Tectonic evolution of the eastern margin of the Thaumasia Plateau (Mars) as inferred from detailed structural mapping and analysis

Abstract

The eastern margin of the Thaumasia Plateau (EMTP) is characterized by a diversity of tectonic features, which recorded its complex, and still controversial, tectonic history. A detailed structural survey and analyses have been carried out in order to assess the kinematics and relative age of the main deformational events. Combining results from statistics of lineament orientations and density of fault length for each geologic unit and taking into account crosscutting relationships among tectonic structures, three main deformational events have been recognized. The early stage of the tectonic evolution of EMTP is recorded by Noachian units at the southern edge of Melas Dorsa and is represented by N‐S oriented grabens sutured by Early Hesperian formations. Starting from Late Noachian, the extensional stress field became NE‐SW oriented and resulted in the formation of NW‐SE striking sets of grabens. At the boundary between Noachian and Hesperian, the most important change in tectonic regime occurred. The Hesperian tectonics are characterized by an E‐W shortening possibly related to an eastward motion of the Thaumasia Plateau. This tectonic phase likely produced a N‐S‐oriented wrinkle ridges as well as regional folds and thrust faults. E‐W‐oriented preexisting tectonic lineaments could have been reactivated forming regional transfer zones. In this scenario, Coprates Rise, Melas Dorsa, and Thaumasia Ridge could be interpreted as mountain belts resulting from buckling and thrust faulting of the eastern and southern margins of the Thaumasia plateau. The proto‐Valles Marineris could have experienced a left‐lateral component of displacement and played a role of a transfer shear zone.

Lateral ramps and strike-slip kinematics on Mercury

“…Evidence of strike-slip faulting has also been recognized on Mars (e.g. Schultz 1989;Bistacchi et al 2004;Okubo & Schultz 2006;Borraccini et al 2007;Andrews-Hanna et al 2008;Yin 2012), Venus (Koenig & Aydin 1998), Europa Hoppa et al 1999;Kattenhorn 2004;Kattenhorn & Marshall 2006;Aydin 2006) and Enceladus (Patthoff & Kattenhorn 2011).…”

An episodic slab-rollback model for the origin of the Tharsis rise on Mars: Implications for initiation of local plate subduction and final unification of a kinematically linked global plate-tectonic network on Earth

“…Gravity modeling indicates a 70-90-km-thick crust in the region, which is 2-3 times thicker than that of the nearby northern lowlands crust at ~32 km (Zuber et al, 2000;Neumann et al, 2004;Andrews-Hanna et al, 2008a). The formation of the mountain belt may have been created by motion on the east-directed Thaumasia thrust (Plescia and Golombek, 1986;Schultz and Tanaka, 1994;Anguita et al, 2001Anguita et al, , 2006Borraccini et al, 2007;Montgomery et al, 2009;Nahm and Schultz, 2010), assisted by the deposition of a thick volcanic pile in the Early Noachian .…”

“…3 and 4; e.g., Watters, 1991Watters, , 1993Schultz, 1998;Dohm and Tanaka, 1999;Anderson et al, 2001;Dohm et al, 2009b;Anguita et al, 2001Anguita et al, , 2006Okubo and Schultz, 2004;Mueller and Golombek, 2004;Borraccini et al, 2007;Williams et al, 2008;Montgomery et al, 2009). Folds are expressed as wrinkle ridges spaced at ~30-60 km and may have been created by blind thrusting (Watters, 1991;Okubo and Schultz, 2004;Mueller and Golombek, 2004).…”

Evaluation of the orogenic belt hypothesis for the formation of the Thaumasia Highlands, Mars

“…The first hypothesis postulates that the Thaumasia Plateau moved downslope from Syria Planum as a single coherent lithospheric block [ Anguita et al , 2001; Webb and Head , 2002; Borraccini et al , 2007] along a weak horizon (or décollement) [ Montgomery et al , 2009], either by gravitational collapse of some large volcanic edifice [ Webb and Head , 2002, Borraccini et al , 2007], gravity flow and sliding of near‐surface lithosphere off Tharsis [ Wise et al , 1979], or as a result of gravitationally driven continental‐scale salt tectonics [ Montgomery et al , 2009]. During the conjectural southeastward movement of the Thaumasia Plateau lithospheric block, proto‐Valles Marineris would have functioned as a left lateral strike‐slip zone [ Borraccini et al , 2007], and Claritas Fossae as a right lateral strike‐slip zone [ Wise et al , 1979; Webb and Head , 2002], in contradiction to the evidence for predominantly normal faulting in these areas [e.g., Tanaka et al , 1991; Banerdt et al , 1992; Lucchitta et al , 1992; Hauber and Kronberg , 2005]. Alternately, southeastward motion of the Thaumasia Plateau was conjectured to have produced right lateral strike‐slip motion along proto‐Valles Marineris [as suggested by Webb and Head , 2002; Borraccini et al , 2007], for which there is also no evidence [e.g., Schultz , 1991, 1998; Mège and Masson , 1996].…”