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Results of this study are based on core materials description, thin sections, Cathodoluminescence (CL), and Scanning Electron Microscope (SEM) examinations. The Lower Cretaceous over the Euphrates Graben area was characterized by carbonate sedimentation in shallow marine environments. The low energy lagoonal to inner shelf sediments of the Judea Formation includes micritic mudstone to wackestone texture, dolomitic limestones and dolostones. Two types of dolomites recognized in the carbonates of the Judea Formation, the preserving microcrystalline dolomites which commonly founded in the partially dolomitized micritic limestones, and the destructive coarsely crystalline dolomites which commonly founded in the dolostones and dolomitic limestones. Petrographic examinations indicate that the preserving microcrystalline dolomites represent subtidal cycles developed in a shoal to open marine depositional environments, they probably formed under conditions of the shallow burial diagenesis. The destructive coarsely crystalline dolomites may develop in more basinward, open marine environments under conditions of the deep burial diagenesis that accompanied by rising in temperature, pressure, and burial depth. It is believed that evolution of the diagenetic history of the Judean Formation sediments occurred in two diagenetic stages; the shallow burial diagenesis, and the deep burial diagenesis. Compaction processes, early fracturing, micritization, early calcite, and the early phase of dolomitization were part of the multiple diagenetic alterations during the shallow burial diagenesis. The deep burial diagenesis was marked by dissolution, late stage of dolomitization and replacement, mechanical and chemical compaction, and the late calcite precipitation. It is believed that dolomitization of the Judea Formation carbonates in the Euphrates Graben has contributed to improving the reservoir properties by increasing the porosity and thus the permeability.

Upper Carboniferous deposits of the Rod El-Hamal Formation are well exposed at Wadi Araba, north Eastern Desert, Egypt. The upper part of the Formation includes late Moscovian (Middle Pennsylvanian) mounds formed by filamentous microbes and phylloid algae. Phylloid algae are loosely accumulated and supported by micritic encrustations that were formed by filamentous microbes. The filamentous microbes growing perpendicularly to the phylloid algal surfaces produced concentrated areas of peloids-A (peloid-A aggregations). The spaces between the phylloid algal-microbial frameworks were filled with concentrated areas of peloids-B (peloid-B aggregations) oriented perpendicular to the phylloid algae surfaces. Microbial communities as well as phylloid algae constitute significant components in the late Moscovian buildups in the study area. Below and above the mound facies, the non-reefs carbonates of Unit (IV) of the Rod El-Hamal Formation are composed of molluscan wackestone, ferruginous-molluscan packstone, and bioclastic rudstone facies, reflecting shallow subtidal depositional environment. Pennsylvanian phylloid algal-bearing buildups were divided into Tethyan and Pangean buildups. The Tethyan buildups are widely distributed in the circum-equatorial tropical paleolatitudes. The Egyptian buildups exhibit similarity in the building organisms to those of the Tethyan, but with a higher proportion of microbialites. Therefore, the subtropical Egyptian buildups are regarded as a sub-type of the tropical Tethyan buildups.

Carbonate microfacies analysis was conducted on the exposed sediments of Dukul Formation from Yola Sub-basin of the Northern Benue Trough with an objective to reconstruct the paleodepositional environment. The study revealed four (4) major microfacies; oyster wackestone, ostracod oyster wackestone-packestone, bioclastic wackestone and bioclastic packestone microfacies. The microfacies assemblages indicate and affirm that the Dukul Formation sediments were deposited in shallow marine (mid-inner ramp) environment under suboxic to relatively anoxic conditions due to sea-level drop. This is further supported owing to the occurence of corals, brachiopods, bivalves and ostracods immediately below the mean fair-weather wave base (FWWB)

Late Visean foraminiferal assemblages from a section in the Sikasya (Sikaza) River Valley (South Urals) are studied to provide a reliable framework for stratigraphy and correlation of the Visean-Serpukhovian boundary beds on the western slope of the South Urals. The middle–upper Visean deposits on the Sikasya River are composed of shallow shelf carbonates with abundant foraminifers, corals, and brachiopods, and are represented by four regional substages: Tulian, Aleksinian, Mikhailovian, and Venevian. This section is known as the “Sikaza Section”. The upper Visean deposits are overlain by Serpukhovian beds composed mainly of dolomites. The Tulian and Aleksinian successions consist of bioclastic and foraminiferal wackestone and packstone. In the Mikhailovian, there are packages of dolomites with interbeds of bioclastic grainstone to packstone, containing foraminifers. The Venevian is represented by bioclastic and foraminiferal grainstone and packstone. The following foraminiferal units are discussed: in the middle Visean: (1) Paraarchaediscus koktjubensis–Endothyranopsis compressa; in the upper Visean: (2) Ikensieformis proikensis–Archaediscus gigas, (3) beds with Vissarionovella (corresponding to the Ikensieformis ikensis Zone), and (4) Ikensieformis tenebrosa; the Serpukhovian is represented by (5) beds with Eostaffellina decurta.

In easternTexas, a thick (150-200 ft) interval of Lower Cretaceous upper Glen Rose D strata was deposited in the Houston trough intrashelf basin landward of the Stuart City reef margin and seaward of the main eastern Texas intrashelf basin. The stratigraphic section in this intrashelf basin forms a primarily oil-bearing hydrocarbon system where porous grainstones in the Alabama Ferry and Fort Trinidad fields were deposited coevally with organic-rich calcareous argillaceous mudstones. Here, we present evidence to suggest that the depositional setting within the Houston trough and the contained ooid grainstone beds were of deeper-water origin (400-500 ft), below storm wave base. Further, the water column was stratified, allowing dysaerobic to anaerobic conditions to develop, fostering accumulation and preservation of organic matter. Grain-rich gravity flows consisting of ooids, intraclasts, and thin-walled mollusks, derived from the shallower shelf to the northwest, were deposited in the basin, forming the Alabama Ferry and Fort Trinidad fields. The upper Glen Rose interval is composed of lithofacies that vary laterally within the Houston trough. Five lithofacies are recognized on the basis of sedimentary features, texture, fabric, biota, and organic-matter content: (1) laminated to nonlaminated argillaceous lime mudstone to lime wackestone; (2) laminated to nonlaminated calcareous siliciclastic mudstone to siltstone; (3) intraclast–ooid skeletal lime packstone; (4) intraclast–bivalve–ooid lime grainstone; and (5) oyster lime floatstone and rudstone. Grain-rich lithofacies laterally adjacent to and interbedded with organic-rich argillaceous lime mudstones and calcareous siliciclastic mudstones were previously interpreted as being deposited in a tidally influenced, high-energy, shallow-water shoal environment; however, reconstruction of the depositional setting and interpretation of the vertical and lateral distribution of lithofacies suggest that these lithofacies were deposited as grain-rich gravity flows into the deeper-water Houston trough. This interpretation suggests a new conceptual framework integrating facies models from submarine channel and fan complexes to explore for grainstone reservoirs similar to Alabama Ferry and Fort Trinidad fields.

The aim of this study is to investigate the sedimentation environments and diagenetic processes of the Ibrahim Formation (Oligocene-early Miocene) in Zurbatiya, eastern Iraq. The Ibrahim Formation is comprised mostly of clayey micrite and skeletal grains composed of planktonic foraminifera, calcispheres, radiolaria, and benthic foraminifera. Glauconite and pyrite were documented in some restricted zones of this formation; they reflect quiet and reducing conditions. Radiolaria were identified in Late-Oligocene which was not known previously at this age regionally in carbonate formations of the Arabian Plate (AP). Mudstone, wackestone, and planktonic foraminiferal wackepackstone are the main microfacies that are affected by dissolution, cementation (granular), and replacement covering the age of the latest Eocene-Oligocene to the early-middle Miocene. Microfacies analysis indicates a basinal environment with a hemipelagic character of the deep shelf, toe-of-slope, and lower slope. Oligocene-Miocene outcrops have not been known previously in eastern Iraq although they have 160 m thick was first recorded in this study, whereas it was estimated as 56 m in the type section (well-1). Hence, the studied section is therefore suggested to be considered as a type section of the Ibrahim Formation. The Oligo-Miocene boundary is marked by restricted shallow-marine facies at the middle part of the formation indicating a short-term sea-level regression.

The studied section is located in the core of the Gara Anticline, about 12 km southeast of Amedi Town. The Baluti Formation is generally composed of grey and green shale, calcareous, dolostone with intercalations of thinly bedded dolostones, dolomitic limestones, and silicified limestones which are occasionally brecciated. The petrographic study shows five main microfacies in the Baluti Formation namely; finely laminated dolomudstone, fossil-barren and lime mudstone, fenestral mudstone/packstone, peloids and ooids wackestone, and lithoclasts (intraclasts) grainstones. The mudstones facies with no fauna and radial-fibrous ooids can point to a protected and low energy environment. Moreover, fenestral structures are reliable criteria for identifying a tidal flat environment. The presence of the lithoclasts (intraclasts) with radial ooids and a few terrestrial fragments may represent a quiet environment, albeit one affected by infrequent storm deposits. As a supplementary to microfacies, the biomarker characterizations were used to deduce the depositional environment of the Baluti Formation. Biomarker parameters show that the Baluti Formation could be deposited in anoxic to suboxic environment, and organic matter input is more likely characterized by land plant organic matter. This study showed that the most likely paleoenvironments for the Baluti Formation were supratidal, intertidal, subtidal, and sand shoals setting. However, the lack and/or very low diversity of skeletal fauna, and the lack of subaerial exposure may indicate that some parts of the formation seem to be deposited in low energy and restricted environment (Lagoon).

In this paper, we describe porosity variations in Miocene to Holocene carbonates off the west coast of Australia and assess their compaction trends. The porosity values were measured using discrete samples of Sites U1459–U1464 obtained by the International Ocean Discovery Program Expedition 356. The carbonate deposits have been influenced by a range of textures and diagenetic conditions throughout a nearly continuous sequence of geological ages from the Miocene to Holocene and at core depths from 0 to 1100 m below the seafloor. The collected samples were mostly grainstone, packstone, wackestone and mudstone textures. Dolostones and dolomitic carbonates were described at the Miocene intervals. Compaction trends were estimated exponentially and linearly based on cored sites, carbonate textures and dominant mineralogies (dolomite, calcite/aragonite). At all six sites, porosity distribution and reduction were generally depth-dependent. The porosity converged to about 30% between 750 and 1100 m, which suggests that the carbonates were close to the densest packing by mechanical compaction at a burial depth of ∼750 m. The porosity deviations are associated with textures and dominant mineralogies. Increasing mud content from grainstone to mudstone is a controlling factor for initial porosity and porosity reduction rate. Dolomitisation, dolomitic cementation, aragonite needle-rich mud and non-skeletal grains cause deviations from the depth-dependent compaction trends. Reflux-related cementation generally decreases porosity in Miocene dolomitic intervals. Higher porosity values of the Quaternary wackestone and mudstone at Site U1461 resulted from the presence of aragonite needle-rich mud hosting abundant micropores and from a high sedimentation rate. The occurrence of non-skeletal grains, such as ooids and peloids, as well as occasional meteoric exposure led to porosity inversion, occluding interparticle permeability and the creation of moldic pores.

