Spatial and temporal analysis of geographical biodiversity dynamics and reconstruction of species distribution areas are essential for revealing the patterns of evolution of graptolites and their survival strategies during bio-events. Over 800 occurrences of graptolites representing 84 species from five graptolite biozones (GB) through the interval of the end-Ordovician mass extinction ( from the late Katian Dicellograptus complexus GB up to the early Rhuddanian Akidograptus ascensus GB) coming from 60 localities in South China were integrated for this study. All earlier identifications of taxa were updated following a unified taxonomic scheme and their distribution presented in a biozone-level stratigraphic correlation framework. The distribution areas of 26 species occurring in the study interval were reconstructed using GIS software whereby the convex hull areas and maximum distribution distances were calculated. Based on variations in geographical distribution and the relationship with the end-Ordovician mass extinction, graptolite species can be divided into three evolutionary types: the background extinction type, the mass extinction type, and the origination type. The first and second types belong to Diplograptina, and the third one belongs to Neograptina. The analysis of the reduction rate in the geographic distribution of diplograptid species shows that the extinction event not only hit the mass extinction type taxa, but also impacted those of the background extinction type. It also shows that the original distribution area of selected species is not directly related to their extinction risk. Changes in distribution areas of the graptolite species indicate the replacement of neograptids for diplograptids during the end-Ordovician mass extinction. To study patterns and changes in the spatial distribution of graptolite fauna, quantitative analyses of species-level α -, β -diversity, and occurrences were performed. Our results demonstrate that the end-Ordovician extinction mainly affected graptolites in the offshore and low-energy areas. Meanwhile, the extinction not only led to a sudden decline in the total diversity, but also resulted in a significant change in the composition and geographic dif - ferentiation of the graptolite fauna. Cluster analysis demonstrates that, before the extinction, the graptolite fauna showed two different geographic clusters, which resulted from the hydrodynamic conditions rather than from the distance to the coastline. After the extinction, the fauna became highly similar all over the study area, from nearshore to offshore and from high-energy to low-energy environments, which were mainly comprised by widespread, eurytopic species all over South China.
{"title":"Biogeographic dynamics of graptolite species during the end-Ordovician mass extinction in South China","authors":"Qing Chen, Linna Zhang","doi":"10.3176/earth.2023.70","DOIUrl":"https://doi.org/10.3176/earth.2023.70","url":null,"abstract":"Spatial and temporal analysis of geographical biodiversity dynamics and reconstruction of species distribution areas are essential for revealing the patterns of evolution of graptolites and their survival strategies during bio-events. Over 800 occurrences of graptolites representing 84 species from five graptolite biozones (GB) through the interval of the end-Ordovician mass extinction ( from the late Katian Dicellograptus complexus GB up to the early Rhuddanian Akidograptus ascensus GB) coming from 60 localities in South China were integrated for this study. All earlier identifications of taxa were updated following a unified taxonomic scheme and their distribution presented in a biozone-level stratigraphic correlation framework. The distribution areas of 26 species occurring in the study interval were reconstructed using GIS software whereby the convex hull areas and maximum distribution distances were calculated. Based on variations in geographical distribution and the relationship with the end-Ordovician mass extinction, graptolite species can be divided into three evolutionary types: the background extinction type, the mass extinction type, and the origination type. The first and second types belong to Diplograptina, and the third one belongs to Neograptina. The analysis of the reduction rate in the geographic distribution of diplograptid species shows that the extinction event not only hit the mass extinction type taxa, but also impacted those of the background extinction type. It also shows that the original distribution area of selected species is not directly related to their extinction risk. Changes in