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Topic: Cosmogenic

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	SAHRA - Isotopes
		Cosmogenic isotopes are a result of cosmic ray activity in the atmosphere.
		Cosmogenic isotopes are also produced at the surface of the earth by direct cosmic ray irradiation of atoms in solid geologic materials.
		Cosmogenic nuclides, since they are produced in the atmosphere or on the surface of the earth and have relatively short half-lives (10 to 30,000 years), are often used for age dating of waters.
	www.sahra.arizona.edu /programs/isotopes/types/radioactive.html (649 words)

	Welcome to Adobe GoLive 5
		Cosmogenic nuclide exposure ages along a vertical transect in western Norway: implications for the height of the Fennoscandian Icesheet.
		Cosmogenic analysis of glacial terrains in the eastern Canadian arctic: a test for inherited nuclides and the effectiveness of glacial erosion.
		Cosmogenic Neon in ultramafic nodules from Asia and in quartzite from Antarctica.
	cnef.earthsciences.dal.ca /NewFiles/tcnweb/qsr_refs.html (7213 words)

	Cosmogenic isotope - Wikipedia, the free encyclopedia
		Cosmogenic isotopes are rare radioactive isotopes created when cosmic radiation interacts with an atomic nucleus.
		These isotopes are produced on Earth, in Earth's atmosphere, and in extraterrestrial items such as meteorites.
		Because cosmogenic isotopes have very long lives (anywhere from thousands to millions of years), scientists find them useful for dating extremely old geological features and activities.
	en.wikipedia.org /wiki/Cosmogenic (92 words)

	NMBGMR Staff - Nelia W. Dunbar - Cosmogenic dating of young basaltic lava flows (Site not responding. Last check: 2007-11-04)
		Cosmogenic dating techniques have been successfully applied to dating of geomorphically-young surfaces, such as glacial moraines, beach terraces, and basaltic lava flows that have intact surface features, and hence have undergone little erosion (e.g.
		Therefore, cosmogenic techniques can be applied to dating of any surface that is composed of material that was not exposed to cosmic rays prior to formation of the surface, and has been exposed more-or-less continuously since.
		In the case of an extrusive volcanic rock, buildup of cosmogenic nuclides begins when the rock is erupted, so measurement of the ratio of a cosmogenic isotope to a non-cosmogenic isotope can provide an estimate of eruption age (Phillips et al., 1986).
	www.geoinfo.nmt.edu /staff/dunbar/basalt.html (397 words)

	Terrestrial Cosmogenic Nuclides,
		The rates at which cosmogenic nuclides are produced in rocks and minerals at the earth's surface have been estimated by three methods.
		This is an ideal situation for the application of cosmogenic dating techniques, since the the cratering event would quickly exposure previously shielded rock to the cosmic ray flux, and since the morphology of the crater itself indicates only a small amount of erosion.
		Cosmogenic noble gas studies in the oldest landscape on earth: surface exposure ages of the Dry Valleys.
	www.geocities.com /earthhistory/tcn.htm (3038 words)

	Derek Fabel - Department of Geography and Geomatics - University of Glasgow
		Measurement of erosion rates with cosmogenic nuclides, to study long-term landscape evolution, soil development and transport, and the effects of neotectonics and climate change.
		Cosmogenic nuclide evidence for minimal erosion across two subglacial sliding boundaries of the late glacial Fennoscandian ice sheet.
		Characteristic cosmogenic nuclide concentrations in relict surfaces of formerly glaciated regions.
	www.geog.gla.ac.uk:443 /staff/dfabel (321 words)

	NICL Science Management Office
		U.S. Cosmogenic isotopes in ice cores can be used to determine a chronology for the core, to study the history of terrestrial magnetic field and of solar activity and to investigate global atmospheric mixing.
		The major uncertainty in interpreting cosmogenic isotope levels in ice cores is the role of atmospheric transport and chemistry.
		It is important, however, that the cosmogenic: isotope measurements be directly comparable with other chemical and isotopic data in the same core.
	www.nicl-smo.sr.unh.edu /documents/1988/cosmogenicIsotopes_main.html (1494 words)

	From Asteroid to Earth: Cosmic Ray Exposure Ages of Meteorites (Site not responding. Last check: 2007-11-04)
		Cosmogenic stable and radiogenic nuclides are produced by high-energy particles of galactic cosmic rays in the ejected m-sized meteoroids.
		The production rates of cosmogenic nuclides are a function of the chemical composition of the meteoritic matter, the size of the meteoroid, and the position of the measured sample within the meteoroid ("shielding").
		The concentrations of cosmogenic nuclides in meteorites are rather low, thus, for experimental reasons, mainly cosmogenic noble gas isotopes are used to determine exposure ages.
	ecf.hq.eso.org /~ralbrech/amico/intabs/schultzl.html (418 words)

