The potential of using K-rich feldspars for optical dating of young coastal sediments – A test case from Darss-Zingst peninsula (southern Baltic Sea coast)

Abstract

The potential use of a modified elevated temperature post-IR IR (pIRIR) SAR protocol for K-rich feldspar was tested for seven late Pleistocene and Holocene samples from a coastal sediment succession from the southern Baltic Sea (Darss-Zingst peninsula). This modified pIRIR protocol observes a pIRIR signal at 180 °C after the IRSL measurement at 50 °C. After thorough performance testing, equivalent doses (D e) were measured and corrected for the residual doses and fading. The results showed that thermal transfer and residual doses are more significant for pIRIR signal than for quartz OSL and IRSL signal. The calculated K-feldspar ages (IRSL and pIRIR) were then compared with quartz-SAR and two independent radiocarbon ages. The ages of the investigated sediments range from the late Pleistocene (∼13.5 ka) to a few hundred years. The laboratory-fading rate of the pIRIR signal was significantly lower ( g-value of 0–2%/decade) than that of the IRSL (g-values of 3–10%/decade). We observed a systematic overestimation of fading-corrected IRSL ages based on high g-values (>5%), whereas the pIRIR ages showed a good agreement with the quartz ages and with the radiocarbon ages for the well-bleached mid-Holocene and the late Pleistocene samples, suggesting that our modified pIRIR protocol is suitable for well-bleached young sediments. For the incompletely bleached uppermost samples the minimum age model (MAM) was applied. For these samples it is concluded that both IRSL and pIRIR ages derived from K-feldspar overestimated the true burial age.