Channel-scale erosional bedforms in bedrock and in loose granular material: character, processes and implications

Carling, Paul A., Herget, Juergen, Lanz, Julia K., Richardson, Keith and Pacifici, Andrea (2009) Channel-scale erosional bedforms in bedrock and in loose granular material: character, processes and implications. In, Burr, Devon, Carling, Paul and Baker, Vic (eds.) Megaflooding on Earth and Mars. Cambridge, UK. Cambridge University Press, pp. 13-32.

Abstract

High energy fluid flows such as occur in large water floods can produce large scale erosional landforms on Earth and potentially on Mars. These forms are distinguished from depositional forms in that structural and stratigraphical aspects of the sediments or bedrock may have a significant influence on the morphology of the landforms. Erosional features are remnant, in contrast to the depositional (constructional) landforms that consist of accreted waterborne sediments. A diversity of erosional forms exist in fluvial channels on Earth at a range of scales that includes the mm and the km scales. For comparison with Mars and given the present-day resolution of satellite imagery, erosional landforms at the larger scales can be identified. Some examples include: periodic transverse undulating bedforms, longitudinal scour hollows, horse-shoe scour holes around obstacles, waterfalls, plunge pools, potholes, residual streamlined hills, and complexes of channels. On Earth, many of these landforms are associated with present day or former (Quaternary) proglacial landscapes that were host to jökulhlaups (e.g., Iceland, Washington State Scablands, Altai Mountains of Southern Siberia), while on Mars they are associated with pro-volcanic landscapes that were likely host to mega-floods produced by enormous eruptions of groundwater. The formative conditions of some erosional landforms are not well understood, yet such information is vital to interpreting the genesis and paleohydraulic conditions of past mega-flood landscapes. Thus, examples of erosional bedforms on Earth are presented and reviewed and supposed similar forms on Mars are identified for comparison with the Earth examples. Correct identification of some landforms allow estimation of their genesis, including paleohydraulic conditions

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