Journal of African Earth Sciences最新文献

{"title":"Highly siderophile elements and mineral chemistry of chromitites from the Kırdağ ophiolite (NE Turkey): Constraints on genesis and subduction initiation","authors":"Özgür Bilici","doi":"10.1016/j.jafrearsci.2025.105726","DOIUrl":"10.1016/j.jafrearsci.2025.105726","url":null,"abstract":"<div><div>This study presents the first petrological and geochemical characterisation of chromitites from the mantle section of the Kırdağ ophiolite (NE Turkey), focusing on concentrations of highly siderophile elements (HSE; PGE and Au) and the mineralogical features of chromian spinel and olivine. Field and petrographic observations found that the chromitites occur as small bodies, predominantly with disseminated texture and less commonly as semi-massive structures, hosted within dunite lenses enclosed by harzburgitic mantle rocks. Chromian spinels exhibit Cr# values of 0.66–0.68 and Mg# values of 0.65–0.72, classifying the Kırdağ chromitites as intermediate-Cr type ophiolitic chromitites. The low TiO₂ content (0.18–0.32 wt%) suggest derivation from melts transitional between boninite and island arc tholeiitic composition. Olivine occurs both as inclusions in spinel and within the interstitial matrix, with forsterite (Fo) contents higher in inclusions (96.21–97.18) compared to the matrix (94.25–94.68). The low Ca concentrations in olivine support formation from a highly magnesian melt interacting with a depleted mantle source. The chromitites display low total PGE concentration (73–153 ppb), relative enrichment in Ir-group (IPGE) over Pd-group (PPGE), and low Au content (&lt;5–8 ppb), consistent with typical ophiolitic chromitite signatures. Pd/Ir ratios (0.77–2.33) and Pt anomalies (Pt/Pt∗ = 0.24–0.76) indicate that partial melting was the primary control on PGE distribution, although increasing Pd/Ir ratios suggest a minor role for magmatic fractionation. The estimated parental magma composition, characterised by low TiO₂ (0.29–0.44 wt%), moderate Al₂O₃ (13.52–13.80 wt%), and FeO/MgO ratios (0.82–1.02), points to arc-related affinity. These results suggest that the Kırdağ chromitites formed during the early stages of subduction initiation, in a supra-subduction zone forearc setting, from a progressively evolving mantle source.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"230 ","pages":"Article 105726"},"PeriodicalIF":2.2,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144298217","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":"Modeling overthrust structures for hydrocarbon exploration by 3D magnetotellurics","authors":"Özlem Hacıoğlu","doi":"10.1016/j.jafrearsci.2025.105715","DOIUrl":"10.1016/j.jafrearsci.2025.105715","url":null,"abstract":"<div><div>The seismic reflection method is widely used in hydrocarbon exploration due to its ability to provide detailed imaging of sedimentary layers. However, in overthrust terrains where high velocity rocks (e.g., volcanic cover) overlie low velocity sediments, seismic methods often struggle to distinguish hydrocarbon-bearing zones from other sedimentary layers. These challenges arise due to seismic velocity reduction at the base of volcanic layers and the dispersive nature of volcanic rocks. In such complex geological settings, magnetotellurics (MT) offers an alternative approach, as it can penetrate deeper and resolve subsurface resistivity contrasts more effectively. This study evaluates three-dimensional (3D) MT for hydrocarbon exploration in overthrust settings with high resistivity cover layers. Synthetic models incorporating overthrust structures were developed, and their MT responses were analyzed through 3D inversion. The results demonstrate that 3D MT inversions adequately recover hydrocarbon-bearing structures but may underestimate their resistivity due to the influence of overlying layers. Constrained inversions, incorporating additional constraints such as basement resistivity values, improve overall model resolution, yet do not significantly enhance hydrocarbon trap definition. These findings suggest that incorporating additional constraints can enhance subsurface imaging. Ultimately, this study suggests that 3D MT should be more widely utilized in contractional tectonic settings, particularly in fold-and-thrust belts, to enhance hydrocarbon exploration strategies. While MT alone provides valuable imaging capabilities, its integration with other geophysical methods could further improves inversion accuracy and hydrocarbon detection in complex geological environments.