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A graben is a section of crust that has lowered relative to the blocks on either side, which is a result of its bounding faults dipping towards each other. [2] The plural of graben can be either graben or grabens. Graben form low-lying features such as basins and rift valleys. [1] [2] They can be very long relative to their width.
Graben often occur side by side with horsts. Horst and graben structures indicate tensional forces and crustal stretching. Graben are produced from parallel normal faults, where the displacement of the hanging wall is downward, while that of the footwall is upward. The faults typically dip toward the center of the graben from both sides.
In physical geography and geology, a horst is a raised fault block bounded by normal faults. [1] Horsts are typically found together with grabens. While a horst is lifted or remains stationary, the grabens on either side subside. [2] This is often caused by extensional forces pulling apart the crust.
Fault scarp – Small vertical offset on the ground surface; Graben – Depressed block of planetary crust bordered by parallel normal faults; Horst – Raised fault block bounded by normal faults; Mid-ocean ridge – Basaltic underwater mountain system formed by plate tectonic spreading
However, the Brannon Member was not limited purely to this graben structure - it gradually pinches out northeastward as well, and overlies the southwestern Tanglewood area, apparently as a result of its horst subsiding. It lies atop a hardground that was rapidly flooded by waters coming from the western Sebree trough. The rocks themselves ...
With crustal extension, a series of normal faults which occur in groups, form in close proximity and dipping in opposite directions. [4] As the crust extends it fractures in series of fault planes, some blocks sink down due to gravity, creating long linear valleys or basins also known as grabens, while the blocks remaining up or uplifted produce mountains or ranges, also known as horsts.
The geology of Kentucky formed beginning more than one billion years ago, in the Proterozoic eon of the Precambrian. The oldest igneous and metamorphic crystalline basement rock is part of the Grenville Province, a small continent that collided with the early North American continent.
A few kilometers south of Cairo there are en echelon minor faults between two major faults that produce a relay ramp style transfer zone. In the northern part of the Suez rift system the Gharandal transfer zone accommodates deformation in a broad anticlinal structure between two listric faults in a collateral horst and graben.