Julien Richirt, M. Schweizer, A. Mouret, Sophie Quinchard, Salha A. Saad, V. Bouchet, C. Wade, F. Jorissen
Abstract. Ammonia is one of the most widespread foraminiferal genera worldwide. Three phylotypes (Ammonia sp. T1, T2 and T6), commonly encountered in the northeast Atlantic, are usually associated with the morphospecies Ammonia tepida. The biogeographic distribution of these three types was previously investigated in coastal environments around Great Britain based on genetic assignations. A new method was recently developed to recognize these three phylotypes based on morphological criteria (i.e. pore size and suture elevation on spiral side), avoiding the need to use molecular analyses to identify them. The results presented here allow us to validate the consistency of the morphometric determination method but also to define more precisely the pore size variability of each of the three phylotypes, which is a main criterion for their recognition. Moreover, these results, combined with earlier molecular and morphological data, enable us to refine the biogeographic distribution previously established by genetic analyses alone. The biogeographical distribution pattern presented here supports the putatively invasive character of Ammonia sp. T6, by suggesting that this phylotype is currently spreading out over large areas and is supplanting autochthonous phylotypes (T1 and T2) along the coastlines of the British Isles and northern France. In fact, only the southwest coast of England and Ireland and the northwest coast of France have not been colonized by Ammonia sp. T6 yet. Our results also suggest that within the areas colonized by phylotype T6, T2 may find refuges in the inner parts of estuaries. We further suggest that the absence of Ammonia sp. T6 in the western part of the English Channel may be explained by the general surface current circulation pattern, which impedes further expansion. The high reliability of the determination method of phylotypes T1, T2 and T6 based on morphology also allows us to quickly generate large datasets for sub-recent and fossil material. This new method will make it possible to gain an understanding of the ecological differences between the three phylotypes and of the historical changes in their distribution patterns (for example due to changing anthropogenic factors). Finally, it will allow us to confirm or invalidate the putative invasive character of phylotype T6.
{"title":"Biogeographic distribution of three phylotypes (T1, T2 and T6) of Ammonia (foraminifera, Rhizaria) around Great Britain: new insights from combined molecular and morphological recognition","authors":"Julien Richirt, M. Schweizer, A. Mouret, Sophie Quinchard, Salha A. Saad, V. Bouchet, C. Wade, F. Jorissen","doi":"10.5194/JM-40-61-2021","DOIUrl":"https://doi.org/10.5194/JM-40-61-2021","url":null,"abstract":"Abstract. Ammonia is one of the most widespread foraminiferal genera\u0000worldwide. Three phylotypes (Ammonia sp. T1, T2 and T6), commonly encountered in\u0000the northeast Atlantic, are usually associated with the morphospecies\u0000Ammonia tepida. The biogeographic distribution of these three types was previously\u0000investigated in coastal environments around Great Britain based on genetic\u0000assignations. A new method was recently developed to recognize these three\u0000phylotypes based on morphological criteria (i.e. pore size and suture\u0000elevation on spiral side), avoiding the need to use molecular analyses to\u0000identify them. The results presented here allow us to validate the\u0000consistency of the morphometric determination method but also to define more\u0000precisely the pore size variability of each of the three phylotypes, which\u0000is a main criterion for their recognition. Moreover, these results, combined\u0000with earlier molecular and morphological data, enable us to refine the\u0000biogeographic distribution previously established by genetic analyses alone.\u0000The biogeographical distribution pattern presented here supports the\u0000putatively invasive character of Ammonia sp. T6, by suggesting that this phylotype\u0000is currently spreading out over large areas and is supplanting\u0000autochthonous phylotypes (T1 and T2) along the coastlines of the British\u0000Isles and northern France. In fact, only the southwest coast of England and Ireland and the northwest coast of France have not been colonized by\u0000Ammonia sp. T6 yet. Our results also suggest that within the areas colonized by\u0000phylotype T6, T2 may find refuges in the inner parts of estuaries. We\u0000further suggest that the absence of Ammonia sp. T6 in the western part of the\u0000English Channel may be explained by the general surface current circulation\u0000pattern, which impedes further expansion. The high reliability of the\u0000determination method of phylotypes T1, T2 and T6 based on morphology also\u0000allows us to quickly generate large datasets for sub-recent and fossil material.\u0000This new method will make it possible to gain an understanding of the\u0000ecological differences between the three phylotypes and of the historical\u0000changes in their distribution patterns (for example due to changing\u0000anthropogenic factors). Finally, it will allow us to confirm or invalidate\u0000the putative invasive character of phylotype T6.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":"40 1","pages":"61-74"},"PeriodicalIF":2.0,"publicationDate":"2021-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45779043","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Cage, A. Pieńkowski, A. Jennings, K. Knudsen, M. Seidenkrantz
