Marine Micropaleontology最新文献

{"title":"Sea-level fluctuations during the Danian-Selandian interval in Sinai, Egypt: Insights from benthic foraminiferal biofacies analysis","authors":"Youssef S. Bazeen ,&nbsp;Sherif Farouk ,&nbsp;Khaled Al-Kahtany ,&nbsp;Fayez Ahmad ,&nbsp;Amr S. Zaky","doi":"10.1016/j.marmicro.2024.102362","DOIUrl":"10.1016/j.marmicro.2024.102362","url":null,"abstract":"<div><p>The Paleocene hemipelagic deposits of the Dakhla Formation in Sinai offer an ideal setting to investigate paleoenvironmental fluctuations using benthic foraminifera. This study examined a Danian-Selandian sedimentary succession at Themed, Sinai using quantitative foraminiferal analysis within a sequence stratigraphic framework. Quantitative multivariate analyses, including R-mode clustering and non-metric multidimensional scaling (NMDS) ordination of biofacies trends and diversity parameters, indicate considerable paleoenvironmental and paleobathymetric changes throughout the studied succession. Five transgressive-regressive (T-R) sequences were identified based primarily on benthic foraminiferal biofacies trends. The sequence boundaries correlated well with major global sea-level lowstands. Benthic foraminiferal assemblages elucidated paleobathymetry fluctuations between upper bathyal and middle-outer neritic settings across the sequences. The identified sequences strongly correlate to global eustatic cycles, with subtle disparities suggesting a subordinate role for regional tectonics overprinting the dominant sea level control. The Latest Danian Event (LDE) interval coincides with the regressive phase of the fourth T-R sequence, as revealed from the biostratigraphic-constrained isotopic signature. It showed pronounced peaks in the relative abundance of the eutrophic buliminids, likely reflecting enhanced export productivity. Overall, benthic foraminifera provided vital paleoenvironmental insights, enabling sequence stratigraphic interpretation in the monotonous hemipelagites and highlighting possible coupled dynamics of both the carbon cycle and sea level.</p></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"189 ","pages":"Article 102362"},"PeriodicalIF":1.9,"publicationDate":"2024-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140399799","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":"The record of marine ingression in western Gondwana from Devonian conodonts in the Amazonas and Solimões basins, Brazil","authors":"Jordana Maria Viccari,&nbsp;Sara Nascimento,&nbsp;Ana Karina Scomazzon,&nbsp;Amanda Pericolo da Rosa,&nbsp;Andrés Felipe Rojas Mantilla,&nbsp;Sanmya Karolyne Rodrigues Dias,&nbsp;Paulo A. Souza,&nbsp;Valesca Brasil Lemos,&nbsp;Danielle Dall Amaria Soffiatti,&nbsp;Martín Andrés León Caffroni","doi":"10.1016/j.marmicro.2024.102352","DOIUrl":"10.1016/j.marmicro.2024.102352","url":null,"abstract":"<div><p>During the Devonian, the Gondwana supercontinent was in a paleogeographic position in high-latitudes, close to the South Pole. The arrangement of continents, tectonic activity, climate fluctuations, and the evolution of marine life played an important role in the marine ecosystems during this period. Conodont occurrences in high-latitudes are scarce. In the Upper Devonian (Frasnian/Famenian) of western Gondwana, conodonts have been found in anoxic black-shale deposits associated with maximum flooding surface (MFS) of a distal platform, in the Barreirinha Formation of the Amazonas Basin and Jandiatuba Formation of the Solimões Basin, in northern Brazil. The fauna is characterized by low diversity and well-preserved platform and ramiform elements of <em>Mehlina gradata</em>, <em>Ozarkodina</em> sp. aff. <em>O. sannemanni</em>, <em>Cryptotaxis</em> sp. and <em>Polygnathus</em> sp. in the Amazonas Basin and <em>Cryptotaxis</em> sp., <em>Parapolygnathus</em> sp., <em>Pandorinellina</em> sp.<em>,</em> and <em>Hibbardella</em> sp. in the Solimões Basin. The conodont faunal association and sedimentary succession suggest a marine ingression in cool water conditions to the Devonian sea of the Amazonian region.