GEOL 4010 QUATERNARY GEOLOGY Instructor: Dr' Hester Jiskoot

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GEOL 4010QUATERNARY GEOLOGYInstructor Dr.
Hester Jiskoot
LECTURE 13
Glacial Landsystems
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WHAT IS THE GLACIAL LANDSYSTEMS APPROACH?
Eyles (1983), Benn Evans (1998)
Holistic assessment of glacial sediment/landform
associations across scales
Process-form relationships physiographic/tectoni
c settings glacier ice
characteristics sediment properties
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LANDSYSTEMS APPROACH GUIDELINES FOR STUDYING
GLACIATED BASINS

• SEDIMENTS
• Significance of a sediment F(depositional
  position surroundings)
• Sediment assemblages reflect the processes
• Sediment assemblages should be complementary at
  all scales

• LEVELS OF SPATIAL HIERARCHY
• Sediment organisation in landscape reflects
• - depositional processes -
  environmental controls
• Controls on sedimentary system become larger in
  scale and longer-lasting in effect the larger the
  spatial context.
• Preservation/erosion of preglacial landforms
  also informative

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IMPLICATION FOR REGIONAL-SCALE INVESTIGATIONS

• Glacial sediments and landforms
• reveal patterns and processes of glaciation over
  complete glacial cycles
• provide a valuable complement to short-term
  studies of modern glacial environments
• Linking sediment-landform associations to genetic
  processes
• provides a framework for using geological
  evidence to reconstruct long-term patterns of
  environmental change.

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LINKING PAST AND PRESENT
Reconstruction of glaciated environments
F(observations and assumptions) ?Largest scale
largest errors
The present is the key to the past 1) Choose
correct contemporary analogues 2) More
knowledge about modern systems less errors
in past systems
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ICE MARGINAL LANDSYSTEMS
Distinctive ice marginal processes and products
in different climate settings
Melt ----- glacifluvial and gravitational
processes reworking No Melt-- glacitectonics Ic
e marginal systems morphologically most
impressive belt but subglacial tills reflect
more complete picture of ice sheet extent
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TEMPERATE GLACIER MARGINS
WET BASED ICE, DISCONTINUOUS PERMAFROST
Debris rich basal ice thin or absent Little
upward transport Thrust moraines not common
(décollement at shallow depth frozen layer)
Restricted supra- and fluviglacial sediment
supply ? small moraines Well developed drainage
systems ? high sediment input, large
reworking Morpho-sequences of spatially
associated glacifluvial landforms
Rapid climate response ? fluctuating margins
? suites of recessional moraines
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COMMON GLACIFLUVIAL LANDFORMS
Characteristics of glacifluvial material Rounded
clasts Sorted grains (unimodal
coarse) Sedimentary structures/bedding Often
cross-bedded Imbrication common kames kettles esk
ers marginal channel sandurs
Characteristics of ice contact material Transition
from proximal to distal Range and abrupt changes
in grain size Clasts more subangular than
rounded Association with till bodies Slumping
common alluvial fans (ice-contact)
Example Cheshire-Shropshire lowland Confluence
Devensian Irish Sea Ice and Welsh Ice fig
12.6b (Benn and Evans, 1998)
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SUBPOLAR GLACIER MARGINS
OUTER COLD ZONE, INNER WET-BASED ZONE CONTINUOUS
PERMAFROST
Thermal regime and geomorphic impact F(ice
thickness and activity)

• Erosion from wet zone ? material transported to
  cold zone ? freeze-on and/or thrust-up produces
  thick sequences of debris-rich basal ice
• Colder ice ? less material
• Overriding of dead ice

Compressive stresses at margin sediment
composite ridges/thrusting Well developed lateral
meltwater channels
Example Victoria Island, Arctic
Canada Northern margin of Laurentide
icesheet figs 12.7 and 12.10 (Benn and
Evans,1998)
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LANDFORM ASSOCIATIONS WOLLASTON PENINSULA (fig
12.10)
i. GROUND MORAINE ii. HUMMOCKY MORAINE iii. LATERA
L AND SHEAR MORAINES iv. STREAMLINED LANDFORMS
(DRUMLINS AND FLUTES)
REFLECTING GLACIOLOGICAL AND TOPOGRAPHIC
CONTROLS OF SUBPOLAR ICE
i. Thin active ice extending flow ii. Compression
al flow followed by stagnation iii. Ice marginal
compressional (fast) flow against
enscarpment iv. Subglacial associated with fast
flow of iii.
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POLAR GLACIER MARGINS
COLD INACTIVE DRY ICE CONTINUOUS PERMAFROST
Debris free ice or stacked basal debris sequences
(when wet base) Thrust moraines only where
glaciolacustrine muds are present Generally small
moraine ridges
Deposition by gravitation ? no water ? no
reworking Marginal aprons reflecting englacial
structures Ice cored ridges and tills overlying
dead ice No marginal channels (sublimation
controls ablation process)
Aeolian reworking ? ventifacts and removal of
fines
Example Dry Valleys, Antarctica Pliocene and
Miocene glaciations preserved
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COMMONWEALTH GLACIER, ANTARCTICA
Typical vertical front of a polar glacier
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FACIES MODELLING
Descriptive and predictive models of
relationships between different deposits
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Subaquatic depositional system
Bear Glacier, Alaska. Low profile calving
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ALLUVIAL FAN/LAKE BED, MATANUSKA GLACIER, AK
2 m
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STRATIGRAPHIC ARCHITECTURE OF SUBAQUATIC
DEPOSITIONAL SYSTEMS

• Controls
• topography and tectonic setting
• extent, configuration dynamics of glacier-
  floating ice
• water depth fluctuations (isostacy/eustacy, lake
  drainage)

Subglacial zone Ice-proximal zone Ice shelf
zone Ice-distal zone figs 12.54 and 12.55
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GLACIOMARINE DELTA, HEGRA, CENTRAL NORWAY
Photo J.S. Aber 3/87
Long, inclined foreset beds of sand and gravel
(outer slope of delta). Irregular pods or lenses
of flow till moved down the delta slope as debris
flows.
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DROPSTONE IN GLACIOLACUSTRINE VARVES PRECAMBRIAN
DEPOSIT AT TEMAGAMI, NE ONTARIO
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STRATIGRAPHIC ARCHITECTURE OF MOUNTAIN SYSTEM
Low-relief mountains fig 12.71 High-relief
mountains fig 12.80