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Actinomma sogndalensis n. sp. (Radiolaria, Polycystina) an endemic species to the Sognefjord, western Norway
IF 0.7
REVUE DE MICROPALEONTOLOGIE Pub Date : 2024-09-16 DOI: 10.1016/j.revmic.2024.100818
Jane K. Dolven , Kjell R. Bjørklund
{"title":"Actinomma sogndalensis n. sp. (Radiolaria, Polycystina) an endemic species to the Sognefjord, western Norway","authors":"Jane K. Dolven ,&nbsp;Kjell R. Bjørklund","doi":"10.1016/j.revmic.2024.100818","DOIUrl":"10.1016/j.revmic.2024.100818","url":null,"abstract":"<div><div>Studies of polycystine radiolarians (marine planktonic protists) have shown that great faunistic differences occur between the different Norwegian fjord systems. Plankton studies by Swanberg and Bjørklund in the early 1980′s identified more than 55 polycystine radiolarian species, including two unidentified forms of <em>Actinomma</em> noted as sp. A and sp. B. The discovery of fully developed adult individuals of the same taxa in plankton material from the Sogndalsfjord in 2010 revealed that the sp. A form in fact was a juvenile stage of the sp. B form. Its general morphologic skeletal structure differs so much from the other local <em>Actinomma</em> species that the whole concept of how to define, and what to include in, this genus has been taken up here for discussion.</div><div>This new species, described herein as <em>Actinomma sogndalensis</em>, has mainly been found in the Sognefjord, which leads us to conclude that <em>A. sogndalensis</em> might be an example of a real endemic fjord species. Due to the fragility of the latticed cortical shells, only the two thick primary medullary shells are preserved in the sediment. This led us to include a discussion regarding the number of concentric shells and their relevance or usefulness as a taxonomic criterion at the genus level in conjunction with this description of the new species. The genus <em>Actinomma</em> is emended to include species with two or multiple lattice spheres. <em>Cromyechinus</em> is by us still regarded as a junior synonym of <em>Actinomma</em>.</div></div>","PeriodicalId":45442,"journal":{"name":"REVUE DE MICROPALEONTOLOGIE","volume":"86 ","pages":"Article 100818"},"PeriodicalIF":0.7,"publicationDate":"2024-09-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143570510","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Late Silurian – Early Devonian marine ostracods from Kuan Tung Formation, Satun Province, southern Thailand
IF 0.7
REVUE DE MICROPALEONTOLOGIE Pub Date : 2024-09-10 DOI: 10.1016/j.revmic.2024.100817
Anucha Promduang, Anisong Chitnarin
{"title":"Late Silurian – Early Devonian marine ostracods from Kuan Tung Formation, Satun Province, southern Thailand","authors":"Anucha Promduang,&nbsp;Anisong Chitnarin","doi":"10.1016/j.revmic.2024.100817","DOIUrl":"10.1016/j.revmic.2024.100817","url":null,"abstract":"<div><div>Late Silurian to Early Devonian ostracods are reported for the first time from the Kuan Tung Formation (Sibumasu terrane) in southern Thailand. The studied limestone samples yielded abundant ostracods belonging to five suborders, six superfamilies, 17 genera, and 34 species, including the newly described <em>Ampuloides thungsamedensis</em> nov. sp. Other species are members of <em>Ampuloides, Microcheilinella, Bairdiocypris, Baschkirina?, Rectella?, Pseudorayella, Acratia, Bairdia, Fabalicypris, Cytherellina, Healdia, Kummerowia</em>?<em>, Aparchites, Brevidorsa, Samarella, Coelonella, Knoxiella</em>? with a few specimens of Eridoconchidae. Overall, the composition of ostracod assemblages is stable from the lower to middle subunits of the study section and points to shallow water environment on a carbonate deep shelf below the fair-weather wave base. The fauna shows relationships with Early to Late Devonian ostracods from South China, suggesting a narrow seaway between Sibumasu and South China terranes during Late Silurian to Early Devonian (late Ludlow to early Emsian).</div></div>","PeriodicalId":45442,"journal":{"name":"REVUE DE MICROPALEONTOLOGIE","volume":"86 ","pages":"Article 100817"},"PeriodicalIF":0.7,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143570509","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
