The Ediacaran–Cambrian Ara Group of the South Oman Salt Basin in the Sultanate of Oman is one of the world’s oldest petroleum systems and holds some of the most important hydrocarbon reserves in the country. However, the Ara Group salt and isolated carbonate platforms, or ‘stringers’, are known only from the subsurface and deformed fragments brought to the surface in salt-piercing domes. Thus, determining Ara source and reservoir facies architecture at high resolution is a particular problem. Here we present the results of field surveying in the Haushi-Huqf region over a number of years specifically to investigate the possibility of Ara Group equivalents being exposed in outcrop. Defined here, for the first time, is the new Sirab Formation, which we incorporate into the top of the Neoproterozoic–Cambrian Huqf Supergroup. In general, it conformably overlies the Buah Formation. However, at some localities on what were probably fault-bounded palaeo-topographic highs, the Sirab Formation rests unconformably on eroded Buah Formation or directly on the even older Shuram Formation. The Sirab Formation is overlain with marked angular unconformity by the siliciclastics of the Haima Supergroup. As such, the Sirab Formation occupies the same lithostratigraphic position as the Ara Group subsurface. We subdivide the formation into three principal members; the lower Ramayli Member, middle Shital Member and upper Aswad Member. A fourth, the Salutiyyat Member, can be recognised where the Sirab Formation lies on eroded Nafun Group palaeo-topographic highs and is probably the chrono-stratigraphic lateral equivalent at least in part of the upper Ramayli Member. The Ramayli and Shital members contain evaporite units, including halite beds, and fault- or eustatically-controlled cyclical peritidal carbonates indicating that the Al Huqf area was a shallow trough or graben during this period within a regional structural high. The middle and upper members contain significant microbial build-ups including thrombolite framestone reefs, which are the principal reservoir subsurface in the Ara ‘stringers’, and rare crinkly laminites which are the presumed source rock at depth. Whilst the precise age dates for the formation and chronostratigraphy of each member still need to be resolved, it is clear that the Sirab Formation includes exposures of litho- and bio-facies present in the Ara Group and thus could provide useful surface analogues for the petroleum geology of the South Oman Salt Basin and Central Oman High in the future.
{"title":"Ediacaran–Cambrian Sirab Formation of the Al Huqf region, Sultanate of Oman","authors":"C. Nicholas, S. Gold","doi":"10.2113/geoarabia170149","DOIUrl":"https://doi.org/10.2113/geoarabia170149","url":null,"abstract":"\u0000 The Ediacaran–Cambrian Ara Group of the South Oman Salt Basin in the Sultanate of Oman is one of the world’s oldest petroleum systems and holds some of the most important hydrocarbon reserves in the country. However, the Ara Group salt and isolated carbonate platforms, or ‘stringers’, are known only from the subsurface and deformed fragments brought to the surface in salt-piercing domes. Thus, determining Ara source and reservoir facies architecture at high resolution is a particular problem. Here we present the results of field surveying in the Haushi-Huqf region over a number of years specifically to investigate the possibility of Ara Group equivalents being exposed in outcrop. Defined here, for the first time, is the new Sirab Formation, which we incorporate into the top of the Neoproterozoic–Cambrian Huqf Supergroup. In general, it conformably overlies the Buah Formation. However, at some localities on what were probably fault-bounded palaeo-topographic highs, the Sirab Formation rests unconformably on eroded Buah Formation or directly on the even older Shuram Formation. The Sirab Formation is overlain with marked angular unconformity by the siliciclastics of the Haima Supergroup. As such, the Sirab Formation occupies the same lithostratigraphic position as the Ara Group subsurface. We subdivide the formation into three principal members; the lower Ramayli Member, middle Shital Member and upper Aswad Member. A fourth, the Salutiyyat Member, can be recognised where the Sirab Formation lies on eroded Nafun Group palaeo-topographic highs and is probably the chrono-stratigraphic lateral equivalent at least in part of the upper Ramayli Member. The Ramayli and Shital members contain evaporite units, including halite beds, and fault- or eustatically-controlled cyclical peritidal carbonates indicating that the Al Huqf area was a shallow trough or graben during this period within a regional structural high. The middle and upper members contain significant microbial build-ups including thrombolite framestone reefs, which are the principal reservoir subsurface in the Ara ‘stringers’, and rare crinkly laminites which are the presumed source rock at depth. Whilst the precise age dates for the formation and chronostratigraphy of each member still need to be resolved, it is clear that the Sirab Formation includes exposures of litho- and bio-facies present in the Ara Group and thus could provide useful surface analogues for the petroleum geology of the South Oman Salt Basin and Central Oman High in the future.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2012-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68184652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Following a preliminary palynological report of two samples from the lower part of the Kuhlan Formation (Unit A) near Kuhlan village, northwest Yemen (Stephenson and Al-Mashaikie, 2010), a further seven samples from Unit A, and an additional 22 samples from the underlying Akbarah Formation in the same locality are reported. The seven new samples from the Kuhlan Formation support the 2165A to 2141A Biozone age originally suggested by Stephenson and Al-Mashaikie (2010), and the new Akbarah Formation samples suggest an age not markedly different since Anapiculatisporites concinnus and Spelaeotriletes triangulus are also present in the Akbarah Formation (e.g. samples AK-11 and AK-12). This correlation confirms that the lower Kuhlan Formation and the Akbarah Formation, are likely to be late Carboniferous in age and equivalent to the lower parts of the Al Khlata Formation of Oman.
