Cosmogenic burial dating

Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves.Absolute geochronology can be accomplished through radioactive isotopes, whereas relative geochronology is provided by tools such as palaeomagnetism and stable isotope ratios.The polarity timescale has been previously determined by dating of seafloor magnetic anomalies, radiometrically dating volcanic rocks within magnetostratigraphic sections, and astronomically dating magnetostratigraphic sections.Global trends in isotope compositions, particularly Carbon 13 and strontium isotopes, can be used to correlate strata.With the exception of the radiocarbon method, most of these techniques are actually based on measuring an increase in the abundance of a radiogenic isotope, which is the decay-product of the radioactive parent isotope.A series of related techniques for determining the age at which a geomorphic surface was created (exposure dating), or at which formerly surficial materials were buried (burial dating).

More slowly decaying isotopes are useful for longer periods of time, but less accurate in absolute years.The burial dating technique was initially applied to allogenic sediments in caves, and has since been used for dating fluvial sediments, glacial tills, and buried marine terraces.The relative decay of cosmogenic nuclides has also been applied to establish the nature of bedrock erosion by ice sheets, and to constrain the half-life of 10Be.The second class of application uses Be to date discrete burial events, in cases where sediment has experienced a simple history of exposure followed by rapid burial.Examples include cave sediments, alluvial deposits, and sediment buried beneath glacial till.

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By combining multiple geochronological (and biostratigraphic) indicators the precision of the recovered age can be improved.

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