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"230 ","pages":"Article 105715"},"PeriodicalIF":2.2,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144243283","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":"Anatectic origin of the pegmatite-aplite dykes from the Paleoproterozoic basement of the Bas Draa inlier (Anti-Atlas-Morocco): Insights from whole rock geochemistry, Sm-Nd isotopes and tourmaline chemistry","authors":"Fatiha Askkour ,&nbsp;Moha Ikenne ,&nbsp;Brian L. Cousens ,&nbsp;Mehdi Ousbih ,&nbsp;Chetan Nathwani ,&nbsp;Mustapha Souhassou ,&nbsp;Mohamed Mahmoud Sebbab ,&nbsp;Mohamed Ez-Zghoudy ,&nbsp;Abdessamad El Atillah ,&nbsp;Moulay Ahmed Boumehdi","doi":"10.1016/j.jafrearsci.2025.105703","DOIUrl":"10.1016/j.jafrearsci.2025.105703","url":null,"abstract":"<div><div>Although many critical metals used today are derived from granitic pegmatites, the debate is still ongoing about the origin of these enigmatic rocks. It is evident that certain pegmatites represent the most fractionated products of a parental granitic magma, whereas others were formed by the anatexis of the local basement protolith. The Bas Draa inlier, located in the western part of the Anti-Atlas belt of Morocco, includes numerous pegmatitic and aplitic dykes. They mainly intrude Paleoproterozoic metasedimentary rocks and some Paleoproterozoic granitoid intrusions. They range in size from a few centimeters to greater than 10 m in width and a length that can reach several hundred meters. They are composed mainly of abundant quartz, muscovite, feldspars, tourmaline, apatite, zircon, garnet, and gahnite. They have a strongly peraluminous composition, a low total REE content (&lt;500 ppm), characteristic mineral assemblages (tourmaline, garnet, gahnite), enrichment in Pb, Rb, and Cs, and depletion in Ba and Nb compared with the mantle<strong>.</strong> The highly mafic tourmaline compositions (schorl-foitite), the presence of epidote and field observations preclude the possibility that these pegmatites were derived from the neighboring granite and were most likely formed by crustal anatexis of the host metasedimentary rocks during the Statherian. The peraluminous nature of the pegmatites strongly points towards a metasedimentary source. Notably, within the Bas Draa inlier, the densest pegmatite-aplite swarms are mainly found in areas where a metasedimentary source is prevalent and negative epsilon Nd values corroborate their crustal derivation. The findings align with earlier research which also raises questions about the commonly accepted model that all rare-metal pegmatites are formed by fractionation from a parental granite.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"230 ","pages":"Article 105703"},"PeriodicalIF":2.2,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144279757","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":"Variations, paleoenvironment implications, and agronomic considerations of glauconite expandable layers: A case study from Egypt","authors":"Mahmoud Abdel-Hakeem","doi":"10.1016/j.jafrearsci.2025.105713","DOIUrl":"10.1016/j.jafrearsci.2025.105713","url":null,"abstract":"<div><div>As a contribution to many works conducted on glauconites, the current study represents an interdisciplinary approach combining geoscience and agronomy of these K-mineral resources, depending on the variations of expandable layers %. Through this context, two condensed sections of the Up. Cretaceous and Up. Eocene glauconites, located in the Western Desert of Egypt, were undergone field, petrographic, mineralogical, and geochemical investigations. The agronomic considerations were studied by simulating the organic acid-solubility of glauconite, using 2 % oxalic acid, in cases of its direct application as a slow-release K-fertilizer. Geologically, all of the studied glauconites were deposited authigenically by the neoformation of Fe-smectite precursor. The latter is thought to be more ferruginous in case of the Up. Cretaceous glauconite (nascent species, 3–4.1 wt% K₂O) than