We describe a sediment sequence comprising a thick till covered by thin beds of lacustrine sediments containing pollen and plant macrofossils derived from pioneer vegetation. Four consistent radiocarbon dates on terrestrial plant remains from the lacustrine sediments yielded an age of 10,500 calibrated years BP (cal years BP). This is the first accurate and precise age obtained for the deglaciation of the Mjosa region in eastern Norway. We estimate that the ice-margin retreat rate in this area was about 250 m per year. Light-demanding herbs and Hippophae rhamnoides were the first to colonise locally. When soils matured, birch immigrated to the area forming the first forests at around 10,200 cal years BP. This was rapidly followed by pine and aspen and, later, by black alder at c. 9000 cal years BP. The lacustrine sediments are covered by 50 cm of peat and capped by a two-metre thick, coarse-grained, debris-flow deposit. The latter was surprising because of the very gentle slopes, four degrees in the failure area and less than three in the run-out and depositional area. We propose that the landslide, postdating the top of the peat that is dated to 6360 cal years BP, was triggered by a strong earthquake.
This study represents a marine baseline study for the Longyearbyen CO 2 Lab, in which CO 2 may be injected in the Upper Triassic–Middle Jurassic Kapp Toscana Group, which comprises several permeable beds. The target saline aquifer dips 1–3° southwest and thus crops out 14–16 km northeast from the proposed injection site in both offshore and onshore settings. Since the aquifer is exposed at the surface, a carefully documented pre-injection baseline study is required prior to any injection. The seafloor and its subsurface conditions are analysed and interpreted, where the targeted aquifer and organic-rich top-seal shales sub-crop. High-resolution multibeam bathymetric and backscatter imaging, sub-bottom acoustic profiles, sidescan sonar data and multichannel 2D seismic data were used to analyse seepage-related features on the seafloor and their link to subsurface tectonic structures. In total, 398 pockmarks have been identified on the seafloor, suggesting significant past and/or present natural fluid seepage. Beneath the pockmarks, acoustic features such as enhanced reflections, acoustic turbid zones and acoustic blankings interpreted on subbottom acoustic profiles suggest possible gas accumulation and migration linked to various fault systems reaching the seafloor. This paper discusses fluid migration in a fold-and-thrust belt setting, broadened by secondary sealing mechanisms in Arctic conditions. We conclude by illustrating the various types of reported fluid seepage, particularly along permeable fault planes and at the rims of igneous intrusions.
We address the spatial and temporal development during the Triassic to Middle Jurassic of the NW Barents Shelf in order to provide a regional framework for the targeted reservoir of the Longyearbyen CO2 Lab. The reservoir is Middle Triassic to Middle Jurassic stacked sandstones at a depth of 670-970 m in Adventdalen, Svalbard. The predominantly Carnian De Geerdalen Formation, the lower reservoir, is composed of immature shallow-marine, deltaic to paralic mudstones and sandstones of which over 250 m have been cored at the proposed CO2 injection site. The overlying mid-Norian to Bathonian Knorringfjellet Formation is distinctly more mature and very condensed, with a thickness of just 25 m at the same site. While Early to Mid Triassic sediment influx in Western Svalbard appears dominated by a western source, the De Geerdalen Formation is regionally linked to advancing delta systems from the Uralide mountains and Fennoscandian Shield. The Gardarbanken high hindered Early Triassic progradation and Late Triassic sediment deposition was influenced by the Edgeoya platform. The platform was structurally higher than surrounding areas and limited accommodation space combined with high sediment influx probably caused a rapid advance of the platform edge. The Upper Triassic to Middle Jurassic deposits are condensed with several hiati onshore, and thin and in places eroded offshore. This indicates a strongly linked development across the whole northern Barents Shelf related to limited accommodation space, condensation and/or sediment starvation and erosion.
