Shoy Lyakhovsky Island Research Articles

Terrestrial environmental conditions during the Last Interstadial based on analysis of aquatic invertebrate communities from coastal exposures at the Dmitry Laptev Strait

For the first time, data on the composition of cladoceran communities in lake bottom sediments from Bol’shoy Lyakhovsky Island and Oyogos Yar on the coast of the Dmitry Laptev Strait during the last major interglacial period (MIS 5e, 124-119 thousand years ago) have been obtained. 13 Cladocera taxa were identified in the composition of the taphocenoses. The composition of the Cladocera taphocenoses of Oyogos Yar indicates the presence of a well-developed littoral zone in the paleolakes, as most of the cladoceran remains belong to littoral-phytophilic taxa closely associated with macrophytes. In the Cladocera communities of Oyogos Yar, both cold-water representatives and more southern thermophilic taxa, such as Leydigia leydigi, were found. The findings of Cladocera remains from the MIS 5e period on the coast of the Laptev Sea, significantly north of their current ranges, allow for the reconstruction of warmer climatic conditions than those of today. The data obtained on Cladocera are well consistent with the results of chironomid analysis.

Mammoth Fauna Remains From Late Pleistocene Deposits of the Dmitry Laptev Strait South Coast (Northern Yakutia, Russia)

The Yedoma Ice Complex in northern Yakutia provides perfect preservation conditions for frozen remains of vertebrate animals. Even complete mummified specimens of the late Pleistocene Beringian Mammoth fauna such as woolly mammoth, woolly rhinoceros, horse, and bison are occasionally found in permafrost deposits across eastern Siberia, i.e., in West Beringia, although bones are much more commonly found. The present study characterizes mammal bones from late Pleistocene and Holocene permafrost deposits exposed on the Oyogos Yar coast, part of the southern shore of the Dmitry Laptev Strait that connects the Laptev and East Siberian seas. The study applies a method to characterize fossil bone samples by the location of their discovery and by the accuracy of their relation to a depositional horizon. We analyzed a total of 38 finite radiocarbon ages of bone material from mammoth, horse, and musk ox, spanning from about 48.8 to 4.5 ka BP and including both our own data and data from the literature, in addition to previous publications that reported numerous bones with infinite ages from the Oyogos Yar coast. The distribution of bones and tooth along the coastal permafrost exposure is not uniform; it depends upon whether the material was found in situ, on thermo-terraces, or on the shore. The overall bone collection consists of 13 species of which Mammuthus primigenius (woolly mammoth, 41%), Bison priscus (bison, 19%), Equus ex gr., caballus (horse, 19%), and Rangifer tarandus (reindeer, 16%) predominate. The fossil bone species distribution is similar to those of other prominent Yedoma outcrops in the region, i.e., on Bykovsky Peninsula and on Bol’shoy Lyakhovsky Island. Correlation analysis shows that the Oyogos Yar bone sampling sites of different geomorphological settings are similar to each other but not to all sampling sites within the other two locations on Bykovsky Peninsula and on Bol’shoy Lykahovsky Island. High similarities in terms of correlation coefficients between specific sampling sites are often not represented in the cluster analysis.

Cryolithostratigraphy of the Middle Pleistocene to Holocene Deposits in the Dmitry Laptev Strait, Northern Yakutia

The northernmost part of continental Yakutia in the Dmitry Laptev Strait region developed under non-glacial conditions during the Quaternary period. During cooling periods, ice-rich deposits with syngenetic ice wedges, called the Ice Complex, formed here. During periods of warming, they partially thawed under thermokarst lakes and a peculiar complex of lacustrine-boggy deposits (the Alas Complex) was formed. The article presents a description of ice-rich deposit sequences in several Ice Complex horizons and their transformation in lake taliks from the Middle Pleistocene to the Holocene (MIS 7—MIS 1). The Oyogos Yar section structure is considered as an example using additional geological data from the southern coast of Bol’shoy Lyakhovsky Island. Specific examples show the results of changes in the structure of sections via cryogenic processes—ice wedge formation and thawing. We confirm that cryogenic processes are important factors, along with accumulation and erosion processes, which change the geological and cryolithological structure of the sections. It is shown that to clearly understand the stratigraphic subdivision of Quarternary deposits in areas of Ice Complex development, geological and analytical studies of the sections are insufficient; an elucidation of the sequence of sediment freezing and thawing and the resulting cryolithogical phenomena is necessary.

