Abu Qada Formations Research Articles

Paleoenvironment, sequence stratigraphy and source rock potentiality of the Cenomanian-Turonian boundary sediments of Southern Tethys

The Abu Qada Formation is a reference interval for the Cenomanian–Turonian boundary event in the northeastern margin of Africa. In this paper, geochemical, biostratigraphical, and carbon isotope ratio studies are presented using high-resolution well data yielded from the Gulf of Suez, Egypt to evaluate the paleoenvironmental condition, sequence stratigraphy and source rock potential of the Upper Cenomanian/Lower Turonian Abu Qada Formation. A total of 12 core samples and 4 ditch cuttings were collected from OCT-A8St1 well in the October Oil Field for geochemical, palynological and calcareous nannoplankton analyses. Cyclostratigraphic analysis was prepared to characterize the electrofacies change along the Cenomanian/Turonian boundary interval including the Oceanic Anoxic Event 2 (OAE2). The Predictive Error Filter Analysis (PEFA) patterns and Integrated Predictive Error Filter Analysis (INPEFA) curves found 3rd order cycle of the OAE2 within the global third-order cycle Ce5. A stable carbonate isotope analyses with total organic carbon (TOC) resulted in a remarkable positive excursion δ13Ccarb (3.67‰) associated with change in the TOC content. The quantitative analysis of calcareous nannofossils indicates the high productiveness of nannoplankton around the Cenomanian/Turonian boundary interval. The high abundance of the Discorhabdus genus proves the paleoenvironmental change during the OAE2 interval. The palynofacies interpretation indicates the lower part of Abu Qada Formation to be deposited in a slightly reducing conditions at the inner neritic setting, while the upper part of Abu Qada to lower part of Wata formations were deposited in deeper marine setting under anoxic conditions. These changes in the overall depositional conditions are documented by the remarkable change in palynofacies and organic carbon content (TOC). Dark gray shale and carbonate sediments are interpreted to be a good source rock potential by kerogen quantified palynofacies analysis indicating oil and gas prone producing materials (Kerogen types II and II/III). The best source rock quality is associated with the Abu Qada Formation's OAE2 record. These criteria allow us to identify the occurrence of OAE2 record in the Gulf of Suez petroleum province as a useful tool for high-resolution chronostratigraphic analysis.

Palaeoecological and palaeoenvironmental analyses of Cenomanian–early Turonian macrobenthic faunas from the northern Eastern Desert of Egypt

The palaeoecology and palaeoenvironments of the Cenomanian–lower Turonian succession in the northern Eastern Desert of Egypt are interpreted, based on a detailed study of macrofaunal assemblages and sedimentary facies. The abundant molluscs and echinoids of the mixed carbonate-siliciclastic Galala and Abu Qada formations have been studied in three sections with ammonites that provide a well-correlated stratigraphical framework. Three unconformities (two Cenomanian sequence boundaries and a first Turonian one) bound two third-order depositional sequences. Facies development shows a strong relationship to the sequence architecture recognised. In addition, the facies characteristics indicate depositional palaeoenvironments ranging from lagoonal to deep subtidal settings on a homoclinal carbonate ramp that was proximally influenced by clastic input. The macrobenthic taxa identified in 51 samples, collected from the sections studied, are grouped into seven assemblages (A–G) that are described and interpreted as remnants of communities. The faunal distribution and trophic structure of most of the assemblages recorded confirm fully oxygenated and euhaline shallow-marine environments with mesotrophic productivity level, i.e., relatively stable and low-stress conditions. The trophic structure of some other assemblages, in contrast, reflects the influence of particular environmental parameters, dissolution of aragonitic shells and/or sample size effects. Environmental parameters controlling the faunal distribution include substrate consistency, bathymetry, water energy, surface-water productivity, rate of sedimentation and oxygen availability. The integrated litho- and biofacies results certify that the sequences were deposited during an interval dominated by different perturbations that resulted in a wide spectrum of depositional features and significant palaeoecological variations.

