loess deposits in the Mississippi Valley compared to those of the Polygyridae, Helicinidae, and Discidae families. In this study, we conducted several tests to determine whether shells of these gastropods could provide reliable ages for loess deposits in the Mississippi Valley. Our results show that most of the taxa that we investigated incorporate small amounts (1–5%) of old carbon from limestone in their shells, meaning that they should yield ages that are accurate to within a few hundred years. In contrast, shells of the genus Mesodon(Mesodon elevatus and Mesodon zaletus) contain significant and variable amounts of old carbon, yielding ages that are up to a couple thousand 14C years too old. Although terrestrial gastropod shells have tremendous potential for 14C dating loess deposits throughout North America, we acknowledge that accuracy to within a few hundred years may not be sufficient for those interested in developing high-resolution loess chronologies. Even with this limitation, however, 14C dating of terrestrial gastropod shells present in Mississippi Valley loess deposits may prove useful for researchers interested in processes that took place over multi-millennial timescales or in differentiating stratigraphic units that have significantly different ages but similar physical and geochemical properties. The results presented here may also be useful to researchers studying loess deposits outside North America that contain similar gastropod taxa..

Sample preparation for radiocarbon ( 14C) measurements of carbonyl compounds in the atmosphere . quantifying the biogenic contribution

NASA Astrophysics Data System (ADS)

Larsen, B. R.; Brussol, C.; Kotzias, D.; Veltkamp, T.; Zwaagstra, O.; Slanina, J.

A method has been developed for the preparation of samples for radiocarbon ( 14C) measurements of carbonyl compounds in the atmosphere. Sampling on 25 ml 2,4-dinitrophenylhydrazine (DNPH)- coated silica gel cartridges can be carried out with up to 10.000 ℓ of ambient air with no adverse effects on sample integrity. Methods for the selective clean-up of the extracts have been investigated. This is a necessary step in preparing ambient carbonyl samples for a measurement of the radiocarbon ( 14C) content. The method which gave the best results include extraction of the DNPH cartridge with CH 3CN and purification of the carbonyl hydrazones over activated silica gel to remove excess DNPH and non target compounds. This method has been validated with laboratory samples and has been proved to give reliable results The radiocarbon data from the first field experiment showed that ambient air over a semi-rural test site in Ispra, Italy on a late summer day contained mainly five carbonyls (formaldehyde>acetaldehyde>acetone>propanal>butanal) of a mixed biogenic (41-57%) and anthropogenic (43-59%) origin. The method will be used in future monitoring of radiocarbon ( 14C) on a number of test sites in Europe.

Radiocarbon Production by Thunderstorms

NASA Astrophysics Data System (ADS)

Babich, L. P.

2017-11-01

In view of the neutron flux enhancements observed in thunderstorms, a contribution of thunderstorm neutrons to atmospheric radiocarbon (isotope 614C) production is analyzed in connection with the archaeometry. Herein, estimates of neutron fluence per lightning electromagnetic pulse in regions with severe thunderstorm activity, at which a local rate of the 614C production is comparable to the observed rates, are shown to be consistent with the measured magnitudes of thunderstorm neutron fluence. At present, available observations of atmospheric neutron and parent gamma ray flashes correlated with thunderstorms do not allow making final conclusions about thunderstorm contributions to 614C production. For this, numerous studies of high-energy phenomena in thunderstorms are required, especially in the tropical belt where the thunderstorm activity is especially severe and where the 614C production by galactic cosmic rays is almost independent of the solar activity disturbing the Earth's magnetic field shielding the Earth from cosmic rays.

AMS Radiocarbon dating of paleosols intercalated with tephra layers from Mayon Volcano, southern Luzon, Philippines: A preliminary report

USGS Publications Warehouse

Mirabueno, Ma. Hannah T.; Okuno, Mitsuru; Nakamura, Toshio; Newhall, Christopher G.; Kobayashi, Tetsuo

2006-01-01

This paper presents the AMS 14C dates of paleosols intercalated with tephra layers in the vicinity of Mayon Volcano, southern Luzon, Philippines. the obtained 14C dates are almost consistent with the stratigraphy of the Mayon tephra group. On the basis of calibrated 14C age of soil layer directly overlying the lowest ash layer, the oldest eruptive event must have taken place shortly before 20 cal kyr BP. This age is younger than the previous estimates for Mayon.

Atmospheric radiocarbon as a Southern Ocean wind proxy over the last 1000 years

NASA Astrophysics Data System (ADS)

Rodgers, K. B.; Mikaloff Fletcher, S.; Galbraith, E.; Sarmiento, J. L.; Gnanadesikan, A.; Slater, R. D.; Naegler, T.

2009-04-01

Measurements of radiocarbon in tree rings over the last 1000 years indicate that there was a pre-industrial latitudinal gradient of atmospheric radiocarbon of 3.9-4.5 per mail and that this gradient had temporal variability of order 6 per mil. Here we test the idea that the mean gradient as well as variability in he gradient is dominated by the strength of the winds over the Southern Ocean. This is done using an ocean model and an atmospheric transport model. The ocean model is used to derive fluxes of 12CO2 and 14CO2 at the sea surface, and these fluxes are used as a lower boundary condition for the transport model. For the mean state, strong winds in the Southern Ocean drive significant upwelling of radiocarbon-depleted Circumpolar Deep Water (CDW), leading to a net flux of 14CO2 relative to 12CO2 into the ocean. This serves to maintain a hemispheric gradient in pre-anthropogenic atmospheric delta-c14. For perturbations, increased/decreased Southern Ocean winds drive increased/decreased uptake of 14CO2 relative to 12CO2, thus increasing/decreasing the hemispheric gradient in atmospheric delta-c14. The tree ring data is interpreted to reveal a decrease in the strength of the Southern Ocean winds at the transition between the Little Ice Age and the Medieval Warm Period.

Bayesian integration of radioisotope dating (210Pb, 137Cs, 241Am, 14C) and an 18-20th century mining history of Brotherswater, English Lake District

NASA Astrophysics Data System (ADS)

Schillereff, Daniel; Chiverrell, Richard; Macdonald, Neil; Hooke, Janet; Welsh, Katharine; Piliposyan, Gayane; Appleby, Peter

2014-05-01

Lake sediment records are often a useful tool for investigating landscape evolution as geomorphic changes in the catchment are reflected by altered sediment properties in the material transported through the watershed and deposited at the lake bed. Recent research at Brotherswater, an upland waterbody in the Lake District, northwest England, has focused on reconstructing historical floods from their sedimentary signatures and calculating long-term sediment and carbon budgets from fourteen sediment cores extracted from across the basin. Developing accurate chronological control is essential for these tasks. One sediment core (BW11-2; 3.5 m length) from the central basin has been dated using artificial radionuclide measurements (210Pb, 137Cs, 241Am) for the uppermost sediments and radiocarbon (14C) for lower sediments. The core appears to span the past 1500 years, however a number of problems have arisen. We present our explanations for these errors, the independent chronological techniques used to generate an accurate age-depth model for this core and methods for its transferral to the other 13 cores extracted from the basin. Two distinct 137Cs markers, corresponding to the 1986 Chernobyl disaster and 1960s weapons testing, confirm the 210Pb profile for sediment deposition since ~1950, but calculations prior to this appear erroneous, possibly due to a hiatus in the sediment record. We used high-resolution geochemical profiles (measured by XRF) to cross-correlate with a second 210Pb-dated chronology from a more distal location, which returned more sensible results. Unfortunately, the longer 14C sequence exhibits two age-reversals (radiocarbon dates that are too old). We believe the uppermost two dates are erroneous, due to a shift in inflow location as a flood prevention method ~1900 A.D., dated using information from historical maps. The lower age-reversal coincides with greater supply of terrigenous material to the lake (increased Zr, K, Ti concentrations

Earliest Directly-Dated Human Skull-Cups

PubMed Central

Bello, Silvia M.; Parfitt, Simon A.; Stringer, Chris B.

2011-01-01

Background The use of human braincases as drinking cups and containers has extensive historic and ethnographic documentation, but archaeological examples are extremely rare. In the Upper Palaeolithic of western Europe, cut-marked and broken human bones are widespread in the Magdalenian (∼15 to 12,000 years BP) and skull-cup preparation is an element of this tradition. Principal Findings Here we describe the post-mortem processing of human heads at the Upper Palaeolithic site of Gough's Cave (Somerset, England) and identify a range of modifications associated with the production of skull-cups. New analyses of human remains from Gough's Cave demonstrate the skilled post-mortem manipulation of human bodies. Results of the research suggest the processing of cadavers for the consumption of body tissues (bone marrow), accompanied by meticulous shaping of cranial vaults. The distribution of cut-marks and percussion features indicates that the skulls were scrupulously 'cleaned' of any soft tissues, and subsequently modified by controlled removal of the facial region and breakage of the cranial base along a sub-horizontal plane. The vaults were also ‘retouched’, possibly to make the broken edges more regular. This manipulation suggests the shaping of skulls to produce skull-cups. Conclusions Three skull-cups have been identified amongst the human bones from Gough's Cave. New ultrafiltered radiocarbon determinations provide direct dates of about 14,700 cal BP, making these the oldest directly dated skull-cups and the only examples known from the British Isles. PMID:21359211

Exploring global carbon turnover and radiocarbon cycling in terrestrial biosphere models

NASA Astrophysics Data System (ADS)

Graven, H. D.; Warren, H.

2017-12-01

The uptake of carbon into terrestrial ecosystems through net primary productivity (NPP) and the turnover of that carbon through various pathways are the fundamental drivers of changing carbon stocks on land, in addition to human-induced and natural disturbances. Terrestrial biosphere models use different formulations for carbon uptake and release, resulting in a range of values in NPP of 40-70 PgC/yr and biomass turnover times of about 25-40 years for the preindustrial period in current-generation models from CMIP5. Biases in carbon uptake and turnover impact simulated carbon uptake and storage in the historical period and later in the century under changing climate and CO2 concentration, however evaluating global-scale NPP and carbon turnover is challenging. Scaling up of plot-scale measurements involves uncertainty due to the large heterogeneity across ecosystems and biomass types, some of which are not well-observed. We are developing the modelling of radiocarbon in terrestrial biosphere models, with a particular focus on decadal 14C dynamics after the nuclear weapons testing in the 1950s-60s, including the impact of carbon flux trends and variability on 14C cycling. We use an estimate of the total inventory of excess 14C in the biosphere constructed by Naegler and Levin (2009) using a 14C budget approach incorporating estimates of total 14C produced by the weapons tests and atmospheric and oceanic 14C observations. By simulating radiocarbon in simple biosphere box models using carbon fluxes from the CMIP5 models, we find that carbon turnover is too rapid in many of the simple models - the models appear to take up too much 14C and release it too quickly. Therefore many CMIP5 models may also simulate carbon turnover that is too rapid. A caveat is that the simple box models we use may not adequately represent carbon dynamics in the full-scale models. Explicit simulation of radiocarbon in terrestrial biosphere models would allow more robust evaluation of biosphere

New Progress on Radiocarbon Geochronology in Southern Lake Tanganyika (East Africa)

NASA Astrophysics Data System (ADS)

McGlue, M. M.; Soreghan, M. J.

2017-12-01

Our limnogeological research in Lake Tanganyika focuses on elucidating the patterns of sediment accumulation on deepwater horsts, outer platforms, and littoral environments in the lake's southern basin ( 6-8°S latitude). Here, we present new radiocarbon (14C) dates from high-quality surface sediment cores, in order to make comparisons with previously published age models, to address the presence and spatiotemporal variability of a reservoir effect, and to constrain sedimentation rates and facies at sites that may be important targets for future scientific drilling. Plant macrofossils are rare in deepwater sediment cores, so charcoal and bulk organic matter have been the primary materials used for dating. On the Kavala Island Ridge (KIR) horst, initial core descriptions revealed variations in laminae presence, thickness, and chemistry. Sediment cores from the KIR at 172m water depth consist of thickly laminated diatom oozes. Charcoal from the bases of these cores returned median ages of 2.1-2.2 cal ka, suggesting linear accumulation rates on the order of 0.51 mm/yr. By contrast, a core from 420 m water depth on the KIR exhibited very thin laminations and diatom layers were much less prominent. Charcoal at the base of this core produced a median age of 8.1 cal ka, suggesting a linear accumulation rate of 0.11 mm/yr. These initial results suggest that sedimentation rates may vary considerably over sublacustrine horst blocks. We will test this initial discovery with additional sedimentation rate information from the Kalya and Nitiri horsts. In addition, we report new 14C dates made on both dead and live-collected shells of the endemic gastropod Neothauma tanganyicense. These shells form vast accumulations along shallow-water platforms of the lake and form an important substrate for a number of other endemic species. The discovery of living snails in southern Lake Tanganyika may allow for the development of a species-specific reservoir correction. A limited N

Radiocarbon studies of latest Pleistocene and Holocene lava flows of the Snake River Plain, Idaho: Data, lessons, interpretations

USGS Publications Warehouse

Kuntz, M.A.; Spiker, E. C.; Rubin, M.; Champion, D.E.; Lefebvre, R.H.

1986-01-01

Latest Pleistocene-Holocene basaltic lava fields of the Snake River Plain, Idaho, have been dated by the radiocarbon method. Backhoe excavations beneath lava flows typically yielded carbon-bearing, charred eolian sediment. This material provided most of the samples for this study; the sediment typically contains less than 0.2% carbon. Charcoal fragments were obtained from tree molds but only from a few backhoe excavations. Contamination of the charred sediments and charcoal by younger carbon components is extensive; the effects of contamination were mitigated but appropriate pretreatment of samples using acid and alkali leaches. Twenty of the more than 60 lava flows of the Craters of the Moon lava field have been dated; their ages range from about 15,000 to about 2000 yr B.P. The ages permit assignment of the flows to eight distinct eruptive periods with an average recurrence interval of about 2000 yr. The seven other latest Pleistocene-Holocene lava fields were all emplaced in short eruptive bursts. Their 14C ages (yr B.P.) are: Kings Bowl (2222?? 100), Wapi (2270 ?? 50), Hells Half Acre (5200 ?? 150), Shoshone (10,130 ?? 350), North Robbers and South Robbers (11.980 ?? 300), and Cerro Grande (13,380 ?? 350). ?? 1986.

Radiocarbon studies of latest Pleistocene and Holocene lava flows of the Snake River Plain, Idaho: Data, lessons, interpretations

NASA Astrophysics Data System (ADS)

Kuntz, Mel A.; Spiker, Elliott C.; Rubin, Meyer; Champion, Duane E.; Lefebvre, Richard H.

1986-03-01

Latest Pleistocene-Holocene basaltic lava fields of the Snake River Plain, Idaho, have been dated by the radiocarbon method. Backhoe excavations beneath lava flows typically yielded carbon-bearing, charred eolian sediment. This material provided most of the samples for this study; the sediment typically contains less than 0.2% carbon. Charcoal fragments were obtained from tree molds but only from a few backhoe excavations. Contamination of the charred sediments and charcoal by younger carbon components is extensive; the effects of contamination were mitigated but appropriate pretreatment of samples using acid and alkali leaches. Twenty of the more than 60 lava flows of the Craters of the Moon lava field have been dated; their ages range from about 15,000 to about 2000 yr B.P. The ages permit assignment of the flows to eight distinct eruptive periods with an average recurrence interval of about 2000 yr. The seven other latest Pleistocene-Holocene lava fields were all emplaced in short eruptive bursts. Their 14C ages (yr B.P.) are: Kings Bowl (2222± 100), Wapi (2270 ± 50), Hells Half Acre (5200 ± 150), Shoshone (10,130 ± 350), North Robbers and South Robbers (11.980 ± 300), and Cerro Grande (13,380 ± 350).

Late Glacial and Holocene Fire History From Radiocarbon Dating of Charcoal in Valley-Bottom Sediments in Small Watersheds of the Oregon Coast Range

NASA Astrophysics Data System (ADS)

Lancaster, S. T.; Frueh, W. T.

2011-12-01

A large number (N = 351) of radiocarbon dates of charcoal from valley-bottom sediments in headwater valleys of the southern Oregon Coast Range provides the basis for a new index of fire frequency during the past 17,000 years in this steep landscape covered by dense coniferous forest. Study areas were chosen for their relative lack of recent forest disturbance by harvest or fire, and sampling of stream banks and terrace risers was random, weighted by deposit volume and bank or riser area. This sampling methodology was designed to characterize sediment residence times within valley-bottom storage, and the overall shape of the calibrated age distribution is therefore assumed representative of the dependence of charcoal preservation probability on calibrated age. A proxy record of fire history in the study areas is obtained by fitting a gamma distribution to the weighted mean calibrated charcoal ages by the method of moments; calculating the relative difference between the fit and the normalized histogram, with 50-year bin-widths, of charcoal ages; and smoothing that relative difference with a gaussian distribution, the standard deviation of which is at least two bin-widths and inversely proportional to the value of the fit distribution at larger ages. The calibrated charcoal age mean and variance of 1900 yrs BP and 7.39 x 106 yr2, respectively, yield shape and scale parameters of the fit gamma distribution of 0.490 and 3880 yrs, respectively. This heavy-tailed distribution indicates that probabilities of charcoal evacuation are not simply proportional to relative volume of encasing sediment deposits but, rather, decrease with deposit age. The smoothed proxy record of relative fire frequency has a global maximum at 7700 BP and prominent local maxima at 600 BP and 5700 BP, in order of decreasing magnitude; a global minimum at 4500 BP and local minimum at 1800 BP roughly bracket a period of fluctuating but relatively low fire frequency during the period 5000-1500 BP

Chronostratigraphical Subdivision of the Late Glacial and the Holocene for the Alaska Region

NASA Astrophysics Data System (ADS)

Michczynska, D. J.; Hajdas, I.

