Syngenetic Wedges Research Articles

Estimation of atmospheric paleo-circulation based on isotope composition of ice wedges

Cryostratigraphy of frozen late-Pleistocene sediments was studied in natural exposures at the Arctic coastal area. The isotope composition of ice wedges was determined. The data base on isotope composition of syngenetic ice wedges and modern elementary ice veins was compiled for the Eurasian Arctic based on obtained data and available literature sources. Spatial distribution of the isotope composition of ice wedges, which indicates paleo-climatic conditions, was determined separately for Marine Isotope Stages (MISs) from MIS 1 to MIS 4 for the Eurasian Arctic. The pattern of this distribution has remained stable during the last 50 000 years, which indicates a stable trend in atmospheric circulation from 50 000 yr BP to the present.

A geosystems approach to permafrost investigations for engineering applications, an example from a road stabilization experiment, Beaver Creek, Yukon, Canada

The Alaska Highway crosses numerous terrain units underlined by warm and ice-rich discontinuous permafrost highly susceptible to thermal degradation. For years, this infrastructure, which is essential to transportation in northwestern Canada and Alaska, has been showing signs of road damage induced by permafrost degradation. In 2008, Yukon Highways and Public Works, and its international collaborators, implemented a road experimental site near Beaver Creek (Yukon) to test mitigation techniques aiming to control permafrost degradation. Permafrost investigations were done accordingly to a geosystem approach based on the hypothesis that permafrost has a distinctive sensitivity to climate and terrain conditions at a local scale and that changes (dynamics) in the system must be integrated in the analysis to obtain a holistic understanding of permafrost conditions and consequences of potential changes through time. Therefore, permafrost assessment at BC-RES came along with other components assessment such as local climate, natural terrain and embankment conditions.Four main units identified were typically ice-rich, with the exception of one shallow sub-unit (2B) that was ice-poor, but which contained the top of inactive ice-wedges, and Unit 3 at depth. The extent of the syngenetic ice wedges was not encountered, but reached at least a depth of 10.7m. Units 1 and 2 (likely eolian periglacial deposits) were fine-grained soils characterized by a potential to liquefy, if soils thaw and maintain their natural moisture content, and to differential thaw-settlement. Unit 3 (likely interglacial deposit) was mainly made of peat, while Unit 4 (likely glacial deposit) was a diamicton with a fine-grained matrix containing abundant excess ice. Impact from road embankment was measured at many locations in permafrost below the infrastructure. Isothermal profile under the road and embankment subsidence, assessed from core-drilling combination with GPR and ground temperatures, reflected the thermal impact of embankment and its interaction with other geosystem components (e.g. snow, groundwater) on the underlying ice-rich cryostratigraphic units. Thaw depth below embankment sideslopes had mostly reached sub-unit 2B, exposing now excess ground ice from the underlying very ice-rich sub-unit 2C and ice wedge to melting. In this context, an increase in permafrost degradation is expected in the near future, regardless of the mitigation technique performance.Application of the geosystem approach for road infrastructure in permafrost regions was beneficial at the BC-RES to identify the comprehensive critical engineering conditions that should be considered at the infrastructure spatial scale for road sustainability through timescale of its life. This approach emphasized the importance of changes in properties and processes, including their variability and dynamic related to interactions within the system. Overall, engineering studies in permafrost regions, which are typically sensitive to changes in conditions, would clearly benefit from applications of the geosystem approach, which can be adapted to spatial and time scales of these studies.

Field observations of syngenetic ice wedge polygons, outer Mackenzie Delta, western Arctic coast, Canada

AbstractLow‐centered ice wedge polygons in the Big Lake Delta Plain of the outer Mackenzie Delta are unusual because their bounding ramparts appear to have a single ridge. Twenty‐two ice wedges in the area were examined between 2006 and 2009 to describe their morphology and diagnose their growth processes. The ground above ice wedges had a subtle microtopography, with ridges of 0.12 m relief and 4.0 m total width, bisected by troughs only 0.05 m wide and 0.09 m deep. The troughs, initially obscured by vegetation growth and organic matter, were underlain by ice wedges with average widths that increased downward in the uppermost 1 m of permafrost from 0.03 to 0.95 m. “Shoulders” on the ice wedges indicated vertical growth stages. Temperatures near the top of permafrost were favorable to thermal‐contraction cracking, and ice veins connected to the top of wedge ice were observed in the active layer at five sites. These observations indicate the ice wedges are syngenetic and active, although without dating control, we cannot unequivocally dismiss the possibility that the wedges are epigenetic features that were truncated by a recent thaw unconformity. Muted relief above the ice wedges, which is uncommon above epigenetic ice wedges, was largely due to aggradation of the surface. Secondary ice wedges have not developed within the polygons, suggesting that climate variability has not led to polygon network development in this area. Wedge ice occupied only about 1.5% of the uppermost 1 m of permafrost, a much smaller volumetric proportion than in epigenetic settings.

