Fluted moraine formation and till genesis below a temperate valley glacier: Slettmarkbreen, Jotunheimen, southern Norway

Clast fabric and morphological data have been used to determine the origin of fluted subglacial tills exposed by recent retreat of the Slettmarkbreen glacier, Norway. A new method for the interpretation of clast fabric data allows aspects of the strain and depositional history of the till to be reconstructed. The till formed by a combination of lodgement and subsole deformation by slip along discrete shear planes. Lodgement was dominant for the larger size fractions (>125 mm), while the smaller material was more susceptible to deformation. The fluted till surface reflects the tendency for the till matrix to deform into regions of low confining pressure in the lee of lodged boulders. Downglacier components of till flow are thought to have resulted in significant sediment transfer towards the margin.     

Podzol development, vegetation change and glacier variations at Haugabreen, southern Norway

¹⁴C dating and pollen analysis of the surface organic (LFH) horizons of several humo-ferric podzol profiles forming a soil catena close to the 'Little Ice Agc' outer moraine ridge of Haugabreen, southern Norway, are used to examine the timing and nature of podzol development at the low-/sub-alpine margin of the Jostedalsbreen area. Comparison with results from a palaeosol buried beneath the outer moraine shows that FH horizon development began as early as 5,265 ± 65 B.P., but that it was not synehronous across the profiles, the latest profile having a date of 3,590 ± 65 B.P. It is argued that surface organic horizons developed as a response to a deterioration of climate and possibly the recrudescence of the Myklebustbreen ice cap at c . 5,000 B.P., and that the dates for horizon initiation vary according to local topographic and soil-hydrologic conditions. It is still uncertain whether the hump-ferric podzols were preceded by brown earths or weakly podzolised sub-alpine podzolic soils, but at all sites where pollen evidence is available it appears that FH initiation took place beneath Betula woodland.     

Processes of annual moraine formation at a temperate alpine valley glacier: insights into glacier dynamics and climatic controls

This paper presents the first detailed sedimentological study of annual moraines formed by an alpine valley glacier. The moraines have been forming since at least AD 1980 by a subsidiary lobe of Gornergletscher, Switzerland that advances up a reverse bedrock slope. They reach heights of 0.5–1.5 m, widths of up to 6 m and lengths of up to several hundreds of metres. Sediments in these moraines are composed of proglacial outwash and debris flow units; subglacial traction till is absent entirely. Based on four representative sections, three genetic process combinations have been identified: (i) inefficient bulldozing of a gently sloping ice margin transfers proglacial sediments onto the ice, causing differential ablation and dead‐ice incorporation upon retreat; (ii) terrestrial ice‐contact fans are formed by the dumping of englacial and supraglacial material from point sources such as englacial conduit fills; debris flows and associated fluvial sediments are stacked against a temporarily stationary margin at the start, and deformed during glacier advance in the remainder, of the accumulation season; (iii) a steep ice margin without supraglacial input leads to efficient bulldozing and deformation of pre‐existing foreland sediments by wholesale folding. Ice‐surface slope appears to be a key control on the type of process responsible for moraine formation in any given place and year. The second and third modes result in stable and higher moraines that have a higher preservation potential than those containing dead ice. Analysis of the spacing and climatic records at Gornergletscher reveals that winter temperature controls marginal retreat and hence moraine formation. However, any climatic signal is complicated by other factors, most notably the presence of a reverse bedrock slope, so that the extraction of a clear climatic signal is not straightforward. This study highlights the complexity of annual moraine formation in high‐mountain environments and suggests avenues for further research.     

