Pub Date : 2025-01-08DOI: 10.1016/j.jafrearsci.2025.105541
Tyler Greenfield
Capasso et al. (2024) reported an exceptionally large rostrum of the sawskate Onchopristis sp. from the Maastrichtian Dakhla Formation of Egypt. They also described four isolated lateral rostral denticles which were referred to the same taxon. However, here it is demonstrated that neither can be assigned to Onchopristis; the rostrum is Sclerorhynchoidei indet. and the rostral denticles are Sclerorhynchus cf. leptodon. Additionally, the status of the actual longest Onchopristis rostrum is clarified.
{"title":"No evidence for a giant, late-surviving Onchopristis: Comment on Capasso et al. (2024)","authors":"Tyler Greenfield","doi":"10.1016/j.jafrearsci.2025.105541","DOIUrl":"10.1016/j.jafrearsci.2025.105541","url":null,"abstract":"<div><div>Capasso et al. (2024) reported an exceptionally large rostrum of the sawskate <em>Onchopristis</em> sp. from the Maastrichtian Dakhla Formation of Egypt. They also described four isolated lateral rostral denticles which were referred to the same taxon. However, here it is demonstrated that neither can be assigned to <em>Onchopristis</em>; the rostrum is Sclerorhynchoidei indet. and the rostral denticles are <em>Sclerorhynchus</em> cf. <em>leptodon</em>. Additionally, the status of the actual longest <em>Onchopristis</em> rostrum is clarified.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105541"},"PeriodicalIF":2.2,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143152733","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}
The Iouaridène Formation (Upper Jurassic, High Atlas, Morocco) is a relevant area for the study of dinosaur footprints, but up to now little is known about the palaeoenvironmental conditions at the time of its formation. This work consists of a sedimentological, geochemical, and mineralogical study of part of the sedimentary succession of the Iouaridène Formation, especially Units B and C. The cyclic sedimentation pattern in Unit B, characterized by alternating soft claystones and siltstone layers and hard sandstone layers with ripples and mudcracks, reflects a dynamic environment shaped by recurring flooding and emersion events. This cyclicity is marked by fluctuations in quartz, clay and analcime content, leading to sedimentary sequences capped by silcretes, which indicate sedimentation hiatuses. The formation of mudcracks and the preservation of dinosaur footprints further highlight the depositional conditions. Mineralogical and geochemical analyses reveal an upwards trend to increasingly arid conditions during the deposition of Unit B, with an increase in quartz and decrease in kaolinite, as well as palaeoclimatic geochemical proxies. The presence of analcime supports a lacustrine environment under arid or semi-arid conditions and fluctuations in the alkalinity of pore waters. The CIA and CIW values reflect moderate to weak weathering congruent with the arid conditions indicated by other proxies. Decreasing C-values towards the top of the section points to environmental changes from semi-arid toward more arid conditions. Other indexes of salinity and aridity (Sr/Ba and Zr/Rb ratios), also support the trend towards increasing aridity in Unit B. In contrast to this, Unit C indicates more humid and deeper conditions, marked by the record of cross-bedding, lacustrine ostracods and fish bones, and the absence of mudcracks, silcretes, and dinosaur footprints. This variability underscores the dynamic climatic and environmental history of the Iouaridène Formation, reflecting the final phase of the Atlasic Basin fill during the Late Jurassic. This is the first work on the palaeoclimatic conditions of the Iouaridène Formation and the first study that integrates sedimentology, geochemistry and mineralogy of this formation. These findings enhance the understanding of the geological evolution of the Jurassic of the M'Goun Geopark and set the background for future research on the area to explore the interactions between climatic conditions, sedimentary processes, and biological activity in Jurassic lacustrine environments.
