Using a GIS filtering approach to replicate patterns of glacial erosion

Jansson, Krister N.; Stroeven, Arjen P.; Alm, Göran; Dahlgren, Kristin; Glasser, Neil F.; Goodfellow, Bradley W.

doi:10.1002/esp.2056

Cited by 6 publications

(3 citation statements)

References 86 publications

(136 reference statements)

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“…According to this interpretation, blockfields indicate surfaces that persisted as nunataks or were inundated by non-erosive cold-based ice during glacial periods. Blockfield-mantled surfaces may provide useful markers for quantifying Quaternary glacial erosion volumes in surrounding landscapes (Nesje and Whillans, 1994;Glasser and Hall, 1997;Kleman and Stroeven, 1997;Staiger et al, 2005;Goodfellow, 2007;Jansson et al, 2011). However, recent studies of landscape evolution and Quaternary sediment budgets along the Norwegian margin (Nielsen et al, 2009;Steer et al, 2012) imply that, rather than providing these markers, autochthonous blockfield-mantled surfaces have also undergone surface lowering of some hundreds of metres through the action of a Quaternary glacial and periglacial "buzz saw".…”

Section: Introductionmentioning

confidence: 99%

Arctic–alpine blockfields in the northern Swedish Scandes: late Quaternary – not Neogene

et al. 2014

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Abstract. Autochthonous blockfield mantles may indicate alpine surfaces that have not been glacially eroded. These surfaces may therefore serve as markers against which to determine Quaternary erosion volumes in adjacent glacially eroded sectors. To explore these potential utilities, chemical weathering features, erosion rates, and regolith residence durations of mountain blockfields are investigated in the northern Swedish Scandes. This is done, firstly, by assessing the intensity of regolith chemical weathering along altitudinal transects descending from three blockfield-mantled summits. Clay / silt ratios, secondary mineral assemblages, and imaging of chemical etching of primary mineral grains in fine matrix are each used for this purpose. Secondly, erosion rates and regolith residence durations of two of the summits are inferred from concentrations of in situ-produced cosmogenic 10Be and 26Al in quartz at the blockfield surfaces. An interpretative model is adopted that includes temporal variations in nuclide production rates through surface burial by glacial ice and glacial isostasy-induced elevation changes of the blockfield surfaces. Together, our data indicate that these blockfields are not derived from remnants of intensely weathered Neogene weathering profiles, as is commonly considered. Evidence for this interpretation includes minor chemical weathering in each of the three examined blockfields, despite consistent variability according to slope position. In addition, average erosion rates of ~16.2 and ~6.7 mm ka−1, calculated for the two blockfield-mantled summits, are low but of sufficient magnitude to remove present blockfield mantles, of up to a few metres in thickness, within a late Quaternary time frame. Hence, blockfield mantles appear to be replenished by regolith formation through, primarily physical, weathering processes that have operated during the Quaternary. The persistence of autochthonous blockfields over multiple glacial–interglacial cycles confirms their importance as key markers of surfaces that were not glacially eroded through, at least, the late Quaternary. However, presently blockfield-mantled surfaces may potentially be subjected to large spatial variations in erosion rates, and their Neogene regolith mantles may have been comprehensively eroded during the late Pliocene and early Pleistocene. Their role as markers by which to estimate glacial erosion volumes in surrounding landscape elements therefore remains uncertain.

