scispace - formally typeset
Search or ask a question
Journal Article•DOI•

A Combination of Relative-Numerical Dating Methods Indicates Two High Alpine Rock Glacier Activity Phases After the Glacier Advance of the Younger Dryas

Ralph Böhlert1, Michael Compeer1, Markus Egli1, Dagmar Brandová1, Max Maisch1, Peter W. Kubik2, Wilfried Haeberli1 •
University of Zurich1, ETH Zurich2
18 Jan 2011-The Open Geography Journal (Bentham Open)-Vol. 4, Iss: 1, pp 115-130
TL;DR: In this paper, Schmidt-hammer and weathering rind measurements were used to date rock glaciers in the Albula area of the eastern Swiss Alps, and the results showed that the number of active and relict glaciers increased with increasing surface ages.
Abstract: To exploit the potential of rock glaciers as indicators of past climate condition it is first necessary to date them. The combined application of both relative and absolute dating techniques is a promising approach. In this study, we present Schmidt-hammer rebound value measurements and weathering rind thicknesses on four active and one relict rock glacier in the Albula area of the eastern Swiss Alps. Associated landforms such as the moraines in front of rock glaciers and glacially polished bedrock also were used to set up the temporal framework. This was done using soil chemical analyses, radiocarbon dating of the stable fraction of soil organic matter and surface exposure dating of boulders. Schmidt-hammer and weathering rind measurements showed, in most cases, well-pronounced trends with increasing surface ages. These values are in line with measurements from other nearby rock glaciers with comparable lithologies. Use of this information together with the numeric ages makes it possible to derive two main activity phases: one started soon after the ice retreat following the Younger Dryas, the main activity occurred most likely in the early Holocene and lasted approximately until the Holocene climate optimum. The second activity phase continues today and had an unclear start between 10 to 6 cal ky BP.

Summary (3 min read)

Jump to: [INTRODUCTION] – [STUDY AREA] – [Schmidt-Hammer Rebound Values] – [Soil Chemistry and Physics] – [Fractionation of Organic Matter] – [Cosmogenic Dating] – [Weathering rind Thicknesses] – [Soils and Weathering Losses] – [DISCUSSION] and [CONCLUSIONS]

INTRODUCTION

  • Rock glaciers as distinct tongue-shaped landforms are perennially frozen and ice-rich debris on non-glacierised mountain slopes creeps steadily under the influence of gravity [1].
  • With time, the surface of rock glaciers is increasingly subject to weathering processes.
  • Relative and numeric age dating by measuring the weathering rind thickness or the Schmidt-hammer rebound value was successfully performed on moraines and rock glaciers developed on sandstones in New Zealand [4-8], basaltic and andesitic boulders in North America and Japan [9, 10] and on granites and gneiss in the Alps [2, 11].
  • A ‘cross-check’ of these methods allows an extended interpretation and reciprocal control of the results.

STUDY AREA

  • The study area is located in the eastern Swiss Alps (Fig. 1).
  • The area of the Albula pass is characterised by many glacial and geomorphic features such as moraines, polished bedrock with roches moutonnées, scree slopes, rock glaciers, traces of glacial erosion (such as grooves, striations, etc.) and plucking processes.
  • The mean annual precipitation is rather low with around 900 mm in the lower parts near Preda and up to 1100 mm towards the mountain ridges [21].
  • While the active rock glaciers show a simple structure with a clearly identifiable rooting zone and a compact steep tongue, the conditions in case of the rock glacier Alvra are more complex.
  • In close vicinity, previously-reported data of a peat bog was available [25].

Schmidt-Hammer Rebound Values

  • The measured Schmidt-hammer rebound values for all rock glaciers are given in Fig. (8A-D).
  • The standard error after [30] was in most cases relatively small.
  • Close to the cirque, the values were usually near 50-55.
  • This suggests that the activity of rock glacier Alvra began soon after the retreat of the Egesen-age glaciers.
  • The measured Schmidt-hammer values at the distal front of these rock glaciers correspond approximately to the initial values of rock glacier Alvra (near 40-45).

Soil Chemistry and Physics

  • The soil samples were air-dried, large aggregates were gently broken by hand and sieved to <2 mm.
  • Total C and N contents of the soil were measured with a C/H/N analyser (Elementar Vario EL, Elementar Analysensysteme GmbH) using oven-dried and ball-milled fine earth.
  • Oven-dried samples were dissolved using a mixture of HF, HCl, HNO3, and H3BO3 in a closed system [38] (microwave oven and under high pressure, 25 bar).
  • Concentrations were determined by AAS (Atomic Absorption Spectrometry – AAnalyst 700, Perkin Elmer, USA).
  • The dithionite- and oxalate-extractable fractions were measured for the elements Fe, Al and Si [39].

Fractionation of Organic Matter

  • Acting on the assumption that chemical oxidation mimics natural oxidative processes, the authors treated the soils with 10% H2O2 to eliminate the more labile organic material from the more refractory organic matter [41-44].
  • Profile photos and horizon designations of the investigated soils (see also Fig. 1).
  • First organic matter formed in the sediment after glacier retreat [45] and may, under certain circumstances, provide a minimum age of deposition of the moraines and of deglaciation.
  • The beakers were closed with two layers of parafilm to avoid evaporation of the reagent.
  • At the end of the treatment the samples were washed three times with 40 ml deionised water, freeze-dried, weighed, analysed for total C and N and 14 C dated.

Cosmogenic Dating

  • The cosmogenic nuclide concentrations (e.g. 10 Be) in the surface of moraine boulders and polished bedrock exposure reflect the time that has passed since the moraine stabilised [48] and the ice retreated and exposed the landform to cosmic ray flux.
  • The rock samples were crushed, sieved and leached in order to obtain pure quartz following [50, 51].
  • The Be was isolated using anion and cation exchange columns followed by selective pH Be(OH)2 precipitation [51].
  • Production-rate scaling for latitude and altitude was based on [52] and corrected for sample thickness assuming an exponential depth profile, a rock density of 2.65 g cm -3 and an effective radiation attenuation length of 155 g/cm 2 [48].
  • The theoretical snow height for the sample site was estimated using a mean snow height gradient of 0.08 m/100 m altitude difference [54].

Weathering rind Thicknesses

  • The weathering rinds were generally very thin (Fig. 7).
  • Nonetheless, the median and mean values showed a clear increase from the youngest part near the rockwall to the frontal talus of the rock glacier (Fig. 7A-E).
  • Thicknesses of weathering rinds increased towards the distal front of the rock glaciers.
  • The literature indicates that the modal values should be used to delineate trends along a rock glacier.
  • The time dependent tendency looked, however, more disturbed.

