S. Sasaki, T. Irizuki, T. Itaki, Y. Tokuda, T. Ishiwa, Y. Suganuma
Abstract. This study investigated the relationship between the distribution of modern ostracod biofacies and environmental factors in Lützow–Holm Bay, off Cape Darnley, and off Totten Glacier in East Antarctica. We collected study samples from water depths of 219 to 987 m by the 61st Japanese Antarctic Research Expedition. Nineteen species belonging to 13 genera and 47 species belonging to 31 genera of ostracods were found in three samples from Lützow–Holm Bay and ten samples from off Totten Glacier, respectively. We found no ostracods in the samples off Cape Darnley. Q-mode cluster analysis reveals four ostracod biofacies (A to D). Antarctiloxoconcha frigida (Neale, 1967) and Australicythere polylyca (Müller, 1908) were common under the influence of cold water in the upper bathyal zone (biofacies A to C). The genus Krithe was the most abundant taxon in biofacies D with low dissolved oxygen and high-water temperature (0.38°C, 34.66, and 5.0 ml/L, respectively), indicating the presence of warm deep seawater, i.e., modified Circumpolar Deep Water. Thus, we have checked the relationships between the ostracod assemblages and the environmental parameters analyzed in Lützow–Holm Bay and off Totten Glacier, and so strengthened the previous ostracod and environmental data.
{"title":"Relationship between Modern Deep-Sea Ostracods and Water Mass Structure in East Antarctica","authors":"S. Sasaki, T. Irizuki, T. Itaki, Y. Tokuda, T. Ishiwa, Y. Suganuma","doi":"10.2517/PR210033","DOIUrl":"https://doi.org/10.2517/PR210033","url":null,"abstract":"Abstract. This study investigated the relationship between the distribution of modern ostracod biofacies and environmental factors in Lützow–Holm Bay, off Cape Darnley, and off Totten Glacier in East Antarctica. We collected study samples from water depths of 219 to 987 m by the 61st Japanese Antarctic Research Expedition. Nineteen species belonging to 13 genera and 47 species belonging to 31 genera of ostracods were found in three samples from Lützow–Holm Bay and ten samples from off Totten Glacier, respectively. We found no ostracods in the samples off Cape Darnley. Q-mode cluster analysis reveals four ostracod biofacies (A to D). Antarctiloxoconcha frigida (Neale, 1967) and Australicythere polylyca (Müller, 1908) were common under the influence of cold water in the upper bathyal zone (biofacies A to C). The genus Krithe was the most abundant taxon in biofacies D with low dissolved oxygen and high-water temperature (0.38°C, 34.66, and 5.0 ml/L, respectively), indicating the presence of warm deep seawater, i.e., modified Circumpolar Deep Water. Thus, we have checked the relationships between the ostracod assemblages and the environmental parameters analyzed in Lützow–Holm Bay and off Totten Glacier, and so strengthened the previous ostracod and environmental data.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"27 1","pages":"211 - 230"},"PeriodicalIF":0.9,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47374631","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}
Abstract. The Isanacetus-group is one of the most enigmatic groups of cetaceans. Although their phylogeny is still controversial, many previous studies suggested that they are a paraphyletic group of baleen whales, including an ancestor of Balaenopteridae and Eschrichtiidae. A new fossil from an Isanacetus-group baleen whale has been recovered from the Minamishirado Formation (latest early Miocene, Burdigalian), Iwaki, Fukushima Prefecture, Japan. The specimen consists of a cranium, mandible, and postcranial elements, including cervical, thoracic, and lumbar vertebrae, scapula, ulna, and ribs. We describe and diagnose the specimen as a new genus and species, Jobancetus pacificus. A unique combination of morphological characters characterized the specimen, e.g. frontals forming a triangular elevated plateau at the vertex, sharp, and well-developed transverse crest on the supraorbital process of frontal, sagittal crest formed by frontals and parietals, and large squamosal fossa, which is posteriorly extended well beyond the level of the posterior surface of the occipital condyle. Phylogenetic analysis under equal weighting suggests that J. pacificus is a stem group of Pligogulae, whereas the phylogenetic analyses under implied weightings suggest that J. pacificus is a stem group of Balaenopteridae + Eschrichtiidae. The discovery of J. pacificus expands our knowledge of the enigmatic Isanacetus-group.
