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Sample records for 10be 26al 36cl

  1. Aluminum 26, {sup 10}Be, and {sup 36}Cl depth profiles in the Canyon Diablo iron meteorite

    SciTech Connect

    Michlovich, E.S.; Elmore, D.; Vogt, S.; Lipschutz, M.E.; Masarik, J.; Reedy, R.C.

    1994-11-25

    The authors have measured activities of the long-lived cosmogenic radionuclides {sup 26}Al, {sup 10}Be, and {sup 36}Cl in 12 fragments of the iron meteorite Canyon Diablo and have constructed production rate-versus-depth profiles of those radionuclides. Profiles determined using differential particle fluxes calculated with the LAHET code system are in good agreement with {sup 26}Al, {sup 10}Be, and {sup 36}Cl experimental data, but the agreement for {sup 36}Cl was obtained only after neutron-induced cross sections were modified. Profiles calculated with lunar particle fluxes are much lower than experimental Canyon Diablo profiles. The cosmic ray exposure ages of most samples are near 540 m.y. 34 refs., 4 figs., 2 tabs.

  2. Shielding Effects on 10Be and 26Al in Diogenites

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Lindner, L.; van der Borg, K.; Loeken, Th.; Schultz, L.

    1995-09-01

    Due to the attenuation of primary particles and the variations in secondary part fluxes with depth, production rates of cosmogenic nuclides are affected by the s shape of the irradiated object. The effects of shielding conditions on the produduction rates of noble gases can be estimated on the basis of the cosmogenic 22Ne/21Ne r [1]. For the production of cosmogenic radionuclides, shielding studies mainly fo on large meteorites like St. Severin [2], Knyahinya [3], Chico [4] and Jilin [5] estimated preatmospheric radii between 25 and 85 cm. The 10Be and 26Al production were also measured in three smaller meteorites, but the cosmogenic 22Ne/21Ne rat were obscured by large amounts of trapped neon [6]. Therefore we carried out a systematic study on the 10Be and 26Al activities as a function of the 22Ne/21Ne in 7 non-Antarctic and 15 Antarctic diogenite samples. Diogenites show exposure long enough (>10 Ma) to have reached saturation levels for 10Be and 26Al and are similar to ordinary chondrites with respect to the target element composition fo production of 10Be, 26Al and Ne isotopes. The measured 10Be and 26Al activities were normalized to average diogenite compo on the basis of ICP and XRF measurements and the experimental production rate eq of [7] and [8]. For the Antarctic samples with known terrestrial ages [9] correc were made for radioactive decay. In figure 1, the resulting 10Be and 26Al production rates are plotted against the 22Ne/21Ne ratios, which were measured on the same The solid lines represent the results of an exponential fitting procedure, from two samples were excluded: EET83246 because of SCR-produced 26Al and LEW88008 be of an anomalously low 26Al/10Be ratio, which is not yet understood. Figure 1 illustrates that the 10Be and 26Al production rates are similarly affect shielding conditions: both 10Be and 26Al decrease about 30 - 40% when going from objects with low 22Ne/21Ne ratios (<1.10) to small objects with high 22Ne/21Ne r (>1.25). Recently

  3. 26Al and 10Be Activities of Lodranites and Winona

    NASA Astrophysics Data System (ADS)

    Herzog, G. F.; Xue, S.; Klein, J.; Juenemann, D.; Middleton, R.

    1993-07-01

    Noble gas measurements by [1] indicate that four lodranites LEW 88280, Lodran (a fall), MAC 88177, and Yamato 791491 have the same cosmic ray exposure age of a few million years. The elevated ^22Ne/^21Ne ratios of these lodranites, from 1.22 to 1.28 [1], suggest that shielding was light and production rates appreciably lower than in average chondrites. Cosmic-ray irradiation in space for, say, 4 My would bring ^26Al and ^10Be to within 2% and 16% of their respective saturation values. Thus measurement of ^26Al may provide information about production rates and shielding and ^10Be about exposure age. We separated magnetically metal- and silicate-rich material from the four lodranites mentioned above and from Winona. The ^26Al and/or ^10Be activities (Table 1) were measured by accelerator mass spectrometry [2] with the statistical 1-sigma precision shown; the activities are thought to have an overall accuracy of 6-8%. Although the metal phases were etched with HF, they retained some silicate. To get a quantitative indication of the amounts of silicate present, the Mg concentrations in aliquots of the dissolved metal samples (Table 1) were measured by ICP/MS. The Mg, Al, Ca, Ti, Mn, and Fe contents of the silicate phases were determined by DCP emission spectrometry [3]. The measured activities in silicates from LEW 88280, Lodran, and Y 791491 resemble one another closely: The average ^26Al and ^10Be activities are 50.9 and 16.7 dpm/kg compared to estimated production rates of about 55 and 23 dpm/kg. These results lead to an exposure age of ~3.3 My, but do not indicate substantial lowering of production rates. The ^26Al and ^10Be contents of MAC 88177 are about half the values expected at saturation under normal shielding and are lower than those in the other three lodranites. These results are consistent with the very light shielding inferred from the exceptionally high ^22Ne/^21Ne ratio of 1.28, and perhaps with some lowering due to terrestrial age. Kirsten et al. [4

  4. The cosmogenic radionuclides {sup 7}Be, {sup 10}Be, and {sup 36}Cl in precipitation

    SciTech Connect

    Knies, D.L.

    1994-12-31

    Two-thirds of atmospheric {sup 7}Be (t{sub 1/2}=53 d), {sup 10}Be(t{sub 1/2}= 1.5 My), and {sup 36}Cl(t{sub 1/2}=0.3 My) is produced in the stratosphere and one-third in the troposphere. The residence time of these radionuclides in the stratosphere is a few years and in the troposphere is a few weeks. Since {sup 7}Be`s half-life is short compared to its residence time in the stratosphere and similar to its residence time in the troposphere, the {sup 7}Be/{sup 10}Be and {sup 7}Be/{sup 36}Cl ratios should have distinct tropospheric and stratospheric values. Consequently, these isotopes can be used to study processes that involve mixing of air from the troposphere and stratosphere. Relationships between the radionuclide concentrations and air mass history, event type, season, and the major cation and anion concentrations will be presented. Evidence and mechanisms for the fractionation of the {sup 36}Cl and {sup 10}Be concentrations as a function of event type will be presented. Evidence and mechanisms for the fractionation of the {sup 36}Cl and {sup 10}Be concentrations as a function of event type will be presented. A departure from the theoretical {sup 10}Be/{sup 36}Cl production rate ratio of {approx}40 is seen only in one direction with an apparent limit right at the calculated ratio. For this reason, a new theoretical calculation of the {sup 10}Be/{sup 36}Cl production rate ratio was undertaken. The new calculated value is {approx}9.3. This value is in good agreement with the measured mean values in both the Greenland ice sheet and West Lafayette, IN wet precipitation of 8.1 and 9.1 respectively.

  5. 10Be and 26Al in Individual Cosmic Spherules

    NASA Astrophysics Data System (ADS)

    Nishiizumi, K.; Arnold, J. R.; Chaffee, M. W.; Finkel, R. C.; Southon, J.; Brownlee, D. E.; Harvey, R. P.

    1992-07-01

    Cosmic spherules and fragments in the size range 0.1-1 mm, originally extracted magnetically from deep-sea deposits, have now been isolated from ice in Greenland and Antarctica (Maurette et al., 1986; Koeberl and Hagen, 1989; Harvey and Maurette, 1990). Studies of cosmogenic radionuclides in individual spherules made possible by accelerator mass spectrometry (Raisbeck et al., 1985; Nishiizumi et al., 1991, 1992), have verified the model calculations that suggested that the spherules are mainly fused micrometeoroids, rather than spall droplets from larger objects (Dohnanyi, 1978; Grun et al., 1985; Olinger et al., 1990). However, the exposure lifetimes observed are much longer than those deduced from models (10^5- 10^7 years as against a few times 10^4) (Dohnanyi, 1978; Grun et al., 1985). As new sources of spherules become available, it is important to verify their extraterrestrial origin, and to see whether they confirm or modify earlier findings. It is also interesting to continue to search for spall droplets. In this paper we report on a group of large spherules collected from glacial till near Lewis Cliff, Antarctica (84.3 degrees S, 161.6 degrees E) (Harvey and Maurette, 1990). The concentrations of cosmogenic ^10Be and ^26Al were measured in 10 such spherules (LC-7 to LC-16). Typically these spherules have a lower Fe content, and are more weakly magnetic, than those studied earlier. In addition to these spherules, we analyzed 8 individual deep sea spherules (90-250 micrograms) (Murrell et al., 1980). All particles were individually mounted in acrylic resin and a small surface was polished flat with aluminum oxide. The quantitative elemental analysis of these polished surfaces was performed using an electron microprobe. After electron microprobe analysis, each particle was dissolved and Be and Al were separated for AMS. The ^10Be and ^26Al concentrations were determined at LLNL. In this and a preceding group of LC and deep-sea particles, three (LC-6, reported

  6. Radiogenic production of 10Be and 26Al in uranium and thorium ores: Implications for studying terrestrial samples containing low levels of 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Sharma, P.; Middleton, R.

    1989-03-01

    10Be and 26Al are produced by cosmic-ray-induced spallation of atmospheric constituents, and also as has recently been shown, by spallation in the rocks exposed to cosmic rays. We now present experimental data showing that these two isotopes can also be produced by radiation from uranium and thorium decay chain radionuclides contained within the host rocks. We have measured the 10Be and 26Al concentrations in a number of shielded uranium (spontaneous fission half-life ~10 26 years) and thorium (no spontaneous-fission-decay mode) ores using accelerator mass spectrometry. The concentrations of 10Be and 26Al range from 2.8·10 6 to 29.6·10 6 and 1.1 · 10 7 to 1.43· 10 atoms g -, respectively. The high concentrations of 10Be and 26Al imply unacceptably-high branching ratios (~ 10 -4 to 10 -1) for their production from spontaneous fission and coupled with the presence of 10Be and 26A1 in the Th ores, eliminate spontaneous fission as the major source of either isotope. The large 26A1 to 10Be ratio found in all the samples eliminates atmospheric production. The most likely sources are the alpha reactions, 7Li( α, p) 10Be and 23Na( α, n) 26Al, and neutron reactions, 9Be( n, γ) 10Be, 10B( n, p) 10Be and 13C( n, α) 10Be. Our work provides an upper limit on the contribution of in situ radioactivity to samples containing low levels of 10Be and 26Al. We have calculated the equilibrium concentrations of 10Be and 26Al in a wide variety of geologic materials including granites, ultramafic rocks, basalts, shales, pelagic sediments, ferromanganese nodules, tektites and Libyan Desert Glass. The calculated concentrations of 10Be and 26Al range from <1 to 4100 and 9 to 10.3 · 10 6 atoms g -1, respectively. Implications of these calculations are discussed. In general, the calculated amounts of radiogenically produced 10Be in geological materials are quite small and frequently negligible compared to cosmogenic production, while that of 26Al are significant and sometimes the

  7. 26 Al - 10 Be burial ages of a Pleistocene Terrace in the Vienna Basin

    NASA Astrophysics Data System (ADS)

    Neuhuber, Stephanie; Braumann, Sandra; Lüthgens, Christopher; Schäfter, Jörg; Häuselmann, Philipp; Fiebig, Markus

    2015-04-01

    The Vienna Basin is a pull-apart basin located between the Eastern Alps and the Western Carpathians. Its main subsidence started in the Miocene and resulted in a maximum of 6 km sedimentary infill. Up to five Pleistocene terraces formed by the Danube river and its tributaries and are separated by their geometic cross cutting and topographic relationships. The ongoing tectonic displacement results in tilting of terrace levels and prevents the correlation of similar levels to one sedimentation event. For this reason absolute age dating is essential in this setting. This research applies 26Al/10Be isochrone dating of one selected Pleistocene Terrace, the Gänserndorf terrace at two different sampling sites. This terrace has already a numerical age determined by OSL age of 250 +/- 50 kyr. Isochrone age dating may be used for samples with different transport histories and exposition duration that share the same last burial event and is ideal for the sedimentary setting of the terrace gravels of the Gänserndorf terrace. The source area of the terrace consists mainly of metamorphic rocks that contain large quartz pebbles that are suitable for cosmogenic 26Al and 10Be extraction.

  8. A global compilation of glacial 10Be and 26Al exposure ages

    NASA Astrophysics Data System (ADS)

    Heyman, Jakob

    2015-04-01

    Cosmogenic dating has enabled direct dating of glacial landforms and deposits, greatly improving our understanding of past glaciations in terms of timing as well as glacial erosion and preservation. Over the last 25 years a large (and growing) number of publications have reported cosmogenic exposure ages from glacial landforms around the world. Here a global compilation of glacial 10Be and 26Al exposure ages will be presented aiming at an analysis and quantification of cosmogenic dating uncertainties. The dataset consists of >9300 10Be exposure ages and >1400 26Al exposure ages with full input data (location, elevation, sample type, sample thickness, concentration, standardization etc.). All exposure ages have been recalculated with updated reference production rates and organized in discrete glacial landform groups enabling evaluation of exposure age scatter due to prior and incomplete exposure. Exposure age scatter is common and increase significantly for glacial landforms older than the global last glacial maximum, making precise cosmogenic dating of older glaciations difficult. The data will be used to evaluate exposure dating of different sample types (boulder vs bedrock surfaces) and sample selection based on boulder size. Exposure ages from the paleo-ice sheets will be compared with mountain glacier exposure ages, aiming at picking out the good (well-clustered) exposure ages. The full dataset will eventually be posted online and continuously updated with published exposure age data.

  9. Erosion rate study at the Allchar deposit (Macedonia) based on radioactive and stable cosmogenic nuclides (26 Al, 36 Cl, 3 He, and 21 Ne)

    PubMed Central

    Cvetković, V.; Niedermann, S.; Pejović, V.; Amthauer, G.; Boev, B.; Bosch, F.; Aničin, I.; Henning, W. F.

    2016-01-01

    Abstract This paper focuses on constraining the erosion rate in the area of the Allchar Sb‐As‐Tl‐Au deposit (Macedonia). It contains the largest known reserves of lorandite (TlAsS2), which is essential for the LORanditeEXperiment (LOREX), aimed at determining the long‐term solar neutrino flux. Because the erosion history of the Allchar area is crucial for the success of LOREX, we applied terrestrial in situ cosmogenic nuclides including both radioactive (26Al and 36Cl) and stable (3He and 21Ne) nuclides in quartz, dolomite/calcite, sanidine, and diopside. The obtained results suggest that there is accordance in the values obtained by applying 26Al, 36Cl, and 21Ne for around 85% of the entire sample collection, with resulting erosion rates varying from several tens of m/Ma to ∼165 m/Ma. The samples from four locations (L‐8 CD, L1b/R, L1c/R, and L‐4/ADR) give erosion rates between 300 and 400 m/Ma. Although these localities reveal remarkably higher values, which may be explained by burial events that occurred in part of Allchar, the erosion rate estimates mostly in the range between 50 and 100 m/Ma. This range further enables us to estimate the vertical erosion rate values for the two main ore bodies Crven Dol and Centralni Deo. We also estimate that the lower and upper limits of average paleo‐depths for the ore body Centralni Deo from 4.3 Ma to the present are 250–290 and 750–790 m, respectively, whereas the upper limit of paleo‐depth for the ore body Crven Dol over the same geological age is 860 m. The estimated paleo‐depth values allow estimating the relative contributions of 205Pb derived from pp‐neutrino and fast cosmic‐ray muons, respectively, which is an important prerequisite for the LOREX experiment. PMID:27587984

  10. Erosion rate study at the Allchar deposit (Macedonia) based on radioactive and stable cosmogenic nuclides (26Al, 36Cl, 3He, and 21Ne)

    NASA Astrophysics Data System (ADS)

    Pavićević, M. K.; Cvetković, V.; Niedermann, S.; Pejović, V.; Amthauer, G.; Boev, B.; Bosch, F.; Aničin, I.; Henning, W. F.

    2016-02-01

    This paper focuses on constraining the erosion rate in the area of the Allchar Sb-As-Tl-Au deposit (Macedonia). It contains the largest known reserves of lorandite (TlAsS2), which is essential for the LORanditeEXperiment (LOREX), aimed at determining the long-term solar neutrino flux. Because the erosion history of the Allchar area is crucial for the success of LOREX, we applied terrestrial in situ cosmogenic nuclides including both radioactive (26Al and 36Cl) and stable (3He and 21Ne) nuclides in quartz, dolomite/calcite, sanidine, and diopside. The obtained results suggest that there is accordance in the values obtained by applying 26Al, 36Cl, and 21Ne for around 85% of the entire sample collection, with resulting erosion rates varying from several tens of m/Ma to ˜165 m/Ma. The samples from four locations (L-8 CD, L1b/R, L1c/R, and L-4/ADR) give erosion rates between 300 and 400 m/Ma. Although these localities reveal remarkably higher values, which may be explained by burial events that occurred in part of Allchar, the erosion rate estimates mostly in the range between 50 and 100 m/Ma. This range further enables us to estimate the vertical erosion rate values for the two main ore bodies Crven Dol and Centralni Deo. We also estimate that the lower and upper limits of average paleo-depths for the ore body Centralni Deo from 4.3 Ma to the present are 250-290 and 750-790 m, respectively, whereas the upper limit of paleo-depth for the ore body Crven Dol over the same geological age is 860 m. The estimated paleo-depth values allow estimating the relative contributions of 205Pb derived from pp-neutrino and fast cosmic-ray muons, respectively, which is an important prerequisite for the LOREX experiment.

  11. 26Al/10Be burial dating of Xujiayao-Houjiayao site in Nihewan Basin, northern China.

    PubMed

    Tu, Hua; Shen, Guanjun; Li, Haixu; Xie, Fei; Granger, Darryl E

    2015-01-01

    The Xujiayao-Houjiayao site in Nihewan Basin is among the most important Paleolithic sites in China for having provided a rich collection of hominin and mammalian fossils and lithic artifacts. Based on biostratigraphical correlation and exploratory results from a variety of dating methods, the site has been widely accepted as early Upper Pleistocene in time. However, more recent paleomagnetic analyses assigned a much older age of ∼500 ka (thousand years). This paper reports the application of 26Al/10Be burial dating as an independent check. Two quartz samples from a lower cultural horizon give a weighted mean age of 0.24 ± 0.05 Ma (million years, 1σ). The site is thus younger than 340 ka at 95% confidence, which is at variance with the previous paleomagnetic results. On the other hand, our result suggests an age of older than 140 ka for the site's lower cultural deposits, which is consistent with recent post-infrared infrared stimulated luminescence (pIR-IRSL) dating at 160-220 ka. PMID:25706272

  12. 26Al/10Be Burial Dating of Xujiayao-Houjiayao Site in Nihewan Basin, Northern China

    PubMed Central

    Tu, Hua; Shen, Guanjun; Li, Haixu; Xie, Fei; Granger, Darryl E.

    2015-01-01

    The Xujiayao-Houjiayao site in Nihewan Basin is among the most important Paleolithic sites in China for having provided a rich collection of hominin and mammalian fossils and lithic artifacts. Based on biostratigraphical correlation and exploratory results from a variety of dating methods, the site has been widely accepted as early Upper Pleistocene in time. However, more recent paleomagnetic analyses assigned a much older age of ∼500 ka (thousand years). This paper reports the application of 26Al/10Be burial dating as an independent check. Two quartz samples from a lower cultural horizon give a weighted mean age of 0.24 ± 0.05 Ma (million years, 1σ). The site is thus younger than 340 ka at 95% confidence, which is at variance with the previous paleomagnetic results. On the other hand, our result suggests an age of older than 140 ka for the site’s lower cultural deposits, which is consistent with recent post-infrared infrared stimulated luminescence (pIR-IRSL) dating at 160–220 ka. PMID:25706272

  13. Dating Plio-Pleistocene glacial sediments using the cosmic-ray-produced radionuclides 10Be and 26Al

    USGS Publications Warehouse

    Balco, G.; Stone, J.O.H.; Jennings, C.

    2005-01-01

    We use the cosmic-ray-produced radionuclides 26Al and 10Be to date Plio-Pleistocene glacial sediment sequences. These two nuclides are produced in quartz at a fixed ratio, but have different decay constants. If a sample is exposed at the surface for a time and then buried by overburden and thus removed from the cosmic-ray flux, the 26Al/10Be ratio is related to the duration of burial. We first attempted to date pre-Wisconsinan tills by measuring 26Al and 10Be in fluvial sediments beneath them and applying the method of "burial dating," which previous authors have used to date river sediment carried into caves. This method, however, requires simplifying assumptions about the 26Al and 10Be concentrations in the sediment at the time of burial. We show that these assumptions are not valid for river sediment in glaciated regions. 26Al and 10Be analyses of such sediment do not provide accurate ages for these tills, although they do yield limiting ages in some cases. We overcome this difficulty by instead measuring 26Al and 10Be in quartz from paleosols that are buried by tills. We use a more general mathematical approach to determine the initial nuclide concentrations in the paleosol at the time it was buried, as well as the duration of burial. This technique provides a widely applicable improvement on other means of dating Plio-Pleistocene terrestrial glacial sediments, as well as a framework for applying cosmogenic-nuclide dating techniques in complicated stratigraphic settings. We apply it to pre-Wisconsinan glacial sediment sequences in southwest Minnesota and eastern South Dakota. Pre-Wisconsinan tills underlying the Minnesota River Valley were deposited 0.5 to 1.5 Ma, and tills beneath the Prairie Coteau in eastern South Dakota and adjacent Minnesota were deposited 1 to 2 Ma.

  14. Dating chert using in-situ produced 10Be: Possible complications revealed on landslide scarps through a comparison with 36Cl applied to coexisting limestone.

    NASA Astrophysics Data System (ADS)

    Zerathe, Swann; Braucher, Régis; Lebourg, Thomas; Leani, Leatitia; Manetti, Michel; Bourles, Didier

    2013-04-01

    This abstract and presentation highlights potential complications that may arise while using in situ produced 10Be to date diagenetic silica (chert)exposure or burial event. The initiation and evolution of large gravitational collapses in sedimentary rocks were constrained using cosmic ray exposure dating. Because these collapses occurred in a stratigraphic level composed of chert (diagenetic silica) concretions interbedded in limestone layers, their development was studied by performing in situ-produced 36Cl and 10Be concentration measurements in both the limestone and coexisting diagenetic silica (chert), respectively. Following the routinely used decontamination and preparation protocols for 10Be produced in diagenetic silica, large discrepancies were observed with exposure ages determined by 36Cl within carbonate for samples originating from the same scarp. While 36Cl exposure ages were clustered as expected for a unique single gravitational event, 10Be exposure ages were scattered along the same studied scarps. To determine the origin of such a bias, petrological investigations were carried out for chert (diagenetic silica). Thin sections highlighted a complex mineralogical texture characterized by remnant silicified ooids showing calcitic cores, calcite inclusions and a dominant amorphous hydrated silica (grain > 20 μm). To decipher and characterize the potential origins of the excess measured 10Be within diagenetic silica, all samples were first reprocessed following the routine decontamination protocol (HCL-H2SiF6 leachings and three partial HF dissolutions) but starting from three different grain size fractions (GS1: 1000-500, GS2: 500-250 and GS3: 250-50 μm). The resulting concentrations clearly showed a decreasing 10Be content as a function of the grain size, but still yielded 10Be exposure ages significantly higher than 36Cl counterparts. Because potential adsorption of 10Be at the surface of amorphous silica grains was suspected, partial dissolution

  15. Investigation of the possible association of 10Be and 26Al with biogenic matter in the marine environment

    NASA Astrophysics Data System (ADS)

    Bourles, D.; Raisbeck, G. M.; Yiou, F.; Loiseaux, J. M.; Lieuvin, M.; Klein, J.; Middleton, R.

    1984-11-01

    As part of a more general investigation of the mechanism by which 10Be and 26Al are transported in the ocean, and eventually incorporated in various marine reservoirs, and the extent to which they are homogenized with 9Be and 27Al, we are studying the possible association of these isotopes with biogenic matter in the marine environment. To this end we have made measurements of 10Be and 9Be in: (a) the carbonate fraction of several marine animals (clam, cockel, starfish, mussel) and the organic fraction of mussels; (b) 20 samples of a 460 m coral reef core extending from the present to ˜ 7 Ma ago; (c) 2 samples of marine plankton; (d) 1 sample of paniculate matter in ocean surface water. 26Al has been measured in two coral samples. 10Be measurements have been made on the Grenoble cyclotron, the University of Pennsylvania tandem and, most recently, on the French Tandetron. 26Al was measured at the Pennsylvania tandem. 9Be and 27Al were measured using flameless atomic absorption spectrometry. These investigations have taken on added significance with the discovery of 10Be in crude petroleum, and the possibility that 14Be concentration (or 10Be/ 9Be ratios) might be used to estimate the age of recent petroleum, or petroleum precursor, formation.

  16. Examination of surface exposure age of Antarctic moraines using in situ produced [sup 10]Be and [sup 26]Al

    SciTech Connect

    Brown, E.T.; Edmond, J.M. ); Raisbeck, G.M.; Yiou, F. ); Kurz, M.D.; Brook, E.J. )

    1991-08-01

    Concentrations of [sup 10]Be (t[sub 1/2] = 1.5 [times] 10[sup 6]y) and [sup 26]Al (t[sub 1/2] = 0.72 [times] 10[sup 6]y) have been determined by accelerator mass spectrometry (AMS) in a suite of quartz samples taken from sandstone boulders in several moraines in Arena Valley, a dry valley adjacent to the Taylor Glacier in the Quatermain Mountains, Southern Victoria Land, East Antarctica. These isotopes are produced in surficial quartz by cosmic ray spallation of O and Si. The concentrations in these samples ranged from 6.1 [times] 10[sup 5] to 3.0 [times] 10[sup 7] at g[sup [minus]1] for [sup 10]Be and from 9.4 [times] 10[sup 6] to 1.2 [times] 10[sup 8] at g[sup [minus]1] for [sup 26]Al, depending upon the extent of exposure at the surface. Production rates of 17[sub [minus]4][sup +16] at g[sup [minus]1]y[sup [minus]1] for [sup 10]Be and 113[sub [minus]16][sup +54] at g[sup [minus]1]y[sup [minus]1] for [sup 26]Al at 1300 m and 87[degree]S and a [sup 26]Al:[sup 10]Be production ratio of 6.5[sub [minus]1.3][sup +1.3] were calculated from the data. These values correspond to sea-level production rates at high geomagnetic latitude of 6.4 at g[sup [minus]1]y[sup [minus]1] and 41.7 at g[sup [minus]1]y[sup [minus]1] for [sup 10]Be and [sup 26]Al, respectively, consistent with determinations based on [approximately]11 Ky glacially polished surfaces in the Sierra Nevada in California. These production rates imply exposure ages for the various moraines ranging from 50 Ky to 2.5 My, in accordance with other geological evidence. The [sup 10]Be and [sup 26]Al ages of these rocks compare favorably with those found using a similar dating method based on in situ production of [sup 3]He.

  17. Constraints on 10Be and 41Ca distribution in the early solar system from 26Al and 10Be studies of Efremovka CAIs

    NASA Astrophysics Data System (ADS)

    Srinivasan, Gopalan; Chaussidon, Marc

    2013-07-01

    Three refractory coarse grained CAIs from the Efremovka CV3 chondrite, one (E65) previously shown to have formed with live 41Ca, were studied by ion microprobe for their 26Al-26Mg and 10Be-10B systematic in order to better understand the origin of 10Be. The high precision Al-Mg data and the inferred 26Al/27Al values attest that the precursors of the three CAIs evolved in the solar nebula over a period of few hundred thousand years before last melting-crystallization events. The initial 10Be/9Be ratios and δ10B values defined by the 10Be isochrons for the three Efremovka CAIs are similar within errors. The CAI 10Be abundance in published data underscores the large range for initial 10Be/9Be ratios. This is contrary to the relatively small range of 26Al/27Al variations in CAIs around the canonical ratio. Two models that could explain the origin of this large 10Be/9Be range are assessed from the collateral variations predicted for the initial δ10B values: (i) closed system decay of 10Be from a "canonical" 10Be/9Be ratio and (ii) formation of CAIs from a mixture of solid precursors and nebula gas irradiated during up to a few hundred thousand years. The second scenario is shown to be the most consistent with the data. This shows that the major fraction of 10Be in CAIs was produced by irradiation of refractory grains, while contributions of galactic cosmic rays trapping and early solar wind irradiation are less dominant. The case for 10Be production by solar cosmic rays irradiation of solid refractory precursors poses a conundrum for 41Ca because the latter is easily produced by irradiation and should be more abundant than what is observed in CAIs. 10Be production by irradiation from solar energetic particles requires high 41Ca abundance in early solar system, however, this is not observed in CAIs.

  18. Dating offset fans along the Mojave section of the San Andreas fault using cosmogenic 26Al and 10Be

    USGS Publications Warehouse

    Matmon, A.; Schwartz, D.P.; Finkel, R.; Clemmens, S.; Hanks, T.

    2005-01-01

    Analysis of cosmogenic 10Be and 26Al in samples collected from exposed boulders (n = 20) and from buried sediment (n = 3) from offset fans along the San Andreas fault near Little Rock, California, yielded ages, ranging from 16 to 413 ka, which increase with distance from their source at the mouth of Little Rock Creek. In order to determine the age of the relatively younger fans, the erosion rate of the boulders and the cosmogenic nuclide inheritance from exposure prior to deposition in the fan were established. Cosmogenic nuclide inheritance values that range between 8.5 ?? 103 and 196 ?? 103 atoms 10Be g-1 quartz were determined by measuring the concentrations and ratios of 10Be and 26Al in boulders (n = 10) and fine sediment (n = 7) at the outlet of the present active stream. Boulder erosion rate, ranging between 17 and 160 mm k.y.-1, was estimated by measuring 10Be and 26Al concentrations in nearby bedrock outcrops (n = 8). Since the boulders on the fans represent the most resistant rocks in this environment, we used the lowest rate for the age calculations. Monte Carlo simulations were used to determine ages of 16 ?? 5 and 29 ?? 7 ka for the two younger fan surfaces. Older fans (older than 100 ka) were dated by analyzing 10Be and 26Al concentrations in buried sand samples. The ages of the three oldest fans range between 227 ?? 242 and 413 ?? 185 ka. Although fan age determinations are accompanied by large uncertainties, the results of this study show a clear trend of increasing fan ages with increasing distance from the source near Little Rock Creek and provide a long-term slip rate along this section of the San Andreas fault. Slip rate along the Mojave section of the San Andreas fault for the past 413 k.y. can be determined in several ways. The average slip rate calculated from the individual fan ages is 4.2 ?? 0.9 cm yr-1. A linear regression through the data points implies a slip rate of 3.7 ?? 1.0 cm yr-1. A most probable slip rate of 3.0 ?? 1.0 cm yr-1 is

  19. 26Al/10Be dating of an aeolian dust mantle soil in western New South Wales, Australia

    NASA Astrophysics Data System (ADS)

    Fisher, Adrian; Fink, David; Chappell, John; Melville, Michael

    2014-08-01

    Aeolian dust mantle soils are an important element of many landscapes in south-eastern Australia, though the age of these aeolian deposits has not been radiometrically determined. At Fowlers Gap in western New South Wales, surface cobbles of silcrete and quartz overlie a stone-free, aeolian dust mantle soil, which has a thickness of about 1.6 m. The clay-rich aeolian dust deposit in turn lies upon a buried silcrete and quartz stone layer. Modelling in-situ cosmogenic 26Al and 10Be concentrations measured in both the surface quartz stones and in the buried quartz layer of rocks, reveals that each has experienced a complex exposure-burial history. Due to the absence of quartz stones or sand at intermediate depths, our cosmogenic 26Al and 10Be modelling was not able to determine a definitive mechanism of stone pavement formation and stone burial. Various scenarios of stone formation, transport, burial and exhumation were tested that constrain the age of the deposit to range from 0.9 ± 0.2 Ma to 1.8 ± 0.2 Ma, based largely on different assumptions taken for the time-dependency of the net sedimentation rate. This corresponds with the initiation of the Simpson Desert dune fields and the deflation of lakes in central Australia, which probably responded to the shift to longer-wavelength, larger-amplitude Quaternary glacial cycles at around 1 Ma. Sensitivity analyses were carried out to identify those parameters which better constrained model outputs. Within model errors, which largely are the result of analytical errors in measured 26Al and 10Be concentrations, all three competing theories of colluvial wash, upward displacement of stones, and cumulic pedogenesis are possible mechanisms for the formation of the surface stone pavement.

  20. XCAMS: The compact 14C accelerator mass spectrometer extended for 10Be and 26Al at GNS Science, New Zealand

    NASA Astrophysics Data System (ADS)

    Zondervan, A.; Hauser, T. M.; Kaiser, J.; Kitchen, R. L.; Turnbull, J. C.; West, J. G.

    2015-10-01

    A detailed description is given of the 0.5 MV tandem accelerator mass spectrometry (AMS) system for 10Be, 14C, 26Al, installed in early 2010 at GNS Science, New Zealand. Its design follows that of previously commissioned Compact 14C-only AMS (CAMS) systems based on the Pelletron tandem accelerator. The only basic departure from that design is an extension of the rare-isotope achromat with a 45° magnet and a two-anode gas-ionisation detector, to provide additional filtering for 10Be. Realised performance of the three AMS modes is discussed in terms of acceptance-test scores, 14C Poisson and non-Poisson errors, and 10Be detection limit and sensitivity. Operational details and hardware improvements, such as 10Be beam transport and particle detector setup, are highlighted. Statistics of repeat measurements of all graphitised 14C calibration cathodes since start-up show that 91% of their total uncertainty values are less than 0.3%, indicating that the rare-isotope beamline extension has not affected precision of 14C measurement. For 10Be, the limit of detection in terms of the isotopic abundance ratio 10Be/9Be is 6 × 10-15 at at-1 and the total efficiency of counting atoms in the sample cathode is 1/8500 (0.012%).

  1. Potentials and pitfalls of depth profile (10Be), burial isochron (26Al/10Be) and palaeomagnetic techniques for dating Early Pleistocene terrace deposits of the Moselle valley (Germany)

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; Cordier, Stéphane; May, Simon Matthias; Kelterbaum, Daniel; Szemkus, Nina; Keulertz, Rebecca; Dunai, Tibor; Binnie, Steven; Hambach, Ulrich; Scheidt, Stephanie; Brueckner, Helmut

    2016-04-01

    Throughout the river network of the Rhenish Massif the so-called main terraces complex (MTC) forms the morphological transition between a wide upper palaeovalley and a deeply incised lower valley. The youngest level of this complex (YMT), directly located at the edge of the incised valley, represents a dominant geomorphic feature; it is often used as a reference level to identify the beginning of the main middle Pleistocene incision episode (Demoulin & Hallot, 2009). Although the main terraces are particularly well preserved in the lower Moselle valley, a questionable age of ca. 800 ka is assumed for the YMT, mainly based on the uncertain extrapolation of controversially interpreted palaeomagnetic data obtained in the Rhine valley. In this study, we applied terrestrial cosmogenic nuclide (TCN) dating (10Be/26Al) and palaeomagnetic dating to Moselle fluvial sediments of the MTC. To unravel the spatio-temporal characteristics of the Pleistocene evolution of the valley, several sites along the lower Moselle were sampled following two distinct TCN dating strategies: depth profiles where the original terrace (palaeo-) surface is well preserved and did not experience a major post-depositional burial (e.g., loess cover); and the isochron technique, where the sediment thickness exceeds 4.5-5 m. One terrace deposit was sampled for both approaches (reference site). In addition, palaeomagnetic sampling was systematically performed in each terrace sampled for TCN measurements. The TCN dating techniques show contrasting results for our reference site. Three main issues are observed for the depth profile method: (i) an inability of the modeled profile to constrain the 10Be concentration of the uppermost sample; (ii) an overestimated density value as model output; and (iii) a probable concentration steady state of the terrace deposits. By contrast, the isochron method yields a burial age estimate of 1.26 +0.29/-0.25 Ma, although one sample showed a depleted 26Al/10Be ratio

  2. Production of cosmogenic isotopes 7Be, 10Be, 14C, 22Na, and 36Cl in the atmosphere: Altitudinal profiles of yield functions

    NASA Astrophysics Data System (ADS)

    Poluianov, S. V.; Kovaltsov, G. A.; Mishev, A. L.; Usoskin, I. G.

    2016-07-01

    New consistent and precise computations of the production of five cosmogenic radioisotopes, 7Be, 10Be, 14C, 22Na, and 36Cl, in the Earth's atmosphere by cosmic rays are presented in the form of tabulated yield functions. For the first time, a detailed set of the altitude profiles of the production functions is provided which makes it possible to apply the results directly as input for atmospheric transport models. Good agreement with most of the earlier published works for columnar and global isotopic production rates is shown. Altitude profiles of the production are important, in particular for such tasks as studies of strong solar particle events in the past, precise reconstructions of solar activity on long-term scale, tracing air mass dynamics using cosmogenic radioisotopes, etc. As an example, computations of the 10Be deposition flux in the polar region are shown for the last decades and also for a period around 780 A.D. and confronted with the actual measurements in Greenland and Antarctic ice cores.

  3. Cosmogenic 10Be and 36Cl geochronology of offset alluvial fans along the northern Death Valley fault zone: Implications for transient strain in the eastern California shear zone

    USGS Publications Warehouse

    Frankel, K.L.; Brantley, K.S.; Dolan, J.F.; Finkel, R.C.; Klinger, R.E.; Knott, J.R.; Machette, M.N.; Owen, L.A.; Phillips, F.M.; Slate, J.L.; Wernicke, B.P.

    2007-01-01

    The northern Death Valley fault zone (NDVFZ) has long been recognized as a major right-lateral strike-slip fault in the eastern California shear zone (ECSZ). However, its geologic slip rate has been difficult to determine. Using high-resolution digital topographic imagery and terrestrial cosmogenic nuclide dating, we present the first geochronologically determined slip rate for the NDVFZ. Our study focuses on the Red Wall Canyon alluvial fan, which exposes clean dextral offsets of seven channels. Analysis of airborne laser swath mapping data indicates ???297 ?? 9 m of right-lateral displacement on the fault system since the late Pleistocene. In situ terrestrial cosmogenic 10Be and 36C1 geochronology was used to date the Red Wall Canyon fan and a second, correlative fan also cut by the fault. Beryllium 10 dates from large cobbles and boulders provide a maximum age of 70 +22/-20 ka for the offset landforms. The minimum age of the alluvial fan deposits based on 36Cl depth profiles is 63 ?? 8 ka. Combining the offset measurement with the cosmogenic 10Be date yields a geologic fault slip rate of 4.2 +1.9/-1.1 mm yr-1, whereas the 36Cl data indicate 4.7 +0.9/-0.6 mm yr-1 of slip. Summing these slip rates with known rates on the Owens Valley, Hunter Mountain, and Stateline faults at similar latitudes suggests a total geologic slip rate across the northern ECSZ of ???8.5 to 10 mm yr-1. This rate is commensurate with the overall geodetic rate and implies that the apparent discrepancy between geologic and geodetic data observed in the Mojave section of the ECSZ does not extend north of the Garlock fault. Although the overall geodetic rates are similar, the best estimates based on geology predict higher strain rates in the eastern part of the ECSZ than to the west, whereas the observed geodetic strain is relatively constant. Copyright 2007 by the American Geophysical Union.

  4. Eroding and Inflating the Atacama Desert, Chile: Insights Through Cosmogenic 10-Be, 26-Al and 21-Ne

    NASA Astrophysics Data System (ADS)

    Heimsath, A. M.; Jungers, M. C.; Amundson, R.; Balco, G.; Shuster, D. L.

    2010-12-01

    Enigmas of the Atacama Desert are as abundant as the hypotheses formulated to explain them. This fascinating and extreme landscape attracts scientists from disparate disciplines, spawning remarkable insights into the connections between climate, tectonics, biota and landscape evolution. Recent work explores such connections on timescales ranging from millions to thousands of years. Both the timing of the onset of hyperaridity in the Atacama and its relationship to the uplift of the Andes are especially well-debated topics. Similarly enigmatic, but less widely studied, are the connections between the timing of hyperaridity and the surface morphology of the region. Specifically, the extent, nature, and timing of formation for the extensive salars across the Atacama are undeniably linked to the climate history of the region. Adjacent to the extensive salars are landscapes that appear to be shaped by processes more typically associated with temperate landscapes: rilling and gullying, extensive terrace deposition, steep fault scarps, landslide deposits, and extensive fan and paleosurface deposits. Our primary goal in this project is to establish chronologies and rates for the surface processes driving landscape evolution for two field regions in the Atacama. To achieve this goal we are also testing and expanding upon the burial dating methodology (Balco and Shuster, 2009) that couples the stable cosmogenic nuclide, 21Ne, with the radiogenic nuclides, 10Be and 26Al. Here we present new results from remarkably different field settings from the north-central Atacama. The southern region, inland from Antofagasta, is relatively well studied to determine how the onset of hyperaridity impacted water-driven processes. The northern region, north of the Rio Loa and Calama, differs most notably by the enormous basin fills of salt (e.g. Salar de Llamara and Salar Grande) and evidence of more extensive recently active salars. Across both regions we use in 10Be, 26Al, and 21Ne to

  5. Formation and geomorphologic history of the Lonar impact crater deduced from in situ cosmogenic 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Nakamura, Atsunori; Yokoyama, Yusuke; Sekine, Yasuhito; Goto, Kazuhisa; Komatsu, Goro; Kumar, P. Senthil; Matsuzaki, Hiroyuki; Kaneoka, Ichiro; Matsui, Takafumi

    2014-08-01

    Lonar impact crater is one of a few craters on Earth formed directly in basalt, providing a unique opportunity to study an analog for crater degradation processes on Mars. Here we present surface 10Be and 26Al exposure dates in order to determine the age and geomorphic evolution of Lonar crater. Together with a 14C age of preimpact soil, we obtain a crater age of 37.5 ± 5.0 ka, which contrasts with a recently reported and apparently older 40Ar/39Ar age (570 ± 47 ka). This suggests that the 40Ar/39Ar age may have been affected by inherited radiogenic 40Ar (40Ar*inherited) in the impact glass. The spatial distribution of surface exposure ages of Lonar crater differs from that for Barringer crater, indicating Lonar crater rim is actively eroding. Our new chronology provides a unique opportunity to compare the geomorphological history of the two craters, which have similar ages and diameters, but are located in different climate and geologic settings.

  6. Rates of sediment supply to arroyos from upland erosion determined using in situ produced cosmogenic 10Be and 26Al

    USGS Publications Warehouse

    Clapp, Erik M.; Bierman, Paul R.; Nichols, Kyle K.; Pavich, Milan; Caffee, Marc A.

    2001-01-01

    Using 10Be and 26Al measured in sediment and bedrock, we quantify rates of upland erosion and sediment supply to a small basin in northwestern New Mexico. This and many other similar basins in the southwestern United States have been affected by cycles of arroyo incision and backfilling several times in the past few millennia. The sediment generation (275 ± 65 g m−2 yr−1) and bedrock equivalent lowering rates (102 ± 24 m myr−1) we determine are sufficient to support at least three arroyo cycles in the past 3,000 years, consistent with rates calculated from a physical sediment budget within the basin and regional rates determined using other techniques. Nuclide concentrations measured in different sediment sources and reservoirs suggest that the arroyo is a good spatial and temporal integrator of sediment and associated nuclide concentrations from throughout the basin, that the basin is in steady-state, and that nuclide concentration is independent of sediment grain size. Differences between nuclide concentrations measured in sediment sources and reservoirs reflect sediment residence times and indicate that subcolluvial bedrock weathering on hillslopes supplies more sediment to the basin than erosion of exposed bedrock.

  7. 26Al - 10Be cosmogenic nuclide isochron burial dating in combination with luminescence dating of two Danube terraces

    NASA Astrophysics Data System (ADS)

    Neuhuber, Stephanie; Braumann, Sandra; Lüthgens, Christopher; Fiebig, Markus; Häuselmann, Philipp; Schäfer, Jörg

    2016-04-01

    The Quaternary sediment record in the Vienna Basin is influenced by two main factors: (1) the tectonic development of a pull apart basin along a sinistral strike slip fault system between the Eastern Alps and the West Carpathians and by (2) strongly varying sediment supply during the Plio- and Pleistocene. From the Late Pannonian (8.8 Ma) onward a large-scale regional uplift (Decker et al., 2005) controls terrace formation in the Vienna Basin. The main sediment supply into the Vienna Basin originates from the Danube, and subordinately from tributaries to the south such as Piesting, Fischa, Leitha and from the north by the river March. Today the Danube forms a large floodplain that is bordered to the north by one large Pleistocene terrace, the Gänserndorf Terrace that is situated 17 m above todays water level. Farther to the east a smaller terrace, the Schlosshof Terrace, reaches 25 m above todays water level. These terrace levels are tilted by movement of underlying blocks (Peresson, 2006). Both, the Schlosshof and Gänserndorf terraces consist of successions of up to 2 m thick gravel beds with intercalated sand layers or -lenses that may locally reach thicknesses up to 0.8 m. At each terrace one gavel pit was selected to calculate the time of terrace deposition by luminescence dating in combination with 26Al/10Be cosmogenic nuclide isochrone dating (Balco and Rovery, 2008). Five quartz stones from the base of each terrace were physically and chemically processed to obtain Al and Be oxides for Acceleration Mass Spectrometry. Sand samples for luminescence dating were taken above the cosmogenic nuclide samples from the closest suitable sand body. Decker et al., 2005. QSR 24, 307-322 Peresson, 2006 Geologie der österreichischen Bundesländer Niederösterreich 255-258 Balco and Rovey, 2008. AJS 908, 1083-1114 Thanks to FWF P 23138-N19, OMAA 90öu17

  8. Formation age and geomorphologic history of the Lonar impact crater deduced from in- situ cosmogenic 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Nakamura, A.; Yokoyama, Y.; Sekine, Y.; Goto, K.; Komatsu, G.; Kumar, P.; Matsuzaki, H.; Matsui, T.

    2013-12-01

    Impact cratering is a dominant surface modification process on planetary surfaces. In the inner solar system, the large majority of impacts occur on bodies covered by primitive igneous rocks. However, most of the impacts remaining on Earth surface are on different rock types than that of the inner planet and hence geologic knowledge derived from Earth's surface cannot be translated readily. The Lonar crater is a 1.88-km-diameter crater located on the Deccan basaltic traps in India (ca. 65 Ma), and is one of a few craters on Earth bombarded directly on basaltic lava flows. Thus, the Lonar crater provides a rare opportunity to study impact structures on the basaltic surfaces of other terrestrial planets and the Moon. Since the ages of terrestrial impact structures is a key to understand geomorphological processes after the impact, various dating methods have been applied to the Lonar Crater such as fission track (Storzer and Koeberl, 2004), radiocarbon (Maloof, 2010), thermoluminescence (Sengupta et al., 1997), and 40Ar/39Ar (Jourdan et al., 2011). Yet, a large discrepancy between these methods ranging from ca. 1.79 to 570 ka has been resulted. Here we report surface exposure ages based on in-situ cosmogenic 10Be and 26Al in order to obtain a precise age of the Lonar crater formation as well as to study the geomorphologic evolution. The samples are collected from the topographic highs on the rim of the crater and from the ejecta blanket. Exposure ages together with newly obtained radiocarbon age of pre-impact soil indicate much younger ages than that of obtained from 40Ar/39Ar method. This suggests the potential bias because of inherited 40Ar in impact glass. Systematically young exposure age from the rim samples compared to the samples from the ejecta blanket indicate that the rim of the Lonar crater is being actively eroded. Spatial distributions of geomorphic ages observed from the Lonar creator is not the same as the pattern reported from the well

  9. Quaternary downcutting rate of the new river, Virginia, measured from differential decay of cosmogenic {sup 26}Al and {sup 10}Be in cave-deposited alluvium

    SciTech Connect

    Granger, D.E.; Kirchner, J.W.; Finkel, R.C.

    1997-02-01

    The concentrations of the cosmogenic radionuclides {sup 26}Al and {sup 10}Be in quartz can be used to date sediment burial. Here we use {sup 26} Al and {sup 10}Be in cave-deposited river sediment to infer the time of sediment emplacement. Sediment burial dates from a vertical sequence of caves along the New River constrain its Quaternary downcutting rate to 27.3{+-}4.5 m/m.y. and may provide evidence of regional tectonic tilt. 32 refs., 3 figs., 1 tab.

  10. The new AMS system at CEDAD for the analysis of 10Be, 26Al, 129I and actinides: Set-up and performances

    NASA Astrophysics Data System (ADS)

    Calcagnile, Lucio; Quarta, Gianluca; Maruccio, Lucio; Synal, Hans-Arno; Müller, Arnold Milenko

    2015-10-01

    The Centre for Dating and Diagnostics (CEDAD) at the University of Salento was established in 2001 and became fully operational for routine 14C radiocarbon dating in 2003. The facility has been continuously upgraded over the years with the installation of different beam lines for high energy ion implantation, IBA analyses both in vacuum and in air and nuclear microprobe. In 2011 a second AMS beamline was installed consisting of a dedicated high energy mass spectrometer for the AMS analysis of rare nuclides such as 10Be, 26Al, 129I and actinides. First tests on 10Be allowed to optimize the operating parameters resulting in the proper separation of 10Be from the interfering isobar 10B. In this paper we present the further tests and optimizations which resulted in an enhancement of the overall transmission efficiency, the reduction of the background (in the 10-15 range) and in the possibility to obtain precision levels in routine 10Be/9Be measurements of the order of 0.5%. Furthermore the first results obtained for the analysis of 26Al and 129I are also presented.

  11. Measurement of proton production cross sections of (sup 10)Be and (sup 26)Al from elements found in lunar rocks

    NASA Technical Reports Server (NTRS)

    Sisterson, J. M.; Kim, K.; Englert, P. A. J.; Caffee, M.; Jull, A. J. T.; Donahue, D. J.; McHargue, L.; Castaneda, C.; Vincent, J.; Reedy, R. C.

    1996-01-01

    Cosmic rays penetrate the lunar surface and interact with the lunar rocks to produce both radionuclides and stable nuclides. Production depth profiles for long-lived radionuclides produce in lunar rocks are measured using Accelerator Mass Spectrometry (AMS). For a particular radionuclide these production depth profiles can be interpreted to give an estimate for the solar proton flux over a time period characterized by the half life of the radionuclide under study. This analysis is possible if and only if all the cross sections for the interactions of all cosmic ray particles with all elements found in lunar rocks are well known. In practice, the most important cross sections needed are the proton production cross sections, because 98% of solar cosmic rays and (similar to)87% of galactic cosmic rays are protons. The cross sections for the production of long-lived radionuclides were very difficult to measure before the development of AMS and only in recent years has significant progress been made in determining these essential cross sections. Oxygen and silicon are major constituents of lunar rocks. We have reported already C-14 production cross sections from O and Si for proton energies 25-500 MeV, and O(p,x)(sup 10)Be from 58 160 MeV[6]. Here we present new measurements for the cross sections O(p,x)Be-10,O(p,x)Be-7, Si(p,x)Be-7,Si(p,x)Al-26, and Si(p,x)Na-22 from approximately 30 - 500 MeV.

  12. B and Mg isotopic variations in Leoville mrs-06 type B1 cai:origin of 10Be and 26Al

    NASA Astrophysics Data System (ADS)

    Chaussidon, M.; Robert, F.; Russel, S. S.; Gounelle, M.; Ash, R. D.

    2003-04-01

    The finding [1-3] in Ca-Al-rich refractory inclusions (CAI) of primitive chondrites of traces of the in situ decay of radioactive 10Be (half-life 1.5Myr) indicates that irradiation of the protosolar nebula by the young Sun in its T-Tauri phase has produced significant amounts of the Li-Be-B elements. This irradiation may have produced also some or all of the short-lived 26Al (half-life 0.7Myr) and 41Ca (half-life 0.1Myr) previously detected in CAIs. To constrain the origin of 10Be and 10Al it is important to look for coupled variations in the 10Be/9Be and 26Al/27Al ratios in CAIs and to understand the processes responsible for these variations (e.g. variations in the fluences of irradiation, secondary perturbations of the CAIs, ...) We have thus studied the Li and B isotopic compositions and the Be/Li and Be/B concentration ratios in one CAI (MRS-06) from the Leoville CV3 chondrite in which large variations of the Mg isotopic compositions showing both the in situ decay of 26Al and the secondary redistribution of Mg isotopes have been observed [4]. The results show large variations for the Li and B isotopic compositions (^7Li/^6Li ranging from 11.02±0.21 to 11.82±0.07, and 10B/11B ratios ranging from 0.2457±0.0053 to 0.2980±0.0085). The ^7Li/^6Li ratio tend to decrease towards the rim of the inclusion. The 10B/11B ratios are positively correlated with the ^9Be/11B ratios indicating the in situ decay of 10Be. However perturbations of the 10Be/B system are observed. They would correspond to an event which occurred approximately 2Myr after the formation of the CAI and the irradiation of the CAI precursors which is responsible for the 10Be observed in the core of the CAI. These perturbations seem compatible with those observed for the 26Al/Mg system but they might be due to an irradiation of the already-formed, isolated CAI which would have resulted in increased 10Be/^9Be ratios and low ^7Li/^6Li ratios in the margin of the CAI. [1] McKeegan K. D. et al. (2000

  13. 21Ne, 10Be and 26Al cosmogenic burial ages of near-surface eolian sand from the Packard Dune field, McMurdo Dry Valleys, Antarctica.

    NASA Astrophysics Data System (ADS)

    Fink, David; Augustinus, Paul; Rhodes, Ed; Bristow, Charles; Balco, Greg

    2015-04-01

    The McMurdo Dry Valleys, Antarctica, have been ice-free for at least 10 Ma. In Victoria Valley, the largest of the Dry Valleys, permafrosted yet still actively migrating dune-fields, occupy an area of ~8 km2 with dune thicknesses varying from ~5 to 70 meters. High-resolution ground penetrating radar (GPR) imaging of selected dunes reveal numerous unconformities and complex stratigraphy inferring cycles of sand accretion and deflation from westerly katabatic winter winds sourced from the East Antarctic Ice Sheet and anabatic summer winds sourced from the Ross Sea. Samples above permafrost depth were taken for OSL and cosmogenic 26Al/10Be burial ages. OSL ages from shallow (<1m) pits range from modern to ~1.3ka suggesting that deposition/reworking of the dunes is on-going and their present configuration is a late Holocene feature. The same 7 samples gave a mean 26Al/10Be = 4.53 +/- 5% with an average apparent continuous 10Be surface exposure age of 525 +/- 25 ka surprisingly indicating a common pre-history independent of depth. Correcting for minor post-burial production based on OSL ages, the minimum (integrated) burial period for these sand grains is 0.51+/- 0.12 Ma which represents the burial age at the time of arrival at the dune. A possible explanation is that this common burial signal reflects recycling episodes of exposure, deposition, burial and deflation, sufficiently frequent to move all grains towards a common pre-dune deposition history. However, it is unclear over what length of time this processes has been active and fraction of time the sand has been buried. Consequently we also analysed purified quartz aliquots of the same samples for a third and stable nuclide, 21Ne, to determine the total surface and burial exposure periods. Using the 21Ne/10Be system we obtain burial ages of 1.10 +/- 0.10 Ma. Further coring below permafrost is planned for austral summer 2015.

  14. Paleo-ocean chemistry records in marine opal: Implications for fluxes of trace elements, cosmogenic nuclides ( 10Be and 26Al), and biological productivity

    NASA Astrophysics Data System (ADS)

    Lal, D.; Charles, C.; Vacher, L.; Goswami, J. N.; Jull, A. J. T.; McHargue, L.; Finkel, R. C.

    2006-07-01

    Here, we provide evidence suggesting that marine (diatom) opal contains not only a high fidelity record of dissolved oceanic concentrations of cosmic ray-produced radionuclides, 10Be and 26Al, but also a record of temporal variations in a large number of trace elements such as Ti, Fe, Zn and Mn. This finding is derived from measurements in purified biogenic opal that can be separated from detrital materials using a newly developed technique based on surface charge characteristics. Initial results from a sediment core taken near the present-day position of the Antarctic Polar Front (ODP Site 1093) show dramatic changes in the intrinsic concentrations of, Be, Al, Ti, Fe, Mn and Zn in the opal assemblages during the past ˜140 kyr BP. The results imply appreciable climatically controlled fluctuations in the level of bioreactive trace elements. The time series of total Be, Al, Ti, Fe and 10Be in the sediment core are all well correlated with each other and with dust records in the polar ice cores. The observations suggest that a significant flux of these trace metals to oceans is contributed by the aeolian dust, in this case, presumably from the Patagonia. This observation also allows determination of fluxes of dust-contributed 10Be to the Antarctica ice sheets. However, our data show that the relationships among the various metals are not perfectly linear. During periods of higher dissolved concentrations of trace elements (indicated by Fe and Ti) the relative concentrations of bioreactive elements, Be, Al, Mn and Zn are decreased. By contrast, the Fe/Zn and Fe/Mn ratios decrease significantly during each transition from cold to warm periods. The relative behavior could be consistent with any of the following processes: (i) enhanced biological productivity due to greater supply of the bioreactive elements (e.g. Zn) during cold periods (ii) increased biological and inorganic scavenging of particle active elements (e.g. Be and Al) during early interglacial periods (iii

  15. Long-term slip rate of the southern San Andreas Fault, from 10Be-26Al surface exposure dating of an offset alluvial fan

    SciTech Connect

    der Woerd, J v; Klinger, Y; Sieh, K; Tapponnier, P; Ryerson, F; M?riaux, A

    2006-01-13

    We determine the long-term slip rate of the southern San Andreas Fault in the southeastern Indio Hills using {sup 10}Be and {sup 26}Al isotopes to date an offset alluvial fan surface. Field mapping complemented with topographic data, air photos and satellite images allow to precisely determine piercing points across the fault zone that are used to measure an offset of 565 {+-} 80 m. A total of twenty-six quartz-rich cobbles from three different fan surfaces were collected and dated. The tight cluster of nuclide concentrations from 19 samples out of 20 from the offset fan surface implies a simple exposure history, negligible prior exposure and erosion, and yield an age of 35.5 {+-} 2.5 ka. The long-term slip rate of the San Andreas Fault south of Biskra Palms is thus 15.9 {+-} 3.4 mm/yr. This rate is about 10 mm/yr slower than geological (0-14 ka) and short-term geodetic estimates for this part of the San Andreas Fault implying changes in slip rate or in faulting behavior. This result puts new constraints on the slip rate of the San Jacinto and on the Eastern California Shear Zone for the last 35 ka. Our study shows that more sites along the major faults of southern California need to be targeted to better constrain the slip-rates over different time scales.

  16. Quantifying denudation rates on inselbergs in the central Namib Desert using in situ-produced cosmogenic {sup 10}Be and {sup 26}Al

    SciTech Connect

    Cockburn, H.A.P.; Summerfield, M.A.; Seidl, M.A.

    1999-05-01

    In situ-produced cosmogenic isotope concentrations in bedrock surfaces provide valuable estimates of site-specific, long-term rates of denudation and provide constraints for numerical landscape-evolution models. Measurements of cosmogenic {sup 10}Be and {sup 26}Al from graphite inselbergs in the arid to hyperarid central Namib Desert, Namibia, indicate a mean rate of summit lowering of 5.07 {+-} 1.1 m/m.y. over the past {ge} 10{sup 5} yr. The persistence of an arid climate in the region suggests that a similar rate may have prevailed for the past {approximately} 10 m.y. and possibly throughout much of the Cenozoic. Some samples have complex exposure histories that can be explained by the mode of inselberg weathering and mass wasting. The denudation rates estimated here are an order of magnitude higher than those reported for inselbergs in a significantly more humid environment in South Australia. This difference may largely be due to active salt weathering in the central Namib as a result of high levels of coastal fog precipitation.

  17. Unraveling the Quaternary river incision in the Moselle valley (Rhenish Massif, Germany): new insights from cosmogenic nuclide dating (10Be/26Al) of the Main Terrace complex

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; Cordier, Stéphane; Harmand, Dominique; May, Simon Matthias; Kelterbaum, Daniel; Dunai, Tibor; Binnie, Steven; Brückner, Helmut

    2014-05-01

    Throughout the whole river network of the Rhenish Massif, the terrace complex of the so-called Main Terrace forms the morphological transition between a wide upper palaeovalley (plateau valley) and a deeply incised lower valley. The youngest level of this Main Terrace complex (YMT), directly located at the edge of the incised valley, represents a dominant geomorphic feature in the terrace flight; it is often used as a reference level to identify the start of the main middle Pleistocene incision episode (Demoulin & Hallot, 2009). The latter probably reflects the major tectonic pulse that affected the whole Massif and was related to an acceleration of the uplift rates (Demoulin & Hallot, 2009). The Main terraces are particularly well preserved in the lower Moselle valley and are characterized by a constant absolute elevation of their base along a 150 km-long reach. Despite that various hypotheses have been proposed to explain this horizontality (updoming, faulting...), all studies assumed an age of ca. 800 ka for the YMT, mainly based on the questionable extrapolation of palaeomagnetic data obtained in the Rhine valley. Therefore, a reliable chronological framework is still required to unravel the spatio-temporal characteristics of the Pleistocene evolution of the Moselle valley. In this study, we apply cosmogenic nuclide dating (10Be/26Al) to fluvial sediments pertaining to the Main Terrace complex or to the upper Middle Terraces. Several sites along the lower Moselle were sampled following two distinct sampling strategies: (i) depth profiles where the original terrace (palaeo-)surface is well preserved and did not experience much postdepositional burial (e.g., loess cover); and (ii) the isochron technique where the sediment thickness exceeds 3 m. Cosmogenic nuclide ages recently obtained for three rivers in the Meuse catchment in the western Rhenish Massif demonstrated that the Main Terraces were younger than expected and their abandonment was diachronic along the

  18. Deglaciation of Antarctica since the Last Glacial Maximum - what can we learn from cosmogenic 10Be and 26Al exposure ages?

    NASA Astrophysics Data System (ADS)

    Fink, David

    2015-04-01

    Ice volume changes at the coastal margins of Antarctica during the global LGM are uncertain. The little evidence available suggests that behaviour of the East and West Antarctic Ice Sheets are markedly different and complex. It is hypothesised that during interglacials, thinning of the Ross Ice Shelf, a more open-water environment and increased precipitation, allowed outlet glaciers draining the Transantarctic Mnts and fed by interior Ice Sheets to advance during moist warmer periods, out of phase with colder arid periods. In contrast, glacier dynamics along the vast coastal perimeter of East Antarctica is strongly influenced by Southern Ocean conditions. Cosmogenic 10Be and 26Al chronologies, although restricted to ice-free oasis and mountains flanking drainage glaciers, has become an invaluable, if not unique, tool to quantify spatial and temporal Pleistocene ice sheet variability over the past 2 Ma. Despite an increasing number of well documented areas, extracting reliable ages from glacial deposits in polar regions is problematic. Recycling of previously exposed/ buried debris and continual post-depositional modification leads to age ambiguities for a coeval glacial landform. More importantly, passage of cold-based ice can leave a landform unmodified resulting in young erratics deposited on ancient bedrock. Advances in delivering in-situ radiocarbon to routine application offer some relief. Exposure ages from different localities throughout East Antarctica (Framnes Mnts, Lutzow-Holm Bay, Vestfold Hills) and West Antarctica (Denton Ranges, Hatherton Glacier, Shackleton Range) highlight some of the new findings. This talk presents results which quantify the magnitude and timing of paleo-ice sheet thickness changes, questions the validity of an Antarctic LGM and discusses the complexities encountered in the often excessive spread in exposure ages.

  19. Roter Kamm Impact Crater, Namibia: Age Constraints from K-Ar, Rb-Sr, Fission Track, 10Be-26Al Studies

    NASA Astrophysics Data System (ADS)

    Koeberl, C.; Klein, J.; Matsuda, J.; Nagao, K.; Reimold, W. U.; Storzer, D.

    1992-07-01

    INTRODUCTION. The Roter Kamm impact crater is located in the Namib Desert in Namibia. The impact occurred in Precambrian granitic-granodioritic orthogneisses of the 1200-900-Ma-old Namaqualand Metamorphic Complex. The granites are invaded by quartz veins and quartz-feldspar-pegmatites. Gariep metasediments probably overlaid the Namaqualand complex at the time of the impact (Reimold and Miller, 1989). Previous estimates for the crater age are not well constrained: regional geology suggests an age of 5-10 Ma, while the only available ^40Ar-^39Ar age (Hartung et al., 1991) is 3.7 Ma. Fission tracks measured in apatites from granites found on or near the crater rim were not completely reset by the impact and suggest an uplift event around 20 Ma ago (Storzer et al., 1990). We are using several approaches to bracket the age of the crater: we have measured melt breccia and pseudotachylite K-Ar ages, and apatite fission track ages in several rim granites. We are comparing Rb-Sr isotope data for rim granites with known ages of regional resetting events (Allsopp et al., 1979). Finally, we are using ^10Be-^26Al measured by accelerator mass spectrometry to determine surface exposure ages for quartz excavated during the impact event. RESULTS AND DISCUSSION. The target rock composition and stratigraphy at Roter Kamm is relatively complicated. Melt breccias formed from pegmatites, gneisses, or schists, while pseudotachylites probably formed from gneissic basement or quartz-feldspar-pegmatites (Reimold and Miller, 1989). Whole rock Rb-Sr data for several granites yield 1498 Ma, and mineral separates from sample URK-M indicate an "age" of 466 Ma; these ages are similar to those of country rocks from the general area of the northwestern Cape/southern Namibia (Allsopp et al., 1979) which indicate two widespread regional resetting events at ca. 700 Ma (related to the Pan-African orogenic deformation), and ca. 500 Ma, related to a subsequent metamorphic event. For K-Ar ages, we

  20. Cosmogenic 10Be and 26Al exposure ages of tors and erratics, Cairngorm Mountains, Scotland: Timescales for the development of a classic landscape of selective linear glacial erosion

    USGS Publications Warehouse

    Phillips, W.M.; Hall, A.M.; Mottram, R.; Fifield, L.K.; Sugden, D.E.

    2006-01-01

    The occurrence of tors within glaciated regions has been widely cited as evidence for the preservation of relic pre-Quaternary landscapes beneath protective covers of non-erosive dry-based ice. Here, we test for the preservation of pre-Quaternary landscapes with cosmogenic surface exposure dating of tors. Numerous granite tors are present on summit plateaus in the Cairngorm Mountains of Scotland where they were covered by local ice caps many times during the Pleistocene. Cosmogenic 10Be and 26Al data together with geomorphic relationships reveal that these landforms are more dynamic and younger than previously suspected. Many Cairngorm tors have been bulldozed and toppled along horizontal joints by ice motion, leaving event surfaces on tor remnants and erratics that can be dated with cosmogenic nuclides. As the surfaces have been subject to episodic burial by ice, an exposure model based upon ice and marine sediment core proxies for local glacial cover is necessary to interpret the cosmogenic nuclide data. Exposure ages and weathering characteristics of tors are closely correlated. Glacially modified tors and boulder erratics with slightly weathered surfaces have 10Be exposure ages of about 15 to 43 ka. Nuclide inheritance is present in many of these surfaces. Correction for inheritance indicates that the eastern Cairngorms were deglaciated at 15.6 ?? 0.9 ka. Glacially modified tors with moderate to advanced weathering features have 10Be exposure ages of 19 to 92 ka. These surfaces were only slightly modified during the last glacial cycle and gained much of their exposure during the interstadial of marine Oxygen Isotope Stage 5 or earlier. Tors lacking evidence of glacial modification and exhibiting advanced weathering have 10Be exposure ages between 52 and 297 ka. Nuclide concentrations in these surfaces are probably controlled by bedrock erosion rates instead of discrete glacial events. Maximum erosion rates estimated from 10Be range from 2.8 to 12.0 mm/ka, with

  1. Formation of the Short-lived Radionuclide 36Cl in the Protoplanetary Disk During Late-stage Irradiation of a Volatile-rich Reservoir

    NASA Astrophysics Data System (ADS)

    Jacobsen, Benjamin; Matzel, Jennifer; Hutcheon, Ian D.; Krot, Alexander N.; Yin, Qing-Zhu; Nagashima, Kazuhide; Ramon, Erick C.; Weber, Peter K.; Ishii, Hope A.; Ciesla, Fred J.

    2011-04-01

    Short-lived radionuclides (SLRs) in the early solar system provide fundamental insight into protoplanetary disk evolution. We measured the 36Cl-36S-isotope abundance in wadalite (<15 μm), a secondary chlorine-bearing mineral found in calcium-aluminum-rich inclusions (CAIs) in the Allende CV chondrite, to decipher the origin of the SLR 36Cl (τ 1/2 ~ 3 × 105 yr) in the early solar system. Its presence, initial abundance, and the noticeable decoupling from 26Al raise serious questions about the origin of SLRs. The inferred initial 36Cl abundance for wadalite, corresponding to a 36Cl/35Cl ratio of (1.81 ± 0.13) × 10-5, is the highest 36Cl abundance ever reported in any early solar system material. The high level of 36Cl in wadalite and the absence of 26Al (26Al/27Al <= 3.9 × 10-6) in co-existing grossular (1) unequivocally support the production of 36Cl by late-stage solar energetic particle irradiation in the protoplanetary disk and (2) indicates that the production of 36Cl, recorded by wadalite, is unrelated to the origin of 26Al and other SLRs (10Be, 53Mn) recorded by primary minerals of CAIs and chondrules. We infer that 36Cl was largely produced by irradiation of a volatile-rich reservoir in an optically thin protoplanetary disk adjacent to the region in which the CV chondrite parent asteroid accreted while the Sun was a weak T Tauri star. Subsequently, 36Cl accreted into the Allende CV chondrite together with condensed water ices.

  2. FORMATION OF THE SHORT-LIVED RADIONUCLIDE {sup 36}Cl IN THE PROTOPLANETARY DISK DURING LATE-STAGE IRRADIATION OF A VOLATILE-RICH RESERVOIR

    SciTech Connect

    Jacobsen, Benjamin; Yin Qingzhu; Matzel, Jennifer; Hutcheon, Ian D.; Ramon, Erick C.; Weber, Peter K.; Krot, Alexander N.; Nagashima, Kazuhide; Ishii, Hope A.; Ciesla, Fred J.

    2011-04-20

    Short-lived radionuclides (SLRs) in the early solar system provide fundamental insight into protoplanetary disk evolution. We measured the {sup 36}Cl-{sup 36}S-isotope abundance in wadalite (<15 {mu}m), a secondary chlorine-bearing mineral found in calcium-aluminum-rich inclusions (CAIs) in the Allende CV chondrite, to decipher the origin of the SLR {sup 36}Cl ({tau}{sub 1/2} {approx} 3 x 10{sup 5} yr) in the early solar system. Its presence, initial abundance, and the noticeable decoupling from {sup 26}Al raise serious questions about the origin of SLRs. The inferred initial {sup 36}Cl abundance for wadalite, corresponding to a {sup 36}Cl/{sup 35}Cl ratio of (1.81 {+-} 0.13) x 10{sup -5}, is the highest {sup 36}Cl abundance ever reported in any early solar system material. The high level of {sup 36}Cl in wadalite and the absence of {sup 26}Al ({sup 26}Al/{sup 27}Al {<=} 3.9 x 10{sup -6}) in co-existing grossular (1) unequivocally support the production of {sup 36}Cl by late-stage solar energetic particle irradiation in the protoplanetary disk and (2) indicates that the production of {sup 36}Cl, recorded by wadalite, is unrelated to the origin of {sup 26}Al and other SLRs ({sup 10}Be, {sup 53}Mn) recorded by primary minerals of CAIs and chondrules. We infer that {sup 36}Cl was largely produced by irradiation of a volatile-rich reservoir in an optically thin protoplanetary disk adjacent to the region in which the CV chondrite parent asteroid accreted while the Sun was a weak T Tauri star. Subsequently, {sup 36}Cl accreted into the Allende CV chondrite together with condensed water ices.

  3. Measurements of production cross sections of 10Be and 26Al by 120 GeV and 392 MeV proton bombardment of 89Y, 159Tb, and natCu targets

    DOE PAGESBeta

    Sekimoto, S.; Okumura, S.; Yashima, H.; Matsushi, Y.; Matsuzaki, H.; Matsumura, H.; Toyoda, A.; Oishi, K.; Matsuda, N.; Kasugai, Y.; et al

    2015-08-12

    The production cross sections of 10Be and 26Al were measured by accelerator mass spectrometry using 89Y, 159Tb, and natCu targets bombarded by protons with energies Ep of 120 GeV and 392 MeV. The production cross sections obtained for 10Be and 26Al were compared with those previously reported using Ep = 50 MeV–24 GeV and various targets. It was found that the production cross sections of 10Be monotonically increased with increasing target mass number when the proton energy was greater than a few GeV. On the other hand, it was also found that the production cross sections of 10Be decreased asmore » the target mass number increased from that of carbon to those near the mass numbers of nickel and zinc when the proton energy was below approximately 1 GeV. They also increased as the target mass number increased from near those of nickel and zinc to that of bismuth, in the same proton energy range. Similar results were observed in the production cross sections of 26Al, though the absolute values were quite different between 10Be and 26Al. As a result, the difference between these production cross sections may depend on the impact parameter (nuclear radius) and/or the target nucleus stiffness.« less

  4. Measurements of the {sup 25}Mg({sup 11}B,{sup 12}C){sup 24}Na and {sup 25}Mg({sup 11}B,{sup 10}Be){sup 26}Al proton transfer reactions

    SciTech Connect

    Faria, P. N. de; Lichtenthaeler, R.; Guimaraes, V.; Lepine-Szily, A.; Benjamim, E. A.; Lima, G. F.; Moro, A. M.

    2006-08-15

    Angular distributions for the {sup 11}B+{sup 25}Mg elastic scattering, {sup 25}Mg({sup 11}B,{sup 12}C){sup 24}Na proton pickup, and {sup 25}Mg({sup 11}B,{sup 10}Be){sup 26}Al stripping reactions have been measured at E{sub {sup 11}B}=35 MeV. The angular distributions have been analyzed by the distorted-waves Born approximation calculations using the code fresco. The spectroscopic factors for the overlaps <{sup 25}Mg|{sup 26}Al>,<{sup 25}Mg|{sup 24}Na> for the ground state and excited states of {sup 26}Al and {sup 24}Na have been obtained and compared to previous measurements and shell-model calculations.

  5. Search for extinct 36Cl: Vigarano CAIs, the Pink Angel from Allende, and a Ningqiang chondrule

    NASA Astrophysics Data System (ADS)

    Nakashima, Daisuke; Ott, Ulrich; Hoppe, Peter; El Goresy, Ahmed

    2008-12-01

    We have searched for excesses of 36S derived from the decay of extinct 36Cl in sodalite, a secondary Cl-rich mineral, in Ca-Al-rich inclusions (CAIs) from the Vigarano and Allende CV3 chondrites and in a chondrule from the Ningqiang carbonaceous chondrite. The presence of sodalite in two CAIs from Vigarano and its absence from surrounding CAI fragments suggests sodalite formation after CAI fragmentation. As for sodalite in the Allende Pink Angel CAI, oxygen isotopic compositions have been interpreted as indicative of high temperature interactions, thus suggesting formation prior to accretion to the parent body, probably in a nebular setting. Sodalite in the Ningqiang chondrule is considered to have formed via alkali-Ca exchange, which is believed to have occurred before accretion to the parent body. Sodalites in the Vigarano CAIs and in the Ningqiang chondrule show no clear evidence for the presence of radiogenic 36S. The inferred 2 σ upper limits for 36Cl/ 35Cl at the time of sodalite formation are 1.6 × 10 -6 (Vigarano CAIs) and 3.3 × 10 -6 (Ningqiang chondrule), respectively. In the Pink Angel CAI sodalite exhibits small 36S excesses which weakly correlate with 35Cl/ 34S ratios. The inferred 36Cl/ 35Cl ratio of (1.8 ± 2.2) × 10 -6 (2 σ error) is lower than that found by Hsu et al. [Hsu, W., Guan, Y., Leshin, L. A., Ushikubo, T. and Wasserburg, G. J. (2006) A late episode of irradiation in the early solar system: Evidence from extinct 36Cl and 26Al in meteorites. Astrophys. J. 640, 525-529], thus indicative of heterogeneous distribution of 36Cl in this CAI. Spallation reactions induced by energetic particles from the young Sun are suggested for the origin of 36Cl, similar to the case of 10Be. While 10Be appears to be present in roughly equal abundance in all studied CAIs, our study indicates the level of 36Cl abundances to be variable so that there seems to be no simple relationship between 10Be and 36Cl. This would be expected if trapped cosmic rays rather

  6. Calibration of cosmogenic noble gas production in ordinary chondrites based on 36Cl-36Ar ages. Part 1: Refined produced rates for cosmogenic 21Ne and 38Ar

    NASA Astrophysics Data System (ADS)

    Dalcher, N.; Caffee, M. W.; Nishiizumi, K.; Welten, K. C.; Vogel, N.; Wieler, R.; Leya, I.

    2013-10-01

    We measured the concentrations and isotopic compositions of He, Ne, and Ar in bulk samples and metal separates of 14 ordinary chondrite falls with long exposure ages and high metamorphic grades. In addition, we measured concentrations of the cosmogenic radionuclides 10Be, 26Al, and 36Cl in metal separates and in the nonmagnetic fractions of the selected meteorites. Using cosmogenic 36Cl and 36Ar measured in the metal separates, we determined 36Cl-36Ar cosmic-ray exposure (CRE) ages, which are shielding-independent and therefore particularly reliable. Using the cosmogenic noble gases and radionuclides, we are able to decipher the CRE history for the studied objects. Based on the correlation 3He/21Ne versus 22Ne/21Ne, we demonstrate that, among the meteorites studied, only one suffered significant diffusive losses (about 35%). The data confirm that the linear correlation 3He/21Ne versus 22Ne/21Ne breaks down at high shielding. Using 36Cl-36Ar exposure ages and measured noble gas concentrations, we determine 21Ne and 38Ar production rates as a function of 22Ne/21Ne. The new data agree with recent model calculations for the relationship between 21Ne and 38Ar production rates and the 22Ne/21Ne ratio, which does not always provide unique shielding information. Based on the model calculations, we determine a new correlation line for 21Ne and 38Ar production rates as a function of the shielding indicator 22Ne/21Ne for H, L, and LL chondrites with preatmospheric radii less than about 65 cm. We also calculated the 10Be/21Ne and 26Al/21Ne production rate ratios for the investigated samples, which show good agreement with recent model calculations.

  7. Temporal evolution of (36)Cl abundances in the Great Lakes.

    PubMed

    Poghosyan, Armen; Sturchio, Neil C

    2015-06-01

    The observed (36)Cl isotopic abundance in Great Lakes water decreases from west to east, with the highest (36)Cl/Cl ratio of 1332 × 10(-15) in Lake Superior and the lowest (36)Cl/Cl ratio of 151 × 10(-15) in Lake Erie, whereas the (36)Cl concentration ((36)Cl atoms/L) is lowest in Lake Superior and higher in the other Great Lakes. The (36)Cl concentration in Lake Superior is much higher than expected from normal atmospheric deposition over the basin, consistent with deposition of nuclear bomb-produced (36)Cl during 1952-1964. A conservative mass-balance model constrained by hydrological parameters and available (36)Cl fluence measurements predicts the (36)Cl abundances in the Great Lakes from 1945 to 2015, in excellent agreement with available data for Lakes Superior, Michigan, and Huron, but the model underestimates (36)Cl abundances for Lakes Erie and Ontario. However, assuming that (36)Cl demonstrates non-conservative behavior and is significantly retained in the drainage basins, a model incorporating a delayed input parameter successfully predicts observed (36)Cl concentrations in all of the Great Lakes. PMID:25817926

  8. Infiltration at yucca mountain, nevada, traced by 36Cl

    NASA Astrophysics Data System (ADS)

    Norris, A. E.; Wolfsberg, K.; Gifford, S. K.; Bentley, H. W.; Elmore, D.

    1987-11-01

    Measurements of chloride and 36Cl in soils from two locations near Yucca Mountain, Nevada, have been used to trace the infiltration of precipitation in this arid region. The results show that the 36Cl fallout from nuclear-weapons testing formed a well-defined peak at one location, with a maximum 36Cl/Cl ratio 0.5 m below the surface. The structure of the 36Cl bomb pulse at the other location was much more complex, and the quantity of 36Cl in the bomb pulse was < 1% of the 6 × 10 12 atoms {36Cl }/{m 2} in the bomb pulse at the first location. The data indicate hydrologic activity subsequent to the 36Cl bomb-pulse fallout at one location, but none at the other location.

  9. Correcting for nucleogenic ^{36}Cl in cosmogenic ^{36}Cl dating of volcanic rocks from the Erciyes volcano, Central Turkey

    NASA Astrophysics Data System (ADS)

    Sarikaya, M. A.; Zreda, M.; Desilets, D.; Ciner, A.; Sen, E.

    2006-12-01

    Many radiometric methods are suitable for dating lava flows, but none is reliable for routine dating of lava flows younger than 10 ky. The cosmogenic ^{36}Cl method seems promising because it can be applied to any type of rock and laboratory and analytical work is easy and fast. But low cosmogenic ^{36}Cl inventory (after short exposure duration), combined with possible large non-cosmogenic component, makes this technique difficult to apply in a routine fashion. We applied the ^{36}Cl method to date a lava flow and the 14C technique to date the associated ash flow from the Erciyes (Argaeus) volcano, central Turkey. The average of three cosmogenic ^{36}Cl ages is 7.3 \\mp 0.5 ky and the average of two radiocarbon ages is 9.5 \\mp 0.3 ky (calibrated using Calib 5.0). The difference could be due to the overestimation of the calculated nucleogenic ^{36}Cl, which makes up almost one-third of the measured ^{36}Cl. If the nucleogenic component were set to zero, the average ^{36}Cl age would be 10.3 \\mp 0.2 ky. Thus, the ^{36}Cl age should be in the range between 7.3 ky and 10.2 ky, which includes the 14C age near the upper end of the interval. Under the assumption that the 14C age is correct and that the nucleogenic ^{36}Cl has reached a secular equilibrium with the magma, the nucleogenic ^{36}Cl needed to reconcile the ^{36}Cl and 14C ages is only about one-fifth of that previously calculated. In order to investigate this disparity of ages and possible calculating errors of nucleogenic ^{36}Cl, we are analyzing rock samples from where we can directly measure nucleogenic component of ^{36}Cl. This work is important for developing better ways to estimate the nucleogenic ^{36}Cl, which will improve the accuracy of ^{36}Cl dating of young volcanic rocks.

  10. Infiltration at Yucca Mountain, Nevada, traced by {sup 36}Cl

    SciTech Connect

    Norris, A.E.; Wolfsberg, K.; Gifford, S.K.; Bentley, H.W.; Elmore, D.

