scholarly journals Structural and Stratigraphical Setting of the Faiyah Range, Northwestern Oman Mountain Front, United Arab Emirates

GeoArabia ◽  
1998 ◽  
Vol 3 (3) ◽  
pp. 387-398
Author(s):  
M. Atef Noweir ◽  
Abdulrahman S. Alsharhan ◽  
Mohamed A. Boukhary
Keyword(s):  
United Arab Emirates ◽  
Marine Environment ◽  
Upper Cretaceous ◽  
Sedimentary Rocks ◽  
Fold Axis ◽  
Oman Mountains ◽  
Mountain Front ◽  
Dextral Strike Slip Fault ◽  
Semail Ophiolite ◽  
Dextral Strike Slip

ABSTRACT The Faiyah Range belongs to a group of regional ridges that formed by post-obduction folding of the Upper Cretaceous-Tertiary sedimentary rocks exposed along the western margin of the Northern Oman Mountains. The Faiyah Anticline, generally trends north-northeast to south-southwest with thrust faults striking parallel to the fold axis. The anticlinal hinge was later displaced by a dextral strike-slip fault, named here as the Faiyah Fault, into two segments. The northeastern segment includes Jebels Rumaylah, Faiyah and Mulayhah, and the southwestern segment includes Jebels Buhays and Aqabah. The anticline is interpreted to result from northeast-southwest compression during the Tertiary. In the Faiyah Range the neoautochthonous sedimentary rocks are the Maastrichtian Qahlah and Simsima formations, and the Eocene Dammam Formation. Stratigraphic evidence shows that the lower part of the Qahlah was deposited in a non-marine environment while the upper part was deposited during a marine transgression. The Simsima was deposited in a shallow-marine environment. These units unconformably overlap the allochthonous Semail Ophiolite. The microfaunal content of the so-called Muthaymimah Formation (?Tertiary), of earlier authors, indicates that it is of Maastrichtian age in the Faiyah Range. This sequence is also conformable to the Simsima and therefore it is considered to be the upper member of the Simsima in this area.

scholarly journals Structural Style and Stratigraphy of the Huwayyah Anticline: an Example of an Al-Ain Tertiary Fold, Northern Oman Mountains

GeoArabia ◽  
2000 ◽  
Vol 5 (3) ◽  
pp. 387-402 ◽  
Author(s):  
M. Atef Noweir ◽  
Abdulrahman S. Alsharhan
Keyword(s):  
Late Cretaceous ◽  
Middle Eocene ◽  
Fold Axis ◽  
The North ◽  
Oman Mountains ◽  
Structural Style ◽  
Dammam Formation ◽  
Al Ain ◽  
Mountain Front ◽  
Semail Ophiolite

ABSTRACT Detailed field mapping and structural studies in the Jebel Auha-Jebel Huwayyah area northeast of Al-Ain indicate that folding of neoautochthonous sedimentary rocks produced the north-northwest-trending Huwayyah Anticline. The anticline at the surface is composed of the Maastrichtian Qahlah and Simsima formations unconformably overlain by shallow-marine carbonate rocks that are correlated on faunal grounds with the Middle Eocene Dammam Formation. The investigation of the Huwayyah Anticline has identified three microfacies of bioclastic packstone, nummulitic packstone, and nummulitic packstone-grainstone in the local Dammam Formation. Diagenesis in the form of silicification, cementation, recrystallization, dissolution, compaction and neomorphism is widespread. The Huwayyah Anticline is a fault-propagation fold above a thrust ramp. The ramp developed from a pre-existing Late Cretaceous basal thrust within the Semail Ophiolite on the Oman Mountain Front. The anticline was formed as a result of regional compressive deformation due to rejuvenation of the Late Cretaceous thrust in post-Middle Eocene times. Westward-directed high-angle reverse faults of Jebel Auha trend parallel to the fold axis of the anticline. The Auha faults probably originated as west-dipping thrusts on the western flank of the anticline and were subsequently rotated to their present attitude as the flank of the anticline became steeper due to compression from the east.

