The Late Permian-Triassic system of rifts of the South Kara sedimentary basin

Based on the new geophysical survey data within the South Kara basin, a system of rift troughs was established. The time of formation of the rifts was the Late Permian-Early Triassic by analogy with that of the West Siberian basin. It is probable that inversion processes took place in the Middle Triassic in rifts, located close to Novaya Zemlya. Morphologically, the rifts are represented mainly by semi-grabens. In plan view, they form closed isometric basins, similar in shape to pull-apart basins, which formed as result of sinistral transtension. The Upper Triassic sediments are widespread throughout the basin, forming the lower part of the post-rift sedimentary cover.     

The Arctida Craton and Neoproterozoic-Mesozoic orogenic belts of the Circum-Polar region

An attempt is made to characterize an assembly of Arctic tectonic units formed before the opening of the Arctic Ocean. This assembly comprises the epi-Grenville Arctida Craton (a fragment of Rodinia) and the marginal parts of the Precambrian Laurentia, Baltica, and Siberian cratons. The cratons are amalgamated by orogenic belts (trails of formerly closed oceans). These are the Late Neoproterozoic belts (Baikalides), Middle Paleozoic belts (Caledonides), Permo-Triassic belts (Hercynides), and Early Cretaceous belts (Late Kimmerides). Arctida encompasses an area from the Svalbard Archipelago in the west to North Alaska in the east. The Svalbard, Barents, Kara, and other cratons are often considered independent Precambrian minicratons, but actually they are constituents of Arctida subsequently broken down into several blocks. The Neoproterozoic orogenic belt extends as a discontinuous tract from the Barents-Ural-Novaya Zemlya region via the Taimyr Peninsula and shelf of the East Siberian Sea to North Alaska as an arcuate framework of Arctida, which separates it from the Baltica and Siberian cratons. The Caledonian orogenic belt consisting of the Scandian and Ellesmerian segments frames Arctida on the opposite side, separating it from the Laurentian Craton. The opposite position of the Baikalian and Caledonian orogenic belts in the Arctida framework makes it possible to judge about the time when the boundaries of this craton formed as a result of its detachment from Rodinia. The Hercynian orogenic belt in the Arctic Region comprises the Novozemel’sky (Novaya Zemlya) and Taimyr segments, which initially were an ending of the Ural Hercynides subsequenly separated by a strike-slip fault. The Mid-Cretaceous (Late Kimmerian) orogenic belt as an offset of Pacific is divergent. It was formed under the effect of the opened Canada Basin and accretion and collision at the Pacific margins. The undertaken typification of pre-Late Mesozoic tectonic units, for the time being debatable in some aspects, allows reconstruction of the oceanic basins that predated the formation of the Arctic Ocean.     

Structure of the North Kara Shelf from results of seismostratigraphic analysis

The sedimentary cover section of the North Kara Shelf had been subdivided based on extensive seismic data, and seismic correlation was carried out. The predominant role of Upper Riphean-Middle Paleozoic rocks has been corroborated. A series of relatively deepwater basins filled with primarily terrigenous fly-schoid rocks up to 7–9 km in thickness existed in the Late Riphean-Vendian at the place of the shelf. In the Cambrian, isolated basins merged into a wide and shallow-water basin as a result of the Baikalian reactivation in southeast Severnaya Zemlya and probably in Taimyr. After the pre-Ordovician hiatus, a vast sedimentation basin with a regressive section was formed on the shelf from Ordovician to Late Devonian. Shallow-water marine and near-shore carbonate and carbonate-terrigenous sequences accumulated in this basin and gave way to continental and less frequent near-shore, marine, variegated, and red beds in the Devonian. The thickness of the Ordovician-Devonian sequence reaches 6 km. Since the Mid-Carboniferous, block emergence and deep erosion of Ordovician-Devonian complexes have occurred in the north Kara shelf as a result of Hercynian events in northern Taimyr, Severnaya Zemlya, and in the southern Kara Sea. No Permian-Triassic rifts existed on the North Kara Shelf. At that time, the shelf was an area of erosion. The thickness of the Middle Carboniferous-Cretaceous sequence was insignificant and gradually increased toward Barents Sea troughs. The newly formed Svyataya Anna and Voronin troughs arose due to opening of the Eurasia Basin of the Arctic Ocean. The terrane concept has been subjected to criticism. The available data show that a large epi-Grenvillian continental block existed, and the North Kara region was part of it. Collision of the northern continent with the Paleosiberian Platform in the Late Paleozoic resulted in the formation of the Hercynian fold arc to the south of the North Kara Shelf, and an inverted orogenic arch arose at the place of shelf basin. The individual geological features that distinguish the North Kara Shelf from the Barents Sea troughs and the South Kara Syneclise are emphasized. The ancient pre-Riphean basement, a system of Late Riphean-Vendian relatively deepwater troughs and basins, Hercynian tectonic inversion, deep erosion of the most uplifted part of the arch, and significant block motions are the distinguishing features of the North Kara Shelf.     