the Up. Eocene counterpart (slightly evolved-evolved species, 5.05–6.71 wt% K₂O). Depending on K₂O contents and ethylene glycol solvation of glauconite grains, expandable layers were calculated and averaged at 40.53 % and 24.03 % for the Up. Cretaceous and Up. Eocene glauconites, respectively. Also, expandable layers showed a gradual increment from base to top of the studied sections where shoaling upward occurs. Depending on field observations, mineralogical, and geochemical data, along with literature, Fe²⁺ availability and sea level changes are found to be the main controlling factors of glauconite expandable layers. Agronomically, oxalic acid-based solubility tests showed that K⁺ ions aren't completely tightly fixed into the interstratified structure of the highly expandable glauconite, causing faster solubility rates than the less expandable species. According to the concept of slow-release fertilizers, the more evolved, less expandable glauconite deposits are preferred for the long-lasting K supply required by plants and keeping the soil fertility of plant macro-nutrients. On the other side, the smectite-rich glauconite can be exploited as a soil conditioner for enhancing its cation exchange capacity.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"229 ","pages":"Article 105713"},"PeriodicalIF":2.2,"publicationDate":"2025-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144222235","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":"Adaptive utilization of Castagna and Biot-Gassmann equations in fluid replacement mechanism (FRM), with elastic logs analysis and petrophysical cross-plots for fluid discrimination in an offshore basin, Niger Delta, Nigeria","authors":"Abdulbariu Ibrahim ,&nbsp;Wasiu O. Raji","doi":"10.1016/j.jafrearsci.2025.105712","DOIUrl":"10.1016/j.jafrearsci.2025.105712","url":null,"abstract":"<div><div>Determination of reservoir fluid type is a useful basic procedure in reservoir fluid characterization. Among the ways to achieve this, are through elastic logs and cross plotting in conjunction with fluid replacement mechanism (FRM) which have the capability to discriminate one fluid type from another thereby removing - uncertainties and ambiguity from the reservoir fluid interpretation and isolation. The aim of the study was to accurately identify hydrocarbon and distinguishes it from the brine. This was achieved through elastic log cross-plotting and fluid substitution with clear objectives of diagnosing various reservoir fluid content, removing ambiguities, clearing uncertainties and reducing risks. The novelty in this study lies in its ability to combine the sophisticated fluid identification templates by employing different parameterization approaches including the use of bulk modulus of the rock matrix, dry rock, fluid, and saturated rock frame. It also involved the utilization of reservoir porosity, saturated rigidity modulus, dry-rock shear modulus and densities. Elastic logs were generated from the P-wave (Vp), S-wave (Vs) and density (ρ) logs and was followed by cross plotting to determine the fluid zones within the field. Castagna and Biot-Gassmann equations were utilised for the replacement mechanism to identify the nature of fluid present in each of the reservoirs. Findings from the study revealed the presence of hydrocarbon within the field as indicated by the low values of elastic logs such P-impedance (Zp), S-impedance (Zs), Vp/Vs ratio, Lambda-Rho (λρ) and Mu-Rho (μρ) and their cross plots. The hydrocarbon-bearing intervals were isolated in the cross plot space while the reservoir saturated with brine and shaly units formed the background effect. Also, the result of fluid replacement techniques revealed that the reservoirs with hydrocarbon as insitu fluid developed a new log response tracking the original insitu log when the insitu fluid was replaced with hydrocarbon except at the water bearing intervals where the log departed from the path of tracking each other. But the new log deviated from the insitu original log when the insitu fluid was replaced with brine at the oil and gas zones. Again when the reservoir insitu fluid was brine and substituted with brine, the new modified log also tracked the original insitu log except at hydrocarbon intervals where it deviated. The