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Schmidt-hammer exposure-age dating (SHD) was performed on blockfields and related landforms on Blåhø, Southern Norway. By developing a linear high-precision age-calibration curve through young and old control points of known age from terrestrial cosmogenic nuclide dating, it was possible to gain landform age estimates based on Schmidt hammer R-values. The aim of this study is to relate formation and subsequent stabilization of the landforms investigated to climate fluctuations since the Last Glacial Maximum (LGM) and to explore the palaeoclimatic implication of such periglacial landforms. The SHD ages range from 19.14 ± 0.91 ka for the Rundhø blockfield to 5.32 ± 0.73 ka for the lowest elevation rock-slope failure. The R-value frequency distributions obtained on the landforms studied indicate complex, longterm formation histories. Landforms above 1450 m a.s.l. share comparable SHD ages and seem to have stabilized during the Karmøy/ Bremanger readvance (~18.5-16.5 ka). The lower elevation rock-slope failures most likely occurred during the Bølling-Allerød interstadial (~14.7-12.9 ka) and the Holocene Thermal Maximum (~8.0-5.0 ka). The results contrast with the established model that rock-slope failures occur within the first millennia following deglaciation. Instead of the inferred ice coverage above 1450 m a.s.l. until 15.0 ± 1.0 10Be ka, our results suggest severe periglacial and ice-free conditions occurred earlier. Landforms above 1450 m a.s.l. do not show any form of reactivation during cold periods within the Late Glacial and Holocene. Our SHD results suggest that the landforms investigated were (at least partly) generated prior the LGM and survived beneath cold-based ice or were located on nunataks. [ABSTRACT FROM AUTHOR]

ABSTRACT Periglacial patterned ground (sorted circles and polygons) along an altitudinal profile at Juvflya in central Jotunheimen, southern Norway, is investigated using Schmidt-hammer exposure-age dating (SHD). The patterned ground surfaces exhibit R-value distributions with platycurtic modes, broad plateaus, narrow tails, and a negative skew. Sample sites located between 1500 and 1925 m a.s.l. indicate a distinct altitudinal gradient of increasing mean R-values towards higher altitudes interpreted as a chronological function. An established regional SHD calibration curve for Jotunheimen yielded mean boulder exposure ages in the range 6910 ± 510 to 8240 ± 495 years ago. These SHD ages are indicative of the timing of patterned ground formation, representing minimum ages for active boulder upfreezing and maximum ages for the stabilization of boulders in the encircling gutters. Despite uncertainties associated with the calibration curve and the age distribution of the boulders, the early-Holocene age of the patterned ground surfaces, the apparent cessation of major activity during the Holocene Thermal Maximum (HTM) and continuing lack of late-Holocene activity clarify existing understanding of the process dynamics and palaeoclimatic significance of large-scale sorted patterned ground as an indicator of a permafrost environment. The interpretation of SHD ages from patterned ground surfaces remains challenging, however, owing to their diachronous nature, the potential for a complex history of formation, and the influence of local, non-climatic factors. [ABSTRACT FROM AUTHOR]

High-precision Schmidt-hammer exposure-age dating ( SHD) is applied to ice-cored moraine-ridge complexes at three high-alpine glaciers in Jotunheimen and Breheimen, southern Norway. Local calibration curves were established using moraine ridges dating from the last 50 years and bedrock surfaces deglaciated ∼9700 years ago. SHD ages, with 95% statistical confidence intervals, ranged from 3920 ± 790 years to a negative (futuristic) age of -890 ± 580 years at Gråsubreen, 420 ± 700 to 260 ± 710 years at Vesle-Juvbreen and 2250 ± 450 to 1605 ± 410 years at Østre Tundradalskyrkjabreen. Negatively skewed R-value distributions were interpreted as the result of weathered boulders from reworked surfaces. This leads to the interpretation of these SHD ages as maximum estimates of moraine-ridge age. Østrem's hypothesis (that the proximal ridges are the oldest and survived being overridden many times) is rejected on the basis of our SHD ages. Although ice-cored moraine ridges resemble the flow structures of rock glaciers, Barsch's hypothesis (that these ice-cored moraine complexes are rock glaciers) is also rejected. Instead, the ice-cored moraine-ridge complexes are considered to be glaciotectonic structures produced by the interaction of polythermal glaciers and alpine permafrost over the late Holocene. All the individual ridges were essentially formed during the ' Little Ice Age' glacier advance from material deposited earlier by multiple neoglacial events. The considerable size of the moraine complexes is attributed not only to the accumulation of material from these different events over a long period of time but also to their survival in the landscape during phases of glacier retreat when ice cores do not melt and fluvial and other destructive processes remain ineffective in the permafrost environment. [ABSTRACT FROM AUTHOR]

ABSTRACT. Owing to increased winter balances especially since AD 1988/89, almost all valley outlet glaciers of Jostedalsbreen in western Norway are experiencing the largest advance since that of the early 18th century, the regional "Little Ice Age" maximum. Brigsdalsbreen advanced 441 m between 1987 and 1997. By the end of this period, the glacier had reached the outlet of the proglacial lake Brigsdalsvatnet, ploughing into unfrozen, fine-grained, water-soaked glaciolimnic sediments from the lake bottom and forming frontal moraines. These moraines are characterised by a lack of internal structures and preferred fabric. Owing to the strong advance, the moraine morphology is constantly changing, leaving only temporary moraine ridges. Observations made along the glacier front suggest that the formation of these moraines can best be described as "bulldozed moraines", since the term push moraine, commonly associated with advancing glaciers, should be restricted to permafrost environments. Different processes involved in moraine formation at frontal and lateral glacier margins result from variations in proglacial sediment properties, microrelief and glacier dynamics. Among these processes, large boulders left in the proglacial areas are pushed forward, forming pressure ridges on the distal side. Some of the largest boulders (c. 80-120 m[sup 3]) are overturned or rotated by the glacier. [ABSTRACT FROM AUTHOR]

Eleven snow-avalanche boulder fans were dated from two high-alpine sites in Jotunheimen using Schmidt-hammer exposure-age dating (SHD) and lichenometry. Average exposure ages of the surface boulders ranged from 2285 ± 725 to 7445 ± 1020 years and demonstrate the potential of SHD for dating active landforms and diachronous surfaces. Application of GIS-based morphometric analyses showed that the volume of rock material within 10 of the fans is accounted for by 16–68% of the combined volume of their respective bedrock chutes and transport zones. It is inferred that the fans were deposited entirely within the Holocene, mainly within the early- to mid Holocene, by frequent avalanches carrying very small debris loads. Relatively small transport-zone volumes are consistent with avalanches of low erosivity. Excess chute volumes appear to represent subaerial erosion in the Younger Dryas and possibly earlier. Debris supply to the fans was likely enhanced by early-Holocene paraglacial processes following deglaciation, and by later permafrost degradation associated with the mid-Holocene Thermal Maximum. The latter, together with the youngest SHD age from one of the fans, may presage a similar increase in geomorphic activity in response to current warming trends. [ABSTRACT FROM AUTHOR]