The western Trondheim Nappe Complex contains one of the most complete and best-exposed successions of Ordovician to Silurian sedimentary and volcanic rocks in the entire Scandinavian Caledonides. We present a new stratigraphic framework for the succession overlying the Ilfjellet and Holonda Groups, comprising four distinct stratigraphic groups separated by distinct unconformities. (1) The Holsjoen Group (c. 461-453 Ma), unconformably overlying the Ilfjellet Group, represents turbiditic deposition along a continental slope, with sediment contributions from both continental and ophiolitic/backarc sources. (2) The Trivja Group (c. 453-450 Ma) unconformably overlies the Holsjoen Group, representing a submarine slope with transitions into shallower settings, characterised by sediments derived mainly from continental sources, with minor input from a distal contemporaneous arc. (3) The Hogknippen Group (c. 450-444 Ma) marks a transition to shallow-marine and subaerial settings dominated by rhyolitic to dacitic tuffs and volcaniclastic deposits with a clear continental-arc geochemical signature. Hafnium isotope compositions of detrital Cambro-Ordovician zircons are consistent with a continental-arc provenance. (4) The Foss Group (<432 Ma) formed in shallow-marine to fluvial settings with epiclastic sediments sourced from the underlying units as well as more distal continental rocks, including exhumed c. 432 Ma felsic plutonic sources. Together, these groups provide a detailed record of Late Ordovician to Silurian basin evolution adjacent to a continental arc which developed along the Laurentian margin during the closure of the Iapetus Ocean.

Fjords are steep sided glacially carved troughs that have been inundated by the sea. Several global assessments have aimed to establish the role of fjords in the carbon cycle. According to these studies, fjords bury 18 Tg of organic carbon per year, and 55 % to 62 % of that organic carbon is terrestrially sourced. Such quantitative estimates, while important for understanding the role of fjords in the global carbon cycle, often rest on data compilations that might not be representative for fjord environments as a whole due to unaccounted spatial heterogeneity in terms of substrate types, depositional environments and characteristics of sedimentary organic carbon. Here, we present a local case study from fjords around Stavanger (Norway). Based on detailed investigations, we show that the seabed is heterogeneous in terms of substrate types covering the full grain-size spectrum from mud to boulders. Seabed areas where fine-grained sediment, and hence organic carbon, accumulates account for 50 % of the area while the remainder is characterised by coarse-grained sediment indicating erosion and transport. In depositional areas, rates of organic carbon accumulation vary between 18.7 and 82.6 gm-2yr-1 and stocks from 0.1 and 1.37 kgm-2. The fraction of labile organic matter varies between 19 % and 44 %, while delta 13C-values of the organic carbon fraction range from -27.44 parts per thousand to -21.23 parts per thousand, indicating a strong variability of the sources of organic carbon over a comparatively small area. Taken together, these results attest to high environmental variability and spatial heterogeneity in the study site, putting several assumptions used in global assessments into question. We suggest steps to achieve more realistic results when upscaling from local studies to a higher level. Using available data on organic carbon accumulation rates from Norwegian coastal areas, we demonstrate how local results could be upscaled in a more robust way. We arrive at a tentative estimate of 0.41-3.68 Tgyr-1 of organic carbon accumulating in surface sediments (upper 10 cm) of fjords in mainland Norway.

Through the Phanerozoic eon, the trace fossil Macaronichnus—made by sediment-burrowing polychaetes—appears to be restricted to intermediate- and high-latitude shallow-marine habitats with cold to temperate waters or coastal areas closer to the equator with cold-water upwelling. We present records of such trace fossils in Ordovician (Darriwilian−Sandbian?) shallow- and deep-water marine deposits in the Central Norwegian Caledonides, pointing toward previously undocumented deep-ocean circulation and upwelling of cold water along the subtropical eastern Laurentian margin and adjacent volcanic arcs and microcontinents in the early Paleozoic Iapetus Ocean. Possible implications for Middle Ordovician ocean circulation patterns are discussed in relation to paleogeographic reconstructions and paleoclimatic models.

