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Testing the application of post IR-IRSL dating to fine grain waterlain sediments
Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
2012 (English)In: Quaternary Geochronology, ISSN 1871-1014Article in journal (Refereed) Published
Abstract [en]

The polymineral fine grain fraction of a set of ten known age samples were used to test the suitability ofelevated temperature post-IR infrared stimulated luminescence (pIRIR) to date waterlain sediments inSwitzerland. Equivalent Dose (De) values were obtained using elevated temperatures of 225 C (pIRIR225)and 290 C (pIRIR290) and IRSL50/225 (preceding measurement of pIRIR225), and these displayeda systematic increase with increasing stimulation temperature, which brought those derived from thepIRIR protocols into saturation for the older half of the samples (>100 ka). Significant residuals wererecorded for the pIRIR signals, and these were found to further increase following attenuation of thebleaching source confirming that these signals are harder to bleach than the IRSL measured at 50 C.Fading tests recorded g-values of between 1 and 4%, and displayed no obvious decrease with increasingstimulation temperature. For the younger half of the samples, fading corrected ages for all protocolsresulted in overestimation compared to robust independent dating for all samples, and draw intoquestion the relationship of fading measured in a laboratory generated signal to that which is naturallygenerated. Uncorrected IRSL50/225 ages for all samples were in good agreement with independent dating,but still displayed a general overestimation using pIRIR signals. These overestimations may largely bedue to the significant residual doses resulting from the harder to bleach nature of the elevatedtemperature signal, and present a considerable problem when dating waterlain sediments. A considerablechallenge when using the pIRIR signal is to be able to separate the effects of both residual doses andfading and confirm that one is not masking the other. Despite this, the pIRIR protocols were successful atone site, although they offered no benefit compared to dating with more conventional luminescencesignals. A comparison of De values derived from a standard IRSL signal to that from IRSL50/225, suggestthat the latter overestimates by w10% due to a decrease in sensitivity of the sample prior to measurementof the test dose.

Place, publisher, year, edition, pages
Keyword [en]
Post IR-IRSL Polymineral fine grains Waterlain Residual dose Age overestimation Fading tests
National Category
Geosciences, Multidisciplinary
Research subject
Quarternary Geology
URN: urn:nbn:se:su:diva-85254OAI: diva2:583151
Available from: 2013-01-07 Created: 2013-01-07 Last updated: 2013-01-07Bibliographically approved

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