Article

Thermokarst sediments and sedimentary structures, Tuktoyaktuk Coastlands, western Arctic Canada

February 2001
Global and Planetary Change 28(1)

Authors:

University of Sussex

Abrupt climate warming during glacial–interglacial transitions promotes regional thermokarst activity in areas of ice-rich permafrost. The ensuing thaw-related processes of melt-out, soft-sediment deformation and resedimentation may produce widespread thermokarst sediments and sedimentary structures. Examples of the most distinctive thermokarst sediments and sedimentary structures from the Tuktoyaktuk Coastlands, western Arctic Canada, comprise: (1) soft-sediment deformation structures (thermokarst involutions) in a palaeoactive layer; (2) ice-wedge casts and composite-wedge casts; (3) peaty to sandy diamicton deposited mainly by debris flows in retrogressive thaw slumps; and (4) a basal unit of diamicton and/or impure sand in some thermokarst-basin sequences, deposited by progradation of resedimented materials in thermokarst lakes. Many of the thermokarst sediments and sedimentary structures in the Tuktoyaktuk Coastlands formed as a result of rapid climate warming during the last glacial–interglacial transition, although some continue to form at present due to local (non-climatic) factors.Identification of thermokarst sediments and sedimentary structures in the geological record requires evidence for the thaw of excess ice. Direct evidence for the former occurrence of excess ice includes: (1) ice-wedge casts; (2) composite-wedge casts; (3) lenticular platy microstructures in frost-susceptible sediment; (4) certain near-surface brecciation of frost-susceptible bedrock; and (5) ramparted depressions attributed to the decay of frost mounds. Indirect evidence for former excess ice results where thaw consolidation initiates soft-sediment deformation or gelifluction.

Cold climatic snaps during the Eocene-Oligocene transition in the central Tibetan Plateau: Implications for ice-induced sedimentary structures and isotope geochemistry

Article

Mar 2024
PALAEOGEOGR PALAEOCL

The Eocene-Oligocene transition was a time of major climate instability and a shift from an ice-free world to a predominant icehouse climate. Identifying the ancient glacial deposits and their associated sedimentary structures are of paramount significance for understanding the Earth’s climate in the Cryogenian Period. Ice-induced sedimentary structures (IISS) are considered as types of primary structures preserved on surfaces and in upper parts of unconsolidated sediments by physical cryospheric processes of seasonal ice freezing and thawing, and therefore sensitive not only to climate, but also to paleogeography, hydrology, and type of environment. Despite the common occurrence of modern IISS in a wide variety of environments, from high-latitude regions to low-latitude areas of high altitude, available records from ancient geologic archives are scarce. Herein, we integrated sedimentological and geochemical proxies to study IISS and geochemical signals as reliable indicators of cold climate in an outstanding example of the Eocene-Oligocene interval from the Niubao Formation in the Lunpola Basin, central Tibet. Detailed field sedimentological, petrographic microscopic investigations, and bulk carbonate oxygen (δ18Ocarb) and carbon (δ13Ccarb) isotope geochemistry were conducted in this lacustrine succession. Seven sets of IISS are represented by ice crystal marks, frozen cracks, ice-frozen bubbles, ice-expanding laminae, ice-rafted debris (dropstones), ice water pea-like, and ice water pits. They are classified into three groups based on major deriving mechanisms: ice-related crystal marks, deformation-related ice structures, and gravitational fall IISS. Positive δ18Ocarb excursions at the Eocene-Oligocene transition provide evidence of a shift toward cold or near-freezing climatic snaps in response to global cooling episodes at this time. Integrating the paleogeomorphic scenario of central Tibet with the stratigraphically reported IISS and glendonite clusters, the results support that the Lunpola lake sustained cold or near-freezing conditions at Eocene-Oligocene transition. These findings provide one of the most comprehensive sedimentological and isotopic analyses of ancient IISS and a more direct spatial-temporal constraint for the regional climate system of central Tibet.

Typical Soft–Sediment Deformation Structures Induced by Freeze/Thaw Cycles: A Case Study of Quaternary Alluvial Deposits in the Northern Qiangtang Basin, Tibetan Plateau

Article

Full-text available

Jul 2019

With the objective of establishing a distinction between deformation structures caused by freeze/thaw cycles and those resulting from seismic activity, we studied three well–exposed alluvial deposits in a section at Dogai Coring, northern Qiangtang Basin, Tibetan Plateau. Deformation is present in the form of plastic structures (diapirs, folds and clastic dykes), brittle structures (micro–faults) and cryogenic wedges. These soft–sediment deformation features (except the micro–faults) are mainly characterized by meter–scale, non–interlayered, low–speed and low–pressure displacements within soft sediments, most commonly in the form of plastic deformation. Taking into account the geographic setting, lithology and deformation features, we interpret these soft–sediment deformation features as the products of freeze/thaw cycles, rather than of earthquake–induced shock waves, thus reflecting regional temperature changes and fluctuations of hydrothermal conditions in the uppermost sediments. The micro–faults (close to linear hot springs) are ascribed to regional fault activity; however, we were unable to identify the nature of the micro–faults, perhaps due to disturbance by subsequent freeze/thaw cycles. This study may serve as a guide to recognizing the differences between deformation structures attributed to freeze/thaw cycles and seismic processes.

Review article: Retrogressive thaw slump characteristics and terminology

Article

Full-text available

Oct 2024
TC

Retrogressive thaw slumps (RTSs) are spectacular landforms that occur due to the thawing of ice-rich permafrost or melting of massive ground ice, often in hillslope terrain. RTSs occur in the Arctic, the subarctic, and high mountain (Qinghai–Tibet Plateau) permafrost regions and are observed to expand in size and number due to climate warming. As the observation of RTSs is receiving more and more attention due to their important role in permafrost thaw; impacts on topography; mobilization of sediment, carbon, nutrients, and contaminants; and their effects on downstream hydrology and water quality, the thematic breadth of studies increases and scientists from different scientific backgrounds and perspectives contribute to new RTS research. At this point, a wide range of terminologies originating from different scientific schools is used, and we identified the need to provide an overview of variable characteristics of RTSs to clarify terminologies and ease the understanding of the literature related to RTS processes, dynamics, and feedbacks. We review the theoretical geomorphological background of RTS formation and landform characteristics to provide an up-to-date understanding of the current views on terminology and underlying processes. The presented overview can be used not only by the international permafrost community but also by scientists working on ecological, hydrological, and biogeochemical consequences of RTS occurrence and by remote-sensing specialists developing automated methods for mapping RTS dynamics. The review will foster a better understanding of the nature and diversity of RTS phenomena and provide a useful base for experts in the field but also ease the introduction to the topic of RTSs for scientists who are new to it.

Review article: Retrogressive thaw slump theory and terminology

Preprint

Full-text available

Jan 2024

Retrogressive thaw slumps (RTSs in plural and RTS in singular) are spectacular landforms that occur due to the thawing of ice-rich permafrost or melting of massive ground ice often in hillslope terrain. RTSs occur in the Arctic, Subarctic as well as high mountain (Tibetan Plateau) permafrost regions and are observed to expand in size and number due to climate warming. As the observation of RTS is receiving more and more attention due to their important role in permafrost thaw, impacts on topography, mobilization of sediment, carbon, nutrients, and contaminants, and their effects on downstream hydrology and water quality, the thematic breadth of studies increases and scientists from different scientific backgrounds and perspectives contribute to new RTS research. At this point, a wide range of terminologies originating from different scientific schools is being used and we identified the need to provide an overview of theoretical approaches, terms, and variable characteristics of RTS to clarify terminologies and create common ground for understanding RTS processes, dynamics, and feedbacks. We here review the theoretical geomorphological background of RTS formation and landform characteristics to provide an up-to-date understanding of the current views on terminology and underlying processes. The presented overview can be used not only by the international permafrost community but also by scientists working on ecological, hydrological, and biogeochemical consequences of RTS occurrence as well as remote sensing specialists developing automated methods for mapping RTS dynamics. The framework will foster a better understanding of the nature and diversity of RTS phenomena and provide a useful base for experts in the field but also ease the introduction to the topic of RTSs for scientists who are new to it.

Climatic drivers of limnological change in Iqallukvik Lake, Tuktoyaktuk, Northwest Territories, Canada

Article

Full-text available

Mar 2022

The Tuktoyaktuk coastlands contain thousands of lakes along an area of the Beaufort Sea in the rapidly changing western Arctic. These lakes may be susceptible to a range of impacts associated with climate warming, including potential increased marine influence changes associated with reduced lake ice cover and thawing permafrost. We examined a ²¹⁰Pb-dated sediment core from Iqallukvik Lake to reconstruct ecosystem changes over the last several hundred years using sediment particle size analysis and diatom subfossils. Changes in sediment texture over the past ∼200 years were broadly aligned with inferred changes in regional precipitation, known to be an important driver of regional lake level in the Tuktoyaktuk coastlands. Diatoms were functionally absent at the bottom of the sediment core, but increased after ∼1850, likely in response to early warming, with further floristic changes due to accelerated warming over the last century. Diatoms throughout the core are predominantly freshwater species tolerant of broad salinity concentrations, indicating that Iqallukvik Lake is likely subject to minimal direct marine influence and has not been impacted by notable inundation over the recent past. Overall, this research suggests that climate impacts Iqallukvik Lake mainly on the length of the ice-free season.

Pingo-like mounds and possible polyphase periglaciation/glaciation at/adjacent to the Moreux impact crater

Chapter

Full-text available

Jan 2021

Small-sized mounds that exhibit a sweep of similarities, that is, shape, scale (in height and long axes), surface features, and framing landscapes with perennially ice-cored mounds on Earth, that is, pingos, occur within and adjacent to the Moreux impact-crater (42.1°N; 44.4°E). The crater is located in northern Arabia Terra and lies astride the Martian crustal-dichotomy. Here, we do three things: 1.Describe the possible glacial and periglacial landscapes in which the Moreux mounds are ensconced and attempt to synthesize each of these landscape types with “open” or “closed” pingo formation-pathways. 2.Suggest that the closed-system hypothesis, if valid, places mound origin in a scale of time that is neither current nor in the recent past. 3.Suggest that the open-system hypothesis, if valid, situates mound origin in a scale of time that could be current or in the recent past.

Possible polyphase periglaciation and glaciation adjacent to the Moreux impact-crater, Mars

Research

Full-text available

Mar 2021

Possible polyphase periglaciation and glaciation, adjacent to the, Moreux impact-crater, Mars

Article

Mar 2021

The cyclicity and temporal succession of glacial-periglacial periods or epochs are keynotes of cold-climate geology on Earth. Relatively recent work within the Mars community has begun to dissect the mid- to higher-latitudinal terrain of Mars for analogical evidence of similar cold-climate cyclicity and succession. Here, we carry on with this work by focusing on the terrain immediately to the north of the Moreux impact-crater (40–44° N, 43–47° E). The crater is located in northern Arabia Terra, to the south of Protonilus Mensae. It lies astride of and postdates Mars' crustal-dichotomy. The latter is a global geological-boundary that separates the ancient southern-highlands from the relatively younger northern-lowland plains. Using cross-cutting relationships, relative stratigraphy and crater-size frequency distributions (CSFDs) we identify three glacial and two periglacial periods that are temporally intertwined and differentiated by a suite of features unique to each of these periods. For example, we report and discuss clusters of pingo-like mounds amidst ridge and trough terrain or “brain terrain”. On Earth, the former are the work of freeze-thaw cycling; on Mars, the latter are thought to be glacial remnants. In turn, the brain terrain is underlain by small-sized polygons possibly formed by thermal contraction cracking and with margins underlain by degraded ice-wedges. Age estimates derived of CSFDs suggest that the polygonised terrain could as much as ~100 Ma, whereas the brain terrain and pingo-like mounds are thought to be ~1–~10 Ma. Possible terminal-moraines that intercept brain-terrain fragments point to an even more recent period of glaciation. If the CSFD age-estimates are valid, then the polygons that underlie the brain terrain and incise the basin floors of our study zone could be an order of magnitude older than most of the age estimates associated with polygonised terrain at other locations on Mars. The fact that there are two distinct periods of polygonization and periglacial activity with a wide offset of time within one relatively small study zone also highlights the extent to which the freeze-thaw cycling of water might be rooted as iteratively and as deeply in Mars' geological history as is its glaciation.

