Journal of African Earth Sciences最新文献_第8页

Machine learning approaches for predicting reservoir lithofacies: Geological implications in the Tendrara-Missour basin, Morocco

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2024-12-16 DOI: 10.1016/j.jafrearsci.2024.105518

Youssef Elbouazaoui , Achour Margoum , Mohammed Et-Touhami , Rabah Bouchta , Allal El ouarghioui

Lithofacies identification is crucial for reservoir characterization, as reservoir quality is closely tied to lithofacies distribution, directly impacting hydrocarbon recovery. Conventional core analysis, while informative, is often limited to partially cored reservoirs. Well logs, such as gamma ray, density, and sonic logs, offer continuous reservoir information, making them valuable for lithofacies identification. In the Tendrara-Missour basin, four TAGI (Trias Argilo-Gréseux Inférieur) reservoir lithofacies were identified: sandstone, pebbly sandstone, conglomerate, and claystone-siltstone.

This research represents the first application of machine learning for reservoir lithofacies identification in Morocco, aimed to predict and reconstruct lithofacies in 417 m of non-cored sections from three wells using machine learning models: Random Forest (RF), Multi-Layer Perceptron Neural Network (MLPNN), and Cluster Analysis (CA). MLPNN achieved the highest accuracy (87%), capturing complex non-linear relationships in well-log data. RF performed reasonably well (82%) but struggled to differentiate pebbly sandstone from conglomerate due to similar log responses. CA, with an accuracy of 44%, faced challenges distinguishing lithofacies with overlapping log responses.

The MLPNN model revealed rapid lateral lithofacies variation despite well proximity and identified fining upward sequences, indicating energy transitions typical of fluvial and alluvial settings. These findings underscore the effectiveness of machine learning in reservoir characterization, offering a cost-efficient alternative to extensive core analysis. The successful application of the MLPNN model in well log data demonstrates its suitability for lithological discrimination, making it a valuable tool for reservoir studies. Future integration of MLPNN results with seismic data could further enhance lithofacies mapping and support hydrocarbon exploration and reservoir management efforts in the Tendrara-Missour basin.

{"title":"Machine learning approaches for predicting reservoir lithofacies: Geological implications in the Tendrara-Missour basin, Morocco","authors":"Youssef Elbouazaoui , Achour Margoum , Mohammed Et-Touhami , Rabah Bouchta , Allal El ouarghioui","doi":"10.1016/j.jafrearsci.2024.105518","DOIUrl":"10.1016/j.jafrearsci.2024.105518","url":null,"abstract":"<div><div>Lithofacies identification is crucial for reservoir characterization, as reservoir quality is closely tied to lithofacies distribution, directly impacting hydrocarbon recovery. Conventional core analysis, while informative, is often limited to partially cored reservoirs. Well logs, such as gamma ray, density, and sonic logs, offer continuous reservoir information, making them valuable for lithofacies identification. In the Tendrara-Missour basin, four TAGI (Trias Argilo-Gréseux Inférieur) reservoir lithofacies were identified: sandstone, pebbly sandstone, conglomerate, and claystone-siltstone.</div><div>This research represents the first application of machine learning for reservoir lithofacies identification in Morocco, aimed to predict and reconstruct lithofacies in 417 m of non-cored sections from three wells using machine learning models: Random Forest (RF), Multi-Layer Perceptron Neural Network (MLPNN), and Cluster Analysis (CA). MLPNN achieved the highest accuracy (87%), capturing complex non-linear relationships in well-log data. RF performed reasonably well (82%) but struggled to differentiate pebbly sandstone from conglomerate due to similar log responses. CA, with an accuracy of 44%, faced challenges distinguishing lithofacies with overlapping log responses.</div><div>The MLPNN model revealed rapid lateral lithofacies variation despite well proximity and identified fining upward sequences, indicating energy transitions typical of fluvial and alluvial settings. These findings underscore the effectiveness of machine learning in reservoir characterization, offering a cost-efficient alternative to extensive core analysis. The successful application of the MLPNN model in well log data demonstrates its suitability for lithological discrimination, making it a valuable tool for reservoir studies. Future integration of MLPNN results with seismic data could further enhance lithofacies mapping and support hydrocarbon exploration and reservoir management efforts in the Tendrara-Missour basin.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105518"},"PeriodicalIF":2.2,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153286","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The influence of the Nile water system on groundwater recharge and discharge at Khartoum City- Central Sudan

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2024-12-13 DOI: 10.1016/j.jafrearsci.2024.105517

