Geoarabia最新文献

{"title":"Repairing the Aged Parkinsonian Striatum: Lessons from the Lab and Clinic.","authors":"Natosha M Mercado, Timothy J Collier, Thomas Freeman, Kathy Steece-Collier","doi":"10.4172/2155-9899.1000476","DOIUrl":"10.4172/2155-9899.1000476","url":null,"abstract":"<p><p>The primary risk factor associated with Parkinson's disease (PD) is advanced age. While there are symptomatic therapies for PD, efficacy of these eventually wane and/or side-effects develop over time. An alternative experimental therapy that has received a great deal of attention over the past several decades has been neural transplantation aimed at replacing nigral dopamine (DA) neurons that degenerate in PD. However, in PD patients and parkinsonian rats, advanced age is associated with inferior benefit following intrastriatal grafting of embryonic DA neurons. Traditionally it has been thought that decreased therapeutic benefit results from the decreased survival of grafted DA neurons and the accompanying poor reinnervation observed in the aged host. However, recent clinical and preclinical data suggest that factors inherent to the aged striatum <i>per se</i> limit successful brain repair. In this short communication, we focus discussion on the implications of our recent grafting study in aged parkinsonian rats, with additional emphasis on a recent clinical report of the outcome of cell therapy in an aged PD patient with long-term (24 years) survival of DA neuron grafts. To address aging as a limiting factor in successful brain repair, we use the example of cell transplantation as a means to interrogate the environment of the aged striatum and identify factors that may, or may not, respond to interventions aimed at improving the prospects for adequate repair of the aged brain. We offer discussion of how these recent reports, in the context of other historical grafting studies, might provide new insight into specific risk factors that have potential to negatively impact all DA cell or terminal replacement strategies for clinical use in PD.</p>","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2016-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5243125/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90107882","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Facies analysis and sequence stratigraphy of the uppermost Jurassic– Lower Cretaceous Sulaiy Formation in outcrops of central Saudi Arabia","authors":"P. Wolpert, M. Bartenbach, P. Suess, R. Rausch, T. Aigner, Y. L. Nindre","doi":"10.15496/PUBLIKATION-9089","DOIUrl":"https://doi.org/10.15496/PUBLIKATION-9089","url":null,"abstract":"\u0000 Uppermost Jurassic–Lower Cretaceous carbonates of the Sulaiy Formation are well exposed at the type locality Dahal Hit, and along the entire natural escarpment near Ar Riyad, the capital of the Kingdom of Saudi Arabia. This study provides a facies and sequence-stratigraphic analysis based on detailed sedimentological and gamma-ray logging of 12 outcrop sections. The sections represent the Sulaiy Formation along a 60 km-long outcrop belt, including the Hith-Sulaiy transition in a large solution cavity named Dahal Hit, situated south of Ar Riyad. The latter section is studied in detail because it is the only locality in Saudi Arabia where the Hith Anhyrite (Hith Formation in this study) to the Sulaiy Formation transition crops out.\u0000 Ten lithofacies types were identified for the Sulaiy Formation including potential reservoirs such as oolitic cross-bedded grainstones, biostromal boundstones, and bioclast-rich, graded pack-to-grainstones. Lithofacies types are grouped into five facies associations: (1) offshoal, (2) transition zone, foreshoal, (4) shoal margin, and (5) shoal, distributed along a carbonate ramp. Their vertical stacking pattern revealed a systematic hierarchy of cyclicity consisting of small-scale cycles, medium-scale cycle sets and two large-scale sequences for the Sulaiy Formation. Four cycle motifs, with an average thickness of 2–4 m, are present: (1) offshoal to transition zone cycle motif, (2) offshoal to foreshoal cycle motif, (3) transition zone to shoal margin cycle motif, and foreshoal to shoal margin cycle motif.