The late Early to early Middle Ordovician Fjellvollen Formation, Central Norwegian Caledonides, is a part of the Ilfjellet Group volcano-sedimentary succession formed in a rift basin that opened along the Laurentian margin. Depositional facies and trace fossils indicate the Nereites ichnofacies, typically found in distal turbidites and deep marine deposits. The recovered trace fossils include ?Alcyonidiopsis, Chondrites, Dictyodora, Gordia, Helminthoidichnites, Macaronichnus, Monomorphichnus, Nereites, Oikobesalon, Palaeophycus, Protovirgularia and Treptichnus. No body-fossils have been reported from the Fjellvollen Formation, but the trace fossils indicate the presence of varied epi- and infaunas of arthropods, bivalves, gastropods and polychaets. The abundance of meandering and looping trace fossils is comparable to what is found in the inferrably time-equivalent Vuddudalen Group farther north, although lack of graphoglyptids like Megagrapton in the Fjellvollen Formation may indicate more proximal, unstable depositional conditions in fan-fringe and adjacent basin-plain settings.

&lt;p&gt;Recently, international focus on the United Nations Sustainable Development Goals has led to the proposal of Essential Geodiversity Variables (EGVs), a framework for geological (geodiversity) information, intended to stand alongside Essential Variables (EVs) already defined for Climate, Biodiversity and Oceans (limited to ocean physics, biochemistry, biology, and ecosystems). In Norway, the Nature Diversity Act, which acknowledges geological and landscape diversity alongside biodiversity, has helped establish geology as part of an essential foundation for knowledge-based management, on land, in the coastal zone and offshore. In keeping with this, geological mapping is a core component of two ongoing national multidisciplinary seabed mapping initiatives [MAREANO, Marine Base Maps for the Coastal Zone (pilot)].&lt;/p&gt; &lt;p&gt;Here we examine to what extent marine geological map products from the Geological Survey of Norway generated under these mapping initiatives fit within this EGV framework and how well it is suited to information on marine geodiversity. Further, we examine opportunities for highlighting quantitative geodiversity information through the development of non-traditional marine geological map products. We present some thematic examples at different spatial scales which explore the potential for delivering seabed geodiversity and related geological information more directly. It is important that such information is available in forms that are readily accessible and understandable to a wide range of end users who are largely non-geologists, and that it complements existing information used in coastal and offshore management. &amp;#160;&lt;/p&gt;

The Hølonda area of the central Scandinavian Caledonides is a key for models of the Caledonian orogen owing to its Ordovician fauna of Laurentian affinity, now stranded on the Baltic side during opening of the North Atlantic. Here, we present a revised stratigraphic and tectonomagmatic model based on remapping, sedimentology, igneous geochemistry, Nd and Sr isotopes and geochronology. The Hølonda Group ( c. 470–461 Ma) reflects a transition from subaerial and shallow-marine deposition on a continental shelf to deeper-water sedimentation along a subsiding slope. Adakitic and mid-ocean ridge basalt type magmatism at c. 468 Ma was succeeded by benmoreitic–rhyolitic, shoshonitic, calc-alkaline and ultra-alkaline volcanism at c. 467–465 Ma. The complex magmatism followed arc–continent collision along a microcontinent outboard of Laurentia, associated with subduction polarity flip and slab rollback. This led to rifting and opening of a wide basin and its adjoining shelf on thickened orogenic lithosphere. Associated mantle upwelling and partial melting of depleted and variably metasomatized mantle occurred in a tectonomagmatic setting comparable with that of the central Mediterranean. The Hølonda–Ilfjellet setting is unique along the Caledonian–Appalachian orogen, possibly reflecting interaction with Laurentia-derived continental terranes at the northeastern end of the Taconian–Grampian orogenic tract. Supplementary material: Analytical data and supplementary figures are available at https://doi.org/10.6084/m9.figshare.c.6368922 Thematic collection: This article is part of the Caledonian Wilson cycle collection available at: https://www.lyellcollection.org/topic/collections/the-caledonian-wilson-cycle

