Journal of African Earth Sciences最新文献

{"title":"Bartonian coral biostromes in a storm-dominated ramp setting of the El-Ramliya-Akheider block: sedimentology, sequence stratigraphy and regional paleogeographic insights, Cairo-Sukhna region, Egypt","authors":"George Henry,&nbsp;Mounir El-Azabi,&nbsp;Walid Kassab","doi":"10.1016/j.jafrearsci.2025.105542","DOIUrl":"10.1016/j.jafrearsci.2025.105542","url":null,"abstract":"<div><div>Scleractinian coral reefs are pivotal carbonate producers in the late Cenozoic era, they are useful in understanding the early Paleogene thermal events. Despite challenges in studying the Eocene due to scarce data and poor outcrop quality, the El-Ramliya-Akheider block has provided critical insights into its Bartonian carbonate succession. The succession is characterized by extensive coral carpets (biostromes) and a wide range of sedimentary structures, including large-scale channels. To investigate the facies organization and sedimentary pattern of the succession, we integrated sedimentological (outcrop studies, facies analysis) and paleontological approaches. <em>Acropora</em> coral carpets, which thrived in mid-ramp settings, have been altered by sedimentological changes caused by storm currents. The inner ramp environment with bioshoals of larger miliolids and seagrass meadows shows a rhythmic intercalation pattern with biostromes. This intercalation, along with the formation of channels filled with carbonate fragments, is influenced by the dynamic interplay of storm-driven currents and return currents. The presence of coral fragments (coralline float-/rudstone) as para-to allochthonous accumulations suggests that coral colonies initially grew as carpets in a calm, mid-ramp environment. These fragments were subsequently transported and redeposited during storm currents. The return currents generated channel deposits (abraded foraminiferal pack-/grainstone) characterized by large-scale cross-beddings. These channels, filled with inner-ramp foraminiferal pack-/grainstone, were scoured into the mid-ramp coral biostromes, highlighting the significant role of storm-related processes in sediment transport and channel formation. Notably, coral biostromes in a stable, euphotic mid-ramp setting mark the earliest recovery during the Bartonian cooling period after the Middle Eocene Climatic Optimum event (MECO). The dominance of Bartonian lagoonal marine conditions in the Cairo-Sukhna region is attributed to global transgression, shallow depositional basin, and restricted water circulation caused by uplifted barriers. Overall, this study enhances understanding of the Eocene paleoenvironment and the capability of coral ecosystems.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105542"},"PeriodicalIF":2.2,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Provenance and source area weathering of sandstones from the Tarkwaian Group at the northeastern extent of the Paleoproterozoic Ashanti Belt, Ghana: Constraints from petrography and geochemistry","authors":"Victor Sedziafa ,&nbsp;Ying Song ,&nbsp;Emmanuel Daanoba Sunkari ,&nbsp;Daniel Kwayisi ,&nbsp;Chris Y. Anani ,&nbsp;Daniel K. Asiedu","doi":"10.1016/j.jafrearsci.2025.105536","DOIUrl":"10.1016/j.jafrearsci.2025.105536","url":null,"abstract":"<div><div>An integrated geochemical and petrographic study was conducted on the Paleoproterozoic sandstones of the Tarkwaian Group exposed at the northeastern extent of the Ashanti Belt, Ghana. Recognizing the economic importance of the Tarkwaian Group, particularly owing to its extensive gold deposits, the primary objective was to investigate the provenance, tectonic setting, and crustal evolution of the Tarkwaian Group. The dominant quartz (polycrystalline and monocrystalline), together with minor muscovite, feldspar, hematite, and lithic fragments, characterize the sandstones and thus, the sandstones are classified as sublitharenite, and lithicsubarkose. Based on mineralogical composition and major element content, the sandstones can be classified as litharenite, sublitharenite, and minor greywacke. The high values of SiO₂/Al₂O₃ (average: 12.74), relatively moderate values of K₂O/NaO₂ (average: 1.42), and high quartz content (average: 88%) suggest that the sediments are compositionally sub-mature to mature. The sandstones likely underwent low to moderate levels of sedimentary sorting and recycling owing to angular to sub-rounded grains and moderate Zr/Sc and Th/Sc values. The high Chemical Index of Alteration (CIA) signature (average: 76.79 wt%), Plagioclase Index of Alteration (PIA) values (average: 90.13 wt%), and Index of Compositional Variability (ICV) (average: 0.61 wt%) suggest moderate to intense chemical weathering within the region of origin. Overall, the mineralogical and geochemical features of the sandstones, such as a high proportion of quartz and feldspar, and elevated concentrations of elements such as Zr, Sc and Th, and moderate to high ratios of Al₂O₃/TiO₂ and La/Sc indicate that they were likely sourced from felsic to intermediate igneous rocks and deposited in an active continental margin such as magmatic arc setting.