Abdalla Eltom Mohamed Elsheikh , Braa Abdelwdood Ali Ahmed

The study area lies at the confluence of the Blue and White Niles in Khartoum, the capital of Sudan. The main objective of the current study is to assess the influence of the Niles water system on groundwater recharge and discharge. Three methods of investigations were applied; base-flow Recession Method, Water Levels Fluctuations (WLF) and the Darcy Method. The amount of water discharge of the Niles varies seasonally; the highest flows were registered in the autumn seasons. The amount of 816 × 10⁶m³/day was registered in 1988 as maximum discharge and 49 × 10⁶m³/day in 1984 as minimum one in Soba Station on the Blue Nile. Groundwater is mainly stored in two aquifers, Gezira and Sandstone formations, both aquifers are hydraulically interconnected to form one aquifer system. Gezira formation represents the saturated upper zone that let it in direct contact with Niles waters. The hydraulic gradients range from ≥0.005 to ≤0.002 from west to the east direction; indicating that, the White Nile is the main source of recharge for groundwater rather than the Blue Nile. Using the Darcy method, the groundwater recharge from the While Nile is more than twice the recharge from the Blue Nile. In general the groundwater recharge from the River Niles using the three methods is estimated at about 130 × 10⁶ m³ annually. The strong interface between the Niles surface water and groundwater in the Khartoum area will raises concerns on Niles waters contamination with already polluted shallow groundwater aquifers.

{"title":"The influence of the Nile water system on groundwater recharge and discharge at Khartoum City- Central Sudan","authors":"Abdalla Eltom Mohamed Elsheikh , Braa Abdelwdood Ali Ahmed","doi":"10.1016/j.jafrearsci.2024.105517","DOIUrl":"10.1016/j.jafrearsci.2024.105517","url":null,"abstract":"<div><div>The study area lies at the confluence of the Blue and White Niles in Khartoum, the capital of Sudan. The main objective of the current study is to assess the influence of the Niles water system on groundwater recharge and discharge. Three methods of investigations were applied; base-flow Recession Method, Water Levels Fluctuations (WLF) and the Darcy Method. The amount of water discharge of the Niles varies seasonally; the highest flows were registered in the autumn seasons. The amount of 816 × 10<sup>6</sup>m<sup>3</sup>/day was registered in 1988 as maximum discharge and 49 × 10<sup>6</sup>m<sup>3</sup>/day in 1984 as minimum one in Soba Station on the Blue Nile. Groundwater is mainly stored in two aquifers, Gezira and Sandstone formations, both aquifers are hydraulically interconnected to form one aquifer system. Gezira formation represents the saturated upper zone that let it in direct contact with Niles waters. The hydraulic gradients range from ≥0.005 to ≤0.002 from west to the east direction; indicating that, the White Nile is the main source of recharge for groundwater rather than the Blue Nile. Using the Darcy method, the groundwater recharge from the While Nile is more than twice the recharge from the Blue Nile. In general the groundwater recharge from the River Niles using the three methods is estimated at about 130 × 10<sup>6</sup> m<sup>3</sup> annually. The strong interface between the Niles surface water and groundwater in the Khartoum area will raises concerns on Niles waters contamination with already polluted shallow groundwater aquifers.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105517"},"PeriodicalIF":2.2,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Geospatial mapping of groundwater potential zones using multi-criteria decision-making AHP approach: A study of Kadugli district, south Kurdufan, Sudan

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2024-12-09 DOI: 10.1016/j.jafrearsci.2024.105513

Majdi Sultan Hamdan , Rakesh Singh , Rahul Pathak , Shalini Kumari , Vishal Chauhan

Groundwater availability is crucial for sustaining agricultural activities and ensuring the availability of clean water in arid regions like Kadugli district, South Kordofan State, Sudan. This project focuses on delineating areas with high groundwater potential using Geographic Information Systems (GIS), Remote Sensing (RS), and the Analytic Hierarchy Process (AHP). Sentinel-2 and STRM DEM satellite images, along with traditional data sources, were utilized. Remote sensing imagery was employed to extract relevant features such as slope, land use/land cover (LULC), lithology, and landform characteristics. Thematic layers depicting LULC, soil type, rainfall, drainage density, geology, lineament density, and slope were created. Groundwater potential areas were identified using weighted overlay analysis and the AHP algorithm, assigning data weights based on their relative importance with Saaty's scale. Rainfall and geology had higher weights, while soil had less. The study found that 38% of the southern area had outstanding groundwater potential, 46% was classified as good, and 16% as fair. The northern half exhibited fair to good groundwater potential zones. This interdisciplinary approach enhances our understanding of groundwater dynamics in arid regions and supports efforts to achieve water security and resilience in Sudan.