Detailed Characterization and Monitoring of a Retrogressive Thaw Slump from Remotely Piloted Aircraft Systems and Identifying Associated Influence on Carbon and Nitrogen Export

Article

Full-text available

Jan 2021

Ice-rich permafrost landscapes are sensitive to ongoing changes in climate. Permafrost retrogressive thaw slumps (RTSs) represent one of the more abrupt and prolonged disturbances, which occur along Arctic river and lake shorelines. These features impact local travel and infrastructure, and there are many questions regarding associated impacts on biogeochemical cycling. Predicting the duration and magnitude of impacts requires that we enhance our knowledge of RTS geomorphological drivers and rates of change. Here we demonstrate the utility of remotely piloted aircraft systems (RPAS) for documenting the volumetric change, associated drivers and potential impacts of the largest active RTS along the Old Crow River in Old Crow Flats, Yukon, Canada. RPAS surveys revealed that 29,174 m3 of sediment was exported during the initial evacuation in June 2016 and an additional 18,845 m3 continued to be exported until June 2019. More sediment export occurred during the warmer 2017 summer that experienced less cumulative rainfall than summer 2018. However, several rain events during 2017 were of higher intensity than during 2018. Overall mean soil organic carbon (SOC) and total nitrogen (TN) within sampled thaw slump sediment was 1.36% and 0.11%, respectively. A combination of multispectral, thermal and irradiance (derived from the RPAS digital surface model) data provided detailed classification of thaw slump floor terrain types including raised dry clay lobes, shaded and relatively stable, and low-lying evacuation-prone sediments. Notably, the path of evacuation-prone sediments extended to a series of ice wedges in the northern headwall, where total irradiance was highest. Using thaw slump floor mean SOC and TN values in conjunction with sediment bulk density and thaw slump fill volume, we estimated that 713 t SOC and 58 t TN were exported to the Old Crow River during the three-year study. Findings showcase the utility of high-resolution RPAS datasets for refining our knowledge of thaw slump geomorphology and associated impacts.

Mid- to Late Holocene environmental dynamics on the Yukon Coastal Plain and Herschel Island (Canada) - envidence from polygonal peatlands and lake sediment

Thesis

Full-text available

Feb 2017

Juliane Wolter

Climate-driven thaw of permafrost preserved glacial landscapes, northwestern Canada

Article

Feb 2017
GEOLOGY

Ice-marginal glaciated landscapes demarcate former boundaries of the continental ice sheets. Throughout circumpolar regions, permafrost has preserved relict ground ice and glacigenic sediments, delaying the sequence of postglacial landscape change that transformed temperate environments millennia earlier. Here we show that within 7 × 10⁶ km² of glaciated permafrost terrain, extensive landscapes remain poised for major climate-driven change. Across northwestern Canada, 60-100-km-wide concentric swaths of thaw slump-affected terrain delineate the maximum and recessional positions of the Laurentide Ice Sheet. These landscapes comprise ~17% of continuous permafrost terrain in a 1.27 × 10⁶ km² study area, indicating widespread preservation of late Pleistocene ground ice. These thaw slump, relict ground ice, and glacigenic terrain associations are also evident at the circumpolar scale. Recent intensification of thaw slumping across northwestern Canada has mobilized primary glacial sediments, triggering a cascade of fluvial, lacustrine, and coastal effects. These geologically significant processes, highlighted by the spatial distribution of thaw slumps and patterns of fluvial sediment mobilization, signal the climate-driven renewal of deglaciation and postglacial permafrost landscape evolution.

Passive Seismology: Lightweight and Rapid Detection of Arctic Subsea and Sub‐Aquatic Permafrost

Article

Full-text available

Sep 2024

Low sea levels during the last Ice Age exposed millions of square kilometers of Arctic shelves which have been subsequently submerged, creating subsea permafrost. In onshore settings, permafrost can also exist beneath water bodies such as coastal lagoons, rivers, and thermokarst lakes. We explored passive seismology as a method for mapping unfrozen sediment thickness above subsea and sub‐aquatic permafrost. We present passive seismic data collected with the Mobile Ocean Bottom Seismic Instrument (MOBSI) from the Beaufort Sea near Tuktoyaktuk in Canada, Ivashkina Lagoon on the Bykovsky Peninsula, as well as a lake and river in the Lena Delta, Siberia, Russia. We use borehole data and frost probe measurements to identify permafrost‐related H/V measurement peaks and calibrate shear wave velocities for frequency‐to‐depth conversion. We employ the shortest path and maximum signal amplitude to connect peaks and generate geological profiles. The MOBSI detected the ice‐bonded permafrost table beneath the Beaufort Sea, as well as beneath a Siberian lake and lagoon. At Tuktoyaktuk, an ocean bottom seismometer revealed a 5% scatter about the peak frequency for three‐minute time windows and over 8 hr of recording time. With peak frequencies ranging from 4.9 ± 0.2 Hz to 27.6 ± 1.4 Hz, the depth to subsea permafrost ranged from 1.4 ± 0.1 m bsl at the shoreline to 14.0 ± 0.4 m bsl 240 m offshore. Given an accurate shear wave velocity, our findings highlight that MOBSI deployment times as short as 3 min are adequate for detecting Arctic subsea and sub‐aquatic permafrost.

Retrogressive thaw slump susceptibility in the northern hemisphere permafrost region

Article

Full-text available

May 2024
EARTH SURF PROC LAND

Mean annual temperatures in the Arctic and subarctic have increased in recent decades, increasing the number of permafrost hazards. Retrogressive thaw slumps (RTSs), triggered by the thawing of ground ice in permafrost soil, have become more common in the Arctic. Many studies report an increase in RTS activity on a local or regional scale. In this study, the primary goals are to (i) examine the spatial patterns of the RTS occurrences across the circumpolar permafrost region, (ii) assess the environmental factors associated with their occurrence, and (iii) create the first susceptibility map for RTS occurrence across the Northern Hemisphere. Based on our results, we predicted high RTS susceptibility in the continuous permafrost regions above the 60th latitude, especially in northern Alaska, northwestern Canada, the Yamal Peninsula, eastern Russia and the Qinghai-Tibetan Plateau. The model indicated that air temperature and soil properties are the most critical environmental factors for the occurrence of RTSs on a circumpolar scale. Especially, the climatic conditions of thaw season were highlighted. This study provided new insights into the circumpolar susceptibility of ice-rich permafrost soils to rapid permafrost-related hazards like RTSs and the associated impacts on landscape evolution, infrastructure, hydrology and carbon fluxes that contribute to global warming. K E Y W O R D S: circumpolar susceptibility, mass-movements, permafrost degradation, retrogressive thaw slumps, statistical modeling, Thermokarst

A glaciotectonic landform in the Shyok valley, Trans-Himalayan Karakoram Range, India

Article

Full-text available

Mar 2024

This study reports and discusses the first case of glaciotectonic landforms in the Shyok valley of the Trans-Himalayan Karakoram Range, Ladakh, where a large decomposed granite megablock (8.2 km2) along with underlying diamicton is thrust over the unconsolidated Quaternary glaciofluvial sediments along a fault gouge zone near the village of Khalsar. The absence of deformation signatures below the fault gouge indicates that the brittle fault acted as a décollement surface under frozen conditions along which the glaciotectonic megablock was translated. The other deformation features include slickensides, ductile shear, thrust propagation fold noses, clastic dykes and rafts of granite and slate within the diamicton sediments. These features indicate a subglacial glaciotectonic nappe origin of the landform. The presence of juxtaposed brittle to ductile deformation fabric, clastic dykes and the superimposition of deformed decomposed granite and diamicton over the undisturbed fluvial sediments indicates a permafrost glacial margin and proglacial environment under sufficient subglacial hydrodynamic conditions for the entrapment and transportation of the glaciotectonic megablock. The deformation fabric consistently shows a southeast orientation, indicating an advancing glacier motion from northwest to southeast. The Siachen Glacier which formerly flowed down the Nubra valley is the most likely cause of the Khalsar glaciotectonic landform.

Ice Exploration on Mars: Whereto and when?

Chapter

Jan 2024

The role of dead ice in transforming glacier forelands under the rapid climate warming of recent decades, Oscar II Land, Svalbard

Article

Full-text available

Jun 2023

The rapid climate changes of recent decades are causing rapid glacier recession in the high Arctic and the loss of large patches and blocks of dead ice. Their temporally differentiated melting is very significantly transforming the relief of marginal zones, creating dead-ice landscapes. The article focuses on dead-ice degradation processes in the forelands of two glaciers (Erikkabreen and Haakenbreen) on Oscar II Land in Spitsbergen. Detailed in-field geomorphological mappings have been conducted twice (in 1989 and 2022) in the two glaciers' forelands. These were combined with analysis of available photogrammetry and Digital Elevation Models, allowing the authors to describe the dynamics of dead-ice melting processes within various landforms and the effect of those processes on the forms' ultimate morphology. This provided a broad view of the trajectory of melt processes depending on local geomorphological and hydrological conditions. Particular attention was paid to the interactions between the evolution of permafrost and the course of melting of dead ice. In light of the highly dynamic thermokarst processes in the forelands of Svalbard glaciers, the term ‘dead-ice-rich permafrost’ is proposed. It was found that global climate changes are increasing the role of dead ice in transforming the relief of glacier forelands, thereby increasing the occurrence of dead-ice landscapes. The conclusions confirmed those for other contemporary glaciation areas and may significantly help in interpreting the morphogenesis of glacial relief formed during past continental glaciations.

Permafrost in the Cretaceous supergreenhouse

Article

Full-text available

Dec 2022

Earth’s climate during the last 4.6 billion years has changed repeatedly between cold (icehouse) and warm (greenhouse) conditions. The hottest conditions (supergreenhouse) are widely assumed to have lacked an active cryosphere. Here we show that during the archetypal supergreenhouse Cretaceous Earth, an active cryosphere with permafrost existed in Chinese plateau deserts (astrochonological age ca. 132.49–132.17 Ma), and that a modern analogue for these plateau cryospheric conditions is the aeolian–permafrost system we report from the Qiongkuai Lebashi Lake area, Xinjiang Uygur Autonomous Region, China. Significantly, Cretaceous plateau permafrost was coeval with largely marine cryospheric indicators in the Arctic and Australia, indicating a strong coupling of the ocean–atmosphere system. The Cretaceous permafrost contained a rich microbiome at subtropical palaeolatitude and 3–4 km palaeoaltitude, analogous to recent permafrost in the western Himalayas. A mindset of persistent ice-free greenhouse conditions during the Cretaceous has stifled consideration of permafrost thaw as a contributor of C and nutrients to the palaeo-oceans and palaeo-atmosphere.

A billion or more years of possible periglacial/glacial cycling in Protonilus Mensae, Mars

Preprint

Full-text available

Oct 2022

Rare bacterial biosphere is more environmental controlled and deterministically governed than abundant one in sediment of thermokarst lakes across the Qinghai-Tibet Plateau

Article

Full-text available

Jul 2022

Thermokarst lakes are widely distributed in cold regions as a result of ice-rich permafrost thaw. Disentangling the biogeography of abundant and rare microbes is essential to understanding the environmental influences, assembly mechanisms, and responses to climate change of bacterial communities in thermokarst lakes. In light of this, we assessed the abundant and rare bacterial subcommunities in sediments from thermokarst lakes across the Qinghai-Tibet Plateau (QTP). The operational taxonomic unit (OTU) richness was more strongly associated with location and climate factors for abundant subcommunities, while more strongly associated with physicochemical variables for rare subcommunities. The relative abundance of abundant and rare taxa showed opposite patterns with abundant taxa having greater relative abundance at higher latitude and pH, but at lower mean annual precipitation and nutrients. Both the abundant and rare subcommunities had a clear distribution pattern along the gradient of latitude and mean annual precipitation. Abundant subcommunities were dominantly shaped by dispersal limitation processes (80.9%), while rare subcommunities were shaped almost equally by deterministic (47.3%) and stochastic (52.7%) processes. The balance between stochastic and deterministic processes was strongly environmentally adjusted for rare subcommunities, while not associated with environmental changes for abundant subcommunities. The results shed light on biogeography patterns and structuring mechanisms of bacterial communities in thermokarst lakes, improving our ability to predict the influences of future climate change on these lakes.