Northeast Siberian Permafrost Ice‐Wedge Stable Isotopes Depict Pronounced Last Glacial Maximum Winter Cooling

AbstractStable isotopes (δ18O, δD) of wedge ice hold potential to reconstruct past winter climate conditions. Here, we present records of the marine isotope stages (MIS) 3 and 2 including the last Glacial maximum (LGM) from Bol’shoy Lyakhovsky Island (NE Siberia). MIS 3 wedge ice dated from 52 to 40 Kyr b2k varies between −32 and −29‰ in δ18O. Colder LGM conditions are implied by δ18O of −37‰ around 25 Kyr b2k. Similar Deuterium excess values indicate comparable moisture sources during MIS 3 and MIS 2. Regional LGM climate reconstructions depend on the seasonal resolution of the proxies and model simulations. Our wedge‐ice record reflects coldest winters during global minima in atmospheric CO2 and sea level. The extreme LGM winter cooling is not represented in model projections of global LGM climate where West Beringia shows noticeably little cooling or even warming in mean annual temperatures compared to the late Holocene.

Ice Complex formation on Bol'shoy Lyakhovsky Island (New Siberian Archipelago, East Siberian Arctic) since about 200 ka

AbstractLate Quaternary landscapes of unglaciated Beringia were largely shaped by ice-wedge polygon tundra. Ice Complex (IC) strata preserve such ancient polygon formations. Here we report on the Yukagir IC from Bol'shoy Lyakhovsky Island in northeastern Siberia and suggest that new radioisotope disequilibria (230Th/U) dates of the Yukagir IC peat confirm its formation during the Marine Oxygen Isotope Stage (MIS) 7a–c interglacial period. The preservation of the ice-rich Yukagir IC proves its resilience to last interglacial and late glacial–Holocene warming. This study compares the Yukagir IC to IC strata of MIS 5, MIS 3, and MIS 2 ages exposed on Bol'shoy Lyakhovsky Island. Besides high intrasedimental ice content and syngenetic ice wedges intersecting silts, sandy silts, the Yukagir IC is characterized by high organic matter (OM) accumulation and low OM decomposition of a distinctive Drepanocladus moss-peat. The Yukagir IC pollen data reveal grass-shrub-moss tundra indicating rather wet summer conditions similar to modern ones. The stable isotope composition of Yukagir IC wedge ice is similar to those of the MIS 5 and MIS 3 ICs pointing to similar atmospheric moisture generation and transport patterns in winter. IC data from glacial and interglacial periods provide insights into permafrost and climate dynamics since about 200 ka.

Substrate potential of last interglacial to Holocene permafrost organic matter for future microbial greenhouse gas production