{"title":"Geospatial mapping of groundwater potential zones using multi-criteria decision-making AHP approach: A study of Kadugli district, south Kurdufan, Sudan","authors":"Majdi Sultan Hamdan , Rakesh Singh , Rahul Pathak , Shalini Kumari , Vishal Chauhan","doi":"10.1016/j.jafrearsci.2024.105513","DOIUrl":"10.1016/j.jafrearsci.2024.105513","url":null,"abstract":"<div><div>Groundwater availability is crucial for sustaining agricultural activities and ensuring the availability of clean water in arid regions like Kadugli district, South Kordofan State, Sudan. This project focuses on delineating areas with high groundwater potential using Geographic Information Systems (GIS), Remote Sensing (RS), and the Analytic Hierarchy Process (AHP). Sentinel-2 and STRM DEM satellite images, along with traditional data sources, were utilized. Remote sensing imagery was employed to extract relevant features such as slope, land use/land cover (LULC), lithology, and landform characteristics. Thematic layers depicting LULC, soil type, rainfall, drainage density, geology, lineament density, and slope were created. Groundwater potential areas were identified using weighted overlay analysis and the AHP algorithm, assigning data weights based on their relative importance with Saaty's scale. Rainfall and geology had higher weights, while soil had less. The study found that 38% of the southern area had outstanding groundwater potential, 46% was classified as good, and 16% as fair. The northern half exhibited fair to good groundwater potential zones. This interdisciplinary approach enhances our understanding of groundwater dynamics in arid regions and supports efforts to achieve water security and resilience in Sudan.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105513"},"PeriodicalIF":2.2,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153287","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Vanadium distribution and behavior in the Paleoproterozoic of the Reguibat Shield: insights from statistical and geochemical analyses

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2024-12-09 DOI: 10.1016/j.jafrearsci.2024.105514

Didi Maghlah , Sidi Biha , Sid’Ahmed Mohamed Lemine

Reliable geochemical databases for vanadium ores in thin the vast Precambrian domains of the West African Craton are insufficient to establish regional deposition model that can help in its exploration. Despite the economic interest in vanadium is rapidly expanding, the limited number of geochemical and mineralogical studies focused on its deposition and accumulation in the region restricts our understanding of its behavior and hinders the discovery of potentially exploitable ore deposits. In this study, conducted as part of the Tiris Uranium Project, data from 1195 geochemical analyses using the ICP-MS method, performed on 1065 borehole samples, were statistically processed using Python. The objective is to characterize the geochemical behavior of vanadium and the processes responsible for its concentration in Precambrian granites and surface colluvium of the Reguibat Shield in northern Mauritania. Our results indicate that vanadium behaves as a high field strength element (HFSE) in granites, with a particular concentration in hydrothermalized context. Vanadium shows a strong affinity for FeOt and TiO₂, preferentially concentrating in ferromagnesian-rich granites and titaniferous minerals such as iron oxides, biotite, and ilmenite.

{"title":"Vanadium distribution and behavior in the Paleoproterozoic of the Reguibat Shield: insights from statistical and geochemical analyses","authors":"Didi Maghlah , Sidi Biha , Sid’Ahmed Mohamed Lemine","doi":"10.1016/j.jafrearsci.2024.105514","DOIUrl":"10.1016/j.jafrearsci.2024.105514","url":null,"abstract":"<div><div>Reliable geochemical databases for vanadium ores in thin the vast Precambrian domains of the West African Craton are insufficient to establish regional deposition model that can help in its exploration. Despite the economic interest in vanadium is rapidly expanding, the limited number of geochemical and mineralogical studies focused on its deposition and accumulation in the region restricts our understanding of its behavior and hinders the discovery of potentially exploitable ore deposits. In this study, conducted as part of the Tiris Uranium Project, data from 1195 geochemical analyses using the ICP-MS method, performed on 1065 borehole samples, were statistically processed using Python. The objective is to characterize the geochemical behavior of vanadium and the processes responsible for its concentration in Precambrian granites and surface colluvium of the Reguibat Shield in northern Mauritania. Our results indicate that vanadium behaves as a high field strength element (HFSE) in granites, with a particular concentration in hydrothermalized context. Vanadium shows a strong affinity for FeOt and TiO<sub>2</sub>, preferentially concentrating in ferromagnesian-rich granites and titaniferous minerals such as iron oxides, biotite, and ilmenite.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105514"},"PeriodicalIF":2.2,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The Koudiat El Madene unit (Kabylian “Dorsal”, Algeria) and its correlation with similar units belonging to the Rif-Betic Arc (Morocco and Spain)

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2024-12-06 DOI: 10.1016/j.jafrearsci.2024.105515

Sabiha Talmat , Manuel Martín-Martín , Madani Benyoucef , Bruno Ferré , Djelloul Belhai

The Koudiat El Madene Unit (Arba Massif) belongs to the Kabylian “Dorsal” (Algerian Internal Zone). The stratigraphy and tectonic structuring of the area is equivalent to the western Moroccan Internal Rif and its counterpart in the Spanish Internal Betic Cordillera. In fact, all these chain segments are due to a common Cenozoic geodynamic evolution related to the closure of the westernmost Tethys and the later opening of the Mediterranean Sea. Nevertheless, a comparison of the Kabylian internal units at the western Mediterranean scale was still missing. This study means a revisiting of the outcrops of the Koudiat El Madene Unit and a revision of the existent literature on the area aimed to a comparation of this area with the Algerian Kabylian “Dorsal” and with the Ghomaride (Moroccan Rif) and Malaguide (Spanish Betic Cordillera) equivalents units. This unit crops out in a tectonic window under different backthrusting units of the Maghrebian Flysch Basin Zone and overthrusts southwards the Maghrebian Flysch Basin Zone itself and the External Tellian Zones. This is a frequent tectonic situation of this kind of units in the internal Rif-Betic chains. The condensed succession of the Koudiat El Madene Unit, separated by unconformities but also by internal erosive boundaries, is divided into five stratigraphic formations. Nowadays, the stratigraphic division and dating of the Koudiat El Madene Unit (Algerian Kabyle Unit) are less detailed than its equivalents in the Ghomarides, especially those of the Malaguides. Nevertheless, a correlation with the Ghomaride Units from the Tetouan-Chaouen area (Northern Morocco) and the Malaguide Complex from the Sierra Espuña area (Southeastern Spain) has been performed revealing great similarities. The good correlation can be due to a close paleogeographic position in the southern margin of the Paleo- and Mesomediterranean Microplate. Minor variations should be proposed in relation to the position in the margin. Detailed and modern stratigraphic and sedimentological studies are required to propose a more precise paleogeographic framework.

