HR: 1340h
AN: P13B-1291    [Abstracts]
TI: Continental-Scale Salt Tectonics on Mars and the Origin of Valles Marineris and Associated Outflow Channels
AU: * Montgomery, D R
EM: dave@ess.washington.edu
AF: Quaternary Research Center, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310, United States
AU: * Montgomery, D R
EM: dave@ess.washington.edu
AF: Astrobiology Program, University of Washington, Seattle, WA 98195-1310, United States
AU: Som, S M
EM: sanjoy@u.washington.edu
AF: Quaternary Research Center, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310, United States
AU: Som, S M
EM: sanjoy@u.washington.edu
AF: Astrobiology Program, University of Washington, Seattle, WA 98195-1310, United States
AU: Schreiber, B C
EM: geologo@comcast.net
AF: Quaternary Research Center, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310, United States
AU: Schreiber, B C
EM: geologo@comcast.net
AF: Astrobiology Program, University of Washington, Seattle, WA 98195-1310, United States
AU: Jackson, M P
EM: martin.jackson@beg.utexas.edu
AF: Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78713-8924, United States
AU: Gillespie, A R
EM: alan@rad.ess.washington.edu
AF: Quaternary Research Center, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310, United States
AU: Gillespie, A R
EM: alan@rad.ess.washington.edu
AF: Astrobiology Program, University of Washington, Seattle, WA 98195-1310, United States
AU: Adams, J B
EM: bearfight@methownet.com
AF: Quaternary Research Center, Department of Earth and Space Sciences, University of Washington, Seattle, WA 98195-1310, United States
AB: A synthesis of regional deformation patterns of the Thaumasia Plateau, Mars, leads to a new interpretation for regional deformation and the origin of Valles Marineris and associated outflow channels. The morphology of the Thaumasia Plateau is typical of thin-skinned deformation, akin to a "mega-slide," in which extensional deformation in Syria Planum and Noctis Labyrinthus connects via zones of lateral transtension — Claritas Fossae and Valles Marineris — to a broad zone of compressional uplift and shortening defined by truncated craters and thrust faults along the Coprates Rise and Thaumasia Highlands. However, the low regional slope (?1°) results in gravitational body forces that are too small to deform the basaltic lava flows conventionally thought to compose the flanks of the Tharsis volcanic province. Instead, we conclude that geothermal heating and topographic loading of extensive buried deposits of salts (or mixtures of salts, ice, and basaltic debris) would allow for weak detachments and large-scale gravity spreading. We propose that the generally linear chasmata of Valles Marineris reflect collapse and excavation along pre-existing extension fractures radial to Tharsis, reactivated as part of one lateral margin of the Thaumasia gravity spreading system. The other, dextral, lateral margin is a massive splay of extensional faults forming the Claritas Fossae, which resembles a trailing extensional imbricate fan. The compressional mountain belt defined by the Coprates Rise and Thaumasia Highlands forms the toe of the "mega-slide." Topographic observations and previous structural analyses reveal evidence for a failed volcanic plume below Syria Planum that could have provided both thermal energy and topographic potential for initiating regional deformation. Increased geothermal heating over time, or heating simply due to increasing depth in the crust due to continuing burial, would have contributed to flow of salt deposits, as well as formation of groundwater from melting ice and dewatering hydrous salts. We further propose that connection of overpressured groundwater from aquifers near the base of the detachment through the cryosphere to the martian surface created the outflow channels of Echus, Coprates and Juventae chasmata at relatively uniform source elevations along the northern margin of the "mega-slide" where regional groundwater flow would have been directed toward the surface. Our hypothesis provides a unifying framework to explain perplexing relationships between the rise of the Tharsis volcanic province, deformation of the Thaumasia Plateau, and the formation of Valles Marineris and associated outburst floods.
DE: 5415 Erosion and weathering
DE: 5419 Hydrology and fluvial processes
DE: 5475 Tectonics (8149)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting