Journal of African Earth Sciences最新文献

Jurassic tectonic and paleogeographic evolution of the junction zone between the Middle Atlas and High Atlas (Morocco)

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-04-18 DOI: 10.1016/j.jafrearsci.2025.105673

Youssef Ouahzizi, Mohammed Charroud, Driss El Azzab

The Middle Atlas (MA) and High Atlas (HA) chains are considered intraplate basins developed during the Mesozoic Era. The Jurassic structural evolution of the junction between MA-HA recorded three successive tectonic events beginning with a NE-SW extensional tectonic regime responsible for the differentiation between a nearshore environment to northwest with sandstone and pelite deposits, the platform domain with its metric carbonate marls, and a basin domain filled with black marls and limestones with an euxinic character during the Toarcian. In this episode, the sedimentary thickness is controlled by High Atlas trending faults (N120-N110). The second tectonic event corresponds to a tectonic extension regime with an NW-SE to NNW-SSE directed σ3 axis, causing subsidence towards the southeastern part delimited by the Middle Atlas direction faults (NE-SW). The sedimentary series indicates an evolution from a continental environment in the northwest (conglomerates and sandstones) to platform and basin sedimentation in the southeast, noted by the intercalation of marls and bioclastic limestones of the Aalenian–Bajocian age. During the third tectonic event (Bathonian–Barremian), the sedimentary series becomes continental lagoonal deposits represented by marls with limestones, grading into sandstone and gypsum marl, and conglomerates overlain by marls and sandstones of the "Red beds". This evolution associated with by the establishment of a transpressional tectonic regime with NNE-SSW compression σ1 axis responsible for uplift using High Atlas direction faults (E-W to ENE-WSW), caused marine regression; this compression is accompanied by WNW-ESE extension σ3 axis responsible for subsidence towards the southern part with the establishment of basalt lava flows and gabbroic dykes of the Bathonian–Barremian magmatism complex.

中阿特拉斯（MA）链和高阿特拉斯（HA）链被认为是中生代时期形成的板内盆地。中阿特拉斯-高阿特拉斯链交界处的侏罗纪构造演化记录了三个连续的构造事件，首先是东北-西南伸展构造体系，导致西北部近岸环境与砂岩和辉绿岩沉积之间的分化；其次是平台域及其公元碳酸盐泥灰岩；最后是盆地域，其中充满了黑色泥灰岩和石灰岩，具有托阿尔克世时期的曙光特征。在这一时期，沉积厚度由高阿特拉斯走向断层（N120-N110）控制。第二个构造事件与构造延伸机制相对应，其σ3轴线方向为NW-SE至NNW-SSE，导致中阿特拉斯走向断层（NE-SW）划定的东南部沉降。沉积系列显示了从西北部的大陆环境（砾岩和砂岩）到东南部的地台和盆地沉积的演变过程，其中夹杂着泥灰岩和 Aalenian-Bajocian 时代的生物碎屑灰岩。在第三次构造事件（巴托尼安-巴里米安时期）中，沉积系列变成了大陆泻湖沉积，其代表是泥灰岩和灰岩，逐渐变成砂岩和石膏泥灰岩，以及覆盖在泥灰岩和砂岩 "红床 "上的砾岩。与这种演变相关联的是换位构造体系的形成，其 NNE-SSW 压缩σ1 轴负责利用高阿特拉斯方向的断层（E-W 至 ENE-WSW）进行抬升，造成了海洋回归；这种压缩伴随着 WNW-ESE 延伸σ3 轴负责向南部地区下沉，并形成了玄武岩熔岩流和巴吞纪-巴里米亚岩浆复合体的辉长岩堤。

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引用次数: 0

Optimizing permeability and porosity prediction with advanced machine learning: A case study unlocking the complexities of late cretaceous reservoirs, gulf of suez, Egypt

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-04-16 DOI: 10.1016/j.jafrearsci.2025.105670

Amer A. Shehata , Mohamed Ahmed , Ahmed A. Kassem , Ramadan Abdelrehim , Takeshi Tsuji , Amir Ismail

