bluuebunny/crossref_metadata_2025_split huggingface dataset:
Guadalupian (Permian) brachiopods from the Ruteh Limestone, North Iran
Authors: Crippa Gaia , Angiolini Lucia 
Published: October 2021

ABSTRACTThirty-three brachiopod species from the Guadalupian Ruteh Limestone of North Iran are here systematically described and illustrated. Brachiopods have been collected bed-by-bed along five stratigraphic sections and in one fossiliferous locality in the region between Dorud and Shirinibad in the Alborz Mountains. Four new species and one new genus are erected in the present paper: Haydenella eminens n. sp. Perigeyerella rutehiana n. sp., Martinia bassa n. sp. and Bisolcatelasma iraniana n. gen. n. sp.Quantitative biostratigraphic analysis of the brachiopod data based on the Unitary Association method (Guex, 1991) has lead to the construction of a local sequence of three discrete biozones: the Squamularia sp. B-M. bassa Biozone at the base of the formation, the H. kiangsiensis-N. (N.) asseretoi Biozone in its middle part and the R. exile-R. gemmellaroi Biozone at its top. The latter however has been recognized only in the Shirinabad section.As already envisaged for the Carboniferous and Lower Permian brachiopod faunas from North Iran, the Guadalupian fauna is comprised mostly of cosmopolitan taxa, confirming the role of the Iranian microplate as a staging-post for most of the late Palaeozoic. When compared to the younger Lopingian faunas collected in the same regions of North Iran, the Ruteh brachiopods appear significantly different, indicating a marked biotic change in the brachiopod communities across the end-Guadalupian biotic crisis.
Late Oligocene–Early Miocene Nukhul Sequence, Gulf of Suez and Red Sea
Authors: Al-Husseini Moujahed I. 
Published: October 2021

ABSTRACT
Egypt’s Late Oligocene–Early Miocene Nukhul Formation was deposited during the earliest geological evolution of the Gulf of Suez and Red Sea Rift System. In this paper the formation is cast as a depositional sequence based on published sections, and correlated across the Gulf of Suez and northern Red Sea. The resulting correlations indicate that deposition was initiated in local grabens by the oldest continental clastics of the lower member of the Nukhul Formation, the Shoab Ali Member. The member overlies the Suez Rift Unconformity, a term proposed for the entire Red Sea. Although this member can attain a thickness of ca. 1,000 ft (305 m) locally in grabens, it is generally absent over horsts. Sedimentary facies of the member are interpreted as indicating an initial alluvial-fluvial setting that evolved to an estuarine and coastal setting.
The upper part of the Nukhul Formation records a regional shallow-marine transgression, which can be subdivided into three correlative Upper Nukhul members. These sediments are absent over the highest paleo-horsts, but reach up to 900 ft (275 m) in thickness in grabens. In the southern Gulf of Suez the Ghara Member represents the Upper Nukhul members. In places it consists of four cycles, each of which starts with an anhydrite bed and is overlain by deposits of mixed lithology (sandstone, marl, and limestone). The four cycles are interpreted as transgressive-regressive subsequences that can be correlated across ca. 60 km in the Gulf of Suez. The Ghara Member correlates to Saudi Arabia’s Yanbu Formation, which consists of massive salt in wells drilled on the Red Sea coastal plains. The Yanbu Salt is dated by strontium-isotope analysis at ca. 23.1–21.6 Ma (earliest Aquitanian).
The Nukhul Formation is capped by the Sub-Rudeis Unconformity or correlative Rudeis Sequence Boundary, and overlain by the Rudeis Formation. The Nukhul Formation is here proposed as the Nukhul Sequence and defined in the Wadi Dib-1 Well, wherein it consists of Nukhul subsequences 1 to 10 (in descending order, ranging in thickness between 33–84 m). The lower six Nukhul subsequences 10 to 5 are characterized by shale-to-sandstone cycles of the Shoab Ali Member, and the upper four are represented by the cycles of the Ghara Member. The 10 subsequences are interpreted as tracking the 405,000 year eccentricity signal of the Earth’s orbit and to span ca. 4.0 million years between ca. 25.0 and 21.0 Ma.
Geochemistry, and carbon, oxygen and strontium isotope composition of brachiopods from the Khuff Formation of Oman and Saudi Arabia
Authors: Stephenson Michael H. , Angiolini Lucia , Leng Melanie J. , Darbyshire D.P. Fiona 
Published: October 2021