Abstract. Morphologically similar benthic foraminiferal taxa can be difficult to separate. Aside from causing issues in taxonomy, incorrect identifications complicate our understanding of species-specific ecological preferences and result in flawed palaeoenvironmental reconstructions and geochemical results. Over the years, a number of studies have grouped together several key Arctic–North Atlantic species in various combinations, despite their distinct environmental preferences and/or stratigraphical differences, causing great confusion in the literature. These species include Cassidulina laevigata, Cassidulina neoteretis, Cassidulina teretis, Paracassidulina neocarinata, Islandiella helenae, and Islandiella norcrossi. Here, we provide for the first time a detailed comparison of these taxa. We present a compilation of the original species descriptions, along with clear, illustrated guidelines on how to separate these taxa to circumvent taxonomic confusion. We acknowledge that some features cannot easily be seen with a standard low-powered microscope, especially if specimens are not well preserved. In those cases, we recommend the following actions: (i) always strive to make a precise identification and at least differentiate between the three genera; (ii) where C. neoteretis and C. teretis cannot be separated, and where the stratigraphical context does not make the species identification obvious, specimens belonging to these taxa should be reported as C. teretis/C. neoteretis; and (iii) where specimens in a sample cannot be confidently assigned to a specific species of Islandiella or Cassidulina, specimens should be grouped as Islandiella spp. or Cassidulina spp., followed by naming the most dominant species in brackets. The improved identification of Cassidulina, Paracassidulina, and Islandiella specimens will ensure development of a better understanding of the ecological affinities of these key Arctic–North Atlantic taxa, consequently resulting in more accurate palaeoenvironmental reconstructions and geochemical data.
{"title":"Comparative analysis of six common foraminiferal species of the genera Cassidulina, Paracassidulina, and Islandiella from the Arctic–North Atlantic domain","authors":"A. Cage, A. Pieńkowski, A. Jennings, K. Knudsen, M. Seidenkrantz","doi":"10.5194/JM-40-37-2021","DOIUrl":"https://doi.org/10.5194/JM-40-37-2021","url":null,"abstract":"Abstract. Morphologically similar benthic foraminiferal taxa can be\u0000difficult to separate. Aside from causing issues in taxonomy, incorrect\u0000identifications complicate our understanding of species-specific ecological\u0000preferences and result in flawed palaeoenvironmental reconstructions and\u0000geochemical results. Over the years, a number of studies have grouped\u0000together several key Arctic–North Atlantic species in various combinations,\u0000despite their distinct environmental preferences and/or stratigraphical\u0000differences, causing great confusion in the literature. These species\u0000include Cassidulina laevigata, Cassidulina neoteretis, Cassidulina teretis, Paracassidulina neocarinata, Islandiella helenae, and Islandiella norcrossi. Here, we provide for the first time a detailed comparison of\u0000these taxa. We present a compilation of the original species descriptions,\u0000along with clear, illustrated guidelines on how to separate these taxa to\u0000circumvent taxonomic confusion. We acknowledge that some features cannot\u0000easily be seen with a standard low-powered microscope, especially if\u0000specimens are not well preserved. In those cases, we recommend the following\u0000actions: (i) always strive to make a precise identification and at least\u0000differentiate between the three genera; (ii) where C. neoteretis and C. teretis cannot be separated, and\u0000where the stratigraphical context does not make the species identification\u0000obvious, specimens belonging to these taxa should be reported as C. teretis/C. neoteretis; and (iii) where specimens in a sample cannot be confidently assigned to a specific\u0000species of Islandiella or Cassidulina, specimens should be grouped as Islandiella spp. or Cassidulina spp., followed by\u0000naming the most dominant species in brackets. The improved identification of\u0000Cassidulina, Paracassidulina, and Islandiella specimens will ensure development of a better understanding of the\u0000ecological affinities of these key Arctic–North Atlantic taxa, consequently\u0000resulting in more accurate palaeoenvironmental reconstructions and\u0000geochemical data.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":"40 1","pages":"37-60"},"PeriodicalIF":2.0,"publicationDate":"2021-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49562529","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Melis, L. Capotondi, F. Torricella, P. Ferretti, A. Geniram, J. Hong, G. Kuhn, B. Khim, Sookwan Kim, E. Malinverno, K. Yoo, E. Colizza