{"title":"Palaeoenvironmental and palaeoclimatic characterization of Upper Jurassic sedimentary sequences with dinosaur footprints of the M'Goun Geopark (High Atlas, Morocco)","authors":"Matías Reolid , Jesús Reolid , Elisa Laita , Mohamed Boutakiout , Moussa Masrour , Félix Pérez-Lorente","doi":"10.1016/j.jafrearsci.2025.105539","DOIUrl":"10.1016/j.jafrearsci.2025.105539","url":null,"abstract":"<div><div>The Iouaridène Formation (Upper Jurassic, High Atlas, Morocco) is a relevant area for the study of dinosaur footprints, but up to now little is known about the palaeoenvironmental conditions at the time of its formation. This work consists of a sedimentological, geochemical, and mineralogical study of part of the sedimentary succession of the Iouaridène Formation, especially Units B and C. The cyclic sedimentation pattern in Unit B, characterized by alternating soft claystones and siltstone layers and hard sandstone layers with ripples and mudcracks, reflects a dynamic environment shaped by recurring flooding and emersion events. This cyclicity is marked by fluctuations in quartz, clay and analcime content, leading to sedimentary sequences capped by silcretes, which indicate sedimentation hiatuses. The formation of mudcracks and the preservation of dinosaur footprints further highlight the depositional conditions. Mineralogical and geochemical analyses reveal an upwards trend to increasingly arid conditions during the deposition of Unit B, with an increase in quartz and decrease in kaolinite, as well as palaeoclimatic geochemical proxies. The presence of analcime supports a lacustrine environment under arid or semi-arid conditions and fluctuations in the alkalinity of pore waters. The CIA and CIW values reflect moderate to weak weathering congruent with the arid conditions indicated by other proxies. Decreasing C-values towards the top of the section points to environmental changes from semi-arid toward more arid conditions. Other indexes of salinity and aridity (Sr/Ba and Zr/Rb ratios), also support the trend towards increasing aridity in Unit B. In contrast to this, Unit C indicates more humid and deeper conditions, marked by the record of cross-bedding, lacustrine ostracods and fish bones, and the absence of mudcracks, silcretes, and dinosaur footprints. This variability underscores the dynamic climatic and environmental history of the Iouaridène Formation, reflecting the final phase of the Atlasic Basin fill during the Late Jurassic. This is the first work on the palaeoclimatic conditions of the Iouaridène Formation and the first study that integrates sedimentology, geochemistry and mineralogy of this formation. These findings enhance the understanding of the geological evolution of the Jurassic of the M'Goun Geopark and set the background for future research on the area to explore the interactions between climatic conditions, sedimentary processes, and biological activity in Jurassic lacustrine environments.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105539"},"PeriodicalIF":2.2,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153762","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}
Pub Date : 2025-01-06DOI: 10.1016/j.jafrearsci.2024.105527
Tamer Farag , Ali Mostafa , Ahmed A. El Husseiny
This study aims to enhance our understanding of groundwater accumulations in the Wadi Al-Assiuty region, with an emphasis on supporting the development of new urban settlements and national industrial initiatives. To achieve this objective, airborne magnetic data were processed and analyzed, enabling the delineating the subsurface structures and their impact on groundwater flow patterns. The research also aimed to assess the aquifer’s thickness within the area. Satellite-based digital elevation data were interpreted to map the primary drainage patterns, highlighting watersheds and basins where surface water tends to accumulate. Additionally, aerial magnetic data were employed to detect the sedimentary cover and evaluate the thickness distribution of the Nubian aquifer, ultimately identifying the most promising aquifer with the highest thickness and greatest potential groundwater reserves.
The magnetic data analysis employed three primary techniques. First, source edge detection was applied to identify sources with varying magnetic intensity anomalies. Second, the depth of the basement surface was calculated, corresponding to the base of the Nubian aquifer in the study area. Third, 3D magnetic data inversion was used to create a three-dimensional model of the basement rocks, aiding in the identification of optimal locations for drilling deep groundwater wells. The overarching goal is to locate areas with strong groundwater exploration potential, which is critical for Egypt’s sustainable development. To ensure accuracy, the results are constrained by incorporating previous geological, geophysical, and drilled wells data.
Wadi Al-Assiuty, a major Egyptian wadi, exhibits a rectangular drainage pattern (angular streams) interspersed with sub-dendritic to subparallel sub-basins, which reflects the structural control of the stream network. The resulting maps, generated through linear transformations and derivative-based techniques, reveal that NW-SE and E-W fault systems play a significant role in controlling the recharge of the aquifers from surface run-off water, the deep Nubian sandstone aquifer, and the Nile River. Notably, the depth to the basement varies widely, ranging from 200 m to 4800 m below the surface. This study aligns with Egypt’s 2030 sustainable development plan, particularly focusing on promising desert areas that could be transformed into agricultural development zones.
