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Sample records for 10be cosmogenic radionuclide

  1. 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

  2. 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

    NASA Astrophysics Data System (ADS)

    Owen, Lewis A.; Finkel, Robert C.; Barnard, Patrick L.; Haizhou, Ma; Asahi, Katsuhiko; Caffee, Marc W.; Derbyshire, Edward

    2005-07-01

    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

  3. Reconstructing Former Sea Cliff Chronologies using Cosmogenic 10Be Concentrations

    NASA Astrophysics Data System (ADS)

    Barlow, J.; Rosser, N. J.; Petley, D. N.; Densmore, A.; Lim, M.

    2010-12-01

    The long-term evolution of coastal cliffs is poorly constrained, with implications for future coastal planning, for estimates of coastal sediment generation and for models of coastal landform evolution. While general consensus has been reached on principles governing the evolution of sea cliffs and shore platforms, process rates and the relative importance of bedrock material properties and environmental boundary conditions have not been established in any quantitative way. This is primarily the result of a lack of calibration data due to the destruction of previous cliff positions through erosive processes. A recurrent problem is that rates of erosion and retreat are often comparable to measurement uncertainties over short time scales and across representative spatial extents. Therefore, long-term rates of retreat for rock coasts remain unknown and the magnitude and pattern of coastal change during the Holocene remains at best anecdotal. With this research we address these issues by reconstructing former cliff chronologies at Staithes, UK using cosmogenic radionuclide (CRN) concentrations measured across the shore platform. While individual samples provide little certainty as to their true exposure age due to variability in topographic shielding through time, the differences in CRN concentrations taken in transect normal to the cliff are indicative of the recession rate. This relationship forms the basis of our reconstruction. Studying erosion using the concentration of cosmogenically-derived 10Be within quartz has a proven track record. This type of analysis involves the use of accelerator mass spectrometry (AMS) to quantify the concentration of cosmogenic 10Be that has accumulated in the upper portion of the Earth’s surface. Our model of CRN accumulation assumes: negligible down-wearing of the shore platform following cliff recession, supported by studies that have directly measured erosion rates, and evidenced in the present foreshore morphology at the study

  4. 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

  5. Cosmogenic radionuclides in stone meteorites

    NASA Technical Reports Server (NTRS)

    Cressy, P. J., Jr.

    1976-01-01

    This document presents the techniques and compilation of results of cosmogenic Al-26 measurements at Goddard Space Flight Center on 91 samples of 76 stone meteorites. Short-lived radionuclides, including Na-22, Sc-46, Mn-54, and Co-60, were measured in 13 of these meteorites. About one-third of these data has not previously been published. The results are discussed briefly in terms of (1) depletion of Al-26 and natural potassium due to weathering, (2) possible exposure of several chondrites to an unusually high cosmic-ray flux, (3) comparison of Al-26, Na-22, Sc-46, and Mn5-54 in chondrites with the spallation Ne-22/Ne-21 ratio as a shielding indicator, and (4) comparison of (Al-26)-(Ne-22)/Ne-21 data for achondrite classes with the chondrite trend.

  6. 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

    for different populations on the basis of their exposure histories. Figure 1 shows the experimental relation between 10Be contents and 22Ne/21Ne ratios measured in diogenites. The 10Be contents decrease by 30-35%, while corresponding 22Ne/21Ne ratios increase from 1.07 to 1.29. Graf's semi- experimental model predicts--for L chondrites with preatmospheric radii less than 50 cm--a decrease of about 50% in 10Be over this interval of 22Ne/21Ne ratios [7]. This discrepancy cannot be explained by the minor differences in composition with respect to 10Be production. Therefore, our results indicate that this model is slightly overestimating the shielding sensitivity of 10Be. Five points do not fall within 2 sigma on the best (exponential) fit. Measurements of additional radionuclides may contribute to a better understanding of their outlying character. Acknowledgments: We thank the MWG in the USA, the NIPR in Tokyo and the National Museums for Natural History in Washington, London, and Paris for diogenite samples. This work was financially supported by the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO). References: [1] Welten K. C. et al. (1991) Meteoritics, 26, 408. [2] Schultz L. (1987) LPSC XVIII, 884-885. [3] Alymer D. et al. (1988) GCA, 52, 1691-1698. [4] Schultz L. and Kruse H. (1989) Meteoritics, 24, 155-172. [5] Takeda H. (1991) GCA, 55, 35-57. [6] Berkley J. L. and Boynton N. J. (1992) Meteoritics, 27, 387-394. [7] Graf Th. et al. (1990) GCA, 54, 2521-2534. Figure 1, which appears in the hard copy, shows shielding effects on P10 in diogenites.

  7. Chemical studies of H chondrites 11. Cosmogenic radionuclides in falls

    NASA Astrophysics Data System (ADS)

    Ferko, T. E.; Wang, M.-S.; Lipschutz, M. E.

    2002-10-01

    We measured the long-lived cosmogenic radionuclides 10Be, 26Al, and 36Cl in 47 H chondrite falls: 13 ``Cluster 1'' members, 9 ``Cluster 5'' members, and 25 random falls. From the date and time of fall, Clusters 1 and 5 were previously identified as possible coorbital meteoroid streams with distinctive thermal histories being confirmed by contents of volatile trace elements. Here, we use model data, including a three-radionuclide plot (10Bebulk/26Albulk versus 36Clmetal/26Albulk) and the multivariate statistical techniques of logistic regression and linear discriminant analysis to compare radionuclide levels and their utility to differentiate specific suites from other H chondrites. From our radionuclide results and from noble gas data from other workers, we identified 35 falls with simple irradiation histories and cosmic ray exposure ages >4 Ma. Eight others exhibit evidence for shorter (<=4 Ma) exposure, three of which had complex exposure histories (two having been reported by others previously); three others may have had such a history. In any event, the small proportion of H chondrite falls with complex exposure histories supports recent suggestions that they are not commonly encountered, as earlier workers suggested. Although cosmogenic radionuclides do not differentiate between Cluster 1 and a random set of H chondrites, H chondrites that lost 3He from solar heating are distinguishable from those with normal 3He levels.

  8. Long-term cosmogenic 10Be catchment-wide erosion rates in the Kruger National Park

    NASA Astrophysics Data System (ADS)

    Glotzbach, Christoph; Paape, Alexander; Reinwarth, Bastian; Baade, Jussi; Miller, Jordan; Rowntree, Kate

    2015-04-01

    In this study we estimated long-term catchment-wide erosion rates in the central and southern Kruger National Park with cosmogenic 10Be analyses. Samples were collected in small catchments (2-100 km2) upstream of dams, which were used to determine short-term sediment yield rates. 10Be-derived erosion rates vary from 4-15 mm/kyr. Although there are significant site-specific differences in geomorphic parameters and precipitation we could not identify a single parameter controlling long-term erosion. Geomorphic fieldwork reveals that an unknown fraction of sampled sand-sized channel sediments derived from partly extensive and up to a few-meters deep gully erosion, which may lead to an overestimation of 10Be-derived erosion rates. Cosmogenic nuclide production is rapidly decreasing with depth and consequently the measured 10Be concentration of stream sediments is a mixture of (i) sand with high 10Be concentration from colluvial creep or sheet flow from hillslopes and (ii) sand with low 10Be concentration from gully erosion. To correct erosion rates, we quantify sediments derived from gullies using a combination of mapping gullies using remote sensing data and field work and geochemical characterisation of intact hillslopes and gully side walls.

  9. Flint mining in prehistory recorded by in situ-produced cosmogenic 10Be.

    PubMed

    Verri, G; Barkai, R; Bordeanu, C; Gopher, A; Hass, M; Kaufman, A; Kubik, P; Montanari, E; Paul, M; Ronen, A; Weiner, S; Boaretto, E

    2004-05-25

    The development of mining to acquire the best raw materials for producing stone tools represents a breakthrough in human technological and intellectual development. We present a new approach to studying the history of flint mining, using in situ-produced cosmogenic 10Be concentrations. We show that the raw material used to manufacture flint artifacts approximately 300,000 years old from Qesem Cave (Israel) was most likely surface-collected or obtained from shallow quarries, whereas artifacts of the same period from Tabun Cave (Israel) were made of flint originating from layers 2 or more meters deep, possibly mined or quarried by humans.

  10. Determination of cosmogenic production rates of 10Be, 3He and 3H in water

    NASA Astrophysics Data System (ADS)

    Brown, Erik T.; Trull, Thomas W.; Jean-Baptiste, Philippe; Raisbeck, Grant; Bourlès, Didier; Yiou, Françoise; Marty, Bernard

    2000-10-01

    To improve our understanding of present-day cosmogenic production systematics of 10Be, 3H and 3He, we exposed three sets of targets of purified water at altitudes of 620, 3810 and 4745 m in the Mont Blanc Massif of the French Alps. In addition, tanks were stored 1780 m underground to quantify 3He contributions from decay of "inherited" tritium initially present in the water. After analyses of 3He and 10Be, both the summit and tunnel 3H- 3He tanks were re-degassed and stored underground for an additional year. The stored summit tanks were then analyzed to determine cosmogenic 3H levels by the 3He ingrowth method, and the tunnel tanks used to re-determine inherited tritium. Production rates (in atoms per g H 2O per year) for direct production of 3He and 10Be were 1824±52 and 112±9; 1013±16 and 70±5; and 134±58 and 5.9±0.7 at the three elevations, respectively. We determined production ratios of 0.32±0.08 for 3H: 3He and 20.2±1.5 for ( 3H+ 3He): 10Be. Our 10Be production rates, when normalized for inter-laboratory calibration and for differences in geomagnetic latitude of exposure, are somewhat lower than results of a similar experiment undertaken by Nishiizumi et al. (1996). Our 3H: 3He ratio is consistent with theoretical and meteorite estimates (Kruger and D. Heymann, 1968), but considerably lower than values assumed in many exposure age studies of igneous rocks (e.g., (Kurz, 1986; Trull et al., 1995)).

  11. Cosmogenic 10Be Age Constraints on the Holocene Deglaciation of the Scandinavian Ice Sheet

    NASA Astrophysics Data System (ADS)

    Cuzzone, J. K.; Clark, P. U.; Wohlfarth, B.; Lunkka, J.

    2011-12-01

    An important question in climate science is how ice sheets will respond to a climate warmer than present. Because our understanding of how these changes will occur remains limited, reconstructing the deglaciation of former ice sheets allows for a better understanding of how past ice sheets responded to a climate warmer than present along with understanding their contribution to sea-level rise. We will present new cosmogenic 10Be ages from erratic boulders along three transects spanning southern to northern Sweden and Finland that improve our understanding of the deglaciation of the Scandinavian Ice Sheet (SIS) beginning ~ 11.7ka through its final demise during the early Holocene. By constraining the Holocene deglaciation of the SIS and its associated retreat rates, we will establish the SIS contribution to Holocene sea level rise, improving our understanding of ice-sheet response to warming climates.

  12. 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.

  13. 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.

  14. Cosmogenic 10Be, 21Ne and 36Cl in sanidine and quartz from Chilean ignimbrites

    NASA Astrophysics Data System (ADS)

    Ivy-Ochs, S.; Kober, F.; Alfimov, V.; Kubik, P. W.; Synal, H.-A.

    2007-06-01

    Our initial results indicate that three cosmogenic nuclides: 10Be, 21Ne and 36Cl can be analyzed in sanidine. To uncover complex exposure histories or marked changes in denudation rates over time several nuclides with different half-lives (or stable) must be measured. Because of its shorter half-life, the combination of 36Cl and a long-lived nuclide 10Be or stable nuclide 21Ne will provide more information than the pairs 10Be and 26Al or 10Be and 21Ne (in quartz). Sanidine (alkali feldspar) is a common high temperature mineral and often dominates the phenocryst assemblage in silicic to intermediate volcanic rocks. Bedrock surfaces studied come from the Oxaya (erupted 19-23 Ma) and Lauca (erupted 2.7 Ma) ignimbrites of northern Chile. Quartz and sanidine phenocrysts coexist; therefore, we can check the viability of sanidine through direct comparison with nuclide concentrations in quartz. In addition, as quartz has no target for 36Cl in significant abundance we show that the unique power of sanidine is that 36Cl can be measured. We have obtained very good agreement between 10Be and 21Ne concentrations measured in sanidine and coexisting quartz. No meteoric 10Be was apparent in these sanidines. Concentrations of all three nuclides in mineral separates from rock sample CN309 from the Lauca ignimbrite in the Western Cordillera agree well and correspond to minimum exposure ages of 30-50 ka. 10Be and 21Ne measured in both sanidine and quartz from three rock samples from the Oxaya ignimbrite (CN19, CN23, CN104a) in the Western Escarpment record low average landscape modification rates (<0.70 m/Ma) over the last several million years. In contrast, 36Cl data from sanidine in CN23 seem to indicate shorter minimum exposures and more rapid maximum erosion rates.

  15. 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.

  16. 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.

  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. Cosmogenic 10Be and Paleoaccumulation Rates at WAIS Divide from 12-19 kyr BP

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Concentrations of cosmogenic 10Be in polar ice samples are affected by variations in solar activity, geomagnetic field strength, atmospheric mixing and annual snow accumulation rates. We are presently engaged in a study to obtain a continuous 10Be record in a deep ice core (WDC06A) that was drilled at the West Antarctic Ice Sheet (WAIS) Divide, a site with an average snow accumulation rate of ~20 cm weq/yr, similar to the GISP2 site in Greenland. We previously reported 10Be in annual layers in the top 114 m of WDC06A (Woodruff et al. 2011) and 10Be and 36Cl at decadal resolution in the top 560 m (Welten et al. 2009), and are now measuring 10Be in samples from a depth of 1800-2500 m, corresponding to preliminary ages of 10-20 kyr BP. We separated 10Be from ice samples of 300-600 g, following procedures described previously (Finkel and Nishiizumi 1997) and measured 10Be concentrations by accelerator mass spectrometry at PRIME lab. So far, we measured 10Be in 50 ice samples with ages between 12.3-13.9 kyr BP, at a resolution of ~30 yr/sample, and 50 samples from 15.6-19.0 kyr BP at an average resolution of ~70 yr/sample. The 10Be depth profile shows a relative constant value of (28 ± 3) x 10^3 atoms/g for samples younger than 18 kyr BP and a value of (41 ± 3) x 10^3 atoms/g for ice from 18.2-19.0 kyr BP. These values are 50-120% higher than the average concentration of 18.4 x 10^3 atoms/g for WAIS Divide ice samples from the last 420 year of snow accumulation. Although the higher 10Be concentrations in ice from the last glacial stage can be partly attributed to a 10-20% lower geomagnetic field strength (and thus a higher global 10Be production rate), they are mainly due to lower snow accumulation rates during the last glacial stage. After applying corrections for changes in geomagnetic field strength based on the SINT-800 record, we derive average snow accumulation rates of 13-15 cm weq/yr for the age interval of 12-18 kyr BP and of ~10 cm weq/yr for 18.2-19.0 kyr

  19. Cosmogenic in situ production of radionuclides: Exposure ages and erosion rates

    NASA Astrophysics Data System (ADS)

    Heisinger, B.; Nolte, E.

    2000-10-01

    Experimental data for the cosmogenic in situ production of radionuclides and its depth dependence are used for two applications, the determination of exposure ages and of erosion rates. Concentrations of the long-lived radionuclides 10Be, 14C and 26Al in quartz are presented as function of exposure age, depth before exposure and erosion rate after exposure. It is shown that the cosmogenic production before exposure can introduce important corrections to the representation without consideration of pre-exposure production. Depth profiles of 10Be, 14C and 26Al in quartz and sulfur, of 36Cl in K 2O, CaCO 3, granite and concrete and of 53Mn in Fe 2O 3 are given as function of erosion rate. Consequences to determinations of neutron fluences in Hiroshima are discussed.

  20. Cosmogenic radionuclides and noble gases in the Wethersfield (1982) chondrite

    NASA Technical Reports Server (NTRS)

    Evans, J. C.; Reeves, J. H.; Bogard, D. D.

    1986-01-01

    The Wethersfield (1982) chondrite was assayed for a suite of cosmogenic radionuclides shortly after fall. Data are reported for Be-7, Na-22, All-26, Sc-46, V-48, Cr-51, Mn-54, Co-56, Co-57, and Co-60. A comparison is made with predicted results based on a scaling to the Deep River Neutron Monitor. Noble gases were also assayed in a subsample. The cosmic-ray-exposure age is estimated to be 45 Myr.

  1. Cosmogenic radionuclides on LDEF: An unexpected Be-10 result

    NASA Technical Reports Server (NTRS)

    Gregory, J. C.; Albrecht, A.; Herzog, G.; Klein, J.; Middleton, R.; Dezfouly-Arjomandy, B.; Harmon, B. A.

    1993-01-01

    Following the discovery of the atmospheric derived cosmogenic radionuclide Be-7 on the Long Duration Exposure Facility (LDEF), a search began for other known nuclides produced by similar mechanisms. None of the others have the narrow gamma-ray line emission of Be-7 decay which enabled its rapid detection and quantification. A search for Be-10 atoms on LDEF clamp plates using accelerator mass spectrometry is described. An unexpected result was obtained.

  2. 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.

  3. 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

  4. The Revised Sunspot Record in Comparison to Cosmogenic Radionuclide-Based Solar Activity Reconstructions

    NASA Astrophysics Data System (ADS)

    Muscheler, Raimund; Adolphi, Florian; Herbst, Konstantin; Nilsson, Andreas

    2016-09-01

    Recent revisions in the sunspot records illustrate the challenges related to obtaining a 400-year-long observational record of past solar-activity changes. Cosmogenic radionuclides offer the possibility of obtaining an alternative and completely independent record of solar variability. Here, we illustrate that these records offer great potential for quantitative solar-activity reconstructions far back into the past, and we provide updated radionuclide-based solar-activity reconstructions for the past 2000 years. However, cosmogenic-radionuclide records are also influenced by processes independent of solar activity, leading to the need for critical assessment and correction for the non-solar influences. Independent of these uncertainties, we show a very good agreement between the revised sunspot records and the 10Be records from Antarctica and, in particular, the 14C-based solar-activity reconstructions. This comparison offers the potential of identifying remaining non-solar processes in the radionuclide-based solar-activity reconstructions, but it also helps identifying remaining biases in the recently revised sunspot records.

  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. 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 it

  7. 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.

  8. 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

  9. Depth-dependent Concentrations of Cosmogenic 10Be, 26Al, 36Cl, HEc, NEc, and ARc in the Old Woman Iron Meteorite

    NASA Astrophysics Data System (ADS)

    Lavielle, B.; Nishiizumi, K.; Marti, K.; Jeannot, J.-P.; Caffee, M. W.; Finkel, R. C.

    1995-09-01

    We report measurements of 1OBe7 26AI, 36CI, and of light noble gases in 6 samples of the type IIB Old Woman iron meteorite. The aim of this work is to study the depth dependence of the production rates of cosmogenic nuclides in iron meteorites. Old Woman is a large single mass of 2753 kg. Five samples have been taken from a slice of about 100 cm x 50 cm. One other sample was located roughly 40 cm above the center of the slice in a perpendicular direction. The distances between any two samples vary from 36.5 cm to 57.5 cm. Studies of cosmogenic nuclides in samples of known locations are very useful for the validation of models describing the production of cosmogenic nuclides in meteorites. Cosmogenic radionuclides were measured by accelerator mass spectrometry at Lawrence Livermore National Laboratory. Partial results have been reported earlier [1]. Concentrations of 4He, 21Ne and 38Ar in aliquots of the samples were determined by conventional mass spectrometry using an isotopic dilution method. The ratio 3He/4He appears to be almost constant with a value of 0.12 - ().13. This is about half the value generally observed in iron meteorites. Similar low ratios have been previously observed in some irons and in chondritic metal and reflect diffusion losses of 3H 12,31. The ratios 4He/38Ar, 4He/21Ne and 36Ar/38Ar are similar to those observed in iron meteorites indicating no significant losses of 4He. The measured ratio S = 4He/21Ne which represents one of the best indicators of shielding depth in iron meteorites, varies from 310 to 375 in samples from the slice. By using this as a shielding parameter, profiles were obtained for the different nuclides investigated in this work. Systematic decreases from the surface to the center of the meteorite are observed and the center of the meteoroid can be determined. As expected from nuclear systematics, the ratio 36Cl/36Ar is almost constant. The ratio 36Cl/10Be is relatively constant with a mean value of 4.7 indicating that the

  10. Noble gases and cosmogenic radionuclides in the Eltanin Pacific meteorite

    SciTech Connect

    Bogard, D D; Garrison, D H; Caffee, M W; Kyte, F; Nishiizumi, K

    2000-01-14

    A 1.5 cm long, 1.2 g specimen of the Eltanin meteorite was found at 10.97 m depth in Polarstern piston core PS2704-1. The early studies indicated that the small fragments of the Eltanin meteorite was debris from a km-sized asteroid which impacted into the deep-ocean basin. In this study, the authors measured {sup 39}Ar-{sup 40}Ar age, noble gases, and cosmogenic radionuclides in splits of specimen as a part of consortium studies of Eltanin meteorite. They concluded that the specimen was about 3 m deep from the asteroid surface. The exposure age of the Eltanin asteroid was about 20 Myr.

  11. 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

  12. Surface exposure dating of the Great Aletsch Glacier Egesen moraine system, western Swiss Alps, using the cosmogenic nuclide 10Be

    NASA Astrophysics Data System (ADS)

    Kelly, Meredith A.; Kubik, Peter W.; von Blanckenburg, Friedhelm; Schlüchter, Christian

    2004-07-01

    Egesen moraines throughout the Alps mark a glacial advance that has been correlated with the Younger Dryas cold period. Using the surface exposure dating method, in particular the measurement of the cosmogenic nuclide 10Be in rock surfaces, we attained four ages for boulders on a prominent Egesen moraine of Great Aletsch Glacier, in the western Swiss Alps. The 10Be dates range from 10 460+/-1100 to 9040+/-1020 yr ago. Three 10Be dates between 9630+/-810 and 9040+/-1020 yr ago are based upon samples from the surfaces of granite boulders. Two 10Be dates, 10 460+/-1100 and 9910+/-970 yr ago, are based upon a sample from a quartz vein at the surface of a schist boulder. In consideration of the numerous factors that can influence apparently young 10Be dates and the scatter within the data, we interpret the weighted mean of four boulder ages, 9640+/-430 yr (including the weighted mean of two 10Be dates of the quartz vein), as a minimum age of deposition of the moraine.All 10Be dates from the Great Aletsch Glacier Egesen moraine are consistent with radiocarbon dates of nearby bog-bottom organic sediments, which provide minimum ages of deglaciation from the moraine. The 10Be dates from boulders on the Great Aletsch Glacier Egesen moraine also are similar to 10Be dates from Egesen moraines of Vadret Lagrev Glacier on Julier Pass, in the eastern Swiss Alps. Both the morphology of the Great Aletsch Glacier Egesen moraine and the comparison with 10Be dates from the inner Vadret Lagrev Egesen moraine support the hypothesis that the climatic cooling that occurred during the Younger Dryas cold episode influenced the glacial advance that deposited the Great Aletsch Glacier Egesen moraine. Because of the large size and slow response time of Great Aletsch Glacier, we suggest that the Great Aletsch Glacier Egesen moraine was formed during the last glacial advance of the multiphased Egesen cold period, the Kromer stage, during the Preboreal chron. Copyright

  13. 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.

  14. 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

  15. Paleoseismology of the Mejillones Fault, northern Chile: Insights from cosmogenic 10Be and optically stimulated luminescence determinations

    NASA Astrophysics Data System (ADS)

    CortéS A., J.; GonzáLez L., Gabriel; Binnie, S. A.; Robinson, R.; Freeman, S. P. H. T.; Vargas E., G.

    2012-04-01

    We have undertaken the first paleoseismological study on an upper plate fault in Chile. The selected structure was the Mejillones Fault, which is marked by a conspicuous fault-scarp. Using cosmogenic 10Be and OSL dating and detailed sedimentary logging of trenches, we have constrained the abandonment of two alluvial surfaces by fault activity at ca. 35 ka and ca.14 ka. Based on stratigraphic observation we characterized the fault evolution in four intervals over the last ca. 35 ka. During the first three intervals the fault had a steady slip rate of 0.61 ± 0.26 m/ka. The fourth interval is delineated by the last vertical fault slip and the accumulation of un-deformed hillslope deposits after ca. 3.3 ka and has a slip rate of 0.22 ± 0.06 m/ka. The younger surface abandonment was caused by two Mw ˜ 7 paleoearthquakes with a recurrence interval of 5.0 ± 3.5 ka. The third interval is characterized by the interaction of hillslope deposits and aseismic slip and/or centimeter scale seismic slip events. At ca. 3.5 ka, a last large (Mw ˜ 6.6) earthquake took place. The recurrence intervals of large (Mw > 8.5) subduction earthquakes do not appear to be the same as the recurrence intervals of the Mw ˜ 7 events on the upper plate Mejillones Fault.

  16. 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

  17. Grain-size dependent concentration of cosmogenic 10Be and erosion dynamics in a landslide-dominated Himalayan watershed

    NASA Astrophysics Data System (ADS)

    Puchol, Nicolas; Lavé, Jérôme; Lupker, Maarten; Blard, Pierre-Henri; Gallo, Florian; France-Lanord, Christian

    2014-11-01

    For documenting recent or Late Quaternary erosion rates at the scale of a small watershed, or even an entire mountain range, the use of in-situ terrestrial cosmogenic nuclides (TCN), such as 10Be, in river sediments has become widespread over the last decade. In mountainous settings, however, landslides may induce a two-fold complication in the cosmogenic nuclide budget. First, they may episodically deliver large amounts of sediment with low TCN concentrations to the river channel. Second, they may generate a grain-size-concentration dependence in these sediments. However, studies that have explored grain-size dependence in landslide-dominated areas have reached differing conclusions and the underlying mechanisms remain poorly understood. The present study focuses on the Khudi Khola river basin, a small drainage basin in the central Himalayas. The area is characterized by steep slopes, heavy rainfall, and high sediment production rates. Importantly, the watershed contains a large area of active landsliding. In-situ 10Be was analyzed in sediments of grain sizes ranging from 75 μm to ~ 4 cm, collected from five locations: upstream, downstream, and in the small tributaries which drain the landslides. In all sampling locations, including those situated upstream of the landslides, the finest grains (75-250 μm) are two to four times more concentrated in 10Be than the largest clasts (> 4.7 mm). We developed a numerical slope model which includes a low level of background soil erosion and episodic denudation from large mass-wasting events. We then introduced a coarsening of average grain-size with soil-depth to the model. Our simulation shows that the data available for this valley are compatible with a scenario in which landslides deliver coarse grains to the channel that are less concentrated in TCN and have deeper provenance. Best-fit estimates of the model parameters suggest recurrence times of 3000 to 9000 years for a major landslide on the same slope, and mean long

  18. The deep accumulation of 10Be at Utsira, southwestern Norway: Implications for cosmogenic nuclide exposure dating in peripheral ice sheet landscapes

    NASA Astrophysics Data System (ADS)

    Briner, Jason P.; Goehring, Brent M.; Mangerud, Jan; Svendsen, John Inge

    2016-09-01

    Cosmogenic nuclide exposure dating is a widely used method for constraining past ice sheet histories. We scrutinize a recently published data set of cosmogenic 10Be data from erratic boulders in Norway used to constrain the deglaciation of the western Scandinavian Ice Sheet to 20 ka. Our model of the 10Be inventory in glacial surfaces leads us to conclude that the chronology may be afflicted by the deep subsurface accumulation of 10Be during long-lasting ice-free periods that resulted in 10Be ages >10% too old. We suggest that the majority of the dated erratic boulders contain a uniform level of inherited muon-produced 10Be and were derived from bedrock depths >2.5 m and most likely ~4 m. The implication of our finding is that for landscapes that experience long ice-free periods between brief maximum glacial phases, glacial erosion of >5 m is required to remove detectable traces of inherited 10Be.

  19. Early Holocene and Late Pleistocene slip rates of the southern Dead Sea Fault determined from 10Be cosmogenic dating of offset alluvial deposits

    NASA Astrophysics Data System (ADS)

    Le BéOn, Maryline; Klinger, Yann; Al-Qaryouti, Mahmoud; MéRiaux, Anne-Sophie; Finkel, Robert C.; Elias, Ata; Mayyas, Omar; Ryerson, Frederick J.; Tapponnier, Paul

    2010-11-01

    Two sites located along the Wadi Araba Fault (WAF) segment of the Dead Sea Fault are targeted for tectonic-morphological analysis. 10Be cosmogenic radionuclide (CRN) dating of embedded cobbles is used to constrain the age of offset alluvial surfaces. At the first site a 48 ± 7 m offset alluvial fan, for which 10Be CRN model ages average 11.1 ± 4.3 ka, yield a slip rate of 5.4 ± 2.7 mm/a, with conservative bounds of 1.3-16.4 mm/a. At the second site the scattered distributions of the 10Be CRN ages from an offset bajada attest to the complex processes involved in sediment transport and emplacement. There, two offsets were identified. The 160 ± 8 m offset of an incised alluvial fan dated at 37 ± 5 ka shows a slip rate of 4.5 ± 0.9 mm/a, with a conservative minimum value of 3.2 mm/a. A larger offset, 626 ± 37 m, is derived from a prominent channel incised into the bajada. Cobbles from the bajada surface have ages from 33 to 141 ka, with a mean of 87 ± 26 ka. A slip rate of 8.1 ± 2.9 mm/a is derived from the mean age, with conservative bounds of 3.8-22.1 mm/a. These results and other published slip rates along the linear WAF segment, from GPS to geological time scales, lack the resolution to fully resolve the question of temporal variations versus consistency of the fault slip rate of the WAF. Yet, given the uncertainties, they are not inconsistent with each other.

  20. 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

  1. Reconciling radiocarbon and ice core timescales over the Holocene - Cosmogenic radionuclides as synchronization tools

    NASA Astrophysics Data System (ADS)

    Muscheler, R.; Adolphi, F.; Mekhaldi, F.

    2015-12-01

    The atmospheric production rates of cosmogenic radionuclides, such as 14C and 10Be, vary globally due to external processes, namely the solar and geomagnetic modulation of the galactic cosmic ray flux as well as solar proton events. This signature is recorded in various archives such as ice cores (10Be) and tree-rings (14C). Hence, cosmogenic radionuclides offer a means to continuously assess timescale differences between two of the most widely used timescales in paleoclimatology - the radiocarbon and the ice core timescales. Short lived solar proton events additionally provide distinct marker horizons that allow synchronization of discrete horizons at annual precision. We will present a cosmogenic radionuclide based synchronization of the Greenland ice core timescale (GICC05, Svensson et al., 2008) and the radiocarbon timescale (IntCal13, Reimer et al., 2013) over the Holocene. This synchronization allows radiocarbon dated and ice core paleoclimate records to be compared on a common timescale at down to sub-decadal precision. We will compare these results to independent discrete isochrones obtained from tephrochronology and solar proton events. In addition, we will discuss implications for the accuracy and uncertainty estimates of GICC05 over the Holocene. Reimer, P. J., Bard, E., Bayliss, A., Beck, J. W., Blackwell, P. G., Bronk Ramsey, C., Buck, C. E., Cheng, H., Edwards, R. L., Friedrich, M., Grootes, P. M., Guilderson, T. P., Haflidason, H., Hajdas, I., Hatté, C., Heaton, T. J., Hoffmann, D. L., Hogg, A. G., Hughen, K. A., Kaiser, K. F., Kromer, B., Manning, S. W., Niu, M., Reimer, R. W., Richards, D. A., Scott, E. M., Southon, J. R., Staff, R. A., Turney, C. S. M., and van der Plicht, J.: IntCal13 and Marine13 Radiocarbon Age Calibration Curves 0-50,000 Years cal BP, Radiocarbon, 55, 1869-1887, 10.2458/azu_js_rc.55.16947, 2013. Svensson, A., Andersen, K. K., Bigler, M., Clausen, H. B., Dahl-Jensen, D., Davies, S. M., Johnsen, S. J., Muscheler, R., Parrenin

  2. 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.

  3. 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

  4. The interactions of atmospheric cosmogenic radionuclides with spacecraft surfaces

    NASA Technical Reports Server (NTRS)

    Gregory, J. C.; Fishman, G. J.; Harmon, B. A.; Parnell, T. A.

    1992-01-01

    The discovery of the cosmogenic radionuclide Be-7 on the front surface of the Long Duration Exposure Facility (LDEF) spacecraft has opened opportunities to investigate new phenomena in several disciplines of space science. The experiments performed for this work show that the Be-7 results only if the source of the isotope is the atmosphere through which the spacecraft passed. We should expect that the uptake of beryllium in such circumstances will depend on the chemical form of the Be and the chemical nature of the substrate. It was found that the observed concentration of Be-7 does, in fact, differ between metal surfaces and organic surfaces such as PTFE (teflon). It is noted, however, that: (1) organic surfaces, even PTFE, are etched by the atomic oxygen found under these orbital conditions, and (2) the relative velocity of the species is 8 km(exp -1)s relative to the surface and the interaction chemistry and physics may differ from the norm. The Be-7 is formed by spallation of O and N nuclei under cosmic ray proton bombardment. The principal source region is at altitudes of 12-15 km. While very small quantities are produced above 300 km, the amount measured on the LDEF was 3 to 4 orders of magnitude higher than expected from production at orbital altitude. The most reasonable explanation is that Be-7 is rapidly transported from low altitudes by some unknown mechanism. The process must take place on a time scale similar to the half-life of the isotope (53 days). Many other isotopes are produced by cosmic ray reactions, and some of these are suited to measurement by the extremely sensitive methods of accelerator mass spectrometry. A program was initiated to search for these isotopes and it is hoped that such studies will provide new methods for studying mixing in the upper atmosphere.

  5. The interactions of atmospheric cosmogenic radionuclides with spacecraft surfaces

    NASA Technical Reports Server (NTRS)

    Gregory, John C.; Fishman, G. J.; Harmon, B. A.; Parnell, T. A.

    1991-01-01

    The discovery of the cosmogenic radionuclide Be-7 on the front surface (and the front surface only) of the Long Duration Exposure Facility (LDEF) spacecraft has opened opportunities to investigate new phenomena in several disciplines of space science. The experiments performed for this work show that the Be-7 results only if the source of the isotope is the atmosphere through which the spacecraft passed. We should expect that the uptake of beryllium in such circumstances will depend on the chemical form of the Be and the chemical nature of the substrate. It was found that the observed concentration of Be-7 does, in fact, differ between metal surfaces and organic surfaces such as PTFE (teflon). It is noted, however, that: (1) organic surfaces, even PTFE, are etched by the atomic oxygen found under these orbital conditions, and (2) the relative velocity of the species is 8 km(exp -1)s relative to the surface and the interaction chemistry and physics may differ from the norm. The Be-7 is formed by spallation of O and N nuclei under cosmic ray proton bombardment. The principal source region is at altitudes of 12-15 km. While very small quantities are produced above 300 km, the amount measured on the LDEF was 3 to 4 orders of magnitude higher than expected from production at orbital attitude. The most reasonable explanation is that Be-7 is rapidly transported from low altitudes by some unknown mechanism. The process must take place on a time scale similar to the half-life of the isotope (53 days). Many other isotopes are produced by cosmic ray reactions, and some of these are suited to measurement by the extremely sensitive methods of accelerator mass spectrometry. A program was initiated to search for these isotopes and it is hoped that such studies will provide new methods for studying mixing in the upper atmosphere.

  6. Cosmogenic-radionuclide Profile of the Mocs Meteorite Strewnfield

    NASA Astrophysics Data System (ADS)

    Ferko, T. E.; Lipschutz, M. E.

    1996-03-01

    Cosmic-ray produced nuclides were measured in samples from eight pieces of the L5-6 chondrite Mocs from known locations in the strewnfield. We measured 10Be and 26Al in the bulk phase along with 36Cl in both the metal and silicate phases. Relationships of the activities of these radionuclides from various meteorite pieces in the Mocs strewnfield provide new insight into the association of meteorite fragments to each other in the pre-atmospheric parent body. Results suggest a >2pi irradiation for the Mocs meteoroid which was less than 1 meter in radius.

  7. 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

  8. 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

  9. Cosmogenic Radionuclides in the Campo Del Cielo Iron Meteorite

    NASA Technical Reports Server (NTRS)

    Liberman, R. G.; FernandezNiello, J. O.; Reedy, R. C.; Fifield, L. K.; diTada, M. L.

    2001-01-01

    Cosmogenic Be-10, Al-26, Cl-36, Ca-41, and Ni-59 were measured in the Campo del Cielo iron meteorite. Our results led us to conclude that the pre-atmospheric radius might have been approximately 2 m. Comparisons with other big bodies are also presented. Additional information is contained in the original extended abstract.

  10. Cosmogenic Radionuclide Contents of Antarctic Meteorites from Allan Hills Having High Natural Thermoluminescence

    NASA Astrophysics Data System (ADS)

    Mokos, J.; Vogt, S.; Lipschutz, M. E.

    1996-03-01

    Cosmic ray bombardment produces stable and radioactive nuclides, as well as thermoluminescence (TL). Concentrations of long-lived radionuclides have been measured in fifteen Antarctic H-chondrites with high TL levels. Sears et al. studied these fifteen meteorites and postulated an unusual history. They noted that two have a young terrestrial age. We decided to examine their irradiation histories by measuring long-lived cosmogenic radionuclides in the fifteen H4-6 chondrites by accelerator mass spectrometry (AMS). The radionuclide concentration, TL data, and petrographic type, supports the idea that these meteorites originated from a single source with a unique orbital history.

  11. Cosmogenic radionuclide production in NaI(Tl) crystals

    NASA Astrophysics Data System (ADS)

    Amaré, J.; Cebrián, S.; Cuesta, C.; García, E.; Ginestra, C.; Martínez, M.; Oliván, M. A.; Ortigoza, Y.; Ortiz de Solórzano, A.; Pobes, C.; Puimedón, J.; Sarsa, M. L.; Villar, J. A.; Villar, P.

    2015-02-01

    The production of long-lived radioactive isotopes in materials due to the exposure to cosmic rays on Earth surface can be an hazard for experiments demanding ultra-low background conditions, typically performed deep underground. Production rates of cosmogenic isotopes in all the materials present in the experimental set-up, as well as the corresponding cosmic rays exposure history, must be both well known in order to assess the relevance of this effect in the achievable sensitivity of a given experiment. Although NaI(Tl) scintillators are being used in experiments aiming at the direct detection of dark matter since the first nineties of the last century, very few data about cosmogenic isotopes production rates have been published up to date. In this work we present data from two 12.5 kg NaI(Tl) detectors, developed in the frame of the ANAIS project, which were installed inside a convenient shielding at the Canfranc Underground Laboratory just after finishing surface exposure to cosmic rays. The very fast start of data taking allowed to identify and quantify isotopes with half-lives of the order of tens of days. Initial activities underground have been measured and then production rates at sea level have been estimated following the history of detectors; values of about a few tens of nuclei per kg and day for Te isotopes and 22Na and of a few hundreds for I isotopes have been found. These are the first direct estimates of production rates of cosmogenic nuclides in NaI crystals. A comparison of the so deduced rates with calculations using typical cosmic neutron flux at sea level and a carefully selected description of excitation functions will be also presented together with an estimate of the corresponding contribution to the background at low and high energies, which can be relevant for experiments aiming at rare events searches.

  12. The Constancy of the Galactic Cosmic Rays: The Contribution of Cosmogenic Noble Gases and Radionuclides in Iron Meteorites

    NASA Astrophysics Data System (ADS)

    Smith, T.; Leya, I.; Merchel, S.; Rugel, G.; Pavetich, S.; Scharf, A.

    2016-08-01

    We measured cosmogenic noble gas and radionuclide concentrations in iron meteorites and calculated their cosmic ray exposure (CRE) ages. We set up CRE age histograms and searched for periodic peaks to study galactic cosmic ray flux variations.

  13. 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.

  14. 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

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Interplanetary magnetic field during the past 9300 years inferred from cosmogenic radionuclides

    NASA Astrophysics Data System (ADS)

    Steinhilber, F.; Abreu, J. A.; Beer, J.; McCracken, K. G.

    2010-01-01

    We have reconstructed the interplanetary magnetic field (IMF), its radial component, and the open solar magnetic flux using the solar modulation potential derived from cosmogenic 10Be radionuclide data for a period covering the past 9300 years. Reconstructions using the assumption of both constant and variable solar wind speeds yielded closely similar results. During the Maunder Minimum, the strength of the IMF was approximately 2 nT compared to a mean value of 6.6 nT for the past 40 years, corresponding to an increase of the open solar magnetic flux of about 350%. We examine four cycles of the Hallstatt periodicity in the IMF with a mean period of ˜2250 years and an amplitude of ˜0.75 nT. Grand solar minima have largely occurred in clusters during the Hallstatt cycle minima around the years -5300, -3400, -1100, and +1500 A.D. The last cluster includes the Dalton, Maunder, and Spörer minima. We predict that the next such cluster will occur in about 1500 years. The long-term IMF has varied between ˜2 nT and ˜8 nT and does not confirm a proposed floor (lower limit). There is a slowly changing long-term trend of amplitude 1.5 nT, with a minimum around the year -4600 and a maximum around 0 A.D. that may be of solar origin but which also may be due to unknown long-term changes in the atmospheric effects or geomagnetic field intensity.

  2. 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

  3. Using 10Be cosmogenic surface exposure dating to determine the evolution of the Purgatorio active fault in the Andean forearc, southern Peru

    NASA Astrophysics Data System (ADS)

    Carlos, Benavente; Swann, Zerathe; Laurence, Audin; Fabrizio, Delgado; Marianne, Saillard; Sarah, Hall R.; Aster Team

    2015-04-01

    Active transpressive deformation has been occurring along the Andean hyperarid forearc for the last 3 Myrs but many of these faults are still not described even if able to produce large damaging earthquakes. Active faulting along the northern part of the Arica Bend can be recognized due to the presence of well-preserved and sharp fault scarps indicating recent surface slip. During the Mio-Pliocene, deposition within the forearc continental basins resulted in the formation of vast fan deposits and conglomerates of the Moquegua Formation, which can be considered as bedrock in this exposure study (~45-4 Ma; Tosdal et al., 1984; Sebrier et al., 1988a; Roperch et al., 2006). The typical vertical Purgatorio fault scarps offset both the Moquegua bedrock and several younger geomorphic features associated with <300kyrs climatic and 400 years old volcanic extreme events. This study focus on quantifying slip rate variations in time along a 5-meters high vertical fault scarp to understand how the fault is evolving. These results are achieved via surface exposure dating of the sampled seismically broken cobbolds of the Moquegua formation outcroping vertically along the fault scarp. These samples are well-suited to the application of in situ produced cosmogenic radionuclides for surface exposure dating, as the hyperarid region has extremely low erosion rates. We sampled the scarp away from any significant drainage so as to avoid possibly disturbed areas. The sampling did involve extracting quarzite conglomeratic material along the bedrock scarp and on the upper surrounding crests. The aim has been to measure Berylium-20 TCN (Terrestrial in situ Cosmogenic Nuclides) concentrations to determine exposure age as a function of height on the scarp. This has been successfully employed on one scarp in Italy based on Chlorine-36 TCN (Palumbo et al., 2004). However, slow faults behaviour remains unclear and more contributions are needed. Quaternary activity of the Purgatorio fault system

  4. 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.

  5. 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.

  6. Regolith evolution on the millennial timescale from combined U-Th-Ra isotopes and in situ cosmogenic 10Be analysis in a weathering profile (Strengbach catchment, France)

    NASA Astrophysics Data System (ADS)

    Ackerer, J.; Chabaux, F.; Van der Woerd, J.; Viville, D.; Pelt, E.; Kali, E.; Lerouge, C.; Ackerer, P.; di Chiara Roupert, R.; Négrel, P.

    2016-11-01

    U-Th-Ra disequilibria, cosmogenic in situ 10Be concentrations and major and trace element concentrations have been analyzed in a 2 m-deep weathering profile sampled at the summit of the granitic Strengbach catchment (France). The data have been used to independently estimate both the long-term regolith production and denudation rates and the weathering and erosion rates. Modeling of the 238U-234U-230Th-226Ra disequilibrium variations in the lower part of the profile yields a regolith production rate of 12 ± 4 mm/kyr (30 ± 10 T/km2/yr), while modeling of the high-resolution 10Be concentration profile leads to an exposure age of 19.7 ± 2.2 kyr, an inherited concentration of 15,000 ± 1,000 at/g in quartz and a mean denudation rate of 22 ± 10 mm/kyr (37 ± 15 T/km2/yr). The consistency between production and denudation rates suggests that, on a millennial timescale, the regolith mass balance at the summit of the catchment is close to a steady state, even if the watershed may have been impacted by Quaternary climatic changes and by recent anthropogenic perturbations (e.g., 20th century acid rain and recent afforestation efforts). The results also indicate that physical erosion is likely the dominant long-term process of regolith denudation in the catchment. Furthermore, the comparison of the long-term production and denudation rates and of weathering and erosion rates determined from the depth profile analyses with the current weathering and erosion rates estimated at the outlet of the watershed based on monitoring of the water chemistry and sediment fluxes suggests that physical erosion may have varied more than the chemical weathering flux during the last 150 kyr. Although very few other sites with U-series, in situ 10Be and stream monitoring data are available for comparison, the current data suggest that (1) the mass balance steady state of regolith might be commonly achieved in soil mantled landscapes, and (2) physical erosion has varied much more than

  7. A Complex Exposure History of the Gold Basin L4-Chondrite Shower from Cosmogenic Radionuclides and Noble Gases

    NASA Technical Reports Server (NTRS)

    Welten, K. C.; Nishiizumi, K.; Caffee, M. W.; Masarik, J.; Wieler, R.

    2001-01-01

    Cosmogenic radionuclides and noble gases in samples of the Gold Basin L-chondrite shower indicate a complex exposure history, with a first stage exposure on the parent body, followed by a second stage of approx. 19 Myr in a meteoroid 3-4 m in radius. Additional information is contained in the original extended abstract.

  8. Signatures of cosmic-ray increase attributed to exceptional solar storms inferred from multiple cosmogenic radionuclide records

    NASA Astrophysics Data System (ADS)

    Mekhaldi, Florian; Muscheler, Raimund; Adolphi, Florian; Svensson, Anders; Aldahan, Ala; Possnert, Göran; McConnell, Joseph R.; Sigl, Michael; Welten, Kees C.; Woodruff, Thomas E.

    2014-05-01

    Miyake et al. (2012, 2013) discovered rapid increases of 14C content in tree rings dated to AD 774-5 and AD 993-4 which they have attributed to cosmic-ray events. These extreme particle events have no counterparts in the instrumental record and have been tentatively associated with solar proton events, supernovae and short gamma-ray bursts, which have very different energy spectra. Cosmogenic radionuclides such as 14C, 10Be and 36Cl arise from the interaction of cosmic rays with atmospheric nitrogen, oxygen and argon. These radio-isotopes are produced through different reaction pathways and vary with different energy dependencies of the production rate cross section. Owing to this, yield functions can be used to determine the energy level of incident particles. However, only 14C has been measured at high resolution to quantify the energy and thus the origin of the outbursts. We present an annually resolved record of 10Be from the NGRIP ice core for the two events. In addition, we also utilized the GRIP ice core 36Cl record in our analysis. Our results show that the differential production of cosmogenic 14C, 10Be and 36Cl is consistent with a solar energy spectrum. Considering the notable increase in radionuclides, the solar storms would have had to be substantially greater than the largest recorded geomagnetic storm, the so-called Carrington event. This challenges our understanding of the sun's dynamics. Furthermore, the events could possibly be of interest for the investigation of potential cosmic ray-cloud linkages (Svensmark & Friis-Christensen, 1997). Alternatively, such outbursts of energetic particles have the potential to deplete atmospheric ozone and alter atmospheric circulation. Ultimately, the magnitude of such particle events draws attention to the perhaps underestimated potential of the sun to cause great damage to modern technologies. References Miyake, F., Masuda, K. & Nakamura, T. Another rapid event in the carbon-14 content of tree rings. Nature

  9. 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

  10. 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.

  11. Primordial radioelements and cosmogenic radionuclides in lunar samples from apollo 15.

    PubMed

    O'kelley, G D; Eldridge, J S; Schonfeld, E; Northcutt, K J

    1972-01-28

    Two basalts, two breccias, and two soils from Apollo 15 were analyzed by nondestructive gamma-ray spectrometry. The concentrations of potassium, thorium, and uranium in the basalts were similar to those in the Apollo 12 basalts, but the potassium: uranium ratios were somewhat higher. Primordial radioelements were enriched in the soils and breccia, consistent with a two-component mixture of mare basalt and up to 20 percent foreign component (KREEP). The abundance patterns for cosmogenic radionuclides implied surface sampling for all specimens. The galactic cosmic-ray production rate of vanadium-48 was determined as 57 +/- 11 disintegrations per minute per kilogram of iron. Cobalt-56 concentrations were used to estimate the intensity of the solar flare of 25 January 1971.

  12. 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

  13. 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

  14. Cosmogenic Radionuclides in Antarctic Meteorites: Preliminary Results on Terrestrial Ages and Temporal Phenomena

    NASA Astrophysics Data System (ADS)

    Michlovich, E.; Vogt, S.; Wolf, S. F.; Elmore, D.; Lipschutz, M. E.

    1993-07-01

    Since 1969, more than 15,000 meteorites have been recovered from various sites in Antarctica. Differences have been reported between the Antarctic populations and the population of non-Antarctic meteorites in volatile trace- element content, thermoluminescence properties, physical size, and relative distribution of meteorite type [1]. Lipschutz and Samuels [2] developed a method based upon multivariate linear and logistic regression that they applied to interpret trace-element content in Antarctic and non-Antarctic meteorites, showing that the two populations can be chemically distinguished. Since Antarctic meteorites have, on the whole, much longer terrestrial ages than non-Antarctic falls, such differences have been used to support the notion that the flux of meteorites sampled by the Earth has changed in the recent past. A subsequent study [3] showed a statistically significant difference in trace-element content between meteorites from Victoria Land and those found in Queen Maud Land, two groups that seem to have different terrestrial age distributions. Changes in meteorite flux patterns on the order of 60 yr are indicated from a study of Cluster 1 vs. non-Cluster 1 falls [4]. Rapid fluctuations would almost certainly require the existence of co-orbital meteoroid streams, an idea that has been criticized by some [5] on dynamical grounds. To quantify the discussion of a temporal dependence of meteorite flux patterns, and to continue systematic study of Antarctic meteorites, we have measured the contents of the cosmogenic radionuclides ^10Be and ^26Al in the bulk phase, and ^36Cl in the metal phase, of 40 Antarctic specimens that are from the same suite of samples analyzed in the trace-element studies and that were chosen to minimize any chances of paired meteorites. The means and standard deviations of ^10Be and ^26Al activities are 16.4 +/- 3.5 and 48 +/- 8 dpm/kg respectively. Correction for cosmic ray exposure [6,7] and terrestrial ages allows us to estimate

  15. 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

  16. 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

  17. Use of radon and cosmogenic radionuclides as indicators of exchange between troposphere and stratosphere

    NASA Technical Reports Server (NTRS)

    Kritz, Mark A.

    1994-01-01

    This research grant covered participation in the operational phase of NASA's Stratosphere-Troposphere Exchange Project (STEP), a multi-agency airborne science program conducted aboard NASA U-2 and ER-2 high altitude research aircraft. The primary goals of STEP were to investigate the mechanisms of irreversible movement of mass, trace gases, and aerosols from the troposphere into the stratosphere, and to explain the observed dryness of the stratosphere. Three flight experiments were conducted to address these questions: two extratropical experiments, in 1984 and 1986, and a tropical experiment, in 1987. The cosmogenic radionuclides Be-7 and P-32, produced in the stratosphere by cosmic rays, and Rn-222 (radon), emitted from continental soils, were well-suited as tracers of intra-stratospheric air mass movements, and to follow episodes of troposphere to stratosphere exchange. Measurements of Be-7 and P-32 were made in all three STEP experiments. Measurements of radon were made in the tropical experiment only. The equipment worked well, and produced a valuable data set in support of the STEP objectives, as indicated by the 'quick-look' results outlined.

  18. Cosmogenic radionuclides and noble gases in Antarctic H chondrites with high and normal natural thermoluminescence levels

    NASA Astrophysics Data System (ADS)

    Mokos, Jennifer L.; Franke, Luitgard; Scherer, Peter; Schultz, Ludolf; Lipschutz, Michael E.

    2000-07-01

    We report noble gas data for 37 H chondrites collected from the Allan Hills by EUROMET in the 1988/1989 Field Season. Among these are 16 specimens with high levels (>100 krad) of natural thermoluminescence (NTL), originally interpreted as signaling their derivation from a single meteoroid with an orbit that became Earth-crossing -~100 ka ago. One of these 16 is an H3 with a cosmic ray exposure age of ~33 Ma and clearly represents a separate fall. The other 15 H4-6 chondrites derive from 3 separate meteoroids, each of which is represented by a 5- or 6-member group. These groups have mean exposure ages of 3.7, 4.1 and 6.6 Ma: the middle-group members all contain solar Ne. The 2 younger groups also seem to each include a few H chondrites with normal NTL levels. Measurements of cosmogenic 10Be (1.5 Ma), 26Al (710 ka) and 36Cl (301 ka) in 14 of the high NTL chondrites indicate that all reflect a simple irradiation history. In contrast, many of a different, 38-member, randomly-selected suite of Antarctic H chondrites seem to have different cosmic ray irradiation histories. The 3.7 and 6.6 Ma groups from the 37-member Allan Hills suite come, respectively, from about 5-30 cm and about 5-10 cm depths in 80-125 cm and 60-125 cm-radius meteoroids.

  19. Near-Earth heliospheric magnetic field intensity since 1750: 2. Cosmogenic radionuclide reconstructions

    NASA Astrophysics Data System (ADS)

    Owens, M. J.; Cliver, E.; McCracken, K. G.; Beer, J.; Barnard, L.; Lockwood, M.; Rouillard, A.; Passos, D.; Riley, P.; Usoskin, I.; Wang, Y.-M.