    1987-04-01

    Measurements of chloride and {sup 36}Cl in soils from two locations near Yucca Mountain, Nevada, have been used to trace the infiltration of precipitation in this arid region. The results show that the {sup 36}Cl fallout from nuclear weapons testing formed a well-defined peak at one location, with a maximum 0.5m below the surface. The structure of the {sup 36}Cl bomb pulse at the other location was much more complex, and quantity of {sup 36}Cl in the bomb pulse was <1% of the 6 x 10{sup 12} atoms {sup 36}Cl/m{sup 2} in the bomb pulse at the first location. The data indicate hydrologic activity subsequent to the {sup 36}Cl bomb pulse fallout at one location, but none at the other location. 11 refs.

  11. Medical application of 26Al

    NASA Astrophysics Data System (ADS)

    Steinhausen, C.; Gerisch, P.; Heisinger, B.; Hohl, Ch.; Kislinger, G.; Korschinek, G.; Niedermayer, M.; Nolte, E.; Dumitru, M.; Alvarez-Brückmann, M.; Schneider, M.; Ittel, T. H.

    1996-06-01

    Accelerator mass spectrometry (AMS) measurements with 26Al as tracer were performed in order to study the aluminium metabolism and anomalies in the human body and in rats. In particular, the differences between healthy volunteers and patients with renal failure were investigated. The obtained data points of 26Al in blood and urine were described by an open compartment model with three peripheral compartments. It was found that the minimum of peripheral compartments needed to describe 26Al concentrations in blood and urine over a time period of three years is at least three.

  12. Comparison of 36Cl and 3He measurements in glacial surfaces on the tropical Altiplano (Cerro Tunupa volcano, 20°S)

    NASA Astrophysics Data System (ADS)

    Schimmelpfennig, Irene; Blard, Pierre-Henri; Lavé, Jérôme; Benedetti, Lucilla; Aster Team

    2016-04-01

    The combination of two or more cosmogenic nuclides measured in the same rock samples allow complex landscape exposure histories to be quantified, due to the nuclide-specific production and decay rates. In supposedly simple exposure scenarios, such as moraine chronologies, the use of more than one nuclide can also help identify outliers caused by geomorphological bias (e.g. "inheritance") or analytical problems (e.g. nuclide loss or contamination during chemical extraction). The two cosmogenic in situ nuclides 3He and 36Cl are potentially very useful to be simultaneously measured in quartz-lacking lithologies, but their application is more challenging than that of combined 10Be and 26Al measurements, which are routinely employed in quartz-bearing rocks. This is, amongst other things, because the production of 3He and 36Cl depend on various compositional factors. Therefore, 3He and 36Cl have rarely been measured in the same samples so far. Here, we present 36Cl measurements in plagioclases extracted from four moraine boulders and one roche moutonnée on the southern flank of Cerro Tunupa volcano, located in the tropical Bolivian Andes (3800-4500 m, 20°S). In pyroxenes of these samples, 3He has previously been measured to gain insights into the local deglaciation history and climate conditions about 15 kyr ago during the Lake Tauca highstand (Blard et al., 2009, 2013). The ages calculated from the measured 3He and 36Cl concentrations of the 5 samples range from 12 kyr to 180 kyr and are generally in good agreement. The good age agreement of a boulder surface (TU-1C) that is significantly older than the other boulder ages from this moraine confirm the suspicion, that it was exposed to cosmic radiation previous to its last deposition (Blard et al., 2009, 2013). In contrast, the 36Cl age of the roche moutonnée surface (TU2) is significantly younger than the corresponding 3He age, but fits well with the adjacent moraine mean age. It thus arises the question if the 3He

  13. Accelerator mass spectrometry with fully stripped 26Al, 63Cl, 41Ca and (su59)Ni ions

    NASA Astrophysics Data System (ADS)

    Faestermann, H.; Kato, K.; Korschinek, G.; Krauthan, P.; Nolte, E.; Rühm, W.; Zerle, L.

    1990-04-01

    The detection system of accelerator mass spectrometry (AMS) with completely stripped ions of 26Al, 36Cl, 41Ca and 59Ni at the Munich accelerator laboratory and measurements with these ions are presented. Detection limits are given. The presented applications are: dating of groundwater of the Milk River aquifer and deduction of the neutron fluence and spectrum of the Hiroshima A-bomb.

  14. High (36)Cl/Cl ratios in Chernobyl groundwater.

    PubMed

    Roux, Céline; Le Gal La Salle, Corinne; Simonucci, Caroline; Van Meir, Nathalie; Fifield, L Keith; Diez, Olivier; Bassot, Sylvain; Simler, Roland; Bugai, Dmitri; Kashparov, Valery; Lancelot, Joël

    2014-12-01

    After the explosion of the Chernobyl Nuclear Power Plant in April 1986, contaminated material was buried in shallow trenches within the exclusion zone. A (90)Sr plume was evidenced downgradient of one of these trenches, trench T22. Due to its conservative properties, (36)Cl is investigated here as a potential tracer to determine the maximal extent of the contamination plume from the trench in groundwater. (36)Cl/Cl ratios measured in groundwater, trench soil water and leaf leachates are 1-5 orders of magnitude higher than the theoretical natural (36)Cl/Cl ratio. This contamination occurred after the Chernobyl explosion and currently persists. Trench T22 acts as an obvious modern point source of (36)Cl, however other sources have to be involved to explain such contamination. (36)Cl contamination of groundwater can be explained by dilution of trench soil water by uncontaminated water (rainwater or deep groundwater). With a plume extending further than that of (90)Sr, radionuclide which is impacted by retention and decay processes, (36)Cl can be considered as a suitable tracer of contamination from the trench in groundwater provided that modern release processes of (36)Cl from trench soil are better characterized. PMID:25128774

  15. Distribution and Origin of 36Cl In Allende CAIs

    SciTech Connect

    Matzel, J P; Jacobsen, B; Hutcheon, I D; Krot, A N; Nagashima, K; Yin, Q; Ramon, E C; Weber, P; Wasserburg, G J

    2009-12-11

    The abundance of short-lived radionuclides (SLRs) in early solar system materials provide key information about their nucleosynthetic origin and can constrain the timing of early solar system events. Excesses of {sup 36}S ({sup 36}S*) correlated with {sup 35}Cl/{sup 34}S ratios provide direct evidence for in situ decay of {sup 36}Cl ({tau}{sub 1/2} {approx} 0.3 Ma) and have been reported in sodalite (Na{sub 8}Al{sub 6}Si{sub 6}O{sub 24}Cl{sub 2}) and wadalite (Ca{sub 6}Al{sub 5}Si{sub 2}O{sub 16}Cl{sub 3}) in CAIs and chondrules from the Allende and Ningqiang CV carbonaceous chondrites. While previous studies demonstrate unequivocally that {sup 36}Cl was extant in the early solar system, no consensus on the origin or initial abundance of {sup 36}Cl has emerged. Understanding the origin of {sup 36}Cl, as well as the reported variation in the initial {sup 36}Cl/{sup 35}Cl ratio, requires addressing when, where and how chlorine was incorporated into CAIs and chondrules. These factors are key to distinguishing between stellar nucleosynthesis or energetic particle irradiation for the origin of {sup 36}Cl. Wadalite is a chlorine-rich secondary mineral with structural and chemical affinities to grossular. The high chlorine ({approx}12 wt%) and very low sulfur content (<<0.01 wt%) make wadalite ideal for studies of the {sup 36}Cl-{sup 36}S system. Wadalite is present in Allende CAIs exclusively in the interior regions either in veins crosscutting melilite or in zones between melilite and anorthite associated with intergrowths of grossular, monticellite, and wollastonite. Wadalite and sodalite most likely resulted from open-system alteration of primary minerals with a chlorine-rich fluid phase. We recently reported large {sup 36}S* correlated with {sup 35}Cl/{sup 34}S in wadalite in Allende Type B CAI AJEF, yielding a ({sup 36}Cl/{sup 35}Cl){sub 0} ratio of (1.7 {+-} 0.3) x 10{sup -5}. This value is the highest reported {sup 36}Cl/{sup 35}Cl ratio and is {approx}5 times

  16. Perchlorate isotope forensics with naturally produced 36Cl

    NASA Astrophysics Data System (ADS)

    Hillegonds, D.; Parker, D.; Singleton, M.; Buchholz, B.; Esser, B.; Moran, J.; Rood, D.; Finkel, R.

    2008-12-01

    The source of perchlorate (ClO4-) in many surface and groundwaters is not known. Recent studies (Parker et al., 2008) suggest that natural production is widespread and common, and may involve atmospheric processes. The isotopic composition of perchlorate chlorine and oxygen has proven useful for identifying anthropogenic/natural perchlorate sources (Bohlke et al, 2005) and for exploring biodegradation in environmental samples (Sturchio et al, 2007). The stable isotope approach, however, requires processing very large volumes of water to obtain milligrams of rigorously separated perchlorate for analysis, limiting its widespread application. Chlorine-36 (36Cl) is a long-lived and rare radionuclide produced cosmogenically in the upper atmosphere. The measurement of 36Cl/Cl by accelerator mass spectrometry (AMS) only requires micrograms of sample chlorine enabling lower volume extractions (less than 1/10th that required for stable isotope techniques), and potentially less rigorous perchlorate chemistry. The primary technical goal of our work is to determine the utility of 36Cl in distinguishing perchlorate source and in constraining mechanisms of natural perchlorate formation. We expect that synthetic perchlorate compounds produced using chloride brines from ancient sources and concentrated modern deposits will have low 36Cl/Cl ratios that will be distinct from natural perchlorate produced in the atmosphere. High levels of 36Cl in groundwater or rainwater perchlorate would then be an unambiguous indication of a natural atmospheric production, and the distribution of 36Cl/Cl in precipitation and groundwater (in conjunction with stable isotope compositions) would constrain the mechanism for natural perchlorate production in the atmosphere. Using accelerator mass spectrometry (AMS), we have measured 36Cl/Cl in a number of synthetic perchlorate salts (including potassium, sodium, magnesium, and ammonium salts). Synthetic salt 36Cl/Cl atom ratios range from 1 to 35 e-15

  17. 36Cl accelerator mass spectrometry with a bespoke instrument

    NASA Astrophysics Data System (ADS)

    Wilcken, K. M.; Freeman, S. P. H. T.; Schnabel, C.; Binnie, S. A.; Xu, S.; Phillips, R. J.

    2013-01-01

    Cosmogenic 36Cl analysis by accelerator mass spectrometry (AMS) is a valuable environmental and geological sciences research tool. Overcoming the stable nuclide 36S isobar interfering with measurement is challenging, however. Traditionally this has required large accelerators, but following recent technical advances it is now possible with ∼30 MeV ion energies. Consequently 5 MV or even smaller modern bespoke spectrometers are now 36Cl-capable, increasing accessibility and promoting wider and more varied 36Cl use. However, the technical ability to identify 36Cl ions is quite distinct from demonstrated high-performance AMS. Such is the theme of this paper. We present a systematic analysis of the accurate measurement of sample radioisotope relative to the stable chlorine, the normalisation of the measured ratio and correction for remaining 36S interference, all combined with the use of stable-isotope dilution to determine sample Cl concentration to begin with. We conclude by showing that repeated analyses support our claims for routine 3% 36Cl-AMS data. Accordingly, the modest SUERC spectrometer well competes with the performance of larger longer-established instruments, and the results may be quite generic for modern bespoke instruments.

  18. 26Al/10Be burial ages for a Pleistocene terrace in the Vienna Basin, Austria

    NASA Astrophysics Data System (ADS)

    Braumann, S.; Fiebig, M.; Neuhuber, S.; Schaefer, J. M.; Haeuselmann, P.; Schwartz, R.; Finkel, R. C.

    2014-12-01

    The Vienna Basin in the northeastern part of Austria between the Eastern Alps and the West Carpathians is a pull-apart basin crossed by the Danube river. The structure is filled with marine and terrestrial sediments showing thicknesses of up to 6 km. An increase in glacial melt water discharges, typically linked to high productivity of Alpine glaciers, had an essential impact on the formation of the investigated terrace. The scale of erosion and sediment transport translates to deposition rates in the foreland and is influenced by the magnitude of melt water discharges in Alpine catchment areas. Variations in layer characteristics (i.e. grain size, sorting, thickness) are an indicator for glacial pulses. Burial dates of ten quartz pebbles originating from the Gaenserndorfer terrace, situated in the northeastern part of the basin, set time dependent constraints on the required hydrological regime for mobilization, transport and sedimentation of bedloads and allow relating the deposition of glacial sediments to past glacial periods. But the geomorphic evolution of the Vienna Basin was not only determined by sedimentation processes. A number of irregularities manifest that tectonics affected the area as well: Terrace tilts are dipping against the slope of the Danube and offsets of some decameters between sediment layers showing the same facies, but located several kilometers apart from each other, could be identified. An extensive Miocene fault system was partly reactivated during the Middle Pleistocene and could have caused the formation of these discontinuities. It is of great interest to discriminate impacts on the area due to deposition from morphological elements formed by seismic events. The preliminary burial ages afford for putting the sampled terrace segment into a coherent geochronological context and provide a dataset to compare ages of the Gaenserndofer terrace to ages of sediment layers at other locations within the basin in order to either validate or reject the hypothesis that they belong to the same stratigraphical unit. The dating of the terrace helps to analyze the processes dominating this complex area and can contribute to a better understanding of the prevalent climate conditions in the Alps, the Alpine foreland and the inner Alpine basins during the Quaternary.

  19. Survey on Cosmogenic 26Al in Lewis Cliff Meteorites

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Alderliesten, C.; Lindner, L.

    1992-07-01

    levels of 56 +- 7 and 60 +- 7 for H and L chondrites, respectively [3], range up to 800 ka with an average of about 290 ka. Altogether this may indicate that the Lewis Cliff blue-ice region is a relatively old meteorite stranding area. This is supported by preliminary conclusions based on ^36Cl, measured in 8 Lewis Cliff meteorites [4]. However, it is likely that some of our terrestrial ages have been overestimated due to (i) lower ^26Al saturation values for meteorites with preatmospheric radii less than 20 cm [3] and (ii) low exposure ages, resulting in initial ^26Al levels below 90-95% of the saturation level. These effects make individual terrestrial age determinations solely based on ^26Al content speculative as long as additional cosmogenic nuclide data are lacking. Dramatic changes in the overall picture are not expected, because (i) we have measured relatively large samples with an average recovered weight of about 500 g (one 11-kg sample excluded) and (ii) anomalously low exposure ages occur in about only 5% of the cases [5,6]. Possible correlations between terrestrial age and place of find will be discussed. UNUSUAL EXPOSURE HISTORIES: We excluded samples with extremely low NTL (<1 krad) from the above discussion, because these may have been exposed to high SCR-fluxes due to smallperihelia orbits (<0.7 A.U.) [7]. This hypothesis is supported by LEW 87169 and 87143, which have extremely low NTL-values in combination with high ^26Al contents. PAIRING CRITERIA: In order to impose additional constraints on pairing possibilities we critically used--besides classification, location of find and TL-properties--the cosmogenic ^26Al and also the natural ^40K content of ordinary chondrites. As an example we will show that the 15 measured Lewis Cliff L6 chondrites are representing at least 10 separate falls. Acknowledgements. This work was performed with financial support from the "Nederlandse Organisatie voor Wetenschappelijk Onderzoek" (NWO). References: 1. Komura K. et

  20. Survey on Cosmogenic 26Al in Lewis Cliff Meteorites

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Alderliesten, C.; Lindner, L.

    1992-07-01

    levels of 56 +- 7 and 60 +- 7 for H and L chondrites, respectively [3], range up to 800 ka with an average of about 290 ka. Altogether this may indicate that the Lewis Cliff blue-ice region is a relatively old meteorite stranding area. This is supported by preliminary conclusions based on ^36Cl, measured in 8 Lewis Cliff meteorites [4]. However, it is likely that some of our terrestrial ages have been overestimated due to (i) lower ^26Al saturation values for meteorites with preatmospheric radii less than 20 cm [3] and (ii) low exposure ages, resulting in initial ^26Al levels below 90-95% of the saturation level. These effects make individual terrestrial age determinations solely based on ^26Al content speculative as long as additional cosmogenic nuclide data are lacking. Dramatic changes in the overall picture are not expected, because (i) we have measured relatively large samples with an average recovered weight of about 500 g (one 11-kg sample excluded) and (ii) anomalously low exposure ages occur in about only 5% of the cases [5,6]. Possible correlations between terrestrial age and place of find will be discussed. UNUSUAL EXPOSURE HISTORIES: We excluded samples with extremely low NTL (<1 krad) from the above discussion, because these may have been exposed to high SCR-fluxes due to smallperihelia orbits (<0.7 A.U.) [7]. This hypothesis is supported by LEW 87169 and 87143, which have extremely low NTL-values in combination with high ^26Al contents. PAIRING CRITERIA: In order to impose additional constraints on pairing possibilities we critically used--besides classification, location of find and TL-properties--the cosmogenic ^26Al and also the natural ^40K content of ordinary chondrites. As an example we will show that the 15 measured Lewis Cliff L6 chondrites are representing at least 10 separate falls. Acknowledgements. This work was performed with financial support from the "Nederlandse Organisatie voor Wetenschappelijk Onderzoek" (NWO). References: 1. Komura K. et

  1. 36Cl-36Ar Exposure Ages of Chondritic Metals

    NASA Astrophysics Data System (ADS)

    Graf, Th.; Caffee, M. W.; Finkel, R. C.; Marti, K.; Nishiizumi, K.; Ponganis, K. V.

    1995-09-01

    Metal separates were prepared to determine ^36Cl-^36Ar exposure ages for six H4 p.m. falls (with reported bulk exposure ages of 4 to 10Ma), for ten H5 a.m. falls (T(sub)e = 4-10 Ma) and for the Acapulco meteorite (T(^36Cl-^36Ar)= 5.7 Ma). This dating method uses production rate ratios P(^36Cl)/P(^36Ar) and is independent of the shielding-sensitive absolute production rates. It is also known that for protons the production rate ratio is rather insensitive to changes in the energy spectrum; the dependence of this ratio for secondary neutrons is at present less understood. First results were already reported [1]. The cosmic-ray-produced ^3He/^38Ar ratios show a bimodal distribution with two clusters at about 15 and about 9 (Fig. 1). About half of the ^3He is produced via ^3H which is known to diffuse in metal at relatively low temperatures. Therefore, Fig. 1 provides evidence for a quasi-continuous loss of ^3H from such metals. If this loss mechanism is due to solar heating, perihelia <1 AU are indicated for these meteorites. Losses are prominent for H5 a.m. falls, but not for H4 p.m. falls. The orbital implications are consistent with those already known from the time-of-fall parameter (p.m. falls / total falls) which was used in the selection of the H4,H5 sample sets [2]. The exposure age histograms of both H groups show the well known clusters at about 7 Ma. The width of the exposure age peaks differ, however, and the collisional break-up event can be further constrained. Except for Nassirah, all members of the H4 p.m. group fall into the range 7.0 +/- 0.3 Ma. Bulk rock ages (8.2-9.3 Ma) [3] as well as the ^36Cl-^36Ar age (8.3 Ma) of Nassirah are higher and may indicate that this meteorite does not belong to the collisional event. We observe a small but systematic difference in calculated exposure ages by the ^36Cl-^36Ar method, when compared with ages obtained by conventional noble gas production rates. This shift (about 10%) does not appear to be dependent on

  2. 26Al+p elastic and inelastic scattering reactions and galactic abundances of 26Al

    NASA Astrophysics Data System (ADS)

    Pittman, S. T.; Bardayan, D. W.; Chae, K. Y.; Chipps, K. A.; Jones, K. L.; Kozub, R. L.; Matei, C.; Matos, M.; Moazen, B. H.; Nesaraja, C. D.; O'Malley, P. D.; Pain, S. D.; Parker, P. D.; Peters, W. A.; Shriner, J. F., Jr.; Smith, M. S.

    2012-06-01

    Galactic 26Al is the first radioactive nucleus to be positively identified by γ-ray astronomy with detection of the 1.809 MeV γ ray associated with its decay. This nucleus is destroyed in astrophysical environments in the 26Al(p,γ)27Si and inelastic 26Al+p scattering reactions where properties of 27Si levels determine reaction rates. To investigate these properties, elastic and inelastic 26Al+p scattering reactions were measured between Ec.m. = 0.5-1.5 MeV at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). A candidate for a new resonance in the 26Al(p,γ)27Si reaction was identified. Upper limits were also set on the strengths of postulated resonances and on the cross section of the inelastic reaction, but there is little effect on current reaction rate calculations.

  3. SPI measurements of Galactic 26Al

    NASA Astrophysics Data System (ADS)

    Diehl, R.; Knödlseder, J.; Lichti, G. G.; Kretschmer, K.; Schanne, S.; Schönfelder, V.; Strong, A. W.; von Kienlin, A.; Weidenspointner, G.; Winkler, C.; Wunderer, C.

    2003-11-01

    The precision measurement of the 1809 keV gamma-ray line from Galactic 26Al is one of the goals of the SPI spectrometer on INTEGRAL with its Ge detector camera. We aim for determination of the detailed shape of this gamma-ray line, and its variation for different source regions along the plane of the Galaxy. Data from the first part of the core program observations of the first mission year have been inspected. A clear detection of the 26Al line at =~ 5-7 sigma significance demonstrates that SPI will deepen 26Al studies. The line intensity is consistent with expectations from previous experiments, and the line appears narrower than the 5.4 keV FWHM reported by GRIS, more consistent with RHESSI's recent value. Only preliminary statements can be made at this time, however, due to the multi-component background underlying the signal at =~ 40 times higher intensity than the signal from Galactic 26Al.

  4. Observable Proxies For 26 Al Enhancement

    SciTech Connect

    Fryer, Christopher L; Young, Patrick A; Ellinger, Carola I; Arnett, William D

    2008-01-01

    We consider the cospatial production of elements in supernova explosions to find observationally detectable proxies for enhancement of {sup 26}Al in supernova ejecta and stellar systems. Using four progenitors we explore a range of 1D explosions at different energies and an asymmetric 3D explosion. We find that the most reliable indicator of the presence of {sup 26}Al in unmixed ejecta is a very low S/Si ratio ({approx} 0.05). Production of N in O/S/Si-rich regions is also indicative. The biologically important element P is produced at its highest abundance in the same regions. Proxies should be detectable in supernova ejecta with high spatial resolution multi wavelength observations, but the small absolute abundance of material injected into a proto-planetary disk makes detection unlikely in existing or forming stellar/planetary systems.

  5. Determination of 36Cl in biological shield concrete using pyrohydrolysis and liquid scintillation counting.

    PubMed

    Itoh, Mitsuo; Watanabe, Kazuo; Hatakeyama, Mutsuo; Tachibana, Mitsuo

    2002-07-01

    A method for the determination of 36Cl in biological shield concrete of nuclear reactors was developed. Cl in the concrete sample was extracted quantitatively by pyrohydrolysis at 900 degrees C and recovered in Na2CO3 solution for subsequent measurement of 36Cl by liquid scintillation counting. WO3 was used as an accelerator in the pyrohydrolysis. The Cl extraction procedure was optimized by investigating experimental conditions with the use of ion chromatography and its recovery was evaluated by the analysis of the geochemical reference samples. The detection limit of 36Cl was 0.02 Bq g(-1) for a sample weight of 2 g. The relative standard deviation was 3-7% for the samples containing 0.5 Bq g(-1) levels of 36Cl. The method was applied to determine 36Cl in biological shield concrete of the Japan Power Demonstration Reactor. PMID:12173658

  6. The Hiroshima thermal-neutron discrepancy for (36)Cl at large distances. Part I: New (36)Cl measurements in granite samples exposed to A-bomb neutrons.

    PubMed

    Huber, Thomas; Rühm, Werner; Kato, Kazuo; Egbert, Stephen D; Kubo, Florian; Lazarev, Vitali; Nolte, Eckehart

    2005-10-01

    The long-lived radioisotope (36)Cl (half-life: 301,000 years) was measured in granite samples exposed to A-bomb neutrons at distances from 94 to 1,591 m from the hypocenter in Hiroshima, by means of accelerator mass spectrometry (AMS). Measured (36)Cl/Cl ratios decrease from 1.6 x 10(-10) close to the hypocenter to about 1-2 x 10(-13), at a distance of 1,300 m from the hypocenter. At this distance and beyond the measured (36)Cl/Cl ratios do not change significantly and scatter around values of 1-2 x 10(-13). These findings suggest that the (36)Cl had been predominantly produced by thermalized neutrons from the A-bomb via neutron capture on stable (35)Cl, at distances from the hypocenter smaller than about 1,200 m. At larger distances, however, confounding processes induced by cosmic rays or neutrons from the decay of uranium and thorium become important. This hypothesis is theoretically and experimentally supported in a consecutive paper. The results are compared to calculations that are based on the most recent dosimetry system DS02. Close to the hypocenter, measured (36)Cl/Cl ratios are lower than those calculated, while they are significantly higher at large distances from the hypocenter. If the contribution of the cosmic rays and of the neutrons from the decay of uranium and thorium in the sample was subtracted, however, no significant deviation from the DS02 calculations was observed, at those distances. Thus, the Hiroshima neutron discrepancy reported in the literature for (36)Cl for samples from large distances from the hypocenter, i.e., higher measured (36)Cl/Cl ratios than predicted by the previous dosimetry system DS86, was not confirmed. PMID:16177928

  7. The distribution of meteoric 36Cl/Cl in the United States: A comparison of models

    USGS Publications Warehouse

    Moysey, S.; Davis, S.N.; Zreda, M.; Cecil, L.D.

    2003-01-01

    The natural distribution of 36Cl/Cl in groundwater across the continental United States has recently been reported by Davis et al. (2003). In this paper, the large-scale processes and atmospheric sources of 36Cl and chloride responsible for controlling the observed 36Cl/Cl distribution are discussed. The dominant process that affects 36Cl/Cl in meteoric groundwater at the continental scale is the fallout of stable chloride from the atmosphere, which is mainly derived from oceanic sources. Atmospheric circulation transports marine chloride to the continental interior, where distance from the coast, topography, and wind patterns define the chloride distribution. The only major deviation from this pattern is observed in northern Utah and southern Idaho where it is inferred that a continental source of chloride exists in the Bonneville Salt Flats, Utah. In contrast to previous studies, the atmospheric flux of 36Cl to the land surface was found to be approximately constant over the United States, without a strong correlation between local 36Cl fallout and annual precipitation. However, the correlation between these variables was significantly improved (R 2=0.15 to R 2=0.55) when data from the southeastern USA, which presumably have lower than average atmospheric 36Cl concentrations, were excluded. The total mean flux of 36Cl over the continental United States and total global mean flux of 36Cl are calculated to be 30.5??7.0 and 19.6??4.5 atoms m-2 s-1, respectively. The 36Cl/Cl distribution calculated by Bentley et al. (1996) underestimates the magnitude and variability observed for the measured 36Cl/Cl distribution across the continental United States. The model proposed by Hainsworth (1994) provides the best overall fit to the observed 36Cl/Cl distribution in this study. A process-oriented model by Phillips (2000) generally overestimates 36Cl/Cl in most parts of the country and has several significant local departures from the empirical data.

  8. Accelerator mass spectrometry of 36Cl produced by neutrons from the Hiroshima bomb.

    PubMed

    Kato, K; Habara, M; Yoshizawa, Y; Biebel, U; Haberstock, G; Heinzl, J; Korschinek, G; Morinaga, H; Nolte, E

    1990-10-01

    Accelerator mass spectrometry was performed at the Munich tandem laboratory to determine 36Cl/Cl ratios of samples from a tombstone exposed to neutrons from the Hiroshima bomb. The ratios were determined from the surface to deeper positions. The depth profile of 36Cl/Cl can be used for estimating the neutron energy distribution and intensity near the hypocentre in Hiroshima. PMID:1976726

  9. Cosmogenic {sup 36}Cl accumulation in unstable landforms 2. Simulations and measurements on eroding moraines

    SciTech Connect

    Zreda, M.G.; Phillips, F.M.; Elmore, D.

    1994-11-01

    Cosmogenic {sup 36}Cl ages of boulders from late Pleistocene moraines in Bishop Creek, Sierra Nevada, California, provided valuable details about {sup 36}Cl surface exposure dating and the nature of post depositional processes that modify glacial landforms. The natural variability of the apparent {sup 36}Cl ages among morainal boulders is due to soil erosion and gradual exposure of boulders at the surface. Two mechanisms are responsible for the resulting distributions of the apparent {sup 36}Cl ages. Variability of the initial burial depth among boulders and variability in the chemical composition of boulders from the same depth both result in different {sup 36}Cl ages due to the dependence of the depth production profile on the boulder chemistry. The authors measured cosmogenic {sup 36}Cl in boulders from a late Pleistocene moraine. The distribution of the calculated apparent ages allowed them to calculate the true age of 85 kyr and the erosion rate of 570 g cm{sup -2}. These results are in excellent agreement with independently estimated values of 87 kyr and 600 g cm{sup -2} for the age and erosion depth, respectively. These results indicate that the model satisfactorily simulates effects of erosion processes and can thus aid in surface exposure dating of eroding landforms.

  10. 26Al uptake and accumulation in the rat brain

    NASA Astrophysics Data System (ADS)

    Yumoto, S.; Nagai, H.; Imamura, M.; Matsuzaki, H.; Hayashi, K.; Masuda, A.; Kumazawa, H.; Ohashi, H.; Kobayashi, K.

    1997-03-01

    To investigate the cause of Alzheimer's disease (senile dementia), 26Al incorporation in the rat brain was studied by accelerator mass spectrometry (AMS). When 26Al was injected into healthy rats, a considerable amount of 26Al entered the brain (cerebrum) through the blood-brain barrier 5 days after a single injection, and the brain 26Al level remained almost constant from 5 to 270 days. On the other hand, the level of 26Al in the blood decreased remarkably 75 days after injection. Approximately 89% of the 26Al taken in by the brain cell nuclei bound to chromatin. This study supports the theory that Alzheimer's disease is caused by irreversible accumulation of aluminium (Al) in the brain, and brain cell nuclei.

  11. Study of nuclear reactions producing 36Cl by micro-AMS

    NASA Astrophysics Data System (ADS)

    Luís, H.; Jesus, A. P.; Fonseca, M.; Cruz, J.; Galaviz, D.; Franco, N.; Alves, E.

    2016-01-01

    36Cl is one of several short to medium lived isotopes (as compared to the earth age) whose abundances at the earlier solar system may help to clarify its formation process. There are two generally accepted possible models for the production of this radionuclide: it originated from the ejecta of a nearby supernova (where 36Cl was most probably produced in the s-process by neutron irradiation of 35Cl) and/or it was produced by in-situ irradiation of nebular dust by energetic particles (mostly, p, a, 3He -X-wind irradiation model). The objective of the present work is to measure the cross section of the 37Cl(p,d)36Cl and 35Cl(d,p)36Cl nuclear reactions, by measuring the 36Cl content of AgCl samples (previously bombarded with high energy protons and deuterons) with AMS, taking advantage of the very low detection limits of this technique for chlorine measurements. For that, the micro-AMS system of the LF1/ITN laboratory had to be optimized for chlorine measurements, as to our knowledge this type of measurements had never been performed in such a system (AMS with micro-beam). Here are presented the first results of these developments, namely the tests in terms of precision and reproducibility that were done by comparing AgCl blanks irradiated at the Portuguese National Reactor with standards produced by the dilution of the NIST SRM 4943 standard material.

  12. Transplacental passage of 26Al from pregnant rats to fetuses and 26Al transfer through maternal milk to suckling rats

    NASA Astrophysics Data System (ADS)

    Yumoto, S.; Nagai, H.; Matsuzaki, H.; Kobayashi, T.; Tada, W.; Ohki, Y.; Kakimi, S.; Kobayashi, K.

    2000-10-01

    Aluminium (Al) is toxic to the growth of fetuses and sucklings. However, the incorporation of Al into fetuses and sucklings in the periods of gestation and lactation has not been well clarified because Al lacks a suitable isotope for a tracer experiment. In this study, we used 26Al (a radioisotope of Al with half-life of 716,000 yr) as a tracer, and measured 26Al incorporation into fetuses and sucklings by accelerator mass spectrometry (AMS). To investigate Al incorporation into fetuses through transplacental passage, 26Al ( 26AlCl 3) was subcutaneously injected into pregnant rats on day 15 of gestation. 26Al was also subcutaneoulsy injected into lactating rats from day 1 to day 20 postpartum. By day 20 of gestation, 0.2% of the 26Al injected into a pregnant rat had been transferred to the fetuses, and 26Al was detected in the brain and liver of the fetuses. On day 9 postpartum, high levels of 26Al were demonstrated in the brain, liver, kidneys and blood of suckling rats. It is concluded that 26Al subcutaneously injected into pregnant rats and/or lactating rats is incorporated into their offspring through transplacental passage and/or maternal milk.

  13. The sup 36 Cl ages of the brines in the Magadi-Natron basin, east Africa

    SciTech Connect

    Kaufman, A.; Margaritz, M.A.; Hollos, G. ); Paul, M.; Boaretto, E. ); Hillaire-Marcel, C. ); Taieb, M. )

    1990-10-01

    The depression in the East African Rift which includes both Lake Magadi and Lake Natron forms a closed basin within which almost all the dissolved chloride originates in precipitation, since there is no important source of very ancient sedimentary chloride. This provides an ideal setting for the evaluation of the {sup 36}Cl methodology as a geochemical and hydrological tracer. The main source of recent water, as represented by the most dilute samples measured, is characterized by a {sup 36}Cl/Cl ratio of 2.5 {times} 10{sup {minus}14}, in agreement with the calculated value expected in precipitation. Surface evaporation increases the chlorinity of the local freshwater inflow by about a factor of 110 without changing the isotopic ratio, indicating that little chloride enters the system in the form of sediment leachate. A second type of brine found in the basin occurs in a hot deep groundwater reservoir and is characterized by lower {sup 36}Cl/Cl ratios (<1.2 {times} 10{sup {minus}14}). By comparing this value with the 2.5 {times} 10{sup {minus}14} in recent recharge, one obtains an approximate salt accumulation age of 760 Ka which is consistent with thee time of the first appearance of the lake. These older brines also have lower {sup 18}O and {sup 2}H values which indicate that they were recharged during a climatically different era. The {sup 36}Cl/Cl ratios in the inflowing waters and in the accumulated brine, together with the known age of the Lake Magadi basin, may be used to estimate the importance of the hypogene and epigene, as opposed to the meteoric, mode of {sup 36}Cl production. Such a calculation shows that the hypogene and epigene processes together contribute less than 6% of the total {sup 36}Cl present in the lake.

  14. Attempt to determine the environmental 36Cl concentration in water by liquid scintillation counting

    NASA Astrophysics Data System (ADS)

    Florkowski, T.; Schuszler, Ch.

    1986-11-01

    A low-background liquid scintillation spectrometer (ALOKA SL-1) located in the IAEA Isotope Hydrology Laboratory in Vienna was used for 36Cl activity measurement in water samples. The procedure of sample preparation consists of synthesizing of silicon tetrachloride or sodium chloride followed by purification. In both cases the limiting factor in the analysis appeared to be the pure reproducibility of the sample preparation procedure. The conclusion from these experiments is that the liquid scintillation method could be feasible only for the identification of the "bomb chlorine" but is far from being suitable for the accurate determination of 36Cl in groundwater for dating purposes.

  15. Radiocarbon dating and the 36Cl/Cl evolution of three Great Artesian Basin wells at Dalhousie, South Australia

    NASA Astrophysics Data System (ADS)

    Abu Risha, Usama A.

    2016-06-01

    The use of 14C (half-life = 5,730 years) in modeling the evolution of the 36Cl/Cl ratios in groundwater is reported for the first time. The complexity of the Cl-36Cl system due to the occurrence of different Cl and 36Cl sources and the difficulty of the determination of the initial groundwater 36Cl/Cl ratios have raised concerns about the reliability of using 36Cl (half-life = 301 thousand years, a) as a groundwater-dating tool. This work uses groundwater 14C age as a calibrating parameter of the Cl-36Cl/Cl decay-mixing models of three wells from the southwestern Great Artesian Basin (GAB), Australia. It aims to allow for the different sources of Cl and 36Cl in the southwestern GAB aquifer. The results show that the initial Cl concentrations range from 245 to 320 mg/l and stable Cl is added to groundwater along flowpaths at rates ranging from 1.4 to 3.5 mg/l/ka. The 36Cl content of the groundwater is assumed to be completely of atmospheric origin. The samples have different Cl-36Cl/Cl mixing-decay models reflecting recharge under different conditions as well as the heterogeneity of the aquifer.

  16. Radiocarbon dating and the 36Cl/Cl evolution of three Great Artesian Basin wells at Dalhousie, South Australia

    NASA Astrophysics Data System (ADS)

    Abu Risha, Usama A.

    2016-01-01

    The use of 14C (half-life = 5,730 years) in modeling the evolution of the 36Cl/Cl ratios in groundwater is reported for the first time. The complexity of the Cl-36Cl system due to the occurrence of different Cl and 36Cl sources and the difficulty of the determination of the initial groundwater 36Cl/Cl ratios have raised concerns about the reliability of using 36Cl (half-life = 301 thousand years, a) as a groundwater-dating tool. This work uses groundwater 14C age as a calibrating parameter of the Cl-36Cl/Cl decay-mixing models of three wells from the southwestern Great Artesian Basin (GAB), Australia. It aims to allow for the different sources of Cl and 36Cl in the southwestern GAB aquifer. The results show that the initial Cl concentrations range from 245 to 320 mg/l and stable Cl is added to groundwater along flowpaths at rates ranging from 1.4 to 3.5 mg/l/ka. The 36Cl content of the groundwater is assumed to be completely of atmospheric origin. The samples have different Cl-36Cl/Cl mixing-decay models reflecting recharge under different conditions as well as the heterogeneity of the aquifer.

  17. Radioactive 26Al from massive stars in the Galaxy.

    PubMed

    Diehl, Roland; Halloin, Hubert; Kretschmer, Karsten; Lichti, Giselher G; Schönfelder, Volker; Strong, Andrew W; von Kienlin, Andreas; Wang, Wei; Jean, Pierre; Knödlseder, Jürgen; Roques, Jean-Pierre; Weidenspointner, Georg; Schanne, Stephane; Hartmann, Dieter H; Winkler, Christoph; Wunderer, Cornelia

    2006-01-01

    Gamma-rays from radioactive 26Al (half-life approximately 7.2 x 10(5) years) provide a 'snapshot' view of continuing nucleosynthesis in the Galaxy. The Galaxy is relatively transparent to such gamma-rays, and emission has been found concentrated along its plane. This led to the conclusion that massive stars throughout the Galaxy dominate the production of 26Al. On the other hand, meteoritic data show evidence for locally produced 26Al, perhaps from spallation reactions in the protosolar disk. Furthermore, prominent gamma-ray emission from the Cygnus region suggests that a substantial fraction of Galactic 26Al could originate in localized star-forming regions. Here we report high spectral resolution measurements of 26Al emission at 1808.65 keV, which demonstrate that the 26Al source regions corotate with the Galaxy, supporting its Galaxy-wide origin. We determine a present-day equilibrium mass of 2.8 (+/- 0.8) solar masses of 26Al. We use this to determine that the frequency of core collapse (that is, type Ib/c and type II) supernovae is 1.9 (+/- 1.1) events per century. PMID:16397491

  18. Probing Galactic 26Al with Exotic Ion Beams

    NASA Astrophysics Data System (ADS)

    Chen, Alan A.

    2006-07-01

    The goal of understanding the production of galactic 26Al brings together progress in nuclear astrophysics from observations, theory, meteoritics, and laboratory experiments. In the case of experimental work, nuclear reactions involving unstable isotopes are being studied to elucidate the production of 26Al in stellar explosive nucleosynthesis. We discuss a direct measurement of the 26Al(p,γ)27Si reaction with the DRAGON collaboration at TRIUMF, and a measurement of 25Al+p elastic scattering with the CRIB (CNS-U.Tokyo) collaboration, toward constraining the 25Al(p,γ)26Si reaction.

  19. Distribution and chemical fate of 36Cl-chlorine dioxide gas during the fumigation of tomatoes and cantaloupe

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The distribution and chemical fate of 36Cl-ClO2 gas subsequent to fumigation of tomatoes or cantaloupe was investigated as was major factors that affect the formation of chloroxyanion byproducts. Approximately 22% of the generated 36Cl-ClO2 was present on fumigated tomatoes after a 2-hour exposure t...

  20. Observation of 23 Supernovae that Exploded <300 pc from Earth During the Past 300 kyr in the Radiocarbon and 10Be Cosmogenic Isotope Record

    NASA Astrophysics Data System (ADS)

    Firestone, R. B.

    2014-12-01

    The global excess radiocarbon abundance record for the past 50 kyr can be entirely explained by the explosion of four supernovae 44, 37, 32, and 22 kyr ago less than 250 pc from Earth. Each supernova left a nearly identical signature beginning with a sudden increase at the time of the explosion, followed by a hiatus of 1500 years, and continuing with a sustained, 2000 year increase in radiocarbon from gamma rays produced by diffusive shock in the supernova remnant. For the past 18 kyr excess radiocarbon from SN22kyrBP, identified as the Vela supernova, has decayed with the 5700 year half-life of 14C. The absolute scale for radiocarbon abundance has been determined from the decay curve as Δ14C=5±2% in 1950. Small oscillations in the decay curve are shown to coincide with variations in Earth's Virtual Axial Dipole Moment (VADM). SN44kyrBP exploded approximately 110 pc from Earth doubling the radiocarbon abundance. These supernovae are confirmed in the 10Be, 26Al, 36Cl and nitrate geological records. An additional 19 supernovae are observed 50-300 kyr ago in the 10Be record. Using the Earth as a calorimeter I have determined that approximated 2×1049 ergs were released at the time of each supernova explosion and 1049-50 ergs afterwards, consistent with theoretical predictions. The background rate of radiocarbon productions from more distant sources was determined as 1.61 atoms/cm2s at the top of the atmosphere. Although little danger to life on Earth is expected from these supernovae, each of the recent events were shown to correlate with concurrent global warming of 3-4°C.

  1. Measurement of cosmogenic /sup 36/Cl/Cl in young volcanic rocks: An application of accelerator mass spectrometry in geochronology

    SciTech Connect

    Leavy, B.D.; Phillips, F.M.; Elmore, D.; Kubik, P.W.

    1987-01-01

    We have measured /sup 36/Cl/Cl ratios in a number of young volcanic rocks in order to test the feasibility of using /sup 36/Cl buildup as a geochronometer for materials less than about 700,000 years old. All of the analyzed rocks have been dated independently using K-Ar or other radiometric dating methods and have exposure histories that are known or can be reasonably assumed. Measured /sup 36/Cl/Cl ratios in these rocks are in good agreement with the calculated in-situ /sup 36/Cl buildup curve. These analyses indicate that AMS measurement of /sup 36/Cl buildup in young rocks is a potentially powerful new method for dating materials that had previously been undatable, and as such will have broad applications in volcanology, tectonics, geophysics, and Quaternary research.

  2. 36Cl: A tracer in groundwater in the aquia formation of Southern Maryland

    USGS Publications Warehouse

    Purdy, C.B.; Mignerey, A.C.; Helz, G.R.; Drummond, D.D.; Kubik, P.W.; Elmore, D.; Hemmick, T.

    1987-01-01

    The Aquia Formation (Paleocene) of Southern Maryland, a marine unit consisting predominantly of quartz sands, but containing 20-40% glauconite, represents one of the many productive, heavily pumped aquifers of the Southeastern Coastal Plain. An unusually high 36Cl activity ( ~ 15 ?? modem water) measured in an outcrop sample is interpreted as a result of the bomb pulse input. About 25 km downdip from the recharge area, a minimum in total chloride concentration occurs. This minimum is thought to correlate with the latest low-stand of sea-level, and thus to provide time information which is in general agreement with ages calculated from hydrodynamic data. However, significant increases in the 36Cl concentrations are observed along the flow path which may be due to ion filtration or to leakage of modem, bomb-contaminated water into the Aquia aquifer. ?? 1987.

  3. Depth dependence of soil carbonate accumulation based on cosmogenic 36Cl dating

    NASA Astrophysics Data System (ADS)

    Liu, Beiling; Phillips, Fred M.; Elmore, David; Sharma, Pankaj

    1994-12-01

    Indurated pedogenic carbonate layers (calcretes) are common in soils on stable surfaces in arid to semiarid climates. The morphology and composition of calcretes provide important information on the geomorphic and climatic histories of the regions where they are formed, but they have proved difficult to date with conventional radiometric methods. We report cosmogenic 36Cl-buildup ages from three fractions (leachable Cl, carbonate, silicate) of a calcrete from the surface of an alluvial slope below the Ajo Mountains in southern Arizona. All three fractions give reasonably concordant ages, ranging from 700 ka at the base of the calcrete horizon to 200 ka at its top. These ages are in good agreement both with estimates of age based on correlation with similar, independently dated, soils in the region and with 36Cl-buildup ages on surficial boulders. These results support the ideas that calcretes accumulate upward with time and that water movement through the carbonate matrix is very limited after induration.

  4. Cosmogenic 36Cl ages of Quaternary basalt flows in the Mojave Desert, California, USA

    NASA Astrophysics Data System (ADS)

    Phillips, Fred M.

    2003-07-01

    Basalt flows provide excellent opportunities for calibration and intercomparison of Quaternary dating methods, remote sensing methods, and rates of geomorphic processes. The immediate motivation for this study was to provide chronology for a blind test of the utility of rock varnish microstratigraphy as an indicator of the age of flow emplacement. Five basaltic eruptive centers in the Mojave Desert of California were sampled for cosmogenic 36Cl analysis. Multiple samples were taken from most centers and, with one exception, produced good agreement. Assuming a surficial erosion rate of 1 mm/kyr -1, the flows yielded the following ages: Amboy Crater, 79±5 ka; Pisgah Crater, 22.5±1.3 ka; Cima field, I-Cone, 27±1.3 ka; Cima field, A-Cone, 21±1.6 ka and 11.5±1.5 ka; Cima field, flow of unidentified origin, 46±2 ka. The ages from the Cima I and A cones are in good agreement with previous cosmogenic 3He dating. Ages from the three previously undated flows are significantly older than previous estimates based on flow appearance. Tanzhou Liu performed varnish microstratigraphic analysis on samples collected from the same sites. His results were submitted for publication without knowledge of the 36Cl ages. His age estimates agree well with the 36Cl ages for the three previously undated flows, strongly supporting the validity of varnish microstratigraphy as a chronological correlation tool.

  5. Cosmogenic {sup 36}Cl accumulation in unstable landforms 1. Effects of the thermal neutron distribution

    SciTech Connect

    Liu, B.; Phillips, F.M.; Stone, W.D.; Fabryka-Martin, J.T.; Fowler, M.M.

    1994-11-01

    Cosmogenic nuclides produced in situ within minerals at the surface of the Earth are proving to be an effective means of assessing geomorphic histories. The use of multiple cosmogenic nuclides permits both exposure times and erosion rates to be determined. However, if two nuclides are produced only by spallation reactions, the systematic differences in their accumulation rates depend only on the differences in their production rates and half-lives. The relatively small differences that result require a high degree of analytical precision to yield useful results. In contrast to other spallogenic nuclides, {sup 36}Cl is also produced by low-energy neutron, absorption, which creates a different pattern of production as a function of depth. We have measured the thermal flux with depth in a concrete block using {sup 3}He-filled neutron detectors. The measured thermal neutron profile agrees well with predictions from a simple diffusion-based thermal neutron distribution model. Calculations of {sup 36}Cl production using the model suggest that the use of {sup 36}Cl along with a purely spallogenic nuclide to determine erosion rates and exposure times should be less sensitive to analytical error than are determinations from two purely spallogenic nuclides. 31 refs., 7 figs., 3 tabs.

  6. An Alluvial Surface Chronology Based on Cosmogenic 36Cl Dating, Ajo Mountains (Organ Pipe Cactus National Monument), Southern Arizona

    NASA Astrophysics Data System (ADS)

    Liu, Beiling; Phillips, Fred M.; Pohl, Molly M.; Sharma, Pankaj

    1996-01-01

    A chronology of alluvial surfaces on piedmont slopes below the western Ajo Mountains, southern Arizona, has been obtained using cosmogenic 36Cl accumulation and AMS radiocarbon dating. The apparent 36Cl ages of individual boulders range from 520,000 to 13,000 yr, and the 14C ages of organic material in the two young terraces are 2750-2350 and 17,800 cal yr B.P. The sequence of 36Cl ages is consistent with the apparent stratigraphic order, but groupings of similar ages for different surfaces appear to result from repeated reworking of older surfaces associated with the deposition of younger ones. The youngest surface gave a distribution of 36Cl ages about 30,000 yr older than the 14C and soil ages; however, this distribution had 36Cl ages that overlapped with 36Cl ages from active channels and hillslopes. We attribute the older-than-expected exposure ages of sampled boulders to inheritance of 36Cl while residing near the surface during very slow erosion on the mountain front. Our results show that although cosmogenic nuclide accumulation can help establish chronologies for surfaces in piedmont settings, care must be used in evaluating the effects of complex exposure histories.

  7. Cosmogenic 36Cl in karst waters from Bunker Cave North Western Germany - A tool to derive local evapotranspiration?

    NASA Astrophysics Data System (ADS)

    Münsterer, C.; Fohlmeister, J.; Christl, M.; Schröder-Ritzrau, A.; Alfimov, V.; Ivy-Ochs, S.; Wackerbarth, A.; Mangini, A.

    2012-06-01

    Monthly rain and drip waters were collected over a period of 10 months at Bunker Cave, Germany. The concentration of 36Cl and the 36Cl/Cl-ratios were determined by accelerator mass spectrometry (AMS), while stable (35+37)Cl concentrations were measured with both, ion chromatography (IC) and AMS. The measured 36Cl-fluxes of (0.97 ± 0.57) × 104 atoms cm-2 month-1 (0.97 atoms m-2 month-1) in precipitation were on average twice as high as the global mean atmospheric production rate. This observation is consistent with the local fallout pattern, which is characterized by a maximum at mid-latitudes. The stable chloride concentration in drip waters (ranging from 13.2 to 20.9 mg/l) and the 36Cl-concentrations (ranging from 16.9 × 106 to 35.3 × 106 atoms/l) are a factor of 7 and 10 above the values expected from empirical evapotranspiration formulas and the rain water concentrations, respectively. Most likely the additional stable Cl is due to human impact from a nearby urban conglomeration. The large 36Cl-enrichment is attributed to the local evapotranspiration effect, which appears to be higher than the calculated values and to additional bomb-derived 36Cl from nuclear weapons tests in the 1950s and 60s stored in the soil above the cave. In the densely vegetated soil above Bunker Cave, 36Cl seems not to behave as a completely conservative tracer. The bomb derived 36Cl might be retained in the soil due to uptake by minerals and organic material and is still being released now. Based on our data, the residence time of 36Cl in the soil is estimated to be about 75-85 years.

  8. Determination of paleoseismic activity over a large time-scale: Fault scarp dating with 36Cl

    NASA Astrophysics Data System (ADS)

    Mozafari Amiri, Nasim; Tikhomirov, Dmitry; Sümer, Ökmen; Özkaymak, Çaǧlar; Uzel, Bora; Ivy-Ochs, Susan; Vockenhuber, Christof; Sözbilir, Hasan; Akçar, Naki

    2016-04-01

    Bedrock fault scarps are the most direct evidence of past earthquakes to reconstruct seismic activity in a large time-scale using cosmogenic 36Cl dating if built in carbonates. For this method, a surface along the fault scarp with a minimum amount of erosion is required to be chosen as an ideal target point. The section of the fault selected for sampling should cover at least two meters of the fault surface from the lower part of the scarp, where intersects with colluvium wedge. Ideally, sampling should be performed on a continuous strip along the direction of the fault slip direction. First, samples of 10 cm high and 15 cm wide are marked on the fault surface. Then, they are collected using cutters, hammer and chisel in a thickness of 3 cm. The main geometrical factors of scarp dip, scarp height, top surface dip and colluvium dip are also measured. Topographic shielding in the sampling spot is important to be estimated as well. Moreover, density of the fault scarp and colluvium are calculated. The physical and chemical preparations are carried in laboratory for AMS and chemical analysis of the samples. A Matlab® code is used for modelling of seismically active periods based on increasing production rate of 36Cl following each rupture, when a buried section of a fault is exposed. Therefore, by measuring the amount of cosmogenic 36Cl versus height, the timing of major ruptures and their offsets are determined. In our study, Manastır, Mugırtepe and Rahmiye faults in Gediz graben, Priene-Sazlı, Kalafat and Yavansu faults in Büyük Menderes graben and Ören fault in Gökava half-graben have been examined in the seismically active region of Western Turkey. Our results reconstruct at least five periods of high seismic activity during the Holocene time, three of which reveal seismic ruptures beyond the historical pre-existing data.

  9. Estimation of thermal neutron fluences in the concrete of proton accelerator facilities from 36Cl production

    NASA Astrophysics Data System (ADS)

    Bessho, K.; Matsumura, H.; Miura, T.; Wang, Q.; Masumoto, K.; Hagura, H.; Nagashima, Y.; Seki, R.; Takahashi, T.; Sasa, K.; Sueki, K.; Matsuhiro, T.; Tosaki, Y.

    2007-06-01

    The thermal neutron fluence that poured into the shielding concrete of proton accelerator facilities was estimated from the in situ production of 36Cl. The thermal neutron fluences at concrete surfaces during 10-30 years of operation were in the range of 1012-1014 n/cm2. The maxima in thermal neutron fluences were observed at ≈5-15 cm in the depths analyzed for 36Cl/35Cl by AMS. These characteristics imply that thermalization of neutrons occurred inside the concrete. Compared to the several tens of MeV cyclotrons, secondary neutrons penetrate deeper into the concrete at the high-energy accelerators possessing acceleration energies of 400 MeV and 12 GeV. The attenuation length of neutrons reflects the energy spectra of secondary neutrons emitted by the nuclear reaction at the beam-loss points. Increasing the energy of secondary neutrons shifts the maximum in the thermal neutron fluences to deeper positions. The data obtained in this study will be useful for the radioactive waste management at accelerator facilities.

  10. Depth dependence of soil carbonate accumulation based on cosmogenic [sup 36]Cl dating

    SciTech Connect

    Liu, B.; Phillips, F.M. ); Elmore, D.; Sharma, P. )

    1994-12-01

    Indurated pedogenic carbonate layers (calcretes) are common in soils on stable surfaces in arid to semiarid climates. The morphology and composition of calcretes provide important information on the geomorphic and climatic histories of the regions where they are formed, but they have proved difficult to date with conventional radiometric methods. We report cosmogenic [sup 36]Cl-buildup ages from three fractions (leachable Cl, carbonate, silicate) of a calcrete from the surface of an alluvial slope below the Ajo Mountains in southern Arizona. All three fractions give reasonably concordant ages, ranging from 700 ka at the base of the calcrete horizon to 200 ka at its top. These ages are in good agreement both with estimates of age based on correlation with similar, independently dated, soils in the region and with [sup 36]Cl-buildup ages on surficial boulders. These results support the ideas that calcretes accumulate upward with time and that water movement through the carbonate matrix is very limited after induration. 19 refs., 2 figs., 1 tab.

  11. 36Cl/Cl ratios in geothermal systems: preliminary measurements from the Coso Field

    SciTech Connect

    Nimz, G.J.; Moore, J.N.; Kasameyer, P.W.

    1997-07-01

    The {sub 36}Cl/Cl isotopic composition of chlorine in geothermal systems can be a useful diagnostic tool in characterizing hydrologic structure, in determining the origins and age of waters within the systems, and in differentiating the sources of chlorine (and other solutes) in the thermal waters. The {sub 36}Cl/Cl values for several geothermal water samples and reservoir host rock samples from the Coso, California geothermal field have been measured for these purposes. The results indicate that most of the chlorine is not derived from the dominant granitoid that host the geothermal system. If the chlorine was originally input into the Coso subsurface through meteoric recharge, that input occurred at least 1-1.25 million years ago. The results suggest that the thermal waters could be connate waters derived from sedimentary formations, presumably underlying and adjacent top the granitic rocks, which have recently migrated into the host rocks. Alternatively, most of the chlorine but not the water, may have recently input into the system from magmatic sources. In either case, the results indicate that most of the chlorine in the thermal waters has existed within the granitoid host rocks for no more than about 100,00-200,00 years. this residence time for the chlorine is similar to residence times suggested by other researchers for chlorine in deep groundwaters of the Mono Basin north of the Coso field.

  12. Estimating groundwater recharge in fractured rock from environmental 3H and 36Cl, Clare Valley, South Australia

    NASA Astrophysics Data System (ADS)

    Cook, P. G.; Robinson, N. I.

    2002-08-01

    Vertical profiles of 3H and 36Cl concentrations are obtained from piezometer nests installed in fractured metasedimentary aquifers in the Clare Valley, South Australia. Because 3H is lost during evapotranspiration with negligible fractionation, while 36Cl is retained within the soil, comparison of 3H and 36Cl concentrations allows estimation of the aquifer recharge rate. An analytical solution for the transport of 3H and 36Cl through planar, parallel fractures is used to investigate the effect of variations in matrix porosity, tortuosity, fracture aperture, fracture spacing and aquifer recharge rate on tracer profiles and then to reproduce observed profiles within piezometer nests. While the measured distributions of these tracers are not able to constrain most model parameters, they are able to tightly constrain the aquifer recharge rate. The broad nature of the 36Cl and 3H peaks measured at our sites is simulated using a constant fracture spacing, lognormal distributions of fracture apertures, and mean recharge rates of 60-75 mm yr-1.

  13. 36Cl measurements in Hiroshima granite samples as part of an international intercomparison study. Results from the Munich group.

    PubMed

    Huber, T; Rühm, W; Hoshi, M; Egbert, S D; Nolte, E

    2003-04-01

    Within the effort to resolve the so-called Hiroshima neutron discrepancy, an international intercomparison study has been carried out on granite samples from Hiroshima, with participating institutions from Japan, the US, and Germany. (36)Cl and (152)Eu produced in these samples by thermal neutrons from the A-bomb explosion were assessed independently by means of different techniques. At the Maier-Leibnitz-Laboratory near Munich, Germany, (36)Cl concentrations were measured by accelerator mass spectrometry. Measured (36)Cl/Cl ratios ranged from 1,670 x 10(-13) (at a distance of 146 m from the hypocenter) to 2.2 x 10(-13) (at a distance of 1,163 m from the hypocenter). One granite sample not exposed to A-bomb neutrons was measured as a control, and a (36)Cl/Cl ratio of 2.6 x 10(-13) was obtained. On average, our experimental results are 20-30% lower than those provided by model calculations based on the dosimetry system DS86. The results presented here do not support previous assessments of (36)Cl, (60)Co, and (152)Eu which had suggested much larger thermal neutron fluences than those calculated on the basis of DS86 for distances from the hypocenter of more than 1,000 m. PMID:12684827

  14. A new Holocene eruptive history of Erebus volcano, Antarctica using cosmogenic 3He and 36Cl

    NASA Astrophysics Data System (ADS)

    Parmelee, D. E.; Kyle, P. R.; Kurz, M. D.; Marrero, S.

    2013-12-01

    Unraveling the timing of a volcano's most recent eruptions is crucial to understanding its present and future behavior. In this study, we use cosmogenic 3He and 36Cl in mineral separates (clinopyroxene and anorthoclase, respectively) to date the 10 most recent lava flows on Erebus volcano. Erebus is a 2,170-km3 active stratovolcano on Ross Island, Antarctica that is known for its persistent anorthoclase phonolite lava lake and frequent Strombolian eruptions. Previous anorthoclase 40Ar/39Ar ages from the 10 flows [1, 2] suggest they were erupted at roughly regular intervals between 17 and 0 ka. However, the uncertainties on the Ar ages are large (up to 39 %), and the likelihood of excess 40Ar in melt inclusions may skew the Ar ages older than eruption ages. The new cosmogenic ages provide new insights into Erebus eruption chronology. We used two different models to scale production rates: the Lal/Stone model [3] and the new Sato/Lifton model [4]. We find ~20-25 % younger ages with the Sato/Lifton model, attributable to different treatment of atmospheric pressure effects, solar modulation effects, and muogenic production rates in each model. 3He and 36Cl exposure ages of the same 10 flows range from 4.5 × 0.1 to 9.7 × 0.2 ka (Lal/Stone) or 3.5 × 0.1 to 7.5 × 0.2 ka (Sato/Lifton), significantly different than the Ar ages, with a much shorter eruption period. Surprisingly, three of the flows have exposure ages older than their Ar ages, despite the exposure ages being considered minimum ages of eruption and the Ar ages maxima. Concordance of the 3He and 36Cl ages measured in the same samples strengthens the validity of our results and implies that the 3He and 36Cl production rates [5] are well-calibrated for high latitude, high altitude sites and that the methodologies are robust. Regardless of which scaling model is used, the results yield a new understanding of the current eruptive phase of Erebus, particularly in documenting the short timespan over which the

  15. In-Situ Cosmogenic 36Cl Production Rate Calibration from Basaltic Flows of Mount Etna (Sicily, 38° N)

    NASA Astrophysics Data System (ADS)

    Schimmelpfennig, I.; Benedetti, L.; Pik, R.; Burnard, P.; Blard, P. H.; Bourles, D.

    2007-12-01

    One of the CRONUS-EU goals is to provide high quality calibration sites from independently dated surfaces. Several previous studies have been conducted on 36Cl production rate calibration (e.g. Stone et al. 1996, Phillips et al. 2001), which, however, used different protocols and yielded 36Cl production rates with up to 40% discrepancies. The objectives of this study are 1- to understand the source of these discrepancies and 2- to calibrate 36Cl production rates from its target elements Ca and K. As a first step we focused on testing the chemical protocol by performing a sequential 36Cl extraction experiment on whole rock grains and Ca-rich plagioclase from the same sample. The sample was collected at Mt. Etna on a pahoehoe flow, which has a K-Ar fossil exposure time of (10±3) kyr. Cosmogenic 3He was also precisely measured within cogenetic olivine phenocrysts of this sample (Blard et al. 2005) and yields an exposure time of (10.4±1.5) kyr. Both, total Cl and 36Cl concentrations from the first dissolution steps are high, 5800 ppm (whole rock) and 450 ppm (plagioclase) Cl, and 107 - 106 atoms 36Cl/g of rock dissolved. After about 20% dissolution of the plagioclase sample, Cl is almost completely removed (1-3ppm) and 36Cl concentrations reach a plateau value of 2*105 atoms/g of rock. Using the Stone et al. (1996) and Evans et al. (1997) 36Cl production rates for the target elements Ca and K, respectively, this plateau concentration yields an exposure age which is in excellent agreement with K-Ar dating and cosmogenic 3He ages. On the contrary, in the whole rock sample total Cl concentrations remain high (>330ppm) resulting in a considerable 36Cl production from capture of low-energy neutrons by 35Cl, an additional and still not well-constrained 36Cl production mechanism. The resulting exposure ages from the whole rock are 35-45% higher than the independent 3He ages. For 36Cl production rate calibration from Ca, we will use separated Ca-rich plagioclase from various

  16. Determination of 36Cl Production Rates Derived from the Well-Dated Deglaciation Surfaces of Whidbey and Fidalgo Islands, Washington

    NASA Astrophysics Data System (ADS)

    Swanson, Terry W.; Caffee, Marc L.

    2001-11-01

    The 36Cl dating method is increasingly being used to determine the surface-exposure history of Quaternary landforms. Production rates for the 36Cl isotopic system, a critical component of the dating method, have now been refined using the well-constrained radiocarbon-based deglaciation history of Whidbey and Fidalgo Islands, Washington. The calculated total production rates due to calcium and potassium are 91±5 atoms 36Cl (g Ca) -1 yr -1 and are 228±18 atoms 36Cl (g K) -1 yr -1, respectively. The calculated ground-level secondary neutron production rate in air, P f(0), inferred from thermal neutron absorption by 35Cl is 762±28 neutrons (g air) -1 yr -1 for samples with low water content (1-2 wt.%). Neutron absorption by serpentinized harzburgite samples of the same exposure age, having higher water content (8-12 wt.%), is ˜40% greater relative to that for dry samples. These data suggest that existing models do not adequately describe thermalization and capture of neutrons for hydrous rock samples. Calculated 36Cl ages of samples collected from the surfaces of a well-dated dacite flow (10,600-12,800 cal yr B.P.) and three disparate deglaciated localities are consistent with close limiting calibrated 14C ages, thereby supporting the validity of our 36Cl production rates integrated over the last ˜15,500 cal yr between latitudes of 46.5° and 51°N. Although our production rates are internally consistent and yield reasonable exposure ages for other localities, there nevertheless are significant differences between these production rates and those of other investigators.

  17. Age and geomorphic history of Meteor Crater, Arizona, from cosmogenic 36Cl and 14C in rock varnish

    USGS Publications Warehouse

    Phillips, F.M.; Zreda, M.G.; Smith, S.S.; Elmore, D.; Kubik, P.W.; Dorn, R.I.; Roddy, D.J.

    1991-01-01

    Using cosmogenic 36Cl buildup and rock varnish radiocarbon, we have measured the exposure age of rock surfaces at Meteor Crater, Arizona. Our 36Cl measurements on four dolomite boulders ejected from the crater by the impact yield a mean age of 49.7 ?? 0.85 ka, which is in excellent agreement with an average age of 49 ?? 3 ka obtained from thermoluminescence studies on shock-metamorphosed dolomite and quartz. These ages are supported by undetectably low 14C in the oldest rock varnish sample. ?? 1991.

  18. 10Be accumulation in a soil chronosequence

    USGS Publications Warehouse

    Pavich, M.J.; Brown, L.; Klein, J.; Middleton, R.

    1984-01-01

    We have measured the concentration of the cosmogenic isotope 10Be in soil samples from various horizons at six sites, including three independently dated Rappahannock River terraces and a previously undated Piedmont soil to which we have assigned an age. All of the incident 10Be can be accounted for in one of these soils and a second is within a factor of two. In three soils, whose concentrations vary widely with depth, a significant fraction of the incident 10Be cannot be accounted for. Incomplete sampling, and enhanced Be mobility caused by organic components, are the probable reasons for the low inventory of Be from these three soils. Overall, the data from these six sites indicate that 10Be accumulation could be used to assign ages to soils if Be is not mobilized and lost from the soil profile. ?? 1984.

  19. 10Be dating of Neogene halite

    NASA Astrophysics Data System (ADS)

    Belmaker, Reuven; Lazar, Boaz; Beer, Jürg; Christl, Marcus; Tepelyakov, Natalya; Stein, Mordechai

    2013-12-01

    Direct radioactive dating of ancient halite formations is difficult because this mineral typically lacks conventionally datable material. We describe an attempt to date Neogene halite using the cosmogenic isotope 10Be (T1/2 = 1.39 Ma). We dated marine-derived salt deposits from the Sedom and Amora (The Hebrew forms of Sodom and Gomorrah) Formations, Dead Sea basin, Israel. To verify whether Be is incorporated into marine halite we measured the stable isotope 9Be, 7Be (the short lived “cosmogenic brother” of 10Be having T1/2 = 53.3 d), and 10Be in evaporation pans of sea-salt production plants. The data suggest that seawater beryllium is incorporated into the halite with a halite-brine distribution coefficient, (KD) of about unity. A 10Be/9Be decay curve constructed for Sedom Formation halite yielded an age that lies in the range of ∼2-6 Ma. The 10Be decay curve constructed for Sedom Formation halite yielded an age that lies in the range of 3-5 Ma. This age is consistent with previous estimates of the Sedom Formation age. Furthermore, this age lies in the same range of 10Be in situ ages obtained on the lacustrine Erq El Ahmer Formation located in the northern Jordan Valley. This may imply that during the Mid Pliocene the Sedom Lagoon, the water-body that deposited the Sedom Formation, might have been already disconnected from the open sea.

  20. Cosmogenic 10Be and Noble Gases in Diogenites

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Lindner, L.; van der Borg, K.; Loeken, Th.; Scherer, P.; Schultz, L.

    1993-07-01

    Introduction: A recent reevaluation of the 3He, 21Ne, and 38Ar cosmic-ray exposure ages of eight non-Antarctic and three Antarctic diogenite falls led to a consistent set of exposure ages with a major cluster at 22 Ma and a possible second cluster around 40 Ma [1]. These clusters coincide with two major peaks in the exposure-age distributions of the genetically related eucrites and howardites [2], but the scarcity of young diogenites is remarkable [3]. An update of the exposure-age distribution for diogenites, including nine separate Antarctic falls, will be presented and possible differences in exposure history between Antarctic and non-Antarctic diogenites will be discussed. The exposure-age distributions of eucrites and howardites are still controversial [2,3], as conventional shielding corrections--on the basis of the 22Ne/21Ne ratio--cannot be applied. Therefore, the use of other shielding parameters, such as 10Be or 26Al, is considered. We examined the relation between 10Be contents and 22Ne/21Ne ratios in diogenites to obtain more insight into the shielding sensitivity of the 10Be production rate. Experimental: In addition to the existing database of more than 30 noble gas analyses [4] we carried out noble gas measurements on 5 non-Antarctic diogenites and on 12 Antarctic samples from 9 separate falls. On the same samples 10Be was measured by AMS. The experimental uncertainties in the 10Be values are 2-3%, those in the 22Ne/21Ne ratios are 0.5-1.0%. Results and Conclusions: The major exposure-age cluster at 22 Ma contains about 45% of the diogenite falls, indicating a major impact on its parent body. However, the presence of several younger diogenites suggests that this collisional event was not necessarily as destructive as previously suggested [3]. Four diogenites show exposure ages around 40 Ma, indicating a second major impact on the HED parent body. Although some Antarctic diogenites have unique mineralogical features [5,6], we didn't find any evidence

  1. Experimental determination of the {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections and the consequences on the origin of {sup 36}S

    SciTech Connect

    Smet, L. de; Wagemans, C.; Goeminne, G.; Heyse, J.; Gils, J. van

    2007-03-15

    The {sup 36}Cl(n,p){sup 36}S and {sup 36}Cl(n,{alpha}){sup 33}P reaction cross sections have been studied with resonance neutrons at the linear accelerator GELINA of the IRMM in Geel (Belgium) and have been determined up to approximately 250 keV using the time-of-flight technique. In this energy region, 17 resonances were observed, whereas eight were identified before. For some resonances the resonance strength, the spin, and the total width could be determined. From the obtained cross section data, the MACS has been calculated by numerical integration. These updated MACS values were used in stellar models to trace the origin of the rare isotope {sup 36}S.

  2. Using 36Cl data to quantify the paleorecharge in arid region. Example of the North Western Saharan Aquifer System.

    NASA Astrophysics Data System (ADS)

    Oriane Petersen, Jade; Deschamps, Pierre; Gonçalvès, Julio; Hamelin, Bruno; Michelot, Jean-Luc; Guendouz, Abdelhamid; Zouari, Kamel

    2014-05-01

    A comprehensive understanding of large-scale systems such as multi-layer aquifers in sedimentary basins (e.g. North Western Saharan Aquifer System -NWSAS- or the Great Artesian Basin) requires to investigate the recharge history to Quaternary timescale. In fact, for such systems, the residence time of groundwater is often in the order of 100 000 years to 1 million years, the recharge occurring during past, intermittent humid periods paced by the quaternary climatic cycles. In this study, we propose to reconstruct the history of the recharge over the Continental Intercalaire (CI) aquifer, one of the two main aquifers of the NWSAS. It extends over 1 million km2, shared between Algeria, Tunisia and Libya. We focus on the main recharge area of the CI aquifer located in the Algerian Atlas Mountains. Existing chlorine-36 data (36Cl half-life: 301 ka) indicate that groundwater residence time in this system is around 1 million years. A set of modeling approaches is combined to model the theoretical 36Cl/Cl distribution within the aquifer as a function of different recharge scenarios. Seventeen 36Cl/Cl data from two distinct flowpaths provide temporal constraints on groundwater ages. A simple piston model is used to simulate the distribution of theoretical 36Cl along these flowlines as a function of the distance from the outcrop with respect to a recharge scenario. Simplified climatic scenarios are constructed considering humid periods only during interglacial cycles. This allows to define 9 recharge rates (Rh(i)) associated to last interglacials (from marine isotope stages MIS1 to MIS19). In addition, a constant recharge Rg was considered during glacial periods. For each recharge scenario, the recharge values are constrained by using a Markov Chain Monte Carlo (MCMC) inversion, which yields the best agreement between measured and modeled 36Cl/Cl. This MCMC probabilistic inversion approach allows identifying plausible sets of the 10 parameters (9 Rh(i) and Rg) involved in

  3. Evidence from cosmic-ray exposure dating based on 36Cl for the pre-Minoan caldera on Santorini, Greece

    NASA Astrophysics Data System (ADS)

    Athanassas, Constantin; Bourlès, Didier; Braucher, Regis; Druitt, Tim; Nomikou, Paraskevi; Léanni, Laetitia

    2016-04-01

    The physiography of Santorini prior to the Minoan (Late Bronze Age) eruption (17th century BCE) is of great archaeological interest, given the importance of Santorini as a commercial centre and port in the Minoan empire. However, the paleogeography of the pre-Minoan caldera has been a point of controversy: Heiken and McCoy (1984) advocated the existence, in the southern part of the present-day caldera, of a pre-existing caldera formed during the 172 ka Lower Pumice eruption, whereas Druitt and Francaviglia (1992), based on the presence of in situ plinian pumice from the Minoan eruption adhering to the modern cliff, conceived the pre-Minoan (22 ka) caldera as having occupied much of the northern basin of the present-day caldera. With the goal of settling the debate we performed cosmic ray exposure dating employing in situ-produced cosmogenic 36Cl to date different generations of caldera cliffs at Santorini, and hence to identify those cliffs predating the Minoan eruption. Our methodology involved the determination of the in situ-produced cosmogenic 36Cl in basaltic and andesitic rocks cropping out in the cliffs. The samples returned 36Cl CRE ages consistent with previously published field mapping of cliff populations based on geomorphological and stratigraphic arguments (Druitt and Francaviglia 1992), suggesting that much of the present cliff line of northern Santorini predated the Minoan eruption, or was superficially modified by landslips and rockfalls during that eruption. The 36Cl CRE ages enable us to better define the paleogeography of the pre-Minoan caldera. References [1] Druitt, T. H. and Francaviglia, V.1992. Caldera formation on Santorini and the physiography of the islands in the Late Bronze Age. Bulletin of Volcanology 54, 484-493. [2] Heiken G and McCoy F (1984) Caldera development during the Minoan eruption, Thira, Cyclades, Greece. Journal of Geophysical Research: 89 (B10), 8841-8862.

  4. Methodological study on exposure date of Tiankeng by AMS measurement of in situ produced cosmogenic 36Cl

    NASA Astrophysics Data System (ADS)

    Kejun, Dong; Shizhuo, Li; Ming, He; Sasa, Kimikazu; Matsushi, Yuki; Baojian, Huang; Xiangdong, Ruan; Yongjing, Guan; Takahashi, Tsutomu; Sueki, Keisuke; Chaoli, Li; Shaoyong, Wu; Xianggao, Wang; Hongtao, Shen; Nagashima, Yasuo; Shan, Jiang

    2013-01-01

    Tiankeng is a typical Karst relief of the late Quaternary Period. Studies on the exposure ages of Tiankeng are very important in geographical research to elucidate the formation condition, the developing process, and the features of biological species. 36Cl on the surface layer of the rupture cross-section of Tiankeng is largely produced by cosmogenic high-energy neutron induced reactions 40Ca(n, αp) and 39K(n, α), and has accumulated since the formation of the Tiankeng. Low-energy neutron reaction 35Cl(n, γ) contributes a small portion of 36Cl. In this work, the concentration of the cosmogenic 36Cl in rock samples taken from Dashiwei Tiankeng, Leye County, Guangxi Zhuang Autonomous Region, China, was measured jointly by Accelerator Mass Spectrometry (AMS) laboratories of CIAE and University of Tsukuba in an effort to estimate the formation time (or exposure age) of the Tiankeng. The results show that the exposure time of Da Shiwei Tiankeng is about 26 ± 9.6 ka (without erosion correction). The sampling strategy and procedures, experimental set-up, and preliminary results will be presented in detail.

  5. 26Al incorporation into the tissues of suckling rats through maternal milk

    NASA Astrophysics Data System (ADS)

    Yumoto, S.; Nagai, H.; Kobayashi, K.; Tada, W.; Horikawa, T.; Matsuzaki, H.

    2004-08-01

    Aluminium (Al) is highly neurotoxic and inhibits prenatal and postnatal development of the brain in humans and experimental animals. However, Al incorporation into the brain of sucklings through maternal milk has not yet been well clarified because Al lacks a suitable isotope for radioactive tracer experiments. Using 26Al as a tracer, we measured 26Al incorporation into the brain of suckling rats by accelerator mass spectrometry. Lactating rats were subcutaneously injected with 26AlCl3 from day 1 to day 20 postpartum. Suckling rats were weaned from day 21 postpartum. From day 5 to day 20 postpartum, the 26Al levels measured in the brain, liver, kidneys and bone of suckling rats increased significantly. After weaning, the amounts of 26Al in the liver and kidneys decreased remarkably. However, the 26Al amount in the brain had diminished only slightly up to 140 days after weaning.

  6. Total radioactive residues and residues of [36Cl]chlorate in market size broilers.

    PubMed

    Smith, David J; Byrd, James A; Anderson, Robin C

    2007-07-11

    The oral administration of chlorate salts reduces the numbers of Gram-negative pathogens in gastrointestinal tracts of live food animals. Although the efficacy of chlorate salts has been demonstrated repeatedly, the technology cannot be introduced into commercial settings without first demonstrating that chlorate residues, and metabolites of chlorate remaining in edible tissues, represent a negligible risk to consumers. Typically, a first step in this risk assessment is to quantify the parent compound and to identify metabolites remaining in edible tissues of animals treated with the experimental compound. The objectives of this study were to determine the pathway(s) of chlorate metabolism in market broilers and to determine the magnitude of chlorate residues remaining in edible tissues. To this end, 12 broilers (6 weeks; 2.70+/-0.34 kg) were randomly assigned to three treatments of 7.4, 15.0, and 22.5 mM sodium [36Cl]chlorate dissolved in drinking water (n=4 broilers per treatment). Exposure to chlorate, dissolved in drinking water, occurred at 0 and 24 h (250 mL per exposure), feed was withdrawn at hour 38, water was removed at hour 48, and birds were slaughtered at hour 54 (16 h after feed removal and 8 h after water removal). The radioactivity was rapidly eliminated in excreta with 69-78% of the total administered radioactivity being excreted by slaughter. Total radioactive residues were proportional to dose in all edible tissues with chloride ion comprising greater than 98.5% of the radioactive residue for the tissue (9.4-97.8 ppm chlorate equivalents). Chlorate residues were typically greatest in the skin (0.33-0.82 ppm), gizzard (0.1-0.137 ppm), and dark muscle (0.05-0.14 ppm). Adipose, liver, and white muscle tissue contained chlorate concentrations from 0.03 to 0.13 ppm. In contrast, chlorate concentrations in excreta eliminated during the 6 h period prior to slaughter ranged from 53 to 71 ppm. Collectively, these data indicate that broilers rapidly

  7. Towards improvement of aluminium assay in quartz for in situ cosmogenic 26Al analysis at ANSTO

    NASA Astrophysics Data System (ADS)

    Fujioka, Toshiyuki; Fink, David; Mifsud, Charles

    2015-10-01

    Accuracy and precision in the measurement of natural aluminium abundances in quartz can affect the reliability of 26Al exposure dating and 26Al/10Be burial dating. At ANSTO, aliquots extracted from the HF solutions of dissolved quartz are treated in our laboratory, whereas ICP-OES analysis is performed at a commercial laboratory. The long-term inter-run reproducibility of our in-house standards show a limiting precision in Al measurements of 3-4% (1σ), which is lower than the claimed precision of Al analysis by ICP-OES. This indicates that unaccounted random errors are incorporated during our aliquot preparation. In this study, we performed several controlled tests to investigate effects of possible inconsistencies and variances during our aliquot preparation procedure. The results indicate that our procedure is robust against any subtle change in the preparation procedure, e.g., fuming temperatures, fuming reagents, and drying conditions. We found that the density of the solutions dispatched for ICP analysis is occasionally variable due to the presence of residual fuming reagents in the solution. A comparison of the results between the calibration curve and standard addition methods show that the former results are consistently lower than the latter by up to ∼14%. Similar offsets have been reported by previous studies. The reason for these discrepancies is mostly likely matrix effect, which is not accounted for by the calibration curve method. Further tests by varying matrix with impurities such as HF, HClO4, H2SO4 and Si identified that Si could cause lower offset in Al measurements; however, our ICP solutions are confirmed to be free from Si and the cause of matrix effect remains to be investigated. Hence, care must be taken for the measurement of Al concentrations in quartz by ICP-OES, either by ensuring that matrix effect is fully accounted for or by routinely employing standard additions when required.

  8. A 420 Year Annual 10Be Record from the WAIS Divide Ice Core

    NASA Astrophysics Data System (ADS)

    Woodruff, T. E.; Welten, K. C.; Caffee, M. W.; Nishiizumi, K.

    2011-12-01

    Annual ice layers archive the cosmogenic radionuclide 10Be, which is in turn an important proxy for solar activity, complementary to the 14C tree ring archive. Although production is primarily determined by the strength of the solar magnetic field 10Be deposition is also determined by local weather phenomena and snow accumulation rates, especially within shorter timescales. Accordingly, multiple ice core records of varying locations and accumulation rates are necessary to build a representative 10Be archive. We are presently engaged in a study to obtain continuous 10Be and 36Cl records in the West Antarctic Ice Sheet (WAIS) Divide ice core, a high snow accumulation site analogous to the GISP2 core from Greenland (Finkel and Nishiizumi1997). Here we present an annual resolution record of 10Be in the WAIS Divide core spanning the last 420 years including the Maunder (1645-1715 AD) and Dalton (1790-1830 AD) solar minima. Preliminary results for the periods of 1580-1740 and 1945-2006 AD show that the10Be flux during the Maunder Minimum was ~60% higher than in the last 60 years (4.8 vs. 3.0 x 105 atoms yr-1 cm-2). Although the low sunspot numbers during the Maunder Minimum suggest little change in solar activity, the 10Be data show that the heliomagnetic field strength continued to vary in a 11-year cycle, as observed in other annual 10Be records (e.g., Beer et al. 1990; Berggren et al. 2009). The 10Be record for the WAIS Divide core will be compared to 10Be records of Greenland ice cores as well as the 14C tree ring record. Acknowledgment. This work was supported by NSF grants ANT-0839042 and 0839137. Beer J. et al. 1990.Nature 347, 164. Finkel R. C. and Nishiizumi K. 1997.J. Geophys. Res. 102, 26,699. Berggren A.- M., et al. 2009. Geophys. Res. Lett. 36, L11801.