</p></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"188 ","pages":"Article 102352"},"PeriodicalIF":1.9,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139949719","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":"Unravelling the distribution of three Ammonia species (Foraminifera, Rhizaria) in French Atlantic Coast estuaries using morphological and metabarcoding approaches","authors":"Marie P.A. Fouet ,&nbsp;Magali Schweizer ,&nbsp;David Singer ,&nbsp;Julien Richirt ,&nbsp;Sophie Quinchard ,&nbsp;Frans J. Jorissen","doi":"10.1016/j.marmicro.2024.102353","DOIUrl":"10.1016/j.marmicro.2024.102353","url":null,"abstract":"<div><p>Assessing the distribution of species in natural environments is essential for their use in environmental surveys. Here, we investigate the distribution of three pseudo-cryptic species formerly lumped in the morphospecies <em>Ammonia tepida</em> (Cushman, 1926)<em>,</em> commonly found on estuarine mudflats along the European coasts: <em>Ammonia veneta</em> Schultze, 1854 (T1), <em>Ammonia aberdoveyensis</em> Haynes, 1973 (T2) and <em>Ammonia confertitesta</em> Zheng, 1978 (T6). We studied their distribution at 51 sites located in seven estuaries of the French North Atlantic coast (Elorn, Aulne, Odet, Crac'h, Auray, Vilaine, Vie), using both morphological and molecular identification methods. <em>Ammonia veneta</em> was detected by both approaches at most of the stations. While <em>A. aberdoveyensis</em> was frequently identified by the morphological method but not detected with metabarcoding, the presence of <em>A. confertitesta</em> in the eDNA data often contrasted with its absence in the morphological analysis. The absence of <em>A. aberdoveyensis</em> in eDNA of sites where it was identified morphologically could be the consequence of its relative scarcity, and eventually a patchy distribution. Concerning <em>A. confertitesta,</em> we hypothesise that these contradictory results can be explained by the supposedly invasive character of this species. Despite the widespread presence of <em>A. confertitesta</em> genetic material (including adults, juveniles and propagules), a mature population has not yet fully developed everywhere. The seven investigated estuaries seem to represent different stages of replacement of the autochthonous species <em>A. veneta</em> and <em>A. aberdoveyensis</em> by <em>A. confertitesta</em>. Our study demonstrates that the combination of visual observations and molecular approaches is ideal for monitoring the progressive spreading of exotic species.</p></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"188 ","pages":"Article 102353"},"PeriodicalIF":1.9,"publicationDate":"2024-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139949697","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":"Relative abundance and biometry of Bolivina ordinaria on the northern continental slope of the Pelotas basin during the late Quaternary","authors":"Patrícia Tortora Kother ,&nbsp;Maria Alejandra Gomez Pivel ,&nbsp;Kalina Manabe Brauko ,&nbsp;Carla Bonetti","doi":"10.1016/j.marmicro.2024.102345","DOIUrl":"10.1016/j.marmicro.2024.102345","url":null,"abstract":"<div><p>This study examines the variations in relative abundance, test size, and biomass of the species <em>Bolivina ordinaria</em> (Foraminifera) over the last 112 ka BP on the northern slope of the Pelotas Basin, Southern Brazil. The analyses were based on 651 individuals from 42 samples distributed along the cores SIS-249 (Marine Isotope Stage 5 to 3) and SIS-188 (Marine Isotope Stage 3 to 1). <em>Bolivina ordinaria</em> was the most abundant species of the Bolivinitidae family in these cores, particularly during warmer periods (MIS 1 and 5). Nine other species of this family were identified: <em>B. compacta, B. doniezi, B. lowmani, Bolivina</em> sp., <em>B.striatula, Brizalina</em> sp., <em>Brizalina spinescens, Brizalina subaenariensis,</em> and <em>Brizalina subspinescens.</em> Larger test lengths were observed during MIS 3 in the both cores. The summed biomass was higher during MIS 5 in the SIS-249 core and lower during MIS 3 in the SIS-188 core. The fluctuations observed in the relative abundance and summed biomass of <em>B. ordinaria</em> are consistent with the oscillations in total organic carbon flow, and the variations in primary productivity between the interglacial and glacial periods. The results suggest that this infaunal species is favored by the regular supply of refractory organic matter during warmer periods but faces increased competition from shallow infaunal and epifaunal species during glacial periods, when the flow of labile organic matter increases.