Malha Formation Research Articles

Delineating the uranium anomalous zones using remote sensing and radiometric data: a case study from Gabal Umm Tinassib area, North Eastern Desert, Egypt

AbstractRemote sensing (RS) and airborne gamma-ray spectrometric (AGS) methods are utilized to delineate significant uranium zones and altered mineralization areas in Gabal Umm Tinassib and its surrounding region, situated in the northern section of the Egyptian Eastern Desert. AGS serves as a valuable tool for mapping surface geology and conducting mineral exploration. It assesses the concentrations of radioactive elements such as potassium (K), equivalent uranium (eU), and equivalent thorium (eTh). The concentration of radioelements exhibits measurable and significant variation according to lithology. On the other hand, several processing steps are employed for the RS data to generate high-quality images for geological mapping and to identify the mineralized alteration zones. The analysis of RS and AGS data in this study led to insightful conclusions. The utilization of False Color Composite (FCC) with the three best bands derived from the Optimum Index Factor (OIF), Principal Component Analysis (PCA) to extract two highly informative datasets, and the application of two band ratios contributed to accurate geological mapping. These band ratios notably identified identical alteration locations on both younger and older granite basement rocks. Additionally, the constrained energy minimization (CEM) technique effectively pinpointed alterations across these strata. The statistical analysis of AGS data revealed that radioactivity levels in the region range from 1.3 to 19.3 Ur for the total-count (TC), 0.2–3.6% for K, 0.09–11.6 ppm for eU, and 1.1–30.0 ppm for eTh. The estimated coefficient of variability (CoV) demonstrated that the three radio-elements exhibited normal distribution patterns across different rock units, with CoV values of less than 100%, except for K in the Malha Formation. High radiometric readings are observed in the outcroppings of younger and older granites. However, the lowest readings are recorded over undifferentiated Upper-Cretaceous sediments, Abu Rimth Formation, Galala Formation, and some parts of Quaternary sediments. The derived ternary radio-elements map highlights significant radiometric and related uranium anomalous zones as bright white regions. A strong correlation was found between high radiometric anomalous zones and the presumed occurrence of alteration zones in the study area.

Incorporation of granitic wastes and Malha Formation clays in the sewage pipes industry: insights on industrial using and environmental impact

Incorporation of granitic wastes and Malha Formation clays in the sewage pipes industry: insights on industrial using and environmental impact

El-Gendi Fortress: a new military and religious geo-archaeological site, Sinai, Egypt: geomorphological and hydrogeological remarks

El-Gendi Fortress is a unique geo-archaeological site in Sinai, Egypt. It reflects the progress of the Islamic military architecture during Saladin’s reign (Salah ad-din al Ayyubi), the founder of the Ayyubid dynasty (1174-1260AD). The fortress's location met two major geo-criteria. One is geographical; it is located on a mound 655 m above sea level (a.s.l) and 152 m above El-Tih El-plateau; this elevation contributes to the exploration of the surrounding areas and provides the fortress with a strong defensive position against the Crusaders' invasions of Egypt (1163–1169 AD). The second is Hydro-geological; it provides exceptional access to both meteoric surface (via barrages) and groundwater (through Sudr spring). The latter is from deep aquifers of the Nubian sandstones (Malha Formation) across the fractured carbonates (Raha and Sudr Formations of Cenomanian to Maastrichtian age). Such water was accumulated since the Pleistocene pluvial age until the fortress’ most recent use. The barrages’ location upstream of a sub-basin “a” at Wadi Sudr, in a similar direction to the deep ditch side, confirms that the priority of their design is to protect the region from flash flood risks and to store water on a relatively flat-lying land. The study reveals that the fortress’ geographical location is used to safeguard the Hajj route in central Sinai and to provide facilities for pilgrims’ caravans when they travel from North Africa to Mecca. The study concludes that the fortress should be a part of the Sinai tourism itinerary and promoted globally as a geo-archaeological site for Geo-tourism. In addition, the government should implement a strategy for conserving, rehabilitating, and managing the heritage sites, to improve facilities and increase public awareness of these sites to maximize the outcomes.

