Sedimentology (2009)
doi: 10.1111/j.1365-3091.2008.01018.x
Anatomy of a subaqueous ice-contact fan and delta complex,
Middle Pleistocene, North-west Germany
JUTTA WINSEMAN N*, JAHN J. HORNUNG* 1 , JANINE MEINSEN*, ULRICH ASPRION*,
ULRICH POLOM, CHRISTIAN BRA NDES*, MICHAEL BUßMANN* and
CHRISTIAN WEBER*
*Institut für Geologie, Leibniz Universität Hannover, Callinstr. 30, D-30167 Hannover, Germany
(E-mail: [email protected])
Leibniz Institute of Applied Geosciences (GGA), Stilleweg, Hannover, Germany
Associate Editor: Nick Eyles
ABSTRACT
This paper presents a detailed analysis of the high-resolution facies
architecture of the Middle Pleistocene Porta subaqueous ice-contact fan and
delta complex, deposited on the northern margin of glacial Lake Weser (Northwest Germany). A total of 10 sand and gravel pits and more than 100 wells
were examined to document the complex facies architecture. The field study
was supplemented with a ground-penetrating radar survey and a shear-wave
seismic survey. All collected sedimentological and geophysical data were
integrated into a high-resolution three-dimensional geological model for
reconstructing the spatial distribution of facies associations. The Porta
subaqueous fan and delta complex consist of three fan bodies deposited on a
flat lake-bottom surface at the margin of a retreating ice lobe. The northernmost
fan complex is up to 55 m thick, 6Æ2 km wide and 6Æ5 km long. The incipient
fan deposition is characterized by high-energy flows of a plane-wall jet. Very
coarse-grained, highly scoured jet-efflux deposits with an elongate plan shape
indicate a high Froude number, probably >5. These jet-efflux sediments are
deposited in front of a large 3Æ2 km long, up to 1Æ2 km wide, and up to 25 m
deep flute-like scour, indicating the most proximal erosion and bypass area of
the jet that widens and deepens with distance downstream to the region of
maximum turbulence (approximately five times the conduit diameter).
Evidence for subsequent flow splitting is given by the presence of two
marginal gravel fan lobes, deposited in front of 1Æ3 to 2Æ5 km long flute-like
scours, that are 0Æ8 to 1 km wide and 7 to 20 m deep. In response to continued
aggradation, small jets developed at the periphery of these bar-like deposits
and filled in the low areas adjacent to the original superelevated regions,
locally raising the depositional surface and characterized by large-scale trough
cross-stratified sand and pebbly sand. The incision of an up to 1Æ2 km wide
and up to 35 m deep channel into the evolving fan is attributed to a
catastrophic drainage event, probably related to a lake outburst and lake-level
fall in the range of 40 to 60 m. At the mouth of this channel, highly scoured
jet-efflux deposits formed under hydraulic-jump conditions during flow
expansion. Subsequently, Gilbert-type deltas formed on the truncated fan
margin, recording a second lake-level drop in the range of 30 to 40 m. These
catastrophic lake-level falls were probably caused by rapid ice-lobe retreat
controlled by the convex-up bottom topography of the ice valley.
1
Present address: Geowissenschaftliches Zentrum der Universität Göttingen, Abt. Museum, Sammlungen und Geopark, Goldschmidtstr. 1-5, 37077 Göttingen, Germany.
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists
1
2
J. Winsemann et al.
Keywords Glacial lake, GOCAD, GPR, jet-efflux deposits, shear-wave seismic,
shoal-water delta, subaqueous ice-contact fan.
INTRODUCTION
Glaciolacustrine ice-marginal depositional systems are complex and deposition is commonly
governed by an interplay of several physical
factors, such as the mode of sediment supply,
type and range of depositional processes, glacial
dynamics and lake-level change (e.g. Gorell &
Shaw, 1991; Ashley, 1995; Teller, 1995; Brookfield & Martini, 1999; Russell & Arnott, 2003;
Johnsen & Brennand, 2006). During deglaciation,
subaqueous ice-contact fans may build up to the
lake-level and evolve into ice-contact deltas and
glaciofluvial deltas as the distance between the
glacier terminus and the prograding delta front
increases (cf. Lønne, 1995).
Point-source meltwater-dominated subaqueous
ice-contact fans are characterized by coarsegrained, bed-load sediments (e.g. Lønne, 1995).
Early in the history of a fan, flows entering the
basin experience minimal interaction with the
lake-floor and expand and decelerate. These
initial fan bodies can best be described as deposits from jet-flows (Powell, 1990; Gorell & Shaw,
1991; Russell & Arnott, 2003) which, depending
upon the position of the efflux in the water
column, can be an axisymmetric jet, a plane jet or
a plane-wall jet. For subaqueous fans with flows
existing along a basin floor, the jet is appropriately modelled as a plane-wall jet, expulsed at the
mouth of a glacial conduit. These jet-flows are
characterized by a typical subdivision along the
streamwise profile [zone of flow establishment
(ZFE), zone of flow transition (ZFT), zone of
established flow (ZET)] leading towards a continuous succession of a distinct lithofacies in the
downflow direction (e.g. Powell, 1990; Gorell &
Shaw, 1991; Russell & Arnott, 2003). Although
boundary and stratification conditions vary between jets in different depositional environments,
the functional form of the velocity decay and
dependence on controlling variables is the same
because of the universality of the jet deceleration
mechanism. Strong turbulence in the jet region
has great potential for eroding the substrate,
creating a flute-like erosional scour. The jet
erosional scour widens and deepens with distance downstream to the region of maximum
turbulence (four to eight conduit diameters)
where it shallows, widens and then merges with
the depositional surface (Hoyal et al., 2003). At
high Froude numbers (>5), the deposit approaches an elongate shape about four times
longer than the width. This relationship between
body shape and Froude number can be used to
estimate the Froude number of the flows that
deposit natural sediment bodies. The exponential
coefficient of the down-axis grain-size decay is
also a function of Froude number but varies
inversely to grain-size. Spatial grain-size decay is
faster for low-conduit Froude number flows
and asymptotically reaches a slower decay at
high Froude numbers. The sediment thickness
decreases in an exponential-linear fashion downstream and in a Gaussian-like fashion acrossstream (Hoyal et al., 2003). Flow experiments by
Van Wagoner et al. (2003) show that many properties of the jet may be inherited by the later, more
complex fan body. These properties include:
(i) an incipient channel region that controls
proximal channel evolution; (ii) branching pathways of preferred flow that control flow splitting
and downdip channel location; (iii) the location
of maximum regions of deposition that controls
locations of avulsion and a characteristic distribution of erosion at the base of the jet; and
(iv) jet deposits that control subsequent erosional
patterns.
This study aimed at contributing to a better
understanding of the stratigraphic evolution and
internal facies architecture of a meltwaterdominated subaqueous fan and delta complex.
Depositional processes, principal architectural
elements and stacking patterns will be discussed
and related to lake-level changes.
STUDY AREA AND PREVIOUS RESEARCH
The study area is located south of the North
German Lowlands, mainly built up by Mesozoic
sedimentary rocks and characterized by several
low ridges up to 400 m above sea level (a.s.l.).
The southern margin of the Scandinavian Ice
Sheet terminated in front of the northernmost
mountain ranges (e.g. Ehlers et al., 2004) and
glacial lobes advanced from the north, northwest and north-east into the Weser Valley
(Fig. 1). Field data indicate an ice thickness of
200 to 400 m in front of the mountain ranges; ice
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
3
A
B
Fig. 1. Location and topography of the study area. (A) Extent of the Early Saalian (Saalian maximum) and Late
Saalian (Warthe) Ice Sheets in Central Europe (modified after Ehlers et al., 2004). (B) The hill-shaded relief model
shows the maximum extent of the Early Saalian ice sheet in the study area. Overspills of the lake basin (glacial Lake
Weser) were located on the south-western margin (Teutoburger Wald). Modified from Winsemann et al. (2007).
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
4
J. Winsemann et al.
lobes within the southern valleys probably
reached a maximum ice thickness of 120 to
200 m (Seraphim, 1972; Thome, 1983; Skupin
et al., 2003). The Weser Valley became
ice-dammed and closed, leading to the formation of a deep glacial lake (Thome, 1983;
Klostermann, 1992).
Glacial Lake Weser
During the maximum extent of the Early Saalian
(Drenthe) ice sheet, an ice-dammed lake developed within the Upper Weser Valley, referred to
as ‘Glacial Lake Rinteln’ (Spethmann, 1908),
‘Glacial Lake Weser’ (Thome, 1983) or ‘Glacial
Lake Weserbergland’ (Klostermann, 1992). Glacial
Lake Rinteln refers to the northernmost part of the
Upper Weser Valley, named by Spethmann (1908)
after the small town of Rinteln. However, as the
lake occupied the entire Upper Weser Valley, the
term ‘Glacial Lake Weser’ is the most appropriate
designation and the continued use of this name is
suggested.
The spillway system of Glacial Lake Weser is
a series of valleys in the Teutoburger Wald
Mountain range over an altitude range of 40 to
215 m a.s.l., through which the proglacial lake
drained southward (Fig. 1B). Existing channels
were used or channels were cut during drainage
as the lake filled and overtopped low points
along the southern rim of the Teutoburger
Wald Mountain (Thome, 1983; Klostermann,
1992).
The principal lithological evidence for a large
and deep glacial lake in the Upper Weser Valley
is the occurrence of subaqueous ice-marginal
deposits, fine-grained lake-bottom sediments,
and ice-rafted debris far beyond the former ice
margin. The stratigraphic evidence comes from
both surface exposures and subsurface data. A
total of 20 sand and gravel pits and more than
2300 well logs were evaluated in order to document the regional pattern and characteristics of
the Middle Pleistocene deposits of the Upper
Weser Valley (Fig. 2). Outcrop data are available
mainly for the coarse-grained ice-marginal deposits, where sand and gravel have been excavated in
numerous open pits (Winsemann et al., 2003,
2004, 2007). The subsurface data are derived from
borings drilled along the river valleys and tributaries. Well logs and several clay pits record the
widespread occurrence of up to 20 m thick
fine-grained lake-bottom sediments (Hauptbeckenton), overlying Middle Pleistocene fluvial
deposits of the River Weser (Mittelterrasse) or
bedrock. Former clay pits in the northern lake
basin reveal that these lake-bottom sediments are
commonly laminated and frequently contain
dropstones (e.g. Rausch, 1975; Wellmann, 1998).
These fine-grained lake-bottom sediments occur
at topographic levels from 55 to 180 m a.s.l.
Towards the south, the thickness of lake-bottom
sediments decreases (< 8 m) and relics of lakebottom sediments are preserved mainly at the
valley sides or in areas with higher subsidence
because of salt dissolution in the subsurface
(Fig. 2).
Erratic clasts with a Scandinavian provenance
occur within the entire study area (Fig. 2) and
have been reported from altitudes of 114 to
200 m a.s.l. (e.g. Kaltwang, 1992). These deposits
are associated with fine-grained lake-bottom sediments or overlie older fluvial deposits and are
interpreted as representing ice-rafted debris.
Within the Weser Valley these erratic clasts occur
in clusters at altitudes of 130 and 185 m,
probably indicating stranded icebergs at former
lake shores. Associated beaches or shoreline
features, such as wave-cut benches, have not
been recognized. It is not clear whether beaches
could have formed at the steep shores or whether
they have been destroyed or obscured by later
periglacial processes and human modification.
Although shoreline features have been reported
from other high-relief lake areas (e.g. Johnsen &
Brennand, 2006), they are probably rare in steep
short-lived glacial lakes, characterized by rapid
lake-level fluctuation (e.g. Colman et al., 1994;
LaRoque et al., 2003).
The longevity of the ice-dammed lake can only
be estimated roughly because varve deposits of
the basin centre are only poorly exposed and no
undisturbed core data are available. According to
Litt et al. (2007), the Early Saalian Drenthe ice
advance probably occurred during Marine
Isotope Stage (MIS) 6 and lasted 5000 years
(Lambeck et al., 2006). The longevity of Glacial
Lake Weser, therefore, was probably very short
and has been a few hundred to thousand years
(Junge, 1998; Winsemann et al., 2007). At the
initial stage, glacial Lake Weser had its level at
an altitude of ca 55 m a.s.l. The lake level then
rose by as much as 120 m to a highstand of at
least 175 m a.s.l., as is indicated by the vertically
stacked Emme delta and subaqueous fans located on the eastern lake margin (Winsemann
et al., 2003, 2004, 2007). The distribution of finegrained lake-bottom sediments and ice-rafted
debris in the Upper Weser Valley even points
to a higher lake-level of 190 to 200 m a.s.l.