Chapter 2 Tectonostratigraphy of the eastern part of the Oman Mountains

10.1144/m54.2 ◽  
2021 ◽  
Vol 54 (1) ◽  
pp. 11-47 ◽  
Author(s):  
Andreas Scharf ◽  
Frank Mattern ◽  
Mohammed Al-Wardi ◽  
Gianluca Frijia ◽  
Daniel Moraetis ◽  
...  
Keyword(s):  
Deep Sea ◽  
Upper Cretaceous ◽  
Sedimentary Rocks ◽  
Passive Margin ◽  
Quaternary Deposits ◽  
Oman Mountains ◽  
Tethys Ocean ◽  
Carbonate Formations ◽  
Semail Ophiolite ◽  
Stratigraphic Chart

AbstractThis chapter provides comprehensive descriptions of 52 numbered formations/rock units of the Southeastern Oman Mountains, based on available literature. The oldest eight siliciclastic and carbonate formations are positioned below the ‘Hercynian’ Unconformity. The overlying formation (9–16) mostly represent carbonates which accumulated in a passive margin platform setting during or after the opening of the Neo-Tethys Ocean. The passive margin slope and platform collapsed during the late Cretaceous because of the obduction of the Semail Ophiolite along with the deep marine Hawasina sedimentary rocks. The collapsing passive margin interval was recorded within the syn-obductional Aruma Group (17; Muti Formation). Above this formation are the allochthonous units (18–42) of the tectonically lower Hawasina deep-sea basin and the structurally overlying Semail Ophiolite. The former contains Permian to Upper Cretaceous formations, while the latter is Cenomanian in age. Above the allochthonous rocks, the Neo-autochthonous formations were deposited, starting with the post-obductional uppermost Cretaceous Aruma Group (43; Al-Khod Formation) until the Quaternary deposits (52). All these formations/rock units are depicted on an accompanying map and stratigraphic chart.

scholarly journals Shallow-marine serpentinization-derived fluid seepage in the Upper Cretaceous Qahlah Formation, United Arab Emirates

2021 ◽  
pp. 1-11
Author(s):  
Benjamin Eickmann ◽  
Crispin T. S. Little ◽  
Jörn Peckmann ◽  
Paul D. Taylor ◽  
Adrian J. Boyce ◽  
...  
Keyword(s):  
United Arab Emirates ◽  
Upper Cretaceous ◽  
Rock Interaction ◽  
Cemented Sand ◽  
Shallow Marine ◽  
Fluid Seepage ◽  
Lower Maastrichtian ◽  
Calcite Cement ◽  
Semail Ophiolite ◽  
Upper Campanian

Abstract Serpentinization of ultramafic rocks in the sea and on land leads to the generation of alkaline fluids rich in molecular hydrogen (H2) and methane (CH4) that favour the formation of carbonate mineralization, such as veins in the sub-seafloor, seafloor carbonate chimneys and terrestrial hyperalkaline spring deposits. Examples of this type of seawater–rock interaction and the formation of serpentinization-derived carbonates in a shallow-marine environment are scarce, and almost entirely lacking in the geological record. Here we present evidence for serpentinization-induced fluid seepage in shallow-marine sedimentary rocks from the Upper Cretaceous (upper Campanian to lower Maastrichtian) Qahlah Formation at Jebel Huwayyah, United Arab Emirates. The research object is a metre-scale structure (the Jebel Huwayyah Mound) formed of calcite-cemented sand grains, which formed a positive seafloor feature. The Jebel Huwayyah Mound contains numerous vertically orientated fluid conduits containing two main phases of calcite cement. We use C and O stable isotopes and elemental composition to reconstruct the fluids from which these cements precipitated and infer that the fluids consisted of variable mixtures of seawater and fluids derived from serpentinization of the underlying Semail Ophiolite. Based on their negative δ13C values, hardgrounds in the same section as the Jebel Huwayyah Mound may also have had a similar origin. The Jebel Huwayyah Mound shows that serpentinization of the Semail Ophiolite by seawater occurred very soon after obduction and marine transgression, a process that continued through to the Miocene, and, with interaction of meteoric water, up to the present day.

