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Jane K. Willenbring - One of the best experts on this subject based on the ideXlab platform.
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cosmogenic Nuclides dates and rates of earth surface change
Elements, 2014Co-Authors: Friedhelm Von Blanckenburg, Jane K. WillenbringAbstract:Cosmogenic Nuclides are very rare isotopes that are produced when particles generated in supernovas in our galaxy hit the atmosphere and then the Earth's surface. When the rocks and soils in this thin, ever-changing surface layer are bombarded by such cosmic radiation, the nuclide clock begins to tick, thus providing dates and rates of Earth-surface processes. The measurement of cosmogenic Nuclides tells us when earthquakes created topography at faults, when changing climate led to the growth of glaciers, how fast rivers grind mountains down, and how fast rocks weather to soil and withdraw atmospheric CO2. The use of cosmogenic Nuclides is currently revolutionizing our understanding of Earth-surface processes and has significant implications for many Earth science disciplines. * Accelerator mass spectrometer (AMS) : Detection system that first accelerates ions to MeV-level energy and then separates them by mass. The technique measures the extremely small number of rare cosmogenic Nuclides relative to a stable reference nuclide present in known amounts. Cosmic ray attenuation mean free path and attenuation depth scale : The depth, Λ, at which the intensity of cosmic rays is reduced by a factor of 1/e by interaction with material (units: g cm-2). 150 g cm-2 corresponds to an attenuation depth, z* = Λ/ρ, of 600 mm in silicate rock whose density (ρ) is 2.6 g cm-3. Cosmic rays, primary : High-energy (0.1 to 1020 GeV) galactic particles that are composed primarily of protons (83%), α-particles (13%), and heavier nuclei (1%) Cosmic rays, secondary : Nucleons (neutrons, protons) and muons of 0.1 to 500 MeV energy that are produced by interactions between primary cosmic rays and molecules in the Earth's atmosphere. Secondary cosmic rays form a cascade of particles whose flux decreases with increasing atmospheric pressure. Cosmogenic Nuclides, in situ : Nuclides that are produced by interaction of secondary cosmic rays with solids (spallation, negative muon capture) at the Earth's surface. Other acronyms frequently used are TCN (terrestrial cosmogenic Nuclides) and CRN (cosmogenic radioactive Nuclides). Cosmogenic Nuclides, meteoric : Cosmogenic Nuclides that are produced in the atmosphere, the flux of some of which (e.g. meteoric 10Be) is ca 103 times greater than the production rate of in situ cosmogenic Nuclides. Cosmogenic Nuclides, radioactive : Cosmogenic Nuclides that decay, and are therefore usually absent in eroding Earth materials prior to exposure (e.g. 10Be, 14C, 26Al, 36Cl) Cosmogenic Nuclides, stable : Cosmogenic Nuclides that are stable, and therefore might be present in eroding surface material from previous exposure episodes. These cosmogenic Nuclides are the rare gases (e.g. 3He, 21Ne, 22Ne). Denudation rate : The total rate of removal of mass from the Earth's surface. It is the combined effect of physical (erosion rate) and chemical (weathering rate) processes. Electron volt (eV) : Energy of the charge of a single electron moved across an electric potential difference of one volt. MeV = mega–electron volt, one million eV. Erosion rate : The rate of removal of material from the Earth's surface by mechanical processes Fault : A planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of Earth movement Geomagnetic latitude : Analogous to geographic latitude, except that bearing is with respect to the magnetic pole, which changes through time, as opposed to the geographic pole Moraine : Debris that forms at the margins of a glacier Muon : A low-mass particle from cosmic radiation that is able to penetrate deeper into the Earth's surface than neutrons due to the low probability that it will interact with target atoms Nucleons : the particles that make up atomic nuclei: neutrons and protons Production rate : The rate at which in situ cosmogenic Nuclides are produced in a given mass of chemically defined target material in a given time [units: atoms g-1 (mineral) y-1]. For meteoric cosmogenic Nuclides a flux is used [units: atoms cm-2 y-1]. Regolith : The mantle of weathered material overlying bedrock Soil : A mixture of regolith and weathered material from below with organic matter, dust, and chemical precipitates from above Spallation : The ejection of nucleons due to impact causing production of a different nuclide without fission of the product Weathering rate : Partial dissolution of bedrock by surficial fluids, and removal of soluble ions in solution
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Cosmogenic Nuclides: Dates and rates of earth-surface change
Elements, 2014Co-Authors: Friedhelm Von Blanckenburg, Jane K. WillenbringAbstract:Cosmogenic Nuclides are very rare isotopes that are produced when particles generated in supernovas in our galaxy hit the atmosphere and then the Earth's surface. When the rocks and soils in this thin, ever-changing surface layer are bombarded by such cosmic radiation, the nuclide clock begins to tick, thus providing dates and rates of Earth-surface processes. The measurement of cosmogenic Nuclides tells us when earthquakes created topography at faults, when changing climate led to the growth of glaciers, how fast rivers grind mountains down, and how fast rocks weather to soil and withdraw atmospheric CO2. The use of cosmogenic Nuclides is currently revolutionizing our understanding of Earth-surface processes and has significant implications for many Earth science disciplines.