  9. The Production of (26)Al in the Early Solar System by the (16)O((16)O, X)(26)Al(Gs) and (14)N((16)O, X)(26)Al(Gs) Reactions

    NASA Astrophysics Data System (ADS)

    Yildiz, Kazim Orhan

    1998-12-01

    The astrophysically short half life (0.74 Myr) of 26Al isotope makes it one of the more important extinct nuclides whose abundances in the early solar system can be used as a probe of the environment in which the solar system formed. The abundance of 26Al in the present galaxy deduced from the gamma ray observations ( (Mah84) and (Die95)) is about an order of magnitude lower than its meteoritic abundances measured in the form of an enhancement in the abundance of 26Mg (daughter of 26Al) over the solar system level (Was85). The existence of 26Al in the meteorites is an indication that some sort of nucleosynthesis event occurred less than a few million years before the collapse of the proto-solar cloud, perhaps during that collapse. The most widely accepted explanation is that a nearby stellar explosion (such as a supernova) injected large amounts of 26Al and some other extinct nuclides into the proto-solar cloud, possibly triggering the collapse of the cloud in the process (e.g., (Cam77), (Cam92) and (Cam95)). Motivated by the COMPTEL observation (Blo94) of unexpectedly high fluxes of gamma rays in the energy range of 3-7 MeV from the direction of the Orion complex, Clayton and Jin ( (Cla94), (Cla95a) and (Cla95b)) proposed several cosmic-ray scenarios for the production of 26Al in the early solar system. One of their scenarios is that the meteoritic 26Al was produced by the irradiation of the proto-solar material by oxygen-rich cosmic rays (with energies up to 10 MeV/nucleon) through the 12C(16O,x)26Algs reaction. In order to test this proposal Bateman et al. (Bat96b) measured the yield of the 12C(16O,x)26Al reaction and determined that the yield of this reaction alone is not large enough to produce the meteoritic abundances of 26Al. Even though Clayton and Jin (Cla95a) assumed the contribution to the yield from the 16O(16O,x)26Algs would not be significant, the yield of this reaction was measured in the experimental work of this thesis. Due to higher solar system

  10. EVIDENCE FOR MULTIPLE SOURCES OF {sup 10}Be IN THE EARLY SOLAR SYSTEM

    SciTech Connect

    Wielandt, Daniel; Krot, Alexander N.; Bizzarro, Martin; Nagashima, Kazuhide; Huss, Gary R.; Ivanova, Marina A.

    2012-04-01

    Beryllium-10 is a short-lived radionuclide (t{sub 1/2} = 1.4 Myr) uniquely synthesized by spallation reactions and inferred to have been present when the solar system's oldest solids (calcium-aluminum-rich inclusions, CAIs) formed. Yet, the astrophysical site of {sup 10}Be nucleosynthesis is uncertain. We report Li-Be-B isotope measurements of CAIs from CV chondrites, including CAIs that formed with the canonical {sup 26}Al/{sup 27}Al ratio of {approx}5 Multiplication-Sign 10{sup -5} (canonical CAIs) and CAIs with Fractionation and Unidentified Nuclear isotope effects (FUN-CAIs) characterized by {sup 26}Al/{sup 27}Al ratios much lower than the canonical value. Our measurements demonstrate the presence of four distinct fossil {sup 10}Be/{sup 9}Be isochrons, lower in the FUN-CAIs than in the canonical CAIs, and variable within these classes. Given that FUN-CAI precursors escaped evaporation-recondensation prior to evaporative melting, we suggest that the {sup 10}Be/{sup 9}Be ratio recorded by FUN-CAIs represents a baseline level present in presolar material inherited from the protosolar molecular cloud, generated via enhanced trapping of galactic cosmic rays. The higher and possibly variable apparent {sup 10}Be/{sup 9}Be ratios of canonical CAIs reflect additional spallogenesis, either in the gaseous CAI-forming reservoir, or in the inclusions themselves: this indicates at least two nucleosynthetic sources of {sup 10}Be in the early solar system. The most promising locale for {sup 10}Be synthesis is close to the proto-Sun during its early mass-accreting stages, as these are thought to coincide with periods of intense particle irradiation occurring on timescales significantly shorter than the formation interval of canonical CAIs.

  11. "Groundwater ages" of the Lake Chad multi-layer aquifers system inferred from 14C and 36Cl data

    NASA Astrophysics Data System (ADS)

    Bouchez, Camille; Deschamps, Pierre; Goncalves, Julio; Hamelin, Bruno; Seidel, Jean-Luc; Doumnang, Jean-Claude

    2014-05-01

    Assessment of recharge, paleo-recharge and groundwater residence time of aquifer systems of the Sahel is pivotal for a sustainable management of this vulnerable resource. Due to its stratified aquifer system, the Lake Chad Basin (LCB) offers the opportunity to assess recharge processes over time and to link climate and hydrology in the Sahel. Located in north-central Africa at the fringe between the Sahel and the Sahara, the lake Chad basin (LCB) is an endorheic basin of 2,5.106 km2. With a monsoon climate, the majority of the rainfall occurs in the southern one third of the basin, the Chari/Logone River system transporting about 90% of the runoff generated within the drainage basin. A complex multi-layer aquifer system is located in the central part of the LCB. The Quaternary unconfined aquifer, covering 500 000 km2, is characterized by the occurrence of poorly understood piezometric depressions. Artesian groundwaters are found in the Plio-Pleistocene lacustrine and deltaic sedimentary aquifers (early Pliocene and Continental Terminal). The present-day lake is in hydraulic contact with the Quaternary Aquifer, but during past megalake phases, most of the Quaternary aquifer was submerged and may experience major recharge events. To identify active recharge area and assess groundwater dynamics, one hundred surface and groundwater samples of all layers have been collected over the southern part of the LCB. Major and trace elements have been analyzed. Measurements of 36Cl have been carried out at CEREGE, on the French 5 MV AMS National Facility ASTER and 14C activities have been analyzed for 17 samples on the French AMS ARTEMIS. Additionally, the stable isotopic composition was measured on the artesian aquifer samples. In the Quaternary aquifer, results show a large scatter with waters having very different isotopic and geochemical signature. In its southern part and in the vicinity of the surface waters, groundwaters are predominantly Ca-Mg-HCO3 type waters with very

  12. Timing of maximum glacial extent and deglaciation from HualcaHualca volcano (southern Peru), obtained with cosmogenic 36Cl.

    NASA Astrophysics Data System (ADS)

    Alcalá, Jesus; Palacios, David; Vazquez, Lorenzo; Juan Zamorano, Jose

    2015-04-01

    Andean glacial deposits are key records of climate fluctuations in the southern hemisphere. During the last decades, in situ cosmogenic nuclides have provided fresh and significant dates to determine past glacier behavior in this region. But still there are many important discrepancies such as the impact of Last Glacial Maximum or the influence of Late Glacial climatic events on glacial mass balances. Furthermore, glacial chronologies from many sites are still missing, such as HualcaHualca (15° 43' S; 71° 52' W; 6,025 masl), a high volcano of the Peruvian Andes located 70 km northwest of Arequipa. The goal of this study is to establish the age of the Maximum Glacier Extent (MGE) and deglaciation at HualcaHualca volcano. To achieve this objetive, we focused in four valleys (Huayuray, Pujro Huayjo, Mollebaya and Mucurca) characterized by a well-preserved sequence of moraines and roches moutonnées. The method is based on geomorphological analysis supported by cosmogenic 36Cl surface exposure dating. 36Cl ages have been estimated with the CHLOE calculator and were compared with other central Andean glacial chronologies as well as paleoclimatological proxies. In Huayuray valley, exposure ages indicates that MGE occurred ~ 18 - 16 ka. Later, the ice mass gradually retreated but this process was interrupted by at least two readvances; the last one has been dated at ~ 12 ka. In the other hand, 36Cl result reflects a MGE age of ~ 13 ka in Mollebaya valley. Also, two samples obtained in Pujro-Huayjo and Mucurca valleys associated with MGE have an exposure age of 10-9 ka, but likely are moraine boulders affected by exhumation or erosion processes. Deglaciation in HualcaHualca volcano began abruptly ~ 11.5 ka ago according to a 36Cl age from a polished and striated bedrock in Pujro Huayjo valley, presumably as a result of reduced precipitation as well as a global increase of temperatures. The glacier evolution at HualcaHualca volcano presents a high correlation with

  13. Seismic slip history of the Pizzalto fault (Central Apennines, Italy) using in situ 36Cl cosmogenic dating

    NASA Astrophysics Data System (ADS)

    Delli Rocioli, Mattia; Pace, Bruno; Benedetti, Lucilla; Visini, Francesco; Guillou, Valery; Bourlès, Didier; Arnorld, Maurice; Aumaître, Georges; Keddadouche, Karim

    2013-04-01

    A prerequisite to constrain fault-based and time-dependent earthquake rupture forecast models is to acquire data on the past large earthquake frequency on an individual seismogenic source. Here we present a paleoseismological study on the Pizzalto fault using the in situ produced cosmogenic nuclide 36Cl (Schlagenhauf et al., 2011). The Pizzalto fault, located in central Italy about 50 km southeast of the epicenter of L'Aquila 2009 earthquake, is about 12 km long, SW dipping and belongs to the 30 km long Rotella-Aremogna active normal fault system. Recent activity along the Pizzalto fault is suggested by the presence of a continuous and linear 2 to 5 m high limestone fault scarp that was sampled every 10 cm at a site located in its particularly well-preserved central portion. 49 samples have been chemically processed and measured, and their 36Cl and Cl concentrations have been determined using isotope dilution mass spectrometry at the French AMS national facility ASTER located at CEREGE. Modeling the in situ 36Cl concentration with the scarp height allow deciphering the age and slip of the last major earthquake events on the fault. To derive those earthquake parameters, we used the published Matlab code from Schlagenhauf et al. (2011) that we implemented with a Monte Carlo approach to explore a large number of earthquake recurrence scenarios varying both the number of events, their slip and their ages. The "a priori" constraints input in the Monte Carlo code were: 1-the number of events, which is given by the stacking of individual probability density functions (assumed to be Gaussian) of each sample concentration; and, 2-the cumulative slip that should be equal to the height of the fault scarp. The first results show that 36Cl concentrations are reproduced better considering five events occurring over the last 5 ka and a previous one at about 13 ka. This suggests that most earthquake events clustered during a period of intense seismic activity preceded by a longer

  14. Excess 36Ar in the Efremovka Meteorite: Evidence for Live 36Cl in the Early Solar System

    NASA Astrophysics Data System (ADS)

    Murty, S. V. S.; Shukolyukov, Yu. A.; Goswami, J. N.

    1995-09-01

    The recent discovery of the presence of ^41Ca (t = 0.15 Ma) in the early solar system at the time of formation of the Efremovka CAIs [1] has prompted us to look for the possible presence of ^36Cl (t = 0.43 Ma) in this meteorite. Since ^36Cl decays to ^36Ar, an excess ^36Ar will in principle be a signature of the presence of extinct ^36Cl. However in situ (n,g) reaction on ^35Cl can also produce ^36Cl and generate excess ^36Ar. A study of all noble gases is helpful in decoupling the various ^36Ar components. Here we report the noble gas results on a bulk sample of Efremovka (a single chip adjacent to CAI E60). Work on two CAIs E40 (coarse-grained) and E42 (fine-grained) is currently in progress. All the noble gases have been analysed on VG 1200 mass spectrometer by standard procedure. After 400 degrees C combustion in 2 torr O2, mainly intended to get rid of surfical contaminants, the subsequent extractions at 900, 1200 and 1500 degrees C are carried out by pyrolysis. The Ne and Ar data for the total sample given in Table-1 have been corrected for blanks, mass discrimination and interferences as detailed in [2]. From the Ne data, we derive ^21Ne(sub)c = 4.1x10^-8ccSTP/g and (^22Ne/^21Ne)(sub)c = 1.043 +/-0.011. Using the ^21Ne production rate of Eugster [3] an exposure age of 9.0 Ma is obtained. The maximum ^36Ar release (about 86%) occurs at 1200 degrees C wherein the minimum ^38Ar/^36Ar (0.1795) is also observed. Even the ^38Ar/^36Ar value of 0.1801 for the total sample is less than the value of 0.1880 for the planetary component[4], indicating the presence of additional Ar-components in Efremovka and in particular, Ar produced by neutron capture on chlorine. If we assume that the measured ^38Ar/^36Ar value in Efremovka is a mixture of three components (trapped = 0.1880; spallogenic = 1.45-1.60 and neutron produced from Cl = 3x10^-3 [5,6]), the abundance of each of these components can be obtained, with the aid of Ne data, to be (in units of 10^-8ccSTP/g) ^36Ar

  15. 26Al incorporation into the brain of rat fetuses through the placental barrier and subsequent metabolism in postnatal development

    NASA Astrophysics Data System (ADS)

    Yumoto, Sakae; Nagai, Hisao; Kakimi, Shigeo; Matsuzaki, Hiroyuki

    2010-04-01

    Aluminium (Al) inhibits prenatal and postnatal development of the brain. We used 26Al as a tracer, and measured 26Al incorporation into rat fetuses through the placental barrier by accelerator mass spectrometry (AMS). From day 15 to day 18 of gestation, 26AlCl 3 was subcutaneously injected into pregnant rats. Considerable amounts of 26Al were measured in the tissues of newborn rats immediately after birth. The amounts of 26Al in the liver and kidneys decreased rapidly during postnatal development. However, approximately 15% of 26Al incorporated into the brain of fetuses remained in the brain of adult rats 730 days after birth.

  16. Tritium and 36Cl as constraints on fast fracture flow and percolation flux in the unsaturated zone at Yucca Mountain

    NASA Astrophysics Data System (ADS)

    Guerin, Marianne

    2001-10-01

    An analysis of tritium and 36Cl data collected at Yucca Mountain, Nevada suggests that fracture flow may occur at high velocities through the thick unsaturated zone. The mechanisms and extent of this "fast flow" in fractures at Yucca Mountain are investigated with data analysis, mixing models and several one-dimensional modeling scenarios. The model results and data analysis provide evidence substantiating the weeps model [Gauthier, J.H., Wilson, M.L., Lauffer, F.C., 1992. Proceedings of the Third Annual International High-level Radioactive Waste Management Conference, vol. 1, Las Vegas, NV. American Nuclear Society, La Grange Park, IL, pp. 891-989] and suggest that fast flow in fractures with minimal fracture-matrix interaction may comprise a substantial proportion of the total infiltration through Yucca Mountain. Mixing calculations suggest that bomb-pulse tritium measurements, in general, represent the tail end of travel times for thermonuclear-test-era (bomb-pulse) infiltration. The data analysis shows that bomb-pulse tritium and 36Cl measurements are correlated with discrete features such as horizontal fractures and areas where lateral flow may occur. The results presented here imply that fast flow in fractures may be ubiquitous at Yucca Mountain, occurring when transient infiltration (storms) generates flow in the connected fracture network.

  17. Tritium and 36Cl as constraints on fast fracture flow and percolation flux in the unsaturated zone at Yucca Mountain.

    PubMed

    Guerin, M

    2001-10-01

    An analysis of tritium and 36Cl data collected at Yucca Mountain, Nevada suggests that fracture flow may occur at high velocities through the thick unsaturated zone. The mechanisms and extent of this "fast flow" in fractures at Yucca Mountain are investigated with data analysis, mixing models and several one-dimensional modeling scenarios. The model results and data analysis provide evidence substantiating the weeps model [Gauthier, J.H., Wilson, M.L., Lauffer, F.C., 1992. Proceedings of the Third Annual International High-level Radioactive Waste Management Conference, vol. 1, Las Vegas, NV. American Nuclear Society, La Grange Park, IL, pp. 891-989] and suggest that fast flow in fractures with minimal fracture-matrix interaction may comprise a substantial proportion of the total infiltration through Yucca Mountain. Mixing calculations suggest that bomb-pulse tritium measurements, in general, represent the tail end of travel times for thermonuclear-test-era (bomb-pulse) infiltration. The data analysis shows that bomb-pulse tritium and 36Cl measurements are correlated with discrete features such as horizontal fractures and areas where lateral flow may occur. The results presented here imply that fast flow in fractures may be ubiquitous at Yucca Mountain, occurring when transient infiltration (storms) generates flow in the connected fracture network. PMID:11588829

  18. Theoretical evaluation of the reaction rates for {sup 26}Al(n,p){sup 26}Mg and {sup 26}Al(n,{alpha}){sup 23}Na

    SciTech Connect

    Oginni, B. M.; Iliadis, C.; Champagne, A. E.

    2011-02-15

    The reactions that destroy {sup 26}Al in massive stars have significance in a number of astrophysical contexts. We evaluate the reaction rates of {sup 26}Al(n,p){sup 26}Mg and {sup 26}Al(n,{alpha}){sup 23}Na using cross sections obtained from the codes empire and talys. These have been compared to the published rates obtained from the non-smoker code and to some experimental data. We show that the results obtained from empire and talys are comparable to those from non-smoker. We also show how the theoretical results vary with respect to changes in the input parameters. Finally, we present recommended rates for these reactions using the available experimental data and our new theoretical results.

  19. 26Al-containing acidic and basic sodium aluminum phosphate preparation and use in studies of oral aluminum bioavailability from foods utilizing 26Al as an aluminum tracer

    NASA Astrophysics Data System (ADS)

    Yokel, Robert A.; Urbas, Aaron A.; Lodder, Robert A.; Selegue, John P.; Florence, Rebecca L.

    2005-04-01

    We synthesized 26Al-containing acidic and basic (alkaline) sodium aluminum phosphates (SALPs) which are FDA-approved leavening and emulsifying agents, respectively, and used them to determine the oral bioavailability of aluminum incorporated in selected foods. We selected applicable methods from published syntheses (patents) and scaled them down (∼3000- and 850-fold) to prepare ∼300-400 mg of each SALP. The 26Al was incorporated at the beginning of the syntheses to maximize 26Al and 27Al equilibration and incorporate the 26Al in the naturally-occurring Al-containing chemical species of the products. Near infrared spectroscopy (NIR) and X-ray powder diffraction (XRD) were used to characterize the two SALP samples and some intermediate samples. Multi-elemental analysis (MEA) was used to determine Na, Al and P content. Commercial products were included for comparison. Satisfactory XRD analyses, near infrared spectra and MEA results confirmed that we synthesized acidic and basic SALP, as well as some of the syntheses intermediates. The 26Al-containing acidic and basic SALPs were incorporated into a biscuit material and a processed cheese, respectively. These were used in oral bioavailability studies conducted in rats in which the 26Al present in blood after its oral absorption was quantified by accelerator mass spectrometry. The results showed oral Al bioavailability from acidic SALP in biscuit was ∼0.02% and from basic SALP in cheese ∼0.05%, lower than our previous determination of Al bioavailability from drinking water, ∼0.3%. Both food and water can appreciably contribute to the Al absorbed from typical human Al intake.

  20. Resonances in 14C observed in the 4He(10Be ,α )10Be reaction

    NASA Astrophysics Data System (ADS)

    Freer, M.; Malcolm, J. D.; Achouri, N. L.; Ashwood, N. I.; Bardayan, D. W.; Brown, S. M.; Catford, W. N.; Chipps, K. A.; Cizewski, J.; Curtis, N.; Jones, K. L.; Munoz-Britton, T.; Pain, S. D.; Soić, N.; Wheldon, C.; Wilson, G. L.; Ziman, V. A.

    2014-11-01

    The α (10Be,α )10Be resonant scattering reaction has been measured at nine 10Be beam energies from 25 to 48 MeV, scanning out resonances in 14C from excitation energies of 13 to 24 MeV. Angular distribution measurements were used to assign the spin and parity of 5- to resonances at Ex=18.82 (2 ) and 19.67(2) MeV and 6+ at Ex=20.80 (2 ) MeV. The data also strongly indicate a 3- resonance at 17.32(2) MeV. The systematic uncertainty on the excitation energies is 175 keV. An R -matrix analysis has been performed for the excitation energy range 16.5 to 22 MeV. The data are discussed in terms of cluster bands in 14C.

  1. Millennial strain partitioning and fault interaction revealed by 36Cl cosmogenic nuclide datasets from Abruzzo, Central Italy

    NASA Astrophysics Data System (ADS)

    Gregory, L. C.; Phillips, R. J.; Roberts, G.; Cowie, P. A.; Shanks, R. P.; McCaffrey, K. J. W.; Wedmore, L. N. J.; Zijerveld, L.

    2015-12-01

    In zones of distributed continental faulting, it is critical to understand how slip is partitioned onto brittle structures over both long-term millennial time scales and shorter-term individual earthquake cycles. The comparison of slip distributions on different timescales is challenging due to earthquake repeat-times being longer or similar to historical earthquake records, and a paucity of data on fault activity covering millennial to Quaternary scales in detail. Cosmogenic isotope analyses from bedrock fault scarps have the potential to bridge the gap, as these datasets track the exposure of fault planes due to earthquakes with better-than-millennial resolution. In this presentation, we will use an extensive 36Cl dataset to characterise late Holocene activity across a complicated network of normal faults in Abruzzo, Italy, comparing the most recent fault behaviour with the historical earthquake record in the region. Extensional faulting in Abruzzo has produced scarps of exposed bedrock limestone fault planes that have been preserved since the last glacial maximum (LGM). 36Cl accumulates in bedrock fault scarps as the plane is progressively exhumed by earthquakes and thus the concentration of 36Cl measured up the fault plane reflects the rate and patterns of slip. In this presentation, we will focus on the most recent record, revealed at the base of the fault. Utilising new Bayesian modelling techniques on new and previously collected data, we compare evidence for this most recent period of slip (over the last several thousands of years) across 5-6 fault zones located across strike from each other. Each sampling site is carefully characterised using LiDAR and GPR. We demonstrate that the rate of slip on individual fault strands varies significantly, between having periods of accelerated slip to relative quiescence. Where data is compared between across-strike fault zones and with the historical catalogue, it appears that slip is partitioned such that one fault

  2. A comparison of groundwater dating with 81Kr, 36Cl and 4He in four wells of the Great Artesian Basin, Australia

    NASA Astrophysics Data System (ADS)

    Lehmann, B. E.; Love, A.; Purtschert, R.; Collon, P.; Loosli, H. H.; Kutschera, W.; Beyerle, U.; Aeschbach-Hertig, W.; Kipfer, R.; Frape, S. K.; Herczeg, A.; Moran, J.; Tolstikhin, I. N.; Gröning, M.

    2003-06-01

    The isotopic ratios 81Kr/Kr and 36Cl/Cl and the 4He concentrations measured in groundwater from four artesian wells in the western part of the Great Artesian Basin (GAB) in Australia are discussed. Based on radioactive decay along a water flow path the 81Kr/Kr ratios are directly converted to groundwater residence times. Results are in a range of 225-400 kyr with error bars in the order of 15% primarily due to counting statistics in the cyclotron accelerator mass spectrometer measurement. Additional uncertainties from subsurface production and/or exchange with stagnant porewaters in the confining shales appear to be of the same order of magnitude. These 81Kr ages are then used to calibrate the 36Cl and the 4He dating methods. Based on elemental analyses of rock samples from the sandstone aquifer as well as from the confining Bulldog shale the in situ flux of thermal neutrons and the corresponding 3He/ 4He and 36Cl/Cl ratios are calculated. From a comparison of: (i) the 3He/ 4He ratios measured in the groundwater samples with the calculated in situ ratios in rocks and (ii) the measured δ 37Cl ratios with the 4He concentrations measured in groundwater it is concluded that both helium and chloride are most likely added to the aquifer from sources in the stagnant porewaters of the confining shale by diffusion and/or mixing. Based on this 'working hypothesis' the 36Cl transport equation in groundwater is solved taking into account: (i) radioactive decay, (ii) subsurface production in the sandstone aquifer (with an in situ 36Cl/Cl ratio of 6×10 -15) and (iii) addition of chloride from a source in the confining shale (with a 36Cl/Cl ratio of 13×10 -15). Lacking better information it is assumed that the chloride concentration increased linearly with time from an (unknown) initial value Ci to its measured present value C= Ci+ Ca, where Ca represents the (unknown) amount of chloride added from subsurface sources. Using the 81Kr ages of the four groundwater samples and a

  3. HETEROGENEOUS DISTRIBUTION OF {sup 26}Al AT THE BIRTH OF THE SOLAR SYSTEM

    SciTech Connect

    Makide, Kentaro; Nagashima, Kazuhide; Krot, Alexander N.; Huss, Gary R.; Ciesla, Fred J.; Yang, Le; Hellebrand, Eric; Gaidos, Eric

    2011-06-01

    It is believed that {sup 26}Al, a short-lived (t{sub 1/2} = 0.73 Ma) and now extinct radionuclide, was uniformly distributed in the nascent solar system (SS) with the initial {sup 26}Al/{sup 27}Al ratio of {approx}5.2 x 10{sup -5}, suggesting an external, stellar origin rather than local, solar source. However, the stellar source of {sup 26}Al and the manner in which it was injected into the SS remain controversial: the {sup 26}Al could have been produced by an asymptotic giant branch star, a supernova, or a Wolf-Rayet star and injected either into the protosolar molecular cloud, protosolar cloud core, or protoplanetary disk. Corundum (Al{sub 2}O{sub 3}) is predicted to be the first condensate from a cooling gas of solar composition. Here we show that micron-sized corundum condensates from {sup 16}O-rich ({Delta}{sup 17}O {approx} -25 per mille ) gas of solar composition recorded heterogeneous distribution of {sup 26}Al at the birth of the SS: the inferred initial {sup 26}Al/{sup 27}Al ratio ranges from {approx}6.5x10{sup -5} to <2x10{sup -6}; 52% of corundum grains measured are {sup 26}Al-poor. Abundant {sup 26}Al-poor, {sup 16}O-rich refractory objects include grossite- and hibonite-rich calcium-aluminum-rich inclusions (CAIs) in CH (high metal abundance and high iron concentration) chondrites, platy hibonite crystals in CM (Mighei-like) chondrites, and CAIs with fractionation and unidentified nuclear effects CAIs chondrites. Considering the apparently early and short duration (<0.3 Ma) of condensation of refractory {sup 16}O-rich solids in the SS, we infer that {sup 26}Al was injected into the collapsing protosolar molecular cloud and later homogenized in the protoplanetary disk. The apparent lack of correlation between {sup 26}Al abundance and O-isotope composition of corundum grains constrains the stellar source of {sup 26}Al in the SS.

  4. 26Al in the Early Solar System: Not So Unusual after All

    NASA Astrophysics Data System (ADS)

    Jura, M.; Xu, S.; Young, E. D.

    2013-10-01

    Recently acquired evidence shows that extrasolar asteroids exhibit over a factor of 100 variation in the iron to aluminum abundance ratio. This large range likely is a consequence of igneous differentiation that resulted from heating produced by radioactive decay of 26Al with an abundance comparable to that in the solar system's protoplanetary disk at birth. If so, the conventional view that our solar system began with an unusually high amount of 26Al should be discarded.

  5. Excited states of 26Al studied via the reaction 27Al(d,t)

    NASA Astrophysics Data System (ADS)

    Srivastava, Vishal; Bhattacharya, C.; Rana, T. K.; Manna, S.; Kundu, S.; Bhattacharya, S.; Banerjee, K.; Roy, P.; Pandey, R.; Mukherjee, G.; Ghosh, T. K.; Meena, J. K.; Roy, T.; Chaudhuri, A.; Sinha, M.; Saha, A. K.; Asgar, Md. A.; Dey, A.; Roy, Subinit; Moin Shaikh, Md.

    2016-05-01

    The reaction 27Al(d,t) at 25 MeV was utilized to study the excited states of 26Al. The angular distributions of the observed excited states of 26Al were analyzed with zero range distorted wave Born approximation as well as by incorporating finite range correction parameters to extract spectroscopic factors. The two sets of extracted spectroscopic factors were compared with each other to see the effect of using finite range correction in the transfer form factor.

  6. {sup 26}Al IN THE EARLY SOLAR SYSTEM: NOT SO UNUSUAL AFTER ALL

    SciTech Connect

    Jura, M.; Xu, S.; Young, E. D. E-mail: sxu@astro.ucla.edu

    2013-10-01

    Recently acquired evidence shows that extrasolar asteroids exhibit over a factor of 100 variation in the iron to aluminum abundance ratio. This large range likely is a consequence of igneous differentiation that resulted from heating produced by radioactive decay of {sup 26}Al with an abundance comparable to that in the solar system's protoplanetary disk at birth. If so, the conventional view that our solar system began with an unusually high amount of {sup 26}Al should be discarded.

  7. Heating and melting of small icy satellites by the decay of 26Al

    NASA Technical Reports Server (NTRS)

    Prialnik, D.; Bar-Nun, A.; Owen, T. (Principal Investigator)

    1990-01-01

    We study the effect of radiogenic heating due to 26Al on the thermal evolution of small icy satellites. Our object is to find the extent of internal melting as a function of the satellite radius and of the initial 26Al abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of approximately 10(6) yr (comparable with the lifetime of 26Al). The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of 40K, 232Th, 235U, 238U, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10(9) yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. Our main conclusion is that the initial 26Al abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, approximately 7 x 10(-7) by mass). We find, for example, that an initial 26Al mass fraction of approximately 4 x 10(-8) is sufficient for melting almost completely icy spheres with radii of 800 km, typical of the larger icy planetary satellites. We also find that for any given 26Al abundance, there is a narrow range of radii below which only marginal melting occurs and above which most of the ice melts (and refreezes later). Since extensive melting may have important consequences, such as differentiation, gas release, and volcanic activity, the effect of 26Al should be included in future studies of satellite interiors.

  8. Heating and melting of small icy satellites by the decay of 26Al.

    PubMed

    Prialnik, D; Bar-Nun, A

    1990-05-20

    We study the effect of radiogenic heating due to 26Al on the thermal evolution of small icy satellites. Our object is to find the extent of internal melting as a function of the satellite radius and of the initial 26Al abundance. The implicit assumption, based on observations of young stars, is that planet and satellite accretion occurred on a time scale of approximately 10(6) yr (comparable with the lifetime of 26Al). The icy satellites are modeled as spheres of initially amorphous ice, with chondritic abundances of 40K, 232Th, 235U, 238U, corresponding to an ice/dust mass ratio of 1. Evolutionary calculations are carried out, spanning 4.5 x 10(9) yr, for different combinations of the two free parameters. Heat transfer by subsolidus convection is neglected for these small satellites. Our main conclusion is that the initial 26Al abundance capable of melting icy bodies of satellite size to a significant extent is more than 10 times lower than that prevailing in the interstellar medium (or that inferred from the Ca-Al rich inclusions of the Allende meteorite, approximately 7 x 10(-7) by mass). We find, for example, that an initial 26Al mass fraction of approximately 4 x 10(-8) is sufficient for melting almost completely icy spheres with radii of 800 km, typical of the larger icy planetary satellites. We also find that for any given 26Al abundance, there is a narrow range of radii below which only marginal melting occurs and above which most of the ice melts (and refreezes later). Since extensive melting may have important consequences, such as differentiation, gas release, and volcanic activity, the effect of 26Al should be included in future studies of satellite interiors. PMID:11538079

  9. 26Al production: The Allende meteorite (Chihuahua) stellar nucleosynthesis and solar models

    NASA Astrophysics Data System (ADS)

    Araujo-Escalona, V.; Andrade, E.; Barrón-Palos, L.; Canto, C.; Favela, F.; Huerta, A.; de Lucio, O.; Ortiz, M. E.; Solís, C.; Chávez, E.

    2015-07-01

    In 1969 a meteorite fell near the small town of Allende, state of Chihuahua in the north of Mexico. Its study yielded information that changed the current understanding of the solar model. In particular traces of 26Al were found. Abundances of that isotope had been seen in the universe and were related to regions of active heavy nucleosynthesis. Its presence on the solar system was unexpected. It is now understood that cosmic rays induce nuclear reactions on materials to produce 26Al, on Earth this is well known and it is the basis of many environmental studies, so it is not only the product of some high metalicity star collapse. Taking advantage of the recently reinforced laboratory infrastructure of the Instituto de Física, at UNAM in Mexico City, we proposed to measure the cross section for 26Al production via some of the most likely reactions, from the nuclear physics point of view (highest Q-values). In this paper the study of the 28Si(d,α)26 Al nuclear reaction is shown. A target is prepared by a mixture of silicon and aluminum powders. It is irradiated with a deuteron beam (≈1 µA current) at the MV CN-Van de Graaff accelerator laboratory. The number of projectiles is deduced by Rutherford Backscattering Spectrometry (RBS). The produced 26Al nuclei are then counted at the Accelerator Mass Spectrometry Laboratory.

  10. {sup 26}Al production: The Allende meteorite (Chihuahua) stellar nucleosynthesis and solar models

    SciTech Connect

    Araujo-Escalona, V.; Andrade, E.; Barrón-Palos, L.; Canto, C.; Favela, F.; Huerta, A.; Lucio, O. de; Ortiz, M. E.; Solís, C.; Chávez, E.

    2015-07-23

    In 1969 a meteorite fell near the small town of Allende, state of Chihuahua in the north of Mexico. Its study yielded information that changed the current understanding of the solar model. In particular traces of {sup 26}Al were found. Abundances of that isotope had been seen in the universe and were related to regions of active heavy nucleosynthesis. Its presence on the solar system was unexpected. It is now understood that cosmic rays induce nuclear reactions on materials to produce {sup 26}Al, on Earth this is well known and it is the basis of many environmental studies, so it is not only the product of some high metalicity star collapse. Taking advantage of the recently reinforced laboratory infrastructure of the Instituto de Física, at UNAM in Mexico City, we proposed to measure the cross section for {sup 26}Al production via some of the most likely reactions, from the nuclear physics point of view (highest Q-values). In this paper the study of the {sup 28}Si(d,α){sup 26} Al nuclear reaction is shown. A target is prepared by a mixture of silicon and aluminum powders. It is irradiated with a deuteron beam (≈1 µA current) at the MV CN-Van de Graaff accelerator laboratory. The number of projectiles is deduced by Rutherford Backscattering Spectrometry (RBS). The produced {sup 26}Al nuclei are then counted at the Accelerator Mass Spectrometry Laboratory.

  11. Homogeneous distribution of 26Al in the solar system from the Mg isotopic composition of chondrules.

    PubMed

    Villeneuve, Johan; Chaussidon, Marc; Libourel, Guy

    2009-08-21

    The timing of the formation of the first solids in the solar system remains poorly constrained. Micrometer-scale, high-precision magnesium (Mg) isotopic analyses demonstrate that Earth, refractory inclusions, and chondrules from primitive meteorites formed from a reservoir in which short-lived aluminum-26 (26Al) and Mg isotopes were homogeneously distributed at +/-10%. This level of homogeneity validates the use of 26Al as a precise chronometer for early solar system events. High-precision chondrule 26Al isochrons show that several distinct chondrule melting events took place from approximately 1.2 million years (My) to approximately 4 My after the first solids condensed from the solar nebula, with peaks between approximately 1.5 and approximately 3 My, and that chondrule precursors formed as early as 0.87(-0.16)(+0.19) My after. PMID:19696348

  12. The Hiroshima thermal-neutron discrepancy for (36)Cl at large distances. Part II: Natural in situ production as a source.

    PubMed

    Nolte, Eckehart; Huber, Thomas; Rühm, Werner; Kato, Kazuo; Lazarev, Vitali; Schultz, Ludolf

    2005-10-01

    For Hiroshima, a large discrepancy between calculated and measured thermal-neutron fluences had been reported in the past, for distances to the epicenter larger than about 1,000 m. To be more specific, measured (36)Cl concentrations in environmental samples from Hiroshima were too large at these distances, and the ratio of measured to calculated values reached about 70, at a distance of 1,800 m. In an attempt to identify other sources that might also produce (36)Cl in Hiroshima samples, the role of cosmic rays and of neutrons from natural terrestrial sources was investigated. Four reaction mechanisms were taken into account: spallation reactions of the nucleonic (hadronic) component of the cosmic rays on potassium (K) and calcium (Ca) in the sample material, particle emission after nuclear capture of negative muons by K and Ca, reactions of fast-muon induced electromagnetic, and hadronic showers with K and Ca, and neutron capture reactions with (35)Cl in the sample where the neutrons originate from the above three reaction mechanisms and from uranium and thorium decay. These mechanisms are physically described and mathematically quantified. It is shown that among those parameters important for the production of (36)Cl in granite, the chemical composition of the sample, the depth in the quarry where the sample had initially been taken, and the erosion rate at the site of the quarry are most important. Based on these physical, chemical, and geological parameters, (36)Cl concentrations were calculated for different types of granite that are typical for the Hiroshima area. In samples that were of these granite types and that had not been exposed to atomic bomb(A-bomb) neutrons, the (36)Cl concentration was also determined experimentally by means of accelerator mass spectrometry, and good agreement was found with the calculated values. The (36)Cl signal due to natural in situ production was also calculated in granite samples that had been exposed to A-bomb neutrons at

  13. Variation in background concentrations and specific activities of 36Cl, 129I and U/Th-series radionuclides in surface waters.

    PubMed

    Sheppard, S C; Herod, M

    2012-04-01

    Assessment of the potential environmental impacts of nuclear fuel waste involves multiple lines of argument, one of which is an evaluation of the possible increments to background concentrations of certain radionuclides. This is especially relevant for radionuclides such as (3)H, (36)Cl and (129)I where there is continuous cosmogenic or geogenic production. However, for (36)Cl and (129)I and certain U/Th-series radionuclides, data are scarce because the analysis methods are complex and costly. The present study used accelerator mass spectroscopy (AMS) to measure(36)Cl and (129)I in river waters throughout Canada. Radiochemical methods were used for (3)H and the selected U/Th-series radionuclides, and stable element concentrations were also determined. There were distinct differences in concentrations among the sites. Stable Cl and I tended to be at higher concentrations near the ocean or population centres. The (3)H was high in regions with power reactors. The (226)Ra, (235)U and (238)U concentrations were high in areas with known U mineralizations, as expected. The (36)Cl and (129)I concentrations were generally homogenous in mid-latitudes, but the (129)I concentration was lower in the one arctic site sampled. Because the stable and radioactive isotopes of Cl and I varied in response to different factors, the resulting specific activities were especially variable. Both Cl and I are homeostatically controlled in animals, thus it follows that dose from (36)Cl and (129)I will depend more closely on specific activity than concentration, and therefore the environmental increments of interest are in the specific activities rather than simply concentrations. PMID:22304997

  14. Early accretion of protoplanets inferred from a reduced inner solar system 26Al inventory

    PubMed Central

    Schiller, Martin; Connelly, James N.; Glad, Aslaug C.; Mikouchi, Takashi; Bizzarro, Martin

    2016-01-01

    The mechanisms and timescales of accretion of 10–1000 km sized planetesimals, the building blocks of planets, are not yet well understood. With planetesimal melting predominantly driven by the decay of the short-lived radionuclide 26Al (26Al→26Mg; t1/2 = 0.73 Ma), its initial abundance determines the permissible timeframe of planetesimal-scale melting and its subsequent cooling history. Currently, precise knowledge about the initial 26Al abundance [(26Al/27Al)0] exists only for the oldest known solids, calcium aluminum-rich inclusions (CAIs) – the so-called canonical value. We have determined the 26Al/27Al of three angrite meteorites, D’Orbigny, Sahara 99555 and NWA 1670, at their time of crystallization, which corresponds to (3.98 ± 0.15)×10−7, (3.64 ± 0.18)×10−7, and (5.92 ± 0.59)×10−7, respectively. Combined with a newly determined absolute U-corrected Pb–Pb age for NWA 1670 of 4564.39 ± 0.24 Ma and published U-corrected Pb–Pb ages for the other two angrites, this allows us to calculate an initial (26Al/27Al)0 of (1.33−0.18+0.21)×10−5 for the angrite parent body (APB) precursor material at the time of CAI formation, a value four times lower than the accepted canonical value of 5.25 × 10−5. Based on their similar 54Cr/52Cr ratios, most inner solar system materials likely accreted from material containing a similar 26Al/27Al ratio as the APB precursor at the time of CAI formation. To satisfy the abundant evidence for widespread planetesimal differentiation, the subcanonical 26Al budget requires that differentiated planetesimals, and hence protoplanets, accreted rapidly within 0.25 ± 0.15 Ma of the formation of canonical CAIs. PMID:27429474

  15. Evidence for 26Al in Feldspars from the H4 Chondrite Ste. Marguerite

    NASA Astrophysics Data System (ADS)

    Zinner, E.; Gopel, C.

    1992-07-01

    One of the important questions for the history of the early solar system is whether or not there was enough ^26Al to melt small planetary bodies through the heat released by its decay. Although there is ample evidence for the existence of live ^26Al in refractory inclusions (Wasserburg and Papanastassiou, 1982; Hutcheon, 1982; Podosek et al., 1991), CAIs are special objects with peculiar properties and their Al is not necessarily representative of that of their host meteorites nor the early solar systems. Furthermore, some inclusions do not show any evidence for ^26Al (Wasserburg and Papanastassiou, 1982; Ireland, 1990; Virag et al., 1991), raising the possibility of ^26Al heterogeneity. The only previous observation of ^26Mg excesses attributed to the decay of ^26Al outside of CAIs was in an igneous clast from Semarkona (Hutcheon and Hutchison, 1989) leading to the conclusion that ^26Al indeed could have been a heat source for planetary melting. We have measured Al-Mg in plagioclase grains from the H4 chondrite Ste. Marguerite by ion microprobe mass spectrometry. Feldspars from H4 chondrites are good samples for addressing the problem of ^26Al as heat source because most Al resides in this phase and some H4s experienced fast cooling (Pellas and Storzer, 1981); in fact, the possibility of live ^26Al in feldspars from H4 chondrites that cooled fast has been predicted by Pellas and Storzer (1981). Furthermore, extremely precise absolute Pb/Pb ages exist for these meteorites (Gopel et al., 1991). Figure 1 shows the measurements on five feldspar crystals. All show ^26Mg excesses. A fit through the data points and the normal ^26Mg/^24Mg ratio of 0.13962 obtained from Lake County plagioclase measured under the same instrumental conditions as the Ste. Marguerite samples yields a (^26Al/^27Al)(sub)0 ratio of (2.0 +- 0.6) x 10^-7. If interpreted chronologically this ratio dates the retention of radiogenic ^26Mg in Ste. Marguerite feldspar to 5.6 +- 0.4 Ma after the

  16. Radiogenic heating of comets by 26Al and implications for their time of formation

    NASA Technical Reports Server (NTRS)

    Prialnik, D.; Bar-Nun, A.; Podolak, M.; Owen, T. (Principal Investigator)

    1987-01-01

    The effect of radiogenic heating on the thermal evolution of spherical icy bodies with radii 1 km < R < 100 km was investigated. The radioisotopes considered were 26Al, 40K, 232Th, 235U, and 238U. Except for the 26Al abundance, which was varied, the other initial abundances were kept fixed, at values derived from those of chondritic meteorites and corresponding to a gas-to-dust ratio of 1. The initial models were homogeneous and isothermal (To = 10 K) amorphous ice spheres, in a circular orbit at 10(4) AU from the Sun. The main object of this study was to examine the conditions under which the transition temperature from amorphous into cubic ice (Ta = 137 K) would be reached. It was shown that the influence of the short-lived radionuclide 26Al dominates the effect of other radioactive species for bodies of radii up to approximately 50 km. Consequently, if we require comets to retain their ice in amorphous form, as suggested by observations, an upper limit of approximately 4 x 10(-9) is obtained for the initial 26Al abundance in comets, a factor of 100 lower than that of the inclusions in the Allende meteorite. A lower limit for the formation time of comets may thus be derived. The possibility of a coexistence of molten cometary cores and extended amorphous ice mantles is ruled out. Larger icy spheres (R > 100 km) reached Ta even in the absence of 26Al, due to the decay of the other radionuclides. As a result, a crystalline core formed whose relative size depended on the composition assumed. Thus the outermost icy satellites in the solar system, which might have been formed of ice in the amorphous state, have probably undergone crystallization and may have exhibited eruptive activity when the gas trapped in the amorphous ice was released (e.g., Miranda).

  17. Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

    NASA Astrophysics Data System (ADS)

    Vazquez, J. A.; Woolford, J. M.

    2015-09-01

    The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ˜1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ˜17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ˜17 ka, and produced a lava flow field covering ˜35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

  18. Late Pleistocene ages for the most recent volcanism and glacial-pluvial deposits at Big Pine volcanic field, California, USA, from cosmogenic 36Cl dating

    USGS Publications Warehouse

    Vazquez, Jorge A.; Woolford, Jeff M

    2015-01-01

    The Big Pine volcanic field is one of several Quaternary volcanic fields that poses a potential volcanic hazard along the tectonically active Owens Valley of east-central California, and whose lavas are interbedded with deposits from Pleistocene glaciations in the Sierra Nevada Range. Previous geochronology indicates an ∼1.2 Ma history of volcanism, but the eruption ages and distribution of volcanic products associated with the most-recent eruptions have been poorly resolved. To delimit the timing and products of the youngest volcanism, we combine field mapping and cosmogenic 36Cl dating of basaltic lava flows in the area where lavas with youthful morphology and well-preserved flow structures are concentrated. Field mapping and petrology reveal approximately 15 vents and 6 principal flow units with variable geochemical composition and mineralogy. Cosmogenic 36Cl exposure ages for lava flow units from the top, middle, and bottom of the volcanic stratigraphy indicate eruptions at ∼17, 27, and 40 ka, revealing several different and previously unrecognized episodes of late Pleistocene volcanism. Olivine to plagioclase-pyroxene phyric basalt erupted from several vents during the most recent episode of volcanism at ∼17 ka, and produced a lava flow field covering ∼35 km2. The late Pleistocene 36Cl exposure ages indicate that moraine and pluvial shoreline deposits that overlie or modify the youngest Big Pine lavas reflect Tioga stage glaciation in the Sierra Nevada and the shore of paleo-Owens Lake during the last glacial cycle.

  19. The rock avalanche of the Mt. Peron (Eastern Alps, Italy): new insights from 36Cl exposure dating

    NASA Astrophysics Data System (ADS)

    Martin, Silvana; Ivy-ochs, Susan; Alfimov, Vasili; Vockenhuber, %Christof; Surian, Nicola; Campedel, Paolo; Rigo, Manuel; Viganò, Alfio; De Zorzi, Manuel

    2016-04-01

    In the Late Pleistocene, in the southern side of the Eastern Alps (Veneto region, Italy), when the glacier tongues retreated from the end moraine system areas towards the Dolomitic region, large rock avalanches took place. In the Belluno Valley, occupied by the Piave river, the left side is represented by the Belluno Prealps range, corresponding to the northern flank of a km-scale WSW-ENE oriented alpine syncline formed by rocks from Late Triassic to Late Tertiary in age. The Mt. Peron, belonging to this mountain range, shows its southern lower slope covered by debris cones with scattered boulders and its higher slope, corresponding to the scarp, made of vertical rock strata. At the foot of Mt. Peron, at a distance varying from 500 to 4500 m, there is a 4.5 km2 fan like area delimited by a perimeter of about 15 km. This is a hilly area of poortly sorted, chaotic deposits composed of heterogeneous debris, sandy and silty gravels, angular blocks and very large boulders of carbonatic rocks up to 20 m in diameter. The average thickness of the deposit was estimated to be 80 m, with maximum of 120 m. According to previous works, the main event occurred during the first phases of deglaciation, between 17,000 and 15,000 years BP. Popular stories narrate about two legendary villages destroyed by a mass of stones rolling down in the valley. This is confirmed by archeological findings in the Piave valley which indicate the presence of almost one pre-historic settlement dating 40000-20000 years a B.P., (i.e. before the Last Glacial Maximum).. Recent 36Cl exposure dating have yielded historical ages for both the boulders at the foot of the Mt Peron and those located a few km far from the main scarp. According to these exposure ages we can not exclude the hypothesis that earthquakes related to the Venetian faults could have played a key role for triggering of the rock avalanche and that the main gravitational event took place in historical times rather than during the

  20. Tracking the Distribution of 26Al and 60Fe during the Early Phases of Star and Disk Evolution

    NASA Astrophysics Data System (ADS)

    Kuffmeier, Michael; Frostholm Mogensen, Troels; Haugbølle, Troels; Bizzarro, Martin; Nordlund, Åke

    2016-07-01

    The short-lived 26Al and 60Fe radionuclides are synthesized and expelled into the interstellar medium by core-collapse supernova events. The solar system’s first solids, calcium–aluminum refractory inclusions (CAIs), contain evidence for the former presence of the 26 Al nuclide defining the canonical 26Al/27 Al ratio of ˜ 5× {10}-5. A different class of objects temporally related to canonical CAIs are CAIs with fractionation and unidentified nuclear effects (FUN CAIs), which record a low initial 26Al/27Al of 10‑6. The contrasting level of 26Al between these objects is often interpreted as reflecting the admixing of the 26Al nuclides during the early formative phase of the Sun. We use giant molecular cloud scale adaptive mesh-refinement numerical simulations to trace the abundance of 26Al and 60Fe in star-forming gas during the early stages of accretion of individual low-mass protostars. We find that the 26Al/27Al and 60Fe/56Fe ratios of accreting gas within a vicinity of 1000 au of the stars follow the predicted decay curves of the initial abundances at the time of star formation without evidence of spatial or temporal heterogeneities for the first 100 kyr of star formation. Therefore, the observed differences in 26Al/27Al ratios between FUN and canonical CAIs are likely not caused by admixing of supernova material during the early evolution of the proto-Sun. Selective thermal processing of dust grains is a more viable scenario to account for the heterogeneity in 26Al/27Al ratios at the time of solar system formation.

  1. Experimental investigation of T =1 analog states of 26Al and 26Mg

    NASA Astrophysics Data System (ADS)

    Srivastava, Vishal; Bhattacharya, C.; Rana, T. K.; Manna, S.; Kundu, S.; Bhattacharya, S.; Banerjee, K.; Roy, P.; Pandey, R.; Mukherjee, G.; Ghosh, T. K.; Meena, J. K.; Roy, T.; Chaudhuri, A.; Sinha, M.; Saha, A. K.; Asgar, Md. A.; Dey, A.; Roy, Subinit; Shaikh, Md. M.

    2016-04-01

    The even-even nucleus 26Mg has been studied through the reaction 27Al(d ,3He) at 25 MeV beam energy. The spectroscopic factors of the lowest (T =1 ) states of 26Mg have been extracted using the zero-range distorted wave Born approximation. These spectroscopic factors are compared with those of T =1 analog states in 26Al and found to be in good agreement.

  2. Investigations of the human aluminium biokinetics with 26Al and AMS

    NASA Astrophysics Data System (ADS)

    Kislinger, G.; Steinhausen, C.; Alvarez-Brückmann, M.; Winklhofer, C.; Ittel, T.-H.; Nolte, E.

    1997-03-01

    Continuing the investigations on two healthy volunteers and on two patients with renal failure, the aluminium biokinetics in humans was studied by administering oral and intravenous doses of 26Al to three further healthy volunteers. Blood samples were drawn at times between 20 min and half a year after administration of the doses. The complete daily urine was collected during the first nine days, spot urine samples were taken at later times when blood samples were obtained. Creatinin renal clearances and haematocrit values were also obtained in the time period of the investigations. The 26Al concentrations of the samples were measured using the Munich Tandem accelerator. An open compartment model was developed to describe the time dependences of the measured 26Al concentrations in blood and urine and to establish the human Al biokinetics. The model comprises stomach and duodenum for oral administration, a central compartment consisting of blood plasma and interstitial fluid with transferrin and citrate binding and three peripheral compartments which are needed to describe the time dependence for the long observation period of up to three years. Excretion of Al was mainly described from plasma citrate via the kidneys into the urine and to a lesser extent from the plasma transferrin via the liver into the stool. Time constants between the compartments, fractional intestinal absorption factors and aluminium renal clearances were derived. It was found that the sizes of two peripheral compartments of the patients with renal failure were different to those of the healthy volunteers.

  3. 10Be chronometry of bedrock-to-soil conversion rates

    NASA Astrophysics Data System (ADS)

    Monaghan, Marc C.; McKean, James; Dietrich, William; Klein, Jeffrey

    1992-07-01

    We report concentrations of cosmogenic 10Be ( t1/2 = 1.5 × 10 6 yrs) in soil excavated from a soil-mantled hillslope in Black Diamond Mines Regional Park, Contra Costa County, California. The most striking features of the data are: (1) the similarity in the downward decreasing trends of 10Be concentrations in two soil profiles collected 75 m apart, (2) the coincidence in each soil profile of the soil/bedrock interface (as defined by visual inspection of soil pits) and the level at which 10Be concentrations attain very low values ( ˜4 × 10 6 atoms/g), and (3) the extremely low 10Be concentrations in the underlying regolith (0.5 × 10 6 atoms/gram). The inventory of 10Be in these soils is low, equivalent to about 6000 yrs of 10Be accumulation in a soil initially containing no 10Be. On the basis of these measurements, and with the aid of simple models of soil ( 10Be) motions on the hillslope, we conclude that 10Be loss from the surface is dominated by its removal in soil by creep. We calculate local rates of bedrock-to-soil conversion of between 0.15 and 0.27 km/10 6 yrs. Comparing these with uplift rates determined for coastal regions of California indicates that soil creep alone is capable of removing soil from the local geomorphic system at a rate equivalent to the rate of uplift of much of the coast.

  4. Accretion timescales and style of asteroidal differentiation in an 26Al-poor protoplanetary disk

    NASA Astrophysics Data System (ADS)

    Larsen, K. K.; Schiller, M.; Bizzarro, M.

    2016-03-01

    The decay of radioactive 26Al to 26Mg (half-life of 730,000 years) is postulated to have been the main energy source promoting asteroidal melting and differentiation in the nascent solar system. High-resolution chronological information provided by the 26Al-26Mg decay system is, therefore, intrinsically linked to the thermal evolution of early-formed planetesimals. In this paper, we explore the timing and style of asteroidal differentiation by combining high-precision Mg isotope measurements of meteorites with thermal evolution models for planetesimals. In detail, we report Mg isotope data for a suite of olivine-rich [Al/Mg ∼ 0] achondritic meteorites, as well as a few chondrites. Main Group, pyroxene and the Zinder pallasites as well as the lodranite all record deficits in the mass-independent component of μ26Mg (μ26Mg∗) relative to chondrites and Earth. This isotope signal is expected for the retarded ingrowth of radiogenic 26Mg∗ in olivine-rich residues produced through partial silicate melting during 26Al decay and consistent with their marginally heavy Mg isotope composition relative to ordinary chondrites, which may reflect the early extraction of isotopically light partial melts from the source rock. We propose that their parent planetesimals started forming within ∼250,000 years of solar system formation from a hot (>∼500 K) inner protoplanetary disk region characterized by a reduced initial (26Al/27Al)0 abundance (∼1-2 × 10-5) relative to the (26Al/27Al)0 value in CAIs of 5.25 × 10-5. This effectively reduced the total heat production and allowed for the preservation of solid residues produced through progressive silicate melting with depth within the planetesimals. These 'non-carbonaceous' planetesimals acquired their mass throughout an extended period (>3 Myr) of continuous accretion, thereby generating onion-shell structures of incompletely differentiated zones, consisting of olivine-rich residues, overlaid by metachondrites and

  5. 26Al Production in the Early Solar Nebula by Neutral High-Energy Plasma Winds

    NASA Astrophysics Data System (ADS)

    Spergel, M. S.

    1995-09-01

    In the light of recent observations, I believe that the sources for the presence of ^26Al within the solar nebula must be reconsidered [2,3]. Recent low observational estimates of the probability of encounters between mass-losing evolved stars and molecular clouds [4] for the production of ^26Al and the observed low production [5] of 26 Al from AGB (Asymptotic Giant Branch stars) along with the predicted low abundance of cosmic ray induced local production [6] in the early solar nebula all support continued investigation for additional sources of the solar nebula ^26Al presence. It is suggested based on the presences of new cross section data [7], that an important source of this ^26Al presence might be from enhanced interactions from the collisions of the local "T. Tauri" like plasma winds with the atomic and molecular Early Solar Nebula (ESN). Interactions like ^26Mg (p,n) ^26Al in this "neutral" electrical setting may provide the needed selective production. The ESN provides an environment where plasma winds can lead to such nucleosynthesis. Stellar winds of 300-700 km/s (about 3x10^7 K) are seen to T. Tauri like stars, presumed precursor to solar like stars, and also within the Solar heliosphere [8.9]. These winds provide the source of Solar High Energy Particles which can interact with such in situ targets such as ^26Mg to produce the ^26Al. The presence of the atomic and molecular environments, will enhance [10] nucleosynthesis over that seen in scattering of protons off bare nuclei. Such enhancement has been recently observed in low energy scattering on electrically shield targets [7]. There it was also suggested that in stellar convective zones, electron clouds of the plasma shield may also shield bare target nuclei. Measured values of low energy proton scattered on atomic and molecular targets indicated [7] that fusion cross sections are enlarged and elastic cross sections are reduced, therefore simple extrapolation of accelerator data can lead to an

  6. Late Pleistocene piedmont glaciations in the Eastern Mediterranean; insights from cosmogenic 36Cl dating of hummocky moraines in southern Turkey

    NASA Astrophysics Data System (ADS)

    Çiner, Attila; Sarıkaya, Mehmet Akif; Yıldırım, Cengiz

    2015-05-01

    We report the presence of Late Pleistocene piedmont glaciers represented by the largest hummocky moraine field observed in the Eastern Mediterranean. The piedmont glaciers originated from the Geyikdağ ice cap (∼40 km2), situated between 2350 and 2650 m above sea level (a.s.l.) (Central Tauride Mountains of Turkey), and deeply carved the north-facing hillslopes before reaching the Namaras Valley (2000-2050 m a.s.l). The hummocky moraines resulted from in-situ deposition of stagnant glacier ice where debris cover was heterogeneously distributed on the glacier surface. Thirty-four boulders from hummocky, disintegration, lateral and terminal moraines from the Namaras Valley and the tributary Susam Valley (2100-2200 m a.s.l.) were dated by cosmogenic 36Cl surface exposure dating. The moraine ages indicate three phases of deglaciation during the Late Pleistocene. The oldest deglaciation occurred in the Namaras Valley at 18.0 ± 1.1 ka (ka: thousand years ago) towards the end of the Last Glacial Maximum (LGM) and is recorded entirely by hummocky moraines. We speculate that hummocky moraine forming processes with cycles of relief inversion gave rise to boulder apparent ages up to a few thousand years younger in our study area. Therefore, 18.0 ± 1.1 ka should be regarded as a minimum age with a probable true age much closer to the local-LGM values (∼20 ka) as observed in the surrounding mountains. Paleo-piedmont glaciers also deposited several lateral moraines that are ∼50 m higher than the hummocky moraines. Although the lateral moraines probably represent the build-up and the hummocky moraines the final phase of the same local-LGM-pulse, both lateral moraines started to retreat from the Late-glacial (14.0 ± 2.7 ka) and gradually disappeared by mid-Holocene (5.2 ± 1.0 ka), encompassing the Younger Dryas (YD) stadial. In the Susam Valley, the Late-glacial is represented by a terminal moraine (13.4 ± 1.5 ka). The glacier retreat was very fast as indicated by an

  7. Experimental Plan of the 25Mg(p, γ)26Al Resonance Capture Reaction at Jinping Underground Laboratory

    NASA Astrophysics Data System (ADS)

    Li, Z. H.; Su, J.; Li, Y. J.; Guo, B.; Yan, S. Q.; Wang, Y. B.; Lian, G.; Zeng, S.; Zhang, Q. W.; He, G. Z.; Gan, L.; Zhou, C.; Liu, W. P.; Li, K. A.; Yu, X. Q.; Tang, X. D.; He, J. J.; Qian, Y. Z.

    The observation of 26Al is an useful tool for γ-ray astronomy and in studies of galactic chemical evolution. The most likely mechanism for 26A1 nucleosynthesis is in the hydrogen burning MgAl cycle, and the 26A1 production from the 25Mg(p, γ)26Al reaction at the important temperature range below T = 0.2 is still not well known. We present a proposal to measure the resonance strength of 58 keV resonance level of the 25Mg(p, γ)26Al reaction, and the effective counting rate is estimated for the direct measurement at Jinping underground laboratory.

  8. Recent progress of 10Be tracer studies in Chinese loess

    NASA Astrophysics Data System (ADS)

    Zhou, Weijian; Xie, Xingjun; Beck, Warren; Kong, Xianghui; Xian, Feng; Du, Yajuan; Wu, Zhenkun

    2015-10-01

    Studies of cosmogenic 10Be in Chinese loess began about twenty-five years ago and since then a number of research groups worldwide have contributed to a firm understanding of the production, transport, deposition and storage of 10Be in loess. The essential characteristics that make 10Be a useful isotopic tracer in loess, include: (1) dominant atmospheric production directly linked to the intensity of the Earth's magnetic field; (2) climate-dependent deposition; and (3) subsequent immobility, so that as 10Be accumulates in a loess profile its stratigraphic integrity is preserved. This fact, combined with very high deposition rates in loess on the Chinese Loess Plateau, makes 10Be an especially valuable continental archive of paleoclimate and paleomagnetism, complementing marine and ice-core records. Here we provide in particular the most recent progress of 10Be tracer studies in Chinese loess, including the determination of the correct age of the Brunhes-Matuyama polarity reversal at 780 ± 3 ka B.P., in accord with marine and ice records, and quantitative reconstruction of 130-ka paleoprecipitation using 10Be from Chinese loess profiles.

  9. 10Be distribution in soils from Merced River terraces, California

    USGS Publications Warehouse

    Pavich, M.J.; Brown, L.; Harden, J.; Klein, J.; Middleton, R.

    1986-01-01

    The distribution and residence time of cosmogenic 10Be in clay-rich soil horizons is fundamental to understanding and modelling the migration of 10Be on terrestrial sediments and in groundwater solutions. We have analyzed seven profiles of clay-rich soils developed from terrace sediments of the Merced River, California. The terraces and soils of increasing age are used to compare the 10Be inventory with a simple model of accumulation, decay and erosion. The data show that the distribution of 10Be varies with soil horizon clay content, that the residence time of 10Be in these horizons exceeds 105 years, and that to a rough approximation the inventory of 10Be in a thoroughly sampled soil profile fits the equation: N = (q - Em)(1 - e-????)/?? where q is delivery rate, E is erosion rate, m is the concentration of 10Be in the eroding surface layer, ?? is the decay constant, and t is the age of the depositional unit from which the soil has developed. The general applicability of this model is uncertain and warrants further testing in well-calibrated terrace sequences. ?? 1986.

  10. Vibrations and reorientations of NH3 molecules in [Mn(NH3)6](ClO4)2 studied by infrared spectroscopy and theoretical (DFT) calculations.

    PubMed

    Hetmańczyk, Joanna; Hetmańczyk, Łukasz; Migdał-Mikuli, Anna; Mikuli, Edward

    2015-02-01

    The vibrational and reorientational motions of NH3 ligands and ClO4(-) anions were investigated by Fourier transform middle-infrared spectroscopy (FT-IR) in the high- and low-temperature phases of [Mn(NH3)6](ClO4)2. The temperature dependencies of full width at half maximum (FWHM) of the infrared bands at: 591 and 3385cm(-1), associated with: ρr(NH3) and νas(N-H) modes, respectively, indicate that there exist fast (correlation times τR≈10(-12)-10(-13)s) reorientational motions of NH3 ligands, with a mean values of activation energies: 7.8 and 4.5kJmol(-1), in the phase I and II, respectively. These reorientational motions of NH3 ligands are only slightly disturbed in the phase transition region and do not significantly contribute to the phase transition mechanism. Fourier transform far-infrared and middle-infrared spectra with decreasing of temperature indicated characteristic changes at the vicinity of PT at TC(c)=137.6K (on cooling), which suggested lowering of the crystal structure symmetry. Infrared spectra of [Mn(NH3)6](ClO4)2 were recorded and interpreted by comparison with respective theoretical spectra calculated using DFT method (B3LYP functional, LANL2DZ ECP basis set (on Mn atom) and 6-311+G(d,p) basis set (on H, N, Cl, O atoms) for the isolated equilibrium two models (Model 1 - separate isolated [Mn(NH3)6](2+) cation and ClO4(-) anion and Model 2 - [Mn(NH3)6(ClO4)2] complex system). Calculated optical spectra show a good agreement with the experimental infrared spectra (FT-FIR and FT-MIR) for the both models. PMID:25459713

  11. Vibrations and reorientations of NH3 molecules in [Mn(NH3)6](ClO4)2 studied by infrared spectroscopy and theoretical (DFT) calculations

    NASA Astrophysics Data System (ADS)

    Hetmańczyk, Joanna; Hetmańczyk, Łukasz; Migdał-Mikuli, Anna; Mikuli, Edward

    2015-02-01

    The vibrational and reorientational motions of NH3 ligands and ClO4- anions were investigated by Fourier transform middle-infrared spectroscopy (FT-IR) in the high- and low-temperature phases of [Mn(NH3)6](ClO4)2. The temperature dependencies of full width at half maximum (FWHM) of the infrared bands at: 591 and 3385 cm-1, associated with: ρr(NH3) and νas(N-H) modes, respectively, indicate that there exist fast (correlation times τR ≈ 10-12-10-13 s) reorientational motions of NH3 ligands, with a mean values of activation energies: 7.8 and 4.5 kJ mol-1, in the phase I and II, respectively. These reorientational motions of NH3 ligands are only slightly disturbed in the phase transition region and do not significantly contribute to the phase transition mechanism. Fourier transform far-infrared and middle-infrared spectra with decreasing of temperature indicated characteristic changes at the vicinity of PT at TCc = 137.6 K (on cooling), which suggested lowering of the crystal structure symmetry. Infrared spectra of [Mn(NH3)6](ClO4)2 were recorded and interpreted by comparison with respective theoretical spectra calculated using DFT method (B3LYP functional, LANL2DZ ECP basis set (on Mn atom) and 6-311 + G(d,p) basis set (on H, N, Cl, O atoms) for the isolated equilibrium two models (Model 1 - separate isolated [Mn(NH3)6]2+ cation and ClO4- anion and Model 2 - [Mn(NH3)6(ClO4)2] complex system). Calculated optical spectra show a good agreement with the experimental infrared spectra (FT-FIR and FT-MIR) for the both models.

  12. Intercomparison study on (152)Eu gamma ray and (36)Cl AMS measurements for development of the new Hiroshima-Nagasaki Atomic Bomb Dosimetry System 2002 (DS02).

    PubMed

    Hoshi, M; Endo, S; Tanaka, K; Ishikawa, M; Straume, T; Komura, K; Rühm, W; Nolte, E; Huber, T; Nagashima, Y; Seki, R; Sasa, K; Sueki, K; Fukushima, H; Egbert, S D; Imanaka, T

    2008-07-01

    In the process of developing a new dosimetry system for atomic bomb survivors in Hiroshima and Nagasaki (DS02), an intercomparison study between (152)Eu and (36)Cl measurements was proposed, to reconcile the discrepancy previously observed in the Hiroshima data between measurements and calculations of thermal neutron activation products. Nine granite samples, exposed to the atomic-bomb radiation in Hiroshima within 1,200 m of the hypocenter, as well as mixed standard solutions containing known amounts of europium and chlorine that were neutron-activated by a (252)Cf source, were used for the intercomparison. Gamma-ray spectrometry for (152)Eu was carried out with ultra low-background Ge detectors at the Ogoya Underground Laboratory, Kanazawa University, while three laboratories participated in the (36)Cl measurement using accelerator mass spectrometry (AMS): The Technical University of Munich, Germany, the Lawrence Livermore National Laboratory, USA and the University of Tsukuba, Japan. Measured values for the mixed standard solutions showed good agreement among the participant laboratories. They also agreed well with activation calculations, using the neutron fluences monitored during the (252)Cf irradiation, and the corresponding activation cross-sections taken from the JENDL-3.3 library. The measured-to-calculated ratios obtained were 1.02 for (152)Eu and 0.91-1.02 for (36)Cl, respectively. Similarly, the results of the granite intercomparison indicated good agreement with the DS02 calculation for these samples. An average measured-to-calculated ratio of 0.98 was obtained for all granite intercomparison measurements. The so-called neutron discrepancy that was previously observed and that which included increasing measured-to-calculated ratios for thermal neutron activation products for increasing distances beyond 1,000 m from the hypocenter was not seen in the results of the intercomparison study. The previously claimed discrepancy could be explained by

  13. Ion irradiation of 37Cl implanted nuclear graphite: Effect of the energy deposition on the chlorine behavior and consequences for the mobility of 36Cl in irradiated graphite

    NASA Astrophysics Data System (ADS)

    Toulhoat, N.; Moncoffre, N.; Bérerd, N.; Pipon, Y.; Blondel, A.; Galy, N.; Sainsot, P.; Rouzaud, J.-N.; Deldicque, D.

    2015-09-01

    Graphite is used in many types of nuclear reactors due to its ability to slow down fast neutrons without capturing them. Whatever the reactor design, the irradiated graphite waste management has to be faced sooner or later regarding the production of long lived or dose determining radioactive species such as 14C, 3H or 36Cl. The first carbon dioxide cooled, graphite moderated nuclear reactors resulted in a huge quantity of irradiated graphite waste for which the management needs a previous assessment of the radioactive inventory and the radionuclide's location and speciation. As the detection limits of usual spectroscopic methods are generally not adequate to detect the low concentration levels (<1 ppm) of the radionuclides, we used an indirect approach based on the implantation of 37Cl, to simulate the presence of 36Cl. Our previous studies show that temperature is one of the main factors to be considered regarding the structural evolution of nuclear graphite and chlorine mobility during reactor operation. However, thermal release of chlorine cannot be solely responsible for the depletion of the 36Cl inventory. We propose in this paper to study the impact of irradiation and its synergetic effects with temperature on chlorine release. Indeed, the collision of the impinging neutrons with the graphite matrix carbon atoms induces mainly ballistic collisions. However, a small part of the recoil carbon atom energy is also transferred to the lattice through electronic excitation. This paper aims at elucidating the effects of the different irradiation regimes (ballistic and electronic) using ion irradiation, on the mobility of implanted 37Cl, taking into account the initial disorder level of the nuclear graphite.

  14. Accretion timescales and style of asteroidal differentiation in an 26Al-poor protoplanetary disk

    PubMed Central

    Larsen, K.K.; Schiller, M.; Bizzarro, M.

    2016-01-01

    The decay of radioactive 26Al to 26Mg (half-life of 730,000 years) is postulated to have been the main energy source promoting asteroidal melting and differentiation in the nascent solar system. High-resolution chronological information provided by the 26Al−26Mg decay system is, therefore, intrinsically linked to the thermal evolution of early-formed planetesimals. In this paper, we explore the timing and style of asteroidal differentiation by combining high-precision Mg isotope measurements of meteorites with thermal evolution models for planetesimals. In detail, we report Mg isotope data for a suite of olivine-rich [Al/Mg ~ 0] achondritic meteorites, as well as a few chondrites. Main Group, pyroxene and the Zinder pallasites as well as the lodranite all record deficits in the mass-independent component of μ26Mg (μ26Mg*) relative to chondrites and Earth. This isotope signal is expected for the retarded ingrowth of radiogenic 26Mg* in olivine-rich residues produced through partial silicate melting during 26Al decay and consistent with their marginally heavy Mg isotope composition relative to ordinary chondrites, which may reflect the early extraction of isotopically light partial melts from the source rock. We propose that their parent planetesimals started forming within ~250,000 years of solar system formation from a hot (>~500 K) inner protoplanetary disk region characterized by a reduced initial (26Al/27Al)0 abundance (~1–2 × 10−5) relative to the (26Al/27Al)0 value in CAIs of 5.25 × 10−5. This effectively reduced the total heat production and allowed for the preservation of solid residues produced through progressive silicate melting with depth within the planetesimals. These ‘non-carbonaceous’ planetesimals acquired their mass throughout an extended period (>3 Myr) of continuous accretion, thereby generating onion-shell structures of incompletely differentiated zones, consisting of olivine-rich residues, overlaid by metachondrites and

  15. APMP comparison of measurement of surface emission rate of 36Cl large area source (APMP.RI(II)-K2.Cl-36).

    PubMed

    Yunoki, Akira; Hino, Yoshio

    2012-09-01

    An international comparison of measurement of beta particle surface emission rate from a (36)Cl large area source (APMP.RI(II)-S1.Cl-36) was carried out within the framework of the Asia-Pacific Metrology Program (APMP). Participants from APMP were NMIJ (Japan), KRISS (Korea) and INER (Chinese Taipei). Participants from the other RMOs were NIST (United States), PTB (Germany), NMISA (South Africa) and VNIIM (Russia). All the results of the participants agreed within ±1%. This was the first international comparison of measurement of surface emission rate of beta particle from a large area source. PMID:22424747

  16. Supra-canonical 26Al/27Al and the residence time of CAIs in the solar protoplanetary disk.

    PubMed

    Young, Edward D; Simon, Justin I; Galy, Albert; Russell, Sara S; Tonui, Eric; Lovera, Oscar

    2005-04-01

    The canonical initial 26Al/27Al ratio of 4.5 x 10(-5) has been a fiducial marker for the beginning of the solar system. Laser ablation and whole-rock multiple-collector inductively coupled plasma-source mass spectrometry magnesium isotope analyses of calcium- and aluminum-rich inclusions (CAIs) from CV3 meteorites demonstrate that some CAIs had initial 26Al/27Al values at least 25% greater than canonical and that the canonical initial 26Al/27Al cannot mark the beginning of solar system formation. Using rates of Mg diffusion in minerals, we find that the canonical initial 26Al/27Al is instead the culmination of thousands of brief high-temperature events incurred by CAIs during a 10(5)-year residence time in the solar protoplanetary disk. PMID:15746387

  17. Aluminium and Alzheimer's disease: sites of aluminium binding in human neuroblastoma cells determined using 26Al and accelerator mass spectrometry

    NASA Astrophysics Data System (ADS)

    King, S. J.; Templar, J.; Miller, R. V.; Day, J. P.; Dobson, C. B.; Itzhaki, R. F.; Fifield, L. K.; Allan, G. L.

    1994-06-01

    The aluminium distribution between the major cell compartments of human neuroblastoma cells grown in culture has been determined using 21Al and accelerator mass spectrometry (AMS). Cells (IMR-32) were grown for eight days in a culture medium containing Al-EDTA (0.2mM) spiked with 26Al, harvested, and fractionated by standard biochemical techniques. 26Al in fractions after ashing to Al 2O 3 was determined by AMS using the 14UD accelerator at ANU Canberra. The cytoplasmic and nuclear cell compartments appeared to have reached diffusive equilibrium with the culture medium. Whilst 26Al was retained by the nuclear proteins and nuclear sap, 26Al did not appear to bind to the nucleic acids (DNA/RNA).

  18. 10Be in late deglacial climate simulated by ECHAM5-HAM - Part 1: Climatological influences on 10Be deposition

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Phipps, S. J.; Smith, A. M.

    2013-11-01

    Reconstruction of solar irradiance has only been possible for the Holocene so far. During the last deglaciation, two solar proxies (10Be and 14C) deviate strongly, both of them being influenced by climatic changes in a different way. This work addresses the climate influence on 10Be deposition by means of ECHAM5-HAM atmospheric aerosol-climate model simulations, forced by sea surface temperatures and sea ice extent created by the CSIRO Mk3L coupled climate system model. Three time slice simulations were performed during the last deglaciation: 10 000 BP ("10k"), 11 000 BP ("11k") and 12 000 BP ("12k"), each 30 yr long. The same, theoretical, 10Be production rate was used in each simulation to isolate the impact of climate on 10Be deposition. The changes are found to follow roughly the reduction in the greenhouse gas concentrations within the simulations. The 10k and 11k simulations produce a surface cooling which is symmetrically amplified in the 12k simulation. The precipitation rate is only slightly reduced at high latitudes, but there is a northward shift in the polar jet in the Northern Hemisphere, and the stratospheric westerly winds are significantly weakened. These changes occur where the sea ice change is largest in the deglaciation simulations. This leads to a longer residence time of 10Be in the stratosphere by 30 (10k and 11k) to 80 (12k) days, increasing the atmospheric concentrations (25-30% in 10k and 11k and 100% in 12k). Furthermore the shift of westerlies in the troposphere leads to an increase of tropospheric 10Be concentrations, especially at high latitudes. The contribution of dry deposition generally increases, but decreases where sea ice changes are largest. In total, the 10Be deposition rate changes by no more than 20% at mid- to high latitudes, but by up to 50% in the tropics. We conclude that on "long" time scales (a year to a few years), climatic influences on 10Be deposition remain small (less than 50%) even though atmospheric

  19. Production Rate of Cosmogenic 10Be in Magnetite

    NASA Astrophysics Data System (ADS)

    Granger, D. E.; Rogers, H. E.; Riebe, C. S.; Lifton, N. A.

    2013-12-01

    Cosmogenic 10Be is widely used for determining exposure ages, soil production rates, and catchment-wide erosion rates. To date, measurements have been almost exclusively in the mineral quartz (SiO2), which is resistant to weathering and easily cleaned of meteoric 10Be contamination. However, this limits the method to quartz-bearing rocks and requires specialized laboratories due to the need for large quantities of hydrofluoric acid (HF). Here, we present initial results for 10Be production in the mineral magnetite (Fe3O4). Magnetite offers several advantages over quartz; it is (1) present in mafic rocks, (2) easily collected in the field, (3) quickly and easily separated in the lab, and (4) digested without HF. In addition, 10Be can be measured in both detrital quartz and magnetite from the same catchment to yield information about the intensity of chemical weathering (Rogers et al., this conference). The 10Be production rate in magnetite relative to quartz was determined for a granitic boulder from Mt. Evans, Colorado, USA. The boulder was crushed and homogenized to facilitate production rate comparisons among various minerals. We separated magnetite using a combination of hand magnets, froth flotation, and a variety of selective chemical dissolutions in dithionite-citrate-bicarbonate solution, 5% nitric acid (HNO3) and 1% HF/HNO3. Six aliquots of magnetite were analyzed for 10Be and compared to quartz. Three aliquots that were not exposed to 1% HF/HNO3 were contaminated with meteoric 10Be, probably associated with residual mica. Three aliquots that were exposed to 1% HF/HNO3 treatments agreed to within 2% measurement uncertainty. Our preliminary results indicate that the relative production rate by mass of 10Be in magnetite and quartz is 0.462 × 0.012. Our results are similar to theoretically predicted values. Recently updated excitation functions for neutron and proton spallation reactions allow us to partition 10Be production in quartz and magnetite among

  20. Study of states in 14C via the 10Be(4He,4He)10Be reaction

    NASA Astrophysics Data System (ADS)

    Malcolm, J. D.; Freer, M.; Ashwood, N. I.; Curtis, N.; Munoz-Britton, T.; Wheldon, C.; Ziman, V. A.; Catford, W. N.; Brown, S.; Wilson, G.; Soic, N.; Bardayan, D.; Pain, S. D.; Achouri, N. L.; Chipps, K.; Crzywacz-Jones, K.

    2012-09-01

    A study of the 10Be(4He,4He)10Be reaction has been performed at 10Be beam energies of 25.0, 27.0, 29.0, 32.0, 34.0, 38.0, 40.0, 42.0, 44.0 and 46.0 MeV. The measurements were to explore possible molecular rotational bands in 14C. Three states at excitation energies of Ex = 18.8, 19.76 and 20.66 MeV have been measured and their spins have been determined to be 5-, 5- and 6+, respectively.

  1. Do Fungi Transport 10Be During Wood Degradation?

    NASA Astrophysics Data System (ADS)

    Conyers, G.; Granger, D. E.

    2010-12-01

    Meteoric cosmogenic 10Be is increasingly used to determine erosion and soil transport rates. To calculate these rates, it is assumed that 10Be is a conservative passive tracer of soil particles. However, there is experimental evidence that beryllium is mobilized in natural soils complexed with organic acids. For example, up to 50% of beryllium can be mobilized by humic acids in soils at pH 7 (Takahashi et al., 1999). Beryllium is also known to be taken up in plants such as tobacco and vegetables (World Health Organization, 1990) at ppm levels, primarily as organic acid chelates. It is not known to what extent biological beryllium transport in the environment affects the cosmogenic 10Be budget, or how it influences beryllium mobility. In this study, we address a problem recognized early in the development of meteoric 10Be methods. It has been observed that decayed organic matter in soils and sediments contains very high concentrations of 10Be of up to 109-1010 atoms/g (Lundberg, et al., 1983). On the other hand, living trees contain much lower concentrations of 106 atoms/g (Klein et al., 1982). The driving question for this study is how 10Be becomes bound to decayed organic matter. Direct fallout seems unlikely as the residence time of organic matter in soil is too short. One possibility is that 10Be is transported by fungi. Wood-degrading fungi are known to transport and bioaccumulate metals from large areas, facilitated by acids such as oxalic acid in the fungal hyphae. To test the hypothesis that fungi transport 10Be, we analyzed both intact and fungally degraded wood of oak, hickory, and hemlock. From these data, we reached two conclusions (observations?): 1) Oak has a 10Be concentration of about 2x106 at/g, similar to that observed by Klein et al. (1982). Hickory has a significantly higher concentration of about 3x107 atoms/g, confirming observations that hickory bioaccumulates beryllium. Using these data, the inventory of 10Be in a temperate forest is expected

  2. 10Be in last deglacial climate simulated by ECHAM5-HAM - Part 1: Climatological influences on 10Be deposition

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Phipps, S. J.; Smith, A. M.