Permeability and porosity are critical parameters that influence the evaluation and management of hydrocarbon reservoirs. Conventional permeability and porosity estimation techniques are constrained by data scarcity and geological variability, necessitating advanced predictive models. This study presents a fully automated machine learning (AML) framework that combines four advanced models—Gradient Boosting Machine (GBM), Distributed Random Forest (DRF), Generalized Linear Model (GLM), and Deep Neural Network (DNN)—to predict permeability and porosity based on well log data. The approach integrates twelve well-log responses (i.e. caliper, gamma ray, sonic, density, porosity, water saturation, volume of shale, resistivity) from five wells (inputs), demonstrating enhanced prediction accuracy for permeability and porosity in the Late Cretaceous reservoirs of the Gulf of Suez, Egypt. To ensure robust model training and validation, the dataset was divided into training (60 %), validation (20 %), and testing (20 %) subsets, and model performance was evaluated using Nash-Sutcliffe Efficiency (NSE), correlation coefficient (r), normalized root mean square error (NRMSE), and bias (B). The DNN model excelled in permeability estimation (testing: NRMSE: 0.57 ± 0.09; NSE: 0.68 ± 0.14; r: 0.82 ± 0.10; B: 9.17), while the DRF model outperformed in predicting porosity (testing: NRMSE: 0.72 ± 0.02; r: 0.69 ± 0.03; NSE: 0.47 ± 0.04; B: 0.93) compared to other models, showcasing superior performance metrics such as Nash-Sutcliff efficiency, correlation coefficients, and normalized root mean square error. The GLM model exhibits the least favorable performance when compared to other ML models. Additionally, this study identifies key well log responses, such as sonic, gamma ray, and deep resistivity logs, as major controlling factors for permeability and porosity predictions, highlighting their nonlinear relationships. The developed AML models provide a cost-efficient, computationally effective, and scalable solution for petrophysical property estimation, enhancing reservoir characterization and enabling broader applications in hydrocarbon exploration and beyond.

渗透率和孔隙度是影响油气藏评估和管理的关键参数。传统的渗透率和孔隙度估算技术受到数据匮乏和地质多变性的制约，因此需要先进的预测模型。本研究提出了一种全自动机器学习（AML）框架，该框架结合了四种先进模型--梯度提升机（GBM）、分布式随机森林（DRF）、广义线性模型（GLM）和深度神经网络（DNN）--根据测井数据预测渗透率和孔隙度。该方法整合了来自五口井（输入）的十二个测井记录响应（即卡尺、伽马射线、声波、密度、孔隙度、水饱和度、页岩体积、电阻率），显示出埃及苏伊士湾晚白垩世储层渗透率和孔隙度预测精度的提高。为确保模型训练和验证的稳健性，数据集被分为训练子集（60%）、验证子集（20%）和测试子集（20%），并使用纳什-苏克里夫效率（NSE）、相关系数（r）、归一化均方根误差（NRMSE）和偏差（B）对模型性能进行了评估。DNN 模型在渗透率估计方面表现出色（测试：NRMSE：0.57 ± 0.09；NSE：0.68 ± 0.14；r：0.82 ± 0.10；B：9.17），而 DRF 模型在预测孔隙度方面表现出色（测试：NRMSE：0.72 ± 0.02；r：0.69 ± 0.03；NSE：0.47 ± 0.04；B：0.93），在纳什-苏特克利夫效率、相关系数和归一化均方根误差等性能指标上均优于其他模型。与其他 ML 模型相比，GLM 模型的性能最差。此外，这项研究还确定了主要的测井反应，如声波、伽马射线和深层电阻率测井，作为渗透率和孔隙度预测的主要控制因素，并强调了它们之间的非线性关系。所开发的 AML 模型为岩石物理特性估算提供了一种成本效益高、计算效率高、可扩展的解决方案，可增强储层特征描述，并在油气勘探及其他领域实现更广泛的应用。

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引用次数: 0

Application of time domain induced polarization technique to study perched groundwater at the northwestern coast of Egypt: A case study of Fuka basin

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-04-16 DOI: 10.1016/j.jafrearsci.2025.105671

Ahmed Elshenawy

Perched groundwater resources, essential for drinking, tourism, and irrigation, have not been extensively studied. These resources are finite, vary in salinity, and are threatened by overexploitation, contamination, and rising sea levels due to climate change. A survey using Two-Dimensional Electrical Resistivity Tomography (2DERT) and Time Domain Induced Polarization (2DTDIP) techniques was conducted in the Fuka basin to map the shallow perched aquifer, determine stratigraphic units, and assess the effectiveness of differentiating between aquifer and aquitard deposits with low resistivity. The study tested the condition of perched groundwater by performed two synthetic models. These models can considerably help in the interpretation of real field measurements since they provide a reference for predicted observations under known settings. Moreover, four combined 2DERT/2DTDIP profiles were carried out in Fuka basin where the low permeability clay bands were investigated in the subsurface succession. The comprehensive examination of four 2DERT/2DTDIP lines reveals significant differences in electrical resistivity, chargeability, and normalized chargeability profiles. The 2DTDIP effectively identified the perched water zone at various depths between 20 and 30 m, indicated by high chargeability and normalized chargeability associated with clay bands which underlain the floating perched water layer. Low resistivity (11–23 Ω m) longitudinal anomalies were interpreted as saturated fracture limestone, allowing penetrating rainfalls to accumulate above this zone. High chargeability anomalies (20-25mv/v) appearing directly below fractured limestone were inferred to impermeable lenses of clay. The simultaneous interpretation of electrical resistivity and induced polarization datasets successfully differentiate between aquifer and aquitard deposits offering a highly promising strategy for identifying perched water zones at conductive at low resistivity deposits.

