Do Periglacial Landscapes Exist? A Discussion of the Upland Landscapes of Northern Interior Yukon, Canada

French, Hugh M.

doi:10.1002/ppp.1866

Cited by 17 publications

(29 citation statements)

References 47 publications

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“…There is a tendency, moreover, to attribute all bench-like landforms on hillslopes in periglacial environments to cryoplanation (Ballantyne, 2018). Furthermore, most examples referred to in the literature appear to be relict and it has even been suggested that some such terraces are not characteristic of a periglacial environment at all, may be pre-Quaternary in age and/or may simply reflect geological structure (Büdel, 1982;French, 2016French, , 2018. Although this study is heavily reliant on morphological evidence, an advantage of the cryoplanation terraces at Svartkampan is that they are currently active, at least in part.…”

Section: Recognising Cryoplanation Terracesmentioning

confidence: 99%

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Age and development of active cryoplanation terraces in the alpine permafrost zone at Svartkampan, Jotunheimen, southern Norway

et al. 2019

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Schmidt-hammer exposure-age dating (SHD) of boulders on cryoplanation terrace treads and associated bedrock cliff faces revealed Holocene ages ranging from 0 ± 825 to 8890 ± 1185 yr. The cliffs were significantly younger than the inner treads, which tended to be younger than the outer treads. Radiocarbon dates from the regolith of 3854 to 4821 cal yr BP (2σ range) indicated maximum rates of cliff recession of ~0.1 mm/yr, which suggests the onset of terrace formation before the last glacial maximum. Age, angularity, and size of clasts, together with planation across bedrock structures and the seepage of groundwater from the cliff foot, all support a process-based conceptual model of cryoplanation terrace development in which frost weathering leads to parallel cliff recession and, hence, terrace extension. The availability of groundwater during autumn freezeback is viewed as critical for frost wedging and/or the growth of segregation ice during prolonged winter frost penetration. Permafrost promotes cryoplanation by providing an impermeable frost table beneath the active layer, focusing groundwater flow, and supplying water for sediment transport by solifluction across the tread. Snow beds are considered an effect rather than a cause of cryoplanation terraces, and cryoplanation is seen as distinct from nivation.

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Section: Recognising Cryoplanation Terracesmentioning

confidence: 99%

“…The processes of cryoplanation also underpin attempts to define distinctive models of periglacial hillslope and landscape evolution (cf. Peltier, 1950; Richter et al, 1963; French, 2016).…”

Section: Introductionmentioning

confidence: 99%

Age and development of active cryoplanation terraces in the alpine permafrost zone at Svartkampan, Jotunheimen, southern Norway

et al. 2019

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“…Three distinct hypotheses for CT formation are supported in contemporary literature: (1) CTs are the result of geologic structure (e.g., Waters, 1962;Hall and André, 2010;French, 2016); (2) CTs are the result of a distinctively periglacial set of weathering and transportation processes associated with snowbanks circumscribed by the term nivation (e.g., Demek, 1969;Reger and Péwé, 1976;Nelson, 1989Nelson, , 1998Nelson and Nyland, 2017;and (3) CT formation can be dependent on the presence of permafrost, and nivation can be a secondary process suite operating on these features (Matthews et al, 2019).…”

Section: Introductionmentioning

confidence: 98%

Cosmogenic¹⁰Be and³⁶Cl geochronology of cryoplanation terraces in the Alaskan Yukon-Tanana Upland

2020

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Cryoplanation terraces are prominent but enigmatic landforms found in present and past periglacial environments. Geomorphologists have debated for more than a century over processes involved in the formation of these elevated, step-like, bedrock features. Presented here are the first numerical surface exposure ages and scarp retreat rates from cryoplanation terraces in the Yukon-Tanana Upland (YTU) in Alaska, part of unglaciated eastern Beringia, obtained from terrestrial cosmogenic nuclides (TCN) in surface boulders. Ages comprise six 10Be TCN ages from two terrace treads near Eagle Summit and six 36 Cl ages from two treads on Mt. Fairplay. Based on these exposure ages, scarps at both locations were last actively eroding from 49 to 22.4 ka. Both locations exhibit time-transgressive development, particularly near scarp-tread junctions. Boulder exposure ages and distances between sampled boulder locations were used to estimate scarp retreat rates of 0.11 to 0.56 cm/yr. These numerical exposure ages presented here demonstrate that the cryoplanation terraces in the YTU are diachronous surfaces actively eroding during multiple cold intervals. With these results, hypotheses for cryoplanation terrace formation are discussed and evaluated for the YTU, including those based on geologic structure, nivation, and the influence of permafrost.

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“…(cf. 10 ) and concluded 9, p.298 that periglacial landscapes in geomorphic equilibrium comprise (1) cold-climate deltas currently forming at the mouths of northern rivers, (2) unglaciated Pleistocene lowlands in high northern latitudes, and (3) some ice-free areas of Antarctica.…”

mentioning

confidence: 99%

What and where are periglacial landscapes?

Murton

2021

Permafrost & Periglacial

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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, frostsusceptible and nonfrost-susceptible terrains, cryopediments, and glacial-periglacial landscapes. Periglaciation can produce topographic fingerprints at mesospatial scales (10 3 -10 5 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.

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Do Periglacial Landscapes Exist? A Discussion of the Upland Landscapes of Northern Interior Yukon, Canada

Cited by 17 publications

References 47 publications

Age and development of active cryoplanation terraces in the alpine permafrost zone at Svartkampan, Jotunheimen, southern Norway

Age and development of active cryoplanation terraces in the alpine permafrost zone at Svartkampan, Jotunheimen, southern Norway

Cosmogenic¹⁰Be and³⁶Cl geochronology of cryoplanation terraces in the Alaskan Yukon-Tanana Upland

What and where are periglacial landscapes?

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Do Periglacial Landscapes Exist? A Discussion of the Upland Landscapes of Northern Interior Yukon, Canada

Cited by 17 publications

References 47 publications

Age and development of active cryoplanation terraces in the alpine permafrost zone at Svartkampan, Jotunheimen, southern Norway

Age and development of active cryoplanation terraces in the alpine permafrost zone at Svartkampan, Jotunheimen, southern Norway

Cosmogenic10Be and36Cl geochronology of cryoplanation terraces in the Alaskan Yukon-Tanana Upland

What and where are periglacial landscapes?

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Cosmogenic¹⁰Be and³⁶Cl geochronology of cryoplanation terraces in the Alaskan Yukon-Tanana Upland