DOCSLIB.ORG

Interpretation of Cosmogenic Nuclides in Meteorites on the Basis of Accelerator Experiments and Physical Model Calculations

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Interpretation of Cosmogenic Nuclides in Meteorites on the Basis of Accelerator Experiments and Physical Model Calculations Interpretation of cosmogenic nuclides in meteorites on the basis of accelerator experiments and physical model calculations R MICHEL and S NEUMANN Center for Radiation Protection and Radioecology, University Hannover, Am Kleinen Felde 30, D-30167 Hannover, Germany e-mail: [email protected], uni-hannover.de Cosmogenic nuclides in extraterrestrial matter provide a wealth of information on the exposure and collision histories of small objects in space and on the history of the solar and galactic cosmic radiation. The interpretation of the observed abundances of cosmogenic nuclides requires detailed and accurate knowledge of their production rates. Accelerator experiments provide a quantitative basis and the ground truth for modeling cosmogenic nuclide production by measurements of the relevant cross sections and by realistic simulations of the interaction of galactic protons with meteoroids under completely controlled conditions, respectively. We ' review the establishment of physical model calculations of cosmogenic nuclide production in extraterrestrial matter on the basis of such accelerator experiments and exemplify this approach by presenting new experimental and theoretical results for the cosmogenic nuclide aaTi. The model calculations describe all aspects of cosmogenic nuclide production and allow the determination of long-term solar and galactic cosmic ray spectra and a consistent interpretation of cosmogenic nuclides in extraterrestrial matter. 1. Introduction energies are a few GeV/n. GCR spectra are modulated by interaction of GCR particles with the solar mag- In the solar system, one observes two types of natural netic field and thus depend on the solar activity. medium- and high-energy corpuscular radiation, the Typical SCR and GCR proton spectra at 1 A.U. are solar cosmic radiation (SCR) and the galactic cosmic shown in figure 1. For both, SCR and GCR spectra, radiation (GCR). SCR particles are emitted during suitable mathematical parameterizations exist. energetic solar events from the sun and consist on the For SCR particles, it is convenient to describe the average of 98% protons and 2% a-particles (Goswami differential flux density OJ/OR as function of the rigi- et al 1988). Their spectral distributions and intensities dity R. R is the relativistic momentum of the particle vary from event to event, typical energies going up to over its charge. This means for SCR protons a few hundred MeV/n. GCR particles come from out- OJ,,scR side the solar system. They are injected into the inter- OR - J0,sCR(47r, Ep > 10 MeV)-exp(-R/R0) stellar medium by supernova explosions and are (1) accelerated stochastically by complicated processes (Bryant et al 1992) and occasionally attain extreme with a characteristic rigidity, R0 [MV], and a 4r- energies up to 1021 eV. GCR consists of 87% protons, integral flux density of protons with energies Ep above 12% s-particles and 1% heavier ions which show 10MeV, J0,sca (47r, Ep > 10 MeV) [am -2 s-l]. similar energy spectra when compared as function of The energy-differential flux densities of GCR energy per nucleon (Alsmiller et al 1972). Mean GCR spectra OJcca/OE can be parameterized according to Keywords. Cosmogenic nuclides; meteorites; simulation experiments; cross sections; modeling of production rates. Proc. Indian Acad. Sci. (Earth Planet. Sci.), 107, No. 4, December 1998, pp. 441-457 Printed in India 441 442 R Michel and S Neumann ,1_0 +2 called cosmogenic nuclides have found manifold appli- cations. On Earth, they are produced by interactions with the atmosphere and these cosmogenic nuclides are