Tectonics of Oman—from the Precambrian to the Present

A special issue of Geosciences (ISSN 2076-3263).

Deadline for manuscript submissions: closed (29 February 2020) | Viewed by 21250

Special Issue Editors


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Guest Editor
Sultan Qaboos University, Muscat, Oman
Interests: structural geology; tectonics; basin studies; tectonics & sedimentation; geology of Oman

E-Mail Website
Guest Editor
Sultan Qaboos University, Muscat, Oman
Interests: structural geology; tectonics; geodymnics; mineralogy/petrology; geochronology; field mapping; geology of Oman

E-Mail Website
Guest Editor
University of Sharjah, Sharjah, United Arab Emirates
Interests: geomorphology; coastal geomorphology; Quaternary geomorphology; geochemistry; hydrogeology; environmental geochemistry

Special Issue Information

Dear Colleagues,

The main objective of this Special Issue of Geosciences is to publish new structural data and tectonic interpretations of Oman as part of the Arabian Plate. The plate’s margins are marked by convergence, divergence and transform shearing. Thus, much of the Arabian Plate’s geology is relevant to understand the tectonics of Oman. As the tectonic history and present-day setting of Oman is so diverse the scope of this topic will produce multifaceted contributions making for interesting and diversified reading as well as exciting progress. The targeted area belongs to the world’s largest hydrocarbon province. Thus, improving the understanding of the Precambrian to the present-day tectonics is also in the interest of the global society.

Contributions to this Special Issue will be peer-reviewed, published swiftly and widely accessible. This special issue aims to cover, without being limited to, the following areas:

  • Any study (surface or subsurface) related to the tectonic evolution of Oman and relevant margins of the  Arabian Plate with structures at any scale and time
  • Studies related to the plate tectonic setting (e.g., orogenies, Gulf of Aden, Owen Fracture Zone, and Zagros-Makran Mts.)
  • Regional neotectonics
  • Regional morphotectonics (e.g., coastal geomorphology, including marine terraces; tectonic evolution of fluvial and mountainous landscapes)
  • Salt tectonics
  • Tectonic impacts on hydrocarbon systems

Dr. Frank Mattern
Dr. Andreas Scharf
Dr. Daniel Moraetis
Guest Editors

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Keywords

  • Continental collision
  • Subduction
  • Obduction
  • Rifting
  • Strike-slip tectonics
  • Regional geology
  • Thick-skinned and thin-skinned deformation
  • Salt tectonics
  • Orogenesis

Published Papers (6 papers)

