Presentation on theme: "Principle of Electron Spin Resonance dating ESR dating in earth sciences and achaeology refers to the effect of accumulated radiation in a mineral relative."— Presentation transcript:
Principle of Electron Spin Resonance dating ESR dating in earth sciences and achaeology refers to the effect of accumulated radiation in a mineral relative to time. Thus, it is – just as luminescence – an absolute dating method. Uranium Potassium Thorium e.g. quartz grain/coral/ mollusc shell cosmic rays Paramagnetic centres are detected in the crystal lattice of the mineral by means of microwave absorption spectroscopy.
Principle of Electron Spin Resonance dating Wagner, G.A. (1995) AB A = rotating electron creates a magnetic moment B = resonance occurs after microwave absorption C = the absorbed microwave is transformed into an ESR-signal by the spectrometer. Relative ESR-signalintensity Magnetic field [Gauss] Al-impurity centre Ti-impurity centre
Principle of Electron Spin Resonance dating At the Geography Department in Cologne, the newest spectrometer by Bruker, the Elexys 500 spectrometer (X-band), is at use. The height of the ESR signal is a measure of the radiation dose experienced by the sample, and thus of the time since the signal was last zeroed.
MaterialGeological EventDating RangePrecision Quartz - Volcanic events (mineralisation) - Fault gauge (pressure) - Sedimentation (bleaching) Quaternary PeriodExcept for sediments, ESR dating of quartz is established Bicarbonates Corals and Mollusc Shells - Mineralisation (Aragonite, Calcite) ~ 700 ka-very precise data for coral dating - problems with De and dosimetry for mollusc shells Tooth Enamel - mammalian - - mineralisationbetween a few thousand up to a few million years - problems with u-uptake Cave Deposits - mineralisation> 3 Ma- problems with u-uptake