A reassessment of the type-materials of Ostracoda (Crustacea, Oligostraca) lost in the “Museu Nacional” Great Fire of September 2, 2018
IF 0.7
REVUE DE MICROPALEONTOLOGIE Pub Date : 2024-08-29 DOI: 10.1016/j.revmic.2024.100807
Lucas Silveira Antonietto , David Ian Machado Alves , Cláudio Magalhães Almeida , Dermeval Aparecido do Carmo , Vera Maria Medina da Fonseca
{"title":"A reassessment of the type-materials of Ostracoda (Crustacea, Oligostraca) lost in the “Museu Nacional” Great Fire of September 2, 2018","authors":"Lucas Silveira Antonietto ,&nbsp;David Ian Machado Alves ,&nbsp;Cláudio Magalhães Almeida ,&nbsp;Dermeval Aparecido do Carmo ,&nbsp;Vera Maria Medina da Fonseca","doi":"10.1016/j.revmic.2024.100807","DOIUrl":"10.1016/j.revmic.2024.100807","url":null,"abstract":"<div><div>On September 2, 2018, a catastrophic fire occurred at the “Museu Nacional” in Rio de Janeiro, Brazil, nearly destroying its once rich scientific collections. That accident latter generated a movement from the museum and the scientific community to restore their collections, either by bringing new specimens to the institution or by providing information about the ones lost in the tragedy. Herein we present our contribution to that effort: high-resolution scanning electron microscope images of holotypes and paratypes of 23 fossil ostracod species and subspecies that were destroyed by the “Museu Nacional” fire. These taxa occur in several Brazilian and central West African Lower Cretaceous lithological units, and some of them (<em>Cypridea [Pseudocypridina] faveolata</em> and <em>Sebastianites fida minor</em>) are even guide fossils to these strata. The present images and taxonomical updates of species – including new combinations for <em>Sebastianites fida minor, Sebastianites</em>? <em>minima, Sebastianites</em>? <em>sostensis granulata</em> and <em>Theriosynoecum ventrostriatum</em> – will also enable future studies of ostracod species from Brazilian and central West African Lower Cretaceous basins, as they provide an accurate system of identification in absence of direct observation of these type specimens once housed at the “Museu Nacional” scientific collections.</div></div>","PeriodicalId":45442,"journal":{"name":"REVUE DE MICROPALEONTOLOGIE","volume":"86 ","pages":"Article 100807"},"PeriodicalIF":0.7,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143570508","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Taxonomic significance of the radiolarian family Tetraspinocyrtiidae Kozur and Mostler and related families from the Sorgun Ophiolitic Mélange, southern Turkey 土耳其南部索尔贡蛇绿岩夹层中的放射虫科 Tetraspinocyrtiidae Kozur 和 Mostler 及相关科的分类意义
IF 0.7
REVUE DE MICROPALEONTOLOGIE Pub Date : 2024-08-22 DOI: 10.1016/j.revmic.2024.100808
Péter Ozsvárt , Paulian Dumitrica , Patrice Moix
{"title":"Taxonomic significance of the radiolarian family Tetraspinocyrtiidae Kozur and Mostler and related families from the Sorgun Ophiolitic Mélange, southern Turkey","authors":"Péter Ozsvárt ,&nbsp;Paulian Dumitrica ,&nbsp;Patrice Moix","doi":"10.1016/j.revmic.2024.100808","DOIUrl":"10.1016/j.revmic.2024.100808","url":null,"abstract":"<div><div>The present work evaluates the significance of the early Tuvalian (late Carnian, Late Triassic) Tetraspinocyrtiidae and related families (radiolarians) from the Sorgun Ophiolitic Mélange, southern Turkey. Two new genera: <em>Nogursa</em> and <em>Sorgunocyrtis</em> and additional fifteen new species and a new subspecies are described from the Tavusçayırı Block, northeast of Sorgun village, Mersin, southern Turkey. The radiolarian fauna belongs to the <em>Spongotortilispinus moixi</em> Radiolarian Zone (equivalent to <em>Paragondolella postinclinata – Paragondolella noah</em> Conodont Zone).</div></div>","PeriodicalId":45442,"journal":{"name":"REVUE DE MICROPALEONTOLOGIE","volume":"86 ","pages":"Article 100808"},"PeriodicalIF":0.7,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143570514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Late Famennian (latest Strunian) palynomorph assemblages and their role in the Neves Formation depositional environment—The Neves-Corvo mine case study (Iberian Pyrite Belt, Portugal) 法门纪晚期(志留纪晚期)古生物组合及其在内韦斯地层沉积环境中的作用--内韦斯-科沃矿区案例研究(葡萄牙伊比利亚黄铁矿带)