\u0000 A total of 15 cycle sets, ranging between 8 and 12 m in thickness each, were interpreted. They were correlated, where possible, across the study area. Three types of medium-scale cycle sets are observed: (1) offshoal to shoal cycle set motif, (2) offshoal to foreshoal cycle set motif, and (3) shoal margin to offshoal cycle set motif. The Lower Sulaiy Sequence consists of twelve cycle sets and is interpreted to contain two Arabian Plate maximum flooding surfaces (MFS): (1) Upper Tithonian MFS J110 (147 Ma) in its lowermost part, which is interpreted to be the time-equivalent of the Manifa reservoir in subsurface Arabia. (2) Lower Berriasian MFS K10 (144 Ma) in the seventh-up cycle set. The Upper Sulaiy Sequence is only represented in the Wadi Nisah Section and is believed to be incomplete because the Sulaiy/Yamama Formation boundary was not included in our study. It is presumed to contain Upper Berriasian MFS K20 (141 Ma).","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"236 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2015-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67157630","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}

{"title":"History of hydrocarbon exploration in the Kurdistan Region of Iraq","authors":"D. Mackertich, A. Samarrai","doi":"10.2113/geoarabia2002181","DOIUrl":"https://doi.org/10.2113/geoarabia2002181","url":null,"abstract":"\u0000 The Kurdistan Region of Iraq has witnessed extraordinary levels of exploration activity since the first exploration well to be drilled in over two decades was spudded in 2005. Since then almost 200 wells have been drilled encountering recoverable reserves estimated to be in excess of 15 billion barrels of oil equivalent. Whilst the region is in close proximity to many of the giant and supergiant fields of Iran and Iraq, the reservoirs in which discoveries have been made are largely different. In Iraq a large percentage of discovered reserves reside in Cenozoic and Cretaceous sediments capped by Cenozoic evaporite sequences. Over much of Kurdistan, particularly the north and northeastern parts of the region, Cenozoic strata are absent.\u0000 A decade ago many were doubtful that significant quantities of hydrocarbons could be trapped in the absence of the Cenozoic evaporite sequences. Furthermore, whilst the presence of large surface structures and significant oil seeps were encouraging to some, to others it fueled concerns about trap leakage. Today the majority of the surface anticlinal features in Kurdistan have been drilled, but remain to be fully evaluated. Almost all of the exploration activity in Kurdistan has taken place on 2-D seismic with vertical exploration wells. In the last few years, a number of 3-D seismic surveys have been acquired and these will undoubtedly lead to production and reserve enhancements in parallel with increased subsurface complexity.\u0000 Following a decade of exploration, three fields have been fully appraised and have a reasonable early production history: Tawke, Taq Taq and Khurmala. Reserve additions in the Tawke Field have been significant as a result of increased production performance due to better than originally anticipated reservoir properties, better pressure communication and additional reserves found in older reservoirs. It is probable that similar trends will occur in other fields and discoveries.\u0000 Whilst a small number of horizontal wells have been drilled, advanced techniques used for producing from tight fractured carbonates such as multilateral wells, hydraulic fracturing, selective completions, proping and water injection have not as yet been used in the region. Almost all wells in Kurdistan have been drilled on surface or near subsurface structures within the foreland or the fold belt. Some wells have drilled through thrusts, more often by accident as opposed to on purpose. There have been virtually no dedicated wells for pure sub-thrust plays or stratigraphic traps although hydrocarbons have been found below significant thrusts and also beyond apparent structural closure in some structures.\u0000 Challenges remain in what is a structurally complex and recently deformed region. High levels of exploration and appraisal activity persist and new pipeline infrastructure is under construction. It is likely that the Kurdistan Region of Iraq will develop to become an important contributor to world oil and gas produ","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2015-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68187672","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}

