scholarly journals Regional Structural Style of the Central and Southern Oman Mountains: Jebel Akhdar, Saih Hatat, and the Northern Ghaba Basin

GeoArabia ◽  
1998 ◽  
Vol 3 (4) ◽  
pp. 475-490 ◽  
Author(s):  
Van S. Mount ◽  
Roderick I.S. Crawford ◽  
Steven C. Bergman
Keyword(s):  
Large Scale ◽  
Carbonate Platform ◽  
Great Distance ◽  
Reverse Fault ◽  
High Angle ◽  
Shallow Marine ◽  
Oman Mountains ◽  
Structural Style ◽  
Central Platform ◽  
Deformation Event

ABSTRACT Three quantitative regional transects across the Saih Hatat and Jebel Akhdar anticlines in the Central and Southern Oman Mountains and the Northern Ghaba Basin have been constructed based on surface, well and seismic data. Interpreted large-scale structural geometries suggest that the Saih Hatat and Jebel Akhdar anticlines are basement-involved compressional structures, underlain by north-dipping, high-angle, blind, reverse faults located beneath their southern limbs. A compressional deformation event initiated in the Oligocene (constrained by apatite fission track data) involving the high-angle reverse faults is interpreted in which pre-Permian strata and Permian-through-Lower Cretaceous strata, exposed in the Saih Hatat and Jebel Akhdar anticlines, were parautochthonous - uplifted over the underlying reverse faults, and not displaced a great distance laterally. The allochthonous Hawasina and Sumeini sedimentary rocks and the Semail Ophiolite complex are interpreted to have been emplaced onto the carbonate platform during the Late Cretaceous, and have subsequently been parautochthonous during the Tertiary deformation. The upper portion of the pre-Permian section in the Ghaba Basin consists predominantly of a thick (>4 kilometers) sequence of Cambrian-through-Silurian, predominantly non-marine to shallow-marine, clastics of the Haima Supergroup. In contrast, out of the Ghaba Basin proper in the Central Platform or Musallim High region, the Haima Supergroup is generally less than 2 kilometers thick, and interpreted to thin to the north. The fundamental difference in pre-Permian strata exposed in the Saih Hatat and Jebel Akhdar Anticline windows is the thick (>3.4 kilometers) section of Ordovician age, shallow-marine strata (Amdeh Formation) present in the Saih Hatat Anticline, but absent in the Jebel Akhdar Anticline. In our interpretation, the shallow-marine clastics exposed in the Saih Hatat Anticline represent the northern extension of the Early Paleozoic Ghaba Basin, which have been uplifted over a high-angle reverse fault in the Early Tertiary deformation event. The cross-section through Jebel Akhdar is located to the northwest of the Ghaba Salt Basin, along the Musallim High. In this area the thickness of the Ordovician strata deposited is interpreted to be less than in the Ghaba Basin. The Ordovician section is not present in the Jebel Akhdar structure - the thinned section likely eroded in a Late Paleozoic deformation event.

scholarly journals Diagenesis and fluid system evolution in the northern Oman Mountains, United Arab Emirates: Implications for petroleum exploration

GeoArabia ◽  
2011 ◽  
Vol 16 (2) ◽  
pp. 111-148 ◽  
Author(s):  
Liesbeth Breesch ◽  
Rudy Swennen ◽  
Ben Dewever ◽  
François Roure ◽  
Benoit Vincent
Keyword(s):  
United Arab Emirates ◽  
Large Scale ◽  
Carbonate Platform ◽  
Petroleum Exploration ◽  
Schematic Model ◽  
Reverse Fault ◽  
Fluid System ◽  
System Evolution ◽  
Oman Mountains ◽  
Geochemical Analyses

