| 1. |
- Agic, Heda, et al.
(författare)
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Unusual organic-walled microfossil from the late Neoproterozoic Nyborg Formation, Digermulen Peninsula, Arctic Norway
- 2017
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Ingår i: ISECT 2017.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The late Neoproterozoic Nyborg Formation is exposed in the Tanafjord area, Finnmark, Arctic Norway, on Digermulen and Varanger Peninsulas. The succession is composed of ~400 m of interbedded shales, siltstone and purple to grey sandstone, deposited between Neoproterozoic low latitude glacial deposits. The Nyborg Fm. lies on top of the Smalfjord diamictite, and is overlain by the Mortensnes diamictite (the latter was attributed to both Marinoan (650-635 Ma) and Gaskiers (579 Ma) glaciations) and the Ediacaran-Cambrian Stáhpogieddi Formation. Thus, the Nyborg Fm. represents late Neoproterozoic, probably the last Cryogenian interglacial interval. Presented material was collected in 2014 by members of Digermulen Early Life Research Group, from organic-rich, grey-green shales and siltstones of the Nyborg Mbr. D, uppermost Nyborg Fm. between Árasulluokta and Guvssájohka valleys. Organic-walled microfossils were extracted from shale via standard palynological acetolysis in hydrofluoric acid, and studied via light and scanning electron microscopy. Microfossils from the Nyborg Fm. include Synsphaeridium-type aggregated cells, unbranched bacterial filaments (Polythrichoides and Siphonophycus), sphaeromorph and envelope-bearing acritarchs (leiosphaerids, Stictosphaeridium, Simia), and previously unrecognized aggregated tubular microfossils. These taxa are long-ranging, but common in glacial-interglacial units worldwide, and thus broadly corroborate the Cryogenian age of the Nyborg sediments. The novel fossil, up to 300 μm in size, is a parenchymatous meshwork of interconnected organic-walled tubes that terminate in cup-shaped apices 4-11 µm in diameter. Irregular tube clusters are truncated both in macerates and in thin sections, suggesting post mortem transport. Elemental EDXS analysis indicates that extracted meshwork microfossils are predominantly composed of carbonaceous material and also associated with small amounts of titanium and vanadium. Considering the branching and adjoined body plan of carbonaceous fossil, it was likely multicellular and of eukaryotic affinity. As such, it may represent an important step in the evolution of complex multicellularity and morphological complexity several million years before the appearance of Ediacaran organisms.
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| 2. |
- Ebbestad, Jan Ove R., 1967-, et al.
(författare)
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Stratigraphy of the Ediacaran and basal Cambrian of the Digermulen Peninsula, Northern Norway
- 2015
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Ingår i: Geological Society of America Abstracts with Programs, vol 47.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The succession of the Digermulen Peninsula in Finnmark, northern Norway, is the only fossiliferous site inScandinavia with sedimentation across the Ediacaran–Cambrian transition without a significant hiatus. Geologicalinvestigations started in the 1930’s, but the Peninsula was first mapped in the 60’s. Ediacara-type fossils werefirst discovered in the late 80’s but recent discoveries will establish the Digermulen Peninsula as one of the mostsignificant Ediacaran sites in northern Europe. The parautochthonous strata are exposed in the Tanafjord areaalong the coast and in valleys on the east side of the Peninsula. The beds dip slightly to the west with the strikefollowing the coastline (ca. 045°). The Ediacaran succession is close to 1000 m thick and dominantly siliciclastic.It starts with interglacial sediments of the Nyborg Formation (tentatively the earliest Ediacaran), overlying astacked succession of diamictites of the Cryogenian Smalfjord Formation. After a hiatus follows the glaciogenicdiamictites of the Mortensnes Formation (~60 m thick), which is commonly seen to represent the ~582 Ma-oldGaskiers glaciation. Upwards, the contact to the overlying Stáhpogiedde Formation is not exposed locally, but hasbeen shown to represent a hiatus followed by transitional fluvial to marine sediments of the Lillevannet Member.Ediacaran-type fossils appear in the succeeding Innerelva Member. This is a two-cycle deepening upwardssuccession of laminated mudstone with intercalated sand bodies showing load structures. Preliminary microfossilssamples of the Member have so far proven almost barren, making dating more challenging. The basal part of thesucceeding Manndraperelva Member consists of three cycles; first a succession of reddish sandstone followed bytwo coarsening-upward cycles. Each starts with mudstone and fine sandstone and terminates in cross-beddedsandstone. The Ediacaran–Cambrian boundary is located within the third cycle, identified by the trace fossilTreptichnus pedum and associated trilobed trace fossils.The Digermulen Early Life Research Group has since2011 made significant new finds, and focused fieldwork aims to resolve tighter age constraints, provenance of thesediments and the range and diversity of the extended Ediacaran biota.