Early Carboniferous paleogeography of the northern Verkhoyansk passive margin as derived from U–Pb dating of detrital zircons: role of erosion products of the Central Asian and Taimyr–Severnaya Zemlya fold belts

The first U–Pb dating of detrital zircons from the Lower Carboniferous sandstones in the frontal part of the northern Verkhoyansk fold-and-thrust belt showed that detrital zircon age spectra for the Lower Visean (Krestyakh Formation) and the Upper Visean–Serpukhovian (Tiksi Formation) rocks are quite different. The Early Visean sandstones contain up to 95% detrital zircons of Precambrian age, while those of Late Visean–Serpukhovian age, only 55%. The shape of age distribution plots of Precambrian zircons for both samples is similar, indicating that reworking of terrigenous sediments of the Krestyakh Formation or the same sources dominated in Early Visean time (crystalline basement of the craton, eroded Meso- and Neoproterozoic sedimentary complexes, and igneous rocks of Central Taimyr) contributed significantly to the accumulation of the Late Visean–Serpukhovian deposits. In the rocks of the Tiksi Formation, 45% of detrital zircons are of Paleozoic age, while 24% are Early Paleozoic, with prevailing Cambrian and Ordovician ages. Possible provenance areas with abundant igneous rocks of this age could be the Taimyr–Severnaya Zemlya and Central Asian fold belts extending along the northern, western or southwestern margins of the Siberia. The presence of Middle–Late Devonian zircons is thought to be related to the erosion of granitoids of the Yenisei Ridge and the Altai–Sayan region. Early Carboniferous detrital zircons probably had a provenance in igneous rocks of the Taimyr–Severnaya Zemlya fold belt, on the assumption that collision between the Kara block and the northern margin of the Siberian continent had already occurred by that time. In Early Visean time, sedimentation occurred in small deltaic fans, likely along steep fault scarps that formed as a result of Middle Paleozoic (Devonian–Carboniferous) rifting. The clastic material came from small rivers that eroded the nearby area. Late Visean–Serpukhovian time was marked by a sharp increase in the amount of clastic material and by the appearance of detrital zircons coming from new provenance regions, such as fold belts extending along the northern and southwestern margins of the Siberian continent. A large river system, which was able to transport clastic material over large distances to deposit it in submarine fans on the northern Verkhoyansk passive continental margin, had already existed by that time.     

