Transport ofBe andBe in the ocean

Beryllium isotopes (¹⁰Be and⁹Be) have been measured in suspended particles of < 1 mm size collected by mid-water sediment traps deployed in the eastern Pacific at MANOP sites H (6°32′N, 92°50′W, water depth 3600 m) and M (8°50′N, 104°00′W, 3100 m). For comparison, surface sediments from box cores taken from the two sites were also studied. The concentrations of¹⁰Be and⁹Be in sediment-trap particles are about an order of magnitude smaller than those in the bottom sediments which contain about 8 × 10⁹ and 6 × 10¹⁶ atoms g⁻¹ of¹⁰Be and⁹Be, respectively. The sediment trap samples collected from 50 m off the bottom showed significant (26–63%) contributions from resuspended bottom sediments. The¹⁰Be/⁹Be ratio in trap samples varies from 3 to 20 × 10⁻⁸. The variation may partly result from varied proportion of authigenic/detrital material. The fluxes of both isotopes exhibit a very strong seasonality. The fluxes of¹⁰Be into the traps at about 1500 m are estimated as 9 × 10⁵ and 4 × 10⁵ atoms cm⁻² a⁻¹ at sites H and M respectively. These values are to be compared with the fluxes into the sediments of 4–5 × 10⁵ atoms cm⁻² a⁻¹ at both locations. Good correlations exist between¹⁰Be,⁹Be and²⁷Al indicating that the primary carrier phase(s) for the beryllium isotopes in the water column may be aluminosilicates.     

Lithium isotope variations in Tonga–Kermadec arc–Lau back‐arc lavas and Deep Sea Drilling Project (DSDP) Site 204 sediments

Lithium isotopes have been identified as a promising tracer of subducted materials in arc lavas due to the observable variations in related reservoirs such as subducting sediments and altered oceanic crust. The Tonga–Kermadec arc–Lau back‐arc provides an end‐member of subduction zones with the coldest thermal structure on Earth. Reported here are Li isotope data for 14 lavas from the arc front and 7 back‐arc lavas as well as 12 pelagic and volcaniclastic sediments along a profile through the sedimentary sequence at DSDP Site 204. The arc and back‐arc lavas range from basalts to dacites in composition with SiO₂ = 48.3–65.3 wt% over which Li concentrations increase from 2 ppm to 16 ppm. Li/Y ratios range from 0.08 to 0.77 and from 0.24 to 0.65 in the arc and back‐arc lavas, respectively. The majority of the lavas have δ⁷Li that ranges from 2.5 ‰ to 5.0 ‰ with an average of (3.6 ±0.7) ‰, similar to that reported from other arcs and there is no distinction between the arc front and back‐arc lavas. The pelagic sediments have variable Li concentrations (33–133 ppm) and δ⁷Li that ranges from 1.2 ‰ to 10.2 ‰ while the volcaniclastic sediments have an even greater range of Li concentrations (3.6–165 ppm) and generally higher δ⁷Li values (8–14 ‰). However, δ⁷Li in the lavas does not correlate with commonly used trace element ratio or isotope signatures indicative of slab‐derived fluids or the sediments. This is probably because the range of δ⁷Li in the lavas and sediments overlap. Calculated sediment mass‐balance models require significantly more sediment than previous estimates based on Th–Nd–Be isotopes. This may indicate that a sizeable proportion of the total Li budget in the lavas is provided by Li‐enriched fluids from the subducting sediments and/or altered oceanic crust.     