{"title":"The Koudiat El Madene unit (Kabylian “Dorsal”, Algeria) and its correlation with similar units belonging to the Rif-Betic Arc (Morocco and Spain)","authors":"Sabiha Talmat , Manuel Martín-Martín , Madani Benyoucef , Bruno Ferré , Djelloul Belhai","doi":"10.1016/j.jafrearsci.2024.105515","DOIUrl":"10.1016/j.jafrearsci.2024.105515","url":null,"abstract":"<div><div>The Koudiat El Madene Unit (Arba Massif) belongs to the Kabylian “Dorsal” (Algerian Internal Zone). The stratigraphy and tectonic structuring of the area is equivalent to the western Moroccan Internal Rif and its counterpart in the Spanish Internal Betic Cordillera. In fact, all these chain segments are due to a common Cenozoic geodynamic evolution related to the closure of the westernmost Tethys and the later opening of the Mediterranean Sea. Nevertheless, a comparison of the Kabylian internal units at the western Mediterranean scale was still missing. This study means a revisiting of the outcrops of the Koudiat El Madene Unit and a revision of the existent literature on the area aimed to a comparation of this area with the Algerian Kabylian “Dorsal” and with the Ghomaride (Moroccan Rif) and Malaguide (Spanish Betic Cordillera) equivalents units. This unit crops out in a tectonic window under different backthrusting units of the Maghrebian <em>Flysch</em> Basin Zone and overthrusts southwards the Maghrebian <em>Flysch</em> Basin Zone itself and the External Tellian Zones. This is a frequent tectonic situation of this kind of units in the internal Rif-Betic chains. The condensed succession of the Koudiat El Madene Unit, separated by unconformities but also by internal erosive boundaries, is divided into five stratigraphic formations. Nowadays, the stratigraphic division and dating of the Koudiat El Madene Unit (Algerian Kabyle Unit) are less detailed than its equivalents in the Ghomarides, especially those of the Malaguides. Nevertheless, a correlation with the Ghomaride Units from the Tetouan-Chaouen area (Northern Morocco) and the Malaguide Complex from the Sierra Espuña area (Southeastern Spain) has been performed revealing great similarities. The good correlation can be due to a close paleogeographic position in the southern margin of the Paleo- and Mesomediterranean Microplate. Minor variations should be proposed in relation to the position in the margin. Detailed and modern stratigraphic and sedimentological studies are required to propose a more precise paleogeographic framework.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105515"},"PeriodicalIF":2.2,"publicationDate":"2024-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143152701","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}

引用次数: 0

A geochemical and palynological study of lake sediments at Mboandong, Cameroon: Chemical weathering and vegetation linked to Holocene palaeoclimate

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2024-12-04 DOI: 10.1016/j.jafrearsci.2024.105512

Armel Z. Ekoa Bessa , Keith Richards , Awo M. Egbe , Fonge B. Ambo

Geochemical and palynological analyses of core samples from Mboandong, a crater lake in western Cameroon, provide a record of response to climate and vegetation change in West Africa over the last 7000 years. Three palaeoclimatic phases were identified: a humid phase (6800-5700 cal. BP), characterized by a humid and warm palaeoclimate; a drying phase (5700-2000 cal. BP) with a less humid palaeoclimate; finally, a seasonal phase (2000 cal. BP to present), characterized by a seasonally varied, mainly humid and warm palaeoclimate. Pollen components show swamp and humid rainforest taxa being gradually replaced by semi-deciduous, regrowth and non-tree taxa such as grasses (Poaceae). There is a suggestion of increasing aridity over the last 200 years. The sediments are primarily weathered deposits mixed with volcanic eruptive material, rather than detritus derived from the UCC (upper continental crust). Chemical Index of Alteration (CIA) values are mostly high (mean 90.65%) and indicate a variable but mostly humid palaeoclimate. CIA values are most likely influenced by climate, as well as by runoff and physical erosion. Bands of volcanic ash are associated with frequent freshwater sponge spicules and diatoms, probably due to increased availability of silica. Ca and Na depletion is probably linked with soil leaching, while K depletion and Mg enrichment were probably caused by chemical alteration. Humid intervals may have higher organic carbon content, whereas increased amounts of iron occur in potentially drier intervals. A greatly increased presence of oil palm pollen (Elaeis guineensis) is interpreted as evidence of cultivation after 1700 cal. BP.