{"title":"3D inversion of magnetic data to delineate subsurface structures controlling groundwater recharge and discharge at Wadi Al-Assiuty, Egypt","authors":"Tamer Farag , Ali Mostafa , Ahmed A. El Husseiny","doi":"10.1016/j.jafrearsci.2024.105527","DOIUrl":"10.1016/j.jafrearsci.2024.105527","url":null,"abstract":"<div><div>This study aims to enhance our understanding of groundwater accumulations in the Wadi Al-Assiuty region, with an emphasis on supporting the development of new urban settlements and national industrial initiatives. To achieve this objective, airborne magnetic data were processed and analyzed, enabling the delineating the subsurface structures and their impact on groundwater flow patterns. The research also aimed to assess the aquifer’s thickness within the area. Satellite-based digital elevation data were interpreted to map the primary drainage patterns, highlighting watersheds and basins where surface water tends to accumulate. Additionally, aerial magnetic data were employed to detect the sedimentary cover and evaluate the thickness distribution of the Nubian aquifer, ultimately identifying the most promising aquifer with the highest thickness and greatest potential groundwater reserves.</div><div>The magnetic data analysis employed three primary techniques. First, source edge detection was applied to identify sources with varying magnetic intensity anomalies. Second, the depth of the basement surface was calculated, corresponding to the base of the Nubian aquifer in the study area. Third, 3D magnetic data inversion was used to create a three-dimensional model of the basement rocks, aiding in the identification of optimal locations for drilling deep groundwater wells. The overarching goal is to locate areas with strong groundwater exploration potential, which is critical for Egypt’s sustainable development. To ensure accuracy, the results are constrained by incorporating previous geological, geophysical, and drilled wells data.</div><div>Wadi Al-Assiuty, a major Egyptian wadi, exhibits a rectangular drainage pattern (angular streams) interspersed with sub-dendritic to subparallel sub-basins, which reflects the structural control of the stream network. The resulting maps, generated through linear transformations and derivative-based techniques, reveal that NW-SE and E-W fault systems play a significant role in controlling the recharge of the aquifers from surface run-off water, the deep Nubian sandstone aquifer, and the Nile River. Notably, the depth to the basement varies widely, ranging from 200 m to 4800 m below the surface. This study aligns with Egypt’s 2030 sustainable development plan, particularly focusing on promising desert areas that could be transformed into agricultural development zones.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105527"},"PeriodicalIF":2.2,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153807","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}
In-depth field investigations have allowed us to assess the coastal sector of Rabat-Salé by describing various forms of erosion, the condition of historical monuments located by the ocean, and the ineffectiveness of hard solutions implemented against erosion. This emphasizes the primary anthropogenic causes of the degradation of the studied coastal environments, including former calcarenite quarries and old sewage drainage canals. The interaction of these anthropogenic factors with natural processes has led to a significant retreat of the coastal cliff, which is clearly visible on-site, posing a threat to certain constructions, notably historical monuments of great cultural value to the Kingdom. To quantify the retreat in the study area between 1993 and 2022, we utilized the Digital Shoreline Analysis System (DSAS), version 5 integrated into ArcGIS 10.4, which revealed relatively high rates with an average rate of 1.2 m per year. We also adopted another method by using threatened historical monuments to calculate average retreat rates of the shoreline using two old plans, one dating back to 1935 (1/1000 scale) for Fort Rottembourg and another from 1922 (1/2000 scale) containing two historical monuments: Borj Sirat and Borj Eddar. The calculations yielded average rates that align with those obtained through DSAS. Despite the risks associated with erosion in the study area, a regulatory framework for the protection and enhancement of the coastal environment (Law 81-12) has been in place since 2015, prohibiting any construction within 100 m of the shoreline. This distance can be extended in cases of significant threats, such as severe erosive activity. However, some projects are still located in high-risk erosion areas, where erosion may be further exacerbated by karstic phenomena affecting the substrate. The results of this study align well with the provisions of Law 81-12 (Article 12).
{"title":"Erosion and shoreline retreat indicators in the Rabat-Salé littoral and their impact on coastal planning","authors":"El Miloudiya Naji , M'hamed Aberkan , Abderrahim Saadane , M'hamed Nmiss","doi":"10.1016/j.jafrearsci.2025.105534","DOIUrl":"10.1016/j.jafrearsci.2025.105534","url":null,"abstract":"<div><div>In-depth field investigations have allowed us to assess the coastal sector of Rabat-Salé by describing various forms of erosion, the condition of historical monuments located by the ocean, and the ineffectiveness of hard solutions implemented against erosion. This emphasizes the primary anthropogenic causes of the degradation of the studied coastal environments, including former calcarenite quarries and old sewage drainage canals. The interaction of these anthropogenic factors with natural processes has led to a significant retreat of the coastal cliff, which is clearly visible on-site, posing a threat to certain constructions, notably historical monuments of great cultural value to the Kingdom. To quantify the retreat in the study area between 1993 and 2022, we utilized the Digital Shoreline Analysis System (DSAS), version 5 integrated into ArcGIS 10.4, which revealed relatively high rates with an average rate of 1.2 m per year. We also adopted another method by using threatened historical monuments to calculate average retreat rates of the shoreline using two old plans, one dating back to 1935 (1/1000 scale) for Fort Rottembourg and another from 1922 (1/2000 scale) containing two historical monuments: Borj Sirat and Borj Eddar. The calculations yielded average rates that align with those obtained through DSAS. Despite the risks associated with erosion in the study area, a regulatory framework for the protection and enhancement of the coastal environment (Law 81-12) has been in place since 2015, prohibiting any construction within 100 m of the shoreline. This distance can be extended in cases of significant threats, such as severe erosive activity. However, some projects are still located in high-risk erosion areas, where erosion may be further exacerbated by karstic phenomena affecting the substrate. The results of this study align well with the provisions of Law 81-12 (Article 12).</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105534"},"PeriodicalIF":2.2,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153763","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}
Pub Date : 2025-01-03DOI: 10.1016/j.jafrearsci.2025.105535
H.M. Rajesh , G.A. Belyanin , T. Mokatse , D.T. Mfa , C. Vorster , Y. Wan
Meta-supracrustal rocks in medium-to high-grade terranes along Archean craton margins are, in the common case, more deformed than similar rocks within the craton. Multiple deformation episodes are possible and could be related to different stages of a single tectonic event or disparate ones. Geochronologic characterization of fabric forming minerals helps to place an individual deformational episode with respect to spatially associated tectonic events along the craton margin. This study focuses on the Shashe Group of metasedimentary rocks that define the large-scale Gulushabe fold structure in northeastern Motloutse Complex, Botswana, near its contact with the southwestern margin of the Zimbabwe Craton. Available detrital zircon geochronologic data indicate a depositional age of c.2.66–2.51 Ga for the protolith of these continental margin-type metasedimentary rocks. The upright NNE-trending Gulushabe fold structure is at variance with the regional northeasterly vergent folds from the northern–central Motloutse Complex and related to the Neoarchean (<2.65 Ga) NE-directed thrusting of the medium-grade terrane over the craton margin. 40Ar/39Ar geochronology of muscovite in quartz mica schist from the NNE-trending refolded northwestern minor fold closure of the Gulushabe fold structure yielded a plateau (96% of 39Ar) age of 2018 ± 11 Ma. The significance of the age is addressed in terms of Paleoproterozoic tectonics in the bounding terranes: Limpopo Complex to the south and Magondi Belt to the north. In the process, the Archean antiquity and extent of the Motloutse Complex, and the provenance of Shashe Group rocks are clarified. The results highlight the importance of delineating overprint events to better understand the tectonics along the contact of Archean craton and medium-to high-grade terranes.
