Pub Date : 2026-01-19DOI: 10.1016/j.jafrearsci.2026.106030
Muhammed Sami Us , Erdoğan Tekin , Funda Akgün , Mine Sezgül Kayseri-Özer , Baki Erdoğan Varol
This study presents an integrated sedimentological, microfacies, and palynological analyses of the Late Eocene–?Early Oligocene (Priabonian–?Rupelian) Akçapınar Formation, exposed along the Soğanlı Stream in the Intra-Pontide Belt of the Western Black Sea region, Turkey. The formation, which overlies the evaporitic Pürçükören Formation and locally the Soğanlı Formation, records deposition in restricted shallow-marine to a lagoonal setting during a phase of significant tectonic and climatic reorganization. Detailed field mapping and measured stratigraphic sections, supported by petrographic, XRD, and SEM analyses, reveal mud-supported textures, limited faunal diversity, and thin-shelled gastropods, consistent with low-energy, brackish conditions. Palynological assemblages, identified here for the first time, refine the age constraints and document freshwater influence, whereas mineralogical data indicate alternating arid (smectite-rich) and humid (chlorite–illite-rich) intervals. Microfacies patterns (Mf1–Mf4) and lithofacies associations (Lf1–Lf8) were synthesized into three-dimensional depositional models, illustrating progressive basin restriction, episodic subaerial exposure, and evaporite precipitation. The multi-proxy approach, integrating sedimentology, microfacies, palynology, and mineralogy, refined the depositional model of the Akçapınar Formation, revealing facies heterogeneity driven by the interplay of tectonically induced basin isolation, relative sea-level fluctuations, and paleoclimatic oscillations during the Eocene–Oligocene transition, and providing new insights into the paleogeographic evolution of the northern Neo-Tethys during the final stages of its closure.
{"title":"Depositional settings and basin-fill evolution of the restricted platform system on the Intra Pontide belt during the Late Eocene-?Early Oligocene transition, western black sea region, Turkey","authors":"Muhammed Sami Us , Erdoğan Tekin , Funda Akgün , Mine Sezgül Kayseri-Özer , Baki Erdoğan Varol","doi":"10.1016/j.jafrearsci.2026.106030","DOIUrl":"10.1016/j.jafrearsci.2026.106030","url":null,"abstract":"<div><div>This study presents an integrated sedimentological, microfacies, and palynological analyses of the Late Eocene–?Early Oligocene (Priabonian–?Rupelian) Akçapınar Formation, exposed along the Soğanlı Stream in the Intra-Pontide Belt of the Western Black Sea region, Turkey. The formation, which overlies the evaporitic Pürçükören Formation and locally the Soğanlı Formation, records deposition in restricted shallow-marine to a lagoonal setting during a phase of significant tectonic and climatic reorganization. Detailed field mapping and measured stratigraphic sections, supported by petrographic, XRD, and SEM analyses, reveal mud-supported textures, limited faunal diversity, and thin-shelled gastropods, consistent with low-energy, brackish conditions. Palynological assemblages, identified here for the first time, refine the age constraints and document freshwater influence, whereas mineralogical data indicate alternating arid (smectite-rich) and humid (chlorite–illite-rich) intervals. Microfacies patterns (Mf1–Mf4) and lithofacies associations (Lf1–Lf8) were synthesized into three-dimensional depositional models, illustrating progressive basin restriction, episodic subaerial exposure, and evaporite precipitation. The multi-proxy approach, integrating sedimentology, microfacies, palynology, and mineralogy, refined the depositional model of the Akçapınar Formation, revealing facies heterogeneity driven by the interplay of tectonically induced basin isolation, relative sea-level fluctuations, and paleoclimatic oscillations during the Eocene–Oligocene transition, and providing new insights into the paleogeographic evolution of the northern Neo-Tethys during the final stages of its closure.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"237 ","pages":"Article 106030"},"PeriodicalIF":2.2,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090367","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 : 2026-01-18DOI: 10.1016/j.jafrearsci.2026.106035
Mohamed Ait Addi , Mohamed Aissa , Ilyasse Loudaoued , Abdel-Ali Kharis , Mohammed El Azmi , Fouad Lotfi , Mohmed Aissa , Abderrahim Ardouz , Antonio Delgado Huertas , Daoud El Azmi
The Bou Skour copper deposit is located in the eastern part of the Moroccan Anti-Atlas, approximately 56km east of Ouarzazate city, exhibits geological, textural and mineralogical characteristics that attest to a complex development history. Copper mineralization is hosted mainly in Lower Ediacaran andesite and granodiorite. The deposit resulted from at least two superimposed mineralizing events: i) a first, early event produced porphyry-type mineralization with chalcopyrite, bornite, pyrite and sphalerite. ii) A second, later event was responsible for the development of vein-type mineralization, mainly materialized by three veins: Filon Principal, Filon 1 and Filon 2. The mineralization is predominantly composed of pyrite, chalcopyrite, bornite, arsenopyrite, sphalerite, galena, tennantite, aikinite and wittichenite. Hydrothermal fluids have altered the granodiorite and andesite in several phases, forming potassic (K-feldspar + biotite), phyllic (chlorite), argillic (kaolinite), and propylitic (epidote) mineral zones. A portion of the silver in the Bou Skour deposit occurs in native form, while another fraction is present as trace elements within copper sulfides, primarily bornite and chalcocite. The ore-associated calcite has δ13C values range of - 9 to +2.9 ‰ and δ18O values of +19.5 to +22 ‰. These isotopic signatures are consistent with interaction of a crust sourced fluid and surrounding rocks, or with meteoric waters enriched in organic matter. In addition, sulfur isotopic signatures (δ34S) measured in bornite and chalcopyrite are relatively homogeneous, with values of between −7.86 andto −4.14 ‰, indicating a purely magmatic origin for sulfur.
