GeoArabia, v. 15, no. 4, 2010, p. 147-188 Gulf PetroLink, Bahrain Structures of the Kirkuk Embayment, northern Iraq: Foreland structures or Zagros Fold Belt structures? W. Norman Kent ABSTRACT 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. INTRODUCTION The Zagros Fold Belt extends more than 1,800 km from southern Anatolia through northern Iraq and Iran to the Strait of Hormuz (Figure 1). The fold belt has been studied extensively since 1855 when Loftus presented one of the earliest technical papers on the region to the Geological Society (London). The majority of published articles regarding the Zagros are in international journals and focus on the Iranian part of the orogenic belt, especially those published within the last few years (Bahroudi and Talbot, 2003; Blanc et al., 2003; Bosold et al., 2005; Sherkati et al., 2005; Authemayou et al., 2006; Hessami et al., 2006; Alavi, 2007; Stephenson et al., 2007). A review of previous works indicated that the genesis of the anticlinal structures of northern Iraq has long been a subject of debate. Conclusions of early investigators were strongly influenced by the part of the orogen they studied as indicated by the discussion following Henson’s 1951 paper presented at the Third World Petroleum Congress. He recognized four structural trends based on topography and tectonic maps: (1) N-S East African, (2) E-W Tethyan, (3) NW Erythrean and (4) NE Aualitic. Henson found no direct evidence that the features along these structural trends had any common genetic relationships, but noted several episodes of faulting along each of the four structural trends. From this observation, he suggested that there was recurrent movement on basement fracture systems aligned along these trends. Lees (1952) viewed: “the Iraq-Persian mountain belt as the product of extreme compression with the development of thrust sheets.” He dismissed the emphasis Henson placed on block faulting, and his opinion was that Henson’s 1951 interpretation was “quite misleading”. Accumulation of geological data since the early 1950s has only enhanced the importance of these four structural trends (Figures 1a, b). Structures of Henson’s Tethyan Trend and the Aualitic Trend are now commonly referred to the Taurus and Palmyra trends, respectively. Subsequent authors have provided 147 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/15/4/147/4565881/kent.pdf by guest on 25 September 2021 Kent Regional Index Map with Geology Tectonic Zones of the Zagros Fold Belt a 35°E 40° 45° 50° Mardin-Urfa TURKMENISTAN Caspian Sea Sub-Hercynian Simply Folded TURKEY c 35°E 40° Imbricate Zone 2 45° 50° TURKMENISTAN Subcrop Zone 2 Caspian Sea Cambrian TURKEY Si Proterozoic Mardin- m CYPRUS Urfa ply Folded 35°N Triassic 35° IRAN CYPRUS 3 Zone SYRIA Imbricate Zone 1 35°N 1 35° LEBANON Khleisia Fault High SYRIA Mediterranean LEBANON IRAQ Simply Folded Zone Khleisia Thrus IRAN Sea High Mediterranean t Belt PALESTINE Sea Neoproterozoic IRAQ t High PALESTINE Simply Neoproterozoic JORDAN Faul EGYPT Folded Zone 1 High 30° 30° Gulf of EGYPT JORDAN Suez 30° 30° KUWAIT Gulf of Dead Sea SAUDI ARABIA Suez KUWAIT SAUDI ARABIA Imbricate Zone 1 BAHRAIN Arabian Platform QATAR BAHRAIN 25° 25° QATAR Outcrop Proterozoic – Ordovician – 25° 25° N Paleozoic UAECambrian 0 300 N Permo – Triassic Cambrian Red km Red 0 300 Arabian UAE Proterozoic Sea Upper Paleozoic Sea Shield undifferentiated km OMAN SUDAN Devonian Lower Paleozoic OMAN 35° 40° 45° 50° 55° SUDAN 35° 40° 45° 50° 55° Subdivisions of the Zagros Orogenic Belt Figure 1: (continued) b 35°E 40° Aziz-Bashiqa 45° 50° TURKMENISTAN inversion TURKEY Taurus Main Rece Caspian Sea (a) Surface geology is from USGS digital maps by Pollastro et al. (1999a, b). Paleozoic outcrops in Province a Iraq are from Al-Hadidy (2007). Paleozoic outcrops along the South Mardin Fault Zone in EmbaymenKirku nt Fault Turkey are from Binbol (1989). Neoproterozoic and Cambrian subcrop associated with the CYPRUS k Mardin-Urfa basement high in southeastern Turkey are adapted from Temple and Perry (1962). 