Harsches Periglazial-Klima am MIS3/MIS2-Übergang im Spiegel mitteleuropäischer Löss-Paläoboden-Sequenzen
Zusammenfassung der Projektergebnisse
The aim of this study is to check the validity of luminescence ages obtained from last glacial-interglacial Polish loess palaeosol sequences (LPSs) by several established current protocols, with respect to sound geomorphological and chronostratigraphic interpretations. We report 38 new optically stimulated luminescence (OSL) ages from fine-grained (4-11 micrometers) quartz separates extracted from four loess palaeosol sequences in Poland, measured in the Bayreuth Luminescence Laboratory, Germany. The investigated sections are situated in Lower Silesia in the southwest (Zaprezyn, Trzebnica Hills, and Bialy Kosciól, Strzelin Hills), the Sandomierz Upland (Zlota) in central Poland, and the Volhynian Upland (Tyszowce) in the east, allowing for regional comparison. From one Silesian section (Bialy Kosciól) 12 new post-infrared infrared stimulated luminescence (pIRIR) ages are presented in addition to the quartz ages of identical sample material. The obtained ages are compared to already published independently elaborated middle-grain (45-63 micrometers) and coarse-grain (90-125 micrometers) quartz ages and pIRIR ages from fine grains produced in the Gliwice Luminescence Laboratory (Poland). This comparison shows that in many cases the middle- and coarse-grain quartz ages underestimate the fine-grain quartz ages, but a general rule has not been able to be established so far, likely due to different geological origin of the quartz grains. Even fine-grain quartz ages >=~ 50 ka may be underestimated with respect to lithostratigraphic expectations. For pIRIR ages, however, no evidence for age underestimates has been found in the studied sections, but they are more easily prone to age overestimates due to unknown residual doses at deposition in a periglacial environment. Basic agreement between the luminescence-based chronologies elaborated in the two involved laboratories can be stated for the first time in contrast to other previous studies. The observed age differences are, however, critical for the accurate time bracketing of geomorphologic and pedostratigraphic features such as ice wedging, thermokarst erosion events, and interstadial soil formations and for their attribution to marine isotope stages. Alternative interpretations are discussed including possible periglacial mirroring of pre-LGM ice advances (Ristinge and Klintholm advances) in the southwestern Baltic Sea area. The uncertainty in luminescence ages from pre-Holocene loess due to fossil ice during permafrost conditions is the major systematic error source which will be addressed but at present is far from an unambiguous solution. The present study focuses on a complex of interstadial soils now labelled L1SS1 and on harsh periglacial climate afterwards and before, yielding some unexpected results for the timing of ice wedging and thermokarst processes. In order not to leave the users alone with the decision about the most credible dating, the suggested way forward is to simultaneously apply various luminescence dating protocols including different quartz grain sizes and pIRIR from fine polymineral grains, as an honest approach to reliable time bracketing of geomorphological processes and stratigraphic events under debate. A refinement of this approach remains challenging as far as the sole reliable dating protocol is not ensured.
Projektbezogene Publikationen (Auswahl)
- New OSL ages from last glacial loess in Silesia, Poland. Geophysical Research Abstracts Vol. 19, EGU2017
Ludwig Zoeller, Antoine Pierre, Jary Zdzislaw, and Moska Piotr
- A refined chronology of the Biały Kościół loess key section (Silesia, Poland) and comparison with other sections in European Lowlands. 20th Congress INQUA Dublin 2019
Ludwig Zoeller, Zdzislaw Jary, Marcin Krawczyk
- Chronostratigraphy of Late Pleistocene loesspalaeosol sequences in Poland – record of discontinuous sedimentation. 20th Congress INQUA Dublin 2019
Zdzislaw Jary, Piotr Moska, Grzegorz Adamiec, Andrzej Bluszcz, Ludwig Zoeller, Pierre Antoine, Marcin Krawczyk, Jerzy Raczyk, Jacek Skurzyński
- Environmental magnetic and colorimetric screening of a last glacial loess profile from Lower Silesia: evidence for a harsh periglacial environment. 20th Congress INQUA Dublin 2019
Christian Laag, Ulrich Hambach, Marcin Krawczyk, Jerzy Raczyk, Zdzisław Jary, Ludwig Zöller
