• 10Be Analyses with a Compact AMS Facility—Are BeF2 Samples the Solution?

      Wacker, L.; Grajcar, M.; Ivy-Ochs, S.; Kubik, PW; Suter, M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      The injection of 10BeFinstead of10BeOinto a compact accelerator mass spectrometry system with a terminal voltage of 0.58 MV was investigated, because BFmolecules are unstable and isobaric interference of 10B with 10Be can thus be significantly reduced. We describe the method we developed to prepare BeF2samples. 10Be was measured in a segmented gas ionization detector. Separation of 10Be from 10B could be achieved both for ions in the 1+ charge state with an energy of 0.8 MeV and in the 2+ charge state with an energy of 1.4 MeV. The 2+ ions are better separated, whereas the 1+ charge state has a higher transmission. 10Be/9Be ratios (approximately 10^-12) in a suite of rock samples were successfully determined for exposure dating in either charge state and compared with measurements made on the 6MV tandem.
    • 10Be, 14C Distribution, and Soil Production Rate in a Soil Profile of a Grassland Slope at Heshan Hilly Land, Guangdong

      Shen, C. D.; Beer, J.; Ivy-Ochs, S.; Sun, Y.; Yi, W.; Kubik, P. W.; Suter, M.; Li, Z.; Peng, S.; Yang, Y. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Concentrations of organic carbon, carbon isotopes (13C and 14C), atmospheric 10Be in soil, and in situ 10Be in bedrock and weathering rock were determined in a study of a profile of a grassland slope at the Heshan Hilly Land Interdisciplinary Experimental Station, Chinese Academy of Sciences, in Guangdong Province, China. A good linear relationship between depth and the 14C apparent age of the organic carbon demonstrates that the rock weathering process and the accumulation process of organic matter in the slope are relatively stable. Both 14C and 10Be results show that about 34% of soil in the grassland slope has been eroded during the past 3800 yr. The 10Be results for interstitial soil from weathered rocks show that the 90-cm-thick weathering rock layer above the bedrock has evolved over a period of 1.36 Myr. The concentrations of in situ 10Be in the weathered rock and bedrock are 10.7 X 10^4 atoms/g and 8.31 X 10^-4 atoms/g, respectively. The weathering rate of the bedrock, equivalent to the soil production rate, was estimated at 8.8 X 10^-4 cm/yr, and the exposure ages of the weathered rock and the bedrock were 72 kyr and 230 kyr, respectively.
    • 14C Dating Compared to Art Historical Dating of Roman and Coptic Textiles from Egypt

      Van Strydonck, Mark; De Moor, Antoine; Bénazeth, Dominique (Department of Geosciences, The University of Arizona, 2004-01-01)
      A representative selection of Roman and Coptic textiles is used to compare the radiocarbon dating results with the chronology proposed by art historians. In some cases, the comparison was made on individual objects, but in other cases, groups of stylistically and/or technologically related textiles were compared. In the case of the latter, the interquartile range was calculated. The results of this comparison show that some individual samples and groups are dated older than expected, while for another group the opposite is the case. One group was matching well with the presumed period as a whole, but not on the basis of the individual pieces. The analyses showed the necessity of 14C dating to obtain a more accurate dating of Coptic textiles.
    • 14C Dating of the Settlement of Iceland

      Sveinbjörnsdóttir, Arny E.; Heinemeier, Jan; Gudmundsson, Gardar (Department of Geosciences, The University of Arizona, 2004-01-01)
      The dating of the settlement of Iceland has been debated for many years. According to written sources (sagas) from the early 12th century, the first Norwegian settlers arrived in Iceland in AD 874. However, some 14C dates from the earliest archaeological sites in Iceland, invariably from samples of birch and other indigenous wood species, have yielded surprisingly old ages, older by 100-150 yr than the historical date, suggesting that the settlement took place in the 7th or 8th century. In this paper, we report 16 new 14C dates of pairs of barley grain and wood samples from an excavation in Reykjavík in 2001. The new results show that the wood samples tend to be older than the grain samples by up to about 100 yr. We argue that the barley grains give the true date (AD 890), whereas the wood dates are too old. The grain dates are in close agreement with the settlement year quoted in the written sources. In particular, our new data eliminate the need of any of the ad hoc theories introduced up to now to explain the suspiciously high 14C ages of wood samples from the settlement of Iceland, namely, 1) the island effect, 2) the volcanic or geothermal effect, or 3) that settlement actually took place significantly before the time recorded in the sagas.
    • A Novel Approach for Developing High-Resolution Sub-Fossil Peat Chronologies with 14C Dating