Subduction zone metamorphism during formation and emplacement of the Semail ophiolite in the Oman Mountains

2002 ◽  
Vol 139 (3) ◽  
pp. 241-255 ◽  
Author(s):  
MICHAEL P. SEARLE ◽  
JON COX
Keyword(s):  
Subduction Zone ◽  
United Arab Emirates ◽  
Volcanic Rocks ◽  
Granulite Facies ◽  
Granulite Facies Metamorphism ◽  
Metalliferous Sediments ◽  
Oman Mountains ◽  
Low Degrees ◽  
Semail Ophiolite ◽  
Record Peak

The metamorphic sole along the base of the Semail ophiolite in Oman records the earliest thrust slice subducted and accreted to the base of the ophiolite mantle sequence. In the Bani Hamid area (United Arab Emirates) a c. 870 m thick thrust slice of granulite facies rocks includes garnet+ diopside amphibolites, enstatite+cordierite+sillimanite+spinel±sapphirine quartzites, alkaline mafic granulites (meta-jacupirangites) quartzo-feldspathic gneisses and calc-silicates. The latter contain garnet+diopside+scapolite+plagioclase±wollastonite. P–T conditions of granulite facies metamorphism are in the range 800–860°C and 10.5±1.1 kbar to 14.7±2.8 kbar. Garnet+clinopyroxene+hornblende+plagioclase amphibolites from the metamorphic sole record peak P–T conditions of 840±70°C and 11.6±1.6 kbar (THERMOCALC average P–T mode) and 840–870°C and 13.9–11.8 kbar (conventional thermobarometry) with low degrees of partial melting producing very small melt segregations of tonalitic material. Pressure estimates are equivalent to depths of 57–46 km beneath oceanic crust, much deeper than can be accounted for by the thickness of the ophiolite. 40Ar39Ar hornblende ages from the amphibolites range from 95–93 Ma, synchronous with formation of the plagiogranites in the ophiolite crustal sequence (95 Ma), eruption of the Lasail (V2) volcanic sequence and deposition of Cenomanian–Turonian radiolaria in metalliferous sediments between the Geotimes (V1) and Lasail (V2) lavas. Protoliths of the metamorphic sole were Triassic–Jurassic and early Cretaceous Haybi volcanic rocks, Exotic limestones and quartzites and were clearly not equivalent to the Semail ophiolite rocks, showing that initiation of subduction could not have occurred at the ridge axis. Heat for metamorphism was derived from the mantle sequence harzburgites and dunites which were at or around 1100–1500°C. All data from the sub-ophiolite metamorphic sole in Oman and the United Arab Emirates indicate that the ophiolite was formed in a Supra-Subduction zone setting and that obduction occurred along a NE-dipping high-temperature subduction zone during Late Cretaceous times.

K—Ar ages of alkaline igneous rocks in the northern Oman mountains, NE Arabia, and their relations to rifting, passive margin development and destruction of the Oman Tethys

1982 ◽  
Vol 119 (5) ◽  
pp. 497-503 ◽  
Author(s):  
S. J. Lippard ◽  
D. C. Rex
Keyword(s):  
Upper Cretaceous ◽  
Oceanic Lithosphere ◽  
Passive Margin ◽  
Igneous Rocks ◽  
Oman Mountains ◽  
Intrusive Rocks ◽  
Igneous Activity ◽  
Ophiolite Emplacement ◽  
Alkaline Activity ◽  
Semail Ophiolite

SummaryK–Ar ages of biotites from a variety of alkaline volcanics and minor intrusive rocks in the nothern Oman mountains allochthon give a range of ages from Triassic (230 Ma) to mid Cretaceous (92 Ma) and represent igneous activity on the Oman continental margin throughout the Mesozoic. This was a passive margin destroyed by the emplacement across it of a pile of nappes in the late Cretaceous, including a largely intact thrust sheet of Upper Cretaceous oceanic lithosphere (the Semail ophiolite). Biotite ankaramite dykes, cutting compositionally similar volcanics, in the thrust complex immediately beneath the ophiolite, give Triassic ages and are related to the rifting and break-up of the northeast Arabian margin at the beginning of formation of the Oman Tethys. Mid Cretaceous (Cenomanian–Turonian) ages are mostly recorded from the northern part of the mountains where there are alkaline tuffs in a sedimentary melange. They are approximately the same age as the ophiolite and may be related to tectonic instability of the Oman margin immediately prior to ophiolite emplacement. Alkaline sills, intrusive into a variety of rocks, including Triassic volcanics, give Jurassic and Cretaceous ages and are interpreted as periodic alkaline activity on the Oman margin throughout passive margin development.

scholarly journals Origin of gypsiferous intrusions in the Hawasina Window, Oman Mountains: Implications from structural and gravity investigations

