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| 7. |
- Bonow, Johan M., et al.
(författare)
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Elevated erosion surfaces in central West Greenland and southern Norway: their significance in integrated studies of passive margin development
- 2007
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Ingår i: Norwegian Journal of Geology. - 0029-196X. ; 87, s. 197-206
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Tidskriftsartikel (refereegranskat)abstract
- Elevated erosion surfaces were used as an independant data set in an integrated study of the landscape development in central West Greenland. The study resulted in a time-constrained model describing multiple episodes of post-rift uplift, erosion and burial on a passive margin. The model is based on full integration of three data sets: analysis of large-scale landforms, apatite fission track analysis (AFTA) of samples from outcrops and deep boreholes, and the geological record. These data are equally important as they record specific an unique parts of the landscape history. The relative chronology obtained from the landform record is constrained by geology, which gives the maximum age of an erosin surface, and AFTA that records the cooling history of the subsurface rock. This combined approach validates the interpretation of erosion surface as having been goverened by different base levels in the past, and shows that erosion surfaces can be used to reconstruct tectonic events. Geomorphological key observations for the landscapes of southern Norway are presented and the similarities with landscapes in central West Greenland emphasised, especially the elevated plateaux and the Mesozoic etch surfaces. This similarity suggests that it may be possible to construct a time-constrained model for the landscape development of southern Norway based on our West Greenland approach.
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| 8. |
- Bremer, Oskar, 1985-, et al.
(författare)
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Silurian vertebrate remains from the Oslo Region, Norway, and their implications for regional biostratigraphy
- 2019
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Ingår i: Norsk Geologisk Tidsskrift. - : GEOLOGICAL SOC NORWAY. - 0029-196X .- 1502-5322. ; 99:1, s. 129-155
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Tidskriftsartikel (refereegranskat)abstract
- Several vertebrate assemblages are described from the Silurian of the Oslo Region, Norway, based on the review and revision of previous reports of microremains, as well as unpublished material from museum collections. Articulated thelodont specimens from the Rudstangen Fauna, Ringerike Group, are also described here for the first time, revealing a seemingly monogeneric loganelliid assemblage. The oldest assemblage (mid-Llandovery) only contains the thelodont Loganellia cf. aldridgei, while a single sample from upper Llandovery strata produced four Thelodus sp. scales. These scales share features with those from younger Thelodus taxa and give additional support to an early appearance of this genus. The mid-Wenlock faunas consist of thelodonts Loganellia grossi, Loganellia einari and Thelodus laevis. These are joined by the thelodont Paralogania martinssoni, anaspids Rhyncholepis parvula and cf. Pterygolepis nitida, as well as the osteostracans cf. Tyriaspis whitei and Osteostraci gen. et sp. indet. in late Wenlock and earliest Ludlow faunas. These complement the previously described anaspids and osteostracans of the Rudstangen Fauna based on articulated specimens. The faunas of a number of calcarenite samples collectively contain the thelodonts L. grossi, L. einari, P. martinssoni and T. laevis, and are most likely of early Ludlow age. When the vertebrate-producing samples are put in the proposed stratigraphical framework for the Oslo Region that has been refined in recent decades, the faunas fit well into the vertebrate biozonation established for the Silurian, contrary to previous claims. The earliest faunas in the area show similarities to the Llandovery of Britain, whereas thelodonts and anaspids, but not osteostracans, from late Wenlock and early Ludlow are more closely related to Baltic forms. Additional sampling of the area may assist in refining the biostratigraphy and provide insights into Silurian vertebrate distributions in Norway and related regions.
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| 9. |
- Ebbestad, Jan Ove R., et al.
(författare)
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Isostrophic molluscs (Tergomya and Gastropoda) from the Upper Ordovician of Norway
- 2000
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Ingår i: NORSK GEOLOGISK TIDSSKRIFT. - 0029-196X. ; 80:3, s. 187-202
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Tidskriftsartikel (refereegranskat)abstract
- Ten species of Upper Ordovician isostrophic Tergomya and Gastropoda (Mollusca) are described from the Oslo Region, Norway. Sinuitina, represented by Sinuitina? planilata sp, nov., is considered a cyrtonellid tergomyan, based on interpretation of the umbil
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| 10. |
- Ebert, Karin, 1976-, et al.