Soils and Weathering Losses

  • The physical and chemical characteristics of the soils are given in Tables 1 and 2.
  • The parameter Alo + 0.5Feo (Table 2) clearly reflects the spodic characteristics of the soil at Igls Plans (see [55]).
  • Long-term weathering rates of soils were derived using immobile element contents [56-58].
  • This gives another indication of the minimum age of the present-day active rock glaciers and an indication of when the rock glacier Alvra became inactive.

DISCUSSION

  • Frauenfelder et al. [2] and Laustela et al. [11] measured Schmidt-hammer rebound values that varied from approx.
  • The median as well as the modal values of weathering rind measurements [11] are equally suitable to delineate the increasing weathering rind thicknesses with the duration of exposure.
  • The soil “Igls Plans” is more weathered than soil “Peidra Mora” and shows relative element losses that are close to soils that developed over post-Egesen time [60, 61, 64, 65].
  • This finding was only made possible using a multi-parameter approach that consequently clearly shows its advantages [66, 67].
  • Two main phases of rock glacier activity could be derived: one starting immediately after the retreat of glaciers during the Younger Dryas (Egesen glacial states) and the other one during the Holocene.

CONCLUSIONS

  • The authors obtained the following main findings: A distinct increase in weathering rind thickness and decrease of the Schmidt hammer rebound values along the rock glaciers (i.e. with increasing age) could be measured.
  • Both methods reflect equally well the effect of weathering with increasing age.
  • Soil analyses confirmed and added an additional time constraint.
  • The older soil, in front of the relict rock glacier, was highly weathered and must have started its evolution in the Lateglacial (shortly after the Younger Dryas).
  • This leads to additional datasets, provides the ability to cross-check each of the methods and to revise previous interpretations.

Did you find this useful? Give us your feedback

Figures (2)

