Late Lutetian (Eocene) mafic intrusion into shallow marine platform deposits north of the Oman Mountains (Rusayl Embayment) and its tectonic significance

2020 ◽  
Vol 170 ◽  
pp. 103941
Author(s):  
Andreas Scharf ◽  
Masafumi Sudo ◽  
Bernhard Pracejus ◽  
Frank Mattern ◽  
Ivan Callegari ◽  
...  
Keyword(s):  
Shallow Marine ◽  
Mafic Intrusion ◽  
Oman Mountains ◽  
Tectonic Significance ◽  
Marine Platform

scholarly journals Fabric Preserving and Fabric Destroying Dolomitization: A case of Seawater Dolomitization

2006 ◽  
Vol 11 ◽  
pp. 39
Author(s):  
Alham Jassim Al-Langawi
Keyword(s):  
Crystal Size ◽  
Mixing Zone ◽  
Shallow Marine ◽  
Oman Mountains ◽  
Complete Obliteration ◽  
Tethys Ocean ◽  
Inclusion Distribution ◽  
Short Time ◽  
Lagoon Reef ◽  
Arabian Platform

This study is based on field, petrographic and geochemical investigations of Hajar Supergroup autochthonous rocks: Ruus Al Jibal Group- Musandam Peninsula, and Akhdar Group- Jebel Akhdar, Oman and U.A.E., and para-autochthonous Maqam Formation-Sumeini Group-Jebel Sumeini-U.A.E.  Petrographic evidence indicates that the rocks were deposited in a shallow marine shelf environment, particularly tidal flat, lagoon, reef, back-reef and shoal environments that were part of the Arabian Platform during Permian and Triassic times. However, they are almost entirely dolomitized and the rocks show different petrographic features ranging from perfect preservation of original texture by mimetic dolomitization to complete obliteration and destruction of the original limestones giving rise to inequicrystalline and equicrystalline fabrics.  Dolomites analyzed by geochemical methods were categorized on the basis of textural variations; crystal size, shape and impurity or inclusion distribution within crystals, and whether these crystals are found as rock forming (replacive) or cements. The dolomites display variations in stoichiometry, ordering and trace element concentrations indicating differences in dolomitizing fluid chemistry and recrystallization stages that prevailed through time. It indicates also that although dolomitization is pervasive, dolomites are petrographically and chemically immature. All the petrographic and geochemical evidence strongly indicates seawater and/or mixing zone dolomitization which may have been initiated soon after deposition of the host sediments.  Rocks showing preservation of allochems as well as the marine cements by mimetic dolomite crystals, suggest that dolomitization was early (at shallow depths) with very active marine-water circulation and occurred in a relatively short time.  Evidence from crystalline dolomites indicates several crystallization events at shallow burial depths, under marine waters modified by increased temperature and mixing probably with evaporitic brines. The only fluid capable of early dolomitization in the case of the Oman Mountains dolomites was warm seawater from the Tethys Ocean which was circulating in the subsurface. KEYWORDS: 

Mid-late Devonian calcified marine algae and cyanobacteria, South China

2010 ◽  
Vol 84 (4) ◽  
pp. 569-587 ◽  
Author(s):  
Qi Feng ◽  
Yi-Ming Gong ◽  
Robert Riding
Keyword(s):  
Environmental Stress ◽  
South China ◽  
Food Supply ◽  
Marine Algae ◽  
Southern China ◽  
Late Devonian ◽  
Shallow Marine ◽  
Marine Platform