Geological and engineering appraisal of hydraulic frac sand in some Egyptian localities as a proppant of oil well drilling

Sand that comprises high purity silica grains, in large percent, is of the best naturally occurring grains that can be used as proppants during hydraulic fracturing processes. Proppants are used to increase formations' permeability; to increase reservoirs' productivity, or to reopen plays and utilize unconventional reservoirs. The potentiality of these grains to be used as frac proppants is determined according to certain physical, mechanical, petrographical and chemical evaluations that include particle size analysis, acid solubility, turbidity, bulk density, crush resistance and hardness, sphericity and roundness, mineral and chemical composition. This study shows the evaluation of the silica sand samples collected from Malha Formation in Wadi El Dakhal, Eastern Desert; Naqus Formation in Wadi Qena, Eastern Desert; and Bahariya Formation at Gabal El-Dist area in Bahariya Oasis, Western Desert, Egypt. The samples were examined according to frac sand international standards. The results showed the potentiality of the tested samples to be utilized as frac sand proppants. Wadi El-Dakhal and Wadi Qena studied areas possess very promising samples for frac sand production. But, the quality of Wadi El-Dakhal samples is somewhat better than that of Wadi Qena samples. The samples of Gabal El-Dist in Bahariya Oasis are relatively less to achieve the requirements; however, they can be utilized in shallow depths.The assessment testing of the studied samples revealed a good results and verifying the standard requirements, where SiO2 content is 89.1% in Wadi Qena, 99.3 % in Wadi Dakhal and 78.1% in Gebel El Dist, crush resistance at 5000 psi gives fine percent 4.71 W.Q, 6.78 W.D, and 14.11 B.O, turbidity readings raining from 100.5 to 133.25 NTU, the grain roundness are rounded to sub rounded, and grain size distribution range is 30/50 to 40/70 grading (710 um to 210 um).

Further evidence for Cretaceous wildfires: macro-charcoal from the Malha Formation at Wadi Budra, west-central Sinai, Egypt

Abstract Fossil evidence for wildfires, in form of fossil charcoal, is known from a large number of Cretaceous localities worldwide and it has repeatedly been argued that wildfires were connected to the evolution and radiation of angiosperms during this period. The present study provides new evidence (in form of macro-charcoal) for the occurrence of wildfires during deposition of the Lower Cretaceous (pre-Aptian) Malha Formation at Wadi Budra of the Sinai Peninsula, Egypt. Despite growing evidence for the worldwide occurrence of wildfires during the Cretaceous, the available database for pre-Aptian wildfires is still rather scarce for large regions when seen on a global scale, hampering causal interpretations concerning the interactions between fire ecology and the evolution of ecosystems during these stages.

Mineralogy and lithogeochemistry of lower Cretaceous kaolin deposits in the Malha Formation, Southwestern Sinai, Egypt: Implications for the building and construction industry

This study analyses the exposed outcrops of the Lower Cretaceous (Aptian-Albian) kaolin deposits of the Malha Formation, and characterizes them in terms of lithological, mineralogical, and chemical composition. In addition, the effect of thermal treatment on kaolinite mineral behavior is evaluated. The Malha Formation comprises kaolin deposits, which were sampled at the Rewekna, Ras Watta, Abu El-Nomerat, Essela, and Mosaba Salama sections. The studied samples are composed of kaolinite and quartz as the main constituents, followed by anatase and hematite as accessory (coloring) minerals. X-ray fluorescence (XRF) analysis reveals high Al2O3, SiO2, and LOI, low CaO, MgO, Cl, SO3, and P2O5 contents as well as alkali metals (e.g., K2O and Na2O). An increase in aluminum and silicon oxides is observed along with the presence of high kaolinite content in these samples. Calcination of the studied kaolinite, by thermal treatment, leads to dehydroxylation and/or transformation to High Reactive Metakaolinite (HRM). The partial replacement of cement by different ratios (3, 5, 10, 15, and 20%) of the produced Metakaolinite (MK) was completed to enhance the physical and mechanical properties. These procedures make the concrete more flexible and workable, increase durability, and are stronger. Besides, reduce the temperature produced from the hydration, as well as decreasing permeability and water absorption of the concrete. This work concludes that the cement substitution and mineral admixtures using Metakaolinite (MK) between 10 and 15% by weight of cement gave rise in compressive strength by 20% if compared by the control mix.

