Constraints on the Late Weichselian ice sheet over the Barents Sea from observations of raised shorelines

Direct evidence for Late Weichselian grounded glacier ice over extensive areas of the Barents Sea is based largely on indirect observations, including elevations of old shorelines on Svalbard and arguments of isostatic rebound. Such isostatic models are discussed here for two cases representing maximum and minimum ice-sheet reconstructions. In the former model the ice extends over the Kara Sea, whereas in the latter the ice is limited to the Barents Sea and island archipelagos. Comparisons of predictions with observations from a number of areas, including Spitsbergen, Nordaustlandet, Edgeøya, Kong Karls Land, Franz Josef Land, Novaya Zemlya and Finnmark, support arguments for the existence of a large ice sheet over the region at the time of the last glacial maximum. This ice sheet is likely to have had the following characteristics, conclusions that are independent of assumptions made about the Earth's rheological parameters. (i) The maximum thickness of this ice was about 1500–2000 m with the centre of the load occurring to the south and east of Kong Karls Land. (ii) The ice sheet extended out to the western edge of the continental shelf and its maximum thickness over western Spitsbergen was about 800 m. (iii) To the north of Svalberg and Frans Josef Land the ice sheet extended out to the northern shelf edge. (iv) Retreat of the grounded ice across the southern Barents Sea occurred relatively early such that this region was largely ice free by about 15,000 BP. (v) By 12,000 BP the grounded ice had retreated to the northern archipelagos and was largely gone by 10,000 BP. (vi) The ice sheet may have extended to the Kara Sea but ice thicknesses were only a fraction of those proposed in those reconstructions where the maximum ice thickness is centered on Novaya Zemlya. Models for the palaeobathymetry for the Barents Sea at the time of the last glacial maximum indicate that large parts of the Barents Sea were either very shallow or above sea level, providing the opportunity for ice growth on the emerged plateaux, as well as on the islands, but only towards the end of the period of Fennoscandian ice sheet build-up.     

Late Weichselian Glaciation of the Russian High Arctic

A numerical ice-sheet model was used to reconstruct the Late Weichselian glaciation of the Eurasian High Arctic, between Franz Josef Land and Severnaya Zemlya. An ice sheet was developed over the entire Eurasian High Arctic so that ice flow from the central Barents and Kara seas toward the northern Russian Arctic could be accounted for. An inverse approach to modeling was utilized, where ice-sheet results were forced to be compatible with geological information indicating ice-free conditions over the Taymyr Peninsula during the Late Weichselian. The model indicates complete glaciation of the Barents and Kara seas and predicts a “maximum-sized” ice sheet for the Late Weichselian Russian High Arctic. In this scenario, full-glacial conditions are characterized by a 1500-m-thick ice mass over the Barents Sea, from which ice flowed to the north and west within several bathymetric troughs as large ice streams. In contrast to this reconstruction, a “minimum” model of glaciation involves restricted glaciation in the Kara Sea, where the ice thickness is only 300 m in the south and which is free of ice in the north across Severnaya Zemlya. Our maximum reconstruction is compatible with geological information that indicates complete glaciation of the Barents Sea. However, geological data from Severnaya Zemlya suggest our minimum model is more relevant further east. This, in turn, implies a strong paleoclimatic gradient to colder and drier conditions eastward across the Eurasian Arctic during the Late Weichselian.     