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
5
Fig. 2. Detailed map of the study area, showing a palaeogeographic reconstruction of glacial Lake Weser (190 m
level) and associated ice-marginal deposits, fine-grained lake-bottom sediments and ice-rafted debris. Data are
compiled from Rausch (1975), Kaltwang (1992), Winsemann et al. (2003, 2004, 2007) and unpublished well logs.
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
6
J. Winsemann et al.
Fig. 3. (A) Detailed map of the study area, showing a palaeogeographic reconstruction of the Porta Complex and
location of measured logs. (B) NW to SE-trending cross-section of the Porta complex. Modified from Winsemann
et al. (2007).
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
The Porta fan complex
The so-called ‘Porta ice-margin deposits’ are
located on the northern margin of Glacial Lake
Weser, south of the Porta Westfalica pass (42 m
a.s.l.). These coarse-grained deposits overlie 0Æ3 to
20 m thick glaciolacustrine mud and patchy
occurrences of till (Wellmann, 1998); they are
exposed in various gravel pits at an altitude of 70
to 130 m a.s.l. (Fig. 3). Clasts consist mainly of
local material derived from the adjacent Mesozoic
basement rocks and reworked fluvial gravel,
previously deposited by the River Weser. Clasts
of a Nordic provenance (derived from Scandinavia and/or the Baltic area) account for 2% to
12% (Wellmann, 1998). Measured palaeoflow
directions and clast compositions indicate that
meltwater flows were the main source of sediment.
Three fan bodies can be recognized, deposited
on a flat lake-bottom surface (Fig. 3), characterized
by vertically and laterally stacked, moderately to
7
steeply dipping fan bodies. The occurrence of
glaciotectonic deformation structures, flow till,
resedimented till clasts and dropstones points to
an ice-contact or very ice-proximal subaqueous
fan setting (cf. Lønne, 1995). The extent, morphology and sedimentary facies indicate deposition into a lake at the margin of the retreating
Porta ice lobe (Winsemann et al., 2007).
Fan complex I
The stratigraphically lowest fan (fan complex I;
Fig. 3) is up to 60 m thick and consists of
moderately to steeply dipping mid-fan deposits,
characterized by graded-stratified sand and
channellized large-scale trough cross-stratified
sand and gravel. These mid-fan deposits unconformably overlie flat-lying planar cross-stratified
proximal fan gravel (Winsemann et al., 2007).
The sedimentary sequence is partly deformed,
displaying thrusts, dipping towards the northwest and overlain by flow till and glaciolacustrine
mud (Wellmann, 1998). Towards the south, the
Fig. 4. Hill-shaded relief model of the Northern Porta complex (fan complex III), showing the location of wells,
measured logs, georadar and shear-wave seismic profiles, and modelled 2D cross-sections (a–a¢ to g–g¢).
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
8
J. Winsemann et al.
fan deposits interfinger with dropstone laminites
(Rausch, 1975).
Fan complex II
Fan complex II consists of 9 m thick, massive,
normally graded or large-scale, trough-crossstratified proximal fan gravel, unconformably
overlain by 15 m thick moderately to steeply
dipping, distal mid-fan deposits, characterized by
medium-bedded to thick-bedded normally graded
sand to mud beds, showing Bouma structures
Ta–d. This succession shows an overall fining
upward and thinning upward trend.
Fan complex III
Fan complex III is exposed in several gravel pits
south of the Porta Westfalica pass (Fig. 3). The
greatest thickness of fan deposits is recorded from
a central, 1 km wide and 5Æ4 km long, NW to
SE-trending zone. Deposits exposed in this
central zone consist of highly scoured massive,
normally graded, planar-parallel or cross-stratified gravel, interpreted to have been deposited
from a friction-dominated plane-wall jet at the
mouth of a subglacial meltwater tunnel (Hornung
et al., 2007). In contrast, deposits exposed in the
marginal fan zone are characterized by aggradational successions of upward-steepening gravelly
and sandy foreset beds inclined at 5 to 35. Both
successions are overlain by large-scale troughcross-stratified and convex-up, sigmoidally crossstratified sand and pebbly sand with an overall
subhorizontal geometry.
DATABASE AND METHODS
A total of eight sand and gravel pits and 101 wells
(Figs 3 and 4) were examined to document the
complex facies architecture of the northernmost
Porta complex (fan complex III). The outcrops are
characterized from lateral and vertical measured
sections across two-dimensional (2D) and threedimensional (3D) exposures. The sections were
measured at the scale of individual beds, noting
grain-size, bed thickness, bed contacts, bed geometry, internal sedimentary structures and palaeocurrent directions. The spatial distribution of
particular lithofacies was determined through
detailed mapping. The field study was supplemented with a ground-penetrating radar (GPR)
survey and a shear-wave seismic survey. The GPR
device used was a GSSI SIR-10 (Geophysical
Survey Systems Inc., Salem, NH, USA), together
with a 100 MHz or 300 MHz bistatic antenna.
Processing was limited to a minimum to avoid
information loss and artefacts (e.g. Asprion &
Aigner, 1999). No migration was applied because
of velocity uncertainties and limited data quality
enhancements.
Shallow shear wave reflection seismic profiling
was carried out using horizontally-polarized
source and receivers both oriented perpendicular
to the profiling direction (SH–SH wave configuration), parameterized to a maximum target depth
of 70 m. For a high-resolution and fast data
acquisition, a Land Streamer unit (Leibniz Institute for Applied Geosciences, Hannover, Germany) of 72 SH geophones in 1 m intervals was
combined with a small, electrodynamic driven SH
shaker source system mounted on a wheelbarrow
unit utilizing the shear wave vibroseis method
(Beilecke et al., 2006). Seismic data processing was
mainly focused on shear wave velocity analysis
after pre-processing of the raw data. Elevation
static corrections were applied relative to 120 m
a.s.l. elevation datum at the peak of the profile.
[Correction added after online publication 15/Jan/
2009: the above paragraph has been reworded]
All collected sedimentological and geophysical
data were integrated into a 3D geological model
(GOCAD). The developed facies model is represented by triangular surfaces and regular orthogonal grids. The generation of the 3D model
followed a two-step approach, integrating all
available sedimentological and geophysical data.
The first step comprised the subdivision of the
model into various lithofacies geobodies by triangulated surfaces. In the second step, the spatial
distribution of lithofacies associations was modelled within the gridded geobodies. Based on 2D
cross-sections, various triangulated surfaces were
mapped in GOCAD confining distinct lithofacies
associations. These surfaces were constrained by
core data and were adjusted locally to match
observations from outcrops.
SEDIMENTARY FACIES AND FACIES
ASSOCIATIONS
Fourteen facies types (F) are defined on the basis
of grain-size, bed thickness, bed contacts and
sedimentary structures (Table 1), and were
grouped into nine facies associations, characterized by distinct depositional processes and bed
geometries. The terminology for gravel characteristics is after Walker (1975). The fabric notation
uses symbols ‘a’ and ‘b’ for the clast long and
intermediate axes, with indices (t) and (p) denoting
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
9
Table 1. Classification of sedimentary facies.
Bed/unit
Bed contact thickness
Facies
Lithology
Interpretation
F1
Diamicton
Matrix-supported, poorly sorted
Sharp
massive granule to cobble-sized
diamicton. The matrix (40 to 50%
vol.) consists of clay, silt and finegrained to coarse-grained sand.
Clasts have a high proportion (up
to 25%) of material derived from
Scandinavia and/or the Baltic area.
0Æ3 to 0Æ7 m
F2
Massive,
inversely
or normally
graded gravel
Sharp
Massive, inversely or normally
graded clast-supported pebble to
boulder-sized gravel. The matrix
(5 to 25% vol.) consists of finegrained to medium-grained sand.
Larger clasts can be oriented parallel to dip and show a steeply
imbricate clast fabric a(p) a(i).
Some beds show upslope-dipping
internal shears, listric or sigmoidal
in shape.
0Æ05 to 0Æ5 m Massive, inversely or normally
graded clast-supported gravel with
sharp, non-erosive bed contacts
indicates deposition from noncohesive debris flows (Shanmugam, 2000). Upslope-dipping
internal shears indicate syndepositional thrusts (Nemec,
1990).
F3
Poorly sorted
gravel with
gravel clusters
Poorly sorted, clast to matrix-sup- Erosive
ported (10 to 40% vol.) granulesized to boulder-sized gravel with
a coarse-grained sandy matrix. The
clast fabric is random but locally
irregular clusters of cobble-sized to
boulder-sized clasts occur. Many
beds show a weak coarse-tail normal grading. Rarely, large, up to
2 m long, diamicton or sand clasts
are embedded.
0Æ2 to 3 m
Rapid deposition from turbulent
hyperconcentrated flows (Mulder
& Alexander, 2001), or
high-density turbidity currents
(Lowe, 1982; Kneller, 1995). The
coarser gravel clusters are attributed to hydraulic lateral grain size
segregation, indicating moving
gravelly beds under supercritical
flow conditions (Carling, 1990).
F4
Large-scale
planar
cross-stratified
gravel
Large-scale planar cross-stratified Erosive
clast-supported, matrix-poor to
openwork pebble to boulder-sized
gravel. The matrix consists of
coarse sand and granules, increasing from less than 5% vol. at the
basal one-third of the bed to ca
30% vol. at the top. Individual
foreset beds are 30 to 40 cm thick,
have dip-angles from 10 to >30
and tangential or sigmoidal basal
contacts. Small lenses (up to
50 cm wide and 30 cm thick) of
matrix-poor (<10% vol.) pebble to
cobble-sized gravel locally occur at
the base or within a foreset. Occasionally up to 25 cm long diamicton clasts are embedded. The
foresets commonly are stacked
upon one another with planar to
erosional, concave-upward
boundaries and have filled deep
scours. Larger scours are characterized by gravel lags.
0Æ2 to 3 m
(cross-sets)
Deposition from high-energy turbulent flows in the leeward flow
separation eddy of preformed deep
scours (Allen, 1982; Carling &
Glaister, 1987). The occurrence of
both open-work and matrix-filled
gravel indicates effective hydraulic
grain size segregation of sand and
gravel (Carling, 1990). The thick
foreset beds and isolated lenses of
coarse gravel indicate intense
slipface avalanching combined
with discrete collapses, indicating
a high and fluctuating sediment
flux. The inclination of foreset
beds commonly declines in
downflow direction, gradually
passing into facies 5. The formation of gravel lags at the base of
larger scours indicates intense
reworking of underlying strata and
outwash of finer-grained material
(Nemec et al., 1999).
Deposition from cohesive debris
flows (Nemec, 1990) from the
ablating ice-front or as flow till
(Lønne, 1995).
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
10
J. Winsemann et al.
Table 1. Continued
Bed/unit
Bed contact thickness
Facies
Lithology
Interpretation
F5
Normally
graded
gravel
Clast-supported, granule to cobble- Sharp or
sized gravel with normal distribu- erosive
tion grading. Outsized clasts occur
scattered at the bed base. The
matrix (10 to 30% vol.) consists of
medium to coarse-grained sand,
commonly increasing upwards.
Some beds contain small gravel
lenses, 0Æ5 to 1 m wide and 0Æ2 to
0Æ5 m thick, which are distinctly
poor in matrix (<10% vol.).
0Æ05 to 1 m
Deposition from waning highdensity turbidity flows (R3;
cf. Lowe, 1982; Kneller, 1995;
Mulder & Alexander, 2001). The
lenticular bed geometry indicates deposition in shallow
chutes or scours (Postma &
Cruickshank, 1988; Prior &
Bornhold, 1990).