{"title":"A New Species of Baleen Whale (Isanacetus-Group) from the Early Miocene, Japan","authors":"T. Kimura, Y. Hasegawa, Tadashi Suzuki","doi":"10.2517/PR210009","DOIUrl":"https://doi.org/10.2517/PR210009","url":null,"abstract":"Abstract. The Isanacetus-group is one of the most enigmatic groups of cetaceans. Although their phylogeny is still controversial, many previous studies suggested that they are a paraphyletic group of baleen whales, including an ancestor of Balaenopteridae and Eschrichtiidae. A new fossil from an Isanacetus-group baleen whale has been recovered from the Minamishirado Formation (latest early Miocene, Burdigalian), Iwaki, Fukushima Prefecture, Japan. The specimen consists of a cranium, mandible, and postcranial elements, including cervical, thoracic, and lumbar vertebrae, scapula, ulna, and ribs. We describe and diagnose the specimen as a new genus and species, Jobancetus pacificus. A unique combination of morphological characters characterized the specimen, e.g. frontals forming a triangular elevated plateau at the vertex, sharp, and well-developed transverse crest on the supraorbital process of frontal, sagittal crest formed by frontals and parietals, and large squamosal fossa, which is posteriorly extended well beyond the level of the posterior surface of the occipital condyle. Phylogenetic analysis under equal weighting suggests that J. pacificus is a stem group of Pligogulae, whereas the phylogenetic analyses under implied weightings suggest that J. pacificus is a stem group of Balaenopteridae + Eschrichtiidae. The discovery of J. pacificus expands our knowledge of the enigmatic Isanacetus-group.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"27 1","pages":"85 - 101"},"PeriodicalIF":0.9,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49348100","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}
Hirochika Ueda, Y. Sakai, M. Manabe, T. Tsuihiji, S. Isaji, Masatoshi Okura
Abstract. An isolated theropod tooth was found in the Hauterivian–Barremian Itsuki Formation of the Tetori Group in the Kuzuryu district, Ono City, Fukui Prefecture, central Japan. The present specimen, OMFJ V-1, shows a thick lanceolate basal cross-section and small mesial and distal denticles. A cladistic analysis based on the dental characters suggested that OMFJ V-1 be classified as belonging to Allosauroidea or Tyrannosauroidea. Principal component and linear discriminant analyses also suggested that OMFJ V-1 belongs to either of these two theropod clades. The posterior probabilities obtained in the linear discriminant analyses indicated that the confidence of the classification as Allosauroidea is slightly higher than that for Tyrannosauridae. However, because these analyses also supported possibilities of OMFJ V-1 belonging to other theropod clades to lesser extents, its taxonomic referral remains ambiguous. If OMFJ V-1 belongs to Tyrannosauroidea, it would indicate that a medium-sized tyrannosauroid already appeared in central Japan during the Hauterivian–Barremian age. On the other hand, if OMFJ V-1 belongs to Allosauroidea, it would indicate that at least two medium-to-large-sized theropods, allosaurids and tyrannosaurids, lived almost coevally in this region. The third possibility is that OMFJ V-1 belongs to Megaraptora. If such affinities are established, it would represent the oldest record of this clade of theropods.