{"title":"Stratigraphic Note: Update on the palynology of the Akbarah and Kuhlan formations, northwest Yemen","authors":"M. Stephenson, Sa'ad Z. Al-Mashaikie","doi":"10.2113/geoarabia160417","DOIUrl":"https://doi.org/10.2113/geoarabia160417","url":null,"abstract":"\u0000 Following a preliminary palynological report of two samples from the lower part of the Kuhlan Formation (Unit A) near Kuhlan village, northwest Yemen (Stephenson and Al-Mashaikie, 2010), a further seven samples from Unit A, and an additional 22 samples from the underlying Akbarah Formation in the same locality are reported. The seven new samples from the Kuhlan Formation support the 2165A to 2141A Biozone age originally suggested by Stephenson and Al-Mashaikie (2010), and the new Akbarah Formation samples suggest an age not markedly different since Anapiculatisporites concinnus and Spelaeotriletes triangulus are also present in the Akbarah Formation (e.g. samples AK-11 and AK-12). This correlation confirms that the lower Kuhlan Formation and the Akbarah Formation, are likely to be late Carboniferous in age and equivalent to the lower parts of the Al Khlata Formation of Oman.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68184467","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-01DOI: 10.2113/geoarabia1604157
The following abstracts are a selection from those accepted for presentation at GEO 2010, the Ninth Middle East Geosciences Exhibition and Conference that was held in Bahrain on March 7–10, 2010. GEO 2010 was organized by Arabian Exhibition Management (AEM), the American Association of Petroleum Geologists (AAPG) in collaboration with the European Association of Geoscientists and Engineers (EAGE), and was supported by the Society of Exploration Geophysicists (SEG), Dhahran Geoscience Society (DGS), Bahrain Geoscience Society (BGS), Geological Society of Oman (GSO) and Emirates Society of Geoscience (ESG). The abstracts that are published here by permission of the organizers represent the fourth group that primarily cover: (1) Structure and Tectonics; and (2) Applied Case Studies from the Middle East. The abstracts have been slightly edited and/or reworded so as to conform to a more common style and format; for example, capitalization of formal names for formations, geological periods and stages, etc. Some abstracts required rewording to clarify the scientific content or were submitted as short papers. Every effort was made to present these as concisely and accurately as possible. GeoArabia sent the pre-press version of all the abstracts to the primary authors for their approval, but regrettably some could not be reached or did not respond. Throughout volume 16 of GeoArabia, four groups of GEO 2010 abstracts are now published so that a permanent record of these important studies is available to GeoArabia’s readers and the international geoscience community.