ABSTRACT
Brachiopods are abundant in the Oman Khuff Formation and similar brachiopod faunas are present at a few horizons in the same formation in Central Saudi Arabia. Following extensive systematic and biostratigraphic studies of these faunas, specimens from the base of the Midhnab Member of the Khuff Formation of Saudi Arabia (Buraydah Quadrangle), and from Member 3 of the Khuff Formation of the Huqf outcrop of Oman were assessed for isotope geochemistry (Sr, O and C). Dating using 87Sr/86Sr alone is not conclusive. Five pristine Oman brachiopods from biostratigraphically well-constrained lower Wordian horizons record a range of 87Sr/86Sr values that form a separate cluster offset from the current Sr isotope seawater curve, which defines the Early Permian and earliest Mid-Permian. The 87Sr/86Sr of the pristine Saudi Arabian brachiopod sits in an area which corresponds to a wide scatter of 87Sr/86Sr in the seawater curve data. However, the Saudi Arabian data does indicate that the Midhnab Member is likely younger than Member 3 of the Khuff Formation of the Huqf outcrop.
The well-preserved brachiopod carbonate allows deductions to be made about the palaeotemperature of the Oman Khuff Formation Member 3 seawater using its oxygen isotope composition (δ18O). Assuming δ18O of seawater &lt; –0.5‰, then palaeotemperature derived from brachiopods in the Oman horizons would be +25°C, +22°C and +17°C respectively. This is consistent with the trend of shallowing within Member 3, suggested by facies.
Sedimentological characterization of the mid-Cretaceous Mishrif reservoir in southern Mesopotamian Basin, Iraq
Authors: Mahdi Thamer A. , Aqrawi Adnan A.M. , Horbury Andrew D. , Sherwani Govand H. 
Published: October 2021

ABSTRACT
The CenomanianÐEarly Turonian reservoirs of the Mishrif Formation of the Mesopotamian Basin hold more than one-third of the proven Iraqi oil reserves. Difficulty in predicting the presence of these mostly rudistic reservoir units is mainly due to the complex paleogeography of the Mishrif depositional basin, which has not been helped by numerous previous studies using differing facies schemes over local areas. Here we present a regional microfacies-based study that incorporates earlier data into a comprehensive facies model. This shows that extensive accumulation of rudist banks usually occurred along an exterior shelf margin of the basin along an axis that runs from Hamrin to Badra and southeast of that, with additional interior rudist margins around an intra-shelf basin to the southwest. Regional tectonism defined the accommodation sites during the platform development.
Facies analysis allowed the recognition of 21 microfacies types and their transgressive-regressive cyclic stacking pattern. Sequence-stratigraphic analysis led to the recognition of three complete third-order sequences within the studied Mishrif succession. Eustatic sea-level changes were the primary control on this sequence development but local tectonics was important at the Cenomanian/Turonian boundary. Rudist biostromes are stacked as thicker shallowing-up cycles composed of several smaller-scale cycles. In places, smaller cycles are clearly shingled (stacked laterally). Iraq’s Mishrif sequences are thus analogous to coeval systems across the Arabian Plate in Oman, United Arab Emirates, offshore Saudi Arabia and Kuwait, southwest Iran and the Levant.
Analysis of poroperm trends shows porosity increasing beneath sequence boundaries due to karstification and meteoric dissolution. The presence of interconnected vugs in grain-dominated fabric make the rudist biostromes the best reservoir units. Dissolution of aragonitic components of rudist shells was the most important diagenetic process that enhanced reservoir characteristics. The presence of rudist-bearing facies with their diagenetic overprint within regressive cycles is considered the primary factor in effective porosity development and distribution. As a result, because of depositional heterogeneities (facies type distribution and their 3-D geometries) and the influence of sequence boundaries on reservoir quality, each field shows unique geometrical combinations of pay zones, barriers and seals.
The eastern Mediterranean phosphorite giants: An interplay between tectonics and upwelling
Authors: Abed Abdulkader M. 
Published: October 2021

