Glacial Facies
chapter 10
Glacial Facies
and Fabrics
General Review of Facies

Facies
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A body of sediment with a distinctive
combination of properties that distinguish it
from neighboring sediments.
Stratigraphic units distinguished by lithologic,
structural, and organic characteristics
detectable in the field.
3 Methods of Describing Facies

Lithofacies

Describes physical characteristics of the deposit
Silt laminae
 Cross-bedded sand
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Genetic facies
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State or imply a specific mode of formation
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Fluvial or eolian dune-bedded sands
Biofacies
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Defined by the presence / lack of some kind of
biological material
Glacial Facies and
Walther’s Law
Travis Corthouts
I“It is a basic statement
of far-reaching
significance that only
those facies and faciesareas can be
superimposed primarily
which can be observed
beside each other at the
present time.”
"Facies adjacent to one another in a continuous vertical
sequence also accumulated adjacent to one another laterally"
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As adjacent depositional environments migrate laterally,
sediments from one environment will come to lie on top of
another.
This overlapping will produce a vertical progression of facies
which mirrors the original lateral distribution of depositional
environments.
Puget lobe glacial facies –
lateral movement  vertical sequence
Walther’s Law Exceptions
•
The law is invalid where the contact between
different lithologies is non-conformable (due to
lack of deposition), or during cases of rapid
environmental change when non-adjacent
environments may replace one another.
Facies Characteristics
Ice Contact Facies:
•
•
•
•
•
Unstratified diamictites and
tillites
Poorly sorted sediment
Striated or polished clasts
Preferred orientation of long axis
(crude imbrication)
Diverse clast assemblages
Proglacial to Periglagial
Facies:
• Reworked by melt-water, which may
produce sedimentary structures.
•Better sorting
•Freeze-thaw process in periglacial
zones = better stratification.
•Loess
Glacial E.O.Ds and
Associated Facies
Most diverse grain size sedimentary system
Primary Glacigenic
Glacifluvial Deposits
(Ice-Contact Zone)
•Ripples crosslaminated facies
•Cross-bedded
facies
•Gravel sheets
•Silt and mud drapes
Deposits
•Lodgement till
•Glaciotectonite
•Deformation till
•Melt-out till
•Other tills…
(Proglacial)
Gravity Mass-Movement
Deposits
(Glacilacustrine/–marine)
•Scree/debris-fall
deposits
•Debris-flow deposits
•Turbidites
•Slide and slump
deposits
E.O.D = Environment of Deposition
Suspension Settling and
Ice-Rafting
(Glacilacustrine/ –marine)
•Varves
•Mud and diamicton
dropstones
•Undermelt diamicton
Ice-contact zone = very
poorly sorted sediment =
glaciotectonite... TILLS!
Pro/periglacial zone with a braded meltwater stream. Facies will be more sorted
and stratified, as well as more fine grained.
Possible cross-bedded facies.
Stratigraphic
Column
A
B
C
Glacial sedimentation is dominated by
retreat deposits.


Advancing glaciers are more likely to
destroy older glacial facies sequences than
retreating glaciers.
Therefore, Walther’s Law is most applicable
to facies sequences and associations for
receding glaciers.
Indicator Facies

Diamictites: Commonly deposited at ablation
zones along glacial margins as melt-out tills or any
poorly sorted gravelly deposit.

Loess: Often accumulates in periglacial region as
wind-blown deposits.

Varves: Usually originate from annual deposits in
proglacial and periglacial lakes but may also
originate from other cyclic deposits caused by
seasonal waxing/waning of glaciers.

Dropstones: Good indicator of glacial lacustrine/marine environments where ice rafted debris was
deposited as dropstones.
How we know it’s a
dropstone:
Deformation/penetration
of laminated sediment at
bottom contact.
“On-lap” of sediment
at top contact
Facies model (Anderson, 1989)
Ice-marginal environments
Air / ice
Till **
Ablation till
Ice / rock
Till
Lodgment till
Ice  river
Ice  lake
G-lac. drift
Dropstones
Ice / rock  lake
G-lac. drift
Kame deltas
Air / ice / rock
Air / ice / rock / river
Till
Moraines
Alluvium **
Kame terraces
Ice / stream / rock
Alluvium
Alluvium
Outwash/drift Eskers
Air / rock
Alluvium
Outwash
THE
END
from here on – not presented in
class
slides from MSU class
Sequences: Events and Materials

Active ice
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Lodgment
Flowtill
Outwash
Stagnant ice
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Melt-out
Till Fabrics
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Orientation of clasts in space
Reflects accumulated deformation
Till Fabrics
Modified
Foliation

Finally,
foliation
fabric
forms
fully!
Glacial Sequences (Boulton)

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Spatial and
temporal
distribution of
erosion AND
deposition
Marginal till
sequences
Glacial Sequences (Boulton)



Spatial and
temporal
distribution of
erosion AND
deposition
Marginal till
sequences
Ice sheet
synthesis
Glacial Sequences (Boulton)