{"title":"Morphometric and Cladistic Analyses of a Theropod Tooth from the Itsuki Formation of the Tetori Group in the Kuzuryu District, Ono City, Fukui Prefecture, Japan","authors":"Hirochika Ueda, Y. Sakai, M. Manabe, T. Tsuihiji, S. Isaji, Masatoshi Okura","doi":"10.2517/PR210002","DOIUrl":"https://doi.org/10.2517/PR210002","url":null,"abstract":"Abstract. An isolated theropod tooth was found in the Hauterivian–Barremian Itsuki Formation of the Tetori Group in the Kuzuryu district, Ono City, Fukui Prefecture, central Japan. The present specimen, OMFJ V-1, shows a thick lanceolate basal cross-section and small mesial and distal denticles. A cladistic analysis based on the dental characters suggested that OMFJ V-1 be classified as belonging to Allosauroidea or Tyrannosauroidea. Principal component and linear discriminant analyses also suggested that OMFJ V-1 belongs to either of these two theropod clades. The posterior probabilities obtained in the linear discriminant analyses indicated that the confidence of the classification as Allosauroidea is slightly higher than that for Tyrannosauridae. However, because these analyses also supported possibilities of OMFJ V-1 belonging to other theropod clades to lesser extents, its taxonomic referral remains ambiguous. If OMFJ V-1 belongs to Tyrannosauroidea, it would indicate that a medium-sized tyrannosauroid already appeared in central Japan during the Hauterivian–Barremian age. On the other hand, if OMFJ V-1 belongs to Allosauroidea, it would indicate that at least two medium-to-large-sized theropods, allosaurids and tyrannosaurids, lived almost coevally in this region. The third possibility is that OMFJ V-1 belongs to Megaraptora. If such affinities are established, it would represent the oldest record of this clade of theropods.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"27 1","pages":"51 - 72"},"PeriodicalIF":0.9,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41501228","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}
Abstract. A new Miocene phidoloporid, Iodictyum akaishiensis sp. nov., was collected from the Moniwa Formation (Langhian) near the Akaishi Bridge, Sendai City, Japan. It is the first fossil record of Iodictyum in Japan, and the fifth discovery of Miocene fossils of the genus from the Indo-Pacific area. The species resembles some Recent species from the western Pacific, especially in the large marginal pores, an open peristomial sinus and shaft, and subtriangular ooecial labellum. The characteristics of Iodictyum from Eocene to Recent are compared, and the trend of evolution in the genus is inferred.
{"title":"Iodictyum akaishiensis sp. nov.: A New Miocene Phidoloporid (Bryozoa, Cheilostomata) from the Moniwa Formation, Sendai, Japan","authors":"S. Arakawa","doi":"10.2517/PR200041","DOIUrl":"https://doi.org/10.2517/PR200041","url":null,"abstract":"Abstract. A new Miocene phidoloporid, Iodictyum akaishiensis sp. nov., was collected from the Moniwa Formation (Langhian) near the Akaishi Bridge, Sendai City, Japan. It is the first fossil record of Iodictyum in Japan, and the fifth discovery of Miocene fossils of the genus from the Indo-Pacific area. The species resembles some Recent species from the western Pacific, especially in the large marginal pores, an open peristomial sinus and shaft, and subtriangular ooecial labellum. The characteristics of Iodictyum from Eocene to Recent are compared, and the trend of evolution in the genus is inferred.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"27 1","pages":"25 - 33"},"PeriodicalIF":0.9,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49620885","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}
