Northern Taimyr Research Articles

Tectonothermal model and magmatism evolution of the postcollisional (pre-plume) development stage of the Kara orogen (Northern Taimyr, Central Arctic)

Tectonothermal model and magmatism evolution of the postcollisional (pre-plume) development stage of the Kara orogen (Northern Taimyr, Central Arctic)

Food web interactions of two breeding Arctic shorebird species, little stint Calidris minuta and red knot Calidris canutus, are shaped by their elevational distribution

Birds often have to choose their nest site location along a food safety axis, balancing nest predation danger with the food requirements of themselves and their offspring. This is probably most important for precocial species, such as most shorebirds, in which both chicks and parents need access to food resources in the surroundings of the nest, at least during the first days of life of the chicks. In many Arctic ecosystems, shorebird nests are typically prone to predation by both avian and terrestrial predators, especially in lemming-poor years. Among other factors, the strength of the trophic interactions between shorebirds, their prey, and their predators depend on how all of these are distributed across space. During two breeding seasons in northern Taimyr, North-Central Russia, we investigated how the spatial distribution of red knot Calidris canutus and little stint Calidris minuta nests and broods overlaps with the local food landscape and also with the distribution of avian predators and their main prey, lemmings. We found that the two shorebird species use different habitats that vary in arthropod community structure in accordance with the birds’ diet: while little stints selected lower elevations where chironomid midges Chironomidae are more abundant, red knots selected higher elevations where crane flies Tipulidae are more abundant. Furthermore, little stints share low-elevation habitats with lemmings and predators, while red knots inhabit higher elevations averted by both lemmings and avian predators. We found higher nest predation for little stint nests than for red knots nests, especially in a low-lemming year. Our results thus support the idea that food web interactions are driven by landscape and community aspects.

Tectonothermal Model and Magmatism Evolution of the Postcollisional (pre-Plume) Stage of the Kara Orogen (Northern Taimyr, Central Arctic)

Tectonothermal Model and Magmatism Evolution of the Postcollisional (pre-Plume) Stage of the Kara Orogen (Northern Taimyr, Central Arctic)

Tectonothermal Model for the Late Paleozoic Syncollisional Formation Stage of the Kara Orogen (Northern Taimyr, Central Arctic)

AbstractWe present a tectonothermal model for the late Paleozoic syncollisional formation stage of the Kara orogen in northern Taimyr in the Central Arctic. The model is based on new and published structural, petrological, geochemical, and geochronological data, as well as thermophysical properties obtained for the Kara orogen. The latter hosts a significant volume of granites formed as a result of the collision between the Kara microcontinent and the Siberian craton. Based on geological, geochemical, and U–Th–Pb isotope data, the granites were differentiated into syncollisional and postcollisional intrusions that were emplaced in the intervals 315–282 and 264–248 Ma, respectively. The presented tectonothermal model covers only the syncollisional formation stage of the Kara orogen, during which anatectic granites formed. The 2D models help to reconstruct the main tectonothermal processes of the syncollisional stage of formation of this structure, taking into account the local peculiarities of the thermal state of the Earth’s crust in the region. The model shows the mechanisms of increase in the lower crust temperature necessary for the formation of syncollisional anatectic granites. The estimates obtained from the model constrain the time interval between collision/tectonic stacking and the granite formation. The modeling also showed the general regularities typical for orogens on syncollisional stages.

Late Palaeozoic magmatism of Northern Taimyr: new insights into the tectonic evolution of the Russian High Arctic

ABSTRACT We report new results of a comprehensive study into Carboniferous – Early Permian granite magmatism of the northern Taimyr Peninsula, Russia (southern part of the Kara Terrane). U-Pb zircon ages (SHRIMP and LA–ICP–MS) represent the crystallization ages of these intrusions and range from ca. 344.5 to 288.4 Ma, defining the onset of granite magmatism during the Early Carboniferous (Visean; ca. 344 Ma) and its termination in the Early Permian (Artinskian; ca. 288 Ma). Ar-Ar dating of micas and amphiboles indicates that Late Palaeozoic tectonic activity in northern Taimyr ceased during the Middle Permian (Roadian; ca. 272 Ma). Rb/Sr and Sm/Nd isotopic data from the same intrusions, show initial (87Sr/86Sr)i ratios of between 0.70288 and 0.71027, with εNd(t) values range between −3.3 and +3.1. The combined geochemical and isotopic compositions of the granites describe an affinity to peraluminous I-type granites, probably formed in an Andean-type active continental margin setting. Our new geochemical, isotopic, and geochronological data indicate the existence of a long-lived (ca. 56 Myr) Andean-type active continental margin along the southern edge of the Kara Terrane during the Late Palaeozoic. Furthermore, our study reveals a causal relationship between Late Palaeozoic magmatism across northern Taimyr and closure of the Uralian Ocean.

