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Principle of Paleostress Analysis
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Although the mathematics behind the concept of stress may be a bit complicated, the determination in the field of the orientation in space of the paleostress ellipsoid responsible for the development of stylolithes, fractures and faults is relatively easy. We have seen that there is a simple set of relationships between the orientation of the paleostress ellipsoid and the orientation of stylolitic joints, shear fractures and extensional fractures that develop in response to an applied state of stress.
The sketch on the right shows a set of microstructures that develop due to a tectonic regime in compression. From a stress point of view, a tectonic regime in compression is characterized by σ3 being the vertical stress axis. From a strain point of view it is characterized by vertical stylolitic joints and horizontal extensional fractures.The stylolitic cones point in the direction of σ1. The normal of the extensional fractures is parallel to σ3. σ2 is perpendicular to both σ1 and σ3. |
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