• Balance and Behavior of Carbon Dioxide at an Urban Forest Inferred from the Isotopic and Meteorological Approaches

      Takahashi, Hiroshi Aoki; Hiyama, Tetsuya; Konohira, Eiichi; Takahashi, Atsuhiro; Yoshida, Naohiro; Nakamura, Toshio (Department of Geosciences, The University of Arizona, 2001-01-01)
      Diurnal variations in δ14C, delta-13C and the concentration of atmospheric carbon dioxide in an urban forest were measured on 9 February 1999 to discriminate and quantify contributions from different CO2 sources. The biogenic CO2 concentration remained relatively constant throughout the day. However, anthropogenic CO2 concentration fluctuated with the atmospheric CO2 concentration, and seemed to be controlled by wind velocity and the amount of exhaust gases from fossil fuel burning. The vertical profiles of anthropogenic, biogenic, and total CO2 showed a constant concentration within forest during daytime because of the large vertical CO2 influx, strong winds, and neutral atmospheric condition. The biogenic contribution at night decreased from the forest floor upwards with a smooth gradient, while the anthropogenic contribution showed a direct mirror because of the location of respective CO2 sources—the vertical gradient of wind velocity and the horizontal CO2 supply
    • Bomb Carbon as a Tracer of Dietary Carbon Sources in Omnivorous Mammals

      Beavan-Athfield, Nancy; Sparks, Rodger J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We have isolated amino acid groups from modern bone hydrolysates and compared their relative ∆14C value to assess the carbon contribution of diet to the overall radiocarbon signal in bone. We find that both essential and non-essential amino acids may produce widely varying 14C, relative to other amino acid groups in the hydrolysate and to the original whole bone protein. We hypothesize that the 14C variations in non-essential amino acids may be due to metabolic effects that utilize essential amino acid carbon skeletons in the creation of non-essential amino acids.
    • Bomb Radiocarbon Dating of Animal Tissues and Hair

      Geyh, Mebus A. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Initially, radiocarbon dating by bomb 14C was used to check vintages of wine and whisky and to estimate the turnover times of carbon in various biological tissues. However, this technique has never been widely used for routine dating, although it has a wide field of application in geriatric medicine and forensic investigations. Fifteen years’ experience in this field has shown the potential and limits of this technique. Taking into account the decisive biological factors, such as growth and aging, a complicated picture is obtained. Recent human bones cannot be dated with a constant precision. Despite an incomplete understanding of the process of incorporation of 14C into human bones, the present dating technique is still more precise than most estimates by geriatric experts, for conventional 14C dating follows that 14C dates of bone collagen represent the years of the termination of puberty rather than those of death. Another application is the identification of furs of illegally hunted animals on the “Red List of threatened species” of the World Conservation Union (IUCN). For court cases, the year the animals were killed must be precisely determined. Due to the long and variable turnover time of more than one year of leather hair is the best dating material for animals
    • Calibration of Lacustrine Sediment Ages Using the Relationship between 14C Levels in Lake Waters and in the Atmosphere: The Case of Lake Kinneret

      Stiller, Mariana; Kaufman, Aaron; Carmi, Israel; Mintz, Genia (Department of Geosciences, The University of Arizona, 2001-01-01)
      The source of endogenic organic and inorganic carbon in lacustrine sediments is the dissolved inorganic carbon (DIC) in the lake water. The relation between the radiocarbon levels of DIC in Lake Kinneret and of CO2 in the atmosphere has been investigated. The ratio of the former to the latter was found to be 0.814 +/0.013. This ratio is used for calibrating the age of the sediment according to the natural fluctuations in the atmospheric levels of 14C that occurred during the past 10,000 years.
    • Can We Use Cosmogenic Isotopes to Date Stone Artifacts?