distribution areas of the graptolite species indicate the replacement of neograptids for diplograptids during the end-Ordovician mass extinction. To study patterns and changes in the spatial distribution of graptolite fauna, quantitative analyses of species-level α -, β -diversity, and occurrences were performed. Our results demonstrate that the end-Ordovician extinction mainly affected graptolites in the offshore and low-energy areas. Meanwhile, the extinction not only led to a sudden decline in the total diversity, but also resulted in a significant change in the composition and geographic dif - ferentiation of the graptolite fauna. Cluster analysis demonstrates that, before the extinction, the graptolite fauna showed two different geographic clusters, which resulted from the hydrodynamic conditions rather than from the distance to the coastline. After the extinction, the fauna became highly similar all over the study area, from nearshore to offshore and from high-energy to low-energy environments, which were mainly comprised by widespread, eurytopic species all over South China.","PeriodicalId":50498,"journal":{"name":"Estonian Journal of Earth Sciences","volume":"43 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78739932","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}
T. Paton, P. McLaughlin, P. Emsbo, T. Vandenbroucke, C. Brett
{"title":"Upper Ordovician hardgrounds – from localized surfaces to global biogeochemical events","authors":"T. Paton, P. McLaughlin, P. Emsbo, T. Vandenbroucke, C. Brett","doi":"10.3176/earth.2023.77","DOIUrl":"https://doi.org/10.3176/earth.2023.77","url":null,"abstract":"","PeriodicalId":50498,"journal":{"name":"Estonian Journal of Earth Sciences","volume":"65 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73630223","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}
A. Morrison, A. Lefebvre, A. van Patter, A. Davis, M. Oelschlagel, N. Blamey, J. Jin, S. Riechelmann, U. Brand
{"title":"Drivers of the Late Ordovician Mass Extinction: redox, volcanism, atmospheric oxygen/carbon dioxide and/or glaciation","authors":"A. Morrison, A. Lefebvre, A. van Patter, A. Davis, M. Oelschlagel, N. Blamey, J. Jin, S. Riechelmann, U. Brand","doi":"10.3176/earth.2023.27","DOIUrl":"https://doi.org/10.3176/earth.2023.27","url":null,"abstract":"","PeriodicalId":50498,"journal":{"name":"Estonian Journal of Earth Sciences","volume":"41 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76285322","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}
The most extensive sea-level event of the Early Ordovician is known as the Evae transgression. During the highstand of this event, the conodont index species Oepikodus evae reached its acme and often coincided with the peak in conodont generic diversity. The main objective of this study is to statistically evaluate the degree of similarity in conodont species composition be tween the Argentine Precordillera, Laurentia, Baltica, Kazakhstania, South China, and Australia at that time. Cluster analysis shows two main faunal groups moderately to poorly differentiated, indicating that some paleogeographic barriers may not have decreased during the Evae trans gression. On the other hand, a paleolatitudinal control over the distribution of species is suspected, considering the occurrence of a higher number of species dwelling in mid-low lati tudes than in mid-latitudes. This suggests that this event could have been of a lesser magnitude or duration than previously claimed.
{"title":"The Evae transgression: a major event?","authors":"G. M. Della Costa, G. Albanesi","doi":"10.3176/earth.2023.79","DOIUrl":"https://doi.org/10.3176/earth.2023.79","url":null,"abstract":"The most extensive sea-level event of the Early Ordovician is known as the Evae transgression. During the highstand of this event, the conodont index species Oepikodus evae reached its acme and often coincided with the peak in conodont generic diversity. The main objective of this study is to statistically evaluate the degree of similarity in conodont species composition be tween the Argentine Precordillera, Laurentia, Baltica, Kazakhstania, South China, and Australia at that time. Cluster analysis shows two main faunal groups moderately to poorly differentiated, indicating that some paleogeographic barriers may not have decreased during the Evae trans gression. On the other hand, a paleolatitudinal control over the distribution of species is suspected, considering the occurrence of a higher number of species dwelling in mid-low lati tudes than in mid-latitudes. This suggests that this event could have been of a lesser magnitude or duration than previously claimed.","PeriodicalId":50498,"journal":{"name":"Estonian Journal of Earth Sciences","volume":"6 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75269479","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}
