East Carolina University * Luminescence Dosimetry Laboratory
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Optical ages were determined for samples from delta and sand dune deposits associated with Glacial Lake Hitchcock near Amherst, Massachusetts using the single aliquot regenerative-dose (SAR) optically stimulated luminescence (OSL) technique. However, a strong unstable ultrafast component caused initial rejection of data from a large proportion of aliquots. A linearly modulated blue OSL (LM-OSL) study was undertaken on the sample with the strongest ultrafast component, with the data modelled using the equation of Bulur et al. (2000) as 5 fast, medium and slow components, and 1 ultrafast component.
The ultrafast component dominates the LM–OSL, almost completely obscuring the fast component. As suggested by Jain et al. (2003), the thermal stability of the ultrafast component was examined, using temperatures between 180°C and 300°C (10s preheat) and extended preheats at 300°C (10-60s). Preheats of sufficient stringency to remove the ultrafast component (300ºC for ≥ 20s) also strongly depleted the fast component. The stabilities of the ultrafast and fast components were also examined as a function of low-power, short-duration continuous-wave bluelight stimulations (CW-OSL). A 3.0s, 0.35 mW.cm-2 (1% diode power), 125ºC preshine in combination with a 240ºC/10s preheat removed the ultrafast component, and caused significantly less fast component depletion than more stringent preheats. Data from a modified SAR procedure in which each OSL measurement is preceded by a low-power preshine have improved recycling ratios and reduced equivalent dose (De) errors. De values and resultant ages determined using the preshine-based SAR proposed here are consistent with regional age constraints on the delta and sand dune samples from Glacial Lake Hitchcock.
Goble, R.J. and Rittenour, T.M., 2006, A Linear Modulation OSL Study of the Unstable Ultrafast Component in Samples from Glacial Lake Hitchcock, Massachusetts, USA: Ancient TL, v. 24, p. 37-46.