Luminescence dating of eolian and fluvial archives in the Middle and Lower Danube catchment and the paleoenvironmental implications

The presented doctoral dissertation uses luminescence dating techniques to reconstruct the paleoenvironmental and paleoclimatic conditions in the Middle and Lower Danube catchments, especially during the period of anatomically modern human emergence. It is embedded in the Collaborative Research Center 806 "Our Way to Europe - Culture-Environment Interaction and Human Mobility in the Late Quaternary". To increase ones understanding of the environmental conditions during the last 150 ka, four loess-paleosol sequences and one fluvial section were investigated. The research area is located at the junction of Atlantic, Mediterranean and continental climatic regimes, which makes it sensitive to climatic changes. Moreover, the geographical position between Asia, Near East and Central Europe and the vast river network connecting these regions, make the area a favorable pathway for anatomically modern human migration. The sediments of the five investigated sites cover various time frames from the penultimate interglacial (MIS 7) to the Holocene. The methodological approach focused on optically stimulated luminescence dating, but for some of the sections the geochronological methods were combined with physical, biological, and geochemical proxy data to reconstruct the paleoenvironmental conditions. In the Middle Danube Basin three sites were investigated. The Ságvár loess-paleosol sequence is located in the central basin and its sediments accumulated during the last glacial maximum from approximately 25 − 17 ka. The sequence can be correlated to two Gravettian occupation layers. Paleoenvironmental conditions changed from short grassland (25 − 24 ka), to a mosaic of mammoth steppe, forest steppe, continental steppe, and tundra (25 − 18 ka), towards continental grassland ( 130 ka in the lower 7 m of the profile. These ages are in contrast with the expectation of a well developed MIS 5 paleosol in the lowermost part of the section. Several hypothesis trying to explain these findings were explored, but could not be solved satisfactorily.The doctoral dissertation demonstrates that a detailed investigation is necessary in order tobuild robust age models. For quartz samples, the importance of preheat plateau and dose recovery tests are pointed out. Some samples of Stalac and Urluia, that have high equivalent doses, show falling preheat plateaus, while the quartz samples of Crvenka-At are already in saturation at very low doses. These findings indicate that these samples cannot be dated reliably using the SAR protocol. Most samples of this dissertation were dated with the pIRIR protocol. The necessary first IR stimulation temperature tests, dose recovery tests, fading experiments and residual dose measurements are presented. It is demonstrated that polymineral and kalifeldspar samples can be dated with higher doses than quartz. However, it remains unclear up to which dose range age estimates are reliable. E.g. at Urluia, the lowermost samples approach saturation even within the polymineral fraction and at Stalac the lowermost two ages underestimate the accepted correlative stratigraphy. Overall, this doctoral dissertation highlights the importance of luminescence dating in paleoenvironmental and geoarcheological studies. It demonstrates how the combination of multiple proxy data enhances the paleoenvironmental interpretations, and identifies remaining challenges. The paleoclimatic dynamics in the research area at the junction of Atlantic, Mediterranean and continental climatic regimes are discussed. Finally, paleoenvironmental conditions during phases of Upper Paleolithic occupation were equally diverse highlighting anatomically modern humans’ ability to adapt to changing paleoenvironments

Direct and indirect luminescence dating of tephra: A review

In Quaternary studies, tephras are widely used as marker horizons to correlate geological deposits. Therefore, accurate and precise dating is crucial. Among radiometric dating techniques, luminescence dating has the potential to date tephra directly using glass shards, volcanic minerals that formed during the eruption or mineral fragments that originate from the shattered country rock. Moreover, sediments that frame the tephra can be dated to attain an indirect age bracket. A review of numerous luminescence dating studies highlights the method's potential and challenges. While reliable direct dating of volcanic quartz and feldspar as a component in tephra is still methodically difficult mainly due to thermal and athermal signal instability, red thermoluminescence of volcanic quartz and the far-red emission of volcanic feldspar have been used successfully. Furthermore, the dating of xenolithic quartz within tephra shows great potential. Numerous studies date tephra successfully indirectly. Dating surrounding sediments is generally straightforward as long as samples are not taken too close to the tephra horizons. Here, issues arise from the occurrence of glass shards within the sediments or unreliable determination of dose rates. This includes relocation of radioelements, mixing of tephra into the sediment and disregarding different dose rates of adjacent material