2009-04-01

Our work is a kind of so called data mining. The first step of our work was collection of the radiocarbon data for samples coming from Alaska. We construct data base using Radiocarbon Measurements Lists published by different radiocarbon laboratories (mainly in the journal 'Radiocaron'). The next step was careful analysis of collected dates. We excluded from our analysis all dates suspected of contamination by younger or older organic matter. Such fact could be stated, for instance, on the base of inconsistency of radiocarbon age and stratigraphy or palynology. Finally, we calibrated whole large set of chosen radiocarbon dates and construct probability density function (PDF). Analysis of the shape of PDF was the subject of the previous research (eg. Michczynska and Pazdur, 2004; Macklin et al., 2006; Starkel et al., 2006, Michczynska et al., 2007). In our analysis we take into account the distinct tendency to collect samples from specific horizons. It is a general rule to take samples for radiocarbon dating from places of visible sedimentation changes or changes in palynological diagram. Therefore the culminations of the PDF represent periods of environmental changes and could be helpful in identifying the chronostratigraphical boundaries on the calendar time scale. References: Michczyńska D.J., Pazdur A., 2004. A shape analysis of cumulative probability density function of radiocarbon dates set in the study of climate change in Late Glacial and Holocene. Radiocarbon 46(2): 733-744. Michczyńska D.J., Michczyński A., Pazdur A. 2007. Frequency distribution of radiocarbon dates as a tool for reconstructing environmental changes. Radiocarbon 49(2): 799-806. Macklin M.G., Benito G., Gregory K.J., Johnstone E., Lewin J., Michczyńska D.J., Soja R., Starkel L., Thorndycraft V.R., 2006. Past hydrological events reflected in the Holocene fluvial record of Europe. CATENA 66: 145-154. Starkel L., Soja R., Michczyńska D.J., 2006. Past hydrological events reflected in

First direct dating of a presumed Pleistocene hominid from China: AMS radiocarbon age of a femur from the Ordos Plateau.

PubMed

Keates, Susan G; Hodgins, Gregory W L; Kuzmin, Yaroslav V; Orlova, Lyobov A

2007-07-01

Human remains from the Xarusgol Valley, Ordos Plateau, northwestern China, have been considered to date to the Late Pleistocene. In order to ascertain their true age, direct AMS (14)C dating of a femur collected in the early 1920s was conducted. The results demonstrate that the femur is very young, with one sample of 'post-bomb' age and the other sample c. 200 years old. This first direct dating of a Chinese fossil hominid underscores the need to apply the same methodology to other Chinese modern human fossils currently believed to be of Pleistocene age.

Synthetic Constraint of Ecosystem C Models Using Radiocarbon and Net Primary Production (NPP) in New Zealand Grazing Land

NASA Astrophysics Data System (ADS)

Baisden, W. T.

2011-12-01

Time-series radiocarbon measurements have substantial ability to constrain the size and residence time of the soil C pools commonly represented in ecosystem models. Radiocarbon remains unique in the ability to constrain the large stabilized C pool with decadal residence times. Radiocarbon also contributes usefully to constraining the size and turnover rate of the passive pool, but typically struggles to constrain pools with residence times less than a few years. Overall, the number of pools and associated turnover rates that can be constrained depends upon the number of time-series samples available, the appropriateness of chemical or physical fractions to isolate unequivocal pools, and the utility of additional C flux data to provide additional constraints. In New Zealand pasture soils, we demonstrate the ability to constrain decadal turnover times with in a few years for the stabilized pool and reasonably constrain the passive fraction. Good constraint is obtained with two time-series samples spaced 10 or more years apart after 1970. Three or more time-series samples further improve the level of constraint. Work within this context shows that a two-pool model does explain soil radiocarbon data for the most detailed profiles available (11 time-series samples), and identifies clear and consistent differences in rates of C turnover and passive fraction in Andisols vs Non-Andisols. Furthermore, samples from multiple horizons can commonly be combined, yielding consistent residence times and passive fraction estimates that are stable with, or increase with, depth in different sites. Radiocarbon generally fails to quantify rapid C turnover, however. Given that the strength of radiocarbon is estimating the size and turnover of the stabilized (decadal) and passive (millennial) pools, the magnitude of fast cycling pool(s) can be estimated by subtracting the radiocarbon-based estimates of turnover within stabilized and passive pools from total estimates of NPP. In grazing

Insights into Holocene megafauna survival and extinction in southeastern Brazil from new AMS 14C dates

NASA Astrophysics Data System (ADS)

Hubbe, Alex; Hubbe, Mark; Karmann, Ivo; Cruz, Francisco W.; Neves, Walter A.

2013-03-01

The extinction of late Quaternary megafauna in South America has been extensively debated in past decades. The majority of the hypotheses explaining this phenomenon argue that the extinction was the result of human activities, environmental changes, or even synergism between the two. Although still limited, a good chronological framework is imperative to discuss the plausibility of the available hypotheses. Here we present six new direct AMS 14C radiocarbon dates from the state of São Paulo (Brazil) to further characterize the chronological distribution of extinct fauna in this part of South America. The new dates make evident that ground sloths, toxodonts, and saber-toothed cats lived in the region around the Pleistocene/Holocene transition, and, in agreement with previous studies, also suggest an early Holocene survival for the ground sloth Catonyx cuvieri. Taken together with local paleoclimatic and archaeological data, the new dates do not support hunting or indirect human activities as a major cause for megafauna extinction. Although more data are required, parsimony suggests that climatic changes played a major role in this extinction event.

The Effect of the Younger Dryas on Paleoindian Occupations in Eastern North America Evidence from Artifactual, Pollen, and Radiocarbon Records

NASA Astrophysics Data System (ADS)

Anderson, D. G.; Meeks, S. C.; Miller, D. S.; Yerka, S. J.; Gillam, J. C.; Goodyear, A. C.; Johanson, E. N.; West, A.

2008-12-01

The Younger Dryas appears to have been a period when human populations in Eastern North America were undergoing significant stress. Attribute and locational data on Paleoindian materials from across the continent is available from the Paleoindian Database of the Americas or PIDBA, available on-line at http://pidba.utk.edu. Tallying the diagnostic projectile point sample from PIDBA in the on-line "entire sample" dated 24 April 2008, suggests that a population decline followed by a rebound may have occurred, particularly in southeastern North America. Following Clovis, fluted points with deeply indented bases and short to full flutes occur in many areas, such as the Redstone, Barnes, Cumberland, and Folsom types. In southeastern North America, these are thought to have been replaced by unfluted lanceolate and waisted forms, including the Beaver Lake, Suwannee/Simpson, and Quad types, which are in turn replaced by Dalton forms. Within the Southeast, a significant decline occurs between Clovis (N=1993 points) and presumably immediate post-Clovis full fluted forms (N=947 points). This may correspond to a similar decline in population, assuming the point types occurred for comparable periods of time, and were used in a similar fashion. Goodyear noted a similar pattern between Clovis (n=179) and presumed immediate post-Clovis Redstone (n=40) forms in South Carolina. Comparable declines have also been observed in North Carolina by Daniel and Goodyear ( and in Virginia by MacAvoy. In the PIDBA database across the Southeast, projectile point numbers increase following the immediate post Clovis decline, from 947 full fluted to 1717 unfluted and then 2594 Dalton points. The increase in the latter part of the Younger Dryas may actually be even more pronounced, since Dalton points, which are quite widespread, are only systematically recorded in a few states. Radiocarbon dates from Paleoindian and Early Archaic assemblages reveal a similar pattern. Dates falling in the initial

Insights into soil carbon dynamics across climatic and geologic gradients from time-series and fraction-specific radiocarbon analysis

NASA Astrophysics Data System (ADS)

van der Voort, Tessa Sophia; Hagedorn, Frank; Zell, Claudia; McIntyre, Cameron; Eglinton, Tim

2016-04-01

Understanding the interaction between soil organic matter (SOM) and climatic, geologic and ecological factors is essential for the understanding of potential susceptibility and vulnerability to climate and land use change. Radiocarbon constitutes a powerful tool for unraveling SOM dynamics and is increasingly used in studies of carbon turnover. The complex and inherently heterogeneous nature of SOM renders it challenging to assess the processes that govern SOM stability by solely looking at the bulk signature on a plot-scale level. This project combines bulk radiocarbon measurements on a regional-scale spanning wide climatic and geologic gradients with a more in-depth approach for a subset of locations. For this subset, time-series and carbon pool-specific radiocarbon data has been acquired for both topsoil and deeper soils. These well-studied sites are part of the Long-Term Forest Ecosystem Research (LWF) program of the Swiss Federal Institute for Forest, Snow and Landscape research (WSL). Statistical analysis was performed to examine relationships of radiocarbon signatures with variables such as temperature, precipitation and elevation. Bomb-curve modeling was applied determine carbon turnover using time-series data. Results indicate that (1) there is no significant correlation between Δ14C signature and environmental conditions except a weak positive correlation with mean annual temperature, (2) vertical gradients in Δ14C signatures in surface and deeper soils are highly similar despite covering disparate soil-types and climatic systems, and (3) radiocarbon signatures vary significantly between time-series samples and carbon pools. Overall, this study provides a uniquely comprehensive dataset that allows for a better understanding of links between carbon dynamics and environmental settings, as well as for pool-specific and long-term trends in carbon (de)stabilization.

A 50,000 year insect record from Rancho La Brea, Southern California: Insights into past climate and fossil deposition

NASA Astrophysics Data System (ADS)

Holden, Anna R.; Southon, John R.; Will, Kipling; Kirby, Matthew E.; Aalbu, Rolf L.; Markey, Molly J.

2017-07-01

Rigorously studied and dated Late Quaternary paleoenvironmental reconstructions from Ranch La Brea (RLB) and the Los Angeles Basin are scarce. Here, we use data from AMS radiocarbon dated insect fragments to infer local climates over the past 50,000 years. Our results indicate: 1) Quaternary insect remains can be located with great accuracy in radiocarbon time, and 2) well-dated and documented climate indicator beetle species are sensitive proxies for environmental change in the Los Angeles Basin. A total of 182 extant RLB ground and darkling beetle species (Coleoptera: Carabidae, Tenebrionidae) were radiocarbon dated. The resulting radiocarbon dates form a semi-continuous range from ∼50 to 28, 16-7.5, and 4 kcal yrs BP to the present. Associated insect climate ranges indicate past conditions consistent with, or very similar to, the current Los Angeles Basin Mediterranean climate. Importantly, these insect data suggest higher temperatures and aridity than inferred previously from other RLB proxies. Furthermore, wider-than-assumed dating spreads for some deposits emphasize the lack of biostratigraphy for RLB, and challenge inferences based on limited sets of radiocarbon dates and assumptions about stratigraphic integrity. Our results demonstrate the necessity to independently radiocarbon date each taxon. The insect paleoclimate interpretations were compared to regional pollen data, primarily from various southern Californian sites including Lake Elsinore and Santa Barbara Basin. These comparisons reveal an important difference in climate interpretations for the last Glacial: the RLB insect data suggest climate similar to the current one, while the regional pollen data have been interpreted as indicating a climate wetter than present.

Dating human skeletal remains: investigating the viability of measuring the equilibrium between 210Po and 210Pb as a means of estimating the post-mortem interval.

PubMed

Swift, B

1998-11-30

Estimating the post-mortem interval in skeletal remains is a notoriously difficult task; forensic pathologists often rely heavily upon experience in recognising morphological appearances. Previous techniques have involved measuring physical or chemical changes within the hydroxyapatite matrix, radiocarbon dating and 90Sr dating, though no individual test has been advocated. Within this paper it is proposed that measuring the equilibrium between two naturally occurring radio-isotopes, 210Po and 210Pb, and comparison with post-mortem examination samples would produce a new method of dating human skeletal remains. Possible limitations exist, notably the effect of diagenesis, time limitations and relative cost, though this technique could provide a relatively accurate means of determining the post-mortem interval. It is therefore proposed that a large study be undertaken to provide a calibration scale against which bones uncovered can be dated.

Radial ooids from Great Salt Lake (Utah) as paleoenvironmental archives: Insights from radiocarbon chronology and stable isotopes

NASA Astrophysics Data System (ADS)

Paradis, O. P.; Corsetti, F. A.; Bardsley, A.; Hammond, D. E.; Xu, X.; Walker, J. C.

2017-12-01

Ooids (laminated, carbonate coated grains) are ubiquitous in the geologic record in marine and lacustrine settings, and thus remain a common target for geochemical analysis to understand modern and ancient aqueous environments. However, the processes governing ooid formation remain unclear. Recently, radiocarbon dating has revealed that modern marine ooids grow slowly (Beaupre et al. 2015), and laboratory experiments have highlighted the importance of sediment transport and abrasion on net growth rates and ooid size (Trower et al. 2017). Ooid cortex structure includes micritic, tangential and/or radially oriented fabrics. Most modern marine ooids have tangential or micritic cortices, whereas many ancient ooids have radial cortices—thus, there is a need to understand how radial ooids in ancient rocks might inform us about their depositional environment. The Great Salt Lake (GSL), Utah, provides a unique environment to assess the growth rate of primary radial aragonitic ooids. Ooids collected near Antelope Island in the south arm of GSL were sieved, the 355-500 µm fraction was sequentially leached, and 14C of the evolved gas was analyzed to provide a time series of growth. The oldest inorganic carbon of this size fraction has an apparent 14C age of 6600 yr BP, with subsequent growth spanning over 6,000 years. Closed-basin lakes are particularly susceptible to a "reservoir effect" which results in anomalously old apparent radiocarbon ages. The 14C age of the modern dissolved inorganic carbon (DIC) of the south arm was measured to be 295 yr BP, a reservoir age comparable to estimates from lacustrine cave carbonates (McGee et al. 2012). Net growth rate of south arm ooids ranges between 0.01-0.025 µm per year. The δ13C of the outermost cortex suggests that the ooids resemble the modern DIC in the south arm water, suggesting ooids precipitate in equilibrium with lake water. Finer-scale structure in the δ13C of the ooid cortex through time suggests lake level changed

Blade-order-dependent radiocarbon variability in brown seaweed (Undaria pinnatifida) reflected a cold Oyashio water intrusion event in an embayment of the Sanriku coast, northeastern Japan

NASA Astrophysics Data System (ADS)

Satoh, N.; Fukuda, H.; Miyairi, Y.; Yokoyama, Y.; Nagata, T.

2015-12-01

Radiocarbon in dissolved inorganic carbon (DIC) in seawater varies greatly, both geographically and with depth. This "reservoir effect" is thought to be reflected in the radiocarbon content (Δ14C) of marine organisms, via DIC fixation by primary producers and subsequent trophic transfer. The Δ14C of marine organismal soft tissues might thus provide unique information about their habitats, diets, migration and other environmental histories. However, the effectiveness of this approach has yet to be extensively explored, with data on Δ14C variability in soft tissues of marine organisms being markedly limited. Here we examined whether Δ14C values of individual pinnate blades (leaf-like structures) of brown seaweed (Undaria pinnatifida) reflect the Δ14C of DIC in the water current prevailing at the time of blade formation. The study was conducted in Otsuchi Bay located in the Sanriku coastal region, northeastern Japan, where 14C-depleted cold Oyashio current and warm Tsugaru current (high Δ14C) converge, affecting the physiology and growth of marine organisms growing there. U. pinnatifida individuals cultured in the bay (length of saprophytes, 140-215 cm) were harvested in April 2014 and Δ14C of blades were determined by accelerator mass spectrometry. Younger blades formed after the Oyashio water intrusion had significantly lower Δ14C values compared to older blades formed before the event. The Δ14C values of younger and older blades were generally consistent with the Δ14C of DIC in Oyashio (-60.5 ‰) and Tsugaru (24.9 ‰) waters, respectively. Thus, despite possible turnover of organic carbon in seaweed soft tissues, blade-order-dependent Δ14C variability appeared to strongly reflect the Oyashio intrusion event (radiocarbon shift) in the bay.

Radiocarbon chronology of the last deglaciation in the Baffin Bay reveals asynchronous melting of Arctic and Laurentide ice sheets

NASA Astrophysics Data System (ADS)

Jackson, Rebecca; Kucera, Michal; Vogt, Christoph; Wacker, Lukas

2016-04-01

The transition from the last ice age into the Holocene interglacial was characterised by rapid retreat of North American ice sheets, discharging large quantities of meltwater into the Labrador Sea. Whereas the meltwater chronology of the Laurentide Ice Sheet is well documented, the deglacial history of the American Arctic ice sheets (Inuit Ice sheet and northern Greenland Ice Sheet) draining into the Labrador Sea via the Baffin Bay is less well constrained. Here we present the first high-resolution radiocarbon-dated deglacial records from the Canadian and Greenland margins of the central Baffin Bay. Sedimentological and geochemical data confirm the presence during Termination I of two events of enhanced delivery of detrital carbonate (Baffin Bay Detrital Carbonate Events) dated to 14.2-13.7 ka BP and 12.7-11 ka BP. The events are synchronous across the Baffin Bay and their mineralogical signature indicates a common source of detrital carbonate from the Canadian Arctic, with a synchronous clastic source proximal to Greenland. The events postdate Heinrich layers and their onset is not linked to Greenland temperature change. This indicates that the deglaciation of American Arctic ice sheets and associated meltwater discharge were decoupled from the dominant North Atlantic climate mode.

Geology and radiocarbon ages of Tláloc, Tlacotenco, Cuauhtzin, Hijo del Cuauhtzin, Teuhtli, and Ocusacayo monogenetic volcanoes in the central part of the Sierra Chichinautzin, México

NASA Astrophysics Data System (ADS)

Siebe, Claus; Arana-Salinas, Lilia; Abrams, Michael

2005-03-01

Tláloc, Tlacotenco, Cuauhtzin, Hijo del Cuauhtzin, Teuhtli, and Ocusacayo monogenetic volcanoes located within the Sierra del Chichinautzin Volcanic Field (SCVF) at the southern margin of Mexico City were studied to further refine attendant volcanic hazards in this heavily populated region. Based on fieldwork and Landsat imagery interpretation, a geologic map was produced, morphometric parameters characterizing the cones and lava flows were determined, and the areal extent and volumes of erupted products were estimated. The longest lava flow was produced by Tlacotenco and reached 9.5 km from its source; total areas covered by lava flows from each eruption range between 12.8 km 2 (Tlacotenco) and 54.4 km 2 (Tláloc); and total erupted volumes range between 0.26 and 1.36 km 3 per volcano. Radiocarbon measurements of a paleosol underneath an ash layer from the Tláloc scoria cone yielded an age of 6200 years BP, while charcoal found within block-and-ash flow and lahar deposits from Cuauhtzin dome yielded ages of 7360 and 8225 years BP, respectively. The Tlacotenco dacite lava flow overlies Popocatépetl's Tutti Frutti Plinian pumice fall deposit dated at 14,000 years BP and is therefore younger than this prominent stratigraphic marker. On the other hand, Teuhtli and Hijo del Cuauhtzin scoria cones and the Ocusacayo andesite lava flows are overlain by the Tutti Frutti and therefore older than 14,000 years BP. These new dates together with other published dates for scoria cones in the SCVF imply that the previously determined recurrence interval during the Holocene for monogenetic eruptions in the SCVF of <1700 years [Siebe, C., Rodríguez-Lara, V., Schaaf, P., Abrams, M., 2004a. Radiocarbon ages of Holocene Pelado, Guespalapa, and Chichinautzin scoria cones, south of Mexico_City: implications for archaeology and future hazards. Bull. Volcanol. 66, 203-225.] needs to be corrected to <1250 years. This means that the time of quiescence since the last eruption of the SCVF

Dating Last Interglacial Coastal Systems Using New Feldspar Luminescence Technologies

NASA Astrophysics Data System (ADS)

Lamothe, M.