As igneous rocks have widely chemical and mineralogical compositions, there are many ways to classify these rocks. These ways are classical approved methods to give a reliable classification and nomenclature of rocks. Some igneous rocks may be classified by digital image processing to assist in classical methods. Five igneous samples were cut, prepared of thin sections, and polished to classify them by classical methods and digital image processing by ENVI software. Moreover, part of these samples crushed an analysis of major oxides. The current igneous samples have referred to the basic and mesocratic rocks based on the classical methods and this has corresponded to ENVI software. The igneous samples have reflected the leucogabbros when classify them by classical and ENVI classifications, except the G5 sample, which has been referred to as gabbro by ENVI. There is a clear similarity between the classical and ENVI classifications. ENVI classification is a reliable classification to assist the classical methods in the nomenclature of igneous rocks, especially, plutonic rocks, it can be also applied to thin sections of volcanic rocks to classify and nomenclature classification by ENVI has been applied on fifty thin sections of limestones to identify microfacies which are classified beforehand by classical (optical) classification. According to optical classification, microfacies have classified as mudstone, wackestone, packstone, and grainstone. When the digital classification is applied to them, there is no grainstone texture found in these them. Digital thin sections, where the true name of these microfacies is packstone. Therefore, the positive sides of the digital image processing by ENVI software appeared and contrasted to the optical classification which contained some mistakes when applied to the nomenclature of these microfacies.

The Qamchuqa Formation was studied in Chwarqauran section, Sulaimanyia, Kurdistan region, Northeastern Iraq. The lithology of the formation contains limestone throughout the whole section except for one bed of dolomite at the Middle part. Twenty-four slides were prepared from 24 rock samples that were taken from this section to discriminate the petrography and fossil content. The petrographic study shows four main microfacies including lime mudstone, wackestone, packstone, and floatstone. Additionally, there are four sub microfacies: bioclast wackestone, miliolid wackestone, bioclast packstone and orbitolinid packstone. However, the fossil content shows the abundance of benthic foraminifera against the planktonic. All the microfacies indicate facies zone 7, 8 and 9A which reflect deposition in the platform interior between the tidal flat to the mid ramp and back reef environment

The Early Eocene succession of the Salt Range from base to top comprises the Nammal Formation, Sakesar Limestone and Chor Gali Formation. The Nammal Formation of Ypresian age is well exposed throughout the Salt Range. Detailed sedimentological and palaeontological analyses of the Nammal Formation were carried out, based on six stratigraphically important measured sections in the Salt Range. Lithologically, the formation is predominantly composed of interbedded nodular limestone, marl and shale. Wackestone, packstone, wackestone to packstone, dolomitic limestone and grainstone facies dominate the Nammal Formation in a fine-grained bioclastic matrix with abundant grains of larger benthic foraminifera. The diagnostic larger benthic foraminifera are recorded, which includes Nummulites mamillatus, Assilina spinosa, Assilina subspinosa, Assilina granulosa, Assilina laminosa, Discocyclina dispansa, Alveolina dolioliformis, Alveolina pasticillata, Alveolina globula, Lockhartia tipperi, and Lockhartia conditi. Stable carbon and oxygen isotopic signatures of the Nammal Formation designate shallow marine depositional environment. During Eocene a carbonate sequence developed in the Salt Range, lower boundary of which is marked as SB-II at the base of the Nammal Formation overlying the Palaeocene Patala Formation. The Nammal Formation presents the retrogradational facies suggesting the transgressive system tracts. The Sakesar Limestone shows agradational to progradational pattern of facies, which developed in highstand system tracts. The Chor Gali Formation possesses shallowing-upward trend by forming progradational shift of facies, and represents the falling stage system tracts. Early Eocene carbonate sequence is terminated by a regional sub-aerial unconformity SB-I marked between marine carbonate sequence of the Chor Gali Formation and the overlying non-marine clastic Miocene Kamlial Formation. Overall, the Nammal Formation presents shallow water neritic carbonate deposits containing larger benthic foraminifers.

The Hartha Formation is one of the important formations deposited during Late Campanian age. The present study deals with four boreholes (EB-53, 54, 55 and 56) within the East Baghdad oil field to diagnoses the microfacies and interpret the depositional environments. Six major microfacies were recognized in the succession of the Hartha Formation. Their characteristic grain types and depositional texture enabled the recognition of paleoenvironment. There are Orbitoides wackestone-packstone , Orbitoides - miliolid wackestone, Peloidal and Pellets - echinoderm wackestone to packstone, Peloidal wackestone to packstone, Pelletal wackestone to packstone, and Planktonic foraminifera wackestone-packstone. Four associations’ facies were recognized in this succession, which are shallow open marine, deep open marine, semi-resricted, and restricted. The distribution of these associations led to the recognition of three major depositional stages in the studied succession. The first stage is represented by the semi-restricted facies within the lower part of the Hartha Formation, which is characterized by Orbitoides - miliolid wackestone to the northwest direction and developed to shallow open marine and deep marine to the southeast direction. In the second stage, the sea level was rising to deposit the deep open marine facies represented by planktonic foraminifera wackestone-packstone microfacies above the semi-restricted facies ,where the succession became characterized by Peloidal and Pellets - echinoderm wackestone to packstone microfacies of restricted association. The third stage is represented by the continuation of sea level rise. This caused the building of carbonate ramp of Shiranish Formation above the shallow open marine of Hartha Formation with conformable surface.

Carbonate reservoir in “R” Oil Field is a reef limestone that has a very complex porosity and permeability characteristics caused by its diverse pore types (interparticle, stiff, and crack). This study aims to characterize the carbonate reservoir by estimating its interparticle porosity and permeability based on rock types distribution model. Modified Rock-Fabric Classification is used to determine the distribution of rock types in three reference wells (R2, R9, R20). Rock Types (RT) distribution model is generated by integrating Acoustic Impedance (AI) and Shear Impedance (SI) attributes from seismic simultaneous inversion with rock types distribution in reference wells using Naive-Bayes Classifier. Three-dimensional (3D) interparticle porosity and permeability are then estimated from the rock types distribution model. The result shows RT3 which is characterized by crack pores as the most dominant rock type in the reservoir followed by RT5, RT4, and RT6 which are characterized by interparticle pores. Relatively high interparticle porosity values ranges from 0.18 to 0.22 can be associated with RT6 of mud-dominated packstone or wackestone. Meanwhile, relatively high permeability values range from 70 to 80 millidarcy (mD) can be associated with RT4 of grainstone. Laterally, there are clusters of spots in the south of the three reference wells that showed relatively high permeability value.

Актуальность. Значительная часть мировых запасов углеводородов приурочена к карбонатным резервуарам, характеризующимся сложным строением пустотного пространства. Подсчет запасов и проектирование разработки таких залежей требуют детального изучения структуры пустотного пространства, которая напрямую определяет коллекторские свойства пород. Выделение петрофизических классов пород является неотъемлемой частью построения петрофизической модели залежи углеводородов. Метод ядерного магнитного резонанса (ЯМР) является одним из методов изучения структуры пустотного пространства горных пород и имеет ряд преимуществ перед другими методами. Однако в опубликованной литературе отсутствует информация о применении данного метода для решения задач петротипизации. Результаты выделения петрофизических классов на основе комплексирования данных ядерного магнитного резонанса и микролитологического описания шлифов позволят значительно улучшить качество петрофизического обеспечения геологического и гидродинамического моделирования залежи и, следовательно, повысить точность подсчета запасов углеводородов и эффективность их разработки. Цель: выделение петрофизических типов карбонатных пород на основе комплексирования данных ядерного магнитного резонанса и микроописания шлифов, а также оценка правильности выделения классов методами математической статистики. Объект: карбонатные породы формации Мишриф, являющейся продуктивной в разрезе одного из месторождений Месопотамской нефтегазоносной провинции. Методы: анализ результатов ЯМР-исследований образцов керна, микроописания шлифов и стандартных лабораторных исследований керна, методы математической статистики. Результаты. На основе комплексного анализа результатов ЯМР-исследований керна и микроописания шлифов выделены три петрофизических класса в разрезе изучаемой скважины, вскрывшей продуктивные отложения: образцы со структурами породы вакстоун и вакстоун/флаутстоун объединены в 1 класс, со структурами пакстоун, грейнстоун и рудстоун - во 2 класс, и со структурой фреймстоун - в 3 класс. Данная петротипизация подтверждена результатами статистического анализа. The relevance. Significant part of world hydrocarbons reserves is confined to carbonate reservoirs, which are characterized by complex structure of voids. Reserves estimation and development design of such reservoirs require detailed study of porous media structure, that directly influences the reservoir properties. Identification of petrophysical rock classes is an integral part of hydrocarbons reservoir petrophysical model building. Nuclear magnetic resonance (NMR) method is one of the methods of rock porous structure research and has a number of advantages over other methods. However, there is no information in the published literature about application of this method for petrophysical typing. The results of petrophysical classes identification based on integration of NMR experiments and thin sections description data enhance the quality of reservoir geological and hydrodynamic simulation and hence improve accuracy of hydrocarbons reserves estimation and efficiency of field development. The main aim of the research is carbonate rock petrophysical typing based on integration of NMR experiments and thin sections description data, and estimation of classes identification accuracy with the methods of mathematical statistics. Object: carbonate rocks of Mishrif formation, which is productive in the field of Mesopotamian oil-and-gas province. Methods: analysis of core sample NMR experiments results, thin sections description and routine core analysis, methods of mathematical statistics. Results. Three petrophysical rock types are identified in the log of the well, which intersects productive deposits. The types are: 1st class (wackestone and wackestone/floatstone rock structure), 2nd class (packstone, grainstone and rudstone rock structure) and 3rd class (framestone rock structure). These petrophysical classes are proved with statistical analysis results.

Based on comprehensive analysis of core, cast thin section, logging and seismic data, the sedimentary and reservoir architectures of the MB1-2 sub-member of Mishrif Formation in Halfaya Oilfield, Iraq, are studied. The MB1-2 sub-member of Mishrif Formation has three types of microfacies, lagoon, bioclastic shoal, and tidal channel, and facies architecture controlled by sequence stratigraphy. In the 4th-order sequence, the lagoon facies aggradated vertically, and the bioclastic shoals in lenticular shape embed in the background of lagoon, the end of the sequence is incised by the “meandering river” shape tide channel, which represents the depositional discontinuity. Three types of reservoirs including tidal channel grainstone to packstone reservoirs, bioclastic shoal grainstone to packstone reservoirs and dissolved lagoon wackestone reservoirs are developed. The reservoir architectures within tidal channel and bioclastic shoal are strickly controlled by grainy facies, whereas the dissolved lagoon reservoirs controlled by both facies and dissolution are related to the sequence boundary. The reservoir sections occur mainly in the 4th sequence highstand systems tract (HST) and are separated by barriers formed in the transgressive systems tract (TST). Complicated facies architecture and dissolution modification resulted in strong heterogeneity within the reservoir, which showed the characteristics of “attic type” architecture. The results of this study can guide the development of similar reservoirs in the Middle East.

