Ice-Marginal and Periglacial Processes and Sediments ppt

Understanding the sediments deposited by glaciers or other cold-climate processes assumes enhancedsignificance in the context of current global warming and the predicted melt and retreat

Understanding the sediments deposited by glaciers or other cold-climate processes assumes enhancedsignificance in the context of current global warming and the predicted melt and retreat of glaciers andice sheets.

This volume analyses glacial, proglacial and periglacial settings focusing, among others, on tation at termini of tidewater glaciers, on hitherto not-well-understood high-mountain features, and on sedi-ments such as slope and aeolian deposits whose clasts were sourced in glacial and periglacial regions, buthave been transported and deposited by azonal processes Difficulties are thus often encountered in inferringPleistocene and pre-Pleistocene cold-climate conditions when the sedimentary record lacks many of thespecific diagnostic indicators The main objective of this volume is to establish the validity and limitations

sedimen-of the evidence that can be obtained from widely distributed clastic deposits, in order to achieve reliablepalaeogeographic and palaeoclimatic reconstructions At a more general level and on the much longer geo-logical timescale, an understanding of ice-marginal and periglacial environments may better prepare us forthe unavoidable reversal towards cooler and perhaps even glacial times in the future

Ice-Marginal and Periglacial Processes and Sediments

The Geological Society of London Books Editorial Committee

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It is recommended that reference to all or part of this book should be made in one of the following ways:Martini, I P., French, H M & Pe´rez Alberti, A (eds) 2011 Ice-Marginal and Periglacial Processesand Sediments Geological Society, London, Special Publications, 354

Levy J S., Head, J W & Marchant, D R 2011 Gullies, polygons and mantles in Martian permafrostenvironments: cold desert landforms and sedimentary processes during recent Martian geological history.In: Martini, I P., French, H M & Pe´rez Alberti, A (eds) Ice-Marginal and Periglacial Processes andSediments Geological Society, London, Special Publications, 354, 167 – 182

Ice-Marginal and Periglacial Processes and Sediments

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Preface vii

MARTINI, I P., FRENCH, H M & ALBERTI, A P Ice-marginal and periglacial processes and sediments:

an introduction

1

LØNNE, I & NEMEC, W Modes of sediment delivery to the grounding line of a fast-flowing tidewaterglacier: implications for ice-margin conditions and glacier dynamics

PE ´ REZALBERTI, A., DI´AZ, M V., MARTINI, I P., PASCUCCI, V & ANDREUCCI, S Upper Pleistocene

glacial valley-junction sediments at Pias, Trevinca Mountains, NW Spain

93

CARLING, P A., KNAAPEN, M., BORODAVKO, P., HERGET, J., KOPTEV, I., HUGGENBERGER, P & PARNACHEV,

S Palaeoshorelines of glacial Lake Kuray – Chuja, south-central Siberia: form, sediments and process

111

KELLER, M., HINDERER, M., AL-AJMI, H & RAUSCH, R Palaeozoic glacial depositional environments of

SW Saudi Arabia: process and product

129

LEVY, J S., HEAD, J W & MARCHANT, D R Gullies, polygons and mantles in Martian permafrostenvironments: cold desert landforms and sedimentary processes during recent Martian

geological history

167

THORN, C E., DARMODY, R G & DIXON, J C Rethinking weathering and pedogenesis in alpine

periglacial regions: some Scandinavian evidence

183

GUGLIELMIN, M., FAVERO-LONGO, S E., CANNONE, N., PIERVITTORI, R & STRINI, A Role of lichens ingranite weathering in cold and arid environments of continental Antarctic

195

VANSTEIJN, H Stratified slope deposits: periglacial and other processes involved 213

OLIVA, M & ORTIZ, A G Holocene slope dynamics in Sierra Nevada (south Spain) Sedimentologicalanalysis of solifluction landforms and lake deposits

227

NEWELL, W L & DEJONG, B D Cold-climate slope deposits and landscape modifications of the

Mid-Atlantic Coastal Plain, Eastern USA

259

an introduction

I PETER MARTINI1*, HUGH M FRENCH2& AUGUSTO PE ´ REZ ALBERTI3

1School of Environmental Sciences, University of Guelph, Guelph,

Ontario N1 G 2W, Canada

2Departments of Geography and Earth Sciences, University of Ottawa, Ottawa,

Ontario K1N 6N5, Canada

3Departamento de Xeografı´a, Universidade de Santiago de Compostela,

Santjago de Compostela, Spain

*Corresponding author (e-mail: pmartini@uoguelph.ca)

Abstract: The volume focuses on the analysis of glacial clastic sedimentary deposits, both ancient

and recent The papers range from reviews of glacial systems and cold-climate weathering products

and processes to conceptual and field studies of specific ice-marginal and cold-climate sediments.

Papers are included that deal with tidewater glaciers, mountain settings on Earth, permafrost

areas on both Earth and Mars and detailed regional analyses of cold-climate sediments of Late

Pleistocene and Holocene age The identification of sedimentary facies allows an accurate

reconstruction of many of the developmental processes that are involved in ice-marginal and

periglacial environments Lithostratigraphic characteristics of clastic deposits also constitute

circumstantial evidence for the previous existence of ancient, and certainly pre-Quaternary,

cold-climate systems This is demonstrated by a study on putative Palaeozoic glacial deposits

in Saudi Arabia.

This volume presents a number of papers that relate

to both current and ancient ice-marginal and

cold-climate environments Studies of their sediments,

weathering and transportation processes contribute

to an understanding of the cryosphere The

cryo-sphere includes Earth’s surface areas that

experi-ence one or more of the following: snow cover, sea

ice, glaciers, perennial and seasonal frost (Fig 1)

Here, we are concerned with the sediments and

weathering processes that occur in the environments

that are immediately adjacent to glaciers as well as

the frost-dominated environments that characterize

cold-climate settings in general We include

contri-butions that involve not only present-day cases but

also those that occurred in the Pleistocene and, in

minor measure, the more ancient geological past

In addition, and in anticipation of the future, we

include a paper that summarizes recent progress in

planetary (Martian) observations

Glacial and periglacial environments

Vast continental areas of Earth have been

sculpted by glaciers and many regions are now

covered by glaciogenic sediments Remnants of

these Pleistocene-age ice sheets still exist today,the largest being in Antarctica and Greenland.These ice bodies and the many other smaller gla-ciers, together with their immediate pro-glacial orice-marginal surroundings, constitute the glacialenvironments of today Equally extensive, bothnow and in the past, are vast ice-free areas thathave either experienced or currently experiencecold-climate conditions These may have lasted forthousands, and in some cases millions, of years.These areas constitute the so-called periglacialenvironments Collectively, these two environmentsextend over approximately one-third of the Earth’sland surface; they undoubtedly occupied muchmore during the cold periods of the Pleistoceneand even earlier during the cold events in ancientgeological time

The extraordinarily high erosive and tational power of glaciers has been well known forover 150 years Prior to that, during the first half

transpor-of the 1800s, the full potential transpor-of glaciers was notrecognized although icebergs and the biblicalflood were considered suitable agents for movinglarge erratic boulders and heterogeneous sedi-ments over considerable distances The early devel-opment of the glacial hypothesis encountered

From: Martini, I P., French, H M & Pe´rez Alberti, A (eds) Ice-Marginal and Periglacial Processes and Sediments Geological Society, London, Special Publications, 354, 1 – 13.

