Zagros fold and thrust belt
This article may be too technical for most readers to understand.(January 2013) |
The Zagros fold and thrust belt (Zagros FTB) is an approximately 1,800-kilometre (1,100 mi) long zone of deformed crustal rocks, formed in the foreland of the collision between the Arabian Plate and the Eurasian Plate. It is host to one of the world's largest petroleum provinces, containing about 49% of the established hydrocarbon reserves in fold and thrust belts (FTBs) and about 7% of all reserves globally.[1]
Plate tectonic setting
The Zagros
Geometry
The Zagros FTB extends for about 1,800 km (1,100 mi) from the
Kirkuk embayment
In northern Iraq, the Zagros FTB is relatively narrow and this area is referred to as the Kirkuk embayment. This part of the fold belt lacks an effective basal Hormuz salt detachment.[citation needed]
Lorestan domain
The
Dezful embayment
Between the two main salients of the Zagros FTB, the Dezful embayment developed in an area that lacked an effective basal Hormuz salt detachment, resulting in a steeper topographic slope of 2°, compared to 1° for both the Lorestan and Fars domains.[6] During the Miocene, this area became a depocentre in which locally thick Gachsaran salt was deposited. The presence of locally thick Gachsaran salt has caused disharmonic folding between the sequences above and below that layer.[7]
Fars domain
The Fars salient forms the southeastern end of the Zagros FTB. This area is underlain by a thick Hormuz salt layer that comes to the surface in several places where it extrudes from the crests of anticlines, forming salt glaciers, although it may be missing over the Fars platform, a continuation of an area of the foreland in which the salt layer is not present.[8]
Kazerun fault system
This dextral fault system transfers some of the dextral displacement along the Main Recent Fault onto thrust faults and folds of the Fars domain as the relative motion changes from strongly oblique to near orthogonal. It also forms the effective southeastern boundary to the Dezful embayment. In detail the Kazerun fault system consist of a series of en echelon segments within an overall fan shaped zone. From the focal depth of earthquakes along this zone it is clear that these faults are developed within the underlying basement rocks.[9]
Persian Gulf
The Persian Gulf and the area of lowland occupied by the alluvial plain of the Tigris–Euphrates river system, known as the 'Mesopotamian Basin', together represent the active foreland basin to the Zagros FTB, caused by the loading of the leading edge of the Arabian Plate by the Zagros thrust sheets. The gulf is being progressively infilled by the southeastward prograding delta of the river system.[10]
Development of the Zagros FTB
Northeastward subduction of
There is no evidence of continued subduction of oceanic crust beneath the Eurasian Plate along this part of the plate boundary, in contrast to the neighbouring segment along the Makran Trench, an active subduction zone, where a dipping slab is well imaged by seismic tomography.[13] The ending of subduction has been linked to evidence that the Main Zagros Reverse Fault is no longer active, suggesting that further deformation is occurring by distributed deformation of the leading edge of the Arabian Plate. This is consistent with observations of recent seismicity.[4]
Economic importance
The Zagros FTB contains 49% of the world's hydrocarbon reserves hosted in fold and thrust belts and about 7% of all reserves. The Zagros province includes many giant and supergiant oilfields, such as the
References
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- ^ ISBN 978-1-86239-293-9. Retrieved 10 July 2011.
- S2CID 128746209. Retrieved 2 July 2011.
- ^ . Retrieved 9 July 2011.
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- ISBN 978-1-4443-3910-9. Retrieved 2 July 2011.
- ISBN 978-3-540-69425-0. Retrieved 10 July 2011.
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- . Retrieved 10 July 2011.
- ^ Hull, C. E.; Warman, H. R., Halbouty, M. T. (ed.), Asmari Oil Fields of Iran, in Geology of Giant Petroleum Fields, AAPG Memori 14, Tulsa: American Association of Petroleum Geologists, p. 428