Luminescence-chronology of the loess palaeosol sequence Toshan, Northern Iran - A highly resolved climate archive for the last glacial-interglacial cycle

Loess-palaeosol sequences are highly resolved archives for palaeoenvironmental reconstruction and build an important link to correlate European and Central Asian loess sequences. For the loess palaeosol sequence at Toshan, Northern Iran, a luminescence-based chronological framework was established. The timing of dust accumulation and soil formation was investigated and thereby information on changes in palaeoenvironmental conditions in the region obtained. For luminescence dating, the 4-11 μm grain size fraction was used and the pIRIR290 approach was applied to polyminerals. Tests concerning bleachability, dose recovery and anomalous fading were conducted. The results show that residual doses have only minor influence on the determination of the equivalent dose. The Eemian (MIS 5e) soil seems to be preserved but a chronological classification based on luminescence ages for this soil remains difficult. The pIRIR290 age estimates from the lower part of the profile range from 104 ± 9 to 127 ± 8 ka. Luminescence ages from the central profile-part point to an increase in dust accumulation starting around the MIS 4/MIS 3 transition. Furthermore, a chronological framework for interstadial soils was developed indicating e.g. soil formation at around 40 ka during MIS 3 and 26 ka during MIS 2. The top part of the profile was dated to about 22 ka. The age estimates show that the Toshan loess profile is a highly resolved loess record providing a valuable climate archive for the last glacial-interglacial cycle reflecting several climatic shifts represented by dust accumulation or enhanced degrees of soil formation (stadials and interstadials).