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引用次数: 0

The Volta basin in Burkina Faso: Lithologic and structural geology constraints along the leading edge of the foreland Dahomeyide fold-thrust belt

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-04-16 DOI: 10.1016/j.jafrearsci.2025.105660

Kim A.A. Hein , Stephan Séjourné , Clément Ouédraogo , Gnissa Sidibé , Richard Dahl , Guy Kevin Coulibaly

The Volta basin in Ghana, Togo and Benin has a narrow NE-striking panhandle extension into Burkina Faso where the Pan-African Dahomeyide fold-thrust belt approaches Paleoproterozoic basement rocks (ca. 2.25–2.10 Ga). We present the results of integrated stratigraphic, structural geology studies of the Volta Basin in Burkina Faso that combines interpretations of high-resolution remote sensing imagery, radiometrics and magnetics to appraise the metasedimentary sequences and stratigraphic setting. We evaluate the degree of deformation and metamorphism across the Volta basin in Burkina Faso and contextualize the tectonic domains with reference to published data for the broader Volta Basin.

The results indicate that felspathic sandstones and greywackes of the Madjoari and Gobnangou massifs were deposited in the Tonian Period (ca. 1000-855 Ma) in a shallow marine environment along the Rodinia continental passive margin. Diamictites, dolomite, chert, phosphorite (576 ± 13 Ma) of the Kodjari Group and siltstone-shale sequences of the Porga Group were deposited in an offshore basin in the middle Ediacaran Period (ca. 635-538 Ma) syn-to post Ediacaran glaciation and possibly during a period of deglaciation.

These metasedimentary rocks were deformed during two deformation events, D1 and D2. D1 ductile-brittle deformation was concomitant to NW-directed fold-thrust formation within the foreland Dahomeyide fold-thrust belt. The intensity of deformation decreases across the panhandle (SE to NW) from isoclinal folding and thrust formation in Atacora Structural Unit, to open style low fold forms near the Madjoari and Gobnangou massifs. In concert, metamorphic grade decreases from greenschist-amphibolite to very low grade (anchimetamorphic).

D2 brittle deformation was progressive, with incremental development of joints, fracture-corridors, fracture-faults and open fold forms during east-west directed shortening.

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引用次数: 0

The potential of Middle Eocene to early Miocene benthic foraminifera as paleoecological indicators in the Qattara Depression, Western desert, Egypt

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-04-11 DOI: 10.1016/j.jafrearsci.2025.105668

Abdalla Shahin, Samar El Khawagah, Banan Shahin

A comprehensive investigation and analysis were conducted on a total of 105 benthic foraminiferal species. They were extracted from the subsurface Middle Eocene to Lower Miocene strata in the N. El Faras - 1X Well, located in the Qattara Depression of the northern Western Desert, Egypt. The stratigraphic succession primarily encompasses the upper part of the Apollonia Formation (middle to late Eocene), the Dabaa Formation (late Eocene and Oligocene), and the lower part of the Moghra Formation (Early Miocene). Paleoecological multi-proxies analysis were leveraged, including Total Foraminiferal Number (TFN), Planktonic/Benthic Ratio (%P), Species Richness (SR), Diversity Index (Fisher alpha index), Ternary plot for foraminiferal assemblage structure, Agglutinated/Calcareous Ratio (Aggl/Calc), Epifaunal/Infaunal Ratio (Ep/In), and the Trophic-Oxygen (TROX) Model.

Qualitative and quantitative analyses of the encountered benthic foraminifera, alongside CONISS cluster analysis, facilitated the delineation of five distinct clusters, each characterized by unique fossil content and paleoenvironmental attributes. Generally, the first cluster was characterized by oxic to dysoxic conditions and oligotrophic to highly oligotrophic conditions within middle to outer neritic setting. Clusters 2 and 3 were characterized by oxic to dysoxic conditions and oligotrophic to mesotrophic settings. The fourth cluster exhibited oxic to dysoxic conditions alongside mesotrophic to eutrophic conditions, and situated within a middle neritic and euphotic zone. Lastly, the fifth cluster demonstrated a gradual decrease in paleodepth within the inner neritic and euphotic zone, featuring a well oxygenated environment and mesotrophic to eutrophic conditions.