Material cement industry are mostly formed by carbonate and silica. Geology of Muara Dua area was contain those material used in cement industry. Mineralogy of carbonate this area mostly formed by Calcium (Ca) contained on Calcite (CaCO3), Dolomite (CaMg(CO3)2) while Silica, Alumina, Iron Oxide element found as SiO2, Al2O3, Fe2O3, MgO on rock. Research area mostly generated by tectonically complex where the sedimentation mostly controlled the existence of material using in cement industry. Three analysis method were conducted which are Geological Mapping to describe macro petrology, Petrography analysis to determine mineralogy microscopic and Geochemical method using XRF to identified chemical mineralogy of rock. Limestone is one of lithology unit that develop on research area where known as Packstone to Wackestone (Petrography) while "Calcitic Limestone” to “Marly Limestone” classification from Geochemical analysis (XRF). Another material such as Silica and trass material are definitely found on this research area to support cement industry. Element for support cement industry that exist on Muara Dua area formed due to sedimentation process that effected by tectonic and volcanic.

The paper aims to establish a possible link between the sequence stratigraphy and reservoir potential of the Middle Jurassic carbonates of Samana Suk Formation, Kala Chitta Range, North Pakistan. The Samana Suk Formation is comprised of a monotonous sequence of thin- to thick-bedded bioturbated, cross-bedded, ripple marked, sandy, bioclastic carbonates with shale interbeds. The rock unit is the best analog of shallow to marginal marine carbonates due to its pronounced thickness, enhanced lithological variations, and diverse diagenetic features. To establish a possible link between the sequence stratigraphy and reservoir potential of the rock unit, the outcrop and petrographic features are used to record eight microfacies, deposited in a wide range of shallow to marginal marine environments including mudflats, lagoon, back shoals, and sand shoals. Based on the vertical stacking pattern of microfacies in a given time of deposition (170–160 Ma), one second-order local cycle (SLC-1), three regressive systems tracts (RSTs) and two transgressive systems tracts (TSTs) are delineated within the succession. The primary and secondary porosity of selected microfacies from each systems tracts are investigated using petrography, scanning electron microscopy, and energy-dispersive spectroscopy. The direct measurements of porosity and permeability of these microfacies types are carried out using high overburden pressure plug porosity and permeability analyses. Based on these investigations, higher reservoir potential is recorded for mudstones/wackestone microfacies of RST as compared to grainstone microfacies of TST. The higher porosity within RST and higher interconnectivity of available pores both in RST and in TST suggest that the Samana Suk Formation carries good reservoir potential.

Lower–Middle Ordovician platform carbonates are important oil and gas reservoir rocks in the Ordos Basin of the North China craton (NCC). In recent years, numerous cores have been recovered from these units, but the depositional environments and facies architecture of this large carbonate platform system have not yet been reported in detail. This study integrates sedimentological and magnetic fabric data collected from outcrops and cores to document variation in microfacies and facies associations within the Shanganning carbonate platform (SCP), infer paleowind directions and the paleogeographic location of the SCP, and evaluate tectonic and paleogeographic controls on platform development. This analysis documented 25 microfacies belonging to 7 microfacies fabric and sediment types: carbonate mudstone, wackestone, packstone–grainstone, evaporite, bindstone–framestone, siliciclastics, and dolostone. Microfacies can be grouped into facies associations that represent tidal-flat, open-platform, restricted-platform, evaporite-platform, platform-margin, slope, and deep-basinal depositional environments. These environments are mainly distributed zonally around the L-shaped Qingyang paleo-uplift on the western and southern margins of the SCP. Anisotropy of magnetic susceptibility measurements at five platform-margin locales yielded paleocurrent directions of (all approximately) 318°–348°, 51°–81°, 42°–72°, 80°–110°, and 54°–84° from paleo-north after correction for a 120°–150° clockwise rotation of the NCC since the Ordovician. The depositional architecture of the SCP depended on a combination of tectonic and paleogeographic (wind) influences. Local tectonic movements controlled the spatial distribution of facies associations around the Qingyang paleo-uplift, which was characterized by open, restricted, and evaporite-platform facies in the platform interior and mainly slope and basinal facies on the outer-platform margin (to the west and south of the Qingyang paleo-uplift). Vertical tectonic movements resulted in cyclic submergence and emergence of the platform over its approximately 20-m.y.-long formation history. Paleo–trade winds influenced aspects of facies zonation across the platform, including growth of metazoan reefs on the windward platform margin and formation of oolitic grainstone and microbial reefs on the leeward platform margin. The facies model for the SCP developed in this study should provide a useful reference framework for future carbonate oil and gas exploration in Lower–Middle Ordovician units of the Ordos Basin. Furthermore, this study makes innovative use of magnetic anisotropy data, in combination with standard petrographic, core, and field data, to discern facies patterns and controls on a paleo-carbonate platform, which is an integrated methodology that may serve as a model for future studies of other carbonate platforms.

This paper studies the microfacies, fossil contents, and the depositional environment of Wadi As Sir Limestone Formation exposed in the Al-tayyar area Zarqa Governorate, Northeastern Jordan. A total number of 35 samples were collected from a 30 m thick quarry section and used to prepare 35 thin sections. Some samples were washed over a 63 μm sieve, oven-dried at 50°C, sieved, and picked for benthic foraminifera analysis. Microscope analysis used to describe the microfacies and fossil contents. Four microfacies types and four lithological units are distinguished and described from the bottom to the top; the chalky unit (Unit-1) composed of bioclastic wackestone and biomicrite microfacies, and the dolomitic unit (Unit-2) immediately is existed above unit 1 composed dominantly of bioclastic mudstone and biomicrite microfacies. Marly limestone (Unit-3) is the following upwardly unit composed of bioclastic packestone and biosparite Microfacies, and the uppermost unit is limestone (Unit-4) consisted of bioclastic grainstone and biosparite microfacies. The fossil contents that were recognized in the studied thin sections and samples; bivalves, gastropods, pelecypods, cephalopods echinoderms, radiolarian, stromatoporoids, bone fragments, Saccaminopsis sp., Cibicidoides sp., Cibicides sp., Cyclammina sp., calcareous algae (Koninckopora and gymnocodiaceans), worm tubes, serpulids, and plentiful ostracods. The current study indicates that the Wadi As Sir Limestone Formation has deposited in a restricted circulation shallow shelf with low energy conditions most probably lagoonal environment.

The present study main focused on reservoir Characterization of the Upper Cretaceous Kawagarh Formation from Qamar Mela Section, Nizampur Basin. The samples were collected from the field by using standard procedures involving section measurement, lithological logging and photography. The collected samples were used to prepare the thin sections followed by petrographic analysis using Optika microscope in the laboratory. To explore the reservoir potential, we studied the impact of diagenesis on reservoir potential, supplemented by plug porosity and permeability, and SEM analysis. The outcrop is mainly composed of limestone and marl. Fifteen samples were studied from 45m thick section and two main microfacies were identified. The microfacies includes; (1). Mudstone microfacies (planktonic foraminiferal mudstone and dolomitic mudstone sub-microfacies), (2). Radiolarian bioclastic planktonic foraminiferal wackestone microfacies. The environment of deposition interpreted on the basis of microfacies for Kawagarh Formation is inner ramp to outer ramp and deep basinal settings. The Kawagarh Formation is also modified by various diagenetic features including compaction, dolomitization, dissolution, pyrite precipitation, cementation and spar filled fractures representing meteoric to marine phreatic with mixing zone and burial diagenetic environments. Dissolution, fracturing and dolomitization are the diagenetic processes which enhanced the porosity while cementation, pyrite precipitation and compaction decreased the porosity. Plug porosity and permeability of four rock samples averages 1.69% and 0.267 Ka/md, respectively. SEM analysis shows different types of porosity includes vuggy, shelter and intergranular. The low porosity and permeability levels of Kawagarh Formation suggest only a modest reservoir potential. The present study main focused on reservoir Characterization of the Upper Cretaceous Kawagarh Formation from Qamar Mela Section, Nizampur Basin. The samples were collected from the field by using standard procedures involving section measurement, lithological logging and photography. The collected samples were used to prepare the thin sections followed by petrographic analysis using Optika microscope in the laboratory. To explore the reservoir potential, we studied the impact of diagenesis on reservoir potential, supplemented by plug porosity and permeability, and SEM analysis. The outcrop is mainly composed of limestone and marl. Fifteen samples were studied from 45m thick section and two main microfacies were identified. The microfacies includes; (1). Mudstone microfacies (planktonic foraminiferal mudstone and dolomitic mudstone sub-microfacies), (2). Radiolarian bioclastic planktonic foraminiferal wackestone microfacies. The environment of deposition interpreted on the basis of microfacies for Kawagarh Formation is inner ramp to outer ramp and deep basinal settings. The Kawagarh Formation is also modified by various diagenetic features including compaction, dolomitization, dissolution, pyrite precipitation, cementation and spar filled fractures representing meteoric to marine phreatic with mixing zone and burial diagenetic environments. Dissolution, fracturing and dolomitization are the diagenetic processes which enhanced the porosity while cementation, pyrite precipitation and compaction decreased the porosity. Plug porosity and permeability of four rock samples averages 1.69% and 0.267 Ka/md, respectively. SEM analysis shows different types of porosity includes vuggy, shelter and intergranular. The low porosity and permeability levels of Kawagarh Formation suggest only a modest reservoir potential.