Clay-mineral distribution in surface sediments of the Eurasian Arctic Ocean and continental margin as indicator for source areas and transport pathways — a synthesis

Clay-mineral distributions in the Arctic Ocean and the adjacent Eurasian shelf areas are discussed to identify source areas and transport pathways of terrigenous material in the Arctic Ocean. The main clay minerals in Eurasian Arctic Ocean sediments are illite and chlorite. Smectite and kaolinite occur in minor amounts in these sediments, but show strong variations in the shelf areas. These two minerals are therefore reliable in reconstructions of source areas of sediments from the Eurasian Arctic. The Kara Sea and the western part of the Laptev Sea are enriched in smectite, with highest values of up to 70% in the deltas of the Ob and Yenisey rivers. Illite is the dominant clay mineral in all the investigated sediments except for parts of the Kara Sea. The highest concentrations with more than 70% illite occur in the East Siberian Sea and around Svalbard. Chlorite represents the clay mineral with lowest concentration changes in the Eastern Arctic, ranging between 10 and 25%. The main source areas for kaolinite in the Eurasian Arctic are Mesozoic sedimentary rocks on Franz-Josef Land islands. Based on clay-mineral data, transport of the clay fraction via sea ice is of minor importance for the modern sedimentary budget in the Arctic basins.     

Structure of the Earth’s crust in the northern part of the Barents–Kara region along the 4-AR DSS profile

The 1370 km long 4-AR reference profile crosses the North Barents Basin, the northern end of the Novaya Zemlya Rise, and the North Kara Basin. Integrated geophysical studies including common deep point (CDP) survey and deep seismic sounding (DSS) were carried out along the profiles. The DSS was performed using autonomous bottom seismic stations (ABSS) spaced 10–20 km apart and a powerful air gun producing seismic signals with a step size of 250 m. As a result, detailed P- and S-wave velocity structures of the crust and upper mantle were studied. The basic method was ray-tracing modeling. The Earth’s crust along the entire profile is typically continental with compressional wave velocities of 5.8–7.2 km/s in the consolidated part. Crustal thickness increases from 30 km near the islands of Franz Josef Land to 35 km beneath the North Barents Basin, 50 km beneath the Novaya Zemlya Rise, and 40 km beneath the North Kara Basin. The North Barents Basin 15 km deep is characterized by unusually low velocities in the consolidated crust: The upper crust layer with velocities of 5.8–6.4 km/s has a thickness of about 15 km beneath the basin (usually, this layer wedges beneath deep sedimentary basins). Another special property of the crust in the North Barents Basin is the destroyed structure of the Moho.     

The impact of glaciation, river-discharge and sea-level change on Late Quaternary environments in the southwestern Kara Sea

Sedimentary records from the southwestern Kara Sea were investigated to better understand the extent of the last glaciation on the Eurasian Arctic shelf, sea-level change, and history of the Ob' and Yenisey river discharge. Sediment-core and seismic-reflection data indicate that the Quaternary depositional sequence in the southwestern Kara Sea consists of glacial, glaciomarine, and marine sedimentary units. Glaciogenic sediments in the deep Novaya Zemlya Trough are presumably related to the Last Glacial Maximum (LGM), whereas further east they may represent an earlier glaciation. Thus, it is inferred that the southeastern margin of the LGM Barents-Kara ice sheet was contained in the southwestern Kara Sea east of the Novaya Zemlya Trough. Changes in mineralogical, foraminiferal, and stable-isotopic composition of sediment cores indicate that riverine discharge strongly influenced sedimentary and biotic environments in the study area during the Late Weichselian and early Holocene until ca. 9 ka, consistent with lowered sea levels. Subsequent proxy records reflect minor changes in the Holocene hydrographic regime, generally characterized by reduced riverine inputs.     

Numerical reconstructions of the Eurasian Ice Sheet and climate during the Late Weichselian