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a cosmic trip 25 years of cosmogenic Nuclides in geology
Geological Society of America Bulletin, 2013Co-Authors: Darryl E Granger, Nathaniel A Lifton, Jane K. WillenbringAbstract: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.
Keran Obrien - One of the best experts on this subject based on the ideXlab platform.
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physics based modeling of cosmogenic Nuclides part i radiation transport methods and new insights
Quaternary Geochronology, 2015Co-Authors: David C Argento, John O Stone, R C Reedy, Keran ObrienAbstract:Abstract We present a comprehensive, nuclear-physics-based cosmogenic nuclide production rate model combining radiation transport modeling with excitation functions for commonly measured Nuclides. This model allows investigation of factors influencing nuclide production, such as the energy spectrum and angular distribution of the incident radiation that cannot be easily isolated in calibration measurements on natural samples. We present neutron and proton fluxes over a range of atmospheric depths and cut-off rigidities. Calculated production rates for 3He, 10Be, 14C, 21Ne, 26Al, and 36Cl based on these fluxes are presented. The model predicts that production rates for these Nuclides diverge from one another with altitude, hence that production ratios depend on altitude. Compared to existing scaling schemes, the model predicts a larger difference between sea-level production rates at low and high latitude.
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physics based modeling of cosmogenic Nuclides part ii key aspects of in situ cosmogenic nuclide production
Quaternary Geochronology, 2015Co-Authors: David C Argento, John O Stone, R C Reedy, Keran ObrienAbstract:Abstract Characteristics of the spallogenic component of nuclide production are investigated through the use of a physics-based model. Calculated production rates for commonly used Nuclides indicate differences in scaling up to 15% at very high altitude. Angular distribution of nuclide forming particles suggests the current method of shielding correction, which is neither altitude nor latitude dependent, can be improved on. Subsurface production profiles suggest that erosion corrections should be performed with non-constant attenuation lengths. Results are parameterized for easy application.
Friedhelm Von Blanckenburg - One of the best experts on this subject based on the ideXlab platform.
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cosmogenic Nuclides dates and rates of earth surface change
Elements, 2014Co-Authors: Friedhelm Von Blanckenburg, Jane K. WillenbringAbstract:Cosmogenic Nuclides are very rare isotopes that are produced when particles generated in supernovas in our galaxy hit the atmosphere and then the Earth's surface. When the rocks and soils in this thin, ever-changing surface layer are bombarded by such cosmic radiation, the nuclide clock begins to tick, thus providing dates and rates of Earth-surface processes. The measurement of cosmogenic Nuclides tells us when earthquakes created topography at faults, when changing climate led to the growth of glaciers, how fast rivers grind mountains down, and how fast rocks weather to soil and withdraw atmospheric CO2. The use of cosmogenic Nuclides is currently revolutionizing our understanding of Earth-surface processes and has significant implications for many Earth science disciplines. * Accelerator mass spectrometer (AMS) : Detection system that first accelerates ions to MeV-level energy and then separates them by mass. The technique measures the extremely small number of rare cosmogenic Nuclides relative to a stable reference nuclide present in known amounts. Cosmic ray attenuation mean free path and attenuation depth scale : The depth, Λ, at which the intensity of cosmic rays is reduced by a factor of 1/e by interaction with material (units: g cm-2). 150 g cm-2 corresponds to an attenuation depth, z* = Λ/ρ, of 600 mm in silicate rock whose density (ρ) is 2.6 g cm-3. Cosmic rays, primary : High-energy (0.1 to 1020 GeV) galactic particles that are composed primarily of protons (83%), α-particles (13%), and heavier nuclei (1%) Cosmic rays, secondary : Nucleons (neutrons, protons) and muons of 0.1 to 500 MeV energy that are produced by interactions between primary cosmic rays and molecules in the Earth's atmosphere. Secondary cosmic rays form a cascade of particles whose flux decreases with increasing atmospheric pressure. Cosmogenic Nuclides, in situ : Nuclides that are produced by interaction of secondary cosmic rays with solids (spallation, negative muon capture) at the Earth's surface. Other acronyms frequently used are TCN (terrestrial cosmogenic Nuclides) and CRN (cosmogenic radioactive Nuclides). Cosmogenic Nuclides, meteoric : Cosmogenic Nuclides that are produced in the atmosphere, the flux of some of which (e.g. meteoric 10Be) is ca 103 times greater than the production rate of in situ cosmogenic Nuclides. Cosmogenic Nuclides, radioactive : Cosmogenic Nuclides that decay, and are therefore usually absent in eroding Earth materials prior to exposure (e.g. 10Be, 14C, 26Al, 36Cl) Cosmogenic Nuclides, stable : Cosmogenic Nuclides that are stable, and