Abstract. The Paleozoic Era experienced 4 major mass extinctions; i.e., end-Ordovician, Late Devonian, end-Guadalupian, and end-Permian episodes. As a cause of significant biodiversity decline, non-biological environmental change on global scale was inevitable; nonetheless, popular claims of bolide impact and/or large igneous province (LIP) with too many ad-hoc assumptions have not yet been accepted as common/universal explanations for the Paleozoic extinctions. Recent research on extinction causes evolved through two stages; i.e., the heyday of the bolide impact scenario in the 1980s, and the overtaking by a LIP-mantle plume scenario in the 1990–2000s. Lately, we may sense a return trend to extraterrestrial causes since the late 2000s, which is not a simple revival of the old bolide-impact model but a new proposal for a cosmoclimatological scenario relevant to extra-solar processes; i.e., supernovae explosions and relevant migration of dark clouds over the Solar System. This short article reviews the current status of extinction-related research, which emphasizes two key issues; i.e., the categorization of extinction causes and new perspectives on non-bolide extraterrestrial causes. The categorizing of extinction causes at four distinct levels is effective in separating “global triggers” on the Earth's surface from more essential “ultimate cases” within the Earth and/or on outside of the planet. Causes of extinction can be grouped into four distinct categories in a hierarchy, from small to large scale: i.e., Category 1 – direct kill mechanism for each local biota, Category 2 – background change in global environment, Category 3 – major geological phenomenon on the planet's surface, and Category 4 – ultimate cause from the interior and exterior of the planet. Recent advances in He isotope analysis for extinction-related sedimentary records suggest extraterrestrial causes, not of bolide impact but of the encounter with a dark cloud (nebula). Emerging new perspectives of cosmoclimatology leads to an alternative extinction scenario; e.g. 1) increased flux of galactic cosmic radiation (GCR) with extensive cloud cover and 2) passage of a dark cloud (nebula) enriched with micro-dusts (IDPs) enveloping the Solar System. Both meteoric cloud coverage and IDP-screen can induce lowering/shutdown of solar irradiance, which may drive global cooling and sea-level drop associated with biodiversity decline. The past star-burst events detected in the Milky Way Galaxy apparently coincide in timing with the cooling episodes associated with major extinctions of the Paleozoic, i.e., at the end-Ordovician, Late Devonian, and Late Permian. Given such astronomical processes associated with global cooling in the past, much older global freezing episodes, i.e., Proterozoic snowball Earth events developed under high atmospheric CO2 levels, can be likewise explained. The study of mass extinctions on the Earth is entering a new stage under new astrobiological perspectives.
{"title":"Paleozoic Extinctions in Cosmoclimatological Context: ‘Non-Bolide’ Extraterrestrial Causes for Global Chilling","authors":"Y. Isozaki","doi":"10.2517/PRS220002","DOIUrl":"https://doi.org/10.2517/PRS220002","url":null,"abstract":"Abstract. The Paleozoic Era experienced 4 major mass extinctions; i.e., end-Ordovician, Late Devonian, end-Guadalupian, and end-Permian episodes. As a cause of significant biodiversity decline, non-biological environmental change on global scale was inevitable; nonetheless, popular claims of bolide impact and/or large igneous province (LIP) with too many ad-hoc assumptions have not yet been accepted as common/universal explanations for the Paleozoic extinctions. Recent research on extinction causes evolved through two stages; i.e., the heyday of the bolide impact scenario in the 1980s, and the overtaking by a LIP-mantle plume scenario in the 1990–2000s. Lately, we may sense a return trend to extraterrestrial causes since the late 2000s, which is not a simple revival of the old bolide-impact model but a new proposal for a cosmoclimatological scenario relevant to extra-solar processes; i.e., supernovae explosions and relevant migration of dark clouds over the Solar System. This short article reviews the current status of extinction-related research, which emphasizes two key issues; i.e., the categorization of extinction causes and new perspectives on non-bolide extraterrestrial causes. The categorizing of extinction causes at four distinct levels is effective in separating “global triggers” on