Journal of African Earth Sciences最新文献

{"title":"Hybrid turbidite-contourite system on the upper-slope continental margin of the offshore southern Tanzania","authors":"Emily Barnabas Kiswaka ,&nbsp;Dicky Harishidayat ,&nbsp;Oras Joseph Mkinga ,&nbsp;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}

{"title":"Lithogeochemistry and origin of the komatiites from Mundonguara mine in the Manica greenstone belt, Mozambique","authors":"L.N. Mendes ,&nbsp;O. Martinsson ,&nbsp;D.L. Jamal ,&nbsp;A.M. Azim Zadeh ,&nbsp;C. Wanhainen","doi":"10.1016/j.jafrearsci.2024.105494","DOIUrl":"10.1016/j.jafrearsci.2024.105494","url":null,"abstract":"<div><div>The Manica greenstones belt in western Mozambique constitutes the eastern extension of the Odzi-Mutare greenstone belt in Zimbabwe that is one of several Archean greenstone belts within the Zimbabwe Craton. These greenstones are in Mozambique constituting the Manica Group and are subdivided in two main lithostratigraphic units: The Macequece Formation and the Vengo Formation. The former is hosting the Mundonguara Cu-Au mine and is dominated by volcanic rocks, while the younger Vengo Formation is consisting of epiclastic sedimentary rocks. This paper considers the character and origin of the ultramafic, mafic, and felsic rocks within the Macequece Formation. They include peridotitic komatiite, pyroxenitic komatiite, komatiitic cumulate rocks, gabbroic dykes, rhyolitic units, and a granitic rock intruding the komatiites. Samples of these rocks have been collected from outcrops and drill cores and are investigated through petrographic studies of thin sections and whole rock geochemistry including major and trace elements to interpret the geological environment and tectonic setting.</div><div>The supracrustal rocks are metamorphosed to greenschist facies and the komatiites consists of varying proportions of serpentine, talc, chlorite, and amphibole. Primary features are partly preserved, with spinifex, vesicular, and cumulate textures. The komatiites are variously affected by carbonate alteration and deformation and the rhyolitic rocks are mostly strongly silicified. The komatiites are of the Al-undepleted type, with a MgO content of 25–45 wt %, while the mafic intrusions are tholeiitic in character, varying from gabbronorite to diorite in composition. Trace element diagrams used for interpretation of tectonic setting gives ambiguous results that could be an effect of crustal contamination of the ultramafic and mafic magmas. Using diagrams less sensitive to crustal contamination suggests the mafic and ultramafic magma to have a mantle source Minor rhyolitic rocks are chemically similar to granitic rocks intruding the komatiites and might have a mainly crustal magma source. This suggested that the Manica greenstones belt formed from magmas generated by mantle plume activity in a continental rift setting and were deposited on older Archean continental crust. These rocks are tentatively correlated with the Bends or Brookland formations belonging to the 2.9–2.8 Ga Mtshingwe Group in the Belingwe greenstone belts in Zimbabwe.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105494"},"PeriodicalIF":2.2,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758890","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}

{"title":"Combined geophysical approach as a tool to identify spatial groundwater aquifer distribution in structurally complex area. Case study of Kasserine aquifer system (central Tunisia)","authors":"Mouez Gouasmia ,&nbsp;Hajer Azaiez ,&nbsp;Ferid Dhahri ,&nbsp;Karim Abidette ,&nbsp;Hakim Gabtni ,&nbsp;Mohamed Soussi","doi":"10.1016/j.jafrearsci.2024.105493","DOIUrl":"10.1016/j.jafrearsci.2024.105493","url":null,"abstract":"<div><div>Many countries are facing water resource scarcity. The Kasserine region in central Tunisia, is characterized with semi-arid climate and it is one of the most affected areas by drought in the country. Groundwater constitutes the main resource for drinking and irrigation water in Kasserine region. The groundwater aquifer levels are very structured, in this geologically complex zone, and their geometry needs to be well characterized. The present study aims to identify the geometry and the distribution of Campanian to Quaternary main aquifers in the Kasserine hydrogeological basin.