F6
Normally
graded
gravel-mud
couplets
Erosive
Interbedded gravel and finegrained sand, silt and clayey silt
beds. The granule-sized to cobblesized gravel beds are clast to
matrix-supported (20 to 50% vol.),
poorly sorted and commonly
weakly normally graded. Beds
have concave-upward erosional
bases. The matrix consists of
medium-grained to fine-grained
sand, silt and mud and its content
increases towards the bed top. The
intervening fine-grained beds are 3
to 15 cm thick and consist of
massive or current-ripple crosslaminated fine-grained sand, silt or
mud, with local ball and pillow
structures.
0Æ6 to 1 m
The scour-based weakly normally graded gravel is interpreted to have been deposited
from high-density turbidity
currents (R3; cf. Lowe, 1982) or
turbulent watery debris flows
(Mulder & Alexander, 2001).
The interbedded fine-grained
beds indicate deposition from
waning low-density turbidity
flows (Tc-d, cf. Bouma, 1962).
F7
Inversely-tonormally
graded gravel
and sand
Sharp or
Poorly sorted, matrix-supported
erosive
(30 to 50% vol.), granule-sized to
pebble-sized gravel passing upwards into coarse-grained sand,
with trains of larger pebbles ‘floating’ at the gravel/sand boundary.
Normal coarse-tail grading can be
observed in the lower part of some
beds. The matrix consists of medium-grained to coarse-grained
sand.
0Æ03 to 0Æ15 m Deposition from waning pulses
of high-density flows, with
large clasts dragged along the
boundary between a basal inertia-flow layer and the overlying,
faster-moving turbulent current
(Postma et al., 1988), or the
partial fluidization of subaqueous debris flows (Sohn
et al., 2002).
F8
Convex-up
large-scale
cross-stratified
gravel and
pebbly sand
Flat
Sandy pebble-sized gravel and
pebbly sand with tangential to
sigmoidal cross-stratification.
Individual foreset beds are 3 to
30 cm thick and laterally graded.
Sigmoidal convex-upward crossstratification is best preserved in
the thickest beds. Thinner foresets
are often more sandy and inclination of cross-strata are commonly
no steeper than 10 and apparently
represent erosional relics of originally thicker cross-sets.
0Æ3 to 3 m
(cross-sets)
The convex-up cross-stratified
gravel and pebbly sand is
interpreted to represent
channel-mouth bars, where
hydraulic-jump conditions
caused an abrupt flow
expansion (Powell, 1990;
Mulder & Alexander, 2001).
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
11
Table 1. Continued
Bed/unit
Bed contact thickness
Facies
Lithology
F9
Convex-up,
large-scale
sigmoidally
cross-stratified
sand to pebbly
sand
Flat
Thick medium to coarsegrained sand and pebbly sand
with convex-up large-scale planar to sigmoidal cross-stratification. Individual foreset beds
are 2 to 15 cm thick and laterally graded. Dip angles are 5 to
30. Up-flow foreset beds pass
into subhorizontally stratified
sand. Bedding is slightly aggradational with each foreset bed
prograding over a thin (1 to
2 cm) subhorizontal bottomset
layer.
F10
Diffusely
planar-parallel
stratified sand
and pebbly sand
Diffusely planar-parallel stratified sand and pebbly sand.
Some beds contain granules
and pebbles at the base or as
subhorizontal trains.
F11
Subhorizontally
stratified sand
and pebbly sand
Coarse-grained to mediumgrained, well-sorted sand and
rarely pebbly sand forming
subhorizontal bedsets dipping
very gently (<3) either down or
upflow. The bedded sand aggrades conformably to slightly
convex-up climbing bedforms,
which are 0Æ2 to 0Æ8 m thick and
have a wave-length of several
metres to tens of metres. Locally
small (1 m wide, 0Æ1 m deep)
scours filled with massive sand
occur. Bedform cosets locally
pass upward gradually into
medium-scale trough crossstratification.
0Æ8 to 1Æ8 m
Subhorizontal to convex-up,
(bedform cosets) conformable bedding indicates
formation of antidunes in the
upper flow regime (Cheel, 1990;
Alexander et al., 2001). Subsequent waning flow conditions
are indicated by a gradual vertical transition into trough
cross-stratification (cf. Southard
& Boguchwal, 1990).
F12
Planar and
trough
cross-stratified
sand and gravel
Erosive
Medium-grained to coarsegrained sand, pebbly sand or
sandy, poorly sorted pebblesized gravel with large-scale
planar or trough cross-stratification. Troughs are 0Æ3 to 8 m
wide and 0Æ15 to 1Æ5 m thick.
Intrasets of climbing-ripple
cross-lamination are present
locally at the stoss-side parts of
large cross-sets, where preserved. Angular sandy intraclasts, up to 40 cm long, may
occur at the bases of cosets.
0Æ3 to 2Æ5 m
(cosets)
Sharp or
erosive
Interpretation
1Æ5 to 2 m
The convex-up cross-stratified
sand and pebbly sand is interpreted to represent channel
mouth bars, where hydraulicjump conditions caused an
abrupt flow expansion (Chough
& Hwang, 1997).
0Æ2 to 1 m
Traction deposition from highdensity turbidity currents
(Lowe, 1982; Kneller, 1995) or
deposition from thin diluted
cohensionless debris flows
(Sohn et al., 1997). Thicker
beds with subhorizontal pebble
trains indicate more sustained,
fluctuating flows (Plink-Björklund & Ronnert, 1999).
Downflow migration of 2D or
3D dunes (Allen, 1982) which
implies current in the uppermost part of the lower flow
regime. This deposition
requires flows that are
sustained at a relatively
constant discharge for longer
periods (Kneller, 1995; Mulder
& Alexander, 2001).
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
12
J. Winsemann et al.
Table 1. Continued
Facies
Lithology
Bed contact
Bed/unit
thickness
F13
Massive and
inversely graded
pebbly sand
and sand
Massive or inversely graded
pebbly sand and coarse to
fine-grained sand. Clasts are
commonly pebble-sized
Flat or sharp
0Æ05 to 0Æ5 m
Massive or inversely graded
pebbly sand and sand with a
non-erosive base indicate
deposition from non-turbulent
sandy debris flows. Sediment is
supported by matrix strength,
dispersive pressure, and buoyant lift (Mulder & Cochonat,
1996; Shanmugam, 2000).
F14
Normally graded
sand to mud beds
Individual beds consist of
intervals of normally graded
or massive sand or pebbly
sand that fines upwards into
planar-parallel laminated
and ripple or climbing-ripple
cross-laminate mediumgrained to fine-grained sand
and silt, laminated silt and,
finally, into laminated or
massive mud. Beds are most
commonly ‘incomplete’ and
contain both ‘top-absent’ or
‘base-absent’ successions.
Scattered pebbles are common and thin beds often
show flame and/or ball-andpillow structures.
Flat, sharp
or erosive
0Æ05 to 0Æ4 m
Normal grading and fining of
individual beds reflect deposition from waning surge-like
low-density turbidity currents
(Ta–d, cf. Bouma, 1962; Lowe,
1982; Kneller, 1995). Thick
fining upward beds with
planar-parallel lamination or
climbing-ripple cross-lamination indicate deposition from
waning sustained low-density
turbidity flows (Mulder &
Alexander, 2001). Scattered
pebbles may represent coeval
debris fall from steep upper
delta slopes (Nemec et al.,
1999).
axis orientation transverse or parallel to flow
direction, respectively, and index (i) denoting
axis imbrication. The notation of turbidites, Tabcde,
refers to Bouma divisions (cf. Bouma, 1962), and
S1–3; R1–3 to Lowe divisions (cf. Lowe, 1982).
FA1 Subaqueous fan deposits
FA1Æ1: Scoured massive, normally graded or
planar cross-stratified gravel
Description. FA1Æ1 is exposed at the Brinkmeyer,
Edler 1 and Edler 2 pits (Figs 3 and 5 to 8)
and consists of mostly lenticular (0Æ3 to 3 m deep
and up to 25 m wide), granule-sized to bouldersized, massive (F3), normally graded (F5), planar
cross-stratified gravel (F4), inversely to normally
graded sandy gravel and pebbly sand (F7), normally graded gravel–mud couplets (F6) and
diamicton (F1). These lenticular beds occasionally contain 0Æ25 to 2 m long, unconsolidated
sand or diamicton clasts. At the base of large
scours, commonly a clast-supported gravel-lag
Interpretation
can be observed, comprising the coarsest material
(Fig. 8A and B). Measured palaeoflow directions
are highly variable and range from easterly,
south-easterly, south-westerly to north-westerly
directions. Across stream, a rapid decrease in
scour width and depth can be observed over a
distance of 300 m (Figs 6, 8A and D) which is
associated with a decrease in grain-size and the
preservation of mud drapes. The larger-scale
facies architecture has been studied at the Edler
pit with several GPR profiles, located along a
series of parallel offset benches at 81, 87 and
94 m a.s.l. (Fig. 7). The GPR profiles show a
complex pattern of nested concave-upward
reflectors, up to 25 m wide, 1 to 3 m deep and
laterally filled with south to south-eastwarddipping reflectors. The continuity and dip angles
of reflectors vary along the GPR profiles. The
lowermost profile is characterized by a lowamplitude, high-angle reflector pattern; the middle profile shows a more diffuse reflector pattern;
and the uppermost profile shows a high-amplitude, low-angle reflector pattern with a higher
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
13
continuity. Deposits are 6 to 28 m thick and
characterized by an overall wedge-shaped lowangle geometry (3 to 5).
Interpretation. Intensive scouring and deposition of massive or normally graded gravel with
unconsolidated intraclasts indicate sedimentation from coarse-grained hyperconcentrated turbulent flows (cf. Mulder & Alexander, 2001),
typical for the proximal region of ice-contact fans
and intra-conduit (esker) deposits (e.g. Gorell &
Shaw, 1991; Brennand, 1994; Russell & Arnott,
2003). Clustering of outsized clasts within otherwise poorly stratified coarse-grained gravel is
interpreted as resulting from lateral hydraulical
grain-size segregation under supercritical flow
conditions (Carling, 1990) or may indicate intense
reworking of underlying strata and armouring of
newly scoured pool floors (e.g. Nemec et al.,
1999). Rare intercalation of diamicton indicates
deposition from the ablating ice-front (Lønne,
1995). The complex nested concave-upward
reflector pattern of the GPR profiles is interpreted
as representing multiple large-scale scours which
have been laterally filled with large-scale planar
cross-stratified gravel. The observed variations of
reflector patterns (dip angle, amplitude) might
correlate with the upward decrease in grain-size
(Figs 5 and 7). FA1Æ1 is interpreted as representing proximal jet-efflux deposits (proximal zone of
flow transition) in front of a subglacial conduit.
The decrease of erosive features and grain-size in
both flow and across-stream directions reflects the
velocity and concentration decay of a jet-flow (e.g.
Hoyal et al., 2003).
FA1Æ2: Convex-up, sigmoidally to planar crossstratified sand and gravel
Fig. 5. Sedimentological log measured at the Edler 1
pit (modified after Hornung et al., 2007). For key see
Fig. 12, for location see Figs 3 and 4.
Description. FA1Æ2 is exposed at the Groh 1 and
Heesen pits (Figs 3A and 9 to 11) and consists
predominantly of large-scale, high-angle sigmoidally to planar cross-stratified, coarse-grained
sand to cobble-sized gravel (F8). The sigmoidally
or planar cross-stratified beds form large-scale
convex-up structures with flat bases, which are
up to 25 m wide und 2 m thick, and are vertically
and laterally stacked (Fig. 10). Some beds contain
sandy intraclasts. The convex-up structures are
incised by small, isolated, lenticular channels (up
to 8 m wide and 1 m deep), filled with largescale, trough cross-stratified medium-grained
sand and pebbly sand (F12). Less commonly,
laterally extensive 5 to 15 cm thick, massive or
planar-parallel laminated sandy silt beds (F14)
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
14
J. Winsemann et al.
Fig. 6. Sedimentological log measured at the Brinkmeyer and Edler 2 pit (modified after Hornung et al., 2007). For
key see Fig. 12, for location see Figs 3 and 4.