DOI: 10.1144/SP354.1 0305-8719/11/$15.00 # The Geological Society of London 2011.

opposition but the ever-increasing evidence

gradu-ally converted the leading earth scientists of the

time such as William Buckland and Charles Lyell

(Chorley et al 1964) A somewhat refined glacial

hypothesis was developed by Louis Agassiz in

1840 but the first real scientific glacial study was

published by Archibald Geikie in 1863 for Scotland

(followed by several other publications that

in-cluded the first edition of The Great Ice Age;

Geikie 1874) By the turn of the century, the

theory of Pleistocene ice ages was well established

both in Europe and North America (Wright 1890;

Geikie 1897; Daly 1934; North 1943)

The periglacial concept is more recent in origin

The term was first used by a Polish geologist,

Walery von Łozinski, in the context of the

mechan-ical disintegration of sandstones in the Gorgany

Range of the southern Carpathian Mountains (a

region now part of central Romania) He described

the angular rock-rubble surfaces that

charac-terize the mountain summits as ‘periglacial facies’

formed by the previous action of intense frost

(Łozinski 1909) Subsequently, the concept of a

‘periglacial zone’ was introduced (Łozinski 1912)

to refer to the climatic and geomorphic conditions

of areas peripheral to Pleistocene ice sheets and

glaciers Theoretically, this was a tundra zone that

extended as far south as the treeline In the

moun-tains, it was a zone between the timberline and

snowline

Today, Łozinski’s definition is regarded asunnecessarily restricting; few, if any, modernanalogues exist (French 2000) There are two mainreasons First, frost action phenomena are known

to occur at great distances from both present-dayand Pleistocene ice margins In fact, frost-actionphenomena can be completely unrelated to ice-marginal conditions Second, the term has beenincreasingly understood to refer to a complex ofcold-dominated geomorphic processes Theseinclude not only unique frost-action and perma-frost-related processes but also a range of azonalprocesses, such as those associated with snow,running water and wind, which demand neither aperipheral ice-marginal location nor excessivecold Instead, these processes assume distinctive

or extreme characteristics under cold, non-glacialconditions

Studies of the ice-marginal and periglacialenvironments do not differ tactically from those ofother Earth surface systems except for one impor-tant fact: one is dealing with environments inwhich an unusual mineral (ice, H2O) is very close

to its melting point It also experiences sublimation

As a result, the presence of snow and ice generatesconditions and landscapes that are unusual andhighly variable over both short and long timespans (night and day, seasonal and multi-annual,century, millennia) A number of texts cover thebroad fields of ice, glaciology and glacial

Fig 1 (a, b) A schematic diagram that illustrates how geography and geomorphology interact with the related physical science disciplines and (c) the major constituents of the cryosphere Studies of the sediments associated with either ice-marginal or periglacial environments lie within either the shaded or cross-hatched areas in (c) (from French 2007).

I P MARTINI ET AL.

2

geomorphology (Souchez & Lorrain 1991; Paterson

1994; Benn & Evans 1998; Liestol 2000; Martini

et al 2001)

Ancient environments and geological

contexts

In the study of Earth systems, we are trained to learn

from the present in order to interpret the past

However, we must be mindful of the very different

settings that are involved and that some events are so

rare they may not be observed directly during a

life-time and need to be inferred from the sediment/rock

record they leave Moreover, the geo(morpho)logic

system is complex; a full understanding requires

contributions from a myriad of sciences that have

become increasingly complex in the last two to

three decades For example, the basic sciences such

as physics, chemistry and biology must be applied

to understand the main component of both the

ter-restrial glacial and periglacial systems and Martian

geology, namely ice The rheological behaviour of

glaciers and the landscape, both erosive and

deposi-tional, that glaciers leave behind are also central

concerns while an understanding of the freezing

process, be it seasonal or perennial, is an essential

but not defining aspect of periglacial

geomorphol-ogy There is also overlap with other subdisciplines;

for example, in both glacial and periglacial

environ-ments, azonal processes such as running water, wind

and gravity-induced displacements often assume

critical importance The same combination of

pro-cesses must also be considered when inferring the

nature of wind-related processes on the Martian

surface

Since early times, Earth’s climate has

experien-ced variations from cool long-lasting (‘Ice-house’)

periods to warm (‘Greenhouse’) periods (Fig 2)

Humans have evolved and still live in the last

Ice-house period, the Quaternary, a period punctuated

by relatively short warmer stages when glaciers

retreated (interglacial) and longer colder stages

(glacial) during which glaciers advanced and snow

and ice covered large expanses of the Earth’s

surface Within each glacial stage, smaller

tem-perature variations determined colder periods

when glaciers expanded and warmer periods when

melting prevailed Currently, Earth is in an

inter-stadial stage and experiencing a global temperature

increase

Planetary environments

The recent growth in the study of planetary

environ-ments presents special problems for the two

dis-ciplines of glacial and periglacial geomorphology

On Mars for example, temperatures fall to as low

as 2250 K and the planet is correctly viewed aspossessing not only a cryotic (temperature lessthan 0 8C) environment but also several Ice Ages(Head et al 2003) It is highly probable that theMartian near-surface contains H2O in the form ofburied icy bodies (Mellon & Jakowsky 1995) andthere is morphological evidence that suggests theephemeral occurrence of surface water in the geo-logical past (Baker 2001) The weathering and

Fig 2 A graph showing estimated changes in global Earth temperature during geological time and alternating cold and warm periods (modified from Scotese 2008).

landscape models associated with traditional

(Earth-based) ice-marginal and periglacial processes and

sediments are therefore uniquely challenged when

totally cryotic environments are considered

The glacier system

By definition, glaciers form on land but may extend

into large lakes and the ocean where they form ice

shelves They respond to accumulations of snow

and ice in the upper part of their system by

flowing under gravity across the surrounding land

as a sort of gigantic debris flow When armoured

with rock and sediment acquired from

surround-ing exposed terrain or from the glacier substrate

through various processes, they abrade and pluck

sediment along the way and transport and release

it elsewhere The latter is achieved directly either

by plastering on the substrate or in situ melt-out,

or indirectly by providing water for gravitational

mass movements such as debris flows or for

over-land, rill and channel fluid flows Erosional features,

from large-scale features such as glaciated valleys

and tunnel valleys to smaller features such as

stria-tions on bedrock, may survive repeated glaciastria-tions

By contrast, the sedimentary records of older events

may be partially or totally removed by younger

glaciations

Different features form in different parts of

the glacier and at the ice margin at different times

Glacial sediment sequences, often partially

rewor-ked and modified by proglacial processes, typically

become visible upon retreat of a glacier These

sequences vary depending on the morphology and

lithology of the substrate and the type of glacier

that formed them: valley glaciers or large ice

sheets They may be either temperate or polar and

either prevalently warm- or cold-based

The features of glaciers and glacial sediments

have been well studied and do not need to be

repea-ted One exception is to mention the debate on

whether features were formed by direct action of

glacier ice or by other processes such as sediment

gravity flows (mainly debris flows and turbidity

currents) and canalized fluid flows An example of

this debate involves the origin of unsorted, usually

polymictic, massive or poorly structured deposits

These are generally called ‘tills’ when released

directly from the glacier ice or ‘diamicton’ when

their origin is uncertain even if their material may

have a glaciogenic source Another example is the

origin of drumlins These may have various internal

compositions ranging from massive diamicton to

mostly stratified sand and gravel (Shaw & Kvill

1984; Menzies 1995, 1996) The uncertainty

regard-ing depositional process becomes critical when the

existence of pre-Quaternary glaciations and their

spatial extension needs to be established (Hambrey

& Harland 1981; Deynoux 1985; Eyles 1993;Crowell 1999)

It is obvious that no single feature representing

a clearly defined process can determine a enviroment; rather, reliable interpretation mustrely upon an assemblage of features, representing

palaeo-a reoccurrence of processes in repepalaeo-ating verticpalaeo-aland/or lateral successions and occurring in a well-established stratigraphic framework

To place the various contributions on marginal sediments and environments within anappropriate context, the following briefly summar-izes several of the characteristic features associatedwith this environment

ice-First, physical weathering by either armouredglacier ice or by meltwater flows under or in theproximal parts of a glacier leads to a progressivecomminution of terrigenous material Fracturing

of particles under the weight of moving glacier icegenerates characteristic microscopic and submicro-scopic surface textures (Mahaney 1996; Whalley1996) Pebbles and large clasts, transported at thebase of the glacier and subject to vertical movementdue to repeated pressure variations and phasechange of the ice/water, are moulded into charac-teristic polished, striated, facetted iron-shaped(flatiron) forms (Fig 3) The high occurrence ofsuch clasts within a sedimentary deposit is a goodindication of glacial origin Furthermore, striationsgenerated on bedrock surfaces may be a good indi-cation of direct glacial activity and provide palaeo-flow directions

Second, a variety of meso- to mega-scale sional features are created by armoured ice or bysubglacial meltwater flows For example, swarms

ero-of partially to totally infilled large channels and nel valleys have been interpreted as indicators ofice-marginal proximity in many places in Europe

tun-Fig 3 Typical striated, facetted flatiron cobble transported at the base of a temperate Pleistocene glacier,

S Ontario, Canada (modified from Martini et al 2001).

I P MARTINI ET AL.