{"title":"GEO 2010 Abstracts Part IV","authors":"","doi":"10.2113/geoarabia1604157","DOIUrl":"https://doi.org/10.2113/geoarabia1604157","url":null,"abstract":"The following abstracts are a selection from those accepted for presentation at GEO 2010, the Ninth Middle East Geosciences Exhibition and Conference that was held in Bahrain on March 7–10, 2010. GEO 2010 was organized by Arabian Exhibition Management (AEM), the American Association of Petroleum Geologists (AAPG) in collaboration with the European Association of Geoscientists and Engineers (EAGE), and was supported by the Society of Exploration Geophysicists (SEG), Dhahran Geoscience Society (DGS), Bahrain Geoscience Society (BGS), Geological Society of Oman (GSO) and Emirates Society of Geoscience (ESG).\u0000 The abstracts that are published here by permission of the organizers represent the fourth group that primarily cover: (1) Structure and Tectonics; and (2) Applied Case Studies from the Middle East. The abstracts have been slightly edited and/or reworded so as to conform to a more common style and format; for example, capitalization of formal names for formations, geological periods and stages, etc. Some abstracts required rewording to clarify the scientific content or were submitted as short papers. Every effort was made to present these as concisely and accurately as possible. GeoArabia sent the pre-press version of all the abstracts to the primary authors for their approval, but regrettably some could not be reached or did not respond.\u0000 Throughout volume 16 of GeoArabia, four groups of GEO 2010 abstracts are now published so that a permanent record of these important studies is available to GeoArabia’s readers and the international geoscience community.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68184354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Cretaceous to Eocene succession in central and south Jordan is characterised by passive continental margin depositional sequences, which pass upward from alluvial/paralic to carbonate shelf and pelagic ramp settings. Detailed section logging and outcrop mapping have produced robust lithostratigraphic and lithofacies schemes that can be correlated throughout the region and in the subsurface. These schemes are set in a sequence-stratigraphic context in relation to the evolution sedimentation on the Arabian and Levant plates. Three major megasequences are described (Kurnub, Ajlun and Belqa), and these are further subdivided into large-scale depositional sequences separated by regional sequence boundaries that represent maximum flooding surfaces. There is close correspondence between maximum flooding surfaces recording major sea-level rise with those derived for the Arabian and Levant plates, although there are some discrepancies with the precise timing of global sea-level fluctuations. An upward change from braided to meandering stream fluvial environments in central and south Jordan during the Early Cretaceous, reflects a decreasing geomorphological gradient of the alluvial plain, declining siliciclastic sediment flux, and increased floodplain accommodation, associated with a regional Late Albian (second-order) rise in relative sea-level. The Late Albian to Early Cenomanian marine transgression across the coastal alluvial plain marks a major sequence boundary. During Cenomanian to Turonian times a rimmed carbonate-shelf was established, characterised by skeletal carbonates showing small-scale, upward-shallowing cycles (fourth- to fifth-order parasequences) ranging from subtidal to intertidal facies, arranged into parasequence sets. Rimmed carbonate shelf sequences pass laterally to coeval coastal/alluvial plain facies to the south and east. Eustatic (third-order) fluctuations in relative sea level during the Cenomanian and Early Turonian resulted in deposition of ammonite-rich wackestones and organic-rich marls, during high sea-level stands (maximum flooding surfaces). Progradational sabkha/salina facies passing landwards to fluvial siliciclastics were deposited during an Early Turonian sea-level low stand, marks a regional sequence boundary, above which a highstand carbonate platform was established. A second-order, regional rise in sea level and marine transgression during the Early Coniacian marks a Type 2 sequence boundary, and subsequent drowning of the rimmed carbonate shelf by Late Coniacian times. Sedimentation during the Santonian to Maastrichtian was characterised by a hemi-pelagic chalk-chert-phosphorite lithofacies association, deposited in shallow to moderate water depths on a homoclinal ramp setting, although thicker coeval sequences were deposited in extensional rifts. The marked change in sedimentation from rimmed carbonate shelf to pelagic ramp is attributed to Neo-Tethyan mid-oceanic rifting, tilting, intracratonic deforma