Cosmic ray flux variations, modulated by the solar and earth’s magnetic fields, and climate changes. 1. Time interval from the present to 10–12 ka ago (the Holocene Epoch)

Direct and indirect data on variations in cosmic rays, solar activity, geomagnetic dipole moment, and climate from the present to 10–12ka ago (the Holocene Epoch), registered in different natural archives (tree rings, ice layers, etc.), have been analyzed. The concentration of cosmogenic isotopes, generated in the Earth’s atmosphere under the action of cosmic ray fluxes and coming into the Earth archives, makes it possible to obtain valuable information about variations in a number of natural processes. The cosmogenic isotopes ¹⁴C in tree rings and ¹⁰Be in ice layers, as well as cosmic rays, are modulated by solar activity and geomagnetic field variations, and time variations in these concentrations gives information about past solar and geomagnetic activities. Since the characteristics of natural reservoirs with cosmogenic ¹⁴C and ¹⁰Be vary with climate changes, the concentrations of these isotopes also inform about climate changes in the past. A performed analysis indicates that cosmic ray flux variations are apparently the most effective natural factor of climate changes on a large time scale.     

Beryllium‐7 wet deposition variation with storm height,synoptic classification,and tree canopy state in the mid‐Atlantic USA

Short‐lived fallout isotopes, such as beryllium‐7 (⁷Be), are increasingly used as erosion and sediment tracers in watersheds. ⁷Be is produced in the atmosphere and delivered to the Earth's surface primarily in precipitation. However, relatively little has been published about the variation in ⁷Be wet deposition caused by storm type and vegetation cover. Our analysis of precipitation, throughfall, and sediments in two forested, headwater catchments in the mid‐Atlantic USA indicates significant variation in isotope deposition with storm type and storm height. Individual summer convective thunderstorms were associated with ⁷Be activity concentrations up to 5.0 Bq l^?1 in precipitation and 4.7 Bq l^?1 in throughfall, while single‐event wet depositional fluxes reached 168 Bq m^?2 in precipitation and 103 Bq m^?2 in throughfall. Storms originating from the continental USA were associated with lower ⁷Be activity concentrations and single‐event wet depositional fluxes for precipitation (0.7–1.2 Bq l^?1 and 15.8–65.0 Bq m^?2) and throughfall (0.1–0.3 Bq l^?1 and 13.5–98.9 Bq m^?2). Tropical systems had relatively low activity concentrations, 0.2–0.5 Bq l^?1 in precipitation and 0.2–1.0 Bq l^?1 in throughfall, but relatively high single‐event depositional fluxes due to large rainfall volumes, 32.8–67.6 Bq m^?2 in precipitation and 25.7–134 Bq m^?2 in throughfall. The largest sources of ⁷Be depositional variation were attributed to storm characteristics including precipitation amount and maximum storm height. ⁷Be activity associated with fluvial suspended sediments also exhibited the highest concentration and variability in summer (175–1450 Bq kg^?1). We conclude the dominant source of variation on event‐level ⁷Be deposition is storm type. Our results illustrate the complex relationships between ⁷Be deposition in precipitation and throughfall and demonstrate event‐scale relationships between the ⁷Be in precipitation and on suspended sediment. Copyright © 2015 John Wiley & Sons, Ltd.     

10Be dating of large manganese nodules from world oceans

The results of ¹⁰Be and ⁹Be measurements in several sections of ten large manganese nodules are presented along with U and Th isotope data on five of them.The ¹⁰Be and ¹⁰Be/⁹Be methods yield growth rates (covering a period of 5–10 Ma) which are in excellent agreement with each other. In three cases, these rates are also in very good agreement with those derived from the ²³⁰Th methods, whereas in the other two the ²³⁰Th-based rates are faster by over a factor of two.Based on the discrepancy between the inventory of ¹⁰Be (as well as ²³⁰Th) in nodules and the overhead seawater column, it is calculated that the former scavenge their Be and Th isotopes from 2–900 m of the overhead water column. The deduced ⁹Be concentrations of ocean water based on its ¹⁰Be contents and the ¹⁰Be/⁹Be ratios of nodule surfaces are found to be in good agreement with the direct ⁹Be measurements of seawater implying that ⁹Be in nodules (like¹⁰Be) is mostly authigenic.     