Understanding of fluid-mixture properties relevant to the Longyearbyen CO2 Lab pilot project (LYBCO2) is of great importance for the assessment of the injection performance. Phase equilibria and density of the binary, ternary and quaternary systems containing CO2, CH4, H2O and NaCl were investigated using a Statistical Associating Fluid Theory (SAFT)-based equation of state (EoS) at ambient temperature and pressure, and salt concentrations up to 5 mol kgw(-1), all relevant to LYBCO2. Binary interaction parameters of the subsystems (CO2-CH4, CH4-H2O, and CH4-NaCl) were tuned against available experimental data, using previously adjusted parameters for pure components and CO2-H2O subsystems. Solubility of CH4 and CO2 and subsequent mixture densities were predicted at 298 K and pressure up to 100 bar. It is found that by increasing the hydrocarbon in the injection stream (even in small amounts) and also the salt concentration and solubility of the CO2 in the aqueous phase, then consequently the density of the mixture will reduce. Moreover, hydrocarbon impurities like CH4 would result in a favourable density difference and faster plume migration; however, the probability of a three-phase state (two liquid and one vapour phase) near the bubble line is very high too. The results of this work are applicable to estimation of storage capacity as well as simulation of plume migration and fate in all projects involving a CO2, CH4, H2O and NaCl-bearing fluid system.
In unconventional, naturally fractured reservoirs, networks of structural discontinuities largely control fluid flow. In this study, we mapped and analysed systematic fracture patterns within the Mesozoic succession of Central Spitsbergen to characterise the reservoir-caprock system explored for geological CO2 storage by the Longyearbyen CO2 Lab project. We carried out and integrated structural and stratigraphic analyses of outcrop and borehole data, subdividing the investigated sedimentary interval into five litho-structural units (LSUs): (A) massive to laminated shales characterised by predominant low-angle fractures, (B) heterogeneous, fine-grained intervals with both low- and high-angled fractures, (C) massive, coarse-grained intervals dominated by high-angle fractures, (D) igneous intrusions characterised by syn- and post-emplacement fractures and veins, and (E) carbonate beds dominated by high-angle fractures and veins. LSUs are identified on the basis of their fracture associations, lithologies and dominant sedimentary facies, and thus implicitly include information on the primary porosity and permeability. In general, two main, subvertical extensional fracture sets are recognised: (i) a principal fracture set trending approximately NE-SW to ENE-WSW (J1) and (ii) a subordinate fracture set trending about NNW-SSE to NNE-SSW (J2). Conjugate shear fractures (Si) are trending roughly NE-SW and NW-SE in the coarser-grained and more cemented lithologies. A low-angle fracture set (S2) striking approximately NNW-SSE to WNW-ESE is also observed. Variations in fracture patterns suggest that the LSUs are pseudo-mechanical units, which are able to steer, baffle or impede horizontal and vertical fluid migration due to their primary matrix (i.e., grain size and mineralogy) and fracture network properties. At a larger scale, the resultant stratigraphic and structural architecture controls the hydrogeological regime of the investigated reservoir-caprock succession, providing: (1) fracture-related secondary porosity and permeability, (2) enhanced microfracturing matrix connectivity, and (3) preferential directions of subsurface fluid-flow pathways. We conclude that, given the present-day stress field, subsurface fluid flow would be augmented in an ENE-WSW trend, with possible additional NE-SW communication.
Rocks of the Knorringfjellet Formation in Central Spitsbergen form a potential storage reservoir for CO2 below Longyearbyen. They are characterised by a moderate porosity and low permeability. However, water injection tests have shown positive results and fractures are considered to facilitate fluid flow. Therefore, hard data on fracture parameters and pore characteristics should be analysed to better understand flow characteristics. Consequently, sandstone and conglomerate samples from the Knorringfjellet Formation were sampled and characterised with High Resolution X-ray Computed Tomography (HRXCT) at the Centre for X-ray Tomography at Ghent University, Belgium (UGCT). The dataset includes samples taken from drillholes in the vicinity of Longyearbyen drilled during the pilot phase of the Longyearbyen CO2 project, as well as from the Knorringfjellet Formation outcrops at Konusdalen and Criocerasdalen. This was done in order to compare micro-fracture and pore parameters in both settings. With HRXCT, the samples were analysed at pore scale and quantitative information of the pore network and fractures was extracted. Pore networks were used for the modelling of CO2 flow in specific samples and information on fracture aperture was obtained at a micrometre scale. The acquired dataset can be directly used for a better understanding of flow in the aquifer.