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105536"},"PeriodicalIF":2.2,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"K-Pg transition in neritic limestones: Deciphering the first bio/chemo-stratigraphic records and tectono-sedimentary evolution, eastern Neotethys (NE Türkiye)","authors":"Fatih Köroğlu ,&nbsp;Bilal Sarı ,&nbsp;Raif Kandemir ,&nbsp;İsmail Ömer Yılmaz ,&nbsp;Sacit Özer","doi":"10.1016/j.jafrearsci.2025.105540","DOIUrl":"10.1016/j.jafrearsci.2025.105540","url":null,"abstract":"<div><div>Interestingly, the K-Pg transition from the Cretaceous to the Paleogene is the closest to our time and, from today's perspective, the most dramatic extinction that has ever occurred on Earth. Using different methods and lithologies, K-Pg transition records have been identified in different areas around the Earth. In this study, the neritic carbonate successions in the arc sedimentary cover of eastern Neotethys (Eastern Sakarya Zone, NE Türkiye) were studied using high-resolution bio-chemo/stratigraphy and sedimentary geology methods. The Ziyarettepe Formation, which is the subject of this study, is characterized by its neritic and hemipelagic sedimentary features. Notwithstanding, the clastic and irregular distribution of macro- and microfossils in the Ziyarettepe Formation was realized in parallel with sea level changes, regional tectonism, and global event effects. As a result of these events, the shell structure of the fossils shows the processes of transport from shallow habitats, transport to the platform-platform edge-slope edge, and deposition under these conditions. On the other hand, the neritic and hemipelagic limestones of the Ziyarettepe Formation allow the study of benthic and planktonic foraminifera biostratigraphy, as well as other fossil groups in the stratigraphic interval around the K-Pg transition. According to the results, the stratigraphic age of the Ziyarettepe Formation is given as late Campanian-Thanetian, both chemostratigraphically and biostratigraphically (mainly foraminifera). The Ziyarettepe Formation (Tosunlu Tunnel) stratigraphic section was examined for stable δ¹³C and δ¹⁸O isotopes, rare earth elements, and whole rock carbonate geochemistry records within the Ziyarettepe Formation. Geochemical trends across the K-Pg transition are distinguished by anomalies resulting from many impact signals, including mainly the Deccan Traps and the Chicxulub Impact. The geochemical profile of the K-Pg transition was influenced by paleoenvironmental impacts, as in this example of a neritic succession in the eastern Neotethys. Together with multi-chemostratigraphic analyses, it could be shown for the first time that the K-Pg transition was also recorded in this basin. According to the tectono-sedimentary evolution in the region, these neritic successions were deposited in a back-arc environment during the northward subduction of the northern branch of Neotethys.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105540"},"PeriodicalIF":2.2,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143100091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"No evidence for a giant, late-surviving Onchopristis: Comment on Capasso et al. (2024)","authors":"Tyler Greenfield","doi":"10.1016/j.jafrearsci.2025.105541","DOIUrl":"10.1016/j.jafrearsci.2025.105541","url":null,"abstract":"<div><div>Capasso et al. (2024) reported an exceptionally large rostrum of the sawskate <em>Onchopristis</em> sp. from the Maastrichtian Dakhla Formation of Egypt. They also described four isolated lateral rostral denticles which were referred to the same taxon. However, here it is demonstrated that neither can be assigned to <em>Onchopristis</em>; the rostrum is Sclerorhynchoidei indet. and the rostral denticles are <em>Sclerorhynchus</em> cf. <em>leptodon</em>. Additionally, the status of the actual longest <em>Onchopristis</em> rostrum is clarified.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105541"},"PeriodicalIF":2.2,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143152733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Palaeoenvironmental and palaeoclimatic characterization of Upper Jurassic sedimentary sequences with dinosaur footprints of the M'Goun Geopark (High Atlas, Morocco)","authors":"Matías Reolid ,&nbsp;Jesús Reolid ,&nbsp;Elisa Laita ,&nbsp;Mohamed Boutakiout ,&nbsp;Moussa Masrour ,&nbsp;Félix Pérez-Lorente","doi":"10.1016/j.jafrearsci.2025.105539","DOIUrl":"10.1016/j.jafrearsci.2025.105539","url":null,"abstract":"<div><div>The Iouaridène Formation (Upper Jurassic, High Atlas, Morocco) is a relevant area for the study of dinosaur footprints, but up to now little is known about the palaeoenvironmental conditions at the time of its formation. This work consists