Ordovician turbidites and black shales of Bennett Island (De Long Islands, Russian Arctic), and their significance for Arctic correlations and palaeogeography

AbstractBennett Island stands alone in a remote part of the Arctic and information on its geology is essential to ascertain relations with other terranes in order to restore the early Palaeozoic Arctic palaeogeography. Lower Palaeozoic sedimentary rocks throughout the island were studied thoroughly for the first time. The Ordovician section (> 1.1 km thick) comprises three units: Tremadocian, lowest Floian black shale (130–140 m); Floian, lower Dapingian carbonate turbidite (> 250 m); and Dapingian, lower Darriwilian siliciclastic turbidite (> 730 m). Ordovician deposits conformably overlie Cambrian rocks deposited within the Siberian shelf, as shown earlier. Most of the Ordovician succession was formed in a deep trough that received carbonate debris from a nearby carbonate platform and silicate material from a distant landmass located to the NE (present coordinates). The Bennett Island Ordovician rocks have much in common with those of both the Central and Northern Taimyr belts. It could be tentatively suggested that both belts merged at their eastern continuation in the vicinity of De Long Islands. The whole system probably extends further eastwards. The Ordovician facies patterns and faunal assemblages in the New Siberian Islands are notably similar to those of northwestern Alaska, where the same lateral transition from turbidites to shelf limestones was reported.

U–Pb Age and Hf Isotope Geochemistry of Detrital Zircons from Cambrian Sandstones of the Severnaya Zemlya Archipelago and Northern Taimyr (Russian High Arctic)

U–Pb and Lu–Hf isotope analyses of detrital zircons collected from metasedimentary rocks from the southern part of Kara Terrane (northern Taimyr and Severnaya Zemlya archipelago) provide vital information about the paleogeographic and tectonic evolution of the Russian High Arctic. The detrital zircon signatures of the seven dated samples are very similar, suggesting a common provenance for the clastic detritus. The majority of the dated grains belong to the late Neoproterozoic to Cambrian ages, which suggests the maximum depositional age of the enclosing sedimentary units to be Cambrian. The εHf(t) values indicate that juvenile magma mixed with evolved continental crust and the zircons crystallized within a continental magmatic arc setting. Our data strongly suggest that the main provenance for the studied clastics was located within the Timanian Orogen. A review of the available detrital zircon ages from late Neoproterozoic to Cambrian strata across the wider Arctic strongly suggests that Kara Terrane, Novaya Zemlya, Seward Peninsula (Arctic Alaska), Alexander Terrane, De Long Islands, and Scandinavian Caledonides all formed a single tectonic domain during the Cambrian age, with clastics predominantly sourced from the Timanian Orogen.

The Key Section for the Upper Palaeozoic of the New Siberian Islands (Tas-Ary Peninsula, Kotel’ny Island)

