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Processes of lateral moraine formation at a debris-covered glacier, Suldenferner (Vedretta di Solda), Italy

Rabanser, Monika LU (2019) In Dissertations in Geology at Lund University GEOR02 20191
Department of Geology
Abstract
Lateral moraines are key features of glacial landscapes in high-alpine mountain areas. Research on lateral moraine formation is mostly limited to clean-ice glaciers; lateral moraine formation at the margins of debris-covered glaciers is currently poorly understood in an Alpine and sedimentological context. This thesis focuses on the reconstruction of processes of lateral moraine formation at the debris-covered glacier Suldenferner (Vedretta di Solda) in NE Italy. The most important geomorphological elements of the Suldenferner foreland are: (i) the lateral moraines, (ii) former areas of stagnant ice, (iii) a moraine from 1927, (iv) ice-moulded bedrock giving the direction of ice-flow, (v) outwash terraces, (vi) erosional remnants of the... (More)
Lateral moraines are key features of glacial landscapes in high-alpine mountain areas. Research on lateral moraine formation is mostly limited to clean-ice glaciers; lateral moraine formation at the margins of debris-covered glaciers is currently poorly understood in an Alpine and sedimentological context. This thesis focuses on the reconstruction of processes of lateral moraine formation at the debris-covered glacier Suldenferner (Vedretta di Solda) in NE Italy. The most important geomorphological elements of the Suldenferner foreland are: (i) the lateral moraines, (ii) former areas of stagnant ice, (iii) a moraine from 1927, (iv) ice-moulded bedrock giving the direction of ice-flow, (v) outwash terraces, (vi) erosional remnants of the lateral moraines, (vii) gullied glaciogenic material and (vii) glacially-overridden outwash.
The studied lateral moraines at Suldenferner reach heights between 110 and 130 m above their bases and are up to 3 km wide. The eastern lateral moraine is characterised by a pronounced cross-profile asymmetry, with gentle distal slopes (14°-30°) and steeper proximal slopes (40°-60°), while the western lateral moraine is only slightly asymmetrical, with steep slopes ranging between 60°-80°. Clasts within the lateral moraine along the western margin of the glacier are exclusively dolomite, while the clasts within the lateral moraine along the eastern margin of the glacier contain mainly micaschist, with some dolomite and paragneiss.
Sediments within the lateral moraines are divided into three lithofacies associations: lithofacies association 1 (LFA 1) is a silty-sandy, matrix-supported diamicton (DgMm3-2), lithofacies association 2 (LFA 2) comprises a clayey-silty, massive diamicton (DgFm2-2) and a clayey-silty, matrix-supported diamicton (DhMm3-2) and lithofacies association 3 (LFA 3) is a sandy-gravelly, clast-rich diamicton (DmCm1-1, DmCm2-1). These lithofacies associations are interpreted as reworked, glaciofluvial deposits (LFA 1), subaerial debris flows that have been stacked in an ice-marginal position (LFA 2) and debris flows that have incorporated distinctive amounts of micaschist (LFA 3).
Clast shape analysis reveals that the sediment delivery towards the lateral moraines contains a signal of mixed sources: the main mode of transport consists of subglacial and englacial sources (active transport), aided by minor contributions of supraglacial/extraglacial sources (passive transport). The presented conceptional model for lateral moraine formation in the Alps highlights the value of active clast delivery, whiles the importance of a supraglacial debris cover, and its final emplacement into laterally forming moraine ridges, exerts a limited influence on the moraine’s sedimentology. The model implies that lateral moraines have a complex formation history with glacier fluctuations, characterised by multiple glacial advance and retreat cycles. (Less)
Popular Abstract (Swedish)
Lateralmoräner är karaktäristiska för glaciala landskap bildade i höga bergsområden med dalglaciärer. Forskningen om lateralmoräners bildning är dock ofta begränsatsade till glaciärisar med lågt materialinnehåll. När lateralmoräner bildas längs kanten av materialrika glaciärer, med det glaciala materialet i sin senare fas huvudsakligen transporterat över glaciärens yta tillkommer sedimentationsprocesser som delvis är dåligt utforskade. Föreliggande arbete fokuserar på rekonstruktionen av de processer som är aktiva för bildandet av lateralmoräner vid den sedimenttäckta glaciären Suldenferner (Vedretta di Solda) i nordöstra Italien. De viktigaste geomorfologiska elementen i förlandet av Suldenferner-glaciären är (i) lateralamoräner, (ii) ett... (More)
Lateralmoräner är karaktäristiska för glaciala landskap bildade i höga bergsområden med dalglaciärer. Forskningen om lateralmoräners bildning är dock ofta begränsatsade till glaciärisar med lågt materialinnehåll. När lateralmoräner bildas längs kanten av materialrika glaciärer, med det glaciala materialet i sin senare fas huvudsakligen transporterat över glaciärens yta tillkommer sedimentationsprocesser som delvis är dåligt utforskade. Föreliggande arbete fokuserar på rekonstruktionen av de processer som är aktiva för bildandet av lateralmoräner vid den sedimenttäckta glaciären Suldenferner (Vedretta di Solda) i nordöstra Italien. De viktigaste geomorfologiska elementen i förlandet av Suldenferner-glaciären är (i) lateralamoräner, (ii) ett område med stagnant is, (iii) en moränrygg bildad 1927, (iv) isskulpterad berggrund med isflödesriktningsindikationer, (v) glacifluviala smältvattenterrasser, (vi) erosionsrester av lateralmoräner, (vii) smältvattenkanaler i glacigent material och (vii) glaciäröverskrida smältvattensediment.
