91Ö±²¥

The 91Ö±²¥ Luminescence Dating Facility specialises in the measurement of quartz and feldspar-rich sands from sedimentary sequences, which can be absolutely dated within a range of 10 to 300,000+ years.

The suite of laboratories are fully equipped to isolate and clean mineral fractions from samples, under controlled darkroom conditions, for measurement both at single aliquot and single grain levels.

In recent years samples from all around the world have been dated, including archaeological sediments from the USA and South Africa, relict cold-climate desert sands from Arctic Canada, dune sands from Zambia, Zimbabwe, The Netherlands and UK and lake sediments from Mexico.

How does it work?

Sediments everywhere contain low concentrations of uranium, thorium and potassium which produce, over geological periods, a constant flux of ionising radiation. Both quartz and many feldspar minerals act as dosimeters recording their exposure to this ionizing radiation.

After being exposed to radiation these minerals, when stimulated by either heat or light, emit light. This is known as luminescence. The amount of luminescence emitted is proportional to accumulated dose since the minerals were last exposed to heat, e.g. by pot firing or light, eg to day-light during sediment transport.

With careful measurements, luminescence can be used to establish the total amount of accumulated dose since the last resetting event. This, when combined with measurement of the present-day annual ionizing dose rate, can be used to calculate an age.

Dating service

The 91Ö±²¥ luminescence dating facility undertakes dating of sediments for coarse grain samples including feldspar and quartz at the multi-grain and single grain level. If you are interested in getting material dated, contact the laboratory - we are happy to provide advice on luminescence sampling procedures, strategies to optimise the utility of dates and shipping requirements.

Luminescence only works if sediment samples have been exposed to sufficient sunlight immediately prior to deposition to zero the OSL signal, eg dunes, beaches, rivers. Other depositional contexts, such as colluvial and slope deposits or glacial sediments, may in certain circumstances be unsuitable or require different approached to OSL measurement. Thus it can also be advisable to discuss the details of different sedimentary environments prior to sampling as this may also affect decisions on what and where to sample.

Where larger or complex sampling programmes are being undertaken, it may be advisable that a member of the laboratory should personally collect samples. This will assist in sampling strategies and allows in-situ measurements of dose rate, which enhances accuracy and precision.

What to sample and send

For each sample, a minimum of 300cm³ of quartz-rich sand (90-250 μm) should be collected in a light-tight tube. As a few seconds' exposure of sediment to sunlight drastically alters the OSL age of a sample, great care should be taken at this stage.

Samples should then be sent double-wrapped and clearly labelled with their sample code. Packages should be clearly marked "Inert geological samples, no commercial value to be tested to destruction. Do not expose to light". In addition to this, with each sample should be a fully completed Submission Sheet, full details of the site stratigraphy including sample locations.

Please do not send samples before contacting the laboratory to establish cost and turnaround times.

Report results

OSL dating results are provided in a report detailing the full procedures undertaken to measure the samples and the sample ages. Through the use of multiple replicate measurements, the report also details an assessment of the reliability of the data used to generate the ages, and highlights any associated problems. We are happy to discuss dating results and have in the past contributed to technical reports, presentations and publications.

The cost of OSL dating varies principally according to whether or not the research is undertaken on a collaborative basis with joint publication of results. It also varies according to the number of samples involved and their depositional context and antiquity.

For further information, or to discuss sample analysis costs, please get in contact with Prof. Mark D. Bateman. For further conditions associated with OSL dating see above.

Contact Mark D. Bateman for more information.