Blar i Artikler på forfatter "Roberts, David"
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A likely Early Ordovician age for the regional penetrative cleavage in the Gaissa Nappe Complex.
Sundvoll, Bjørn; Roberts, David (NGU Bulletin (441), Journal article, 2003)Pervasively cleaved mudstones and claystones from two different parts of the Gaissa Nappe Complex in Finnmark wre subjected to Rb-Sr whole-rock analytical investigation. Although neither of the two groups of samples yielded ... -
A U-Pb zircon, Archaean age for granitoid rocks in the Kunes Nappe, Laksefjord Nappe Complex, Finnmark, North Norway
Roberts, David; Gromet, L. Peter (NGU Bulletin (449), Journal article, 2009)Nappes in the middle parts of the Caledonian tectonostratigraphy in Finnmark, northern Norway, contain slices of granitoid basement that hitherto have not been reliably dated. Zircons extracted from two, high-K, calc-alkaline ... -
Adamsfjord og Ul'lugai'sa. Beskrivelse til de berggrunngeologiske kart 2135 I og 2135 II - M 1:50 000 (med fargetrykt kart).
Chapman, Timothy John; Roberts, David; Føyn, Sven (NGU; Skrifter (381; 40), Journal article, 1983)Descriptions are presented of the different rock-types occurring in either autochthonous or allochthonous position within the confines of these two map-sheets. Five principal geological or tectonostratigraphical elements ... -
Aeromagnetic and gravimetric interpretation of regional structural features in the Caledonides of West Finnmark and North Troms, Northern Norway.
Olesen, Odleiv; Torsvik, Trond H.; Lile, Ole Bernt; Henkel, Herbert; Roberts, David (NGU Bulletin (419), Journal article, 1990)Forkortet.Interpretation of aeromagnetic and gravity data from Finnmark and North Tromshas resulted in a new map of depth to Precambrian basement. The integratedinterpretation of the data shows that the Seiland Igneous ... -
Age determination from the Trondheim Region Caledonides, Norway: a preliminary report.
Roberts, David; Wolff, Fredrik Chr.; Wilson, M. R. (NGU (288), Journal article, 1973)Twenty-four potassium-argon age determinations have been made on metamorphic minerals and whole-rocks (phyllites) from the Caledonides of the Trondheim region, Norway. Nineteen of the apparent ages fall between 438 and 402 ... -
Brittle deformation history of fault rocks on the Fosen Peninsula, Trøndelag, Central Norway.
Grønlie, Arne; Roberts, David; Nilsen, Bjørn (NGU Bulletin (421), Journal article, 1991)Late and post-Caledonian fault deformation of rock units on the Fosen Peninsula follows a time sequence wherein lower crustal ductile deformation was followed by several episodes of brittle fragmentation, some with coeval ... -
Caledonian and Baikalian tectonic structures on Varanger Peninsula, Finnmark, Norway, and coastal areas of Kola Peninsula, NW Russia
Roberts, David (NGU Bulletin (431), Journal article, 1996)Based on data compiled from biostratigraphy, radiometric dating and palaeomag- netic studies, contractional deformation and low-grade metamorphism in the Neo- proterozoic to earliest Palaeozoic successions of coastal areas ... -
Contemporary stress orientation features in bedrock, Trøndelag, central Norway, and some regional implications.
Roberts, David; Myrvang, Arne (NGU Bulletin (442), Journal article, 2004)Based on in situ rock stress measurements and contemporary stress orientation structures observed at diverse sites in Trøndelag, it can be shown that the Møre-Trøndelag Fault Complex marks an important structural divide ... -
Depositional environment and apparent age of the Fauske carbonate conglomerate, North Norwegian Caledonides.
Heldal, Tom; Fallick, Anthony E.; Gorokhov, Igor M.; Roberts, David; Melezhik, Victor A. (NGU Bulletin (436), Journal article, 2000)The Fauske conglomerate represents a rather rare case of a monomict carbonate conglomerate in the Late Neoproterozoic to Silurian, lithostratigraphic successions of the Norwegian Caledonides. Lithological varieties of this ... -
Devonian ages from 40 Ar/39Ar dating of plagioclase in dolerite dykes, eastern Varanger Peninsula, North Norway.