      Donders, T. H.; Wagner, F.; Van der Borg, K.; De Jong, A. F. M.; Visscher, H. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Sub-fossil sections from a Florida wetland were accelerator mass spectrometry (AMS) dated and the sedimentological conditions were determined. 14C data were calibrated using a combined wiggle-match and 14C bomb-pulse approach. Repeatable results were obtained providing accurate peat chronologies for the last 130 calendar yr. Assessment of the different errors involved led to age models with 3-5 yr precision. This allows direct calibration of paleoenvironmental proxies with meteorological data. The time frame in which 14C dating is commonly applied can possibly be extended to include the 20th century.
    • A Pretreatment Procedure for the AMS Radiocarbon Dating of Sub-Fossil Insect Remains

      Tripp, J. A.; Higham, T. F. G.; Hedges, R. E. M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Two pretreatment methods for accelerator mass spectrometry (AMS) dating of insect remains were explored. One method involves a simple acid wash that removes carbonate, while the other is based on the industrial purification of chitin and results in isolation of polymeric chitosan. No contamination is observed from Maillard reactions during the deacetylation reaction used to isolate the chitosan. The methods were tested on Coleoptera samples from two Roman Britain sites. Our results demonstrate that both methods produce acceptable AMS dates that correspond well to the expected age of the deposits from which they came.
    • A Puzzling Body from the River Thames in London

      Bayliss, Alex; Marshall, Peter; Sidell, Jane (Department of Geosciences, The University of Arizona, 2004-01-01)
      Radiocarbon measurements on a partially articulated female human skeleton, recovered from the foreshore of the river Thames in London, raised interesting questions of interpretation when the body did not produce the anticipated Neolithic date. A relatively recent 14C age and a strong marine component to the individuals diet, identified by stable isotope measurements, means that the date of death is difficult to estimate accurately, although the body probably does not constitute a forensic case.
    • A Review of the Evidence for Extinction Chronologies for Five Species of Upper Pleistocene Megafauna in Siberia

      Orlova, Lyobov A.; Kuzmin, Yaroslav V.; Dementiev, Vyacheslav N. (Department of Geosciences, The University of Arizona, 2004-01-01)
      A review of the radiocarbon chronology of some late Upper Pleistocene mammals from Siberia is presented. Previously published data has been supplemented by new 14C dates for 5 species (woolly mammoth, woolly rhinoceros, bison, horse, and muskox) to reconstruct chronological extinction patterns. The final extinction of woolly rhinoceros and bison in Siberia can be dated to approximately 11,000-9700 BP, but some megafaunal species (woolly mammoth, horse, and muskox) survived into the Late Holocene, about 3700-2200 BP.
    • Ages of Ostracodes from Pleistocene Lake Sediments of the Western Great Basin, USA—Results of Progressive Acid Leaching

      Hajdas, Irka; Bonani, Georges; Zimmerman, Susan Herrgesell; Mendelson, Millie; Hemming, Sidney (Department of Geosciences, The University of Arizona, 2004-01-01)
      Progressive dissolution experiments were performed on samples of ostracode shells from lacustrine sediments from the western Great Basin to remove contamination of the surface by secondary calcite. The observed age differences between the external and residual fractions were as great as 2000 to 6000 yr. A "plateau" in ages of the last fractions was obtained only for 1 sample; however, results of repeated experiments resulted in very good agreement of the final ages. A comparison with previously published chronologies based on bulk radiocarbon ages of ostracodes from Wilson Creek (Benson et al. 1990) shows that leaching is imperative for dating samples older than 20 ka BP. This study focuses on the problem of contamination and its removal. However, the final chronology of the Wilson Creek Formation (and other late Pleistocene lacustrine sediments) will require additional dating of other sections as well as establishment of a reservoir effect correction.
    • AMS 14C Dating of Iron Artifacts: Development and Application