A billion or more years of possible periglacial/glacial cycling in Protonilus Mensae, Mars

Article

Full-text available

Jun 2022
ICARUS

The long-term cyclicity and temporal succession of glacial-periglacial (or deglacial) periods or epochs are keynotes of Quaternary geology on Earth. Relatively recent work has begun to explore the histories of the mid-to higher-latitudinal terrain of Mars, especially in the northern hemisphere, for evidence of similar cyclicity and succession in the Mid to Late Amazonian Epoch. Here, we carry on with this work by focusing on Protonilus Mensae [PM] (43-49 0 N, 37-59 0 E). More specifically , we discuss, describe and evaluate an area within PM that straddles a geological contact between two ancient units: [HNt], a Noachian-Hesperian Epoch transition unit; and [eHT] an early Hesperian Epoch transition unit. Dark-toned terrain within the eHt unit (HiRISE image ESP_028457_2255) shows continuous coverage by structures akin to clastically-sorted circles [CSCs]. The latter are observed in permafrost regions on Earth where the freeze-thaw cycling of surface and/or near-surface water is commonplace and cryoturbation is not exceptional. The crater-size frequency distribution of the dark-toned terrain suggests a minimum age of ~100 Ma and a maximum age of ~1 Ga. The age estimates of the candidate CSCs fall within this dispersion. Geochronologically, this places the candidate CSCs among the oldest periglacial landforms identified on Mars so far, by at least one and possibly two orders of magnitude. Unit HNt is adjacent to unit eHt and shows surface material that is relatively light in tone. The coverage is topographically irregular and, at some locations, discontinuous. Amidst the light-toned surface, structures are observed that are akin to clastically non-sorted polygons [NSPs] and polygonised thermokarst-depressions on Earth. Terrestrial polygon/thermokarst assemblages occur in permafrost regions where the freeze thaw cycling of surface and/or near-surface water is commonplace and the permafrost is ice-rich. The crater-size frequency distribution of the light-toned terrain suggests a minimum age of ~10 Ma and a maximum age of ~100 Ma. The age estimates of the candidate ice-rich assemblages fall within this dispersion. Geochronologically, this places them well beyond the million-year ages associated with most of the other candidate ice-rich assemblages reported in the literature. Stratigraphically intertwined with the two possible periglacial terrains are landforms and landscape features (observed or unobserved but modelled) that are indicative of relatively recent glaciation (~10 Ma-100 Ma) and glaciation long past (≥~ 1 Ga) to decametres of depth: glacier-(cirque) like features; viscous-flow features, lobate-debris aprons; moraine-like ridges at the fore, sides and midst of the aprons; and, patches of irregularly shaped (and possibly volatile-depleted) small-sized ridge/trough assemblages. Collectively, this deeply-seated intertwining of glacial and periglacial cycles suggests that the Mid to Late Amazonian Epochs might be more Earth-like in their cold-climate geology than has been thought hitherto.

A billion or more years of possible periglacial/glacial cycling in Protonilus Mensae, Mars

Article

May 2022
ICARUS

The long-term cyclicity and temporal succession of glacial-periglacial (or deglacial) periods or epochs are keynotes of Quaternary geology on Earth. Relatively recent work has begun to explore the histories of the mid- to higher-latitudinal terrain of Mars, especially in the northern hemisphere, for evidence of similar cyclicity and succession in the Mid to Late Amazonian Epoch. Here, we carry on with this work by focusing on Protonilus Mensae [PM] (43–49⁰ N, 37–59⁰ E). More specifically, we discuss, describe and evaluate an area within PM that straddles a geological contact between two ancient units: [HNt], a Noachian-Hesperian Epoch transition unit; and [eHT] an early Hesperian Epoch transition unit. Dark-toned terrain within the eHt unit (HiRISE image ESP_028457_2255) shows continuous coverage by structures akin to clastically-sorted circles [CSCs]. The latter are observed in permafrost regions on Earth where the freeze-thaw cycling of surface and/or near-surface water is commonplace and cryoturbation is not exceptional. The crater-size frequency distribution of the dark-toned terrain suggests a minimum age of ~100 Ma and a maximum age of ~1 Ga. The age estimates of the candidate CSCs fall within this dispersion. Geochronologically, this places the candidate CSCs among the oldest periglacial landforms identified on Mars so far, by at least one and possibly two orders of magnitude. Unit HNt is adjacent to unit eHt and shows surface material that is relatively light in tone. The coverage is topographically irregular and, at some locations, discontinuous. Amidst the light-toned surface, structures are observed that are akin to clastically non-sorted polygons [NSPs] and polygonised thermokarst-depressions on Earth. Terrestrial polygon/thermokarst assemblages occur in permafrost regions where the freeze thaw cycling of surface and/or near-surface water is commonplace and the permafrost is ice-rich. The crater-size frequency distribution of the light-toned terrain suggests a minimum age of ~10 Ma and a maximum age of ~100 Ma. The age estimates of the candidate ice-rich assemblages fall within this dispersion. Geochronologically, this places them well beyond the million-year ages associated with most of the other candidate ice-rich assemblages reported in the literature. Stratigraphically intertwined with the two possible periglacial terrains are landforms and landscape features (observed or unobserved but modelled) that are indicative of relatively recent glaciation (~10 Ma - 100 Ma) and glaciation long past (≥ ~ 1 Ga) to decametres of depth: glacier-(cirque) like features; viscous-flow features, lobate-debris aprons; moraine-like ridges at the fore, sides and midst of the aprons; and, patches of irregularly shaped (and possibly volatile-depleted) small-sized ridge/trough assemblages. Collectively, this deeply-seated intertwining of glacial and periglacial cycles suggests that the Mid to Late Amazonian Epochs might be more Earth-like in their cold-climate geology than has been thought hitherto.

Chronostratigraphic and geomorphologic challenges of last glacial loess in Poland in the light of new luminescence ages

Article

Full-text available

Apr 2022

The aim of this study is to check the validity of luminescence ages obtained from last glacial–interglacial Polish loess palaeosol sequences (LPSs) by several established current protocols, with respect to sound geomorphological and chronostratigraphic interpretations. We report 38 new optically stimulated luminescence (OSL) ages from fine-grained (4–11 µm) quartz separates extracted from four loess palaeosol sequences in Poland, measured in the Bayreuth Luminescence Laboratory, Germany. The investigated sections are situated in Lower Silesia in the southwest (Zaprężyn, Trzebnica Hills, and Biały Kościół, Strzelin Hills), the Sandomierz Upland (Złota) in central Poland, and the Volhynian Upland (Tyszowce) in the east, allowing for regional comparison. From one Silesian section (Biały Kościół) 12 new post-infrared infrared stimulated luminescence (pIRIR) ages are presented in addition to the quartz ages of identical sample material. The obtained ages are compared to already published independently elaborated middle-grain (45–63 µm) and coarse-grain (90–125 µm) quartz ages and pIRIR ages from fine grains produced in the Gliwice Luminescence Laboratory (Poland). This comparison shows that in many cases the middle- and coarse-grain quartz ages underestimate the fine-grain quartz ages, but a general rule has not been able to be established so far, likely due to different geological origin of the quartz grains. Even fine-grain quartz ages ≥∼ 50 ka may be underestimated with respect to lithostratigraphic expectations. For pIRIR ages, however, no evidence for age underestimates has been found in the studied sections, but they are more easily prone to age overestimates due to unknown residual doses at deposition in a periglacial environment. Basic agreement between the luminescence-based chronologies elaborated in the two involved laboratories can be stated for the first time in contrast to other previous studies. The observed age differences are, however, critical for the accurate time bracketing of geomorphologic and pedostratigraphic features such as ice wedging, thermokarst erosion events, and interstadial soil formations and for their attribution to marine isotope stages. Alternative interpretations are discussed including possible periglacial mirroring of pre-LGM ice advances (Ristinge and Klintholm advances) in the southwestern Baltic Sea area. The uncertainty in luminescence ages from pre-Holocene loess due to fossil ice during permafrost conditions is the major systematic error source which will be addressed but at present is far from an unambiguous solution. The present study focuses on a complex of interstadial soils now labelled L1SS1 and on harsh periglacial climate afterwards and before, yielding some unexpected results for the timing of ice wedging and thermokarst processes. In order not to leave the users alone with the decision about the most credible dating, the suggested way forwards is to simultaneously apply various luminescence dating protocols including different quartz grain sizes and pIRIR from fine polymineral grains, as an honest approach to reliable time bracketing of geomorphological processes and stratigraphic events under debate. A refinement of this approach remains challenging as far as the sole reliable dating protocol is not ensured.

Thaw-driven mass wasting couples slopes with downstream systems, and effects propagate through Arctic drainage networks

Article

Full-text available

Jul 2021
TC

The intensification of thaw-driven mass wasting is transforming glacially conditioned permafrost terrain, coupling slopes with aquatic systems, and triggering a cascade of downstream effects. Within the context of recent, rapidly evolving climate controls on the geomorphology of permafrost terrain, we (A) quantify three-dimensional retrogressive thaw slump enlargement and describe the processes and thresholds coupling slopes to downstream systems, (B) investigate catchment-scale patterns of slope thermokarst impacts and the geomorphic implications, and (C) map the propagation of effects through hydrological networks draining permafrost terrain of northwestern Canada. Power-law relationships between retrogressive thaw slump area and volume (R2=0.90), as well as the thickness of permafrost thawed (R2=0.63), combined with the multi-decadal (1986–2018) increase in the areal extent of thaw slump disturbance, show a 2 order of magnitude increase in catchment-scale geomorphic activity and the coupling of slope and hydrological systems. Predominant effects are to first- and second-order streams where sediment delivery, often indicated by formation of recent debris tongue deposits, commonly exceeds the transport capacity of headwater streams by orders of magnitude, signaling centennial- to millennial-scale perturbation of downstream systems. Assessment of hydrological networks indicates that thaw-driven mass wasting directly affects over 5538 km of stream segments, 889 km of coastline, and 1379 lakes in the 994 860 km2 study area. Downstream propagation of slope thermokarst indicates a potential increase in the number of affected lakes by at least a factor of 4 (n>5692) and impacted stream length by a factor of 8 (>44343 km), and it defines several major impact zones on lakes, deltas, and coastal areas. Prince of Wales Strait is the receiving marine environment for greatly increased sediment and geochemical fluxes from numerous slump-impacted hydrological networks draining Banks Island and Victoria Island. The Peel and Mackenzie rivers are globally significant conveyors of the slope thermokarst cascade, delivering effects to North America's largest Arctic delta and the Beaufort Sea. Climate-driven erosion of ice-rich slopes in permafrost-preserved glaciated terrain has triggered a time-transient cascade of downstream effects that signal the rejuvenation of post-glacial landscape evolution. Glacial legacy, ground-ice conditions, and continental drainage patterns dictate that terrestrial, freshwater, coastal, and marine environments of western Arctic Canada will be an interconnected hotspot of thaw-driven change through the coming millennia.

What and where are periglacial landscapes?

Article

Full-text available

Feb 2021

Julian Murton

Uncertainties about landscape evolution under cold, nonglacial conditions raise a question fundamental to periglacial geomorphology: what and where are periglacial landscapes? To answer this, with an emphasis on lowland periglacial areas, the present study distinguishes between characteristic and polygenetic periglacial landscapes, and considers how complete is the footprint of periglaciation? Using a conceptual framework of landscape sensitivity and change, the study applies four geological criteria (periglacial persistence, extraglacial regions, ice‐rich substrates, and aggradation of sediment and permafrost) through the last 3.5 million years of the late Cenozoic to identify permafrost regions in the Northern Hemisphere. In limited areas of unglaciated permafrost regions are characteristic periglacial landscapes whose morphology has been adjusted essentially to present (i.e., Holocene interglacial) process conditions, namely thermokarst landscapes, and mixed periglacial–alluvial and periglacial–deltaic landscapes. More widespread in past and present permafrost regions are polygenetic periglacial landscapes, which inherit ancient landsurfaces on which periglacial landforms are superimposed to varying degrees, presently or previously. Such landscapes comprise relict accumulation plains and aprons, frost‐susceptible and nonfrost‐susceptible terrains, cryopediments, and glacial–periglacial landscapes. Periglaciation can produce topographic fingerprints at mesospatial scales (10³–10⁵ m): (1) relict accumulation plains and aprons form where long‐term sedimentation buried landsurfaces; and (2) plateaux with convexo–concave hillslopes and inset with valleys, formed by bedrock brecciation, mass wasting, and stream incision in frost‐susceptible terrain.

