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Title [sv]
Ekologi och evolution av tidiga eukaryoter i neoproterozoikum: mikro och geokemisk undersökning
Title [en]
Ecology and evolution of early eukaryotes in the Neoproterozoic: microstructural and geochemical investigation
Abstract [en]
The Neoproterozoic Era (1000-541 million years ago) was a time of major environmental change in Earth´s history such as the oxygenation of the atmosphere and the oceans, low-latitude glacial episodes (Snowball Earth), radiation of eukaryotic clades and the origin of animals. Life in this period is predominantly represented by organic-walled microfossils. However evolutionary relationships between these eukaryotic fossils and their ecology are poorly understood.This multidisciplinary project combines a systematic study of the microfossil communities via high-resolution microscopy and chemical composition analysis, to investigate fossils diagnostic features and palaeoenvironments they inhabited. Sampling of several poorly investigated Tonian-Cryogenian rock successions from Baltica and Laurentia will provide fossils suitable for microstructural studies via SEM, TEM, FIB-EM. These data will reveal characters overlooked by usual light microscopy studies, show detailed morphological evolution in early eukaryotes and enable a better comparison with modern protists. ¬†Analysis of carbon isotopic composition of individual fossils will help differentiate between the autotrophic and heterotrophic modes of life, revealing their place in the Neoproterozoic food pyramid. Additionally, comparison between these assemblages and geochemical change in their environments may provide further insight into adaptations of marine communities in various regions through Tonian and Cryogenian Periods.
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Agic, H., Jensen, S., Meinhold, G., Hogstrom, A. E. S., Ebbestad, J. O., Hoyberget, M., . . . Taylor, W. L. (2024). Life through an Ediacaran glaciation: Shale- and diamictite-hosted organic-walled microfossil assemblages from the late Neoproterozoic of the Tanafjorden area, northern Norway. Palaeogeography, Palaeoclimatology, Palaeoecology, 635, Article ID 111956.
Open this publication in new window or tab >>Life through an Ediacaran glaciation: Shale- and diamictite-hosted organic-walled microfossil assemblages from the late Neoproterozoic of the Tanafjorden area, northern Norway
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2024 (English)In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 635, article id 111956Article in journal (Refereed) Published
Abstract [en]

New organic-walled microfossil (OWM) assemblages are reported from upper Neoproterozoic glacial and interglacial siliciclastic deposits in Finnmark, northern Norway. A nearly continuous sedimentary succession of the Vestertana Group contains two glaciogenic units, the Smalfjorden and Mortensnes formations, interpreted as end-Cryogenian Marinoan and Ediacaran glaciations, respectively. We investigated the OWM record in the Nyborg, Mortensnes, and St ' ahpogieddi formations to assess the impact of a glacial interval on the diversity of microscopic eukaryotes. A modified acid-extraction technique was applied to recover OWM from the diamictite matrix. The upper Nyborg Formation contains morphologically complex Doushantuo-Pertatataka acritarchs (DPA), restricting the age of the Nyborg Formation to early-mid Ediacaran. DPA occur below the dolostones that record a negative carbon isotope excursion correlated with the Shuram anomaly and below a glacial diamictite. A decline in species richness and compositional change is observed in the Mortensnes glacial assemblage. DPA are replaced by bacterial filaments and cell aggregates. The overlying Indreelva Member, St ' ahpogieddi Formation contains Ediacara-type biota and palaeopascichnids, but only a depauperate OWM assemblage of leiosphaerids and flask-shaped microfossils characteristic of the late Ediacaran.The succession of assemblages in the Vestertana Group demonstrates a turnover from large eukaryotic OWM to a microbial community in the glacial interval, to a low diversity post-glacial assemblage during the rise of macroscopic life. We compared the Vestertana record to global DPA occurrences. Although one DPA assemblage zone postdates the Shuram excursion, no DPA occur above Ediacaran glacial diamictites in successions where those deposits are present. Considering this, and the community changes in the Vestertana succession, we suggest that DPA were affected by the onset of an Ediacaran glaciation. Lastly, we combined the biostratigraphic markers in the Vestertana Group to constrain the age of the Mortensnes diamictite.

Place, publisher, year, edition, pages
Elsevier, 2024
Keywords
Organic-walled microfossils, Neoproterozoic, Ediacaran, Diamictite, Biostratigraphy, Palynological acid maceration
National Category
Geology Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-523232 (URN)10.1016/j.palaeo.2023.111956 (DOI)001140581900001 ()
Funder
Swedish Research Council, VR2016-06810
Available from: 2024-02-19 Created: 2024-02-19 Last updated: 2024-02-19Bibliographically approved
Principal InvestigatorAgić, Heda
Coordinating organisation
Uppsala University
Funder
Period
2017-01-01 - 2019-12-31
National Category
Materials ChemistryGeosciences, MultidisciplinaryEvolutionary Biology
Identifiers
DiVA, id: project:6076Project, id: 2016-06810_VR