2017-12-01

The recent explosion in new luminescence dating technologies offers new opportunities to explore Quaternary marine coastal facies and landforms. However, tectonic and climatic processes controlling the development of Pleistocene coastal lithosomes are commonly obscured by their poorly constrained geological age. Luminescence dating of feldspar probes one order of magnitude deeper into geological time than radiocarbon and more than 5 times the current age range of quartz optically-stimulated luminescence, routinely used in luminescence dating. However, feldspar luminescence stimulated by infrared photons (eg IRSL) is hampered by anomalous fading. Successful correction methods developed by us over the last 15 years did produce sound chronologies but the fading-corrected ages carried large uncertainties. New approaches initiated by other laboratories, mainly in Europe, have isolated high temperature post-IRSL luminescence as this signal seems to be only slightly affected by fading. However, the gain in stability seems to be lessened due to bleachibility issues, generating age overestimations. We developed a novel protocol known as post-isothermal IRSL dating (Pit-IR) that focuses on a dual system of luminescence signals, probing low (50C) and medium (225C) temperature IRSL signals following isothermal treatments of various intensities. These protocols have been tested on Last interglacial coastal sediments in strikingly different GIA contexts along the Atlantic coastal areas of SE USA as well as from Morocco, Brazil and LIG sites in the Mediterranean basin. A systematic analysis of these results would suggest that a) falling-stages sequences are more commonly preserved as the OSL/IRSL ages are preferentially dating from the end of the MIS5e high stand and b) MIS5a marine sediments may be detectable away from areas generally thought to be affected by peripheral bulge collapse.

The effect of changing land use on soil radiocarbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harrison, K.G.; Broecker, W.S.; Bonani, G.

Most carbon budgets require greening of the terrestrial biosphere as a sink for some of the excess carbon dioxide produced by fossil fuel burning and deforestation. Much of this storage is thought to occur in soils, but running counter to this conclusion is the observation that cultivation has reduced the agricultural reservoir of soil humus. Radiocarbon measurements in agricultural soils lend support to this browning of agricultural lands. Moreover, the loss is from the fast cycling portion of the humus.

76 FR 71468 - Defense Federal Acquisition Regulation Supplement: Accelerate Small Business Payments (DFARS Case...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-18

... all small business concerns. In combination with the change to the regulations, DoD immediately began... Federal Acquisition Regulation Supplement: Accelerate Small Business Payments (DFARS Case 2011-D008... Regulation Supplement to accelerate payments to all small business concerns. DATES: Effective Date: November...

New data on OSL dating of Early Khalynian deposits of Northern Caspian

NASA Astrophysics Data System (ADS)

Sychev, Nikita; Yanina, Tamara; Svitoch, Alexander; Kurbanov, Redzhep; Badyukova, Ekaterina

2016-04-01

Ponto-Caspian region is the key region the study of which can provide information about the paleogeographic history of the central Eurasia, particularly revealing the history of the East European Plain, the Caucasus and Central Asia. However, despite the long history of the study, today there is no accepted general stratigraphic scheme of the Caspian Sea. One of the most interesting and important stages of Late Pleistocene history of Caspian is Khalynian transgression which is divided into two major phases: early and ate. In the Caspian lowland Lower Khalynian stage are represented by a unique type of deposit - "chocolate clays". A distinctive feature of these sediments is widely distributed among Lower Khalynian deposits of Northern Caspian and the Volga region. All clay deposits are confined to the diverse origins of depression before-Khalynian relief. Chocolate clays formation consists of facies: mono-clay (typological), layered, sand- and silty-clay (Svitoch, Yanina, 1997). Determining the age of chocolate clays by optically stimulated luminescence (OSL) in our view will allow bettering the understanding of their genesis. Age of chocolate clays of Lower Volga was widely dated using the radiocarbon. However, the existing chronology is controversial, raises a number of issues, primarily due to the material of which are used for dating - thin shells of Caspian mollusks of the Didacna Eichw. genus, which are characterized by a significant isotopic exchange with the enclosing sediments (Arslanov, 2015). Lower Volga region is characterized by very complex geological structure of the Late Pleistocene deposits (alternating continental aeolian, alluvial and slope sediments with marine Caspian deposits of different age). There are many conflicting opinions, not only with respect to paleogeographic features of the area, but also to its precise chronology. The differences in opinion over the age of the individual stages of development of the Caspian Sea (transgressions and

Holocene history of deep-seated landsliding in the North Fork Stillaguamish River valley (Washington, USA) in the context of climate change from surface roughness analysis, radiocarbon dating, and numerical landscape evolution modeling

NASA Astrophysics Data System (ADS)

Booth, A. M.; LaHusen, S. R.; Duvall, A. R.; Montgomery, D. R.

2016-12-01

Landslides are commonly triggered by prolonged or intense precipitation and earthquakes, suggesting that a region's record of landsliding reflects its climatic and tectonic history. Deciphering that history by documenting spatial and temporal patterns of past landsliding is an essential step in quantifying a region's landslide hazard as well as the contribution of landslides to landscape evolution over geomorphic time. While routine landslide inventories can map spatial distributions, lack of dateable material, landslide reactivations, or time, access, and cost constraints generally limit dating large numbers of landslides to analyze temporal patterns. Here, we quantify the record of the Holocene history of deep-seated landsliding in glacial sediment along a 25 km stretch of the North Fork Stillaguamish River, Washington State, USA, including the 2014 Oso landslide, which killed 43 people. Climate at the study site has shifted from relatively cool and dry ( 16-10 kybp), to relatively warm and dry ( 10-6 kybp), to the cool, wet, maritime climate the region experiences today. We estimate the ages of 219 deep-seated landslides spanning these climate shifts by defining an empirical relationship between landslide deposit age from radiocarbon dating and landslide deposit surface roughness. Roughness systematically decreases with age as a function of topographic wavelength, consistent with disturbance-driven soil transport theory. The nonlinear age-roughness relationship suggests that changing regional climate and the process of vegetation recolonizing an initially bare landslide deposit has affected the efficiency of soil transport through bioturbation. The age-roughness model predicts that only 3% of the mapped landslide deposits are older than 6 kybp, likely reflecting a combination of preservation bias and local climate transitioning to cooler and wetter at that time. More recently, there is a broad peak in landslide frequency between 1200 and 600 cal. ybp, and then

Alkenone radiocarbon stratigraphy at high resolution continental marigin sites

NASA Astrophysics Data System (ADS)

Mollenhauer, G.; Eglinton, T.; Freudenthal, T.; Lamy, F.

2003-04-01

Radiocarbon stratigraphy is an essential tool for high resolution Late Quaternary paleoceanographic studies. For this purpose, radiocarbon ages of foraminifera have been extensively measured. Age models based on these measurements are commonly applied to a wide range of sediment proxy information, including the investigation of temporal leads and lags. The critical assumption made in these studies is that temporal coupling between foraminifera and other sediment constituents, including specific biomarkers of marine phytoplankton, e.g. alkenones, is maintained in the sediments. A recent study using coupled foraminifera and alkenone ages was conducted at a high sedimentation rate site situated at the Bermuda Rise sediment drift body. Ages of formanifera and alkenones differed by up to 8000 years. As an interpreation of these data, it was suggested that sediment constituents residing in different grain size fractions may have different current transport properties and may thus originate from different source areas separated by large geographical distances. Sediment retrieved from a site influenced by lateral advection would thus have to be regarded as a mixture of material from different sources. The time span between production and final deposition may be site dependent and remains largely unknown. Continental margins underlying high productivity areas are sites of high sediment accumulation. The major part of this sediment is believed to be biogenic and is produced in the overlying water column. Sediment particles are expected to be deposited rapidly at or near the site of production regardless of their size. To evaluate this premise, we have measured coupled radiocarbon ages of foraminifera, TOC and alkenones in samples taken from sediment cores retreived from three continental margin high accumulation rate sites. Cores from the Benguela upwelling system, the North West African upwelling system and from the Chilean margin high productivity area were chosen. All

Characterization of Arctic elemental carbon in Barrow, AK using radiocarbon source apportionment

NASA Astrophysics Data System (ADS)

Barrett, T. E.; Usenko, S.; Robinson, E. M.; Sheesley, R. J.

2013-12-01

Currently, the Arctic is one of the fastest warming regions on earth with surface temperatures increasing at a rate nearly double the global mean over recent decades. Despite the fact that atmospheric concentrations of elemental carbon (EC) are lower in the Arctic than in lower latitudes, deposition of EC on snow and ice may exacerbate regional warming by simultaneously decreasing albedo and increasing melt rates. Due to the intensifying Arctic oil exploration in areas such as the Beaufort and Chukchi seas, the impact of new emission sources such as heavy fuel and heavy diesel combustion on regional carbon needs to be assessed. The first step in developing mitigation strategies for reducing current and future EC emissions in the Arctic is to determine emission source contributions. This study aims to determine the relative contributions of fossil fuel and biomass combustion and to identify major source regions of EC to the Arctic. Radiocarbon analysis of both total organic carbon (TOC) and EC combined with organic tracer and back trajectory analysis has been applied to a set of wintertime coarse particulate matter (PM10) samples from Barrow, AK. Preliminary apportionment for January 2013 indicates roughly half of TOC is from biogenic/biomass burning emissions and one third of EC is due to biomass burning emissions. The radiocarbon results will be combined with organic tracer analysis (polycyclic aromatic hydrocarbons, petroleum biomarkers and normal alkanes), increasing the specificity of the relative contribution of both the fossil and modern (biogenic/biomass burning) carbon emission sources. This research represents the first reported radiocarbon values for Arctic EC, providing highly conclusive source apportionment prior to the influence of increased drilling operations and ship traffic in the Beaufort and Chukchi seas.

The radiocarbon signature of microorganisms in the mesopelagic ocean.

PubMed

Hansman, Roberta L; Griffin, Sheila; Watson, Jordan T; Druffel, Ellen R M; Ingalls, Anitra E; Pearson, Ann; Aluwihare, Lihini I

2009-04-21

Several lines of evidence indicate that microorganisms in the meso- and bathypelagic ocean are metabolically active and respiring carbon. In addition, growing evidence suggests that archaea are fixing inorganic carbon in this environment. However, direct quantification of the contribution from deep ocean carbon sources to community production in the dark ocean remains a challenge. In this study, carbon flow through the microbial community at 2 depths in the mesopelagic zone of the North Pacific Subtropical Gyre was examined by exploiting the unique radiocarbon signatures (Delta(14)C) of the 3 major carbon sources in this environment. The radiocarbon content of nucleic acids, a biomarker for viable cells, isolated from size-fractionated particles (0.2-0.5 microm and >0.5 microm) showed the direct incorporation of carbon delivered by rapidly sinking particles. Most significantly, at the 2 mesopelagic depths examined (670 m and 915 m), carbon derived from in situ autotrophic fixation supported a significant fraction of the free-living microbial community (0.2-0.5 microm size fraction), but the contribution of chemoautotrophy varied markedly between the 2 depths. Results further showed that utilization of the ocean's largest reduced carbon reservoir, (14)C-depleted, dissolved organic carbon, was negligible in this environment. This isotopic portrait of carbon assimilation by the in situ, free-living microbial community, integrated over >50,000 L of seawater, implies that recent, photosynthetic carbon is not always the major carbon source supporting microbial community production in the mesopelagic realm.

RADIOCARBON 14C MEASUREMENTS ON ATMOSPHERIC SAMPLES OF PARTICULATE MATTER (& VOLATILE ORGANIC COMPOUNDS)

EPA Science Inventory

Following a brief history of radiocarbon work at EPA since the 1980's, the presentation focuses on recent non-winter measurements for PM-2.5 in the Southeastern U.S. (Houston, TX; Nashville, TN; and particularly, Tampa, FL) and what the measurements suggest about the importance o...

A portable molecular-sieve-based CO2 sampling system for radiocarbon measurements

NASA Astrophysics Data System (ADS)

Palonen, V.

2015-12-01

We have developed a field-capable sampling system for the collection of CO2 samples for radiocarbon-concentration measurements. Most target systems in environmental research are limited in volume and CO2 concentration, making conventional flask sampling hard or impossible for radiocarbon studies. The present system captures the CO2 selectively to cartridges containing 13X molecular sieve material. The sampling does not introduce significant under-pressures or significant losses of moisture to the target system, making it suitable for most environmental targets. The system also incorporates a significantly larger sieve container for the removal of CO2 from chambers prior to the CO2 build-up phase and sampling. In addition, both the CO2 and H2O content of the sample gas are measured continuously. This enables in situ estimation of the amount of collected CO2 and the determination of CO2 flux to a chamber. The portable sampling system is described in detail and tests for the reliability of the method are presented.

A portable molecular-sieve-based CO2 sampling system for radiocarbon measurements.

PubMed

Palonen, V

2015-12-01

We have developed a field-capable sampling system for the collection of CO2 samples for radiocarbon-concentration measurements. Most target systems in environmental research are limited in volume and CO2 concentration, making conventional flask sampling hard or impossible for radiocarbon studies. The present system captures the CO2 selectively to cartridges containing 13X molecular sieve material. The sampling does not introduce significant under-pressures or significant losses of moisture to the target system, making it suitable for most environmental targets. The system also incorporates a significantly larger sieve container for the removal of CO2 from chambers prior to the CO2 build-up phase and sampling. In addition, both the CO2 and H2O content of the sample gas are measured continuously. This enables in situ estimation of the amount of collected CO2 and the determination of CO2 flux to a chamber. The portable sampling system is described in detail and tests for the reliability of the method are presented.

Assessing Soil Organic C Stability at the Continental Scale: An Analysis of Soil C and Radiocarbon Profiles Across the NEON Sites

NASA Astrophysics Data System (ADS)

Heckman, K. A.; Gallo, A.; Hatten, J. A.; Swanston, C.; McKnight, D. M.; Strahm, B. D.; Sanclements, M.

2017-12-01

Soil carbon stocks have become recognized as increasingly important in the context of climate change and global C cycle modeling. As modelers seek to identify key parameters affecting the size and stability of belowground C stocks, attention has been drawn to the mineral matrix and the soil physiochemical factors influenced by it. Though clay content has often been utilized as a convenient and key explanatory variable for soil C dynamics, its utility has recently come under scrutiny as new paradigms of soil organic matter stabilization have been developed. We utilized soil cores from a range of National Ecological Observatory Network (NEON) experimental plots to examine the influence of physicochemical parameters on soil C stocks and turnover, and their relative importance in comparison to climatic variables. Soils were cored at NEON sites, sampled by genetic horizon, and density separated into light fractions (particulate organics neither occluded within aggregates nor associated with mineral surfaces), occluded fractions (particulate organics occluded within aggregates), and heavy fractions (organics associated with mineral surfaces). Bulk soils and density fractions were measured for % C and radiocarbon abundance (as a measure of C stability). Carbon and radiocarbon abundances were examined among fractions and in the context of climatic variables (temperature, precipitation, elevation) and soil physiochemical variables (% clay and pH). No direct relationships between temperature and soil C or radiocarbon abundances were found. As a whole, soil radiocarbon abundance in density fractions decreased in the order of light>heavy>occluded, highlighting the importance of both surface sorption and aggregation to the preservation of organics. Radiocarbon abundance was correlated with pH, with variance also grouping by dominate vegetation type. Soil order was also identified as an important proxy variable for C and radiocarbon abundance. Preliminary results suggest that

Assessment of Contribution of Contemporary Carbon Sources to Size-Fractionated Particulate Matter and Time-Resolved Bulk Particulate Matter Using the Measurement of Radiocarbon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hwang, H M; Young, T M; Buchholz, B A

2009-04-16

This study was motivated by a desire to improve understanding of the sources contributing to the carbon that is an important component of airborne particulate matter (PM). The ultimate goal of this project was to lay a ground work for future tools that might be easily implemented with archived or routinely collected samples. A key feature of this study was application of radiocarbon measurement that can be interpreted to indicate the relative contributions from fossil and non-fossil carbon sources of atmospheric PM. Size-resolved PM and time-resolved PM{sub 10} collected from a site in Sacramento, CA in November 2007 (Phase I)more » and March 2008 (Phase II) were analyzed for radiocarbon and source markers such as levoglucosan, cholesterol, and elemental carbon. Radiocarbon data indicates that the contributions of non-fossil carbon sources were much greater than that from fossil carbon sources in all samples. Radiocarbon and source marker measurements confirm that a greater contribution of non-fossil carbon sources in Phase I samples was highly likely due to residential wood combustion. The present study proves that measurement of radiocarbon and source markers can be readily applied to archived or routinely collected samples for better characterization of PM sources. More accurate source apportionment will support ARB in developing more efficient control strategies.« less

High precise measurements of cosmogenic radiocarbon abundance by complex of scintillation equipments

NASA Technical Reports Server (NTRS)

Kocharov, G. E.; Metskvarishvili, R. Y.; Tsereteli, S. L.

1985-01-01

The main characteristics of scintillation equipments which enable the measurements of radiocarbon content with high accuracy of 0.2 to 0.3% were considered. The complex of scintillation devices operated very well for the last 15 years and allowed the investigation of the temporal variation of solar activity and intensity of cosmic rays for the last 300 years.