Onshore-offshore correlation of brittle faults and tectonic lineaments has been undertaken along the SW Barents Sea margin off northern Norway. The study has focused on onshore mapping of fault zones, the mapping of offshore fault complexes and associated basins from seismic interpretation, and the linkage of fault complexes onshore and offshore by integrating a high-resolution DEM, covering both onshore and offshore portions of the study area, and processed magnetic anomaly data. This study shows that both onshore and offshore brittle faults manifest themselves mainly as alternating NNE-SSW- and ENE-WSW-trending, steeply to moderately dipping, normal fault zones constituting at least two major NE-SW-trending fault complexes, the Troms-Finnmark and Vestfiorden-Vanna fault complexes. These fault complexes in western Troms bound a major basement horst (the West Troms Basement Complex), run partly onshore and offshore and link up with the offshore Nysleppen and Masoy fault complexes. Pre-existing structures in the basement, such as foliation, Ethological boundaries and ductile shear zones are shown, at least on a local scale, to have exerted a controlling effect on faulting. On a larger scale, at least two major transfer fault zone systems, one along the reactivated Precambrian Senja Shear Belt and the other, the Fugloya transfer zone, accommodate changes in brittle fault polarity along the margin. Our results suggest that distributed rifting during Carboniferous and Late Permian/Early Triassic time was followed by a northwestward localisation of displacement to the Troms-Finnmark and Ringvassoy-Loppa fault complexes during the Late Jurassic/Early Cretaceous, resulting in the formation of a short-tapered, hyperextended margin with final break-up at similar to 55 Ma. An uplift of the margin and preservation of the West Troms Basement Complex as a basement outlier is suggested to be due to unloading and crustal flexure of the short-tapered margin in the region.
Igneous intrusions emplaced during the Early Cretaceous are well exposed in central Spitsbergen within the Permian-Jurassic sedimentary succession. The doleritic intrusions are collectively classified as the Diabasodden Suite, and form part of the High Arctic Large Igneous Province. Though relatively easily accessible and very well exposed in places, the Diabasodden Suite dolerites remain underexplored and their prevalent geometry is particularly poorly understood. In this contribution we address this deficiency by mapping the distribution of the igneous complexes in both onshore and offshore areas of central Spitsbergen, using an integrated dataset incorporating 2D seismic data with magnetic profiles, high-resolution multibeam bathymetric data, digital elevation models, aerial photos, geological maps, a lidar model and fieldwork. The intrusions occur primarily as sills, typically less than 50 m thick but extending over 10 km laterally. Subordinate dykes, transgressive sill segments and saucer-shaped intrusions are also present. Increased structural complexity is evident in the higher parts of the stratigraphy, with sill/dyke interactions relatively common. Some exposed positive relief features on the seafloor are interpreted as resistant dolerite intrusions, based on bathymetric data, 2D seismic lines and magnetic profiles. An increased presence of pockmarks along the rims of these intrusions cropping out at the seafloor suggests a causal relationship between focused fluid flow and igneous intrusions. As well as describing the overall geometry of the igneous complex, we investigate the implications of igneous intrusions for fluid flow within a siliciclastic aquifer, highlighted by a study addressing potential subsurface CO2 storage in central Spitsbergen. Fracture corridors along dykes suggest that fluid flow may be channelled along dykes across the stratigraphy, perhaps leaking into the lower part of the caprock. Furthermore, both enhanced flow along dykes and hampering of flow across dykes may affect the areal distribution of the CO2 plume following injection of CO2 into the affected aquifer.
