Indicating the Role of Geological Conditions in Shaping the Hareer Anticline, Iraqi Kurdistan Region

The Hareer anticline is within the High Folded Zone, facing southwards towards the Low Folded Zone. Both zones are part of the Outer Platform of the Arabian Plate. Moreover, both zones are part of the Zagros Fold-Thrust Belt located within the Zagros Foreland Basin. Although the Hareer anticline is a double plunging anticline oriented in a NW-SE trend, both plunges are abnormal. The northwestern plunge is gradually passing to the southwestern limb of the Pirat anticline; although there is a very shallow syncline in between them, giving a right-hand en-echelon form to the plunge. Whereas, the southeastern plunge disappears between the Kamosk anticline located southeast wards and the Shakrook anticline is located southwards. Both the Hareer and the Kamosk anticlines are thrusted over the Shakrook anticline by means of two long thrust faults that run almost parallel to the Hareer anticline. It is clearly observed that the anticline is growing northwest wards; according to the recognized geomorphological and structural features. High-Quality satellite images were interpreted to elucidate the abnormal form of the Hareer anticline. The interpreted data and different types of geomorphological features including the estimation of the rate of stream incision were checked in the field.


Introduction
The Iraqi Kurdistan Region includes tens of anticlines of different types and shapes located in different parts of the region. They are oriented in a NW-SE trend at the eastern part of the region and change to an E-W trend; approximately west of latitude E43˚30'. This change in the trend of the anticlines is attributed to the main trends of the Zagros and Taurus ranges, respectively. In tectonically active areas such as the Iraqi Kurdistan Region, which forms the northeastern part of the Arabian Plate; the lateral growth of anticlines is a very common phenomenon [1]- [7]. The lateral growth of the anticlines in the Iraqi Kurdistan Region is still active, as witnessed from different geomorphological and structural forms covered by different authors. The anticlines; accompanied with synclines are developed due to a clockwise movement of the Arabian Plate and its collision with the Eurasian (Iranian) Plate, forming a convergent tectonic plate boundary [8] [9]. The exerted forces due to the plates collision have developed regional trust faults and other local thrusts, reverse and normal faults; some of them are few kilometers in length, others attaining 30 km in length; like the one along the southwestern limb of the Hareer anticlines [10].
Anticlines can have abnormal structural shapes due to overturning, over-thrusting, en-echelon plunging, doming, extensive erosion and due to exposure of different rock types with different competencies (example: [2] [11] [12]). The Hareer anticline is one of those anticlines which has an abnormal structural shape.
The Hareer anticline is located in the central part of the Iraqi Kurdistan Region (Figure 1), and it forms part of the main chain of mountains which form the southern limits of the High Amplitude Mountains Province [10]. Hareer town is located along the most western part of the southwestern limb of the Hareer anticline which is about 50 km north of Erbil city. The town can be reached by a paved road from Erbil as well as by many other routes, whereas the anticline can be accessed through an unpaved road, which runs through the hinge zone of the anticline. The aim of this research is to elucidate the abnormal shape of the Hareer anticline and the status of its both plunges which are also unusual plunges, and to discuss the reasons for the development of these abnormal forms depending mainly on Campbell [13], Burbank and Anderson [11] and Fossen [12]. Moreover, to estimate the rate of the incision of the streams which dissect the anticline, through studying the abandoned alluvial fans following the Exposure Dating Method [14].
No special studies are available which deal especifically with the Hareer anticline; however, many studies are available in which the Hareer anticline was included. Among them are De Vera et al. [15] studied the Zagros Fold-Thrust Belt in the Kurdistan Region and considered the Hareer anticline as a continuous anticline with the existing east-west wards anticlines. Moreover, in a cross-section, they considered two subsurface thrust faults to exist along both plunges of the anticline. However, they do not present the long thrust fault which runs along the southwestern limb of the anticline. Burtscher et al. [16] conducted tectonic geomorphological investigations of antiforms using differential geometry at the Permam anticline, in northern Iraq and considered the Hareer anticline as a normal double plunging anticline. Sissakian and Fouad [10] updated the geological map of Iraq including the Hareer anticline. Sissakian and Abdul Jabbar [17] studied some of the transversal gorges in the Kurdistan Region and considered the streams which dissect the Hareer anticline as Neotectonic activity. Sissakian et al. [18] studied the origin and development of the Gulley Ali Beg gorge and concluded that the stream which flows in the studied gorge was originally flowing across the Hareer anticline and was diverted north-wards, due to the lateral growth of the Hareer anticline. Omar and Syan [19] constructed a structural model of the Hareer anticline and considered it as a double plunging asymmetrical anticline, dissected by three strike slipfaults. Le Garzica et al. [20], conducted a regional balanced and restored sections, across the northwestern part of the Zagros Fold-and-Thrust Belt in the Kurdistan Region of Iraq and a kinematic model that illustrates the evolution of the belt since Late Cretaceous time. They considered the Hareer anticline as a box fold characterized by short, steep dip domains along the flanks of the anticline. Moreover, they described the anticline as "whaleback anticline geometry which is highlighted by serial topographic profiles".

