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  • 1
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    Online Resource
    A late Caledonian tectono-thermal event in the Gaissa Nappe Complex, Arctic Norway: evidence from fine-fraction K‒Ar dating and illite crystallinity from the Digermulen Peninsula
    Informa UK Limited ; 2019
    In:  GFF Vol. 141, No. 4 ( 2019-10-02), p. 289-294
    Details
    In: GFF, Informa UK Limited, Vol. 141, No. 4 ( 2019-10-02), p. 289-294
    Type of Medium: Online Resource
    ISSN: 1103-5897 , 2000-0863
    URL: Article
    DOI: 10.1080/11035897.2019.1583685
    Language: English
    Publisher: Informa UK Limited
    Publication Date: 2019
    detail.hit.zdb_id: 2187205-3
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  • 2
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    U–Pb dating of calcite in ancient carbonates for age estimates of syn- to post-depositional processes: a case study from the upper Ediacaran strata of Finnmark, Arctic Norway
    Cambridge University Press (CUP) ; 2020
    In:  Geological Magazine Vol. 157, No. 8 ( 2020-08), p. 1367-1372
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 157, No. 8 ( 2020-08), p. 1367-1372
    Abstract: Results of in situ U–Pb dating of calcite spherulites, cone-in-cone (CIC) calcite and calcite fibres from a calcareous concretion of the upper Ediacaran of Finnmark, Arctic Norway, are reported. Calcite spherulites from the innermost layers of the concretion yielded a lower intercept age of 563 ± 70 Ma, which, although imprecise, is within uncertainty of the age of sedimentation based on fossil assemblages. Non-deformed CIC calcite from the bottom part of the concretion yielded an age of 475 ± 25 Ma, which is interpreted as the age of CIC calcite formation during a period of fluid overpressure induced during burial of the sediments. Deformed CIC calcite from the top part of the concretion yielded an age of 418 ± 23 Ma, which overlaps with a known Caledonian tectono-metamorphic event, and indicates a potential post-depositional overprint at this time. Calcite fibres that grew in small fissures along spherulite rims, which are interpreted as a recrystallization feature during deformation and formation of a cleavage, gave an imprecise age of 486 ± 161 Ma. Our results show that U–Pb dating of calcite can provide age constraints for ancient carbonates and syn- to post-depositional processes that operated during burial and metamorphic overprinting.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756820000564
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2020
    detail.hit.zdb_id: 956405-6
    detail.hit.zdb_id: 1479206-0
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  • 3
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    First record of carbonates with spherulites and cone-in-cone structures from the Precambrian of Arctic Norway, and their palaeoenvironmental significance
    Elsevier BV ; 2019
    In:  Precambrian Research Vol. 328 ( 2019-07), p. 99-110
    Details
    In: Precambrian Research, Elsevier BV, Vol. 328 ( 2019-07), p. 99-110
    Type of Medium: Online Resource
    ISSN: 0301-9268
    URL: Article
    DOI: 10.1016/j.precamres.2019.04.014
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2019
    detail.hit.zdb_id: 1500672-4
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  • 4
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    Diversity of organic-walled microfossils from the early Mesoproterozoic Ruyang Group, North China Craton – A window into the early eukaryote evolution
    Elsevier BV ; 2017
    In:  Precambrian Research Vol. 297 ( 2017-08), p. 101-130
    Details
    In: Precambrian Research, Elsevier BV, Vol. 297 ( 2017-08), p. 101-130
    Type of Medium: Online Resource
    ISSN: 0301-9268
    URL: Article
    DOI: 10.1016/j.precamres.2017.04.042
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2017
    detail.hit.zdb_id: 1500672-4
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  • 5
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    Affinity, life cycle, and intracellular complexity of organic-walled microfossils from the Mesoproterozoic of Shanxi, China
    Cambridge University Press (CUP) ; 2015
    In:  Journal of Paleontology Vol. 89, No. 1 ( 2015-01), p. 28-50
    Details
    In: Journal of Paleontology, Cambridge University Press (CUP), Vol. 89, No. 1 ( 2015-01), p. 28-50
    Abstract: Light microscope and scanning electron microscope observations on new material of unicellular microfossils Dictyosphaera macroreticulata and Shuiyousphaeridium macroreticulatum, from the Mesoproterozoic Ruyang Group in China, provide insights into the microorganisms’ biological affinity, life cycle and cellular complexity. Gigantosphaeridium fibratum n. gen. et sp., is described and is one of the largest Mesoproterozoic microfossils recorded. Phenotypic characters of vesicle ornamentation and excystment structures, properties of resistance and cell wall structure in Dictyosphaera and Shuiyousphaeridium are all diagnostic of microalgal cysts. The wide size ranges of the various morphotypes indicate growth phases compatible with the development of reproductive cysts. Conspecific biologically, each morphotype represents an asexual (resting cyst) or sexual (zygotic cyst) stage in the life cycle, respectively. We reconstruct this hypothetical life cycle and infer that the organism demonstrates a reproductive strategy of alternation of heteromorphic generations. Similarly in Gigantosphaeridium, a metabolically expensive vesicle with processes suggests its protective role as a zygotic cyst. In combination with all these characters and from the resemblance to extant green algae, we propose the placement of these ancient microorganisms in the stem group of Chloroplastida (Viridiplantae). A cell wall composed of primary and secondary layers in Dictyosphaera and Shuiyouisphaeridium required a high cellular complexity for their synthesis and the presence of an endomembrane system and the Golgi apparatus. The plastid was also present, accepting the organism was photosynthetic. The biota reveals a high degree of morphological and cell structural complexity, and provides an insight into ongoing eukaryotic evolution and the development of complex life cycles with sexual reproduction by 1200 Ma.