</div><div>In this study, we adopted a combined geophysical approach; we analyzed and interpreted gravity and seismic existent data in addition to acquiring conventional vertical electrical soundings. The gravity data analysis and mapping revealed that the study area is structured in numerous geological blocks. It highlighted the existence of two major negative gravity anomalies associated with the Megdoudech basin and the Kasserine graben. The gravity maps illustrated the role of the NW-SE Kasserine major Fault in the block structuring. The seismic reflection sections have emphasized the same structuring of the basins. They have exposed the fault network responsible for the compartmentalization of geological structures and which plays an important role in the hydrodynamics of the aquifer system in the region. The geoelectrical investigation highlighted the existence of three aquifer units: the sandy to sandy-clay levels of the Plio-Quaternary in the Kasserine graben, the sandstones of the middle Miocene with an average resistivity of 75 Ω m profiled at different depths, and the Campanian limestones with high resistivities in the Kasserine plateau.</div><div>This combined approach is proven to be very useful to understand groundwater distribution in such geologically complex zones. The results will help the decision makers to ensure the safe management of groundwater resources especially in semi-arid and arid regions.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"222 ","pages":"Article 105493"},"PeriodicalIF":2.2,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142746199","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":"Paleodepositional reconstruction of Lokpanta Shale, Anambra Basin, Nigeria, using organic geochemistry, scanning electron microscopy, and trace elemental analysis","authors":"Gabriel C. Unomah ,&nbsp;Manika Prasad ,&nbsp;Michael A. Oladunjoye ,&nbsp;Idowu A. Olayinka","doi":"10.1016/j.jafrearsci.2024.105491","DOIUrl":"10.1016/j.jafrearsci.2024.105491","url":null,"abstract":"<div><div>The organic-rich Lokpanta shale in the Anambra Basin is considered a potential unconventional hydrocarbon resource in Nigeria. Exploration of unconventional shales requires the paleoenvironmental reconstruction of organic matter productivity and preservation for sweet spot mapping. However, limited studies have been conducted on the paleodepositional factors governing organic matter accumulation in the Lokpanta Shale. This study used scanning electron microscopic and geochemical analyses to reconstruct the paleodepositional settings. Total organic carbon (TOC) content averages 4.34%, indicating very good hydrocarbon generative potential. Lokpanta shale contains Type II organic matter and planktonic foraminifera without benthos, suggesting a marine but limitedly oxygenated setting. The Sr/Ba (1.28–9.27) and Rb/K (37.18–51.93) ratios indicate high paleosalinity, aiding organic matter preservation. Certain enriched trace elements (Mo, Cd, As, Cu, Ti, Ni, and Fe) are similar to signatures in modern hypoxic (e.g., Namibian shelf) and anoxic-euxinic (e.g., Mediterranean sapropels and Black Sea) marine environments, which are both associated with sulfidation for organic matter preservation. Observed pyrite exhibits a primarily spheroidal framboid morphology with an average size of &lt;5.2 μm and a standard deviation of ∼2, indicating a syngenetic origin of an euxinic depositional environment. The paleoredox proxies (Mo/TOC &lt;15 ppm/gTOC, Th/U &gt; 2, V/Sc &gt; 16, V/(V + Ni) &gt; 0.70, and Ni/Co &gt; 6) indicate deposition in highly anoxic and intensely sulfidic waters within a highly restricted sill basin exhibits characteristics of an euxinic setting. In addition, Rb/Sr (0.031–0.132) and Sr/Cu (13.77–28.45) and C-value (&lt;0.1) ratios suggest hot and arid paleoclimate, which aided carbonate productivity. The enrichment of CaO, Si, Ti, Zr, and depletion of Th and rare earth elements (REE) contents suggests low clastic influx aiding in carbonate productivity and organic matter preservation. However, the ratios of Ba/Al (18.5–46.7), Baxs (56.63–489.14), Fe/Ti (4.85–11.29), and Al/Al + Fe (0.58–0.79) suggest that organic matter accumulation was governed by neither primary paleoproductivity nor hydrothermal activities. This euxinic setting may not have extended to coeval shales in other coastal basins of West Africa, even though anoxic conditions existed in those areas.