RESEARCH METHOD
OSL dating
Absolute dating of the last light exposure of mineral grains.
01
What the method shows
Time since the luminescence signal of mineral grains was last effectively reset by light. Sediment dating commonly uses quartz or feldspar.
How we use it in HEL
Daylight can reset the inherited signal before deposition. After burial, energy from natural ionising radiation accumulates again. The laboratory estimates equivalent dose and combines it with environmental dose rate to calculate age.
Light exposure before deposition empties part of the trapped charge in mineral grains.
After burial, natural ionising radiation causes trapped charge to accumulate again.
Laboratory optical stimulation releases luminescence used to estimate equivalent dose.
Age is calculated as equivalent dose divided by dose rate.
02
How the method works
OSL uses energy stored in defects within mineral crystal lattices. Light exposure before deposition releases much of the trapped charge; after burial, charge accumulates again under natural ionising radiation.
In the laboratory optical stimulation determines the equivalent dose, representing energy accumulated since the last effective bleaching. Age is calculated as equivalent dose divided by environmental dose rate, so light-safe sampling and an independent dose-rate estimate are both required.
The result dates deposition only when grains were sufficiently bleached before burial and subsequently behaved as a closed system. Partial bleaching can make ages appear too old.
stratigraphy, sedimentology, geochemistry and independent chronological evidence where available.
03
In practice
- Input / materiallight-sensitive sediment containing quartz or feldspar
- Scale / resolutiona suitable stratigraphic unit or depositional event
- Sampling / preparationlight-safe sampling; environmental dose rate must also be established
- Typical outputnumerical age with uncertainty, equivalent dose and dose rate
04
Limits and control
Sufficient bleaching before deposition is critical. Partially bleached sediments may yield ages that are too old. Reliable dose-rate assessment and mineral behaviour also matter; feldspar can require correction for anomalous fading.
HEL separates this from pOSL profiling: OSL is a dating method, whereas pOSL at Tel Burna is used as a rapid relative profile signal.
05
References and HEL studies
Selected studies underpinning the method descriptions and examples used by Human Earth Lab.