Content maybe subject to copyright    Report

ZurichOpenRepositoryand
Archive
UniversityofZurich
UniversityLibrary
Strickhofstrasse39
CH-8057Zurich
www.zora.uzh.ch
Year:2011
Acombinationofrelative-numericaldatingmethodsindicatestwohigh
AlpinerockglacieractivityphasesaftertheglacieradvanceoftheYounger
Dryas
Böhlert,R;Compeer,M;Egli,M;Brandova,D;Maisch,M;Kubik,PW;Haeberli,W
Abstract:To exploitthe potentialof rockglaciers as indicatorsof pastclimate conditionit isrst
necessarytodatethem.Thecombinedapplicationofbothrelativeandabsolutedatingtechniquesis
apromising approach.Inthis study, wepresentSchmidt-hammerrebound valuemeasurementsand
weatheringrindthicknessesonfouractiveandonerelictrockglacierintheAlbulaareaoftheeastern
SwissAlps.Associatedlandformssuchasthemorainesinfrontofrockglaciersandglaciallypolished
bedrockalsowereusedtosetupthetemporalframework.Thiswasdoneusingsoilchemicalanalyses,
radiocarbondatingofthestablefractionofsoilorganicmatterandsurfaceexposuredatingofboulders.
Schmidt-hammerandweatheringrindmeasurementsshowed,inmostcases,well-pronouncedtrendswith
increasingsurfaceages.Thesevaluesareinlinewithmeasurementsfromothernearbyrockglacierswith
comparablelithologies.Useofthisinformationtogetherwiththenumericagesmakesitpossibletoderive
twomainactivityphases: onestartedsoonaftertheiceretreatfollowingtheYoungerDryas,themain
activityoccurredmostlikelyintheearlyHoloceneandlastedapproximatelyuntiltheHoloceneclimate
optimum.Thesecondactivityphasecontinuestodayandhadanunclearstartbetween10to6calky
BP.
DOI:https://doi.org/10.2174/1874923201104010115
PostedattheZurichOpenRepositoryandArchive,UniversityofZurich
ZORAURL:https://doi.org/10.5167/uzh-42941
JournalArticle
Originallypublishedat:
Böhlert,R; Compeer,M; Egli, M; Brandova,D; Maisch,M; Kubik, P W; Haeberli,W (2011).A
combinationofrelative-numericaldatingmethodsindicatestwohighAlpinerockglacieractivityphases
aftertheglacieradvanceoftheYoungerDryas.OpenGeographyJournal,(4):115-130.
DOI:https://doi.org/10.2174/1874923201104010115
The Open Geography Journal, 2010, 3, 281-296 281!
!
1874-9232/10 2010 Bentham Open
Open Access
A Combination of Relative-Numerical Dating Methods Indicates Two High
Alpine Rock Glacier Activity Phases After the Glacier Advance of the
Younger Dryas
"#$%&!'(&$)*+
,
-!./0&#)$!123%))*
,
-!.#*456!78$/
9-,
-!:#83#*!'*#;<2=>
,
-!.#?!.#/60&
,
-!!
@)+)*!AB!C5D/4
E
-!A/$F*/)<!G#)D)*$/
,
!
1
Department of Geography, University of Zurich, CH-8057 Zurich, Switzerland
2
Institute of Ion Beam Physics, ETH-Hönggerberg, CH-8093 Zurich, Switzerland
Abstract: H2!)?%$2/+!+&)!%2+);+/#$!2F!*204!8$#0/)*6!#6!/;</0#+2*6!2F!%#6+!0$/3#+)!02;</+/2;!/+!/6!F/*6+!;)0)66#*I!+2!<#+)!+&)3B!
H&)! 023D/;)<! #%%$/0#+/2;! 2F! D2+&! *)$#+/=)! #;<! #D62$5+)! <#+/;8! +)0&;/J5)6! /6! #! %*23/6/;8! #%%*2#0&B! K;! +&/6! 6+5<I-! L)!
%*)6);+!M0&3/<+N&#33)*!*)D25;<!=#$5)!3)#65*)3);+6!#;<!L)#+&)*/;8!*/;<!+&/04;)66)6!2;!F25*!#0+/=)!#;<!2;)!*)$/0+!*204!
8$#0/)*!/;!+&)!O$D5$#!#*)#!2F!+&)!)#6+)*;!ML/66!O$%6B!O6620/#+)<!$#;<F2*36!650&!#6!+&)!32*#/;)6!/;!F*2;+!2F!*204!8$#0/)*6!
#;<! 8$#0/#$$I! %2$/6&)<! D)<*204! #$62! L)*)! 56)<! +2! 6)+! 5%! +&)! +)3%2*#$! F*#3)L2*4B! H&/6! L#6! <2;)! 56/;8! 62/$! 0&)3/0#$!
#;#$I6)6-! *#</20#*D2;! <#+/;8! 2F! +&)! 6+#D$)! F*#0+/2;! 2F! 62/$! 2*8#;/0! 3#++)*! #;<! 65*F#0)! )?%265*)! <#+/;8! 2F! D25$<)*6B!
M0&3/<+N&#33)*! #;<! L)#+&)*/;8! */;<! 3)#65*)3);+6! 6&2L)<-! /;! 326+! 0#6)6-! L)$$N%*2;25;0)<! +*);<6! L/+&! /;0*)#6/;8!
65*F#0)! #8)6B!H&)6)! =#$5)6! #*)! /;! $/;)! L/+&! 3)#65*)3);+6! F*23! 2+&)*! ;)#*DI! *204! 8$#0/)*6! L/+&! 023%#*#D$)!$/+&2$28/)6B!
P6)!2F!+&/6! /;F2*3#+/2;!+28)+&)*!L/+&!+&)!;53)*/0!#8)6!3#4)6!/+!%266/D$)!+2!<)*/=)!+L2!3#/;!#0+/=/+I!%&#6)6Q!2;)!6+#*+)<!
622;!#F+)*! +&)!/0)! *)+*)#+!F2$$2L/;8!+&)!R25;8)*!:*I#6-!+&)!3#/;!#0+/=/+I!2005**)<!326+! $/4)$I!/;!+&)!)#*$I!G2$20);)! #;<!
$#6+)<!#%%*2?/3#+)$I!5;+/$!+&)!G2$20);)!0$/3#+)!2%+/353B!H&)!6)02;<!#0+/=/+I!%&#6)!02;+/;5)6!+2<#I!#;<!&#<!#;!5;0$)#*!
6+#*+!D)+L));!,S!+2!T!0#$!4I!'@B!
Keywords: "204!8$#0/)*6-!*)$#+/=)!#;<!;53)*/0#$!<#+/;8!+)0&;/J5)6-!62/$6-!32*#/;)6B!
INTRODUCTION
!"204!8$#0/)*6!#6!</6+/;0+!+2;85)N6&#%)<!$#;<F2*36!#*)!
%)*);;/#$$I! F*2U);! #;<! /0)N*/0&! <)D*/6! 2;! ;2;N8$#0/)*/6)<!
325;+#/;! 6$2%)6! 0*))%6! 6+)#</$I! 5;<)*! +&)! /;F$5);0)! 2F!
8*#=/+I! V,WB! O0+/=)! *204! 8$#0/)*6! X/B)B-! +&)I! 02;+#/;! /0)! #;<!
<)F2*3Y!#*)!65%%26)<!+2!&#=)!F2*3)<!#;<!)=2$=)<!<5*/;8!+&)!