Fluid inclusion study of porphyry-type mineralization reveals formation by paleo magmatic-hydrothermal circulation involving two distinct fluid types: (1) a hot magmatic fluid that underwent phase separation through boiling, generating both a hypersaline liquid (44.78–61.64 wt% NaCl equiv.) and a vapor phase (5.86–7.86 wt% NaCl equiv.), exhibiting comparable homogenization temperatures (450–500 °C); and (2) a second aqueous fluid characterized by moderate temperatures (237.9–452 °C) and low to intermediate salinity (19.4–38.78 wt% NaCl equiv.), indicating mixing with external fluids. The vein-type mineralization which represents hydrothermal conduits exhibiting moderately low temperatures (180–310 °C) and moderate salinities (14.25–28.66 wt% NaCl equiv.) records the late-stage evolution of the hydrothermal system associated with Hercynian tectonic activity.
{"title":"The Bou Skour Cu–Ag deposit (Anti-Atlas. Morocco): Evidence of a porphyry copper system from mineralogy, alteration, geochemistry, isotopes, and fluid inclusions","authors":"Mohamed Ait Addi , Mohamed Aissa , Ilyasse Loudaoued , Abdel-Ali Kharis , Mohammed El Azmi , Fouad Lotfi , Mohmed Aissa , Abderrahim Ardouz , Antonio Delgado Huertas , Daoud El Azmi","doi":"10.1016/j.jafrearsci.2026.106035","DOIUrl":"10.1016/j.jafrearsci.2026.106035","url":null,"abstract":"<div><div>The Bou Skour copper deposit is located in the eastern part of the Moroccan Anti-Atlas, approximately 56km east of Ouarzazate city, exhibits geological, textural and mineralogical characteristics that attest to a complex development history. Copper mineralization is hosted mainly in Lower Ediacaran andesite and granodiorite. The deposit resulted from at least two superimposed mineralizing events: i) a first, early event produced porphyry-type mineralization with chalcopyrite, bornite, pyrite and sphalerite. ii) A second, later event was responsible for the development of vein-type mineralization, mainly materialized by three veins: Filon Principal, Filon 1 and Filon 2. The mineralization is predominantly composed of pyrite, chalcopyrite, bornite, arsenopyrite, sphalerite, galena, tennantite, aikinite and wittichenite. Hydrothermal fluids have altered the granodiorite and andesite in several phases, forming potassic (K-feldspar + biotite), phyllic (chlorite), argillic (kaolinite), and propylitic (epidote) mineral zones. A portion of the silver in the Bou Skour deposit occurs in native form, while another fraction is present as trace elements within copper sulfides, primarily bornite and chalcocite. The ore-associated calcite has δ<sup>13</sup>C values range of - 9 to +2.9 ‰ and δ<sup>18</sup>O values of +19.5 to +22 ‰. These isotopic signatures are consistent with interaction of a crust sourced fluid and surrounding rocks, or with meteoric waters enriched in organic matter. In addition, sulfur isotopic signatures (δ<sup>34</sup>S) measured in bornite and chalcopyrite are relatively homogeneous, with values of between −7.86 andto −4.14 ‰, indicating a purely magmatic origin for sulfur.</div><div>Fluid inclusion study of porphyry-type mineralization reveals formation by paleo magmatic-hydrothermal circulation involving two distinct fluid types: (1) a hot magmatic fluid that underwent phase separation through boiling, generating both a hypersaline liquid (44.78–61.64 wt% NaCl equiv.) and a vapor phase (5.86–7.86 wt% NaCl equiv.), exhibiting comparable homogenization temperatures (450–500 °C); and (2) a second aqueous fluid characterized by moderate temperatures (237.9–452 °C) and low to intermediate salinity (19.4–38.78 wt% NaCl equiv.), indicating mixing with external fluids. The vein-type mineralization which represents hydrothermal conduits exhibiting moderately low temperatures (180–310 °C) and moderate salinities (14.25–28.66 wt% NaCl equiv.) records the late-stage evolution of the hydrothermal system associated with Hercynian tectonic activity.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"236 ","pages":"Article 106035"},"PeriodicalIF":2.2,"publicationDate":"2026-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034962","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 : 2026-01-17DOI: 10.1016/j.jafrearsci.2026.106021
Ahmed Talhi , Moulley Charaf Chabou , Ahcene Bourefis
The Moul ed Demamene massif is located within the suture zone between the internal and external zones of the Maghrebides chain in north-eastern Algeria. It contains a rare outcrop of Maghrebian flysch basement, including a complex of mafic rocks (gabbros and basalts). This study provides a detailed petrological and geochemical investigation of these rocks in order to constrain their origin and the geodynamic context of their emplacement within the framework of the Maghrebide orogeny. The studied rocks consist of gabbros, dolerites and basalts, which are predominantly composed of plagioclase, clinopyroxene (augite) and titanomagnetite. The altered mineral assemblages consist of albite, chlorite, epidote and actinolite, which are characteristic of greenschist-facies metamorphism of oceanic crust. Geochemical results indicate that the mafic rocks of the Moul ed Demamene massif have a homogeneous tholeiitic composition and a T-MORB affinity. This suggests that they formed during the initial stages of the oceanization of the Maghrebian Tethys basin. These rocks form the oceanic basement crust onto which the Maghrebian Mauretanian flysch was deposited. The Moul ed Demamene mafic rocks have a similar composition to T-MORB mafic rocks found in ophiolitic complexes in Corsica and the Texenna ophiolite in the western Mediterranean. Furthermore, this study suggests that the Boukredeche Formation of the Moul ed Demamene massif, comprising the studied mafic rocks and the Mauretanian flysch cover, is distinct from the Achaiches series. Until now, the Achaiches series was considered to be the only complete Paleozoic-to-Upper Jurassic basement in the Mauretanian flysch domain. The rocks of the Achaiches series probably originate from an eastern Tethyan terrane as they contain Triassic radiolarite, which is absent from the western Tethys. Finally, the mafic rocks of Moul ed Demamene constitute the second known ophiolitic outcrop remnant of the Maghrebides chain.
