Arctic Chukotka Research Articles

The Enmynveem mammoth and vegetation changes in arctic Chukotka during the Late Quaternary

Abstract Mining operations in the Enmynveem valley, northeastern Siberia, exposed a well-preserved right hind leg of Mammuthus primigenius (woolly mammoth), dated to ca. 37,500 cal yr BP. The leg had a fracture that crosscut the midsections of the tibia and fibula. Additional skeletal and soft tissue remains, including two mummified adults (Berezovka, ca. 47,200 cal yr BP; Bolshoi Lyakhovsky, ca. 37,000 cal yr BP), document the presence of mammoths in interior mountain valleys and across both northern and southern coasts of far northeastern Siberia during Marine Isotope Stage (MIS) 3. A mosaic of herb-dominated tundra communities characterized the vegetation of the Enmynveem site during late to middle MIS 3 and MIS 2 (ca. 37,000–17,000 cal yr BP). Shrubs were limited to Salix during the late Pleistocene, whereas Betula also may have been present in sheltered sites during MIS 3. Herb communities remained dominant during the late Pleistocene–Early Holocene transition, although shrub Betula increased during this interval. By ca. 10,200 cal yr BP, the vegetation was Betula–Alnus shrub tundra. Larix and Pinus pumila were established in the valley by ca. 8700 cal yr BP and ca. 5700 cal yr BP, respectively.

Изменения растительных сообществ арктической Чукотки в изотопные стадии 40-49

The palynological record from Lake El'gygytgyn, spanning the interval between c. 1.286 and 1.492 million years ago, shows repeated changes in plant communities in Arctic Chukotka, which reflect variations in glacial, interstadial, and interglacial climatic conditions. Thirteen pollen zones were defined, corresponding to marine oxygen isotope stages 40-49. The consistent presence of Larix pollen in these pollen spectra indicates that even under extremely severe climatic conditions that occurred in areas of the Anadyr plateau and Lake El'gygytgyn during the Calabrian Age, larch forest-tundra survived. The continued presence of forest habitats differs sharply from the herb- dominated tundra that characterized many glacial intervals in the Arctic during the Middle and Late Pleisto?ene. The warmest climate within the 1.286-1.492 million year interval, seen in pollen zone 9, appeared during isotope stage 43. The maximum in cold conditions occurred during the second half of isotope stage 44 (pollen zone 8).

Vegetation Response to Climate Change during the Middle Calabrian in Arctic Chukotka

A palynological record obtained from El'gygytgyn Lake sediments, which spans the 1.244-1.304 million years (Ma) interval of the Calabrian Stage, shows repeated changes in the plant communities of Arctic Chukotka. These variations in the vegetation further suggest a dominance of interstadial and interglacial climates. Eight pollen zones were distinguished within this interval. According to the working age model for the composite El'gygytgyn core, these pollen zones correspond to marine oxygen isotope stages (MIS) 40, 39, and 38. The upper boundary of MIS 38 coincides with magnetic event the Cobb Mountain (1.240 Ma), which is one of the main chronological landmarks used in creating the core's chronology. The features of modern pollen-spore spectra obtained from the water-sediment interface within the lake aided in reconstructing both the local and regional paleovegetation. The consistent presence of Larix pollen throughout the 1.244-1.304 Ma interval indicates that even under the severest climatic conditions Larix forest-tundra persisted on the Anadyr Plateau and near El'gygytgyn Lake. This pattern differs sharply from that seen in the Middle and Late Pleistocene when herb-dominated tundra characterized the glacial intervals in the Arctic. The spore-pollen spectra further show that the warmest climatic conditions occurred during MIS 39. The data from the 1.244-1.304 Ma interval represent the last step in completing the Quaternary vegetation history from this unique site in Arctic Siberia.