4

(Piotrowski 1994; Jørgensen & Sandersen 2006),

North America (Barnett et al 1998; Russell et al

2003; Hooke & Jennings 2006), South Africa

(Visser 1988; Eyles & de Broekert 2001) North

Africa (Ghienne & Deynoux 1998; Hirst et al

2002) and the Middle East (Aoudeh & Al-Hajri

1995; Le Heron et al 2009) (Fig 4)

Third, materials transported by a glacier usually

retain the characteristics imparted by cold-climate

weathering such as angular clasts and unsorted

matrix, even when being moved in either

supragla-cial or englasupragla-cial positions Some of this material,

frequently polymictic and with large erratic clasts,

may be transported from distant and geologically

different areas Material transported at the base

may be subject to polishing, rounding and sculpting

but the sediment retains a generally poorly sorted,

massive and compacted nature Glacier movements

during normal advances, surges or related repeated

retreats and re-advances of the terminus can deform

these deposits in a characteristic fashion These

deformations therefore provide useful information

for interpreting Pleistocene and older putatively

glacial deposits (Fig 5) (Le Heron et al 2005;

Evans et al 2006)

Fourth, the presence of till or till-like deposits

is one of the principal lines of circumstantial

evi-dence for past glacier activity in Pleistocene and

older successions (Crowell 1999) However, many

processes contribute to the release, reworking and

sedimentation of glaciogenic material at its

termi-nus, particularly of temperate glaciers These

mainly include debris flows that generate diamicton

(similar to tills in terrestrial settings), turbidity flows

that move glaciogenic material into the deeper parts

of lake and marine basins and water flows that

generate a variety of fluvial sedimentary sequences

generally of the braided river type in proglacial

settings (Fig 6) These processes may obscure and

sometime obliterate most of the direct evidence ofglacial activity (Eyles 1987) However, some tell-tale features of glaciations may persist in sedimentsthat allow a glaciogenic interpretation When placed

in the appropriate stratigraphic, gical and regional palaeoenvironmental contexts,they hint to past proglacial activity Such types

palaeoclimatolo-of evidence include the polymictic composition

of clasts, the occurrence of erratics, the presence

of deformations in sandy gravelly deposits ably due to the melting of stranded or partiallyburied ice blocs; Price 1973; Fay 2002; Russell &Knudsen 2002) and lonestones that pierce or other-wise deform laminations in fine-grained marineand lacustrine deposits which can be interpreted asice-rafted dropstones (Fig 7)

(prob-The periglacial systemLozinski’s original concept of the periglacial zonewas that of a northern mid-latitude mountainzone lying between timberline and snowline The

‘zone’ reflected climatic zonation When consideredsubsequently in the Pleistocene context, it was aproglacial zone peripheral to the mid-latitude icesheets and glaciers A complication is that so-calledperiglacial conditions often extend south of thelatitudinal treeline and below the altitudinal timber-line This is because many areas of the northernboreal forest or taiga are underlain by relict per-mafrost and glaciers may extend below the timber-line and into the forest zone in alpine areas Thesevarious concepts are illustrated schematically inFigure 8

Today, the periglacial concept is slightly broader

in definition and usually refers to a range of coldnon-glacial processes (French 2007) Snow, ice andpermafrost are central, but not defining, elements.Fig 4 Map illustrating the distribution of buried uppermost Ordovician valleys around the Arabian Shield interpreted

as tunnel valleys (modified from Aoudeh & Al-Hairi 1995; Le Heron et al 2009).

It can be argued that typical periglacial regions do not

exist and, if they do, lack well-defined boundaries

It is more realistic to envisage periglacial areas as

being cold-climate ‘zones’ in which seasonal and

perennial frost, snow and normal azonal processes

are present to a greater or lesser degree The

reality is that most periglacial landscapes inherit

the imprint, in varying degrees, of either glacial or

non-glacial climatic conditions

The essence of both the current periglacial

system and the proglacial or Lozinski’s Pleistocene

‘periglacial zone’ can best be illustrated with

reference to an area of northwest Banks Island in

the western Canadian Arctic Located at latitude

748N (Fig 9), not only is the area an obviously

active periglacial environment but it also illustrates

the nature of the ice-marginal proglacial

environ-ment (French 1972) Part of the region is shown in

an aerial photograph (Fig 10)

During the Late Pleistocene, an ice lobe

associ-ated with the late Wisconsinan ice sheet impinged

on the north coast of Banks Island A developed lateral moraine system was formed and,

well-in the proglacial zone to the immediate south, aseries of broad meandering ice-marginal chan-nels were eroded These are very clearly shown inFigure 10 Some channels appear to have been sub-sequently abandoned when they became pluggedwith material that either slumped or soliflucted offthe moraine The ice lobe also blocked northwardsdrainage and a number of ice-dammed lakes formed

in the lower reaches of valleys One such proglaciallake overflowed westwards, forming a strikingspillway channel visible on the aerial photograph

A radiocarbon date of 8380 + 150 a BP provides

a minimal age for the ice-dammed lake and hence

a terminal date for when ice impinged upon theland in that area

In summary, northwest Banks Island was a sic Late Pleistocene – early Holocene proglacialenvironment At the same time, NW Banks Island

clas-is today a classic active periglacial environment

Fig 5 Idealized scheme of possible soft-sediment deformation generated by glaciers (modified from Le Heron et al 2005).

I P MARTINI ET AL.

6

characterized by intense frost action and the

pres-ence of permafrost It is the first of these two sorts

of environments and its associated sediments that

is the central focus of Part One of the volume The

second environment relates to Part Two of thevolume

Prior to reading the various contributions inPart Two, it is instructive to describe the processescurrently operating on northwest Banks Island.Temperatures rise to between þ5 and þ7 8C forapproximately 3 months in the summer and fall tobelow 225 8C during the polar night; permafrost

is estimated to be over 400 m thick The landscape

is being eroded by a combination of wind-inducedand snow-related mass-wasting processes togetherwith fluvial activity over frozen ground duringthe short summer months (French 1970, 1971).The surface is being dissected by west- andnorthwest-flowing streams in shallow valleys withdendritically arranged tributary valleys (Fig 11).Preferential mass wasting (gelifluction) onnortheast- and east-facing slopes reflects thedominant southwest winds in winter that depositsnow on lee (northeast-facing) slopes and keepexposed (southwest-facing) slopes and uplandsurfaces largely snow-free This produces a striking

Fig 6 Schematic model of principal terrestrial and marine environments and sedimentary sequences formed during a single advance and retreat of a temperate glacier (from Eyles & Eyles 1992).

Fig 7 Lonestone (dropstone) in laminated marine

deposits, ‘Palaeozoic Itarare’ Formation, Brazil

(modified from Martini et al 2001).

asymmetry of slopes and drainage patterns in which

south- and southwest-facing slopes are steeper

than north- and northeast-facing slopes The

sur-face of the plain is characterized by large

thermal-contraction crack polygons

In summary, this Arctic island and other areas

of the circumpolar region are classic examples of

periglacial landscapes currently being fashioned

by frost action and mass wasting (gelifluction)

pro-cesses in conjunction with the operation of the

azonal processes of wind, snow and fluvial activity

It is this sort of environment and the associated

processes and sediments that are central to PartTwo of the volume

Contributions in this volumeMuch is now known about glaciers and cold-climateenvironments The transition from the ice-marginalsetting to that of the cold but essentially non-glacialsetting is however of particular interest during

a period of active glacier retreat when the greatvariety of ice-marginal conditions can be observed

Fig 8 Schematic diagram illustrating the limits of the periglacial zone: (a) high latitudes and (b) alpine areas (from French 2007).

I P MARTINI ET AL.

8

What we can learn from modern and Pleistocenesettings can be used to interpret more ancientoccurrences of cold-climate conditions Whereasthe occurrence of cold conditions and glaciers

is readily recognized (at least for the Pleistocene),

it is still difficult to establish with confidencethe glacier margin; the occurrence and actual dis-tribution of more ancient pre-Pleistocene glacialand periglacial systems is therefore especiallyambiguous Many of the contributions (a numberderive from presentations made at a session devo-ted to glacial and periglacial deposits at the 27thMeeting of the International Association of Sedi-mentologists held in Alghero, Italy in September2008; others are invited) published in this volumeaddress some of these concerns The volume issubdivided into two parts

The first part deals with ice-marginal ment and sediments The first paper by Igo´lfssonpresents a brief review of the glaciations of Sval-bard This provides a good, confined model forFig 9 Location map of northwest Banks Island in the

environ-western Canadian Arctic.