of a sedimentological, geochemical, and mineralogical study of part of the sedimentary succession of the Iouaridène Formation, especially Units B and C. The cyclic sedimentation pattern in Unit B, characterized by alternating soft claystones and siltstone layers and hard sandstone layers with ripples and mudcracks, reflects a dynamic environment shaped by recurring flooding and emersion events. This cyclicity is marked by fluctuations in quartz, clay and analcime content, leading to sedimentary sequences capped by silcretes, which indicate sedimentation hiatuses. The formation of mudcracks and the preservation of dinosaur footprints further highlight the depositional conditions. Mineralogical and geochemical analyses reveal an upwards trend to increasingly arid conditions during the deposition of Unit B, with an increase in quartz and decrease in kaolinite, as well as palaeoclimatic geochemical proxies. The presence of analcime supports a lacustrine environment under arid or semi-arid conditions and fluctuations in the alkalinity of pore waters. The CIA and CIW values reflect moderate to weak weathering congruent with the arid conditions indicated by other proxies. Decreasing C-values towards the top of the section points to environmental changes from semi-arid toward more arid conditions. Other indexes of salinity and aridity (Sr/Ba and Zr/Rb ratios), also support the trend towards increasing aridity in Unit B. In contrast to this, Unit C indicates more humid and deeper conditions, marked by the record of cross-bedding, lacustrine ostracods and fish bones, and the absence of mudcracks, silcretes, and dinosaur footprints. This variability underscores the dynamic climatic and environmental history of the Iouaridène Formation, reflecting the final phase of the Atlasic Basin fill during the Late Jurassic. This is the first work on the palaeoclimatic conditions of the Iouaridène Formation and the first study that integrates sedimentology, geochemistry and mineralogy of this formation. These findings enhance the understanding of the geological evolution of the Jurassic of the M'Goun Geopark and set the background for future research on the area to explore the interactions between climatic conditions, sedimentary processes, and biological activity in Jurassic lacustrine environments.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105539"},"PeriodicalIF":2.2,"publicationDate":"2025-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153762","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"3D inversion of magnetic data to delineate subsurface structures controlling groundwater recharge and discharge at Wadi Al-Assiuty, Egypt","authors":"Tamer Farag ,&nbsp;Ali Mostafa ,&nbsp;Ahmed A. El Husseiny","doi":"10.1016/j.jafrearsci.2024.105527","DOIUrl":"10.1016/j.jafrearsci.2024.105527","url":null,"abstract":"<div><div>This study aims to enhance our understanding of groundwater accumulations in the Wadi Al-Assiuty region, with an emphasis on supporting the development of new urban settlements and national industrial initiatives. To achieve this objective, airborne magnetic data were processed and analyzed, enabling the delineating the subsurface structures and their impact on groundwater flow patterns. The research also aimed to assess the aquifer’s thickness within the area. Satellite-based digital elevation data were interpreted to map the primary drainage patterns, highlighting watersheds and basins where surface water tends to accumulate. Additionally, aerial magnetic data were employed to detect the sedimentary cover and evaluate the thickness distribution of the Nubian aquifer, ultimately identifying the most promising aquifer with the highest thickness and greatest potential groundwater reserves.</div><div>The magnetic data analysis employed three primary techniques. First, source edge detection was applied to identify sources with varying magnetic intensity anomalies. Second, the depth of the basement surface was calculated, corresponding to the base of the Nubian aquifer in the study area. Third, 3D magnetic data inversion was used to create a three-dimensional model of the basement rocks, aiding in the identification of optimal locations for drilling deep groundwater wells. The overarching goal is to locate areas with strong groundwater exploration potential, which is critical for Egypt’s sustainable development. To ensure accuracy, the results are constrained by incorporating previous geological, geophysical, and drilled wells data.</div><div>Wadi Al-Assiuty, a major Egyptian wadi, exhibits a rectangular drainage pattern (angular streams) interspersed with sub-dendritic to subparallel sub-basins, which reflects the structural control of the stream network. The resulting maps, generated through linear transformations and derivative-based techniques, reveal that NW-SE and E-W fault systems play a significant role in controlling the recharge of the aquifers from surface run-off water, the deep Nubian sandstone aquifer, and the Nile River. Notably, the depth to the basement varies widely, ranging from 200 m to 4800 m below the surface. This study aligns with Egypt’s 2030 sustainable development plan, particularly focusing on promising desert areas that could be transformed into agricultural development zones.