{"title":"A geochemical and palynological study of lake sediments at Mboandong, Cameroon: Chemical weathering and vegetation linked to Holocene palaeoclimate","authors":"Armel Z. Ekoa Bessa , Keith Richards , Awo M. Egbe , Fonge B. Ambo","doi":"10.1016/j.jafrearsci.2024.105512","DOIUrl":"10.1016/j.jafrearsci.2024.105512","url":null,"abstract":"<div><div>Geochemical and palynological analyses of core samples from Mboandong, a crater lake in western Cameroon, provide a record of response to climate and vegetation change in West Africa over the last 7000 years. Three palaeoclimatic phases were identified: a humid phase (6800-5700 cal. BP), characterized by a humid and warm palaeoclimate; a drying phase (5700-2000 cal. BP) with a less humid palaeoclimate; finally, a seasonal phase (2000 cal. BP to present), characterized by a seasonally varied, mainly humid and warm palaeoclimate. Pollen components show swamp and humid rainforest taxa being gradually replaced by semi-deciduous, regrowth and non-tree taxa such as grasses (Poaceae). There is a suggestion of increasing aridity over the last 200 years. The sediments are primarily weathered deposits mixed with volcanic eruptive material, rather than detritus derived from the UCC (upper continental crust). Chemical Index of Alteration (CIA) values are mostly high (mean 90.65%) and indicate a variable but mostly humid palaeoclimate. CIA values are most likely influenced by climate, as well as by runoff and physical erosion. Bands of volcanic ash are associated with frequent freshwater sponge spicules and diatoms, probably due to increased availability of silica. Ca and Na depletion is probably linked with soil leaching, while K depletion and Mg enrichment were probably caused by chemical alteration. Humid intervals may have higher organic carbon content, whereas increased amounts of iron occur in potentially drier intervals. A greatly increased presence of oil palm pollen (<em>Elaeis guineensis</em>) is interpreted as evidence of cultivation after 1700 cal. BP.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105512"},"PeriodicalIF":2.2,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143152722","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}

引用次数: 0

Evolution of the West African fold belts: Review, new geochronological data, new correlations and new geodynamic hypothesis

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2024-11-30 DOI: 10.1016/j.jafrearsci.2024.105484

M. Villeneuve , H. Bellon , O. Guillou , A. Gärtner , P.A. Mueller , A.L. Heatherington , P.M. Ndiaye , H. Theveniaut , M. Corsini , U. Linnemann , A. El Archi , A. Aghzer , N. Youbi

Several synthetic papers have been published about the geological structure of the threeWest African fold belts (Rokelides, Bassarides and Mauritanides), which were attached to the western margin of the West African Craton. Owing to the paucity of radiometric ages, some orogens and tectonic events have previously been confused and little consensus exists regarding their geodynamic evolution. Matching previous geological geochronological and geophysic data with nine new radiometric U-Pb ages on zircon, allows us to propose a new geodynamic model. Apart from ages of Mesoproterozoic events, four different orogens have been distinguished: Pan-African I (ca. 900 to 640 Ma), Pan-African II (ca. 640 to 520 Ma), Mali-Rokel River (ca. 490 to 450 Ma) and Variscan (ca. 450 to 300 Ma). The pan-African I orogeny is characterized by a complex evolution, terminating with a subduction process to the West, including the formation of a volcanic arc and a collisional event between ca. 660 and 640 Ma. The pan-African II orogen corresponds to a subduction process to the East leading to the building of a new volcanic arc and the formation of a back-arc basin to the East. Thenewly evidencedMali-Rokel River orogenic event led to the formation of extensive intra-continental N-S directed basins. The latter were folded and thrusted before the deposition of early Palaeozoic molasses. In the course of the Variscan Orogeny the Palaeozoicbasins setting in Mauritania and Northern Senegal were deformed during the Carboniferous Pangaea assembly. These two later orogensare intra-continental in the area but likely linked to far-field oceanic subduction to the West.For each orogenic period in the belts there are contemporaneous sedimentary deposits on the West African Craton and, of course, related unconformities between them. These data have facilitated correlations between the West African Belts and with the belts setting in adjacent areas like the Appalachians to the West and the northern Brazilian belts to the South.