Moul ed Demamene地块位于阿尔及利亚东北部Maghrebides链内外带之间的缝合带内。它包含一个罕见的马格里布复理石基露头，包括一个基性岩（辉长岩和玄武岩）复合体。本研究对这些岩石进行了详细的岩石学和地球化学调查，以便在马格里布德造山带的框架内限制它们的起源和它们的侵位的地球动力学背景。研究岩石由辉长岩、白云岩和玄武岩组成，主要由斜长石、斜辉石（辉长岩）和钛磁铁矿组成。蚀变矿物组合由钠长石、绿泥石、绿帘石和放线石组成，具有洋壳绿片岩相变质作用的特征。地球化学结果表明，摩尔-德玛门地块的基性岩石具有均匀的拉斑岩组成和T-MORB亲和力。这表明它们形成于马格里布-特提斯盆地海洋化的初始阶段。这些岩石形成了海洋基底壳，马格里布-毛利塔尼亚复理石就沉积在上面。mol - demenene基性岩的组成与科西嘉蛇绿杂岩和西地中海Texenna蛇绿岩中的T-MORB基性岩相似。此外，本研究还表明，由所研究的基性岩和毛利塔尼亚复理石盖层组成的穆尔-德玛门地块的Boukredeche组与亚该奇系列不同。迄今为止，Achaiches系列被认为是毛里塔尼亚复理石域唯一完整的古生代-上侏罗统基底。亚该士系列的岩石可能起源于特提斯东部地体，因为它们含有三叠纪放射性长石，而这在特提斯西部是不存在的。最后，moled Demamene的基性岩构成了已知的Maghrebides链的第二个蛇绿岩露头遗迹。
{"title":"Petrological and geochemical evidence of new ophiolitic remnants in the Maghrebides chain (Moul ed Demamene Massif, north-eastern Algeria). Geodynamic implications","authors":"Ahmed Talhi , Moulley Charaf Chabou , Ahcene Bourefis","doi":"10.1016/j.jafrearsci.2026.106021","DOIUrl":"10.1016/j.jafrearsci.2026.106021","url":null,"abstract":"<div><div>The Moul ed Demamene massif is located within the suture zone between the internal and external zones of the Maghrebides chain in north-eastern Algeria. It contains a rare outcrop of Maghrebian flysch basement, including a complex of mafic rocks (gabbros and basalts). This study provides a detailed petrological and geochemical investigation of these rocks in order to constrain their origin and the geodynamic context of their emplacement within the framework of the Maghrebide orogeny. The studied rocks consist of gabbros, dolerites and basalts, which are predominantly composed of plagioclase, clinopyroxene (augite) and titanomagnetite. The altered mineral assemblages consist of albite, chlorite, epidote and actinolite, which are characteristic of greenschist-facies metamorphism of oceanic crust. Geochemical results indicate that the mafic rocks of the Moul ed Demamene massif have a homogeneous tholeiitic composition and a T-MORB affinity. This suggests that they formed during the initial stages of the oceanization of the Maghrebian Tethys basin. These rocks form the oceanic basement crust onto which the Maghrebian Mauretanian flysch was deposited. The Moul ed Demamene mafic rocks have a similar composition to T-MORB mafic rocks found in ophiolitic complexes in Corsica and the Texenna ophiolite in the western Mediterranean. Furthermore, this study suggests that the Boukredeche Formation of the Moul ed Demamene massif, comprising the studied mafic rocks and the Mauretanian flysch cover, is distinct from the Achaiches series. Until now, the Achaiches series was considered to be the only complete Paleozoic-to-Upper Jurassic basement in the Mauretanian flysch domain. The rocks of the Achaiches series probably originate from an eastern Tethyan terrane as they contain Triassic radiolarite, which is absent from the western Tethys. Finally, the mafic rocks of Moul ed Demamene constitute the second known ophiolitic outcrop remnant of the Maghrebides chain.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"236 ","pages":"Article 106021"},"PeriodicalIF":2.2,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034961","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 : 2026-01-17DOI: 10.1016/j.jafrearsci.2026.106032
Mohamed A. Agamy , Mahmoud Y. Zein El Din , Mohamed M. El Nady , Walid A. Makled
This study addresses the long-standing controversy regarding the source rocks for oil in the Apollonia carbonate reservoir of the East Razzak Field, Western Desert, Egypt. While previous research correlated the oil with the Jurassic Khatatba Formation, new geochemical evidence presents a conflicting hypothesis. We employed high-resolution geochemical characterization, including Rock-Eval pyrolysis, visual kerogen analysis, and gas chromatography-mass spectrometry (GC-MS), on samples from potential source rocks, including the Abu Roash and Khatatba formations, and compared them to the oil from the Apollonia reservoir. The present findings reveal that the Abu Roash F and G members, previously considered immature, are in fact thermally mature and oil-prone, with thermal alteration indices (TAI) and oxidation Tmax values indicating they are within the oil generation window. These elaborate new evidences that were not presented before in the record about East Razzak Field. The stable carbon isotope compositions and bulk geochemical parameters demonstrate that the Apollonia oils originated from a marine, medium-sulfur Type II kerogen source, specifically linking the hydrocarbons to the Abu Roash F and G members rather than the more terrigenous Khatatba or Alam El Bueib formations. The oil from the Apollonia reservoir exhibits a low Pristane/Phytane (Pr/Ph) ratio of less than 1.0, which is a strong indicator of an anoxic, marine depositional environment. This signature is consistent with the Abu Roash F and G members, which also exhibit low Pr/Ph ratios and a Type II kerogen classification. In contrast, the Khatatba Formation shows a different signature, with a Pr/Ph ratio greater than 1.0, suggesting a more oxidizing, mixed terrestrial and marine environment. The consistency of the biomarker signatures, particularly the Pr/Ph ratio, provides compelling evidence of a genetic link between the Abu Roash Formation and the Apollonia oil. This research resolves the origin controversy, establishes the Upper Cretaceous Abu Roash Formation as the main source rock, and refines our understanding of the petroleum system in the Razzak Field.
