Optically Stimulated Luminescence

Definition

Optically Stimulated Luminescence (OSL) is a dating method used to determine the last time mineral grains were exposed to sunlight or heat. This technique is crucial in constructing chronologies for archaeological sites, especially those that are too old for radiocarbon dating. OSL measures the accumulated energy from radiation within minerals like quartz and feldspar, allowing archaeologists to date sedimentary layers and artifacts effectively.

5 Must Know Facts For Your Next Test

1. OSL dating can provide dates for sedimentary deposits ranging from a few decades to over 100,000 years old.
2. The method is particularly useful for dating materials such as pottery, sediments, and certain geological formations where organic materials are not present.
3. Unlike radiocarbon dating, OSL does not require organic materials, making it applicable in a wider range of archaeological contexts.
4. OSL dating relies on the principle that minerals accumulate energy from radiation over time, which is released as luminescence when stimulated by light.
5. The precision of OSL dating can be affected by factors such as the mineral type, burial conditions, and the accuracy of the laboratory procedures used.

Review Questions

• How does Optically Stimulated Luminescence (OSL) differ from other dating methods like radiocarbon dating?
  • OSL differs from radiocarbon dating primarily in the types of materials it can date and the mechanisms it uses. While radiocarbon dating relies on the decay of carbon isotopes in organic material, OSL measures the amount of luminescent light emitted from mineral grains that have been exposed to sunlight or heat. This allows OSL to date inorganic materials such as quartz and feldspar, which are often found in sedimentary deposits where organic remains may be absent.
• Discuss the process involved in obtaining an OSL date and what factors might influence its accuracy.
  • To obtain an OSL date, mineral grains are first collected from sediment layers in a way that prevents exposure to light. In the lab, they are stimulated using specific wavelengths of light to release stored energy as luminescence. The emitted light is measured to calculate the age since last exposure to sunlight. Factors influencing accuracy include the type of mineral used (like quartz or feldspar), environmental conditions during burial, and laboratory techniques employed in measuring luminescence.
• Evaluate the impact of Optically Stimulated Luminescence on our understanding of human activity and environmental changes over time.
  • Optically Stimulated Luminescence has greatly enhanced our understanding of human activity and environmental changes by providing reliable dates for sediment layers that reflect past landscapes and habitation. This method allows researchers to establish timelines for when sites were occupied or abandoned, correlating these events with climatic shifts or cultural developments. By filling gaps where other dating methods may fall short, OSL contributes valuable data that helps construct a more comprehensive picture of historical timelines and interactions between humans and their environment.

Related terms

Luminescence Dating: A group of dating techniques that measure the amount of light released when a mineral is stimulated by heat or light, including methods like thermoluminescence and optically stimulated luminescence.

Quartz: A common mineral used in OSL dating due to its ability to trap electrons, which can later be released as luminescence when stimulated.

Feldspar: Another important mineral used in OSL dating that also traps charge carriers, making it suitable for determining the age of sediment and artifacts.