P24A-07
Meteor Crater: An Analog for Using Landforms to Reconstruct Past Hydrologic Conditions

Tuesday, 15 December 2015: 17:30
2007 (Moscone West)
Marisa C Palucis, California Institute of Technology, Pasadena, CA, United States, William E Dietrich, University of California Berkeley, Berkeley, CA, United States, Alan D Howard, University of Virginia Main Campus, Charlottesville, VA, United States, Kunihiko Nishiizumi, Univ California Berkeley, Berkeley, CA, United States, Marc W Caffee, Purdue University, Department of Physics and Astronomy, West Lafayette, IN, United States and David A Kring, Universities Space Research Association Houston, Houston, TX, United States
Abstract:
Recent work suggests that debris flow activity has occurred on Mars in the last few million years during high orbital obliquities, but estimating the amount and frequency of liquid water needed to generate these types of flows is still poorly constrained. While it is relatively common to estimate water amounts needed to produce landforms on Mars, such as gullies or alluvial fans, this is something rarely done on Earth. Consequently, there is little field data on the linkage between climate (snowmelt or rainfall events) and the amount of runoff needed to produce specific volumes of sediment in a landform.

Here, we present field and modeling data from Meteor Crater, which is a ~50,000 year old impact crater in northern Arizona (USA). Though it is very well preserved, it has developed gullies along its inner wall, similar in form to many gullies on Mars. Meteor Crater, similar to many Martian craters, has also gone through a change in a climate based on the ~30 m of lake sediments on its now dry floor, and what has eroded from its walls has deposited on its floor, making it a closed system. We show using LiDAR-derived topographic data and field observations that debris flows, likely generated by runoff entrainment into talus bordering bedrock cliffs of the crater walls, drove erosion and deposition processes at Meteor Crater. Cosmogenic dating of levee deposits indicates that debris flows ceased in the early Holocene, synchronous with regional drying. For a water-to-rock ratio of 0.3 at the time of transport, which is based on data from rotating drum experiments, it would have taken ~150,000 m3 of water to transport the estimated ~500,000 m3 of debris flow deposits found at the surface of the crater floor. This extensive erosion would require less than 0.4 m of total runoff over the 0.35 km2 upslope source area of the crater, or ~26 mm of runoff per debris flow event. Much more runoff did occur however, as evidenced by lake deposits on the crater floor and Holocene fluvial activity. Our analysis suggests that depositional landforms may record only a small fraction of the total runoff, which has implications for analyses on Mars. Current work is focused on using a hydrodynamic model to predict the conditions (frequency-intensity-duration) that can produce runoff capable of transporting sediment and initiating debris flow failures at Meteor Crater.

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