ABSTRACT The diagenesis and fluid system evolution of outcrop analogues of potential sub-thrust Cretaceous carbonate reservoirs in the Musandam Peninsula, northern United Arab Emirates, is reconstructed during the successive stages of the Oman Mountains development. Detailed petrographic and geochemical analyses were carried out on fracture cements in limestones and dolomites mostly situated close to the main faults, which were the locations of major fluid fluxes. The main result of this study is a generalised paragenesis subdivided into four diagenetic time periods. Based on analyses of syn-tectonic veins and dolomites a large-scale fluid system is inferred with migration of hot brines with H2O-NaCl-CaCl2 composition along Cenozoic reverse faults. These brines were sourced from deeper formations or even from the basal decollement and infiltrated in the footwall. These results are compared with similar studies, which were carried out in other regions worldwide. Furthermore some implications for reservoir characteristics and hydrocarbon scenarios could be postulated. It must be noted that the majority of the analysed rocks do not have sufficiently high porosities to be regarded as reservoir rocks. However, some diagenetic processes that can improve the reservoir quality were observed. For example dolomite recrystallisation occurred in patches at the carbonate platform border, which created poorly connected reservoirs. Other possible exploration targets could be the footwall blocks of the Cenozoic reverse fault zones. When the migration of hot brines along these faults and into the footwall would be combined with petroleum migration, the footwall block could act as a potential hycrocarbon trap sealed by the fault. The fluid system evolution is incorporated in a schematic model of the geodynamic framework of the region in order to summarise the different diagenetic and fluid events, which took place during the northern Oman Mountains evolution up to now.

scholarly journals Multiphase, decoupled faulting in the southern German Molasse Basin – evidence from 3D seismic data

2020 ◽  
Author(s):  
Vladimir Shipilin ◽  
David Colin Tanner ◽  
Hartwig von Hartmann ◽  
Inga Moeck
Keyword(s):  
Large Scale ◽  
Carbonate Platform ◽  
Stress Component ◽  
Phase 1 ◽  
Molasse Basin ◽  
Phase 2 ◽  
Maximum Displacement ◽  
Seismic Reflection Data ◽  
Structural Style ◽  
Cenozoic Sediments

Abstract. We use three-dimensional seismic reflection data from the southern German Molasse Basin to investigate the struc-tural style and evolution of a geometrically decoupled fault network in close proximity to the Alpine deformation front. We recognise two fault arrays that are vertically separated by a clay-rich detachment horizon. A large-scale thrust partially over-prints the upper fault array. Analysis of seismic stratigraphy, syn-kinematic strata, throw distribution, and spatial relationships between faults suggest a multiphase fault evolution: (1) initiation of the lower fault array in the Upper Jurassic carbonate platform during the Rupelian, (2) development of the upper fault array in the Cenozoic sediments during the Chattian, and (3) reverse reactivation of the upper faults and thrusting during the mid-Miocene. These phases document the evolution of the stress field during the migration of the forebulge (phase 1), foredeep (phase 2) and the toe of the orogenic front (phase 3) across the investigated area. We postulate that phase 2 was controlled by the vertical stress gradients, whereby a lower horizontal stress component within the Cenozoic sediments defined the independent development of the upper faults above the lower faults. Mechanical behaviour of the clay-rich horizon precluded the subsequent linkage of the fault arrays. A large-scale thrust must have been facilitated by the reverse reactivation of the upper normal faults, as its maximum displacement and extent correlate with the occurrence of these faults. We conclude that the evolving tectonic stresses were the primary mechanism of fault activation, whereas the mechanical stratigraphy and pre-existing structures locally governed the structural style.

The Spieden Group: an anomalous piece of the Cordilleran paleogeographic puzzle

1981 ◽  
Vol 18 (11) ◽  
pp. 1694-1707 ◽  
Author(s):  
Samuel Y. Johnson
Keyword(s):  
Large Scale ◽  
Upper Jurassic ◽  
Alluvial Fan ◽  
San Juan ◽  
Island Formation ◽  
Shallow Marine ◽  
San Juan Islands ◽  
Structural Style ◽  
Lower Member ◽  
Volcanic Source