{"title":"Evolution of the West African fold belts: Review, new geochronological data, new correlations and new geodynamic hypothesis","authors":"M. Villeneuve , H. Bellon , O. Guillou , A. Gärtner , P.A. Mueller , A.L. Heatherington , P.M. Ndiaye , H. Theveniaut , M. Corsini , U. Linnemann , A. El Archi , A. Aghzer , N. Youbi","doi":"10.1016/j.jafrearsci.2024.105484","DOIUrl":"10.1016/j.jafrearsci.2024.105484","url":null,"abstract":"<div><div>Several synthetic papers have been published about the geological structure of the threeWest African fold belts (Rokelides, Bassarides and Mauritanides), which were attached to the western margin of the West African Craton. Owing to the paucity of radiometric ages, some orogens and tectonic events have previously been confused and little consensus exists regarding their geodynamic evolution. Matching previous geological geochronological and geophysic data with nine new radiometric U-Pb ages on zircon, allows us to propose a new geodynamic model. Apart from ages of Mesoproterozoic events, four different orogens have been distinguished: Pan-African I (ca. 900 to 640 Ma), Pan-African II (ca. 640 to 520 Ma), Mali-Rokel River (ca. 490 to 450 Ma) and Variscan (ca. 450 to 300 Ma). The pan-African I orogeny is characterized by a complex evolution, terminating with a subduction process to the West, including the formation of a volcanic arc and a collisional event between ca. 660 and 640 Ma. The pan-African II orogen corresponds to a subduction process to the East leading to the building of a new volcanic arc and the formation of a back-arc basin to the East. Thenewly evidencedMali-Rokel River orogenic event led to the formation of extensive intra-continental N-S directed basins. The latter were folded and thrusted before the deposition of early Palaeozoic molasses. In the course of the Variscan Orogeny the Palaeozoicbasins setting in Mauritania and Northern Senegal were deformed during the Carboniferous Pangaea assembly. These two later orogensare intra-continental in the area but likely linked to far-field oceanic subduction to the West.For each orogenic period in the belts there are contemporaneous sedimentary deposits on the West African Craton and, of course, related unconformities between them. These data have facilitated correlations between the West African Belts and with the belts setting in adjacent areas like the Appalachians to the West and the northern Brazilian belts to the South.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105484"},"PeriodicalIF":2.2,"publicationDate":"2024-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143152721","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Mineralogy and geochemical characteristics of the Ibaga copper ore deposit in Singida-Tanzania: Implication for source of copper mineralization and ore quality

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2024-11-29 DOI: 10.1016/j.jafrearsci.2024.105495

Adam Kutarasa , Athanas S. Macheyeki , Gaduputi Sankaranna

The Ibaga copper deposit in the Nzega-Sekenke terrane is hosted in meta-sedimentary rocks and it has been rudimentarily mined by small scale miners for more than a decade. To study mineralogy and geochemical characteristics of the deposit, samples from outcrops and mining pit were collected for XRD, XRF and ICP-MS analysis. Results show that the ore is composed of chalcopyrite, covellite, cuprite, malachite and azurite as ore minerals; whereas augite, chlorite, actinolite, greenalite, birnessite, quartz, magnetite, berlinite, cristobalite, hematite, calcite and parisite are gangue minerals. The deposit is characterized by Cu (3.2–31.3 wt %), Fe (2.1–25.1 wt %), Ag (0.6–16.6 wt %) and lower concentration of penalized impurities Sb, Bi, As, Cd and (Al₂O₃ + MgO) than threshold limit set by copper smelters and refineries. The ore shows significant variation of Y/Ho = 21.75–40.00, Zr/Hf = 23.33–58.61 and Nb/Ta = 4.20–27.17. Presence of higher REE values of up to 2000 ppm in sample BG04 due to REE minerals known as parisite indicates that the deposit is potential prospect for REE. Consistent with the granites, the ore has Sm/Nd < 0.24 and enriched in LREE relative to HREE where ∑LREE/∑HREE = 4.7–9.0 and La/Lu = 32–769.3. The scatter plot of δCe versus δEu for ore and rock samples suggests closer genetic relationship between the ore, granite and quartz-sericite-schist. These results imply that the granitic intrusion triggered mineralization by skarnification into meta-sedimentary rocks and subsequently the ore underwent supergene enrichment.

{"title":"Mineralogy and geochemical characteristics of the Ibaga copper ore deposit in Singida-Tanzania: Implication for source of copper mineralization and ore quality","authors":"Adam Kutarasa , Athanas S. Macheyeki , Gaduputi Sankaranna","doi":"10.1016/j.jafrearsci.2024.105495","DOIUrl":"10.1016/j.jafrearsci.2024.105495","url":null,"abstract":"<div><div>The Ibaga copper deposit in the Nzega-Sekenke terrane is hosted in meta-sedimentary rocks and it has been rudimentarily mined by small scale miners for more than a decade. To study mineralogy and geochemical characteristics of the deposit, samples from outcrops and mining pit were collected for XRD, XRF and ICP-MS analysis. Results show that the ore is composed of chalcopyrite, covellite, cuprite, malachite and azurite as ore minerals; whereas augite, chlorite, actinolite, greenalite, birnessite, quartz, magnetite, berlinite, cristobalite, hematite, calcite and parisite are gangue minerals. The deposit is characterized by Cu (3.2–31.3 wt %), Fe (2.1–25.1 wt %), Ag (0.6–16.6 wt %) and lower concentration of penalized impurities Sb, Bi, As, Cd and (Al<sub>2</sub>O<sub>3</sub> + MgO) than threshold limit set by copper smelters and refineries. The ore shows significant variation of Y/Ho = 21.75–40.00, Zr/Hf = 23.33–58.61 and Nb/Ta = 4.20–27.17. Presence of higher REE values of up to 2000 ppm in sample BG04 due to REE minerals known as parisite indicates that the deposit is potential prospect for REE. Consistent with the granites, the ore has Sm/Nd < 0.24 and enriched in LREE relative to HREE where ∑LREE/∑HREE = 4.7–9.0 and La/Lu = 32–769.3. The scatter plot of δCe versus δEu for ore and rock samples suggests closer genetic relationship between the ore, granite and quartz-sericite-schist. These results imply that the granitic intrusion triggered mineralization by skarnification into meta-sedimentary rocks and subsequently the ore underwent supergene enrichment.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105495"},"PeriodicalIF":2.2,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143152700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Flood hazard in Malawi