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105527"},"PeriodicalIF":2.2,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153807","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Erosion and shoreline retreat indicators in the Rabat-Salé littoral and their impact on coastal planning","authors":"El Miloudiya Naji ,&nbsp;M'hamed Aberkan ,&nbsp;Abderrahim Saadane ,&nbsp;M'hamed Nmiss","doi":"10.1016/j.jafrearsci.2025.105534","DOIUrl":"10.1016/j.jafrearsci.2025.105534","url":null,"abstract":"<div><div>In-depth field investigations have allowed us to assess the coastal sector of Rabat-Salé by describing various forms of erosion, the condition of historical monuments located by the ocean, and the ineffectiveness of hard solutions implemented against erosion. This emphasizes the primary anthropogenic causes of the degradation of the studied coastal environments, including former calcarenite quarries and old sewage drainage canals. The interaction of these anthropogenic factors with natural processes has led to a significant retreat of the coastal cliff, which is clearly visible on-site, posing a threat to certain constructions, notably historical monuments of great cultural value to the Kingdom. To quantify the retreat in the study area between 1993 and 2022, we utilized the Digital Shoreline Analysis System (DSAS), version 5 integrated into ArcGIS 10.4, which revealed relatively high rates with an average rate of 1.2 m per year. We also adopted another method by using threatened historical monuments to calculate average retreat rates of the shoreline using two old plans, one dating back to 1935 (1/1000 scale) for Fort Rottembourg and another from 1922 (1/2000 scale) containing two historical monuments: Borj Sirat and Borj Eddar. The calculations yielded average rates that align with those obtained through DSAS. Despite the risks associated with erosion in the study area, a regulatory framework for the protection and enhancement of the coastal environment (Law 81-12) has been in place since 2015, prohibiting any construction within 100 m of the shoreline. This distance can be extended in cases of significant threats, such as severe erosive activity. However, some projects are still located in high-risk erosion areas, where erosion may be further exacerbated by karstic phenomena affecting the substrate. The results of this study align well with the provisions of Law 81-12 (Article 12).</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105534"},"PeriodicalIF":2.2,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"c.2.02 Ga Ar40–Ar39 muscovite age from the Gulushabe fold structure, Motloutse Complex, near SW margin of Zimbabwe Craton: Imprint of Limpopo Complex or Magondi Belt tectonics?","authors":"H.M. Rajesh ,&nbsp;G.A. Belyanin ,&nbsp;T. Mokatse ,&nbsp;D.T. Mfa ,&nbsp;C. Vorster ,&nbsp;Y. Wan","doi":"10.1016/j.jafrearsci.2025.105535","DOIUrl":"10.1016/j.jafrearsci.2025.105535","url":null,"abstract":"<div><div>Meta-supracrustal rocks in medium-to high-grade terranes along Archean craton margins are, in the common case, more deformed than similar rocks within the craton. Multiple deformation episodes are possible and could be related to different stages of a single tectonic event or disparate ones. Geochronologic characterization of fabric forming minerals helps to place an individual deformational episode with respect to spatially associated tectonic events along the craton margin. This study focuses on the Shashe Group of metasedimentary rocks that define the large-scale Gulushabe fold structure in northeastern Motloutse Complex, Botswana, near its contact with the southwestern margin of the Zimbabwe Craton. Available detrital zircon geochronologic data indicate a depositional age of c.2.66–2.51 Ga for the protolith of these continental margin-type metasedimentary rocks. The upright NNE-trending Gulushabe fold structure is at variance with the regional northeasterly vergent folds from the northern–central Motloutse Complex and related to the Neoarchean (&lt;2.65 Ga) NE-directed thrusting of the medium-grade terrane over the craton margin. ⁴⁰Ar/³⁹Ar geochronology of muscovite in quartz mica schist from the NNE-trending refolded northwestern minor fold closure of the Gulushabe fold structure yielded a plateau (96% of ³⁹Ar) age of 2018 ± 11 Ma. The significance of the age is addressed in terms of Paleoproterozoic tectonics in the bounding terranes: Limpopo Complex to the south and Magondi Belt to the north. In the process, the Archean antiquity and extent of the Motloutse Complex, and the provenance of Shashe Group rocks are clarified. The results highlight the importance of delineating overprint events to better understand the tectonics along the contact of Archean craton and medium-to high-grade terranes.