Η περιοχή μελέτης καλύπτει ένα μέρος των ανθρακικών αποθέσεων της ζώνης Παξών στο νησί της Κεφαλονιάς το οποίο ανήκει στις Εξωτερικές Ελληνίδες και δομείται από δύο διαφορετικές γεωτεκτονικές ζώνες, την Προαπούλια ή ζώνη Παξών στα δυτικά και την Ιόνια ζώνη στα ανατολικά η οποία και επωθείται στην προηγούμενη. Πιο συγκεκριμένα, η περιοχή μελέτης τοποθετείται στις Ανατολικές περιοχές του Αίνου, Δυτικά της περιοχής της Σάμης, με γεωγραφικές συντεταγμένες της [ x , y ] σε προβολικό σύστημα κατά ΕΓΣΑ ‘ 87x:0205125 y:4235904. Η παρούσα διδακτορική διατριβή έχει ως αντικείμενο μελέτης τον προσδιορισμό του περιβάλλοντος απόθεσης, της ενέργειας του εκάστοτε περιβάλλοντος καθώς και της παλαιογεωγραφίας και της χωροχρονικής εξέλιξη της συγκεκριμένης ανθρακικής ακολουθίας με τη βοήθεια της Μικροφασικής ανάλυσης. Για λόγους ευκολίας η ανθρακική ακολουθία μελετήθηκε τμηματικά σε συνολικά 7 θέσεις, από οποίες και συλλέχθηκαν 300 περίπου δείγματα πετρωμάτων. Από τα δείγματα που συλέχθηκαν κόπηκαν συνολικά 300 λεπτές τομές με σκοπό την μικροφασική τους ανάλυση. Οι λεπτές τομές μελετήθηκαν σε πολωτικό μικροσκόπιο και ταξινομήθηκαν κατά τα ταξινομικά σχήματα των Dunham (1962) και Folk (1959) και στη συνέχεια πραγματοποιήθηκε λεπτομερής μικροφασική ανάλυση σύμφωνα με τους Flügel (2004), Wilson (1975) και Embry & Klovan (1971). Επιπλέον ο προσδιορισμός της ηλικίας της ανθρακικής ακολουθίας πραγματοποιήθηκε με τη βοήθεια των πλαγκτονικών και βενθονικών τρηματοφόρων καθώς και με τον προσδιορισμό ασβεστολιθικών ναννοαπολιθωμάτων όπου ήταν εφικτό. Τέλος, ολοκληρώνουμε με τη μελέτη του ολικού οργανικού άνθρακα και των ισοτόπων του οξυγόνου και του άνθρακα με σκοπό την αναγνώριση πιθανών Ανοξικών Επεισοδίων και παλαιοκλιματολογικών συνθηκών. Η λεπτομερής μικροφασική ανάλυση των ιζηματογενών δομών και των πρώιμων διαγενετικών χαρακτήρων οδήγησε στην αναγνώριση έντεκα λιθοφάσεων/μικροφάσεων (φάσεις απόθεσης και διαγενετικές φάσεις) στην περιοχή μελέτης. Αυτές μπορούν να ομαδοποιηθούν σε τέσσερεις ενότητες (βαθειά υποπαλιρροιακή ενότητα, υποπαλιρροιακή, μεσοπαλιρροιακή και επιπαλιρροιακή), και αντιπροσωπεύουν τα αντίστοιχα περιβάλλοντα απόθεσης/Φασικές ζώνες:ΦΖ 9/ Eβαπορίτες πλατφόρμας, συνθήκες ξηρού κλίματος και αυξημένη αλατότηταςΠεριβάλλον απόθεσης: Ανοιχτή πλατφόρμα, παλιρροιακή ζώνη, επιφανειακό αβαθές παράκτιο περιβάλλον απόθεσης.Μικροφάσεις: ΜΦΤ-19 Λεπτοστρωσιγενή wackestone που κατά περίπτωση εξελίσσεται σε πελσπαρίτη με παραθυροειδείς δομές με ελάχιστα απολιθώματα, ΜΦΤ-20 Στρωματολιθικός wackestone-bindstone με φύκη και ΜΦΤ-21 Μη απολιθωματοφόρο δολομικρίτης.ΦΖ 8/ Περιορισμένη πλατφόρμα Περιβάλλον απόθεσης: Αποτελεί ένα σχετικά ήρεμο περιβάλλον περιορισμένης πλατφόρμας. Μικροφάσεις: ΜΦΤ-16 Packstone με πελοειδή, κατά θέσεις ογκοειδή και βενθονικά τρηματοφόρα, και ΜΦΤ-18 Grainstone με βενθονικά τρηματοφόρα. ΦΖ 7/ Ανοιχτή πλατφόρμα χαμηλής ενέργειας υδάτωνΠεριβάλλον απόθεσης: Ανοικτή λιμνοθάλασσα, κόλποι και στενά πίσω από το άκρο της εξωτερικής πλατφόρμας, βάθους κυμαινόμενου από λίγα μέτρα έως δεκάδες μέτρα, όπου η κυκλοφορία των υδάτων είναι πολύ μέτρια. Μικροφάσεις: ΜΦΤ-8 Βιομικρίτης τύπου Wackestone με βενθονικά τρηματοφόρα, οστρακώδη και Thaumatoporella, ΜΦΤ-9 Floatstone με ολόκληρα θραύσματα ρουδιστών και φυκών σε μικριτική μάζα και ΜΦΤ-10 Βιοκλαστικός ασβεστόλιθος τύπου Wackestone με θραύσματα διαφόρων σκελετικών κόκκων όπως βενθονικά τρηματοφόρα, ρουδιστές και φύκη.ΦΖ 7/ Υφαλογενής σχηματισμό στα περιθώρια της πλατφόρμαςΜικροφάσεις: ΜΦΤ-7 Βιολιθίτες ρουδιστώνΦΖ 3/ 4 Όριο υφαλοκρηπίδαςΠεριβάλλον απόθεσης: ‘Όριο βαθειάς υφαλοκρηπίδας.Μικροφάσεις: ΜΦΤ-3 Πελαγικό wackestone, μικριτική ιλύς η οποία περιέχει διάσπαρτα globogerinids και ραδιολάρια.Ολοκληρώνοντας θα πρέπει να προσθέσουμε πως με βάση τα αποτελέσματα των δΟ18, σε συνδυασμό με την παρουσία των βενθονικών τρηματοφόρων, η θερμοκρασία της περιοχής μελέτης την συγκεκριμένη χρονική περίοδο Ανώτερο Τουρόνιο-Κατώτερο Μαιστρίχτιο είναι περίπου 25οC. Στη περιοχή μελέτης όλα τα δείγματα που μελετήθηκαν έχουν περιεκτικότητα σε οργανικό υλικό μέχρι 0,05 % το οποίο είναι πολύ χαμηλότερο από το ελάχιστο απαιτούμενο 0,7 % για να είναι πιθανή ή γένεση υδρογονανθράκων. Στη βάση όσων έχουν προαναφερθεί και σύμφωνα με τα δεδομένα που προέκυψαν ύστερα από τη μικροφασική και μικροπαλαιοντολογική ανάλυση της περιοχής μελέτης, καταλήξαμε στο γεγονός ότι η συγκεκριμένη ανθρακική ακολουθία αποτελεί ανθρακική απόθεση εσωτερικής περιορισμένης πλατφόρμας με περιθώριο (rimmed platform) ή πλατφόρμα τύπου ράμπα καθώς οι Μικροφασικοί τύποι που προσδιορίστηκαν και η κυκλική οργάνωση ταιριάζουν και στις δύο περιπτώσεις, ηλικίας Κονιάσιο (UC10) έως Μαιστρίχτιο (UC 15d-17) του Ανώτερου Κρητιδικού .

The Cauvery Basin at the southeastern tip of the Indian plate was an Albian to Danian marine embayment. The Dalmiapuram Formation is composed of bioclastic wackestone and coral boundstone. Benthic foraminifera and calcareous algae are relatively common in the Dalmiapuram Formation. The fossils support an age range of upper Albian to Cenomanian, which complements previously reported nannofossils that suggest an early Albian to Turonian age. The low diversity assemblage of foraminifera and calcareous algae and other organisms in the Dalmiapuram Formation is characteristic of a near-shore carbonate shelf or ramp. The low diversity and abundance of planktic species with coral and coral-algal buildups suggests more offshore conditions, probably within storm wave-base. The δ13C and δ18O values vary greatly. The absence of correlation between Mn and Sr indicates that these limestones retain their primary isotopic signatures. Gray shale/limestone unit has positive carbon isotope excursion (CIE) of ~ 0.8 to 1.0‰ that correlate with OAE 1c event. Similarly, significant positive CIE noticed in the lower part of the coral algal limestone is attributed to OAE 1d event. This suggests that oceanic conditions that created deep-water low oxygen conditions affected the shallow-water photic zone.

This studied rocks form part of the southern Hazara basin in the NW Himalayan Fold and Thrust belt, Pakistan. Thick inner to mid ramp carbonate platform deposits of Samana Suk Formation (Bajocian-Callovian) mostly composed of medium to thick bedded limestone with occasional dolostone beds are exposed in various localities. In the present studies, attempt has been made to understand degree of diagenetic alterations (i.e., dolomitization) within various limestone facies due to fluid-rock interaction phenomenon, and its impact on the reservoir behavior of altered rocks based on field investigations, petrographic studies, stable isotope signatures and porosity/permeability analysis. Field observations revealed various limestone types (oolitic, burrowed, fossiliferous, micritic and sandy), whereas dolomite occurs as completely replacive phase (Dol-I), and partially replacive patchy bodies (Dol-II) respectively. Petrographic studies showed various limestone and dolomite facies, which include: (i) Grainstone facies (bioclastic grainstone, peloidal grainstone, ooidal grainstone and pel-bioclastic grainstone), (ii) Packstone facies (bioclastic packstone and peloidal packstone), (iii) Wackestone facies (bioclastic wackestone), (iv) Mudstone facies (lime mudstone, and (v) Dolomite facies (coarse crystalline strata-bound Dol-I, and fine crystalline patchy Dol-II) respectively. O/C isotope analysis revealed that Dol-I shows signatures of δ18O (−5.84 to −3.91‰ V-PDB), and δ13C (+0.6 to +2.37‰ V-PDB) are within the limit of the carbonate marine seawater signatures, hence originated from sea-water or modified sea-water, whereas Dol-II exhibited depleted δ18O values (−6.88 to −5.87‰ V-PDB) and slightly depleted δ13C signatures (+0.968 to +1.85‰ V-PDB), indicating high temperature dolomitizing fluids. During early stage of marine diagenesis, which resulted in the cementation of pores within the grainstone-packstone facies, whereas mudstone-wackestone facies remained unaltered due to low porosity and permeability. Late stage dolomitization caused partial to complete alteration of mudstone-wackestone facies, in contrast grainstone-packstone facies are not affected by dolomitizing fluids due to the fact that the pore network of these coarser facies had already been occluded by the preceding marine cementation event. Porosity and permeability analyses revealed relatively high porosity values (4–8%) and permeability values (11.5 mD) in the dolomitized facies, whereas unaltered limestone facies showed considerably low porosity/permeability values (> 1%). In conclusion, less porous/permeable fine-grained facies evolved into more porous and permeable units due to the interaction of dolomitizing fluids of hydrothermal origin, which confirms that the original sedimentary texture of rock has implications on the selectivity of any diagenetic alteration.