{"title":"The potential of Middle Eocene to early Miocene benthic foraminifera as paleoecological indicators in the Qattara Depression, Western desert, Egypt","authors":"Abdalla Shahin, Samar El Khawagah, Banan Shahin","doi":"10.1016/j.jafrearsci.2025.105668","DOIUrl":"10.1016/j.jafrearsci.2025.105668","url":null,"abstract":"<div><div>A comprehensive investigation and analysis were conducted on a total of 105 benthic foraminiferal species. They were extracted from the subsurface Middle Eocene to Lower Miocene strata in the N. El Faras - 1X Well, located in the Qattara Depression of the northern Western Desert, Egypt. The stratigraphic succession primarily encompasses the upper part of the Apollonia Formation (middle to late Eocene), the Dabaa Formation (late Eocene and Oligocene), and the lower part of the Moghra Formation (Early Miocene). Paleoecological multi-proxies analysis were leveraged, including Total Foraminiferal Number (TFN), Planktonic/Benthic Ratio (%P), Species Richness (SR), Diversity Index (Fisher alpha index), Ternary plot for foraminiferal assemblage structure, Agglutinated/Calcareous Ratio (Aggl/Calc), Epifaunal/Infaunal Ratio (Ep/In), and the Trophic-Oxygen (TROX) Model.</div><div>Qualitative and quantitative analyses of the encountered benthic foraminifera, alongside CONISS cluster analysis, facilitated the delineation of five distinct clusters, each characterized by unique fossil content and paleoenvironmental attributes. Generally, the first cluster was characterized by oxic to dysoxic conditions and oligotrophic to highly oligotrophic conditions within middle to outer neritic setting. Clusters 2 and 3 were characterized by oxic to dysoxic conditions and oligotrophic to mesotrophic settings. The fourth cluster exhibited oxic to dysoxic conditions alongside mesotrophic to eutrophic conditions, and situated within a middle neritic and euphotic zone. Lastly, the fifth cluster demonstrated a gradual decrease in paleodepth within the inner neritic and euphotic zone, featuring a well oxygenated environment and mesotrophic to eutrophic conditions.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105668"},"PeriodicalIF":2.2,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Zircon U–Pb ages and Sr-Nd isotope ratios for the mafic microgranular enclaves in the sirstan cretaceous granitoids, NE Iraq: Evidence of cogenetic magmatic origin

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-04-11 DOI: 10.1016/j.jafrearsci.2025.105665

Imad Kadhim Abdulzahra , Yoshihiro Asahara , Yousif Mohammad , Irfan Yara

Mafic microgranular enclaves (MMEs) are observed in the Sirstan granitoid (SG) body in the Shalair Valley area, northeastern Iraq, within the Zagros Orogenic Belt. Zircon U–Pb ages for the MMEs are 110 Ma with an I-type affinity closely resembling the enclosing rocks. The MMEs are gabbroic-diorite to diorite in composition, and the main mineral assemblage are plagioclase, hornblende, and K-feldspar. The MMEs are intermediate in composition and have low SiO₂ (52.0–60.2 wt%) and high Fe₂O₃, Al₂O₃, TiO₂ and CaO contents (Fe₂O₃ = 8.7–13.3 wt%; Al₂O₃ = 14.8–17.2 wt%; TiO₂ = 0.71–1.02 wt%; CaO = 3.4–11.4 wt%). The enclaves have analogous Sr and Nd isotope compositions with positive εNd_(t) values (⁸⁷Sr/⁸⁶Sr(i) = 0.7047 to 0.7058; εNd_(t) = +2.0 to +2.5) as their host granitoids (⁸⁷Sr/⁸⁶Sr(i) = 0.7044 to 0.7057; εNd_(t) = +0.1 to +2.7). The uniform REE patterns and the fractionation trends of major and trace elements of the MMEs with their host rocks indicate simultaneous crystallization by fractionation from the same magma source. According to the geochemical aspects of the MMEs and their host SG rocks with young T_DM ages (676–720 Ma), the low ratios of the Rb/Sr and Nb/Y ratios, in addition to the same ages and Sr-Nd isotope ratios, infer that the same source magma was derived from a young depleted mantle without the contribution of ancient crustal components.

