Optical dating sediments updating stairs


As sediment is transported by wind, water, or ice, it is exposed to sunlight and zeroed of any previous luminescence signal.

Once this sediment is deposited and subsequently buried, it is removed from light and is exposed to low levels of natural radiation in the surrounding sediment.

We conclude that exposure of quartz and feldspar extracts from various samples to the light from an LED with emission peak at 594 nm results in a ≤1% OSL or IRSL signal loss for a 48-h exposure at a power density of ∼0.2 μW.cm⁻².

ABSTRACT: Rock-walled archaeological features are notoriously hard to date, largely because of the absence of suitable organic material for radiocarbon dating.

OSL is an acronym for Optically-Stimulated Luminescence.

Optically-Stimulated Luminescence is a late Quaternary dating technique used to date the last time quartz sediment was exposed to light.

We applied single-aliquot optical dating of coarse grained quartz of wadi deposits and investigated the luminescence properties in detail to achieve more accurate age information about the time of human occupation.

Weak luminescence signals and scattered dose distributions characterise the multi-grain aliquots.

The released electrons emit a photon of light upon recombination at a similar site.At Wadi Sabra (SW Jordan) human occupation dates back to the Palaeolithic and Epipalaeolithic.Although there is stratigraphic correlation based on archaeological finds of Ahmarian origin, numerical age estimates are lacking.Stimulating these mineral grains using either light (blue or green for OSL; infrared for IRSL) or heat (for TL) causes a luminescence signal to be emitted as the stored unstable electron energy is released, the intensity of which varies depending on the amount of radiation absorbed during burial and specific properties of the mineral.Most luminescence dating methods rely on the assumption that the mineral grains were sufficiently "bleached" at the time of the event being dated.All sediments and soils contain trace amounts of radioactive isotopes of elements such as potassium, uranium, thorium, and rubidium.These slowly decay over time and the ionizing radiation they produce is absorbed by mineral grains in the sediments such as quartz and potassium feldspar.A new method for dating sediments is proposed, which determines the time since the sediment was last exposed to sunlight.An argon-ion laser is used to excite electrons from thermally-stable light-sensitive traps and the subsequent luminescence used as a measure of the past radiation dose.The predicted relative decay rates of quartz optically stimulated luminescence (OSL) and feldspar infrared stimulated luminescence (IRSL) signals by an incandescent light bulb and a compact fluorescent lamp (CFL) through an ILFORD 902 filter are first derived.These predicted decay rates are then compared with those of three relevant light-emitting diodes (LEDs); this comparison demonstrates the significant advantage of the LED sources over the filtered light sources, because essentially all of the reduction of both OSL and IRSL signals by the LEDs occurs at wavelengths to which the human eye is most sensitive.

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