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
15
Fig. 7. GPR profiles measured at the Edler 1 pit. The GPR profiles show a complex pattern of nested concave-upward
reflectors, up to 25 m wide, 1 to 3 m deep and filled laterally with south to south-eastward dipping reflectors. The
lowermost profile is characterized by a low amplitude high angle reflector pattern; the middle profile shows a more
diffuse reflector pattern; and the uppermost profile shows a high-amplitude low angle reflector pattern with a higher
continuity. This complex nested concave-upward reflector pattern is interpreted as representing multiple large-scale
scours which have been filled laterally (FA1Æ1). The observed variations of reflector patterns (dip angle, amplitude)
might correlate with the upward decrease in grain size. The strong horizontal reflector, which can be observed in all
profiles at 100 ns, probably indicates a seepage front from a former rainstorm. For location, see Fig. 4.
can be observed, which drape the large-scale
convex-up structures and commonly show flame
structures. FA1Æ2 is up to 12 m thick, shows an
overall fining-upward trend and has a larger-scale
subhorizontal geometry.
Interpretation. The sandy to gravelly, large-scale,
convex-up clinoforms are interpreted as mouthbar-like bedforms, deposited in response to a
sudden decrease in flow energy. This deposition
happens potentially at the mouth of a channel,
chute or subglacial conduit (e.g. Postma & Cruickshank, 1988; Sohn & Son, 2004). Rip-up clasts
and load features indicate erosive flows and rapid
deposition of coarse-grained material. Channels
on top of these mouth bars became filled during
decreasing flow energy and mud drapes were
deposited from low-density turbulent flows and
suspension fall-out during times of reduced flow
energy (e.g. Russell & Arnott, 2003). FA1.2 is
interpreted as representing lower energy jet-efflux
deposits in front of a subglacial conduit (e.g.
Powell, 1990).
FA1Æ3: Trough cross-stratified sand and pebbly
sand
Description. FA1Æ3 is exposed at the Heesen pit
(Figs 3A and 11). The succession consists exclusively of medium-bedded to thick-bedded, trough
cross-stratified, medium-grained to coarsegrained sand and pebbly sand (F12). Troughs
are 2 to 8 m wide and 0Æ2 to 0Æ8 m thick. Because
of the poor outcrop conditions, a larger-scale
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
16
J. Winsemann et al.
A
B
C
D
E
F
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
organization of this facies association could not
be observed. FA1Æ3 has a wedge-shaped low-angle
geometry (1 to 10).
Interpretation. The large-scale trough cross-stratified sand and pebbly sand represent 3D dunes,
indicating sustained turbulent flows under subcritical conditions (e.g. Allen, 1982; Mulder &
Alexander, 2001). FA1Æ3 is interpreted as representing low-energy jet-efflux deposits (zone of
established flow, cf. Russell & Arnott, 2003).
FA1Æ4: Scoured, subhorizontally and
cross-stratified gravel and sand
Description. FA1Æ4 is exposed at the Brinkmeyer
and Edler 2 pits (Figs 3A, 6 and 8). The sedimentary facies within FA1Æ4 shows a gradual facies
change in flow direction. The most proximal
facies assemblage includes normally graded
gravel, deposited in small scours (F5), mediumbedded to thick-bedded planar and trough crossstratified gravel and pebbly sand (F12), and
medium-bedded to thick-bedded subhorizontally
stratified sand (F11). This assemblage (Fig. 8)
passes downflow into scour-based normally
graded gravel-mud couplets (F6), subhorizontally
stratified sand (F11), large-scale trough crossstratified sand and gravel (F12), and diffusely
planar-parallel stratified sand (F10), forming vertically stacked, 3 to 4 m thick units, consisting of
subhorizontally stratified sand, passing upwards
into trough cross-stratified sand and diffusely
stratified sand locally draped by medium-grained
to fine-grained sand with climbing-ripple crosslamination and mud drapes (F14). Most distally,
the succession consists of laterally extensive, very
thick-bedded (2 to 4 m thick cosets) large-scale
cross-stratified sand (F12), which partly contains
large sandy intraclasts and which is intercalated
with subhorizontally stratified medium-grained
17
sand (F11). Rarely, lenticular beds (1 to 2 m wide
and 0Æ6 m deep), filled with massive sand and
intraclasts occur (Fig. 8F). The base of the cosets
coincides laterally with the base of the depositional units from the medial part, described
above. FA1Æ4 has a wedge-shaped distally steepening geometry (3 to 10) and unconformably
overlies deeply truncated poorly sorted gravel of
FA1Æ1 (Figs 6 and 8).
Interpretation. FA1Æ4 is interpreted as representing deposits of a high-energy jet-flow, episodically climaxing to supercritical efflux conditions
during peak discharge. Parts of the downflow
succession are in accordance with facies assemblages previously described for deposition under
hydraulic jump conditions during flow expansion
(Gorell & Shaw, 1991; Russell & Arnott, 2003;
Hornung et al., 2007). Supercritical flow conditions near the hydraulic jump are indicated by
subhorizontally stratified sand (antidunes,
Fig. 8E), passing downflow into 3D dunes migrating over the unconfined slope, driven by quasisteady underflows. Vertical transitions from
antidunes to dunes indicate waning flows
(Southard & Boguchwal, 1990). During decreased
discharge, the diffusely stratified sand was deposited from highly concentrated, turbulent flows
under subcritical conditions. Intercalated finegrained sand with climbing-ripple cross-lamination and mud drapes represent episodes of flow
cessations (Hornung et al., 2007). Lenticular
massive sand beds within large-scale troughcross-stratified sand are interpreted as scour-fills,
recording rapid cut-and-fill processes by turbulent flows, probably associated with hydraulic
jumps (e.g. Gorell & Shaw, 1991). The facies
assemblage of FA1Æ4 indicates jet-efflux deposits
of the distal zone of flow establishment to the
proximal zone of established flow (Hornung
Fig. 8. Facies association FA1Æ1 and FA1Æ4 exposed at the Brinkmeyer pit. (A) Massive and planar cross-stratified
granule-sized to boulder-sized gravel, deposited in 2 to 3 m deep and up to 20 m wide scours. Gravel lags commonly
occur at the base of scours (FA1Æ1, ZFT; 3Æ9 km downflow of the subglacial conduit). These deposits are unconformably overlain by cross-stratified granule to cobble-sized gravel (FA1Æ4). (B) Deeply truncated scoured massive
gravel (FA1Æ1), unconformably overlain by scoured planar and trough cross-stratified gravel and pebbly sand,
deposited at the mouth of a large fan channel (FA1Æ4, ZFT). Person for scale is approximately 1Æ85 m tall. (C) Highly
scoured trough cross-stratified and subhorizontally stratified gravel, pebbly sand and sand (FA1Æ4; ZFT), deposited at
the mouth of a large fan channel (100 m downflow of the gravel dominated facies shown in photograph B (Photo by
B. Garlt). Persons for scale are approximately 1Æ80 m tall. (D) Massive and normally graded gravel, deposited in small,
1 to 3 m wide and 0Æ4 to 1 m deep scours (FA1Æ1, ZFT; 150 m across-stream of facies shown in photograph (A).
Person for scale is approximately 1Æ60 m tall. (E) Subhorizontally stratified coarse-grained to medium-grained sand,
interpreted as antidunes. The low-angle dipping strata onlap an erosional surface and strata pinch and swell along
strike (FA1Æ4). Trowel for scale is 28 cm. (F) Large-scale trough cross-stratified sand, cut by a steep scour, filled with
massive sand and large intraclasts, recording rapid cut-and-fill processes by turbulent flows, probably associated
with a hydraulic jump. Note the complex fault pattern at the scour margin (FA1Æ4). Field book for scale is 21 cm.
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
18
J. Winsemann et al.
consists of very thin-bedded to medium-bedded
(1Æ5 to 20 cm), fine-grained sand, silt and clay
alternations (F14). The fine-grained sand beds are
massive, normally graded, planar parallel-laminated or climbing-ripple cross-laminated often
with preserved stoss sides, passing upwards into
draping lamination. Silt, silty clay and clay beds
are massive, normally graded or planar parallellaminated and locally contain scattered pebbles.
The geometry is sheet-like and beds may form
drapes.
Interpretation. The sand, silt and clay alternations have been deposited from low-density turbidity flows (Ta–e; cf. Bouma, 1962), waning
underflows and/or suspension fall-out. Massive
sand, silt and clay beds as well as climbing-ripple
cross-lamination indicate high suspension fallout
rates (Ashley, 1995). The scattered pebbles probably represent ice-rafted debris dumped from
icebergs (Thomas & Connell, 1985). Facies association FA1Æ5 is interpreted as lake-bottom sediments (Lønne, 1995; Nemec et al., 1999).
FA2: Delta deposits
FA2Æ1: Massive, inversely and normally
graded gravel
Fig. 9. Sedimentological log measured at the Groh 1
pit. For key see Fig.12, for location see Figs 3 and 4.
et al., 2007). The erosive channel-form contact
between FA1Æ1 and FA1Æ4 (Figs 6 and 8B) suggests that FA1Æ4 was deposited at the mouth of a
fan channel.
FA1Æ5: Interbedded fine-grained sand,
silt and clay
Description. FA1Æ5 is exposed at the base of the
Groh 1 pit, Edler 1 pit and Müller 2 pit and
Description. FA2Æ1 is exposed at the Hainholz pit
(Figs 3A and 12) and consists of steeply dipping
thin-bedded to thick-bedded (0Æ05 to 0Æ5 m)
matrix and clast-supported massive, inversely
and normally graded gravel (F2), often showing
a steeply imbricate clast fabric a(p) a(i). The
matrix is mainly coarse-grained sand. Floating
outsized clasts (up to 1 m long) are common and
aligned parallel to the beds (Fig. 12). Some beds
show upslope-dipping internal shears, listric or
sigmoidal in shape, marked by pebble stringers or
sandy bands nearly devoid of gravel. FA2Æ1 has a
wedge-shaped, high-angle geometry (25 to 35)
and is 13 to 30 m thick.
Interpretation. The absence of current-produced
structures and the occurrence of sharp, nonerosive bases suggest a steep delta slope with
gravity-driven sediment transport (e.g. Postma &
Cruickshank, 1988; Nemec, 1990). The coarsegrained sandy matrix nearly devoid of mud
indicates that these debris flows were probably
cohensionless, controlled mainly by the frictional
strength of the sediment (Nemec et al., 1999).
Upslope-dipping internal shears, listric or
sigmoidal in shape, represent syndepositional
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
19
A
B
Fig. 10. Photograph and sketch of facies association FA1Æ2 exposed at the Groh 1 pit. The convex-up large-scale
cross-stratified gravel (F8) intercalated with mud (F14) and trough cross-stratified sand (F12) is interpreted as representing channel-mouth bar deposits which formed during the incipient stage of fan development.
thrusts. Metre-scale outsize clasts may indicate
downslope sliding of individual blocks (Nemec,
1990).
FA2Æ2: Massive, graded-stratified and
cross-stratified sand and gravel
Description. FA2Æ2 is exposed at the Müller 2 pit
(Figs 3A and 13) and consists of thin-bedded to
medium-bedded, massive, normally graded, or
graded-stratified fine-grained to coarse-grained
sand (F14), alternating with massive and inversely graded pebbly sand and sand (F13), normally
to inversely graded pebbly sand (F7), mediumbedded diffusely stratified pebbly sand and sand
(F10), and thin-bedded to medium-bedded massive gravel (F2). Bed contacts are sharp or erosive
and load features (ball and pillow structures) are
abundant. These laterally extensive beds display
a large-scale convex-up reflector pattern (SSW to
NNE-trending GPR profile; Fig. 14A) and are
incised by lenticular channels, up to 60 m wide
and 4 to 5 m deep (SSE to NNW-trending GPR
profile; Fig. 14A). The channels are commonly
filled with medium-bedded to thick-bedded largescale trough cross-stratified medium-grained to
coarse-grained sand (F12) and graded-stratified
sand (F14). Larger-scale channel-fills show highangle (65 to 90) normal faults (vertical offset 0Æ1
to 1Æ2 m), which are parallel to the channel
margins. These channels are vertically stacked
(Fig. 14A) and characterized by internal smallerscale lenticular beds (1 to 6 m wide, 0Æ2 to 1Æ5 m
thick) with partly coarser-grained infills of massive or normally graded cobble-sized gravel (F3,
F5). FA2Æ2 has a wedge-shaped, upward-steepening geometry (6 to 25), is 20 m thick and
unconformably overlies poorly sorted gravel with
large, up to 2 m long, diamicton and sand intraclasts (FA1Æ1).
