E. V. Shipilov

Jurassic-cretaceous Barents-Amerasian superplume and initial stage of geodynamic evolution of the Arctic Ocean

The distribution area of the Jurassic‐Cretaceous plume-derived basaltoid magmatism in the Barents Sea region and the entire Arctic was first outlined and reconstructed based on geological study of continental margins and interpretation of multidisciplinary marine geological‐geophysical data. It was shown that this magmatism occurred during the corresponding tectonomagmatic stage, which was caused by a plume event and led to the opening of the Canadian oceanic basin. This plume (called the Barents‐Amerasian plume [5]) is comparable in size with the Siberian (Triassic) and proto-Iceland (Cenozoic). The study of materials indicates that the Barents Sea area of the basaltoid magmatism has a much wider distribution than supposed previously, being only part of a “large igneous province,” which was formed prior to the opening of the Canadian basin. The reconstructions carried out showed that an extended Protoarctic oceanic basin existed at this time north of the Barents‐Kara Sea paleomargin. This basin was situated between the Siberia and North America margins and contained blocks of the New Siberian‐Chukchi region and Arctic Alaska. The Eastern Barents megatrough was the apical part of this oceanic basin at the paleomargin [3]. What was the geodynamic setting at the initial stage of the ocean formation in the Jurassic‐Cretaceous time? Which tectonic transformation of continental margins accompanied the formation of the Arctic’s largest Canadian oceanic basin?

The barents sea magmatic province: Geological-geophysical evidence and new 40 Ar/ 39 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.

The Submeridional Strike Slip Zone in the Structure of the Chukchi Sea Continental Margin and the Mechanism of Opening of the Canada Oceanic Basin

The Chukchi segment of the Eurasian Arctic pas� sive continental margin that commenced forming in response to initiation and opening of the Canada oce� anic basin in the Jurassic–Cretaceous is of importance for reconstructing the initial stage in the geodynamic evolution of the formation of the ocean in the Arctic region. The available paleogeodynamic reconstructions of the Arctic region evolution [4, 7] show that the eastern Arctic margin of Eurasia was characterized by devel� opment of collision–convergence belts with shear and compressive strains subconformable with simulta� neously forming sublatitudinal sedimentary basins of several generations. Moreover, it cannot be ruled out that these processes were accompanied by develop� ment of major fault zones orthogonal to these struc� tures [2, 3, 6, 13, 14] and related deformations deter� mined by differently oriented strains in the lithosphere at the stage of differentiated motion of blocks and microplates that are now involved in the Chukotka– North Alaska continental margin. In this communication, we discuss different geo� logical–geophysical data indicating the existence of one such submeridional transverse strike slip zone in the region under consideration. It extends from the Canada Basin along the eastern escarp of the North� wind Rise and across the shelf continental margin in the Chukchi Sea toward the Bering Strait (Fig. 1). The role of this zone in the geodynamic evolution of the Canada oceanic basin and the adjacent continental margin of the Chukchi Sea is also a subject of this research.

Neotectonics of the Northern Norwegian-Greenland Basin: Specific Features and Evolution of the Knipovich Ridge and Pomorsky Perioceanic Trough

The Earth’s crust beneath the Atlantic Ocean has a heterogeneous tectonic structure. The northern (Arctic and subarctic) region is characterized by a particularly specific structure. The region is located between two demarcation fracture zones. The Spitsbergen fracture zone, which separates the study region from structures of the Polar Basin, is situated in the north. The Charley Gibbs fracture zone (52 ° N) is located in the south. The Reykjanes spreading ridge, which extends from Iceland to the southwest, is obviously a member of the MidAtlantic Ridge system. Iceland and its thick crust separate the Reykjanes Ridge from the Arctic system of Cenozoic spreading ridges (Kolbinsey, Mohns, and Knipovich). All these ridges have nearly similar dimensions but different strikes [2]. The Kolbinsey Ridge represents a gentle NW-oriented arc. The Mohns Ridge separated by the Jan Mayen transverse fault is slightly bent toward the northeast. The northernmost Knipovich Ridge shows a nearly meridional strike. Many researchers have noted that, in contrast to the Mid-Atlantic Ridge, the Knipovich Ridge is not located between continents but shifted toward the Spitsbergen Archipelago. The study region incorporates numerous diverse structures in a relatively small space. They are characterized not only by the oceanic or continental type of the Earth’s crust, but also by the presence of transitional types of crust. The present paper is devoted to the northernmost sector of the Norwegian‐Greenland Basin, which includes the Knipovich Ridge and the Pomorsky perioceanic trough. Special attention is given to neotectonics of the study region. The Norwegian‐Greenland segment is the northernmost and youngest member of the Atlantic‐Arctic geodynamic system characterized by low-spreading processes of the opening of oceanic basins. This segment

Paleogeographic Settings and Tectonic Deformations of the Barents Sea Continental Margin in the Cenozoic