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| 3. |
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| 4. |
- Högström, Anette, et al.
(författare)
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New occurrences and extension of the stratigraphical range of discoidal Ediacara‑type fossils on the Digermul Peninsula, northern Norway
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In Scandinavia the evolutionary events across the Ediacaran–Cambrian transition can only be studied in continuous section on the Digermul Peninsula, northern Norway, in the siliciclastic Stáhpogiedde Formation. This roughly 500 m-thick unit comprises, in ascending order, the Lillevannet, Innerelva and Manndraperelva members. Trace fossils, including Treptichnus pedum, and organic-walled microfossils, including Granomarginata prima, position the base of the Cambrian in the upper part of the Manndraperelva Member. Some 20 years ago discoidal Ediacara-type fossils were found in the middle part of Innerelva Member. Recent field seasons have provided abundant new material of Aspidella-type fossils and extended their stratigraphical range to within about 15 m above the Lillevannet Member. The exclusive presence of discoidal forms may reflect a taphonomic bias and/or be evidence of a greater age than that of the more diverse Ediacaran assemblages. That the latter may be the case is indicated by the stratigraphic proximity of the lowest occurrences of Aspidella to the Mortensnes diamictite, recently tentatively considered a Gaskiers glaciation equivalent (c.580 Ma). This raises the question of hitherto unrecognised breaks in sedimentation in the Stáhpogiedde Formation. In order to explore this question we have sampled the succession for organic-walled microfossils, detrital mineral geochronology and sediment geochemistry.
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| 5. |
- Meinhold, Guido, et al.
(författare)
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Changes of sediment composition at the dawn of animal life: Insights from the Ediacaran‒Cambrian boundary section of the Digermulen Peninsula (Finnmark, Arctic Norway)
- 2016
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Ingår i: Abstract Volume of GeoTirol2016 - Annual Meeting of DGGV and PANGEO Austria, 25-28. September 2016, Innsbruck.. ; , s. 205-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digermulen Peninsula in northern Norway is the only fossiliferous site in Scandinavia with sedimentationacross the Ediacaran–Cambrian transition without a significant hiatus. Furthermore, it is the only locality inScandinavia where Ediacara-type fossils have been found. The site is located at the edge of Baltica during theEdiacaran–Cambrian transition, where potentially the dramatic climatic turnover from icehouse to greenhouseconditions can be deduced and tied to large-scale plate tectonics. Since 2011, studies by the Digermulen EarlyLife Research Group have recorded significant new finds, promising to establish the site as a significant Ediacaranbiota locality. The Ediacaran succession is about 1000 m thick. Ediacara-type fossils occur in the InnerelvaMember of the Stáhpogiedde Formation. Discoidal fossils dominate the Ediacaran assemblage, although apotentially much greater diversity is suggested because of the recent discovery of a frond-shaped fossil. TheEdiacaran–Cambrian boundary is located within the Manndraperelva Member of the Stáhpogiedde Formation,based on biostratigraphic age control, followed by the Lower Cambrian Breidvika Formation. The successionconsists mainly of quartz-rich sandstones and mudrocks. Deposition took place in various environments, includingfluvial, shallow marine and deeper marine settings. As shown by previous studies using palaeocurrent data,sediment supply was from the Baltic Shield toward the passive margin of Baltica in pre-Ediacaran time. At onepoint within the Ediacaran succession, it shifted by 180 degrees due to the newly formed Timanian orogen. Thisorogen formed in north-eastern Baltica during the late Neoproterozoic and caused a shift in sediment transportdirection and change in source area due to the formation of the Timanian foreland basin to the east of DigermulenPeninsula. In order to track sediment supply and to test current palaeotectonic models a multi-disciplinaryapproach on late Neoproterozoic and Cambrian sediments of the Digermulen Peninsula has been applied. Themethods include, amongst other things, thin section petrography, bulk rock geochemistry (XRF, ICP-MS, ICPOES),bulk rock mineralogy (XRD), heavy mineral analysis, single grain chemistry (EMP, LA-ICP-MS) and zirconU-Pb geochronology.
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