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Two brachiopod species, Terebratulina tenuistriata (Leymerie, 1846) and Orthothyris pectinoides (von Koenen, 1984), have been recorded for the first time from the Middle Eocene (Late Lutetian) nummulitic limestone beds in the Darnah Formation at the Wadi Darnah area in Northeast Libya. These brachiopod species are associated here with Nummulites discorbinus (Schlotheim), Nummulites praelyelli (Boukhary and Kamal), and Nummulites bullatus (Schaub) and are widely distributed on this Middle Eocene Nummulites carbonate platform. The two recorded species are common in the Eocene rocks of Europe and the Arabian Gulf. In northern Africa, the brachiopod species Terebratulina tenuistriata (Leymerie) was only recorded from the Middle Eocene (Bartonian) of Egypt, while Orthothyris pectinoides (von Koenen) is firstly recorded from the Middle Eocene of the southern Tethyan Province (NE Libya) in the present work. [ABSTRACT FROM AUTHOR]

Identifying deformational mechanisms and associated structures at various scales, ranging from regional‐scale structures to microscopic fabric, is crucial for the assessment of tectonic development. Thirty‐three samples were taken from the Qazzaz metamorphic core complex to estimate the finite strain for felsic and mafic minerals. These samples included gneisses rocks, monzogranite, and metavolcano–sedimentary rocks for both the Thalbah and Bayda groups. Using the Rf/j and Fry methods, the axial ratios (XZ) range about 2.20 to 7.10 and 1.90 to 9.10, respectively. For various rock units, the strain measurements show moderate to highly deformation. Most of the observed samples show shallow WNW dipping along a N to WNW trend of finite strain (X). The short axes (Z) based to be subvertical foliation related with a subhorizontal foliation. The results demonstrate that contacts generated at semi‐brittle to ductile deformation and that the strain of magnitude has the same value for different lithologic units. It concluded that nappe generation in orogens results from pure shear deformation. [ABSTRACT FROM AUTHOR]

This study investigates the processes leading to karst development in the southeastern part of Riyadh city extending up to Al Kharj. Numerous solution features such as sinkholes, collapsed dolines, and solution caverns are common in the area. The role of water in the development of the karst features was investigated using an integrated geological and hydrochemical approach. Geological investigations included the petrographic analysis of rock samples collected from zones of intense karstification with special emphasis on mineral dissolution. The study showed that the Sulaiy Formation is commonly fractured, brecciated, foliated, and contains numerous cavities, vugs, and openings. These features have formed by mineral dissolution by circulating groundwater, which has removed anhydrite beds from the underlying Arab–Hith sequence. Karstification likely started from the tectonically weak zones when there was more groundwater recharge. Studies show that during the early to mid-Holocene period, the climate in the Arabian Peninsula was humid, promoting groundwater recharge and subsequent mineral dissolution, though the process of karstification must have started much earlier. Hydrochemical findings reveal that mineral dissolution (halite and calcium sulfate) is the main process affecting groundwater chemistry. The Piper plot revealed two main hydrochemical facies: the (Ca2+ + Mg2+)–(Cl+ SO42−) Type (Type A) and the (Na+ + K+)–(SO42− + Cl) Type (Type B). Most of the samples belong to Type B, typical of groundwater facies affected by dissolution of halite and anhydrite mineral. The absence of the (Ca2+ + Mg2+)–(CO32− + HCO3−) type of groundwater facies indicates a lack of recent groundwater recharge and the removal of carbonate minerals from the system through precipitation, as evidenced by the saturation indices. Plots of the major ionic pairs (cations vs. anions) in groundwater indicate strong halite and gypsum/anhydrite dissolution. Of the three carbonate minerals, calcite has the highest average saturation index followed by aragonite and dolomite. This suggests significant past rock–water interaction leading to carbonate dissolution. Presently, any additional calcium or carbonate ions introduced into the water lead to calcite precipitation. The study indicates that the process of karst development may not be active today. Currently, groundwater chemistry is mainly influenced by rock–water interaction leading to gypsum/anhydrite dissolution, which has resulted in a high concentration of Na+, Ca2+, Cl− and SO42− ions in groundwater. The dissolution of gypsum and halite from the Hith Formation weakens the structural integrity of the overlying Sulaiy Formation, creating large underground cavities. These cavities increase the risk of roof collapse, leading to cover-collapse sinkholes as the roof becomes too thin to support the weight above. [ABSTRACT FROM AUTHOR]

AbstractThis study presents a comprehensive characterization of the Pliocene reservoir formation in the Temsah gas field, located 65 km NNW of Port Said in the northeastern Nile Delta Basin. The research integrates seismic data with well log analysis to enhance reservoir characterization. The Temsah gas field is distinguished by its intricate geological structure, featuring numerous normal faults oriented along northeast-southwest and northwest-southeast trends. The field’s stratigraphy is predominantly composed of sandstone and shale facies, which are considered highly prospective for hydrocarbon accumulation. A full geological field analysis was conducted to identify key prospects for enhancing productivity. To accurately delineate seismic features, data from four wells and twenty-nine 2D seismic lines were interpreted. Depth maps of the reservoir layers were constructed, highlighting critical transitions between sandstone and shale facies, which are pivotal for future exploration efforts. A detailed 3D static model was developed to illustrate the impact of lithological composition on reservoir characteristics, with a specific focus on the Upper Sand of Kafr El-Sheikh Formation. Petrophysical properties, including effective porosity (13–23%), shale content (7–31%), and water saturation (30–45%), were meticulously evaluated to inform the creation of a robust 3D property model. This model provides a detailed spatial distribution of rock facies and petrophysical parameters within the Temsah gas field. The integration of these studies identified two promising areas, with estimated original gas in place (OGIP) ranging from 2.86 to 4.04 stock cubic feet (SCF), indicating significant potential for field development and enhancement. [ABSTRACT FROM AUTHOR]