Modelling the extensional tectonic setting of the Claritas Fossae

Unravelling the tectonic styles that affected the Martian crust is crucial to better understand the evolutionary stages that a rocky planet can experience. Here, we explore the tectonic setting of a key region of Mars, namely the Claritas Fossae (CF). The CF is located in the Highlands to the south-west of the Valles Marineris and is characterized by an elongated system of scarps and troughs, fault sets, and grabens, nearly N-S trending. These morphotectonic features strongly resemble terrestrial grabens (e.g.; Thingvellir in south Iceland) and, for this reason, the CF has been interpreted as a rift-like system (Hauber & Kronberg, 2005). In this work we apply a kinematic numerical forward modelling (HCA method; Salvini & Storti, 2004) to reproduce the geometry of the main fault(s) that likely generated the CF in order to better understand the leading tectonic mechanisms. This method allows replicating the superficial morphologies by considering the development of one or multiple faults with given geometry, throw and displacement rate and the relative movement between hanging-wall and foot-wall crustal blocks. It has been successfully used to simulate tectonically controlled morphologies on Earth such as ice buried landscape in the interiors of Antarctica (Cianfarra & Salvini, 2016), a negligible erosional environment considered as a good Martian analogue. In our model, we reproduced the morphology of the central-northern sector of the CF, characterized by an asymmetric valley with a steeper eastern slope and a gently rounded western one, along a topographical profile perpendicular to the strike of the main structure. The eastern valley slope allows locating the upper tip of the fault for the modelling in which we set the crustal thickness (i.e., the bottom of the model) to 70 km (Watters et al., 2007), considered no significant rheological vertical variation and tried different values of initial dip in the range 50°-70° and throw in the range 1000-2000 m. The preliminary results of our modelling show that the topography, including the rounded shape of the western slope, is well replicated by a crustal (listric) normal fault characterized by an initial dip of ca. 60° that gently decrease to ca. 40° and a throw of ca. 1800 m. This allows including the development of the CF in a past extensional tectonic regime of regional relevance. Further modelling on new topographical profiles to the north and to the south respect to the already modelled one will allow better highlighting the 3D shape of the main CF fault and the presence of further secondary but not negligible faults.