EXCEPTIONAL CHANNEL AGGRADATION ON MARS AND WHAT IT MEANS FOR WATER LEVEL RISE

Despite currently being devoid of liquid water, the surface of Mars boasts an impressive plethora of distinctive fluvially-derived landforms. The most distinctive of these landforms are perched sinuous ridges raised tens of metres above the surrounding surface, typically indicative of the contrasting lithologies between the inferred channel fill deposits and the surrounding floodplains. The growth and evolution of sinuous channels on Earth is typically preserved in the stratigraphic record as assemblages of scroll bars. However, on Mars, this preservation is rare, which makes interpreting and understanding how these channels evolved more complex. We use a well-preserved sinuous ridge in the Aeolis Dorsa to examine the topographic characteristics of scroll bar complexes and outer bank levees on 17 meander bends to explore possible mechanisms of formation. The exceptional heights attained by scroll bar complexes on Mars were over double the maximum elevation attained by actively meandering systems on Earth with levee thicknesses and slopes an order of magnitude larger, too. We suggest that the exceptional topography observed on this channel could only have been created by a rapidly-rising downstream water body. The notion of a downstream basin is supported by evidence of multiple delta lobes across the region and by the identification of other potential feeder channels. We suggest that rising water levels forced channel bed aggradation and likely represents the upstream portion of a backstepping bayhead delta complex that formed in response to reservoir expansion. This raises questions over the trigger, timing, and persistence of liquid water on Mars and may offer insights into where evidence to resolve these outstanding questions could be found.