      Ivy-Ochs, Susan; Wüst, Raphael; Kubik, Peter W.; Müller-Beck, Hansjürgen; Schlüchter, Christian (Department of Geosciences, The University of Arizona, 2001-01-01)
      Two chert artifacts from the region near Luxor, Egypt have yielded concentrations of cosmogenic 10Be that allow calculation of nominal exposure ages of 326,000 and 304,000 years. Both artifacts are flakes that were collected atop limestone benches of the Eocene Thebes Formation which form cliffs along the west side of the Nile. The site is at elevation 240 m and is about 15 km from the Nile. Tools associated with these artifacts can be attributed to the Late Acheulean or early Middle Paleolithic (the transition has been suggested to have been on the order of 250,000-300,000 years ago). This area, where abundant chert nodules have weathered out, has been a collection, extraction, and fabrication site since the Early Paleolithic (since at least 400,000 years ago). Surface exposure dating records all periods of exposure. That means these ages represent composite ages, comprised of exposures both before and after working. But what fraction of the 10Be concentration we have measured was acquired before the flakes were produced? Here we propose several approaches to deconvolute the different exposure periods and better approximate the real age of the artifacts. As there is no a priori reason that the two ages should agree with the typological ages of the artifacts, nor for the two independent ages to agree, these first results are especially exciting and intriguing.
    • Changes of 14C Concentration in Modern Trees from Upper Silesia Region, Poland

      Rakowski, Andrzej Z.; Pawelczyk, Slawomica; Pazdur, Anna (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon concentration measurements in tree rings from Upper Silesia indicate significantly lower 14C concentration as compared to the concentrations occurring in “clean air” areas. This phenomenon is known as the Suess effect and is caused by contamination with inactive carbon that originates from fossil fuels combustion. This effect is observed in large urban and industrial areas. Samples for the measurements presented in the paper were collected in some of the largest cities in Upper Silesia: Gliwice, Ruda Śląska, and Chorzów. The samples were annual tree rings (Populus nigra, Pinus silvestris) covering years 1965–1992 and the atmospheric CO2 collected weekly between December 1994 and December 1995.
    • Chronology of Soil Evolution and Climatic Changes in the Dry Steppe Zone of the Northern Caucasus, Russia, During the 3rd Millennium BC

      Alexandrovskiy, A. L.; van der Plicht, J.; Belinsky, A. B.; Khokhlova, O. S. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Chrono-sequences of paleosols buried under different mounds of the large Ipatovo Kurgan, constructed during the Bronze age, have been studied to reconstruct climatic changes in the dry steppe zone of the Northern Caucasus, Russia. Abrupt climatic and environmental changes in the third millennium BC have been reconstructed, using morphological and analytical data of the soil. Based on accelerator mass spectrometry (AMS) dates of small charcoal fragments from the soil chrono-sequence, we concluded that two upper paleosols (with the clearest evidence of arid pedogenesis) developed between about 2600-2450 BC.
    • Chronology of the Atmospheric Mercury in Lagoa da Pata Basin, Upper Rio Negro Region of Brazilian Amazon

      Santos, G. M.; Cordeiro, R. C.; Silva Filho, E. V.; Turcq, B.; Lacerda, L. D.; Fifield, L. K.; Gomes, P. R. S.; Hausladen, P. A.; Sifeddine, A.; Albuquerque, A. L. S. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We present prehistoric mercury accumulation rates in a dated sediment core from Lagoa da Pata, a remote lake in Sao Gabriel da Cachoeira, northern Amazon. The sediment samples were subdivided for mercury and radiocarbon analyses. A group of 18 samples have been prepared at ANU for 14C dating by accelerator mass spectrometry (AMS). The dating results show a good correlation with depth in the core, down to 41,500 BP. Three distinct sections are clearly identified in the core. They consist of upper and lower organic-rich layer, separated by an inorganic layer which represents a short period of rapid accumulation around 18 ka BP. The mercury accumulation rate is found to be larger in the upper layer (18 ka to present) than in the lower one (41 ka to 25 ka), by a factor of three. The larger accumulation rate of mercury is probably associated with warmer temperatures and a higher frequency of forest fires during the Holocene.
    • Compound-Specific Radiocarbon Ages of Fatty Acids in Marine Sediments from the Western North Pacific