Green mosses date the Storegga tsunami to the chilliest decades of the 8.2 ka cold event

NASA Astrophysics Data System (ADS)

Bondevik, Stein; Stormo, Svein Kristian; Skjerdal, Gudrun

2012-06-01

Chlorophyll in dead plants ordinarily decomposes completely before permanent burial through exposure to light, water and oxygen. Here we describe 8000-year-old terrestrial mosses that retain several percent of its original chlorophyll. The mosses were ripped of the land surface, carried 50-100 m off the Norwegian coast of the time, and deposited in depressions on the sea floor by the Storegga tsunami. A little of the chlorophyll survived because, within hours after entraining it, the tsunami buried the mosses in shell-rich sediments. These sediments preserved the chlorophyll by keeping out light and oxygen, and by keeping the pH above 7—three factors known to favour chlorophyll's stability. Because the green mosses were buried alive, their radiocarbon clock started ticking within hours after the Storegga Slide had set off the tsunami. Radiocarbon measurement of the mosses therefore give slide ages of uncommon geological precision, and these, together with a sequence of ages above and below the boundary, date the Storegga Slide to the chilliest decades of the 8.2 ka cold event at 8120-8175 years before AD 1950. North Atlantic coastal- and fjord- climatic records claimed to show evidence of the 8.2 cold event should be carefully examined for possible contamination and disturbance from the Storegga tsunami.

Dating the last Neanderthals in Central Iberia - New evidence from Abrigo del Molino, Segovia, Spain

NASA Astrophysics Data System (ADS)

Kehl, Martin; Álvarez-Alonso, David; de Andrés-Herrero, María; Díez-Herrero, Andrés; Klasen, Nicole; Rojo-Hernández, Julio; Weniger, Gerd-Christian

2017-04-01

The timing of Neanderthal disappearance in the Iberian Peninsula is a hotly debated subject in Palaeolithic archaeology. Several studies suggested a late survival in South and Central Iberia until about 32,000 year ago (ka), but were probably subject to significant age underestimation due to contamination of dating samples and/or lack of stratigraphic integrity. More recently, Late Neanderthal presence was dated to no later than 38 ka. In Central Iberia, few archaeological sites contain Mousterian levels attesting occupation by Neanderthals. The newly discovered rock shelter of Abrigo del Molino contains chronologically well-constraint Mousterian levels, which, according to radiocarbon dating on bone, place the latest Neanderthal occupation to around 42-44 ka and within Greenland interstadial 11. Accumulation of these levels took place after deposition of fluvial and slope sediments, dated to around 46 ± 3.5 ka using luminescence techniques, and probably correlating with Greenland stadial 13 including Heinrich event 5. Micromorphological evidence of banded sediment fabrics suggests frost dynamics pointing to cold climate conditions during that time in Central Spain. Abrigo del Molino thus provides a detailed and chronologically well-constrained record on Late Neanderthal presence and morphodynamic change in Central Iberia during times of millennial-scale climate changes. The site gives further evidence for an early rather than late disappearance of Neanderthals in Iberia.

Radiocarbon Analysis of Individual Amino Acids: Carbon Blank Quantification for a Small-Sample High-Pressure Liquid Chromatography Purification Method.

PubMed

Bour, Amy L; Walker, Brett D; Broek, Taylor A B; McCarthy, Matthew D

2016-04-05

Compound-specific radiocarbon analysis (CSRA) of amino acids (AAs) is of great interest as a proxy for organic nitrogen (N) cycling rates, dating archeological bone collagen, and investigating processes shaping the biogeochemistry of global N reservoirs. However, recoverable quantities of individual compounds from natural samples are often insufficient for radiocarbon ((14)C) analyses (<50 μg C). Constraining procedural carbon (C) blanks and their isotopic contributions is critical for reporting of accurate CSRA measurements. Here, we report the first detailed quantification of C blanks (including sources, magnitudes, and variability) for a high-pressure liquid chromatography (HPLC) method designed to purify individual AAs from natural samples. We used pairs of AA standards with either modern (M) or dead (D) fraction modern (Fm) values to quantify MC and DC blanks within several chromatographic regions. Blanks were determined for both individual and mixed AA standard injections with peak loadings ranging from 10 to 85 μg C. We found 0.8 ± 0.4 μg of MC and 1.0 ± 0.5 μg of DC were introduced by downstream sample preparation (drying, combustion, and graphitization), which accounted for essentially the entire procedural blank for early eluting AAs. For late-eluting AAs, higher eluent organic content and fraction collected volumes contributed to total blanks of 1.5 ± 0.75 μg of MC and 3.0 ± 1.5 μg of DC. Our final measurement uncertainty for 20 μg of C of most AAs was ±0.02 Fm, although sample size requirements are larger for similar uncertainty in late-eluting AAs. These results demonstrate the first CSRA protocol for many protein AAs with uncertainties comparable to the lowest achieved in prior studies.

Holocene environmental change resets lichen surface dates on Recess Peak glacial deposits in the Sierra Nevada, California

NASA Astrophysics Data System (ADS)

Scuderi, Louis A.; Fawcett, Peter J.

2013-09-01

Development of an accurate chronology for glacial deposits in the Sierra Nevada has long been problematic given the lack of suitable organic material for radiocarbon dating. Lichenometry initially appeared promising as ages showed an increase from cirque headwalls to down-canyon moraines. However, while Recess Peak lichen age estimates range from 2 to 3 ka, recent work shows these deposits to be at least 10 ka older. Here, we present evidence for a late Holocene reset of Recess Peak lichen ages by significant post-depositional climate change. Following late-Pleistocene deposition of Recess Peak moraines, warming through the mid-Holocene allowed forests to advance into shallow basins eliminating local inverted tree lines. This produced a partial canopy where shading killed the original post-Pleistocene crustose lichen colonies. Late-Holocene cooling resulted in forest retreat from these basins as alpine tree line fell. Lichens then recolonized the re-exposed Recess Peak deposits. We conclude that while Recess Peak lichen ages are accurate to within the dating uncertainty of the technique, existing lichen ages actually date the timing of post-mid-Holocene cooling and recolonization, and not the original emplacement of these deposits. Thus, applications of Lichenometry should consider post-depositional environmental change when interpreting the meaning of these dates.

Radiocarbon dates for lava flows from northeast rift zone of Mauna Loa Volcano, Hilo 7 1/2 minute quadrangle, Island of Hawaii

USGS Publications Warehouse

Buchanan-Banks, J. M.; Lockwood, J.P.; Rubin, M.

1989-01-01

Twenty-eight 14C analyses are reported for carbonized roots and other plant material collected from beneath 15 prehistoric lava flows erupted from the northeast rift zone (NERZ) of Mauna Loa Volcano (ML). The new 14C dates establish ages for 13 previously undated lava flows, and correct or add to information previously reported. Limiting ages on other flows that lie either above or below the dated flows are also established. These dates help to unravel the eruptive history of ML's NERZ. -from Authors

Integrated Tree-Ring-Radiocarbon High-Resolution Timeframe to Resolve Earlier Second Millennium BCE Mesopotamian Chronology.

PubMed

Manning, Sturt W; Griggs, Carol B; Lorentzen, Brita; Barjamovic, Gojko; Ramsey, Christopher Bronk; Kromer, Bernd; Wild, Eva Maria

2016-01-01

500 years of ancient Near Eastern history from the earlier second millennium BCE, including such pivotal figures as Hammurabi of Babylon, Šamši-Adad I (who conquered Aššur) and Zimrilim of Mari, has long floated in calendar time subject to rival chronological schemes up to 150+ years apart. Texts preserved on clay tablets provide much information, including some astronomical references, but despite 100+ years of scholarly effort, chronological resolution has proved impossible. Documents linked with specific Assyrian officials and rulers have been found and associated with archaeological wood samples at Kültepe and Acemhöyük in Turkey, and offer the potential to resolve this long-running problem. Here we show that previous work using tree-ring dating to place these timbers in absolute time has fundamental problems with key dendrochronological crossdates due to small sample numbers in overlapping years and insufficient critical assessment. To address, we have integrated secure dendrochronological sequences directly with radiocarbon (14C) measurements to achieve tightly resolved absolute (calendar) chronological associations and identify the secure links of this tree-ring chronology with the archaeological-historical evidence. The revised tree-ring-sequenced 14C time-series for Kültepe and Acemhöyük is compatible only with the so-called Middle Chronology and not with the rival High, Low or New Chronologies. This finding provides a robust resolution to a century of uncertainty in Mesopotamian chronology and scholarship, and a secure basis for construction of a coherent timeframe and history across the Near East and East Mediterranean in the earlier second millennium BCE. Our re-dating also affects an unusual tree-ring growth anomaly in wood from Porsuk, Turkey, previously tentatively associated with the Minoan eruption of the Santorini volcano. This tree-ring growth anomaly is now directly dated ~1681-1673 BCE (68.2% highest posterior density range), ~20

Integrated Tree-Ring-Radiocarbon High-Resolution Timeframe to Resolve Earlier Second Millennium BCE Mesopotamian Chronology

PubMed Central

Griggs, Carol B.; Lorentzen, Brita; Barjamovic, Gojko; Ramsey, Christopher Bronk; Kromer, Bernd; Wild, Eva Maria

2016-01-01

500 years of ancient Near Eastern history from the earlier second millennium BCE, including such pivotal figures as Hammurabi of Babylon, Šamši-Adad I (who conquered Aššur) and Zimrilim of Mari, has long floated in calendar time subject to rival chronological schemes up to 150+ years apart. Texts preserved on clay tablets provide much information, including some astronomical references, but despite 100+ years of scholarly effort, chronological resolution has proved impossible. Documents linked with specific Assyrian officials and rulers have been found and associated with archaeological wood samples at Kültepe and Acemhöyük in Turkey, and offer the potential to resolve this long-running problem. Here we show that previous work using tree-ring dating to place these timbers in absolute time has fundamental problems with key dendrochronological crossdates due to small sample numbers in overlapping years and insufficient critical assessment. To address, we have integrated secure dendrochronological sequences directly with radiocarbon (14C) measurements to achieve tightly resolved absolute (calendar) chronological associations and identify the secure links of this tree-ring chronology with the archaeological-historical evidence. The revised tree-ring-sequenced 14C time-series for Kültepe and Acemhöyük is compatible only with the so-called Middle Chronology and not with the rival High, Low or New Chronologies. This finding provides a robust resolution to a century of uncertainty in Mesopotamian chronology and scholarship, and a secure basis for construction of a coherent timeframe and history across the Near East and East Mediterranean in the earlier second millennium BCE. Our re-dating also affects an unusual tree-ring growth anomaly in wood from Porsuk, Turkey, previously tentatively associated with the Minoan eruption of the Santorini volcano. This tree-ring growth anomaly is now directly dated ~1681–1673 BCE (68.2% highest posterior density range), ~20

Radiocarbon-based assessment of fossil fuel-derived contaminant associations in sediments.

PubMed

White, Helen K; Reddy, Christopher M; Eglinton, Timothy I

2008-08-01

Hydrophobic organic contaminants (HOCs) are associated with natural organic matter (OM) in the environment via mechanisms such as sorption or chemical binding. The latter interactions are difficult to quantitatively constrain, as HOCs can reside in different OM pools outside of conventional analytical windows. Here, we exploited natural abundance variations in radiocarbon (14C) to trace various fossil fuel-derived HOCs (14C-free) within chemically defined fractions of contemporary OM (modern 14C content) in 13 samples including marine and freshwater sediments and one dust and one soil sample. Samples were sequentially treated by solvent extraction followed by saponification. Radiocarbon analysis of the bulk sample and resulting residues was then performed. Fossil fuel-derived HOCs released by these treatments were quantified from an isotope mass balance approach as well as by gas chromatography-mass spectrometry. For the majority of samples (n = 13), 98-100% of the total HOC pool was solvent extractable. Nonextracted HOCs are only significant (29% of total HOC pool)in one sample containing p,p-2,2-bis(chlorophenyl)-1,1,1-trichloroethane and its metabolites. The infrequency of significant incorporation of HOCs into nonextracted OM residues suggests that most HOCs are mobile and bioavailable in the environment and, as such, have a greater potential to exert adverse effects.

Calibration of high frequency pollen sequences and tree-ring records

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wigand, P.E.; Rose, M.R.

This paper examines two radiocarbon dated paleoenvironmental records from southern Nevada for the possibility of correlating high-frequency pollen samples with nearby long-term tree-ring sequences. Variable deposition rate are discussed. Radiocarbon dating control of the pollen cores, as well as closer interval sampling is presented.

Radiocarbon ages and age models for the past 30,000 years in Bear Lake, Utah and Idaho

USGS Publications Warehouse

Colman, Steven M.; Rosenbaum, J.G.; Kaufman, D.S.; Dean, W.E.; McGeehin, J.P.

2009-01-01

Radiocarbon analyses of pollen, ostracodes, and total organic carbon (TOC) provide a reliable chronology for the sediments deposited in Bear Lake over the past 30,000 years. The differences in apparent age between TOC, pollen, and carbonate fractions are consistent and in accord with the origins of these fractions. Comparisons among different fractions indicate that pollen sample ages are the most reliable, at least for the past 15,000 years. The post-glacial radiocarbon data also agree with ages independently estimated from aspartic acid racemization in ostracodes. Ages in the red, siliclastic unit, inferred to be of last glacial age, appear to be several thousand years too old, probably because of a high proportion of reworked, refractory organic carbon in the pollen samples. Age-depth models for five piston cores and the Bear Lake drill core (BL00-1) were constructed by using two methods: quadratic equations and smooth cubic-splinefits. The two types of age models differ only in detail for individual cores, and each approach has its own advantages. Specific lithological horizons were dated in several cores and correlated among them, producing robust average ages for these horizons. The age of the correlated horizons in the red, siliclastic unit can be estimated from the age model for BL00-1, which is controlled by ages above and below the red, siliclastic unit. These ages were then transferred to the correlative horizons in the shorter piston cores, providing control for the sections of the age models in those cores in the red, siliclastic unit. These age models are the backbone for reconstructions of past environmental conditions in Bear Lake. In general, sedimentation rates in Bear Lake have been quite uniform, mostly between 0.3 and 0.8 mm yr-1 in the Holocene, and close to 0.5 mm yr-1 for the longer sedimentary record in the drill core from the deepest part of the lake. Copyright ?? 2009 The Geological Society of America.

Fossils reject climate change as the cause of extinction of Caribbean bats.

PubMed

Soto-Centeno, J Angel; Steadman, David W

2015-01-22

We combined novel radiocarbon dates of bat fossils with time-scaled ecological niche models (ENM) to study bat extinctions in the Caribbean. Radiocarbon-dated fossils show that late Quaternary losses of bat populations took place during the late Holocene (<4 ka) rather than late Pleistocene (>10 ka). All bat radiocarbon dates from Abaco (Bahamas) that represent extirpated populations are younger than 4 ka. We include data on six bat species, three of which are Caribbean endemics, and include nectarivores as well as insectivores. Climate-based ENMs from the Last Glacial Maximum to the present reflect overall stability in distributions, with suitable climatic habitat being present over time. In the absence of radiocarbon dates, bat extinctions had been presumed to take place during the last glacial-interglacial transition (ca. 10 ka). Now we see that extirpation of bats on these tropical islands is more complex than previously thought and primarily postdates the major climate changes that took place during the late Pleistocene-Holocene transition.

Radiocarbon signal of a low and intermediate level radioactive waste disposal facility in nearby trees.

PubMed

Janovics, R; Kelemen, D I; Kern, Z; Kapitány, S; Veres, M; Jull, A J T; Molnár, M

2016-03-01

Tree ring series were collected from the vicinity of a Hungarian radioactive waste treatment and disposal facility and from a distant control background site, which is not influenced by the radiocarbon discharge of the disposal facility but it represents the natural regional (14)C level. The (14)C concentration of the cellulose content of tree rings was measured by AMS. Data of the tree ring series from the disposal facility was compared to the control site for each year. The results were also compared to the (14)C data of the atmospheric (14)C monitoring stations at the disposal facility and to international background measurements. On the basis of the results, the excess radiocarbon of the disposal facility can unambiguously be detected in the tree from the repository site. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dating human occupation and adaptation in the southern European last glacial refuge: The chronostratigraphy of Grotta del Romito (Italy)

NASA Astrophysics Data System (ADS)

Blockley, Simon; Pellegrini, Maura; Colonese, Andre C.; Lo Vetro, Domenico; Albert, Paul G.; Brauer, Achim; Di Giuseppe, Zelia; Evans, Adrian; Harding, Poppy; Lee-Thorp, Julia; Lincoln, Paul; Martini, Fabio; Pollard, Mark; Smith, Victoria; Donahue, Randolph

2018-03-01

Grotta del Romito has been the subject of numerous archaeological, chronological and palaeoenvironmental investigations for more than a decade. During the Upper Palaeolithic period the site contains evidence of human occupation through the Gravettian and Epigravettian periods, multiple human burials, changes in the pattern of human occupation, and faunal, isotopic and sedimentological evidence for local environmental change. In spite of this rich record, the chronological control is insufficient to resolve shifts in subsistence and mobility patterns at sufficiently high resolution to match the abrupt climate fluctuations at this time. To resolve this we present new radiocarbon and tephrostratigraphic dates in combination with existing radiocarbon dates, and develop a Bayesian age model framework for the site. This improved chronology reveals that local environmental conditions reflect abrupt and long-term changes in climate, and that these also directly influence changing patterns of human occupation of the site. In particular, we show that the environmental record for the site, based on small mammal habitat preferences, is chronologically in phase with the main changes in climate and environment seen in key regional archives from Italy and Greenland. We also calculate the timing of the transitions between different cultural phases and their spans. We also show that the intensification in occupation of the site is chronologically coincident with a rapid rise in Mesic Woody taxa seen in key regional pollen records and is associated with the Late Epigravettian occupation of the site. This change in the record of Grotta del Romito is also closely associated stratigraphically with a new tephra (the ROM-D30 tephra), which may act as a critical marker in environmental records of the region.

