Lateral ramps and strike-slip kinematics on Mercury

Abstract

At a global scale, Mercury is dominated by contractional features manifested as lobate\ud scarps, wrinkle ridges and high-relief ridges. Here, we show that some of these features are associated\ud with strike-slip kinematic indicators, which we identified using flyby and orbital Mercury Dual\ud Imaging System (MDIS) data and digital terrain models. We recognize oblique-shear kinematics\ud along lobate scarps and high-relief ridges by means of (1) map geometries of fault patterns\ud (frontal thrusts bordered by lateral ramps, strike-slip duplexes, restraining bends); (2) structural\ud morphologies indicating lateral shearing (en echelon folding, pop-ups, pull-aparts); and (3) estimates\ud of offsets based on displaced crater rims and differences in elevation between pop-up structures\ud and pull-apart basins and their surroundings. Transpressional faults, documented across a\ud wide range of latitudes, are found associated with reactivated rims of ancient buried basins and,\ud in most cases, linked to frontal thrusts as lateral ramps hundreds of kilometres long. This latter\ud observation suggests stable directions of tectonic transport over wide regions of Mercury’s\ud surface. In contrast, global cooling would imply an overall isotropic contraction with limited processes\ud of lateral shearing induced by pre-existent lithospheric heterogeneities. Mantle convection\ud therefore may have played an important role during the tectonic evolution of Mercury

Sinuous Rille

“…On Mercury strike-slip kinematics is always associated with some compressional deformation leading to transpressional structures (Massironi et al 2014). These structures often represent oblique and lateral ramps of frontal thrusts (Rothery and Massironi 2010, Massironi et al 2014.…”

“…These structures often represent oblique and lateral ramps of frontal thrusts (Rothery and Massironi 2010, Massironi et al 2014. Their presence could be indicative of mantle convection and/or tidal despinning acting as a major geodynamic processes together with the dominant cooling and contraction of the planet.…”

Volcanism and tectonism across the inner solar system: an overview

“…Their models provide renewed insights into how subsurface magma reservoirs inflate and rupture, and how these processes relate to volcano growth, caldera formation, and the associated emplacement of circumferential and radial dykes. Lateral ramps and strike-slip kinematics on Mercury Massironi et al (2014) investigate contractional features on Mercury for evidence of strike-slip deformation. Such evidence includes en echelon fold arrays, restraining bends, positive flower structures, stike-slip duplexes and crater rims that have been displaced by lobate scarps and high-relief ridges.…”

Structural Analysis of the Victoria Quadrangle Fault Systems on Mercury: Timing, Geometries, Kinematics, and Relationship with the High‐Mg Region

“…The systematic orientation of structures in some areas of the planet (Melosh & McKinnon, ; Watters et al, ) strengthened the idea that, besides global contraction, a tidal despinning process influenced Mercury's tectonics in the past (Melosh & Dzurisin, ; Pechmann & Melosh, ). However, model predictions indicate that tidal despinning alone would have created a globally recognizable pattern of thrusts, strike‐slip, and normal faults (Beuthe, ; Melosh, ), whereas tectonics governed solely by global contraction should have caused isotropic stresses and a random orientation distribution of thrust faults (e.g., Klimczak et al, ; Massironi, di Achille, et al, ). Since this is not observed at a global scale, it has been suggested that despinning acted concurrently with global contraction during the early evolution of Mercury (e.g., Klimczak et al, ; Matsuyama and Nimmo, ), with some global contraction reworking inherited despinning faults (Dombard & Hauck, ).…”

“…Recent thermal models do not exclude this scenario, albeit it is more likely that the mantle is currently in a conductive state (Michel et al, ; Tosi et al, ). The occurrence of fold‐and‐thrust systems where extensive thrusts are bounded by lateral ramps that indicate a constant vergence has been suggested to be one surface evidence for the contribution of mantle convection to the total shortening (Massironi, di Achille, et al, ).…”