This image shows a portion of Lethe Vallis, an outflow channel that also transported lava. Another investigation of this area (Balme et al., 2011) discovered a repeat pattern of dune-like forms in the channel interpreted as fluvial dunes (or, giant current ripples) which are dunes formed by flowing water.
This is one of only a few places on Mars where these pristine-appearing landforms have been identified. The channel formed by catastrophic floods… [More at link]