{"title":"Evolution of Cretaceous to Eocene alluvial and carbonate platform sequences in central and south Jordan","authors":"J. Powell, B. Moh’d","doi":"10.2113/geoarabia160429","DOIUrl":"https://doi.org/10.2113/geoarabia160429","url":null,"abstract":"\u0000 The Cretaceous to Eocene succession in central and south Jordan is characterised by passive continental margin depositional sequences, which pass upward from alluvial/paralic to carbonate shelf and pelagic ramp settings. Detailed section logging and outcrop mapping have produced robust lithostratigraphic and lithofacies schemes that can be correlated throughout the region and in the subsurface. These schemes are set in a sequence-stratigraphic context in relation to the evolution sedimentation on the Arabian and Levant plates. Three major megasequences are described (Kurnub, Ajlun and Belqa), and these are further subdivided into large-scale depositional sequences separated by regional sequence boundaries that represent maximum flooding surfaces. There is close correspondence between maximum flooding surfaces recording major sea-level rise with those derived for the Arabian and Levant plates, although there are some discrepancies with the precise timing of global sea-level fluctuations.\u0000 An upward change from braided to meandering stream fluvial environments in central and south Jordan during the Early Cretaceous, reflects a decreasing geomorphological gradient of the alluvial plain, declining siliciclastic sediment flux, and increased floodplain accommodation, associated with a regional Late Albian (second-order) rise in relative sea-level. The Late Albian to Early Cenomanian marine transgression across the coastal alluvial plain marks a major sequence boundary. During Cenomanian to Turonian times a rimmed carbonate-shelf was established, characterised by skeletal carbonates showing small-scale, upward-shallowing cycles (fourth- to fifth-order parasequences) ranging from subtidal to intertidal facies, arranged into parasequence sets. Rimmed carbonate shelf sequences pass laterally to coeval coastal/alluvial plain facies to the south and east. Eustatic (third-order) fluctuations in relative sea level during the Cenomanian and Early Turonian resulted in deposition of ammonite-rich wackestones and organic-rich marls, during high sea-level stands (maximum flooding surfaces). Progradational sabkha/salina facies passing landwards to fluvial siliciclastics were deposited during an Early Turonian sea-level low stand, marks a regional sequence boundary, above which a highstand carbonate platform was established.\u0000 A second-order, regional rise in sea level and marine transgression during the Early Coniacian marks a Type 2 sequence boundary, and subsequent drowning of the rimmed carbonate shelf by Late Coniacian times. Sedimentation during the Santonian to Maastrichtian was characterised by a hemi-pelagic chalk-chert-phosphorite lithofacies association, deposited in shallow to moderate water depths on a homoclinal ramp setting, although thicker coeval sequences were deposited in extensional rifts. The marked change in sedimentation from rimmed carbonate shelf to pelagic ramp is attributed to Neo-Tethyan mid-oceanic rifting, tilting, intracratonic deforma","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68184522","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-10-01DOI: 10.2113/geoarabia1604127
R. Fortey, A. Heward, C. Miller
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.
{"title":"Sedimentary facies and trilobite and conodont faunas of the Ordovician Rann Formation, Ras Al Khaimah, United Arab Emirates","authors":"R. Fortey, A. Heward, C. Miller","doi":"10.2113/geoarabia1604127","DOIUrl":"https://doi.org/10.2113/geoarabia1604127","url":null,"abstract":"\u0000 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.\u0000 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.\u0000 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.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68184241","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
New and rare Jurassic ammonites have been found in Oman. A latest Bajocian Arabian Platform-type species was discovered in the Haushi-Huqf Massif autochthon of southwestern Oman, and Bajocian species typical of the Mediterranean Tethys and northwestern Europe were found in the Kawr-Misfah exotic unit of the Hawasina Nappes in the Oman Mountains. The dates provided by the new fauna have resulted in a reinterpretation of the geologic history of the containing rocks, and of their paleoecology and paleobiogeography. It is significant that ammonites from shallow-marine environments of the Arabian Platform are in close proximity to species from open-sea environments of the Mediterranean Tethys and northwestern Europe. This shows that endemism of the Arabian Province resulted from ecological isolation, whereas open-marine environments on the Oman margin, especially the pelagic seamounts off the margin, form part of a migration route between western and eastern Tethys (or Indo-Southwest Pacific), and perhaps far beyond. The occurrences among the Tethyan and pandemic components of ammonite faunas in the Canadian Pacific Cordillera of most of the taxa of the open-marine environments on the Oman margin reopens the question of Pacific biogeography during the Early Jurassic before the Hispanic oceanic corridor was completely open. Among the proposed models, the Pantropic Distribution Model of Newton is examined in the light of the Cretaceous paleobiogeography, with particular reference to rudists.