G2$20);)! #;<! 0#;! D)! 6));! #6! +*#;6%2*+! 6I6+)36B! H&)I! 3#I!
D)#*! $2;8N+)*3! %#$#)20$/3#+/0! /;F2*3#+/2;!VEWB! ")$/0+!F2*36!
2;! $2L)*! #$+/+5<)6! &#=)! $26+! +&)/*! /0)! 02;+);+! #;<! <2! ;2+!
0*))%! #;I32*)B! O6! +&)I! /;/+/#$$I! 356+! &#=)! F2*3)<! 5;<)*!
%)*3#F*26+! 02;</+/2;6! #6! L)$$-! +&)I! &#=)! #! 02;6/<)*#D$)!
%2+);+/#$! F2*! 02;6+*#/;/;8! F2*3)*! 0$/3#+/0! 02;</+/2;6! VZWB!
H&56-! <#+/;8! 2F! 650&! $#;<F2*36! /6! *)$)=#;+! F2*! #;I! 4/;<! 2F!
%#$)20$/3#+/0!*)02;6+*50+/2;6!#;<!/;+)*%*)+#+/2;B!
!A/+&!+/3)-!+&)!65*F#0)!2F!*204!8$#0/)*6!/6!/;0*)#6/;8$I!
65D[)0+! +2! L)#+&)*/;8! %*20)66)6B! P65#$$I-! +&)! 2$<)*! +&)!
65*F#0)!2F!*204!<)D*/6!+&)!32*)!%*2;25;0)<!/6!+&)!/3%*/;+!2F!
L)#+&)*/;8B! ")$#+/=)! #;<! ;53)*/0! #8)! <#+/;8! DI! 3)#65*/;8!
+&)! L)#+&)*/;8! */;<! +&/04;)66! 2*! +&)! M0&3/<+N&#33)*!
*)D25;<!=#$5)!L#6!6500)66F5$$I!%)*F2*3)<!2;!32*#/;)6!#;<!
*204!8$#0/)*6!<)=)$2%)<!2;!6#;<6+2;)6!/;!\)L!])#$#;<!V^N_W-!
D#6#$+/0!#;<!#;<)6/+/0! D25$<)*6! /;!\2*+&!O3)*/0#!#;<!`#%#;!!
Va-! ,SW! #;<! 2;! 8*#;/+)6! #;<! 8;)/66! /;! +&)! O$%6! VE-! ,,WB!
A)#+&)*/;8! */;<6! &#=)! #$62! #! 0)*+#/;! %2+);+/#$! F2*! ;53)*/0!
<#+/;8!56/;8!/62+2%)6!V,EWB!
!
!
9O<<*)66! 02**)6%2;<);0)! +2! +&/6! #5+&2*! #+! +&)! :)%#*+3);+! 2F! b)28*#%&I-!
P;/=)*6/+I!2F!]5*/0&-!1GN_Scd!]5*/0&-!ML/+U)*$#;<e!H)$Q!f^,!XSY^^!TZc!c,!
,^gE,e!h#?Q!f^,!XSY^^!TZc!T_!^,e!7N3#/$Q!3#*456B)8$/i8)2B5U&B0&!
!:5*/;8!+&)!%#6+!<)0#<)6-!6)=)*#$!6+5</)6!&#=)!D));!
0#**/)<! 25+! +2! <)+)*3/;)! +&)! #8)! 2F! *204! 8$#0/)*6! /;! +&)!
75*2%)#;! O$%6! V,ZN,cWB! CjjD! et alB! V,TW! 56)<!
%&2+28*#33)+*/0! 3)+&2<6! +2!2D+#/;!F$2L!+*#[)0+2*/)6!#;<!+2!
)6+/3#+)! #8)6! 2F! *2048$#0/)*! 65*F#0)6B! G#)D)*$/! et alB! V,dW!
%*2%26)<! #! 35$+/%$)! #%%*2#0&! 56/;8! *)$#+/=)! #;<! ;53)*/0#$!
<#+/;8! +2! 2D+#/;! 32*)! 02;0$56/=)! /;F2*3#+/2;! 2;! *204N
8$#0/)*6!<I;#3/06B!O!k0*266N0&)04l!2F!+&)6)!3)+&2<6!#$$2L6!
#;! )?+);<)<! /;+)*%*)+#+/2;! #;<! *)0/%*20#$! 02;+*2$! 2F! +&)!
*)65$+6B!M50&!#;!#%%*2#0&!&#6!5;+/$!;2L!*#*)$I!D));!<2;)!F2*!
O$%/;)!8)232*%&/0!F)#+5*)6B!H&)!602%)!2F!+&)!%*)6);+!%#%)*!
/6-! +&)*)F2*)-! +2! +)6+! #;<! #%%$I! 6)=)*#$! <#+/;8! +)0&;/J5)6! F2*!
#66)66/;8!+&)!#8)!#;<!#0+/=/+I!%&#6)6!2F!6)=)*#$!*204!8$#0/)*6!
/;!#!&/8&!O$%/;)!*)8/2;!2F!+&)!ML/66!O$%6B!
STUDY AREA
!H&)!6+5<I!#*)#!/6!$20#+)<!/;!+&)!)#6+)*;!ML/66!O$%6!Xh/8B!
1YB! H&)! #*)#! 2F! +&)! O$D5$#! %#66! /6! 0&#*#0+)*/6)<! DI! 3#;I!
8$#0/#$! #;<!8)232*%&/0! F)#+5*)6!650&! #6! 32*#/;)6-!%2$/6&)<!
D)<*204!L/+&!*20&)6!325+2;;m)6-!60*))!6$2%)6-!*204!8$#0/)*6-!
+*#0)6!2F!8$#0/#$!)*26/2;!X650&!#6!8*22=)6-!6+*/#+/2;6-!)+0BY!#;<!
%$504/;8!%*20)66)6B!H)0+2;/0#$$I-!+&)!*)8/2;!625+&)*;!2F! +&)!
O$D5$#! %#66! /6! 6/+5#+)<! L/+&/;! +&)! 7**N')*;/;#! ;#%! +&#+!
D)$2;86! +2! +&)! $2L)*! O56+*2#$%/;)B! H&)! 8*));/6&! kO$D5$#!
b*#;/+)l!/6!+&)!<23/;#;+!*204!+I%)!V,_NESWB!H&)!#<[#0);+!#*)#!
+2! +&)! ;2*+&! 2F! +&)! O$D5$#! %#66! D)$2;86! +2! +&)! 7$#! ;#%-!
023%26)<! 3#/;$I! 2F! 6)</3);+#*I! *204! +I%)6! #;<! <);2+)6! #!
6&#*%! 02;+*#6+! +2! +&)! 7**N');/;#! ;#%B! H&)! 3)#;! #;;5#$!
%*)0/%/+#+/2;!/6!*#+&)*!$2L!L/+&!#*25;<!aSS!33!/;!+&)!$2L)*!
%#*+6!;)#*! @*)<#! #;<!5%! +2!,,SS! 33!+2L#*<6!+&)! 325;+#/;!
282 The Open Geography Journal, 2010, Volume 3 Böhlert et al.
!"#$%&' ()*+,' -.%' !%/01&2!3/2%#' 45&2' 675/"57' 859":3:'
;468<' "/%' &3!=5/%' $%0:%2!>' ?5&%#' 01' $75/"57@$%070$"/57'
:5AA"1$' &.0B&' 2.52' 2.%' 5!%5' B5&' &"2352%#' 1%5!' 2.%'
CD1$5#"1%E'"/%'#0:%'/37:"152"1$'"1'2.%'FAA%!'D1$5#"1%'())G'
)H+,' -!":7"1%' 51#' 02.%!' %!0&"0157' =%523!%&' "1#"/52%' 2.52'
#3!"1$'468'2.%'I7?375'A5&&'=0!:%#'5'2!51&=73%1/%'B"2.'"/%'
=70B"1$'=!0:'2.%'D1$5#"1%'"120'2.%'J."1%'!"K%!'&>&2%:'()L+,'
-.%' 452%$75/"57' =002A!"12' ;:0!5"1%' &%M3%1/%<' 10!2.' 20' 2.%'
!"#$%'N"O'#5'75&'P75"&'Q'R!5&25'80!5';S"$,'1<'B5&'=0!:%#'5&'5'
!%&372' 0=' 5' &70A%@$75/"52"01' ()T+U' 017>' 52' 2.%' B%&2%!1'
?031#5!>' 0=' 2.%' =0!:%!' $75/"%!' #"#' 5' #"&2"1/2' "/%@201$3%'
#%K%70AG'5&'"1#"/52%#'?>' :0!5"1%&,'-."&'=0!:%!'201$3%'5!%5'
"&' 20#5>' 0//3A"%#' ?>' 2.%' !%752"K%7>' 701$' !0/V' $75/"%!' I7K!5'
;!0/V' $75/"%!' DG' S"$,' 1<,' D9/%A2' =0!' 2.%' 2B0' /"!M3%&' 20' 2.%'
WX' 51#' WD' 0=' R!5&25' 80!5G' 2.%!%' 5!%' 10' &"$1&' =0!' 2.%'
%9"&2%1/%' 0=' $75/"%!' "/%' #3!"1$' 2.%' 4"227%' Y/%' I$%' ()TG' )Z+,'
S"$,' ;2<' $"K%&' 51' 0K%!K"%B' 0=' 2.%' /57/3752%#' :0#%!1'
A%!:5=!0&2' #"&2!"?32"01' ()[+,' -.%' A0&"2"01' 0=' 2.%' !0/V'
$75/"%!&'I'Q'\'"1'2.%'10!2.'%9A0&%#'&70A%&';&%%'57&0'S"$,'3<'"&'