Abstract. In this study the organic matter (OM) in several permafrost cores from Bol'shoy Lyakhovsky Island in NE Siberia was investigated. In the context of the observed global warming the aim was to evaluate the potential of freeze-locked OM from different depositional ages to act as a substrate provider for microbial production of greenhouse gases from thawing permafrost. To assess this potential, the concentrations of free and bound acetate, which form an appropriate substrate for methanogenesis, were determined. The largest free-acetate (in pore water) and bound-acetate (organic-matrix-linked) substrate pools were present in interstadial marine isotope stage (MIS) 3 and stadial MIS 4 Yedoma permafrost deposits. In contrast, deposits from the last interglacial MIS 5e (Eemian) contained only a small pool of substrates. The Holocene (MIS 1) deposits revealed a significant bound-acetate pool, representing a future substrate potential upon release during OM degradation. Additionally, pyrolysis experiments on the OM allocated an increased aliphatic character to the MIS 3 and 4 Late Pleistocene deposits, which might indicate less decomposed and presumably more easily degradable OM. Biomarkers for past microbial communities, including those for methanogenic archaea, also showed the highest abundance during MIS 3 and 4, which indicated OM-stimulated microbial degradation and presumably greenhouse gas production during time of deposition. On a broader perspective, Arctic warming will increase and deepen permafrost thaw and favor substrate availability from older freeze-locked permafrost deposits. Thus, the Yedoma deposits especially showed a high potential for providing substrates relevant for microbial greenhouse gas production.

The History of Tree and Shrub Taxa on Bol'shoy Lyakhovsky Island (New Siberian Archipelago) since the Last Interglacial Uncovered by Sedimentary Ancient DNA and Pollen Data.

Ecosystem boundaries, such as the Arctic-Boreal treeline, are strongly coupled with climate and were spatially highly dynamic during past glacial-interglacial cycles. Only a few studies cover vegetation changes since the last interglacial, as most of the former landscapes are inundated and difficult to access. Using pollen analysis and sedimentary ancient DNA (sedaDNA) metabarcoding, we reveal vegetation changes on Bol’shoy Lyakhovsky Island since the last interglacial from permafrost sediments. Last interglacial samples depict high levels of floral diversity with the presence of trees (Larix, Picea, Populus) and shrubs (Alnus, Betula, Ribes, Cornus, Saliceae) on the currently treeless island. After the Last Glacial Maximum, Larix re-colonised the island but disappeared along with most shrub taxa. This was probably caused by Holocene sea-level rise, which led to increased oceanic conditions on the island. Additionally, we applied two newly developed larch-specific chloroplast markers to evaluate their potential for tracking past population dynamics from environmental samples. The novel markers were successfully re-sequenced and exhibited two variants of each marker in last interglacial samples. SedaDNA can track vegetation changes as well as genetic changes across geographic space through time and can improve our understanding of past processes that shape modern patterns.

Modern and fossil diatom assemblages from Bol’shoy Lyakhovsky Island (New Siberian Archipelago, Arctic Siberia)

This article discusses the results of a taxonomic and ecological investigation of diatoms from polygonal ponds and Quaternary permafrost deposits of Bol’shoy Lyakhovsky Island (New Siberian Archipelago) and the reconstruction of climatic changes on the Island during late Pleistocene/Holocene transition using fossil diatom assemblages from the permafrost deposits. The taxonomic list of diatoms includes 159 diatom species. The main ecological factors that determine the distribution of diatoms in the investigated data set are mean July air temperature, рН, electrical conductivity, water depth, and concentrations of Si4+ and Al3+. An increase in water depth and stable lacustrine conditions in the Lateglacial–Holocene in the ancient thermokarst lake relate to Lateglacial warming before 11860 ± 160 years BP and during the early Holocene between 11210 ± 160 and 7095 ± 60 years BP.

Ground-ice stable isotopes and cryostratigraphy reflect late Quaternary palaeoclimate in the Northeast Siberian Arctic (Oyogos Yar coast, Dmitry Laptev Strait)