NATURAL HAZARDS AT THE SITE OF THE WATER MAIN IN CENTRAL YAKUTIA, CAUSED BY ANTHROPOGENIC THERMOEROSIVE AND THERMOKARST

Article

Jan 2019

Andrey М. Salva

http://izvestiya.tpu.ru/archive/article/view/2344 The relevance. The problems of the cryolithozone territories are related to the wide development and activity of thermal erosion, thermokarst and other cryogenic processes. On one of the sections of the route of the water main «Lena–Myuryu» in Central Yakutia the danger occurs. It has negative impact on stability of the pipeline. Man made cryogenic processes (thermokarst, thermal erosion, etc.) on the scale and consequences bring great material and economic damage to the main water pipeline and road maintenance. Why anthropogenic? Because the main factor – technogenic cutting of the surface layer by earthmoving machinery. The main aim of the research is to identify and disclose the causes of natural hazards of cryogenic processes (thermokarst and thermal erosion) on the route of the main water pipeline. The object of the study is the geocryological environment considered in operation of the section of the main water conduit «Syrdah–Borogontsy» in Central Yakutia. Methods: field route observations, simple empirical studies (observation, description, measurement) and some types of engineering geological surveys. The study of archival materials and the latest information allowed tracing the development of cryogenic processes in dynamics. Results. At detection and disclosure of the reasons of thermal erosion on the route of the water main the factors of its formation were determined and its map chart was made. The author has identified and characterized the places with natural hazards from the influence of cryogenic processes. The geocryological conditions of the territory are favorable for development of thermokarst and thermal erosion, but the key factor is technogenic pruning of the soil and vegetation layer, the presence of the ice complex, including the upper Quaternary deposits of sandy loams and silty sands, as well as the flooding of thermokarst basins.

New ground ice maps for Canada using a paleogeographic modelling approach

Article

Full-text available

Mar 2019
TC

Ground ice melt caused by climate-induced permafrost degradation may trigger significant ecological change, damage infrastructure, and alter biogeochemical cycles. The fundamental ground ice mapping for Canada is now >20 years old and does not include significant new insights gained from recent field- and remote-sensing-based studies. New modelling incorporating paleogeography is presented in this paper to depict the distribution of three ground ice types (relict ice, segregated ice, and wedge ice) in northern Canada. The modelling uses an expert-system approach in a geographic information system (GIS), founded in conceptual principles gained from empirically based research, to predict ground ice abundance in near-surface permafrost. Datasets of surficial geology, deglaciation, paleovegetation, glacial lake and marine limits, and modern permafrost distribution allow representations in the models of paleoclimatic shifts, tree line migration, marine and glacial lake inundation, and terrestrial emergence, and their effect on ground ice abundance. The model outputs are generally consistent with field observations, indicating abundant relict ice in the western Arctic, where it has remained preserved since deglaciation in thick glacigenic sediments in continuous permafrost. Segregated ice is widely distributed in fine-grained deposits, occurring in the highest abundance in glacial lake and marine sediments. The modelled abundance of wedge ice largely reflects the exposure time of terrain to low air temperatures in tundra environments following deglaciation or marine/glacial lake inundation and is thus highest in the western Arctic. Holocene environmental changes result in reduced ice abundance where the tree line advanced during warmer periods. Published observations of thaw slumps and massive ice exposures, segregated ice and associated landforms, and ice wedges allow a favourable preliminary assessment of the models, and the results are generally comparable with the previous ground ice mapping for Canada. However, the model outputs are more spatially explicit and better reflect observed ground ice conditions in many regions. Synthetic modelling products that incorporated the previous ground ice information may therefore include inaccuracies. The presented modelling approach is a significant advance in permafrost mapping, but additional field observations and volumetric ice estimates from more areas in Canada are required to improve calibration and validation of small-scale ground ice modelling. The ground ice maps from this paper are available in the supplement in GeoTIFF format.

Arctic Deltas and Estuaries: A Canadian Perspective

Chapter

Jan 2019

Donald L Forbes

Deltas and estuaries in high latitudes have many features in common with river-mouth systems everywhere. In addition, they share a suite of polar characteristics driving distinctly Arctic processes and outcomes. Various forms of ice (including ground ice, river and sea ice, glacial ice, and snow) are the primary distinguishing factors, but extreme seasonality and the near-absence of trees are also important. The glacial legacy is a key influence, through sediment supply, affecting delta growth and survival, and glacial-isostatic crustal motion, leading to both falling and rising relative sea levels. High-latitude amplification of climate warming is causing dramatic losses of sea ice, land-based ice, and ice shelves, and accelerating coastal erosion. Moreover, Arctic deltas and estuaries (including ice shelves) provide critical ecosystem services, are responding to global climate forcing, and serve as sentinel systems for detection and tracking of climate warming effects at high latitudes. © 2019 Crown

Experimental Research on Frost Heave Characteristics of Gravel Soil and Multifactor Regression Prediction

Article

Full-text available

Dec 2018

Gravel soil is usually considered to be insensitive to frost heave. However, many frost heave deformations of foundation in seasonal frozen region indicate that gravel soil may also produce frost heave under certain special conditions. In order to gain a deep insight into the frost heave characteristics of gravel soil, a series of laboratory experiments on one-dimensional frost heave were conducted under the open- and closed-water replenishing condition using an improved experiment apparatus. The influence of various factors including initial moisture content, clay content, compactness, overlying load, and water replenishing on frost-heaving ratio of gravel soil were analyzed. And the basic frost heave characteristics including frost heave amount, frost heave speed, frozen depth, freezing speed, and moisture content distribution after freezing in a gravel soil sample were analyzed. The corresponding mechanisms were also discussed. Results showed that in the open water replenishing condition, there exists a linear relationship between initial moisture content, overlying load, and frost-heaving ratio and a quadratic polynomial relationship between clay content, compactness, and frost-heaving ratio. Frost-heaving ratio in the open water replenishing condition can be found to increase over three times than that under the closed water replenishing condition. Multifactor regression empirical formula was obtained by multiple regression analysis to predict the frost-heaving ratio of gravel soil under certain collocation of factors and levels under the closed water replenishing condition. The significant effects on frost-heaving ratio were, in order, water replenishing > initial moisture content > clay content > compactness > overlying load.

On shaky ground: Arctic communities in uneasy transition to a new climatic order

Chapter

Full-text available

Jan 2009

Much attention has recently been given to the Arctic within a context of climate change. Its high latitude has made the Arctic one of the most sensitive regions on Earth, conveying landscape modifications in a warming world. This chapter examines the evidence of landscape change from a combined geomorphologic and socio-political approach by considering permafrost and thermokarst development, issues around the opening of the region (i.e. the Northwest Passage in Canada), as well as varied implications on local communities, international affairs, and geopolitics. The consideration of these issues is based on the assumption that climatic warming is changing the Arctic landscape and that northern regions will be a focal point in the search for resources.

Climatic, geomorphologic and hydrologic perturbations as drivers for mid‐ to late Holocene development of ice‐wedge polygons in the western Canadian Arctic

Article

Full-text available

Jul 2018

Ice‐wedge polygons are widespread periglacial features and influence landscape hydrology and carbon storage. The influence of climate and topography on polygon development is not entirely clear, however, giving high uncertainties to projections of permafrost development. We studied the mid‐ to late Holocene development of modern ice‐wedge polygon sites to explore drivers of change and reasons for long‐term stability. We analyzed organic carbon, total nitrogen, stable carbon isotopes, grain size composition and plant macrofossils in six cores from three polygons. We found that all sites developed from aquatic to wetland conditions. In the mid‐Holocene, shallow lakes and partly submerged ice‐wedge polygons existed at the studied sites. An erosional hiatus of ca 5000 years followed, and ice‐wedge polygons re‐initiated within the last millennium. Ice‐wedge melt and surface drying during the last century were linked to climatic warming. The influence of climate on ice‐wedge polygon development was outweighed by geomorphology during most of the late Holocene. Recent warming, however, caused ice‐wedge degradation at all sites. Our study showed that where waterlogged ground was maintained, low‐centered polygons persisted for millennia. Ice‐wedge melt and increased drainage through geomorphic disturbance, however, triggered conversion into high‐centered polygons and may lead to self‐enhancing degradation under continued warming.

Regional environmental change versus local signal preservation in Holocene thermokarst lake sediments: A case study from Herschel Island, Yukon (Canada)

Article

Full-text available

Jun 2018
J PALEOLIMNOL

Thermokarst lakes cover nearly one fourth of ice-rich permafrost lowlands in the Arctic. Sediments from an athalassic subsaline thermokarst lake on Herschel Island (69°36′N; 139°04′W, Canadian Arctic) were used to understand regional changes in climate and in sediment transport, hydrology, nutrient availability and permafrost disturbance. The sediment record spans the last ~ 11,700 years and the basal date is in good agreement with the Holocene onset of thermokarst initiation in the region. Electrical conductivity in pore water continuously decreases, thus indicating desalinization and continuous increase of lake size and water level. The inc/coh ratio of XRF scans provides a high-resolution organic-carbon proxy which correlates with TOC measurements. XRF-derived Mn/Fe ratios indicate aerobic versus anaerobic conditions which moderate the preservation potential of organic matter in lake sediments. The coexistence of marine, brackish and freshwater ostracods and foraminifera is explained by (1) oligohaline to mesohaline water chemistry of the past lake and (2) redeposition of Pleistocene specimens found within upthrusted marine sediments around the lake. Episodes of catchment disturbance are identified when calcareous fossils and allochthonous material were transported into the lake by thermokarst processes such as active-layer detachments, slumping and erosion of ice-rich shores. The pollen record does not show major variations and the pollen-based climate record does not match well with other summer air temperature reconstructions from this region. Local vegetation patterns in small catchments are strongly linked to morphology and sub-surface permafrost conditions rather than to climate. Multidisciplinary studies can identify the onset and life cycle of thermokarst lakes as they play a crucial role in Arctic freshwater ecosystems and in the global carbon cycle of the past, present and future.

Aeolian stratigraphy describes ice-age paleoenvironments in unglaciated Arctic Alaska

Article

Feb 2018
QUATERNARY SCI REV

Chapter 3 Geomorphological framework: glacial and periglacial sediments, structures and landforms

Article

Nov 2017

The development of the conceptual ground model (CGM) is a critical component of any desk study or ground engineering project planning process. A key task of the engineering geologist is to develop the CGM in order to predict the occurrence of known terrain units, elements and facets within a given landsystem, and to communicate the lateral and vertical variability of engineering rocks and soils found within that system. This chapter details the significant ground components of glacial and periglacial landsystems within a geomorphological framework describing the sediments, structures and landforms that could reasonably be expected to be encountered in these terrains. Examples are provided of both modern and relict glacial and periglacial landforms, their mode of formation and their field recognition. Glaciogenic and periglacial sediments are described both in terms of their sedimentological and formal engineering description. The chapter provides a suggested naming nomenclature for these sediments that can be used within a BS 5930 description. An extensive photo-glossary is presented as a field aide memoir, enabling the engineering geologist to identify these features once on site. © 2017 The Author(s). Published by The Geological Society of London. All rights reserved.

Tundra vegetation stability versus lake-basin variability on the Yukon Coastal Plain (NW Canada) during the past three centuries

Article

Jun 2017

Palaeoclimatic reconstructions of the northern Yukon show cooler conditions before AD 1850 followed by gradual warming, and 20th-century temperature measurements indicate decadal-scale temperature fluctuations. The impact of climate on regional vegetation and lake systems has seldom been observed on this scale, however. With this study, we provide a sub-decadal reconstruction of regional vegetation and lake-basin development for the past 300 years, covering the ‘Little Ice Age’ and the period of recent warming, in low Arctic tundra. We analysed a short lake sediment core from the Yukon Coastal Plain. The age–depth relationship of the core is based on ²¹⁰Pb/¹³⁷Cs validated by AMS radiocarbon dating. We analysed terrestrial pollen abundances as proxies for regional vegetation development, and we used grain size and biogeochemical analyses (TOC, TN, TOC/TN, δ¹³C) and the analysis of semiaquatic pollen to describe the lake development. Stable abundances of regional pollen taxa between AD 1730 and AD 2012 accompanied by climatic warming indicated that the regional vegetation was not sensitive to climate change. Based on changes in TOC/TN, δ¹³C and pollen of shallow-water taxa, we reconstructed an increase in lake water depth after AD 1910 that likely followed climatic warming. We attributed this development to climate-driven thaw subsidence in the lake basin. The impact of widespread permafrost thaw on regional vegetation needs to be better constrained in order to predict the limits of vegetation stability and drivers of lake changes in the region.

