Schmidt‐hammer exposure‐age dating (SHD) of snow‐avalanche impact ramparts in southern Norway: approaches, results and implications for landform age, dynamics and development

Abstract

Schmidt‐hammer exposure‐age dating (SHD) was applied to the problem of dating the diachronous surfaces of five distal river‐bank boulder ramparts deposited by snow avalanches plunging into the Jostedøla and Sprongdøla rivers in the Jostedalsbreen region of southern Norway. Approaches to local high‐precision linear age calibration, which controlled in different ways for boulder roundness, were developed. The mean age (SHDmean) and the maximum age (SHDmax) of surface boulders were estimated for whole ramparts, crests and distal fringes. Interpretation was further assisted by reference to R‐value distributions. SHDmean ages (with 95% confidence intervals) ranged from 520 ± 270 years to 5375 ± 965 years, whereas SHDmax ages (expected to be exceeded by <5% of surface boulders) ranged from 675 to 9065 years. SHD ages from the Jostedøla ramparts tended to be older than those associated with the Sprongdøla, rampart crests were younger than the respective distal fringes, and use of relatively rounded boulders yielded more consistent SHD ages than angular boulders. The SHDmean ages indicate differences in recent levels of snow‐avalanche activity between ramparts and provide insights into rampart dynamics as boulders are deposited on rampart crests and, in smaller numbers, on the distal fringes. SHDmax ages provide minimum age estimates of rampart age (i.e. the time elapsed since the ramparts began to form) and suggest that at least some of the ramparts have been developing since the early Holocene. Copyright © 2015 John Wiley & Sons, Ltd.

Schmidt‐hammer exposure ages from periglacial patterned ground (sorted circles) in jotunheimen, norway, and their interpretative problems

“…R ‐value distribution from relatively inactive pronival ramparts exhibit somewhat broader plateaus (Matthews and Wilson ), as do long‐active avalanche‐impact ramparts (Matthews et al . ). Only those distributions presented by Matthews et al .…”

“…; Matthews and Wilson ), snow‐avalanche impact ramparts (Matthews et al . ), moraines (Matthews and Shakesby ; Evans et al . ; Aa and Sjåstad ; Winkler , Ffoulkes and Harrison, ), rock fall/avalanches (Nesje et al .…”

Spatial Modeling of Snow Avalanche Using Machine Learning Models and Geo-Environmental Factors: Comparison of Effectiveness in Two Mountain Regions

“…LS is a compound geomorphometric factor that has been used in geomorphological and environmental hazard studies [71][72][73]. LS was computed using one of the modules available in SAGA-GIS [26].…”

Field estimate of paleoseismic slip on a normal fault using the Schmidt hammer and terrestrial LiDAR: Methods and application to the Hebgen fault (Montana, USA)

“…Depending on the lithology and climate conditions, this weathering usually degrades the mechanical integrity of the rock and increases surface roughness through time (Benedict, 1985;Crook and Gillespie, 1986;Maizels, 1989;McCarroll, 1991;Stewart, 1996). Relative and calibrated exposure dating techniques applied to rock surfaces have been used to date moraines (Matthews and Shakesby, 1984;Winkler, 2005), rock glaciers (Laustela et al, 2003;Aa et al, 2007), snow avalanche ramparts (Matthews et al, 2015), bedrock surfaces (Gupta et al, 2009;Matthews and Owen, 2010), fluvial terraces (Stahl et al, 2013), patterned ground , and erratic boulder trains (Darvill et al, 2015), among others. Relative and calibrated exposure dating techniques applied to rock surfaces have been used to date moraines (Matthews and Shakesby, 1984;Winkler, 2005), rock glaciers (Laustela et al, 2003;Aa et al, 2007), snow avalanche ramparts (Matthews et al, 2015), bedrock surfaces (Gupta et al, 2009;Matthews and Owen, 2010), fluvial terraces (Stahl et al, 2013), patterned ground , and erratic boulder trains (Darvill et al, 2015), among others.…”

“…Relative exposure age dating techniques were developed on the premise that these weathering-related changes can be quantified and used to compare the ages of rocks and landforms, and are usually supported empirically via calibration on surfaces of known age (Colman and Dethier, 1986, and references cited therein). Relative and calibrated exposure dating techniques applied to rock surfaces have been used to date moraines (Matthews and Shakesby, 1984;Winkler, 2005), rock glaciers (Laustela et al, 2003;Aa et al, 2007), snow avalanche ramparts (Matthews et al, 2015), bedrock surfaces (Gupta et al, 2009;Matthews and Owen, 2010), fluvial terraces (Stahl et al, 2013), patterned ground , and erratic boulder trains (Darvill et al, 2015), among others. They have also been used in the field of paleoseismology to date coseismic rock avalanche deposits (e.g.…”