• 14C Dating of Peat and delta-18O-delta-D in Ground Ice from Northwest Siberia

      Vasil'chuk, Y. K.; Jungner, Högne; Vasil'chuk, A. C. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We present new radiocarbon dates from a number of Holocene peat deposits along a north-south transect across the Yamal Peninsula. The samples were collected from frozen peat deposits with large ice wedges in: the northern tundra near Seyaha Settlement, in the Central Yamal Peninsula, the southern tundra in Shchuch'ya River valley at the Edem'yaha mouth, the southern part of the Yamal Peninsula, and the southern forest tundra near Labytnangi Town. 14C dates of wood remains from the tundra in the Yamal Peninsula could be used to reconstruct a northern limit of forest during the Holocene Optimum. The wood layers at the bottom of the peat give evidence for immigration of trees further north beyond the present boundary. The first forest appearance in the Seyaha River valley area is dated about 9 ka BP according to the oldest peat date in the Seyaha cross section. This suggests that summer temperatures were higher than at present. Very fast accumulation of peat (around 5 m/ka: about 9-8 ka BP at Seyaha and about 7-6 ka BP at Shchuch'ya) also supports this observation. In contrast, oxygen isotope composition of Holocene syngenetic ice wedges from the area (delta-18O = -19.1 to -20.3 per mil in the Seyaha cross-section and -17.3 to -20.3 per mil in the Shchuch'ya River) show that winter temperatures were significantly lower than presently, i.e. The climate during the Holocene Optimum was slightly more continental. The frozen peat near Labytnangi has thawed during the last 20 years, indicating global warming.
    • 32Si Dating of Marine Sediments from Bangladesh

      Morgenstern, Uwe; Geyh, M. A.; Kudrass, Herrmann Rudolf; Ditchburn, R. G.; Graham, I. J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Appropriate dating tools are essential for paleoenvironmental studies. Cosmogenic 32Si with a half-life of about 140 years is ideally suited to cover the dating range 30-1000 years. Here we have applied scintillation spectrometry for detection of natural 32Si to date marine shelf sediments. High detection efficiency, combined with stable background, allows for the detection of extremely low 32Si specific activities found in such sediments with counting rates below one count per hour. For a sediment core from the Ganges-Brahmaputra delta 32Si dating yields mean sedimentation rates of 0.7 +/0.2 cm/yr for 50 to several hundred years BP and 3.1 +/0.8 cm/yr for the past 50 years. The four-fold increase of the sedimentation rate over the past 50 years may reflect increased sediment loads in the rivers due to increasing human colonization within the rivers' drainage basins.
    • 5.2-5.8 ka BP Paleoenvironment of the Southern Slope of Mount Raizan, Japan

      Okuno, Mitsuru; Nagaoka, Shinji; Hase, Yoshitaka; Mori, Yuichi; Konomatsu, Masahiko; Takahashi, Toshihiko; Nakamura, Toshio; Nishida, Tamio (Department of Geosciences, The University of Arizona, 2001-01-01)
      Accelerator mass spectrometry (AMS) radiocarbon dating and paleoecological analysis of slope deposits at Mt Raizan provided seven 14C dates indicating that landslides occurred in that area at 6.0 to 6.3 cal ka BP and 6.5 cal ka BP. Plant macrofossils, pollen grains, and spores point to a mixed forest at that time, consisting of conifers and broad-leaved trees. On the other hand, insect fossil indicates slightly colder climate than that of the flora. This difference may be attributed to varied sensitivities of each proxy to climatic changes.
    • A Chronology of the Scythian Antiquities of Eurasia Based On New Archaeological and 14C Data

      Alekseev, A. Yu.; Bokovenko, N. A.; Boltrik, Yu; Chugunov, K. A.; Cook, G.; Dergachev, V. A.; Kovalyukh, N.; Possnert, G.; van der Plicht, J.; Scott, E. M.; et al. (Department of Geosciences, The University of Arizona, 2001-01-01)
      The paper is compares the chronology of the monuments of the Scythian epoch located in the east and west of the Eurasian steppe zone on the basis of both archaeological and radiocarbon data. The lists of 14C dates for the monuments located in different parts of Eurasia are presented according to the periods of their existence. Generally, the 14C dates are confirmed the archaeological point of view and allow us to compare the chronological position of the European and Asian Scythian monuments on the united 14C time scale.
    • A New 13C Correction for Radiocarbon Samples from Elevated-CO2 Experiments