Geology is a core component of two major multidisciplinary seabed-mapping initiatives in Norway (MAREANO, Marine Base Maps for the Coastal Zone). Helped by Norway's Nature Diversity Act, which acknowledges geological and landscape diversity alongside biodiversity, geological infor-mation has gained recognition nationally as part of an essential foundation for knowledge-based management, both in the coastal zone and offshore. Recently, international focus on the United Nations Sustainable Development Goals has led to the proposal of Essential Geodiversity Variables, a framework for geological (geodiversity) information, intended to stand alongside Essential Vari-ables already defined for climate, biodiversity and oceans (limited to ocean physics, biochemistry, biology and ecosystems). Here, we examine to what extent map products from the Geological Sur-vey of Norway generated under these multidisciplinary mapping initiatives fit within this framework of Essential Geodiversity Variables, and how well it is suited to information on marine geodiversity. Although we conclude that the framework is generally a good fit for the marine-relevant Essential Geodiversity Variable classes (geology and geomorphology), we examine opportunities for further highlighting quantitative geodiversity information. We present preliminary examples of substrate diversity and morphological diversity and discuss our experience of geological mapping as part of multidisciplinary initiatives. We highlight many benefits, which far outweigh any perceived or real compromises of this approach in monetary, practical and scientific terms.

Arc-continent collision, followed by subduction polarity flip, occurs during closure of oceanic basins and contributes to the growth of continental crust. Such a setting may lead to a highly unusual association of ultrapotassic and mid-ocean ridge basalt (MORB)-type volcanic rocks as documented here from an Ordovician succession of the Scandinavian Caledonides. Interbedded with deep-marine turbidites, pillow basalts evolve from depleted-MORB (εNdt 9.4) to enriched-MORB (εNdt 4.8) stratigraphically upward, reflecting increasingly deeper melting of asthenospheric mantle. Intercalated intermediate to felsic lava and pyroclastic units, dated at ca. 474−469 Ma, are extremely enriched in incompatible trace elements (e.g., Th) and have low εNdt (−8.0 to −6.6) and high Sri (0.7089−0.7175). These are interpreted as ultrapotassic magmas derived from lithospheric mantle domains metasomatized by late Paleoproterozoic to Neoproterozoic crust-derived material (isotopic model ages 1.7−1.3 Ga). Detrital zircon spectra reveal a composite source for the interbedded turbidites, including Archean, Paleo-, to Neoproterozoic, and Cambro-Ordovician elements; clasts of Hølonda Porphyrite provide a link to the Hølonda terrane of Laurentian affinity. The entire volcano-sedimentary succession is interpreted to have formed in a rift basin that opened along the Laurentian margin as a result of slab rollback subsequent to arc-continent collision, ophiolite obduction and subduction polarity flip. The association of MORBs and ultrapotassic rocks is apparently a unique feature along the Caledonian-Appalachian orogen. Near-analogous modern settings include northern Taiwan and the Tyrrhenian region of the Mediterranean, but other examples of strictly concurrent MORB and ultrapotassic volcanism remain to be documented.