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"222 ","pages":"Article 105491"},"PeriodicalIF":2.2,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722985","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":"Imaging upper lithospheric structures of the Benue Trough and adjoining basement areas in Nigeria and Cameroon from satellite gravity data","authors":"Goodluck K. Anudu ,&nbsp;Charles O. Ofoegbu ,&nbsp;Stephen E. Obrike ,&nbsp;Obeid S. Lemna","doi":"10.1016/j.jafrearsci.2024.105488","DOIUrl":"10.1016/j.jafrearsci.2024.105488","url":null,"abstract":"&lt;div&gt;&lt;div&gt;This study investigates the structures of upper lithosphere in the Benue Trough (BT) and its abutting basements in Nigeria and Cameroon through detailed analyses and interpretation of satellite Bouguer gravity anomaly (BA) data. Matched bandpass filtering, edge enhancements (tilt- and theta-derivatives), 3D inversion, and 2D modelling methods were applied to the BA data. The result from matched bandpass filtering reveals four gravity layer sources with their respective average depths, namely near-surface geological bodies (c. 0.6274 km), depth to basement (sediment thickness; c. 5.8921 km), intra-crustal boundary (c. 12.7538 km) and Moho (c. 27.980 km). Tilt- and theta-derivatives of the BA imaged numerous regional tectonic fabrics/structures exhibiting ENE – WSW, NNE –SSW, and NE – SW major trends coupled with N – S, NW – SE and E − W minor trends across the area, with the major regional tectonic trends mostly dominant in the BT and Adamawa Plateau/Cameroon Volcanic Line (AP/CVL) regions. Positive tilt cum positive theta derivatives of BA indicate that high-density (dense) geological bodies occur within the underlying sediments and crustal basements, particularly within the BT. 3D inversion result reveals a conspicuous and elongated (c. &gt; 600 km long, 120 km wide) NE – SW orientated shallow (c. 23–30 ± 3 km) Moho structure beneath the BT and a prominent elongated, large (c. &gt; 550 km long, 115 km wide) NE – SW striking deep (c. 34–44 ± 3 km) Moho structure below the AP/CVL region in the Western Cameroon Domain/Adamawa-Yade Domain (WCD/AYD) of Cameroon. Also, it shows that the Northern Nigerian Basement Complex (NNBC) and Eastern Nigerian Basement Complex (ENBC) regions are characterised by highly variable Moho morphology and depths (c. 26 to 36 ± 3 km). Generated 3D Moho model represents the first detailed Moho model for this studied area. The result from 2-D forward modelling of a NW – SE representative profile, constrained by known outcrop regional geology and available nearby seismic/teleseismic information, indicates the presence of two variable sedimentary sub-basins (c. 2–5 ± 0.4 km deep), a basement ridge and shallow Moho (c. 23–27 km ± 2 km) in BT region with occurrences of shallow intrusive bodies (e.g. granites), dense lower crustal body and deep Moho (c. 30–40 ± 2 km) underneath the basement regions, particularly in the AYD region. It also highlights that the underlying crust in BT is thinnest while thickest in basement regions of NNBC, ENBC, WCD (particularly AP/CVL area) and AYD along the NW – SE profile. The Moho depth values obtained in this study are within ±3.5 km with all those previously published from teleseismic works in the studied area. The imaged major NE – SW and ENE –WSW orientated tectonic fabrics/structures of the Precambrian crustal basement may have strongly influenced the location, emplacement and orientations of the BT, AP/CVL and Younger Granite complexes. Also, the BT developed in response to mech","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"222 ","pages":"Article 105488"},"PeriodicalIF":2.2,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723090","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":"Automated