Abstract
The loess-palaeosol section Achajur is part of the Sevkar loess area in north-eastern Armenia and comprises three prominent pedocomplexes with intercalated loess units, probably spanning at least three glacial-interglacial cycles. With its central position between the Black Sea and the Caspian Sea, the Sevkar loess area serves as important bridge between loess sections in southeastern Europe and Central Asia. Establishing a numerical chronology of the Achajur loess section enables correlation with other loess-palaeosol sections and a palaeoenvironmental reconstruction of the region. In this paper, we focus on the chronology of the last glacial-interglacial cycle using luminescence dating on fine grain (4–11 µm) material. We compare two post-IR-IRSL protocols on polymineral fine grain using different stimulation temperatures, in order to evaluate the influence of fading and potential unbleachable residuals on our samples. For a backup of the younger ages (<50 ka), we also applied a single aliquot protocol on the quartz fine grain fraction. The results indicate that the upper loess unit was deposited during MIS3 and 4, while MIS2 ages are not present. The underlying pedocomplex and loess unit fall into MIS5 and MIS6, respectively. This confirms that the loess was deposited during dry phases and pedocomplexes formed during wetter phases, as is also shown by comparison with other palaeoenvironmental proxies from the area.
Highlights
Loess-palaeosol sequences (LPS) play an important role in reconstructing Quaternary climates and environments
Assuming that the quartz ages are reliable in this age range, this argues for negligible fading of the polymineral fine grain ages for samples
Sample Gi549 below the P1 pedocomplex shows a discrepancy between the quartz and the polymineral fine grain fraction, most likely caused by an underestimation of the quartz fine grain fraction
Summary
Loess-palaeosol sequences (LPS) play an important role in reconstructing Quaternary climates and environments They provide information on past climate conditions by comparison with Marine Isotope Stages (MIS) and pollen records In the recent decade feldspar luminescence protocols have been developed which decrease or even overcome the problem of fading in feldspar dating These protocols use a first lower temperature IRSL which empties luminescence traps prone to fading, followed by a second or consecutive IRSL steps at elevated temperatures, which sample the luminescence of more stable traps (Thomsen et al, 2008; Buylaert et al, 2009; Li and Li, 2011, 2012; Thiel et al, 2011; Zhang and Li, 2020). There is so far no general protocol for feldspar samples, and a wide range of protocols and approaches exist and their application is dependent on the individual local geoconditions
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