Beryllium-10 contents of shergottites,nakhlites, and Chassigny

Accelerator mass spectrometry gives the following ¹⁰Be contents (dpm/kg) for the SNC meteorites: Shergotty, 13.0 ± 1.5 and 17.3 ± 2.7; Zagami, 18.6 ± 2.5 and 20.0 ± 3.2; ALHA 77005, 15 ± 3; EETA 79001A, 7.8 ± 1.1 and 6.3 ± 0.5; EETA 79001B, 8.5 ± 1.1; Nakhla, 19.7 ± 3.3; Lafayette, 18.1 ± 2.5; Governador Valadares, 25.6 ± 3.6; Chassigny, 20.5 ± 3.1. The ¹⁰Be contents of the NC meteorites indicate that significant accumulation of cosmogenic nuclides occurred in decimeter rather than planetary-size bodies. The agreement of the ³He, ²¹Ne, and ¹⁰Be exposure ages of the shergottites also supports small-body irradiation. A long terrestrial age for EETA 79001 appears unlikely.     

Aluminum-26 in meteorites—VII. Ureilites,their unique radiation history

Cosmogenic ²⁶A1 activities have been measured by γ-γ coincidence counting in the three ureilites which had not previously been studied. The values in dpm/kg are: Dingo Pup Donga, 38.4 ± 2.4; North Haig, 39.3 ± 4.8; Dyalpur, 55.8 ± 4.8. Five of the six known ureilites thus have lower ²⁶A1 contents, 63 per cent to 77 per cent, than the calculated saturation values, in marked contrast to most other stony meteorites. This cannot be attributed to short cosmic ray exposure ages. Nor do size and depth effects account for the narrow range of ²⁶A1 activities, because a nuclear particle track study indicates that preatmospheric radii were highly variable, from ≥ 40 cm for Goalpara to only a few cm for Dingo Pup Donga. By default, the most likely explanation is that the ureilites had much smaller or much larger orbits than all other stony meteorites.     

Use of in situ-produced Be in carbonate-rich environments: A first attempt

We have determined the production rate of in situ-produced ¹⁰Be in calcite through measurements of ¹⁰Be and ³⁶Cl concentrations in the same calcite samples and of ¹⁰Be concentrations in depth profiles of flint from the same erosional surface. This yields a ¹⁰Be production rate in calcite of 37.9 ± 6.0 at/g/yr at sea level and high latitude, approximately sixfold higher than production in the coexisting flint. We propose that this higher rate of production may be due to high production cross sections for C spallation by cosmic rays with energies below 50 MeV. These results also open the possibility of dating burial events in carbonate-rich environments by differential radioactive decay of ¹⁰Be and ³⁶Cl.     

The dissolved Beryllium isotope composition of the Arctic Ocean

We present the first comprehensive set of dissolved ¹⁰Be and ⁹Be concentrations in surface waters and vertical profiles of all major sub-basins of the Arctic Ocean, which are complemented by data from the major Arctic rivers Mackenzie, Lena, Yenisey and Ob. The results show that ¹⁰Be and ⁹Be concentrations in waters below 150 m depth are low and only vary within a factor of 2 throughout the Arctic Basin (350-750 atoms/g and 9-15 pmol/kg, respectively). In marked contrast, Be isotope compositions in the upper 150 m are highly variable and show systematic variations. Cosmogenic ¹⁰Be concentrations range from 150 to 1000 atoms/g and concentrations of terrigenous ⁹Be range from 7 to 65 pmol/kg, resulting in ¹⁰Be/⁹Be ratios (atom/atom) between 0.5 and 14 × 10⁻⁸. Inflowing Atlantic water masses in the Eurasian Basin are characterized by a ¹⁰Be/⁹Be signature of 7 × 10⁻⁸. The inflow of Pacific water masses across the Bering Strait is characterized by lower ratios of 2-3 × 10⁻⁸, which can be traced into the central Arctic Ocean, possibly as far as the Fram Strait. A comparison of the high dissolved surface ¹⁰Be and ⁹Be concentrations (corresponding to low ¹⁰Be/⁹Be signatures of ∼2 × 10⁻⁸) in the Eurasian Basin with hydrographic parameters and river data documents efficient and rapid transport of Be with Siberian river waters across the Siberian Arctic shelves into the central Arctic Basin, although significant loss and exchange of Be on the shelves occurs. In contrast, fresh surface waters from the Canada Basin also show high cosmogenic ¹⁰Be contents, but are not enriched in terrigenous ⁹Be (resulting in high ¹⁰Be/⁹Be signatures of up to 14 × 10⁻⁸). This is explained by a combination of efficient scavenging of Be in the Mackenzie River estuary and the shelves and additional supply of cosmogenic ¹⁰Be via atmospheric fallout and melting of old sea ice. The residence time of Be in the deep Arctic Ocean estimated from our data is 800 years and thus similar to the average Be residence time in the global ocean.     