Radiocarbon and stable-isotope geochemistry of organic and inorganic carbon in Lake Superior

NASA Astrophysics Data System (ADS)

Zigah, Prosper K.; Minor, Elizabeth C.; Werne, Josef P.

2012-03-01

We present a lake-wide investigation of Lake Superior carbon and organic matter biogeochemistry using radiocarbon, stable isotope, and carbon concentrations. Dissolved inorganic carbon (DIC) abundance in the lake was 121-122 Tg C, with offshore concentration andδ13C values being laterally homogenous and tightly coupled to the physical and thermal regime and biochemical processes. Offshore Δ14C of DIC (50-65‰) exhibited lateral homogeneity and was more 14C enriched than co-occurring atmospheric CO2 (˜38‰); nearshore Δ14C of DIC (36-38‰) was similar to atmospheric CO2. Dissolved organic carbon (DOC) abundance was 14.2-16.4 Tg C. DOC's concentration and δ13C were homogenous in June (mixed lake), but varied laterally during August (stratification) possibly due to spatial differences in lake productivity. Throughout sampling, DOC had modern radiocarbon values (14-58‰) indicating a semilabile nature with a turnover time of ≤60 years. Lake particulate organic carbon (POC, 0.9-1.3 Tg C) was consistently 13C depleted relative to DOC. The δ15N of epilimnetic particulate organic nitrogen shifted to more negative values during stratification possibly indicating greater use of nitrate (rather than ammonium) by phytoplankton in August. POC's radiocarbon was spatially heterogeneous (Δ14C range: 58‰ to -303‰), and generally 14C depleted relative to DOC and DIC. POC 14C depletion could not be accounted for by black carbon in the lake but, because of its spatial and temporal distribution, is attributed to sediment resuspension. The presence of old POC within the epilimnion of the open lake indicates possible benthic-pelagic coupling in the lake's organic carbon cycle; the ultimate fate of this old POC bears further investigation.

A portable molecular-sieve-based CO{sub 2} sampling system for radiocarbon measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palonen, V., E-mail: vesa.palonen@helsinki.fi

We have developed a field-capable sampling system for the collection of CO{sub 2} samples for radiocarbon-concentration measurements. Most target systems in environmental research are limited in volume and CO{sub 2} concentration, making conventional flask sampling hard or impossible for radiocarbon studies. The present system captures the CO{sub 2} selectively to cartridges containing 13X molecular sieve material. The sampling does not introduce significant under-pressures or significant losses of moisture to the target system, making it suitable for most environmental targets. The system also incorporates a significantly larger sieve container for the removal of CO{sub 2} from chambers prior to the CO{submore » 2} build-up phase and sampling. In addition, both the CO{sub 2} and H{sub 2}O content of the sample gas are measured continuously. This enables in situ estimation of the amount of collected CO{sub 2} and the determination of CO{sub 2} flux to a chamber. The portable sampling system is described in detail and tests for the reliability of the method are presented.« less

Cosmic ray event in 994 C.E. recorded in radiocarbon from Danish oak

NASA Astrophysics Data System (ADS)

Fogtmann-Schulz, A.; Østbø, S. M.; Nielsen, S. G. B.; Olsen, J.; Karoff, C.; Knudsen, M. F.

2017-08-01

We present measurements of radiocarbon in annual tree rings from the time period 980-1006 Common Era (C.E.), hereby covering the cosmic ray event in 994 C.E. The new radiocarbon record from Danish oak is based on both earlywood and latewood fractions of the tree rings, which makes it possible to study seasonal variations in 14C production. The measurements show a rapid increase of ˜10‰ from 993 to 994 C.E. in latewood, followed by a modest decline and relatively high values over the ensuing ˜10 years. This rapid increase occurs from 994 to 995 C.E. in earlywood, suggesting that the cosmic ray event most likely occurred during the period between April and June 994 C.E. Our new record from Danish oak shows strong agreement with existing Δ14C records from Japan, thus supporting the hypothesis that the 994 C.E. cosmic ray event was uniform throughout the Northern Hemisphere and therefore can be used as an astrochronological tie point to anchor floating chronologies of ancient history.

Archaeomagnetic studies in central Mexico—dating of Mesoamerican lime-plasters

NASA Astrophysics Data System (ADS)

Hueda-Tanabe, Y.; Soler-Arechalde, A. M.; Urrutia-Fucugauchi, J.; Barba, L.; Manzanilla, L.; Rebolledo-Vieyra, M.; Goguitchaichvili, A.

2004-11-01

For the first time results of an archaeomagnetic study of unburned lime-plasters from Teotihuacan and Tenochtitlan in central Mesoamerica are presented. Plasters made of lime, lithic clasts and water, appear during the Formative Period and were used for a variety of purposes in floors, sculptures, ceramics and supporting media for mural paintings in the Oaxaca and Maya area. In Central Mexico, grinded volcanic scoria rich in iron minerals is incorporated into the lime-plasters mixture. Samples were selected from two archaeological excavation projects in the Teopancazco residential compound of Teotihuacan and the large multi-stage structure of Templo Mayor in Tenochtitlan, where chronological information is available. The intensity of remanent magnetization (natural remanent magnetization (NRM)) and low-field susceptibility are weak reflecting low relative content of magnetic minerals. NRM directions are well grouped and alternating field demagnetization shows single or two-component magnetizations. Rockmagnetic experiments point to fine-grained titanomagnetites with pseudo-single domain behavior. Anisotropy of magnetic susceptibility (AMS) measurements document a depositional fabric, with normal to free-surface minimum AMS axes. Characteristic mean site directions were correlated to the paleosecular variation curve for Mesoamerica. Data from Templo Mayor reflect recent tilting of the structures. Teopancazco mean site declinations show good correspondence with the reference curve, in agreement with the radiocarbon dating. Dates for four stages of Teotihuacan occupancy based on the study of lime-plasters range from AD 350 to 550. A date for a possible Mazapa occupation around AD 850 or 950 is also suggested based on the archaeomagnetic correlation. The archaeomagnetic record of a plaster floor in Teopancazco differed from the other nearby sites pointing to a thermoremanent magnetization; comparison with the reference curve suggests dates around AD 1375 or 1415. The

Geochemical characterization and dating of R tephra, a post-glacial marker bed in Mount Rainier National Park, Washington, U.S.A.

USGS Publications Warehouse

Samolczyk, Mary; Vallance, James W.; Cubley, Joel; Osborn, Gerald; Clark, Douglas H.

2016-01-01

The oldest postglacial lapilli–ash tephra recognized in sedimentary records surrounding Mount Rainier (Washington State, USA) is R tephra, a very early Holocene deposit that acts as an important stratigraphic and geochronologic marker bed. This multidisciplinary study incorporates tephrostratigraphy, radiocarbon dating, petrography, and electron microprobe analysis to characterize R tephra. Tephra samples were collected from Tipsoo Lake and a stream-cut exposure in the Cowlitz Divide area of Mount Rainier National Park. Field evidence from 25 new sites suggests that R tephra locally contains internal bedding and has a wider distribution than previously reported. Herein, we provide the first robust suite of geochemical data that characterize the tephra. Glass compositions are heterogeneous, predominantly ranging from andesite to rhyolite in ash- to lapilli-sized clasts. The mineral assemblage consists of plagioclase, orthopyroxene, clinopyroxene, and magnetite with trace apatite and ilmenite. Subaerial R tephra deposits appear more weathered in hand sample than subaqueous deposits, but weathering indices suggest negligible chemical weathering in both deposits. Statistical analysis of radiocarbon ages provides a median age for R tephra of ∼10 050 cal years BP, and a 2σ error range between 9960 and 10 130 cal years BP.

Particle acceleration on a chip: A laser-driven micro-accelerator for research and industry

NASA Astrophysics Data System (ADS)

Yoder, R. B.; Travish, G.

2013-03-01

Particle accelerators are conventionally built from radio-frequency metal cavities, but this technology limits the maximum energy available and prevents miniaturization. In the past decade, laser-powered acceleration has been intensively studied as an alternative technology promising much higher accelerating fields in a smaller footprint and taking advantage of recent advances in photonics. Among the more promising approaches are those based on dielectric field-shaping structures. These ``dielectric laser accelerators'' (DLAs) scale with the laser wavelength employed and can be many orders of magnitude smaller than conventional accelerators; DLAs may enable the production of high-intensity, ultra-short relativistic electron bunches in a chip-scale device. When combined with a high- Z target or an optical-period undulator, these systems could produce high-brilliance x-rays from a breadbox-sized device having multiple applications in imaging, medicine, and homeland security. In our research program we have developed one such DLA, the Micro-Accelerator Platform (MAP). We describe the fundamental physics, our fabrication and testing program, and experimental results to date, along with future prospects for MAP-based light-sources and some remaining challenges. Supported in part by the Defense Threat Reduction Agency and National Nuclear Security Administration.

Accelerator 14C dates for early upper paleolithic (basal Aurignacian) at El Castillo Cave (Spain)

USGS Publications Warehouse

Valdes, V.C.; Bischoff, J.L.

1989-01-01

Three fragments of charcoal taken from different parts of the lowermost bed containing Aurignacian artifacts at El Castillo Cave yielded AMS dates of 37??7 (?? 1??8) ka bp, 38??5 (?? 1??8) ka bp, and 40??0 (?? 2??1) ka bp (average 38??7 ?? 1??9 ka bp). These dates are almost identical to new AMS dates from l'Arbreda cave in Catalunya on the same cultural horizon (average 38??5 ?? 1??0 ka bp) and are significantly older than the earliest dates for Aurignacian industries in the Aquitaine and in other parts of Central and Western Europe. ?? 1989.

The importance of radiocarbon dates and tephra for developing chronologies of Holocene environmental changes from lake sediments, North Far East

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lozhkin, Anatoly V.; Brown, Thomas A.; Anderson, Patricia M.

One problem with developing continuous chronologies of paleoenvironmental change in northern areas of the Far East using 14C is the low organic content in lake sediments. However, Holocene age-models can be supplemented by widespread tephra deposits reported in the Magadan region. The best documented of these tephras has been correlated to the KO tephra from southern Kamchatka dated to 7600 BP. Though a key chronostratigraphic marker, no detailed compendium of the distribution of this tephra and its associated 14C dates has been available from sites in the northern Far East. We provide such a summary. Known locally as the Elikchanmore » tephra, lake cores indicate an ash fall that extended ~1800 km north of the Kamchatkan caldera with a ~500 km wide trajectory in the Magadan region. Other Holocene tephras preserved in lake sediments have poorer age control and possibly date to ~2500 BP, ~2700 BP and ~6000 BP. These ashes seem to be restricted to coastal or near-coastal sites. Finally, a single record of a ~25,000 BP tephra has also been documented ~100 km to the northeast of Magadan.« less

The importance of radiocarbon dates and tephra for developing chronologies of Holocene environmental changes from lake sediments, North Far East

DOE PAGES

Lozhkin, Anatoly V.; Brown, Thomas A.; Anderson, Patricia M.; ...

2016-08-12

One problem with developing continuous chronologies of paleoenvironmental change in northern areas of the Far East using 14C is the low organic content in lake sediments. However, Holocene age-models can be supplemented by widespread tephra deposits reported in the Magadan region. The best documented of these tephras has been correlated to the KO tephra from southern Kamchatka dated to 7600 BP. Though a key chronostratigraphic marker, no detailed compendium of the distribution of this tephra and its associated 14C dates has been available from sites in the northern Far East. We provide such a summary. Known locally as the Elikchanmore » tephra, lake cores indicate an ash fall that extended ~1800 km north of the Kamchatkan caldera with a ~500 km wide trajectory in the Magadan region. Other Holocene tephras preserved in lake sediments have poorer age control and possibly date to ~2500 BP, ~2700 BP and ~6000 BP. These ashes seem to be restricted to coastal or near-coastal sites. Finally, a single record of a ~25,000 BP tephra has also been documented ~100 km to the northeast of Magadan.« less

Insights into soil carbon dynamics across climatic gradients from carbon-pool specific radiocarbon analyses

NASA Astrophysics Data System (ADS)

van der Voort, Tessa Sophia; Hagedorn, Frank; McIntyre, Cameron; Zell, Claudia; Eglinton, Timothy Ian

2017-04-01

Soil carbon constitutes the largest terrestrial reservoir of organic carbon, and therefore understanding the mechanisms and drivers of carbon stabilization is crucial, especially in the framework of climate change. The understanding of the dependence of soil organic turnover in specific carbon pools as related to e.g. climate, soil texture and mineralogy is limited. In this framework, radiocarbon constitutes a uniquely powerful tool that help to unravel carbon dynamics from decadal to millennial timescales. This project combines bulk and pool-specific radiocarbon analyses in the top and deep soil on a wide range of forested soils that span a large climatic gradient (MAT 1.3-9.2°C, MAP 600 to 2100 mm m-2y-1). These well-studies sites are part of the Long-Term Forest Ecosystem Research (LWF) program of the Swiss Federal Institute for Forest, Snow and Landscape research (WSL). This study aims to combine the insights gained from bulk and pool-specific turnover to environmental conditions and molecular composition of soil carbon. The pools investigated span the mineral-associated (occluded and heavy fractions from density fractionation) and potentially water-soluble (free light fractions from density fractionation and water extractable organic carbon) organic carbon fractions. Pool-specific radiocarbon work is augmented by the measurement of abundance of compounds such as alkanes, fatty acids and lignin phenols on a subset of samples. Initial results show disparate patterns depending on soil type and in particular soil texture, which could be indicative of various stabilization mechanisms in different soils. Overall, this study provides new insights into the controls of soil organic matter dynamics as related to environmental conditions, in particular in specific sub-pools of carbon.

OSL dating of a Pleistocene maar: Birket Ram, the Golan heights

USGS Publications Warehouse

Shaanan, U.; Porat, N.; Navon, O.; Weinberger, R.; Calvert, A.; Weinstein, Y.

2011-01-01

Direct dating of maars and their phreatomagmatic deposits is difficult due to the dominance of lithic (host rock) fragments and glassy particles of the juvenile magma. In this paper we demonstrate that optically stimulated luminescence (OSL) dating can be successfully used for age determination of phreatomagmatic deposits. We studied the tuff deposit of Birket Ram, a basanitic maar located at the northern edge of the Golan heights on the western Arabian plate. The maar is underlain by a thick section of Pleistocene basalts, and currently hosts a small lake. It is filled by approximately 90m of lacustrine sediments with radiocarbon ages extrapolated to 108ka at the base. OSL was applied to quartz grains extracted from tuffs and paleosols in order to set the time frame of the phreatomagmatism at the site. A maximum age constraint of 179??13ka was determined for a paleosol that underlies the maar ejecta. Quartz grains from two layers in the tuff section yielded a direct age of 129??6ka for the phreatomagmatic eruption. A younger age of 104??7ka, which was determined for a tuff layer underlying a basaltic flow, was attributed to thermal resetting during the lava emplacement. This was confirmed by an 40Ar/39Ar age of 101??3ka determined on the overlying basalt. The internal consistency of the OSL ages and the agreement with the 40Ar/39Ar age determination as well as with previous estimates demonstrates the potential of OSL for maar dating. ?? 2010 Elsevier B.V.

Pego do Diabo (Loures, Portugal): Dating the Emergence of Anatomical Modernity in Westernmost Eurasia

PubMed Central

Zilhão, João; Davis, Simon J. M.; Duarte, Cidália; Soares, António M. M.; Steier, Peter; Wild, Eva

2010-01-01

Background Neandertals and the Middle Paleolithic persisted in the Iberian Peninsula south of the Ebro drainage system for several millennia beyond their assimilation/replacement elsewhere in Europe. As only modern humans are associated with the later stages of the Aurignacian, the duration of this persistence pattern can be assessed via the dating of diagnostic occurrences of such stages. Methodology/Principal Findings Using AMS radiocarbon and advanced pretreatment techniques, we dated a set of stratigraphically associated faunal samples from an Aurignacian III–IV context excavated at the Portuguese cave site of Pego do Diabo. Our results establish a secure terminus ante quem of ca.34,500 calendar years ago for the assimilation/replacement process in westernmost Eurasia. Combined with the chronology of the regional Late Mousterian and with less precise dating evidence for the Aurignacian II, they place the denouement of that process in the 37th millennium before present. Conclusions/Significance These findings have implications for the understanding of the emergence of anatomical modernity in the Old World as a whole, support explanations of the archaic features of the Lagar Velho child's anatomy that invoke evolutionarily significant Neandertal/modern admixture at the time of contact, and counter suggestions that Neandertals could have survived in southwest Iberia until as late as the Last Glacial Maximum. PMID:20111705

Establishment and formation of fog-dependent Tillandsia landbeckii dunes in the Atacama Desert: Evidence from radiocarbon and stable isotopes

NASA Astrophysics Data System (ADS)

Latorre, Claudio; GonzáLez, AngéLica L.; Quade, Jay; FariñA, José M.; Pinto, Raquel; Marquet, Pablo A.

2011-09-01

Extensive dune fields made up exclusively of the bromeliad Tillandsia landbeckii thrive in the Atacama Desert, one of the most extreme landscapes on earth. These plants survive by adapting exclusively to take in abundant advective fog and dew as moisture sources. Although some information has been gathered regarding their modern distribution and adaptations, very little is known about how these dune systems actually form and accumulate over time. We present evidence based on 20 radiocarbon dates for the establishment age and development of five different such dune systems located along a ˜215 km transect in northern Chile. Using stratigraphy, geochronology and stable C and N isotopes, we (1) develop an establishment chronology of these ecosystems, (2) explain how the unique T. landbeckii dunes form, and (3) link changes in foliar δ15N values to moisture availability in buried fossil T. landbeckii layers. We conclude by pointing out the potential that these systems have for reconstructing past climate change along coastal northern Chile during the late Holocene.

