MEMORY AND INHERITANCE IN SLOPE EVOLUTION: THE COLORADO PLATEAU AND MARS

Inferring past erosional and environmental history from slope form is generally difficult. A given profile of a regolith-mantled slope might result from a variety of erosional histories. For example, convexo-concave slopes can arise from pure creep and waning downcutting or from a combination of creep and wash processes. In such cases the spatial distribution of slope profiles may help to resolve erosional history. Even convex slope profiles are not a unique signature of regolith mantled slopes: similar profiles can result in sandstone bedrock slopes and ablating glaciers. In some settings slopes that combine weathering-limited and transport-limited components retain a strong climatic record because of different sensitivities of weathering and transport processes to climate change. Two examples will be discussed from late Quaternary climate change on the Colorado Plateau: 1) Badland slopes in weak shale abutting vertical slopes in the same material beneath stable caprock; and 2) Bare sandstone slopes beneath inactive cliffs that previously had a talus cover. Martian examples of enigmatic slope processes and historical change in erosional history will also be discussed.