incorporated in the large scale environmental SCR protons processes. There they act as natural tracers for use in 10 +o [~,J0] (years) archaeology, hydrology, glaciology, climatology, and other environmental sciences (Finkel and Surer 1993). [75,200] (1954-1964) ,.7 ;:>r"'~ Cosmogenic nuclides produced in situ in the earth's - [70,110] (1954-1986) crust have a high potential for studying processes like "7 erosion, deglaciation (Lal 1986; Lal et al 1987) and to [50,55] (1977-1986) I0-2 M [MeV] date individual events e.g. impacts of extraterrestrial (year) objects (Nishiizumi et al 1991b). Investigations of cosmogenic nuclides in extrater- 300 / restrial matter allow us to study the history of the -(1977) matter exposed to SCR and GCR particles as well as / the dependence on time of the spectral distribution of 9OO SCR and GCR over time scales of millions of years GCRprotons (1969) (Geiss et al 1962; Lal 1972). Cosmogenic nuclides in extraterrestrial matter provide a past record which can- 1 0 -6 not be retrieved by any other means. Already these very first reviews demonstrated the scientific potential of cosmogenic nuclides in extraterrestrial matter. The 10 *o 10 *2 10 +4 Table 1. List of cosmogenic nuclides in meteorites with half- lives above 0.5 month and their target elements. ENERGY [MeV] Nuclide Half-life Main target elements Figure 1. Free space GCR proton spectra at 1 A.U. for times of a quiet (1977) and an active sun (1969) and average SCR 48V 0.0438 a Ti, Fe, Ni proton spectra for three periods from 1954 to 1986. SCR spectra 51Cr 0.0759 a Fe, Ni can be parameterized for individual flares as well as for time- 3TAr 0.096 a Ca, Ti, Fe, Ni averaged spectra by exponentially falling rigidity spectra 7Be 0.146 a C,O, Mg, A1, Si, S*, P*, Ca, Ti, Fe, Ni (McGuire and yon Rosenvinge 1984) characterized by a char- 5SCo 0.194 a Fe~, Ni acteristic rigidity, R0 [MV], and a 41r integral flux density of 56Co 0.213a Fe, Ni protons with energies above 10MeV, J0(41r, E >10MeV) 46Sc 0.230 a Ti, Fe, Ni [cm-2 s-l]. Rigidities of the observed flare spectra show a much 57Co 0.743 a Fe, Ni broader range (20MV - 150MV) than shown here for solar 54Mn 0.855 a Fe, Ni, Mn cycle averaged SCR spectra (Shea and Smart 1990). According 22Na 2.6 a Mg, A1, Si, Ca, Ti, Fe, Ni to Castagnoli and Lal (1980), GCR spectra can be character- 55Fe 2.7a Mn, Fe, Ni ized by only one parameter M [MeV] which describes the 6~ " 5.26 a CoS, Ni modulation by the solar magnetic field of GCR particles when aH 12.3a C, O, Mg, A1, Si, S*, P*, Ca, Ti, Fe, Ni entering the solar system. M is equivalent to the energy a GCR 44Ti 59.2 a Ti, Fe, Ni particle looses when penetrating into the solar system to a 328i 133 a Ca, Ti, Fe, Ni given heliocentric distance. 39Ar 269 a Ca, Ti, Fe, Ni 14C 5.73ka O, Mg, A1, Si, S*, P*, Ca, Ti, Fe, Ni 59Ni 75 ka Feg, Ni Castagnoli and Lal (1980) using a modulation para- 41Ca 103ka Ca $, Ti, Fe, Ni meter M [MeV] which represents the energy loss which 81Kr 210ka Rb, Sr, Y, Zr a particle undergoes when it enters the solar system 36C1 300ka C1$, Ca, Ti, Fe, Ni 26A1 716ka Mg, A1, Si, S*, P*, Ca, Ti, Fe, Ni and propagates to a certain heliocentric distance. For ~~ 1.5 Ma Ni GCR protons one obtains 1~ 1.51 Ma C, O, Mg, A1, Si, S*, P*, Ca, Ti, Fe, Ni 53Mn 3.7 Ma Fe, Ni OJp,GCR Ep.(Ep+2mp . c2) (Ep + x + M) -2"65 129I 15.7Ma Te$, Ba, I~EE OEp ( Ep + M) . ( Ep + 2mp . c 2 + M) 4~ 1.28 Ga Ca, Ti, Fe, Ni He stable C, O, Mg, A1, Si, S*, P*, Ca, Ti, Fe, Ni (2) Ne stable Na, Mg, A1, Si, S*, P*, Ca, Ti, Fe, Ni with x = 780- exp(-2.5 104Ep) and c = 1.244- 106 Ar stable C1$, Ca, Fe, Ni Kr stable Br$, Rb, Sr, Y, Zr cm -2 s -1 MeV -1. For heavier GCR particles analogous Xe stable Te, I S, Ba $, REE parameterizations exist. In the solar system, SCR and GCR interact with Note: Special relevance of target elements (exclusively or also) with respect to production of cosmogenic nRclides by neutron cosmic