Abstract. During the Late Pleistocene–Holocene, the Ross Sea Ice Shelf exhibited strong spatial variability in relation to the atmospheric and oceanographic climatic variations. Despite being thoroughly investigated, the timing of the ice sheet retreat from the outer continental shelf since the Last Glacial Maximum (LGM) still remains controversial, mainly due to a lack of sediment cores with a robust chronostratigraphy. For this reason, the recent recovery of sediments containing a continuous occurrence of calcareous foraminifera provides the important opportunity to create a reliable age model and document the early deglacial phase in particular. Here we present a multiproxy study from a sediment core collected at the Hallett Ridge (1800 m of depth), where significant occurrences of calcareous planktonic and benthic foraminifera allow us to document the first evidence of the deglaciation after the LGM at about 20.2 ka. Our results suggest that the co-occurrence of large Neogloboquadrina pachyderma tests and abundant juvenile forms reflects the beginning of open-water conditions and coverage of seasonal sea ice. Our multiproxy approach based on diatoms, silicoflagellates, carbon and oxygen stable isotopes on N. pachyderma, sediment texture, and geochemistry indicates that abrupt warming occurred at approximately 17.8 ka, followed by a period of increasing biological productivity. During the Holocene, the exclusive dominance of agglutinated benthic foraminifera suggests that dissolution was the main controlling factor on calcareous test accumulation and preservation. Diatoms and silicoflagellates show that ocean conditions were variable during the middle Holocene and the beginning of the Neoglacial period at around 4 ka. In the Neoglacial, an increase in sand content testifies to a strengthening of bottom-water currents, supported by an increase in the abundance of the tycopelagic fossil diatom Paralia sulcata transported from the coastal regions, while an increase in ice-rafted debris suggests more glacial transport by icebergs.
{"title":"Last Glacial Maximum to Holocene paleoceanography of the northwestern Ross Sea inferred from sediment core geochemistry and micropaleontology at Hallett Ridge","authors":"R. Melis, L. Capotondi, F. Torricella, P. Ferretti, A. Geniram, J. Hong, G. Kuhn, B. Khim, Sookwan Kim, E. Malinverno, K. Yoo, E. Colizza","doi":"10.5194/JM-40-15-2021","DOIUrl":"https://doi.org/10.5194/JM-40-15-2021","url":null,"abstract":"Abstract. During the Late Pleistocene–Holocene, the Ross Sea Ice Shelf exhibited\u0000strong spatial variability in relation to the atmospheric and oceanographic\u0000climatic variations. Despite being thoroughly investigated, the timing of\u0000the ice sheet retreat from the outer continental shelf since the Last\u0000Glacial Maximum (LGM) still remains controversial, mainly due to a lack of\u0000sediment cores with a robust chronostratigraphy. For this reason, the recent\u0000recovery of sediments containing a continuous occurrence of calcareous\u0000foraminifera provides the important opportunity to create a reliable age\u0000model and document the early deglacial phase in particular. Here we present\u0000a multiproxy study from a sediment core collected at the Hallett Ridge (1800 m of depth), where significant occurrences of calcareous planktonic and benthic\u0000foraminifera allow us to document the first evidence of the deglaciation\u0000after the LGM at about 20.2 ka. Our results suggest that the\u0000co-occurrence of large Neogloboquadrina pachyderma tests and abundant juvenile forms reflects the\u0000beginning of open-water conditions and coverage of seasonal sea ice. Our\u0000multiproxy approach based on diatoms, silicoflagellates, carbon and oxygen\u0000stable isotopes on N. pachyderma, sediment texture, and geochemistry indicates that\u0000abrupt warming occurred at approximately 17.8 ka, followed by a period of\u0000increasing biological productivity. During the Holocene, the exclusive\u0000dominance of agglutinated benthic foraminifera suggests that dissolution was\u0000the main controlling factor on calcareous test accumulation and preservation.\u0000Diatoms and silicoflagellates show that ocean conditions were variable\u0000during the middle Holocene and the beginning of the Neoglacial period at\u0000around 4 ka. In the Neoglacial, an increase in sand content testifies to\u0000a strengthening of bottom-water currents, supported by an increase in the\u0000abundance of the tycopelagic fossil diatom Paralia sulcata transported from the coastal\u0000regions, while an increase in ice-rafted debris suggests more glacial\u0000transport by icebergs.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":"40 1","pages":"15-35"},"PeriodicalIF":2.0,"publicationDate":"2021-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49500614","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. Jurassic (Bathonian–Oxfordian) planktic foraminifera from the epicontinental strata of the Polish Basin have been investigated. The palaeoecology, palaeobiogeography, and biostratigraphical potential of the recorded taxa are discussed. Four species are recorded: Conoglobigerina helvetojurassica (Haeusler, 1881), Globuligerina balakhmatovae (Morozova, 1961), G. bathoniana (Pazdrowa, 1969), and G. oxfordiana (Grigelis, 1958). This assemblage is probably the most diverse of those described to date from the epicontinental areas of Europe. The recorded taxa are thought to represent three different ecological morphotypes. The clear relationship between transgressive–regressive facies and the palaeobiogeography of the recorded planktic foraminifera indicates a morphotype-related depth–distribution pattern in which small, simple, globular-chambered morphotypes occupied shallow waters whereas slightly larger, more complex forms, or those with hemispherical chambers, inhabited deeper and more open-water environments.
