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dc.contributor.authorHeldal, Tom
dc.date.accessioned2020-08-26T09:03:57Z
dc.date.available2020-08-26T09:03:57Z
dc.date.issued2001
dc.identifier.urihttps://hdl.handle.net/11250/2674124
dc.description.abstractIn the western part of the Helgeland Nappe Complex, a small ophiolite fragment (the Bolvær Complex) and a metasedimentary succession (the Brønnøysund Group) are exposed on several islands to the west of Brønnøysund. The Bolvær Complex was emplaced, uplifted and subject to subaerial weathering and erosion prior to the deposition of the Brønnøysund Group. The uncomformity defines an irregular topographic surface which was gradually filled with sediments during a regional transgression, probably influenced by active tectonics. The sedimentation of the Brønnøysund Group initially started with the build-up of a coastal setting, delivering coarse and fince clastiscs into a shallow-marine environment (Risøy Formation). This formation is stratigraphically overlain by calcareous turbidites (Torgnes Formation), pelites (Aspøy Formation) and carbonate rocks (Toftsund Formation). The Brønnøysund Group is correlated with several cover sequences above ophiolites in the Helgeland Nappe Complex, and deposition in Early to Middle Orodovician time is suggested. The clast population in conglomerates and the composition of finer clastic sediments show an exotic, ensialic source for the detritus, in addition to the ophiolite. The ensialic source consisted essentially ofpsammites and schists, deformed and metamorphosed prior to the deposition of the Brønnøysund Group.
dc.language.isoeng
dc.relation.ispartofseriesNGU Bulletin (438)
dc.rightsNavngivelse 4.0 Internasjonal
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/deed.no
dc.subjectKONGLOMERAT
dc.subjectKALKSTEIN
dc.subjectOFIOLITT
dc.subjectORDOVICIUM
dc.subjectSANDSTEIN
dc.subjectSEDIMENTÆR BERGART
dc.subjectSTRATIGRAFI
dc.titleOrdovician stratigraphy in the western Helgeland Nappe Complex in the Brønnøysund area, North-central Norway.
dc.typeJournal article
dc.description.localcode49802
dc.source.pagenumber47-61


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    Artikler fra seriene NGU, NGU Bulletin og NGU Skrifter

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Navngivelse 4.0 Internasjonal
Except where otherwise noted, this item's license is described as Navngivelse 4.0 Internasjonal