Depression of the ancient Lumparn meteorite impact structure in the Åland Islands is partly infilled with the lower Palaeozoic sediments, lying presently below sea level. The Cambrian and Ordovician sedimentary cover is distributed in the area of 15 km 2 , with a total thickness of up to 70 m. The Ordovician carbonate rocks of this site, known by the erratic boulders and by the drill ing project in the late 1950s, are particularly interesting because of the isolated distant position of this outlier from other distribution areas of the Ordovician sediments preserved in the Baltoscandian Palaeobasin. Ordovician sections in the Lumparn Bay are com posed of two distinct lithological units. The older, argillaceous wackestone-packstone unit has been tradi - tionally named ‘Orthoceras limestone‘ or ‘Orthoceratite Limestone’, and the younger micritic limestone unit is addressed as ‘Östersjö Limestone’ (or ‘Baltic Limestone’). Here we present new data on ostracod biostratigraphy and stable carbon isotope chemo - stratigraphy derived from three old drillcores from the Tranvik area of the Lumparn Bay. The comparison of ostracod distribution with its succession in Estonia generally supports the previous Darriwilian and Sandbian age interpretations for the Orthoceras Limestone. Considering the ostracod distribution together with earlier acritarch and conodont datings, stable carbon isotopic data and limestone lithology, the Orthoceras Limestone unit might correspond to the Kunda, Aseri, Lasnamägi, Uhaku, Kukruse, Haljala, and Keila regional stages (RSs). The Österjö Limestone comprises almost the entire Katian, corresponding to the Rakvere, Nabala, Vormsi and Pirgu RSs in the Baltoscandian stratigraphic chart. The uppermost sample yielded the most abundant and diverse assemblage of ostracods that suggests it to correspond to the Vormsi or lower-middle Pirgu (late Katian) RSs. The global Middle Darriwilian Carbon Isotopic Excursion ( MDICE ) and Guttenberg Carbon Isotopic Excursion ( GICE ) as well as the Katian Rakvere and Saunja carbon isotopic excursions are recorded in the studied succession. The δ 13 C carb bulk rock curve of the Orthoceras Limestone shows a positive excursion up to 1‰ in the lower part of the interval followed by a negative excursion up to –1‰ in the middle part and another positive excursion reaching 2‰ in the upper part of the interval. This curve resembles well the carbon isotope curve from the Darriwilian and Sandbian in the core sections of the Hiiumaa Island, NW Estonia, and could be interpreted as the MDICE and the rising limb of the GICE. The δ 13 C curve of the Östersjö Limestone interval shows two positive excursions. The lower one comprises most likely the peak of the Rakvere Excursion ( Rakvere RS ) in Estonia, which is also supported by the ostracod data. The upper carbon isotopic excursion may represent the Saunja Excursion correlated with the upper part of the Nabala RS. The ostracod biofacies characterized by faunal assoc
{"title":"Age of the Ordovician sedimentary succession in Lumparn Bay, Åland Islands, Finland","authors":"L. Ainsaar, T. Meidla","doi":"10.3176/earth.2023.01","DOIUrl":"https://doi.org/10.3176/earth.2023.01","url":null,"abstract":"Depression of the ancient Lumparn meteorite impact structure in the Åland Islands is partly infilled with the lower Palaeozoic sediments, lying presently below sea level. The Cambrian and Ordovician sedimentary cover is distributed in the area of 15 km 2 , with a total thickness of up to 70 m. The Ordovician carbonate rocks of this site, known by the erratic boulders and by the drill ing project in the late 1950s, are particularly interesting because of the isolated distant position of this outlier from other distribution areas of the Ordovician sediments preserved in the Baltoscandian Palaeobasin. Ordovician sections in the Lumparn Bay are com posed of two distinct lithological units. The older, argillaceous wackestone-packstone unit has been tradi - tionally named ‘Orthoceras limestone‘ or ‘Orthoceratite Limestone’, and the younger micritic limestone unit is addressed as ‘Östersjö Limestone’ (or ‘Baltic Limestone’). Here we present new data on ostracod biostratigraphy and stable carbon isotope chemo - stratigraphy derived from three old drillcores from the Tranvik area of the Lumparn Bay. The comparison of ostracod distribution