Atmospherically-derived radionuclides as tracers of sediment mixing and accumulation in near-shore marine and lake sediments: Evidence from7Be,210Pb,and239,240Pu

Cosmogenic⁷Be(t_1/2 = 53.3days) has been used to estimate particle-mixing rates in the upper layers of lacustrine and near-shore marine sediments. Excess²¹⁰Pb and/or^239,240Pu have provided limits on rates of sediment accumulation in these environments and indices of the efficiency of the sediments as collectors of reactive nuclides over longer time scale.In sediment cores from Long Island Sound (marine) and Lake Whitney (fresh-water)⁷Be was measurable in the top 2–3 cm. Diffusion-analog particle-mixing coefficients calculated from these data are in the range of 10^?7 cm²/s. For Long Island Sound the coefficients are lower by factors of 3–6 than those estimated from the depth distributions of excess²³⁴Th at the same stations [14]. For Lake Whitney the calculated mixing coefficient is an upper limit because of the possibility of a sampling artifact.Measurements of total (wet + dry) atmospheric deposition of⁷Be in New Haven give an average flux of 0.07 dpm/cm² day during March-November, 1977; this is equivalent to a steady-state inventory of 5.4 dpm/cm² in a perfect collector. Sediment cores from Long Island Sound contain about half this⁷Be inventory, consistent with either a mean residence time for⁷Be in the water column of about one half-life or with post-depositional loss of⁷Be from Long Island Sound sediments. The Lake Whitney cores contain about 5 dpm/cm², much nearer the atmospheric delivery. A higher inventory of⁷Be in fresh-water, as compared to marine, sediments could be due either to a shorter mean residence time for⁷Be in fresh water or to lateral transport processes in the lake or its catchment. High inventories of excess²¹⁰Pb and^239,240Pu in Lake Whitney sediments demonstrate the importance of lateral transport on longer time scales at least.     

Distribution ofBe andBe in the Pacific Ocean

The vertical distributions of¹⁰Be and⁹Be at three locations in the Pacific (25°N, 170°E; 17°N, 118°W; 3°S, 117°W) are presented. The results show that both isotopes exhibit nutrient-like profiles. From the surface to the bottom, the increase for¹⁰Be is two- to threefold and that for⁹Be is about fivefold. While the inter-station variations in surface water concentrations may reach a factor of two, deep-water values tend to be much more uniform averaging about 2000 atoms/g for¹⁰Be and 30 pM for⁹Be. A similar situation applies to the¹⁰Be/⁹Be ratio; it varies approximately from 1 to 3 × 10⁻⁷ (atom/atom) at shallow depths but tends toward a value close to 1.1 × 10⁻⁷ in the deep ocean. The variation of¹⁰Be/⁹Be can be viewed as resulting from the fact that¹⁰Be in a given parcel of water consists of two components: recycled and primary. The recycled component is that part of¹⁰Be which has reached tracer equilibrium with⁹Be, as opposed to the primary component which, upon entering the sea from the atmosphere, has yet to equilibrate with⁹Be through particle cycling and mixing processes. It is estimated that 70% to nearly 100% of¹⁰Be at the three stations are being recycled, and the recycled beryllium bears an atomic ratio of¹⁰Be/⁹Be close to 1 × 10⁻⁷. The oceanic residence time of Be is of the order of 1000–4000 years, comparable to or slightly longer than the ocean mixing time.     