{"title":"Toarcian and Bajocian ammonites from the Haushi-Huqf Massif of southwestern Oman and the Hawasina Nappes of the Oman Mountains: Implications for paleoecology and paleobiogeography","authors":"R. Énay","doi":"10.2113/geoarabia160487","DOIUrl":"https://doi.org/10.2113/geoarabia160487","url":null,"abstract":"\u0000 New and rare Jurassic ammonites have been found in Oman. A latest Bajocian Arabian Platform-type species was discovered in the Haushi-Huqf Massif autochthon of southwestern Oman, and Bajocian species typical of the Mediterranean Tethys and northwestern Europe were found in the Kawr-Misfah exotic unit of the Hawasina Nappes in the Oman Mountains.\u0000 The dates provided by the new fauna have resulted in a reinterpretation of the geologic history of the containing rocks, and of their paleoecology and paleobiogeography. It is significant that ammonites from shallow-marine environments of the Arabian Platform are in close proximity to species from open-sea environments of the Mediterranean Tethys and northwestern Europe. This shows that endemism of the Arabian Province resulted from ecological isolation, whereas open-marine environments on the Oman margin, especially the pelagic seamounts off the margin, form part of a migration route between western and eastern Tethys (or Indo-Southwest Pacific), and perhaps far beyond. The occurrences among the Tethyan and pandemic components of ammonite faunas in the Canadian Pacific Cordillera of most of the taxa of the open-marine environments on the Oman margin reopens the question of Pacific biogeography during the Early Jurassic before the Hispanic oceanic corridor was completely open. Among the proposed models, the Pantropic Distribution Model of Newton is examined in the light of the Cretaceous paleobiogeography, with particular reference to rudists.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68184624","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2011-07-01DOI: 10.2113/geoarabia1603129
M. Bahrammanesh, L. Angiolini, A. Antonelli, B. Aghababalou, M. Gaetani
Following detailed stratigraphic work on the Mississippian marlstone and bioclastic limestone of the Mobarak Formation of the Alborz Mountains in North Iran, forty-eight of the most important brachiopod taxa are here systematically described and illustrated. The ranges of the taxa are given along the Abrendan and Simeh Kuh stratigraphic sections, located north of Damgham. The examined brachiopod species date the base of the Mobarak Formation to the Tournaisian, in absence of age-diagnostic foraminifers. Change in brachiopod settling preferences indicates a shift from high energy, shallow-water settings with high nutrient supply in the lower part of the formation to quieter, soft, but not soppy substrates, with lower nutrient supply in the middle part of the Mobarak Formation. Brachiopod occurrence is instead scanty at its top. The palaeobiogeographic affinity of the Tournaisian brachiopods from North Iran indicates a closer relationship to North America, Western Europe and the Russian Platform than to cold-water Australian faunas, confirming the affinity of the other biota of the Alborz Mountains. This can be explained by the occurrence of warm surface-current gyres widely distributing brachiopod larvae across the Palaeotethys Ocean, where North Iran as other peri-Gondwanan blocks acted as staging-posts.
{"title":"Tournaisian (Mississippian) brachiopods from the Mobarak Formation, North Iran","authors":"M. Bahrammanesh, L. Angiolini, A. Antonelli, B. Aghababalou, M. Gaetani","doi":"10.2113/geoarabia1603129","DOIUrl":"https://doi.org/10.2113/geoarabia1603129","url":null,"abstract":"\u0000 Following detailed stratigraphic work on the Mississippian marlstone and bioclastic limestone of the Mobarak Formation of the Alborz Mountains in North Iran, forty-eight of the most important brachiopod taxa are here systematically described and illustrated. The ranges of the taxa are given along the Abrendan and Simeh Kuh stratigraphic sections, located north of Damgham. The examined brachiopod species date the base of the Mobarak Formation to the Tournaisian, in absence of age-diagnostic foraminifers. Change in brachiopod settling preferences indicates a shift from high energy, shallow-water settings with high nutrient supply in the lower part of the formation to quieter, soft, but not soppy substrates, with lower nutrient supply in the middle part of the Mobarak Formation. Brachiopod occurrence is instead scanty at its top. The palaeobiogeographic affinity of the Tournaisian brachiopods from North Iran indicates a closer relationship to North America, Western Europe and the Russian Platform than to cold-water Australian faunas, confirming the affinity of the other biota of the Alborz Mountains. This can be explained by the occurrence of warm surface-current gyres widely distributing brachiopod larvae across the Palaeotethys Ocean, where North Iran as other peri-Gondwanan blocks acted as staging-posts.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68184103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The architecture of a new alveolinacean, Decastroia razini, from the Cenomanian shallow-water sediments of Socotra Island is described. The shape of the new genus is globular to slightly elongated. The internal structure is characterised by septula and floors that individualise two rows of superposed tubular chamberlets, an upper row of large, cortical chamberlets and a lower row of small, medullar ones. The chamberlets of the same chamber are communicated by preseptal passage.