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Research

42 pages, 16555 KiB  
Article
Lagoonal Microfacies, Lithostratigraphy, Correlation and Shale Migration of the Basal Middle Eocene Seeb Formation (Rusayl Embayment, Sultanate of Oman)
by Frank Mattern, Andreas Scharf, Abdul Razak Al-Sayigh, Nada Al-Wahaibi, Laura Galluccio, Gianluca Frijia and Mazin Al-Salmani
Geosciences 2023, 13(9), 254; https://doi.org/10.3390/geosciences13090254 - 22 Aug 2023
Cited by 2 | Viewed by 1754
Abstract
The study improves the understanding of the basal part of the Eocene Seeb Formation of Oman, informally known as “Unit 1”, in terms of microfacies, lithostratigraphy and shale migration within the context of regional tectonics. We logged four sections bed-by-bed over a distance [...] Read more.
The study improves the understanding of the basal part of the Eocene Seeb Formation of Oman, informally known as “Unit 1”, in terms of microfacies, lithostratigraphy and shale migration within the context of regional tectonics. We logged four sections bed-by-bed over a distance of 8.3 km, collected samples and analyzed thin-sections as well as XRD samples. For the first time, the microfacies and stratigraphic correlation of the lowermost part of the limestone-dominated Seeb Formation were studied in detail. In the analyzed area, Unit 1 is ~20 to 40 m thick, with the thickness increasing to the SE. In the upper part of Unit 1 is a laterally continuous shale horizon. The limestones of Unit 1 contain mostly packstones and grainstones. The dominant standard microfacies types are SMF 18-FOR and SMF 16. The former is dominated by benthic foraminifera, and the latter by peloids. Both SMFs indicate restricted lagoonal conditions. Foraminifera are common in Unit 1 and indicate a middle Eocene age. Considering the abundance of encountered foraminiferal bioclasts, it appears probable that the lagoon barrier was mainly composed of foraminiferal tests. Gutter casts, slumps and debrites indicate an active, partly unstable syndepositional slope, which was likely initially created by uplift of the Saih Hatat Dome and Jabal Nakhl Subdome. Differential regional uplift due to a more pronounced overall doming in the NW (Jabal Nakhl Subdome) than in the SE (Saih Hatat Dome) explains more accommodation space and greater thickness towards the SE. For the first time, we report visco-plastic shale migration/intrusion within the Seeb Formation, related to a shale horizon of Unit 1. This shale locally migrated as indicated by (1) local thickness variations, (2) detached limestone boulders floating in the shale, (3) limestone beds that have been cut-off by the shale and (4) dragged by the shale (5) an upward shale intrusion/injection which then spread parallelly to bedding similar to a salt tongue and (6) tilting overlying limestones. We suggest that shale migration is related to post-“mid”-Eocene E-W convergence between Arabia and India and to faulting or to the second, late Paleogene/early Neogene, faulting interval of the Frontal Range Fault. The shale horizon in the upper part of Unit 1 is a marker bed, which can be correlated across the study area. Full article
(This article belongs to the Special Issue Tectonics of Oman—from the Precambrian to the Present)
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15 pages, 9002 KiB  
Article
Texture and Shape Analysis of Quartzite Mylonites of the Metamorphic Sole of the Samail Ophiolite (Oman): Evidence for Syn- and Post-Obduction Deformation
by Peter Hallas and Wilfried Bauer
Geosciences 2021, 11(3), 111; https://doi.org/10.3390/geosciences11030111 - 01 Mar 2021
Viewed by 2127
Abstract
The metamorphic sole, tectonically welded to the base of the Samail ophiolite in a supra-subduction system, is assumed to play the main role in strain accumulation during later thrusting onto the Arabian Plate (i.e., during obduction). The present study deals with five quartzite [...] Read more.
The metamorphic sole, tectonically welded to the base of the Samail ophiolite in a supra-subduction system, is assumed to play the main role in strain accumulation during later thrusting onto the Arabian Plate (i.e., during obduction). The present study deals with five quartzite samples representative of the upper amphibolite and lower greenschist facies parts of the sole. Whole-rock textures obtained by neutron time-of-flight technique were coupled with microstructural observation using electron backscatter diffraction analyses. The quartz microstructural fabrics and textures in the upper and lower parts of the sole represent grain boundary migration and [c]-in-Y textures and subgrain rotation recrystallization and {r}-in-Z textures, respectively. The shear sense in these samples points to top-to-the-SW to SSW shear. One sample of the upper part, yielding a higher calcite amount, is later overprinted by bulging and displays top-to-the-NNE shear. We postulate to differentiate two main deformation steps. The first is the overall present subgrain rotation and grain boundary migration recrystallization combined to top ~SW shear is related to the sole accretion to the ophiolite and the eventually following thrusting onto the Arabian Plate. The second is correlated to a post-obduction extensional top-to-the-NNE shearing, which is associated with tectonic thinning of the ophiolite and mainly documented in the underlying autochthonous units. Full article
(This article belongs to the Special Issue Tectonics of Oman—from the Precambrian to the Present)
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28 pages, 13786 KiB  
Article
Understanding the Relationship between Large-Scale Fold Structures and Small-Scale Fracture Patterns: A Case Study from the Oman Mountains
by Mohammed H. N. Al-Kindi
