Investigations on blockfields and related landforms at Blåhø (Southern Norway) using Schmidt-hammer exposure-age dating: palaeoclimatic and morphodynamic implications

Marr, Philipp; Winkler, Stefan; Löffler, Jörg

doi:10.1080/04353676.2018.1474350

Cited by 24 publications

(17 citation statements)

References 104 publications

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“…Cliff sites from the upper terraces (sites 9 and 10) exhibit intermediate values. The R-value distributions ( Figure 9) consolidate these results and show highly variable, multimodal, negatively skewed and/or relatively broad platykurtic distributions indicative of mixed-age populations and hence diachronous surfaces (Matthews et al, 2014Winkler et al, 2016;Marr et al, 2018). Only cliff site 8 exhibits the low-variability, unimodal, symmetrical distribution of R-values that is expected for a surface of uniform age.…”

Section: R-values From Terrace Treads and Cliffssupporting

confidence: 60%

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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: R-values From Terrace Treads and Cliffssupporting

confidence: 60%

“…Norway and broad-scale reconstruction of the Scandinavian ice-sheet deglaciation (Goehring et al, 2008;Nesje, 2009;Mangerud et al, 2011;Hughes et al, 2016;Stroeven et al, 2016;Marr et al, 2018).…”

Section: Location and Environmentmentioning

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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“…age overestimation due to post-depositional shielding by burial and subsequent exhumation by frost heave, deposition prior to LGM followed by long-term shielding, or deposition during a readvance following LGM (Briner et al, 2006;Heymann et al, 2011). But Marr et al (2018) show evidence that the blockfield stabilized ∼ 18 ka during severe periglacial conditions, which indicates the absence of ice cover close to the inferred time of boulder deposition. The alternative interpretation of the bedrock 10 Be nuclide concentration assumes continuous surface exposure since at least 46.4±1.7 ka.…”

Section: Implications Of 10 Be Exposure Ages From Blåhømentioning

confidence: 87%

“…The alternative interpretation of the bedrock 10 Be nuclide concentration assumes continuous surface exposure since at least 46.4±1.7 ka. Geomorphic evidence, such as periglacial activity of the summit blockfield until 18 ka, challenges the inferred presence of cold-based ice on Blåhø during the LGM (Marr et al, 2018). Recently, Andersen et al (2018b) stated that high-elevation low-relief areas in south-central Norway were not covered by cold-based but warm-based ice as they calculated significant erosion rates.…”

Section: Implications Of 10 Be Exposure Ages From Blåhømentioning

confidence: 99%

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<sup>10</sup>Be-based exploration of the timing of deglaciation in two selected areas of southern Norway

Marr

Winkler

Binnie

et al. 2019

E&G Quaternary Sci. J.

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Abstract. We present new 10Be surface exposure ages from two selected locations in southern Norway. A total of five 10Be samples allow a first assessment of local deglaciation dynamics of the Scandinavian Ice Sheet at Dalsnibba (1476 m a.s.l.) in southwestern Norway. The bedrock ages from the summit of Dalsnibba range from 13.3±0.6 to 12.7±0.5 ka and probably indicate the onset of deglaciation as a glacially transported boulder age (16.5±0.6 ka) from the same elevation likely shows inheritance. These ages indicate initial deglaciation commencing at the end of the Bølling–Allerød interstadial (∼ 14.7–12.9 kyr BP) and ice-free conditions at Dalsnibba's summit during the Younger Dryas. Bedrock samples at lower elevations imply vertical ice surface lowering down to 1334 m a.s.l. at 10.3±0.5 ka and a longer overall period of downwasting than previously assumed. Two further 10Be samples add to the existing chronology at Blåhø (1617 m a.s.l.) in south-central Norway. The 10Be erratic boulder sample on the summit of Blåhø sample yields 20.9±0.8 ka, whereas a 10Be age of 46.4±1.7 ka for exposed summit bedrock predates the Late Weichselian Maximum. This anomalously old bedrock age infers inherited cosmogenic nuclide concentrations and suggests low erosive cold-based ice cover during the Last Glacial Maximum. However, due to possible effects of cryoturbation and frost heave processes affecting the erratic boulder age and insufficient numbers of 10Be samples, the glaciation history on Blåhø cannot conclusively be resolved. Comparing the different timing of deglaciation at both locations in a rather short west–east distance demonstrates the complex dynamics of deglaciation in relation to other areas in southern Norway.

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Quantifying the effects of carborundum rock surface smoothing for Schmidt hammer R‐value metrics measured on glacial erratics in the North American Great Lakes region

Shepherd,

Portenga,

Peplinski

2024

Earth Surf Processes Landf

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Schmidt hammer R‐values, which reflect the degree of rock surface weathering, can be paired with independent rock surface exposure ages to produce Schmidt hammer exposure‐age dating (SHD) calibration curves that are used to provide rapid estimations of exposure ages for undated rock surfaces. In this Letter, we lay the groundwork for later establishing a SHD calibration curve based on glacial erratics deposited by the Laurentide Ice Sheet in the North American Great Lakes region. First, we establish a reference R‐value for a calibration boulder, which may be used to facilitate direct comparison of R‐values collected by different individuals using mechanical N‐type Schmidt hammers, specifically. We then assess how no, light or heavy use of a carborundum puck to smooth rock surfaces affects resulting R‐value data. Lastly, we compare two different R‐value metrics on the same rock surface: Rmean (n = 30) versus ΔR (Rmax − Rmin of five consecutive R‐values on the same spot). In all assessments, Rmean is similar for erratic surfaces with no and light surface treatment, and both are significantly lower than Rmean of surfaces with heavy treatment. Thus, we advise against the use of heavy surface treatment in SHD applications. We observe no relationship between inferred erratic age and either Rmean or ΔR, which could arise from inferred ages of erratics being inaccurate, from inferred ages of erratics being too similar or from measuring too few erratics from each landform.

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Investigations on blockfields and related landforms at Blåhø (Southern Norway) using Schmidt-hammer exposure-age dating: palaeoclimatic and morphodynamic implications

Cited by 24 publications

References 104 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

<sup>10</sup>Be-based exploration of the timing of deglaciation in two selected areas of southern Norway

Quantifying the effects of carborundum rock surface smoothing for Schmidt hammer R‐value metrics measured on glacial erratics in the North American Great Lakes region

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Investigations on blockfields and related landforms at Blåhø (Southern Norway) using Schmidt-hammer exposure-age dating: palaeoclimatic and morphodynamic implications

Cited by 24 publications

References 104 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

&lt;sup&gt;10&lt;/sup&gt;Be-based exploration of the timing of deglaciation in two selected areas of southern Norway

Quantifying the effects of carborundum rock surface smoothing for Schmidt hammer R‐value metrics measured on glacial erratics in the North American Great Lakes region

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<sup>10</sup>Be-based exploration of the timing of deglaciation in two selected areas of southern Norway