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Optical dating sediments

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Both experiments indicate that the luminescence signal is partially bleached prior to deposition.The dose distributions of all samples are broadly scattered and have overdispersion values between 25 and 43%, some samples are significantly skewed.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.In our laboratory, these sediments are exposed to an external stimulus (blue-green light) and the trapped electrons are released.The released electrons emit a photon of light upon recombination at a similar site.The residual doses of the investigated modern wadi sediment are between 0 and 7 Gy.

Most luminescence dating methods rely on the assumption that the mineral grains were sufficiently "bleached" at the time of the event being dated.

The shape of the dose distributions points to other sources of scatter, in addition to partial bleaching.

Comparison of 1 mm multi-grain and single-grain data demonstrates that the luminescence signal of one multi-grain aliquot most likely is from a single grain.

Through geologic time, quartz minerals accumulate a luminescence signal as ionizing radiation excites electrons within parent nuclei in the crystal lattice.

A certain percent of the freed electrons become trapped in defects or holes in the crystal lattice of the quartz sand grain (referred to as luminescent centers) and accumulate over time (Aitken, 1998).

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.

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.

Two sample sequences spanning the periods 0–700 kyr and 0–6 kyr show steadily increasing luminescence with age.

An age of 62±8 kyr is obtained for a silt radiocarbon dated at 58.8±0.3 kyr. ABSTRACT: As part of the development of new laboratory lighting, we present a methodological approach applicable to the characterization of any light source intended for illumination in optical dating laboratories.