Ágnes Novothny

Fluvial and aeolian landscape evolution in Hungary - Results of the last 20 years research

Present study provides a review of the latest results on fluvial and aeolian landscape evolution in Hungary achieved by our team during the last 20 years. – The Hungarian river terrace system and its chronology was described with special emphasise on the novel threshold concept. A revised terrace system was created by the compilation of novel terrace chronology and MIS data. Evolution of river terraces was not only governed by climatic factors but tectonic ones too. Incision rate of the Danube, and uplift rate of the Transdanubian Range (TR) was around 0.1-0.3 mm/a in the marginal zones of the TR (mostly based on the published U-series data) and was above 1 mm/a in its axial zone (based on 3 He exposure age dating of strath terraces). – According to a detailed geomorphological investigation of the different channel-planform morphologies in the Middle Tisza region and Sajo-Hernad alluvial fan, six phases of river pattern change and four incision periods were detected during the last 20,000 years. – Wind polished rock surfaces dated by in situ produced cosmogenic 10 Be suggest that deflation was active in Hungary as early as 1.5 Ma ago. According to these exposure age data, Pleistocene denudation rate of the study area (Balaton Highland) was 40-80 m/Ma. – In sand covered areas the alternations of wind-blown layers and buried fossil soils provide information about climate and environment changes. In this study, periods of sand movement were mostly determined by optically stimulated luminescence (OSL) dating methods and five aeolian sand accumulation periods were recognised during the last 25 000 years. – A new loess stratigraphical view was elaborated using the most recent dating methods (luminescence, AAR). The lower part of Mende Upper (MF 1-2 ) pedokomplex is suggested to represent the last interglacial period (MIS 5e). During the last interglacial/glacial period (MIS 5 - MIS 2) several soil-forming periods existed but the preservation of these paleosoils is variable depending on their paleogeomorphological position.

Late Pleistocene millennial scale cycles of aeolian sedimentation in the Dunaszekcső loess record, south Hungary: preliminary data and interpretations

Millennial scale warm-cold oscillations in air temperature over Greenland and rapid sea surface temperature changes were recorded in ice cores and North Atlantic sediments for the last glaciation. These events must have been associated with profound environmental changes in Europe, and indeed, millennial scale oscillations in grain size records have been found in loess deposits of Europe and Asia. Unfortunately, the timing of these events are still unresolved due to chronological uncertainties on the order of thousands of years. Major problems are the low precision of luminescence ages and the general lack of materials that can reliably be dated using 14 C. As demonstrated by 24 OSL/IRSL ages, the Dunaszekcső loess-palaeosol sequence is an archive of climate and environmental changes of the last glacial-interglacial cycles. For the upper part of the section (<33 cal yr BP), the chronology is further refined based on charcoal and mollusc shell radiocarbon ages. Here we show that AMS 14 C ages of some mollusc species having small shells (<10 mm) seem to yield reliable ages in a comparison with charcoal 14 C ages. These radiocarbon ages are consistent, have low variability and define age-depth models with sufficient precision to examine the timing of paleoenvironmental changes in the context of North Atlantic climatic variations.