GeoArabia ◽  
2014 ◽  
Vol 19 (2) ◽  
pp. 107-132
Author(s):  
Mohammed Y. Ali ◽  
David J.W. Cooper ◽  
Michael P. Searle ◽  
Ali Al-Lazki
Keyword(s):  
Upper Cretaceous ◽  
Country Rock ◽  
Isotope Analysis ◽  
Arabian Plate ◽  
Fine Grained ◽  
Oman Mountains ◽  
South Central ◽  
Thrust Sheets ◽  
Semail Ophiolite ◽  
Structural Levels

ABSTRACT Gypsiferous intrusions are exposed in road-cuts in the south-central Hawasina Window in the central Oman Mountains. They are located at lower structural levels in the allochthonous Hawasina Complex and lie along faults that cut Upper Cretaceous structures related to the obduction of the Semail Ophiolite and Hawasina Complex deep-water sediments onto the Arabian Plate. The intrusions form gypsiferous pods that are up to 200 m long, in which the gypsum occurs as a dark, fine-grained matrix that contains a pervasive network of anastomosing veins of gypsum and anhydrite. The intrusions contain abundant sub-angular to sub-rounded litharenites, and less common fragments of chert and fine-grained limestone. Although these clast types are undated, their petrographic characteristics suggest they originate from the local Hawasina (Hamrat Duru Group) country rock. Very well-rounded pebbles and cobbles of feldspathic litharenites, some of which show a well-developed cleavage, and rarer cobbles of well-rounded vein quartz appear to have come from the basement. Gravity investigations indicate salt diapirs are not present beneath the Hawasina Window. Instead, the gypsiferous intrusions are interpreted as having been brought up from depth during compression to form disconnected pods along deep-rooted faults, bringing with them small amounts of the basement country rock. Strontium isotope analysis and regional considerations, in particular the distribution, age and nature of other evaporite units on the eastern Arabian Plate, suggest the gypsum may have its origins in the Neoproterozoic (Ediacaran) to lower Cambrian Ara Group evaporites, perhaps from a previously unknown extension of the Fahud Salt Basin beneath the Hawasina thrust sheets.

scholarly journals Back-thrust Origin of the Hafit Structure, Northern Oman Mountain Front, United Arab Emirates

GeoArabia ◽  
2000 ◽  
Vol 5 (2) ◽  
pp. 215-228 ◽  
Author(s):  
M. Atef Noweir
Keyword(s):  
United Arab Emirates ◽  
Tertiary Structures ◽  
The North ◽  
Oman Mountains ◽  
Al Ain ◽  
Mountain Front ◽  
Fault Propagation Fold ◽  
Deformation Event ◽  
Basal Detachment ◽  
Recent Interpretation

ABSTRACT The Tertiary structures of the Northern Oman Mountains are marked by a discontinuous belt of jebels peripheral to their western margin. Detailed field mapping of the northern Hafit structure in the Northern Oman Mountains indicates that the structures consist of two en echelon anticlines, the main Hafit Anticline to the south, and the Al-Ain Anticline to the north. Both anticlines are related to the same deformation event. Structural analysis, using geometric balancing techniques suggests that the Hafit structure developed over a west-vergent basal thrust. The depth to detachment of the thrust indicates that the basal detachment occurs at different stratigraphic positions and progressively increases northward, while the magnitude of deformation increases southward. The thrust wedges back to the east and propagated upward through the structure during a major Tertiary deformational event resulting in an east-vergent, fault-propagation fold. The recent interpretation that the Hafit structure grew as a detachment fold above a basal decollement and synchronously with sedimentation, is at variance with structural evidence from the Hafit area. It is believed that the Hafit structure formed after the Miocene time.

Structure and metamorphism of rocks beneath the Semail ophiolite of Oman and their significance in ophiolite obduction

1980 ◽  
Vol 71 (4) ◽  
pp. 247-262 ◽  
Author(s):  
M. P. Searle ◽  
J. Malpas
Keyword(s):  
Heat Source ◽  
Upper Cretaceous ◽  
Frictional Heating ◽  
Metamorphic Rocks ◽  
Polyphase Deformation ◽  
Oman Mountains ◽  
Wide Range ◽  
Semail Ophiolite ◽  
Low Pressures ◽  
Residual Heat