      Torn, Margaret S.; Southon, John (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon can be a valuable tracer of carbon cycling in elevated CO2 experiments. However, the standard method of calculating ∆14C, which corrects sample 14C activity for isotopic fractionation by correcting the sample delta-13C to -25‰, introduces significant errors to the reported 14C values. For elevated-CO2 treatments the error arises because the delta-13C of the sample is not an appropriate measure of isotopic fractionation to use when correcting sample 14C activity for isotopic fractionation. A suggested replacement approach, developed in this paper, is to use the delta-13C of the same type of material (e.g. Leaf, soil organic matter) from the control (ambient-CO2) treatment in place of the sample delta-13C in the correction.
    • A Recent History of 14C, 137Cs, 210Pb, and 241Am Accumulation at Two Irish Peat Bog Sites: An East versus West Coast Comparison

      Gallagher, Donal; McGee, E. J.; Mitchell, P. I. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Data on radiocarbon (14C), 137Cs, 210Pb, and 241Am levels in an ombrotrophic peat sequence from a montane site on the east coast of Ireland are compared with data from a similar sequence at an Atlantic peatland site on the west coast. The 14C profiles from the west and east coasts show a broadly similar pattern. Levels increase from 100 pMC or less in the deepest horizons examined, to peak values at the west and east coast sites of 117 +/0.6 pMC and 132 +/0.7 pMC, respectively (corresponding to maximal fallout from nuclear weapons testing around 1964), thereafter diminishing to levels of 110-113 pMC near the surface. Significantly, peak levels at the east coast site are considerably higher than corresponding levels at the west coast site, though both are lower than reported peak values for continental regions. The possibility of significant 14C enrichment at the east coast site due to past discharges from nuclear installations in the UK seems unlikely. The 210Pb(ex) inventory at the east coast site (6500 Bq m-2 is significantly higher than at the west coast (5300 Bq m-2) and is consistent with the difference in rainfall at the two sites. Finally, 137Cs and 241Am inventories at the east coast site also exceed those at the west coast site by similar proportions (east:west ratio of approximately 1:1.2).
    • A Time History of Pre- and Post-Bomb Radiocarbon in the Barents Sea Derived from Arcto-Norwegian Cod Otoliths

      Kalish, John M.; Nydal, Reidar; Nedreaas, Kjell H.; Burr, George S.; Eine, Gro L. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon measured in seawater dissolved inorganic carbon (DIC) can be used to investigate ocean circulation, atmosphere/ocean carbon flux, and provide powerful constraints for the fine-tuning of general circulation models (GCMs). Time series of 14C in seawater are derived most frequently from annual bands of hermatypic corals. However, this proxy is unavailable in temperate and polar oceans. Fish otoliths, calcium carbonate auditory, and gravity receptors in the membranous labyrinths of teleost fishes, can act as proxies for 14C in most oceans and at most depths. Arcto-Norwegian cod otoliths are suited to this application due to the well-defined distribution of this species in the Barents Sea, the ability to determine ages of individual Arcto-Norwegian cod with a high level of accuracy, and the availability of archived otoliths collectedfor fisheries research over the past 60 years. Using measurements of 14C derived from Arcto-Norwegian cod otoliths, wepresent the first preand post-bomb time series (1919-1992) of 14C from polar seas and consider the significance of these data in relation to ocean circulation and atmosphere/ocean flux of 14C. The data provide evidence for a minor Suess effect of only 0.2‰ per year between 1919 and 1950. Bomb 14C was evident in the Barents Sea as early as 1957 and the highest 14C value was measured in an otolith core from a cod with a birth date of 1967. The otolith 14C data display key features common to records of 14C obtained from a Georges Bank mollusc and corals from the tropical and subtropical North Atlantic.
    • Absolute Dating of Recent Sediments in the Cyclone-Influenced Shelf Area off Bangladesh: Comparison of Gamma Spectrometric (137Cs, 210Pb, 228Ra), Radiocarbon, and 32Si Ages

