Origin of theater-headed valleys in the Valles Marineris region, Mars

Abstract

This paper reports high-resolution observations of theater-headed valleys in the Valles Marineris region and proposes an integrated model of their formation and localization across the walls of the canyons of Valles Marineris. These theater-headed valleys have formed over a long period of time from Middle-Hesperian to Early-Amazonian. The valleys show several common features, namely, proximity to areas of high ejecta mobility on the Tharsis plateau; alignment along the major tectonic features such as wrinkle ridges, grabens, pit crater chains; association with fluvial channels and layered deposits on the plateau adjacent to the valley heads; and occurrences of mass wasting features at the valley mouths. Elevation profiles of the walls of Valles Marineris display ramp and cliff topography indicating mechanical stratification in the wall rocks. These observations reveal multiple controls over the formation and localization of theater-headed valleys in Valles Marineris. However, the major controls appear to be strong-over-weak stratigraphy in the canyon walls and the pre-existing zones of structural weakness in the Valles Marineris region. The source of water could likely be groundwater; however, snowmelt accumulated on the upper parts of the wallrock would additionally facilitate the process. Based on the above observations, we propose a sequence of events for the evolution of theater-headed valleys in the Valles Marineris region.