Fig 10 Aerial photograph of part of northwest Banks Island, providing a field example of the spatial overlap of a Late Pleistocene ice-marginal environment and a current periglacial environment (part of A17381-137, National Air Photo Library, Ottawa; produced under license from Her Majesty the Queen in Right of Canada, with permission from Natural Resources Canada).

both terrestrial and marine glacial processes,

land-forms and sediments It is followed by two papers

by Lønne & Nemec that examine the deposits of

the end moraines associated with tidewater glaciers

These settings are impossible to deal with directly

during their formation, but the products can be

examined in emerged systems The first paper

examines the sedimentological/stratigraphic

char-acteristics of one of these moraines and reconstructs

the processes responsible for its formation The

second paper develops a sedimentological/

stratigraphic model that can be used to study and

better understand the processes active at the

termini of tidewater and other glaciers

The following three papers deal with glaciated

mountain settings The paper by Lucas & Sass

ana-lyses the development of high-mountain lateral

moraines It utilizes field observations and

geo-physical methods (ground-penetrating radar) to

establish their evolution and develops a model of

formation different from that of larger lateral

mor-aines located further downvalley The paper by

Pe´rez Alberti et al examines the Pleistocene

deposits formed at the junction of two valley

gla-ciers where one temporarily dams the valley of the

other, faster-retreating glacier This is a common

occurrence in modern mountains where recurring

breaks of the ice dam lead to local highly dissected

sedimentary sequences The paper presented in

this volume examines sedimentologically the

suc-cessions and, aided by OSL (optically stimulated

luminescence) dates, establishes the relationships

between the remnant parts of the dissected record

and reconstructs a glaciation model of the areaduring MIS 3 – 4 (marine isotope stages) The lastmountain paper by Carling et al examines a verylarge Upper Pleistocene lake dammed by a glacier

in the Altai Mountains of Siberia The lake oped in an unglaciated valley surrounded by acrown of glaciated mountains The ice dams brokeseveral times leading to megafloods The studyreported here examines the sequences of beachesand shoreline notches left by the lake along theflanks of the valley, and reconstructs and modelsthe palaeohydrology and palaeowinds of the area.Part 1 ends with a paper by Keller et al.that shows how the previous existence of ancientpre-Pleistocene glaciers can be inferred withsome confidence from detailed sedimentological/stratigraphic analysis The study deals with Palaeo-zoic petroleum-bearing horizons of SW SaudiArabia Although the normal diagnostic character-istics used to recognize the direct action of glacierscannot be used with great confidence in this case,certain macrofeatures such as tunnel-valley patternsand their sedimentary fills constitute circumstantialevidence

devel-The second part of the volume deals with glacial settings, which fall into four groups First,two papers discuss the typical permafrost-relatedfeatures that develop in perennially frozen surficialmaterials: one in the relatively humid and warmhumid Earth setting (French) and the other in theintense cold (cryotic) conditions that exist on Mars(Levy et al.) Although strong differences existbetween the two systems because of these very

peri-Fig 11 An oblique aerial view of northwest Banks Island showing: the current fluvial dissection; the asymmetrical nature of the valleys; large-scale thermal-contraction crack polygons on the upland surface; and snow remaining on lee slopes and in valley bottoms and small gullies The photograph was taken in early July.

I P MARTINI ET AL.

10

different environments, there are sufficient

simi-larities to warrant the application of remote sensing

concepts and terrestrial knowledge (particularly in

Antarctica) to interpretation of Martian surface and

near-surface sediments

A second group examines weathering processes

in cold-climate settings Thorn et al conclude

that strong, active chemical weathering occurs in

mountainous sub-arctic environments, further

dis-pelling the traditional idea of the overwhelming

efficacy of physical weathering in such settings

To place the physical v chemical weathering

dis-cussion in an even better perspective, the paper by

Guglielmin et al is a case study of the role of

biological weathering in the extreme cold-climate

environments of Northern Victoria Land,

Antarc-tica They report on the role of lichens in hardening

the exterior of the cupola of tafoni in Antarctica The

fact that these unusual weathering structures also

develop in hot environments, and that saline

con-ditions appear to be intimately involved, also

high-lights the lack of understanding of some aspects of

the nature of cold-climate weathering

A third group focuses upon the stratified slope

deposits that occur widely in Pleistocene periglacial

environments and in today’s alpine environments

of the middle and low latitudes The initial paper

by Vandenberghe discusses the apparently

seman-tic but essentially fundamental problems associated

with the recognition of so-called ‘periglacial

sedi-ments’ It is clear that there are cold-climate

envi-ronments where particular types of weathering

such as frost shattering are highly efficient and

typical deposits, such as blockfields (the so-called

‘periglacial facies’ of Lozinski), are generated

However, in many cold-climate environments, the

typical modes of transport and sedimentation do

not produce clastic sediments that are

fundamen-tally different from those produced in other climatic

zones It follows that the use of sedimentary facies

alone are insufficient to infer ancient periglacial

environments from ancient sediments Instead,

the existence of ancient periglacial (permafrost)

environments must be inferred from the presence

of post-depositional features such as frost-fissure

casts and pseudomorphs In the following paper,

Van Steijn reviews stratified slope deposits He

concludes that although the component particles

may have been generated in periglacial settings

and may preserve their shape (for instance,

forming breccias), other characteristics reflect

azonal modes of transport such as rock falls,

debris slides and mostly wet and dry debris flows

and fluid flows The third paper by Oliva &

Go´mez Ortiz examines sediment movement on

slopes in the current periglacial zone of Sierra

Nevada (Spain) They ascribe the coarse-grained

clastics alternating with organic-rich finer-grained

sediments as well as the coeval alternation ofcoarser and finer grained sediments in an adjacentsmall mountain lake to variations in climatic (temp-erature and precipitation) conditions from themid-Holocene onwards

The fourth and final group contains two papersdealing with cold-climate sediments on a broaderscale The first, by Brookfield, reviews aeoliandeposits including the putative cold-climate depos-its Loess is included in the discussion Again, exceptfor certain particular features such as the freshness

of the component particles indicating limited cal weathering, the sedimentological character ofwind-blown sediment does not specifically identify

chemi-a cold-climchemi-ate origin or specific periglchemi-acichemi-al cesses Indeed, large quantities of fines generated

pro-by glacial abrasion glacier are stored temporarily

in proglacial/periglacial settings and are partlyeroded and redistributed continent-wide by wind,both in periglacial and non-periglacial settings (Der-byshire & Owen 1996) The existence of periglacialsettings is indicated primarily by post-depositionalfeatures that indicate frozen ground, such as therelatively well-known frost cracks and cryostruc-tures but also by the less well-known secondary pre-cipitates, neoformed clay minerals and fragipanlayers, as described by French The final paper byNewell et al.brings together many of the variousconcepts and preoccupations examined in theSpecial Publication and reports upon the natureand distribution of Late Pleistocene sediments onthe Mid-Atlantic Coastal Plain of the eastern US

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O ´ INGO´LFSSON Faculty of Earth Sciences, University of Iceland, Sturlugata 7, Is-101 Reykjavı´k, Iceland and The University Centre in Svalbard (UNIS) (e-mail: oi@hi.is)

Abstract: Marine and terrestrial archives can be used to reconstruct the development of glacially

influenced depositional environments on Svalbard in time and space during the late Cenozoic.

The marine archives document sedimentary environments, deposits and landforms associated

with the Last Glacial Maximum (LGM) when Svalbard and the Barents Sea were covered by

continental-scale marine-based ice sheet, the last deglaciation and the work of tidewater glaciers

in interglacial setting as today The terrestrial archives record large-scale Quaternary glacial

sculpturing and repeated build-up and decay of the Svalbard– Barents Sea ice sheet The

finger-printing of Quaternary glaciations on Svalbard reflects the transition from a full-glacial mode,

with very extensive coverage by the Svalbard – Barents Sea ice sheet and subsequent deglaciation,

to an interglacial mode with valley, cirque and tidewater glaciers as active agents of erosion and

deposition Conceptual models for Svalbard glacial environments are useful for understanding

developments of glacial landforms and sediments in formerly glaciated areas Svalbard glacial

environments, past and present, may serve as analogues for interpreting geological records of

marine-terminating and marine-based ice sheets in the past.