Spieden and Sentinel Islands, San Juan Islands, Washington, are underlain by the only known occurrence of the Spieden Group, composed of the Upper Jurassic (Oxfordian or Kimmeridgian) Spieden Bluff Formation and the Lower Cretaceous (Valanginian and Hauterivian and possibly younger) Sentinel Island Formation, separated by a disconformity.The 100 m thick Spieden Bluff Formation is subdivided into two members: (1) an 80 m thick lower member, consisting of 5 m of sandstone, siltstone, and tuff overlain by 75 m of volcanic breccia–conglomerate largely of debris flow (laharic?) origin; and (2) a 20 m thick upper member consisting of fossiliferous sandstone and siltstone deposited on a shallow marine slope. Sedimentologic, petrologic, and geochronologic data suggest that sediments of the Spieden Bluff Formation accumulated near an active volcanic source to the north contributing primarily andesite, dacite, and basaltic andesite.The 740 m thick Sentinel Island Formation is also subdivided into two members: (1) a 140 m thick lower member consisting of fossiliferous sandstone and siltstone deposited in a shallow marine environment; and (2) an unconformably overlying 600 m thick upper member consisting of volcanic conglomerate deposited as an alluvial fan. The source terrane for the Sentinel Island Formation was also primarily Upper Jurassic volcanic rocks and lay to the northeast.Rocks of equivalent age occur in the southern part of the San Juan Islands and in neighboring geologic provinces, but most of these correlative rocks differ from the Spieden in sedimentology, structural style, and metamorphism. Juxtaposition of the Spieden Group and these correlative rocks might have been accomplished by shortening and fragmentation of a regional convergent margin, by large-scale transport of allochthonous blocks, or by some combination of the two mechanisms.

scholarly journals Development of fault and vein networks in a carbonate sequence near Hayl al-Shaz, Oman Mountains

GeoArabia ◽  
2013 ◽  
Vol 18 (2) ◽  
pp. 99-136
Author(s):  
Simon Virgo ◽  
Max Arndt ◽  
Zoé Sobisch ◽  
Janos L. Urai
Keyword(s):  
United Arab Emirates ◽  
Coarse Grained ◽  
Normal Faults ◽  
Structural Elements ◽  
High Angle ◽  
Oman Mountains ◽  
Bedding Planes ◽  
Fracture Systems ◽  
Calcite Veins ◽  
Al Jabal Al Akhdar

ABSTRACT We present a high-resolution structural study on the dip slope of the southern flank of Jabal Shams in the central Oman Mountains. The objectives of the study were: (1) to test existing satellite-based interpretations of structural elements in the area; (2) prepare an accurate geological map; and (3) collect an extensive structural dataset of fault and bedding planes, fault throws, veins and joints. These data are compared with existing models of tectonic evolution in the Oman Mountains and the subsurface, and used to assess the applicability of these structures as analogs for fault and fracture systems in subsurface carbonate reservoirs in Oman. The complete exposure of clean rock incised by deep wadis allowed detailed mapping of the complex fault, vein and joint system hosted by Member 3 of the Cretaceous Kahmah Group. The member was divided into eight units for mapping purposes, in about 100 m of vertical stratigraphy. The map was almost exclusively based on direct field observations. It includes measurement of fault throw in many locations and the construction of profiles, which are accurate to within a few meters. Ground-truthing of existing satellite-based interpretations of structural elements showed that faults can be mapped with high confidence using remote-sensing data. The faults range into the subseismic scale with throws as little as a few decimeters. However, the existing interpretation of lineaments as cemented fractures was shown to be incorrect: the majority of these are open fractures formed along reactivated veins. The most prominent structure in the study area is a conjugate set of ESE-striking faults with throws resolvable from several centimeters to hundreds of meters. These faults contain bundles of coarse-grained calcite veins, which may be brecciated during reactivation. We interpret these faults to be a conjugate normal- to oblique fault set, which was rotated together with bedding during the folding of the Al Jabal al-Akhdar anticline. There are many generations of calcite veins with minor offset and at high-angle-to-bedding, sometimes in en-echelon sets. Analysis of clear overprinting relationships between veins at high-angle-to-bedding is consistent with the interpretations of Holland et al. (2009a); however we interpret the anticlockwise rotation of vein strike orientation to start before and end after the normal faulting. The normal faults post-date the bedding-parallel shear veins in the study area. Thus these faults formed after the emplacement of the Semail and Hawasina Nappes. They were previously interpreted to be of the same age as the regional normal- to oblique-slip faults in the subsurface of northern Oman and the United Arab Emirates, which evolved during the early deposition of the Campanian Fiqa Formation as proposed by Filbrandt et al. (2006). We interpret them also to be coeval with the Phase I extension of Fournier et al. (2006). The reactivation of these faults and the evolution of new veins was followed by folding of the Al Jabal al-Akhdar anticline and final uplift and jointing by reactivation of pre-existing microveins. Thus the faults in the study area are of comparable kinematics and age as those in the subsurface. However they formed at much greater depth and fluid pressures, so that direct use of these structures as analogs for fault and fracture systems in subsurface reservoirs in Oman should be undertaken with care.