Demography of the Early Neolithic Population in Central Balkans: Population Dynamics Reconstruction Using Summed Radiocarbon Probability Distributions

PubMed Central

2016-01-01

The Central Balkans region is of great importance for understanding the spread of the Neolithic in Europe but the Early Neolithic population dynamics of the region is unknown. In this study we apply the method of summed calibrated probability distributions to a set of published radiocarbon dates from the Republic of Serbia in order to reconstruct population dynamics in the Early Neolithic in this part of the Central Balkans. The results indicate that there was a significant population growth after ~6200 calBC, when the Neolithic was introduced into the region, followed by a bust at the end of the Early Neolithic phase (~5400 calBC). These results are broadly consistent with the predictions of the Neolithic Demographic Transition theory and the patterns of population booms and busts detected in other regions of Europe. These results suggest that the cultural process that underlies the patterns observed in Central and Western Europe was also in operation in the Central Balkan Neolithic and that the population increase component of this process can be considered as an important factor for the spread of the Neolithic as envisioned in the demic diffusion hypothesis. PMID:27508413

Fossils reject climate change as the cause of extinction of Caribbean bats

PubMed Central

Soto-Centeno, J. Angel; Steadman, David W.

2015-01-01

We combined novel radiocarbon dates of bat fossils with time-scaled ecological niche models (ENM) to study bat extinctions in the Caribbean. Radiocarbon-dated fossils show that late Quaternary losses of bat populations took place during the late Holocene (<4 ka) rather than late Pleistocene (>10 ka). All bat radiocarbon dates from Abaco (Bahamas) that represent extirpated populations are younger than 4 ka. We include data on six bat species, three of which are Caribbean endemics, and include nectarivores as well as insectivores. Climate-based ENMs from the Last Glacial Maximum to the present reflect overall stability in distributions, with suitable climatic habitat being present over time. In the absence of radiocarbon dates, bat extinctions had been presumed to take place during the last glacial-interglacial transition (ca. 10 ka). Now we see that extirpation of bats on these tropical islands is more complex than previously thought and primarily postdates the major climate changes that took place during the late Pleistocene-Holocene transition. PMID:25610991

Verifying the new luminescence surface-exposure dating technique--rock falls in Canyonlands National Park, Utah

NASA Astrophysics Data System (ADS)

Pederson, J. L.; Sohbati, R.; Murray, A. S.; Jain, M.

2015-12-01

Recent studies have helped develop the optically stimulated luminescence (OSL) dating of rock surfaces, as applied to the age of the famous Great Gallery rock art panel in Canyonlands National Park. Chapot et al. (2012) dated a key rock fall to ~900 yrs ago by applying OSL to the outer 1-mm buried surface of a sandstone talus boulder, an age confirmed by independent radiocarbon dating. Later, in a novel approach and with the use of a local known-age calibration sample, Sohbati et al. (2012) modelled the millimeter-scale OSL-depth profile to determine a pre-burial exposure duration of ~700 years for the same rock fall. This combination of rock-fall dating and exposure dating--an approach with broad potential to date Holocene mass movements--constrains the creation of the Great Gallery rock art to a time window of 900 to ~1600 years ago (Pederson et al., 2014), a result met with some controversy. Here we report on a new phase of research to verify these results and further refine OSL-profile exposure dating for mass movements. New analyses from within and near the Great Gallery alcove include: i) exposure dating of the same alcove surface upon which the rock art is painted with a predicted exposure age of ~1600 years; ii) exposure dating of the top (light-exposed) side of the same rock-fall boulder whose buried side was previously dated to test for reproduction of the known age; and iii) an improved calibration sample from a nearby trail/road-cut for verification. The residual OSL signal is measured with depth in millimeter-thick increments of all samples. We first determine the site-specific luminescence reduction rate at the rock surface by fitting the OSL surface-exposure dating model to the calibration profile from the trail/road-cut. This parameterized model then provides exposure ages for the bleaching profiles observed in the other samples. Results have implications for the application of OSL rock-surface and exposure-profile dating in other settings where

14C Analysis of Protein Extracts from Bacillus Spores

PubMed Central

Cappucio, Jenny A.; Sarachine Falso, Miranda J.; Kashgarian, Michaele; Buchholz, Bruce A.

2014-01-01

Investigators of bioagent incidents or interdicted materials need validated, independent analytical methods that will allow them to distinguish between recently made bioagent samples versus material drawn from the archives of a historical program. Heterotrophic bacteria convert the carbon in their food sources, growth substrate or culture media, into the biomolecules they need. The F14C (fraction modern radiocarbon) of a variety of media, Bacillus spores, and separated proteins from Bacillus spores was measured by accelerator mass spectrometry (AMS). AMS precisely measures F14C values of biological materials and has been used to date the synthesis of biomaterials over the bomb pulse era (1955 to present). The F14C of Bacillus spores reflects the radiocarbon content of the media in which they were grown. In a survey of commercial media we found that the F14C value indicated that carbon sources for the media were alive within about a year of the date of manufacture and generally of terrestrial origin. Hence, bacteria and their products can be dated using their 14C signature. Bacillus spore samples were generated onsite with defined media and carbon free purification and also obtained from archived material. Using mechanical lysis and a variety of washes with carbon free acids and bases, contaminant carbon was removed from soluble proteins to enable accurate 14C bomb-pulse dating. Since media is contemporary, 14C bomb-pulse dating of isolated soluble proteins can be used to distinguish between historical archives of bioagents and those produced from recent media. PMID:24814329

14C Analysis of protein extracts from Bacillus spores.

PubMed

Cappuccio, Jenny A; Falso, Miranda J Sarachine; Kashgarian, Michaele; Buchholz, Bruce A

2014-07-01

Investigators of bioagent incidents or interdicted materials need validated, independent analytical methods that will allow them to distinguish between recently made bioagent samples versus material drawn from the archives of a historical program. Heterotrophic bacteria convert the carbon in their food sources, growth substrate or culture media, into the biomolecules they need. The F(14)C (fraction modern radiocarbon) of a variety of media, Bacillus spores, and separated proteins from Bacillus spores was measured by accelerator mass spectrometry (AMS). AMS precisely measures F(14)C values of biological materials and has been used to date the synthesis of biomaterials over the bomb pulse era (1955 to present). The F(14)C of Bacillus spores reflects the radiocarbon content of the media in which they were grown. In a survey of commercial media we found that the F(14)C value indicated that carbon sources for the media were alive within about a year of the date of manufacture and generally of terrestrial origin. Hence, bacteria and their products can be dated using their (14)C signature. Bacillus spore samples were generated onsite with defined media and carbon free purification and also obtained from archived material. Using mechanical lysis and a variety of washes with carbon free acids and bases, contaminant carbon was removed from soluble proteins to enable accurate (14)C bomb-pulse dating. Since media is contemporary, (14)C bomb-pulse dating of isolated soluble proteins can be used to distinguish between historical archives of bioagents and those produced from recent media. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Paleoseismology of the Nephi Segment of the Wasatch Fault Zone, Juab County, Utah - Preliminary Results From Two Large Exploratory Trenches at Willow Creek

USGS Publications Warehouse

Machette, Michael N.; Crone, Anthony J.; Personius, Stephen F.; Mahan, Shannon; Dart, Richard L.; Lidke, David J.; Olig, Susan S.

2007-01-01

In 2004, we identified a small parcel of U.S. Forest Service land at the mouth of Willow Creek (about 5 km west of Mona, Utah) that was suitable for trenching. At the Willow Creek site, which is near the middle of the southern strand of the Nephi segment, the WFZ has vertically displaced alluvial-fan deposits >6-7 m, forming large, steep, multiple-event scarps. In May 2005, we dug two 4- to 5-m-deep backhoe trenches at the Willow Creek site, identified three colluvial wedges in each trench, and collected samples of charcoal and A-horizon organic material for AMS (acceleration mass spectrometry) radiocarbon dating, and sampled fine-grained eolian and colluvial sediment for luminescence dating. The trenches yielded a stratigraphic assemblage composed of moderately coarse-grained fluvial and debris-flow deposits and discrete colluvial wedges associated with three faulting events (P1, P2, and P3). About one-half of the net vertical displacement is accommodated by monoclinal tilting of fan deposits on the hanging-wall block, possibly related to massive ductile landslide deposits that are present beneath the Willow Creek fan. The timing of the three surface-faulting events is bracketed by radiocarbon dates and results in a much different fault chronology and higher slip rates than previously considered for this segment of the Wasatch fault zone.

Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum

NASA Astrophysics Data System (ADS)

Hillenbrand, C. D.; Klages, J. P.; Kuhn, G.; Smith, J.; Graham, A. G. C.; Gohl, K.; Wacker, L.

2016-02-01

We present the first age control and sedimentological data for the upper part of a stratified seismic unit that is unusually thick ( 6-9 m) for the outer shelf of the ASE and overlies an acoustically transparent unit. The transparent unit probably consists of soft till deposited during the last advance of grounded ice onto the outer shelf. We mapped subtle mega-scale glacial lineations (MSGL) on the seafloor and suggest that these are probably the expressions of bedforms originally moulded into the surface of the underlying till layer. We note that the lineations are less distinct when compared to MSGLs recorded in bathymetric data collected further upstream and suggest that this is because of the blanketing influence of the thick overlying drape. The uppermost part (≤ 3 m) of the stratified drape was sampled by two of our sediment cores and contains sufficient amounts of calcareous foraminifera throughout to establish reliable age models by radiocarbon dating. In combination with facies analysis of the recovered sediments the obtained radiocarbon dates suggest deposition of the draping unit in a sub-ice shelf/sub-sea ice to seasonal-open marine environment that existed on the outer shelf from well before (>45 ka BP) the Last Glacial Maximum until today. This indicates the maximum extent of grounded ice at the LGM must have been situated south of the two core locations, where a well-defined grounding-zone wedge (`GZWa') was deposited. The third sediment core was recovered from the toe of this wedge and retrieved grounding-line proximal glaciogenic debris flow sediments that were deposited by 14 cal. ka BP. Our new data therefore provide direct evidence for 1) the maximum extent of grounded ice in the easternmost ASE at the LGM (=GZWa), 2) the existence of a large shelf area seawards the wedge that was not covered by grounded ice during that time, and 3) landward grounding line retreat from GZWa prior to 14 cal. ka BP. This knowledge will help to improve LGM ice

Age of Barrier Canyon-style rock art constrained by cross-cutting relations and luminescence dating techniques.

PubMed

Pederson, Joel L; Chapot, Melissa S; Simms, Steven R; Sohbati, Reza; Rittenour, Tammy M; Murray, Andrew S; Cox, Gary

2014-09-09

Rock art compels interest from both researchers and a broader public, inspiring many hypotheses about its cultural origin and meaning, but it is notoriously difficult to date numerically. Barrier Canyon-style (BCS) pictographs of the Colorado Plateau are among the most debated examples; hypotheses about its age span the entire Holocene epoch and previous attempts at direct radiocarbon dating have failed. We provide multiple age constraints through the use of cross-cutting relations and new and broadly applicable approaches in optically stimulated luminescence dating at the Great Gallery panel, the type section of BCS art in Canyonlands National Park, southeastern Utah. Alluvial chronostratigraphy constrains the burial and exhumation of the alcove containing the panel, and limits are also set by our related research dating both a rockfall that removed some figures and the rock's exposure duration before that time. Results provide a maximum possible age, a minimum age, and an exposure time window for the creation of the Great Gallery panel, respectively. The only prior hypothesis not disproven is a late Archaic origin for BCS rock art, although our age result of A.D. ∼ 1-1100 coincides better with the transition to and rise of the subsequent Fremont culture. This chronology is for the type locality only, and variability in the age of other sites is likely. Nevertheless, results suggest that BCS rock art represents an artistic tradition that spanned cultures and the transition from foraging to farming in the region.

Age of Barrier Canyon-style rock art constrained by cross-cutting relations and luminescence dating techniques

PubMed Central

Pederson, Joel L.; Chapot, Melissa S.; Simms, Steven R.; Sohbati, Reza; Rittenour, Tammy M.; Murray, Andrew S.; Cox, Gary

2014-01-01

Rock art compels interest from both researchers and a broader public, inspiring many hypotheses about its cultural origin and meaning, but it is notoriously difficult to date numerically. Barrier Canyon-style (BCS) pictographs of the Colorado Plateau are among the most debated examples; hypotheses about its age span the entire Holocene epoch and previous attempts at direct radiocarbon dating have failed. We provide multiple age constraints through the use of cross-cutting relations and new and broadly applicable approaches in optically stimulated luminescence dating at the Great Gallery panel, the type section of BCS art in Canyonlands National Park, southeastern Utah. Alluvial chronostratigraphy constrains the burial and exhumation of the alcove containing the panel, and limits are also set by our related research dating both a rockfall that removed some figures and the rock’s exposure duration before that time. Results provide a maximum possible age, a minimum age, and an exposure time window for the creation of the Great Gallery panel, respectively. The only prior hypothesis not disproven is a late Archaic origin for BCS rock art, although our age result of A.D. ∼1–1100 coincides better with the transition to and rise of the subsequent Fremont culture. This chronology is for the type locality only, and variability in the age of other sites is likely. Nevertheless, results suggest that BCS rock art represents an artistic tradition that spanned cultures and the transition from foraging to farming in the region. PMID:25157162

Soil development in OSL dated sandy dune substrates under Quercus robur Forest (Netherlands)

NASA Astrophysics Data System (ADS)

van Mourik, J. M.; Nierop, Ir. K.; Verstraten, J. M.

2009-04-01

Coastal dune landscapes are very dynamic. The present distribution of vegetation and soil is the result of over 2000 years of natural processes and human management. The initial soil development was controlled by an increase of the organic matter content, which consisted mainly of decomposed roots of grasses (rhizomull), and a decrease of the soil pH to 3-4 by decalcification. This stage was followed by the development of a deciduous forest, which was dominated by Quercus robur. Since 1600 AD, a large part of the deciduous forest that dominated the east side of the coastal dune landscape transferred in expensive residential areas and urbanizations. Nevertheless some parts of the oak forest belt remained. The present forest soils are acid and the controlling soil processes are leaching of sesquioxides and storage of organic matter in mormoder humus forms. The sustainability of ecosystems is closely related to the quality of the humus form, controlling nutrient cycling and water supply. Therefore, improve of knowledge of humus form development and properties is important. We applied soil micromorphology and pyrolysis-gas chromatography/mass spectrometry (GC/MS) to investigate more details of humus form development at two locations (Duivendrift and Hoek van Klaas) in the coastal dune area of the Amsterdamse Waterleidingduinen (near Haarlem, the Netherlands). However, to understand forest soil development, including the organic matter composition in the humus form, the age of the substrate and the forest is required. Therefore, we used tradition techniques as pollen analysis and radiocarbon dating but also the recently introduced optical stimulated luminescence (OSL) dating technique. OSL dating works excellent for aeolian sandy deposits with a high percentage of quartz grains. The OSL age is defined as the time after the last bleaching by solar radiation of mineral grains. Or in other words, the start of a stable period without sand drifting. In the Ah horizons we

Development of radiocarbon-based methods to investigate atmospheric fossil carbon pollution

NASA Astrophysics Data System (ADS)

Major, István; Vodila, Gergely; Furu, Enikő; Kertész, Zsófia; Haszpra, László; Hajdas, Irka; Molnár, Mihály

2013-04-01

Gaseous and solid state carbon containing compounds significantly affect global climate change based on current atmospheric research results. Major part of the anthropogenic changes of the atmospheric carbon dioxide can be attributed to the combustion of fossil fuels and 95% of their emission is realised in the industrially active areas of the northern hemisphere. Anthropogenic carbonaceous aerosol particles play also a key role in the atmosphere modifying indirectly climate change and the quality of the environment and affecting directly human health. Since September 2008, the CO2 concentration of the air and its specific radiocarbon content (14C) has been monitored in the city of Debrecen (Hungary) and in a rural background site, Hegyhátsál (Hungary). To obtain a more representative view regarding anthropogenic contribution of the atmospheric carbon species, our measurement programme was enhanced by including the investigation of atmospheric aerosols in 2010. An aerosol cascade sampler for continuous monitoring was installed close to the atmospheric CO2 sampling station in the inner city of Debrecen. For 14C measurements, special sample preparation system and method was developed for the tiny total carbon content of the aerosol samples collected synchronously with the carbon dioxide observations. The radiocarbon measurement of the aerosol samples was performed by a high-sensitivity accelerator mass spectrometer (AMS) dedicated to environmental samples (EnvironMICADAS) developed together with ETH Zürich. The δ13C values of the samples were measured by the Dual Inlet system of a Delta PLUS XP Isotope Ratio Mass Spectrometer from the tiny CO2 amount aimed to reserve. The atmospheric fossil CO2 and fossil PM2.5 concentration variations show high similarity in the air of Debrecen city. During the winter heating period, due to the meteorological conditions (frequent thermal inversion, decreasing rate of mixing and upwelling), significantly higher total PM2

On the radiocarbon record in banded corals: exchange parameters and net transport of /sup 14/CO/sub 2/ between atmosphere and surface ocean

DOE Office of Scientific and Technical Information (OSTI.GOV)

Druffel, E.M.; Suess, H.E.