Within-valley asymmetry and related problems of Neoglacial lateral moraine development at certain Jotunheimen glaciers, southern Norway

A difference in the size of Neoglacial lateral moraines on either side of a valley axis (within-valley asymmetry of lateral moraine development) is described. Analysis of clast roundness has revealed subangular material in latero-terminal and terminal moraines; lateral moraines, however, exhibit a compositional gradient of increasing angularity with distance from the former glacier snout. Comparisons with clasts of known origin suggest that this 'roundness gradient' may be explained with reference to either or both of two hypotheses: (1) a variable proportion of supraglacial (or englacial) to subglacial transported material; and (2) the variable composition of regolith incorporated by a push mechanism from the valley sides. Within-valley asymmetry is inferred to result where the supply of debris to lateral moraines from these sources is unequal either side of a valley axis. Both interpretations are also consistent with the relatively large size of latero-terminal sections of end moraines. In order to account for the discrepancy between moraine size and apparent debris supply rates, it is suggested that the largest lateral moraines may have been formed over a longer time scale than the 'Little Ice Age', and that reworking of deposits may have occurred. The supply of debris to the north-facing lateral moraine at Nordre Illåbreen has been so great that it has developed into a rock glacier; this suggests the possibility that subglacial material and valley-side regolith, as well as supraglacial material, contributes to the formation of ice-cored rock glaciers.     

The formation of a geometrical ridge network by the surge-type glacier Kongsvegen,Svalbard

Traditionally, geometrical ridge networks are interpreted as the product of the flow of subglacial sediment into open basal crevasses at the cessation of a glacier surge (‘crevasse-fill’ ridges). They are widely regarded as a characteristic landform of glacier surges. Understanding the range of processes by which these ridge networks form is therefore of importance in the recognition of palaeosurges within the landform record. The geometrical ridge network at the surge-type glacier Kongsvegen in Svalbard, does not form by crevasse filling. The networks consist of transverse and longitudinal ridges that can be seen forming at the current ice margin. The transverse ridges form as a result of the incorporation of basal debris along thrust planes within the ice. The thrusts were apparently formed during a glacier surge in 1948. Longitudinal ridges form through the meltout of elongated pods of debris, which on the glacier surface are subparallel to the ice foliation and pre-date the surge. This work adds to the range of landforms associated with glacier surges.     

The age and origin of Neoglacial moraines in Jotunheimen, southern Norway: new evidence from weathering-based data

This paper considers the controversial issue of the existence of pre-'Little Ice Age' Neoglacial moraines in southern Norway. Schmidt hammer rebound values are combined with measures of boulder roundness and weathering rind thickness in an attempt to isolate moraines that include weathered boulders. A critical approach is used in distinguishing sites where boulders have weathered in situ from those where previously weathered clasts have been incorporated into relatively young moraines. The results confirm that possible pre-'Little Ice Age' Neoglacial moraines seem to be restricted to small, high-altitude glaciers in eastern Jotunheimen. It is concluded that at these glaciers a particularly large response to a short-lived earlier Holocene climatic event is more likely to explain the survival of such moraines than a particularly subdued response to the climatic deterioration of the 'Little Ice Age'. More refined dating techniques are required to determine the age of formation of the anomalous moraines, but before the palaeoclimatic significance of such dates can be assessed, a critical test is required to establish whether the moraines mark former ice-front positions, and therefore reflect lowering of equilibrium line altitudes, or whether they have been displaced forwards by later and more extensive glacier advances.     

Holocene glacier history of Bjørnbreen and climatic reconstruction in central Jotunheimen,Norway, based on proximal glaciofluvial stream-bank mires