      Uchida, Masao; Shibata, Yasuyuki; Kawamura, Kimitaka; Kumamoto, Yuichiro; Yoneda, Minoru; Okhushi, Ken Ichi; Harada, Naomi; Hirota, Masashi; Mukai, Hitoshi; Tanaka, Atsushi; et al. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Compound-specific radiocarbon analysis of five fatty-acid biomarkers was conducted for marine sediments collected from the western North Pacific. The fatty acids (C12 to C3 4) showed a typical bimodal distribution pattern with two maxima at C16 and C26. Their carbon isotopic compositions ranged from -25.1 per mil (C16) to -31.8 per mil (C28), suggesting that they derived from terrestrial higher plants and marine organisms. A large variations of 14C ages were found among the fatty acids detected in the same sedimentary horizon of the core, ranging from 530 BP (C18) to 3250 BP (C28). The results of 14C analysis of fatty acids could be divided into two groups, i.e., lower molecular weight (LMW) fatty acids (C16, C18) derived from marine organisms and higher molecular weight (HMW) fatty acids (C24, C26, C28) derived from terrestrial higher plants. The HMW fatty acids showed older ages, ranging from 2550 BP (C24) to 3250 BP (C28), than LMW fatty acids (530 BP [C18] to 1,820 years BP [C16]). On the other hand, bulk-phase total organic matter (TOM) showed the age of 2260 BP that is between those two groups, suggesting that it was likely a mixture of organic matter derived from marine and terrestrial sources. The compound specific 14C ages and delta-13C data of sedimentary fatty acids presented here could provide useful information to decipher the fate and transport process of terrestrial organic matter to marine sediments.
    • Coral Reef Evolution at the Leeward Side of Ishigaki Island, Southwest Japan

      Yamano, Hiroya; Abe, Osamu; Kitagawa, Hiroyuki; Niu, Etsuko; Nakamura, Toshio (Department of Geosciences, The University of Arizona, 2001-01-01)
      In comparison with windward coral reefs, the facies and evolution of leeward coral reefs has been discussed to a lesser extent. By accelerator mass spectrometry (AMS) carbon-14 dating of coral specimens collected from the trench excavated across a modern coral reef during a fishery port repair, we revealed the internal facies and Holocene evolution of a leeward reef in Ishigaki Island, Ryukyu Island, southwest Japan. The reef facies can be split into three facies: the tabular Acropora reworked facies first formed a ridge by 3500 BP. Then, the tabular Acropora framework facies grew both upward and seaward. The accumulation rates of the tabular Acropora framework facies ranged from 2.2 to 8.3 m/ka. Thus, the reef framework facies and accumulation rates of this leeward reef is similar to those of windward reefs, although the age of the reef top is younger than that of windward reefs.
    • Dating of Ancient Icons from Kiev Art Collections

      Kovalyukh, N.; van der Plicht, J.; Possnert, G.; Skripkin, V.; Chlenova, L. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Icon painting in the Ukraine is rooted in the Byzantine culture, after the conversion to the Christian religion. During the medieval epoch, Kiev became the artistic center for highly skilled icon painters. The icons were painted on woodenboards, specially made for this purpose. Historic dating of some even well-known icons is uncertain or not precise. Here we present for the first time radiocarbon dates for selected icons. Both liquid scintillation counting (LSC) and accelerator mass spectrometry (AMS) dating methods were applied, allowing intercomparison.
    • Dating of Biodeposits of Oxalates at the Arc de Berà in Tarragona, Spain

      Girbal, J.; Prada, J. L.; Rocabayera, R.; Argemi, M. (Department of Geosciences, The University of Arizona, 2001-01-01)
      This research stems from an earlier study of the lichen covering with oxalate deposits at the Arc de Berà monument. The initial objective of dating these biodeposits opened up other questions concerning the structure of these deposits and how they were formed. Some dating results gave an absolute age greater than the monument itself, which posed various hypotheses on the possible ageing mechanisms.
    • Development of Accurate and Reliable 14C Chronologies for Loess Deposits: Application to the Loess Sequence of Nussloch (Rhine Valley, Germany)

