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Basic Structural Features II

Listric Faults

The 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.


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
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.

Fig 4.2.3. The evolution of a listric fault
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