Rock typing based on hydraulic and electric flow units for reservoir characterization of Nubia Sandstone, southwest Sinai, Egypt

The present work describes and evaluates the reservoir quality of the sandstone of the Nubia Formation at the Gebel Abu Hasswa outcrop in southwest Sinai, Egypt. Hydraulic flow unit (HFU) and electrical flow unit (EFU) concepts are implied to achieve this purpose. The Paleozoic section made up of four formations has been studied. The oldest is Araba Formation followed by Naqus formations (Nubia C and D) overlay by Abu Durba, Ahemir and Qiseib formations (Nubia B), where the Lower Cretaceous (Nubia A) is represented by the Malha Formation. The studied samples have been collected from Araba, Abu Durba, Ahemir and the Malha formations. The hydraulic flow unit (HFU) discrimination was carried out based on permeability and porosity relationship, whereas the electrical flow unit (EFU) differentiation was carried out based on the relationship between formation resistivity factor and porosity. Petrographic investigation of the studied thin sections illustrates that the studied samples are mainly quartz arenite. Important roles to enhance or reduce the pore size and/or pore throats controlling the reservoir petrophysical behavior are due to the diagenetic processes. The present study used the reservoir quality index (RQI) and Winland R35 as additional parameters applied to discriminate the HFUs. The study samples have five hydraulic flow units of different rock types, where the detected electrical flow units are only three. The differences between them are may be due to the cementation process with iron oxides that might act as pore filling, lining and pore bridging, sometimes bridges helping to decrease permeability without serious reduction in porosity. The reduction between the number of EFUs and HFUs comes from the effect of diagenesis processes which is responsible for a precipitation of different cement types such as different clay minerals and iron oxides.

Water resources exploration and management based on remote sensing and geophysical data analysis: Al-Naqab Watershed, East Central Sinai, Egypt

This study integrates remote sensing and geophysical data to identify the hydrological conditions of the Naqab reservoir watershed. The main objectives of this study are identification and the interpretation of subsurface structures and their impact on groundwater flow, the relationships between structures and groundwater and the optimum way for watershed management in this sub-basin. Geophysical data including, ground magnetic survey and 1D electrical resistivity sounding helped in identifying the lithology and delineating zones of groundwater occurrence. The magnetic data delineated the basement rock, aided in characterizing the geometry of the subsurface structures that control the land surface features and constrain groundwater flow system. The interpreted subsurface structure elements include six sets of faults trending NE-SW, NW-SE, NWW-SEE, NEE-SWW, N-S and E-W. The basement depth was estimated at zero at the southern part and about 5187 m at the northern part. Two aquifer systems were characterized, the shallow aquifer of the Wata Formation (Upper Cretaceous) and the deep aquifer of the Malha Formation (Lower Cretaceous). The probability of groundwater occurrence increases towards the central part of the study area to north direction, where the thickness of the sedimentary basin reaches its maximum at the center of the study area. Different trends of faults were interpreted from are the geo-electrical cross-sections along two transects. Three patterns of faults were characterized including step faults, graben faults and horst faults. These faults could be indicated on the geo-electrical section by a marked difference in the layers` thicknesses. The magnetic data confirmed the locations of the faults delineated by the electrical resistivity profiles. The outlined faults are trending mainly in NE-SW, NW-SE, NWW-SEE, NEE-SWW and E-W directions. Lineament structures delineation and drainage pattern analysis were evaluated and interpreted from the analysis of remote sensing (RS) data and geographic information system (GIS) technique. The SRTM-DEM (Shuttle Radar Topographic Mission-Digital Elevation Model) was also utilized to automatically identify and extract drainage network. Interpretation and analysis of the inferred lineament structures indicate the presence of a number of main lineament populations that trends: NE-SW, NW-SE, NNW-SSE, NWW-SEE, E-W and N-S. Meanwhile, the interpretation and analysis of drainage pattern network indicate the presence of three main lineament structures that trends: NW-SE, NE-SW and NWW-SEE. Azimuth distribution analysis of both the measured structures and drainage channels shows similar trends, except for very few differences in the prevailing trends. Similarity in orientation of lineament structures, drainage system, and subsurface structural trends were recognized in the area under study. In conclusion, the integration between remote sensing and geophysical data revealed a close matching between the surface structural lineaments and subsurface structural trends could be verified. The preferred conduits of surface run-off and groundwater flow, as well as, the proper locations for groundwater exploitation could be determined.