The information on the Late Palaeozoic deposits of the New Siberian Islands is essential to clarify the palaeogeography of the surrounding Arctic Region and to quest the original location of the New Siberian continental block prior to the Amerasian ocean opening. The best Upper Palaeozoic section of the islands, located in the western part of the Kotel’ny Island (Tas-Ary Peninsula), was examined in detail. The studied rocks characterize a transitional facial zone between the northeastern shallow-water (central areas of the Kotel’ny Island) and the southwestern deep-water ones (Bel’kov Island). The stratigraphy of the Carboniferous and partly Permian strata was specified by the study of four fauna groups, detrital zircon dating, and structure interpretation. The section demonstrates a gradual change of depositional environments from shallow-marine in the Lower Carboniferous to deep-water in the middle Carboniferous and Permian. The Tournaisian and Visean rocks (Tas-Ary Formation, not less than 950 m) were formed on the open shelf or ramp with predominant carbonate sedimentation. They were deposited above the storm-wave base during the early Tournaisian and at greater depth later. The Serpukhovian–Middle (?) Permian rocks (Bel’kov Formation, not less than 300 m) were accumulated on the deep-water subaqueous slope and, possibly, at its base. Black shales and turbidite sandstones compose a significant part of the Bel’kov Formation. Sandstones have a siliciclastic–carbonate composition in the upper Lower Carboniferous and are carbonate-free up the section. The boundary between Tas-Ary and Bel’kov formations corresponds to a change in the shelf-to-basin profile and depositional style. At this time (the beginning of the Serpukhovian), the subsidence rate increased, a pronounced slope was formed, and a new source of clastics appeared on land. This reorganization was probably related to the Northern Taimyr orogen rise. The lithological similarity of the Lower Carboniferous deposits of the Tas-Ary Peninsula and Southern Taimyr, the synchronous shift in sedimentation from carbonate to terrigenous rocks, and the same source of clastic material for the Upper Carboniferous–Permian sandstones in both regions indicate their belonging to the same sedimentary basin in the Late Palaeozoic. We believe that the western part of the New Siberian Islands represented a continental margin in Late Devonian, Carboniferous and Permian times, and that it was a continuation of the Verkhoyansk margin. The latter is possible, taking into account rotation of the New Siberian Islands block according to the two-pole rotational model of the Amerasian basin opening.

Identifying multidisciplinary research gaps across Arctic terrestrial gradients

Global warming is driving environmental change in the Arctic. However, our current understanding of this change varies strongly among different environmental disciplines and is limited by the number and distribution of field sampling locations. Here, we use a quantitative framework based on multivariate statistical modeling to present the current state of sampling across environmental disciplines in the Arctic. We utilize an existing database of georeferenced Arctic field studies to investigate how sampling locations and citations of disciplines are distributed across Arctic topographical, soil and vegetation conditions, and highlight critical regions for potential new research areas in different disciplines. Continuous permafrost landscapes, and the northernmost Arctic bioclimatic zones are studied and cited the least in relation to their extent in many disciplines. We show that the clusters of sampling locations and citations are not uniform across disciplines. Sampling locations in Botany and Biogeochemistry cover environmental gradients the best, and Microbiology, Meteorology, Geosciences And Geographic Information Systems/remote Sensing/Modeling have the worst coverage. We conclude that across all disciplines, more research is needed particularly in the Canadian Arctic Archipelago, northern Greenland, central and eastern Siberia, and in some disciplines, in Canadian mainland, central Alaska, western Siberia and northern Taimyr region. We provide detailed maps of potential new sampling locations for each environmental discipline that consider multiple variables simultaneously. These results will help prioritize future research efforts, thus increasing our knowledge about the Arctic environmental change.

Carboniferous Granitoid Magmatism of Northern Taimyr: Results of Isotopic-Geochemical Study and Geodynamic Interpretation

Data on the petrography, geochemistry, and isotopic geochronology of granites from the northern part of the Taimyr Peninsula are considered. The Early–Middle Carboniferous age of these rocks has been established (U–Pb, SIMS). Judging by the results of 40Ar/39Ar dating, the rocks underwent metamorphism in the Middle Permian. In geochemical and isotopic composition, the granitic rocks have much in common with evolved I-type granites. This makes it possible to specify a suprasubduction marginal continental formation setting. The existence of an active Carboniferous margin along the southern edge of the Kara Block (in presentday coordinates) corroborates the close relationship of the studied region with the continent of Baltia.