      Enami, Hiroki; Nakamura, Toshio; Yamada, Tetsuyo; Tsukamoto, Toshio; Oda, Hirotaka (Department of Geosciences, The University of Arizona, 2004-01-01)
      We have developed a prototype carbon extraction system for accelerator mass spectrometry (AMS) radiocarbon dating of archaeological iron remains by combusting them with a RF induction furnace. We have also successfully tested and used a method of carbon extraction from iron using a CuCl2 solution. Modifications to our carbon extraction systems and methods provide us acceptable performances; carbon yield is normally around 80% and the 14C background level is as low as 42-48 ka BP in 14C apparent age. We have also conducted an iron refining experiment to examine the sources for carbon 14C age derived from iron, using established AMS 14C dating and carbon extraction systems. Our refining experiment was conducted on iron slag, which are by-products formed during iron smelting methods in the 7th century AD, and using modern charcoal as fuel. The aim of the experiment was to determine whether original carbon characteristics in the original iron materials would be preserved, or if the carbon signature would be replaced to some degree by the modern charcoal. AMS 14C measurements on the refined iron yielded 14C ages equivalent to those of the modern charcoal fuel. The result indicates that the original carbon signatures in the iron slag from 7th century production was replaced completely by modern carbon used in our experiment. The experiment confirms the assumption that 14C ages on iron products are associated with the fuel source of the iron smelting or refining process. We also report on the dating of iron slag materials excavated from the Gennaitouge iron smelting site, where 14C dates were consistent with the age of the site estimated by archaeological evidence.
    • AMS 14C Dating Using Black Pottery and Fiber Pottery

      Mihara, Shozo; Miyamoto, Kazuo; Ogawa, Hidefumi; Kurosaka, Teiji; Nakamura, Toshio; Koike, Hiroko (Department of Geosciences, The University of Arizona, 2004-01-01)
      A technique of accelerator mass spectrometry (AMS) has made it possible to directly measure radiocarbon ages of pottery by isolating organic materials sealed in the pottery when the pottery was formed. We analyzed the carbon contents and 14C ages for black pottery from the Philippines and fiber pottery from Japan using the relevant carbonaceous materials extracted from the pottery samples, i.e., adhered chaff or grass fibers that were incorporated in the pottery matrix, respectively. The carbon yield of the pottery sample varied largely depending on the pottery types, the preservation conditions, as well as the chemical pretreatment methods to purify carbonaceous materials for 14C dating. We will discuss criteria for sample selection of well-preserved pottery, and a modified method, instead of the standard alkali treatment, to obtain sufficient material for precise 14C dating.
    • Anomalous Radiocarbon Dates from Easter Island

      Butler, Kevin; Prior, Christine A.; Flenley, John R. (Department of Geosciences, The University of Arizona, 2004-01-01)
      The largest volcanic crater on Easter Island in the South Pacific contains a lake 1 km in diameter with large floating mats of vegetation, mainly Scirpus californicus. A core taken through a mat near the center produced anomalous dates, with older dates above younger ones. The possibility that the mat had become inverted was considered, but palynological evidence refutes this idea because it shows a progressive upward decline of forest pollen, which is well known from other swamp cores on the island. A new series of radiocarbon dates made directly on pollen concentrates was obtained. These dates also produced inconsistencies, particularly when pollen concentrate ages were compared with 14C ages on plant fragments from the same depth. This series of 14C ages seems to indicate that both old and young organic components in the sediment are deposited contiguously and that the depositional history of these cores is more complex than previously known. Previous age determinations on bulk sediments from Easter Island, which also show anomalous dates, may be too simplistic. This paper provides a warning to other researchers dating sediments from Easter Island. We suggest that sample selection and dating procedures be carefully considered for these sediments.
    • Calculating Sediment Compaction for Radiocarbon Dating of Intertidal Sediments

