MORAINES
Anders Schomacker
Department of Geology and Mineral Resources
Engineering, Norwegian University of Science and
Technology, Trondheim, Norway
Synonyms
Glacial landform; glacial sediment; till
Definition
“Moraine” is a genetic term for a landform deposited in a
glacial environment (Benn and Evans, 2010; Schomacker,
2011). Commonly, “moraine” refers to a ridge-shaped glacial landform such as an end moraine. It also describes
large-scale terrestrial glacial landscapes, i.e., hummocky
moraines formed by the melt-out of debris-charged deadice or ground moraines (till plains) formed in subglacial
environments. In marine settings, “moraine” almost
entirely refers to ridge- or wedge-shaped landforms deposited at the margin of tidewater glaciers and oriented transverse to the ice-flow direction. Moraines consist of
sediments directly deposited by a glacier and/or deformed
by a glacier.
Introduction
“Moraine” spans over an extremely wide range of glacial
landforms deposited in many different environments.
End moraines and other marginal moraines form at the
margins of glaciers and both in terrestrial and aquatic environments (e.g., Boulton et al., 1999; Bennett, 2001;
Benediktsson et al., 2008, 2009, 2010; Evans et al.,
2012). Till plains or ground moraines form in the subglacial environment of terrestrial glaciers (e.g., Dyke and
Prest, 1987; Ross et al., 2009; Schomacker et al., 2010).
Its analogue in aquatic environments is subglacially
streamlined terrains, typically formed by (paleo-) ice
streams (Figure 1a; Dowdeswell et al., 2008; Winsborrow
et al., 2010; Jakobsson et al., 2011; Howe et al., 2012;
Livingstone et al., 2012; Nitsche et al., 2013). On land,
hummocky moraines form in dead-ice environments by
the melt-out of stagnant, debris-covered glacier ice (e.g.,
Boulton, 1972; Clayton et al., 2008; Schomacker, 2008).
Numerous other types of moraines are known to form in
these glacial environments or in a combination of them.
They comprise landforms such as ribbed moraines
(Figure 1b), controlled moraines, morainal banks, and
many more (e.g., Möller, 2006, 2010; Evans, 2009; Benn
and Evans, 2010; Goff et al., 2012).
The interior of moraines consists of a variety of sediments. Overall, they can be divided into sediments deposited at the same time as the moraine (e.g., basal till plain,
ground moraine, ice-marginal dump moraine) and glacially deformed sediments that were originally deposited
prior to the moraine formation (e.g., glaciotectonic end
moraines, Figure 2). Sedimentologic and geomorphologic
features of moraines formed in glaciomarine environments are mainly described from studies of Pleistocene
moraines that have been isostatically uplifted and are
now accessible on land (e.g., Nemec et al., 1999; Lindén
and Möller, 2005; Evans et al., 2012). Numerous studies
have described the processes of terrestrial ice-marginal
moraine formation, whereas much less is known of the
processes forming moraines at ice margins terminating in
the sea due to the inaccessible environment. The morphology and internal architecture of submarine moraine ridges
have also been deciphered by geophysical methods such
as multibeam and seismic reflection surveys (e.g.,
Dowdeswell et al., 2008; Shaw et al., 2009; Jakobsson
et al., 2011; Goff et al., 2012).
This entry aims to briefly review the most important
moraine types formed in marine glacial environments.
Focus is on the geomorphology and sedimentology of
ice-marginal moraines as well as their implication for glaciation history.
Ice-marginal moraines formed at tidewater
glaciers
Moraine ridges formed at the margins of tidewater glaciers
reflect deposition in complex environments where the
action of meltwater, gravity, and subglacial processes control the morphology and sedimentary facies. The range of
“moraines” formed in this environment spans from subaqueous fans, mainly of glaciofluvial sediments, to transverse moraine ridges built up by both subglacial till and
glaciofluvial sediments, e.g., so-called De Geer moraines.
In paleoglaciological reconstructions, such moraine ridges
are interpreted as formed at a quasi-stationary ice margin.
During longer glacier stillstands, large subaqueous fans
might accumulate and merge or even build up to the water
surface of the basin as an ice-contact delta (Fyfe, 1990;
Nemec et al., 1999). It may be confusing that these landforms are often referred to as “moraines” although they
should be regarded as marginal ice-contact deltas (Fyfe,
1990; Nemec et al., 1999). The use of the term “moraine”
to describe these landforms is probably because they are
broadly ridge shaped and delineate a former ice margin.
Their paleoglaciological significance is therefore similar
to terrestrially formed end moraines that mark the extent
of a glacier advance or the position of a stationary ice margin (e.g., Bakker, 2005).
Excellent geological sections in gravel pits in the
Kregnes “moraine” in Gauldalen in mid-Norway allowed
Nemec et al. (1999) to study the sedimentology and architecture of this ice-marginal deposit. The Kregnes moraine
was formed during the Younger Dryas cold period along
the western margin of the last Scandinavian ice sheet.