FRM categorically characterised the fluids and confirmed the interpretation from both elastic log and cross plot and all the results corroborated well. The significance of the study is the delineation of hydrocarbon-charged intervals and characterization of various reservoir fluids Therefore, elastic logs, cross plot and FRM served as important means of fluid isolation and discrimination in AbdulBaari-Field. The techiques holds the potential to solve similar problems in any hydrocarbon field in different parts of the world</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"230 ","pages":"Article 105712"},"PeriodicalIF":2.2,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144263768","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":"Anomaly separation of gravity data using filtering techniques: Case study of the Ziway and Koka sub basins, central main Ethiopian rift, Ethiopia","authors":"Habtamu Tesfaye ,&nbsp;Abera Alemu ,&nbsp;Mebatsion Shawel ,&nbsp;Behailu Birhanu","doi":"10.1016/j.jafrearsci.2025.105710","DOIUrl":"10.1016/j.jafrearsci.2025.105710","url":null,"abstract":"<div><div>This study applies three filtering techniques: frequency, upward continuation (UC), and trend surface polynomial filters, to the ground and satellite gravity data from the Ziway–Koka sub-basins to separate the regional and residual anomaly components of the complete Bougour anomaly (CBA). The estimated regional anomalies are then evaluated to identify the relatively reliable filtering technique for the study area. For the UC filter, regional anomaly grids were evaluated using successive UC to heights ranging from 0.5 to 5 km to determine the optimum height for estimating the regional anomalies. Consequently, a UC height of 5 km was determined to best represent the regional anomaly with enhanced resolution. Radial average power spectrum curves were used to determine the cut-off frequency applied in compiling the regional anomaly grid map. As a result, a cut-off frequency of 0.0970525097 cycles/km was applied to the ground-based gravity data, and 0.0918813153 cycles/km to the satellite-based data for estimating the regional anomaly component. Moreover, first, second, and third-order polynomial filters were applied to estimate the regional anomaly component to determine which order offers the best resolution. Among these, the first-order polynomial filter provides a smooth and linear representation of the regional field and was therefore selected as suitable for estimating the regional anomaly with improved resolution. The residual anomaly grids obtained from each filter are quantitatively compared by correlating the anomalies extracted along the profile AA with their corresponding analytical signal anomaly values determined from the CBA grids. For the ground-based gravity data, the correlation coefficients for the frequency, UC, and first-order polynomial filters are 0.64, 0.89, and 0.79, respectively, while for the satellite-based data, the corresponding values are 0.60, 0.86, and 0.84. These results indicate that the UC filter is relatively more reliable for estimating the regional anomaly as compared to the other filters and also effective in decomposing the CBA into its regional and residual components.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"229 ","pages":"Article 105710"},"PeriodicalIF":2.2,"publicationDate":"2025-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144204327","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":"Source rock maturity and 1-D basin modelling in blocks 2 and 3 sector, Offshore Orange Basin, South Africa","authors":"Nura Abdulmumini Yelwa ,&nbsp;Khairul Azlan Mustapha ,&nbsp;Mimonitu Opuwari ,&nbsp;Hafzan Eva Mansor","doi":"10.1016/j.jafrearsci.2025.105711","DOIUrl":"10.1016/j.jafrearsci.2025.105711","url":null,"abstract":"<div><div>The passive continental margins of South Africa are virtually unexplored, although some potential is assumed in the Orange Basin and even proven by the Kudu gas field offshore Namibia and the Ibhubesi gas field offshore South Africa. The present research uses source rock samples and basin modelling to evaluate the hydrocarbon potential in the Cretaceous South African exploration license blocks 2 and 3, Sector, Offshore Orange Basin. With an emphasis on the development of source rock maturity, the study seeks to comprehend the geological processes that led to the formation of the Orange Basin. These organic deposits have average TOC values across the several stratigraphic units, with a relatively fair to good TOC composition ranging from 0.53 to 1.89 wt %. Out of the 23 samples that were examined, 17 had TOC concentrations of more than 1 %, and the remaining 6 had contents between 0.53 and 0.98 wt %. The examined organic sediments have a relatively low sulphur (TS, wt.