(författare)
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Pre-glacial landforms on a glaciated shield : the inselberg plains of northern Sweden
- 2012
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Ingår i: Norsk Geologisk Tidsskrift. - 0029-196X. ; 92:1, s. 1-17
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the long-term geomorphological evolution of the inselberg plains on the glaciated northern Fennoscandian shield. The shield surface has been largely stripped of pre-Quaternary correlative sediments and saprolites by non-glacial and glacial erosion, which makes investigations of pre-Quaternary landscape development a challenge. The relief of the study area, covering 33,000 km3 in the centre of the shield in northern Sweden, includes an abundance of inselbergs that provide the basis for the study. We examine the relief of the inselberg plains, integrated with glacial-geomorphologic features, geology, and weathering remnants, by using GIS-analysis and fieldwork. Several key areas are used to demonstrate the impact of glaciations on the large scale relief, and the influence of geology, structure and deep weathering on relief formation.Glacial erosion had only a minor impact on the large-scale bedrock morphology of northern Sweden. Based on excavations and observations in the Parkajoki area, an area largely preserved under cold-based ice during Quaternary glaciations, we infer that grus weathering, resulting in saprolite covers of up to 10-20 m thickness, occurred in the Neogene. However, inselbergs are considerably higher than that, and must therefore be the result of older deep weathering and erosional events. Narrow fracture zones associated with deep kaolins found in northern Fennoscandia may represent the roots of older generations of deep weathering covers but their age and formation is yet unclear. The geology of the area has greatly influenced the present surface relief. The positions and footprints of the inselbergs are often closely controlled by bedrock type and fracturing. Granite inselbergs generally have dome forms where dome shape and slopes are determined by joint patterns. Steps between palaeosurfaces locally coincide with lithological boundaries and major faults. These links indicate the fundamental importance of etch processes in shaping the relief through multiple cycles of deep weathering and stripping. Palaeosurfaces have been extended and lowered through time, with isolation of small inselbergs during erosion of higher palaeosurfaces. The timescales for relief generation remain uncertain and there is a pressing need to understand the significance of and to date the sediments, saprolites and weathered ore bodies that rest on the surface of the northern Fennoscandian shield.
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| 11. |
- Hall, Adrian Malcolm
(författare)
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Phanerozoic denudation across the Kola Peninsula, northwest Russia : implications for long term stability of Precambrian shield margins
- 2015
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Ingår i: Norsk Geologisk Tidsskrift. - : Geological Society of Norway. - 0029-196X. ; 95:2, s. 153-169
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Tidskriftsartikel (refereegranskat)abstract
- Contrasting views exist on the stability of the Earth’s shield regions over the last 1 Ga that have major implications for reconstructing erosion patterns on shields and the supply of sediment to intra-cratonic and marginal basins. This paper explores Phanerozoic denudation rates and patterns on the northern part of the Fennoscandian Shield in the Kola Peninsula, Northwest Russia. This shield region was intruded by magmatic rocks of the Kola Alkaline Province (KAP) in the Devonian and Early Carboniferous. The KAP comprises a varied suite of alkali–ultramafic plutonic and hypabyssal intrusions, diatremes and dykes that was emplaced at various depths in the crust and allows assessment of depths and rates of erosion during and since the KAP magmatic episode. Further evidence of long-term denudation is provided by Mesoproterozoic and Neoproterozoic cover rocks found around the margins of the Kola Peninsula and in the White Sea. The burial and exhumation history is compared to available Apatite Fission Track (AFT) data for the Kola Peninsula and adjacent areas. Post-Devonian denudation rates on the