Journal of African Earth Sciences最新文献

{"title":"Reservoir characterization and facies modeling of the gas-bearing Kafr El Sheikh and Abu Madi reservoirs in the Disouq Field, Nile delta, Egypt: An integrated petrophysical, pressure, and seismic study","authors":"Mennat Allah Nafady ,&nbsp;Munir Elmahdy ,&nbsp;Ahmed A. Radwan ,&nbsp;Bassem S. Nabawy ,&nbsp;Ahmed Abdelhady ,&nbsp;Abdalla Mousa El-Ayyat ,&nbsp;Ezzat A. Ahmed","doi":"10.1016/j.jafrearsci.2025.105566","DOIUrl":"10.1016/j.jafrearsci.2025.105566","url":null,"abstract":"<div><div>Kafr El Sheikh (KES) and Abu Madi formations are among the potential gas-producing reservoirs in the Nile Delta, promoting numerous efforts to characterize them. Based on a full set of conventional well log data from four wells in the Disouq Field in the northwestern Desert, the petrophysical properties and hydrocarbon potentiality of these two formations were figured out. When litho-saturation, neutron-density, and M-N plots are integrated together, they show that the two studied reservoirs are mostly made up of shale with some sand lenses and lobes that could be potential reservoirs. We further subdivide the KES Formation into KES IIIA, KES IIIB, KES IIIC, and KES IIID based on the petrophysical data. The petrophysical parameters of both the Abu Madi Formation (7.77 m &lt; net-pay &lt;13.72 m, 20.8% &lt; ∅e &lt; 25.8%, 34.4% &lt; Sw &lt; 51.8%, and 20.3% &lt; Vsh &lt;22.6%) and the KES Formation (1.98 m &lt; net-pay &lt;10.0 m, 23.1% &lt; ∅e &lt; 25.3%, 29.5% &lt; Sw &lt; 42.4%, and 29.0% &lt; Vsh &lt;32.0%) indicate a high potentiality for these two reservoirs. The seismic data revealed the existence of an E-W trending 4-way dip closure and a major N-S normal fault that intersects the field, forming an anticline in its upper block. The pressure data from the repeat formation tester (RFT) helped figure out the free water level (FWL) between the gas and water aquifer at depths of 7296 ft and 7850 ft for the DSQ 1–3 and DSQ 1–5 wells. In the DSQ-2X well, the water is found at a shallower depth interval (upper compartment at 1943–2170 m depth interval) than in two deeper gas-bearing reservoirs (middle and lower compartments at 2170–2230 m and 2230–2270 m depth intervals), which means that there are three separate compartments.</div><div>The integration between the well log and seismic data enabled more detailed delineation for the complex structural setting of the field and detailed characterization for its reservoir and petrophysical properties. This study is applicable to the similar 4-way dip closure, which is dominant in the Nile Delta and other similar prograding river-dominated deltas. Analogous sequences in deltaic and nearshore areas in Africa and worldwide can utilize the applied workflow.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"225 ","pages":"Article 105566"},"PeriodicalIF":2.2,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143419528","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}

{"title":"Petrological constraints of the Ediacaran magmatic intrusions, Homrit Mukpid area, southeastern Desert, Egypt: Bulk rock geochemistry and mineralogy","authors":"El Saeed R. Lasheen ,&nbsp;Rainer Abart ,&nbsp;Mohamed S. Ahmed ,&nbsp;Khaled M. Abdelfadil ,&nbsp;Esam S. Farahat ,&nbsp;Mabrouk Sami","doi":"10.1016/j.jafrearsci.2025.105567","DOIUrl":"10.1016/j.jafrearsci.2025.105567","url":null,"abstract":"<div><div>The study provides a comprehensive investigation into the evolution and petrogenesis of the Homrit Mukpid (HM) granitic suites, emphasizing their petrological characteristics. The HM granitic rocks comprise two main suites: the older granodioritic suite (GHM) and the younger alkali-feldspar granite suite (AHM). The GHM exhibits notable enrichment in TiO₂, MgO, CaO, Fe₂O₃, Sr, Ba, Cr, V, and Sc, and lower concentrations of Ta, Th, Rb, Y, Nb, Sn, Ga, U, Pb, Zn, and ∑REEs compared to the AHM. Geochemically, GHM is distinguished by pronounced negative P, Ti, and Nb anomalies, as well as a decrease in HREEs (avg. ≈ 11 ppm) relative to LREEs (avg. ≈ 83 ppm) and a moderately negative Eu anomaly (avg. ≈ Eu/Eu∗ = 0.78), characteristic of substantially fractionated, subduction-related I-type magmatic sources. In contrast, the AHM displays high SiO₂ (avg. ≈ 