    2016-07-01

    This is Part 2 of a study of the near-Earth heliospheric magnetic field strength, B, since 1750. Part 1 produced composite estimates of B from geomagnetic and sunspot data over the period 1750-2013. Sunspot-based reconstructions can be extended back to 1610, but the paleocosmic ray (PCR) record is the only data set capable of providing a record of solar activity on millennial timescales. The process for converting 10Be concentrations measured in ice cores to B is more complex than with geomagnetic and sunspot data, and the uncertainties in B derived from cosmogenic nuclides (~20% for any individual year) are much larger. Within this level of uncertainty, we find reasonable overall agreement between PCR-based B and the geomagnetic- and sunspot number-based series. This agreement was enhanced by excising low values in PCR-based B attributed to high-energy solar proton events. Other discordant intervals, with as yet unspecified causes remain included in our analysis. Comparison of 3 year averages centered on sunspot minimum yields reasonable agreement between the three estimates, providing a means to investigate the long-term changes in the heliospheric magnetic field into the past even without a means to remove solar proton events from the records.

  20. The cosmogenic record of mountain erosion transmitted across a foreland basin: Source-to-sink analysis of in situ10Be, 26Al and 21Ne in sediment of the Po river catchment

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    We analyze the source-to-sink variations of in situ10Be, 26Al and 21Ne concentrations in modern sediment of the Po river catchment, from Alpine, Apennine, floodplain, and delta samples, in order to investigate how the cosmogenic record of orogenic erosion is transmitted across a fast-subsiding foreland basin. The in situ10Be concentrations in the analyzed samples range from ∼ 0.8 ×104 at /gQTZ to ∼ 6.5 ×104 at /gQTZ. The 10Be-derived denudation rates range from 0.1 to 1.5 mm/yr in the Alpine source areas and from 0.3 to 0.5 mm/yr in the Apenninic source areas. The highest 10Be-derived denudation rates are found in the western Central Alps (1.5 mm/yr). From these data, we constrain a sediment flux leaving the Alpine and the Apenninic source areas (>27 Mt/yr and ca. 5 Mt/yr, respectively) that is notably higher than the estimates of sediment export provided by gauging (∼10 Mt/yr at the Po delta). We observe a high variability in 10Be concentrations and 10Be-derived denudation rates in the source areas. In the Po Plain, little variability is observed, and at the same time, the area-weighed 10Be concentration of (2.29 ± 1.57) ×104 at /gQTZ (±1 SD of the dataset) from both the Alps and the Apennines is poorly modified (by tributary input) in sediment of the Po Plain ((2.68 ± 0.78 , ± 1 SD) ×104 at /gQTZ). The buffering effect of the Po floodplain largely removes scatter in 10Be signals. We test for several potential perturbations of the cosmogenic nuclide record during source to sink transfer in the Po basin. We find that sediment trapping in deep glacial lakes or behind dams does not significantly change the 10Be-mountain record. For example, similar 10Be concentrations are measured upstream and downstream of the postglacial Lake Maggiore, suggesting that denudation rates prior to lake formation were similar to today's. On the scale of the entire basin, the 10Be concentration of basins with major dams is similar to those without major dams. A potential

  1. 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.

  2. Combination of in situ cosmogenic nuclide (10Be) and Schmidt-hammer dating for the investigation of Late-Holocene lateral moraines in the Southern Alps of New Zealand

    NASA Astrophysics Data System (ADS)

    Winkler, S.

    2009-04-01

    absolute' age of the boulder surfaces was needed to allow the construction of a dating curve by reliable fixed points to, radiocarbon (14C) dating could not provide those information because of the lack of organic material indisputable be related to the glacier advance forming the moraine ridges. On base on these considerations, this study comprises the first attempt to combine in situ (terrestrial) cosmogenic nuclide (10Be) surface exposure dating with Schmidt-hammer measurements for the dating of Holocene moraines and the reconstruction of a regional glacier chronology. Cosmogenic 10Be dating has the important advantage of delivering an ‘absolute' age for the exposure of boulder or bedrock surfaces, i.e. the same surface tested with the Schmidt-hammer. One disadvantage of cosmogenic nuclide exposure dating is, however, the limited number of boulders sampled due to high costs. From this background, a combination with the Schmidt-hammer technique seems ideal as the latter could provide measurement of a large number of boulders. The Schmidt-hammer measurements can, on the other hand, help with the selection of representative boulders for cosmogenic nuclide (10Be) surface exposure dating avoiding boulders that have been exposed to post-depositional movement (e.g. rotation). Results from the application of this combined ‘multi-proxy-approach' at Strauchon Glacier in Westland/Tai Poutini National Park and Hooker Glacier in Mt Cook/Aoraki National Park on large lateral moraine complex with several individual moraine ridges proof its potential. Three pre-‘Little Ice Age' moraine sequences each related to an individual Late-Holocene Little Ice Age-type event unambiguously distinguished by Schmidt-hammer measurements provides cosmogenic (10Be) ages of 2,400/2,500 a BP, c. 1,700 a BP, and c. 1,000/1,100 a BP. The preliminary construction of a dating curve based on both Schmidt-hammer and cosmogenic (10Be) dating results shows high significance and confirms the successful

  3. 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

  4. 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

  5. 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.

  6. Combination of in situ cosmogenic nuclide (10Be) and Schmidt-hammer dating for the investigation of Late-Holocene lateral moraines in the Southern Alps of New Zealand

    NASA Astrophysics Data System (ADS)

    Winkler, S.

    2009-04-01

    absolute' age of the boulder surfaces was needed to allow the construction of a dating curve by reliable fixed points to, radiocarbon (14C) dating could not provide those information because of the lack of organic material indisputable be related to the glacier advance forming the moraine ridges. On base on these considerations, this study comprises the first attempt to combine in situ (terrestrial) cosmogenic nuclide (10Be) surface exposure dating with Schmidt-hammer measurements for the dating of Holocene moraines and the reconstruction of a regional glacier chronology. Cosmogenic 10Be dating has the important advantage of delivering an ‘absolute' age for the exposure of boulder or bedrock surfaces, i.e. the same surface tested with the Schmidt-hammer. One disadvantage of cosmogenic nuclide exposure dating is, however, the limited number of boulders sampled due to high costs. From this background, a combination with the Schmidt-hammer technique seems ideal as the latter could provide measurement of a large number of boulders. The Schmidt-hammer measurements can, on the other hand, help with the selection of representative boulders for cosmogenic nuclide (10Be) surface exposure dating avoiding boulders that have been exposed to post-depositional movement (e.g. rotation). Results from the application of this combined ‘multi-proxy-approach' at Strauchon Glacier in Westland/Tai Poutini National Park and Hooker Glacier in Mt Cook/Aoraki National Park on large lateral moraine complex with several individual moraine ridges proof its potential. Three pre-‘Little Ice Age' moraine sequences each related to an individual Late-Holocene Little Ice Age-type event unambiguously distinguished by Schmidt-hammer measurements provides cosmogenic (10Be) ages of 2,400/2,500 a BP, c. 1,700 a BP, and c. 1,000/1,100 a BP. The preliminary construction of a dating curve based on both Schmidt-hammer and cosmogenic (10Be) dating results shows high significance and confirms the successful

  7. Cosmogenic Nuclides 10Be-21Ne Burial Dating of Middle Miocene Sedimentary Formation of the Hongliu Valley in Southern Ningxia Basin: A Case of Isotopic Geochronology Study for the Cenozoic Sedimentary Strata

    NASA Astrophysics Data System (ADS)

    Ma, Yan; Zhang, Huiping; Wang, Weitao; Pang, Jianzhang; Zheng, Dewen

    2016-04-01

    Chronology studies for the Cenozoic sedimentary strata based on the magnetostratigraphy cannot afford the unique chronological sequences in the absence of absolute ages from biostratigraphy or volcanic ash chronology. In situ-produced cosmogenic nuclides provide a powerful tool for the sediment dating based on the time-dependent concentration ratio of two nuclides, which are produced in the same mineral but with different half-lives. Thereinto,10Be-26Al is the most widely used nuclide pairs, of which the available dating range spans the Plio-Pleistocene. But the coupling of 10Be with the stable nuclide 21Ne would significantly improve the burial dating range up to the middle Miocene, which is promising in revolutionizing the chronology study for the Late Cenozoic terrestrial sedimentary sequences. We have applied 10Be-21Ne pair for dating the middle Miocene sediments of the Hongliu Valley in southern Ningxia basin. Two major features of the sediments are involved in our study: (1) sediments originated from the steady erosion of the source area, and (2) the burial depth of our sample after deposition is time dependent due to the gradual accumulation of sediments into basin. The post-burial nuclide production is estimated to be less than 3%, including the contribution by muon interactions, of the total nuclide concentrations measured in our sample. Our 10Be-21Ne analysis demonstrates the age of the burial sample is 12.4(+0.6/-0.4) Ma, and the erosion rate at the source area is 0.26±0.01 cm ka-1. The sample's burial age is consistent with the age constraint set by the Hongliugou Formation (16.7-5.4 Ma) which we collected the sample in. Vertebrate fossils of Platybelodon tongxinensis with an age between 12 and 15 Ma exhumated along with our sample further verifies the reliability of our dating results for the middle Miocene sediments.This study has shown the improved age range of cosmogenic-nuclide burial dating method by incorporating the stable nuclide 21Ne, and has

  8. Production and relevance of cosmogenic radionuclides in NaI(Tl) crystals

    SciTech Connect

    Amaré, J.; Cebrián, S.; Cuesta, C.; García, E.; Ginestra, C.; Martínez, M.; Oliván, M. A.; Ortigoza, Y.; Ortiz de Solórzano, A.; Pobes, C.; Puimedón, J.; Sarsa, M. L.; Villar, J. A.; Villar, P.

    2015-08-17

    The cosmogenic production of long-lived radioactive isotopes in materials is an hazard for experiments demanding ultra-low background conditions. Although NaI(Tl) scintillators have been used in this context for a long time, very few activation data were available. We present results from two 12.5 kg NaI(Tl) detectors, developed within the ANAIS project and installed at the Canfranc Underground Laboratory. The prompt data taking starting made possible a reliable quantification of production of some I, Te and Na isotopes with half-lives larger than ten days. Tnitial activities underground were measured and then production rates at sea level were estimated following the history of detectors; a comparison of these rates with calculations using typical cosmic neutron flux at sea level and a selected description of excitation functions was also carried out. After including the contribution from the identified cosmogenic products in the detector background model, we found that the presence of {sup 3}H in the crystal bulk would help to fit much better our background model and experimental data. We have analyzed the cosmogenic production of {sup 3}H in NaI, and although precise quantification has not been attempted, we can conclude that it could imply a very relevant contribution to the total background below 15 ke in NaI detectors.

  9. Production and relevance of cosmogenic radionuclides in NaI(Tl) crystals

    NASA Astrophysics Data System (ADS)

    Amaré, J.; Cebrián, S.; Cuesta, C.; García, E.; Ginestra, C.; Martínez, M.; Oliván, M. A.; Ortigoza, Y.; de Solórzano, A. Ortiz; Pobes, C.; Puimedón, J.; Sarsa, M. L.; Villar, J. A.; Villar, P.

    2015-08-01

    The cosmogenic production of long-lived radioactive isotopes in materials is an hazard for experiments demanding ultra-low background conditions. Although NaI(Tl) scintillators have been used in this context for a long time, very few activation data were available. We present results from two 12.5 kg NaI(Tl) detectors, developed within the ANAIS project and installed at the Canfranc Underground Laboratory. The prompt data taking starting made possible a reliable quantification of production of some I, Te and Na isotopes with half-lives larger than ten days. Tnitial activities underground were measured and then production rates at sea level were estimated following the history of detectors; a comparison of these rates with calculations using typical cosmic neutron flux at sea level and a selected description of excitation functions was also carried out. After including the contribution from the identified cosmogenic products in the detector background model, we found that the presence of 3H in the crystal bulk would help to fit much better our background model and experimental data. We have analyzed the cosmogenic production of 3H in NaI, and although precise quantification has not been attempted, we can conclude that it could imply a very relevant contribution to the total background below 15 ke in NaI detectors.

  10. Cosmogenic radionuclides in metals as indicator for sea level exposure history.

    PubMed

    Laubenstein, M; Heusser, G

    2009-05-01

    Copper and stainless steel used in neutrino related experiments have been screened for primordial and cosmogenic isotopes with highly sensitive germanium gamma spectroscopy. Aliquots of these materials have been exposed to cosmic rays at the LNGS site. The obtained production rates (saturation activities) are checked against experimental and theoretical literature values. The data is used to evaluate the cosmic ray exposure histories of the originally measured samples. Two stainless steel samples offer the possibility to compare the obtained exposure ages with a time scale based on the disequilibrium in the thorium decay chain.

  11. Cosmogenic radionuclides and mineralogical properties of the Chelyabinsk (LL5) meteorite: What do we learn about the meteoroid?

    NASA Astrophysics Data System (ADS)

    Povinec, Pavel P.; Laubenstein, Matthias; Jull, A. J. Timothy; FerrièRe, Ludovic; BrandstäTter, Franz; Sýkora, Ivan; Masarik, Jozef; BeåO, Juraj; KováčIk, Andrej; Topa, Dan; Koeberl, Christian

    2015-02-01

    On February 15, 2013, after the observation of a brilliant fireball and a spectacular airburst over the southern Ural region (Russia), thousands of stones fell and were rapidly recovered, bringing some extremely fresh material for scientific investigations. We undertook a multidisciplinary study of a dozen stones of the Chelyabinsk meteorite, including petrographic and microprobe investigations to unravel intrinsic characteristics of this meteorite. We also study the short and long-lived cosmogenic radionuclides to characterize the initial meteoroid size and exposure age. Petrographic observations, as well as the mineral compositions obtained by electron microprobe analyses, allow us to confirm the classification of the Chelyabinsk meteorite as an LL5 chondrite. The fragments studied, a few of which are impact melt rocks, contain abundant shock melt veins and melt pockets. It is likely that the catastrophic explosion and fragmentation of the Chelyabinsk meteoroid into thousands of stones was in part determined by the initial state of the meteoroid. The radionuclide results obtained show a wide range of concentrations of 14C, 22Na, 26Al, 54Mn, 57Co, 58Co, and 60Co, which indicate that the pre-atmospheric object had a radius >5 m, consistent with other size estimates based on the magnitude of the airburst caused by the atmospheric entry and breakup of the Chelyabinsk meteoroid. Considering the observed 26Al activities of the investigated samples, Monte Carlo simulations, and taking into account the 26Al half-life (0.717 Myr), the cosmic-ray exposure age of the Chelyabinsk meteorite is estimated to be 1.2 ± 0.2 Myr. In contrast to the other radionuclides, 14C showed a very large range only consistent with most samples having been exposed to anthropogenic sources of 14C, which we associate with radioactive contamination of the Chelyabinsk region by past nuclear accidents and waste disposal, which has also been confirmed by elevated levels of anthropogenic 137Cs and

  12. A search for cosmogenic production of β-neutron emitting radionuclides in water

    NASA Astrophysics Data System (ADS)

    Dazeley, S.; Askins, M.; Bergevin, M.; Bernstein, A.; Bowden, N. S.; Shokair, T. M.; Jaffke, P.; Rountree, S. D.; Sweany, M.

    2016-06-01

    Here we present the first results of WATCHBOY, a water Cherenkov detector designed to measure the yield of β-neutron emitting radionuclides produced by cosmic ray muons in water. In addition to the β-neutron measurement, we also provide a first look at isolating single-β producing radionuclides following muon-induced hadronic showers as a check of the detection capabilities of WATCHBOY. The data taken over 207 live days indicates a 9Li production yield upper limit of 1.9 ×10-7μ-1g-1cm2 at ~400 m water equivalent (m.w.e.) overburden at the 90% confidence level. In this work the 9Li signal in WATCHBOY was used as a proxy for the combined search for 9Li and 8He production. This result will provide a constraint on estimates of antineutrino-like backgrounds in future water-based antineutrino detectors.

  13. A search for cosmogenic production of β-neutron emitting radionuclides in water

    DOE PAGES

    Dazeley, S.; Askins, M.; Bergevin, M.; Bernstein, A.; Bowden, N. S.; Shokair, T. M.; Jaffke, P.; Rountree, S. D.; Sweany, M.

    2016-03-08

    Here we present the first results of WATCHBOY, a water Cherenkov detector designed to measure the yield of β-neutron emitting radionuclides produced by cosmic ray muons in water. In addition to the β-neutron measurement, we also provide a first look at isolating single-β producing radionuclides following muon-induced hadronic showers as a check of the detection capabilities of WATCHBOY. The data taken over 207 live days indicates a 9Li production yield upper limit ofmore » $$1.9\\times10^{-7}\\mu^{-1}g^{-1}\\mathrm{cm}^2$$ at $$\\sim400$$ meters water equivalent (m.w.e.) overburden at the 90% confidence level. In this work the 9Li signal in WATCHBOY was used as a proxy for the combined search for 9Li and 8He production. This result will provide a constraint on estimates of antineutrino-like backgrounds in future water-based antineutrino detectors.« less

  14. 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.

  15. Cosmogenic noble gas paleothermometry

    NASA Astrophysics Data System (ADS)

    Tremblay, Marissa M.; Shuster, David L.; Balco, Greg

    2014-08-01

    We present a theoretical basis for reconstructing paleotemperatures from the open-system behavior of cosmogenic noble gases produced in minerals at Earth's surface. Experimentally-determined diffusion kinetics predicts diffusive loss of cosmogenic 3He and 21Ne from common minerals like quartz and feldspars at ambient temperatures; incomplete retention has also been observed empirically in field studies. We show that the theory of simultaneous production and diffusion that applies to radiogenic noble gases in minerals-the basis of thermochronology-can also be applied to cosmogenic noble gases to reconstruct past surface temperatures on Earth. We use published diffusion kinetics and production rates for 3He in quartz and 21Ne in orthoclase to demonstrate the resolving power of cosmogenic noble gas paleothermometry with respect to exposure duration, temperature, and diffusion domain size. Calculations indicate that, when paired with a quantitatively retained cosmogenic nuclide such as 21Ne or 10Be, observations of cosmogenic 3He in quartz can constrain temperatures during surface exposure in polar and high altitude environments. Likewise, 21Ne retention in feldspars is sensitive to temperatures at lower latitudes and elevations, expanding the potential geographic applicability of this technique to most latitudes. As an example, we present paired measurements of 3He and 10Be in quartz from a suite of Antarctic sandstone erratics to test whether the abundances of cosmogenic 3He agree with what is predicted from first principles and laboratory-determined diffusion kinetics. We find that the amounts of cosmogenic 3He present in these samples are consistent with the known mean annual temperature (MAT) for this region of Antarctica between -25 and -30 °C. These results demonstrate the method's ability to record paleotemperatures through geologic time.

  16. 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.

  17. Cosmogenic nuclei

    NASA Technical Reports Server (NTRS)

    Raisbeck, G. M.

    1986-01-01

    Cosmogenic nuclei, nuclides formed by nuclear interactions of galactic and solar cosmic rays with extraterrestrial or terrestrial matter are discussed. Long lived radioactive cosmogenic isotopes are focused upon. Their uses in dating, as tracers of the interactions of cosmic rays with matter, and in obtaining information on the variation of primary cosmic ray flux in the past are discussed.

  18. Production rates of terrestrial in-situ-produced cosmogenic nuclides

    SciTech Connect

    Reedy, R.C.; Tuniz, C.; Fink, D.

    1993-12-31

    Production rates of cosmogenic nuclides made in situ in terrestrial samples and how they are applied to the interpretation of measured radionuclide concentrations were discussed at a one-day Workshop held 2 October 1993 in Sydney, Australia. The status of terrestrial in-situ studies using the long-lived radionuclides {sup 10}Be, {sup 14}C, {sup 26}Al, {sup 36}Cl, and {sup 41}Ca and of various modeling and related studies were presented. The relative uncertainties in the various factors that go into the interpretation of these terrestrial in-situ cosmogenic nuclides were discussed. The magnitudes of the errors for these factors were estimated and none dominated the final uncertainty.

  19. Use of radon and cosmogenic radionuclides as indicators of exchange between troposphere and stratosphere. Final technical report, 1 January 1984-31 October 1987

    SciTech Connect

    Kritz, M.A.

    1994-08-01

    This research grant covered participation in the operational phase of NASA's Stratosphere-Troposphere Exchange Project (STEP), a multi-agency airborne science program conducted aboard NASA U-2 and ER-2 high altitude research aircraft. The primary goals of STEP were to investigate the mechanisms of irreversible movement of mass, trace gases, and aerosols from the troposphere into the stratosphere, and to explain the observed dryness of the stratosphere. Three flight experiments were conducted to address these questions: two extratropical experiments, in 1984 and 1986, and a tropical experiment, in 1987. The cosmogenic radionuclides Be-7 and P-32, produced in the stratosphere by cosmic rays, and Rn-222 (radon), emitted from continental soils, were well-suited as tracers of intra-stratospheric air mass movements, and to follow episodes of troposphere to stratosphere exchange. Measurements of Be-7 and P-32 were made in all three STEP experiments. Measurements of radon were made in the tropical experiment only. The equipment worked well, and produced a valuable data set in support of the STEP objectives, as indicated by the 'quick-look' results outlined.

  20. 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

  1. The Pingding segment of the Altyn Tagh Fault (91 °E): Holocene slip-rate determination from cosmogenic radionuclide dating of offset fluvial terraces

    DOE PAGES

    Meriaux, A. -S.; Van der Woerd, J.; Tapponnier, P.; Ryerson, F. J.; Finkel, R. C.; Lasserre, C.; Xu, X.

    2012-09-25

    Morphochronologic slip-rates on the Altyn Tagh Fault (ATF) along the southern front of the Pingding Shan at ~90.5°E are determined by cosmogenic radionuclide (CRN) dating of seven offset terraces at two sites. The terraces are defined based upon morphology, elevation and dating, together with fieldwork and high-resolution satellite analysis. The majority of the CRN model ages fall within narrow ranges (<2 ka) on the four main terraces (T1, T2, T3 and T3′), and allow a detailed terrace chronology. Bounds on the terrace ages and offsets of 5 independent terraces yield consistent slip-rate estimates. The long-term slip-rate of 13.9 ± 1.1more » mm/yr is defined at the 95% confidence level, as the joint rate probability distribution of the rate derived from each independent terrace. It falls within the bounds of all the rates defined on the central Altyn Tagh Fault between the Cherchen He (86.4°E) and Akato Tagh (~88°E) sites. This rate is ~10 mm/yr less than the upper rate determined near Tura at ~87°E, in keeping with the inference of an eastward decreasing rate due to progressive loss of slip to thrusts branching off the fault southwards but it is greater than the 9 ± 4 mm/yr rate determined at ~90°E by GPS surveys and other geodetic short-term rates defined elsewhere along the ATF. Furthermore, whether such disparate rates will ultimately be reconciled by a better understanding of fault mechanics, resolved transient deformations during the seismic cycle or by more accurate measurements made with either approach remains an important issue.« less

  2. The Pingding segment of the Altyn Tagh Fault (91 °E): Holocene slip-rate determination from cosmogenic radionuclide dating of offset fluvial terraces

    SciTech Connect

    Meriaux, A. -S.; Van der Woerd, J.; Tapponnier, P.; Ryerson, F. J.; Finkel, R. C.; Lasserre, C.; Xu, X.

    2012-09-25

    Morphochronologic slip-rates on the Altyn Tagh Fault (ATF) along the southern front of the Pingding Shan at ~90.5°E are determined by cosmogenic radionuclide (CRN) dating of seven offset terraces at two sites. The terraces are defined based upon morphology, elevation and dating, together with fieldwork and high-resolution satellite analysis. The majority of the CRN model ages fall within narrow ranges (<2 ka) on the four main terraces (T1, T2, T3 and T3′), and allow a detailed terrace chronology. Bounds on the terrace ages and offsets of 5 independent terraces yield consistent slip-rate estimates. The long-term slip-rate of 13.9 ± 1.1 mm/yr is defined at the 95% confidence level, as the joint rate probability distribution of the rate derived from each independent terrace. It falls within the bounds of all the rates defined on the central Altyn Tagh Fault between the Cherchen He (86.4°E) and Akato Tagh (~88°E) sites. This rate is ~10 mm/yr less than the upper rate determined near Tura at ~87°E, in keeping with the inference of an eastward decreasing rate due to progressive loss of slip to thrusts branching off the fault southwards but it is greater than the 9 ± 4 mm/yr rate determined at ~90°E by GPS surveys and other geodetic short-term rates defined elsewhere along the ATF. Furthermore, whether such disparate rates will ultimately be reconciled by a better understanding of fault mechanics, resolved transient deformations during the seismic cycle or by more accurate measurements made with either approach remains an important issue.

  3. Synchronizing the Greenland ice core and radiocarbon timescales over the Holocene - Bayesian wiggle-matching of cosmogenic radionuclide records

    NASA Astrophysics Data System (ADS)

    Adolphi, F.; Muscheler, R.

    2016-01-01

    Investigations of past climate dynamics rely on accurate and precise chronologies of the employed climate reconstructions. The radiocarbon dating calibration curve (IntCal13) and the Greenland ice core chronology (GICC05) represent two of the most widely used chronological frameworks in paleoclimatology of the past ˜ 50 000 years. However, comparisons of climate records anchored on these chronologies are hampered by the precision and accuracy of both timescales. Here we use common variations in the production rates of 14C and 10Be recorded in tree-rings and ice cores, respectively, to assess the differences between both timescales during the Holocene. Compared to earlier work, we employ a novel statistical approach which leads to strongly reduced and yet, more robust, uncertainty estimates. Furthermore, we demonstrate that the inferred timescale differences are robust independent of (i) the applied ice core 10Be records, (ii) assumptions of the mode of 10Be deposition, as well as (iii) carbon cycle effects on 14C, and (iv) in agreement with independent estimates of the timescale differences. Our results imply that the GICC05 counting error is likely underestimated during the most recent 2000 years leading to a dating bias that propagates throughout large parts of the Holocene. Nevertheless, our analysis indicates that the GICC05 counting error is generally a robust uncertainty measurement but care has to be taken when treating it as a nearly Gaussian error distribution. The proposed IntCal13-GICC05 transfer function facilitates the comparison of ice core and radiocarbon dated paleoclimate records at high chronological precision.

  4. Reconstructing the cosmogenic 21Ne inventory of Neogene sedimentary sequences

    NASA Astrophysics Data System (ADS)

    Stuart, Finlay; Sinclair, Hugh; McCann, Louise

    2016-04-01

    The cosmogenic radionuclides, in particular 10Be, have found use in modern sediments as a way of determining the erosion rate of river catchments. Cosmogenic 21Ne in quartz is easier and faster to measure than 10Be and has the potential to record erosion rates back 10s million years. However the routine use of cosmogenic 21Ne in quartz sand is hampered by ubiquitous nucleogenic 21Ne. When the eroding lithology can be identified it is possible to measure the nucleogenic in samples that are shielded from cosmic rays and correct for it in exposed bedrock [1]. However, identifying the lithologies that contributes quartz sand in large river catchments, and determining precise nucleogenic contributions is more problematic. The North and South Platte rivers drain early Prototerozoic lithologies of the Laramie and Front Ranges in the high Rockies of Wyoming. They have deposited several km of coarse clastic fluvial deposits on the Great Plains of Nebraska and Colorado up to 200 km from the mountain front. Quartz from shielded samples of granite and gneiss - the dominant quartz-bearing rocks - has high concentrations of nucleogenic 21Ne (60-140 e6 atoms/g). The 21Ne concentration in modern sand from the river (n=10) overlaps that measured in the shielded granite and gneiss. The sand data rarely lie on the air-spallation mixing line in the Ne three isotope plot indicating that it is dominantly derived from the granite and gneiss and has no resolvable cosmogenic 21Ne. Building on previous studies of cosmogenic 21Ne in pebbles [2] we have started a programme of analysis of pebbles derived from the Medicine Bow quartzite that are abundant throughout the Cenozoic alluvial sequence. Nucleogenic 21Ne in shielded quartzite is lower than granites (3-7 e6 atoms/g, n=4) and the data tend to lie on the air-spallation mixing line. All pebbles (n=14) from modern sediments analysed so far contain 2-80 times more excess 21Ne than the highest shielded quartzite suggesting that cosmogenic 21

  5. 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.

  6. 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.

  7. Surficial Studies of Mars Using Cosmogenic Nuclides

    NASA Technical Reports Server (NTRS)

    Nishiizumi, K.

    2001-01-01

    Cosmogenic nuclides (CNs) are produced by cosmic-ray nuclear interactions with target nuclei in rocks, soils, ice, and the atmosphere. Cosmogenic nuclides have been widely used for investigation of solar system matter for several decades. Stable nuclides, such as He-3, Ne-21, and Ar-38, are built up over time as the surface is exposed to cosmic rays. The concentrations of cosmogenic radionuclides, such as Be-10, Al-26, and C-14 also build up with exposure time but reach saturation values after several half-lives. Especially since the development of accelerator mass spectrometry (AMS), CNs in terrestrial samples have been routinely used for geomorphic studies such as glaciation, surface erosion, and tectonics, and studies of atmospheric and ocean circulation. Cosmogenic nuclides on Mars will be able to answer questions of exposure ages, erosion rates, tectonic events, and deposition rates of sediments and/or volatiles. The concentrations of cosmogenic stable nuclides give the integrated exposure time of the rock/mineral, and the activities of radionuclides give recent records for times back as long as a few half-lives.

  8. Measurement of 26Al for atmospheric and climate research and the potential of 26Al/ 10Be ratios

    NASA Astrophysics Data System (ADS)

    Auer, M.; Kutschera, W.; Priller, A.; Wagenbach, D.; Wallner, A.; Wild, E. M.

    2007-06-01

    The measurement of the paired cosmogenic radionuclides 26Al and 10Be in environmental samples has potential applications in atmospheric and climate research. For this study, we report the first measurements of the 26Al/10Be atomic ratio in tropospheric aerosol samples from sites in Europe and Antarctica performed at the Vienna Environmental Research Accelerator (VERA). These initial results show that the 26Al/10Be atomic ratio in tropospheric aerosols averages 1.78 × 10-3 and does not vary significantly between the different locations. We also report results of systematic investigations of the ionization and detection efficiency which we performed to improve the measurement precision for 26Al by AMS. Maximum detection efficiencies of up to 9 × 10-4 (in units of 26Al atoms detected/initial) were achieved for chemically pure Al2O3, while for atmospheric samples we reached efficiencies of up to 2.2 × 10-4.

  9. 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.

  10. 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

  11. 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 of

  12. Arctic ocean water mass distribution and particle flux from dissolved 10Be and 9Be

    NASA Astrophysics Data System (ADS)

    Frank, M.; Porcelli, D.; Andersson, P.; Halliday, A. N.; Kubik, P. W.; Hattendorf, B.; Guenther, D.

    2003-04-01

    The Arctic Ocean basin is confined by landmasses similar to the Mediterranean. There is only little deep water formed seasonally on the shelves of the Arctic Ocean despite the low temperatures. This is due to a freshwater lid at the surface which originates from the Arctic rivers. The deeper Arctic Ocean water masses can thus only be renewed at comparatively low rates via the only deep connection to the Atlantic Ocean, the Fram Strait. At the same time the biogenic particulate fluxes in the central Arctic Ocean are very low due to perennial sea ice cover and detrital particle fluxes from either eolian or riverine sources are also very low. We will present the first combined dissolved 10Be (cosmogenic) and ^9Be (continental sources) depth profiles from water samples of the major deep basins of the Arctic Ocean collected during the Swedish Arctic Ocean 2001 expedition. Be is 5-10 times less particle-reactive than other previously investigated radionuclides such as Th or Pa and should therefore even at the relatively low Arctic Ocean renewal rates serve as a quasi-conservative tracer for different origins of water masses (Atlantic Ocean/Norwegian Sea, Pacific Ocean, Arctic Shelves). ^9Be and Nd isotope analyses provide complementary information to cosmogenic 10Be on the pathways of dissolved material originating from the Arctic continents. Results obtained ten years ago at similar locations as in our study indicated a uniform distribution of 10Be at low values of 500±100 atoms/g suggesting restricted input and efficient homogenisation. In contrast, our new results show that in 2001 the inflowing waters from the Atlantic are traced by 10Be concentrations of up to 1100 atoms/g. Preliminary measurements indicate relatively low ^9Be concentrations around 10 pMol/litre resulting in 10Be/^9Be ratios of ˜ 1 x 10-7 in the deep Arctic Ocean. In addition, the surface 10Be concentrations vary considerably. It will be discussed wether this is a consequence of a seasonal

  13. The geomagnetic dipole moment variation between 250 and 800 ka BP reconstructed from the authigenic 10Be/9Be signature in West Equatorial Pacific sediments

    NASA Astrophysics Data System (ADS)

    Ménabréaz, Lucie; Thouveny, Nicolas; Bourlès, Didier L.; Vidal, Laurence

    2014-01-01

    The authigenic 10Be/9Be ratio, proxy of the cosmogenic radionuclide 10Be production rate in the atmosphere, was measured in sediments deposited in the West Equatorial Pacific (Gulf of Papua; 10°25 S; 146°15 E), in order to reconstruct the geomagnetic dipole moment variations in the 250-800 ka time interval, independently from paleomagnetic methods. The pelagic clayey-carbonate muds continuously deposited between marine isotope stages 8 and 20 were subsampled every 10 cm. The 10Be production rate record reconstructed for the 250-800 ka interval is described and compared over the same time interval with global paleomagnetic stacks (SINT-2000 and PISO-1500). The highlighted cosmogenic 10Be overproductions appear to be triggered by the series of Geomagnetic Dipole Lows (GDL) that have occurred since the Brunhes-Matuyama reversal. Calibration using absolute values of the geomagnetic dipole moment drawn from a paleomagnetic database produces a new record of the dipole moment variations over the 250-800 ka time interval. The timing and amplitude of the GDL succession revealed by such records will contribute to improving knowledge of the geodynamo rhythms and rate of changes at millennial to million year scales.

  14. Cosmogenic Nuclides in a Large Meteoroid - Another Example of a Complex Exposure?

    NASA Astrophysics Data System (ADS)

    Ferko, T. E.; Schultz, L.; Francke, L.; Bogard, D. D.; Garrison, D. H.; Hutchison, R.; Lipschutz, M. E.

    1999-03-01

    Cosmogenic radionuclide and noble gas measurement results are reported for ten samples from the Mocs meteorite strewnfield. While evidence of a simple exposure history is examined a more likely complex exposure is also described.

  15. 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

  16. Timing and mechanism of uplift from cosmogenic radionuclides and structural data: a case study from an actively uplifting forearc, Calabria, Southern Italy

    NASA Astrophysics Data System (ADS)

    Steckler, M. S.; Reitz, M. A.; Seeber, L.; Schaefer, J. M.

    2014-12-01

    The Calabrian Arc is a subduction-rollback system that has experienced remarkably peaceful forearc tectonics during the last 12 My of rollback, even with 780 km of backarc extension. In contrast, during the Middle Pleistocene rollback slowed and the forearc experienced a surge of tectonic activity including 15-20° of clockwise rotation, arc-parallel extension, and widespread uplift. This rapid and continuous uplift (1-1.2 mm/yr) has affected the entire forearc and is striking because subduction is presumed to be ongoing. No discernable structure or mechanism has been identified to account for all phenomena. We combine structural mapping and erosion rates from 10Be concentrations in river sediment to model river erosion into the Sila Massif, the most prominent highland in northern Calabria. Interfluves between river gorges on the east side of the Sila Massif preserve a tilted paleosurface, which we interpret as subhorizontal until post-Early Pliocene. We reconstruct uplift and river incision using a forward model that is calibrated using the current erosion rates and the elevation of the paleosurface above the Neto River bed. The model tests two end-member structural growth models of uplift: tilting a fixed hinge and tilting from a propagating hinge. The propagating hinge model generates a better fit with the modern river profile and the modern erosion rates. We independently constrain uplift to beginning between 800 ka and 900 ka, consistent with the Late Pleistocene tectonic upheaval. In addition, the results show the Sila Massif grew via tilting with a propagating hinge. This method can be applied to other tectonic regions as a new way to quantify and identify young and active structures.

  17. River fluxes to the sea from the ocean's 10Be/9Be ratio

    NASA Astrophysics Data System (ADS)

    von Blanckenburg, F.; Bouchez, J.

    2013-12-01

    The ratio of the meteoric cosmogenic radionuclide 10Be to the stable isotope 9Be is proposed here to be a flux proxy of terrigenous input into the oceans. The ocean's dissolved 10Be/9Be is set by (1) the flux of meteoric 10Be produced in the atmosphere; (2) the denudational flux of the rivers discharging into a given ocean basin; (3) the fraction of 9Be that is released from primary minerals during weathering (meaning the 9Be transported by rivers in either the dissolved form or adsorbed onto sedimentary particles and incorporated into secondary oxides); and (4) the fraction of riverine 10Be and 9Be actually released into seawater. Using published 10Be/9Be data of rivers for which independent denudation rate estimates exist we first find that the global average fraction of 9Be released during weathering into river waters and their particulate load is 20% and does not depend on denudation rate. We then evaluate this quantitative denudation rate proxy by using published dissolved seawater Be isotope data and a compilation of global river loads (15Gt/yr). We find that the measured global average oceanic dissolved 10Be/9Be ratio of about 0.9E-7 is satisfied by the mass balance if only 6.5% of the dissolved and reactive riverine Be is eventually released to the open ocean by boundary exchange. Except for the South Atlantic and the South Pacific, in which the 10Be/9Be ratio is dominated by Be advected through ocean circulation, good agreement results between 10Be/9Be ratios predicted by denudation rates and measured ocean 10Be/9Be ratios when we establish this mass balance for individual ocean basins. As the seawater 10Be/9Be ratio is faithfully recorded in marine chemical precipitates the 10Be/9Be ratio extracted from authigenic sediments can now serve to estimate relative changes in terrigenous input into the oceans back through time on a global and on a basin scale.

  18. River fluxes to the sea from the oceanʼs 10Be/9Be ratio

    NASA Astrophysics Data System (ADS)

    von Blanckenburg, Friedhelm; Bouchez, Julien

    2014-02-01

    The ratio of the meteoric cosmogenic radionuclide 10Be to the stable isotope 9Be is proposed here to be a flux proxy of terrigenous input into the oceans. The ocean's dissolved 10Be/9Be is set by (1) the flux of meteoric 10Be produced in the atmosphere; (2) the denudational flux of the rivers discharging into a given ocean basin; (3) the fraction of 9Be that is released from primary minerals during weathering (meaning the 9Be transported by rivers in either the dissolved form or adsorbed onto sedimentary particles and incorporated into secondary oxides); and (4) the fraction of riverine 10Be and 9Be actually released into seawater. Using published 10Be/9Be data of rivers for which independent denudation rate estimates exist we first find that the global average fraction of 9Be released during weathering into river waters and their particulate load is 20% and does not depend on denudation rate. We then evaluate this quantitative proxy for terrigenous inputs by using published dissolved seawater Be isotope data and a compilation of global river loads. We find that the measured global average oceanic dissolved 10Be/9Be ratio of about 0.9×10-7 is satisfied by the mass balance if only about 6% of the dissolved and adsorbed riverine Be is eventually released to the open ocean after escaping the coastal zone. When we establish this mass balance for individual ocean basins good agreement results between 10Be/9Be ratios predicted from known river basin denudation rates and measured ocean 10Be/9Be ratios. Only in the South Atlantic and the South Pacific the 10Be/9Be ratio is dominated by advected Be and in these basins the ratio is a proxy for ocean circulation. As the seawater 10Be/9Be ratio is faithfully recorded in marine chemical precipitates the 10Be/9Be ratio extracted from authigenic sediments can now serve to estimate relative changes in terrigenous input into the oceans back through time on a global and on an ocean basin scale.

  19. Proceedings of a Workshop on Cosmogenic Nuclide Production Rates

    NASA Technical Reports Server (NTRS)

    Englert, Peter A. J. (Editor); Reedy, Robert C. (Editor); Michel, Rolf (Editor)

    1989-01-01

    Abstracts of reports from the proceedings are presented. The presentations were divided into discussion topics. The following general topic areas were used: (1) measured cosmogenic noble gas and radionuclide production rates in meteorite and planetary surface samples; (2) cross-section measurements and simulation experiments; and (3) interpretation of sample studies and simulation experiments.

  20. 10Be evidence for delayed acquisition of remanent magnetization in marine sediments: Implication for a new age for the Matuyama-Brunhes boundary

    NASA Astrophysics Data System (ADS)

    Suganuma, Yusuke; Yokoyama, Yusuke; Yamazaki, Toshitsugu; Kawamura, Kenji; Horng, Chorng-Shern; Matsuzaki, Hiroyuki

    2010-08-01

    Fluxes of the meteoric cosmogenic radionuclide 10Be vary with changes in the incoming cosmic rays modulated by geomagnetic field intensity variations. The variability in the 10Be flux can be used to synchronize ice cores, as well as marine sediments, by comparison with the relative paleointensity variations of the geomagnetic field. However, lock-in of the paleomagnetic signal at some depth below the sediment-water interface in marine sediments through acquisition of a post-depositional remanent magnetization (PDRM) adds uncertainty to synchronization. Despite the long history of such studies, the magnitude of the PDRM lock-in depth remains controversial. In this article, we present clear evidence for a downward offset of the paleointensity minimum relative to the 10Be flux anomaly at the Matuyama-Brunhes (M-B) geomagnetic polarity boundary, which we interpret to result from a ˜ 15 cm PDRM lock in depth. This lock-in depth indicates that up to several tens of thousands years of age offset probably occurs when a paleomagnetic record is used for dating marine sediments, and the age of the M-B boundary should be revised to ca. 10 kyr younger, which is consistent with a younger ice core derived age of 770 ± 6 ka (2 σ). This cosmogenic age tuning strategy will contribute to refining paleomagnetic-based age models for marine sediments and identifying of lead-lag relationships for global abrupt environmental changes.

  1. Workshop on Cosmogenic Nuclides

    NASA Technical Reports Server (NTRS)

    Reedy, R. C. (Editor); Englert, P. (Editor)

    1986-01-01

    Abstracts of papers presented at the Workshop on Cosmogenic Nuclides are compiled. The major topic areas covered include: new techniques for measuring nuclides such as tandem accelerator and resonance mass spectrometry; solar modulation of cosmic rays; pre-irradiation histories of extraterrestrial materials; terrestrial studies; simulations and cross sections; nuclide production rate calculations; and meteoritic nuclides.

  2. 10Be Production in the Atmosphere by Galactic Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Matthiä, Daniel; Herbst, Klaudia; Heber, Bernd; Berger, Thomas; Reitz, Günther

    2013-06-01

    Galactic cosmic ray nuclei and energetic protons produced in solar flares and accelerated by coronal mass ejections are the main sources of high-energy particles of extraterrestrial origin in near-Earth space and inside the Earth's atmosphere. The intensity of galactic cosmic rays inside the heliosphere is strongly influenced by the modulation of the interstellar source particles on their way through interplanetary space. Among others, this modulation depends on the activity of the Sun, and the resulting intensity of the energetic particles in the atmosphere is an indicator of the solar activity. Therefore, rare isotopes found in historical archives and produced by spallation reactions of primary and secondary hadrons of cosmic origin in the atmosphere, so-called cosmogenic nuclides, can be used to reconstruct the solar activity in the past. The production rate of 10Be, one of the cosmogenic nuclides most adequate to study the solar activity, is presented showing its variations with geographic latitude and altitude and the dependence on different production cross-sections present in literature. In addition, estimates for altitude integrated production rates of 10Be at different locations since the early nineteen sixties are shown.

  3. 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.

  4. 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.

  5. The Chondrite Neagari: Petrography, Mineralogy, Chemical Compositions, and Cosmogenic Nuclides

    NASA Astrophysics Data System (ADS)

    Okada, A.; Komura, K.; Nagao, K.; Nishiizumi, K.; Miyamoto, Y.; Sakamoto, K.; Ebihara, M.; Shima, M.

    1995-09-01

    ) have been identified and their contents were determined by using a mock sample having known amounts of natural radioactivities. Among these nuclides, ^44mSc has the shortest half life (2.44 d) and has also been measured in the Mihonoseki meteorite [1]. Cosmogenic components were also observed for ^3He, ^21Ne, and ^38Ar by noble gas mass spectrometry. Cosmic-ray exposure ages calculated from cosmogenic ^21Ne and ^38Ar contents coupled with production rates by Eugster [2] and Schultz et al. [3], respectively, seem to be consistent (about 45 Ma), but the age from ^3He is significantly lower. Considering the loss of radiogenic ^4He, the Neagari meteorite must have experienced a high temperature event in space. Cosmogenic radionuclides ^10Be, ^26Al, and ^36Cl were also measured in an aliquot (77 mg) of the Neagari meteorite using an AMS facility at Lawrence Livermore National Laboratory. The concentrations of these nuclides in conjunction with the noble gas data as well as data of elemental abundances provide better knowledge of the exposure history of this meteorite. References: [1] Shima M. et al. (1993) LPS XXIV, 1297-1298. [2] Eugster O. (1988) GCA, 52, 1649-1662. [3] Schultz L. et al. (1991) GCA, 55, 59-66.

  6. sup 10 Be study of rapid erosion in Taiwan

    SciTech Connect

    Chenfeng You; Juchin Chen National Taiwan Univ., Taipei ); Typhoon Lee; Jason Jiunsan Shen ); Brown, L. )

    1988-11-01

    Cosmogenic {sup 10}Be was measured using accelerator mass spectrometry in soils and sediments to study the erosion of Taiwan, which has the highest denudation rate in the world. The river sediments in Taiwan have very low {sup 10}Be concentrations, around 5 million atoms per gram, about 1/45 the world wide average. This is the direct consequence of its high sediment yield of ore than 1,000 mg/cm{sup 2}/yr, 70 times the world average. Combining these values the authors found that, for Taiwan as a whole, the {sup 10}Be output to the sea only slightly exceeds the input from the rain, a situation typical of many areas around the world. Therefore, even in this example of extremely rapid erosion, {sup 10}Be seems to remain a useful indicator for erosion status. The total {sup 10}Be inventory found in a soil profile from a geologically stable area is at least 18% of the maximum possible inventory. The minimum age thus estimated for the soil is 0.11 Ma, in reasonable agreement with estimates from other means. The maximum erosion rate for this area thus estimated is at most 0.14 mg/cm{sup 2}/yr, four orders of magnitude slower than the average value observed for Taiwan. They also demonstrate that the shelf sediments around Taiwan have received the admixing of a {sup 10}be rich component from the ocean and would give a poor estimate for material eroded from Taiwan.

  7. 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

  8. Cosmogenic activation of materials

    SciTech Connect

    Amare, J.; Beltran, B.; Carmona, J.M.; Cebrian, S.; Garcia, E.; Irastorza, I.G.; Gomez, H.; Luzon, G.; Martinez, M.; Morales, J.; Ortiz de Solorzano, A.; Pobes, C.; Puimedon, J.; Rodriguez, A.; Ruz, J.; Sarsa, M. L.; Torres, L.; Villar, J.A.; Capelli, S.; Capozzi, F.

    2005-09-08

    The problem of cosmogenic activation produced at sea level in materials typically used in underground experiments looking for rare events is being studied. Several nuclear data libraries have been screened looking for relevant isotope production cross-sections and different codes which can be applied to activation studies have been reviewed. The excitation functions for some problems of interest like production of 60Co and 68Ge in germanium and production of 60Co in tellurium have been obtained taking into account both measurements and calculations and a preliminary estimate of the corresponding rates of production at sea level has been performed.

  9. 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

  10. 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

  11. 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

  12. 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

  13. 10Be content in clasts from fallout suevitic breccia in drill cores from the Bosumtwi impact crater, Ghana: Clues to preimpact target distribution

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    Rocks from drill cores LB-07A (crater fill) and LB-08A (central uplift) into the Bosumtwi impact crater, Ghana, were analyzed for the presence of the cosmogenic radionuclide 10Be. The aim of the study was to determine the extent to which target rocks of various depths were mixed during the formation of the crater-filling breccia, and also to detect meteoric water infiltration within the impactite layer. 10Be abundances above background were found in two (out of 24) samples from the LB-07A core, and in none of five samples from the LB-08A core. After excluding other possible explanations for an elevated 10Be signal, we conclude that it is most probably due to a preimpact origin of those clasts from target rocks close to the surface. Our results suggest that in-crater breccias were well mixed during the impact cratering process. In addition, the lack of a 10Be signal within the rocks located very close to the lake sediment-impactite boundary suggests that infiltration of meteoric water below the postimpact crater floor was limited. This may suggest that the infiltration of the meteoric water within the crater takes place not through the aerial pore-space, but rather through a localized system of fractures.

  14. Cosmogenic Nuclide Studies And Geomorphological Implications In The Hyperarid Central Western Andes, Northern Chile

    NASA Astrophysics Data System (ADS)

    Kober, F.; Schlunegger, F.; Ivy-Ochs, S.; Baur, H.; Wieler, R.; Kubik, P. W.; Schneider, H.

    2003-12-01

    We have conducted geomorphological and cosmogenic nuclide studies in the central Andes of Northern Chile (Arica area) in order to quantify landscape evolution at the Western Andean Escarpment. The area is characterized by broad abandoned middle to late Miocene plains that are cut by deeply incised rivers. The major phase of incision has been active since ca. 8 My with different magnitudes and accelerated backward erosion forces through time. Important processes must have been a base level change in the Coastal Cordillera area and climatic changes driven by orogenic growth. Fluvial incision rates are ca. 50m/My across the Escarpment during the middle/late Miocene and early Pliocene and about two to four times higher from the Pliocene until the present, especially in more distal parts relative to the pinned base level control (enhanced backward erosion). Bedrock erosion rates on the broad plains determined with cosmogenic nuclides are several orders of magnitude lower than fluvial incision rates. Erosion rates of ignimbrites determined by paired studies of radionuclides (10Be, 26Al) and stable 21Ne are 10 to 100cm/My at medium elevations and increase towards the high Andes to >250cm/My. This increase is largely controlled by the effect of orographic precipitation that correlates with increasing rates and intensities of rainfall towards the Western Cordillera. Coastal areas, subjected only to coastal fog, show abandoned hanging rivers and smoothed diffusive hillslopes. These landscapes exhibit also extremely low cosmogenically derived erosion rates (<100cm/My). Therefore, the large parts of the landscapes at the northern tip of the Atacama Desert have retained their relict landscape aspect since they formed in Middle Micocene. The comparison of river incision and bedrock erosion clearly shows a strong decoupling between both geomorphic landscape units. A change towards a coupled system can only be found in the high, rainy parts of the Andes (>3500m), which are

  15. Cosmogenic Isotope Variability During the Maunder Minimum: Normal 11-year Cycles Are Expected

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    The amplitude of the 11-year cycle measured in the cosmogenic isotope 10Be during the Maunder Minimum is comparable to that during the recent epoch of high solar activity. Because of the virtual absence of the cyclic variability of sunspot activity during the Maunder Minimum this seemingly contradicts an intuitive expectation that lower activity would result in smaller solar-cycle variations in cosmogenic radio-isotope data, or in none, leading to confusing and misleading conclusions. It is shown here that large 11-year solar cycles in cosmogenic data observed during periods of suppressed sunspot activity do not necessarily imply strong heliospheric fields. Normal-amplitude cycles in the cosmogenic radio-isotopes observed during the Maunder Minimum are consistent with theoretical expectations because of the nonlinear relation between solar activity and isotope production. Thus, cosmogenic-isotope data provide a good tool to study solar-cycle variability even during grand minima of solar activity.

  16. 10Be in bauxite and commercial aluminum

    NASA Astrophysics Data System (ADS)

    Middleton, R.; Klein, J.; Dezfouly-Arjomandy, B.; Albrecht, A.; Xue, S.; Herzog, G. F.; Gregory, J.

    1994-06-01

    Five different samples of commercial aluminum have 10Be concentrations that range from a low of 40 × 10 6 to a high of 100 × 10 6 (atom 10Be)/(g Al). The beryllium-10 is probably produced in the atmosphere and introduced into aluminum ore deposits in varying amounts by rainwater during ore genesis. One modern ore, a bauxite from Haiti, contains ~ 6 × 10 9 atom 10Be/(g sample) or 5.7 × 10 10 atom 10Be/(g Al). Geologically older, allocthonous bauxite from Arkansas contains considerably less 10Be; this observation suggests that 10Be can be used to constrain the age of the deposit. The presence of 10Be in commercial aluminum makes it inadvisable to add modern Al to small samples in which very low levels of 10Be are to be determined.

  17. 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

  18. Cosmogenic nuclide budgeting of floodplain sediment transfer

    NASA Astrophysics Data System (ADS)

    Wittmann, H.; von Blanckenburg, F.

    2009-08-01

    Cosmogenic nuclides produced in quartz may either decay or accumulate while sediment is moved through a river basin. A change in nuclide concentration resulting from storage in a floodplain is potentially important in large drainage basins in which sediment is prone to repeated burial and remobilization as a river migrates through its floodplain. We have modeled depth- and time-dependent cosmogenic nuclide concentration changes for 10Be, 26Al, and 14C during sediment storage and mixing in various active floodplain settings ranging from confined, shallow rivers with small floodplains to foreland-basin scale floodplains traversed by deep rivers. Floodplain storage time, estimated from channel migration rates, ranges from 0.4 kyr for the Beni River basin (Bolivia) to 7 kyr for the Amazon River basin, while floodplain storage depth, estimated from channel depth, ranges from 1 to 25 m. For all modeled active floodplain settings, the long-lived nuclides 10Be and 26Al show neither significant increase in nuclide concentration from irradiation nor decrease from decay. We predict a hypothetical response time after which changes in 10Be or 26Al concentrations become analytically resolvable. This interval ranges from 0.07 to 2 Myr and exceeds in all cases the typical residence time of sediment in a floodplain. Due to the much shorter half life of 14C, nuclide concentrations modeled for the in situ-produced variety of this nuclide are, however, sensitive to floodplain storage on residence times of < 20 kyr. The cosmogenic nuclide composition of old deposits in currently inactive floodplains that have been isolated for periods of millions of years from the river that once deposited them is predicted to either increase or decrease in 10Be and 26Al concentration, depending on the depositional depth. These conditions can be evaluated using the 26Al/ 10Be ratio that readily discloses the depth and duration of storage. We illustrate these models with examples from the Amazon basin

  19. Cosmic-ray interactions and dating of meteorite stranding surfaces with cosmogenic nuclides

    SciTech Connect

    Reedy, R.C.