{"title":"Zircon U–Pb ages and Sr-Nd isotope ratios for the mafic microgranular enclaves in the sirstan cretaceous granitoids, NE Iraq: Evidence of cogenetic magmatic origin","authors":"Imad Kadhim Abdulzahra , Yoshihiro Asahara , Yousif Mohammad , Irfan Yara","doi":"10.1016/j.jafrearsci.2025.105665","DOIUrl":"10.1016/j.jafrearsci.2025.105665","url":null,"abstract":"<div><div>Mafic microgranular enclaves (MMEs) are observed in the Sirstan granitoid (SG) body in the Shalair Valley area, northeastern Iraq, within the Zagros Orogenic Belt. Zircon U–Pb ages for the MMEs are 110 Ma with an I-type affinity closely resembling the enclosing rocks. The MMEs are gabbroic-diorite to diorite in composition, and the main mineral assemblage are plagioclase, hornblende, and K-feldspar. The MMEs are intermediate in composition and have low SiO<sub>2</sub> (52.0–60.2 wt%) and high Fe<sub>2</sub>O<sub>3</sub>, Al<sub>2</sub>O<sub>3</sub>, TiO<sub>2</sub> and CaO contents (Fe<sub>2</sub>O<sub>3</sub> = 8.7–13.3 wt%; Al<sub>2</sub>O<sub>3</sub> = 14.8–17.2 wt%; TiO<sub>2</sub> = 0.71–1.02 wt%; CaO = 3.4–11.4 wt%). The enclaves have analogous Sr and Nd isotope compositions with positive εNd<sub>(t)</sub> values (<sup>87</sup>Sr/<sup>86</sup>Sr(i) = 0.7047 to 0.7058; εNd<sub>(t)</sub> = +2.0 to +2.5) as their host granitoids (<sup>87</sup>Sr/<sup>86</sup>Sr(i) = 0.7044 to 0.7057; εNd<sub>(t)</sub> = +0.1 to +2.7). The uniform REE patterns and the fractionation trends of major and trace elements of the MMEs with their host rocks indicate simultaneous crystallization by fractionation from the same magma source. According to the geochemical aspects of the MMEs and their host SG rocks with young T<sub>DM</sub> ages (676–720 Ma), the low ratios of the Rb/Sr and Nb/Y ratios, in addition to the same ages and Sr-Nd isotope ratios, infer that the same source magma was derived from a young depleted mantle without the contribution of ancient crustal components.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105665"},"PeriodicalIF":2.2,"publicationDate":"2025-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143854861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The structure of Precambrian crust in sub-Saharan Africa: An AfricaArray synthesis and review

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-04-10 DOI: 10.1016/j.jafrearsci.2025.105664

Alexandra Sabattier , Andrew Nyblade , Raymond Durrheim , Fenitra Andriampenomanana , Andriamiranto Raveloson , Islam Fadel , Mark van der Meijde , Amanda Willet

We combine new estimates of crustal thickness and shear wave velocities from 48 broadband seismic stations in Mozambique, Namibia, South Africa and Uganda with previously published results to review and examine Precambrian crustal structure in sub-Saharan Africa for secular trends. The ensemble of crustal structure estimates used relies heavily on data obtained through the AfricaArray initiative, which is briefly reviewed. Whether or not Precambrian crustal structure exhibits notable changes from the Mesoarchean through the Neoproterozoic places a key constraint on continental crustal genesis and evolution. Our 48 new estimates of Moho depth and crustal shear wave velocity profiles, combined with results from similar previous studies, yield an average crustal thickness for all Precambrian terranes of 39 ± 4 km. We find that average crustal thicknesses are essentially identical for Mesoarchean (38 ± 3 km), Neoarchean (39 ± 4 km), Paleoproterozoic (40 ± 4 km), Mesoproterozoic (40 ± 4 km) and Neoproterozoic (39 ± 4 km) terranes. The average thickness of the mafic lower crust, identified by high velocity layering (Vs > 4.0 km/s), is also almost identical in Archean and Proterozoic terranes (7 ± 4 km and 6 ± 4 km, respectively). Finally, the average crustal shear wave velocities for all terranes fall within 1 standard deviation of a mean velocity of 3.7 km/s. These results are consistent with findings from other studies highlighting a lack of evidence for secular variation in crustal structure or composition within Precambrian terranes in sub-Saharan Africa, suggesting that secular trends, if they existed at the time of crust formation, have been obscured by crustal reworking during later orogenic and/or magmatic events.