Source rock evaluation of the Central Gulf of Suez, Egypt: A 1D basin modelling and petroleum system analysis

Geochemical studies were applied to evaluate the possible source rocks of Cretaceous–Eocene formations in the October oil field, including pyrolysis analysis data such as total organic carbon (TOC %), generating source potential (S2), production index (PI), oxygen, and hydrogen indices (OI, HI) and (Tmax). Three source rocks are characterized by fair to good and very good TOC%, which are Thebes, Duwi, and Abu Qada formations with kerogen type I and type II, respectively, and some samples are in the type III region reflecting the degree of maturation and can generate oil and gas. 1D basin models were constructed for five wells to simulate the multi‐tectonic phases and multiple burial histories, migration path, and event chart in the study area. The sedimentation rates from Cretaceous to Palaeocene age are characterized by low burial rate sedimentation, low to medium in the Eocene age, and high burial rate and rapid sedimentation in the Miocene and post‐Miocene age. The petroleum system of the October oil field was studied, and two petroleum systems can be recognized, according to the integration studies between the source rock evaluation and petroleum basin modelling.

New Lights on Mineralogical and Geochemical Characteristics of Cretaceous Rocks, Gabal Qabaliat Area, South West Sinai, Egypt

The Cretaceous sedimentary succession at Gabal El-Qabaliat range in age from Aptian-Albian to Maastrichtian. Lithostratigraphically, the succession is subdivided into Malha, Raha, Abu Qada, Wata, Matulla and Sudr formations. The mineralogy of bulk samples of Malha Formation reveals one association (quartz, kaolinite, anhydrite, muscovite and calcite followed by dolomite). The Raha Formation reveals the presence of two cycles of environmental conditions. (calcite then quartz, kaolinite and gypsum; quartz, halite, hematite, muscovite, kaolinite and gypsum). Abu Qada Formation has two cycles of environmental conditions (quartz, halite, montmorillonite, kaolinite, muscovite and calcite; quartz, anhydrite, glauconite and hematite) but Wata Formation has one cycle (calcite, dolomite and quartz). Matulla Formation has four associations (calcite, dolomite, anhydrite, hematite, quartz; calcite, dolomite, quartz, goethite, hematite and gypsum; quartz, goethite, gypsum, calcite, hematite, glauconite, kaolinite; quartz, montmorillonite, halite, anhydrite, muscovite and calcite). The clay mineralogy of Raha Formation reveals one clay association (montmorillonite, saponite and kaolinite), but Abu Qada Formation reveals the presence of two cycles of environmental conditions (lower one: kaolinite, chlorite, saponite, illite and goethite; second: montmorillonite, saponite, chlorite=kaolinite, goethite). Matulla Formation has two clay associations [montmorillonite with monor illite, saponite > kaolinite (lower cycle; middle part of this formation), montmorillonite= saponite (2^nd cycle)]. Form the geochemical studies, the variation in each major oxides and trace elements either in clastic or non-clastic rocks discussed revealing the kind of clay mineral associations and other minor components present. Two groups were identified based on CaO and MgO contents; 1^st group has > 54% CaO and low MgO including Raha, Matulla and Sudr limestones while the other group including the moredolomitic facies of Abu Qada. The dolomitic facies of Abu Qada exhibit high CaO compared with the Wata and Matulla formations. Four groups were identified based on SiO₂ and CaO contents, the 1^st group has <1% SiO₂ and > 54% CaO including Sudr, Matulla and Raha limestones; the 2^nd one has 1-2.2% SiO₂ and 47-54% CaO including Abu Qada samples; the 3^rd one has ~3% SiO₂ and 35% CaO as in Wata dolomitic limestone and the 4^th one has 27% SiO₂ and 37% CaO including dolomitic limestone of Matulla Formation. Ba and Sr contents of limestone facies reflect a separation between the different types, where Ba contents of dolomitic facies are more than their contents in limestone facies of Abu Qada, Wata, and Matulla. The Sr contents have the opposite trend where Sr content of limestone are more than that of dolomitic facies (Raha and Matulla).

