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Lecture 14

GEO 330 Lecture Notes - Lecture 14: Valles Marineris, Melas Chasma, Chasma

Course Code
GEO 330
Timothy Glotch

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East of Melas Chasma is Coprates Chasma, consisting of several parallel sections divided by ridges
Flat-floor of Coprates is generally free of landside material
Western canyon walls are roughly 10km high
East of Coprates, Valles Mariners canyon system changes significantly
All are much shallower than Coprates and
All have irregular outlines rather than being bounded by fault scarps
Canyons start to turn northward towards Chryse basin
Ganges, Capri, and Eos don't follow WNW-ESE trend of other canyons in Valles Mariners System
Capri Chasma contains layered mounds rich in sulfates and hematite
Many of these knobs are rich in SiO2phase such as chert or opaline silica
Floors covered with small knobs and hills, except for smooth areas with streamlined forms
East and South of Ganges, channels start in plains and flow into canyon
East of Eos, canyons transition to circum Chyrse chaos terrain
Valles Marineris -- Physiography
Canyons cut into layered volcanic rocks of Hesperian age that make up the surrounding Hesperian
Layers best seen in upper walls because lower walls are covered with talus
Location of transition between Hesperian and Nochian units is unclear
Branching side canyons cut deeply into some walls
May indicate that valley erosion was contemporaneous with downfaulting that formed the
Sediment is generally not seen accumulated at the mouths of these side canyons/valleys
Valles Marineris -- Canyon Walls
Layered rocks are volcanic and Hesperian in age
Layers most prominent at top of canyon walls
Layers not visible downslope due to presence of talus
Hesperian-Noachian transition not visible
Layered deposits on North wall of Melas Chasma
Up to 100km across and 80km long
Lucchitta (1979) identified 35 landside in Valles Mariners totaling 104km3in volume
Unconfined that flowed without meeting any barrier
Confined that ran into (and sometimes up) an opposing wall
Two basic types of landslides
Upper parts of consist of coarse, rotated, and displaced blocks in which original layering can
still be seen
(a) Bottom unit for unconfined landslides consists of longitudinally striated fan-shaped
apron extending across the canyon floor
(b) Bottom unit for confined landslides has transverse ridges instead of longitudinal
Landslides usually have 2 distinct units
Landslide deposits showing A) upper and lower units and B) overlapping landslides
Two different units probably reflect compositional differences -- upper unit probably more
competent volcanic rocks while lower unit could be finer-grained, possibly more weathered
Valles Marineris -- Landslides
Friday, March 30, 2018
1:16 PM
GEO 330 Page 1
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