De lateralmoräner som har studerats vid Suldenferner-glaciären reser sig mellan 110 och 130 från sin bas och är upp till 3 km breda. De kännetecknas av en uttalad tvärprofilsasymmetri med en svagt lutande distalsluttning (14˚-30˚) och en mer brant lutande proximalsluttning (40˚-80˚). Sten och block i lateralmoränen längs kanten av glaciären består uteslutande av dolomit, medan klastermaterialet i lateralmoränen längs den östra glaciärkanten huvudsakligen består av glimmerskiffer, dolomit och paragnejs.
Sedimenten som bygger upp lateralmoränerna har delats in i the sedimentfacie: litofacies association 1 (LFA 1) består av en siltig-sandig, matrix-stödd diamikt (DgMm3-2), litofacies association 2 (LFA 2) innehålle en lerig-siltig, massiv diamikt (DgFm2-2) och en lerig-siltig, matrix-stödd diamikt (DhMm3-2) och litofacies association 3 (LFA 3) är sandig-grusig, klaster-rik diamikt (DmCm1-1 och DmCm2-2). Dessa sedimentfacies tolkas processgenetiskt som glacialt omarbetade, glacifluviala sediment (LFA 1), subaerila flytjordssediment, vertikalt ackumulerade i ismarginalt läge (LFA 2) och, slutligen, flytjordssediment med stort tillskott av jordströmmar med inslag av stenfalls-processer (LFA 3).
Formanalys av claster visar att sedimentleveransen mot laterala moränerna skett från blandade källor. Det huvudsakliga transportsättet består av subglacial och englacial aktiv transport av klastermaterial med mindre bidrag från supraglaciala källor (passiv transport). Den presenterade konceptuella modellen för lateral-moränbildning i Alperna belyser betydelsen av aktiv klastertillförsel, medan vikten av supraglacial klastertillförsel och dessas slutliga avsättning i de lateralt bildande moränsryggarna utövar ett begränsat inflytande på moränsryggarnas sedimentologi. Den presenterade konceptuella modellen påvisar att lateralmoränerna vid Suldenferner-glaciären har en komplex bildhistoria med glaciärfluktuationer-kännetecknade av flera glaciala framstöts-och reträttcyckler. (Less)
Please use this url to cite or link to this publication:
author
Rabanser, Monika LU
supervisor
organization
course
GEOR02 20191
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Lateral moraines, Moraine genesis, Moraine stability, Debris-covered glaciers, Clast shape, Alps, Sedimentology, Glacier fluctuations
publication/series
Dissertations in Geology at Lund University
report number
556
language
English
id
8973354
date added to LUP
2019-03-24 21:54:24
date last changed
2019-03-24 21:54:24
@misc{8973354,
  abstract     = {{Lateral moraines are key features of glacial landscapes in high-alpine mountain areas. Research on lateral moraine formation is mostly limited to clean-ice glaciers; lateral moraine formation at the margins of debris-covered glaciers is currently poorly understood in an Alpine and sedimentological context. This thesis focuses on the reconstruction of processes of lateral moraine formation at the debris-covered glacier Suldenferner (Vedretta di Solda) in NE Italy. The most important geomorphological elements of the Suldenferner foreland are: (i) the lateral moraines, (ii) former areas of stagnant ice, (iii) a moraine from 1927, (iv) ice-moulded bedrock giving the direction of ice-flow, (v) outwash terraces, (vi) erosional remnants of the lateral moraines, (vii) gullied glaciogenic material and (vii) glacially-overridden outwash.
The studied lateral moraines at Suldenferner reach heights between 110 and 130 m above their bases and are up to 3 km wide. The eastern lateral moraine is characterised by a pronounced cross-profile asymmetry, with gentle distal slopes (14°-30°) and steeper proximal slopes (40°-60°), while the western lateral moraine is only slightly asymmetrical, with steep slopes ranging between 60°-80°. Clasts within the lateral moraine along the western margin of the glacier are exclusively dolomite, while the clasts within the lateral moraine along the eastern margin of the glacier contain mainly micaschist, with some dolomite and paragneiss. 
Sediments within the lateral moraines are divided into three lithofacies associations: lithofacies association 1 (LFA 1) is a silty-sandy, matrix-supported diamicton (DgMm3-2), lithofacies association 2 (LFA 2) comprises a clayey-silty, massive diamicton (DgFm2-2) and a clayey-silty, matrix-supported diamicton (DhMm3-2) and lithofacies association 3 (LFA 3) is a sandy-gravelly, clast-rich diamicton (DmCm1-1, DmCm2-1). These lithofacies associations are interpreted as reworked, glaciofluvial deposits (LFA 1), subaerial debris flows that have been stacked in an ice-marginal position (LFA 2) and debris flows that have incorporated distinctive amounts of micaschist (LFA 3).
Clast shape analysis reveals that the sediment delivery towards the lateral moraines contains a signal of mixed sources: the main mode of transport consists of subglacial and englacial sources (active transport), aided by minor contributions of supraglacial/extraglacial sources (passive transport). The presented conceptional model for lateral moraine formation in the Alps highlights the value of active clast delivery, whiles the importance of a supraglacial debris cover, and its final emplacement into laterally forming moraine ridges, exerts a limited influence on the moraine’s sedimentology. The model implies that lateral moraines have a complex formation history with glacier fluctuations, characterised by multiple glacial advance and retreat cycles.}},
  author       = {{Rabanser, Monika}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Dissertations in Geology at Lund University}},
  title        = {{Processes of lateral moraine formation at a debris-covered glacier, Suldenferner (Vedretta di Solda), Italy}},
  year         = {{2019}},
}