dust, meteoroids, asteroids, comets and lunar capture ($) or by a-induced reactions (~) are indicated. and planetary surfaces, thereby producing a wide range Elements marked with (*) are only relevant in iron meteorites of stable and radioactive nuclides (table 1). These so- or the metal phase of stony irons. Cosmogenic nuclides in meteorites 443 exploitation of this potential, however, suffered for a sophisticated chemical separation schemes (Vogt and long time from large experimental and theoretical Herpers 1988), AMS measurements can be performed uncertainties due to limited analytical techniques as on many of these nuclides simultaneously from one well as due to crude and empirical modeling. individual sample. AMS is sensitive enough to even Shortly after the discovery of the first cosmogenic allow for the determination of cosmogenic nuclides in radionuclide (3H) in meteoritic material (Begemann individual grains of cosmic dust (Nishiizumi et a11991a) et al 1957; Fireman and Schwaxzer 1957), the whole and to investigate in situ produced cosmogenic nuclides variety of cosmogenic radio nuclides measurable in in terrestrial surface samples (Lal 1986, Lal et al 1987); meteorites became evident (Ehmann and Kohman see (Finkel and Suter 1993) for further references. 1958; Shedlovsky 1960; Arnold et al 1961). These Today, the advanced measuring techniques allow for investigations used radiochemical techniques to the determination of the whole suite of stable and extract the whole suite of cosmogenic radionuclides long-lived cosmogenic nuclides in a single sample of from hundreds of grams or even kilograms of meteo- 500rag combining rare gas mass spectrometry and ritic materials to allow for the detection of their decay AMS by consortia studies by different laboratories. with the measuring techniques available at that time. With respect to the short-lived radionuclides with Stable cosmogenic nuclides in extraterrestrial matter half-lives between a few days and several decades, were observed as positive isotopic abundance anomalies measuring techniques also have improved.
Load more

Recommended publications
  • EXTRACTION of BERYLLIUM-10 from SOIL by FUSION Summary
    EXTRACTION OF BERYLLIUM-10 FROM SOIL BY FUSION Summary This method is used to separate Be from soil and sediment samples, for AMS analysis. After adding Be carrier, the sample is fused with KHF2. Be is extracted from the fusion cake with hot water. K is removed by precipitation, the sample is dried to expel fluoride, and Be is recovered as Be(OH)2. Yields are typically 70-80 %, but can be increased by additional leaching of the fusion cake. Version Written by John Stone, 1996-2002. This version revised May 2004 by Greg Balco. Available at: http://depts.washington.edu/cosmolab/chem.html References If you use this method, please cite: Stone, J.O.H. (1998). A rapid fusion method for the extraction of Be-10 from soils and silicates. Geochimica et Cosmochimica Acta (Scientific comment) 62, 555-561. Sampling and grinding Mix and grind an unbiased ∼ 50-100 g sample of the material. If possible, mix the original sample bag before opening and take representative proportions of coarse and fine material. Fine soil, carbonate nodules, clay lumps, rock fragments, etc., all have different 10Be concentrations. Grinding homogenises the sample and ensures that these components are evenly represented in the small subsample used for the analysis. If the sample is wet, you will need to dry it before grinding. Initial sample drying Samples are best run in batches of four. This is because we currently have four Pt crucibles. Given more crucibles and sufficient hotplate space, batches of 8 or even 12 are equally feasible. ————————————————— UW Cosmogenic Nuclide Lab – 10Be fusion process 1 – Label and tare four disposable aluminum foil drying dishes and transfer a few grams of ground sediment to each with a steel spatula.