The CRONUS-Earth inter-comparison for cosmogenic isotope analysis

As part of the NSF-funded program CRONUS-Earth, a series of natural reference materials for in situ produced ²⁶Al, ¹⁰Be, ¹⁴C, and ³⁶Cl were prepared and circulated to United States, Australian, and European laboratories for analysis to explore the comparability of results from the different laboratories and generate preliminary consensus values for a range of reference material. Such reference materials, which did not exist for these isotopes, assist laboratories in independently assessing quality and are useful to quantify precision and accuracy. Currently, most researchers report only internal analytical uncertainties for all results. While researchers have acknowledged the need for realistic inter-laboratory uncertainties for in situ produced cosmogenic isotopes, few previous studies have addressed this issue. Two samples (denoted A and N) were provided for ²⁶Al, ¹⁰Be and in situ ¹⁴C analysis, one from the Antarctic, high in ²⁶Al and ¹⁰Be and the other from Australia, lower in both ²⁶Al and ¹⁰Be. Both samples were prepared to quartz at the University of Vermont. For each sample, results have been summarised in terms of the mean reported concentration, standard deviation both between (inter) and within (intra) laboratories to describe inter- and intra-laboratory variability. Coefficients of variation (CoV) expressed as a percentage of the mean are also reported. For in-situ ¹⁴C, a small number of laboratories reported results, so they are summarised separately. Initial uncorrected results for ¹⁰Be for samples A and N showed significant variation (greater than 8% CoV) in results. When corrected to a common standardisation basis, the CoV was 2.9% for ¹⁰Be measurements of sample A (high concentration) and to 4.1% for sample N (lower concentration), which is closer to typical cosmogenic samples. ²⁶Al measurements had greater variation; a CoV of 4.9% was achieved for sample A (high concentration) but for the lower concentration sample N, the CoV was 10.1%.     

Anomalous cosmogenic 3He production and elevation scaling in the high Himalaya

The production rate of cosmogenic ³He in apatite, zircon, kyanite and garnet was obtained by cross-calibration against ¹⁰Be in co-existing quartz in glacial moraine boulders from the Nepalese Himalaya. The boulders have ¹⁰Be ages between 6 and 16 kyr and span elevations from 3200 to 4800 m. In all of these minerals ³He correlates with ¹⁰Be and is dominantly cosmogenic in origin. After modest correction for non-cosmogenic components, ³He/¹⁰Be systematics imply apparent sea-level high-latitude (SLHL) apparent production rates for ³He of 226 atoms g^? 1 yr^? 1 in zircon, 254 atoms g^? 1 yr^? 1 in apatite, 177 atoms g^? 1 yr^? 1 in kyanite, and 153 atoms g^? 1 yr^? 1 in garnet. These production rates are unexpectedly high compared with rates measured elsewhere in the world, and also compared with proposed element-specific production rates. For apatite and zircon, the data are sufficient to conclude that the ³He/¹⁰Be ratio increases with elevation. If this reflects different altitudinal scaling between production rates for the two isotopes then the SLHL production rates estimated by our approach are overestimates. We consider several hypotheses to explain these observations, including production of ³He via thermal neutron capture on ⁶Li, altitudinal variations in the energy spectrum of cosmic-ray neutrons, and the effects of snow cover. Because all of these effects are small, we conclude that the altitudinal variations in production rates of cosmogenic ³He and ¹⁰Be are distinct from each other at least at this location over the last ～ 10 kyr. This conclusion calls into question commonly adopted geographic scaling laws for at least some cosmogenic nuclides. If confirmed, this distinction may provide a mechanism by which to obtain paleoelevation estimates.     

Aerosol deposition velocities on the Pacific and Atlantic oceans calculated from7Be measurements

The concentrations of⁷Be have been measured in Pacific and Atlantic ocean water for the past several years to determine the deposition velocity of aerosol particles on the ocean surface.⁷Be is produced at a relatively constant rate in the atmosphere by spallation reactions of cosmic rays with atmospheric nitrogen and oxygen. Immediately after its formation⁷Be becomes attached to aerosol particles, and therefore can serve as tracers of the subsequent behavior of these particles. Isopleths of⁷Be surface water concentrations,⁷Be inventory in the ocean, and deposition velocity have been prepared for the Pacific Ocean from 30°S to 60°N and for the Atlantic Ocean from 10°N to 55°N. The concentrations, inventories and deposition velocities tended to be higher in regions where precipitation was high, and generally increased with latitude. The average flux of⁷Be across the ocean surface was calculated to be 0.027 atoms cm^?2 s^?1 which is probably not significantly greater than the worldwide average⁷Be flux across land and ocean surfaces of 0.022 atoms cm^?2 s^?1 calculated by Lal and Peters. The average deposition velocity was calculated to be 0.80 cm s^?1. This value may be 10–50% too low, since it was calculated using atmospheric⁷Be concentrations which were measured at continental stations. Measurements of atmospheric⁷Be concentrations at ocean stations suggest that the concentrations at the continental stations averaged 10–50% higher than the concentrations over the ocean.     

