INVESTIGATING THE COARSEST GRAVEL RIPPLES ON EARTH ? FIELD RELATIONSHIPS, SEDIMENTOLOGICAL CHARACTER AND IMPLICATIONS FOR MARS.

DE SILVA, S.L.; BRIDGES, N.T.; ZIMBELMAN, J.R.; SPAGNUOLO, M. G.; BURR, D.M.; SHEIDT, S.; ORTIZ, A.

Flagstaff

Workshop; Third International Planetary Dunes Workshop; 2012

LPI

Coarse gravel megaripples in the Puna ofArgentina represent some of the most extreme aeolianbedforms on Earth in terms of particle properties andformation conditions. These gravel ripples are builton a bedrock of ignimbrites and composed of a bimodalassociation of dense (>2 g cm-3) lava and metamorphicclasts up to 2.5cm in diameter and pumice clasts (<1.5 gcm-3) up to 5 cm in diameter, making these the coarsestgrained ripples yet described on Earth. Whilethe mechanisms of origin and formation are debated[1,2,3], it is clear that these ripples must represent extremeconditions that define an end member of the spectrum ofgranule ripples on Earth. The relevance to Mars isthreefold: First, these aeolian gravel bedforms consist ofmaterials that have similar equivalent weight to thosecomposing the granule ripples at Meridiani Planum, Mars.Second, the spatial relationships among these Punamegaripples, topography, and bedrock are analogous torelationships among Transverse Aeolian Ridges (TARs),topography, and bedrock on Mars. Third, the gravels arelocally derived and may point to an alternative source toglobally transported dark dune sediments on Mars [4,5].We report here the progress we have made studying thesemegaripples, conducted under the auspices of NASAMFRP grant NNX10AP79G. We dedicate this work to thememory of our collaborator Ron Greeley.