Guise, Philip G.; Roberts, David (NGU Bulletin (440), Journal article, 2002)Gas-release spectra derived from the analysis of plagioclase from three geographically distinct but geochemically comparable dolerite dykes from the eastern part of Varanger Peninsula, northern Norway, show similar features ... -
Devonian tectonic deformation in the Norwegian Caledonides and its regional perspectives.
Roberts, David (NGU (380), Journal article, 1983)Late-Caledonian megascopic folds deforming the Old Red Sandstone sequences of southern Norway are mostly synclines of E-W to NE-SW trend and E to NE plunge. Thrusts along the eastern and southern margins of several ORS ... -
Disparate geochemical patterns from Snåsavatn greenstone, Nord-Trøndelag, Central Norway.
Roberts, David (NGU (373), Journal article, 1982)Greenstone volcanites of Middle Ordovician age from the Snåsavatn area of the Central Norwegian Caledonides can be divided into two distinctive groups on the basis of their geochemical patterns. The bulk of the lavas sampled ... -
Early Ordovician ages of zircons from felsic rocks and a conglomerate clast, Frosta peninsula, Central Norwegian Caledonides
Gromet, L. Peter; Roberts, David (NGU Bulletin (450), Journal article, 2010)Zircons extracted from a felsic sheet in the bimodal, magmatic, Fånes complex of the Støren Nappe on Frosta peninsula yielded a U-Pb age of 488 \u00B1 5 Ma, interpreted as the age of crystallisation. A large clast of ... -
Geochemical changes accompanying mylonitisation of granite at the base of the Helgeland Nappe Complex, Nord-Trøndelag, central Norway
Roberts, David; Nissen, August L. (NGU Bulletin (446), Journal article, 2006)A progressive conversion of megacrystic granite into mylonites at the base of the Helgeland Nappe Complex in the Caledonides of central Norway is reflected in microstructural, textural and modal changes. These mylonites ... -
Geochemistry and palaeogeographical setting of greenstone units on Frosta peninsula, Nord-Trøndelag, Central Norwegian Caledonides
Lippard, Stephen J.; Roberts, David (NGU Bulletin (450), Journal article, 2010)Volcanic and high-level intrusive rocks of the Støren Nappe exposed on the west coast of Frosta peninsula occur in two, distinct, magmatic units; the bimodal Fånes complex and the metabasaltic Granheim greenstone. North ... -
Geochemistry and petrogenesis of trondhjemites and granodiorite from Gauldalen, Central Norwegian Caledonides
Pannemans, Bart; Roberts, David (NGU Bulletin (437), Journal article, 2000)In the Gauldalen district of Central Norway, three varieties of trondhjemite cutting rocks of the Gula Complex have been distinguished on the basis of nuances of colour and field relationships. The high Al2O3, Rb and Sr, ... -
Geochemistry and Rb-Sr dating of the Muruvik rhyolite tuff, Trondheimsfjord, Central Norway.
Roberts, David (NGU Bulletin (412), Journal article, 1988)A geochemical study of a low greenschist facies, felsic lapill-ash tuff fromnear the stratigraphic top of the Ordovician Lower Hovin Group at Muruvik,Trondheimsfjord, has shown that the pyroclastite is clearly calc-alkaline ... -
Geochemistry and Rb-Sr isochron age of trondhjemite dykes from the Gula Complex, near Snøan, Central Norway.
Sundvoll, Bjørn; Roberts, David (NGU Bulletin (437), Journal article, 2000)Trondhjemite dykes trending c.ENE-WSW and transecting early metamorphic fabrics in rocks of the Gula Complex south-southwest of Støren, are themselves weakly metamorphosed and foliate. Geochemical data show that the dykes ... -
Geochemistry of dolerite and metadolerite dykes from Varanger Peninsula, Finnmark, North Norway.
Roberts, David (NGU (322), Journal article, 1975)Dolerite dykes provide the only manifestation of igneous activity in the thick, Riphean to Lower Cambrian, weakly metamorphosed sedimentary sequence of Varanger Peninsula. Major and trace element abundances and ratios from ... -
Geochemistry of mafic dykes in the Corrovarre Nappe, Troms, North Norway
Roberts, David (NGU Bulletin (419), Journal article, 1990)Tholeiitic metadolerite dyke rocks in the Corrovarre Nappe of the Kalak Nappe Complex in North Troms show chemical traits which indicate T-MORB affinities, with fairly flat, chondrite-normalised REE patterns in a (La\/Nb)N ...