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Sedimentological analyses of martian gullies: The subsurface as the key to the surface

de Haas, Tjalling; Ventra, Dario; Hauber, Ernst; Conway, Susan J. and Kleinhans, Maarten G. (2015). Sedimentological analyses of martian gullies: The subsurface as the key to the surface. Icarus, 258 pp. 92–108.

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DOI (Digital Object Identifier) Link: https://doi.org/10.1016/j.icarus.2015.06.017
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Abstract

Gullies are among the youngest landforms formed by liquid water on Mars, and therefore of critical importance in resolving the planets most recent hydrologic and climatic history. Water-free sediment flows, debris flows and fluvial flows have all been identified in gullies. These processes require very different amounts of liquid water, and therefore their relative contribution to gully-formation is of key importance for climatic inferences. We show that many gullies dominantly formed by debris flows, based on sedimentological analysis of outcrops in gully-fans in 51 HiRISE images widely distributed over the southern midlatitudes. The great majority (96%) of outcrop exposures in gully-fans fed by catchments which mainly comprise bedrock and thus host boulders, contain sedimentological evidence for debris-flow formation. These exposures contain many randomly distributed large boulders (>1 m) suspended in a finer matrix and in some cases lens-shaped and truncated layering. Such diagnostic features are rare in gully-fan exposures mainly fed by catchments comprising abundant latitude dependent mantle deposits (LDM; a smooth, often meters-thick deposit consisting mainly of ice and dust), wherein boulders are largely absent. These LDM-fed gullies may have formed by fine-grained debris flows, but this cannot be determined from outcrop sedimentology alone because of the lack of boulders in these systems. The fan surface morphology, in contrast to the subsurface, is dominated by secondary, post-depositional, processes, mainly weathering, wind erosion, and ice-dust mantling. These processes have removed or severely reworked the original, primary, debris-flow morphology over time. This explains the controversy between previously published morphometric analyses implying debris-flow formation and observations of gully-fan surfaces, which are often interpreted as the product of fluvial flows because of the absence of surficial debris-flow morphology. The inferred debris-flow origin for many gullies implies limited and ephemeral liquid water during gully-formation.

Item Type: Journal Item
Copyright Holders: 2015 Elsevier Inc.
ISSN: 0019-1035
Project Funding Details:
Funded Project NameProject IDFunding Body
Wet, moist, or dry? Using digital terrain models to determine the amount of water that has shaped the surfaces of Earth, Mars and the Moon. (SE-10-183-MB)RPG-397The Leverhulme Trust
Keywords: Mars; martian surface; martian climate; martian atmosphere
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Physical Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 44429
Depositing User: Susan Conway
Date Deposited: 25 Sep 2015 09:37
Last Modified: 24 Jun 2019 15:32
URI: http://oro.open.ac.uk/id/eprint/44429
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