IF 0.7
REVUE DE MICROPALEONTOLOGIE Pub Date : 2024-07-26 DOI: 10.1016/j.revmic.2024.100805
Márcia Mendes , Zélia Pereira , João X. Matos , Luis Albardeiro , Igor Morais , Vitor Araújo
{"title":"Late Famennian (latest Strunian) palynomorph assemblages and their role in the Neves Formation depositional environment—The Neves-Corvo mine case study (Iberian Pyrite Belt, Portugal)","authors":"Márcia Mendes ,&nbsp;Zélia Pereira ,&nbsp;João X. Matos ,&nbsp;Luis Albardeiro ,&nbsp;Igor Morais ,&nbsp;Vitor Araújo","doi":"10.1016/j.revmic.2024.100805","DOIUrl":"10.1016/j.revmic.2024.100805","url":null,"abstract":"<div><p>This research examines palynomorph assemblages preserved in sediments of the Iberian Pyrite Belt (IPB) that host the Neves-Corvo massive sulfide deposit and its importance for mineral exploration. The sediments belong to the Neves Formation, characterized by black shales and minor occurrences of siltstones and cherts, indicative of reduced environmental conditions, favorable to sulfide deposition in a hydrothermal context dominated by submarine felsic volcanism and graben structures. Analysis was performed in barren drill holes (e.g., Monte Novo), as opposed to productive sectors with massive sulfide mineralization and/or stockwork vein networks (e.g., Lombador, Corvo and Semblana deposits) and favorable sectors like Algaré. The recovered palynological assemblages are assigned to the LN Miospore Biozone, indicating a Late Famennian (latest Strunian) age. Several characteristic species of this age are identified, such as <em>Retispora lepidophyta</em> and <em>Verrucosisporites nitidus</em> in close association with <em>Densosporites spitbergensis, Dictyotriletes fimbriatus, Retusotriletes</em> cf. <em>incohatus, Retusotriletes crassus, Vallatisporites</em> spp. (including <em>V. pusillites,</em> and <em>V. verrucosus</em>)<em>.</em> Despite some palynomorphs showing signs of breakage, folding, and indistinctness, no significant preservation or diversity differences were noted between barren and mineralized areas. The high abundance of marine phytoplankton in all studied black shales indicates ecologically stressed setting, dominated by dysoxic to anoxic conditions in a distal marine setting with active felsic volcanism and hydrothermal mineralizing events during Late Famennian time. This geologic context correlates with other IPB deposits and the global latest Devonian anoxic Hangenberg event.</p></div>","PeriodicalId":45442,"journal":{"name":"REVUE DE MICROPALEONTOLOGIE","volume":"84 ","pages":"Article 100805"},"PeriodicalIF":0.7,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141853690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Middle Triassic and middle Permian radiolarians from the Kamitaki Complex in the Sasayama area, Hyogo Prefecture, Southwest Japan: Evidence for Triassic plate subduction along the eastern margin of Paleo-Asia 日本西南部兵库县筱山地区上泷复合体中三叠世和中二叠世放射虫:古亚洲东缘三叠纪板块俯冲的证据
IF 0.7
REVUE DE MICROPALEONTOLOGIE Pub Date : 2024-06-26 DOI: 10.1016/j.revmic.2024.100788
Yoshiaki Sugamori
{"title":"Middle Triassic and middle Permian radiolarians from the Kamitaki Complex in the Sasayama area, Hyogo Prefecture, Southwest Japan: Evidence for Triassic plate subduction along the eastern margin of Paleo-Asia","authors":"Yoshiaki Sugamori","doi":"10.1016/j.revmic.2024.100788","DOIUrl":"10.1016/j.revmic.2024.100788","url":null,"abstract":"<div><p>The Kamitaki Complex, situated in the Sasayama area in Southwest Japan, has long been presumed to be a Permian<span><span> subduction-related accretionary complex based on correlations from previous studies. However, because of the lack of fossil evidence, the exact age of the complex remained uncertain for a long time period. To address this gap in knowledge, a geological survey and </span>microfossil mapping were conducted in the Kamitaki Complex to determine its age and geological context.