The Cenomanian–Turonian boundary event in Egypt: Foraminiferal turnover and carbon isotopic change

This study deals with the integration between geochemical data (carbon isotope and, total organic carbon) and foraminiferal turnover to track the Oceanic Anoxic Event 2 (OAE2) from the OCT-A8st1 well, which located in October field, central part of Gulf of Suez, Egypt. The studied well is subdivided into two formations, namely the Galala (Early–Late Cenomanian) and Abu Qada (Late Cenomanian–Early Turonian). Concerning the foraminiferal assemblage, agglutinated foraminifera dominate the Galala Formation, while planktonic taxa only occur within a few levels in the Abu Qada Formation. Due to the absence of keeled planktonic forms, the biostratigraphic framework is established on the integration between benthonic and planktonic foraminifera. Three biozones are recognized, including Thomasinella aegyptia–Merlingina cretacea Interval Zone (Early–Middle Cenomanian), Thomasinella fragmentaria–Praebulimina aspera Interval Zone (Middle–Late Cenomanian), and Whiteinella archaeocretacea Taxon Range Zone (Late Cenomanian–Early Turonian). Therefore, the Cenomanian–Turonian boundary interval (CTBI) is placed within the lower part of the Abu Qada Formation, which is characterized by the presence of black shales and low richness of both foraminifera and ostracods. A remarkable increase in TOC values is observed close to the CTBI. Also, the carbon isotope curve shows a distinctive positive δ13C anomaly at the same level of the maximum TOC. The comparison between the recorded δ13C data and those obtained from other sections worldwide, indicates that the base of the Turonian is placed directly above the δ13C excursion. Furthermore, the recorded foraminiferal community shows evidence for the deepening of the environment and extension of the oxygen minimum zone during the CTBI. This conclusion is based on a sequence of bioevents starting with the disappearance of some agglutinated benthic foraminifera, followed by the dominance of opportunistic groups including buliminids, whiteinellids and heterohelicids. Consequently, the studied well may be considered as a local reference section for OAE2.

Biostratigraphy and Paleobiogeographic implications of the Cenomanian–Early Turonian Ostracods of Egypt

The present study deals with the Cenomanian–early Turonian ostracods in the southern Sinai, Egypt. The investigated sequence includes the Raha and Abu Qada formations. The Raha Formation consists of distinctive Cenomanian taxa such as Cytherella aegyptiensis, Veeniacythereis maghrebensis, V. jezzineensis, V. streblolophata streblolophata, Monoceratina trituberculata, and Glenocythere reticulata. Based on the ostracod species, four local biozones are recognized, including Veeniacythereis jezzineensis – Metacythereopteron berbericum, Cytherella eosulcata – Xestoleberis derorimensis, Amphicytherura ziregensis and Perissocytheridea istriana – Cythereis fahrioni. The paleobiogeography of the considered ostracods suggests that there are two bioprovinces, the first of which is the North African province and includes Egypt, Tunisia and Algeria. The second bioprovince represents the Middle East province and includes Lebanon, Oman and Iran. The strong resemblance between the two bioprovince indicates a relatively good communication along the margin of Southern Tethys during the Cenomanian and improved marine ostracod exchange.

Factors controlling facies distribution during the early Late Cretaceous in the Eastern Desert of Egypt: Paleoenvironmental reconstruction and relationship to sequence stratigraphy

