Norwegian Journal of Geology最新文献

{"title":"Silurian vertebrate remains from the Oslo Region, Norway, and their implications for regional biostratigraphy","authors":"Oskar Bremer, S. Turner, T. Märss, H. Blom","doi":"10.17850/njg99-1-07","DOIUrl":"https://doi.org/10.17850/njg99-1-07","url":null,"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Silurian of the Oslo Region, Norway, based on the review and revision of previous reports of microremains, as well as unpublished material from ...","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47986317","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":"What is the appropriate sample size for strike and dip measurements? An evaluation from compass, smartphone and LiDAR measurements","authors":"C. Trede, N. Cardozo, Lisa Watson","doi":"10.17850/njg99-3-4","DOIUrl":"https://doi.org/10.17850/njg99-3-4","url":null,"abstract":"Geological planar surfaces are irregular and therefore, an important question is: what is the appropriate sample size for measuring their orientations? We explore this question by measuring the orientation of two metre-sized surfaces, a shallow foliation in an overhang and a more irregular steep joint plane, in Cambro–Ordovician mica schists of the Svarthola cave, Rogaland, SW Norway. We use three methods: a geological compass; smartphones with digital compass clinometer applications, i.e., Stereonet Mobile (iPhone) and Fieldmove Clino (iPhone and Android); and LiDAR scans of increasing resolution. While geological compass measurements are generally robust, they provide inaccurate measurements in the challenging foliation overhang. Stereonet Mobile measurements are more accurate, while Fieldmove Clino is reliable in the iPhone but not in the Android device. Mean surface orientations reach a consistent result after 100–150 smartphone measurements. However, neither the compass nor the smartphone measurements can clearly define the joint-surface orientation. Triangulated surfaces from the LiDAR scans deliver precise but inconsistent results, especially at the highest resolution in the joint plane. Kriging of the surfaces significantly improves the representativeness of the computed orientations to reflect a more realistic model. A best-fit to plane routine using points within a radius, r, delivers the most representative results. At r ~0.5 m, the estimated orientations stabilise, and all scans deliver similar results. This is the appropriate sample size for measuring the studied planes. Similar strategies should be taken into consideration when measuring planes in outcrop (sighting as opposed to direct measurement) or from 3D geological models.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49423439","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":"Early history of petroleum exploration offshore Norway and its impact on geoscience teaching and research","authors":"K. Bjørlykke","doi":"10.17850/NJG99-3-2","DOIUrl":"https://doi.org/10.17850/NJG99-3-2","url":null,"abstract":"The Norwegian government and also the universities were unprepared for an offshore oil province. Very little information about the offshore geology was then available due to the thick cover of Quaternary and Tertiary sediments in the North Sea basins. The potential for oil and gas in the North Sea could not have been predicted before the Norwegian Continental Shelf (NCS) was opened for petroleum exploration and drilling in 1965. Statements from the Geological Survey of Norway (NGU) in 1958 that there was no potential for oil offshore Norway referred specifically to the coastal areas, where no oil has been found. The midline principle was introduced in 1964, through an agreement with the UK. A continental shelf committee led by Jens Evensen from 1963 to1965 prepared the legal aspects and the regulations applicable for oil companies applying for licences to explore and produce oil and gas offshore Norway. A proposal for a Norwegian petroleum-related research project in 1964 was not funded and it took several years before petroleum-related teaching and research were established. After several dry wells the Ekofisk Field was discovered late 1969–early 1970, making it clear that Norway would become a significant oil-producing country. However, at that time nearly all the expertise was inside the major international oil companies and petroleum-related research at Norwegian universities and research institutes had a slow start. In 1972, Statoil and the Norwegian Petroleum Directorate (NPD) were established and also government funding for petroleumrelated teaching and research. This was met with considerable scepticism and resistance from some students and faculty and some claimed that a general education in geology would be sufficient. The University of Bergen developed a strong research group in marine geophysics and later one in petroleum geology. The need for petroleum-related teaching and research created a great challenge for the Norwegian universities. The standard was variable and the output of graduates with a professional qualification was generally too low. What we know about sedimentary basins and many fundamental geological processes is the result of petroleum prospecting and data from drilling and seismic data, contributing to Norwegian geology and general geological principles.