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Wyświetlanie 1-5 z 5
Tytuł:
Early Silurian (Llandovery) graptolite assemblages of Saudi Arabia: biozonation, palaeoenvironmental significance and biogeography
Autorzy:
Williams, M.
Zalasiewicz, J.
Boukhamsin, H.
Cesari, C.
Powiązania:
https://bibliotekanauki.pl/articles/2060177.pdf
Data publikacji:
2016
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Saudi Arabia
Silurian
graptolites
biozonation
Opis:
Analysis of Silurian graptolite assemblages from 1017 sample horizons in 132 cores (from 65 boreholes) through the Qusaiba Member, Qalibah Formation of Saudi Arabia, provides a refined graptolite biostratigraphy for the Arabian Peninsula comparable in its resolution to that from the British Isles and the Czech Republic. Over 150 graptolite species characterize 11 biozones from the lowermost Rhuddanian lubricus Biozone to the lower Telychian guerichi Biozone, with sub-zonal resolution for several intervals. Graptolite biozonal boundaries and the Rhuddanian-Aeronian and Aeronian-Telychian stage boundaries can be placed with high precision. Detailed analysis of graptolite spatial distribution suggests persistent depth-stratified marine assemblages across the Silurian palaeo-Arabian Plate. Near-surface-dwelling assemblages probably occupied the mixed-layer of Silurian oceans, enabling colonization of shallow shelf environments. They are low-diversity (1-2 species) assemblages characterized by Neodiplograptus, Coronograptus, Neolagarograptus and Stimulograptus species and often are preserved in strata with extensive shelly faunas. Deeper marine assemblages are of higher diversity (up to 15 species per horizon), and are characterized by dorsally curved or helically coiled species of Spirograptus, Demirastrites, Lituigraptus, Rastrites and Torquigraptus. Recognition of depth-stratified graptolite assemblages provides an important tool for establishing palaeo-basin topography and water depth at the time of sedimentary deposition. At the species level, the graptolite assemblages of Saudi Arabia are remarkably similar to contemporaneous faunas from peri-Gondwanan Europe and, from the middle Rhuddanian onwards, also to the Avalonian and Laurentian Llandovery graptolites of the UK.
Źródło:
Geological Quarterly; 2016, 60, 1; 3--25
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sedimentology and Diagenesis of the Miocene Nutaysh Member of the Burqan Formation in the Midyan Area, Northwestern Saudi Arabia
Autorzy:
Al-Ramadan, K.
Dogan, A.
Senalp, M.
Powiązania:
https://bibliotekanauki.pl/articles/2060020.pdf
Data publikacji:
2013
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Turbidite
lithofacies
diagenesis
Early Miocene
Saudi Arabia
Opis:
Turbidite sandstones deposited in rift settings are currently among the main targets of hydrocarbon exploration. However, the impact of style of sedimentation, cyclicity and diagenesis on reservoir quality of such sandstones is relatively poorly explored in the literature. The sedimentology, stratigraphic architecture, and diagenetic alterations of deep marine sandstones of the Mocene Nutaysh member of the Burqan Formation in the Midyan area (Saudi Arabia) are described based on number of measured sedimentologic sections, lithofacies identification in the field and laboratory studies. Three lithofacies types are here identified in the measured sections. These are from bottom to top: (1) “Lithofacies A” consisting of massive to thickly-bedded, coarse-to-very coarse-grained sandstone and conglomerates; (2) “Lithofacies B” consisting of well-bedded, coarse-to-medium-grained, well-sorted sandstone, and (3) “Lithofacies C” consisting of thin-bedded, fine to very fine-grained, current-rippled sandstone, bioturbated shaley siltstone and marl. The main diagenetic processes in the sandstones include the formation of grain-coating smectite and rhombic dolomite. Small amounts of cements include the formation of authigenic kaolinite and calcite. The reservoir quality is anticipated to have been preserved under the transformation of smectite to deep burial illite, which is believed to prevent formation of quartz cements.