The Vestertana Group on the Digermul Peninsula, Finnmark, northern Norway, presents one of the few, potentially continuous Ediacaran-Cambrian sections in Scandinavia. Trace fossils provide the main age constraint, with the boundary traditionally placed at the base of the Breidvika Formation. Here, we provide trace-fossil evidence to show that this boundary is at least as low as the third cycle of the Manndraperelva Member, Stahpogieddi Formation, where Treptichnus pedum is associated with trilobed trace fossils. Organic-walled microfossils from the same stratigraphic interval include Granomarginata prima and the first report from Scandinavia of Cochleatina. The second cycle of the Manndraperelva Member contains trace fossils, including treptichnids and ?Cochlichnus isp. tentatively interpreted as latest Ediacaran. Reports of palaeopascichnids suggest a late Ediacaran age for the first cycle. The age of lower parts of the Stahpogieddi Formation is poorly constrained but discoidal Ediacara-type fossils, vendotaenids, and possible simple trace fossils, suggest that the middle part of the Innerelva Member is younger than c. 560 Ma.
Issue ISBN: 978-82-92-39488-5 This work is supported by the Carnegie Trust for the Universities of Scotland
Plesiosaurian relationships have been subject to considerable debate at both higher and lower levels within the date. Recent fieldwork in the Uppermost Jurassic of the Agardhfjellet Formation on central Spitsbergen has uncovered numerous ichthyosaurians and plesiosaurian remains, including three new plesiosauroids, one new pliosauroid referrable to Pliosaurus, and a previously described, re-classified taxon. The phylogenetic relationships of these five taxa were investigated based on data sets previously constructed for global plesiosaurian relationships. Two specimens from the British Kimmeridge Clay Formation and a Russian Volgian (uppermost Jurassic) taxon referrable to Pliosaurus were added to the data matrix to improve the phylogenetic resolution of this genus. The results yielded a tree topology closely conforming to the traditional plesiosauroid and pliosauroid dichotomy, nesting Leptocleidia within the latter. Pliosaurus forms a monophyletic clade containing all currently recognised species. The three new long-necked taxa form a monophyletic sister group to the Cretaceous Elasmosauridae. These results should, however, be considered preliminary pending the discovery of more complete cranial material and adult specimens.
A series of Upper Jurassic to Lower Cretaceous samples of hydrocarbon seep bodies from central Spitsbergen (Svalbard) were treated with acetic acid to retrieve insoluble micro and macrofossils. The Lower Cretaceous samples yielded abundant lingulid material of Lingularia similis? Biernat & Ernig 1993, represented by well preserved, but invariably fragmented shells. They provide the first critical ultrastructural information for this important extinct member of the extant Lingulidae.
We investigate the long-term geomorphological evolution of the inselberg plains on the glaciated northern Fennoscandian shield. The shield surface has been largely stripped of pre-Quaternary correlative sediments and saprolites by non-glacial and glacial erosion, which make investigations of pre-Quaternary landscape development a challenge. The relief of the study area, covering 33,000 km(2) in the centre of the shield in northern Sweden, includes an abundance of inselbergs that provide the basis for the study. We examine the relief of the inselberg plains, integrated with glacial-geomorphologic features, geology, and weathering remnants, by using GIS-analysis and fieldwork. Several key areas are used to demonstrate the impact of glaciations on the large-scale relief, and the influence of geology, structure and deep weathering on relief formation.Glacial erosion had only a minor impact on the large-scale bedrock morphology of northern Sweden. Based on excavations and observations in the Parkajoki area, an area largely preserved under cold-based ice during Quaternary glaciations, we infer that grus weathering, resulting in saprolite covers of up to 10-20 m thickness, occurred in the Neogene. However, inselbergs are considerably higher than that, and must therefore be the result of older deep weathering and erosional events. Narrow fracture zones associated with deep kaolins found in northern Fennoscandia may represent the roots of older generations of deep weathering covers but their age and formation is yet unclear. The geology of the area has greatly influenced the present surface relief. The positions and footprints of the inselbergs are often closely controlled by bedrock type and fracturing. Granite inselbergs generally have dome forms where dome shape and slopes are determined by joint patterns. Steps between palaeosurfaces locally coincide with lithological boundaries and major faults. These links indicate the fundamental importance of etch processes in shaping the relief through multiple cycles of deep weathering and stripping. Palaeosurfaces have been extended and lowered through time, with isolation of small inselbergs during erosion of higher palaeosurfaces. The timescales for relief generation remain uncertain and there is a pressing need to understand the significance of and to date the sediments, saprolites and weathered ore bodies that rest on the surface of the northern Fennoscandian shield.
