Optically stimulated luminescence dating method endometrial dating images
OSL dating is predicated on measurements of a specific mineral and particle size, usually quartz or potassium feldspar.
Mineral separations are performed by standard techniques using heavy liquids and hydrofluoric acid (HF) to digest non-quartz minerals and etch the outer 10 to 20 µm of quartz grains which are affected alpha radiation.
Free electrons are generated within the mineral matrix by exposure to ionizing radiation from the radioactive decay of daughter isotopes in the 235U, 238U and 232Th decay series, and a radioactive isotope of potassium, 40K, with lesser contributions from the decay of 85Rb and cosmic sources.
In contrast, feldspar minerals are often less abundant, and have a troubling signal instability (anomalous fading), though yield considerably brighter OSL emissions.
Exposure of mineral grains to light or heat (at least 300˚C) reduces the luminescence to a low and definable residual level.
Often this luminescence “cycle" occurs repeatedly in many depositional environments with signal acquisition of mineral grains by exposure to ionizing radiation during the burial period and signal resetting (“zeroing") with light exposure concurrent to sediment erosion and transportation. (a) Luminescence is acquired in mineral grains with exposure to ionizing radiation and trapping of electrons.
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.
The advent of single aliquot regenerative (SAR) dose procedures for quartz (Murray and Wintle, 2003; Wintle and Murray, 2006) has provided the needed analy tical flexibility to compensate for variable luminescence properties of quartz and feldspar grains and laboratory-induced sensitivity changes, particularly associated with preheat treatments and with laboratory beta irradiation.