      Hatté, Christine; Pessenda, Luiz Carlos; Lang, Andreas; Paterne, Martine (Department of Geosciences, The University of Arizona, 2001-01-01)
      Due to very high accumulation rates, loess sequences are best suited archives for the continental paleoclimate of glacial periods. Accurate chronologies cannot be easily established by radiocarbon-dating, because of the lack of organic macrorests, the only material for reliable 14C dating so far. A chemical protocol is reported to extract the organic matter of loess (organic carbon content lower than 0.1% by weight) for accelerator mass spectrometry (AMS) 14C dating. Sediments were taken from the loess sequence of Nussloch, for which a large dataset of luminescence ages (TL, IRSL/OSL) is available. The 14C chronology of the organic matter extracted from loess is in good agreement with the corresponding luminescence ages. It allows high resolution correlations with climatic proxy signals (magnetic susceptibility, malacological assemblages, delta-13C on organic matter, etc.) derived from the loess sequence and global environmental proxy records.
    • Distribution of 14C and 13C in Forest Soils of the Dinghushan Biosphere Reserve

      Shen, Chengde; Yi, Weixi; Sun, Yanmin; Xing, Changping; Yang, Ying; Yuan, Chao; Li, Zhian; Peng, Shaolin; An, Zhisheng; Liu, Tungsheng (Department of Geosciences, The University of Arizona, 2001-01-01)
      We report here first results on the bulk soil organic carbon (SOC), apparent radiocarbon ages and delta-13C characteristics of the tropical and subtropical forest soil in Dinghushan Biosphere Reserve (DHSBR). The forest oxisolin Dinghushan has developed during the Holocene. The delta-13C variation curves in all three profiles may be divided into two sections. The upper section from 0 to 40 cm has delta-13C values varying from -27.4 to -24.1‰, -27.5 to -22.2‰, and -24.4 to -20.1‰ in the Wukesong, Qingyunsi and Kengkou profiles, respectively. The lower section, including the 40-160 cm horizons, has a uniform delta-13C. The mean delta-13C values of the soil organic carbon could be used not only to discriminate between C3 and C4 plants, but also to distinguish between coniferous and broad-leaf plants.
    • Distribution of Radiocarbon in the Southwestern North Pacific

      Aramaki, T.; Mizushima, T.; Kuji, T.; Povinec, P. P.; Togawa, O. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon measurements in seawater samples taken at six stations in the southwestern North Pacific visited during the International Atomic Energy Agency (IAEA) 1997 Pacific Ocean Expedition were carried out at the accelerator mass spectrometry (AMS) facility of the Japan Atomic Energy Research Institute (JAERI). Three stations were located close to GEOSECS stations, and three were in the vicinity of Bikini and Enewetak Atolls, which may be influenced by former nuclear weapons testing. Compared with the GEOSECS data (1973), our results show an increase of 14C in intermediate waters. Furthermore, it is estimated that bomb-produced 14C inventories in the water column have increased by more than 20% during the last 24 years. However, vertical profiles of ∆14C at the stations near Bikini and Enewetak Atolls show a similar general trend to those found in other stations.
    • Editorial Board

      Department of Geosciences, The University of Arizona, 2001-01-01
    • Environmental and Climatic Change as Recorded in Geological Sediments from the Arid to Semi-Arid Zone of China

      Zhou, Weijian; Zhengkun, Wu; Jull, A. J. T.; Burr, G.; Donahue, D. D.; Baosheng, Li; Head, J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Stratigraphic investigations together with climatic proxy data measurements and reliable radiocarbon dating show a history of fluctuations of dry and wet environmental conditions in the arid to semi-arid zone of northern China since the late Pleistocene. Based on these data, we are able to reconstruct shifts of the desert margin in two period extremes, the last glacial maximum (21-15 ka) and the Holocene Optimum (9-5 ka). We have compared the present desert margin with that for the two extremes. The results indicate that a southward shift of the present margin of about 3 degrees in latitude might be caused by anthropogenic impact. Hence the influence of human activity must be taken into consideration for sustainable development and environment protection. Future research will be to find a two-way feedback existing between climate and anthropogenic impacts.
    • Further Attempts at Dating the Palynological Sequence of the Hula L07 Core, Upper Jordan Valley, Israel

