Abstract:
The paleo-meanders in the Aeolis Dorsa (AD) region show that meandering channels can develop in the absence of vegetation. Three possible mechanisms other than vegetation could contribute to the bank cohesion required to promote meandering: permafrost, abundant mud, and chemical cementation. Banks at the meandering Quinn River show little vegetation cover. Almost all sediment samples collected from the Quinn River deposits contain at least 41% mud (silt/clay), which is much higher than for most meandering streams. Ion chromatography (IC) analysis and scanning electron microscope (SEM) images showed presence of salts in river waters and sediments which may induce fine sediment to flocculate and be deposited. We find that bank cohesion promoting meandering can be provided by silt/clay, the deposition of which may be induced by dissolved salts. The sinuous Usuktuk River in the continuous permafrost region near Barrow, Alaska exhibited no exposed permafrost on stream banks. Instead vegetation seemed to be the dominant control of bank erosion. We have not found evidence for ice control of bank cohesion in this or other for terrestrial rivers of similar size and meandering pattern to the martian AD meanders. We conclude that bank cohesion in the AD meanders was probably provided by deposition of fine suspended sediment that was flocculated by dissolved salts.
