Information for Prospective Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) Users

Introduction | Section I | Section II | Section III | Section IV | Section V | Other U.S. Labs

Section V: Explanation for Differences in TL and OSL Techniques and Other Closing Comments

Advantages of TL over OSL:

1. Stability of luminescence can be judged by "plateau test"
2. Less sample preparation and analysis time required
3. Wider age range published in literature
4. More reliable older ages past 200 Ka (published or otherwise)

Advantages of OSL over TL:

1. Deals with easily bleached component, requires less "resetting" time (5 minutes versus 8 hours)
2. No brute heating of sample needed, can be measured easily
3. Single grain or aliquot analyses readily available (great for fluvial, glacial and lacustrine sediments)
4. Thoroughly bleached grains can be picked out for analysis

General outside agency pricing: $1200/sample (US$)

USGS in-house pricing: one pay period of time ($4,700) allows for six samples to be processed

Services offered: TL on 4-11 micron (µ) silts, IR-OSL (infrared stimulated luminescence) on 4-11 µ polymineralic or feldspar grains or 90-125 µ feldspar grains and BLUE-OSL (blue light optically stimulated luminescence) on 90-125 µ quartz grains

Methods offered:

• Additive, multi-aliquot; partial bleach; multi-aliquot for TL
• Additive, multi-aliquot; single aliquot for IRSL
• Single aliquot regeneration for Blue light-OSL
• Anomalous fading tests (every sample) and sunlight sensitivity tests (one sample per site)

Dose Rate: Field measurement by gamma spectrometry (K , U, Th and cosmic ray) or lab gamma spectrometry with NAI crystals (K , U and Th). Optional measurements of K by XRF; of U, Th with ICP-MS; or K , U and Th by INAA.

Sample turnaround time: Six (6) samples take three months to date (from time of sample receipt in lab). No ages are released until we are satisfied about the quality of the data. Sample turnaround times may be slower, but never faster. Remember that these samples have accumulated for thousands of years; it takes a few months to reveal their secrets.

Range of TL: 1,000-800,000 years with the 800,000 years heavily dependent on Dose Rate. Most samples have a practical application of 1,000 to 500,000 years.

Range of OSL: 10 - 175,000 years.

USGS lab: In operation since 1992. Latest equipment from Riso Labs offering Blue-light OSL capability. Specializes in all geological applications, with published results mostly in the western U.S..

Contact: SHANNON MAHAN, Box 25046, MS 974, Denver Federal Center, Denver, CO 80225, E-mail: (smahan @ usgs.gov)