    Type of Medium: Online Resource
    ISSN: 0022-3360 , 1937-2337
    URL: Article
    DOI: 10.1017/jpa.2014.4
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2015
    detail.hit.zdb_id: 219113-1
    detail.hit.zdb_id: 2047591-3
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  • 6
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    Organically-preserved multicellular eukaryote from the early Ediacaran Nyborg Formation, Arctic Norway
    Springer Science and Business Media LLC ; 2019
    In:  Scientific Reports Vol. 9, No. 1 ( 2019-10-10)
    Details
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 9, No. 1 ( 2019-10-10)
    Abstract: Eukaryotic multicellularity originated in the Mesoproterozoic Era and evolved multiple times since, yet early multicellular fossils are scarce until the terminal Neoproterozoic and often restricted to cases of exceptional preservation. Here we describe unusual organically-preserved fossils from mudrocks, that provide support for the presence of organisms with differentiated cells (potentially an epithelial layer) in the late Neoproterozoic. Cyathinema digermulense gen. et sp. nov. from the Nyborg Formation, Vestertana Group, Digermulen Peninsula in Arctic Norway, is a new carbonaceous organ-taxon which consists of stacked tubes with cup-shaped ends. It represents parts of a larger organism (multicellular eukaryote or a colony), likely with greater preservation potential than its other elements. Arrangement of open-ended tubes invites comparison with cells of an epithelial layer present in a variety of eukaryotic clades. This tissue may have benefitted the organism in: avoiding overgrowth, limiting fouling, reproduction, or water filtration. C . digermulense shares characteristics with extant and fossil groups including red algae and their fossils, demosponge larvae and putative sponge fossils, colonial protists, and nematophytes. Regardless of its precise affinity, C . digermulense was a complex and likely benthic marine eukaryote exhibiting cellular differentiation, and a rare occurrence of early multicellularity outside of Konservat-Lagerstätten.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    URL: Article
    DOI: 10.1038/s41598-019-50650-x
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2019
    detail.hit.zdb_id: 2615211-3
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  • 7
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    Ecdysozoan-like sclerites among Ediacaran microfossils
    Cambridge University Press (CUP) ; 2015
    In:  Geological Magazine Vol. 152, No. 6 ( 2015-11), p. 1145-1148
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 152, No. 6 ( 2015-11), p. 1145-1148
    Abstract: We report the occurrence of organically preserved microfossils from the subsurface Ediacaran strata overlying the East European Platform in Poland, in the form of sclerites and cuticle fragments of larger organisms. They are morphologically similar to those known from Cambrian strata and associated with various metazoan fossils of recognized phyla. The Ediacaran age of the microfossils is evident from the stratigraphic position below the base of the Cambrian System and above the isotopically dated tuff layers at c. 551±4Ma. Within this strata interval, other characteristic Ediacaran microorganisms co-occur such as cyanobacteria, vendotaenids, microalgae, Ceratophyton , Valkyria and macroscopic annelidan Sabellidites . The recent contributions of organic sclerites in revealing the scope of the Cambrian explosion are therefore also potentially extendable back to the Ediacaran Period when animals first appear in the fossil record.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S001675681500045X
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2015
    detail.hit.zdb_id: 956405-6
    detail.hit.zdb_id: 1479206-0
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  • 8
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    Distribution and correlation of Sabellidites cambriensis (Annelida?) in the basal Cambrian on Baltica
    Cambridge University Press (CUP) ; 2022
    In:  Geological Magazine Vol. 159, No. 7 ( 2022-07), p. 1262-1283
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 159, No. 7 ( 2022-07), p. 1262-1283
    Abstract: Sabellidites cambriensis is a tubular non-mineralized metazoan that appears as compressed ribbon-shaped imprints with transverse wrinkling, thick walls and an even tube diameter of up to 3 mm. The distribution of Sabellidites is investigated in three Ediacaran–Cambrian sections on the Digermulen Peninsula in Arctic Norway, spanning the Manndrapselva Member of the Stáhpogieddi Formation and the lower member of the Breidvika Formation. Here, the Ediacaran–Cambrian boundary is located in the lower part of the upper parasequence (third cycle) of the Manndrapselva Member. Specimens of Sabellidites are rare but consistently present close to the lowest level of Treptichnus pedum and upsection, whereas the taxon is common and abundant in the lower part of the lower member of the Breidvika Formation, with an upper record at c. 55 m above the base. The range is comparable with that of the GSSP section in Newfoundland, Canada, establishing Sabellidites as an index fossil for the lowermost Cambrian. In the Manndrapselva Member, Sabellidites co-occurs with the acritarch Granomarginata , indicative of the lowermost Cambrian Granomarginata Zone, whereas in the Breidvika Formation it co-occurs with Asteridium . Sabellidites is widely distributed in Baltica, through the Rovnian and Lontovan regional stages but confined to the Fortunian global stage. In its lower range, Sabellidites is associated with a Treptichnus pedum trace fossil association and a depauperate leiosphaerid acritarch assemblage, followed by a Granomarginata assemblage. In its upper range, Sabellidites co-occurs with acritarchs of the Asteridium–Comasphaeridium Zone and the tubular foraminiferan Platysolenites . In Baltica, Sabellidites is a useful index fossil.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756821001187