</p></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"188 ","pages":"Article 102345"},"PeriodicalIF":1.9,"publicationDate":"2024-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139949631","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":"Spatial and vertical distribution of the genus Amphistegina and its relationship with the indigenous benthic foraminiferal assemblages in the Pelagian Archipelago (Central Mediterranean Sea)","authors":"Claudia Cosentino ,&nbsp;Roberta Guastella ,&nbsp;Nicoletta Mancin ,&nbsp;Antonio Caruso","doi":"10.1016/j.marmicro.2024.102344","DOIUrl":"10.1016/j.marmicro.2024.102344","url":null,"abstract":"<div><p>A serious threat affecting the Mediterranean Sea is the migration of Indo-Pacific marine species through the Suez Canal following its opening in 1869. This phenomenon gives extreme causes for concern as many non-indigenous species are highly invasive and seriously threaten native biodiversity. Particularly insidious are small-size taxa such as benthic foraminifera, which are able to invade wide areas un-noticed.</p><p>The objective of this study is to evaluate the stage of invasion of non-indigenous foraminifer <em>Amphistegina lobifera</em> and the re-colonization of <em>Amphistegina lessonii</em> in two islands of the Pelagian Archipelago (Central Mediterranean) where both species were first recorded in 2005.</p><p>Absolute abundances quantified in seabed and algal samples collected in 2014 were compared with those detected in 2005 and 2009. Results show that, in the innermost part of the neritic environment, amphisteginids were so abundant and widespread as to have replaced native benthic foraminifera just a few years after earlier reports.</p><p>On Lampedusa Island, Amphisteginids seem to compete mainly with other symbiont-bearing foraminifera, such as the milioliid <em>Peneroplis pertusus</em> and <em>Peneroplis planatus</em>; we hypothesize that the different algal symbionts housed by the invasive species could play an important role in the invasion success in the Mediterranean Sea. In the most severe case of amphisteginid invasion, as seen around the volcanic island of Linosa, the accumulation of their carbonatic remains is causing a sedimentation switch: increasing the content of white carbonatic sands and replacing the black volcanic substrates, as already observed in Indian Ocean atolls.</p></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"188 ","pages":"Article 102344"},"PeriodicalIF":1.9,"publicationDate":"2024-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377839824000148/pdfft?md5=c8fb133aa751b6827f2e6d983d2aa18f&pid=1-s2.0-S0377839824000148-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139890530","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":"Morphometric changes in Watznaueria barnesiae across the mid Cretaceous: Paleoecological implications","authors":"Chiara Bettoni ,&nbsp;Elisabetta Erba ,&nbsp;Silvia Castiglione ,&nbsp;Pasquale Raia ,&nbsp;Cinzia Bottini","doi":"10.1016/j.marmicro.2024.102343","DOIUrl":"https://doi.org/10.1016/j.marmicro.2024.102343","url":null,"abstract":"<div><p>This study reveals moderate yet important variations in <em>Watznaueria barnesiae</em> coccolith and central unit size throughout the Aptian–late Cenomanian (27 my) time interval in western Tethys. A new statistical approach was applied to determine whether non-random size trends apply to these metrics and to identify possible links between their variation and fertility or temperature. During OAE 1a, <em>W. barnesiae</em> coccoliths were the smallest and the most elliptical, with reduced central unit size. A further minor size decrease occurs during OAE 1b but not during OAE 1d. From the middle Albian to the middle Cenomanian, larger and less elliptical coccoliths are observed, with unchanged central unit dimensions. These results, together with concomitantly larger size changes in <em>Biscutum constans</em> confirm that <em>W. barnesiae</em> is a tolerant taxon. High-frequency, high-amplitude paleoenvironmental changes during the Aptian–early Albian indicate that temperature and fertility – either individually or in combination – had no direct impact on the mean coccolith size and potentially other factors affected coccolith size. Instead, lower nutrients with lower temperatures probably played a role in promoting larger <em>W. barnesiae</em> but smaller <em>B. constans</em> coccoliths during the middle Albian–Cenomanian. The size and ellipticity changes during OAE 1a and 1b were the strongest, likely resulting from ocean acidification and trace metal inputs, in addition to (or independently of) fertility and temperature variations.