New insight on the structural framework of the Geneva Basin and its impact on the structuration of the Swiss foreland and geothermal exploration
Creators: name: Moscariello, Andrea
name: Eruteya, Ovie Emmanuel
name: Mondino, Fiammetta
Publisher: name: Zenodo
Year: 2024

description: The Swiss Alpine foreland is described as generally moderately deformed plateau where the shortening related to the Alpine compression is accommodated mostly by fault surfaces sliding of the thick Mesozoic series over the Triassic evaporites. These observations led to the thin-skin theory which for many scientists in the only logical model to explain the current structural deformation of the Jura and neighbouring Swiss Plateau.  In addition to this a series of long NW-SE deep regional strike slip faults supposedly compartmentalizing of the entire sedimentary succession. The role of these deeply rooted faults has been challenged by the recent examination of reprocessed and newly acquired 2D and 3D seismic in the Geneva Basin highlighting a variety of deformation affecting in different shape, scale and style the entire sedimentary succession. In summary:

1)    The study area shows a different style of deformation when comparing the northern and SW sectors. The former is dominated by E-W oriented lineaments while the latter by NE-SW lineaments including low angle thrusts (Clerc & Moscariello, 2020).

2)    A newly identified system of conjugate regional lineaments oriented respectively E12N and E16S has been described in the centre of the basin. The main one (E12N) called the Rhone fault as it follows the path of the homonymous river, has a right-lateral kinematic overall displaying a transpressional character. This regional system might be responsible for the decoupling of the northern from the SW sector and their different styles as described before.

3)    The occurrence of a high degree of deformation at small scale (100s of meters in length) distributed within the Mesozoic succession is observed. These deformations consist of low-angle thrusts which root generally in shale and marly intervals. 

4)    Thrust anticlines formed in the low-angle hanging wall have also been observed accounting for an ongoing deformation affecting the centre of the basin. 

5)    The importance of Triassic salt displacement and dissolution in influencing the deformation style of the overburden sequence has been identified indicating the role that salt tectonics have played at early stage of burial of Triassic strata. 

6)    Compressional deformation is observed affecting the ancient normal faults bordering the Permo-Carboniferous throughs which have been inverted most likely in Alpine time. 

In this structurally complex context, distribution of fault and dense fracture network associated with the different type of deformations described above are controlled by the geomechanical properties of lithological units. These structural features can play a key role in controlling the subsurface circulations of both hydrocarbon and geothermal fluids: the accurate description of their geometry, extension architecture and intersections will be key to predict fluid-flow behavior and identify possible targets for geothermal exploration wells (Moscariello, 2019).