The Neoproterozoic Hedmark Group (Lower Allochthon), Valdres Group (Middle Allochthon) and Engerdalen Group (Middle Allochthon) contain allochthonous basement slices with tectonic and depositional contacts to sedimentary rocks. The basement slices were transported from the western margin of the continent Baltica during the Caledonian Orogeny. Zircon U-Pb and Lu-Hf isotopes reveal that allochthonous basement rocks in the Osen-Roa Nappe Complex, forming the depositional substrate of the Hedmark Group, are related to the Transscandinavian Igneous Belt (TIB) in terms of age and petrogenetic history. The Kvitvola Nappe Complex of the Middle Allochthon, carrying the sedimentary Engerdalen Group, contains c.1620 Ma and 1180 Ma augen gneisses. The oldest augen gneiss has TIB-like Hf characteristics, while the younger gneiss is more juvenile. These basement rocks may originally have been separated by a major lithotectonic boundary. A sample from the basement slice, located stratigraphically beneath the Valdres Group in the Valdres Nappe Complex, is dated at c.1480 Ma and also has juvenile Hf composition. The apparent younging of basement ages from Lower to Middle Allochthon suggests age zonation at the SW Baltican margin. The juvenile 1180 Ma and 1480 Ma samples are probably derived from the same crust as what is today known as SW Norway or "Telemarkia'. Crustal rocks of present-day SW Norway must have continued further to the northwest (according to present geography) and were probably bordered by TIB rocks in the NE. We also present new U-Pb and Lu-Hf data from the autochthonous basement in front of and tectonostratigraphically beneath the Osen-Roa Nappe Complex, sampled along a transect from the Romerike Complex across the Mylonite Zone to Lake Storsjoen. Hf isotopes show the juvenile character of the gneisses on the western side of the Mylonite Zone and typical TIB 3 compositions on the eastern side. Hafnium isotopes from the Hustad Igneous Complex in the Western Gneiss Region (WGR) show strong similarity with the TIB, which supports a genetic connection between the TIB and WGR. Hafnium isotopes from the late Sveconorwegian Fla granite show crustal contamination, which supports models where the TIB continues underneath the Gothian domain.
The 800 m thick Brumunddal sandstone is partly an eolian, partly a fluvial sandstone deposited in a fault-bounded basin in the northern part of the Oslo Rift in Permian time.The sandstone is the youngest rift-related deposit in the northern part of the Oslo Rift. Well rounded detrital zircons are common accessory mineral grains in the sandstone. U-Pb dating of detrital zircon from a sample of the Brumunddal sandstone by LAM-ICPMS gives a range of ages from (rare) late Archaean ages to Permian (283 +/- 4 Ma). The age and initial epsilon Hf pattern of zircons in the sediment match the main rock- forming events in Fennoscandia from Archaean to Phanerozoic time. This kind of diverse provenance was most likely obtained by repeated recycling of clastic sediments of Fennoscandian origin, with Silurian, continental sandstones as the most probable direct precursors. Trace element distributions show a conspicuous absence of patterns with the high level of U and Th enrichment typical of zircon from granitic rocks. This is consistent with a complex transport and redepositional history: High U-Th, metamict zircons were selectively removed by abrasion during repeated transport-deposition-erosion cycles. In addition to recycled material. Caledonian syn-orogenic intrusions and Permian intermediate to felsic plutonic rocks in the Oslo Rift itself were minor, but still significant sources of detrital zircon.