scholarly journals Seismic characterisation of carbonate platforms and reservoirs: an introduction and review

2021 ◽  
pp. SP509-2021-51
Author(s):  
J. Hendry ◽  
P. Burgess ◽  
D. Hunt ◽  
X. Janson ◽  
V. Zampetti
Keyword(s):  
Seismic Data ◽  
Large Scale ◽  
Carbonate Platform ◽  
Energy Transition ◽  
Carbonate Platforms ◽  
Seismic Attribute ◽  
Sequence Stratigraphic ◽  
3D Data ◽  
Diagenetic Facies ◽  
Central Atlantic

AbstractImproved seismic data quality in the last 10–15 years, innovative use of seismic attribute combinations, extraction of geomorphological data, and new quantitative techniques, have significantly enhanced understanding of ancient carbonate platforms and processes. 3D data have become a fundamental toolkit for mapping carbonate depositional and diagenetic facies and associated flow units and barriers, giving a unique perspective how their relationships changed through time in response to tectonic, oceanographic and climatic forcing. Sophisticated predictions of lithology and porosity are being made from seismic data in reservoirs with good borehole log and core calibration for detailed integration with structural, paleoenvironmental and sequence stratigraphic interpretations. Geologists can now characterise entire carbonate platform systems and their large-scale evolution in time and space, including systems with few outcrop analogues such as the Lower Cretaceous Central Atlantic “Pre-Salt” carbonates. The papers introduced in this review illustrate opportunities, workflows, and potential pitfalls of modern carbonate seismic interpretation. They demonstrate advances in knowledge of carbonate systems achieved when geologists and geophysicists collaborate and innovate to maximise the value of seismic data from acquisition, through processing to interpretation. Future trends and developments, including machine learning and the significance of the energy transition, are briefly discussed.

Chapter 6 Conclusions, differences between the Jabal Akhdar and Saih Hatat domes and unanswered questions

10.1144/m54.6 ◽  
2021 ◽  
Vol 54 (1) ◽  
pp. 105-111 ◽  
Author(s):  
Andreas Scharf ◽  
Frank Mattern ◽  
Mohammed Al-Wardi ◽  
Gianluca Frijia ◽  
Daniel Moraetis ◽  
...  
Keyword(s):  
Large Scale ◽  
Late Paleozoic ◽  
Future Research ◽  
Early Paleozoic ◽  
Chronological Order ◽  
Oman Mountains ◽  
Tectonic Events ◽  
Major Fault ◽  
Tethys Ocean ◽  
Semail Ophiolite

AbstractThis chapter provides the conclusions/outlines of the tectonics, affecting the Southeastern Oman Mountains, including the Jabal Akhdar and Saih Hatat domes. The main tectonic events include amongst others (1) Neoproterozoic rifting, (2) two distinct early Paleozoic compressive events, (3) large-scale open ‘Hercynian’ folding and formation of a pronounced unconformity during the late Paleozoic, (4) rifting preceding the opening of the Neo-Tethys Ocean during the late Paleozoic, (5) late Cretaceous obduction of the Semail Ophiolite and the response of the Arabian lithosphere as well as (6) post-obductional tectonics. Also of major geological significance are the three major glaciations (Sturtian, Marinoan and Late Paleozoic Gondwana glaciation) which have been recorded in the rocks of northern Oman. Moreover, major lithological, structural and metamorphic differences exist between the Jabal Akhdar and Saih Hatat domes. It appears likely that a major fault, striking parallel to the eastern margin of the Jabal Akhdar Dome, probably originating during Neoproterozoic terrain accretion, acted as a divide between both domes until present. This fault was multiple times reactivated and could explain the differences between the two domes. A catalogue of unanswered questions is included in chronological order to express that many geological aspects need further investigation and future research projects.