Spatial distribution of mean winter air temperatures in Siberian permafrost at 20−18 ka BP using oxygen isotope data

Palaeotemperature reconstruction for the period of 20−18 ka BP in Siberia is here based on δ18O analysis and 14C dating of large syngenetic ice wedges. Dozens of yedoma exposures, from Yamal Peninsula to Chukotka, have been studied. Snow meltwater is considered to be the main source of ice‐wedge ice. The modern relationship between δ18O composition of ice‐wedge ice and winter temperature is used as a base for reconstruction. In modern ice wedges (elementary veins that have accumulated during the last 60–100 years) δ18O fluctuates between −14 and −20‰ in western Siberia and between −23 and −28‰ in northern Yakutia. The trend in δ18O distribution in ice wedges dated at 20−18 ka BP is similar to the modern one. For example, the δ18O values in Late Pleistocene wedges are more negative going from west to east by 8–10‰, i.e. from −19 to −25‰ in western Siberian ice wedges to −30 to −35‰ in northern Yakutia. However, values are as high as −28 to −33‰ in north Chukotka and the central areas of the Magadan Region and even as high as −23 to −29‰ in the east of Chukotka. The same difference between the oxygen isotope composition of ice wedges in the eastern and western regions of Siberian permafrost (about 8–10‰) is also preserved from 20−18 ka BP to the present: δ18O values obtained from large ice wedges from the Late Pleistocene vary from −19 to −25‰ in western Siberia to −30 to −35‰ in northern Yakutia. We conclude that, at 20−18 ka BP, mean January temperatures were about 8–12°C lower (in Chukotka up to 17–18°C) than at present.

Syngenetic Ice Wedges: Cyclical Formation, Radiocarbon Age and Stable Isotope Records by Yurij K. Vasil’chuk, Moscow University Press, Moscow, 2006. 404 pp. ISBN 5‐211‐05212‐9

ABSTRACTThe monograph summarises radiocarbon and stable isotope research on syngenetic ice wedges. The southern boundary of active and inactive ice wedges in Russian permafrost is re‐evaluated and revised. A new model of cyclical growth of syngenetic ice wedges is proposed, involving three cycles in ice‐wedge development: micro‐, meso‐ and macrocycles. Direct dating of syngenetic ice wedges can be carried out by accelerator mass spectrometry (AMS) radiocarbon dating of organic microinclusions and pollen concentrates from ice‐wedge ice. Dating reveals vertical and lateral variation in the age of yedoma at Duvanny Yar (NE Yakutia), one of the key syngenetic permafrost exposures in Eurasia. Radiocarbon ages and oxygen and deuterium isotopic values of syngenetic ice wedges in northern Russia and North America provide insights into palaeoenvironmental history and palaeogeocryology. Syngenetic ice wedges sometimes show complex cryostratigraphic relationships with other types of ice, including massive ice, icing ice and pingo ice. Comparison of isotope records from syngenetic ice wedges with those from Greenland ice cores reveals evidence for Dansgaard‐Oeschger (D/O) events preserved in Siberian permafrost. Copyright © 2013 John Wiley & Sons, Ltd.

Cryostratigraphy of late Pleistocene syngenetic permafrost (yedoma) in northern Alaska, Itkillik River exposure

Extremely ice-rich syngenetic permafrost, or yedoma, developed extensively under the cold climate of the Pleistocene in unglaciated regions of Eurasia and North America. In Alaska, yedoma occurs in the Arctic Foothills, the northern part of the Seward Peninsula, and in interior Alaska. A remarkable 33-m-high exposure along the lower Itkillik River in northern Alaska opened an opportunity to study the unmodified yedoma, including stratigraphy, particle-size distribution, soil carbon contents, morphology and quantity of segregated, wedge, and thermokarst-cave ice. The exposed permafrost sequence comprised seven cryostratigraphic units, which formed over a period from > 48,000 to 5,000 14C yr BP, including: 1) active layer; 2) intermediate layer of the upper permafrost; 3–4) two yedoma silt units with different thicknesses of syngenetic ice wedges; 5) buried peat layer; 6) buried intermediate layer beneath the peat; and 7) silt layer with short ice wedges. This exposure is comparable to the well known Mus-Khaya and Duvanny Yar yedoma exposures in Russia. Based on our field observations, literature sources, and interpretation of satellite images and aerial photography, we have developed a preliminary map of yedoma distribution in Alaska.

