Structural and Tectonic Study of Qara Sard Anticline and Choplagh Syncline, from Sulaimaniya Area, Kurdistan Region, Northeastern Iraq

Abstract

The study of the structural geology and tectonics of Qara Sard anticline and Goblagh syncline is carried out within the northwestern part of Zagros Fold-Thrust Belt (ZFTB) in Sulaimaniya area, Kurdistan region, Iraq. Qamchuqa Formation (Early Cretaceous) builds up the core of the anticline and overlain by Kometan, Shiranish and Tanjero formations (Late Cretaceous). Moreover, Khalakan Formation overlies Kometan Formation on the northeastern limb of the anticline. Tanjero Formation appears at the core of Choplaghsyncline. The structural geometrical analyses of seven traverses (P) cutting across the anticline and the syncline, revealed that the two folds are double plunging, and asymmetrical in all traverses except in P5 and P6 in Qara Sard anticline. Both folds are verging toward northeast; however, the anticline verges toward southwest and being vertical in P4 and P5 respectively. The geometrical analysis using PI diagrams reveal that the fold axis of Qara Sard anticline is sinuous and changing its trend in three attitudes. The first is NW-SE in the traverses P1, P2 and P3 with gradual clockwise drifting. The second one is WNW-ESE in P4, P5 and P6 and then returning in the third to the first attitude NW-SE in the traverse P7. Consequently, the area was influenced by four strike-slip faults. They are either transverse or inclined to the fold axis. These faults are Dolma Reza dextral, Choplaghsinistral, Lower Zab dextral and Dokan sinistral. They divided the area into four blocks moved in opposite directions depending on the strike-slip faults displacements. On the other hand, the study folds are affected by three reverse listric faults. They are suture-verged and parallel with the fold axis. Two of them affected the northeastern limb of Qara Sard anticline, whereas the third disturbed its southwestern limb. By investigations of the vertical changes of fold style, the reactivation of the suture listric fault (2) is detected. It appears as a rotational type so as its larger effect is on traverse P7 and its displacement is gradually reduced toward P4. Moreover, the reactivation time of this suture rotational listric fault was Turonian, it is reflected throughout verging change of the fault between Qamchuqa and Kometan formations in traverse P6.