      Bird, M. I.; Fifield, L. K.; Chua, S.; Goh, B. (Department of Geosciences, The University of Arizona, 2004-01-01)
      This study estimates the maximum and minimum degrees of autocompaction for radiocarbon-dated Holocene mangrove sediments in Singapore, in order to correct apparent sediment accretion rates for the effects of sediment compression due to autocompaction. Relationships developed for a suite of modern (surface) sediment samples between bulk density, particle-size distribution, and organic matter content were used to estimate the initial (uncompacted) bulk density of buried and variably compressed Holocene sediments, based on the grain-size distribution and organic matter content of the sediment. The difference between measured (compacted) and initial (uncompacted) bulk density of each buried sediment interval can be interpreted as the amount of length shortening experienced by each interval since burial. This allows the elevation of samples selected for 14C dating to be corrected for the effects of autocompaction of the underlying sediment sequence, so that accurate estimates of vertical sediment accretion rates can be calculated. The 3 Holocene mangrove sequences analyzed and dated for this study ranged in age from 2000 to 8500 cal BP. The effects of autocompaction are significant, even in comparatively thin sequences, with subsidence of up to 56 cm calculated for carbon-dated samples presently 2 m above incompressible basement. The vertical sediment accretion rates for these mangrove sequences ranged from 0.99 to 6.84 mm/yr and carbon sequestration rates ranged from 0.9 to 1.7 t/ha/yr, all within the range observed for comparable Holocene and modern mangrove sediments elsewhere.
    • Capabilities of the New SUERC 5MV AMS Facility for 14C Dating

      Xu, S.; Anderson, R.; Bryant, C.; Cook, G. T.; Dougans, A.; Freeman, S.; Naysmith, P.; Schnabel, C.; Scott, E. M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      A new National Electrostatic Corporation (NEC) 5MV accelerator mass spectrometer became operational at the Scottish Universities Environmental Research Centre (SUERC) in July 2002. It has 2 Cs sputter negative ion sources: a 134-sample source (S1) for the routine measurement of all species, and a hybrid source (S2) with 40 spaces for radiocarbon measurements with either graphite or CO2 samples. A number of performance tests on graphite samples have been carried out on both sources. A precision of better than 0.3% is feasible for modern samples on a routine basis. The 14C background of the machine and the graphite preparation process blank are 0.04 +/0.01 and 0.16 +/0.05 pMC, respectively, indicating that 14C dating back to approximately 50 kyr BP is possible. The normalized 14C values for a series of reference materials agree well with the IAEA, TIRI, and FIRI consensus values. Routine measurement of 14C has been underway since May 2003. Preliminary results of performance tests on the CO2 gas ion source are also reported.
    • Chronological Studies of the Arzhan-2 Scythian Monument in Tuva (Russia)

      Chugunov, K. V.; Dergachev, V. A.; Nagler, A.; Parzinger, G.; Scott, E. M.; Sementsov, A. A.; Vasiliev, S.; van Geel, B.; van der Plicht, J.; Lebedeva, L. M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      The first radiocarbon dates from the unique early Scythian monument Arzhan-2, discovered in 2001, are presented. The monument contained a royal burial (grave nr 5). Unfortunately, precise dating is hampered by the Hallstatt plateau in the calibration curve. However, using both accelerator mass spectrometry measurements from buried materials and conventional dates for floating tree rings from the burial chamber, we were able to date the construction of the monument to the 7th century BC. This is consistent with archaeological expectations. Other graves located inside the barrow were also dated. Grave nr 11, located on the edge of the barrow, is younger, showing that the monument was a place of burial ritual for many years for this ancient population.
    • Chronology and Possible Links between Climatic and Cultural Change During the First Millennium BC in Southern Siberia and Central Asia

      Zaitseva, G. I.; van Geel, B.; Bokovenko, N. A.; Chugunov, K. V.; Dergahev, V. A.; Dirksen, V. G.; Koulkova, M. A.; Nagler, A.; Parzinger, G.; van der Plicht, J.; et al. (Department of Geosciences, The University of Arizona, 2004-01-01)
      We reconstructed climate change during the second half of the Holocene for the Minusinsk (southern Siberia) and the Uyuk (Central Asia) valleys in the Eurasian steppe zone. Sediment cores from 2 lakes and a soil profile from the Arzhan-2 burial mount were investigated. We combined pollen and geochemical analyses and radiocarbon dating with the archaeological record. A sharp increase of human population density occurred at the transition from the Bronze Age to Iron Age (about 2700 cal BP). The most representative Scythian culture started in the Uyuk and the Minusinsk valleys after increased humidity and occupation capacity of the steppe zone during the 9th century BC.
    • Chronology of Prehistoric Cultural Complexes of Sakhalin Island (Russian Far East)

