Optically stimulated luminescence dating of fluvial deposits a review

29-Mar-2015 14:28 by 4 Comments

Optically stimulated luminescence dating of fluvial deposits a review

OSL specialists overcome these challenges through only sampling certain glacial landforms, where greater sunlight exposure is likely to have occurred prior to deposition e.g. Quartz luminescence dating of Anglian Stage (MIS 12) fluvial sediments: Comparison of SAR age estimates to the terrace chronology of the Middle Thames valley, UK. glacial sandars (or outwash plains) and proglacial deltas are likely to have well bleached sediments.

optically stimulated luminescence dating of fluvial deposits a review-90optically stimulated luminescence dating of fluvial deposits a review-61optically stimulated luminescence dating of fluvial deposits a review-68

Other important factors that need to be considered when calculating the radiation dose rate are the water content of the sediment and how much sediment is on top of the sample site.

From this curve we can calculate the dose that our sample must have received to produce the amount of light that we measured first.

We call this measurement our “equivalent dose”, because it is equivalent to the dose that the sample received in nature.

In the Aberystwyth Luminescence Laboratory our instruments are made by a Danish manufacturer and are called “Risø OSL/TL readers”.

This instrument stimulates the luminescence signal of the sand through shining the sample with blue or infrared light-emitting-didoes (LEDs), which give the electrons enough energy to escape their traps and recombine elsewhere, emitting a photon of light.

When these quartz or feldspar minerals are exposed to the ionising radiation emitted by the radioactive isotopes in zircons, electrons within the crystals migrate and become trapped in their crystal structure.

The number of trapped electrons depends on the total amount of radiation that the mineral has been exposed to. This can be measured either at the sample location using a portable gamma spectrometer, through measurement of alpha, beta and gamma counts in the laboratory, or through direct measurement of uranium, thorium and potassium concentrations using inductively-coupled plasma mass spectrometry. The methods through which dose rates are calculated vary between different laboratories worldwide. If we assume that the radiation dose rate of the sediment has remained constant over time, then if we measure that dose rate, we can calculate the sample age. Hollie Wynne (Aberystwyth University) stirs OSL samples being treated with acid in the preparation lab of the Aberystwyth Luminescence Research Laboratory. We make an approximation of the number of trapped electrons by measuring the light that they emit following stimulation by light (hence the name of the technique, “Optically stimulated luminescence”). The way that we do this is through sampling sand from the landforms in opaque plastic tubes and taking the sample back to a luminescence laboratory where only red light conditions are used. Optically stimulated luminescence dating of glaciofluvial sediments on the Canterbury Plains, South Island, New Zealand.

  1. incest mama mau memeknya dimasuki sesuatu sebelum dientot 23-Dec-2016 04:23

    Such dating usually end of exchange of contacts data (), then the possible real meetings.

  2. on line dating scammers 22-Jun-2015 19:22

    DK: So the reason that the 2005 ACA Code of Ethics continues to give no leeway and to ban all sexual or romantic interactions with clients is because we know that harm always occurs when that happens? Even if it appears on the surface that a client is open to a sexual/romantic relationship, there are always things that happen, and the client could later turn around and say that he or she wasn’t able to make a decision that was in their best interest at the time and therefore felt coerced.