    2013-07-01

    Reconstruction of solar irradiance has only been possible for the Holocene so far. During the last deglaciation two solar proxies (10Be and 14C) deviate strongly, both of them being influenced by climatic changes in a different way. This work addresses the climate influence on 10Be deposition by means of ECHAM5-HAM atmospheric aerosol-climate model simulations, forced by sea surface temperatures and sea ice extent created by the coupled climate system model CSIRO Mk3L. Three time slice simulations were performed during the last deglaciation: 10 000 BP ("10k"), 11 000 BP ("11k") and 12 000 BP ("12k"), each 30 yr long. The same 10Be production rate was used in each simulation to isolate the impact of climate on 10Be deposition. The changes are found to follow roughly the reduction in the greenhouse gas concentrations within the simulations. The 10k and 11k simulations produce a surface cooling which is symmetrically amplified in the 12k simulation. The precipitation rate is only slightly reduced at high latitudes, but there is a northward shift in the polar jet in the Northern Hemisphere and the stratospheric westerly winds are significantly weakened. These changes occur where the sea ice change is largest in the deglaciation simulations. This leads to a longer residence time of 10Be in the stratosphere by 30 (10k and 11k) to 80 (12k) days, heavily increasing the atmospheric concentrations. Furthermore the shift of westerlies in the troposphere leads to an increase of tropospheric 10Be concentrations, especially at high latitudes. The contribution of dry deposition generally increases, but decreases where sea ice changes are largest. In total, the 10Be deposition rate changes by no more than 20% at mid- to high latitudes, but by up to 50% in the tropics. We conclude that on "long" time scales (a year to a few years), climatic influences on 10Be deposition remain small even though atmospheric concentrations can vary significantly. Averaged over a longer period all 10

  3. The Effects of Thermonuclear Reaction Rate Variations on 26Al Production in Massive Stars: A Sensitivity Study

    NASA Astrophysics Data System (ADS)

    Iliadis, Christian; Champagne, Art; Chieffi, Alessandro; Limongi, Marco

    2011-03-01

    We investigate the effects of thermonuclear reaction rate variations on 26Al production in massive stars. The dominant production sites in such events were recently investigated by using stellar model calculations: explosive neon-carbon burning, convective shell carbon burning, and convective core hydrogen burning. Post-processing nucleosynthesis calculations are performed for each of these sites by adopting temperature-density-time profiles from recent stellar evolution models. For each profile, we individually multiplied the rates of all relevant reactions by factors of 10, 2, 0.5, and 0.1, and analyzed the resulting abundance changes of 26Al. In total, we performed ≈900 nuclear reaction network calculations. Our simulations are based on a next-generation nuclear physics library, called STARLIB, which contains a recent evaluation of Monte Carlo reaction rates. Particular attention is paid to quantifying the rate uncertainties of those reactions that most sensitively influence 26Al production. For stellar modelers our results indicate to what degree predictions of 26Al nucleosynthesis depend on currently uncertain nuclear physics input, while for nuclear experimentalists our results represent a guide for future measurements. We also investigate equilibration effects of 26Al. In all previous massive star investigations, either a single species or two species of 26Al were taken into account, depending on whether thermal equilibrium was achieved or not. These are two extreme assumptions, and in a hot stellar plasma the ground and isomeric states may communicate via γ-ray transitions involving higher-lying 26Al levels. We tabulate the results of our reaction rate sensitivity study for each of the three distinct massive star sites referred to above. It is found that several current reaction rate uncertainties influence the production of 26Al. Particularly important reactions are 26Al(n,p)26Mg, 25Mg(α,n)28Si, 24Mg(n,γ)25Mg, and 23Na(α,p)26Mg. These reactions

  4. Preliminary AMS measurements of 10Be at the CENTA facility

    NASA Astrophysics Data System (ADS)

    Ješkovský, Miroslav; Steier, Peter; Priller, Alfred; Breier, Robert; Povinec, Pavel P.; Golser, Robin

    2015-10-01

    Very sensitive methods, presently mainly accelerator mass spectrometry (AMS) are necessary for analysis of cosmogenic 10Be in the environment. AMS is mainly limited by the stable isobar 10B, while the requirements for mass separation are the least stringent of all standard isotopes analyzed by AMS. We tested a possibility to measure 10Be using a small switching magnet as an analyzer of accelerated ions, and an ionization chamber with a silicon nitride foil stack used as a passive absorber. A detection limit of 10-12 for the 10Be/9Be isotopic ratio was obtained using this technique, which was mainly determined by scattering of 9Be+2 ions on residual gas inside the switching magnet.

  5. Seismic slip history of the Pizzalto fault (central Apennines, Italy) using in situ-produced 36Cl cosmic ray exposure dating and rare earth element concentrations

    NASA Astrophysics Data System (ADS)

    Tesson, J.; Pace, B.; Benedetti, L.; Visini, F.; Delli Rocioli, M.; Arnold, M.; Aumaître, G.; Bourlès, D. L.; Keddadouche, K.

    2016-03-01

    Morphological and geological observations reveal that most Apenninic faults are highly segmented and that the majority of the fault segments are less than 10 km long. Although these faults have undergone numerous paleoseismological investigations, quantitative data remain crucially lacking for a large number of fault segments. Because such data are essential to understanding how these faults have ruptured and interacted in the past and how they might behave in the future, we investigated the Holocene seismic history of the Pizzalto normal fault, a 13 km long fault segment belonging to the Pizzalto-Rotella-Aremogna fault system in the Apennines. We collected 44 samples from the Pizzalto fault plane exhumed during the Holocene and analyzed the 36Cl and rare earth element (REE) contents. Together, the 36Cl and REE concentrations show that at least six events have exhumed 4.4 m of the fault scarp between 3 and 1 ka, with slip per event values ranging from 0.3 to 1.2 m. No major events have been detected over the last 1 kyr. The Rotella-Aremogna-Pizzalto fault system has a clustered earthquake behavior with a mean recurrence time of 1.2 kyr and a low to moderate probability (ranging from 4% to 26%) of earthquake occurrence over the next 50 years.

  6. 26Al measurements below 500 kV in charge state 2+

    NASA Astrophysics Data System (ADS)

    Müller, Arnold Milenko; Christl, Marcus; Lachner, Johannes; Synal, Hans-Arno; Vockenhuber, Christof; Zanella, Claudia

    2015-10-01

    The use of helium as stripper gas improved the measurement efficiency of compact AMS systems for many radionuclides significantly because of a higher mean charge state and reduced scattering losses compared with other conventional gases. Recent tests at the ETH 500 kV AMS facility (Tandy) with aluminum have demonstrated that a transmission of more than 50% is achievable in the charge state 2+ at terminal voltages between 300 and 500 kV. On the other hand the m/q interference of 13C1+ entering the detector at very high intensity has to be suppressed. Based on first positive results with a very simple absorber cell a more elaborate absorber detector configuration was designed and built in order to eliminate the carbon interference. The suppression of carbon with the new detector-absorber design has been studied extensively at 300 kV (950 keV) and 500 kV (1550 keV) and the results are compared with simulated data. With the new configuration an overall transmission for 26Al of more than 42% at 500 kV and about 30% at 300 kV terminal voltage is achieved, while 26Al/27Al blank ratios of aluminum targets in the range of 5-14·10-15 are measured.

  7. Activation Measurements for Thermal Neutrons, U.S. Measurements of 36Cl in Mineral Samples from Hiroshima and Nagasaki; and Measurement of 63 Ni in Copper Samples From Hiroshima by Accelerator Mass Spectrometry

    SciTech Connect

    Tore Straume; Alfredo A. Marchetti; Stephen D. Egbert; James A. Roberts; Ping Men; Shoichiro Fujita; Kiyoshi Shizuma; Masaharu Hoshi; G. Rugel; W. Ruhm; G. Korschinek; J. E. McAninch; K. L. Carroll; T. Faestermann; K. Knie; R. E. Martinelli; A. Wallner; C. Wallner

    2005-01-14

    The present paper presents the {sup 36}Cl measurement effort in the US. A large number of {sup 36}Cl measurements have been made in both granite and concrete samples obtained from various locations and distances in Hiroshima and Nagasaki. These measurements employed accelerator mass spectrometry (AMS) to quantify the number of atoms of {sup 36}Cl per atom of total Cl in the sample. Results from these measurements are presented here and discussed in the context of the DS02 dosimetry reevaluation effort for Hiroshima and Nagasaki atomic-bomb survivors. The production of {sup 36}Cl by bomb neutrons in mineral samples from Hiroshima and Nagasaki was primarily via the reaction {sup 35}Cl(n,{gamma}){sup 36}Cl. This reaction has a substantial thermal neutron cross-section (43.6 b at 0.025 eV) and the product has a long half-life (301,000 y). hence, it is well suited for neutron-activation detection in Hiroshima and Nagasaki using AMS more than 50 years after the bombings. A less important reaction for bomb neutrons, {sup 39}K(n,{alpha}){sup 36}Cl, typically produces less than 10% of the {sup 36}Cl in mineral samples such as granite and concrete, which contain {approx} 2% potassium. In 1988, only a year after the publication of the DS86 final report (Roesch 1987), it was demonstrated experimentally that {sup 36}Cl measured using AMS should be able to detect the thermal neutron fluences at the large distances most relevant to the A-bomb survivor dosimetry. Subsequent measurements in mineral samples from both Hiroshima and Nagasaki validated the experimental findings. The potential utility of {sup 36}Cl as a thermal neutron detector in Hiroshima was first presented by Haberstock et al. who employed the Munich AMS facility to measure {sup 36}Cl/Cl ratios in a gravestone from near the hypocenter. That work subsequently resulted in an expanded {sup 36}Cl effort in Germany that paralleled the US work. More recently, there have also been {sup 36}Cl measurements made by a Japanese

  8. 26Al in plagioclase-rich chondrules in carbonaceous chondrites: Evidence for an extended duration of chondrule formation

    NASA Astrophysics Data System (ADS)

    Hutcheon, I. D.; Marhas, K. K.; Krot, A. N.; Goswami, J. N.; Jones, R. H.

    2009-09-01

    The 26Al- 26Mg isotope systematics in 33 petrographically and mineralogically characterized plagioclase-rich chondrules (PRCs) from 13 carbonaceous chondrites (CCs) - one ungrouped (Acfer 094), six CR, five CV, and one CO - reveal large variations in the initial 26Al/ 27Al ratio, ( 26Al/ 27Al) 0. Well-resolved 26Mg excesses (δ 26Mg) from the in situ decay of the short-lived nuclide 26Al ( t1/2 ˜ 0.72 Ma) were found in nine chondrules, two from Acfer 094, five from the CV chondrites, Allende and Efremovka, and one each from the paired CR chondrites, EET 92147 and EET 92042, with ( 26Al/ 27Al) 0 values ranging from ˜3 × 10 -6 to ˜1.5 × 10 -5. Data for seven additional chondrules from three CV and two CR chondrites show evidence suggestive of the presence of 26Al but do not yield well defined values for ( 26Al/ 27Al) 0, while the remaining chondrules do not contain excess radiogenic 26Mg and yield corresponding upper limits of (11-2) × 10 -6 for ( 26Al/ 27Al) 0. The observed range of ( 26Al/ 27Al) 0 in PRCs from CCs is similar to the range seen in chondrules from unequilibrated ordinary chondrites (UOCs) of low metamorphic grade (3.0-3.4). However, unlike the UOC chondrules, there is no clear trend between the ( 26Al/ 27Al) 0 values in PRCs from CCs and the degree of thermal metamorphism experienced by the host meteorites. High and low values of ( 26Al/ 27Al) 0 are found equally in PRCs from both CCs lacking evidence for thermal metamorphism (e.g., CRs) and CCs where such evidence is abundant (e.g., CVs). The lower ( 26Al/ 27Al) 0 values in PRCs from CCs, relative to most CAIs, are consistent with a model in which 26Al was distributed uniformly in the nebula when chondrule formation began, approximately a million years after the formation of the majority of CAIs. The observed range of ( 26Al/ 27Al) 0 values in PRCs from CCs is most plausibly explained in terms of an extended duration of ˜2-3 Ma for the formation of CC chondrules. This interval is in sharp

  9. The quantitative reconstruction of paleoprecipitation from Chinese loess 10Be

    NASA Astrophysics Data System (ADS)

    Zhou, Weijian; Xian, Feng; Du, Yajuan; Kong, Xianghui; Wu, Zhenkun

    2016-04-01

    Cosmogenic 10Be is a promising precipitation index, because its fallout flux in sediments is mainly controlled by wet precipitation after its production in the atmosphere. Here we report on a new study for reconstructing precipitation during the last 130 ka using 10Be measurements from Chinese loess, with multivariable linear regression to remove the geomagnetic field modulation and dust flux dilution effects from the loess 10Be record. The broad similarity between our result and speleothem δ18O indicates that the new precipitation record is robust. It also records an interesting increase in precipitation that occurred during Marine Isotope Stage 3 (MIS 3), exhibiting a similar rainfall amount with that of MIS 5, suggesting that MIS 3 is a special period with strengthened summer Monsoon intensity. By comparison with a stacked marine isotope record and a summer insolation record, our precipitation data clearly show a close correspondence with Northern Hemisphere summer (June, July, and August) solar insolation changes on orbital timescales. During MIS 3, our record follows the insolation differential between 30°N and 30°S, suggesting that rising rainfall changes during MIS 3 are a response to the interhemispheric summer insolation differential forcing.

  10. Deriving earthquake history of the Knidos Fault Zone, SW Turkey, using cosmogenic 36Cl surface exposure dating of the fault scarp.

    NASA Astrophysics Data System (ADS)

    Yildirim, Cengiz; Ersen Aksoy, Murat; Akif Sarikaya, Mehmet; Tuysuz, Okan; Genc, S. Can; Ertekin Doksanalti, Mustafa; Sahin, Sefa; Benedetti, Lucilla; Tesson, Jim; Aster Team

    2016-04-01

    Formation of bedrock fault scarps in extensional provinces is a result of large and successive earthquakes that ruptured the surface several times. Extraction of seismic history of such faults is critical to understand the recurrence intervals and the magnitude of paleo-earthquakes and to better constrain the regional seismic hazard. Knidos on the Datca Peninsula (SW Turkey) is one of the largest cities of the antique times and sits on a terraced hill slope formed by en-echelon W-SW oriented normal faults. The Datça Peninsula constitutes the southern boundary of the Gulf of Gökova, one of the largest grabens developed on the southernmost part of the Western Anatolian Extensional Province. Our investigation relies on cosmogenic 36Cl surface exposure dating of limestone faults scarps. This method is a powerful tool to reconstruct the seismic history of normal faults (e.g. Schlagenhauf et al 2010, Benedetti et al. 2013). We focus on one of the most prominent fault scarp (hereinafter Mezarlık Fault) of the Knidos fault zone cutting through the antique Knidos city. We collected 128 pieces of tablet size (10x20cm) 3-cm thick samples along the fault dip and opened 4 conventional paleoseismic trenches at the base of the fault scarp. Our 36Cl concentration profile indicates that 3 to 4 seismic events ruptured the Mezarlık Fault since Last Glacial Maximum (LGM). The results from the paleoseismic trenching are also compatible with 36Cl results, indicating 3 or 4 seismic events that disturbed the colluvium deposited at the base of the scarp. Here we will present implications for the seismic history and the derived slip-rate of the Mezarlık Fault based on those results. This project is supported by The Scientific and Technological Research Council of Turkey (TUBITAK, Grant number: 113Y436) and it was conducted with the Decision of the Council of Ministers with No. 2013/5387 on the date 30.09.2013 and was done with the permission of Knidos Presidency of excavation in

  11. 26Al kinematics: superbubbles following the spiral arms?. Constraints from the statistics of star clusters and HI supershells

    NASA Astrophysics Data System (ADS)

    Krause, Martin G. H.; Diehl, Roland; Bagetakos, Yiannis; Brinks, Elias; Burkert, Andreas; Gerhard, Ortwin; Greiner, Jochen; Kretschmer, Karsten; Siegert, Thomas

    2015-06-01

    Context. High-energy resolution spectroscopy of the 1.8 MeV radioactive decay line of 26Al with the SPI instrument onboard the INTEGRAL satellite has recently revealed that diffuse 26Al has higher velocities than other components of the interstellar medium in the Milky Way. 26Al shows Galactic rotation in the same sense as the stars and other gas tracers, but reaches excess velocities of up to 300 km s-1. Aims: We investigate whether this result can be understood in the context of superbubbles, taking into account the statistics of young star clusters and HI supershells as well as the association of young star clusters with spiral arms. Methods: We derived energy output and 26Al mass of star clusters as a function of the cluster mass by population synthesis from stellar evolutionary tracks of massive stars. Using the limiting cases of weakly and strongly dissipative superbubble expansion, we linked this to the size distribution of HI supershells and assessed the properties of possible 26Al-carrying superbubbles. Results: 26Al is produced by star clusters of all masses above ≈200 M⊙, is roughly equally contributed over a logarithmic star cluster mass scale and strongly linked to the injection of feedback energy. The observed superbubble size distribution cannot be related to the star cluster mass function in a straightforward manner. To avoid the added volume of all superbubbles exceeding the volume of the Milky Way, individual superbubbles have to merge frequently. If any two superbubbles merge, or if 26Al is injected off-centre into a larger HI supershell, we expect the hot 26Al-carrying gas to obtain velocities of the order of the typical sound speed in superbubbles, ≈300 km s-1 before decay. For star formation coordinated by the spiral arm pattern which, inside co-rotation, is overtaken by the faster moving stars and gas, outflows from spiral arm star clusters would preferentially flow into the cavities that are inflated by previous star formation

  12. Reprocessing of 10B-contaminated 10Be AMS targets

    NASA Astrophysics Data System (ADS)

    Simon, K. J.; Pedro, J. B.; Smith, A. M.; Child, D. P.; Fink, D.

    2013-01-01

    10Be accelerator mass spectrometry (AMS) is an increasingly important tool in studies ranging from exposure age dating and palaeo-geomagnetism to the impact of solar variability on the Earth’s climate. High levels of boron in BeO AMS targets can adversely impact the quality of 10Be measurements through interference from the isobar 10B. Numerous methods in chemical sample preparation and AMS measurement have been employed in order to reduce the impact of excessive boron rates. We present details of a method developed to chemically reprocess a set of forty boron-contaminated BeO targets derived from modern Antarctic ice. Previously, the excessive boron levels in these samples, as measured in an argon-filled absorber cell preceding the ionisation detector, had precluded routine AMS measurement. The procedure involved removing the BeO + Nb mixture from the target holders and dissolving the BeO in hot concentrated H2SO4. The solution was then heated with HF to remove the boron as volatile BF3 before re-precipitating as Be(OH)2 and calcining to BeO. This was again mixed with niobium and pressed into fresh target holders. Following reprocessing, the samples gave boron rates reduced by 10-100×, which were sufficiently low and similar to previous successful batches of ice core, snow and associated blank samples, thus allowing a successful 10Be measurement in the absence of any boron correction. Overall recovery of the BeO for this process averaged 40%. Extensive testing of relevant processing equipment and reagents failed to determine the source of the boron. As a precautionary measure, a similar H2SO4 + HF step has been subsequently added to the standard ice processing method.

  13. Atmospheric deposition of sup 7 Be and sup 10 Be

    SciTech Connect

    Brown, L. ); Stensland, G.J. ); Klein, J.; Middleton, R. )

    1989-01-01

    Measurements of {sup 10}Be in precipitation taken in Hawaii, Illinois and New Jersey over a period of five years are reported. The problem of contamination by the isotope being resuspended on wind blown soil that is also collected is addressed. Rain collected at Mauna Loa, Hawaii has such low values of dust contamination that it has been taken as clean, and the data from Illinois and New Jersey are evaluated on that assumption. The conclusion is that the deposition in a given amount of rain for the non-resuspended component is the same for all three stations, and the authors propose that the annual rate for mid-latitude locations have moderate rainfall is proportional to the local rainfall. {sup 7}Be, which is probably negligibly contributed to the measurements by soil contamination was measured for individual rains in Illinois and found to have a deposition of 1.4 {times} 10{sup 4} atom/cm{sup 3}. The authors have found that concentration variations between precipitation events greater than a factor of 20 exist for both isotopes and that relatively rare, high concentration events dominate deposition, thereby requiring long periods of observation to avoid significant error. Based on their own and other data they conclude that the best value for {sup 10}Be deposition is 1.5 {times} 10{sup 4} atom/cm{sup 3}, uncertain by 20%, and for {sup 7}Be is 1.2 {times} 10{sup 4} atom/cm{sup 3}, uncertain by 25%. A global average deposition rate cannot be inferred directly for either isotope from these kinds of data; however, the theoretical global deposition rate for {sup 10}Be is shown to be consistent with the deposition reported here, if the concentration in equatorial rain is about 3300 atom/g.

  14. High-Precision Half-Life Measurement for the Superallowed {beta}{sup +} Emitter {sup 26}Al{sup m}

    SciTech Connect

    Finlay, P.; Svensson, C. E.; Green, K. L.; Leach, K. G.; Phillips, A. A.; Sumithrarachchi, C. S.; Ettenauer, S.; Ball, G. C.; Bandyopadhyay, D.; Djongolov, M.; Hackman, G.; Pearson, C. J.; Williams, S. J; Leslie, J. R.; Andreoiu, C.; Cross, D. S.; Austin, R. A. E.; Demand, G.; Garrett, P. E.; Triambak, S.

    2011-01-21

    A high-precision half-life measurement for the superallowed {beta}{sup +} emitter {sup 26}Al{sup m} was performed at the TRIUMF-ISAC radioactive ion beam facility yielding T{sub 1/2}=6346.54{+-}0.46{sub stat{+-}}0.60{sub syst} ms, consistent with, but 2.5 times more precise than, the previous world average. The {sup 26}Al{sup m} half-life and ft value, 3037.53(61) s, are now the most precisely determined for any superallowed {beta} decay. Combined with recent theoretical corrections for isospin-symmetry-breaking and radiative effects, the corrected Ft value for {sup 26}Al{sup m}, 3073.0(12) s, sets a new benchmark for the high-precision superallowed Fermi {beta}-decay studies used to test the conserved vector current hypothesis and determine the V{sub ud} element of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

  15. Reconciling tectonic shortening, sedimentation and spatial patterns of erosion from 10Be paleo-erosion rates in the Argentine Precordillera

    NASA Astrophysics Data System (ADS)

    Val, Pedro; Hoke, Gregory D.; Fosdick, Julie C.; Wittmann, Hella

    2016-09-01

    The temporal evolution of erosion over million-year timescales is key to understand the development of mountain ranges and adjacent fold-and-thrust belts. While models of orogenic wedge dynamics predict an instantaneous response of erosion to pulses of rock uplift, stream-power based models predict that catchment-wide erosion maxima significantly lag behind a pulse of rock uplift. Here, we explore the relationships between rock uplift, erosion, and sediment deposition in the Argentine Precordillera fold-and-thrust belt at 30°S. Using a combination of 10Be-derived paleo-erosion rates, constraints on re-exposure using 26Al/10Be ratios, geomorphic observations and detrital zircon provenance, we demonstrate that the attainment of maximum upland erosion rates lags the maximum rate of deformation over million-year timescales. The magnitudes and causes of the erosional delays shed new light on the catchment erosional response to tectonic deformation and rock uplift in orogenic wedges.

  16. A RUNAWAY WOLF-RAYET STAR AS THE ORIGIN OF {sup 26}Al IN THE EARLY SOLAR SYSTEM

    SciTech Connect

    Tatischeff, Vincent; Duprat, Jean; De Sereville, Nicolas

    2010-05-01

    Establishing the origin of the short-lived radionuclide (SLR) {sup 26}Al, which was present in refractory inclusions in primitive meteorites, has profound implications for the astrophysical context of solar system formation. Recent observations that {sup 26}Al was homogeneously distributed in the inner solar system prove that this SLR has a stellar origin. In this Letter, we address the issue of the incorporation of hot {sup 26}Al-rich stellar ejecta into the cold protosolar nebula. We first show that the {sup 26}Al atoms produced by a population of massive stars in an OB association cannot be injected into protostellar cores with enough efficiency. We then show that this SLR likely originated in a Wolf-Rayet star that escaped from its parent cluster and interacted with a neighboring molecular cloud. The explosion of this runaway star as a supernova probably triggered the formation of the solar system. This scenario also accounts for the meteoritic abundance of {sup 41}Ca.

  17. Calibration of cosmogenic noble gas production based on 36Cl-36Ar ages. Part 2. The 81Kr-Kr dating technique

    NASA Astrophysics Data System (ADS)

    Leya, I.; Dalcher, N.; Vogel, N.; Wieler, R.; Caffee, M. W.; Welten, K. C.; Nishiizumi, K.

    2015-11-01

    We calibrated the 81Kr-Kr dating system for ordinary chondrites of different sizes using independent shielding-corrected 36Cl-36Ar ages. Krypton concentrations and isotopic compositions were measured in bulk samples from 14 ordinary chondrites of high petrologic type and the cosmogenic Kr component was obtained by subtracting trapped Kr from phase Q. The thus-determined average cosmogenic 78Kr/83Kr, 80Kr/83Kr, 82Kr/83Kr, and 84Kr/83Kr ratiC(Lavielle and Marti 1988; Wieler 2002). The cosmogenic 78Kr/83Kr ratio is correlated with the cosmogenic 22Ne/21Ne ratio, confirming that 78Kr/83Kr is a reliable shielding indicator. Previously, 81Kr-Kr ages have been determined by assuming the cosmogenic production rate of 81Kr, P(81Kr)c, to be 0.95 times the average of the cosmogenic production rates of 80Kr and 82Kr; the factor Y = 0.95 therefore accounts for the unequal production of the various Kr isotopes (Marti 1967a). However, Y should be regarded as an empirical adjustment. For samples whose 80Kr and 82Kr concentrations may be affected by neutron-capture reactions, the shielding-dependent cosmogenic (78Kr/83Kr)c ratio has been used instead to calculate P(81Kr)/P(83Kr), as for some lunar samples, this ratio has been shown to linearly increase with (78Kr/83Kr)c (Marti and Lugmair 1971). However, the 81Kr-Kr ages of our samples calculated with these methods are on average ~30% higher than their 36Cl-36Ar ages, indicating that most if not all the 81Kr-Kr ages determined so far are significantly too high. We therefore re-evaluated both methods to determine P(81Kr)c/P(83Kr)c. Our new Y value of 0.70 ± 0.04 is more than 25% lower than the value of 0.95 used so far. Furthermore, together with literature data, our data indicate that for chondrites, P(81Kr)c/P(83Kr)c is rather constant at 0.43 ± 0.02, at least for the shielding range covered by our samples ([78Kr/83Kr]c = 0.119-0.185; [22Ne/21Ne]c = 1.083-1.144), in contrast to the observations on lunar samples. As expected

  18. Inferred Initial 26Al/27Al Ratios in Presolar Stardust Grains from Supernovae are Higher than Previously Estimated

    NASA Astrophysics Data System (ADS)

    Groopman, Evan; Zinner, Ernst; Amari, Sachiko; Gyngard, Frank; Hoppe, Peter; Jadhav, Manavi; Lin, Yangting; Xu, Yuchen; Marhas, Kuljeet; Nittler, Larry R.

    2015-08-01

    We performed an in-depth exploration of the Al-Mg system for presolar graphite, SiC, and Si3N4 grains found to contain large excesses of 26Mg, indicative of the initial presence of live 26Al. Ninety of the more than 450 presolar grains processed in this study contain well-correlated {δ }26{Mg}{/}24{Mg} and 27Al/24Mg ratios, derived from Nano-scale Secondary Ion Mass Spectrometer depth profiles, whose isochron-like regression lines yield inferred initial {}26{Al}{/}27{Al} ratios that, on average, are ˜1.5-2 times larger than the ratios previously reported for the grains. The majority of presolar graphite and SiC grains are heavily affected by Al contamination, resulting in large negative {δ }26{Mg}{/}24{Mg} intercepts of the isochron lines. Al contamination is potentially due to etching of the grains’ surfaces and subsequent capture of dissolved Al during the acid dissolution of their meteorite host rocks. From the isochron fits, the magnitude of Al contamination was quantified for each grain. The amount of Al contamination on each grain was found to be random and independent of grain size, following a uniform distribution with an upper bound at 59% contamination. The Al contamination causes conventional whole-grain estimates to underpredict the initial {}26{Al}{/}27{Al} ratios. The presolar grains with the highest {}26{Al}{/}27{Al} ratios are from Type II supernovae whose isochron-derived initial {}26{Al}{/}27{Al} ratios greatly exceed those predicted in the He/C and He/N zones of SN models.

  19. Toward determining the uncertainties associated with the seismic histories retrieved from in situ 36Cl cosmogenic nuclide fault scarp dating: model reappraisal.

    NASA Astrophysics Data System (ADS)

    Tesson, Jim; Benedetti, Lucilla

    2016-04-01

    How the past seismic activity of faults has varied over the last 20 ky is a crucial information for seismic hazard assessment and for the understanding of fault-interaction processes. Chlorine 36 in situ produced cosmogenic nuclide is increasingly used to retrieve past earthquakes histories on seismically exhumed limestone normal fault-scarps. Schlagenhauf et al. in 2010 developed a modeling code with a forward approach enabling the test of scenarii generated with a priori constraints (number of events, age and slip of events and pre-exposure time). The main shortcomings of this forward approach were the limited number of testable scenarii and the difficulty to derive the associated uncertainties. We present here a reappraisal methodology with an inverse approach using an optimization algorithm. This modelling approach enables 1-exploring the parameter space (age and slip of events), 2-finding the best scenario without a priori constraints and 3-precisely quantifying the associated uncertainties by determining the range of plausible models. Through a series of synthetic tests, we observed that the algorithm revealed a great capacity to constrain event slips and ages in a short computational time (several hours) with an accuracy that can reach 0.1 ky and 0.5 m for the age and slip of exhumation event, respectively. We also explore the influence of the pre-exposure history (amount of 36Cl accumulated when the sampled fault-plane was still buried under the colluvial wedge) and show that it has an important impact on the generated scenarii. This new modeling also allows now to accurately determining this parameter. Finally, the results show that any given [36Cl] profile results in a unique exhumation solution. We then apply this new model to the Magnola fault (Italy) dataset (Schlgenhauf et al. 2011). In agreement the previously published results, our model also results in 3 intense periods of seismic activity. However, the contribution of the pre-exposure history is

  20. Slip rate variability over the Holocene period in the middle Aterno fault system (Italy), retrieved from in situ 36Cl cosmogenic nuclide dating of exhumed fault-plane.

    NASA Astrophysics Data System (ADS)

    Tesson, Jim; Benedetti, Lucilla; Pucci, Stefano; Villani, Fabio; Bourles, Didier; Keddadouche, Karim; Aumaitre, Georges

    2016-04-01

    Numerous numerical modeling studies have described and quantified non-stochastic spatio-temporal variations of earthquake occurrences within fault-networks, such as temporal clustered earthquakes or fault synchronization. However, very few long-enough paleoseismological and geological records are available to test those models against well-constrained dataset and thus account for such variability in the fault behavior. The prerequisites for improving our understanding of fault-rupture processes and thus our capacity to better assess seismic hazard are to acquire paleoseismological records that enable to derive both long-term slip-rate and short-term variability, on a large population of faults and/or within a fault system. These conditions met in Central Apennines, an extensional province where substantial paleoseismological dataset accurately described the Holocene seismic history of a dense network of normal faults. In this study we use 36Cl in situ cosmogenic nuclide to retrieve the seismic history of 3 faults belonging to the Middle Aterno fault system, from north to south: the Bazzano fault, the Roccapreturo fault and the Sulmona fault, a portion of which ruptured during the 2009 L'Aquila earthquake in Italy. We use a new modeling approach to determine the age and slip of past seismic events from the 36Cl concentration profiles. This model is based on an inverse approach and uses an optimization algorithm enabling all the parameter space (number of events, age and slip of events, pre-exposure) to be explored without a priori constraints (see Tesson et al. in session TS4.2/NH4.16/SM3.8). Using this new approach, we precisely determine the slip events occurrences over the Holocene period of those three faults. The results indicate that the three studied faults have ruptured between 4.5 and 5.5 ka, while the southernmost part of the system has also ruptured between at 1.5-3 ka (Sulmona fault and southern segment of Roccapreturo). Those results are in agreement

  1. Heterogeneous Distribution of ^2^6Al at the Birth of the Solar System: Evidence from Corundum-Bearing Refractory Inclusions

    NASA Astrophysics Data System (ADS)

    Krot, A. N.; Makide, K.; Nagashima, K.; Huss, G. R.; Hellebrand, E.; Petaev, M. I.

    2012-03-01

    Corundum-bearing CAIs recorded heterogeneous distribution of ^2^6Al at the birth of the solar system. We suggest that ^2^6Al was injected into the protosolar molecular cloud core by a wind from a massive star and was later homogenized through the disk.

  2. EARLY SOLAR NEBULA CONDENSATES WITH CANONICAL, NOT SUPRACANONICAL, INITIAL {sup 26}Al/{sup 27}Al RATIOS

    SciTech Connect

    MacPherson, G. J.; Bullock, E. S.; Janney, P. E.; Wadhwa, M.; Kita, N. T.; Ushikubo, T.; Davis, A. M.; Krot, A. N.

    2010-03-10

    The short-lived radionuclide {sup 26}Al existed throughout the solar nebula 4.57 Ga ago, and the initial abundance ratio ({sup 26}Al/{sup 27}Al){sub 0}, as inferred from magnesium isotopic compositions of calcium-aluminum-rich inclusions (CAIs) in chondritic meteorites, has become a benchmark for understanding early solar system chronology. Internal mineral isochrons in most CAIs measured by secondary ion mass spectrometry (SIMS) give ({sup 26}Al/{sup 27}Al){sub 0} {approx} (4-5) x 10{sup -5}, called 'canonical'. Some recent high-precision analyses of (1) bulk CAIs measured by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS), (2) individual CAI minerals and their mixtures measured by laser-ablation MC-ICPMS, and (3) internal isochrons measured by multicollector (MC)-SIMS indicated a somewhat higher 'supracanonical' ({sup 26}Al/{sup 27}Al){sub 0} ranging from (5.85 {+-} 0.05) x 10{sup -5} to >7 x 10{sup -5}. These measurements were done on coarse-grained Type B and Type A CAIs that probably formed by recrystallization and/or melting of fine-grained condensate precursors. Thus the supracanonical ratios might record an earlier event, the actual nebular condensation of the CAI precursors. We tested this idea by performing in situ high-precision magnesium isotope measurements of individual minerals in a fine-grained CAI whose structures and volatility-fractionated trace element abundances mark it as a primary solar nebula condensate. Such CAIs are ideal candidates for the fine-grained precursors to the coarse-grained CAIs, and thus should best preserve a supracanonical ratio. Yet, our measured internal isochron yields ({sup 26}Al/{sup 27}Al){sub 0} = (5.27 {+-} 0.17) x 10{sup -5}. Thus our data do not support the existence of supracanonical ({sup 26}Al/{sup 27}Al){sub 0} = (5.85-7) x 10{sup -5}. There may not have been a significant time interval between condensation of the CAI precursors and their subsequent melting into coarse-grained CAIs.

  3. LITHIUM-BERYLLIUM-BORON ISOTOPIC COMPOSITIONS IN METEORITIC HIBONITE: IMPLICATIONS FOR ORIGIN OF {sup 10}Be AND EARLY SOLAR SYSTEM IRRADIATION

    SciTech Connect

    Liu, Ming-Chang; Nittler, Larry R.; Alexander, Conel M. O'D.; Lee, Typhoon

    2010-08-10

    NanoSIMS isotopic measurements of Li, Be, and B in individual hibonite grains extracted from the Murchison meteorite revealed that {sup 10}B excesses correlate with the {sup 9}Be/{sup 11}B ratios in {sup 26}Al-free PLAty hibonite Crystals. From these data, an initial {sup 10}Be/{sup 9}Be = (5.5 {+-} 1.6) x 10{sup -4} (2{sigma}) and {sup 10}B/{sup 11}B = 0.2508 {+-} 0.0015 can be inferred. On the other hand, chondritic boron isotopic compositions were found in {sup 26}Al-bearing Spinel-HIBonite spherules, most likely due to contamination with normal boron. No {sup 7}Li excesses due to {sup 7}Be decay were observed. When combined with previously reported data, the new data yield the best defined {sup 10}Be/{sup 9}Be = (5.3 {+-} 1.0) x 10{sup -4} (2{sigma}) and {sup 10}B/{sup 11}B = 0.2513 {+-} 0.0012 for PLACs. A comparison of this value and the best constrained {sup 10}Be/{sup 9}Be = (8.8 {+-} 0.6) x 10{sup -4} in CV Ca-Al-rich inclusions supports a heterogeneous distribution of {sup 10}Be and its protosolar irradiation origin. We consider two possible irradiation scenarios that could potentially lead to the observed Li-Be-B isotopic compositions in PLACs. Although in situ irradiation of solids with hibonite chemistry seems to provide the simplest explanation, more high quality data will be needed for quantitatively constraining the irradiation history.

  4. Lowest l=0 proton resonance in {sup 26}Si and implications for nucleosynthesis of {sup 26}Al

    SciTech Connect

    Peplowski, P. N.; Baby, L. T.; Wiedenhoever, I.; Diffenderfer, E.; Hoeflich, P.; Rojas, A.; Volya, A.; Dekat, S. E.; Gay, D. L.; Grubor-Urosevic, O.; Kaye, R. A.; Keeley, N.

    2009-03-15

    Using a beam of the radioactive isotope {sup 25}Al, produced with the new RESOLUT facility, we measured the direct (d,n) proton-transfer reaction leading to low-lying proton resonances in {sup 26}Si. We observed the lowest l=0 proton resonance, identified with the 3{sup +} state at 5.914-MeV excitation energy. This result eliminates the largest uncertainty in astrophysical reaction rates involved in the nucleosynthesis of {sup 26}Al.

  5. Whole-rock 26Al-26Mg systematics of amoeboid olivine aggregates from the oxidized CV3 carbonaceous chondrite Allende

    NASA Astrophysics Data System (ADS)

    Olsen, M. B.; Krot, A. N.; Larsen, K.; Paton, C.; Wielandt, D.; Schiller, M.; Bizzarro, M.

    2011-11-01

    We report on mineralogy, petrography, and whole-rock 26Al-26Mg systematics of eight amoeboid olivine aggregates (AOAs) from the oxidized CV chondrite Allende. The AOAs consist of forsteritic olivine, opaque nodules, and variable amounts of Ca,Al-rich inclusions (CAIs) of different types, and show evidence for alteration to varying degrees. Melilite and anorthite are replaced by nepheline, sodalite, and grossular; spinel is enriched in FeO; opaque nodules are replaced by Fe,Ni-sulfides, ferroan olivine and Ca,Fe-rich pyroxenes; forsteritic olivine is enriched in FeO and often overgrown by ferroan olivine. The AOAs are surrounded by fine-grained, matrix-like rims composed mainly of ferroan olivine and by a discontinuous layer of Ca,Fe-rich silicates. These observations indicate that AOAs experienced in situ elemental open-system iron-alkali-halogen metasomatic alteration during which Fe, Na, Cl, and Si were introduced, whereas Ca was removed from AOAs and used to form the Ca,Fe-rich silicate rims around AOAs. The whole-rock 26Al-26Mg systematics of the Allende AOAs plot above the isochron of the whole-rock Allende CAIs with a slope of (5.23 ± 0.13) × 10-5 reported by Jacobsen et al. (2008). In contrast, whole-rock 26Al-26Mg isotope systematics of CAIs and AOAs from the reduced CV chondrite Efremovka define a single isochron with a slope of (5.25± 0.01) × 10-5 (Larsen et al. 2011). We infer that the excesses in 26Mg* present in Allende AOAs are due to their late-stage open-system metasomatic alteration. Thus, the 26Al-26Mg isotope systematics of Allende CAIs and AOAs are disturbed by parent body alteration processes, and may not be suitable for high-precision chronology of the early solar system events and processes.

  6. Measurement of 23Na(α,p)26Mg at Energies Relevant to 26Al Production in Massive Stars.

    PubMed

    Tomlinson, J R; Fallis, J; Laird, A M; Fox, S P; Akers, C; Alcorta, M; Bentley, M A; Christian, G; Davids, B; Davinson, T; Fulton, B R; Galinski, N; Rojas, A; Ruiz, C; de Séréville, N; Shen, M; Shotter, A C

    2015-07-31

    26Al is an important radioisotope in astrophysics that provides evidence of ongoing nucleosynthesis in the Galaxy. The 23Na(α, p)26Mg reaction has been identified by a sensitivity study as being one of the most important reactions for the production of 26Al in the convective C/Ne burning shell of massive stars. Owing to large uncertainties in previous experimental data, model calculations are used for the reaction rate of 23Na(α, p)26Mg in this sensitivity study. Current experimental data suggest a reaction rate a factor of ∼40 higher than model calculations. However, a new measurement of this reaction cross section has been made in inverse kinematics in the energy range E(c.m.)=1.28-3.15  MeV at TRIUMF, and found to be in reasonable agreement with the model calculation. A new reaction rate is calculated and tight constraints on the uncertainty in the production of 26Al, due to this reaction, are determined. PMID:26274415

  7. {sup 60}Fe AND {sup 26}Al IN CHONDRULES FROM UNEQUILIBRATED CHONDRITES: IMPLICATIONS FOR EARLY SOLAR SYSTEM PROCESSES

    SciTech Connect

    Mishra, R. K.; Goswami, J. N.; Rudraswami, N. G.; Tachibana, S.; Huss, G. R.

    2010-05-10

    The presence of about a dozen short-lived nuclides in the early solar system, including {sup 60}Fe and {sup 26}Al, has been established from isotopic studies of meteorite samples. An accurate estimation of solar system initial abundance of {sup 60}Fe, a distinct product of stellar nucleosynthesis, is important to infer the stellar source of this nuclide. Previous studies in this regard suffered from the lack of exact knowledge of the time of formation of the analyzed meteorite samples. We present here results obtained from the first combined study of {sup 60}Fe and {sup 26}Al records in early solar system objects to remove this ambiguity. Chondrules from unequilibrated ordinary chondrites belonging to low petrologic grades were analyzed for their Fe-Ni and Al-Mg isotope systematics. The Al-Mg isotope data provide the time of formation of the analyzed chondrules relative to the first solar system solids, the Ca-Al-rich inclusions. The inferred initial {sup 60}Fe/{sup 56}Fe values of four chondrules, combined with their time of formation based on Al-Mg isotope data, yielded a weighted mean value of (6.3 {+-} 2) x 10{sup -7} for solar system initial {sup 60}Fe/{sup 56}Fe. This argues for a high-mass supernova as the source of {sup 60}Fe along with {sup 26}Al and several other short-lived nuclides present in the early solar system.

  8. Multiple dating approach (14C, U/Th and 36Cl) of tsunami-transported reef-top megaclasts on Bonaire (Leeward Antilles) - potential and current limitations

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; May, Simon Matthias; Engel, Max; Mechernich, Silke; Keulertz, Rebecca; Schroeder-Ritzrau, Andrea; Fohlmeister, Jens; Frank, Norbert; Dunai, Tibor; Brueckner, Helmut

    2016-04-01

    Coastal hazard assessment depends on reliable information on the magnitude and frequency of past high-energy wave events (EWE: tsunamis, storms). For this purpose onshore sedimentary records represent promising geo-archives for the mid- and late-Holocene EWE history. In comparison to fine-grained sediments which have been extensively studied in the recent past, supralittoral megaclasts are less investigated, essentially due to the difficulties related to the dating of corresponding depositional events, and thus their limited value for inferring the timing of major events. On Bonaire (Leeward Antilles, Caribbean), supratidal coarse-clast deposits form prominent landforms all around the island. Fields of large boulders (up to 150 t) are among the best-studied reef-top megaclasts worldwide. Transport by Holocene tsunamis is assumed at least for the largest boulders (Engel and May, 2012). Although a large dataset of 14C and electron spin resonance (ESR) ages is available for major coral rubble ridges and ramparts, showing some age clusters during the Late Holocene, it is still debated whether these data reflect the timing of major depositional/transport event(s), and how these data sets are biased by reworking of coral fragments. In addition, different processes may be responsible for the deposition of the coral rubble ridges and ramparts (storm) and the solitary megaclasts (tsunami). As an attempt to overcome the current challenges for dating the dislocation of the megaclasts, three distinct dating methods were implemented: (i) 14C dating of boring bivalves (Lithophaga) attached to the boulders; (ii) uranium-series (U/Th) dating of post-depositional, secondary calcitic flowstone at the underside of the boulders; and (iii) surface exposure dating of overturned boulders via 36Cl concentration measurements in corals. The three 14C datings yield age estimates >37 ka, i.e. most probably beyond the applicability of the method, which sheds doubt on the usefulness of this

  9. 182Hf-182W age dating of a 26Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System.

    PubMed

    Holst, Jesper C; Olsen, Mia B; Paton, Chad; Nagashima, Kazuhide; Schiller, Martin; Wielandt, Daniel; Larsen, Kirsten K; Connelly, James N; Jørgensen, Jes K; Krot, Alexander N; Nordlund, Ake; Bizzarro, Martin

    2013-05-28

    Refractory inclusions [calcium-aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., (26)Al, (41)Ca, and (182)Hf) synthesized in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs formed with the canonical abundance of (26)Al corresponding to (26)Al/(27)Al of ∼5 × 10(-5), rare CAIs with fractionation and unidentified nuclear isotope effects (FUN CAIs) record nucleosynthetic isotopic heterogeneity and (26)Al/(27)Al of <5 × 10(-6), possibly reflecting their formation before canonical CAIs. Thus, FUN CAIs may provide a unique window into the earliest Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the (182)Hf-(182)W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs, but with (26)Al/(27)Al of ∼3 × 10(-6). The decoupling between (182)Hf and (26)Al requires distinct stellar origins: steady-state galactic stellar nucleosynthesis for (182)Hf and late-stage contamination of the protosolar molecular cloud by a massive star(s) for (26)Al. Admixing of stellar-derived (26)Al to the protoplanetary disk occurred during the epoch of CAI formation and, therefore, the (26)Al-(26)Mg systematics of CAIs cannot be used to define their formation interval. In contrast, our results support (182)Hf homogeneity and chronological significance of the (182)Hf-(182)W clock. PMID:23671077

  10. Direct measurement of the (23)Na(α,p)(26)Mg reaction cross section at energies relevant for the production of galactic (26)Al.

    PubMed

    Almaraz-Calderon, S; Bertone, P F; Alcorta, M; Albers, M; Deibel, C M; Hoffman, C R; Jiang, C L; Marley, S T; Rehm, K E; Ugalde, C

    2014-04-18

    The 1809-keV γ ray from the decay of (26)Al(g) is an important target for γ-ray astronomy. In the convective C/Ne burning shell of massive presupernova stars, the (23)Na(α,p)(26)Mg reaction directly influences the production of (26)Al. We have performed a direct measurement of the (23)Na(α,p)(26)Mg reaction cross section at the appropriate astrophysically important energies. The stellar rate calculated in the present work is larger than the recommended rate by nearly a factor of 40 and could strongly affect the production of (26)Al in massive stars. PMID:24785033

  11. Correlation between relative ages inferred from 26Al and bulk compositions of ferromagnesian chondrules in least equilibrated ordinary chondrites

    NASA Astrophysics Data System (ADS)

    Tachibana, S.; Nagahara, H.; Mostefaoui, S.; Kita, N. T.

    2003-06-01

    We have studied the relationship between bulk chemical compositions and relative formation ages inferred from the initial 26Al/27Al ratios for sixteen ferromagnesian chondrules in least equilibrated ordinary chondrites, Semarkona (LL3.0) and Bishunpur (LL3.1). The initial 26Al/27Al ratios of these chondrules were obtained by Kita et al. (2000) and Mostefaoui et al. (2002), corresponding to relative ages from 0.7 ± 0.2 to 2.4 -0.4/+0.7 Myr after calcium-aluminum-rich inclusions (CAIs), by assuming a homogeneous distribution of 26Al in the early solar system. The measured bulk compositions of the chondrules cover the compositional range of ferromagnesian chondrules reported in the literature and, thus, the chondrules in this study are regarded as representatives of ferromagnesian chondrules. The relative ages of the chondrules appear to correlate with bulk abundances of Si and the volatile elements (Na, K, Mn, and Cr), but there seems to exist no correlation of relative ages neither with Fe nor with refractory elements. Younger chondrules tend to be richer in Si and volatile elements. Our result supports the result of Mostefaoui et al. (2002) who suggested that pyroxene-rich chondrules are younger than olivine-rich ones. The correlation provides an important constraint on chondrule formation in the early solar system. It is explained by chondrule formation in an open system, where silicon and volatile elements evaporated from chondrule melts during chondrule formation and recondensed as chondrule precursors of the next generation.

  12. Experimental determination of the {sup 26}Al(n,{alpha}){sup 23}Na reaction cross section and calculation of the Maxwellian averaged cross section at stellar temperatures

    SciTech Connect

    Smet, L. de; Wagemans, C.; Wagemans, J.; Heyse, J.; Gils, J. van

    2007-10-15

    The {sup 26}Al(n,{alpha}){sup 23}Na reaction cross section has been studied at the linear accelerator GELINA of the Institute for Reference Materials and Measurements in Geel, Belgium, and has been determined up to a neutron energy of about 100 keV using the time-of-flight technique. Six resonances could be observed in this energy region, whereas before only one had been identified experimentally. For four of them, resonance parameters such as resonance energy, total width, area, and spin of the state could be determined. From the obtained {sup 26}Al(n,{alpha}){sup 23}Na cross section data, Maxwellian averaged cross section (MACS) values were calculated by numerical integration. Since neutron induced reactions are among the major destruction mechanisms of {sup 26}Al in our Galaxy, these new MACS values contribute to a better understanding of the observed {sup 26}Al abundance.

  13. 182Hf–182W age dating of a 26Al-poor inclusion and implications for the origin of short-lived radioisotopes in the early Solar System

    PubMed Central

    Holst, Jesper C.; Olsen, Mia B.; Paton, Chad; Nagashima, Kazuhide; Schiller, Martin; Wielandt, Daniel; Larsen, Kirsten K.; Connelly, James N.; Jørgensen, Jes K.; Krot, Alexander N.; Nordlund, Åke; Bizzarro, Martin

    2013-01-01

    Refractory inclusions [calcium–aluminum-rich inclusions, (CAIs)] represent the oldest Solar System solids and provide information regarding the formation of the Sun and its protoplanetary disk. CAIs contain evidence of now extinct short-lived radioisotopes (e.g., 26Al, 41Ca, and 182Hf) synthesized in one or multiple stars and added to the protosolar molecular cloud before or during its collapse. Understanding how and when short-lived radioisotopes were added to the Solar System is necessary to assess their validity as chronometers and constrain the birthplace of the Sun. Whereas most CAIs formed with the canonical abundance of 26Al corresponding to 26Al/27Al of ∼5 × 10−5, rare CAIs with fractionation and unidentified nuclear isotope effects (FUN CAIs) record nucleosynthetic isotopic heterogeneity and 26Al/27Al of <5 × 10−6, possibly reflecting their formation before canonical CAIs. Thus, FUN CAIs may provide a unique window into the earliest Solar System, including the origin of short-lived radioisotopes. However, their chronology is unknown. Using the 182Hf–182W chronometer, we show that a FUN CAI recording a condensation origin from a solar gas formed coevally with canonical CAIs, but with 26Al/27Al of ∼3 × 10−6. The decoupling between 182Hf and 26Al requires distinct stellar origins: steady-state galactic stellar nucleosynthesis for 182Hf and late-stage contamination of the protosolar molecular cloud by a massive star(s) for 26Al. Admixing of stellar-derived 26Al to the protoplanetary disk occurred during the epoch of CAI formation and, therefore, the 26Al–26Mg systematics of CAIs cannot be used to define their formation interval. In contrast, our results support 182Hf homogeneity and chronological significance of the 182Hf–182W clock. PMID:23671077

  14. Update on terrestrial ages of Antarctic meteorites

    SciTech Connect

    Welten, K C; Nishiizumi, K; Caffee, M W

    2000-01-14

    Terrestrial ages of Antarctic meteorites are one of the few parameters that will help us to understand the meteorite concentration mechanism on blue-ice fields. Traditionally, terrestrial ages were determined on the basis of {sup 36}Cl in the metal phase, which has an uncertainty of about 70 ky. For young meteorites (< 40 ky), the terrestrial age is usually and most accurately determined using {sup 14}C in the stone phase. In recent years two methods have been developed which are independent of shielding effects, the {sup 10}Be-{sup 36}Cl/{sup 10}Be method and the {sup 41}Ca/{sup 36}Cl method. These methods have reduced the typical uncertainties in terrestrial ages by a factor of 2, to about 30 ky. The {sup 10}Be-{sup 36}Cl/{sup 10}Be method is quite dependent on the exposure age, which is unknown for most Antarctic meteorites. The authors therefore also attempt to use the relation between {sup 26}Al and {sup 36}Cl/{sup 26}Al to derive a terrestrial age less dependent on the exposure age. The authors have measured the concentrations of cosmogenic {sup 10}Be, {sup 26}Al and {sup 36}Cl in the metal phase of {approximately} 70 Antarctic meteorites, from more than 10 different ice-fields, including many new ones. They then discuss the trends in terrestrial ages of meteorites from different ice-fields.

  15. Late Holocene denudation rates and sediment fluxes in the Po basin from source to sink based on in situ cosmogenic 10Be

    NASA Astrophysics Data System (ADS)

    Wittmann, Hella; Malusà, Marco; Resentini, Alberto; Garzanti, Eduardo; Niedermann, Samuel

    2016-04-01

    We constrain the long-term sediment delivery within the Po basin from source to lowland sink using sediment fluxes from in situ 10Be-derived denudation rates and compare these to published short-term estimates from gauging. We measured in situ 10Be concentrations in nearly all Alpine and Apennine upstream catchments draining to the Po River and in the Po lowlands down to the Po delta, respectively. In the upstream reaches of the Po basin, short-term sediment interception in dams and reservoirs and long-term sediment trapping in periglacial lakes may modify 10Be concentrations, whereas in lowland reaches, sediment burial and storage may affect nuclide concentrations. From the comparison of 10Be nuclide data measured upstream of dam influence to those measured downstream of major dams, we find that the average 10Be signal is not significantly modified. In the lowland reaches, we find that the average 10Be concentration is only marginally modified by floodplain processes, as 26Al/10Be ratios do not show differential decay due to burial and 21Ne concentrations change only slightly along the floodplain reach. Thus we interpret the average 10Be concentration of lowland samples to reflect the average 10Be concentration of all upstream catchments in terms of a preservation of the source area erosion signal. The close similarity in 10Be concentrations from the sources to the Po lowland sink suggests that LGM denudation rates prior to sediment trapping in periglacial lakes were similar to today's, as the sediment now contained in the Po lowlands must have been eroded from the orogen and deposited in the lowlands prior to lake formation. This source-sink assessment shows the robustness of cosmogenic 10Be as erosion rate tracer. From these in situ 10Be-derived denudation rates integrating over the last few thousand years, we constrain the sediment contributions of the Alpine and Apennine source areas arriving at the Po delta. In total, ca. 60 Mt/yr of sediment are exported to

  16. Morphogenetic evolution of the Têt river valley (eastern Pyrenees) using 10Be/21Ne cosmogenic burial dating

    NASA Astrophysics Data System (ADS)

    Sartégou, Amandine; Blard, Pierre-Henri; Braucher, Régis; Bourlès, Didier L.; Calvet, Marc; Zimmermann, Laurent; Tibari, Bouchaïb; Hez, Gabriel; Gunnell, Yanni; Aumaitre, Georges; Keddadouche, Karim

    2016-04-01

    The rates and chronologies of valley incision are closely modulated by the tectonic uplift of active mountain ranges and were controlled by repeated climate changes during the Quaternary. The continental collision between the Iberian and Eurasian plates induced a double vergence orogen, the Pyrenees, which has been considered as a mature mountain range in spite of significant seismicity (e.g. Chevrot et al., 2011) and evidence of neotectonics (e.g. Goula et al., 1999). Nevertheless, recent studies indicate that the range may have never reached a steady state (Ford et al., in press). One option for resolving this controversy is to quantify the incision rates since the Miocene by reconstructing the vertical movement of geometric markers such as fluvial terraces. However, the few available ages from the Pyrenean terrace systems do not exceed the middle Pleistocene. Thus, to enlarge the time span of this dataset, we studied alluvium-filled horizontal epiphreatic passages in limestone karstic networks. Such landforms are used as substitutes of fluvial terraces because they represent former valley floors (e.g. Palmer, 2007; Audra et al., 2013). They record the transient position of former local base levels during the process of valley deepening. The Têt river valley (southern Pyrenees) was studied near the Villefranche-de-Conflent limestone gorge where 8 cave levels have been recognized over a vertical height of 600 meters. Given that 26Al/10Be cosmogenic burial dating in this setting was limited to the last ~5 Ma (Calvet et al., 2015), here we used the cosmogenic 10Be/21Ne method in order to restore a more complete chronology of valley incision (e.g. Balco & Shuster, 2009; McPhilipps et al., 2016). Burial age results for alluvial deposits from 12 caves document incision rates since the Langhian (~14 Ma). Preliminary results indicate a history of valley deepening in successive stages. The data show a regular incision rate of 70-80 mm/a from the Langhian to the Messinian

  17. The use of multiple probe molecules for the study of the acid-base properties of aluminium hydroxyfluoride having the hexagonal tungsten bronze structure: FTIR and [36Cl] radiotracer studies.

    PubMed

    Dambournet, Damien; Leclerc, Hervé; Vimont, Alexandre; Lavalley, Jean-Claude; Nickkho-Amiry, Mahmood; Daturi, Marco; Winfield, John M

    2009-03-01

    The combination of several probe molecules has enabled the construction of a detailed picture of the surface of aluminium hydroxyl fluoride, AlF(2.6)(OH)(0.4), which has the hexagonal tungsten bronze (HTB) structure. Using pyridine as a probe leads to features at 1628 cm(-1), ascribed to very strong Lewis acid sites, and at 1620-1623 cm(-1), which is the result of several different types of Lewis sites. This heterogeneity is indicated also from CO adsorption at 100 K; the presence of five different types of Lewis site is deduced and is suggested to arise from the hydroxylated environment. Brønsted acid sites of medium strength are indicated by adsorption of lutidine and CO. Adsorption of lutidine occurs at OH groups, which are exposed at the surface and CO reveals that these OH groups have a single environment that can be correlated with their specific location inside the bulk, assuming that the surface OH group may reflect the bulk OH periodicity. A correlation between the data obtained from CO and pyridine molecules has been established using co-adsorption experiments, which also highlight the inductive effect produced by pyridine. Adsorption of the strong Brønsted acid, anhydrous hydrogen chloride, detected by monitoring the beta(-) emission of [(36)Cl]-HCl at the surface, indicates that surface hydroxyl groups can behave also as a Brønsted base and that H(2)O-HCl interactions, either within the hexagonal channels or at the surface are possible. Finally, the formation of strongly bound H(36)Cl as a result of the room temperature dehydrochlorination of [(36)Cl]-labelled tert-butyl chloride provides additional evidence that HTB-AlF(2.6)(OH)(0.4) can behave as a Lewis acid. PMID:19224038

  18. Authigenic 10Be/9Be ratios and 10Be-fluxes (230Thxs-normalized) in central Baffin Bay sediments during the last glacial cycle: Paleoenvironmental implications

    NASA Astrophysics Data System (ADS)

    Simon, Quentin; Thouveny, Nicolas; Bourlès, Didier L.; Nuttin, Laurence; Hillaire-Marcel, Claude; St-Onge, Guillaume

    2016-05-01

    Authigenic 10Be/9Be ratios and 10Be-fluxes reconstructed using the 230Thxs normalization, proxies of the cosmogenic radionuclide 10Be production rate in the atmosphere, have been measured in a sedimentary core from Baffin Bay (North Atlantic) spanning the last 136 ka BP. The normalization applied on the exchangeable (authigenic) 10Be concentrations using the authigenic 9Be isotope and 230Thxs methods yield equivalent results strongly correlated with sedimentological parameters (grain-size and mineralogy). Lower authigenic beryllium (Be) concentrations and 10Be/9Be ratios are associated with coarse-grained carbonate-rich layers, while higher authigenic Be values are related to fine-grained felspar-rich sediments. This variability is due to: i) sediment composition control over beryllium-scavenging efficiency and, ii) glacial history that contributed to modify the 10Be concentration in Baffin Bay by input and boundary scavenging condition changes. Most paleo-denudation rates inferred from the 10Be/9Be ratio vary weakly around 220 ± 76 tons.km-2.yr-1 (0.09 ± 0.03 mm.yr-1) corresponding to relatively steady weathering fluxes over the last glacial cycle except for six brief intervals characterized by sharp increases of the denudation rate. These intervals are related to ice-surging episodes coeval with Heinrich events and the last deglaciation period. An average freshwater flux of 180.6 km3.yr-1 (0.006 Sv), consistent with recent models, has been calculated in order to sustain glacially-derived 10Be inputs into Baffin Bay. It is concluded that in such environments, the authigenic 10Be measured mainly depends on climatic effects related to the glacial dynamics, which masks the 10Be production variation modulated by geomagnetic field changes. Altogether, these results challenge the simple interpretation of 10Be-concentration variation as a proxy of Interglacial/Glacial (interstadial/stadial) cycles in Arctic and sub-Arctic regions. They rather suggest the effect

  19. Impact of a Revised 25Mg(p, γ)26Al Reaction Rate on the Operation of the Mg-Al Cycle

    NASA Astrophysics Data System (ADS)

    Straniero, O.; Imbriani, G.; Strieder, F.; Bemmerer, D.; Broggini, C.; Caciolli, A.; Corvisiero, P.; Costantini, H.; Cristallo, S.; DiLeva, A.; Formicola, A.; Elekes, Z.; Fülöp, Zs.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, Gy.; Junker, M.; Lemut, A.; Limata, B.; Marta, M.; Mazzocchi, C.; Menegazzo, R.; Piersanti, L.; Prati, P.; Roca, V.; Rolfs, C.; Rossi Alvarez, C.; Somorjai, E.; Terrasi, F.; Trautvetter, H.-P.

    2013-02-01

    Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-burning regions. In particular, low-energy nuclear resonances in the 25Mg(p, γ)26Al reaction affect the production of radioactive 26Algs as well as the resulting Mg/Al abundance ratio. Reliable estimations of these quantities require precise measurements of the strengths of low-energy resonances. Based on a new experimental study performed at the Laboratory for Underground Nuclear Astrophysics, we provide revised rates of the 25Mg(p, γ)26Algs and the 25Mg(p, γ)26Al m reactions with corresponding uncertainties. In the temperature range 50-150 MK, the new recommended rate of 26Al m production is up to five times higher than previously assumed. In addition, at T = 100 MK, the revised total reaction rate is a factor of two higher. Note that this is the range of temperature at which the Mg-Al cycle operates in a H-burning zone. The effects of this revision are discussed. Due to the significantly larger 25Mg(p, γ)26Al m rate, the estimated production of 26Algs in H-burning regions is less efficient than previously obtained. As a result, the new rates should imply a smaller contribution from Wolf-Rayet stars to the galactic 26Al budget. Similarly, we show that the asymptotic giant branch (AGB) extra-mixing scenario does not appear able to explain the most extreme values of 26Al/27Al, i.e., >10-2, found in some O-rich presolar grains. Finally, the substantial increase of the total reaction rate makes the hypothesis of self-pollution by massive AGBs a more robust explanation for the Mg-Al anticorrelation observed in globular-cluster stars.

  20. Testing the 14C ages and conservative behavior of dissolved 14C in a carbonate aquifer in Yucca Flat, Nevada (USA), using 36Cl from groundwater and packrat middens

    NASA Astrophysics Data System (ADS)

    Kwicklis, Edward; Farnham, Irene

    2014-09-01

    Corrected groundwater 14C ages from the carbonate aquifer in Yucca Flat at the former Nevada Test Site (now the Nevada National Security Site), USA, were evaluated by comparing temporal variations of groundwater 36Cl/Cl estimated with these 14C ages with published records of meteoric 36Cl/Cl variations preserved in packrat middens (piles of plant fragments, fecal matter and urine). Good agreement between these records indicates that the groundwater 14C ages are reasonable and that 14C is moving with chloride without sorbing to the carbonate rock matrix or fracture coatings, despite opposing evidence from laboratory experiments. The groundwater 14C ages are consistent with other hydrologic evidence that indicates significant basin infiltration ceased 8,000 to 10,000 years ago, and that recharge to the carbonate aquifer is from paleowater draining through overlying tuff confining units along major faults. This interpretation is supported by the relative age differences as well as hydraulic head differences between the alluvial and volcanic aquifers and the carbonate aquifer. The carbonate aquifer 14C ages suggest that groundwater velocities throughout much of Yucca Flat are about 2 m/yr, consistent with the long-held conceptual model that blocking ridges of low-permeability rock hydrologically isolate the carbonate aquifer in Yucca Flat from the outlying regional carbonate flow system.

  1. Angle-integrated measurements of the 26Al (d, n)27Si reaction cross section: a probe of spectroscopic factors and astrophysical resonance strengths

    NASA Astrophysics Data System (ADS)

    Kankainen, A.; Woods, P. J.; Nunes, F.; Langer, C.; Schatz, H.; Bader, V.; Baugher, T.; Bazin, D.; Brown, B. A.; Browne, J.; Doherty, D. T.; Estrade, A.; Gade, A.; Kontos, A.; Lotay, G.; Meisel, Z.; Montes, F.; Noji, S.; Perdikakis, G.; Pereira, J.; Recchia, F.; Redpath, T.; Stroberg, R.; Scott, M.; Seweryniak, D.; Stevens, J.; Weisshaar, D.; Wimmer, K.; Zegers, R.

    2016-01-01

    Measurements of angle-integrated cross sections to discrete states in 27Si have been performed studying the 26Al ( d, n) reaction in inverse kinematics by tagging states by their characteristic γ -decays using the GRETINA array. Transfer reaction theory has been applied to derive spectroscopic factors for strong single-particle states below the proton threshold, and astrophysical resonances in the 26Al ( p, γ) 27Si reaction. Comparisons are made between predictions of the shell model and known characteristics of the resonances. Overall very good agreement is obtained, indicating this method can be used to make estimates of resonance strengths for key reactions currently largely unconstrained by experiment.

  2. Meteoric 10Be in soil profiles - A global meta-analysis

    NASA Astrophysics Data System (ADS)

    Graly, Joseph A.; Bierman, Paul R.; Reusser, Lucas J.; Pavich, Milan J.

    2010-12-01

    In order to assess current understanding of meteoric 10Be dynamics and distribution in terrestrial soils, we assembled a database of all published meteoric 10Be soil depth profiles, including 104 profiles from 27 studies in globally diverse locations, collectively containing 679 individual measurements. This allows for the systematic comparison of meteoric 10Be concentration to other soil characteristics and the comparison of profile depth distributions between geologic settings. Percent clay, 9Be, and dithionite-citrate extracted Al positively correlate to meteoric 10Be in more than half of the soils where they were measured, but the lack of significant correlation in other soils suggests that no one soil factor controls meteoric 10Be distribution with depth. Dithionite-citrate extracted Fe and cation exchange capacity are only weakly correlated to meteoric 10Be. Percent organic carbon and pH are not significantly related to meteoric 10Be concentration when all data are complied. The compilation shows that meteoric 10Be concentration is seldom uniform with depth in a soil profile. In young or rapidly eroding soils, maximum meteoric 10Be concentrations are typically found in the uppermost 20 cm. In older, more slowly eroding soils, the highest meteoric 10Be concentrations are found at depth, usually between 50 and 200 cm. We find that the highest measured meteoric 10Be concentration in a soil profile is an important metric, as both the value and the depth of the maximum meteoric 10Be concentration correlate with the total measured meteoric 10Be inventory of the soil profile. In order to refine the use of meteoric 10Be as an estimator of soil erosion rate, we compare near-surface meteoric 10Be concentrations to total meteoric 10Be soil inventories. These trends are used to calibrate models of meteoric 10Be loss by soil erosion. Erosion rates calculated using this method vary based on the assumed depth and timing of erosional events and on the reference data selected.

  3. 10Be in late deglacial climate simulated by ECHAM5-HAM - Part 2: Isolating the solar signal from 10Be deposition

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Shi, X.; Phipps, S. J.; Smith, A. M.

    2013-10-01

    This study investigates the effect of deglacial climate on the deposition of the solar proxy 10Be globally, and at two specific locations, the GRIP site at Summit, Central Greenland, and the Law Dome site in coastal Antarctica. The deglacial climate is represented by three 30 yr time slice simulations of 10 000 BP (years before present = 1950 CE), 11 000 BP and 12 000 BP, compared with a preindustrial control simulation. The model used is the ECHAM5-HAM atmospheric aerosol-climate model, driven with sea surface temperatures and sea ice cover simulated using the CSIRO Mk3L coupled climate system model. The focus is on isolating the 10Be production signal, driven by solar variability, from the weather or climate driven noise in the 10Be deposition flux during different stages of climate. The production signal varies on lower frequencies, dominated by the 11yr solar cycle within the 30 yr time scale of these experiments. The climatic noise is of higher frequencies. We first apply empirical orthogonal functions (EOF) analysis to global 10Be deposition on the annual scale and find that the first principal component, consisting of the spatial pattern of mean 10Be deposition and the temporally varying solar signal, explains 64% of the variability. The following principal components are closely related to those of precipitation. Then, we apply ensemble empirical decomposition (EEMD) analysis on the time series of 10Be deposition at GRIP and at Law Dome, which is an effective method for adaptively decomposing the time series into different frequency components. The low frequency components and the long term trend represent production and have reduced noise compared to the entire frequency spectrum of the deposition. The high frequency components represent climate driven noise related to the seasonal cycle of e.g. precipitation and are closely connected to high frequencies of precipitation. These results firstly show that the 10Be atmospheric production signal is preserved

  4. 10Be in late deglacial climate simulated by ECHAM5-HAM - Part 2: Isolating the solar signal from 10Be deposition

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Shi, X.; Phipps, S. J.; Smith, A. M.

    2014-04-01

    This study investigates the effect of deglacial climate on the deposition of the solar proxy 10Be globally, and at two specific locations, the GRIP site at Summit, Central Greenland, and the Law Dome site in coastal Antarctica. The deglacial climate is represented by three 30 year time slice simulations of 10 000 BP (years before present = 1950 CE), 11 000 and 12 000 BP, compared with a preindustrial control simulation. The model used is the ECHAM5-HAM atmospheric aerosol-climate model, driven with sea-surface temperatures and sea ice cover simulated using the CSIRO Mk3L coupled climate system model. The focus is on isolating the 10Be production signal, driven by solar variability, from the weather- or climate-driven noise in the 10Be deposition flux during different stages of climate. The production signal varies at lower frequencies, dominated by the 11 year solar cycle within the 30 year timescale of these experiments. The climatic noise is of higher frequencies than 11 years during the 30 year period studied. We first apply empirical orthogonal function (EOF) analysis to global 10Be deposition on the annual scale and find that the first principal component, consisting of the spatial pattern of mean 10Be deposition and the temporally varying solar signal, explains 64% of the variability. The following principal components are closely related to those of precipitation. Then, we apply ensemble empirical decomposition (EEMD) analysis to the time series of 10Be deposition at GRIP and at Law Dome, which is an effective method for adaptively decomposing the time series into different frequency components. The low-frequency components and the long-term trend represent production and have reduced noise compared to the entire frequency spectrum of the deposition. The high-frequency components represent climate-driven noise related to the seasonal cycle of e.g. precipitation and are closely connected to high frequencies of precipitation. These results firstly show that

  5. Heterogeneous distribution of 26Al at the birth of the Solar System: Evidence from corundum-bearing refractory inclusions in carbonaceous chondrites

    NASA Astrophysics Data System (ADS)

    Makide, Kentaro; Nagashima, Kazuhide; Krot, Alexander N.; Huss, Gary R.; Hutcheon, Ian D.; Hellebrand, Eric; Petaev, Michail I.

    2013-06-01

    We report on the mineralogy, petrology, and in situ oxygen- and magnesium-isotope measurements using secondary ion mass spectrometry of 10 corundum-bearing calcium-aluminum-rich inclusions (CAIs) from the Adelaide (ungrouped), Murray and Murchison (CM) carbonaceous chondrites. We also measured in situ oxygen-isotope compositions of several isolated corundum grains in the matrices of Murray and Murchison. Most of the corundum-bearing objects studied are uniformly 16O-rich [Δ17O values range from -17‰ to -28‰ (2σ = ±2.5‰) (Δ17Oavr = -23 ± 5‰)], suggesting that they formed in a 16O-rich gas of approximately solar composition and largely avoided subsequent thermal processing in an 16O-poor gaseous reservoir. There is a large spread of the initial 26Al/27Al ratio [(26Al/27Al)0] in the corundum-bearing CAIs. Two Adelaide CAIs show no resolvable excess of radiogenic 26Mg (δ26Mg∗): the inferred (26Al/27Al)0 are (0.6 ± 2.0) × 10-6 and (-0.9 ± 1.2) × 10-6, respectively. Slopes of the model 26Al-26Mg isochrons in five CAIs from Murray and Murchison are (4.4 ± 0.2) × 10-5, (3.3 ± 0.3) × 10-5, (4.1 ± 0.3) × 10-5, (3.9 ± 0.4) × 10-5, and (4.0 ± 2.0) × 10-6, respectively. These values are lower than the canonical (26Al/27Al)0 ratio of (5.23 ± 0.13) × 10-5 inferred from the whole-rock magnesium-isotope measurements of the CV CAIs, but similar to the (26Al/27Al)0 ratio of (4.1 ± 0.2) × 10-5 in the corundum-bearing CAI F5 from Murray. Five other previously studied corundum-bearing CAIs from Acfer 094 (ungrouped) and CM carbonaceous chondrites showed no resolvable δ26Mg∗. We conclude that the corundum-bearing CAIs, as well as the solar corundum grains from matrices and acid-resistant residues of unequilibrated ordinary and carbonaceous chondrites, recorded heterogeneous distribution of 26Al in the Solar System during an epoch of CAI formation. The 26Al-rich and 26Al-poor corundum-bearing CAIs and solar corundum grains represent different

  6. Evidence of Disturbance in the 26Al-26Mg Systematics of the Efremovka E60 CAI: Implications for the High-Resolution Chronology of the Early Solar System

    NASA Astrophysics Data System (ADS)

    Wadhwa, M.; Janney, P. E.; Krot, A. N.

    2009-03-01

    We report results of a laser ablation MC-ICPMS study of the Efremovka E60 CAI. Our data indicate that the 26Al-26Mg systematics in E60 are disturbed and we present the chronological implications of this finding.

  7. 26Al-26Mg systematics in D’Orbigny and Sahara 99555 angrites: Implications for high-resolution chronology using extinct chronometers

    NASA Astrophysics Data System (ADS)

    Spivak-Birndorf, Lev; Wadhwa, Meenakshi; Janney, Philip

    2009-09-01

    We report on an investigation of the 26Al- 26Mg isotope systematics in the D'Orbigny and Sahara 99555 angrites. High precision Mg isotope compositions and Al/Mg ratios were measured in mineral separates and whole rock samples from D'Orbigny and Sahara 99555 using multiple-collector inductively coupled plasma mass spectrometry (MC-ICPMS). Plagioclase separates from both angrites have resolvable excesses in 26Mg ( Δ26Mg) that correlate with their respective Al/Mg ratios. 26Al- 26Mg systematics in the mineral separates and whole rocks define precise isochrons that correspond to 26Al/ 27Al ratios of (5.06 ± 0.92) × 10 -7 and (5.13 ± 1.90) × 10 -7 and initial Δ26Mg values of -0.006 ± 0.040‰ and -0.016 ± 0.047‰ for D'Orbigny and Sahara 99555, respectively. The slopes and initial Δ26Mg values are identical for these two meteorites within errors and the data for both angrites considered together define an isochron corresponding to a 26Al/ 27Al ratio of (5.10 ± 0.55) × 10 -7 and initial Δ26Mg value of -0.012 ± 0.019. Relative to the Efremovka E60 CAI, the 26Al/ 27Al values reported here for these angrites imply 26Al- 26Mg ages of 4562.42 ± 0.29 Ma and 4562.43 ± 0.53 Ma for D'Orbigny and Sahara 99555, respectively. These 26Al- 26Mg ages are concordant with model ages determined using other extinct radionuclide chronometers (e.g., 53Mn- 53Cr and 182Hf- 182W), but are ˜2 Myr younger than the absolute 207Pb- 206Pb ages that have been reported recently for these angrites. The reason for this discrepancy is not presently known, but may imply disturbance of one or more of the isotope systems under consideration or a possible bias in the 207Pb- 206Pb ages of the angrites resulting from natural or analytical causes.

  8. Crystal chemistry of mimetite, Pb10(AsO4)6Cl1.48O0.26, and finnemanite, Pb10(AsO3)6Cl2.

    PubMed

    Baikie, Tom; Ferraris, Cristiano; Klooster, Wim T; Madhavi, S; Pramana, Stevin S; Pring, Allan; Schmidt, G; White, T J

    2008-02-01

    The crystal chemistries of synthetic mimetite, Pb(10)(As(5+)O(4))(6)(Cl(2 - x)O(x/2)), a neutral apatite, and finnemanite, Pb(10)(As(3+)O(3))(6)Cl(2), a reduced apatite, were characterized using a combination of X-ray powder diffraction, neutron diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Both phases conform to hexagonal P6(3)/m symmetry; however, the temperature-driven transformation of clinomimetite to mimetite described earlier was not confirmed. The average mimetite structure is best described through the introduction of partially occupied oxygen sites. A better understanding of the mixed arsenic speciation in apatites can guide the formulation of waste form ceramics and improve models of long-term durability after landfill disposal. PMID:18204209

  9. Formation of short-lived radionuclides in the protoplanetary disk during late-stage irradiation of a volatile-rich reservoir

    SciTech Connect

    Jacobsen, B; Matzel, J; Hutcheon, I D; Krot, A N; Yin, Q -; Nagashima, K; Ramon, E; Weber, P; Ishii, H; Ciesla, F

    2010-11-30

    The origin of short-lived (t{sub 1/2} < 5 Myr) and now extinct radionuclides ({sup 10}Be, {sup 26}Al, {sup 36}Cl, {sup 41}Ca, {sup 53}Mn, {sup 60}Fe; hereafter SLRs) is fundamental to understanding the formation of the early solar system. Two distinct classes of models have been proposed to explain the origin of SLRs: (1) injection from a nearby stellar source (e.g., supernova, asymptotic giant branch star or Wolf-Rayet star) and (2) solar energetic particle irradiation of dust and gas near the proto-Sun. Recent studies have demonstrated that {sup 36}Cl was extant in the early solar system. However, its presence, initial abundance and the noticeable decoupling from {sup 26}Al raise serious questions about the origin of SLRs. Here we report {sup 36}Cl-{sup 36}S and {sup 26}Al-{sup 26}Mg systematics for wadalite and grossular, secondary minerals in a calcium-aluminum-rich inclusion (CAI) from the CV chondrite Allende that allow us to reassess the origin of SLRs. The inferred abundance of {sup 36}Cl in wadalite, corresponding to a {sup 36}Cl/{sup 35}Cl ratio of (1.81 {+-} 0.13) x 10{sup -5}, is the highest {sup 36}Cl abundance reported in any early solar system material. The high level of {sup 36}Cl in wadalite and the absence of {sup 26}Al ({sup 26}Al/{sup 27}Al {le} 3.9 x 10{sup -6}) in co-existing grossular indicates that (1) {sup 36}Cl formed by late-stage solar energetic particle irradiation and (2) the production of {sup 36}Cl, recorded by secondary minerals, is unrelated to the origin of {sup 26}Al and other SLRs ({sup 10}Be, {sup 53}Mn) recorded by primary minerals of CAIs and chondrules. We conclude that 36Cl was produced by solar energetic particle irradiation of a volatile-rich reservoir in an optically thin protoplanetary disk adjacent to the accretion region of the CV chondrite parent asteroid.

  10. 26Al- 26Mg deficit dating ultramafic meteorites and silicate planetesimal differentiation in the early Solar System?

    NASA Astrophysics Data System (ADS)

    Baker, Joel A.; Schiller, Martin; Bizzarro, Martin

    2012-01-01

    Meteorites with significantly sub-chondritic Al/Mg that formed in the first 2 million years of the Solar System should be characterised by deficits in the abundance of 26Mg (δ26Mg∗) due to the absence of in-growth of 26Mg from the decay of short-lived 26Al (t1/2 = 0.73 Myr). However, these 26Mg deficits will be small (δ26Mg∗ >-0.037‰) even for material that formed at the same time as the Solar System’s oldest solids - calcium-aluminium-rich inclusions - and thus measurement of these deficits is analytically challenging. Here, we report on a search for 26Mg deficits in three types of ultramafic meteorites (pallasites, ureilites and aubrites) by multiple-collector inductively coupled plasma mass spectrometry. A range of analytical tests were carried out including analysis of: (1) a range of synthetic Mg solution standards; (2) Mg gravimetrically doped with a high purity 26Mg spike; (3) Mg cuts collected sequentially from cation exchange separation columns with fractionated stable Mg isotope compositions; (4) Mg separated from samples that was bracketed by analyses of both DSM-3 and Mg separated from a natural olivine sample subjected to the same chemical processing as the samples. These tests confirm it is possible to resolve differences in δ26Mg∗ from the terrestrial materials that are ⩽0.005‰. However, if Mg yields from chemical separation are low or an inappropriate equilibrium-isotopically fractionated standard is used this will generate analytical artefacts on δ26Mg∗ when this is calculated with the kinetic/exponential mass fractionation law as is the case when correcting for instrumental mass bias during mass spectrometric analysis. Olivine from four different main group pallasites and four bulk ureilites have small deficits in the abundance of 26Mg with δ26MgDSM-3∗=-0.0120±0.0018‰ and δ26MgDSM-3∗=-0.0062±0.0023‰, respectively, relative to terrestrial olivine (δ26MgDSM-3∗=+0.0029±0.0028‰). Six aubrites have δ26MgDSM-3

  11. 10Be application to soil development on Marion Island, southern Indian Ocean

    NASA Astrophysics Data System (ADS)

    Haussmann, N.; Aldahan, A.; Boelhouwers, J.; Possnert, G.

    2010-04-01

    Marion Island, located in the southern Indian Ocean, constitutes the summit of an active shield volcano. It is a small terrestrial environment where glacially abraded bedrock became exposed c × 10 kyr ago. These conditions provide an interesting possibility for the assessment of 10Be accumulation rates and their application to soil erosion studies on the island. 10Be concentrations were measured in precipitation, soil profiles and an Azorella selago cushion plant. The data reveal a 10Be precipitation flux several times higher than model prediction. Estimation of the 10Be accumulation based on the soil inventory suggests a span between 2000 and 7000 yr. This time span is not in accordance with the accepted notion that the island was covered with ice about 10,000 yr ago and suggests either removal of 10Be from the soil profile, an overestimated Holocene 10Be-flux or a delayed soil development history. Our results provide new data on 10Be concentrations from the sub-Antarctic islands and contribute towards enlarging the southern-hemisphere 10Be database.

  12. 10Be in Lake Lisan sediments — A proxy for production or climate?