Lower and Middle Devonian brachiopod-dominated communities of Nevada, and their position in a biofacies-province-realm model

1990 ◽  
Vol 64 (6) ◽  
pp. 902-941 ◽  
Author(s):  
J. G. Johnson ◽  
G. Klapper ◽  
J. G. Johnson
Keyword(s):  
Relative Abundance ◽  
Middle Devonian ◽  
Large Scale ◽  
Carbonate Platform ◽  
Specific Content ◽  
Sea Level Fluctuations ◽  
Community Associations ◽  
Key Species ◽  
Platform Margin ◽  
Conodont Zone

Lower and Middle Devonian brachiopod-dominated communities of Nevada are numerous (46) and most are positioned on or adjacent to the carbonate-platform foreslope or ramp. Level-bottom community chains are fundamentally different from community associations that are interrupted by a platform margin. All communities require relative abundance data of constituent species for recognition. These communities prove to be endemic to the Nevada-southeastern California area, even though faunal similarities with distant regions in North America can be recognized. Analogous communities, the same age as comparable communities in Nevada, differ in overall specific content and in relative abundance of diagnostic species. Identification of analogous communities requires recognition of common physical environments (first) and faunal similarity (second). Groupings of communities based on presence-absence data of key species and genera are not meaningful.Biofacies boundaries sited on carbonate-platform foreslopes separate community associations and also act as filter boundaries for faunal realms. The platform and peripheral biofacies thus delineated are also realms, a pattern that is repeated by different organisms from Cambrian to Cenozoic. Biofacies boundaries shift in concert with large-scale sea-level fluctuations. During platform emergence, most faunas are peripheral and therefore cosmopolitan. Transgression initially forms small, isolated epeiric seas populated from offshore, and endemic faunas evolve. Increased transgression merges epeiric seas and faunas, reducing provinciality and diversity through competition. Regression results in extinctions in proportion to its rate and the area involved. The cycle repeats.Thehermanni-cristatusconodont Zone is replaced with the namehermanniZone. ThedisparilisZone is divided into Lower and Upper Subzones. ThenorrisiZone is proposed at the top of the Middle Devonian.

A FRENCH ARMADA? THE AZORES CAMPAIGNS, 1580–1583

2012 ◽  
Vol 55 (1) ◽  
pp. 1-20 ◽  
Author(s):  
ALAN JAMES
Keyword(s):  
Foreign Policy ◽  
Large Scale ◽  
Great Distance ◽  
Considerable Extent ◽  
French History ◽  
Wars Of Religion ◽  
Royal Authority ◽  
International History ◽  
Catherine De Medici ◽  
Queen Mother

ABSTRACTThe Spanish Armada and the battle of Lepanto loom large in a remarkable period of international history shaped to a considerable extent by the deployment of sea power. Yet between 1581 and 1583, France also conducted a large-scale naval operation at great distance. A series of expeditions to the Azores reached a climax with the defeat in battle of a French fleet of sixty ships off the island of São Miguel in July 1582. Acting under the authority of Catherine de Medici and in the name of her rival legal claim to the Portuguese throne, the commander Philippe Strozzi had not only led the most ambitious oceanic operation in French history up to that date and a bid to extend France's overseas empire but a serious challenge to Philip II's union of the Iberian crowns. Yet this was more than just a puzzling anomaly in France's foreign policy. It was also an act of royal authority and the pursuit of reputation and status by the queen mother that was entirely consistent with the domestic priorities of the crown in the context of the Wars of Religion.

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