Position of Quaternary Lower Boundary of the Arctic Chukotka According to Diatom Analysis

Position of Quaternary Lower Boundary of the Arctic Chukotka According to Diatom Analysis

Environmental changes in Arctic Chukotka during Marine Isotope Stages 38‐31: implications for the Early to Middle Pleistocene transition

Lake El'gygytgyn in far northeastern Russia provides one of the few records that can improve understanding of terrestrial responses to climatic changes during the Early to Middle Pleistocene transition (EMPT; 1400–400 ka). Palynological data from MIS 38‐31 (~1260 to 1060 ka) help clarify the complex nature of that transition. In contrast to the evergreen conifer forest of the MIS 31 ‘super’ interglaciation, Larix‐Betula‐Alnus forest with shrub tundra characterized MIS 37 and MIS 35. The Larix forest‐tundra of MIS 33 represents an even cooler interglaciation. The landscapes of MIS 38, MIS 36 and early MIS 34 were a tundra mosaic with areas of Larix‐forest tundra. Although marine records suggest that MIS 38 and MIS 36 were exceptionally harsh glaciations, the decrease in woody taxa (particularly Alnus and Pinus) indicate the coolest conditions at El'gygytgyn occurred during MIS 32 and late MIS 34. When combined with other palynological data from El'gygytgyn, the EMPT portion of the record indicates that Betula was important in the vegetation during both cool and warm periods prior to MIS 24. Following the build‐up of global ice volumes ~900 ka, the taxon was characteristic of warm intervals only, marking the establishment of the herb‐dominated tundra, which typifies the remainder of the Pleistocene glaciations. The more complex successional patterns in post‐900 ka vegetation suggest greater climate variability as ice volume increased. Pinus pumila became a significant component of interglacial vegetation following the shift from a 41 ka to a quasi‐100 ka orbital cycle, indicating an increase in snow cover and a lessening of aridification, at least in this part of the Arctic.

Климатические изменения времени МИС-5 арктической Чукотки и Аляски

Климатические изменения времени МИС-5 арктической Чукотки и Аляски

Evaluation of P–T and fO2 Conditions of Crystallization of Monzonitic Rocks of the Velitkenay Granite–Migmatite Massif (Arctic Chukotka) Based on Mineral Thermobaro- and Oxybarometry

The physico-chemical parameters of crystallization of the Early Cretaceous Velitkenay granite–migmatite pluton (Arctic coast of Chukotka, near Cape Billings) are reconstructed using mineral thermobarometry and oxybarometry. The magmatic rocks are dominated by monzonitic rocks (quartz monzodiorites and monzodiorites), with less common granodiorites and leucogranites. The limitations on and critical parameters of the amphibole composition are considered for correct application of thermobarometry. The most reliable pressure estimations for the early-phase monzonitic rocks are calculated using an amphibole geobarometer range from 2.2 to 4.2 kbar. The calculated crystallization temperature varies from 684 to 823°C (plagioclase–amphibole geothermometer) at oxygen fugacity from +0.2 to +0.7 relative to NNO buffer. The obtained P–T data on the Velitkenay monzonitic rocks are consistent with the conditions of amphibolite facies metamorphism typical of the Chukotka granite–metamorphic domes, the formation of which is related to post-collisional extension.

Neoproterozoic basement history of Wrangel Island and Arctic Chukotka: integrated insights from zircon U–Pb, O and Hf isotopic studies