{"title":"Cretaceous ammonites from the Sultanate of Oman (Adam Foothills)","authors":"C. Meister, A. Piuz","doi":"10.2113/geoarabia200219","DOIUrl":"https://doi.org/10.2113/geoarabia200219","url":null,"abstract":"\u0000 Twenty taxa are described from the Cretaceous of Oman (Adam Foothills). The genera Puzosia, Placenticeras, Cunningtoniceras, Nigericeras, Metoicoceras, Rubroceras and Hoplitoides and the subgenus C. (Gentoniceras) are recorded for the first time from the Arabian Peninsula. Based on the ammonite ranges, a sequence of nine bioevents of the Albian–Turonian is correlated within the zonation, and some markers allow correlations at a larger scale, at least along the southern Neo-Tethys margin. The ammonite data give new constraints for the correlations of the lithological units along the Adam Foothills West-East transect and they question the definition of the lithostratigraphic units within the Natih Formation, especially the Natih A and B members. From a paleogeographic point of view Oman is a landmark for the distribution of the ammonites between the western Neo-Tethys (Europe, North Africa, Middle East) and the eastern Neo-Tethys (Africa, Madagascar and India).","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2015-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68187829","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}

{"title":"Diagenesis of a light, tight-oil chert reservoir at the Ediacaran/Cambrian boundary, Sultanate of Oman","authors":"J. Amthor, K. Ramseyer, A. Matter, T. Pettke, A. Fallick","doi":"10.2113/geoarabia2002147","DOIUrl":"https://doi.org/10.2113/geoarabia2002147","url":null,"abstract":"\u0000 The Al Shomou Silicilyte Member (Athel Formation) in the South Oman Salt Basin shares many of the characteristics of a light, tight-oil (LTO) reservoir: it is a prolific source rock mature for light oil, it produces light oil from a very tight matrix and reservoir, and hydraulic fracking technology is required to produce the oil. What is intriguing about the Al Shomou Silicilyte, and different from other LTO reservoirs, is its position related to the Precambrian/Cambrian Boundary (PCB) and the fact that it is a ‘laminated chert’ rather than a shale. In an integrated diagenetic study we applied microstructural analyses (SEM, BSE) combined with state-of-the-art stable isotope and trace element analysis of the silicilyte matrix and fractures. Fluid inclusion microthermometry was applied to record the salinity and minimum trapping temperatures. The microstructural investigations reveal a fine lamination of the silicilyte matrix with a mean lamina thickness of ca. 20 μm consisting of predominantly organic matter-rich and finely crystalline quartz-rich layers, respectively. Authigenic, micron-sized idiomorphic quartz crystals are the main matrix components of the silicilyte. Other diagenetic phases are pyrite, apatite, dolomite, magnesite and barite cements.\u0000 Porosity values based on neutron density logs and core plug data indicate porosity in the silicilyte ranges from less than 2% to almost to 40%. The majority of the pore space in the silicilyte is related to (primary) inter-crystalline pores, with locally important oversized secondary pores. Pore casts of the silica matrix show that pores are extremely irregular in three dimensions, and are generally interconnected by a complex web or meshwork of fine elongate pore throats. Mercury injection capillary data are in line with the microstructural observations suggesting two populations of pore throats, with an effective average modal diameter of 0.4 μm. The acquired geochemical data support the interpretation that the primary source of the silica is the ambient seawater rather than hydrothermal or biogenic. A maximum temperature of ca. 45°C for the formation of microcrystalline quartz in the silicilyte is good evidence that the lithification and crystallization of quartz occurred in the first 5 Ma after deposition.\u0000 Several phases of brittle fracturing and mineralization occurred in response to salt tectonics during burial. The sequences of fracture-filling mineral phases (dolomite - layered chalcedony – quartz – apatite - magnesite I+II - barite – halite) indicates a complex fluid evolution after silicilyte lithification. Primary, all-liquid fluid inclusions in the fracture-filling quartz are good evidence of growth beginning at low temperatures, i.e. ≤ 50ºC. Continuous precipitation during increasing temperature and burial is documented by primary two-phase fluid inclusions in quartz cements that show brines at 50°C and first hydrocarbons at ca. 70°C. The absolute timing of each mineral phase can b","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2015-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68187650","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}