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Spatial and
temporal
distribution of
erosion AND
deposition
Marginal till
sequences
Ice sheet
synthesis
Till Sequence example: Illinois
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Loess / Malden till / red Tiskilwa till /
gray Tiskilwa till / bedrock
Unclear boundaries and genesis
Interpretation of genetic facies
Till Sequence example: Illinois
Montana plains

Fullerton et al., 2004, USGS SI-2843
Till sequence
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“Illinoisan”
Wisconsinan
Late
Wisconsinan
But…

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How know
age?
Alternative
working
hypotheses?
Till facies
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Glacier tills
Ice sheet
tills
Modified
tills
Till facies
Drift of Coastal New England
“Ground Moraine”
Interlobate
Moraine
Outwash
Terrestrial End Moraines
Marine(?) End Moraines
Outwash
End Moraine Facies
A (mass flow
deposits dominated icemarginal fan)
B (mass flow and
waterlaid icemarginal fan)
C (waterlaid
deposits dominated icemarginal fan)
Coarse
Debrisdiamict
flow
Fine
diamictflow
Mud/debris
Debris
flow
Coarse
diamict
Massive
gravel
Sheetflow
Bar gravel
Imbricate
gravel
Fine
diamict
Distal
flowtill
Sheetflow
Massive
gravel
Sandy
diamict
HyperX
flow
HyperX
flow
Bedded
diamict
Sand
sheets
Sheetflow
Sandy
diamict
HyperX
flow
Bedded
sand
Sheetflow
X-stratified
sand
Stream flow
Stream flow
X-stratified
sand
Gelifluction
Massive
silts
Laminated
silts
Overbank
Proximal FineFlowtill
diamict
Distal
Facies
Distribution

NOTE:

May be
gradation
from pure
till to type
A as well
as among
types!
Distinction from Outwash
Features
End moraine fan
Braidplain
Location
Extent
Planform
ice contact zone
small (km)
fan asymmetric ridge
or rampart
steep (2-20°)
Extraglacial
large (X0-X00 km)
irregular plain,
valley fill
Slope
Long. profile
Sed/water
source
segmented
Supraglacial stream
usually low
uniform
Subglacial stream
Discharge
Unsteady
More uniform
Hydraulics
 downstream
Uniform
Grounded Ice and
Glaciofluvial Locations
Grounded Ice Facies:
Unstratified Diamicts

Bimodal Particle Size Distribution:
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Unsorted pebbles, cobbles, and boulders
Interstitial matrix of sand, silt, and clay
Elongate particles show preferred
orientation
Some crude imbrication

Long axes dipping upstream
Stratified Diamicts
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Sediments generated by:
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Supraglacial, englacial, subglacial processes
Better sorting
Lack the bimodal size distribution associated
with direct deposition
Pebbles may be rounded by meltwater
transport
Some stratification from reworking
Seen in the form of kames, kame terraces,
eskers
Glaciofluvial Deposits
Glaciofluvial Deposits
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Can be deposited in:
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Subglacial and englacial conduits
Supraglacial and proglacial streams
Lithofacies reflect local sediment supply
Well stratified and feature sedimentary
structures at varying scales

Dependent on stream discharge and sediment
supply
Kames
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Small mound-shaped
accumulations of sand
or gravel
Form in pockets or
crevasses in the ice
Commonly feature
fining upwards
sequences
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Large unsorted clasts
overlain by sands & silts
Thermal?
Eskers
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Narrow, sinuous
ridges of sediment
parallel to ice flow
Can include gravels,
sands, and silt
Some facies may be
extremely well
stratified
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Feature gravels
overlain by fine, fluvial
sediments
Topped or interbedded
with diamictites
Glacier Marine Sediment Facies
By: Scott Patterson
Geol 445 Glacier Geology
4/5/03
Glacier Marine Sediment Facies:
Definitions
Till – terrestrial, primary glacier deposited
diamicton
Glacimarine drift – “marine till”
Facies – stratigraphic units distinguished by
lithologic, structural and organic
characteristics detectable in the field (Boggs
2001)
Proximal vs. Distal
Eyles et al 1991 & Boggs 2001
Distal Glacier Marine Facies
Characteristics
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Settled sediment
Extreme variation in clast type (lithology
and source)
Dropstones – with soft sediment
deformation
Stratification
Marine fossils (forams and diatoms)
Sediment plumes off a glacier
(Cofaigh, 2001)
Soon to be Settled Sediment; Norway
Settled Sediment - Varves
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Sources: outer/inter
flows
Stratification
Fine-grained laminae
[fine sand/silt –
silt/clay]
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thin from ice
dark from organics
Eyles et al 1991
Dropstones
Clast lithology –
gneiss in
mudstone
 Boulder
 Subrounded
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http://geologyindy.byu.edu/faculty/rah/slides/Rock%20Canyon/Precambrian%20Glaciers/dropstones%20page.htm