eprintid: 1468955
rev_number: 43
eprint_status: archive
userid: 608
dir: disk0/01/46/89/55
datestamp: 2015-06-03 08:46:06
lastmod: 2021-11-07 23:46:45
status_changed: 2015-06-03 08:46:06
type: article
metadata_visibility: show
item_issues_count: 0
creators_name: Harrison, SK
creators_name: Balme, MR
creators_name: Hagermann, A
creators_name: Murray, JB
creators_name: Muller, J-P
creators_name: Wilson, A
title: A branching, positive relief network in the middle member of the Medusae Fossae Formation, equatorial Mars—Evidence for sapping?
ispublished: pub
divisions: UCL
divisions: B04
divisions: C06
divisions: F63
note: This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
abstract: The Medusae Fossae Formation (MFF) is a geological formation comprising three geological units (members) spread across five principal lobes. It dominates a quarter of the longitudinal extent of the equatorial region of Mars. Positive relief features referred to as ‘sinuous ridges’ (commonly interpreted as inverted paleoflow channel or valley fills) have been observed in the lowest member of the western MFF, but have not been identified within the central and eastern portions of the formation, in the middle and upper members. This paper presents the identification and analysis of a branching, positive relief system which occurs in the central lobe of the MFF in what appears to be an exposure of the middle member. A simple geomorphological map of the system is presented, from which we have adopted the working hypothesis that this is an inverted fill of a branching fluvial channel or valley system. A suite of morphological and topographic evidence supporting this hypothesis is presented, including analysis of the network using a ∼15 m/pixel digital terrain model derived from a Context Imager (CTX) stereo image pair. The evidence supporting this hypothesis includes: (1) the local slope and topography of the upper surface of the network are consistent with a contributory network; (2) the braided, fan-like form at the termination of the branching network is consistent in morphology with it being a depositional fan at the end of a fluvial system; (3) the terminal fan and surrounding deposits show layering and polygonization; and (4) there is strong association between the lower order branches and amphitheater shaped scarps in the depression walls. We evaluate the possible origins of this fluvial system and suggest that seepage sapping is the most probable. Two possible models for the evolution of the network and related features are presented; both require melt of ice within the MFF to form liquid water. We conclude that at least some portions of the Medusae Fossae Formation, if not the entire formation, were once volatile-rich. Finally, we note that our observations do not rule out the case that this network formed before MFF emplacement, and has since been exhumed. However, this conclusion would suggest that much of the surrounding terrain, currently mapped as middle-member MFF, is not in fact MFF material at all.
date: 2013-09
official_url: http://dx.doi.org/10.1016/j.pss.2013.06.004
vfaculties: VMPS
oa_status: green
full_text_type: pub
language: eng
primo: open
primo_central: open_green
verified: verified_manual
elements_source: crossref
elements_id: 1035724
doi: 10.1016/j.pss.2013.06.004
lyricists_name: Muller, Jan-Peter
lyricists_id: JPALM41
full_text_status: public
publication: Planetary and Space Science
volume: 85
pagerange: 142 - 163
issn: 0032-0633
citation:        Harrison, SK;    Balme, MR;    Hagermann, A;    Murray, JB;    Muller, J-P;    Wilson, A;      (2013)    A branching, positive relief network in the middle member of the Medusae Fossae Formation, equatorial Mars—Evidence for sapping?                   Planetary and Space Science , 85    142 - 163.    10.1016/j.pss.2013.06.004 <https://doi.org/10.1016/j.pss.2013.06.004>.       Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/1468955/1/1-s2.0-S0032063313001451-main.pdf