Changes in the development of frost wedges in the Middle Warta valley deposits (Central Poland)

In the alluvia of the middle Warta River valley, different kinds of frost wedges and fissures such as syngenetic ice wedge pseudomorphs, epigenetic ice wedge pseudomorphs and wedges, and fissures with primary mineral infilling were documented. The formation of ice wedges of the older generation is dated to the transition from the Middle Plenivistulian to the Upper Plenivistulian, and ice wedges of the younger generation and sand wedges date to the coldest period of the Upper Plenivistulian. The thawing of some ice wedges preceded the degradation of permafrost and was due to thermokrast processes in the Upper Plenivistulian. Keywords: ice-wedge pseudomorphs, sand wedges, thermokrast, Vistulian, middle Warta River valley, Central Poland

Isotopic composition of syngenetic ice wedges and palaeoclimatic reconstruction, western Taymyr, Russian Arctic

AbstractRecent, Holocene and Late Weichselian (Sartan) generations of syngenetic ice wedges developed in loess‐like and alluvial sediments were investigated along the coast of the Yenisey Bay from Sopochnaya Karga Cape (71°88'N, 82°68'E) to Dikson (73°31'N, 80°34'E). Ages of about 3.4 − 4.6 ka BP were determined for peat layer and wood fragments in ice‐rich deposits surrounding ice wedges near Dikson. The isotopic composition of these wedges reflects relatively cold winter temperatures in the Holocene. The lightest isotope composition characterises older ice wedges near Dikson and Sopochnaya Karga Cape. A warming trend between ice wedges of different generations was indicated by a distinct increase in O (4 − 5 ‰) and H (35 − 40‰) stable isotopes. Palaeotemperature reconstruction based on the data shows that winter temperatures during the formation of older generation ice wedges were lower than Holocene winter temperatures, indicating that they developed in the Late Weichselian (MIS2). The presence of syngenetic ice wedges strongly suggests that the coast of western Taymyr was not ice‐covered at this time. Copyright © 2011 John Wiley & Sons, Ltd.

Sedimentary characteristics and origin of the Late Pleistocene Ice Complex on north-east Siberian Arctic coastal lowlands and islands – A review

The origin of Late Pleistocene ice-rich, fine-grained permafrost sequences (Ice Complex deposits) in arctic and subarctic Siberia has been in dispute for a long time. Corresponding permafrost sequences are frequently exposed along seacoasts and river banks in Yedoma hills, which are considered to be erosional remnants of Late Pleistocene accumulation plains. Detailed cryolithological, sedimentological, geochronological, and stratigraphical results from 14 study sites along the Laptev and East Siberian seacoasts were summarized for the first time in order to compare and correlate the local datasets on a large regional scale. The sediments of the Ice Complex are characterized by poorly-sorted silt to fine-sand, buried cryosols, TOC contents of 1.2–4.8 wt%, and very high ground ice content (40–60 wt% absolute). A second large constituent of the Ice Complex are large syngenetic ice wedges, resulting in a total ice content of the Ice Complex of up to 80 vol%. Ice Complex deposits were mostly formed during the Middle Weichselian interstadial and/or during the Late Weichselian stadial periods. A conceptual model of nival lithogenesis of Ice Complex deposits was developed that integrates various other formation hypotheses. A combination of various local and regional paleogeographical, geological, and paleoclimate conditions controlled the formation of Ice Complex sequences during the Late Pleistocene in northern East Siberia. They are chronologically and stratigraphically, but not genetically equivalent to Eurasian and Alaskan loess deposits.

The Late Pleistocene–Holocene climate history in the western Todzha basin ( Eastern Tuva)

The Late Quaternary history of climate and deposition environments in the western Todzha basin has been reconstructed from the respective lacustrine and fluvial deposits. Data from sedimentary sections have provided clues to the causes and timing of sudden deposition changes, including those associated with Holocene tectonic activity in the Taskyl fault. Especially informative are permafrost, diatom, spore-pollen, and tree-ring data from a section at the Merzly Yar locality where frozen ground has preserved the pristine rhythmic pattern of sediments. The Merzly Yar section stores a record of dramatic consequences of large earthquakes generated by the fault which produced a large damlake. The revealed pattern of discontinuous limnic deposition, with prominent tree markers and syngenetic ice wedges, places exact constraints on the stratigraphy of the section and allows its correlation with Holocene climate events within the intervals of fossil soils and vegetation.

