The Application of Luminescence to Tectonics: Improvements to Luminescent Dating and its Utilization in High-Energy Depositional Environments
- Author(s): Lawson, Michael
- Advisor(s): Rhodes, Edward J.;
- Yin, An
- et al.
The dissertation presents improvements made to luminescent dating in tectonic areas, with examples of the application of luminescence to tectonic questions north of Death Valley, CA. The study of tectonics is incomplete without an understanding of fault processes through time. This can be difficult in areas with limited Quaternary age control. The technique of luminescence dating can provide absolute ages, but tectonic areas tend to exhume fresh material that can have poor luminescent properties. The “quartziness test” is outlined which numerically accesses the contamination of feldspar grains within quartz samples for small aliquots and single grain measurements. A new illumination protocol called Sinusodially Modulated Optically Stimulated Luminescence (SM-OSL) is presented which can also address contamination through trap component analysis and provides more rapid measurement then tranditional Linearly Modulated Optically Stimulated Luminescence (LM-OSL)
Post- infrared infrared-stimulated luminescence (pIRIR) has been shown to be effective dating protocol that does not fade to the same degree as traditional IRSL measurements. Post-IRIR is applied to several studies pairing luminescence dating with geomorphic analysis. In Deep Springs Valley, a series of shorelines have been rotated vertically due to local extension. Two shorelines are dated as having ages of 7.51 ï¿½ 0.67 ka and 10.94 ï¿½ 0.95 ka, suggesting ~0.3 mm/yr vertical slip on the Deep Springs fault. These are comparable to long-term rates of 0.2 mm/yr (vertical and horizontal). In Eureka Valley, a tectonically controlled basin east of Deep Springs, slip recurrence is analyzed by pairing pIRIR with geomorphic modeling to produce a new mass diffusivity constant (κ) of 1.79 m2ka-1. In this area, a 6.1 moment magnitude earthquake occurred on May 17, 1993. Geomorphic modeling of the northern strand of this oblique-normal fault suggests a vertical slip rate of 0.6 mm/yr. Field mapping in the area uncovered a right lateral fault that may be the cause of an observed decrease of slip on the Fish Lake Valley Fault Zone (FLVFZ).