	Fabel (Site not responding. Last check: 2007-11-04)
		With careful interpretation of geomorphological settings, cosmogenic nuclides produced in rocks near the ground surface by reactions with cosmic rays can be used to determine apparent surface exposure age and landscape preservation, and constrain erosion depths and duration of burial by ice.
		Cosmogenic 10Be and 26Al data from 3 tors and a meltwater channel in the Parkajoki area were used to test this hypothesis of landscape preservation through multiple glacial cycles.
		Cosmogenic 26Al and 10Be in sediments washed into Mammoth Cave, Kentucky record the history of 3.5 million years of water-table position, governed by incision and aggradation of the Green River, a tributary of the Ohio River.
	rses.anu.edu.au /environment/eePages/eePeople/eeDerekFabel.html (3130 words)

	Isotope Tracers in Catchment Hydrology -- Chapter 19 references
		Cosmogenic isotopes and the evolution of granitic landforms.
		Erosional response to tectonic forcing inferred from cosmogenic isotopes in alluvial sediment.
		Role of in situ cosmogenic nuclides 10Be and 26Al in the study of diverse geomorphic processes.
	wwwrcamnl.wr.usgs.gov /isoig/isopubs/itch19refs.html (1969 words)

	Tilak Hewawasam (Site not responding. Last check: 2007-11-04)
		In situ-produced cosmogenic nuclides, such as 10Be and 26Al, are formed within mineral grains on and near Earth's surface due to bombardment by secondary cosmic rays.
		As a result, agriculturally-utilised catchments deviate from the steady-state assumption the cosmogenic nuclide erosion rate approach is based on and their nuclide concentrations may not be suitable to constrain spatially-averaged erosion rates.
		Natural, pre-anthropogenic erosion rates from cosmogenic nuclides are as low as 2-15 mm/ky in all parts of the landscape, including soil-covered slopes, high plateaus, and lowland inselbergs.
	www.earthsci.unibe.ch /abstracts/tilak.html (1456 words)

	Background Radiation
		Cosmogenic radionuclides arise from the collision of highly energetic cosmic ray particles with stable elements in the atmosphere and in the ground.
		Most of the other cosmogenically produced radionuclides in the atmosphere are oxidized and become attached to aerosol particles.
		About 10 to 20% of cosmogenically produced radionuclides are removed from the atmosphere by dry deposition on the earth's surface.
	www.tenorm.com /bkgrnd.htm (1220 words)

	Cosmogenic Isotope Dating (Site not responding. Last check: 2007-11-04)
		Rock samples were collected from both Bremehammer (top) and Store Solnkletten (bottom) during the summer of 1999 for dating of ice molded surfaces using cosmogenic nuclides.
		Cosmic rays produce rare (cosmogenic) isotopes in surface rocks at predictable rates.
		We are interested in a variety of aspects of cosmogenic isotope geochemistry, but current work focuses on glacial geochronology in Norway and Labrador.
	www.vancouver.wsu.edu /fac/brook/cosmogen.htm (189 words)

	Cosmogenic Isotope Laboratory
		Cosmogenic isotopes derive their name from the fact that they are formed as a consequence of the interaction of cosmic rays with atoms of the atmosphere, hydrosphere, or the top layers of the lithosphere.
		The release into the environment of some of these isotopes from nuclear explosions and reprocessing has also made possible applications of these isotopes in environmental studies and in short-term geologic questions.
		Iodine-129 is derived from cosmogenic, natural fissiogenic, and anthropogenic sources.
	siena.earth.rochester.edu /fehnlab (303 words)

	Cosmogenic nuclides
		Cosmogenic nuclides, on the other hand, are introduced into the atmosphere in a uniform and predictable way.
		We have been involved for a number of years in an effort to simulate cosmogenic nuclide production rates in the extraterrestrial and later terrestrial samples, including those from polar ice cores, to investigate long-term variations in their concentration and to relate these variations to the fundamental processes at work.
		Cl are influenced both by factors external to the atmosphere, such as changes in solar activity or in the galactic cosmic ray flux, and by internal factors, such as changes in the atmospheric circulation, in stratosphere-troposphere exchange processes, in snow accumulation rat, and in the geomagnetic field.
	www.internal.eawag.ch /~masarik/atmcgn.html (685 words)