Distribution of clay minerals in surface sediments from the eastern Barents and south-western Kara seas

Surface samples from the eastern Barents and south-western Kara seas have been analysed for clay mineralogy. Transport paths, the role of regional sources and local bedrock outcrops and the influence of hydrodynamic and glacigenous processes for clay distribution on the shelves are discussed in relation to central Arctic Ocean deep sea and sea ice sediments. Franz Josef Land and Novaya Zemlya show significantly different clay mineral associations. Although smectite concentrations are fairly high, Franz Josef Land can be excluded as a source for central Arctic sea ice sediments, which are relatively rich in smectite. In the Kara Sea, smectite concentrations in coastal sediments surpass even the Franz Josef Land concentrations. The large cyclonic gyre in the eastern Barents Sea between Novaya Zemlya and Franz Josef Land, which serves as a mixing zone between Arctic and North Atlantic water, is apparently reflected within the smectite distribution pattern. With the exception of Franz Josef Land, the area of investigation is typically low in kaolinite. In particular, coastal areas and areas north of Novaya Zemlya, influenced by the inflow of Arctic waters, show the lowest kaolinite concentrations. A high kaolinite occurrence within the Nansen Basin is most probably related to Franz Josef Land and emphasizes the importance of long-range downslope transport of sediments across the continental slope. The surface water circulation pattern in close interaction with local outcrops onshore Novaya Zemlya and locally restricted occurrences within the eastern Barents Sea significantly alter the illite dispersal pattern. Illite concentrations are lowest around Franz Josef Land. Chlorite is generally low in the area of investigation. Submarine outcrops and important chlorite occurrences onshore Novaya Zemlya bias its distribution pattern.     

The Taimyr fold belt, Arctic Siberia: timing of prefold remagnetisation and regional tectonics

Late Precambrian and Palaeozoic platform sediments from the Central–South Taimyr Peninsula (Arctic Siberia) are all remagnetised. The remagnetisation is prefold and is related to thermal remagnetisation caused by Taimyr Trap magmatism. The remagnetisation age is estimated to 220–230 Ma and, hence, is considerably younger than the ca. 251 Ma age for the main body of Siberian Trap flood basalts. The folding that affected the Taimyr region platform sediments also included the Taimyr “Traps,” hence, relegating Taimyr deformation to post-Mid Triassic time, and most probably, to a Late Triassic age. This shows that whilst thrusting terminated in the Urals during the Permian, crustal shortening continued in Taimyr, Novaya–Zemlya and the South Barents Sea, well into the Mesozoic.     

Estimation of the oil-and-gas potential of sedimentary depressions in the Far East and West Siberia based on gravimetry and geothermy data

The results of geodensity, geothermal, and paleotectonic modeling of some sedimentary depressions in the Far East region and central West Siberia are interpreted from a petroleum-geological standpoint. The prospects of the possibly oil-and-gas-bearing Paleogene and Upper Cretaceous rock complexes in the Lunsk, Makarovsk, and Aniva troughs, West Sakhalin uplift, and Middle Amur intermontane depression are estimated. Petroleum accumulation zones in the preplate complex are forecasted. Localization of Jurassic oil generation centers is defined at a new large oil field in the central West Siberian plate (West Siberian plate). Experience in petroleum geology modeling for structures of different tectonic patterns, lithologies, and rock ages makes it possible to recommend the adopted methodical approach and technology of gravimetric and geothermal interpretation as universal and efficient methods.     

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.     

Reconstruction of provenances and carboniferous tectonic events in the North-East Siberian Craton framework according to U-Pb dating of detrital zircons

The U-Pb dating of detrital zircons from Carboniferous rocks in the northern frontal zone of the Verkhoyansk Fold-and-Thrust Belt (Kharaulakh Anticlinorium) at the boundary with the Siberian Platform is carried out for the first time. The age distribution of detrital zircons from the four dated samples has much in common, indicating that the same sources of clastic material were predominant. All of the samples are dominated by Precambrian zircons; the majority of them are Paleo- and Neoproterozoic grains. Early Ordovician and Late Devonian-Early Carboniferous detrital zircons are also numerous. The igneous rocks of the Taimyr-Severnaya Zemlya and/or Central Asian foldbelts extending along the northern, western, and southwestern margins of the Siberian continent probably were the main source areas of the studied sedimentary successions. The clastic material was transferred at a great distance by large river systems similar to the present-day Mississippi River and deposited in submarine fans at the passive margin of the Siberian continent. The occurrence of the detrital zircons whose age is synchronous to the time of sedimentation of the Carboniferous successions in the northern Verkhoyansk region (320–340 Ma) allows us to suggest that they were derived from the Taimyr-Severnaya Zemlya Foldbelt and that collision of the Kara Block with the Siberian continent began in the Early Carboniferous. The performed study shows the dating of detrital zircons is very helpful for the paleogeographic and tectonic reconstructions.     