{"title":"c.2.02 Ga Ar40–Ar39 muscovite age from the Gulushabe fold structure, Motloutse Complex, near SW margin of Zimbabwe Craton: Imprint of Limpopo Complex or Magondi Belt tectonics?","authors":"H.M. Rajesh , G.A. Belyanin , T. Mokatse , D.T. Mfa , C. Vorster , Y. Wan","doi":"10.1016/j.jafrearsci.2025.105535","DOIUrl":"10.1016/j.jafrearsci.2025.105535","url":null,"abstract":"<div><div>Meta-supracrustal rocks in medium-to high-grade terranes along Archean craton margins are, in the common case, more deformed than similar rocks within the craton. Multiple deformation episodes are possible and could be related to different stages of a single tectonic event or disparate ones. Geochronologic characterization of fabric forming minerals helps to place an individual deformational episode with respect to spatially associated tectonic events along the craton margin. This study focuses on the Shashe Group of metasedimentary rocks that define the large-scale Gulushabe fold structure in northeastern Motloutse Complex, Botswana, near its contact with the southwestern margin of the Zimbabwe Craton. Available detrital zircon geochronologic data indicate a depositional age of c.2.66–2.51 Ga for the protolith of these continental margin-type metasedimentary rocks. The upright NNE-trending Gulushabe fold structure is at variance with the regional northeasterly vergent folds from the northern–central Motloutse Complex and related to the Neoarchean (<2.65 Ga) NE-directed thrusting of the medium-grade terrane over the craton margin. <sup>40</sup>Ar/<sup>39</sup>Ar geochronology of muscovite in quartz mica schist from the NNE-trending refolded northwestern minor fold closure of the Gulushabe fold structure yielded a plateau (96% of <sup>39</sup>Ar) age of 2018 ± 11 Ma. The significance of the age is addressed in terms of Paleoproterozoic tectonics in the bounding terranes: Limpopo Complex to the south and Magondi Belt to the north. In the process, the Archean antiquity and extent of the Motloutse Complex, and the provenance of Shashe Group rocks are clarified. The results highlight the importance of delineating overprint events to better understand the tectonics along the contact of Archean craton and medium-to high-grade terranes.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105535"},"PeriodicalIF":2.2,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143152734","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}
Pub Date : 2024-12-30DOI: 10.1016/j.jafrearsci.2024.105533
Christian Wolkersdorfer , Kagiso S. More , Elke Mugova , Nokuthula Nchabeleng , Anna Johanna Sotiralis
This study examined the hydrogeological and hydrochemical conditions around Bulembu, eSwatini, two decades post-closure of the Havelock asbestos mine. On-site parameters and water samples underwent chemical and stable isotope analysis, supplemented by flow measurements and tracer tests with NaCl and uranine. Multivariate statistical analysis and PHREEQC modelling identified three water groups: i) low mineralised surface water (32 mg/L TDS), ii) mining-influenced water from the Havelock mine pool (212 mg/L TDS), and iii) tailings seepage water (411 mg/L TDS). All are earth alkaline, hydrogen carbonate-dominant, dominated by Mg and hydrogen carbonate ions. Surface water complies with WHO standards, except for elevated As in the mine pool and Cr in waste rock seepage. Chemical and tracer test results indicate a well-mixed, low-residence-time mine pool. Both the Tutusi river catchment and the upper Nkomazana catchment as well as water courses downstream of the abandoned mine exhibit pristine water quality. The authors propose inclusion of the area in a trans-boundary national park with the Barbeton Makhonjwa Mountains UNESCO World Heritage Site. They recommend amelioration of tailings, not remining, to safeguard the environment and local population from asbestos exposure.