Źródło:
Geological Quarterly; 2013, 57, 1; 165--174
1641-7291
Pojawia się w:
Geological Quarterly
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Biofacies and palaeoenvironments of the Jurassic Shaqra Group of Saudi Arabia
Autorzy:
Hughes, G.
Powiązania:
https://bibliotekanauki.pl/articles/2061339.pdf
Data publikacji:
2008
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Saudi Arabia
biofacies
palaeoenvironments
Shaqra Group
subsidence rates
Opis:
The Jurassic succession in Saudi Arabia consists of seven formations, forming the Shaqra Group, of which most are carbonate and some are partly evaporitic, and is of economic importance because it hosts twelve hydrocarbon reservoirs, including the Arab-D Reservoir within the world’s largest oilfield at Ghawar. The Minjur-Marrat formational boundary marks the Triassic-Jurassic boundary, of which the Marrat is dated as Toarcian. A significant unconformity separates this unit from the overlying Dhruma Formation, of Bajocian to Bathonian ages. The Tuwaiq Mountain Formation, of Callovian age, overlies the Dhruma Formation, with reduced hiatus. The Hanifa Formation, of Oxfordian age, is separated from the Tuwaiq Mountain Formation by a minor hiatus, as are the successive Jubaila, Arab and Hith formations, of Kimmeridgian to Tithonian ages. The Jurassic-Cretaceous boundary is currently placed within the lower part of the overlying Sulaiy Formation. A combination of semi-quantitative micropalaeontological and macropalaeontological analysis of closely-spaced thin sections from these carbonates displays a tiered relay of clearly defined microbiofacies cycles. These cycles reveal palaeoenvironmental trends that subdivide the succession into parasequences, transgressive and highstand systems tracts that are not always evident from the sedimentology alone. The biofacies approach to elucidating palaeoenvironmental variations of the Shaqra Group provides significant insights to the Jurassic history of the Arabian Plate, as well as serving to explain the origin and stratigraphic location of hydrocarbon reservoirs, seals and potential source rocks. The Shaqra Group spans at least 36 Ma, and qualifies as a second order depositional sequence, within which the formations can be considered as third order sequences. Better chronostratigraphic constraint of the depositional sequences reveals elevated subsidence rates for the Dhruma, Tuwaiq Mountain and Hanifa formations that can be related to established episodes of global plate readjustment. Tectonoeustatic and possibly glacioeustatic controls on depositional cyclicity probably exerted an influence on the major unconformities within the Shaqra Group.
Źródło:
Volumina Jurassica; 2008, 6, 1; 33-45
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Oxfordian biofacies and palaeoenvironments of Saudi Arabia
Autorzy:
Hughes, G.
Al-Khaled, M.
Varol, O.