shield rocks of the Kola Peninsula have varied in space and time. Around the periphery of the Kola Peninsula, low long-term denudation of shield rocks is indicated by the survival of Riphean cover rocks and Late Devonian lavas, kimberlite crater facies and near-surface emplacement of dykes. In contrast, in the main belts of KAP intrusions, 4–6 km of rock was removed in response to doming between 460 and 360 Ma. Deep denudation is indicated by the emplacement depths of alkaline intrusions and Phoscorite–Carbonatite pipes (PCPs). Erosion on the Kola Peninsula since 360 Ma has been far more limited. Extensive, shallow, late-stage magmatism associated with PCPs, dykes and the large alkaline intrusions in the KAP indicates that erosion depths nowhere exceeded 2 km. Post-Devonian denudation has removed <1 km of rock from the margins of the Kola Peninsula and from the backslope of the Saariselkä–Karelia scarp in northern Finland. AFT data point to an important phase of erosion in the early Mesozoic but depths of unroofing of 3–5 km based on AFT cooling ages for this later phase are in conflict with the evidence of lesser erosion provided by the late-stage KAP intrusions and also require unrealistic depths of former Devonian to Triassic cover rocks. Mean denudation rates were greatest (up to 40 m/Myr) during the KAP magmatic phase. Post-Devonian rates across the Kola Peninsula and adjacent shield areas were much lower (<3–6 m/Myr) and are compatible with low long-term denudation rates for other cratons. Further resolution of longterm denudation patterns and rates on the Kola Peninsula requires the application of low-temperature thermochronometry, detailed examination of the regional geomorphology and firmer dating of ancient weathering episodes.
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| 12. |
- Hall, Adrian M.
(författare)
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The last glaciation of Shetland : local ice cap or invasive ice sheet?
- 2013
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Ingår i: Norsk Geologisk Tidsskrift. - 0029-196X .- 1502-5322. ; 93:3-4, s. 229-242
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Tidskriftsartikel (refereegranskat)abstract
- The question of whether the Shetland Islands were covered by an ice cap or by an ice sheet during the last glacial cycle (40-10 ka) remains unresolved. This paper addresses this problem using existing and new data on glacial erratic carry, striae, glacial lineaments and roche moutonnee asymmetry. Its focus is on eastern Shetland, where ice-cap and ice-sheet glaciation would lead to opposed ice-flow directions, towards and away from the North Sea. Evidence cited in support of ice-sheet glaciation of Shetland is questioned. The primary survey of striae correctly identified striae orientation but the direction of ice flow from striae on eastern Shetland was misinterpreted: it was not from, but towards the North Sea. Glacial lineaments interpolated to cross the spine of Shetland instead are discontinuous and diverge away from an axial ice-shed zone that lacks lineaments. Glacitectonic structures cited recently as evidence for westward flow of an ice sheet across eastern Shetland have been partly misinterpreted and other ice-flow indicators in the vicinity of key sites indicate former eastward ice flow towards the North Sea. Westward carry of erratics over short distances in N and S Shetland may be partly accounted for by shifts in ice sheds during ice-cap deglaciation. Collectively, the evidence for movement of the Fennoscandian ice sheet across Shetland is weak. Any ice-sheet incursion over Shetland occurred before the last glacial cycle. The cleansed ice-flow directional data for Shetland show a simple pattern of divergent ice flow from an axial ice-shed zone beneath an ice cap. The deglaciation sequence for the ice cap is evident from sea-bed moraine systems. The Shetland ice cap at the Last Glacial Maximum was substantial, attaining a thickness of 1 km and a diameter of >160 km. The ice cap was of sufficient size to restrain the Fennoscandian ice sheet on the western edge of the Norwegian Channel and to divert the British ice sheet over Orkney. Glacial landscapes on Shetland indicate that ice-cap glaciation has been the dominant mode of glaciation during the Pleistocene.
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| 13. |
- Holmer, Lars E., et al.