{"title":"Hydrogeochemical and hydrogeological baseline study following the mining of asbestos at the Havelock Mine, Bulembu, eSwatini","authors":"Christian Wolkersdorfer , Kagiso S. More , Elke Mugova , Nokuthula Nchabeleng , Anna Johanna Sotiralis","doi":"10.1016/j.jafrearsci.2024.105533","DOIUrl":"10.1016/j.jafrearsci.2024.105533","url":null,"abstract":"<div><div>This study examined the hydrogeological and hydrochemical conditions around Bulembu, eSwatini, two decades post-closure of the Havelock asbestos mine. On-site parameters and water samples underwent chemical and stable isotope analysis, supplemented by flow measurements and tracer tests with NaCl and uranine. Multivariate statistical analysis and PHREEQC modelling identified three water groups: i) low mineralised surface water (32 mg/L TDS), ii) mining-influenced water from the Havelock mine pool (212 mg/L TDS), and iii) tailings seepage water (411 mg/L TDS). All are earth alkaline, hydrogen carbonate-dominant, dominated by Mg and hydrogen carbonate ions. Surface water complies with WHO standards, except for elevated As in the mine pool and Cr in waste rock seepage. Chemical and tracer test results indicate a well-mixed, low-residence-time mine pool. Both the Tutusi river catchment and the upper Nkomazana catchment as well as water courses downstream of the abandoned mine exhibit pristine water quality. The authors propose inclusion of the area in a trans-boundary national park with the Barbeton Makhonjwa Mountains UNESCO World Heritage Site. They recommend amelioration of tailings, not remining, to safeguard the environment and local population from asbestos exposure.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105533"},"PeriodicalIF":2.2,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171383","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}
Pub Date : 2024-12-30DOI: 10.1016/j.jafrearsci.2024.105526
Sihem Salmi-Laouar , Samira Mendir , Riadh Aouissi , Gamal M.EL. Qot , Rachel Kruft-Welton , Mohamed S. Ahmed , Ahmed A. Abdelhady
Environmental changes can impact benthic fauna at multiple levels. To better understand these changes at both the species and community levels, the Cenomanian macrofossils from two regions in northeastern Algeria, Tébessa and Batna, were analyzed. The results revealed that while changes at the species level (morphology) and community level (ecology) followed similar patterns, they were not identical. Non-metric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA) tests of the morphological variations of 114 complete shells of the suspension-feeding trigonoid bivalve Scabrotrigonia scabra (Lamarck, 1819) showed significant differences (P < 0.001) between the two regions. Two distinct echophenotypes were identified, with the first dominating in Tébessa and the second in Batna. The Batna echophenotype is characterized by smaller, flattened shells with numerous ribs, an adaptive strategy for stabilizing in soft substrates. Additionally, the smaller shells in Batna were linked to the oligotrophic conditions of the outer ramp setting, in contrast to the deeper outer ramp setting in Tébessa (mesotrophic). To further investigate environmental variations, the macrofaunal associations of the Cenomanian were examined. The NPMANOVA test indicated significant differences in faunal associations between the regions, with Batna exhibiting less diversity and a higher proportion of deposit-feeders, suggesting soft substrate conditions. In contrast, no significant differences were found among the faunal associations of the different Cenomanian substages, though ecological attributes showed minor, gradual changes. The early and middle Cenomanian fauna were dominated by epifaunal byssate taxa, while deposit-feeder taxa increased in the late Cenomanian, likely due to the global sea-level rise toward the end of the period. Overall, the paleogeographic setting (middle versus outer ramp) appears to have played a major role in shaping the ecological and morphological variations between Tébessa and Batna.