Abstract The pre-Cenozoic kinematic and tectonic history of the Arctic Alaska Chukotka (AAC) terrane is not well known. The difficulties in assessing the history of the AAC terrane are predominantly due to a lack of comprehensive knowledge about the composition and age of its basement. During the Mesozoic, the AAC terrane was involved in crustal shortening, followed by magmatism and extension with localized high-grade metamorphism and partial melting, all of which obscured its pre-orogenic geological relationships. New zircon geochronology and isotope geochemistry results from Wrangel Island and western Chukotka basement rocks establish and strengthen intra- and inter-terrane lithological and tectonic correlations of the AAC terrane. Zircon U–Pb ages of five granitic and one volcanic sample from greenschist facies rocks on Wrangel Island range between 620±6 and 711±4 Ma, whereas two samples from the migmatitic basement of the Velitkenay massif near the Arctic coast of Chukotka yield 612±7 and 661±11 Ma ages. The age spectrum (0.95–2.0 Ga with a peak at 1.1 Ga and minor 2.5–2.7 Ga) and trace element geochemistry of inherited detrital zircons in a 703±5 Ma granodiorite on Wrangel Island suggests a Grenville–Sveconorwegian provenance for metasedimentary strata in the Wrangel Complex basement and correlates with the detrital zircon spectra of strata from Arctic Alaska and Pearya. Temporal patterns of zircon inheritance and O–Hf isotopes are consistent with Cryogenian–Ediacaran AAC magmatism in a peripheral/external orogenic setting (i.e. a fringing arc on rifted continental margin crust).

Age and composition of basement beneath the De Long archipelago, Arctic Russia, based on zircon U–Pb geochronology and O–Hf isotopic systematics from crustal xenoliths in basalts of Zhokhov Island

U–Pb ages, in conjunction with oxygen isotope and hafnium isotope geochemistry of zircons from granitic and siliciclastic crustal xenoliths from Cenozoic alkali basalts on Zhokhov Island (De Long Archipelago, Russian Arctic), provide new insights about the island’s subsurface geology. Zircons from granitic gneiss xenoliths yield 206Pb/238U ages ranging from 600 to 660 Ma, similar to protolith ages of granite intrusions and orthogneisses in Protouralian–Timanian magmatic basement of the northern Urals as well as to rocks that form the basement of Arctic Chukotka and Wrangel Island, thus suggesting continuity between these three regions. Depleted mantle-like Hf and O isotopic signatures in the dated zircons suggest juvenile crust that originally formed in the Neoproterozoic and was later reworked during the Paleozoic and Mesozoic. Sandstone xenoliths contain detrital zircon (DZ) populations that establish their depositional age as younger than Permian and reveal similarities to DZ populations of Permian and Triassic strata of Taimyr and Chukotka.

Monitoring of persistent organic pollutants in the ambient air as an element of implementation of the Stockholm Convention on persistent organic pollutants

The results of monitoring of persistent organic pollutants (POPs) in the atmosphere of the Russian Arctic are presented. The concentrations of POPs in different regions of the Russian and foreign Arctic are compared. It was revealed that the concentrations of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) are higher in the Northern Chukotka (Valkarkai) as compared to that at the other Russian stations (Amderma and Dunay) and foreign global POPs monitoring stations. The composition of PCB congeners in the air of the Arctic Chukotka turned out to be different from that observed at the other monitoring stations, being similar to commercial PCBs mixtures. In contrast to observations at most of the global POPs monitoring stations, monitoring in the Far East Russian Arctic has revealed increased levels of PCBs in the air for the last 6–8 years. The levels of DDT in the past 6–8 years have remained virtually unchanged, whereas those hexachlorocyclohexane have decreased somewhat. It was shown that polybrominated diphenyl ethers (PBDEs) are ubiquitous and are found in significant quantities in the air in both the central cities (Moscow, Obninsk) and remote locations (Arkhangelsk, Amderma, Valkarkai). The gas phase contains largely more volatile low-brominated DEs, while atmospheric aerosols contain predominantly highly brominated congeners. The indoor air at all sampling locations contained substantially higher concentrations of PBDEs as compared to the atmospheric air. Priorities for the establishment of a national system for monitoring of POPs within the framework of the Stockholm Convention on POPs control are proposed.