the Earth's surface from more essential “ultimate cases” within the Earth and/or on outside of the planet. Causes of extinction can be grouped into four distinct categories in a hierarchy, from small to large scale: i.e., Category 1 – direct kill mechanism for each local biota, Category 2 – background change in global environment, Category 3 – major geological phenomenon on the planet's surface, and Category 4 – ultimate cause from the interior and exterior of the planet. Recent advances in He isotope analysis for extinction-related sedimentary records suggest extraterrestrial causes, not of bolide impact but of the encounter with a dark cloud (nebula). Emerging new perspectives of cosmoclimatology leads to an alternative extinction scenario; e.g. 1) increased flux of galactic cosmic radiation (GCR) with extensive cloud cover and 2) passage of a dark cloud (nebula) enriched with micro-dusts (IDPs) enveloping the Solar System. Both meteoric cloud coverage and IDP-screen can induce lowering/shutdown of solar irradiance, which may drive global cooling and sea-level drop associated with biodiversity decline. The past star-burst events detected in the Milky Way Galaxy apparently coincide in timing with the cooling episodes associated with major extinctions of the Paleozoic, i.e., at the end-Ordovician, Late Devonian, and Late Permian. Given such astronomical processes associated with global cooling in the past, much older global freezing episodes, i.e., Proterozoic snowball Earth events developed under high atmospheric CO2 levels, can be likewise explained. The study of mass extinctions on the Earth is entering a new stage under new astrobiological perspectives.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"27 1","pages":"14 - 24"},"PeriodicalIF":0.9,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47885790","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}
This is the Part 2 of the thematic issue; Part 1 was published in Paleontological Research (PR) vol. 25 in 2021. Part 2 adds two more articles that introduce new views and concepts for Paleozoic paleontology, i.e., one for Early-Middle Paleozoic microfossil studies from the long-term terra incognito, central Asia, and the other for essential reconsideration of the causes for the Phanerozoic major extinctions from a non-conventional cosmoclimatology viewpoint. Obut (2023) introduces the latest knowledge on Early Paleozoic micropaleontology from Siberia where precious pieces of information are potentially archived for the lost ocean called the Paleo-Asian Ocean. In addition to classic fossils, such as graptolites and trilobites, a long list of conodonts and radiolarians recently became available from cherts, mudstones, and some limestones. These new fossil data provide prime clues for reconstructing the biogeographic provinciality and geotectonic setting of the Paleo-Asian Ocean. It is noteworthy that the essential research scheme for those ancient mid-oceanic sediments was imported from Japan (e.g. Buslov and Watanabe, 1996; Iwata et al., 1997; Uchio et al., 2004; Ota et al., 2007), and thus is highly suitable for publication in PR. Isozaki (2023) reviews studies on the causes of the Phanerozoic mass extinctions, emphasizing the categorization of previously proposed causes into four distinct groups (see Isozaki, 2019). Besides the currently widely discussed possible causes, such as bolide impact and a large igneous province, a new possibility—non-bolide extraterrestrial effects—is explored on the basis of the astrophysical observations of galaxies (e.g. Rocha-Pinto et al., 2000; Ruiz-Lara et al., 2020) and a new line of material evidence from deep-sea cherts in Japan. The latest finding of an unusually high helium isotope ratio (3He/4He) from the Permo-Triassic boundary extinction interval (Onoue et al., 2019; Takahata et al., 2019) suggests that our Solar System had encountered a dark cloud and that abundant interplanetary dust particles have Theme Issue “Renaissance for Paleozoic evolution studies: radiation and extinction”: Preface for Part 2