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42242126","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":"Sedimentology and palynology of the Lower Cretaceous succession of central Spitsbergen: integration of subsurface and outcrop data","authors":"S. Grundvåg, M. E. Jelby, K. Śliwińska, H. Nøhr-Hansen, T. Aadland, S. E. Sandvik, Ingrid Tennvassås, T. Engen, S. Olaussen","doi":"10.17850/NJG006","DOIUrl":"https://doi.org/10.17850/NJG006","url":null,"abstract":"Source at https://dx.doi.org/10.17850/njg006. © Copyright the authors. \u0000This work is licensed under a Creative Commons Attribution 4.0 International License.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49187223","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":"Palaeoecology and palaeoenvironments of the Middle Jurassic to lowermost Cretaceous Agardhfjellet Formation (Bathonian–Ryazanian), Spitsbergen, Svalbard","authors":"M. Koevoets, Ø. Hammer, C. Little","doi":"10.17850/NJG99-1-02","DOIUrl":"https://doi.org/10.17850/NJG99-1-02","url":null,"abstract":"We describe the invertebrate assemblages in the Middle Jurassic to lowermost Cretaceous of the Agardhfjellet Formation present in the DH2 rock core material of Central Spitsbergen (Svalbard). Previous studies of the Agardhfjellet Formation do not accurately reflect the distribution of invertebrates throughout the unit as they were limited to sampling discontinuous intervals at outcrop. The rock core material shows the benthic bivalve fauna to reflect dysoxic, but not anoxic environments for the Oxfordian – lower Kimmeridgian interval with sporadic monospecific assemblages of epifaunal bivalves, and more favourable conditions in the Volgian, with major increases in abundance and diversity of Hartwellia sp. assemblages. Overall, the new information from cores show that abundance, diversity and stratigraphic continuity of the fossil record in the Upper Jurassic of Spitsbergen are considerably higher than indicated in outcrop studies. The inferred life positions and feeding habits of the benthic fauna refine the understanding of the depositional environments of the Agardhfjellet Formation. The occurrence pattern of the bivalve genera is correlated with published studies of Arctic localities in East Greenland and Northern Siberia and shows similarities in palaeoecology with the former but not the latter. Ammonite biostratigraphy is used as a tool to date bivalve assemblage overturning events to help identify similar changes in other sections.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43212714","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":"Pegmatites of the Larvik Plutonic Complex, Oslo Rift, Norway: field relations and characterisation","authors":"Øyvind Sunde, H. Friis, T. Andersen","doi":"10.17850/NJG99-1-05","DOIUrl":"https://doi.org/10.17850/NJG99-1-05","url":null,"abstract":"The Larvik Plutonic Complex (LPC) contains pegmatites with a wide array of mineral assemblages and morphological features. The pegmatites have traditionally been described as nepheline syenite and syenite pegmatites which carry agpaitic or miaskitic mineral assemblages, respectively. However, several pegmatites fall outside this simple characterisation due to ‘agpaitic-like’ late magmatic mineral assemblages such as hiortdahlite and eudialyte group minerals. Morphological and mineralogical differences between pegmatites are not unique to, or related with, specific areas of the LPC. Compositional variation and deformation features of the host pluton are the main mechanisms for differing morphology and mineral assemblages between LPC pegmatites. Natrolite replacement of feldspathoid is the most common alteration feature in the nepheline syenite pegmatites. The extent of alteration is closely associated with crystallisation of saccharoidal albite and aegirine. Detailed description of a nepheline syenite pegmatite situated in the Sagåsen quarry provides new insights into the internal evolution and mineral distribution of a large representative pegmatite body. The most important mechanism driving hydrous alteration is the crystallisation of anhydrous primary minerals which leads to an immiscible hydrous fluid driving in situ alterations of primary mineral assemblages.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-06-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42326614","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":"Petroleum, coal and research drilling onshore Svalbard: a historical perspective","authors":"K. Senger, P. Brugmans, S. Grundvåg, M. Jochmann, A. Nøttvedt, S. Olaussen, Asbjørn Skotte, A. Smyrak‐Sikora","doi":"10.17850/NJG99-3-1","DOIUrl":"https://doi.org/10.17850/NJG99-3-1","url":null,"abstract":"Source at https://dx.doi.org/10.17850/njg99-3-1. © Copyright the authors. \u0000This work is licensed under a Creative Commons Attribution 4.0 International License","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41843576","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":"Anatomy of a mega-rock slide at Forkastningsfjellet, Spitsbergen and its implications for landslide hazard and risk considerations","authors":"D. Kuhn, T. Redfield, R. Hermanns, M. Fuchs, J. Torizin, D. Balzer","doi":"10.17850/NJG99-1-03","DOIUrl":"https://doi.org/10.17850/NJG99-1-03","url":null,"abstract":"Rock slope failures are a potential source of danger in polar regions. A causal connection between slope failures and climate-related glacial and deglacial processes has been inferred for the growing number of documented events. In this context, we investigated a large-scale rotational rock slide affecting the coastal ridge of Spitsbergen’s Forkastningsfjellet. Based