Evidence, arguments, and cold-climate geomorphology that favour periglacial cycling at the Martian mid-to-high latitudes in the Late Amazonian Epoch

Chapter

Jan 2024

Recognizing deformation origins: a review of deformation structures and hypothesis on the perspective of sediment consolidation

Article

Jul 2022

Key information on sedimentary or tectonic events is recorded in deformation structures formed in unlithified and lithified sediments. Disputes about the classification and identification of the two types of deformation have become increasingly relevant. The present study systematically summarizes, based on consolidation states, the genetic mechanisms of deformation. Consolidation conditions may affect deformation patterns and morphology; this can be a clue to distinguish soft-sediment deformation from tectonic deformation. Liquefaction is a typical state of unconsolidated sediment and can create clastic dikes, liquefied breccia, convolute laminae, load cast, and water-escape structures. Synsedimentary faults may be formed in weakly consolidated sediments. Most deformation structures of lithified sediments are large-scale folds and faults, but small-scale structures – especially microfolds – are difficult to distinguish from slump folds. Tectonic folds can be formed in different strata and induced by tectonic events; they differ from slump folds in morphology, distribution, and related structures. We demonstrated that consideration of liquefaction, folds in different strata – matched with the regional geological regime, related deformation structures, and micro-deformation structures – can be clues to the identification of deformation origins.

Mass-Movements in Cold and Polar Climates

Chapter

Jan 2021

Mass-movements in cold and Polar climates often involve permafrost and ice and hence these two phenomena are recurring themes throughout this chapter. We consider specifically mass movements in glacial, periglacial and paraglacial settings. For each environmental setting we describe the types of mass movement that have been documented in the literature, describing the current research foci and remaining challenges. We specifically highlight that mass-movements in cold and Polar climates are particularly sensitive to climate change, because of the involvement of permafrost and ice in their triggering and dynamics and therefore we may anticipate an increasing frequency and increased hazard from these phenomena in the future in response to unprecedented rates of environmental change.

Permafrost thaw couples slopes with downstream systems and effects propagate through Arctic drainage networks

Preprint

Full-text available

Sep 2020

The intensification of thaw-driven mass wasting is transforming glacially-conditioned permafrost terrain, coupling slopes with aquatic systems, and triggering a cascade of downstream effects. Within the context of recent, rapidly evolving climate controls on the geomorphology of permafrost terrain we: A) quantify three-dimensional slump enlargement and described the processes and thresholds coupling slopes to downstream systems; B) investigate catchment-scale patterns of slope thermokarst (thaw slumps and slides) impacts and the geomorphic implications; and C) project the propagation of effects through hydrological networks draining continuous permafrost of northwestern Canada. Power-law relationships between thaw-slump area and volume (R2 = 0.90), and thickness of permafrost thawed (R2 = 0.63), combined with the multi-decadal (1985–2018) increase in areal extent of thaw-slump disturbance show a two-order of magnitude increase in catchment-scale geomorphic activity and the coupling of slope and hydrological systems. Predominant catchment effects are to first- and second-order streams where sediment delivery commonly exceeds stream transport capacity by orders of magnitude indicating millennial-scale perturbation of downstream systems. Assessment of hydrological networks indicates thaw-driven mass wasting directly affects over 6,760 km of stream segments, 890 km of coastline, and 1,370 lakes in the 994,860 km2 study area. Downstream propagation of slope thermokarst indicates a potential increase in the number of affected lakes by at least a factor of 4 (n > 5,600), impacted stream length by a factor of 7 (> 48,000 km) and defines several major impact zones to lakes, deltas, and coastal areas. Prince of Wales Strait is the receiving marine environment for greatly increased sediment and geochemical fluxes from numerous slump impacted hydrological networks draining the landmasses of Banks and Victoria Islands. Peel and Mackenzie Rivers are globally significant conveyors of the slope thermokarst cascade delivering effects to North America’s largest Delta and the Beaufort Sea. Climate-driven erosion of ice-rich slopes in permafrost preserved glaciated terrain has triggered a time-transient cascade of downstream effects that signal the renewal of post-glacial landscape evolution. Glacial legacy and the patterns of continental drainage dictate that terrestrial, freshwater and marine environments of western Arctic Canada will be an interconnected hotspot of thaw-driven change through the coming millennia.

Possible ice-wedge polygonisation in Utopia Planitia, Mars and its latitudinal gradient of distribution

Article

Full-text available

Nov 2020

On Earth, ice complexes are commonplace landscapes amidst the continuous permafrost of coastal or near-coastal plains in the Arctic. Formed by the freeze-thaw cycling of water, ice complex features include: hummocky (thermokarstic) terrain, inflated or deflated by the presence of absence of excess ice; thermokarst lakes (i.e. excess ice that has thawed and pooled); alases (i.e. thermokarst basins emptied of water); and, ice-wedge polygons, often characterized by raised (ice-aggraded) or lowered (ice-degraded) margins relative to the polygon centres. The origin and development of these complexes is rooted in inter-or intra-glacial pulses of temperature that engender widespread thaw, meltwater distribution and migration through the soil column (sometimes to decametres of depth), and the freeze-thaw cycling of the meltwater. The possible existence of ice-rich terrain on Mars revised by the freeze-thaw cycling of water dates back to the grainy Mariner-mission photographs of the 1960s and 1970s. However, absent of regolith samples from areas where this terrain is hypothesised, attempts to validate the ice-rich hypothesis often have ended abruptly, either with spectrometric inferences of water-equivalent hydrogen to one metre or so of depth or with “looks-like”, therefore “must-be” analogies derived of Earth-based ice-complexes. In the case of small-sized Martian polygons with low- and high-centres, the similarities of form between ice and sand-wedge polygons on Earth has equivocated the reach of ice-wedge hypotheses on Mars. Here, we show that: 1)The plains' terrain of our study region in Utopia Planitia (40-50o N; 100-125o E) displays a statistically-significant and positive (linear) correlation between the ratio of low-centred to high-centred polygons (lcps vs hcps) and a poleward latitude of distribution. 2)This linear correlation would be expected, in as much as ground-ice stability increases with latitude, were the shoulders of higher-latitude lcps underlain by (aggraded) ice-wedges and those of lower-latitude hcps underlain by (degraded) ice-wedges. 3)The change of polygon morphology with latitude would not be expected were the lcps and hcps underlain by sand wedges, in as much as ground-ice stability is unrelated to their aggradation or degradation. 4)Crater counts of the polygonised terrain indicate that it is less youthful than previous studies have suggested, perhaps by an order of magnitude. This attenuates the possible inconsistency between the more temperate boundary-conditions required by the formation of ice-wedge polygons and the current constraints of extreme aridity, low temperatures and low atmospheric pressure.

Permafrost active layer

Article

Jul 2020
EARTH-SCI REV

Wojciech Dobinski

This article discusses the properties and occurrence of an active layer (AL) in the near-surface of the lithosphere in glacial and periglacial environments. This layer shows a seasonal variability in temperature, as a result of the climate. The AL, as classically understood, seasonally thaws and freezes, while in glacial environments it usually only reaches 0 °C. The definition of AL is currently not consistent with the definition of permafrost, even though both concepts usually appear linked. For these terms to be comparable, both should be defined based on temperature variability and not exclusively on phase change. Thus, the AL would be described not only as the upper section of perennially frozen ground presenting seasonal thaw-freeze cycles (# 1) but as a layer presenting a seasonal variation in temperature (# 2). Classical active layer can be thawed to a depth of approximately 2–8 cm, the thickest AL reaches over 20 m. In the particularly favorable conditions AL might be completely absent with the permafrost beginning at the ground surface. In glacial and sub-marine permafrost environments, the AL includes a layer of liquid water that seasonally accompanies the permafrost. Glaciers and ice sheets are usually devoid of the classical AL. In both cases, the AL is usually horizontal, but in specific terrains such as sea shore cliffs or karst environments, the AL may have a vertical course and may even be reversed. Both AL and permafrost are common in other frozen bodies in the solar system, differing mainly in their thermal character.

Specific Features of Soil Formation in Alas Landscapes of the Cryolithozone

Article

Apr 2020

Roman Vasilievich Desyatkin

Features of Engineering Surveys in Areas of Permafrost Prevalence by the Example of the Project “Northern Latitudinal Way”

Chapter

Jan 2020

The Role of Ground Ice

Chapter

Jan 2020

Ko Van Huissteden

The ice content of permafrost soils has a large impact on processes that occur when permafrost thaws; exposed ground ice is the primary cause of destructive abrupt thaw processes. This chapter presents the origin of common forms of ground ice: segregation ice, ice wedges and larger ground ice bodies. The presence of ground ice is expressed at the surface as geomorphological features such as ice wedge polygon networks, palsas and pingos. A processes that is important for transfer of carbon in permafrost soils is cryoturbation; it is also linked to micro-relief at the soil surface in the shape of various forms of patterned ground. The processes and landforms that result from thawing ground ice are discussed: erosional forms such as cryogenic landslides. Next, permafrost has a profound effect on the hydrology; a frozen subsurface acts as a barrier to groundwater movement. This affects also runoff and river discharge, which are further determined by water storage as snow in winter, and its sudden release in spring during snowmelt. Permafrost thaw results in hydrological changes: the development of thaw lakes and increased groundwater flow. The chapter concludes with a short presentation of geophysical methods to detect and map ground ice and permafrost in the subsurface.

Permafrost in Transition

Chapter

Jan 2020

Ko Van Huissteden

Climate change results in physical changes in permafrost soils: active layer thickness, temperature, soil hydrology and abrupt thaw features in ice-rich soils. Abrupt thaw features create new landforms such as ponds, lakes and erosion phenomena. In this chapter, current observations of physical changes in permafrost soils are discussed, including their effect on the soil carbon cycle. For the carbon cycle changes, the results of observations and experimental studies are emphasized. First, the effects of soil warming without further geomorphological change is considered. The potential effect of self-amplifying soil warming by heat production from bacterial production is discussed. Next, the changes in geomorphological processes expressed by formation of thaw ponds, lakes and erosion features are considered. These contribute to an increase of CO2 and non-CO2 greenhouse gas emissions. Hydrological changes include the effects of permafrost thaw on the water cycle via groundwater flow and directly climate-driven changes in precipitation and evapotranspiration. These result in river discharge changes with effects on floodplains, and influence transport of carbon from permafrost regions to the Arctic Ocean. Soil hydrology changes – wetting or drying – induce changes in the pattern of greenhouse gas emissions of permafrost soils.

ПРИРОДНЫЕ ОПАСНОСТИ НА УЧАСТКЕ МАГИСТРАЛЬНОГО ВОДОВОДА В ЦЕНТРАЛЬНОЙ ЯКУТИИ, ВЫЗВАННЫЕ ТЕХНОГЕННОЙ ТЕРМОЭРОЗИЕЙ И ТЕРМОКАРСТОМ

Article

Nov 2019

Андрей Михайлович Сальва

Актуальность. Проблемы территорий криолитозоны связаны с широким развитием и активностью распространения процессов термоэрозии, термокарста и других криогенных процессов. На одном из участков трассы магистрального водовода «Лена–Мюрю» в Центральной Якутии возникли опасности, оказывающие негативное воздействие на устойчивость трубопровода. Техногенные криогенные процессы (термокарст, термоэрозия и др.) по масштабам и последствиям приносят магистральному водоводу и обслуживающей автодороге огромный материальный и экономический ущерб. Почему техногенные? Потому, что основной фактор – техногенный – срезка поверхностного слоя землеройной техникой. Цель: выявление и раскрытие причин природных опасностей криогенных процессов (термокарст и термоэрозия) на трассе магистрального водовода. Объектом исследования является геокриологическая среда, рассматриваемая при эксплуатации участка магистрального водовода «Сырдах–Борогонцы» в Центральной Якутии. Методы: полевые маршрутные наблюдения, простые эмпирические исследования (наблюдение, описание, измерение) и некоторые виды инженерно-геологических изысканий. Изучение архивных материалов и новейших сведений позволили проследить развитие криогенных процессов в динамике. Результаты. При выявлении и раскрытии причин термоэрозии на трассе магистрального водовода были установлены факторы образования термоэрозии и составлена ее картосхема. Выявлены и охарактеризованы места с природными опасностями от влияния криогенных процессов. Геокриологические условия территории благоприятны для развития термокарста и термоэрозии, но ключевым фактором является техногенный – подрезка почвенно-растительного слоя, наличие ледового комплекса, включая верхнечетвертичные отложения супесей и пылеватых песков, а также обводнение термокарстовых котловин.