    1988-01-01

    A wide variety of products from cosmic-ray interactions have been measured in terrestrial or extraterrestrial samples. These ''cosmogenic'' products include radiation damage tracks and rare nuclides that are made by nuclear reactions. They often have been used to determine the fluxes and composition of cosmic-ray particles in the past, but they are usually used to study the history of the ''target'' (such as the time period that it was exposed to cosmic-ray particles). Products made by both the high-energy galactic cosmic rays and energetic particles emitted irregularly from the Sun have been extensively studied. Some of these cosmogenic products, especially nuclides, have been or can be applied to studies of Antarctic meteorite stranding surfaces, the ice surfaces in Antarctica where meteorites have been found. Cosmogenic nuclides studied in samples from Antarctica and reported by others elsewhere in this volume include those in meteorites, especially radionuclides used to determine terrestrial ages, and those made in situ in terrestrial rocks. Cosmogenic nuclides made in the Earth's atmosphere or brought in with cosmic dust have also been studied in polar ice, and it should also be possible to measure nuclides made in situ in ice. As an introduction to cosmogenic nuclides and their applications, cosmic rays and their interactions will be presented below and production systematics of cosmogenic nuclides in these various media will be discussed later. 20 refs., 2 tabs.

  20. Cross Sections Needed for the Interpretation of Long-Lived and Short-Lived Cosmogenic Nuclide Production in Extraterrestrial Materials

    NASA Astrophysics Data System (ADS)

    Sisterson, J. M.; Beverding, A.; Kim, K. J.; Englert, P. A. J.; Jull, A. J. T.; Donahue, D. J.; Cloudt, S.; Castaneda, C.; Vincent, J.; Caffee, M. W.; Osazuwa, C. O.; Reedy, R. C.

    1995-09-01

    Radionuclides produced by cosmic rays in extraterrestrial materials archive information that can be used to determine cosmic-ray fluxes and to study the history of the irradiated object. Long-lived radionuclides give information about the last ~5 Myr; short-lived radionuclides give information about recent events. To calculate the solar cosmic ray (SCR) flux from measured depth profiles for cosmogenic radionuclides produced in lunar rocks, accurate and precise cross section values for the production of these radionuclides from all relevant elements are needed. About 98% of SCR and ~87% of galactic cosmic rays (GCR) falling on extraterrestrial materials are protons. Cross section measurements were made using three proton accelerators to cover the energy range ~20 - 500 MeV. Thin target techniques used in the irradiations minimized the number of protons scattered out of the stack and the neutron production within the stack. After irradiation, the short-lived radionuclides e.g. 22Na, 7Be, 24Na, 54Mn, and 56Co were determined using gamma-ray spectroscopy. 14C, 10Be, and 26Al were determined using Accelerator Mass Spectrometry. Our main objective is to measure the production cross sections of long-lived radionuclides. We have reported new cross section values for making 10Be from O and 14C from O, Mg, Al, Si, Fe, and Ni [1,2]. Using these new results, better estimates for the solar proton flux over several time periods in the past were determined [3]. However, no single value for the SCR flux could explain the measured data from different time periods. Further cross section measurements are being made to verify that the values used in these estimates were accurate. Irradiations designed to give good cross section measurements for long-lived radionuclides also give good cross section measurements for short-lived radionuclides. Results will be presented for proton production cross sections of 22Na from Mg, Al and Si, and 54Mn and 56Co from Fe and Ni; some values at low

  1. The effect of permafrost on soil erosion using meteoric 10Be, 137Cs and 239+240Pu in the Eastern Swiss Alps

    NASA Astrophysics Data System (ADS)

    Pichler, Barbara; Brandovà, Dagmar; Alewell, Christine; Ivy-Ochs, Susan; Kubik, Peter W.; Kneisel, Christof; Meusburger, Katrin; Ketterer, Michael; Egli, Markus

    2013-04-01

    Permafrost ecosystems are highly sensitive to climate warming. The expected changes in the thermal and hydrological soil regime might have crucial consequences on soil erosion processes. Therefore, the determination of erosional activities on the long- (since the beginning of soil formation) and mid-term (last 50-60 yr) using cosmogenic and anthropogenic radionuclides can provide important information on past and ongoing processes. Permafrost soils in the Alps and their behaviour with climate change are only rarely studied. The expected new insights will lead to a better understanding of the processes of high mountain soils and are a further step towards improving climate-related modelling of fast warming scenarios and increasing system disequilibria. Our aim is to quantify soil erosion processes in permafrost soils and nearby unfrozen soils in the Alpine (sites at 2700 m asl) and the sub-Alpine (sites 1800 m asl) range of the Swiss Alps (Upper Engadine). We hypothesise that permafrost soils differ distinctly in their long- and mid-term soil erosion rates due to different water retention capacities. Long-term soil erosion was assessed using meteoric 10Be. Meteoric 10Be in a soil profile was estimated assuming that it is has been deposited as a function of precipitation and adsorbed in the fine earth fraction (

  2. Predicting the production rates of cosmogenic nuclides in extraterrestrial matter

    SciTech Connect

    Reedy, R.C.

    1987-01-01

    The production rates of nuclides made by the galactic and solar cosmic rays are important in the interpretations of measurements made with lunar samples, meteorites, and cosmic spherules. Production rates of cosmogenic nuclides have been predicted by a variety of methods that are reviewed in this paper, ranging from systematic studies of one or a group of meteorites to purely theoretical calculations. Production rates can vary with the chemical composition and the preatmospheric depth of the sample and with the size and shape of the object. While the production systematics for cosmogenic nuclides are fairly well known, our ability to predict their production rates can be improved, with a corresponding increase in the scientific return. Additional detailed studies of cosmogenic nuclides in extraterrestrial objects are needed, especially for fairly small and very large objects. Nuclides made in simulation experiments and cross sections for many major nuclear reactions should be measured. Such studies are especially needed for the long-lived radionuclides that have only recently become readily measurable by accelerator mass spectrometry. 34 refs., 5 figs.

  3. Stable nickel isotopes and cosmogenic berellium-b and aluniinum-26 in metallic spheroids from Meteor Crater, Arizona

    NASA Astrophysics Data System (ADS)

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

    1995-05-01

    The isotopic abundances of Ni in 17 metallic spheroids from Meteor Crater, Arizona, were determined by inductively coupled plasma mass spectrometry (ICP-MS). Sixteen spheroids have normal isotopic abundances. A 17th shows a marginally detectable mass fractionation of 0.40±0.14%/AMU in favor of the heavier isotopes. The general absence of mass fractionation indicates that open system evaporation caused little loss of Ni. Variable activities of the cosmogenic radionuclides 10Be and 26Al were measured by accelerator mass spectrometry in separate suites of spheroids. Activities of 26Al in most samples and of 10Be in metal cores separated from spheroids indicate that they either (1) come from greater depths in the parent meteoroid than do hand specimens, or (2) lost Al and Be during the process of spheroid formation. One individual spheroid has 10Be and 26Al activities comparable to those of bulk specimens. This result suggests that spheroid formation may occasionally include material from the outermost meter or so of the impactor. Relatively high activities of 10Be, ˜3 dpm/kg, in the siliceous shells of Canyon Diablo spheroids very likely have a meteoric origin.

  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. 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

  6. Constraining local subglacial bedrock erosion rates with cosmogenic nuclides

    NASA Astrophysics Data System (ADS)

    Wirsig, Christian; Ivy-Ochs, Susan; Christl, Marcus; Reitner, Jürgen; Reindl, Martin; Bichler, Mathias; Vockenhuber, Christof; Akcar, Naki; Schlüchter, Christian

    2014-05-01

    The constant buildup of cosmogenic nuclides, most prominently 10Be, in exposed rock surfaces is routinely employed for dating various landforms such as landslides or glacial moraines. One fundamental assumption is that no cosmogenic nuclides were initially present in the rock, before the event to be dated. In the context of glacially formed landscapes it is commonly assumed that subglacial erosion of at least a few meters of bedrock during the period of ice coverage is sufficient to remove any previously accumulated nuclides, since the production of 10Be ceases at a depth of 2-3 m. Insufficient subglacial erosion leads to overestimation of surface exposure ages. If the time since the retreat of the glacier is known, however, a discordant concentration of cosmogenic nuclides delivers information about the depth of subglacial erosion. Here we present data from proglacial bedrock at two sites in the Alps. Goldbergkees in the Hohe Tauern National Park in Austria and Gruebengletscher in the Grimsel Pass area in Switzerland. Samples were taken inside as well as outside of the glaciers' Little Ice Age extent. Measured nuclide concentrations are analyzed with the help of a MATLAB model simulating periods of exposure or glacial cover of user-definable length and erosion rates.

  7. Cosmogenic Nuclides in Metal and Stone Separates of an Antarctic L5/LL5 Chondrite Shower with a Large Pre-Atmospheric Size: QUE 90201

    NASA Technical Reports Server (NTRS)

    Welten, K. C.; Nishiizumi, K.; Caffee, M. W.; Masarik, J.; Leya, I.; Wieler, R.

    2002-01-01

    Based on cosmogenic radionuclides in stone and metal fractions, we identified six members of a large Antarctic L5/LL5 chondrite shower. The radionuclides suggest a pre-atmospheric radius of 100-200 cm and a cosmic-ray exposure age of at least 5 Myr. Additional information is contained in the original extended abstract.

  8. Water Mass Distribution and Particle Flux in the Arctic Ocean From Dissolved 10Be and 9Be Concentrations

    NASA Astrophysics Data System (ADS)

    Frank, M.; Porcelli, D.; Andersson, P.; Halliday, A. N.; Kubik, P. W.; Hattendorf, B.; Guenther, D.

    2002-12-01

    The Arctic Ocean basin is confined by landmasses similar to the Mediterranean. There is only little deep water formed seasonally on the shelves of the Arctic Ocean despite the low temperatures. This is due to a freshwater lid at the surface which originates from the Arctic rivers. The deeper Arctic Ocean water masses can thus only be renewed at comparatively low rates through the only deep connection to the Atlantic Ocean, the Fram Strait. At the same time the biogenic particulate fluxes in the central Arctic Ocean are very low due to perennial sea ice cover and the organic matter produced in the surface waters is remineralised efficiently. Detrital particle fluxes from either eolian or riverine sources are also very low. We will present the first combined dissolved 10Be (cosmogenic) and 9Be (continental sources) depth profiles from water samples of the major deep basins of the Arctic Ocean collected during the Swedish Arctic Ocean 2001 expedition. Be is 5-10 times less particle-reactive than other previously investigated radionuclides such as Th or Pa and should therefore even at the relatively low Arctic Ocean renewal rates serve as a quasi-conservative tracer for different origins of water masses (Atlantic Ocean/Norwegian Sea, Pacific Ocean, Arctic Shelves). 9Be and Nd isotope analyses provide complementary information on the pathways of dissolved material originating from the Arctic continents. Results obtained ten years ago at similar locations as in our study indicated a uniform distribution of 10Be at low values of 500 +/- 100 atoms/g suggesting restricted input and efficient homogenisation. In contrast, our new results show that in 2001 the inflowing waters from the Atlantic are traced by 10Be concentrations of up to 1100 atoms/g. In addition, the surface concentrations vary considerably. It will be discussed wether this is a consequence of a seasonal/decadal variability in the distribution of surface water masses, which has been deduced from oceanographic

  9. The 10Be contents of SNC meteorites

    NASA Technical Reports Server (NTRS)

    Pal, D. K.; Tuniz, C.; Moniot, R. K.; Savin, W.; Vajda, S.; Kruse, T.; Herzog, G. F.

    1986-01-01

    Several authors have explored the possibility that the Shergottites, Nakhlites, and Chassigny (SNC) came from Mars. The spallogenic gas contents of the SNC meteorites have been used to: constrain the sizes of the SNC's during the last few million years; to establish groupings independent of the geochemical ones; and to estimate the likelihood of certain entries in the catalog of all conceivable passages from Mars to Earth. The particular shielding dependence of Be-10 makes the isotope a good probe of the irradiation conditions experienced by the SNC meteorites. The Be-10 contents of nine members of the group were measured using the technique of accelerator mass spectrometry. The Be-10 contents of Nakhla, Governador Valadares, Chassigny, and probably Lafayette, about 20 dpm/kg, exceed the values expected from irradiation of the surface of a large body. The Be-10 data therfore do not support scenario III of Bogard et al., one in which most of the Be-10 in the SNC meteorites would have formed on the Martian surface; they resemble rather the Be-10 contents found in many ordinary chondrites subjected to 4 Pi exposures. The uncertainties of the Be-10 contents lead to appreciable errors in the Be-10 ages, t(1) = -1/lambda ln(1 Be-10/Be-10). Nonetheless, the Be-10 ages are consistent with the Ne-21 ages calculated assuming conventional, small-body production rates and short terrestrial ages for the finds. It is believed that this concordance strengthens the case for at least 3 different irradiation ages for the SNC meteorites. Given the similar half-thicknesses of the Be-10 and Ne-21 production rates, the ratios of the Be-10 and Ne-21 contents do not appear consistent with common ages for any of the groups. In view of the general agreement between the Be-10 and Ne-21 ages it does not seem useful at this time to construct multiple-stage irradiation histories for the SNC meteorites.

  10. Catchment-scale denudation and chemical erosion rates determined from 10Be and mass balance geochemistry (Mt. Lofty Ranges of South Australia)

    NASA Astrophysics Data System (ADS)

    Bestland, Erick A.; Liccioli, Caterina; Soloninka, Lesja; Chittleborough, David J.; Fink, David

    2016-10-01

    Global biogeochemical cycles have, as a central component, estimates of physical and chemical erosion rates. These erosion rates are becoming better quantified by the development of a global database of cosmogenic radionuclide 10Be (CRN) analyses of soil, sediment, and outcrops. Here we report the denudation rates for two small catchments (~ 0.9 km2) in the Mt. Lofty Ranges of South Australia as determined from 10Be concentrations from quartz sand from the following landscape elements: 1) dissected plateaux, or summit surfaces (14.10 ± 1.61 t km- 2 y- 1), 2) sandstone outcrops (15.37 ± 1.32 t km- 2 y- 1), 3) zero-order drainages (27.70 ± 1.42 t km- 2 y- 1), and 4) stream sediment which reflect a mix of landscape elements (19.80 ± 1.01 t km- 2 y- 1). Thus, the more slowly eroding plateaux and ridges, when juxtaposed with the more rapidly eroding side-slopes, are leading to increased relief in this landscape. Chemical erosion rates for this landscape are determined by combining cosmogenic denudation rates with the geochemical mass balance of parent rock, soil and saprolite utilizing zirconium immobility and existing mass balance methods. Two different methods were used to correct for chemical weathering and erosion in the saprolite zone that is shielded at depth from CRN production. The corrected values are higher than uncorrected values: total denudation of 33.24 or 29.11 t km- 2 y- 1, and total chemical erosion of 15.64 or 13.68 t km- 2 y- 1. Thus, according to these methods, 32-40% of the denudation is taking place by chemical weathering and erosion in the saprolite below CRN production depth. Compared with other similar areas, the overall denudation and chemical erosion rates are low. In most areas with sub-humid climates and tectonic uplift, physical erosion is much greater than chemical erosion. The low physical erosion rates in these Mt. Lofty Range catchments, in what is a relatively active tectonic setting, are thought to be due to low rainfall intensity

  11. Effects of Bedrock Landsliding on Cosmogenically Determined Erosion Rates

    NASA Technical Reports Server (NTRS)

    Niemi, Nathan; Oskin, Mike; Burbank, Douglas; Heimsath, Arjun

    2005-01-01

    The successful quantification of long-term erosion rates underpins our understanding of landscape. formation, the topographic evolution of mountain ranges, and the mass balance within active orogens. The measurement of in situ-produced cosmogenic radionuclides (CRNs) in fluvial and alluvial sediments is perhaps the method with the greatest ability to provide such long-term erosion rates. In active orogens, however, deep-seated bedrock landsliding is an important erosional process, the effect of which on CRN-derived erosion rates is largely unquantified. We present a numerical simulation of cosmogenic nuclide production and distribution in landslide-dominated catchments to address the effect of bedrock landsliding on cosmogenic erosion rates in actively eroding landscapes. Results of the simulation indicate that the temporal stability of erosion rates determined from CRN concentrations in sediment decreases with increased ratios of landsliding to sediment detachment rates within a given catchment area, and that larger catchment areas must be sampled with increased frequency of landsliding in order to accurately evaluate long-term erosion rates. In addition, results of this simulation suggest that sediment sampling for CRNs is the appropriate method for determining long-term erosion rates in regions dominated by mass-wasting processes, while bedrock surface sampling for CRNs is generally an ineffective means of determining long-term erosion rates. Response times of CRN concentrations to changes in erosion rate indicate that climatically driven cycles of erosion may be detected relatively quickly after such changes occur, but that complete equilibration of CRN concentrations to new erosional conditions may take tens of thousands of years. Simulation results of CRN erosion rates are compared with a new, rich dataset of CRN concentrations from the Nepalese Himalaya, supporting conclusions drawn from the simulation.

  12. The 41Ca bomb pulse and atmospheric transport of radionuclides

    NASA Astrophysics Data System (ADS)

    Zerle, L.; Faestermann, T.; Knie, K.; Korschinek, G.; Nolte, E.; Beer, J.; Schotterer, U.

    1997-08-01

    For the first time, the 41Ca signal from the nuclear weapon tests has been measured. Calcium 41 concentrations have been determined in alpine ice of the Fiescherhorn glacier (Switzerland) with accelerator mass spectrometry. The peak concentrations have been observed to be about 3×106 atoms of 41Ca per kilogram of ice in. the 1950s. It has been found that 41Ca is produced essentially by the atoll bombs. A universal box model, able to describe atmospheric transport of radionuclides that are in gaseous form or attached to aerosols, has been developed. The model has been applied to calculate the bomb pulses of 14C, 36Cl, 41Ca, 90Sr, and 137Cs, For the transport of radionuclides that are attached to aerosols such as 41Ca, 90Sr, and 137Cs, sedimentation (gravitational settling) in the upper stratosphere has been taken into account. It has been found that the deposition of bomb-produced 36Cl on the Earth's surface is delayed compared to that of 90Sr by about 1 year because 36Cl stays gaseous in the stratosphere. The model can also be used to calculate the deposition of cosmogenic radionuclides, e.g., 36Cl and 10Be, in their natural archives, such as polar ice sheets.

  13. Calibrating a long-term meteoric 10Be accumulation rate in soil

    NASA Astrophysics Data System (ADS)

    Reusser, Lucas; Graly, Joseph; Bierman, Paul; Rood, Dylan

    2010-10-01

    Using 13 samples collected from a 4.1 meter profile in a well-dated and stable New Zealand fluvial terrace, we present the first long-term accumulation rate for meteoric 10Be in soil (1.68 to 1.72 × 106 at/(cm2·yr)) integrated over the past ˜18 ka. Site-specific accumulation data, such as these, are prerequisite to the application of meteoric 10Be in surface process studies. Our data begin the process of calibrating long-term meteoric 10Be delivery rates across latitude and precipitation gradients. Our integrated rate is lower than contemporary meteoric 10Be fluxes measured in New Zealand rainfall, suggesting that long-term average precipitation, dust flux, or both, at this site were less than modern values. With accurately calibrated long-term delivery rates, such as this, meteoric 10Be will be a powerful tool for studying rates of landscape change in environments where other cosmogenic nuclides, such as in situ 10Be, cannot be used.

  14. 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

  15. Cosmogenic radionuclides in the Allende and Murchison carbonaceous chondrites.

    NASA Technical Reports Server (NTRS)

    Cressy, P. J., Jr.

    1972-01-01

    Measurements were made of Na-22, Al-26, Mn-54, and Co-60 produced by cosmic rays in five samples of the Allende C3 meteorite and in one specimen of Murchison (C2); Sc-46, V-48, Cr-51, and Co-57 were also measured in several of these samples. Comparison of observed Allende Co-60 activities with calculated neutron-capture production rates yields a depth scale for Allende that appears unambiguous to about 30-cm depth. Using this scale, the production of Al-26 is constant to a depth in excess of 30 cm, Na-22 activity increases 30% from near the surface of Allende to 20- to 30-cm depth, and Mn-54 production increases 50% over the same depth range.

  16. Cosmogenic Radionuclides in Recently Fallen Chondrites Mihonoseki and Tahara

    NASA Astrophysics Data System (ADS)

    Shima, M.; Honda, M.; Yabuki, S.; Takahashi, K.

    1993-07-01

    Introduction: The chondrite Mihonoseki, L6, 6.38 kg, fell on December 10, 1992 [1]. The other chondrite, Tahara, fell on March 26, 1991, on the deck of car- carrier ship, M.S. Century-Highway No.1 of Kawasaki Kisen Kaisha Ltd., anchored at T-3 berth of Toyota Pier, at Toyohashi harbor, in Tahara-Center, Toyota Motor Corp., Tahara-machi, Atsumi-gun, Aichi-ken, Japan. Although the total mass is estimated to be more than 5 kg, only several fragments were recovered by crews. In fact, this was recognized by the event of Mihonoseki. Tahara was classified as H5 [2]. Gamma-Ray Counting: With whole mass of Mihonoseki, nondestructive gamma-ray countings started on December 15, 1992, using a pure Ge detector (ORTEC), 45 mm x 39 mm, horizontal type. Data collections were performed every day in the beginning and later about every week through February 3, 1993. A sample chamber was shielded with 15-cm-thick lead, 6-cm-thick iron, and 0.5-cm-thick plastic plates. For Tahara, another set (Canberra), 44 mm x 42 mm, coaxial type, was used. The 420-g fragment was mounted in the sample chamber shielded with 15-cm-thick lead, 2-cm-thick iron, 2-cm-thick copper, and 2-cm-thick plastic plates. The counting started in January 1993. The counting efficiencies for gamma rays as a function of energy, ranging between 122 keV (57Co) and 1809 keV (26Al), have been determined using three different standards. A mixed standard solution of nine-species gamma-ray emitters, QCY-44, reference time 12:00 GMT on February 1, 1993, was supplied from Amersham, England. The solution was dropped onto (1) chips of Al-foil, (2) chips of filter paper, or (3) olivine sand. Those standards were mixed thoroughly with mock materials, fine and coarse olivine sand and iron powder, and reagent KCl, standard for 40K, then filled into mock shells of Mihonoseki and Tahara, which were made of hard plastic and aluminum foil with epoxy resin, respectively. For Tahara, mocks with all three types of standards were examined for comparison, while for Mihonoseki only (3) was used. The difficulty was to prepare a suitable mock sample having the same density as chondrites 3.5. Especially for a large sample like Mihonoseki, even when we use about equal fractions of olivine sand and metallic iron, the weight of the mock was about 80%, and when we intend to obtain heavier than 90%, we have to use a larger portion of metallic iron, which causes some reductions in the efficiencies of 20-30%, depending on energies. Results: The contents of 14 gamma emitters were studied as shown in the Table (which appears in the hard copy). Errors quoted are only from counting statistics. The most striking may be to learn that Mihonoseki contains a very low level of 60Co; the content is lower than 1 dpm/kg, which could not be determined accurately by a current-direct gamma counting. This reflects the smaller preatmospheric size of the body, and consistent with other observations such as 22Ne/21Ne = 1.180 [1] and lower activity levels of general products such as 46 dpm 26Al/kg, which is about three-fourths of a common level among L chondrites. Besides, relatively high 56Co in respect to 58Co is also noticed in Mihonoseki. References: [1] Shima M. et al.(1993) LPSC XXIV 1297-1298. [2] Shima M. et al.(1993) Meteoritical Bull., in press.

  17. Cosmogenic helium in a terrestrial igneous rock

    NASA Technical Reports Server (NTRS)

    Kurz, M. D.

    1986-01-01

    New helium isotopic measurements on samples from the Kula formation of Haleakala volcano of Hawaii are presented that are best explained by an in situ cosmogenic origin for a significant fraction of the He-3. Results from crushing and stepwise heating experiments, and consideration of the exposure age of the sample at the surface and the cosmic ray fluxes strongly support this hypothesis. Although crustal cosmogenic helium has been proposed previously, this represents its first unambiguous identification in a terrestrial sample.

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

    NASA Astrophysics Data System (ADS)

    von Blanckenburg, Friedhelm; Bouchez, Julien; Wittmann, Hella

    2012-10-01

    The isotope ratio of the meteoric cosmogenic nuclide 10Be to the mineral-derived stable isotope 9Be discloses both the Earth surface denudation rate and its weathering intensity. We develop a set of steady state mass balance equations that describes this system from a soil column over the hillslope scale to an entire river basin. The prerequisites making this new approach possible are: (1) the 9Be concentration of parent rock (typically 2.5±0.5 ppm in granitic and clastic sedimentary lithologies) is known; (2) both Be isotopes equilibrate between the fluids decomposing rock and reactive solids formed during weathering; and (3) a critical spatial scale is exceeded at which the fluxes of both isotopes into and out of the weathering zone are at steady state over the time scale of weathering (typically ˜10 kyr). For these cases the isotope ratios can be determined in bulk sediment or soil, on leachates from the reactive (adsorbed and pedogenic mineral-bound) phase in sediment or soil, and even on the dissolved phase in river water. The 10Be/9Be ratio offers substantial advantages over the single-isotope system of meteoric 10Be. The latter system allows to directly determine erosion rates only in the case that 10Be is fully retentive in the weathering zone and that riverine sorting has not introduced grain size-dependent 10Be concentration gradients in sediments. We show the feasibility of the 10Be/9Be tracer approach at the river scale for sediment and water samples in the Amazon basin, where independent estimates of denudation rates from in situ-produced 10Be exist. We furthermore calculate meaningful denudation rates from a set of published 10Be/9Be ratios measured in the dissolved load of globally distributed rivers. We conclude that this isotope ratio can be used to reconstruct global paleo-denudation from sedimentary records.

  19. Cosmogenic nuclide-derived sediment budget of the Amazon basin

    NASA Astrophysics Data System (ADS)

    Wittmann, Dr.; von Blanckenburg, Dr.; Guyot, Dr.; Maurice, Dr.; Kubik, Dr.

    2009-04-01

    Sediment gauging suggests that the annual sediment mass discharged into the main Amazon basin from the Andes and the cratonic shields is not in steady state with the mass discharged to the Atlantic Ocean. Here we use sediment production rates from cosmogenic 10Be in sediment to compare these with transport rates from river load gauging. About 1 million km2 or 95% of the total Andean area draining to the Amazon provide sediment to the central Amazon river with an averaged 10Be nuclide concentration of 5.0 +- 0.5x1e4 at/g(Qz). Average nuclide concentrations for Brazilian shield headwaters amount to 15.3 +- 1.2x1e4 at/g(Qz), and to 38.6 +- 2.4x1e4 at/g(Qz) for the Guyana shield headwaters, respectively. For the Andes, nuclide concentrations translate to an integrated Andean denudation rate of 0.35 ± 0.05 mm/yr. Sediment from the headwaters of the Brazilian and Guyana shields translate into very low denudation rates (0.02 and 0.01 mm/yr, respectively), as is expected for tectonically stable tropical highlands. These headwater 10Be nuclide concentrations and derived denudation rates can now be compared with those derived from central Amazon stream sediment including the main Amazon, which was sampled over ~1000 km from Manaus to Óbidos. Cosmogenic nuclide concentration analyses of several grain sizes (from 125 up to 800 µm) show large variations; we found that coarse-grained material records the nuclide signal of the cratonic shield areas, whereas the Andean signal is best represented by the fine sand fraction, which is preserved virtually unaltered over 1000s of km of sediment transport. In all central Amazon trunk stream samples and tributaries, the fine grain size fraction (125-250 µm) contains 10Be at 6.5 +- 1.2x1e4 at/g(Qz), which is similar to that of the Andean source areas. The integrated denudation rate from this fraction is 0.23 +- 0.04 mm/yr for the entire Amazon basin at Óbidos, which compares well with the mean Andean denudation rate of 0.35 +- 0.05 mm

  20. 10Be climate fingerprints during the Eemian in the NEEM ice core, Greenland

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

  1. 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

  2. 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.

  3. Cosmogenic records in Antarctic meteorites

    NASA Technical Reports Server (NTRS)

    Goswami, J. N.; Nishiizumi, K.

    1983-01-01

    Aliquot samples of 29 Antarctic L and H chondrites are analyzed for their nuclear track records and Mn-53 activities. The track density in the analyzed samples ranges from 10 to the 4th to approximately 6 x 10 to the 6th per sq cm. A significant finding is the observation of track-rich grains in a set of four L3 chondrites (ALHA 77215, 77216, 77217, and 77252), suspected of belonging to the same fall based on petrographic observations. An additional sample, ALHA 78105, an L6 chondrite, also has track-rich grains. Mn-53 activity is at near saturation level in approximately 65 percent of the analyzed samples, suggesting exposure ages of greater than 10 m.y. in these cases. Very few H chondrites from the 7-m.y. exposure age peak are apparently sampled among the ones investigated in this study. Approximately 6 percent and 4 percent, respectively, of the Antarctic H and L chondrites analyzed thus far for their cosmogenic records have precompaction irradiation features. A combined analysis of Mn-53 and nuclear track data makes it possible to confirm or rule out the proposed pairing of several sets of Antarctic meteorites and to estimate the preatmospheric sizes of some of these meteorites. The results suggest that most of the small Antarctic meteorites (less than 1 kg) have suffered high (greater than 95 percent) ablation mass-loss.

  4. 10Be inventories in Alpine soils and their potential for dating land surfaces

    NASA Astrophysics Data System (ADS)

    Egli, Markus; Brandová, Dagmar; Böhlert, Ralph; Favilli, Filippo; Kubik, Peter W.

    2010-07-01

    To exploit natural sedimentary archives and geomorphic landforms it is necessary to date them first. Landscape evolution of Alpine areas is often strongly related to the activities of glaciers in the Pleistocene and Holocene. At sites where no organic matter for radiocarbon dating exists and where suitable boulders for surface exposure dating (using in situ produced cosmogenic nuclides) are absent, dating of soils could give information about the timing of landscape evolution. This paper explores the applicability of soil dating using the inventory of meteoric 10Be in Alpine soils. For this purpose, a set of 6 soil profiles in the Swiss and Italian Alps was investigated. The surface at these sites had already been dated (using the radiocarbon technique or the surface exposure determination using in situ produced 10Be). Consequently, a direct comparison of the ages of the soils using meteoric 10Be and other dating techniques was made possible. The estimation of 10Be deposition rates is subject to severe limitations and strongly influences the obtained results. We tested three scenarios using a) the meteoric 10Be deposition rates as a function of the annual precipitation rate, b) a constant 10Be input for the Central Alps, and c) as b) but assuming a pre-exposure of the parent material. The obtained ages that are based on the 10Be inventory in soils and on scenario a) for the 10Be input agreed reasonably well with the age using surface exposure or radiocarbon dating. The ages obtained from soils using scenario b) produced ages that were mostly too old whereas the approach using scenario c) seemed to yield better results than scenario b). Erosion calculations can, in theory, be performed using the 10Be inventory and 10Be deposition rates. An erosion estimation was possible using scenario a) and c), but not using b). The calculated erosion rates using these scenarios seemed to be plausible with values in the range of 0-57 mm/ky. The dating of soils using 10Be has

  5. Late Cenozoic Himalayan Erosion Rates Revealed by Cosmogenic Isotopes in Foreland Sediments, Northern India

    NASA Astrophysics Data System (ADS)

    Scherler, D.; Barnes, J. B.; Insel, N.; Densmore, A.

    2015-12-01

    Most surface processes that transport sediment are influenced by climate. For example, more rainfall enhances runoff and stream capacity, and colder temperatures expand glaciers at the expense of rivers. Late Cenozoic cooling and glacial cycles during the Quaternary should thus have affected erosion of the Earth's surface. But whether these changes were also associated with an overall increase of erosion rates is not clear. Here, we assess the erosional response of the fluvial-dominated Yamuna catchment in the Garhwal Himalaya, northern India, to late Cenozoic cooling and Quaternary climatic oscillations. Our approach is to measure cosmogenic radionuclide (10Be) concentrations in fluvial sediments (n = 14) eroded from uplifting foreland deposits and compare them with modelled concentrations for different paleo-erosion rate scenarios. This approach differs from previous ones that determine paleo-erosion rates from 10Be concentrations in distinct samples from stratigraphic sections, and avoids misinterpreting short-term fluctuations in 10Be concentrations that are unrelated to erosion rates. We tested this approach in the Mohand Range in northwest India, where Miocene to Quaternary deposits of the paleo-Yamuna River are actively uplifting, and where a robust kinematic model and published stratigraphic age constraints exist. Our model free parameters are the shortening rate across the Main Frontal Thrust (MFT) and the onset of shortening, within a known amount of total MFT slip (4-5 km). Preliminary results show that we can reproduce the measured 10Be concentrations best when Himalayan erosion rates were lower in the past than they are now, or have been increasing towards the present. Within uncertainties, the best-fit parameter combinations give shortening rates between 10 and 20 mm/yr, which is consistent with independent estimates from a nearby dated strath terrace and expected uplift rates based on channel steepness indices. Scenarios in which erosion rates are

  6. Production rates of cosmogenic nuclei on the lunar surface

    NASA Astrophysics Data System (ADS)

    Dong, Tie-Kuang; Yun, Su-Jun; Ma, Tao; Chang, Jin; Dong, Wu-Dong; Zhang, Xiao-Ping; Li, Guo-Long; Ren, Zhong-Zhou

    2014-07-01

    A physical model for Geant4-based simulation of the galactic cosmic ray (GCR) particles' interaction with the lunar surface matter has been developed to investigate the production rates of cosmogenic nuclei. In this model the GCRs, mainly very high energy protons and α particles, bombard the surface of the Moon and produce many secondary particles, such as protons and neutrons. The energies of protons and neutrons at different depths are recorded and saved as ROOT files, and the analytical expressions for the differential proton and neutron fluxes are obtained through the best-fit procedure using ROOT software. To test the validity of this model, we calculate the production rates of the long-lived nuclei 10Be and 26Al in the Apollo 15 long drill core by combining the above differential fluxes and the newly evaluated spallation reaction cross sections. Our numerical results show that the theoretical production rates agree quite well with the measured data, which means that this model works well. Therefore, it can be expected that this model can be used to investigate the cosmogenic nuclei in future lunar samples returned by the Chinese lunar exploration program and can be extended to study other objects, such as meteorites and the Earth's atmosphere.

  7. 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

  8. Radionuclide Therapy

    NASA Astrophysics Data System (ADS)

    Zalutsky, M. R.

    Radionuclide therapy utilizes unsealed sources of radionuclides as a treatment for cancer or other pathological conditions such as rheumatoid arthritis. Radionuclides that decay by the emission of β and α particles, as well as those that emit Auger electrons, have been used for this purpose. In this chapter, radiochemical aspects of radionuclide therapy, including criteria for radionuclide selection, radionuclide production, radiolabeling chemistry, and radiation dosimetry are discussed.

  9. Cosmogenic nuclides in the solar gas-rich H3-6 chondrite breccia Frontier Mountain 90174

    NASA Astrophysics Data System (ADS)

    Leya, I.; Welten, K. C.; Nishiizumi, K.; Caffee, M. W.

    2009-03-01

    We re-evaluated the cosmic-ray exposure history of the H3-6 chondrite shower Frontier Mountain (FRO) 90174, which previously was reported to have a simple exposure history, an irradiation time of about 7 Ma, and a pre-atmospheric radius of 80-100 cm (Welten et al. 2001). Here we measured the concentrations and isotopic compositions of He, Ne, and Ar in 8 aliquots of 6 additional fragments of this shower, and 10Be and 26Al in the stone fractions of seven fragments. The radionuclide concentrations in the stone fractions, combined with those in the metal fractions, confirm that all samples are fragments of the FRO 90174 shower. Four of the fragments contain solarwind- implanted noble gases with a solar 20Ne/22Ne ratio of ˜12.0, indicating that FRO 90174 is a regolith breccia. The concentrations of solar gases and cosmogenic 21Ne in the samples analyzed by us and by Welten et al. (2001) overlap with those of the FRO H-chondrites from the 1984 season, suggesting that many of these samples are also part of the large FRO 90174 chondrite shower. The cosmogenic 21Ne concentrations in FRO 90174 show no simple correlation with 10Be and 26Al activities. We found 21Ne excesses between 0.3-1.1 × 10-8 cm3 STP/g in 6 of the 17 samples. Since excess 21Ne and trapped solar gases are not homogeneously distributed, i.e., we found in one fragment aliquots with and without excess 21Ne and solar 20Ne, we conclude that excess 21Ne is due to GCR irradiation of the regolith before compaction of the FRO 90174 object. Therefore, the chondrite shower FRO 90174 did not simply experience an exposure history, but some material was already irradiated at the surface of an asteroid leading to excess 21Ne. This excess 21Ne is correlated to implanted solar gases, clearly indicating that both processes occurred on the regolith.

  10. 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. 

  11. 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

  12. 10Be-derived Himalayan denudation rates and sediment budgets in the Ganga basin

    NASA Astrophysics Data System (ADS)

    Lupker, Maarten; Blard, Pierre-Henri; Lavé, Jérôme; France-Lanord, Christian; Leanni, Laetitia; Puchol, Nicolas; Charreau, Julien; Bourlès, Didier

    2012-06-01

    The Himalayas represent the archetype of mountain building due to active continental collision and are considered in many studies as the locus of intense interactions between climate, denudation and tectonics. Estimates of modern denudation rates across the entire range remain, however, relatively sparse. In this study, in situ-produced cosmogenic 10Be concentrations were measured in detritic quartz in order to determine basin-scale denudation rates for the central part of the Himalayan range. River sand was sampled over several years in the main trans-Himalayan rivers, from the Himalayan front to the Ganga outlet in Bangladesh. The calculated 10Be denudation rates of the trans-Himalayan river basins range from 0.5 to 2.4 mm yr-1 (average 1.3 mm yr-1) and vary by up to a factor of 3 between sampling years. These denudation rates strongly contrast with the 0.007 mm yr-1 denudation rate of southern tributary basins draining the Indian craton. This work also shows that in the Ganga basin, no systematic evolution of average 10Be concentrations is observed during floodplain transfer, implying that distal samples can be used to estimate the integrated denudation rate of the whole central Himalayan range. Samples from the Ganga in Bangladesh display remarkably low variability in 10Be concentration, implying an average Himalayan denudation rate of 1.0-1.1 mm yr-1. However, within the floodplain, several samples suggest a recent perturbation of sediment transport dynamics with a recent increase in the relative sediment contribution from southern tributaries. The Himalayan sediment flux, deduced from the 10Be denudation rate of the range, is 610±230 Mt yr-1. This flux is consistent, within uncertainty, with sediment fluxes derived from sediment gauging. The similarity of the two flux estimates suggests that Himalayan erosion fluxes have remained stable over the last centuries, even if the large uncertainties associated with each method hamper more precise assessments.

  13. FLUKA: Predictive power for cosmogenic backgrounds

    SciTech Connect

    Empl, A. Hungerford, E. V.; Ferrari, A.; Smirnov, G. I.

    2015-08-17

    The next generation of experiments searching for rare physics events with increased sensitivity will require precise predictions of cosmogenic backgrounds. Recent high quality deep underground measurements for cosmogenic neutrons in large liquid scintillator targets were used to study the FLUKA simulation package for this purpose. The results and conclusions drawn from a detailed benchmark comparison with data from the Borexino experiment were reported recently. In general, good agreement between data and simulation results were found with some identified discrepancies. Improved physics models already implemented in the current version of the FLUKA code, which will be publicly available with the upcoming code release, address the more important identified issues. A careful evaluation of the improved predictions is ongoing. However, the agreement between preliminary FLUKA simulation results and the Borexino experimental data are excellent. The preliminary findings will be discussed.

  14. FLUKA: Predictive power for cosmogenic backgrounds

    NASA Astrophysics Data System (ADS)

    Empl, A.; Ferrari, A.; Hungerford, E. V.; Smirnov, G. I.

    2015-08-01

    The next generation of experiments searching for rare physics events with increased sensitivity will require precise predictions of cosmogenic backgrounds. Recent high quality deep underground measurements for cosmogenic neutrons in large liquid scintillator targets were used to study the FLUKA simulation package for this purpose. The results and conclusions drawn from a detailed benchmark comparison with data from the Borexino experiment were reported recently. In general, good agreement between data and simulation results were found with some identified discrepancies. Improved physics models already implemented in the current version of the FLUKA code, which will be publicly available with the upcoming code release, address the more important identified issues. A careful evaluation of the improved predictions is ongoing. However, the agreement between preliminary FLUKA simulation results and the Borexino experimental data are excellent. The preliminary findings will be discussed.

  15. 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.

  16. Age of Zhoukoudian Homo erectus determined with (26)Al/(10)Be burial dating.

    PubMed

    Shen, Guanjun; Gao, Xing; Gao, Bin; Granger, Darryl E

    2009-03-12

    The age of Zhoukoudian Homo erectus, commonly known as 'Peking Man', has long been pursued, but has remained problematic owing to the lack of suitable dating methods. Here we report cosmogenic (26)Al/(10)Be burial dating of quartz sediments and artefacts from the lower strata of Locality 1 in the southwestern suburb of Beijing, China, where early representatives of Zhoukoudian Homo erectus were discovered. This study marks the first radioisotopic dating of any early hominin site in China beyond the range of mass spectrometric U-series dating. The weighted mean of six meaningful age measurements, 0.77 +/- 0.08 million years (Myr, mean +/- s.e.m.), provides the best age estimate for lower cultural layers 7-10. Together with previously reported U-series dating of speleothem calcite and palaeomagnetic stratigraphy, as well as sedimentological considerations, these layers may be further correlated to S6-S7 in Chinese loess stratigraphy or marine isotope stages (MIS) 17-19, in the range of approximately 0.68 to 0.78 Myr ago. These ages are substantially older than previously supposed and may imply early hominin's presence at the site in northern China through a relatively mild glacial period corresponding to MIS 18.

  17. Radionuclide trap

    DOEpatents

    McGuire, Joseph C.

    1978-01-01

    The deposition of radionuclides manganese-54, cobalt-58 and cobalt-60 from liquid sodium coolant is controlled by providing surfaces of nickel or high nickel alloys to extract the radionuclides from the liquid sodium, and by providing surfaces of tungsten, molybdenum or tantalum to prevent or retard radionuclide deposition.

  18. 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.

  19. 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

  20. 10Be, OSL/IRSL Luminescence and 14C Cross-Dating of a Series of Abandoned Alluvial Surfaces Laterally Offset by the Dead Sea Fault, Jordan

    NASA Astrophysics Data System (ADS)

    Le Beon, M.; Jaiswal, M.; Al-Qaryouti, M.; Moumani, K.; Burr, G. S.; Chen, Y.; Klinger, Y.; Abdelghafoor, M.; Suppe, J.

    2010-12-01

    Active tectonics studies are often limited by the uncertainties in accurately and precisely dating Late Quaternary deposits, especially alluvial deposits that often lack organic matter datable by 14C method. This is the case along the Wadi Araba Fault (WAF), the southernmost segment of the Dead Sea Fault, which delineates the 1000-km long plate boundary between the Arabia plate and the Sinai sub-plate. Geodetic, geomorphic and geologic studies converge to a fault slip rate of 5 ± 2 mm/a. Yet, long-term Late Pleistocene slip rates cover a wide range due to large uncertainties, mostly related 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 seismic behavior of the WAF, we targeted one of the sites previously investigated for detailed morphotectonic analysis and 10Be CRN dating and we apply other chronometers, such as Optically stimulated luminescence (OSL) dating on quartz and feldspar minerals, and 14C dating when possible. The site consists in an abandoned bajada composed of four alluvial surface levels, offset by the WAF. We extensively sampled the terraces F2 and F4, which are offset by 160 ± 8 m and 626 ± 37 m, respectively. Our samples are collected from ~50-cm deep pits on the top of the terraces. On F2, we collected one OSL sample downstream from the fault and two upstream, where land snail shells were also found. Preliminary OSL ages agree on ~8 ± 2 ka upstream, also consistent with a 14C date, whereas the OSL age downstream is much older, ~41 ± 4 ka. On F4, we collected three samples downstream from the fault and two upstream. Preliminary OSL ages cluster between ~32 ± 4 ka and ~46 ± 5 ka. Five of the OSL samples have been collected at a similar location to surficial cobbles for 10Be, both on

  1. Reconstructing the recent failure chronology of a multistage landslide complex using cosmogenic isotope concentrations: St Catherine's Point, UK

    NASA Astrophysics Data System (ADS)

    Barlow, John; Moore, Roger; Gheorghiu, Delia M.

    2016-09-01

    The pre-existing multistage landslide complex at St Catherine's Point comprises a series of large rotational and translational failures that form the western section of the Isle of Wight Undercliff, UK. Cosmogenic beryllium and aluminum concentrations extracted from chert samples of the Upper Greensand are used to date the most recent sequential failure events. We use our understanding of the failure mechanics and landslide geomorphology to produce a cosmogenic exposure model that incorporates pre-failure topography into our shielding calculations. This method allowed us to date two successive landslides at the site using 10Be, the most recent of which occurred ~ 1064 ± 348 (± 1 σ) 10Be years ago, much more recently than was previously thought. An earlier failure event is dated at ~ 3471 ± 348 10Be years, supporting the hypothesis that the St Catherine's Point landslide complex was reactivated by relative sea-level rise at the end of the Holocene Climatic Optimum period.

  2. A Model for Interpreting 10Be Basin-Wide Erosion Rates in Post-Glacial Environments, Northwest Scotland

    NASA Astrophysics Data System (ADS)

    Fame, M. L.; Owen, L. A.; Balco, G.; Spotila, J. A.

    2015-12-01

    Meaningful interpretation of in-situ cosmogenic 10Be basin-wide erosion rates in slowly eroding postglacial catchments is complicated because 10Be is inherited through shifts between glacial and fluvial regimes and ice shielding prevents 10Be production. Such environments do not attain isotopic and landscape steady state, conditions necessary for the current method of calculating basin-wide erosion rates. We propose an alternate set of assumptions, specific to postglacial regions, which make it possible to calculate basin-wide erosion rates in the post-glacial Highlands of NW Scotland. From 20 Scottish basins basin-wide 10Be concentrations range from 2.129 x 104 to 4.870 x 104 atoms/g qtz. Average 10Be concentrations from shallow till and bank deposits within the basins are 2.856 x 104 atoms/g qtz, similar to the basin-wide concentrations, whereas average bedrock concentrations in the basins are 1.747 x 105 atoms/g qtz. This suggests that during the postglacial time most active sediment is derived from reworked deposits rather then sub-aerially eroded bedrock. Therefore, we make the simplifying assumption that most bedrock erosion occurs during glaciation. A deeply buried till that has experienced no nuclide production since deglaciation has a 10Be concentration of 6.810 x 103 atoms/g qtz and allows us to estimate how much of the 10Be in basin-wide samples was produced since deglaciation. A glacial ice thickness of only 2 m would shield all 10Be production; therefore we assume that no 10Be production occurred during glacial periods and that all production occurs during interglacial periods. Using 100 ka as the approximate duration of a Pleistocene glacial-interglacial cycle, comprised of a 15 ka interglacial period and an 85 ka glacial period, and the aforementioned assumptions we have derived a numerical model to calculate basin-wide glacial erosion rates in NW Scotland.

  3. Bridging the timescales between thermochronological and cosmogenic nuclide data

    NASA Astrophysics Data System (ADS)

    Glotzbach, Christoph

    2015-04-01

    Reconstructing the evolution of Earth's landscape is a key to understand its future evolution and to identify the driving forces that shape Earth's surface. Cosmogenic nuclide and thermochronological methods are routinely used to quantify Earth surface processes over 102-104 yr and 106-107 yr, respectively (e.g. Lal 1991; Reiners and Ehlers 2005; von Blanckenburg 2006). A comparison of the rates of surface processes derived from these methods is, however, hampered by the large difference in their timescales. For instance, a constant erosion rate of 0.1 mm/yr yield an apatite (U-Th)/He age of ~24 Ma and a 10Be age of ~6 ka, respectively. Analytical methods that bridge this time gap are on the way, but are not yet fully established (e.g. Herman et al. 2010). A ready to use alternative are river profiles, which record the regional uplift history over 102-107 yr (e.g. Pritchard et al. 2009). Changes in uplift are retained in knickzones that propagate with a distinct velocity upstream, and therefore the time of an uplift event can be estimated. Here I present an integrative inverse modelling approach to simultaneously reconstruct river profiles, model thermochronological and cosmogenic nuclide data and to derive robust information about landscape evolution over thousands to millions of years. An efficient inversion routine is used to solve the forward problem and find the best uplift history and erosional parameters that reproduce the observed data. I test the performance of the algorithm by inverting a synthetic dataset and a dataset from the Sila massif (Italy). Results show that even complicated uplift histories can be reliably retrieved by the combined interpretation of river profiles, thermochronological and cosmogenic nuclide data. References Gallagher, K., Brown, R. & Johnson, C. (1998): Fission track analysis and its applications to geological problems. - Annu. Rev. Earth Planet., 26: 519-572. Herman, F., Rhodes, E.J., Braun, J. & Heiniger, L. (2010): Uniform

  4. Lithogenic and cosmogenic tracers in catchment hydrology

    SciTech Connect

    Nimz, G.J.

    1995-01-01

    A variety of physical processes affect solute concentrations within catchment waters. The isotopic compositions of the solutes can indicate which processes have determined the observed concentrations. These processes together constitute the physical history of the water, which is one of the primary concerns in hydrology. Many groundwater solutes are derived as a result of interaction between the water and the rock and/or soil within the system. These are termed {open_quotes}lithogenic{close_quotes} solutes. The isotopic compositions of these solutes provide information regarding rock-water interactions. Many other solutes have their isotopic compositions determined both internally and externally to the catchment system. Important members of this group include solutes that have isotopic compositions produced by atomic particle interactions with other nuclides. The source of the atomic particles can be cosmic radiation (producing {open_quotes}cosmogenic{close_quotes} nuclides in the atmosphere and land surface), anthropogenic nuclear reactions (producing {open_quotes}thermonuclear{close_quotes} nuclides), or radioactive and fission decay of naturally-occurring elements, such as U and Th (producing {open_quotes}in-situ{close_quotes} lithogenic nuclides in the deep subsurface). Current language usage often combines all of the atomic particle-produced nuclides under the heading {open_quotes}cosmogenic nuclides{close_quotes}, and for simplicity we will often follow that usage, although always clearly indicating which variety is being discussed. This paper addresses the processes that affect the lithogenic and cosmogenic solute compositions in groundwater, and how these compositions can therefore be used in integrative ways to understand the physical history of groundwater within a catchment system.

  5. An inter-comparison of 10Be and 26Al AMS reference standards and the 10Be half-life

    NASA Astrophysics Data System (ADS)

    Fink, David; Smith, Andrew

    2007-06-01

    We have completed a survey and inter-comparison of several 10Be and 26Al standard reference materials (SRMs) that are in routine use at various AMS laboratories to assess their relative values and the accuracy of their quoted nominal ratios. The accelerator measurement cycle, analysis procedure and setup used at the ANTARES AMS facility for this survey are described. We focused on a new set of 10Be and 26Al serial dilutions of standard reference materials (SRMs) prepared by Kuni Nishiizumii at the University of California, Berkeley, and found excellent systematic reproducibility and internal consistency. For other standard materials, minor deviations are evident even when the results have been recalibrated to a common half-life. In particular, we confirm that the NIST 10Be SRM-4325 has a 14% greater 10Be/Be ratio than that certified by NIST when it is calibrated against other SRMs whose ratios have been normalized to a common 1.5 Ma 10Be half-life. In order to investigate this apparent discrepancy, we report on the results of an absolute, normalization independent, measure of the NIST-4325 10Be/Be ratio. Within the constraints of this type of measurement and its systematic errors, we determine an absolute value for the 10Be/Be SRM-4325 ratio in the range 26,050 to 24,800 × 10-15 in support of the certified value of 26,800 × 10-15 given by NIST. We hesitate to directly infer as a consequence that the 10Be half-life is 1.34 Ma because such an inference is contingent on a direct and accurate specific activity in the parent solution, which at present is not available.

  6. 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

  7. 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

  8. Using cosmogenic isotopes to measure basin-scale rates of erosion

    SciTech Connect

    Bierman, P.R.; Steig, E. . Dept. of Geology)

    1992-01-01

    The authors present a new and different approach to interpreting the abundance of in situ-produced cosmogenic nuclides such as [sup 36]Cl, [sup 26]Al, and [sup 10]Be. Unlike most existing models, which are appropriate for evaluating isotope concentrations on bedrock surfaces, this model can be used to interpret isotope concentration in fluvial sediment. Because sediment is a mixture of material derived from the entire drainage basin, measured isotope abundances can be used to estimate spatially-averaged rates of erosion and sediment transport. Their approach has the potential to provide geomorphologists with a relatively simple but powerful means by which to constrain rates of landscape evolution. The model considers the flux of cosmogenic isotopes into and out of various reservoirs. Implicit in model development are the assumptions that a geomorphic steady-state has been reached and that sampled sediment is spatially and temporally representative of all sediment leaving the basin. Each year, the impinging cosmic-ray flux produces a certain quantity of cosmogenic isotopes in the rock and soil of a drainage basin. For a basin in steady state, the outgoing isotope flux is also constant. They solve for the rate of mass loss as a function of isotope abundance in the sediment, the cosmic ray attenuation length, the isotope half life, and the effective isotope production rate. There are only a few published measurements of cosmogenic isotope abundance in sediment. They calculated model denudation rates for sediment samples from Zaire and central Texas. The denudation rates they calculated appear reasonable and are similar to those they have measured directly on granite landforms in Georgia and southeastern California and those calculated for the Appalachian Piedmont.