      Kuzmin, Yaroslav V.; Vasilevski, Alexander A.; Gorbunov, Sergei V.; Burr, G. S.; Jull, A. J. Timothy; Orlova, Lyobov A.; Shubina, Olga A. (Department of Geosciences, The University of Arizona, 2004-01-01)
      A chronological framework for the prehistoric cultural complexes of Sakhalin Island is presented based on 160 radiocarbon dates from 74 sites. The earliest 14C-dated site, Ogonki 5, corresponds to the Upper Paleolithic, about 19,500-17,800 BP. According to the 14C data, since about 8800 BP, there is a continuous sequence of Neolithic, Early Iron Age, and Medieval complexes. The Neolithic existed during approximately 8800-2800 BP. Transitional Neolithic-Early Iron Age complexes are dated to about 2800-2300 BP. The Early Iron Age may be dated to about 2500-1300 BP. The Middle Ages period is dated to approximately 1300-300 BP (VII-XVII centuries AD).
    • Chronology of the Beginning of Pottery Manufacture in East Asia

      Keally, Charles T.; Taniguchi, Yasuhiro; Kuzmin, Yaroslav V.; Shewkomud, Igor Y. (Department of Geosciences, The University of Arizona, 2004-01-01)
      This paper presents an updated radiocarbon chronology of the earliest pottery sites in the Old World. Ceramic production originated in the Late Glacial period in several regions of East Asiathe Japanese Islands, the Russian Far East, and southern Chinaat approximately the same time, about 13,70013,300 BP (about 17,20014,900 cal BP).
    • Complexity of Soil Organic Matter: AMS 14C Analysis of Soil Lipid Fractions and Individual Compounds

      Rethemeyer, Janet; Kramer, Christiane; Gleixner, Gerd; Wiesenberg, Guido L. B.; Schwark, Lorenz; Andersen, Nils; Nadeau, Marie-J.; Grootes, Pieter M. (Department of Geosciences, The University of Arizona, 2004-01-01)
      Radiocarbon measurements of different lipid fractions and individual compounds, isolated from soil samples collected on 2 different agricultural long-term study sites, located in the rural area of Rotthalmunster (Germany) and in the city of Halle/Saale (Germany), were analyzed to obtain information about sources and the stability of soil organic matter (SOM). Different lipid compound classes were isolated by automated solvent extraction and subsequent medium-pressure liquid chromatography. Generally, 14C contents of lipid compound classes from topsoil samples of maize plots at Rotthalmünster are close to the modern atmospheric 14C content. Lower 14C values of aliphatic and aromatic hydrocarbons isolated from neutral lipids suggest a contribution of old carbon to these fractions. In contrast, 14C values of bulk soil (52 pMC) as well as isolated lipid classes from Halle are highly depleted. This can be attributed to a significant contribution of fossil carbon at this site. Extremely low 14C contents of aromatic (7 pMC) and aliphatic hydrocarbons (19 pMC) reflect the admixture of fossil hydrocarbons at the Halle site. Individual phospholipid fatty acids (PLFA), which are used as a proxy for viable microbial biomass, were isolated by preparative capillary gas chromatography (PCGC) from topsoils at Rotthalmünster and Halle. PLFA 14C values are close to atmospheric 14C values and, thus, indicate a clear microbial preference for relatively young SOM. At Rotthalmünster, the 14C concentration of short-chain unsaturated PLFAs is not significantly different from that of the atmosphere, while the saturated PLFAs show a contribution of sub-recent SOM extending over the last decades. At Halle, up to 14% fossil carbon is incorporated in PLFAs n-C17:0 and cy-C18:0, which suggests the use of fossil carbon by soil microorganisms. Moreover, it can be concluded that the 14C age of soil carbon is not indicative of its stability.
    • Conference Participants

      Department of Geosciences, The University of Arizona, 2004-01-01