Geological investigations undertaken through the Quaternary Environments of the Eurasian North programme established ice-sheet limits for the Eurasian Arctic at the Last Glacial Maximum (LGM), sedimentary records of palaeo-ice streams and uplift information relating to ice-sheet configuration and the pattern of deglaciation. Ice-sheet numerical modelling was used to reconstruct a history of the Eurasian Ice Sheet compatible with these geological datasets. The result was a quantitative assessment of the time-dependent behaviour of the ice sheet, its mass balance and climate, and predictions of glaciological products including sediments, icebergs and meltwater. At the LGM, ice cover was continuous from Scandinavia to the Arctic Ocean margin of the Barents Sea to the north, and the Kara Sea to the east. In the west, along the continental margin between the Norwegian Channel and Svalbard, the ice sheet was characterised by fast flowing ice streams occupying bathymetric troughs, which fed large volumes of sediment to the continental margin that were deposited as a series of trough mouth fans. Ice streams may also have been present in bathymetric troughs to the north between Svalbard and Franz Josef Land. Further east, however, the ice sheet was thinner. Across the Kara Sea, the ice thickness was predicted to be less than 300 m, while on Severnaya Zemlya the ice cover may have been thinner at the LGM than at present. It is likely that the Taymyr Peninsula was mainly free of ice at the LGM. In the south, the ice margin was located close to the shoreline of the Russian mainland. The climate associated with this ice sheet is maritime to the west and, in stark contrast, desert-like in the east. Atmospheric General Circulation Modelling has revealed that such a contrast is possible under relatively warm north Atlantic conditions because a circulation system develops across the Kara Sea, isolating it from the moisture-laden westerlies, which are diverted to the south. Ice-sheet decay began through enhanced iceberg calving in the deepest regions of the Barents Sea, which caused a significant ice embayment within the Bear Island Trough. By about 12,000 years ago, further iceberg calving reduced ice extent to the northern archipelagos and their surrounding shallow seas. Ice decay was complete by about 10,000 years ago.     

Glacigenic deposits of the Central Deep: a key to the Late Quaternary evolution of the eastern Barents Sea

Sparker and shallow drilling data indicate that the Quaternary deposits in the Central Deep of the Barents Sea are mainly composed of glacigenic sediments. They comprise basal till and proximal and distal glaciomarine sediments deposited during the last glacial cycle. Apparent glaciotectonic features imply strong glacial erosion of Mesozoic bedrock. The general ice movement is assumed to have been from off Novaya Zemlya and it is concluded that the whole eastern Barents Sea was covered by the Late Weichselian ice-sheet.     

Modern river discharge and pathways of supplied material in the Eurasian Arctic Ocean: evidence from mineral assemblages and major and minor element distribution

Clay-mineral, heavy-mineral, and elemental distributions in sediments from the Arctic Ocean and the adjacent Laptev and Kara seas can be attributed to the geology of the hinterland and the transport of terrigenous material by rivers onto the shelves. Kara Sea sediments are characterized by increased contents of smectite and elevated Ni/Al-, Ti/Al-, and Cr/Al ratios. In the western Laptev Sea sediments are enriched in smectite and clinopyroxene and increased in Ti/Al-, Cr/Al-, and Ca/Al ratios. The composition of the sediments reflects suspended matter input from the large trap basalt of the Putoran Mountains. The eastern Laptev Sea sediments display increased illite and amphibole contents as well as a chemical composition similar to average shale. This composition is due to the discharge from the Lena and Yana rivers, which drain a large catchment area consisting of sedimentary Mesozoic and Paleozoic rocks. Material from the eastern Laptev Sea is transported by ocean currents and sediment-laden sea ice along the Transpolar Drift into the central Arctic Ocean. This is indicated by similar values of Ti/Al-, Cr/Al-, Rb/Al-, and K/Al ratios as well as increased concentrations of amphibole and illite, determined in sediments from the Lomonosov Ridge. A minor input from the Beaufort Sea into the central Arctic Ocean is suggested from increased Ca/Al ratios and increased contents of opaque minerals.     

Source potential of the upper Jurassic rocks of the Barents Sea petroleum basin

A preliminary assessment of the source potential of the Jurassic section was obtained using organic geochemical data on samples collected from outcrops on Franz Josef Land and Svalbard archipelagoes as well as boreholes in the Barents Sea basin. The presence of organic-rich shale units with good source potential was reported for the first time within the studied section of Early to Middle Jurassic age, along with well-documented Upper Jurassic source rocks. The study provides an assessment of regional variations in the kerogen type, hydrocarbon generation potential, and maturation of organic matter from Jurassic sediments.     

