Evolution of major sedimentary mounds on Mars: Buildup via anticompensational stacking modulated by climate change

Abstract

AbstractWe present a new database of >300 layer orientations from sedimentary mounds on Mars (Mount Sharp/Aeolis Mons, plus Nia, Juventae, Ophir, Ceti, Melas, Coprates, and Ganges Mensae). Together, these mounds make up ~ ½ of the total volume of canyon/crater‐hosted sedimentary mounds on Mars. The layer orientations, together with draped landslides, and draping of rocks over differentially eroded paleodomes, indicate that for the stratigraphically uppermost ~1 km, the mounds formed by the accretion of draping strata in a mound shape. The layer‐orientation data further suggest that layers lower down in the stratigraphy also formed by the accretion of draping strata in a mound shape. The data are consistent with terrain‐influenced wind erosion but inconsistent with tilting by flexure, differential compaction over basement, or viscoelastic rebound. We use a simple model of landscape evolution to show how the erosion and deposition of mound strata can be modulated by shifts in obliquity. The model is driven by multi‐Gyr calculations of Mars' chaotic obliquity and a parameterization of terrain‐influenced wind erosion that is derived from mesoscale modeling. The model predicts that Mars mound stratigraphy emerges from a drape‐and‐scrape cycle. Our results suggest that mound‐spanning unconformities with kilometers of relief emerge as the result of chaotic obliquity shifts. Our results support the interpretation that Mars' rocks record intermittent liquid‐water runoff during a ≫ 108 yr interval of sedimentary rock emplacement.