这是主题问题的第二部分;第一部分于2021年发表在《古生物研究》(PR)第25卷。第二部分增加了两篇文章，介绍了古生代古生物学的新观点和新概念，即一篇是关于中亚长期未被发现的早-中古生代微化石研究，另一篇是从非传统的宇宙气候学角度对显生代大灭绝的原因进行了必要的重新思考。Obut(2023)介绍了西伯利亚早古生代微古生物学的最新知识，在那里，宝贵的信息有可能被存档，用于被称为古亚洲海洋的失落海洋。除了笔石和三叶虫等经典化石外，最近从燧石、泥岩和一些石灰石中发现了一长串牙形刺和放射虫化石。这些新的化石资料为重建古亚洲海洋的生物地理区域和大地构造背景提供了重要线索。值得注意的是，这些古中大洋沉积物的基本研究方案是从日本引进的(例如Buslov和Watanabe, 1996;Iwata等人，1997;Uchio et al.， 2004;Ota et al.， 2007)，因此非常适合在PR上发表。Isozaki(2023)回顾了显生宙大灭绝原因的研究，强调将先前提出的原因分为四个不同的组(见Isozaki, 2019)。除了目前广泛讨论的可能原因，如火成岩撞击和大火成岩省，在星系天体物理观测的基础上，探索了一种新的可能性-非火成岩地外效应(如Rocha-Pinto et al.， 2000;Ruiz-Lara et al.， 2020)以及来自日本深海燧石的新材料证据。在二叠纪-三叠纪边界灭绝区间发现异常高氦同位素比率(3He/4He)的最新发现(Onoue et al.， 2019;Takahata et al.， 2019)表明我们的太阳系遇到了一团黑云，并且大量的行星际尘埃粒子。主题议题“古生代进化研究的复兴:辐射和灭绝”:第2部分的序言
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Khadijeh Changaei, S. Babazadeh, M. Arian, Borzou Asgari Pirbaloti
Abstract. The Jahrum Formation is characterized by abundant benthic Foraminifera in carbonate beds, partly marly and dolomitic limestones in the Kuh-e-Soukhteh (Shahrekord region). This formation covers a huge stretch of the Zagros Zone which is a part of the central Tethyian realm during the Paleogene time. Bio-stratigraphic analysis of the larger benthic Foraminifera distinguishes one assemblage zone assigned to the late middle Eocene (Bartonian). This new biostratigraphic range is represented by the index fossil Rhabdorites malatyaensis (Sirel) and is correlated with calcareous rocks in the Shiraz area (south Iran), Dhofar section (Oman), and Socotra Island (Yemen). The Jahrum Formation is dominated by rich miliolids-agglutinated Foraminifera with rare small rotaliids and without Nummulites Lamarck and Alveolina d'Orbigny indicating that the formation was deposited in a shallow water environment (nearshore lagoonal zone) with low energy.
{"title":"Systematic Paleontology of Bartonian Larger Benthic Foraminifera from Shahrekord Region in High Zagros, Iran","authors":"Khadijeh Changaei, S. Babazadeh, M. Arian, Borzou Asgari Pirbaloti","doi":"10.2517/PR200055","DOIUrl":"https://doi.org/10.2517/PR200055","url":null,"abstract":"Abstract. The Jahrum Formation is characterized by abundant benthic Foraminifera in carbonate beds, partly marly and dolomitic limestones in the Kuh-e-Soukhteh (Shahrekord region). This formation covers a huge stretch of the Zagros Zone which is a part of the central Tethyian realm during the Paleogene time. Bio-stratigraphic analysis of the larger benthic Foraminifera distinguishes one assemblage zone assigned to the late middle Eocene (Bartonian). This new biostratigraphic range is represented by the index fossil Rhabdorites malatyaensis (Sirel) and is correlated with calcareous rocks in the Shiraz area (south Iran), Dhofar section (Oman), and Socotra Island (Yemen). The Jahrum Formation is dominated by rich miliolids-agglutinated Foraminifera with rare small rotaliids and without Nummulites Lamarck and Alveolina d'Orbigny indicating that the formation was deposited in a shallow water environment (nearshore lagoonal zone) with low energy.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"27 1","pages":"73 - 84"},"PeriodicalIF":0.9,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47767924","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}
Abstract. The mountainous Gorny Altai in southern Siberia constitutes the western part of the Altai–Sayan Folded Belt in the northwestern part of the Central Asian orogenic belt, which contains precious records of the lost major Proterozoic–Paleozoic ocean called the Paleo-Asian Ocean (PAO). This paper briefly introduces the latest microfossil (radiolarian and conodont) information recovered from the Lower Paleozoic siliceous and carbonate sequences of the Gorny Altai. The fossils of planktonic biota inhabited in PAO range back to the early Cambrian, in which the world's oldest radiolarians are included. In addition, numerous well-preserved conodonts as well as graptolites were recovered from Cambrian, Ordovician, and Silurian strata in the Gorny Altai. These recorded the Early Paleozoic biodiversity and their secular change both in pelagic and continental margin settings within PAO.