Holocene variations of Bjørnbreen, Smørstabbtinden massif, west-central Jotunheimen are reconstructed from the lithostratigraphy of two alpine stream-bank mires flooded episodically by meltwater. The approach uses multiple sedimentological indicators (weight loss-on-ignition, mean grain size, grain-size fractions, bulk density, moisture content and magnetic susceptibility), an a priori model of overbank deposition of suspended glaciofluvial sediments, a detailed chronology based on 56 radiocarbon dates, and a Little Ice Age sedimentological analogue. Rapid, late-Preboreal deglaciation was indicated by immigration of Betula pubescens by 9700 cal. BP. An interval of at least 3000 years in the early Holocene when glaciers were absent was interrupted by two abrupt episodes of glacier expansion around the time of the Finse Event, the first at ca 8270–7900 cal. BP (Bjørnbreen I Event) and the second at ca 7770–7540 cal. BP (Bjørnbreen II Event). Neoglaciation began shortly before ca 5730 cal. BP with gradual build-up to the maximum of the Bjørnbreen III Event at ca 4420 cal. BP. Later maxima occurred at ca 2750 cal. BP (Bjørnbreen IV Event) and at 1300, 1260, 1060 and 790 cal. BP (all within the Bjørnbreen V Event). Glaciers were smaller than today and possibly melted away on several occasions in the late Holocene (ca 3950, 1410 and 750 cal. BP). Minor maxima also occurred at ca 660 and 540 cal. BP, within the late Mediaeval Warm Period and the early Little Ice Age, respectively. The Little Ice Age maximum was dated to 213±25 BP (ca 205 cal. BP). The relative magnitudes of the main glacier maxima were determined: Erdalen Event>Little Ice Age Event (Bjørnbreen VI)>Bjørnbreen I (Finse Event) ≈ Bjørnbreen II>Bjørnbreen V⩾Bjørnbreen IV>Bjørnbreen III. These episodic events of varying magnitude and abruptness were used in conjunction with an independent summer-temperature proxy to reconstruct variations in equilibrium-line altitude (ELA) and a Holocene record of winter precipitation. Since the Preboreal, ELA varied within a range of about 390 m, and winter precipitation ranged between 40 and 160% of modern values. Winter precipitation variations appear to have been the main cause of these century- to millennial-scale Holocene glacier variations.     

Lake shoreline development, frost weathering and rock platform erosion in an alpine periglacial environment, Jotunheimen, southern Norway

Ice-dammed lake Boverbrevatnet existed for 75–125 years in the 'Little Ice Age'. After about A.D. 1826, glacier retreat led to a fall in lake level and to exposure of the former shoreline, which includes well-developed platforms cut in metamorphic bedrock. The rock platforms, up to 5.3 m wide and backed by cliffs up to 1.55 m high, are partially covered by large angular boulders which form pavements. Accurate levelling has permitted correlation of platform fragments, overflow cols and related features of the shoreline, such as benches eroded in moraines, ice-push ridges, a perched delta, vegetation trim-lines, lichen limits and a 'lichen-kill' zone. The evolution of the lake, the chronology of deglaciation and the period of formation of the rock platforms have been dated by lichenometry, supported by ¹⁴C dating, Schmidt hammer 'R'-values and historical data. The morphology of the rock platforms, together with estimates of their rate of erosion ranging from 1.4 to 7.1 cm/year, indicate the importance of frost shattering (frost riving, frost wedging or macrogelivation) at the lake margin under a periglacial climate, while the permanence of such platforms as landscape features suggests their use in the reconstruction of former periglacial environments. A semi-quantitative model is outlined for the development of rock platforms which emphasises deep penetration of the annual freeze-thaw cycle, the movement of unfrozen lake water towards the freezing plane, and the growth of segregation ice in fissures and cracks at the interface between lake ice and bedrock. Ice-push and ice-pull processes are involved primarily as transporting agents in the formation of boulder pavements and in the removal of debris from the platforms. Analogous processes may occur on polar coasts producing coastal rock platforms.     