The Rosten Formation is a debris-flow conglomerate in the Kvitvola Nappe Complex of the Caledonian Middle Allochthon. It mainly consists of granitic gneiss clasts and was deposited on an augen-gneiss basement, the Hovringen Gneiss Complex. The gneiss-forming event of the clasts is clearly pre-Caledonian. The conglomerate is overlain by arkosic sandstone that is trough cross-bedded and includes some cobbles. The succession is interpreted as typical alluvial fan - braided river and probably marks an early syn-rift deposit. Zircon extracted from five conglomerate clasts and one sandstone sample was analysed for U-Pb and Lu-Hf isotopes. The clasts are c.1180-1220 Ma in age and have a moderately juvenile Hi-signature (epsilon(Hf) approximate to 1). Some c.1650 Ma inherited zircon is also present. Zircon from the sandstone sample shows a pronounced c.1200 Ma mode and a minor 1650-1500 Ma age mode. The clasts have similar Hf signatures and ages to the underlying Hovringen Gneiss Complex that includes c.1180 Ma gneiss unit. The sandstone was also probably derived from the same source. The c.1650 Ma zircons, inherited in the clasts and in the sandstone, correspond to sources in the Western Gneiss Region. The Rosten Formation probably marks the beginning of the rifting process that led to the break-up of supercontinent Rodinia, opening of the Iapetus Ocean and formation of the pericratonic Engerdalen Basin in the Neoproterozoic. The westernmost margin of the Baltica continent consisted of a c.1200 Ma magmatic province that was probably deformed in late Sveconorwegian time.
Normal-sense movements along two major strands of the Billefjorden Fault Zone controlled sedimentation in the Carboniferous Billefjorden Trough. The Billefjorden Trough is a more than 2000 meters thick, west-clipping half-graben basin where accommodation was provided by combinations of extensional faulting and folding throughout the basin history. Whereas previous workers have interpreted several of these folds as due to Tertiary contraction, we argue that they developed during rifting, as extensional forced folds in the style described by other workers from rifts such as the Gulf of Suez. The present basin geometry indicates that accommodation was facilitated by a combination of fault relief and fault-related folds such as extensional fault-propagation monoclines, longitudinal rollover folds and a broad syncline that developed in the hanging wall of the master faults. Major fault-tip monoclines with sharp hinges and steep fold-limbs were allowed to develop in the basin as it became dominated by thick sabhka deposits. Some of the monoclines can be traced laterally into intra-basinal half-grabens where we document significant growth of the hanging wall stratigraphy. The basin shows a close link between structural style and the distribution of main facies associations, confirming a tectonic control on the main depositional systems. Three major alluvial fan complexes formed the main fairways for elastic supply into the basin; of which two were associated with relay ramps. The alluvial fan systems mostly kept up with subsidence or prograded far into the basin. This restricted the extent of marine incursions, and resulted in the development of isolated playas. Initial floodplain deposition in the gently subsiding rift-basin centre was followed by marine flooding events localized mainly to the hinges of longitudinal folds and to relay zones. The gently dipping fold flanks caused tidal flats to be developed in lenticular depocentres. As the main segments of the BFZ linked during strain localization, the western basin-margin monocline was likely breached, triggering rapid subsidence with marine flooding and a change to a westward thickening, wedge-shaped depocenter. Subsequently, a gentle relief was gradually re-established in the basin during renewed growth of fault-monoclines. Finally, the entire basin became submerged, with fault-monoclines being reactivated. Causes for this late subsidence include eustacy, thermal relaxation, differential compaction of the basin fill, or faulting driven by regional extension.