{"title":"Jurassic planktic foraminifera from the Polish Basin","authors":"M. Gajewska, Zofia Dubicka, M. Hart","doi":"10.5194/JM-40-1-2021","DOIUrl":"https://doi.org/10.5194/JM-40-1-2021","url":null,"abstract":"Abstract. Jurassic (Bathonian–Oxfordian) planktic foraminifera from the\u0000epicontinental strata of the Polish Basin have been investigated. The\u0000palaeoecology, palaeobiogeography, and biostratigraphical potential of the\u0000recorded taxa are discussed. Four species are recorded: Conoglobigerina helvetojurassica (Haeusler, 1881),\u0000Globuligerina balakhmatovae (Morozova, 1961), G. bathoniana (Pazdrowa, 1969), and G. oxfordiana (Grigelis, 1958). This assemblage is\u0000probably the most diverse of those described to date from the epicontinental\u0000areas of Europe. The recorded taxa are thought to represent three different\u0000ecological morphotypes. The clear relationship between\u0000transgressive–regressive facies and the palaeobiogeography of the recorded\u0000planktic foraminifera indicates a morphotype-related depth–distribution\u0000pattern in which small, simple, globular-chambered morphotypes occupied\u0000shallow waters whereas slightly larger, more complex forms, or those with\u0000hemispherical chambers, inhabited deeper and more open-water environments.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":"40 1","pages":"1-13"},"PeriodicalIF":2.0,"publicationDate":"2021-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47180813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Keuter, J. Young, Gil Koplovitz, A. Zingone, M. Frada
Abstract. Coccolithophores are a diverse group of calcifying phytoplankton, which are responsible for a large part of the modern oceanic carbonate production. Here, we describe novel or poorly known coccolithophores and novel life cycle combination coccospheres detected in samples collected either in the Gulf of Aqaba in the northern Red Sea or in the Gulf of Naples in the western Mediterranean. These include Syracosphaera winteri, for which detached coccoliths have previously been recorded but both a formal description and taxonomic affiliation were lacking, and five undescribed sets of combination cells linking HET and HOL forms for S. pulchra, S. mediterranea, S. azureaplaneta, S. lamina and S. orbicula. We also propose the replacement name S. kareniae for the fossil species Deutschlandia gaarderae. We describe a new species of the genus Ophiaster, O. macrospinus, displaying a unique morphological and ecological distribution as well as putative combination cells of two variants of the deep-dwelling Florisphaera profunda, which provide new insights on the affiliation of this genus within the Calcihaptophycideae. Additionally, in the family Papposphaeraceae we detected a new species, Pappomonas vexillata, and combination cells of Picarola margalefi and of a species resembling Papposphaera arctica. Finally, we detected three novel, unpaired holococcolithophore forms (Calyptrosphaera lluisae, Calicasphaera bipora and one form designated as Holococcolithophore A). Overall, this set of novel observations and ensuing discussions provide further insights into the diversity, evolution and life cycle complexity of coccolithophores in the oceans.