Dietary exposure to persistent organic pollutants and metals among Inuit and Chukchi in Russian Arctic Chukotka

Objectives. The general aim was to assess dietary exposure to selected persistent organic pollutants (POPs) and metals among Eskimo (Inuit) and Chukchi of the Chukotka Peninsula of the Russian Arctic, and to establish recommendations for exposure risk reduction.Study design. A cross-sectional evaluation of nutritional patterns of coastal and inland indigenous peoples of the Chukotka Autonomous Okrug (in 2001–2003); assessment of the levels of persistent toxic substances (PTSs) in traditional foods and their comparison to Russian food safety limits; the identification of local sources of food contamination; and the recommendation and implementation of risk management measures.Methods. Community-based dietary survey of self reported food frequencies (453 persons), chemical analyses (POPs and metals) of local foods and indoor matters (397 samples), substantiation of recommendations for daily (weekly, monthly) intakes of traditional food.Results. POPs in traditional food items are generally below the Russian food safety limits except marine mammal fat, while Hg and Cd are high mainly in mammal viscera. Lead is relatively low in tissues of all animals studied. For the Chukotka coastal communities, seals constitute the principal source of the whole suite of PTSs considered. Consumption restrictions are recommended for marine and freshwater fish, some wild meats (waterfowl and seal), fats (whale and seal), liver (most animals) and kidney (reindeer, walrus and seal). Evidence is presented that contamination of foodstuffs may be significantly increased during storing/processing/cooking of food due to indoor and outdoor environmental conditions.Conclusions. Based on the analytical findings and the local PTSs sources identified, guidelines on food safety are suggested, as well as measures to reduce food contamination and domestic and local sources. Important and urgent remedial actions are recommended to minimize PTSs environmental and domestic contamination. Waste clean-up activities started in coastal Chukotka in 2007.

Geochronology and thermochronology of Cretaceous plutons and metamorphic country rocks, Anyui-Chukotka fold belt, North East Arctic Russia

Abstract. U-Pb isotopic dating of seven granitoid plutons and associated intrusions from the Bilibino region (Arctic Chukotka, Russia) was carried out using the SHRIMP-RG. The crystallization ages of these granitoids, which range from approximately 116.9±2.5 to 108.5±2.7 Ma, bracket two regionally significant deformational events. The plutons cut folds, steep foliations and thrust-related structures related to sub-horizontal shortening at lower greenschist facies conditions (D1), believed to be the result of the collision of the Arctic Alaska-Chukotka microplate with Eurasia along the South Anyui Zone (SAZ). Deformation began in the Late Jurassic, based on fossil ages of syn-orogenic clastic strata, and involves strata as young as early Cretaceous (Valanginian) north of Bilibino and as young as Hauterivian-Barremian, in the SAZ. The second phase of deformation (D2) is developed across a broad region around and to the east of the Lupveem batholith of the Alarmaut massif and is interpreted to be coeval with magmatism. D2 formed gently-dipping, high-strain foliations (S2). Growth of biotite, muscovite and actinolite define S2 adjacent to the batholith, while chlorite and white mica define S2 away from the batholith. Sillimanite (± andalusite) at the southeastern edge the Lupveem batholith represent the highest grade metamorphic minerals associated with D2. D2 is interpreted to have developed during regional extension and crustal thinning. Extension directions as measured by stretching lineations, quartz veins, boudinaged quartz veins is NE-SW to NW-SE. Mapped dikes associated with the plutons trend mostly NW-SE and indicate NE-SW directed extension. 40Ar/39Ar ages from S2 micas range from 109.3±1.2 to 103.0±1.8 Ma and are interpreted as post-crystallization cooling ages following a protracted period of magmatism and high heat flow. Regional uplift and erosion of many kilometers of cover produced a subdued erosional surface prior to the eruption of volcanic rocks of the Okhotsk-Chukotka volcanic belt (OCVB) whose basal units (~87 Ma) overlie this profound regional unconformity. A single fission track age on apatite from granite in the Alarmaut massif yielded an age of 90±11 Ma, in good agreement with this inference.