      Weinstein, Evron M.; Vogel, J. C.; Kronfeld, J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      The palynological sequence of the Hula L07 core was previously correlated with the global oxygen isotope stages 3-5, based on a radiocarbon age determination and comparison with other Levantine paleoclimatological curves. An attempt was made to validate this correlation with Th/U dating. Unlike typical European peat, which is acidic, the soil pH of the Hula peat is mildly basic. Not only does this contribute to the oxidation of palynomorphs, but it also helps to preserve the carbonate material that can be a variable mixture of allogenic, endogenic, and authigenic components. Each component may represent a different degree of uranium series disequilibrium. The thorium (232Th) concentrations of the carbonate are low. Total digestion or acid leach of the sample may not always enable the proper correction for initial thorium. The dating derived from a NaOH-extraction of the organic material, while giving apparently better ages, also suffers from the presence of the carbonate admixture. It appears that, while 14C dating can be considered suitable for the younger portions of the core, techniques based upon the U-series may not be as efficacious in dating this important record of climatic change.
    • High-Resolution AMS 14C Dating of Post-Bomb Peat Archives of Atmospheric Pollutants

      Goodsite, Michael E.; Rom, Werner; Heinemeier, Jan; Lange, Todd; Ooi, Suat; Appleby, Peter G.; Shotyk, William; van der Knapp, W. O.; Lohse, Christian; Hansen, Torben S. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Peat deposits in Greenland and Denmark were investigated to show that high-resolution dating of these archives of atmospheric deposition can be provided for the last 50 years by radiocarbon dating using the atmospheric bomb pulse. 14C was determined in macrofossils from sequential one cm slices using accelerator mass spectrometry (AMS). Values were calibrated with a general-purpose curve derived from annually averaged atmospheric 14CO2 values in the northernmost northern hemisphere (NNH, 30 degrees to 90 degrees N). We present a through review of 14C bomb-pulse data from the NNH including our own measurements made in tree rings and seeds from Arizona as well as other previously published data. We show that our general-purpose calibration curve is valid for the whole NNH producing accurate dates within 1-2 years. In consequence, 14C AMS can precisely date individual points in recent peat deposits within the range of the bomb-pulse (from the mid-1950s on). Comparing the 14C AMS results with the customary dating method for recent peat profiles by 210Pb, we show that the use of 137Cs to validate and correct 210Pb dates proves to be more problematic than previously supposed. As a unique example of our technique, we show how this chronometer can be applied to identify temporal changes in Hg concentrations from Danish and Greenland peat cores.
    • In-Situ Cosmogenic 14C: Production and Examples of its Unique Applications in Studies of Terrestrial and Extraterrestrial Processes

      Lal, D.; Jull, A. J. T. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Nuclear interactions of cosmic rays produce a number of stable and radioactive isotopes on the earth (Lal and Peters 1967). Two of these, 14C and 10Be, find applications as tracers in a wide variety of earth science problems by virtue of their special combination of attributes: 1) their source functions, 2) their half-lives, and 3) their chemical properties. The radioisotope, 14C (half-life = 5730 yr) produced in the earth's atmosphere was the first to be discovered (Anderson et al. 1947; Libby 1952). The next longer-lived isotope, also produced in the earth's atmosphere, 10Be (half-life = 1.5 myr) was discovered independently by two groups within a decade (Arnold 1956; Goel et al. 1957; Lal 1991a). Both the isotopes are produced efficiently in the earth's atmosphere, and also in solids on the earth's surface. Independently and jointly they serve as useful tracers for characterizing the evolutionary history of a wide range of materials and artifacts. Here, we specifically focus on the production of 14C in terrestrial solids, designated as in-situ-produced 14C (to differentiate it from atmospheric 14C, initially produced in the atmosphere). We also illustrate the application to several earth science problems. This is a relatively new area of investigations, using 14C as a tracer, which was made possible by the development of accelerator mass spectrometry (AMS). The availability of the in-situ 14C variety has enormously enhanced the overall scope of 14C as a tracer (singly or together with in-situ-produced 10Be), which eminently qualifies it as a unique tracer for studying earth sciences.