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2022
    detail.hit.zdb_id: 956405-6
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  • 9
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    A Tonian age for the Visingsö Group in Sweden constrained by detrital zircon dating and biochronology: implications for evolutionary events
    Cambridge University Press (CUP) ; 2018
    In:  Geological Magazine Vol. 155, No. 5 ( 2018-07), p. 1175-1189
    Details
    In: Geological Magazine, Cambridge University Press (CUP), Vol. 155, No. 5 ( 2018-07), p. 1175-1189
    Abstract: Detrital zircon U–Pb ages from samples of the Neoproterozoic Visingsö Group, Sweden, yield a maximum depositional age of ≤ 886±9 Ma (2σ). A minimum depositional age is established biochronologically using organic-walled and vase-shaped microfossils present in the upper formation of the Visingsö Group; the upper formation correlates with the Kwagunt Formation of the 780–740 Ma Chuar Group in Arizona, USA, and the lower Mount Harper Group, Yukon, Canada, that is older than 740 Ma. Mineralized scale microfossils of the type recorded from the upper Fifteenmile Group, Yukon, Canada, where they occur in a narrow stratigraphic range and are younger than 788 Ma, are recognized for the first time outside Laurentia. The mineralized scale microfossils in the upper formation of the Visingsö Group seem to have a wider stratigraphic range, and are older than c . 740 Ma. The inferred age range of mineralized scale microfossils is 788–740 Ma. This time interval coincides with the vase-shaped microfossil range because both microfossil groups co-occur. The combined isotopic and biochronologic ages constrain the Visingsö Group to between ≤ 886 and 740 Ma, thus Tonian in age. This is the first robust age determination for the Visingsö Group, which preserves a rich microfossil assemblage of worldwide distribution. The organic and mineralized microorganisms preserved in the Visingsö Group and coeval successions elsewhere document global evolutionary events of auto- and heterotrophic protist radiations that are crucial to the reconstruction of eukaryotic phylogeny based on the fossil record and are useful for the Neoproterozoic chronostratigraphic subdivision.
    Type of Medium: Online Resource
    ISSN: 0016-7568 , 1469-5081
    URL: Article
    DOI: 10.1017/S0016756817000085
    Language: English
    Publisher: Cambridge University Press (CUP)
    Publication Date: 2018
    detail.hit.zdb_id: 956405-6
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  • 10
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    Anoxic ecosystems and early eukaryotes
    Portland Press Ltd. ; 2018
    In:  Emerging Topics in Life Sciences Vol. 2, No. 2 ( 2018-09-28), p. 299-309
    Details
    In: Emerging Topics in Life Sciences, Portland Press Ltd., Vol. 2, No. 2 ( 2018-09-28), p. 299-309
    Abstract: Through much of the Proterozoic Eon (2.5–0.54 billion years ago, Ga), oceans were dominantly anoxic. It is often assumed that this put a brake on early eukaryote diversification because eukaryotes lived only in oxygenated habitats, which were restricted to surface waters and benthic environments near cyanobacterial mats. Studies of extant microbial eukaryotes show, however, that they are diverse and abundant in anoxic (including sulfidic) environments, often through partnerships with endo- and ectosymbiotic bacteria and archaea. Though the last common ancestor of extant eukaryotes was capable of aerobic respiration, we propose that at least some, and perhaps many, early eukaryotes were adapted to anoxic settings, and outline a way to test this with the microfossil and redox-proxy record in Proterozoic shales. This hypothesis might explain the mismatch between the record of eukaryotic body fossils, which extends back to & gt;1.6 Ga, and the record of sterane biomarkers, which become diverse and abundant only after 659 Ma, as modern eukaryotes adapted to anoxic habitats do not make sterols (sterane precursors). In addition, an anoxic habitat might make sense for several long-ranging ( & gt;800 million years) and globally widespread eukaryotic taxa, which disappear in the late Neoproterozoic around the time oxic environments are thought to have become more widespread.
    Type of Medium: Online Resource
    ISSN: 2397-8554 , 2397-8562
    URL: Article
    DOI: 10.1042/ETLS20170162
    Language: English
    Publisher: Portland Press Ltd.
    Publication Date: 2018
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