Givetian, Frasnian and Famennian limestones from southern China contain microfossils generally regarded as calcified algae and cyanobacteria. These are present in 61 out of 253 sampled horizons in four sections from three widely spaced localities in Guangxi and southern Guizhou. Three of the sections sampled are Givetian-Frasnian-Famennian; one section is Frasnian-Famennian. They include reef and non-reef carbonates of shallow marine platform facies. The following taxa are identified with differing degrees of confidence, and placed in algae, cyanobacteria or microproblematica. Algae: Halysis, ‘solenoporaceans’, Vermiporella. Cyanobacteria: Bevocastria, Girvanella, Hedstroemia, Subtifloria. Microproblematica: ?Chabakovia, Garwoodia, ?Issinella, Izhella, Paraepiphyton, Rothpletzella, Shuguria, ?Stenophycus, Tharama, Wetheredella. As a whole, the abundance of algae, cyanobacteria and microproblematica increases by 34% from Givetian to Frasnian, and declines by 63% in the Famennian. This secular pattern of marked Famennian decrease does not support recognition of them as “disaster forms” in the immediate aftermath of late Frasnian extinction. Nonetheless, their survival into the Famennian could indicate tolerance of environmental stress, independence of changes in food supply, morphologic plasticity, and ability to occupy a range of habitats and depths. Uncertainties concerning the affinities of the problematic taxa hinder assessment of their significance.

Sedimentology, stratigraphy and clinoform architectures of a siliciclastic shallow-marine platform: insights from the Late Ordovician of the Anti-Atlas (Morocco)

2021 ◽  
Author(s):  
Déborah Harlet ◽  
Guilhem Amin Douillet ◽  
Jean-François Ghienne ◽  
Chloé Bouscary ◽  
Philippe Razin ◽  
...  
Keyword(s):  
Late Ordovician ◽  
Shallow Marine ◽  
North East ◽  
The North ◽  
Stratigraphic Framework ◽  
Facies Associations ◽  
Basin Geometry ◽  
Marine Platform ◽  
Stacking Patterns ◽  
Early Late

<p><span><span>The Moroccan Anti-Atlas consists of a several kilometers thick sediment pile accumulated on the northern Gondwana platform since the latest Precambrian (Ediacaran). This study focuses on the Ktaoua Group, early Late Ordovician (Mid-Sandbian to Katian) in age, which records a major and multiphase transgressive/regressive cycle above the shallow marine sandstones of the underlying First Bani Group. In the western Central Anti-Atlas, the Ktaoua Group is formed by offshore shales to coastal sandstones organized in regressive parasequences. Here, high-resolution field-based stratigraphy is used to constrain the shelf architecture and clinoforms geometries within the Ktaoua Group.</span></span></p><p><span><span>Whereas the lower part of the Ktaoua Group records parasequences from silty-shale to fine to coarse sandstones with hummocky-cross-stratification (HCS), its upper part oscillates between HCS beds and very coarse sandstones. Ferruginous, condensed horizons usually drape the parasequences. In this study, we investigate the platform geometry through the correlation of the stacking patterns of seventeen stratigraphic logs along an 85 km long, well-exposed cliff. Drone images support the logging and the correlations of the sections by imaging clinoforms geometries. </span></span></p><p><span><span>Several decameters of fine to coarse sandstones can be observed to grade laterally into condensed level(s) within a few kilometers, hence evidencing clinoforms pinching out. The visible orientation of the clinoforms along the cliff exposures show a proximal to distal trend from the south-west to the north-east, in agreement with the overall basin geometry. Three clinoforms with distinct geometries and lateral evolution of facies associations are highlighted. The distal part of a clinoform, 15 m in thickness, pinches out onto the top of the underlying First Bani Group within 7 km. The overlying regressive parasequence, approximatively 50 m thick, remains consistent more than 50 km, and is understood as a prograding clinoform. A third clinoform, capped by a prominent sandstone body constantly thicker than 20 m over ca. 20 km, disappears within its last 3.5 km onto the underlying clinoform. This study offers new details on the progradation and regression geometries along a giant platform within a detailed stratigraphic framework.</span></span></p><p><span><em><span>We would like to thank the Pacha and the Gendarmerie Royale of Foum-Zguid, the governor of Tata and the different persons who gave their approval and facilitated the use of the drone in the region of Souss-Massa for their precious help.</span></em></span></p>

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.