  9. Terrestrial cosmogenic 3He: where are we 30 years after its discovery?

    NASA Astrophysics Data System (ADS)

    Blard, Pierre-Henri; Pik, Raphaël; Farley, Kenneth A.; Lavé, Jérôme; Marrocchi, Yves

    2016-04-01

    It is now 30 years since cosmogenic 3He has been detected for the first time in a terrestrial sample (Kurz, 1986). 3He is now a widely used geochemical tool in many fields of Earth sciences: volcanology, tectonics, paleoclimatology. 3He has the advantage to have a high "production rate" to "detection limit" ratio, allowing surfaces as young as hundred of years to be dated. Although its nuclear stability implies several limitations, it moreover represents a useful alternative to 10Be in mafic environments. This contribution is a review of the progresses that have been accomplished since this discovery, and discuss strategies to improve both the accuracy and the precision of this geochronometer. 1) Measurement of cosmogenic 3He Correction of magmatic 3He. To estimate the non-cosmogenic magmatic 3He, Kurz (1986) invented a two steps method involving crushing of phenocrysts (to analyze the isotopic ratio of the magmatic component), followed by a subsequent melting of the sample, to extract the remaining components, including the cosmogenic 3He: 3Hec = 3Hemelt ‑4Hemelt x (3He/4He)magmatic (1) Several studies suggested that the preliminary crushing may induce a loss of cosmogenic 3He (Hilton et al., 1993; Yokochi et al., 2005; Blard et al., 2006), implying an underestimate of the cosmogenic 3He measurement. However, subsequent work did not replicate these observations (Blard et al., 2008; Goerhing et al., 2010), suggesting an influence of the used apparatus. An isochron method (by directly melting several phenocrysts aliquots) is an alternative to avoid the preliminary crushing step (Blard and Pik, 2008). Atmospheric contamination. Protin et al. (in press) provides robust evidences for a large and irreversible contamination of atmospheric helium on silicate surfaces. This unexpected behavior may reconcile the contrasted observations about the amplitude of crushing loss. This undesirable atmospheric contamination is negligible if grain fractions smaller than 150 mm are

  10. Terrestrial cosmogenic 3He: where are we 30 years after its discovery?

    NASA Astrophysics Data System (ADS)

    Blard, Pierre-Henri; Pik, Raphaël; Farley, Kenneth A.; Lavé, Jérôme; Marrocchi, Yves

    2016-04-01

    It is now 30 years since cosmogenic 3He has been detected for the first time in a terrestrial sample (Kurz, 1986). 3He is now a widely used geochemical tool in many fields of Earth sciences: volcanology, tectonics, paleoclimatology. 3He has the advantage to have a high "production rate" to "detection limit" ratio, allowing surfaces as young as hundred of years to be dated. Although its nuclear stability implies several limitations, it moreover represents a useful alternative to 10Be in mafic environments. This contribution is a review of the progresses that have been accomplished since this discovery, and discuss strategies to improve both the accuracy and the precision of this geochronometer. 1) Measurement of cosmogenic 3He Correction of magmatic 3He. To estimate the non-cosmogenic magmatic 3He, Kurz (1986) invented a two steps method involving crushing of phenocrysts (to analyze the isotopic ratio of the magmatic component), followed by a subsequent melting of the sample, to extract the remaining components, including the cosmogenic 3He: 3Hec = 3Hemelt -4Hemelt x (3He/4He)magmatic (1) Several studies suggested that the preliminary crushing may induce a loss of cosmogenic 3He (Hilton et al., 1993; Yokochi et al., 2005; Blard et al., 2006), implying an underestimate of the cosmogenic 3He measurement. However, subsequent work did not replicate these observations (Blard et al., 2008; Goerhing et al., 2010), suggesting an influence of the used apparatus. An isochron method (by directly melting several phenocrysts aliquots) is an alternative to avoid the preliminary crushing step (Blard and Pik, 2008). Atmospheric contamination. Protin et al. (in press) provides robust evidences for a large and irreversible contamination of atmospheric helium on silicate surfaces. This unexpected behavior may reconcile the contrasted observations about the amplitude of crushing loss. This undesirable atmospheric contamination is negligible if grain fractions smaller than 150 mm are

  11. Evidence for Multiple Sources of 10 Be in the Early Solar System

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    Beryllium-10 is a short-lived radionuclide (t 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 10Be nucleosynthesis is uncertain. We report Li-Be-B isotope measurements of CAIs from CV chondrites, including CAIs that formed with the canonical 26Al/27Al ratio of ~5 × 10-5 (canonical CAIs) and CAIs with Fractionation and Unidentified Nuclear isotope effects (FUN-CAIs) characterized by 26Al/27Al ratios much lower than the canonical value. Our measurements demonstrate the presence of four distinct fossil 10Be/9Be 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 10Be/9Be 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 10Be/9Be 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 10Be in the early solar system. The most promising locale for 10Be 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.

  12. 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.

  13. Recent developments in cosmogenic nuclide production rate scaling

    NASA Astrophysics Data System (ADS)

    Lifton, N. A.

    2013-12-01

    A new cosmogenic nuclide production rate scaling model based on analytical fits to Monte Carlo simulations of atmospheric cosmic ray flux spectra (both of which agree well with measured spectra) enables identification and quantification of the biases in previously published models (Lifton, N., Sato, T., Dunai, T., in review, Earth and Planet. Sci. Lett.). Scaling predictions derived from the new model (termed LSD) suggest two potential sources of bias in the previous models: different energy responses of the secondary neutron detectors used in developing the models, and different geomagnetic parameterizations. In addition, the particle flux spectra generated by the LSD model allow one to generate nuclide-specific scaling factors that reflect the influences of the flux energy distribution and the relevant excitation functions (probability of nuclide production in a given nuclear reaction as a function of energy). Resulting scaling factors indicate 3He shows the strongest positive deviation from the flux-based scaling, while 14C exhibits a negative deviation. These results are consistent with previous studies showing an increasing 3He/10Be ratio with altitude in the Himalayas, but with a much lower magnitude for the effect. Furthermore, the new model provides a flexible framework for exploring the implications of future advances in model inputs. For example, the effects of recently updated paleomagnetic models (e.g. Korte et al., 2011, Earth and Planet Sci. Lett. 312, 497-505) on scaling predictions will also be presented.

  14. New assignments for 10Be states from the 12C( 12C, 14O) 10Be reaction

    NASA Astrophysics Data System (ADS)

    Bohlen, H. G.; Dorsch, T.; Kokalova, Tz.; von Oertzen, W.; Schulz, Ch.; Wheldon, C.

    2007-05-01

    The two-proton pick-up reaction 12C( 12C, 14O) 10Be has been measured at 211.4 MeV incident energy to study the structure of 10Be states. This reaction populates most strongly 0 + and 2 + two-proton hole-configurations in the Ip-shell, but also odd-parity states. A two-step mechanism is needed in the latter case with particle-hole excitations of the type (lp) -1(2sld) 1 in inelastic excitation (including neutron excitations) in the one step, and the pick-up of a pair of protons from 12C in the other step. For all observed states the oscillatory structure of the angular distributions is characteristic of their spins, as can be verified for states with known spins. In this way we can make the firm spin assignments of 4 + and 3 - for the states at 11.8 MeV and 10.55 MeV, respectively. From the reaction mechanism, which offers optimum conditions to populate the 4 + configuration in the Ip-shell, and from the J(J+l)-rule for excitation energies within a rotational band we conclude, that the assigned 4 + state is most probably a member of the ground state band of 10Be.

  15. The lost sunspot cycle: New support from 10Be measurements

    NASA Astrophysics Data System (ADS)

    Karoff, C.; Inceoglu, F.; Knudsen, M. F.; Olsen, J.; Fogtmann-Schulz, A.

    2015-03-01

    It has been suggested that the shortage in the number of spots on the surface of the Sun between 1790 and 1830, known as the Dalton minimum, contained an extra cycle that was not identified in the original sunspot record by Wolf. Though this cycle was shorter and weaker than the average solar cycle, it shifted the magnetic parity of the solar magnetic field of the earlier cycles. This extra cycle is sometimes referred to as the "lost solar cycle" or "cycle 4b". Here we reanalyse 10Be measurements with annual resolution from the North Greenland Ice Core Project in order to investigate if the hypothesis regarding a lost sunspot cycle is supported by these measurements. Specifically, we make use of the fact that the Galactic cosmic rays, responsible for forming 10Be in the Earth's atmosphere, are affected differently by the open solar magnetic field during even and odd solar cycles. This enables us to evaluate if the numbering of cycles earlier than cycle 5 is correct. For the evaluation, we use Bayesian analysis, which reveals that the lost sunspot cycle hypothesis is likely to be correct. We also discuss whether this cycle 4b is a real cycle or a phase catastrophe, and what implications this has for our understanding of stellar activity cycles in general.

  16. Cosmogenic Backgrounds to Neutrinoless Double-Beta Decay in EXO-200

    NASA Astrophysics Data System (ADS)

    Albert, Joshua; EXO-200 Collaboration

    2016-03-01

    As neutrinoless double-beta decay (0 νββ) experiments become more sensitive and intrinsic radioactivity in detector materials is reduced, previously minor contributions to the background must be understood and eliminated. With this in mind, cosmogenic backgrounds have been studied with the EXO-200 experiment. Simulations of muon-induced backgrounds in EXO-200 using Geant4 and FLUKA identified several potential cosmogenic radionuclides, though only 137Xe provides a significant background for the 136Xe 0 νββ search with EXO-200. The simulations were normalized based on a measurement of the muon flux underground using the EXO-200 TPC. Muon-induced neutron backgrounds were measured using γ-rays from neutron capture on the detector materials, in data coincident with veto triggers. This provided a measurement of 137Xe yield, and a test of the accuracy of the neutron production and transport simulations. Simulations agree with data to within ~40 % . The ability to identify 136 Xe (n , γ) events will allow for rejection of 137Xe backgrounds in future 0 νββ analyses.

  17. The production rate of cosmogenic 21-Ne in chondrites deduced from 81-Kr measurements

    NASA Technical Reports Server (NTRS)

    Schultz, L.; Freundel, M.

    1986-01-01

    Cosmogenic Ne-21 is used widely to calculate exposure ages of stone meteorites. In order to do so, the production rate P(21) must be known. This rate, however, is dependent on the chemical composition of the meteorite as well as the mass of, and position within, the meteoroid during its exposure to the cosmic radiation. Even for a mean shielding the production rates determined from measurments of different radionuclides vary by a factor of two. A method that can be used to determine exposure ages of meteorites that avoids shielding and chemical composition corrections is the -81-Kr-Kr-method. However, for chondrites, in many cases, the direct determination of production rates for the Kr isotopes is prevented by the trapped gases and the neutron effects on bromine. Therefore, this method was applied to four eucrite falls and then their 81-Kr-83-Kr-ages were compared to their cosmogenic Ne-21 and Ar-38 concentrations. The eucrites Bouvante-le-Haut, Juvinas, Sioux County, and Stannern were chosen for these measurements because of their similar chemical composition regarding the major elements.

  18. Cosmogenic activation of a natural tellurium target

    NASA Astrophysics Data System (ADS)

    Lozza, V.; Petzoldt, J.

    2015-02-01

    130Te is one of the candidates for the search for neutrinoless double beta decay. It is currently planned to be used in two experiments: CUORE and SNO+. In the CUORE experiment TeO2 crystals cooled at cryogenic temperatures will be used. In the SNO+ experiment natTe will be deployed up to 0.3% loading in the liquid scintillator volume. A possible background for the signal searched for, are the high Q-value, long-lived isotopes, produced by cosmogenic neutron and proton spallation reaction on the target material. A total of 18 isotopes with Q-value larger than 2 MeV and T1/2 > 20 days have been identified as potential backgrounds. In addition low Q-value, high rate isotopes can be problematic due to pile-up effects, specially in liquid scintillator based detectors. Production rates have been calculated using the ACTIVIA program, the TENDL library, and the cosmogenic neutron and proton flux parametrization at sea level from Armstrong and Gehrels for both long and short lived isotopes. The obtained values for the cross sections are compared with the existing experimental data and calculations. Good agreement has been generally found. The results have been applied to the SNO+ experiment for one year of exposure at sea level. Two possible cases have been considered: a two years of cooling down period deep underground, or a first purification on surface and 6 months of cooling down deep underground. Deep underground activation at the SNOLAB location has been considered.

  19. Cross Sections for the Production of Cosmogenic Nuclides with Protons up to 400 MeV for the Interpretation of Cosmic-Ray-produced Nuclides

    NASA Astrophysics Data System (ADS)

    Schiekel, Th.; Rosel, R.; Herpers, U.; Bodemann, R.; Leya, I.; Gloris, M.; Michel, R.; Dittrich, B.; Kubik, P.; Suter, M.

    1993-07-01

    Integral excitation functions of the cosmogenic nuclides are the basic requirement for the interpretation of interactions between cosmic ray particles and extraterrestrial and terrestrial matter. Together with the knowledge of primary and secondary particle fields inside an irradiated body, model calculations can be developed to interpret abundances of cosmogenic nuclides in dependencies of the irradiation history of the irradiated body and of the cosmic particle ray itself. The quality of those model calculations depends on the quality of the available cross-section database, which is neither comprehensive nor reliable for the most important nuclides like the long-lived radionuclides (i.e., 10Be, 26Al, 36Cl, 41Ca) and the stable rare gas isotopes. For a systematic investigation in this field of science we carried out several irradiation experiments with protons in the energy region between 45 MeV and 400 MeV at the Paul Scherrer Institut (Villigen, Switzerland) and the Laboratoire Nationale Saturne (Saclay, France) using the stacked foil technique. We included 21 different target elements with Z between 6 and 79 (C, N as Si3N4, O as SiO2, Mg, Al, Si, Ca as CaC2H2O4, Ti, V, Mn as Mn/Ni alloy, Fe, Co, Ni, Cu, Sr as SrF2, Y, Zr, Nb, Rh, Ba as Ba containing glass and Au) in our experiments. The proton fluxes were monitored via the reaction 27Al(p,3p3n)22Na using the evaluated data of [1]. Residual nuclides were measured by X-, gamma-, and after a chemical separation by accelerator mass spectrometry. In order to check the quality of our experimental procedures we included some target elements in our new experiments for which consistent excitation functions have already been determined [2,3,4]. Our new data show excellent agreement with the earlier measurements. We measured cross sections for more than 120 different reactions. Here we report on the results for target elements with Z up to 28. The exsisting database of experimental excitation functions for the production

  20. Cosmogenic Records in 18 Ordinary Chondrites from the Dar Al Gani Region, Libya. 1; Noble Gases

    NASA Technical Reports Server (NTRS)

    Schultz, L.; Franke, L.; Welten, K. C.; Nishiizumi, K.; Jull, A. J. T.

    2003-01-01

    In the last decade thousands of meteorites have been recovered from hot deserts in the Sahara and Oman. One of the main meteorite concentration surfaces in the Sahara is the Dar al Gani plateau in Libya, which covers a total area of 8000 km2. More than 1000 meteorites have been reported from this area. The geological setting, meteorite pairings and the meteorite density of the Dar al Gani (DaG) field are described in more detail in [1]. In this work we report concentrations of the noble gas isotopes of He, Ne, Ar as well as 84Kr and 132Xe in 18 DaG meteorites. In a separate paper we will report the cosmogenic radionuclides [2]. We discuss the thermal history and cosmic-ray exposure (CRE) history of these meteorites, and evaluate the effects of the hot desert environment on the noble gas record.

  1. Cross-Spectral Comparison of Dust and Cosmogenic Nuclide Records from Greenland Ice Cores Demonstrate Synchronicity at Millennial Timescales

    NASA Astrophysics Data System (ADS)

    Balbas, A.; Cuzzone, J. K.; Mix, A. C.; Clark, P. U.

    2013-12-01

    Greenland ice core records of dust and cosmogenic nuclides, converted to flux, share a striking resemblance on millennial timescales. However, to date, the significance of the relationship between these two parameters has received little attention. Here, we compare records of 10Be, 36Cl, and dust spanning ~18ky to ~33ky from the GRIP and GISP2 ice cores using cross-spectral analysis. Our findings demonstrate a statistically robust relationship between the cosmogenic nuclide flux and the dust flux, revealing a common mode of in-phase variability with a period of ~1600 years and coincident with the Northern Hemisphere Dansgaard-Oeschger events. Millennial-scale variability in cosmogenic nuclides from Greenland ice cores is commonly attributed to solar variability while variations in Greenland dust concentrations are associated with changes in atmospheric circulation, but why these two processes would co-vary remains unclear. We suggest that circulation could also act as a previously unrecognized control on cosmogenic nuclide fluxes, whereby variable mixing between the troposphere and stratosphere could explain the portion of the observed millennial-scale variability which cannot be explained by solar variability alone. Our proposed mechanism invokes changes in atmospheric mixing due to upper level (troposphere-stratosphere boundary) wind shear, which climate models predict may change during climate changes as a result of baroclinic variability. GCM simulations suggest that changes in baroclinicity between the LGM and present day lead to changes in the upper level jet velocities (500mb), which in turn, affect the vertical wind shear at upper levels (200-300mb). Because dust deposition scales closely with changes in wind velocity and chemical constituent exchange from the stratosphere to the troposphere is largely a function of jet proximal clear air turbulence provoked by instabilities in vertical shear, the Greenland dust and cosmogenic records may be particularly

  2. Radionuclide cisternogram

    MedlinePlus

    ... please enable JavaScript. A radionuclide cisternogram is a nuclear scan test. It is used to diagnose problems ... damage. The amount of radiation used during the nuclear scan is very small. Almost all of the ...

  3. Meteoric cosmogenic Beryllium-10 adsorbed to river sediment and soil: Applications for Earth-surface dynamics

    NASA Astrophysics Data System (ADS)

    Willenbring, Jane K.; von Blanckenburg, Friedhelm

    2010-01-01

    Rainfall scavenges meteoric cosmogenic 10Be from the atmosphere. 10Be falls to the Earth's surface, where it binds tightly to sediment particles in non-acidic soils over the life-span of those soils. As such, meteoric 10Be has the potential to be an excellent geochemical tracer of erosion and stability of surfaces in a diverse range of natural settings. Meteoric 10Be has great potential as a recorder of first-order erosion rates and soil residence times. Even though this tracer was first developed in the late 1980s and showed great promise as a geomorphic tool, it was sidelined in the past two decades with the rise of the "sister nuclide", in situ10Be, which is produced at a known rate inside quartz minerals. Since these early days, substantial progress has been made in several areas that now shed new light on the applicability of the meteoric variety of this cosmogenic nuclide. Here, we revisit the potential of this tracer and we summarize the progress: (1) the atmospheric production and fallout is now described by numeric models, and agrees with present-day measurements and paleo-archives such as from rain and ice cores; (2) short-term fluctuations in solar modulation of cosmic rays or in the delivery of 10Be are averaged out over the time scale soils accumulate; (3) in many cases, the delivery of 10Be is not dependent on the amount of precipitation; (4) we explore where 10Be is retained in soils and sediment; (5) we suggest a law to account for the strong grain-size dependence that controls adsorption and the measured nuclide concentrations; and (6) we present a set of algebraic expressions that allows calculation of both soil or sediment ages and erosion rates from the inventory of meteoric 10Be distributed through a vertical soil column. The mathematical description is greatly simplified if the accumulation of 10Be is at a steady state with its export through erosion. In this case, a surface sample allows for the calculation of an erosion rate. Explored

  4. 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.

  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. 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

  7. 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

  8. 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

  9. Contrasting Modern and 10Be- derived erosion rates for the Southern Betic Cordillera, Spain

    NASA Astrophysics Data System (ADS)

    Bellin, N.; Vanacker, V.; Kubik, P.

    2012-04-01

    In Europe, Southeast Spain was identified as one of the regions with major treat of desertification in the context of future land use and climate change. During the last years, significant progress has been made to understand spatial patterns of modern erosion rates in these semi-arid degraded environments. Numerous European projects have contributed to the collection of modern erosion data at different spatial scales for Southeast Spain. However, these data are rarely analysed in the context of long-term changes in vegetation, climate and human occupation. In this paper, we present Modern and Holocene denudation rates for small river basins (1 to 10 km2) located in the Spanish Betic Cordillera. Long-term erosion data were derived from cosmogenic nuclide analyses of river-borne sediment. Modern erosion data were quantified through analysis of sediment deposition volumes behind check dams, and represent average erosion rates over the last 10 to 40 years. Modern erosion rates are surprisingly low (mean erosion rate = 0.048 mm y-1; n=36). They indicate that the steep, sparsely vegetated hillslopes in the Betic Cordillera cannot directly be associated with high erosion rates. 10Be -derived erosion rates integrate over the last 37500 to 3500 years, and are roughly of the same magnitude. They range from 0.013 to 0.243 mm y-1 (mean denudation rate = 0.062 mm y-1 ± 0.054; n=20). Our data suggest that the modern erosion rates are similar to the long-term erosion rates in this area. This result is in contrast with the numerous reports on human-accelerated modern erosion rates for Southeast Spain. Interestingly, our new data on long-term erosion rates show a clear spatial pattern, with higher erosion rates in the Sierra Cabrera and lower erosion rates in Sierra de las Estancias, and Sierra Torrecilla. Preliminary geomorphometric analyses suggest that the spatial variation that we observe in long-term erosion rates is related to the gradient in uplift rates of the Betic

  10. 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

  11. How does a single precipitation event erode a landscape? Clues from meteoric 7Be and 10Be analysis of suspended sediments and soils

    NASA Astrophysics Data System (ADS)

    Occhi, M.; Willenbring, J. K.; Kaste, J. M.; Scholl, M. A.; Shanley, J. B.

    2012-12-01

    Stream sediment contains a history recorded in isotopes that cling to suspended particles. In this study we exploit this recorded history in order to understand how a single precipitation event erodes the landscape at two watershed sites (Bisley I and Mameyes) within the Luquillo Critical Zone Observatory, Puerto Rico. We use fallout cosmogenic radionuclides Beryllium-7 (7Be) and Beryllium-10 (10Be) to determine the provenance of suspended sediment at various stages of a hydrograph. Sediments from source areas within the watersheds, such as stable ridge crests and active landslide scars, were also sampled and analyzed. Exploiting the large difference in half-life, the 10Be/7Be ratio of suspended sediments coupled with the concentration and nature of organic material present show original depth of mobilized stream sediment in the hillslope. The storm hydrographs of a one-month recurrence interval storm on June 7th, 2011 were sampled at both watersheds. In the small watershed (0.067 km2), storm discharge and total suspended solids (TSS) show short lag times between the initiation of precipitation and the initial rise of the hydrograph and no lag time between peak discharge and peak TSS. The larger site (17.8 km2) had a lag time of approximately 30 minutes between the initiation of precipitation and a rise in discharge and had a 15-minute lag between peak stage (which occurred first) and peak TSS, highlighting the longer travel distances that particles must take to reach the stream sampling point in the larger basin. We compare fallout 7Be nuclide concentration in source sediments and assume a simple, two end-member model to mix these sources in the stream. Soil sediments collected from stable ridge crests ('old') have relatively high average 7Be concentrations of 2.7x106 atoms/g±10% and sediments collected from active landslide scars ('new') have relatively low 7Be concentrations of 4.0x104 atoms/g±15%. Suspended sediments had an average 7Be concentration of 7.2x

  12. Measurement of proton production cross sections of {sup 10}Be and {sup 26}Al from elements found in lunar rocks

    SciTech Connect

    Sisterson, J.M.; Kim, K.; Englert, P.A.J.

    1996-07-01

    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 {sup 14}C 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){sup 10}Be,O(p,x){sup 7}Be, Si(p,x){sup 7}Be,Si(p,x){sup 26}Al, and Si(p,x){sup 22}Na from {approximately}30 - 500 MeV.

  13. Search for cosmogenic Ar-42 in meteorites

    NASA Astrophysics Data System (ADS)

    Cini Castagnoli, G.; Cane, D.; Taricco, C.; Bhandari, N.

    2003-04-01

    We have evidence for decreasing galactic cosmic ray (GCR) flux in the past 3 centuries by a factor about two [1]. The measurements of the activity of cosmogenic 44Ti (T1/2 = 59.2 y) produced by GCR in stony meteorites that fell during the last two centuries are in good agreement with the calculated values and validate the decreasing trend of GCR flux. The measurements were obtained by an hyperpure (372 cm3) Ge-NaI(Tl) spectrometer operating in the Monte dei Cappuccini laboratory in Torino[2]. To further improve upon statistical precision of 44Ti data and also to be able to measure the 42Ar (T1/2 = 33 y) which is produced in even smaller amounts by GCR in meteorites, we have set up in the same laboratory a larger (581 cm3) hyperpure Ge detector operating in coincidence with a 100 kg NaI(Tl) crystal assembly. This should enable us to confirm the above results about GCR variations. We wish to acknowledge our deep gratitude to professor Bonino, deceased on September 29, 2002, to whom the assemblage of the new equipment is due. [1] G. Bonino, G. Cini Castagnoli, D. Cane, C. Taricco and N. Bhandari,Proc. XXVII Intern. Cosmic Ray Conf. (Hamburg, 2001) 3769-3772. [2] Bonino G., Cini Castagnoli G., Cane D., Taricco C., Bhandari N, textit {34th COSPAR Sci. Ass. Houston 2002 (Adv. Space Res.)}, in press

  14. Regular Cosmogenic Nuclide Dosing of Sediment Moving Down Desert Piedmonts

    NASA Astrophysics Data System (ADS)

    Nichols, K. K.; Bierman, P. R.; Hooke, R. L.; Eppes, M. C.; Persico, L.; Caffee, M.; Finkel, R.

    2001-12-01

    Low-gradient alluvial piedmonts are common in desert areas throughout the world; however, long-term rates of processes that modify these landscapes are poorly understood. Using cosmogenic 10Be and 26Al, we attempt to quantify the long-term (>103 y) behavior of desert piedmonts in Southern California. We measured the activity of 10Be and 26Al in three samples of drainage basin alluvium and six amalgamated samples from transects spaced at 1-km intervals down a piedmont in Fort Irwin, Mojave Desert, California. Each transect sample consists of sediment from 21 collection sites spaced at 150 m intervals. Such sampling averages the variability of nuclide activity between sub-sample locations and thus gives a long-term dosing history of sediment as it is transported from uplands to the distal piedmont. The piedmont is heavily used during military training exercises during which hundreds of wheeled and tracked vehicles traverse the surface. The piedmont surface is planar, and fan-head incision is minimal at the rangefront decreasing to zero between the first and second transects, 1.5 km from the rangefront. 10Be activity increases steadily from 5.87 X 105 atoms g-1 at the rangefront to 1.02 X 6 atoms g-1 at the piedmont bottom. Nuclide activity and distance are well correlated (r2 = 0.95) suggesting that sediment is dosed uniformly as it is transported down piedmont. We have measured similar increases in nuclide activity in transect samples collected from two other Mojave Desert piedmonts, those fringing the Iron and Granite Mountains (Nichols et al, in press, Geomorphology). These piedmonts have nuclide activities that also correlate well with distance (r2 = 0.98 and 0.96, respectively) from their rangefronts, but nuclides increase at a lower rate down piedmont. Modeled sediment transport speeds for the Iron and Granite Mountain piedmonts are decimeters per year. The regular increase in nuclide activities down three different Mojave Desert piedmonts suggests that

  15. Preliminary Cosmogenic Nuclide Chronology of Late Pleistocene Missoula Floods

    NASA Astrophysics Data System (ADS)

    Balbas, A.; Clark, J.; Clark, P. U.; Caffey, M. W.; Woodruff, T. E.; Baker, V. R.

    2014-12-01

    The Missoula floods had the largest known peak flood discharges of fresh water known from the geologic record. Multiple floods are believed to have originated from the failure of the Purcell trench ice lobe, which dammed glacial Lake Missoula. The flood waters traveled westward creating the Channeled Scabland region, a spectacular complex of anastomosing channels, coulees, cataracts, loess islands, rock basins, broad gravel deposits, and immense gravel bars in east-central Washington State. Several important questions about the Missoula floods and the formation of the Channeled Scabland remain, primarily due to the few geochronological constraints on their timing. Attempts to date the duration of the multiple floods have produced a wide range of ages (13-19 ka from land deposits and 13-31 ka from marine cores), but few of these directly constrain the age of the major flood landscape elements. Here we present 14 new in situ cosmogenic 10Be ages from quartz-bearing boulders deposited at four sites in eastern Washington. Wallula Gap is a narrow constriction along the Columbia River between Oregon and Washington. Hydraulic damming of floodwater at Wallula Gap created glacial Lake Lewis. Surface exposure ages on large boulders found at over 300 m elevation above the river at this site will date the largest flood events. The Wenatchee region represents the most northwestern area influenced by flooding. Dates from this area will determine when flooding occurred after the retreat of the Okanogan lobe. We sampled boulders from the lower Pangborn Bar, ice-rafted boulders north of Wenatchee, and boulders from a flood bar on the Columbia River north of Wenatchee. A boulder from the Mattawa Fan was sampled to assess the last time a megaflood came through the Sentinel Gap. Finally, in order to constrain the last debris dam failure at the southern end of the Upper Grand Coulee, we sampled flood boulders deposited on the Ephrata Fan.

  16. Cosmogenic helium and volatile-rich fluid in Sierra leone alluvial diamonds

    SciTech Connect

    McConville, P.; Reynolds, J.H. )

    1989-09-01

    Pursuant to the discovery elsewhere of cosmogenic {sup 10}Be in alluvial diamond fragments from Zaire, noble gas measurements were made on two identical splits of a finely powdered, harshly acid-washed sample derived from selected (for clarity) fragments of a single alluvial diamond from Sierra Leone (sample LJA {yields} L4 and L5). Essentially identical results were obtained for both splits. Isotopic ratios for Ar, Kr, and Xe were atmospheric and their elemental abundances were high relative to published data, owing to shock implantation in the crushing as verified in a supplementary experiment. No neon was detected above blank level. {sup 3}He was exceptionally abundant, {sup 4}He exceptionally depleted, possibly from the acid wash, and the ratio {sup 3}He/{sup 4}He almost unprecedentedly high at an R/R{sub a} value of 246 {plus minus} 16. The results support the hypothesis that excess {sup 3}He in diamonds is cosmogenic, although a cosmic-ray exposure of 5, 35, or (impossibly) 152 Ma for cyclic gardening of the sample to a maximum depth of 0, 4.6 m, or 20 m, respectively, is required. Troublesome for the cosmogenic hypothesis is a sample from very deep in the Finsch mine, South Africa, found by Zadnik et al (1987) to have an R/R{sub a} value of 1,000. This paper includes histograms of noble gas data published prior to mid-1988 for diamonds of known provenance. The Sierra Leone diamond studied in the supplementary experiment belongs to a distinct population of {sup 40*}Ar-rich diamonds consisting mostly of cubic diamonds for Zaire.

  17. 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.

  18. Survey on Cosmogenic 26Al in Lewis Cliff Meteorites

    NASA Astrophysics Data System (ADS)

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

    1992-07-01

    INTRODUCTION: We have embarked upon a ^26Al gamma-ray survey of meteorites selected from about 2000 samples recently recovered from the Lewis Cliff Ice Fields (84 degrees 18'S/161 degrees 20'E). Due to its 705-ka half-life ^26Al can be used for estimating terrestrial ages and thus contribute to further characterization of Antarctic meteorites in addition to their classification and thermoluminescence (TL) properties. The ^26Al survey is also useful for identifying meteorites with unusual exposure histories, which merit additional measurements of cosmogenic radionuclides (by AMS) and noble gases. In addition, it provides clues on possible pairings. METHOD: Low-level gamma-ray spectroscopy is well suited for ^26Al survey work, since bulk meteorite samples can be measured routinely and nondestructively without any previous sample preparation. The required size of the samples (30-500 g) makes the method relatively independent of depth effects and compositional inhomogeneities. The use of a high-resolution GeLi detector also allows the determination of the natural ^40K activity and thus the K content of the samples, which can be used as an additional pairing criterion for ordinary chondrites. Also ^137Cs, a fall-out surface contamination [1], is simultaneously measured; low values may be characteristic for meteorites recently fallen or released from the ablating ice. For the detector an efficiency calibration curve has been made that adequately accounts for differences in size and shape of the meteorite samples. RESULTS and DISCUSSION: TERRESTRIAL AGES: So far, we have measured over 30 Lewis Cliff equilibrated H and L chondrites, collected from widely differing locations. Normalized to L-chondrite composition, the ^26Al contents range from 27 to 110 dpm/kg with peaks around 43 and 53 dpm/kg. This bimodal ^26Al distribution is reminiscent of that observed for Allan Hills ordinary chondrites [2]. Tentative terrestrial ages, calculated on the basis of ^26Al saturation

  19. Survey on Cosmogenic 26Al in Lewis Cliff Meteorites

    NASA Astrophysics Data System (ADS)

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

    1992-07-01

    INTRODUCTION: We have embarked upon a ^26Al gamma-ray survey of meteorites selected from about 2000 samples recently recovered from the Lewis Cliff Ice Fields (84 degrees 18'S/161 degrees 20'E). Due to its 705-ka half-life ^26Al can be used for estimating terrestrial ages and thus contribute to further characterization of Antarctic meteorites in addition to their classification and thermoluminescence (TL) properties. The ^26Al survey is also useful for identifying meteorites with unusual exposure histories, which merit additional measurements of cosmogenic radionuclides (by AMS) and noble gases. In addition, it provides clues on possible pairings. METHOD: Low-level gamma-ray spectroscopy is well suited for ^26Al survey work, since bulk meteorite samples can be measured routinely and nondestructively without any previous sample preparation. The required size of the samples (30-500 g) makes the method relatively independent of depth effects and compositional inhomogeneities. The use of a high-resolution GeLi detector also allows the determination of the natural ^40K activity and thus the K content of the samples, which can be used as an additional pairing criterion for ordinary chondrites. Also ^137Cs, a fall-out surface contamination [1], is simultaneously measured; low values may be characteristic for meteorites recently fallen or released from the ablating ice. For the detector an efficiency calibration curve has been made that adequately accounts for differences in size and shape of the meteorite samples. RESULTS and DISCUSSION: TERRESTRIAL AGES: So far, we have measured over 30 Lewis Cliff equilibrated H and L chondrites, collected from widely differing locations. Normalized to L-chondrite composition, the ^26Al contents range from 27 to 110 dpm/kg with peaks around 43 and 53 dpm/kg. This bimodal ^26Al distribution is reminiscent of that observed for Allan Hills ordinary chondrites [2]. Tentative terrestrial ages, calculated on the basis of ^26Al saturation

  20. Glacial Erosion Rates from Bayesian Inversion of Cosmogenic Nuclide Concentrations in a Bedrock Core, Streaked Mtn., ME

    NASA Astrophysics Data System (ADS)

    Ploskey, Z. T.; Stone, J. O.

    2014-12-01

    Glacial erosion is an important source of sediment and could be an important coupling to glacier and ice sheet models that track sediment. However, glacial erosion is difficult to quantify, and models of glacial erosion can benefit from independent erosion rate estimates. Here we present the results of a Bayesian Markov chain Monte Carlo (MCMC) inversion of a cosmogenic nuclide (CN) geomorphic model for glacial erosion rates on a bedrock landform formerly eroded beneath the Laurentide ice sheet. The CN 10Be was measured in quartz to 8 m depth in a bedrock core from the summit of Streaked Mountain, ME. The accumulation of 10Be was modeled over multiple glacial cycles of alternating exposure and glacial erosion. This model was invertedfor glacial erosion rates and burial history using MCMC algorithms implemented in PyMC (Patil et al., 2010). This Bayesian approach allows us to incorporate prior constraints on ice cover history, including oxygen isotope records and radiometric dates, which is otherwise difficult to differentiate from erosion in rapidly eroding areas. We compare these results to depth profile and surface CN measurements elsewhere in Maine (Ploskey and Stone, 2013).The forward model of CN production used in the inversion is part of Cosmogenic (github.com/cosmolab/cosmogenic), an open-source Python-based software library we developed for modeling the growth and decay of in-situ CN inventories in rock during geomorphic evolution. It includes calibrated production rates for 10Be and 26Al in quartz and 36Cl in K-feldspar by both neutrons and muons, with more isotopic production pathways and material targets to be added in the future. Production rates are scaled to the site altitude and latitude using modular scaling schemes. Cosmogenic includes a variety of functions representing common geomorphic histories, and can be used to model any arbitrary exposure, erosion and burial history that can be defined as Python function.ReferencesPatil, A., D. Huard and C

  1. Cosmogenic beryllium cycling in a natural forest setting

    NASA Astrophysics Data System (ADS)

    Conyers, Grace

    10Bemet, or cosmogenic beryllium, has a long half-life of 1.4 million years and quick adsorption on soil particles, which may make it ideal for dating soil erosion in historical context. However, there are questions on about the fundamental assumptions of the retentivity of 10Bemet. This manuscript explores these assumptions and the context of nutrient cycling in a natural forest setting. To see if 10Bemet was being cycled through the trees, and at what rate, we looked at the[10Bemet ] in the soil, 4 species of trees, and their leaves. The isotopic ratio 10Be/9Be in all four tree species was comparable to the soil on which they grow, ranging from 6-8 x 10 -9. However, there was one exception with hickory (Carya spp.) which strongly bioaccumulate beryllium with an average of 0.38 ppm dry weight in the wood. Abscised hickory leaves have a higher [Be] of 2.0 ppm, over 10 times higher than in the soil. Using standard allometric equations relating tree biomass to trunk diameter, and assuming that belowground biomass has the same [Be] as aboveground, we calculate that hickory trees at our site contain approximately 1% of the total 10Bemet under their canopy and that ~10% of this Be is cycled annually by leaf abscission. It is not clear at this point what fraction of litterfall Be is recycled into the plant, returned to the soil, or carried to groundwater as organic chelates. Hickory trees occupy an average of ~10% of the oak-hickory forest area. Assuming that trees are randomly distributed, that litterfall Be is returned to the soil, and maintaining a constant 10Bemet budget over time for simplicity, then more than half of all 10Be met in the forest soil will have passed through a hickory tree over the past 10 ky. Fully 90% of all 10Bemet will pass through a hickory tree over a period of ~25 ky. It is clear that hickory trees can transport a sizable fraction of the total 10Bemet in their nutrient cycle, and that they may be responsible for landscape-scale Be mobility.

  2. Cosmogenic nuclide age constraints on Middle Stone Age lithics from Niassa, Mozambique

    NASA Astrophysics Data System (ADS)

    Mercader, Julio; Gosse, John C.; Bennett, Tim; Hidy, Alan J.; Rood, Dylan H.

    2012-07-01

    The late phases of the Middle Stone Age (MSA) in the East African Rift System (EARS) are known for their evolutionary shifts and association with bottlenecks, transcontinental expansion, and climatic fluctuations. The chronology of MSA sites contemporaneous with these eco-demographic upheavals is uncertain because of the scarcity of datable sites and the poor understanding of their depositional and erosional histories. We apply terrestrial cosmogenic nuclide dating in a stratigraphic section with a complex exposure history to the study of the Luchamange Beds, a widespread sedimentological unit underlying MSA sites from the shores of Lake Niassa (Mozambican EARS). We use an innovative approach, which may be applicable elsewhere, to calculate their age using a Monte Carlo-based Bayesian model that links depth profiles of 26Al and 10Be, and uses other geomorphic and cosmogenic nuclide age constraints on episodic erosion and burial. The age of the basal Luchamange Beds is 42 + 77/-15 ka, and the MSA occupation on top is 29 + 3/-11 ka. These dates suggest temporal overlap between MSA and the earliest Later Stone Age and diversity in cultural manifestations at the end of the MSA.

  3. Atmospheric Fragmentation of the Gold Basin Meteoroid as Constrained from Cosmogenic Nuclides

    NASA Technical Reports Server (NTRS)

    Welten, K. C.; Hillegonds, D. J.; Jull, A. J. T.; Kring, D. A.

    2005-01-01

    Since the discovery of the Gold Basin L4 chondrite shower almost ten years ago in the northwestern corner of Arizona, many thousands of L-chondrite specimens have been recovered from an area of approx.22 km long and approx.10 km wide. Concentrations of cosmogenic 14C and 10Be in a number of these samples indicated a terrestrial age of approx.15,000 years and a large pre-atmospheric size [1]. Additional measurements of cosmogenic Be-10, Al-26, Cl-36, and Ca-41 in the metal and stone fractions of fifteen Gold Basin samples constrained the pre-atmospheric radius to 3-5 m [2]. This implies that Gold Basin is by far the largest stone meteorite in the present meteorite collection, providing us with an opportunity to study the fragmentation process of a large chondritic object during atmospheric entry. Knowledge about the fragmentation process provides information about the mechanical strength of large meteoroids, which is important for the evaluation of future hazards of small asteroid impacts on Earth and possible defensive scenarios to avoid those impacts.

  4. Sand residence times of one million years in the Namib Sand Sea from cosmogenic nuclides

    NASA Astrophysics Data System (ADS)

    Vermeesch, P.; Fenton, C. R.; Kober, F.; Wiggs, G. F. S.; Bristow, C. S.; Xu, S.

    2010-12-01

    The Namib Sand Sea is one of the world's oldest and largest sand deserts, yet little is known about the source of the sand in this, or other large deserts. In particular, it is unclear whether the sand is derived from local sediment or comes from remote sources. The relatively uniform appearance of dune sands and low compositional variability within dune fields make it difficult to address this question. Here we combine cosmogenic-nuclide measurements and geochronological techniques to assess the provenance and migration history of sand grains in the Namib Sand Sea. We use U-Pb geochronology of detrital zircons to show that the primary source of sand is the Orange River at the southern edge of the Namib desert. Our burial ages obtained from measurements of the cosmogenic nuclides 10Be, 26Al and 21Ne suggest that the residence time of sand within the sand sea is at least one million years. We therefore conclude that, despite large climatic changes in the Namib region associated with Quaternary glacial-interglacial cycles, the area currently occupied by the Namib Sand Sea has never been entirely devoid of sand during the past million years.

  5. Cosmogenic activation of materials used in rare event search experiments

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Mei, D.-M.; Kudryavtsev, V. A.; Fiorucci, S.

    2016-11-01

    We evaluate the cosmogenic production rates in some materials that are commonly used as targets and shielding/supporting components for detecting rare events. The results from Geant4 simulations and the calculations of ACTIVIA are compared with the available experimental data. We demonstrate that the production rates from the Geant4-based simulations agree with the available data reasonably well. As a result, we report that the cosmogenic production of several isotopes in various materials can generate potential backgrounds for direct detection of dark matter and neutrinoless double-beta decay.

  6. 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.

  7. Delayed response of cosmogenic-derived denudation in the eastern Himalaya

    NASA Astrophysics Data System (ADS)

    Lupker, Maarten; Lavé, Jérôme; France-Lanord, Christian

    2016-04-01

    The Tsangpo/Siang/Brahmaputra River flows from the high and arid Tibetan Plateau through the dissected Himalayan range and further over a flat and humid floodplain to the Bay of Bengal. Intense fluvial incision and erosion along the Brahmaputra in the eastern Himalaya syntaxis has been suggested by some to drive high uplift rates in the region through lithospheric unloading [e.g. 1]. Despite being a potential key region to better understand the couplings between erosion, tectonics and climate, modern denudation in the Brahmaputra watershed is still poorly quantified. To address these questions, we measured cosmogenic 10Be in river sediments along the entire length of the river, from the Tsangpo in Tibet to the Brahmaputra in Bangladesh including the main tributaries, to retrieve modern erosion rates and sediment fluxes. These measurements suggest low denudation rates on the Tibetan Plateau (< 0.1 mm/a) that increase locally to 2 to 3 mm/a in the region of the eastern syntaxis of the Himalayan range. While sediment samples from the Tibetan plateau show stable 10Be concentrations, samples from the syntaxis all the way downstream to Bangladesh show a higher variability depending on sampling season or grain size. The river reach through the eastern Himalayan range coincides with a sharp decrease in the mainstream sediment 10Be concentrations that fingerprints the addition of sediments from intensely eroding areas. However, this erosive signal is only recorded by the cosmogenic nuclide signal 100 km or more downstream of the reach where steep river gradients, high uplift rates and landslide frequencies have been observed and measured [1,2]. Similar effects have been observed elsewhere in the Himalayan range [3] and these need to be understood in order to further use detrital cosmogenic nuclides as denudation tracers in tectonically active regions. We explore possible causes of this downstream shift in the denudation signal that may be caused, amongst other, by temporary

  8. Radionuclide removal

    SciTech Connect

    Sorg, T.J.

    1991-01-01

    The U.S. Environmental Protection Agency proposed new and revised regulations on radionuclide contaminants in drinking water in June 1991. During the 1980's, the Drinking Water Research Division, USEPA conducted a research program to evaluate various technologies to remove radium, uranium and radon from drinking water. The research consisted of laboratory and field studies conducted by USEPA, universities and consultants. The paper summarizes the results of the most significant projects completed. General information is also presented on the general chemistry of the three radionuclides. The information presented indicates that the most practical treatment methods for radium are ion exchange and lime-soda softening and reverse osmosis. The methods tested for radon are aeration and granular activated carbon and the methods for uranium are anion exchange and reverse osmosis.

  9. Cosmogenic backgrounds to 0νββ in EXO-200

    NASA Astrophysics Data System (ADS)

    Albert, J. B.; Auty, D. J.; Barbeau, P. S.; Beck, D.; Belov, V.; Breidenbach, M.; Brunner, T.; Burenkov, A.; Cao, G. F.; Chambers, C.; Cleveland, B.; Coon, M.; Craycraft, A.; Daniels, T.; Danilov, M.; Daugherty, S. J.; Davis, J.; Delaquis, S.; Der Mesrobian-Kabakian, A.; DeVoe, R.; Didberidze, T.; Dilling, J.; Dolgolenko, A.; Dolinski, M. J.; Dunford, M.; Fairbank, W., Jr.; Farine, J.; Feldmeier, W.; Feyzbakhsh, S.; Fierlinger, P.; Fudenberg, D.; Gornea, R.; Graham, K.; Gratta, G.; Hall, C.; Herrin, S.; Hughes, M.; Jewell, M. J.; Johnson, A.; Johnson, T. N.; Johnston, S.; Karelin, A.; Kaufman, L. J.; Killick, R.; Koffas, T.; Kravitz, S.; Krücken, R.; Kuchenkov, A.; Kumar, K. S.; Leonard, D. S.; Licciardi, C.; Lin, Y. H.; Ling, J.; MacLellan, R.; Marino, M. G.; Mong, B.; Moore, D.; Njoya, O.; Nelson, R.; Odian, A.; Ostrovskiy, I.; Piepke, A.; Pocar, A.; Prescott, C. Y.; Retière, F.; Rowson, P. C.; Russell, J. J.; Schubert, A.; Sinclair, D.; Smith, E.; Stekhanov, V.; Tarka, M.; Tolba, T.; Tsang, R.; Twelker, K.; Vuilleumier, J.-L.; Waite, A.; Walton, J.; Walton, T.; Weber, M.; Wen, L. J.; Wichoski, U.; Wood, J.; Yang, L.; Yen, Y.-R.; Zeldovich, O. Ya.

    2016-04-01

    As neutrinoless double-beta decay experiments become more sensitive and intrinsic radioactivity in detector materials is reduced, previously minor contributions to the background must be understood and eliminated. With this in mind, cosmogenic backgrounds have been studied with the EXO-200 experiment. Using the EXO-200 TPC, the muon flux (through a flat horizontal surface) underground at the Waste Isolation Pilot Plant (WIPP) has been measured to be Φ = 4.07 ± 0.14 (sys) ± 0.03 (stat) × 10‑7 cm‑2 s‑1, with a vertical intensity of Iv = 2.97+0.14‑0.13 (sys) ± 0.02 (stat) × 10‑7 cm‑2 s‑1 sr‑1. Simulations of muon-induced backgrounds identified several potential cosmogenic radionuclides, though only 137Xe is a significant background for the 136Xe 0νββ search with EXO-200. Muon-induced neutron backgrounds were measured using γ-rays from neutron capture on the detector materials. This provided a measurement of 137Xe yield, and a test of the accuracy of the neutron production and transport simulations. The independently measured rates of 136Xe neutron capture and of 137Xe decay agree within uncertainties. Geant4 and FLUKA simulations were performed to estimate neutron capture rates, and these estimates agreed to within ~ 40% or better with measurements. The ability to identify 136Xe(n,γ) events will allow for rejection of 137Xe backgrounds in future 0νββ analyses.

  10. Cosmogenic backgrounds to 0νββ in EXO-200

    NASA Astrophysics Data System (ADS)

    Albert, J. B.; Auty, D. J.; Barbeau, P. S.; Beck, D.; Belov, V.; Breidenbach, M.; Brunner, T.; Burenkov, A.; Cao, G. F.; Chambers, C.; Cleveland, B.; Coon, M.; Craycraft, A.; Daniels, T.; Danilov, M.; Daugherty, S. J.; Davis, J.; Delaquis, S.; Der Mesrobian-Kabakian, A.; DeVoe, R.; Didberidze, T.; Dilling, J.; Dolgolenko, A.; Dolinski, M. J.; Dunford, M.; Fairbank, W., Jr.; Farine, J.; Feldmeier, W.; Feyzbakhsh, S.; Fierlinger, P.; Fudenberg, D.; Gornea, R.; Graham, K.; Gratta, G.; Hall, C.; Herrin, S.; Hughes, M.; Jewell, M. J.; Johnson, A.; Johnson, T. N.; Johnston, S.; Karelin, A.; Kaufman, L. J.; Killick, R.; Koffas, T.; Kravitz, S.; Krücken, R.; Kuchenkov, A.; Kumar, K. S.; Leonard, D. S.; Licciardi, C.; Lin, Y. H.; Ling, J.; MacLellan, R.; Marino, M. G.; Mong, B.; Moore, D.; Njoya, O.; Nelson, R.; Odian, A.; Ostrovskiy, I.; Piepke, A.; Pocar, A.; Prescott, C. Y.; Retière, F.; Rowson, P. C.; Russell, J. J.; Schubert, A.; Sinclair, D.; Smith, E.; Stekhanov, V.; Tarka, M.; Tolba, T.; Tsang, R.; Twelker, K.; Vuilleumier, J.-L.; Waite, A.; Walton, J.; Walton, T.; Weber, M.; Wen, L. J.; Wichoski, U.; Wood, J.; Yang, L.; Yen, Y.-R.; Zeldovich, O. Ya.

    2016-04-01

    As neutrinoless double-beta decay experiments become more sensitive and intrinsic radioactivity in detector materials is reduced, previously minor contributions to the background must be understood and eliminated. With this in mind, cosmogenic backgrounds have been studied with the EXO-200 experiment. Using the EXO-200 TPC, the muon flux (through a flat horizontal surface) underground at the Waste Isolation Pilot Plant (WIPP) has been measured to be Φ = 4.07 ± 0.14 (sys) ± 0.03 (stat) × 10-7 cm-2 s-1, with a vertical intensity of Iv = 2.97+0.14-0.13 (sys) ± 0.02 (stat) × 10-7 cm-2 s-1 sr-1. Simulations of muon-induced backgrounds identified several potential cosmogenic radionuclides, though only 137Xe is a significant background for the 136Xe 0νββ search with EXO-200. Muon-induced neutron backgrounds were measured using γ-rays from neutron capture on the detector materials. This provided a measurement of 137Xe yield, and a test of the accuracy of the neutron production and transport simulations. The independently measured rates of 136Xe neutron capture and of 137Xe decay agree within uncertainties. Geant4 and FLUKA simulations were performed to estimate neutron capture rates, and these estimates agreed to within ~ 40% or better with measurements. The ability to identify 136Xe(n,γ) events will allow for rejection of 137Xe backgrounds in future 0νββ analyses.

  11. Cosmogenic nuclide concentrations in Neogene rivers of the Great Plains reveal the evolution of fluvial storage and recycling

    NASA Astrophysics Data System (ADS)

    Sinclair, Hugh; Stuart, Fin; McCann, Louise; Tao, Zui

    2016-04-01

    The measurement of the duration of near surface residence of sediment grains from the stratigraphic record has the potential to quantitatively reconstruct processes such as stratal condensation, sediment recycling and the exposure histories of unconformities. Geomorphological measurements of dates and rates of surfaces and erosion respectively has enabled significant advances in understanding, however, the radiogenic half life of typical cosmogenic nuclides such as 10Be and 26Al means they are not suitable for the stratigraphic record. Instead, we have applied the stable cosmogenic nuclide of 21Ne to quartz-rich sediment to quantify the routing history of the river systems that have drained the southern Rockies of Wyoming and Colorado during Neogene times. The Neogene sediments of Nebraska record fluvial systems of the Great Plains that flow from the Rockies towards the east and into the Mississippi catchment. This succession is <300 m thick, and records successive episodes of fluvial incision and aggradation associated with regional tilting from 6 to 4 Ma and periods of climate change. As part of an evaluation of the application of 21Ne to the stratigraphic record, we sampled quartzite pebbles from an Upper Miocene, Pliocene and modern river channel of the North Platte approximately 400 km from their mountainous source. The quartzite is derived from a single exposure of the Medicine Bow quartzites in Wyoming, therefore all three intervals recorded the same travel distance from source. Additionally, we know the erosion rate of the Medicine Bow quartzites from detrital 10Be analyses, and we also sampled shielded bedrock samples from the quartzite to evaluate for any non-cosmogenic 21Ne. This means that the concentrations of 21Ne in detrital pebbles >400 km from their source could be corrected for both inherited non-cosmogenic and erosion induced accumulation at source. Therefore, any additional amounts of 21Ne must record storage and exposure during transport down

  12. Dating of Pliocene Colorado River sediments: implications for cosmogenic burial dating and the evolution of the lower Colorado River

    USGS Publications Warehouse

    Matmon, Ari; Stock, Greg M.; Granger, Darryl E.; Howard, Keith A.

    2011-01-01

    We applied cosmogenic 26Al/10Be burial dating to sedimentary deposits of the ancestral Colorado River. We compared cosmogenic burial ages of sediments to the age of an independently well-dated overlying basalt flow at one site, and also applied cosmogenic burial dating to sediments with less precise independent age constraints. All dated gravels yielded old ages that suggest several episodes of sediment burial over the past ∼5.3 m.y. Comparison of burial ages to the overlying 4.4 Ma basalt yielded good agreement and suggests that under the most favorable conditions, cosmogenic burial dating can extend back 4–5 m.y. In contrast, results from other sites with more broadly independent age constraints highlight the complexities inherent in burial dating; these complexities arise from unknown and complicated burial histories, insufficient shielding, postburial production of cosmogenic isotopes by muons, and unknown initial 26Al/10Be ratios. Nevertheless, and in spite of the large range of burial ages and large uncertainties, we identify samples that provide reasonable burial age constraints on the depositional history of sediment along the lower ancestral Colorado River. These samples suggest possible sediment deposition and burial at ca. 5.3, 4.7, and 3.6 Ma. Our calculated basinwide erosion rate for sediment transported by the modern Colorado River (∼187 mm k.y.−1) is higher than the modern erosion rates inferred from the historic sediment load (80–100 mm k.y.−1). In contrast, basinwide paleo-erosion rates calculated from Pliocene sediments are all under 40 mm k.y.−1 The comparatively lower denudation rates calculated for the Pliocene sediment samples are surprising given that the sampled time intervals include significant Pliocene aggradation and may include much incision of the Grand Canyon and its tributaries. This conflict may arise from extensive storage of sediment along the route of the Colorado River, slower paleobedrock erosion, or the inclusion

  13. 10Be dating reveals early-middle Holocene age of the Drygalski Moraines in central West Greenland

    NASA Astrophysics Data System (ADS)

    Cronauer, Sandra L.; Briner, Jason P.; Kelley, Samuel E.; Zimmerman, Susan R. H.; Morlighem, Mathieu

    2016-09-01

    We reconstruct the history of the Greenland Ice Sheet margin on the Nuussuaq Peninsula in central West Greenland through the Holocene using lake sediment analysis and cosmogenic 10Be exposure dating of the prominent Drygalski Moraines. Erratics perched on bedrock outboard of the Drygalski Moraines constrain local deglaciation to ∼9.9 ± 0.6 ka (n = 2). Three Drygalski Moraine crests yield mean 10Be ages of 8.6 ± 0.4 ka (n = 2), 8.5 ± 0.2 ka (n = 3), and 7.6 ± 0.1 ka (n = 2) from outer to inner. Perched erratics between the inner two moraines average 7.8 ± 0.1 ka (n = 2) and are consistent with the moraine ages. Sediments from a proglacial lake with a catchment area extending an estimated 2 km beneath (inland of) the present ice sheet terminus constrain an ice sheet minimum extent from 5.4 ka to 0.6 ka. The moraine chronology paired with the lake sediment stratigraphy reveals that the ice margin likely remained within ∼2 km of its present position from ∼9.9 to 5.4 ka. This unexpected early Holocene stability, preceded by rapid ice retreat and followed by minimum ice extent between ∼5.4 and 0.6 ka, contrasts with many records of early Holocene warmth and the Northern Hemisphere summer insolation maximum. We suggest ice margin stability may instead be tied to adjacent ocean temperatures, which reached an optimum in the middle Holocene.