Interpretation. The graded-stratified pebbly sand
and sand with erosive bed contacts have been
deposited from surge-like, high-density and lowdensity turbidity flows (cf. Bouma, 1962; Lowe,
1982; Postma et al., 1988; Kneller, 1995). Intercalated massive, inversely graded or diffusely
stratified gravel, pebbly sand and sand with a
non-erosive base indicate deposition from cohesionless debris flows or sandy debris flows,
respectively (e.g. Sohn et al., 1997; Nemec et al.,
1999; Shanmugam, 2000). Large-scale vertically
stacked lenticular channels represent delta-slope
channels (e.g. Postma & Cruickshank, 1988; Bornhold & Prior, 1990). These channels are filled
mainly with large-scale cross-stratified pebbly
sand, indicating currents that are sustained at a
relatively constant discharge for longer periods
(Kneller & Branney, 1995; Plink-Björklund &
Ronnert, 1999). The synsedimentary normal
faults located at the channel margins seem to
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
20
J. Winsemann et al.
Fig. 11. Sedimentological log measured at the Heesen pit. For key, see Fig. 12; for location, see Figs 3 and 4.
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
21
Fig. 12. Sedimentological log measured at the Hainholz pit. For location, see Figs 3 and 4.
have favoured a vertical channel stacking, as
known from marine deep-water channel–levée
systems (e.g. Clark & Pickering, 1996). Moderateangle to high-angle bedding, the occurrence of
large distributary channels and lobes indicate
a proximal to distal delta-slope environment
(e.g. Postma & Cruickshank, 1988; Nemec et al.,
1999).
FA2Æ3 Planar parallel-stratified, troughcross-stratified and ripple crosslaminated fine-grained to mediumgrained sand
Description. FA2Æ3 is exposed at the Hainholz pit
(Figs 3A and 12) and consists of diffusely planar
parallel stratified, trough cross-stratified, ripple
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
22
J. Winsemann et al.
Fig. 13. Sedimentological log measured at the Müller pit. For key, see Fig. 12; for location, see Figs 3 and 4.
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
23
B
A
Fig. 14. (A) GPR profile measured at the Müller 2 pit. The large-scale convex-up reflector pattern is interpreted as
representing delta lobes. The vertically stacked large concave-up structures (60 m wide, 4 to 5 m deep) are interpreted as representing distributary channels. (B) GPR profile and sedimentological log measured at the Brinkmeyer
pit. The convex-up reflector pattern is interpreted to represent delta mouth bar deposits, exposed on top of the Edler
and Brinkmeyer pits. For location, see Fig. 4.
trough cross-laminated and climbing-ripple
cross-laminated fine-grained to coarse-grained
sand and pebbly sand (F10, F12, and F14). Beds
are thin-bedded to thick-bedded (0Æ1 to 0Æ7 m) and
have sharp or erosive contacts. Rarely lenticular,
1 m wide and 0Æ1 m thick pebble to cobble-sized
clast-supported massive gravel beds can be
observed (F2). FA2Æ3 has a wedge-shaped, upward-steepening geometry (5 to 20), is 11 to
20 m thick and unconformably overlies deeply
truncated coarse-grained, mass flow dominated
delta deposits (FA2Æ1).
Interpretation. The thin-bedded to thickbedded, ripple cross-laminated and cross-stratified, fine-grained to coarse-grained sand beds
are interpreted as resulting from sustained lowdensity turbulent flows (Ashley, 1995; Mulder &
Alexander, 2001), creating small fan-shaped
delta lobes on the delta front, indicated by
changing palaeoflow and dip directions
(Fig. 12). The diffusely planar parallel-stratified
pebbly sand probably records deposition from
diluted cohesionless debris flows (Sohn et al.,
1997). The low-angle to medium-angle bedding
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
24
J. Winsemann et al.
Fig. 15. Photograph of facies association FA2Æ4, exposed at the Edler 1 pit. Large-scale trough cross-stratified pebbly
sand (F12) is overlain by convex-up large-scale cross-stratified sand and pebbly sand (F9), interpreted as representing
mouth bar deposits of a shoal-water delta overlying delta plain deposits. Note vertical accretion, sigmoidal bedding
and thin bottomsets of mouth bars (F9).
(5 to 20) and good sorting of sediments
suggest that facies association FA2Æ3 was
deposited in a lower delta foreset to delta
toeset environment (e.g. Ashley, 1995). Clastsupported gravel lenses, deposited from
cohesionless debris flows, are interpreted as
shallow low-sinuosity chute-fills (e.g. Postma &
Cruickshank, 1988).
FA2Æ4: Trough cross-stratified and convex-up,
sigmoidally cross-stratified sand and pebbly
sand
Description. FA2Æ4 is exposed at the top of the
Edler 2, Brinkmeyer, Edler 1 and Müller 2 pits
(Figs 3A, 14B and 15) and consists of large-scale
trough cross-stratified, medium-grained to coarsegrained sand and pebbly sand (F12), locally
including some isolated larger, cobble-sized
clasts. The cross-stratified sand is deposited
within lenticular channels (up to 10 m wide
and 2 m deep), which show a nested off-set
stacking pattern. The succession passes upwards
into two vertically stacked sets of large, flatbased, convex-up, sigmoidally cross-stratified
pebbly sand (F9, Fig. 15), which can be traced
laterally for 70 m. Clinoforms are partly incised
by small channels (2 to 3 m wide and 0Æ2 to 0Æ5 m
deep) filled with large-scale trough cross-stratified medium-grained sand (F12). The larger-scale
geometry of these deposits can be seen in the
georadar profile measured at the top of the
Brinkmeyer pit (Fig. 14B). The WSW to ENEtrending georadar profile displays two layers of
convex-up reflectors, overlying a poorly defined
lower horizon with large concave-up reflectors.
The convex-up structures are more than 25 m
wide. The shorter NNE to ENE-trending profile
shows subhorizontal reflectors. FA2Æ4 is up to
10 m thick and has a sheet-like and moundshaped geometry.
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
C
Fig. 16. Shear-wave seismic profile measured north of the gravel pits Brinkmeyer, Edler 2 and Müller 2 (for location, see Fig. 4). Coarse-grained subaqueous fan
deposits (seismic facies D and H) overlie fluvial deposits of the River Weser (seismic facies B) and lake-bottom sediments (seismic facies C). The subaqueous fan
deposits are unconformably overlain by deltaic deposits (seismic facies E–I). The uppermost 5 to 10 m of the section (seismic facies I) represent younger, Late
Pleistocene aeolian deposits.
B
A
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
25
26
J. Winsemann et al.
Table 2. Classification of seismic facies.
Seismic facies
Shape of seismic unit
Reflector pattern
Interpretation
A
?
Set of continuous, parallel highamplitude reflectors
Mesozoic basement rocks
B
Sheet-like
Discontinuous high-amplitude
reflectors
Fluvial deposits (pebble to boulder
sized gravel)
C
Sheet-like
Two parallel and relatively
continuous reflectors with high
amplitudes
Lake-bottom sediments (mud and
fine-grained sand)
D
Mound-shape
Discontinuous slightly hummocky
high-amplitude reflectors
Coarse-grained subaqueous fan
deposits (sand and gravel)
E
Lenticular
Diffuse and transparent reflector
pattern, bounded at the base by a
continuous reflector with a high
amplitude
Channel-fill (coarse-grained
gravel)
F
Lenticular
Discontinuous to continuous concave
reflectors
Channel-fill (sand and fine-grained
gravel)
G
Wedge-shape
Sets of inclined parallel reflectors
Delta foresets (sand and gravel)
H
Sheet-like
Sheet-like set of very tight and
continuous, very high-amplitude
reflectors
Delta plain (sand and pebbly sand)
I
Sheet-like to
lenticular
Parallel to hummocky reflector
pattern, bounded at the base by a
continuous reflector with a high
amplitude
Delta plain and delta-mouth bars
(sand and pebbly sand), overlain
by Late Pleistocene aeolian
deposits
Interpretation. The channellized large-scale
trough cross-stratified, medium-grained to
coarse-grained sand and pebbly sand is interpreted as glaciofluvial delta plain deposits, based
upon the subhorizontal bedding geometry and the
presence of channels, filled with large-scale
trough cross-stratified sand and pebbly sand
(e.g. Bridge, 1993). The vertically stacked, largescale convex-up bedforms with good preservation
of formsets suggests aggradation within increasing accommodation space (Chough & Hwang,
1997; Sohn & Son, 2004). Therefore, these deposits are interpreted as mouth bars, which formed in
front of a retrograding shoal-water delta on a
drowned glaciofluvial delta plain.
Stacking pattern of facies associations
To determine the larger-scale architecture of the
Northern Porta fan and delta complex, a 1 km
long shear wave seismic reflection profile was
generated north of the gravel pits, Brinkmeyer,
Edler 2 and Müller 2 (Figs 4 and 16). Lithological
control is provided by outcrops and several
wells. The fan and delta complex exhibits a range
of seismic facies (Table 2) and contains sheetlike, lobate and channel-form depositional elements.
The base of the seismic section shows a
continuous set of parallel high-amplitude reflectors (seismic facies A; Table 2), representing
the Mesozoic basement rocks. The overlying
discontinuous high-amplitude reflectors (seismic
facies B, Table 2) represent pebble-sized to bouldersized fluvial gravel deposits of the River Weser.
The middle part of the section displays two
relatively continuous reflectors with a vertical
spacing of 5 to 15 m (seismic facies C; Table 2).
This strong high-amplitude reflector can be traced
along the complete section and represents finegrained lake-bottom sediments.
The upper part of the section (above 30 m)
shows a truncated, large-scale convex-up structure, draped by tight, very high-amplitude reflectors that pass downslope into steeper inclined
reflectors. Strong across-fan seismic facies variations indicate lithological changes within this
section. The large convex-up structure is interpreted as representing the subaqueous fan deposits. The internal seismic facies is low amplitude,
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
A
27
A’
B
B’
C
C’
D
D’
E
E’
Fig. 17. Modelled 2D cross-sections, based on well data, measured logs, GPR and shear-wave seismic profiles (for
location, see Fig. 4).
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
28
J. Winsemann et al.
A
C
B
D
E
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
discontinuous and slightly hummocky (seismic
facies D, Table 2), indicating the coarse-grained,
highly scoured jet-efflux deposits of the incipient
fan. The upper part is characterized by a lenticular reflector with an internal transparent facies
(seismic facies E), interpreted as coarse-grained
channel-fill. At the western flank, the central
convex-up zone is truncated and overlain by
discontinuous to continuous concave reflector
patterns (seismic facies F), interpreted as a large
channel-fill, which can also be seen in crosssections based on well data (Fig. 17C and D).
Within this large channel-fill, some weakly
developed reflectors can be observed onlapping
the channel margin, probably indicating finergrained, well-bedded channel-margin deposits.
At the eastern flank, the truncated central zone
is overlain by a set of inclined, parallel reflectors, downlapping the basal truncation surface
(seismic facies G). These clinoforms are interpreted as delta foreset beds, exposed at the
Müller 2 pit. These clinoforms are unconformably overlain by horizontal, continuous very
high-amplitude reflectors that pass eastward into
steeply dipping reflectors (seismic facies H),
interpreted as sand-rich delta plain deposits that
pass basinward into steeply dipping delta-slope
deposits.
Tight and continuous, very high-amplitude
reflectors (seismic facies I, Table 2) overlie the
subaqueous fan and delta complex, passing into
hummocky reflectors at the western flank. The
basal subhorizontal reflectors are interpreted as
delta-plain deposits, observed at the top of the
Brinkmeyer, Edler 1 and Müller 2 pits. The
hummocky reflectors display both sheet-like and
lenticular external forms, representing delta
mouth bar deposits, which can be correlated with
GPR data from the Brinkmeyer pit (Fig. 14A). The
29
uppermost 5 to 10 m of the section represents
younger, Late Pleistocene aeolian deposits.