Geological and geodynamic reconstruction of the East Barents megabasin from analysis of the 4-AR regional seismic profile

The article considers problems related to the geological structure and geodynamic history of sedimentary basins of the Barents Sea. We analyze new seismic survey data obtained in 2005–2016 to refine the geological structure model for the study area and to render it in more detail. Based on the data of geological surveys in adjacent land (Novaya Zemlya, Franz Josef Land, and Kolguev Island), drilling, and seismic survey, we identified the following geodynamic stages of formation of the East Barents megabasin: Late Devonian rifting, the onset of postrift sinking and formation of the deep basin in Carboniferous–Permian, unique (in terms of extent) and very rapid sedimentation in the Early Triassic, continued thermal sinking with episodes of inversion vertical movements in the Middle Triassic–Early Cretaceous, folded pressure deformations that formed gently sloping anticlines in the Late Cretaceous–Cenozoic, and glacial erosion in the Quaternary. We performed paleoreconstructions for key episodes in evolution of the East Barents megabasin based on the 4-AR regional profile. From the geometric modeling results, we estimated the value of total crustal extension caused by Late Devonian rifting for the existing crustal model.     

Isotope (δD, δ<Superscript>18</Superscript>О) systematics in waters of the Russian Arctic seas

Oxygen and hydrogen isotope analysis was performed to study the processes of distribution of water masses and modification of their salinity in the Russian Arctic seas. A wealth of new isotopic data was obtained for freshwater (river runoff, Novaya Zemlya glaciers) and seawater samples collected along a set of extended 2D profiles in the Barents, Kara, and Laptev Seas. The study presents the first δD values measured for the Northeast Atlantic Deep Water NEADW dominated the water column of the Barents Sea (S = 34.90 ± 0.05, δD = +1.55 ± 0.4‰, δ¹⁸O = +0.26 ± 0.1‰, n = 44). This water mass is present in the Kara Sea and western Laptev Sea. The relationship between δD, δ18О, and salinity data was used to calculate the fractions of waters of different origin, including the fractions of continental runoff in waters of the Barents, Kara, and Laptev Seas. It was shown that the relationships between the isotopic parameters (δD, δ¹⁸О) and salinity in waters of the Kara and Laptev Seas is controlled by the intensity of continental runoff and sea ice processes. Sea ice formation is the main factor controlling the formation of the water column on the Laptev Sea shelf, whereas the surface waters of the middle Kara Sea are dominated by the contribution of river runoff. A very strong stratification in the Kara Sea is caused by the presence of a relatively fresh surface layer mostly contributed by estuarine water inputs from the Ob and Yenisei Rivers. The contribution of river waters reaches 40–60% in the surface layer in the central part of the sea and decreases to a few percent down 100 m water depth. Stratification in the western part of the Laptev Sea is controlled by the contribution of freshwater input from the Lena River and modification of salinity by sea ice formation.     

Features of seismicity of the Euro-Arctic region

New results from seismic monitoring in the Euro-Arctic region, including the seismicity of Gakkel Ridge and the Barents–Kara Sea shelf, are presented. The data used were obtained from the Arkhan-gelsk seismic network. The role of island-based seismic stations, in particular, those in Franz Josef Land, in the monitoring network is discussed. The possibility of specifying the nature of seismicity by waveform spectral-temporal analysis, even in the case of a single station, is considered.     