espanolThe Valles-San Luis Potosi Platform is part of an extensive carbonate platform system that rimmed the ancestral Gulf of Mexico during the middle (Albian) through Upper Cretaceous. The El Abra Formation consists of a shallow-water deposit; it contains a benthic foraminiferal assemblage that includes 18 species, which are described and illustrated in this paper. The studied successions from the upper part of the El Abra Formation were dated as mid-late Cenomanian. On the basis of these findings, two zones are proposed Pseudolituonella reicheli Assemblage Zone and Nezzazatinella picardi Interval Zone. The first Assemblage Zone is characterized by an abundant benthic foraminiferal association. It is overlain by the Nezzazatinella picardi Interval Zone where the species richness of the fora-miniferal assemblage is reduced and later disappears. The benthic foraminiferal demise is coincident with major sea-level changes and an increase in siliciclastic input from the hemipelagic deposit of the Soyatal Formation, which contains abundant pithonellids and r and r-k strategist planktic foraminifera (Whiteinella archaeo-cretacea Partial Range Zone). Two stratigraphically correlative facies have been recognized in the El Abra Formation: the Taninul and the El Abra Facies. A warm, shallow-water, open marine platform deposit (Taninul Facies) is inferred. It includes peloidal-foraminiferal packstone, packstone-grainstone, and packstone- wackestone. A restricted environment (El Abra Facies) can be deduced from the abundant miliolids and ostreids. The texture is a wackestone-packstone. Another microfacies (Soyatal Formation) consists of wackestone-packstone with an acme of pithonellids and the occurrence of r and r-k strategist planktic foraminifers deposited during the platform drowning. EnglishLa Plataforma Valles-San Luis Potosi es parte de un sistema de plataformas extenso que se encontraba bordeando el antiguo Golfo de Mexico en el Albiano hasta el Cretacico Superior. La caliza El Abra es un deposito de aguas poco profundas; esta contiene un conjunto de foraminiferos bentonicos que incluye 18 especies, que se describen e ilustran en este documento. Las sucesiones estudiadas de la parte superior de la Formacion de El Abra fueron datadas como del Cenomaniano medio- tardio; se proponen dos zonas (Zona de Conjunto Pseudolituonella reicheli y Zona de Intervalo Nezzazatinella picardi). La primera Zona de Conjunto se caracteriza por una asociacion abundante de foraminiferos bentonicos. Esta sobreyacida por la Zona de Intervalo Nezzazatinella picardi donde se reduce la riqueza de especies de las asociaciones de foraminiferos y luego desaparece. La desaparicion de foraminiferos bentonicos es coincidente con grandes cambios de nivel del mar y un aumento en el aporte de sedimentos desde el deposito hemipelagico de la Formacion Soyatal que contiene abundantes pithonelidos y foraminiferos planctonicos de estrategia r y r-k (Zona de Alcance Parcial (Whiteinella archaeocretacea)). Dos facies estratigraficamente correlacionables han sidoreconocidas en la Formacion El Abra: la Facies Taninul y la Facies El Abra. Se infiere un deposito de plataforma marina abierta de aguas calidas someras (Facies Taninul). Esta incluye un packstone peloidal con foraminiferos, packstone y packstone-wackestone. Un ambiente restringido (Facies El Abra) puede deducirse por los abundantes miliolidos y ostreidos. La textura de la roca es un wackestone-packstone. Otra microfacies consiste de un wackestone-packstone con un auge de pithonelidos y la presencia de foraminiferos de estrategia r y r-k depositados durante la inundacion de la plataforma (Formacion Soyatal).

The current work is focused on the rock typing and flow unit classification for reservoir characterization in carbonate reservoir, a Yamama Reservoir in south of Iraq (Ratawi Field) has been selected, and the study is depending on the logs and cores data from five wells which penetrate Yamama formation. Yamama Reservoir was divided into twenty flow units and rock types, depending on the Microfacies and Electrofacies Character, the well logs pattern, Porosity–Water saturation relationship, flow zone indicator (FZI) method, capillary pressure analysis, and Porosity–Permeability relationship (R35) and cluster analysis method. Four rock types and groups have been identified in the Yamama formation depending on the FZI method, where the first group represents the bad reservoir quality (FZI-1) (Mudstone Microfacies and Foraminiferal wackestone Microfacies), the second group reflects a moderate quality of reservoir (FZI-2) (Algal wackestone–Packstone Microfacies and Bioclastic wackestone–Packstone Microfacies), the third group represents good reservoir quality (FZI-3) (Peloidal Packstone–Grainstone Microfacies), and the fourth group represents a very good reservoir quality (FZI-4) (Peloidal–oolitic Grainstone Microfacies). Capillary pressure curves and cluster analysis methods show four different rock types: a very good quality of reservoir and porous (Mega port type) (FZI-4) (Peloidal–oolitic Grainstone Microfacies) with a low irreducible Water saturation (Swi), good quality of reservoir and porous (Macro port type) (FZI-3) (Peloidal Packstone–Grainstone Microfacies), moderate quality of reservoir (Meso port type) (FZI-2) (Algal wackestone–Packstone Microfacies and Bioclastic wackestone–Packstone Microfacies), and a very fine-grained with bad reservoir quality (Micro port type) (FZI-1) (Mudstone Microfacies and Foraminiferal wackestone Microfacies) and with the higher displacement of pressure). These capillary pressure curves support the subdivision of the main reservoir unit to flow units.

WOS: 000471294100010, Ilerdian (early Eocene) carbonates in the northwestern Tosya region, northern Turkey, are characterized by porcellaneous larger benthic foraminifera; Glomalveolina, Alveolina, Orbitolites, Opertorbitolites and Cyclopertorbitolites are common in the southeastern Kastamonu region, in facies deposited on a low-gradient carbonate ramp. The inner ramp comprises of Miliolid-soritid wackestone, Soritid wackestone, Alveolinid-soritid wackestone-packstone, Alveolinid wackestone, Alveolinid-Nummulitid wackestone-packstone, algal wackestone, and Coralline algal pack-grainstone microfacies. The middle ramp deposits are composed of Alveolinid-nummulitid wackestone-packstone and Nummulitid wackestone-packstone microfacies. Overall, the succession reflects a long term deepening trend.

Deposition environment and diagenesis processes are very important factors which affect and control the reservoir properties. The carbonate Mishrif Formation has been selected as a carbonate reservoir in selected wells from southeastern Iraq to understand the influence of the Deposition environment and diagenesis processes on the carbonate reservoir. A core examination of thin sections, shows that Mishrif Formation comprises of six depositional environments, these are: deep marine, lagoon, rudist biostrome, back shoal, and shallow open marine. These environments have effect by many diagenetic processes, including dolomitization, dissolution, micritization, cementation, recrystallization and Stylolite, some of these processes have improved the reservoir properties of the Mishrif reservoir, these are: dissolution, dolomitization and the stylolization. The others diagenetic processes have negative influence on the Petrophysical properties, such as cementation, compaction, and recrystallization processes, which damage the porosity and decrease the pore size. The reservoir properties are controlled by deposition environment, where lagoon environment is mostly compact with low porosity, shoal environment reflects a high energy and grain-supported environment and has good reservoir potential, deep-marine environments consist of mudstone to wackestone, which represents low energy level with low porosity and represents the non-reservoir environment.

The carbonate platform deposits of the Angostura Formation are widely distributed in the central and eastern part of the Sierra de Chiapas, SE Mexico. The Angostura Formation contains a rich assemblage of foraminifera associated with mollusks (rudists, gastropods), corals, and dasycladacean green algae. A detailed foraminiferal study was carried out on samples from the El Coyol section of the Angostura succession. The studied section crops out in the El Coyol Hacienda located north of the Angostura dam, SE of the city of Tuxtla Gutierrez in Central Chiapas. The foraminiferal assemblage consists mostly of benthic larger foraminifera but minor pelagic influence is represented by the presence of a number of planktic foraminifera. The benthic foraminiferal association is taxonomically diverse, being composed of Chubbina jamaicensis Robinson, Chubbina macgillavry Robinson, Caribealveolina michaudi Pecheux, C. fourcadei Vicedo, Caus and Frijia, C. obesa (Fourcade and Fleury), Praechubbina breviclaustra Fourcade and Fleury, Omphalocyclus macroporus (Lamarck), Asterorbis rooki Vaughan and Cole, Vaughanina cubensis (Palmer), V. barkeri, Bronnimann, Sulcoperculina dickersoni (Palmer), S. globosa de Cizancourt, S. vermunti (Thiadens), Lepidorbitoides minima Douville, Orbitoides cf. O. apiculata Schlumberger, Planorbulina cretae (Marsson), Smoutina cruysi Drooger, and Nezzazatinella sp. In addition, the occurrence of Fleuryana adriatica De Castro, Drobne and Gusic, Rhapydionina cf. R. liburnica Stache, Cuneolina ketini Inan, Valvulina cf. V. triangularis d'Orbigny and Minouxia sp. is documented for the first time from the Angostura Formation. The planktic foraminifera are Rugoglobigerina macrocephala Bronnimann, R. cf. R. hexacamerata Bronnimann, R. rugosa (Plummer), Kuglerina rotundata (Bronnimmann), Muricohedbergella monmouthensis (Olson), Planoglobulina cf. P. carseyae (Plummer), Globotruncanita stuarti (de Lapparent), Globotruncanita pettersi (Gandolfi), Planoheterohelix globulosa (Ehrenberg), Pseudoguembelina sp., Macroglobigerinelloides prairielillensis (Pessagno) and the pithonellids Pithonella ovalis (Kaufmann) and P. sphaerica (Kaufmann). The age of the Angostura Formation in the studied section is late to latest Maastrichtian. A Chubbina jamaicensis Taxon Range Zone is proposed on the basis of the occurrence of the nominal taxon and foraminiferal association. The lithological and faunal evidence enable the paleoenvironment to be reconstructed. The microfacies (wackestone–packstone, wackestone–floatstone, wackestone, grainstone and packstone) as well as the foraminiferal assemblage suggest that the deposit was developed in a shallow water marine setting with low to moderate energy, with sporadic intercropping of an open platform deposit characterized by planktic foraminifera and pithonellids. The paleobiogeographical distribution of the foraminiferal association from the Angostura Formation contains cosmopolitan genera as well as endemic forms of the Caribbean Province from the Tethys Realm.

The municipality of the town of Ulldecona (Catalonia) is notable for extensive quarrying activities, which exploit limestone, popularly named Stone from Ulldecona, for ornamental and building purposes. The Stone from Ulldecona, commercially known as Senia stone, is one of the most important ornamental and building stones quarried in Catalonia, and is used worldwide in all kinds of public and private buildings. Little is known about the geological nature of this stratigraphic interval of commercial value. Therefore, this study explores the geology of the Stone from Ulldecona in open pit quarries and natural outcrops. The Stone from Ulldecona consists of limestones of upper lower Aptian age, including wackestone, packstone and grainstone textures containing peloids, miliolids, Palorbitolina lenticularis, Orbitolinopsis simplex, Paracoskinolina maynci, Lithocodium aggregatum, Choffatella decipiens, Salpingoporella muehlbergi, Chondrodonta, Toucasia carinata, Polyconites sp. and Mathesia darderi. These platform carbonates rich in orbitolinids and rudists belong to the Villarroya de los Pinares Formation of the Maestrat Basin. Locally, the limestones are highly bioturbated and/or dolomitized. Dolomitic limestones, calcitic dolostones and dolostones are stratabound tabular geobodies with thicknesses of up to 60 m. Dolomitic limestones and calcitic dolostones corresponding to initial and intermediate stages of dolomitization mainly exhibit isolated euhedral dolomite crystals or idiotopic mosaics. Dolostones (advanced dolomitization stages) are sucrose, exhibit vacuolar and cave porosities, and are characterized by idiotopic and hypidiotopic mosaics, which indicate temperatures lower than 50-60 °C during dolomitization. Dolomite textures are mainly fabric-destructive and pervasive, but locally retentive and/or selective fabrics also occur. The limestones of the Villarroya de los Pinares Formation, the underlying marls of the Forcall Formation and the overlying marls and platform carbonates of the Benassal Formation examined can be arranged into two high-rank, low-frequency transgressive-regressive sequences. Similar coeval long-term transgressive-regressive trends have been reported from other basins, indicating that eustatism largely controlled accommodation of the Aptian succession studied in Ulldecona.

