Challenges and opportunities in high-precision Be-10 measurements at CAMS

Rood, Dylan H.; Hall, Sarah R.; Guilderson, Thomas P.; Finkel, Robert C.; Brown, Thomas A.

doi:10.1016/j.nimb.2009.10.016

Cited by 77 publications

(49 citation statements)

References 5 publications

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“…The final Be fractions were precipitated at pH 8 as hydroxides, centrifuged, washed with 18.2 MΩ water, centrifuged, decanted, and dried. The dried material was ignited in a furnace to convert to Be oxide, mixed with Nb in a 1:1 molar ratio, and packed into stainless steel cathodes for isotopic analysis at LLNL by AMS (40).…”

Section: Methodsmentioning

confidence: 99%

Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain

Hurst

Rood

Ellis

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

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105

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Rising sea levels and increased storminess are expected to accelerate the erosion of soft-cliff coastlines, threatening coastal infrastructure and livelihoods. To develop predictive models of future coastal change we need fundamentally to know how rapidly coasts have been eroding in the past, and to understand the driving mechanisms of coastal change. Direct observations of cliff retreat rarely extend beyond 150 y, during which humans have significantly modified the coastal system. Cliff retreat rates are unknown in prior centuries and millennia. In this study, we derived retreat rates of chalk cliffs on the south coast of Great Britain over millennial time scales by coupling high-precision cosmogenic radionuclide geochronology and rigorous numerical modeling. Measured 10 Be concentrations on rocky coastal platforms were compared with simulations of coastal evolution using a Monte Carlo approach to determine the most likely history of cliff retreat. The 10 Be concentrations are consistent with retreat rates of chalk cliffs that were relatively slow (2-6 cm·y −1 ) until a few hundred years ago. Historical observations reveal that retreat rates have subsequently accelerated by an order of magnitude (22-32 cm·y −1 ). We suggest that acceleration is the result of thinning of cliff-front beaches, exacerbated by regional storminess and anthropogenic modification of the coast.geomorphology | coasts | cosmogenic radionuclides | erosion | cliffs R ocky coasts are "erosional environments formed as a result of the landward retreat of bedrock at the shoreline" (1). They leave scant evidence of any previous state, making it difficult to interpret their history. Cliff retreat is driven by a combination of wave-driven cliff-base erosion, subaerial weathering, and mass wasting processes, whose efficiencies are dependent on lithology and climate. Sediment generated by mass wasting processes such as abrasion, plucking, landslides, and rockfalls tends to be reworked and transported away by waves and currents, particularly for softer rock types.Cliff erosion due to mass wasting threatens livelihoods and both public and private clifftop infrastructure and development; quantitative estimates of the rate of cliff retreat are necessary to assess the associated risk. Rising sea levels and increased storminess may lead to accelerated coastal erosion rates in the future, potentially increasing hazard exposure (2-5). To accurately assess coastal hazards in the face of future climate and land-use changes, it is necessary to understand the dynamics of cliff erosion over length and time scales relevant to the processes that drive change. To establish the context for modern change, we must quantify the natural variability and the long-term behavior of cliff retreat. Historical records are too short to allow us to do this: they typically span no longer than ∼150 y (6, 7), which can be less than the characteristic return period of significant coastal failures (8), and they coincide with the period over which humans have significantly modified th...

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Section: Methodsmentioning

confidence: 99%

Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain

Hurst

Rood

Ellis

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

105

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“…accessory elements that could interfere with measurement; Hunt et al (2008), 15 Merchel et al (2008)), cathode geometry (e.g. depth to the sputtering surface and shape of the 16 surface; Hunt et al (2007), Rood et al (2010), Shanks and Freeman (2015)), total mass, and 17 performance during measurement (the ion source yield, or "beam current", which we measure as 18 the 9 Be 3+ current but which can alternatively be measured as the 9 Be 16 O -current). The similarity 19 of beam currents between standards and samples across multiple measurement cycles is 20 particularly important (Rood et al, 2014).…”

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confidence: 99%

“…The total number 2 of attainable counts is a product of the 10 Be concentration of the material being analyzed, the 3 total mass of the sample, and the AMS total system efficiency (including ionization, 4 transmission, transport, and detection efficiencies), all of which dictate the number of 10 Be 5 counts that can be obtained before the sample material is ablated away during sputtering (Rood 6 et al, 2013;Rood et al, 2010). For higher 10 Be/ 9 Be samples, precision is primarily controlled by 7 the reproducibility of ratio measurements, which is often poorer than that predicted by counting 8 statistics alone (Rood et al, 2013).…”