Svalbard is an archipelago in the Arctic Ocean that

comprises all islands between 748N – 818N and

108E – 358E (Fig 1) The principal islands are

Spits-bergen, Nordaustlandet, Barentsøya, Edgeøya,

Kong Karls Land, Prins Karls Forland and Bjørnøya

(Bear Island) The total area of Svalbard is

62 160 km2 The West Spitsbergen Current, which

is a branch of the North Atlantic Current, reaches

the west coast of Svalbard, keeping water open

most of the year The present climate of Svalbard

is Arctic, with mean annual air temperature of

c 26 8C at sea level and as low as 215 8C in

the high mountains Most of Svalbard is situated

within the zone of continuous permafrost (Humlum

et al 2003) Precipitation at sea level is low, only

c 200 mm water equivalent (w.e.) in central

Spits-bergen and c 400 – 600 mm w.e along the western

and eastern coasts of the island The Svalbard

landscape, in particularly the island of Spitsbergen,

is generally mountainous with the highest

eleva-tion of c 1700 m a.s.l on north-eastern Spitsbergen

Large glacially eroded fjords are numerous,

parti-cularly at the northern and western coasts of

Spits-bergen where the Wijdefjorden, Isfjorden and Van

Mijenfjorden fjords have lengths of 108, 107 and

83 km, respectively Some coastal areas are

charac-terized by strandflat topography: low-lying bedrock

plains often blanketed by raised beaches

About 60% of Svalbard is covered by glaciers

(Hagen et al 1993, 2003), with many outlet glaciers

terminating in the sea Svalbard ice caps and

gla-ciers cover about 36 600 km2, with an estimated

total volume of c 7000 km3 (Hagen et al 1993)

Most of the ice volume is contained in the

high-land ice fields and ice caps on Spitsbergen and

Nordaustlandet, but large valley glaciers andcirque glaciers are frequent along both the westand east coasts of Spitsbergen Small ice caps alsoexist on the eastern islands, Edgeøya and Barentsøya(Fig 1) On Spitsbergen, glaciation is most extensive

in areas near the eastern and western coasts, wheremany glaciers terminate in the sea In contrast, gla-ciers in the central part of the island are smaller,mainly because of low precipitation (Humlum2002) A significant number of glaciers in Svalbardare of the surging type The surges are relativelyshort intervals (,1 to 10 a) of extraordinary fastflow which transfer mass rapidly down-glacier,punctuating much longer quiescent periods (,10

to 200 a) characterized by stagnation when icebuilds up in an upper accumulation area forming areservoir of mass for the next surge (Dowdeswell

et al 1991, 1999; Lønne 2004; Sund 2006) connier & Hagen (1991) suggested that the majority

Lefau-of Svalbard glaciers surged The mass balance Lefau-ofmany glaciers in Svalbard is partly controlled bysnowdrift during the winter (Humlum et al 2005).The equilibrium-line altitude (ELA) rises on a trans-ect from west to east across Spitsbergen (Fig 1),reflecting the distribution of precipitation very well

On Prins Karls Forland and along the central westcoast it lies at 300 m a.s.l., but reaches 700 m inthe highlands of north-eastern Spitsbergen.There are two end-member modes of glacieri-zation on Svalbard: a full-glacial mode, whenSvalbard and the Barents Sea were covered by alarge marine-based ice sheet, and an interglacialmode (like today) when the Svalbard glacialsystem is dominated by highland ice fields, icecaps and numerous valley and cirque glaciers TheFrom: Martini, I P., French, H M & Pe´rez Alberti, A (eds) Ice-Marginal and Periglacial Processes and Sediments Geological Society, London, Special Publications, 354, 15 – 31.

DOI: 10.1144/SP354.2 0305-8719/11/$15.00 # The Geological Society of London 2011.

full-glacial mode leaves pronounced fingerprints on

the continental shelf margins and slopes, and during

deglaciation sediments and landforms are

deposi-ted on the continental shelf and in fjords around

Svalbard Most sedimentation occurs subglacially

in fjords and on the shelf, and ice-marginally on

the continental break and slope There is prevailing

erosion inside the present coast, but a strong

sig-nal of glacial isostasy in response to deglaciation

where sets of raised beaches mark deglaciation

and marine transgression The interglacial mode is

characterized by fjord and valley sedimentation

below and in front of polythermal and surging

glaciers The interglacial mode of glacierization

produces landform-sediment assemblages that can

be related to the tidewater glacier landsystem

(Ottesen & Dowdeswell 2006), the glaciated valley

landsystem (Eyles 1983) and the surging glacier

landsystem (Evans & Rea 1999) The glacial

finger-printing on Svalbard is primarily reflecting the

transition from a full-glacial mode to an

Hemi-as early Hemi-as the middle Eocene 47.5 million yearsago (Ma) (Stickley et al 2009) It is recognizedthat sea-ice cover existed in the central Arctic basin

by the middle Miocene (Darby 2008; Krylov et al.2008), but ice-sheet build-up over the Svalbard –Barents Sea region probably did not initiateuntil the Pliocene – Pleistocene, 3.6 – 2.4 Ma (Knies

et al 2009) Sejrup et al (2005) suggested thatextensive shelf glaciations started around Svalbard

at 1.6 – 1.3 Ma The number of full-scale ice-sheetglaciations over Svalbard – Barents Sea is notknown, but Solheim et al (1996) suggest at least

16 major glacial expansion events occurred overthe past 1 Ma Laberg et al (2010) reconstructed the

Fig 1 The Svalbard archipelago with distribution pattern of the equilibrium-line altitude (ELA) given as 100 m contour intervals (modified from Hagen et al 2003) The islands of Hopen (SE from the Svalbard archipelago) and Bjørnøya (midway between Norwegian mainland and Spitsbergen) are not on the map.

O ´ INGO´LFSSON 16

late Pliocene – Pleistocene history of the Barents Sea

ice sheet, based on three-dimensional seismic data

from the south-western Barents Sea continental

margin They inferred that a temperate Barents

Sea ice sheet with channelized meltwater flow

developed during the late Pliocene – Early

Pleisto-cene More polar ice conditions and a Barents

Sea ice sheet that included large ice streams, with

little or no channelized meltwater flow, occurred

in the Middle and Late Pleistocene There are both

marine and terrestrial geological archives that

high-light full-glacial-mode conditions and subsequent

deglaciation

Marine archives

The dimensions and dynamics of the Last Glacial

Maximum (LGM) Svalbard – Barents Sea ice sheet

are reflected in the submarine sediments and

land-forms preserved on the seafloor of the deglaciated

shelves and fjords (Ottesen et al 2005) Marine

archives that contain information on former

ice-extent and ice dynamics include the following

Shelf bathymetry Landforms include glacial

troughs, submarine transverse ridges, mega-scale

glacial lineations, elongated drumlins and

rhombohe-dral ridge systems These delineate the drainage of

glaciers and show that the shelf areas have

been shaped by erosion and deposition below and in

front of moving outlet glaciers and ice streams

High-resolution seismic records These show

glacial unconformities and give information on

thickness, extensions and architecture of sediments

above basement rocks These records signify the

extent of glacial erosion and subsequent deposition

on the shelf

Sediment cores These include sedimentological and

petrographic analyses for identifying tills and

gla-ciomarine sediments Sediment cores are used to

verify seismic records The tills are first-order

evidence on former ice extent, and14C dates from

glaciomarine sediments provide constraining

mini-mum dates for deglaciation of the shelf areas

The seafloor morphology of the Svalbard margin

west and north of the archipelago is characterized

by a series of deep fjord-trough systems separated

from one another by intervening shallow banks

This is caused by the actions of ice sheets and ice

streams during the Pleistocene, where the extent of

the Svalbard – Barents ice sheet during peak

gla-ciations was repeatedly limited by the shelf edge

(Solheim et al 1996; Vorren et al 1998) Sejrup

et al (2005) concluded that the morphology

strongly reflected that fast-moving ice streams

had repeatedly entered the continental shelf areas,

creating numerous glacial troughs/channels that

are separated by shallow bank areas Less dynamicice probably existed on shallower banks (Landvik

et al 2005; Sejrup et al 2005; Ottesen et al 2007).Studies of large-scale margin morphology andseismic profiles have identified large submarinetrough-mouth fans (TMF) at the mouths of severalmajor cross-shelf troughs (Fig 2) (Vorren et al.1989; Sejrup et al 2005) These are stacked units

of glaciogenic debris flows interbedded with pelagic sediments displaying thickness maximaalong the shelf edge, and reflect direct sedimentdelivery from an ice stream reaching the shelfedge (Vorren et al 1989; Vorren & Laberg 1997).Andersen et al (1996) defined five lithofaciesgroups from cores retrieved from the westernSvalbard continental slope Laminated-to-layeredmud and turbidites reflect post-depositional rework-ing of the shelf banks, caused by eustatic sea-levelfall during ice growth Hemipelagic mud representsthe background sediments and is evenly dispersedover the entire continental margin Homogeneousand heterogeneous diamictons were depositedduring glacial melt events (hemipelagic mud withice-rafted debris) and during peak glaciation on thesubmarine fans (debris-flow deposits) Large-scaleslope failures have affected the glaciogenic depositsalong the western Barents Sea margin (Kuvaas &Kristoffersen 1996; Laberg & Vorren 1996) Thelargest TMFs occur in front of the Storfjordenand Bear Island trough mouths (Fig 2), probablyreflecting where the largest Svalbard – BarentsSea palaeo-ice streams entered the western shelfbreak (Faleide et al 1996; Vorren & Laberg 1997;Andreassen et al 2008) The oldest Storfjordenand Bear Island TMF sediments have been esti-mated to be c 1.6 Ma (Forsberg et al 1999; Butt

hemi-et al 2000)

