Norwegian Journal of Geology最新文献

{"title":"Detrital zircons of the vast Triassic Snadd and De Geerdalen formations, Barents Shelf, reveal temporal changes in sediment source","authors":"","doi":"10.17850/njg103-2-3","DOIUrl":"https://doi.org/10.17850/njg103-2-3","url":null,"abstract":"Studies of detrital-zircon age distributions from Triassic sedimentary rock successions on the Arctic Barents Shelf have resulted in different provenance interpretations. Here, we provide new U–Pb/Hf detrital-zircon data from eleven samples of the Snadd and De Geerdalen formations, covering the Barents Shelf in a north–south transect, that help refine the provenance of these sedimentary rocks and show how stratigraphic variations reflect changing source regions. The sample locations cover different stratigraphic levels and geographic locations within the formations. The detrital-zircon age spectra in the lower part (lowest Ladinian and lower Carnian) are dominated by two age peaks at 300 and 540 Ma, whereas the zircon distributions in the stratigraphically younger deposits (latest Carnian and early Norian) are dominated by a 235 Ma age peak and two minor peaks at 300 and 425 Ma. The apparent relative contribution of detritus of different ages changes gradually from lower to higher stratigraphic levels, marked by an increase in both the 235 and 425 Ma age peaks, a decrease in the 300 Ma component and a progressive loss of the 540 Ma age peak. The zircon Hf-isotopic compositions display predominantly juvenile zircon populations, except for a mixed juvenile and evolved signature in the youngest Permo-Triassic grains. A regional comparison of detrital-zircon age spectra in latest Carnian/early Norian deposits extends the depositional system into the Sverdrup Basin, supporting a much larger depositional system than hitherto known. The gradual change in detrital-zircon age spectra likely represents a gradual shift in zircon provenance. We interpret these variations to reflect an early source region in the north Urals, gradually changing to a dominant source region in the Taimyr Peninsula region.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":" 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135191851","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magmatism during late Ordovician-early Silurian accretion of the Caledonides of Arctic Scandinavia: the Halti–Guolasjávri area revisited","authors":"Per-Gunnar Andréasson, Davod G. Gee","doi":"10.17850/njg103-2-5","DOIUrl":"https://doi.org/10.17850/njg103-2-5","url":null,"abstract":"In the Scandinavian Caledonides, evidence of syn-collisional magmatism related to extensional basin development immediately prior to late Silurian Baltica–Laurentia collision was considered restricted to exotic terranes until late Silurian ages were obtained from the Halti Igneous Complex (HIC), hosted by a thrust sheet (Corrovarre Nappe, CN) of continental affinity. Various orogenic models for the extension and magmatism, a. o. subduction flip, slab roll-back, and ridge subduction have been proposed. Crucial factors include the affinity (Baltican or exotic) of the CN, and the nature of the debated unconformity at the base of the overlying exotic Vaddas Nappe (Köli). This study reexamines a critical tectonostratigraphic section and reports U–Pb zircon ages (441–436 Ma) of palingenetic granitic dykes generated by the HIC. We reinterpret the CN as a slice of the continental margin and accreted with some other nappes of the Seve Nappe Complex (SNC) which decoupled from the continent-ocean transition (COT) at an early stage of subduction of the margin. The lower part of the bipartite Vaddas Nappe, composed of a very dense dolerite dyke swarm with screens of quartzite, marble and subordinate black schist, is reinterpreted as a continuation northwards of the uppermost nappe of the SNC in Indre Troms, derived from the Ediacaran outermost continental margin. The contact with the overlying telescoped succession of conglomerates, marbles, volcanics and turbidites of the Vaddas Nappe is tentatively interpreted as a tectonised unconformity. To a classical model of back-arc spreading outboard of Laurentia during closure of the Iapetus Ocean, we add the arrival of Baltica, with a prism of decoupled slices of the COT and exhumed/exhuming UHP nappes. The spreading centre of the basin provides a plausible setting for gabbros and pillow lavas of the Vaddas Nappe, and the shores of the basin for a Seve–Köli unconformity. Future PTt studies are required in order to be able to relate the proposed shallow, syn-exhumation HIC magmatism to the tectonometamorphic evolution of the HP–UHP nappes of the SNC.