Geosciences 2020, 10(12), 490; https://doi.org/10.3390/geosciences10120490 - 04 Dec 2020
Cited by 6 | Viewed by 2896
Abstract
Considering the foreland fold belt of the Salakh Arch in the northern Oman Mountains, predictions made from two-dimensional (2D) restorations and geometrical analyses are tested here to assess the relationship between large-scale folds and small-scale fractures. The Salakh Arch is composed of six [...] Read more.
Considering the foreland fold belt of the Salakh Arch in the northern Oman Mountains, predictions made from two-dimensional (2D) restorations and geometrical analyses are tested here to assess the relationship between large-scale folds and small-scale fractures. The Salakh Arch is composed of six anticlines that are interpreted as faulted detachment folds. They have an overall stratigraphy of a 2-km-thick carbonate platform underlain by more than 1.5 km of interbedded sandstone and shale sequences. These sequences are most likely detached on a regionally extensive evaporite horizon. The folding of the Salakh Arch structures most likely occurred during the Neogene Period, and perhaps partly in the early Quaternary Period. This is evident from the thrusting of the Late Neogene Barzaman Formation which was deposited during the Late Neogene Period. Robust outcrop and subsurface fracture data are used to test these predictions. The results from the study indicate that most fractures are related to the orientation of the local structure, with some sets parallel and some sets perpendicular to local hinge lines. Prefolding regional fractures are also widely distributed, and these were mostly formed during the Late Cretaceous Period. Many pre-existing fractures are associated with faults that formed during the Late Cretaceous Period under a NW–SE compression. The local fractures generally have orientations that are consistent with being formed by the flexural slip/flexural flow of fold limbs and tangential longitudinal strains on fold hinges. These structures can be predicted from finite stratal dips, simple curvatures, and three-dimensional (3D) folding restoration maps. The Gaussian curvatures and 3D faulting restoration maps can be used as proxies for fault-related fractures. Local hinge-related fractures may reflect local tangential longitudinal strain during large-scale fold tightening. Fold structures that have formed at an oblique orientation to the regional shortening direction show additional fracture arrays perpendicular to the hinge, indicating weak axial extension. This is presumed to develop as the arcuate thrust belt of Salakh Arch was amplified. The analysis here illustrates the importance of taking a 3D approach, especially for noncylindrical folds. The protocols developed in this study and their results may have general applicability to investigations of fracture patterns in other folds. Full article
(This article belongs to the Special Issue Tectonics of Oman—from the Precambrian to the Present)
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14 pages, 4362 KiB  
Article
Quaternary Thrusting in the Central Oman Mountains—Novel Observations and Causes: Insights from Optical Stimulate Luminescence Dating and Kinematic Fault Analyses
by Daniel Moraetis, Andreas Scharf, Frank Mattern, Kosmas Pavlopoulos and Steven Forman
Geosciences 2020, 10(5), 166; https://doi.org/10.3390/geosciences10050166 - 05 May 2020
Cited by 8 | Viewed by 3774
Abstract
For the first time, Quaternary thrusts are documented within the Central Oman Mountains to the northwest of the Jabal Akhdar Dome. Thrusts with a throw of up to 1.1 m displace Quaternary alluvial fan conglomerates. These conglomerates have an Optical Stimulate Luminescence (OSL) [...] Read more.
For the first time, Quaternary thrusts are documented within the Central Oman Mountains to the northwest of the Jabal Akhdar Dome. Thrusts with a throw of up to 1.1 m displace Quaternary alluvial fan conglomerates. These conglomerates have an Optical Stimulate Luminescence (OSL) age of 159 ± 7.9 ka BP and were deposited during MIS 6 (Marine Isotope Stage). The thrusts occur in two sets. Sets 1 and 2 formed during NE/SW and NW/SE shortening, respectively. Set-1-thusts correlate with the present-day stress field of NE/SW shortening which is related to subduction in the Makran Subduction Zone, and they strike parallel to the main continuous fold axis of the Jabal Akhdar and Hawasina windows. Set-2-thrusts correspond to NW/SE shortening and Plio-Pleistocene contractional structures in the southwestern Jabal Akhdar Dome. Set-2-thrusts are probably related to local variations of the present-day stress field originating from the Musandam area which is a part of the Zagros Collision Zone. Both thrust sets mimic the main thrust directions (NW/SE and NE/SW) within the Permo-Mesozoic allochthonous units (Semail Ophiolite, Hawasina napps) of the larger study area. The investigated thrusts imply some reactivation of the Hawasina and Semail thrusts due to far-field stress either from the Makran Subduction Zone and/or the Zagros Collision Zone. The ongoing tectonic activity of this part of the Oman Mountains, which has been considered of moderate activity, is for first time identified by structural data as contractional. Full article
(This article belongs to the Special Issue Tectonics of Oman—from the Precambrian to the Present)
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27 pages, 18481 KiB  
Article
Timing, Mechanics and Controls of the Evolution of the Southernmost Part of the Oman Mountains: The Salakh Arch
by Mohammed H. N. Al-Kindi
Geosciences 2020, 10(3), 95; https://doi.org/10.3390/geosciences10030095 - 01 Mar 2020
Cited by 2 | Viewed by 4587
Abstract