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.     

Geology of the Severnaya Zemlya Archipelago and the North Kara Terrane in the Russian high Arctic

The Severnaya Zemlya Archipelago is located at 80°N near the continental shelf break, between the Kara and Laptev seas. Sedimentary successions of Neoproterozoic and Palaeozoic age dominate the bedrock geology. Together with Northern Tajmyr, Severnaya Zemlya constitutes the main land areas of the North Kara Terrane (NKT), which is inferred here to have been a part of the Timanide margin of Baltica, i.e. an integral part of Baltica at least since the Vendian. Vendian turbidites derived from the Timanide Orogen are inferred to have been deposited on Neoproterozoic greenschist facies, granite-intruded basement. Shallow-water siliclastic deposition in the Early to Mid-Cambrian was followed by highly organic-rich shales in the Late Cambrian and influx of more turbidites. An episode of folding, the Kan’on River deformation, separates these formations from the overlying Tremadocian conglomerates and sandstones. In the Early Ordovician, rift-related magmatic rocks accompanied the deposition of variegated marls, sandstones, carbonates and evaporites. Dark shales and gypsiferous limestones characterise the Mid-Ordovician. Late Ordovician quartz-sandstones mark a hiatus, followed by carbonate rocks that extend up into and through most of the Silurian. The latter give way upwards into Old Red Sandstones, which are inferred to have been deposited in a Caledonian foreland basin. Deformation, reaching the area in the latest Devonian or earliest Carboniferous and referred to as the Severnaya Zemlya episode, is thought to be Caledonian-related. The dominating E-vergent structure was controlled by décollement zones in Ordovician evaporite-bearing strata; detachment folds and thrusts developed in the west and were apparently impeded by a barrier of Ordovician igneous rocks in the east. Below the décollement zones, the Neoproterozoic to Early Ordovician succession was deformed into open to close folds. The exposed strata in the lower structural level have been juxtaposed with those in the upper structural level along the major N-trending Fiordovoe Lake Fault Zone, which involved several kilometres of dextral strike-slip movement and downthrow to the west. A major Early Carboniferous unconformity separates the folded Mid-Palaeozoic and older rocks from overlying Carboniferous formations, as on Franz Joseph Land and Svalbard. Subsequent latest Palaeozoic to Early Mesozoic orogeny, as on Taimyr, apparently had little influence on the Severnaya Zemlya successions.     

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.     

Deep structure of the South Kara sedimentary basin

The structure and evolution of the passive continental margins of the Arctic Ocean are considered on the example of the South Kara Basin. Its development is associated with the evolution of the West Siberian Plate and the formation of the Arctic Ocean. Until the Late Cretaceous, the South Kara Basin was the north margin of the West Siberian Plate, whose formation is related to the Permian–Triassic processes of riftogenesis accompanied by the eruptions of traps. In the Mesozoic, due to the opening of the Arctic Ocean, the South Kara basin became a part of the continental margin, where the accumulation of marine sandy–clayey rocks continued.     

Alkaline rocks of Meso-Cenozoic volcanosedimentary complex of the West Siberian Plate: petrologic composition

This paper is concerned with study of tephriphonolites, rare rocks that have been first found in the pre-Jurassic basement of West Siberia. Based on geological observations of the bedding of different types of volcanics and their geochemical peculiarities, the conclusion about the synchronous occurrence of subalkaline and alkaline volcanism is drawn. This is confirmed by the coexistence of compositionally contrasting volcanics in the borehole section. The hypothesis is put forward that these rocks alternate in the section, as is the case in the Tunguska syneclise of the Siberian Platform. The new data on Sr and Nd isotopy suggest the participation of crustal material in the formation of alkaline rocks. The rift nature of the regional intraplate volcanism is confirmed.     

