STRUCTURAL INTERPRETATION OF THRUST FAULT-RELATED LANDFORMS ON MERCURY USING EARTH ANALOGUE FAULT MODELS

Thrust fault-related landforms in the Northern Smooth Plains of Mercury have been compared the Yakima Fold Province of Washington state. Both sets of landforms represent the deformation of flood basalts. They are positive topographic expressions of anticlinal folds above thrust faults and are characterized by gently dipping back limbs and steeply dipping forelimbs. Recent modeling efforts propose that the morphology of a Yakima fold is caused by displacement of rock along two parallel listric faults: an upper listric thrust shallowing into a sub-basalt detachment and a deep, older listric thrust rooting into basement rock. Long-lived activity along the lower fault and more recent activity on the upper fault produced current topography and structural patterns. In particular, reactivation of the deeper fault appears critical for developing aspects of fold morphology. On Mercury, reactivation may also play a role in shaping fault-related landforms. Analyses of fault and fold orientations in the Northern Smooth Plains have shown that many thrust faults have orientations predicted for landforms resulting from combined stresses from global contraction (reduction in planet volume) and tidal despinning (slowing of planet rotation). Structures in the relatively young basalts displaying the influence of tidal despinning implies that this process either happened later than expected or that deep, older faults related to this process were able to influence more shallow, younger faults. Work presented here evaluates the topography of at least ten thrust fault-related landforms in the Northern Smooth Plains and attempts to reproduce topography through forward modeling deformation using a two-fault model similar to that developed for Yakima folds. Results may allow for the characterization of fault geometry in the Northern Smooth Plains, estimation of slip along faults, and identification of a reactivation signature in the topography of thrust fault-related landforms.