    NASA Astrophysics Data System (ADS)

    Belmaker, Reuven; Lazar, Boaz; Tepelyakov, Natalya; Stein, Mordechai; Beer, Jürg

    2008-05-01

    The geochemical behavior of 10Be in the modern Dead Sea hydrological-limnological system was studied in order to evaluate the feasibility of using Dead Sea and Lake Lisan (the late Pleistocene precursor of the Dead Sea) sediments as archives of the variations in the 10Be production rate. 10Be concentrations in detrital and aragonite material from Lake Lisan laminated sediments were compared to those measured in modern dust, terra rossa soil (aeolian in origin), loess from the Negev Desert, flood suspended load and waters along a rain-flood development pathway (the transition from rain to incipient runoff and fully developed floods). 10Be concentrations decreased throughout the flood development profile, from 8.2 × 10 3 atoms g - 1 in the runoff down to ~ 1 × 10 3 atoms g - 1 in Dead Sea brine due to fast removal of 10Be by the soil and dust particles. Thus, most of the 10Be in the lake is contained within the detrital sediments that collect the 10Be transported by particles from the surrounding terrain (e.g. desert dust with 1.6 ± 0.8 × 10 8 atoms g - 1 and terra rossa soil-material with up to 12.5 ± 0.5 × 10 8 atoms g - 1 ). The high-stand periods of Lake Lisan were characterized by annual deposition of silty-detritus sediments reflecting rapid transfer of desert dust to the lake by floods. Indeed, the bulk sediments of Lake Lisan (in which 10Be is associated mainly with silty-detritus) display 10Be concentrations similar to those of desert dust. This demonstrates that 10Be variations were modulated by climate (i.e., particle transport). Significant positive 10Be peaks (up to 1.6 × 10 8 atoms g - 1 ) appear during intervals of geomagnetic anomalies in Lake Lisan stratigraphy and in the global record (i.e. during the Laschamp geomagnetic event at ~ 41 ka BP). This indicates that 10Be atmospheric production signal is superimposed on the climatic 10Be variations. We conclude that after "de-trending" of the climatic signal, Lake Lisan sediments may be used as

  13. Meteoric 10Be in Lake Cores as a Measure of Climatic and Erosional Change

    NASA Astrophysics Data System (ADS)

    Jensen, R. E.; Dixon, J. L.

    2015-12-01

    Utilization of meteoric 10Be as a paleoenvironmental proxy has the potential to offer new insights into paleoprecipitation records and paleoclimate models, as well as to long-term variations in erosion with climate. The delivery of meteoric 10Be to the surface varies with precipitation and its strong adsorption to sediment has already proven useful in studies of erosion. Thus, it is likely meteoric 10Be concentrations in lake sediments vary under both changing climate and changing sediment influx. Assessment of the relative importance of these changes requires the comparison of 10Be concentrations in well-dated lake cores with independent paleoenvironmental proxies, including oxygen isotope, pollen, and charcoal records, as well as variation in geochemical composition of the sediments. Blacktail Pond details 15,000 years of climatic change in the Yellowstone region. We develop a new model framework for predicting meteoric 10Be concentrations with depth in the core, based on sedimentation rates of both lake-derived and terrigenous sediments and changes in the flux of meteoric 10Be with precipitation. Titanium concentrations and previously determined 10Be concentrations in wind-derived loess provide proxies for changing delivery of 10Be to the lake by terrigenous sources. We use existing paleoenvironmental data obtained from this core and the surrounding region to develop models for changing rainfall across the region and predict meteoric 10Be delivery to the lake by precipitation. Based on a suite of ~10 models, sedimentation rate is the primary control of meteoric 10Be in the Blacktail Pond core unless terrestrial input is very high, as it was post-glacial in the early Holocene when the lake experienced a high influx of loess and terrigenous sediments. We used these models to inform sample selection for 10Be analysis along the Blacktail pond core. Core sediments are processed for meteoric 10Be analysis using sequential digestions and standard extraction procedures

  14. PRIME Lab Radiocarbon Measurements

    NASA Astrophysics Data System (ADS)

    Hillegonds, D. J.; Mueller, K. A.; Ma, X.; Lipschutz, M. E.

    1996-03-01

    The Purdue Rare Isotope Measurement Laboratory (PRIME Lab) is one of three NSF national facilities for accelerator mass spectrometry (AMS), and is the only one capable of determining six cosmogenic radionuclides: 10Be, 14C, 26Al, 36Cl, 41Ca, and 129I. This abstract describes the current status of the radiocarbon analysis program at PRIME Lab.

  15. A model-based evaluation of sedimentary reconstructions of 10Be production rates

    NASA Astrophysics Data System (ADS)

    Carney, Lewis; Plancherel, Yves; Khatiwala, Samar; Henderson, Gideon

    2016-04-01

    Atmospheric production of 10Be is small when solar activity and, therefore, solar magnetic field and total solar irradiance are strong. Variations in solar activity affect climate and the production of other climate-relevant isotopes, such as 14C. Solar activity is thus an important variable to constrain. Since 10Be production is clearly related to solar activity and the cycle of beryllium is simpler than that of carbon, 10Be records in ice cores have been used to reconstruct total solar irradiance variability. Unfortunately, 10Be records in ice cores are not only affected by variations in atmospheric production, but are also modulated by changes in wind patterns since spatiotemporal atmospheric 10Be gradients are quite large. In that context, sedimentary 10Be records from the abyssal ocean could be of great interest: since the residence time of 10Be in the ocean is thought to be comparable to the overturning time-scale of the ocean, spatial 10Be gradients may be relatively weaker than those in the atmosphere. Under these conditions, regional oceanic variability should only weakly affect the distribution of 10Be in the ocean and local sedimentary 10Be records are expected to represent the global average 10Be production better than 10Be measured in ice cores. We here show results from a global ocean model of 10Be that we use to investigate the spatial variability of simulated sedimentary 10Be records and test the sensitivity of the 10Be sedimentary flux to uncertainties in the circulation field and in the particle chemistry of beryllium. Our ocean model is based on the Transport Matrix method. The surface 10Be input fluxes are taken from atmospheric model simulations. Our model experiments, constrained by available dissolved 10Be data, show that there exist regions in the ocean where the sedimentary 10Be flux is relatively insensitive to changes in input patterns and magnitudes, assumed particle chemistry and flux patterns, and ocean circulation. We submit that

  16. Further improvement for 10Be measurement on an upgraded compact AMS radiocarbon facility

    NASA Astrophysics Data System (ADS)

    Fu, Dongpo; Ding, Xingfang; Liu, Kexin; Müller, Arnold Milenko; Suter, Martin; Christl, Marcus; Zhou, Liping; Synal, Hans-Arno

    2015-10-01

    The Peking University 500 kV NEC compact AMS radiocarbon facility (PKU-CAMS) has been modified in order to have additionally the possibility to measure 10Be. In the preliminary experiment a silicon nitride foil was mounted in front of the electrostatic deflector as passive boron degrader, and the original Si detector for radiocarbon detection was replaced by an ETHZ-designed high-resolution ΔE - Eres gas ionization chamber (GIC) for 10Be identification. This simple arrangement has yielded an overall 10Be transmission of 2.2% and a 10Be/9Be background level of 3.5 × 10-14. To further reduce the background and increase the transmission by re-focusing the 10Be ions, an additional 90° bending magnet with 350 mm radius was installed after the electrostatic deflector. The silicon detector was shifted slightly relative to its position of original NEC system setup in opposite direction of beam and can be lifted up manually without breaking vacuum when 10Be measurements are carried out. In this way the system can be easily and fast set up for 10Be without affecting any parameters for radiocarbon measurement. The gas detector for 10Be was mounted at the end of the beam line after the additional magnet. The lay-out of the upgraded spectrometer is very compact and does not require more space than the original instrument. Using this compact setup, the overall transmission for 10Be was doubled to 5-6% and the 10Be/9Be background level was reduced to radios as low as 2.4 × 10-15.

  17. Meteoric 10Be as a tool to investigate human induced soil fluxes: a conceptual model

    NASA Astrophysics Data System (ADS)

    Campforts, Benjamin; Govers, Gerard; Vanacker, Veerle; De Vente, Joris; Boix-Fayos, Carolina; Minella, Jean; Baken, Stijn; Smolders, Erik

    2014-05-01

    The use of meteoric 10Be as a tool to understand long term landscape behavior is becoming increasingly popular. Due its high residence time, meteoric 10Be allows in principle to investigate in situ erosion rates over time scales exceeding the period studied with classical approaches such as 137Cs. The use of meteoric 10Be strongly contributes to the traditional interpretation of sedimentary archives which cannot be unequivocally coupled to sediment production and could provide biased information over longer time scales (Sadler, 1981). So far, meteoric 10Be has successfully been used in geochemical fingerprinting of sediments, to date soil profiles, to assess soil residence times and to quantify downslope soil fluxes using accumulated 10Be inventories along a hill slope. However, less attention is given to the potential use of the tracer to directly asses human induced changes in soil fluxes through deforestation, cultivation and reforestation. A good understanding of the processes governing the distribution of meteoric 10Be both within the soil profile and at landscape scale is essential before meteoric 10Be can be successfully applied to assess human impact. We developed a spatially explicit 2D-model (Be2D) in order to gain insight in meteoric 10Be movement along a hillslope that is subject to human disturbance. Be2D integrates both horizontal soil fluxes and vertical meteoric 10Be movement throughout the soil prolife. Horizontal soil fluxes are predicted using (i) well studied geomorphical laws for natural erosion and soil formation as well as (ii) human accelerated water and tillage erosion. Vertical movement of meteoric 10Be throughout the soil profile is implemented by inserting depth dependent retardation calculated using experimentally determined partition coefficients (Kd). The model was applied to different environments such as (i) the Belgian loess belt, characterized by aeolian deposits enriched in inherited meteoric 10Be, (ii) highly degraded and stony

  18. 10Be in ice - four decades, two ice sheets, 15 deep coring sites

    NASA Astrophysics Data System (ADS)

    Berggren, Ann-Marie; Aldahan, Ala; Possnert, Göran

    2010-05-01

    Over the last few decades, numerous studies of 10Be in ice cores from Antarctica and Greenland have comprised a significant source of information on climate, solar activity and geomagnetic field intensity over the past 800 000 years. There is, however, a large variability in the available 10Be records in terms of resolution and time coverage. We here present a comprehensive summary of results that have been put forward since the 1960s. Marine sediment was the first type of natural archive in which 10Be was detected (Arnold, 1956), and a decade later McCorkell et al. (1967) pioneered the ice archive field by counting 10Be beta activity in samples from Camp Century, Greenland. The method demands a large amount of material; in this case 1.2×106 litres of water were used. Using accelerator mass spectrometry, AMS, Raisbeck et al. (1978) undertook the second study of 10Be in polar ice, measuring 10Be concentrations in ice from Dome C, Antarctica. The AMS technique is exclusively used today for measurements of 10Be in small ice volumes (

  19. A preliminary study on the use of (10)Be in forensic radioecology of nuclear explosion sites.

    PubMed

    Whitehead, N E; Endo, S; Tanaka, K; Takatsuji, T; Hoshi, M; Fukutani, S; Ditchburn, R G; Zondervan, A

    2008-02-01

    Cosmogenic (10)Be, known for use in dating studies, unexpectedly is also produced in nuclear explosions with an atom yield almost comparable to (e.g.) (137)Cs. There are major production routes via (13)C(n, alpha)(10)Be, from carbon dioxide in the air and the organic explosives, possibly from other bomb components and to a minor extent from the direct fission reaction. Although the detailed bomb components are speculative, carbon was certainly present in the explosives and an order of magnitude calculation is possible. The (n, alpha) cross-section was determined by irradiating graphite in a nuclear reactor, and the resulting (10)Be estimated by Accelerator Mass Spectrometry (AMS) giving a cross-section of 34.5+/-0.7mb (6-9.3MeV), within error of previous work. (10)Be should have applications in forensic radioecology. Historical environmental samples from Hiroshima, and Semipalatinsk (Kazakhstan) showed two to threefold (10)Be excesses compared with the background cosmogenic levels. A sample from Lake Chagan (a Soviet nuclear cratering experiment) contained more (10)Be than previously reported soils. (10)Be may be useful for measuring the fast neutron dose near the Hiroshima bomb hypocenter at neutron energies double those previously available. PMID:17904707

  20. Short term variations of 7Be, 10Be concentrations in atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Yamagata, Takeyasu; Sugihara, Sinji; Morinaga, Ichiro; Matsuzaki, Hiroyuki; Nagai, Hisao

    2010-04-01

    To compare meteorological conditions, short term variations of atmospheric concentrations of 7Be ( T1/2 = 53.3 days) and 10Be ( T1/2 = 1.5 × 10 6 years) were investigated at Tokyo and Fukuoka, Japan, and Pacific Ocean nearby Japan. Atmospheric concentrations of 7Be and 10Be at anticyclone condition were higher than that at cyclone condition to a factor of 2-10. Because of being influenced by re-suspended components from soil ( 10Be/ 7Be > 1000), temporal variability of 10Be/ 7Be was high in daytime and low in nighttime. But when corrected for re-suspended component using Al concentration as an indicator of soil the 10Be/ 7Be ratio was constant. Comparing 7Be and 10Be concentrations with 212Pb concentration as soil-generated component, we make a conclusion that high 7Be and 10Be concentration air mass is brought into boundary layer by high convection at daytime. Those diurnal variations were not observed in marine boundary layer. When cyclone passed through Fukuoka to Tokyo, which is 12 h behind, 7Be and 10Be concentrations also decreased with 12 h lag between Fukuoka and Tokyo. The 10Be/ 7Be ratio was constant during anticyclone to cyclone condition, and between Tokyo and Fukuoka. We conclude that after stratospheric aerosols enter into the upper troposphere they reside there for a certain period and mix uniformly in horizontal strata; later they are transported down to lower troposphere by anticyclone and penetrate into ground level air at daytime by convective strong mixing of boundary layer.

  1. Distribution of 10Be and 9Be in the Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Kusakabe, M.; Ku, T. L.; Southon, J. R.; Vogel, J. S.; Nelson, D. E.; Measures, C. I.; Nozaki, Y.

    1987-04-01

    The vertical distributions of 10Be and 9Be at three locations in the Pacific (25°N, 170°E; 17°N, 118°W; 3°S, 117°W) are presented. The results show that both isotopes exhibit nutrient-like profiles. From the surface to the bottom, the increase for 10Be is two- to threefold and that for 9Be is about fivefold. While the inter-station variations in surface water concentrations may reach a factor of two, deep-water values tend to be much more uniform averaging about 2000 atoms/g for 10Be and 30 pM for 9Be. A similar situation applies to the 10Be/ 9Be ratio; it varies approximately from 1 to 3 × 10 -7 (atom/atom) at shallow depths but tends toward a value close to 1.1 × 10 -7 in the deep ocean. The variation of 10Be/ 9Be can be viewed as resulting from the fact that 10Be in a given parcel of water consists of two components: recycled and primary. The recycled component is that part of 10Be which has reached tracer equilibrium with 9Be, as opposed to the primary component which, upon entering the sea from the atmosphere, has yet to equilibrate with 9Be through particle cycling and mixing processes. It is estimated that 70% to nearly 100% of 10Be at the three stations are being recycled, and the recycled beryllium bears an atomic ratio of 10Be/ 9Be close to 1 × 10 -7. The oceanic residence time of Be is of the order of 1000-4000 years, comparable to or slightly longer than the ocean mixing time.

  2. Testing the potential of 10Be in varved sediments from two lakes for solar activity reconstruction

    NASA Astrophysics Data System (ADS)

    Czymzik, Markus; Muscheler, Raimund; Brauer, Achim; Adolphi, Florian; Ott, Florian; Kienel, Ulrike; Dräger, Nadine; Slowinski, Michal; Aldahan, Ala; Possnert, Göran

    2015-04-01

    The potential of 10Be in annually laminated (varved) lake sediments for solar activity reconstruction is, to date, largely unexplored. It is hypothesized that 10Be contents in sediments from well-chosen lakes reflect the solar induced atmospheric production signal. The varved nature of these archives provides the chance to establish solar activity time-series with very high temporal precision. However, so far solar activity reconstruction from 10Be in varved lake sediments is hampered due to a lack of detailed knowledge of the process chain from production in the atmosphere to deposition on the lake floor. Calibrating 10Be time-series from varved lake sediments against complementary proxy records from the same sediment archive as well as instrumental meteorological and solar activity data will allow a process-based understanding of 10Be deposition in these lakes and a quantitative evaluation of their potential for solar activity reconstruction. 10Be concentration and flux time-series at annual resolution were constructed for the period 1983 to 2007 (approx. solar cycles 22 and 23) conducting accelerator mass spectrometry and varve chronology on varved sediments of Lakes Tiefer See and Czechowski, located on an east-west transect at a distance of about 450 km in the lowlands of northern-central Europe. 10Be concentrations vary between 0.9 and 1.8*108atoms/g, with a mean of 1.3*108atoms/g in Lake Tiefer See and between 0.6 and 1.6*108atoms/g, with a mean of 1*108atoms/g in Lake Czechowski. Calculated mean 10Be flux is 2.3*108atoms/cm2/year for Lake Tiefer See and 0.7*108atoms/cm2/year for Lake Czechowski. Calibrating the 10Be time-series against corresponding geochemical μ-XRF profiles, varve thickness and total organic carbon records as well as precipitation data from the nearby stations Schwerin for Lake Tiefer See and Koscierzyna for Lake Czechowski and a neutron monitor record of solar activity suggests (1) a complex interaction of varying processes influencing

  3. Investigation of 10Be and its cluster dynamics with the nonlocalized clustering approach

    NASA Astrophysics Data System (ADS)

    Lyu, Mengjiao; Ren, Zhongzhou; Zhou, Bo; Funaki, Yasuro; Horiuchi, Hisashi; Röpke, Gerd; Schuck, Peter; Tohsaki, Akihiro; Xu, Chang; Yamada, Taiichi

    2016-05-01

    We extend the concept of nonlocalized clustering to the nucleus 10Be with proton number Z =4 and neutron number N =6 (N =Z +2 ). The Tohsaki-Horiuchi-Schuck-Röpke (THSR) wave function is formulated for the description of different structures of 10Be. Physical properties such as energy spectrum and root-mean-square radii are calculated for the first two 0+ states and corresponding rotational bands. With only one single THSR wave function, the calculated results show good agreement with other models and experimental values. We apply, for the first time, the THSR wave function on the chain orbit (σ -orbit) structure in the 02+ state of 10Be. The ring-orbit (π -orbit) and σ -orbit structures are further illustrated by calculating the density distribution of the valence neutrons. We also investigate the nonlocalized dynamics of α clusters and the correlations of two valence neutrons in 10Be.

  4. 10Be analysis of a Quaternary weathering profile in the Virginia Piedmont.

    USGS Publications Warehouse

    Pavich, M.J.; Brown, Louis; Valette-Silver, J. Nathalie; Klein, Jeffrey; Middleton, Roy

    1985-01-01

    Samples from a residual weathering profile in the Virginia Piedmont have been analyzed for cosmogenic 10Be. Concentrations are highest in clay-rich soil and decrease exponentially to a depth of about 15 m. Despite uncertainties about the processes by which 10Be may be intercepted before entering the solum and eroded after incorporation, a minimum age may be calculated for the regolith. This calculation is based on the delivery rate of 10Be and its decay rate and suggests that this residual profile developed during a period no shorter than 8 × 105 yr. The calculated minimum age may be within a factor of 2 of maximum-age estimates based on surface lowering by erosion and on the rate of rock weathering to saprolite. The vertical distribution of 10Be in the profile could result from a steady-state balance of deposition, weathering, radioactive decay, and erosion.

  5. Analysis of T = 1 {sup 10}B States Analogue to {sup 10}Be Cluster States

    SciTech Connect

    Uroic, M.; Miljanic, D.; Blagus, S.; Bogovac, M.; Prepolec, L.; Skukan, N.; Soic, N.; Majer, M.; Milin, M.; Lattuada, M.; Musumarra, A.; Acosta, L.

    2009-08-26

    Current status of the search for T = 1 cluster states in {sup 10}Be, {sup 10}B and {sup 10}C is presented. The best known of the three, {sup 10}Be, has an established rotational band (6.18, 7.54 and 10.15 MeV) with unusually large moment of inertia. Search of their isobaric analogue in {sup 10}B is presented, with emphasis on {sup 3}He+{sup 11}B reaction.

  6. /sup 10/Be in polar ice: Data reflect changes in cosmic ray flux or polar meteorology

    SciTech Connect

    Lal, D.

    1987-08-01

    We have theoretically estimated the expected changes in the global cosmic ray production of /sup 10/Be in the atmosphere with changes in solar activity, and the consequent variations in its fallout in the polar regions. The global /sup 10/Be production rate is found to be about 20% higher during periods of very low solar activity, compared to the average solar modulation level observed during the past 3 solar cycles. The stratospheric /sup 10/Be fallout pattern has been derived using the fallout data for /sup 90/Sr as an analog. This fallout shows an amplitude attenuation by a factor of about three at 70/sup 0/; the higher the latitude, the higher the attenuation. The results have been compared with the long time series available for /sup 10/Be in polar ice in Greenland and in Antarctica, 70/sup 0/--78/sup 0/ latitude. It is concluded that the observed variations in /sup 10/Be concentrations in ice cores are primarily due to climatic changes, for both short and long period variations. Thus /sup 10/Be data can be used as a proxy for climate induced meteorological changes in the polar region. copyright American Geophysical Union 1987

  7. Preparation of ASTER in-house 10Be/9Be standard solutions

    NASA Astrophysics Data System (ADS)

    Braucher, R.; Guillou, V.; Bourlès, D. L.; Arnold, M.; Aumaître, G.; Keddadouche, K.; Nottoli, E.

    2015-10-01

    Since its commissioning in 2006, the commercially available certificated National Institute of Standards and Technology standard reference material NIST SRM 4325 is used at the French national facility ASTER (CEREGE, Aix-en-Provence) to normalize 10Be measurements. This standard solution being no longer disposable, we thus decided to produce in-house standards. As a first attempt, a STD-12 standard (10Be/9Be = (4.939 ± 0.053) × 10-12) has been prepared from 2.5 kg of marine sediments with an adapted chemical protocol. Then, a 10Be enriched solution of known concentration being available, a STD-11 standard (10Be/9Be = (1.191 ± 0.013) × 10-11) that will be used at ASTER in the near future to calibrate 10Be measurements and its dilution to the 10-14 level (STD-14 (10Be/9Be = (5.468 ± 0.064) × 10-14)) have been prepared from it.

  8. High-purity radionuclide production: material, construction, target chemistry for 26Al, 97Ru, 178W, 235Np, 236,237Pu

    NASA Astrophysics Data System (ADS)

    Dmitriev, S. N.; Zaitseva, N. G.; Starodub, G. Ya.; Maslov, O. D.; Shishkin, S. V.; Shishkina, T. V.; Buklanov, G. V.; Sabelnikov, A. V.

    1997-02-01

    The work on isotopically pure 26Al, 97Ru, 178W/ 178Ta, 235Np, 236Pu and 237Pu production was initiated because of intensive research on their applications in the biomedical field and environmental chemistry. The conditions for isotopically pure production have been investigated. This paper describes the data for the nuclear reactions of the radionuclide production, the different target designs and target chemistry procedures.

  9. Be2D: A model to understand the distribution of meteoric 10Be in soilscapes

    NASA Astrophysics Data System (ADS)

    Campforts, Benjamin; Vanacker, Veerle; Vanderborght, Jan; Govers, Gerard

    2016-04-01

    Cosmogenic nuclides have revolutionised our understanding of earth surface process rates. They have become one of the standard tools to quantify soil production by weathering, soil redistribution and erosion. Especially Beryllium-10 has gained much attention due to its long half-live and propensity to be relatively conservative in the landscape. The latter makes 10Be an excellent tool to assess denudation rates over the last 1000 to 100 × 103 years, bridging the anthropogenic and geological time scale. Nevertheless, the mobility of meteoric 10Be in soil systems makes translation of meteoric 10Be inventories into erosion and deposition rates difficult. Here we present a coupled soil hillslope model, Be2D, that is applied to synthetic and real topography to address the following three research questions. (i) What is the influence of vertical meteoric Be10 mobility, caused by chemical mobility, clay translocation and bioturbation, on its lateral redistribution over the soilscape, (ii) How does vertical mobility influence erosion rates and soil residence times inferred from meteoric 10Be inventories and (iii) To what extent can a tracer with a half-life of 1.36 Myr be used to distinguish between natural and human-disturbed soil redistribution rates? The model architecture of Be2D is designed to answer these research questions. Be2D is a dynamic model including physical processes such as soil formation, physical weathering, clay migration, bioturbation, creep, overland flow and tillage erosion. Pathways of meteoric 10Be mobility are simulated using a two step approach which is updated each timestep. First, advective and diffusive mobility of meteoric 10Be is simulated within the soil profile and second, lateral redistribution because of lateral soil fluxes is calculated. The performance and functionality of the model is demonstrated through a number of synthetic and real model runs using existing datasets of meteoric 10Be from case-studies in southeastern US. Brute

  10. 10Be variation in surficial sediments of the Central Indian Basin

    NASA Astrophysics Data System (ADS)

    Nagender Nath, B.; Aldahan, A.; Possnert, G.; Selvaraj, K.; Mascarenhas-Pereira, M. B. L.; Chen, C. T. A.

    2007-06-01

    Distribution of 10Be in systematically collected (degree × degree interval at 10 to 16 °S; 73.5 to 76.5 °E) surficial siliceous ooze, siliceous clay and pelagic clay sediments (top 2 cm) from the abyssal Central Indian Basin and the Andaman Sea is used to evaluate sources and to decipher the transport pathways of sediment particles, demarcate sediment depocenters and erosional areas. While 10Be concentrations display a wide variation (0.12-5.56 × 109 atoms g-1) with an average of 3.58 × 109 atoms g-1 in the Central Indian Basin, the values in the Andaman Sea are uniform with an average of 1.49 × 109 atoms g-1. The 10Be/9Be values in the Central Indian Basin sediments range between 0.06 and 2.99 × 10-8 atoms atoms-1 and average to ∼1.56 × 10-8 atoms atoms-1. Correlation of 10Be data with some selected major (Al, Mn, Ti) and trace (Rb and Ba) elements suggest that large part of the isotope has been supplied through direct atmospheric fallout from the water column and minor part from lithogenic detrital flux. Significantly lower 10Be accumulation rates in the Central Indian Basin and an order of magnitude higher in the Andaman Sea sediments compared to the estimated global average production rates indicate removal of the isotopes at the continental margins. Bottom topography seems to exert control on local 10Be variation, where sediments deposited in valleys or topographic depressions contain higher 10Be concentrations in contrast to the probably erosion-dominated areas at the slopes and troughs.

  11. Tropical glacier fluctuations in the Cordillera Blanca, Peru between 12.5 and 7.6 ka from cosmogenic 10Be dating

    NASA Astrophysics Data System (ADS)

    Glasser, Neil F.; Clemmens, Samuel; Schnabel, Christoph; Fenton, Cassandra R.; McHargue, Lanny

    2009-12-01

    We report cosmogenic surface exposure 10Be ages of 21 boulders on moraines in the Jeullesh and Tuco Valleys, Cordillera Blanca, Peru (˜10°S at altitudes above 4200 m). Ages are based on the sea-level at high-latitude reference production rate and scaling system of Lifton et al. (2005. Addressing solar modulation and long-term uncertainties in scaling secondary cosmic rays for in situ cosmogenic nuclide applications. Earth and Planetary Science Letters 239, 140-161) in the CRONUS-Earth online calculator of Balco et al. (2008. A complete and easily accessible means of calculating surface exposure ages or erosion rates from 10Be and 26Al measurements. Quaternary Geochronology 3, 174-195). Using the Lifton system, large outer lateral moraines in the Jeullesh Valley have a 10Be exposure age of 12.4 ka, inside of which are smaller moraine systems dated to 10.8, 9.7 and 7.6 ka. Large outer lateral moraines in the Tuco Valley have a 10Be exposure age of 12.5 ka, with inner moraines dated to 11.3 and 10.7 ka. Collectively, these data indicate that glacier recession from the Last Glacial Maximum (LGM) in the Cordillera Blanca was punctuated by three to four stillstands or minor advances during the period 12.5-7.6 ka, spanning the Younger Dryas Chronozone (YDC; ˜12.9-11.6 ka) and the cold event identified in Greenland ice cores and many other parts of the world at 8.2 ka. The inferred fluctuations of tropical glaciers at these times, well after their withdrawal from the LGM, indicate an increase in precipitation or a decrease in temperature in this region. Although palaeoenvironmental records show regional and temporal variability, comparison with proxy records (lacustrine sediments and ice cores) indicate that regionally this was a cold, dry period so we ascribe these glacier advances to reduced atmospheric temperature rather than increased precipitation.

  12. Using the 10-Be Grain Size Dependency in Alluvial Sediments to Investigate Hillslope and Channel Processes

    NASA Astrophysics Data System (ADS)

    Belmont, P.; Pazzaglia, F. J.; Gosse, J.

    2006-12-01

    The method for estimating basin-wide erosion rates from in situ produced 10-Be in alluvial sediments has matured over the past decade; nevertheless, several applications have not been fully explored. Foremost among these is identifying hillslope weathering and erosion processes through a study of the cosmogenic inventories of specific grain-size fractions of alluvial sediment. We applied a nested sampling strategy to two (6-12 km 2) basins on the Olympic Peninsula, western Washington State, to investigate how cosmogenic nuclides are sequestered across different alluvial grain sizes. Alluvium was sampled near the mouth and headwaters of each basin. The 10-Be concentration in river-borne quartz was measured for two grain-size fractions, medium-sized sand (0.25 - 0.50 mm) and an amalgamation of 80+ cobbles (22.6 - 90 mm). Extensive granulometry was conducted at each site and several different methods were used to qualify weathering intensity of channel boulders, which differs substantially for the two basins. We observed different concentrations of 10-Be in all eight grain size fractions. At both headwater sites the cobbles consistently exhibit 25% lower 10-Be concentrations, compared to sand. In contrast, the cobbles in the downstream sites differed with one basin exhibiting 22% higher 10-Be concentration compared to sand and the other site exhibiting 55% lower 10-Be concentration in the cobbles, compared to sand. A GIS was used to extract basin morphological metrics including basin hypsometry, hillslope gradient and channel gradient. Concentrations of 10-Be at the headwater sites are best explained by shielding of the coarser grain size fraction and its delivery to the channel by deep-seated landslide processes. The contrasting grain-size dependency at the two downstream sites requires a more complex interplay between hillslope and channel processes including cobble weathering and grain size reduction during fluvial transport. Although preliminary, these results

  13. Exploring ice core drilling chips from a cold Alpine glacier for cosmogenic radionuclide (10Be) analysis

    NASA Astrophysics Data System (ADS)

    Zipf, Lars; Merchel, Silke; Bohleber, Pascal; Rugel, Georg; Scharf, Andreas

    Ice cores offer unique multi-proxy paleoclimate records, but provide only very limited sample material, which has to be carefully distributed for various proxy analyses. Beryllium-10, for example, is analysed in polar ice cores to investigate past changes of the geomagnetic field, solar activity, and the aerosol cycle, as well as to more accurately date the material. This paper explores the suitability of a drilling by-product, the so-called drilling chips, for 10Be-analysis. An ice core recently drilled at a cold Alpine glacier is used to directly compare 10Be-data from ice core samples with corresponding drilling chips. Both sample types have been spiked with 9Be-carrier and identically treated to chemically isolate beryllium. The resulting BeO has been investigated by accelerator mass spectrometry (AMS) for 10Be/9Be-ratios to calculate 10Be-concentrations in the ice. As a promising first result, four out of five sample-combinations (ice core and drilling chips) agree within 2-sigma uncertainty range. However, further studies are needed in order to fully demonstrate the potential of drilling chips for 10Be-analysis in alpine and shallow polar ice cores.

  14. Reactive and dissolved meteoric 10Be/9Be ratios in the Amazon basin

    NASA Astrophysics Data System (ADS)

    Wittmann, Hella; Dannhaus, Nadine; von Blanckenburg, Friedhelm; Bouchez, Julien; Suessenberger, Annette; Guyot, Jean-Loup; Maurice, Laurence; Filizola, Naziano; Gaillardet, Jerome; Christl, Marcus

    2014-05-01

    Recently, the ratio of the meteoric cosmogenic nuclide 10Be to stable 9Be has been established as a weathering and erosion proxy where meteoric 10Be/9Be ratios in reactive phases of secondary weathering products leached from detrital Amazonian river sediment were measured[1]. For this dataset, we derived a new 10Be-based mass balance, which compares the fluxes exported during erosion and weathering, Fout, calculated by the sum of [10Be]reac multiplied by gauging-derived sediment discharge and [10Be]dissmultiplied by water discharge, to the meteoric depositional flux Fin. This assessment allows evaluating the weathering state of the Amazon basin. Further, in order to assess equilibration of reactive phases in the water column, we measured (10Be/9Be)reac ratios leached from suspended sediments for two depth profiles of the Amazon (55m depth) and Madeira (12m depth) Rivers, their corresponding surface dissolved 10Be/9Be ratios, as well as dissolved ratios of smaller Amazon tributaries (Beni, Madre de Dios) to compare with published reactive ratios[1]. In these rivers, modest pH and salinity fluctuations help to constrain a 'simple' system that might however still be affected by seasonally changing isotopic compositions between water and suspended sediment[2] and seasonal fluctuations of TSS and TDS[3]. The 10Be-based mass balance shows that in Andean source areas Fout/Fin ≡1, indicating a balance between ingoing and exported flux, whereas in the Shield headwaters, Fout/Fin=0.3, indicating a combination of decay of 10Be during storage and little export of 10Be associated with particulate and dissolved loads. In central Amazonia, the export of 10Be decreases slightly relative to its atmospheric flux as evidenced by Fout/Fin=0.8 for the Amazon and Madeira Rivers. This value is interpreted as being close to steady state, but its modification could be due to additions of Shield-derived sediment to sediment carried in the main river[4]. Regarding the depth profiles, our

  15. Cosmogenic 36Cl exposure ages reveal a 9.3 ka BP glacier advance and the Late Weichselian-Early Holocene glacial history of the Drangajökull region, northwest Iceland

    NASA Astrophysics Data System (ADS)

    Brynjólfsson, Skafti; Schomacker, Anders; Ingólfsson, Ólafur; Keiding, Jakob K.

    2015-10-01

    We present twenty-four new cosmogenic isotope (36Cl) surface exposure ages from erratic boulders, moraine boulders and glacially eroded bedrock that constrain the late Weichselian to Holocene glacial history of the Drangajökull region, northwest Iceland. The results suggest a topographically controlled ice sheet over the Vestfirðir (Westfjords) peninsula during the last glaciation. Cold based non-erosive sectors of the ice sheet covered most of the mountains while fjords and valleys were occupied with erosive, warm-based ice. Old36Cl exposure ages from highlands and mountain plateaux (L8; 76.5 ka and H1; 41.6 ka) in combination with younger erratic boulders (L7; 26.2 and K1-K4; 15.0-13.8 ka) superimposed on such surfaces suggest the presence of non-erosive ice over uplands and plateaux in the Vestfirðir peninsula during the last glaciation. Glacially scoured terrain and erratic boulders yielding younger exposure ages (L1-L6; 11.3-9.1 ka and R1, R6-R7; 10.6-9.4 ka) in the lowland areas indicate that the valleys and fjords of the Vestfirðir peninsula were occupied by warm-based, dynamic ice during the last glaciation. The deglaciation of mountain Leirufjall by 26.2 ka BP suggests that ice thinning and deglaciation of some mountains and plateaux preceded any significant lateral retreat of the ice sheet. Subsequently this initial ice thinning was followed by break-up of the shelf based ice sheet off Vestfirðir about 15 ka BP. Hence, the new exposure ages suggest a stepwise asynchronous deglaciation on land, following the shelf break-up with some valleys and most of the highlands, ice free by 14-15 ka BP. The outermost moraine at the mouth of Leirufjörður is dated to 9.3 ka BP, and we suggest the moraine to be formed by a glacier re-advance in response to a cooler climate forced by the reduced Atlantic Meridional Overturning Circulation at around 9.3 ka BP. A system of moraines proximal to the 9.3 ka moraine in Leirufjörður as well as a 9.4 ka deglaciation age

  16. Late Pleistocene glacial chronology of the Retezat Mts, Southern Carpathians, using 10Be exposure ages

    NASA Astrophysics Data System (ADS)

    Ruszkiczay-Rüdiger, Zsófia; Kern, Zoltán; Urdea, Petru; Braucher, Régis; Madarász, Balázs; Schimmelpfennig, Irene

    2015-04-01

    Our knowledge on the timing of glacial advances in the Southern Carpathians is limited. Recently, some attempts have been made to develop an improved temporal framework for the glaciations of the region using cosmogenic 10Be exposure dating. However, glacial chronology of the Romanian Carpathians remains contradictory. E.g. the timing of the maximum ice advance appears to be asynchronous within the area and also with other dated glacial events in Europe. Main objective of our study is to utilize cosmogenic in situ produced 10Be dating to disentangle the contradictions of the Southern Carpathian Late Pleistocene glacial chronology. Firstly, previously published 10Be data are recalculated in accordance with the new half-life, standardization and production rate of 10Be. The recalculated 10Be exposure ages of the second largest (M2) moraines in the Retezat Mts. appear to be ca. 19-24% older than exposure ages calculated by Reuther et al. (2007, Quat. Int. 164-165, 151-169). This contradicts the earlier conclusions suggesting post LGM age of M2 glacial advance and suggests that M2 moraines can be connected to the end of the LGM with final stabilization possibly at the beginning of the Late Glacial. We emphasize that it is ambiguous to correlate directly the exposure-dated glacier chronologies with millennial scale climate changes due to uncertainties in sample collection and in computation of exposure ages from measured nuclide concentrations. New 10Be samples were collected in order to determine the 10Be exposure age of moraines outside the most prominent generation (M2) including the largest and oldest moraine (M1) and the landforms connected to the smallest ice advances (M4), which remained undated so far. The new exposure ages of M2 moraines are well in harmony with the recalculated ages of Reuther at al. (2007). 10Be exposure age of boulders on the smallest moraine suggest that the last glaciers disappeared in the area during the Late Glacial, indicating no

  17. Earth surface erosion and weathering from the 10Be (meteoric)/9Be ratio

    NASA Astrophysics Data System (ADS)

    von Blanckenburg, F.; Bouchez, J.; Wittmann, H.; Dannhaus, N.

    2012-12-01

    A perfect clock of the stability of the Earth surface is one that combines a first isotope the flux of which depends on the release rate during erosion, and a second isotope produced at constant rate. The ratio of the meteoric cosmogenic nuclide 10Be to stable 9Be is such a system. We provide a quantitative framework for its use. In a weathering zone some of the 9Be, present typically in 2.5ppm concentrations in silicate minerals, is released and partitioned between a reactive phase (adsorbed to clay and hydroxide surfaces, given the high partition coefficients at intermediate pH), and into the dissolved phase. The combined mass flux of both phases is defined by the soil formation rate and a mineral dissolution rate - and is hence proportional to the chemical weathering rate and the denudation rate. At the same time, the surface of the weathering zone is continuously exposed to fallout of meteoric 10Be. This 10Be percolates into the weathering zone where it mixes with dissolved 9Be. Both isotopes may exchange with the adsorbed Be, given that equilibration rate of Be is fast relative to soil residence times. Hence a 10Be/9Be(reactive) ratio results in soils from which the total denudation rate can be calculated. A prerequisite is that the flux of meteoric 10Be is known from field experiments or from global production models [1], that the 9Be concentration in bedrock (mostly 2.5ppm) is known [2], and that the reactive Be can be chemically extracted from soil or sediment [3]. In rivers, when reactive Be and dissolved Be equilibrate, a catchment-wide denudation rate can be determined from both sediment and a sample of filtered river water, where the sediment 10Be/9Be ratio is independent of grain size. We have tested this approach in sediment-bound Be and dissolved Be in water of the Amazon and Orinoco basin. The reactive Be was extracted from sediment by combined hydroxylamine and HCl leaches [2]. In the Amazon trunk stream, the Orinoco, Apure, and La Tigra river 10Be

  18. Constraints on the sedimentation history of San Francisco Bay from 14C and 10Be

    USGS Publications Warehouse

    VanGeen, A.; Valette-Silver, N. J.; Luoma, S.N.; Fuller, C.C.; Baskaran, M.; Tera, F.; Klein, J.

    1999-01-01

    Industrialization and urbanization around San Francisco Bay as well as mining and agriculture in the watersheds of the Sacramento and San Joaquin rivers have profoundly modified sedimentation patterns throughout the estuary. We provide some constraints on the onset of these erosional disturbances with 10Be data for three sediment cores: two from Richardson Bay, a small embayment near the mouth of San Francisco Bay, and one from San Pablo Bay, mid-way between the river delta and the mouth. Comparison of pre-disturbance sediment accumulation determined from three 14C-dated mollusk shells in one Richardson Bay core with more recent conditions determined from the distribution of 210Pb and 234Th [Fuller, C.C., van Geen, A., Baskaran, M, Anima, R.J., 1999. Sediment chronology in San Francisco Bay, California, defined by 210Pb, 234Th, 239,240Pu.] shows that the accumulation rate increased by an order of magnitude at this particular site. All three cores from San Francisco Bay show subsurface maxima in 10Be concentrations ranging in magnitude from 170 to 520 x 106 atoms/g. The transient nature of the increased 10Be input suggests that deforestation and agricultural develop- ment caused basin-wide erosion of surface soils enriched in 10Be. probably before the turn of the century.

  19. 10Be climate fingerprints during the Eemian in the NEEM ice core, Greenland

    PubMed Central

    Sturevik-Storm, Anna; Aldahan, Ala; Possnert, Göran; Berggren, Ann-Marie; Muscheler, Raimund; Dahl-Jensen, Dorthe; Vinther, Bo M.; Usoskin, Ilya

    2014-01-01

    Several deep Greenland ice cores have been retrieved, however, capturing the Eemian period has been problematic due to stratigraphic disturbances in the ice. The new Greenland deep ice core from the NEEM site (77.45°N, 51.06°W, 2450 m.a.s.l) recovered a relatively complete Eemian record. Here we discuss the cosmogenic 10Be isotope record from this core. The results show Eemian average 10Be concentrations about 0.7 times lower than in the Holocene which suggests a warmer climate and approximately 65–90% higher precipitation in Northern Greenland compared to today. Effects of shorter solar variations on 10Be concentration are smoothed out due to coarse time resolution, but occurrence of a solar maximum at 115.26–115.36 kyr BP is proposed. Relatively high 10Be concentrations are found in the basal ice sections of the core which may originate from the glacial-interglacial transition and relate to a geomagnetic excursion about 200 kyr BP. PMID:25266953

  20. The drainage of the Baltic Ice Lake and a new Scandinavian reference 10Be production rate

    NASA Astrophysics Data System (ADS)

    Stroeven, Arjen P.; Heyman, Jakob; Fabel, Derek; Björck, Svante; Caffee, Marc W.; Fredin, Ola; Harbor, Jonathan M.

    2015-04-01

    An important constraint on the reliability of cosmogenic nuclide exposure dating is the derivation of tightly controlled production rates. We present a new dataset for 10Be production rate calibration from Mount Billingen, southern Sweden, the site of the final drainage of the Baltic Ice Lake, an event dated to 11,620 ± 100 cal yr BP. Nine samples of flood-scoured bedrock surfaces and depositional boulders and cobbles unambiguously connected to the drainage event yield a reference 10Be production rate of 4.09 ± 0.22 atoms g-1 yr-1 for the CRONUS Lm scaling and 3.93 ± 0.21 atoms g-1 yr-1 for the LSD general spallation scaling. We also recalibrate the reference 10Be production rates for four sites in Norway and combine these with the Billingen results to derive a tightly clustered Scandinavian reference 10Be production rate of 4.12 ± 0.10 (4.12 ± 0.25 for altitude scaling) atoms g-1 yr-1 for the Lm scaling scheme and 3.96 ± 0.10 (3.96 ± 0.24 for altitude scaling) atoms g-1 yr-1 for the LSD scaling scheme.

  1. A new 3D numerical model of cosmogenic nuclide 10Be production in the atmosphere

    NASA Astrophysics Data System (ADS)

    Kovaltsov, Gennady A.; Usoskin, Ilya G.

    2010-03-01

    A new quantitative model of production of the cosmogenic isotope 10Be by cosmic rays in the Earth's atmosphere is presented. The CRAC:10Be (Cosmic Ray induced Atmospheric Cascade for 10Be) model is based on a full numerical Monte-Carlo simulation of the nucleonic-electromagnetic-muon cascade induced by cosmic rays in the atmosphere and is able to compute the isotope's production rate at any given 3D location (geographical and altitude) and time, for all possible parameters including solar energetic particle events. The model was tested against the results of direct measurements of the 10Be production in a number of dedicated experiments to confirm its quantitative correctness. A set of tabulated values for the yield function is provided along with a detailed numerical recipe forming a "do-it-yourself" kit, which allows anyone interested to apply the model for any given conditions. This provides a useful tool for applying the cosmogenic isotope method in direct integration with other models, e.g., dynamical atmospheric transport.

  2. Dilute Nuclear States: {sup 12}C, {sup 10}Be and {sup 14}C

    SciTech Connect

    Freer, M.

    2008-11-11

    The experimental evidence for dilute {alpha}-particle states in {sup 12}C, {sup 10}Be and {sup 14}C is discussed. The question of the location of the 2{sup +} excitation of the 7.65 MeV {sup 12}C state remains unresolved, as does the existence of possible analogue states in {sup 14}C.

  3. Cosmogenic production of 7Be and 10Be in water targets

    NASA Astrophysics Data System (ADS)

    Nishiizumi, K.; Finkel, R. C.; Klein, J.; Kohl, C. P.

    1996-10-01

    We have measured 10Be (t1/2=1.5×106 years) and 7Be (t1/2=53.28 days) concentrations in water targets exposed for 1 to 2 years at Echo Lake, Colorado (elevation=3246 m) and at La Jolla, California (140 m). Neutron monitor data were used to normalize the measured concentrations in order to calculate production rates equivalent to the cosmic ray flux averaged over four solar cycles (43 years). The 7Be production rates thus obtained correspond to 6.03+/-0.07×10-6 atomg-1.Os-1 at Echo Lake and 5.06+/-0.20×10-7 atomg-1.Os-1 at La Jolla. The 10Be production rates correspond to 3.14+/-0.18×10-6 atomg-1.Os-1 at Echo Lake and 2.68+/-0.47×10-7 atomg-1.Os-1 at La Jolla. When compared with 10Be production rates determined in 10Be-saturated rocks from the Antarctic and with theoretical calculations based on meteorite and lunar sample data, we find that the million-year average production rate is about 14-17% greater than the present production rate averaged over the last four solar cycles. Comparison with production rates determined by measuring glacially polished rocks from the Sierra Nevada in California indicates that average production (based on a revised 13,000-year deglaciation age and a geographic latitude correction) is about 11% greater than the average over the last four solar cycles. The measured 10Be/7Be production ratio in oxygen is 0.52+/-0.03 at Echo Lake and 0.55+/-0.07 at La Jolla.

  4. Particle trajectories on hillslopes: Implications for particle age and 10Be structure

    NASA Astrophysics Data System (ADS)

    Anderson, Robert S.

    2015-09-01

    Many geomorphic systems act as conveyor belts onto which material is loaded at a particular rate and is transported in one direction toward another system that serves as a sink. As the material travels, it ages, it changes in grain size, it accumulates cosmogenic radionuclides, it adsorbs or releases nutrients, and it weathers. Here I address the hillslope conveyor. As many geochemical processes are depth-dependent, the depth history of a particle becomes important to know. I calculate soil particle trajectories in the horizontal-depth plane and address three cases, one in which horizontal speeds decline exponentially with depth, a second in which they are uniform with depth, and a third in which horizontal speeds are also uniform but all profile values are vertically well-mixed. Vertical speeds are governed by continuity in an incompressible medium and by the boundary condition of zero vertical particle speed at the soil surface. Particle trajectories must therefore become surface parallel at the surface. Knowledge of soil particle trajectories allows calculation of residence times and concentration profiles of 10Be in the soil. The results inform strategies for interpretation of nuclide concentrations in soils and stream sediments and for inference of transport rate profiles. In all steady cases, the particle age and 10Be structure are uniform with distance from the divide. When significant vertical gradients in horizontal speed occur, the patterns of particle age and of 10Be concentration are dominated by the depth scale of the transport process. In unmixed cases, the particle age and 10Be concentration in near-surface samples can greatly exceed the vertically averaged values, reflecting the fact that the vertical speeds of particles slow dramatically as they near the surface. In cases in which horizontal speed varies significantly with depth, the vertically averaged concentration of 10Be within the soil can significantly underpredict the mean 10Be concentration

  5. Headwall erosion rates from cosmogenic (10) Be in supraglacial debris, Chhota Shigri Glacier, Indian Himalaya

    NASA Astrophysics Data System (ADS)

    Scherler, Dirk; Egholm, David

    2016-04-01

    Debris-covered glaciers are widespread within the Himalaya and other steep mountain ranges. They testify to active erosion of ice-free bedrock hillslopes that tower above valley glaciers, sometimes more than 1 km high. It is long known that debris cover significantly reduces surface ablation rates and thereby influences glacial mass balances; but its dynamic evolution along with climatic and topographic changes is poorly studied. Better understanding the coupling of ice-free bedrock hillslopes and glaciers in steep mountains requires means to assess headwall erosion rates. Here, we present headwall erosion rates derived from 10Be concentrations in the ablation-dominated medial moraine of the Chhota Shigri Glacier, Indian Himalaya. We combine our empirical, field-based approach with a numerical model of headwall erosion and glacial debris transport to assess permissible patterns of headwall erosion on the ice-free bedrock hillslopes surrounding the Chhota Shigri Glacier. Our five samples, each separated by approximately 500 m along the glacier, consist of an amalgamation of >1000 surface clasts with grain sizes between ˜1 and ˜30 mm that were taken from the medial moraine. Our results show that 10Be concentrations increase downglacier from ˜3×104 to ˜6×104 atoms g‑1, yielding headwall erosion rates of ˜1.3-0.6 mm yr‑1. The accumulation of 10Be during debris residence on the ice surface can only account for a small fraction (<20%) of the downglacier increase. Other potential explanations include (1) heterogeneous source areas with differences average productions rates, and (2) homogeneous source areas but temporally variable headwall erosion rates. We use the 10Be-derived headwall erosion rates to define debris supply rates from ice-free bedrock hillslopes in the numerical ice model iSOSIA. Headwall debris that is deposited in the ablation zone of the ice surface becomes englacial, is passively advected with the ice and emerges in the ablation zone where

  6. 10Be Content in Suevite Breccia from the Bosumtwi Impact Crater

    NASA Astrophysics Data System (ADS)

    Losiak, Anna; Wild, Eva Maria; Michlmayr, Leonard; Koeberl, Christian

    2013-04-01

    Introduction: According to the current understanding of meteorite impact processes, surface target material is transported from a crater in the form of ejecta or is vaporized/melted (e.g., [1]). The formation model of tektites from the surface of the target rocks has been established using the 10Be content of tektites (e.g., [2]), and chemical comparison with the possible target surface material (e.g., [3]); it was also reproduced by computer modeling (e.g., [4]). On the other hand, some observations ([5, 6]) suggest that part of the surface material may be incorporated into the crater-fill. The aim of this study is to check if surface-derived material is present in suevitic breccias to better understand formation mechanisms of fallback breccias. Also, 10Be can be used to trace contamination of rocks in the top layer of the suevitic layer by meteoric (lake) water. This abstract is an update (based on more data now available) of the previous report presented during the Metsoc75 conference. Samples: The Bosumtwi crater was chosen as study site because of its relatively large size (10.5 km in diameter), young age of 1.07 Ma [7], good state of preservation, and availability of core samples. Clasts from suevitic breccia selected for this study come from the LB-07A and LB-08A cores that are located within the crater and represent fallback breccia (e.g., [7]). Of 41 analyzed samples (22 single clasts and 21 matrix samples - 11 of those being monomictic breccia), 36 came from core LB-07A (in the zone outside the central uplift) and represent depths of 333.7 - 407.9 m and 5 are from core LB-08A (on the flank of the central uplift) from depths 239.5 - 264.9 m. Methods: For each sample, 0.8 g of finely grounded material from clasts containing in situ produced and meteoric 10Be was dissolved in a mixture of HF and HNO3 by microwave digestion. A 9Be carrier (1 mg or 0.6 mg, 10Be/9Be ratio: 2.82±0.31*10-15 [2? uncertainty]) was added to the sample, and then Be was chemically

  7. Radiative 10Be(n, γ)11Be capture at thermal and astrophysical energies

    NASA Astrophysics Data System (ADS)

    Dubovichenko, S. B.; Dzhazairov-Kakhramanov, A. V.

    2016-09-01

    The modified potential cluster model with the forbidden states and the classification of states according to the Young tableaux, which are irreducible representations of permutation symmetric group SU(4), was used in this paper. Within the framework of this model the possibility of describing the experimental data available for the total reaction cross sections and the reaction rate of neutron radiative capture on 10Be at thermal and astrophysical energies has been shown.

  8. 10Be exposure dating of Holocene moraines in the Sierra Nevada, California

    NASA Astrophysics Data System (ADS)

    Hidy, Alan; Zimmerman, Susan; Finkel, Robert; Schaefer, Jeorg; Clark, Douglas

    2016-04-01

    Constraint on the extent and timing of Holocene glaciations is critical to addressing standing hypotheses that ascribe climatic fluctuations to changes in atmospheric and oceanic circulation patterns, or anthropogenic forcing. In the terrestrial record, such constraint typically relies on chronologies obtained from 10Be exposure dating of moraine deposits. However, the short exposure time of Holocene moraines, particularly those formed during the Little Ice Age (LIA), makes obtaining precise chronologies extremely challenging. To date, only a handful of LIA deposits in two locations (New Zealand and the Swiss Alps) have been successfully dated with 10Be. Here, we report new 10Be exposure ages from LIA and Neoglacial moraines from multiple sites in the Sierra Nevada (Lyell, Maclure, and Palisade glaciers). The Sierran LIA record will be compared to those from New Zealand and the Swiss Alps to test whether LIA deglaciation was globally synchronous. This result would support the contention that the LIA was terminated by anthropogenically-driven warming. Chronology from the neoglacial deposits will be used to test whether the timing of the return to glacial conditions in the Sierras correlates to a southward shift in the Intertropical Convergence Zone, which has been hypothesized to increase El Nino-like conditions in the Pacific Ocean. This record should be ideal for testing this hypothesis since precipitation in the Sierras is highly sensitive to El Nino conditions.

  9. 41Ca, 14C and 10Be concentrations in coral sand from the Bikini atoll.

    PubMed

    Lachner, Johannes; Christl, Marcus; Alfimov, Vasily; Hajdas, Irka; Kubik, Peter W; Schulze-König, Tim; Wacker, Lukas; Synal, Hans-Arno

    2014-03-01

    Activation measurements of materials exposed to nuclear bomb explosions are widely used to reconstruct the neutron flux for retrospective dosimetry. In this study the applicability of coral CaCO3 as a biogenic neutron fluence dosimeter is tested. The long-lived radioisotopes (41)Ca, (14)C and (10)Be, which had been produced in nuclear bomb explosions, are measured in several coral sand samples from the Bikini atoll at the 600 kV and 200 kV AMS facilities of ETH Zurich. Elevated concentrations of all studied isotopes are found in a sample from the crater that was initially formed by the high-yield nuclear explosion Castle Bravo in 1954 and that had been used as site for several tests afterward. The observed (14)C concentration is considered too large to originate from neutron irradiation of CaCO3 alone. The relatively low concentration of (10)Be found in the crater sample indicates that production of (10)Be during nuclear bomb testing is generally minor. A simple neutron fluence reconstruction is performed on basis of the (41)Ca/(40)Ca ratio. PMID:24378732

  10. Brunhes-Matuyama Magnetic Polarity Reversal Tracing using Chinese loess10Be

    NASA Astrophysics Data System (ADS)

    Zhou, W.; Beck, W.; Kong, X.; An, Z.; Qiang, X.; Wu, Z.; Xian, F.; Ao, H.

    2014-12-01

    The geomagnetic polarity reversal is generally considered to occur synchronously around the world, and is commonly used as a time marker. However, in the case of the most recent reversal, the Brunhes-Matuyama (B-M) reversal (~780 ka), comparison of paleomagnetic studies in Chinese loess-paleosol sequences versus marine sediments revealed a marked discrepancy in timing of this event (Tauxe et al., 1996; Zhou and Shackleton, 1999), leading to the debate on uncertainties of paleoclimatic correlation between the Chinese loess-paleosol sequences and marine sediments (Wang et al., 2006; Liu et al., 2008; Jin and Liu, 2011). Based on this issue, here we propose to use the cosmogenic 10Be to address this conundrum. 10Be is a long-lived radionuclide produced in the atmosphere by cosmic ray spallation reactions and carried to the ground attached to aerosols. Its atmospheric production rate is inversely proportional to the geomagnetic field intensity (Masarik and Beer, 1999). This allows us to reconstruct past geomagnetic field intensity variations using 10Be concentrations recorded in different sedimentary archives. We carried out the 10Be studies in Luochuan and Xifeng sections in Chinese Loess Plateau, both loess profiles show that 10Be production rate was at a maximum-an indication of the dipole field reversal-at ca. 780 ± 3 ka BP., in paleosol unit S7corresponding to MIS 19. These results have proven that the timing of B-M reversal recorded in Chinese loess is synchronous with that seen in marine records (Tauxe et al., 1996) and reaffirmed the conventional paleoclimatic correlation of loess-paleosol sequences with marine isotope stages and the standard loess timescale as correct. However, it is ~25 ka younger than the age (depth) of the magnetic polarity reversal recorded in these same Chinese loess-paleosol sequences, demonstrating that loess magnetic overprinting has occurred. 1.Jin, C.S.,et al., 2011,PALAEOGEOGR PALAEOCL, 299, 309-3172.Liu, Q.S., et al., 2008, EARTH

  11. Loess 10Be evidence for an asynchronous Brunhes-Matuyama magnetic polarity reversal

    NASA Astrophysics Data System (ADS)

    Zhou, W.; Beck, W.; Kong, X.; An, Z.; Qiang, X.; Wu, Z.; Xian, F.; Ao, H.

    2015-12-01

    In Chinese loess the Brunhes-Matuyama (B-M) geomagnetic reversal appears to occur about 25 ka prior to the established axial dipole reversal age found in many marine sediments, i.e., in Chinese loess this magnetic reversal boundary is found in glacial loess unit L8 which is thought to be correlated with Marine Isotope Stage 20 (MIS 20), in marine sediment records, however, this boundary is commonly found in interglacial period of MIS 19[1-2], leading to the debate on uncertainties of paleoclimatic correlation between the Chinese loess-paleosol sequences and marine sediments[3-5]. Based on this issue, here we propose to use the cosmogenic 10Be to address this conundrum. 10Be is a long-lived radionuclide produced in the atmosphere by cosmic ray spallation reactions and carried to the ground attached to aerosols. Its atmospheric production rate is inversely proportional to the geomagnetic field intensity [6]. This allows us to reconstruct past geomagnetic field intensity variations using 10Be concentrations recorded in different sedimentary archives. We carried out both the 10Be studies and paleogeomagnetic measurements in Luochuan and Xifeng sections in Chinese Loess Plateau. Both loess profiles show that 10Be production rate was at a maximum-an indication of the dipole field reversal-at ca. 780 ± 3 ka BP., in paleosol unit S7 corresponding to MIS 19, proving that the timing of B-M reversal recorded in Chinese loess is synchronous with that seen in marine records [1]. These results reaffirmed the conventional paleoclimatic correlation of loess-paleosol sequences with marine isotope stages and the standard loess timescale as correct. However, it is ~25 ka younger than the age (depth) of the paleogeomagnetic measurements, which show that the B-M boundary is in L8 in these two Chinese loess-paleosol sequences, demonstrating that loess magnetic overprinting has occurred. 1.Tauxe, L., et al., 1996, EARTH PLANET SC LETT, 140, 133-1462.Zhou, L.P., and Shackleton, 1999

  12. Detrital 10Be Response to the 2008 Wenchuan Earthquake and Quantifying Evacuation of Coseismic Landslide Debris

    NASA Astrophysics Data System (ADS)

    Wang, W.; Godard, V.; Liu-Zeng, J.; Scherler, D.; Xu, C.; Xu, Q.; Xie, K.; Bellier, O.; Bourles, D. L.; Ansberque, C.

    2014-12-01

    In reverse fault-bounded high relief mountain ranges, large-magnitude earthquakes contribute to the topographic growth by co- and inter-seismic surface uplift on the hanging wall. Meanwhile, they also trigger widespread landslides along ridge lines or hillslopes. Coseismic landsliding lowers relief and causes a phase of high erosion in the period following the quake. The net effect of large-magnitude earthquakes in topographic evolution of active orogens partially depends on how fast the landslide debris are being evacuated out of the mountain range. The 2008 Mw7.9 Wenchuan earthquake, China activated the Longmen Shan reverse fault system in eastern Tibetan plateau, also induced enormous amount of landslides, volume comparable to the coseismic uplift, providing an excellent opportunity to address the question. We use cosmogenic 10Be concentration in river sand as a tracer to study the sediment routing process of coseismic landslide debris, because landslide debris contains low 10Be concentration. We sampling annually during 2008-2013, at 19 locations along the rivers that traverse the fault ruptures, with upstream catchment area varying between 4.4 km2 and 21775 km2, including 10 catchments sampled before Wenchuan earthquake in 2004 and 2005. A comparison with pre-earthquake measurements show reduced 10Be concentration at all sites. This dilution is more significant for small catchments on short range-front rivers: mostly half to one-fourth, and down to one-fifth in some cases. Multi-year time series of 10Be concentration at single sites show roughly constant level of dilution six years after the quake, with moderate temporal fluctuations, which may be related to the variation in precipitation and storm intensity. Under the assumption of constant dilution rate and a depth-mixing of 10Be concentration for landslide input, a simple calculation indicates it would take ~ 200 to 3000 years to completely evacuate the landslides debris within range-front transverse rivers

  13. Alpine Cliff Backwearing Rates Derived From Cosmogenic 10-Be in Active Medial Moraines

    NASA Astrophysics Data System (ADS)

    Ward, D. J.; Anderson, R. S.

    2008-12-01

    We use cosmogenic 10Be concentrations in rock samples from an active, ice-cored medial moraine to constrain glacial valley sidewall backwearing rates in the Kichatna Mountains, Alaska Range, Alaska. Kilometer-tall granite walls that tower over active glaciers are some of the most dramatic landscape features of the Alaska Range. The sheer scale of the relief speaks to the relative rates of valley incision by glaciers and rockwall retreat, but these rates are difficult to determine independently of one another. We present a method that uses cosmogenic nuclides to measure rockwall backwearing rates in glaciated settings on timescales of 103 yr, with a straightforward sampling strategy that exploits active medial moraines. Ablation-dominated medial moraines form by exhumation of debris-rich ice in the ablation zone of a glacier. Exhumed debris insulates the underlying ice and reduces its ablation rate relative to bare ice, promoting formation of a ridge-like, ice cored moraine. The rock debris is primarily derived from supraglacial rockfalls, which become incorporated in the ice along the glacier margins in the accumulation area. These lateral bands of debris-rich ice merge to form a medial debris band when glacial tributaries converge. The debris is minimally mixed until it is exhumed on the moraine crest. In the simplest case, such a system serves as a conveyor belt, bringing material from a specific part of the ablation zone valley wall to a specific point on a medial moraine in the ablation zone. We collected 5 grab samples, each consisting of ~30 2-10 cm rock fragments of the same lithology, from a 4.5 km longitudinal transect on the crest of the medial moraine of the Shadows glacier. We sampled the crest to minimize the amount of post-exhumation transport and mixing that may have occurred; each sample probably contains rocks from only one to a few rockfall events. Measured 10Be concentrations range from 1.5x104 to 3x104 at/g-qtz and are higher downvalley. First

  14. A 10Be Chronology of Late Pleistocene and Holocene Glaciation in the Rwenzori Mountains, Uganda

    NASA Astrophysics Data System (ADS)

    Baber, M.; Kelly, M. A.; Russell, J. M.; Loomis, S. E.

    2012-12-01

    Although the retreat of glaciers in East Africa has been monitored over the last century, longer-term records of African glacier fluctuations are scarce. The Rwenzori Mountains, located on the border of Uganda and the Democratic Republic of Congo, host the largest glacial system in Africa and provide an opportunity for extensive investigation of past glaciations. We mapped and applied surface exposure (10Be) dating to glacial moraines deposited since the end of the last ice age in the Rwenzori Mountains to test the feasibility of 10Be dating at this site and to develop a chronology of glacial fluctuations. Our study is the first to use 10Be dating of glacial features in Africa and is possible because the Rwenzori host quartz-rich lithologies. By comparing the timing of Rwenzori glacial advances with other paleoclimate records from East Africa, we also will examine the climatic conditions which influenced tropical glacier fluctuations. Osmaston (1989) mapped moraines in the Rwenzori Mountains, documenting three stages of Pleistocene and Holocene glaciations, the Mahoma, Omurubaho and Lac Gris stages. The Mahoma stage moraines are estimated to be older than 17,980 ± 780 yr BP (D. M. Livingstone, 1962) by basal 14C dating of sediments from Lake Mahoma, situated in large lateral moraine at 2990 m asl. The age of the Omurubaho stage moraine is estimated from a basal 14C age (7,730 ± 150 yr BP) Lower Kitandara Lake (3990 m asl) and dammed by an Omurubaho stage moraine. The Lac Gris moraines are estimated at ~150-700 yr BP (de Heinzelin, 1953; Bergström, 1955) based on rates of lichen growth and plant colonization on moraines about 200 m below current glacial positions on Mt. Stanley. Though considerable uncertainty remains for the ages of these glacier deposits, these three stages most likely represent ages from the LGM to the LIA. We present two new 10Be ages of boulders from two moraines in the Nyamagusani Valley, ~4000 m asl. Sample KOP-2 (4033 m asl) is from the

  15. Cosmogenic 10Be constraints on Little Ice Age glacial advances in the eastern Tian Shan, China

    NASA Astrophysics Data System (ADS)

    Li, Yanan; Li, Yingkui; Harbor, Jon; Liu, Gengnian; Yi, Chaolu; Caffee, Marc W.

    2016-04-01

    Presumed Little Ice Age (LIA) glacial advances, represented by a set of fresh, sharp-crested, boulder covered and compact moraines a few hundred meters downstream from modern glaciers, have been widely recognized in the Central Asian highlands. However, few studies have constrained the formation ages of these moraines. We report 31 10Be exposure ages from presumed LIA moraines in six glacial valleys in the Urumqi River headwater area and the Haxilegen Pass area of the eastern Tian Shan, China. Our results reveal that the maximum LIA glacial extent occurred mainly around 430 ± 100 yr, a cold and wet period as indicated by proxy data from ice cores, tree rings, and lake sediments in Central Asia. We also dated a later glacial advance to 270 ± 55 yr. However, 10Be exposure ages on several presumed LIA moraines in front of small, thin glaciers are widely scattered and much older than the globally recognized timing of the LIA. Historical topographic maps indicate that most glaciers were more extensive in the early 1960s, and two of our 10Be sample sites were located close to the ice front at that time. Boulders transported by these small and thin glaciers may be reworked from deposits originally formed prior to the LIA glacial advances, producing apparently old and widely scattered exposure ages due to varied nuclide inheritance. Other published ages indicated an earlier LIA advance around 790 ± 300 yr in the easternmost Tian Shan, but in our study area the more extensive advance around 430 ± 100 yr likely reworked or covered deposits from this earlier event.

  16. Extremely eroded or incredibly young - 10Be depth profile dating of moraines in the Swiss Midlands

    NASA Astrophysics Data System (ADS)

    Wüthrich, Lorenz; Zech, Roland; Haghipour, Negar; Gnägi, Christian; Christl, Markus; Ivy-Ochs, Susan; Veit, Heinz

    2014-05-01

    During the Pleistocene, glaciers advanced repeatedly from the Alps into the Swiss Midlands. The exact extent and timing are still under debate, even for the last glacial advances. Decalcification depths, for example, increase from west to east in the western Swiss Midlands and have been interpreted to indicate that the Valais (Rhone) glacier may have been less extensive during the global Last Glacial Maximum (LGM) at 20 ka than assumed so far [1]. In an attempt to provide more quantitative age control, we applied 10Be depth profile dating [2] on moraines at two locations. Steinhof has previously been dated to the global LGM based on exposure ages from four boulders [3], and Niederbuchsiten presumably lies outside the last glacial ice extent [1]. The 10Be concentrations at both sites decrease consistently with depth, but are very similar. Assuming only a few decimeters of erosion since moraine deposition, we obtain apparent exposure ages of ~20 ka. Niederbuchsiten would thus be unexpectedly young, implying a much more extensive extent of the LGM glacier than assumed so far. Alternatively, if the till at Niederbuchsiten was deposited during or before the penultimate glaciation (>130 ka), the surprisingly low 10Be concentrations indicate several meters of erosion during the last glacial cycle and/or the Holocene, which seems to be at odds with the deep and intensive soil formation. References: [1] Bitterli et al. (2011) Geologischer Atlas der Schweiz, Blatt 1108. [2] Hidy et al. (2010) Geochem. Geophys. Geosyst. 11, doi:10.1029/2010GC003084. [3] Ivy- Ochs et al. (2004) Ecl. Geol. Helv. 97, 47-55.

  17. Millennial Rates of Sea Cliff Retreat Derived From Cosmogenic 10Be and Coastal Platform Morphology

    NASA Astrophysics Data System (ADS)

    Hurst, M. D.; Ellis, M. A.; Rood, D. H.

    2014-12-01

    Observation of cliff erosion are often limited to relatively short timescales (a few decades), which are within the timeframe of anthropogenic modification of the coast and may be shorter than the recurrence interval for erosion events. Here we present long-term (centennial-millennial) averaged rates of sea cliff retreat for chalk cliffs in SE England derived from cosmogenic isotopes and coastal morphology. We determine long-term rates of sea cliff erosion from 10Be measured from in situ flint samples collected from three transects across the coastal platform in East Sussex. A numerical model of 10Be accumulation on an evolving coastal profile allows estimation of cliff retreat rate averaged over several hundred years. The model accounts for variation in 10Be accumulation with tides and sea-level rise, and takes into account platform downwear and topographic shielding by adjacent cliffs. Additionally, we use high-resolution (1m) multibeam bathymetry to map the extent of the coastal platform based on the surface texture in order to infer the position of the coast at ~8 ka. The difference in position to the current coastline provides estimates of Holocene-averaged rates of cliff erosion for all chalk cliffed coastline in the region. Comparison to historic records of cliff retreat reveals key similarities and differences between long and short-term signals. In certain locations, there are significant discrepancies (either faster or slower) between historic records and long-term rates of retreat. Each type of discrepancy may be the result of human interaction with the coastal environment, whether that interaction is local or non-local, and it is worthwhile noting that sites of relatively low historic rates of erosion are likely subject to high-magnitude, low-frequency failure events that could have devastating effects on human lives and infrastructure in areas that are considered to be low risk.

  18. Precise Electromagnetic Tests of Ab Initio Calculations of Light Nuclei: States in {sup 10}Be

    SciTech Connect

    McCutchan, E. A.; Lister, C. J.; Wiringa, R. B.; Pieper, Steven C.; Seweryniak, D.; Greene, J. P.; Carpenter, M. P.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Zhu, S.; Chiara, C. J.; Stefanescu, I.

    2009-11-06

    In order to test ab initio calculations of light nuclei, we have remeasured lifetimes in {sup 10}Be using the Doppler shift attenuation method (DSAM) following the {sup 7}Li({sup 7}Li,alpha){sup 10}Be reaction at 8 and 10 MeV. The new experiments significantly reduce systematic uncertainties in the DSAM technique. The J{sup p}i=2{sub 1}{sup +} state at 3.37 MeV has tau=205+-(5){sub stat}+-(7){sub sys} fs corresponding to a B(E2arrow down) of 9.2(3)e{sup 2} fm{sup 4} in broad agreement with many calculations. The J{sup p}i=2{sub 2}{sup +} state at 5.96 MeV was found to have a B(E2arrow down) of 0.11(2)e{sup 2} fm{sup 4} and provides a more discriminating test of nuclear models. New Green's function Monte Carlo calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment.

  19. Reactions with a 10Be beam to study the one-neutron halo nucleus 11Be

    NASA Astrophysics Data System (ADS)

    Jones, K. L.

    2016-07-01

    Halo nuclei are excellent examples of few-body systems consisting of a core and weakly-bound halo nucleons. Where there is only one nucleon in the halo, as in 11Be, the many-body problem can be reduced to a two-body problem. The contribution of the 1s1/2 orbital to the ground state configuration in 11Be, characterized by the spectroscopic factor, S, has been extracted from direct reaction data by many groups over the past five decades with discrepant results. An experiment was performed at the Holifield Radioactive Ion Beam Facility using a 10Be primary beam at four different energies with the goal of resolving the discrepancy through a consistent analysis of elastic, inelastic, and transfer channels. Faddeev-type calculations, released after the publication of the experimental results, show that dynamic core excitation in the transfer process can lead to reduced differential cross sections at higher beam energies. This reduction would lead to the extraction of decreasing values of S with increasing beam energy. A 10Be(d,p) measurement at Ed greater than 25 MeV is necessary to investigate the effects of core excitation in the reaction.

  20. Improved Timing of Deglaciation of the Southwestern Scandinavian Ice Sheet Using 10Be Dating

    NASA Astrophysics Data System (ADS)

    Gump, D.; Briner, J. P.; Svendsen, J. I.; Mangerud, J.

    2015-12-01

    We present 28 new 10Be ages from glacial erratic boulders to constrain Scandinavian Ice Sheet deglaciation along the major fjord system of Boknafjorden in southwest Norway. Results indicate ages in the range 20-14 ka and complement our previous findings that the Norwegian Channel Ice Stream (NCIS) had retreated some 400 km as early as ~20 ka (Svendsen et al., 2015) and further corroborate that this was followed by a second pulse of deglaciation at ~16 ka. After the immediate coast was rendered an ice-free corridor at ~20 ka, our new suite of ages identifies ~16 ka as a period of a possible culmination of re-advance, and almost certainly the onset of a subsequent period of retreat. These findings are promising for the possibility of long lake sediment archives from areas around the mouth of Boknafjorden. Additionally, by coupling our new 10Be ages of erratic boulders from sea level and from summits bordering Boknafjorden with topographic profiles and rudimentary ice-sheet profile calculations (Benn and Hulton, 2010), we are able to estimate spatial and temporal Scandinavian Ice Sheet history along both vertical and horizontal transects. Our results not only fill chronological gaps and add to a growing database of ages of deglaciation from the southwest Norway, but also provide new constraints for a three-dimensional reconstruction of the Scandinavian Ice Sheet during deglaciation.

  1. Cosmogenic 10Be Exposure Age for the Cut Bank Creek terminal moraine, Glacier National Park, MT

    NASA Astrophysics Data System (ADS)

    Quirk, B.; Laabs, B. J.; Leonard, E. M.; Caffee, M. W.

    2012-12-01

    Mountain glaciers are highly sensitive to temperature and precipitation with geologic records that are superb proxies of climate change. In the Rocky Mountains of the western United States, abundant records of Late Pleistocene glaciation provide an opportunity for understanding paleoclimate throughout this region, especially in places where the chronology of glaciation is precisely known. Cosmogenic 10Be exposure dating has been widely applied to glacial deposits in the Rocky Mountains, providing precise numerical ages and improving the understanding of glacial chronologies in this region. Despite these improvements, the chronology of the last Pleistocene glaciation of the northernmost Rocky Mountains is not completely understood. Cosmogenic 10Be exposure dating was applied to the Cut Bank Creek valley in the Lewis Range of the Northern Rocky Mountains, where a discrete mountain glacier deposited a broad terminal moraine during the last Pleistocene glaciation. Exposure ages of eight quartzite and sandstone boulders at the crest of the ice-distal sector of the terminal moraine indicate that abandonment occurred at 15.6 ± 0.8 ka. This age is consistent with age limits of several terminal moraines elsewhere in the Northern Rocky Mountains, suggesting that the last Pleistocene glaciation culminated in this region after the global Last Glacial Maximum.

  2. Studies of Be migration in the JET tokamak using AMS with 10Be marker

    NASA Astrophysics Data System (ADS)

    Bykov, I.; Bergsåker, H.; Possnert, G.; Zhou, Y.; Heinola, K.; Pettersson, J.; Conroy, S.; Likonen, J.; Petersson, P.; Widdowson, A.

    2016-03-01

    The JET tokamak is operated with beryllium limiter tiles in the main chamber and tungsten coated carbon fiber composite tiles and solid W tiles in the divertor. One important issue is how wall materials are migrating during plasma operation. To study beryllium redistribution in the main chamber and in the divertor, a 10Be enriched limiter tile was installed prior to plasma operations in 2011-2012. Methods to take surface samples have been developed, an abrasive method for bulk Be tiles in the main chamber, which permits reuse of the tiles, and leaching with hot HCl to remove all Be deposited at W coated surfaces in the divertor. Quantitative analysis of the total amount of Be in cm2 sized samples was made with inductively coupled plasma atomic emission spectroscopy (ICP-AES). The 10Be/9Be ratio in the samples was measured with accelerator mass spectrometry (AMS). The experimental setup and methods are described in detail, including sample preparation, measures to eliminate contributions in AMS from the 10B isobar, possible activation due to plasma generated neutrons and effects of diffusive isotope mixing. For the first time marker concentrations are measured in the divertor deposits. They are in the range 0.4-1.2% of the source concentration, with moderate poloidal variation.

  3. Loess 10Be evidence for an asynchronous Brunhes-Matuyama magnetic polarity reversal

    NASA Astrophysics Data System (ADS)

    Zhou, Weijian; Beck, J. Warren; Kong, Xianghui; An, Zhisheng; Qiang, Xiaoke; Wu, Zhenkun; Xian, Feng; Ao, Hong

    2015-04-01

    In Chinese loess the Brunhes-Matuyama (B-M) geomagnetic reversal appears to occur about 25 ka prior to the established axial dipole reversal age found in many marine sediments, i.e., in Chinese loess this magnetic reversal boundary is found in glacial loess unit L8 which is thought to be correlated with Marine Isotope Stage 20 (MIS 20), in marine sediment records, however, this boundary is commonly found in interglacial period of MIS 19 (Tauxe et al., 1996; Zhou and Shackleton, 1999), leading to the debate on uncertainties of paleoclimatic correlation between the Chinese loess-paleosol sequences and marine sediments (Wang et al., 2006; Liu et al., 2008; Jin and Liu, 2011). Based on this issue, here we propose to use the cosmogenic 10Be to address this conundrum. 10Be is a long-lived radionuclide produced in the atmosphere by cosmic ray spallation reactions and carried to the ground attached to aerosols. Its atmospheric production rate is inversely proportional to the geomagnetic field intensity (Masarik and Beer, 1999). This allows us to reconstruct past geomagnetic field intensity variations using 10Be concentrations recorded in different sedimentary archives. We carried out both the 10Be studies and paleogeomagnetic measurements in Luochuan and Xifeng sections in Chinese Loess Plateau. Both loess profiles show that 10Be production rate was at a maximum-an indication of the dipole field reversal-at ca. 780 ± 3 ka BP., in paleosol unit S7 corresponding to MIS 19, proving that the timing of B-M reversal recorded in Chinese loess is synchronous with that seen in marine records (Tauxe et al., 1996). These results reaffirmed the conventional paleoclimatic correlation of loess-paleosol sequences with marine isotope stages and the standard loess timescale as correct. However, it is ~25 ka younger than the age (depth) of the paleogeomagnetic measurements which show that the B-M boundary is in L8 in these two Chinese loess-paleosol sequences, demonstrating that loess

  4. Experimental Investigation of Weak Non-Mesonic Decay of 10Be(Lambda)Hypernuclei at CEBAF

    SciTech Connect

    S. Majewski; L. Majling; A. Margaryan; L. Tang

    2005-08-05

    Hypernuclei are convenient laboratory to study the baryon-baryon weak interaction and associated effective Hamiltonian. The strangeness changing process, in which a Lambda hyperon converts to a neutron with a release up to 176 MeV, provides a clear signal for a conversion of an s-quark to a d-quark. We propose to perform a non-mesonic weak decay study of 10Be(Lambda)hypernuclei using the (e,eK) reaction. These investigations will fully utilize the unique parameters of the CEBAF CW electron beam and RF system and are enabled by (1) the use of new detector for alpha particles based on the recently developed RF timing technique with picosecond resolution and (2) the small angle and large acceptance kaon spectrometer-HKS in Hall C.

  5. Extent of the last ice sheet in northern Scotland tested with cosmogenic 10Be exposure ages

    USGS Publications Warehouse

    Phillips, W.M.; Hall, A.M.; Ballantyne, C.K.; Binnie, S.; Kubik, P.W.; Freeman, S.

    2008-01-01

    The extent of the last British-Irish Ice Sheet (BIIS) in northern Scotland is disputed. A restricted ice sheet model holds that at the global Last Glacial Maximum (LGM; ca. 23-19 ka) the BIIS terminated on land in northern Scotland, leaving Buchan, Caithness and the Orkney Islands ice-free. An alternative model implies that these three areas were ice-covered at the LGM, with the BIIS extending offshore onto the adjacent shelves. We test the two models using cosmogenic 10Be surface exposure dating of erratic boulders and glacially eroded bedrock from the three areas. Our results indicate that the last BIIS covered all of northern Scotland during the LGM, but that widespread deglaciation of Caithness and Orkney occurred prior to rapid warming at ca. 14.5 ka. Copyright ?? 2008 John Wiley & Sons, Ltd.

  6. New constraints on the relationship between 26Al and oxygen, calcium, and titanium isotopic variation in the early Solar System from a multielement isotopic study of spinel-hibonite inclusions

    NASA Astrophysics Data System (ADS)

    Kööp, Levke; Nakashima, Daisuke; Heck, Philipp R.; Kita, Noriko T.; Tenner, Travis J.; Krot, Alexander N.; Nagashima, Kazuhide; Park, Changkun; Davis, Andrew M.

    2016-07-01

    We report oxygen, calcium, titanium and 26Al-26Mg isotope systematics for spinel-hibonite inclusions (SHIBs), a class of calcium-aluminum-rich inclusions (CAI) common in CM chondrites. In contrast to previous studies, our analyses of 33 SHIBs and four SHIB-related objects obtained with high spatial resolution demonstrate that these CAIs have a uniform Δ17O value of approximately -23‰, similar to many other mineralogically pristine CAIs from unmetamorphosed chondrites (e.g., CR, CV, and Acfer 094). Five SHIBs studied for calcium and titanium isotopes have no resolvable anomalies beyond 3σ uncertainties. This suggests that nucleosynthetic anomalies in the refractory elements had been significantly diluted in the environment where SHIBs with uniform Δ17O formed. We established internal 26Al-26Mg isochrons for eight SHIBs and found that seven of these formed with uniformly high levels of 26Al (a multi-CAI mineral isochron yields an initial 26Al/27Al ratio of ∼4.8 × 10-5), but one SHIB has a smaller initial 26Al/27Al of ∼ 2.5 × 10-5, indicating variation in 26Al/27Al ratios when SHIBs formed. The uniform calcium, titanium and oxygen isotopic characteristics found in SHIBs with both high and low initial 26Al/27Al ratios allow for two interpretations. (1) If subcanonical initial 26Al/27Al ratios in SHIBs are due to early formation, as suggested by Liu et al. (2012), our data would indicate that the CAI formation region had achieved a high degree of isotopic homogeneity in oxygen and refractory elements before a homogeneous distribution of 26Al was achieved. (2) Alternatively, if subcanonical ratios were the result of 26Al-26Mg system resetting, the clustering of SHIBs at a Δ17O value of ∼-23‰ would imply that a 16O-rich gaseous reservoir existed in the nebula until at least ∼0.7 Ma after the formation of the majority of CAIs.