{"title":"Multi-level stratigraphic heterogeneities in a Triassic shoal grainstone, Oman Mountains, Sultanate of Oman: Layer-cake or shingles?","authors":"M. Obermaier, N. Ritzmann, T. Aigner","doi":"10.2113/geoarabia2002115","DOIUrl":"https://doi.org/10.2113/geoarabia2002115","url":null,"abstract":"\u0000 A fundamental question in the correlation of 1-D sedimentologic data is whether to use a layer-cake or shingled correlation approach. The resulting reservoir geometry has important implications for the characterization of reservoir heterogeneities and fluid flow. On the Saiq Plateau in Oman, epeiric carbonate ramp deposits of the Triassic Sudair Formation are well exposed and can be investigated in detail over several kilometers. There, reservoir heterogeneities on different scales have been documented by creating various outcrop wall panels and 2-D correlations. Multi-level architectural elements with different depositional geometries were discovered, which were linked to a sequence-stratigraphic hierarchy consisting of three levels. Level 1: A “layer-cake”-type stratigraphic architecture with minor thickness variations over several kilometers becomes apparent when correlating fourth-order cycle set boundaries. Level 2: The correlation of fifth-order cycle boundaries reflects horizontally continuous geometries, within which, however, internal grainstone layers were discovered to be arranged in a shingled fashion. Muddy layers in between these shingles illustrate sixth-order mini-cycle boundaries. Level 3: Within sixth-order mini-cycles another scale of a shingle-like architecture can be observed. Amalgamated cm-thick grainstone units form thin wedges with subtle but clearly inclined dipping geometry.\u0000 Fourth-order cycle sets and fifth-order cycles can be traced over several kilometers, and therefore assumed to be related to allocyclic stratigraphic processes. The internal shingle geometries within fifth-order cycles are traceable over 100s of meters and presumably reflect an autocyclic lateral migration of a shoal complex. Cm-thick shingling grainstone wedges within sixth-order mini-cycles are interpreted as storm-related spill deposits. Their event-driven character is reflected by frequent amalgamation and reworking of the preceding deposits.\u0000 The results of this study of epeiric carbonate ramp deposits suggest that a “layer-cake” correlation approach is appropriate when correlating 10s of m-thick grainstone units over a distance of several kilometers. However in the documented example, these thick grainstone units consist internally of small-scale architectural elements, which show inclined geometries and require a shingled correlation approach. These small-scale heterogeneities within an overall “layer-cake” architecture might have an impact on fluid flow in similar subsurface reservoirs and should be taken into account for detailed reservoir correlations and static reservoir models.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2015-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68187587","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}

{"title":"Depositional environment of Late Cretaceous to Eocene organic-rich marls from Jordan","authors":"M. Hussein, Mohammad Alqudah, Myrna Blessenohl, O. Podlaha, J. Mutterlose","doi":"10.2113/geoarabia2001191","DOIUrl":"https://doi.org/10.2113/geoarabia2001191","url":null,"abstract":"\u0000 Oil-shale beds formed under anoxic conditions that were controlled by various local, regional and global factors. The Jordanian oil shales, which were deposited during the Late Cretaceous to Eocene, are considered as an example for the interplay of these factors. Two cores of organic-rich marls were investigated and analyzed with respect to their lithology, ichnofabrics and carbonate microfacies. The first core (OS-01, 183.3 m; South Jordan) is of Late Cretaceous age, the second one (OS-23, 256.3 m; Central Jordan) is of Eocene age. Our studies revealed that the Upper Cretaceous oil shales were deposited in a shallow-water carbonate shelf. Oyster bioherms acted as physical barriers that reduced the water circulation with the open shelf, thereby causing anoxic conditions. The Eocene oil shales also accumulated on a shallow-water carbonate shelf. In this case, however, synsedimentary tectonics caused subsiding grabens and half grabens, which in turn gave way to anoxic conditions. Both deposition and richness of the Jordanian oil shales were affected by regional sea-level fluctuations and global climatic changes.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68186920","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}