%) content, ranging from 0.21 to 1.18 wt%, with the Turonian–Coniacian sequence having a slightly higher sulphur content of up to 1.18 wt%. These results show that free petroleum exists (S₁) and that oil generated by kerogen heat cracking (S₂) delivers oil with low petroleum potential. The analysis of the shale deposits shows that their low petroleum potential is supported by the S₂ and S₃ petroleum yields, which are consistent with TOC content. The average hydrogen index (HI) in the study area indicating low-source rock quality capable of producing type III kerogen. A one-dimensional simulation was constructed for four wells, which reveals subsidence and the influence of multi-tectonism on the burial and thermal history, reaching a maximum burial thickness from Cenomanian to Turonian up to 2110 m. The integrated studies between the analyses of source rocks and petroleum basin modelling from the Orange Basin reveal a certain petroleum potential of the Cretaceous source rocks and three petroleum systems in the lower post-rift pattern and an extrapolated topmost post-rift play.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"230 ","pages":"Article 105711"},"PeriodicalIF":2.2,"publicationDate":"2025-05-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144255337","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":"Mineralogy and whole-rock geochemistry of alkali basalts from the Bashtin area, west Sabzevar, Iran: Implications for mantle source variations","authors":"Seyed Ali Mazhari ,&nbsp;Kwan-Nang Pang ,&nbsp;Yoshiyuki Iizuka ,&nbsp;Hao-Yang Lee ,&nbsp;Kazem Aliabadi","doi":"10.1016/j.jafrearsci.2025.105708","DOIUrl":"10.1016/j.jafrearsci.2025.105708","url":null,"abstract":"<div><div>This study examines post-collisional alkali basalts in the Bashtin area, west of the Sabzevar Range, focusing on their whole-rock geochemistry and mineral composition. The alkali basalts are classified into three groups: two lava groups and one group of feeder dyke basalts, the latter affected by crystal accumulation processes. Group 2 basalts show significantly elevated values of FCKANTMS (&gt;0.3), FCMS (0.45–0.60), and Mn/Fe (72–80) compared to group 1, which has lower values for these parameters (FCKANTMS &lt;0.035, FCMS 0.02–0.28, and Mn/Fe 42–61). Conversely, group 1 basalts display higher Co/Fe (3.3–5.9), Ni/Co (5.3–6.7), and Mn/Zn (14–18) ratios than group 2 (Co/Fe 2.6–2.9, Ni/Co 1.5–3.7, and Mn/Zn 6–6.5). These geochemical differences suggest that group 1 arises from a peridotite-dominated source, while group 2 derives from a pyroxenite-dominated lithology.</div><div>Mineral compositions were analyzed using Electron Probe Microanalysis (EPMA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). In group 1, olivine crystals contain higher MgO, MnO, and SiO₂ but lower FeO and NiO than those in group 2. The clinopyroxenes in group 2 exhibited a more fractionated REE pattern, with La_N/Yb_N (3.5–17.4) and higher LREE/HREE (17.2–47) and MREE/HREE (6.2–7.8) ratios than those in group 1, which had La_N/Yb_N (2.3–3.0), MREE/HREE (3.8–4.6), and LREE/HREE (10.4–13). Although the feeder dyke's overall composition does not directly reflect the liquid composition, minerals composition suggest that the primary magma likely originated from a pyroxenite-dominated source, underscoring the importance of mineral geochemistry in assessing the origins of mafic rocks, particularly cumulates, where whole-rock compositions are not representative of the primary magma.