The Grossae-Totak supracrustal belt is part of the several-kilometre thick Telemark supracrustal sequences that are exposed in southern Norway. Deposition of the Telemark supracrustals spans the period between Telemarkian continental growth at similar to 1.52-1.48 Ga and Sveconorwegian orogenesis associated with continental collision at similar to 1.1-0.9 Ga. The timing of deposition is largely constrained by U-Pb geochronology of detrital zircons in sedimentary units, and igneous zircons within felsic volcanics. A younger Supergroup that has been referred to as the Sveconorwegian Supergroup comprises depositional ages younger than 1.16 Ga; units of the Grossae-Totak belt have been mapped as part of this Supergroup. This study presents a new U-Pb age of 1233 +/- 29 Ma for the Fjellhovdane rhyolite, one of the lowermost units within the Grossae-Totak belt; this age suggests that at least the lower part of this sequence is not part of the Sveconorwegian Supergroup, but formed in an earlier volcano-sedimentary basin that is correlative in age to the Saesvatn-Valldal and Setesdal supracrustal belts that occur to the west and south respectively. The geochemistry of the Fjellhovdane rhyolite is compatible with crustal melting of previously-formed supra-subduction rocks, as has been advocated for the Saesvatn-Valldal rhyolites.
Dinoflagellate cyst (dinocyst) assemblages were analyzed in 43 surface sediment samples from the Barents Sea. They can be divided into five major assemblage types, the distribution of which can clearly be linked to the overlying water masses. Notably, a very clear distinction between sites influenced by Atlantic water and Arctic water, respectively, is seen in the change in dominance from O. centrocarpum s.l. to I. minutum and is strongly related to sea-surface temperature. More subtle hydrographical features are also recorded in the assemblages, as can be seen from the spatially coherent distribution of the Atlantic assemblages, which allows discrimination between the Norwegian Coastal Current zone, the Norwegian Atlantic Current zone and two regions of modified Norwegian Atlantic Current waters. Here sea-surface temperature does not seem to be the primary parameter controlling the distribution of the assemblages. Multivariate analyses suggest that the assemblages are associated with the stratification and productivity annual cycles. Cysts of P. dalei seem to favour stratified environments, while O. centrocarpum s.l. might be more adapted to unstable conditions. Cysts of P dalei are also associated with early spring stratification and productivity, whereas other species such as S. ramosus are related to late spring/summer productivity and stratification.
The MAREANO programme (2006 - 2010) has collected video-footage and surface sediment samples in the Southern Barents Sea during the cruise in 2006. The sampled marine areas included Ingoydjupet, a depression that serves as a depositional sink with a predominance of fine-grained muddy sediments. Human impact, both physical and chemical, can be assessed using different methods: Video recordings and geochemical parameters recorded in the sediments reveal evidence of human impact on the sedimentary regime in Ingoydjupet. Bottom trawling fisheries have disturbed the sedimentary surface, and affected benthic organisms and biological communities. The heavy metals mercury (Hg), lead (Pb) and cadmium (Cd), which were analysed in the surface sediments, are of a major concern due to their toxic effects, even at low concentrations. Although there are no serious pollution threats as yet it is evident that increments of Hg and Pb in sediments have increased in recent decades. The most likely cause of these increases is anthropogenic activity, when looking at changes in Hg and Pb concentrations in two (210)Pb-dated Ingoydjupet cores. Cadmium does not show a similar temporal trend. The increases in Hg and Pb in Ingoydjupet surface sediments are most likely associated with atmospheric or oceanic long-range transport and deposition in the muddy sediments. The main source for anthropogenic Hg is considered to be coal combustion. Anthropogenic sources for Pb include leaded gasoline, which was in use until the 1970'ies in the western world, and is still in use in other parts of the world.