摘要球石藻是一种多样化的钙化浮游植物，它们负责现代海洋碳酸盐岩的大部分生产。在这里，我们描述了在红海北部亚喀巴湾或地中海西部那不勒斯湾收集的样品中检测到的新颖或鲜为人知的球石藻和新颖的生命周期组合球球。其中包括Syracosphaera winteri，其分离的球石先前已被记录，但缺乏正式的描述和分类关系，以及S. pulchra, S. mediterranea, S. azureaplaneta, S. lamina和S. orbicula的五组未描述的连接HET和HOL形式的组合细胞。我们还建议用S. kareniae代替化石种Deutschlandia gaarderae。我们描述了蛇麻属的一个新种，O. macrospinus，显示了独特的形态和生态分布，以及深居florisphaera profunda的两个变体的组合细胞，这为该属在calcihaptophycidae中的隶属关系提供了新的见解。此外，在Papposphaeraceae科中，我们还发现了一个新种——Pappomonas vexillata，以及margalefi Picarola和一个类似北极Papposphaera的种的组合细胞。最后，我们发现了三种新的、未成双的全粒石藻改革(Calyptrosphaera lluisae, Calicasphaera bipora和一种被称为全粒石藻A的形式)。总的来说，这组新的观察结果和随后的讨论为海洋中粒石藻的多样性、进化和生命周期复杂性提供了进一步的见解。
{"title":"Novel heterococcolithophores, holococcolithophores and life cycle combinations from the families Syracosphaeraceae and Papposphaeraceae and the genus Florisphaera","authors":"S. Keuter, J. Young, Gil Koplovitz, A. Zingone, M. Frada","doi":"10.5194/jm-40-75-2021","DOIUrl":"https://doi.org/10.5194/jm-40-75-2021","url":null,"abstract":"Abstract. Coccolithophores are a diverse group of calcifying phytoplankton, which are responsible for a large part of the modern oceanic carbonate production. Here, we describe novel or poorly known coccolithophores and novel life cycle combination coccospheres detected in samples collected either in the Gulf of Aqaba in the northern Red Sea or in the Gulf of Naples in the western Mediterranean. These include Syracosphaera winteri, for which detached coccoliths have previously been recorded but both a formal description and taxonomic affiliation were lacking, and five undescribed sets of combination cells linking HET and HOL forms for S. pulchra, S. mediterranea, S. azureaplaneta, S. lamina and S. orbicula. We also propose the replacement name S. kareniae for the fossil species Deutschlandia gaarderae. We describe a new species of the genus Ophiaster, O. macrospinus, displaying a unique morphological and ecological distribution as well as putative combination cells of two variants of the deep-dwelling Florisphaera profunda, which provide new insights on the affiliation of this genus within the Calcihaptophycideae. Additionally, in the family Papposphaeraceae we detected a new species, Pappomonas vexillata, and combination cells of Picarola margalefi and of a species resembling Papposphaera arctica. Finally, we detected three novel, unpaired holococcolithophore forms (Calyptrosphaera lluisae, Calicasphaera bipora and one form designated as Holococcolithophore A). Overall, this set of novel observations and ensuing discussions provide further insights into the diversity, evolution and life cycle complexity of coccolithophores in the oceans.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":"1 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2021-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"70626855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract. By studying the facies, geochemistry, and microfossil assemblages of the uppermost Pliensbachian and lower Toarcian of the Cueva del Agua section, I was able to appraise the impact of the Jenkyns Event in the eastern part of the South Iberian Palaeomargin (Western Tethys). Depleted oxygen conditions are envisaged for the Polymorphum–Serpentinum Zone boundary (lower Toarcian), represented by dark marls, precisely in a laminated interval. The decrease in the α diversity of foraminifera and ostracods, along with greater proportions of opportunists such as Lenticulina, Eoguttulina, and Cytherella just before the negative carbon isotopic excursion (CIE), would indicate a disturbance of the environmental conditions during the initial phase of the biotic crisis. The peak of the biotic crisis is characterized by an absence of trace fossils, increased organic matter content, an increased Mo∕Al ratio, and negative CIE and δ18 O, as well as fewer specialist forms and more opportunists. This biotic crisis peak is related to oxygen-depleted conditions in the bottom waters and in the sediment pore water, while warming negatively affected microfauna – to the point of leaving a barren benthic horizon in the record. Recovery is evidenced by the occurrence of carbonate layers with hummocky cross-stratification and a decrease in organic matter content, the Mo∕Al ratio, and the trace fossil record. In terms of microfauna, the first phase of recovery shows highly abundant foraminifera, ostracods, and microgastropods, mainly opportunist forms. After the proliferation of opportunist forms, a second phase of recovery is marked by a progressive increase in α diversity.
