A new branch of the Pedealpine Backthrust highlighted in the area of Lake Maggiore (Italy) through the revision of seismic profiles and wells data

Ferdinando Cazzini^1
1Freelance researcher.
Corresponding author e-mail: ferdinando.cazzini@gmail.com

The Pedealpine Backthrust is one of the main tectonic lineaments of the Western Southern Alps margin. It extends from the city of Como (Italy) to the southernmost tip of Switzerland and to the city of Varese (Italy). The fault plane coincides with the base of the “Chiasso formation” or with the base of the “Gallare marl”. The outcrops of the fault seldom occur between the Swiss border and the city of Varese making it difficult to map. The possible subsurface continuation of the fault in the Lake Maggiore area was never proved, due to the presence of an extensive cover of Pliocene-Quaternary sedimentary units. Seismic reflection profiles and well data were utilised to verify its subsurface presence and geometry. The results confirm the extension of the Pedealpine Backthrust to the south-west of Lake Varese. In addition, a previously unknown branch of the backthrust was detected in the Lake Maggiore area. Remarkably, there is also a probable additional extension of the fault bending through the area of Lake Monate and connecting the two branches. The interpretation allows also to determine that the south and north verging thrusts are all linked to the same detachment horizon, proving their common origin.

Pedealpine Backthrust (PB), Western Southern Alps (WSA), Gonfolite Lombarda Group (GF), Neoalpine Foredeep (NAF).