References

Chapter

Oct 2017

Hugh M. French

References

Chapter

Jun 2013

Hugh M. French

Permafrost

Chapter

Jan 2013

Julian Murton

Quaternary thermokarst and thermal erosion features in northern France: Origin and palaeoenvironments

Article

Full-text available

Dec 2016
BOREAS

A thermokarst is a collapse feature resulting from the thawing of ice-rich permafrost or of massive ice of various origins. Little attention has been paid to the sedimentary fabric resulting from this type of collapse, except for glaciotectonic features. In western Europe, two palaeo-forms are commonly studied: lithalsas and ice-wedge casts. Collapsed pingos are much rarer. Very few papers have compiled present-day and fossil data. Here, field data collected from quarries in the eastern Paris Basin were analysed, providing useful records of thermokarst collapses in alluvial calcareous silts, sands, and gravels. These forms have a circular shape when viewed on satellite images. Permafrost is attested regionally by the recurrent occurrence of meter-sized pattern grounds at the surface of the chalk and of ice-wedge casts. Traces of segregation and reticulate ice are common. These features are primarily connected to a major interstadial, c. 150 ka BP, orbitally forced and commonly associated with a major glacial retreat. They occur both in drained and waterlogged situations, resulting in a specific pattern of deformation. They are controlled by the brittle and plastic behaviour of sediments and resemble passive glaciotectonism. Normal and reverse faults, with the offset decreasing downward, are common, and those with local shear are reported. Lithalsas, seasonal frost blisters, spring frost blisters and perhaps pingos seem to have formed. Most of these deformations correspond to thermokarst sinkholes bordered by gravitational collapse faults. The offset of these faults increases towards the surface, and the faults have been recurrently confused with neotectonism triggered by palaeo-earthquakes. However, there are no faults beneath the observed deformation features, and the region lacks recorded seismic activity over the last century. Our data may be helpful in interpreting similar structures elsewhere.

Quaternary thermokarst and thermal erosion features in Northern France: dynamic and palaeoenvironments

Article

Jan 2016

Frost effects in soils

Article

Full-text available

Jan 1985

Brigitte Van Vliet-Lanoë

Geological conditions for the burial of Pleistocene glacier ice on the Yenisey

Article

Full-text available

Oct 1986

Valery Astakhov

Geological and geomorphological conditions pertaining to Ledyanaya Gora, the well‐known body of buried Pleistocene glacier ice on the lower reaches of the Yenisey, were investigated. It was found that the beds of folded ice are located in the cores of ridges and hummocks and that the sediments overlying the ice consist mainly of flow tills. A terrace abutting on this ridged topography and composed of glaciolacustrine rhythmites, lies at the same or higher elevations. Hence the Boulton model of relief inversion is quite appropriate here. Eight phases of delayed deglaciation during the late‐Pleistocene and Holocene have been distinguished. Since the flow tills contain many blocks of peat and fossil wood it is suggested that the present‐day relief was formed after the Holocene climatic optimum. Apparently Holocene deposits overridden by flow tills during the course of delayed deglaciation have been reported as “interstadial”; or “interglacial”; sections from elsewhere in Northern Siberia or the North of the European part of the USSR.

Massive ice of the Tuktoyaktuk area, western Arctic coast, Canada

Article

Full-text available

Feb 2011

The extensive coastal exposure of massive underground ice at Peninsula Point, southwest of Tuktoyaktuk, Northwest Territories, is believed to be intrasedimental ice. The ice grew beneath a frozen diamicton during the downward aggradation of permafrost. The water source was probably glacier meltwater, with low negative δ18O values, that flowed, under a substantial pressure, through permeable unfrozen sands. Evidence for a high water pressure is shown by ice dikes, which extend upward from the massive ice into the superincumbent diamicton. The diamicton was frozen when the dike water was injected, as proven by the chill contacts and petrofabrics. The diamicton – massive ice contact is a conformable contact with features characteristic of downward freezing. The continuity of δ18O and δD profiles from the top of the massive ice downward to a depth of 10 m into the underlying frozen sand demonstrates a common water source for the massive ice and interstitial ice in the underlying sand. A similar continuity of δ18O profiles has been determined from three drill holes at another site 15 km northeast of Tuktoyaktuk, Northwest Territories. The ages of both the diamicton and massive ice at the Peninsula Point site are uncertain, because of unexplained differences in published radiocarbon dates.

Mid-Wisconsinan eolian deposits of the Kittigazuit Formation, Tuktoyaktuk Coastlands, Northwest Territories, Canada

Article

Full-text available

Apr 2011

The Kittigazuit Formation is a late Quaternary sand unit commonly observed throughout the Tuktoyaktuk Coastlands and in subbottom sediments of the southern Beaufort Shelf. Stratigraphic and sedimentology data, including sedimentary structures, grain-surface characteristics, and heavy and light mineralogy, assist in characterizing the deposit and indicate that it is eolian in origin. Plant and arthropod macrofossils suggest that, although the summer climate during deposition was as warm or slightly warmer than today, conditions were likely more arid. Permafrost is interpreted as being widespread during deposition. Accelerator mass spectrometry radiocarbon dates indicate that the Kittigazuit Formation was deposited between 37 and 33 ka BP. The unit is therefore interpreted as a Mid-Wisconsinan eolian dune deposit, formed by reworking of underlying alluvial sediments of the Kidluit Formation under nonglacial conditions. Glaciogenic sediments overlying the Kittigazuit Formation indicate that glacial ice covered the Tuktoyaktuk Peninsula, Richards Island, and parts of the Beaufort Shelf sometime after 33 ka BP, whereas several terrestrial dates indicate that the area may have been ice free by about 20 ka BP.

Field investigations of permafrost and climatic change in north - west North America

Article

Full-text available

Jan 1998

C. R. Burn

Evidence of general instability of past climate from a 250-kyr ice-core record

Article

Full-text available

Jul 1993
NATURE

A detailed stable-isotope record is presented for the full length of the Greenland Ice-core Project Summit ice core covering the last 250,000 years according to a graduated timescale. It appears that the climatic stability of the Holocene is the exception rather than the rule; the last interglacial is also noted to have lasted longer than is implied by the deep-sea SPECMAP record. This discrepancy may be accounted for if the climate instability at the outset of the last interglacial delayed the melting of the Saalean ice sheets in America and Eurasia.

Deep circulation of groundwater in overpressured subglacial aquifers and its geologic consequences

Article

Full-text available

Dec 1993
QUATERNARY SCI REV

It is generally assumed that meltwater from the base of ice sheets is discharged in a relatively thin subglacial zone. Whereas this may be true for ice sheets resting on impermeable beds, many ice sheets, such as the glacial period ice sheets of North America and Europe, flowed over extensive aquifers. A theory is developed which suggests that high rates of meltwater discharge into these aquifers would have completely reorganised their flow fields, producing intergrated patterns of glacially pressurised flow controlled by the continental-scale form of the ice sheet surface rather than the small-scale topographic basins which determine modern aquifer extent. The theory is applied to the aquifers which underlay the Saalian ice sheet in The Netherlands, where it is shown that potential gradients and groundwater flow velocities would have developed which were two orders of magnitude greater than modern values and that the dominant flow vectors would have been normal to those of the modern flow. Thus, glacial/interglacial cycling in areas which have suffered periodic glaciation during the late Cenozoic may have experienced alternating phases of greater and lesser flow energy. It represents another example of climatically-driven cyclical change in the earth.Under highly energised glacial conditions, potential gradients much larger than modern values may have produced many common features of sediment disruption, such as diapirs, liquifaction structures and pipes, and forms such as glacial ‘doughnuts’ and pock marks, which have hitherto been explained by other processes. Deep and penetrative flushing of aquifers by glacial meltwater may have left a distinctive geochemical signal in them which may be used to test the theory. Gases such as methane, generated at shallow depth, may have been trapped beneath the glacial ‘cap-rock’, and may also have played an important role in these processes.

The ‘Ice Hill’: An example of ‘retarded deglaciation’ in siberia

Article

Full-text available

Dec 1988
QUATERNARY SCI REV

The geological structure of one of the southernmost sites of thick ice beds in the Yenisei valley near the Arctic Circle is discussed. The erosion contacts of the foliated and contorted ice, abundance of glacial debris and the position between the basal till and ablation cover indicate a glacial origin for the ice layer. The ice occurs in the cores of arcuate accretion ridges built of ablation materials. The overlying sequence consists of a series of diamicton flows alternating with lacustrine and outwash sediments. Laterally the ice-rock complex changes into thick lacustrine rhythmites underlain by basal tills. The ice-containing hummocky terrain is often lower than the adjacent lacustrine plain. Therefore inversion of ice-controlled topography is suggested. Several stages of glaciokarst development are supposed to have occurred after an eastward moving ice lobe stagnated more than 50 ka BP. The main depositional events are associated with the Middle Weichselian draining of ice-dammed Lake Igarka, and with Early Holocene topographic inversion. The Holocene warming apparently caused diapiric deformation of the buried ice probably because of the density and thickness differences between the ice and the overburden.

Quaternary geology of the Tuktoyaktuk Coastlands, Northwest Territories

Article

Jan 1988

V.N. Rampton

Summer thaw depths in cold regions and fossil cryoturbation.

Article

Jan 1981

G.C. Maarleveld

An analysis of data from the literature, on summer thaw depths and cryoturbation in present-day cold areas, shows that the thickness of fossil cryoturbated deposits cannot be correlated to the July temperature of that time. It is suggested that the thickness of fossil cryoturbated deposits has been positively influenced by thermokarst.-Author University of Amsterdam, Dapperstraat 115, 1093 BS, Netherlands.

Pleistocene diapiric upturning of lignites and clayey sediments as periglacial phenomena in central Europe.

Article

Jan 1983

H. Strunk

Diapirlike intrusions of lignite into gritty or sandy topsoil, several meters thick, are widespread in the central European lignite fields and wherever clayey sediments lying near the surface. These structures occur outside the limits of the Scandinavian ice sheet. This eliminates the assumption that their formation was primarily caused by the weight of the ice. Rather, the upturnings were caused by density inversions during the degradation of permafrost. The maximum thickness of Pleistocene permafrost in central Europe decreases rapidly from several dozen meters in the NE to less than 10m in the W and SW. -from Author

Frost mounds. In Focus: Permafrost geomorphology, French HM (ed.)

Article

Jan 1986
CAN GEOGR-GEOGR CAN

J.R. Mackay

The influence of ground ice and thermokarst upon the geomorphology of the mackenzie-beaufort region, in fahey, b.d., and thompson, r.d., eds., research in polar and alpine geomorphology: Proceedings of the 3rd guelph symposium on geomorphology

Article

Jan 1974

V.N. Rampton

The rapidity of tundra polygon growth and destruction Tuktoyaktuk Peninsula

Article

Jan 1974

J.R. Mackay

Deep thaw lake basins in the inner Arctic Coastal Plain, Alaska

Article

Jan 1979

Regularities in formation of frost-fissures and development of frost-fissure polygons

Article

Jan 1973

N.N. Romanovskij

Loess and deep thermokarst basins in Arctic Alaska

Article

Jan 1988

L.D. Carter

True and False Ice-Wedges in Southern Sweden

Article

Jan 1959

Gunnar Johnsson

Thermokarst within the territory of the USSR

Article

Jan 1962

S.P. Kachurin

Effect of permafrost upon cultivated fields

Article

Jan 1954

T.L. Péwé

(Origin and age of an ancient periglacial hill ( pingo or palsa) at Konnerzvenn, Hautes Fagnes, Belgium).