Abstract. To reconstruct palaeoclimate and palaeoenvironmental conditions in the northeast Siberian Arctic, we studied late Quaternary permafrost at the Oyogos Yar coast (Dmitry Laptev Strait). New infrared-stimulated luminescence ages for distinctive floodplain deposits of the Kuchchugui Suite (112.5 ± 9.6 kyr) and thermokarst-lake deposits of the Krest Yuryakh Suite (102.4 ± 9.7 kyr), respectively, provide new substantial geochronological data and shed light on the landscape history of the Dmitry Laptev Strait region during Marine Isotope Stage (MIS) 5. Ground-ice stable-isotope data are presented together with cryolithological information for eight cryostratigraphic units and are complemented by data from nearby Bol'shoy Lyakhovsky Island. Our combined record of ice-wedge stable isotopes as a proxy for past winter climate conditions covers about 200 000 years and is supplemented by stable isotopes of pore and segregated ice which reflect annual climate conditions overprinted by freezing processes. Our ice-wedge stable-isotope data indicate substantial variations in northeast Siberian Arctic winter climate conditions during the late Quaternary, in particular between glacial and interglacial times but also over the last millennia to centuries. Stable isotope values of ice complex ice wedges indicate cold to very cold winter temperatures about 200 kyr ago (MIS7), very cold winter conditions about 100 kyr ago (MIS5), very cold to moderate winter conditions between about 60 and 30 kyr ago, and extremely cold winter temperatures during the Last Glacial Maximum (MIS2). Much warmer winter conditions are reflected by extensive thermokarst development during MIS5c and by Holocene ice-wedge stable isotopes. Modern ice-wedge stable isotopes are most enriched and testify to the recent winter warming in the Arctic. Hence, ice-wedge-based reconstructions of changes in winter climate conditions add substantial information to those derived from paleoecological proxies stored in permafrost and allow a distinction between seasonal trends of past climate dynamics. Future progress in ice-wedge dating and an improved temporal resolution of ice-wedge-derived climate information may help to fully explore the palaeoclimatic potential of ice wedges.

Modern and Fossil Diatom Assemblages from Bol'shoy Lyakhovsky Island (New Siberian Archipelago, Arctic Siberia)

Modern and Fossil Diatom Assemblages from Bol'shoy Lyakhovsky Island (New Siberian Archipelago, Arctic Siberia)

Ice Complex formation in arctic East Siberia during the MIS3 Interstadial

A continuous 15 m long sequence of Ice Complex permafrost (Yedoma) exposed in a thermo-cirque at the southern coast of Bol'shoy Lyakhovsky Island (New Siberian Archipelago, Dmitry Laptev Strait) was studied to reconstruct past landscape and environmental dynamics. The sequence accumulated during the Marine Isotope Stage 3 (MIS3) Interstadial between >49 and 29 ka BP in an ice-wedge polygon. The frozen deposits were cryolithologically described and sampled on a vertical bluff between two ice wedges. According to sedimentological and geochronological data, the section is subdivided into three units which correlate with environmental conditions of the early, middle, and late MIS3 period. Palynological data support this stratification. The stable isotope signature of texture ice in the polygon structure reflects fractionation due to local freeze–thaw processes, while the signature of an approximately 5 m wide and more than 17 m high ice wedge fits very well into the regional stable-water isotope record. Regional climate dynamics during the MIS3 Interstadial and local landscape conditions of the polygonal patterned ground controlled the Ice Complex formation. The sequence presented here completes previously published MIS3 permafrost records in Northeast Siberia. Late Quaternary stadial-interstadial climate variability in arctic West Beringia is preserved at millennial resolution in the Ice Complex. A MIS3 climate optimum was revealed between 48 and 38 ka BP from the Ice Complex on Bol'shoy Lyakhovsky Island.

Last Glacial Maximum records in permafrost of the East Siberian Arctic

Palaeontological proxy data and cryolithological information from Siberian Arctic permafrost preserves records of late Quaternary climate and environmental conditions in West Beringia and their variability which results from interglacial-glacial and interstadial-stadial dynamics. To date, the Last Glacial Maximum (LGM) period has been rather poorly represented in East Siberian permafrost records. Here, we present pollen, sediment, and ground-ice stable water isotope data obtained from coastal exposures on Bol’shoy Lyakhovsky Island (New Siberian Archipelago, Arctic Ocean) that mirror the coldest conditions during the Sartan period between about 26 and 22 ka BP, using pollen and sediment data for summer conditions and stable water isotope data for winter conditions. The pollen record revealed a cold tundra-steppe vegetation with characteristic predominance of grass pollen over sedge pollen while the stable isotope ice-wedges data indicate extremely cold winter temperatures with mean values of δ 18O of about −37‰, δD of about −290‰. Combined with available regional LGM permafrost records that extend from the Taymyr Peninsula in the west to the Yana River lowland in the east, the new data set from Bol’shoy Lyakhovsky Island indicate that the regional appearance of LGM conditions depended on atmospheric circulation patterns that were influenced by the extent of the Northern Hemisphere glaciation.