  14. Production and Recoil Loss of Cosmogenic Nuclides in Presolar Grains

    NASA Astrophysics Data System (ADS)

    Trappitsch, Reto; Leya, Ingo

    2016-05-01

    Presolar grains are small particles that condensed in the vicinity of dying stars. Some of these grains survived the voyage through the interstellar medium (ISM) and were incorporated into meteorite parent bodies at the formation of the Solar System. An important question is when these stellar processes happened, i.e., how long presolar grains were drifting through the ISM. While conventional radiometric dating of such small grains is very difficult, presolar grains are irradiated with galactic cosmic rays (GCRs) in the ISM, which induce the production of cosmogenic nuclides. This opens the possibility to determine cosmic-ray exposure (CRE) ages, i.e., how long presolar grains were irradiated in the ISM. Here, we present a new model for the production and loss of cosmogenic 3He, 6,7Li, and 21,22Ne in presolar SiC grains. The cosmogenic production rates are calculated using a state-of-the-art nuclear cross-section database and a GCR spectrum in the ISM consistent with recent Voyager data. Our findings are that previously measured 3He and 21Ne CRE ages agree within the (sometimes large) 2σ uncertainties and that the CRE ages for most presolar grains are smaller than the predicted survival times. The obtained results are relatively robust since interferences from implanted low-energy GCRs into the presolar SiC grains and/or from cosmogenic production within the meteoroid can be neglected.

  15. Cosmogenic neon from precompaction irradiation of Kapoeta and Murchison

    NASA Technical Reports Server (NTRS)

    Caffee, M. W.; Hohenberg, C. M.; Swindle, T. D.; Goswami, J. N.

    1983-01-01

    Neon from hand-picked Murchison and Kapoeta grains, selected on the basis of the presence or absence of solar flare particle tracks, was analyzed in order to delineate the precompaction history of this material. The irradiated grains showed large enrichments of cosmogenic neon relative to the unirradiated grains. Galactic cosmic ray (GCR) exposure ages for the unirradiated grains yield the nominal values reported for the recent exposure history of these meteorites. Apparent minimum precompaction galactic exposure ages of 28 m.y. and 56 m.y. would have been obtained for Murchison and Kapoeta, respectively, if the cosmogenic effects in the irradiated grains were due to GCR irradiation. Since this seems unreasonably long, the cosmogenic neon in the irradiated grains may be due to spallation by solar cosmic rays. This, however, would require a more active early sun. The isotopic composition of the cosmogenic neon in these grains suggests a harder energy spectrum than is characteristic of present solar flares. Lack of apparent solar wind effects may require some kind of shielding, such as nebular gas.

  16. Orbital forcing of the East Asian summer monsoon based on quantitative paleorainfall records from Chinese Loess using 10Be

    NASA Astrophysics Data System (ADS)

    Beck, W.; White, L.; Cheng, L.; Wu, Z.; zhou, W.; Kong, X.

    2013-12-01

    Here we outline a method for deriving quantitative records of paleoprecipitation using meteoric 10Be flux as recorded in Quaternary loess sediments, and apply this method to derive a ~500ka rainfall record from Chinese loess. The method involves measuring loess 10Be concentration by AMS, then applying corrections for radioactive decay, recycled 10Be in reaerosolized dust, and for variations in geomagnetic field to correct for atmospheric 10Be production rate variations. 10Be flux is calculated by multiplying the corrected 10Be concentrations with loess accumulation rate, where the later is derived from a (non-orbitally tuned) timescale determined from correlating variations in loess magnetic susceptibility with U/Th dated Chinese speleothem δ18O records. The dependence of 10Be flux on rainfall rate is determined using modern observations of 7Be flux in rainfall, and atmospheric 10Be/7Be cosmogenic nuclide production ratios. Modern rainfall on the Chinese Loess Plateau has been shown to be primarily a function of East Asian Summer Monsoon (EASM) intensity. Our 10Be rainfall proxy shows that glacial to peak interglacial rainfall rates in this region have varied by about a factor of two over the last 0.5 Ma. Our results suggests EASM intensity during interglacials MIS11, MIS 9c and MIS13 were all comparable (~850 mm/yr), but slightly less (by ~8%) than for MIS1, and about 15% less than for MIS5e, which is similar to the high latitude ice volume pattern of response except for MIS11. We note that the 10Be rainfall record of MIS13 differs from typical Chinese loess magnetic susceptibility records that suggest MIS13 was the strongest EASM of the last 6 interglacials. Our record instead indicates a relative subdued MIS13 EASM, more consistent with the Antarctic EPICA ice core deuterium or marine δ18O records. We correlate our results with orbital forced solar insolation variations at high and low latitudes as well as with interhemispheric insolation gradients. We find

  17. Using 10-Be in sediment to understand the long-term behavior of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Bierman, Paul; Rood, Dylan; Corbett, Lee; Nelson, Alice; Shakun, Jeremy

    2013-04-01

    We have used in situ and meteoric cosmogenic 10-Be, measured in sediment and rock, to understand better the history and erosional processes of the Greenland Ice Sheet over the many thousand to several million-year time scale. Measured concentrations of in situ 10-Be constrain Holocene emergence histories at the head of Igaliku fiord in southern Greenland. We sampled two well-preserved gravel beach ridges that are the highest marine deposits. Below one beach ridge, we sampled 4 quartzite outcrops at progressively lower elevations and above a nearby beach ridge, we sampled an erratic boulder and the underlying bedrock. We also sampled a beach ridge at a similar elevation at Qassiarsuk on Tunulliarfik Fiord about 20 km away. The data show rapid emergence after 11 ky. All three beach ridges (average and standard error of 6, 6 and 10 clast ages) have the same age (10.98±0.09, 11.07±0.51ky, and 10.96±0.33 ky). Ages of outcrops below the beach ridges are in stratigraphic order and show steady emergence; the outcrop just above modern high water has an age of 8.80 ky. The bedrock/boulder ages from above the beach ridge are slightly younger (10.45 and 10.73 ky, respectively), consistent with inheritance of about 1400 atoms/g 10-Be in beach clasts. Low levels of inheritance in deglacial beach gravels are consistent with the 10-Be content of clasts collected directly from the GIS in western Greenland. Most clasts have the equivalent of only a few hundred to a few thousand atoms/g 10-Be. Sand-sized sediment collected from outwash streams exiting the ice margin at Kangerlussuaq (western Greenland), Narsarsuaq (southern Greenland), and Tasilaq (eastern Greenland) has two to five thousand atoms/g of 10-Be - several times the median amount of in situ 10-Be measured in clasts collected from the ice. These data indicate efficient erosion by the ice sheet of both pre-glacial and interglacial regolith at least near the ice sheet margins. In contrast, chemical and meteoric 10-Be

  18. Using Multiple Cosmogenic Nuclides to Investigate Ice Elevation Changes in the Ellsworth Mountains, Antarctica

    NASA Astrophysics Data System (ADS)

    Marrero, Shasta; Hein, Andy; Sugden, David; Woodward, John; Dunning, Stuart; Freeman, Stewart; Shanks, Richard

    2015-04-01

    Well-dated geologic data points provide important indicators that can be used for the reconstruction of ice sheet dynamics and as constraints in ice sheet models predicting future change. Cosmogenic nuclides, which accumulate in rocks exposed at the earth's surface, can be used to directly date the exposure age of the rock surfaces that have been created through glacial erosion or deposition. The technique requires a detailed understanding of the local geomorphology as well as awareness of the post-depositional processes that may affect the interpretation of exposure ages. Surface exposure ages (10Be, 26Al, 21Ne, and 36Cl) from local limestone bedrock and other glacially deposited exotic lithologies provide a history spanning from 0 to more than 1 million years in the Patriot, Independence, and Marble Hills in the southern Ellsworth Mountains, Antarctica. Using the new surface exposure ages combined with geomorphological mapping, we will discuss the implications for the glacial history of the southern Ellsworth Mountains.

  19. Ice Elevation Changes in the Ellsworth Mountains, Antarctica Using Multiple Cosmogenic Nuclides

    NASA Astrophysics Data System (ADS)

    Marrero, S.; Hein, A.; Sugden, D.; Woodward, J.; Dunning, S.; Reid, K.

    2014-12-01

    Well-dated geologic data points provide important indicators that can be used for the reconstruction of ice sheet dynamics and as constraints in ice sheet models predicting future change. Cosmogenic nuclides, which accumulate in rocks exposed at the earth's surface, can be used to directly date the exposure age of the rock surfaces that have been created through glacial erosion or deposition. The technique requires a detailed understanding of the local geomorphology as well as awareness of the post-depositional processes that may affect the interpretation of exposure ages. Initial surface exposure ages (10Be, 26Al, 21Ne, and 36Cl ) from local limestone bedrock and other glacially deposited exotic lithologies provide a history spanning from 0 to 1.1 Ma in the Patriot, Independence, and Marble Hills in the southern Ellsworth Mountains, Antarctica. Using the new surface exposure ages combined with geomorphological mapping, we will discuss the implications for the glacial history of the southern Ellsworth Mountains.

  20. Applications of in situ cosmogenic nuclides in the geologic site characterization of Yucca Mountain, Nevada

    SciTech Connect

    Gosse, J.C.; Harrington, C.D.; Whitney, J.W.

    1996-08-01

    The gradual buildup of rare isotopes from interactions between cosmic rays and atoms in an exposed rock provides a new method of directly determining the exposure age of rock surfaces. The cosmogenic nuclide method can also provide constraints on erosion rates and the length of time surface exposure was interrupted by burial. Numerous successful applications of the technique have been imperative to the complete surface geologic characterization of Yucca Mountain, Nevada, a potential high level nuclear waste repository. The {sup 10}Be exposure age of Black Cone lava, within a ten mile radius of the proposed repository site, is 840 {+-} 210 kyr (in agreement with previous K/Ar dates of 1.0 {+-} 0.1 Ma). Rates of erosion of the tuff bedrock (< 0.4 cm/kyr from 7 {sup 10}Be measurements) and of hillslope colluvium ({approximately} 0.5 cm/kyr from {sup 10}Be dates on boulder deposits) preclude denudation of the mountain as a concern. Neotectonic concerns (rate of slip and timing of last significant movement along faults) are also being addressed with in situ {sup 14}C and {sup 10}Be measurements on scarp surfaces and on fault-dissected landforms where no surficial expression of the fault is preserved.

  1. Deciphering the Glacial-Interglacial Landscape History in Greenland Based on Markov Chain Monte Carlo Inversion of Existing 10Be-26Al Data

    NASA Astrophysics Data System (ADS)

    Strunk, A.; Knudsen, M. F.; Larsen, N. K.; Egholm, D. L.; Jacobsen, B. H.

    2015-12-01

    Surface exposure dating with cosmogenic nuclides is a dating method under continuous development. It is particularly useful for dating ice-sheet fluctuations in glacial environments, which is essential to increase our understanding of past climate fluctuations and glacial dynamics. Constraining the landscape history in previously glaciated terrains may be difficult, however, due to unknown erosion rates and the presence of inherited nuclides. The potential use of cosmogenic nuclides in landscapes with a complex history of exposure and erosion is therefore often quite limited. In this study, we investigate the landscape history in eastern and western Greenland by applying a novel Markov Chain Monte Carlo (MCMC) inversion approach to the existing 10Be-26Al data from these regions. The new MCMC approach allows us to constrain the most likely landscape history based on comparisons between simulated and measured cosmogenic nuclide concentrations. It is a fundamental assumption of the model approach that the exposure history at the site/location can be divided into two distinct regimes: i) interglacial periods characterized by zero shielding due to overlying ice and a uniform interglacial erosion rate, and ii) glacial periods characterized by 100 % shielding and a uniform glacial erosion rate. We incorporate the exposure/burial history in the model framework by applying a threshold value to the global marine benthic d18O record and include the threshold value as a free model parameter, hereby taking into account global changes in climate. The other free parameters include the glacial and interglacial erosion rates as well as the timing of the Holocene deglaciation. The model essentially simulates numerous different landscape scenarios based on these four parameters and zooms in on the most plausible combination of model parameters. Here, we apply the MCMC-model to the concentrations of 10Be and 26Al measured in three previous studies of glacial fluctuations in Greenland

  2. Old transient landscapes and surface processes: Multiple cosmogenic nuclide and sediment yield data from the Central Andes of northern Chile

    NASA Astrophysics Data System (ADS)

    Kober, F.; Ivy-Ochs, S.; Schlunegger, F.; Zeilinger, G.; Kubik, P. W.; Baur, H.; Wieler, R.

    2005-12-01

    The desert parts of the Andes of northern Chile are regarded as being one of the oldest landscapes on Earth and hence landscape forming processes must act at very slow rates. These slow rates have promoted controversial ideas on the evolution of the Andean mountain chain and discussions whether climatic or tectonic forces predominate the geodynamic evolution of the Andes. Here we present erosion rates of hillslope interfluves across the slope of the western Central Andes (Arica area, northern Chile) derived from several long-lived terrestrial cosmogenic nuclides (10Be, 21Ne, 26Al). Erosion rates positively correlate with elevation and the historical precipitation record, suggesting a coupling between climate and erosion. In addition, it is suggested that the very old landscapes could be preserved in the western Central Andes thanks to low tectonic activity and the prevailing dry climate. Erosion rates estimated back into the middle to late Miocene are on the order of 10-100cm/My at the hyperarid Western Escarpment (Atacama Desert) and the Costal Cordillera. In contrast, erosion rates for the semiarid Western Cordillera are up to >3000cm/My, at least back into the Holocene/late Pleistocene. Here sediment yield data obtained on a decadal scale indicate denudation rates of a similar order of magnitude. In comparison, erosion rates obtained from long-lived cosmogenic nuclides on hillsope interfluves for the Western Cordillera and those derived from preliminary data (21Ne) on catchment wide erosion rates of the Lluta-drainage system yield similar orders of magnitudes. Additionally, catchment wide erosion rates remain largely constant throughout the entire catchment. The analyses of multiple terrestrial cosmogenic nuclides and the use of various "erosion-island" diagrams allowed the identification of system states and of possible complex exposure histories. Complex exposure was identified for non-bedrock samples, such as boulders or amalgamated clast samples. Cosmogenic

  3. Rate of fluvial incision in the Central Alps constrained through joint inversion of detrital 10Be and thermochronometric data

    NASA Astrophysics Data System (ADS)

    Fox, M.; Leith, K.; Bodin, T.; Balco, G.; Shuster, D. L.

    2015-12-01

    Catchment-wide cosmogenic nuclide concentration (CNCs) measurements of erosion rates have revolutionized the interpretation of processes responsible for generating mountainous landscapes. However, surface processes can vary within a single catchment, leading to spatial and temporal variations in erosion rates. This is particularly apparent for landscapes that have transient topographic features due to changes in tectonics or inherited glacial topography. Detrital thermochronometry provides a means to assess where modern sediment is derived as a function of elevation, and constrains the relative erosion rates across a catchment. To solve the corresponding inverse problem, we build on the Bayesian interpretation of probability of observing a detrital age (Avdeev et al., 2011) and use a reversible jump Markov chain Monte Carlo algorithm to sample both the parameter space and also the model complexity. Rivers within the Codera watershed of the Bergell Intrusion (Central European Alps) have incised into a glacial valley. We integrate constraints from detrital apatite fission track ages and detrital 10Be concentrations to interrogate the primary erosion processes shaping this Alpine landscape and constrain rates of erosion across the catchment. We find that modern erosion rates within most downstream portions of the landscape are too low to permit the inferred ˜500 m of incision during the most recent interglacial. Based on the spatial pattern of modern erosion rates, we predict that if the incised fluvial valley was formed solely during interglacial periods, incision is likely to have initiated almost 400,000 years BP. We explore the potential for this type of analysis to study inaccessible landscapes currently covered by ice. Avdeev, B., Niemi, N.A., Clark, M.K., 2011. Doing more with less: Bayesian estimation of erosion models with detrital thermochronometric data. Earth Planet. Sci. Lett. 305 (3), 385-395.

  4. Isotopic hysteresis in detrital cosmogenic nuclide-derived denudation rate studies (Invited)

    NASA Astrophysics Data System (ADS)

    Willenbring, J.; Gasparini, N. M.; Crosby, B. T.; Brocard, G. Y.; Belmont, P.

    2013-12-01

    In equilibrium landscapes, the concentration of beryllium-10 (10Be) from fluvially transported material is expected to quantitatively reflect basin-wide denudation rates. No isotopic time-dependent path is considered because the concentrations reflect an integrated measurement over a sufficiently long period of time to be static. However, the responses of landscapes to changing conditions are often addressed with cosmogenic nuclides in transient landscapes to identify and quantify the primary topographic and climatic controls on erosion. With the advent of techniques that allow event-scale measurement of cosmogenic nuclide concentrations over the course of a flood wave, in the case of meteoric 10Be, or over the course of an uplift wave, in the case of in situ-produced 10Be, we can now evaluate the how the isotope changes and what the 'mean' denudation rate from a single time means. Meteoric 10Be concentrations can be extracted from, and measured in, milligram-sized sediment samples. This attribute enables us to measure suspended sediment through a hydrograph. Here, we give a case study in an agricultural setting. The meteoric 10Be concentration in river sediment changes with the source areas of the fine sediment and fluxes of material supplied to the stream. The average concentration from the couplet of the rising and falling limbs of the hydrograph can differ from the concentration of the sediment that is preserved in depo-centers. Using traditional in situ-produced 10Be, the timescale of the perturbation must be sufficiently long to change the isotopic composition of the bedload, but also for the landscape to respond to the forcing factor. Here, we give an example from a transient landscape where a wave of uplift moves through the basin and a wave of incision follows in its wake. In this setting, 10Be from detrital quartz is derived from both the incising, adjusting lowland and the unadjusted, relict upland, and the integrated 10Be concentrations still provide a

  5. Studies of lunar regolith dynamics using measurements of cosmogenic radionuclides in lunar rocks, soils and cores

    NASA Technical Reports Server (NTRS)

    Fruchter, J. S.; Reeves, J. H.; Evans, J. C.; Perkins, R. W.

    1982-01-01

    The present investigation is concerned with two types of measurements. The first deals with the use of Al-26 to define regolith gardening processes which have occurred in the upper portion of the lunar cores that were collected both by the deep drilling and drive tube operations. The second portion of the study involves the use of Mn-53 and Al-26 concentrations to determine the surface exposure histories of individual rocks over the past ten million years. It is found that during the past two million years, 15011 has had a history of simple gardening with an accumulation rate of 2 cm/m.y. The Apollo 15 Station 2 boulder appears to have been in place for about five million years. The 'shadowed' soil (75237) shows a shielding effect of about 40%. The Apollo 16 Station 9 boulder appears to have been in place for about four million years and thus is apparently not related to the South Ray Crater event.

  6. Cosmogenic nuclide dating of Sahelanthropus tchadensis and Australopithecus bahrelghazali: Mio-Pliocene hominids from Chad.

    PubMed

    Lebatard, Anne-Elisabeth; Bourlès, Didier L; Duringer, Philippe; Jolivet, Marc; Braucher, Régis; Carcaillet, Julien; Schuster, Mathieu; Arnaud, Nicolas; Monié, Patrick; Lihoreau, Fabrice; Likius, Andossa; Mackaye, Hassan Taisso; Vignaud, Patrick; Brunet, Michel

    2008-03-01

    Ages were determined at two hominid localities from the Chad Basin in the Djurab Desert (Northern Chad). In the Koro Toro fossiliferous area, KT 12 locality (16 degrees 00'N, 18 degrees 53'E) was the site of discovery of Australopithecus bahrelghazali (Abel) and in the Toros-Menalla fossiliferous area, TM 266 locality (16 degrees 15'N, 17 degrees 29'E) was the site of discovery of Sahelanthropus tchadensis (Toumaï). At both localities, the evolutive degree of the associated fossil mammal assemblages allowed a biochronological estimation of the hominid remains: early Pliocene (3-3.5 Ma) at KT 12 and late Miocene ( approximately 7 Ma) at TM 266. Atmospheric (10)Be, a cosmogenic nuclide, was used to quasicontinuously date these sedimentary units. The authigenic (10)Be/(9)Be dating of a pelite relic within the sedimentary level containing Abel yields an age of 3.58 +/- 0.27 Ma that points to the contemporaneity of Australopithecus bahrelghazali (Abel) with Australopithecus afarensis (Lucy). The 28 (10)Be/(9)Be ages obtained within the anthracotheriid unit containing Toumaï bracket, by absolute dating, the age of Sahelanthropus tchadensis to lie between 6.8 and 7.2 Ma. This chronological constraint is an important cornerstone both for establishing the earliest stages of hominid evolution and for new calibrations of the molecular clock.

  7. Implications of two Holocene time-dependent geomagnetic models for cosmogenic nuclide production rate scaling

    NASA Astrophysics Data System (ADS)

    Lifton, Nathaniel

    2016-01-01

    The geomagnetic field is a major influence on in situ cosmogenic nuclide production rates at a given location (in addition to atmospheric pressure and, to a lesser extent, solar modulation effects). A better understanding of how past fluctuations in these influences affected production rates should allow more accurate application of cosmogenic nuclides. As such, this work explores the cosmogenic nuclide production rate scaling implications of two recent time-dependent spherical harmonic geomagnetic models spanning the Holocene. Korte and Constable (2011, Phys. Earth Planet. Inter.188, 247-259) and Korte et al. (2011, Earth Planet. Sci. Lett. 312, 497-505) recently updated earlier spherical harmonic paleomagnetic models with new paleomagnetic data from sediment cores in addition to new archeomagnetic and volcanic data. These updated models offer improved resolution and accuracy over the previous versions, in part due to increased temporal and spatial data coverage. In addition, Pavón-Carrasco et al. (2014, Earth Planet. Sci. Lett. 388, 98-109) developed another time-dependent spherical harmonic model of the Holocene geomagnetic field, based solely on archeomagnetic and volcanic paleomagnetic data from the same underlying paleomagnetic database as the Korte et al. models, but extending to 14 ka. With the new models as input, trajectory-traced estimates of effective vertical cutoff rigidity (RC - the standard method for ordering cosmic ray data) yield significantly different time-integrated scaling predictions when compared to each other and to results using the earlier models. In addition, predictions of each new model using RC are tested empirically using recently published production rate calibration data for both 10Be and 3He, and compared to predictions using corresponding time-varying geocentric dipolar RC formulations and a static geocentric axial dipole (GAD) model. Results for the few calibration sites from geomagnetically sensitive regions suggest that the

  8. Erosion of mountain plateaus along Sognefjord, Norway, constrained by cosmogenic nuclides

    NASA Astrophysics Data System (ADS)

    Andersen, Jane Lund; Egholm, David L.; Knudsen, Mads F.; Linge, Henriette; Jansen, John D.

    2016-04-01

    Norway is famous for its deeply incised, steep-sided fjords, carved out by glacial erosion. The high relief of the fjords stands in contrast to the extensive areas of relatively low relief found between the fjords. The origin and development of these low-relief areas remain debated. The classical interpretation relates them to a Mesozoic peneplanation surface, uplifted to the current high elevation in the early Cenozoic (e.g. Nesje, 1994). The validity of this interpretation has, however, been repeatedly questioned in recent times (e.g. Nielsen et al. 2009, Steer et al. 2012). Recent studies point instead to a significant impact of glacial and periglacial erosion processes on the long-term development of the low-relief surfaces (Egholm et al. 2015). Here, we present a large new dataset of in-situ produced cosmogenic 10Be and 26Al in bedrock and boulders from the high, flat summit surfaces along a transect from the coast to the inner parts of Sognefjorden in Norway. Our results indicate substantial glacial modification of the sampled low-relief surfaces within the last 50 ka. Close to the coast, at an elevation of around 700 meters, the cosmogenic nuclide signal was reset around the Younger Dryas due to extensive glacial erosion. Regarding the higher surfaces further inland, our results indicate a maximum cosmogenic nuclide inheritance of 20-30 ka prior to the last deglaciation. We do not find any signs of exceptional longevity of the low-relief landscape. In contrast, our results indicate that the low-relief areas were continuously eroded by glacial and periglacial processes in the Quaternary. Nesje & Whillans. Erosion of Sognefjord, Norway. Geomorphology 9(1), 33-45, 1994. Nielsen et al. The evolution of western Scandinavian topography: a review of Neogene uplift versus the ICE (isostasy-climate-erosion) hypothesis. Journal of Geodynamics 47(2), 72-95, 2009. Steer et al. Bimodal Plio-Quaternary glacial erosion of fjords and low-relief surfaces in Scandinavia

  9. Cosmogenic Neutrinos Challenge the Cosmic-ray Proton Dip Model

    NASA Astrophysics Data System (ADS)

    Heinze, Jonas; Boncioli, Denise; Bustamante, Mauricio; Winter, Walter

    2016-07-01

    The origin and composition of ultra-high-energy cosmic rays (UHECRs) remain a mystery. The proton dip model describes their spectral shape in the energy range above 109 GeV by pair production and photohadronic interactions with the cosmic microwave background. The photohadronic interactions also produce cosmogenic neutrinos peaking around 109 GeV. We test whether this model is still viable in light of recent UHECR spectrum measurements from the Telescope Array experiment and upper limits on the cosmogenic neutrino flux from IceCube. While two-parameter fits have been already presented, we perform a full scan of the three main physical model parameters: source redshift evolution, injected proton maximal energy, and spectral index. We find qualitatively different conclusions compared to earlier two-parameter fits in the literature: a mild preference for a maximal energy cutoff at the sources instead of the Greisen-Zatsepin-Kuzmin cutoff, hard injection spectra, and strong source evolution. The predicted cosmogenic neutrino flux exceeds the IceCube limit for any parameter combination. As a result, the proton dip model is challenged at more than 95% C.L. This is strong evidence against this model independent of mass composition measurements.

  10. Cosmogenic neon in recent lavas from the western United States

    SciTech Connect

    Poreda, R.J.; Cerling, T.E. Utah Univ., Salt Lake City )

    1992-09-01

    Measurements of the absolute cosmogenic production of 21Ne and H3 in olivine for the well-dated Tabernacle Hill flow are reported. Values scaled to sea level and high latitude are 45 atoms/g yr for 21 NeC and 109 atoms/g yr for 3HeC for the past 17,800 yr. A ratio of 21NeC/3HeC of 0.41 +/- 0.05 is measured in olivines that have a range of 25 in cosmogenic exposure; there is no evidence of 3HeC loss in samples older than 100,000 yr. Volcanic plagioclase is shown to be a suitable mineral for cosmogenic 21HeC dating of surfaces. 21NeC in coexisting plagioclase and olivine phenocrysts have a constant ratio of 0.43 +/- 0.04 in samples with more than 10 exp 6 atoms of 21NeC. The production of 21NeC from 23Na is estimated at 160 +/- 50 atoms/g yr at 60 deg and sea level or equivalent to that on 24Mg. 15 refs.

  11. Detection of landscape transience using cosmogenic nuclides and topography

    NASA Astrophysics Data System (ADS)

    Mudd, S. M.

    2015-12-01

    Upland landscapes are frequently perturbed by changing tectonics and climate, which can lead to temporally and spatially varying erosion rates. Hillslopes and channels respond to these changes with different rates, and the dissonance between hillslope and channel response times can be exploited to gain information about the nature and timing of landscape transience. I explore the limits to which differences between channel and hillslope processes can be used to detect transience. Slowing channel erosion rates are difficult to detect, whereas increased erosion rates can be detected if erosion rates more than double. Signals of transient erosion driven by upslope propagation of channel incision can persist for thousands to tens of thousands of years; the time perturbations can be detected is proportional to the square of the hillslope length and the inverse of the hillslope sediment transport coefficient. Climate driven ("top down") and tectonic driven ("bottom up") have different responses to transient perturbation, and lead to different sediment flux responses that are reflected in basinwide cosmogenic nuclide concentrations. Climate driven perturbations are mirrored in cosmogenic concentrations leaving basins whereas tectonic perturbations tend to be averaged when estimated from basinwide cosmogenics.

  12. Lichenometry and Cosmogenic Surface Exposure Dating of Possible Fossil Talus Deposits, Devil's Lake State Park, Wisconsin

    NASA Astrophysics Data System (ADS)

    Knochenhauer, K. J.; Weber, J. C.

    2011-12-01

    Lichenometry and cosmogenic surface exposure dating have been highly successful in deciphering landform evolution in tectonically active regions, but have not been widely applied in mid-continent settings. We propose to test the idea that many of the talus deposits in Devil's Lake State Park (DLSP) are ancient, fossil, periglacial deposits that have been frozen in space and time not moving since ~18,000 years ago. Our results may provide valuable information that could be applied to other settings and may also offer information on the effects of 2nd order climatic events such as the Little Ice Age of the 16th-19th centuries, and also help determine the relation between the last glacial maximum about 18ky ago and its related timing to major mass sediment movements. Our preliminary data was collected methodologically offering tight, unimodal peaks of lichen diameters/ages for Aspicilia cinerea and Dimelaena oreina most consistent with the idea that the deposits have not moved since the last ice age. A growth curve for Dimelaena oreina was established through the use of a neighboring cemetery giving a local growth rate of 67.13mm/100yr with R=68. Size-distribution results for DLSP peaked at only 65.2mm. This suggests that current talus block lichen cover is not a record of the first generation. We will pair our lichenometric results with the future use of 10Be cosmogenic surface exposure dating to determine the ages of the 3 major talus deposits themselves (as opposed to lichen initialization ages) which should allow us to test our initial hypothesis, enhance our lichenometry data set, and begin to develop a more robust sampling strategy for further work. Deciphering the landform evolution of this area would offer insight to past landslides and mass debris flows.

  13. Extensive MIS 3 glaciation in southernmost Patagonia revealed by cosmogenic nuclide dating of outwash sediments

    NASA Astrophysics Data System (ADS)

    Darvill, Christopher M.; Bentley, Michael J.; Stokes, Chris R.; Hein, Andrew S.; Rodés, Ángel

    2015-11-01

    The timing and extent of former glacial advances can demonstrate leads and lags during periods of climatic change and their forcing, but this requires robust glacial chronologies. In parts of southernmost Patagonia, dating pre-global Last Glacial Maximum (gLGM) ice limits has proven difficult due to post-deposition processes affecting the build-up of cosmogenic nuclides in moraine boulders. Here we provide ages for the Río Cullen and San Sebastián glacial limits of the former Bahía Inútil-San Sebastián (BI-SSb) ice lobe on Tierra del Fuego (53-54°S), previously hypothesised to represent advances during Marine Isotope Stages (MIS) 12 and 10, respectively. Our approach uses cosmogenic 10Be and 26Al exposure dating, but targets glacial outwash associated with these limits and uses depth-profiles and surface cobble samples, thereby accounting for surface deflation and inheritance. The data reveal that the limits formed more recently than previously thought, giving ages of 45.6 ka (139.9/-14.3) for the Río Cullen, and 30.1 ka (+45.6/-23.1) for the San Sebastián limits. These dates indicate extensive glaciation in southern Patagonia during MIS 3, prior to the well-constrained, but much less extensive MIS 2 (gLGM) limit. This suggests the pattern of ice advances in the region was different to northern Patagonia, with the terrestrial limits relating to the last glacial cycle, rather than progressively less extensive glaciations over hundreds of thousands of years. However, the dates are consistent with MIS 3 glaciation elsewhere in the southern mid-latitudes, and the combination of cooler summers and warmer winters with increased precipitation, may have caused extensive glaciation prior to the gLGM.

  14. 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

  15. New Insights on Long Term Geomagnetic Moment Variation from Cosmogenic Nuclide and Paleointensity Signatures along Ocean Sediment Cores.

    NASA Astrophysics Data System (ADS)

    Thouveny, N.; Bourles, D. L.; Valet, J. P.; Bassinot, F. C.; Ménabréaz, L.; Simon, Q.; Demory, F.; Valery, G.; Vidal, L.; Beaufort, L.; de Garidel-Thoron, T.

    2015-12-01

    Some numerical and experimental simulations suggest that precession might supply enough power to influence planetary dynamos. The demonstration of a causal relationship between the Earth's orbital motion and variations of the geomagnetic field intensity, would open interesting perspective for modelling the past and future geomagnetic field behaviour and its eventual relationships to past and future orbitally constrained, climatic changes. Although pristine geomagnetic signals can be extracted by filtering and stacking multiple normalized intensity records, the reconstruction of high resolution geomagnetic field variations still raises questions. Namely, significant variance at orbital frequencies in relative paleointensity (RPI) records are generally considered as clues of residual contamination by paleoclimatically induced variations of magnetic carriers size ranges or mineralogy. Such questions can be adressed using other indicators of the geomagnetic dipole moment variation, such as the cosmogenic production modulated by the magnetospheric shielding. During the MAGORB project (ANR-09-BLAN-053-001) cosmogenic nuclide geochemistry, d18O, and paleomagnetic records were constructed along thick clayey-carbonate sequences deposited in the equatorial pacific and indian oceans over the last million of years. Authigenic 10Be/9Be ratio and RPI variations generally exhibit similar ranges of oscillations. However significant offsets appear between some RPI lows and their corresponding 10Be/9Be peaks, suggesting delayed lock-in of the remanent magnetization. After transfer on time scales the new geomagnetic moment series can be compared with the PISO-1500 and SINT-2000 stacks, and with the 10Be ice core record of EPICA Dome C. These new authigenic 10Be/9Be ratio records provide new opportunities to: 1) assess the validity of high resolution RPI records, 2) evaluate address the question of the presence of orbital periods in the paleo-field geomagnetic spectrum, and 3) to

  16. 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.

  17. 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.

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

    USGS Publications Warehouse

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

    2010-01-01

    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.

  19. A Step Toward Physics-Based Cosmogenic Nuclide Production Rates: Measurements of High-Energy Neutron Cross Sections

    NASA Astrophysics Data System (ADS)

    Caffee, M. W.; Welten, K. C.; Ninomiya, K.; Omoto, T.; Nakagaki, R.; Takahashi, N.; Kasamatsu, Y.; Shima, T.; Sekimoto, S.; Yashima, H.; Shibata, S.; Matsumura, H.; Bajo, K.; Nagao, K.; Satoh, D.; Iwamoto, Y.; Hagiwara, M.; Shinohara, A.; Imamura, M.; Nishiizumi, K.

    2010-12-01

    -lived nuclides were measured by low-level γ-ray counting [e.g., 2, 3]. After completion of these measurements, the long-lived nuclides were chemically isolated and measured using AMS. The noble gases were measured by high-sensitivity noble gas mass spectrometry. We will present high-energy neutron cross sections for 10Be, 26Al, 36Cl, and 21Ne from various target elements. [1] Imamura et al. (1990) NIM B52, 595-600. [2] Ninomiya et al. (2009) Radiochim. Acta [3] Sekimoto et al. (2010) J. Nucl. Sci. Technol.

  20. A Fluka study of underground cosmogenic neutron production

    NASA Astrophysics Data System (ADS)

    Empl, A.; Hungerford, E. V.; Jasim, R.; Mosteiro, P.

    2014-08-01

    Neutrons produced by cosmic muon interactions are important contributors to backgrounds in underground detectors when searching for rare events. Typically such neutrons can dominate the background, as they are particularly difficult to shield and detect. Since actual data is sparse and not well documented, simulation studies must be used to design shields and predict background rates. Thus validation of any simulation code is necessary to assure reliable results. This work compares in detail predictions of the FLUKA simulation code to existing data, and uses this code to report a simulation of cosmogenic backgrounds for typical detectors embedded in a water tank with liquid scintillator shielding.

  1. Depth Profiles of Cosmogenic Noble Gases in the Chondrite Knyahinya

    NASA Astrophysics Data System (ADS)

    Toe, S.; Lavielle, B.; Gilabert, E.; Simonoff, G. N.

    1993-07-01

    Concentrations and isotopic ratios of Ne, Ar, Kr, and Xe have been analyzed in 5-g size samples from different positions within the L5 chondrite Knyahinya. A previous work [1] has shown that Knyahinya experienced a single-stage exposure history (duration 40.5 Ma) as a meteoroid of approximately spherical shape (radius 45 cm). For these reasons, this meteorite represents a very interesting object to study depth profiles of cosmogenic nuclide concentrations and to test and improve model calculations of production rates. The procedure of extraction of noble gases adopted for this work, includes two pyrolyses respectively at about 450 degrees C and 650 degrees C, followed by a combustion step in pure O2 (15-25 torr pressure) at 650 degrees C before the complete melting of the sample [2]. This procedure allows a low-temperature extraction of a significant fraction of the Kr and Xe trapped noble gas component, leading to an enrichment of the cosmogenic component during the last temperature step. Concentration of trapped Ar, Kr, and Xe is 2-3 times lower than expected for a type 5 chondrite. The isotopic composition of the trapped Xe component analyzed in the combustion step is identical with the OC- Xe composition measured in Forest Vale [3]. Preliminary results show that concentration of cosmogenic 83Kr increases by 16% from the surface to the center when the ratio of cosmogenic 78Kr to 83Kr decreases from 0.157 to 0.136. The concentration of 81Kr has been measured in each sample. It increases from 0.0220 10^-12 cm^3 STP/g near the surface to 0.0255 10^-12 cm^3 STP/g at the center, in excellent agreement with the variations measured by Eugster [4] in other ordinary chondrites. Acknowledgments: This work was supported by C.N.R.S., by IN2P3 and by INSU (Programme National de Planetologie). References: [1] Graf Th. et al. (1990) GCA, 54, 2511-2520. [2] Gilabert E. and Lavielle B. (1991) Meteoritics, 26, 337. [3] Lavielle B. and Marti K. (1992) JGR, 97, 20875-20881. [4

  2. Solar Wind Implantation Model for 10Be in Calcium-Aluminum Inclusions

    NASA Astrophysics Data System (ADS)

    Bricker, Glynn E.; Caffee, Marc W.

    2010-12-01

    We propose a model for the incorporation of 10Be within calcium-aluminum inclusions (CAIs) in primitive carbonaceous meteorites. In this model, 10Be is produced by energetic particle reactions in the proto-solar atmosphere of a more active proto-Sun characterized by energetic particle fluxes higher than contemporary particle fluxes. This 10Be is incorporated into the solar wind that is then implanted into CAI precursor material. This production mechanism is operational in the contemporary solar system implanting 10Be in lunar materials. The contemporary production rate of 10Be at the surface of the Sun is ~0.1 10Be cm-2 s-1. Scaling up the contemporary 10Be production in the proto-Sun by a factor of 105 would increase the production rate to 104 10Be cm-2 s-1. Using this enhanced production value in conjunction with refractory mass inflow rates at 0.06 AU from the proto-Sun we model 10Be concentrations in CAI precursors. We calculate the content of solar-wind-implanted 10Be would have been of the order of 1012 10Be g-1 in CAIs, consistent with initial10Be content found from boron-beryllium isotopic systematics in CAIs.

  3. Gallbladder radionuclide scan

    MedlinePlus

    Radionuclide - gallbladder; Gallbladder scan; Biliary scan; Cholescintigraphy: HIDA; Hepatobiliary nuclear imaging scan ... small amount of morphine. This can help the radionuclide get into the gallbladder. The morphine may cause ...

  4. Short and long-term delivery rates of meteoric 10Be to terrestrial soils

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

    Well-constrained, long-term average meteoric 10Be deposition rates are important when meteoric 10Be is used as a chronometer or tracer of Earth surface processes. To constrain meteoric 10Be delivery to terrestrial soils, we estimate time-integrated 10Be deposition rates from meteoric 10Be inventories measured in dated soils and compare these results to a new synthesis of short-term measurements of 10Be in precipitation. Comparison of these long-term rates to short-term measurements suggests that short-term measurements likely predict long-term meteoric 10Be deposition rates within uncertainties of ~ 20%. In precipitation measurements, it is possible to deconvolve the contribution of atmospherically-produced "primary" meteoric 10Be from "recycled" meteoric 10Be delivered by terrestrial dust if a second isotope is measured that quantifies either the recycled or primary components of meteoric 10Be deposition. We use dust-concentration dependent differences between 7Be and 10Be measurements to make new estimates of the recycled contribution to total meteoric 10Be flux delivered to the Earth's surface. These dust-corrected data show a strong linear dependence between precipitation amount and primary meteoric 10Be flux. Concentrations of primary meteoric 10Be in mid- and low-latitude precipitation vary predictably by latitude between 0.63 · 10 4 and 2.05 · 10 4 atoms/cm 3 of precipitation, providing a first-order estimate of primary meteoric 10Be deposition for a given latitude and precipitation rate.

  5. 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

  6. Radionuclide deposition control

    DOEpatents

    Brehm, William F.; McGuire, Joseph C.

    1980-01-01

    The deposition of radionuclides manganese-54, cobalt-58 and cobalt-60 from liquid sodium coolant is controlled by providing surfaces of nickel or high nickel alloys to extract the radionuclides from the liquid sodium, and by providing surfaces of tungsten, molybdenum or tantalum to prevent or retard radionuclide deposition.

  7. Forbush decreases geomagnetic and atmospheric effects cosmogenic nuclides

    NASA Technical Reports Server (NTRS)

    Flueckiger, E. O.

    1986-01-01

    An overview and synthesis is given of recent developments that have occurred in the areas of Forbush decreases, geomagnetic and atmospheric effects, and cosmogenic nuclides. Experimental evidence has been found for substantial differences in the effects of the various types of interplanetary perturbations on cosmic rays, and for a dependence of these effects on the three-dimensional configuration of the interplanetary medium. In order to fully understand and to be able to simulate the solar cosmic ray particle access to the polar regions of the earth we need accurate models of the magnetospheric magnetic field. These models must include all major magnetospheric current systems (in particular the field aligned currents), and they should represent magnetically quiet time periods as well as different levels of geomagnetic activity. In the evolution of magnetospheric magnetic field models, cosmic ray and magnetospheric physicists should work closely together since cosmic ray measurements are a powerful additional tool in the study of the perturbed magnetosphere. In the field of cosmogenic nuclides, finally, exciting new results and developments follow in rapid succession. Thanks to new techniques and new isotopes the analysis of cosmic ray history has entered into a new dimension.

  8. Isotope hydrology of catchment basins: lithogenic and cosmogenic isotopic systems

    SciTech Connect

    Nimz, G. J., LLNL

    1998-06-01

    A variety of physical processes affect solute concentrations within catchment waters. The isotopic compositions of the solutes can indicate which processes have determined the observed concentrations. These processes together constitute the physical history of the water. Many solutes in natural waters are derived from the interaction between the water and the rock and/or soil within the system - these are termed `lithogenic` solutes. The isotopic compositions of these solutes provide information regarding rock-water interactions. Many other solutes have their isotopic compositions determined both within and outside of the catchment - i.e., in addition to being derived from catchment rock and soil, they are solutes that are also transported into the catchment. Important members of this group include solutes that have isotopic compositions produced by atomic particle interactions with other nuclides. The source of the atomic particles can be cosmic radiation (producing `cosmogenic` nuclides in the atmosphere and land surface), anthropogenic nuclear reactions (producing `thermonuclear` nuclides), or radioactive and fission decay of naturally-occurring elements, principally {sup 238}U (producing `in-situ` lithogenic nuclides in the deep subsurface). Current language usage often combines all of the atomic particle-produced nuclides under the heading `cosmogenic nuclides`, and for simplicity we will often follow that usage here, although always indicating which variety is being discussed. This paper addresses the processes that affect the lithogenic and cosmogenic solute concentrations in catchment waters, and how the isotopic compositions of the solutes can be used in integrative ways to identify these processes, thereby revealing the physical history of the water within a catchment system. The concept of a `system` is important in catchment hydrology. A catchment is the smallest landscape unit that can both participate in all of the aspects of the hydrologic cycle and

  9. Cosmogenic production vs. climate for the nitrate record in the TALDICE Antarctic ice core

    NASA Astrophysics Data System (ADS)

    Poluianov, Stepan; Usoskin, Ilya; Traversi, Rita

    Reconstructions of solar activity on the multimillennial scale are based usually on records of two cosmogenic isotopes (14) C and (10) Be, measured in tree trunks or ice cores. In addition to these well-known proxies, a chemical tracer was recently proposed (Traversi et al., 2012), viz. nitrate, measured in an Antarctic ice sheet with moderate snow deposition rate. Tropo-stratospheric production of nitrate by cosmic rays is significant in polar regions because of the effect of energetic galactic cosmic rays. However, some climatic factors can influence a nitrate record there. Since the strongest source of nitrate is located at low and middle latitudes as driven by thunderstorm activity, the possible air transport from the lower latitudes to the polar region may significantly distort the signal of solar activity in a nitrate record. The present work is focused on a statistical study of the relation between the air transport from low and middle latitudes and the nitrate deposition in the polar region. We used the data from the TALDICE drilling project (Talos Dome, Antarctica). As galactic cosmic ray indices we used the reconstructions of heliospheric moderation parameter based on (14) C from INTCAL09 and (10) Be from GRIP. The data series cover the age range from 675 till 12000 years BP (i.e. before 1950). We applied the wavelet coherence analysis to compare the nitrate series with a number of substances/proxies: Na(+) , Ca(2+) , MSA (methanesulphonic acid), delta(18) O, no-sea-salt-SO_4(2-) and reconstructions of heliospheric modulation parameter from the (14) C and (10) Be records. We found (1) a confirmation that the multimillennial variability of nitrate is in inverse relation with cosmic ray flux; (2) no sign of the nitrate transport from lower latitudes to the site of deposition. This suggests that variations in the nitrate record in the time scale of hundreds-thousands of years are most likely caused by local production and deposition processes.

  10. SOLAR WIND IMPLANTATION MODEL FOR {sup 10}Be IN CALCIUM-ALUMINUM INCLUSIONS

    SciTech Connect

    Bricker, Glynn E.; Caffee, Marc W. E-mail: mcaffee@purdue.ed

    2010-12-10

    We propose a model for the incorporation of {sup 10}Be within calcium-aluminum inclusions (CAIs) in primitive carbonaceous meteorites. In this model, {sup 10}Be is produced by energetic particle reactions in the proto-solar atmosphere of a more active proto-Sun characterized by energetic particle fluxes higher than contemporary particle fluxes. This {sup 10}Be is incorporated into the solar wind that is then implanted into CAI precursor material. This production mechanism is operational in the contemporary solar system implanting {sup 10}Be in lunar materials. The contemporary production rate of {sup 10}Be at the surface of the Sun is {approx}0.1 {sup 10}Be cm{sup -2} s{sup -1}. Scaling up the contemporary {sup 10}Be production in the proto-Sun by a factor of 10{sup 5} would increase the production rate to 10{sup 410}Be cm{sup -2} s{sup -1}. Using this enhanced production value in conjunction with refractory mass inflow rates at 0.06 AU from the proto-Sun we model {sup 10}Be concentrations in CAI precursors. We calculate the content of solar-wind-implanted {sup 10}Be would have been of the order of 10{sup 1210}Be g{sup -1} in CAIs, consistent with initial{sup 10}Be content found from boron-beryllium isotopic systematics in CAIs.

  11. 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.

  12. Galactic cosmic-ray-produced radionuclides in Antarctic meteorites and a lunar core

    SciTech Connect

    Fox, R.L.

    1987-01-01

    Radionuclide depth effects in a meteorite, the history and pairing of Antarctic meteorites and processes on the lunar surface are discussed in six chapters. A depth profile of /sup 26/Al, /sup 10/Be and /sup 53/Mn activities have been measured in eleven metal phase samples of the Antarctic meteorite ALHA78084 to determine the importance of the secondary cascade in producing these nuclides in a 30 centimeter diameter meteorite. The results show a buildup of lower energy reaction products and a flat profile for high energy reaction products with depth. The activity of /sup 53/Mn has been measured as a function of depth in eleven soil samples from the lunar double drive tubes 15011/15010. The results agree within error with the previous results of Nishiizumi. These data are consistent with the previously published /sup 26/Al results of the Battelle Northwest group which indicated a disturbed profile down to 17 g/cm/sup 2/ and an accumulation rate of 2 cm/My. Comparison with the gardening models of Arnold and Langevin and the local topography suggests such a continuous accumulation is the result of steady downslope transport of surface soil for 7 to 10 My at this site. The /sup 53/Mn activity was determined in eleven samples in eight Allan Hills-80 Antarctic meteorites and one sample from an Elephant Moraine Antarctic meteorite. Mineralogic and field relation data suggest that Allan Hills meteorites to be two sets of paired falls. The /sup 53/Mn results are consistent with the grouping of these meteorites as paired falls excluding the meteorite ALHA80127. comparison with future nuclear particle track work and results from the measurement of other cosmogenic nuclides will provide more definitive results.

  13. A Numerical Model to Assess Soil Fluxes from Meteoric 10Be Data

    NASA Astrophysics Data System (ADS)

    Campforts, B.; Govers, G.; Vanacker, V.; Vanderborght, J.; Smolders, E.; Baken, S.

    2015-12-01

    Meteoric 10Be may be mobile in the soil system. The latter hampers a direct translation of meteoric 10Be inventories into spatial variations in erosion and deposition rates. Here, we present a spatially explicit 2D model that allows us to simulate the behaviour of meteoric 10Be in the soil system. The Be2D model is then used to analyse the potential impact of human-accelerated soil fluxes on meteoric 10Be inventories. The model consists of two parts. A first component deals with advective and diffusive mobility of meteoric 10Be within the soil profile including particle migration, chemical leaching and bioturbation, whereas a second component describes lateral soil (and meteoric 10Be) fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering and lateral soil fluxes from creep, water and tillage erosion. Model simulations show that meteoric 10Be inventories can indeed be related to erosion and deposition, across a wide range of geomorphological and pedological settings. However, quantification of the effects of vertical mobility is essential for a correct interpretation of the observed spatial patterns in 10Be data. Moreover, our simulations suggest that meteoric 10Be can be used as a tracer to unravel human impact on soil fluxes when soils have a high retention capacity for meteoric meteoric 10Be. Application of the Be2D model to existing data sets shows that model parameters can reliably be constrained, resulting in a good agreement between simulated and observed meteoric 10Be concentrations and inventories. This confirms the suitability of the Be2D model as a robust tool to underpin quantitative interpretations of spatial variability in meteoric 10Be data for eroding landscapes.

  14. Holocene dynamics of the Rhone Glacier, Switzerland, deduced from ice flow models and cosmogenic nuclides

    NASA Astrophysics Data System (ADS)

    Goehring, Brent M.; Vacco, David A.; Alley, Richard B.; Schaefer, Joerg M.

    2012-10-01

    We describe efforts to model the Holocene extent of the Rhone Glacier, Switzerland, using four paleoclimate records as templates for paleo-equilibrium line altitude to identify candidate driving mechanisms of glaciers in the Alps. We evaluate the success of each paleoclimate template by comparing cosmogenic 10Be and 14C concentrations in pro-glacial bedrock derived from modeled glacier configurations to measured values. An adequate fit can be obtained using mean summer insolation for 46.5°N. However, use of the Dongee Cave, China, speleothem record yields the best fit by accounting for both sub-millennial (e.g. Little Ice Age and Medieval Warm Period) and multi-millennial climate variations (summer insolation). Our result indicates that glaciers in the Alps primarily responded to changes in insolation during the Holocene were smaller than today during the early Holocene when insolation was relatively high, and became larger during the mid to late Holocene. Superimposed on the first-order insolation response were shorter, sometimes large amplitude, length changes in response to short-lived climate events such as the Medieval Warm Period and the LIA.

  15. Chemical isolation of quartz for measurement of in-situ-produced cosmogenic nuclides

    SciTech Connect

    Kohl, C.P.; Nishiizumi, K. )

    1992-09-01

    Measurement of cosmogenic nuclides produced in situ in terrestrial samples shows great potential as a tool for quantifying continental erosion rates, determining exposure ages of rocks, dating various geologic events, and elucidating past climates. An isolation method relying totally on chemical steps was developed to separate large quantities (10-200 g) of clean mono-minerallic quartz samples from a variety of terrestrial rocks and soils for the purpose of measuring [sup 10]Be (t[sub 1/2] = 1.5 Myr) and [sup 26]Al (t[sub 1/2] = 0.705 Myr) produced by cosmic rays in situ in the quartz phase. The procedure consists of grinding the sample, heating it in HCl, and treating it with a series of leaches using a dilute HF/HNO[sub 3] mixture in a heated ultrasonic tank. The purified quartz was also used for the measurements of in-situ-cosmic-ray-produced [sup 21]Ne and [sup 14]C (t[sub 1/2] = 5,730 yr). The method is applicable to any problem requiring purified quartz on a large scale.

