Keywords : Perat

Analysis of Slope Failure at the Southwestern Limb of Perat Anticline - NE Iraq Using Stereographic Projection

Iraqi National Journal of Earth Sciences, 2018, Volume 18, Issue 1, Pages 59-76

Rock slopes analysis in south western limb of Perat anticline, near Bekhme village, were studied. Seven stations were chosen to study these slopes which distributed along several exposed formations of Bekhme, Shiranish, Tanjero, Kolosh, Khurmala, and Gercus interbeded with Pila Spi according to their existence on the road, beginning from the Iron Bridge of Bekhme.
Stereographic projection technique was used in analyzing and classifying these slopes. Plane sliding along bedding planes and joints is the predominant in the formations of Bekhme, Shiranish, Pila Spi and some of khurmala Formation. Clastic rock Formations of Tanjero, Kolosh, and Gercus help to failure in steep and moderate slopes. Because of no distinctive favorable discontinuities to slide along, these slopes are suffering from raveling processes which means granular disintegration into small components by different processes. The rock slopes of Khurmala Formation are affected by wedge sliding along discontinuities intersections with bedding planes.

Structural Analysis and Tectonic Interpretation of Brittle Failure Structures at Perat Anticline – NE Iraq

Mohsen S. Dawlat; Rabeea Kh. Al-Hamdani; Hadeer Gh. M. Adeeb; Ibrahim S. Al-Jumaily

Iraqi National Journal of Earth Sciences, 2012, Volume 12, Issue 2, Pages 17-42

Perat anticline is located about 100 km. northeast Mosul city. It extends
NW-SE for about 35 km through high folded zone of the foreland fold belt of the Zagros collision zone.
Joints were classified into sets and systems according to their relations with three mutually perpendicular tectonic axes. Tension sets are ac and bc, the first one formed by extension along fold axis accompanying direct compression perpendicular to fold trend, whereas the second is the product of relaxation that succeeded the primary compression. The shear systems are hko, hol and okl developed successively during direct compression and subsequent relaxation episodes of each tectonic pulse.
Planar calcite veins occupying ac, bc and hko joint sets and systems are also prevalent in the study area. Furthermore, singular and conjugate enechelon lenticular vein arrays are displayed within some carbonate units of study area. They enclose acute angles either with a or b tectonic axes indicating that they have been formed under two alternating stress regimes. The maximum horizontal compressive stress axis was perpendicular and parallel to the fold axis in the first and second regimes respectively.
The planar and lenticular vein arrays are associated with two orthogonal pressure solution sets (stylolite seams). The peaks of them refer also to the mentioned directions of the maximum horizontal compressive stress. The juxtaposition of these two brittle structure types reflects their kinematic interrelation and hence non-dilation deformation type.
Paleostress analysis of mesofaults falls into compressive, extensional and strike slip states. σ1 axis of compressive and strike slip states lies in normal and parallel orientations with respected fold axis. Whereas σ3 axis of extensional state lies normally to the same fold axis. This state seems compatible with the final uplift of the fold which supplemented also by development of bedding parallel stylolite seams with vertically pointing peaks.