75 wt%), total alkalis (avg. ≈ 9 wt%), and higher FeO/MgO, and Rb contents. Their REEs pattern shows a strong negative Eu anomaly (av. Eu/Eu∗ ≈0.08) and HREEs enrichment, indicative of post-collisional A₂-type granites. Importantly, there is no evidence of M-type tetrad effect, as determined using both the lambda and Irber methods. The evoultion of the HM, as a part of the Arabian Nubian Shield, is marked by distinct stages of collision and post-collision, as inferred from the mineralogical and geochemical data of granitic rocks. The GHM is formed from the subducted slab dehydrating, which facilitated the melting of the upper mantle, providing underplating of high K-mafic melts. The GHM formation is attributed to the dehydration of a subducted slab, which triggered upper mantle melting and the generation of high-K mafic melts. This melt subsequently underwent melting and fractionation at elevated temperatures (avg. ≈ 809 °C, using zircon saturation temperature). Conversely, the AHM formed through slab delamination, inducing asthenospheric upwelling and the melting of tonalitic/clay-rich metapelite rocks, followed by extreme fractional crystallization processes during a post-collisional extension episode at low temperatures (avg. ≈ 784 °C) and shallow depths.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"225 ","pages":"Article 105567"},"PeriodicalIF":2.2,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143419529","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}

{"title":"Petrogenesis of migmatites from Liman Katagum area (Bauchi) North-East Nigeria: Constraints from U-Pb and Lu-Hf isotopic data","authors":"Maimunatu Halilu ,&nbsp;Ahmed Isah Haruna ,&nbsp;Faisal Abdullahi ,&nbsp;Mohamed S. Ahmed ,&nbsp;Vandi Dlama Kamaunji ,&nbsp;Musa Bala Girei ,&nbsp;Ioan V. Sanislav ,&nbsp;El Saeed R. Lasheen ,&nbsp;Mabrouk Sami","doi":"10.1016/j.jafrearsci.2025.105562","DOIUrl":"10.1016/j.jafrearsci.2025.105562","url":null,"abstract":"<div><div>This study investigates the petrogenesis and tectonic evolution of migmatites from the Liman Katagum area in northeast Nigeria. In-situ Lu-Hf isotopic analyses of zircon reveal a complex source history, with εHf(t) values ranging from −13.43 to +8.95 at different ages (482 ± 120 Ma, 582.2 ± 9.0 Ma, and 498 ± 43 Ma). These values suggest contributions from both ancient reworked and juvenile crustal materials, spanning the Chondrite Uniform Reservoir (CHUR) and various crustal domains, indicating significant crustal recycling and juvenile additions. High zircon U/Yb ratios, along with elevated Y and Hf, reflect a strong continental arc affinity, supporting a crustal origin for the migmatites. Geochemical and morphological evidence, including enriched heavy rare earth elements (HREEs) and variable Th/U ratios, indicate both magmatic and metamorphic origins for the zircons, consistent with early Silurian arc magmatism. U-Pb zircon ages of 582.2 ± 9.0 Ma, 498 ± 43 Ma, and 482 ± 120 Ma correspond to distinct tectonic events, including the Pan-African orogeny. The earliest stage, at 582.2 Ma, shows significant juvenile crustal input during continental arc magmatism in the Neoproterozoic. By 498 Ma, tectonic reactivation led to partial melting and zircon crystallization, while the final stage at 482 Ma is linked to high-pressure metamorphism and crustal thickening during the collision of the West African Craton and the Tuareg Shield. Two distinct zircon age groups (582.2 ± 9.0 Ma and 498 ± 43 Ma) reflect the reworking of the Paleoproterozoic and Mesoproterozoic crust, with substantial juvenile input. This tectonic evolution, initiated around 482 Ma, involved crustal thickening, metamorphism, and partial melting, forming migmatites. Continued tectonic activity around 582 Ma caused shear zone development and crustal reworking, while reactivation at 498 Ma led to the crystallization of new zircons and the formation of migmatites. This study, similar to migmatite studies across Africa, elucidates the dual-source history of the Liman Katagum migmatites, with contributions from both reworked and juvenile crustal materials during the late Neoproterozoic and Early Paleozoic, highlighting episodes of partial melting and magma intrusion associated with the breakup of Rodinia and the assembly of Gondwana.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105562"},"PeriodicalIF":2.2,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349399","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}

