Normal faults in sand-box experiments:
Physical models (=analogue experiments) allow to investigate how simplified, but properly scaled, geological systems react to simple boundaries conditions. Because sand has similar response to stress (i.e. similar rheology) than rocks at low temperature/low lithostatic pressure, it is a good analogue for the upper crust. Sand-box experiments simulating contractional, extensional and transcurrent tectonic regimes, have been successful in describing the first order characteristics of deformation in the upper crust.
McClay's team (from The Univ. of London) successfully creates, in its experimental laboratory, structures observed in nature. The top right picture illustrates the development a graben across an extended region. The graben is bounded by a set of symmetrically distributed planar normal faults. Bleu/black sands represent pre-extension sediments, the red sand is deposited during extension.
The bottom picture illustrates extension along a main detachment fault. There is a few secondary detachement faults that develop above and parallel to the main fault. The pre and syn-extension layers are curved downward in a configuration named roll-over anticline. In the right part of the box a horts (elevated block) and graben (block displaced downward) develop.
More at-> http://www.gl.rhbnc.ac.uk/FDP/Modellingframe.html |
 |
|
|