A soft substrate community with edrioasteroids, from the Verulam Formation (Middle Ordovician) at Gamebridge, Ontario

1980 ◽  
Vol 17 (5) ◽  
pp. 674-679 ◽  
Author(s):  
Janet B. Waddington
Keyword(s):  
Soft Bottom ◽  
Associated Fauna ◽  
Soft Substrate ◽  
Shallow Marine ◽  
Middle Ordovician ◽  
Lower Member ◽  
Marine Platform

The edrioasteroids Isorophusella incondita (Raymond) and Cryptogoleus chapmani (Raymond) occur in profusion on one horizon in the lower member of the Verulam Formation (Middle Ordovician) near Gamebridge, Ontario. The associated fauna, including brachiopods, trilobites, and gastropods, suggests a smothered life assemblage from soft bottom shallow marine platform conditions. The edrioasteroids settled on overturned shells of Rafinesquina alternata and on local hard surfaces provided by previously formed internal moulds of molluscs.

scholarly journals Lower Jurassic benthic foraminiferal assemblages from shallow-marine platform carbonates of Mallorca (Spain): stratigraphic implications

2019 ◽  
Vol 46 (1) ◽  
pp. 77-94 ◽  
Author(s):  
Ana Sevillano ◽  
Michel Septfontaine ◽  
Idoia Rosales ◽  
Antonio Barnolas ◽  
Beatriz Bádenas ◽  
...  
Keyword(s):  
Lower Jurassic ◽  
Shallow Marine ◽  
Platform Carbonates ◽  
Marine Platform

scholarly journals Jurassic shelf sedimentation and sequence stratigraphy of the Surghar Range, Pakistan

1997 ◽  
Vol 15 ◽  
Author(s):  
S. Ahmed ◽  
D. Mertmann ◽  
E. Manutsoglu
Keyword(s):  
Sea Level ◽  
Sequence Stratigraphy ◽  
Intertidal Sediments ◽  
Shallow Marine ◽  
Delta Plain ◽  
Platform Development ◽  
Shelf Sedimentation ◽  
Marine Platform ◽  
Middle Callovian ◽  
Lower Callovian

In the Surghar Range, facies and biostratigraphical analysis of Jurassic deposits show that the platform development was affected by both the variations in sea-level and the influences of a nearby hinterland. The well exposed shallow marine to intertidal sediments of the Shinawari Formation and the Samana Suk Formation were deposited from the Toarcian to the middle Callovian. A rise in sea-level during the lower Toarcian submerged the area which was a delta plain before. Shallowing upward cycles and smaller-scale paracycles are characteristic for the marine sequence. Relative sea-level lowstands occurred during the Bajocian, the Bathonian and the Callovian. The lower two coincide with terrigenous influx from the southeast. A lower Callovian hardground is overlain by transgressive middle Callovian open marine limestones. The Jurassic shallow marine platform development ends with another hardground. Drowning of the platform is indicated by the overlying deeper shelf deposits of the Oxfordian - Neocomian Chichali Formation.

scholarly journals PETROLOGICAL INVESTIGATION OF CARBONATE ROCKS FROM THE IONIAN ZONE (ETOLOAKARNANIA, WESTERN GREECE)

2017 ◽  
Vol 43 (5) ◽  
pp. 2540
Author(s):  
P. Bourouni ◽  
B. Tsikouras ◽  
K. Hatzipanagiotou
Keyword(s):  
Clay Minerals ◽  
Deep Water ◽  
Carbonate Rocks ◽  
Shallow Marine ◽  
Water Basin ◽  
Marine Platform ◽  
Western Greece ◽  
Deep Water Basin

The petrographic features of the carbonate rocks from the Ionian Zone in the Etoloakarnania Prefecture are presented. They are represented by limestones with minor dolomite. The limestones include: (i) wackestones (or sparse micrites), with poor presence of allochems within a mud matrix; (ii) packstones (or packed micrites) with increasing levels of carbonate grains that are still surrounded by micrite matrix, and (iii) grainstones (or sparites) containing allochems that are cemented with sparry calcite crystals, while the mud matrix is absent. Bioclasts are the dominant carbonate components in most of the samples accompanied by infrequent pelloids, intraclasts, lithoclasts and ooids. Crystalline limestones were not identified. Quartz, apatite, barite, anhydrite, halite, clay minerals, magnetite and ilmenite have been determined as accessory phases. The results show that mineralogical and petrographic features of the analyzed carbonate rocks are related to their evolution during the development of the Ionian Zone from a shallow-marine platform to a deep water basin.

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