{"title":"The structure of Precambrian crust in sub-Saharan Africa: An AfricaArray synthesis and review","authors":"Alexandra Sabattier , Andrew Nyblade , Raymond Durrheim , Fenitra Andriampenomanana , Andriamiranto Raveloson , Islam Fadel , Mark van der Meijde , Amanda Willet","doi":"10.1016/j.jafrearsci.2025.105664","DOIUrl":"10.1016/j.jafrearsci.2025.105664","url":null,"abstract":"<div><div>We combine new estimates of crustal thickness and shear wave velocities from 48 broadband seismic stations in Mozambique, Namibia, South Africa and Uganda with previously published results to review and examine Precambrian crustal structure in sub-Saharan Africa for secular trends. The ensemble of crustal structure estimates used relies heavily on data obtained through the AfricaArray initiative, which is briefly reviewed. Whether or not Precambrian crustal structure exhibits notable changes from the Mesoarchean through the Neoproterozoic places a key constraint on continental crustal genesis and evolution. Our 48 new estimates of Moho depth and crustal shear wave velocity profiles, combined with results from similar previous studies, yield an average crustal thickness for all Precambrian terranes of 39 ± 4 km. We find that average crustal thicknesses are essentially identical for Mesoarchean (38 ± 3 km), Neoarchean (39 ± 4 km), Paleoproterozoic (40 ± 4 km), Mesoproterozoic (40 ± 4 km) and Neoproterozoic (39 ± 4 km) terranes. The average thickness of the mafic lower crust, identified by high velocity layering (Vs > 4.0 km/s), is also almost identical in Archean and Proterozoic terranes (7 ± 4 km and 6 ± 4 km, respectively). Finally, the average crustal shear wave velocities for all terranes fall within 1 standard deviation of a mean velocity of 3.7 km/s. These results are consistent with findings from other studies highlighting a lack of evidence for secular variation in crustal structure or composition within Precambrian terranes in sub-Saharan Africa, suggesting that secular trends, if they existed at the time of crust formation, have been obscured by crustal reworking during later orogenic and/or magmatic events.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105664"},"PeriodicalIF":2.2,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143834841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The first definitive Albian ammonites from the Kribi-Campo sub-basin in Cameroon and biostratigraphic implications for the opening of the South Atlantic

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-04-09 DOI: 10.1016/j.jafrearsci.2025.105659

Elie Fosso Menkem , Emmanuel Robert , Paul Gustave Fowe Kwetche , Marie-Joseph Ntamak Nida , Jeremy E. Martin

The timing of the opening of the Equatorial South Atlantic Ocean during the Cretaceous is poorly constrained. Despite previous research carried out along the West African continental margin, the biostratigraphic attribution of the Kribi-Campo sedimentary deposits in Cameroon remain poorly known leading to uncertainties in the ages of the formation and thus leading to incorrect interpretations and correlations of stratigraphic sequences. To date, the deposits are known to correspond to alluvial fan facies from the Lower Mundeck Formation and the assigned age is Barremian?-Aptian. We carried out a prospection in the sedimentary outcrops along the shoreline in the Kribi-Campo sub-Basin where poorly preserved but identifiable ammonite specimens were discovered and collected for analysis in order to determine the age of the formation. The marker bed containing the ammonite fossils consists of thin carbonaceous sandy shale. Our determinations revealed the following ammonites: Douvilleiceras sp. and Uhligellinae that characterize the basal Lower Albian (Douvilleiceras leightonense Zone) interval. This result allows us to suggest a reconsideration of the Kribi-Campo sub-basin deposits to be part of the upper Mundeck Formation. Our results confirm a diachronic separation of South America and Africa and a full connection between the North and South Atlantic Ocean during the Lower Albian.

{"title":"The first definitive Albian ammonites from the Kribi-Campo sub-basin in Cameroon and biostratigraphic implications for the opening of the South Atlantic","authors":"Elie Fosso Menkem , Emmanuel Robert , Paul Gustave Fowe Kwetche , Marie-Joseph Ntamak Nida , Jeremy E. Martin","doi":"10.1016/j.jafrearsci.2025.105659","DOIUrl":"10.1016/j.jafrearsci.2025.105659","url":null,"abstract":"<div><div>The timing of the opening of the Equatorial South Atlantic Ocean during the Cretaceous is poorly constrained. Despite previous research carried out along the West African continental margin, the biostratigraphic attribution of the Kribi-Campo sedimentary deposits in Cameroon remain poorly known leading to uncertainties in the ages of the formation and thus leading to incorrect interpretations and correlations of stratigraphic sequences. To date, the deposits are known to correspond to alluvial fan facies from the Lower Mundeck Formation and the assigned age is Barremian?-Aptian. We carried out a prospection in the sedimentary outcrops along the shoreline in the Kribi-Campo sub-Basin where poorly preserved but identifiable ammonite specimens were discovered and collected for analysis in order to determine the age of the formation. The marker bed containing the ammonite fossils consists of thin carbonaceous sandy shale. Our determinations revealed the following ammonites: <em>Douvilleiceras</em> sp. and Uhligellinae that characterize the basal Lower Albian (<em>Douvilleiceras leightonense</em> Zone) interval. This result allows us to suggest a reconsideration of the Kribi-Campo sub-basin deposits to be part of the upper Mundeck Formation. Our results confirm a diachronic separation of South America and Africa and a full connection between the North and South Atlantic Ocean during the Lower Albian.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105659"},"PeriodicalIF":2.2,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143839691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Integrated geophysical assessment of Miocene Belayim reservoirs in the Tawila West Oil Field, offshore southern Gulf of Suez, Egypt