Sedimentary facies and landform genesis at a temperate outlet glacier: Soler Glacier, North Patagonian Icefield

This paper focuses on the structural glaciology, dynamics, debris transport paths and sedimentology of the forefield of Soler Glacier, a temperate outlet glacier of the North Patagonian Icefield in southern Chile. The glacier is fed by an icefall from the icefield and by snow and ice avalanches from surrounding mountain slopes. The dominant structures in the glacier are ogives, crevasses and crevasse traces. Thrusts and recumbent folds are developed where the glacier encounters a reverse slope, elevating basal and englacial material to the ice surface. Other debris sources for the glacier include avalanche and rockfall material, some of which is ingested in marginal crevasses. Debris incorporated in the ice and on its surface controls both the distribution of sedimentary facies on the forefield and moraine ridge morphology. Lithofacies in moraine ridges on the glacier forefield include large isolated boulders, diamictons, gravel, sand and fine-grained facies. In relative abundance terms, the dominant lithofacies and their interpretation are sandy boulder gravel (ice-marginal), sandy gravel (glaciofluvial), angular gravel (supraglacial) and diamicton (basal glacial). Proglacial water bodies are currently developing between the receding glacier and its frontal and lateral moraines. The presence of folded sand and laminites in moraine ridges in front of the glacier suggests that, during a previous advance, Soler Glacier over-rode a former proglacial lake, reworking lacustrine deposits. Post-depositional modification of the landform/sediment assemblage includes melting of the ice-core beneath the sediment cover, redistribution of finer material across the proglacial area by aeolian processes and fluvial reworking. Overall, the preservation potential of this landform/sediment assemblage is high on the centennial to millennial timescale.     

Glacier thermal regime linked to processes of annual moraine formation at Midtdalsbreen,southern Norway

Glacier thermal regime is shown to have a significant influence on the formation of ice‐marginal moraines. Annual moraines at the margin of Midtdalsbreen are asymmetrical and contain sorted fine sediment and diamicton layers dipping gently up‐glacier. The sorted fine sediments include sands and gravels that were initially deposited fluvially directly in front of the glacier. Clast‐form data indicate that the diamictons have a mixed subglacial and fluvial origin. Winter cold is able to penetrate through the thin (<10 m) ice margin and freeze these sediments to the glacier sole. During winter, sediment becomes elevated along the wedge‐shaped advancing glacier snout before melting out and being deposited as asymmetrical ridges. These annual moraines have a limited preservation potential of ～40 years, and this is reflected in the evolution of landforms across the glacier foreland. Despite changing climatic conditions since the Little Ice Age and particularly within the last 10 years when frontal retreat has significantly speeded up, glacier dynamics have remained relatively constant with moraines deposited via basal freeze‐on, which requires stable glacier geometry. While the annual moraines on the eastern side of Midtdalsbreen indicate a slow steady retreat, the western foreland contains contrasting ice‐stagnation topography, highlighting the importance of local forcing factors such as shielding, aspect and debris cover in addition to changing climate. This study indicates that, even in temperate glacial environments, restricted or localised areas of cold‐based ice can have a significant impact on the geomorphic imprint of the glacier system and may actually be more widespread within both modern and ancient glacial environments than previously thought.     

A preliminary history of Holocene colluvial (debris-flow) activity,Leirdalen, Jotunheimen,Norway

A stratigraphic succession of alternating peat and minerogenic sediments at the foot of a steep mountain slope provides the basis for the reconstruction of a preliminary colluvial history from the alpine zone of Jotunheimen, southern Norway. Layers of silty sand and sandy silt, typically 5–10 cm thick and interpreted as distal debris-flow facies, are separated by layers of peat that have been radiocarbon dated. Deposition from at least 7500 to about 3800 ¹⁴C yr BP of predominantly minerogenic material suggests relatively infrequent but large-magnitude debris-flow events in an environment warmer and/or drier than today. Particularly low colluvial activity between about 6500 and 3900 ¹⁴C yr BP was terminated by a succession of major debris-flow events between about 3800 and 3400 ¹⁴C yr BP. Unhumified peats indicative of higher water tables, separate six debris-flows that occurred between about 3300 and 2300 ¹⁴C yr BP and signify a continuing high frequency of colluvial activity. Uninterrupted peat accumulation between about 2400 and 1600 ¹⁴C yr BP indicates reduced debris-flow activity; subsequent renewed activity appears to have culuminated in the ‘Little Ice Age’ after about 600 ¹⁴C yr BP. This pattern of colluvial deposition demonstrates a long history of natural Holocene low-alpine landscape instability, suggests an increase first in the magnitude and then in the frequency of debris-flow activity coincident with late Holocene climatic deterioration, and points to the potential of debris-flow records as a unique source of palaeoclimatic information related to extreme rainfall events. © 1997 John Wiley & Sons, Ltd.     