Eemian and Late Glacial/Holocene palaeoenvironmental records from permafrost sequences at the Dmitry Laptev Strait (NE Siberia, Russia)

Terrestrial permafrost sections from the southern and northern coasts of Dmitry Laptev Strait have preserved records of landscape transition from glacial to interglacial periods. They allow geomorphologic and environmental changes to be traced from pre-Eemian time to the Eemian, and from the Late Glacial to the Holocene. The transition from one period to another induced extensive thawing of permafrost (thermokarst). Evolving thermokarst depressions transformed formerly frozen ground into taberal (unfrozen) deposits with accumulating overlying lacustrine deposits. Lacustrine horizons rich in palaeontological remains retain evidence of changes in environmental conditions. The pollen records reflect changes from grass-sedge dominated vegetation during the Early Eemian to shrub dominated spectra during the Middle Eemian thermal optimum followed by Late Eemian grass-sedge dominated tundra vegetation. Abundant Larix pollen have been found in Middle Eemian deposits from the south coast of the Dmitry Laptev Strait (Oyogos Yar), but are absent in similar deposits from the north coast (Bol'shoy Lyakhovsky Island), likely indicating that the northern tree line was located near the Oyogos Yar region during the Eemian thermal optimum. Grass-sedge dominated tundra vegetation occurred during the Late Glacial/Holocene transition which was replaced by shrub tundra during the early Holocene. Rich fossil ostracod records from Eemian and Late Glacial/Holocene lacustrine deposits could be correlated with the Eemian thermal optimum and the Late Glacial Allerød warm period. For both periods, the stable oxygen isotope data from the fossil ostracods suggest an approximate mean summer water temperature range between about 10 and 19 °C in the palaeo-lakes.

Weichselian and Holocene palaeoenvironmental history of the Bol'shoy Lyakhovsky Island, New Siberian Archipelago, Arctic Siberia

Cryolithological, ground ice and fossil bioindicator (pollen, diatoms, plant macrofossils, rhizopods, insects, mammal bones) records from Bol'shoy Lyakhovsky Island permafrost sequences (73°20′N, 141°30′E) document the environmental history in the region for the past c. 115 kyr. Vegetation similar to modern subarctic tundra communities prevailed during the Eemian/Early Weichselian transition with a climate warmer than the present. Sparse tundra‐like vegetation and harsher climate conditions were predominant during the Early Weichselian. The Middle Weichselian deposits contain peat and peaty soil horizons with bioindicators documenting climate amelioration. Although dwarf willows grew in more protected places, tundra and steppe vegetation prevailed. Climate conditions became colder and drier c. 30 kyr BP. No sediments dated between c. 28.5 and 12.05 14C kyr BP were found, which may reflect active erosion during that time. Herb and shrubby vegetation were predominant 11.6–11.3 14C kyr BP. Summer temperatures were c. 4 °C higher than today. Typical arctic environments prevailed around 10.5 14C kyr BP. Shrub alder and dwarf birch tundra were predominant between c. 9 and 7.6 kyr BP. Reconstructed summer temperatures were at least 4 °C higher than present. However, insect remains reflect that steppe‐like habitats existed until c. 8 kyr BP. After 7.6 kyr BP, shrubs gradually disappeared and the vegetation cover became similar to that of modern tundra. Pollen and beetles indicate a severe arctic environment c. 3.7 kyr BP. However, Betula nana, absent on the island today, was still present. Together with our previous study on Bol'shoy Lyakhovsky Island covering the period between about 200 and 115 kyr, a comprehensive terrestrial palaeoenvironmental data set from this area in western Beringia is now available for the past two glacial–interglacial cycles.