{"title":"Distribution of recent ostracods and benthic foraminifera from Farwa Lagoon (NW Libya)","authors":"Sherif M. El Baz ,&nbsp;Abdalla Shahin ,&nbsp;Ahmed Al Furjany ,&nbsp;Hatem Aboelkhair ,&nbsp;Asmaa Awad","doi":"10.1016/j.jafrearsci.2025.105564","DOIUrl":"10.1016/j.jafrearsci.2025.105564","url":null,"abstract":"<div><div>This paper presents the first detailed study of recent ostracods and foraminiferal assemblages found in the bottom sediments of the Farwa Lagoon on the northwestern coast of Libya. The studied assemblages consist of 25 ostracod species belonging to 17 genera, and 49 foraminiferal species, belonging to 21 genera. The abundance and diversity of these two groups of microorganisms vary among sites, providing the possibility of using ostracods and benthic foraminifera as bio-indicators in the Farwa Lagoon. Their distributions are influenced by many limnological conditions, including salinity, sediment types, the presence of seagrass cover, and hydrodynamic forces, as well as by pollution sources. <em>Xestoleberis communis</em> Müller, a common marine species, is the source of &gt;40% of the ostracod valves counted and is found at 12 of the 15 sites. Six other species account for ∼30% of the valves, including <em>Cyprideis torosa</em> (Jones), <em>Aurila convexa</em> (Baird)<em>, A. woodwardii</em> (Brady)<em>, Pontocythere turbida</em> (Müller), <em>Celtia emaciata</em> (Brady)<em>,</em> and <em>Loxoconcha rhomboidea</em> (Fischer). Foraminiferal tests are more abundant as well as more species rich, with tests of <em>Ammonia parkinsoniana</em> (d'Orbigny) making up 13% of the assemblage and only four other species accounting for at least 5%, notably <em>Elphidium crispum</em> (Linnaeus), <em>Peneroplis planatus</em> (Fichtel and Moll), <em>Ammonia beccarii</em> (Linnaeus), <em>Quinqueloculina seminulum</em> (Linnaeus)<em>.</em> The foraminiferal species can be categorized as free-living (e.g., <em>Quinqueloculina</em>)<em>,</em> and epiphytic taxa (e.g., <em>Peneroplis, Ammonia, Elphidium</em>). The identified assemblages are widely distributed in the shallow marine environments along the Mediterranean coasts, such as Morocco, Tunisia, Egypt, Turkey, Spain and Italy.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105564"},"PeriodicalIF":2.2,"publicationDate":"2025-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143347925","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}

{"title":"Geological/petrophysical characterisation and permeability mapping using ANN in the Algerian tight gas reservoir, Illizi Basin","authors":"Chehili Djamel ,&nbsp;Bacetti Abdelmoumen ,&nbsp;Bendali Mehdi ,&nbsp;Rahmani Badr Eddine ,&nbsp;Sadek Kaddour ,&nbsp;Bennour Mohamed amin","doi":"10.1016/j.jafrearsci.2025.105561","DOIUrl":"10.1016/j.jafrearsci.2025.105561","url":null,"abstract":"<div><div>The study of reservoir permeability and porosity is paramount for effective reservoir management and formulation of a production strategy. The Illizi Basin is a Palaeozoic–Mesozoic intraplate depression that preserves over 7000 m of sedimentary rock record and contains world-class petroleum systems with an estimated ultimate recovery (EUR) of over 39 billion barrels of oil equivalent (BBOE) in hydrocarbon reserves. However, predicting and characterising high-permeability (K) zones in such tight gas reservoirs remains challenging due to their complex geological settings and limited well data. This research addresses the critical dilemma of accurately identifying and classifying high-permeability zones in the Illizi Basin. We propose a novel approach that combines conventional geological, sedimentological, and petrophysical analyses with advanced artificial neural networks (ANNs) optimised using deep learning techniques. The study focuses on the north-western part of the basin, where distinguishing permeability facies using conventional methods is particularly difficult. The novelty of this work lies in the application of a highly efficient ANN model for detecting and classifying high-permeability zones, significantly improving the understanding of permeability distribution within the reservoir. The ANN approach demonstrated exceptional performance, enabling the accurate classification of permeability facies and the detection of high-permeability zones in all wells across the study area. This innovative integration of deep learning with traditional reservoir characterisation techniques provides a more reliable framework for reservoir management in tight gas formations like in the Illizi Basin.