摘要通过研究Cueva del Agua剖面的最上层Pliensbachian和下层Toarcian的相、地球化学和微化石组合，我能够评估Jenkyns事件对南伊比利亚古边缘(西特提斯)东部的影响。贫氧条件被设想为多态-蛇形带边界(下托瓦纪)，由深色泥灰岩代表，精确地在层压间隔中。有孔虫和介形虫α多样性的减少，以及在负碳同位素偏移(CIE)之前机会虫如Lenticulina, Eoguttulina和Cytherella的比例增加，表明在生物危机的初始阶段环境条件受到干扰。生物危机的高峰表现为化石缺失，有机质含量增加，钼铝比增加，CIE和δ18 O为负，专业形式减少，机会主义形式增多。这个生物危机高峰与底部水域和沉积物孔隙水的缺氧条件有关，而变暖对微型动物产生了负面影响——在记录中留下了一个贫瘠的底栖生物地平线。碳酸盐层呈丘状交叉层状，有机质含量、钼铝比和微量化石记录均有所下降，证明了该区的恢复。在小动物群方面，恢复的第一阶段显示出丰富的有孔虫、介形虫和小腹足类，主要是机会动物。在机会主义形式激增之后，第二阶段的恢复是以α多样性的逐步增加为标志的。
{"title":"Microfossil assemblages and geochemistry for interpreting the incidence of the Jenkyns Event (early Toarcian) in the south-eastern Iberian Palaeomargin (External Subbetic, SE Spain)","authors":"M. Reolid","doi":"10.5194/jm-39-233-2020","DOIUrl":"https://doi.org/10.5194/jm-39-233-2020","url":null,"abstract":"Abstract. By studying the facies, geochemistry, and microfossil assemblages of the\u0000uppermost Pliensbachian and lower Toarcian of the Cueva del Agua section, I\u0000was able to appraise the impact of the Jenkyns Event in the eastern part of\u0000the South Iberian Palaeomargin (Western Tethys). Depleted oxygen conditions\u0000are envisaged for the Polymorphum–Serpentinum Zone boundary (lower\u0000Toarcian), represented by dark marls, precisely in a laminated interval. The\u0000decrease in the α diversity of foraminifera and ostracods, along\u0000with greater proportions of opportunists such as Lenticulina, Eoguttulina, and Cytherella just before the\u0000negative carbon isotopic excursion (CIE), would indicate a disturbance of the\u0000environmental conditions during the initial phase of the biotic crisis. The\u0000peak of the biotic crisis is characterized by an absence of trace fossils,\u0000increased organic matter content, an increased Mo∕Al ratio, and negative CIE and\u0000 δ18 O, as well as fewer specialist forms and more opportunists.\u0000This biotic crisis peak is related to oxygen-depleted conditions in the\u0000bottom waters and in the sediment pore water, while warming negatively\u0000affected microfauna – to the point of leaving a barren benthic horizon in\u0000the record. Recovery is evidenced by the occurrence of carbonate layers with\u0000hummocky cross-stratification and a decrease in organic matter content, the\u0000 Mo∕Al ratio, and the trace fossil record. In terms of microfauna, the\u0000first phase of recovery shows highly abundant foraminifera, ostracods, and\u0000microgastropods, mainly opportunist forms. After the proliferation of\u0000opportunist forms, a second phase of recovery is marked by a progressive\u0000increase in α diversity.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":"39 1","pages":"233-258"},"PeriodicalIF":2.0,"publicationDate":"2020-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48262629","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Simmons, V. Vicedo, İ. Yılmaz, I. Hoşgör, O. Mülayim, Bilal Sarı
Abstract. The micropalaeontology of the mid-Cretaceous Derdere Formation (Mardin Group) from outcrops close to the town of Derik in south-eastern Turkey is described here. In thin sections from the carbonates that form the majority of this formation, rich and diverse micropalaeontological assemblages are present. These include larger benthonic foraminifera, planktonic foraminifera, and other microfossils, including calcareous algae. Alveolinid foraminifera are particularly common and include a new species – Simplalveolina mardinensis. In contrast to some previous studies, the majority of the section can be demonstrated to be Cenomanian (notably middle Cenomanian) in age with no confirmation of extension into the Albian or Turonian. Deposition took place on a carbonate ramp within a range of discrete deposition settings ranging from peritidal to outer ramp. A notable feature is the small-scale (a few metres) shallowing-up cycles within the inner-ramp facies that may be allocyclic or autocyclic in origin. Three major deepening events are recognised within the succession, characterised by more open marine microfauna and microfacies. These occur at the base of the formation, within the mid-Cenomanian lower part, and towards the top of the formation. These may correlate with three Cenomanian deepening phases seen in other parts of the Arabian Plate.
