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U.S. Geological Survey Scientific Investigations Map 3041

Prepared for the National Aeronautics and Space Administration

Geologic Map of MTM –20012 and –25012 Quadrangles, Margaritifer Terra Region of Mars

By J.A. Grant, S.A. Wilson, C.M. Fortezzo, and D.A. Clark



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Mars Transverse Mercator (MTM) –20012 and –25012 quadrangles (lat 17.5°–27.5° S., long 345°–350° E.) cover a portion of Margaritifer Terra near the east end of Valles Marineris. The map area consists of a diverse assemblage of geologic surfaces including isolated knobs of rugged mountainous material, heavily cratered and dissected ancient highland material, a variety of plains materials, chaotic terrain materials, and one of the highest densities of preserved valleys and their associated deposits on the planet (Saunders, 1979; Baker, 1982; Phillips and others, 2000, 2001). The map area is centered on a degraded, partially filled, ~200-km-diameter impact structure (lat 22° S., long 347.5° E.), informally referred to as Paraná basin, located between Paraná Valles to the east and Loire Valles to the west. Paraná Valles is a network of multidigitate, mostly east-west-oriented valleys that flowed west and discharged into Paraná basin (Grant, 1987, 2000; Grant and Parker, 2002). Loire Valles, broadly comparable in length to the Grand Canyon on Earth, has a deeply incised channel within the map area that originates at the west-northwest edge of Erythraeum Chaos within Paraná basin (Grant, 1987, 2000; Grant and Parker, 2002; Strom and others, 2000). Paraná and Loire Valles, combined with Samara Valles to the west, form one of the most laterally extensive, well-integrated valley networks on Mars (Grant, 2000) and record a long history of modification by fluvial processes. The origin and morphology of the valley networks, therefore, provide insight into past environmental conditions, whereas their relation with other landforms helps constrain the timing and role of fluvial processes in the evolution and modification of the Margaritifer Terra region.

Version 1.0

First posted May 5, 2009

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For additional information contact:
Ken Tanaka

Astrogeology Research Program

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Suggested citation:

Grant, J.A., Wilson, S.A., Fortezzo, C.M., and Clark, D.A., 2009, Geologic map of MTM-20012 and -25012 quadrangles, Margaritifer Terra region of Mars: U.S. Geological Survey Scientific Investigations Map 3041, Version 1.0, 1:1,000,000, 1 sheet and pamphlet [].

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