Continental climate in the East Siberian Arctic during the last interglacial: Implications from palaeobotanical records

To evaluate the consequences of possible future climate changes and to identify the main climate drivers in high latitudes, the vegetation and climate in the East Siberian Arctic during the last interglacial are reconstructed and compared with Holocene conditions. Plant macrofossils from permafrost deposits on Bol'shoy Lyakhovsky Island, New Siberian Archipelago, in the Russian Arctic revealed the existence of a shrubland dominated by Duschekia fruticosa, Betula nana and Ledum palustre and interspersed with lakes and grasslands during the last interglacial. The reconstructed vegetation differs fundamentally from the high arctic tundra that exists in this region today, but resembles an open variant of subarctic shrub tundra as occurring near the tree line about 350 km southwest of the study site. Such difference in the plant cover implies that, during the last interglacial, the mean summer temperature was considerably higher, the growing season was longer, and soils outside the range of thermokarst depressions were drier than today. Our pollen-based climatic reconstruction suggests a mean temperature of the warmest month (MTWA) range of 9–14.5 °C during the warmest interval of the last interglacial. The reconstruction from plant macrofossils, representing more local environments, reached MTWA values above 12.5 °C in contrast to today's 2.8 °C. We explain this contrast in summer temperature and soil moisture with a combination of summer insolation higher than present and climatic continentality in arctic Yakutia stronger than present as result of a considerably less inundated Laptev Shelf during the last interglacial.

Interglacial History of a Palaeo-lake and Regional Environment: A Multi-proxy Study of a Permafrost Deposit from Bol’shoy Lyakhovsky Island, Arctic Siberia

Chironomid, pollen, and rhizopod records from a permafrost sequence at Bol’shoy Lyakhovsky Island (New Siberian Archipelago) document the development of a thermokarst palaeo-lake and environmental conditions in the region during the last Interglacial (MIS 5e). Open Poaceae and Artemisia associations dominated vegetation at the beginning of the interglacial period. Rare shrub thickets (Salix, Betula nana, Alnus fruticosa) grew in more protected and wetter places as well. Saalian ice wedges started to melt during this time, resulting in the formation of an initial thermokarst water body. The high percentage of semi-aquatic chironomids suggests that a peatland-pool initially existed at the site. A distinct decrease in semi-aquatic chironomid taxa and an increase in lacustrine ones point to a gradual pooling of water in the basin, which could in turn induce thermokarst and create a permanent pond during the subsequent period. The highest relative abundance of Chironomus and Procladius reflects unfrozen water remaining under the ice throughout the ice-covered period during the later stage of palaeo-lake development. The chironomid record points to three successive stages during the history of the lake: (1) a peatland pool; (2) a pond (i.e., shallower than the maximum ice-cover thickness); and (3) a shallow lake (i.e., deeper than the maximum ice-cover thickness). The trend of palaeo-lake development indicates that intensive thermokarst processes occurred in the region during the last Interglacial. Shrub tundra communities with Alnus fruticosa and Betula nana dominated the vegetation during the interglacial optimum. The climate was moister and warmer than present. The results of this study suggest that quantitative chironomid-based temperature reconstructions from Arctic thermokarst ponds/lakes may be problematic due to other key environmental factors, such as prolonged periods of winter anoxia and local hydrological/geomorphological processes, controlling the chironomid assemblages.