{"title":"Micropalaeontology, biostratigraphy, and depositional setting of the mid-Cretaceous Derdere Formation at Derik, Mardin, south-eastern Turkey","authors":"M. Simmons, V. Vicedo, İ. Yılmaz, I. Hoşgör, O. Mülayim, Bilal Sarı","doi":"10.5194/jm-39-203-2020","DOIUrl":"https://doi.org/10.5194/jm-39-203-2020","url":null,"abstract":"Abstract. The micropalaeontology of the mid-Cretaceous Derdere Formation (Mardin\u0000Group) from outcrops close to the town of Derik in south-eastern Turkey is\u0000described here. In thin sections from the carbonates that form the majority of\u0000this formation, rich and diverse micropalaeontological assemblages are\u0000present. These include larger benthonic foraminifera, planktonic\u0000foraminifera, and other microfossils, including calcareous algae.\u0000Alveolinid foraminifera are particularly common and include a new species – Simplalveolina mardinensis. In contrast to some previous studies, the majority of the section can be\u0000demonstrated to be Cenomanian (notably middle Cenomanian) in age with no\u0000confirmation of extension into the Albian or Turonian. Deposition took place\u0000on a carbonate ramp within a range of discrete deposition settings ranging\u0000from peritidal to outer ramp. A notable feature is the small-scale (a few\u0000metres) shallowing-up cycles within the inner-ramp facies that may be\u0000allocyclic or autocyclic in origin. Three major deepening events are\u0000recognised within the succession, characterised by more open marine\u0000microfauna and microfacies. These occur at the base of the formation,\u0000within the mid-Cenomanian lower part, and towards the top of the formation.\u0000These may correlate with three Cenomanian deepening phases seen in other\u0000parts of the Arabian Plate.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":"39 1","pages":"203-232"},"PeriodicalIF":2.0,"publicationDate":"2020-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48115865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
R. Marchant, M. Tetard, Adnya Pratiwi, M. Adebayo, T. de Garidel-Thoron
Abstract. Manual identification of foraminiferal morphospecies or morphotypes under stereo microscopes is time consuming for micropalaeontologists and not possible for nonspecialists. Therefore, a long-term goal has been to automate this process to improve its efficiency and repeatability. Recent advances in computation hardware have seen deep convolutional neural networks emerge as the state-of-the-art technique for image-based automated classification. Here, we describe a method for classifying large foraminifera image sets using convolutional neural networks. Construction of the classifier is demonstrated on the publicly available Endless Forams image set with a best accuracy of approximately 90 %. A complete automatic analysis is performed for benthic species dated to the last deglacial period for a sediment core from the north-eastern Pacific and for planktonic species dated from the present until 180 000 years ago in a core from the western Pacific warm pool. The relative abundances from automatic counting based on more than 500 000 images compare favourably with manual counting, showing the same signal dynamics. Our workflow opens the way to automated palaeoceanographic reconstruction based on computer image analysis and is freely available for use.
{"title":"Automated analysis of foraminifera fossil records by image classification using a convolutional neural network","authors":"R. Marchant, M. Tetard, Adnya Pratiwi, M. Adebayo, T. de Garidel-Thoron","doi":"10.5194/jm-39-183-2020","DOIUrl":"https://doi.org/10.5194/jm-39-183-2020","url":null,"abstract":"Abstract. Manual identification of foraminiferal morphospecies or morphotypes under stereo microscopes is time consuming for micropalaeontologists and not possible for nonspecialists. Therefore, a long-term goal has been to automate this process to improve its efficiency and repeatability. Recent advances in computation hardware have seen deep convolutional neural networks emerge as the state-of-the-art technique for image-based automated classification. Here, we describe a method for classifying large foraminifera image sets using convolutional neural networks. Construction of the classifier is demonstrated on the publicly available Endless Forams image set with a best accuracy of approximately 90 %. A complete automatic analysis is performed for benthic species dated to the last deglacial period for a sediment core from the north-eastern Pacific and for planktonic species dated from the present until 180 000 years ago in a core from the western Pacific warm pool. The relative abundances from automatic counting based on more than 500 000 images compare favourably with manual counting, showing the same signal dynamics. Our workflow opens the way to automated palaeoceanographic reconstruction based on computer image analysis and is freely available for use.\u0000","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2020-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45680951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Beasley, Daniel B. Parvaz, L. Cotton, K. Littler
Abstract. Three disaggregation methods, i.e. Calgon, acetic acid and electric pulse fragmentation (EPF), have been applied to a range of heavily lithified, carbonate-rich sedimentary rock samples of Paleogene age. Samples are predominantly from the carbonate-rich, shallow water domain ( m palaeo-water depth) of Tanzania, Malta and the United Arab Emirates (Paleogene Tethys Ocean). The effectiveness and efficiency of each method has been compared, in addition to the preservation of the resultant liberated microfossil material (primarily larger foraminifera; LF). Of the three methods, the most efficient and effective was EPF, which liberated the largest number of LF in a very short processing time and resulted in the best preservation. Samples with calcitic, silicic, and clay matrices and cements were successfully disaggregated using EPF. In this study, recovered microfossils were largely >500 µ m, suggesting this technique may be more appropriate for liberating larger microfossils (e.g. LFs); however, we discuss nuances to the method that would allow for more effective recovery of smaller microfossil specimens. The more traditional acetic acid method was also able to disaggregate a number of the samples; however, preservation of the LF was compromised. We suggest a best-practice methodology for implementing EPF in micropalaeontological studies.
