Relationships between Helmintoid Flysch and Brianconnais Units along the italian-french boundary (Marguareis Massif, Maritime Alps)

The Punta Marguareis Massif is located in the Southern sector of the Maritime Alps. This area is characterized by several tectonic units showing different paleogeographic affinity and Alpine deformation histories. The Helmintoid Flysch Unit here called San Remo-Monte Saccarello Unit is one of them. Despite the wide available data, there are no aggrement among the different authors about structural setting and paleogeographic origin of the tectonic units outcropping in the study area. For this reason, the goal of this Thesis is define stratigraphic succession of the tectonic units and recostruct their deformation histories. In the study area, three tectonic units have been documented. They are, from the bottom to the top: Cabanaira Unit (CAU - Sub-briançonnais Domain), Campanin Sub-unit (CNU - here considered as part of the San Remo-Monte Saccarello Unit) and Marguareis Unit (MU - Ligurian Briançonnais Domain). The first consist of Triassic platform limestones and Nummulites-rich limestones and siliclastic turbidite depositsof Eocene age. Campanin Sub-unit is formed by Cretaceous varicoulured shales grading upward to the Cretaceous siliciclastic arenites alternated to marls and shales. Marguareis Unit is formed by Triassic massive dolostones, followed by Jurassic carbonate deposits and Cretaceous-Paleocene marly-limestones. Eocene Nummulites-rich limestones and turbiditic arenites top the succession. A tectonic slice, comparable with Marguareis Unit, is interposed between CAU and CNU. A multidisciplinary approach that included: 1:10.000 geological survey and structural analysis from micro- to map-scale. Provenance study on the arenitic formation of the CAU and CNU was also performed. The modal analysis suggests two different source areas. Cabanaira Unit’s source area was characterized by upper continental crust and related cover sedimentary (carbonate), while, for the Campanin Sub-unit the source area was characterized by upper to lower continental crust. Structural analysis highlighted different deformation histories for the three tectonic units. In the Cabanaira Unit, a deformation event (D1CAU) has been documented. D1CAU event is testified by S1CAU foliaton parallel to sub-isoclinal to tight folds axial planes. In the Campanin Sub-unit, two deformation events (D1CNU-D2CNU) have been recognized. D1CNU event is testified by S1CNU foliation. D2CNU produces tight to open F2CNU folds associated to S2CNU foliation. Marguareis Unit showing three deformation events (D1MU-D3MU). D1MU event produces S1MU foliation associated to the isoclinal to tight F1MU folds with scattered fold axes. D2MU event is testified by S2MU foliation associated to F2MU folds. D3MU event produces a km-scale fold with NW-SE trending. The latter is responsible of the rotation of the previous sructures. Tectonic stack is reworked by later folds FPS (PS= Post-stacking) with sub-horizontal to SW-dipping axial planes. Three normal to transtensive fault systems locally displace the previous architecture. The collected data allow to produce a new interpretation for this sector. Source areas of the Cabanaira Unit and Campanin Sub-unit can be located in the european and adriatic paleomargin, respectively. Structural analysis highlighted a new and complex structural setting for the Marguareis Massif area