Central Vienna Basin Research Articles

Regional mudstone compaction trends in the Vienna Basin: top seal assessment and implications for uplift history

Seal quality assessment is not only essential in petroleum systems studies but also in the context of other geo energy applications such as underground hydrogen storage. Capillary breakthrough pressure controls top seal capacity in the absence of faults or other discontinuities. In basins that lack measured capillary pressure data (e.g., from drill cores), regional compaction-porosity trends can be used as a first prediction tool to estimate the capillary properties of mudstones. Mathematical compaction models exist but need to be calibrated for each basin. This study aims to establish a compaction trend based on theoretical models, then compare it with theoretical maximum hydrocarbon column heights inferred from true measured capillary pressure curves. Middle to upper Miocene mudstone core samples from the Vienna Basin, covering a broad depth interval from 700 to 3400 m, were investigated by X-ray diffractometry, with an Eltra C/S analyzer, and by Rock–Eval pyrolysis for bulk mineralogy, total organic carbon, and free hydrocarbon contents. Broad ion beam—scanning electron microscopy, mercury intrusion capillary porosimetry, and helium pycnometry were applied to obtain pore structural properties to compare the mathematical compaction models with actual porosity data from the Vienna Basin. Clear decreasing porosity depth trends imply that mechanical compaction was rather uniform in the central Vienna Basin. Comparing the Vienna Basin trend to global mudstone compaction trends, regional uplift causing erosion of up to ~ 500 m upper Miocene strata is inferred. A trend of increasing Rock–Eval parameters S1 and production index [PI = S1/(S1 + S2)] with decreasing capillary sealing capacity of the investigated mudstones possibly indicates vertical hydrocarbon migration through the low-permeable mudstone horizons. This observation must be considered in future top-seal studies for secondary storage applications in the Vienna Basin.

Late miocene evolution of the Paleo-Danube Delta (Vienna Basin, Austria)

The first deltas of the Paleo-Danube formed around 11.5 Ma ago along the northwestern margin of the Vienna Basin, during a lowstand of Lake Pannon. We present a detailed description of the depositional architecture of five individual lobes of these deltas in the Austrian part of the central Vienna Basin based on the integration of 3D seismic surveys and well-log data, covering an area of about 600 km2. Based on geometry, steep clinoforms and the development of beach ridges, the delta is classified as mostly river-dominated with significant influence of wave-reworking processes. The development and shifts of individual lobes suggest a stepwise northward movement of the delta system, which is discussed in relation to a stepwise activity of regional fault systems. True vertical depth measurements between topset and bottomset deposits document a decrease of lake water depth from about 180 m during the early phase of delta formation at 11.5 Ma down to about 100 m during its mature phase. A major lake level rise of Lake Pannon around 11.3 Ma caused the flooding of the margins of the Vienna Basin, resulting in back stepping of fluvial deposits into the North Alpine Foreland Basin, which led to the termination of delta deposition in the study area. The Paleo-Danube delta of the Vienna Basin is comparable in many ways to the Holocene to modern Danube delta, located in the Black Sea. Size, sediment volume and speed of progradation of the lobes, however, indicate, that this primeval delta was distinctly smaller than its modern successor and had a much smaller sediment load.

Miocene lithostratigraphy of the northern and central Vienna Basin (Austria)

AbstractFor the first time, a concise lithostratigraphic scheme for the lower and middle Miocene (Ottnangian – Badenian) of the northern and central Vienna Basin is proposed, which is based on the integration of core-material, well-log data and seismic information from OMV. For all formations and members type sections are proposed, geographic distribution and thickness are provided, typical depositional environments and fossils are described and age constraints are discussed. This time frame allows for a more reliable calculation of sedimentation rates. This in turn might be important for the reconstruction of the tectonic history of the Vienna Basin as we do not see fundamental differences between the piggy-back stage and the subsequent pull-apart regime. Following lithostratigraphic units are formalized herein and/or are newly introduced: Bockfließ Formation (Ottnangian), Aderklaa Formation, Gänserndorf Member and Schönkirchen Member (Karpatian), Baden Group, Rothneusiedl Formation and Mannsdorf Formation (lower Badenian), Auersthal Formation, Matzen Formation, Baden Formation, Leitha Formation (middle Badenian) and Rabensburg Formation (upper Badenian).