Regional surface and subsurface mapping of the front range of the Oman Mountains, Salakh Arch’s fold-and-thrust belt, is conducted to understand the timing and nature of its deformation and to analyze the main controls on its position, geometry and evolution. The results from [...] Read more.
Regional surface and subsurface mapping of the front range of the Oman Mountains, Salakh Arch’s fold-and-thrust belt, is conducted to understand the timing and nature of its deformation and to analyze the main controls on its position, geometry and evolution. The results from this study can be applied to other fold-and-thrust belts, as the area offers surface and subsurface datasets that allow good understanding of its evolution history. The deformation of the outcropping Middle Miocene to Pliocene deposits and the displacement of the Cenozoic seismic reflections imply that folding and thrusting was active during the Neogene and possibly ceased during the Early Quaternary. The palaeostress-tensor analyses from the kinematic fault data along with the fold-axes trends show that the regional transport direction was, overall, directed to the south. Lateral movements over oblique or lateral ramps, between the frontal ramps, have caused local deflections of the regional stress trajectories. The shortening values measured from restored seismic sections were utilized to restore the arch in map view. The restoration indicates that the arch initiated as a primary arc right from the start of deformation. As the shortening proceeded, clockwise and anticlockwise rotations occurred in some areas as a consequence of displacement gradients across adjacent areas along the arch. This rotation was most likely accommodated by angular shear strain, which results in arch-parallel extension or transtension. Various factors have controlled the position, geometry and segmentation of the fold segments in the Salakh Arch. The folds that developed in areas of thicker deformed sediments are wider and more uplifted and advanced to the foreland than the folds that develop in thin deformed sediments. Pre-existing faults were reactivated as lateral and frontal ramps during the arch’s evolution. They have contributed in the location and segmentation of the fold patches. On the other hand, the depth-to-detachment measurements and restoration results suggest that the folds detach along the Ediacaran-Early Cambrian Ara Salt. Overall, the deformation in the Salakh Arch could be described as an interaction between thin- and thick-skinned tectonics. Full article
(This article belongs to the Special Issue Tectonics of Oman—from the Precambrian to the Present)
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23 pages, 10340 KiB  
Article
Deformation of the Cambro-Ordovician Amdeh Formation (Members 1 and 2): Characteristics, Origins, and Stratigraphic Significance (Wadi Amdeh, Saih Hatat Dome, Oman Mountains)
by Frank Mattern, Andreas Scharf, Pu-Jun Wang, Ivan Callegari, Iftikhar Abbasi, Saja Al-Wahaibi, Bernhard Pracejus and Katharina Scharf
Geosciences 2020, 10(2), 48; https://doi.org/10.3390/geosciences10020048 - 27 Jan 2020
Cited by 11 | Viewed by 4731
Abstract
The Angudan Orogeny affected Cryogenian to earliest Cambrian sedimentary rock formations of the Jabal Akhdar Dome of the Oman Mountains. These rocks were folded and cleaved at 525 ± 5 Ma. We studied the Cambro-Ordovician (Terreneuvian to Darriwillian) Amdeh Formation of the neighboring [...] Read more.
The Angudan Orogeny affected Cryogenian to earliest Cambrian sedimentary rock formations of the Jabal Akhdar Dome of the Oman Mountains. These rocks were folded and cleaved at 525 ± 5 Ma. We studied the Cambro-Ordovician (Terreneuvian to Darriwillian) Amdeh Formation of the neighboring Saih Hatat Dome to see whether this formation was also affected by the Angudan Orogeny. The Angudan deformation within the Jabal Akhdar Dome is known for its folds and cleavage. Due to age considerations (see above), we studied the folds and cleavages within the two oldest members of the Amdeh Formation (Am 1 and Am 2) in order to compare them with the ones that are known from the Jabal Akhdar Dome to possibly detect Angudan-related deformation in Am 1 and Am 2. Angudan folds of the Jabal Akhdar Dome display fold axes that are oriented NE/SW, but the two lowest members of the Amdeh Formation reveal one set of folds with subhorizontal fold axes that trend NW-NNW/SE-SSE. The lack of Angudan-related folds suggests that the lowest Amdeh Member (Am 1) postdates the Angudan Orogeny. The age of Am 1 is uncertain. Based on our structural results, we consider an upper Terreneuvian age (late stage 2) for Am 1. The folds in Am 1 and 2 are related to the Late Cretaceous–Cenozoic Semail Orogeny (term introduced here). The observed fold vergences (mainly to the W and SW) were caused by shear deformation during descent into the subduction zone by simple shear. The contact between the stratigraphically underlying Hiyam Formation and the Amdeh Formation is generally considered to be an unconformity. We observed a distinct NW/SE-striking deformation zone along the contact of both formations which is located in proximity to the largest observed fold. Tectonically, this contact is defined by the sinistral Wadi Amdeh Fault (name introduced here). The unconformity should be present in the subsurface of the southwestern fault block. Near the contact between the Hiyam and the Amdeh formations, a 20 cm thick unit of reddish cataclasite/tectonic breccia occurs within the basal part of Am 1 which represents a deformed acidic layer or sill. This rock unit could be the first evidence for Cambrian igneous activity. Full article
(This article belongs to the Special Issue Tectonics of Oman—from the Precambrian to the Present)
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