Sea-ice transport of riverine particles from the Laptev Sea to Fram Strait based on clay mineral studies

The aim of this study was to identify pathways and processes of modern sediment transport from the Siberian hinterland to the Laptev Sea and further to the Arctic Ocean. Clay mineral analyses were performed on riverine suspended particulate material (SPM), surface sediments of the Laptev Sea shelf, and sea-ice sediments (SIS). Material collected during seven expeditions was included in this study. Clay mineral assemblages are used to decipher the distribution of riverine sediments on the shallow Laptev Sea shelf, the entrainment of fine particles into newly forming ice, and the transport of SIS from the Laptev Sea towards the ablation areas. A cluster analysis of our data set shows that the clay mineral assemblages of Laptev Sea shelf sediments and SIS are controlled mainly by the input of riverine SPM supplied by the Khatanga, Lena, and Yana Rivers. Whereas the western shelf clay-mineral province is characterized by enhanced smectite concentrations supplied by the Khatanga River, the eastern Laptev Sea is dominated by illite discharged through the Lena and Yana Rivers. The SIS smectite concentration serves as an indicator for sediment source areas on the circum-Arctic shelves. Subsequently, the Transpolar Drift can be distinguished into a Siberian Branch fed from the eastern Kara Sea and the western Laptev Sea, and a Polar Branch originating from the eastern Laptev Sea.     

New data on the basement of Franz Josef Land,Arctic region

We have studied pebbles of igneous rocks from the Lower Jurassic sedimentary succession of Hall Island, Franz Josef Land. Pebbles are represented by felsic intrusive and extrusive rocks, often cataclased and greisenized. The U–Pb age of crystallization for zircons of the studied samples yielded the Latest Devonian–Early Carboniferous and Early–Middle Permian ages. In addition, the studied zircons demonstrate a broad scatter of ages, from Middle Paleozoic to Mesozoic, suggesting repeated thermal reworking and metamorphism of granites. It is shown that coeval Late Paleozoic magmatism indicates the similarity of the geological evolution of the northern Barents Sea and the Severnaya Zemlya archipelago.     

Detrital zircon geochronology of Palaeozoic Novaya Zemlya – a key to understanding the basement of the Barents Shelf

The Novaya Zemlya fold‐and‐thrust‐belt is the northern continuation of the late Palaeozoic Uralide Orogen. Little is known about its deeper structure and the basement history of the adjacent Barents and Kara shelves. Based on geological evidence and detrital zircon analysis of 28 samples from the northeastern and stratigraphically deepest part of the archipelago, we demonstrate that Cambro‐Ordovician turbidite‐dominated deposition was almost exclusively sourced from rocks consolidated during the Timanian orogeny (Timanian basement). A profound change in provenance occurred near the end of the Ordovician. Over 90% of the zircons from Silurian and about 80% from Devonian strata have ages characteristic of the Sveconorwegian Orogen, implying uplift of these rocks in the vicinity of Novaya Zemlya. The presence of Sveconorwegian and Grenvillian rocks in the high Arctic suggests revision of recent reconstructions of the Rodinia supercontinent, its break‐up and subsequent Caledonian orogeny.     

Pleistocene sediments of the eastern Barents Sea (Central Deep and Murmansk Bank): Communication 2. Lithological composition and formation conditions

Llithology of massive diamictons was studied in two areas of the eastern Barents Sea using cores and geophysical data. These sediments dominate in the Pleistocene section as two seismostratigraphic complexes (SSC): Upper Weichselian (SSC III) and locally distributed Lower Weichselian (SSC V). Diamictons of these complexes represent tills produced by the geological activity of the Pleistocene Novaya Zemlya and Scandinavian ice sheets. The Upper Weichselian glacial sequence is laterally heterogeneous. It includes two seismic facies represented by ordinary (overconsolidated) tills (they also constitute SSC V) and a spacious moraine of the specific type with the normally consolidated sediments (they avoided compaction by the ice load) and certain lithological specifics. The last glacial sediments were formed in a specific subglacial setting similar to the sediments under fast ice streams of Antarctica. However, the specific features allow us to define these sediments as a new (Barents Sea) facies of tills related to zones of intense basal melting of glaciers.     