</p></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"188 ","pages":"Article 102343"},"PeriodicalIF":1.9,"publicationDate":"2024-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377839824000136/pdfft?md5=4f111a88b163a05adda2be7a27cb4dc7&pid=1-s2.0-S0377839824000136-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139699971","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":"Paleoecology of selected Danian marine ostracods, geochemically pre-characterized by analysis of stable carbon (δ13C) and oxygen (δ18O) isotopes","authors":"Marlone H.H. Bom ,&nbsp;Daiane Ceolin ,&nbsp;Karlos G.D. Kochhann ,&nbsp;Rodrigo Do Monte Guerra ,&nbsp;Guilherme Krahl ,&nbsp;German Patarroyo ,&nbsp;Mírian L.F.A. Pacheco ,&nbsp;Lucas V. Oliveira ,&nbsp;Telma Musso ,&nbsp;Andrea Concheyro ,&nbsp;Gerson Fauth","doi":"10.1016/j.marmicro.2024.102342","DOIUrl":"10.1016/j.marmicro.2024.102342","url":null,"abstract":"<div><p>The Cerro Azul Section provides a continuous record of the Cretaceous-Paleogene (K-Pg) transition in a shallow marine context of the South Atlantic Ocean in the Neuquén Basin. Ostracod assemblages were severely affected by environmental changes across the event. Excellent ostracod preservation at the Cerro Azul Section allows to infer paleoecological preferences of four Danian species based on carbon and oxygen stable isotopes. The studied species were <em>Paracypris bertelsae</em> Ceolin and Whatley, 2015, <em>Cytherella</em> spp., <em>Togoina argentinensis</em> and <em>Henryhowella</em> (<em>Wichmannella) meridionalis</em> (Bertels, 1974). To assess the reliability of ostracod δ¹³C and δ¹⁸O values as paleoenvironmental proxies, we pre-characterized valves with micro x-ray microdiffraction (μXRD) and microRaman (μRaman spectroscopy). <em>Togoina argentinensis</em> and <em>Henryhowella</em> (<em>Wichmannella) meridionalis</em> present in their major calcitic compositions, with small differences of crystallinity within intervals of environmental stress, but no authigenic phases formed during diagenesis. δ¹³C and δ¹⁸O values depict clear interspecific differences between smooth specimens and ornamented specimens. These differences in stable isotope values were likely controlled by microhabitat preferences, which would be comparable with patterns described for benthic foraminifera as well as paleonutrients variations, suing Ba/Ti and P/Ti ratios.</p></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"188 ","pages":"Article 102342"},"PeriodicalIF":1.9,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139662258","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":"Humid climate phases on the Island of Rhodes (Greece) during the late Pliocene at times of sapropel formation","authors":"Daniela Eichner ,&nbsp;Gerhard Schmiedl ,&nbsp;Jürgen Titschack ,&nbsp;Malu Ferreira ,&nbsp;Maria Triantaphyllou ,&nbsp;Nils Andersen ,&nbsp;Yvonne Milker","doi":"10.1016/j.marmicro.2024.102341","DOIUrl":"10.1016/j.marmicro.2024.102341","url":null,"abstract":"<div><p>The Island of Rhodes, located in the Eastern Mediterranean Sea, is affected by an active convergent plate boundary. In this context, marine sediments of Plio-Pleistocene age have been uplifted and are outcropping along the eastern coast of Rhodes. These archives provide an excellent opportunity to unravel the hydrological and climatic changes of the region during the late Pliocene. Our results provide new evidence for a more humid climate and an increased precipitation on the island during times of Northern Hemisphere summer insolation maxima and related sapropel formation in the Mediterranean deep sea. The periodic occurrence of eutrophic conditions at the shelf and upper slope off Rhodes is indicated by the recurrent dominance of eutrophic indicator species (of the genera <em>Bolivina</em>, <em>Eubuliminella</em> and <em>Rectuvigerina</em>), simultaneously with a decline in diversity and oligotrophic indicator species. These conditions resulted from higher primary productivity, triggered by local effects, such as enhanced precipitation and river run-off, which consequently favors the appearance of eutrophic taxa. The ∆δ¹³C records of the epibenthic foraminifera <em>Cibicidoides pseudoungerianus</em> and the shallow infaunal species <em>Uvigerina peregrina</em> indicate a slight productivity decrease towards younger times.