  16. CosmoCalc: An Excel add-in for cosmogenic nuclide calculations

    NASA Astrophysics Data System (ADS)

    Vermeesch, Pieter

    2007-08-01

    As dating methods using Terrestrial Cosmogenic Nuclides (TCN) become more popular, the need arises for a general-purpose and easy-to-use data reduction software. The CosmoCalc Excel add-in calculates TCN production rate scaling factors (using Lal, Stone, Dunai, and Desilets methods); topographic, snow, and self-shielding factors; and exposure ages, erosion rates, and burial ages and visualizes the results on banana-style plots. It uses an internally consistent TCN production equation that is based on the quadruple exponential approach of Granger and Smith (2000). CosmoCalc was designed to be as user-friendly as possible. Although the user interface is extremely simple, the program is also very flexible, and nearly all default parameter values can be changed. To facilitate the comparison of different scaling factors, a set of converter tools is provided, allowing the user to easily convert cut-off rigidities to magnetic inclinations, elevations to atmospheric depths, and so forth. Because it is important to use a consistent set of scaling factors for the sample measurements and the production rate calibration sites, CosmoCalc defines the production rates implicitly, as a function of the original TCN concentrations of the calibration site. The program is best suited for 10Be, 26Al, 3He, and 21Ne calculations, although basic functionality for 36Cl and 14C is also provided. CosmoCalc can be downloaded along with a set of test data from http://cosmocalc.googlepages.com.

  17. 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

  18. The Gas-Filled-Magnet at PRIME Lab: Increased Sensitivity of Cosmogenic Nuclide Measurements

    NASA Astrophysics Data System (ADS)

    Caffee, M. W.; Granger, D. E.; Woodruff, T. E.

    2015-12-01

    Abstract: Using accelerator mass spectrometry (AMS), radionuclides produced either by cosmic-ray interactions or by nucleogenic means can be measured. Typical isotopic abundance ratios range from 1 x 10-10 to 1 x 10-15. The routinely measured radionuclides are 10Be, 14C, 26Al, 36Cl, and 129I. Be-10, 26Al, and 36Cl have isobaric interferences that cannot be eliminated mass through mass analysis, but dE/dx techniques suppresses these isobars enough to allow successful measurements. There are compromises, the isobar for 26Al, 26Mg, precludes successful measurement of 26Al if AlO- is injected into the accelerator. Mg- doesn't form a stable negative ion so a 26Al measurement requires injection of 26Al-. But the Al- ion is formed inefficiently; secondary ion currents using Al- are ~ 10 times less than an AlO- secondary ion beam. Precision scales with count rate so precise measurement of the 26Al/Al for all but higher ratio samples is difficult. It has long been recognized that a gas-filled-magnet (GFM) could potentially improve the measurement of those radionuclides with intractable isobar interferences. A GFM works on the principle that each element of an isobar pair, e.g. 26Mg and 26Al, has a different average charge state as it traverses a gas (3-4 Torr of N2) contained within the vacuum jacket of a magnet. The magnet steers each species with its own momentum-to-charge ratio on its own distinct radius of curvature. The magnet can be tuned to allow the isotope of interest into a dE/dx detector; most of the isobar doesn't make it into the detector. Using the PRIME Lab GFM we are now able to routinely run 26Al with a precision that is comparable to that obtained with 10Be. We are also using the GFM for routine measurements of 10Be and 36Cl. Although the improvement for these nuclides is not as pronounced as it is for 26Al, the GFM has improved the detection sensitivity for both. Our 10Be background is now ~ 5 x 10-16 and for 36Cl we can now run the source more

  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. Rates of surface lowering and landscape development in southern South Africa: a cosmogenic view

    NASA Astrophysics Data System (ADS)

    Richardson, Janet; Vanacker, Veerle; Lang, Andreas; Hodgson, David

    2016-04-01

    The landscape of southern South Africa is characterised by large-scale erosion surfaces, including extensive pediments and multiple strath terraces, which document discordant river evolution through resistant quarzitic lithologies of the Cape Fold Belt (CFB). The timing and rate of erosion is poorly constrained. New cosmogenic ages from surfaces in South Africa are presented using in situ produced 10Be. Strath terraces in deeply incised rivers at two sites within the CFB indicate slow rates of erosion (1.54 - 11.79 m/Ma), which are some of the lowest rates recorded globally. Four pediment surfaces and a depth profile of the thickest pediment were also dated, and the results indicate that there are low rates of surface lowering on the pediments (0.44 - 1.24 m/Ma). The pediments are long-lived features (minimum exposure ages of 0.47 - 1.09 Ma), and are now deeply dissected. Given the minimum exposure ages, calculated river incision rates (42- 203 m/Ma) suggest that after a long period of geomorphic stability during pediment formation there was a discrete phase of increased geomorphic activity. The calculated minimum exposure ages are considered dubious because: 1) known rates of surrounding river incision (published and ours); 2) the climate conditions and time necessary for ferricrete formation on the pediment surfaces and; 3) the deeply incised catchments in the CFB on which the pediments sit, which all point to the pediments being much older. The pediments are fossilised remnants of a much larger geomorphic surface that formed after the main phase of exhumation in southern Africa. They form a store of sediment that currently sit above the surrounding rivers that have some of the lowest erosion rates in the world. These results indicate that steep topography can prevail even in areas of low erosion and tectonic quiescence, and that whilst cosmogenic dating of landscapes is an exciting development in earth sciences, care is needed especially in ancient settings. We

  1. 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

  2. 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

  3. 10Be concentrations of Red soils in Southwest Japan and its possibility of dating

    NASA Astrophysics Data System (ADS)

    Maejima, Y.; Matsuzaki, H.; Nakano, C.

    2004-08-01

    10Be concentrations of six Red soils distributed in Southwest Japan ranged from 0.8 × 108 to 2.7 × 109 atoms g-1, and minimum absolute ages were estimated by inventory of meteoric 10Be. The results are follows: Red soils on Toyota derived from granite (⩽25 ka), Kashii derived from Tertiary shale (⩽24 ka), Akiyoshidai derived from limestone (⩽110 ka), Okinawa Island derived from Kunigami gravel bed (⩽9 ka) and Ogasawara Island derived from agglomerate and Boninite (⩽22 and ⩽7 ka) were obtained, respectively. Soil age except with Akiyoshidai indicated younger age. It suggested that the loss of 10Be from the soil was caused by leaching of 10Be or by soil erosion, and 10Be is susceptible to leaching out from these Red soils under the humid climate condition such as Southwest Japan.

  4. Production rates of cosmogenic nuclides in stony meteorites

    SciTech Connect

    Divadeenam, M.; Gabriel, T.A.; Lazareth, O.W.; Spergel, M.S.; Ward, T.E.

    1989-01-01

    Monte Carlo calculations of /sup 26/Al and /sup 53/Mn production due to spallation induced by cosmogenic protons in model meteorite composition similar to L Chondrite has yielded predictions which are consistent with the observed decay rates in L Chondrite stony meteorites. The calculated /sup 26/Al production rate (54 dpm/kg) in a 1 m diameter meteorite is within 1/2 S.D. of the mean (49 +- 11 dpm/kg) taken from 100 bulk determinations in L Chondrite samples compiled in Nishiizumi (1987). Similarly calculated average value for /sup 53/Mn (223 dpm/kg) is consistent with one S.D. off the mean in the widely scattered /sup 53/Mn data (362 +- 113 dpm/kg) compiled by Nishiizumi (1987). 9 refs.

  5. Cosmogenic neutrinos and ultra-high energy cosmic ray models

    SciTech Connect

    Aloisio, R.; Petrera, S.; Boncioli, D.; Grillo, A.F.; Salamida, F. E-mail: denise.boncioli@lngs.infn.it E-mail: aurelio.grillo@lngs.infn.it E-mail: salamida@ipno.in2p3.fr

    2015-10-01

    We use an updated version of SimProp, a Monte Carlo simulation scheme for the propagation of ultra-high energy cosmic rays, to compute cosmogenic neutrino fluxes expected on Earth in various scenarios. These fluxes are compared with the newly detected IceCube events at PeV energies and with recent experimental limits at EeV energies of the Pierre Auger Observatory. This comparison allows us to draw some interesting conclusions about the source models for ultra-high energy cosmic rays. We will show how the available experimental observations are almost at the level of constraining such models, mainly in terms of the injected chemical composition and cosmological evolution of sources. The results presented here will also be important in the evaluation of the discovery capabilities of the future planned ultra-high energy cosmic ray and neutrino observatories.

  6. Showering cosmogenic muons in a large liquid scintillator

    NASA Astrophysics Data System (ADS)

    Grassi, Marco; Evslin, Jarah; Ciuffoli, Emilio; Zhang, Xinmin

    2014-09-01

    We present the results of FLUKA simulations of the propagation of cosmogenic muons in a 20 kton spherical liquid scintillator detector underneath 700 to 900 meters of rock. A showering muon is one which deposits at least 3 GeV in the detector in addition to ionization energy. We find that 20 percent of muons are showering and a further 11 percent of muon events are muon bundles, of which more than one muon enters the detector. In this range the showering and bundle fractions are robust against changes in the depth and topography, thus the total shower and bundle rate for a given experiment can be obtained by combining our results with an estimate for the total muon flux. One consequence is that a straightforward adaptation of the full detector showering muon cuts used by KamLAND to JUNO or RENO 50 would yield a nearly vanishing detector efficiency.

  7. Measurements of cosmogenic nuclides in lunar rock 64455

    NASA Technical Reports Server (NTRS)

    Arnold, J. R.; Kohl, C. P.; Nishiizumi, K.; Caffee, M. W.; Finkel, R. C.; Southon, J. R.

    1993-01-01

    Eleven samples were ground from the glass coated surface of lunar rock 64455,82 with an average depth resolution of 50 microns and were measured for Be-10, Al-26, and Cl-36 using AMS (accelerator mass spectrometry). Results show no evidence of SCR (solar cosmic ray) effects. The flat cosmogenic nuclide profiles and activity levels are consistent with a 2 My exposure history for the rock and a sample location on the bottom of the rock. These AMS measurements are some of the most precise ever obtained for these three nuclides. This precision and the demonstrated fine depth resolution will enable us to conduct a number of detailed studies of depth effects in lunar and meteoritic samples, including investigating SCR effects in the surface exposed top of the glass coating of 64455 and possibly in the underlying rock.

  8. Simulations for Tracking Cosmogenic Activation in Germanium and Copper

    SciTech Connect

    Aguayo, Estanislao; Kouzes, Richard T.; Orrell, John L.

    2011-11-01

    High-purity germanium (HPGe) detectors housed in copper cryostats and shielding materials are used in measurements of the extraordinarily rare nuclear decay process, neutrinoless double-beta decay (0νββ), and for dark matter searches. Cosmogenic production of 68Ge and 60Co in the germanium and copper represent an irreducible background to these experiments as the subsequent decays of these isotopes can mimic the signals of interest. These radioactive isotopes can be removed by chemical and/or isotopic separation, but begin to grow-in to the material after separation until the material is moved deep underground. This work is motivated by the need to have a reliable, experimentally benchmarked simulation tool for evaluating shielding materials used during transportation and near-surface manufacturing of experiment components. The resulting simulations tool has been used to enhance the effectiveness of an existing transport shield used to ship enriched germanium from the separations facility to the detector manufacturing facility.

  9. Assessing soil fluxes using meteoric 10Be: development and application of the Be2D model

    NASA Astrophysics Data System (ADS)

    Campforts, Benjamin; Govers, Gerard; Vanacker, Veerle; Baken, Stijn; Smolders, Erik; Vanderborght, Jan

    2015-04-01

    Meteoric 10Be is a promising and increasingly popular tool to better understand soil fluxes at different timescales. Unlike other, more classical, methods such as the study of sedimentary archives it enables a direct coupling between eroding and deposition sites. However, meteoric 10Be can be mobilized within the soil. Therefore, spatial variations in meteoric 10Be inventories cannot directly be translated into spatial variations in erosion and sedimentation rates: a correct interpretation of measured 10Be inventories requires that both lateral and vertical movement of meteoric 10Be are accounted for. Here, we present a spatially explicit 2D model that allows to simulate the behaviour of meteoric 10Be in the soil system over timescales of up to 1 million year and use the model to investigate the impact of accelerated erosion on meteoric 10Be inventories. The model consists of two parts. A first component deals with advective and diffusive mobility within the soil profile, whereas a second component describes lateral soil (and meteoric 10Be) fluxes over the hillslope. Soil depth is calculated dynamically, accounting for soil production through weathering and lateral soil fluxes. Different types of erosion such as creep, water and tillage erosion are supported. Model runs show that natural soil fluxes can be well reconstructed based on meteoric 10Be inventories, and this for a wide range of geomorphological and pedological conditions. However, extracting signals of human impact and distinguishing them from natural soil fluxes is only feasible when the soil has a rather high retention capacity so that meteoric 10Be is retained in the top soil layer. Application of the Be2D model to an existing data set in the Appalachian Mountains [West et al.,2013] using realistic parameter values for the soil retention capacity as well as for vertical advection resulted in a good agreement between simulated and observed 10Be inventories. This confirms the robustness of the model. We

  10. Quantitative radionuclide angiocardiography

    SciTech Connect

    Scholz, P.M.; Rerych, S.K.; Moran, J.F.; Newman, G.E.; Douglas, J.M.; Sabiston, D.C. Jr.; Jones, R.H.

    1980-01-01

    This study introduces a new method for calculating actual left ventricular volumes and cardiac output from data recorded during a single transit of a radionuclide bolus through the heart, and describes in detail current radionuclide angiocardiography methodology. A group of 64 healthy adults with a wide age range were studied to define the normal range of hemodynamic parameters determined by the technique. Radionuclide angiocardiograms were performed in patients undergoing cardiac catherization to validate the measurements. In 33 patients studied by both techniques on the same day, a close correlation was documented for measurement of ejection fraction and end-diastolic volume. To validate the method of volumetric cardiac output calcuation, 33 simultaneous radionuclide and indocyanine green dye determinations of cardiac output were performed in 18 normal young adults. These independent comparisons of radionuclide measurements with two separate methods document that initial transit radionuclide angiocardiography accurately assesses left ventricular function.

  11. 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

  12. 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 (

  13. Contribution of Paleomagnetic and Cosmogenic Nuclide Production Records to Solve the Question of Orbital Constraint on the Geodynamo

    NASA Astrophysics Data System (ADS)

    Thouveny, N.; Ménabréaz, L.; Bourles, D. L.; Demory, F.; Guillou, V.; Arnold, M.; Magorb Team

    2013-05-01

    The contribution of axial precession to the geodynamo energy budget recently rebounded with the demonstrations through theoretical and experimental studies that its amount of energy had been underestimated, while on the contrary the energy required to disturb the geodynamo was overestimated (e.g. Vanyo, 2004, Roberts et Wu, 2005, Tilgner 2005). Paleomagnetic tests of such an hypothesis remain yet highly controversial because relative paleointensity reconstructions are suspected of paleoenvironmental biases. Many available indicators [i) depositional remanent magnetization of sediment (paleodirections and paleointensity), ii) magnetization of the deep sea floor basalts, iii) geochemical records of cosmogenic nuclides production rates] however converge to produce a robust series of geomagnetic dipole lows related to paleomagnetic excursions of the last Ma. These series evidence periodicities in the 30 kyr-120 kyr range and present phase relationships with obliquity variations and δ18O records. Yet, such paleomagnetic time series are presently not precise and complete enough to firmly validate such fundamental but still hypothetic relationship. To further contribute solving this issue, the MAG-ORB project, funded for a 4 years period by the French Agence Nationale de la Recherche, aims at reconstructing the time series of the geomagnetic dipole lows over the last 2 Ma using paleomagnetism coupled with cosmogenic nuclide 10Be and lithogenic 9Be isotopes measurements on sedimentary cores from mid and low latitudes, i.e. where the geomagnetic modulation of the cosmic ray penetration is the most efficient. New results (Ménabréaz et al., 2011; 2012; Ménabréaz, 2012) confirm and complete former results (Carcaillet et al., 2003; 2004) to demonstrate that over the last 1.2 Ma the excursions and reversals, and their respective relative paleointensity lows, are accompanied by significant enhancements of the cosmogenic 10Be production rate, pointing out a global collapse of

  14. Glacial-interglacial variation in denudation rates from interior Texas, USA, established with cosmogenic nuclides

    NASA Astrophysics Data System (ADS)

    Hidy, Alan J.; Gosse, John C.; Blum, Michael D.; Gibling, Martin R.

    2014-03-01

    The Brazos, Colorado, and Trinity rivers of Texas drain a tectonically quiescent, non-glaciated, and low-relief landscape inland from the Gulf of Mexico, where long-term [103-105 a] changes in denudation rates are probably driven largely by climate change. Here, we use cosmogenic 10Be to obtain spatially averaged denudation rates for these river catchments, primarily from terrace deposits associated with glacial or interglacial intervals over the past half million years. The denudation rates are ∼30-35% higher during interglacial periods than during glacial periods, and correlate broadly with temperature. The results are consistent with predictions from the BQART sediment flux model, and support the hypothesis that increased weathering rates associated with warmer climates will accelerate landscape erosion. Furthermore, by analyzing 26Al/10Be in these deposits, we can estimate the bed load sourced from up-catchment surfaces. The stored coastal plain fraction varies from ∼10% to 30%, and is greater during times of relatively lower sea level. The results indicate that although sediment flux is moderated by coastal-plain storage, increased up-catchment flux during warmer interglacial periods outpaces evacuation of stored sediment during glacial periods, resulting in a net increase in sediment flux to the ocean during warm intervals. If this temperature-sediment flux relationship is valid beyond the Plio-Pleistocene transition, then global sediment flux to the ocean from passive, non-glaciated, and low-relief landscapes would have been greater during the Pliocene than in the cooler Quaternary.

  15. Geomagnetic field intensity and quantitative paleorainfall reconstruction from Chinese loess using 10Be and magnetic susceptibility

    NASA Astrophysics Data System (ADS)

    Beck, W.; zhou, W.; Li, C.; Wu, Z.; White, L.; Xian, F.

    2011-12-01

    7Be is produced in the atmosphere by cosmic ray spallation reactions and carried to the ground attached to aerosols, usually encapsulated in rain or snow. Numerous studies have shown that its flux to the ground is proportional to rainfall amount. Unfortunately, with a half life of only a few weeks, this observation has little relevance for reconstruction past rainfall amounts in paleosoils. Fortunately, 7Be has a long-lived sister isotope (10Be) with a half life of ~1.5 Ma which can be used for such purposes. There are a number of complications, however. First, 10Be atmospheric production rate changes when the geomagnetic field intensity changes. Secondly, 10Be half life is long enough that 10Be which fell to the ground attached to dust some time in the past can become resuspended, meaning that there are two sources of 10Be, one meteoric, and the other recycled aeolian dust. Fortunately, we have found a method to deconvolute this knotty situation and have applied it to soils of the Chinese Loess Plateau, allowing us to reconstruct records of both geomagnetic field intensity and paleorainfall. To do so, we use the additional parameters magnetic susceptibility and coercivity to help define the inherited amount of each component, and to define what fraction of the variations in 10Be are associated with magnetic field fluctuations, versus that linked to rainfall variations. We also use a sediment age/depth model to convert 10Be concentration to 10Be flux, and finally, we use the modern 7Be vs. rainfall relationship and 10Be/7Be atmospheric production rate ratio to calculate quantitative paleorainfall rates. We have used these techniques to generate several such records ranging from the Holocene to MIS13 (Circa 525 ka BP), and will compare some of these to U-series dated speleothem records of δ18O.

  16. 10Be dating of the Main Terrace level in the Amblève valley (Ardennes, Belgium): new age constraint on the archaeological and palaeontological filling of the Belle-Roche palaeokarst

    NASA Astrophysics Data System (ADS)

    Rixhon, Gilles; Bourlès, Didier L.; Braucher, Régis; Siame, Lionel; Cordy, Jean-Marie; Demoulin, Alain

    2014-05-01

    It is still disputed whether very old archaeological and palaeontological remains found in the Belle-Roche palaeocave (eastern Belgium) pertain to the Early (˜1 Ma) or Middle (˜0.5 Ma) Pleistocene. Here, in situ-produced cosmogenic 10Be concentrations from a depth profile in nearby sediments of the Belle-Roche terrace (Amblève Main Terrace level) are used as an indirect solution of this chronological issue. The distribution of 10Be concentrations in the upper 3 m of this profile displays the theoretically expected exponential decrease with depth. Assuming a single exposure episode, we obtain a best fit age of 222.5±31 ka for the time of terrace abandonment. However, below 3 m, the 10Be concentrations show a marked progressive increase with depth. This distinctive cosmogenic signal is interpreted as the result of slow aggradation of the fluvial deposits over a lengthy interval. Modelling of the whole profile thus suggests that the onset of the terrace formation occurred at around 550 ka, with a sediment accumulation rate of ˜20 mm/ka. Based on two slightly different reconstructions of the geomorphic evolution of the area and a discussion of the temporal link between the cave and Main Terrace levels, we conclude that the fossil-bearing layers in the palaeokarst pertain most probably to MIS 14-13 (or possibly MIS 12-11) and the artifact-bearing layer to MIS 13 (or possibly MIS 11). This age estimate for the large mammal association identified in the Belle-Roche palaeokarst and the attribution to MIS 14-13 of a similar fauna found in the lowermost fossiliferous layers of the Caune de l'Arago (Tautavel) are in mutual support. Our results therefore confirm the status of the Belle-Roche site as a reference site for the Cromerian mammal association and the Early Palaeolithic industry in NW Europe.

  17. 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.

  18. 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

  19. A background simulation method for cosmogenic nuclides inside HPGe detectors for rare event experiments

    NASA Astrophysics Data System (ADS)

    Su, Jian; Zeng, Zhi; Ma, Hao; Yue, Qian; Cheng, Jianping; Li, Jin

    2014-11-01

    Cosmogenic nuclides inside germanium detectors contribute background noise spectra quite different from ordinary external sources. We propose and discuss a nuclide decay and level transition model based on graph theory to understand the background contribution of the decay of cosmogenic nuclides inside a germanium crystal. In this work, not only the level transition process, but the detector response time was also taken into consideration to decide whether or not to apply coincidence summing-up. We simulated the background spectrum of the internal cosmogenic nuclides in a germanium detector, and found some unique phenomena caused by the coincidence summing-up effect in the simulated spectrum. Thus, the background spectrum of each cosmogenic nuclide can be quantitatively obtained.

  20. Monopole transitions to cluster states in 10Be and 9Li

    NASA Astrophysics Data System (ADS)

    Kanada-En'yo, Yoshiko

    2016-08-01

    Isoscalar monopole transitions from the ground states to cluster states in 10Be and 9Li are investigated using 6He+ α and 6He+ t cluster models, respectively. In 10Be, significant monopole strengths are obtained for 6He+ α cluster resonances of 10Be(03,4 +) above the α -decay threshold, whereas the strengths for 6He+ t cluster resonances in 9Li are not enhanced because of the large fragmentation of strengths in the corresponding energy region. The monopole transition to 10Be(02+) with the molecular orbital structure is relatively weak compared with those to 6He+ α cluster resonances. Monopole strength distributions do not directly correspond to distributions of 6He(0+)+ α and 6He(0+)+ t components but reflect the component of the deformed 6He cluster with a specific orientation, which is originally embedded in the ground state.

  1. Measurements of Cosmogenic Nuclides in and their Significance for Samples Returned from Asteroids

    NASA Technical Reports Server (NTRS)

    Nishiizumi, K.; Herzog, G. F.; Reedy, R. C.

    2000-01-01

    Nuclear interactions of cosmic rays with matter produce cosmogenic nuclides (CNs). Ever since they were first measured nearly 50 years ago, cosmogenic nuclides have been used to infer the irradiation histories of terrestrial and extraterrestrial materials. Here we call for an extension of such measurements to samples returned from an asteroidal surface. The information gained in this way will be important for elucidating the evolution of the asteroidal surface. Additional information is contained in the original extended abstract.

  2. 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.

  3. 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.

  4. 10Be inventories in Alpine soils and their potentiality for dating land surfaces

    NASA Astrophysics Data System (ADS)

    Egli, Markus; Brandová, Dagmar; Böhlert, Ralph; Favilli, Filippo; Kubik, Peter W.

    2010-05-01

    To exploit natural archives and geomorphic objects it is necessary to date them first. Landscape evolution of Alpine areas is often strongly related to the activities of glaciers in the Pleistocene and Holocene. At sites where no organic matter for radiocarbon dating exists and where suitable boulders for surface exposure dating (using in situ produced cosmogenic nuclides) are absent, dating of soils could give information about the timing of landscape evolution. We explored the applicability of soil dating using the inventory of meteoric Be-10 in Alpine soils. For this purpose, a set of 6 soil profiles in the Swiss and Italian Alps was investigated. The surface at these sites had already been dated (using the radiocarbon technique or surface exposure dating using in situ produced Be-10). Consequently, a direct comparison of the ages of the soils using meteoric Be-10 and other dating techniques was made possible. The estimation of Be-10 deposition rates is subject to severe limitations and strongly influences the obtained results. We tested three scenarios using a) the meteoric Be-10 deposition rates as a function of the annual precipitation rate, b) a constant Be-10 input for the Central Alps and c) as b) but assuming a pre-exposure of the parent material. The obtained ages that are based on the Be-10 inventory in soils and on scenario a) for the Be-10 input agreed reasonably well with the expected age (obtained from surface exposure or radiocarbon dating). The ages obtained from soils using scenario b) produced mostly ages that were too old whereas the approach using scenario c) seemed to yield better results than scenario b). Erosion calculations can, in theory, be performed using the Be-10 inventory and Be-10 deposition rates. An erosion estimation was possible using scenario a) and c), but not using b). The estimated erosion rates are in a reasonable range. The dating of soils using Be-10 has several potential error sources. Analytical errors as well as errors

  5. Tracing hillslope sediment production and transport with in situ and meteoric 10Be

    NASA Astrophysics Data System (ADS)

    Jungers, Matthew C.; Bierman, Paul R.; Matmon, Ari; Nichols, Kyle; Larsen, Jennifer; Finkel, Robert

    2009-12-01

    We use in situ-produced and meteoric 10Be, analyzed in soils from 28 pits on four hillcrest-parallel transects along a 14° hillslope in the Great Smoky Mountains, North Carolina, as tracers of soil production and transport. We rely upon amalgamation both to investigate and smooth spatial variability in 10Be concentrations. Lidar indicates that the hillslope is topographically complex and that soil is moved downslope diffusively until it encounters the ephemeral channel network and is rapidly exported. In situ-produced 10Be, measured in depth profiles, indicates that over millennial timescales, soils are mixed above the soil-saprolite boundary. In contrast, meteoric 10Be concentrations increase with depth and are correlated to concurrent increases of dithionite-extractable Al and pH, observations explained by similar Al and Be mobility in the soil. The concentrations of both meteoric and in situ-produced 10Be increase downslope proportional to the maximum soil particle path length. The data suggest virtual downslope soil velocities of 1.1-1.7 cm yr-1 in a well-mixed active transport layer ˜60 cm thick. The thickness of this transport layer is constant downslope and depends on the rooting depth and consequent root wad thickness of downed trees on the slope, both of which reflect depth to the soil/saprolite boundary. Both meteoric and in situ-produced 10Be suggest that soil production is balanced by surface denudation at rates between 10 and 13 m Myr-1. Soil residence times on the slope range from 21 to 33 kyr based on the meteoric 10Be inventories. Major element geochemical analysis suggests little if any elemental loss during soil transport downslope.

  6. Unexpected Delivery of Meteoric 10Be to Critical Zone Soils, Front Range, Colorado

    NASA Astrophysics Data System (ADS)

    Ouimet, W. B.; Dethier, D. P.; Bierman, P. R.; Wyshnytsky, C.; Rood, D. H.

    2011-12-01

    Using meteoric 10Be in geomorphic studies requires knowing its long-term delivery rate to the earth surface. Delivery rates vary by latitude due to the influence of geomagnetic field intensity and solar activity and locally due to differences in precipitation and rates of dustfall accumulation, which are responsible for depositing primary and recycled meteoric 10Be to geomorphic surfaces, respectively. Because influences on delivery rate vary in space and time, recent studies emphasize the use of inventory sites where the total concentration of meteoric 10Be is measured on stable landforms of known age to determine site-specific, long-term delivery rates. To date, measured long-term delivery rates typically have fallen within the range of expected rates for the site's latitude and modern annual rate of precipitation, including minor contributions of dust to the total inventory of meteoric 10Be. Here, we present the results of a meteoric 10Be inventory measured on a Pinedale (~15 ka) moraine within the Boulder Creek Critical Zone Observatory, Front Range, Colorado. We report a long-term delivery rate of meteoric 10Be for this site of 4.2 to 4.6 × 106 atoms/cm2/yr, significantly higher than the expected delivery rate (1 to 1.3 × 106 atoms/cm2/yr) for it's latitude (40 degrees) and annual precipitation rate (85-95 cm/yr). A detailed analysis of soils in the Front Range (of various age) indicate that long-term dust accumulation rates are less than ~0.1 grams/cm2/kyr and therefore do not significantly influence the total amount of meteoric 10Be delivered to geomorphic surfaces. When applied to measured concentrations of meteoric 10Be in soils within the Gordon Gulch CZO catchment, our high, inventory-based delivery rate suggests that hillslopes are 10 to 40 ka younger (all post-LGM) than suggested by published precipitation based delivery rates. Furthermore, this result, combined with a long-term delivery rate calibrated nearby on the High Plains (1200 m lower in

  7. Eight Million Years of Land-Based Antarctic Ice Sheet Stability Recorded By In Situ 10Be from the ANDRILL-1B Core

    NASA Astrophysics Data System (ADS)

    Shakun, J. D.; Corbett, L. B.; Bierman, P. R.

    2015-12-01

    The response of the East Antarctic Ice Sheet (EAIS) to Pliocene warmth provides a critical way to gauge its sensitivity to climate change. Considerable uncertainty surrounds the Pliocene behavior of the EAIS, however. For instance, global sea level estimates for the mid-Pliocene warm period range from <10 m to >30 m, and numerous cosmogenic nuclide and sedimentological studies from the Transantarctic Mountains imply extreme landscape stability over the last several Myr whereas ocean records suggest orbital-scale instability of at least marine-based sectors of the ice sheet. These stabilist versus dynamicist views are difficult to resolve because onshore records are generally biased toward intervals of expanded ice cover and limited to areas with exposed land, while marine sediments typically provide indirect evidence for conditions on land and cannot distinguish between marine versus land-based ice sheet collapse. The AND-1B marine sediment core drilled beneath the Ross Ice Shelf contains a remarkably complete late Cenozoic sequence of glacial diamictons sourced from the adjacent EAIS, intercalated with open-water sediments likely associated with West Antarctic Ice Sheet collapse. We measured concentrations of in situ 10Be - produced only when ice cover is reduced and the landscape is exposed - in eight samples of glacially-derived quartz sand from AND-1B spanning parts of the last 8 Myr. Decay-corrected concentrations are low and show a long-term decline from 13,000 atoms/g to 1000 atoms/g over the record. These low values and the monotonic trend suggest that land-based ice sheet sectors have experienced little, if any, exposure during the past 8 Myr; the 10Be concentrations we measured are equivalent to only centuries or a few kyr of surface exposure. Perhaps more likely, the small quantities of 10Be were produced prior to the establishment of a full EAIS in the mid-Miocene, and reflect deeply-exhumed and thus 10Be-poor material that has been radioactively

  8. A geologically constrained Monte Carlo approach to modeling exposure ages from profiles of cosmogenic nuclides: An example from Lees Ferry, Arizona

    NASA Astrophysics Data System (ADS)

    Hidy, Alan J.; Gosse, John C.; Pederson, Joel L.; Mattern, Jann Paul; Finkel, Robert C.

    2010-09-01

    We present a user-friendly and versatile Monte Carlo simulator for modeling profiles of in situ terrestrial cosmogenic nuclides (TCNs). Our program (available online at http://geochronology.earthsciences.dal.ca/downloads-models.html) permits the incorporation of site-specific geologic knowledge to calculate most probable values for exposure age, erosion rate, and inherited nuclide concentration while providing a rigorous treatment of their uncertainties. The simulator is demonstrated with 10Be data from a fluvial terrace at Lees Ferry, Arizona. Interpreted constraints on erosion, based on local soil properties and terrace morphology, yield a most probable exposure age and inheritance of 83.9-14.1+19.1 ka, and 9.49-2.52+1.21 × 104 atoms g-1, respectively (2σ). Without the ability to apply some constraint to either erosion rate or age, shallow depth profiles of any cosmogenic nuclide (except for nuclides produced via thermal and epithermal neutron capture, e.g., 36Cl) cannot be optimized to resolve either parameter. Contrasting simulations of 10Be data from both sand- and pebble-sized clasts within the same deposit indicate grain size can significantly affect the ability to model ages with TCN depth profiles and, when possible, sand—not pebbles—should be used for depth profile exposure dating.

  9. 10Be measurements at MALT using reduced-size samples of bulk sediments

    NASA Astrophysics Data System (ADS)

    Horiuchi, Kazuho; Oniyanagi, Itsumi; Wasada, Hiroshi; Matsuzaki, Hiroyuki

    2013-01-01

    In order to establish 10Be measurements on reduced-size (1-10 mg) samples of bulk sediments, we investigated four different pretreatment designs using lacustrine and marginal-sea sediments and the AMS system of the Micro Analysis Laboratory, Tandem accelerator (MALT) at The University of Tokyo. The 10Be concentrations obtained from the samples of 1-10 mg agreed within a precision of 3-5% with the values previously determined using corresponding ordinary-size (∼200 mg) samples and the same AMS system. This fact demonstrates reliable determinations of 10Be with milligram levels of recent bulk sediments at MALT. On the other hand, a clear decline of the BeO- beam with tens of micrograms of 9Be carrier suggests that the combination of ten milligrams of sediments and a few hundred micrograms of the 9Be carrier is more convenient at this stage.

  10. Cosmogenic Helium In Alluvial Diamonds From Namaqualand, South Africa

    NASA Astrophysics Data System (ADS)

    Burgess, R.; Harris, J. W.

    2005-12-01

    The interpretation of He in diamonds is not straightforward, potential sources include trapped mantle-derived He, radiogenic 4He, and 3He produced in situ by cosmic-ray spallation. The presence of cosmogenic 3He is manifested by high 3He/4He values and ratios of >200 Ra have been measured. 3He contents can be used to distinguish pipe from alluvial diamonds and the time interval that they have been involved in the sedimentary cycle, i.e. their surface exposure history. This is important information for locating the source of alluvial diamonds, understanding their transport histories and may provide a useful tool for diamond exploration. In this study we are analysing the He composition of ten alluvial diamonds from the Koignass-Namaqualand area along the south-west coast of South Africa and Namibia. Diamonds are currently mined at a depth of 100m below the surface from deposits of gravel beaches and river channels. Helium is extracted from the diamonds using a newly developed high temperature filament furnace having a blank approximately 200x lower than conventional resistance furnaces. The low blank of this system means it is possible to extract He by stepwise heating of diamonds weighing 0.05 g. Helium isotopes were analysed using a mass spectrometer with a 3He detection limit of 2,000,000 atoms equivalent to about 20 ka of surface exposure. Results from one diamond from Namaqualand illustrate the range of data obtained so far. This diamond was analysed using eight temperature steps and shows an overall increase in 3He/4He value with temperature from 8.8 x 10-6 to 2.6 x 10-2, the latter being only 10x lower than the pure spallogenic ratio. The cosmogenic 3He content is estimated at 73.5 x 10-12 cm3/g which is at the upper end of the range determined previously in alluvial diamonds from west African sources. Assuming a sea level 3He production rate at 30°S, then the 3He content of this diamond is equivalent to 16 Ma of surface exposure. Most of this exposure is

  11. 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.

  12. 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.

  13. In situ 10Be-26Al exposure ages at Meteor Crater, Arizona

    USGS Publications Warehouse

    Nishiizumi, K.; Kohl, C.P.; Shoemaker, E.M.; Arnold, J.R.; Klein, J.; Fink, D.; Middleton, R.

    1991-01-01

    A new method of dating the surface exposure of rocks from in situ production of 10Be and 26Al has been applied to determine the age of Meteor Crater, Arizona. A lower bound on the crater age of 49,200 ?? 1,700 years has been obtained by this method. ?? 1991.

  14. Using 10Be records to identify possible 14C calibration uncertainties during the Holocene

    NASA Astrophysics Data System (ADS)

    Raimund, Muscheler

    2010-05-01

    The Intcal04 and Intcal09 radiocarbon calibration records are based on multiple tree-ring 14C data sets for Holocene period (Reimer et al. 2004, Reimer et al. 2009). While the dendrochronolgical dating of the trees is supposedly free of errors there are differences between various 14C data sets that underlie the 14C calibration curve. Due to lack of knowledge about the reasons for the differences the Intcal04/09 calibration curves provide a smoothed average of the underlying 14C records. Therefore, problems in one or several of the underlying 14C records would translate directly into errors in the 14C age calibration. Additional knowledge about expected variations in the 14C production rate could help to improve the calibration record since it would allow us to assess how well the different 14C records represent the atmospheric 14C concentration. I propose that 10Be records could be used as additional criteria to chose which of the published 14C records should be preferred (or given stronger weight) for the construction of the calibration curve. Alternatively, 10Be records could point to periods where 14C data should be re-measured in order to improve the calibration curve. I will show for some case studies that the 10Be records from the Greenland ice cores (Muscheler et al. 2004, Vonmoos et al. 2006) indeed provide useful information to scrutinise the Intcal04/09 calibration curve, which could help to improve the 14C calibration curve during the Holocene. Especially shorter-term changes are strongly dampened in the Intcal04/09 calibration record. However, 10Be and some 14C records do exhibit more variability as compared to the calibration record. Therefore, the combined 10Be/14C approach could add confidence that these should be reflected in the 14C calibration record. References: Muscheler, R., Beer, J. et al., 2004. Changes in the carbon cycle during the last deglaciation as indicated by the comparison of 10Be and 14C records. Earth and Planetary Science Letters

  15. Cosmogenic Samarium-150 and Calcium-41 in Norton County

    NASA Technical Reports Server (NTRS)

    Fink, D.; Klein, J.; Middleton, R.; Albrecht, A.; Ma, P.; Herzog, G. F.; Bogard, D. D.; Nyquist, L. E.; Shih, C.-Y.; Reese, Y.; Garrison, D. H.; Masarik, J.; Reedy, R. C.; Rugel, G.; Faestermann, T.; Korschinek, G.

    2010-01-01

    Though brecciated, the Norton County (NC) aubrite contains little or no trapped noble gas and has been widely assumed to have a simple if unusually long cosmic ray exposure (CRE), 115 Ma. One goal of this ongoing study of NC has been to search for signs of pre-irradiation as proposed. One may test for multiple stages of CRE by comparing thermal neutron fluences inferred from Ca-41 (t(sub 1/2)=0.1 Ma) activities, which reflect irradiation conditions over the last approximately 0.3 Ma, with those inferred from (stable) Sm isotope abundances, which integrate over the entire CRE history. In the case of a one-stage exposure the fluences should agree. We focus on these particular comparisons because the properties of NC - its long CRE exposure, relatively large size, and low iron concentration - all promised high production rates and ease of measurement. Previously, we reported on several cosmogenic nuclides in NC. Here we present new Ca-41 data, Sm isotope measurements, and comparisons with model calculations of cosmic ray production.

  16. Analytical Method for Measuring Cosmogenic (35)S in Natural Waters.

    PubMed

    Urióstegui, Stephanie H; Bibby, Richard K; Esser, Bradley K; Clark, Jordan F

    2015-06-16

    Cosmogenic sulfur-35 in water as dissolved sulfate ((35)SO4) has successfully been used as an intrinsic hydrologic tracer in low-SO4, high-elevation basins. Its application in environmental waters containing high SO4 concentrations has been limited because only small amounts of SO4 can be analyzed using current liquid scintillation counting (LSC) techniques. We present a new analytical method for analyzing large amounts of BaSO4 for (35)S. We quantify efficiency gains when suspending BaSO4 precipitate in Inta-Gel Plus cocktail, purify BaSO4 precipitate to remove dissolved organic matter, mitigate interference of radium-226 and its daughter products by selection of high purity barium chloride, and optimize LSC counting parameters for (35)S determination in larger masses of BaSO4. Using this improved procedure, we achieved counting efficiencies that are comparable to published LSC techniques despite a 10-fold increase in the SO4 sample load. (35)SO4 was successfully measured in high SO4 surface waters and groundwaters containing low ratios of (35)S activity to SO4 mass demonstrating that this new analytical method expands the analytical range of (35)SO4 and broadens the utility of (35)SO4 as an intrinsic tracer in hydrologic settings. PMID:25981756

  17. Insights on the post-seismic geomorphological response to the 2008 Wenchuan Earthquake from detrital cosmogenic nuclides data

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Godard, Vincent; Liu-Zeng, Jing; Scherler, Dirk; Xu, Chong; Xu, Quiang; Xie, Kejia; Bellier, Olivier; Ansberque, Claire; de Sigoyer, Julia; Aster Team

    2016-04-01

    In high-relief mountain ranges bounded by reverse faults, large-magnitude earthquakes can contribute to topographic growth by co- and inter-seismic surface uplift of the hanging wall; meanwhile, earthquakes can also lower relief by causing erosion through extensive landslides. Quantifying evacuation process of co-seismic landslides material is central to our understanding of mass redistribution at the earth surface and the evolution of active mountain ranges. The 2008 Mw 7.9 Wenchuan earthquake in the Longmen Shan range of eastern Tibet provides a valuable opportunity to evaluate such direct impact. Cosmogenic nuclides concentrations in river sands are diluted by the input of low-concentration landslide debris materials after the earthquake (West et al., 2014), and we document the evolution 10Be concentrations in quartz for several years after the Wenchuan earthquake to trace the routing processes of co-seismic landslides. Over the 2008-2013 period we collected river sand samples at 19 locations annually along the rivers that flow through the rupture zone. When compared with published pre-earthquake data, our results show that the 10Be concentration in river sand declined dramatically after the earthquake at all sampling sites. Meanwhile, multi-year time series of 10Be concentration at single sites present roughly constant level of dilution with moderate fluctuations. Our analyses indicate that the 10Be dilution amplitude is closely controlled by local catchment slope and landslide density, rather than by the location of landslides with respect to sampling sites. The perturbation we observed for 10Be concentrations in the 0.25~1 mm size fraction appears to be sustained over the timescale of our survey with no clear relaxation, which is consistent with independent results from suspended sediment analysis (Wang et al., 2015).

  18. Using cosmogenic and geochemical data to understand the evolution of modern Himalayan megafans.

    NASA Astrophysics Data System (ADS)

    Abrahami, Rachel; Huyghe, Pascale; Carcaillet, Julien; van der Beek, Peter

    2013-04-01

    Megafans are very large (10's to 100's of km2) alluvial accumulations deposited in foreland basins by laterally mobile river systems. They are located at the topographic front of large mountain belts and in areas subjected to marked seasonal rainfall such as the Himalaya. They may thus be considered in the geological record as marking drainage of significant relief submitted to a monsoonal climate (Horton and Decelles 2001, Leier et al. 2005). Several megafans are present in the Ganga plain, associated with rivers draining vast catchments of the central Himalaya. The easternmost ones are the Kosi and the Tista megafans. Many questions arise from the comparison of their catchment area (size and elevation), their sedimentary characteristics (mean grain size) and finally their recent evolution. While the Kosi megafan is currently still aggrading (Chakraborty, 2010), the Tista megafan located 150 km further east has recently been incised by about 30 meters (Chakraborty & Ghosh, 2010). We combine several methods to consider these questions and to understand which tectonic and climatic parameters impose the major controls on the development of modern Himalayan megafans. Cosmogenic isotopes (10Be, 26Al) are used to date the abandonment of the tree different lobes of the Tista megafan and determine both present-day and paleo-erosion rates averaged over the source area. These data are combined with existing and new 14C and OSL ages of the deposits in order to compare erosional and depositional fluxes through time. In addition, isotope geochemistry (ɛNd and 87Sr/86Sr) of the Tista megafan deposits provides information about sediment provenance through time and its variation in response to climatic conditions.

  19. Radionuclides in US coals

    SciTech Connect

    Bisselle, C. A.; Brown, R. D.

    1984-03-01

    The current state of knowledge with respect to radionuclide concentrations in US coals is discussed. Emphasis is placed on the levels of uranium in coal (and lignite) which are considered to represent a concern resulting from coal combustion; areas of the US where such levels have been found; and possible origins of high radionuclide levels in coal. The report reviews relevant studies and presents new data derived from a computerized search of radionuclide content in about 4000 coal samples collected throughout the coterminous US. 103 references, 5 figures, 5 tables.

  20. Synchronizing the North American Varve Chronology with Greenland ice core records using meteoric 10Be flux

    NASA Astrophysics Data System (ADS)

    DeJong, B.; Balco, G.; Ridge, J. C.; Rood, D. H.; Bierman, P. R.

    2012-12-01

    The North American Varve Chronology (NAVC) is a floating 5700-year sequence of glacial lake varves deposited in the Connecticut River Valley of the northeast US ~18,000-12,500 years ago. The NAVC is an annually resolved record of regional climate and ice-marginal processes at 40-45° N latitude, near the margin of the retreating Laurentide Ice Sheet (LIS). NAVC deposition occurred at the same time as rapid and abrupt Arctic and North Atlantic climate changes that took place during the last deglaciation. An age estimate for the NAVC based on radiocarbon dated plant macrofossils in individual varves implies a relationship between ice-marginal events recorded by the NAVC and climate events recorded in Greenland ice cores. For example, the retreat rate of the LIS up the Connecticut River Valley increased during the Bolling warming in Greenland, a readvance of the LIS margin took place during the Older Dryas cold period, and a correlation between an outburst flood from glacial Lake Iroquois and the Intra-Allerod Cold Period supports the hypothesis that the flood affected North Atlantic thermohaline circulation. On the other hand, a doubling of the ice-margin retreat rate recorded by the NAVC around 16,000 years ago coincides with a relatively cold period in Greenland. Our goal is to investigate the precise time relationship between these events by synchronizing the NAVC with the Greenland ice core time scale using atmospherically-produced 10Be. Existing 10Be flux records, including those from Greenland ice cores, exhibit solar variability on a range of time scales. Because this variability is globally synchronous, a 10Be flux record for the NAVC can, in principle, be used to align NAVC and ice core timescales. We are generating such a record at present. First, we are analyzing short varve sections at high temporal resolution to evaluate the magnitude of solar variability signals; a single section analyzed so far displays interannual variability with a period consistent

  1. Paired proglacial lake sediment and cosmogenic ages reveal the timing of Late Glacial and Holocene glacier fluctuations in the Huaguruncho Massif of Peru

    NASA Astrophysics Data System (ADS)

    Stansell, Nathan; Rodbell, Donald; Licciardi, Joseph; Schweinsberg, Avriel; Huss, Elizabeth; Finkel, Robert; Zimmerman, Susan

    2015-04-01

    The pairing of cosmogenic ages on moraine boulders and radiocarbon-dated lake sediments provides a powerful tool for reconstructing past climates based on former ice positions. Surface exposure ages (10Be) and clastic sediment records from a proglacial lake at Nevado Huaguruncho, Peru, document the waxing and waning of tropical alpine glaciers in the Eastern Cordillera during the last ca. 15 ka. Moraine ages indicate that glaciers were advanced at ca. 14.1 ± 0.4 ka, a pattern that is consistent with cooling associated with the Antarctic Cold Reversal. Yanacocha is located immediately upvalley from this 14.1 ka moraine, and lake sediments and cosmogenic ages also suggest that glaciers advanced just prior to, or at the start of, the Younger Dryas from 13.1 to 12.5 ka. Lake sediments and cosmogenic ages then indicate that glaciers retreated after ca. 12.5 ka, and again advanced during the early Holocene between ca. 12 and 9 ka. Short-lived increases in clastic lake sediment values suggest that ice margins advanced briefly at times through the middle Holocene from ca. 8 to 4 ka, and the lack of moraine boulders dating to this interval suggest that glaciers were less extensive than during the late Holocene. Lake sediments suggest that glaciers experienced a relatively limited advance at the start of the late Holocene from ca. 4 to 2 ka, followed by retreat until the start of the Medieval Climate Anomaly at ca. 1.1 ka. Clastic sediment values in the lake sediments then suggest that ice began advancing during the MCA, and the most pronounced Holocene advance at Huaguruncho occurred during the Little Ice Age (ca. 0.4 to 0.2 ka) under colder and wetter conditions. The pattern of glacier variability in Huaguruncho during the Late Glacial and Holocene provides further evidence that tropical Atlantic Ocean conditions drove much of the observed temperature and precipitation changes along the Eastern Cordillera.

  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. Erosion rates along fault scarps and rift-shoulder environments in central and northern Kenya: Insights from new 10Be-derived basin-wide erosion rates

    NASA Astrophysics Data System (ADS)

    Torres-Acosta, V.; Strecker, M. R.; Schildgen, T. F.; Wittmann, H.; Scherler, D.; Bookhagen, B.

    2011-12-01

    The Kenya Rift is typical example of an active continental rift zone and is a fundamental part of the East African Rift system. The rift valley plays a central role in archiving the relationships between sedimentation, erosion, and climate in the region. However, the links between surface processes (i.e., erosion, sedimentation) and tectonic setting are currently poorly understood. In this study we analyze to what degree tectono-geomorphic setting and/or climatic characteristics control erosion rates in the region. We extract morphometric characteristics of the rift flanks and the plateau surface from SRTM 90-m resolution digital elevation data. We rely on calibrated, satellite-derived Tropical Rainfall Measurement Mission (TRMM 2B31) rainfall to characterize the different climatic compartments throughout the study region. We calculate specific stream power amounts using integrated rainfall as discharge amounts. Next, we analyze the relation between cosmogenic radionuclide (CRN) basin-wide erosion rates and climatic and geomorphic parameters. We determined erosion rates from twenty-six river sand samples acquired from along the flanks of the Elgeyo Escarpment (northern section of western rift flank), the Nguruman Escarpment (southern section of western flank), the Tirr Tirr Plateau (north), the Kapute Plains, and the Suguta Valley. Catchment-wide erosion rates range from 0.001 to 0.1 mm/y across the different climatic compartments. Comparisons to catchment climate and topographic characteristics suggest that more than 60% of variation in erosion can be explain by specific stream power amounts using rainfall as discharge component. The catchment-averaged normalized channel steepness index, which doesn't take into account variations in precipitation, explains only 42% of the variation in erosion rates. These observations demonstrate that the strong spatial variations in erosion rates are largely controlled by both catchment morphology and climatic gradients. In

  4. The Lesser Himalaya stripped naked: tecto-climatic induced fluvial response during the Quaternary inferred from in situ 10Be exposure ages

    NASA Astrophysics Data System (ADS)

    Swander, Z.; Dosseto, A.; Fink, D.; Mifsud, C.

    2011-12-01

    Deciphering a catchment's response to climatic and tectonic forcings requires a spatially extensive geochronology of aggradation-degradation. The Alaknanda River, a major tributary of the Ganga River, constitutes an ideal area for studying this question. From its glacial headwaters sourcing sediment from 7,000+ meter peaks, fueled by glacial meltwater and the Indian Summer Monsoon (ISM) that annually brings the river to sustained flood levels; the Alaknanda River transports a tremendous volume of sediment to the fertile floodplain and delta of the Ganga River. Seven study sites lie within a 200km tectonically active stretch of the river valley transecting the Lesser Himalayan lithological units; demarcated by the Main Central and Main Boundary Thrusts. Twenty bedrock strath surface exposure ages, spreading over two orders of magnitude (102-104 years), were established by measuring the cosmogenic radionuclide (CRN) concentration of beryllium-10. A majority of the bedrock exposure ages support a prior hypothesis for climate driven onset of early-mid Holocene erosion, which resulted in the cessation of catchment-wide fluvial aggradation period at 8ka (Juyal et al. 2010) and culminated with renewed incision of underlying bedrock. Incision rates have a narrow range of 3-7 mm×yr-1 suggesting spatial uniformity, and agree largely with previous estimates (4 mm×yr-1; Barnard et al. 2001).

    When comparing the Holocene aggradation-degradation transition to paleoclimate records from the Guliya Ice Core (Thompson et al. 1997), an apparent correlation exists with the waxing and waning of the ISM as postulated by Juyal et al. (2010). However, preceding the Last Glacial Maximum, a sustained decline in the ISM strength coincided with both periods of active alluvial deposition and erosion. Two episodes of valley wide aggradation occur during extensive regional glaciation 49-25ka, and

  5. 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

  6. Variable and Extreme Irradiation Conditions in the Early Solar System Inferred from the Initial Abundance of 10Be in Isheyevo CAIs

    NASA Astrophysics Data System (ADS)

    Gounelle, Matthieu; Chaussidon, Marc; Rollion-Bard, Claire

    2013-02-01

    A search for short-lived 10Be in 21 calcium-aluminum-rich inclusions (CAIs) from Isheyevo, a rare CB/CH chondrite, showed that only 5 CAIs had 10B/11B ratios higher than chondritic correlating with the elemental ratio 9Be/11B, suggestive of in situ decay of this key short-lived radionuclide. The initial (10Be/9Be)0 ratios vary between ~10-3 and ~10-2 for CAI 411. The initial ratio of CAI 411 is one order of magnitude higher than the highest ratio found in CV3 CAIs, suggesting that the more likely origin of CAI 411 10Be is early solar system irradiation. The low (26Al/27Al)0 [<= 8.9 × 10-7] with which CAI 411 formed indicates that it was exposed to gradual flares with a proton fluence of a few 1019 protons cm-2, during the earliest phases of the solar system, possibly the infrared class 0. The irradiation conditions for other CAIs are less well constrained, with calculated fluences ranging between a few 1019 and 1020 protons cm-2. The variable and extreme value of the initial 10Be/9Be ratios in carbonaceous chondrite CAIs is the reflection of the variable and extreme magnetic activity in young stars observed in the X-ray domain.

  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. Dynamics of erosion in a compressional mountain range revealed by 10Be paleoerosion rates

    NASA Astrophysics Data System (ADS)

    Val, P.; Hoke, G. D.; Fosdick, J. C.; Wittmann, H.

    2015-12-01

    The temporal evolution of erosion over million-year timescales is key to understanding the evolution of mountain ranges and adjacent fold-and-thrust belts. While models of orogenic wedge evolution predict an instantaneous response of erosion to pulses of rock uplift, stream-power based landscape evolution models predict catchment-wide erosion maxima that lag behind a rock uplift pulse. Here, we explore the relationships between rock uplift, erosion, and sediment deposition in the Argentine Precordillera fold-and-thrust belt at 30°S where extensive previous work documents deformation, climate and sediment accumulation histories. Sandstone samples spanning 8.8 to 1.8 Ma were collected from the previously dated wedge-top (Iglesia) and foredeep basins (Bermejo) for quartz purification and 10Be extraction. 10Be concentrations due to burial and exhumation were estimated and subtracted from the measured concentrations and yielded the inherited 10Be concentrations, which were then corrected for sample magnetostratigraphic age. The inherited concentrations were then used to calculate paleoerosion rates. We modeled various pre-burial and post-burial exposure scenarios in order to assess potential sources of uncertainty in the recovered paleoerosion rates. The modeling results reveal that pre-burial and post-burial exposure periods only marginally affect our results. By combining the 10Be-derived paleoerosion rates and geomorphic observations with detrital zircon provenance, we document the isolation of the wedge-top basin, which was later reconnected by an upstream migrating pulse of erosion in a process that was directly controlled by thrust activity and base level. The data further indicate that the attainment of maximum upland erosion rates lags maximum rates of deformation and subsidence 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

  9. 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.