  7. 10Be depth-profile dating of glaciofluvial sediments in the northern Alpine Foreland

    NASA Astrophysics Data System (ADS)

    Claude, Anne; Akçar, Naki; Ivy-Ochs, Susan; Schlunegger, Fritz; Kubik, Peter; Christl, Marcus; Vockenhuber, Christof; Dehnert, Andreas; Rahn, Meinert; Schlüchter, Christian

    2016-04-01

    10Be depth-profile dating is based on the fact that nuclide production is decreasing as an exponential function of depth. This method requires collecting at least four sediment samples in a vertical profile. The obtained nuclide concentrations are plotted against depth and fitted depth-profiles to the measured dataset. The age is then calculated based on the best-fit. The requirements for this method are the following: sampling geological units in artificial outcrops with minimum thickness of soil (less than around 80 cm), preferably with a flat-topped landform in order to guarantee that the uppermost surface of the deposit remains as unmodified as possible and is related to a defined geomorphologic process. Additionally at least one sample, preferably three, from the uppermost one meter of the profile as the exponential decrease mainly occurs around this depth. No sample is collected from the overlying soil. In this study, we aim to establish the chronology of the oldest Quaternary sediments in the northern Alpine Foreland using depth-profile dating with 10Be. These ages contribute to the understanding of the Quaternary landscape evolution of the Alpine Foreland. Here, we unravel the chronology of five sites at different morphostratigraphic positions: Mandach and Ängi (canton Aargau), Stadlerberg and Irchel (canton Zurich) and Rechberg (Germany, 4 km from the border to Switzerland). All sites are abandoned gravel pits and at each site we collected between four and seven sediment samples. First results yielded chronologies between 0.8 and 2 Ma for these glaciofluvial deposits. Our study shows that this relatively new method is successful when the geological setting matches the methodological requirements.

  8. Tectonic control on 10Be-derived erosion rates in the Garhwal Himalaya, India

    NASA Astrophysics Data System (ADS)

    Scherler, Dirk; Bookhagen, Bodo; Strecker, Manfred R.

    2014-02-01

    Erosion in the Himalaya is responsible for one of the greatest mass redistributions on Earth and has fueled models of feedback loops between climate and tectonics. Although the general trends of erosion across the Himalaya are reasonably well known, the relative importance of factors controlling erosion is less well constrained. Here we present 25 10Be-derived catchment-averaged erosion rates from the Yamuna catchment in the Garhwal Himalaya, northern India. Tributary erosion rates range between ~0.1 and 0.5 mm yr-1 in the Lesser Himalaya and ~1 and 2 mm yr-1 in the High Himalaya, despite uniform hillslope angles. The erosion-rate data correlate with catchment-averaged values of 5 km radius relief, channel steepness indices, and specific stream power but to varying degrees of nonlinearity. Similar nonlinear relationships and coefficients of determination suggest that topographic steepness is the major control on the spatial variability of erosion and that twofold to threefold differences in annual runoff are of minor importance in this area. Instead, the spatial distribution of erosion in the study area is consistent with a tectonic model in which the rock uplift pattern is largely controlled by the shortening rate and the geometry of the Main Himalayan Thrust fault (MHT). Our data support a shallow dip of the MHT underneath the Lesser Himalaya, followed by a midcrustal ramp underneath the High Himalaya, as indicated by geophysical data. Finally, analysis of sample results from larger main stem rivers indicates significant variability of 10Be-derived erosion rates, possibly related to nonproportional sediment supply from different tributaries and incomplete mixing in main stem channels.

  9. OSL and Cosmogenic 10Be Dating of Fluvial Terraces on the Northeast Pamir Margin, Northwest China

    NASA Astrophysics Data System (ADS)

    Thompson, J. A.; Chen, J.; Yang, H.; Li, T.; Bookhagen, B.; Burbank, D. W.; Bufe, A.

    2015-12-01

    Along the northeast Pamir margin in northwest China, flights of late Pleistocene fluvial terraces span actively deforming structures. We present detailed results on three terraces that we dated using optically stimulated luminescence (OSL) and cosmogenic 10Be techniques. Quartz OSL dating of two different grain sizes (4-11 and 90-180 μm) revealed the fine-grain quartz fraction overestimates the terrace ages by up to an order of magnitude. Two-mm, small-aliquot, coarse-grain quartz OSL ages, calculated using the finite mixture model, yielded stratigraphically consistent ages within error and dated times of terrace deposition to ~15 ka, ~18.5 ka, and ~75 ka. We speculate the observed grain-size dependence of OSL ages is likely related to the mode of transport of the grains in the fluvial system, with coarser grains sizes spending more time on sand bars where they are more thoroughly bleached than grains in the turbid, commonly episodic flows that carry the silt fraction. Our study suggests that, in flashy, turbid fluvial systems, coarse-grain OSL samples are likely to yield more reliable depositional ages than will fine-grain samples. Cosmogenic 10Be depth profiles date the times of terrace abandonment to ~8 ka, ~15 ka, and ~75 ka, yielding ages in overall agreement with the coarse-grain OSL ages. These ages are generally consistent with other dated terraces in the region that place their deposition and subsequent abandonment during the last deglaciation (13-18 ka) and suggest the formation of these terraces on the margins of the Tarim Basin and along the flanks of the Tian Shan is climatically controlled.

  10. Isovector and isoscalar dipole excitations in 9Be and 10Be studied with antisymmetrized molecular dynamics

    NASA Astrophysics Data System (ADS)

    Kanada-En'yo, Yoshiko

    2016-02-01

    Isovector and isoscalar dipole excitations in 9Be and 10Be are investigated in the framework of antisymmetrized molecular dynamics, in which angular-momentum and parity projections are performed. In the present method, 1p-1h excitation modes built on the ground state and a large amplitude α -cluster mode are taken into account. The isovector giant dipole resonance (GDR) in E >20 MeV shows the two-peak structure, which is understood from the dipole excitation in the 2 α core part with the prolate deformation. Because of valence neutron modes against the 2 α core, low-energy E 1 resonances appear in E <20 MeV, exhausting about 20 % of the Thomas-Reiche-Kuhn sum rule and 10 % of the calculated energy-weighted sum. The dipole resonance at E ˜15 MeV in 10Be can be interpreted as the parity partner of the ground state having a 6He+α structure and has remarkable E 1 strength because of the coherent contribution of two valence neutrons. The isoscalar dipole strength for some low-energy resonances is significantly enhanced by the coupling with the α -cluster mode. For the E 1 strength of 9Be, the calculation overestimates the energy-weighted sum (EWS) in the low-energy (E <20 MeV) and GDR (20

  11. 10Be surface exposure dating of rock glaciers in Larstigtal, Tyrol, Austria

    NASA Astrophysics Data System (ADS)

    Ivy-Ochs, S.; Kerschner, H.; Maisch, M.; Christl, M.; Kubik, P. W.; Schluchter, C.

    2009-04-01

    In the context of Lateglacial and Holocene climate change research, rock glaciers (creeping mountain permafrost) also play an important role. They are phenomena of discontinuous alpine permafrost and as such good indicators for the mean annual air temperature for the period they are active. We have 10Be surface exposure dated boulders from two relict rock glaciers in Larstigtal, Austria. This is the type area for a postulated mid-Holocene cold period called the Larstig oscillation. The period of activity was suggested to be of similar age as the mid-Holocene Frosnitz advance of glaciers in the Venediger Mountains farther to the east (Patzelt and Bortenschlager, 1973). For rock glaciers of this size to be active at 2200 m a.s.l. in Larstig valley would have required a significant drop in temperatures, thus a marked mid-Holocene cold pulse, for at least several centuries at around 7.0 ka. In contrast, our exposure dates show that the rock glaciers stabilized during the early Preboreal (Ivy-Ochs et al., submitted). We see no distinct pattern with respect to exposure age and boulder location on the rock glaciers. This implies that for our site the blocks did not acquire inherited 10Be during exposure in the free rock face, in the talus at the base of the slope, or during transport on the rock glaciers. Our data point to final stabilization of the Larstigtal rock glaciers in the earliest Holocene and not in the middle Holocene. Combined with data from other archives (Nicolussi et al., 2005), there appears to have been no time window in the middle Holocene long enough for rock glaciers of the size and at the elevation of the Larstig site to have formed. Ivy-Ochs, S., Kerschner, H., Maisch, M., Christl, M., Kubik, P.W., Schlüchter, C., Latest Pleistocene and Holocene glacier variations in the European Alps. Quaternary Science Reviews (submitted). Nicolussi, K., Kaufmann, M., Patzelt, G., van der Plicht, J., Thurner, A., 2005. Holocene tree-line variability in the Kauner

  12. Cosmic rays 10Be biennal data and their relationship to aurorae and sunspots

    NASA Technical Reports Server (NTRS)

    Attolini, M. R.; Cecchini, S.; Castagnoli, G. C.; Galli, M.; Nanni, T.

    1985-01-01

    The galactic cosmic ray (C.R.) variations which should give information on three dimensional aspects of the heliospheric magnetic fields and on the solar wind, which modulate their influx into the Solar System were studied. In order to decode the information from the C.R. series it is necessary to know the mechanisms through which the modulation is produced. It it clear that a balance of effects with sources at different heliospheric latitudes results in the modulated C.R. intensity. It is found that the modulation of 10Be in polar ice may be due to at least two main contributions: (1) negative and in phase with the Solar flare activity modulating the cosmic ray flux in Forbush-type decreases, and (2) positive in phase with the appearance of large wind streams situated at both polar coronal holes. It is found that the high heliolatitude activity is related to a stable periodicity of 11.1y whereas the low heliolatitude activity contributes to the wondering of the solar cycles.

  13. Influence of periglacial cover beds on in situ-produced cosmogenic 10Be in soil sections

    NASA Astrophysics Data System (ADS)

    Schaller, M.; von Blanckenburg, F.; Veit, H.; Kubik, P. W.

    2003-01-01

    Cover beds, widespread on hillslopes of temperate climate zones, represent layers of allochthonous material laterally transported by periglacial processes during the Late Pleistocene. Two soil sections comprised of cover beds from the Bavarian Forest, SE Germany, have been analysed for in situ-produced cosmogenic 10Be. Major changes in the nuclide concentration agree well with soil section boundaries defined by field observations and grain size analyses. Numeric modeling of these cosmogenic nuclide sections demonstrates that simple continuous erosion and regolith mixing models fail to explain the measured nuclide concentrations. Instead, the measured data can be best described by modeling an admixture of material such as loess or reworked allochthonous material, which have different nuclide concentrations. A comparison of cosmogenic nuclide concentrations from the two cover bed sections with concentrations from river bedload sediments of the Regen catchment reveals that cover bed formation might affect the result of basin-wide erosion rate determinations based on cosmogenic nuclides. Nuclide concentration of river bedload is potentially a binary mixture produced by (1) spatial erosion of the soil surfaces; and (2) spatially nonuniform incision into deep cover bed layers that contributes sediment low in nuclide concentration.

  14. 10Be depth profile dating in the Swiss Midlands: deposition ages versus erosion

    NASA Astrophysics Data System (ADS)

    Wüthrich, Lorenz; Zech, Roland; Haghipour, Negar; Terrizzano, Carla; Christl, Marcus; Gnägi, Christian; Veit, Heinz; Ivy-Ochs, Susan

    2015-04-01

    During the Pleistocene, glaciers advanced repeatedly from the Alps into the Swiss Midlands. The exact extents and timing are still under debate, even for the last glacial advances. Decalcification depths, for example, increase from west to east in the western Swiss Midlands and have been interpreted to indicate that the Rhone glacier may have been less extensive during the global Last Glacial Maximum (LGM) at 20 ka than assumed so far [1]. In an attempt to provide more quantitative age control, we applied 10Be depth profile dating [2] on till at five locations in the western part of Switzerland. Two of them lie outside the assumed LGM extent of the Rhone glacier (Niederbuchsiten, St.Urban), two inside the extent of the LGM Rhone glacier (Steinhof, Deisswil) and one profile was taken from the Berne stade (LGM) of the Aare glacier [3]. All surface concentrations are relatively low and indicate massive erosion. Without constrains for age and erosion, depth profile dating yields ages between roughly 15 ka up to more than 1 Ma for the profiles in St. Urban, Niederbuchsiten and Deisswil whereas the profiles in Steinhof and Bern yields only last glacial ages. The wide range of possible exposure ages illustrates, that independent estimates for erosion would be needed to precisely determine the deposition ages of the investigated tills. However, at this point, we interpret the best model fits to our depth profile concentrations as tentative verification of the assumed LGM extent [3]. The spatial patterns of decalcification depths and soil development in the Swiss Midlands deserves further evaluation. [1] Bitterli et al. (2011) Geologischer Atlas der Schweiz, Blatt 1108, Swisstopo [2] Hidy et al. (2010) Geochem. Geophys. Geosyst. 11, doi:10.1029/2010GC003084 . [3] Bini et al. (2009) Switzerland during the Last Glacial Maximum, Swisstopo

  15. Global scale analysis of the stream power law parameters based on worldwide 10Be denudation rates

    NASA Astrophysics Data System (ADS)

    Harel, Marie-Alice; Mudd, Simon; Attal, Mikael

    2015-04-01

    The stream power law, expressed as E = KAmSn where E is erosion rate [LT-1], K is erodibility [T-1L(1-2m)], A is drainage area [L2], S is channel gradient [L/L] and m and n are constants, is the most widely used model for bedrock channel incision. Despite its simplicity and limitations, the model has proved useful for a large number of applications such as topographic evolution, knickpoint migration, palaeotopography reconstruction, and the determination of uplift patterns and rates. However, the unknown parameters K, m and n are often fixed arbitrarily or are based on assumptions about the physics of the erosion processes that are not always valid, which considerably alters the use and interpretation of the model. In this study, we compile published 10Be basin-wide erosion rates (n = 1335) in order to assess the m/n ratio (or concavity index), the slope exponent n and erodibility coefficient K using the integral method of channel profile analysis. These three parameters are calculated for 66 areas and allow for a global scale analysis in terms of climatic, tectonic and environmental settings. Our results suggest that (i) many sites are too noisy or do not have enough data to predict n and K with a satisfying level of confidence; (ii) the slope exponent is predominantly greater than one, meaning that the relationship between erosion rate and the channel gradient is non-linear, supporting the idea that incision is a threshold controlled process. Furthermore, a multi-regression analysis and the calculation of n and K using a reference concavity index m/n = 0.45 demonstrate that (iii) many intuitive or previously demonstrated local-scale trends, such as the correlation between erosion rate and climate, do not appear at a global scale.

  16. Cosmogenic 10Be Exposure Age Limits on the Angel Lake Glaciation, Ruby Mountains, Northeastern Nevada

    NASA Astrophysics Data System (ADS)

    Laabs, B. J.; Munroe, J. S.; Best, L. C.; Caffee, M. W.

    2011-12-01

    Evidence of Pleistocene glaciations in the northern Great Basin of the interior western U.S. has been known for decades. Nonetheless, this area has received considerably less attention than the eastern and western extremes of the Great Basin, despite being centrally located among numerous well-dated Pleistocene glacial chronologies and in a setting where such chronologies can provide clues to the influence of North American ice sheets, Great Basin paleolakes, and atmospheric circulation changes on climate change. Among the most extensively glaciated mountains in the Great Basin are the Ruby and East Humboldt Mountains in northeastern Nevada, where the type localities for the last two Pleistocene glaciations in the region, the Lamoille and Angel Lake Glaciations, are found. The glacial record in these two ranges includes sequences of moraines deposited during the Angel Lake Glaciation, displaying abundant material suitable for terrestrial cosmogenic 10Be surface-exposure dating. Exposure ages of boulders from atop a sequence of well-preserved moraines in Seitz Canyon in the western Ruby Mountains limit the end of the Angel Lake Glaciation to 19.3 ± 1.0 ka. This preliminary age limit verifies that the Angel Lake Glaciation coincided with marine oxygen-isotope stage 2 and the global Last Glacial Maximum, and suggests that mountain glaciers in northeastern Nevada began retreating in step with the Laurentide Ice Sheet. When compared to glacial chronologies from elsewhere in the region, this age limit indicates an early start of the last deglaciation relative to the Sierra Nevada and the Wasatch Mountains, at the western and eastern extremes of the Great Basin respectively. Furthermore, this age limit suggests that ice retreat began before the highstands of the largest Great Basin paleolakes, Lakes Bonneville and Lahontan. Further development of the glacial chronology of the northern Great Basin is needed to evaluate the significance of these apparent age differences

  17. Global Scale Analysis of the Stream Power Law Parameters based on Worldwide 10Be Denudation Rates

    NASA Astrophysics Data System (ADS)

    Harel, M. A.; Mudd, S. M.; Attal, M.

    2015-12-01

    The stream power law, expressed as E = KAmSn where E is erosion rate [LT-1], K is erodibility [T-1L(1-2m)], A is drainage area [L2], S is channel gradient [L/L] and m and n are constants, is the most widely used model for bedrock channel incision. Despite its simplicity and limitations, the model has proved useful for a large number of applications such as topographic evolution, knickpoint migration, palaeotopography reconstruction, and the determination of uplift patterns and rates. However, the unknown parameters K, m and n are often fixed arbitrarily or are based on assumptions about the physics of the erosion processes that are not always valid, which considerably alters the use and interpretation of the model. In this study, we compile published 10Be basin-wide erosion rates (N= 1423) in order to assess the m/n ratio (or concavity index), the slope exponent n and erodibility coefficient K using the integral method of channel profile analysis. These three parameters are calculated for 67 areas and allow for a global scale analysis in terms of climatic, tectonic and environmental settings. Our results suggest that (i) many sites are too noisy or do not have enough data to predict n and K with a satisfying level of confidence; (ii) the slope exponent is predominantly greater than one, meaning that the relationship between erosion rate and the channel gradient is non-linear, supporting the idea that incision is a threshold controlled process. Furthermore, a multi-regression analysis and the calculation of n and K using a reference concavity index m/n = 0.45 demonstrates that (iii) many intuitive or previously demonstrated local-scale trends, such as the correlation between erosion rate and climate, do not appear at a global scale.

  18. Examples of sackungen in the French Western Alps and their geochronology based on the 10Be cosmic ray exposure dating method (Invited)

    NASA Astrophysics Data System (ADS)

    Hippolyte, J.; Bourles, D. L.; Braucher, R.; Léanni, L.; Chauvet, F.; Lebatard, A.; Arnold, M.; Aumaître, G.; Keddadouche, K.

    2013-12-01

    In the French Alps, sackung scarps were often interpreted as surface traces of active faults. A detailed mapping of the Arc and Rognier mountains shows that these scarps result from deep-seated gravitational slope deformation (DSGSD). They are short (less than 2.1 km long), numerous and organized in swarms (5.3 km long at the Arc; 9 km long at Rognier). There are mainly uphill facing scarps developed on steep slopes. Open tension cracks are present at ridge tops. These sackung fractures created ridge-top troughs, closed depressions and multiple-crests landforms. That the sackung scarps are parallel to the contour lines, and that they result from opening of fractures or from normal slips, indicates that they are controlled by topography and gravity. In the Western Alps, glacial erosion and subsequent debuttressing of oversteepened slopes seem to be the main factors for the occurrence of sackungen. However, gradual loss of rock strength, groundwater fluctuations, subsidence due to evaporite dissolution and earthquake shaking, may contribute to their formation. For a better understanding of the origin of sackungen, chronological data are crucial. We used the cosmic ray exposure (CRE) dating method for deciphering the activity of the Arc and Rognier sackungen. This method allows quantification of the exposure duration of a surface to cosmic rays, by measuring the amount of accumulated cosmogenic nuclides in surficial rocks. Because sackung scarps usually form in hard rocks containing quartz, we used the 10Be cosmogenic nuclide which is produced in situ by spallation reactions on Si and O (36Cl can be used for limestone). The measurements were performed at ASTER, the French accelerator mass spectrometry facility located at the CEREGE laboratory in Aix-en-Provence. The CRE dating method allows direct dating of most of the geomorphologic structures involved in sackungen: sackung fault scarps, rock slopes, debris slopes, screes, rock glaciers, glacier-polished rock surface

  19. Inverse Kinematic Study of the Alg26(d ,p )27Al Reaction and Implications for Destruction of 26Al in Wolf-Rayet and Asymptotic Giant Branch Stars

    NASA Astrophysics Data System (ADS)

    Margerin, V.; Lotay, G.; Woods, P. J.; Aliotta, M.; Christian, G.; Davids, B.; Davinson, T.; Doherty, D. T.; Fallis, J.; Howell, D.; Kirsebom, O. S.; Mountford, D. J.; Rojas, A.; Ruiz, C.; Tostevin, J. A.

    2015-08-01

    In Wolf-Rayet and asymptotic giant branch (AGB) stars, the Alg26(p ,γ )27Si reaction is expected to govern the destruction of the cosmic γ -ray emitting nucleus 26Al. The rate of this reaction, however, is highly uncertain due to the unknown properties of key resonances in the temperature regime of hydrogen burning. We present a high-resolution inverse kinematic study of the Alg26(d ,p )27Al reaction as a method for constraining the strengths of key astrophysical resonances in the Alg26(p ,γ )27Si reaction. In particular, the results indicate that the resonance at Er=127 keV in 27Si determines the entire Alg26(p ,γ )27Si reaction rate over almost the complete temperature range of Wolf-Rayet stars and AGB stars.

  20. Spatial variations in 10Be-derived catchment wide denudation rates and the timing of glaciation in the NW Pamir SW Tien Shan Mountains, Tajikistan

    NASA Astrophysics Data System (ADS)

    Grin, E.; Ehlers, T. A.; Schaller, M.

    2014-12-01

    Mountain topography evolves in response to interactions between climate and tectonic processes. This study investigates the role of glaciation and catchment wide denudation rates in forming the 40.000 km2 large Vakhsh catchment in Tajikistan. The Vakhsh river is located in the Pamir - Tian Shan transition zone. The river drains the North Pamir as well as parts of the Alay Range, which is the western extension of the Tian Shan Mountains. The southward Vakhsh -Trans -Alay thrusting is the expression of ongoing tectonic activity in this area. Today the rate of convergence between the two mountain ranges adds up to at least 15 mm/yr. We analyzed the upstream part of the Vakhsh catchment with in situ-produced cosmogenic 10Be and 26Al in quartz. Modern river samples, terrace depth profiles, and moraine boulder samples were used for quantifying modern and paleo-denudation rates, and timing of the most recent glaciation. A recessional moraine was dated with a total number of 18 boulders and a sequence of five lateral moraines with 41 samples. Results from well-preserved moraines indicate in the North Pamir a maximal glacial extent at around 17 ka (+/- 1.9 ka). The analysis of modern river samples derived from several locations along the main channel of the Vakhsh river reveal denudation rates between 1.8 - 2.6 mm/yr. Spatial variations in denudation were also evaluated using cosmogenic nuclide-derived denudation rates from rivers ranging between Strahler order 4 and 7. Preliminary results for these rates vary between 0.7 and 2.9 mm/yr within the catchments. A correlation between Strahler order and the denudation rate has not been observed. Exposure ages for the lowest, middle, and highest of the 10 terraces are all ~3.2 ka (+/- 0.29 ka) indicating synchronous and rapid terrace formation in the late Holocene. Taken together, these results indicate: a) the most recent maximum extent of glaciation is in this valley is ~17 ka, b) terrace formation significantly post

  1. An episode of rapid bedrock channel incision during the last glacial cycle, measured with 10Be

    USGS Publications Warehouse

    Reusser, L.; Bierman, P.; Pavich, M.; Larsen, J.; Finkel, R.

    2006-01-01

    We use 10Be to infer when, how fast, and why the Susquehanna River incised through bedrock along the U.S. Atlantic seaboard, one of the world's most prominent and ancient passive margins. Although the rate at which large rivers incise rock is a fundamental control on the development of landscapes, relatively few studies have directly measured how quickly such incision occurs either in tectonically active environments or along passive margins. Exposure ages of fluvially carve d, bedrock strath terraces, preserved along the lower Susquehanna River, demonstrate that even along a passive margin, large rivers are capable of incising through rock for short periods of time at rates approaching those recorded in tectonically active regions, such as the Himalayas. Over eighty samples, collected along and between three prominent levels of strath terraces within Holtwood Gorge, indicate that the Susquehanna River incised more than 10 meters into the Appalachian Piedmont during the last glacial cycle. Beginning ???36 ka, incision rates increased dramatically, and remained elevated until ???14 ka. The northern half of the Susquehanna basin was glaciated during the late Wisconsinan; however, similar rates and timing of incision occurred in the unglaciated Potomac River basin immediately to the south. The concurrence of incision periods on both rivers suggests that glaciation and associated meltwater were not the primary drivers of incision. Instead, it appears that changing climatic conditions during the late Pleistocene promoted an increase in the frequency and magnitude of flood events capable of exceeding thresholds for rock detachment and bedrock erosion, thus enabling a short-lived episode of rapid incision into rock. Although this study has constraine d the timing and rate of bedrock incision along the largest river draining the Atlantic passive margin, the dates alone cannot explain fully why, or by what processes, this incision occurred. However, cosmogenic dating offers

  2. Last Glacial Maximum Dated by Means of 10Be in the Maritime Alps (Italy)

    NASA Astrophysics Data System (ADS)

    Granger, D. E.; Spagnolo, M.; Federici, P.; Pappalardo, M.; Ribolini, A.; Cyr, A. J.

    2006-12-01

    Relatively few exposure dates of LGM moraines boulders are available for the European Alps, and none on the southern flank. Ponte Murato (PM) is a frontal moraine at 860 m asl in the Gesso Basin (Maritime Alps, SW European Alps). The PM moraine dams the 157 km2 Gesso della Barra Valley and it represents the lowermost frontal moraine of the entire Gesso Valley, near the outlet of the valley in the Po Plain. Its ELA, determined from the paleo- shape of the supposed Gesso della Barra glacier, is 1746 m asl. Tetti Bandito (TB) is a small and badly preserved glacial deposit, tentatively attributed to a lateral-frontal moraine, that is positioned 5 km downvalley from the PM deposit at 800 m asl. There are no other glacial deposits downvalley from the TB moraine in the Gesso Basin or farther NE in the piedmont region of the upper Po Plain. Boulders sampled on the PM and on the TB moraine crests gave a 10Be cosmogenic age of respectively 16300 ± 880 ka (average value) and 18798 ± 973 ka. This result constrains the PM frontal moraine within the LGM interval but also suggests that the maximum expansion of the Gesso Basin glacier was more downvalley at some point during the last glaciation. If the TB is a lateral-frontal moraine as supposed, the two TB and PM moraines would represent the outer and inner moraine crests of the same LGM stadial, with the outer moraine much less pronounced than the inner moraine, similarly to the maximalstand and the hochstand described in the Eastern Alps (Van Husen, 1997). Within this perspective, the PM and TB dates are consistent with a European Alps LGM corresponding to MIS 2 (Ivy-Ochs et al., 2004). This study of the Maritime Alps moraines is also in agreement with the Upper Würm climatic theory (Florineth and Schlüchter, 2000) of a stronger influence of the W and SW incoming humid airflows in the European Alps, differently from the nearby Vosges and Pyrenees mountain chains where more dry conditions were probably responsible for a very

  3. The CREp program, a fully parameterizable program to compute exposure ages (3He, 10Be)

    NASA Astrophysics Data System (ADS)

    Martin, L.; Blard, P. H.; Lave, J.; Delunel, R.; Balco, G.

    2015-12-01

    Over the last decades, cosmogenic exposure dating permitted major advances in Earth surface sciences, and particularly in paleoclimatology. Yet, exposure age calculation is a dense procedure. It requires numerous choices of parameterization and the use of an appropriate production rate. Nowadays, Earth surface scientists may either calculate exposure ages on their own or use the available programs. However, these programs do not offer the possibility to include all the most recent advances in Cosmic Ray Exposure (CRE) dating. Notably, they do not propose the most recent production rate datasets and they only offer few possibilities to test the impact of the atmosphere model and the geomagnetic model on the computed ages. We present the CREp program, a Matlab © code that computes CRE ages for 3He and 10Be over the last 2 million years. The CREp program includes the scaling models of Lal-Stone in the "Lal modified" version (Balco et al., 2008; Lal, 1991; Stone, 2000) and the LSD model (Lifton et al., 2014). For any of these models, CREP allows choosing between the ERA-40 atmosphere model (Uppala et al., 2005) and the standard atmosphere (National Oceanic and Atmospheric Administration, 1976). Regarding the geomagnetic database, users can opt for one of the three proposed datasets: Muscheler et al. 2005, GLOPIS-75 (Laj et al. 2004) and the geomagnetic framework proposed in the LSD model (Lifton et al., 2014). They may also import their own geomagnetic database. Importantly, the reference production rate can be chosen among a large variety of possibilities. We made an effort to propose a wide and homogenous calibration database in order to promote the use of local calibration rates: CREp includes all the calibration data published until July 2015 and will be able to access an updated online database including all the newly published production rates. This is crucial for improving the ages accuracy. Users may also choose a global production rate or use their own data

  4. 10Be surface exposure dating reveals strong active deformation in the central Andean backarc interior

    NASA Astrophysics Data System (ADS)

    García Morabito, Ezequiel; Terrizzano, Carla; Zech, Roland; Willett, Sean; Yamin, Marcela; Haghipour, Negar; Wuethrich, Lorenz; Christl, Marcus; María Cortes, José; Ramos, Victor

    2016-04-01

    Understanding the deformation associated with active thrust wedges is essential to evaluate seismic hazard. How is active faulting distributed throughout the wedge, and how much deformation is taken up by individual structures? We address these questions for our study region, the central Andean backarc of Argentina. We combined a structural and geomorphological approach with surface exposure dating (10Be) of alluvial fans and strath terraces in two key localities at ~32° S: the Cerro Salinas, located in the active orogenic front of the Precordillera, and the Barreal block in the interior of the Andean mountain range. We analysed 22 surface samples and 6 depth profiles. At the thrust front, the oldest terrace (T1) yields an age of 100-130 ka, the intermediate terrace (T2) between 40-95 ka, and the youngest terrace (T3) an age of ~20 ka. In the Andean interior, T1´ dates to 117-146 ka, T2´ to ~70 ka, and T3´ to ~20 ka, all calculations assuming negligible erosion and using the scaling scheme for spallation based on Lal 1991, Stone 2000. Vertical slip rates of fault offsets are 0.3-0.5 mm/yr and of 0.6-1.2 mm/yr at the thrust front and in the Andean interior, respectively. Our results highlight: i) fault activity related to the growth of the Andean orogenic wedge is not only limited to a narrow thrust front zone. Internal structures have been active during the last 150 ka, ii) deformation rates in the Andean interior are comparable or even higher that those estimated and reported along the emerging thrust front, iii) distribution of active faulting seems to account for unsteady state conditions, and iv) seismic hazards may be more relevant in the internal parts of the Andean orogen than assumed so far. References Lal, D., 1991: Cosmic ray labeling of erosion surfaces: In situ nuclide production rates and erosion models. Earth and Planetary Science Letters 104: 424-439. Stone, J.O., 2000: Air pressure and cosmogenic isotope production. Journal of Geophysical

  5. Global analysis of the stream power law parameters based on worldwide 10Be denudation rates

    NASA Astrophysics Data System (ADS)

    Harel, M.-A.; Mudd, S. M.; Attal, M.

    2016-09-01

    The stream power law, expressed as E = KAmSn - where E is erosion rate [LT - 1], K is an erodibility coefficient [T - 1L (1 - 2m)], A is drainage area [L 2], S is channel gradient [L/L], and m and n are constants - is the most widely used model for bedrock channel incision. Despite its simplicity and limitations, the model has proved useful for topographic evolution, knickpoint migration, palaeotopography reconstruction, and the determination of rock uplift patterns and rates. However, the unknown parameters K, m, and n are often fixed arbitrarily or are based on assumptions about the physics of the erosion processes that are not always valid, which considerably limits the use and interpretation of the model. In this study, we compile a unique global data set of published basin-averaged erosion rates that use detrital cosmogenic 10Be. These data (N = 1457) enable values for fundamental river properties to be empirically constrained, often for the first time, such as the concavity of the river profile (m/n ratio or concavity index), the link between channel slope and erosion rate (slope exponent n), and substrate erodibility (K). These three parameters are calculated for 59 geographic areas using the integral method of channel profile analysis and allow for a global scale analysis in terms of climatic, tectonic, and environmental settings. In order to compare multiple sites, we also normalize n and K using a reference concavity index m/n = 0.5. A multiple regression analysis demonstrates that intuitive or previously demonstrated local-scale trends, such as the correlation between K and precipitation rates, do not appear at a global scale. Our results suggest that the slope exponent is generally > 1, meaning that the relationship between erosion rate and the channel gradient is nonlinear and thus support the hypothesis that incision is a threshold controlled process. This result questions the validity of many regional interpretations of climate and/or tectonics where

  6. Study of cluster structures in 10Be and 16C neutron-rich nuclei via break-up reactions

    NASA Astrophysics Data System (ADS)

    Dell'Aquila, D.; Acosta, L.; Amorini, F.; Andolina, R.; Auditore, L.; Berceanu, I.; Cardella, G.; Chatterjiee, M. B.; De Filippo, E.; Francalanza, L.; Gnoffo, B.; Grzeszczuk, A.; Lanzalone, G.; Lombardo, I.; Martorana, N.; Minniti, T.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Pop, A.; Porto, F.; Quattrocchi, L.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

    2016-05-01

    Projectile break-up reactions induced on polyethylene (CH2) target are used in order to study the spectroscopy of 10Be and 16C nuclei. For the present experiment we used 10Be and 16C beams delivered by the FRIBs facility at INFN-LNS, and the CHIMERA 4π multi-detector. 10Be and 16C structures are studied via a relative energy analysis of break-up fragments. The 4He+6He break-up channel allowed us to study the spectroscopy of 10Be; in particular we find evidence of a new state in 10Be at 13.5 MeV excitation energy. The 16C nucleus is studied via 6He-10Be correlation; we find the fingerprint of a possible state at about 20.6 MeV

  7. Simulating the mobility of meteoric 10Be in the landscape through a coupled soil-hillslope model (Be2D)

    NASA Astrophysics Data System (ADS)

    Campforts, Benjamin; Vanacker, Veerle; Vanderborght, Jan; Baken, Stijn; Smolders, Erik; Govers, Gerard

    2016-04-01

    Meteoric 10Be allows for the quantification of vertical and lateral soil fluxes over long time scales (103-105 yr). However, the mobility of meteoric 10Be in the soil system makes a translation of meteoric 10Be inventories into erosion and deposition rates complex. Here, we present a spatially explicit 2D model simulating the behaviour of meteoric 10Be on a hillslope. The model consists of two parts. The first component deals with advective and diffusive mobility of meteoric 10Be within the soil profile, and the second component describes lateral soil and meteoric 10Be fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering as well as downslope fluxes of soil due to creep, water and tillage erosion. Synthetic model simulations show that meteoric 10Be inventories can be related to erosion and deposition across a wide range of geomorphological and pedological settings. Our results also show that meteoric 10Be can be used as a tracer to detect human impact on soil fluxes for soils with a high affinity for meteoric 10Be. However, the quantification of vertical mobility is essential for a correct interpretation of the observed variations in meteoric 10Be profiles and inventories. Application of the Be2D model to natural conditions using data sets from the Southern Piedmont (Bacon et al., 2012) and Appalachian Mountains (Jungers et al., 2009; West et al., 2013) allows to reliably constrain parameter values. Good agreement between simulated and observed meteoric 10Be concentrations and inventories is obtained with realistic parameter values. Furthermore, our results provide detailed insights into the processes redistributing meteoric 10Be at the soil-hillslope scale.

  8. A continuous ice-core 10Be record from Mongolian mid-latitudes: Influences of solar variability and local climate

    NASA Astrophysics Data System (ADS)

    Inceoglu, F.; Knudsen, M. F.; Olsen, J.; Karoff, C.; Herren, P.-A.; Schwikowski, M.; Aldahan, A.; Possnert, G.

    2016-03-01

    High-resolution 10Be records used for studies of detailed changes in atmospheric 10Be production rates predominantly derive from polar ice cores. In this study, we present the first 10Be record from a mid-latitude ice core. The ice core derives from the Tsambagarav mountain range located in the Mongolian Altai region. The new 10Be concentration record spans the period from AD 1550 to 2009, while the flux record extends from AD 1816 to 2009. The 10Be concentration in the Tsambagarav ice core ranges between ˜ 1.5 ×104 and ˜ 10 ×104 atomsg-1, whereas the 10Be flux changes from ˜0.02 to ˜0.15 atoms cm-2 s-1. The average 10Be flux at Tsambagarav is four times higher than the average 10Be flux recorded in the NGRIP and Dome Fuji ice cores, which is in accordance with model predictions. In general, the long-term trends observed in the Tsambagarav 10Be concentration and flux records are reasonably similar to those observed in the NGRIP ice core. A comparison between the Tsambagarav 10Be record, group sunspot numbers (GSNs), and solar modulation potentials based on 14C in tree rings suggests that the Maunder Minimum was associated with a prolonged maximum in 10Be concentrations at Tsambagarav, whereas the Dalton Minimum was associated with a minor increase in the 10Be concentration and flux that was delayed relative to the primary minimum in GSNs. The sulphate record from Tsambagarav shows that large positive anomalies in the sulphate concentration are associated with negative anomalies in the 10Be concentration. A concurrent positive sulphate anomaly may explain why the main phase of the Dalton Minimum is subdued in the 10Be record from Tsambagarav. Spectral analysis indicates that the 11-yr solar-cycle signal may have influenced the new 10Be record, but the evidence supporting a direct link is ambiguous. Local and regional climatic changes, such as cyclonic versus anticyclonic conditions and related storm tracks, most likely played a significant role for the 10Be

  9. Multiple 10Be records revealing the history of cosmic-ray variations across the Iceland Basin excursion

    NASA Astrophysics Data System (ADS)

    Horiuchi, Kazuho; Kamata, Kanae; Maejima, Shun; Sasaki, Sho; Sasaki, Nobuyoshi; Yamazaki, Toshitsugu; Fujita, Shuji; Motoyama, Hideaki; Matsuzaki, Hiroyuki

    2016-04-01

    Cosmogenic 10Be is a proxy of cosmic-ray flux, and its natural records provide vital information about the past intensity variability of the geomagnetic field and solar activity. 10Be records also serve as powerful tools for global synchronization among a variety of paleoarchives and for elucidating sedimentary processes on natural remanent magnetization acquisition. However, high-resolution (multi-decadal to multi-centennial) records of 10Be are scarce, especially those older than several tens of thousands of years. Here we present multiple high-resolution 10Be records of the Iceland Basin geomagnetic excursion interval (ca. 170-200 kyr ago) obtained from sediment cores (authigenic 10Be/9Be ratio) and an ice core (atmospheric 10Be flux). Comparing sedimentary 10Be records with relative paleointensity from the same cores, we found differences in the magnetic lock-in depth, even between adjacent cores. The 10Be-proxy records from the sediment and ice cores exhibit common characteristics: an asymmetric large-scale variation, a ∼7-kyr quasi-plateau around the maximum with a characteristic mid-term depression, and multi-millennial fluctuations in cosmic-ray flux during this interval. Minimal-synchronized and stacked 10Be records show that maximum cosmic-ray flux occurred 188.5-190.0 kyr ago and was double the present flux. A wavelet analysis of the stacked curve reveals dominant 4-kyr and secondary 8-kyr periodicities, both of which can be interpreted as intrinsic geomagnetic cycles. The wavelet spectrum of the high-resolution ice-core record shows a periodicity of 1.7 kyr and somewhat intermingled multi-centennial cycles around the maxima of 10Be, which likely represent solar cycles in this period. High-resolution 10Be records from multiple paleoarchives provide both a robust proxy record of cosmic-ray flux and a valuable tool for detailed global synchronization based on cosmic-ray variations.

  10. Modeling cosmogenic radionuclides 10Be and 7Be during the Maunder Minimum using the ECHAM5-HAM General Circulation Model

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Beer, J.; Feichter, J.

    2007-11-01

    All existing 10Be records from Greenland and Antarctica show increasing concentrations during the Maunder Minimum period (MM), 1645-1715, when solar activity was very low and the climate was colder (little ice age). In detail, however, the 10Be records deviate from each other. We investigate to what extent climatic changes influence the 10Be measured in ice by modeling this period using the ECHAM5-HAM general circulation model. Production calculations show that during the MM the mean global 10Be production was higher by 32% than at present due to lower solar activity. Our modeling shows that the zonally averaged modeled 10Be deposition flux deviates by only ~8% from the average increase of 32%, indicating that climatic effects are much smaller than the production change. Due to increased stratospheric production, the 10Be content in the downward fluxes is larger during MM, leading to larger 10Be deposition fluxes in the subtropics, where stratosphere-troposphere exchange (STE) is strongest. In polar regions the effect is small. In Greenland the deposition change depends on latitude and altitude. In Antarctica the change is larger in the east than in the west. We use the 10Be/7Be ratio to study changes in STE. We find larger change between 20° N-40° N during spring, pointing to a stronger STE in the Northern Hemisphere during MM. In the Southern Hemisphere the change is small. These findings indicate that climate changes do influence the 10Be deposition fluxes, but not enough to significantly disturb the production signal. Climate-induced changes remain small, especially in polar regions.

  11. Modeling cosmogenic radionuclides 10Be and 7Be during the Maunder Minimum using the ECHAM5-HAM General Circulation Model

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Beer, J.; Feichter, J.

    2008-05-01

    All existing 10Be records from Greenland and Antarctica show increasing concentrations during the Maunder Minimum period (MM), 1645-1715, when solar activity was very low and the climate was colder (little ice age). In detail, however, the 10Be records deviate from each other. We investigate to what extent climatic changes influence the 10Be measured in ice by modeling this period using the ECHAM5-HAM general circulation model. Production calculations show that during the MM the mean global 10Be production was higher by 32% than at present due to lower solar activity. Our modeling shows that the zonally averaged modeled 10Be deposition flux deviates by only ~8% from the average increase of 32%, indicating that climatic effects are much smaller than the production change. Due to increased stratospheric production, the 10Be content in the downward fluxes is larger during MM, leading to larger 10Be deposition fluxes in the subtropics, where stratosphere-troposphere exchange (STE) is strongest. In polar regions the effect is small. In Greenland the deposition change depends on latitude and altitude. In Antarctica the change is larger in the east than in the west. We use the 10Be/7Be ratio to study changes in STE. We find larger change between 20° N-40° N during spring, pointing to a stronger STE in the Northern Hemisphere during MM. In the Southern Hemisphere the change is small. These findings indicate that climate changes do influence the 10Be deposition fluxes, but not enough to significantly disturb the production signal. Climate-induced changes remain small, especially in polar regions.

  12. Beryllium geochemistry in soils: Evaluation of 10Be/9Be ratios in authigenic minerals as a basis for age models

    USGS Publications Warehouse

    Barg, E.; Lal, D.; Pavich, M.J.; Caffee, M.W.; Southon, J.R.

    1997-01-01

    Soils contain a diverse and complex set of chemicals and minerals. Being an 'open system', both in the chemical and nuclear sense, soils have defied quantitative nuclear dating. However, based on the published studies of the cosmogenic atmospheric 10Be in soils, its relatively long half-life (1.5 Ma), and the fact that 10Be gets quickly incorporated in most soil minerals, this radionuclide appears to be potentially the most useful for soil dating. We therefore studied the natural variations in the specific activities of 10Be with respect to the isotope 9Be in mineral phases in eight profiles of diverse soils from temperate to tropical climatic regimes and evaluated the implications of the data for determining the time of formation of soil minerals, following an earlier suggestion [Lal et al., 1991. Development of cosmogenic nuclear methods for the study of soil erosion and formation rates. Current Sci. 61, 636-639.]. We find that the 10Be/9Be ratios in both bulk soils and in the authigenic mineral phases are confined within a narrower range than in 10Be concentrations. Also, the highest 10Be/9Be ratios in authigenic minerals are observed at the soil-rock interface as predicted by the model. We present model 10Be/9Be ages of the B-horizon and the corresponding soil formation rates for several soil profiles. The present study demonstrates that the 10Be/9Be ratios in the authigenic phases, e.g. clay and Fe-hydroxides, can indeed be used for obtaining useful model ages for soils younger than 10-15 Ma. However, the present work has to be pushed considerably further, to take into account more realistic age models in which, for instance, downward transport of 10Be and clays, and in-situ dissolution of clay minerals at depths, altering the 10Be/9Be ratios of the acidic solutions, are included. We show that in the case of younger soils (< 1 Ma) studied here, their 10Be inventories and 10Be/9Be ratios have been significantly disturbed possibly by mixing with transported

  13. New ways of using an old isotopic system - meteoric 10-Be is back and ready to do geomorphology

    NASA Astrophysics Data System (ADS)

    Bierman, P.; Reusser, L.; Pavich, M.

    2009-04-01

    Meteoric 10-Be, produced in the atmosphere and delivered in precipitation, is an important tracer of sediment and geomorphic processes. This talk will review several decades of work measuring 10-Be adhered to soil and sediment collected from varied terrains around the world. We will then present new data and modeling approaches demonstrating the rich potential but complex, dynamic nature of this isotope system. Considering all of these data, we will examine the utility of meteoric10-Be, produced in the atmosphere and delivered in precipitation, as a tracer of watershed and hillslope sediment transport processes at a variety of spatial scales. We will finish the talk by examining uncertainties that require additional research to resolve. After a brief hay-day in the 1980s, tracing sediment down rivers, dating a few terraces, and following sediment through subduction zones, meteoric or garden variety 10-Be was largely forgotten. It's been lurking somewhere in the dark corners of isotope geoscience while its more famous but difficult-to-measure twin, the 10-Be produced in quartz, got all the attention. Recently, several research groups have again begun to build upon the excellent foundation constructed by those working in the 1980s and early 1990s. New data from a series of soil pits on hillslopes from around the world suggest that meteoric 10-Be is mobile in the soil column moving from the more acidic, organic-rich A-horizon to the B-horizon. Meteoric 10-Be concentrations are well correlated with both soil pH and extractable Al suggesting that Be is retained in Al-rich grain coatings that we know, from numerous attempts to purify riverine quartz, survive fluvial transport all too well. The important take-away message is that meteoric 10-Be is mobile in soil fluids while in situ 10-Be only moves with the quartz grains in which it resides. Depth profiles of in situ and meteoric 10-Be can be quite different, helping us to learn about rates of soil stirring and 10-Be

  14. Using meteoric 10Be to constrain the age and structure of the frontal wedge at the Japan Trench

    NASA Astrophysics Data System (ADS)

    Regalla, C.; Bierman, P. R.; Rood, D.; Motoyama, I.; Fisher, D. M.

    2013-12-01

    We present new meteoric 10Be concentration data from marine sediments recovered during International Ocean Drilling Program (IODP) Exp. 343 that help constrain the age and internal structure of the frontal prism at the Japan trench in the vicinity of the 2011 Tohoku-oki M9 earthquake rupture. Exp. 343 recovered sediments from an ~200 m interval of the frontal wedge at site C0019. Core and log observations identify the plate boundary décollement at ~820 mbsf, which separates a deformed sedimentary wedge from relatively undeformed underthrust sediments. However, reconstructions of the structural evolution of the wedge are difficult because of similarity in lithology between sediments from the incoming and overriding plate, and the chaotic character of seismic reflectors in the frontal wedge. We utilize the radiogenic decay of 10Be (t1/2 =1.36 Ma) in marine sediments to constrain variations in sediment age with depth in core C0019. Meteoric 10Be was isolated from marine sediments at the University of Vermont using total fusion and 10Be/9Be ratios were measured at the Scottish Universities Environmental Research Centre. Concentrations of meteoric 10Be in core C0019 range from 1.7x107 to 2.1x109 atm/g and are consistent with 10Be concentrations at nearby DSDP sites 436 and 434. We calculate 10Be sediment ages for analyzed samples assuming a range of initial 10Be concentrations from 1.6 to 2.1x109 atm/g. These concentrations are constrained by a 10Be sample co-located with a radiolarian micropaleontology sample at 780 mbsf that yields a Quaternary age, and from previously reported 10Be concentrations for Quaternary sediments in nearby DSDP cores. 10Be and radiolarian micropaleontology samples from similar depths yield consistent ages for late Miocene to Quaternary sediments (R2 = 0.89). Calculated 10Be ages range from 0-10 Ma, with ~50% of analyzed samples yielding ages <2 Ma. Repetition and inversion of high (109 atm/g) and low (107 atm/g) concentration sediments with

  15. Advances in cosmogenic surface exposure dating: Using combined in situ 14C-10Be analysis for deglaciation scenarios

    NASA Astrophysics Data System (ADS)

    Hippe, Kristina; Ivy-Ochs, Susan; Kober, Florian; Christl, Marcus; Fogwill, Christopher; Turney, Chris; Rood, Dylan; Lupker, Maarten; Schlücher, Christian; Wieler, Rainer

    2016-04-01

    Cosmogenic nuclides are routinely used to investigate deglaciation histories by exposure dating of rock surfaces after glacier retreat. For bedrock surfaces that have been efficiently eroded by glacier ice, the most commonly applied cosmogenic 10Be isotope has proven to give reliable estimates of the integrated time of surface exposure since major ice decay. Due to its long half-life (~1.4 Ma), however, 10Be does not record short episodes of intermittent surface cover, e.g. during phases of glacier readvance, which might have interrupted the general deglaciation trend. To detect such cases of "complex exposure", 10Be-based dating can be combined with the analysis of the short-lived (5730 a) in situ cosmogenic 14C nuclide. We present two examples, in which combined in situ 14C-10Be analysis has been successfully applied to reconstruct in detail post-LGM surface exposures histories - in the Swiss Alps [1] and in Antarctica [2]. In a study on the Gotthard Pass, Central Swiss Alps, in situ 14C-10Be exposure dating was combined with extensive mapping of glacial erosional features. Data from both cosmogenic nuclides are in overall good agreement with each other confirming continuous exposure of the Gotthard Pass area throughout the Holocene. Some slightly younger in situ 14C ages compared to the corresponding 10Be ages are interpreted to result from partial surface shielding due to snow cover. Constraining the average Holocene snow depth from the in situ 14C data allowed to apply an appropriate snow shielding correction for the 10Be exposure ages. Integration of the snow-corrected exposure ages with field observations provided a detailed chronology of a progressive downwasting of ice from the maximum LGM ice volume with a gradual reorganization of the ice flow pattern and a southward migration of the ice divide. In a study on the evolution and reorganization of ice streams entering the Weddell Sea, Antarctica, during the last deglaciation, ice sheet modelling was

  16. New experimental investigation of the structure of 10Be and 16C by means of intermediate-energy sequential breakup

    NASA Astrophysics Data System (ADS)

    Dell'Aquila, D.; Lombardo, I.; Acosta, L.; Andolina, R.; Auditore, L.; Cardella, G.; Chatterjiee, M. B.; De Filippo, E.; Francalanza, L.; Gnoffo, B.; Lanzalone, G.; Pagano, A.; Pagano, E. V.; Papa, M.; Pirrone, S.; Politi, G.; Porto, F.; Quattrocchi, L.; Rizzo, F.; Rosato, E.; Russotto, P.; Trifirò, A.; Trimarchi, M.; Verde, G.; Vigilante, M.

    2016-02-01

    10Be and 16C spectroscopy has been investigated by analyzing their breakup events on CH2 and CD2 targets. Breakup fragments have been detected by means of the CHIMERA detector. In particular, we investigated cluster decays of 10Be in 4He+6He and of 16C in 6He+10Be and 4He+6He+6He . From the relative energy analysis of breakup fragments, we investigate the spectroscopy of excited states of projectile nuclei. In the 10Be case we observe known states at 9.51, 10.16, 10.6, and 11.8 MeV. Further, we suggest the existence of a new state at 13.5 MeV, possibly 6+ as indicated from angular correlation analysis. The relative energy (Erel+Eth) spectrum of 16C, reconstructed starting from 6He+10Be correlations, shows a peak at about 20.6 MeV, probably related to the existence of an high-lying excited state. Non-vanishing yields are also seen in the triple coincidences 4He+6He+6He .

  17. Studying 10Be and 11Be Halo States through the (p,d) Single-Neutron Transfer Reaction

    NASA Astrophysics Data System (ADS)

    Kuhn, Keri; Sarazin, Fred; (Pcb)2 Collaboration; Tigress Collaboration

    2015-10-01

    One-neutron transfer reactions are being used to study single-particle neutron states in nuclei. For one-neutron halo nuclei, such as 11Be, the (p,d) reaction enables the removal of the halo neutron or of one of the core neutrons. This way, it is possible to simultaneously study the halo wavefunction of the 11Be ground-state but also a possible excited halo state in 10Be. The 11Be(p, d)10Be transfer reaction at 10 MeV/nucleon is being investigated at the TRIUMF-ISAC II facility with the Printed Circuit Board Based Charged Particle ((PCB)2) array inside the TRIUMF ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS). The ground state and first excited state of 10Be can be directly identified using deuteron identification and kinematics from the charged particle array, while the four excited states in10Be around 6 MeV, including the suspected halo state (2- state), are identified using coincident gamma rays from TIGRESS with the identified deuterons. Angular distributions for the 10Be populated states will be shown along with their FRESCO fits. This work is partially supported by the US Department of Energy through Grant/Contract No. DE-FG03-93ER40789 (Colorado School of Mines).

  18. Denudation rates determined from the accumulation of in situ-produced 10Be in the luquillo experimental forest, Puerto Rico

    USGS Publications Warehouse

    Brown, Erik Thorson; Stallard, Robert F.; Larsen, Matthew C.; Raisbeck, Grant M.; Yiou, Francoise

    1995-01-01

    We present a simple method for estimation of long-term mean denudation rates using in situ-produced cosmogenic 10Be in fluvial sediments. Procedures are discussed to account for the effects of soil bioturbation, mass wasting and attenuation of cosmic rays by biomass and by local topography. Our analyses of 10Be in quartz from bedrock outcrops, soils, mass-wasting sites and riverine sediment from the Icacos River basin in the Luquillo Experimental Forest, Puerto Rico, are used to characterize denudation for major landform elements in that basin. The 10Be concentration of a discharge-weighted average of size classes of river sediment corresponds to a long-term average denudation of ≈ 43 m Ma −1, consistent with mass balance results. 

  19. 10Be concentrations and the long-term fate of particle-reactive nuclides in five soil profiles from California

    NASA Astrophysics Data System (ADS)

    Monaghan, M. C.; Krishnaswami, S.; Thomas, J. H.

    1983-10-01

    Concentration-depth profiles of cosmic-ray-produced 10Be ( t1/2 = 1.5m.y.) have been measured by accelerator-mass spectrometry in five soil profiles. These measurements were made in an effort (1) to understand the retentivity of soil surfaces for particle-reactive tracers depositing from the atmosphere on time scales of 10 4-10 6 years, and (2) to explore the application of 10Be as a chronometer of geomorphic surface age. The profiles sampled are from two wave-cut terraces located near Mendocino, California, a table mountain top and an alluvial fan, both located near Friant, California. The ages of the Mendocino terraces are inferred to be (1-5) × 10 5 years based on amino-stratigraphic correlations and models of terrace evolution; those of the table mountain top and alluvial fan are 9.5 × 10 6 years and 6.0 × 10 5 years, respectively, based on K-Ar analyses. All the surfaces sampled are nearly flat and exhibit few erosional features. In addition to 10Be we measured 210Pb, 239,240Pu and 7Be to ascertain the retentivity of the soils for particle-reactive nuclides and to assess the present-day delivery rate of nuclides from the atmosphere. The 7Be inventory is 4.0 dpm/cm 2 similar to those observed at nearby locations. The inventories of 210Pb and Pu isotopes conform to those predicted from model calculations and suggest that the soil surfaces sampled retain the entire burden of particle-reactive nuclides delivered to them over short time scales, ˜ 100 years. The 10Be concentrations in the sample range between (0.2 and 7) × 10 8 atoms/g soil and show strong correlations with leachable Fe and/or Al. The inventory of 10Be in the soil domain sampled is 1-2 orders of magnitude lower than that expected from the geological age of the surface and an average delivery rate of 10Be from the atmosphere, 5.2 × 10 5 atoms/cm 2 yr. The low inventory of 10Be is attributed to its loss from the soil domain sampled by solution transport. Based on a simple ☐-model type

  20. Constraining Regolith Production on a Hillslope Over Long Timescales: Interpreting In Situ 10Be Concentrations on an Evolving Landscape

    NASA Astrophysics Data System (ADS)

    Foster, M. A.; Anderson, R. S.; Duehnforth, M.; Kelly, P. J.

    2011-12-01

    In situ produced 10Be cosmogenic radionuclide (CRN) concentrations provide geomorphologists with a quantitative tool to calculate regolith production rates in a variety of landscapes. However, the power of CRN dating is limited by the care with which these hard-earned numbers are interpreted. As rock is exhumed through the weathered zone, it accumulates in situ produced CRNs. Most studies assume a steady-state condition to calculate regolith production rates from 10Be concentrations obtained from rock at the base of mobile regolith; ignoring decay, the regolith production rate becomes simply Poe-H/z*/[10Be]. Although the balance of regolith production and the spatial pattern of divergence required to maintain steady regolith thickness is valid in some landscapes, steady-state is unlikely on hillslopes where time scales for generating soils are longer than climatic cycles. We report in situ 10Be concentrations to calculate production rates for mobile regolith in 8 soil pits along north- and south-facing slopes in Gordon Gulch, an intensively studied catchment in the Boulder Creek CZO. Gordon Gulch hillslopes exhibit variable regolith and saprolite thicknesses over gneissic and granitic parent rock; mean regolith thickness is 0.65 m. Local denudation rates in nearby catchments are 25 ± 8 m/Ma (Dethier and Lazarus, 2006). The mean residence time of mobile regolith in Gordon Gulch catchment is therefore 20-45 ka; less than half of this time is spent in Holocene climatic conditions. Although Gordon Gulch presently has mean annual temperature (MAT) ~4°C, it was likely at least 6°C cooler during the Last Glacial Maximum, meaning that periglacial conditions likely dominated. We therefore anticipate that parent rock could be more rapidly damaged by increased frost-cracking, and regolith transport be enhanced by increased frost-heave; thus steady-state conditions cannot be assumed over this timescale. To develop strategies for interpretation of 10Be, we employ a 1D

  1. 13C(n,α0)10Be cross section measurement with sCVD diamond detector

    NASA Astrophysics Data System (ADS)

    Kavrigin, P.; Griesmayer, E.; Belloni, F.; Plompen, A. J. M.; Schillebeeckx, P.; Weiss, C.

    2016-06-01

    This paper presents 13C(n, α0)10Be cross section measurements performed at the Van de Graaff facility of the Joint Research Centre Geel. The 13C(n, α0)10Be cross section was measured relative to the 12C(n, α0)9Be cross section at 14.3 MeV and 17.0 MeV neutron energies. The measurements were performed with an sCVD (single-crystal chemical vapor deposition) diamond detector which acted as sample and as sensor simultaneously. A novel analysis technique was applied, which is based on the pulse-shape analysis of the detector's ionization current. This technique resulted in an efficient separation of background events and consequently in a well-determined selection of the nuclear reaction channels 12C(n, α0)9Be and 13C(n, α0)10Be.

  2. High-resolution authigenic 10Be/9Be records : A proxy indicator of the past geomagnetic field variability

    NASA Astrophysics Data System (ADS)

    Carcaillet, J.; Thouveny, N.; Bourlès, D. L.

    2003-04-01

    At global scale, the synchronicity of abnormal directions of the paleomagnetic field and minimum intensities supports the hypothesis of a relationship between the occurrence of excursions and/or polarity changes and the collapse of the dipolar component. We present quantitative evaluations of relationships between 10Be production rate variations and geomagnetic events using high resolution authigenic 10Be/9Be ratios and continuous paleointensity records measured in three marine sediment sequences located on the Portuguese margin, (MD95-2042 and MD95-2040), and in the Western Pacific, (MD97-2140). Since 10Be concentrations measured in marine sediments not only depend on 10Be production rates but also on oceanic and sedimentary effects, authigenic (i.e. adsorbed onto particles from the water column) 10Be concentrations were normalized to their related authigenic 9Be concentrations in order to account for these disturbing effects on the sedimentation rate as well as on the chemical and granulometric composition of the sediments. Due to their different sources, only the soluble form of both beryllium isotopes may indeed have been homogenized in the water column before deposition in the sediment. The measured 10Be/9Be ratios increase significantly at all identified excursions and reversals, associated with decreased paleointensities, consistently with the expected relationship between magnetic moment and cosmic ray flux (Q/Qo=(M/Mo)-1/2). Our results confirm the global occurrence of well-recognized and well-dated phases of low geomagnetic moments associated to well known geomagnetic excursions, short events or polarity reversals that occurred between 0 and 300 ka BP and between 0.6 and 1.3 Ma BP: the Laschamp excursion, the Blake event, the Jamaica/Pringle falls excursion, the Brunhes-Matuyama Reversal, the upper and lower Jaramillo transitions and the Cobb Mountain event. They strengthen the validity of recently reported excursions: Icelandic basin, Calabrian Ridge 0

  3. A new 10Be record recovered from an Antarctic ice core: validity and limitations to record the solar activity

    NASA Astrophysics Data System (ADS)

    Baroni, Mélanie; Bard, Edouard; Aster Team

    2015-04-01

    Cosmogenic nuclides provide the only possibility to document solar activity over millennia. Carbon-14 (14C) and beryllium-10 (10Be) records are retrieved from tree rings and ice cores, respectively. Recently, 14C records have also proven to be reliable to detect two large Solar Proton Events (SPE) (Miyake et al., Nature, 2012, Miyake et al., Nat. Commun., 2013) that occurred in 774-775 A.D. and in 993-994 A.D.. The origin of these events is still under debate but it opens new perspectives for the interpretation of 10Be ice core records. We present a new 10Be record from an ice core from Dome C (Antarctica) covering the last millennium. The chronology of this new ice core has been established by matching volcanic events on the WAIS Divide ice core (WDC06A) that is the best dated record in Antarctica over the Holocene (Sigl et al., JGR, 2013, Sigl et al., Nat. Clim. Change, 2014). The five minima of solar activity (Oort, Wolf, Spörer, Maunder and Dalton) are detected and characterized by a 10Be concentration increase of ca. 20% above average in agreement with previous studies of ice cores drilled at South Pole and Dome Fuji in Antarctica (Bard et al., EPSL, 1997; Horiuchi et al., Quat. Geochrono., 2008) and at NGRIP and Dye3 in Greenland (Berggren et al., GRL, 2009). The high resolution, on the order of a year, allows the detection of the 11-year solar cycle. Sulfate concentration, a proxy for volcanic eruptions, has also been measured in the very same samples, allowing a precise comparison of both 10Be and sulfate profiles. We confirm the systematic relationship between stratospheric eruptions and 10Be concentration increases, first evidenced by observations of the stratospheric volcanic eruptions of Agung in 1963 and Pinatubo in 1991 (Baroni et al., GCA, 2011). This relationship is due to an increase in 10Be deposition linked to the role played by the sedimentation of volcanic aerosols. In the light of these new elements, we will discuss the limitations and

  4. Cosmogenic 10Be Depth Profile in top 560 m of West Antarctic Ice Sheet Divide Ice Core

    NASA Astrophysics Data System (ADS)

    Welten, K. C.; Woodruff, T. E.; Caffee, M. W.; Edwards, R.; McConnell, J. R.; Bisiaux, M. M.; Nishiizumi, K.

    2009-12-01

    Concentrations of cosmogenic 10Be in polar ice samples are a function of variations in solar activity, geomagnetic field strength, atmospheric mixing and annual snow accumulation rates. The 10Be depth profile in ice cores also provides independent chronological markers to tie Antarctic to Greenland ice cores and to tie Holocene ice cores to the 14C dendrochronology record. We measured 10Be concentrations in 187 samples from depths of 0-560 m of the main WAIS Divide core, WDC06A. The ice samples are typically 1-2 kg and represent 2-4 m of ice, equivalent to an average temporal resolution of ~12 years, based on the preliminary age-depth scale proposed for the WDC core, (McConnell et al., in prep). Be, Al and Cl were separated using ion exchange chromatography techniques and the 10Be concentrations were measured by accelerator mass spectrometry (AMS) at PRIME lab. The 10Be concentrations range from 8.1 to 19.1 x 10^3 at/g, yielding an average of (13.1±2.1) x 10^3 at/g. Adopting an average snow accumulation rate of 20.9 cm weq/yr, as derived from the age-depth scale, this value corresponds to an average 10Be flux of (2.7±0.5) x 10^5 atoms/yr/cm2. This flux is similar to that of the Holocene part of the Siple Dome (Nishiizumi and Finkel, 2007) and Dome Fuji (Horiuchi et al. 2008) ice cores, but ~30% lower than the value of 4.0 x 10^5 atoms/yr/cm2 for GISP2 (Finkel and Nishiizumi, 1997). The periods of low solar activity, known as Oort, Wolf, Spörer, Maunder and Dalton minima, show ~20% higher 10Be concentrations/fluxes than the periods of average solar activity in the last millennium. The maximum 10Be fluxes during some of these periods of low solar activity are up to ~50% higher than average 10Be fluxes, as seen in other polar ice cores, which makes these peaks suitable as chronologic markers. We will compare the 10Be record in the WAIS Divide ice core with that in other Antarctic as well as Greenland ice cores and with the 14C treering record. Acknowledgment. This

  5. The study of the geomagnetic excursions and the relative intensities from Chinese loess 10Be over the past 130 ka

    NASA Astrophysics Data System (ADS)

    Zhou, W.; Xian, F.; Beck, J.; An, Z.; Wu, Z.; Liu, M.; Chen, M.; Priller, A.; Kutschera, W.; Jull, A. T.; Yu, H.; Song, S.; Cheng, P.; Kong, X.

    2009-12-01

    Chinese loess is well-known archive for the paleogeomagnetic and paleoclimatic studies [Zhou et al., 1990; An et al., 1990; Zhu et al., 2007]. However, earlier efforts to extract weak geomagnetic excursion signals from Chinese loess 10Be were always unsuccessful due to the complexities of loess 10Be, which results in the fact that loess 10Be was only used as a climatic proxy [Shen et al., 1992; Beer et al.,1993; Gu et al.,1996]. Meanwhile, knowledge on the precise stratigraphic horizons of geomagnetic excursions with a reliable dating [Channell, 2006], on whether the short-lived excursions such as Blake can not be recorded in paleosol unit are still controversial. Here, we present the reconstructed past 130ka geomagnetic excursions and relative paleointensities for the first time from 10Be records in two Chinese loess sections. Results are comparative with those of independent geomagnetic research on Atlantic and Pacific sediments. The derived Laschamp and Blake events lie in the loess-paleosol (L1SS1 and S1SS3) corresponding to mid MIS 3 and 5e respectively. Our studies prove the potential application of the complex loess 10Be for long-term geomagnetic tracing and provide new evidence to answer the long-existing debates on the precise stratigraphic horizon of geomagnetic excursions. Our study suggests the potential application of loess-paleosol 10Be for reconstructing geomagnetic intensity variations spanning the whole Quaternary. References 1. Zhou, L. P., F. Oldfield, A. G. Wintle, S. G. Robinson, and J. T. Wang (1990), Partly pedogenic origin of magnetic variations in Chinese loess, Nature, 346, 737-739. 2. An, Z. S., T. S. Liu, Y. C. Lu, S. C. Porter, G. Kukla, X. H. Wu, and Y. M. Hua (1990), The long-term paleomonsoon variation recorded by the loess-paleosol sequence in Central China, Quat. Int., 7-8, 91-95. 3. Zhu, R. X., R. Zhang, C. L. Deng, Y. X. Pan, Q. S. Liu, and Y. B. Sun (2007), Are Chinese loess deposits essentially continuous?, Geophys. Res. Lett

  6. Intra-catchment variability and significance of catchment-averaged denudation rates from 10Be concentrations in stream sediments: a 10Be-budget of the Etages catchment, French Western Alps

    NASA Astrophysics Data System (ADS)

    Delunel, Romain; van der Beek, Peter; Carcaillet, Julien; Bourlès, Didier

    2010-05-01

    As most of the European Alps, The Ecrins-Pelvoux massif (French Western Alps) was extensively glaciated during Quaternary glaciations, leading to strong rejuvenation of its morphology. The massif therefore provides a suitable area to study the efficiency of erosion processes in relief evolution on postglacial timescales. Denudation rates inferred from in-situ produced 10Be concentrations in stream sediments, obtained from 12 catchments throughout the Ecrins-Pelvoux massif, have been recently shown to correlate with mean catchment elevation in the absence of significant relationships with other morphometric parameters (Delunel et al., in press). We have proposed that the present-day denudation of Ecrins-Pelvoux massif climatically driven trough increasing frost-controlled processes with elevation, providing a mechanistic link for the inferred feedback between uplift, elevation and denudation rates observed in the European Alps (Wittmann et al., 2007; Champagnac et al., 2009). However, cosmogenic isotope measurements of stream sediments do not allow distinguishing the intrinsic spatial variability of denudation within a catchment. Therefore, we have sought to verify our previous conclusions on a smaller scale within a single catchment, from exhaustive measurements of 10Be concentrations carried by quartz fraction of different sources feeding the high-altitude stream sediment routing system. We focus our current study on the Etages catchment, a high-elevation hanging tributary of the Vénéon valley (western part of the Ecrins-Pelvoux massif) underlain by homogenous granitic bedrock. This 14 km2 catchment presents elevations ranging from 1600 m to ~3600 m (mean catchment elevation ~2700 m), within the altitudinal range where frost-controlled processes are most efficient in the Western Alps (Delunel et al., in press). This catchment also hosts a small cirque-glacier, remaining from the Little Ice Age glacial advance. We have collected 19 samples on the most

  7. A link between oxygen, calcium and titanium isotopes in 26Al-poor hibonite-rich CAIs from Murchison and implications for the heterogeneity of dust reservoirs in the solar nebula

    NASA Astrophysics Data System (ADS)

    Kööp, Levke; Davis, Andrew M.; Nakashima, Daisuke; Park, Changkun; Krot, Alexander N.; Nagashima, Kazuhide; Tenner, Travis J.; Heck, Philipp R.; Kita, Noriko T.

    2016-09-01

    PLACs (platy hibonite crystals) and related hibonite-rich calcium-, aluminum-rich inclusions (CAIs; hereafter collectively referred to as PLAC-like CAIs) have the largest nucleosynthetic isotope anomalies of all materials believed to have formed in the solar system. Most PLAC-like CAIs have low inferred initial 26Al/27Al ratios and could have formed prior to injection or widespread distribution of 26Al in the solar nebula. In this study, we report 26Al-26Mg systematics combined with oxygen, calcium, and titanium isotopic compositions for a large number of newly separated PLAC-like CAIs from the Murchison CM2 chondrite (32 CAIs studied for oxygen, 26 of these also for 26Al-26Mg, calcium and titanium). Our results confirm (1) the large range of nucleosynthetic anomalies in 50Ti and 48Ca (our data range from -70‰ to +170‰ and -60‰ to +80‰, respectively), (2) the substantial range of Δ17O values (-28‰ to -17‰, with Δ17O = δ17O - 0.52 × δ18O), and (3) general 26Al-depletion in PLAC-like CAIs. The multielement approach reveals a relationship between Δ17O and the degree of variability in 50Ti and 48Ca: PLAC-like CAIs with the highest Δ17O (∼-17‰) show large positive and negative 50Ti and 48Ca anomalies, while those with the lowest Δ17O (∼-28‰) have small to no anomalies in 50Ti and 48Ca. These observations could suggest a physical link between anomalous 48Ca and 50Ti carriers and an 16O-poor reservoir. We suggest that the solar nebula was isotopically heterogeneous shortly after collapse of the protosolar molecular cloud, and that the primordial dust reservoir, in which anomalous carrier phases were heterogeneously distributed, was 16O-poor (Δ17O ⩾ -17‰) relative to the primordial gaseous (CO + H2O) reservoir (Δ17O < -35‰). However, other models such as CO self-shielding in the protoplanetary disk are also considered to explain the link between oxygen and calcium and titanium isotopes in PLAC-like CAIs.

  8. 10Be-derived denudation rates from the Burdekin catchment: The largest contributor of sediment to the Great Barrier Reef

    NASA Astrophysics Data System (ADS)

    Croke, Jacky; Bartley, Rebecca; Chappell, John; Austin, Jenet M.; Fifield, Keith; Tims, Stephen G.; Thompson, Chris J.; Furuichi, Takahisa

    2015-07-01

    Terrestrial cosmogenic nuclides (TCNs) such as Beryllium-10 (10Be) are now routinely used to reconstruct erosional rates over tens of thousands of years at increasingly large basin scales (> 100,000 km2). In Australia, however, the approach and its assumptions have not been systematically tested within a single, large drainage basin. This study measures 10Be concentrations in river sediments from the Burdekin catchment, one of Australia's largest coastal catchments, to determine long-term (> 10,000 years), time-integrated rates of sediment generation and denudation. A nested-sampling design was used to test for effects of increasing catchment scale on nuclide concentrations with upstream catchment areas ranging from 4 to 130,000 km2. Beryllium-10 concentrations in sediment samples collected from the upstream headwater tributaries and mid-stream locations range from 1.8 to 2.89 × 105 atoms g- 1 and data confirm that nuclide concentrations are well and rapidly mixed downstream. Sediment from the same tributaries consistently yielded 10Be concentrations in the range of their upstream samples. Overall, no decrease in 10Be concentrations can be observed at the range of catchment scales measured here. The mean denudation rate for all river sediment samples throughout the Fanning subcatchment (1100 km2) is 18.47 m Ma- 1, which compares with the estimate at the end of the Burdekin catchment (130,000 km2) of 16.22 m Ma- 1. Nuclide concentrations in the lower gradient western and southern catchments show a higher degree of variability, and several complications emerged as a result of the contrasting geomorphic processes and settings. This study confirms the ability of TCNs to determine long-term denudation rates in Australia and highlights some important considerations in the model assumptions that may affect the accuracy of limited sampling in large, low-gradient catchments with long storage times.

  9. Observations of historical sea cliff retreat rates exceed long-term estimates derived from cosmogenic 10Be

    NASA Astrophysics Data System (ADS)

    Hurst, Martin D.; Rood, Dylan H.; Ellis, Michael A.; Anderson, Robert S.

    2015-04-01

    Historical observation of coastal retreat are limited to relatively short timescales (< 150 years), during which time humans may have modified the coastal environment. There is growing concern that rates of coastal change may be accelerated in the face of anticipated stormier climates and rising sea level, yet there is little knowledge of rates of coastal change prior to the relatively brief historical records. In order to make predictions about potential future coastal change it is important to establish baseline conditions averaged over longer time periods. Here we present analysis of sea cliff retreat throughout the Holocene averaged for chalk cliffs in south-east England using cosmogenic isotopes. We determine long-term rates of sea cliff erosion from 10Be measured from in-situ flint samples collected from three transects across coastal platforms in East Sussex. A numerical model of 10Be accumulation on an evolving coastal profile allows estimation of cliff retreat rate during the Holocene. The model accounts for variation in 10Be accumulation with tides and sea-level rise, and takes into account platform downwear and topographic shielding by adjacent cliffs. We find that cliff retreat rates during the Holocene were significantly slower (2-6 cm yr-1) than those derived from recent historical observations (15-25 cm yr-1). Modelled accumulation of 10Be requires retreat rates that increase rapidly in recent times, potentially reflecting human modification of the coastal sediment budget through construction of sea defences, flood defenses and aggregate extraction. Therefore knowledge of past human activity at the coastline may be important in anticipating future rates of coastal retreat.

  10. 10Be measured in a GRIP snow pit and modeled using the ECHAM5-HAM general circulation model

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Beer, J.; Jouzel, J.; Feichter, J.; Kubik, P.

    2008-03-01

    10Be measured in a Greenland Ice Core Project (GRIP) snow pit (1986-1990) with a seasonal resolution is compared with the ECHAM5-HAM GCM run. The mean modeled 10Be concentration in ice (1.0.104 atoms/g) agrees well with the measured value (1.2.104 atoms/g). The measured 10Be deposition flux (88 atoms/m2/s) also agrees well with the modeled flux (69 atoms/m2/s) and the measured precipitation rate (0.67 mm/day) agrees with the modeled rate (0.61 mm/day). The mean surface temperature of -31°C estimated from δ 18O is lower than the temperature measured at a near-by weather station (-29°C) and the modeled temperature (-26°C). During the 5-year period the concentrations and deposition fluxes, both measured and modeled, show a decreasing trend consistent with the increase in the solar activity. The variability of the measured and modeled concentrations and deposition fluxes is very similar suggesting that the variability is linked to a variability in production rather than the local meteorology.

  11. Coexistence of {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in {sup 10}Be

    SciTech Connect

    Itagaki, N.; Ito, M.; Milin, M.; Hashimoto, T.; Ishiyama, H.; Miyatake, H.

    2008-06-15

    The coexistence of the {alpha}+{alpha}+n+n and {alpha}+t+t cluster structures in the excited states of {sup 10}Be has been discussed. In the previous analysis, all the low-lying states of {sup 10}Be were found to be well described by the motion of the two valence neutrons around two {alpha} clusters. However, the {alpha}+t+t cluster structure was found to coexist with the {alpha}+{alpha}+n+n structure around E{sub x}=15 MeV, close to the corresponding threshold. We have introduced a microscopic model to solve the coupling effect between these two configurations. The K=0 and K=1 states are generated from the {alpha}+t+t configurations due to the spin coupling of two triton clusters. The present case of {sup 10}Be is one of the few examples in which completely different configurations of triton-type ({alpha}+t+t three-center) and {alpha}-type ({alpha}+{alpha}+n+n two-center) clusters coexist in a single nucleus in the same energy region.

  12. Spatial patterns of mobile regolith thickness and meteoric 10Be in the Boulder Creek Critical Zone Observatory, Front Range, Colorado

    NASA Astrophysics Data System (ADS)

    Shea, N.; Ouimet, W. B.; Dethier, D. P.; Bierman, P. R.; Rood, D. H.

    2012-12-01

    The Boulder Creek Critical Zone Observatory (BcCZO) aims to understand the history, architecture and evolution of hillslopes found within the diverse topography and climate regimes of the Colorado Front Range. This information is crucial for testing and developing models of hillslope evolution, giving especial consideration to the production and downslope transport of mobile regolith on the hillslopes. Here, we present the results of a systematic study aiming to document spatial patterns of mobile regolith thickness and meteoric Beryllium-10 (10Be) concentrations in the Gordon Gulch basin of the BcCZO. Gordon Gulch lies within the unglaciated portion of the Colorado Front Range and is thought to be an artifact of long-term steady state evolution. The basin is characterized by mixed bedrock-soil mantled hillslopes, with intermittent bedrock outcrops (tors) on ~10% of slopes. It is currently unclear how the hillslopes of Gordon Gulch have evolved given the variable rock type and strength (i.e., fracture spacing), gradients (steep slopes in lower basin compared to gradual in the upper), and hillslope aspects (north versus south facing hillslopes, with varying tree types and soil moisture for frost cracking and heaving) that exist within the basin. Furthermore, climate data suggest that the current climate regime (relatively warm) is representative of only 20% of the last 65 ka. Mobile regolith thickness measurements provide a snapshot of hillslope evolution in the basin given these controls, and meteoric 10Be can used to constrain residence times and trace mobile regolith transport. We measure mobile regolith thickness as the depth to immobile weathered bedrock and/or saprolite. Preliminary analysis of over 200 soil pits reveals a high degree of variability in mobile regolith thickness. In general, the mobile regolith cover is thinner on the south facing slopes than the north facing and a general thickening of mobile regolith occurs on steeper slopes, especially along

  13. Incision of the Danube River (Hungary), inferred by cosmogenic in situ 10Be and luminescence dating of terrace sediments

    NASA Astrophysics Data System (ADS)

    Ruszkiczay-Rüdiger, Zsófia; Novothny, Ágnes; Braucher, Régis; Csillag, Gábor; Fodor, László; Molnár, Gábor; Thamó-Bozsó, Edit

    2014-05-01

    Major part of the former chronological studies showed that Danube terraces, and connected uplift of the surrounding hills are significantly younger than it was suggested before. On the other hand, some studies provided older than expected ages. Accordingly, a novel terrace chronology is necessary, which we try to approach by using two different dating methods on the alluvial terraces: luminescence dating, which provides the burial ages and cosmogenic in situ 10Be dating, which yields the exposure ages of the sediments. Cosmogenic 10Be and luminescence samples were collected from several terrace horizons. Cosmogenic in situ 10Be sampling occurred along depth profiles, because this method allows determining both the exposure time and the denudation rate at each locality by using all particles involved in the cosmogenic nuclide production. Post-Infrared Infrared Stimulated Luminescence (post-IR IRSL) measurements were carried out on K-feldspar samples, comparing the post-IR IRSL 290 and post-IR IRSL 225 signals. Besides, quartz from younger samples was also measured using Optically Stimulated Luminescence (OSL). The lower horizons (tIIa,b) were datable by both luminescence and cosmogenic exposure age dating methods. However, the upper horizons (tIV, tV) were frequently above the datable time range for one or both methods. In these cases, instead of the 'exact' ages with errors, only minimum ages could be assessed. Most of the luminescence data show older ages than 10Be exposure ages for the terrace surfaces. This may be due to the fact that the dated processes are different. Luminescence ages reveal the time of deposition of the sediment, while 10Be ages show the time since the actual terrace surface has been exposed to cosmic irradiation. The effect of considerable surface erosion also has to be taken into account, as well as the possibility of incomplete bleaching of the luminescence signal. The possible effect of post-depositional sediment mixing could be excluded

  14. Search for the isovector monopole resonance via the 28Si(10Be,10B+ γ)28Al reaction

    NASA Astrophysics Data System (ADS)

    Scott, Michael; e11021 Collaboration Team

    2013-10-01

    The isovector giant monopole resonance (IVGMR) is a fundamental mode of collective oscillation in which the neutron and proton fluids in a nucleus radially expand and contract in an out-of-phase manner. Observation of the IVGMR has been difficult due to the lack of a probe that will excite only its non-spin-flip (ΔS = 0) transitions. The IVGMR's spin-transfer (ΔS = 1) counterpart, the isovector spin giant monopole resonance, is much more strongly excited at bombarding energies higher than 60 MeV/ u. By way of the (10Be,10B+ γ) charge-exchange reaction, the selectivity for the excitation of the IVGMR can be gained. In this probe, the superallowed Fermi transition 10Be(0+,g.s.) -->10B(01+,1.74 MeV, T = 1) allows a nearly pure isolation of the ΔS = 0 component by detecting the 1022 keV gamma rays from the deexcitation of the 10B. We measured the double differential cross sections for the 28Si(10Be,10B+ γ) reaction at 100 MeV/ u using the large acceptance S800 Spectrometer at the National Superconducting Cyclotron Laboratory with the GRETINA array detecting the gamma rays emitted from the 10B ejectile. In this presentation, we will report preliminary reults of the IVGMR in 28Al. GRETINA was funded by the US DOE - Office of Science. Operation of the array at NSCL is supported by NSF under Cooperative Agreement PHY-1102511(NSCL) and DOE under grant DE-AC02-05CH11231(LBNL).