</span></p><p><span><span><span>A geological survey revealed that the Kamitaki Complex mainly consists of clastic rocks, and a mixture of sandstone, </span>basalt, and </span>chert<span><span><span> blocks within the mudstones. The Kamitaki Complex is tectonically intercalated into the </span>Lopingian (Late Permian) accretionary complex of the Ultra-Tamba </span>Terrane<span><span> and Late Triassic accretionary complex of the Tamba Terrane. The lithological and structural characteristics of the Kamitaki Complex confirm that it is an accretionary complex. Microfossil mapping yielded depositional ages, with </span>radiolarian fauna such as </span></span></span><em>Eptingium nakasekoi, Pseudostylosphaera japonica, Cryptostephanidium japonicum</em>, and <em>Oertlispongus</em> cf. <em>diacanthus</em><span> identified in mudstones suggesting an Anisian (early Middle Triassic) age. In contrast, radiolarian fauna found in cherts, including </span><em>Pseudoalbaillella</em>? aff. <em>longicornis</em>, and <em>Follicucullus</em> cf. <em>porrectus</em><span><span>, indicate an early Capitanian (late Guadalupian, middle Permian) depositional age. These findings suggest that the Kamitaki Complex records a trenchward migration of the oceanic plate in a </span>pelagic environment<span> from the early Capitanian and an accretion at the trench during the Anisian period.</span></span></p><p><span><span>Conventionally, the plate boundary between the Panthalassa and Paleo-Asia during the latest Permian to </span>Middle Triassic was of the transform type, primarily because no subduction-related accretionary complexes from this period have been identified in the Japanese Islands. However, the discovery of Kamitaki Complex, an Anisian accretionary complex, provides evidence of Middle Triassic subduction activity along the eastern margin of Paleo-Asia. According to the internal structure and age polarity of the Ultra-Tamba and Tamba terranes, an accretionary complex developed over a prolonged period (approximately 120 million years) in a </span>tectonic setting<span> that persisted along the eastern margin of Paleo-Asia from the late Guadalupian to the earliest Cretaceous period.</span></p></div>","PeriodicalId":45442,"journal":{"name":"REVUE DE MICROPALEONTOLOGIE","volume":"84 ","pages":"Article 100788"},"PeriodicalIF":0.7,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141963998","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Radiolarian dating of cherts from the Artofago Cave: Insights into prehistoric lithic tool production and resource exploitation in Southern Tuscany, Italy 阿尔托法戈洞穴白垩的放射虫测年:意大利南托斯卡纳史前石器制作和资源开发的启示
IF 0.7
REVUE DE MICROPALEONTOLOGIE Pub Date : 2024-06-20 DOI: 10.1016/j.revmic.2024.100790
Dario Ferrari , Marco Chiari , Enrico Pandeli , Luca Bachechi
{"title":"Radiolarian dating of cherts from the Artofago Cave: Insights into prehistoric lithic tool production and resource exploitation in Southern Tuscany, Italy","authors":"Dario Ferrari ,&nbsp;Marco Chiari ,&nbsp;Enrico Pandeli ,&nbsp;Luca Bachechi","doi":"10.1016/j.revmic.2024.100790","DOIUrl":"10.1016/j.revmic.2024.100790","url":null,"abstract":"<div><p>New perspectives in the archaeometric investigation of the chert used in lithic tool assemblages allow us to learn more about the socio−economic behavior of prehistoric human groups. The case study presented here is from the Artofago Cave in South Tuscany, Italy. Among other findings, an Upper Paleolithic lithic complex was excavated from a large fireplace near the entrance.