DATING BY LUMINESCENCE OF ANCIENT MEGALITHIC MASONRY

Abstract

An updated abridgement of the novel thermoluminescence(TL) technique that dates monuments made by large stone blocks, as well as stone objects, is made. During the process of stone block preparation (cutting and carving,or sculpturing) and prior its construction, the solar radiation(UV and optical spectrum) bleaches the optically sensitive electron traps in the carved surface down to a variable depth. During exposure for a time interval the sunlight sets the light-sensitive TL clock to zero.If the stone is made of granite, basalt,sandstone rock types, the sun-exposed interval in minutes is enough to erase luminescencent traps. However, for calcitic stones this period varies between several hours to dozen of hours. In the latter case a technique is devised to estmate the bleaching time in antiquity, and thus the residual value, which serves as the 'zero time' upon which luminescence builds up until today.

The total archaeological equivalent dose or total luminescence acquired by the minerals in the particular stone is measured by Optical Stmulated Luminescence (OSL) techniques, while for calcitic stones only thermoluminescence is at present applied with involved errors of the order of 7-15% (Liritzis 2001). A new quartz/ feldspar technique for limestone monuments is presented enabling their dating by established single aliquot /single gain OSL methodology.

Application examples from Greece covering the period 34 millennium to classical time,and the potential to dating world megalithics is explored.