{"title":"Decastroia razini n. gen. n. sp. – A new alveolinacean (foraminifera) from the Cenomanian of Socotra Island (Yemen)","authors":"V. Vicedo, J. Serra-Kiel","doi":"10.2113/geoarabia160317","DOIUrl":"https://doi.org/10.2113/geoarabia160317","url":null,"abstract":"\u0000 The architecture of a new alveolinacean, Decastroia razini, from the Cenomanian shallow-water sediments of Socotra Island is described. The shape of the new genus is globular to slightly elongated. The internal structure is characterised by septula and floors that individualise two rows of superposed tubular chamberlets, an upper row of large, cortical chamberlets and a lower row of small, medullar ones. The chamberlets of the same chamber are communicated by preseptal passage.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"43 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68184184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Improved methods of analysis and quantification of heavy mineral assemblages in Cambrian to Early Cretaceous sandstones of southwest Sinai have revealed successive changes in provenance that reflect both rejuvenation of the Arabian Shield and changes in the topographic configuration of the source area. Three mineral units have been identified in the Cambrian succession, at least three in the Carboniferous and three in the Cretaceous. It is predicted that the genetic units defined by these successive changes in mineralogy will be of regional extent and thus assist in elucidating the history of uplift of the Arabian-Nubian Shield and provide a better means of correlating sandstone units into adjacent areas. Variation in the abundance of apatite in the Cambrian succession is independent of provenance signature and is interpreted as reflecting alternating dry and humid climatic conditions.
{"title":"Heavy mineral stratigraphy of Palaeozoic and Mesozoic sandstones of southwestern Sinai, Egypt: A reassessment","authors":"R. Knox, M. Soliman, M. Essa","doi":"10.2113/geoarabia160331","DOIUrl":"https://doi.org/10.2113/geoarabia160331","url":null,"abstract":"\u0000 Improved methods of analysis and quantification of heavy mineral assemblages in Cambrian to Early Cretaceous sandstones of southwest Sinai have revealed successive changes in provenance that reflect both rejuvenation of the Arabian Shield and changes in the topographic configuration of the source area. Three mineral units have been identified in the Cambrian succession, at least three in the Carboniferous and three in the Cretaceous. It is predicted that the genetic units defined by these successive changes in mineralogy will be of regional extent and thus assist in elucidating the history of uplift of the Arabian-Nubian Shield and provide a better means of correlating sandstone units into adjacent areas. Variation in the abundance of apatite in the Cambrian succession is independent of provenance signature and is interpreted as reflecting alternating dry and humid climatic conditions.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68184220","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper is one of a series that document the Neoproterozoic – Cambrian rock units in the Middle East Geologic Time Scale. It is focused on the oldest sedimentary succession in Saudi Arabia, the late Ediacaran – early Cambrian (Infracambrian) Jibalah Group (ca. 585 to 530–520 Ma). The group crops out in disconnected, pull-apart basins (ca. 10–100 km long and up to 20 km wide) along the NW-trending, strike-slip Najd Fault System in the Arabian Shield. It was described and mapped in the 1960s to 1980s, and several formations were defined and named in two areas separated by ca. 400 km. The stratigraphic successions in these two areas have not been correlated, nor has their relationship to the subsurface been resolved. This paper reviews the nomenclature, type sections, lithologies and ages of the formations and members (sometimes units and/or facies) of the Jibalah Group. The Jibalah Group unconformably overlies the Ediacaran Shammar Group (ca. 620–585 Ma, consisting mainly of rhyolite or granitic plutons), or older Proterozoic rocks. The age of the intervening Sub-Jibalah Unconformity is here estimated at ca. 585 Ma based on radiometric data and regional correlations. The lower part of the Jibalah Group is defined in the northern Arabian Shield in the Mashhad area, where it consists of three formations, in ascending