with its succession in Estonia generally supports the previous Darriwilian and Sandbian age interpretations for the Orthoceras Limestone. Considering the ostracod distribution together with earlier acritarch and conodont datings, stable carbon isotopic data and limestone lithology, the Orthoceras Limestone unit might correspond to the Kunda, Aseri, Lasnamägi, Uhaku, Kukruse, Haljala, and Keila regional stages (RSs). The Österjö Limestone comprises almost the entire Katian, corresponding to the Rakvere, Nabala, Vormsi and Pirgu RSs in the Baltoscandian stratigraphic chart. The uppermost sample yielded the most abundant and diverse assemblage of ostracods that suggests it to correspond to the Vormsi or lower-middle Pirgu (late Katian) RSs. The global Middle Darriwilian Carbon Isotopic Excursion ( MDICE ) and Guttenberg Carbon Isotopic Excursion ( GICE ) as well as the Katian Rakvere and Saunja carbon isotopic excursions are recorded in the studied succession. The δ 13 C carb bulk rock curve of the Orthoceras Limestone shows a positive excursion up to 1‰ in the lower part of the interval followed by a negative excursion up to –1‰ in the middle part and another positive excursion reaching 2‰ in the upper part of the interval. This curve resembles well the carbon isotope curve from the Darriwilian and Sandbian in the core sections of the Hiiumaa Island, NW Estonia, and could be interpreted as the MDICE and the rising limb of the GICE. The δ 13 C curve of the Östersjö Limestone interval shows two positive excursions. The lower one comprises most likely the peak of the Rakvere Excursion ( Rakvere RS ) in Estonia, which is also supported by the ostracod data. The upper carbon isotopic excursion may represent the Saunja Excursion correlated with the upper part of the Nabala RS. The ostracod biofacies characterized by faunal assoc","PeriodicalId":50498,"journal":{"name":"Estonian Journal of Earth Sciences","volume":"63 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76606568","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}
Trilobites are organized in packages; the adult trilobite body plan is composed of a cephalon (head), thorax (midsection), and pygidium (tail). These packages, or modules, are composed of traits that evolve semi-independently such that change in one module does not necessarily beget change in another module. At the macroevolutionary level, this decoupling and relaxation of evolutionary constraints is thought to promote evolvability. Thus, it is thought that modularity facilitates rapid diversification in diverse evolutionary directions, the hallmark of an adaptive radiation, as evolutionary rates among modules can vary along phylogenetic branches. Trilobites provide an unmatched fossil record, due to their biomineralized exoskeleton, to examine the long-term relationship between macroevolutionary diversification and modularity. However, the lack of a phylogenetic framework for major trilobite groups hampers the study of macroevolutionary questions. For instance, the trilobite family Pterygometopidae diversified during the Middle and Late Ordovician in Baltica, Avalonia, Laurentia, and Siberia. This group traditionally comprises four subfamilies with strong biogeographic signal including Ptery - gometopinae, Chasmopinae, Eomonorachinae, and Monokainae. However, relationships between and within subfamilies remain unresolved. Further, relationships with other families in the sub - order Phacopina, especially with Phacopidae, remain unclear. To even begin tackling the relationship between macroevolution and modularity, phylo - genetic relationships must be resolved in this trilobite group. To do so, we constructed a comprehensive character matrix comprising >240 characters including discrete, meristic, and con - tinuous characters. Analyses include taxa from all 36 genera assigned to Pterygometopidae and include Ordovician exemplars from the trilobite families Diaphanome topidae, Phacopidae, Dalmanitidae, and Acastidae. We ran Bayesian phylogenetic analyses to produce trees that would co-estimate topology and evolutionary rates using the birth-death model. Further, we quantified the 3D morphology of the trilobite head using high-density geometric morphometrics for exemplar taxa within Pterygometopidae to identify the structure and degree of modularity of the trilobite head in this group. Future work will assess evolutionary rates for the trilobite head and, importantly, evolutionary rates of individual modules over the Ordovician Radiation to determine an increase or decrease in modularity over this diversification event.
