Morphology and pattern of Quaternary sedimentation in the North Sea Basin

The Quaternary North Sea Basin, which extends from northwest mainland Europe in the south (52°N) to the Norwegian Sea in the north (62°N), contains a thick (up to 1 km) sedimentary succession that records the changing nature of sediment supply from surrounding land areas during the last c.2.6 Ma. We use an extensive 2D and 3D seismic database to correlate major Quaternary seismo-stratigraphic surfaces and units across the North Sea and reconstruct the broad-scale infill pattern of the entire Quaternary North Sea Basin. The total volume of Quaternary sediments in the North Sea (350,000 km²) is c.140,000 km3, while the area inside the 500 m contour of the base-Quaternary surface has a volume of 109,000 km3. Two largely independent depocentres developed in the North Sea Basin during the early Quaternary: the southern and central sub-basin was infilled by shelf fluvio-deltaic and prodeltaic sediments delivered from the east and south-east, whilst the northern sub-basin was infilled mainly by prograding glacigenic debris-flows deposited from an ice mass centred on the Norwegian mainland. Contour currents were an important mechanism of sediment deposition and reworking, with water circulation in the basin probably occurring in an anti-clockwise direction. Whilst most of the southern North Sea Basin was infilled by around 1.6-1.7 Ma, a depression persisted in the central North Sea until around 1 Ma. The analysis of landforms on 3D seismic data suggests that the Fennoscandian Ice Sheet (FIS) extended intermittently to the palaeo-shelf break in the northern North Sea during the earliest Quaternary and expanded into the central North Sea prior to the excavation of the Norwegian Channel

Multiple Late Holocene surges of a High-Arctic tidewater glacier system in Svalbard

Most large tidewater glaciers in Svalbard are known to have surged at least once in the last few hundredyears. However, very little information exists on the frequency, timing or magnitude of surges prior to theLittle Ice Age (LIA) maximum in ~1900. We investigate the sediment-landform assemblages produced bymultiple advances of the Nathorstbreen glacier system (NGS) in order to reconstruct its Late Holocenesurge history. The glacier has recently undergone one of the largest surges ever observed in Svalbard,advancing ~16 km from 2008 to 2016. We present flow velocities and ice-marginal observations (ter-minus change, proglacial geomorphological processes) from the later stages of this surge. A first detailedassessment of the development of a glaciotectonic mud apron within the fjord during a surge is provided.Geomorphological and sedimentological examination of the terrestrial moraine areas for med prior to themost recent surge reveals that at least two advances were responsible for their formation, based on theidentification of a previously unrecognised ice-contact zone recorded by the distribution of sedimentfacies in coastal exposures. We distinguish between an outer, older advance to the distal part of themoraine system and an inner, younger advance to a position ~2 km upfjord. Radiocarbon dating of shellsembedded in glaciotectonic composite ridges formed by the onshore bulldozing of marine mud duringthe outer (older) of the two advances shows that it occurred at some point during the interval 700e890 cal. yr BP (i.e. ~1160 AD), and not during the LIA as previously assumed. We instead attribute theinner (younger) advance to the LIA at ~1890. By combining these data with previous marine geologicalinvestigations in inner and outer Van Keulenfjorden, we demonstrate that NGS has advanced at least fourtimes prior to the recent 2008e2016 surge: twice at ~2.7 kyr BP, at ~1160 AD, and in ~1890. This rep-resents a unique record of the timing and magnitude of Late Holocene tidewater glacier surges inSvalbar

Aktiv forvaltning av marine ressurser - Frøya og Hitra - Arbeidsrapport 2017-2018

Prosjektet ‘Aktiv forvaltning av marine ressurser- Frøya og Hitra’ ble formelt startet opp høsten 2017. Den overordnete målsetting med prosjektet er å etablere en solid kunnskapsplattform for å sikre de marine verdiene og verdiskapningsmulighetene i de to kommunene. Et viktig element i dette arbeidet er å styrke grunnlagsdataene for kommunene for en kunnskapsbasert kystsoneforvaltning og studere effekten av menneskelig påvirkning på marine bestander ved bruk av soneforvaltning. Prosjektbeskrivelsen i sin helhet er å finne her: https://aktivforvaltning.hi.no/prosjekter/aktiv-forvaltning-i-kystsonen/froya-hitra. Dette er en arbeidsrapport som oppsummerer arbeidet som er blitt gjort i prosjektet fra oppstart i august 2017 og frem til desember 2018. Hovedaktivitetene for 2019 er også presentert. Bilde forside: Torsk og leppefisk (Erling Svensen), Kamskjell (Ragni Olssøn, HI), Sjøkreps (HI), Storeggaraset (NGU)publishedVersio

Aktiv forvaltning av marine ressurser - Frøya og Hitra - Arbeidsrapport 2017-2018

publishedVersio

Ice-sheet dynamics and glacial development of the Norwegian continental margin during the last 3 million years

This thesis is mainly about the dynamics of the palaeo-ice sheets that covered Scandinavia, Barents Sea and Svalbard during the last glaciation. Morphological interpretation of regional and detailed bathymetric data sets on the Norwegian shelf from the North Sea (57°N) to Svalbard (80°N) has elucidated the ice-flow patterns along the western margin of the Scandinavian and Barents/Svalbard ice sheets. About 20 cross-shelf troughs with glacial lineations are interpreted as former pathways for fast-flowing ice streams. The two largest palaeo-ice streams were the Norwegian Channel Ice Stream and Bear Island Ice Stream, each 150-200 km wide at their mouths. Studies of large-scale margin morphology and seismic-reflection profiles have identified large submarine fans at the mouths of several major cross-shelf troughs. Improved knowledge of the regional development of the margin, and detailed morphological maps of the buried palaeo-surfaces, show that similar large-scale glacial processes have been active in a substantial part of the Late Pliocene/Pleistocene (c. last 3 million years). Interpretation of a large seismic data base has made it possible to map the whole Naust Formation, which comprises sediments deposited on the mid-Norwegian margin during the last 3 million years. During this period, large quantities of glacially derived material were transported westward from the Norwegian mainland and the inner parts of the shelf, and deposited mainly as prograding sediment wedges into a basin of intermediate depth offshore of Mid Norway. The deposits are more than 1000 m thick over an extensive area, and the shelf edge migrated up to 150 km westwards. Very-high-resolution bathymetric data has made it possible to study sedimentary processes related to recently surging glaciers on Svalbard (the last few hundred years). The data sets also show that mega-scale glacial lineations not only can form beneath large ice streams, but are also produced over a few years beneath surging tidewater glaciers lying on deforming sedimentary beds

Calanoid copepods from South Georgia, with special reference to size dimorphism within the genus Pseudoboeckella

Three species of calanoid copepods, Boeckella michaelseni, Parabroteas sarsii and Pseudoboeckella poppei were recorded from 6 freshwater localities in the Husvik area, South Georgia. Of the latter species two distinct size morphs occurred, with no overlap in size even in closely situated populations. The large morph was recorded in lakes, the small was found in ponds. The small morph did not coexist with the large predatory P. sarsii, and we suggest predation pressure from this species as the major cause for the observed distribution of these morphs. The pronounced size segregation as well as small morphological dissimilarities suggest that these morphs are reproductively isolated. While the large morphotype corresponds to that of P. poppei, the taxonomic affinities of the small morph are uncertain