      Suckow, Axel; Morgenstern, Uwe; Kudrass, Herrmann-Rudolf (Department of Geosciences, The University of Arizona, 2001-01-01)
      A geochronological survey of the Bengal shelf area involved results from more than 20 sediment cores dated using gamma spectrometry and the nuclides 137Cs, 228Ra, 226Ra, and 210Pb. In some cores, which contained older sediments, 32Si and 14C were determined to examine the possibility to extrapolate the obtained chronologies to century and millennial scale. Geochronological work in this region is faced with problems of cyclone-induced sediment reworking, grain-size effects on fallout nuclides, scarcity of carbonates, unknown 14C reservoir effect and sedimentation rates that are too high to obtain sediment cores long enough to establish a chronology. Despite these problems, comparison between the results of the different dating methods provided the most reliable sediment balance to date for the submarine delta of the Ganges-Brahmaputra river system and indicated that on a time scale of several centuries at least 35% of the annual sediment load is deposited.
    • Absolute Production of Radiocarbon and the Long-Term Trend of Atmospheric Radiocarbon

      Goslar, Tomasz (Department of Geosciences, The University of Arizona, 2001-01-01)
      This paper presents simulations of the long-term trend of atmospheric radiocarbon, performed with the modified PANDORA model. The author shows that taking into account the outflow-supply carbon fluxes makes the decrease of D14C between 40 and 0 ka BP larger by 40-80 per mil, not much depending on which data (sedimentary magnetism, archaeomagnetism or 10Be) is used for the scenario of relative variations of 14C production. This together with the effect of CO2 increase reasonably reconciles model-simulated and observed decline of atmospheric Delta-14C.
    • Age Determination of Fossil Bones from the Vindija Neanderthal Site in Croatia

      Wild, Eva Maria; Paunovic, Maja; Rabeder, Gernot; Steffan, Ilse; Steier, Peter (Department of Geosciences, The University of Arizona, 2001-01-01)
      Vindija cave in Croatia is famous for the Neanderthal bones found in layer G of its sediment profile. Radiocarbon dating has been performed mainly on this layer due to the great interest in its fossils. In addition to Neanderthal remains, the sediment in layer G contains bones from the cave bear. Cave bear bones are found also in other layers of the sediment profile and offer the possibility of studying the bears' evolutionary mode. Therefore, we tried to determine the time span covered by the entire profile. The U/Th age determination method was applied to cave bear bones from different layers of the profile. For the younger part of the profile, the U/Th ages were compared with the results of the 14C and the amino-acid racemization method. The agreement of the different methods indicates that closed-system behavior can be assumed for the fossil bones from Vindija cave. From this finding it may be deduced that bones from the lower sediment layers are also closed systems and that the U/Th ages of these layers are reliable. This conclusion is corroborated by the stratigraphy of the cave profile.
    • AMS Radiocarbon Dating of Tianma-Qucun Site in Shanxi, China

      Guo, Zhiyu; Liu, Kexin; Lu, Xiangyang; Ma, Hongji; Li, Kun; Yuan, Jinglin; Yuan, Sixun; Wu, Xiaohong; Liu, Xu (Department of Geosciences, The University of Arizona, 2001-01-01)
      Tianma-Qucun is the biggest site of Western Zhou Dynasty discovered in Shanxi Province, China. It has been recognized as the early capital of Jin, a vassal state of Western Zhou. The territories were granted to the first Marquis of Jin with the title in the early days of Western Zhou. Bone sample series from the site were radiocarbon-dated by accelerator mass spectrometry (AMS) and calibrated with the Oxford calibration program OxCal 3.5. Bayesian analysis of the calibrated ages shows that the earliest residents of the Western Zhou came to Tianma-Qucun area in 1020–940 BC and the lower boundary of the Western Zhou is 796–754 BC, which corresponds well to the historical record 770 BC.
    • 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.