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105561"},"PeriodicalIF":2.2,"publicationDate":"2025-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143372835","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}

{"title":"Tracing 8,000 years of climate change and human influence in the Middle Atlas, Morocco: A palynological study from Lake Iffer","authors":"Mariam Bourchachen ,&nbsp;Bouchra Lemdeghri Alaoui ,&nbsp;Khalil Azennoud ,&nbsp;Abdennasser Baali","doi":"10.1016/j.jafrearsci.2025.105563","DOIUrl":"10.1016/j.jafrearsci.2025.105563","url":null,"abstract":"<div><div>This study reconstructs Middle to Late Holocene environmental changes and human impacts in the Moroccan Middle Atlas, using palynological data from Lake (Dayet) Iffer. The sedimentary sequence spans the last 8000 calendar years <em>before present</em> (cal yr BP), revealing a dynamic interaction between natural and anthropogenic factors shaping the vegetation in the region. Tree taxa, primarily <em>Pinus</em>, <em>Pistacia</em>, and <em>Quercus</em> (ilex-type and faginea-type), dominated the landscape until ca. 5500 cal yr BP. The onset of the expansion of drought-tolerant species and herbaceous plants aligns with increasing human activities, as inferred from a significant rise in <em>Olea europaea</em> pollen and forest degradation after ca. 3500 cal yr BP. This period recorded the retreat of pine forests and the emergence of <em>Cistus</em> species, reflecting intensified anthropogenic pressures and changing land use. The study also identifies a major shift around 2500 cal yr BP, characterized by extensive deforestation, soil erosion, and the decline of <em>Cedrus atlantica</em>, likely due to combined effects of aridification and sustained human exploitation.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105563"},"PeriodicalIF":2.2,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143347924","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}

{"title":"Growth anatomical anomalies in Cenomanian echinoids of the Bellezma-Batna Mountains (NE Algeria)","authors":"Benmansour Sana ,&nbsp;Benmessaouda Hadil ,&nbsp;Drifi Naima","doi":"10.1016/j.jafrearsci.2025.105560","DOIUrl":"10.1016/j.jafrearsci.2025.105560","url":null,"abstract":"<div><div>This article reports cases of growth anatomical anomalies in two echinoid species, <em>Macraster douvillei</em> (Gauthier) and <em>Mecaster pseudofourneli</em> (Péron and Gauthier), from the Cenomanian deposits of the Bellezma-Batna mountains (northeastern Algeria). Such a topic is first reported in Algeria ever. The large collection (400 specimens) made it possible to distinguish several types of these rare pathologies, each one being illustrated by explanatory drawings. Three types of deformation directly concerning the pentamery, are presented. They are most often resulting from an additional growth zone (6 ambulacra), a complete tetramery represented by a missing growth zone (4 ambulacra) and constrictions or strangulation of the ambulacres. Abnormalities can develop in the rudiment as soon as the larva enters metamorphosis, or shortly afterwards in juvenile broods. They may alter the plate arrangement and the general shape of the test or, on the contrary, result in local deformations, influencing the arrangement or shape of the ambulacra, etc. These malformations resulted from either intrinsic (genetic) or extrinsic (ambiental) conditions.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105560"},"PeriodicalIF":2.2,"publicationDate":"2025-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143347923","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}