10Be dating of North Pacific sediment cores up to 2.5 million years B.P.

The¹⁰Be method of dating of marine sediment cores is applied to five North Pacific cores. Assuming a constant¹⁰Be precipitation rate and varying sedimentation rates with time during the past 2.5 m.y. dating confirms to that obtained from paleomagnetic stratigraphy. The¹⁰Be concentration variations with depth in the cores are primarily due to changes in sediment dilution and do not reflect cosmic ray intensity or global climate variations. The limits of¹⁰Be deposition rate variation in the investigated cores are less than ± 10% for periods of (2–7) × 10⁵ years and less than ±30% for periods of 1 × 10⁵ years. The data set gives a half-life of¹⁰Be is 1.50 × 10⁶ years. The latitudinal effect of¹⁰Be concentrations and¹⁰Be/⁹Be ratios relates to a frequency of particulate matter occurrence (detrital and biological particles) in the oceans and to oceanic circulation.     

Solar forcing on the 7Be-air concentration variability at ground level

This paper analyzes the correlation between the temporal and spatial variability of ⁷Be-air concentration at ground level to precipitation. Data, obtained from 26 stations distributed throughout North and South America, Australia and Antarctica, were analyzed. Variations in the data were extracted by the empirical orthogonal function (EOF) and principal component (PC) analysis. The results presented here show that the variability of ⁷Be-air concentration at ground level is influenced simultaneously both by solar cycle and atmospheric processes, such as precipitation, turbulent transport and advection. Solar forcing dominates ⁷Be annual variability worldwide. On the other hand, atmospheric processes influence ⁷Be air–concentration at ground level regionally and seasonally.     

Long-term solar activity as a controlling factor for global warming in the 20th century

Such high-resolution indirect data on solar activity as the ¹⁴C and ¹⁰Be cosmogenic isotopes have been considered. The long-term solar activity cyclicity during the last millennium with periods of approximately 90 and 210 years, which can be related to substantial climatic warming and cooling events in this millennium, has been established based on an analysis of these data. It has been indicated that long-term recent climate warming can result from the effect of the ∼90- and ∼210-year solar cycles on the climatic system, which is characterized by the nonlinear dynamics.     

Tracing environmental change in southern Patagonia using beryllium isotopes,Laguna Potrok Aike,Argentina

We have examined the relationship between beryllium isotopes and the hydrological record of Laguna Potrok Aike, a maar lake in southern Argentina for the past 16,000 cal BP. Our study shows that sedimentary ¹⁰Be and ⁹Be records of Laguna Potrok Aike are associated with the hydrological balance, when compared to other proxies such as Ca, Ti and total inorganic carbon (TIC). During drier periods, the level of ⁹Be is decreased. ¹⁰Be follows this trend from 16,000 to 8000 cal BP, for younger samples, the concentration of ¹⁰Be increases at about 5000 cal BP and in recent times, but is otherwise relatively constant. At 13,000 cal BP total beryllium (⁹Be) was relatively low, but the ¹⁰Be/⁹Be ratio was the highest for the entire record studied. Our study shows that beryllium isotopes can be used for tracing climatic signals associated with lake level changes, i.e., dry or wet conditions at Laguna Potrok Aike.     

