• In-Situ Radiocarbon Production by Neutrons and Muons in an Antarctic Blue Ice Field at Scharffenbergbotnen: A Status Report

      van der Borg, K.; van der Kemp, W. J. M.; Alderliesten, C.; de Jong, A. F. M.; Lamers, R. A. N.; Oerlemans, J.; Thomassen, M.; van de Wal, R. S. W. (Department of Geosciences, The University of Arizona, 2001-01-01)
      In the radiocarbon accelerator mass spectrometry (14C AMS) analysis of gases obtained in a dry extraction from a 52-m Antarctic ice core, we observed 14CO2 and 14CO concentrations decreasing with depth. The concentrations are explained in terms of in-situ production by neutrons and captured muons in ablating ice. The ratio of the 14CO2 concentration to that of 14CO has been found to be constant at 1.9 +/0.3. The ablation rates obtained of 42 +/18 cm.yr-1 and 40 +/13 cm.yr-1 for the neutron and muon components, respectively, are about three times higher than observed from stake readings. The discrepancy may point to an incomplete extraction of the dry extraction method. Using the constant ratio in 14CO2 and 14CO concentrations we correct for the in-situ component in the trapped 14CO2 and deduce an age of 10,300 +/900 BP for the ice core.
    • Influence of the Bomb-Produced 14C on the Radiocarbon Concentration in the Youngest Sediments of Lake Gościąż, Central Poland

      Pawlyta, Jacek; Pazdur, Anna; Goslar, Tomasz; Hałas, Stanisław (Department of Geosciences, The University of Arizona, 2001-01-01)
      This work is a study of changes of the radiocarbon concentration in the youngest part of Lake Gościąż sediments in the calendar time scale during the last 150 years. This period includes the time of the nuclear weapons tests performed in the upper atmosphere in the 1950s, and the 1960s, which caused large release of 14C and 137Cs into the environment. On the basis of this study, the isotope dilution factor for 14C and the exchange time of carbon between the atmosphere and Lake Gościąż was estimated. The chronology of the upper part of the sediments was constructed using many interdisciplinary investigations. Among them, measurements of 137Cs in the sediment were used. An unexpected discrepancy between the previously constructed time scale and that suggested by 137Cs is observed in one of the cases.
    • Measurement of Radiocarbon Content in Leaves from Some Japanese Sites

      Muraki, Yasushi; Masuda, Kimiaki; Arslanov, K.; Toyoizumi, Hiroaki; Kato, Masataka; Naruse, Yukiko; Murata, Takuya; Nishiyama, Tohru (Department of Geosciences, The University of Arizona, 2001-01-01)
      We have measured radiocarbon contents in leaves collected from 15 sites in Japan, including mountain areas and big city areas for last three years. Comparing the radiocarbon contents in various areas, high 14C concentrations (80-100‰ as δ14C) are seen for the leaves from the mountain and country sites. On the contrary, low concentrations (5-40‰) were observed for the leaves from city region, especially near the road with heavy traffic. These results indicate that the atmosphere of the mountain and country sites in Japan is still clean but the CO2 gas coming from fossil non-radioactive carbon significantly pollutes the atmosphere of the city sites. The value of δ14C for the mountain areas implies that 14C produced by nuclear bomb test in 1960s still remains. The decrease of δ14C at heavy traffic sites in Tokyo is consistent with the increase of CO2 concentration in the atmosphere assuming that almost all CO2 gas in this region originates from the fossil fuel.
    • 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.
    • New Chronological Frame for the Young Neolithic Baden Culture in Central Europe (4th Millennium BC)

      Wild, Eva Maria; Stadler, Peter; Bondár, Maria; Draxler, Susanne; Friesinger, Herwig; Kutschera, Walter; Priller, Alfred; Rom, Werner; Ruttkay, Elisabeth; Steier, Peter (Department of Geosciences, The University of Arizona, 2001-01-01)
      The Baden Culture is a widely spread culture of the Young Neolithics in east-central Europe. In southeast Europe, several parallel cultures are found at different places. The main innovations in east-central Europe associated with the Baden Culture were traditionally thought to originate in southeast Europe, Anatolia, and the Levant. However, in recent years, doubt about this theory has arisen among archaeologists. Here, we try to contribute to this question by increasing the radiocarbon data set available for the Baden Culture. Thirty-two age determinations of samples from different sites assigned to the Baden Culture were performed by accelerator mass spectrometry (AMS) 14C dating. The new data were combined with previously published 14C dates. Data from the individual cultural phases of the entire Baden period and the parallel cultures in southeast Europe (Sitagroi, Cernavoda, and Ezero) were analyzed by sum calibration. Comparison of the results indicates that the southeastern cultures cannot be synchronized with the Boleráz period, the early phase of the Baden Culture. It seems that these cultures were parallel to the Baden Classical period. This finding, which has to be verified by more data from the southeastern cultures, contradicts the theory of the east–west spreading of these cultures.
    • New Radiocarbon Dates of the North Asian Steppe Zone and its Consequences for the Chronology

