Investigating age underestimation in the high dose region of optically stimulated luminescence using fine grain quartz
2011 (English)In: Quaternary Geochronology, ISSN 1871-1014, Vol. 6, 33-41 p.Article in journal (Refereed) Published
The age range of the single-aliquot regenerative-dose (SAR) protocol applied to quartz optically stimulatedluminescence (OSL) has become the subject of debate as age underestimations for samples ofEemian age (ca. 125 ka) and older are increasingly reported. In order to investigate the origin of the ageunderestimation, the behaviour of fine grain quartz samples taken from two sites was compared.Sediment from both sites originates in the Alps, with those from Azzano Decimo, northeastern Italy,already displaying a significant age underestimation before reaching the Eemian, while ages for samplesfrom Niederweningen, northern Switzerland, agree with expected ages well beyond the Eemian. Estimateddose (De) values for both sets of samples are up to around 400 Gy, and all meet the usualperformance criteria for testing the reliability of the SAR protocol. De values determined using a sensitivity-corrected multiple aliquot regenerative-dose (MAR) protocol were within 10% of those determinedusing a SAR protocol for both sites, and so could not overcome the significant underestimation seen atAzzano Decimo. Lifetime calculations confirmed the stability of the signal well beyond the age rangerequired at both sites, for both the initial integral as well as that used for an early backgroundsubtraction. The relative percentage contribution of the fast and medium OSL components to the initialintegral remained constant in both the natural signal and similar sized laboratory generated doses. Thequartz OSL from both sites displayed similar characteristics under all analyses and no indication wasfound for the possible origin of the age underestimation seen at Azzano Decimo. In the comparisonsmade between the doseeresponse of both laboratory and naturally generated signals in these samples,no evidence was found to suggest that the presence of the high dose linear region is restricted to thelaboratory. The reliability of quartz OSL ages derived from this part of the curve however, remain inquestion, and require the support of independent age control until a performance criterion can be foundwith which to test it.
Place, publisher, year, edition, pages
2011. Vol. 6, 33-41 p.
Quartz, OSL, Fine grains, Age underestimation, Signal stability, Dose response, Exponential plus linear, Alps
IdentifiersURN: urn:nbn:se:su:diva-66376DOI: 10.1016/j.quageo.2011.12.003ISI: 000301311900004OAI: oai:DiVA.org:su-66376DiVA: diva2:467634