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"229 ","pages":"Article 105708"},"PeriodicalIF":2.2,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144184445","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":"Palaeontological and palaeoenvironmental study of Coniacian–Santonian bivalves (Upper Cretaceous) from Cap Estérias in the northern Gabon coastal basin","authors":"Wilma Linda-Belle Mougola ,&nbsp;Urlain Gaël Yakouya-Moubamba ,&nbsp;Mohamed Benzaggagh ,&nbsp;Benjamin Musavu Moussavou","doi":"10.1016/j.jafrearsci.2025.105701","DOIUrl":"10.1016/j.jafrearsci.2025.105701","url":null,"abstract":"<div><div>A study of Coniacian-Santonian bivalves (Upper Cretaceous) was conducted in three stratigraphic sections from the northern part of the Gabon coastal basin, specifically located at Cap Estérias in the Akanda commune. Thirteen species, belonging to ten genera and seven families, were identified. Among these taxa, three genera — <em>Cataceramus</em> Heinz, <em>Rhyssomytiloides</em> Hessel and <em>Sergipia</em> Maury— and twelve species: <em>Arca</em> cf. <em>ligeriensis</em> d'Orbigny, ? <em>Cataceramus barabini</em> Morton, <em>Cataceramus</em> sp., <em>Cyprina</em> sp. 1, <em>Cyprina</em> sp. 2, <em>Fragum subperobliquum</em> (Riedel), ? <em>Fragum</em> sp., <em>Lima</em> (<em>Plagiostoma</em>) sp., <em>Pleuromya ligeriensis</em> (d’Orbigny), <em>Rhyssomytiloides</em> cf. <em>retirensis</em> Hessel, <em>Rhyssomytiloides</em> sp., <em>Sergipia</em> cf. <em>posidonomyaformis</em> (Maury) and <em>Venericardia</em> cf. <em>crossensis</em> Reyment, were characterised and illustrated for the first time in the Gabon coastal basin. The newly recorded taxa from this study extend the known geographical distribution of these species to Gabon. The bivalve assemblage, dominated by epifaunal form, suggests a high-energy marine environment; However, the presence of infaunal species also indicates the existence of a moderately soft substrate.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"229 ","pages":"Article 105701"},"PeriodicalIF":2.2,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144211836","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":"Reassessing tectono-structural units and crustal thickness variations in southwest Cameroon using satellite gravity and seismic data","authors":"Stephane Landry Kwega Ghomsi ,&nbsp;Dieudonné Bisso ,&nbsp;Sylvestre Ganno ,&nbsp;Luan Thanh Pham ,&nbsp;Robert Tenzer ,&nbsp;Franck Eitel Kemgang Ghomsi","doi":"10.1016/j.jafrearsci.2025.105698","DOIUrl":"10.1016/j.jafrearsci.2025.105698","url":null,"abstract":"<div><div>Southwest Cameroon has long lacked detailed geological data, prompting an investigation into its geological and tectonic features through innovative edge detection techniques applied to gravity data. We employed various methods, including the Analytical Signal (AS), Tilt Angle (TDR), Total Horizontal Gradient of the Tilt Angle (TDR_THDR), and the Logistic Filter (IL) to delineate geological features that manifest as lineaments and contacts on gravity anomaly maps. Main findings of this study involve identification of key tectonic boundaries, notably the Kribi-Campo faults (KCF) and the Ebolowa pseudo-karstic circular network, the latter being mapped for the first time. This work reveals the continuity of the Ebolowa network and integrates connections such as the Mbilibekon and Mfuda caves, enhancing our understanding of the region's geological evolution. Additionally, we detailed the north-south extension of the KCF, which extends into both oceanic and terrestrial domains, aligning with the eastern margin of the Congo Craton. This finding suggests the fault system's role as a transition between the stable cratonic core and the dynamic mobile belts, necessitating a re-evaluation of regional tectonic models. To support our edge detection interpretations, we estimated Moho depths using gravity and seismic data, finding a Moho depth range between 34.5 km and 45.9 km, correlating with significant faulting and sedimentary features. This research enhances the understanding of subsurface structures in Southwestern Cameroon and provides a robust foundation for future geological and geophysical studies, emphasizing the critical interplay between surface and subsurface processes.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"229 ","pages":"Article 105698"},"PeriodicalIF":2.2,"publicationDate":"2025-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144196054","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}