Initiation and development of normal faults within the German alpine foreland basin: The inconspicuous role of basement structures

• Published in: Tectonics (Washington, D.C.) D.C.), 2016-06, Vol.35 (6), p.1560-1574
• Main Authors: Hartmann, Hartwig, Tanner, David C., Schumacher, Sandra
• Format: Article
• Language: English
• Subjects: 2‐D numerical mechanical model; 3‐D juxtaposition fault map; 3‐D seismics; Basins; decoupling; Fault lines; foreland basin; Molasse; Sediments; Structural analysis
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1002/2016TC004176

In a large seismic cube within the German Alpine Molasse Basin, we recognize large normal faults with lateral alternating dips that displace the Molasse sediments. They are disconnected but strike parallel to fault lineaments of the underlying carbonate platform. This raises the question how such faults could independently develop. Structural analysis suggests that the faults grew both upward and downward from the middle of the Molasse package, i.e., they newly initiated within the Molasse sediments and were not caused by reactivation of the faults in the carbonate platform and/or crystalline basement. Numerical modeling of the basin proves that temporarily and spatially confined extensional stresses existed within the Molasse sediments but not in the carbonate platform and basement during lithospheric bending. The workflow shown here gives a new and as yet undocumented insight in the tectonic and structural processes within a foreland basin that was affected by buckling and bending in front of the orogen. Key Points Normal fault evolution in contractional stress regimes of foreland basins Fault system initiated due to rheological behaviors of Molasse sediments and underlying strata during bending of the downgoing plate Stresses within the downgoing plate cause normal fault initiation at the basinward side of the foreland bulge