Buraimi Region, Northern Oman and Eastern United Arab Emirates
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GeoArabia, vol. 14, no. 1, 2009, p. 115-142 Gulf PetroLink, Bahrain Structural and tectonic evolution of the Jabal Sumeini – Al Ain – Buraimi region, northern Oman and eastern United Arab Emirates Michael P. Searle and Mohammed Y. Ali ABSTRACT Four main Late Cretaceous and Tertiary phases of crustal shortening and thrust- related deformation are recognised in the northern Oman Mountains, each phase ending with a regional unconformity throughout the Oman Mountains and the UAE foreland. The earliest is the major thrust emplacement of the Semail Ophiolite, and underlying Haybi, Hawasina and Sumeini duplexes from NE to SW onto the depressed northeastern continental margin of the Arabian Plate during the Cenomanian to Campanian-early Maastrichtian (D1). A prominent widespread unconformity that places Maastrichtian Qahlah Formation laterite, sandstones and conglomerates and Simsima Formation rudist - Acteonellid gastropod limestones over all underlying allochthonous units is recognised throughout the Oman Mountains. SW-verging folds and thrusts in Triassic to Cretaceous carbonate slope facies rocks exposed in Jabal Sumeini (Sumeini Group and Hamrat Duru Group) have been emplaced over uppermost Cretaceous Juweiza Formation conglomerates at the highest level of the Aruma foreland basin. These Sumeini D1 structures are abruptly truncated by an unconformity, above which are Middle Maastrichtian beds showing up to 95% ‘death assemblage’ rudists and gastropods just below the Cretaceous – Tertiary boundary (top of Simsima Formation). A second deformation event (D2) affected the Simsima Formation and underlying Sumeini Group, Hamrat Duru complex and Semail Ophiolite rocks. This phase shows gentle folding about NW-SE fold axes (e.g. Jabal Rawdah), along a similar trend to the Late Cretaceous D1 event. This trend is also parallel to a regional set of NW-SE aligned fractures in the UAE foreland. A major angular unconformity occurs beneath the Upper Palaeocene – Eocene shallow-marine limestones (Umm Er Radhuma, Rus and Dammam formations). Many foreland jabals in eastern Abu Dhabi (Jabals Qatar, Malaqet, Mundasa) show gentle post-Eocene folding formed during the third stage of crustal shortening (D3). The large pericline of Jabal Hafit is a double-plunging, east-verging box fold that formed after deposition of the Oligocene Asmari Formation limestones and Miocene Fars Formation gypsum and clays, the youngest beds affected by the fold. This Late Miocene – Pliocene phase of crustal shortening (D4) is the youngest phase of deformation in the eastern Al Ain-Buraimi region. INTRODUCTION The northern Oman Mountains (Figure 1) expose a stack of thrust sheets emplaced from the Tethyan oceanic domain, from northeast to southwest onto the Arabian continental margin during the Late Cretaceous (Figure 2; Glennie et al., 1973, 1974; Lippard et al., 1986). These thrust sheets include (1) the Semail Ophiolite complex, an up to 8–15 km thick Cenomanian oceanic crust and upper mantle, (2) Haybi thrust sheet comprising Upper Permian to Cenomanian distal oceanic sediments, alkaline