</p></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"187 ","pages":"Article 102341"},"PeriodicalIF":1.9,"publicationDate":"2024-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377839824000112/pdfft?md5=f144cdb77c61f231b2a04405d884141b&pid=1-s2.0-S0377839824000112-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139517364","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":"Paleoecological and paleobiogeographic implications of a seagrass-indicating foralgal skeletal assemblage: Retracing the Burdigalian Quilon Limestone (Kerala Basin, SW India)","authors":"Suman Sarkar ,&nbsp;Yogesh Pal Singh ,&nbsp;Poonam Verma","doi":"10.1016/j.marmicro.2023.102330","DOIUrl":"https://doi.org/10.1016/j.marmicro.2023.102330","url":null,"abstract":"<div><p><span><span><span>Seagrasses are marine angiosperms documented in shallow-marine, soft bottom settings across the Cenozoic. They proliferated globally after their divergence from other alismatid monocots in the </span>late Cretaceous followed by an adaptation to the marine environment. Detailed evaluation of seagrasses in the geological archives is of utmost importance to understand their responses to climatic and environmental alterations in the deep time perspective. Here we examine the lower </span>Miocene Quilon Limestone from the Kerala Basin (southwest India) that encompasses a </span><em>Pseudotaberina</em>-<em>Halimeda</em> floatstone signalling a robust photozoan foralgal skeletal assemblage. This is characterized by the dominant soritid foraminifer <em>Pseudotaberina</em><span> and the calcareous green alga </span><em>Halimeda</em><span><span>, in association with other foraminifera and representatives from various biotic groups that indicate a tropical seagrass </span>paleoenvironment. Abundant soritids together with various bryopsidalean </span><em>Halimeda</em> species indicate light and temperature as the major ecological drivers regulating the Quilon Limestone seagrass paleocommunity during the early Miocene (Burdigalian). The spatio-temporal distribution patterns of <em>Halimeda</em> also indicate temperature as the most prominent ecological constraint determining its dispersal and evolution at multiple latitudes. A well illuminated substrate is envisaged to support the development and calcification of the <em>Halimeda</em><span> thalli. Abundance of K-strategist foraminifera with minor occurrence of suspension-feeding bryozoans and some gastropods, bivalves indicate a low-nutrient environment.</span></p></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"187 ","pages":"Article 102330"},"PeriodicalIF":1.9,"publicationDate":"2024-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139503863","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":"Calcareous nannoplankton response to middle-late Eocene climate and sea-level changes in the SW Neo-Tethys","authors":"Jihede Haj Messaoud ,&nbsp;Nicolas Thibault ,&nbsp;Mohammed H. Aljahdali ,&nbsp;Chokri Yaich ,&nbsp;Yang-Guang Gu","doi":"10.1016/j.marmicro.2023.102329","DOIUrl":"10.1016/j.marmicro.2023.102329","url":null,"abstract":"<div><p><span>We investigate the response of calcareous nannoplankton<span><span><span> to the middle-late Eocene transition in the SW Neo-Tethys and compare our data to published results from X-ray diffraction (XRD) analysis, element content from X-ray fluorescence (XRF) and the abundance of </span>microfossils in the coarse fractions of the sediment. The </span>nannofossil assemblage is mainly composed of </span></span><em>Reticulofenestra</em> spp. (avg. 44%), <em>Sphenolithus</em> spp. (avg. 20%), <em>Discoaste</em>r spp. (avg. 18%) and <em>Pontosphaera</em> spp. (avg. 10%). The Relative abundance of <em>Zygrhablithus bijugatus</em> and the <em>Chiasmolithus</em> ratio are used with the visual assessment to evaluate the preservation. The <em>Sphenolithus</em>-<em>Reticulofenestra</em><span> turnover occurred before the MECO at the Lutetian-Bartonian boundary. Besides the significant influence of an evolutionary gradient caused by the disappearance of numerous species of Sphenoliths, Discoasterids, and Coccolithaceae, and the first appearance of multiple species of reticulofenestrids, paleoenvironmental conditions imposed a significant impact on the calcareous nannofossil assemblages. The abundance of ostracods<span> and the planktic/benthic foraminifera ratio depict relative sea-level changes. The microfossil assemblages and the lithological composition of the sediments track paleoclimatic and paleoenvironmental changes across the Lutetian to Priabonian. Dry conditions marked the middle Lutetian, followed by increased variability in hydrolyzing conditions during the late Lutetian and early Bartonian. An eutrophic and restricted ecosystem with high fine-grained material input is suggested for the Priabonian.</span></span></p></div>","PeriodicalId":49881,"journal":{"name":"Marine Micropaleontology","volume":"187 ","pages":"Article 102329"},"PeriodicalIF":1.9,"publicationDate":"2024-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139464264","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}