{"title":"Early Paleozoic Plankton Evolution in the Paleo-Asian Ocean: Insights from New and Reviewed Fossil Records from the Gorny Altai, West Siberia","authors":"O. Obut","doi":"10.2517/PR210035","DOIUrl":"https://doi.org/10.2517/PR210035","url":null,"abstract":"Abstract. The mountainous Gorny Altai in southern Siberia constitutes the western part of the Altai–Sayan Folded Belt in the northwestern part of the Central Asian orogenic belt, which contains precious records of the lost major Proterozoic–Paleozoic ocean called the Paleo-Asian Ocean (PAO). This paper briefly introduces the latest microfossil (radiolarian and conodont) information recovered from the Lower Paleozoic siliceous and carbonate sequences of the Gorny Altai. The fossils of planktonic biota inhabited in PAO range back to the early Cambrian, in which the world's oldest radiolarians are included. In addition, numerous well-preserved conodonts as well as graptolites were recovered from Cambrian, Ordovician, and Silurian strata in the Gorny Altai. These recorded the Early Paleozoic biodiversity and their secular change both in pelagic and continental margin settings within PAO.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"27 1","pages":"3 - 13"},"PeriodicalIF":0.9,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48682177","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}
Abstract. The Baghamshah Formation was previously assigned to Jurassic age in Iran, based on stratigraphic distribution of ammonites. But, recent studies of calcareous nannofossils in the Lut Block show that the age of this formation should be assigned to the Early Cretaceous (early Berriasian to early Barremian). This study analyzed stratigraphic distribution of calcareous nannofossils of the Baghamshah Formation in the Esfandiar section located in the southeast of the Tabas Block (close to the type section). Examinination of samples identified 39 calcareous nannofossil and 6 didemnid ascidian spicules species belonging to 19 genera, corresponding from CC1 to CC5 biozones with the age of early Berriasian to early Barremian. Index nannofossil species in the succession indicate that the sedimentary basin of the Baghamshah Formation in the Esfandiar section was located in low latitudes of the Tethyan realm with warm surface water toward the top of the section. Also, the oceanic basin was an oligotrophic type with low-fertility, as its nutrient supply dropped toward the top of the section. The oligotrophic paleoenvironment during the late Berriasian to early Valanginian in the study area in eastern Iran may have corresponded to a global low sea-level.
{"title":"Early Berriasian to Early Barremian Calcareous Nannofossils Biostratigraphy and Paleoecology of Baghamshah Formation (Esfandiar Section, Tabas Block), Eastern Iran","authors":"Ensieh Behdani, F. Hadavi, M. N. Moghaddam","doi":"10.2517/PR200018","DOIUrl":"https://doi.org/10.2517/PR200018","url":null,"abstract":"Abstract. The Baghamshah Formation was previously assigned to Jurassic age in Iran, based on stratigraphic distribution of ammonites. But, recent studies of calcareous nannofossils in the Lut Block show that the age of this formation should be assigned to the Early Cretaceous (early Berriasian to early Barremian). This study analyzed stratigraphic distribution of calcareous nannofossils of the Baghamshah Formation in the Esfandiar section located in the southeast of the Tabas Block (close to the type section). Examinination of samples identified 39 calcareous nannofossil and 6 didemnid ascidian spicules species belonging to 19 genera, corresponding from CC1 to CC5 biozones with the age of early Berriasian to early Barremian. Index nannofossil species in the succession indicate that the sedimentary basin of the Baghamshah Formation in the Esfandiar section was located in low latitudes of the Tethyan realm with warm surface water toward the top of the section. Also, the oceanic basin was an oligotrophic type with low-fertility, as its nutrient supply dropped toward the top of the section. The oligotrophic paleoenvironment during the late Berriasian to early Valanginian in the study area in eastern Iran may have corresponded to a global low sea-level.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"27 1","pages":"34 - 50"},"PeriodicalIF":0.9,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42695239","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}