Laboratory studies of the diagenesis and mobility of 239,240pu and 137Cs in nearshore sediments

Controlled laboratory experiments have been used to study the diagenetic chemistry of ^239,240Pu ¹³⁷Cs, and ⁵⁵Fe. Experiments using Buzzards Bay sediments in small tanks show that sulfate reduction is accompanied by the production of large pore water concentration gradients of alkalinity, phosphate, ammonia and dissolved organic carbon and the formation of subsurface maxima in Fe and Mn. These pore water profiles demonstrate that bacterially-mediated processes of organic matter degradation and redox reactions can be simulated in the laboratory.A vertical profile of ⁵⁵Fe in pore waters is reported for the first time: it follows the profile of stable Fe and as such has a large (200 dpm/100 kg) subsurface maximum between 2–4 cm depth. Comparison of ⁵⁵Fe/Fe ratios in sediments and pore waters shows that there is preferential solubilization of ⁵⁵Fe over stable Fe.The pore water activities of ^239,240Pu show no gradients within the large uncertainties of the counting statistics, but are two to four times higher than Buzzards Bay seawater (0.05 dpm/100 kg).The activity of ¹³⁷Cs in the pore water profile is constant (40 dpm/100 kg) within the large counting uncertainties and is twice that of Buzzards Bay seawater. Cs-137 does not appear to be involved in diagenetic chemistry but may increase in pore waters as a result of ion exchange reactions.Flux estimates based on the pore water data show that remobilization and transport of ^239,240 Pu in coastal sediments are not significant processes while the transport of ^l37Cs may be.     

The pore water chemistry of 239,240Pu and 137Cs in sediments of Buzzards Bay,Massachusetts

The collection of large volumes of pore water (1–2 liters per 2 cm horizon of sediment) and low level radiochemical measurements of ^239,240Pu and ¹³⁷Cs have been combined to produce the first study of these fallout artificial radionuclides in marine pore waters. Profiles from box cores taken in June and September 1982 from Buzzards Bay, Mass., are reported along with profiles of many diagenetic constituents (i.e. SO₄^2?, alkalinity, Fe, Mn, DOC, and nutrients).The ^239,240Pu pore water profile is characterized by a subsurface maximum of about 0.28 dpm/100 kg lying between 3–11 cm. Overlying seawater, in contrast, has an activity of $\text{0.01 ± 0.02}$ dpm/100 kg. Below about 11 cm, the pore water ^239,240Pu distribution follows that of the solid phase which decreases rapidly with depth. The pore water profiles of ¹³⁷Cs are characterized by a broad and deeply penetrating maximum where activities of about 35–40 dpm/100 kg extend from 3 to 20 cm. Overlying seawater, in contrast, has an activity of 17–24 dpm/100 kg. The ¹³⁷Cs and ^239,240Pu pore water data show that there is preferential downward transport of ¹³⁷Cs and that ^239,240Pu does not have an active diagenetic chemistry and is not significantly mobile in these coastal sediments.     

The 21Ne production rate in stony meteorites estimated from 10Be and other radionuclides

The ¹⁰Be contents of 28 stony meteorites with known ²¹Ne contents range from 0.97 to 23 dpm/kg and give an average ²¹Ne production rate (P₂₁) of (0.28 ± 0.02) × 10⁸ cm³ STP/g-Myr for shielding conditions corresponding to ${}^{22}\text{Ne}{}^{21}\text{Ne}\text{= 1.114}$ in an H-chondrite. Our $\text{P}{}_{21}\text{(}{}^{10}\text{Be)}$ agrees with others' P₂₁ based on ²²Na, ⁸¹Kr and ⁵³Mn but not on ²⁶A1. Temporal variations in the cosmic ray flux do not explain the disagreement satisfactorily; major errors in the radionuclide half-lives are not indicated. The discrepancy seems rooted in the data selection and the difficulties of making accurate corrections for shielding, chemical composition and other sources of variability.     

