Journal of African Earth Sciences最新文献

{"title":"Structural and facies modeling of the Aptian Dahab Formation, Matruh Basin, northern Western Desert, Egypt","authors":"Marwa Yousef ,&nbsp;Luis Vergara ,&nbsp;Adel R. Moustafa ,&nbsp;William Bosworth","doi":"10.1016/j.jafrearsci.2025.105573","DOIUrl":"10.1016/j.jafrearsci.2025.105573","url":null,"abstract":"<div><div>This paper presents a comprehensive study of the structural geometry and tectonic evolution of the Aptian Dahab Formation in the Matruh Basin, Egypt, using high-quality 3D seismic and well data. It also details the methodologies used to develop precise 3D structural and facies models for the Dahab Formation in the study area, which elucidate the stratigraphic succession, depositional environments and facies, tectonic and eustatic influences on deposition, and the spatial distribution of the Dahab Formation.</div><div>Detailed well log correlations indicate the presence of normal faults, affecting the preservation of the upper part of the Dahab Formation in the boreholes. The study employs a 3D structural modeling workflow, integrating seismic and well data, structural cross-sections, and maps. Velocity modeling and depth conversion highlight the complex structural setting resulting from the impact of Late Cretaceous faulting and folding on the Aptian Dahab Formation.</div><div>Further, a 3D facies model was constructed, that incorporated upscaled well logs and variogram analysis. The results indicate that the lithological composition of the Dahab Formation in the study area is 38.4% shale, 28.96% siltstone, 15.35% sandstone, 12.36% limestone, and 4.92% dolostone. Hence, the facies model shows the dominance of shale facies, which increase towards the south, while siltstone and sandstone facies become more prevalent towards the north, likely sourced from that direction. Two cross sections were constructed that illustrate the lateral and vertical facies variations within the Dahab Formation, which thickens as it extends northwestward. Consequently, the facies distribution model of the Aptian Dahab Formation could serve as a global analogue for potential siliciclastic reservoirs deposited in a shallow water environment.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"225 ","pages":"Article 105573"},"PeriodicalIF":2.2,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143394491","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":"Gravity-based structural and tectonic characterization of the Shendi-Atbara Basin, Central Sudan","authors":"Ali A. Mohieldain ,&nbsp;Mihály Dobróka ,&nbsp;Musaab A.A. Mohammed ,&nbsp;Norbert P. Szabó","doi":"10.1016/j.jafrearsci.2025.105571","DOIUrl":"10.1016/j.jafrearsci.2025.105571","url":null,"abstract":"<div><div>This study employs gravity data analysis techniques to investigate the subsurface structural framework and lithological variations of the Shendi-Atbara Basin in Sudan. This basin is influenced by both the Mesozoic rifting associated with the West and Central African Rift System (WCARS) and the Neoproterozoic tectonics of the Nubian Shield. High-resolution satellite gravity data were analyzed using potential field methods including anomaly separation, edge detection, and 2D and 3D modeling to delineate primary structural features and density interfaces. Various edge detection techniques were applied to identify lineament structures, and the results were integrated to construct a comprehensive structural map of the region. This map was subsequently analyzed to interpret the tectonic evolution and subsurface geology. Structural analysis revealed three dominant fracture sets: NW-SE extensional fractures, NE-SW release fractures, and N-S shear fractures. Gravity modeling indicated that the thickness of the sedimentary sequences in the Shendi-Atbara Basin reaches up to 4800 m. A notable high-density anomaly southeast of Shendi is interpreted as an intermediate to mafic igneous intrusion, corroborated by surrounding structural patterns identified through edge detection and modeling. These findings provide valuable insights into the basin's tectonic evolution. The identified fractures serve as important guides for groundwater and mineral resource exploration, particularly given the presence of high-density sources and iron-rich sedimentary formations in the region.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"225 ","pages":"Article 105571"},"PeriodicalIF":2.2,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143394489","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":"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}