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Continental-scale salt tectonics on Mars and the origin of Valles Marineris and associated outflow channels

David R. Montgomery, Sanjoy M. Som, Martin P. A. Jackson, B. Charlotte Schreiber, Alan R. Gillespie and John B. Adams
Continental-scale salt tectonics on Mars and the origin of Valles Marineris and associated outflow channels
Geological Society of America Bulletin (January 2009) 121 (1-2): 117-133


A synthesis of deformation patterns within and around the Thaumasia Plateau, Mars, points 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 lateral zones of transtension and strike-slip--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 (approximately 1 degrees ) 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 and/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 extension, collapse, and excavation along fractures radial to Tharsis, either forming or 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 further thermal energy and topographic potential for initiating regional deformation, either intrusively through inflation or extrusively through lava flow and/or ash fall emplacement. Higher heat flow during Noachian time, or geothermal heating due to burial by Tharsis-derived volcanic rocks, would have contributed to flow of salt deposits, as well as formation of groundwater from melting ice and dewatering of 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 outflow channels.

ISSN: 0016-7606
EISSN: 1943-2674
Serial Title: Geological Society of America Bulletin
Serial Volume: 121
Serial Issue: 1-2
Title: Continental-scale salt tectonics on Mars and the origin of Valles Marineris and associated outflow channels
Affiliation: University of Washington, Quaternary Research Center, Seattle, WA, United States
Pages: 117-133
Published: 200901
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 128
Accession Number: 2009-017707
Categories: Extraterrestrial geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. block diag., 2 tables, sketch maps
Secondary Affiliation: University of Texas at Austin, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200911
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