In the context of a high-resolution stratigraphic perspective, facies analysis is carried out to interpret the paleoenvironments that prevailed during the Cenomanian–Turonian sedimentation in the Eastern Desert of Egypt. Particular emphasis is placed on the possible reasons for observed changes in the facies distribution. The facies associations indicate that the mixed carbonate and siliciclastic successions were deposited on a long-extended ramp setting with a gentle dip from a proximal position in the south to a distal position in the north. The late Cenomanian transgression covered the study area and formed a shallow fully marine environment, in which the Galala Formation was deposited. The sea-level rose continuously to reach a maximum during the early Turonian, with a deep subtidal setting in which the Maghra El Hadida and Abu Qada formations were deposited at relatively high and low paleo-depths, respectively. Changes in the facies distribution reveal a strong relationship to sea-level fluctuations; each sea-level stage of the studied sequences is characterized by similar facies associations with the same facies arrangements. In addition, at the proximal southern part of the study area, where shallow facies are expected to occur, deep marine facies are instead recorded, which is interpreted here as a tectonic effect of the Syrian arc folding system. Furthermore, the dominant paleoenvironmental perturbations during the Cenomanian–Turonian as represented by major lateral and vertical litho- and biofacies changes also affected the studied facies distribution. Therefore, the Cenomanian–Turonian facies development in northeast Egypt was not only controlled by eustatic sea-level changes as commonly suggested but was also influenced by tectonic and environmental changes.

Cenomanian/Turonian oceanic anoxic event 2 in October oil field, central Gulf of Suez, Egypt

Gulf of Suez is one of the world most prolific Cretaceous and Miocene oil provinces in Egypt. In this basin the Late Cenomanian/Early Turonian organic rich limestone and shale sediments are referred to oceanic anoxic event 2 (OAE2). Two oil-cored wells (GS 197-2 and OCT-A8) have encountered the Late Cenomanian/Early Turonian Abu Qada Formation in October Field, central part of Gulf of Suez. The aim of this work is to pick the global Cenomanian/Turonian anoxic boundary in the subsurface sediments within the Gulf of Suez basin. Consequently, the core samples of the studied wells have been investigated in order to recognize the lithofacies, biostratigraphy, geochemistry and isotope content of upper Raha, Abu Qada and lower Wata formations. The microfacies association of anoxic middle to outer shelf marine were recognized. In addition, remarkable turnover and significant change in biostratigraphy and ichnological diversity and abundance were confirmed the abrupt change in oxidation and nutrition the Cenomanian-Turonian boundary. The recorded positive δ13C excursion (1.8‰) matched with maximum TOC value encountered to mark OAE2 as well as source rock maturity and potentiality of Abu Qada Formation. The neighboring exposed section of Abu Qada Formation in Gabal Nezzazat show similar isotopic and biostratigraphic characteristics that recorded in the studied wells. This work define the Cenomanian-Turonian OAE2 as material based chronostratigraphic surface boundary in Nezzazat Group from surface to subsurface integrated data to improve sequence stratigraphic interpretation of the heterogeneous Upper Cretaceous shallow marine reservoirs in Gulf of Suez.

Contribution to the stratigraphy and sedimentology of the Upper Jurassic – lower Eocene succession of the Mitla–El Giddi stretches, west Central Sinai, Egypt

The present study deals with the stratigraphy, petrography and facies analysis of the stratigraphic succession of Mitla-El Giddi stretches (west Central Sinai, Egypt). Lithostratigraphically, the study area is covered by a thick succession extending from Late Jurassic to early Eocene time. This succession is subdivided into the Masajid Formation (Upper Jurassic (Oxfordian) at the base followed upwardly by the Risan Aneiza Formation (Lower Cretaceous (? Aptian- Albian), the Galala Fm. (Cenomanian), the Abu Qada Formation (lower Turonian), the Buttum Formation (middle Turonian), the Wata Formation (middle–upper Turonian), the Themed Formation (Coniacian–Santonian), the Sudr Chalk (Campanian–Maastrichtian), the Mitla Formation (= Esna Shale) (Paleocene–lower Eocene), the Thebes Formation (lower Ypresian) and the Minia Formation (upper Ypresian) at top. The Aptian – Albian Risan Aneiza Formation is first recorded at G. El Hamra in the study area. As well, a new formational name (the Mitla Formation) is used to describe the Paleocene – lower Eocene unit equivalent to the Esna Shale due to variation in lithology mainly represented by chalky limestone and argillaceous limestone. Many unconformities, represented by variable sedimentologic features, i.e., red paleosols, conglomerates, crustified laminated limestone and glauconitic facies were investigated and mostly attributed to the Syrian Arc System.The petrographic investigations especially for the lithified rocks revealed eighteen limestone microfacies, three dolostone microfacies and four sandstone microfacies, besides the non-lithified shale, sandy shale, clay and marl lithofacies. The recognized facies and their related paleoenvironments document lateral and common vertical transition between inner, middle and outer ramp setting. These facies could be subdivided into eight associations that are related to six depositional environments: peritidal flat/beach clastics, peritidal flat carbonates, lagoonal clastics, lagoonal carbonates, high energy shoal of ooids and patch reefs (oolitic shoal), intertidal-subtidal open marine, storm influenced subtidal open marine (mid-ramp) and hemipelagic outer ramp facies.The study indicates that, the area was controlled by a long-term transgressive phase and several higher order sea level fluctuations during the deposition of the studied succession. The main factors controlling the ramp deposition and the described events are; structure control mainly Syrian Arc deformation, eustatic sea level fluctuations combined with environmental influences such as autochthonous carbonate productivity-siliciclastic supply and paleorelief conditions.