Esker formation and glacier dynamics in eastern Skane and adjacent areas, southern Sweden

Eskers were investigated in an area with overall terrestrial deglaciation - the eastern part of the province of Skåne and adjacent areas in southern Sweden. On the basis of the proposed model of esker formation, the dynamics of the receding Weichselian Ice Sheet are discussed. The deglaciation was characterized by the gradual retreat of an active ice sheet, bordered by a zone of thin, stagnant ice. For the most part, the ice sheet was probably at the pressure melting point in a marginal zone, where it was penetrated by surface meltwater which constituted most of the subglacially flowing meltwater. The esker sediments, consisting of glaciofluvially reworked basal debris and basal till, accumulated progressively in an up-glacier direction. Deposition took place close to the live ice boundary in the zone with stagnant ice that fringed the receding ice sheet. The time-transgressive formation of the eskers is reflected by repeated sediment sequences (morphosequences), i.e. sedimentary units composed of ridges that merge into extended hummocky deposits in a down-glacier direction. They represent the momentary deposition of stratified drift in the proximal portion of the zone with stagnant ice.     

Hydrochemical characteristics of typical rivers in a temperate glacier basin, China

This study focused on the chemical compositions of the rivers around Yulong Mountain, one of the typical monsoonal temperate glacier regions in China. Water samples were collected from Baishui, Sanshu and Geji hydrological stations around Mt. Yulong during rainy season. The chemical analyses indicated that the river water around Mt. Yulong was characterized by high pH values (>8.0) and EC values varied from 36.4 to 71.7 μS/cm with an average of 52.6 μS/cm. Ca²⁺ and Mg²⁺ were the dominant cations, together accounting for about 90 % of the total cations. HCO₃ ^?, followed by SO₄ ^2?, was the dominant anion. Obvious variations had been perceived during the rainy season. River water chemistry in rainy season was mainly influenced by precipitation and rock weathering. The proportions of Na⁺, K⁺, Ca²⁺, Mg²⁺ and SO₄ ^2? from precipitation in river water were 23.44, 9.66, 3.10, 17.81 and 10.48 %, respectively. In addition, the ion characteristics of river water were mainly influenced by carbonate weathering. The human activities should not be ignored though its influence was little.     

Recent,very rapid retreat of a temperate glacier in SE Iceland

Iceland's glaciers are particularly sensitive to climate change, and their margins respond to trends in air temperature. Most Icelandic glaciers have been in retreat since c. 1990, and almost all since 1995. Using ice‐front measurements, photographic and geomorphological evidence, we examined the record of ice‐front fluctuations of Virkisjökull–Falljökull, a steep high‐mass‐turnover outlet glacier in maritime SE Iceland, in order to place recent changes in a longer‐term (80‐year) context. Detailed geomorphological mapping identifies two suites of annual push moraines: one suite formed between c. 1935 and 1945, supported by lichenometric dating; the other between 1990 and 2004. Using moraine spacing as a proxy for ice‐front retreat rates, we show that average retreat rates during the 1930s and 1940s (28 m a^?1) were twice as high as during the period from 1990 to 2004 (14 m a^?1). Furthermore, we show that both suites of annual moraines are associated with above‐average summer temperatures. Since 2005, however, retreat rates have increased considerably – averaging 35 m a^?1 – with the last 5 years representing the greatest amount of ice‐front retreat (～190 m) in any 5‐year period since measurements began in 1932. We propose that this recent, rapid, ice‐front retreat and thinning in a decade of unusually warm summers has resulted in a glaciological threshold being breached, with subsequent large‐scale stagnation of the glacier terminus (i.e. no forward movement) and the cessation of annual push‐moraine formation. Breaching this threshold has, we suggest, caused further very rapid non‐uniform retreat and downwasting since 2005 via a system feedback between surface melting, glacier thinning, decreased driving stress and decreased forward motion.     