Results from geological mapping within the MAREANO (Marine Areal Database for Norwegian Coasts and Sea Areas) programme and mapping projects in the coastal zone reveal a rich and diverse seafloor in Norwegian territories. The geomorphology and sediment distribution patterns reflect a complex geological history, as well as various modern-day hydrodynamic processes. By early 2019, MAREANO has mapped more than 200 000 km (c. 10%) of Norwegian offshore areas, spanning environmental gradients from shallow water to more than 3000 m depth, with ocean currents in places exceeding 1 m s−1 and water temperatures below −1°C. Inshore, along the 100 000 km-long Norwegian coastline, the Geological Survey of Norway (NGU) has conducted a series of seabed mapping projects in collaboration with local communities, industry and other stakeholders, resulting in detailed seabed and thematic maps of seabed properties covering c. 10 000 km (11% of the areas). Bathymetric and geological maps produced by MAREANO and coastal mapping projects provide the foundation for benthic habitat mapping when combined with biological and oceanographic data. Results from the mapping conducted over the past decade have significantly increased our understanding of Norway’s seabed and contributed to the knowledge base for sustainable management. Here we summarize the main results of these mapping efforts. The multidisciplinary Norwegian seabed mapping programme MAREANO (Thorsnes et al. 2008; MAREANO 2019) is a collaboration between the Geological Survey of Norway (NGU), the Institute of Marine Research (IMR) and the Norwegian Mapping Authority (Norwegian Hydrographic Service (NHS)). The programme is financed by the Ministry of Trade, Industry and Fisheries, and the Ministry of Climate and Environment. These ministries, along with the ministries of Petroleum and Energy, Local Government and Modernisation, and Transport and Communications, form the MAREANO Steering Board. Between 2006 and early 2019, more than 200 000 km of seabed have been mapped (Fig. 1), corresponding to around 10% of the Norwegian offshore area. The areas mapped span broad environmental gradients with water depths extending to more than 3000 m, ocean currents exceeding 1 m s−1 and seawater temperatures below −1°C. Dramatic landscapes (Fig. 2) have been observed, with canyons up to 1 km deep formed by fluid-flow processes and sliding, and locally almost subvertical margins. Continental slopes vary in width from 30 km to more than 100 km, with gradients locally reaching 60°. Shelf plains and banks (30–300 m water depth) and cross-shelf troughs (200–500 m water depth) occur over wide areas, and a rich faunal diversity has been observed (e.g. Bellec et al. 2008, 2009, 2010, 2016, 2017a, b, 2019; Chand et al. 2008, 2009, 2012; Thorsnes et al. 2008, 2009, 2016a, b, 2017; Bøe et al. 2009, 2012, 2015, 2016; Buhl-Mortensen et al. 2009a, b, 2012, 2015; Dolan et al. 2009, 2012b; Elvenes et al. 2012, 2013, 2016; Rise et al. 2013, 2015, 2016a, b; Elvenes 2014; King et al. 2014; Bjarnadóttir et al. 2016, 2017; Diesing and Thorsnes 2018). Results from MAREANO (MAREANO 2019) have contributed significantly to the revision of Norway’s management plan for the Barents Sea–Lofoten areas, as well as the management plan for the Norwegian Sea (Fig. 2). These plans are used by Norwegian authorities in their management of the northern seas, particularly in relation to fisheries and petroleum activities. Spatial management of the Norwegian nearshore areas is the responsibility of coastal municipalities. Municipal jurisdiction extends to 1 nautical mile offshore of a baseline joining the outermost islets and skerries. Coastal marine areas cover c. 90 000 km, comprising a wide range of environments from rocky, exposed shallows to fjords up to 1300 m From: Asch, K., Kitazato, H. and Vallius, H. (eds) From Continental Shelf to Slope: Mapping the Oceanic Realm. Geological Society, London, Special Publications, 505, https://doi.org/10.1144/SP505-2019-82 © 2020 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/). Published by The Geological Society of London. Publishing disclaimer: www.geolsoc.org.uk/pub_ethics by guest on March 6, 2021 http://sp.lyellcollection.org/ Downloaded from

New high-resolution multibeam bathymetry and sub-bottom profile datasets from Fingerdjupet are used for the first detailed geomorphological mapping of the seafloor in this area. The mapped landforms provide evidence for a palaeo-ice stream flowing in a southeasterly direction from Spitsbergenbanken into Fingerdjupet, merging with Bjørnøyrenna ice stream, and confirm a theorised palaeo-ice divide located along the bank. The combined landform records and acoustic stratigraphy allow a detailed reconstruction of the glacial dynamics during the last deglaciation. The withdrawal of the Fingerdjupet ice stream from Bjørnøyrenna was characterised by rapid retreat, punctuated by periods of stable ice marginal conditions. Five to six major ice margin stillstands and/or readvances associated with the last deglaciation are identified in the seafloor record and acoustic stratigraphy. During these events, large grounding zone wedges were deposited at the ice stream margin. The seabed geomorphology indicates that ice stream dynamics changed as the ice stream retreated from the trough onto the shallower bank. Here, numerous retreat moraines indicate that a grounded ice margin retreated slowly, with several minor stillstands, towards north-northwest. Several controls and/or drivers on the style of ice flow and retreat have been suggested, including catchment size reduction, sea level rise, bedrock topography, drawdown of bank ice and/or migration of the main ice divide over the bank.