lithofacies classification: A comprehensive machine learning approach in Shushan Basin reservoirs, Western Desert, Egypt","authors":"Amr M. Abuzeid ,&nbsp;Ashraf R. Baghdady ,&nbsp;Ahmed A. Kassem","doi":"10.1016/j.jafrearsci.2024.105487","DOIUrl":"10.1016/j.jafrearsci.2024.105487","url":null,"abstract":"<div><div>The application of machine learning serves as a pivotal tool for petroleum geologists in facies classification. This new workflow distinguishes itself from existing classifiers by leveraging hidden statistical patterns in logging data to present a few recognizable clustering options for geologists. These choices are guided by other geological data sources, allowing geologists to retain the dimensional locations of chosen clusters for identification in other wells lacking these additional sources. The classification technique maximizes the value of conventional logging data (gamma ray, resistivity, density, neutron and sonic) for discerning rock typing, porosity ranking, fluid content, highlighting similar petrographic characteristics and elements composition, facilitating the inference of porosity and permeability degrees with high confidence.</div><div>The workflow is designed in this study to predict siltstone, shale, limestone, basaltic intrusions, and coal, accurately identifies various sandstone sub-facies, differentiates between tight and hydrocarbon-bearing sandstone across four wells, with blind validation on a separate well. The classification is validated using Litho Scanner tool, petrography thin sections, and laboratory analysis.</div><div>This comprehensive approach demonstrates the efficiency and applicability of the methodology, marking significant advancements in facies classification within petroleum geology.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"223 ","pages":"Article 105487"},"PeriodicalIF":2.2,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142756736","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":"Seasonal analysis of heavy metaloids concentrations in water and sediments of selective Karu rivers, Nigeria: Ecological implications and risk assessment","authors":"U. Rilwan ,&nbsp;M.I. Sayyed ,&nbsp;M.U. Sarki ,&nbsp;M.K. Raliatu ,&nbsp;A.A. Auwal ,&nbsp;S.A. Nata'la ,&nbsp;M.Y. Hanfi","doi":"10.1016/j.jafrearsci.2024.105485","DOIUrl":"10.1016/j.jafrearsci.2024.105485","url":null,"abstract":"<div><div>There is currently no universally agreed-upon standard for acceptable levels of heavy metals in the surface water and sediment of selected Nigerian rivers. In the study, the concentrations of heavy metals were determined in the surface water and sediments of rivers located in Karu, Nasarawa state, Nigeria. An inductively coupled plasma mass spectrometer was employed to analyze both water and sediment samples. When both seasons are considered, the mean levels of zinc (Zn), copper (Cu), iron (Fe), cadmium (Cd), lead (Pb), and arsenic (As) in water samples from the cold season are approximately two times higher than the mean values in the hot season. The mean values for the cold season were 0.238, 0.278, 0.272, 0.003, 0.075, and 0.082 mg/L for zinc, copper, iron, cadmium, lead, and arsenic, respectively. In sediment samples, the mean concentrations of Zn, Cu, Fe, Cd, Pb, and As in the cold season were 1.72, 0.57, 372.45, 0.80, 0.68, and 14.35 mg/kg, respectively. The geo-accumulation index (Igeo) and the potential ecological risk index (RI) indicated that the contamination levels of the river sediment were low. Nevertheless, a more comprehensive analysis of heavy metals in both water and sediment is required to fully evaluate the health of the ecosystem and effectively manage any potential risks.