      Göersdorf, Jochen; Parzinger, Hermann; Nagler, Anatoli (Department of Geosciences, The University of Arizona, 2001-01-01)
      The chronological problems of the Steppe zone have been under intensive investigation during the last years but no generally accepted chronological system existed up to now. We present new radiocarbon dates of samples from several excavation sites. The dates allow a comparison of the Bronze Age development in the Siberian Steppe Zone with other neighboring regions.
    • 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.
    • New Data on Chronology of Landscape-Paleoclimatic Stages in Northwestern Russia During the Late Glacial and Holocene

      Arslanov, Kh A.; Savelieva, L. A.; Klimanov, V. A.; Chernov, S. B.; Maksimov, F. E.; Tertychnaya, T. V.; Subetto, D. A. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Two lake and bog sediments have been thoroughly studied using palynological and radiocarbon dating methods. These are the Lembolovskoye Lake section located in the southern part of the Karelian Ithmus and the Mshinskoye bog section located in the southwestern part of the Leningrad province. The data obtained allow us to reconstruct the main features of the vegetation cover evolution, the chronology for the appearance and a real distribution of the main arboreal species from the south of the Leningrad province to the north, and to construct curves of the paleoclimate parameter changes for the area under study. Thirty-six 14C dates were obtained for the Lembolovskoye Lake section (7 m thick). According to those dates, the organic gyttja formation in the lake began 9870 +/170 BP. Spore-pollen spectra with high percentage of herbs, arborescent, and shrub-birch dated back to the Younger Dryas were found out in clay layers at a depth of 6.5 m. An appearance of spruce and alder pollen is dated at 6860 +/120 and 7510 +/150 BP, respectively. The maximal percentage of broad-leaved species falls on the first half of the Atlantic (AT-1). Thirty-two dates were obtained for the Mshinskoye bog section (6 m thick): from 60 +/70 to 9520 +/170 BP (the last date fixed the beginning of peat formation); 12 palinozones from the Preboreal to the Subatlantic were recognized there. The spruce and alder pollen began to appear 7520 +/110 and 7670 +/130 BP, respectively. The maximal amount of broad-leaved species is observed at 4690 +/80 BP. The detailed reconstruction of changes in vegetation communities during the Late Glacial and Holocene was correlated with paleoclimatic characteristics, which have been reconstructed for the section under study by using the information from a statistical method of spore-pollen data processing.
    • 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.
    • Radiocarbon AMS Dates for Paleolithic Cave Paintings

      Valladas, H.; Tisnérat-Laborde, N.; Cachier, H.; Arnold, M.; de Quirós, F. Bernaldo; Cabrera-Valdés, V.; Clottes, J.; Courtin, J.; Fortea-Pérez, J. J.; Gonzáles-Sainz, C.; et al. (Department of Geosciences, The University of Arizona, 2001-01-01)
      Advances in radiocarbon dating by accelerator mass spectrometry (AMS) have made it possible to date prehistoric cave paintings by sampling the pigment itself instead of relying on dates derived from miscellaneous prehistoric remains recovered in the vicinity of the paintings. The work at the Laboratoire des Sciences du Climat et de l’Environnement (LSCE) concentrated on prehistoric charcoal cave paintings from southern France and northern Spain. In most caves, pigment samples were collected from several paintings, and in some instances the sample size allowed for multiple independent measurements on the same figure, so that the coherence of the calculated dates could be tested. Before being dated, each specimen was subjected to a thermal treatment preceded by an acid and basic treatment of intensity commensurate with the sample size. Nine bison drawings from three caves in the Cantabrian region of Spain—two from Covaciella, three from Altamira, and four from El Castillo—were sampled and dated. The 27 dates fell between 13,000 and 14,500 BP, allowing us to attribute the drawings to the Magdalenian period. The 24 dates for 13 drawings in the Cosquer cave indicated two distinct periods of painting activity—one around 28,000 BP and the other around 19,000 BP. The Chauvet cave paintings turned out to be the oldest recorded to date, as five dates fell between 32,000 and 31,000 BP. After discussing the sample preparation protocol in more detail, we will discuss the ages obtained and compare them with other chronological data.
    • 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.
    • Radiocarbon Age Profiles and Size Dependency of Mixing in Northeast Atlantic Sediments