Fluvial dynamics and 14C-10Be disequilibrium on the Bolivian Altiplano

Determining sediment transfer times is key to understanding source-to-sink dynamics and the transmission of environmental signals through the fluvial system. Previous work on the Bolivian Altiplano applied the in situ cosmogenic ¹⁴C-¹⁰Be-chronometer to river sands and proposed sediment storage times of ~10–20 kyr in four catchments southeast of Lake Titicaca. However, the fidelity of those results hinges upon isotopic steady-state within sediment supplied from the source area. With the aim of independently quantifying sediment storage times and testing the ¹⁴C-¹⁰Be steady-state assumption, we dated sediment storage units within one of the previously investigated catchments using radiocarbon dating, cosmogenic ¹⁰Be-²⁶Al isochron burial dating, and ¹⁰Be-²⁶Al depth-profile dating. Palaeosurfaces appear to preserve remnants of a former fluvial system, which has undergone drainage reversal, reduction in catchment area, and local isostatic uplift since ~2.8 Ma. From alluvium mantling the palaeosurfaces we gained a deposition age of ~580 ka, while lower down fluvial terraces yielded ≤34 ka, and floodplains ~3–1 ka. Owing to restricted channel connectivity with the terraces and palaeosurfaces, the main source of channel sediment is via reworking of the late Holocene floodplain. Yet modelling a set of feasible scenarios reveals that floodplain storage and burial depth are incompatible with the ¹⁴C-¹⁰Be disequilibrium measured in the channel. Instead we propose that the ¹⁴C-¹⁰Be offset results from: (i) non-uniform erosion whereby deep gullies supply hillslope-derived debris; and/or (ii) holocene landscape transience associated with climate or human impact. The reliability of the ¹⁴C-¹⁰Be chronometer vitally depends upon careful evaluation of sources of isotopic disequilibrium in a wide range of depositional and erosional landforms in the landscape. © 2018 John Wiley & Sons, Ltd.     

Non-cosmogenic lithium-6 in iron meteorites

A neutron activation method is used to measure⁶Li via the reaction⁶Li(n, α)³H in iron meteorites. It is found that most⁶Li occurs in non-metallic inclusions which can be separated by dissolution of the metal in 4 M H₂SO₄. The non-magnetic portion of such a residue has as high as 0.9 ppm⁶Li, while in the bulk sample⁶Li ranges from 0.02 to 10 ppb. Average⁶Li contents (ppb) for various classes are IA, 1.8; IIAB, 1.6; and IIIA, 0.4. Cosmic-ray-produced⁶Li is generally much smaller than the native⁶Li.     

Meteoric 10Be speciation in subglacial sediments of East Antarctica

A sequential chemical extraction procedure was developed and tested to investigate the utility of meteoric ¹⁰Be as a tracer for authigenic mineral formation beneath the East Antarctic Ice Sheet. Subglacial meltwater is widely available under the Antarctic Ice Sheet and dissolved gases within it have the potential to drive chemical weathering processes in the subglacial environment. Meteoric ¹⁰Be is a cosmogenic nuclide with a half-life of 1.39·10⁶ years that is incorporated into glacier ice, therefore its abundance in the subglacial environment in Antarctica is meltwater dependent. It is known to adsorb to fine-grained particles in aqueous solution, precipitate with amorphous oxides/hydroxides, and/or be incorporated into authigenic clay minerals during chemical weathering. The presence of ¹⁰Be in chemical weathering products derived from beneath the ice therefore indicates chemical weathering processes in the subglacial environment. Freshly emerging subglacial sediments from the Mt. Achernar blue ice moraine were subject to chemical extractions where these weathering phases were isolated and ¹⁰Be concentrations therein quantified. Optimization of the phase isolation was developed by examining the effects of each extraction on the sample mineralogy and chemical composition. Experiments on ¹⁰Be desorption revealed that pH 3.2–3.5 was optimal for the extraction of adsorbed ¹⁰Be. Vigorous disaggregation of the samples before grain size separations and acid extractions is crucial due to the incorporation of the nuclide in clay minerals and its preferential absorption to clay-sized particles. ¹⁰Be concentrations of 2–22·10⁷ atoms·g⁻¹ measured in oxides and clay minerals in freshly emerging sediments strongly indicate subglacial chemical weathering in the catchment of the Mt. Achernar moraine. Based on total ¹⁰Be sample concentrations, local basal melt rates, and ¹⁰Be ice concentrations, sediment-meltwater contact in the subglacial environment is on the order of thousands of years per gram of underlying fine sediment. Strong correlation (R = 0.97) between ¹⁰Be and smectite abundance in the sediments supports authigenic clay formation in the subglacial environment. This suggests meteoric ¹⁰Be is a useful tool to characterize subglacial geochemical weathering processes under the Antarctic Ice Sheet.     