DEPOSITIONAL MODEL
Subaqueous fan deposits
The incipient stage of subaqueous fan deposition
of the northernmost Porta fan complex (fan complex III) is characterized by a succession of up to
20 m thick medium-grained to coarse-grained sand
and pebbly sand that erosively overlies the finegrained lake-bottom sediments. These deposits are
only recorded from well data and occur immediately downstream of the Porta Westfalica pass,
probably representing jet-efflux deposits associated with low meltwater discharges.
Coarse-grained subaqueous fan sediments,
deposited from high-energy jet-flows, overlie this
basal succession. Up to 50 m thick coarse-grained
gravel occurs within a 1 km wide NW to SEtrending central fan zone (Figs 17 and 18C),
characterized by a flat to low-angle geometry
(3 to 5). Highly scoured gravel indicates sedimentation from hyperconcentrated turbulent
flows (e.g. Mulder & Alexander, 2001), typical of
proximal jet-efflux deposits of ice-contact fans
(e.g. Russell & Arnott, 2003; Hornung et al.,
2007). This gravel facies [zone of flow transition
(ZFT)] is deposited in front of a large, up to
1Æ2 km wide and 3Æ2 km long scour or incipient
channel, indicating the most proximal erosion
and bypass area of the jet that widens and
deepens with distance downstream to the region
of maximum turbulence where it shallows,
widens and then merges with the depositional
surface (Fig. 18D). Assuming a conduit diameter
of 600 m (corresponding to the width of the Porta
Fig. 18. (A) Shapes of experimental jet-flow deposits for different Froude numbers. At high Froude numbers (>s) the
deposit approaches an elongate shape about four times longer than wide. The sediment thickness decreases in an
exponential-linear fashion downstream and in a Gaussian-like fashion across-stream (modified from Hoyal et al.,
2003). (B) Cross-plot of plan shape against Froude number where the plan-shape is calculated as the ratio of maximum length to maximum width of a specific thickness contour (0Æ5 relative thickness), modified from Hoyal et al.
(2003). (C) Thickness contours of fan complex III and outline of large flute-like scours and channels, mapped in the
subsurface. The central scour is up to 1Æ2 km wide, 3Æ2 km long and up to 25 m deep and the plan shape of the jetefflux deposits in front of the scour suggests high-energy flows with a Froude number >5. The two marginal scours
are 1Æ2 to 2Æ5 km long, 0Æ8 to 1 km wide and up to 7 to 20 m deep, indicating flow splitting and the formation of
marginal scours or incipient channels allowing new jets to develop. The deposits of the incipient fan are deeply
incised by an up to 1Æ2 km wide and up 35 m deep channel. (D) Longitudinal cross-section of the central scour or
incipient channel. The scour widens and deepens downstream and the zone of maximum turbulence (at 2Æ9 to
3Æ3 km) occurs at a distance of approximately five times the conduit diameter. (E) Longitudinal cross-section of the
western marginal scour or incipient channel. At the mouth of this shallow scour gravelly mouth bars were deposited,
indicating low-energy jet-flows. For legend see Fig 17.
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
30
J. Winsemann et al.
Westfalica pass) the zone of maximum turbulence
(Fig. 18D; 2Æ9 to 3Æ2 km) occurs at a distance of
approximately five times the conduit diameter,
matching well the results from theoretical and
experimental jet-flow models (four to eight conduit diameters, e.g. Powell, 1990; Hoyal et al.,
2003; Russell & Arnott, 2003; and references cited
therein). Flows with high Froude numbers would
have the turbulent energy to erode rapidly and
deeply into the underlying sediments and subsequently resediment this material as poorly sorted
massive gravel with large intraclasts. Rapid
downflow evolution from hyperconcentrated flow
dispersions to more fluidal flow conditions is
indicated by the lateral transition from massive
gravel to cross-stratified gravel which occurred
approximately 700 m downflow of the zone of
maximum turbulence. The strong facies variation
perpendicular to the flow, which can be observed
in the basal section of the Brinkmeyer and Edler 2
pit, is attributed to the across-stream velocity
decrease of a jet-flow (e.g. Hoyal et al., 2003). The
zone of flow transition has a similar scaling
relationship as the zone of flow establishment
(e.g. Russell & Arnott, 2003) and should be about
3Æ2 km long, corresponding to the length of the
gravel ridge south of the central scour (2Æ7 km).
Deposits of the zone of established flow are not
exposed in the central fan zone and probably
have been deposited further basinward (‡15
diameter). Figure 18B shows the shapes of experimental jet-flow deposits for different Froude
numbers (Hoyal et al., 2003). At high Froude
numbers (>5), the deposit approaches an elongate
shape about four times longer than it is wide. The
plan shape is calculated as the ratio of maximum
length to maximum width of a specific thickness
contour (0Æ5 relative thickness). The plan shape of
the central zone of the Porta complex indicates a
Froude number of >5. However, the estimation of
the Froude number is rather approximate because
the exact ratio of maximum length to maximum
width of a specific thickness contour cannot be
determined.
The central fan zone is flanked by two marginal
gravel lobes, trending SW to NE and WSW to ENE
(Figs 17 and 18). These marginal fan zones are
characterized by 1Æ3 to 2Æ5 km long scours that are
0Æ8 to 1 km wide and 7 to 20 m deep, indicating
flow splitting and the formation of marginal scour
or incipient channels allowing new jets to
develop (cf. Van Wagoner et al., 2003). In front
of the shallow (<7 m) marginal SW to NE-trending scour (Groh and Heesen pits; Figs 3, 18C and
E) gravelly mouth bar deposits (FA1Æ2) are
exposed, representing low-energy jet-efflux
deposits (e.g. Powell, 1990). The low area between
the elevated gravel ridges is filled with gently
dipping large-scale cross-stratified sand (FA1Æ3;
Fig. 17). Flow experiments by Van Wagoner et al.
(2003) show that maximum deposition occurs in
the region of maximum kinetic energy dissipation
and a roughly triangular, superelevated region
forms at the distal end of the bedform field.
Ultimately, optimization requires the flow to split
around the elevated region. In response to continued aggradation, small jets develop at the periphery of these bar-like deposits and their deposits
fill in the low areas adjacent to the original superelevated regions, locally raising the depositional
surface. The deposits of this incipient fan are
deeply incised by an up to 1Æ2 km wide and up to
35 m deep channel (Figs 16 to 18). Deposits are
characterized by a flat to low-angle, distally steepening geometry (3 to 10). Highly scoured gravel
and sand, including antidunes and 3D dunes,
indicate sedimentation from turbulent flows (e.g.
Mulder & Alexander, 2001). Parts of the downflow
succession are in accordance with facies assemblages previously described for deposition under
hydraulic-jump conditions during flow expansion
(Gorell & Shaw, 1991; Russell & Arnott, 2003;
Hornung et al., 2007). The dimensions of this large
fan channel could indicate a catastrophic drainage
event associated with an abrupt lake-level fall (e.g.
Powell, 1990; Sharpe & Cowan, 1990). Flow expansion at the mouth of this large channel would give
rise to the formation of highly scoured large-scale
cross-stratified gravel and pebbly sand and unconfined sandy dune fields, characterized by steepening bed geometries (e.g. Morris et al., 1998).
Delta deposits
The subaqueous fan subsequently became overlain
by delta deposits. Gilbert-type deltas are exposed
east of the truncated central fan zone (Müller and
Hainholz pits) and are characterized by steep delta
foreset beds, deposited from cohesionless debris
flows and high-density to low-density turbidity
currents (FA2Æ1 to FA2Æ3). At the Hainholz pit very
coarse-grained delta foreset beds (29 to 35)
suggest a steep delta slope where the sediment
avalanched downslope as debris flows and was
stopped by freezing when the slope diminished
(e.g. Nemec, 1990; Ashley, 1995; Lønne, 1995;
Nemec et al., 1999). Flows overpassed the fan
surface and were progressively partitioned, or split
into multiple channels over time. At the mouths of
these distributary channels, terminal sand-rich
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
31
D
Fig. 19. Depositional model of fan
complex III. (A) The incipient fan is
characterized by up to 20 m thick
medium-grained to coarse-grained
sand and pebbly sand representing a
period of low meltwater discharge.
This basal succession is overlain by
coarse-grained jet-efflux deposits
(FA1Æ1, FA1Æ2). In response to continued aggradation, smaller jets
developed at the periphery of these
bar-like deposits. These jets and
their deposits (FA1Æ3) filled in the
low areas adjacent to the original
superelevated regions, locally
raising the depositional surface.
(B) A dramatic lake-level fall
probably triggered a catastrophic
drainage event, leading to the
truncation of the subaqueous fan
and incision of a deep channel.
(C) Formation of mass-flow dominated Gilbert-type deltas on the
truncated fan margin. (D) A second
strong lake-level fall led to the deep
truncation of these Gilbert-type
deltas. Subsequently a delta system
formed in a shallower, lower energy
setting, associated with the formation of a larger delta plain. The
vertical transition from delta plain
to delta mouth bar deposits
indicates drowning of the delta
plain and aggradation within
increasing accommodation space
during lake-level rise.
C
B
A
lobes formed. The GPR profiles at the Müller 2 pit
(Fig. 14A) show characteristic convex-up reflector
patterns (ca 30 to 35 m wide and 3 to 4 m thick),
interpreted as delta lobes (e.g. Postma & Cruickshank, 1988; Nemec et al., 1999). Large concaveup reflectors (ca 60 m wide and 4 m deep)
represent vertically stacked distributary channels.
These coarse-grained mass-flow dominated delta
deposits could be mapped over an altitude range of
82 to 132 m a.s.l. and are unconformably overlain
by finer-grained delta deposits, exposed over an
altitude range of 99 to 124 m a.s.l. At the Hainholz
pit, the coarse-grained delta foreset deposits are
deeply truncated and overlain by sandy low-angle
to medium-angle delta foreset and toeset beds (5
to 20). Sedimentation occurred mainly from
quasi-steady turbulent density flows or diluted
cohesionless debris flows, creating small fanshaped delta lobes on the delta front. A deep
truncation of older delta deposits can also be
observed in the seismic profile north of the Müller
2 pit, pointing to a rapid lake-level fall (e.g. Muto &
Steel, 2004; Ritchie et al., 2004). Subsequently, a
new delta system formed in a shallower, lowerenergy setting, associated with the formation of a
larger delta plain (cf. Prior & Bornhold, 1990;
Ashley, 1995). The stacking pattern of these delta
deposits is progradational to aggradational
(Fig. 16) which is characteristic of deposition
during lake-level lowstand and early lake-level
rise (e.g. Ritchie et al., 2004). The vertical transition from delta plain to delta mouth bar deposits
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
32
J. Winsemann et al.
indicates drowning of the delta plain and aggradation within increasing accommodation space
during continued lake-level rise (e.g. Chough &
Hwang, 1997).
DISCUSSION
The depositional model shows that each facies
association is formed by a specific combination of
depositional processes, and has a specific geometry, which can be best explained in terms of a
jet-efflux subaqueous fan and Gilbert-type delta
model. The sedimentation of the basal sandy
subaqueous fan deposits reflects a period of low
meltwater discharge. Overlying thick, highly
scoured gravelly and sandy fan deposits indicate
high-energy flows associated with high discharges (e.g. Powell, 1990; Lønne, 1995), probably
representing short-lived flood events rather than a
seasonal steady-state meltwater regime (e.g.
Sharpe & Cowan, 1990). The inferred rapid
aggradation of these deposits indicates deposition
in a relatively deep subaqueous environment
unconstrained by base-level or accommodation
space (e.g. Russell & Arnott, 2003) and is therefore associated with the supposed lake-level
highstand of 175 to 190 m a.s.l.
The incipient fan deposition is characterized by
high-energy jet-flows, forming bar-like deposits in
front of large, up to 1Æ2 km wide, 3Æ2 km long and
25 m deep, scours or channels, indicating the most
proximal erosion and bypass area of the jet. The
extensive scouring of the central fan zone gravel is
consistent with the strong vortices that characterize the hydraulic jump zone in a supercritical jet
with jump (Hornung et al., 2007), although the
spatial scaling relationship may indicate a planewall jet without hydraulic jump (e.g. Russell &
Arnott, 2003). The central scour subsequently
became filled by lower-energy flows and, in
response to continued aggradation, smaller jets
developed at the periphery of these bar-like deposits and filled in the low areas adjacent to the
original superelevated regions, locally raising the
depositional surface (Figs 17, 18 and 19A).
