1
Site Descriptions
2
Site 1: The “Latitude Dependent Mantle” (LDM) deposit and gully are located within the
3
fresh ~3 km diameter Tivat impact crater in Noachis Terra. The deposit is restricted to the
4
pole-facing half of both the interior and exterior crater walls and displays polygonal
5
patterning (Fig. S1). The deposit does not extend up to the crater rim and is covered by
6
boulders, which seem to have been shed from the crater rim. Smaller gullies are located on
7
the west-facing and north-west facing interior crater walls, which do not incise into
8
polygonally patterned LDM. The gully studied is almost entirely constrained within the
9
LDM, with some evidence for contribution from the non-mantled crater wall in the
10
easternmost portion.
11
Site 2: The LDM deposit and gully are located inside a 1.6 km impact into the southeast-
12
facing slope of the Nereidum Montes on the northern rim of the Argyre impact basin. Slopes
13
of all orientations are covered by a mantling material at this location and the summits are free
14
from mantling [Raack et al., 2012]. The material inside of the study-crater is distinguishable
15
from these other mantles as it displays polygonal patterning, hence we interpret it as LDM
16
(Fig. S1). To the southeast and southwest of, and topographically lower than, the crater there
17
are arcuate ridges. The gully is contained within the LDM, but some rills extend from its
18
upper-edge, suggesting a possible contribution from the exposed crater rim. The deposits of
19
the gully are bright compared to the surrounding terrain, similar to deposits which have
20
appeared on other gullies in the last few decades [McEwen et al., 2007], however these
21
deposits are visible in the earliest image dating from 2004 (Mars Orbiter Camera R13/04753).
22
Site 3: The LDM deposit and gullies are located on the pole-facing slope of a 28 km diameter
23
impact crater, which is flat-floored and lacks an ejecta blanket or raised rim typical of
24
Noachian aged impacts [Craddock and Maxwell, 1993]. The gullies in this crater were
25
studied by Parsons and Nimmo [2010] and the LDM deposit extends for at least 18 km
26
laterally along the crater wall. The LDM superposes another mantling unit located at the base
27
of the crater wall. The underlying unit is pitted at the decametre-scale at its margins and is
28
smooth otherwise, with no polygonisation. The LDM here has downslope lineations similar
29
to those exhibited by the LDM studied in Schon and Head [2011] and polygons are expressed
30
within the gully-incisions. Five of the ten gullies studied (Fig. S1) have their source areas
31
restricted to the LDM, whereas the others are also connected to the rocky upslope areas.
32
Hence, significant contribution of debris cannot be discounted for these gully-systems.
33
Site 4: The LDM deposit and gullies are on the pole-facing slope of an 8 km diameter impact
34
crater. The impact crater has a central peak, rampart ejecta and terraces on its western to
35
south-western rim, indicating post-impact collapse. The crater floor contains polygonised,
36
pitted and ridged material resembling concentric crater fill (CCF) [Levy et al., 2010; Dickson
37
et al., 2012; Fastook and Head, 2014], which appears to deform around the central peak, with
38
a southwards inferred flow direction. The LDM on the pole-facing wall lacks the ridges and
39
pitting of the CCF, but grades seamlessly into it. These two deposits could be one and the
40
same or the LDM could simply be blanketing the whole CCF deposit.
41
Site 5: The gully at this site is located on the equator-facing wall of a 4.6 km fresh impact
42
crater located to the NW of Lyot Crater in the northern plains of Mars. The crater is unfilled,
43
has a sharp rim and rampart and rayed ejecta deposits. Gullies are found at all orientations,
44
with the largest gully-system forming the object of this study. The crater walls have abundant
45
boulders and evidence of some aeolian mantling, but no polygonisation, downslope-lineation,
46
fractures or pits which are often associated with the LDM.
47
References cited:
48
Craddock, R. A., and T. A. Maxwell (1993), Geomorphic evolution of the Martian highlands
49
through ancient fluvial processes, J. Geophys. Res. Planets, 98(E2), 3453–3468,
50
doi:10.1029/92JE02508.
51
Dickson, J. L., J. W. Head, and C. I. Fassett (2012), Patterns of accumulation and flow of ice
52
in the mid-latitudes of Mars during the Amazonian, Icarus, 219(2), 723–732,
53
doi:10.1016/j.icarus.2012.03.010.
54
Fastook, J. L., and J. W. Head (2014), Amazonian mid- to high-latitude glaciation on Mars:
55
Supply-limited ice sources, ice accumulation patterns, and concentric crater fill glacial
56
flow and ice sequestration, Planet. Space Sci., 91(0), 60–76,
57
doi:10.1016/j.pss.2013.12.002.
58
Levy, J., J. W. Head, and D. R. Marchant (2010), Concentric crater fill in the northern mid-
59
latitudes of Mars: Formation processes and relationships to similar landforms of
60
glacial origin, Icarus, 209(2), 390–404, doi:10.1016/j.icarus.2010.03.036.
61
62
63
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
64
transport: Testing the fluvial hypothesis, J Geophys Res, 115(E6),
65
doi:10.1029/2009JE003517, doi:10.1029/2009je003517.
66
Raack, J., D. Reiss, and H. Hiesinger (2012), Gullies and their relationships to the dust-ice
67
mantle in the northwestern Argyre Basin, Mars, Icarus, 219, 129–141,
68
doi:10.1016/j.icarus.2012.02.025.
69
Schon, S. C., and J. W. Head (2011), Keys to gully formation processes on Mars: Relation to
70
climate cycles and sources of meltwater, Icarus, 213(1), 428–432,
71
doi:10.1016/j.icarus.2011.02.020.
72
Figure Captions
73
74
Fig. S1: Overview and detail panels for each of our study sites 1-5. North is up in all panels
75
and the scale bars in row 1 are applicable for every panel in that column. Column A:
76
Overview of each site, with the gullies studied outlined in green and labelled where there is
77
more than one. The location of the panels in columns B and C are indicated by boxes.
78
Column B: Textures of the terrain into which the gullies are incised, sites 1-4 have
79
polygonally patterned ground and site 5 has smooth material. Column C: Texture of the
80
surrounding terrain away from the gullies. Polygonally patterned ground is pervasive at sites
81
1, 2 and 4. Site 3 shows some evidence of polygonal pattern, but the dominant pattern is
82
downslope lineations. HiRISE images used as follows: site 1:
83
ESP_013624_1335_RED_A_01_ORTHO site 2: ESP_013850_1415_RED_A_01_ORTHO
84
site 3: PSP_002659_1420 (orthorectified) site 4: ESP_011672_1395 (orthorectified) and site
85
5: ESP_027231_2340 (orthorectified). Credit NASA/JPL/UofA.
86
87
Fig. S2: Superposition relationships of channels and fans in sites 3 and 4. Part (A) for each
88
site gives the context for part (B). Features labelled i-iv are channel-fan systems where
89
superposition gives the reltive age, with feautres marked “i” being youngest and “iv” being
90
oldest. “?” indicates where the interpretation of the relative age is uncertain. HiRISE images
91
used as follows: site 3: PSP_002659_1420 (orthorectified) and site 4: ESP_011672_1395
92
(orthorectified). Credit NASA/JPL/UofA.
93