Late Paleozoic – Mesozoic tectonic evolution of the Eastern Taimyr-Severnaya Zemlya Fold and Thrust Belt and adjoining Yenisey-Khatanga Depression

Combined structural, thermochronological and geochronological studies were carried out to unravel the complex late Paleozoic – Mesozoic tectonic evolution of the eastern Taimyr – Severnaya Zemlya Fold and Thrust Belt, along with the adjoining Yenisey-Khatanga Depression and Olenek Fold Zone. New detailed field mapping, a fault and fold geometry and kinematic study, and paleostress reconstruction were undertaken for key areas within the Central and Southern Taimyr domains and the Olenek Fold Zone. Thirty seven samples were used for apatite fission track (AFT) analysis along with two samples for U-Pb zircon granite dating, and three samples for Ar-Ar metamorphic muscovite dating.The late Paleozoic (Early Carboniferous – Permian) tectonic event is recognized only in a relatively narrow zone including the Northern Taimyr Domain and part of the Central Taimyr Domain. It started in the Early Carboniferous (Visean) and is synchronous with the earliest stages of collision in the Uralian Orogen. Our results reveal a widespread distribution of latest Triassic – earliest Jurassic and Cretaceous deformations. The latest Triassic – earliest Jurassic tectonic event significantly overprinted the Northern and Central Taimyr domains and original unaltered late Paleozoic AFT ages are identified only locally. New completely reset AFT cooling ages group at 195-180 Ma, in reasonable agreement with structural data. Older Neoproterozoic and late Paleozoic Ar-Ar ages of metamorphic muscovite are retained, demonstrating that the dated rocks were not heated above 300 °C. An Early Cretaceous tectonic event is inferred from both the structural study and ca. 115–125 Ma AFT cooling ages, and is most widespread in the Southern Taimyr Domain, Olenek Fold Zone and adjoining parts of the Yenisey-Khatanga Depression, modifying older geological structures. A younger Late Cretaceous tectonic event at ca. 100-60 Ma is also inferred from AFT cooling ages, but its distribution is poorly constrained.Our study reveals that the distribution of late Mesozoic tectonic events has been significantly underestimated in previous structural studies of the region. The latest Triassic – earliest Jurassic and Cretaceous tectonic events are easily correlated with those in the Pai-Khoi – Novaya Zemlya and northern Verkhoyansk fold and thrust belts.

Reconstruction of tectonic events on the northern Eurasia margin of the Arctic, from U-Pb detrital zircon provenance investigations of late Paleozoic to Mesozoic sandstones in southern Taimyr Peninsula

The Taimyr fold-and-thrust belt records late Paleozoic compression, presumably related to Uralian orogenesis, overprinted by Mesozoic dextral strike-slip faulting. U-Pb detrital zircon analyses of 38 sandstones from southern Taimyr were conducted using laser ablation–inductively coupled plasma–mass spectrometry to investigate late Paleozoic to Mesozoic sediment provenance and the tectonic evolution of Taimyr within a regional framework. The Pennsylvanian to Permian sandstones contain detrital zircon populations of 370–260 Ma, which are consistent with derivation from the late Paleozoic Uralian orogen in northern Taimyr and/or the polar Urals. Late Neoproterozoic through Silurian ages (688–420 Ma), most consistent with derivation from Timanian and Caledonian age sources, suggest an ultimate Baltica source. Southern Taimyr represents the proforeland basin of the bivergent Uralian orogen in the late Paleozoic. Triassic sedimentary rocks contain detrital zircon populations of Carboniferous–Permian (355–260 Ma), late Neoproterozoic to Early Devonian (650–410 Ma), and minor Neoproterozoic (1000–700 Ma) ages, which suggest a similar provenance as the Carboniferous to Permian strata. The addition of a Permian–Triassic (260–220 Ma) zircon population indicates derivation of detritus from Siberian Trap–related magmatism. Jurassic samples have a dominant age peak at 255 Ma and a distinct reduction in Carboniferous–Permian and late Neoproterozoic to Early Devonian input, suggesting that erosion and contributions from Uralian sources ceased while greater input from Siberian Trap–related rocks of Taimyr dominated. Comparison of these results to the published literature demonstrates that detritus from the Uralian orogen was deposited in Taimyr, Novaya Zemlya, and the New Siberian Islands in the Permian, but not in the Lisburne Hills or Wrangel Island. In the Triassic, Taimyr, Chukotka, Wrangel Island, the Kular Dome in the northern Verkhoyansk of Siberia, Lisburne Hills, Franz Josef Land, and Svalbard shared sources from Taimyr, the Siberian Traps, and the polar Urals, indicating that there were no geographic barriers among these locations prior to opening of the Amerasia Basin. Detritus from the Uralian orogen in Taimyr was shed northward into the retroforeland basin and was then transported farther 20–30 m.y. after Uralian orogenesis. The widespread distribution of material eroded from Taimyr and the polar Urals during the Triassic is likely due to the arrival of, and sublithospheric spreading associated with, the Siberian mantle plume head at ca. 250 Ma. The subsequent motion of the lithosphere relative to the plume-swell likely caused a northwestward migration of the uplifted regions. Taimyr and the polar Urals were probably affected. In the Jurassic, detrital zircon spectra from Taimyr, Chukotka, the Kular Dome, and Svalbard show great differences, suggesting that these locations no longer shared the same provenance from Taimyr and the Urals. The restricted distribution of detritus from Taimyr and the Urals indicates that erosion of the Uralian orogen was reduced. In the Late Jurassic, the depositional setting of southern Taimyr probably changed from a foreland to an intracratonic basin.