(författare)
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The lingulid brachiopod Lingularia from lowermost Cretaceous hydrocarbon seep bodies, Sassenfjorden area, central Spitsbergen, Svalbard
- 2012
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Ingår i: Norsk Geologisk Tidsskrift. - 0029-196X .- 1502-5322. ; 92:2-3, s. 167-174
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Tidskriftsartikel (refereegranskat)abstract
- A series of Upper Jurassic to Lower Cretaceous samples of hydrocarbon seep bodies from central Spitsbergen (Svalbard) were treated with acetic acid to retrieve insoluble micro and macrofossils. The Lower Cretaceous samples yielded abundant lingulid material of Lingularia similis? Biernat & Emig 1993, represented by well preserved, but invariably fragmented shells. They provide the first critical ultrastructural information for this important extinct member of the extant Lingulidae.
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| 14. |
- Högström, Anette E. S., et al.
(författare)
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New information on the Ediacaran-Cambrian transition in the Vestertana Group, Finnmark, northern Norway, from trace fossils and organic-walled microfossils
- 2013
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Ingår i: Norsk Geologisk Tidsskrift. - 0029-196X .- 1502-5322. ; 93:2, s. 95-106
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Tidskriftsartikel (refereegranskat)abstract
- The Vestertana Group on the Digermul Peninsula, Finnmark, northern Norway, presents one of the few, potentially continuous Ediacaran-Cambrian sections in Scandinavia. Trace fossils provide the main age constraint, with the boundary traditionally placed at the base of the Breidvika Formation. Here, we provide trace-fossil evidence to show that this boundary is at least as low as the third cycle of the Manndraperelva Member, Stahpogieddi Formation, where Treptichnus pedum is associated with trilobed trace fossils. Organic-walled microfossils from the same stratigraphic interval include Granomarginata prima and the first report from Scandinavia of Cochleatina. The second cycle of the Manndraperelva Member contains trace fossils, including treptichnids and ?Cochlichnus isp. tentatively interpreted as latest Ediacaran. Reports of palaeopascichnids suggest a late Ediacaran age for the first cycle. The age of lower parts of the Stahpogieddi Formation is poorly constrained but discoidal Ediacara-type fossils, vendotaenids, and possible simple trace fossils, suggest that the middle part of the Innerelva Member is younger than c. 560 Ma.
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| 15. |
- Høyberget, Magne, et al.
(författare)
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Re-evaluation of the stratigraphically important olenellid trilobite Holmia cf. mobergi from the Cambrian Series 2, Stage 3 and its implications for the lower Cambrian stratigraphy in the Mjøsa area, Norway
- 2019
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Ingår i: Norsk Geologisk Tidsskrift. - : Geological Society of Norway. - 0029-196X .- 1502-5322. ; 99:1, s. 63-92
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Tidskriftsartikel (refereegranskat)abstract
- The olenellid trilobite Holmia cf. mobergi, known from a single cephalon in the upper lower Cambrian strata from a river section in Flagstadelva, Hamar, has played a significant stratigraphic role in interpreting the lower Cambrian informal Series 2, Stage 3 in the Mjøsa area, Norway, sinceits discovery in the early 1950s. It was considered one of the oldest trilobite taxa in the lower Cambrian of Scandinavia, but the stratigraphic leveland biozonation of the cephalon were problematic and a matter of discussion for decades. Moreover, organic-walled microfossil biostratigraphyquestioned the supposed age of the trilobite. New specimens of this taxon collected from the type locality show that the species occurs at a differentstratigraphic level than first reported, prompting a new description of the species and a re-evaluation of the taxon’s biostratigraphic significance.Holmia cf. mobergi is compared with new and well-preserved topotype material of Holmia inusitata, a very rare taxon hitherto known from onesingle outcrop in an autochthonous setting in Norway. Holmia cf. mobergi and Holmia inusitata are here considered conspecific.
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| 16. |
- Høyberget, Magne, et al.