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).

Egyptian Cretaceous clay deposits: Insights on Mineralogy, Geochemistry, and Industrial uses

Development of products which can be produced from a country’s natural resources is very important as far as the industrialization of a nation and saving foreign exchange is concerned. The recent vast expansion of the ceramic industry in Egypt results in an excessively high consumption rate of Aswan clays, so the current study aims to explore other potential materials for application in the vitrified clay pipes industry. Based on the abundance of ceramic raw materials in Egypt and the demand for vitrified clay pipes, it is pertinent to develop and manufacture vitrified clay pipes by exploiting the locally available raw materials in other localities. This research thus concerns the characterization of some clay materials of the Cretaceous. Three economic clay formations were selected for the study: (1) the Malha Formation at Abu Darag and Zafarana, North Eastern Desert; (2) Naqb El Sillim Formation at the Bahariya Oasis, North Western Desert; and (3) Abu Aggag Formation at Aswan, South Eastern Desert. The clayey formations were investigated to assess their potential in the manufacture of vitrified clay pipes. Based on the obtained results of mechanical, chemical, and technical characteristics, the Naqb El Sillim Formation has the best results in a wide range of firing temperatures (1140–1180 °C) compared with the required limits of the international standards for clay pipes application. On the other hand, the Malha and Abu Aggag formations needed some additives to satisfy the standard limits of clay pipes application so, the granite wastes were selected and added by 20% to these samples, then fired at 1180 °C. The experimental results obtained from the studied samples indeed revealed the viability of manufacturing vitrified clay pipes from the raw materials.

Deformation bands in normal fault damage zones, Southwestern Sinai, Suez rift, Egypt

The present study provides evidence that the NW-SE normal faults in Nubian Sandstone reservoirs (Malha and Naqus formations) are surrounded by damage zones in which the rocks are affected by cataclastic deformation bands and small scale faults. The paleostress analysis of the small faults indicates that σ3 has NE-SW direction while σ1 is sub-vertical. The thickness of the bands is ranging from 3 mm to 1 cm. The density and thickness of the bands increase toward the faults and decrease backward. The deformation bands form two prominent sets. The first set is running in the NW-SE direction parallel to the main faults and dip towards the northeast and southwest, i.e. synthetic and antithetic conjugate sets. The second set has NE-SW direction and dip mainly in the NW in the Malha Formation and in the SE in Naqus Formation. The two sets of deformation bands mutually crosscut each other, suggesting that both sets developed during the same deformation event. The deformation bands are planar features and occur singly or form braided clusters. The microscopic studies indicate that the host rock is mainly quartz arenite and composed of fine to very fine, well sorted quartz grains which weakly fractured and cemented by calcite. The microscopic studies of the bands indicate that they composed of strong grain crushing (cataclasis) and clay minerals. This composition is probably causes reduction of porosity and permeability within the deformation bands. The reservoir rocks in the damage zones of the normal faults are divided into polygonal areas by the deformation bands.

Combined application of electrical resistivity and GIS for subsurface mapping and groundwater exploration at El-Themed, Southeast Sinai, Egypt