order: (1) undated Rubtayn Formation, divided informally into the “Volcanic Conglomerate Member” (up to ca. 700 m thick), “Polymictic Conglomerate Member” (up to ca. 1,500 m thick) and “Sandstone Member” (up to ca. 1,000 m thick); (2) poorly dated Badayi Formation consisting of andesite-basalt flows (ca. 150 m thick); (3) undated Muraykhah Formation (330–370 m thick) consisting of the informal “Cherty Limestone Member” (ca. 135 m thick), “Siltstone and Mudstone Member” (ca. 20 m thick) and “Dolomitic Limestone Member” (ca. 135–175 m thick). The Rubtayn, Badayi and Muraykhah formations in the northern Arabian Shield, by stratigraphic position and lithology, correspond to the Umm Al ‘Aisah Formation in the Najd pull-apart basins of the central Arabian Shield. In particular, the Cherty Limestone unit (300–500 m thick) of the Umm Al ‘Aisah Formation is correlated to the Muraykhah Formation, which represents a marine flooding event. Above the Muraykhah Formation, the uppermost part of the group is defined in the central Arabian Shield by the undated Jifn Formation (up to ca. 2,500 m thick). The Jibalah Group is unconformably overlain by the lower Cambrian Siq Sandstone Formation (Asfar Sequence), and the intervening Sub-Siq Unconformity (Angudan Unconformity) has an estimated age between ca. 530–520 Ma.
{"title":"Late Ediacaran to early Cambrian (Infracambrian) Jibalah Group of Saudi Arabia","authors":"M. Al-Husseini","doi":"10.2113/geoarabia160369","DOIUrl":"https://doi.org/10.2113/geoarabia160369","url":null,"abstract":"\u0000 This paper is one of a series that document the Neoproterozoic – Cambrian rock units in the Middle East Geologic Time Scale. It is focused on the oldest sedimentary succession in Saudi Arabia, the late Ediacaran – early Cambrian (Infracambrian) Jibalah Group (ca. 585 to 530–520 Ma). The group crops out in disconnected, pull-apart basins (ca. 10–100 km long and up to 20 km wide) along the NW-trending, strike-slip Najd Fault System in the Arabian Shield. It was described and mapped in the 1960s to 1980s, and several formations were defined and named in two areas separated by ca. 400 km. The stratigraphic successions in these two areas have not been correlated, nor has their relationship to the subsurface been resolved. This paper reviews the nomenclature, type sections, lithologies and ages of the formations and members (sometimes units and/or facies) of the Jibalah Group.\u0000 The Jibalah Group unconformably overlies the Ediacaran Shammar Group (ca. 620–585 Ma, consisting mainly of rhyolite or granitic plutons), or older Proterozoic rocks. The age of the intervening Sub-Jibalah Unconformity is here estimated at ca. 585 Ma based on radiometric data and regional correlations. The lower part of the Jibalah Group is defined in the northern Arabian Shield in the Mashhad area, where it consists of three formations, in ascending order: (1) undated Rubtayn Formation, divided informally into the “Volcanic Conglomerate Member” (up to ca. 700 m thick), “Polymictic Conglomerate Member” (up to ca. 1,500 m thick) and “Sandstone Member” (up to ca. 1,000 m thick); (2) poorly dated Badayi Formation consisting of andesite-basalt flows (ca. 150 m thick); (3) undated Muraykhah Formation (330–370 m thick) consisting of the informal “Cherty Limestone Member” (ca. 135 m thick), “Siltstone and Mudstone Member” (ca. 20 m thick) and “Dolomitic Limestone Member” (ca. 135–175 m thick).\u0000 The Rubtayn, Badayi and Muraykhah formations in the northern Arabian Shield, by stratigraphic position and lithology, correspond to the Umm Al ‘Aisah Formation in the Najd pull-apart basins of the central Arabian Shield. In particular, the Cherty Limestone unit (300–500 m thick) of the Umm Al ‘Aisah Formation is correlated to the Muraykhah Formation, which represents a marine flooding event. Above the Muraykhah Formation, the uppermost part of the group is defined in the central Arabian Shield by the undated Jifn Formation (up to ca. 2,500 m thick). The Jibalah Group is unconformably overlain by the lower Cambrian Siq Sandstone Formation (Asfar Sequence), and the intervening Sub-Siq Unconformity (Angudan Unconformity) has an estimated age between ca. 530–520 Ma.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2011-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68183972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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