{"title":"Lithofacies, depositional environments and stratigraphic architecture of the Wajid Group outcrops in southern Saudi Arabia","authors":"H. Al-Ajmi, M. Keller, M. Hinderer, C. Filomena","doi":"10.2113/geoarabia200149","DOIUrl":"https://doi.org/10.2113/geoarabia200149","url":null,"abstract":"\u0000 The Wajid Group is a Palaeozoic siliciclastic succession of southern Saudi Arabia. In the outcrop belt it is ca. 500 m thick, whereas in the subsurface, the thickness increases to more than 4,500 m. The siliciclastic sediments have great reservoir potential for hydrocarbons and for groundwater. Although they represent one of the most important aquifers of the Arabian Peninsula, neither their sedimentologic, lithostratigraphic, nor their reservoir characteristics are satisfactorily known. In this study, a detailed description of lithology and sedimentology is given and the Wajid Group sediments are interpreted in terms of depositional environment and facies architecture. Thirteen lithofacies (LF 1 to LF 13) have been recognised, most of them composed of different subfacies. These lithofacies are grouped into 9 lithofacies associations (LF-A1 through LF-A9). LF-A1 through LF-A3 and LF-A7 represent shallow-marine siliciclastic environments. The remaining lithofacies associations describe periglacial environments of the Hirnantian (Late Ordovician) and Permian Gondwana glaciations. Except for a few pro-glacial fluvial deposits, fluvial successions and aeolian sediments are absent in the outcrops of the Wajid Sandstone.\u0000 Five formations are recognised in the Wajid Group: the Dibsiyah, Sanamah, Qalibah, Khusayyayn, and Juwayl formations. They are all separated by major unconformities. The Dibsiyah Formation represents a vast sand-sheet complex with core and margin facies formed under shallow-marine conditions. These marine conditions enabled an abundant fauna to proliferate and leave its traces in the form of Skolithos piperock and Cruziana sp. A late Cambrian to Early Ordovician age is inferred for these deposits from regional considerations. The Sanamah Formation records the Late Ordovician Hirnantian glaciation with coarse sandstones and conglomerates. A variety of glacier-induced sedimentary structures are present. The internal succession is composed of three major sediment packages reflecting three ice advance-retreat cycles. The latest of these cycles is overlain by a few metres of marginal-marine sediments of the Qalibah Formation. The Khusayyayn Formation was deposited probably during Early Devonian times. It also represents a sand-sheet environment characterised by the dominance of mega-scale and giant cross beds and bed sets. A marine depositional environment is assumed from scarce Skolithos sp., and because nearly all indicators of a braided river system are absent. The Juwayl Formation of Permian age was deposited at the interface of the Late Palaeozoic Gondwana ice shield with a large lake that may have covered most of southern Arabia and adjacent areas. Proglacial sandstones and conglomerates were deposited close to the glaciers, whereas fine-grained sediment with dropstones, boulder pavements and a wide spectrum of soft-sediment deformation are characteristic of the lake environment. While the two glacial successions and the Khusayyayn","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68187182","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}

{"title":"Ediacaran Araba Complex of Jordan","authors":"J. Powell, A. Abed, G. Jarrar","doi":"10.2113/geoarabia200199","DOIUrl":"https://doi.org/10.2113/geoarabia200199","url":null,"abstract":"\u0000 The Ediacaran Araba Complex in Jordan is defined and described for the first time in lexicon style, with an emphasis on the sedimentary, volcanic and volcaniclastic units outcropping adjacent to Wadi Araba, and from seismic and deep exploration well data. The Araba Complex ranges in age from ca. 605 to 550 Ma and comprises a major cycle of sedimentary, volcanic and volcaniclastic, and igneous rocks emplaced in an overall extensional tectonic regime that followed intrusion and amalgamation of the granitoid and metamorphic Aqaba Complex, a part of the Gondwanan Arabian-Nubian Shield (ANS; ca. 900 to 610 Ma).\u0000 The Araba Complex is bounded by two major erosional unconformities, the newly defined Ediacaran Araba Unconformity (ca. 605 Ma) at its base, underlain by the Aqaba Complex, and the post-extensional, regional lower Cambrian Ram Unconformity (ca. 530 Ma) that is marked by the widespread deposition of thick alluvial and marginal-marine siliciclastics (Ram Group).