{"title":"High-resolution geochemical characterization of source rocks for the Apollonia carbonate reservoir, East Razzak Field, Western Desert, Egypt: A solution to the origin controversy","authors":"Mohamed A. Agamy , Mahmoud Y. Zein El Din , Mohamed M. El Nady , Walid A. Makled","doi":"10.1016/j.jafrearsci.2026.106032","DOIUrl":"10.1016/j.jafrearsci.2026.106032","url":null,"abstract":"<div><div>This study addresses the long-standing controversy regarding the source rocks for oil in the Apollonia carbonate reservoir of the East Razzak Field, Western Desert, Egypt. While previous research correlated the oil with the Jurassic Khatatba Formation, new geochemical evidence presents a conflicting hypothesis. We employed high-resolution geochemical characterization, including Rock-Eval pyrolysis, visual kerogen analysis, and gas chromatography-mass spectrometry (GC-MS), on samples from potential source rocks, including the Abu Roash and Khatatba formations, and compared them to the oil from the Apollonia reservoir. The present findings reveal that the Abu Roash F and G members, previously considered immature, are in fact thermally mature and oil-prone, with thermal alteration indices (TAI) and oxidation Tmax values indicating they are within the oil generation window. These elaborate new evidences that were not presented before in the record about East Razzak Field. The stable carbon isotope compositions and bulk geochemical parameters demonstrate that the Apollonia oils originated from a marine, medium-sulfur Type II kerogen source, specifically linking the hydrocarbons to the Abu Roash F and G members rather than the more terrigenous Khatatba or Alam El Bueib formations. The oil from the Apollonia reservoir exhibits a low Pristane/Phytane (Pr/Ph) ratio of less than 1.0, which is a strong indicator of an anoxic, marine depositional environment. This signature is consistent with the Abu Roash F and G members, which also exhibit low Pr/Ph ratios and a Type II kerogen classification. In contrast, the Khatatba Formation shows a different signature, with a Pr/Ph ratio greater than 1.0, suggesting a more oxidizing, mixed terrestrial and marine environment. The consistency of the biomarker signatures, particularly the Pr/Ph ratio, provides compelling evidence of a genetic link between the Abu Roash Formation and the Apollonia oil. This research resolves the origin controversy, establishes the Upper Cretaceous Abu Roash Formation as the main source rock, and refines our understanding of the petroleum system in the Razzak Field.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"236 ","pages":"Article 106032"},"PeriodicalIF":2.2,"publicationDate":"2026-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034963","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 : 2026-01-16DOI: 10.1016/j.jafrearsci.2026.106034
Houssem Tabbabi , Rim Temani , Gabriele Niccolini , Nadia Ben Moktar , Barbara Balestra , Hayet Khayati Ammar , Salah Mahmoudi , Adele Bertini
The CNH (Coupe Nabeul Houwaria) sedimentary succession (Cap Bon, NE Tunisia) was previously attributed to the Piacenzian-Gelasian transition based on preliminary micropaleontological data. This study re-evaluates that hypothesis through an integrated stratigraphic approach that combines calcareous nannofossils, planktonic foraminifera, and palynological data. Calcareous nannofossil assemblages are dominated by Reticulofenestra and Sphenolithus, with the consistent presence of Reticulofenestra pseudoumbilicus >7 μm and the absence of Quaternary marker taxa, constraining the succession to no younger than 3.82 Ma (top of Zone CNPL3). Palynological evidence, including subtropical to warm-temperate vegetation and dinoflagellate cyst assemblages lacking cold indicators, supports a warm climate incompatible with glacial conditions. This interpretation is further reinforced by the absence of Bythocythere turgida, an ostracod known as a significant “Northern guest”. The presence of Globorotalia puncticulata restricts the maximum age of the succession to no older than its first occurrence at ca. 4.52 Ma, while the absence of Globorotalia margaritae suggests even an age younger than 3.98 Ma (its last common occurrence). Taken together, these data frame the CNH succession within a time interval between ca. 4.52 (or 3.98 Ma) and 3.82 Ma, indicating a late Zanclean age and calling for a substantial revision of its lithostratigraphic assignment. The study highlights the need for high-resolution, multi-proxy analyses and, in particular, future magnetostratigraphic investigations, to improve regional chronostratigraphic models in NE Tunisia and strengthen correlations with the global stratigraphic framework.