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-04-09 DOI: 10.1016/j.jafrearsci.2025.105661

Mohammad Abdelfattah Sarhan , Mu'ayyad Al Hseinat , Malek AlZidaneen

This study evaluates the Miocene Belayim reservoirs in the Tawila West Oil Field (TWOF), located offshore in the southern Gulf of Suez Basin, Egypt. By integrating seismic interpretation with petrophysical data from four wells (TW-1, TW-2, TW-5 ST3-A, and TW-6), the research characterizes reservoir properties and evaluates hydrocarbon potential. Seismic data reveal that NW-SE trending fault systems, forming graben structures within the Belayim Formation, significantly influence the distribution and thickness of the reservoirs. Depth-structure maps for key horizons, Belayim #1 and Belayim #4, highlight notable vertical displacements and structural heterogeneity. These faults align with the Early Miocene tectonic activity associated with the Red Sea-Gulf of Suez rift system and play a critical role in shaping reservoir intervals. Petrophysical analysis indicates that Belayim #1 exhibits superior reservoir quality, with low shale volume (∼10 %), low water saturation (∼20 %), high hydrocarbon saturation (∼80 %), and effective porosity ranging from 15 % to 18 %. In contrast, Belayim #4 displays higher shale volume, lower effective porosity (8 %–12 %), and variable hydrocarbon saturation (40 %–55 %). Belayim #1 emerges as the primary target for hydrocarbon extraction, while Belayim #4 requires careful evaluation due to its structural and petrophysical characteristics. This study underscores the value of integrating seismic and petrophysical data to enhance reservoir characterization and optimize hydrocarbon recovery in TWOF.

{"title":"Integrated geophysical assessment of Miocene Belayim reservoirs in the Tawila West Oil Field, offshore southern Gulf of Suez, Egypt","authors":"Mohammad Abdelfattah Sarhan , Mu'ayyad Al Hseinat , Malek AlZidaneen","doi":"10.1016/j.jafrearsci.2025.105661","DOIUrl":"10.1016/j.jafrearsci.2025.105661","url":null,"abstract":"<div><div>This study evaluates the Miocene Belayim reservoirs in the Tawila West Oil Field (TWOF), located offshore in the southern Gulf of Suez Basin, Egypt. By integrating seismic interpretation with petrophysical data from four wells (TW-1, TW-2, TW-5 ST3-A, and TW-6), the research characterizes reservoir properties and evaluates hydrocarbon potential. Seismic data reveal that NW-SE trending fault systems, forming graben structures within the Belayim Formation, significantly influence the distribution and thickness of the reservoirs. Depth-structure maps for key horizons, Belayim #1 and Belayim #4, highlight notable vertical displacements and structural heterogeneity. These faults align with the Early Miocene tectonic activity associated with the Red Sea-Gulf of Suez rift system and play a critical role in shaping reservoir intervals. Petrophysical analysis indicates that Belayim #1 exhibits superior reservoir quality, with low shale volume (∼10 %), low water saturation (∼20 %), high hydrocarbon saturation (∼80 %), and effective porosity ranging from 15 % to 18 %. In contrast, Belayim #4 displays higher shale volume, lower effective porosity (8 %–12 %), and variable hydrocarbon saturation (40 %–55 %). Belayim #1 emerges as the primary target for hydrocarbon extraction, while Belayim #4 requires careful evaluation due to its structural and petrophysical characteristics. This study underscores the value of integrating seismic and petrophysical data to enhance reservoir characterization and optimize hydrocarbon recovery in TWOF.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105661"},"PeriodicalIF":2.2,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143854862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Extreme impact of the Late Cretaceous–Paleocene tectonic events on the evolution of the southern Tethyan margin: a case study from Eastern Desert, Egypt