The study area is located at south central part of Sinai Peninsula at El-Thamed area. Geoelectrical resistivity method was used by measuring eighteen vertical electrical soundings using the Schlumberger configuration with total current electrode separation ranging between 3m and 4000m in order to investigate the deep groundwater aquifer and to delineate the subsurface structures of this area.The geoelectrical cross-sections show that the subsurface section consists of six geoelectrical units. The first unit is Quaternary deposits with thickness ranging from 0.6m to 30.9m and the resistivity values ranging from 177Ohm.m. to 39680Ohm.m. The second geoelectrical unit is composed of Egma Formation, with thickness ranging from 9.2m to 12.8m and the resistivity values ranging between 21Ohm.m. and 82Ohm.m. The third geo-electrical unit is composed of Paleocene Esna shale, also not detected at the study area with exception at profile 2, its thickness ranges from 15.6m to 166.5m and resistivity range from 8.9Ohm.m. to 20Ohm.m. This layer has not been detected at the extremely southern part of this profile, its depth ranges from 9.63m to 15.5m. The fourth geoelectrical unit is composed of Nubian Sandstone of Malha Formation (Lower Cretaceous) with depth ranging from 0.5m to 8.9m and its resistivity values ranging from 14Ohm.m. to 133Ohm.m. This layer represents the main aquifer in the study area with thickness ranging between 14.2m and 283m. The fifth geoelectrical unit is composed of claystone of Naqus Formation with depth ranging from 14.2 to 349m and its resistivity values ranging from 2.7Ohm.m. to 13Ohm.m., sometimes, it is extends to the maximum depth of penetration. The sixth geoelectrical unit is composed of Basement rocks. It is characterized by resistivity ranging from 970Ohm.m. to 25462Ohm.m. and depth ranging from 60.1m to 283m. This unit is detected at the eastern part of the study area.Structurally, the study area is affected by sets of faults trending mainly NE-SW (Aqaba Trend).

Characterization of Egyptian kaolins for health-care uses

This work aimed to evaluate by first time the suitability of the Egyptian Abu Zenima (Sinai Peninsula) kaolins to be used in pharmaceutical and cosmetic applications. Sixty five kaolin samples were collected from six stratigraphic sections: Wadi Khaboba, Gabal Hazbar and Wadi Abu Natash sections, belonging to the Abu Thora Formation (Carboniferous age), and Gabal El Dehessa, Gabal Farsh El Ghozlan and Wadi Budra sections, belonging to the Malha Formation (Lower Cretaceous), and characterized by mean of X-ray diffraction and fluorescence, electron microscopy, spectrophotometry and rheometry.Most of the samples were dominated by kaolinite, and half of the samples contained >75% of this mineral, reaching up to 96%. Quartz was the main impurity, with very variables quantities; it was always present except in some parts of the Wadi Abu Natash and Wadi Budra sections. Mica, anatase and hematite were frequently present, but they normally did not exceed 10%. Other detected impurities were carbonates (calcite, dolomite, ankerite), sulfates (gypsum, alunite), smectite, feldspars, magnetite, pyrite, halite and heulandite, but in lesser amounts and only in some samples.Carboniferous kaolinites exhibited a high crystallinity (Hinckley Index >1), while most of Cretaceous kaolinites were medium to poorly crystallized (Hinckley Index normally <1). CIELAB colorimetric parameters put into evidence the general grayish color of the samples, some of which showing light tints of redness and yellowness in correlation with their iron content.The rheological characterization of the 31 purest kaolin samples revealed that their dispersion exhibited similar and good pseudoplastic flow behavior at 50% W/W solid concentrations. The apparent viscosity and yield stress values of Carboniferous samples showed a widest range of variations when compared to Cretaceous ones. The observed variations were interpreted to be correlated with both, the kaolinite content as well as microtexture and the dimensions of kaolinite particles.With these premises, some of the studied kaolins are considered to have a very high economic potential, once the detected impurities are removed easily by the appropriate process, and then suitable for pharmaceutical and cosmetic purposes. Even if there were zones rich in kaolinite in all the studied sections, the highest quality for the target purposes is found at the lower part of the Wadi Abu Natash section, where quartz was absent and include the samples with the highest viscosities.

Isolated Paleomagnetic Component and its Dating from the Malha Formation, Southwestern Sinai, Egypt

The age of Malha Formation that located at Gebel Sarbut el-Gamal in the southwestern Sinai is a controversial point, due to the absence of index fossils. Therefore, 125 oriented core samples have been collected for paleomagnetic investigation to determine the age assignments of this formation. Rock magnetic experiments revealed that, the hematite is the main magnetic carrier within the studied rocks. Analysis of the demagnetization data isolated a single primary component of magnetization with D=351°, I=36.2° with α95=3.7° and the corresponding pole lies at lat.=77.8°N and long.=257.4°E. The calculated paleomagnetic pole has been found to be primary and enforced, suggesting the age of Malha Formation to be (Aptian-Albian). For the reliability of the obtained pole, a comparison with the published corresponding poles of Cretaceous age in Egypt was done.