Foraminiferal biostratigraphy and bioevents of the Cenomanian-Turonian succession in southern Sinai, Egypt and relationship to OAE2

Abstract: The shallow water Cenomanian–Turonian succession exposed in the southern Sinai was examined to distinguish the biostratigraphic zonations , based on the foraminiferal associations, and to define the significant bioevents that occurred during this interval. This succession is subdivided into two rock units, namely the Raha and Abu Qada formations. According to the lithological characteristics, the Raha Formation is subdivided into the Abu Had and Mellaha Sand members. The foraminiferal association consists of 33 species (23 benthic and 10 planktic). Planktic foraminifera are distributed only in sporadic intervals. Relying on the combination of benthic and planktic foraminifera, four local biozones are established including, Daxia cenomana–Mayncina d'orbignyi, Biplanata peneropliformis-Nezzazata convexa, Thomasinella punica, and Whiteinella archaeocretacea . In this study, the Cenomanian/Turonian boundary is characterized by a sequence of significant bioevents beginning with the extinction of some benthic foraminifera (e.g., Thomasinella spp.), followed by a bloom of the low-oxygen tolerant planktic foraminifera (heterohelicids), a flood of calcispheres and microfilaments, and then the dominance of whiteinellids. These bioevents could be recognized as a key for a global turnover that occurred across the Cenomanian –Turonian boundary associated with Oceanic Anoxic Event 2.

Pore fabric assignment using electrical conductivity of some Albian–Cenomanian sequences in north Eastern Desert, Egypt

The electric pore fabric concept has been testified in many previous studies, mostly concerned with sandstone rock samples. The present study is a further trial to testify the reliability of the proposed concept on carbonate and clastic facies. The studied facies are representative for the Albian–Cenomanian Raha and Abu Qada Formations at the western side of the Gulf of Suez in Egypt. A total of 37 samples have been studied petrophysically by measuring electric conductivity in 3-D to rank their petrophysical potentiality and to detect their electric pore fabric. The studied samples are grouped into four facies, namely: (1) facies 1 (calcareous sandy siltstones) and (2) facies 4 (glauconitic quartz arenite) as clastic facies as well as (3) facies 2 (bioclastic limestones, and dolostones) and (4) facies 3 (clayey to sandy limestones) as carbonate facies. Porosity values of the studied carbonate facies are very good due to dolomitization and dissolution, whereas porosity values of the clastic facies are poor due to their high clay content. The formation resistivity factor values are low to medium values due to the reducing effect of the clay content and the very good porosity values. Archie’s parameters a and m are mostly related to the formation resistivity factor and to some extent to the mineralogical composition as well as the electric tortuosity. The electric pore fabrics of the studied facies are slightly anisotropic, mostly as primary depositional fabrics affected by slight foliation rather than lineation. Presence of a slight fracturing system can be revealed by assigning the minimum formation resistivity factor through the vertical direction perpendicular to the bedding plain. However, the fracturing system is still not strong enough to affect the electric pore anisotropy by increasing the electric pore lineation as a secondary fabrics’ indicator.