{"title":"Palynological and biostratigraphical contributions to the stratigraphic understanding of Pliocene-Pleistocene deposits in the Cap Bon area (northeast Tunisia)","authors":"Houssem Tabbabi , Rim Temani , Gabriele Niccolini , Nadia Ben Moktar , Barbara Balestra , Hayet Khayati Ammar , Salah Mahmoudi , Adele Bertini","doi":"10.1016/j.jafrearsci.2026.106034","DOIUrl":"10.1016/j.jafrearsci.2026.106034","url":null,"abstract":"<div><div>The CNH (Coupe Nabeul Houwaria) sedimentary succession (Cap Bon, NE Tunisia) was previously attributed to the Piacenzian-Gelasian transition based on preliminary micropaleontological data. This study re-evaluates that hypothesis through an integrated stratigraphic approach that combines calcareous nannofossils, planktonic foraminifera, and palynological data. Calcareous nannofossil assemblages are dominated by <em>Reticulofenestra</em> and <em>Sphenolithus</em>, with the consistent presence of <em>Reticulofenestra pseudoumbilicus</em> >7 μm and the absence of Quaternary marker taxa, constraining the succession to no younger than 3.82 Ma (top of Zone CNPL3). Palynological evidence, including subtropical to warm-temperate vegetation and dinoflagellate cyst assemblages lacking cold indicators, supports a warm climate incompatible with glacial conditions. This interpretation is further reinforced by the absence of <em>Bythocythere turgida</em>, an ostracod known as a significant “Northern guest”. The presence of <em>Globorotalia puncticulata</em> restricts the maximum age of the succession to no older than its first occurrence at ca. 4.52 Ma, while the absence of <em>Globorotalia margaritae</em> suggests even an age younger than 3.98 Ma (its last common occurrence). Taken together, these data frame the CNH succession within a time interval between ca. 4.52 (or 3.98 Ma) and 3.82 Ma, indicating a late Zanclean age and calling for a substantial revision of its lithostratigraphic assignment. The study highlights the need for high-resolution, multi-proxy analyses and, in particular, future magnetostratigraphic investigations, to improve regional chronostratigraphic models in NE Tunisia and strengthen correlations with the global stratigraphic framework.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"236 ","pages":"Article 106034"},"PeriodicalIF":2.2,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034959","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 : 2026-01-14DOI: 10.1016/j.jafrearsci.2026.106023
Mahmoud E. Mesbah , Eman I.M. Ibrahim , Abdel-Kader M. Moghazi , Hassan I. El Sundoly , Mahmoud K. Alawy
The North Romite area, in the South Eastern Desert of Egypt, comprises a structurally controlled gold deposit (up to 8.8 g/t Au) that shares several characteristics with orogenic gold mineralization. This deposit has not received attention in geological studies because it is buried beneath Recent sand deposits. Here, we present new field, structural, and geochemical data for the North Romite deposit to investigate its mineralogical and geochemical characteristics, as well as its relationship to the regional tectonic context. The host rocks of gold mineralization in the study area are late Neoproterozoic arc metavolcanics and metagabbro-diorite, which underwent greenschist facies metamorphism and deformation. The mineralized zones are represented by sheared and folded quartz/carbonate veins and wall rock alterations that extend along transpressional NNE-, NE- and NW-trending shear zones. These shear zones splay from the major post-accretionary N-S Hamisana zone that was formed by collisional tectonics during the final assembly of Gondwana ∼640–600 Ma. The wall rock alterations around the quartz veins contain chlorite and epidote in the distal zones and quartz-sericite-carbonate-pyrite-chalcopyrite-gold in the intermediate and proximal zones. The geochemical signature of the North Romite deposit is defined by a metallic association of Au- Ag-As, as indicated by the elevated contents of these elements in the proximal alteration zones. The lack of syn-tectonic magmatism and the intense deformation in the deposit area indicate that the fluids responsible for gold mineralization were produced by metamorphic devolatilization. Gold precipitation was most likely controlled by phase separation, accompanied by decreasing confining pressure and lowering pH.
{"title":"The late Neoproterozoic orogenic gold mineralization at the North Romite area, South Eastern Desert, Egypt: geological, geochemical, and structural constraints","authors":"Mahmoud E. Mesbah , Eman I.M. Ibrahim , Abdel-Kader M. Moghazi , Hassan I. El Sundoly , Mahmoud K. Alawy","doi":"10.1016/j.jafrearsci.2026.106023","DOIUrl":"10.1016/j.jafrearsci.2026.106023","url":null,"abstract":"<div><div>The North Romite area, in the South Eastern Desert of Egypt, comprises a structurally controlled gold deposit (up to 8.8 g/t Au) that shares several characteristics with orogenic gold mineralization. This deposit has not received attention in geological studies because it is buried beneath Recent sand deposits. Here, we present new field, structural, and geochemical data for the North Romite deposit to investigate its mineralogical and geochemical characteristics, as well as its relationship to the regional tectonic context. The host rocks of gold mineralization in the study area are late Neoproterozoic arc metavolcanics and metagabbro-diorite, which underwent greenschist facies metamorphism and deformation. The mineralized zones are represented by sheared and folded quartz/carbonate veins and wall rock alterations that extend along transpressional NNE-, NE- and NW-trending shear zones. These shear zones splay from the major post-accretionary N-S Hamisana zone that was formed by collisional tectonics during the final assembly of Gondwana ∼640–600 Ma. The wall rock alterations around the quartz veins contain chlorite and epidote in the distal zones and quartz-sericite-carbonate-pyrite-chalcopyrite-gold in the intermediate and proximal zones. The geochemical signature of the North Romite deposit is defined by a metallic association of Au- Ag-As, as indicated by the elevated contents of these elements in the proximal alteration zones. The lack of syn-tectonic magmatism and the intense deformation in the deposit area indicate that the fluids responsible for gold mineralization were produced by metamorphic devolatilization. Gold precipitation was most likely controlled by phase separation, accompanied by decreasing confining pressure and lowering pH.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"236 ","pages":"Article 106023"},"PeriodicalIF":2.2,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034965","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 : 2026-01-14DOI: 10.1016/j.jafrearsci.2026.106019
Mohammed Jalal Tazi , Mohammed Ouchchen , Driss El Azzab , Driss Benyahia , Abdelhamid Bajadi , Hafsa Boufakri , Bouchra Dadi
This study adopts a multidisciplinary approach integrating ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) satellite imagery and airborne gamma-ray spectrometry data using a GIS-based fuzzy logic model to delineate the spatial distribution and zonal patterns of hydrothermal alteration assemblages in the southern part of the Sirwa Massif in the central Anti-Atlas belt (Morocco). This area records a complex tectono-magmatic history associated with significant hydrothermal Au–Ag–Cu deposits, yet remains largely underexplored. ASTER remote sensing data were analyzed using Band Ratio (BR) and Crosta techniques, enabling the identification of phyllic, argillic, propylitic and iron oxides alteration zones. Additional gamma spectrometry data, including uranium (eU), thorium (eTh), potassium K (%) and the K (%)/eTh ratio, were used to define zones of potassic alteration closely associated with hydrothermal activity.