Seismogeological analysis of the pre-Jurassic sediment complexes of the South Kara syneclise in connection with the tectonic zoning of the sedimentary cover

We present new data on the structure of deep horizons of the sedimentary cover of the South Kara syneclise, based on an integrated interpretation of data from modern seismic prospecting and data on the geologic structure of the adjacent folded areas. A network of seismic base profiles reprocessed with up-to-date programs is used to determine the structure of the wave fields of the pre-Jurassic sediments of the South Kara syneclise. The interpretation of the wave fields with the use of the network of seismic base profiles shows that the wave fields of the Pai-Khoi-Novaya Zemlya monoclise and the Novaya Zemlya-Taimyr terrace are fundamentally different from those of the South Kara central area of depressions and uplifts. We substantiate a new structural and tectonic zonation of the northern West Siberian Plate, with areas of Hercynian and Early Cimmerian consolidation. The geologic evolution of the South Kara syneclise and adjacent areas in the Late Paleozoic-Early Jurassic is considered. The studies show that the Hercynides of the northern Taimyr Peninsula occupy the deepest central part of the South Kara syneclise, including the North Siberian step. They are separated from the coeval sediments of the surface part of the northern West Siberian Plate by the Early Cimmerian folded area of the Yamal-Pai-Khoi saddle, which joins the Early Cimmerian West Taimyr folded area to the Early Cimmerides of Pai-Khoi and Novaya Zemlya.The Permo-Triassic rifts distinguished in central West Siberia have no shelf extension. Areal structural studies along the surface of the acoustic basement and analysis of wave fields showed that the structures of the South Kara syneclise were semiconcentric and concentric intermontane depressions and troughs in the Permian and Lower-Middle Triassic. They formed at the orogenic stage of evolution of the Hercynides. In the Devonian-Carboniferous, the South Kara syneclise was an intracontinental block structure. It is presumed that elevated blocks consist of carbonate sediments, whereas the separating troughs consist of bathyal terrigenous sediments. The Hercynian folding, which affected mainly deep-water sediment complexes, was followed by an inversion of the troughs, their uplifting and disintegration. The intermontane depressions which formed instead of carbonate shelf in the Permian were filled with sediments from the uplifts which formed instead of the troughs.A well-grounded conclusion is made about the hydrocarbon potential of the pre-Jurassic basement of the South Kara syneclise. The layered seismic record of the pre-Jurassic sediments suggests their heterogeneous composition, i.e., the presence of sand and clay series (reservoirs and caps). The pools might be of the arch-bedded and lithologic (traps which formed in the case of the toplap of beds onto the eroded surface) types or be localized along the line of pinching-out of the Triassic sediments. The largest number of Paleozoic structures is concentrated on the Rogozinskii and Vilkitsky arches, in the Monskaya and Matusevich saddles, and in the northern Rusanov-Skuratov arch.© 2014, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

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.