Microspherules-Bearing White Sandstone: Implication of Cosmic Impact Event near Jurassic-Cretaceous Boundary in West Central Sinai, Egypt

The presence of glass microspherules enclosing relict grains, shattered quartz and silicon carbide in white sandstone beds near the Jurassic-Cretaceous boundary in west central Sinai indicates a cosmic impact event. Characterization of the impact microspherules and proposing a reasonable scenario for their origin are the aims of this work. Field observations, optical, binocular, scanning electron and high-resolution transmitted electron microscopy investigations and chemical analyses were carried out. The study revealed that glass microspherules have high Al2O3 and FeO contents and low CaO and MgO contents. The high content of Al2O3 indicates that the source of microtektite-like microspherules is attributed to the melting of a clay-rich sandstone and carbonaceous matter, while the high content of FeO indicates admixing with projectile matter. The reaction between silica and carbon was carried out under conditions of high temperature (T > 1000&#176C) and carbon (C/Si > 1) which resulted in the production of silicon carbide with microdiamond intergrowth. Consequently, this intergrowth is in accordance with the impact origin via rapid condensation and growth within a vapor phase. In spite of the fact that no source crater has been recognized to date in the study area, the authors propose at least a single cosmic impact event scenario for the recorded glass microspherules in west central Sinai. The impact excavated the Paleozoic siliciclastic sedimentary rocks and then the glass microspherules showered the area of study. The deposition of microtektite-like glass particles within the white sandstone beds of the Malha Formation took place in the fluvial plain terrestrial environment. This setting precluded severe post-depositional reworking, yielding preservation of the glass particles in a primary layer. Eventually, lateral migration of the braided channels led to the reworking of the microspherules layer and the spatial dispersal of the shattered quartz.

Petrography, diagenesis and reservoir characteristics of the Pre-Cenomanian sandstone, Sheikh Attia area, East Central Sinai, Egypt

The diagenetic influence on reservoir characteristics was investigated for the Pre-Cenomanian (Early Paleozoic and Early Cretaceous) sandstone sequence in the Sheikh Attia area, East Central Sinai. This sequence can be distinguished into four formations: Sarabit El-Khadim Formation (Cambrian) at the base, Abu Hamata Formation (Cambro-Ordovician), Adedia Formation (Ordovician-Silurian) and Malha Formation (Early Cretaceous) on the top. The sandstones of Pre-Cenomanian sequence in the Sheikh Attia area are dominantly quartz arenites and subarkoses, where the quartz grains constitute about 82.3–98.4% of the framework composition with an average value of approximately 94% of the framework composition. Feldspars range in abundance from 0% to14.2%, with an average value of about 3% of the framework composition. The rock fragments constitute up to 9.8% of volume percent of framework grains, with an average of about 2.7%.Diagenetic events identified in these sandstones include compaction, cementation by calcite, quartz, clay minerals and iron oxides, dissolution and alteration of unstable clastic grains, and tectonically induced grain fracturing. Unstable clastic grains like feldspars suffered considerable alteration to kaolinite.The Pre-Cenomanian (Early Paleozoic and Early Cretaceous) sandstones possess good reservoir characteristics because they retain sufficient porosity and permeability in some intervals. These sandstones are characterized by porosity ranges between 3.80% and 27.60%, and have a permeability range from k⩽0.03mD, for tight sandstones to k⩾50mD, for the more permeable parts. The Pre-Cenomanian sandstones can be classified into four petrophysical flow units (megaport, macroport, mesoport and microport) with varying reservoir performances and are distinguished by comparable ranges of R35.Petrographic observations showed that the Early Paleozoic sandstones are texturally immature owing to the abundance of angular grains, non-uniformity of grain size, high amounts of matrix clay mineral, and high amounts of feldspar grains. The Early Cretaceous sandstones have low amounts of rock fragments, clay minerals, and feldspars grains. Statistical analysis of the petrophysical data confirms that the reservoir quality of Early Cretaceous sandstone is higher than that of Early Paleozoic sandstones (the reservoir quality index of Early Cretaceous sandstone is 0.383μm and for Early Paleozoic sandstones is 0.205μm).

