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Several anticlines in northern Iraq and Syria have been studied through the construction of balanced and restored cross sections. Based upon structural analysis, each of the studied anticlines is a fault-propagation fold that developed due to Zagros-related, recent inversion of much older normal faults. Studies on the Iranian part of the Zagros Fold Belt have suggested that the regional variation in the character of the fold belt is related to weak detachment surfaces in the stratigraphic section, primarily the decollement developed near the top of the Hormuz Salt where the salt is present. No evidence for Hormuz Salt has been found within the Kirkuk Embayment, and although detachment surfaces contribute the area’s structural character, the prominent folds seem to originate mainly from basement involved faults. Two distinct inversion structural trends exist: E-W system and a NW system of inverted grabens. In Syria, several of the faults associated with the EW-trending system cut the basement on seismic data and have stratigraphic relationships indicating that their displacement originated in the Neoproterozoic. In Iraq, the thicker sedimentary section did not allow the deep parts of the fault systems to be imaged on the available seismic. While the NW fault system of inverted normal faults could be linked to the Zagros Orogen by a decollement surface in the sedimentary section, regional relationships and potential-field data suggest that this trend also is basement involved and has a Neoproterozoic origin.

Jebel Abd Al Aziz, one of the most prominent topographic features in northeastern Syria, is a large surface anticline. An integrated structural and stratigraphic study conducted by Unocal from 1988 to 1995 resulted in recognition that Jebel Abd Al Aziz originated from inversion of a pre-existing graben. Understanding the complex structural and stratigraphic history of the Jebel Abd Al Aziz is important to hydrocarbon exploration and development in the northern Arabian tectonic plate. This importance is demonstrated by the strong correlation between hydrocarbon productive areas and the areas of Plio-Pleistocene structural inversion. Our study illustrates how the evolution of this structure is recorded in its local stratigraphy. Prior to the development of the Jebel Abd Al Aziz structure, Senonian shelf carbonates prograded southward from Turkey into the Palmyride-Sinjar Trough that extended from west central to northeastern Syria. The shelf edge of this carbonate system was south of and subparallel to the Syrian border. In the Jebel Abd Al Aziz area, fine-grained basinal mudstones were deposited on a thin, transgressive, rudistid, bioclastic unit. In Early Maastrichtian, an east-west-trending graben developed at the present site of Jebel Abd Al Aziz. Reactivated northwest- and northeast-striking faults bound structural blocks within the graben. Seismic data indicate that the edges of the rift basin were deeply eroded. Valleys, cut into the sides of the basin along the trend of the older cross-cutting regional faults, exposed Carboniferous and possibly older strata. Olistostromes formed along the basin-bounding fault scarps and small turbidite fans developed at the channel mouths. Paleocurrent direction data from the turbidite sand bodies corresponds well with the trends of the valleys mapped on seismic data. Maastrichtian-age sediments are largely confined to the graben proper. Early Tertiary sediments filled a wider basin, but there is evidence that minor episodic inversion on some northeast and northwest trending faults occurred during the Eocene and early Miocene. The main inversion of the Jebel Abd Al Aziz structure occurred in the Late Pliocene and Pleistocene. Inversion produced a large fault-propagation fold above east-west trending faults near the northern margin of the graben. Smaller folds developed above other graben-bounding faults and the northeast- and northwest-striking faults within the graben underwent oblique slip during the deformation.

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