  15. Grand solar minima and maxima deduced from 10Be and 14C: magnetic dynamo configuration and polarity reversal

    NASA Astrophysics Data System (ADS)

    Inceoglu, F.; Simoniello, R.; Knudsen, M. F.; Karoff, C.; Olsen, J.; Turck-Chiéze, S.; Jacobsen, B. H.

    2015-05-01

    Aims: This study aims to improve our understanding of the occurrence and origin of grand solar maxima and minima. Methods: We first investigate the statistics of peaks and dips simultaneously occurring in the solar modulation potentials reconstructed using the Greenland Ice Core Project (GRIP) 10Be and IntCal13 14C records for the overlapping time period spanning between ~1650 AD to 6600 BC. Based on the distribution of these events, we propose a method to identify grand minima and maxima periods. By using waiting time distribution analysis, we investigate the nature of grand minima and maxima periods identified based on the criteria as well as the variance and significance of the Hale cycle during these kinds of events throughout the Holocene epoch. Results: Analysis of grand minima and maxima events occurring simultaneously in the solar modulation potentials, reconstructed based on the 14C and the 10Be records, shows that the majority of events characterized by periods of moderate activity levels tend to last less than 50 years: grand maxima periods do not last longer than 100 years, while grand minima can persist slightly longer. The power and the variance of the 22-year Hale cycle increases during grand maxima and decreases during grand minima, compared to periods characterized by moderate activity levels. Conclusions: We present the first reconstruction of the occurrence of grand solar maxima and minima during the Holocene based on simultaneous changes in records of past solar variability derived from tree-ring 14C and ice-core 10Be, respectively. This robust determination of the occurrence of grand solar minima and maxima periods will enable systematic investigations of the influence of grand solar minima and maxima episodes on Earth's climate.

  16. Understanding complex exposure history of Mount Hampton, West Antarctica using cosmogenic 3He, 21Ne and 10Be in olivine

    NASA Astrophysics Data System (ADS)

    Carracedo, Ana; Rodes, Angel; Stuart, Finlay; Smellie, John

    2016-04-01

    Combining stable and radioactive cosmogenic nuclides is an established tool for revealing the complexities of long-term landscape development. To date most studies have concentrated on 21Ne and 10Be in quartz. We have combined different chemical protocols for extraction of cosmogenic 10Be from olivine, and measured concentrations in olivine from lherzolite xenoliths from the peak of Mount Hampton (~3,200 m), an 11 Ma shield volcano on the West Antarctic rift flank. We combine this data with cosmogenic 3He (and 21Ne) in the olivines in order to unravel the long-term environmental history of the region. The mean 3He/21Ne ratio (1.98 ± 0.22) is consistent with the theoretical value and previous determinations. 10Be/3He ratios (0.012 to 0.018) are significantly lower than the instantaneous production ratio (~0.045). The data are consistent with 1-3 Ma of burial. The altitude of the volcano rules out over-topping of the peak by the West Antarctic Ice Sheet only possible burial could be generated by the growth of an ice cap although this contradicts the absence of evidence for ice cover. The 3He-10Be data can also be generated during episodic erosion of the volcanic ash over the last few million years. The data requires a minimum depth of 1 to 2.5 m for the samples during a minimum age of 5 Ma and maximum long-term erosion rate of ~0.5 m/Ma with at least one erosive episode reflecting short-term erosion rate of ~7 m/Ma that would have brought the samples into the surface during the last ~350 ka. Erosion in this type of landscape could be related to interglacial periods where cryostatic erosion can occur generating an increase in the erosion rate. This study shows that episodic erosion can produce stable-radioactive cosmogenic isotope systematics that are similar to those generated by exposure-burial cycles.

  17. Precise electromagnetic tests of ab-initio calculations of light nucle i: states in {sup10}Be.

    SciTech Connect

    McCutchan, E. A.; Lister, C. J.; Wiringa, R. B.; Pieper, S. C.; Seweryniak, D.; Greene, J. P.; Carpenter, M. P.; Chiara, C. J.; Janssens, R. V. F.; Khoo, T. L.; Lauritsen, T.; Stefanescu, I.; Zhu, S.; Physics; Univ. of Maryland

    2009-01-01

    In order to test ab initio calculations of light nuclei, we have remeasured lifetimes in {sup 10}Be using the Doppler shift attenuation method (DSAM) following the {sup 7}Li({sup 7}Li,{alpha}){sup 10}Be reaction at 8 and 10 MeV. The new experiments significantly reduce systematic uncertainties in the DSAM technique. The J{sup TT} = 2{sub 1}{sup +} state at 3.37 MeV has T = 205 {+-} (5){sub stat}{+-}(7){sub sys} fs corresponding to a B(E2{down_arrow}) of 9.2(3)e{sup 2}fm{sup 4} in broad agreement with many calculations. The J{sup TT} = 2{sub 2}{sup +} state at 5.96 MeV was found to have a B(E2{down_arrow}) of 0.11(2)e{sup 2}fm{sup 4} and provides a more discriminating test of nuclear models. New Green's function Monte Carlo calculations for these states and transitions with a number of Hamiltonians are also reported and compared to experiment.

  18. Rapid thinning of the Welsh Ice Cap at 20-19 ka based on 10Be ages

    NASA Astrophysics Data System (ADS)

    Hughes, Philip D.; Glasser, Neil F.; Fink, David

    2016-01-01

    New 10Be ages from the summits of three mountain areas of North Wales reveal a very similar exposure timing as the Welsh Ice Cap thinned after the global Last Glacial Maximum. Eight bedrock and one boulder sample gave a combined arithmetic mean exposure age of 19.08 ± 0.80 ka (4.2%, 1σ). Similar exposure ages over a 320 m vertical range (824 to 581 m altitude) show that ice cap thinning was very rapid and spatially uniform. Using the same production rate and scaling scheme, we recalculated six published 10Be exposure ages from the nearby Arans, which also covered a similar elevation range from 608 to 901 m and obtained an arithmetic mean of 19.41 ± 1.45 ka (7.5%, 1σ). The average exposure age of all 15 accepted deglaciation ages is 19.21 ± 1.07 (5.6%, 1σ). The complete dataset from North Wales provides very strong evidence indicating that these summits became exposed as nunataks at 20-19 ka. This result provides important insight to the magnitude of ice surface lowering and behavior of the Welsh Ice Cap during the last deglaciation that can be compared to other ice masses that made up the British-Irish Ice Sheet.

  19. Structures in 9,10Be and 10B studied with the tensor-optimized shell model

    NASA Astrophysics Data System (ADS)

    Myo, Takayuki; Umeya, Atsushi; Toki, Hiroshi; Ikeda, Kiyomi

    2015-06-01

    We study the structures of ^{9,10}Be and ^{10}B with the tensor-optimized shell model (TOSM) using an effective interaction based on the bare nucleon-nucleon interaction AV8^'. The tensor correlation is treated in TOSM using the full space of 2p2h configurations including high-momentum components. The short-range correlation is treated with the unitary correlation operator method. It is found that the level orders of the low-lying states of ^{9,10}Be and ^{10}B are entirely reproduced. For ^9Be, ground band states are located at relatively higher energies than the experiments, which indicates missing α clustering correlation in these states as seen in the case of ^8Be. In addition, the tensor force gives a larger attraction for T=1/2 states than for T=3/2 ones for ^9Be. The level order of the three nuclei is found to be sensitive to the presence of the tensor force in comparison with the results using the Minnesota effective interaction without the tensor force.

  20. Neotectonic deformation versus climate control in the Central Andes of Argentina, insights from 10Be Surface Exposure Dating

    NASA Astrophysics Data System (ADS)

    Terrizzano, Carla; Zech, Roland; Garcia Morabito, Ezequiel; Yamin, Marcela; Haghipour, Negar; Wüthrich, Lorenz; Christl, Marcus

    2015-04-01

    Mountainous regions and their forelands commonly supports a suite of landforms sensitive to climate change and tectonics, providing -if addressed with appropriate geomorphological and geochronological approaches- record for landscape, climate, and tectonic evolution. In particular, alluvial fans are valuable archives of Quaternary climate and tectonics. The southern Central Andes and their forelands provide a perfect setting to study such forcings, since first, the extreme aridity favors the geomorphological preservation of the fan surfaces, so that 10Be surface exposure dating can be applied to establish robust and precise chronologies. And second, the neotectonic activity in this region results in widespread deformation of Quaternary deposits and recent devastating earthquakes. However, rates of uplift and shortening on the reverse faults remain largely unknown and very little is known yet about the Pleistocene climate history in the southern Central Andes, which limits a robust evaluation of the role of climate for the alluvial fan formation and landscape evolution. We combined structural and geomorphic investigations with 10Be surface exposure dating in the western Precordillera of the Southern Central Andes of Argentina (31°30'-31°53' SL/69°20' WL) in order to establish a numeric chronology for four deformed alluvial fan surfaces, to estimate uplift rates and to evaluate the potential climate role in controlling the fan construction and evolution. Surface exposure ages were determined for a few large boulders, amalgamated pebbles, and via depth profiles on sand samples. Boulder ages range from 145 to 212 ka for the oldest well-preserved fan remnants (Q1a, n=3), from 63 to 108 ka (Q2, n=3) and 21-28 ka (Q3, n=2), amalgamated pebbles yield ages range from 106 to 127 ka for the oldest fan surface (Q1b, n=79), all calculations assuming no erosion and using the scaling scheme for spallation based on Lal 1991, Stone 2000. Boulders from current channels have 10Be

  1. Identifying signals of Late Pleistocene climate change from cosmogenic 10Be chronologies of moraines in the western U.S.

    NASA Astrophysics Data System (ADS)

    Laabs, B. J. C.; Licciardi, J. M.; Leonard, E. M.; Munroe, J. S.

    2015-12-01

    Cosmogenic 10Be exposure dating has become the most widely applied method of developing ages of terminal moraines in the western U.S. Advances in the precision of analytical measurements along with a more accurate understanding of spatial and temporal variations in the production of in situ 10Be have improved the accuracy of cosmogenic exposure dating of moraines. Such improvements afford more accurate assessment of the impact of regional and global-scale climate changes of the Late Pleistocene on glaciation in the western U.S. A great number of new and recalculated cosmogenic 10Be exposure ages of moraines are considered here to identify the most probable drivers of changes in ice extent at the end of the last glacial period. The last Pleistocene glaciation culminated in the western U.S. during marine oxygen isotope stage 2, before or during the onset of the global Last Glacial Maximum at ca. 26.5 ka. Terminal moraine abandonment in several ranges corresponds to the end of the Last Glacial Maximum at ca. 19.0 ka. This observation indicates that most mountain glaciers started retreating in step with the decline of global ice volume, and possibly in response to rising insolation at northern middle latitudes. In some regions, such as the Northern Rocky Mountains and the Great Basin, mountain glaciers apparently advanced to or persisted near their maximum terminus positions well after the start of global deglaciation, during the interval of the Oldest Dryas/Heinrich Stadial 1 (ca. 19.0-14.6 ka). Although changes in atmospheric circulation and precipitation patterns during this time likely affected mountain glacier extent, rapid ice retreat commenced in nearly all settings by 17.0-16.0 ka. This indication of warming prior to the onset of the Bølling-Allerød interval at ca. 14.6 ka is consistent with records from elsewhere at northern middle latitudes, and supports the hypothesis that warming of the region was in phase with a global rise in atmospheric CO2. This

  2. Long-term background denudation rates of southern and southeastern Brazilian watersheds estimated with cosmogenic 10Be

    NASA Astrophysics Data System (ADS)

    Sosa Gonzalez, Veronica; Bierman, Paul R.; Fernandes, Nelson F.; Rood, Dylan H.

    2016-09-01

    In comparison to humid temperate regions of the Northern Hemisphere, less is known about the long-term (millennial scale) background rates of erosion in Southern Hemisphere tropical watersheds. In order to better understand the rate at which watersheds in southern and southeastern Brazil erode, and the relationship of that erosion to climate and landscape characteristics, we made new measurements of in situ produced 10Be in river sediments and we compiled all extant measurements from this part of the country. New data from 14 watersheds in the states of Santa Catarina (n = 7) and Rio de Janeiro (n = 7) show that erosion rates vary there from 13 to 90 m/My (mean = 32 m/My; median = 23 m/My) and that the difference between erosion rates of basins we sampled in the two states is not significant. Sampled basin area ranges between 3 and 14,987 km2, mean basin elevation between 235 and 1606 m, and mean basin slope between 11 and 29°. Basins sampled in Rio de Janeiro, including three that drain the Serra do Mar escarpment, have an average basin slope of 19°, whereas the average slope for the Santa Catarina basins is 14°. Mean basin slope (R2 = 0.73) and annual precipitation (R2 = 0.57) are most strongly correlated with erosion in the basins we studied. At three sites where we sampled river sand and cobbles, the 10Be concentration in river sand was greater than in the cobbles, suggesting that these grain sizes are sourced from different parts of the landscape. Compiling all cosmogenic 10Be-derived erosion rates previously published for southern and southeastern Brazil watersheds to date (n = 76) with our 14 sampled basins, we find that regional erosion rates (though low) are higher than those of watersheds also located on other passive margins including Namibia and the southeastern North America. Brazilian basins erode at a pace similar to escarpments in southeastern North America. Erosion rates in southern and southeastern Brazil are directly and positively related to

  3. Application of in situ-produced 10Be to the study of Australian stone line induced by termite activity

    NASA Astrophysics Data System (ADS)

    Colin, F.; Gurarie, E.; Bourles, D.; Braucher, R.; Brown, E.; Anan, R.; Gilkes, R.; Meunier, J. D.; Varajao, C.

    2001-12-01

    The aim of this study is to understand the genesis of a stoneline sequence located at the border of the Yilgarn Craton in southwest Austrtalia. The sequence was selected because a well-defined line of siliceous pebbles traces the limit between a typical tropical saprolite and a soil almost entirely composed of termite nests, providing an opportunity to study the role of biological processes in stoneline genesis. A roadcut along the Boyup Brook Road provided the opportunity to examine and sample a 100 m wide section of weathering mantle developed on a gently sloping hill. The sequence consists, from base to top, of three main weathering layers: a gneiss- and schist-inherited yellow saprolite that includes subvertical quartz veins ; a 10 to 20 cm thick stone line composed primarily of angular quartz pebble; and a 40 to 50 cm thick dark brown surficial soil rich in both active and dormant termite nests. The distribution of these layers does not vary significantly across the hill, but quartz rich veins are most abundant in the central part of the hill. Kaolinite and quartz are the major mineralogical components throughout the sequence. There is little variation in grain size distributions, other than a modest increase in the >63 micron fractions of surface samples due to termite activity (mixing of minerals with woody and grassy debris). Chemical and mineralogical analyses were used to characterise the weathering layers and to investigate the role of termite colonies. We determined the in situ produced 10Be contents of samples collected from a depth profile through the quartz-rich schist and of pebbles from the stoneline at distances up to 40 m from central quartz veins. The 10Be depth profile shows a simple exponential decrease with depth, consistent with attenuation of cosmic ray neutrons and erosion at a rate of 20 mMyr, consistent with rates of excavation by termites. The pebbles from the stoneline have nearly constant 10Be concentrations that are approximately

  4. The impact of geomagnetic spikes on the production rates of cosmogenic 14C and 10Be in the Earth's atmosphere

    NASA Astrophysics Data System (ADS)

    Fournier, Alexandre; Gallet, Yves; Usoskin, Ilya; Livermore, Philip W.; Kovaltsov, Gennady A.

    2015-04-01

    We seek corroborative evidence of the geomagnetic spikes detected in the Near East ca. 980 BC and 890 BC in the records of the past production rates of the cosmogenic nuclides 14C and 10Be. Our forward modeling strategy rests on global, time-dependent, geomagnetic spike field models feeding state-of-the-art models of cosmogenic nuclide production. We find that spike models with an energy budget in line with presently inferred large-scale flow at Earth's core surface fail to produce a visible imprint in the nuclide record. Spike models able to reproduce the intensity changes reported in the Near East require an unaccountably high-magnitude core flow, yet their computed impact on cosmogenic isotope production rates remains ambiguous. No simple and unequivocal agreement is obtained between the observed and modeled nuclide records at the epochs of interest. This indicates that cosmogenic nuclides cannot immediately be used to confirm the occurrence of these two geomagnetic spikes.

  5. 10Be exposure dating of onset and timing of Neoglacial glacier advances in the Ecrins massif, French Alps

    NASA Astrophysics Data System (ADS)

    Le Roy, Melaine; Deline, Philip; Carcaillet, Julien

    2013-04-01

    Alpine glaciers are known to be highly sensitive to change in temperature and precipitation on decadal to centennial time scales. For two decades, numerous studies on Holocene climate revealed a period marked by abrupt cold reversals (e.g. 8.2 ka event) with increasing frequency and magnitude after the Holocene Climatic Optimum, during the so-called Neoglacial period (roughly the last 4 ka). State-of-the-art studies indicate that largest alpine glaciers failed to exceed their Little Ice Age (LIA) extent during these LIA Type-Events, unlike certain smaller glaciers. In the French Alps, very few investigations were conducted to date on Holocene glacier variability. Almost all studies focused on the most glacierized area: the Mont Blanc massif, where suitable organic remains to apply radiocarbon dating and dendrochronology are available. Other glacierized massifs are poorly studied, without any Holocene/Neoglacial glacier chronology up to now. Here, we present the results of a study focusing on six glacier forefields distributed in the Ecrins massif. Detailed geomorphological mapping and in-situ produced 10Be dating were carried on multi-crested so-called "LIA composite moraines". The targeted ridges are located in distal position with respect to late LIA drift in order to identify Holocene cold pulses that have led to (or slightly exceeded) LIA-like glacier extent. The 35 10Be ages obtained revealed that the onset of Neoglacial occurred at ~4.2 ka, and that at least two other advances were recorded at ~3.3 ka and ~0.85 ka. One site has yielded a nearly complete Neoglacial record as four discrete events have been dated. These results highlight the potential of lateral moraine ridge stratigraphy which could yield accurate record when sufficiently preserved, but also the different preservation of landforms along the glacier margin which could censor the record.

  6. Bedrock gorges incising glacial hanging valleys (Western Alps, France): results from morphometric analysis, numerical modeling and 10Be cosmogenic dating

    NASA Astrophysics Data System (ADS)

    Valla, Pierre G.; van der Beek, Peter A.; Lague, Dimitri; Carcaillet, Julien

    2010-05-01

    Bedrock gorges are frequent features in glacial or post-glacial landscapes and allow measurements of fluvial bedrock incision in mountainous relief. Using digital elevation models, aerial photographs, topographic maps and field reconnaissance in the Pelvoux-Ecrins Massif (French Western Alps), we have identified ~30 tributary hanging valleys incised by gorges toward their confluence with the trunk streams. Longitudinal profiles of these tributaries are all convex and have abrupt knickpoints at the upper limit of oversteepened gorge reaches. From morphometric analyses, we find that mean channel gradients and widths, as well as knickpoint retreat rates, display a drainage-area dependence modulated by bedrock lithology. However, there appears to be no relation between horizontal retreat and vertical downwearing of knickpoints. Numerical modeling has been performed to test the capacity of different fluvial incision models to predict the inferred evolution of the gorges. Results from simple end-member models suggest transport-limited behavior of the bedrock gorges. Using a more sophisticated model including dynamic width adjustment and sediment-dependent incision rates, we show that bedrock gorge evolution requires significant supply of sediment from the gorge sidewalls triggered by gorge deepening, combined with pronounced inhibition of bedrock incision by sediment transport and deposition. We then use in-situ produced 10Be cosmogenic nuclides to date and quantify bedrock gorge incision into a single glacial hanging valley (Gorge du Diable). We have sampled gorge sidewalls and the active channel bed to derive both long-term and present-day incision rates. 10Be ages of sidewall profiles reveal rapid incision through the late Holocene (ca 5 ka), implying either delayed initiation of gorge incision after final ice retreat from internal Alpine valleys at ca 12 ka, or post-glacial surface reburial of the gorge. Both modeling results and cosmogenic dating suggest that

  7. A first 10Be cosmogenic glacial chronology from the High Atlas, Morocco, during the last glacial cycle.

    NASA Astrophysics Data System (ADS)

    Fink, David; Hughes, Philip; Fenton, Cassie

    2014-05-01

    Glacial geomorphological mapping, 10Be cosmogenic exposure ages of 21 erratics from cirque-valley systems and paleo-glacier climate modelling in the High Atlas Mountains, Morocco (31.1° N, 7.9° W), provides new and novel insights as to the history and evolution of the largest desert region on Earth. The Atlas Mountains display evidence of extensive and multiple Late Pleistocene glaciations whose extent is significantly larger than that recognised by previous workers. The largest glaciers formed in the Toubkal massif where we find 3 distinct phases of glacial advances within the last glacial cycle. The oldest moraines occurring at the lowest elevations have yielded eight 10Be ages ranging from 30 to 88 ka. Six of eight samples from moraines at intermediate elevations gave ages of 19 to 25 ka (2 outliers) which correlates well with the global Last Glacial Maximum (ca. 26-21 ka) and the last termination during marine isotope stage 2. Five erratics from the youngest and most elevated moraines yielded a suite of normally distributed exposure ages from 11 to 13 ka which supports a correlation with the northern hemisphere Younger Dryas (12.9-11.7 ka). The glacial record of the High Atlas effectively reflects moisture supply to the north-western Sahara Desert and can provide an indication of shifts between arid and pluvial conditions. The plaeo equilibrium line altitudes (ELA) of these three glacier phases was more than 1000 m lower than the predicted ELA based on today's temperatures. Glacier-climate modelling indicates that for each of these glacier phases climate was not only significantly cooler than today, but also much wetter. The new evidence on the extent, timing and palaeoclimatic significance of glaciations in this region has major implications for understanding moisture transfer between the North Atlantic Ocean and the Sahara Desert during Pleistocene cold stages.

  8. 10Be evidence for the Matuyama-Brunhes geomagnetic reversal in the EPICA Dome C ice core.

    PubMed

    Raisbeck, G M; Yiou, F; Cattani, O; Jouzel, J

    2006-11-01

    An ice core drilled at Dome C, Antarctica, is the oldest ice core so far retrieved. On the basis of ice flow modelling and a comparison between the deuterium signal in the ice with climate records from marine sediment cores, the ice at a depth of 3,190 m in the Dome C core is believed to have been deposited around 800,000 years ago, offering a rare opportunity to study climatic and environmental conditions over this time period. However, an independent determination of this age is important because the deuterium profile below a depth of 3,190 m depth does not show the expected correlation with the marine record. Here we present evidence for enhanced 10Be deposition in the ice at 3,160-3,170 m, which we interpret as a result of the low dipole field strength during the Matuyama-Brunhes geomagnetic reversal, which occurred about 780,000 years ago. If correct, this provides a crucial tie point between ice cores, marine cores and a radiometric timescale. PMID:17080088

  9. 10Be exposure age chronology of the last glaciation in the Krkonoše Mountains, Central Europe

    NASA Astrophysics Data System (ADS)

    Engel, Zbyněk; Braucher, Régis; Traczyk, Andrzej; Laetitia, Léanni; AsterTeam

    2014-02-01

    A new chronology of the last glaciation is established for the Krkonoše (Giant) Mountains, Central Europe, based on in-situ produced 10Be in moraine boulders. Exposure ages and Schmidt Hammer rebound values obtained for terminal moraines on the northern and southern flank of the mountains suggest that the oldest preserved moraines represent early phases of the Last Glacial Maximum (LGM). Large moraines at the outlet of the Snowy Cirques (Śnieżne Kotły) and in the middle part of the Úpa (Obří důl) trough were deposited around 21 ka while a series of smaller moraines above the LGM deposits represent readvances that occurred no later than 18.1 ± 0.6 ka, 15.7 ± 0.5 ka, 13.5 ± 0.5 ka and 12.9 ± 0.7 ka. An exposure age of 13.8 ± 0.4 ka obtained for protalus ramparts at the foot of the Úpská jáma Cirque headwall indicates that glaciers advanced only in north- to east-facing cirques during the Lateglacial. The last glacier fluctuation was synchronous with the Younger Dryas cold event. The timing of local glacier advances during the last glacial episode correlates with the late Weichselian glacier phases in the Alps and in the Bavarian/Bohemian Forest.

  10. Weathering histories of Chinese loess deposits based on uranium and thorium series nuclides and cosmogenic {sup 10}Be

    SciTech Connect

    Gu, Z.Y. |; Lal, D.; Liu, T.S.

    1997-12-01

    The long, continuous deposition of dust in the Chinese loess plateau offers an unique opportunity to study the nature of soil weathering in a wide range of climatic conditions. In this paper we report on measurements of concentrations of U- and Th-series nuclides and of major cations in 150 loess and paleosol samples from five sites, going back 2.5 Ma. Using the results for {sup 10}Be concentrations in these soils, we determined the absolute amounts of water added to several soil units and obtained: (1) first-order leaching constants for U and several cations and (2) the compositions of the soils contributing to the dust-source regions and of the dust at deposition. Further, based on analyses of {sup 230}Th in soils deposited in the past ca. 140 ka, we determined when the soils weathered in the source regions. We conclude that most of the weathering in the dust-source regions may have occurred during the interglacials. 34 refs., 8 figs., 2 tabs.

  11. Timing of terminal Pleistocene deglaciation at high elevations in southern and central British Columbia constrained by 10Be exposure dating

    NASA Astrophysics Data System (ADS)

    Margold, Martin; Stroeven, Arjen P.; Clague, John J.; Heyman, Jakob

    2014-09-01

    The Cordilleran Ice Sheet (CIS) covered most of British Columbia and southern Yukon Territory at the local Last Glacial Maximum (lLGM) during Marine Oxygen Isotope Stage 2. However, its subsequent demise is not well understood, particularly at high elevations east of its ocean-terminating margin. We present 10Be exposure ages from two high-elevation sites in southern and central British Columbia that help constrain the time of initial deglaciation at these sites. We sampled granodiorite erratics at elevations of 2126-2230 m a.s.l. in the Marble Range and 1608-1785 m a.s.l. in the Telkwa Range at the western margin of the Interior Plateau. The erratics at both sites are near ice-marginal meltwater channels that delineate the local ice surface slope and thus the configuration of the ice sheet during deglaciation. The locations of the erratics and their relations to meltwater channels ensure that the resulting 10Be ages date CIS deglaciation and not the retreat of local montane glaciers. Our sample sites emerged above the surface of the CIS as its divide migrated westward from the Interior Plateau to the axis of the Coast Mountains. Two of the four samples from the summit area of the Marble Range yielded apparent exposure ages of 14.0 ± 0.7 and 15.2 ± 0.8 ka. These ages are 1.8-3.0 ka younger than the well-established lLGM age of ca 17 ka for the Puget lobe of the CIS in Washington State; they are 1.7 ka younger than the lLGM age for the Puget lobe if a snow-shielding correction to their uncertainty-weighted mean age is applied. The other two samples yielded much older apparent exposure ages (20.6 ± 1.4 and 33.0 ± 1.5 ka), indicating the presence of inherited isotopes. Four samples collected from the summit area of the Telkwa Range in the Hazelton Mountains yielded well clustered apparent exposure ages of 10.1 ± 0.6, 10.2 ± 0.7, 10.4 ± 0.5, and 11.5 ± 1.1 ka. Significant present-day snow cover introduces a large uncertainty in the apparent exposure ages from

  12. Knickpoint retreat rates from cosmogenic 10Be; 30 exposure ages from western Scotland with implications for paraglacial bedrock incision

    NASA Astrophysics Data System (ADS)

    Jansen, J. D.; Fabel, D.; Codilean, A. T.; Bishop, P.; Hoey, Tb; Schnabel, C.; Xu, S.

    2009-04-01

    When a bedrock river is perturbed by accelerating rock uplift the perturbation is not transmitted instantaneously to the whole landscape; the new base level information must first spread through the channel network to hillslopes. Under detachment-limited conditions the new base level information is spread via knickpoint retreat, the rate of which ultimately governs response times to perturbation and therefore landscape evolution. Yet, owing to difficulties with measuring rates of erosional processes, knickpoint retreat rates are not widely documented. We examine bedrock river response to rapid, continuous rock uplift due to glacio-isostatic rebound following retreat of the Late Devensian icesheet from northern Britain. From four rivers in western Scotland, we infer knickpoint retreat rates from 30 measurements of cosmogenic 10Be concentrations on abandoned, fluvially-sculpted bedrock surfaces downstream of Holocene knickpoints. These data are among the first direct evidence that terrace exposure ages increase downstream consistent with the progressive abandonment of bedrock surfaces in the wake of a retreating knickpoint. We reflect upon our results in the context of paraglacial conditions that we infer to have involved initially high sediment flux declining over the Holocene. A simple unit stream power model is used to demonstrate how knickpoints affect erosional capacity along transient reaches. Bedrock channel width is insensitive to substrate erodibility, but we document here a sharp reduction in channel width at knickpoints, which is largely responsible for up to order-of-magnitude increases in stream power per unit area of the channel bed. The high rates of bedrock river incision that we document for postorogenic western Scotland are comparable to those reported for landside-dominated mountain belts. However, rather than stemming from towering relief or high-magnitude rock uplift, these rapid erosion rates seem to be the product of high sediment flux

  13. U-Th and 10Be constraints on sediment recycling in proglacial settings, Lago Buenos Aires, Patagonia

    NASA Astrophysics Data System (ADS)

    Cogez, Antoine; Herman, Frédéric; Pelt, Eric; Norton, Kevin; Darvill, Christopher; Christl, Marcus; Morvan, Gilles; Reuschlé, Thierry; Chabaux, François

    2016-04-01

    The sedimentary cycle includes the formation by erosion of rocks, transport and deposition. While erosion and deposition can be documented, the history of sediments between the time it is extracted from the rocks and ultimately deposited into basins remains a major challenge. However, the mechanism of transfer and alteration of the sediments during transport plays a key role in the evolution of basins, feedbacks between erosion and climate, and glacial-interglacial variability of sediment transport and weathering. This is particularly true in proglacial settings because large overdeepenings, in particular, are potential sediment traps for which the efficiency at evacuating those sediments is largely unknown. The Lago Buenos Aires moraines in Patagonia are particularly interesting because they are imbricated from the older in the outer part to the younger in the inner part of the system. We sampled fine grained sediments from these moraines and measured U-Th isotopes in the 4-50 μm silicate fraction. Deposition ages were refined using 10Be exposure ages. We show first that the comminution ages model can be improved by measuring also Th isotopes, from which weathering rates can be deduced. Moreover we show from our data that there is a time lag of 300 kyr on average between erosion and deposition in the moraine. This could be attributed to the long residence time of sediments in the lake overdeepening. This conclusion raises perspectives about the transport times and dynamic of the sediments during a whole sedimentary cycle, and the subsequent effect on weathering. This conclusion could also contradict some assumptions commonly made for our erosion rates/sediment fluxes reconstructions based on river sediments analysis, in recently deglaciated catchments.

  14. Erosion rates and landscape evolution of the lowlands of the Upper Paraguay river basin (Brazil) from cosmogenic 10Be

    NASA Astrophysics Data System (ADS)

    Pupim, Fabiano do Nascimento; Bierman, Paul R.; Assine, Mario Luis; Rood, Dylan H.; Silva, Aguinaldo; Merino, Eder Renato

    2015-04-01

    The importance of Earth's low sloping areas in regard to global erosion and sediment fluxes has been widely and vigorously debated. It is a crucial area of research to elucidate geologically meaningful rates of land-surface change and thus the speed of element cycling on Earth. However, there are large portions of Earth where erosion rates have not been well or extensively measured, for example, the tropical lowlands. The Cuiabana lowlands are an extensive low-altitude and low-relief dissected metamorphic terrain situated in the Upper Paraguay river basin, central-west Brazil. Besides exposures of highly variable dissected metamorphic rocks, flat residual lateritic caps related to a Late Cenozoic planation surface dominate interfluves of the Cuiabana lowlands. The timescale over which the lowlands evolved and the planation surface developed, and the rate at which they have been modified by erosion, are poorly known. Here, we present measurements of in situ produced cosmogenic 10Be in outcropping metamorphic bedrock and clastic-lateritic caps to quantify rates of erosion of the surface and associated landforms in order to better understand the Quaternary landscape evolution of these lowlands. Overall, slow erosion rates (mean 10 m/Ma) suggest a stable tectonic environment in these lowlands. Erosion rates vary widely between different lithologies (range 0.57 to 28.3 m/Ma) consistent with differential erosion driving regional landform evolution. The lowest erosion rates are associated with the low-relief area (irregular plains), where clastic-laterite (mean 0.67 m/Ma) and quartzite (mean 2.6 m/Ma) crop out, whereas the highest erosion rates are associated with dissection of residual hills, dominated by metasandstone (mean 11.6 m/Ma) and phyllite (mean 27.6 m/Ma). These data imply that the Cuiabana lowland is comprised of two dominant landform sets with distinct and different dynamics. Because the planation surface (mostly lowlands) is lowering and losing mass more

  15. El Niño forcing on 10Be-based surface denudation rates in the northwestern Peruvian Andes?

    NASA Astrophysics Data System (ADS)

    Abbühl, Luca M.; Norton, Kevin P.; Schlunegger, Fritz; Kracht, Oliver; Aldahan, Ala; Possnert, Göran

    2010-11-01

    therefore interpret that Holocene landscape evolution has largely been controlled by climate. The ky-timescale of the 10Be data together with the transience of the landscape implies that El Niño events in northwestern Peru have occurred since at least the Holocene, and that adjustment to channel incision is still taking place.

  16. Use of Arrott plots to identify Néel temperature (T{sub N}) in metamagnetic Ni{sub 48}Co{sub 6}Mn{sub 26}Al{sub 20} polycrystalline ribbons

    SciTech Connect

    Singh, Rohit; Kumar Srivastava, Saurabh; Chatterjee, Ratnamala E-mail: rmala@physics.iitd.ac.in; Nigam, Arun K.; Khovaylo, Vladimir V.; Varga, Lajos K.

    2013-12-28

    (Ni{sub 48}Co{sub 6})Mn{sub 26}Al{sub 20} polycrystalline ribbons with B2 structure at room temperature are investigated. Considering the presence of competing magnetic interactions, Arrott-plot analysis gives T{sub N} ∼ 170 K. A broad ferromagnetic-paramagnetic transition (T{sub C}) is observed at ∼200 K. H-T phase-diagram is used to validate the presence of competing exchange interactions that persist till very close to T{sub C}. Based on Néel theory, a cluster model is used to explain the presence of ferromagnetic and antiferromagnetic clusters in the sample. Formation of ferromagnetic clusters can be understood in terms of positive exchange interactions among the Mn atoms that are neighboring Co atoms located at Ni sites.

  17. Inverse Kinematic Study of the (26g)Al(d,p)(27)Al Reaction and Implications for Destruction of (26)Al in Wolf-Rayet and Asymptotic Giant Branch Stars.

    PubMed

    Margerin, V; Lotay, G; Woods, P J; Aliotta, M; Christian, G; Davids, B; Davinson, T; Doherty, D T; Fallis, J; Howell, D; Kirsebom, O S; Mountford, D J; Rojas, A; Ruiz, C; Tostevin, J A

    2015-08-01

    In Wolf-Rayet and asymptotic giant branch (AGB) stars, the (26g)Al(p,γ)(27)Si reaction is expected to govern the destruction of the cosmic γ-ray emitting nucleus (26)Al. The rate of this reaction, however, is highly uncertain due to the unknown properties of key resonances in the temperature regime of hydrogen burning. We present a high-resolution inverse kinematic study of the (26g)Al(d,p)(27)Al reaction as a method for constraining the strengths of key astrophysical resonances in the (26g)Al(p,γ)(27)Si reaction. In particular, the results indicate that the resonance at E(r)=127  keV in (27)Si determines the entire (26g)Al(p,γ)(27)Si reaction rate over almost the complete temperature range of Wolf-Rayet stars and AGB stars. PMID:26296114

  18. A preliminary study of direct 10Be2+ counting in AMS using the super-halogen anion BeF3-

    NASA Astrophysics Data System (ADS)

    Fu, Yun-Chong; Zhang, Li; Zhou, Wei-Jian; Zhao, Xiao-Lei; Wu, Zhen-Kun; Zhao, Guo-Qing; Liu, Qi; Lu, Xue-Feng; Zhao, Wen-Nian; Huang, Chun-Hai

    2015-10-01

    The key to effective 10Be measurements by AMS is to efficiently suppress the interference of the isobar 10B and at the same time optimize 10Be transmission. In this work, a new approach of measuring 10Be by AMS has been studied. It uses the super-halogen anion of beryllium, BeF3-, which inherently suppresses 10B interference by nearly 5 orders of magnitude because the accompanying BF3- anion is rarely formed. The resulting 10B suppression factor is not as high as that achieved with energy degrader foils, but the 10B and 10Be separation in the final ionization detector was found to result in sufficient total 10B suppression for 10Be2+ to be counted directly at ∼6 MeV energies. Although the stripping yield from 10BeF3- to 10Be2+ is not as large as that from 10BeO-, this inefficiency is compensated by avoiding the reduction in transmission due to charge fraction splitting and optical transmission losses after the degrader foil. This paper summarizes our first observation of the direct 10Be2+ counting approach using the 3 MV multi-element system at the Xi'an AMS.

  19. Cosmic ray event of A.D. 774-775 shown in quasi-annual 10Be data from the Antarctic Dome Fuji ice core

    NASA Astrophysics Data System (ADS)

    Miyake, Fusa; Suzuki, Asami; Masuda, Kimiaki; Horiuchi, Kazuho; Motoyama, Hideaki; Matsuzaki, Hiroyuki; Motizuki, Yuko; Takahashi, Kazuya; Nakai, Yoichi

    2015-01-01

    content in tree rings and 10Be concentration records in polar ice core provide information about past cosmic ray intensities. The A.D. 774-775 cosmic ray event has been identified by 14C measurement in several tree rings from all over the world. Although the quasi-decadal 10Be Dome Fuji data in the Antarctic ice core also shows a sharp peak around A.D. 775, annual 10Be variations in the Dome Fuji core or in other cores have not been revealed. We have measured quasi-annual 10Be concentrations from approximately A.D. 763-794 in the Dome Fuji ice core, and detected a clear increase (~80% above the baseline) in 10Be concentration around A.D. 775. However, an accurate height of this increase is not straightforwardly estimated due to the background variation in 10Be concentration. The 10Be increase can be due to the same cosmic ray event as shown in the 14C content in A.D. 774-775.

  20. Hillslope lowering rates and mobile-regolith residence times from in situ and meteoric 10Be analysis: Boulder Creek Critical Zone Observatory, Colorado

    NASA Astrophysics Data System (ADS)

    Foster, M. A.; Anderson, R. S.; Wyshnytzky, C.; Ouimet, W. B.; Dethier, D. P.

    2014-12-01

    Mobile regolith is produced as weathered saprolite is entrained into the mobile layer. The rate of mobile-regolith production and its residence time on hillslopes shapes the topography and evolution of hillslopes. We calculate the production rate of mobile regolith and the mobile-regolith residence times on active hillslopes in Gordon Gulch, within the Boulder Creek Critical Zone Observatory (CZO), Colorado. We find mobile-regolith production rates (average 3.1 cm/ka) and residence times (average 10-20 ka) derived from both in situand meteoric methods agree. Lowering-rates derived from our study are also comparable to basin-averaged denudation rates for small basins in the Colorado Front Range (Dethier and Lazarus, 2006). In this study, we have measured both in situ and meteoric 10Be in saprolite and mobile regolith separately. We find that, on average, two-thirds of in situ 10Be is produced within saprolite, and that at least one-tenth of the meteoric 10Be inventories are stored in saprolite. In the case of in situ 10Be, this simply reflects the exponential fall-off in production rates through a thin mobile-regolith cover. In the case of meteoric 10Be, our calculations suggest that >40% of the meteoric 10Be deposition occurs within the saprolite. Most studies that utilize 10Be report residence times and soil-production rates based on concentrations in either the mobile regolith or saprolite; therefore, our 10Be data highlight the importance of clearly identifying mobile and immobile portions of the regolith, constraining its 10Be inventory, and use of consistent terminology for the mobile-layer.

  1. Production rate and climate influences on the variability of 10Be deposition simulated by ECHAM5-HAM: Globally, in Greenland, and in Antarctica

    NASA Astrophysics Data System (ADS)

    Heikkilä, U.; Smith, A. M.

    2013-03-01

    Ice core concentrations of 10Be are used as a proxy for solar activity, but they might be affected by atmospheric transport and deposition and their changes. During the Holocene, the influence is likely to be small, but during glacials it has to be accounted for. First, the climate influence has to be understood during the present climate. This study uses an ECHAM5-HAM 30-year climatological simulation of 10Be to investigate the production and climate-related influences on 10Be deposition with focus on Greenland and Antarctica. We examine the climate modes driving snow accumulation and hence potentially 10Be deposition over a climatologically relevant period. The North Atlantic Oscillation (NAO) is found to be the main driver of changes in precipitation and 10Be deposition in Greenland, in agreement with previous studies. In Antarctica, the picture is more complex as precipitation and 10Be deposition are only weakly correlated with the Southern Annular Mode (SAM), El Niño-Southern Oscillation (ENSO), or Zonal Wave 3 pattern (ZW3). The results suggest that on seasonal scale, 10Be deposition is linked with both precipitation rate and tropopause height, mainly due to the similar seasonal cycle. However, the correlation with tropopause height persists on the annual time scale. All in all, 10Be variability in Antarctica is an interplay of several processes whose contribution varies in time and space. When interpreting 10Be ice core records for solar activity, the time scale is essentially important. On seasonal scale, the 10Be signal is dominated by weather influences, but on multiannual scales, the production rate is the main driver. On multidecadal scale, large long-term trends in climatic factors have the potential to distort the signal again as is seen in 10Be records during glacials. This study shows how climate modes connect to 10Be variability and how this connection could be used to correct for the climate impact. The established connections during present

  2. {alpha}-decaying states in {sup 10,12}Be populated in the {sup 10}Be({sup 14}C,{sup 10,12}Be) reaction

    SciTech Connect

    Curtis, N.; Ashwood, N.I.; Bloxham, T.R.; Freer, M.; McEwan, P.; Price, D.L.; Baby, L.T.; Caussyn, D.D.; Spingler, D.; Wiedenhover, I.; Baldwin, T.D.; Catford, W.N.; Harlin, C.W.

    2006-05-15

    A search has been made for the {sup 6}He+{sup 6}He and {alpha} + {sup 8}He decay of the molecular rotational band in {sup 12}Be using the {sup 10}Be({sup 14}C,{sup 12}Be*){sup 12}C reaction at 88.5 MeV. Although the {alpha} + {sup 6}He decay of {sup 10}Be was observed in the data set there is no evidence for the breakup of {sup 12}Be. The cross-section upper limits for the {sup 10}Be({sup 14}C,{sup 6}He {sup 6}He){sup 12}C and {sup 10}Be({sup 14}C,{alpha} {sup 8}He){sup 12}C reactions are 50 and 300 nb respectively.

  3. Linking the10Be continental record of Lake Baikal to marine and ice archives of the last 50 ka: Implication for the global dust-aerosol input

    USGS Publications Warehouse

    Aldahan, A.; Possnert, G.; Peck, J.; King, J.; Colman, S.

    1999-01-01

    We present here a 10Be profile from the continental sediments of Lake Baikal (the world's largest fresh water lake), which, for the first time, shows the ??? 40 ka 10Be enhancement and a pattern that strongly matches those from the marine and ice records for the last 50 ka. This finding provides a new horizon for global and regional correlation of continental archives. Additionally, our VADM-predicted 10Be production confirms and further strengthens a common global cause (geomagnetic field intensity) for the change in atmospheric 10Be over the last 50 ka. We also show that most of the 10Be inventory to the lake has been provided by riverine input, but with a significant addition from direct precipitation and dust-aerosol fallout. We estimate a higher dust-aerosol contribution of 10Be during the Holocene and interstadial stage 3 (22-50 ka) as compared with the glacial period (12-22 ka). Copyright 1999 by the American Geophysical Union.

  4. Authigenic 10Be/9Be Ratio Signatures of the Cosmogenic Nuclide Production Linked to Geomagnetic Dipole Moment Variation During and Since the Brunhes/Matuyama Boundary

    NASA Astrophysics Data System (ADS)

    Simon, Q.; Thouveny, N.; Bourles, D. L.; Ménabréaz, L.; Valet, J. P.; Valery, G.; Choy, S.

    2015-12-01

    The atmospheric production rate of cosmogenic nuclides is linked to the geomagnetic dipole moment (GDM) by a non-linear inverse relationship. Large amplitude GDM variations associated with reversals and excursions can potentially be reconstructed using time variation of the cosmogenic beryllium-10 (10Be) production recorded in ocean sediments. Downcore profiles of authigenic 10Be/9Be ratios (proxy of atmospheric 10Be production) in oceanic cores provide independent and additional records of the evolution of the geomagnetic intensity and complete previous information derived from relative paleointensity (RPI). Here are presented new authigenic 10Be/9Be results obtained from cores MD05-2920 and from the top of core MD05-2930 collected in the West Equatorial Pacific Ocean. Completing data of Ménabréaz et al. (2012, 2014), these results provide the first continuous 10Be production rate sedimentary record covering the last 800 ka. Along these cores, authigenic 10Be/9Be ratio peaks are recorded - within methodological errors - at the stratigraphic level of RPI lows. High-resolution chronologies (δ18O-derived) lead to interpret these peaks as successive global 10Be overproduction events triggered by geomagnetic dipole lows present in the PISO-1500 and Sint-2000 stacks. The largest amplitude 10Be production enhancement is synchronous to the very large decrease of the dipole field associated with the last polarity reversal (772 ka). It is consistent in shape and duration with the peak recorded in core MD90-0961 from the Maldive area (Indian Ocean) (Valet et al. 2014). Two significant 10Be production enhancements are coeval with the Laschamp (41 ka) and Icelandic basin (190 ka) excursions, while 10Be production peaks of lower amplitude correlate to other recognized excursions such as the Blake (120 ka), Pringle-Falls (215 ka), Portuguese Margin (290 ka), Big Lost (540 ka) among others. This study provides new data on the amplitude and timing of dipole field variations

  5. Initial Test Determination of Cosmogenic Nuclides in Magnetite

    NASA Astrophysics Data System (ADS)

    Matsumura, H.; Caffee, M. W.; Nagao, K.; Nishiizumi, K.

    2014-12-01

    Long-lived radionuclides, such as 10Be, 26Al, and 36Cl, are produced by cosmic rays in surficial materials on Earth, and used for determinations of cosmic-ray exposure ages and erosion rates. Quartz and limestone are routinely used as the target minerals for these geomorphological studies. Magnetite also contains target elements that produce abundant cosmogenic nuclides when exposed to the cosmic rays. Magnetite has several notable merits that enable the measurement of cosmogenic nuclides: (1) the target elements for production of cosmogenic nuclides in magnetite comprise the dominant mineral form of magnetite, Fe3O4; (2) magnetite can be easily isolated, using a magnet, after rock milling; (3) multiple cosmogenic nuclides are produced by exposure of magnetite to cosmic-ray secondaries; and (4) cosmogenic nuclides produced in the rock containing the magnetite, but not within the magnetite itself, can be separated using nitric acid and sodium hydroxide leaches. As part of this initial study, magnetite was separated from a basaltic sample collected from the Atacama Desert in Chili (2,995 m). Then Be, Al, Cl, Ca, and Mn were separated from ~2 g of the purified magnetite. We measured cosmogenic 10Be, 26Al, and 36Cl concentrations in the magnetite by accelerator mass spectrometry at PRIME Lab, Purdue University. Cosmogenic 3He and 21Ne concentrations of aliquot of the magnetite were measured by mass spectrometry at the University of Tokyo. We also measured the nuclide concentrations from magnetite collected from a mine at Ishpeming, Michigan as a blank. The 10Be and 36Cl concentrations as well as 3He concentration produce concordant cosmic ray exposure ages of ~0.4 Myr for the Atacama basalt. However, observed high 26Al and 21Ne concentrations attribute to those nuclides incorporation from silicate impurity.

  6. Constraints on the last deglaciation of the Ross Sea Sector of the West Antarctic Ice Sheet (WAIS) from 10Be dating

    NASA Astrophysics Data System (ADS)

    Bill, N. S.; Clark, P. U.; Kurz, M. D.; Marcott, S. A.; Caffee, M. W.

    2014-12-01

    We present new 10Be surface exposure ages from glacial erratic boulders from several locations in McMurdo Sound in order to constrain the deglacial history of the West Antarctic Ice Sheet. Previous model and field data indicate that the present day Ross Ice Shelf was a grounded ice sheet, with the grounding line extending to near the continental shelf edge during the Last Glacial Maximum (LGM). However, the timing and rate of the last deglaciation of the Ross Sea Sector of the West Antarctic Ice Sheet remain uncertain. We sampled granitic and basaltic erratic boulders for dating with the cosmogenic nuclides 10Be and 3He; in situ 14C dating will be used to assess complex burial histories. The 10Be ages on erratics near or at the upper limit of Ross Sea Drift that do not appear to have inheritance range from 17 to 26 ka. 10Be ages from erratics below the limit of the (LGM) Ross Sea Drift suggest final deglaciation by ~11 ka. New 10Be ages from more highly weathered glacial deposits above the Ross Sea drift near Blue Glacier suggest an age range of 141 to 171 ka.

  7. Detection of erosion events using 10Be profiles: example of the impact of agriculture on soil erosion in the Chesapeake Bay area (U.S.A.)

    USGS Publications Warehouse

    Valette-Silver, J. N.; Brown, L.; Pavich, M.; Klein, J.; Middleton, R.

    1986-01-01

    10Be concentration, total carbon and grain-size were measured in cores collected in undisturbed estuarine sediments of three tributaries of the Chesapeake Bay. These cores were previously studied by Davis [1] and Brush [2,3] for pollen content, age and sedimentation rate. In this work, we compare the results obtained for these various analyses. In the cores, we observed two increases in 10Be concentration concomitant with two major changes in the pollen composition of the sediments. These two pollen changes each correspond to well-dated agricultural horizons reflecting different stages in the introduction of European farming techniques [2]. In the Chesapeake Bay area, the agricultural development, associated with forest clearing, appears to have triggered the erosion, transport, and sedimentation into the river mouths of large quantities of 10Be-rich soils. This phenomenon explains the observed rise in the sedimentation rate associated with increases in agricultural land-use. ?? 1986.

  8. 10Be ages of glacial and meltwater features northwest of Lake Superior: a chronology of Laurentide Ice sheet deglaciation and eastward flooding from Glacial Lake Agassiz

    NASA Astrophysics Data System (ADS)

    Kelly, M. A.; Fisher, T. G.; Lowell, T.; Barnett, P.; Schaefer, J. M.; Schwartz, R.

    2009-12-01

    Significant controversy exists as to the role of Laurentide Ice Sheet meltwater in causing the Younger Dryas cold event. Recently, Lowell et al. (2009) presented a radiocarbon chronology of Laurentide Ice Sheet deglaciation along a north-south transect located northwest of Lake Superior. These authors concluded that the presence of the Laurentide Ice Sheet precluded an eastward drainage of glacial Lake Agassiz until mid-Younger Dryas time. Here, we use 10Be surface exposure dating to examine the timing of the eastward drainage of Lake Agassiz. We present 10Be ages of moraines and erratic boulders in meltwater pathways along the same transect as Lowell et al. (2009), northwest of Lake Superior. In general, 10Be ages of glacial features are similar to, or slightly older than, basal radiocarbon ages of nearby lakes. Based on the 10Be chronology, deglaciation of the Laurentide Ice Sheet in this region occurred between ~13,000 and 10,000 yr BP. We also present the first direct ages of flood deposits in bedrock channels presumably associated with the eastern drainage of Lake Agassiz. Evidence for flooding includes extensive channels incised into bedrock and enormous bedforms located north of Lake Superior. 10Be ages of two flood deposits near the Roaring River and Mundell Lake yield mean 10Be ages of ~11,700 and 11,000 yr BP, respectively. These ages indicate that occupation of the channels postdates initiation of the Younger Dryas by more than 1,000 years and are in general agreement with a basal radiocarbon age from nearby Lower Vail Lake (Teller et al., 2005). Preliminary paleohydrological estimates based on bedform clast sizes and channel geometries are velocities and discharges of 2.8-19.8 ms-1 and 4,200-30,000 m3s-1 at the Roaring River location and 2.5-17.5 ms-1 and 49,000-349,000 m3s-1 at the Mundell Lake location.

  9. EVOLUTION OF THE SOLAR NEBULA. IX. GRADIENTS IN THE SPATIAL HETEROGENEITY OF THE SHORT-LIVED RADIOISOTOPES {sup 60}Fe AND {sup 26}Al AND THE STABLE OXYGEN ISOTOPES

    SciTech Connect

    Boss, Alan P.

    2011-10-01

    Short-lived radioisotopes (SLRIs) such as {sup 60}Fe and {sup 26}Al were likely injected into the solar nebula in a spatially and temporally heterogeneous manner. Marginally gravitationally unstable (MGU) disks, of the type required to form gas giant planets, are capable of rapid homogenization of isotopic heterogeneity as well as of rapid radial transport of dust grains and gases throughout a protoplanetary disk. Two different types of new models of an MGU disk in orbit around a solar-mass protostar are presented. The first set has variations in the number of terms in the spherical harmonic solution for the gravitational potential, effectively studying the effect of varying the spatial resolution of the gravitational torques responsible for MGU disk evolution. The second set explores the effects of varying the initial minimum value of the Toomre Q stability parameter, from values of 1.4 to 2.5, i.e., toward increasingly less unstable disks. The new models show that the basic results are largely independent of both sets of variations. MGU disk models robustly result in rapid mixing of initially highly heterogeneous distributions of SLRIs to levels of {approx}10% in both the inner (<5 AU) and outer (>10 AU) disk regions, and to even lower levels ({approx}2%) in intermediate regions, where gravitational torques are most effective at mixing. These gradients should have cosmochemical implications for the distribution of SLRIs and stable oxygen isotopes contained in planetesimals (e.g., comets) formed in the giant planet region ({approx}5 to {approx}10 AU) compared to those formed elsewhere.

  10. Evaluating the steady-state assumption for mobile-regolith on hillslopes using in situ-produced 10Be, Boulder Creek CZO, Colorado Front Range

    NASA Astrophysics Data System (ADS)

    Foster, M. A.; Anderson, R. S.; Spitzmiller, B. L.

    2012-12-01

    Release of mobile regolith from underlying weathered rock (saprolite) is a crucial process in the evolution of landscapes. To calculate the lowering rate of the saprolite interface with cosmogenic radionuclides (CRN), it is often assumed that the mobile-regolith cover was steady over a timescale characterized by the saprolite-exhumation rate (w) and decay length scale of CRN production. We collected in situ 10Be data along north- and south-facing transects in Gordon Gulch, within the Boulder Creek CZO, to test the steady-state condition on a complex hillslope. At steady state, the mean concentration of 10Be within a mobile-regolith column of thickness H may be calculated if the saprolite-exhumation rate is known independently. In situ 10Be data from saprolite samples may be used to document the saprolite-exhumation rate. We report data from 9 saprolite samples, 24 mobile-regolith samples, and 3 samples from outcrops adjacent to soil pits. In Gordon Gulch study-pits, saprolite-lowering rates (w) vary significantly between 15 and 55 μm/a, with mean values of 36 and 32 μm/a for north- and south-facing slopes, respectively. Calculated mobile-regolith residence times (t=H/w) also vary widely from ~10-115 ka. Local lowering rates (w) exceed the basin-averaged denudation rate of ~22 μm/a calculated from 10Be concentrations in modern Gordon Gulch stream sediment [D. Dethier, unpublished data]. Preliminary results from 10Be concentrations in mobile regolith suggest that vertical mixing is minimal. Mean 10Be concentrations in the mobile-regolith column are close to those expected for the steady-state case. Thus our data appear to support the steady-state assumption. However, these steady state-predictions are only as sound as the local lowering rates calculated from 10Be in saprolite samples. We suspect that the mismatch between local lowering rates and basin-wide denudation may arise from temporal variations in mobile-regolith cover (H). Changes in hillslope transport

  11. Towards sediment residence time in a Himalayan catchment? Insights from paired in-situ 14C and 10Be measurements in river sands

    NASA Astrophysics Data System (ADS)

    Lupker, M.; Hippe, K.; Wacker, L.; Wieler, R.

    2014-12-01

    Cosmogenic nuclides in detrital river sediments have been widely applied to derive denudation rates and sediment fluxes across entire catchments. Nuclides, such as 10Be, allow the derivation of denudation rates integrated over several hundreds to thousands of years, but single isotopic systems often provide little information on the intricate dynamics that control the export of sediments from catchments. The quantification of sediment storage and recycling within catchments is nevertheless crucial for a better understanding of the variability of sediments fluxes and their implication for landscape evolution. The paired measurement of 10Be along with cosmogenic, in-situ 14C in river sediments may provide new insides into sediment dynamics over kyr time scales for which other nuclides are not suitable [1,2]. In an effort to better understand the sediment dynamics in active orogens we combine in-situ 14C and 10Be measurements from the Kosi basin in eastern Nepal (~53 000 km2). Our preliminary 14C/10Be data shows apparent burial/storage ages of 14 to 21 kyr in the sediments currently exported by the river. These elevated burial ages suggest a larger storage component than previously thought in these catchments, even though possible biases associated to the use of 14C/10Be in sediments as burial chronometer have to be considered: First, the short half-life of 14C cannot be neglected and hence basin wide denudation cannot be considered as a simple mixing of sediments from individually eroding surfaces, introducing bias towards higher apparent burial ages in most settings. Second, in steep environments, sediments supplied by deep-seated landslides carry a buried signature that should not be confounded with sediment storage in the catchment. The importance of both biases needs to be quantified carefully, before basin-wide storage can be quantified. [1] Lauer & Willenbring, 2010 - JGR-Earth, vol. 115, F04018. [2] Hippe et al., 2012 - Geomorphology, vol. 179, pp. 58-70.

  12. Comparing past accumulation rate reconstructions in East Antarctic ice cores using 10Be, water isotopes and CMIP5-PMIP3 models

    NASA Astrophysics Data System (ADS)

    Cauquoin, A.; Landais, A.; Raisbeck, G. M.; Jouzel, J.; Bazin, L.; Kageyama, M.; Peterschmitt, J.-Y.; Werner, M.; Bard, E.; Aster Team

    2015-03-01

    Ice cores are exceptional archives which allow us to reconstruct a wealth of climatic parameters as well as past atmospheric composition over the last 800 kyr in Antarctica. Inferring the variations in past accumulation rate in polar regions is essential both for documenting past climate and for ice core chronology. On the East Antarctic Plateau, the accumulation rate is so small that annual layers cannot be identified and accumulation rate is mainly deduced from the water isotopic composition assuming constant temporal relationships between temperature, water isotopic composition and accumulation rate. Such an assumption leads to large uncertainties on the reconstructed past accumulation rate. Here, we use high-resolution beryllium-10 (10Be) as an alternative tool for inferring past accumulation rate for the EPICA Dome C ice core, in East Antarctica. We present a high-resolution 10Be record covering a full climatic cycle over the period 269 to 355 ka from Marine Isotope Stage (MIS) 9 to 10, including a period warmer than pre-industrial (MIS 9.3 optimum). After correcting 10Be for the estimated effect of the palaeomagnetic field, we deduce that the 10Be reconstruction is in reasonably good agreement with EDC3 values for the full cycle except for the period warmer than present. For the latter, the accumulation is up to 13% larger (4.46 cm ie yr-1 instead of 3.95). This result is in agreement with the studies suggesting an underestimation of the deuterium-based accumulation for the optimum of the Holocene (Parrenin et al. 2007a). Using the relationship between accumulation rate and surface temperature from the saturation vapour relationship, the 10Be-based accumulation rate reconstruction suggests that the temperature increase between the MIS 9.3 optimum and present day may be 2.4 K warmer than estimated by the water isotopes reconstruction. We compare these reconstructions to the available model results from CMIP5-PMIP3 for a glacial and an interglacial state, i

  13. Rapid ice collapse in Disko Bugt: A new 10Be chronology of the last recession of the western Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Kelley, S. E.; Briner, J. P.; Young, N. E.

    2012-12-01

    Because key sectors of the Greenland and Antarctic ice sheets are marine-based, understanding the past retreat rates of marine glaciers is relevant to forecasting future ice-sheet change. We present a 10Be chronology of ice retreat from Disko Bugt, western Greenland, by obtaining samples for 10Be dating from six coastal locations surrounding Disko Bugt. Our 10Be chronology uses a locally calibrated 10Be production rate and provides direct age control on ice retreat. We build on the existing radiocarbon chronology by reducing uncertainty related to (1) the reservoir correction of marine fauna and (2) bulk-lake-sediment minimum-radiocarbon ages. Our results so far from three sites reveal that ice retreat through Disko Bugt occurred rapidly, with ages from southern Disko Island, bordering the northwestern portion of Disko Bugt, demonstrating ice-free conditions at 9.7±0.2 ka (n=3). On the eastern coast of Disko Bugt near Ilulissat, samples yield an average age of 10.2±0.3 ka (n=4) for ice recession. Samples from the Nuuk Peninsula in southeastern Disko Bugt, suggest this corner of Disko Bugt became ice free at 9.4±0.2 ka (n=2). In addition, we anticipate that our pending 10Be ages from three additional sites (islands in the western-central potion of Disko Bugt, a coastal site near the town of Aasiaat in the southwestern corner, and the east-central coast of Disko Bugt near the town of Qasigiannguit), combined with existing results (both 10Be ages and previously published radiocarbon ages) will allow us to constrain both the timing and rate of retreat of the Greenland Ice Sheet through Disko Bugt during the early Holocene. Our findings so far constrain the retreat in an area where high-precision records of land-based ice retreat already exist. This will provide one of the longest records of ice-margin recession in western Greenland, which in turn will provide important constraints for modeling efforts focused on understanding the response of the GIS to past and

  14. Determination of predevelopment denudation rates of an agricultural watershed (Cayaguas River, Puerto Rico) using in-situ-produced 10Be in river-borne quartz

    USGS Publications Warehouse

    Brown, E.T.; Stallard, R.F.; Larsen, M.C.; Bourles, D.L.; Raisbeck, G.M.; Yiou, F.

    1998-01-01

    Accurate estimates of watershed denudation absent anthropogenic effects are required to develop strategies for mitigating accelerated physical erosion resulting from human activities, to model global geochemical cycles, and to examine interactions among climate, weathering, and uplift. We present a simple approach to estimate predevelopment denudation rates using in-situ-produced cosmogenic 10Be in fluvial sediments. Denudation processes in an agricultural watershed (Cayaguas River Basin, Puerto Rico) and a matched undisturbed watershed (Icacos River Basin) were compared using 10Be concentrations in quartz for various size fractions of bed material. The coarse fractions in both watersheds bear the imprint of long subsurface residence times. Fine material from old shallow soils contributes little, however, to the present-day sediment output of the Cayaguas. This confirms the recent and presumably anthropogenic origin of the modern high denudation rate in the Cayaguas Basin and suggests that pre-agricultural erosional conditions were comparable to those of the present-day Icacos.

  15. Effect of thermal cycling on the mechanical properties of Zr41Ti14Cu12.5Ni10Be22.5 alloy

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Shao, Yang; Gong, Pan; Yao, KeFu

    2012-12-01

    The effect of thermal cycling treatment on mechanical properties and thermal stability of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass is investigated. The metallic glassy samples are sealed into quartz tubes under high vacuum condition, and liquid nitrogen together with electric furnace are used to control a periodical temperature variation between -196°C and 150°C. The structure and properties of the tested samples for different thermal cycles have been examined by X-ray diffraction analysis, mechanical properties measurement and thermal analysis. It has been found that the structure and properties of the samples do not show a significant change even after 200 cycles, which suggests Zr41Ti14Cu12.5Ni10Be22.5 alloy as having potential in aerospace environment.

  16. 10Be constrains the sediment sources and sediment yields to the Great Barrier Reef from the tropical Barron River catchment, Queensland, Australia

    NASA Astrophysics Data System (ADS)

    Nichols, Kyle K.; Bierman, Paul R.; Rood, Dylan H.

    2014-11-01

    Estimates of long-term, background sediment generation rates place current and future sediment fluxes to the Great Barrier Reef in context. Without reliable estimates of sediment generation rates and without identification of the sources of sediment delivered to the reef prior to European settlement (c. 1850), determining the necessity and effectiveness of contemporary landscape management efforts is difficult. Here, using the ~ 2100-km2 Barron River catchment in Queensland, Australia, as a test case, we use in situ-produced 10Be to derive sediment generation rate estimates and use in situ and meteoric 10Be to identify the source of that sediment, which enters the Coral Sea near Cairns. Previous model-based calculations suggested that background sediment yields were up to an order of magnitude lower than contemporary sediment yields. In contrast, in situ 10Be data indicate that background (43 t km- 2 y- 1) and contemporary sediment yields (~ 45 t km- 2 y- 1) for the Barron River are similar. These data suggest that the reef became established in a sediment flux similar to what it receives today. Since western agricultural practices increased erosion rates, large amounts of sediment mobilized from hillslopes during the last century are probably stored in Queensland catchments and will eventually be transported to the coast, most likely in flows triggered by rare but powerful tropical cyclones that were more common before European settlement and may increase in strength as climate change warms the south Pacific Ocean. In situ and meteoric 10Be concentrations of Coral Sea beach sand near Cairns are similar to those in rivers on the Atherton Tablelands, suggesting that most sediment is derived from the extensive, low-gradient uplands rather than the steep, more rapidly eroding but beach proximal escarpment.

  17. Tectonic and climatic control on terrace formation: Coupling in situ produced 10Be depth profiles and luminescence approach, Danube River, Hungary, Central Europe

    NASA Astrophysics Data System (ADS)

    Ruszkiczay-Rüdiger, Zsófia; Braucher, Régis; Novothny, Ágnes; Csillag, Gábor; Fodor, László; Molnár, Gábor; Madarász, Balázs

    2016-01-01

    The terrace sequence of the Hungarian part of the Danube valley preserves a record of varying tectonic uplift rates along the river course and throughout several climate stages. To establish the chronology of formation of these terraces, two different dating methods were used on alluvial terraces: exposure age dating using in situ produced cosmogenic 10Be and luminescence dating. Using Monte Carlo approach to model the denudation rate-corrected exposure ages, in situ produced cosmogenic 10Be samples originated from vertical depth profiles enabled the determination of both the exposure time and the denudation rate. Post-IR IRSL measurements were carried out on K-feldspar samples to obtain the ages of sedimentation. The highest terrace horizon remnants of the study area provided a best estimate erosion-corrected minimum 10Be exposure age of >700 ka. We propose that the abandonment of the highest terrace of the Hungarian Danube valley was triggered by the combined effect of the beginning tectonic uplift and the onset of major continental glaciations of Quaternary age (around MIS 22). For the lower terraces it was possible to reveal close correlation with MIS stages using IRSL ages. The new chronology enabled the distinction of tIIb (∼90 ka; MIS 5b-c) and tIIIa (∼140 ka; MIS 6) in the study area. Surface denudation rates were well constrained by the cosmogenic 10Be depth profiles between 5.8 m/Ma and 10.0 m/Ma for all terraces. The calculated maximum incision rates of the Danube relevant for the above determined >700 ka time span were increasing from west (<0.06 mm/a) to east (<0.13 mm/a), toward the more elevated Transdanubian Range. Late Pleistocene incision rates derived from the age of the low terraces (∼0.13-0.15 mm/a) may suggest a slight acceleration of uplift towards present.

  18. 10Be constrains the sediment sources and sediment yields to the Great Barrier Reef from the tropical Barron River catchment, Queensland, Australia

    NASA Astrophysics Data System (ADS)

    Nichols, K. K.; Bierman, P. R.; Rood, D. H.

    2014-12-01

    Estimates of long-term, background sediment generation rates place current and future sediment fluxes to the Great Barrier Reef in context. Without reliable estimates of sediment generation rates and without identification of the sources of sediment delivered to the reef prior to European settlement (c. 1850), determining the necessity and effectiveness of contemporary landscape management efforts is difficult. Using the ~2100-km2 Barron River catchment in Queensland, Australia, as a test case, we use in situ-produced 10Be to derive sediment generation rate estimates and use in situ and meteoric 10Be to identify the source of that sediment, which enters the Coral Sea near Cairns. Previous model-based calculations suggested that background sediment yields were up to an order of magnitude lower than contemporary sediment yields. In contrast, in situ 10Be data indicate that background (43 t km-2 y-1) and contemporary sediment yields (~45 t km-2 y-1) for the Barron River are similar. These data suggest that the reef became established in a sediment flux similar to what it receives today. Since western agricultural practices increased erosion rates, large amounts of sediment mobilized from hillslopes during the last century are probably stored in Queensland catchments and will eventually be transported to the coast, most likely in flows triggered by rare but powerful tropical cyclones that were more common before European settlement and may increase in strength as climate change warms the south Pacific Ocean. In situ and meteoric 10Be concentrations of Coral Sea beach sand near Cairns are similar to those in rivers on the Atherton Tablelands, suggesting that most sediment is derived from the extensive, low-gradient uplands rather than the steep, more rapidly eroding but beach proximal escarpment.

  19. Atmospheric production signal in 10Be from varved sediments of Lake Meerfelder Maar during the late glacial-early Holocene transition

    NASA Astrophysics Data System (ADS)

    Czymzik, Markus; Adolphi, Florian; Muscheler, Raimund; Brauer, Achim; Mekhaldi, Florian; Martin-Puertas, Celia; Tjallingii, Rik; Aldahan, Ala; Possnert, Göran

    2016-04-01

    Beryllium 10 concentrations (10Becon) were measured at 20-year resolution in annually laminated (varved) sediments of Lake Meerfelder Maar (western Germany) covering the late glacial-early Holocene transition 11310-13130 varve years before present. Comparing the 10Becon record to environmental proxy records from the same archive indicates that varying sediment accumulation and composition only slightly modify trends, but do not substantially influence multi-decadal to centennial 10Becon excursions. Corrected for potential environmental biases using multiple-regression analysis, the resulting 10Beatmosphere time-series likely represents an alternative mid-latitude 10Be production record, exhibiting broad similarities but also some differences to radionuclide records as 14C in tree rings and 10Be in polar ice cores. The preservation of the globally common atmospheric production signal in 10Be from varved lake sediments indicates the, to date, largely unexplored potential of these archives for the synchronization to other radionuclide records around the globe, complementing existing solar activity reconstructions and Sun-climate studies.

  20. Microscopic analysis of Be,1110 elastic scattering on protons and nuclei, and breakup processes of 11Be within the 10Be +n cluster model

    NASA Astrophysics Data System (ADS)

    Lukyanov, V. K.; Kadrev, D. N.; Zemlyanaya, E. V.; Spasova, K.; Lukyanov, K. V.; Antonov, A. N.; Gaidarov, M. K.

    2015-03-01

    The density distributions of 10Be and 11Be nuclei obtained within the quantum Monte Carlo model and the generator coordinate method are used to calculate the microscopic optical potentials (OPs) and cross sections of elastic scattering of these nuclei on protons and 12C at energies E <100 MeV/nucleon. The real part of the OP is calculated using the folding model with the exchange terms included, while the imaginary part of the OP that reproduces the phase of scattering is obtained in the high-energy approximation. In this hybrid model of OP the free parameters are the depths of the real and imaginary parts obtained by fitting the experimental data. The well-known energy dependence of the volume integrals is used as a physical constraint to resolve the ambiguities of the parameter values. The role of the spin-orbit potential and the surface contribution to the OP is studied for an adequate description of available experimental elastic scattering cross-section data. Also, the cluster model, in which 11Be consists of a n -halo and the 10Be core, is adopted. Within the latter, the breakup cross sections of 11Be nucleus on 9Be,93Nb,181Ta , and 238U targets and momentum distributions of 10Be fragments are calculated and compared with the existing experimental data.

  1. Extended record of 10Be at EPICA Dome C during the last 800 000 years and its synchronization with geomagnetic paleointensity variations from marine sediments

    NASA Astrophysics Data System (ADS)

    Cauquoin, Alexandre; Raisbeck, Grant; Jouzel, Jean; Bard, Edouard; Aster Team

    2013-04-01

    Polar ice cores are exceptional archives that permit the reconstruction of many parameters (variations of temperature, atmospheric composition...) and the reconstitution of the past variations of the Earth climate and environment. They also give access to beryllium-10 (10Be) fallout, an isotope of cosmogenic origin, created by the interaction of Galactic Cosmic Rays (GCR, constituted of high energy charged particles) with the upper atmosphere. The cosmic rays being modulated by solar activity and Earth's magnetic field intensity, the 10Be production is inversely related to the intensity of these two parameters. Most 10Be produced is quickly removed from the atmosphere (residence time in the stratosphere ~1-2 years) and, on the Antarctic plateau, falls mainly by dry deposition as aerosols. So, 10Be can be used as a proxy of paleointensity. It has allowed the improvement of ice cores chronologies thanks to absolute stratigraphic markers linked to excursions and inversions of the geomagnetic field such as the Laschamp excursion [1] or the Matuyama-Brunhes reversal [2, 3]. EPICA Dome C (75° 06' S, 123° 21' E) is a 3270 meter ice core drilled in East Antarctica in the framework of an international project. It offers a complete climate record over the last 800 000 years. As shown at the IPICS 2012 meeting, for the 355 - 800 ka period [4], a continuous high-resolution (11 cm) 10Be profile in this core can be synchronized with continuous variations of paleointensity (PISO-1500) recorded in marine sediments [5] in order to obtain a continuous relative chronology of climate proxies (δD and δ18O respectively) for these two reservoirs. Here, we extend this synchronization down to 269 ka, thus including termination IV and interstadial MIS 9. [1]. Raisbeck et al. (2007) Clim.Past, 3, 541 - 547. [2]. Raisbeck et al. (2006) Nature, 444, 82 - 84. [3]. Dreyfus et al. (2008) Earth and Planet. Sci. Lett., 274, 151 - 156. [4]. G.Raisbeck et al. (2012) IPICS Open Science Conference

  2. [sup 14]C and [sup 10]Be evidence for no incursion of the Lake Michigan lobe in northern Illinois from ca. 170 to 25 ka

    SciTech Connect

    Curry, B.B. ); Pavich, M.J. )

    1994-04-01

    Uncorrected [sup 10]Be inventories of a 2.7 m-long section of core indicate surface exposure lasting 115 ka during development of the Sangamon Geosol and 30 ka for a soil complex developed in overlying loessial sediment (Robein Silt). The latter estimate is in agreement with [sup 14]C assays in the region. Taking into account the age of overlying late Wisconsin drift, the new data indicate an age of about 170 ka for the onset of Sangamon pedogenesis in northern Illinois. Previous to this study, there have been no numerical-age determinations for the start of the last interglacial in northern IL. The data confirm a previous hypothesis that the Lake Michigan Lobe did not invade IL contemporaneous with deposition of Roxana Silt, or during the other period of midcontinental loess deposition suggest by TL ages of ca. 70 to 85 ka. The core was collected immediately south of the IL-WI border (42[degree] 30 minutes N, 88[degree] 30 minutes W) near Hebron, IL. Buried by 14 m of late Wisconsin drift, and the interval assayed for [sup 10]Be included 2.0 m of pedogenically-altered Illinoian sand and gravel, and 0.7 m of Wisconsin silt. One AMS [sup 14]C assay of carbonized fragments from the A-horizon of the Sangamon Geosol yielded an age of 38,500 [+-] 5,000 yr B.P.; conventional [sup 14]C ages for the overlying silt are from wood fragments (24,780 [times] 360 yr B.P.) and a bulk soil sample (26,030 [+-] 450 yr B.P.). The range of ages is typical for this stratigraphic sequence in IL. The [sup 10]Be concentration in the lowest part of the silt is 600 atoms/gm. This value is three times greater than the concentration typical of calcareous Mississippi River valley loess and of the C-horizon of the Sangamon Geosol in the core. High concentration of [sup 10]Be in the Robein Silt likely was caused by redeposition of [sup 10]Be-rich B-horizon material eroded from soil profiles elsewhere in the paleobasin.

  3. Chronology of glaciations in the Cantabrian Mountains (NW Iberia) during the Last Glacial Cycle based on in situ-produced 10Be

    NASA Astrophysics Data System (ADS)

    Rodríguez-Rodríguez, Laura; Jiménez-Sánchez, Montserrat; Domínguez-Cuesta, María José; Rinterknecht, Vincent; Pallàs, Raimon; Bourlès, Didier

    2016-04-01

    The mountain ranges of the Iberian Peninsula preserve a valuable record of past glaciations that may help reconstruct past atmospheric circulation patterns in response to cooling events in the North Atlantic Ocean. Available chronologies for the glacial record of the Cantabrian Mountains, which are mainly based on radiocarbon and luminescence dating of glacial-related sediments, suggest that glaciers recorded their Glacial Maximum (GM) during MIS 3 and experienced a later Last Glacial Maximum (LGM) advance. This LGM extent is not established yet, preventing a fair correlation with available Cosmic Ray Exposure (CRE) based chronologies for the glacial record of the Pyrenees and the Sistema Central. We present a glacial reconstruction and a 10Be CRE chronology for the Porma valley, in the southern slope of the central Cantabrian Mountains. Glacial evidence at the lowest altitudes correspond to erratic boulders and composite moraines whose minimum 10Be CRE age of 113.9 ± 7.1 ka suggests that glaciers were at their maximum extent during MIS 5d, most likely in response to the minima in summertime insolation of the Last Glacial Cycle. Recessional moraines preserved within the glacial maximum limits allow the assessment of subsequent glacier advances or stagnations. The most remarkable advance took place prior to 55.7 ± 4.0 ka (probably at the end of MIS 4), consistently with minimum radiocarbon ages previously reported for lacustrine glacial-related deposits in the Cantabrian Mountains. A limited number of 10Be CRE ages from a composite moraine suggest a possible advance of the Porma glacier coeval with the global LGM; the glacier front attributed to the LGM would be placed within the margins of the previous GM like in the western Pyrenees. Erratic boulders perched on an ice-moulded bedrock surface provided a mean 10Be CRE age of 17.7 ± 1.0 ka, suggesting that part of the recessional moraine sequence corresponds to minor advances or stagnations of the glacier fronts

  4. Energy of the ground and 2{sup +} excited states of {sub {lambda}}{sub {lambda}}{sup 10}Be: A partial ten-body model

    SciTech Connect

    Shoeb, Mohammad; Sonika

    2009-08-15

    The energies of the ground and excited 2{sup +} states of {sub {lambda}}{sub {lambda}}{sup 10}Be have been calculated variationally in the Monte Carlo framework. The hypernucleus is treated as a partial ten-body problem in the {lambda}{lambda}+{alpha}{alpha} model where nucleonic degrees of freedom of {alpha}'s are taken into consideration ignoring the antisymmetrization between two {alpha}'s. The central two-body {lambda}N and {lambda}{lambda} and the three-body dispersive and two-pion exchange {lambda}NN forces, constrained by the {lambda}p scattering data and the observed ground state energies of {sub {lambda}}{sup 5}He and {sub {lambda}}{sub {lambda}}{sup 6}He, are employed. The product-type trial wave function predicts binding energy for the ground state considerably less than for the event reported by Danysz et al.; however, it is consistent with the value deduced assuming a {gamma} ray of 3.04 MeV must have escaped undetected in the decay of the product {sub {lambda}}{sup 9}Be* {yields} {sub {lambda}}{sup 9}Be+{gamma} of the emulsion event {sub {lambda}}{sub {lambda}}{sup 10}Be{yields} {pi}{sup -}+p+{sub {lambda}}{sup 9}Be* and for the excited 2{sup +} state closer to the value measured in the Demachi-Yanagi event. The hypernucleus {sub {lambda}}{sub {lambda}}{sup 10}Be has an oblate shape in the excited state. These results are consistent with the earlier four-body {alpha} cluster model approach where {alpha}'s are assumed to be structureless entities.

  5. Northern San Andreas Fault slip rates on the Santa Cruz Mountain section: 10Be dating of an offset alluvial fan complex, Sanborn County Park, Saratoga, CA

    NASA Astrophysics Data System (ADS)

    Guns, K. A.; Prentice, C. S.; DeLong, S. B.; Kiefer, K.; Blisniuk, K.; Burgmann, R.

    2015-12-01

    To better assess seismic hazard and fault behavior along the southern peninsula in the San Francisco Bay Area on the Santa Cruz Mountain section of the San Andreas Fault, we combine field observations and high-resolution lidar topography data with 10Be exposure dating on offset landforms to estimate geologic fault slip rates. Our mapping at Sanborn County Park near Saratoga reveals a progression of alluvial fans and debris flows offset from their upstream sources by dextral slip on the San Andreas Fault. These upstream sources are 3 drainages, Todd Creek, Service Road Creek and Aubry Creek. Coarse alluvial deposits from each of these creeks contain large Tertiary sandstone boulders of varying size and abundance, derived from the Vaqueros Formation, that allow us to constrain the provenance of offset alluvial deposits to their upstream sources. Initial reconstruction, based on clast-count data on lithology and size from Todd Creek (n=68), Service Road Creek (N=32) and the offset deposits (n=68), suggest ≥140 m of dextral fault movement. Initial 10Be cosmogenic dating of sandstone boulders on an offset deposit from Service Road Creek yields a maximum date of 8 ka, a date uncorrected for hillslope residence and fluvial transport of inherited 10Be concentrations. These data suggest a minimum slip rate of at least 17 mm/yr on the Santa Cruz Mountain section of the San Andreas Fault in the peninsula. Ongoing analysis will refine this fault slip rate. Our preliminary data underscore the potential of this site to provide geologic slip rate estimates, and therefore answer a question critical to seismic hazard assessment, in a region where steep terrain, mass wasting, vegetation and urban development have generally made slip rate estimates challenging to obtain.

  6. A cosmogenic 10Be chronology for the local last glacial maximum and termination in the Cordillera Oriental, southern Peruvian Andes: Implications for the tropical role in global climate

    NASA Astrophysics Data System (ADS)

    Bromley, Gordon R. M.; Schaefer, Joerg M.; Hall, Brenda L.; Rademaker, Kurt M.; Putnam, Aaron E.; Todd, Claire E.; Hegland, Matthew; Winckler, Gisela; Jackson, Margaret S.; Strand, Peter D.