ABSTRACT
About 20 billion tonnes of world-class, high-grade phosphorite resources occur in a small area of the eastern Mediterranean region, including Jordan, northern Negev (Palestine), northwestern Saudi Arabia, western Iraq, and southeastern Syria. Major deposits were formed during Campanian to Eocene times and contribute significantly to the economic development of these countries, particularly Jordan and Syria. The phosphorite deposits consist mainly of reworked granular material. The phosphate particles are peloids, such as pellets, intraclasts, nodules, coated grains and coprolites, and vertebrate fragments (bone and teeth). The phosphorite sequences are associated with extensive bedded chert, porcelanite, and organic-rich marls. The main phosphate mineral is francolite, a carbonate-rich variety of fluorapatite that has a relatively enhanced uranium content as a result of substitution for calcium in its crystal structure.
Two factors are deemed responsible for the deposition of the phosphorites and their associated chert, porcelanite, and marl within this relatively restricted area. The first was a compressional event associated with the initial collision of the oceanic forefront of the Afro-Arabian Plate with the subduction trench of Eurasia that began in Turonian times and continued into the Eocene. This event resulted in gentle folding that produced the Syrian Arc, the Ha’il, Rutba, and Sirhan paleohighs and the Ga’ara Dome, which were loci for the deposition of phosphorites. The second factor was the obstruction and consequent upwelling of oceanic currents by these tectonic highs, enhanced by winds blowing from east to west along the southern platform margin of the Neo-Tethys Ocean. The intense upwelling was associated with the Tethyan Circumglobal Current that flowed along the Afro-Arabian platform on the southern margin of the Neo-Tethys Ocean. In contrast, relatively minor phosphorite deposition took place to the north in southern Europe.
The upwelling spread cold, nutrient-rich oceanic water from the deep Neo-Tethys Ocean to the surface, thereby enhancing bioproductivity to produce organic-rich sediments. The subsequent authigenesis of phosphorites, their diagenesis and the reworking and winnowing of the phosphorite-rich sediments, concentrated the materials into economic deposits. Phosphorite deposition ended in the Late Eocene following the final collision of the Afro-Arabian Plate with Eurasia. The sub-aerial exposure of this formerly productive shallow-marine platform was the result of the separation of the Arabian Plate from the African Plate during the mid-Miocene.
High-resolution anatomy of a grainstone package in Khuff Sequence KS4, Oman Mountains, Sultanate of Oman
Authors: Maria-Louise Haase Marlene , Aigner Thomas 
Published: October 2021

ABSTRACTThis study is part of a large-scale outcrop analog study on Middle Permian to Lower Triassic Khuff-equivalent strata in the Oman Mountains, Al Jabal al-Akhdar, Sultanate of Oman. The Khuff outcrop equivalent can be divided into six sequences (Khuff sequences KS6 to KS1, from base to top). The main focus of this study is the description of the internal anatomy of the shoal grainstone bodies in the lower part of Sequence KS4 (“lower KS4”). High-resolution sedimentological logging of three outcrop sections in wadis Sahtan, Bani Awf and Mistal yielded eight lithofacies types that were grouped into five facies associations. Lower KS4 strata were mainly deposited within a “shoal complex” of an epeiric carbonate ramp, resulting in a thick pile of up to 70 m of grainstones that, on first sight, appear relatively homogeneous. However, detailed facies and microfacies analysis revealed their heterogeneous architecture on various scales: (1) Minor changes in depositional environments directly affected the type of carbonate grains (ooids versus peloids/cortoids versus bioclasts), leading potentially to highly variable pore systems (moldic versus interparticle versus intraparticle). (2) Vertically, detailed sequence-stratigraphic analysis revealed a higher-order of cyclicity (“mini-cycles”) on a decimeter- to meter-scale. Four mini-cycle types were recognized. (3) Laterally, facies changes, the amalgamation of grainstone beds and mini-cycle pinch-outs were observed in 2-D correlations on a scale of a few kilometers. These different types of heterogeneities may contribute to varying production rates commonly observed in the subsurface KS4 reservoir.
Evolution, paleoecology and sequence architecture of an Eocene carbonate ramp, southeast Zagros Basin, Iran
Authors: Zohdi Afshin , Mousavi-Harami Reza , Ali Moallemi Seyed , Mahboubi Asadollah , Immenhauser Adrian 
Published: October 2021