Materials and Methods
In order to fulfill the aim of this research work, different materials were used; such as geological maps of 1:100,000 and 1:250,000 scales, topographical maps at a scale of 1:100,000 and 1:20,000, many published articles, books and reports which deal either with the Hareer anticline or with the geology of the surrounding area.
High quality satellite images were interpreted to recognize the role of the geomorphological and structural features which contributed to creating abnormal shapes of the anticline, especially in the north western plunge and to indi- Field work was carried out to check the interpreted data from the satellite images, to measure the thicknesses of terraces and alluvial fans, and height differences between stream levels and base of terraces and/or alluvial fans. Geological and topographical maps were used to indicate different structural, geomorphological and topographical data of the Hareer anticline, with special attention paid to both plunges and the abnormal shape of the anticline. Satellite images were interpreted to recognize indications that have contributed to the development of the abnormal shape of the Hareer anticline. Moreover, to recognize different geomorphological and structural forms which indicate a lateral growth of the anticline. In this concern, we have emphasized the opinion of Keller and Pinter [14] and Ramsey et al. [4]. River terraces and abandoned alluvial fans were recognized from the satellite images by visual interpretation and were carefully investigated in the field to indicate their heights above nowadays streams levels and the thicknesses of each discovered level. Accordingly, the rates of deposition and incision during the Holocene Period were indicated.

Structural Geology and Tectonics
The Hareer anticline is NW-SE trending, a double plunging anticline with a box shape due to the existence of two anticlinal axes with a very shallow syncline between them ( Figure 1). Towards the north, there are the Pirat and Balisan anticlines, with a long syncline in between ( Figure 1). The northwestern plunge of the Hareer anticline being of right hand en-echelon type; with the Pirat anticline, whereas the southeastern plunge is dissected by a thrust fault which runs parallel to the southwestern limb and disappears between the Shakrook and Kamosk anticlines which are located south and southeast of the Hareer anticline, respectively. This thrust fault has caused the disappearance of the synclinal axis between the Hareer and Shakrook anticlines ( Figure 1). Moreover, the thrust fault has caused the overturning of the Pila Spi Formation along the southwestern limb of the Hareer anticline ( Figure 2). Another thrust fault runs within the southwestern limb of the anticline. It has caused the disappearance of part of the anticlinal axis ( Figure 3 and Figure 4). The northwestern plunge of the Hareer anticline is flat ( Figure 5) and there is a preponderance of a flat plunge, and a very gentle saddle between the Hareer and Pirat anticlines.
Along the main axis of the anticline and northwards, a very gentle antiform exists giving a box shape to the anticline with a maximum width of 4.8 km, whereas the width of the northwestern and southeastern parts does not exceed 1 km. Moreover, along the eastern part of the southwestern limb of the anticline, a low angle thrust fault occurs. It runs parallel to the axis and has caused the overriding part of the exposed rocks of the north-eastern limb, on those of the southwestern limb. Accordingly, forming very steep cliffs and the disappearance of the Qamchuqa Formation and the lower part of the Bekhme Formation ( Figure 3).
Tectonically, Hareer anticline is located within the High Folded Zone of the Hareer anticline which shows a very gentle and long northwestern plunge, whereas the main mass of the anticline has a whale-back shape.