A reconnaissance study of the distribution of Ba, Nb, Y, and Zr in some Jotun kindred gneisses from Central Jotunheimen, southern Norway

Abstract The Bergen-Jotun kindred rocks of this study, the Storådalen Complex (SCX), Svartdalen Gneiss (SG) and Mjølkedøla Purple Gabbro (MPG), have been shown to be a co-magmatic series with calc-alkaline affinities. The analyses of Ba, Nb, Y, and Zr presented here show no variation in these elements between the three rock units and are consistent with the calc-alkaline character of the rocks. The lithophile elements Ba, K, and Sr are enriched relative to MORB and the high field strength elements Nb, Y, and Zr are depleted relative to MORB, Zr especially so.
The SCX contains rocks with low (>30) differentiation indices which are interpreted as plagioclase + pyroxene ± olivine ± amphibole cumulates. The remainder of the SCX, together with the MPG and SG, is regarded as the congealed liquid in equilibrium with these cumulates. The distribution of trace elements between these two components of the SCX can be adequately modelled using a Rayleigh fractionation process, measured 'liquid'compositions, and calculated bulk distribution coefficients. It is thus concluded that the trace element geochemistry of the rocks of this study is consistent with subduction-related, mantle-derived magmas that fractionate within a continental or mature island arc environment. Subsequent high-grade metamorphism and deformation of Sveconorwegian age have been essentially isochemical.     

Arrested charnockite formation at Kottavattam, southern India

Abstract At Kottavattam, southern Kerala (India), late Proterozoic homogeneous leptynitic garnet–biotite gneisses of granitic composition have been transformed on a decimetric scale into coarse-grained massive charnockite sensu stricto along a set of conjugate fractures transecting the gneissic foliation. Charnockitization post-dates the polyphase deformation, regional high-grade metamorphism and anatexis, and evidently occurred at a late stage of the Pan-African tectonothermal history. Geothermobarometric and fluid inclusion data document textural and chemical equilibration of the gneiss and charnockite assemblages at similar P_lith–T conditions (650–700°C, 5–6 kbar) in the presence of carbonic fluids internally buffered by reaction with graphite and opaque mineral phases (X_CO2= 0.7–0.6; X_H2O= 0.2–0.3; X_N2= 0.1; log f_O2= -17.5). Mineralogical zonation indicates that charnockitization of the leptynitic gneiss involved first the breakdown of biotite and oxidation of graphite in narrow, outward-migrating transition zones adjacent to the gneiss, followed by the breakdown of garnet and the neoblastesis of hypersthene in the central charnockite zone. Compared to the host gneiss, the charnockite shows higher concentrations of K, Na, Sr, Ba and Zn and lower concentrations of Mg, Fe, Ti, V, Y, Zr and the HREE, with a complementary pattern in the narrow transition zones of biotite breakdown. The P_lith–T–X_H2O data and chemical zonation patterns indicate charnockitization through subsolidus-dehydration reaction in an open system. Subsequent residence of the carbonic fluids in the charnockite resulted in low-grade alteration causing modification of the syn-charnockitic elemental distribution patterns and the properties of entrapped fluids. We favour an internally controlled process of arrested charnockitization in which, during near-isothermal uplift, the release of carbonic fluids from decrepitating inclusions in the host gneiss into simultaneously developing fracture zones led to a change in the fluid regime from ‘fluid-absent’in the gneiss to ‘fluid-present’in the fracture zones and to the development of an initial fluid-pressure gradient, triggering the dehydration reaction.     

