Effectiveness of natural zeroing of the thermoluminescence in sediments

Abstract

The last exposure to sunlight of detrital feldspars and quartz grains in Quaternary sediments can be dated directly by thermoluminescence (TL) methods, but the effectiveness of zeroing of the light-sensitive TL signal by daylight varies widely, depending upon details of the sedimentation processes. To document this variability and to help develop objective criteria for future sample selection and laboratory procedures, several eolian, fluvial, marine deltaic, and lacustrine samples from less-than-100-year-old deposits as well as suspensions from sediment plumes, have been collected and analysed. Underwater spectral irradiance was measured during recovery of suspensions. TL properties of polymineralic (feldspar dominated) 2-4 μm and 4-11 μm size fractions were measured in the laboratory. Some simple optical-bleaching tests that have a potential use in sample selection and in provenance studies of some surficial detrital sediments are also reported. Finally, a simple mathematical model is presented that helps account for the gross features of the observed bleaching-response curves. -from Author