A new dasycladalean alga is described as Uteria naghanensis n. sp. from the late Maastrichtian Tarbur Formation of the Zagros Zone, SW Iran. It is a small to medium-sized, rather well calcified species with small articles each bearing one fertile ampulla, alternating with close-set verticils of numerous sterile laterals. Another characteristic is its comparably wide main axis. The genus Uteria Michelin was so far only known from the Paleogene (Danian-Lutetian). The discovery of U. naghanensis n. sp. in inner platform wackestone of the Tarbur Fm. documents the origination of the genus already in the uppermost Cretaceous within an area belonging to the Arabian Plate.

During the Late Jurassic, stromatoporoid-rich buildups were developed in south and intra-Tethys realms. These stromatoporoid buildups are mainly characterized by the high percentage of intraclastic-bioclastic debris, as main components of buildup bodies. However, the source of hydrodynamic energy resulted in debris production, is still a matter of debate. This study examines the Upper Jurassic-Lower Cretaceous stromatoporoid-rich buildups of Monte Sacro Limestones (MSL), Apulia Carbonate Platform (ACP), in order to describe the main carbonate facies along the study area, as well as the possible source of turbulence. Three main lithofacies have been distinguished: LF1 — stromatoporoid-rich facies with two subfacies (LF1-S1: floatstone with wackestone to fine-grained packstone, LF1-S2: rudstone-floatstone with intraclastic-bioclastic packstone-grainstone), LF2 — stromatoporoid-coral facies distributed in wackestone to packstone matrix (LF2-S1) and tabular stromatoporoid-corals surrounded by wackestone matrix (LF2-S2) and, LF3 — stromatoporoid-microbial facies. These facies were deposited along the mid part of a distally steepened ramp. The in-situ form of stromatoporoids was developed in a mud-dominated matrix (LF1-S1) under low-energy conditions while the intraclastic-bioclastic rich facies (LF1-S2) were deposited under a high-energy condition. The distribution of LF2 and LF3 in muddy matrix suggests occurrence of these lithofacies in quiet environments. The biotas were influenced by several factors including nutrient and light availability as well as by hydrodynamism. The stromatoporoid-rich buildups in ACP can be categorized as phototrophic-heterotrophic reefs generated in a pure carbonate environment. The light penetration was confined, resulted in the high development of light-independent micro-encrusters (Tubiphytes morronensis), in a mesophotic condition, where the environment was not ideal for light-dependent microencrusters (Lithocodium-Bacinella) to grow. We suggest that debris-dominated stromatoporoid-rich lithofacies (LF1) thrived in meso-oligophotic setting, along the nutricline and were affected by more than episodic high-energy events in a context where the surface waves were not effective. In such environments, internal waves can be an effective candidate to explain the episodic turbulences to produce the debris-rich facies of LF1-S2. Moreover, internal waves can pump the nutrient-rich waters to the buildups, and create an ideal setting where these metazoan communities thrived.

The Early Eocene Chorgali Formation, Eastern Salt Range has been investigated for microfacies, depositional and reservoir analyses. The Formation consists of light to dark gray limestone with shale intercalations. The identified microfacies of Chorgali Formation are: (a) Foraminiferal bioclastic wackestone, (b) Benthonic foram-rich wackestone, (c) Bioclastic wacke-packestone, and (d) Miliolidal bioclastic wackestone. These microfacies represent wackestone depositional fabric with major faunal assemblage of Nummulites, Lockhartia, Assilina, and Miliolids. The environment of deposition is consistent with distal middle to proximal inner ramp settings. Diagenetically, the Chorgali Formation is affected by neomorphism, micritization, rare sparitization, dissolution, microfracturing, chemical and mechanical compactions and very rare dolomitization. Among these features, dissolution, micro-fracturing are the porosity-enhancing processes that increase the reservoir potentiality of the Chorgali Formation. The core plug porosity and permeability values of surface samples are 3.91% and 0.244 mD, respectively, depicting that surface sample porosities are comparatively lower than the subsurface porosities. The petrophysical analysis of the two wells (Balkassar-OXY-01 and Turkwal Deep-01) established that Eocene Chorgali Formation with dominant limestone facies at certain depths has suitable reservoir parameters. The Early Eocene Chorgali Formation of Pakistan depicts analogous features to that of the Early Eocene Naredi Formation (shale and carbonate member) of the Kutch Basin of Western India, based on the Nummulites and Assilina species, depositional fabric and depositional environment. This endeavor may be implied to the future studies of the Chorgali Formation as a hydrocarbon reservoir either in some unexplored oil or gas fields or to extend the limits of already explored fields along with the academic insights.

The main goal of the paper is the reconstruction of a Middle Triassic buildup cropping out in the central part of the Southern Apennines. Middle Triassic reefs of the western Tethys realm are well known in the Northern and Southern Alps. In contrast, few studies of the Anisian–Ladinian carbonate platforms of the southern Apennines are available, due to the diagenetic alteration and tectonic disruption that hinder their paleoenvironmental and stratigraphic reconstruction. In an attempt to fill this gap, and to improve the knowledge on the Anisian–Ladinian carbonates of central Mediterranean area, this research is focused on a carbonate buildup cropping out in the “La Cerchiara” area, Sasso di Castalda (Basilicata, Southern Italy). The buildup, affected by intense tectonic deformation associated with the development of the Apennine thrust and fold belt, was studied using a statistical evaluation of the quantitative microfacies data. The research enabled a reconstruction of the original stratigraphic relationships of the various buildup fragments. A positive linear regression between the sample positions vs the percentage of autochthonous carbonates indicates an increase of the autochthons carbonate toward the top of the succession. The allochthonous fabrics (packstone/wackestone) at the base of the section (Unit IIIa) pass gradually upward into autochthonous (boundstones) facies (Units IIIb, I), consisting of microbialites (clotted peloidal micrite, microbial-derived laminae, and aphanitic micrite), microproblematica and cyanobacterial crusts, with few encrusting skeletal organisms. Statistical data suggest that units IIIa, IIIb, and I are in stratigraphic order while unit II appears to have been moved by tectonic dislocation from its original position at the base of the succession. The absence of metazoan reef framework, and the richness of micro-encrusters, autochthonous micrite and synsedimentary cements, suggest a mud-mound style of growth for the carbonate bodies of the Southern Apennine during the Anisian.

The Nammal Formation of Early Eocene age crops out at Nammal Gorge (NG) and Pail (PL) in the Salt Range, Upper Indus Basin, Pakistan. It comprises mainly medium to thick-bedded and rare thin-bedded limestone with mixed carbonate sequences of limestone, marl, and shale. Allochemical constituents and micrite estimated ratio leads in recognizing seven microfacies including Foraminifer wackestone, mudstone-wackestone, Foraminifer mudstone, and Assilina wackestone in the NG section and Foraminifer wackestone-packstone, Foraminifer wackestone, and Bioclastic packstone in PL section. Based on microfacies and fossil assemblages, the Nammal Formation is interpreted to have been deposited in outer to mid and inner ramp settings. The formation is largely transformed by diverse diagenetic episodes comprising micritization, cementation, dissolution, neomorphism, mechanical compaction, stylolitization, fractures, and vein formation. Fractures and dissolution are inferred to augment the prospect of hydrocarbon for reservoir of the Nammal Formation. ImageJ calculated porosities and log estimated average effective porosity range from 4 to 6% and 1 to 2%, respectively. The calculated log values in Dhermund-01 and Pindori-02 wells suggest that at certain limestone intervals of the encountered Nammal Formation, there is a compacted limestone that can be regarded as a tight reservoir for hydrocarbon accumulation.

Alternations of thin-bedded limestone and shale, or ribbon rock, commonly occur throughout lower Palaeozoic carbonate successions; however, their formative processes are still unclear. In this study, we discuss the origin of the ribbon rocks of the upper Cambrian Hwajeol Formation, Korea, based on detailed microfacies analysis of a ~ 2-m-thick interval. Five sedimentary microfacies were identified: normally graded calcarenite to shale; parallel-laminated shale; lime mudstone; wackestone-to-packstone; and bioclastic–intraclastic packstone-to-conglomerate. Shale facies were most likely formed by frequent storm-induced bottom currents, whereas, lime mudstone facies were deposited in situ by suspension settling of micrite, mudflows, or growth of keratose sponges on the seafloor, and/or formed by early diagenetic growth. Conglomerate/packstone/wackestone indicate infrequent, larger-scale events, e.g., mega-storms, tsunamis, or earthquakes. We propose a new formative model for tempestite-type ribbon rock based on the Hwajeol example, and suggest that this model can be differentiated from the other types of ribbon rocks—tidalite, turbidite, and diagenetic types. Formation of the tempestite-type ribbon rocks would have been promoted by the characteristic environmental conditions of the early Palaeozoic, in particular sea-water chemistry that promoted calcite precipitation and the paucity of burrowers. Detailed microscopic observations can thus provide clues to elucidate previously unknown sedimentary processes in the deeper parts of carbonate platforms.

In this study, two stratigraphic sections of Sarvak Formation were selected which are nominated Bavan and Kherameh sections. Over 379.5 meters of the Sarvak Formation and 260 thin sections have been studied. Index microfacies and foraminifers have been identified. Index microfacies include Boundstone, Wackestone and Packstone. The frequency of bioclast has been determined as larger that of the other microfacies elements. Based on the type and abundance of skeletal and nonskeletal grains and type of matrix, 14 sublithofacies have distinguished in 3 depositional environments which are include 1) Lagoon 2) Reef 3) Open marine. The mentioned determined microfacies were deposited in a Carbonate Platform of Homoclinal Ramp. Based on micropalentological data, the age of the Sarvak Formation is assigned to Cenomanian.

