Keywords : listric

Inferred Inversely Reactivated Listric Fault at Chia Gara Anticline, Northern Iraq

Ibrahim Aljumaily; Nazar Abdullah

Iraqi National Journal of Earth Science, 2019, Volume 19, Issue 2, Pages 11-25
DOI: 10.33899/earth.2019.170280

Chia Gara anticline is an E-W extending doubly plunged fold, parallel to the Taurus Mountains having about (80) km length and (12) km width. It is located within the high folded zone of northern Iraq. The exposed rocks range in age from Late Triassic to Late Miocene. Structural analysis of the anticline performed through three traverses transverse to the general fold trend from western plunge zone towards east. Geometrical analysis of fold elements shows that Chia Gara anticline is asymmetrical vergingtowards north in both first and third traverses, whereas it is more or less symmetrical in the second traverse. Meanwhile, results of Fourier analysis demonstrates that the fold form is more developed in the northern limb of the anticline than in its southern limb, in the first and third traverses. Nevertheless, in the second traverse, the fold form seems more developed in the southern limb compared with the northern limb. The northern vergence of the anticline and its advance development in northern limb in the first and third traverses may reflect the impact of a suture vergent reversely slipped listric fault beneath the anticline sectors in these traverses. However, the obscure of such listric fault in the second traverse may be due to the effect of a sinistral (BF1) and a dextral (BF2) subsurface strike-slip faults transverse to the trend of Chia Gara anticline on either side of the second traverse. The surface expressions of them, as well as others like Zewa and Deralok faults (dextral) are evident in satellite image of the area. The southward pushing of the wedge between (BF1) and (BF2) had opposed the northward reverse displacement of the proposed listric fault beneath thesecond traverse. The effects of these strike-slip faults (BF1) and (BF2) are evident also in anticlockwise deflection of both axial plane and fold axis attitudes from first to the second traverse, and vice versa from second to the third traverse.