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  • 1
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    The Nuts and Bolts of Cosmogenic Nuclide Production (2014)
    Mineralogical Society of America
    In: Elements
    Details
    Publication Date: 2014-10-17
    Description: Over the last 60 years, our understanding of how cosmic rays produce cosmogenic nuclides has grown from basic physical considerations. We introduce the different types of cosmic ray particles and how their flux varies with altitude, latitude, and time. Accurately describing these variations remains a challenge for some regions when calculating production rates. We describe current and emerging computational methods for calculating production rates that address this challenge. Continuing developments in our understanding of modern and prehistoric cosmic ray fluxes and energy spectra in Earth's atmosphere and at its surface are bound to contribute in the future to more robust applications.
    Print ISSN: 1811-5209
    Electronic ISSN: 1811-5217
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 2
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    A cosmic trip: 25 years of cosmogenic nuclides in geology (2013)
    Geological Society of America (GSA)
    Details
    Publication Date: 2013-08-24
    Description: Terrestrial cosmogenic nuclides, produced by secondary cosmic-ray interactions in the atmosphere and in situ within minerals in the shallow lithosphere, are widely used to date surface exposure of rocks and sediments, to estimate erosion and weathering rates, and to date sediment deposition or burial. Their use has transformed geomorphology and Quaternary geology, for the first time allowing landforms to be dated and denudation rates to be measured over soil-forming time scales. The application of cosmogenic nuclides to geology began soon after the invention of accelerator mass spectrometry (AMS) in 1977 and increased dramatically with the measurement of in situ–produced nuclides in mineral grains near Earth’s surface in the 1980s. The past 25 yr have witnessed the development of cosmogenic nuclides from their initial detection to their prevalence today as a standard geochronological and geochemical tool. This review covers the major developments of the past 25 yr by comparing the state of the field in 1988 with that of today, and by identifying key advances in that period that moved the field forward. We emphasize the most commonly used in situ–produced nuclides measured by AMS for geological applications, but we also discuss other nuclides where their applications overlap. Our review covers AMS instrumentation, cosmogenic nuclide production rates, the methods of surface exposure dating, measurement of erosion and weathering, and burial dating, and meteoric 10 Be. —In memoriam: Devendra Lal (1929–2012), whose vision inspired the field.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 3
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    Cold-based Laurentide ice covered New England's highest summits during the Last Glacial Maximum (2015)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2015-11-19
    Description: To better understand glacial history and process in New England (northeastern United States), a mountainous area overrun by the Laurentide Ice Sheet, we measured three cosmogenic nuclides in nine upland samples. The concentrations of 10 Be and 26 Al in some samples collected near the summits of Katahdin (Maine) and Mount Washington and Little Haystack Mountain (New Hampshire) are 2–10 times higher than expected for a single exposure period, considering field evidence indicating that continental ice-covered all New England peaks during the Last Glacial Maximum. In-situ 14 C exposure ages from the summits are much younger, suggesting that high-elevation sampling sites were ice-covered before and during the Last Glacial Maximum. Field and isotopic data are consistent with New England summits being covered in part by cold-based continental ice that did not erode much rock. The contrast in erosion rates between stable summits and deeply eroded valleys likely contributes to the development and maintenance of northern Appalachian topography.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 4
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    Preliminary Results for the Extraction and Measurement of Cosmogenic in Situ 14C from Quartz (2004)
    Cambridge University Press
    Details
    Publication Date: 2004-01-01
    Description: Radiocarbon is produced within minerals at the earth's surface (in situ production) by a number of spallation reactions. Its relatively short half-life of 5730 yr provides us with a unique cosmogenic nuclide tool for the measurement of rapid erosion rates (〉10−3 cm yr−1) and events occurring over the past 25 kyr. At SUERC, we have designed and built a vacuum system to extract 14C from quartz which is based on a system developed at the University of Arizona. This system uses resistance heating of samples to a temperature of approximately 1100° in the presence of lithium metaborate (LiBO2) to dissolve the quartz and liberate any carbon present. During extraction, the carbon is oxidized to CO2 in an O2 atmosphere so that it may be collected cryogenically. The CO2 is subsequently purified and converted to graphite for accelerator mass spectrometry (AMS) measurement. One of the biggest problems in measuring in situ 14C is establishing a low and reproducible system blank and efficient extraction of the in situ 14C component. Here, we present initial data for 14C-free CO2, derived from geological carbonate and added to the vacuum system to determine the system blank. Shielded quartz samples (which should be 14C free) and a surface quartz sample routinely analyzed at the University of Arizona were also analyzed at SUERC, and the data compared with values derived from the University of Arizona system.