{"title":"Numerical terrain analysis of fluvial-marine watersheds on the Isle of Santiago, Cape Verde, based on satellite imagery, ground-truthing and landform indices - A preparatory study in search of Nb -Ta - REE deposits related to hotspot islands","authors":"Harald G. Dill ,&nbsp;Andrei Buzatu ,&nbsp;Sorin-Ionut Balaban ,&nbsp;Dominik Schmitt ,&nbsp;Ulrich Heimhofer ,&nbsp;Astrid Techmer","doi":"10.1016/j.jafrearsci.2025.105548","DOIUrl":"10.1016/j.jafrearsci.2025.105548","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Numerical terrain analysis constitutes the missing link between the classical descriptive geomorphology and geomorphometry providing landform indices by means of which issues in applied and genetic geosciences can be solved. This method is fully satellite-based and supplemented by ground-truthing dealing with the interior parts of the positive landforms and the inter-landform sediments.&lt;/div&gt;&lt;div&gt;This approach can successfully be taken prevalently for immature modern landscapes, exemplified by Cenozoic volcanic hotspot islands such as Santiago, the main island of the Cape Verde Archipelago, where four lithofacies types could be delineated. Corresponding to the scale of observation, a tripartite subdivision is achieved in numerical terrain analysis (1st order regional, 2nd order local, 3rd order outcrop scale).&lt;/div&gt;&lt;div&gt;The first order indices allow for a tripartite compartmentalization of the volcanic island into the presumed paleosurface of all volcanic summits within a certain altitude (“Gipfelflur”), the volcanic pediment and the coastal zone. Among the second order indices, the VaSlAn&lt;sub&gt;alti&lt;/sub&gt; index (Variation of Slope Angle altitude) giving the variation of slope angle as function of altitude is an excellent environmental marker. Its correlation coefficients provide a measure for the homogeneity of volcanogenic, mass wasting, fluvial, and coastal landform series. Among the third order indices, the QuantGrav&lt;sub&gt;situ&lt;/sub&gt; index (Quantification Gravel situmetry) lends much support to the afore-mentioned environmental markers. It is a meticulous measure of the modality, sharpness and fan width of the orientation of clasts with their data, illustrated in semicircle rose diagrams. It is used to fine-tune volcaniclastic deposits at outcrop scale. The compositional quantification encompasses mineralogy, biosedimentology and isotope geochemistry (δ&lt;sup&gt;13&lt;/sup&gt;C, δ&lt;sup&gt;18&lt;/sup&gt;O) as well as &lt;sup&gt;14&lt;/sup&gt;C-dating.&lt;/div&gt;&lt;div&gt;The compositional study of the terrain analysis reveals on the biosedimentological part a low-relief coral accumulation with an impoverished fauna of Caribbean affinity. On the mineralogical part, the two strings heavy and light minerals unravel different processes. The heavy minerals accumulated in the fluvial-marine sediments of the coastal region point to magmatic host rocks from basaltic andesites to picrobasalt and basanite. Zeolites among the light minerals are indicative of a meteoric to low-temperature hydrothermal alteration confined to the lithofacies types C and D.&lt;/div&gt;&lt;div&gt;The coastal zone shows a characteristic quadripartite subdivision. It is the reference terrain for any inter-island comparison regarding volcanogenic islands. And it is the starting level for a more detailed characterization of the volcanic island's upper slope. LFS A1 (Landform Series) is characteristic of a curvilinear-rectilinear cliff coast sculped by a strong marine wave action with subordinate subaerial - submarine point sour","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"227 ","pages":"Article 105548"},"PeriodicalIF":2.2,"publicationDate":"2025-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143696708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Mineralogy and geochemistry of the middle to upper jurassic sargelu, naokelekan, and barsarin formations from northeastern Iraq: Implications for paleoenvironmental, provenance, and tectonic setting proxies","authors":"Rebwar H. Rasool ,&nbsp;Sarmad A. Ali ,&nbsp;Ali I. Al-Juboury ,&nbsp;Nasir Alarifi ,&nbsp;Fadhil A. Lawa ,&nbsp;Harry Rowe ,&nbsp;Giovanni Zanoni ,&nbsp;David L. Dettman","doi":"10.1016/j.jafrearsci.2025.105559","DOIUrl":"10.1016/j.jafrearsci.2025.105559","url":null,"abstract":"<div><div>This study investigates