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.

PALYNOLOGY OF THE MID-CRETACEOUS MALHA AND GALALA FORMATIONS, GEBEL EL MINSHERA, NORTH SINAI, EGYPT

Abstract Palynological investigations of the mid-Cretaceous, delta-influenced Malha Formation and superjacent transgressive Galala Formation exposed at Gebel El Minshera, north Sinai, Egypt, have yielded a sparse but biostratigraphically useful record of spores, pollen, and rare dinoflagellate cysts. A representative of the pollen genus Tricolporites, recovered 18 m above the base of the Malha Formation, is post-Aptian in age. An interval comprising the upper Malha Formation and lower Galala Formation is dated as middle Albian/middle Cenomanian based on the occurrence of Elaterosporites klaszii at the base and Afropollis jardinus at the top. A palynoflora from the upper Malha Formation, which includes ephedroids as well as Elaterosporites, has affinities with the Albian–Cenomanian Elaterates Province. The presence of palynomorphs associated with active fluvio-deltaic settings supports a proximal deltaic environment for the deposition of the Malha Formation, with the superjacent Galala Formation representi...

Paleogeographic relation of the Egyptian Northern Galala with the Tethys during the Cretaceous Period

The present study records eighteen clastic and carbonate microfacies associations within the Cretaceous sediments representing the Malha, Galala, and Adabiya Formations, which are exposed between Khashm El Galala and Wadi Qiseib areas along the eastern scarp of the Northern Galala Plateau. The lithofacies characters and the fossil content of the Malha Formation (Lower Cretaceous) suggest a probable extended shallow marine environment interrupted by moderate fluvial sedimentation with tectonic stability and moderate energy. The fine clastics and the faunal content of the lower part of the Galala Formation indicate shallow oscillating sea with much terreginous outlet in a transgressive phase with the beginning of the Cenomanian, while the limestones and dolostones of the rest of the Galala Formation and the Adabiya Formation suggest the progression of the sea during the Turonian. It was an open shelf of moderately deep warm marine conditions of low energy. Integration of the carbonate and the clastic facies analysis with the lithostratigraphic correlation of the Cretaceous sediments through the Southern and the Northern Galala Plateaux exhibited that the first Tethyan flooding had encroached the area through the Aptian-Albian. The second invasion occurred with the beginning of the Cenomanian and continued throughout the Late Cretaceous on the area of Southern Galala Plateau, which stayed in connection with the Tethys, while the area of Northern Galala Plateau, most probably, had emerged after the Turonian time or the younger Cretaceous ages till Middle Paleocene.

Allogenic and authigenic clays of the Lower Palæozoic sandstones of the Naqus Formation at Gebel Gunna, central Sinai, Egypt: their recognition and geological significance

The Lower Palæozoic Naqus Formation of Gebel Gunna in the Sinai Peninsula is conformably underlain by the Araba Formation and unconformably overlain by the Cenomanian Malha Formation. It consists mainly of fine- to medium-grained pebbly sandstones with a few siltstone and granulestone interbeds. Petrographical, X-ray diffraction, scanning electron microscope and chemical analyses of the sandstones revealed that they are mainly quartzarenite, containing allogenic and authigenic clays. The allogenic clays were found in small amounts. Such clays exhibit some of the characteristic features of infiltration clay coats. The clays coat a few grain surfaces and form meniscus-shaped pore bridges at points of grain contact. In addition, the clays were observed on the surfaces of crystalline authigenic minerals and in-filled elongated pores of partially dissolved feldspar grains. The recorded authigenic clays are mainly kaolinite with a minor amount of illite. The kaolinite exhibits three morphological habits: vermicular, blocky and fan-shaped. The vermicular kaolinite is dominant and was interpreted to have formed by dissolution of feldspar grains. The blocky kaolinite was observed with a textural relationship, indicating that it was neomorphosed after vermicular kaolinite. The fan-shaped kaolinite was found to be a result of mica alteration. Study of both allogenic and authigenic clays has helped in understanding the sedimentological history of the studied sandstones. The sandstones were deposited in a braided stream, buried at depth of about 1–3 km, and afterwards subjected to surface exposure.