    [Show full text]
  • Isotopegeochemistry Chapter4
    Isotope Geochemistry W. M. White Chapter 4 GEOCHRONOLOGY III: OTHER DATING METHODS 4.1 COSMOGENIC NUCLIDES 4.1.1 Cosmic Rays in the Atmosphere As the name implies, cosmogenic nuclides are produced by cosmic rays colliding with atoms in the atmosphere and the surface of the solid Earth. Nuclides so created may be stable or radioactive. Radio- active cosmogenic nuclides, like the U decay series nuclides, have half-lives sufficiently short that they would not exist in the Earth if they were not continually produced. Assuming that the production rate is constant through time, then the abundance of a cosmogenic nuclide in a reservoir isolated from cos- mic ray production is simply given by: −λt N = N0e 4.1 Hence if we know N0 and measure N, we can calculate t. Table 4.1 lists the radioactive cosmogenic nu- clides of principal interest. As we shall, cosmic ray interactions can also produce rare stable nuclides, and their abundance can also be used to measure geologic time. A number of different nuclear reactions create cosmogenic nuclides. “Cosmic rays” are high-energy (several GeV up to 1019 eV!) atomic nuclei, mainly of H and He (because these constitute most of the matter in the universe), but nuclei of all the elements have been recognized. To put these kinds of ener- gies in perspective, the previous gen- eration of accelerators for physics ex- Table 4.1. Data on Cosmogenic Nuclides periments, such as the Cornell Elec- -1 tron Storage Ring produce energies in Nuclide Half-life, years Decay constant, yr the 10’s of GeV (1010 eV); while 14C 5730 1.209x 10-4 CERN’s Large Hadron Collider, 3H 12.33 5.62 x 10-2 mankind’s most powerful accelerator, 10Be 1.500 × 106 4.62 x 10-7 located on the Franco-Swiss border 26Al 7.16 × 105 9.68x 10-5 near Geneva produces energies of 36Cl 3.08 × 105 2.25x 10-6 ~10 TeV range (1013 eV).
    [Show full text]
  • Meteoric Be and Be As Process Tracers in the Environment
    Chapter 5 Meteoric 7Be and 10Be as Process Tracers in the Environment James M. Kaste and Mark Baskaran 7 10 Abstract Be (T1/2 ¼ 53 days) and Be (T1/2 ¼ occurring Be isotopes of use to Earth scientists are the 7 1.4 Ma) form via natural cosmogenic reactions in the short-lived Be (T1/2 ¼ 53.1 days) and the longer- 10 atmosphere and are delivered to Earth’s surface by wet lived Be (T1/2 ¼ 1.4 Ma; Nishiizumi et al. 2007). and dry deposition. The distinct source term and near- Because cosmic rays that cause the initial cascade of constant fallout of these radionuclides onto soils, vege- neutrons and protons in the upper atmosphere respon- tation, waters, ice, and sediments makes them valuable sible for the spallation reactions are attenuated by tracers of a wide range of environmental processes the mass of the atmosphere itself, production rates of operating over timescales from weeks to millions of comsogenic Be are three orders of magnitude higher in years. Beryllium tends to form strong bonds with oxygen the stratosphere than they are at sea-level (Masarik and atoms, so 7Be and 10Be adsorb rapidly to organic and Beer 1999, 2009). Most of the production of cosmo- inorganic solid phases in the terrestrial and marine envi- genic Be therefore occurs in the upper atmosphere ronment. Thus, cosmogenic isotopes of beryllium can be (5–30 km), although there is trace, but measurable used to quantify surface age, sediment source, mixing production as oxygen atoms in minerals at the Earth’s rates, and particle residence and transit times in soils, surface are spallated (in situ produced; see Lal 2011, streams, lakes, and the oceans.