Stratigraphic significance of rapid faunal change across the Cenomanian–Turonian boundary in the Eastern Desert, Egypt

A significant and rapid faunal change across the Cenomanian–Turonian boundary in the Eastern Desert of Egypt has been recognized by reconstructing the stratigraphic ranges of macroinvertebrates within the upper Cenomanian–lower Turonian Galala and Abu Qada formations. The faunal change initiated with a considerable loss of taxa during the late Cenomanian at the top of the Neolobites vibrayeanus ammonite zone, coinciding with sequence boundary SB Ce 5, ∼400 ka before the Cenomanian–Turonian boundary (93.9 Ma). Only 10% of the taxa that existed during the late Cenomanian have been recorded from lower Turonian strata. The changes in the macroinvertebrate faunas continued across the Cenomanian–Turonian boundary and new faunal associations evolved after the earliest Turonian Vascoceras proprium ammonite zone of (∼200 ka after the Cenomanian–Turonian boundary). Therefore, the crisis that caused this faunal change around the Cenomanian–Turonian boundary over approximately 600 ka. The timing of the macrofaunal change recognized in the study area completely overlaps with the well-known Oceanic Anoxic Event (OAE) 2 and most probably it is one of the effects of the major environmental perturbations (critical warming, high atmospheric CO2 concentration, and ocean water acidification) associated with this event. In addition, the sequence-stratigraphic analysis shows strong correlation exists between pattern of first and last occurrences of macroinvertebrate faunas and sea-level changes. Therefore, the oceanographic changes (rapid sea-level rise) may have also contributed to the Cenomanian–Turonian faunal change in the study area.

The Nature of Pre-Miocene and Miocene Sediments in the Offshore Northern Part of the Gulf of Suez, Egypt

The present study deals with subsurface geology pre-Miocene and Miocene rock units penetrated in the extremely northern offshore Gulf of Suez area. Throughout the pre-Miocene and Miocene, changes in the tectonic pattern, depositional environment, and sediment types indicate different magnitudes and tectonic instability. Based on the available seven dry subsurface composite well logs (GS 9-1, Darag 17-1, GS 24-1, X 80-1, GS 56-1, Fina Z 80-1A, and GS78-1 wells) besides dipmeter logs, 39 stratigraphic maps (isopach and facies maps) are constructed to show thickness variations, facies changes, and paleogeology of Jurassic (Massajid Formation), Lower Cretaceous (Nubia Formation), Upper Cretaceous (Raha, Abu Qada, Wata, Matulla, and Sudr formations), Lower Miocene (Nukhul, Rudeis, and Kareem formations), and Middle Miocene (Belayim, South Gharib, and Zeit formations) times. Moreover, two cross sections are constructed to show thickness and lateral variations in facies changes and tectonics affecting the area at that time. Despite this, the study area has suitable conditions for hydrocarbon generation and accumulation, the seven wells drilled in the study area are considered to be dry or nonproductive. They are considered to be dry or not productive due to tilting of strata to the SW direction, absence of cap rocks (evaporites and salts) and shale in most parts of the study area (especially in the extremely northern parts), and affecting the area by a large numbers of normal faults due to active and continuous tectonic events on the Gulf of Suez area. These reasons may be aided to the migration of hydrocarbons from the area to outside and to the adjacent oil fields.

