Application of single-grain OSL to date quartz xenocrysts within a basalt flow, San Francisco volcanic field, northern Arizona, USA

摘要

Previous age estimates for SP Crater in the San Francisco volcanic field in northern Arizona, USA, suggested it erupted 70 ka; however its non-weathered geomorphic character places it as one of the youngest volcanic vents in the region. Samples of quartz xenocrysts were extracted from the SP Crater basalt flows and dated using single-grain dating. Analysis of the luminescence signals indicate they were dominated by medium- to slow-decaying OSL components, which can produce age underestimates if not removed. In order to reduce their contribution, the fast component was deconvolved from the initial OSL signal, a high-temperature bleach (blue-green LED exposure at 280 °C) was added at the end of each measurement cycle and elevated cutheat temperatures were used. Fading tests and crushing experiments indicate no dependence on recovered equivalent dose values. Resultant single-grain quartz xenocryst OSL ages are consistent with the geomorphic character of SP Crater and suggest it erupted 5.5-6 ka. Revision of the age of SP Crater has implications for the eruption recurrence interval in the region and assessment of volcanic hazards in nearby communities.