Quaternary terrace formation in response to climate, regional uplift and local normal faulting: The Danube terrace staircase of Vienna

Abstract

Quaternary terrace sequences can be observed along many mid to high latitudinal rivers, often reflecting a distinct, climate-related cyclicity of the fluvial system in uplifting regions. They are also essential landforms in many continental basins even though local basin subsidence may counteract an existing regional uplift trend. Glacial and periglacial processes may amplify events of river aggradation, with associated terraces providing clear stratigraphic markers. In this study, we explore the opposing lithospheric forces, regional uplift vs. local normal faulting, along a perialpine section of the Danube River, which is strongly affected by a 100-ka depositional cyclicity during the Quaternary. Within the city of Vienna, the Danube formed an extensive terrace staircase across a continental-scale normal fault. This fault demarcates the transition of the Eastern Alps and the Miocene Vienna Basin. Its Quaternary activity remained ambiguous and its impact on terrace configuration largely unexplored. Solifluction processes over several glacial-interglacial cycles typically led to thick colluvial deposits along terrace slopes, resulting, together with the anthropogenic overprint, in obliteration of the terrace morphology. To constrain terrace geometry, elevation and decipher fault kinematics we used electrical resistivity tomography, drill log and historical outcrop data. We applied morphostratigraphic age modelling supported by terrestrial cosmogenic radionuclide burial and luminescence dating to derive rates of uplift and subsidence. Results show how long-wavelength uplift and concomitant normal faulting have controlled terrace development and Quaternary landscape evolution. This study provides clear evidence for fault activity within the city of Vienna.