Abstract. Four sediment samples were collected from an outcrop of the Holocene-raised beach in Skarvsnes (Lützow-Holm Bay, East Antarctica) at an elevation of 0–10 m through a geomorphological survey conducted during the 46th Japanese Antarctic Research Expedition (JARE 46). These samples were used for grain size, CNS (carbon, nitrogen, and sulfur) elemental, and ostracod analyses. The 14C dating of an annelid tube collected from the same outcrop was also conducted using an accelerator mass spectrometry. The resultant age was estimated at approximately 5,800 cal. year BP. A total of 16 ostracod species belonging to 10 genera were identified for the first time from all study samples near Lake Suribachi-Ike, Lützow–Holm Bay, East Antarctica. The phytal species were found to be the most dominant, suggesting rich seagrass and/or seaweeds at that time. Autecological methods and modern analog technique of ostracod assemblages were used to estimate the paleoenvironment. The result from the modern analog technique suggested that the paleo-water depth of approximately 30 m at that time is the most probable estimation, implying the glacial-isostatic uplift of approximately 30–40 m (5.1–6.8 mm/year) until sample date.
摘要第46次日本南极科考(JARE 46)在海拔0 ~ 10 m的Skarvsnes (l佐-霍尔姆湾)全新世隆起海滩露头进行了地貌调查，收集了4个沉积物样本。这些样品用于晶粒尺寸，CNS(碳，氮，硫)元素和介形虫分析。从同一露头处收集的环节动物管也使用加速器质谱法进行了14C测年。由此得出的年龄估计约为5800 cal. year BP。在东南极洲l zow - holm湾suribachii - ike湖附近的所有研究样本中，首次鉴定出16种介形虫，隶属于10属。植物种类是最占优势的，表明当时海草和/或海藻丰富。利用现代介形虫组合模拟技术和古生物学方法对古环境进行了估算。现代模拟技术的结果表明，当时的古水深约为30 m是最可能的估计，这意味着到样品日期为止，冰川均衡隆起约为30 - 40 m (5.1-6.8 mm/年)。
{"title":"Ostracoda and Paleoenvironment of Holocene-Raised Beach Sediment in Skarvsnes, East Antarctica","authors":"S. Sasaki, T. Irizuki, K. Seto, Y. Suganuma","doi":"10.2517/PR210011","DOIUrl":"https://doi.org/10.2517/PR210011","url":null,"abstract":"Abstract. Four sediment samples were collected from an outcrop of the Holocene-raised beach in Skarvsnes (Lützow-Holm Bay, East Antarctica) at an elevation of 0–10 m through a geomorphological survey conducted during the 46th Japanese Antarctic Research Expedition (JARE 46). These samples were used for grain size, CNS (carbon, nitrogen, and sulfur) elemental, and ostracod analyses. The 14C dating of an annelid tube collected from the same outcrop was also conducted using an accelerator mass spectrometry. The resultant age was estimated at approximately 5,800 cal. year BP. A total of 16 ostracod species belonging to 10 genera were identified for the first time from all study samples near Lake Suribachi-Ike, Lützow–Holm Bay, East Antarctica. The phytal species were found to be the most dominant, suggesting rich seagrass and/or seaweeds at that time. Autecological methods and modern analog technique of ostracod assemblages were used to estimate the paleoenvironment. The result from the modern analog technique suggested that the paleo-water depth of approximately 30 m at that time is the most probable estimation, implying the glacial-isostatic uplift of approximately 30–40 m (5.1–6.8 mm/year) until sample date.","PeriodicalId":54645,"journal":{"name":"Paleontological Research","volume":"26 1","pages":"440 - 454"},"PeriodicalIF":0.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41407813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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