The Barents Sea continental margin (hereafter, Barents margin) differs from other passive margins by the most extensive shelf, the giant thickness of sedimentary rocks in basins and troughs, and its unique tectonic position. The outer, almost rectangular promontory of the Barents margin juts out into its deepwater western and northern framing (Fig. 1), identified as the Norwegian‐Greenland and Eurasia basins, respectively. In this regard, the continental margin is affected by two, mutually perpendicular spreading zones (Knipovich and Gakkel ridges). The evolution of oceanic basins proceeded in the course of continuous tectonic and geodynamic interaction with the framing continental margins. In our case, this was expressed, first of all, in the separation and evolution of the Barents Sea shelf platform as an area of neotectonic transformations during the opening of young oceanic basins. Its structures were transformed against the background of breakup and block-shaped disintegration (destruction and fractalization) of the continental crust. This is indicated by Cenozoic volcanism in the Spitsbergen and Novaya Zemlya segments, development of tectonomorphic trenches (grabens), anomalous geophysical properties of the present-day Earth’s crust (including thermal and seismic activity), and specific deformations of the sedimentary cover. All the aforementioned allow us to make a judgement about the contribution of the Cenozoic ocean formation to the modern tectonics and architecture of the Barents margin. The initial breakup of the joint continental lithosphere located between the Barents margin, on the one hand, and Greenland and Lomonosov protoridge, on the other, most likely occurred in the region of the future divergence of plates during the Late Cretaceous‐ Early Paleocene. This is indicated by marine drilling and seismic profiling data suggesting that geological history of the Barents margin included a very important erosion and denudation phase related to the regional uplift before the rift stage. The amount of the material removed from only the inner shelf during the Cenozoic is estimated at 1.5‐2.0 km [1, 2]. In the peripheral zones adjoining the intercontinental rift systems in the Late Cretaceous‐Early Paleogene, the amount of eroded material increases to 3 km or more. However, up to one-half of the material was eroded by glacial processes.

Role of the tectonomagmatic factor in formation of giant hydrocarbon accumulations in the East Barents basin

In terms of tectonics, the East Barents basin(megabasin) represents an extended (~1400 km)wedgeshaped ~500 to 300kmwide structure thatcrosses the West Arctic continental–marginal platform in the meridional direction and is truncated by asystem of pericratonic depressions of the East European Platform on the beam of the Kola Peninsula.According to geological–geophysical data, the Paleozoic–Mesozoic sedimentary cover of the basin is presumably >20 km thick [11, 13], although its exactthickness is unknown so far. Approximately 14 km ofthe sedimentary section are represented by Upper Permian–Mesozoic terrigenous sediments, 11 km ofwhich correspond to the Upper Permian–Triassicsequence. The underlying Paleozoic complex is composed of terrigenous–carbonate and carbonate facies.In the opinion of many researchers, such a giantsize of the basin and its sedimentary prism implydevelopment of significant hydrocarbon accumulations in the latter. These assumptions are confirmed bythe discovery of five hydrocarbon fields in the southernhalf of the megabasin (Fig. 1); they are representedonly by gas and gas condensate accumulations confined to Mesozoic sedimentary complexes [2–4, 8, 9,12, 13, 15, and others].Two gas fields (large Murmanskoe and mediumSeveroKil’dinskoe) are located in the southwesternperipheral part of the South Barents Basin in its slopeand nearslope zones, where productive formationsare represented by Triassic sediments.Another group of accumulations associate with thesocalled Shtokman–Lunin Sill (Uplift) [2–4], whichseparates the South and North Barents basins. Withrespect to hydrocarbon reserves, the Shtokman andLedovoe gas condensate and Ludlovskoe gas fieldswith Jurassic productive formations are classed withunique and large categories, respectively.For hydrocarbon accumulations of both groups,source formations are considered to be represented byPermian–Triassic sediments; in the last case, theyprobably also include Lower Jurassic sediments withhumic and sapropelic organic matter.With respect to the economic potential and geological prerequisites for further searches for analogs andspecifying the factors responsible for their formation,of particular interest is the second group of hydrocarbon accumulations confined to the elevated boundaryzone between the two basins (Fig. 1). These problemsare considered in several publications [1–4, 9, 15],where factors responsible for the formation of suchgiant hydrocarbon accumulations are characterized bya different degree of substantiation and from differentstandpoints.In this connection the following question arises:what are the peculiar features that determine the geological structure of hydrocarbon fields in the Shtokman–Lunin Uplift?It should primarily be noted that all the local anticlinal trap structures hosting hydrocarbon accumulations are distinctly reflected in Triassic and Cretaceoussediments as well as in the surface topography of Jurassic sequences with an amplitude of approximately100–200 m (seismic reflector B, Fig. 1). They are isometric in plan and from 500 to 1500 km

Late mesozoic volcanism of the east-arctic continental margin of Eurasia (East Siberian Sea) based on seismic data

Analysis of the geology of the islands and interpretation of seismic sections of the western part of the East Siberian Sea shelf revealed two types of basaltic magmatism. The Cretaceous fissure volcanism mostly developed in the Anzhu trough. The south wall of the New Siberian basin contains a cone-shaped paleoedifice, which is evidence of the formation of the central type volcanoes.