{"title":"Spatiotemporal variability of the Cenomanian macrobenthic fauna in Northeast Algeria: Species versus community level variations","authors":"Sihem Salmi-Laouar , Samira Mendir , Riadh Aouissi , Gamal M.EL. Qot , Rachel Kruft-Welton , Mohamed S. Ahmed , Ahmed A. Abdelhady","doi":"10.1016/j.jafrearsci.2024.105526","DOIUrl":"10.1016/j.jafrearsci.2024.105526","url":null,"abstract":"<div><div>Environmental changes can impact benthic fauna at multiple levels. To better understand these changes at both the species and community levels, the Cenomanian macrofossils from two regions in northeastern Algeria, Tébessa and Batna, were analyzed. The results revealed that while changes at the species level (morphology) and community level (ecology) followed similar patterns, they were not identical. Non-metric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA) tests of the morphological variations of 114 complete shells of the suspension-feeding trigonoid bivalve <em>Scabrotrigonia scabra</em> (Lamarck, 1819) showed significant differences (P < 0.001) between the two regions. Two distinct echophenotypes were identified, with the first dominating in Tébessa and the second in Batna. The Batna echophenotype is characterized by smaller, flattened shells with numerous ribs, an adaptive strategy for stabilizing in soft substrates. Additionally, the smaller shells in Batna were linked to the oligotrophic conditions of the outer ramp setting, in contrast to the deeper outer ramp setting in Tébessa (mesotrophic). To further investigate environmental variations, the macrofaunal associations of the Cenomanian were examined. The NPMANOVA test indicated significant differences in faunal associations between the regions, with Batna exhibiting less diversity and a higher proportion of deposit-feeders, suggesting soft substrate conditions. In contrast, no significant differences were found among the faunal associations of the different Cenomanian substages, though ecological attributes showed minor, gradual changes. The early and middle Cenomanian fauna were dominated by epifaunal byssate taxa, while deposit-feeder taxa increased in the late Cenomanian, likely due to the global sea-level rise toward the end of the period. Overall, the paleogeographic setting (middle versus outer ramp) appears to have played a major role in shaping the ecological and morphological variations between Tébessa and Batna.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105526"},"PeriodicalIF":2.2,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153352","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}
Unlike numerous Archean-Proterozoic greenstone belts worldwide, which are known to host orogenic and intrusion-related-type gold deposits, the Archean Matsitama Greenstone Belt (MGB) of NE Botswana hosts numerous base metal deposits/occurrences, including the Bushman Lineament (a regional brittle-ductile shear-hosted) Mowana Cu deposit. Economic copper mineralisation therein occurs as hypogene (chalcopyrite), supergene (chalcocite mainly), and oxidised (malachite, cuprite, tenorite, and chrysocolla) ores within quartz-K-feldspar-calcite veins. Due to the insufficiency of radiochronologic data, the geotectonic setting and evolution of the MGB are unclear, and the time of Cu introduction in the MGB remains contentious and unconstrained. In this study, hydrothermal K-feldspar spatially associated with Cu mineral phases in the ore veins was dated by 40Ar/39Ar to shed light on the window time of Cu mineralisation and understand the geological context of the MGB. K-feldspar from the hypogene ore-dominated and the oxidised ore-dominated areas yields similar integrated total fusion 40Ar/39Ar ages of ca. 550 Ma. Our new age is at odds with the Archean geological setting of the MGB and the ca. 2.2-1.9 Ga galena Pb-Pb age previously assigned to the Cu mineralisation within the MGB. This new age, however, reveals for the first time that the Pan-African thermal rejuvenation that was previously recognised in other portions of the Zimbabwe Craton also affected the MGB, therefore refining the spatial extent to which the Zimbabwe Craton underwent thermal rejuvenation. Our ca. 550 Ma age also highlights the possibility of a Neoproterozoic Cu mineralisation event at Mowana Copper Mine, in addition to the known Paleoproterozoic initial Cu introduction. This possible Neoproterozoic Cu mineralisation event at the Mowana Copper Mine is coincident with Cu events within the Kalahari Copper Belt as well as within the Central African and Zambian Copper belts, therefore highlighting the importance of the Pan-African Orogenesis in the Cu endowment of south-central Africa.
{"title":"Ar/Ar geochronology of hydrothermal K-feldspar from the Mowana Cu Mine and implications for geotectonothermal evolution and Cu mineralisation in the Archean Matsitama Greenstone Belt, Zimbabwe Craton, northeastern Botswana","authors":"Thierry Bineli Betsi , Tebogo Kelepile , Kazuyasu Shindo , Read Brown Mapeo , Alfredo Camacho","doi":"10.1016/j.jafrearsci.2024.105521","DOIUrl":"10.1016/j.jafrearsci.2024.105521","url":null,"abstract":"<div><div>Unlike numerous Archean-Proterozoic greenstone belts worldwide, which are known to host orogenic and intrusion-related-type gold deposits, the Archean Matsitama Greenstone Belt (MGB) of NE Botswana hosts numerous base metal deposits/occurrences, including the Bushman Lineament (a regional brittle-ductile shear-hosted) Mowana Cu deposit. Economic copper mineralisation therein occurs as hypogene (chalcopyrite), supergene (chalcocite mainly), and oxidised (malachite, cuprite, tenorite, and chrysocolla) ores within quartz-K-feldspar-calcite veins. Due to the insufficiency of radiochronologic data, the geotectonic setting and evolution of the MGB are unclear, and the time of Cu introduction in the MGB remains contentious and unconstrained. In this study, hydrothermal K-feldspar spatially associated with Cu mineral phases in the ore veins was dated by <sup>40</sup>Ar/<sup>39</sup>Ar to shed light on the window time of Cu mineralisation and understand the geological context of the MGB. K-feldspar from the hypogene ore-dominated and the oxidised ore-dominated areas yields similar integrated total fusion <sup>40</sup>Ar/<sup>39</sup>Ar ages of <em>ca.