New U–Pb isotopic data for detrital zircons from metasedimentary sequences of northwestern Taimyr

This work presents the U–Pb (LA–ICP–MS) data of detrital zircons from metasedimentary sequences of northwestern Taimyr. An analysis of the youngest populations of detrital zircons testifies to the wide distribution of Cambrian sequences in the study area, but not Precambrian sequences as was considered earlier, and the need for a substantial revision of the stratigraphic scheme of this area. The detrital zircon age distribution shows that the Timan margin of the Baltic paleocontinent was a major provenance area of the Cambrian sediments in northern and northwestern Taimyr, as well as the coeval sediments of the Severnaya Zemlya archipelago.     

Recognition of the Cambrian Timan–Severnaya Zemlya orogen and timing of geological evolution of the North Kara sedimentary basin based on detrital zircon dating

New data on the ages of detrital zircons from folded basement rocks and cover sediments of the Severnaya Zemlya archipelago and Izvestiy TSIK islands have been obtained. The basement age is defined as Cambrian (pre-Ordovician). The Ordovician and Silurian sandstones were mainly formed by erosion of the basement rocks. The Devonian sandstones were formed by debris sourced from the Caledonian orogen. The Carboniferous–Early Permian molasse was formed simultaneously with the erosion of the Carboniferous granitoids and weathering of the Ordovician volcanic arc rocks and the Cambrian basement. The North Kara basin was formed in the Ordovician as a back-arc basin. It experienced its main compression deformations at the boundary of the Devonian and Carboniferous and in the Carboniferous.     

Glaciotectonised Quaternary sediments at Cape Shpindler,Yugorski Peninsula,Arctic Russia: implications for glacial history,ice movements and Kara Sea Ice Sheet configuration

The coastal cliffs of Cape Shpindler, Yugorski Peninsula, Arctic Russia, occupy a key position for recording overriding ice sheets during past glaciations in the Kara Sea area, either from the Kara Sea shelf or the uplands of Yugorski Peninsula/Polar Urals. This study on Late Quaternary glacial stratigraphy and glaciotectonic structures of the Cape Shpindler coastal cliffs records two glacier advances and two ice‐free periods older than the Holocene. During interglacial conditions, a sequence of marine to fluvial sediments was deposited. This was followed by a glacial event when ice moved southwards from an ice‐divide over Novaya Zemlya and overrode and disturbed the interglacial sediments. After a second period of fluvial deposition, under interstadial or interglacial conditions, the area was again subject to glacial overriding, with the ice moving northwards from an inland ice divide. The age‐control suggests that the older glacial event could possibly belong to marine oxygen isotope stage (MOIS) 8, Drenthe (300–250 ka), and that the underlying interglacial sediments might be Holsteinian (>300 ka). One implication of this is that relict glacier ice, buried in sediments and incorporated into the permafrost, may survive several interglacial and interstadial events. The younger glacial event recognised in the Cape Shpindler sequence is interpreted to be of Early‐to‐Middle Weichselian age. It is suggested to correlate to a regional glaciation around 90 or 60 ka. The Cape Shpindler record suggests more complex glacial dynamics during that glaciation than can be explained by a concentric ice sheet located in the Kara Sea, as suggested by recent geological and model studies. Copyright © 2003 John Wiley & Sons, Ltd.     

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.     

The First Heat Flow Measurements on the Novaya Zemlya Archipelago

This paper reports the heat flow calculations that were made on the basis of the temperature measurements in the boreholes at the Pavlovskoye deposit (Novaya Zemlya), the definition of the thermal conductivity of the rocks sampled from the boreholes, and the estimation of the radiogenic thermal generation in the drilling interval. This gives the first heat flow measurements in the archipelago. The structure of the heat flow in the Novaya Zemlya archipelago is compared with other fold belts of northern Asia.

     

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.