Underlying structural control of small-scale faults and fractures in West Candor Chasma, Mars

Abstract

Orientations of small-scale faults and fractures within the interior layered deposits of West Candor Chasma were measured to investigate what information about the geologic history of Valles Marineris they can contribute. Deformational features were separated into six categories based on morphology and their orientations were analyzed. The elevations at which the deformational features formed are recorded, as a proxy for stratigraphic level. Deformational features occur over a continuous range of elevations and display regionally consistent preferred orientations, indicating their formation was controlled by a regional stress regime. The two most abundant preferred orientations of ∼35° and ∼110° are approximately parallel to the chasma walls and the inferred underlying normal faults. The alignment of three populations of small faults at 140°, consistent with the morphology of release faults, indicates a large-scale fault underlying the southeastern border of Ceti Mensa. The preferred orientations imply these small-scale deformational features formed from a continuation of the same imposed stresses responsible for the formation of Valles Marineris, indicating these stresses existed past the formation of the interior layered deposits. The origins of a fourth preferred orientation of 70° is less clear but suggests the study area has undergone at least two periods of deformation.