Dating geology singapore dating
Common silicate minerals like quartz and potassium feldspar contain lattice-charge defects formed during crystallization and from subsequent exposure to ionizing radiation.
These charge defects are potential sites of electron storage with a variety of trap-depth energies.
Thanks to the consistency of natural radioactive decay, science has found a measuring tool for seemingly unmeasurable amounts of time.
95% reduction in OSL within 4 seconds of exposure to light from blue diodes Optically stimulated luminescence (OSL) dating or optical dating provides a measure of time since sediment grains were deposited and shielded from further light or heat exposure, which often effectively resets the luminescence signal (Fig.1).
Thus, the population of stored electrons in lattice-charge defects increases with prolonged exposure to ionizing radiation and the resolved luminescence emission increases with time.
Exposure of mineral grains to light or heat (at least 300˚C) reduces the luminescence to a low and definable residual level.
However, some quartz grains yield considerable emissions with infrared excitation and may host feldspathic or other mineral inclusions; such grains should be analyzed as feldspar grains.Multiple soaks in HF may be needed to obtain a pure quartz separate.Purity of the separate is accessed through microscopic inspection and point counting of grain mineralogy.The OSL signal of potassium feldspar is usually more resista nt to solar resetting than most quartz.There is significant variability in the luminescence properties of quartz and potassium feldspar grains related to crystalline structure, minor and rare-earth impurities, solid-solution relations, number of luminescence cycles (Fig. Thus, because of this inherent variability in dose sensitivity of quartz and feldspar, analytical procedures for dating often need to be tailored for a specific geologic provenance.