Abstract Geological maps document knowledge of considerable value (economic, cultural and aesthetic) for societies, enterprises and people in general. Knowledge illustrated in geological maps also helps us to foresee how landscape interventions and climate change may affect our living ground and make us vulnerable to geohazards. The present paper presents an overview of geological mapping carried out by the Geological Survey of Norway since 1858 while also focusing on mapping activities and products produced in the present millennium. Key issues to consider are how we are moving into the digital world, how we use geological mapping to follow up on national agendas like Green Shift and Blue Growth and how national agreements and cooperation help us to make geological and other geographic information available to everyone through open access web portals and services.

ABSTRACT The Scandinavian Caledonides formed during the continental collision between Baltica and Laurentia. During the collision, a complex nappe stack was thrust over the Baltican continental margin. The orogen can be subdivided into segments based on architectural differences within the Scandian nappes. The southern and central segments of the orogen link up in the Gudbrandsdalen area in south-central Norway. Alpine-type metaperidotite-bearing metasedimentary complexes occur in the southern and central segments and can be traced continuously along the strike of the orogen from one into the other segment. Traditionally, these units have been assigned to different tectono-stratigraphic levels, one below the Middle Allochthon and one above the Middle Allochthon. Here, we trace the Alpine-type metaperidotite-bearing units from Bergen to Esandsjøen and show that these units exhibit a common geologic and metamorphic history, consistent with the metaperidotite-bearing units representing a single tectonic unit. We suggest that the metaperidotite-bearing units can be used as a “marker level” to revise the tectono-stratigraphy of the Gudbrandsdalen and adjacent areas. The tectono-stratigraphic revisions imply that the Scandian nappe stack consists of seven tectono-stratigraphic levels that can be traced throughout the southern and central segments of the Scandinavian Caledonides. Moreover, the revision of the tectono-stratigraphy and new U-Pb geochronology data also suggest a revision of the timing of the succession of tectonic events leading up to the Scandian continental collision. The available evidence indicates that Baltica-derived tectonic units collided with the Iapetan/Laurentian subduction complexes as early as ca. 450 Ma. The initial collision was followed by in-sequence nappe formation of Baltican-derived units, which occurred contemporaneously with the opening of a marginal basin in the upper plate. After the arrival of thick, buoyant, unthinned Baltican crust at the trench, the main zone of convergence stepped outboard, the marginal basins closed, and those basins were thrust out-of-sequence over the previously assembled nappe stack.

ABSTRACT The Scandinavian Caledonides have a complex latest Proterozoic–Early Devonian history, but they were finally assembled during the Silurian–Devonian (Scandian orogeny) collision between Baltica and Laurentia. Their dominant structural components are the Lower (Baltican margin), Middle (Baltican and farther outboard), Upper (Iapetan arcs), and Uppermost (Laurentian margin) Allochthons. This study examined the Blåhø Nappe, a complex unit of metamorphosed, intensely deformed igneous and sedimentary rocks assigned to the Middle Allochthon. Metamorphic grades are regionally amphibolite facies, but granulite- and eclogite-facies rocks are locally found. Although most metamorphic ages span a range from Middle Ordovician to Devonian, Blåhø eclogite and other high-pressure rock ages are exclusively Scandian. We analyzed 95 samples of Blåhø Nappe metamorphosed igneous rocks, which were mostly mafic rocks, composed of a minor arc-derived set and a major set transitional between arc and depleted to enriched mid-ocean-ridge basalt (MORB), a range characteristic of back-arc basins. Historically, the Blåhø Nappe has been assigned to the Seve Nappe Complex, the upper part of the Middle Allochthon as mapped in western Sweden and easternmost Norway. In contrast to the Blåhø Nappe, eclogites and other high-pressure rocks in the Seve Nappe Complex have yielded exclusively pre–Scandian orogeny Cambrian and Ordovician ages. Additionally, post–mid-Proterozoic igneous rocks of the Seve Nappe Complex are overwhelmingly dike swarms that were emplaced during the latest Proterozoic breakup of Rodinia, which have rift and MORB-type chemical signatures rather than arc and back-arc signatures, as has the Blåhø Nappe. We hypothesize that the Blåhø Nappe precursors formed on the upper plate, above a west-directed, late Cambrian to Ordovician subduction zone off the Baltican margin. Subduction of the Baltican margin, and possibly rifted fragments on the lower plate, produced the older Seve Nappe Complex eclogites and thrust the Blåhø and Seve Nappe Complex materials onto Baltica. This left the Blåhø Nappe and Seve Nappe Complex precursors on the lower plate during Scandian subduction and collision with Laurentia, allowing exclusively Scandian eclogite formation in the Blåhø Nappe. The Blåhø Nappe and Seve Nappe Complex thus seem to have distinct origins and should not be correlated with one another.

Abstract The Skarfjell oil and gas discovery, situated 50 km north of the Troll Field in the NE North Sea, was discovered by well 35/9-7 and was appraised by three additional wells operated by Wintershall, in the period 2012–14. The Skarfjell discovery is an example of a combined structural/stratigraphic trap. The trap formed along the northern edge of a deep WNW–ESE-trending submarine canyon, which was created by Volgian erosion of intra-Heather, Oxfordian-aged sandstones and then infilled with Draupne Formation shales. This mud-filled canyon forms the top and side seal, with the bottom seal provided by Heather shales. The reservoir comprises mid-Oxfordian deep-water turbidites and sediment gravity flows, which formed in response to tectonic hinterland uplift and erosion of the basin margin, 10–20 km to the east. The Skarfjell discovery contains light oil and gas, and may be subdivided into Skarfjell West, in which the main oil reservoir and gas cap have known contacts, and Skarfjell Southeast, which comprises thinner oil and gas reservoirs with slightly lower pressure and unknown hydrocarbon contacts. The Upper Jurassic Draupne and Heather formations are excellent source rocks in the study area. They have generated large volumes of oil and gas reservoired in fields, and discoveries for which the dominant source rock and its maturity have been established by oil to source rock correlation and geochemical biomarker analysis. The Skarfjell fluids were expelled from mid-mature oil source rocks of mixed Heather and Draupne Formation origin. The recoverable resources are estimated at between 9 and 16 million standard cubic metres (Sm 3 ) of recoverable oil and condensate, and 4–6 billion Sm 3 of recoverable gas. The Skarfjell discovery is currently in the pre-development phase and is expected to come on stream in 2021.

Abstract: Field analysis shows that fault cores of brittle, extensional faults at a medium to mature stage of development are commonly dominated by lozenge-shaped horses (fault-core lenses) characterized by a variety of lithologies, including intact, mildly to strongly deformed country rock derived from the footwalls and hanging walls, various types of fault rocks of the protocatalasite and breccia series, breccia, fault gouge and clay smear. The lenses are sometimes stacked to form complex duplexes. These structures are commonly separated by high-strain zones of sheared cataclasite, and/or clay smear/clay gouge. The geometry and distribution of clay gouge in high-strain zones sometimes display evidence of intrusion, indicating high fluid pressure. Although the sizes of the horses vary over several orders of magnitude, they frequently display a length:thickness (a:c) ratio of between 1:4 and 1:15. The high-strain zones of fault rocks commonly constitute unbroken, 3D membranes that are likely to constrain fluid communication both across and along the fault zone. There are significant contrasts in fault core architecture that are probably related to processes associated with contrasting fluid pressure, strain intensity and strain hardening/strain softening. Faults associated with strain softening are characterized by less abundant brittle deformation products and are less likely to be conduits for fluid flow compared to those that are affected by strain hardening.