therefore might be present in eroding surface material from previous exposure episodes. These cosmogenic Nuclides are the rare gases (e.g. 3He, 21Ne, 22Ne). Denudation rate : The total rate of removal of mass from the Earth's surface. It is the combined effect of physical (erosion rate) and chemical (weathering rate) processes. Electron volt (eV) : Energy of the charge of a single electron moved across an electric potential difference of one volt. MeV = mega–electron volt, one million eV. Erosion rate : The rate of removal of material from the Earth's surface by mechanical processes Fault : A planar fracture or discontinuity in a volume of rock, across which there has been significant displacement as a result of Earth movement Geomagnetic latitude : Analogous to geographic latitude, except that bearing is with respect to the magnetic pole, which changes through time, as opposed to the geographic pole Moraine : Debris that forms at the margins of a glacier Muon : A low-mass particle from cosmic radiation that is able to penetrate deeper into the Earth's surface than neutrons due to the low probability that it will interact with target atoms Nucleons : the particles that make up atomic nuclei: neutrons and protons Production rate : The rate at which in situ cosmogenic Nuclides are produced in a given mass of chemically defined target material in a given time [units: atoms g-1 (mineral) y-1]. For meteoric cosmogenic Nuclides a flux is used [units: atoms cm-2 y-1]. Regolith : The mantle of weathered material overlying bedrock Soil : A mixture of regolith and weathered material from below with organic matter, dust, and chemical precipitates from above Spallation : The ejection of nucleons due to impact causing production of a different nuclide without fission of the product Weathering rate : Partial dissolution of bedrock by surficial fluids, and removal of soluble ions in solution
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a 30 000 yr record of erosion rates from cosmogenic 10be in middle european river terraces
Earth and Planetary Science Letters, 2002Co-Authors: Mirjam Schaller, L Tebbens, Friedhelm Von Blanckenburg, Niels Hovius, A. Veldkamp, Peter W KubikAbstract:Abstract Cosmogenic 10 Be in river-borne quartz sand records a time-integrated erosion rate representative of an entire drainage basin. When sequestered in a terrace of known age, paleo-erosion rates may be recovered from the nuclide content of the terrace material. Paleo-erosion rates between 30 and 80 mm/kyr are determined from terrace sediments 200 to 30 000 yr in age of the Allier and Dore Rivers, France, and the Meuse (Maas) River, the Netherlands. Erosion rates determined from cosmogenic Nuclides on terraces from the Allier River are consistent with rates derived from the sedimentary fill of a lake in the Allier catchment. A strong decrease in cosmogenic nuclide-derived erosion rates from terraces of the Meuse River with Late Pleistocene to Holocene age is observed. The paleo-erosion signal from cosmogenic Nuclides records projection of the elevated Late Pleistocene erosion rate into the time-integrated rates derived from Middle European rivers.
David C Argento - One of the best experts on this subject based on the ideXlab platform.
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physics based modeling of cosmogenic Nuclides part i radiation transport methods and new insights
Quaternary Geochronology, 2015Co-Authors: David C Argento, John O Stone, R C Reedy, Keran ObrienAbstract:Abstract We present a comprehensive, nuclear-physics-based cosmogenic nuclide production rate model combining radiation transport modeling with excitation functions for commonly measured Nuclides. This model allows investigation of factors influencing nuclide production, such as the energy spectrum and angular distribution of the incident radiation that cannot be easily isolated in calibration measurements on natural samples. We present neutron and proton fluxes over a range of atmospheric depths and cut-off rigidities. Calculated production rates for 3He, 10Be, 14C, 21Ne, 26Al, and 36Cl based on these fluxes are presented. The model predicts that production rates for these Nuclides diverge from one another with altitude, hence that production ratios depend on altitude. Compared to existing scaling schemes, the model predicts a larger difference between sea-level production rates at low and high latitude.
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physics based modeling of cosmogenic Nuclides part ii key aspects of in situ cosmogenic nuclide production
Quaternary Geochronology, 2015Co-Authors: David C Argento, John O Stone, R C Reedy, Keran ObrienAbstract:Abstract Characteristics of the spallogenic component of nuclide production are investigated through the use of a physics-based model. Calculated production rates for commonly used Nuclides indicate differences in scaling up to 15% at very high altitude. Angular distribution of nuclide forming particles suggests the current method of shielding correction, which is neither altitude nor latitude dependent, can be improved on. Subsurface production profiles suggest that erosion corrections should be performed with non-constant attenuation lengths. Results are parameterized for easy application.