the mineralogical and geochemical characteristics of the middle-upper Jurassic Sargelu, Naokelekan, and Barsarin formations in the Sargelu area, northeastern Iraq. The study aims to interpret the provenance, tectonic setting, paleoclimate, and paleoweathering processes that shaped these formations using X-ray diffraction, X-ray fluorescence, and stable isotopes of carbon and oxygen. The findings provided valuable insights into the geological history and environmental conditions of the region during the Jurassic period. XRD analysis revealed that the clay minerals in the shale samples primarily consist of illite, kaolinite, and mixed-layer illite-smectite. Geochemical analysis of major and trace elements, along with clay mineralogy and stable oxygen and carbon isotopic data, indicate that arid to semi-arid and semi-humid climatic conditions prevailed during the deposition of the Jurassic formations. The shales from the Sargelu, Naokelekan, and Barsarin formations were derived from a felsic igneous source, as evidenced by multiple multidimensional diagram plots and a bivariate plot of SiO₂ vs log (K₂O/Na₂O). Variations in oxygen and carbon isotopes, along with trace element data, suggested that the Sargelu Formation was deposited in a saline marine environment, the Naokelekan Formation in a saline marine to freshwater environment, and the Barsarin Formation in a highly saline, brackish-to-freshwater environment. Paleoredox and paleoproductivity proxies indicated deposition under anoxic to suboxic conditions, with particularly high productivity observed in the Naokelekan Formation.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105559"},"PeriodicalIF":2.2,"publicationDate":"2025-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350008","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}

{"title":"Ecological differences in upper Pliensbachian (Early Jurassic) reef communities determined by environmental conditions in carbonate settings","authors":"Travis Stone ,&nbsp;Rowan Martindale ,&nbsp;Stéphane Bodin ,&nbsp;Bernard Lathuilière ,&nbsp;François-Nicolas Krencker ,&nbsp;Tanner Fonville ,&nbsp;Lahcen Kabiri","doi":"10.1016/j.jafrearsci.2025.105547","DOIUrl":"10.1016/j.jafrearsci.2025.105547","url":null,"abstract":"<div><div>Reef communities changed dramatically during the Early Jurassic as they recovered from the End-Triassic Mass Extinction. The Atlas Rift Zone in Morocco provided expansive shallow water substrate, which allowed a variety of reef communities to develop, such as lithiotid bivalves that established themselves as new and prolific reef builders alongside corals, microbialites, and sponges in the Sinemurian and Pliensbachian stages. To better understand the dynamics between these reef builders and their environments, a detailed facies analysis of upper Pliensbachian reefs and a quantitative analysis of their composition was undertaken. We describe two distinct environmentally controlled reef types in the Central High Atlas Mountains. Lithiotid bivalves dominated reef construction in lagoonal environments and, together with phaceloid corals, commonly built bioherms and biostromes that ranged from 1 to 2 m tall and up to several hundred meters wide. Meanwhile, on the platform edge, microbialites, corals, and sponges constructed patch reefs up to 7 m tall and 20 m wide. These two reef types share common facies, as many of the same reef inhabitants, and some framework builders, grew in both environments. Despite the facies overlap, the communities in these two environmental settings are distinct, which is likely a result of environmental controls on the dominant reef framework builders. Moderately turbid waters and soft substrate in lagoons were ideal conditions for lithiotids but excluded many corals, sponges, and microbialites. Conversely, the clear, oligotrophic waters at the platform edge allowed photosynthetic and photosymbiotic organisms to thrive (e.g., coral and microbial reefs), while firmer substrate and higher wave energy may have prevented lithiotids from establishing dense populations.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105547"},"PeriodicalIF":2.2,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171379","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}