	Station Information - Cosmogenic
		Cosmogenic refers to rare radioactive isotopes created when cosmic radiation interacts with an atomic nucleus.
		"Cosmogenic Exposure Dating and the Age of the Earth" " class="external">http://www.geocities.com/earthhistory/tcn.htm
		Cosmogenic Isotope Laboratory, Quaternary Research Center and Department of Earth and Space Sciences, University of Washington (note: State of Washington, not DC) http://depts.washington.edu/cosmolab/index.html
	www.stationinformation.com /encyclopedia/c/co/cosmogenic.html (116 words)

	Untitled Document (Site not responding. Last check: 2007-11-04)
		The chlorine-36 method (Phillips et al., 1986) is based on the fact that 36Cl is dominantly produced by cosmogenic reactions near the earth's surface, primarily in the upper 1 m.
		The cosmogenic ages of Carrizozo samples was calculated for erosion rates between 0 and 9 mm/ka(see Figure and discussion in Dunbar, 1999).
		Based on the above-estimated erosion rate, the estimated cosmogenic 36Cl ages for the three Carrizozo lava flow samples are 4.9±0.5, 5.4±1.0 and 5.6±0.9 yrs, yielding an weighted average of 5.2±0.7 ka.
	geoinfo.nmt.edu /staff/dunbar/carrizozo/geochron.html (1323 words)

	Abstract: Shomer, J. Scott (Site not responding. Last check: 2007-11-04)
		In situ accumulation of cosmogenic nuclides can be used to approach the problem of determining erosion rates on small spatial and long temporal scales.
		The oldest morainal boulders, which are most likely to have been exposed at the surface since their deposition, have a greater accumulation of cosmogenic nuclides than the surrounding soil matrix which has been continuously eroding.
		This study utilizes the previously determined ages and the in-situ accumulation of Cl-36 in the top 0.5 meter of soil at the crests of the moraines to calculate a time-integrated erosion rate for the surfaces.
	www.geo.arizona.edu /geodaze/98/program/thursday/shomer.html (362 words)

	Alexandru T. Codilean - Department of Geography and Geomatics - University of Glasgow
		Terrestrial cosmogenic isotopes (TCIs) are trace amounts of isotopes, including 3He, 10Be, 21Ne, 26Al and 36Cl, which are formed by secondary cosmic ray neutron (spallation) and muon bombardment of target elements, such as O, in surficial rocks and sediments.
		The cosmogenic isotope content of a grain reflects its history of erosion, transport and storage and therefore it is a function of the geomorphic setting of the area it originates from.
		Numerical modelling of cosmogenic isotope-based erosion rates offers an alternative way of assessing the cosmogenic isotope contents to be expected under different climatic and tectonic scenarios, thereby to provide a sounder theoretical base for the empirical, field-based measurements.
	www.geog.gla.ac.uk:443 /postgraduates/tcodilean (499 words)

	Darryl Granger's Cosmogenic Nuclide Page (Site not responding. Last check: 2007-11-04)
		Cosmogenic nuclides are produced in rocks near the earth's surface by nuclear reactions with cosmic rays.
		The cosmic rays originate in space, and are mostly absorbed in the atmosphere, creating byproducts such as carbon-14, which is the most common radionuclide used for dating organic matter over the past 50,000 years.
		If a rock is first exposed to cosmic rays at the surface, creating cosmogenic nuclides, and is then buried in a cave or by overlying sediment, then we can use the radioactive decay of the cosmogenic nuclides to date the burial event up to 5 million years into the past.
	www.eas.purdue.edu /~dgranger/cosmo.htm (247 words)

	Naturally occurring radioactive elements
		Secondary radionuclides are derived from radioactive decay of the primordials.
		Cosmogenic radionuclides are continuously produced by bombardment of stable nuclides by cosmic rays, primarily in the atmosphere.
		Some human-made radionuclides persist in the environment, but these are not "natural." A much larger number of radioactive isotopes than now exist were produced when the matter of which the universe is formed first came into being several billion years ago, but most of them have decayed out of existence.
	www.hps.org /publicinformation/ate/q661.html (474 words)

	Cosmogenic Isotope Chronology, Seward Peninsula and NC Brooks Range
		Because of the wealth of relative-age data collected on the glacial sequence in the past and the fact that the glacial deposits interfinger with well-known marine sequences at the coast, we felt that this region was probably most relevant for comparison with the glacial sequences on Chukotka.
		We obtained good to excellent coverage of the Steward River, Salmon Lake, Mt. Osborn- age deposits as well as a few of the inner cirque sequences; we were unable to collect viable material from middle Pleistocene Nome River-age surfaces due to the lack of erratics at the surface.
		One of the surprising observations we made along the north side of the Kigluaik Mountains was the amount of offset expressed by the northern range-front fault.
	www.geo.umass.edu /projects/chukotka/cosmo.html (1161 words)