35°N t 35° Triassic subcrop in Syria is extracted from the maps by the author. The geometry of the b SYRIA Loresian IRAN Khleisia High is from gravity data from Sayyab and Valek (1968). The fault pattern in the LEBANON f Sailent Zagros Orogen are generalized from figures from Hessamie et al. (2001), Bahroudi and Talbot g Mediterranean Palmyra Euphrates (2003), Authemayou et al. (2006) and Sarkarinejad and Azizi (2008). The Neoproterozoic High Sea inversion inversion M Za c Main Zagros Revers es g o ros De Em D in Iran is derived from maps of Szabo and Kheradpir (1978) and Koop and Stoneley (1982). PALESTINE pota ez Mai ba fu n Zagros m ym l Faults of the Najd Fault System in the Arabian Shield are from figure 1 of Moore (1979). IRAQ ia fo n Basin rm en d at t EGYPT JORDAN ion Fault a ee 30° l Fr 30° (b) The inverted graben trends of the northern Arabian Plate are: (1) Palmyra inversion, the most Gulf of on e Fault t Suez Dead Sea Fault prominent of the inverted graben systems; (2) NE-plunging Euphrates inversion; and (3) Agha Jari Fa Aziz-Bashiqa inversion trend. Correlation of these three trends to those recognized by Henson SAUDI ARABIA Sailen h Field rs et al. (1950, 1951) is apparent. The Main Recent Fault (MRF), a dextral fault, and the Main t Zagros Reverse Fault (MZRF) are shown as a single trace. In detail, segments of the MRF BAHRAIN disrupt the MZRF (Authemayou et al., 2005). QATAR 25° 25° (c) The four part subdivision of the Zagros Orogeny that has been used in the literature works in Iran and most of northern Iraq, but fails to describe features in western Iraq, Syria and N Arabian Turkey. 0 300 Red Shield a: South Mardin Fault e: Kazerun Fault UAE Sea b: Khanaqin Fault f: Makhul-Hemrin Fault Trend km c: Bala Rud Fault g: Balad-Dujaila StructuralOMAN Trend d: Hendijan Fault h: Wadi Al Batin Fault SUDAN 35° 40° 45° 50° 55° Figure 1: (See facing page for caption). 148 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/15/4/147/4565881/kent.pdf by guest on 25 September 2021 Kirkuk Embayment, northern Iraq Regional Index Map with Geology Tectonic Zones of the Zagros Fold Belt a 35°E 40° 45° 50° Mardin-Urfa TURKMENISTAN Caspian Sea Sub-Hercynian Simply Folded TURKEY c 35°E 40° Imbricate Zone 2 45° 50° TURKMENISTAN Subcrop Zone 2 Caspian Sea Cambrian TURKEY Si Proterozoic Mardin- m CYPRUS Urfa ply Folded 35°N Triassic 35° IRAN CYPRUS 3 Zone SYRIA Imbricate Zone 1 35°N 1 35° LEBANON Khleisia Fault High SYRIA Mediterranean LEBANON IRAQ Simply Folded Zone Khleisia Thrus IRAN Sea High Mediterranean t Belt PALESTINE Sea Neoproterozoic IRAQ t High PALESTINE Simply Neoproterozoic JORDAN Faul EGYPT Folded Zone 1 High 30° 30° Gulf of EGYPT JORDAN Suez 30° 30° KUWAIT Gulf of Dead Sea SAUDI ARABIA Suez KUWAIT SAUDI ARABIA Imbricate Zone 1 BAHRAIN Arabian Platform QATAR BAHRAIN 25° 25° QATAR Outcrop Proterozoic – Ordovician – 25° 25° N Paleozoic UAECambrian 0 300 N Permo – Triassic Cambrian Red km Red 0 300 Arabian UAE Proterozoic Sea Upper Paleozoic Sea Shield undifferentiated km OMAN SUDAN Devonian Lower Paleozoic OMAN 35° 40° 45° 50° 55° SUDAN 35° 40° 45° 50° 55° Subdivisions of the Zagros Orogenic Belt Figure 1: (continued) b 35°E 40° Aziz-Bashiqa 45° 50° TURKMENISTAN inversion TURKEY Taurus Main Rece Caspian Sea (a) Surface geology is from USGS digital maps by Pollastro et al. (1999a, b). Paleozoic outcrops in Province a Iraq are from Al-Hadidy (2007). Paleozoic outcrops along the South Mardin Fault Zone in EmbaymenKirku nt Fault Turkey are from Binbol (1989). Neoproterozoic and Cambrian subcrop associated with the CYPRUS k Mardin-Urfa basement high in southeastern Turkey are adapted from Temple and Perry (1962). 35°N t 35° Triassic subcrop in Syria is extracted from the maps by the author. The geometry of the b SYRIA Loresian IRAN Khleisia High is from gravity data from Sayyab and Valek (1968). The fault pattern in the LEBANON f Sailent Zagros Orogen are generalized from figures from Hessamie et al. (2001), Bahroudi and Talbot g Mediterranean Palmyra Euphrates (2003), Authemayou et al.