Structural interpretation of thrust fault-related landforms on Mercury using Earth analogue fault models

The Yakima Fold Province has often been referenced as an Earth analogue to thrust fault-related landforms on many solar system bodies including Mars, the Moon, and Mercury. The asymmetric ridges of deformed flood basalts in this region evoke the morphology and topographic expression of the landforms observed in the Smooth Plains units of Mercury. Observed similarities have supported the interpretation that thrust faults and folds comprise both sets of landforms; however, this is an incomplete analogy. Recent modeling efforts have revealed that the terrestrial landforms developed over millions of years with vertical uplift associated with each landform accumulating on multiple faults and accommodated by large folds. These studies highlight the important role that folding plays in accommodating crustal shortening. Work presented here uses the structural geometries and folding styles from the Yakima Fold Province as a framework for constructing ten three-dimensional models of thrust fault-related landforms in Smooth Plains units near Suisei Planitia on Mercury, which traditionally would have been classified as "wrinkle ridges" based on appearance and some aspects of morphology. Forward modeling of topography revealed that multiple faults and folds are necessary to reproduce complex topographic features. Folding was found to account for >50% of vertical uplift associated with the landforms and without considering folding, shortening accommodated by the landforms was underestimated by 61 to 88%. Studies which use thrust fault-related landforms as proxies for stress and strain must therefore consider the effect of folding on these estimates and their associated effect on tectonic and thermal histories. (C) 2020 Elsevier B.V. All rights reserved.