Valles Marineris dune sediment provenance and pathways

•Sources were sought for dunes in Valles Marineris using multiple data sets.•Dunes there appear to be locally and regionally derived from numerous sources.•These include: various wall outcrops, sedimentary-layered deposit, and landslides.•Compelling evidence for sand pathways from extra-rift sources...

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Published in:Icarus (New York, N.Y. 1962) N.Y. 1962), 2014-04, Vol.232, p.187-219
Main Authors: Chojnacki, Matthew, Burr, Devon M., Moersch, Jeffrey E., Wray, James J.
Format: Article
Language:English
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Summary:•Sources were sought for dunes in Valles Marineris using multiple data sets.•Dunes there appear to be locally and regionally derived from numerous sources.•These include: various wall outcrops, sedimentary-layered deposit, and landslides.•Compelling evidence for sand pathways from extra-rift sources was not found.•Compositional heterogeneity argues for distinct sources and aeolian fractionation. Although low-albedo sand is a prevalent component of the martian surface, sources and pathways of the sands are uncertain. As one of the principal present-day martian sediment sinks, the Valles Marineris (VM) rift system hosts a diversity of dune field populations associated with a variety of landforms that serve as potential sediment sources, including spur-and-gully walls, interior layered deposits (ILDs), and landslides. Here, we test the hypothesis that VM dune fields are largely derived from a variety of local and regional (intra-rift) sediment sources. Results show several dune fields are superposed on ancient wall massifs and ILDs that are topographically isolated from extra-rift sand sources. Spectral analysis of dune sand reveals compositional heterogeneity at the basinal-, dune field-, and dune-scales, arguing for discrete, relatively unmixed sediment sources. In Coprates and Melas chasmata, mapping is consistent with the principle sand source for dunes being Noachian-aged upper and lower wall materials composed of primary (igneous) minerals and glasses, some of which show evidence for alteration. In contrast, dune fields in Capri, Juventae, and Ganges chasmata show evidence for partial sediment derivation from adjacent Early Hesperian-aged hydrated sulfate-bearing ILD units. This finding indicates that these ILDs act as secondary sand sources. Dunes containing “soft” secondary minerals (e.g., monohydrated sulfate) are unlikely to have been derived from distant sources due to the physical weathering of sand grains during transport. Isolated extra-rift dune fields, sand sheets, and sand patches are located on the plateaus surrounding VM and the adjoining areas, but do not form interconnected networks of sand pathways into the rift. If past wind regimes (with respect to directionality and seasonality) were consistent with more recent regimes inferred from morphological analysis (i.e., dune slip faces, wind streaks), and were sufficient in strength and duration, small dune populations within Aurorae Chaos and north of eastern VM might have resulted from exte
ISSN:0019-1035
1090-2643
DOI:10.1016/j.icarus.2014.01.011