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Site Descriptions
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Site 1: The “Latitude Dependent Mantle” (LDM) deposit and gully are located within the
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fresh ~3 km diameter Tivat impact crater in Noachis Terra. The deposit is restricted to the
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pole-facing half of both the interior and exterior crater walls and displays polygonal
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patterning (Fig. S1). The deposit does not extend up to the crater rim and is covered by
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boulders, which seem to have been shed from the crater rim. Smaller gullies are located on
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the west-facing and north-west facing interior crater walls, which do not incise into
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polygonally patterned LDM. The gully studied is almost entirely constrained within the
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LDM, with some evidence for contribution from the non-mantled crater wall in the
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easternmost portion.
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Site 2: The LDM deposit and gully are located inside a 1.6 km impact into the southeast-
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facing slope of the Nereidum Montes on the northern rim of the Argyre impact basin. Slopes
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of all orientations are covered by a mantling material at this location and the summits are free
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from mantling [Raack et al., 2012]. The material inside of the study-crater is distinguishable
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from these other mantles as it displays polygonal patterning, hence we interpret it as LDM
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(Fig. S1). To the southeast and southwest of, and topographically lower than, the crater there
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are arcuate ridges. The gully is contained within the LDM, but some rills extend from its
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upper-edge, suggesting a possible contribution from the exposed crater rim. The deposits of
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the gully are bright compared to the surrounding terrain, similar to deposits which have
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appeared on other gullies in the last few decades [McEwen et al., 2007], however these
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deposits are visible in the earliest image dating from 2004 (Mars Orbiter Camera R13/04753).
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Site 3: The LDM deposit and gullies are located on the pole-facing slope of a 28 km diameter
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impact crater, which is flat-floored and lacks an ejecta blanket or raised rim typical of
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Noachian aged impacts [Craddock and Maxwell, 1993]. The gullies in this crater were
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studied by Parsons and Nimmo [2010] and the LDM deposit extends for at least 18 km
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laterally along the crater wall. The LDM superposes another mantling unit located at the base
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of the crater wall. The underlying unit is pitted at the decametre-scale at its margins and is
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smooth otherwise, with no polygonisation. The LDM here has downslope lineations similar
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to those exhibited by the LDM studied in Schon and Head [2011] and polygons are expressed
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within the gully-incisions. Five of the ten gullies studied (Fig. S1) have their source areas
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restricted to the LDM, whereas the others are also connected to the rocky upslope areas.
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Hence, significant contribution of debris cannot be discounted for these gully-systems.
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Site 4: The LDM deposit and gullies are on the pole-facing slope of an 8 km diameter impact
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crater. The impact crater has a central peak, rampart ejecta and terraces on its western to
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south-western rim, indicating post-impact collapse. The crater floor contains polygonised,
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pitted and ridged material resembling concentric crater fill (CCF) [Levy et al., 2010; Dickson
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et al., 2012; Fastook and Head, 2014], which appears to deform around the central peak, with
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a southwards inferred flow direction. The LDM on the pole-facing wall lacks the ridges and
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pitting of the CCF, but grades seamlessly into it. These two deposits could be one and the
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same or the LDM could simply be blanketing the whole CCF deposit.
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Site 5: The gully at this site is located on the equator-facing wall of a 4.6 km fresh impact
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crater located to the NW of Lyot Crater in the northern plains of Mars. The crater is unfilled,
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has a sharp rim and rampart and rayed ejecta deposits. Gullies are found at all orientations,
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with the largest gully-system forming the object of this study. The crater walls have abundant
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boulders and evidence of some aeolian mantling, but no polygonisation, downslope-lineation,
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fractures or pits which are often associated with the LDM.
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References cited:
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Craddock, R. A., and T. A. Maxwell (1993), Geomorphic evolution of the Martian highlands
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through ancient fluvial processes, J. Geophys. Res. Planets, 98(E2), 3453–3468,
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doi:10.1029/92JE02508.
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Dickson, J. L., J. W. Head, and C. I. Fassett (2012), Patterns of accumulation and flow of ice
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in the mid-latitudes of Mars during the Amazonian, Icarus, 219(2), 723–732,
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doi:10.1016/j.icarus.2012.03.010.
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Fastook, J. L., and J. W. Head (2014), Amazonian mid- to high-latitude glaciation on Mars:
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Supply-limited ice sources, ice accumulation patterns, and concentric crater fill glacial
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flow and ice sequestration, Planet. Space Sci., 91(0), 60–76,
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doi:10.1016/j.pss.2013.12.002.
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Levy, J., J. W. Head, and D. R. Marchant (2010), Concentric crater fill in the northern mid-
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latitudes of Mars: Formation processes and relationships to similar landforms of
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glacial origin, Icarus, 209(2), 390–404, doi:10.1016/j.icarus.2010.03.036.
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McEwen, A. S. et al. (2007), A closer look at water-related geologic activity on Mars,
Science, 317(5845), 1706–1709.
Parsons, R. A., and F. Nimmo (2010), Numerical modeling of Martian gully sediment
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transport: Testing the fluvial hypothesis, J Geophys Res, 115(E6),
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doi:10.1029/2009JE003517, doi:10.1029/2009je003517.
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Raack, J., D. Reiss, and H. Hiesinger (2012), Gullies and their relationships to the dust-ice
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mantle in the northwestern Argyre Basin, Mars, Icarus, 219, 129–141,
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doi:10.1016/j.icarus.2012.02.025.
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Schon, S. C., and J. W. Head (2011), Keys to gully formation processes on Mars: Relation to
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climate cycles and sources of meltwater, Icarus, 213(1), 428–432,
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doi:10.1016/j.icarus.2011.02.020.
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Figure Captions
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Fig. S1: Overview and detail panels for each of our study sites 1-5. North is up in all panels
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and the scale bars in row 1 are applicable for every panel in that column. Column A:
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Overview of each site, with the gullies studied outlined in green and labelled where there is
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more than one. The location of the panels in columns B and C are indicated by boxes.
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Column B: Textures of the terrain into which the gullies are incised, sites 1-4 have
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polygonally patterned ground and site 5 has smooth material. Column C: Texture of the
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surrounding terrain away from the gullies. Polygonally patterned ground is pervasive at sites
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1, 2 and 4. Site 3 shows some evidence of polygonal pattern, but the dominant pattern is
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downslope lineations. HiRISE images used as follows: site 1:
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ESP_013624_1335_RED_A_01_ORTHO site 2: ESP_013850_1415_RED_A_01_ORTHO
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site 3: PSP_002659_1420 (orthorectified) site 4: ESP_011672_1395 (orthorectified) and site
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5: ESP_027231_2340 (orthorectified). Credit NASA/JPL/UofA.
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Fig. S2: Superposition relationships of channels and fans in sites 3 and 4. Part (A) for each
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site gives the context for part (B). Features labelled i-iv are channel-fan systems where
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superposition gives the reltive age, with feautres marked “i” being youngest and “iv” being
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oldest. “?” indicates where the interpretation of the relative age is uncertain. HiRISE images
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used as follows: site 3: PSP_002659_1420 (orthorectified) and site 4: ESP_011672_1395
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(orthorectified). Credit NASA/JPL/UofA.
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