Luminescence dating of the PASADO 5022-1D core using IRSL signals from feldspar
In this paper we develop and test a luminescence chronology for the PASADO core 5022-1D taken in the Laguna Potrok Aike Maar Lake. Because of unsuitable quartz OSL characteristics, sand-sized K-feldspar extracts were chosen as a dosimeter and the dose was measured using a recently developed post-IR IRSL (pIRIR290) measurement protocol. Using this approach we were able to access a stable signal and thus avoid the ubiquitous problem of signal instability in feldspar dating. Extensive laboratory tests show that the chosen pIRIR290 protocol is applicable to these samples. We also develop a new criterion based on the known relative bleaching rates of the conventional IRSL signal (IR50) and the pIRIR290 signals and the relationship between the resulting equivalent doses; this is used to identify and reject poorly-bleached samples. Fourteen samples out of 35 were rejected based on this criterion; the resulting age-depth profile is self-consistent, increases smoothly with depth and is in agreement with the independent age control (Reclús, Mt Burney and Hudson tephras) at the top of the core. Our new luminescence chronology suggests the 5022-1D core reaches back to ~65 ka at ~96 m below lake floor.