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Basic Structural Features II
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Listric Faults
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second main type of faults found in extensional regimes, listric faults
can be defined as curved normal faults in which the fault surface in
concave upwards; its dip decreases with depth. These faults also occur
in extension zones where there is a main detachment fracture following a
curved path rather than a planar path. Hanging wall blocks may either
rotate and slide along the fault plane (eg slumps), or they may pull
away from the main fault, slipping instead only along the low dipping
part of the fault. Roll-over anticlines will often form between bedding
planes and the main fault plane as a result of the flexing between the
two. |
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| Fig 4.2.1. Example of listric faults known
as slumps. Hanging wall blocks rotate and slide along the entire fault
plane. |
Fig 4.2.2.
The formation of a roll-over anticline will occur when a listric fault
collapses
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Shown below is an example of what
will happen as the hanging wall block of a listric fault is pulled away
from the foot wall block under extensional forces. The hanging wall
block shown in yellow/orange will collapse under its own weight as it is
pulled away. Sedimentation will then occur in the area created between
the foot and hanging walls. This is particularly true of sedimentary
basins.
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Fig 4.2.3. The evolution of a listric
fault
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