| 1. |
- Agic, Heda, et al.
(författare)
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Life through the 'Varanger ice ages' : microfossil record of late Neoproterozoic glacial-interglacial units from arctic Norway
- 2018
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Ingår i: Geological Society of America <em>Abstracts with Programs</em>. - : Geological Society of America.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The late Neoproterozoic strata in Finnmark (Arctic Norway) provide a good sedimentary record of Neoproterozoic glaciations on the Baltica paleocontinent. The lower Vestertana Group exposed on the Digermulen Peninsula contains two glaciogenic units, the Smalfjord and Mortensnes formations. Chemostratigraphic correlation dated the Smalfjord diamictite to the Marinoan glaciation (650-635 Ma), yet its age was also proposed to be older, per correlation to glacial units in central and southern Scandinavia. The diamictites are bracketing shales and siltstones of the interglacial Nyborg Formation. Stratigraphic, paleontological, and sedimentological data are presented from the interglacial-glacial succession, investigated by the Digermulen Early Life Research Group. Palynological analysis yielded well-preserved organic-walled microfossils (OWM) from the Nyborg Fm., and from fine-grained diamictite matrix in the Mortensnes Fm. via a modified extraction method.The interglacial Nyborg Fm. hosts a moderate diversity assemblage of prokaryotic and eukaryotic OWM, as well as acanthomorphic acritarchs such as Ceratosphaeridium, ?Cavaspina, and a novel process-bearing form. Organically preserved, enigmatic multicellular eukaryotic fossils occur in the upper Nyborg Fm. The Mortensens glacial assemblage is less diverse and contains bacterial filaments, leiosphaerids, toroidal forms, and Micrhystridium-type minute acanthomorphs.The presence of Doushantuo-Pertatataka type acritarchs in the Nyborg Fm., and small acanthomorphs in the Mortensnes diamictite corroborate an early Ediacaran age for the interglacial-glacial succession on Digermulen. In addition to the trace fossil and body-fossil record of Ediacara-biota in the overlying Stáhpogieddi Formation, the microfossil biostratigraphy suggests Marinoan and Gaskiers glaciation equivalent ages of the Varanger glaciations in Finnmark. Protistan diversity in the succession declined through and following the glaciation, until late Ediacaran.
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| 2. |
- 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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| 3. |
- Ebbestad, Jan Ove R., 1967-, et al.
(författare)
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Biostratigraphy and palaeontology of the lower Cambrian Duolbagáisá Formation on the Digermulen Peninsula, Arctic Norway
- 2018
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Ingår i: International Conference on Arctic Margins.
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Konferensbidrag (refereegranskat)abstract
- The lower Cambrian sequence on the Digermulen Peninsula (Finnmark, Arctic Norway) is the northernmost extension of the Cambrian deposits along the Caledonian front. It is exceedingly thick compared to cratonal successions typical of most of Baltica. The Duolbagáisá Formation represents the youngest lower Cambrian unit on the peninsula with the first trilobite-bearing strata, a plethora of trace fossils including diverse arthropod traces and Plagiogmus arcuatus, and abundant and wellpreserved organic walled microfossils (OWM). Extensive field work by the Digermulen Early Life Research Group allows for the first time a detailed appreciation of the age and faunal composition of the unit. The lower member is ~250 m thick with thin-bedded siltstone, sandstone and mudstone. A single unidentifiable holmiid thorax region occurs alongside arthropod trace fossils. OWM indicate the S. ornata-F. membranacea Zone. The upper member is ~390 m thick and consist of several upward shallowing parasequences with fine-grained sandstone, siltstone and mudstone followed by thick mature quartzite. The trace fossil Syringomorpha occurs throughout the upper member and Cruziana and Rusophycus are especially abundant in the upper parts. The first identifiable olenellid trilobites occur in a thick mudstone/siltstone interval at the middle of the member, along with an elliptocephalid trilobite and other arthropods. Abundant OWM indicate the H. dissimilare-S. ciliosa Zone with the higher levels belonging to the Volkovia-Liepaina Zone. The entire sequence thus span the Cambrian Series 2, stages 3–5.
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| 4. |
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| 5. |
- Ebbestad, Jan Ove R., 1967-, et al.
