Structure and Tertiary tectonic history of the Mulhouse High, Upper Rhine Graben: Block faulting modified by changes in the Alpine stress regime

[1] The Mulhouse High (Horst) is situated in the southernmost Upper Rhine Graben, and changes in its tectonic history record the interaction with the adjacent Alpine front. Recently released seismic data show that the Mulhouse High consists of the Sierentz and the Altkirch tilted blocks, separated by the Ferrette fault zone with a throw of several hundred meters. During the Eocene-early Rupelian main rifting phase, the Mulhouse High was the elevated flank of the Dannemarie basin with sedimentation affected by the nearby southern boundary of the Rhine Graben. The Miocene Jura compression extended into the Mulhouse High, creating a series of semiparallel buried folds with no evidence for thin skin tectonics. The change to a NW-SE regional compressive stress reactivated the main graben faults as wrench faults. It also resulted in transpression on the NE-SW trending faults, particularly the northern segment of the Illfurth fault zone. Consequently, the northern part of the Mulhouse High was uplifted. Strike-slip motion along the Ferrette fault zone is shown to be small.