Depositional Trends and Sedimentary Environments of the Cenomanian-Turonian Sediments along G. Nezzazat-G. Ekma, South-West Sinai, Egypt

The Upper Cretaceous sedimentary succession at G. Nezzazat-G. Ekma, west-central Sinai was examined to detect the depositional trends responsible for its development and discuss the depositional sedimentary environments dominated its evolution. The examined succession spanning from early Cenomanian to Turonian age and consists of three rock units namely from the base; Raha, Abu Qada and Wata formations. The detailed lithological and sedimentological characteristics of the concerned succession revealed that Raha Formation has been subdivided into Abu Had Member and Mellaha Sand Member and diagnostically characterized by the presence of both three clastic and three non clastic microfacies association on the other hand, Abu Qada Formation is characterized also by three clastic and four non clastic microfacies association which indicates deposition of both in a mixed siliciclastic- carbonate system on a ramp setting, whereas Wata Formation is characterized by the dominance of non clastic microfacies. All the recorded microfacies association is described and their sedimentary environments are concluded. The Raha Formation was deposited under progressively advancing subtle sea that reached maximum by the mid-parts of the formation and retreated toward the top part of the formation. Abu Qada Formation was deposited under successively advancing sea started in shallow foreshore conditions and continued deepening toward the top of the formation where outer marine shelf facies dominated. Whereas, the Wata Formation is represents a phase of relatively

Cenomanian–Early Turonian Ostracoda of the shallow marine carbonate platform sequence at west central Sinai: Biostratigraphy, paleobathymetry and paleobiogeography

The Cenomanian–Lower Turonian succession exposed in west central Sinai is carefully studied for their ostracode content. The Raha and Abu Qada Formations were studied in 4 sections. Their ostracode content includes the recognition of 70 species belonging to 34 genera. One species is considered as new (Spinoleberis grosdidieri n. sp.). The vertical distribution of the ostracodes in the sections enables the detection of four local biostratigraphic zones with a Barren Interzone in between. In terms of paleobathymetry, each studied sequence reveals deposition on a shallow reefal carbonate platform of less than 100m depth. The flourishing of cytherellids in repeated intervals refers to kenoxic events within the Cenomanian section. These events are enhanced just below the Cenomanian–Turonian boundary referring to the Oceanic Anoxic Event 2. The wide paleobiogeographic distribution of the recorded Cenomanian ostracodes reveals that there was a direct connection throughout the Southern Tethyan Realm countries. Also, there was a migration path between the Southern Tethyan bioprovince and the West African bioprovince during the Cenomanian via the Trans-Saharan Seaway and along the Atlantic coast of West Africa.

Depositional environments and sequence architecture of the Raha and Abu Qada formations (Cenomanian–Turonian), west central Sinai, Egypt

Cenomanian–Turonian deposits are important reservoirs for many oil fields in the Western Desert and the Gulf of Suez region of Egypt. Study of the Raha and Abu Qada formations (Cenomanian–Turonian), from five dip-oriented outcrop locations in west central Sinai; indicates deposition of a mixed siliciclastic-carbonate system on a ramp setting. The inner ramp facies (bivalve and benthonic foraminiferal wackestone) grades northward to the mid ramp facies (echinoderm calcisphere packstone, and oyster floatstone), and outer ramp facies (planktonic foraminiferal wackestone and calcisphere wackestone).The two studied formations comprise one second-order depositional sequence (duration of approximately 10 Million years). This large scale sequence includes four third-order depositional sequences, three of which are observed in the Raha Formation, with the other one recorded in the Abu Qada Formation. Because west central Sinai was tectonically stable during the Cenomanian and Turonian, the main factor controlling the lateral and vertical distribution of facies tracts is likely due to changes in the relative sea level. The Cenomanian–Turonian boundary event is known as the largest oceanic anoxic event during the Cretaceous. This global event has been documented in three of the studied sections. The recorded δ13C excursions range from+3.04‰ to+5.24‰. These high positive excursions in δ13C are associated with highly negative values of δ18O (values range from −6.01‰ to −1.38‰).

