Repeated, Cross‐Cutting, and Spatially Migrating Outflow Channel Formation, Grjótá Valles, Mars

Abstract

AbstractCross‐cutting relationships and the incision history for multiple outflow channels have been mapped and studied to establish their relative chronology in Grjótá Valles, Mars, in order to establish whether observed geomorphic channels were formed in a single event or multiple events. The relative chronology can be established by mapping cross‐cutting relationships between channel margins and successive incisions, where later channels incise downward into older channels. We show that the source areas of five distinct channels can be established, with younger channels progressively sourced further to the east along the Grjótá Valles fault system, and incising downwards into older channels. The channels resemble examples interpreted elsewhere as cut using catastrophic aqueous flow processes (diluvial) due to their regional morphology, the presence of streamlined islands surrounded by anabranching channels marked by incisions, recessional terraces and longitudinal erosional grooves; however, turbulent lava flows may have also been involved. Those five distinct flows occur progressively further to the east may indicate the progressive propagation from west to east of the processes at depth that released the fluid responsible for cutting the channels, such as dike propagation and associated seismicity. Our observation of multiple flows and channel formation episodes implies instantaneous volumes of fluid that are smaller than that for a single flow interpretation.