    Print ISSN: 0033-8222
    Electronic ISSN: 1945-5755
    Topics: Archaeology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Cambridge University Press
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  • 5
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    The Rhone Glacier was smaller than today for most of the Holocene (2011)
    Geological Society of America
    Details
    Publication Date: 2011-05-24
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America
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  • 6
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    The Nuts and Bolts of Cosmogenic Nuclide Production (2014)
    Mineralogical Society of America
    Details
    Publication Date: 2014-10-01
    Print ISSN: 1811-5209
    Electronic ISSN: 1811-5217
    Topics: Geosciences
    Published by Mineralogical Society of America
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  • 7
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    A cosmic trip: 25 years of cosmogenic nuclides in geology (2013)
    Geological Society of America
    Details
    Publication Date: 2013-07-23
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
    Published by Geological Society of America
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  • 8
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    Evaluating the timing of former glacier expansions in the Tian Shan: A key step towards robust spatial correlations (2016)
    Elsevier
    Details
    Publication Date: 2023-08-01
    Description: The timing of past glaciation across the Tian Shan provides a proxy for past climate change in this critical area. Correlating glacial stages across the region is difficult but cosmogenic exposure ages have considerable potential. A drawback is the large observed scatter in 10Be surface exposure data. To quantify the robustness of the dating, we compile, recalculate, and perform statistical analyses on sets of 10Be surface exposure ages from 25 moraines, consisting of 114 new and previously published ages. We assess boulder age scatter by dividing boulder groups into quality classes and rejecting boulder groups of poor quality. This allows us to distinguish and correlate robustly dated glacier limits, resulting in a more conservative chronology than advanced in previous publications. Our analysis shows that only one regional glacial stage can be reliably correlated across the Tian Shan, with glacier expansions occurring between 15 and 28 ka during marine oxygen isotope stage (MIS) 2. However, there are examples of older more extensive indicators of glacial stages between MIS 3 and MIS 6. Paleoglacier extent during MIS 2 was mainly restricted to valley glaciation. Local deviations occur: in the central Kyrgyz Tian Shan paleoglaciers were more extensive and we propose that the topographic context explains this pattern. Correlation between glacial stages prior to late MIS 2 is less reliable, because of the low number of samples and/or the poor resolution of the dating. With the current resolution and spatial coverage of robustly-dated glacier limits we advise that paleoclimatic implications for the Tian Shan glacial chronology beyond MIS 2 are speculative and that continued work toward robust glacial chronologies is needed to resolve questions regarding drivers of past glaciation in the Tian Shan and Central Asia.
    Type: Article , PeerReviewed
    Format: text
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  • 9
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    Combining modelling and field-based reconstructions of changing vertical ice extent across the Dronning Maud Land sector of the East Antarctic Ice Sheet. (2017)
    International Glaciological Socienty
    In:  EPIC3The Cryosphere in a Changing Climate, 2017-02-20-2017-02-17Wellington, New Zealand, International Glaciological Socienty
    Details
    Publication Date: 2016-10-31
    Description: Numerical ice sheet models constrained by theory and refined by comparisons with observational data are a central component of work to address the interactions between the cryosphere and changing climate, at a wide range of scales. Although there continue to be significant advances in modelling, major challenges still exist, in particular in terms of downscaling global climate model output to estimate regional and local climate patterns that are critical controls for the dynamics of glaciers and ice sheets. Ice sheet models are tested and refined by comparing model predictions of past ice geometries with field-based reconstructions from geological, geomorphological, and ice core data. However, on the East Antarctic Ice sheet, there is a critical gap in the empirical data required to reconstruct changes in ice sheet geometry in the Dronning Maud Land (DML) region. In addition, there is poor control on the regional climate history of the ice sheet margin, because ice core locations, where detailed reconstructions of climate history exist, are located on high inland domes. This leaves numerical models of regional glaciation history in this near-coastal area largely unconstrained. MAGIC-DML is an ongoing Swedish-US-Norwegian-German-UK collaboration with a focus on improving ice sheet models by combining advances in modeling with filling critical data gaps that exist in our knowledge of the timing and pattern of ice surface changes on the western Dronning Maud Land margin. A combination of geomorphological mapping using remote sensing data, field investigations, cosmogenic nuclide surface exposure dating, and numerical ice-sheet modelling are being used in an iterative manner to produce a comprehensive reconstruction of the glacial history of western Dronning Maud Land. We present an overview of the project, as well as results of the initial mapping and modelling that has been used to identify high potential sites for field sampling in 2016/17 and 2017/18.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
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