Dating of syngenetic ice wedges in permafrost with 36Cl

A new method of permafrost dating with the cosmogenic radionuclide 36Cl is presented. In the first application, syngenetic ice wedges are dated using the ratio of 36Cl and Cl concentrations in ice as the signal. 36Cl is produced in the atmosphere by nuclear reactions of cosmic rays on argon. Stable chlorine enters the atmosphere from the oceans. Their ratio does not depend on chloride concentration in precipitations and on sublimation of snow. In situ production of 36Cl in permafrost ice via cosmic ray-induced reactions and neutron capture are calculated and the dating age limit is estimated as 3 million years. 36Cl/Cl ratios in permafrost samples from cape Svyatoy Nos (Laptev Sea coast), North-Eastern Siberia, are measured by accelerator mass spectrometry. Analysis of the first results and the calculated dates support the feasibility of the 36Cl permafrost dating method

Syngenetic sand veins and anti‐syngenetic sand wedges, Tuktoyaktuk Coastlands, western Arctic Canada

AbstractSand‐sheet deposits of full‐glacial age in the Tuktoyaktuk Coastlands, western Arctic Canada, contain syngenetic sand veins 1–21 cm wide and sometimes exceeding 9 m in height. Their tall and narrow, chimney‐like morphology differs from that of known syngenetic ice wedges and indicates an unusually close balance between the rate of sand‐sheet aggradation and the frequency of thermal‐contraction cracking. The sand sheets also contain rejuvenated (syngenetic) sand wedges that have grown upward from an erosion surface. By contrast, sand sheets of postglacial age contain few or sometimes no intraformational sand veins and wedges, suggesting that the climatic conditions were unfavourable for thermal‐contraction cracking. Beneath a postglacial sand sheet near Johnson Bay, sand wedges with unusually wide tops (≤3.9 m) extend down from a prominent erosion surface. The wedges grew vertically downward during deflation of the ground surface, and represent anti‐syngenetic wedges. The distribution of sand veins and wedges within the sand sheets indicates that the existence of continuous permafrost during sand‐sheet aggradation can be inferred confidently only during full‐glacial conditions. Copyright © 2007 John Wiley & Sons, Ltd.

AMS14C Dating of Pollen Concentrate from Late Pleistocene ICE Wedges From the Bison and Seyaha Sites in Siberia

Accelerator mass spectrometry (AMS) radiocarbon dates of pollen concentrate were obtained from multistage syngenetic ice wedges of cross-sections from the Late Pleistocene Bison site, located along the Lower Kolyma River (68°34'N, 158°34'E), from ∼43,600 to ∼26,200 BP, and 3 AMS14C dates of pollen concentrate in ice wedges from the Seyaha site cross-section, located on the east coast of the Yamal Peninsula (70°10'N, 72°34'E), from ∼22,400 to ∼25,200 BP. Pollen concentrate samples were prepared using a special pretreatment procedure. Pollen and spores from ice-wedge ice signalize a regional pollen rain. Therefore,14C-dated extracts of pollen and spores from ice-wedge ice enable an adequate reconstruction and chronology of landscape dynamics on a regional scale. The pollen and spores were well preserved despite numerous redepositions in the penecontemporaneous structure in which they were found. Thus, a comparison with dates on other fractions from the same sample is necessary. The youngest date is the most reliable among the intersample AMS14C dates from the ice and permafrost sediments.

AMS14C dating and stable isotope plots of Late Pleistocene ice-wedge ice

Strategy for AMS14C dating of organic micro inclusions from syngenetic ice-wedge ice is considered. AMS14C dates are interpreted in terms of fictitious aging of ice-wedge and permafrost sediments due to high concentration of allochthonous organic material. The dating of organic material from small sample, gives the reliable 14C age. The 14C dates from syngenetic ice-wedges are compared with the dates of the host sediments surrounding syngenetic ice wedges. AMS14C dating of small samples of ice-wedge ice yields to set δ18O plots from ice-wedges to the time scale and to correlate them with ice core δ18O record.

The AMS dating of pollen from syngenetic ice–wedge ice

The features of pollen occurrence in ice–wedge ice such as: size of pollen of tundra plants, incoming pollen into frost cracks together with melt water, dust and partially from host sediment and also clay envelopes around pollen grains caused the pretreatment methods of ice–wedge ice samples. Good preservation of thin-wall pollen grains of Salix and Liliaceae after pretreatment evidenced appropriate pretreatment procedure. There is evident correlation between pollen dates and re-deposited pollen and spores content. However an interpretation of 14C dating of pollen concentrate is required independent time scale such as annual laminas or the AMS dates of macro or microfossils.