A GIS-based fuzzy logic approach was implemented to integrate ASTER-derived hydrothermal alterations and AGRS-based potassic alteration layers to generate a hydrothermal alteration prospectivity map, highlighting zones of high mineralization potential. Six highly prospective zones for hydrothermal mineralization were delineated, located at lithological boundaries between Ouarzazate Group volcano-sedimentary outcrops and Pan-African granodioritic complexes, and the overlying Paleozoic cover. These zones coincide with areas of high structural complexity associated with pre-existing E–W, ENE–WSW, and NE–SW fault systems. The latter, developed during the post-collisional stage of the Pan-African orogeny, which acted as conduits for hydrothermal fluids associated with alkaline to calc-alkaline magmas, forming extensive alteration halos.
The hydrothermal alteration prospectivity map was statistically confirmed using the (ROC-AUC) analysis, complemented by rigorous field validation. This confirms the high accuracy of the adopted mapping approach for delineating hydrothermal zones, consequently optimizing subsequent mineral exploration strategies within the Sirwa Massif.
本研究采用多学科方法，结合ASTER （Advanced Spaceborne Thermal Emission and Reflection Radiometer）卫星图像和机载伽玛能谱数据，利用基于gis的模糊逻辑模型，对摩洛哥中部反阿特拉斯带Sirwa地块南部热液蚀变组合的空间分布和地带性进行了研究。该区具有复杂的构造-岩浆史，并伴有大量的热液金、银、铜矿床，但仍未得到充分勘探。利用波段比（Band Ratio， BR）和Crosta技术对ASTER遥感数据进行分析，识别出叶基、胶基、丙基和氧化铁蚀变带。其他伽马能谱数据，包括铀（eU）、钍（eTh）、钾K（%）和钾(%)/eTh比值，被用来确定与热液活动密切相关的钾蚀变带。采用基于gis的模糊逻辑方法，将aster衍生热液蚀变层与agrs衍生钾蚀变层整合，生成热液蚀变远景图，突出高成矿潜力区。在Ouarzazate群火山-沉积露头与泛非花岗闪长杂岩及其上覆古生代盖层的岩性界线上圈定了6个热液成矿远景带。这些区域与先前存在的东西向、ENE-WSW和NE-SW断裂系统相关的高构造复杂性区域相吻合。后者发育于泛非造山运动的后碰撞阶段，是碱性至钙碱性岩浆相关热液的通道，形成广泛的蚀变晕。利用（ROC-AUC）分析对热液蚀变远景图进行了统计确认，并辅以严格的现场验证。这证实了所采用的热液区圈定方法的高精度，从而优化了Sirwa地块内后续的矿产勘探策略。
{"title":"Integration of ASTER remote sensing and gamma-ray spectrometry for mapping hydrothermal alteration in the Sirwa Massif, central Anti-Atlas, Morocco: A guide for mining exploration","authors":"Mohammed Jalal Tazi , Mohammed Ouchchen , Driss El Azzab , Driss Benyahia , Abdelhamid Bajadi , Hafsa Boufakri , Bouchra Dadi","doi":"10.1016/j.jafrearsci.2026.106019","DOIUrl":"10.1016/j.jafrearsci.2026.106019","url":null,"abstract":"<div><div>This study adopts a multidisciplinary approach integrating ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) satellite imagery and airborne gamma-ray spectrometry data using a GIS-based fuzzy logic model to delineate the spatial distribution and zonal patterns of hydrothermal alteration assemblages in the southern part of the Sirwa Massif in the central Anti-Atlas belt (Morocco). This area records a complex tectono-magmatic history associated with significant hydrothermal Au–Ag–Cu deposits, yet remains largely underexplored. ASTER remote sensing data were analyzed using Band Ratio (BR) and Crosta techniques, enabling the identification of phyllic, argillic, propylitic and iron oxides alteration zones. Additional gamma spectrometry data, including uranium (eU), thorium (eTh), potassium K (%) and the K (%)/eTh ratio, were used to define zones of potassic alteration closely associated with hydrothermal activity.</div><div>A GIS-based fuzzy logic approach was implemented to integrate ASTER-derived hydrothermal alterations and AGRS-based potassic alteration layers to generate a hydrothermal alteration prospectivity map, highlighting zones of high mineralization potential. Six highly prospective zones for hydrothermal mineralization were delineated, located at lithological boundaries between Ouarzazate Group volcano-sedimentary outcrops and Pan-African granodioritic complexes, and the overlying Paleozoic cover. These zones coincide with areas of high structural complexity associated with pre-existing E–W, ENE–WSW, and NE–SW fault systems. The latter, developed during the post-collisional stage of the Pan-African orogeny, which acted as conduits for hydrothermal fluids associated with alkaline to calc-alkaline magmas, forming extensive alteration halos.</div><div>The hydrothermal alteration prospectivity map was statistically confirmed using the (ROC-AUC) analysis, complemented by rigorous field validation. This confirms the high accuracy of the adopted mapping approach for delineating hydrothermal zones, consequently optimizing subsequent mineral exploration strategies within the Sirwa Massif.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"236 ","pages":"Article 106019"},"PeriodicalIF":2.2,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034980","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 : 2026-01-14DOI: 10.1016/j.jafrearsci.2026.106020
Zixuan Liu, Hong Zhang, Yongjie Hu
The Lower Cretaceous Alamein Formation in the northern Western Desert, Egypt, host significant petroleum reserves. Petrographic observation, porosity-permeability analysis and logging-seismic interpretation were performed here using core samples, well log data, and 3D seismic datasets to discuss the sedimentary facies and reservoir evolutions of the Alamein Formation. Sedimentary facies of the Alamein Formation in the Alamein Basin consists of inner ramp, shallow ramp, and outer ramp–deep basin facies. Compared with other carbonate facies, dolo-grainstone, dolo-floatstone, and dolo-rudstone display superior reservoir quality. Most host dolostone experience near-surface evaporation-reflux dolomitization, indicated by three types of anhydrites. Zebra dolostone and saddle dolomite are typical precipitates of deep-burial hydrothermal dolomitization. Reservoir space consists of stratiform dissolution pores, vugs, moldic pores, inter- and intra-crystalline dissolution pores, and fractures. High-energy depositional environment is the foundation of the potential reservoirs, and thus dolo-grainstone, dolo-floatstone, and dolo-rudstone yield higher porosity and permeability than other types of lithofacies. Marine regression-transgression results in better reservoir performance in the top intervals compared to dolostone at the base section within meter-scale cycles. Reservoir performance is further enhanced by meteoric leaching, evaporation and reflux dolomitization through early burial stages. During the intermediate burial regimes, hydrothermal alteration and thermochemical sulfate reduction generate secondary pores, including (i) intra-crystalline dissolution pores within coarse-crystalline dolomite and saddle dolomite, and (ii) vugs developing along stylolites. Moreover, tectonic activities contribute to the development of fracture networks, which significantly enhance fluid flow. Different types of sedimentary facies, complex diagenetic history and tectonic activities result in the different reservoir performance of the Alamein Formation and other carbonate formations in the northern Western Desert. These findings underscore the hydrocarbon potential of reefal and shoal dolostone reservoirs in Lower Cretaceous carbonates worldwide, providing important implications for hydrocarbon exploration.