on a detailed structural description, we discuss the kinematics, timing and potential drivers of rock slide activity and present a preliminary landslide hazard assessment. The Forkastningsfjellet rock slide has a footprint of at least 2.03 km2. A minimum rock mass volume of 0.10 km3 was displaced either catastrophically or over a longer time period. Initial movement in the hanging wall of a NW-dipping listric sliding surface led to the fragmentation of the sliding mass into separated tilt blocks that created the present-day, stair-stepped morphology. The main rock slide release was probably related to the deglaciation of Isfjorden and the resulting instability of the weakened rock mass along the oversteepened slopes during Allerød times (~13,900–12,700 BP). Mass wasting and seacliff erosion, mainly controlled by the inherent discontinuities of the fractured and tilted rock masses, currently take place along the steep slopes of the coastal tilt blocks. A preliminary hazard analysis suggests a medium to high hazard for a reactivation of the slide or individual blocks, but uncertainty margins for this classification are large due to a lack of data. Poor control of total displacement data in particular contributes to the uncertainty. A high-acceleration reactivation of a large compartment of the slide (e.g., on the order of 10 million m3) could cause a displacement wave several metres high in Longyearbyen. These results indicate a need for further multidisciplinary investigations to better understand the extent and nature of the rock slide and parameters such as displacement velocities to support a more reliable hazard and risk assessment for the Longyearbyen region.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41736090","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":"Causes of bias and uncertainty in fracture network analysis","authors":"D. Peacock, D. Sanderson, E. Bastesen, A. Rotevatn, Tor H. Storstein","doi":"10.17850/NJG99-1-06","DOIUrl":"https://doi.org/10.17850/NJG99-1-06","url":null,"abstract":"Fault and fracture networks are analysed to determine the deformation history and to help with such applications as engineering geology and fluidflow modelling. These analyses rely on quantifying such factors as length, frequency and connectivity. Measurements may, however, be influenced by a range of factors relating to resolution, geology, methods used and to the analyst(s). These factors mean that it can be difficult to obtain a single correct solution, with bias and uncertainty being introduced by different analysts, even for something as simple as counting the number of joint intersection points on a well-exposed bedding plane. These problems suggest there are significant issues in comparing databases, for example when using outcrop analogue data to model subsurface data. Our recommendation is that analysts and modellers should be aware of the potential pitfalls in their measurements of structures and, therefore, be more cautious with resultant analyses and models. We suggest that analysts assess their results by testing the reproducibility. Simple ways of doing this include: (1) checking for change in measurements (e.g., fracture frequencies) during the course of a study; (2) remeasuring part of the fracture network to check if the same results are obtained, and; (3) get one or more other analysts to blind-test the fracture network.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42454466","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":"Deglacial patterns and ice-sheet dynamics in the fjords of southern Nordland, Norway","authors":"F. Høgaas, L. Olsen, L. Gislefoss, O. Longva, Anders Romundset, H. Sveian","doi":"10.17850/njg98-4-07","DOIUrl":"https://doi.org/10.17850/njg98-4-07","url":null,"abstract":"This paper presents results from glacial geomorphology mapping in and adjacent to Velfjorden and Ursfjorden in the southern Nordland region of Norway. Submarine and terrestrial landforms were studied and mapped using high-resolution multibeam bathymetric and airborne LiDAR data, in addition to reconnaissance in the field. The work unites ice-marginal deposits related to the established Tautra and Tjøtta glacial events which took place during the Younger Dryas (YD) chronozone. In Ursfjorden, an outlet glacier deposited a c. 100 m-high terminal moraine, whereas moraine ridges and a large sedimentary wedge were deposited in the inner part of Velfjorden. Highly elongated subglacial bedforms located inside the ice-marginal landforms reveal that the fjords were occupied by fast-flowing ice streams during YD. Eighteen new radiocarbon dates from the region, along with twelve recalibrated dates from previous studies, provide time-constraints for ice-sheet configuration and dynamics during deglaciation. Radiocarbon dates suggest that the outer coastal islands became ice-free prior to 14 cal ka BP. Glacially overridden shell-rich units dated to the Allerød Interstadial indicate that the YD ice sheet readvanced at least 5 km before depositing the terminal moraine in Ursfjorden. The ages of shells found near the distinct, regionally correlative, YD raised shoreline indicate that the glacial readvance culminated around early to mid-YD.","PeriodicalId":49741,"journal":{"name":"Norwegian Journal of Geology","volume":null,"pages":null},"PeriodicalIF":0.8,"publicationDate":"2019-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43483603","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}