Article

Jan 1980

A section through the rampart permits the reconstruction of the stages of its formation. A peat layer deposited before the growth of the hill was dated by 14C as Allerod. Volcanic ashes in this peat layer were deposited 11 030 BP. -from English summary

Periglaziäre Prozesse und Permafroststrukturen aus sechs Kaltzeiten des Quartärs

Article

Jan 1981

L. Eissmann

Catastrophic lake drainage, Tuktoyaktuk Peninsula area, District of Mackenzie

Article

Jan 1988

J.R. Mackay

Le thermokarst, phénomène négligée dans les études du Pleistocene

Article

Jan 1964

J. Dylik

GROUND ICE IN PERENNIALLY FROZEN SEDIMENTS, NORTHERN ALASKA.

Article

D.E. Lawson

Composition and cryogenic structure of permafrost

Article

Jan 1969

E.M. Katasonov

Periglacial geomorphology

Article

Mar 1978
PROG PHYS GEOG

H. M. French

Judging by the literature of the last 12 months (1978) the trend towards a permafrost-process-dominated periglacial geomorphology is continuing unabated. Process studies include pingos, seasonal frost mounds, mudboils and mass displacements. -Keith Clayton.

The Periglaciation of Great Britain

Article

Nov 1995

Presents current knowledge on the effects of periglaciation on the British landscape. The book is in 4 parts, the first of which provides an introduction to periglaciation and the Quaternary environment and chronology. The second part deals with the periglaciation of lowland Britain (below 400m asl), including chapters on ice wedge casts, pingos, mass wasting and landscape modification. The third part looks at the periglaciation of upland Britain, which generally is underlain by more resistant rocks, and includes topics on frost weathering, patterned ground, solifluction, talus slopes and related landforms. The final part of the book examines the periglacial enviroments of three contrasting periods: the Dimlington Stadial; the Loch Lomond Stadial and the present day environment in upland Britian. An extensive reference list is provided. -R.Gower

The Past and Present Vegetation of the Far Northwest of Canada

Book

Jan 1984

J. C. Ritchie

One-dimensional Consolidation of Thawing Soils

Article

Jan 2011
CAN GEOTECH J

The physics of consolidation of a thawing soil is formulated in terms of the well-known theories of heat conduction and of linear consolidation of a compressible soil. A moving boundary problem results, and closed form solutions have been obtained for several cases of practical interest. The results are presented in terms of normalized pore pressure distributions. It is shown that the excess pore pressures and the degree of consolidation in thawing soils depend primarily on the thaw consolidation ratio.

Disturbances to the tundra and forest tundra environment of the Western Arctic

Article

Jan 2011
CAN GEOTECH J

J. Ross Mackay

The more important physical disturbances to the tundra environment are discussed with examples. Thermokarst subsidence, not thermal erosion, is shown to be the dominant result of man-induced disturbances, such as those caused by the bulldozing of seismic lines and firebreaks. It is shown that a clear distinction between thermokarst subsidence and thermal erosion is necessary, if the causes of the disturbances are to be prevented and minimized, or the results treated. The typical surface disturbance to the tundra results in a deepening of the active layer. Therefore, foreknowledge of the effect of a disturbance on deepening the active layer, together with information on the ice content of the permafrost affected, makes it possible to predict the amount of thermokarst subsidence likely to take place. Three practical examples of three types of ground disturbance are given: a fire near Inuvik, N.W.T.; a patch of vegetation trampled and killed by a dog at Garry Island, N.W.T.; and seepage down a walking trail in an ice-wedge area at Garry Island, N.W.T. The effects of the disturbances are illustrated and discussed.

Massive ground ice and ice-cored terrain near Sabine Point, Yukon Coastal Plain

Article

Feb 2011

Massive ground ice, 5–6 m in thickness, is exposed within retrogressive thaw flow slides near Sabine Point, Yukon Territory. The ice is present near the upper surface of Buckland Till and is overlain and thaw truncated by mudflow sediments and a thick unit of peat and organic silt. Cryotextural and petrographic analyses suggest that the ice formed primarily by segregation processes. The ice occurs within an area of rolling terrain, surrounded by lacustrine basins. This may form a remnant of an initial post-Buckland surface, degraded by multiple cycles of thermokarst during the period 14 000 to 8000 years BP.

Pingo collapse and Paleoclimatic reconstruction

Article

Feb 2011

J. Ross Mackay

Long-term field studies of contemporary pingo growth, collapse, and rampart formation along the western Arctic coast of Canada provide criteria that may be helpful in the identification of pingo ramparts in nonpermafrost environments. Such criteria include the volume of the ramparts, which should approximate that of the enclosed depressions from which the rampart materials were derived; peripheral deposits associated with mass wasting, streamflow, and debris flow; casts of dilation crack ice trending across the ramparts; and high-angle peripheral normal faults. The conventional method of correlating the present mean annual air temperature with the present pingo distribution to establish warm-side limiting temperatures for paleoclimatic reconstruction is unsound, because most pingos in North America and the Soviet Union commenced growth hundreds to thousands of years ago under mean annual air temperatures that may have differed greatly from those of the present. Some other factors to be considered in paleoclimatic reconstruction are the thermal offset; site availability; the differing requirements for the growth of large pingos as compared with small pingos; and the long time required for pingos to grow to full size.

The origin of hummocks, Western Arctic Coast, Canada

Article

Feb 2011

J. Ross Mackay

Hummocks (nonsorted circles) are widely distributed in arctic and subarctic regions. The hummocks under discussion are composed of fine-grained frost-susceptible soils; the late summer frost table is bowl-shaped; and the hummocks grade from those which are completely vegetated (earth hummocks) to those with bare centres (mud hummocks). The mound form is usually attributed to an upward displacement of material resulting from cryostatic (freeze-back) pressure generated in a confined, wet, unfrozen pocket of the active layer. Theoretically, cryostatic pressure should not develop in a frost-susceptible hummock soil, because ice lensing at the top and (or) bottom of the active layer will desiccate the last unfrozen pocket so that the pore water is under tension, not pressure. Field observations carried out at Garry Island, Northwest Territories, for 1965–1979 and for 1967–1979 at Inuvik, Northwest Territories, involving: summer and winter excavations; the measurement of the deformation of tubes, soil pressure, soil temperature, soil heave, soil moisture migration; and observations on hummock stability provide no field evidence for the cryostatic theory. An alternative model of hummock growth, based upon field observations, is here proposed. The upward displacement of material is believed caused by freeze–thaw of ice lenses at the top and bottom of the active layer with a gravity-induced cell-like movement, because the top and bottom freeze–thaw zones have opposite curvatures. The cell circulation is evident from the grain-size distribution of hummock soils and from upward-moving tongues of saturated soil observable in late summer. The most active period is in late summer. Model experiments in the laboratory have been successful in producing mounds by freeze–thaw of a kaolin slurry in a bowl-shaped container in support of the proposed theory.

Freshwater shelled invertebrate indicators of paleoclimate in northwestern Canada during late glacial times: Discussion

Article

Feb 2011

J. Ross Mackay

The Origin of Massive Icy Beds in Permafrost, Western Arctic Coast, Canada

Article

Feb 2011

J. Ross Mackay

Massive beds of ground ice are shown to exist along the arctic coastal plain east of the Alaska–Yukon boundary for a distance of at least 500 km. The massive ground ice can be seen in both undisturbed and glacially disturbed Pleistocene sediments. An examination of several thousand seismic shot hole logs, from drill holes of 15 to 35 m in depth, also corroborates the widespread occurrence of ground ice. The icy beds typically have an ice content, defined in terms of the weight of ice to dry soil, in excess of 200% for sections as much as 35 m thick. A theory is presented which suggests that: the ice is of segregation origin; the source of excess water was from the expulsion of ground water during the freezing of sands; and high pore water pressures, favorable to ice segregation, developed beneath an aggrading impermeable permafrost cover. Permafrost aggradation may have occurred either on an exposed sea floor during a period of sea level lowering which would have accompanied a glacier advance, or following a warm interval in which there had been deep thaw. Similarities in the origin of pingo ice and massive ice are discussed.

The World Of Underground Ice

Article

Mar 1972

J. R. Mackay

Underground ice is restricted to permafrost areas where its distribution is sporadic and often unpredictable. A knowledge of the distribution and abundance of underground ice is essential to northern development, because a variety of man induced disturbances can cause underground ice to thaw, often with serious consequences. The criteria for a classification of the principal types of underground ice are the source of the water prior to freezing and the processes which transfer water to the freezing plane. The origin of massive icy bodies in the Western Arctic of North America is explained by a water expulsion theory. The excess water now found in the icy bodies is attributed to water expelled from coarse textured sediments by the downward growth of permafrost. The suggested mechanism is illustrated by three pingos which have grown since 1950. The role of glaciation in the formation of relic offshore permafrost in relatively shallow Arctic coastal areas is examined. The evidence suggests that offshore permafrost is present in some shallower portions of the Beaufort Sea from northeastern Alaska eastwards to the high Arctic islands of Canada. If offshore permafrost with underground ice is present, then thermal disturbance problems must be taken into consideration in future offshore exploration.

Near-surface brecciation of Chalk, Isle of Thanet, south-east England: A comparison with ice-rich brecciated bedrocks in Canada and Spitsbergen

Article

Apr 1996
PERMAFROST PERIGLAC

Julian Murton

Chalk on the Isle of Thanet, Kent, is brecciated to depths of a few metres beneath the ground surface. The brecciation commonly comprises (i) an undeformed layer of angular, platy blocks more or less parallel to the surface overlain by (ii) a deformed layer containing small open folds, typically with vertical axial planes. Above the brecciated chalk is an involuted layer (∼0.5 to 2.0 m thick) of chalk diamicton and brickearth.By analogy with brecciated ice-rich limestones, arkoses and shales in areas of continuous permafrost in Arctic Canada and Spitsbergen, it is suggested that brecciation of the Chalk resulted primarily from ice segregation in perennially frozen bedrock, and repeated segregation formed an ice-rich layer just beneath the former permafrost table. Subsequent thaw consolidation of this layer is thought to have formed an involuted layer through soft-sediment deformation.Three implications arise from this study: (i) near-surface brecciation of the Chalk probably took place during conditions of continuous permafrost; (ii) the growth and thaw of the ice-rich layer in chalk was probably an important element in the geomorphological evolution of the English Chalklands, heaving and brecciating the Chalk during permafrost conditions, and deforming or redepositing the overburden during periods of active-layer deepening; and (iii) repeated ice segregation near the top of permafrost may have brecciated other bedrocks in the British Isles.

Evidence of climatic change from oxygen and carbon isotope variations in sediments of a small arctic lake, Canada

Article

Aug 2010
J QUATERNARY SCI

Radiocarbon dating of the organic‐rich sediments of Lake Illisarvik in the outer Mackenzie Delta indicates that formation of the lake occurred approximately 9500yr BP, with maximum expansion around 6000 yr BP. Sedimentation rates have remained relatively constant at an average of 0.3mm/yr. ¹³ C results on biogenic and inorganic carbonates and organics indicate a change from dominantly terrestrial organics (−27 to −28% 0 ) to submerged aquatic vegetation or plankton (−18 to −23% 0 ) upon formation of the lake (9500yr BP), and a dramatic return to dominantly terrestrial organics at 5800yr BP (δ ¹³ C = −27 to −30% 0 ). This latter shift is accompanied by a drastic reduction in the macroflora and fauna populations. ¹⁸ O results suggest that a warmer climate than today existed prior to the shift at 5800yr BP.

Thermokarst involutions, Summer Island, Pleistocene Mackenzie Delta, western Canadian Arctic

Article

Jul 1993
PERMAFROST PERIGLAC

Thermokarst involutions form primarily by loading, buoyancy and water‐escape during the degradation of ice‐rich permafrost. In the Summer Island area of the Pleistocene Mackenzie Delta, they are formed mainly by loading and buoyancy, and occur within a Late Wisconsinan‐Early Holocene thaw layer. Involutions formed by water‐escape (fluidization) occur within slump‐floor deposits. To form thermokarst involutions, ice‐rich permafrost must thaw, drainage conditions must be poor and sediments must vary in texture or composition. In addition, the sediments should be susceptible to fluidization, liquefaction or hydroplastic deformation. Thermokarst involutions formed by loading and buoyancy require a reverse density gradient; those formed by fluidization require open‐system groundwater conditions or associated water‐saturated sediments susceptible to liquefaction.