Fraenfjorden, a fjord on the west coast of Norway, has been studied to increase our knowledge of the environmental effects of submarine tailings placement (STP). Fine-grained tailings consisting primarily of calcite are disposed of by Omya Hustadmarmor. The dataset, including multibeam echosounder data, shallow seismic, video data, grab samples and sediment cores, demonstrates that tailings are primarily deposited in an up to 2 km-wide area with a tailings thickness of up to 20 m. Minor quantities of tailings are spread outside the STP by tidal currents. Sediment cores show the difference in colour, mineralogy and grain size between the natural sediments and the tailings. The tailings have a white/grey colour, are very fine grained, contain high amounts of calcite and have a lower water content than the natural sediments. A series of multibeam echosounder data from 2013 to 2017 show that deposition of tailings has triggered several small gravity flows and slides. The tailings within the STP have a low stability compared to the natural sediments outside the STP because of their fine grain size and higher sensitivity, high slope angles, high sediment accumulation rates preventing normal consolidation, and loading of tailings causing overpressure in the underlying sediments.

Recently acquired multibeam echosounder data from the shallowest part (26-53 m depth) of Spitsbergenbanken in the western Barents Sea reveal a variety of bedforms, including megaripples, sandwaves and sandbanks. The bedforms exhibit varying degrees of superimposition and differ in their age of formation and present depositional regime, being either active or moribund. These are the first observations of co-occurring current induced bedforms in the western Barents Sea and provide evidence of a high energy environment in the study area. The bedforms indicate both sediment erosion and transport and confirm that there is enough sand available in this area to maintain them. Such conditions are not known to be common in the western Barents Sea and reflect the unique oceanographic and benthic environment of Spitsbergenbanken.

An increasing number of activities compete for space in the Norwegian coastal zone, making access to detailed seabed information particularly valuable. We present a suite of thematic marine base maps of the near-shore areas of five municipalities in west Norway (567 km(2); at 62 degrees N/5 degrees E). This set of full-coverage seabed maps includes sediment grain size, seabed terrain (shaded relief), slope, sediment accumulation basins, anchoring conditions, and diggability (trenching properties). The sediment grain size map is a geological interpretation of multibeam echosounder data supported by video observations and physical samples of seabed sediments. The other maps in the suite are derived from this sediment map, and/or directly from the bathymetry data. All maps are at a scale of 1:20,000 and are freely accessible for download or online viewing. Marine base maps are intended for all end-users with a need for knowledge of seabed conditions and may be especially valuable for marine spatial planning.

The Sortlandsundet Basin is a half-graben with Mesozoic sediments located in Sortlandsundet between Langoya and Hinnoya in Vesteralen. The basin is defined by the Hadselfjord Fault Zone in the southeast and by unconformable boundaries to Archaean to Palaeoproterozoic basement rocks to the northeast, northwest and southwest. The basin may have originated as an extensional basin and evolved as a transtensional basin in the Jurassic-Early Cretaceous. Sedimentary strata of probable Jurassic age within the basin are more than 400 m thick, with seismic reflectors dipping slightly to the southeast. Glacial-transported erratic blocks, assumed to derive from the Sortlandsundet Basin, are found along the shores of Sortlandsundet. The blocks comprise quartz-rich sedimentary rocks, varying from conglomerates to tine sandstones, representing terrestrial to shallow-marine deposits. Many of the erratic blocks contain common macro- and microfossils of Middle and Late Jurassic age. A syn-tectonic depositional model for the Sortlandsundet Basin with correlations to the age-equivalent strata offshore Vesterfilen (Ribban Basin) and on Andoya is discussed.