A Burial History of the Sedimentary Succession Preserved in Aeolis Mons, as Recorded by Fracture Networks at Maria Gordon Notch, Gale Crater, Mars

Abstract

Fractures in sedimentary rocks preserved within Gale crater record the deformational and burial history of the sediment infill. Fracture geometries and morphology can be used to time other geologic events, such as: compaction, diagenesis, fluid migration, geochemistry, and broader tectonic stresses within a basin. The rover Curiosity acquired images to construct 3D digital outcrop models used for characterization of fracture sets exposed in aeolian strata of the Mirador formation at Maria Gordon notch, identifying four distinct fracture sets. Three fracture sets formed during burial, and one during exhumation. The first group (Sets 1 and 2) consisted of bedding-parallel and bedding-bounded vertical fractures associated with early lithification and hydraulic fracturing of the rock as water escaped from isolated pores. Fracture Set 3—Vertical sulfate-filled fractures—formed after a second episode of diagenesis, as water escaped from deeper within the sedimentary succession. The final fracture set is barren and associated with exhumation of the crater fill. Modeling burial stress suggests that Sets 1 and 2 would form at depths greater than 1 km. The tensile strength of the rocks is generally higher than anticipated due to the absence of shear fractures (faults). Fracture Sets 1–3 demonstrate dewatering of the strata during burial, which continued up until maximum burial at ∼4.7 km. This water was driven toward the surface, providing water for diagenesis and alteration reactions and could have reasonably extended the habitability window within Gale crater.