(författare)
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Holmiid trilobites from the lower Cambrian of the Digermulen Peninsula, Arctic Norway
- 2017
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Ingår i: 6th International Conference on Trilobites and their Relatives. Tallinn, Estonia, 7-10 July 2017. - Tallinn : Libris Est OU. - 9789949818617
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Konferensbidrag (refereegranskat)abstract
- Lower Cambrian holmiid olenelloids are used for biozonation of lower Cambrian (Series 2) strata in Baltoscandia. About a dozen species have been named since the description of Holmia kjerulfi (Linnarsson, 1868), but except for the classical area in Mjøsa, Norway, the species traditionally occur in small numbers, are variably preserved, occur at one or a few localities only and usually with only one taxon present. Definitions of the biozones are therefore still problematic. One level in the lower Cambrian Duolbasgáissá Formation of the Digermulen Peninsula, Arctic Norway, has yielded more than 50 new specimens of holmiids, preliminarily assigned to Elliptocephala n. sp. and Kjerulfia n. sp. Acritarchs indicate the Heliosphaeridium dissimilare–Skagia ciliosa acritarch Zone which corresponds to the traditional Holmia kjerulfi Assemblage Zone. Elliptocephala n. sp. is known from about a dozen specimens. It is characterized by very long palpebral lobes, a parallel-sided glabella, a short anterior glabellar lobe and short genal spines. A node is developed on the occipital ring. Semi-complete specimens show up to 10 thoracic segments, but the full number of thoracic segments and the pygidium is unknown. The slightly older E. lundgreni (Moberg, 1892), known from the Schmidtiellus mickwitzi Zone of southern Sweden, differs in the proportions of the glabella, the length of the palpebral lobes and definition of the cephalic border. Both H. mobergi and H. sulcata from Sweden show similarities to Elliptocephala n. sp. in the weakly developed lateral border with an effaced anterior border furrow. Nikolaisen & Henningsmoen (1987) described Kjerulfia lata Kiær, 1917 from two fragmentary specimens from this locality in Digermulen. More than 20 new specimens from this site shows that the species differs from Kjerulfia lata from the type area in southern Norway in proportions and features of the glabella, the width of the genal field and the possession of a stout and high spine on the occipital ring, and it is tentatively assigned to Kjerulfia n. sp. The material from the Digermulen Peninsula adds to the diversity of the Baltoscandian holmiids and is tightly constrained stratigraphically.
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| 6. |
- 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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| 7. |
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| 8. |
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| 9. |
- Högström, Anette, et al.
(författare)
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Exploring the Ediacaran Biota of the Digermulen Peninsula, Northern Norway
- 2015
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Ingår i: Geological Society of America Abstracts with Programs, vol 47, no 7..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digermulen Peninsula in northern Norway is the only locality that has yielded Ediacara-type fossils inScandinavia. The Peninsula exhibits an Ediacaran to Lower Ordovician succession consisting of roughly 3000 mof siliciclastic deposits formed in a foreland basin marginal to Baltica. In 2011 a restudy of the Ediacaran deposits(1000 m thick) was launched resulting in new finds that promise to establish the Digermulen Peninsula as asignificant new Ediacaran biota locality. First described in the 1990´s the assemblage is dominated by medusoidtypefossils, such as Cyclomedusa, Ediacaria?, Beltanella and Nimbia? now possibly reinterpreted astaphomorphs of the broadly defined Aspidella as exemplified by the Fermeuse assemblage in Newfoundland.Previous field seasons have produced abundant new material of discoidal forms (tentatively Aspidella), the lowestin stratigraphic proximity to the glacial Mortensnes diamictite (tentatively c. 580 Ma). Recent fieldwork during thesummer of 2015 yielded the first specimen of a multi-vaned Ediacara-type fossil from the Innerelva Member of theStáhpogiedde Formation not far from where the first discoidal fossils were found in the 90´s. Reconstructed toreach approximately 7.5 – 8 cm above the sediment surface this organism appears to have a roughly sphericalshape with three or more vanes, but more detailed study is needed. We know little of the holdfast structure but itappears to possess a generalized Aspidella-like morphology, emphasizing the variety of organisms that may havehad very similar holdfasts. In addition to Aspidella sp., well-preserved Hiemalora are present in these beds.Another important find are several specimens of Palaeopascichnus from near the base of the Innerelva Membermaking them the oldest non-stromatolite macroscopic fossils in Scandinavia. Future work for the DigermulenEarly Life Research Group will focus on extensive excavation and sampling of this important interval to increasethe understanding of the Ediacaran record on the Peninsula.
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| 10. |
- 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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