AMS14C dating and stable isotope plots of Late Pleistocene ice-wedge ice

Strategy for AMS14C dating of organic micro inclusions from syngenetic ice-wedge ice is considered. AMS14C dates are interpreted in terms of fictitious aging of ice-wedge and permafrost sediments due to high concentration of allochthonous organic material. The dating of organic material from small sample, gives the reliable 14C age. The 14C dates from syngenetic ice-wedges are compared with the dates of the host sediments surrounding syngenetic ice wedges. AMS14C dating of small samples of ice-wedge ice yields to set δ18O plots from ice-wedges to the time scale and to correlate them with ice core δ18O record.

Radiocarbon Dating of Pollen and Spores from Ice Wedges of the Yamal and Kolyma Regions

Radiocarbon dating of the pollen concentrate from late Pleistocene syngenetic ice wedges was carried out using accelerator mass spectrometry (AMS) in Seyakha and Bizon sections. Comparison of the results with palynological data and the results of AMS radiocarbon dating previously obtained for other organic fractions of the same samples allowed the accuracy of dating of different fractions to be evaluated. Quantitative criteria for data evaluation in terms of possible autochthonous or allochthonous accumulation of the material on the basis of pre-Pleistocene pollen content in these samples were considered. Paleoecological information content of pollen spectra from late Pleistocene syngenetic wedge ice was evaluated.

14C Dating of Peat and δ18O-δd in Ground Ice From Northwest Siberia

We present new radiocarbon dates from a number of Holocene peat deposits along a north-south transect across the Yamal Peninsula. The samples were collected from frozen peat deposits with large ice wedges in: the northern tundra near Seyaha Settlement, in the Central Yamal Peninsula, the southern tundra in Shchuch'ya River valley at the Edem'yaha mouth, the southern part of the Yamal Peninsula, and the southern forest tundra near Labytnangi Town. 14C dates of wood remains from the tundra in the Yamal Peninsula could be used to reconstruct a northern limit of forest during the Holocene Optimum. The wood layers at the bottom of the peat give evidence for immigration of trees further north beyond the present boundary. The first forest appearance in the Seyaha River valley area is dated about 9 ka BP according to the oldest peat date in the Seyaha cross section. This suggests that summer temperatures were higher than at present. Very fast accumulation of peat (around 5 m/ka: about 9–8 ka BP at Seyaha and about 7–6 ka BP at Shchuch'ya) also supports this observation.In contrast, oxygen isotope composition of Holocene syngenetic ice wedges from the area (δ18O= −19.1 to −20.3‰ in the Seyaha cross-section and −17.3 to −20.3‰ in the Shchuch'ya River) show that winter temperatures were significantly lower than presently, i.e. the climate during the Holocene Optimum was slightly more continental. The frozen peat near Labytnangi has thawed during the last 20 years, indicating global warming.

Radiocarbon Dating of δ18O-δD Plots in Late Pleistocene Ice-Wedges of the Duvanny Yar (Lower Kolyma River, Northern Yakutia)

The Duvanny Yar cross-section located in the Lower Kolyma River valley of Northern Yakutia (69°N, 158°E, height above the Kolyma River level 55 m), has been studied and dated in detail by radiocarbon. The sequence mainly consists of sandy loam sediments with large syngenetic ice wedges. Their width at the top is 1–3.5 m. Allochthonous organic material occurs in high content, concentrating as 0.5–0.7 m lenses. Shrub fragments, twigs, and mammoth bones are accumulated in peaty layers. Through interpolation based on a series of 14C dates, dating of the host sediments provides an approximate age for the ice wedges. The 14C dates of various types of organic material are sometimes very close, but not all in agreement. Therefore, the dates do not accurately show the age of the δ18O and δD plots. A new approach is developed to a 14C dating strategy of syncryogenic sediments with high admixture of allochthonous organic material. The main purpose of this study is to consider detection of inversions or disturbances in the syngenetic permafrost sediment at the Duvanny Yar cross-section by 14C date series. Direct accelerator mass spectrometry (AMS) dating of the ice confirmed the relatively young age of ice wedges.

AMS-dating of Late Pleistocene and Holocene syngenetic ice-wedges

We discuss the 14C dating (both conventional and AMS) of Siberian permafrost sediments and ice-wedge ice. Direct dating of Late Pleistocene and Holocene syngenetic ice-wedges was done on organic material included in the ice. The time of ice formation (in 14C years) is 21,000–14,000 BP for Seyaha, and 7100 BP for Shchuch’ya. The AMS dates show that the ice-wedges stratification is normal, i.e., the older ice is located below the younger. The 14C dates yield for the first time a timescale (in 14C years) for paleoclimatic indicators (oxygen and hydrogen isotope ratios from the ice).