Whereas TMFs can be regarded as archives

of numerous glaciations, most sediments and forms on the shelf and in the fjords relate to theLGM and subsequent deglaciation End-moraineshave been identified at several locations on the shelf(Ottesen et al 2005, 2007; Ottesen & Dowdeswell2009), suggesting outlet glaciers and ice streamsdraining the Svalbard fjords and a shelf-edge glacia-tion along the major part of the margin during theLGM Ottesen et al (2005, 2007) and Ottesen &Dowdeswell (2009) recognized an assemblage ofsediments and landforms that can be used to inferthe flow and dynamics of the last ice sheet onSvalbard (Fig 3) They distinguished betweeninter-ice-stream and ice-stream glacial landformassemblages, which reflect different glacialdynamics associated with ice streams in fjords andtroughs and slower moving ice between thetroughs and ice streams They identified fivesubsets of landforms that make up the inter-ice-stream glacial landform assemblage, and labelled

land-them 1 to 5 by their relative age of deposition

(Fig 3a)

Landforms relating to ice advance to the shelf edge

These are glacial lineations orientated in the

direc-tion of ice flow across the shelf, and a well-defined

linear belt of hummocky terrain inferred to represent

the shelf-edge ice grounding zone (1 on Fig 3a)

The glacial lineations are sets of parallel subdued

ridges that have amplitudes of less than 1 m and a

wavelength of several hundred metres The

hum-mocky belt is a well-defined, continual and linear

belt of irregular hummocky terrain about one

kilo-metre in width, where hummocks and ridges have

amplitudes of c 5 m The belt terminates abruptly

at the shelf edge (Fig 3a), and Ottesen &

Dowdes-well (2009) suggest that this terrain represents the

grounding zone of an ice margin

Landforms of ice retreat across the shelf during

deglaciation These are large and small transverse

moraine ridges; small ridges are interpreted to be

retreat moraines whereas the larger ridges probably

mark stillstands during retreat of a grounded ice

margin (2 on Fig 3a) The lateral continuity of the

ridges over a number of kilometres also implies

systematic retreat along a wide ice front

Landforms of ice retreat from fjord mouths to fjord

heads These are arcuate moraines (suggesting

poss-ible glacial re-advance to fjord mouths and/or

still-stands during deglaciation), crag-and-tail features

and small transverse ridges (suggesting active ice

in fjords prior to deglaciation) The crag-and-taillandforms (3 on Fig 3a) are streamlined featureswith an upstream core of bedrock and glacialsediments deposited in lee of the bedrock knob, pro-duced at the bed of moving ice

The sediment-landform sets (4) and (5) (Fig 3a)defined by Ottesen & Dowdeswell (2009) wereproduced during the Holocene and belong tointerglacial-mode tidewater glacier sediment-landform assemblages These include basin fillswithin fjords (4), representing fine-grained sedimentdeposition linked to the discharge of turbid melt-water from tidewater glacier margins and submarineslides from steep fjord walls, demonstrating slopeinstability Landforms of recent ice re-advance andretreat at fjord heads (5) include large terminalmoraines within a few kilometres of present tide-water glacier margins, recording re-advance associ-ated with the Little Ice Age and subsequent retreatmarked by deposition of small, sometimes annualtransverse ridges

The ice-stream glacial landform assemblage(Fig 3b) of Ottesen & Dowdeswell (2009) recog-nizes sediment-landform subsets that characterizethe action of active ice streams in cross-shelftroughs

Mega-scale glacial lineations and lateral stream moraines The mega-scale glacial lineationsare streamlined linear and curvilinear submarinefeatures elongated in the direction of the long axis

ice-of the depressions, observed in several majorfjords and cross-shelf troughs on the Svalbard

Fig 2 Location of large submarine trough-mouth fans (TMF), reflecting where the largest Svalbard – Barents Sea palaeo-ice streams entered the western shelf break (modified from Vorren et al 1989).

O ´ INGO´LFSSON 18

Fig 3 Schematic models of submarine glacial landforms on Svalbard continental margins (a) An inter-ice-stream glacial landform assemblage, located between fast-flowing ice streams (b) An ice-stream glacial landform assemblage, where fast-flowing ice was fed from large interior drainage basins The landforms are labelled by their relative age

of deposition, where 1 denotes the oldest landform (modified from Ottesen & Dowdeswell 2009).

margin (Ottesen et al 2007; Ottesen & Dowdeswell

2009) They vary from hundreds of metres to more

than 10 km in length and up to 15 m in height

The mega-scale lineations probably result from

soft-sediment deformation at the base of fast-flowing

ice streams (Dowdeswell et al 2004) Lateral

ice-stream moraines (1 on Fig 3b) are individual

linear ridges of tens of kilometres in length and up

to c 40 – 60 m high that have been observed along

some of the lateral margins of cross-shelf troughs

in Svalbard Ottesen et al (2005, 2007) described

linear ridges of tens of kilometres in length and up

to 50 m in relative elevation running along the

lateral margins of the Isfjorden and Kongsfjorden

cross-shelf troughs as they approach the shelf

break west of Svalbard Sub-bottom profilers do

not generally achieve acoustic penetration of these

ridges, implying that they are made up of relatively

coarse diamictic sediments These extensive lateral

ridges are interpreted to define the lateral margins

of fast-flowing former ice streams (Ottesen et al

2005, 2007)

Grounding zone wedges and transverse ridges

Grounding zone wedges are large seafloor ridges

orientated transverse to the direction of former ice

flow and occur both at the shelf edge and in the

troughs and fjords of Svalbard The ridges are

characteristically tens of metres high, up to several

kilometres wide and tens of kilometres long

Acous-tic stratigraphic records show that the ridges form

sedimentary wedges lying above strong basal

reflec-tors Ottesen et al (2007) concluded that although

the sedimentary wedges sometimes only have

rela-tively subtle vertical expression on the sea floor,

they may contain a few cubic kilometres of

sedi-ments Where these extensive ridges and underlying

sedimentary wedges are found in the troughs and

fjords of Svalbard (2 on Fig 3b) they are interpreted

as marking major stillstands of the ice margin during

general deglaciation (Landvik et al 2005; Ottesen

et al 2007), lasting for hundreds rather than tens

of years (Dowdeswell et al 2008) The diamicticgrounding-zone wedges were produced by continu-ing sediment delivery from the deforming beds ofactive ice during the stillstands (Dowdeswell et al.2008) The transverse ridges that are observed onthe continental shelf to the side of the troughs(Fig 3b) have been interpreted to be recessionalpush moraines reflecting stillstands or winter-summer ice-front oscillations during deglaciation(Ottesen & Dowdeswell 2006) Individual ridgesare up to 15 m high, are spaced a few hundred metresapart and usually occur in clusters rather than asisolated individual features

Dowdeswell et al (2008) argued that the scale glacial lineations were products of rapid iceretreat, whereas the grounding-zone wedges sug-gested episodic retreat They interpreted suites oftransverse ridges to be indicative of relatively slowretreat of grounded ice margins

mega-Seismic record and sediment core data These data(Fig 4) concur with the bathymetric data on theglacial origin of landforms and sediments describedabove Unconformities caused by glacial erosionprovide strong reflectors (Solheim et al 1996).When the marine sequence is penetrated by corers,stiff diamictons, interpreted to be subglacial tillsdeposited below grounded glaciers in the fjordsand out on the shelf, are retrieved (Svendsen et al

1992, 1996; Landvik et al 2005) The diamictonsare overlain everywhere by fine-grained marine orglaciomarine muds (Elverhøi et al 1980, 1983;Sexton et al 1992) Radiocarbon ages on subfossilshells from the muds give constraining ages forthe muds as being of deglaciation ages and the dia-mictons having been deposited in connection withthe LGM expansion of ice

Terrestrial recordsWhile the marine archives contain evidence ofrepeated expansions of the Svalbard – Barents Seaice sheet to the continental margin around Svalbard,

Fig 4 Sketch of seismic section along Isfjorden, Svalbard A moraine ridge at the shelf edge marks LGM extension

of an ice stream in the Isfjorden trough, and stiff diamicton is interpreted to be till deposited by the last major glaciations (modified from Svendsen et al 1996).