{"title":"Liberating microfossils from indurated carbonates: comparison of three disaggregation methods","authors":"C. Beasley, Daniel B. Parvaz, L. Cotton, K. Littler","doi":"10.5194/jm-39-169-2020","DOIUrl":"https://doi.org/10.5194/jm-39-169-2020","url":null,"abstract":"Abstract. Three disaggregation methods, i.e. Calgon, acetic acid and electric\u0000pulse fragmentation (EPF), have been applied to a range of heavily\u0000lithified, carbonate-rich sedimentary rock samples of Paleogene age. Samples\u0000are predominantly from the carbonate-rich, shallow water domain ( m palaeo-water depth) of Tanzania, Malta and the United Arab Emirates\u0000(Paleogene Tethys Ocean). The effectiveness and efficiency of each method\u0000has been compared, in addition to the preservation of the resultant liberated\u0000microfossil material (primarily larger foraminifera; LF). Of the three\u0000methods, the most efficient and effective was EPF, which liberated the\u0000largest number of LF in a very short processing time and resulted in the\u0000best preservation. Samples with calcitic, silicic, and clay matrices and\u0000cements were successfully disaggregated using EPF. In this study, recovered\u0000microfossils were largely >500 µ m, suggesting this\u0000technique may be more appropriate for liberating larger microfossils (e.g.\u0000LFs); however, we discuss nuances to the method that would allow for more\u0000effective recovery of smaller microfossil specimens. The more traditional\u0000acetic acid method was also able to disaggregate a number of the samples;\u0000however, preservation of the LF was compromised. We suggest a best-practice\u0000methodology for implementing EPF in micropalaeontological studies.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":"39 1","pages":"169-181"},"PeriodicalIF":2.0,"publicationDate":"2020-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44739182","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 species of dinoflagellate cyst, Desmocysta hadra sp. nov., is described from the early Campanian (Late Cretaceous) in the Norwegian Sea. This new taxon differs from the other three known species by its particularly robust but highly folded wall and the short, fine filaments arising from the antapex. The short stratigraphic range of early Campanian for this new species was calibrated with other regional well-dated dinoflagellate cysts, making it a good biostratigraphic marker. A review of the taxonomic description of the genus has also been undertaken using the available published data. The available data shows a consistent presence of Desmocysta in the fossil record from the Early Cretaceous to the late Paleocene, although some Late Jurassic occurrences have been reported in the North Sea Basin. The current records also indicate that this genus is restricted to higher latitudes in the Northern Hemisphere. Based on Paleocene and Late Cretaceous occurrences of the genus, and its association with dinoflagellate cysts, prasinophytes and acritarchs, a proximal, highly stressed marine environment for Desmocysta is suggested.
{"title":"Desmocysta hadra, a new Late Cretaceous dinoflagellate cyst species: stratigraphic range, palaeogeographic distribution and palaeoecology","authors":"M. Vieira, S. Mahdi","doi":"10.5194/jm-39-155-2020","DOIUrl":"https://doi.org/10.5194/jm-39-155-2020","url":null,"abstract":"Abstract. A new species of dinoflagellate cyst, Desmocysta hadra sp. nov., is described from the early\u0000Campanian (Late Cretaceous) in the Norwegian Sea. This new taxon differs\u0000from the other three known species by its particularly robust but highly\u0000folded wall and the short, fine filaments arising from the antapex. The\u0000short stratigraphic range of early Campanian for this new species was\u0000calibrated with other regional well-dated dinoflagellate cysts, making it a\u0000good biostratigraphic marker. A review of the taxonomic description of the\u0000genus has also been undertaken using the available published data. The\u0000available data shows a consistent presence of Desmocysta in the fossil record from the\u0000Early Cretaceous to the late Paleocene, although some Late Jurassic\u0000occurrences have been reported in the North Sea Basin. The current records\u0000also indicate that this genus is restricted to higher latitudes in the\u0000Northern Hemisphere. Based on Paleocene and Late Cretaceous occurrences of\u0000the genus, and its association with dinoflagellate cysts, prasinophytes and\u0000acritarchs, a proximal, highly stressed marine environment for Desmocysta is\u0000suggested.","PeriodicalId":54786,"journal":{"name":"Journal of Micropalaeontology","volume":"39 1","pages":"155-167"},"PeriodicalIF":2.0,"publicationDate":"2020-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48618785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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