SOLAR BLEACHING OF THERMOLUMINESCENCE OF CALCITES

Original results of solar bleaching of thermoluminescence (TL) of twel ve Greek calcitic (limestone, marble) stone profiles have been obtaine d. The residual TL signal due to sunlight exposures (zero to 130 h) di ffers in samples, but in general follows an exponential decay form con sisting of one or two components. The first component bleaches fast wi thin the first 30-70 h and the second component bleaches slowly; the l atter, occasionally, formed a residual plateau. The first exponential term decays with different rates ranging between 1-6 (%/h) for the 280 degrees C TL peak and slower, 0.1-0.3 (%/h) for the 350 degrees C TL peak. Phototransferred TL (PTIZ) of the 280 and 350 degrees C TL peaks giving rise to a PTIZ peak at around 180 degrees C, was observed. The residual TL glow curve shape variation as a function of daylight expo sure time is provisionally used to further develop the method of datin g carved megalithic masonry [I]. The solar bleached TL signal of calci tes provides leached TL curves characteristics which inhere useful inf ormation regarding dating of calcitic stones derived from archaeologic al sites, and contribute to the complex luminescence phenomenon in cal cites.