Crustal affinities in the Arctic Uralides, northern Russia: significance of detrital zircon ages from Neoproterozoic and Palaeozoic sediments in Novaya Zemlya and Taimyr

Abstract: U–Pb ion microprobe detrital zircon provenance investigations of pre-Mesozoic sediment samples from southern Novaya Zemlya and northern Taimyr, Arctic Russia, provide new constraints on the tectonic evolution of northern Eurasia. Sediments from both areas previously assigned a Neoproterozoic age are shown to be Palaeozoic (≤500 Ma), changing our understanding of the timing of tectonic events and their regional correlation. Samples from Novaya Zemlya provide an a priori Baltica signature, and dominant cumulative probability age peaks between 610 and 530 Ma are consistent with derivation from Timanide sources. Samples from northern Taimyr also contain the unique Timanian ’fingerprint' and are also inferred to be derived from the continental slope of northeastern Baltica, implying that the North Kara block was a part of Baltica in the early Palaeozoic. These data constrain the timing of deformation, metamorphism and development of an unconformity in southern Novaya Zemlya to a restricted period no earlier than late Cambrian–early Ordovician and at least 50 Ma after the peak Timanian event. The unconformity on Novaya Zemlya can be correlated in style and timing with an unconformity on Severnaya Zemlya and may record post-Timanian extensional collapse and onset of spreading in the Uralian Ocean. Supplementary material: U–Th–Pb ion-microprobe analytical results are available at http://www.geolsoc.org.uk/SUP18340 .

The Timanide, Caledonide and Uralide orogens in the Eurasian high Arctic, and relationships to the palaeo-continents Laurentia, Baltica and Siberia

abstract Recent studies of structure, stratigraphy and isotope geochronology on Svalbard and East Greenland have provided a foundation for reconstructing the Laurentian margin of the Arctic segment of the North Atlantic Caledonides. The axial zone of the high Arctic, Barentsian Caledonides has been inferred to trend northwards through the Barents Shelf to the northern edge of the Eurasian margin between Kvitøya (easternmost Svalbard) and western Franz Josef Land, based on analysis of drill-cores that sampled the pre-Carboniferous basement beneath Alexandra Island. The deformation front of the Barentsian Caledonides has been inferred to trend northeastwards between Franz Josef Land and Novaya Zemlya. The North Kara Terrane, reaching from Severnaya Zemlya (SZ) and northernmost Taimyr in the east to northern Novaya Zemlya in the west, comprises the northernmost foreland to the Barentsian orogen. Four lines of independent evidence are presented here demonstrating that the North Kara Terrane is a direct northerly continuation of the Timanide domain, the latter composing the Neoproterozoic accreted margin of Baltica in the Timan-Pechora-Urals region. These lines of evidence, all from October Revolution Island (SZ), include: (1) a westerly source for Old Red Sandstones successions, with 'Caledonian' fish fauna and detrital muscovites yielding Ar/Ar ages of c. 450 Ma; (2) Ordovician igneous rocks containing c. 550 Ma xenocrysts; (3) Cambrian turbidites with c. 545 Ma detrital muscovites; (4) Cambro-Silurian fauna with many species shared with Baltica. In addition, the Neoproterozoic turbidites of northern Taimyr have been previously reported to contain c. 560 Ma zircon populations, a signature that has been recently found in similar lithologies from Bol'shevik Island (SZ). All these late Vendian ages are characteristic of the Timanide Orogen of the Timan-Pechora-Novaya Zemlya region and, together, indicate that the North Kara Terrane was not an independent 'plate' or 'microcontinent' in the Palaeozoic, as previously proposed, but an essential part of southernmost (Ordovician coordinates) Baltica. Comparability of the evolution of the Timanian margin of the North Kara Terrane with the contemporaneous Baikalian evolution of adjacent Taimyr, together with the lack of evidence of Palaeozoic oceanic rocks and Uralian collisional, high-pressure metamorphic assemblages in Taimyr, suggests that the palaeocontinents Siberia and Baltica were never separated by a major ocean in the high Arctic.