南海北部陆架海域表层沉积物黏土矿物分布特征及物源分析

应用X射线衍射(XRD)对南海北部陆架海域225个站位表层沉积物黏土组分进行分析,结果表明,研究区黏土矿物总体以伊利石和绿泥石为主,高岭石和蒙脱石质量分数少,绿泥石、高岭石与蒙脱石质量分数呈明显的负相关关系。根据南海北部陆架海域表层沉积物中黏土矿物空间分布特征,结合邻近河流的黏土矿物组分以及洋流搬运作用,雷州半岛东部海域伊利石主要来源于广东沿海河流和珠江,绿泥石来自台湾岛,蒙脱石主要由吕宋河流提供,高岭石则由广东沿海河流和海南岛入海河流提供;雷州半岛西部海域伊利石来源于珠江,绿泥石和高岭石由红河提供,蒙脱石可能受广西入海河流携带的沉积物影响。     

The Plio-Pleistocene glaciation of the Barents Sea–Svalbard region: a new model based on revised chronostratigraphy

Based on a revised chronostratigraphy, and compilation of borehole data from the Barents Sea continental margin, a coherent glaciation model is proposed for the Barents Sea ice sheet over the past 3.5 million years (Ma). Three phases of ice growth are suggested: (1) The initial build-up phase, covering mountainous regions and reaching the coastline/shelf edge in the northern Barents Sea during short-term glacial intensification, is concomitant with the onset of the Northern Hemisphere Glaciation (3.6–2.4 Ma). (2) A transitional growth phase (2.4–1.0 Ma), during which the ice sheet expanded towards the southern Barents Sea and reached the northwestern Kara Sea. This is inferred from step-wise decrease of Siberian river-supplied smectite-rich sediments, likely caused by ice sheet blockade and possibly reduced sea ice formation in the Kara Sea as well as glacigenic wedge growth along the northwestern Barents Sea margin hampering entrainment and transport of sea ice sediments to the Arctic–Atlantic gateway. (3) Finally, large-scale glaciation in the Barents Sea occurred after 1 Ma with repeated advances to the shelf edge. The timing is inferred from ice grounding on the Yermak Plateau at about 0.95 Ma, and higher frequencies of gravity-driven mass movements along the western Barents Sea margin associated with expansive glacial growth.     

Postglacial emergence and Late Quaternary glaciation on northern Novaya Zemlya, Arctic Russia

Recent observations on postglacial emergence and past glacier extent for one of the least accessible areas in the Arctic, northern Novaya Zemlya are here united. The postglacial marine limit formed 5 to 6 ka is registered on the east and west coasts of the north island at 10 ± 1 and 18 ± 2 m aht, respectively. This modest and late isostatic response along with deglacial ages of >9.2 ka on adjacent marine cores from the northern Barents Sea indicate either early (>13 ka) deglaciation or modest ice sheet loading (<1500 m thick ice sheet) of Novaya Zemlya. Older and higher (up to 50 m aht) raised beaches were identified beneath a discontinuous glacial drift. Shells from the drift and underlying sublittoral sediments yield minimum limiting ¹⁴C ages of 26 to 30 ka on an earlier deglacial event(s). The only moraines identified are within 4 km of present glacier margins and reflect at least three neoglacial advances in the past 2.4 ka.     

The barents sea magmatic province: Geological-geophysical evidence and new <Superscript>40</Superscript>Ar/<Superscript>39</Superscript>Ar dates

Resulting from study of the geological structure of the Franz Josef Land and Svalbard archipelagoes, this work presents new 17 ⁴⁰Ar/³⁹Ar age datings for basalts taken during coastal expeditions in 2006–2010. Radiological age determination for intrusive units (sills) located in the western part of Nordensciold Land (Spitzbergen Island) has been made for the first time. In relation to use of the interpretation results of marine geological-geophysical data, the distribution peculiarities and time ranges for Jurassic-Cretaceous basic magmatism within the studied regions of the Barents Sea continental margin and within the Arctic as a whole are discussed.