ABSTRACTWe document and discuss the results of detailed fieldwork, facies analysis and the subsequent integration of paleoecological evidence from the Middle Eocene carbonate ramp succession in the southeast Zagros Basin (Jahrum Formation). A combination of a sea-level fall and tectonic and diapiric basement uplift favored the initiation of the Jahrum carbonate platform. The lower portions are affected by pervasive, probably early diagenetic dolomitization, whilst the upper Jahrum consists mainly of limestone. Here, the focus is on the limestone portions of the Jahrum Formation. Based on the abundance, diversity and rapid evolutionary turnover of the alveolinids and nummulitids, the limestone intervals of the Jahrum Formation are interpreted for the upper Middle Eocene (Bartonian). The Jahrum Formation is capped by a major unconformity and overlain by the Lower Oligocene mixed clastic/carbonate Razak Formation.Based on data from field sections, eight facies associations and a series of sub-types have been established, which correspond to inner-, middle-and outer-ramp depositional environments. In their overall context, these data show a southward-dipping inner-ramp-to-basin transect. Towards the Coastal Fars (e.g. Hulur-01 Well) the Jahrum grades laterally into deep-marine Pabdeh foredeep shale units. Based on facies analysis and paleoecological evidence from larger benthic foraminifera, a major transgressive-regressive pattern is recognized in all outcrop sections of the Jahrum. The lowermost stratigraphic units of the formation are here interpreted as a distally steepened ramp. Evidence comes from abundant allochthonous shallow-water facies in the distal, deeper-ramp setting. Shallow-water carbonate clasts were exported towards the basin, a feature that is probably linked to relative sea-level fall control. Furthermore, local to regional basement instabilities by salt diapir-related basement reorganization was arguably of significance. Upsection, evidence is found that the ramp system evolved from a distally steepened to a homoclinal geometry with an overall very gentle slope geometry during the Late Bartonian.The data shown here are significant for those concerned with the Paleogene evolution of the southeast Zagros Basin and provide a well-exposed case example of a Middle Eocene carbonate ramp factory.
A refined foraminiferal biostratigraphy for the Late Campanian–Early Maastrichtian succession of northeast Iraq
Authors: Jaff Rawand B.N. , Williams Mark , Wilkinson Ian P. , Lawa Fadhil , Lee Sarah , Zalasiewicz Jan 
Published: October 2021

ABSTRACTSpecies of the benthonic foraminiferal genus Bolivinoides provide a refined biostratigraphic biozonation for the Late Campanian to Early Maastrichtian (Late Cretaceous) Shiranish Formation in NE Iraq. Three biozones and two subzones are identified: the Bolivinoides decoratus Biozone (Late Campanian) subdivided into a lower B. decoratus Subzone and upper B. laevigatus Subzone; the B. miliaris Biozone (Earliest Maastrichtian); and the B. draco Biozone (late Early Maastrichtian). These zones can be related to the biostratigraphical interval of the Globotruncana aegyptiaca (Late Campanian), Gansserina gansseri (latest Campanian–Early Maastrichtian) and Contusotruncana contusa (late Early Maastrichtian) planktonic foraminiferal biozones. Combined, the benthonic and planktonic foraminiferal biostratigraphy enables the informal recognition of lower and upper intervals within both the Globotruncana aegyptiaca and Gansserina gansseri biozones that may be important for more refined inter-regional correlation in the Middle East and North Africa. The new Bolivinoides biozonation precisely locates the Campanian–Maastrichtian boundary in NE Iraq. The foraminiferal assemblages also constrain the timing of a shallowing marine trend in the Shiranish Formation beginning from the latest Campanian that is consistent with shallowing facies noted globally at this time.
Modeling of the Dammam outcrop fractures: Case study for fracture development in salt-cored structures
Authors: Al-Fahmi Mohammed , Michele L. Cooke , Cole John C. 
Published: October 2021