{"title":"Phylogeny and evolutionary modularity of a trilobite family over the Ordovician Radiation","authors":"E. Vargas-Parra, M. Hopkins","doi":"10.3176/earth.2023.43","DOIUrl":"https://doi.org/10.3176/earth.2023.43","url":null,"abstract":"Trilobites are organized in packages; the adult trilobite body plan is composed of a cephalon (head), thorax (midsection), and pygidium (tail). These packages, or modules, are composed of traits that evolve semi-independently such that change in one module does not necessarily beget change in another module. At the macroevolutionary level, this decoupling and relaxation of evolutionary constraints is thought to promote evolvability. Thus, it is thought that modularity facilitates rapid diversification in diverse evolutionary directions, the hallmark of an adaptive radiation, as evolutionary rates among modules can vary along phylogenetic branches. Trilobites provide an unmatched fossil record, due to their biomineralized exoskeleton, to examine the long-term relationship between macroevolutionary diversification and modularity. However, the lack of a phylogenetic framework for major trilobite groups hampers the study of macroevolutionary questions. For instance, the trilobite family Pterygometopidae diversified during the Middle and Late Ordovician in Baltica, Avalonia, Laurentia, and Siberia. This group traditionally comprises four subfamilies with strong biogeographic signal including Ptery - gometopinae, Chasmopinae, Eomonorachinae, and Monokainae. However, relationships between and within subfamilies remain unresolved. Further, relationships with other families in the sub - order Phacopina, especially with Phacopidae, remain unclear. To even begin tackling the relationship between macroevolution and modularity, phylo - genetic relationships must be resolved in this trilobite group. To do so, we constructed a comprehensive character matrix comprising >240 characters including discrete, meristic, and con - tinuous characters. Analyses include taxa from all 36 genera assigned to Pterygometopidae and include Ordovician exemplars from the trilobite families Diaphanome topidae, Phacopidae, Dalmanitidae, and Acastidae. We ran Bayesian phylogenetic analyses to produce trees that would co-estimate topology and evolutionary rates using the birth-death model. Further, we quantified the 3D morphology of the trilobite head using high-density geometric morphometrics for exemplar taxa within Pterygometopidae to identify the structure and degree of modularity of the trilobite head in this group. Future work will assess evolutionary rates for the trilobite head and, importantly, evolutionary rates of individual modules over the Ordovician Radiation to determine an increase or decrease in modularity over this diversification event.","PeriodicalId":50498,"journal":{"name":"Estonian Journal of Earth Sciences","volume":"25 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89772265","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}
M. Nohejlová, C. Dupichaud, B. Lefebvre, E. Nardin, F. Saleh
{"title":"Echinoderm Lagerstätten from high-latitude Gondwana – filling the gap in the Ordovician diversification of the phylum","authors":"M. Nohejlová, C. Dupichaud, B. Lefebvre, E. Nardin, F. Saleh","doi":"10.3176/earth.2023.45","DOIUrl":"https://doi.org/10.3176/earth.2023.45","url":null,"abstract":"","PeriodicalId":50498,"journal":{"name":"Estonian Journal of Earth Sciences","volume":"11 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87690059","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}
Q. Li, L. Na, S. Yu, O. Lehnert, A. Munneck, L. Yue
{"title":"Late Ordovician beachrock as a far-field indicator for glacial meltwater pulse","authors":"Q. Li, L. Na, S. Yu, O. Lehnert, A. Munneck, L. Yue","doi":"10.3176/earth.2023.13","DOIUrl":"https://doi.org/10.3176/earth.2023.13","url":null,"abstract":"","PeriodicalId":50498,"journal":{"name":"Estonian Journal of Earth Sciences","volume":"5 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87900321","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}
The Borenshult-1 core, drilled in the vicinity of Motala, east of Lake Vättern in south central Sweden, comprises a well-dated and nearly complete succession of marine marly carbonates deposited relatively close to land. The 34 core samples analyzed for palynology encompass the upper part of the Darriwilian (Furudal Limestone), the entire Sandbian (Dalby Limestone, the Kinnekulle K-bentonite and the lower Skagen Limestone) and the lower part of the Katian (Skagen Limestone). The age of this interval is well-constrained to the late Darriwilian (Stage slice Dw3)– early Katian (Stage slice Ka1 ) , based on conodonts and 206Pb/238U dating of volcanic ash deposits. The samples yielded predominantly marine organic-walled phytoplankton, mainly acritarchs, with subordinate chitinozoans, scolecodonts and fragments of graptolites. Sparse terrestrial palynomorphs, represented by cryptospores and trilete spores, were also found in 23 of the samples. A total of 154 acritarch species corresponding to 53 genera were identified, as well as low percentages of abnormal forms ( teratological forms) of acritarch species at some levels. The strati graphic distribution of genera and species allowed for three palynological assemblages to be distinguished: Assemblage A of a late Darriwilian age, Assemblage B of a Sandbian age ( further subdivided into sub-assemblages B1 and B2 ) , and Assemblage C dated as Katian.