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105535"},"PeriodicalIF":2.2,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143152734","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrogeochemical and hydrogeological baseline study following the mining of asbestos at the Havelock Mine, Bulembu, eSwatini","authors":"Christian Wolkersdorfer ,&nbsp;Kagiso S. More ,&nbsp;Elke Mugova ,&nbsp;Nokuthula Nchabeleng ,&nbsp;Anna Johanna Sotiralis","doi":"10.1016/j.jafrearsci.2024.105533","DOIUrl":"10.1016/j.jafrearsci.2024.105533","url":null,"abstract":"<div><div>This study examined the hydrogeological and hydrochemical conditions around Bulembu, eSwatini, two decades post-closure of the Havelock asbestos mine. On-site parameters and water samples underwent chemical and stable isotope analysis, supplemented by flow measurements and tracer tests with NaCl and uranine. Multivariate statistical analysis and PHREEQC modelling identified three water groups: i) low mineralised surface water (32 mg/L TDS), ii) mining-influenced water from the Havelock mine pool (212 mg/L TDS), and iii) tailings seepage water (411 mg/L TDS). All are earth alkaline, hydrogen carbonate-dominant, dominated by Mg and hydrogen carbonate ions. Surface water complies with WHO standards, except for elevated As in the mine pool and Cr in waste rock seepage. Chemical and tracer test results indicate a well-mixed, low-residence-time mine pool. Both the Tutusi river catchment and the upper Nkomazana catchment as well as water courses downstream of the abandoned mine exhibit pristine water quality. The authors propose inclusion of the area in a trans-boundary national park with the Barbeton Makhonjwa Mountains UNESCO World Heritage Site. They recommend amelioration of tailings, not remining, to safeguard the environment and local population from asbestos exposure.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"224 ","pages":"Article 105533"},"PeriodicalIF":2.2,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143171383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatiotemporal variability of the Cenomanian macrobenthic fauna in Northeast Algeria: Species versus community level variations","authors":"Sihem Salmi-Laouar ,&nbsp;Samira Mendir ,&nbsp;Riadh Aouissi ,&nbsp;Gamal M.EL. Qot ,&nbsp;Rachel Kruft-Welton ,&nbsp;Mohamed S. Ahmed ,&nbsp;Ahmed A. Abdelhady","doi":"10.1016/j.jafrearsci.2024.105526","DOIUrl":"10.1016/j.jafrearsci.2024.105526","url":null,"abstract":"<div><div>Environmental changes can impact benthic fauna at multiple levels. To better understand these changes at both the species and community levels, the Cenomanian macrofossils from two regions in northeastern Algeria, Tébessa and Batna, were analyzed. The results revealed that while changes at the species level (morphology) and community level (ecology) followed similar patterns, they were not identical. Non-metric multidimensional scaling (NMDS) and permutational multivariate analysis of variance (PERMANOVA) tests of the morphological variations of 114 complete shells of the suspension-feeding trigonoid bivalve <em>Scabrotrigonia scabra</em> (Lamarck, 1819) showed significant differences (P &lt; 0.001) between the two regions. Two distinct echophenotypes were identified, with the first dominating in Tébessa and the second in Batna. The Batna echophenotype is characterized by smaller, flattened shells with numerous ribs, an adaptive strategy for stabilizing in soft substrates. Additionally, the smaller shells in Batna were linked to the oligotrophic conditions of the outer ramp setting, in contrast to the deeper outer ramp setting in Tébessa (mesotrophic). To further investigate environmental variations, the macrofaunal associations of the Cenomanian were examined. The NPMANOVA test indicated significant differences in faunal associations between the regions, with Batna exhibiting less diversity and a higher proportion of deposit-feeders, suggesting soft substrate conditions. In contrast, no significant differences were found among the faunal associations of the different Cenomanian substages, though ecological attributes showed minor, gradual changes. The early and middle Cenomanian fauna were dominated by epifaunal byssate taxa, while deposit-feeder taxa increased in the late Cenomanian, likely due to the global sea-level rise toward the end of the period. Overall, the paleogeographic setting (middle versus outer ramp) appears to have played a major role in shaping the ecological and morphological variations between Tébessa and Batna.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105526"},"PeriodicalIF":2.2,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143153352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}