</p><p><span>The purpose of this study is to gather data aimed at determining the raw material used in the production of these lithic tools, thereby enhancing research into its geographic source area. Here we highlight the significance of the geological age of the rock as one of key factors enabling us to formulate hypotheses about its geological provenance. It showcases a successful application of radiolarian </span>biostratigraphy<span> in dating cherts from the archaeological record. Specifically, 67 chert samples from the Upper Paleolithic lithic complex of the Artofago cave were treated with HF to isolate the radiolarian assemblages. The samples had been carefully chosen in advance between broken chert pieces (chert debris) in the waste material given that the analysis is partially destructive.</span></p><p>Chert samples can be assigned to a Middle − Late Jurassic<span> age, more specifically middle Callovian−early Oxfordian to late Kimmeridgian−early Tithonian (UAZ 8-11).</span></p><p>These ages are comparable with those of the Diaspri di Monte Alpe Formation of the Ligurian Vara Unit, the uppermost tectonic unit of the Northern Apennines.</p></div>","PeriodicalId":45442,"journal":{"name":"REVUE DE MICROPALEONTOLOGIE","volume":"84 ","pages":"Article 100790"},"PeriodicalIF":0.7,"publicationDate":"2024-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141964000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Miocene radiolarian assemblages from the submarine Vityaz Ridge, Northwest Pacific: Biostratigraphy and paleoceanography 西北太平洋维蒂亚兹海脊海底中新世放射虫组合:生物地层学和古海洋学
IF 0.7
REVUE DE MICROPALEONTOLOGIE Pub Date : 2024-05-27 DOI: 10.1016/j.revmic.2024.100789
L.N. Vasilenko , Yu.P. Vasilenko , Xuefa Shi , Yanguang Liu
{"title":"Miocene radiolarian assemblages from the submarine Vityaz Ridge, Northwest Pacific: Biostratigraphy and paleoceanography","authors":"L.N. Vasilenko ,&nbsp;Yu.P. Vasilenko ,&nbsp;Xuefa Shi ,&nbsp;Yanguang Liu","doi":"10.1016/j.revmic.2024.100789","DOIUrl":"10.1016/j.revmic.2024.100789","url":null,"abstract":"<div><p><span><span><span>This study presents the first data on radiolarian fauna from </span>Miocene deposits of the submarine Vityaz Ridge (SVR) and paraxial zone of the Kuril-Kamchatka </span>Trench. Twenty-two dredge samples were studied, and 214 radiolarian taxa were identified. Taxonomic composition allowed their assignment to Miocene assemblage zones, including </span><em>Lipmanella japonica conica-Gondwanaria dogieli, Pentactinosphaera hokurikuensis, Dendrospyris sakaii, Eucyrtidium inflatum</em> Subzone a, <em>Lychnocanoma magnacornuta</em>, and <em>Lychnocanoma parallelipes</em> zones. These radiolarian assemblages correlate with studied sequences of many deep-sea cores in the northern Pacific and some sections of onshore Japan. As a result, we designed a biostratigraphic scheme of Miocene radiolarians for the SVR and reconstructed the environmental conditions in this area. In particular, two Miocene climatic optima that were previously established in the northern Pacific were identified in the Middle and Upper Miocene sediments of the southern plateau and Middle Miocene sediments of the northern plateau of the SVR.</p></div>","PeriodicalId":45442,"journal":{"name":"REVUE DE MICROPALEONTOLOGIE","volume":"84 ","pages":"Article 100789"},"PeriodicalIF":0.7,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141963999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Organic walled dinoflagellate cyst biostratigraphy of the middle-late Miocene western Niger Delta, Nigeria 尼日利亚尼日尔三角洲西部中新世中晚期有机壁甲藻囊生物地层学
IF 0.7
REVUE DE MICROPALEONTOLOGIE Pub Date : 2024-05-21 DOI: 10.1016/j.revmic.2024.100787
{"title":"Organic walled dinoflagellate cyst biostratigraphy of the middle-late Miocene western Niger Delta, Nigeria","authors":"","doi":"10.1016/j.revmic.2024.100787","DOIUrl":"10.1016/j.revmic.2024.100787","url":null,"abstract":"<div><p><span>Palynological analysis of 200 ditch cuttings of wells M6 and M7 from the western Niger Delta yield a diverse assemblage of pollen, spores, freshwater algae, foraminiferal wall linings and dinoflagellate cysts<span>. Based on pollen and spore marker species, the wells date middle – late Miocene (P720-P860). The regular occurrence of dinoflagellate cysts enhances the subdivision of the sequences into eight and seven tentative dinoflagellate cysts assemblage zones for the M6 and M7 wells respectively. The proposed Niger Delta Dinoflagellate