    2016-09-01

    Resolving patterns of tropical climate variability during and since the last glacial maximum (LGM) is fundamental to assessing the role of the tropics in global change, both on ice-age and sub-millennial timescales. Here, we present a10Be moraine chronology from the Cordillera Carabaya (14.3°S), a sub-range of the Cordillera Oriental in southern Peru, covering the LGM and the first half of the last glacial termination. Additionally, we recalculate existing 10Be ages using a new tropical high-altitude production rate in order to put our record into broader spatial context. Our results indicate that glaciers deposited a series of moraines during marine isotope stage 2, broadly synchronous with global glacier maxima, but that maximum glacier extent may have occurred prior to stage 2. Thereafter, atmospheric warming drove widespread deglaciation of the Cordillera Carabaya. A subsequent glacier resurgence culminated at ∼16,100 yrs, followed by a second period of glacier recession. Together, the observed deglaciation corresponds to Heinrich Stadial 1 (HS1: ∼18,000-14,600 yrs), during which pluvial lakes on the adjacent Peruvian-Bolivian altiplano rose to their highest levels of the late Pleistocene as a consequence of southward displacement of the inter-tropical convergence zone and intensification of the South American summer monsoon. Deglaciation in the Cordillera Carabaya also coincided with the retreat of higher-latitude mountain glaciers in the Southern Hemisphere. Our findings suggest that HS1 was characterised by atmospheric warming and indicate that deglaciation of the southern Peruvian Andes was driven by rising temperatures, despite increased precipitation. Recalculated 10Be data from other tropical Andean sites support this model. Finally, we suggest that the broadly uniform response during the LGM and termination of the glaciers examined here involved equatorial Pacific sea-surface temperature anomalies and propose a framework for testing the viability

  7. High-pressure suppression of crystallization in the metallic supercooled liquid Zr41 Ti14 Cu12.5 Ni10 Be22.5 : Influence of viscosity

    NASA Astrophysics Data System (ADS)

    Wang, W. H.; Wang, Z. X.; Zhao, D. Q.; Tang, M. B.; Utsumi, W.; Wang, X.-L.

    2004-09-01

    The supercooled liquid Zr41Ti14Cu12..5Ni10Be22.5 is studied using a high-pressure (HP) and high-temperature x-ray diffraction technique with synchrotron radiation, which allows us for the first time to in situ monitor the crystallization kinetics of metallic supercooled liquid in both cooling and heating processes under HP. We find that more than 6 GPa can completely suppress the crystallization in the melt at low cooling rate, and distinct crystallization from glassy to melt states during fast heating can be bypassed at 8.3 GPa. HP suppresses the crystallization in the supercooled liquid through increasing its viscosity.

  8. Preliminary Vertical Slip Rate for the West Tahoe Fault from six new Cosmogenic 10Be Exposure Ages of Late Pleistocene Glacial Moraines at Cascade Lake, Lake Tahoe, California

    NASA Astrophysics Data System (ADS)

    Pierce, I. K. D.; Wesnousky, S. G.; Kent, G. M.; Owen, L. A.

    2015-12-01

    The West Tahoe Fault is the primary range bounding fault of the Sierra Nevada at the latitude of Lake Tahoe. It is a N-NW striking, east dipping normal fault that has a pronounced onshore quaternary scarp extending from highway 50 southwest of Meyers, CA to Emerald Bay. At Cascade Lake, the fault cuts and progressively offsets late Pleistocene right lateral moraines. The fault vertically offsets the previously mapped Tahoe moraine ~83 m and the Tioga moraine ~23 m, measured from lidar data. Seventeen samples were collected for 10Be cosmogenic age analysis from boulders on both the hanging and footwalls of the fault along the crests of these moraines.We report here the initial analysis of 6 of these boulders and currently await processing of the remainder. The 10Be exposure ages of 3 boulders each on the younger Tioga and older Tahoe moraines range from 12.7 +/- 1.6 to 20.7 +/- 3.3 ka and 13.3 +/- 2.1 to 72.5 +/- 8.8 ka, respectively. Using the oldest ages as minima, these preliminary results suggest that the slip rate has averaged ~1 mm/yr since the penultimate glaciation, in accord with estimates of previous workers, and place additional bounds on the age of glaciation in the Lake Tahoe basin. The Last Glacial Maxima and penultimate glaciation near Lake Tahoe thus appear to coincide with the Tioga and Tahoe II glaciations of the Eastern Sierra.

  9. High-precision Penning trap mass measurements of 9,10Be and the one-neutron halo nuclide 11Be

    NASA Astrophysics Data System (ADS)

    Ringle, R.; Brodeur, M.; Brunner, T.; Ettenauer, S.; Smith, M.; Lapierre, A.; Ryjkov, V. L.; Delheij, P.; Drake, G. W. F.; Lassen, J.; Lunney, D.; Dilling, J.

    2009-05-01

    Penning trap mass measurements of 9Be, 10Be (t1 / 2 = 1.51 My), and the one-neutron halo nuclide 11Be (t1 / 2 = 13.8 s) have been performed using TITAN at TRIUMF. The resulting 11Be mass excess (ME = 20 177.60 (58) keV) is in agreement with the current Atomic Mass Evaluation (AME03) [G. Audi, et al., Nucl. Phys. A 729 (2003) 337] value, but is over an order of magnitude more precise. The precision of the mass values of 9,10Be have been improved by about a factor of four and reveal a ≈ 2 σ deviation from the AME mass values. Results of new atomic physics calculations are presented for the isotope shift of 11Be relative to 9Be, and it is shown that the new mass values essentially remove atomic mass uncertainties as a contributing factor in determining the relative nuclear charge radius from the isotope shift. The new mass values of 10,11Be also allow for a more precise determination of the single-neutron binding energy of the halo neutron in 11Be.

  10. 10Be dating of the Narsarsuaq moraine in southernmost Greenland: evidence for a late-Holocene ice advance exceeding the Little Ice Age maximum

    NASA Astrophysics Data System (ADS)

    Winsor, K.; Carlson, A. E.; Rood, D. H.

    2014-08-01

    In southernmost Greenland near Narsarsuaq, the terminal Narsarsuaq moraine was deposited well outside of a historical Little Ice Age (LIA) moraine adjacent to the modern ice margin. Using 10Be surface exposure dating, we determine Narsarsuaq moraine abandonment at 1.51 ± 0.11 ka. A second set of 10Be ages from a more ice-proximal position shows that ice has been within or at its historical (i.e., LIA) extent since 1.34 ± 0.15 ka. Notably, Narsarsuaq moraine abandonment was coincident with climate amelioration in southern Greenland. Southern Greenland warming at ˜1.5 ka was also concurrent with the end of the Roman Warm Period as climate along the northern North Atlantic sector of Europe cooled into the Dark Ages. The warming of southern Greenland and retreat of ice from the Narsarsuaq moraine is consistent with studies suggesting possible anti-phase centennial-scale climate variability between northwestern Europe and southern Greenland. Other southernmost Greenland ice-margin records do not preclude a pre-LIA ice-margin maximum, potentially concurrent with a Narsarsuaq advance prior to ˜1.51 ka, but also lack sufficient ice-margin control to confirm such a correlation. We conclude that there is a clear need to further determine whether a late-Holocene pre-LIA maximum was a local phenomenon or a regional southern Greenland ice maximum, and if this advance and retreat reflects a regional fluctuation in climate.

  11. Relief evolution of the Continental Rift of Southeast Brazil revealed by in situ-produced 10Be concentrations in river-borne sediments

    NASA Astrophysics Data System (ADS)

    Salgado, André Augusto Rodrigues; Rezende, Eric de Andrade; Bourlès, Didier; Braucher, Régis; da Silva, Juliana Rodrigues; Garcia, Ricardo Alexandrino

    2016-04-01

    This study aims to quantify the denudation dynamics of the Brazilian passive margin along a segment of the Continental Rift of Southeast Brazil. The denudation rates of 30 basins that drain both horsts of the continental rift, including the mountain ranges of the Serra do Mar (seaside horst); and the Serra da Mantiqueira (continental horst); were derived from 10Be concentrations measured in sand-sized river sediment. The mean denudation rate ranges from 9.2 m Ma-1 on the plateau of the Serra do Mar to 37.1 m Ma-1 along the oceanic escarpment of the Serra do Mar. The seaward-facing scarps of both mountain ranges exhibit mean denudation rates that are approximately 1.5 times those of the inland-facing scarps. The escarpments of the horst nearer to the ocean (Serra do Mar) exhibit higher denudation rates (mean 30.2 m Ma-1) than the escarpments of the continental horst (Serra da Mantiqueira) (mean 16.5 m Ma-1). The parameters that impact these denudation rates include the catchment relief, the slope gradient, the rock and the climate. The incongruent combination of a mountainous landscape and moderate to low 10Be-based denudation rates averaging at ∼20 m Ma-1 suggests a reduction in intraplate tectonic activity beginning in the Middle Quaternary or earlier.

  12. A new 3D numerical model for production of cosmogenic spallation products (7) Be, (10) Be, (22) Na in the atmosphere

    NASA Astrophysics Data System (ADS)

    Usoskin, Ilya; Kovaltsov, Gennady

    A new quantitative model of production of the cosmogenic isotopes, produced by spallation of atmospheric constitutes by the nucleonic component of cosmic rays induced cascade in the Earth's atmosphere is presented. We presents the results for three cosmogenic isotopes: 7 Be, 10 Be and 22 Na, using the CRAC (Cosmic Ray induced Atmospheric Cascade) model is based on a full numerical Monte-Carlo simulation of the nucleonic-electromagnetic-muon cascade induced by cosmic rays in the atmosphere and is able to compute the isotope's production rate at any given 3D location (geographical and altitude) and time, for all possible parameters including solar energetic particle events. The model was tested against the results of direct measurements of production of 10 Be and 7 Be in a number of dedicated experiments to confirm its quantitative correctness. A set of tabulated values for the yield function is provided along with a detailed numerical recipe forming a `do-it-yourself' kit, which allows anyone interested to apply the model for any given conditions. This provides a useful tool for applying the cosmogenic isotope method in direct integration with other models, e.g., dynamical atmospheric transport.

  13. 10Be in Quartz Gravel from the Gobi Desert and Evolutionary History of Alluvial Sedimentation in the Ejina Basin, Inner Mongolia, China

    NASA Astrophysics Data System (ADS)

    Lyu, Y.

    2014-12-01

    Reconstructing the evolutionary history of the Gobi deserts developed from alluvial sediments in arid regions has great significance in unraveling changes in both tectonic activity and climate. However, such work is limited by a lack of suitable dating material preserved in the Gobi Desert, but cosmogenic 10Be has great potential to date the Gobi deserts. In the present study, 10Be in quartz gravel from the Gobi deserts of the Ejina Basin in Inner Mongolia of China has been measured to assess exposure ages. Results show that the Gobi Desert in the northern margin of the basin developed 420 ka ago, whereas the Gobi Desert that developed from alluvial plains in the Heihe River drainage basin came about during the last 190 ka. The latter developed gradually northward and eastward to modern terminal lakes of the river. These temporal and spatial variations in the Gobi deserts are a consequence of alluvial processes influenced by Tibetan Plateau uplift and tectonic activities within the Ejina Basin. Possible episodes of Gobi Desert development within the last 420 ka indicate that the advance/retreat of alpine glaciers during glacial/interglacial cycles might have been the dominant factor to influencing the alluvial intensity and water volume in the basin. Intense floods and large water volumes would mainly occur during the short deglacial periods.

  14. 10Be and U-series dating of late Quaternary landforms along the southern San Jacinto fault: Implications for temporal slip rate variability

    NASA Astrophysics Data System (ADS)

    Blisniuk, K.; Oskin, M. E.; Fletcher, K.; Sharp, W. D.; Rockwell, T. K.

    2009-12-01

    Robust age control on faulted landforms with well-constrained offsets is essential to documenting the heterogeneous behavior of a fault zone over time. However, showing late Quaternary temporal slip rate variation is often challenging due to the difficultly of obtaining reliable ages for Quaternary deposits. Exposure ages from cosmogenic isotopes can be significantly affected by surface processes, and U-series dating of pedogenic carbonate provides only minimum ages because carbonate accumulation occurs after deposition. Fortunately, the controlling factors for the resulting age uncertainties of each method are relatively independent from each other, so a combination of cosmogenic isotope and U-series dating may significantly improve the reliability of landform dating and yield more robust slip rate estimates. We present preliminary results of this dual-dating approach at 4 sites along the southern San Jacinto fault zone in California: 2 sites along the Coyote Creek fault, and 2 sites along the Clark fault. These results show age agreement between the two dating methods. Along the southern Clark fault, a 10Be depth profile model age of 34.5 ±6.6 ka and a U-series age of 33.2 ±1.1 ka were obtained for an offset Q2b fan surface, and a Q3b surface yielded a weighted mean 10Be surface exposure age of 5.9 ±1.5 ka, similar to an U-series age of 6.3 ±0.4 ka. Along the northern Coyote Creek fault, preliminary data indicate a 10Be surface exposure age of 11.3 ±3.4 ka and a U-series age of 11.7 ±1.8 ka for an offset Q3a surface, and a 10Be surface exposure age of 6.9 ±1.0 ka and a U-series age of 7.8 ± 0.9 ka for an offset Q3b surface. The remarkable consistency among ages from the two dating methods suggest that: (1) U-series ages of pedogenic carbonate clast rinds closely approach depositional ages of the host alluvium; (2) erosion may be negligible at the sampled sites; and (3) inherited 10Be has been accurately quantified (via depth profile) for the late

  15. In situ produced 10Be depth profiles and luminescence data tracing climatic and tectonic control on terrace formation, Danube River, Central Europe, Hungary

    NASA Astrophysics Data System (ADS)

    Ruszkiczay-Rüdiger, Zsófia; Braucher, Régis; Novothny, Ágnes; Csillag, Gábor; Fodor, László; Molnár, Gábor; Madarász, Balázs; Aster Team

    2015-04-01

    The terrace sequence of the Hungarian part of the Danube valley preserves a record of varying tectonic uplift rates along the river course and throughout several climate stages. To establish the chronology of formation of these terraces, two different dating methods on alluvial terraces were used: 1) in situ produced cosmogenic 10Be, which yield the time of abandonment of the terrace and 2) luminescence dating, which provides burial ages of the sediment. In situ produced cosmogenic 10Be samples originated from vertical depth profiles to enable the determination of both the exposure time and the denudation rate at each locality. We used Monte Carlo approach to model the denudation rate-corrected exposure ages. Post-IR IRSL measurements were carried out on K-feldspar samples to obtain the ages of sedimentation. The highest and oldest terrace remnants (tIV-VI) yield a minimum 10Be exposure age of 800 ka close to MIS 22, the onset of major continental glaciations of Quaternary age, suggesting climatic signal of the abandonment of the uppermost terrace levels. For the lower terraces it was possible to reveal close correlation with MIS stages using IRSL ages. The new chronology enables the distinction of tIIb (60-110 ka; MIS 4-5d) and tIIIa (130-190 ka; MIS 6) in the study area. Surface denudation rates were well constrained by the cosmogenic 10Be depth profiles between 5.9 m/Ma and 10.0 m/Ma for all terraces. Maximum incision rates of the Danube were calculated for middle and late Pleistocene times. These rates were increasing from west to east, toward the more elevated Transdanubian Range from 0.05 mm/a to 0.12 mm/a. Incision rates derived from the age of the low terraces (0.13 mm/a) may suggest a slight acceleration of uplift towards present. Our research was supported by the OTKA PD83610, PD100315, NK60455, K062478, K83150 and F042799, the French-Hungarian Balaton-Tét Project (FR-32/2007; TÉT_11-2-2012-0005), the Bolyai János Scholarship of the Hungarian Academy

  16. Cosmogenic 10Be Chronologies of Moraines and Glacially Scoured Bedrock in the Teton Range, with Implications for Paleoclimatic Events and Tectonic Activity

    NASA Astrophysics Data System (ADS)

    Licciardi, J. M.; Pierce, K. L.; Thackray, G. D.; Finkel, R. C.; Zimmerman, S. R. H.

    2015-12-01

    At its Pleistocene maximum, the greater Yellowstone glacial system consisted of an ice cap on the Yellowstone Plateau joined by glaciers from adjacent high mountains, including the Teton Range. In prior research, we obtained 112 exposure ages from moraines and bedrock in this region. These chronologies identified asynchronous outlet glacier culminations around the periphery of the Yellowstone glacier complex, supporting a model of spatial and temporal progressions in buildup and decay of the various ice source regions. Here we build on this previous work and present >30 recently developed 10Be exposure ages on glacial features in the Teton Range. Although the Tetons harbored a relatively small portion of the greater Yellowstone ice complex, glaciers in this range left behind some of the region's best-preserved moraine sequences and scoured bedrock. Ongoing investigations are focused on developing moraine chronologies in several drainages on the eastern and western Teton Range fronts, and obtaining exposure ages along scoured bedrock transects in glacial troughs upvalley from the dated moraines to define rates of ice recession. Notably, our dating campaign includes lateral moraines that are offset by the Teton fault, providing a rare opportunity to establish direct constraints on integrated long-term slip rates. All new and previously obtained 10Be ages are calculated using recently published calibrations and scaling of 10Be production rates. Initial results show that massive lateral moraines in selected drainages are several thousands of years older than adjacent distal end moraines, implying that the laterals were constructed during an earlier phase of the last glaciation and then acted to topographically confine subsequent ice advances. Mean ages of ca. 17-16 ka from terminal moraine loops along with limiting ages from scoured bedrock upvalley of the moraines indicate glacier culminations followed by the onset of rapid ice retreat long after the end of the global

  17. Dilution of 10Be in detrital quartz by earthquake-induced landslides: Implications for determining denudation rates and potential to provide insights into landslide sediment dynamics

    NASA Astrophysics Data System (ADS)

    West, A. Joshua; Hetzel, Ralf; Li, Gen; Jin, Zhangdong; Zhang, Fei; Hilton, Robert G.; Densmore, Alexander L.

    2014-06-01

    The concentration of 10Be in detrital quartz (10Beqtz) from river sediments is now widely used to quantify catchment-wide denudation rates but may also be sensitive to inputs from bedrock landslides that deliver sediment with low 10Beqtz. Major landslide-triggering events can provide large amounts of low-concentration material to rivers in mountain catchments, but changes in river sediment 10Beqtz due to such events have not yet been measured directly. Here we examine the impact of widespread landslides triggered by the 2008 Wenchuan earthquake on 10Beqtz in sediment samples from the Min Jiang river basin, in Sichuan, China. Landslide deposit material associated with the Wenchuan earthquake has consistently lower 10Beqtz than in river sediment prior to the earthquake. River sediment 10Beqtz decreased significantly following the earthquake downstream of areas of high coseismic landslide occurrence (i.e., with greater than ∼0.3% of the upstream catchment area affected by landslides), because of input of the 10Be-depleted landslide material, but showed no systematic changes where landslide occurrence was low. Changes in river sediment 10Beqtz concentration were largest in small first-order catchments but were still significant in large river basins with areas of 104-105 km. Spatial and temporal variability in river sediment 10Beqtz has important implications for inferring representative denudation rates in tectonically active, landslide-dominated environments, even in large basins. Although the dilution of 10Beqtz in river sediment by landslide inputs may complicate interpretation of denudation rates, it also may provide a possible opportunity to track the transport of landslide sediment. The associated uncertainties are large, but in the Wenchuan case, calculations based on 10Be mixing proportions suggest that river sediment fluxes in the 2-3 years following the earthquake increased by a similar order of magnitude in the 0.25-1 mm and the <0.25 mm size fractions

  18. The deglaciation history of the Simplon region (southern Swiss Alps) constrained by 10Be exposure dating of ice-molded bedrock surfaces

    NASA Astrophysics Data System (ADS)

    Dielforder, Armin; Hetzel, Ralf

    2014-01-01

    The deglaciation history of the Swiss Alps after the Last Glacial Maximum involved the decay of several ice domes and the subsequent disintegration of valley glaciers at high altitude. Here we use bedrock exposure dating to reconstruct the temporal and spatial pattern of ice retreat at the Simplon Pass (altitude: ˜2000 m) located 40 km southwest of the 'Rhône ice dome'. Eleven 10Be exposure ages from glacially polished quartz veins and ice-molded bedrock surfaces cluster tightly between 13.5 ± 0.6 ka and 15.4 ± 0.6 ka (internal errors) indicating that the Simplon Pass depression became ice-free at 14.1 ± 0.4 ka (external error of mean age). This age constraint is interpreted to record the melting of the high valley glaciers in the Simplon Pass region during the warm Bølling-Allerød interstadial shortly after the Oldest Dryas stadial. Two bedrock samples collected a few hundred meters above the pass depression yield older 10Be ages of 17.8 ± 0.6 ka and 18.0 ± 0.6 ka. These ages likely reflect the initial downwasting of the Rhône ice dome and the termination of the ice transfluence from the ice dome across the Simplon Pass toward the southern foreland. There, the retreat of the piedmont glacier in Val d'Ossola was roughly synchronous with the decay of the Rhône ice dome in the interior of the mountain belt, as shown by 10Be ages of 17.7 ± 0.9 ka and 16.1 ± 0.6 ka for a whaleback at ˜500 m elevation near Montecrestese in northern Italy. In combination with well-dated paleoclimate records derived from lake sediments, our new age data suggest that during the deglaciation of the European Alps the decay of ice domes was approximately synchronous with the retreat of piedmont glaciers in the foreland and was followed by the melting of high-altitude valley glaciers after the transition from the Oldest Dryas to the Bølling-Allerød, when mean annual temperatures rose rapidly by ˜3 °C.

  19. Consideration of geomorphological uncertainties with terrestrial cosmogenic nuclide dating (TCND): combining Schmidt-hammer and 10Be dating, Southern Alps, New Zealand

    NASA Astrophysics Data System (ADS)

    Winkler, Stefan

    2010-05-01

    As the importance of glaciers as key indicators of global change has increased during recent years, investigating Holocene glaciers chronologies has gained higher attention accordingly. One reason is the need for a better understanding of the climate - glacier relationship. Comparative studies play a major role in this field of research owing to the natural diversity of glacier behaviour. Detailed Holocene glacier chronologies are, furthermore, necessary to verify and eventually adjust glacier models indispensable for many attempts to predict future glacier changes. The Southern Alps of New Zealand are one of the few key study areas on the Southern Hemisphere where, in general, evidence is still sparse compared to its Northern counterpart. Improvement and reassessment of the Late Holocene glacier chronology in this region is, therefore, an important goal of current research. Recently, terrestrial (in situ) cosmogenic nuclide (10Be) surface exposure dating has been increasingly applied to Holocene moraines in New Zealand and elsewhere. In the context of numerical ("absolute") dating techniques, terrestrial cosmogenic nuclide dating (TCND) seems to have been established as an alternative to the previously dominating radiocarbon (14C) dating of organic material (plant remains, organic-rich soil layers etc.) buried beneath or within moraines. Precision and time resolution achieved by the newest laboratory standards and procedures (Schaefer et al. 2009) is truly a milestone and will promote future attempts of TCND in any comparable context. Maybe, TCND has the potential to at least partially replace radiocarbon (14C) dating in its dominating role for the "absolute" dating of Holocene glacial deposits. By contrast, field sampling for TCND often lacks appropriate consideration of geomorphological uncertainties. Whereas much effort is made with the high precision results achieved in the laboratory, the choice of boulders sampled on Holocene moraines is often purely made

  20. Repeated crystallization in undercooled Zr{sub 41}Ti{sub 14}Cu{sub 12}Ni{sub 10}Be{sub 23} liquids

    SciTech Connect

    Schroers, Jan; Johnson, William L.; Busch, Ralf

    2000-04-24

    Isothermal crystallization studies are performed on Zr{sub 41}Ti{sub 14}Cu{sub 12}Ni{sub 10}Be{sub 23} melts. Undercooling experiments are carried out repeatedly at 907, 860, and 750 K. The scattering of the time to reach the onset of crystallization is investigated. Results from experiments performed at 907 K show a large scatter of the onset time of crystallization. For the experiments carried out at 860 and 750 K, scattering of the onset time is two orders of magnitude smaller. These results indicate that, at high temperatures, the crystallization is governed by the time scale of the statistical nucleation events. At low temperatures, the crystallization is controlled by diffusion, resulting in a well-defined onset time for crystallization. (c) 2000 American Institute of Physics.

  1. Slip rate determination along the Southern Dead Sea fault: optically stimulated luminescence, 10Be cosmogenic radionuclide, and 14C ages brought face to face

    NASA Astrophysics Data System (ADS)

    Le Beon, Maryline; Jaiswal, Manoj; Kunz, Alexander; Al-Qaryouti, Mahmoud; Burr, George; Klinger, Yann; Moumani, Khaled; Chen, Yue-Gau; Abdelghafoor, Mohammed; Suppe, John

    2014-05-01

    Active tectonics studies are often limited by difficulties in accurately and precisely dating Late Quaternary alluvial deposits that commonly lack organic matter or date beyond the 14C dating limit. This is illustrated at a site called Fidan, in arid southern Jordan, where a series of alluvial fans are laterally offset by the southern Dead Sea fault. Geodetic, geomorphic and geologic studies converge to a fault slip rate of 5 ± 2 mm/a. Yet, Late Pleistocene slip rate at Fidan cover a wide range due to the dispersion of 10Be cosmogenic radionuclide (CRN) ages. The maximum slip rate since ~100 ka is up to a value of 11 mm/a, possibly suggesting significant variations in fault activity with time. In order to reduce the uncertainty on the Late Pleistocene slip rate and draw further conclusions regarding the fault seismic behavior, we implement complementary dating using optically stimulated luminescence (OSL) techniques on both quartz and K-feldspar minerals and using 14C when possible. OSL measurements include a newly developed technique called post-infra-red infra-red stimulated luminescence at 290°C (pIR290). We extensively sampled surface levels F2 and F4, digging ~50-cm deep pits into the geomorphic surfaces. Annual dose rates were determined in the laboratory from both geochemical analysis of the sediment and gamma-ray spectrometry. Due to sediment heterogeneity, we consider gamma-ray spectrometry as more reliable because it is based on a larger volume of sediment. Quartz OSL ages and preliminary pIR290 results on K-feldspars give consistent Early Holocene ages of 9-14 ka for F2, also in agreement with a 14C age of 13 ka from a landsnail shell. 10Be CRN exposure ages on F2 were significantly older, with 37 ± 4 ka, probably due to inheritance. On F4, 10Be CRN exposure ages showed a scattered distribution, from ~50 ka to ~120 ka, with most samples comprised in the mean interval of 87 ± 26 ka. Quartz OSL ages from 5 locations on F4 are comprised between 32 ± 3

  2. Alpha particles accompanying the weak decay of {sub {lambda}}{sup 10}Be and {sub {lambda}}{sup 10}B hypernuclei

    SciTech Connect

    Majling, L. Kuzmin, V. A. Tetereva, T. V.

    2006-05-15

    The possibility of a detailed investigation of weak {lambda}N interaction in the {sub {lambda}}{sup 10}Be and {sub {lambda}}{sub /10}B hypernuclei, which stand out owing to their {alpha}{alpha}N{lambda} cluster structure, is discussed. The detection of a few groups of correlated {alpha}{alpha} pairs will furnish information about decays to specific states of product nuclei ({sup 8}Be*, {sup 8}Li, {sup 8}B), thereby paving the way to a phenomenological analysis of the weak decays of p-shell hypernuclei. The ratios of the intensities of individual alpha-particle groups to be measured in experiments at the cyclotron of the Joint Institute for Nuclear Research (JINR, Dubna) will provide a useful criterion for choosing an appropriate model of weak {lambda}N interaction. The current state of hypernuclear physics is briefly reviewed.

  3. Linking morphology across the glaciofluvial interface: A 10Be supported chronology of glacier advances and terrace formation in the Garonne River, northern Pyrenees, France

    NASA Astrophysics Data System (ADS)

    Stange, K. M.; van Balen, R. T.; Kasse, C.; Vandenberghe, J.; Carcaillet, J.

    2014-02-01

    The Garonne River drains an important part of the northern Pyrenees and its northern foreland. We investigated the middle reaches of the Garonne River establishing a detailed morphogenetic profile of its foreland terrace staircase and the preserved palaeoglacier margins. We particularly focussed on the glaciofluvial interface, linking (also genetically) the fluvial sediment archives in the foreland with the terminal glacial basin upstream of the Pyrenees mountain front. Using cosmogenic nuclide 10Be analyses, two terrace exposures have been dated, including a prominent fluvioglacial outwash fan at the foreland transition. We identified three terminal margins of late Pleistocene glacier advances. The prominent Garonne staircase consists of three major terrace complexes, comprising eight individual terrace levels. Results indicate a young age of the lower terrace complex of the Garonne staircase (MIS 4-2). The morphogenetic relationships and the new 10Be exposure age constraints suggest that during the last glaciation (Würmian) the Garonne glacier reached its maximum extent at the north Pyrenean mountain front, apparently already during MIS 4. Two different ice margins were associated with MIS 2, indicating close to maximum ice-extent during early MIS 2 (LGM) and relatively stationary ice-recession in the late MIS 2. The extensive Garonne terrace complexes formed under cold-climate conditions and were abandoned by incision during major glacial-interglacial transitions. During warm-cold climate transitions lateral erosion caused the reworking of previously abandoned palaeofloodplains. The long-term (Quaternary) incision of the Garonne and other north Pyrenean rivers indicates that the proximal Aquitaine foreland basin experienced uplift. However, non-uniform lateral course migrations and valley asymmetries of the north Pyrenean piedmont rivers indicate that uplift magnitude is variable, with maximum amounts in the centre of the molasse-fan of Lannemezan: Rivers on

  4. Erosion rates on different timescales derived from cosmogenic 10Be and river loads: implications for landscape evolution in the Rhenish Massif, Germany

    NASA Astrophysics Data System (ADS)

    Meyer, H.; Hetzel, R.; Strauss, H.

    2010-03-01

    We determined erosion rates on timescales of 101-104 years for two catchments in the northeastern Rhenish Massif, in order to unravel the Quaternary landscape evolution in a Variscan mountain range typical of central Europe. Spatially averaged erosion rates derived from in situ produced 10Be concentrations in stream sediment of the Aabach and Möhne watersheds range from 47 ± 6 to 65 ± 14 mm/ka and integrate over the last 9-13 ka. These erosion rates are similar to local rates of river incision and rock uplift in the Quaternary and to average denudation rates since the Mesozoic derived from fission track data. This suggests that rock uplift is balanced by denudation, i.e., the landscape is in a steady state. Short-term erosion rates were derived from suspended and dissolved river loads subsequent to (1) correcting for atmospheric and anthropogenic inputs, (2) establishing calibration curves that relate the amount of suspended load to discharge, and (3) estimating the amount of bedload. The resulting solid mass fluxes (suspended and bedload) agree with those derived from the sediment volume trapped in three reservoirs. However, resulting geogenic short-term erosion rates range from 9 to 25 mm/ka and are only about one-third of the rates derived from 10Be. Model simulations in combination with published sediment yield data suggest that this discrepancy is caused by at least three factors: (1) phases with higher precipitation and/or lower evapotranspiration, (2) rare flood events not captured in the short-term records, and (3) prolonged periods of climatic deterioration with increased erosion and sediment transport on hillslopes.

  5. Paleopedology plus TL, 10Be, and14C dating as tools in stratigraphic and paleoclimatic investigations, Mississippi River Valley, U.S.A.

    USGS Publications Warehouse

    Markewich, H.W.; Wysocki, D.A.; Pavich, M.J.; Rutledge, E.M.; Millard, H.T., Jr.; Rich, F.J.; Maat, P.B.; Rubin, M.; McGeehin, J.P.

    1998-01-01

    Thick ( ??? 35 m) loess deposits are present on ridges and high bluffs in the northern-half of the Lower Mississippi Valley (LMV), U.S.A. Detailed descriptions of the loess sections and pedologic, physiochemical, and mineralogic analyses and TL, 14C, and 10Be age determinations, allow preliminary paleoclimatic reconstructions for the late Quaternary of central North America. No age data are available for the oldest (Fifth) loess. 10Be and TL age data suggest a 250-200 ka age for the Fourth or Crowleys Ridge(?) Loess, and indicate that the Loveland or Third Loess is time equivalent to oxygen isotope stage 6, ??? 190-120 ka. A weakly developed paleosol is present in the basal-half of the Loveland. The Sangamon Geosol is present in the upper 5 m and represents all of oxygen isotope stage 5, ??? 130-60 ka. It formed in a climate as warm as, but drier and (or) with greater variation in precipitation, than the present. The Roxana Silt (second loess) was deposited during oxygen isotope stages 4 and 3, ??? 65-26 ka. The early Wisconsinan interglacial-glacial transition, represented by the Sangamon Geosol and the unnamed paleosol in the basal Roxana Silt, was slow. The paleoclimate during the 35 k yr of Roxana deposition was cool to cold and wet. Age and pedologic data indicate that deposition of the Peoria Loess (the youngest) began around 25 ka when the area's climate changed abruptly from cool or cold and wet to cold and dry, with periods of sustained high winds.

  6. Placing Absolute Timing on Basin Incision Adjacent to the Colorado Front Range: Results from Meteoric and in Situ 10BE Dating

    NASA Astrophysics Data System (ADS)

    Duehnforth, M.; Anderson, R. S.; Ward, D.

    2010-12-01

    A sequence of six levels of gravel-capped surfaces, mapped as Pliocene to Holocene in age, are cut into Cretaceous shale in the northwestern part of the Denver Basin immediately adjacent to the Colorado Front Range (CFR). The existing relative age constraints and terrace correlations suggest that the incision of the Denver Basin occurred at a steady and uniform rate of 0.1 mm yr-1 since the Pliocene. As absolute ages in this landscape are rare, they have the potential to test the reliability of the existing chronology, and to illuminate the detailed history of incision. We explore the timing of basin incision and the variability of geomorphic process rates through time by dating the three highest surfaces at the northwestern edge of the Denver Basin using both in situ and meteoric 10Be concentrations. As the tectonic conditions have not changed since the Pliocene, much of the variability of generation and abandonment of alluvial surfaces likely reflects the influence of glacial-interglacial climate variations. We selected Gunbarrel Hill (mapped as pre-Rocky Flats (Pliocene)), Table Mountain (mapped as Rocky Flats (early Pleistocene)), and the Pioneer surface (mapped as Verdos (Pleistocene, ~640 ka)) as sample locations. We took two amalgamated clast samples on the Gunbarrel Hill surface, and dated depth profiles using meteoric and in situ 10Be on the Table Mountain and Pioneer surfaces. In addition, we measured the in situ 10Be concentrations of 6 boulder samples from the Table Mountain surface. We find that all three surfaces are significantly younger than expected and that in situ and meteoric age measurements largely agree with each other. The samples from the pre-Rocky Flats site (Gunbarrel Hill) show ages of 250 and 310 ka, ignoring post-depositional surface erosion. The ages of the Table Mountain and Pioneer sites fall within the 120 to 150 ka window. These absolute ages overlap with the timing of the penultimate glaciation during marine isotope stage (MIS) 6

  7. Differential erosion by different-sized glaciers as reflected in 10Be-derived erosion rates of glacier valley walls, Kichatna Mts., Alaska

    NASA Astrophysics Data System (ADS)

    Ward, D.; Anderson, R. S.

    2009-12-01

    The Kichatna Mountains, Alaska Range, Alaska comprise a dramatic landscape carved into a small ~65 Ma granitic pluton about 100 km west of Denali, in which kilometer-tall rock walls and “cathedral” spires tower over a radial array of over a dozen individual valley glaciers. The sheer scale of the relief speaks to the relative rates of valley incision by glaciers and rockwall retreat, but absolute rates are difficult to determine. We use cosmogenic 10Be to measure rockwall backwearing rates (and discuss several very important caveats to this use) on timescales of 103-104 yr, with a straightforward sampling strategy that exploits ablation-dominated medial moraines. In simple cases, a medial moraine and its associated englacial debris serve as a conveyor belt that brings supraglacial rockfall debris from the accumulation zone valley wall to a moraine crest in the ablation zone. Our samples come from the largest medial moraine on each of three glaciers. The northeast-flowing Trident glacier is the largest (15 km long, 1.4 km wide) and most deeply incised, and it has the lowest modern snowline in the range (~1200 m). Its primary medial moraine is sourced from west-facing sidewalls. The north-flowing Shadows glacier is slightly smaller (13 km long, 0.8 km wide) and has a large moraine sourced in dominantly east-facing sidewalls. The south-flowing Caldwell glacier is the smallest of the three (7 km long, 0.7 km wide), has a high modern snowline (~1500 m), and is nearly completely covered in debris. Its primary moraine is sourced from all south-facing aspects. These three glaciers share divides in their headwaters, and so are sourced in identical rock. Sidewall relief is similar (~1 km) in all three catchments. Each sample was amalgamated from 25-35 clasts collected over a 1 km longitudinal transect of each moraine. Replicate samples are internally consistent. The lowest 10Be concentrations (8000 at/g), and thus the highest inferred sidewall erosion rates (1.4 mm

  8. Spatial variability of 10Be-derived erosion rates across the southern Peninsular Indian escarpment: A key to landscape evolution across passive margins

    NASA Astrophysics Data System (ADS)

    Mandal, Sanjay Kumar; Lupker, Maarten; Burg, Jean-Pierre; Valla, Pierre G.; Haghipour, Negar; Christl, Marcus

    2015-09-01

    The persistence of significant topography in ancient, tectonically inactive orogenic belts remains one of the outstanding questions in geomorphology. In southern Peninsular India, the impressive topographic relief of the Western Ghat Mountains in tectonic quiescence since at least ca. 65 Ma has raised important questions concerning the long-term mechanism of topographic evolution. Quantifying the distribution of erosion in space and time is critical to understanding landscape evolution. Although the long-term erosion rates are reasonably well known, the short-term erosion rates and the relative importance of factors controlling erosion in southern Peninsular India are less well constrained. We present a new suite of catchment-averaged and local erosion rates using in situ produced 10Be concentrations in river sediments and exposed bedrock samples in southern Peninsular India. Catchment-averaged erosion rates vary from 9.6 ± 0.8 mMa-1 in the highlands to 114.3 ± 13.8 mMa-1 on the escarpment side. Bedrock erosion rates range from 2.4 ± 0.2 mMa-1 in the ridge-top to 143.4 ± 25.4 mMa-1 in active channel beds of the highlands. Catchment-averaged erosion rates derived from the across-escarpment, westward-draining catchments are significantly higher than those derived from the eastward-draining, over highland catchments. The difference indicates that long-term down-wearing of the highland proceeds at lower rates than in the escarpment zones. Catchment-averaged erosion rates are moderately correlated with mean hillslope angles and local relief whereas they are strongly correlated with catchment-averaged channel steepness index. This suggests that topographic steepness is the major control on the spatial variability of erosion while strong rainfall gradient is of minor importance in this area. 10Be-derived average erosion rates in highlands are consistent with previous long-term erosion rate estimated from thermochronometry. These results collectively point to large

  9. Uplift and denudation rates of an actively growing mountain range inferred from in-situ produced cosmogenic 10Be: the Yumu Shan (NE Tibetan Plateau)

    NASA Astrophysics Data System (ADS)

    Palumbo, L.; Hetzel, R.; Minxing, T.; Li, X.; Guo, J.

    2009-04-01

    Located in the foreland of the Quilian Shan (NE Tibet), the Yumu Shan is an isolated mountain range bounded by an active NW-SE striking thrust fault. Geomorphic and structural features such as fault scarps and wind gaps suggest that the ~70 km long range is actively growing (Hetzel et al., 2004; Tapponnier et al., 1990), hence the tectonic uplift should exceed the rate of denudation. Here we quantify the rate of these two competing processes using in-situ produced cosmogenic 10Be. Catchment-wide denudation rates are derived from 10Be concentrations in stream sediments, whereas rock uplift rates are obtained by combining scarp topographic profiles with dating of geomorphic surfaces deformed by active thrust faults at the Yumu Shan mountain front. Both denudation and rock uplift rates integrate over a similar temporal scale (~10-100 ka) and thus over many earthquake cycles. Our data document that catchment wide-denudation rates vary from ~100 to ~400 mm ka-1 as a function of morphology and lithology, while rock uplift takes place at the rate of ~0.7 mm ka-1. The difference between these values confirms that the Yumu Shan is in a topographic pre-steady state and in accordance with geomorphic and structural features. Tectonic features indicate that over few millions of years the Yumu Shan may rise to a similar height as the main ranges of the Qilian Shan farther south, which have peaks with elevations between ~5 and ~5.5 km. References: Hetzel R., Tao M., Niedermann S., Strecker M.R., Ivy-Ochs S., Kubik P.W., Gao B. (2004). Implications of the fault scaling law for the growth of topography: Mountain ranges in the broken foreland of NE Tibet, Terra Nova, 16, 157-162. Tapponnier P., Meyer B., Avouac J.P., Peltzer G., Gaudemer Y., Guo S., Xiang H., Yin K., Chen Z., Cai S., Dai H. (1990). Active thrusting and folding in the Quilian Shan, and decoupling between upper crust and mantle in northeastern Tibet, Earth Planet. Sci. Lett., 97, 382-403.

  10. Using 10Be erosion rates and fluvial channel morphology to constrain fault throw rates in the southwestern Sacramento River Valley, California, USA

    NASA Astrophysics Data System (ADS)

    Cyr, A. J.

    2013-12-01

    The Sacramento - San Joaquin River Delta, California, USA, is a critical region for California water resources, agriculture, and threatened or endangered species. This landscape is affected by an extensive set of levees that enclose artificial islands created for agricultural use. In addition to their importance for sustaining agriculture, this levee system also supports extensive transport and power transmission infrastructure and urban/suburban development. These levees are susceptible to damage from even moderate ground shaking by either a large earthquake on one of the high-activity faults in the nearby San Francisco Bay region, or even a moderate earthquake on one of the low-activity faults in the Delta region itself. However, despite this danger the earthquake hazards in this region are poorly constrained due to our lack of understanding of faults in and near the Delta region. As part of an effort to better constrain the seismic hazard associated with known, but poorly constrained, faults in the region, a geomorphic analysis of the Dunnigan Hills, northwest of Woodland, CA, is being combined with cosmogenic 10Be catchment-averaged erosion rates. The Dunnigan Hills are a low-relief (maximum elevation 87 m) landscape generated by fault-bend folding above the west-vergent Sweitzer reverse fault that soles into a blind east-vergent reverse fault. These faults have been imaged by seismic reflection data, and local microseismicity indicates that this system is actively propagating to the east. However, the throw rates on the faults in this system remain unconstrained, despite the potential for significant shaking such as that experienced in the nearby April, 1892 earthquake sequence between Winters and Vacaville, Ca, ~25 km to the south, which has been estimated at magnitude 6.0 or greater. Geomorphic and cosmogenic 10Be analyses from 12 catchments draining the eastern flank of the Dunnigan Hills will be used to infer vertical rock uplift rates to better constrain

  11. The new 6 MV AMS-facility DREAMS at Dresden

    NASA Astrophysics Data System (ADS)

    Akhmadaliev, Shavkat; Heller, René; Hanf, Daniel; Rugel, Georg; Merchel, Silke

    2013-01-01

    A new 6 MV electrostatic tandem accelerator has been put into operation at Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The system is equipped for accelerator mass spectrometry and opens a new research field at HZDR and the Helmholtz Association. It will be also used for ion beam analysis as well as for material modification via high-energy ion implantation. The research activity at the DREsden Accelerator Mass Spectrometry facility (DREAMS) based on a 6 MV Tandetron is primarily dedicated to the long-lived radioisotopes of 10Be, 26Al, 36Cl, 41Ca, and 129I. DREAMS background levels have been found to be at 4.5 × 10-16 for 10Be/9Be, 8 × 10-16 for 26Al/27Al, 3 × 10-15 for 36Cl/35Cl and 8 × 10-15 for 41Ca/40Ca, respectively. The observed background of 2 × 10-13 for 129I/127I originates from intrinsic 129I from AgI produced from commercial KI. The introduction of quality assurance approaches for AMS, such as the use of traceable calibration materials and taking part in interlaboratory comparisons, guarantees high accuracy data for future DREAMS users. During first experiments an energy calibration of the accelerator has been carried out using the nuclear reaction 1H(15N,γα)12C yielding an energy correction factor of 1.019.

  12. The first four years of the AMS-facility DREAMS: Status and developments for more accurate radionuclide data

    NASA Astrophysics Data System (ADS)

    Rugel, Georg; Pavetich, Stefan; Akhmadaliev, Shavkat; Enamorado Baez, Santiago Miguel; Scharf, Andreas; Ziegenrücker, René; Merchel, Silke

    2016-03-01

    DREAMS, the DREsden AMS-facility, is performing routine accelerator mass spectrometry of 10Be, 26Al, 36Cl, 41Ca, and 129I for a wide range of applications. All DREAMS-data is normalised directly to primary standards or traceable to those via cross-calibration of secondary standards. Recent technical developments such as a low-memory ion source for 36Cl and 129I and sophisticated tuning strategies for 129I led to improved-accuracy data. Tests of ion source output have been performed with different metal binders, sample-to-binder mixing ratios, and compaction pressures in order to find optimal parameters. The highest and most stable outputs have been obtained for 10Be, 26Al, and 41Ca for the following binders and mixing ratios (by weight): BeO:Nb, 1:4; Al2O3:Ag, 1:1; CaF2:Ag, 1:4. Higher beam currents generally result in reduced statistical uncertainty. Cross-contamination and long-term memory seem to be underestimated problems asking for further tests and improvements such as the development of low-level in-house-standards.

  13. Microscopic analysis of 10,11Be elastic scattering on protons and 12C and breakup processes of 11Be within the 10Be+n cluster model

    NASA Astrophysics Data System (ADS)

    Spasova, K.; Lukyanov, V. K.; Kadrev, D. N.; Antonov, A. N.; Zemlyanaya, E. V.; Lukyanov, K. V.; Gaidarov, M. K.

    2016-06-01

    The elastic scattering cross-sections of 10,11Be on protons and 12C at energy E < 100 MeV/nucleon using microscopically calculated optical potentials (OP) are presented. The real OP is obtained by a folding procedure with effective NN interactions, while the imaginary OP is estimated within the high energy approximation (HEA). The spin-orbit part of the OP is also included. The characteristics of the breakup processes of 11Be on different nuclear targets are also considered. The cross-sections of diffractive breakup and stripping reactions of 11Be on 9Be, 93Nb, 181Ta and 238U at energy E = 63 MeV/nucleon and the longitudinal momentum distributions of 10Be fragments produced in the breakup of 11Be on these nuclei are presented. The results are in a good agreement with the available experimental data, in particular the obtained widths of about 50 MeV/c are closed to the empirical ones.

  14. History dependent crystallization of Zr{sub 41}Ti{sub 14}Cu{sub 12}Ni{sub 10}Be{sub 23} melts

    SciTech Connect

    Schroers, Jan; Johnson, William L.

    2000-07-01

    The crystallization of Zr{sub 41}Ti{sub 14}Cu{sub 12}Ni{sub 10}Be{sub 23} (Vit 1) melts during constant heating is investigated. (Vit 1) melts are cooled with different rates into the amorphous state and the crystallization temperature upon subsequent heating is studied. In addition, Vit 1 melts are cooled using a constant rate to different temperatures and subsequently heated from this temperature with a constant rate. We investigate the influence of the temperature to which the melt was cooled on the crystallization temperature measured upon heating. In both cases the onset temperature of crystallization shows strong history dependence. This can be explained by an accumulating process during cooling and heating. An attempt is made to consider this process in a simple model by steady state nucleation and subsequent growth of the nuclei which results in different crystallization kinetics during cooling or heating. Calculations show qualitative agreement with the experimental results. However, calculated and experimental results differ quantitatively. This difference can be explained by a decomposition process leading to a nonsteady nucleation rate which continuously increases with decreasing temperature. (c) 2000 American Institute of Physics.

  15. Excited states of {sub {lambda}}{sup 9}Be and {sub {lambda}}{sub {lambda}}{sup 10}Be in an {alpha} cluster model

    SciTech Connect

    Shoeb, Mohammad

    2006-12-15

    The energies of the degenerate spin-flip doublet (3{sup +}/2,5{sup +}/2) of {sub {lambda}}{sup 9}Be and of the 2{sup +} state of {sub {lambda}}{sub {lambda}}{sup 10}Be are analyzed in the {alpha} cluster model using a phenomenological dispersive three-body {lambda}{alpha}{alpha} force that reproduces the ground state energy of {sub {lambda}}{sup 9}Be. Two types of phenomenological {lambda}{alpha} and {alpha}{alpha} potentials and a few s-state {lambda}{lambda} potentials are taken as input. The energies of the excited states of the hypernuclei, treated as three- and four-body systems, calculated using the Variational Monte Carlo method, are in good agreement with the experimental values. Our results demonstrate that the existing data are insensitive to whether one employs a dispersive {lambda}{alpha}{alpha} force along with potentials in the relative angular momentum state l=0 and 2 as in the present work or whether one uses nonlocal {lambda}{alpha} potential as in earlier analyses.

  16. Mid-late Pleistocene glacial evolution in the Grove Mountains, East Antarctica, constraints from cosmogenic 10Be surface exposure dating of glacial erratic cobbles

    NASA Astrophysics Data System (ADS)

    Dong, Guocheng; Huang, Feixin; Yi, Chaolu; Liu, Xiaohan; Zhou, Weijian; Caffee, Marc W.

    2016-08-01

    Glacial histories from the East Antarctic Ice Sheet (EAIS) provide keys to understanding correlations between the EAIS and global climate. They are especially helpful in the assessment of global sea level change, and as a means of quantifying the magnitude of past glacial activity and the rate at which ice responded to climate change. Given the significance of EAIS glacial histories, it is imperative that more glacial chronologic data for this region be obtained, especially for the mid-to-late Pleistocene. We report cosmogenic 10Be surface exposure dating results from glacially transported cobbles embedded in blue-ice moraine material at Mount Harding, the Grove Mountains, EAIS. Forty exotic cobbles sampled along two profiles (A and B) on this blue-ice moraine present apparent exposure-ages ranging from 7.2 to 542.2 ka. We explore this scattered dataset by using Principal Component Analysis (PCA) to identify statistically significant trends in the data. We identify a correlation between exposure-age and distance of the cobbles from Mount Harding. In profile A, cobbles further from Mount Harding yield older exposure-ages than those that are relatively close. In profile B, cobbles closer to Mount Harding are found to have relatively older exposure-ages. In term of glacial history we suggest that the direction of ice flow changed during the period from ∼60 to 200 ka, and that multiple glacial fluctuations occurred in the mid-late Pleistocene.

  17. Late Pleistocene to Holocene slip rates for the Gurvan Bulag thrust fault (Gobi-Altay, Mongolia) estimated with 10Be dates

    NASA Astrophysics Data System (ADS)

    Ritz, J.-F.; BourlèS, D.; Brown, E. T.; Carretier, S.; ChéRy, J.; Enhtuvshin, B.; Galsan, P.; Finkel, R. C.; Hanks, T. C.; Kendrick, K. J.; Philip, H.; Raisbeck, G.; Schlupp, A.; Schwartz, D. P.; Yiou, F.

    2003-03-01

    We surveyed morphotectonic markers along the central part of the Gurvan Bulag thrust, a fault that ruptured with the Bogd fault during the Gobi-Altay earthquake (1957, M 8.3), to document climatic and tectonic processes along the fault for the late Pleistocene-Holocene period. The markers were dated using 10Be produced in situ. Two major periods of alluviation ended at 131 ± 20 and 16 ± 4.8 ka. These appear to be contemporaneous with global climatic changes at the terminations of marine isotope stages (MIS) 6 and 2. The vertical slip rates, determined from offset measurements and surfaces ages, are 0.14 ± 0.03 mm/yr over the late Pleistocene-Holocene and between 0.44 ± 0.11 and 1.05 ± 0.25 mm/yr since the end of the late Pleistocene. The higher of these slip rates for the last ˜16 kyr is consistent with paleoseismic investigations along the fault [, 2002], and suggests that, at the end of late Pleistocene, the fault evolved from quiescence to having recurrence intervals of 4.0 ± 1.2 kyr for surface ruptures with ˜4 m vertical offset (similar to that of 1957). The inferred recurrence interval is comparable to that of the Bogd fault (3.7 ± 1.3 kyr) suggesting that the two faults may have ruptured together also earlier during the last ˜16 kyr.

  18. Late glacial 10Be ages for glacial landforms in the upper region of the Taibai glaciation in the Qinling Mountain range, China

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Liu, Liang; Chen, Yixin; Liu, Beibei; Harbor, Jonathan M.; Cui, Zhijiu; Liu, Rui; Liu, Xiao; Zhao, Xu

    2016-01-01

    Glacial landforms are well preserved on Taibai Mountain (3767 m), the main peak of the Qinling mountain range located south of the Loess Plateau and east of the Qinghai-Tibet Plateau. The timing and extent of Quaternary glaciation in the study area is important for reconstructing Quaternary environmental change however numerical ages for glaciation in this study area have not previously been well resolved. Using terrestrial in situ cosmogenic nuclides we dated four samples collected from two glacially eroded rock steps in the upper part of a valley near the main peak, in an area previously identified as having been occupied by ice during the Taibai glaciation. The 10Be results are all late glacial in age: 18.6 ± 1.1 ka, 16.9 ± 1.0 ka, 16.9 ± 1.1 ka and 15.1 ± 1.0 ka. The spatial pattern of ages in the valley suggests fast retreat, with horizontal and vertical retreat rates estimated to be on the order of 0.4 and 0.09 m a-1, respectively. A simple extrapolation of these retreat rates from the ages at the two sample sites suggests that the glacier retreat began during Last Glacial Maximum and that glaciers disappeared from the main peak by about 15 ka.

  19. 10Be dating of river terraces of Santo Domingo river, on Southeastern flank of the Mérida Andes, Venezuela: Tectonic and climatic implications

    NASA Astrophysics Data System (ADS)

    Guzmán, Oswaldo; Vassallo, Riccardo; Audemard, Franck; Mugnier, Jean-Louis; Oropeza, Javier; Yepez, Santiago; Carcaillet, Julien; Alvarado, Miguel; Carrillo, Eduardo

    2013-12-01

    In this study, we discuss the first cosmogenic 10Be dating of river terraces located in the lower reaches of the Santo Domingo river (Southeastern flank of the Mérida Andes, Western Venezuela). The geomorphic observations and dating allowed the restoration of the temporal evolution of incision rate, which was analysed in terms of tectonic, climatic and geomorphic processes. The long-term incision rate in the area has been constantly around 1.1 mm/a over the last 70 ka. Taking into account the geologic and geomorphologic setting, this value can be converted into the Late Pleistocene uplift rate of the Southeastern flank of the Mérida Andes. Our results show that the process of terraces formation in the lower reaches of the Santo Domingo river occurred at a higher frequency (103-104 years) than a glacial/interglacial cycle (104-105 years). According to the global and local climate curve, these terraces were abandoned during warm to cold transitions.

  20. Climatic and topographic controls on the style and timing of Late Quaternary glaciation throughout Tibet and the Himalaya defined by 10Be cosmogenic radionuclide surface exposure dating

    USGS Publications Warehouse

    Owen, L.A.; Finkel, R.C.; Barnard, P.L.; Haizhou, Ma; Asahi, K.; Caffee, M.W.; Derbyshire, E.

    2005-01-01

    Temporal and spatial changes in glacier cover throughout the Late Quaternary in Tibet and the bordering mountains are poorly defined because of the inaccessibility and vastness of the region, and the lack of numerical dating. To help reconstruct the timing and extent of glaciation throughout Tibet and the bordering mountains, we use geomorphic mapping and 10Be cosmogenic radionuclide (CRN) surface dating in study areas in southeastern (Gonga Shan), southern (Karola Pass) and central (Western Nyainqentanggulha Shan and Tanggula Shan) Tibet, and we compare these with recently determined numerical chronologies in other parts of the plateau and its borderlands. Each of the study regions receives its precipitation mainly during the south Asian summer monsoon when it falls as snow at high altitudes. Gonga Shan receives the most precipitation (>2000 mm a-1) while, near the margins of monsoon influence, the Karola Pass receives moderate amounts of precipitation (500-600 mm a-1) and, in the interior of the plateau, little precipitation falls on the western Nyainqentanggulha Shan (???300 mm a -1) and the Tanggula Shan (400-700 mm a-1). The higher precipitation values for the Tanggula Shan are due to strong orographic effects. In each region, at least three sets of moraines and associated landforms are preserved, providing evidence for multiple glaciations. The 10Be CRN surface exposure dating shows that the formation of moraines in Gonga Shan occurred during the early-mid Holocene, Neoglacial and Little Ice Age, on the Karola Pass during the Lateglacial, Early Holocene and Neoglacial, in the Nyainqentanggulha Shan date during the early part of the last glacial cycle, global Last Glacial Maximum and Lateglacial, and on the Tanggula Shan during the penultimate glacial cycle and the early part of the last glacial cycle. The oldest moraine succession in each of these regions varies from the early Holocene (Gonga Shan), Lateglacial (Karola Pass), early Last Glacial (western

  1. The Last Glacial Maximum at 44°S documented by a 10Be moraine chronology at Lake Ohau, Southern Alps of New Zealand

    NASA Astrophysics Data System (ADS)

    Putnam, Aaron E.; Schaefer, Joerg M.; Denton, George H.; Barrell, David J. A.; Birkel, Sean D.; Andersen, Bjørn G.; Kaplan, Michael R.; Finkel, Robert C.; Schwartz, Roseanne; Doughty, Alice M.

    2013-02-01

    Determining whether glaciers registered the classic Last Glacial Maximum (LGM; ˜26,500-˜19,000 yrs ago) coevally between the hemispheres can help to discriminate among hypothesized drivers of ice-age climate. Here, we present a record of glacier behavior from the Southern Alps of New Zealand during the 'local LGM' (LLGM). We used 10Be surface-exposure dating methods and detailed glacial geomorphologic mapping to produce a robust chronology of well-preserved terminal moraines deposited during the LLGM near Lake Ohau on central South Island. We then used a glaciological model to estimate a LLGM glacier snowline and atmospheric temperature from the Ohau glacier record. Seventy-three 10Be surface-exposure ages place culminations of terminal moraine construction, and hence completions of glacier advances to positions outboard of present-day Lake Ohau, at 138,600 ± 10,600 yrs, 32,520 ± 970 yrs ago, 27,400 ± 1300 yrs ago, 22,510 ± 660 yrs ago, and 18,220 ± 500 yrs ago. Recessional moraines document glacier recession into the Lake Ohau trough by 17,690 ± 350 yrs ago. Exposure of an ice-molded bedrock bench located inboard of the innermost LLGM moraines by 17,380 ± 510 yrs ago indicates that the ice tongue had receded about 40% of its overall length by that time. Comparing our chronology with distances of retreat suggests that the Ohau glacier terminus receded at a mean net rate of about 77 m yr-1 and its surface lowered by 200 m between 17,690 and 17,380 yrs ago. A long-term continuation of ice retreat in the Ohau glacier catchment is implied by moraine records at the head of Irishman Stream valley, a tributary of the Ohau glacier valley. The Irishman Stream cirque glacier advanced to produce a set of Lateglacial moraines at 13,000 ± 500 yrs ago, implying that the cirque glacier was less extensive prior to that advance. We employed a glaciological model, fit to these mapped and dated LLGM moraines, to derive snowline elevations and temperature parameters from the

  2. Late Quaternary slip rate gradient defined using high-resolution topography and 10Be dating of offset landforms on the southern San Jacinto Fault zone, California

    NASA Astrophysics Data System (ADS)

    Blisniuk, Kimberly; Rockwell, Thomas; Owen, Lewis A.; Oskin, Michael; Lippincott, Caitlin; Caffee, Marc W.; Dortch, Jason

    2010-08-01

    Recent studies suggest the San Jacinto fault zone may be the dominant structure accommodating PA-NA relative plate motion. However, because the late Quaternary slip history of the southern San Andreas fault system is insufficiently understood, it is difficult to evaluate the partitioning of deformation across the plate boundary and its evolution. Landforms displaced by the Clark fault of the southern San Jacinto fault zone were mapped using high-resolution airborne laser-swath topography and selected offset landforms were dated using cosmogenic 10Be. Beheaded channels at Rockhouse Canyon, displaced by 500 ± 70 m and 220 ± 70 m, have been dated to 47 ± 8 ka and 28 ± 9 ka, respectively. Farther south, near the southern Santa Rosa Mountains, an alluvial deposit displaced by 51 ± 9 m has been dated to 35 ± 7 ka. From these sites, the slip rate of the Clark fault is determined to diminish southward from 8.9 ± 2.0 to 1.5 ± 0.4 mm/yr. This implies a slip-rate decrease along the Clark fault from Anza southeastward to its surface termination near the Salton Trough, where slip is transferred to the Coyote Creek fault, and additional deformation is compensated by folding and thrusting in the basin. These data suggest that since ˜30 to 50 ka, the slip rate along the southern San Jacinto fault zone has been lower than, or equivalent to, the rate along the southernmost San Andreas fault. Accordingly, either the slip rate of the San Jacinto fault has substantially decreased since fault initiation, or fault slip began earlier than previously suggested.

  3. Pleistocene glaciations of Central Asia: results from 10Be surface exposure ages of erratic boulders from the Pamir (Tajikistan), and the Alay Turkestan range (Kyrgyzstan)

    NASA Astrophysics Data System (ADS)

    Abramowski, U.; Bergau, A.; Seebach, D.; Zech, R.; Glaser, B.; Sosin, P.; Kubik, P. W.; Zech, W.

    2006-05-01

    We have determined the timing of glaciations in the Pamir (Tajikistan) and the Alay-Turkestan Range (Kyrgyzstan) using 10Be surface exposure dating. Glacial advances in the area have occurred >93-136, ˜60-80, (40-55), ˜27-25, ˜22-20, ˜19-17, ˜16-15, ˜15-13, and 11-9 cal ka BP. All Late Pleistocene glaciers in the Pamir, and the Alay-Turkestan Ranges have been valley glaciers except for the most extended glaciers on the Pamir plateau, which have formed local piedmont glaciations. In the eastern Pamir, these are characterized by ELA depressions of ˜370-380 m (THAR 0.5). In the Turkestan Range and Alay Range, ELA depressions at the same time were >750 and 600 m, respectively. Late Pleistocene glacier advances all over western High Asia were contemporaneous with climatic cold phases rather than monsoonal maxima. Their maximum extent and that of the western hemisphere ice sheets were asynchronous, due to increasing aridity in the region over the course of the Last Glacial. Late Pleistocene climate in Central Asia seems to have been influenced by the interplay of the westerly circulation and the Siberian anticyclone. Some indirect monsoonal influence in the eastern Pamir may be responsible for the existence of some of the Lateglacial moraine stages in this area. High altitude glaciers seem to have reached their maximum extent earlier (MIS 5-4) than low altitude glaciers (first half of MIS 3), possibly due to prolonged glacial aridity imparting with moisture advection onto high altitude sites, inducing glacial retreat, but prolonged cold during the same time imparting with glacier ablation at lower altitude sites, inducing glacial advance.

  4. Patterns of landscape evolution on the central and northern Tibetan Plateau investigated using in-situ produced 10Be concentrations from river sediments

    NASA Astrophysics Data System (ADS)

    Li, Yingkui; Li, Dewen; Liu, Gengnian; Harbor, Jon; Caffee, Marc; Stroeven, Arjen P.

    2014-07-01

    Quantifying long-term erosion rates across the Tibetan Plateau and its bordering mountains is of critical importance to an understanding of the interaction between climate, tectonic movement, and landscape evolution. We present a new dataset of basin-wide erosion rates from the central and northern Tibetan Plateau derived using in-situ produced 10Be concentrations of river sediments. Basin-wide erosion rates from the central plateau range from 10.1±0.9 to 36.8±3.2 mm/kyr, slightly higher than published local erosion rates measured from bedrock surfaces. These values indicate that long-term downwearing of plateau surfaces proceeds at low rates and that the landscape is demonstrably stable in the central plateau. In contrast, basin-wide erosion rates from the Kunlun Shan on the northern Tibetan Plateau range from 19.9±1.7 to 163.2±15.9 mm/kyr. Although the erosion rates of many of these basins are much higher than the rates from the central plateau, they are lower than published basin-wide erosion rates from other mountains fringing the Tibetan Plateau, probably because the basins in the Kunlun Shan include both areas of low-relief plateau surface and high-relief mountain catchments and may also result from retarded fluvial sediment transport in an arid climate. Significantly higher basin-wide erosion rates derived from the Tibetan Plateau margin, compared to the central plateau, reflect a relatively stable plateau surface that is being dissected at its margins by active fluvial erosion.

  5. A 15 Ky High Resolution 10be-Record of Denudation Rate Change from an Alpine Catchment in the Eastern European Alps

    NASA Astrophysics Data System (ADS)

    Grischott, R.; Kober, F.; Reitner, J.; Hippe, K.; Ivy-Ochs, S.; Hajdas, I.; Willett, S.

    2014-12-01

    The influence of climate on erosion of alpine catchments has been sparsely understood due to the missing temporal or spatial resolution of archives and the quantification of processes. Sediment budget studies in the Alps show severalfold increased lateglacial denudation compared to the present being in line with the concept of paraglacial cycle. Here, we present results coupling a 15-ky record of cosmogenic 10Be-derived paleo-denudation rates (n=42) from a 160 m Stappitz lake archive in the Austrian Alps (Seebach-Valley, 34 km2) and a two-year timeseries of the modern stream. The age-depth chronology was established using 14C dates and relative pollen-stratigraphy. Postdepositional correction for the core samples was not necessary due to sufficient shielding while deposited in a lake. Catchment mapping combined with glacial extents reconstructions of revealed prominent lateglacial moraines which likely decoupled the sediment flux from upper valley flanks to the trunk stream since Younger Dryas. Thus, we interpret the denudational pattern as being dominated by the lower hillslopes for the Holocene with only minimal admixing of glacial material. The latter was probably the dominant sediment source in the lateglacial. The beginning of the Holocene shows decreasing denudation rates down to a minimum at 5 ky BP from 1.0 to 0.3 mm/yr. The transition from 5 to 3 ky BP is marked with increasing rates up to the level of the last 3 ky with 0.6 mm/yr, similar to the modern rate. Given the stratigraphy of the core, we attribute the rather low alpine denudation rates to the stabilising effect of vegetation on the hillslopes. Based on an assumed lag time, the denudation rates increase due to the cooler and wetter climate in the late Holocene resulting in less vegetation (on the slopes), more shallow debris-flows and frost cracking. Our results suggest that in the study area climate modulates denudation by dictating vegetation on the hillslopes and efficient frost cracking

  6. Climatic controls on steady state erosion using the relationship between channel steepness and cosmogenic 10Be-derived catchment averaged erosion rates

    NASA Astrophysics Data System (ADS)

    Rossi, M. W.; Whipple, K. X.; DiBiase, R. A.; Heimsath, A. M.

    2011-12-01

    To understand landscape response to climate change, baseline controls on erosion rates must be established for given climate conditions. Theory suggests a number of climate metrics should be important to erosion (i.e. precipitation, temperature, storminess, seasonality, snow fraction). Nevertheless, definitive field evidence quantifying how climate affects erosion rate has proven difficult to obtain. This is at least partly due to the difficulty of isolating climatic influences on erosion rates from topographic and rock strength influences. We circumvent this problem by evaluating how climate influences the relationship between erosion rate and topography in settings with similar rock types. At steady state, tectonic uplift dictates erosion rate, and climate and rock strength are manifest as changes in erosional efficiency - the topographic relief necessary to maintain the tectonically imposed erosion rate. In fluvial landscapes, bedrock rivers set the relevant scale of topographic relief, which can be described by the channel steepness index. A number of recent studies have shown that the relationship between channel steepness and millennial scale erosion rates is non-linear, implying that erosional efficiency increases with relief. Work in the San Gabriel Mountains suggests this relationship is due to erosion thresholds that limit incision of channels in low relief landscapes. By using a fluvial incision model that incorporates a range of daily discharge events coupled with an erosion threshold (Lague et al., 2005), the influence of flood frequency on the relationship between channel steepness and erosion rate can be explored. We apply this same modeling approach to five other landscapes that exhibit a range of channel steepness, have similar rock types (granitoids), but that are in dramatically different climate regimes ranging from desert to rainforest (annual rainfall, P, from 0.25 to 3 m/yr). Specifically, we present new cosmogenic 10Be erosion rate data from

  7. Surface exposure dating of Holocene basalt flows and cinder cones in the Kula volcanic field (western Turkey) using cosmogenic 3He and 10Be

    NASA Astrophysics Data System (ADS)

    Heineke, Caroline; Niedermann, Samuel; Hetzel, Ralf; Akal, Cüneyt

    2015-04-01

    The Kula volcanic field is the youngest volcanic province in western Anatolia and covers an area of about 600 km2 around the town Kula (Richardson-Bunbury, 1996). Its alkali basalts formed by melting of an isotopically depleted mantle in a region of long-lived continental extension and asthenospheric upwelling (Prelevic et al., 2012). Based on morphological criteria and 40Ar/39Ar dating, four phases of Quaternary activity have been distinguished in the Kula volcanic field (Richardson-Bunbury, 1996; Westaway et al., 2006). The youngest lava flows are thought to be Holocene in age, but so far only one sample from this group was dated by 40Ar/39Ar at 7±2 ka (Westaway et al., 2006). In this study, we analysed cosmogenic 3He in olivine phenocrysts from three basalt flows and one cinder cone to resolve the Holocene history of volcanic eruptions in more detail. In addition, we applied 10Be exposure dating to two quartz-bearing xenoliths found at the surface of one flow and at the top of one cinder cone. The exposure ages fall in the range between ~500 and ~3000 years, demonstrating that the youngest volcanic activity is Late Holocene in age and therefore distinctly younger than previously envisaged. Our results show that the Late Holocene lava flows are not coeval but formed over a period of a few thousand years. We conclude that surface exposure dating of very young volcanic rocks provides a powerful alternative to 40Ar/39Ar dating. References Prelevic, D., Akal, C. Foley, S.F., Romer, R.L., Stracke, A. and van den Bogaard, P. (2012). Ultrapotassic mafic rocks as geochemical proxies for post-collisional dynamics of orogenic lithospheric mantle: the case of southwestern Anatolia, Turkey. Journal of Petrology, 53, 1019-1055. Richardson-Bunbury, J.M. (1996). The Kula Volcanic Field, western Turkey: the development of a Holocene alkali basalt province and the adjacent normal-faulting graben. Geological Magazine, 133, 275-283. Westaway, R., Guillou, H., Yurtmen, S., Beck, A

  8. 10Be dating of the end of low-altitude rock glacier activity in the Alps - evidence for cold conditions during the early Preboreal.

    NASA Astrophysics Data System (ADS)

    Kerschner, Hanns; Ivy-Ochs, Susan

    2010-05-01

    Large relict rock glacier complexes are conspicious features in the Alps. Their occurence can roughly be subdivided into a "lower rock glacier belt", which reaches down to about 1900 m a.s.l., an "intermediate rock glacier belt" with rock glacier snouts at around present-day timberline (approx. 2200 m a.s.l) in the central Alps and an "upper rock glacier belt" at similar altitudes as presently active rock glaciers. All these rock glaciers indicate the former presence of discontinuous permafrost at their respective altitudes and are good indicators for the mean annual air temperature during their active period. The end of rock glacier activity at a given altitude marks also the end of the existence of permafrost conditions. Experience from the Alps shows that it may take about a century until the surface of a rock glacier is stabilized, Hence, if it is possible to date the surface of a relict rock glacier with 10Be, we get a close date for the end of permafrost activity at the altitude of the rock glacier. From the difference between the altitude of the relict rock glacier and presently active rock glaciers, the rise of mean annual air temperature can be calculated. Relict rock glaciers at present-day timberline at Julierpass (Swiss Alps) and at Larstigtal (Austrian Alps) gave ages in the order of 10.5 ka BP for surface stabilization. Both rock glaciers, which belong to the "intermediate rock glacier belt", developed from lateral moraines and scree slopes. They started to move into former glacier beds after ice recession from the Younger Dryas "Egesen" advance. Their age indicates that climatic conditions favouring permafrost existence about 300 - 400 m below 20th century permafrost occurence prevailed during most of the Preboreal. Taken together with the Kartell glacier advance (10.8 ka) they show that rapid climatic warming at the Younger Dryas / Holocene boundary was followed by more unstable climatic conditions and and somewhat slower warming until full Holocene

  9. High-precision 10Be chronology of moraines in the Southern Alps indicates synchronous cooling in Antarctica and New Zealand 42,000 years ago

    NASA Astrophysics Data System (ADS)

    Kelley, Samuel E.; Kaplan, Michael R.; Schaefer, Joerg M.; Andersen, Bjørn G.; Barrell, David J. A.; Putnam, Aaron E.; Denton, George H.; Schwartz, Roseanne; Finkel, Robert C.; Doughty, Alice M.

    2014-11-01

    Millennial-scale temperature variations in Antarctica during the period 80,000 to 18,000 years ago are known to anti-correlate broadly with winter-centric cold-warm episodes revealed in Greenland ice cores. However, the extent to which climate fluctuations in the Southern Hemisphere beat in time with Antarctica, rather than with the Northern Hemisphere, has proved a controversial question. In this study we determine the ages of a prominent sequence of glacial moraines in New Zealand and use the results to assess the phasing of millennial climate change. Forty-four 10Be cosmogenic surface-exposure ages of boulders deposited by the Pukaki glacier in the Southern Alps document four moraine-building events from Marine Isotope Stage 3 (MIS 3) through to the end of the Last Glacial Maximum (∼18,000 years ago; LGM). The earliest moraine-building event is defined by the ages of nine boulders on a belt of moraine that documents the culmination of a glacier advance 42,000 years ago. At the Pukaki locality this advance was of comparable scale to subsequent advances that, from the remaining exposure ages, occurred between 28,000 and 25,000, at 21,000, and at 18,000 years ago. Collectively, all four moraine-building events represent the LGM. The glacier advance 42,000 years ago in the Southern Alps coincides in Antarctica with a cold episode, shown by the isotopic record from the EPICA Dome C ice core, between the prominent A1 and A2 warming events. Therefore, the implication of the Pukaki glacier record is that as early as 42,000 years ago an episode of glacial cold similar to that of the LGM extended in the atmosphere from high on the East Antarctic plateau to at least as far north as the Southern Alps (∼44°S). Such a cold episode is thought to reflect the translation through the atmosphere and/or the ocean of the anti-phased effects of Northern Hemisphere interstadial conditions to the southern half of the Southern Hemisphere. Regardless of the mechanism, any

  10. Using (1)(0)Be cosmogenic isotopes to estimate erosion rates and landscape changes during the Plio-Pleistocene in the Cradle of Humankind, South Africa.

    PubMed

    Dirks, Paul H G M; Placzek, Christa J; Fink, David; Dosseto, Anthony; Roberts, Eric

    2016-07-01

    Concentrations of cosmogenic (10)Be, measured in quartz from chert and river sediment around the Cradle of Humankind (CoH), are used to determine basin-averaged erosion rates and estimate incision rates for local river valleys. This study focusses on the catchment area that hosts Malapa cave with Australopithecus sediba, in order to compare regional versus localized erosion rates, and better constrain the timing of cave formation and fossil entrapment. Basin-averaged erosion rates for six sub-catchments draining the CoH show a narrow range (3.00 ± 0.28 to 4.15 ± 0.37 m/Mega-annum [Ma]; ±1σ) regardless of catchment size or underlying geology; e.g. the sub-catchment with Malapa Cave (3 km(2)) underlain by dolomite erodes at the same rate (3.30 ± 0.30 m/Ma) as the upper Skeerpoort River catchment (87 km(2)) underlain by shale, chert and conglomerate (3.23 ± 0.30 m/Ma). Likewise, the Skeerpoort River catchment (147 km(2)) draining the northern CoH erodes at a rate (3.00 ± 0.28 m/Ma) similar to the Bloubank-Crocodile River catchment (627 km(2)) that drains the southern CoH (at 3.62 ± 0.33 to 4.15 ± 0.37 m/Ma). Dolomite- and siliciclastic-dominated catchments erode at similar rates, consistent with physical weathering as the rate controlling process, and a relatively dry climate in more recent times. Erosion resistant chert dykes along the Grootvleispruit River below Malapa yield an incision rate of ∼8 m/Ma at steady-state erosion rates for chert of 0.86 ± 0.54 m/Ma. Results provide better palaeo-depth estimates for Malapa Cave of 7-16 m at the time of deposition of A. sediba. Low basin-averaged erosion rates and concave river profiles indicate that the landscape across the CoH is old, and eroding slowly; i.e. the physical character of the landscape changed little in the last 3-4 Ma, and dolomite was exposed on surface probably well into the Miocene. The apparent absence of early Pliocene- or Miocene-aged cave deposits and

  11. A test of the cosmogenic 10Be(meteoric)/9Be proxy for simultaneously determining basin-wide erosion rates, denudation rates, and the degree of weathering in the Amazon basin

    NASA Astrophysics Data System (ADS)

    Wittmann, H.; Blanckenburg, F.; Dannhaus, N.; Bouchez, J.; Gaillardet, J.; Guyot, J. L.; Maurice, L.; Roig, H.; Filizola, N.; Christl, M.

    2015-12-01

    We present an extensive investigation of a new erosion and weathering proxy derived from the 10Be(meteoric)/9Be(stable) ratio in the Amazon River basin. This new proxy combines a radioactive atmospheric flux tracer, meteoric cosmogenic 10Be, with 9Be, a trace metal released by weathering. Results show that meteoric 10Be concentrations ([10Be]) and 10Be/9Be ratios increase by >30% from the Andes to the lowlands. We can calculate floodplain transfer times of 2-30 kyr from this increase. Intriguingly however, the riverine exported flux of meteoric 10Be shows a deficit with respect to the atmospheric depositional 10Be flux. Most likely, the actual area from which the 10Be flux is being delivered into the mainstream is smaller than the basin-wide one. Despite this imbalance, denudation rates calculated from 10Be/9Be ratios from bed load, suspended sediment, and water samples from Amazon Rivers agree within a factor of 2 with published in situ 10Be denudation rates. Erosion rates calculated from meteoric [10Be], measured from depth-integrated suspended sediment samples, agree with denudation rates, suggesting that grain size-induced variations in [10Be] are minimized when using such sampling material instead of bed load. In addition, the agreement between erosion and denudation rates implies minor chemical weathering intensity in most Amazon tributaries. Indeed, the Be-specific weathering intensity, calculated from mobilized 9Be comprising reactive and dissolved fractions that are released during weathering, is constant at approximately 40% of the total denudation from the Andes across the lowlands to the Amazon mouth. Therefore, weathering in the Amazon floodplain is not detected.

  12. Evaluating the reliability of Late Quaternary landform ages: Integrating 10Be cosmogenic surface exposure dating with U-series dating of pedogenic carbonate on alluvial and fluvial deposits, Sonoran desert, California

    NASA Astrophysics Data System (ADS)

    Blisniuk, K.; Sharp, W. D.

    2015-12-01

    To assess the reliability of Quaternary age determinations of alluvial and fluvial deposits across the Sonoran Desert (Coachella Valley and Anza Borrego) in southern California, we applied both 10Be exposure age dating of surface clasts and U-series dating of pedogenic carbonate from subsurface clast-coatings to the same deposits. We consider agreement between dates from the two techniques to indicate reliable age estimates because each technique is subject to distinct assumptions and therefore their systematic uncertainties are largely independent. 10Be exposure dates should yield maximum ages when no correction is made for inheritance and post-depositional erosion is negligible. U-series dating, in contrast, provides minimum dates because pedogenic carbonate forms after deposition. Our results show that: (1) For deposits ca. 70 ka or younger, 10Be and U-series dates were generally concordant. We note, however, that in most cases U-series soil dates exceed 10Be exposure dates that are corrected for inheritance when using 10Be in modern alluvium. This suggests that 10Be concentrations of modern alluvium may exceed the 10Be acquired by late Pleistocene deposits during fluvial transport and hillslope residence (i.e., Pleistocene inherited 10Be). (2) For deposits older than ~70 ka, U-series dates are significantly younger than the 10Be dates. This implies that U-series dates in this region may significantly underestimate the depositional age of older alluvium, probably because of delayed onset of deposition, slow accumulation, or poor preservation of secondary carbonate in response to climatic controls. Thus, whenever possible, multiple dating methods should be applied to obtain reliable ages for late Quaternary deposits.

  13. The in vitro reduction of sodium [36Cl]-chlorate in bovine ruminal fluid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sodium chlorate effectively reduces or eliminates the numbers of gram-negative pathogenic bacteria in the gastrointestinal tracts of live cattle. Limitations to the in vivo efficacy of chlorate are its rapid absorption from the gastrointestinal tract and its presumed reduction to chloride within the...

  14. Total radioactive residues and residues of [36Cl]chlorate in market size broilers.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The oral administration of chlorate salts reduces the numbers of Gram-negative pathogens in gastrointestinal tracts of live food animals. Although the efficacy of chlorate salts has been demonstrated repeatedly, the technology cannot be introduced into commercial settings without first demonstrating...

  15. Neutron capture production rates of cosmogenic 60Co, 59Ni and 36Cl in stony meteorites

    NASA Technical Reports Server (NTRS)

    Spergel, M. S.; Reedy, R. C.; Lazareth, O. W.; Levy, P. W.

    1986-01-01

    Results for neutron flux calculations in stony meteoroids (of various radii and compositions) and production rates for Cl-36, Ni-59, and Co-60 are reported. The Ni-59/Co-60 ratio is nearly constant with depth in most meteorites: this effect is consistent with the neutron flux and capture cross section properties. The shape of the neutron flux energy spectrum, varies little with depth in a meteorite. The size of the parent meteorite can be determined from one of its fragments, using the Ni-59/Co-60 ratios, if the parent meteorite was less than 75 g/cm(2) in radius. If the parent meteorite was larger, a lower limit on the size of the parent meteorite can be determined from a fragment. In C3 chondrites this is not possible. In stony meteorites with R less than 50 g/cm(2) the calculated Co-60 production rates (mass less than 4 kg), are below 1 atom/min g-Co. The highest Co-60 production rates occur in stony meteorites with radius about 250 g/cm(2) (1.4 m across). In meteorites with radii greater than 400 g/cm(2), the maximum Co-60 production rate occurs at a depth of about 175 g/cm(2) in L-chondrite, 125 g/cm(2) in C3 chrondrite, and 190 g/cm(2) in aubrites.

  16. TISSUE RESIDUES, METABOLISM, AND EXCRETION OF NA[36CL]O3 IN RATS

    Technology Transfer Automated Retrieval System (TEKTR