Short-term climatic changes recorded by mammoth hair in the Arctic environment

Well-conserved mammoth carcasses can be found only in particular environments such as the Arctic region where the ground is frozen to depths of hundreds of meters and only a thin superficial layer of about 1.0/1.5 m thaws out during the short Arctic summer. In this environment soft tissues such as hairs can be preserved and therefore analysed to obtain information about the short-term (seasonal) environmental changes during the short period right before the animal's death. This study reports the results of a set of about 240 analyses carried out on 4 hairs of a 42,700±1300 radiocarbon years old mammoth from the Bol'shoy Lyakhovsky Island (New Siberian Islands). The hairs were analysed for their C and N stable isotope composition to obtain information about seasonal and annual changes in the mammoth's diet. Isotope analyses were performed on small growth increments along the full length of the hair, which represents a continuous record of the food intake over the growth period of this tissue. The isotope oscillations found represent seasonal changes in the isotope composition of plant food consumed according to the different plant-type availability between the cold and warm season and/or to a physiological adaptation of the plants and the animal to different environmental conditions. Small differences in the isotope values of mammoth food intake from one year to the next are also apparent. By counting the number of oscillations it is possible to define the hair age. The longest hair is representative of the last 39 months of mammoth's life. The mean C isotope composition calculated for the vegetation at the base of the mammoth diet during the Middle Valdai is different by about 2‰ to that of the present vegetation in Northern Siberia suggesting different climatic conditions.

Late Saalian and Eemian palaeoenvironmental history of the Bol'shoy Lyakhovsky Island (Laptev Sea region, Arctic Siberia)

Palaeoenvironmental records from permafrost sequences complemented by infrared stimulated luminescence (IRSL) and 230Th/U dates from Bol'shoy Lyakhovsky Island (7320'N, 14130'E) document the environmental history in the region for at least the past 200 ka. Pollen spectra and insect fauna indicate that relatively wet grass‐sedge tundra habitats dominated during an interstadial c. 200–170 ka BP. Summers were rather warm and wet, while stable isotopes reflect severe winter conditions. The pollen spectra reflect sparser grass‐sedge vegetation during a Taz (Late Saalian) stage, c. 170–130 ka BP, with environmental conditions much more severe compared with the previous interstadial. Open Poaceae and Artemisia plant associations dominated vegetation at the beginning of the Kazantsevo (Eemian) c. 130 ka BP. Some shrubs (Alnus fruticosa, Salix, Betula nana) grew in more protected and wetter places as well. The climate was relatively warm during this time, resulting in the melting of Saalian ice wedges. Later, during the interglacial optimum, shrub tundra with Alnus fruticosa and Betula nana s.l. dominated vegetation. Climate was relatively wet and warm. Quantitative pollen‐based climate reconstruction suggests that mean July temperatures were 4–5 C higher than the present during the optimum of the Eemian, while late Eemian records indicate significant climate deterioration.

Late Saalian and Eemian palaeoenvironmental history of the Bol'shoy Lyakhovsky Island (Laptev Sea region, Arctic Siberia)

Late Saalian and Eemian palaeoenvironmental history of the Bol'shoy Lyakhovsky Island (Laptev Sea region, Arctic Siberia)

230Th/U Dating of Frozen Peat, Bol'shoy Lyakhovsky Island (Northern Siberia)

The chronology of Quaternary paleoenvironment and climate in northeastern Siberia is poorly understood due to a lack of reliable numerical age determinations. The best climatic archives are ice-rich permafrost sequences, which are widely distributed in northeastern Siberia. For this study, 230Th/U-ages were determined by thermal ionization mass spectrometry (TIMS) from frozen peat in a permafrost deposit at the southern cliff of the Bol'shoy Lyakhovsky Island (New Siberian Archipelago), west of the Zimov'e River. These yielded a Pre-Eemian “isochron”-corrected 230Th/U-age of 200,900±3400 yr. This result is reliable because permafrost deposits behave as closed systems with respect to uranium and thorium. Our findings suggest that 230Th/U dating of frozen peat in permafrost deposits is a useful tool for the reconstruction of the Middle Quaternary environment of northern Siberia and of the whole Arctic.