Osmium isotope constraints on contrasting sources and prolonged melting in the Proterozoic upper mantle: evidence from ophiolitic Ru–Os sulfides and Ru–Os–Ir alloys

This study presents the first extensive data set of Os isotopic compositions of primary Ru–Os–Ir alloys and Ru–Os sulfides derived from two Neoproterozoic ophiolite-type ultramafic massifs (Kunar in Northern Taimyr, Russia, and Kraubath in Eastern Alps, Austria). The study employed a multi-technique approach and utilized a number of analytical techniques, including hydroseparation, electron microprobe analysis, negative thermal ionization mass-spectrometry (N-TIMS) and laser ablation attached to multiple collector-inductively coupled plasma-mass spectrometry (LA MC-ICP-MS). The results identify two different Os isotope sources (subchondritic and suprachondritic) for bedrock Ru–Os sulfides at Kraubath, whereas detrital Ru–Os–Ir alloys at Kunar are characterized by ‘unradiogenic’ 187Os/ 188Os values, indicative of a chondritic or subchondritic mantle source of platinum-group elements (PGE). The ‘unradiogenic’ 187Os/ 188Os values yield a very wide range of 187Os/ 188Os (0.1094±0.0003 to 0.1241±0.0004, n=19, N-TIMS data), which is almost identical to the Os isotope composition of bedrock laurite, (Ru,Os)S 2, in podiform chromitite within an ophiolitic mantle section at Kraubath (0.11249±0.00062 to 0.12437±0.00051, n=17, N-TIMS and LA MC-ICP-MS data). These results are consistent with a model in which a prolonged history of melting events of parent ultramafic source rocks took place in the oceanic upper mantle. In contrast, erlichmanite and laurite from banded chromitite within the transition zone at Kraubath show high 187Os/ 188Os (0.13080 to 0.13212) values, indicative of a suprachondritic source of PGE. This signature might be interpreted as either evidence of an enriched mantle source or an indication of a ‘radiogenic’ crustal component, which was introduced during a subduction-related event. The Os isotope results obtained support the conclusion that the Re–Os system, represented by PGM, has remained unchanged from the time of formation of the PGM until now, despite later thermal events, which occurred in the vicinity of ophiolite-type complexes.

Cost of Incubation in a Greater White-Fronted Goose

-In northern Taimyr, Russia, nest attendance and changes in body-mass during incubation of a Greater White-fronted Goose (Anser albifrons albifrons) were studied with the help of a balance under the nest. All the energy required during incubation was derived from catabolism of endogenous stores since the female did not feed during this period. Body-mass loss was 25.4 g per day. The cost during incubation at an average air temperature of 9 OC was estimated to be 610 kJ per day which is only slightly more than Basal Metabolism Rate (BMR, predicted on the basis of an interspecific allometric equation). Cost of thermoregulation during incubation was estimated at 2.1 g body stores per day per oC; this is equivalent to an overall thermal conductance value of 0.59 W oC-. Received 14 February 1999, accepted 22 March 1999.

Body mass changes in waders (Charadrii) in a high arctic area at northern Taimyr, Siberia

Body mass data were collected for 5 species of tundra waders during 6 breeding seasons to study variation in nutrient reserves relative to high arctic climatic conditions and the stage of reproduction. Structural size was accounted for by the 1st Principal Component of external linear measurements: wing length, bill length and tarsus length. SandpipersCalidris spp. were on average lighter in phenologically late seasons, while mass of Turnstones (Arenaria interpres) was similar in all years. Mass of waders was lower during brood-rearing than during incubation. Body mass during pre-nesting was most variable between years, reflecting the unpredictable weather conditions in this period. Monogamous species (KnotsCalidris canutus and Turnstones) began to breed earlier, and were on average, as heavy during the pre-nesting period as during incubation. In contrast, species with a proven or suspected rapid double-clutch breeding system (Little StintsC. minuta and SanderlingsC. alba) began to breed later and had during the laying period masses close to those of adults attending broods, and lower than during incubation. Body mass of the two latter species and Curlew Sandpipers (Calidris ferruginea) varied during incubation, reaching peak at 7 to 13 days after clutch completion.

Biometrics of Sanderlings Calidris alba from the Taimyr

Biometric data were collected for Sanderlings breeding at northern Taimyr in 1982–92. They allowed the calculation of discriminant functions, using wing, bill and (or) total head lengths, for sexing Sanderlings, belonging to Siberian population. Geographic comparisons revealed that birds from Taimyr have shorter bills than birds on South African wintering grounds, which leaves the problem of origin of long‐billed South‐African Sanderlings unsolved. Sanderlings had minimal body mass in pre‐nesting and brood‐rearing periods, and noticeably larger mass during incubation. Females were consistently heavier than males (regardless of size). The mean body mass fell in late seasons due to a probable decrease in food availability.