Morphostructural analysis of the Lake Chambon Basin (Eastern Monts Dore, Massif Central, France)

The Lake Chambon area, located between the Col de la Croix-Morand and Murol (Massif Central, France), consists of a Hercynian crystalline basement partially overlain by Cenozoic formations, largely composed of volcanic products related to the Mont-Dore stratovolcano. The present-day topography, sedimentation patterns, and drainage network are strongly controlled by a complex fault system. A detailed morphostructural analysis identified more than 500 lineaments from a high-resolution digital elevation model (DEM), which were digitized and analyzed in a GIS environment using QGIS. A directional classification combining expert-based interpretation with a semi-supervised machine-learning approach (k-means clustering) revealed seven major fault families, grouped into clusters consistent with a regional dextral shear regime. An interpretive tectonic model is proposed, consistent with the current stress field ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>σ</mml:mi> <mml:mn>1</mml:mn> </mml:msub> </mml:math> trending between N160°E and N170°E). Faults of the F1 family are interpreted as dextral shear zones related to the South Armorican Shear Zone–Cholet–Poitiers Fault–Southern Border Fault of the Limagne graben system, associated with secondary Riedel-type structures. The influence of the sinistral Sillon Houiller Fault is expressed by the F6′′ family (N20°E) and by the F2′ family, whose orientation is comparable to that of the Tauves–Aigueperse fault system (N50°E). The F4 family corresponds to extensional faults, locally reactivated within this broader strike-slip tectonic framework. The proposed neotectonic framework allows for the interpretation of several key geomorphological features. The Lake Chambon Basin may correspond to a transtensional pull-apart structure. In contrast, the slow-moving landslide at Chambon-sur-Lac, located between the transtensional zones of the Rochers de Pousseterre to the west and Lake Chambon to the east, appears to be controlled by the structural inheritance and kinematics of faults F4, F6′′ and F2′, which locally accommodate oblique deformation within a transpressive regime. Finally, the study suggests that deep hydrothermal activity at Chambon-sur-Lac may be linked to regional seismicity associated with the F1 fault system.