Variability in martian sinuous ridge form: Case study of Aeolis Serpens in the Aeolis Dorsa, Mars, and insight from the Mirackina paleoriver, South Australia

In the largest known population of sinuous ridges on Mars, Aeolis Serpens stands out as the longest ( 500 km) feature in Aeolis Dorsa. The formation of this landform, whether from fluvial or glacio-fluvial processes, has been debated in the literature. Here we examine higher-resolution data and use a terrestrial analog (the Mirackina paleoriver, South Australia) to show that both the morphology and contextual evidence for Aeolis Serpens are consistent with development of an inverted fluvial landform from differential erosion of variably cemented deposits. The results of this study demonstrate that the induration mechanism can affect preservation of key characteristics of the paleoriver morphology. For groundwater cemented inverted fluvial landforms, like the Mirackina example, isolated remnants of the paleoriver are preserved because of the temporal and spatial variability of cementation sites. Upon landscape inversion, the result is a landform comprised of aligned mesas and ridges with an undulating longitudinal profile. Recognizing how different induration mechanisms affect preservation of fluvial sediments in denuded regions is relevant to the interpretation of sinuous ridges at other locations on Mars. In particular, double ridge transverse shape may be an instrumental aspect in identifying potential inverted fluvial landforms. There are significant limitations on determining former channel parameters for inverted fluvial landforms that form as a result of variable cementation. Radius of curvature can be accurately determined and an upper-bound constraint for former channel wavelength and width can be made, but it is not possible to reconstruct the paleoslope. Thus, the number of applicable paleohydrologic models is restricted and only first order estimates of flow magnitude can be made. Paleodischarge estimates range between 10 and 10 m/s for both Aeolis Serpens and the Mirackina paleoriver. Located near the base of the Medusae Fossae Formation (MFF), Aeolis Serpens provides insight into the fluvial environment early in the development of that deposit. When Aeolis Serpens was active, climate conditions must have included at least a period conducive to channelized flow for several hundred kilometers. 2013 Elsevier Inc. All rights reserved.