\u0000 Two sub-cycles can be recognised in the Araba Complex mega-cycle. The earliest (Safi Group) followed suturing and extensional rifting of the Aqaba Complex that resulted in rapid basinal subsidence and the deposition of coarse-grained, polymict conglomerates (Saramuj Formation) in predominantly proximal, but evolving to more distal, alluvial fan settings. The early extensional basin appears to have been orientated approximately north-south (depocentre to the west) and can be traced from north Sinai to Lebanon, approximately parallel to the present-day Dead Sea Transform. Rounded clasts, up to boulder-size, include a variety of local to regionally-derived basement lithologies, including granites, diorites, metamorphic rocks; doleritic and rhyolitic dyke rocks. Rapid isostatic uplift and weathering of the granitoid basement resulted in high sediment flux that kept pace with rapid basin subsidence; this, in turn, led to erosion and partial peneplanation of the hinterland ANS. Regional detrital zircon ages from the conglomerate clasts and matrix indicate age ranges from ca. 650 to 600 Ma with a minor cluster between 750 to 700 Ma, indicating mostly a local or, at least, near-field provenance. Subsequent to this early, rapid basin-fill, continued crustal extension resulted in tapping of rhyolitic and basaltic effusive volcanics and volcaniclastics (Haiyala Volcaniclastics and Museimir Effusives, ca. 598–595 Ma), including flow-banded rhyolitic lavas and air-fall tuffs, the latter deposited in a lacustrine or shallow-water environments.\u0000 The second Araba sub-cycle (595–586 Ma) is characterised by renewed basinal subsidence, very low burial metamorphism to about 6 km depth, and associated stock-like intrusion of the Qunaia Monzogabbro (595 ± 2 Ma) that resulted in thermal contact metamorphism of the Saramuj conglomerate, as well as granite plutons (e.g. Feinan-Humrat intrusions) and dolerite dykes. The second cycle is characterised by renewed extension, rifting and the deposition of volcanic ","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68187048","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}

{"title":"Spatio-temporal position of the Ediacaran Thalbah Basin in the Najd Fault System, Arabian Shield","authors":"Richard Al-Husseini","doi":"10.2113/geoarabia200117","DOIUrl":"https://doi.org/10.2113/geoarabia200117","url":null,"abstract":"\u0000 This paper starts with a bibliographic review of the lithostratigraphy and radiometric dating of the Ediacaran Thalbah Group in the northwestern Arabian Shield, Saudi Arabia. It seeks to establish the spatio-temporal position of the group in the ongoing compilation and correlation of Ediacaran–Cambrian sedimentary time-rock units in the Middle East Geologic Time Scale (Al-Husseini, 2010, 2011, 2014). The group is defined and described in the Thalbah Basin, which crops out in the Al Wajh Quadrangle, and is approximately 100 km (NW-SE) by 40 km (SW-NE) in extent (Davies, 1985). The basin is situated within the approximately (ca.) 300 km-long, NW-trending Qazaz Fault Zone of the Najd Fault System.\u0000 The Thalbah Group consists of three siliciclastic units: Hashim Formation (ca. 1,050–1,300 m thick) and likely coeval Zhufar Formation (ca. 600–1,400 m thick), and the younger Ridam Formation (ca. 1,000 m thick). Recently published U-Pb dating of detrital zircons gave ages of ≤ 596 ± 10 Ma for the Hashim Formation, and ≤ 612 ± 7 Ma for the Zhufar Formation (Bezenjani et al., 2014). The maximum depositional ages of the Hashim and Zhufar formations indicate they are approximately coeval to the lower part of the sedimentary and volcanic rocks of the Jibalah Group (≤ 605 ± 5 and ≥ 525 ± 5 Ma). The latter group was deposited in pull-apart basins along the ca. 600 km-long Rika and several other extensive fault zones of the NW-trending Najd Fault System in the northern and eastern parts of the Arabian Shield.\u0000 The Qazaz Fault Zone left-laterally dislocated ophiolites of the NE-trending Yanbu Suture Zone (≥ 700 Ma) by about 100 km. The strike of the Qazaz Fault Zone projects into the Rika Fault Zone, along which five major pull-apart basins contain the Jibalah Group. The Rika Fault Zone dislocated by about 100 km the NS-trending ophiolite outcrop belts of the Ad Dafinah and Hulayfah fault zones (sometimes interpreted as parts the Nabitah Suture Zone, 680–640 Ma). Based on the time correlation of the Thalbah and Jibalah groups, and the highlighted structural features, the Rika and Qazaz fault zones are interpreted as a continuous 30 km-wide, 1,200 km-long, N63°W-striking fault zone, the “Rika-Qazaz Fault Zone”, which left-laterally dislocated the Arabian Shield by approximately 100 km after 605 ± 5 Ma and before 525 ± 5 Ma.","PeriodicalId":55118,"journal":{"name":"Geoarabia","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68186903","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}