Dating chert (diagenetic silica) using in-situ produced 10Be: Possible complications revealed through a comparison with 36Cl applied to coexisting limestone

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

Cosmic ray flux variations,modulated by the solar and terrestrial magnetic fields,and climate changes. Part 2: The time interval from ∼10000 to ∼100000 years ago

A joint analysis of paleodata on variations in cosmic ray fluxes, solar activity, geomagnetic field, and climate during the period from ～10000 to ～100000 years ago has been performed. Data on the time variations in the concentration of ¹⁴C and ¹⁰Be cosmogenic isotopes, which are generated in the Earth’s atmosphere under the action of cosmic ray fluxes modulated by solar activity and geomagnetic field variations, were used to detect variations in solar activity and the geomagnetic dipole. Information about climate changes has been obtained mainly from variations in the concentration of stable isotopes in the natural archives. A performed analysis indicates that the variations in cosmic ray fluxes under the action of variations in the geomagnetic field and solar activity are apparently one of the most effective natural factors of long-term climate changeability on a large time scale.     

Understanding long-term soil processes using meteoric 10Be: A first attempt on loessic deposits

Meteoric ¹⁰Be, due to its high affinity with soil and sediment particles, is widely used in geomorphologic and environmental studies attempting to evaluate the soil production/denudation rates or soil ages up to 10⁷ years. However, the evolution of the ¹⁰Be distribution as a function of depth is poorly known in soils as revealed by recent reviews (Graly et al., 2010; Willenbring and von Blanckenburg, 2010). In this study, ¹⁰Be concentrations in the bulk and the 0–2 μm (lutum) granulometric fraction of samples along Luvisols profiles developed from loess in Northern France have been measured. The bulk ¹⁰Be concentrations are significantly higher in one of the three sites, likely reflecting differences in the inherited ¹⁰Be concentrations of the loess parent material as well as in the accumulation rates of the later. However, the bulk ¹⁰Be concentrations along all profiles are significantly correlated with the lutum (0–2 μm fraction) content, the maximum ¹⁰Be concentrations being evidenced in the Bt-horizon. Dominant adsorption of ¹⁰Be to the lutum has been furthermore corroborated by the mass-balance calculations with as much as 79.8 ± 9.0% of ¹⁰Be being associated with the lutum. Contrary to the bulk ¹⁰Be concentrations, the lutum ¹⁰Be concentrations showed several maxima coinciding with shifts in the coarse to fine silt ratio. This was interpreted as a change in the loess deposit dynamic. Finally, using numerical modeling approach based on the advection-diffusion equation, an average downward migration of ¹⁰Be by clay translocation was estimated. It ranges from 0.01 to 0.08 cm yr⁻¹. Inherited ¹⁰Be in the loess parent material represented from 64 to 71% of the total ¹⁰Be content in the simulated soils. Vertical ¹⁰Be distributions and their maximum concentrations in the Bt-horizon thus mainly result from redistribution of the inherited ¹⁰Be by clay translocation and bioturbation.