ABSTRACTMetamorphic rocks showing an inverted metamorphic zonation from upper amphibolite fades immediately beneath the peridotite to greenschist fades at lower levels, crop out discontinuously along the base of the Semail ophiolite thrust sheet in the Oman Mountains of eastern Arabia. These metamorphic rocks show polyphase deformation, mylonitic fabrics, and have been disrupted, folded and imbricated, and in places form tectonic inclusions in a serpentinite melange. In the more intact sequences, garnet-clinopyroxene amphibolites, with rare hornblende-bearing marbles and banded quartzites, occur at the higher levels, whilst a wide range of metasedimentary and metabasaltic rocks occur in the greenschist fades. Low glaucophane content of amphiboles and low jadeite content of clinopyroxenes suggest relatively low pressures of crystallisation. The distribution coefficient KD for co-existing garnet and clinopyroxene suggests a temperature range of 670 to 750°C. Residual heat from the recently formed ophiolite probably provided the dominant heat source for metamorphism, although frictional heating could have supplemented this. The metamorphic rocks were produced during Cenomanian-Turonian (late Cretaceous) times.The sub-ophiolite metamorphic rocks, together with basal serpentinite, Triassic alkaline and tholeiitic basalts (Haybi volcanic group), mountain-sized ‘exotic’ limestones and an upper Cretaceous sedimentary melange, comprise a distinct thrust slice termed the Haybi complex, which always overlies marine sediments of the allochthonous Hawasina complex and underlies the Semail ophiolite. The rocks of the Haybi complex are bounded by major thrust planes, the Semail thrust above and the Haybi thrust beneath, which truncate all schistosities, fold axes, imbricate thrusts and associated features. A model for ophiolite obducton is presented based on a palinspastic reconstruction of the allochthonous rocks on the Oman continental margin.

scholarly journals Sedimentary facies and trilobite and conodont faunas of the Ordovician Rann Formation, Ras Al Khaimah, United Arab Emirates

GeoArabia ◽  
2011 ◽  
Vol 16 (4) ◽  
pp. 127-152 ◽  
Author(s):  
Richard A. Fortey ◽  
Alan P. Heward ◽  
C. Giles Miller
Keyword(s):  
United Arab Emirates ◽  
Sedimentary Facies ◽  
Middle Ordovician ◽  
Oman Mountains ◽  
Sea Bottom ◽  
Sand Supply ◽  
Shell Beds ◽  
Storm Wave ◽  
Drepanodus Arcuatus ◽  
Semail Ophiolite

ABSTRACT The Rann Formation occurs as unique ‘exotic’ rafts in front of the Semail Ophiolite in the northern Oman Mountains. Its Ordovician age has been poorly constrained and it is often associated with the Ayim rock unit, which has been considered Devonian, Carboniferous or Ordovician by different workers. Here we present new trilobite and conodont evidence for the Ordovician ages of the three members of the Rann Formation, which includes the Ayim. The members are readily distinguishable on sedimentological and faunal grounds. The Lower Member comprises shales, quartzitic sandstones and thin fossiliferous shell beds. Large Cruziana are common, as is lingulacean debris and, at several horizons, possible hyolithids. Assemblages of graptolites, acritarchs, trilobites (Neseuretus cf. arenosus and Taihungshania cf. miqueli) and conodonts (Baltoniodus sp., Drepanodus arcuatus, Drepanoistodus sp. and Protopanderodus sp., Scolopodus sp.) are considered to range in age from Floian to early Dapingian, late Early Ordovician. The Ayim Member (previously formation) consists of fossiliferous shales and griotte-like nodular bioclastic limestones. The member is distinguished by its red colour and by numerous orthoconic nautiloids. Conodont faunas (Complexodus cf. originalis, Eoplacognathus protoramosus, Dapsilodus sp., Cornuodus sp. and Panderodus sp.) imply a late Darriwilian, Middle Ordovician age. The Upper Member consists of siltstones and sandstones generally lacking bioturbation and with rare shell beds and faunas. Trilobites (Deanaspis goldfussii seftenbergi, Vietnamia teichmulleri and Dreyfussina taouzensis) and chitinozoans are interpreted to indicate an early-middle Katian, Late Ordovician age. The three members represent shallow-marine deposits on a continental shelf subject to changing sand supply, storm-wave activity and sea-bottom oxygenation. The three periods of deposition, Floian – early Dapingian, late Darriwilian and early – middle Katian, correspond to highstands of Paleo-Tethys that also flooded interior Oman and Arabia. The limited burial and lack of metamorphism of the Rann is remarkable given its proximity to the Semail Ophiolite and to subduction related metamorphic rocks occurring nearby.

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