MODELING THE PRECIPITATION-RUNOFF REQUIRED TO CARVE GULLIES ON THE WALLS OF METEOR CRATER (ARIZONA, USA) BY DEBRIS FLOWS: IMPLICATIONS FOR MARTIAN GULLY FORMATION

Since its impact ~50,000 years ago, surface runoff has entrained and transported sediment from the walls to the floor of Meteor Crater (Arizona, USA). Recent work based on LiDAR-derived topographic data and field observations has shown that much of this erosion and deposition has been due to debris flows, especially during the cooler and wetter Pleistocene. These flows were likely generated by runoff that entrained talus that borders bedrock cliffs high on the inner crater walls. However, when water inputs are not sufficient to generate a debris flow at Meteor Crater, as was observed during a 2011 storm event, fluvial activity, also driven by overland flow processes, led to minor modification of the gully floor and the transport of finer sediment within the debris-flow tracks. Here, we present initial results using a simple model developed for debris flow initiation via runoff in post-fire landscapes to explore the precipitation intensities necessary to generate debris flows along the gully floors of Meteor Crater. We also explore three hypotheses for why debris flows may have ceased at Meteor Crater: changes in climate, changes in grain size, and/or changes in gully channel morphology. The fact that the Meteor Crater gullies are morphologically similar to Martian gullies, combined with the general consensus that the majority of gullies on Mars required some fluid or fluidization process to form, makes this work especially relevant to determining whether gullies on Mars could have formed by melting of water ice during periods of high obliquity.