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confidence: 99%

“…7). Constant 9 Be mass 6 results in a uniform depth to the material surface and a consistent mixing ratio with Nb, which 7 optimizes the ionization yield, the AMS sputtering efficiency, and the measurement 8 reproducibility (Rood et al, 2010) for sputter sources using front-loaded cathodes.…”

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confidence: 99%

“…Improved AMS techniques now consistently 11 produce machine blanks with 10 Be/ 9 Be ratios well below 10 -15 (Rood et al, 2010), placing 12 greater demands on processing laboratories to both minimize sample cross-talk and lower the 13 amount of the interfering isobar, 10 B. (Licciardi et al, 2009), those that have been subjected to rapid erosion (Portenga et al, 2015), or 22 those that have been buried for long durations (Erlanger et al, 2012;Gibbon et al, 2014).…”

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An approach for optimizing in situ cosmogenic 10Be sample preparation

Corbett

Bierman

Rood

2016

Quaternary Geochronology

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147

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Optimizing sample preparation for the isotopic measurement of 10Be extracted from quartz mineral separates has a direct positive effect on the efficiency of sample production and the accuracy and precision of isotopic analysis. Here, we demonstrate the value of tracing Be throughout the extraction process (both after dissolution and after processing), producing pure Be (by optimizing column chromatography methods and quantifying quartz mineral separate purity), and minimizing backgrounds (through reducing both laboratory process blanks and 10B isobaric interference). These optimization strategies increase the amount of 10Be available for analysis during accelerator mass spectrometry (AMS), while simultaneously decreasing interference and contamination, and ensuring that sample performance matches standard performance during analysis. After optimization of our laboratory's extraction methodology, 9Be3+ beam currents, a metric for sample purity and Be yield through the extraction process, matched the 9Be3+ beam currents of AMS standards analyzed at the same time considering nearly 800 samples. Optimization of laboratory procedures leads to purer samples that perform better, more consistently, and more similarly to standards during AMS analysis, allowing for improved dating and quantification of Earth surface processes. February 2, 2016To the Editor:After performing the revisions suggested by two reviewers, we are resubmitting our manuscript, An Approach for Optimizing In Situ Cosmogenic 10 Be Sample Preparation, for publication in Quaternary Geochronology.We appreciated the comments from both reviewers and found that their suggestions improved the manuscript. In our revisions, we focused particular attention toward broadening our discussion of measurement accuracy, clarifying the impact of Ti impurities in samples, providing more information about beam current normalization, and benchmarking our methods against those previously used in our laboratory. As a group, we considered each suggestion and addressed it in the way that we thought most benefited the manuscript. In the following pages, you will find a list of the reviewers' suggestions and details about how we incorporated those suggestions.We are optimistic that our revisions have addressed the reviewers' concerns and that the manuscript has grown in both clarity and applicability. Thank you in advance for considering our revised draft. The paper of Corbett et al. describes in detail the chemical separation procedure for Be-10 in quartz samples applied at the University of Vermont. They show how their column chemistry was optimized for the purification of Be and they impressively demonstrate, on the statistical base of about 800 samples, that their lab constantly produces high quality Be-10 samples. This paper is important not only for newcomers in the field, e.g. who want to set up their own lab, but also for the existing cosmo labs because it demonstrates the importance of quality control e.g. to avoid systematic errors in the final Be-10 ages. D...

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Dating the incision of the Yangtze River gorge at the First Bend using three‐nuclide burial ages

McPhillips

Hoke

Liu‐Zeng

et al. 2016

Geophysical Research Letters

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Incision of the Yangtze River gorge is widely interpreted as evidence for lower crustal flow beneath the southeast margin of the Tibetan Plateau. Previous work focused on the onset of incision, but the duration of incision remains unknown. Here we present cosmogenic nuclide burial ages of sediments collected from caves on the walls of the gorge that show the gorge was incised ~1 km sometime between 18 and 9 Ma. Thereafter, incision slowed substantially. We resolve middle Miocene burial ages by using three nuclides and accounting for in situ muogenic production. This approach explains the absolute concentrations of 10Be, 26Al, and 21Ne, as well as 26Al/10Be and 21Ne/10Be ratios. A declining incision rate challenges existing geodynamic interpretations by suggesting that either (1) surface uplift has ceased immediately south of the plateau margin or (2) gorge incision is not a useful proxy for the timing of surface uplift.

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Challenges and opportunities in high-precision Be-10 measurements at CAMS

Cited by 77 publications

References 5 publications

Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain

Recent acceleration in coastal cliff retreat rates on the south coast of Great Britain

An approach for optimizing in situ cosmogenic 10Be sample preparation

Dating the incision of the Yangtze River gorge at the First Bend using three‐nuclide burial ages

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