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":" 12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135190885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Configuration of the Scandinavian Ice Sheet in southwestern Norway during the Younger Dryas","authors":"Jason P. Briner, John Inge Svendsen, Jan Mangerud, Henriette Linge, Richard Gyllencreutz, Svein Olaf Dahl, Fabel Derek","doi":"10.17850/njg103-3-1","DOIUrl":"https://doi.org/10.17850/njg103-3-1","url":null,"abstract":"The extent of the Scandinavian Ice Sheet in southwestern Norway is precisely located during the well-characterized Younger Dryas re-advance. However, the thickness of the ice sheet is less well constrained inland from the terminal position. Some exceptions include lateral moraines traced inland and up to 1000 m a.s.l. along Hardangerfjorden. Here, we apply 10Be dating in two areas: (1) bedrock and boulders in the high-relief landscapes near the Younger Dryas margin around the Bergen urban area, and (2) boulders from an upland 1600 m a.s.l. much farther (120 km) inland. We find that coastal summits ranging from ~400 to ~680 m a.s.l. and located only ~10–15 km up-flow from the ice margin, were covered by the Scandinavian Ice Sheet during the Younger Dryas. The scatter in the 10Be age population of 22 boulder samples is best explained by isotopic inheritance owing to inefficient subglacial erosion during the foregoing glaciation. Most of the 11 bedrock samples also exhibit inheritance, pointing to the source of inheritance in boulders and implying inefficient subglacial erosion during the last glaciation even in valley-bottoms near Bergen. Regional glacial striae compilations suggest that ice flow during maximum Younger Dryas ice-sheet configurations was for the most part cross-valley, with potentially low basal slip rates. Five new 10Be ages from the inland site help to constrain ice height far inland. We combine these new results with prior information to generate a cross profile of the Younger Dryas ice sheet in southern Norway.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":" 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135190879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Jurassic heritance of the geomorphology in Mid Norway","authors":"Odleiv Olesen, Håkon G. Rueslåtten, Jasmin Schönenberger, Morten Smelror, Roelant van der Lelij, Bjørn Eskil Larsen, Lars Olsen, Vikas Baranwal, Arne Bjørlykke, Marco Brönner, Jomar Gellein, Jan Steinar Rønning","doi":"10.17850/njg103-3-2","DOIUrl":"https://doi.org/10.17850/njg103-3-2","url":null,"abstract":"The age and formation of the Scandinavian mountains and the Norwegian strandflat have long been the subject of dispute. Some researchers argue that the present-day mountains are remains of the Caledonian orogen while others claim that the Caledonian nappes after erosion were buried by Mesozoic sediments and subsequently exhumed. In order to clarify these issues, we have studied remains of chemically weathered rocks (saprolites) from the coast to the interior of central Norway. The multidisciplinary study includes digital topography, electrical resistivity tomography (ERT), XRD, XRF, palynological analyses and K–Ar dating of samples from outcrops, trenches and core drilling. The coastal areas are dominated by an outer strandflat and an inner joint-valley landscape, while the interior is characterised by smoother landscapes referred to as palaeo-surfaces. Remnants of pre–Tertiary weathering occur in the joint valley landscape as well as on the palaeo-surfaces. The saprolites are found within fault- and fracture-zones and at depths exceeding 50 m in drillholes. It is suggested that the old saprolites were strongly eroded along the coast and in the fjords and valleys such as in Orkdalen and Sunndalen. K–Ar dating of mainland clay alteration most frequently yielded Jurassic ages along a profile extending from the coast to the Dovrefjell mountains (c. 1400 m a.s.l.). The formation age of the smectite- and kaolinite-containing saprolites seems to be almost contemporaneous along this profile implying that the entire area was subject to weathering in a warm and humid climate, such as prevailed during the Late Triassic and Jurassic. Palynological residues containing thermally altered Triassic and Jurassic pollen and spores in the clay-infected bedrock lend support to the saprolite interpretation. The Mesozoic landscape in central Norway was consequently shaped by uplift and deep weathering in the Jurassic. The entire Trøndelag county was most likely covered by Mesozoic sedimentary rocks until Cenozoic exhumation. The landscape was modified by Cenozoic tectonic uplift and erosion, and finally reworked by Pleistocene glacial erosion. We therefore conclude that both the observed saprolites and the shape of the present-day landscape in central Norway give a strong impression of the original Jurassic weathering surface.