New data on basaltoid magmatism of western Spitsbergen

New data on studies of the chemical composition of basaltoids of western Spitsbergen for the purposes of their comparison with the investigated magmatic rocks of the Franz Josef Land Archipelago (FJL) are presented in this study. The aim is to elucidate the features of their geochemical specialization, the distribution area of the Jurassic-Cretaceous magmatism in the Barents Sea region, and its geodynamic nature.

Dikes of Hayes Island (Frantz Josef Land Archipelago): Tectonic position and geodynamic interpretation

The Frantz Josef Land Archipelago is surrounded by a shelf that crowns the block uplift of the basement located in the northern peripheral part of the Barents Sea continental margin. With respect to its morpho structural position, it is bordered by the Frantz Victo ria and Saint Anna troughs in the west and east, respectively. In the north, this uplift is truncated by the slope of the Nansen Basin of the Eurasian oceanic basin (Fig. 1a). By its relatively deep straits, canyons, and fiords directed mostly in the northwestern and northeastern directions, the archipelago is subdivided into individual islands and their groups. Such struc tural patterns provided grounds for a priori imaging a corresponding diagonal system of tectonic fractures and faults frequently of uncertain positions in various sketches and maps. At the same time, the bathymetric and geological maps [7] demonstrate the relatively dis tinct division of the archipelago by the Marcom Strait (with a series of subparallel narrow subordinate straits) and its northwestern continuation between Arthur and Harley islands in two main island groupings: south western and northeastern. The shelf segment of the archipelago located between the latter and Nansen Basin is similarly divided into two parts with a slight deviation of their separating conditional band in the northern direction. This conclusion is also derived from the analysis of the recent map of the anomalous magnetic field. The latter demonstrates that the dom inant linear magnetic anomalies in the archipelago and its surrounding shelf are characterized by a north western strike, while the above mentioned axial zone dividing these structures into two parts is marked by positive linear anomalies against the negative back ground (Fig. 1b). Moreover, the features that would indicate the presence of lineaments in the structure of the anomalous magnetic field determined by NE trend ing faults are poorly recognizable or obscure. Never theless, the available schematic maps of the Frantz Josef Land Archipelago show its three traditional NE oriented lithotectonic zones: Aleksandra, Vil’chek, and Sal’m. The conditional (?) lines that separate these zones are simultaneously considered as representing boundaries of both these lithotectonic zones and structural elements [3, 7]. These NE trend ing boundaries and faults are hypothetically viewed as being inherited from the Baikalian tectonic plan of the basement [3], although their strikes are more likely parallel to the front of the Norwegian Caledonides, as is assumed by some researchers. In our opinion, the tectonic situation under consideration is additionally complicated by the fact that the blocks of its basement are displaced along the listric faults toward the depo center of the North Barents basin, which follows from the distribution and stratigraphic range of deposits constituting the sedimentary cover of the archipelago. The presence of the relatively thick Triassic sedimen tary complex on the archipelago provides grounds for the assumption that this area represented at least the near slope zone of the East Barents megabasin with the corresponding sedimentation regimes and rates or even was its constituent. On the other hand, the absence of Jurassic strata in most of the northwestern archipelago may be explained to certain extent by the influence of fold–thrust processes in the Novaya Zem lya Archipelago at the Triassic–Jurassic transition. At the same time, trap magmatism of Jurassic–Creta ceous age was also registered by the geological–geo physical investigations in the East Barents megatrough [9–11], in addition to the Franz Josef Land Archipel ago [1–3, 5–7, 9–12, 14]. In the megatrough, it is largely reflected in development of sills. In the arch– Dikes of Hayes Island (Frantz Josef Land Archipelago): Tectonic Position and Geodynamic Interpretation

Spatial–temporal trends of Late Mesozoic plume magmatism in the Arctic during formation of the Amerasian Basin

The spatial and temporal characteristics of magmatism caused by the Barents–Amerasian Jurassic–Cretaceous plume in conjunction with the geodynamics of destructive transformations of the lithosphere are presented here. The localities of manifestation of magmatism were concentrated mainly out of general contour of the areal occupied by the Siberian superplume, and they demonstrated certain gravitation to the Caledonide–Ellesmeride belts. This suggests an inherited position of both the J–K plume and the initial detachment zone produced by it: this led to formation of the Canadian Basin. The stages in the evolution and character of polycyclic multiphase plume magmatism are substantiated by the geochronology of magmatic provinces in the Arctic region during formation of the Amerasian Basin.