Challenges in constraining ages of fluvial terraces in the Vienna Basin (Austria) using combined isochron burial and pIRIR225 luminescence dating

Burial dating with terrestrial cosmogenic nuclides and luminescence dating techniques have become two powerful tools to temporally constrain Quaternary deposits. A combination of both methods at the same geological setting has rarely been realized to date, although their viable time frames overlap by several tens of thousands of years. When Middle Pleistocene sediments with depositional ages ranging around ca. 120 ka to ca. 300 ka are targeted, both methods are employed, but come towards their lower and upper limits, respectively. A combined dating approach can be worthwhile at this age range and allows not only exploring the edges of both methods, but holds the opportunity to do a cross-check of results at an age spectrum, where both dating techniques are at risk to become fuzzy.Here we present a case study where numerical ages of two Middle Pleistocene terraces located in the Vienna Basin were generated by combining burial and luminescence dating. A variety of processes, such as changing sediment input rates, erosion, and tectonics controlled the formation of fluvial terraces in the basin and shaped its complex modern surface. Age correlation of the evolved mosaic of blocks and dislocated sediment bodies is challenging and requires quantitative geochronological information in order to establish a coherent terrace stratigraphy. Luminescence and burial samples originating from two fluvial terraces, the lower Gaenserndorf terrace (GDT) and the higher Schlosshof terrace (SHT), were analyzed and evaluated. Luminescence and burial ages at the GDT site are in good agreement and suggest a depositional age of 140 ± 170 ka bracketed by pIRIR225 luminescence ages ranging from 120 ± 10 ka to 260 ± 30 ka. Luminescence samples at the SHT site are in saturation, but provide minimum ages, which are coherent with the burial dating result of 340 ± 170 ka. The new numerical ages indicate that the vertical offset between the GDT site and the SHT site was not purely caused by fault activity, but suggest two independent episodes of sediment accumulation.Besides providing new insights into the stratigraphic and morphological configuration of the central Vienna Basin area, the cosmogenic nuclide data set is compelling from a methodological point of view. At the GDT site, several samples exhibited 26Al/10Be nuclide ratios exceeding the surface production ratio of 6.75. Even though affected samples were excluded from burial age calculations, a detailed investigation on possible scenarios, which could have caused an upwards shift of 26Al/10Be ratios, was carried out.

Active tectonics and geomorphology of the Gaenserndorf Terrace in the Central Vienna Basin (Austria)

In the central Vienna Basin, the area north of the River Danube is dominated by large river terraces consisting mainly of coarse sandy gravels and sand deposited by the Danube and the Morava River. IRSL dating for the terrace body yielded minimum ages from about 200 to 300 ka. The terrace deposits are locally covered with loess and aeolian sand of the last glacial period revealing OSL/IRSL ages of about 15 ka.The terraces are dissected by a system of normal faults. One of these faults, the Aderklaa-Bockfliess Fault, was investigated in 2014 by paleoseismological trenching. Eventually, the exact fault location and its vertical offset of 10 m were defined by combining electrical resistivity measurements and the analysis of remote sensing data.In addition, at the northern part of this so-called Gaenserndorf terrace, high-resolution digital terrain models based on LIDAR measurements show landforms comparable with relief features resulting from permafrost degradation. Large elongated and clam-shaped depressions are interpreted as basins of former thermokarst lakes. Current dry valleys are interpreted as the Pleistocene drainages of the terrace surface. The cryogenic morphology is preserved only in the elevated parts of the terrace and therefore in the footwall of the bounding normal faults. In contrast, Quaternary basins of the hanging wall are filled with up to 40 m thick Pleistocene and Holocene growth strata. Therefore, most characteristics of the recent geomorphology can be interpreted as a result of overlapping neotectonic processes and permafrost degeneration during the Pleistocene.