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135922831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gas seeps in Norwegian waters – distribution and mechanisms","authors":"T. Thorsnes, S. Chand, V. Bellec, F. C. Nixon, H. Brunstad, A. Lepland, S. Aarrestad","doi":"10.17850/njg103-2-4","DOIUrl":"https://doi.org/10.17850/njg103-2-4","url":null,"abstract":"","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44918319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Neoproterozoic Valdres Group - depositional conditions and stratigraphical developments in the Mellane and Grønsennknippa sections, Valdres, Southern Norway","authors":"H. Dypvik, Even Stokkebekk, Eirik N. Nordeng, Rikke Ø. Småkasin, Kathrine Sørhus, A. Morton, R. Gabrielsen","doi":"10.17850/njg103-2-2","DOIUrl":"https://doi.org/10.17850/njg103-2-2","url":null,"abstract":"one diamictite unit. The latter is possibly correlative to the diamictite recognised in the Valdres Group at Mellane and may represent a tillite correlatable to the Moelv Tillite (Marinoan glaciation). The Mellane section is more dominated by sandstones and subordinate conglomerates than those at Grønsennknippa. Mineralogical composition and field observations of the Grønsennknippa and Mellane sections indicate relatively short transport distances of the texturally immature sediments. The petrography also reflects a later metamorphic phase (varying greenschist facies) that overprints the original mineralogy. Comparison between the Valdres Group at Mellane and Grønsennknippa sections indicates that the Grønsennknippa succession exhibits an originally more immature mineralogical and textural signature than those at Mellane. The Grønsennknippa sections are more feldspar-rich and dominated by coarse-grained detritus. This may reflect different positions with respect to the source area/basin margin. In this study, the Valdres Group at Grønsennknippa and Mellane is compared with selected fluvial/alluvial formations of the Hedmark Basin, revealing comparable depositional environments and stratigraphic developments. The occurrence of possible tillites at stratigraphical levels comparable to the Moelv Tillite are of particular interest. The petrographical composition and heavy mineral distribution support comparable sediment sources from mainly Sveconorwegian formations in both the Valdres and Hedmark basins.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49511364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Bivalve beds reveal rapid changes in ocean oxygenation in the Boreal Middle Triassic – a case study from Svalbard, Norway","authors":"V. Engelschiøn, S. Bernhardsen, Fredrik Wesenlund, Ø. Hammer, J. Hurum, A. Mørk","doi":"10.17850/njg103-2-1","DOIUrl":"https://doi.org/10.17850/njg103-2-1","url":null,"abstract":"","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":"1 1","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67528279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fault linkage on southeastern Bjørnøya: Implications for structural interpretations surrounding fertile ore-forming fault systems offshore","authors":"E. Ryan, B. Sørensen, C. Fichler, R. Larsen, J. L. Gresseth, A. Bjørlykke","doi":"10.17850/njg102-4-5","DOIUrl":"https://doi.org/10.17850/njg102-4-5","url":null,"abstract":"","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-03-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45502212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Middle Pennsylvanian megabreccia adjacent to the Odellfjellet Fault in Billefjorden, central Spitsbergen","authors":"Jean-Baptiste P. Koehl, Christoffer Taule, Maxime Collombin","doi":"10.17850/njg103-1-04","DOIUrl":"https://doi.org/10.17850/njg103-1-04","url":null,"abstract":"","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135538040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Middle Pennsylvanian megabreccia adjacent to the Odellfjellet Fault in Billefjorden, central Spitsbergen","authors":"Jean-Baptiste P. Koehl, Christoffer Taule, M. Collombin","doi":"10.17850/njg103-1-4","DOIUrl":"https://doi.org/10.17850/njg103-1-4","url":null,"abstract":"The Billefjorden Trough, a well studied onshore analogue to Carboniferous rift basins in the Ba-rents Sea, is bounded to the west by the Billefjorden Fault Zone. Structural field analysis of a mega-breccia and adjacent strata of the Minkinfjellet Formation in the hanging wall of the Odellfjellet Fault segment of the Billefjorden Fault Zone suggests that slope failure occurred along the basin-bounding fault in the Middle Pennsylvanian during the “through-going fault zones” phase of extension, i","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":" ","pages":""},"PeriodicalIF":0.8,"publicationDate":"2023-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43706559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}