The Lower Cretaceous limestone of the Qamchuqa Formation (QF) in the studied area is located in the northeastern limb of Piramagroon Anticline, Sulaymaniyah Governorate, northeastern Iraq. A section is sampled and 103 samples are collected. From these samples, 106 thin sections are prepared for petrographic analysis under binocular and polarizer microscopes. Qamchuqa Formation is usually mostly dolomitized and microfossils are totally or partially destroyed, but fortunately, the studied section is affected by dolomitization only in the upper part, the lower and middle parts are not dolomitized and are rich in well-preserved microfossils of benthic foraminifera with some algae and corals. The purpose of this study is to determine the microfacies, depositional settings, microfossil assemblages, and age. Based on the petrographic studies of the thin sections, seven main types of microfacies are identified, which are represented by grainstone, packstone, wackestone, bindstone, boundstone, rudstone, and mudstone with other six subtypes. Analysis of these microfacies indicates that the Qamchuqa Formation is deposited in shallow water to open marine environments including intertidal, subtidal, lagoon, shoal, and middle ramp. Very rich benthic foraminiferal assemblages are studied and analyzed in thin sections. Twenty-four species of benthic foraminifers belonging to eighteen genera and one species of algae are recognized, of which sixteen species of benthic foraminifera are discovered for the first time. These fauna assemblages indicate the age of Early Hauterivian to Late Cenomanian.

This article describes a 135-m-thick sequence collection from the lower Eocene limestones of the Dungul Formation that caps the Sinn El-Kaddab Plateau in the Kurkur area. A sedimentological evolution model of these limestones has been constructed for the first time primarily based totally on lithology, microfacies analysis, SEM microscopy, and EDAX microchemical analyses. This carbonate sequence has been subdivided into three shallowing-upward facies. The hemipelagic facies at the base is dominated by foraminiferal wackestone, unconformably overlain by shallow offshore facies dominated by larger benthic foraminiferal grainstone and packstone, and capped by middle ramp facies dominated by bioclastic grainstone and packstone. These facies are analog of the Eocene facies of the Tethys Sea that had been formerly defined from Libya, Tunisia, Spain, and Kirkuk oil field in Iraq. Results suggest deposition in a basin characterized by oscillation in relief, in response to tectonic uplifting coupled with eustatic sea fluctuations associated with and the Syrian arching system. The limestones exhibit four successive diagenetic stages. The first stage is early marine diagenesis with the formation of micrite rim cement and preferential micritization of some skeletal grains. The second stage is shallow burial diagenesis, compaction, drusy calcite cement, and silicification. The third stage is meteoric diagenesis, the formation of isopachous calcite rim cement, dissolution and formation of blocky cement. The fourth stage is vadose diagenesis which includes karstification and ferrugination with iron oxy-hydroxides impregnation.

Given increasing importance of tertiary reservoirs in the Middle East, the Miocene (Upper Aquitanian to mid-Langhian) Dam Formation in eastern Saudi Arabia was cored along a 40 km transect, to develop a high-resolution sequence framework, and examine the role played by astronomical forcing, moderate glacio-eustasy (20- to 40-m sea-level changes), and tectonic deformation in this distal foreland setting. The Dam Formation (up to 80 m thick) contains updip siliciclastics which interfinger downdip with marine carbonates. Siliciclastic facies include paleosol-capped, red mudrock (mudflat), green and gray mudrock (near-shore siliciclastic lagoon), rare mud clast–bearing sandstone (fluvial), and massive very fine to medium sandstone (terrestrial sand sheets, rare tidal channels). Carbonate facies include brecciated carbonates (paleosols), lime/clay-clast quartz wackestone (lag gravel), carbonate laminites and microbial heads and mounds (tidal flat and shallow subtidal), argillaceous quartzose marl (near-shore lagoon), peloid mudstone-wackestone (restricted lagoon), variably quartzose skeletal peloid mudstone to packstone (open lagoon), oolitic grainstone (hypersaline beach, tidal channel), mollusk packstone (hypersaline lagoon border), and foram-mollusk packstone-grainstone (seagrass meadows). The Dam Formation contains eight sequences, each of which contains 2 to 4 parasequence sets or individual parasequences. Sequences and individual parasequences are capped by paleosols and/or erosion surfaces, and microbial laminite caps are rare. Bases of parasequences locally are veneered with ravinement gravel lags or siliciclastics beneath shallowing-upward subtidal carbonates, and lack intercalated deeper water facies. Statistical analysis of core-gamma ray (API) vs depth (m) shows that accumulation rates were ~ 3 to 4 cm/kyr, considerably faster than long-term accommodation rates (~ 1.2 cm/kyr), indicating deposition occurred for only 40% of the time, the remainder of the time being non-depositional during many short-term lowered sea levels, evidenced by the coeval oceanic δ18O curve. Spectral analysis of the core-gamma ray logs show astronomical forcing within the eccentricity, obliquity, and precessional bands. Spectral analysis indicates that the eight Dam sequences (average 10 m thick, range

Oil shale deposits of the mid-Eocene Wadi Shallala Formation in northern Jordan consist of organic-rich limestones and chalks. These organic-rich deposits are exposed at the surface near Wadi Ash Shajara, in a 12-m-thick outcrop. For this study, a total of 21 oil shale samples were analysed for bulk elemental geochemistry, inorganic geochemistry, organic geochemistry and microfacies analysis. Three microfacies types were recognised: pelagic mudstone/wackestone, foraminiferal packstone and bioclastic packstone/wackestone. The observed cyclicity of these microfacies in the study area indicates fluctuations in depositional conditions in Neo-Tethys during the mid-Eocene. A shallow-water, calm, restricted marine environment with limited water circulation and low energy currents evolved into a deeper-water environment with open circulation at or just below the wave base. Wadi Shallala Formation in Wadi Ash Shajara composes mainly of chalk (CaCO3 = ~92 wt%) with a TOC of up to 5 wt % and comprises abundant calcareous nannofossils, foraminifera and ostracods as well as non-clastic components like calcitic fragments. The sulphur content of the analysed samples is significant (1.24 wt %) and is associated with the organic matter. Redox-sensitive elements (Fe, Ni, Zn, S and Zr) are enriched in the oil shale samples, indicating an anoxic depositional environment fluctuating between euxinic and sub-euxinic. These fluctuations in depositional conditions of the basin are a result of many factors such as climate, and tectonisms affected deposition of oil shales during Middle Eocene time.

Anoxic sinkholes are unique geomorphological features of modern reef systems and in terms of “lake-like” sediment successions very special marine depositional environments. This study presents results of a sedimentological survey, which focuses on the “Great Blue Hole”, a circular Pleistocene karst cavity, situated in the shallow eastern lagoon of Lighthouse Reef Atoll (Belize, Central America). The investigated Blue Hole is located within the tropical cyclone belt and acts as consequence of its unique geomorphology as a giant sediment trap for both fair weather and storm sedimentation. As an important innovation step, we applied a multi-proxy approach based on textural, compositional and geochemical data to ensure a more reliable differentiation between sediments with fair weather and storm condition affiliation. Sediments having formed under both conditions were texturally categorized by determination of classical sedimentary parameters such as mean grain size and sorting. Sediment composition has been quantified in thin sections based on 40 samples discretely taken along a core from the bottom of the 125 m deep and 320 m wide cavern. Classification of sedimentary facies follows a modified scheme for unconsolidated carbonate sediments based on the Dunham nomenclature. Fair-weather sediments are generally finer than 20 μm and consist on average of 81% carbonate fine material, 12% Halimeda platelets, 3% coral fragments, 2% organic material, 1% mollusc shells, 1% foraminifer tests, and minor portions of coralline red algae and echinoderm plates (0–1%). Intercalated event bed sediments are coarse-silt to sand-sized (> 20 μm) and differ in terms of generally lower fine carbonate material amounts (50%) and increased abundances of over-washed Halimeda platelets (28%) and coral fragments (6%). Combined analyses of this study have revealed four primary sedimentary facies with affiliation either to the background (mudstone) or cyclonic event sedimentation (Halimeda wackestone, algae-rich packstone, coralgal rudstone) as well as a transitional sub-facies indicating storm-induced background overprinting (background wackestone). The striking compositional and textural differences of the Halimeda wackestone, algae-rich packstone and coralgal rudstone facies are considered to be another helpful (semi)-quantitative proxy to identify event beds of tropical cyclones in unconsolidated sinkhole sediment successions.

Summary With advancement of drill and hydraulic fracturing technologies, shale gas are blooming in recent years. The Middle East also pays high attention to unconventional plays. The Diyab source in western UAE deposited in an intra-shelf basin with mudstone, wackestone, and high argillaceous-carbonaceous matters in the low section. This set is widely developed with high TOC, thickness, maturity and is evaluated to be the main unconventional play of gas bearing. Based on data of wells, cores and seismic, a procedure of basin modelling was implemented to regionally evaluate the Diyab. Generally, good source of the Diyab performs TOC 2-4%, with maximum of 5.2%. Thickness of net play ranges around 100-150ft. This formation has high maturity of Ro 1-1.4. Hydrocarbon generation and expulsion intensity from basin modelling are 25bcf/km2，20bcf/km2 respectively. Focusing on the most favorable area, sweet spot was predicted to capture key parameters of TOC, brittleness, porosity, fracture and strain & stress. Based on evaluation from the factors, one well was drilled in 2019 and yielded gas in vertical borehole after hydraulic fracturing. The result is encouraging and indicates unconventional gas potential in the Diyab.

Campanian planktonic foraminifera and calcareous nannofossil biostratigraphy in the Degala segment positioned in the Bina Bawi anticline in the Kurdistan region, NE Iraq, have been described in detail. The study is concentrated on the Kometan and Shiranish formational boundary which has not been defined formerly. The top of the Kometan Formation is pronounced by sharp variations in lithology from the replication of well-bedded hemipelagic limestone to glauconitic chalky limestone, blue-colored marlstone, and argillaceous limestone of the superimposing Shiranish Formation. The Tethyan standardization of biostratigraphy based on calcareous nannofossil and planktonic foraminifera can be applied to the scrutinized sequences and categorized it into three planktonic foraminiferal (Globotruncanita elevata, Globotruncana ventricosa, and Globotruncana falsostuarti) biozones which are utterly equivalent to two calcareous nannofossil (CC20 and upper part of CC22) biozones. The consecutive Radotruncana calcarata planktonic foraminiferal biozone which locally might be equal to the Uniplanarius sissinghii (CC21) and lower part of the Uniplanarius trifidus (CC22) calcareous nannofossil biozones are lacking. It refers to absences of early Late Campanian which signify the Arabian Plate distinct tectonics and obduction of ophiolite across the northeastern border of Iraq. Moreover, four different microfacies were recognized that include foraminiferal mudstone, foraminiferal wackestone, glauconitic foraminiferal wackestone, and ferruginous foraminiferal mudstone which represent the deposition in open marine environment to submarine disconformity or diastems.