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"222 ","pages":"Article 105485"},"PeriodicalIF":2.2,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723089","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":"New insights from the Choteč Event (early Middle Devonian) in the Marhouma section (Ougarta range, SW Algeria)","authors":"Radia Tandjaoui ,&nbsp;Abdelkader Ouali Mehadji ,&nbsp;Carine Randon ,&nbsp;Houssem Sassi","doi":"10.1016/j.jafrearsci.2024.105486","DOIUrl":"10.1016/j.jafrearsci.2024.105486","url":null,"abstract":"<div><div>The stratigraphic reference section of the Marhouma area (the so-called km 30 section) in the Ougarta Range (North Western Algerian Sahara) provides valuable insights for the Emsian/Eifelian boundary (Lower/Middle Devonian) around the main lithological facies change expressed between the Teferguenite Chefar el Ahmar Formation. This paper presents new data allowing to better constrain and locate regionally the previously established boundary and to locate the Choteč Bioevent. This revision places the boundary below the new record of <em>Icriodus introlevatus</em> Bultynck, 1970 in Bed 3. The ammonoid assemblages place this boundary either at the base of level 25 <em>sensu</em> Göddertz (1987), without excluding placing it a position several meters lower, above the “niveau coralligène of Le Maître (1952)”. The “Choteč” Bioevent is distinguished within a likely polyphase, stepwise local development: i) a facies change well-expressed by a shift from benthic bioclastic packstones to pelagic wackestones (styliolinites); ii) an increasing deepening (thickest marly interval above level 25, Bed 2); iii) the <em>Icriodus introlevatus</em> wackestone Bed 3; iv) a bloom of goniatites (including <em>Pinacites jugleri</em> (Roemer, 1843) and <em>P. eminens</em> Chlupáč and Turek, 1977) in Bed 4, and finally v) a bloom of micromorphic brachiopods in Bed 5, which reflects monospecific mass reproduction due to increased specific trophic levels. This scenario happened in an alternation of marl-limestone layers with a <em>Zoophycus-Chondrites</em> ichnofossil assemblage, interspersed by greenish claystones and calcareous nodule rich in dacryoconarids. The platy shell bed (Bed 5) represented by micromorphic brachiopods represents the peak phase of Choteč Event Interval ranging locally from Bed 4 to Bed 5, and corresponding to Göddertz's level 27.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"222 ","pages":"Article 105486"},"PeriodicalIF":2.2,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723088","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":"Trace fossil association related to the Upper Miocene transgression cycle in the Lower Chelif Basin, NW Algeria","authors":"Imad Bouchemla ,&nbsp;Madani Benyoucef ,&nbsp;Ahmed Belhadji ,&nbsp;Mohamed Amine Zaidi ,&nbsp;Abdelkader Chachour","doi":"10.1016/j.jafrearsci.2024.105489","DOIUrl":"10.1016/j.jafrearsci.2024.105489","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Tortonian transgression is expressed in the Lower Chelif Basin by the deposition of the Blue Marls Formation highlighted at the base by a deposition of sandstone and conglomerate, including ante-Neogene cobble-size clasts, in which the ichnological investigation shows moderately diversified invertebrate ichnofossils preserved mainly in the detrital-dominated deposits. The trace fossil record consists of 18 ichnospecies belonging to 13 ichnogenera, including &lt;em&gt;Arenicolites carbonaria, Diplocraterion parallelum, Gastrochaenolites&lt;/em&gt; isp., &lt;em&gt;Gyrolithes&lt;/em&gt; isp., &lt;em&gt;Macanopsis&lt;/em&gt; isp., &lt;em&gt;Macaronichnus&lt;/em&gt; cf. &lt;em&gt;segregatis, Ophiomorpha nodosa, Palaeophycus tubularis, Phycodes circinnatum, Phycodes&lt;/em&gt; cf. &lt;em&gt;curvipalmatum, Rhizocorallium&lt;/em&gt; isp., &lt;em&gt;Rosselia socialis, Skolithos annulatus, Skolithos linearis, Skolithos verticalis, Thalassinoides horizontalis, Thalassinoides&lt;/em&gt; cf. &lt;em&gt;suevicus&lt;/em&gt;, and &lt;em&gt;Thalassinoides&lt;/em&gt; isp., produced mostly by deposit-, suspension-, and rarely detritus-feeder organisms. Among these traces, &lt;em&gt;Gastrochaenolites&lt;/em&gt; isp. is the only specimen being recorded within the conglomerate deposits and represents, therefore, the evidence of the first colonization after the Tortonian marine ingression. The remaining trace fossils are exclusively reported from the sandstone deposits and are typical of shallow-marine settings composed of vertical and horizontal structures, largely