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Landforms associated w/water (Runoff Valley Morphology (Amphitheatre-like…
Landforms associated w/water
Evidence
for water
especially in sediment transport
evidence for persistent water flow & sediment deposition
Distributary Fans
inverted channels/meanders
preferentially erode soft sediment around channel
more resistant channel deposits remain
Valleys & Channels
sinuous channels incised into bedrock
Contraction-crack polygons
on Northern Plains
akin to ice polygons in periglacial environments
ridge / troughs mark polygon boundaries
Martian Glaciers?
Glacial like forms (GLFs)
Moraine band formations
Lobate debris aprons
Non-directional valley fill
S. Phlegra Montes Glacial Like Forms
Late Amazonian ~150 Myr
Terminal deposits
Moraine-like regions
Remnant glaciers
Glacial thermokarst
Esker system
Remnant ice-cored material
Runoff Channels
Valley networks
Dendritic
Meandering
valley forms
thickly blanketed by dust layer
in heavily cratered S Uplands
Scamander Vallis
Implied formation by precipitation runoff
Gale Crater
Recent discoveries Curiosity Rover
Conglomerates
rounded clasts evince water transport
Mudcracks
Mudstone Mineralogy
from Curiosity's CheMin - 2013 - 2016
Diferences mudstone mineralogy
Due to source of minerals
Deposition by water, sedimentation, rock forming & later alteration
Jarosite - indicator acidic water
Overlying (younger) layers show decreasing acidity (jarosite less abundant)
Runoff Valley Morphology
Amphitheatre
-like valley heads
1-10 km wide & 5-1000 km long
Low drainage density
Hanging valleys
Structural control of networks
Crenulated, steep-sided
valley walls
Lack of uniform downstream increase
valley width
Low junction angle
between tributary & trunk channel
Networks ~parallel to quasi-parallel
though dendritic exist
Some
lack landforms
directly indicating fluid flow
Short first-
order segments
different origin vs Earth
backweathering/collapse where groundwater seaps out
appear from nowhere
Spring sapping
headward
erosion
causes origin to move back away from streamflow direction
erosion at origin of stream channel
canyons formed by erosion by groundwater
includes collapse of saturated material, surface stream erosion & chemical weathering
suggests significant groundwater stores
e.g.
Valles Marineris
side canyons formed by spring sapping
Gullies
Appear to be changing with time
channel&valley walls / dune fields / peaks / crater pits etc
source alcove - incised midlde reach - terminal debris fan deposits (fan lacking in dune)
Possible formation
Debris flow /dry mass wasting
Melting snowpacks
Hyperconcentrated fluid flow
granular flows
e.g. Nirgal Vallis, Hale Crater