  10. Radionuclide Behavior in Containments.

    2000-02-14

    MATADOR analyzes the transport and deposition of radionuclides as vapor or aerosol through Light Water Reactor (LWR) containments during severe accidents and calculates environmental release fractions of radionuclides as a function of time. It is intended for use in system risk studies. The principal output is information on the timing and magnitude of radionuclide releases to the environment as a result of severely degraded core accidents. MATADOR considers the transport of radionuclides through the containmentmore » and their removal by natural deposition and the operation of engineered safety systems such as sprays. Input data on the source term from the primary system, the containment geometry, and thermal-hydraulic conditions are required.« less

  11. Radionuclides in Diagnosis.

    ERIC Educational Resources Information Center

    Williams, E. D.

    1989-01-01

    Discussed is a radionuclide imaging technique, including the gamma camera, image analysis computer, radiopharmaceuticals, and positron emission tomography. Several pictures showing the use of this technique are presented. (YP)

  12. Abundance of Cosmogenic Noble Gases as a Marker of the Organic Degradation by Cosmic Rays in the Surface Martian Rocks. Implications to MSL and Mars 2020

    NASA Astrophysics Data System (ADS)

    Pavlov, A. A.; Vasilyev, G. I.; Ostryakov, V. M.; Pavlov, A. K.; Mahaffy, P.

    2014-07-01

    We conducted a modeling study which links the rates of cosmogenic isotopes production with the radiation accumulation rates on Mars. We calculated the degradation level of the organic molecules at Cumberland based on the observed cosmogenic isotopes.

  13. Simulations of Terrestrial in-situ Cosmogenic-Nuclide Production

    NASA Technical Reports Server (NTRS)

    Reedy, R. C.; Nishiizumi, K.; Lal, D.; Arnold, J. R.; Englert, P. A. J.; Klein, J.; Middleton, R.; Jull, A. J. T.; Donahue, D. J.

    1994-01-01

    Targets of silicon and silicon dioxide were irradiated with spallation neutrons to simulate the production of long-lived radionuclides in the surface of the Earth. Gamma-ray spectroscopy was used to measure Be-7 and Na-22, and accelerator mass spectrometry was used to measure Be-10, C-14, and Al-26. The measured ratios of these nuclides are compared with calculated ratios and with ratios from other simulations and agree well with ratios inferred from terrestrial samples.

  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. Method and apparatus for separating radionuclides from non-radionuclides

    DOEpatents

    Harp, Richard J.

    1990-01-01

    In an apparatus for separating radionuclides from non-radionuclides in a mixture of nuclear waste, a vessel is provided wherein the mixture is heated to a temperature greater than the temperature of vaporization for the non-radionuclides but less than the temperature of vaporization for the radionuclides. Consequently the non-radionuclides are vaporized while the non-radionuclides remain the solid or liquid state. The non-radionuclide vapors are withdrawn from the vessel and condensed to produce a flow of condensate. When this flow decreases the heat is reduced to prevent temperature spikes which might otherwise vaporize the radionuclides. The vessel is removed and capped with the radioactive components of the apparatus and multiple batches of the radionuclide residue disposed therein. Thus the vessel ultimately provides a burial vehicle for all of the radioactive components of the process.

  16. Extracting in situ cosmogenic 14C from olivine: significance for the CRONUS-Earth project

    NASA Astrophysics Data System (ADS)

    Pigati, J. S.; Lifton, N. A.; Quade, J.; Jull, A. T.

    2005-12-01

    One of the main goals of the Cosmic-Ray-prOduced NUclide Systematics on Earth (CRONUS-Earth) project is to compare production rates of in situ cosmogenic nuclides (CNs) at several well-dated locations in various rock types. Quartz is the most commonly used target mineral for several CNs (e.g., 10Be, 26Al, 21Ne, 14C), but is generally absent in mafic volcanic terrains, where flows of different ages can constrain temporal variations in CN production at a given location. Because of its short half-life (5.73 ka), in situ cosmogenic 14C (in situ 14C) can be particularly useful for elucidating temporal variations in CN production over much shorter time scales than other CNs. While CNs such as 36Cl and 21Ne can be measured in both mafic and felsic rocks, clearly it would be advantageous to measure in situ 14C in mafic rocks as well. As such, we have worked to develop reliable protocols to extract in situ 14C from olivine. We conducted numerous stepped combustion experiments testing the efficacy of various chemical pretreatments. We were able to extract a stable and reproducible in situ 14C component from olivine using a LiBO2 flux, following pretreatment with dilute HNO3. However, measured concentrations in olivine (normalized to SiO2 composition) from two known-age basalt flows, the Tabernacle Hill flow (17.3+/-0.4 ka in age) in central Utah and the McCarty's flow (3.0+/-0.2 ka in age) in western New Mexico, were 3 to 5 times lower than predicted in situ 14C concentrations based on measurements in quartz. This discrepancy appears to arise from (1) a synthetic spinel-like mineral formed during our extraction process by the chemical interaction of the Al2O3 sample boat and olivine dissolved within the LiBO2 flux, and (2) undissolved pyroxene phenocrysts (difficult to separate in quantity from olivines). Although we do not fully understand how the formation of the synthetic mineral may affect carbon atoms liberated from olivine, the concentration of in situ 14C atoms that

  17. 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.

  18. Meteoric 10Be in volcanic materials and its behavior during acid-leaching

    NASA Astrophysics Data System (ADS)

    Shimaoka, Akiko; Sakamoto, Minoru; Hiyagon, Hajime; Matsuzaki, Hiroyuki; Kaneoka, Ichiro; Imamura, Mineo

    2004-08-01

    We have investigated the chemical and isotopic behavior of beryllium (Be) during acid leaching for removing meteoric 10Be in volcanic samples. Determination of the Be isotopic ratio in the leachate was carried out using accelerator mass spectrometry (AMS) and inductivity coupled plasma mass spectrometer (ICP-MS). Elemental distribution of Be and other incompatible elements including boron (B) were also examined by ion microprobe (SIMS) for a deeper understanding of their chemical behavior in volcanic samples. SIMS analysis show that Be is concentrated in the groundmass together with B. However, the behavior of their elements during acid leaching is quite different. The Be concentration decreases through progressive leaching, while the concentration of B remains constant. Furthermore, the variation in the Be isotopic ratio after acid leaching is different between the two samples, neither of which has altered minerals under microscopic observation. It is demonstrated that meteoric 10Be resides in a rather narrow region of the rock and can be removed by acid leaching with minimum loss of the main host phase of Be.

  19. 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.

  20. Records of Local Glacier Variability in Western Greenland During the Holocene From Lake Sediments, Ice-cap-killed Vegetation, and 10Be Dating

    NASA Astrophysics Data System (ADS)

    Schweinsberg, A.; Briner, J. P.; Miller, G. H.; Bennike, O.

    2015-12-01

    Local mountain glaciers and ice caps are common and widespread along the periphery of Greenland and provide valuable paleoclimatic records because they respond sensitively to climate change. In contrast to extensive research on Greenland Ice Sheet (GIS) margin changes, the relative timing of mountain glaciation during the Holocene is poorly documented. Here, we use a multi-proxy approach to document the timing of local glacier advance and retreat throughout the past ~10 ka in western Greenland by combining: (1) proglacial lake sediment analysis, (2) 14C-dating of ice-cap-killed in situ plants, and (3) cosmogenic 10Be dating. Radiocarbon-dated sediment cores from Sikuiui and Pauiaivik lakes, eastern Nuussuaq, provide minimum-limiting ages for local deglaciation of 9.4 ± 0.06 and 8.8 ± 0.16 ka, respectively, and are in agreement with 10Be ages of regional deglaciation that average 10.9 ± 0.7 ka (n=8). Radiocarbon ages (n=54) of in situ plants along retreating cold-based ice cap margins reveal net snowline lowering beginning ~5 ka and are concurrent with the onset of Neoglaciation recorded in both lake systems. Modes of vegetation kill dates highlight distinct ice cap expansion phases at ~3.7, ~3.0, ~1.5 ka, and during the Little Ice Age. The most pronounced snowline lowering event ~4-3 ka is expressed in both lake records by deposition of mineral-rich sediments between ~4.5 and 2.5 ka. Ice cap expansion phases are broadly correlative with elevated minerogenic input in both lakes with some modes in the vegetation ages occurring just prior to increases in mineral-rich sediment input. Published studies of the western GIS margin suggest a major cooling event between ~4.3-3.2 ka, which overlaps with periods of enhanced local glacier activity and ice cap expansion in our dataset. Lastly, the dominant ice cap expansion episode ~3.7 ka in western Greenland is synchronous with a significant snowline lowering event on Baffin Island, suggesting a common climate forcing

  1. 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

  2. Cosmogenic and primordial radioisotopes in copper bricks shortly exposed to cosmic rays

    NASA Astrophysics Data System (ADS)

    Coarasa, I.; Amaré, J.; Cebrián, S.; Cuestá, C.; García, E.; Martínez, M.; Oliván, M. A.; Ortigoza, Y.; Ortíz de Solórzano, A.; Puimedón, J.; Sarsa, M. L.; Villar, J. A.; Villar, P.

    2016-05-01

    Cosmogenic activation is the most common source of radioactivity in copper, being 60 Co the most significant because of its long half-life (5.27 y) and saturation activity at sea level of 1 mBq/kg. Copper bricks, which had been exposed to cosmic rays for 41 days after their casting, were used to replace the internal 10 cm of the lead shielding of a HPGe detector placed at the Canfranc Underground Laboratory. We describe the outcome of the new shielding and the cosmogenic and primordial radioisotopes observed.

  3. Accelerator experiments on the contribution of secondary particles to the production of cosmogenic nuclides in meteorites

    NASA Technical Reports Server (NTRS)

    Dragovitsch, P.; Englert, P.

    1985-01-01

    Through the interaction of galactic cosmic particle radiation (GCR) a wide variety of cosmogenic nuclides is produced in meteorites. They provide historical information about the cosmic radiation and the bombarded meteorites. An important way to understand the production mechanisms of cosmogenic nuclides in meteorites is to gather information about the depth and size dependence of the build-up of Galactic Rays Cosmic-secondary particles within meteorites of different sizes and chemical compositions. Simulation experiments with meteorite models offer an alternative to direct observation providing a data basis to describe the development and action of the secondary cascade induced by the GCR in meteorites.

  4. Applications of in situ cosmogenic nuclides in the geologic site characterization of Yucca Mountain, Nevada

    SciTech Connect

    Gosse, J.C.; Harrington, C.D.; Whitney, J.W.

    1995-12-31

    The gradual buildup of rare isotopes from interactions between cosmic rays and atoms in an exposed rock provides a new method of directly determining the exposure age of rock surfaces. The cosmogenic nuclide method can also provide constraints on erosion rates and the length of time surface exposure was interrupted by burial. Numerous successful applications of the technique have been imperative to the complete surface geologic characterization of Yucca Mountain, Nevada, a potential high level nuclear waste repository. In this short paper, we summarize the cosmogenic nuclide method and describe with examples some the utility of the technique in geologic site characterization. We report preliminary results from our ongoing work at Yucca Mountain.

  5. 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.

  6. Cosmogenic exposure-age chronologies of Pinedale and Bull Lake glaciations in greater Yellowstone and the Teton Range, USA

    USGS Publications Warehouse

    Licciardi, J.M.; Pierce, K.L.

    2008-01-01

    We have obtained 69 new cosmogenic 10Be surface exposure ages from boulders on moraines deposited by glaciers of the greater Yellowstone glacial system and Teton Range during the middle and late Pleistocene. These new data, combined with 43 previously obtained 3He and 10Be ages from deposits of the northern Yellowstone outlet glacier, establish a high-resolution chronology for the Yellowstone-Teton mountain glacier complexes. Boulders deposited at the southern limit of the penultimate ice advance of the Yellowstone glacial system yield a mean age of 136??13 10Be ka and oldest ages of ???151-157 10Be ka. These ages support a correlation with the Bull Lake of West Yellowstone, with the type Bull Lake of the Wind River Range, and with Marine Isotope Stage (MIS) 6. End moraines marking the maximum Pinedale positions of outlet glaciers around the periphery of the Yellowstone glacial system range in age from 18.8??0.9 to 16.5??1.4 10Be ka, and possibly as young as 14.6??0.7 10Be ka, suggesting differences in response times of the various ice-cap source regions. Moreover, all dated Pinedale terminal moraines in the greater Yellowstone glacial system post-date the Pinedale maximum in the Wind River Range by ???4-6 kyr, indicating a significant phase relationship between glacial maxima in these adjacent ranges. Boulders on the outermost set and an inner set of Pinedale end moraines enclosing Jenny Lake on the eastern Teton front yield mean ages of 14.6??0.7 and 13.5??1.1 10Be ka, respectively. The outer Jenny Lake moraines are partially buried by outwash from ice on the Yellowstone Plateau, hence their age indicates a major standstill of an expanded valley glacier in the Teton Range prior to the Younger Dryas, followed closely by deglaciation of the Yellowstone Plateau. These new glacial chronologies are indicative of spatially variable regional climate forcing and temporally complex patterns of glacier responses in this region of the Rocky Mountains during the Pleistocene

  7. Cosmogenic 3He in igneous and fossil tooth enamel fluorapatite

    NASA Astrophysics Data System (ADS)

    Farley, K. A.; Cerling, T. E.; Fitzgerald, P. G.

    2001-02-01

    Igneous fluorapatite samples from a suite of six granitic rocks from the Transantarctic Mountains have high 3He concentrations (to 5×10 9 atoms g -1) and high 3He/ 4He ratios (to 9×10 -7). These values are far higher than those found in several hundred igneous apatites from elsewhere around the world and are higher than can be attributed to nuclear reactions on 6Li. This 3He is almost certainly derived from cosmic ray reactions in rocks with high exposure ages at high latitude and elevation. Several samples of fossil tooth enamel fluorapatite from the Turkana Basin of Kenya are similarly rich in 3He, with up to 1×10 7 atoms 3He g -1 and 3He/ 4He ratios up to 4×10 -6. Again, this 3He is most logically attributed to cosmic ray reactions. Provided that cosmogenic 3He, like radiogenic 4He, is quantitatively retained in fluorapatite under Earth surface conditions, routine 3He exposure dating of this common phase may be possible. Based on its chemical composition, the 3He production rate in fluorapatite is about 100 atoms g -1 yr -1 at sea level and high latitude. Using this rate the apatites from the Transantarctic Mountains have apparent exposure ages of 0.5-6.2 Myr, in agreement with values elsewhere in the range. The fossil tooth enamel samples have apparent exposure ages ranging from a few up to 130 kyr. Such high exposure ages suggest some of these fossils may be lag deposits with a very long residence time at or near the Earth's surface. 3He exposure ages can provide insights to the depositional and reworking history of enamel-bearing fossils. At present the major limitations to 3He exposure dating of fluorapatite are purification of sufficient amounts of material and measurement of small amounts of 3He in the presence of large quantities of 4He. In addition, further work is necessary to establish the nucleogenic 3He background in fluorapatite.

  8. Extraction of in situ cosmogenic 14C from olivine

    USGS Publications Warehouse

    Pigati, J.S.; Lifton, N.A.; Timothy, Jull A.J.; Quade, Jay

    2010-01-01

    Chemical pretreatment and extraction techniques have been developed previously to extract in situ cosmogenic radiocarbon (in situ 14C) from quartz and carbonate. These minerals can be found in most environments on Earth, but are usually absent from mafic terrains. To fill this gap, we conducted numerous experiments aimed at extracting in situ 14C from olivine ((Fe,Mg)2SiO4). We were able to extract a stable and reproducible in situ 14C component from olivine using stepped heating and a lithium metaborate (LiBO2) flux, following treatment with dilute HNO3 over a variety of experimental conditions. However, measured concentrations for samples from the Tabernacle Hill basalt flow (17.3 ?? 0.3 ka4) in central Utah and the McCarty's basalt flow (3.0 ?? 0.2 ka) in western New Mexico were significantly lower than expected based on exposure of olivine in our samples to cosmic rays at each site. The source of the discrepancy is not clear. We speculate that in situ 14C atoms may not have been released from Mg-rich crystal lattices (the olivine composition at both sites was ~Fo65Fa35). Alternatively, a portion of the 14C atoms released from the olivine grains may have become trapped in synthetic spinel-like minerals that were created in the olivine-flux mixture during the extraction process, or were simply retained in the mixture itself. Regardless, the magnitude of the discrepancy appears to be inversely proportional to the Fe/(Fe+Mg) ratio of the olivine separates. If we apply a simple correction factor based on the chemical composition of the separates, then corrected in situ 14C concentrations are similar to theoretical values at both sites. At this time, we do not know if this agreement is fortuitous or real. Future research should include measurement of in situ 14C concentrations in olivine from known-age basalt flows with different chemical compositions (i.e. more Fe-rich) to determine if this correction is robust for all olivine-bearing rocks. ?? 2010 by the Arizona

  9. Initial Radionuclide Inventories

    SciTech Connect

    Miller, H

    2005-07-12

    The purpose of this analysis is to provide an initial radionuclide inventory (in grams per waste package) and associated uncertainty distributions for use in the Total System Performance Assessment for the License Application (TSPA-LA) in support of the license application for the repository at Yucca Mountain, Nevada. This document is intended for use in postclosure analysis only. Bounding waste stream information and data were collected that capture probable limits. For commercially generated waste, this analysis considers alternative waste stream projections to bound the characteristics of wastes likely to be encountered using arrival scenarios that potentially impact the commercial spent nuclear fuel (CSNF) waste stream. For TSPA-LA, this radionuclide inventory analysis considers U.S. Department of Energy (DOE) high-level radioactive waste (DHLW) glass and two types of spent nuclear fuel (SNF): CSNF and DOE-owned (DSNF). These wastes are placed in two groups of waste packages: the CSNF waste package and the codisposal waste package (CDSP), which are designated to contain DHLW glass and DSNF, or DHLW glass only. The radionuclide inventory for naval SNF is provided separately in the classified ''Naval Nuclear Propulsion Program Technical Support Document'' for the License Application. As noted previously, the radionuclide inventory data presented here is intended only for TSPA-LA postclosure calculations. It is not applicable to preclosure safety calculations. Safe storage, transportation, and ultimate disposal of these wastes require safety analyses to support the design and licensing of repository equipment and facilities. These analyses will require radionuclide inventories to represent the radioactive source term that must be accommodated during handling, storage and disposition of these wastes. This analysis uses the best available information to identify the radionuclide inventory that is expected at the last year of last emplacement, currently identified as

  10. Initial Radionuclide Inventories

    SciTech Connect

    H. Miller

    2004-09-19

    The purpose of this analysis is to provide an initial radionuclide inventory (in grams per waste package) and associated uncertainty distributions for use in the Total System Performance Assessment for the License Application (TSPA-LA) in support of the license application for the repository at Yucca Mountain, Nevada. This document is intended for use in postclosure analysis only. Bounding waste stream information and data were collected that capture probable limits. For commercially generated waste, this analysis considers alternative waste stream projections to bound the characteristics of wastes likely to be encountered using arrival scenarios that potentially impact the commercial spent nuclear fuel (CSNF) waste stream. For TSPA-LA, this radionuclide inventory analysis considers U.S. Department of Energy (DOE) high-level radioactive waste (DHLW) glass and two types of spent nuclear fuel (SNF): CSNF and DOE-owned (DSNF). These wastes are placed in two groups of waste packages: the CSNF waste package and the codisposal waste package (CDSP), which are designated to contain DHLW glass and DSNF, or DHLW glass only. The radionuclide inventory for naval SNF is provided separately in the classified ''Naval Nuclear Propulsion Program Technical Support Document'' for the License Application. As noted previously, the radionuclide inventory data presented here is intended only for TSPA-LA postclosure calculations. It is not applicable to preclosure safety calculations. Safe storage, transportation, and ultimate disposal of these wastes require safety analyses to support the design and licensing of repository equipment and facilities. These analyses will require radionuclide inventories to represent the radioactive source term that must be accommodated during handling, storage and disposition of these wastes. This analysis uses the best available information to identify the radionuclide inventory that is expected at the last year of last emplacement, currently identified as

  11. Lunar regolith dynamics based on analysis of the cosmogenic radionuclides Na-22, Al-26, and Mn-53

    NASA Technical Reports Server (NTRS)

    Fruchter, J. S.; Rancitelli, L. A.; Laul, J. C.; Perkins, R. W.

    1977-01-01

    Depth profiles of Na-22 and Al-26 in the upper portions of five lunar cores are analyzed. From the analyses, it is concluded that the natural gardening processes on the lunar surface result in mixing of the regolith to a depth of 2-3 cm over a time period which is short compared with the half-life of Al-26 (0.73 m.y.). It is also concluded that the rotary drill processes which were used to obtain the deep drill samples generally resulted in loss and/or mixing of the upper portions of the cores. In contrast, the near-surface regions of the drive tube cores appear to have a well-preserved stratigraphy. Analysis of Mn-53 in samples of six lunar rocks helps substantiate the accuracy of age date estimates by other means, and provides definite information that the total lunar surface exposure of two of these rocks has occurred during a single surface event which continued to their collection.

  12. Radionuclide studies in impotence

    SciTech Connect

    Hilson, A.J.; Lewis, C.A. )

    1991-04-01

    Impotence may be of physiological origin with causes including vascular or neurological pathology. Alternatively, it may be of psychogenic origin. Clinicians can distinguish between psychological and organic impotence by observing nocturnal penile tumescence. Non-radionuclide investigations for organic impotence include penile plethysmography or pulse Doppler analysis for arterial supply, cavernosometry for venous drainage, and biothesiometry or evoked potentials for neurological pathology. Radionuclide studies are primarily based on the use of technetium 99m-pertechnetate, 99mTc-red blood cells, or xenon 133 to study the blood flow, with or without pharmacological intervention, commonly papaverine. 26 references.

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. The cosmogenic induced background estimation for the MAJORANA DEMONSTRATOR enriched 76Ge

    NASA Astrophysics Data System (ADS)

    White, Brandon; Majorana Collaboration

    2016-03-01

    Neutrino-less double beta (0 νββ) decay experiments probe for such rare events that the suppression of backgrounds are major experimental concerns. Cosmogenic induced isotopes have the potential to be a major background for such experiments. For the MAJORANA DEMONSTRATOR Experiment 76Ge isotope is used as both detector and source. The isotope 68Ge is cosmogenically produced when the Ge is on the Earth's surface. The decay of this isotope can mimic events in the region of interest. The experiment is located at the 4850 foot level at the Sanford Underground Research Facility in Lead, South Dakota to suppress cosmogenic activation. In this talk I will present the calculations of cosmogenic background for the enriched 76Ge materials used in the MAJORANA DEMONSTRATOR HPGe detectors. The activation is determined by the surface exposure from the time of production, storage, and delivery of the enriched Ge detectors to the underground experimental site. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, the Particle Astrophysics and Nuclear Physics Programs of the National Science Foundation, and the Sanford Underground Research Faci.

  18. Radiation Doses to Members of the U.S. Population from Ubiquitous Radionuclides in the Body: Part 1, Autopsy and In Vivo Data

    SciTech Connect

    Watson, David J.; Strom, Daniel J.

    2011-02-25

    This paper is part one of a three-part series investigating annual effective doses to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. This series of papers explicitly excludes intakes from inhaling 222Rn, 220Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. The goal of part one of this work was to review, summarize, and characterize all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Forty-five papers and reports were obtained and their data reviewed, and three data sets were obtained via private communication. The 45 radionuclides of interest are the 238U series (14 nuclides), the actinium series (headed by 235U; 11 nuclides), and the 232Th series (11 nuclides); primordial radionuclides 87Rb and 40 K; cosmogenic and fallout radionuclides 14C and 3H; and purely anthropogenic radionuclides 137Cs-137mBa, 129I, and 90Sr-90Y. Measurements judged to be relevant were available for only 15 of these radionuclides: 238U, 235U, 234U, 232Th, 230Th, 228Th, 228Ra, 226Ra, 210Pb, 210Po, 137Cs, 87Rb, 40K, 14C, and 3H. Recent and relevant measurements were not available for 129I and 90Sr-90Y. A total of 11,714 radionuclide concentration measurements were found in one or more tissues or organs from 14 States. Data on age, sex, geographic locations, height, and weight of subjects were available only sporadically. Too often authors did not provide meaningful values of uncertainty of measurements so that variability in data sets is confounded with measurement uncertainty. The following papers detail how these shortcomings are overcome to achieve the goals of the three-part series.

  19. Holocene Deglaciation of the Scandinavian Ice Sheet: Preliminary 10Be Ages

    NASA Astrophysics Data System (ADS)

    Cuzzone, J. K.; Clark, P. U.; Marcott, S. A.; Pekka Lunka, J.; Wohlfarth, B.; Carlson, A. E.

    2012-12-01

    The response of ice sheets to a warming climate is not well understood. Because we are limited in our understanding of present dynamics, reconstructing the deglaciation of former ice sheets allows for a better understanding of how past ice sheets responded to a warming climate along with their contribution to sea-level rise. These reconstructions also serve as critical constraints for ice sheet modeling efforts. Here, we present a suite of new 10Be ages from erratic boulders along three transects spanning southern to northern Sweden and Finland, that improve our understanding of the deglaciation of the Scandinavian Ice Sheet (SIS) beginning ~ 11.7ka through its final demise during the early Holocene. Preliminary dates from southern Finland, beginning at the Salpausselka Youngers Dryas moraine (11.5 ± 0.7 ka, n=2), inland southern Finland near Jyvaskyla (11.5 ± 0.5ka, n=2), and coastal Finland (~60km from Gulf of Bothnia) near Vimpeli (11.5 ± 0.4ka, n=1) indicate a rapid retreat following the Younger Dryas for Southern Finland (~500km within uncertainty of ages). Preliminary dates also exist for Northern Finland, near Inari (10.3 ± 0.5ka, n=2). Additional ages now being processed at PRIME Lab, Purdue University, which will establish a basis for SIS retreat from all sampled sites, will also be presented. These new data will help to constrain the Holocene deglaciation of the SIS and its associated retreat rates, and establish the SIS contribution to Holocene sea level rise, which will improve our understanding of ice-sheet response to a warming climate.

  20. Preliminary Cosmogenic Surface Exposure Ages on Laurentide Ice-sheet Retreat and Opening of the Eastern Lake Agassiz Outlets

    NASA Astrophysics Data System (ADS)

    Leydet, D.; Carlson, A. E.; Sinclair, G.; Teller, J. T.; Breckenridge, A. J.; Caffee, M. W.; Barth, A. M.

    2015-12-01

    The chronology for the eastern outlets of glacial Lake Agassiz holds important consequences for the cause of Younger Dryas cold event during the last deglaciation. Eastward routing of Lake Agassiz runoff was originally hypothesized to have triggered the Younger Dryas. However, currently the chronology of the eastern outlets is only constrained by minimum-limiting radiocarbon ages that could suggest the eastern outlets were still ice covered at the start of the Younger Dryas at ~12.9 ka BP, requiring a different forcing of this abrupt climate event. Nevertheless, the oldest radiocarbon ages are still consistent with an ice-free eastern outlet at the start of the Younger Dryas. Here we will present preliminary 10-Be cosmogenic surface exposure ages from the North Lake, Flat Rock Lake, glacial Lake Kaministiquia, and Lake Nipigon outlets located near Thunder Bay, Ontario. These ages will date the timing of the deglaciation of the Laurentide ice sheet in the eastern outlet region of glacial Lake Agassiz. This will provide an important constraint for the hypothesized freshwater forcing of the cause of Younger Dryas cold event.

  1. Active basement uplift as seen with cosmogenic lenses: the Sierra Pie de Palo case (Western Argentina)

    NASA Astrophysics Data System (ADS)

    Siame, L. L.; Sébrier, M.; Costa, C. H.; Ahumada, E. A.; Bellier, O.

    2013-12-01

    The Andean foreland of western Argentina (28°S-33°S) corresponds to retroarc deformations associated with the ongoing flat subduction of the Nazca plate beneath the South American lithosphere, and associated with high levels of seismic activity and crustal active faulting. To improve earthquake source identification and characterization in the San Juan region, data from seismology, structural geology and quantitative geomorphology can be integrated and combined to provide a seismotectonic model. In this model, the Andean back-arc of western Argentina has to be regarded as an obliquely converging foreland where Plio-Quaternary deformations are partitioned between strike-slip and thrust motions that are localized on the E-verging, thin-skinned Argentine Precordillera, and the W-verging thick-skinned Sierras Pampeanas, respectively. In this domain, the Sierra Pie de Palo is a key structure playing a major role in the partitioning of the Plio-Quaternary deformations. Located in the westernmost Sierras Pampeanas, the Sierra Pie de Palo forms a NNE striking, 80 km-long and 35-40 km-wide, ellipsoid range that reaches elevation as high as 3162 m. This mountain range is an actively growing basement fold associated with a high level of seismic activity (e.g., the November 23, 1977, Caucete, Mw 7.4 earthquake). To evaluate the degree of tectonic activity around the Sierra Pie de Palo, we combined a detailed morphometric analysis of the topography together with in situ-produced cosmogenic 10Be concentrations measured in (1) bedrock outcrops corresponding to the exhumed erosional regional surface, (2) surface boulders abandoned on alluvial fans deformed by active faults, and (3) in fluvial sediments sampled at the outlets of selected watersheds that drains out from the Sierra Pie de Palo. All together, our results allows: (1) assessing quantitative constraints on the rate of tectonic and denudation processes that are responsible for the active growth and erosion of the Sierra

  2. Holocene Deglaciation of the Scandinavian Ice Sheet: Preliminary 10Be Ages

    NASA Astrophysics Data System (ADS)

    Cuzzone, J. K.; Clark, P. U.; Marcott, S. A.; Lunkka, J.; Wohlfarth, B.; Caffee, M. W.; Carlson, A. E.

    2013-12-01

    The response of ice sheets to a warming climate is not well understood. Because we are limited in our understanding of present dynamics, reconstructing the deglaciation of former ice sheets allows for a better understanding of how past ice sheets responded to a warming climate along with their contribution to sea-level rise. These reconstructions also serve as critical constraints for ice sheet modeling efforts. Here, we present a suite of new 10Be ages from erratic boulders along three transects spanning southern to northern Sweden and Finland, that improve our understanding of the deglaciation of the Scandinavian Ice Sheet (SIS) beginning ~ 11.7ka through its final demise during the early Holocene. Dates from southern Finland, beginning at the Salpausselka Younger Dryas moraine (11.5 × 0.7 ka, n=4), inland southern Finland near Jyvaskyla (11.5 × 0.5ka, n=2), and coastal Finland (~60km from Gulf of Bothnia) near Vimpeli (11.5 × 0.4ka, n=4) indicate a rapid retreat following the Younger Dryas for Southern Finland (~500km within uncertainty of ages). Preliminary dates also exist for Northern Finland, near Inari (10.8 × 0.5ka, n=4) and near Oulu (10.5 × 0.6 ka, n = 4) suggesting a later retreat in the north. Dates from southern Sweden, near Skovde (12.73 × 0.8ka, n=4) to Mora (10.41 × 0.6ka, n=5) suggest a slower retreat (over ~400km). Lastly, dates in Northwestern Sweden suggest a final termination of the SIS around 9.4 × 0.7ka (n = 3). Additional ages are now being processed at PRIME Lab, Purdue University, which will further strengthen our understanding of SIS retreat from all sampled sites. These new data will help to constrain the Holocene deglaciation of the SIS and its associated retreat rates, and establish the SIS contribution to Holocene sea level rise, which will improve our understanding of ice-sheet response to a warming climate.

  3. 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

  4. EBS Radionuclide Transport Abstraction

    SciTech Connect

    J. Prouty

    2006-07-14

    The purpose of this report is to develop and analyze the engineered barrier system (EBS) radionuclide transport abstraction model, consistent with Level I and Level II model validation, as identified in Technical Work Plan for: Near-Field Environment and Transport: Engineered Barrier System: Radionuclide Transport Abstraction Model Report Integration (BSC 2005 [DIRS 173617]). The EBS radionuclide transport abstraction (or EBS RT Abstraction) is the conceptual model used in the total system performance assessment (TSPA) to determine the rate of radionuclide releases from the EBS to the unsaturated zone (UZ). The EBS RT Abstraction conceptual model consists of two main components: a flow model and a transport model. Both models are developed mathematically from first principles in order to show explicitly what assumptions, simplifications, and approximations are incorporated into the models used in the TSPA. The flow model defines the pathways for water flow in the EBS and specifies how the flow rate is computed in each pathway. Input to this model includes the seepage flux into a drift. The seepage flux is potentially split by the drip shield, with some (or all) of the flux being diverted by the drip shield and some passing through breaches in the drip shield that might result from corrosion or seismic damage. The flux through drip shield breaches is potentially split by the waste package, with some (or all) of the flux being diverted by the waste package and some passing through waste package breaches that might result from corrosion or seismic damage. Neither the drip shield nor the waste package survives an igneous intrusion, so the flux splitting submodel is not used in the igneous scenario class. The flow model is validated in an independent model validation technical review. The drip shield and waste package flux splitting algorithms are developed and validated using experimental data. The transport model considers advective transport and diffusive transport

  5. Denudation rates derived from spatially-averaged cosmogenic nuclide analysis in Nelson catchments, South Island, New Zealand

    NASA Astrophysics Data System (ADS)

    Burdis, A.; Norton, K. P.; Ditchburn, B.; Zondervan, A.

    2013-12-01

    New Zealand's tectonically and climatically dynamic environment generates erosion rates that outstrip global averages by up to ten times in some locations. In order to assess recent changes in erosion rate, and also to predict future erosion dynamics, it is important to quantify long-term, background erosion. Current research on erosion in New Zealand predominantly covers short-term (100 yrs) erosion dynamics and Myr dynamics from thermochronological proxy data. Without medium-term denudation data for New Zealand, it is uncertain which variables (climate, anthropogenic disturbance of the landscape, tectonic uplift, lithological, or geomorphic characteristics) exert the dominant control on denudation in New Zealand. Spatially-averaged cosmogenic nuclide analysis can effectively offer this information by providing averaged rates of denudation on millennial timescales without the biases and limitations of short-term erosion methods. Basin-averaged denudation rates were obtained in the Nelson region, New Zealand, from analysis of concentrations of meteoric 10Be in clay and in-situ produced 10Be in quartz. The measured denudation rates integrate over ~8000 yrs (meteoric) and ~3000 yrs (in-situ). Not only do the 10Be records produce erosion rates that are remarkably consistent with each other, but they are also independent of topographic metrics. Denudation rates range from ~116 - 306 t km-2 yr-1, with the exception of one basin which is eroding at 789 t km-2 yr-1(derived from meteoric 10Be) and 644 t km-2 yr-1(derived from in-situ 10Be). The homogeneity of rates and absence of a significant correlation with geomorphic or lithological characteristics suggest another factor is exerting the dominant control on landscape denudation in the Nelson region. Storm variability is a likely driver of erosion in this setting. The background rates are higher than current short term rates (~50 - 200 t km-2 yr-1) due to the significant erosion caused by high magnitude, low frequency

  6. Radionuclide bone imaging

    SciTech Connect

    Bassett, L.W.; Gold, R.H.; Webber, M.M.

    1981-12-01

    Radionuclide bone imaging of the skeleton, now well established as the most important diagnostic procedure in detecting bone metastases, is also a reliable method for the evaluation of the progression or regression of metastatic bone disease. The article concentrates on the technetium-99m agents and the value of these agents in the widespread application of low-dose radioisotope scanning in such bone diseases as metastasis, osteomyelitis, trauma, osteonecrosis, and other abnormal skeletal conditions.

  7. Radionuclide therapy beyond radioiodine.

    PubMed

    Gabriel, Michael

    2012-10-01

    For decades, Iodine-131 has been used for the treatment of patients with thyroid cancer. In recent years, increasingly, other radiopharmaceuticals are in clinical use in the treatment of various malignant diseases. Although in principle these therapies-as in all applications of radionuclides-special radiation protection measures are required, a separate nuclear medicine therapy department is not necessary in many cases due to the lower or lack of gamma radiation. In the following article, four different radionuclide therapies are more closely presented which are emerging in the last years. One of them is the "Peptide Receptor Radionuclide Therapy," the so-called PRRT in which radiolabeled somatostatin (SST)-receptor(R) ligands are used in patients with neuroendocrine tumors. On the basis of radiolabeled antibodies against CD20-positive cells, the so-called radioimmunotherapy is used in the treatment of certain forms of malignant lymphoma. In primary or secondary liver tumors, the (90)Y-labeled particles can be administered. Last but not the least, the palliative approach of bone-seeking radiopharmaceuticals is noted in patients with painful bone metastases.

  8. Dating buried glacier ice using cosmogenic 3He in surface clasts: Theory and application to Mullins Glacier, Antarctica

    NASA Astrophysics Data System (ADS)

    Mackay, Sean L.; Marchant, David R.

    2016-05-01

    We develop a modeling framework to describe the accumulation of terrestrial cosmogenic 3He in Antarctic debris-covered glaciers. The framework helps quantify the expected range in cosmogenic-nuclide inventories for measured clasts at the surface of supraglacial debris. We first delineate the physical factors that impact clast movement within, and on top of, debris-covered glaciers, including the effects of (1) ice ablation, (2) erosion at the debris surface, and (3) stochastic geomorphic processes that impact clast movement within and on top of supraglacial debris; we then explicitly calculate the impact of each process in altering the total inventory of cosmogenic nuclides in surface clasts. Assuming basic elements of ice-dynamics and debris entrainment are known, the model results provide an estimate for the total accumulation of cosmogenic nuclides, as well as the expected range in nuclide inventories, for any clast at the surface of debris-covered glaciers. Because the values are quantified, the approach can be applied to help evaluate the robustness of existing and future cosmogenic datasets applied to these systems. As a test, we applied our model framework towards Mullins Glacier, a cold-based debris-covered alpine glacier in the Dry Valleys of Antarctica. Our simulated values for cosmogenic-nuclide inventories compare well with those previously measured from fifteen surface cobbles along Mullins Glacier (3He), both in terms of expected ranges and absolute values, and suggest that our model framework adequately incorporates most of the complicating factors that impact cosmogenic datasets for cold-based, debris-covered glaciers. Relating these cosmogenic-nuclide inventories to ice ages, the results show that ice within Mullins Glacier increases non-linearly, ranging from 12 ka to ∼220 ka in areas of active flow, to ≫1.6 Ma in areas of slow-moving-to-stagnant ice.

  9. A new approach to cosmogenic corrections in 40Ar/39Ar chronometry: Implications for the ages of Martian meteorites

    NASA Astrophysics Data System (ADS)

    Cassata, W. S.; Borg, L. E.

    2016-08-01

    Anomalously old 40Ar/39Ar ages are commonly obtained from Shergottites and are generally attributed to uncertainties regarding the isotopic composition of the trapped component and/or the presence of excess 40Ar. Old ages can also be obtained if inaccurate corrections for cosmogenic 36Ar are applied. Current methods for making the cosmogenic correction require simplifying assumptions regarding the spatial homogeneity of target elements for cosmogenic production and the distribution of cosmogenic nuclides relative to trapped and reactor-derived Ar isotopes. To mitigate uncertainties arising from these assumptions, a new cosmogenic correction approach utilizing the exposure age determined on an un-irradiated aliquot and step-wise production rate estimates that account for spatial variations in Ca and K is described. Data obtained from NWA 4468 and an unofficial pairing of NWA 2975, which yield anomalously old ages when corrected for cosmogenic 36Ar using conventional techniques, are used to illustrate the efficacy of this new approach. For these samples, anomalous age determinations are rectified solely by the improved cosmogenic correction technique described herein. Ages of 188 ± 17 and 184 ± 17 Ma are obtained for NWA 4468 and NWA 2975, respectively, both of which are indistinguishable from ages obtained by other radioisotopic systems. For other Shergottites that have multiple trapped components, have experienced diffusive loss of Ar, or contain excess Ar, more accurate cosmogenic corrections may aid in the interpretation of anomalous ages. The trapped 40Ar/36Ar ratios inferred from inverse isochron diagrams obtained from NWA 4468 and NWA 2975 are significantly lower than the Martian atmospheric value, and may represent upper mantle or crustal components.

  10. Cosmogenic Beryllium Production from Ocean Sediment Sequences Help to Construct Accurate Records of the Geodynamo Variation at the Millennial to Million Year Scale

    NASA Astrophysics Data System (ADS)

    Thouveny, N.; Ménabréaz, L.; Bourles, D. L.; Demory, F.; Guillou, V.; Arnold, M.; Vidal, L.

    2013-12-01

    The possible contribution of the axial precession to the energy of the geodynamo was recently reintroduced by theoretical and experimental studies. It is supported by relative paleointensity stacks and deep sea floor magnetization records documenting series of geomagnetic dipole lows (GDL) with recurrence at periods ranging from 30 to 120 kyr, and intriguing phase relationships with obliquity variations and δ18O records (e.g. Fuller, 2006; Thouveny et al. 2008). Yet, these time-series are presently not precise and complete enough to validate this fundamental and debated relationship. The MAG-ORB project funded by the French "Agence nationale de la Recherche" aims at reconstructing the series of GDL over the last Ma, by coupling -on the very same sedimentary sequences- the reconstructions of paleomagnetic variations, cosmogenic10Be production variations and δ18O isotope variations. Recent results (e.g. Ménabréaz et al., 2012, 2013) demonstrate that 10Be overproduction events are systematically induced by the GDL linked with excursions and reversals -as awaited from the theoretical and empirical non linear inverse relationship established between the magnetic moment value and the penetration rate of cosmic rays and particles. The calibration of the authigenic 10Be/9Be ratio signals using absolute Virtual (axial) Dipole Moment values allowed us to construct 10Be-derived Geomagnetic Dipole Moment records over the last millennium, the last 60 ka and the last Ma, allowing to assess the robustness of the GDL series by a method completely independent from rock and paleo-magnetic methods. These records are comparable with individuals RPI records obtained from the same cores, and with global RPI stacks (e.g. GLOPIS, SINT 800 and PISO-1500). Since the Beryllium atoms are adsorbed on the settling silicate particles, the measured 10Be/9Be ratio signatures of cosmogenic isotope overproductions accurately indicate the exact stratigraphic position of the GDL in the sedimentary

  11. 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

  12. 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.

  13. Cosmogenic neutrinos and signals of TeV gravity in air showers and neutrino telescopes.

    PubMed

    Illana, J I; Masip, M; Meloni, D

    2004-10-01

    The existence of extra dimensions allows the possibility that the fundamental scale of gravity is at the TeV. If that is the case, gravity could dominate the interactions of ultrahigh energy cosmic rays. In particular, the production of microscopic black holes by cosmogenic neutrinos has been estimated in a number of papers. We consider here gravity-mediated interactions at larger distances, where they can be calculated in the eikonal approximation. We show that for the expected flux of cosmogenic neutrinos these elastic processes give a stronger signal than black hole production in neutrino telescopes. Taking the bounds on the higher-dimensional Planck mass M(D) (D=4 + n) from current air shower experiments, for n=2(6) elastic collisions could produce up to 118 (34) events per year at IceCube. On the other hand, the absence of any signal would imply a bound of M(D) > or approximately 5 TeV.

  14. 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 10

  15. A more complex deglaciation chronology of Southern Norway than previously thought. New geochronological constraints based on cosmogenic exposure ages of marginal moraines

    NASA Astrophysics Data System (ADS)

    Fredin, Ola; Akçar, Naki; Romundset, Anders; Reber, Regina; Ivy-Ochs, Susan; Kubik, Peter; Høgaas, Fredrik; Schlüchter, Christian

    2015-04-01

    Glacial landforms from the last deglaciation in southern Norway were mapped by the famous glacial geologist Bjørn Andersen already in the early 1950s, using basic aerial photographs and topographic maps. Andersen reconstructed two distinct glacial sub-stages (the Lista stage and Spangereid stage) that were older than the Younger Dryas (YD), and one main glacial stage of assumed YD age (the Ra stage). This interpretation has remained largely untested and is still used in reconstructions of the Fennoscandian ice sheet. However, absolute chronological control has been lacking and only a handful radiocarbon dates has been used to support the deglaciation chronology. In this study we test the reconstruction of Andersen by remapping the whole area using newly aquired LiDAR data (high resolution laser scanning of terrain), together with in-situ cosmogenic nuclide exposure ages of boulders on marginal moraines. The study comprises mapping of more than 6000 km2 of forested and dissected landscape, 53 10Be ages from boulders/bedrock, one cosmogenic 10Be depth profile in a coarse-grained glaciofluvial deposit, and finally one lake record. Our study shows that the oldest of Andersen's glacial stages, the Lista stage right on the outermost Norwegian south coast, should likely be rejected since it consists of consolidated subglacial till and therefore is not an end moraine system. However, our cosmogenic depth profile indicates that this area might have been ice free already by around 19 ka BP, approximately 4000 years earlier than previously thought. At the same time the ice sheet surface slowly lowered, and the first inland hills of about 450 m. asl. became ice free at around 17 ka BP. Ice retreat continued slowly 10-15 km inland and halted as a calving fjord stage at the Spangereid stage with an approximate age of 15 ka BP. Then the deglaciation appears to have been very rapid and the ice front retreated 30-50 km inland to a position inside of the Ra stage, until a readvance

  16. In situ production of terrestrial cosmogenic helium and some applications to geochronology

    NASA Technical Reports Server (NTRS)

    Kurz, Mark D.

    1986-01-01

    The concentrations of cosmogenic He-3 have been measured in a series of basaltic drill core samples from Hawaiian volcanoes Haleakala and Mauna Loa. The He-3 concentration in the surface of a radiocarbon dated Mauna Loa flow (20,000 years) gives reasonable agreement with a theoretical production rate of 140 atoms/g/yr, and suggests that the uncertainty in this rate is roughly 10 percent. The results illustrate the feasibility of using He-3 to measure exposure ages of young basaltic lava flows and for measuring erosion rates. Erosion rates calculated from the three Haleakala cores range from 7 to 11 meters/million years. The drill core data demonstrate that accurate depth control is crucial to the use and evaluation of cosmogenic helium. Depth profiles from several of the older cores display a nonexponential depth dependence of He-3(c) below 170 g/sq cm, which is attributed to the contribution from Li-6(n, alpha)T, where the neutrons are from stopped muons. This has important implications for depth dependence of cosmogenic He-3 because muons are weakly attenuated compared to the nucleonic component that produces spallation.

  17. Cosmogenic nuclides in the Martian surface: Constraints for sample recovery and transport

    NASA Technical Reports Server (NTRS)

    Englert, Peter A. J.

    1988-01-01

    Stable and radioactive cosmogenic nuclides and radiation damage effects such as cosmic ray tracks can provide information on the surface history of Mars. A recent overview on developments in cosmogenic nuclide research for historical studies of predominantly extraterrestrial materials was published previously. The information content of cosmogenic nuclides and radiation damage effects produced in the Martian surface is based on the different ways of interaction of the primary galactic and solar cosmic radiation (GCR, SCR) and the secondary particle cascade. Generally the kind and extent of interactions as seen in the products depend on the following factors: (1) composition, energy and intensity of the primary SCR and GCR; (2) composition, energy and intensity of the GCR-induced cascade of secondary particles; (3) the target geometry, i.e., the spatial parameters of Martian surface features with respect to the primary radiation source; (4) the target chemistry, i.e., the chemical composition of the Martian surface at the sampling location down to the minor element level or lower; and (5) duration of the exposure. These factors are not independent of each other and have a major influence on sample taking strategies and techniques.

  18. Gamma-ray constraints on maximum cosmogenic neutrino fluxes and UHECR source evolution models

    SciTech Connect

    Gelmini, Graciela B.; Kalashev, Oleg; Semikoz, Dmitri V. E-mail: kalashev@ms2.inr.ac.ru

    2012-01-01

    The dip model assumes that the ultra-high energy cosmic rays (UHECRs) above 10{sup 18} eV consist exclusively of protons and is consistent with the spectrum and composition measure by HiRes. Here we present the range of cosmogenic neutrino fluxes in the dip-model which are compatible with a recent determination of the extragalactic very high energy (VHE) gamma-ray diffuse background derived from 2.5 years of Fermi/LAT data. We show that the largest fluxes predicted in the dip model would be detectable by IceCube in about 10 years of observation and are within the reach of a few years of observation with the ARA project. In the incomplete UHECR model in which protons are assumed to dominate only above 10{sup 19} eV, the cosmogenic neutrino fluxes could be a factor of 2 or 3 larger. Any fraction of heavier nuclei in the UHECR at these energies would reduce the maximum cosmogenic neutrino fluxes. We also consider here special evolution models in which the UHECR sources are assumed to have the same evolution of either the star formation rate (SFR), or the gamma-ray burst (GRB) rate, or the active galactic nuclei (AGN) rate in the Universe and found that the last two are disfavored (and in the dip model rejected) by the new VHE gamma-ray background.

  19. Grain size bias in cosmogenic nuclide studies of stream sediment in steep terrain

    NASA Astrophysics Data System (ADS)

    Lukens, Claire E.; Riebe, Clifford S.; Sklar, Leonard S.; Shuster, David L.

    2016-05-01

    Cosmogenic nuclides in stream sediment are widely used to quantify catchment-average erosion rates. A key assumption is that sampled sediment is representative of erosion from the entire catchment. Here we show that the common practice of collecting a narrow range of sizes—typically sand—may not yield a representative sample when the grain size distribution of sediment produced on slopes is spatially variable. A grain size bias arises when some parts of the catchment produce sand more readily than others. To identify catchments that are prone to this bias, we used a forward model of sediment mixing and erosion to explore the effects of catchment relief and area across a range of altitudinal gradients in sediment size and erosion rate. We found that the bias increases with increasing relief, because higher-relief catchments have a larger fraction of high elevations that are underrepresented in the sampled sand when grain size increases with altitude. The bias also increases with catchment area, because sediment size reduction during transport causes an underrepresentation of more distal, higher elevations within the catchment. Our analysis indicates that grain size bias may be significant at many sites where cosmogenic nuclides have been used to quantify catchment-average erosion rates. We discuss how to quantify and account for the bias using cosmogenic nuclides and detrital thermochronometry in multiple sediment sizes.

  20. EBS Radionuclide Transport Abstraction

    SciTech Connect

    J.D. Schreiber

    2005-08-25

    The purpose of this report is to develop and analyze the engineered barrier system (EBS) radionuclide transport abstraction model, consistent with Level I and Level II model validation, as identified in ''Technical Work Plan for: Near-Field Environment and Transport: Engineered Barrier System: Radionuclide Transport Abstraction Model Report Integration'' (BSC 2005 [DIRS 173617]). The EBS radionuclide transport abstraction (or EBS RT Abstraction) is the conceptual model used in the total system performance assessment for the license application (TSPA-LA) to determine the rate of radionuclide releases from the EBS to the unsaturated zone (UZ). The EBS RT Abstraction conceptual model consists of two main components: a flow model and a transport model. Both models are developed mathematically from first principles in order to show explicitly what assumptions, simplifications, and approximations are incorporated into the models used in the TSPA-LA. The flow model defines the pathways for water flow in the EBS and specifies how the flow rate is computed in each pathway. Input to this model includes the seepage flux into a drift. The seepage flux is potentially split by the drip shield, with some (or all) of the flux being diverted by the drip shield and some passing through breaches in the drip shield that might result from corrosion or seismic damage. The flux through drip shield breaches is potentially split by the waste package, with some (or all) of the flux being diverted by the waste package and some passing through waste package breaches that might result from corrosion or seismic damage. Neither the drip shield nor the waste package survives an igneous intrusion, so the flux splitting submodel is not used in the igneous scenario class. The flow model is validated in an independent model validation technical review. The drip shield and waste package flux splitting algorithms are developed and validated using experimental data. The transport model considers

  1. Coupling data from U-series and 10Be CRN to evaluate soil steady-state in the Betic Cordillera

    NASA Astrophysics Data System (ADS)

    Schoonejans, Jerome; Vanacker, Veerle; Opfergelt, Sophie; Granet, Mathieu; Chabaux, François

    2015-04-01

    The regolith mantel is produced by weathering of bedrock through physical and biochemical processes. At the same time, the upper part of the regolith is eroded by gravity mass movements, water and wind erosion. Feedback's between production and erosion of soil material are important for soil development, and are essential to reach long-term steady-state in soil chemical and physical properties. Nowadays, long-term denudation rates of regolith can be quantified by using in-situ cosmogenic nuclides (CRN). If the soil thickness remains constant over sufficiently long time, soil production rates can be determined. However, the a priori assumption of long-term steady-state can be questionable in highly dynamic environments. In this study, we present analytical data from two independent isotopic techniques, in-situ cosmogenic nuclides and Uranium series disequilibrium. The disequilibrium of Uranium isotopes (238U, 234U, 230Th, 226Ra) is an alternative method that allows assessing soil formation rates through isotopic analysis of weathering products. Nine soil profiles were sampled in three different mountain ranges of the Betic Cordillera (SE Spain): Sierra Estancias, Filabres, Cabrera. All soils overly fractured mica schist and are very thin (< 60cm). In each soil profile, we sampled 4 to 6 depth slices in the soil profile, the soil-bedrock interface and (weathered) bedrock. Three of the nine soil profiles were sampled for U-series isotope measurements at EOST (University of Strasbourg). The surface denudation rates (CRN) are about the same in the Sierra Estancias and Filabres (26 ± 10 mm/ky) and increase up to 103 ± 47 mm/ky in the Sierra Cabrera. The spatial variation in soil denudation rates is in agreement with the variation in catchment-wide denudation rates presented by Bellin et al. (2014) which present the highest rates in the Sierra Cabrera (104-246mm/kyr). Moreover it roughly coincides with the pattern of long-term exhumation of the Betic Cordillera. Results

  2. Radionuclide Sensors for Water Monitoring

    SciTech Connect

    Grate, Jay W.; Egorov, Oleg B.; DeVol, Timothy A.