Summary It is well known that naturally fractured carbonates can make important reservoirs and conduits for hydrocarbons in many basins worldwide. The brittleness of low porosity carbonates when subjected to high stress causes the rock to fail and form associated microfractures close to the failure event, thus, enhancing its porosity and permeability near and along faults and sharp flexures. Although development of these reservoirs can be complex due to the heterogeneous mobility pattern, steep production decline, potentially premature water breakthrough, among other issues, still vast reserves continue to be drained from them in many fields around the world. The deep water Salina Basin presents an excellent opportunity to explore for naturally fractured carbonate reservoirs in the Mesozoic. Regional paleogeographic studies supported by wells evidence the presence of shallow Upper Jurassic limestones and dolomites and basinal Cretaceous limestones. The dominant lithofacies is mudstone and wackestone followed by packstone and the porosity is low, concentrated in microfractures. Most wells targeting the Mesozoic were drilled at the top of structural and although the wells avoided penetrating faults, many of them exhibit microfractures but in general formation tests yielded low hydrocarbon production. Past and current experience exploring and developing naturally fractured carbonates dictate the need to drill wells, perpendicular to the fractures orientation and as close as possible to faults. The fracture orientation can be obtained from current regional stress state, fracture data from neighbor wells and anisotropic studies from 3C seismic if available. The low production of Mesozoic targeted wells in the deep water Salina Basin can be explained by the fact that those wells were drilled away from faults, which are the structural events that concentrate the highest fracture density, thus the best reservoir. Barring the obvious differences, a raw analogy that help understand the concept is that while channels are the reservoir fairways in siliciclastics, faults are the reservoir fairways in naturally fractured carbonates.

Summary The succession of the Eocene at the subsurface of october field (offshore Gulf of suez, Egypt) provides new data and contribution for the evolution of carbonate platform in the Eocene. Sidewall core samples that was obtained from Eocene carbonate sediments so far ascribed to the Thebes formation in the October hydrocarbon field in the Gulf of Suez (Egypt) was studied in terms of sedimentology, paleontology and depositional environment. The study of the Eocene carbonate facies in the October field revealed that 1) The succession is composed of pelagic foraminiferal limestone of varied color, containing abundant planktonic foraminifers and minor traces of chert. 2) Three microfacies are distinguished including wackestone of smaller planktonic foraminifera (53%), wackestone-packstone of planktonic foraminifera (39%) and packstone of planktonic foraminifera, 4) Nannoplankton and Foraminifers indicate that the studied succession is of early Eocene to middle Eocene age, 6) Lithology, fossil content and microfacies indicate a pelagic (basinal) depositional environment in an intraplatform basin at water depths of a few hundred meters. Finally, investigation of this Eocene succession showed that the studied section differs from the typical Thebes Formation concerning lithology, fossil content and facies, so a new Formation name has been introduced (Radwan Formation).

Banggai basin is a tertiary basin with potential carbonate reservoir rocks in Indonesia. The heterogeneity of carbonate rock in the Banggai Basin due to both depositional and post-depositional processes, and it is difficult to understand. Commonly, there are several factors which controlling the measurement of acoustic velocity under ambient conditions. Unlike siliciclastic rocks, carbonate rocks, in general, pose unique challenges regarding how porosity affects seismic velocity. Acoustic velocity on carbonate rocks is often influenced by heterogeneity level, particularly in rock fabric and pore type. This study focuses on the relationship of vp/vs ratio, lithofacies, rock fabric, diagenetic, and porosity. The results obtained are expected to be used to define rock class, which is expected to increase the drilling success ratio. The entire analysis was based on 61 core plug samples supported by P and S wave velocity, petrography analysis, and porosity. Petrographic analysis shows predominant lithofacies in Minahaki Formation are grainstone, while Tomori Formation was dominated by muddy carbonate (wackestone to packstone). The relationship of Vp/Vs ratio and porosity is generally obtained a linear trend. In both muddy carbonate and grainstone, Vp/Vs tends to increase with increasing porosity. The two types of carbonate rock can be separated clearly based on Vp/Vs and porosity.

Well-preserved fossil reef/mound-building communities and shallow microfacies have been recovered from Changhsingian platform−margin sponge reef at the Panlongdong Section and intraplatform sponge skeletal mound at the Yanggudong Section in NE Sichuan Basin, South China. The present contribution focuses on the palaeoenvironmental implication of the differentiated development processes on the platform−margin reef and intraplatform skeletal mound based on the palaeontology and sedimentology. Precise field assessments and macroscopic/microscopic qualitative observations led to the identification of five reef/mound-building community and 14 reef/mound-related microfacies in the 2 sections of Changxing Formation. In the Panlongdong platform−margin sponge reef, reef-building communities are recognized into Amblysiphonella Community, Preperonidella−Amblysiphonella Community, and Preperonidella–Sollasia Community in ascending order. The reef-related microfacies are mainly classified into calcisphere−pelletoid wackestone to packstone, crinoidal wackestone to packstone of shallow water bank environment, hypercalcified sponge bafflestone, calcareous algae−hypercalcified sponge binding framestone, hypercalcifed sponge−calcareous algae bindstone, and calcareous algae−hypercalcifed sponge rudstone of reef environment, and benthic foraminifera−calcareous algae wackestone to packstone of shallower water lagoon environment. Two mound-building communities can only be found in the Yanggudong intraplatform skeletal mound, including Preperonidella−Intrasporeocoelia Community of lower part and Preperonidella−Sollasia Community of upper part. The mound-related microfacies include calcisphere−calcareous algae wackestone to packstone, crinoidal wackestone to packstone and crinoidal packstone to grainstone of shallow water bank environment, hypercalcified sponge bafflestone and cyanobacteria−hypercalcified sponge binding bafflestone of skeletal mound environment, benthic foraminifera−calcareous algae packstone grainstone of shallower water bank environment and benthic foraminifera−calcareous algae wackestone to packstone of shallower water lagoon environment. These palaeontological and sedimentological analysis results have facilitated the classification of sponge reef and skeletal mound sections corresponding to a solitary shallow benthic zone into multiple microfacies attributed to variable environmental depositional conditions. The differentiated evolutional process of multiple reef/mound-building stages at the Panlongdong and Yanggudong sections clearly demonstrate a general shallowing-upward trend from an inner shelf setting to a supratidal and low energy lagoon environment.

In the present paper, sequence stratigraphy and microfacies of the Dariyan Formation in the two sections of the Gadvan and Zana Mountains located were studied in NE and NW of Shiraz (Fars province, SW Iran). An area of 429.5 m of the Dariyan Formation sediments was studied through 187 thin sections. Also, the index microfacies were closely identified. Generally, index microfacies of the studied thin section were mudstone, wackestone, packstone, and grainstone microfacies. Received paleontological data confirm Aptian–lower Albian age of the Dariyan Formation. According to the lithostratigraphic aspect, the lower contact of Dariyan Formation with the Gadvan Formation in the Gadvan Mountain was described as a gradual type and in Zana Mountain; disconformity was found due to the sign of water withdrawal. Given the upper contact of the Dariyan Formation concerning the formation percentage, contact disconformity was observed due to the changes in the Allochem element and the situation of the entity from water and also according to the high percentage of iron nodules and Gluconate. According to the sequence, stratigraphic studies in the section of Gadvan Mountain, the lower border of the Dariyan Formation with Gadvan Formation was in the gradual form [type 2 Sequence Boundary (SB2)] and there was a disconformity in the upper border of this formation with Kazhdumi Formation [type 1 Sequence Boundary (SB1)]. Dariyan Formation included the system tracts (transgressive system tract, early highstand system tract, and late highstand system tract). There was a disconformity in its lower of the Gadvan Formation and disconformity in its upper boundary with the lower of the part Kazhdumi Formation (SB1) and it included the system tracts (highstand system tract, transgressive system tract, and lowstand system tract). Overall, lap sequence grade3 was seen in the two sections.

A combined facies, petrography and isotope geochemistry reveal an extensive pedogenic alteration of platform carbonate deposits of the Upper Cretaceous Bagh Group in the western Narmada basin in central India. The highly fossiliferous carbonate sequence of the Bagh Group consists of two formations, the Nodular Limestone at the base, and the Bryozoan Limestone Formation at top. The Nodular Limestone Formation comprises primarily of mudstone and wackestone, with relics of bioclasts such as gastropods, echinoderms, molluscs, forams and calcispheres, reflecting a low-energy supratidal to upper intertidal environment of deposition. Prolonged pedogenesis leads to pervasive micritization, brecciation, desiccation and recrystallization. The overlying Bryozoan Limestone, dominated by packstone and planar laminated rudstone with bryozoans, gastropods, echinoderms/echinoid spines, and molluscs, indicates deposition within the lower intertidal environment with moderately high-energy conditions. Abundant meniscus cement and biomolds suggest meteoric vadose diagenetic modification, whereas, intense secondary micritization of sediments indicates prolonged calichification. The δ13C and δ18O ratios of both Nodular Limestone and Bryozoan Limestone formations are depleted than the normal marine values, indicating an extensive diagenetic resetting of the carbonates. While the meteoric cement is depleted in both δ13C and δ18O ratio, the burial cement shows a decrease of δ18O at constant δ13C. The pedogenetic horizons within the Bagh carbonates bear subtle evidence of subaerial exposures within the overall transgressive Bagh Group. A glauconite bed at the upper part of the Bryozoan Limestone Formation marks the top part of the transgressive deposit.

The Cretaceous Balambo Formation of the Western Zagros Fold-Thrust Belt, in the Iraqi Kurdistan region, was studied in three sections (the Baraw and Sazan outcrop sections and the Baranan-1.G1 well), using three different techniques for determining hydrocarbon generation potential. Optical techniques included studying thin sections and palynological slides, and a geochemical technique was also employed, by applying Rock-Eval pyrolysis to the samples. Lithologically, limestone and shale comprise the largest proportion of the formation. Five microfacies were identified: planktonic foraminiferal wackestone, radiolarian wackestone, fossiliferous wackestone-packstone, fossiliferous wackestone and fossiliferous mudstone-wackestone. The depositional environment of the Balambo Formation was determined to have been an outer shelf–deep water bathyal environment, and the age of the formation extends from Valanginian to Early Turonian in the Baraw section, and from Valanginian to Cenomanian in the Sazan section. The palynological study revealed that amorphous organic matter is the dominant component of the sedimentary organic materials, and phytoclasts and palynomorphs are rare. The paleo-depositional environment of the type-1 palynofacies was a distal suboxic–anoxic basin and that of the type-2 palynofacies was a distal dysoxic–oxic shelf. Both kerogens are of type II, demonstrating that they are oil-prone. The studied organic matter is indigenous, and is mature to post-mature in the Baraw section, immature to mature in the Bn-1 section and mature in the Sazan section. Samples from the Baraw section are of type II/III and III, with a Hydrogen Index (HI) in the range 57–101 mg HC/g TOC. The Bn-1 and Sazan sections were of mixed type II and III kerogen, with an HI in the range 70–458 mg HC/g TOC for the Bn-1 section, and a single value of 135 mg HC/g TOC was obtained for the Sazan section. The results of this study indicate that the samples are capable of generating hydrocarbons (oil and gas).