Van Mijenfjorden Research Articles

Chapter 20 Paleogene history

The Paleogene chapter of Svalbard history is a quite distinct one. It begins with an unconformity, albeit a sub-parallel one representing a late Cretaceous hiatus. Resting on Albian and older strata, the Van Mijenfjorden Group of six formations totals a thickness of about 2500 m in the Central Basin of Spitsbergen. The outcrop is ringed by Early Cretaceous strata in a broad syncline (Fig. 20.1). The strata are largely non-marine, coal-bearing sandstones, with interbedded marine shales and they range in age through Paleocene and Eocene. From latest Paleocene through Eocene time the West Spitsbergen Orogeny caused (Spitsbergian) deformation along the western border of the Central Basin, but it is most conspicuous in the folding and thrusting of Carboniferous through Early Cretaceous rocks. The orogen extended westwards to and beyond the western coast of central and southern Spitsbergen including Precambrian and Early Paleozoic rocks, which had already been involved in earlier tectogenesis. The eastward-verging thrusting extended beneath the Tertiary basin and reactivated older faults to the east. In the wider context Svalbard, adjacent to the north coast of Greenland, had been an integral part of Pangea from Carboniferous through Cretaceous time. The northward extension of the Atlantic opening reached and initiated the spreading of the Arctic Eurasia Basin at the beginning of the Paleogene Period. This led to the separation of Svalbard together with the Barents Shelf and northern Europe from Greenland by dextral strike-slip transform faulting. In the course of this progression, oblique collision between northeast Greenland and Svalbard caused

The last glacial maximum on Spitsbergen, Svalbard

Most scientists have concluded previously that the west coast of Spitsbergen, Svalbard, remained ice-free during the late Weichselian, between 25,000 and 10,000 yr B.P. We conclude that the glaciation was more extensive. Terraces that were postulated to have been ice-free are covered by a thin, late Weichselian till. Sudden drop in the marine limit and basal radiocarbon dates of raised glaciomarine sediments demonstrates that the glaciers in the main fjords, Isfjorden and Van Mijenfjorden, terminated west (outside) of the fjord mouths. Basal radiocarbon dates from glaciomarine clay above till in cores from the continental shelf west of Spitsbergen yielded ages of about 12,500 yr B.P., from which we conclude that the ice extended to the shelf edge. Based on the extent of amino acid diagenesis in radiocarbon-dated molluscs, the duration of the maximum extension of the late Weichselian glaciation was short, certainly less than 10,000 years. During the ice-free period preceding that glaciation, at least back to 40,000 yr B.P., the glaciers on Svalbard were not significantly larger than at present, as shown by marine deposits close to the glacier snouts. Many radiocarbon dates place deglaciation of the outer coast at about 12,500 yr B.P. At about 10,000 yr B.P., the rest of the archipelago rapidly became ice-free.

The Late Weichselian glacial maximum in western Svalbard

The glacial history of Svalbard and the Barents Sea during the Late Weichselian has been much debated during the last few years; reviews are presented by Andersen (1981), Boulton et al. (1982), ElverhBi & Solheim (1983) and Vorren & Kristoffersen (1986). In our opinion (Mangerud et al. 1984) it is now demonstrated that a relatively large ice-sheet complex existed over most of Svalbard and large parts (if not all) of the Barents Sea. One of the main arguments for a large ice sheet is the pattern of uplift, including the 9,800 B.P. date on the 100 m shoreline in Kong Karls Land (Salvigsen 1981). Important unresolved problems include how large that ice sheet was, the location of the different ice domes and ice fronts, the age and duration of the glacial maximum, and the deglaciation history. We will here report on these problems bringing some results from the Van Mijenfjorden and Isfjorden area (Fig. 1); a more comprehensive paper is in preparation.

Seismic mapping of the post-Caledonian strata in Svalbard

The status of seismic exploration work mapping the post-Caledonian strata in the Svalbard area is presented. Compressional wave velocities are very high throughout the area, around 4km/s in the Tertiary and Mesozoic layers. In the Permian section velocities exceed 5 km/s, with refraction velocities > 6 km/s in the calcareous rocks of the Gipsdalen Group (early Permian/Late Carboniferous). Apart from correlation with carbonate and chert lithology, high velocities reflect the high degree of consolidation and the low porosities of shales and sandstones in the post-Caledonian strata in Svalbard. In van Mijenfjorden seismic reflection events are observed down to 3–4 km depth and associated with Carboniferous and younger strata. The thickness of the Mesozoic layers in this part of the central Spitsbergen syncline seems to be greater than previously suggested, and there is an apparent eastward divergence between the Jurassic and the Triassic reflectors. In south-western Storfjorden, reflections interpreted to originate from Carboniferous and Permian strata might represent the seaward extension of the central Spitsbergen syncline. In the northern part of Storfjorden, carbonate layers within the Gipsdalen Group are interpreted to lie about one kilometre below the sea floor. A prominent fault zone in this area trends NNW-SSE, like the main structural elements on Spitsbergen. It shows block-faulting, presumably caused by extensional movement in late Devonian-Carboniferous time.

Effect of an oil spill in Spitzbergen in 1978

The oil content in the sediment and the marine life along the arctic shores of Van Mijenfjord, Spitzbergen, were investigated about two years after a spill from diesel storage tanks. High values of oil were recorded in the sediment along the shore near the tanks. The shore fauna is generally poor in these areas and the only biological effect detected was the disappearance of the amphipod Gammarus setosus from the surface layers.

The parasitic copepodsClavella adunca(StrøM),Haemobaphes cyclopterina(Fabricius), andSphyrion lumpi(Krøyer) on polar cod,Boreogadus saida(Lepechin) from Spitsbergen

Polar cod was the most abundant fish in 10 trawl hauls sampled July/August 1979. Fish in van Mijenfjorden and Krossfjorden differed in their length distribution from the other samples. C. adunca we...

The genesis and age of the Quaternary deposits in the eastern part of Van Mijenfjorden, West Spitsbergen

Abstract Geomorphological studies carried out on West Spitsbergen in the neighbourhood of Van Mijenfjorden, the dating of deposits by the radiocarbon method, and chemical analyses have enabled us to reconstruct the geological evolution of this area in the Holocene. During this period, the Paula glacier repeatedly crossed Van Mijenfjorden and formed a complex of glacial deposits on the ancient sea terraces on the northern coast of the fiord. One of the most significant advances of the Paula glacier took place 7800–7600 years ago. As this advance was for the first time reliably differentiated on Spitsbergen, it would be expedient to call it the Damesmorenen stage. Among the latest advances of the Paula glacier, the advance during “the little ice age” was dated. On the basis of the results obtained, it is possible to assume that the advances of the Paula glacier were of the nature of surges.