(författare)
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The shelly fauna and biostratigraphy of the lower Cambrian (provisional series 2, stage 4) Evjevik Member, Ringstrand Formation in the Mjøsa area, Norway
- 2015
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Ingår i: Norsk Geologisk Tidsskrift. - 0029-196X. ; 95:1, s. 23-56
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Tidskriftsartikel (refereegranskat)abstract
- New, extensive fossil material collected in situ from the lower Cambrian Evjevik Member in the Mjøsa type area, southern Norway, allows a reevaluationof the faunal distribution and diversity of the ‘Ornamentaspis’ linnarssoni Zone. Described taxa include three holmiid, six ellipsocephalidand one eodiscoid trilobite in addition to five helcionelloid molluscs. A Holmia species with affinities to the Swedish H. lapponica is common in the Evjevik Member. Librigenae, thoracic segments and pygidia from the poorly known, but biostratigraphically important trilobite ’Ornamentaspis’ linnarssoni (Kiær, 1917) are documented for the first time. The species is redescribed and transferred to Ellipsocephalus. Helcionelloid molluscs arerepresented by Helcionella antiqua (Kiær, 1917), Stenotheca norvegica (Resser, 1938), Mackinnonia puppis n. sp., Mackinnonia? sp. and Latouchella sp.These are similar to taxa reported from coeval strata at Gislövshammar in southern Sweden and may prove to have biostratigraphical potential. TheHolmia kjerulfi Zone, the Ellipsocephalus linnarssoni Zone and the Comluella? scanica–Ellipsocephalus lunatus Zone are readily recognised in theLower Allochthon of the Mjøsa area and are in this report treated as distinctive, successive zones. New illustrations are provided of the brachiopod Magnicanalis rotundata (Kiær, 1917), together with the enigmatic fossil Mongolitubulus Missarzhevsky, 1977, recorded for the first time in Norway.
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| 17. |
- Isakar, Mare, et al.
(författare)
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Homeomorphic gastropods from the Silurian of Norway, Estonia and Bohemia
- 1999
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Ingår i: NORSK GEOLOGISK TIDSSKRIFT. - 0029-196X. ; 79:4, s. 281-288
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Tidskriftsartikel (refereegranskat)abstract
- Redescription of the gastropod Euomphalus undiferus Schmidt, 1858 from dir Upper Llandovery Rumba Formation of Estonia requires reinvestigation of the hitherto monotypic genus Kiaeromphalus Peel & Yochelson, 1976, originally described from the Rytteraker
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- Lorenz, Henning, 1972-, et al.
(författare)
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Detrital zircon ages and provenance of the Late Neoproterozoic and Palaeozoic successions on Severnaya Zemlya, Kara Shelf: a tie to Baltica
- 2008
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Ingår i: Norwegian Journal of Geology. - 0029-196X. ; 88:4, s. 235-258
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Tidskriftsartikel (refereegranskat)abstract
- The Neoproterozoic to Devonian sedimentary successions of Severnaya Zemlya, in the Russian high Arctic, have been sampled for detrital zircon provenance studies. 50-100 zircons were analyzed from 11 samples and, of these, about 60% (c. 500 totally) were used for the geological interpreta- tion. Most of the samples show a similar Precambrian age spectrum, including a strong, prominent peak in the Late Vendian to Early Cambrian and well defined Mesoproterozoic populations reaching back into the Late Palaeoproterozoic. Only a few older zircons are present, composing minor populations at c. 2.7 Ga. The younger samples (Ordovician and Devonian) also contain an Early-Mid Ordovician population, probably related to local igneous activity. The detrital zircon age spectrum of Severnaya Zemlya constitutes a strong link to the Timanian margin of northwestern Rus- sia, providing support for the interpretation that this part of the high Arctic was a northern continuation of Baltica’s eastern passive margin in the Early Palaeozoic. It may also have had close connections not only with the Northern Belt of the Tajmyr Orogen, but also to the Central Belt, which was accreted to Siberia in the Vendian.
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| 23. |
- Witt-Nilsson, P, et al.
(författare)
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Tectonostratigraphy of the Caledonian Atomfjella Antiform of northern Ny Friesland, Svalbard
- 1998
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Ingår i: NORSK GEOLOGISK TIDSSKRIFT. - : SCANDINAVIAN UNIVERSITY PRESS. - 0029-196X. ; 78:1, s. 67-80
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A combination of structural mapping and isotopic age-determination studies provides the basis for a new interpretation of the Caledonian geology of northern Ny Friesland. The new mapping has defined the northern extension of the Atomfjella Antiform, a maj
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