Abstract
ABSTRACT We present and discuss the results of a field-based approach including accurate geological mapping and micro- to map-scale structural analysis to highlight the finite strain pattern recorded in Marguareis Unit, a massif deformed at shallow crustal levels at the boundary between Maritime and Ligurian Alps. We describe superposed tectonic structures developed under low-grade metamorphic conditions during the Alpine collision and nowadays exceptionally well recorded in the area of interest. We demonstrate that the structural frame of the Marguareis Unit results from superposition of fourfold systems, later segmented, but without significant displacements, by brittle faults.
Highlights
At shallow structural levels of orogenic belts continental and/or oceanic-derived tectonic units are deformed under low- and very lowgrade metamorphic conditions and can partly preserve their original lithostratigraphy. 1 sur 1224/09/2021 à 12:32they are generally considered for the reconstruction of the pre-collisional paleogeography and/or for estimation of bulk horizontal shortening during the continental collision (Davis et al, 1983; Ford et al, 2006; Gidon, 1972).These units, being involved in collisional systems, are characterized by the development of large-scale penetrative and continuous tectono-metamorphic fabrics, but their finite strain pattern might be underestimated
We discuss the results of field investigations and map updating that revisit a sector of the Marguareis Massif located in the southern termination of the Western Alps, at the boundary between Maritime and Ligurian Alps (Figure 1) along the French-Italian border
The aim is to focus on the relative deformation chronology of tectonic events concealed within the Marguareis Unit characterized by a typical Meso-Cenozoic sequence of the Briançonnais Domain showing a low-grade metamorphic imprint
Summary
At shallow structural levels of orogenic belts (i.e. orogenic suprastructure, De Sitter & Zwart, 1961) continental and/or oceanic-derived tectonic units are deformed under low- and very lowgrade metamorphic conditions and can partly preserve their original lithostratigraphy. They are generally considered for the reconstruction of the pre-collisional paleogeography and/or for estimation of bulk horizontal shortening during the continental collision (Davis et al, 1983; Ford et al, 2006; Gidon, 1972). The excellent exposures of multi-scale structures, from foliations to kilometer-size polyphase fold systems make the Marguareis Massif a privileged area where to unravel histories of sedimentary and tectonic episodes, broadly assisted by well-known solid sedimentological and paleontological supports (i.e. Brizio et al, 1983; D’atri et al, 2016; Lanteaume, 1962; 1968; Sanità et al, 2020; Vanossi, 1972)
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