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2024-11-29 DOI: 10.1016/j.jafrearsci.2024.105490

M. Garcin , H. Mdala , Y. Kalebe

This article presents the methodology and key findings of the first national study of flood hazard conducted across Malawi as part of the 2016–2021 GEMMAP programme. After outlining Malawi's geomorphological, climatic, and hydrographic features, we detail the approach used for flood hazard assessment and mapping. Ten flood types were identified, reflecting diverse morphological, geological, and climatic settings, resulting in flood hazard maps, which cover the entire country and highlight areas at risk based on flood type and magnitude. The total area exposed to flooding in Malawi is estimated at 16% of the country's surface area (around 15 000 km2). Flooding of plains along major rivers, such as the Shire River, which affects hundreds of thousands of people, accounts for approximately 37% (5100 km²) of Malawi's flood-prone areas. Flooding in dambo areas comprise 34% (4700 km²), and lake shores another 10% (1400 km²). Although debris flow flooding is restricted to around 4.2%, it nevertheless frequently causes significant casualties and damage. The remaining surface area corresponds to the narrow flood zones on either side of the secondary rivers. Specific flood contexts are analysed in detail, including the Shire River-Lake Malawi flood connection, debris flows in mountainous regions, and river mobility in lowland areas. The methodology has been designed to be simple and pragmatic, enabling easy adaptation and application in countries with similar geographical contexts and limited flood hazard knowledge.

{"title":"Flood hazard in Malawi","authors":"M. Garcin , H. Mdala , Y. Kalebe","doi":"10.1016/j.jafrearsci.2024.105490","DOIUrl":"10.1016/j.jafrearsci.2024.105490","url":null,"abstract":"<div><div>This article presents the methodology and key findings of the first national study of flood hazard conducted across Malawi as part of the 2016–2021 GEMMAP programme. After outlining Malawi's geomorphological, climatic, and hydrographic features, we detail the approach used for flood hazard assessment and mapping. Ten flood types were identified, reflecting diverse morphological, geological, and climatic settings, resulting in flood hazard maps, which cover the entire country and highlight areas at risk based on flood type and magnitude. The total area exposed to flooding in Malawi is estimated at 16% of the country's surface area (around 15 000 km2). Flooding of plains along major rivers, such as the Shire River, which affects hundreds of thousands of people, accounts for approximately 37% (5100 km<sup>2</sup>) of Malawi's flood-prone areas. Flooding in dambo areas comprise 34% (4700 km<sup>2</sup>), and lake shores another 10% (1400 km<sup>2</sup>). Although debris flow flooding is restricted to around 4.2%, it nevertheless frequently causes significant casualties and damage. The remaining surface area corresponds to the narrow flood zones on either side of the secondary rivers. Specific flood contexts are analysed in detail, including the Shire River-Lake Malawi flood connection, debris flows in mountainous regions, and river mobility in lowland areas. The methodology has been designed to be simple and pragmatic, enabling easy adaptation and application in countries with similar geographical contexts and limited flood hazard knowledge.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105490"},"PeriodicalIF":2.2,"publicationDate":"2024-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143152732","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}

引用次数: 0

Hybrid turbidite-contourite system on the upper-slope continental margin of the offshore southern Tanzania 坦桑尼亚南部近海上斜坡大陆边缘混杂浊积岩-轮廓岩体系

IF 2.2 4区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Journal of African Earth Sciences

Pub Date : 2024-11-28 DOI: 10.1016/j.jafrearsci.2024.105496

Emily Barnabas Kiswaka , Dicky Harishidayat , Oras Joseph Mkinga , John William Gama

