From Bureau of Economic Geology, The
University of Texas at Austin (www.beg.utexas.edu).
Bureau Seminar, February 1, 2008
Continental-Scale Salt Tectonics on Mars
Bureau of Economic Geology, and colleagues at the Department of Earth and Space Sciences, University of Washington
Thaumasia Plateau on Mars is roughly the same size as the contiguous United States. Our structural mapping of the plateau points to a new interpretation for regional deformation and the 2500-km-long canyons, known as the Valles Marineris chasmata, and associated outflow channels. The structure of Thaumasia Plateau is typical of a thin-skinned gravity-spreading system. However, the low regional slope (~1°) results in gravitational body forces too small to deform the basaltic lava flows conventionally thought to exist here. Instead, we infer that geothermal heating and volcanic loading of extensive buried mixtures of salts, ice, and volcanic ash would allow for weak detachments and large-scale gravity spreading. We infer that the linear chasmata of Valles Marineris reflect collapse and excavation along preexisting extension fractures reactivated as a lateral margin of the Thaumasia gravity spreading system. We propose that deformation connected overpressured groundwater 8-10 km deep near the base of the Thaumasia detachment through the cryosphere to the martian surface. This deformation-induced plumbing triggered outburst floods some 2500 to 2000 million years ago.