Meteoric Be in soil profiles - A global meta-analysis

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.     

晚更新世黄土堆积物中的10Be记录

给出西峰黄土剖面0.15Ma以来¹⁰Be浓度、CaCO₃含量、粒度分布和有机质含量曲线。通过与深海沉积物δ¹⁸O曲线拟合,建立了西峰黄土剖面¹⁰Be时标,并与洛川黄土剖面¹⁰Be记录进行了对比研究。进一步计算了黄土堆积速率及¹⁰Be沉降量。     

Sediment incorporation in island-arc magmas: Inferences from 10Be

The radioisotope ¹⁰Be has been used as a tracer to evaluate subduction and recycling of sediments in island arcs. As a cosmogenic isotope strongly enriched in oceanic sediments, it is especially suitable for monitoring sediment subduction.We report here ¹⁰Be results for 106 arc volcanic rocks and 33 basalts from mid-ocean ridges, oceanic islands, continental rifts, and continental flood basalt provinces. The 33 basalts from non-arc environments all contain < 1 × 10⁶ atom/gram (g⁻¹) and form a reference or “control group” against which the arc data may be compared. Lavas from the Sunda, Mariana and Halmahera arcs, each with 12 samples, are indistinguishable from the control group. Nine samples from Japan range from 0.1 × 10⁶ to 13.5 × 10⁶ g⁻¹ of ¹⁰Be. Lavas from the Aleutians and Central America (excluding Costa Rica) consistently have ¹⁰Be contents greater than those of the control group, extending to 15.3 × 10⁶ g⁻¹ for the Aleutians and 24 × 10⁶ g⁻¹ for Central America. Both the Japan and Central American arcs show a geographic variation in ¹⁰Be abundances; the Aleutian arc does not.Conceptually, four models may be used to explain the incorporation of ¹⁰Be in island arcs. Model 1 is the limiting case calculation presented in Brownet al. (1982). Physically, it corresponds to an assumption that all ¹⁰Be in the uppermost sediment layers is carried to depth, the ¹⁰Be is mechanically decoupled from the sediment pile and is added to the arc magma source region. This model results in the highest calculated ¹⁰Be contents in arc lavas. In the more physically reasonable Model 2, the ¹⁰Be-rich upper sediments are assumed to mix with the deeper, ¹⁰Be-poor, sediments and the sediments are subsequently incorporated into the source region. Model 3 assumes ¹⁰Be to be incorporated from sedimentary layers encountered during magma ascent. In Model 4 only sediments contained within grabens in the downgoing slab may be subducted. As yet insufficient data exist to permit conclusive evaluation of these models, but correlations between ¹⁰Be contents in arc volcanic rocks and recent sedimentation rates and sediment thickness, measured outboard of the trench, suggest that Model 2 may be the most important mechanism for ¹⁰Be incorporation in many island arcs.     

黄土和红粘土中宇宙成因核素定年的潜力: 10 Be浓度与化学成分的关系*

宇宙成因核素¹⁰ Be(半衰期1.5Ma)不但是古环境变化的示踪剂,而且具有确定地质年龄的能力。80个全岩样品的¹⁰ Be和化学分析数据表明,黄土高原约6Ma以来的红粘土和黄土序列中年龄校正的¹⁰ Be浓度与沉积物粒度和风化程度的化学指标具有显著的关系。根据这种关系建立的¹⁰ Be浓度与化学指标的经验回归线性模型,可以估计红粘土和黄土形成时的¹⁰ Be浓度,确定红粘土和黄土形成的¹⁰ Be放射性年龄。     