The incision of an up to 1Æ2 km wide and 35 m
deep channel into the evolving fan is attributed to
a catastrophic drainage event, probably related to
a lake outburst and dramatic lake-level fall
(Fig. 19B). The level of glacial Lake Weser must
have partly controlled the potentiometric surface
by acting as a base level for water stored in and
under the Early Saalian ice sheet. High water
levels in glacial Lake Weser caused a relatively
high potentiometric surface in the ice sheet. A
rapid lake level fall would have produced steeper
hydraulic gradients near the ice margin. A drop in
lake level may therefore have triggered a catastrophic drainage event (e.g. Powell, 1990; Sharpe
& Cowan, 1990; Fisher et al., 2002). The truncation of the subaqueous fan and formation of this
large and deep channel corresponds to the formation of an incised valley in the Emme delta,
indicating a lake-level fall in the range of 40 to
60 m to 135 m a.s.l. (Winsemann et al., 2004).
Further evidence for this catastrophic lake outburst comes from subsurface data south-west of
the Teutoburger Wald Mountains (Fig. 1B) where,
in front of the 135 and 155 m lake outlets, up to
1 km wide and more than 25 m deep channels are
incised into the bed rock and older Quaternary
deposits and are now infilled with glaciolacustrine mud, coarse-grained meltwater and fluvial
deposits (Lenz, 2003; Dölling, 2005). The size and
depth of these incised channels are comparable
with valleys that formed proglacially during
major meltwater outbursts (e.g. Kehew, 1993).
Lenz (2003) reported the occurrence of a 20 m
deep ‘hole’ at the channel bed immediately southwest of the 155 m (135 m) outlet (Fig. 1B), probably indicating the formation of a large plunge
pool and providing evidence for extreme palaeoflows (e.g. Baker, 2002; Fisher & Russell, 2005).
The downcutting of the 155 m outlet to 135 m
a.s.l. is therefore attributed to this outburst event.
After this catastrophic lake-level fall coarsegrained mass-flow dominated deltas formed at
the truncated fan margin (Figs 17 and 19C),
mapped over an altitude range of 82 to 132 m
a.s.l. The deep truncation of these delta deposits
indicates a further catastrophic lake-level fall in
the range of 30 to 40 m (Figs 12, 16 and 19D),
probably related to the opening of the 95 m outlet
at the Teutoburger Wald Mountains (Fig. 1B).
Subsequently, sand-rich deltas formed that were
dominated by tractional flows, pointing to shallower water depth and the formation of a larger
delta plain (e.g. Bornhold & Prior, 1990; Ashley,
1995) that became drowned during a new lakelevel rise (Fig. 19D).
The observed abrupt lake-level falls must have
been caused by the rapid opening of lake outlets
at the south-western lake margin (Fig. 1B). Glaciers terminating in deep water potentially are
unstable and vulnerable to catastrophic retreat by
rapid calving. Field data indicate that the ice-lobe
was thin and unstable (Skupin et al., 2003),
probably characterized by low basal shear stress
values (cf. Colman et al., 1994). Ice margin
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
stability is therefore favoured by the presence of
pinning points or constrictions in the enclosing
lake basin. Such constrictions in the valley
occupied by a glacier reduce losses by calving
and, if the calving rate is less than the ice flux, the
glacier will thicken and stabilize. However,
where the bed slopes towards the ice-margin, a
small increase in ice thickness will initiate an
unstable advance into shallowing water. If the
glacier then pulls back from a pinning point into
deeper water, the calving rate may exceed the ice
flux and rapid retreat will result. Such ice masses
with beds largely lying well below lake-level
potentially are sensitive to increases in lake level,
which could accelerate calving and initiate catastrophic retreat (e.g. Thomas, 1979). The western
ice-lobe had an ice thickness of <200 m (Skupin
et al., 2003) -probably 120 to 180 m (Seraphim,
1972; Thome, 1983). The water depth required for
initial flotation would have been 110 to 160 m,
corresponding to the lake-level highstand of
190 m. Collapse of the ice-lobe then led to a
catastrophic ice retreat and the opening of the 155
and 135 m lake outlets. The longitudinal profile
of the Valley between the Wiehengebirge
Mountain and Teutoburger Wald Mountain
ranges has a convex-up geometry. From the
drainage divide (77 m a.s.l.), located north-west
of the 135 m lake outlet (Fig. 1B) the valley slopes
down westward (towards the former ice-margin)
to an altitude of 30 m a.s.l. and eastward (away
from the ice-margin) to an altitude of 50 m. This
drainage divide acted as a pinning point and
favoured ice re-stabilization after the first catastrophic ice-lobe retreat. Subsequently, the icelobe pulled back from the pinning point into
deeper water, leading to a further rapid ice-lobe
retreat and opening of the 95 m outlet channel
(Fig. 1B).
CONCLUSIONS
Abrupt lake-level changes controlled the morphology and internal architecture of the Porta
subaqueous fan and delta complex that was
deposited on a time scale of seventh-order and
eighth-order high-frequency cycles (101 to
102 years). The depositional model shows that
the incipient fan deposition is characterized by
high-energy jet-flows, forming bar-like deposits in
front of large, up to 1Æ2 km wide, 3Æ2 km long and
25 m deep scours or incipient channels, indicating the most proximal erosion and bypass area of
jet-flows that widens and deepens with distance
33
downstream to the region of maximum turbulence [zone of flow establishment (ZFE)]. The
largest scour is recorded from the central fan zone
where the zone of maximum turbulence is
300 m long and occurs at a distance of approximately five times the conduit diameter (2Æ9 to
3Æ2 km), matching well the results from theoretical and experimental jet-flow models. Sediments
deposited in front of this large central scour [zone
of flow transition (ZFT)] consist of clast to matrixsupported lenticular massive and planar crossstratified granule to cobble-sized gravel with
boulder clusters and large unconsolidated sand
or diamicton clasts passing downflow into highly
scoured planar cross-stratified gravel (700 m
downflow of the zone of maximum turbulence).
The ZFT is probably about 2Æ7 km long and the
elongate plan-shape of the deposits indicates a
high Froude number of >5. Subsequent flowsplitting led to the formation of shorter and
shallower jet-flow scours or incipient channels
and the deposition of gravelly mouth bar deposits. In response to continued aggradation, smaller
jets developed at the periphery of these bar-like
deposits and filled in the low areas adjacent to the
original superelevated regions, locally raising the
depositional surface. Deposits of this stage of fan
evolution are characterized by large-scale trough
cross-stratified sand and pebbly sand. The incision of an up to 1Æ2 km wide and 35 m deep
channel into the evolving fan is attributed to a
catastrophic drainage event, probably related to
an abrupt lake-level fall in the range of 40 to 60 m.
At the mouth of this channel, highly scoured jetefflux deposits formed under hydraulic jump
conditions, characterized by a low-angle, distally
steepening geometry and a gradual facies change
in flow direction from scoured normally graded
and planar cross-stratified gravel to large-scale
trough cross-stratified sand and pebbly sand,
diffusely planar-parallel stratified sand and
large-scale trough cross-stratified sand. The truncated fan subsequently became overlain by delta
deposits recording a further catastrophic lakelevel drop in the range of 30 to 40 m. The first
generation of deltas is characterized by steep and
coarse-grained delta foreset beds, deposited from
cohesionless debris flows and high to low-density
turbidity currents, indicating a steep high-energy
setting. These delta deposits are unconformably
overlain by finer-grained delta sediments, deposited mainly from tractional flows and representing a shallower, lower energy setting and the
formation of a larger delta plain. The vertical
transition from delta plain to delta mouth bar
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
34
J. Winsemann et al.
deposits indicates drowning of the delta plain
and aggradation within increasing accommodation space during a new lake-level rise.
ACKNOWLEDGEMENTS
Well data were generously supplied by the Brinkmeyer Kieswerk GmbH & Co. KG., E.ON Westfalen
Weser AG, Geologischer Dienst NRW (Krefeld),
and LBEG (Hannover). S. Cramm, S. Grüneberg,
W. Rode and D. Vogel carried out the seismic
survey and T. Meyer helped with field mapping.
We would like to thank D. Le Heron for commenting on an earlier version of the manuscript and
J. Reid for improving the English. Many thanks are
also due to T. Beilecke, D. Henningsen, H. Preuss,
H. Röhm, P. Rohde, K. Skupin and P. Süss for
discussion. The comments of reviewers T. Brennand, J. Piotrowski, and Associate Editor N. Eyles
are greatly appreciated and helped to improve the
manuscript.
REFERENCES
Alexander, J., Bridge, J.S., Cheel, R.J. and Leclair, S.F. (2001)
Bedforms and associated sedimentary structures formed
under supercritical water flows over aggrading sand beds.
Sedimentology, 48, 133–152.
Allen, J.R.L. (1982) Sedimentary structures: their character
and physical basis. Dev. Sedimentol., 30, 1–679.
Ashley, G.M. (1995) Glaciolacustrine environments. In: Modern Glacial Environments (Ed J. Menzies), pp. 417–444.
Butterworth-Heinemann, Oxford.
Asprion, U. and Aigner, T. (1999) Towards realistic aquifer
models: three-dimensional georadar surveys of Quaternary
gravel deltas (Singen Basin, SW Germany). Sed. Geol., 129,
281–297.
Baker, V.R. (2002) The study of superfloods. Science, 295,
2379–2380.
Beilecke, T., Polom, U. and Hoffmann, S. (2006) Efficient High
Resolution Subsurface Shear Wave Reflection Imaging in
Sealed Urban Environments. Extended Abstract. EAGE Near
Surface 2006 Conference & Exhibition, Helsinki, Finland, 5
pp.
Bornhold, B.D. and Prior, D.B. (1990) Morphology and sedimentary processes on the subaqueous Noeick River delta,
British Columbia, Canada. In: Coarse-Grained Deltas (Eds
A. Colella and B.D. Prior), Spec. Publ. Int. Assoc. Sediment.,
10, 169–181.
Bouma, A. (1962) Sedimentology of some Flysch Deposits.
A Graphic Approach to Facies Interpretation. Elsevier
Publications, Amsterdam, 168 pp.
Brennand, T.A. (1994) Macroforms, large bedforms and
rhythmic sedimentary sequences in subglacial eskers,
south-central Ontario: implications for esker genesis and
meltwater regime. Sed. Geol., 91, 9–55.
Bridge, J.S. (1993) Description and interpretation of fluvial
deposits: a critical evaluation. Sedimentology, 40, 801–810.
Brookfield, M.W. and Martini, I.P. (1999) Facies architecture
and sequence stratigraphy in glacially influenced basins:
basic problems and water-level/glacier input-point controls
(with an example from the Quaternary of Ontario, Canada).
Sed. Geol., 123, 183–197.
Carling, P.A. (1990) Particle over-passing on depth-limited
gravel bars. Sedimentology, 37, 345–355.
Carling, P.A. and Glaister, M.S. (1987) Rapid deposition of
sand and gravel mixtures downstream of a negative step: the
role of matrix infilling and particle over-passing in the
process of bar-front accretion. J. Geol. Soc. London 144,
543–551.
Cheel, R.J. (1990) Horizontal lamination and the sequence of
bed phases and stratification under upper-flow-regime
conditions. Sedimentology, 37, 517–529.
Chough, S.K. and Hwang, I.G. (1997) The Duksung fan delta,
SE Korea: growth of delta lobes on a Gilbert-type topset in
response to relative sea-level rise. J. Sed. Res., 67, 725–739.
Clark, J.D. and Pickering, K.T. (1996) Architectural elements
and growth pattern of submarine channels: application to
hydrocarbon exploration. AAPG Bull. 80, 194–221.
Colman, S.M., Clark, J.A., Clayton, L., Hansel, A.K. and Larsen, C.E. (1994) Deglaciation, lake levels, and meltwater
discharge in the Lake Michigan Basin. Quatern. Sci. Rev.,
13, 879–890.
Dölling, M. (2005) Erläuterungen zu Blatt 3915 Bockhorst.
Geol. Dienst Nordrh.-Westf., Krefeld, 198 pp.