    [Show full text]
  • Beryllium-10 Terrestrial Cosmogenic Nuclide Surface Exposure Dating of Quaternary Landforms in Death Valley
    Geomorphology 125 (2011) 541–557 Contents lists available at ScienceDirect Geomorphology journal homepage: www.elsevier.com/locate/geomorph Beryllium-10 terrestrial cosmogenic nuclide surface exposure dating of Quaternary landforms in Death Valley Lewis A. Owen a,⁎, Kurt L. Frankel b, Jeffrey R. Knott c, Scott Reynhout a, Robert C. Finkel d,e, James F. Dolan f, Jeffrey Lee g a Department of Geology, University of Cincinnati, Cincinnati, Ohio, USA b School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA 30332, USA c Department of Geological Sciences, California State University, Fullerton, California, USA d Department of Earth and Planetary Science Department, University of California, Berkeley, Berkeley, CA 94720-4767, USA e CEREGE, BP 80 Europole Méditerranéen de l'Arbois, 13545 Aix en Provence Cedex 4, France f Department of Earth Sciences, University of Southern California, Los Angeles, California, USA g Department of Geological Sciences, Central Washington University, Ellensburg, Washington, USA article info abstract Article history: Quaternary alluvial fans, and shorelines, spits and beach bars were dated using 10Be terrestrial cosmogenic Received 10 March 2010 nuclide (TCN) surface exposure methods in Death Valley. The 10Be TCN ages show considerable variance on Received in revised form 3 October 2010 individual surfaces. Samples collected in the active channels date from ~6 ka to ~93 ka, showing that there is Accepted 18 October 2010 significant 10Be TCN inheritance within cobbles and boulders. This
    [Show full text]
  • Polar Desert Chronologies Through Quantitative Measurements of Salt Accumulation
    Polar desert chronologies through quantitative measurements of salt accumulation Joseph A. Graly1, Kathy J. Licht1, Gregory K. Druschel1, and Michael R. Kaplan2 1Department of Earth Sciences, Indiana University–Purdue University Indianapolis, Indianapolis, Indiana 46202, USA 2Lamont–Doherty Earth Observatory, Palisades, New York 10964, USA ABSTRACT isotopes suggest a primarily atmospheric ori- We measured salt concentration and speciation in the top horizons of moraine sediments gin, with some trace mineral boron (Leslie et from the Transantarctic Mountains (Antarctica) and compared the salt data to cosmogenic- al., 2014). However, the Dry Valleys boron iso- nuclide exposure ages on the same moraine. Because the salts are primarily of atmospheric tope values that suggest a trace mineral compo- origin, and their delivery to the sediment is constant over relevant time scales, a linear rate of nent could also form from Rayleigh distillation accumulation is expected. When salts are measured in a consistent grain-size fraction and at during the precipitation of atmospheric boron a consistent position within the soil column, a linear correlation between salt concentration (Rose-Koga et al., 2006). and exposure age is evident. This correlation is strongest for boron-containing salts (R2 > 0.99), Atmospheric aerosols exist either as acid 2 but is also strong (R ≈ 0.9) for most other water-extracted salt species. The relative mobility vapors and gases (e.g., HNO3, N2O5, etc.) or of salts in the soil column does not correspond to species solubility (borate is highly soluble). as anion-cation pairs, commonly adhering to Instead, the highly consistent behavior of boron within the soil column is best explained by particulate matter.
