THE MIRACKINA PALEOCHANNEL IN SOUTH AUSTRALIA AS AN ANALOG FOR PAIRED SINUOUS RIDGES ON MARS
Study of terrestrial inverted channels is important for identifying distinguishing attributes to evaluate and interpret sinuous ridge networks on Mars, many of which are interpreted as fluvial deposits preserved in inverted relief. In particular, the twin ridges of the Mirackina paleochannel provide a terrestrial analog for sinuous ridges on Mars with paired ridges, two of which are located in the Aeolis/Zephryia Plana (AZP) region. One of these examples was previously interpreted as an esker based in part on rounded morphology and elevation variations in the longitudinal profile. However, this explanation was always problematic given the absence of additional evidence for glacial activity in the region. A HiRISE stereo anaglyph (~1 m/px) reveals twin ridges that define portions of the sinuous ridge, rather than the rounded shape inferred in lower resolution images. The example of the Mirackina paleochannel suggests a plausible alternative hypothesis: groundwater flow cementation of channel margins producing lateral ridges. This hypothesis is consistent with the inferred fluvial origin of other AZP sinuous ridge networks, obviates the need for special circumstances for this one example, and explains the lack of other glaciogenic features in the region.