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Physics-based modeling of cosmogenic Nuclides part II – Key aspects of in-situ cosmogenic nuclide production
Quaternary Geochronology, 2015Co-Authors: David C Argento, Robert C. Reedy, John O Stone, K. O'brienAbstract:Abstract Characteristics of the spallogenic component of nuclide production are investigated through the use of a physics-based model. Calculated production rates for commonly used Nuclides indicate differences in scaling up to 15% at very high altitude. Angular distribution of nuclide forming particles suggests the current method of shielding correction, which is neither altitude nor latitude dependent, can be improved on. Subsurface production profiles suggest that erosion corrections should be performed with non-constant attenuation lengths. Results are parameterized for easy application.
Devendra Lal - One of the best experts on this subject based on the ideXlab platform.
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Cosmogenic nuclide production rate systematics in terrestrial materials: Present knowledge, needs and future actions for improvement
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2000Co-Authors: Devendra LalAbstract:The growing applications of cosmogenic Nuclides produced in the Earth's atmosphere, and in situ in a variety of terrestrial materials, as tracers in a wide ranging Earth science problems, has put a greater demand on accurate determination of the nuclide production rates in a variety of targets exposed in different settings on the Earth in the troposphere. The present state of our knowledge of cosmogenic production rates is reviewed briefly, in conjunction with the phenomenological and theoretical framework for: (i) the cosmic ray flux incident in the near Earth environment, (ii) the nucleonic cascade set off in the Earth's atmosphere by the primary cosmic radiation, and (iii) the rate for production of Nuclides in terrestrial materials, in widely different settings. These considerations set the stage for the diverse questions, which must be taken into account for determining the source functions of isotopic changes in terrestrial materials. We discuss the different approaches which have been adopted earlier to obtain the source strengths of nuclear interacting particles of the cosmic radiation, and direct measurements of nuclide production rates made by exposing targets to cosmic radiation at sea level and at mountain altitudes. We show that rapid progress in determining nuclide source functions with sufficient information on temporal variability is indeed expected in the near future as a result of: (i) dramatic improvements in the past 2-3 decades in our understanding of the character of propagation of cosmic radiation within the heliosphere, (ii) experiments now being conducted by a few groups to determine the source strengths of cosmic ray slow neutrons, and nuclide production rates in cosmic ray exposed targets, and finally (iii) the emergence of better nuclear codes which deal with the development of nucleonic cascades in the Earth's atmosphere. © 2000 Elsevier Science B.V. All rights reserved.
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Cosmic ray labeling of erosion surfaces: in situ nuclide production rates and erosion models
Earth and Planetary Science Letters, 1991Co-Authors: Devendra LalAbstract:A number of in situ cosmogenic radioNuclides and stable Nuclides have been measured in natural exposed rock surfaces with a view to study their in situ production and rock erosion rates [1]. The in situ radioNuclides can be used for a high-resolution tomography of the erosional history of an exposed surface; two stable Nuclides (3He, 21Ne) and five radioNuclides (10Be, 26Al, 36Cl, 14C, 39Ar) having half-lives in the range of ∼ 300-1.5 × 106 yr half-life are measurable in many rock types. A prerequisite for the application of the in situ Nuclides for the study of erosional histories of surfaces is a knowledge of their production rates under different irradiation conditions; altitude, latitude, irradiation geometry and shielding. Relative nuclide production rates can be determined fairly accurately using the extensive available data on cosmic ray neutrons [2]. Absolute nuclide production rates cannot generally be predicted with any accuracy because of lack of data on excitation functions of Nuclides unless some normalization is possible, as was done in the case of several cosmic ray produced isotopes in the atmosphere [3]. Based on a recent natural calibration experiment in which erosion free surfaces exposed to cosmic radiation for ∼ 11,000 yrs were sampled, the absolute production rates of 10Be and 26Al in quartz have been accurately estimated for mountain altitudes in Sierra Nevada [4]. The absolute production rates of 10Be and 26Al in quartz can therefore be estimated fairly accurately for any given latitude and altitude. Some measurements of 14C in rocks of low erosion rate [5] similarly allow an estimate of its production rate. Attempts made to measure the in situ production rates of 3He in rocks have not yet led to a convergent production rate. In view of the importance of knowing the production rates of isotopes of He, Ne and Ar, I present here theoretical estimates of their production rates based on available cross-section data. I discuss the information that can be extracted from the study of the in situ Nuclides in rocks. Useful parameters characterizing the exposure history of a rock surface are: (1) the effective surface exposure age; and (2) the time-averaged erosion rate. The implications of these parameters for single and multiple nuclide studies are discussed in terms of the erosion models considered. © 1991.