    [Show full text]
  • Calibration of the Production Rates of Cosmogenic 36C1 from Potassium
    CALIBRATION OF THE PRODUCTION RATES OF COSMOGENIC 36C1 FROM POTASSIUM Jodie Manderson Evans A thesis submitted for the degree of Doctor of Philosophy at The Australian National University July, 2001 daran and Heather Preface This thesis describes the complete calibration of J6C1 produced in-situ from potassium. This project was suggested by Dr John Stone and Dr Keith Fifield, and carried out at the Australian National University (ANU) jointly between the Research School of Earth Sciences (RSES), and the Department of Nuclear Physics, RSPhysSE. The author has taken primary responsibility from the beginning of this project to its conclusion. This has involved collecting the samples, performing mineral separations, preparing them for many different measurements, performing the measurements, and finally, carrying out the analysis and interpreting the data. During this process the author was assisted and advised by many people, as discussed below. With the exception of the samples AT-10, AT-11, AT-12 and AT-13, which were collected by Dr Stone, all the Scottish samples were collected by the author with advice from Dr Colin Ballantyne and assistance from Keith Salt, Matt Franks, Angela Lamb and Dr Greg Lane. The samples for the depth profile from Wyangala were collected by the author with Dr Stone, Dr Fifield, Dr Richard Cresswell, Dr Mariana Di Tada and Dr Kexin Liu. The original trace element measurements were made by ICP-MS at RSES with assistance from Mr Leslie Kinsley. X-ray fluorescence measurements (major element whole rock concentrations and some whole rock uranium and thorium concentrations) were made by Dr Bruce Chappell in the Geology Department at ANU.
    [Show full text]
  • Chlorine-36/Beryllium-10 Burial Dating of Alluvial Fan Sediments Associated with the Mission Creek Strand of the San Andreas Fault System, California, USA
    Geochronology, 1, 1–16, 2019 https://doi.org/10.5194/gchron-1-1-2019 © Author(s) 2019. This work is distributed under the Creative Commons Attribution 4.0 License. Chlorine-36=beryllium-10 burial dating of alluvial fan sediments associated with the Mission Creek strand of the San Andreas Fault system, California, USA Greg Balco1, Kimberly Blisniuk2, and Alan Hidy3 1Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94550, USA 2Department of Geology, San Jose State University, San Jose, CA, USA 3Center for Accelerator Mass Spectrometry, Lawrence Livermore National Laboratory, Livermore, CA, USA Correspondence: Greg Balco ([email protected]) Received: 23 April 2019 – Discussion started: 30 April 2019 Revised: 3 July 2019 – Accepted: 5 July 2019 – Published: 18 July 2019 Abstract. We apply cosmogenic-nuclide burial dating using with stratigraphic age constraints as well as independent es- the 36Cl-in-K-feldspar=10Be-in-quartz pair in fluvially trans- timates of long-term fault slip rates, and it highlights the po- ported granitoid clasts to determine the age of alluvial sedi- tential usefulness of the 36Cl=10Be pair for dating Upper and ment displaced by the Mission Creek strand of the San An- Middle Pleistocene clastic sediments. dreas Fault in southern California. Because the half-lives of 36Cl and 10Be are more different than those of the commonly used 26Al=10Be pair, 36Cl=10Be burial dating should be ap- 36 10 plicable to sediments in the range ca. 0.2–0.5 Ma, which is 1 Introduction: Cl= Be burial dating too young to be accurately dated with the 26Al=10Be pair, and should be more precise for Middle and Late Pleistocene sed- In this paper we apply the method of cosmogenic-nuclide 36 iments in general.