Borenshult-1岩心是在瑞典中南部Vättern湖以东的Motala附近钻探的，包含了一个年代久远、几乎完整的海相碳酸盐岩序列，它们沉积在相对靠近陆地的地方。孢粉学分析的34个岩心样品包括达里威廉(Furudal灰岩)上部、整个沙边(Dalby灰岩、Kinnekulle k -膨润土和下斯卡根灰岩)和卡田(Skagen灰岩)下部。根据牙形刺和火山灰沉积物的206Pb/238U定年，该层序的年龄很好地限定在达里威廉晚期(Dw3阶段)-卡天早期(Ka1阶段)。样品中主要有海洋有机壁浮游植物，主要是水螅类，次要有几丁质动物、棘刺类和笔石碎片。在23份样品中还发现了稀疏的陆生孢子，以隐孢子和三孢子为代表。共鉴定出53属154种，在某些层次上有较低的畸形形态(畸形形态)。属和种的地层分布可区分出3个孢粉组合:晚达里威廉时代的组合A、沙边时代的组合B(进一步细分为亚组合B1和B2)和卡天时代的组合C。
{"title":"Middle–Late Ordovician organic- walled phytoplankton from Sweden: diversity and early radiation","authors":"C. V. Rubinstein, V. Vajda","doi":"10.3176/earth.2023.42","DOIUrl":"https://doi.org/10.3176/earth.2023.42","url":null,"abstract":"The Borenshult-1 core, drilled in the vicinity of Motala, east of Lake Vättern in south central Sweden, comprises a well-dated and nearly complete succession of marine marly carbonates deposited relatively close to land. The 34 core samples analyzed for palynology encompass the upper part of the Darriwilian (Furudal Limestone), the entire Sandbian (Dalby Limestone, the Kinnekulle K-bentonite and the lower Skagen Limestone) and the lower part of the Katian (Skagen Limestone). The age of this interval is well-constrained to the late Darriwilian (Stage slice Dw3)– early Katian (Stage slice Ka1 ) , based on conodonts and 206Pb/238U dating of volcanic ash deposits. The samples yielded predominantly marine organic-walled phytoplankton, mainly acritarchs, with subordinate chitinozoans, scolecodonts and fragments of graptolites. Sparse terrestrial palynomorphs, represented by cryptospores and trilete spores, were also found in 23 of the samples. A total of 154 acritarch species corresponding to 53 genera were identified, as well as low percentages of abnormal forms ( teratological forms) of acritarch species at some levels. The strati graphic distribution of genera and species allowed for three palynological assemblages to be distinguished: Assemblage A of a late Darriwilian age, Assemblage B of a Sandbian age ( further subdivided into sub-assemblages B1 and B2 ) , and Assemblage C dated as Katian.","PeriodicalId":50498,"journal":{"name":"Estonian Journal of Earth Sciences","volume":"67 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90830188","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":"Chitinozoan nomenclature and databases","authors":"S. Camiña, O. Hints, A. Butcher","doi":"10.3176/earth.2023.21","DOIUrl":"https://doi.org/10.3176/earth.2023.21","url":null,"abstract":"","PeriodicalId":50498,"journal":{"name":"Estonian Journal of Earth Sciences","volume":"27 1","pages":""},"PeriodicalIF":1.1,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79661410","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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