      Brown, Louise; Cook, Gordon T.; MacKenzie, Angus B.; Thomson, John (Department of Geosciences, The University of Arizona, 2001-01-01)
      In recent years, the most common technique for radiocarbon dating of deep-ocean sediments has been accelerator mass spectrometry (AMS) analysis of hand-picked planktonic forminifera (forams). Some studies have exposed age offsets between different sediment size fractions from the same depth within a core and this has important implications when establishing a chronological framework for palaeoceanographic records associated with a particular sediment component. The mechanisms generating the age offsets are not fully understood, a problem compounded by the fact that the fraction defined as "large"varies between different studies. To explore this problem, we dated samples of hand-picked forams from two Biogeochemical Ocean Flux Study (BOFS) cores, for which the presence of an offset between the bulk carbonate and >150 micrometers foraminiferal calcite had already been demonstrated. The presence of a constant age offset between bulk carbonate and coarse fraction material at the two BOFS sites has been confirmed, but the magnitude of the offset is dependent on whether a simple size-separation technique or hand-picking of well-preserved forams is applied. This may be explained if the selection of well preserved forams biases the sample towards those specimens that have spent least time in the surface mixed layer (SML) or have undergone less size selective mixing. Modeling of the 14C profiles demonstrates that SML depth and sediment accumulation rates are the same for both the bulk and coarse sediment fractions, which is consistent with the hypothesis that size-selective mixing is responsible for the age offset.
    • Radiocarbon Age of Vertisols and its Interpretation Using Data on Gilgai Complex in the North Caucasus

      Kovda, Irina; Lynn, Warren; Williams, Dewayne; Chichagova, Olga (Department of Geosciences, The University of Arizona, 2001-01-01)
      Radiocarbon dates were analyzed to assess Vertisols age around the world. They show an increase of radiocarbon age from mainly modern-3000 BP in 0-100 cm layer up to 10,000 BP at a depth 100-200 cm. Older dates reflect the age of parent material. The inversion of 14C dates seems to be a frequent phenomenon in Vertisols. A series of new dates of Vertisols from gilgai microhigh, microslope and microlow in the North Caucasus was done in order to understand the nature of this inversion. 14C age in the gilgai soil complex ranges from 70 +/45 BP in the microlow to 5610 +/180 BP in the microhigh. A trend of similar depths being younger in the microslope and microlow was found. We explain this by intensive humus rejuvenation in the microlows due to water downward flow. The older date in the microhigh represents the old humus horizon sheared laterally close to the surface and preserved by impermeable water regime. We explain inversions of 14C age-depth curves by the sampling procedures. In a narrow pit, genetically different parts of former gilgai could easily be as a genetically uniform soil profile. Because of this strong microvariability, Vertisols require sampling in a trench accounting for gilgai elements, even when gilgai are not obvious.
    • Paleoenvironment in Dae-Am San High Moor in the Korean Peninsula

      Yoshioka, T.; Lee, J. Y.; Takahashi, H. A.; Kang, S. J. (Department of Geosciences, The University of Arizona, 2001-01-01)
      We discuss paleoenvironmental changes at the Dae-Am San high moor, located near the Demilitarized Zone at 38 degrees N. This area has been reported to be the only high moor in the Korean peninsula. The 14C age of the bottom sediment (75-80 cm in depth) at this site is about 1900 BP. Since the radiocarbon ages for the intervals at 50-55 cm and 75-80 cm were almost the same, we conclude that the deep layers (55-80 cm) in the high moor were all part of the original soil. Low organic C and N contents in the deeper layers support this inference. The 50-55 cm layer consists of sandy material with very low organic content, suggesting erosion from the surrounding area. The surface layer (0-5 cm) was measured as 190 BP, and the middle layer (30-35 cm) was 870 BP. The bulk sedimentation rate was estimated to be about 0.4 mm yr-1 for the 0-30-cm interval. The delta-13C value of organic carbon in the sediments fluctuated with depth. The delta-13C profile of the Dae-Am San high moor may be explained by climatic changes which occurred during the Little Ice Age and Medieval Warm Period.
    • 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.
    • 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.
    • 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.