dominated ethologically by domichnia, fodinichnia, and combined domichnia/fodinichnia behaviour groups. The lower interval of the sandstone deposits is dominated by mid- to deep-tier, vertical post-depositional dwelling (domichnia) forms (&lt;em&gt;Arenicolites, Diplocraterion, Skolithos, Macanopsis, Ophiomorpha,&lt;/em&gt; and &lt;em&gt;Gyrolithes&lt;/em&gt;) attributed to opportunistic suspension-feeding organisms, corresponding to the archetypal &lt;em&gt;Skolithos&lt;/em&gt; ichnofacies that documents an upper-middle shoreface environment, whereas the upper interval is predominantly represented by shallowest- to shallow-tier horizontal deposit-feeders burrows [&lt;em&gt;Macaronichnus, Ophiomorpha&lt;/em&gt; (horizontal components)&lt;em&gt;, Palaeophycus, Phycodes, Rhizocorallium&lt;/em&gt;, &lt;em&gt;Rosselia&lt;/em&gt; (vertical components), and &lt;em&gt;Thalassinoides&lt;/em&gt;] displaying intense degree of bioturbation, reflecting a perfect palaeoecological condition reigning in the water column and sea floor. Thus, the association commonly corresponds to the proximal trend of the &lt;em&gt;Cruziana&lt;/em&gt; ichnofacies developed within the lower shoreface zone. Consequently, the ichnological investigation reveals that the detrital-dominated deposits show a slight deepening of the environment, shifting from a suspension feeder-dominated to a deposit feeder-dominated association, in which polychaete annelid and crustacean animals are the main benthonic epi- and infaunal trace makers of the recorded ichnofossils. The ichnotaxa &lt;em&gt;Arenicolites carbonaria, Phycodes circinnatum, Phycodes&lt;/em&gt; cf. &lt;","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"222 ","pages":"Article 105489"},"PeriodicalIF":2.2,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142745626","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":"Paleoenvironmental and sea level changes across the Paleocene-lower Eocene interval at the central and southwestern Sinai, Egypt","authors":"Azza A. Mohamed ,&nbsp;Nageh A. Obaidalla ,&nbsp;Abdelhamid M. Salman ,&nbsp;Kamel H. Mahfouz ,&nbsp;Amr A. Metwally","doi":"10.1016/j.jafrearsci.2024.105483","DOIUrl":"10.1016/j.jafrearsci.2024.105483","url":null,"abstract":"<div><div>Detailed stratigraphic studies of the Paleocene-lower Eocene interval were conducted on four stratigraphic successions (Sudr-Alhitan, Thamad, Abu-Qada, and Nukhul) in central and southwestern Sinai. These sections are arranged along a North-South direction as: Sudr-Alhitan, Thamad, Abu-Qada, and Nukhul. The biostratigraphic framework was achieved by integrating data of calcareous nannofossils and planktonic foraminifera. The studied area experienced two major tectonic events, most likely related to the Syrian Arc System (SAS), which led to two distinct hiatuses of significant magnitude, evidenced from integrated biostratigraphic analysis and thorough field observations. Benthic foraminifera assemblages suggest a deposition in outer neritic to upper bathyal setting for investigated sites, except for the Tarawan and Thebes formations in Abu-Qada and Sudr-Alhitan sections, which were deposited in middle-outer neritic and outer neritic settings, respectively. Benthic foraminiferal indices indicate an oligo-mesotrophic environment associated with oxic/suboxic conditions at the bottom of the seawater for the studied interval. Low oxygen levels and mesotrophic conditions were seen to mark the Paleocene Eocene Thermal Maximum event, as evidenced by the organic-rich laminated sediment, low benthic foraminiferal indices, and the occurrence of agglutinated taxa <em>Repmanina charoides</em> and <em>Ammobaculites</em> spp., which reflects a major change in food supply. The obtained sequence stratigraphic framework shows that the depositional record of the studied area is significantly influenced by both the regional tectonics and eustatic sea level.</div></div>","PeriodicalId":14874,"journal":{"name":"Journal of African Earth Sciences","volume":"222 ","pages":"Article 105483"},"PeriodicalIF":2.2,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142723087","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}