    2005-09-01

    Radionuclide contamination in the soil and groundwater at U.S. Department of Energy (DOE) sites is a severe problem that requires monitoring and remediation. Radionuclide measurement techniques are needed to monitor surface waters, groundwater, and process waters. Typically, water samples are collected and transported to an analytical laboratory, where costly radiochemical analyses are performed. To date, there has been very little development of selective radionuclide sensors for alpha- and beta-emitting radionuclides such as 90Sr, 99Tc, and various actinides of interest.

  3. History of medical radionuclide production.

    PubMed

    Ice, R D

    1995-11-01

    Radionuclide production for medical use originally was incidental to isotope discoveries by physicists and chemists. Once the available radionuclides were identified they were evaluated for potential medical use. Hevesy first used 32P in 1935 to study phosphorous metabolism in rats. Since that time, the development of cyclotrons, linear accelerators, and nuclear reactors have produced hundreds of radionuclides for potential medical use. The history of medical radionuclide production represents an evolutionary, interdisciplinary development of applied nuclear technology. Today the technology is represented by a mature industry and provides medical benefits to millions of patients annually.

  4. Beryllium-Boron Systematics of Refractory Inclusions in CR2 and CV3 Chondrites: Evidence for 10Be Heterogeneity

    NASA Astrophysics Data System (ADS)

    Dunham, E.; Wadhwa, M.; Simon, S.; Grossman, L.

    2016-08-01

    Be-B systematics of Allende (CV3), Axtell (CV3), and NWA 5028 (CR2) CAIs suggests that 10Be was distributed heterogeneously in the early solar system which implies that 10Be was produced in the solar nebula by irradiation of nebular gas or dust.

  5. Osteopetrosis: radiological & radionuclide imaging.

    PubMed

    Sit, Cherry; Agrawal, Kanhaiyalal; Fogelman, Ignac; Gnanasegaran, Gopinath

    2015-01-01

    Osteopetrosis is a rare inherited bone disease where bones harden and become abnormally dense. While the diagnosis is clinical, it also greatly relies on appearance of the skeleton radiographically. X-ray, radionuclide bone scintigraphy and magnetic resonance imaging have been reported to identify characteristics of osteopetrosis. We present an interesting case of a 59-year-old man with a history of bilateral hip fractures. He underwent (99m)Tc-methylene diphosphonate whole body scan supplemented with single-photon emission computed tomography/computed tomography of spine, which showed increased uptake in the humeri, tibiae and femora, which were in keeping with osteopetrosis.

  6. The Svalbard Barents Sea Ice Sheet deglaciation and its contribution to meltwater pulse 1a: Constraining ice sheet history with geomorphological mapping and 10Be exposure dating on Svalbard's southern cape

    NASA Astrophysics Data System (ADS)

    Nothaft, D. B.; Koffman, T.; Schaefer, J. M.; Young, N. E.; Hormes, A.; Briner, J. P.

    2014-12-01

    Pinpointing the sources of meltwater pulse (MWP) 1a—the most abrupt period of sea level rise during the last glacial termination—remains one of paleoclimatology's greatest challenges, with implications for the understanding of rapid climate change, isostatic rebound, and past ocean circulation. Here, we present an annotated geomorphological map of a southern region of Svalbard, Norway, that we will use in the interpretation of a soon-to-be published 10Be chronology of this study area where no cosmogenic nuclide exposure data has yet been produced. From this map, we infer historic ice sheet thickness, flow rate, and erosivity. Together, this data will enable us to constrain ice sheet volume change over time in southern Svalbard. The map identifies raised beaches at an altitude of 40 m, indicating an ice sheet thickness of 400-800 m during the Last Glacial Maximum (LGM) when compared to other shoreline data from the region and ice sheet models. We also observed an abundance of glacially smoothed features in valleys, despite an absence of such features at higher elevations. This could suggest a transition from warm-based, erosive ice to cold-based, non-destructive ice with increasing elevation. It is also possible that mountain peaks in this region were not glaciated at LGM. It is important to assess the historic erosivity of an ice sheet because cosmogenic nuclides may be inherited from prior interstadials when the bedrock was deglaciated, if not "reset" by erosion. This can result in erroneously old exposure dates. If this portion of the Svalbard Barents Sea Ice Sheet (SBSIS) did contribute largely to MWP-1a, then we would expect exposure dates from sites differing in elevation by 100 m or more to fall within a 500-year range, centered around 14 ka. Expeditions to collect samples for exposure dating at other field sites in southern Svalbard, scheduled for the coming field season, will help to further inform our understanding of the SBSIS deglaciation and the MWP

  7. Targeted radionuclide therapy

    SciTech Connect

    Williams, Lawrence E.; DeNardo, Gerald L.; Meredith, Ruby F.

    2008-07-15

    Targeted radionuclide therapy (TRT) seeks molecular and functional targets within patient tumor sites. A number of agents have been constructed and labeled with beta, alpha, and Auger emitters. Radionuclide carriers spanning a broad range of sizes; e.g., antibodies, liposomes, and constructs such as nanoparticles have been used in these studies. Uptake, in percent-injected dose per gram of malignant tissue, is used to evaluate the specificity of the targeting vehicle. Lymphoma (B-cell) has been the primary clinical application. Extension to solid tumors will require raising the macroscopic absorbed dose by several-fold over values found in present technology. Methods that may effect such changes include multistep targeting, simultaneous chemotherapy, and external sequestration of the agent. Toxicity has primarily involved red marrow so that marrow replacement can also be used to enhance future TRT treatments. Correlation of toxicities and treatment efficiency has been limited by relatively poor absorbed dose estimates partly because of using standard (phantom) organ sizes. These associations will be improved in the future by obtaining patient-specific organ size and activity data with hybrid SPECT/CT and PET/CT scanners.

  8. Targeted radionuclide therapy

    PubMed Central

    Williams, Lawrence E.; DeNardo, Gerald L.; Meredith, Ruby F.

    2008-01-01

    Targeted radionuclide therapy (TRT) seeks molecular and functional targets within patient tumor sites. A number of agents have been constructed and labeled with beta, alpha, and Auger emitters. Radionuclide carriers spanning a broad range of sizes; e.g., antibodies, liposomes, and constructs such as nanoparticles have been used in these studies. Uptake, in percent-injected dose per gram of malignant tissue, is used to evaluate the specificity of the targeting vehicle. Lymphoma (B-cell) has been the primary clinical application. Extension to solid tumors will require raising the macroscopic absorbed dose by several-fold over values found in present technology. Methods that may effect such changes include multistep targeting, simultaneous chemotherapy, and external sequestration of the agent. Toxicity has primarily involved red marrow so that marrow replacement can also be used to enhance future TRT treatments. Correlation of toxicities and treatment efficiency has been limited by relatively poor absorbed dose estimates partly because of using standard (phantom) organ sizes. These associations will be improved in the future by obtaining patient-specific organ size and activity data with hybrid SPECT∕CT and PET∕CT scanners. PMID:18697529

  9. Radionuclide measurements by accelerator mass spectrometry at Arizona

    NASA Technical Reports Server (NTRS)

    Jull, A. J. T.; Donahue, D. J.; Zabel, T. H.

    1986-01-01

    Over the past years, Tandem Accelerator Mass Spectrometry (TAMS) has become established as an important method for radionuclide analysis. In the Arizona system the accelerator is operated at a thermal voltage of 1.8MV for C-14 analysis, and 1.6 to 2MV for Be-10. Samples are inserted into a cesium sputter ion source in solid form. Negative ions sputtered from the target are accelerated to about 25kV, and the injection magnet selects ions of a particular mass. Ions of the 3+ charge state, having an energy of about 9MeV are selected by an electrostatic deflector, surviving ions pass through two magnets, where only ions of the desired mass-energy product are selected. The final detector is a combination ionization chamber to measure energy loss (and hence, Z), and a silicon surface-barrier detector which measures residual energy. After counting the trace iosotope for a fixed time, the injected ions are switched to the major isotope used for normalization. These ions are deflected into a Faraday cup after the first high-energy magnet. Repeated measurements of the isotope ratio of both sample and standards results in a measurement of the concentration of the radionuclide. Recent improvements in sample preparation for C-14 make preparation of high-beam current graphite targets directly from CO2 feasible. Except for some measurements of standards and backgrounds for Be-10 measurements to date have been on C-14. Although most results have been in archaeology and quaternary geology, studies have been expanded to include cosmogenic C-14 in meteorites. The data obtained so far tend to confirm the antiquity of Antarctic meteorites from the Allan Hills site. Data on three samples of Yamato meteorites gave terrestrial ages of between about 3 and 22 thousand years.

  10. In Situ-produced vs. Meteoric 10Be in Hillslope Soils: One Isotope, Two Tracers, Different Stories

    NASA Astrophysics Data System (ADS)

    Jungers, M. C.; Bierman, P. R.; Matmon, A.; Cox, R.; Pavich, M.; Finkel, R. C.

    2009-12-01

    In situ-produced and meteoric 10Be are both powerful tools for tracing the production and transport of hillslope sediment. In situ-produced 10Be is used to infer sediment production rates as well as investigate sediment sources and transport. Meteoric 10Be may also be useful for inferring sediment production and transport rates in some landscapes, especially those that lack the target minerals for in situ-produced 10Be. Few studies have investigated the insights gained by a comparing in situ-produced and meteoric 10Be inventories. We present a series of paired 10Be inventories from different climatic and tectonic regimes to illustrate both the value and the potential pitfalls of coupling these geomorphic tracers. The mean in situ and meteoric 10Be near surface (within a meter) inventories for our field areas are as follows: Great Smoky Mountains, NC, USA: 3.6 x 107 atoms cm-2 and 3.3 x 1010 atoms cm-2; Laurely Fork, PA, USA: 2.6 x 106 atoms cm-2 and 3.0 x 109 atoms cm-2; Oregon Coast Range, OR, USA: no in situ data and 3.87 x 1010 atoms cm-2; North Island, New Zealand: no in situ data and 1.8 x 109 atoms cm-2; and Amparafaravola, Madagascar: 1.86 x 107 atoms cm-2 and 8.0 x 109 atoms cm-2. The associated inferred soil residence times, respectively, are: Great Smoky Mountains, NC, USA: 40.9 ky and 25.6 ky; Laurely Fork, PA, USA: 2.9 ky and 2.3 ky; Oregon Coast Range, OR, USA: n/a and 30ky; North Island, New Zealand: n/a and 1.5 ky; and Amparafaravola, Madagascar: 21 ky and 6.2 ky. Soil residence times inferred from meteoric 10Be assume a global average delivery rate of 1.3 x 106 atoms cm-2 yr-1. These soil residence times are minimum values that assume that all in situ and meteoric 10Be is accounted for. Discrepancies between inferred soil residence times most likely highlight some error in assumptions regarding meteoric 10Be retention in the soil mantles that we sampled. For example, if meteoric 10Be is not retained at the near surface where we collected our samples

  11. 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

  12. Incorporation of short-lived (10)Be in a calcium-aluminum-rich inclusion from the allende meteorite

    PubMed

    McKeegan; Chaussidon; Robert

    2000-08-25

    Enrichments in boron-10/boron-11 in a calcium-aluminum-rich inclusion from the Allende carbonaceous chondrite are correlated with beryllium/boron in a manner indicative of the in situ decay of short-lived beryllium-10. Because this radionuclide is produced only by nuclear spallation reactions, its existence in early solar system materials attests to intense irradiation processes in the solar nebula. The particle fluence inferred from the initial beryllium-10/beryllium-9 is sufficient to produce other short-lived nuclides, calcium-41 and manganese-53, found in meteorites, but the high canonical abundance of aluminum-26 may still require seeding of the solar system by radioactive stellar debris.

  13. Reactor-Produced Medical Radionuclides

    SciTech Connect

    Mirzadeh, Saed; Mausner, Leonard; Garland, Marc A

    2011-01-01

    The therapeutic use of radionuclides in nuclear medicine, oncology and cardiology is the most rapidly growing use of medical radionuclides. Since most therapeutic radionuclides are neutron rich and decay by beta emission, they are reactor-produced. This chapter deals mainly with production approaches with neutrons. Neutron interactions with matter, neutron transmission and activation rates, and neutron spectra of nuclear reactors are discussed in some detail. Further, a short discussion of the neutron-energy dependence of cross sections, reaction rates in thermal reactors, cross section measurements and flux monitoring, and general equations governing the reactor production of radionuclides are presented. Finally, the chapter is concluded by providing a number of examples encompassing the various possible reaction routes for production of a number of medical radionuclides in a reactor.

  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. APT radionuclide production experiment

    SciTech Connect

    Ullmann, J.L.; Gavron, A.; King, J.D.

    1994-07-02

    Tritium ({sup 3}H, a heavy isotope of hydrogen) is produced by low energy neutron-induced reactions on various elements. One such reaction is n+{sup 3}He {yields}>{sup 3}H+{sup 1}H in which {sup 3}He is transmuted to tritium. Another reaction, which has been used in reactor production of tritium, is the n+{sup 6}Li {yields}> {sup 3}H+{sup 4}He reaction. Accelerator Production of Tritium relies on a high-energy proton beam to produce these neutrons using the spallation reaction, in which high-energy proton beam to produce these neutrons using the spallation reaction, in which high-energy protons reacting with a heavy nucleus produce a shower of low-energy neutrons and a lower-mass residual nucleus. It is important to quantify the residual radionuclides produced in the spallation target for two reasons. From an engineering point of view, one must understand short-lived isotopes that may contribute to decay heat. From a safety viewpoint, one must understand what nuclei and decay gammas are produced in order to design adequate shielding, to estimate ultimate waste disposal problems, and to predict possible effects due to accidental dispersion during operation. The authors have performed an experiment to measure the production of radioisotopes in stopping-length W and Pb targets irradiated by a 800 MeV proton beam, and are comparing the results to values obtained from calculations using LAHET and MCNP. The experiment was designed to pay particular attention to the short half-life radionuclides, which have not been previously measured. In the following, they present details of the experiment, explain how they analyzed the data and obtain the results, how they perform the calculations, and finally, how the experimental data agree with the calculations.

  16. Long-term erosion and interglacial period exposure in Western Greenland from meteoric 10Be in ice-bound sediment

    NASA Astrophysics Data System (ADS)

    Graly, J. A.; Corbett, L.; Bierman, P. R.; Neumann, T.; Rood, D. H.; Finkel, R. C.

    2010-12-01

    To examine the history of surface exposure and erosion in areas of Western Greenland presently covered by ice, we measured the concentration of meteoric 10Be in ice-bound fine sediment at three locations: Kangerlussuaq (67.1°N), Ilulissat (69.4°N), and Upernavik (72.5°N). Meteoric 10Be concentrations at Ilulissat and Upernavik range from 2×106 to 2×108 atoms/g and are statistically indistinguishable from each other. Meteoric 10Be concentrations at Kangerlussuaq range from 2×106 to 5×107 atoms/g and are significantly lower than the values found at the northern two sites. Through comparison to typical meteoric 10Be distribution in soils, source soil ages can be estimated at each of these locations. These estimates suggest on the order of 105 years of exposure at the northern sites and on the order of 104 years of exposure at Kangerlussuaq. Because meteoric 10Be is lost from the soil system both by erosion and isotope decay, these exposure ages represent a minimum length of cumulative interglacial exposure. This exposure signal likely developed over several Late Pliocene and Pleistocene interglacial periods and prior to the onset of Northern hemisphere glaciation, ~2.7 Ma before present. To further constrain the glacial history of Western Greenland implied from the meteoric 10Be data, we constructed forward models of interglacial period exposure and glacial period erosion. The high levels of meteoric 10Be at Upernavik and Ilulissat imply erosion rates below 5 m/My and some preservation of pre-glacial regolith. The lower levels of meteoric 10Be at Kangerlussuaq can be explained with erosion rates as high as 20 m/My. Because of the substantial debris fluxes in modern Kangerlussuaq glaciers [Knight, et al., 2002], erosion rates greater than 10 m/My are likely. Meteoric 10Be inventories at Kangerlussuaq under 10-20 m/My of long-term erosion imply substantial interglacial exposure and the slow evacuation of sediment by glacial transport. These results suggest that

  17. Regolith production and transport at the Susquehanna Shale Hills Critical Zone Observatory, Part 2: Insights from meteoric 10Be

    NASA Astrophysics Data System (ADS)

    West, Nicole; Kirby, Eric; Bierman, Paul; Slingerland, Rudy; Ma, Lin; Rood, Dylan; Brantley, Susan

    2013-09-01

    Regolith-mantled hillslopes are ubiquitous features of most temperate landscapes, and their morphology reflects the climatically, biologically, and tectonically mediated interplay between regolith production and downslope transport. Despite intensive research, few studies have quantified both of these mass fluxes in the same field site. Here we present an analysis of 87 meteoric 10Be measurements from regolith and bedrock within the Susquehanna Shale Hills Critical Zone Observatory (SSHO), in central Pennsylvania. Meteoric 10Be concentrations in bulk regolith samples (n = 73) decrease with regolith depth. Comparison of hillslope meteoric 10Be inventories with analyses of rock chip samples (n = 14) from a 24 m bedrock core confirms that >80% of the total inventory is retained in the regolith. The systematic downslope increase of meteoric 10Be inventories observed at SSHO is consistent with 10Be accumulation in slowly creeping regolith (~ 0.2 cm yr-1). Regolith flux inferred from meteoric 10Be varies linearly with topographic gradient (determined from high-resolution light detection and ranging-based topography) along the upper portions of hillslopes at SSHO. However, regolith flux appears to depend on the product of gradient and regolith depth where regolith is thick, near the base of hillslopes. Meteoric 10Be inventories at the north and south ridgetops indicate minimum regolith residence times of 10.5 ± 3.7 and 9.1 ± 2.9 ky, respectively, similar to residence times inferred from U-series isotopes in Ma et al. (2013). The combination of our results with U-series-derived regolith production rates implies that regolith production and erosion rates are similar to within a factor of two on SSHO hillcrests.

  18. 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).

  19. 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 .

  20. Using cosmogenic depth-profiles to establish the timing of glaciations in southernmost South America

    NASA Astrophysics Data System (ADS)

    Darvill, Christopher; Bentley, Mike; Stokes, Chris

    2014-05-01

    Ice sheets in southernmost South America (52 to 54°S) are likely to have been sensitive to oceanic and atmospheric forcing, but the timing of glaciations is poorly constrained. This uncertainty represents a significant gap in our understanding of the southern hemisphere terrestrial-climatic record and stems from two unresolved issues. First, the nature of advance(s) and retreat(s) of the southernmost ice lobes is relatively unknown. Secondly, there is a difficulty in establishing age constraints beyond the Last Glacial Maximum (LGM), with previous cosmogenic nuclide exposure data from boulders yielding ages that are significantly younger (ca. LGM) than the previously hypothesised ages of the ice limits (ca. MIS 8 to 12). This discrepancy was ascribed to post-depositional processes (exhumation and erosion) acting on the boulders. This paper presents the preliminary results of an on-going investigation into the timing of glaciations for these ice lobes, focussing on glacial geomorphological mapping, ice lobe reconstruction and an alternative cosmogenic nuclide depth-profile approach to dating former ice limits. The glacial geomorphological mapping allows ice-sheet reconstruction and highlights locations where there are clear relationships between glaciofluvial outwash and corresponding ice limits. These are the target locations for cosmogenic outwash depth-profiles, which are being used to date the surface of outwash (rather than moraine boulders) whilst accounting for issues of erosion, exhumation and inheritance. The aim is to produce robust ages for the pre-'LGM' limits of the southernmost ice lobes in order to show when ice advances occurred and how this relates to wider Southern Hemispheric climatic change.

  1. Radionuclide therapy for arthritic knees

    SciTech Connect

    Doepel, L.K.

    1985-02-08

    A new radionuclide therapeutic approach for rheumatoid arthritis of the knee is described. This therapy combines a short-lived radionuclide with a carrier whose physical and chemical characteristics aid retention of the radioactive particles within the joint. Joining a radionuclide to a particulate carrier had not been explored previously as a potential method for inhibiting radiation leakage. The treatment couples the rare earth element dysprosium 165 to ferric hydroxide in macroaggregate form (size range: 3 to 10 ..mu..m). After the relatively inert iron complex penetrates the synovium, it causes cell death. Macrophages and phagocytes clear away the cellular debris, essentially eliminating the synovium.

  2. Cosmogenic nuclides in core samples of the Chico L6 chondrite - Evidence for irradiation under high shielding

    NASA Technical Reports Server (NTRS)

    Garrison, D. H.; Bogard, D. D.; Albrecht, A. A.; Vogt, S.; Herzog, G. F.; Klein, J.; Fink, D.; Dezfouly-Arjomandy, B.; Middleton, R.

    1992-01-01

    Results are presented from an analysis of core samples obtained from different depths of the Chico (New Mexico) L6 chondrite for various cosmogenic nuclides (Be-10, Al-26, and stable isotopes of He, Ne, and Ar). The relationships between the measured abundances of cosmogenic nuclides and cosmogenic Ne-22/Ne-21 ratio were compared with predictions of recent semiempirical models of Graf et al. (1990) and Reedy (1991), and it was found that both models closely reproduce the observed trends and absolute values of the data obtained. Noble gas data indicate that Chico experienced shielding similar to that of Jilin and greater than those of the Knyahinya or the Keyes chondrites. The exposure history for Chico is discussed.

  3. Cosmogenic nuclides in core samples of the Chico L6 chondrite - Evidence for irradiation under high shielding

    NASA Astrophysics Data System (ADS)

    Garrison, D. H.; Bogard, D. D.; Albrecht, A. A.; Vogt, S.; Herzog, G. F.; Klein, J.; Fink, D.; Dezfouly-Arjomandy, B.; Middleton, R.

    1992-09-01

    Results are presented from an analysis of core samples obtained from different depths of the Chico (New Mexico) L6 chondrite for various cosmogenic nuclides (Be-10, Al-26, and stable isotopes of He, Ne, and Ar). The relationships between the measured abundances of cosmogenic nuclides and cosmogenic Ne-22/Ne-21 ratio were compared with predictions of recent semiempirical models of Graf et al. (1990) and Reedy (1991), and it was found that both models closely reproduce the observed trends and absolute values of the data obtained. Noble gas data indicate that Chico experienced shielding similar to that of Jilin and greater than those of the Knyahinya or the Keyes chondrites. The exposure history for Chico is discussed.

  4. 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.

  5. Boundary conditions on the early Sun from ancient cosmogenic neon in meteorites

    NASA Technical Reports Server (NTRS)

    Hohenberg, C. M.; Caffee, M. W.; Swindle, T. D.; Goswami, J.

    1986-01-01

    Isotopic analysis of neon from individual grains of the meteorites Murchison (CM) and Kapoeta (howardite) shows large enrichments of cosmogenic neon in grains with solar flare tracks. The quantity of this component is incompatible with galactic cosmic ray or solar cosmic ray irradiation under present conditions and is attributed to irradiation by energetic flares from an early active Sun. Handpicked grains from each meteorite were grouped according to the presence or absence of solar flare heavy ion tracks, and these four samples were analyzed with an ion counting noble gas mass spectrometer.

  6. Scaling in situ cosmogenic nuclide production rates using analytical approximations to atmospheric cosmic-ray fluxes

    NASA Astrophysics Data System (ADS)

    Lifton, Nathaniel; Sato, Tatsuhiko; Dunai, Tibor J.

    2014-01-01

    Several models have been proposed for scaling in situ cosmogenic nuclide production rates from the relatively few sites where they have been measured to other sites of interest. Two main types of models are recognized: (1) those based on data from nuclear disintegrations in photographic emulsions combined with various neutron detectors, and (2) those based largely on neutron monitor data. However, stubborn discrepancies between these model types have led to frequent confusion when calculating surface exposure ages from production rates derived from the models. To help resolve these discrepancies and identify the sources of potential biases in each model, we have developed a new scaling model based on analytical approximations to modeled fluxes of the main atmospheric cosmic-ray particles responsible for in situ cosmogenic nuclide production. Both the analytical formulations and the Monte Carlo model fluxes on which they are based agree well with measured atmospheric fluxes of neutrons, protons, and muons, indicating they can serve as a robust estimate of the atmospheric cosmic-ray flux based on first principles. We are also using updated records for quantifying temporal and spatial variability in geomagnetic and solar modulation effects on the fluxes. A key advantage of this new model (herein termed LSD) over previous Monte Carlo models of cosmogenic nuclide production is that it allows for faster estimation of scaling factors based on time-varying geomagnetic and solar inputs. Comparing scaling predictions derived from the LSD model with those of previously published models suggest potential sources of bias in the latter can be largely attributed to two factors: different energy responses of the secondary neutron detectors used in developing the models, and different geomagnetic parameterizations. Given that the LSD model generates flux spectra for each cosmic-ray particle of interest, it is also relatively straightforward to generate nuclide-specific scaling

  7. 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

  8. Neogene Tectonic History of the Sierra San Pedro Mártir, Baja California Revealed by Careful Pairing of Cosmogenic Sampling with Topographic Analysis

    NASA Astrophysics Data System (ADS)

    Rossi, M. W.; Quigley, M.; Fletcher, J. M.; Whipple, K. X.; Díaz-Torres, J. J.; Seiler, C.; Fifield, L. K.; Heimsath, A. M.

    2015-12-01

    The Sierra San Pedro Mártir (SSPM), MX defines a prominent section of the Main Gulf Escarpment that marks the breakaway fault of the Gulf of California rift. The SSPM is an uplifted rift shoulder that has the highest topography and relief in Baja California, with local elevations exceeding 3,000 m and range relief (summit to baselevel) ranging from ~500 to 2,500 m. Prior studies report Eocene apatite fission track ages from the base of the escarpment and indicate low total exhumation, thus limiting the use of low-temperature thermochronology to constrain the timing and pattern of Neogene faulting of this important structure. However, topography is expected to record tectonic, climatic, and rock strength controls on long-term denudation rates in active margins, and morphometric analysis offers an alternative approach, particularly when combined with cosmogenic 10Be-derived, catchment-averaged denudation rates. Denudation rates and topographic metrics in the SSPM record along-strike gradients in rock uplift that increase asymmetrically from fault tips to a maximum within the northern half of the range. Surface uplift of an Eocene paleo-erosion surface and slope-break knickpoints found at increasingly higher elevations in northern segments of the SSPM fault system suggest that range asymmetry is due to a recent northward acceleration in rock uplift rate. By characterizing the relationship between channel steepness and 10Be-derived denudation rates, we extrapolate millennial-scale denudation rates to million-year time-scales to estimate ages for the transient increase in rock uplift rates as well as the initial onset of faulting. From this, we predict that the SSPM fault system initiated during the Middle Miocene (~16-14 Ma) in the center of the range and ~11-8 Ma ago near the fault tips. These age estimates are consistent with independent, regional geologic constraints and show that careful pairing of cosmogenic denudation rates with topographic analysis can be used

  9. Cosmic ray exposure dating with in situ produced cosmogenic He-3 - Results from young Hawaiian lava flows

    NASA Technical Reports Server (NTRS)

    Kurz, Mark D.; Colodner, Debra; Trull, Thomas W.; Moore, Richard B.; O'Brien, Keran

    1990-01-01

    Cosmogenic helium contents in a suite of Hawaiian radiocarbon-dated lava flows were measured to study the use of the production rate of spallation-produced cosmogenic He-3 as a surface exposure chronometer. Basalt samples from the Mauna Loa and Hualalai volcanoes were analyzed, showing that exposure-age dating is feasible in the 600-13000 year age range. The data suggest a present-day sea-level production rate in olivine of 125 + or - 30 atoms/g yr.

  10. Radionuclide Retention in Concrete Wasteforms

    SciTech Connect

    Bovaird, Chase C.; Jansik, Danielle P.; Wellman, Dawn M.; Wood, Marcus I.

    2011-09-30

    Assessing long-term performance of Category 3 waste cement grouts for radionuclide encasement requires knowledge of the radionuclide-cement interactions and mechanisms of retention (i.e., sorption or precipitation); the mechanism of contaminant release; the significance of contaminant release pathways; how wasteform performance is affected by the full range of environmental conditions within the disposal facility; the process of wasteform aging under conditions that are representative of processes occurring in response to changing environmental conditions within the disposal facility; the effect of wasteform aging on chemical, physical, and radiological properties; and the associated impact on contaminant release. This knowledge will enable accurate prediction of radionuclide fate when the wasteforms come in contact with groundwater. The information present in the report provides data that (1) measures the effect of concrete wasteform properties likely to influence radionuclide migration; and (2) quantifies the rate of carbonation of concrete materials in a simulated vadose zone repository.

  11. Unsteady late Pleistocene incision of streams bounding the Colorado Front Range from measurements of meteoric and in situ 10Be

    NASA Astrophysics Data System (ADS)

    Dühnforth, Miriam; Anderson, Robert S.; Ward, Dylan J.; Blum, Alex

    2012-03-01

    Dating of gravel-capped strath terraces in basins adjacent to western U.S. Laramide Ranges is one approach to document the history of late Cenozoic fluvial exhumation. We use in situ 10Be measurements to date the broad surfaces adjacent to the eastern edge of the Rocky Mountains in Colorado, and compare these calculated ages with results from meteoric 10Be measurements. We analyze three sites near Boulder, Colorado (Gunbarrel Hill, Table Mountain, and Pioneer) that have been mapped as the oldest terrace surfaces with suggested ages ranging from 640 ka to the Plio-Pleistocene transition. Our in situ 10Be results reveal abandonment ages of 95 ± 129 ka at Table Mountain, 175 ± 27 ka at Pioneer, and ages of 251 ± 10 ka and 307 ± 15 ka at Gunbarrel Hill. All are far younger than previously thought. Inventories of meteoric 10Be support this interpretation, yielding ages that are comparable to Table Mountain and ˜20% lower than Pioneer in situ ages. We argue that lateral beveling by rivers dominated during protracted times of even moderate glacial climate, and that vertical incision rates of several mm/yr likely occurred during times of very low sediment supply during the few interglacials that were characterized by particularly warm climate conditions. In contrast to the traditional age chronology in the area, our ages suggest that the deep exhumation of the western edge the High Plains occurred relatively recently and at an unsteady pace.

  12. Lithium-Beryllium-Boron Isotopic Compositions in Meteoritic Hibonite: Implications for Origin of 10Be and Early Solar System Irradiation

    NASA Astrophysics Data System (ADS)

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

    2010-08-01

    NanoSIMS isotopic measurements of Li, Be, and B in individual hibonite grains extracted from the Murchison meteorite revealed that 10B excesses correlate with the 9Be/11B ratios in 26Al-free PLAty hibonite Crystals. From these data, an initial 10Be/9Be = (5.5 ± 1.6) × 10-4 (2σ) and 10B/11B = 0.2508 ± 0.0015 can be inferred. On the other hand, chondritic boron isotopic compositions were found in 26Al-bearing Spinel-HIBonite spherules, most likely due to contamination with normal boron. No 7Li excesses due to 7Be decay were observed. When combined with previously reported data, the new data yield the best defined 10Be/9Be = (5.3 ± 1.0) × 10-4 (2σ) and 10B/11B = 0.2513 ± 0.0012 for PLACs. A comparison of this value and the best constrained 10Be/9Be = (8.8 ± 0.6) × 10-4 in CV Ca-Al-rich inclusions supports a heterogeneous distribution of 10Be 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.

  13. Drift-Scale Radionuclide Transport

    SciTech Connect

    J. Houseworth

    2004-09-22

    The purpose of this model report is to document the drift scale radionuclide transport model, taking into account the effects of emplacement drifts on flow and transport in the vicinity of the drift, which are not captured in the mountain-scale unsaturated zone (UZ) flow and transport models ''UZ Flow Models and Submodels'' (BSC 2004 [DIRS 169861]), ''Radionuclide Transport Models Under Ambient Conditions'' (BSC 2004 [DIRS 164500]), and ''Particle Tracking Model and Abstraction of Transport Process'' (BSC 2004 [DIRS 170041]). The drift scale radionuclide transport model is intended to be used as an alternative model for comparison with the engineered barrier system (EBS) radionuclide transport model ''EBS Radionuclide Transport Abstraction'' (BSC 2004 [DIRS 169868]). For that purpose, two alternative models have been developed for drift-scale radionuclide transport. One of the alternative models is a dual continuum flow and transport model called the drift shadow model. The effects of variations in the flow field and fracture-matrix interaction in the vicinity of a waste emplacement drift are investigated through sensitivity studies using the drift shadow model (Houseworth et al. 2003 [DIRS 164394]). In this model, the flow is significantly perturbed (reduced) beneath the waste emplacement drifts. However, comparisons of transport in this perturbed flow field with transport in an unperturbed flow field show similar results if the transport is initiated in the rock matrix. This has led to a second alternative model, called the fracture-matrix partitioning model, that focuses on the partitioning of radionuclide transport between the fractures and matrix upon exiting the waste emplacement drift. The fracture-matrix partitioning model computes the partitioning, between fractures and matrix, of diffusive radionuclide transport from the invert (for drifts without seepage) into the rock water. The invert is the structure constructed in a drift to provide the floor of the

  14. Radionuclide salivary gland imaging

    SciTech Connect

    Mishkin, F.S.

    1981-10-01

    Salivary gland imaging with 99mTc as pertechnetate provides functional information concerning trapping and excretion of the parotid and submandibular glands. Anatomic information gained often adds little to clinical evaluation. On the other hand, functional information may detect subclinical involvement, which correlates well with biopsy of the minor labial salivary glands. Salivary gland abnormalities in systemic disease such as sarcoidosis, rheumatoid arthritis, lupus erythematosus, and other collagenvascular disorders may be detected before they result in the clinical manifestaions of Sjoegren's syndrome. Such glands, after initially demonstrating increased trapping in the acute phase, tend to have decreased trapping and failure to discharge pertechnetate in response to an appropriate physiologic stimulus. Increased uptake of gallium-67 citrate often accompanies these findings. Inflammatory parotitis can be suspected when increased perfusion is evident on radionuclide angiography with any agent. The ability of the salivary gland image to detect and categorize mass lesions, which result in focal areas of diminished activity such as tumors, cysts, and most other masses, is disappointing, while its ability to detect and categorize Warthin's tumor, which concentrates pertechnetate, is much more valuable, although not specific.

  15. Video instrumentation for radionuclide angiocardiography.

    NASA Technical Reports Server (NTRS)

    Kriss, J. P.

    1973-01-01

    Two types of videoscintiscopes for performing radioisotopic angiocardiography with a scintillation camera are described, and use of these instruments in performing clinical studies is illustrated. Radionuclide angiocardiography is a simple, quick and accurate procedure recommended as a screening test for patients with a variety of congenital and acquired cardiovascular lesions. When performed in conjunction with coronary arterial catheterization, dynamic radionuclide angiography may provide useful information about regional myocardial perfusion. Quantitative capabilities greatly enhance the potential of this diagnostic tool.

  16. Anthropogenic radionuclides in the environment

    SciTech Connect

    Hu, Q; Weng, J; Wang, J

    2007-11-15

    Studies of radionuclides in the environment have entered a new era with the renaissance of nuclear energy and associated fuel reprocessing, geological disposal of high-level nuclear wastes, and concerns about national security with respect to nuclear non-proliferation. This work presents an overview of anthropogenic radionuclide contamination in the environment, as well as the salient geochemical behavior of important radionuclides. We first discuss the following major anthropogenic sources and current development that contribute to the radionuclide contamination of the environment: (1) nuclear weapons program; (2) nuclear weapons testing; (3) nuclear power plants; (4) commercial fuel reprocessing; (5) geological repository of high-level nuclear wastes, and (6) nuclear accidents. Then, we summarize the geochemical behavior for radionuclides {sup 99}Tc, {sup 129}I, and {sup 237}Np, because of their complex geochemical behavior, long half-lives, and presumably high mobility in the environment. Biogeochemical cycling and environment risk assessment must take into account speciation of these redox-sensitive radionuclides.

  17. 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

  18. Cosmogenic Backgrounds in Borexino at 3800 m water-equivalent depth

    SciTech Connect

    Bellini, G.; Avanzini, M. Buizza; Caccianiga, B.; D'Angelo, D.; Benziger, J.; Bick, D.; Bonfini, G.; Cavalcante, P.; Fomenko, K.; Bravo, D.; Cadonati, L.; Calaprice, F.; Chavarria, A.; Galbiati, C.; Chepurnov, A.; Davini, S.; Empl, A.; Derbin, A.; Etenko, A.; Franco, D. [APC, Univ. Paris Diderot, CNRS and others

    2013-08-01

    The solar neutrino experiment Borexino, which is located in the Gran Sasso underground laboratories, is in a unique position to study muon-induced backgrounds in an organic liquid scintillator. In this study, a large sample of cosmic muons is identified and tracked by a muon veto detector external to the liquid scintillator, and by the specific light patterns observed when muons cross the scintillator volume. The yield of muon-induced neutrons is found to be Y{sub n} = (3.10±0.11)·10{sup −4} n/(μ·(g/cm{sup 2})). The distance profile between the parent muon track and the neutron capture point has the average value λ = (81.5±2.7) cm. Additionally the yields of a number of cosmogenic radioisotopes are measured for {sup 12}N, {sup 12}B, {sup 8}He, {sup 9}C, {sup 9}Li, {sup 8}B, {sup 6}He, {sup 8}Li, {sup 11}Be, {sup 10}C and {sup 11}C. All results are compared with Monte Carlo simulation predictions using the FLUKA and GEANT4 packages. General agreement between data and simulation is observed for the cosmogenic production yields with a few exceptions, the most prominent case being {sup 11}C yield for which both codes return about 50% lower values. The predicted μ-n distance profile and the neutron multiplicity distribution are found to be overall consistent with data.

  19. 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.

  20. The CAIRN method: automated, reproducible calculation of catchment-averaged denudation rates from cosmogenic nuclide concentrations

    NASA Astrophysics Data System (ADS)

    Marius Mudd, Simon; Harel, Marie-Alice; Hurst, Martin D.; Grieve, Stuart W. D.; Marrero, Shasta M.

    2016-08-01

    We report a new program for calculating catchment-averaged denudation rates from cosmogenic nuclide concentrations. The method (Catchment-Averaged denudatIon Rates from cosmogenic Nuclides: CAIRN) bundles previously reported production scaling and topographic shielding algorithms. In addition, it calculates production and shielding on a pixel-by-pixel basis. We explore the effect of sampling frequency across both azimuth (Δθ) and altitude (Δϕ) angles for topographic shielding and show that in high relief terrain a relatively high sampling frequency is required, with a good balance achieved between accuracy and computational expense at Δθ = 8° and Δϕ = 5°. CAIRN includes both internal and external uncertainty analysis, and is packaged in freely available software in order to facilitate easily reproducible denudation rate estimates. CAIRN calculates denudation rates but also automates catchment averaging of shielding and production, and thus can be used to provide reproducible input parameters for the CRONUS family of online calculators.

  1. 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.

  2. Cosmogenic Backgrounds in Borexino at 3800 m water-equivalent depth

    NASA Astrophysics Data System (ADS)

    Bellini, G.; Benziger, J.; Bick, D.; Bonfini, G.; Bravo, D.; Buizza Avanzini, M.; Caccianiga, B.; Cadonati, L.; Calaprice, F.; Cavalcante, P.; Chavarria, A.; Chepurnov, A.; D'Angelo, D.; Davini, S.; Derbin, A.; Empl, A.; Etenko, A.; Fomenko, K.; Franco, D.; Galbiati, C.; Gazzana, S.; Ghiano, C.; Giammarchi, M.; Göger-Neff, M.; Goretti, A.; Grandi, L.; Hagner, C.; Hungerford, E.; Ianni, Aldo; Ianni, Andrea; Kobychev, V.; Korablev, D.; Korga, G.; Kryn, D.; Laubenstein, M.; Lewke, T.; Litvinovich, E.; Loer, B.; Lombardi, P.; Lombardi, F.; Ludhova, L.; Lukyanchenko, G.; Machulin, I.; Manecki, S.; Maneschg, W.; Manuzio, G.; Meindl, Q.; Meroni, E.; Miramonti, L.; Misiaszek, M.; Möllenberg, R.; Mosteiro, P.; Muratova, V.; Oberauer, L.; Obolensky, M.; Ortica, F.; Otis, K.; Pallavicini, M.; Papp, L.; Perasso, L.; Perasso, S.; Pocar, A.; Ranucci, G.; Razeto, A.; Re, A.; Romani, A.; Rossi, N.; Saldanha, R.; Salvo, C.; Schönert, S.; Simgen, H.; Skorokhvatov, M.; Smirnov, O.; Sotnikov, A.; Sukhotin, S.; Suvorov, Y.; Tartaglia, R.; Testera, G.; Vignaud, D.; Vogelaar, R. B.; von Feilitzsch, F.; Winter, J.; Wojcik, M.; Wright, A.; Wurm, M.; Xu, J.; Zaimidoroga, O.; Zavatarelli, S.; Zuzel, G.

    2013-08-01

    The solar neutrino experiment Borexino, which is located in the Gran Sasso underground laboratories, is in a unique position to study muon-induced backgrounds in an organic liquid scintillator. In this study, a large sample of cosmic muons is identified and tracked by a muon veto detector external to the liquid scintillator, and by the specific light patterns observed when muons cross the scintillator volume. The yield of muon-induced neutrons is found to be Yn = (3.10±0.11)·10-4 n/(μ·(g/cm2)). The distance profile between the parent muon track and the neutron capture point has the average value λ = (81.5±2.7) cm. Additionally the yields of a number of cosmogenic radioisotopes are measured for 12N, 12B, 8He, 9C, 9Li, 8B, 6He, 8Li, 11Be, 10C and 11C. All results are compared with Monte Carlo simulation predictions using the FLUKA and GEANT4 packages. General agreement between data and simulation is observed for the cosmogenic production yields with a few exceptions, the most prominent case being 11C yield for which both codes return about 50% lower values. The predicted μ-n distance profile and the neutron multiplicity distribution are found to be overall consistent with data.

  3. New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan.

    PubMed

    Granger, Darryl E; Gibbon, Ryan J; Kuman, Kathleen; Clarke, Ronald J; Bruxelles, Laurent; Caffee, Marc W

    2015-06-01

    The cave infills at Sterkfontein contain one of the richest assemblages of Australopithecus fossils in the world, including the nearly complete skeleton StW 573 ('Little Foot') in its lower section, as well as early stone tools in higher sections. However, the chronology of the site remains controversial owing to the complex history of cave infilling. Much of the existing chronology based on uranium-lead dating and palaeomagnetic stratigraphy has recently been called into question by the recognition that dated flowstones fill cavities formed within previously cemented breccias and therefore do not form a stratigraphic sequence. Earlier dating with cosmogenic nuclides suffered a high degree of uncertainty and has been questioned on grounds of sediment reworking. Here we use isochron burial dating with cosmogenic aluminium-26 and beryllium-10 to show that the breccia containing StW 573 did not undergo significant reworking, and that it was deposited 3.67 ± 0.16 million years ago, far earlier than the 2.2 million year flowstones found within it. The skeleton is thus coeval with early Australopithecus afarensis in eastern Africa. We also date the earliest stone tools at Sterkfontein to 2.18 ± 0.21 million years ago, placing them in the Oldowan at a time similar to that found elsewhere in South Africa at Swartkans and Wonderwerk.

  4. Cenozoic rejuvenation events of Massif Central topography (France): Insights from cosmogenic denudation rates and river profiles

    NASA Astrophysics Data System (ADS)

    Olivetti, Valerio; Godard, Vincent; Bellier, Olivier

    2016-06-01

    The French Massif Central is a part of the Hercynian orogenic belt that currently exhibits anomalously high topography. The Alpine orogenesis, which deeply marked Western European topography, involved only marginally the Massif Central, where Cenozoic faulting and short-wavelength crustal deformation is limited to the Oligocene rifting. For this reason the French Massif Central is a key site to study short- and long-term topographic response in a framework of slow tectonic activity. In particular the origin of the Massif Central topography is a topical issue still debated, where the role of mantle upwelling is invoked by different authors. Here we present a landscape analysis using denudation rates derived from basin-averaged cosmogenic nuclide concentrations coupled with longitudinal river profile analysis. This analysis allows us to recognize that the topography of the French Massif Central is not fully equilibrated with the present base level and in transient state. Our data highlight the coexistence of out-of-equilibrium river profiles, incised valleys, and low cosmogenically derived denudation rates ranging between 40 mm/kyr and 80 mm/kyr. Addressing this apparent inconsistency requires investigating the parameters that may govern erosion processes under conditions of reduced active tectonics. The spatial distribution of denudation rates coupled with topography analysis enabled us to trace the signal of the long-term uplift history and to propose a chronology for the uplift evolution of the French Massif Central.

  5. New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan.

    PubMed

    Granger, Darryl E; Gibbon, Ryan J; Kuman, Kathleen; Clarke, Ronald J; Bruxelles, Laurent; Caffee, Marc W

    2015-06-01

    The cave infills at Sterkfontein contain one of the richest assemblages of Australopithecus fossils in the world, including the nearly complete skeleton StW 573 ('Little Foot') in its lower section, as well as early stone tools in higher sections. However, the chronology of the site remains controversial owing to the complex history of cave infilling. Much of the existing chronology based on uranium-lead dating and palaeomagnetic stratigraphy has recently been called into question by the recognition that dated flowstones fill cavities formed within previously cemented breccias and therefore do not form a stratigraphic sequence. Earlier dating with cosmogenic nuclides suffered a high degree of uncertainty and has been questioned on grounds of sediment reworking. Here we use isochron burial dating with cosmogenic aluminium-26 and beryllium-10 to show that the breccia containing StW 573 did not undergo significant reworking, and that it was deposited 3.67 ± 0.16 million years ago, far earlier than the 2.2 million year flowstones found within it. The skeleton is thus coeval with early Australopithecus afarensis in eastern Africa. We also date the earliest stone tools at Sterkfontein to 2.18 ± 0.21 million years ago, placing them in the Oldowan at a time similar to that found elsewhere in South Africa at Swartkans and Wonderwerk. PMID:25830884

  6. 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.

  7. New cosmogenic burial ages for Sterkfontein Member 2 Australopithecus and Member 5 Oldowan

    NASA Astrophysics Data System (ADS)

    Granger, Darryl E.; Gibbon, Ryan J.; Kuman, Kathleen; Clarke, Ronald J.; Bruxelles, Laurent; Caffee, Marc W.

    2015-06-01

    The cave infills at Sterkfontein contain one of the richest assemblages of Australopithecus fossils in the world, including the nearly complete skeleton StW 573 (`Little Foot') in its lower section, as well as early stone tools in higher sections. However, the chronology of the site remains controversial owing to the complex history of cave infilling. Much of the existing chronology based on uranium-lead dating and palaeomagnetic stratigraphy has recently been called into question by the recognition that dated flowstones fill cavities formed within previously cemented breccias and therefore do not form a stratigraphic sequence. Earlier dating with cosmogenic nuclides suffered a high degree of uncertainty and has been questioned on grounds of sediment reworking. Here we use isochron burial dating with cosmogenic aluminium-26 and beryllium-10 to show that the breccia containing StW 573 did not undergo significant reworking, and that it was deposited 3.67 +/- 0.16 million years ago, far earlier than the 2.2 million year flowstones found within it. The skeleton is thus coeval with early Australopithecus afarensis in eastern Africa. We also date the earliest stone tools at Sterkfontein to 2.18 +/- 0.21 million years ago, placing them in the Oldowan at a time similar to that found elsewhere in South Africa at Swartkans and Wonderwerk.

  8. 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.

  9. Radiation doses to members of the U.S. population from ubiquitous radionuclides in the body: Part 1, autopsy and in vivo data.

    PubMed

    Watson, David J; Strom, Daniel J

    2011-04-01

    This paper is Part 1 of a three-part series investigating steady-state effective dose rates to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. This series of papers explicitly excludes intakes from inhaling (222)Rn, (220)Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. In this work, it is assumed that instantaneous dose rates in target organs are proportional to steady-state radionuclide concentrations in source regions. The goal of Part 1 of this work was to review, summarize, and characterize all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Forty-five papers and reports were obtained and their data reviewed, and three data sets were obtained via private communication. The 45 radionuclides of interest are the (238)U series (14 nuclides), the actinium series (headed by (235)U; 11 nuclides), and the (232)Th series (11 nuclides); primordial radionuclides (87)Rb and (40)K; cosmogenic and fallout radionuclides (14)C and (3)H; and purely anthropogenic radionuclides (137)Cs-(137m)Ba, (129)I, and (90)Sr-(90)Y. Measurements judged to be relevant were available for only 15 of these radionuclides: (238)U, (235)U, (234)U, (232)Th, (230)Th, (228)Th, (228)Ra, (226)Ra, (210)Pb, (210)Po, (137)Cs, (87)Rb, (40)K, (14)C, and (3)H. Recent and relevant measurements were not available for (129)I and (90)Sr-(90)Y. A total of 11,741 radionuclide concentration measurements were found in one or more tissues or organs from 14 states. Data on age, gender, geographic locations, height, and weight of subjects were available only sporadically. Too often authors did not provide meaningful values of uncertainty of measurements, so that variability in data sets is confounded with

  10. Radiation doses to members of the U.S. population from ubiquitous radionuclides in the body: Part 1, autopsy and in vivo data.

    PubMed

    Watson, David J; Strom, Daniel J

    2011-04-01

    This paper is Part 1 of a three-part series investigating steady-state effective dose rates to residents of the United States from intakes of ubiquitous radionuclides, including radionuclides occurring naturally, radionuclides whose concentrations are technologically enhanced, and anthropogenic radionuclides. This series of papers explicitly excludes intakes from inhaling (222)Rn, (220)Rn, and their short-lived decay products; it also excludes intakes of radionuclides in occupational and medical settings. In this work, it is assumed that instantaneous dose rates in target organs are proportional to steady-state radionuclide concentrations in source regions. The goal of Part 1 of this work was to review, summarize, and characterize all published and some unpublished data for U.S. residents on ubiquitous radionuclide concentrations in tissues and organs. Forty-five papers and reports were obtained and their data reviewed, and three data sets were obtained via private communication. The 45 radionuclides of interest are the (238)U series (14 nuclides), the actinium series (headed by (235)U; 11 nuclides), and the (232)Th series (11 nuclides); primordial radionuclides (87)Rb and (40)K; cosmogenic and fallout radionuclides (14)C and (3)H; and purely anthropogenic radionuclides (137)Cs-(137m)Ba, (129)I, and (90)Sr-(90)Y. Measurements judged to be relevant were available for only 15 of these radionuclides: (238)U, (235)U, (234)U, (232)Th, (230)Th, (228)Th, (228)Ra, (226)Ra, (210)Pb, (210)Po, (137)Cs, (87)Rb, (40)K, (14)C, and (3)H. Recent and relevant measurements were not available for (129)I and (90)Sr-(90)Y. A total of 11,741 radionuclide concentration measurements were found in one or more tissues or organs from 14 states. Data on age, gender, geographic locations, height, and weight of subjects were available only sporadically. Too often authors did not provide meaningful values of uncertainty of measurements, so that variability in data sets is confounded with

  11. Synchronizing the North American Varve Chronology with Greenland ice core records during late MIS 2 using Meteoric 10Be Flux

    NASA Astrophysics Data System (ADS)

    DeJong, Benjamin D.; Balco, Greg; Ridge, Jack C.; Rood, Dylan H.; Bierman, Paul R.

    2013-04-01

    The North American Varve Chronology (NAVC) is a floating 5700-year sequence of glacial lake varves deposited in the Connecticut River Valley of the northeast US ~18,000-12,500 years ago. The NAVC is an annually resolved record of regional climate and ice-marginal processes at 40-45° N latitude, near the margin of the retreating Laurentide Ice Sheet (LIS). NAVC deposition occurred at the same time as rapid and abrupt Arctic and North Atlantic climate changes that took place during the last deglaciation. Age calibration estimates for the NAVC based on radiocarbon dated plant macrofossils in individual varves imply a relationship between ice-marginal events recorded by the NAVC and climate events recorded in Greenland ice cores. For example, the retreat rate of the LIS up the Connecticut River Valley increased during the Bolling warming in Greenland, a readvance of the LIS margin took place during the Older Dryas cold period, and a correlation between an outburst flood from glacial Lake Iroquois and the Intra-Allerod Cold Period supports the hypothesis that the flood affected North Atlantic thermohaline circulation. On the other hand, a doubling of the ice-margin retreat rate recorded by the NAVC around 16,000 years ago coincides with a relatively cold period in Greenland. Our goal is to investigate the precise time relationship between these two records by synchronizing the NAVC with the Greenland ice core time scale using atmospherically-produced 10Be. Existing 10Be flux records, including those from Greenland ice cores, exhibit solar variability on a range of time scales. Because this variability is globally synchronous, a 10Be flux record for the NAVC can, in principle, be used to align NAVC and ice core timescales. In the first phase of this research we tested this potential by generating 10Be flux records for two 80-year varve sequences and analyzing them using multi-taper spectral analysis for determination of statistically significant periodicities. We were

  12. Quantifying Sub-Glacial Abrasion at Jakobshavn Isbræ: A Novel Approach Using In Situ 10Be Measurements

    NASA Astrophysics Data System (ADS)

    Young, N. E.; Briner, J. P.; Schaefer, J. M.

    2015-12-01

    Warm-based ice sheets and glaciers incontrovertibly erode and modify the terrain that they mantle; yet precise estimates of the rate and magnitude of sub-glacial erosion are rare. Estimates of sub-glacial erosion occurring beneath ice sheets, such as the Greenland Ice Sheet, are particularly important because they can provide key insights into sediment availability at ice-sheet margins that influences ice-sheet stability. Furthermore, estimates of sub-glacial erosion can help inform predictive geophysical ice-sheet models that incorporate a basal sliding parameter. Here, we take advantage of a detailed ice-margin history at Jakobshavn Isbræ over the last ~7,500 years, combined with in situ 10Be measurements from strategic bedrock locations, to quantify the rate of sub-glacial abrasion beneath Jakobshavn Isbræ's land-based margins. Our bedrock samples are from 1) locations that deglaciated ~7,500 years ago and have remained ice-free through present day, and 2) locations that also deglaciated ~7,500 years ago, but were re-occupied by the ice-margin during the last few hundred years. After accounting for the slightly different exposure histories between bedrock locations, and despite the short duration in ice-cover, initial 10Be measurements reveal a detectable difference in 10Be concentrations between the two bedrock surfaces. We hypothesize that the offset in 10Be concentrations reveals the magnitude of sub-glacial abrasion beneath Jakobshavn Isbræ's land-terminating margins.

  13. 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.

  14. 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.

  15. 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