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Section: Introductionmentioning

confidence: 99%

Arctic–alpine blockfields in the northern Swedish Scandes: late Quaternary – not Neogene

et al. 2014

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“…Two mountain areas and one lowland area, with a shared geomorphological history, were chosen for DEM analysis in order to examine stepped relief in contrasting relief settings. In the mountains of the northern Scandes, the impact of glacial erosion has been mainly to fragment the stepped relief through the deepening and extension of glacial valleys and cirques (Jansson et al, 2011), whilst palaeosurface remnants survived over~30% of the terrain (Kleman and Stroeven, 1997) (Fig. 1) beneath partly cold-based and nonerosive parts of the ice sheet (e.g.…”

Section: Introductionmentioning

confidence: 99%

DEM identification of macroscale stepped relief in arctic northern Sweden

et al. 2011

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“…In more detail, the approach is based on neighbourhood analyses that models surfaces using a 198 continuous representation of topography (Jansson et al, 2010). Neighbourhood analysis (or spatial 199 filtering) creates output values for each cell location based on values within a specified 200 neighbourhood, for example calculating a maximum or mean value within such a neighbourhood.…”

Section: Calculations 194mentioning

confidence: 99%

Surface reconstruction and derivation of erosion rates over several glaciations (1Ma) in an alpine setting (Sinks Canyon, Wyoming, USA)

et al. 2014

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At middle to high latitudes, many alpine valleys have been shaped by glaciers associated with periods of Pleistocene glaciation. Present glaciated valleys are characterised by broadened valley floors and U-shaped cross sections, continuously formed by glacial activity from initially V-shaped, fluvial cross sections. Sinks Canyon (Wind River Range, USA) is a glaciated valley characterised by a typical Ushaped cross section, containing till from several glacial advances over a range of at least 1 Ma. The morphostratigraphic records indicate a fourfold difference in ice surface elevation between the youngest and oldest glacial periods, which is not easily explained by the present-day valley topography. To assess possible evolution scenarios of Sinks Canyon, we modelled the palaeovalley topography using a geographic information system (GIS) filtering technique in combination with temporal reference points from relative and numerically dated glacial deposits. Ice thicknesses were calculated using the shallow ice approximation. In our model, the valley became shallower and the topography smoother with increasing years back in time. The results suggest that valley topography with ages between 640 and 1000 ka can clearly be distinguished from the present-day topography. Surfaces with ages of 130-200 ka (attributable to MIS 6; Bull Lake glaciation) still could be discerned from present-day topography, but with relatively high uncertainties. The method did not work for topography less than 100 ka or older than 1 Ma. Erosion depths were calculated using the differences between present-day elevation and the modelled surfaces. Calculated erosion rates were within the range of reference values for glacial erosion (0.001 to 1 mm a¹). Glacial erosion appears to have removed 0.52 to 0.72 mm a¹ of rock within a time frame of 1 Ma, assuming 200 ka of aggregated glacial flow. If the glacial occupation was longer or the impact of fluvial erosion was not negligible (as assumed), then the calculated rate is lower. If the model assumes a less extended time of glacial flow (b 100 ka), the rate exceeds 1 mm a¹. The method used for surface reconstruction and erosion rates calculation is highly dependent on (i) the reliability of the temporal anchor points and (ii) the assumption of physical glacier conditions (basal shear stress). between the youngest and oldest glacial periods, which is not easily explained by the present-day 20 valley topography. To assess possible evolution scenarios of Sinks Canyon, we modelled the 21 palaeovalley topography using a geographic information system (GIS) filtering technique in 22 combination with temporal reference points from relative and numerically dated glacial deposits. 23Ice thicknesses were calculated using the shallow ice approximation. 24In our model, the valley became shallower and the topography smoother with increasing years back 25 in time. The results suggest that valley topography with ages between 640 and 1000 ka can clearly 26 Manuscript Click here to view linked References -2...

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Using a GIS filtering approach to replicate patterns of glacial erosion

Cited by 6 publications

References 86 publications

Arctic–alpine blockfields in the northern Swedish Scandes: late Quaternary – not Neogene

Arctic–alpine blockfields in the northern Swedish Scandes: late Quaternary – not Neogene

DEM identification of macroscale stepped relief in arctic northern Sweden

Surface reconstruction and derivation of erosion rates over several glaciations (1Ma) in an alpine setting (Sinks Canyon, Wyoming, USA)

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