Powiązania:
https://bibliotekanauki.pl/articles/2061341.pdf
Data publikacji:
2008
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Saudi Arabia
Oxfordian
Hanifa Formation
micropalaeontology
nannopalaeontology
stromatoporoids
Opis:
The Hanifa Formation in Saudi Arabia consists of a succession of carbonates, over 100 m thick, that were deposited during the Late Jurassic. It consists of two depositional sequences represented by the lower Hawtah Member and an upper Ulayyah Member, respectively. The Hawtah Member is assigned an Early (?) to Middle Oxfordian age, based on brachiopod, nautiloid and coccolith evidence. The Ulayyah Member is assigned a Late Oxfordian age based on ammonite, nautiloid, coccolith and foraminiferal evidence. Detailed study of the microbiofacies and lithology of the late highstand succession of the Ulayyah sequence in 41 cored wells distributed across the Kingdom was aimed at determining the most suitable locations for porous and permeable grainstone accumulation as lithofacies hosts the Hanifa Reservoir elsewhere in the region. A range of palaeoenvironments has been determined, based on integrated biofacies and lithofacies, that include shallow lagoon packstones and foraminiferal dominated grainstones and deep lagoon wackestones and packstones with Clypeina/Pseudoclypeina dasyclad algae. In addition, a series of basin-margin, shoal-associated biofacies are present that include stromatoporoid back-bank packstones and grainstones with the branched stromatoporoid Cladocoropsis mirabilis, bank-crest grainstones with encrusting and domed stromatoporoids. A few wells also proved the presence of intrashelf basin-flank mudstones and wackestones containing sponge spicules, deep marine foraminifera and coccoliths. This study provided control to delimit an intrashelf basin with an irregular margin situated in the east-central part of the Saudi Arabian portion of the Arabian Plate carbonate platform during Late Oxfordian. The basin is flanked by a belt of stromatoporoid banks that pass laterally into a back-bank facies before developing into a lagoon facies. There is no evidence for the shoreline of this basin, although the presence of rare charophytes in the northwest testifies to possible proximity of fluviatile input. The grainstone dominated basin margin facies presents good hydrocarbon reservoir facies and its juxtaposition to intrashelf basinal sediments with potential source rock character provides exciting new prospects in areas hitherto uninvestigated for hydrocarbon reservoirs.
Źródło:
Volumina Jurassica; 2008, 6, 1; 47-60
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sedimentological and micropalaeontological evidence to elucidate post-evaporitic carbonate palaeoenvironments of the Saudi Arabian latest Jurassic
Autorzy:
Hughes, G.
Naji, N.
Powiązania:
https://bibliotekanauki.pl/articles/2061333.pdf
Data publikacji:
2008
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Saudi Arabia
Tithonian
Hith Firmation
Manifa Reservoir
micropalaeontology
evaporates
carbonates
Opis:
The Hith Formation forms the youngest lithostratigraphic unit of the Jurassic Shaqra Group. It represents the culmination of a succession of hypersaline and euryhaline cycles that characterise the Late Jurassic of Saudi Arabia. The Formation is poorly exposed in central Saudi Arabia, but it has been studied in detail in subsurface eastern Saudi Arabia where the upper carbonate member hosts an important hydrocarbon reservoir called the Manifa Reservoir. Chronostratigraphic control is absent from the formation itself, and the Tithonian age is suggested for the Hith Formation based on its stratigraphic position between the underlying Arab Formation of Late Kimmeridgian age, and the overlying Sulaiy Formation, of Late Tithonian to Berriasian age. The Hith Formation needs redefining in the light of new lithological evidence, and a tripartite member scheme is suggested. This includes the lower anhydrite-dominated member here termed the “anhydrite” member, and considered to represent hypersaline subaqueous deposition within a restricted deep lagoon during the lowstand systems tract of the Manifa sequence. A “transitional“ member consists of interbedded anhydrites and carbonates and approximates with the transgressive zone. The overlying “carbonate” member represents the results of a prograding shallow, normal salinity marine succession related to the highstand systems tract. Interbedded carbonates within the evaporites are interpreted to represent superimposition of a higher frequency, possibly 4th order eustatic cyclicity. The “carbonate“ member hosts the Manifa Reservoir, and here proposed as the Manifa Member, consist of five parasequences, each of which represents a shoaling-upwards cycle with a succession of up to five repeated lithofacies and biofacies that commences with a stromatolitic, microfaunally-barren unit followed by fine-grained grainstones with a monospecific but abundant ostracod biofacies. A succession of coarse pelloidal grainstones with rare foraminifera, including Redmondoides lugeoni, Trocholina alpina with a variety of unidifferentiated valvulinids and miliolids then follows, that passes vertically into coarse ooid grainstones, with rare Redmondoides lugeoni, forming the uppermost part of each parasequence.
Źródło:
Volumina Jurassica; 2008, 6, 1; 61-73
1896-7876
1731-3708
Pojawia się w:
Volumina Jurassica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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