volcanics and oceanic seamounts, (3) Hawasina Complex, comprising a number of thin thrust sheets of oceanic sediments ranging from proximal (Hamrat Duru Group) to distal (Halfa and Haliw formations), and (4) Sumeini complex consisting of proximal carbonate slope facies rocks. The Haybi, Hawasina and Sumeini complexes are time-equivalent units to the Middle Permian to Cenomanian autochthonous shelf carbonates exposed around Al Jabal al Akhdar and the Musandam Peninsula (Glennie et al., 1973, 1974; Searle et al., 1983, 2004; Searle, 1988a, b, 2007; Bernoulli and Weissart, 1987; Robertson and Searle, 1990; Blechschmidt et al., 2004). Mapping in Oman by the BRGM group, Béchennec et al. (1990) and Rabu et al. (1993) reinterpreted the distal Haybi complex rocks and defined two stratigraphic groups, the upper Umar Group (Aqil Formation sedimentary rocks and Sinni 115 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/14/1/115/4565559/searle.pdf by guest on 23 September 2021 Searle and Ali 34°E 38° 42° 46° 50° 54° 58° a 38°N TURKEY Caspian 38° c 55°30’E 55°40’ 55°50’ 56° 56°10’ 55°20’E Sea55°30’ 55°40’ 55°50’ 56° 56°10’ Jabal CYPRUS SYRIA Jabal 34° LEBANON IRAN 34° 25°N 25°NMed IRAQ N Faiyah Faiyah 25° Sea 0 300 25° JORDAN 30° km 30° Gulf KUWAIT of Suez Jabal BAHRAIN N 26° SAUDI ARABIA 26° N QATAR UAE 0 20 Rawdah EGYPT Gulf of 0 20 Arabian Oman 22° Shield Figure 1a 22° km Semail km SUDAN Red OMAN Sea 18° 18° Arabian Thrust Jabal Figure 9 Sea ERITREA YEMEN Semail Rawdah 24°50’ 24°50’ 24°50’ 14° 14° 24°50’ Gulf of Aden SOCOTRA Hatta ETHIOPIA Hatta Jabal 34° 38° 42° 46° 50° 54° 58° Thrus Sumeini t Jabal Sumeini Sumeini window Sume 24°40’ 24°40’ 24°40’ 24°40’ Figure 6 2 ini Well 1 T Well 1 hrus Figure 4 Seismic profile t Seismic profile 2 (Figure 13) Recent deposits Jabal 24°30’ 24°30’ Miocene (Fars Formation) Jifrah 24°30’ Oligocene (Asmari Formation) Jabal As Saifr Eocene (Dammam and Rus Formations) Maastrichtian (Simsima and Qahlah Fm) Jabal As Safir Semail Ophiolite Jabal Jabal Qatar 24°20’ Jabal Qatar 24°20’ Haybi and Hawasina thrust sheets Jabal 24°20’ Auha Auha Sumeini Group Jabal Semail Ophiolite - A separate subsurface thin thrust sheet Huwayyah of mantle sequence (Batty et al., 2004) Jabal Thrust Huwayyah Al Ain Folds Al Ain Reverse/Thrust fault Semail 24°10’ Thrust 24°10’ 24°10’ Hawasina Jabal 1 Jabal Malaqat Al Jaww Malaqat 1 Ja Seimic profile Plain Jabal Seismic profileba Jabal l Mundassa H Jabal a (Figure 12) Mundassa fit Jabal Hafit Al Jaww Plain Hafit Jabal 24° Jabal 53° b24° 54° 55° 56° Khatamah Khatamah Jabal 24° Jabal 24° Ghashnah Musandam Peninsula Ghashnah 26° 26° Ras 55°20’ 55°30’ 55°40’ 55°50’ 56° 56°10’ 55°20’ 55°30’ Al-Khaimah 55°40’ 55°50’ 56° 56°10’ N b 0 50 st Dibba Haga Figure 1: (a) Landsat photo of the northern Oman Mountains, Jabal Sumeini and UAE foreland. Thru km Arabian (b) Geological map of the northern Oman Mountains (after Glennie et al., 1975, and Searle, 2007). Gulf Dubai Gulf of (c) Simplified geological map of the UAE foreland. Black lines show the location of the seismic Oman profile and well locality. 