    [Show full text]
  • Third Nordic Workshop on Cosmogenic Nuclide Techniques
    Third Nordic Workshop on cosmogenic nuclide techniques Third Nordic Workshop June 8–10, 2016 Workshop hosted by Department of Physical Geography, Stockholm University co-sponsored by Svensk Kärnbränslehantering (SKB) Third Nordic Workshop on cosmogenic nuclide techniques Celebrating 30 years of counting cosmogenic atoms Editors Robin Blomdin June 8–10, 2016 June 8–10, Ping Fu Bradley W. Goodfellow Natacha Gribenski Jakob Heyman Jennifer C. Newall Arjen P. Stroeven SVENSK KÄRNBRÄNSLEHANTERING ISBN 978-91-980362-7-5 SKB ID 1545666 June 8–10, 2016 Third Nordic Workshop on cosmogenic nuclide techniques Celebrating 30 years of counting cosmogenic atoms Editors Robin Blomdin1, Ping Fu2, Bradley W. Goodfellow1,3,4, Natacha Gribenski1, Jakob Heyman5, Jennifer C. Newall1,6, Arjen P. Stroeven1 1 Geomorphology and Glaciology, Department of Physical Geography & Bolin Centre for Climate Research, Stockholm University, Sweden 2 School of Geographical Sciences, The University of Nottingham Ningbo, China 3 Department of Geological Sciences & Bolin Centre for Climate Research, Stockholm University, Sweden 4 Department of Geology, Lund University 5 Department of Earth Sciences, University of Gothenburg, Sweden 6 Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, USA Keywords: Glacial erosion, Cosmogenic nuclides, Cosmogenic dating, Forsmark, Excursion guide, Third Nordic Workshop on Cosmogenic Nuclide Techniques A pdf version of this document can be downloaded from www.skb.se. © 2015 Svensk Kärnbränslehantering AB Preface This proceedings volume contains the extended abstracts presented at the Third Nordic Workshop on Cosmogenic Nuclide Techniques: Celebrating 30 years of counting cosmogenic atoms, arranged by Stockholm University, June 8–10, 2016, and co-sponsored by SKB. It also contains the field guide for the post-workshop excursion to Forsmark, held on June 11, 2016.
    [Show full text]
  • Extraction and Measurement of Cosmogenic in Situ 14C from Quartz
    EXTRACTION AND MEASUREMENT OF COSMOGENIC IN SITU 14C FROM QUARTZ PHILIP NAYSMITH Thesis presented for the degree of Master of Science University of Glasgow Scottish Universities Environmental Research Centre East Kilbride © P. Naysmith 2007 TABLE OF CONTENTS ACKNOWLEDGEMENTS ........................................................................................ iv DECLARATION......................................................................................................... v ABSTRACT .............................................................................................................. vi CHAPTER 1: INTRODUCTION................................................................................. 1 1.1. Introduction ..................................................................................................... 1 1.2. History of Surface Exposure Dating ................................................................ 4 1.3. Formation of Cosmogenic Nuclides ................................................................ 5 14 1.4. Advantages of In Situ C for Surface Exposure Dating .................................. 7 14 1.5. Previous Studies of In Situ C........................................................................ 9 14 1.6. Production Rates for In situ C..................................................................... 18 1.7. Measurement Techniques............................................................................. 20 14 1.8. Applications using In Situ C.......................................................................
    [Show full text]
  • Cosmogenic Nuclide Analysis
    ISSN 2047-0371 Cosmogenic nuclide analysis Christopher M. Darvill1 1 Department of Geography, Durham University, South Road, Durham, DH1 3LE, UK ([email protected]) ABSTRACT: Cosmogenic nuclides can be used to directly determine the timing of events and rates of change in the Earth’s surface by measuring their production due to cosmic ray-induced reactions in rocks and sediment. The technique has been widely adopted by the geomorphological community because it can be used on a wide range of landforms across an age range spanning hundreds to millions of years. Consequently, it has been used to successfully analyse exposure and burial events; rates of erosion, denudation and uplift; soil dynamics; and palaeo-altimetric change. This paper offers a brief outline of the theory and application of the technique and necessary considerations when using it. KEYWORDS: Cosmogenic nuclide, dating, chronology, landscape change, Quaternary Introduction by the geomorphological community in addressing issues such as the timing of Geochronology allows the quantification of glacial advances, fault-slip rates, rates of landscape change and timing of bedrock/basin erosion and sediment burial geomorphic events, bridging the gap between (Cockburn and Summerfield, 2004). geomorphological evidence and However, there are a number of practical and environmental or climatic variability over time. theoretical concerns that need to be Cosmogenic nuclide analysis involves the considered when applying the technique. measurement of rare isotopes which build-up in rock minerals predictably over time due to This chapter will briefly explain how bombardment of the upper few metres of the cosmogenic nuclides are produced, describe Earth’s surface by cosmic rays.
