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Hur påverkas luminiscenssignaler från kvarts under laboratorieförhållanden?

På svenska

Author

  • Rebecka Stjern

Summary, in English

Luminescence dating provides an important tool in geology to reconstruct geological depositions events in the Earth’s past. The basic assumption for a reliable dating is that luminescence generated from minerals resets at the time when it was last exposed to sunlight. The accuracy and precision of luminescence dating is therefore strongly dependant on preparation of the sediment to be in dark conditions. If the minerals are exposed to light before the analysis, there is a chance of releasing the stored energy and thus resetting the luminescence signal. The aim is to observe the effect of luminescence signals from quartz in response to change in the natural dose after exposure to artificial light in a laboratory. By determining the time for exposure and which intensity required for a possible effect on the test result. This study has been based on three quartz samples originating from an aeolian-, a glaciofluvial delta- and a fluvial deposition. The experiments were performed by exposing the quartz samples to fluorescent lighting, light inlet from a door, light generated from a computer screen and dark room lighting with different times of exposure. The samples have been analyzed with optically stimulated luminescence (OSL) to ob-serve changes in the natural dose. The result shows that a large part of the luminescence signals remains for expo-sure times shorter than 60 seconds for all light sources. The light source which affects the samples the most was found to be the fluorescent lighting, where the remaining signals are 6,4 ± 0,6 Gy, 6,8 ± 0,8 Gy and 9,9 ± 0,3 Gy (~ 5 % remaining signal) after 15 minutes of exposure. Light with more intensity affects luminescence signals more than light with lower intensity. Exposure times over 60 seconds are required to significantly affect the resetting of the luminescence signal generated by quartz. Based on the obtained results, an assumption is that unintentional exposure to light in the luminescence laboratory leads to a certain effect on the signal, and thus a possible misjudging of the test results through incorrect estimates of the age of the deposited sediment.

Publishing year

2017

Language

Swedish

Publication/Series

Examensarbeten i Geologi vid Lunds universitet

Document type

Student publication for Bachelor's degree

Topic

  • Earth and Environmental Sciences

Keywords

  • kvarts
  • luminiscensdatering
  • optisk stimulerad luminiscens (OSL)
  • luminiscenssignaler
  • blekning

Report number

519

Supervisor

  • Helena Alexanderson (professor)

Scientific presentation