Cretaceous-Cenozoic hybrid turbidite-contourite (HTCs) systems on the upper-slope region of the northern Rovuma Basin, southern offshore Tanzania have been poorly studied. HTCs have been widely studied from several places due to their petroleum prospectivity, link to geohazards, and potential to help understand deep marine circulation processes and past climates. We have studied 3D seismic data into the northern Rovuma Basin to establish variation and orientation of seismic facies, architectural elements and geomorphologies (based on RMS amplitude maps) characterizing the Cretaceous-Cenozoic HTCs linked to channelized sediment transport and deposition. Two different migration patterns for channelized systems are recognized. They include Cretaceous-Middle Miocene and Middle Miocene-Holocene systems migrating toward SE and NW, respectively. Timing of change in migration trends coincides with change in traverse directions of major submarine channels that allowed sediment transportation by gravity flows. Trajectory of the submarine channels shifted from S-N to SW-NE and approximately W-E during the Middle Miocene, agreeing with the change in channel fills migration trends. The trajectory shift, for the revealed submarine channels was caused by tectonic activity linked to East African Rift System, so does the distribution and migration trends of the HTCs. The study area has hydrocarbon accumulations in the Oligo-Miocene sandstones containing HTCs characterized by a clearly defined depositional system with high RMS amplitudes. The Middle Miocene-Early Pliocene interval has a clear depositional configuration as well, but its low RMS amplitude indicates dominance of fine-grained HTCs with limited reservoir potential. The Late Pliocene-Holocene interval has very high RMS amplitude, but its chaotic configuration implies the presence of poorly sorted sedimentary fills having limited reservoir potential as well. This may be one of the reasons for hydrocarbon discoveries in the study area being limited within the Oligo-Miocene sandstones, and not the younger stratigraphic levels.

坦桑尼亚南部近海Rovuma盆地北部上斜坡地区白垩纪-新生代混浊岩-轮廓岩（HTCs）混合体系研究较少。由于其石油勘探前景，与地质灾害的联系，以及有助于了解深海环流过程和过去气候的潜力，HTCs在多个地方得到了广泛的研究。我们研究了Rovuma盆地北部的三维地震数据，以建立地震相、建筑元素和地貌的变化和方向（基于RMS振幅图），以表征白垩纪-新生代与河道化沉积物运输和沉积有关的HTCs。对信道化系统的两种不同迁移模式进行了识别。它们分别为白垩纪—中中新世和中中新世—全新世，分别向东南和西北方向迁移。迁移趋势变化的时间与主要海底通道穿越方向的变化一致，这些通道允许重力流输送沉积物。中新世中期，海底河道轨迹由南北向向西南偏东、近西东方向转变，与河道填充物迁移趋势的变化相一致。显示的海底通道的轨迹变化是由与东非裂谷系有关的构造活动引起的，高温烃的分布和迁移趋势也是如此。研究区渐新世—中新世含烃砂岩具有清晰的沉积体系和高均势振幅特征。中中新世—上新世早段沉积构型也较为清晰，但均势幅值较低，表明储层潜力有限，以细粒烃源岩为主。晚上新世—全新世段的均势幅值非常高，但其混沌结构表明存在分选差的沉积充填体，储层潜力有限。这可能是研究区油气发现局限于渐新世-中新世砂岩而非更年轻地层的原因之一。

{"title":"Hybrid turbidite-contourite system on the upper-slope continental margin of the offshore southern Tanzania","authors":"Emily Barnabas Kiswaka , Dicky Harishidayat , Oras Joseph Mkinga , John William Gama","doi":"10.1016/j.jafrearsci.2024.105496","DOIUrl":"10.1016/j.jafrearsci.2024.105496","url":null,"abstract":"<div><div>Cretaceous-Cenozoic hybrid turbidite-contourite (HTCs) systems on the upper-slope region of the northern Rovuma Basin, southern offshore Tanzania have been poorly studied. HTCs have been widely studied from several places due to their petroleum prospectivity, link to geohazards, and potential to help understand deep marine circulation processes and past climates. We have studied 3D seismic data into the northern Rovuma Basin to establish variation and orientation of seismic facies, architectural elements and geomorphologies (based on RMS amplitude maps) characterizing the Cretaceous-Cenozoic HTCs linked to channelized sediment transport and deposition. Two different migration patterns for channelized systems are recognized. They include Cretaceous-Middle Miocene and Middle Miocene-Holocene systems migrating toward SE and NW, respectively. Timing of change in migration trends coincides with change in traverse directions of major submarine channels that allowed sediment transportation by gravity flows. Trajectory of the submarine channels shifted from S-N to SW-NE and approximately W-E during the Middle Miocene, agreeing with the change in channel fills migration trends. The trajectory shift, for the revealed submarine channels was caused by tectonic activity linked to East African Rift System, so does the distribution and migration trends of the HTCs. The study area has hydrocarbon accumulations in the Oligo-Miocene sandstones containing HTCs characterized by a clearly defined depositional system with high RMS amplitudes. The Middle Miocene-Early Pliocene interval has a clear depositional configuration as well, but its low RMS amplitude indicates dominance of fine-grained HTCs with limited reservoir potential. The Late Pliocene-Holocene interval has very high RMS amplitude, but its chaotic configuration implies the presence of poorly sorted sedimentary fills having limited reservoir potential as well. This may be one of the reasons for hydrocarbon discoveries in the study area being limited within the Oligo-Miocene sandstones, and not the younger stratigraphic levels.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"222 ","pages":"Article 105496"},"PeriodicalIF":2.2,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745627","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0