Publication: Chasma Australe, Mars: Structural Framework
for a Catastrophic Outflow Origin
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Publication Date
2000
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Elsevier Science B.V., Amsterdam
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Abstract
Chasma Australe, 500 km long and up to 80 km wide, is the most
remarkable of the martian south pole erosional reentrants carved in
the polar layered deposits. We have interpreted Chasma Australe
erosional and depositional features as evidence for a flood origin,
which we have reconstructed using a modified Manning equation.
The main characteristics of the flow are a water velocity between
30 and 50 m s¡1 and discharge values between 7 x 10^8 and 3 x 10^9 m3 s-1, very near to MGS data-based estimations for martian
outflow channels (D. E. Smith et al. 1998, Science 279, 1686–1692).
We thus postulate that Chasma Australe originated in a catastrophic
flood.
The tectonic study of an area (roughly 20 million km2 in size)
around Mars’ south pole included the measurement and projection
in rose diagrams of more than 300 lineaments, of which 85 were
wrinkle ridges and the rest straight scarps. The whole set of lineaments
can be explained by a stress field with a d1 N10ºE in strike,
the wrinkle ridges being reverse faults and the other lineaments direct
and strike-slip faults. The straight layout of parts of Chasma
Australe almost 200 km long suggests that the chasma was carved
following a fracture network. The effectiveness of the erosional process
(the canyon is up to 1000 m deep) leads us to suspect that this
carving was preceded by a sapping period. Endogenetic and exogenetic
processes would thus have contributed to the origin of this
landform