</em> 550 Ma. Our new age is at odds with the Archean geological setting of the MGB and the <em>ca.</em> 2.2-1.9 Ga galena Pb-Pb age previously assigned to the Cu mineralisation within the MGB. This new age, however, reveals for the first time that the Pan-African thermal rejuvenation that was previously recognised in other portions of the Zimbabwe Craton also affected the MGB, therefore refining the spatial extent to which the Zimbabwe Craton underwent thermal rejuvenation. Our <em>ca</em>. 550 Ma age also highlights the possibility of a Neoproterozoic Cu mineralisation event at Mowana Copper Mine, in addition to the known Paleoproterozoic initial Cu introduction. This possible Neoproterozoic Cu mineralisation event at the Mowana Copper Mine is coincident with Cu events within the Kalahari Copper Belt as well as within the Central African and Zambian Copper belts, therefore highlighting the importance of the Pan-African Orogenesis in the Cu endowment of south-central Africa.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105521"},"PeriodicalIF":2.2,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153761","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}
Mafic Microgranular Enclaves (MMEs) within granitoids are commonly interpreted as indicators of coexisting mafic magma that were derived from the mantle, which can offer valuable insights into the origins and evolution of primary mafic magmas. In this article, we investigate the petrography and bulk-rock major and trace elements geochemistry of quartz monzonite, the hosted MMEs, and the associated pink granite, from the Bougaffer pluton in the eastern Saghro Inlier. This study aims to clarify the petrogenetic processes that formed the MMEs and their granitoid host rocks. The MMEs are characterized by a microgranular texture and occur as ellipsoidal, angular and rounded shape, ranging in size from 2 to 80 cm, with sharp boundaries. They share the same mineral content as their host rocks though in distinct proportions, and are classified as monzonite and monzodiorite with high-K calc-alkaline to shoshonitic composition. The MMEs show lower SiO2 contents and higher TiO2, CaO, MgO, Fe2O3t, and Al2O3 contents compared to their host granitoids. The MMEs and their host granitoid display several similarities, including the same mineralogy and similar total-rock compositions, suggesting a genetic relationship. The MMEs are most likely cumulates formed during the initial phase of the same magmatic system that produced the Bougaffer quartz monzonite. A two stages model is proposed, involving rapid solidification within the cogenetic host granitoid magma at the chamber boundaries, leading to the formation of crystal accumulations at the bottom of the magma chamber as cumulates. These cumulates were later fragmented and disturbed due to subsequent magma recharge and the convection induced within the magma chamber.
{"title":"Geochemistry and petrogenesis of mafic microgranular enclaves (MMEs) in the bougaffer granitoid, Saghro inlier, eastern anti-atlas belt, Morocco","authors":"Omar Outaaoui , Ezzoura Errami , Kadio Aka Donald Koua , Abdellatif Jouhari , Saber Salmi , Abdelmalek ouadjou , Nasser Ennih","doi":"10.1016/j.jafrearsci.2024.105528","DOIUrl":"10.1016/j.jafrearsci.2024.105528","url":null,"abstract":"<div><div>Mafic Microgranular Enclaves (MMEs) within granitoids are commonly interpreted as indicators of coexisting mafic magma that were derived from the mantle, which can offer valuable insights into the origins and evolution of primary mafic magmas. In this article, we investigate the petrography and bulk-rock major and trace elements geochemistry of quartz monzonite, the hosted MMEs, and the associated pink granite, from the Bougaffer pluton in the eastern Saghro Inlier. This study aims to clarify the petrogenetic processes that formed the MMEs and their granitoid host rocks. The MMEs are characterized by a microgranular texture and occur as ellipsoidal, angular and rounded shape, ranging in size from 2 to 80 cm, with sharp boundaries. They share the same mineral content as their host rocks though in distinct proportions, and are classified as monzonite and monzodiorite with high-K calc-alkaline to shoshonitic composition. The MMEs show lower SiO<sub>2</sub> contents and higher TiO<sub>2</sub>, CaO, MgO, Fe<sub>2</sub>O<sub>3</sub>t, and Al<sub>2</sub>O<sub>3</sub> contents compared to their host granitoids. The MMEs and their host granitoid display several similarities, including the same mineralogy and similar total-rock compositions, suggesting a genetic relationship. The MMEs are most likely cumulates formed during the initial phase of the same magmatic system that produced the Bougaffer quartz monzonite. A two stages model is proposed, involving rapid solidification within the cogenetic host granitoid magma at the chamber boundaries, leading to the formation of crystal accumulations at the bottom of the magma chamber as cumulates. These cumulates were later fragmented and disturbed due to subsequent magma recharge and the convection induced within the magma chamber.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105528"},"PeriodicalIF":2.2,"publicationDate":"2024-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143152735","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}
Pub Date : 2024-12-28DOI: 10.1016/j.jafrearsci.2024.105532
Fahad Abubakar , Ismail Ahmad Abir , Abdulrasheed Adamu Hassan