The majority of the “moraine” is a Gilbert-type delta with
150 m thick gravelly foreset beds and 2–3 m topset beds
with beach deposits reaching the local marine limit of
175 m a.s.l. However, the study by Nemec et al. (1999)
MORAINES
519
Anders Schomacker
Department of Geology and Mineral Resources
Engineering, Norwegian University of Science and
Technology, Trondheim, Norway
Synonyms
Glacial landform; glacial sediment; till
Definition
“Moraine” is a genetic term for a landform deposited in a
glacial environment (Benn and Evans, 2010; Schomacker,
2011). Commonly, “moraine” refers to a ridge-shaped glacial landform such as an end moraine. It also describes
large-scale terrestrial glacial landscapes, i.e., hummocky
moraines formed by the melt-out of debris-charged deadice or ground moraines (till plains) formed in subglacial
environments. In marine settings, “moraine” almost
entirely refers to ridge- or wedge-shaped landforms deposited at the margin of tidewater glaciers and oriented transverse to the ice-flow direction. Moraines consist of
sediments directly deposited by a glacier and/or deformed
by a glacier.
Introduction
“Moraine” spans over an extremely wide range of glacial
landforms deposited in many different environments.
End moraines and other marginal moraines form at the
margins of glaciers and both in terrestrial and aquatic environments (e.g., Boulton et al., 1999; Bennett, 2001;
Benediktsson et al., 2008, 2009, 2010; Evans et al.,
2012). Till plains or ground moraines form in the subglacial environment of terrestrial glaciers (e.g., Dyke and
Prest, 1987; Ross et al., 2009; Schomacker et al., 2010).
Its analogue in aquatic environments is subglacially
streamlined terrains, typically formed by (paleo-) ice
streams (Figure 1a; Dowdeswell et al., 2008; Winsborrow
et al., 2010; Jakobsson et al., 2011; Howe et al., 2012;
Livingstone et al., 2012; Nitsche et al., 2013). On land,
hummocky moraines form in dead-ice environments by
the melt-out of stagnant, debris-covered glacier ice (e.g.,
Boulton, 1972; Clayton et al., 2008; Schomacker, 2008).
Numerous other types of moraines are known to form in
these glacial environments or in a combination of them.
They comprise landforms such as ribbed moraines
(Figure 1b), controlled moraines, morainal banks, and
many more (e.g., Möller, 2006, 2010; Evans, 2009; Benn
and Evans, 2010; Goff et al., 2012).
The interior of moraines consists of a variety of sediments. Overall, they can be divided into sediments deposited at the same time as the moraine (e.g., basal till plain,
ground moraine, ice-marginal dump moraine) and glacially deformed sediments that were originally deposited
prior to the moraine formation (e.g., glaciotectonic end
moraines, Figure 2). Sedimentologic and geomorphologic
features of moraines formed in glaciomarine environments are mainly described from studies of Pleistocene
moraines that have been isostatically uplifted and are
now accessible on land (e.g., Nemec et al., 1999; Lindén
and Möller, 2005; Evans et al., 2012). Numerous studies
have described the processes of terrestrial ice-marginal
moraine formation, whereas much less is known of the
processes forming moraines at ice margins terminating in
the sea due to the inaccessible environment. The morphology and internal architecture of submarine moraine ridges
have also been deciphered by geophysical methods such
as multibeam and seismic reflection surveys (e.g.,
Dowdeswell et al., 2008; Shaw et al., 2009; Jakobsson
et al., 2011; Goff et al., 2012).
This entry aims to briefly review the most important
moraine types formed in marine glacial environments.
Focus is on the geomorphology and sedimentology of
ice-marginal moraines as well as their implication for glaciation history.
Ice-marginal moraines formed at tidewater
glaciers
Moraine ridges formed at the margins of tidewater glaciers
reflect deposition in complex environments where the
action of meltwater, gravity, and subglacial processes control the morphology and sedimentary facies. The range of
“moraines” formed in this environment spans from subaqueous fans, mainly of glaciofluvial sediments, to transverse moraine ridges built up by both subglacial till and
glaciofluvial sediments, e.g., so-called De Geer moraines.
In paleoglaciological reconstructions, such moraine ridges
are interpreted as formed at a quasi-stationary ice margin.
During longer glacier stillstands, large subaqueous fans
might accumulate and merge or even build up to the water
surface of the basin as an ice-contact delta (Fyfe, 1990;
Nemec et al., 1999). It may be confusing that these landforms are often referred to as “moraines” although they
should be regarded as marginal ice-contact deltas (Fyfe,
1990; Nemec et al., 1999). The use of the term “moraine”
to describe these landforms is probably because they are
broadly ridge shaped and delineate a former ice margin.
Their paleoglaciological significance is therefore similar
to terrestrially formed end moraines that mark the extent
of a glacier advance or the position of a stationary ice margin (e.g., Bakker, 2005).
Excellent geological sections in gravel pits in the
Kregnes “moraine” in Gauldalen in mid-Norway allowed
Nemec et al. (1999) to study the sedimentology and architecture of this ice-marginal deposit. The Kregnes moraine
was formed during the Younger Dryas cold period along
the western margin of the last Scandinavian ice sheet.
The majority of the “moraine” is a Gilbert-type delta with
150 m thick gravelly foreset beds and 2–3 m topset beds
with beach deposits reaching the local marine limit of
175 m a.s.l. However, the study by Nemec et al. (1999)
MORAINES
519