    [Show full text]
  • Cosmogenic Nuclide Dating of the Sediments of Bulmer Cavern: Implications for the Uplift History of Southern Northwest Nelson, South Island New Zealand
    Cosmogenic nuclide dating of the sediments of Bulmer Cavern: implications for the uplift history of southern Northwest Nelson, South Island New Zealand Gavin Holden A thesis submitted to Victoria University of Wellington in partial fulfilment of the requirements for the degree of Master of Science in Geology School of Geography, Environment and Earth Sciences Victoria University of Wellington November 2018 1 Frontispiece: A caver in the Wildcat Series, lower levels of Bulmer cavern. 2 Abstract The landscape of Northwest Nelson shows evidence of significant tectonic activity since the inception of the Austro-Pacific plate boundary in the Eocene. Evidence of subsidence followed by rapid uplift from the Eocene to the late Miocene is preserved in the sedimentary basins of Northwest Nelson. However, the effects of erosion mean there is very little evidence of post-Miocene tectonic activity preserved in the Northwest Nelson area. This is a period of particular interest, because it coincides with the onset of rapid uplift along the Alpine Fault, which is located to the south, and the very sparse published data for this period suggest very low uplift rates compared to other areas close to the Alpine Fault. Cosmogenic nuclide burial dating of sediments preserved in Bulmer Cavern, indicate an uplift rate of 0.13mm/a from the mid-Pliocene to the start of the Pleistocene and 0.067mm/a since the start of the Pleistocene. The Pleistocene uplift rate is similar to other published uplift rates for this period from the northern parts of Northwest Nelson, suggesting that the whole of Northwest Nelson has experienced relative tectonic stability compared to other areas close to the Alpine Fault during this period.
    [Show full text]
  • Determination Limits for Cosmogenic 10Be and Their Importance for Geomorphic Applications
    Determination limits for cosmogenic 10Be and their importance for geomorphic applications 1 S1 – Supplementary Text Cosmogenic nuclides are widely used for studying and quantifying geomorphic processes. Because of the broadness and complexity of the topic, we do not intend this text to be an exhaustive review of the method, because many detailed papers already exist on this argument (Nishiizumi et al. 1989; Lal, 1991; Brown et al., 1992; Biermann et al., 1996; Gosse and Phillips, 2001; von Blanckenburg, 2005; Dunai 2010; Balco 2011 among others). Instead, we provide a general and simplified description of how the technique can be used in rapidly eroding landscapes, particularly in the case of samples with low 10Be content. Additionally, we provide a description of how to estimate the amount of material to be collected in the field, and suggestions on how to minimize the loss of quartz during the chemical treatment of samples (Portenga et al., 2015; Corbett et al., 2016). S2 – Challenges arising from samples with low 10Be/9Be ratios In a sample with low 10Be content, the sample’s 10Be/9Be ratio can be very low, and potentially drop below the range that can be precisely measured by an AMS. In cases where a low 10Be content is anticipated, higher 10Be/9Be ratios can be achieved in two ways: 1) by increasing the 10Be content in the sample, and/or 2) by reducing the amount of added 9Be carrier. However, too little carrier added to the samples can result in problematic AMS measurements, so this option may be discarded for samples with low 10Be content.
    [Show full text]