BasinVis 1.0: A MATLAB®-based program for sedimentary basin subsidence analysis and visualization

Stratigraphic and structural mapping is important to understand the internal structure of sedimentary basins. Subsidence analysis provides significant insights for basin evolution. We designed a new software package to process and visualize stratigraphic setting and subsidence evolution of sedimentary basins from well data. BasinVis 1.0 is implemented in MATLAB®, a multi-paradigm numerical computing environment, and employs two numerical methods: interpolation and subsidence analysis. Five different interpolation methods (linear, natural, cubic spline, Kriging, and thin-plate spline) are provided in this program for surface modeling. The subsidence analysis consists of decompaction and backstripping techniques. BasinVis 1.0 incorporates five main processing steps; (1) setup (study area and stratigraphic units), (2) loading well data, (3) stratigraphic setting visualization, (4) subsidence parameter input, and (5) subsidence analysis and visualization. For in-depth analysis, our software provides cross-section and dip-slip fault backstripping tools. The graphical user interface guides users through the workflow and provides tools to analyze and export the results. Interpolation and subsidence results are cached to minimize redundant computations and improve the interactivity of the program. All 2D and 3D visualizations are created by using MATLAB plotting functions, which enables users to fine-tune the results using the full range of available plot options in MATLAB. We demonstrate all functions in a case study of Miocene sediment in the central Vienna Basin.

3D visualization of the sedimentary fill and subsidence evolution in the northern and central Vienna Basin (Miocene)

3D visualization of the sedimentary fill and subsidence evolution in the northern and central Vienna Basin (Miocene)

Identifying fault segments from 3D fault drag analysis (Vienna Basin, Austria)

The segmented growth of the Markgrafneusiedl normal fault in the late Miocene clastic sediments of the central Vienna Basin (Austria) was investigated by construction of a detailed three-dimensional (3D) structural model. Using high resolution 3D seismic data, the fault surface and marker horizons in the hanging wall and the footwall of the Markgrafneusiedl Fault were mapped and orientation, displacement and morphology of the fault surface were quantified. Individual, fault segments were identified by direct mapping of the deflection of the marker horizons close to the fault surface. Correlating the size of the identified segments with the magnitude of fault drag and displacement distribution showed that fault evolution progressed in several stages. The proposed method allows the detection of segments that are not recorded by the magnitude of displacement or fault morphology. Most importantly, detailed mapping of marker deflections in the hanging wall could help to constrain equivalent structures in the footwall, which may represent potential hydrocarbon traps.

Lower Miocene structural evolution of the central Vienna Basin (Austria)

The tectonic evolution of the Vienna Basin overlying the Alpine-Carpathian fold and thrust belt includes two stages of distinct basin subsidence and deformation. The earlier phase contemporaneous with thrusting of the Alpine-Carpathian floor thrust is related to the formation of a wedge-top basin (“piggy-back”), which was connected to the evolving foreland basin (Lower Miocene; c. 18.5–16 Ma). This stage is followed by the formation of a pull-apart basin (Middle to Upper Miocene; c. 16–8 Ma). Sediments of the latter unconformably overly wedge-top basin strata and protected them against erosion. Analyses of subcrop data from the central part of the basin focus on the complex stratal geometries and tectonics of the Lower Miocene wedge-top basin. During that period the overriding allochthon is characterised by syntectonic subsidence and sedimentation, out-of-sequence fold-thrusting, normal faulting and sinistral wrenching. All types of faults are dated as Lower Miocene by the occurrence of growth strata and the age of overlying post-tectonic sediments related to the pull-apart basin stage. Faults mapped in 3D seismic are compared to faults along the SW margin of the Vienna Basin. They prove that complex Lower Miocene deformation occurred in large parts of the Austroalpine overriding nappes concurrent with thrusting at the Alpine floor thrust and in the Molasse unit. The structural analysis of 3D seismic data shows that Lower Miocene sediments of the Ottnangian and Karpatian stage unconformable overly the Alpine-Carpathian thrust nappes with a thickness of up to 1500 m. Geometries include onlaps to the basin floor, internal unconformities and toplaps to the overlying Middle Miocene sediments. These toplaps are the results of tilting and subsequent erosion of the sediment pile by out-of-sequence thrusting in the central part at the Karpatian–Badenian transition (c. 16.3 Ma) prior to the onset of pull-apart deformation.