ABSTRACT
The exposed Cenozoic carbonates of the Dammam Dome are studied to: (1) characterize fractures and associated structures; (2) interpret the fracture mechanism; and (3) gain insights into fracture development within dome-like structures in the subsurface of the Arabian Gulf region. The fieldwork is integrated with structural analysis of the near-surface horizons mapped from interpretations of 3-D reflection seismic and borehole logs. Fractures are mapped from the outcrops of the middle limestone unit of the Eocene Rus Formation. The outcrops are concentrated in the central, northern and western areas of the Dammam Dome. The fractures are interpreted as opening-mode, bed-bounded joints that form orthogonal sets in most areas. The primary (older) joint set (J1) developed in long lineaments, some of which can be traced for over 300 m across entire exposures. The J1 set is found to be broadly consistent in its trend over the dome, indicating that formation of J1 fractures was systematic and not influenced by local structural anomalies (including karst collapse) formed during the Miocene to Recent. The trend of the J1 set does not correlate with the NE-SW compressional orientation of regional stresses associated with the Zagros Orogeny. Field data interpretation, allied with analysis of dome’s growth and curvature, suggest that the overall joint pattern reflects the growth of the strata as a dome. In addition, the joint density is controlled by structural position on the dome and mechanical stratigraphy. The study results provide a first-order conceptual fracture model for the subsurface reservoirs to guide future development.
Proposed correlation of Oman’s Abu Mahara Supergroup and Saudi Arabia’s Jibalah Group
Authors: Al-Husseini Moujahed I. 
Published: October 2021

ABSTRACT
The Ediacaran–Cambrian Middle East Geologic Time Scale is extensively revised in the 2014 version (Enclosure). It suggests the top of the Abu Mahara Group glacial diamictites in Oman represent the termination of the late Cryogenian Marinoan Glaciation at 635 Ma. The overlying Ediacaran Nafun Group of Oman is shown between 635 and 547 Ma based on geochronologic data, and divided into: (1) the Lower Nafun Supersequence (635–582 Ma) consisting of the Hadash Formation (cap carbonate), the Masirah Bay Formation (clastics) and the Khufai Formation (carbonates); and (2) the Upper Nafun Supersequence (582–547 Ma) consisting of the Shuram Formation (clastics and carbonates) and the Buah Formation (carbonates). The Nafun Group lies below the Ediacaran– lower Cambrian Ara Group (evaporites and carbonates), which contains the Ediacaran/Cambrian Boundary currently dated at 541 Ma.
The Sub-Shuram Unconformity, which corresponds to the global Shuram δ13C Negative Excursion, separates the Nafun supersequences. Its age was estimated by assuming the thicknesses of the Nafun formations are proportional to time in the Masirah-1 Well, where the Nafun Group attains its greatest-known thickness of 2,308 m in Oman. This assumption coincidently estimated the unconformity at 582 Ma, the same age as the Ediacaran Gaskiers (Varanger or Varingian) Glaciation. The new calibration was used to correlate the Nafun formations to the rock-time units of the Jibalah Group in several isolated basins along the Najd Fault System in the Arabian Shield, using recently published geochronologic data and δ13C measurements, as follows.
The younger part of the Lower Nafun Supersequence (635–582 Ma) is here correlated to the Lower Jibalah Supersequence (605 ± 5 to 582 Ma), represented by the Umm al-Aisah Formation in the Jifn Basin, located along the Halaban-Zarghat Fault Zone of the Najd Fault System. The Umm al-Aisah Formation consists of volcanics and clastics that give way to the Umm al-Aisah Limestone. The Upper Nafun Supersequence (582–547 Ma) is here correlated to the Upper Jibalah Supersequence, which unconformably overlies the Umm al-Aisah Limestone, with its basal unit being the Gaskiers-coeval Jifn Polymictic Conglomerate (≥ 200 m thick). In the Bir Sija Basin, located along the Rika Fault Zone of the Najd Fault System, the likely Gaskiers-coeval polymictic conglomerate (150 m thick) is overlain by a 20 m-thick limestone unit, the Bir Sija Limestone, possibly a cap carbonate. The Upper Jibalah Supersequence continues with clastics overlain by the Muraykhah Formation (carbonates) or mixed clastics-carbonates of its equivalent formations. In several outcrops the Upper Jibalah Supersequence is overlain by the lower Cambrian Siq Sandstone Formation (≤ 525 ± 5 Ma) implying the Sub-Siq Unconformity represents a hiatus between 547 and 525 ± 5 Ma. The Jifn Formation in the Jifn Basin, however, may represent continuous deposition between 582 Ma and 525 ± 5 Ma.