This study reconstructed the subsidence history by the backstripping and 3D visualization techniques, to understand tectonic evolution of the Neogene Vienna Basin. The backstripping removes the compaction effect of sediment loading and quantifies the tectonic subsidence. The amount of decompaction was calculated by porosity-depth relationships evaluated from seismic velocity data acquired from two boreholes. About 100 wells have been investigated to quantify the subsidence history of the Vienna Basin. The wells have been sorted into 10 groups; N1-4 in the northern part, C1-4 in the central part and L1-2 in the northernmost and easternmost parts, based on their position within the same block bordered by major faults. To visualize 3D subsidence maps, the wells were arranged to a set of 3D points based on their map location (x, y) and depths (z1, z2, z3 ...). The division of the stratigraphic column and age range was arranged based on the Central Paratethys regional Stages. In this study, MATLAB, a numerical computing environment, was used to calculate the TPS interpolation function. The Thin-Plate Spline (TPS) can be employed to reconstruct a smooth surface from a set of 3D points. The basic physical model of the TPS is based on the bending behavior of a thin metal sheet that is constrained only by a sparse set of fixed points. In the Lower Miocene, 3D subsidence maps show strong evidence that the pre-Neogene basement of the Vienna Basin was subsiding along borders of the Alpine-Carpathian nappes. This subsidence event is represented by a piggy-back basin developed on top of the NW-ward moving thrust sheets. In the late Lower Miocene, Group C and N display a typical subsidence pattern for the pull-apart basin with a very high subsidence event (0.2 - 1.0 km/Ma). After the event, Group N shows remarkably decreasing subsidence, following the thin-skinned extension which was regarded as the extension model of the Vienna Basin in the literature. But the subsidence in Group C decreases gradually, which demonstrates a trend of increasing thermal subsidence during the Middle to Upper Miocene. The traditional model cannot explain the thermal subsidence observed in the central part. This study supports a non-uniform extension model changing from the thin-skinned extension in the northern part to the thick-skinned extension in the central part. And 3D subsidence maps propose the existence of a decoupling between lithospheric and crustal extensions along the Steinberg Fault. Group L shows very different subsidence trends compared to Group C and N. In this Group a subsidence halt occurred in the late Lower Miocene. After the halt, Group L1 shows small tectonic and subsidence events. Some former studies presented that the area of Group L1 uplifted during the early Middle Miocene. It can be concluded that the missing sediments were eroded by the local uplift. But the subsidence of Group L2 stopped completely. It suggests that Group L2 was not influenced by the extension of the strike-slip fault system.
Keywords: 8169 TECTONOPHYSICS Sedimentary basin processes, 1994 INFORMATICS Visualization and portrayal