{"title":"Sedimentary facies and reservoir evolution of the Cretaceous Alamein Formation, Alamein Basin, northern Western Desert, Egypt","authors":"Zixuan Liu, Hong Zhang, Yongjie Hu","doi":"10.1016/j.jafrearsci.2026.106020","DOIUrl":"10.1016/j.jafrearsci.2026.106020","url":null,"abstract":"<div><div>The Lower Cretaceous Alamein Formation in the northern Western Desert, Egypt, host significant petroleum reserves. Petrographic observation, porosity-permeability analysis and logging-seismic interpretation were performed here using core samples, well log data, and 3D seismic datasets to discuss the sedimentary facies and reservoir evolutions of the Alamein Formation. Sedimentary facies of the Alamein Formation in the Alamein Basin consists of inner ramp, shallow ramp, and outer ramp–deep basin facies. Compared with other carbonate facies, dolo-grainstone, dolo-floatstone, and dolo-rudstone display superior reservoir quality. Most host dolostone experience near-surface evaporation-reflux dolomitization, indicated by three types of anhydrites. Zebra dolostone and saddle dolomite are typical precipitates of deep-burial hydrothermal dolomitization. Reservoir space consists of stratiform dissolution pores, vugs, moldic pores, inter- and intra-crystalline dissolution pores, and fractures. High-energy depositional environment is the foundation of the potential reservoirs, and thus dolo-grainstone, dolo-floatstone, and dolo-rudstone yield higher porosity and permeability than other types of lithofacies. Marine regression-transgression results in better reservoir performance in the top intervals compared to dolostone at the base section within meter-scale cycles. Reservoir performance is further enhanced by meteoric leaching, evaporation and reflux dolomitization through early burial stages. During the intermediate burial regimes, hydrothermal alteration and thermochemical sulfate reduction generate secondary pores, including (i) intra-crystalline dissolution pores within coarse-crystalline dolomite and saddle dolomite, and (ii) vugs developing along stylolites. Moreover, tectonic activities contribute to the development of fracture networks, which significantly enhance fluid flow. Different types of sedimentary facies, complex diagenetic history and tectonic activities result in the different reservoir performance of the Alamein Formation and other carbonate formations in the northern Western Desert. These findings underscore the hydrocarbon potential of reefal and shoal dolostone reservoirs in Lower Cretaceous carbonates worldwide, providing important implications for hydrocarbon exploration.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"236 ","pages":"Article 106020"},"PeriodicalIF":2.2,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034964","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 : 2026-01-12DOI: 10.1016/j.jafrearsci.2026.106004
Brian G. Jones , Kerrie L. Bann
A moderately deformed succession of the Ordovician Peninsula Formation in the syntaxis zone of the Cape Fold Belt is well exposed at Hermanus, some 120 km east-southeast of Cape Town in South Africa. The oldest deposits recognised at Hermanus represent a regressive shallow-marine prodelta succession of storm-redeposited sandstone, silty bioturbated sandstone and siltstone. Some clean sandstone beds show abundant fugichnia and other trace fossils characteristic of the Skolithos Ichnofacies. The presence of hummocky cross-stratification and evidence of longshore current activity indicates water depths were probably just below storm wave-base. Between storms, flocculation of organic-rich mud from buoyant hypopycnal plumes associated with river floods suggests a prodelta environment in front of the prograding Peninsula Formation fluvial succession. A ravinement surface, with at least 4 m erosional relief, between the marine and fluvial successions may have been induced by a drop in relative sea-level. The overlying fluvial succession shows sedimentary features typical of a bed-load dominated fluvial system with planar and trough cross-stratified sandstone and scattered pebbles. These form upward-fining cosets (4–8 m thick) of predominantly downstream-accreting macroforms that indicate deposition from high-energy channelised flows with up to 90° palaeocurrent variability between cosets. They represent a broad, braided to low-sinuosity, fluvial channel system that drained across a low slope towards the south-southeast. Based on correlation with the ‘Rooiels marker’ north of Hangklip, the shallow-marine and overlying fluvial successions at Hermanus may represent part of the lower Peninsula Formation, equivalent to part of the ‘Leeukop member’ in the Cape Peninsula.