/7%5!7>' "#%12"="5?7%' B"2."1' 2.%' /012"1303&' A%!:5=!0&2,' Y1' 2.%'
5!%5'0='2.%'!0/V'$75/"%!'D'017>'&0:%'&A0!5#"/'A%!:5=!0&2'/51'
?%'%9A%/2%#,'
'S"K%'!0/V'$75/"%!&'1%5!'2.%'I7?375'A5&&'B%!%'"1K%&2"$52%#'
;=0!'#%25"7&G'&%%'S"$&,'3-5<,'S03!'5!%'&2"77'5/2"K%G'5&'"1#"/52%#'
?>' 2.%' 75/V' 0=' K%$%252"01G' ;I' Q' \]' S"$&,' 3G' 4<' B.%!%5&' 2.%'
!0/V'$75/"%!'I7K!5';D<'"&'!%7"/2,'-.%'!0/V'$75/"%!'I7K!5'7"%&'52'
5' 70B%!' 572"23#%' 2.51' 2.%' 02.%!&' ;S"$,' 5<' 51#' 7"%&' ?%2B%%1'
)^L^'51#')H)^':'5&7'B"2.'5'B%&2'0!"%1252"01,'I77'02.%!'!0/V'
$75/"%!&'5!%'52'51'572"23#%'0='5?032')L^^'3A'20')[^^':'5&7'51#'
.5K%'10!2.@=5/"1$' %9A0&3!%&,' X."7%' 2.%' 5/2"K%'!0/V'$75/"%!&'
&.0B' 5' &":A7%' &2!3/23!%' B"2.' 5' /7%5!7>' "#%12"="5?7%' !002"1$'
O01%' 51#' 5' /0:A5/2' &2%%A' 201$3%G' 2.%' /01#"2"01&' "1' /5&%' 0='
2.%' !0/V' $75/"%!' I7K!5' 5!%' :0!%' /0:A7%9,' 6%0:%2!>' ;701$'
&.5A%<' 51#' 5' !52.%!' =752' &70A%' "1' 2.%' :"##7%' 51#' 3AA%!' A5!2'
;S"$,' 5<' &3$$%&2' 5' #%?!"&' &3AA7>' =!0:' &%K%!57' &2%%A' #%?!"&'
&03!/%&'B"2."1'2.%'&70A%&'2.52'5!%'31"="%#'"1'2.%'!0/V'$75/"%!'
I7K!5' ;"1#"/52%#' ?>' 5!!0B&' "1' S"$,' 5<,' R01&%M3%127>G' 5701$'
2.%' =70B' 7"1%' 0=' 2.%' !0/V' $75/"%!' I7K!5G' &%K%!57' &:577' !0/V'
$75/"%!&' 5!%' /!0&&%#' 51#' .%1/%' 5' B%77@#%K%70A%#' 5$%' 2!%1#'
/51102'?%'%9A%/2%#,'Y1'5##"2"01'20'2.%'"1K%&2"$52"01&'01'!0/V'
$75/"%!&G'2B0'&0"7'A!0="7%&'B%!%'&23#"%#';S"$,'6<,'_1%'0='2.%:'
"&'01'5':0!5"1%'5&&"$1%#'20'2.%'D$%&%1'$75/"57'&252%'()T+'51#'
/70&%' 20' 2.%' !%7"/2' !0/V' $75/"%!' ;&"2%U' `Y$7&' N751&a<' 51#' 2.%'
02.%!'01%'#"!%/27>'?%70B'51'5/2"K%'!0/V'$75/"%!';&"2%U'`N%"#!5'
80!5a<,'Y1'5##"2"01G'2B0'&5:A7%&'=0!'&3!=5/%'%9A0&3!%'#52"1$'
=!0:'5'!0/.%':032011b%';&"2%'`R!5A'I7Ka<'B%!%'5157>&%#'20'
#%!"K%' 5' :59":3:' 5$%' =0!' #%$75/"52"01' ;B."/.' :3&2' .5K%'
A!%/%#%#' !0/V' $75/"%!' =0!:52"01<' /70&%' 20' 2.%' !0/V' $75/"%!'
201$3%'51#'/01&%M3%127>'=0!'2.%'&25!2'0='!0/V'$75/"%!'5/2"K"2>,'
Y1'/70&%'K"/"1"2>G'A!%K"03&7>@!%A0!2%#'#525'0='5'A%52'?0$'B5&'
5K5"75?7%'()T+,'
'
'
'
Fig. (1).'40/52"01'0='2.%'"1K%&2"$52"01'&"2%,'
Rock Glacier Activity in a High Alpine Region The Open Geography Journal, 2010, Volume 3 283
MATERIALS AND METHODS
Schmidt-Hammer Rebound Values
The Schmidt-hammer is a portable instrument originally
developed to test concrete quality in a non-destructive way
[28]. A spring-loaded bolt impacting a surface yields a
rebound- or R-value, which is proportional to the hardness
(compressive strength) of a rock surface. Applied in
geomorphology, old rock surfaces exposed to weathering
processes for a long time provide low R-values and vice
versa. Since the 1980s the method has also been successfully
used for relative age dating of gemorphologic features such
as moraines [14, 29, 30], rock glaciers ([2, 31] or rockfall
deposits [32]. Recent publications increasingly discuss the
possibilities and limitations to calibrate R-values, for
instance with results from
10
Be and
14
C-analyses [33, 34] or
optically stimulated luminescence and photogrammetrical
measurements [2, 17].
In this study the N-type Schmidt-Hammer (Proceq,
Switzerland) was used. On each mapped unit (e.g. moraine,
rock glacier lobe) 50 randomly selected boulders/sites were
measured, avoiding edges of boulders [35], spots that
Fig. (2). Spatial distribution of local (sporadic) and continuous permafrost in the investigation area (data source: [27]).
Fig. (3). Aerial photo (with a view in southern direction) of the investigated rock glaciers A-D.
284 The Open Geography Journal, 2010, Volume 3 Böhlert et al.
showed lichen growth as well as visual fissures or cracks.
Only flat parts under dry conditions were considered. The
hardness of an analysed form is represented by the arithmetic
mean of the individual records. Following the suggestions by
[30], we used a standard error based on the standard
deviation in a 95% confidence interval to get statistically
significant hardness variations and by extensions age
differences:
x ± 1.96
/ n
()
(1)
where
x
is the arithmetic mean,
the standard deviation
and
n
corresponds to the number of measurements.
Fig. (4). Detailed view of the investigated rock glaciers A-D. The uppermost part of the relict rock is shown in E1 and the middle and lower
part in E2.
Citations
More filters
Journal Article•DOI•
New evidence for active talus-foot rock glaciers at Øyberget, southern Norway, and their development during the Holocene:

[...]

Atle Nesje1, John A. Matthews2, Henriette Linge1, Marie Bredal, Peter Wilson3, Stefan Winkler •
University of Bergen1, Swansea University2, Ulster University3
15 Aug 2021-The Holocene
TL;DR: In this article, Synthetic aperture radar interferometry (InSAR) measurements demonstrate that lobate, blocky depositional landforms, located in southern Norway at an altitude of ~530m above sea level, with an est
Abstract: Synthetic aperture radar interferometry (InSAR) measurements demonstrate that lobate, blocky depositional landforms, located in southern Norway at an altitude of ~530 m above sea level, with an est...

6 citations

Cites background from "A Combination of Relative-Numerical..."

  • ...Several studies have demonstrated clear patterns of increasing SHD age of boulders down the axis of relatively long rock-glacier tongues (Böhlert et al., 2011; Frauenfelder et al., 2005; Kellerer-Pirklbauer et al., 2008; Rode and Kellerer-Pirklbauer, 2012; Winkler and Lambiel, 2018)....

    [...]

Posted Content•DOI•
Nationwide aerial laser scanning reveals relict rock glaciers and protalus ramparts in Slovenia

[...]

Mihaela Triglav-Čekada, Blaž Barborič, Mateja Ferk1, Matija Zorn1•
Slovenian Academy of Sciences and Arts1
13 Jun 2016-The Cryosphere Discussions
TL;DR: In 2015, the nationwide aerial laser scanning (lidar) of Slovenia became publicly available, enabling a wide range of detailed geomorphological studies, also in areas that are less accessible or covered with dense vegetation as discussed by the authors.
Abstract: . In 2015 the nationwide aerial laser scanning (lidar) of Slovenia became publicly available. These data enable a wide range of detailed geomorphological studies, also in areas that are less accessible or covered with dense vegetation. This makes it possible to identify potential rock glaciers and protalus ramparts in the Slovenian mountains. The laser scanning products, the grey-shaded terrain model and the classified point cloud were used to identify and measure these features. All the mountainous areas at elevations of approximately 1200 m above sea level (a.s.l.) were evaluated. During the Alpine Late Glacial period these were in glacial and periglacial conditions. The mountain ranges of the Julian Alps, Karavanks, Kamnik-Savinja Alps, Pohorje and Dinaric mountains (Trnovski Gozd and Snežnik) were evaluated. Twenty potential rock glaciers and eight potential protalus ramparts were found. They are the most abundant in the Karavanks, followed by the Julian Alps, with one potential rock glacier also on the Snežnik plateau. The majority of the potential rock glaciers are probably relicts, due to the heavy vegetation cover, the low mean elevations (between 1040 m and 1850 m a.s.l.) and because their slopes are directed more towards southern directions (65 % of rock glaciers). The identified rock glaciers rarely exceed 600 m in length. The terminus slope angles of the identified objects are from 20° to 40°. Three of the identified protalus ramparts can be regarded as relict, due to the total vegetation cover; the remaining five can be regarded as intact. The potential protalus ramparts are found at elevations between 1220 m and 1950 m a.s.l. All the identified protalus ramparts are directed towards southern directions, with terminus slope angles from 30° to 40°. The spatial distribution of the discussed permafrost objects in Slovenia with regards to the bedrock composition presented on the geological map of Slovenia (scale 1 : 250 000) reveals that 75 % of all objects can be found in thick-bedded Dachstein limestones with transitions to dolomite, while almost all the remaining objects are found in Triassic dolomite.

4 citations

Cites background from "A Combination of Relative-Numerical..."

  • ...…about 3100 years ago, the relict rock glaciers during the Alpine Late Glacial and they decayed between the end of the Alpine Late Glacial and the beginning of the Holocene around 5 11.6 ka ago (Frauenfelder and Kääb, 2000; Harris et al., 2009; Böhlert et al., 2011a, 2011b; Scotti et al., 2013)....

    [...]

Journal Article•DOI•
Alpine rock glacier activity over Holocene to modern timescales (western French Alps)

[...]

Diego Cusicanqui1, Xavier Bodin1, Kirk Baker2•
University of Savoy1, University of Colorado Boulder2
24 Jun 2022-Earth surface dynamics
TL;DR: In this article , a multi-method approach, including field observations, remote sensing, and geochronology, was adopted to investigate the rock glacier system of the Vallon de la Route (Combeynot Massif, western French Alps).
Abstract: Abstract. Active rock glaciers are some of the most frequent cryospheric landforms in midlatitude high-elevation mountain ranges. Their activity strongly influences the hydrology and geomorphology of alpine environments over short (years to decades) and long (centuries to millennia) timescales. Being conspicuous expressions of mountain permafrost and important water reserves in the form of ground ice, rock glaciers are seen as increasingly important actors in the geomorphological and hydrological evolution of mountain systems, especially in the context of current climate change. Over geological timescales, rock glaciers both reflect paleoclimate conditions and transport rock boulders produced by headwall erosion, and they therefore participate in shaping high mountain slopes. However, the dynamics of rock glaciers and their evolution over different timescales remain under-constrained. In this study, we adopt a multi-method approach, including field observations, remote sensing, and geochronology, to investigate the rock glacier system of the Vallon de la Route (Combeynot Massif, western French Alps). Remotely sensed images and correlation techniques are used to document the displacement field of the rock glacier over timescales ranging from days to decades. Additionally, to estimate displacement over periods from centuries to millennia, we employ terrestrial cosmogenic nuclide (quartz 10Be) surface-exposure dating on rock boulder surfaces located along the central flow line of the rock glacier, targeting different longitudinal positions from the headwall to the rock glacier terminus. The remote sensing analysis demonstrates that between 1960 and 2018 the two lower units of the rock glacier were motionless, the transitional unit presented an integrated surface velocity of 0.03±0.02 m a−1, and the two upper active units above 2600 m a.s.l. showed a velocity between 0.14±0.08 and 0.15±0.05 m a−1. Our results show 10Be surface-exposure ages ranging from 13.10±0.51 to 1.88±0.14 ka. The spatial distribution of dated rock glacier boulders reveals a first-order inverse correlation between 10Be surface-exposure age and elevation and a positive correlation with horizontal distance to the headwall. These observations support the hypothesis of rock boulders falling from the headwall and remaining on the glacier surface as they are transported down valley, and they may therefore be used to estimate rock glacier surface velocity over geological timescales. Our results also suggest that the rock glacier is characterized by two major phases of activity. The first phase, starting around 12 ka, displays a 10Be age gradient with a rock glacier surface velocity of about 0.45 m a−1, following a quiescent period between ca. 6.2 and 3.4 ka before the emplacement of the present-day upper two active units. Climatic conditions have favored an integrated rock glacier motion of around 0.18 m a−1 between 3.4 ka and present day. These results allow us to quantify back-wearing rates of the headwall of between 1.0 and 2.5 mm a−1, higher than catchment-integrated denudation rates estimated over millennial timescales. This suggests that the rock glacier system promotes the maintenance of high rock wall erosion by acting as debris conveyor and allowing freshly exposed bedrock surfaces to be affected by erosion processes.