东北四海龙湾玛珥湖沉积物纹层计年与137Cs、210Pb测年

对东北四海龙湾玛珥湖SHLF6孔纹层沉积物的¹³⁷Cs放射性测量表明:¹³⁷Cs比活度的最大值出现在55cm处,对应于1963年世界原子弹试爆高峰期。纹层计年表明0～6cm共有35个纹层层偶。从75cm到65cm,¹³⁷Cs比活度从256±009dpm/g急剧增加到1868±017dpm/g,可能65cm对应于1954年。通过测量²²⁶Ra子核²¹⁴Pb和²¹⁴Bi（能量为295keV,352keV和609keV）放射的光子数获得²²⁶Ra比活度数据,然后求得过剩²¹⁰Pb_{比活度（²¹⁰Pbuns）。²¹⁰Pbuns比活度随深度增加而呈指数衰减,其异常波动可能与人类活动以及沉积速率变化有关,例如55cm处²¹⁰Pb比活度较高,与¹³⁷Cs的峰值对应,这可能与1963年前后人工核实验的高峰有关,因为核试验不仅产生¹³⁷Cs,而且可以产生208Pb和²¹⁰Pb;45cm处²¹⁰Pb比活度较低,而²²⁶Ra较高,可能与人类活动加剧,导致沉积速率增加有关。根据²¹⁰PbunsCRS模式,SHLF6孔0～19cm的平均沉积速率为20mg/cm²·a,或约为011cm/a。²¹⁰Pb测年数据与¹³⁷Cs时标及纹层计年均有很好的一致性。四海龙湾玛珥湖发育的纹层为年纹层,可以建立高分辨率时间序列。}     

The cosmic ray record in the San Juan Capistrano meteorite

An integrated study of the cosmic ray exposure history of the San Juan Capistrano meteorite was carried out using measurements of rare gas isotopic abundances, particle track densities and radioisotope concentrations. Spallation systematics determined for Kr isotopes in lunar samples are shown to be valid also for the San Juan Capistrano and St. Severin meteorites, thus allowing us to determine a reliable ⁸¹Kr/⁸³Kr production ratio as needed for applying the ⁸¹Kr-Kr dating method. The ⁸¹Kr-Kr age of SJC is 28.7 ± 2.0 Myr, about 35% longer than ages determined by spallation He or Ne. The minimum observed track production rate (2.6 × 10⁵ tracks/cm² · Myr) sets a minimum of 8 cm for the preatmospheric radius of an assumed spherical body. Track density gradients and the low ⁶⁰Co activity (<2.9 dpm/g Co) both set an upper limit of 10 cm to the radius. Track results show that ablation losses have averaged 6cm. The relative spallation yields of ⁷⁸Kr and ⁸³Kr, and the ratios ³He/²¹Ne and ²²Ne/²¹Ne are all compatible with a hard irradiation as would be experienced by a sample depth of about 6 cm in a body of 8–10 cm. The low activities of ⁵⁴Mn, ²²Na and ²⁶Al are also consistent with these irradiation conditions.     

Sixty year10Be record from Greenland and Antarctica

We report in this study the distribution of¹⁰Be in the top 40 m of the Renland ice core (East Greenland) and in a 30 m long core from DML (Dronning Maud Land, Antarctica) for the period 1931–1988. The two sites show differences in¹⁰Be content, the Antarctica site showing smaller variance and a lower average¹⁰Be annual flux. Similarly, the average accumulation rate (cm water equivalent year⁻¹) is higher in the Renland relative to DML. The variability in accumulation (precipitation) rates seems to explain part of the difference in¹⁰Be flux between the two polar sites. Cyclic fluctuations of¹⁰Be flux correlate with the 11-year sunspot number and cosmic ray intensity than with the aa index (perturbation of the geomagnetic activity by the solar wind). Our data corroborate¹⁰Be cyclic fluctuation pattern from the Dye 3 ice core and confirm a promising potential for correlation of global and local events.     