1983-02-20

We have made radiocarbon measurements of banded hermatypic corals from Florida, Belize, and the Galapagos Islands. Interpretation is presented here of these previously reported results. These measurements represent the /sup 14/C//sup 12/C ratios in dissolved inorganic carbon (DIOC) in the surface ocean waters of the Gulf Stream and the Peru Current at the time of coral ring formation. A depletion in radiocarbon concentration was observed incoral rings that grew from A.D. 1900--1952. It was caused by dilution of existing /sup 14/C levels with dead CO/sub 2/ from fossil fuel burning (the Suess effect, or S/sub e/). A similar trend wasmore » observed in the distribution of bomb-produced /sup 14/C in corals that had grown during the years following A.D. 1952. The concentration of bomb-produced radiocarbon was much higher in corals from temperate regions (Florida, Belize, Hawaiian Islands) than in corals from tropical regions (Galapagos Islands and Canton Island). The apparent radiocarbon ages of the surface waters in temperate and tropical oceans during the preanthropogenic period range from about 280 to 520 years B.P. (-40 to -69%). At all investigated locations, it is likely that waters at subsurface depths have the same apparent radiocarbon age of about 670 years B.P. From the change of oceanic ..delta../sup 14/C in the surface during post-bomb times, the approximate annual rate of net input of /sup 14/CO/sub 2/ to the ocean waters is calculated to be about 8% of the prevailing /sup 14/C difference between atmosphere and ocean. From this input and from preanthropogenic ..delta../sup 14/C values found at each location, it can be seen that vertical mixing of water in the Peru Current is about 3 times greater than that in the Gulf Stream.« less

Radiocarbon dating of large termite mounds of the miombo woodland of Katanga, DR Congo

NASA Astrophysics Data System (ADS)

Erens, Hans; Boudin, Mathieu; Mees, Florias; Dumon, Mathijs; Mujinya, Basile; Van Strydonck, Mark; Baert, Geert; Boeckx, Pascal; Van Ranst, Eric

2015-04-01

The miombo woodlands of South Katanga (D.R. Congo) are characterized by a high spatial density of large conic termite mounds built by Macrotermes falciger (3 to 5 ha-1, ~5 m high, ~15 m in diameter). The time it takes for these mounds to attain this size is still largely unknown. In this study, the age of four of these mounds is determined by 14C-dating the acid-insoluble organic carbon fraction of samples taken along the central vertical axis of two active and two abandoned mounds. The age sequence in the active mounds is erratic, but the results for the abandoned mounds show a logical increase of 14C-age with depth. The ages measured at 50 cm above ground level were 2335 - 2119 cal yr BP for the large abandoned mound (630 cm high), and 796 - 684 cal yr BP for the small abandoned mound (320 cm high). Cold-water-extractable organic carbon (CWEOC) measurements combined with spectroscopic analysis revealed that the lower parts of the active mounds may have been contaminated with recent carbon that leached from the active nest. Nonetheless, this method appears to provide reliable age estimates of large, abandoned termite mounds, which are older than previously estimated. Furthermore, historical mound growth rates seem to correspond to past temperature changes, suggesting a relation between past environmental conditions and mound occupancy. Keywords : 14C, water-extractable carbon, low-temperature combustion

Ornaments of the earliest Upper Paleolithic: New insights from the Levant

PubMed Central

Kuhn, Steven L.; Stiner, Mary C.; Reese, David S.; Güleç, Erksin

2001-01-01

Two sites located on the northern Levantine coast, Üçağızlı Cave (Turkey) and Ksar 'Akil (Lebanon) have yielded numerous marine shell beads in association with early Upper Paleolithic stone tools. Accelerator mass spectrometry (AMS) radiocarbon dates indicate ages between 39,000 and 41,000 radiocarbon years (roughly 41,000–43,000 calendar years) for the oldest ornament-bearing levels in Üçağızlı Cave. Based on stratigraphic evidence, the earliest shell beads from Ksar 'Akil may be even older. These artifacts provide some of the earliest evidence for traditions of personal ornament manufacture by Upper Paleolithic humans in western Asia, comparable in age to similar objects from Eastern Europe and Africa. The new data show that the initial appearance of Upper Paleolithic ornament technologies was essentially simultaneous on three continents. The early appearance and proliferation of ornament technologies appears to have been contingent on variable demographic or social conditions. PMID:11390976

Earthquake dating: an application of carbon-14 atom counting.

PubMed

Tucker, A B; Woefli, W; Bonani, G; Suter, M

1983-03-18

Milligram-sized specimens of detrital charcoal from soil layers associated with prehistoric earthquakes on the Wasatch fault in Utah have been dated by direct atom counting of carbon-14 with a tandem Van de Graaff accelerator. The measured ratios of carbon-14 to carbon-12 correspond to ages of 7800, 8800, and 9000 years with uncertainties of +/- 600 years.

Quantification of airborne fossil and biomass carbonylic carbon by combined radiocarbon and liquid chromatography mass spectrometry

NASA Astrophysics Data System (ADS)

Larsen, B. R.; Tudos, A.; Slanina, J.; Van der Borg, K.; Kotzias, D.

Airborne carbonyl compounds have been sampled at three European semi-remote to semi-urban test sites for radiocarbon ( 14C) analysis. The used methodology included collection on 2,4-dinitrophenylhydrazine coated silica gel cartridges, chromatographic isolation of the formed hydrazones, combustion into CO 2, reduction into graphite followed by accelerator mass spectrometry. In combination with this, liquid chromatography coupled to atmospheric pressure chemical ionisation mass spectrometry was used for chemical speciation of the collected carbonyls. At all sites the carbonyls were found to be of a mixed biogenic/anthropogenic origin. The determining factor for the proportion of fossil (anthropogenic) carbon in the samples was the vicinity of urban sources for carbonyls and their photochemical precursors. At meteorological conditions, which gave the test sites semi-rural/semi-remote characteristics the samples contained an average of 24% (range: 10-34%) of fossil carbonylic carbon. When air masses were transported from urban areas to the test-sites significantly higher proportions of fossil carbonylic carbon were determined with a maximum of 61%. Principal component analysis on this limited data set indicated that a low fossil proportion of carbonylic carbon is associated with high proportions of acetaldehyde, acetone, pentanone and acrolein. Until further radicarbon studies are carried out the conclusion remains that for the carbonyl compounds measured European background levels are of a predominant biogenic origin.

Preliminary report on radiocarbon dating of cryptoendolithic microorganisms

NASA Technical Reports Server (NTRS)

Bonani, G.; Friedmann, E. I.; Ocampo-Friedmann, R.; McKay, C. P.; Woelfli, W.

1988-01-01

The existence of microbial communities living inside desert rocks has been reported by FRIEDMANN et al. (1967, 1976), first in rocks collected from the hot and dry Negev desert and later in rocks in the frigid Ross Desert of Southern Victoria Land, Antarctica. The extremely inhospitable climatic conditions in both places has led to the suggestion that these organisms have very low rates of metabolism and may, in addition, be very old (FRIEDMANN 1982). Our preliminary measurements showed a 14C deficiency indicating a carbon age in the order of magnitude of 10(3) years.

Tapping the deglacial secrets of Lake Oneida sediments: Establishing a connection between radiocarbon and paleomagnetics in Fish Creek sediments

NASA Astrophysics Data System (ADS)

Peck, D.; Rosenheim, B. E.; Ridge, J. C.

2017-12-01

Postglacial varved and rhythmically-laminated clays deposited within the Ontario Basin are often associated with the retreat of the Laurentide Ice Sheet immediately preceding the onset of the Younger Dryas. The paleoclimatic significance of the Ontario Basin has made it a popularly studied region. To determine ages that correlate with ice sheet retreat, classical radiocarbon ages were generated. However low total organic carbon (TOC) values found in glaciolacustrine sediments make accuracy of data a concern. Using the magnetic orientation of sediments during deposition, paleomagnetism has presented reliable dates in similar regions across the northeastern United States. While useful, paleomagnetism also comes with limitations, which have left areas of unexplored research. Lake Oneida, last glaciated by the Ontario Lobe, is one of the deepest and most untapped reservoirs of sediment dating back to the retreat of the Laurentide Ice Sheet, due primarily to the difficulty it poses for classical methods. Using samples taken from exposed varved glaciolacustrine sediment exposed by the downcutting of Fish Creek, a fluvial system terminating in eastern Lake Oneida, we compare Ramped Pyrolysis 14C data with paleomagnetic data. Ramped PyrOx 14C data unmask the distribution of ages in the organic matter of these sediments, at least partially separating autochthonous sources of carbon from allochthonous sources that tend to be older in these settings. Our comparison will test whether Ramped PyrOx 14C data match paleomagnetic data well enough to be used as the sole chronometer in sediment cores taken from Lake Oneida cores for which paleomagnetic orientation becomes more difficult to ascertain.

Dendrochronologically dated pine stumps document phase-wise bog expansion at a northwest German site between ca. 6700 and ca. 3400 BC

NASA Astrophysics Data System (ADS)

Maike Achterberg, Inke Elisabeth; Eckstein, Jan; Birkholz, Bernhard; Bauerochse, Andreas; Leuschner, Hanns Hubert

2018-01-01

The investigated northwest German mire site at Totes Moor is densely covered with subfossil pine stumps (Pinus sylvestris L.) from the fen-bog transition. This facilitates the spatio-temporal reconstruction of mire development, which is based on 212 in situ tree stumps in the case study presented here. Six dendrochronologically dated site chronologies together cover 2345 years between 6703 and 3403 BC. The gaps in between are 6 to 550 years long. Additionally, a floating chronology of 309 years, containing 30 trees, was radiocarbon-dated to the beginning of the 7th millennium cal BC. Peat-stratigraphical survey was carried out additionally, and elevations a.s.l. were determined at several locations. Tree dying-off phases, which indicate water level rise at the site, mostly in context of the local fen-bog transition, are evident for ca. 6600-6450, ca. 6350-5750, ca. 5300-4900, ca. 4700-4550, ca. 3900-3850, ca. 3700-3600, ca. 3500-3450 and ca. 3400 BC. The spatial distribution of the dated in situ trees illustrates the phase-wise expansion of raised bog over fen peat at the site. The documented bog expansion pulses likely correspond to climatic wet sifts.

Source apportionment of elevated wintertime PAHs by compound-specific radiocarbon analysis

NASA Astrophysics Data System (ADS)

Sheesley, R. J.; Kruså, M.; Krecl, P.; Johansson, C.; Gustafsson, Ã.-.

2009-05-01

Natural abundance radiocarbon analysis facilitates distinct source apportionment between contemporary biomass/biofuel (14C "alive") versus fossil fuel (14C "dead") combustion. Here, the first compound-specific radiocarbon analysis (CSRA) of atmospheric polycyclic aromatic hydrocarbons (PAHs) was demonstrated for a set of samples collected in Lycksele, Sweden a small town with frequent episodes of severe atmospheric pollution in the winter. Renewed interest in using residential wood combustion (RWC) means that this type of seasonal pollution is of increasing concern in many areas. Five individual/paired PAH isolates from three pooled fortnight-long filter collections were analyzed by CSRA: phenanthrene, fluoranthene, pyrene, benzo[b+k]fluoranthene and indeno[cd]pyrene plus benzo[ghi]perylene; phenanthrene was the only compound also analyzed in the gas phase. The measured Δ14C for PAHs spanned from -138.3‰ to 58.0‰. A simple isotopic mass balance model was applied to estimate the fraction biomass (fbiomass) contribution, which was constrained to 71-87% for the individual PAHs. Indeno[cd]pyrene plus benzo[ghi]perylene had an fbiomass of 71%, while fluoranthene and phenanthrene (gas phase) had the highest biomass contribution at 87%. The total organic carbon (TOC, defined as carbon remaining after removal of inorganic carbon) fbiomass was estimated to be 77%, which falls within the range for PAHs. This CSRA data of atmospheric PAHs established that RWC is the dominating source of atmospheric PAHs to this region of the boreal zone with some variations among RWC contributions to specific PAHs.

Quantifying archaeal community autotrophy in the mesopelagic ocean using natural radiocarbon

PubMed Central

Ingalls, Anitra E.; Shah, Sunita R.; Hansman, Roberta L.; Aluwihare, Lihini I.; Santos, Guaciara M.; Druffel, Ellen R. M.; Pearson, Ann

2006-01-01

An ammonia-oxidizing, carbon-fixing archaeon, Candidatus “Nitrosopumilus maritimus,” recently was isolated from a salt-water aquarium, definitively confirming that chemoautotrophy exists among the marine archaea. However, in other incubation studies, pelagic archaea also were capable of using organic carbon. It has remained unknown what fraction of the total marine archaeal community is autotrophic in situ. If archaea live primarily as autotrophs in the natural environment, a large ammonia-oxidizing population would play a significant role in marine nitrification. Here we use the natural distribution of radiocarbon in archaeal membrane lipids to quantify the bulk carbon metabolism of archaea at two depths in the subtropical North Pacific gyre. Our compound-specific radiocarbon data show that the archaea in surface waters incorporate modern carbon into their membrane lipids, and archaea at 670 m incorporate carbon that is slightly more isotopically enriched than inorganic carbon at the same depth. An isotopic mass balance model shows that the dominant metabolism at depth indeed is autotrophy (83%), whereas heterotrophic consumption of modern organic carbon accounts for the remainder of archaeal biomass. These results reflect the in situ production of the total community that produces tetraether lipids and are not subject to biases associated with incubation and/or culture experiments. The data suggest either that the marine archaeal community includes both autotrophs and heterotrophs or is a single population with a uniformly mixotrophic metabolism. The metabolic and phylogenetic diversity of the marine archaea warrants further exploration; these organisms may play a major role in the marine cycles of nitrogen and carbon. PMID:16614070

High resolution optically stimulated luminescence dating of a sediment core from the southwestern Sea of Okhotsk

NASA Astrophysics Data System (ADS)

Sugisaki, S.; Buylaert, J. P.; Murray, A. S.; Harada, N.; Kimoto, K.; Okazaki, Y.; Sakamoto, T.; Iijima, K.; Tsukamoto, S.; Miura, H.; Nogi, Y.

2012-05-01

Optically stimulated luminescence (OSL) dating is now widely accepted as a chronometer for terrestrial sediment. More recently, it has been suggested that OSL may also be useful in the dating of deep-sea marine sediments. In this paper, we test the usefulness of high resolution quartz OSL dating in application to a 19 m marine sediment core (MR0604-PC04A) taken from the southwestern Sea of Okhotsk, immediately to the north of Hokkaido, Japan. Fine-grained quartz (4 to 11μm) was chosen as the dosimeter, and a single-aliquot regenerative-dose protocol was used for the determination of equivalent dose (De), with stimulation by both infrared and blue light. The suitability of the measurement procedure was confirmed using dose recovery tests. A high resolution record (˜2 OSL ages/m) identified clear sedimentation rate changes down the core. The OSL ages are significantly dependent on the water content model chosen; two alternative interpretations are discussed, and the geologically preferred model identified. However, ages resulting from the observed (non-modeled) water content lie closest to the available radiocarbon ages (in the range back to 20 ka). Our OSL ages confirm the known high sedimentation rates in this locality, and for the first time demonstrate clear differences in sedimentation rate before, during and after deglaciation. Although the apparent accuracy of single sample ages is not always consistent with expectations, average ages are accurate, and our data show that OSL dating can be a powerful method for establishing high resolution marine chronologies.

Timing of Expansions of the Quelccaya Ice Cap, Peru, and Implications for Cosmogenic Nuclide Production Rate Calibration

NASA Astrophysics Data System (ADS)

Lowell, T. V.; Kelly, M. A.; Applegate, P. J.; Smith, C. A.; Phillips, F. M.; Hudson, A. M.

2010-12-01

We calibrate the production rate of the cosmogenic nuclide beryllium-10 (10Be) at a low-latitude, high-elevation site, using nuclide concentrations measured in moraine boulders and an independent chronology determined with bracketing radiocarbon dates. The measurement of terrestrial cosmogenic nuclide (TCN) concentrations in earth surface materials has been an important development for understanding a host of earth surface processes. Uncertainty in cosmogenic nuclide production rates has hampered application of this method. Here, we contribute to the estimation of 10Be production rates by reporting both preliminary 10Be concentrations and independent radiocarbon dates from a low latitude, high elevation site. Our study site in the southeastern Peruvian Andes (~13.9°S, 70.9°W, 4850 m asl) is centered on a moraine set, known as the Huancané II moraines, that represents a ~4 km expansion of Quelccaya Ice Cap during late glacial time. At this location, organic material situated both stratigraphically below and above moraines in two adjacent valleys provide material for radiocarbon dating. Based on geomorphic arguments, we correlate results from the two valleys. The timing of ice cap margin advance is bracketed by 13 radiocarbon ages on organic material within the outermost Huancané II moraines that range from 13.6 to 12.5 ka. Two stratigraphic sections upvalley from the moraines yield 6 radiocarbon ages from 11.3 to 12.4 ka, indicating the time of retreat . We computed the probability density function that lies between these two sets of dates, and assign an age of 12.4 ka (+/-???) for the formation of the Huancané II moraines. Calculating beryllium-10 exposure dates from the measured concentrations yield exposure dates that significantly underestimate the independently determined age of the moraine (~8-30%), if existing production rate estimates are used. We suggest that the radiocarbon age for the moraines can be used as a robust independent calibration for 10Be

The accelerations of the earth and moon from early astronomical observations

NASA Technical Reports Server (NTRS)

Muller, P. M.; Stephenson, F. R.

1975-01-01

An investigation has compiled a very large amount of data on central or near central solar eclipses as recorded in four principal ancient sources (Greek and Roman classics, medieval European chronicles, Chinese annals and astronomical treatises, and Late Babylonian astronomical texts) and applied careful data selectivity criteria and statistical methods to obtain reliable dates, magnitudes, and places of observation of the events, and thereby made estimates of the earth acceleration and lunar acceleration. The basic conclusion is that the lunar acceleration and both tidal and nontidal earth accelerations have been essentially constant during the period from 1375 B.C. to the present.

Deglaciation and postglacial treeline fluctuation in the northern San Juan Mountains, Colorado

USGS Publications Warehouse

Carrara, Paul E.

2011-01-01

higher-than-present elevations by the early Holocene. A comparison of recently obtained accelerator mass spectrometry radiocarbon ages of coniferous wood fragments from Lake Emma, previously dated by conventional radiocarbon methods during the 1980s, led to a slight modification of previously published ages of Holocene treeline fluctuations. As early as 9,200 radiocarbon years before present (about 10,400 calendar years) and probably to about 5,400 radiocarbon years before present (about 6,200 calendar years), treeline was at least 80 meters higher than at present (about 3,660 meters). Furthermore, a large conifer fragment with a complacent annual ring record suggests that timberline may have been at least 140 meters higher than present (about 3,600 meters) about 8,000 radiocarbon years before present (about 8,900 calendar years). These past elevations of treeline and timberline suggest that growing-season temperatures were at least 0.5°-0.9°C warmer than at present. Deuterium data from the Lake Emma wood samples suggests that the maximum average temperature change from about 9,000 to 5,400 radiocarbon years before present (about 10,150 to 6,200 calendar years) was about 4°C. Owing to these warmer temperatures the summer monsoon circulation, which currently brings a large part of the annual precipitation to the San Juan Mountains, probably was more intense during the early and middle Holocene than it is today. Between about 5,400 and 3,500 radiocarbon years before present (about 6,200 and 3,770 calendar years) it appears that treeline was near its present-day limit. After 3,500 radiocarbon years before present (about 3,770 calendar years), evidence of treeline position is very sparse, suggesting that treeline lay at, or below, its present-day elevation. However, a spruce krummholz fragment from the Lake Emma site provided two radiocarbon ages of about 3,100 radiocarbon years before present (about 3,300 cal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jull, A.J.T.

