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Polygenesis and gaps? – The potential of Lower Austrian loess-paleosol sequences for reconstruction of Quaternary environments

Tobias Sprafke1, Birgit Terhorst1, Christine Thiel2
1 Institut für Geographie und Geologie - Physische Geographie, Universität Würzburg
2 Department for Geoscience, Nordic Laboratory for Luminescence Dating, Risø DTU, Aarhus University, Denmark & Centre for Nuclear Technologies, Risø Campus DTU, Technical University of Denmark

P 2.11 in Löss und terrestrische Archive

Detailed loess-paleosol sequences resulting from large amounts of dust input in glacial phases and pedogenesis in warmer stages are valuable archives for paleoenvironmental reconstructions of the Quaternary. High resolution data of climate proxies can be used to quantify changes (e.g. Marcovic et al. 2011). To correlate the fairly well resolved plateau loess-paleosol sequences in the Danube Basin with well understood complex sequences of Central Europe, Lower Austria has a geographical key position which will allow for completing the picture of past climate changes and landscape adaptions in Europe. The best preserved archives in Lower Austria are located in leeward positions of the hilly eastern margin of the Bohemian Massif in the region around Krems a.d. Donau. There, the Danube with its terraces, the most important source of regional dust during glacials, leaves the Wachau Valley and enters the Alpine forelands.

Classical sequences (e.g. Krems, Göttweig, Willendorf, and Paudorf) were studied extensively in the middle of the last century (e.g. Fink 1954, 1976), but a satisfying stratigraphy has never been established due to polygenetic overprints and discontinuities of unknown age in the archives. More recently, loess research in Lower Austria experienced some renaissance, mainly triggered by archeological findings (e.g. Neugebauer-Maresch 1993) and advances in dating techniques (Zöller et al. 1994, Thiel et al. 2011a, b).

The ~11 m thick outcrop at the Paudorf locus typicus is famous for two pedocomplexes, one 1 m thick pedocomplex in the upper part, designated as “Paudorfer Bodenbildung” and one over 2 m thick pedocomplex in the lower part. Our studies are the first complete description and interpretation based on luminescence ages presented in Thiel et al. (2011a). Detailed field survey, laboratory analyses (granulometry, carbonate content and color) and micromorphological investigations were carried out in order to understand the processes leading to the genesis of this very complex sequence at a downslope position.

The loess sediment between the pedocomplexes was dated to Oxygen Isotope Stage (OIS) 6. Eolian sedimentation, redeposition and admixture of local material from upslope have been common during the glacial periods. Bleached horizons (‘Nassböden’) within the loess indicate more stable humid conditions. The upper pedocomplex developed during OIS 5. It is a humic horizon (OIS 5c[-a?]) which developed in a redeposited (OIS 5d) Eemian Cambisol (OIS 5e). The genesis of the lower pedocomplex is much more complicated and the timing has not been established yet. It formed during two or more glacial-interglacial cycles, as it is relatively strongly weathered, completely decalcified and very thick. Granular structure and deformed clay illuviations next to gravel and even rock fragments evidence a complex genesis influenced by both warmer stable phases characterized by pedogenesis and phases of (partly solifluidal) redeposition and admixture of local material and dust.

Our research in Paudorf shows that in addition to high-resolution geochemical and sedimentological data and reliable dating techniques detailed field survey and micromorphological studies are crucial to gain a complete understanding for polygenetic archives. This process-oriented, more qualitative knowledge allows for correlations with other loess-paleosol sequences where fairly reliable high resolution data of climate proxies is available.

 

References

Fink, J. (1954): Die fossilen Böden im österreichischen Löß. – Quartär 6: 85-108.

Fink, J. (1976): Exkursion durch den österreichischen Teil des nördlichen Alpenvorlandes und den Donauraum zwischen Krems und der Wiener Pforte. – Mitteilungen der Kommission für Quartärforschung der Österreichischen Akademie der Wissenschaften 1. 113 pp.

Marković, S.B., Hambach, U., Stevens, T., Kukla, G.J., Heller, F., McCoy, W.D., Ochses, E.A., Buggle, B.& Zöller, L. (2011): The last million years recorded at the Stari Slankamen (Northern Serbia) loess-palaeosol sequence: revised chronostratigraphy and long-term environmental trends. – Quaternary Science Reviews 30: 1142-1154.

Neugebauer-Maresch, C. (1993): Zur altsteinzeitlichen Besiedlungsgeschichte des Galgenberges von Stratzing/Krems - Rehberg. – In: Archäologie Österreichs. - Mitteilungen der Österreichischen Gesellschaft für Ur- und Frühgeschichte 4: 10-19.

Thiel, C., Buylaert, J.-P., Murray, A. S., Terhorst, B. Tsukamoto, S., Frechen, M., Sprafke, T. (2011a): Investigating the chronostratigraphy of prominent palaeosols in Lower Austria using post-IR IRSL dating. – E & G Quaternary Science Journal 60/1: 137-152.

Thiel, C., Buylaert, J.-P., Murray, A. S., Terhorst, B., Hofer, I., Tsukamoto, S., Frechen, M. (2011b). Luminescence dating of the Stratzing loess profile (Austria) - Testing the potential of an elevated temperature post-IR IRSL protocol. – Quaternary International 234: 23-31.

Zöller, L., Oches, E. A. & McCoy, W. D. (1994): Towards a revised chronostratigraphy of loess in Austria with respect to key sections in the Czech Republic and in Hungary. – Quaternary Geochronology (Quaternary Science Reviews) 13: 465-472.

Overview of the studied profiles at Paudorf locus typicus
Overview of the studied profiles at Paudorf locus typicus

Letzte Änderung 26.07.2012