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2025-04-09 DOI: 10.1016/j.jafrearsci.2025.105663

Ibrahim Y. El-Mohandes , Kamel H. Mahfouz , Jun Shen , Nageh A. Obaidalla , Abeer Shreif , Islam El-Sheikh

The well-distributed Late Cretaceous–early Paleogene rocks in Egypt are one of the keys to understanding the geologic history of the southern Tethys. Four Late Cretaceous–early Paleogene successions exposed in the Esh-ElMellaha area were investigated. The integrated stratigraphic analyses, including; field, lithostratigraphy and biostratigraphy of these sections within the Esh-ElMellaha ridge showed interesting results. Intensive tectonic processes throughout Paleocene period substantially influenced all rock units, causing differences in their facies and thickness. In addition, these tectonic processes deformed the sedimentary basins. During the Paleocene, Esh-ElMellaha area experienced two significant syn-sedimentary tectonic events (I and II) related to the Syrian Arc Tectonic Event. The evolution of the Esh-ElMellaha basin has been documented for the first time throughout this period which is extremely dependent upon these tectonic events. Four paleo-relief profiles were created to illustrate how these events impacted the history of sedimentary basins, extending from the North Wadi Qena northward to the Gabal Hamadat southward. The strength of tectonic events caused the Esh-ElMellaha area to undergo substantially varied degrees of instability. These profiles demonstrate the stability of the deposition during the Maastrichtian period. However, during the Danian, the basin experienced the deposition of thin strata expanding from north to south. This uplifted the basin into submarine paleohigh and created an erosional surface. During the late Paleocene (Selandian-Thanetian), the basin was deeper in the south (Hamadat) than in the north (North Wadi Qena). In contrast, the basin in the Esh-ElMellaha area became an aerial paleohigh, an event that began at the end of the Danian and continued until the early Eocene (Ypresian). This uplift led to the formation of significant paleosol layers. Moreover, the depocenter's southern sections of Esh-ElMellaha had a less tectonic effect, while the northern regions of Esh-ElMellaha witnessed extreme tectonic activity.

{"title":"Extreme impact of the Late Cretaceous–Paleocene tectonic events on the evolution of the southern Tethyan margin: a case study from Eastern Desert, Egypt","authors":"Ibrahim Y. El-Mohandes , Kamel H. Mahfouz , Jun Shen , Nageh A. Obaidalla , Abeer Shreif , Islam El-Sheikh","doi":"10.1016/j.jafrearsci.2025.105663","DOIUrl":"10.1016/j.jafrearsci.2025.105663","url":null,"abstract":"<div><div>The well-distributed Late Cretaceous–early Paleogene rocks in Egypt are one of the keys to understanding the geologic history of the southern Tethys. Four Late Cretaceous–early Paleogene successions exposed in the Esh-ElMellaha area were investigated. The integrated stratigraphic analyses, including; field, lithostratigraphy and biostratigraphy of these sections within the Esh-ElMellaha ridge showed interesting results. Intensive tectonic processes throughout Paleocene period substantially influenced all rock units, causing differences in their facies and thickness. In addition, these tectonic processes deformed the sedimentary basins. During the Paleocene, Esh-ElMellaha area experienced two significant syn-sedimentary tectonic events (I and II) related to the Syrian Arc Tectonic Event. The evolution of the Esh-ElMellaha basin has been documented for the first time throughout this period which is extremely dependent upon these tectonic events. Four paleo-relief profiles were created to illustrate how these events impacted the history of sedimentary basins, extending from the North Wadi Qena northward to the Gabal Hamadat southward. The strength of tectonic events caused the Esh-ElMellaha area to undergo substantially varied degrees of instability. These profiles demonstrate the stability of the deposition during the Maastrichtian period. However, during the Danian, the basin experienced the deposition of thin strata expanding from north to south. This uplifted the basin into submarine paleohigh and created an erosional surface. During the late Paleocene (Selandian-Thanetian), the basin was deeper in the south (Hamadat) than in the north (North Wadi Qena). In contrast, the basin in the Esh-ElMellaha area became an aerial paleohigh, an event that began at the end of the Danian and continued until the early Eocene (Ypresian). This uplift led to the formation of significant paleosol layers. Moreover, the depocenter's southern sections of Esh-ElMellaha had a less tectonic effect, while the northern regions of Esh-ElMellaha witnessed extreme tectonic activity.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"228 ","pages":"Article 105663"},"PeriodicalIF":2.2,"publicationDate":"2025-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143820521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0