河流阶地样品中石英纯化和宇宙核素~(10)Be和~(26)Al分离方法研究

经历反复埋藏暴露演化过程的河流阶地样品,难以用常规方法将原生宇宙核素10Be、26Al有效分离。本文在前人实验方法基础上,使用人工挑选、磁选仪分选及酸洗方法,分离样品中碳酸盐、含铁矿物及大气生成的10Be,进一步优化了石英提纯实验流程。结果表明:长度为9 cm、内径为1 cm的阴离子交换树脂装置匹配4 mol/L氢氟酸淋滤液,可将B、Mg、Ca、Cr、Fe、Mn、Ni、Ti和Be、Al有效分离,Be、Al回收率分别可达95.7%、85.7%。阳离子交换树脂能有效分离Be、Al,两元素回收率均达到85%。获得10Be/9Be和26Al/27Al流程空白分别为2.19×10-15和1.63×10-15。优化后的实验方法显著提高了河流阶地样品中原生宇宙核素10Be、26Al的纯化效率,且10Be/9Be和26Al/27Al流程空白数值与国内外实验室具有可比性。采用本方法获得了成都平原冲积物10Be、26Al暴露年龄分别是76.36±9.51 ka和69.44±14.13 ka,为评价龙门山前缘隐伏断裂构造特征和活动性提供了年代学依据。     

210Pb activities in and fluxes to sediments of the Washington continental slope and shelf

Surface sediments of the Washington coast have ²¹⁰Pb activites which average 104 ± 48dpm/g for submarine canyon and slope regimes and 18 ± 12dpm/g for the continental shelf regime. ²¹⁰Pb sedimentary fluxes are also higher in canyons, averaging 18 ± 13dpm/cm² per yr, compared to 5.2 ± 3.1 dpm/cm² per yr for slope and 4.8 ± 1.8dpm/cm² per year for shelf regions. These ²¹⁰Pb activities and fluxes are 2–7 times greater than those reported for other coastal regions. Inputs from the atmosphere and the Columbia River are not sufficient to supply the ²¹⁰Pb, but advection of seawater containing dissolved ²¹⁰Pb produced in situ from ²²⁶Ra provides an input several times larger than the sedimentary fluxes. The sedimentary ²¹⁰Pb flux is limited by scavenging reactions rather than by supply of dissolved ²¹⁰Pb.Calculations of maximum biological uptake and fluxes of ²¹⁰Pb and ‘selective’ chemical leaching experiments all show that the primary scavenging processes are due to hydrous Mn and Fe oxides rather than biological phases. The pattern of higher ²¹⁰Pb depositional fluxes in canyons than in nearby open slope areas of comparable water depth is most reasonably explained by enhanced scavenging of dissolved ²¹⁰Pb near the sea floor, rather than by processes operating throughout the water column. Relatively rapid removal of dissolved ²¹⁰Pb from the near bottom nepheloid layer to slope and canyon sediments is shown by its mean residence time of less than two years in this layer.     

Uranium geochemistry on the Amazon shelf: Evidence for uranium release from bottom sediments

In Amazon-shelf waters, as salinity increases to 36.5 × 10⁻³, dissolved uranium activities increase to a maximum of 4.60 dpm 1⁻¹. This value is much higher than the open-ocean value (2.50 dpm 1⁻¹), indicating a source of dissolved uranium to shelf waters in addition to that supplied from open-ocean and riverine waters. Uranium activities are much lower for surface sediments in the Amazon-shelf seabed (mean: 0.69 ±.09 dpm g⁻¹) than for suspended sediments in the Amazon River (1.82 dpm g⁻¹). Data suggest that the loss of particulate uranium from riverine sediments (and the consequent input of dissolved uranium to shelf waters) is probably the result of uranium desorption from the ferric-oxyhydroxide coatings on sediment particles, and/or uranium release by mobilization of the ferric oxyhydroxides. The total flux (i.e., riverine flux plus desorbed-remobilized particulate flux) of dissolved ²³⁸U from the Amazon shelf (about 1.2 × 10¹⁵ dpm yr⁻¹) constitutes about 15% of uranium input to the world ocean, commensurate to the Amazon River's contribution to world river-water discharge (approximately 18%). Measurement of only the riverine flux of dissolved ²³⁸U underestimates, by a factor of about 5, the flux of dissolved²³⁸U from the Amazon shelf to the open ocean.     

