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The OSL (Optically Stimulated Luminescence) technique is similar to thermal dating. Like thermal, optical dating can be thought of as a "clock setting" event. The minerals in the sediment grains are sensitive to light, and when exposed to light, electrons vacate the sediment grains. This process is known as recombination, which is the "clock setting" event. To detect the age, a comparison must be made between sediment grains with a known amount of added radiation, and sediment grains that were acted upon naturally. Optical dating is suitable for a variety of unheated sediments that are no older than 500,000 years. This includes silty and sandy sediments that were deposited by water. The technique does not apply to sediments that were deposited with little or no exposure to light. Glacial deposits fall into this category. Since the OSL dating technique is sensitive to light the collection of the sample must be done carefully. The sediments must not come into contact with light. The moisture content in the sediment since being deposited is also critical to the dating process. It must also be noted that the OSL dating technique has only been around since 1984, and needs to be fine-tuned. |