Historical building dating: refinement of established sample preparation protocol

Abstract

Abstract: The application of thermal (TL) and optical (OSL) stimulated luminescence on pottery and building materials has allowed to resolve numer-ous problems in both the fields of retrospective do-simetry and dating. Routine measurements request the registration of TL signals obtained on polymineral fine-grained frac-tion (FG) extracted from pottery sherds and bricks used as building material with the Added Dose (AD) technique. One of the reasons of the dispersion of the lumi-nescence measurements when using this fraction is the variability of relative contents of quartz and feld-spars, which due to their differing behaviour influ-encing the equivalent dose (ED) and therefore its uncertainties. The objective of the present work is the solution of this type of problem using the double Single Ali-quot Regeneration (d-SAR) protocol which is widely used to date geological sediments. This allows the ED determination from the quartz-dominated OSL signals obtained from polymineral fraction. Materials and methods: Using bricks taken from a building which is the objet of a specific dating pro-gram, we measured some samples prepared and measured with different techniques in order to deter-mine which technique allows as to obtain date with minimum dispersion. The samples were prepared with FG (4-11 micron) technique and measured with standard AD to obtain TL signals and with d-SAR to register OSL signals. This last methodology requested some adaptation because samples from building materials have low signals and therefore natural doses. The data obtained was compared with those re-corded using OSL emissions of quartz extracted us-ing inclusion technique, QI, (90-150 micron), measured with “classical” SAR protocol. Results: The results from different fractions ex-tracted from bricks using specially adapted FG-OSL-d-SAR methodology, where compared with those obtained by FG-TL-AD and QI-OSL-SAR standard protocols. This comparison showed the prospective for the new approach especially in the chronological determination of historical buildings

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