3 citations

Journal Article•DOI•
Schmidt-hammer exposure-age dating: a review of principles and practice

[...]

USM ADMIN1•
Swansea University1
01 Jul 2022-Earth-Science Reviews
TL;DR: Schmidt-hammer exposure-age dating (SHD) is a numerical, calibrated age dating technique based on the degree of weathering of rock surfaces as mentioned in this paper , which has been found particularly useful in relation to boulder deposits and bedrock surfaces in glacial and periglacial environments.

3 citations

Journal Article•DOI•
Combination of historical and modern data to decipher the geomorphic evolution of the Innere Ölgruben rock glacier, Kaunertal, Austria, over almost a century (1922–2021)

[...]

Fabian Fleischer, Florian Haas, Moritz Altmann, Jakob Rom, Bettina Knoflach, Michael Becht 
18 Dec 2022-Permafrost and Periglacial Processes
TL;DR: In this paper , the development of flow velocity, surface elevation changes, and frontal advance of the two lobes of the composite rock glacier Inner Ölgrube, Kaunertal, Austria, is analyzed and compared over almost a century.
Abstract: Rock glaciers are cryo‐conditioned downslope‐creeping landforms in high mountains. Their dynamics are changing due to external factors influenced by climate change. Although there has been a growing scientific interest in mountain permafrost and thus in rock glaciers in recent years, their historical development, especially before the first alpine‐wide aerial image flights in the 1950s, has hardly been researched. Therefore, we utilize a historical stereophotogrammetric map from 1922 and historical flow velocity profiles (1938–1953) and relate them to data derived from historical aerial photographs and airborne laser scanning data in several time slices between 1953 and 2021. By doing so, the development of flow velocity, surface elevation changes, and frontal advance of the two lobes of the composite rock glacier Inner Ölgrube, Kaunertal, Austria, is analyzed and compared over almost a century. Results indicate an increased frontal advance in the laterally confined area of one lobe and a severe subsidence in the upper area of both lobes between 1922 and 1953. Whereas the former could be explained by a combination of the short warm phase in the 1940s and 1950s and the (subsurface) topography, the latter might be attributed to the strong melting of superimposed debris‐covered dead ice bodies, a relict of the Little Ice Age (LIA) glaciation. Both factors might also contribute to the increased flow velocities between 1938 and 1953, which are still recognizable in the 1953–1970 time step. Although both lobes follow a general similar trend, which is in line with the alpine‐wide trend of flow velocity acceleration in the 1990s, differences in the geomorphic development of the two lobes were identified. In addition to a slightly varying evolution of the flow velocities, the timing and magnitude of the volume changes are different. Furthermore, both lobes display a dissimilar mechanism of frontal advance over the entire study period. Because the external forcing is identical, the varying development might be attributed to variations in internal structure, bedrock topography, or upslope connection of the lobes. Due to the lateral constriction, the subsurface topography, and the LIA maximum extent of the glacier, it is assumed that the geomorphic development of the Innere Ölgruben rock glacier, particularly before 1953, represents a special case, and the results are not simply transferable to other rock glaciers.

2 citations

References
More filters
Methods of soil analysis. Part 3 - chemical methods.

[...]

Donald L. Sparks, A. L. Page, P. A. Helmke, R. H. Loeppert, P. N. Soltanpour, M. A. Tabatabai, Cliff T. Johnston, M. E. Sumner 
01 Jan 1996

6,649 citations

"A Combination of Relative-Numerical..." refers methods in this paper

  • ...Oven-dried samples were dissolved using a mixture of HF, HCl, HNO3, and H3BO3 in a closed system [38] (microwave oven and under high pressure, 25 bar)....

    [...]

Journal Article•DOI•
IntCal04 terrestrial radiocarbon age calibration, 0-26 cal kyr BP

[...]

Paula J. Reimer1, Michael Baillie1, Edouard Bard2, Alex Bayliss3, J. Warren Beck4, Chanda J H Bertrand5, Paul G. Blackwell6, Caitlin E. Buck6, George S. Burr4, K. B. Cutler7, Paul E. Damon4, R. Lawrence Edwards, Richard G. Fairbanks8, Michael Friedrich, Thomas P. Guilderson9, Alan G. Hogg10, Konrad A Hughen5, Bernd Kromer, Gerry McCormac1, Sturt W. Manning11, Christopher Bronk Ramsey12, Ron W Reimer13, Sabine Remmele10, John Southon9, Minze Stuiver14, Sahra Talamo, Frederick W. Taylor15, Johannes van der Plicht, Constanze E. Weyhenmeyer16 •
Queen's University Belfast1, Aix-Marseille University2, Historic England3, University of Arizona4, Woods Hole Oceanographic Institution5, University of Sheffield6, University of Minnesota7, Columbia University8, University of California, Irvine9, University of Waikato10, University of Reading11, University of Oxford12, University of California, Santa Cruz13, University of Washington14, University of Texas at Austin15, Lawrence Livermore National Laboratory16
01 Jan 2004-Radiocarbon
TL;DR: In this paper, a new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0-24 cal kyr BP (Before Present, 0 cal BP = AD 1950).
Abstract: A new calibration curve for the conversion of radiocarbon ages to calibrated (cal) ages has been constructed and internationally ratified to replace IntCal98, which extended from 0-24 cal kyr BP (Before Present, 0 cal BP = AD 1950). The new calibration data set for terrestrial samples extends from 0-26 cal kyr BP, but with much higher resolution beyond 11.4 cal kyr BP than IntCal98. Dendrochronologically-dated tree-ring samples cover the period from 0-12.4 cal kyr BP. Beyond the end of the tree rings, data from marine records (corals and foraminifera) are converted to the atmospheric equivalent with a site-specific marine reservoir correction to provide terrestrial calibration from 12.4-26.0 cal kyr BP. A substantial enhancement relative to IntCal98 is the introduction of a coherent statistical approach based on a random walk model, which takes into account the uncertainty in both the calendar age and the 14C age to calculate the underlying calibration curve (Buck and Blackwell, this issue). The tree-ring data sets, sources of uncertainty, and regional offsets are discussed here. The marine data sets and calibration curve for marine samples from the surface mixed layer (Marine04) are discussed in brief, but details are presented in Hughen et al. (this issue a). We do not make a recommendation for calibration beyond 26 cal kyr BP at this time; however, potential calibration data sets are compared in another paper (van der Plicht et al., this issue).

