Figure 2: Structural sketch of the Thaumasian peripheral mountain ranges, displaying the position of the two frontal thrust arcs, and the displacement directions of the nappes (front advancement). Notice the hypothesized location of the NE-SW trending ovate “Solis planum mega-dome”, produced by plume activity (stippled area). Based on the works of Anguita et al. (2006), Grot et al. (2007a), and Ruiz et al. (2009). For clarity, we do not show here the widespread normal faults and grabens (e.g., Coracis and Claritas fossae) related to post-tectogenic extension. Also not shown are the late Hesperian-aged wrinkle ridges (thrust-related antiformal folds) in Solis and Thaumasia plan. WR = Warrego Rise promontory with an elevation of more than 7.6 km above martian datum.