{"title":"Fluvial‒marine interactions and ichnofacies in the Ordovician Peninsula Formation, Hermanus, South Africa","authors":"Brian G. Jones , Kerrie L. Bann","doi":"10.1016/j.jafrearsci.2026.106004","DOIUrl":"10.1016/j.jafrearsci.2026.106004","url":null,"abstract":"<div><div>A moderately deformed succession of the Ordovician Peninsula Formation in the syntaxis zone of the Cape Fold Belt is well exposed at Hermanus, some 120 km east-southeast of Cape Town in South Africa. The oldest deposits recognised at Hermanus represent a regressive shallow-marine prodelta succession of storm-redeposited sandstone, silty bioturbated sandstone and siltstone. Some clean sandstone beds show abundant fugichnia and other trace fossils characteristic of the <em>Skolithos</em> Ichnofacies. The presence of hummocky cross-stratification and evidence of longshore current activity indicates water depths were probably just below storm wave-base. Between storms, flocculation of organic-rich mud from buoyant hypopycnal plumes associated with river floods suggests a prodelta environment in front of the prograding Peninsula Formation fluvial succession. A ravinement surface, with at least 4 m erosional relief, between the marine and fluvial successions may have been induced by a drop in relative sea-level. The overlying fluvial succession shows sedimentary features typical of a bed-load dominated fluvial system with planar and trough cross-stratified sandstone and scattered pebbles. These form upward-fining cosets (4–8 m thick) of predominantly downstream-accreting macroforms that indicate deposition from high-energy channelised flows with up to 90° palaeocurrent variability between cosets. They represent a broad, braided to low-sinuosity, fluvial channel system that drained across a low slope towards the south-southeast. Based on correlation with the ‘Rooiels marker’ north of Hangklip, the shallow-marine and overlying fluvial successions at Hermanus may represent part of the lower Peninsula Formation, equivalent to part of the ‘Leeukop member’ in the Cape Peninsula.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"236 ","pages":"Article 106004"},"PeriodicalIF":2.2,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145979504","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 : 2026-01-07DOI: 10.1016/j.jafrearsci.2026.106014
Andreas Scharf , Frank Mattern , Abdul Razak Al-Sayigh , Laura Galluccio , Gianluca Frijia
We studied the rarely exposed Oligocene Ma'ahm Beds at Quriyat for their lithostratigraphy, microfacies and depositional environment. In addition, we intend to contribute to the general understanding of coral patch reefs. Our bed-scale logs include thin-section analyses of standard microfacies (SMF) types allowing direct comparisons with those of the Ma'ahm Beds 80 km to the NW in the Al-Khod area, the so far best-described outcrop area of Oligocene age in Oman. The Ma'ahm Beds at Quriyat are ∼50 m thick, which lies within the thickness range of the Ma'ahm Beds at Al-Khod. Coral patch reef complexes occur in both places. The one at Quriyat contains reefs of different symmetries. The SMF types of the massively bedded reefs and the associated bioclastic limestone beds represent facies zone 7 as at Al-Khod, indicating a depositional environment within the photic zone, above fair-weather wave base, in an open lagoon. In both regions, the lagoons were most likely protected by coral barrier reefs with intervening gaps. The patch reefs at Quriyat were abandoned, and new ones formed in oceanward direction to keep up with a dropping eustatic sea-level. At the flanks of the largest patch reef at Quriyat, bioclastic limestones with reef debris display onlap geometries. Only the limestones at Quriyat are associated with silty marl and calcareous, marly sandstone, which accumulated in a foreshore environment, either as longshore drift, or cays or combination/alternation thereof. These siliciclastic deposits are likely more voluminous than the limestones of the Ma'ahm Beds in the eastern part of the Arabian Plate, which should be considered when constructing paleo-facies maps. This abundant fine-grained marly material implies that Oligocene aquiclude horizons exist. We suggest that coral patch reefs should measure at least 5 m in diameter to fulfill typical ecological reef functions.
{"title":"The Oligocene “Ma'ahm Beds” of NE Oman (eastern Arabia): Microfacies and lithostratigraphy of a mixed carbonate system with coral patch reefs","authors":"Andreas Scharf , Frank Mattern , Abdul Razak Al-Sayigh , Laura Galluccio , Gianluca Frijia","doi":"10.1016/j.jafrearsci.2026.106014","DOIUrl":"10.1016/j.jafrearsci.2026.106014","url":null,"abstract":"<div><div>We studied the rarely exposed Oligocene Ma'ahm Beds at Quriyat for their lithostratigraphy, microfacies and depositional environment. In addition, we intend to contribute to the general understanding of coral patch reefs. Our bed-scale logs include thin-section analyses of standard microfacies (SMF) types allowing direct comparisons with those of the Ma'ahm Beds 80 km to the NW in the Al-Khod area, the so far best-described outcrop area of Oligocene age in Oman. The Ma'ahm Beds at Quriyat are ∼50 m thick, which lies within the thickness range of the Ma'ahm Beds at Al-Khod. Coral patch reef complexes occur in both places. The one at Quriyat contains reefs of different symmetries. The SMF types of the massively bedded reefs and the associated bioclastic limestone beds represent facies zone 7 as at Al-Khod, indicating a depositional environment within the photic zone, above fair-weather wave base, in an open lagoon. In both regions, the lagoons were most likely protected by coral barrier reefs with intervening gaps. The patch reefs at Quriyat were abandoned, and new ones formed in oceanward direction to keep up with a dropping eustatic sea-level. At the flanks of the largest patch reef at Quriyat, bioclastic limestones with reef debris display onlap geometries. Only the limestones at Quriyat are associated with silty marl and calcareous, marly sandstone, which accumulated in a foreshore environment, either as longshore drift, or cays or combination/alternation thereof. These siliciclastic deposits are likely more voluminous than the limestones of the Ma'ahm Beds in the eastern part of the Arabian Plate, which should be considered when constructing paleo-facies maps. This abundant fine-grained marly material implies that Oligocene aquiclude horizons exist. We suggest that coral patch reefs should measure at least 5 m in diameter to fulfill typical ecological reef functions.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"236 ","pages":"Article 106014"},"PeriodicalIF":2.2,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146034958","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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