Ehlers, J., Eissmann, L., Lippstreu, L., Stephan, H.-J. and
Wansa, S. (2004) Pleistocene glaciations of North Germany.
In: Quaternary Glaciations. Extent and Chronology Part
I: Europe (Eds J. Ehlers and P. Gibbard), pp. 135–146.
Elsevier, Amsterdam.
Fisher, T.G. and Russell, A.J. (2005) Introduction to reassessing the role of meltwater processes during Quaternary
glaciations. Quatern. Sci. Rev., 24, 2305–2307.
Fisher, T.G., Clague, J.J. and Teller, J.T. (2002) The role of
outburst floods and glacial meltwater in subglacial and
proglacial landform genesis. Quatern. Int., 90, 1–4.
Gorell, G. and Shaw, J. (1991) Deposition in an esker, bead
and fan complex, Lanark, Ontario, Canada. Sed. Geol., 72,
285–314.
Hornung, J.J., Asprion, U. and Winsemann, J. (2007) Jet-efflux
deposits of a subaqueous ice-contact fan, glacial Lake
Rinteln, northwestern Germany. Sed. Geol., 193, 167–192.
Hoyal, D.C.J.D., Van Wagoner, J.C., Adair, N.L., Deffenbaugh,
M., Li, D., Sun, T., Huh, C. and Giffin, D.E. (2003)
Sedimentation from jets: a depositional model for clastic
deposits of all scales and environments. Search and
Discovery Article no. 40082 (Online-Journal; AAPG/Datapages, Inc., 1444 South Boulder, Tulsa, OK, 74119, USA).
Johnsen, T.F. and Brennand, T.A. (2006) The environment in
and around ice-dammed lakes in the moderately high relief
setting of the southern Canadian Cordillera. Boreas, 35,
106–125.
Junge, F.W. (1998) Die Bändertone Mitteldeutschlands und
angrenzender Gebiete. Altenbg. nat. wiss. Forsch. 9, 1–210.
Kaltwang, J. (1992) Die pleistozäne Vereisungsgrenze im
südlichen Niedersachsen und im östlichen Westfalen. Mitt.
Geol. Inst. Univ. Hannover, 33, 1–161.
Kehew, A.E. (1993) Glacial-lake outburst of the Grand Valley,
Michigan, and impacts on glacial lakes in the Lake Michigan Basin. Quatern. Res., 39, 36–44.
Klostermann, J. (1992) Das Quartär der Niederrheinischen
Bucht – Ablagerungen der letzten Eiszeit am Niederrhein.
Geol. La. Nordrh.-Westf., Krefeld, 200 pp.
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
Subaqueous ice-contact fan and delta complex, Middle Pleistocene, NW Germany
Kneller, B.C. (1995) Beyond the turbidite paradigm: physical
models for deposition of turbidites and their implications
for reservoir prediction. In: Characterization of Deep-marine Clastic Systems (Eds A.J. Hartley and D.J. Prosser),
J. Geol. Soc. London Spec. Publ., 94, 31–49.
Kneller, B.C. and Branney, M.J. (1995) Sustained high-density
turbidity currents and the deposition of thick massive
sands. Sedimentology, 42, 607–616.
Lambeck, K., Purcell, A., Funder, S., Kjaer, K.H., Larsen, E.
and Möller, P. (2006) Constraints on the Late Saalian to
early Middle Weichselian ice sheet of Eurasia from the field
data and rebound modelling. Boreas, 35, 539–575.
LaRoque, A., Dubois, J.-M.M. and Leblon, B. (2003) A methology to reconstruct small and short-lived ice-dammed lakes in
the Appalachians of Southern Québec. Quatern. Int., 99–100,
59–71.
Lenz, A. (2003) Erläuterungen zu Blatt 4016 Gütersloh. Geol.
Dienst Nordrh.-Westf., Krefeld, 126 pp.
Litt, T., Behre, K.-E., Meyer, K.-D., Stephan, H.-J. and Wansa, S.
(2007) Stratigraphische Begriffe für das Quartär des
norddeutschen Vereisungsgebietes. Eisz. und Gegenw., 56,
7–65.
Lønne, I. (1995) Sedimentary facies and depositional architecture of ice-contact glaciomarine systems. Sed. Geol., 98,
13–43.
Lowe, D.R. (1982) Sediment gravity flows II: depositional
models with special references to the deposits of highdensity turbidity currents. J. Sed. Petrol., 52, 279–297.
Morris, S.A., Kenyon, N.H., Limonov, A.F. and Alexander, J.
(1998) Downstream changes of large-scale bedforms in
turbidites around the Valencia channel mouth, northwest
Mediterranean: implications for palaeoflow reconstruction.
Sedimentology, 45, 365–377.
Mulder, T. and Alexander, J. (2001) The physical character of
subaqueous sedimentary density flows and their deposits.
Sedimentology, 48, 269–299.
Mulder, T. and Cochonat, P. (1996) Classification of offshore
mass movements. J. Sed. Petrol., 66, 43–57.
Muto, T. and Steel, R.J. (2004) Autogenic response of fluvial
deltas to steady sea-level fall: Implications from flume-tank
experiments. Geology, 32, 401–404.
Nemec, W. (1990) Aspects of sediment movement on steep
delta slopes. In: Coarse-Grained Deltas (Eds A. Colella and
B.D. Prior), Spec. Publ. Int. Assoc. Sediment., 10, 29–73.
Nemec, W., Lønne, I. and Blikra, L.H. (1999) The Kregnes
moraine in Gaudalen, west-central Norway: Anatomy of a
Younger Dryas proglacial delta in a paleofjord basin. Boreas,
28, 454–476.
Plink-Björklund, P. and Ronnert, L. (1999) Depositional processes and internal architecture of late Weichselian icemargin submarine fan and delta settings, Swedish west
coast. Sedimentology, 46, 215–234.
Postma, G. and Cruickshank, C. (1988) Sedimentology of a
late Weichselian to Holocene terraced fan delta, Varangerfjord, northern Norway. In: Fan Deltas: Sedimentology
and Tectonic Settings (Eds W. Nemec and R.J. Steel),
pp. 144–157. Blackie, London.
Postma, G., Nemec, W. and Kleinspehn, K.L. (1988) Large
floating clasts in turbidites: a mechanism for their
emplacement. Sed. Geol., 58, 47–61.
Powell, R.D. (1990) Glacimarine processes at grounding-line
fans and their growth to ice-contact deltas. In: Glacimarine
Environments: Processes and Sediments (Eds J.A. Dowdeswell and J.D. Scourse), J. Geol. Soc. London Spec. Publ., 53,
53–73.
35
Prior, D.B. and Bornhold, B.D. (1990) The underwater development of Holocene fan deltas. In: Coarse-Grained Deltas
(Eds A. Colella and B.D. Prior), Spec. Publ. Int. Assoc.
Sediment., 10, 75–90.
Rausch, M. (1975) Der ‘‘Dropstein-Laminit’’ von Bögerhof und
seine Zuordnung zu den Drenthe-zeitlichen Ablagerungen
des Wesertals bei Rinteln. Mitt. geol. Inst. Univ. Hannover,
12, 51–86.
Ritchie, B.D., Gawthorpe, R.L. and Harddy, S. (2004) Threedimensional numerical modelling of deltaic depositional
sequences 1: influence of the rate and magnitude of sealevel change. J. Sed. Res., 74, 203–220.
Russell, H.A.J. and Arnott, R.W.C. (2003) Hydraulic-jump and
hyperconcentrated-flow deposits of a glacigenic subaqueous
fan: Oak Ridge Moraine, southern Ontario, Canada. J. Sed.
Res., 73, 887–905.
Seraphim, E.T. (1972) Wege und Halte des saalezeitlichen
Inlandeises zwischen Osnig und Weser. Geol. Jb., Reihe A,
3, 1–85.
Shanmugam, G. (2000) 50 years of the turbidite paradigm
(1950s–1990s): Deep-water processes and facies models – a
critical perspective. Mar. Petrol. Geol., 17, 285–342.
Sharpe, D.R. and Cowan, W.R. (1990) Moraine formation in
northwestern Ontario: product of subglacial fluvial and
glacilacustrine sedimentation. Can. J. Earth Sci., 27, 1478–
1486.
Skupin, K., Speetzen, E. and Zandstra, J.G. (2003) Die Eiszeit
in Nordost-Westfalen und angrenzenden Gebieten Niedersachsens. Geologischer Dienst Nordrhein-Westfalen, Krefeld,
96 pp.
Sohn, Y.K. and Son, M. (2004) Synrift stratigraphic
geometry in a transfer zone coarse-grained delta complex,
Miocene Pohang Basin, SE Korea. Sedimentology, 51, 1387–
1408.
Sohn, Y.K., Kim, S.B., Hwang, I.G., Bahk, J.J., Choe, M.Y. and
Chough, S.K. (1997) Characteristics and depositional processes of large-scale gravelly Gilbert-type foresets in the
Miocene Dousan fan delta, Pohang Basin, SE Korea. J. Sed.
Res., 67, 30–141.
Sohn, Y.K., Choe, M.Y. and Jo, H.R. (2002) Transition from
debris flow to hyperconcentrated flow in a submarine
channel (the Cretaceous Cerro Toro Formation, southern
Chile). Terra Nova, 14, 405–415.
Southard, J.B. and Boguchwal, L.A. (1990) Bed configurations
in steady unidirectional water flow part 2. Synthesis of
flume data. J. Sed. Petrol., 60, 658–679.
Spethmann, H. (1908) Glaziale Stillstandslagen im Gebiet der
mittleren Weser. Mitt. Geogr. Ges. Lübeck, 22, 1–17.
Teller, J.T. (1995) History and drainage of large ice-dammed
lakes along the Laurentide Ice Sheet. Quatern. Int., 28, 83–
92.
Thomas, R.H. (1979) Ice shelves: a review. J. Glaciol., 24, 273–
286.
Thomas, G.S.P. and Connell, R.J. (1985) Iceberg drop, dump
and grounding structures from Pleistocene glaciolacustrine
sediments, Scotland. J. Sed. Petrol., 55, 243–249.
Thome, K.N. (1983) Gletschererosion und –akkumulation im
Münsterland und angrenzenden Gebieten. Neues Jb. Geol.
Paläontol. Abh., 166, 116–138.
Van Wagoner, J.C., Hoyal, D.C.J.D., Adair, N.L., Sun, T.,
Beaubouef, R.T., Deffenbaugh, M., Dunn, P.A., Huh, C. and
Li, D. (2003) Energy dissipation and the fundamental shape
of siliciclastic sedimentary bodies. Search and Discovery
Article no. 40080 (Online-Journal; AAPG/Datapages, Inc.,
1444 South Boulder, Tulsa, OK, 74119, USA).
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology
36
J. Winsemann et al.
Walker, R.G. (1975) Conglomerates: sedimentary structures
and facies models. In: Depositional Environments as Interpreted from Primary Sedimentary Structures and Stratification Sequences (Eds J.C. Harms, R.G. Walker and
D. Spearing). SEPM Short Course Lecture Notes 12, 133–161.
Wellmann, P. (1998) Kies-/Sandkörper im Wesertal zwischen
Rinteln und Porta Westfalica. Mitt. Geol. Inst. Univ. Hannover, 38, 203–212.
Winsemann, J., Asprion, U., Meyer, T., Schultz, H. and Victor,
P. (2003) Evidence of iceberg ploughing in a subaqueous
ice-contact fan, glacial Lake Rinteln, Northwest Germany.
Boreas, 32, 386–398.
Winsemann, J., Asprion, U. and Meyer, T. (2004) Sequence
analysis of early Saalian glacial lake deposits (NW Germany): evidence of rapid local ice margin retreat and related
calving processes. Sed. Geol., 165, 223–251.
Winsemann, J., Asprion, U. and Meyer, T. (2007) Lake-level
control on ice-margin subaqueous fans, glacial Lake Rinteln.
In: Glacial Processes and Products (Eds M. Hambrey,
P. Christoffersen, N. Glasser and B. Hubbard), Int. Assoc.
Sed. Spec. Publ., 39, 121–148.
Manuscript received 19 November 2007; revision
accepted 19 August 2008
2009 The Authors. Journal compilation 2009 International Association of Sedimentologists, Sedimentology