A review of open-channel megflood depositional landforms on Earth and Mars

Large freshwater floods on Earth in recent times and in the Quaternary have often been associated with catastrophic out-bursts of water from lakes impounded by glacial-ice or debris (such as moraine). In either case, large-scale depositional sedimentary landforms are found along the courses of the floodwaters. On Mars, similar floods are believed to have resulted from catastrophic efflux of water from within the Martian surface. Within the Martian flood tracts, landforms have been imaged that appear similar to those identified on Earth. These are primarily suites of giant bars – “streamlined forms” – of varying morphology that occur primarily as longitudinal features within the floodways and along the margins as well as in areas of the floodways that were sheltered from the main flow. In addition, flow-transverse bedforms within the floodways have been identified as giant sedimentary dunes or antidunes. Information concerning the flood hydraulics that created these forms may be deduced from their location and plan view morphology. Some other fluvial landforms which have been associated with megafloods on Earth have yet to be identified on Mars. The examples from Earth are described, so as to spur the search for further water-lain landforms on Mar