25° 25° 25° ust r Th Recent deposits Haybi, Hawasina Abu Dhabi Semail OMAN Sohar thrust sheets Maastrichtian - Al-Ain Tertiary sediments Sumeini thrust sheet W1 Semail Ophiolite 24° 24° Figure 1c 24° Permian-Mesozoic Hawasin shelf carbonates UNITED ARAB Thrust Metamorphic sole EMIRATES amphibolites, City 53° 54° 55° green schists 116 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/14/1/115/4565559/searle.pdf by guest on 23 September 2021 Structural and tectonic evolution, Oman and UAE 34°E 38° 42° 46° 50° 54° 58° a 38°N TURKEY Caspian 38° c 55°30’E 55°40’ 55°50’ 56° 56°10’ 55°20’E Sea55°30’ 55°40’ 55°50’ 56° 56°10’ Jabal CYPRUS SYRIA Jabal 34° LEBANON IRAN 34° 25°N 25°NMed IRAQ N Faiyah Faiyah 25° Sea 0 300 25° JORDAN 30° km 30° Gulf KUWAIT of Suez Jabal BAHRAIN N 26° SAUDI ARABIA 26° N QATAR UAE 0 20 Rawdah EGYPT Gulf of 0 20 Arabian Oman 22° Shield Figure 1a 22° km Semail km SUDAN Red OMAN Sea 18° 18° Arabian Thrust Jabal Figure 9 Sea ERITREA YEMEN Semail Rawdah 24°50’ 24°50’ 24°50’ 14° 14° 24°50’ Gulf of Aden SOCOTRA Hatta ETHIOPIA Hatta Jabal 34° 38° 42° 46° 50° 54° 58° Thrus Sumeini t Jabal Sumeini Sumeini window Sume 24°40’ 24°40’ 24°40’ 24°40’ Figure 6 2 ini Well 1 T Well 1 hrus Figure 4 Seismic profile t Seismic profile 2 (Figure 13) Recent deposits Jabal 24°30’ 24°30’ Miocene (Fars Formation) Jifrah 24°30’ Oligocene (Asmari Formation) Jabal As Saifr Eocene (Dammam and Rus Formations) Maastrichtian (Simsima and Qahlah Fm) Jabal As Safir Semail Ophiolite Jabal Jabal Qatar 24°20’ Jabal Qatar 24°20’ Haybi and Hawasina thrust sheets Jabal 24°20’ Auha Auha Sumeini Group Jabal Semail Ophiolite - A separate subsurface thin thrust sheet Huwayyah of mantle sequence (Batty et al., 2004) Jabal Thrust Huwayyah Al Ain Folds Al Ain Reverse/Thrust fault Semail 24°10’ Thrust 24°10’ 24°10’ Hawasina Jabal 1 Jabal Malaqat Al Jaww Malaqat 1 Ja Seimic profile Plain Jabal Seismic profileba Jabal l Mundassa H Jabal a (Figure 12) Mundassa fit Jabal Hafit Al Jaww Plain Hafit Jabal 24° Jabal 53° b24° 54° 55° 56° Khatamah Khatamah Jabal 24° Jabal 24° Ghashnah Musandam Peninsula Ghashnah 26° 26° Ras 55°20’ 55°30’ 55°40’ 55°50’ 56° 56°10’ 55°20’ 55°30’ Al-Khaimah 55°40’ 55°50’ 56° 56°10’ N b 0 50 st Dibba Haga Thru km Arabian Gulf Dubai Gulf of Oman 25° 25° 25° ust r Th Recent deposits Haybi, Hawasina Abu Dhabi Semail OMAN Sohar thrust sheets Maastrichtian - Al-Ain Tertiary sediments Sumeini thrust sheet W1 Semail Ophiolite 24° 24° Figure 1c 24° Permian-Mesozoic Hawasin shelf carbonates UNITED ARAB Thrust Metamorphic sole EMIRATES amphibolites, City 53° 54° 55° green schists 117 Downloaded from http://pubs.geoscienceworld.org/geoarabia/article-pdf/14/1/115/4565559/searle.pdf by guest on 23 September 2021 Searle and Ali Formation volcanics) and the lower Kawr Group (shallow-marine limestones of the Oman Exotics with their volcanic substrate, the Misfah Formation). These stratigraphically defined rock units are within the Haybi complex (Searle and Malpas, 1980, 1982) – a structural definition that includes rocks bounded below by the Haybi thrust and above by the Semail thrust (Figure 2). Whereas the Semail and Haybi thrusts are present everywhere along the Oman Mountains, the Kawr Group limestone exotics are restricted to certain areas, mainly in the Jabal al Akhdar region of Oman.