	NMBMMR Staff - Nelia W. Dunbar - Uplift of the Tibetan Plateau: Insights from cosmogenic exposure ages of young lava ... (Site not responding. Last check: 2007-11-04)
		As a result, they would contain lower concentrations of cosmogenic nuclides than if the plateau were stable, since at the time of eruption they would have been shielded from the cosmic rays by a greater depth of atmosphere.
		Field work in the Ashik-kohl basin of the Tibetan plateau, sorth of the Kun Lun Mountains of nouthern Tibet, was carried out in the summer of 1993.
		Analysis to determine the apparent Cl-36 age and therefore the cosmogenic nuclide "deficit" are underway.
	www.geoinfo.nmt.edu /staff/dunbar/tibet.html (447 words)

	Home
		Cosmogenic radio nuclides are produced in nuclear reactions by fast particles from the cosmic rays.
		As the production is modulated by the activity of the Sun and the geomagnetic field the concentrations of the radio nuclides form an archive with information on these parameters, which may also have induced climatical variations.
		Analyses are performed as part of projects or are as a service at the corresponding tariff.
	www1.phys.uu.nl /ams (309 words)

	Quaternary Research Center (Site not responding. Last check: 2007-11-04)
		In addition to cosmogenic isotope dating, the project has involved work on lake-core records and glacio-isostatic sea-level change.
		Yet cosmogenic isotope measurements on resistant elements - silcretes, laterites and ferricretes - of the same geomorphic surfaces indicates typical Quaternary erosion rates of several metres per million years, higher than the long-term average rates required to ensure their preservation since the Tertiary.
		Measurement of erosion and sediment redistribution rates with cosmogenic isotopes, to study long-term landscape evolution, soil development and the effects of pastoral and agricultural land-use on soil erosion.
	www.ess.washington.edu /qrc/stone.html (922 words)

	[No title]
		It is well known that a few percent of all L chondrites contain Ne implanted by the solar wind in the surface dust layer of their parent body2.
		Obviously, the chromite grains of Ark 002 have not only retained cosmogenic 21Ne in the volume of their grains but even solar Ne on the grain surfaces during 480 Ma of storage on Earth.
		Therefore, probably a major fraction of the total 3He in Ark 002 is from the solar wind and hence we are unable to report the concentrations of cosmogenic 3He in these samples.
	www.nature.com /nature/journal/v430/n6997/extref/nature02736-s3.doc (687 words)

	University News - Communications and Development - University of Canterbury
		The opening of a new Cosmogenic Laboratory at the University of Canterbury this week will be a major boost for local scientists trying to determine the age of landscape features.
		Cosmogenic dating - also known as Exposure Age Dating - is a major new technique for determining the age of landscapes and is likely to become as important as radiocarbon dating.
		Associate Professor Jamie Shulmeister of the University’s Department of Geological Sciences said cosmogenic ages can be used to date events such as landslides, earthquake movement, river terrace formation and glacial erosion.
	www.comsdev.canterbury.ac.nz /news/2004/04012002.shtml (344 words)

	UW Cosmogenic Isotope Lab: measurement and applications of cosmogenic nuclides
		Production rates are almost unimaginably small - a few atoms per gram of rock per year - yet we can detect and count these "cosmogenic isotopes" using accelerator mass spectrometry, down to levels of a few thousand atoms per gram (parts per billion of parts per billion!).
		The build-up of cosmogenic isotopes through time provides us with a way to measure exposure ages for rock surfaces such as fault scarps, lava flows and glacial pavements.
		Where surfaces are gradually evolving, cosmogenic isotope measurements allow us to calculate erosion or soil accumulation rates.
	depts.washington.edu /cosmolab/index.html (178 words)

	ABSTRACT: Cosmogenic nuclide strategies for relative sea level histories.
		Cosmogenic nuclides produced in rocks would seem to be a logical dating method at high latitudes.
		Cobbles and boulders on raised beaches and glacially plucked bedrock surfaces on a seacliff face were collected along the northern coastline of Prescott Island, off the east coast of Prince of Wales Island, Central Arctic, Canada.
		The concentrations of cosmogenic 10Beproduced in quartz phases of Precambrian gneiss and quartz veins were used to calculate the exposure ages of the emerged beach ridges and cliff surfaces.
	cgrg.geog.uvic.ca /abstracts/GosseCosmogenicCrustal.html (475 words)

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