Keywords : Tectonic

Structural and Tectonic Study of Brifka Anticline, Northern Iraq

Iraqi National Journal of Earth Sciences, 2018, Volume 18, Issue 1, Pages 29-58

A structural and tectonic study was carried out in the area between Baikher and Shaikhan anticlines. It is revealed that the main distinct structural feature is an anticline extending 16 Km northwest – southeasterly obeying the Zagros Range trend. This anticline with 6 km width and 16 km length called Brifka Anticline.
Several geologic formations are exposed in the studied area, ranging in time span from the Paleocene to Miocene periods. These formations are Kolosh, Khurmala, Gercus, Avanah and Pila Spi where Kolosh represented the core and Pila Spi makes the carapace of the anticline.
The geometrical analysis of this fold along four selected traverses revealed that the anticline is asymmetrical, mostly overturned and verged towards southwest, except in the fourth traverse it is appeared verging towards south. The anticline axis is oriented northwest -southeasterly in the first three traverses whereas it trended towards east- west in the fourth one.
The study included the vertical investigation of fold style of folded formations. It appeared that the anticline axis in Pila Spi Fn. is slightly changed from that of Kolosh Fn. in the first and forth traverses, whereas it changed anti clockwise 11-16° from Kolosh to Pila Spi formations in the second and third traverses.
The present study showed that the systems okl>c and hol>c are the most dominant joints in the first three traverses whereas hko>a system and ac set are abundant in the fourth traverse. It also revealed that the system hko>a are more abundance than hko>b system which indicate that the compression phase was tensive than the alternative tension.
Faults were investigated by field work and satellite image interpretation. It revealed three strike-slip faults inclined to the fold axis. They are BF1, BF2 and Besary faults. Another fault was concluded from the geometric properties and vergency of Brifka anticline. It is a foreland listric fault. This was followed by the determination of the formation thicknesses in order to conclude the sense of displacement of this fault. The determination appeared that the thicker sediments are in the area of the southwestern limb reflecting that the fault is reactivated as reverse foreland listric fault.(.

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.

Mineralogical Maturity, Weathering Index, Climate and Tectonic Setting of Injana Formation Based on Petrographic Constituents of Sandstones in Komal Syncline–North Iraq

Thamer A. Aghwan

Iraqi National Journal of Earth Sciences, 2004, Volume 4, Issue 1, Pages 47-57

Petrographical study of Injana Formation showed that the sandstones are composed of quartz, feldspars, high proportion of rock fragments, other components and carbonate cement. The sandstones are textuarlly, mineralogically immature as lithic arenite.
Petrographic criteria point out that a semiarid–semihumid climate had prevalied during deposition. The affinity to source area validate a back–arc tectonic environment for the source rocks, which was a sequal of the regional continental collision between the Arabian plate (Iraq) and Turkish, Iranian plate; with concomitant uplift and consequent increase in the erosional and depositional rates.