O ´ INGO´LFSSON 20

the terrestrial record of full-scale glaciations is more

fragmentary because of the prevailing erosion at

times of major ice-sheet expansion Volume

esti-mates of sediments offshore have been argued to

indicate that 2 – 3 km of rock has been removed

from central Spitsbergen since the Eocene (Eiken

& Austegard 1987; Vorren et al 1991) It has

been suggested that at least half of this volume

was removed during the Pleistocene glaciations

(Svendsen et al 1989; Dimakis et al 1998; Elverhøi

et al 1998), and it has been assumed that the

bedrock geomorphology of Svalbard is

predomi-nantly the result of Quaternary sculpturing (Hjelle

1993) The landscapes of Svalbard are

charac-terized by extensive glacial carving of cols,

valleys and fjords where the glaciers have enhanced

pre-glacial fluvial and tectonic landscapes

Svend-sen et al (1989) pointed out that erosion of the

major fjords below sea level requires large ice

sheets with outlet glaciers at the pressure melting

point at their base They also concluded that the

pro-nounced alpine landscape of Svalbard indicated that

cirque and valley glaciers, rather than ice sheets,

were mainly responsible for carving the valleys

and other high-relief landforms and that glacial

erosion by polythermal valley glaciers is the

most important geomorphic process in the present

climate

Evidence of more extensive ice cover than today

during the LGM and previous glaciations is present

on every ice-free lowland area around Svalbard

outside the Neoglacial limits in the form of glacial

drift, erratics and striations (Sollid & Sørbel 1988;

Salvigsen et al 1995) Directional evidence

gener-ally suggests ice flow offshore towards the shelf

areas on western Svalbard (Kristiansen & Sollid

1987; Landvik et al 1998) Evidence on ice

thick-ness and ice movements during the LGM include

ice-abraded ridge crests roche moutonne´es,

stria-tions, erratics and glacial drift on nunataks and

coastal mountains A number of studies have

addressed the thickness of the Svalbard – Barents

Sea ice sheet over Svalbard during the LGM A

long-standing debate exists on whether

morpholo-gical data (such as the existence of pre-LGM sets

of raised beaches and large rock glaciers) could be

taken to suggest the existence of ice-free enclaves

on the lowlands of western and northern Svalbard

(Landvik et al 1998, 2005; Andersson et al 1999;

Houmark-Nielsen & Funder 1999) There is a

grow-ing consensus that although some coastal

moun-tains may have protruded as nunataks above the

ice-sheet surface at LGM on the outer coast of

northern and western Svalbard, there are very little

data to support the existence of any lowland

ice-free enclaves (Landvik et al 2003, 2005; Ottesen

et al 2007) Taken together, marine and terrestrial

evidence suggest a LGM configuration of the

Svalbard – Barents Sea ice sheet that covered most

of Svalbard and its shelf areas (Fig 5)

As there is overall erosion on land on Svalbardduring repeated glaciations, the pre-late Quaternary(Saalian) glacial history of Svalbard lacks all details(Svendsen et al 2004) There are a number of key-lithostratigraphical sections that contain tills andmarine sediments that have been dated or correlated

to late Quaternary Svalbard – Barents Sea icesheet oscillations (Mangerud et al 1998) (Fig 6):Kongsøya (Ingo´lfsson et al 1995), Kapp Ekholm

Fig 5 Reconstruction of the Svalbard – Barents Sea ice sheet and its fast-flowing ice streams (modified from Ottesen et al 2005).

Fig 6 Location of key stratigraphic sites on Svalbard.

(Mangerud & Svendsen 1992), Skilvika (Landvik

et al 1992), Linne´elva (Lønne & Mangerud1991), Site 15 (Miller et al 1989), Kongsfjordhallet(Houmark-Nielsen & Funder 1999) and Poole-pynten (Andersson et al 1999) Most stratigraphickey sites are on the west coast of Svalbard, but therecently described site from Murchisonfjorden,Nordaustlandet (Fig 6) (Kaakinen et al 2009)adds to our understanding of late Quaternary glacialevents on Svalbard One striking characteristic ofthe lithostratigraphical records from coastal Sval-bard is that sections often reflect glaciation events

in the form of repeated regressional sequences(Figs 7 & 8) Each cycle consists of a basal till(Fig 8a) deposited during a regional glaciationlarge enough for isostatic depression to cause trans-gression and deposition of glaciomarine – marinesediments on top of till as the ice sheet retreats(Fig 8b, c) Glacial unloading and isostatic reboundcauses a coarsening-upwards sequence where sub-littoral sediments and beach foresets reflectregression (Fig 8d, e) This is particularly wellexpressed in the stratigraphic record from KappEkholm (Fig 7)

Raised beaches around Svalbard can generally

be regarded as isostatic fingerprinting of earlierexpanded ice volumes compared to present Post-glacial raised beaches have been described frommost ice-free coastal areas (Forman 1990; Landvik

et al 1998), and the elevation of the postglacialmarine limit and history of relative sea-level changesare well known (Fig 9) (Forman 1990; Forman et al.2004) The isostatic fingerprinting (Fig 10) reflectsthe heaviest glacial loading in the central BarentsSea and clearly expresses the differential ice load

of the Svalbard – Barents Sea ice sheet at LGM

Interglacial-mode sediments and landforms

Svalbard did not completely deglaciate duringthe Holocene (Hald et al 2004) Salvigsen et al.(1992) and Salvigsen (2002) documented warmerconditions in Svalbard during the early and midHolocene compared to the present-day climate.Glacier volumes were probably considerably smallerthan present (Svendsen & Mangerud 1997; Forwick

& Vorren 2007) and some valley/cirque glaciersmay have melted away completely Because of theNeoglacial expansion of glaciers that started sometime after mid-Holocene (Svendsen & Mangerud1997) and culminated by the end of the Little IceAge around 1890 – 1900 AD (Werner 1993; Man-gerud & Landvik 2007), the timing, extent andvolume of ice at the early Holocene glacialminima is not well known (Humlum et al 2005).Interglacial-mode glacial landforms and sediments

Fig 7 Composite stratigraphy of the Kapp Ekholm

section Each coarsening-upwards sequence reflects

glaciation (till) and deglaciation (marine-to-littoral

sediments) (modified from Mangerud & Svendsen

1992).

O ´ INGO´LFSSON 22

on Svalbard primarily relate to the Neoglacial

expansion of glaciers Most glaciers in Svalbard

are presently retreating from their 1890 – 1900 AD

maxima, and many glaciers have retreated 1 – 2 km

or more It has been calculated that the net massbalance of Svalbard glaciers has been negative

Fig 8 Examples of Svalbard glacial-deglacial sediments in coastal sections: (a) subglacial till, unit A, Kapp Ekholm (Figs 6 & 7) (pocket knife for scale); (b) dropstones in shallow-marine sediments (pocket knife for scale), site 15 (Fig 6); (c) stratified shallow-marine sediments with subfossil kelp (35 cm scrape for scale), Poolepynten (Fig 6); (d) a whale rib at the contact between sublittoral marine sediments and gravelly beach foresets (1 m stick for scale), site 15 (Fig 6); (e) sublittoral marine sediments with in situ subfossil molluscs, Skilvika (Fig 6) All photographs by

O ´ Ingo´lfsson in 2008.

Fig 9 Relative sea-level curves from Svalbard (modified from Forman et al 2004).

Fig 10 The pattern of postglacial raised beaches combined with well-dated relative sea-level curves fingerprints the isostatic depression caused by the Svalbard– Barents Sea ice sheet (modified from Bondevik 1996).