<div><div>In a recent report by the Nigerian Geological Survey Agency, new minerals, including gold, lepidolite, and tantalite, were discovered in the western part of Kogi State. If found in sufficient quantities, these commercially valuable minerals have the potential to drive technological advancement, create jobs, and promote economic growth, which are crucial for the sustainable development of Nigeria. This study aims to delineate these occurrences, extensions, and other potential mineralisation zones using integrated high-resolution airborne magnetic and gamma-ray spectrometry geophysical datasets aided by the Analytical Hierarchy Process (AHP) and weighted overlay analysis (WOA). The AHP and WOA algorithms were employed based on expert opinions and the accuracy of each signal enhancement technique to delineate the mineralisation potential of the study area (using the IMOs as control). Centre for Exploration Targeting (CET) grid analysis, analytic signal (Asig), and Euler deconvolution were used to enhance the magnetic datasets, while radiometric ratios and ternary images were utilised for the radiometric datasets. The Asig categorises the magnetic amplitude into low (<0.023 nT/m), intermediate (0.023–0.105 nT/m), and high (>0.105 nT/m). It reveals magneto-structures and intrusive zones, which are potential targets for mineralisation. WNW-ESE and NE-SW are the dominant fault trends, with the IMOs being more consistent with NE-SW faults. The estimated depth of potential mineralisation zones ranges from 20.87 to 87.34 m. The ternary image and radiometric ratio maps (K/Th and Th/K) indicate that the mineralisation zones have undergone advanced weathering, resulting in potassium leaching and thorium enrichment. Asig, lineament density, and the Th/K ratio map were integrated to assess the mineralisation potential. Employing the ArcGIS weighted overlay tool and AHP evaluation, the mineralisation potential of Kogi West was classified as high, intermediate, or low. 90% of the IMOs fall within the high class, while 10% are in the intermediate category. The high-potential zones should be prioritised for further exploration and exploitation. The high correspondence indicates the effectiveness of the integrated geophysical approach in identifying regions with favourable geological conditions for mineralisation. However, while the study provides a promising framework for targeting potential mineral deposits, future exploration activities should consider the following implications to improve the reliability and applicability of the results: validation with ground-truthing, incorporating other geophysical methods (such as electrical, gravity, and electromagnetic surveys), and acknowledgement of eventualities that high potential mineralisation zones not been economically viable, may be due to poor mineral grade or volume. These endeavours and acknowledgements will refine the current understanding of the high-potential mineralisation zones and expand t
{"title":"Kogi west geophysical mineralisation appraisal using Analytical Hierarchy Process (AHP)","authors":"Fahad Abubakar , Ismail Ahmad Abir , Abdulrasheed Adamu Hassan","doi":"10.1016/j.jafrearsci.2024.105532","DOIUrl":"10.1016/j.jafrearsci.2024.105532","url":null,"abstract":"<div><div>In a recent report by the Nigerian Geological Survey Agency, new minerals, including gold, lepidolite, and tantalite, were discovered in the western part of Kogi State. If found in sufficient quantities, these commercially valuable minerals have the potential to drive technological advancement, create jobs, and promote economic growth, which are crucial for the sustainable development of Nigeria. This study aims to delineate these occurrences, extensions, and other potential mineralisation zones using integrated high-resolution airborne magnetic and gamma-ray spectrometry geophysical datasets aided by the Analytical Hierarchy Process (AHP) and weighted overlay analysis (WOA). The AHP and WOA algorithms were employed based on expert opinions and the accuracy of each signal enhancement technique to delineate the mineralisation potential of the study area (using the IMOs as control). Centre for Exploration Targeting (CET) grid analysis, analytic signal (Asig), and Euler deconvolution were used to enhance the magnetic datasets, while radiometric ratios and ternary images were utilised for the radiometric datasets. The Asig categorises the magnetic amplitude into low (<0.023 nT/m), intermediate (0.023–0.105 nT/m), and high (>0.105 nT/m). It reveals magneto-structures and intrusive zones, which are potential targets for mineralisation. WNW-ESE and NE-SW are the dominant fault trends, with the IMOs being more consistent with NE-SW faults. The estimated depth of potential mineralisation zones ranges from 20.87 to 87.34 m. The ternary image and radiometric ratio maps (K/Th and Th/K) indicate that the mineralisation zones have undergone advanced weathering, resulting in potassium leaching and thorium enrichment. Asig, lineament density, and the Th/K ratio map were integrated to assess the mineralisation potential. Employing the ArcGIS weighted overlay tool and AHP evaluation, the mineralisation potential of Kogi West was classified as high, intermediate, or low. 90% of the IMOs fall within the high class, while 10% are in the intermediate category. The high-potential zones should be prioritised for further exploration and exploitation. The high correspondence indicates the effectiveness of the integrated geophysical approach in identifying regions with favourable geological conditions for mineralisation. However, while the study provides a promising framework for targeting potential mineral deposits, future exploration activities should consider the following implications to improve the reliability and applicability of the results: validation with ground-truthing, incorporating other geophysical methods (such as electrical, gravity, and electromagnetic surveys), and acknowledgement of eventualities that high potential mineralisation zones not been economically viable, may be due to poor mineral grade or volume. These endeavours and acknowledgements will refine the current understanding of the high-potential mineralisation zones and expand t","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105532"},"PeriodicalIF":2.2,"publicationDate":"2024-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171380","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}
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