Involutions in the Middle Pleistocene (Anglian) Barham Soil, eastern England: a comparison with thermokarst involutions from Arctic Canada

Article

Jan 2008
BOREAS

Involutions in the early Anglian Barham Soil at Newney Green, Essex, and Badwell Ash, Suffolk, in eastern England, are attributed to soft-sediment deformation during an episode of regional thermokarst development. The involutions show a striking resemblance in morphology and size to thermokarst involutions within a palaeo-thaw layer at Crumbling Point, western arctic Canada. By analogy with the thermokarst involutions, the involutions in the Barham Soil are reinterpreted to have formed by loading during the melting of an ice-rich layer at the top of Anglian permafrost. This period of thermokarst development may have coincided with an episode of intra-Anglian climatic amelioration. Reinterpretation of the Barham Soil involutions implies that many other Pleistocene involutions in Britain may have formed during periods of thermokarst development rather than by active-layer cryoturbation.

Thaw modification of frost‐fissure wedges, Richards Island, Pleistocene Mackenzie Delta, Western Arctic Canada

Article

Jan 1993
J QUATERNARY SCI

Thaw modification is the general process whereby frost‐fissure wedges are modified during thaw, and by which frost‐fissure pseudomorphs may develop. Specific processes of thaw modification are inferred from ice‐wedge pseudomorphs, composite‐wedge pseudomorphs and deformed sand wedges in the Pleistocene Mackenzie Delta: i.e. thermal erosion, collapse, subsidence, refreezing, loading, buoyancy, spreading, folding and shearing. Thaw modification is believed to result in selective preservation of pseudomorphs and wedges. Sand wedges are more likely to be preserved than are ice‐wedge pseudomorphs or compositewedge pseudomorphs, because only those sand wedges that penetrate massive ice or icy sediments are prone to thaw modification. Furthermore, whereas ice wedges preferentially develop in ice‐rich, fine‐grained sediments (thaw‐sensitive), their pseudomorphs appear to be selectively preserved in ice‐poor, coarse‐grained sediments (thaw‐stable).

Thermokarst-lake-basin sediments, Tuktoyaktuk Coastlands, Western Arctic Canada

Article

Jun 2006
SEDIMENTOLOGY

Julian Murton

Three stages of deposition are distinguished in thermokarst‐lake‐basin sequences in ice‐rich permafrost of the Tuktoyaktuk Coastlands, western arctic Canada: (1) widespread retrogressive thaw slumping around lake margins that rapidly transports upland sediments into thermokarst lakes, forming a distinctive basal unit of impure sand and/or diamicton; (2) a reduction or cessation of slumping‐because of the pinching out of adjacent ground ice, slump stabilization or climatic cooling, that reduces the input of clastic sediment, permitting reworking of sediment around lake margins and suspension settling, principally in basin centres; (3) lakes drain and deposition may continue by gelifluction and accumulation of in situ peat or aeolian sand. Radiocarbon dating of detrital peat and wood from a progradational sequence (basal unit) defines a lateral younging trend in the direction of progradation. A progradation rate is calculated to be ∼ 4 cm yr ⁻¹ , consistent with rapid deposition during stage (1) above. The nonuniform nature of the trend is attributed to episodic influxes of old organic material by slumping and reworking by waves and currents. In comparison with thermokarst‐lake‐basin sequences previously described in Alaska, Canada and Siberia, the middle unit of those in the Tuktoyaktuk Coastlands is similar, whereas the basal unit is generally thicker and, by contrast, often contains diamicton. These differences are attributed, respectively, to larger‐scale resedimentation of upland sediments by retrogressive thaw slumping and debris‐flow deposition in thermokarst lakes in the Tuktoyaktuk Coastlands. Compared with the sediments within supraglacial lakes in areas of moderate to high relief, the middle unit of thermokarst‐lake‐basin sequences in the Tuktoyaktuk Coastlands lacks clastic varves and the basal unit is much thinner and texturally less variable. These differences are attributed to higher relief and larger volumes of meltwater and glacigenic sediment in supraglacial lakes, which promote more suspension settling and resedimentation of glacigenic sediment than in thermokarst lakes in the Tuktoyaktuk Coastlands. It may be impossible to distinguish glacial and periglacial thermokarst‐lake‐basin sediments in permafrost areas of incomplete deglaciation. Not only is it often difficult to distinguish intrasedimental and buried glacier ice, but the depositional processes associated with thaw of both ice types are presumably the same and the host sediments very similar.

Ice wedges: Growth, thaw transformation, and palaeoenvironmental significance

Article

Jan 1988
J QUATERNARY SCI

Frost-cracking and ice-wedge growth are fundamental processes within the permafrost environment. Extensive areas of contemporary permafrost terrain are characterised by frost-fissure polygons, formed by repeated thermal contraction-cracking of the ground. The incremental growth of ice veins and wedges along the axes of contraction-cracks contributes significantly to the volume of ground ice in near-surface permafrost. In areas beyond the present limit of permafrost, the recognition of ice-wedge pseudomorphs provides one of the few unambiguous indications of the former existence of permafrost conditions. An understanding of the processes of ice-wedge growth and thaw transformation is essential if contemporary ice wedges are to be used as analogues for Pleistocene frost-fissure structures, in palaeoenvironmental reconstructions.

Observations on buried glacier ice and massive segregated ice, Western Arctic Coast, Canada

Article

Jan 2007
PERMAFROST PERIGLAC

The two main theories for the origin of the thick bodies of massive ground ice known to exist in the Western Canadian Arctic are (1) segregation-injection and (2) buried glacier ice. Because buried glacier ice may contain significant quantities of stratified debris and may have experienced thawing and refreezing (regelation) on several occasions, it may be very difficult to distinguish between massive segregated ice and buried basal glacier ice. By use of cryostratigraphic and cryotextural (petrofabric) observations, massive ground ice bodies observed in the Sandhills Moraine, southern Banks Island, and the southern Eskimo Lakes region, Pleistocene Mackenzie Delta, are both interpreted as basal glacier ice. Other massive ground ice bodies which have been examined in the Western Canadian Arctic are best explained in terms of segregation-injection. Les deux théories principales qui ont été avancées pour expliquer l'origine des glaces massives qui existent dans le sol de l'Arctique canadien occidental consistent à les considérer soit comme de la glace de ségrégation-injection, soit comme de la glace de glacier enfouie. Comme la glace de glacier enfouie peut contenir des quantités significatives de débris stratifiés et peut avoir subi des phénomènes de fusion et de regel (regélation) en plusieurs occasions, il est souvent très difficile de distinguer ces deux types de glace. Sur la base d'observations cryostratigraphiques et cryotexturales (petrofabrique), des corps de glace massive observées dans la moraine Sandhills (au sud de l'ǐle de Banks) et dans la région méridionale de la région des lacs Esquimaux (delta pléistocène du Mackenzie) sont toutes deux interprétées comme de la glace du glacier. D'autres corps de glace massive qui ont été examinés dans l'Arctique canadien occidental sont le mieux expliqués comme de la glace de segrégation-injection.

Weichselian Convolution Phenomena and processes in fine sediments.

Article

Dec 1982
BOREAS

In three excavations in the southern Netherlands and northern Belgium, the Weichselian convolutions in fine sand, silt and clay deposits were investigated, and an attempt was made towards a semi-quantitative approach to some sediment parameters. This, together with a detailed field survey, enabled interpretation of the deformations as forms of periglacial loadcasting. They originated from the time of permafrost degradation when large quantites of water were available. The amplitude of the involutions can be related to the depth of the permafrost table at that time. During the weichselian, two periods occurred in which this involution process could have been active

Periglacial Features Indicative of Permafrost: Ice and Soil Wedges

Article

Mar 1976

ROBERT F. BLACK

Ice wedges are wedge-shaped masses of ice, oriented vertically with their apices downward, a few millimeters to many meters wide at the top, and generally less than 10 m vertically. Ice wedges grow in and are confined to humid permafrost regions. Snow, hoar frost, or freezing water partly fill winter contraction cracks outlining polygons, commonly 5–20 m in diameter, on the surface of the ground. Moisture comes from the atmosphere. Increments of ice, generally 0.1–2.0 mm, are added annually to wedges which squeeze enclosing permafrost aside and to the surface to produce striking surface patterns. Soil wedges are not confined to permafrost. One type, sand wedges, now grows in arid permafrost regions. Sand wedges are similar in dimensions, patterns, and growth rates to ice wedges. Drifting sand enters winter contraction cracks instead of ice. Fossil ice and sand wedges are the most diagnostic and widespread indicators of former permafrost, but identification is difficult. Any single wedge is untrustworthy. Evidence of fossil ice wedges includes: wedge forms with collapse structures from replacement of ice; polygonal patterns with dimensions comparable to active forms having similar coefficients of thermal expansion; fabrics in the host showing pressure effects; secondary deposits and fabric indicative of a permafrost table; and other evidence of former permafrost. Sand wedges lack open-wedge, collapse structures, but have complex, nearly vertical, crisscrossing narrow dikelets and fabric. Similar soil wedges are produced by wetting and drying, freezing and thawing, solution, faulting, and other mechanisms. Many forms are multigenetic. Many socalled ice-wedge casts are misidentified, and hence, permafrost along the late-Wisconsinan border in the United States was less extensive than has been proposed.

Thermokarst in Siberia and Its Influence on the Development of Lowland Relief

Article

Sep 1970

“Thermokarst” as a process is the melting of ground ice and the consequent formation of depressions. Thermokarst landforms depend on the tectonic regime of a region, the ground ice content, and the degree to which the permafrost equilibrium is disturbed. Thermokarst forms are especially prominent in the lowlands of the subnival region with permafrost. The authors distinguish two modes of thermokarst development—permafrost back-wearing and down-wearing—based on their investigations in Siberia. The first mode is characteristic of a more dissected relief. In this case permafrost back-wearing takes place and the process is characterized by development of gullies, thermocirques, and parallel retreat of steep walls with ice veins, resulting in a lower lowland level. The second mode of thermokarst development is due to permafrost melting from above and is typical of a flat undissected relief, mainly that of watershed regions. characteristic forms are depressions with steep slopes and flat floors (alases). Thermokarst valleys develop through coalescence of alases. Thermokarst processes destroy the lowland relief of large areas and create characteristic forms resulting in a lower lowland level. Thus thermokarst represents a special type of lowland development in permafrost conditions.

Sedimentary Structures: Their Character and Physical Basis

Article

Jan 1982

John Allen

The Periglacial Environment

Article

Jan 1984

H. M. French

The Periglacial Environment, Third Edition, provides an authoritative overview of the worldâ??s cold, non-glacial environments. Emphasis is placed upon the North American and Eurasian polar lowlands, but examples are also drawn from Antarctica, the Qinghai-Xizang (Tibet) Plateau, and the northern mid-latitudes. First published in 1976 and subsequently revised in 1996, the text has been the international standard forâ over 30 years. The Third Edition continues to be a personal interpretation of the frost-induced conditions, geomorphic processes, and landforms that typify periglacial environments. The text is divided into four parts. Part One discusses the periglacial concept and its interactions with geomorphology, geocryology and Quaternary science. It also outlines the range and variability of periglacial climates and the degree to whichâ landscapes are in geomorphic equilibrium with prevailing periglacial conditions. Part Two describes present-day terrain that is either underlain by permafrost or experiencing intense frost action. The roles played by cryogenic weathering, ground ice, mass wasting, running water, wind action, snow and ice, and coastal processes are systematically analysed. Part Three summarizes evidence for the existence of periglacial conditions during the cold periods of the Pleistocene, with special reference to the mid-latitudes of Europe and North America. Part Four illustrates the geotechnical problems associated with human activity and resource development in periglacial environments, and discusses the potential impact of global climate change in the northern high latitudes. This excellent textbook is an invaluable resource for second and third year undergraduate students of Physical Geography, Geology, Environmental Science and Earth Science. The Periglacial Environment, Third Edition is also anâ informative reading for professionals, researchers and lecturers working and teaching in the field.

Thermokarst sediments and sedimentary structures, Tuktoyaktuk Coastlands, western Arctic Canada

Abstract

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