O ´ INGO´LFSSON 24

most years for the past 100 years, and that the

glacial systems of Svalbard may have lost up to

30% of their volume since 1900 AD (Lefauconnier

& Hagen 1990; Glasser & Hambrey 2003)

Tidewater glacier/fjord environments

There are a number of conceptual models proposed

for tidewater glaciers (Fig 11a) (Elverhøi et al

1980; Bennett et al 1999), identifying and

link-ing sedimentary processes, deposits and landforms

Plassen et al (2004) proposed a model for

sedi-mentation of Svalbard tidewater glaciers (Fig 12a)

based on high-resolution acoustic data and sediment

cores and sedimentation patterns in four tidewater

glacier-influenced inlets of Isfjorden, Svalbard

Their model shows glaciogenic deposition in

proxi-mal and distal basins The proxiproxi-mal basins comprise

morainal ridges and hummocky moraines, bounded

by terminal moraines marking the maximum glacial ice extent The distal basins are characterized

Neo-by debris lobes and draping stratified glaciomarinesediments beyond and, to some extent, beneathand above the lobes Distal glaciomarine sedimentscomprise stratified clayey silt with ice-rafted debriscontent (Forwick & Vorren 2009)

Ottesen & Dowdeswell (2006), Ottesen et al.(2008) and Kristensen et al (2009) identified

an assemblage of submarine landforms from themargins of several Svalbard glaciers that theylinked to glacier surging into the fjord environments(Fig 12b) The submarine landforms include:streamlined landforms found within the limits ofknown surges, interpreted as mega-scale glaciallineations formed subglacially beneath activelysurging ice (1 on Fig 12b); large transverse

Fig 11 Svalbard glaciers: (a) Kongsvegen tidewater glacier, Kongsfjorden; (b) Comfortlessbreen glacier in surge; and (c) Pedersenbreen polythermal glacier, Kongsfjorden All photographs by O ´ Ingo´lfsson in 2008.

ridges, interpreted to be terminal moraines formed

by thrusting at the maximum position of glacier

surges (2a on Fig 12b); sediment lobes at the

distal margins of terminal moraines, interpreted as

glaciogenic debris flows formed either by failure

of the frontal slopes of thrust moraines or from

deforming sediment extruded from beneath the

glacier (2b on Fig 12b); sinuous ridges, interpreted

as eskers, formed after surge termination by the

sedimentary infilling of subglacial conduits (4 on

Fig 12b); concordant ridges parallel to former ice

margins, interpreted as minor push moraines

pro-bably formed annually during winter glacier

re-advance (5 on Fig 12b); and discordant ridges

oblique to former ice margins and interpreted as

crevasse-squeeze ridges, forming when soft

sub-glacial sediments were injected into basal crevasses

(3 on Fig 12b)

Ottesen et al (2008) proposed that these

sub-marine landforms were deposited in the following

sequence based on cross-cutting relationships

between them, linked to stages of the surge cycle

(Fig 12b): (1) mega-scale glacial lineations; (2a)

terminal moraines; (2b) lobe-shaped debris flows;(3) isolated areas of crevasse-fill ridges; (4) eskersand (5) annual retreat ridges

Terrestrial polythermal and surging glaciersThere are numerous studies of the depositionalenvironments of Svalbard terrestrial polythermaland surging glaciers (Fig 11b, c) which outlinestructural properties, landform-sediment associ-ations and dead-ice disintegration (Boulton 1972;Bennett et al 1996, 1999; Boulton et al 1999;Hambrey et al 1999; Lysa˚ & Lønne 2001; Sletten

et al 2001) Glasser & Hambrey (2003) gave anoverview of sediments and landforms associa-ted with glaciated valley landsystems on Svalbard(Fig 13) Characteristics of this landsystem arerockfall debris supply, passive transport and rework-ing of a thick cover of supraglacial morainic till,combined with actively transported debris derivedfrom the glacier bed They identified morainecomplexes produced by thrusting as the most com-mon The sedimentary composition of moraine

Fig 12 Svalbard tidewater glaciers: (a) a model for proglacial sedimentation by Svalbard polythermal tidewater glaciers (modified from Plassen et al 2004); and (b) landform assemblage model for Svalbard surge-type tidewater glaciers (modified from Ottesen et al 2008).

O ´ INGO´LFSSON 26

complexes varies with source materials and ranges

from reworked marine sediments to terrestrial

dia-mictons and gravels Original sedimentary

struc-tures or subfossil marine mollusks are commonly

preserved as a slab of sediments which has been

stacked by the glacier The thrusted moraine

complexes often show evidence of glaciotectonic

deformations, including low-angle thrust faults

and recumbent folds Moraine complexes resulting

from deformation of permafrost also occur on

Svalbard There, stresses beneath the advancing

glaciers are transmitted to the proglacial sediments

and can cause proglacial deformation of the

perma-frost layer This may lead to folding, thrust-faulting

and overriding of proglacial sediments

Glasser & Hambrey (2003) suggested that a

typical receding Svalbard glacier has three zones

within its forefield (Fig 13) as follows

(1) Outer moraine ridge These are arcuate ridges

rising steeply from the surrounding

topo-graphy to heights of 15 – 20 m They are

com-monly ice-cored and may be either the result

of englacial or proglacial thrusts or be a

product of permafrost deformation Some

gla-ciers have large ice-cored lateral moraines

(2) Moraine-mound complex (Fig 13), often

draped by supraglacial debris stripes These

are often present in the form of arcuate belts

of aligned hummocks or mounds comprising

a wide variety of morphological types (oftenice cored), linear ridges up to 100 m long orshort-crested ridges of several metres andnear conical mounds Rectilinear slopes andstacking indicate that the moraine-moundcomplex is a result of thrusting in proglacial,ice-marginal and englacial position

(3) Inner zone, between the moraine-mound plex and the contemporary glacier snout com-prising various quantities of foliation-parallelridges, supraglacial debris stripes, geometricalridge networks, streamlined ridges/flutes andminor moraine mounds Sediment facies arepredominantly glacial diamicton, commonlybeing reworked by proglacial streams.The most widespread deposit on the forefields ofreceding valley glaciers on Svalbard is diamicton(Glasser & Hambrey 2003) produced by basallodgement processes or meltout The diamictonsare in turn reworked by fluvial processes and slump-ing where there is active down-wasting of dead ice(Schomacker & Kjær 2007)

com-Christofferson et al (2005) described sediment assemblages relating to surging Svalbardglaciers They identified ice-flow parallel ridges(flutings), ice-flow oblique ridges (crevasse-fill fea-tures), meandering ridges (infill of basal meltwater),thrust-block moraines, hummocky terrain anddrumlinoid hills Kristensen et al (2009) suggestedFig 13 A landsystem model for terrestrial Svalbard polythermal glacier (modified from Glasser & Hambrey 2003).

landform-that surging glacier ice-marginal landforms on

land closely resemble the corresponding landforms

on the seabed, including debris-flow mud aprons

in front of surge moraines They argued that both

the submarine and the terrestrial mud apron were

formed by a combination of ice push and slope

failure

Conclusion

Conceptual models have been developed that explain

sediment-landform assemblages for Svalbard

shelf-, ice-stream-, fjord-, surging- and

terrestrial-polythermal glacial systems Landsystem models

are useful tools for the reconstruction of past

environments and palaeoglacier dynamics from

geomorphological, sedimentological and

strati-graphical records (Evans 2003) Our understanding

of the dynamics, processes and products of

marine-based ice sheets is hampered by lack of data

(Vaughan & Arthern 2007) The Svalbard models

therefore have the potential to help clarify the

genesis of glacial landforms and sediments in

formerly glaciated areas and to help explain the

geological record of ancient marine-terminating

ice sheets such as the Upper Ordovician Saharan

ice sheet (Le Heron & Craig 2008; Le Heron et al

2010) or the Carboniferous – Permian Gondwana

ice sheet (Visser 1989; Isbell et al 2008) The

stratigraphic record of Svalbard – Barents Sea

glaciations, with recurring shallowing-upwards

marine to littoral sequences separated by tills

(Man-gerud et al 1998), could help in the recognition of

transitions from full-glacial to interglacial situations

recorded in ancient glaciogenic sequences

Epicontinental glaciogenic deposits are

gener-ally poorly preserved in the geological records

(Eyles 1993) and, seen over an interglacial –

glacial cycle, most interglacial deposits and

land-forms will be destroyed by an advancing/growing

ice sheet as the glacial system shifts to full-glacial

mode It has been pointed out that because of

the predominantly ice-cored nature of Neoglacial

moraines on Svalbard and the very active dead-ice

melting, together with the active reworking

pro-cesses and cryoturbation, the preservation potential

of terrestrial glacial landforms on Svalbard is

prob-ably poor (Evans 2009) The use of these moraines

as modern analogues for ancient glaciated

land-scapes therefore may not be appropriate (Lukas

2005) However, geomorphological and

sedimento-logical research on landforms and sediments

result-ing from the last deglaciation and Holocene

oscillations of Svalbard glaciers can provide

impor-tant analogues for palaeoglaciological

reconstruc-tions (Boulton 1972; Boulton et al 1999) This is

particularly important for our understanding of thesignatures of surging glaciers, where the recognition

of palaeosurges within landform and sedimentaryrecords is still somewhat capricious

Valuable and constructive suggestions from the journal reviewers are acknowledged The paper was written during a sabbatical visit to Lund University, Sweden.

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