3,737 citations

"A Combination of Relative-Numerical..." refers methods in this paper

  • ...1 calibration program [46] based on the IntCal 04 calibration curve [47]....

    [...]

Journal Article•DOI•
Air pressure and cosmogenic isotope production

[...]

John O. Stone
10 Oct 2000-Journal of Geophysical Research
TL;DR: In this article, it was shown that the cosmic ray flux increases at higher altitude as air pressure and the shielding effect of the atmosphere decrease, and that altitude-dependent scaling factors are required to compensate for this effect in calculating cosmic ray exposure ages.
Abstract: The cosmic ray flux increases at higher altitude as air pressure and the shielding effect of the atmosphere decrease. Altitude-dependent scaling factors are required to compensate for this effect in calculating cosmic ray exposure ages. Scaling factors in current use assume a uniform relationship between altitude and atmospheric pressure over the Earth's surface. This masks regional differences in mean annual pressure and spatial variation in cosmogenic isotope production rates. Outside Antarctica, air pressures over land depart from the standard atmosphere by ±4.4 hPa (1σ) near sea level, corresponding to offsets of ±3–4% in isotope production rates. Greater offsets occur in regions of persistent high and low pressure such as Siberia and Iceland, where conventional scaling factors predict production rates in error by ±10%. The largest deviations occur over Antarctica where ground level pressures are 20–40 hPa lower than the standard atmosphere at all altitudes. Isotope production rates in Antarctica are therefore 25–30% higher than values calculated by scaling Northern Hemisphere production rates with conventional scaling factors. Exposure ages of old Antarctic surfaces, especially those based on cosmogenic radionuclides at levels close to saturation, may be millions of years younger than published estimates.

2,034 citations

"A Combination of Relative-Numerical..." refers background or methods in this paper

  • ...Production-rate scaling for latitude (geographic) and altitude was based on [52] and corrected for sample thickness assuming an exponential depth profile, a rock density of 2....

    [...]

  • ...2 % production due to muon capture [52]....

    [...]

Journal Article•DOI•
Development of the radiocarbon calibration program

[...]

Christopher Bronk Ramsey
01 Jan 2001-Radiocarbon
TL;DR: This paper highlights some of the main developments to the radiocarbon calibration program, OxCal, including changes to the sampling algorithms used which improve the convergence of the Bayesian analysis.
Abstract: This paper highlights some of the main developments to the radiocarbon calibration program, OxCal In addition to many cosmetic changes, the latest version of OxCal uses some different algorithms for the treatment of multiple phases The theoretical framework behind these is discussed and some model calculations demonstrated Significant changes have also been made to the sampling algorithms used which improve the convergence of the Bayesian analysis The convergence itself is also reported in a more comprehensive way so that problems can be traced to specific parts of the model The use of convergence data, and other techniques for testing the implications of particular models, are described

1,905 citations

"A Combination of Relative-Numerical..." refers methods in this paper

  • ...1 calibration program [46] based on the IntCal 04 calibration curve [47]....

    [...]

Journal Article•DOI•
Chemical isolation of quartz for measurement of in-situ-produced cosmogenic nuclides

[...]

C. P. Kohl1, K. Nishiizumi1•
University of California, San Diego1
01 Sep 1992-Geochimica et Cosmochimica Acta
TL;DR: An isolation method relying totally on chemical steps was developed to separate large quantities (10-200 g) of clean mono-minerallic quartz samples from a variety of terrestrial rocks and soils for the purpose of measuring Be-10 (t 1/2 = 1.5 Myr) and Al-26 (t1 2 = 0.705 Myr) produced by cosmic rays in situ in the quartz phase.

1,131 citations

Related Papers (5)
Application of a combination of dating techniques to reconstruct the Lateglacial and early Holocene landscape history of the Albula region (eastern Switzerland)

[...]

01 Apr 2011-Geomorphology
Ralph Böhlert, Markus Egli, Max Maisch, Dagmar Brandová, Susan Ivy-Ochs, Susan Ivy-Ochs, Peter W. Kubik, Wilfried Haeberli 
Towards a palaeoclimatic model of rock-glacier formation in the Swiss Alps

[...]

01 Jan 2000-Annals of Glaciology
Regula Frauenfelder, Andreas Kääb
Latest Pleistocene and Holocene glacier variations in the European Alps

[...]

01 Oct 2009-Quaternary Science Reviews
Susan Ivy-Ochs, Susan Ivy-Ochs, Hanns Kerschner, Max Maisch, Marcus Christl, Peter W. Kubik, Christian Schlüchter 
Permafrost creep and rock glacier dynamics

[...]

01 Jul 2006-Permafrost and Periglacial Processes
Wilfried Haeberli, Bernard Hallet, Lukas U. Arenson, Roger Elconin, Ole Humlum, Andreas Kääb, Viktor Kaufmann, Branko Ladanyi, Norikazu Matsuoka, Sarah M. Springman, Daniel Vonder Mühll 
Deglaciation in the central Pyrenees during the Pleistocene–Holocene transition: Timing and geomorphological significance

[...]

15 Apr 2017-Quaternary Science Reviews
David Palacios, José María García-Ruiz, Nuria Andrés, Irene Schimmelpfennig, Néstor Campos, Laëtitia Léanni, Georges Aumaître, Didier Bourlès, Karim Keddadouche 
Frequently Asked Questions (1)
Q1. What have the authors contributed in "A combination of relative-numerical dating methods indicates two high alpine rock glacier activity phases after the glacier advance of the younger dryas" ?

In this study, the authors present Schmidt-hammer rebound value measurements and weathering rind thicknesses on four active and one relict rock glacier in the Albula area of the eastern Swiss Alps. Use of this information together with the numeric ages makes it possible to derive two main activity phases: one started soon after the ice retreat following the Younger Dryas, the main activity occurred most likely in the early Holocene and lasted approximately until the Holocene climate optimum.