Cysts (C-I) zones are viz: the </span></span><em>Lingulodinium machaerophorum</em> Assemblage zone; <em>Homotryblium</em> spp./<em>Sumatradinium</em> spp. Assemblage zone; <em>Operculodinium centrocarpum</em> Assemblage zone; <em>Nematosphaeropsis labyrinthus</em> Assemblage zone; and the <em>Protoperidinium</em> spp./<em>Selenopemphix</em><span> spp. Assemblage zone. The boundaries are marked by remarkable dinocysts events such as first downhole occurrences or highest stratigraphic occurrences, supplemented with last downhole occurrences or lowest stratigraphic occurrences as the samples were ditch cuttings. The common presence of dinoflagellate cysts and the dominance of </span><em>Nematosphaeropsis labyrinthus</em> and <em>Impagidinium</em> spp. indicate open marine conditions during the deposition of the studied section.</p></div>","PeriodicalId":45442,"journal":{"name":"REVUE DE MICROPALEONTOLOGIE","volume":"84 ","pages":"Article 100787"},"PeriodicalIF":0.7,"publicationDate":"2024-05-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141144981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Radiolarian occurrence and origin of basaltic rocks in the Hebiki Unit, Northern Chichibu accretionary complex in the Kanto Mountains, Central Japan 日本中部关东山脉北秩父增生复合体 Hebiki 单元玄武岩中放射虫的出现和起源
IF 0.7
REVUE DE MICROPALEONTOLOGIE Pub Date : 2024-05-18 DOI: 10.1016/j.revmic.2024.100782
{"title":"Radiolarian occurrence and origin of basaltic rocks in the Hebiki Unit, Northern Chichibu accretionary complex in the Kanto Mountains, Central Japan","authors":"","doi":"10.1016/j.revmic.2024.100782","DOIUrl":"10.1016/j.revmic.2024.100782","url":null,"abstract":"<div><p><span>Reconstructing ocean plate stratigraphy (OPS) and revealing the places of origin and ages of oceanic rocks of the Jurassic–Early Cretaceous accretionary complex in Eastern Asia are important to clarify the accretion process and the paleogeography and </span>tectonic setting<span><span><span><span> of the Panthalassa Sea during the Paleozoic to Mesozoic times. In this context, many geological investigations of the Middle Jurassic–Early Cretaceous units of the Northern Chichibu accretionary complex (except for an Early Jurassic<span> one) and Mikabu Unit have been performed. In this study, geological mapping, faunal analysis of </span></span>radiolarians, and geochemical analysis of basaltic rocks were conducted for the Hebiki Unit of the Northern Chichibu accretionary complex to obtain prime geological information such as its stratigraphy, ages, and origin of basaltic rock. The Early Jurassic Hebiki Unit consists of chaotic mélange, which contains sandstone, siliceous shale, </span>chert, and basaltic rocks as blocks in a highly sheared shale matrix. Late </span>Permian<span><span><span> and Late Triassic radiolarians were newly identified from chert blocks in this study. Based on the radiolarian evidence from this study and previous ones that identified Jurassic radiolarians from siliceous shale, the OPS of the Hebiki Unit are reconstructed as follows: Upper Permian and Upper Triassic (upper </span>Carnian<span> to Rhaetian) chert, and Lower Jurassic (Pliensbachian) siliceous shale in ascending order. Meanwhile, the basaltic rocks of the Hebiki Unit are divided into two types in terms of the major and trace element composition and REE profiles: low and high Nb/Zr types. The low and high types are interpreted as oceanic island </span></span>basalt (OIB) and mid-ocean ridge basalt (MORB), respectively. Considering the reconstructed OPS of the four tectonostratigraphic units (Kashiwagi, Kamiyoshida, Sumaizuku, and Hebiki) of the Northern Chichibu accretionary complex, the four units are considered to have accreted successively.</span></span></p></div>","PeriodicalId":45442,"journal":{"name":"REVUE DE MICROPALEONTOLOGIE","volume":"84 ","pages":"Article 100782"},"PeriodicalIF":0.7,"publicationDate":"2024-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141140728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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