Contribution to the stratigraphy and sedimentation of the Cretaceous aquifers, SE Sinai, Egypt

Eight formations were recognized in WadiWatir area, SE Sinai; Malha Formation (Early Cretaceous), Galala Formation (Late Cenomanian), Abu Qada Formation (Early Turonian), Buttum Formation (Early Turonian), Wata Formation (Late Turonian), Matulla Formation (Coniacian-Santonian), Brown Limestone Formation (LateCampanian-Early Maastrichtian) and Sudr Chalk Formation (Early-Middle Maastrichtian). The planktonic foraminifera played the great role in age determination for the referred units, in addition to some benthonic foraminifera. Also, three microfacies types were identified; siliciclastic facies, mixed carbonate – siliciclastic facies and carbonate facies reflecting an oscillation of the Cretaceous sea from shoal to shallow marine and marine environments. The diagenetic processes (cementation, neomorphism, dolomitization, silicification, dissolution and compaction) show the impact of textural and mineralogical changes on the studied rock units, groundwater occurrences and possibilities. Furthermore, two main aquifers are dominant in the study area, Lower Cretaceous sandstones and Cenomanian-Turonian Limestones. The geomorphologic and geologic characteristics controlling the groundwater occurrences were discussed.

Facies and sedimentary environments of the Abu Qada Formation at Gabal El-Gunna, Southeastern Sinai, Egypt

The biostratigraphy, microfacies association, mineralogical interferences, depositional environments and geochemical properties of the Abu Qada Formation, which exposed at Gabal El-Gunna Southeastern Sinai, Egypt were delineated. It belongs to the planktonic foraminiferal Whiteinella archaeocretacea Zone of the Late Cenomanian-Early Turonian and consists of calcareous shale and limestone. The calcareous shale facies is characterized by chlorite, smectite and illite with high concentration of P2O5, Zn, Ni, V, and Cr. The carbonate rocks are characterized by foraminiferal wakestone and bioclastic grainstone. These microfacies associations are characterized by barite with high content of Sr. The facies types with faunal contents, geochemical and mineralogical studies suggest a restricted to shelf lagoon open circulation environment.

Petrographical and Petrophysical Studies of Some Upper Cretaceous Rocks, Southwest Sinai, Egypt

Petrographical and petrophysical properties have been studied for the Upper Cretaceous rocks collected from the Gabal Nazzazat area, SW Sinai. They are represented by 14 samples from the Raha Formation, 6 samples from the Abu Qada Formation, and 10 samples from the Wata Formation. The main petrography characteristics, digenetic features, faunal assemblage, and their relation to depositional environments are discussed. The petrophysical study revealed the presence of some sandstone beds within Raha and Matulla formations, which are characterized by moderate to good reservoir quality.

Lithostratigraphy and biostratigraphy of the Cenomanian–Santonian strata of Sinai, Egypt

The Cenomanian–Santonian successions of Sinai mainly consist of inner-shelf siliciclastics and carbonates. Five formations (Halal, Raha, Abu Qada, Wata, Matulla) have been recognized and a multibiostratigraphic framework has been constructed. The biostratigraphic assignments of the formations are mainly based on calcareous nannofossils. Their semiquantitative distribution within nine sections is presented, enabling us to identify the biozones CC10–CC16 in some cases. Ammonites are abundant in the uppermost Lower Turonian Mammites nodosoides Zone only. Planktic foraminifera of the Coniacian–Santonian Dicarinella concavata and D. asymetrica zones have been found. In addition to these groups, ostracods are used to differentiate between the stages supplemented by data in the literature on benthic foraminifera and rudists. Some modifications of previous lithostratigraphic schemes are proposed for the sections studied: from the ammonite data, a hiatus is proposed between the Halal/Raha and Abu Qada formations (Cenomanian/Turonian boundary); the Abu Qada Formation is considered to range from the M. nodosoides Zone to the lowermost Upper Turonian; and the base of the Matulla Formation is uppermost Turonian (CC13). A combined lithostratigraphic and biostratigraphic correlation of ten sections along a N-S transect allows the differentiation of eleven stratigraphic units. Units 1–8 within the Cenomanian–Turonian Halal, Raha, Abu Qada and Wata formations are considered to be synchronous. In contrast, ‘Syrian Arc’ tectonics most probably led to diachronous deposition of units 9–11 within the Coniacian–Santonian Matulla Formation.