Basement controls on the scale of giant polygons in Utopia Planitia, Mars

Details Basement controls on the scale of giant polygons in Utopia Planitia, Mars Basement controls on the scale of giant polygons in Utopia Planitia, Mars

Sep 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011jgre..11609003c&link_type=abstract

Journal of Geophysical Research, Volume 116, Issue E9, CiteID E09003

Physics

1

Planetary Sciences: Solid Surface Planets: Surface Materials And Properties, Planetary Sciences: Solid Surface Planets: Tectonics (8149), Structural Geology: Fractures And Faults, Structural Geology: Mechanics, Theory, And Modeling

Scientific paper

We investigate the role of buried basement topography in controlling the scale of the giant polygons of Utopia Planitia (49°N, 233°W), Mars. Thermal Emission Imaging System (THEMIS) Infrared Daytime image mosaics reveal ˜6 km average spacing of polygon troughs along selected basin-radial transects. If graben spacing correlates to thickness of the Utopia basin sediments, this measured trough spacing suggests ˜3 km of sediment, in contrast to inferences of 1-2 km thick sediments within this portion of the basin. Irregular basement topography can influence trough development within the contracting sediments by localizing stresses at the top of basement slopes so that the trough spacing correlates to topographic variations rather than layer thickness. Along the slopes, locally large strains responsible for graben development may develop with only modest levels of sediment contraction. Mars Orbiter Laser Altimeter (MOLA) data from the highlands region, which may represent the buried topography in Utopia basin, are used to create a stochastic suite of numerical simulations of the Utopia basin, where fracture seeds along the base of the model represent potential basement topography beneath the basin. At low strain, our models that simulate wet, fine sediment produce surface fractures with ˜4-7 km spacing, which matches the spacing of troughs in the polygonal terrain of the Utopia basin. This match supports the idea that buried topography below contracting wet sediments may exert primary control on the scale of polygonal troughs. Furthermore, volumetric contraction can produce locally high extensional strains with or without a contribution from tectonic uplift.

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