Morphological activity of a diverted glacier stream in Western Norway

In connection with the construction of a tunnel collecting water beneath a glacier (Bondhusbreen/Folgefonni) in SW Norway the amount of sediments transported by meltwater has been investigated. According to the values obtained the volume of the sedimentation chamber which has to take a one-years-amount of sediment was fixed at 5000 m³. In 1978 there has been a sedimentation of 3000 m³ of coarse material. The results obtained are not only of practical value, but also of scientific interest.     

Arctic-alpine brown soils as a source of palaeoenvironmental information: Further 14C dating and palynological evidence from Vestre Memurubreen,Jotunheimen, Norway

¹⁴C dating and pollen analytical evidence is presented relating to the usefulness of arctic-alpine Brown Soils for palaeoenvironmental reconstruction. A present-day soil has been examined together with its continuation beneath the outermost ?Little Ice Age’? end moraine of the glacier Vestre Memurubreen at a location well above the tree-line in the mid-alpine belt of southern Norway. Fourteen ¹⁴C dates from chemically-fractionated soil samples, which range in age from 495 ± 55 ¹⁴C yr in the uppermost 1 cm to > 4000 ¹⁴C yr within 13 cm of the buried soil surface, demonstrate near-linear age/depth gradients in the palaeosol. Continuous development of the palaeosol over at least 5000 calendar yr prior to burial confirms that Vestre Memurubreen attained its Neoglacial maximum extent in the ?Little Ice Age’?. Pollen stratification in buried and unburied profiles indicates a single vegetation change from a low-alpine dwarf-shrub heath to a mid-alpine ?grass’? heath, reflecting an altitudinal lowering of vegetation belts and a possible climatic cooling of 2-4°C. Surface additions of allochthonous (aeolian) mineral particles appear to have contributed to soil development, whilst mixing processes have been relatively unimportant at this site. The immobilisation of resistant organic residues and the ineffectiveness of biological and chemical activity are major reasons for the preservation of a palaeoenvironmental record in these high altitude soils.     

Small rock‐slope failures conditioned by Holocene permafrost degradation: a new approach and conceptual model based on Schmidt‐hammer exposure‐age dating,Jotunheimen, southern Norway

Rock‐slope failures (RSFs) constitute significant natural hazards, but the geophysical processes that control their timing are poorly understood. However, robust chronologies can provide valuable information on the environmental controls on RSF occurrence: information that can inform models of RSF activity in response to climatic forcing. This study uses Schmidt‐hammer exposure‐age dating (SHD) of boulder deposits to construct a detailed regional Holocene chronology of the frequency and magnitude of small rock‐slope failures (SRSFs) in Jotunheimen, Norway. By focusing on the depositional fans of SRSFs (≤10³ m³), rather than on the corresponding features of massive RSFs (~10⁸ m³), 92 single‐event RSFs are targeted for chronology building. A weighted SHD age–frequency distribution and probability density function analysis indicated four centennial‐ to millennial‐scale periods of enhanced SRSF frequency, with a dominant mode at ~4.5 ka. Using change detection and discreet Meyer wavelet analysis, in combination with existing permafrost depth models, we propose that enhanced SRSF activity was primarily controlled by permafrost degradation. Long‐term relative change in permafrost depth provides a compelling explanation for the high‐magnitude departures from the SRSF background rate and accounts for: (i) the timing of peak SRSF frequency; (ii) the significant lag (~2.2 ka) between the Holocene Thermal Maximum and the SRSF frequency peak; and (iii) the marked decline in frequency in the late‐Holocene. This interpretation is supported by geomorphological evidence, as the spatial distribution of SRSFs is strongly correlated with the aspect‐dependent lower altitudinal limit of mountain permafrost in cliff faces. Results are indicative of a causal relationship between episodes of relatively warm climate, permafrost degradation and the transition to a seasonal‐freezing climatic regime. This study highlights permafrost degradation as a conditioning factor for cliff collapse, and hence the importance of paraperiglacial processes; a result with implications for slope instability in glacial and periglacial environments under global warming scenarios.