Since 1981 we have operated an NSF Accelerator Mass Spectrometry (AMS) Facility at the University of Arizona. The AMS method allows us to use very small samples of carbon, <1 mg for radiocarbon dating in contrast to earlier counting techniques. This has opened a vast array of applications of radiocarbon dating that was difficult to do before AMS because of sample size limitations of decay counting. Some of the many applications of AMS include paleoclimatic studies, archaeological research and the age of first settlement of North America by man, dating of art works and artifacts, fall times and terrestrial residencemore » ages of meteorites, production of {sup 14}C in lunar samples by galactic and solar cosmic rays, studies of in situ {sup 14}C produced by cosmic ray spallation in rocks and ice, and studies of {sup 14}C in groundwater dissolved inorganic carbon and dissolved organic carbon. At our laboratory, we have also successfully applied AMS {sup 14}C to dating of many types of textiles, including silks and linens, art works, documents and artifacts fabricated from wood, parchment, ivory, and bone. The results for many of these samples are often important in questions of the authenticity of these works of art and artifacts. Our studies have encompassed a wide range of art works ranging from the Dead Sea Scrolls, the Shroud of Turin, and the Chinese silk trade to the works of Raphael, Rembrandt, and Picasso. Recently, we also dated the Vinland Map, a controversial document that shows the eastern coast of North America apparently using information from Viking voyages.« less

Luminescence dating of Holocene dune complexes along the shore of northern France (Picardy)

NASA Astrophysics Data System (ADS)

Lauer, Tobias; Frechen, Manfred; Meurisse-Fort, Murielle; Gosselin, Guillaume; van Vliet-Lanoë, Brigitte

2010-05-01

The Holocene dune and peat complexes along the shore of northern France (Picardy) had already been studied in detail by Meurisse et al. (2005) and Meurisse-Fort (2009). Information about the palaeodevelopment of those dune fields is hence given due to existing 14C data as well as by sedimentological and morphological analyses. Due to the results from radiocarbon dating, different types of aeolian bodies could be correlated along the Picardy coastline and a regional stratigraphic sequence could be established (Meurisse-Fort, 2009). The aim of the ongoing study is to get a higher chronological resolution for the different phases of dune activity in Picardy by luminescence dating what is a powerful tool to determine the time of last sunlight exposure of grains before burial (this information yields important information about dune movement). Samples for OSL dating were taken from dune bodies located in Tardinghen, Hardelot, Saint-Frieux and Saint-Gabriel. For dating, a single aliquot regenerative dose (SAR) protocol (Murray & Wintle 2003) is applied to coarse grained quartz. First tests concerning the signal intensity, the purity of the quartz OSL signal and the bleaching properties showed that quartz OSL dating works well for the dunes of the northern France coastline. The new luminescence ages will help to better unravel the phases of sand dune activity and stabilisation mainly controlled by climate changes and human impact. References: Meurisse, M., Van Vliet-Lanoë, B., Talon, B. & Recourt, P. (2005): Complexes dunaires et tourbeux holocènes du littoral du Nord de la France. - Geoscience, 337 : 675-684. Meurisse-Fort, M. (2009): Enregistrement haute résolution des massifs dunaires ; Manche, mer du Nord et Atlantique - Le rôle des tempêtes. Thèse de Doctorat soutenue en juin 2007, Université de Lille1. Coll. Recherches - Sciences (Sciences de la Terre). EPU-Publibook (ed.), Paris, 310 pp. Murray, A.S. & Wintle, A.G. (2003): The single aliquot regenerative

An evaluation of Mesodon and other larger terrestrial gastropod shells for dating late Holocene and historic alluvium in the Midwestern USA

USGS Publications Warehouse

Rakovan, Monica T.; Rech, Jason A.; Pigati, Jeffery S.; Nekola, Jeffery C.; Wiles, Gregory C.

2013-01-01

Understanding the history of stream erosion and changes in channel morphology is important for managing and restoring unstable streams. One of the significant challenges in this type of research is establishing accurate dating of late Holocene and historic alluvium. Here we evaluate the potential of using 14C dating and amino acid racemization (AAR) to date large terrestrial gastropod shells that are often preserved within alluvial sediments. Many terrestrial gastropods incorporate old carbon from limestone or other carbonate rocks into their shells and therefore are unsuitable for radiocarbon dating. Recent studies, however, have shown that some taxa avoid this ‘limestone problem’ and can yield reliable 14C ages. In this study, we measured the 14C activity of specimens for the genera Mesodon, Ventridens, and Allogona collected live and from alluvial sequences dated independently by dendrochronology, 14C dating of wood, and/or 137Cs analyses. Mesodon zaletus contained old carbon in similar concentrations (up to ~ 30%) found in previous studies of other large taxa and should be avoided for 14C dating when possible. In contrast, shells of Ventridens ligera and Allogona profunda showed minimal limestone effects and therefore may be suitable for dating late Holocene alluvium. These results highlight the importance of taxonomic identification of gastropod taxa prior to their use for 14C dating and demonstrate that shell fragments that are not identifiable should be avoided. We also measured d/l ratios (n = 17) of aspartic and glutamic acid from eight different taxa of terrestrial gastropods recovered from four late Holocene and historic stratigraphic sequences. Average d/l ratios of aspartic and glutamic acid from historic sediments < 300 years old are lower in shells from younger stratigraphic units, indicating that AAR can be used to differentiate between multiple historic stratigraphic units.

Comparison of Soil Organic Matter Dynamics at Four Temperate Deciduous Forests with Physical Fractionation and Radiocarbon Measurements

NASA Astrophysics Data System (ADS)

McFarlane, K. J.; Torn, M. S.; Hanson, P. J.; Swanston, C.; Guilderson, T. P.; Porras, R. C.

2009-12-01

Forest soils represent a significant pool for C sequestration and storage, but the factors controlling soil C cycling are not well constrained. We used density fractionation and radiocarbon measurements to assess differences in soil C cycling amongst four eastern deciduous forests that are part of the AmeriFlux Network and vary in climate, soil type, parent material, and soil ecology. We collected mineral soil from 0-5 cm and 5-15 cm depth at Harvard Forest (HAF) in central Massachusetts, Bartlett Experimental Forest (BEF) in New Hampshire, the University of Michigan Biological Station (UMBS), and Baskett Wildlife Recreation and Education Area in the Missouri Ozarks (MOZ). Deeper soil samples have been collected (to 75 cm in some cases) for future analysis. We fractionated soil samples by density into free light (unprotected SOM), occluded light (physically protected SOM), and dense (mineral-protected) fractions using sodium polytungstate (1.65 g ml-1), measured C concentration and radiocarbon in bulk soil and fractions, and used a three-pool steady-state model to determine radiocarbon-based turnover times for fractions. The northeastern sites, HAF and BEF, had higher bulk soil C (65 and 40 g C kg soil-1, respectively) than did MOZ or UMBS (20 and 10 g C kg soil-1). Bulk soil radiocarbon values (Δ14C) decreased with depth and were lower at northeastern sites than Midwestern sites (36, 8, 113, and 65 ‰ for 0-5 cm at HF, BEF, MOZ, and UMBS, respectively). Soil C distribution amongst fractions was similar at HAF, BEF, and MOZ with the unprotected free light fraction containing about 40% of bulk soil C for 0-5 cm and 20% of bulk soil C for 5-15 cm. At these three sites, the physically protected occluded light fraction contained about 10% of bulk soil C, with the mineral-protected dense fraction containing the remaining 50-70%. In contrast, UMBS, the site with the sandiest soil, had a greater portion of bulk soil C recovered in the unprotected free light fraction and

Accelerating Cogent Confabulation: An Exploration in the Architecture Design Space

DTIC Science & Technology

2008-06-01

DATES COVERED (From - To) 1-8 June 2008 4. TITLE AND SUBTITLE ACCELERATING COGENT CONFABULATION: AN EXPLORATION IN THE ARCHITECTURE DESIGN SPACE 5a...spiking neural networks is proposed in reference [8]. Reference [9] investigates the architecture design of a Brain-state-in-a-box model. The...Richard Linderman2, Thomas Renz2, Qing Wu1 Accelerating Cogent Confabulation: an Exploration in the Architecture Design Space POSTPRINT complexity

Capturing total chronological and spatial uncertainties in palaeo-ice sheet reconstructions: the DATED example

NASA Astrophysics Data System (ADS)

Hughes, Anna; Gyllencreutz, Richard; Mangerud, Jan; Svendsen, John Inge

2017-04-01

Glacial geologists generate empirical reconstructions of former ice-sheet dynamics by combining evidence from the preserved record of glacial landforms (e.g. end moraines, lineations) and sediments with chronological evidence (mainly numerical dates derived predominantly from radiocarbon, exposure and luminescence techniques). However the geomorphological and sedimentological footprints and chronological data are both incomplete records in both space and time, and all have multiple types of uncertainty associated with them. To understand ice sheets' response to climate we need numerical models of ice-sheet dynamics based on physical principles. To test and/or constrain such models, empirical reconstructions of past ice sheets that capture and acknowledge all uncertainties are required. In 2005 we started a project (Database of the Eurasian Deglaciation, DATED) to produce an empirical reconstruction of the evolution of the last Eurasian ice sheets, (including the British-Irish, Scandinavian and Svalbard-Barents-Kara Seas ice sheets) that is fully documented, specified in time, and includes uncertainty estimates. Over 5000 dates relevant to constraining ice build-up and retreat were assessed for reliability and used together with published ice-sheet margin positions based on glacial geomorphology to reconstruct time-slice maps of the ice sheets' extent. The DATED maps show synchronous ice margins with maximum-minimum uncertainty bounds for every 1000 years between 25-10 kyr ago. In the first version of results (DATED-1; Hughes et al. 2016) all uncertainties (both quantitative and qualitative, e.g. precision and accuracy of numerical dates, correlation of moraines, stratigraphic interpretations) were combined based on our best glaciological-geological assessment and expressed in terms of distance as a 'fuzzy' margin. Large uncertainties (>100 km) exist; predominantly across marine sectors and other locations where there are spatial gaps in the dating record (e.g. the

Source apportionment of elevated wintertime PAHs by compound-specific radiocarbon analysis

NASA Astrophysics Data System (ADS)

Sheesley, R. J.; Kruså, M.; Krecl, P.; Johansson, C.; Gustafsson, Ã.-.

2008-12-01

Natural abundance radiocarbon analysis facilitates distinct source apportionment between contemporary biomass/biofuel (14C "alive") versus fossil fuel (14C "dead") combustion. Here, the first compound-specific radiocarbon analysis (CSRA) of atmospheric polycylic aromatic hydrocarbons (PAHs) was demonstrated for a set of samples collected in Lycksele, Sweden a small town with frequent episodes of severe atmospheric pollution in the winter. Renewed interest in residential wood combustion means than this type of seasonal pollution is of increasing concern in many areas. Five individual/paired PAH isolates from three pooled fortnight-long filter collections were analyzed by CSRA: phenanthrene, fluoranthene, pyrene, benzo[b+k]fluoranthene and indeno[cd]pyrene plus benzo[ghi]perylene; phenanthrene was the only compound also analyzed in the gas phase. The measured Δ14C for PAHs spanned from -138.3‰ to 58.0‰. A simple isotopic mass balance model was applied to estimate the fraction biomass (fbiomass) contribution that was constrained to a range of 71% for indeno[cd]pyrene+benzo[ghi]perylene to 87% for the gas phase phenanthrene and particulate fluoranthene, respectively. Indeno[cd]pyrene plus benzo[ghi]perylene, known to be enhanced in gasoline-powered motor vehicle exhaust compared to diesel exhaust, had the lowest contribution of biomass combustion of the measured PAHs by 9%. The total organic carbon (TOC, defined as carbon remaining after removal of inorganic carbon) fbiomass was estimated to be 77%, which falls within the range for PAHs. This CSRA data of atmospheric PAHs demonstrate the non-uniformity of biomass combustion contribution to different PAHs even in a location with limited local emission sources and illustrates that regulatory efforts would not evenly reduce all PAHs.

Radiocarbon of Respired CO2 Following Fire in Alaskan Boreal Forest: Can Disturbance Release Old Soil Carbon to the Atmosphere?

NASA Astrophysics Data System (ADS)

Schuur, E. A.; Randerson, J. A.; Fessenden, J.; Trumbore, S. E.

2002-12-01

Fire in the boreal forest releases carbon stored in vegetation and soil to the atmosphere. Following fire, microbial decomposition is stimulated by inputs of plant detritus and changes in soil microclimate, which can result in large losses of carbon. Furthermore, warmer summer soil temperatures and deeper thaw depths in burned ecosystems may make carbon that was previously climatically protected by low soil temperatures susceptible to decomposition. We used radiocarbon measurements to estimate the age of carbon released by soil respiration following fire in two black spruce (Picea mariana) forests in interior Alaska that burned during the summer of 1999. To isolate soil respiration, we established manipulated plots where vegetation was prevented from recolonizing, and paired control plots in nearby unburned forest. Soil respiration radiocarbon signatures in the burned manipulation ranged from +112\\permil to +192\\permil and differed significantly from the unburned controls that ranged from +100\\permil to +130\\permil. Burned plots appear to respire older carbon than unburned forest, which could either be due to the stimulation of decomposition of intermediate age soil organic matter pools, to the lack of plant respiration that reflects the atmospheric radiocarbon signature of +92\\permil, or both. At least during the initial phase following fire, these data suggest that carbon fluxes from soil are dominated by soil organic matter pools with decadal scale turnover times.

Evaluation of amino-acid racemization/epimerization dating using radiocarbon-dated fossil land snails

NASA Astrophysics Data System (ADS)

Goodfriend, Glenn A.

1987-08-01

The relation between age and amino-acid epimer ratios (alloisoleucine/isoleucine, A/I) of Holocene land snails was quantitatively evaluated through 14C and amino-acid analysis of 33 samples from fluvial and colluvial sediments and rodent middens in the Northern Negev Desert of Israel. A/I is strongly correlated with 14C ages in fluvial and rodent midden deposits (r = 0.95 and 0.94, respectively), permitting age estimates from A/I ratios with precisions of ±700 and ±660 yr. The correlation is weaker in colluvial deposits (r = 0.74), and age estimates from A/I ratios are correspondingly less precise (±1580 yr). This probably results from delayed burial, which exposes the shells to intense radiation on the desert surface. Because of the generally strong relation between age and A/I, amino-acid epimerization analysis of individual shells can be used to identify mixed-age deposits and to reconstruct species chronologies from mixed-age deposits.

Changes in groundwater reserves and radiocarbon and chloride content due to a wet period intercalated in an arid climate sequence in a large unconfined aquifer

NASA Astrophysics Data System (ADS)

Custodio, E.; Jódar, J.; Herrera, C.; Custodio-Ayala, J.; Medina, A.

2018-01-01

The concentration of atmospheric tracers in groundwater samples collected from springs and deep wells is, in most cases, the result of a mixture of waters with a wide range of residence times in the ground. Such is the case of an unconfined aquifer recharged over all its surface area. Concentrations greatly differ from the homogeneous residence time case. Data interpretation relies on knowledge of the groundwater flow pattern. To study relatively large systems, the conservative ion chloride and the decaying radiocarbon (14C) are considered. Radiocarbon (14C) activity in groundwater, after correction to discount the non-biogenic contribution, is often taken as an indication of water age, while chloride can be used to quantify recharge. In both cases, the observed tracer content in groundwater is an average value over a wide range which is related to water renewal time in the ground. This is shown considering an unconfined aquifer recharged all over its area under arid conditions, in which a period of greater recharge happened some millennia ago. The mathematical solution is given. As the solution cannot be made general, to show and discuss the changes in water reserve and in chloride and radiocarbon concentration (apparent ages), two scenarios are worked out, which are loosely related to current conditions in Northern Chile. It is shown that tracer concentration and the estimated water age are not directly related to the time since recharge took place. The existence of a previous wetter-than-present period has an important and lasting effect on current aquifer water reserves and chloride concentration, although the effect on radiocarbon activity is less pronounced. Chloride concentrations are smaller than in current recharge and apparent 14C ages do not coincide with the timing, duration and characteristics of the wet period, except in the case in which recharge before and after the wet period is negligible and dead aquifer reserves are non-significant. The use of

Advanced Accelerator Development Strategy Report: DOE Advanced Accelerator Concepts Research Roadmap Workshop

DOE Office of Scientific and Technical Information (OSTI.GOV)

None, None

Over a full two day period, February 2–3, 2016, the Office of High Energy Physics convened a workshop in Gaithersburg, MD to seek community input on development of an Advanced Accelerator Concepts (AAC) research roadmap. The workshop was in response to a recommendation by the HEPAP Accelerator R&D Subpanel [1] [2] to “convene the university and laboratory proponents of advanced acceleration concepts to develop R&D roadmaps with a series of milestones and common down selection criteria towards the goal for constructing a multi-TeV e+e– collider” (the charge to the workshop can be found in Appendix A). During the workshop, proponentsmore » of laser-driven plasma wakefield acceleration (LWFA), particle-beam-driven plasma wakefield acceleration (PWFA), and dielectric wakefield acceleration (DWFA), along with a limited number of invited university and laboratory experts, presented and critically discussed individual concept roadmaps. The roadmap workshop was preceded by several preparatory workshops. The first day of the workshop featured presentation of three initial individual roadmaps with ample time for discussion. The individual roadmaps covered a time period extending until roughly 2040, with the end date assumed to be roughly appropriate for initial operation of a multi-TeV e+e– collider. The second day of the workshop comprised talks on synergies between the roadmaps and with global efforts, potential early applications, diagnostics needs, simulation needs, and beam issues and challenges related to a collider. During the last half of the day the roadmaps were revisited but with emphasis on the next five to ten years (as specifically requested in the charge) and on common challenges. The workshop concluded with critical and unanimous endorsement of the individual roadmaps and an extended discussion on the characteristics of the common challenges. (For the agenda and list of participants see Appendix B.)« less

High Energy Ion Acceleration by Extreme Laser Radiation Pressure