南黄海、东海陆架及冲绳海槽北部 沉积物的10 Be和9 Be记录*

文章讨论了南黄海泥质区、东海陆架及冲绳海槽北部表层沉积物和柱状岩芯中¹⁰ Be及⁹ Be含量的水平和垂直分布,并与重金属Pb的分布进行了比较。表层沉积物中的¹⁰ Be,⁹ Be和Pb三者表现出完全不同的分布特征。¹⁰ Be的分布主要受黑潮及其支流黄海暖流所支配; ⁹ Be的分布受黄河陆源物质输入的影响,主要集中在南黄海泥质区; Pb则主要分布在长江口和琉球群岛附近,反映了人类活动的影响。冲绳海槽北部末次冰期和全新世时¹⁰ Be的沉积通量变化在整体上反映了¹⁰ Be大气生产率的变化,即地球磁场屏蔽效应的影响。03孔全新世时¹⁰ Be的沉积通量 (1.12×10⁹atoms/cm²ka)基本上等于¹⁰ Be的现代大气平均生产率,而在末次冰期时平均为4.06×10⁹atoms/cm²ka, 高于¹⁰ Be 的现代大气平均生产率3倍以上。在冲绳海槽由于黑潮的缘故,¹⁰ Be对气候的变化响应要比极地冰芯的¹⁰ Be变化响应灵敏的多,对气候变化信号起了放大的作用。冰期时冲绳海槽北部¹⁰ Be的沉积通量远远高于太平洋大洋海区,充分反映了黑潮的传送带作用和边缘海的聚焦沉积作用,并表明末次冰期时在千年尺度上黑潮仍流经冲绳海槽,且强度并未减弱。 ¹⁰ Be的通量在新仙女木时降到整个岩芯所跨时期的最低点,甚至低于¹⁰ Be的现代大气平均生产率,因此推测在新仙女木事件时,黑潮的变动特别大,有可能改向或断流。     

Records of cosmogenic radionuclides Be, Al and Cl in corals: First studies on coral erosion rates and potential of dating very old corals

We present results of measurements of cosmogenic ¹⁰Be, ²⁶Al and ³⁶Cl, and the indigenous (intrinsic) concentrations of the stable elements Be, Al and Cl in 120-200 kyr old corals from Barbados and Puerto Rico. The concentration levels of these radionuclides in the corals lie in the range 10⁴ to 10⁸ atoms/g. A comparison of the measured nuclide concentrations with those expected to be produced in the corals by nuclear interactions of energetic cosmic radiation shows that (i) the radionuclides ²⁶Al and ³⁶Cl are derived from in situ cosmic ray interactions in the corals after their formation, but that (ii) the radionuclide ¹⁰Be owes its provenance in the coralline lattice primarily due to incorporation of dissolved beryllium in seawater in the lattice structure of the corals.     

26Al-10Be systematics in deep-sea sediments

We report the development of a NaOH-leaching technique to extract the authigenic Al and Be in marine sediments, which should allow the sedimentary signals of cosmogenic ²⁶Al and ¹⁰Be to be more effectively studied as geochemical/geophysical tracers. The technique has been applied to the study of ²⁶Al and ¹⁰Be in opal-rich sediments from the North Pacific. The ²⁶Al/²⁷Al and ¹⁰Be/⁹Be ratios of ~3 × 10⁻¹⁴ and 1 × 10⁻⁷ leached from the sediments are higher than those in the total sediments by factors of 3–10 and 2–3, respectively. The authigenic ¹⁰Be/⁹Be ratios are similar to those in deep waters at the study site, pointing to the potential usefulness of the ratios in paleoceanographic studies. The fractions of total Be and Al in the sediment studied that are of authigenic origin average about 40 and 17%, respectively. Estimated ²⁶AL/²⁷A1 ratios in detrital sediments are ≤ 10⁻¹⁵, low enough to indicate that the source of ²⁶Al in the ocean mainly comes from atmospheric production. In the study area, the deposition flux of ²⁶Al is comparable to its atmospheric supply. However, the deposition flux of ¹⁰Be is about threefold higher than the atmospheric input, signifying lateral transport of ¹⁰Be from the open ocean to this area of relatively high particle flux. The ²⁶Al/¹⁰Be ratio, being insensitive to the oceanic influx of lithogenic particles, may serve as a valuable proxy for paleoproductivity. Both the authigenic and total-sediment ²⁶Al/²⁷Al and ¹⁰Be/ ⁹Be ratios decreased significantly at ~6 ka, which could reflect an enhanced input of windblown lithogenic particles to the North Pacific. While the enhanced dust input did not significantly alter the deep-water ⁹Be concentration, it contributed to the observed increase of authigenic ⁹Be flux to the sediment.