Читать книгу Continental Rifted Margins 1 - Gwenn Peron-Pinvidic - Страница 37

Grabens and half-grabens are the most common type of sedimentary basins generated in extensional settings. A graben is typically identified as a valley flanked by distinct topographic escarpments. Structurally, grabens are formed by arrays of oppositely dipping normal faults. In the ideal case, the flanking faults are parallel and antithetic and grow at the same rate so that there is no rotation of the hanging wall. The overall downward movement of the common hanging wall leads to the formation of a symmetric depression: the graben (Figure 1.25). However, faults rarely grow at the same rate, so grabens are usually asymmetric. If several faults form, the hanging wall platform can be further dissected and can generate a horst (Figure 1.25). Half-grabens correspond to the topographic depression developed on the tilted hanging walls of normal faults.

Figure 1.25. Diagram illustrating the structural geometries of a graben, horst and half-graben