Tectonic relationships between the Paleozoic basement and the Mesozoic cover succession in the northern Dora-Maira Massif (Susa Valley, Western Alps)

Abstract

The northernmost sector of the Dora-Maira Massif is a key area for studying the role of basement-cover detachment zones as markers for understanding the multistage tectonic evolution of orogenic belts. The 1:5,000 scale geological map highlights the tectonic relationships between the Paleozoic basement and Mesozoic cover successions, which are separated by the Bussoleno Detachment Shear Zone, representing the basement-cover interface, and are tectonically overlain by the ophiolite-bearing Foresto Shear Zone. The Dora-Maira successions and these shear zones were deformed during four main phases (i.e. D1, D2, D3 and D4), with the – early tectonic setting largely established during the subduction-related D1 phase. Prior to the Alpine polyphase deformation, the basement-cover interface likely originated as a weak horizon within the Early Triassic, localizing deformation and forming the primary detachment zone.

Keywords

• Basement-cover interfaces
• detachment shear zones
• Alpine tectonics
• Dora-Maira Massif
• structural analysis
• susa valley