Breached anticlines can become incised by stream erosion, forming an anticlinal valley. It is an anticlinal structure, with oil trapped stratigraphically by the anticline. These formations occur because anticlinal ridges typically develop above thrust faults during crustal deformations. Gairsain is located along an anticlinal thrust plane of the Almora nappe. Valleys may be synclinal valleys or anticlinal valleys. Hanging Rocks consists of anticlinal stratified sandstone and limestone layers. The center of the Negev is dominated by northeast-southwest anticlinal ridges. The system of "anticlinal ridges" affecting the sedimentary cover is also arranged in this direction. The Southern Range forms the third anticlinal uplift. Folding also can provide tension, such as along the top of an anticlinal fold axis. The Sinjar Mountains are a breached anticlinal structure. Inglewood Fault zone, suspecting it was an anticlinal structure capable of holding oil. The mountain is anticlinal in structure. In the Arcabuco Formation, in the Iguaque Anticlinal, dinosaur tracks have been found. About 80 percent of the world's petroleum has been found in anticlinal traps.