Stratigraphy
The exposed formations along the Hareer anticlines are mentioned briefly from the oldest to the youngest depending on Sissakian and Al-Jibouri [26]. The geological map of the anticline is presented in Figure 4.

Geomorphology
The main geomorphological features within the Hareer anticline are very old alluvial fans (Figure 6

Results
The Hareer anticline is one of the main anticlines in the Kurdistan Region, in the northern part of Iraq. It forms the contact between the High Folded and Low Folded zones [21]. The length and width of the anticline is 25 km and 4.8 km, respectively. The anticline has a unique abnormal form, especially at both the northwestern and southeastern plunges. It forms a left hand en-echelon plunge with the Pirat anticline ( Figure 1 and The longitudinal cross-section, from northwestern plunge to the southeastern plunge (Cross-section L1 -L2, Figure 9) shows clear minor irregularities along the axial zone. The deepest one is a water gap (GZR, Figure 9) represented by Bekhme Gorge (Figure 1, Figure 2, Figure 4) at the extreme northwestern part of the anticline. Before this water gap, there is another deep topographic form near Spilk (Point No. 5, Figure 9), and most probably it represents a very old water gap which forms nowadays opposite the sides valleys ( Figure 10). This is attributed to a high rate of upward movement as compared to the rate of stream    Figure 2 and Figure 9).
incision at the area, besides the presence of a gentle saddle along the main axis of the Hareer anticline (Point A, Figure 9). The last deep topographic form along the longitudinal cross-section L1 -L2 (Point S, Figure 9) is another wind gap located at the southeastern plunge of the Hareer anticline. However, this can be formed due to the main thrust fault which runs parallel to the anticline.

Shape of the Hareer Anticline
The northwestern plunge of the Hareer anticline was east of Spilk (Figure 1 and   (Figure 11). By the continuous growth of the Hareer anticline northwest wards; as indicated from the presence of five wind gaps ( Figure   2, Figure 9 and Figure 12), the Khlaifan stream shifted to its nowadays geographic location, where it flows between the plunge areas of the Pirat and Korek anticlines (Figure 1 and Figure 5) [17]. The northwest wards growth is still continuous, and this is indicated by shifting of the axis of the Pirat anticline more northwards forming en-echelon pattern with the Hareer anticline (Figure 1 and    Figure 4 and Figure 12). This is not a normal form for en-echelon plunging; since there should be a syn-form between them; accordingly, the edges of their limbs should not form a straight line [12] [13] as it is the case in the Hareer and Pirat anticlines.

Rate of Incision of Spilk Stream
The elevation difference between the floor of the feeder channel of the Spilk alluvial fan and its nowadays base is 35 m (Figure 11). The thickness of the abandoned alluvial fan is 18 m. The age of the alluvial fans is most probably Holocene [30] [31], because it is covered by soil and not calcrete as the case with other old alluvial fans ( Figure 6). This means it was deposited during 11,700 years (Holocene, [32]). Therefore, the rate of the deposition of the abandoned Spilk alluvial fan will be 0.154 m/100 years (18 m × 100/11,700). Whereas the rate of the incision of the Spilk stream (the feeder channel) since the Holocene, is about 0.3 m/100 years (35 m × 100/11,700 years).

Conclusions
The authors conclude that the Hareer anticline has an abnormal shape, especially at the northwestern plunge area. This is attributed due to many interpreted and recognized geomorphological and structural forms, mainly due to its lateral and upward growth. Moreover, the anticline has two axes with a very gentle saddle in between, which gives the anticline a box-fold shape. Moreover, the hard