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Sedimentary Geology 165 (2004) 223–251
Sequence analysis of early Saalian glacial lake deposits
(NW Germany): evidence of local ice margin retreat
and associated calving processes
Jutta Winsemann*, Ulrich Asprion, Thomas Meyer
Institut fur Geologie und Palaontologie, Universitat Hannover, Callinstrabe 30, Hanover D-30167, Germany
Abstract
This paper presents a detailed analysis of high-resolution facies architecture of glaciolacustrine ice-margin deposits, which
formed at the southern margin of the Scandinavian ice shield. The ice margin depositional systems are characterised by coarse-
grained deltas and subaqueous fans, which are formed by stacked transgressive–regressive sequences, recording an overall lake
transgression, interrupted by minor short-term lake-level falls. The delta complexes at the northern margin of glacial Lake
Rinteln are thought to reflect a relatively stable position of the ice margin in front of the Weser Chains mountain ridges. The
onset of delta progradation probably represents a halt in ice advance and a related high sediment supply period. The sedimentary
facies and depositional architecture resemble those of nonglacial Gilbert-type deltas, except for the deposition of glacial debris.
The main delta progradation is recorded from the highstand systems tract, when high meltwater and sediment discharge
occurred during the melt season. A forced regression during opening of outlets led to the formation of subaerially exposed
sequence boundaries and the erosion of the highstand systems tract. Deeply incised channels (incised valleys) were filled during
the subsequent transgression.
At the eastern lake margin, subaqueous fan deposits reflect an unstable ice-front that was rapidly retreating and subject to
periodic calving, which resulted in the generation of floating icebergs, dumping ice-rafted debris and ploughing into subaqueous
fan deposits. The rapid retreat of this eastern ice margin is interpreted to result from the overall lake-level rise.
The fan-stacking pattern and bulk geometry were determined by the ice-front fluctuations, the shifting of meltwater outlets and
the short-term lake-level fluctuations. Depositional processes reflect the character of sediment supply and distance from the ice
margin. Ice-proximal upper-fan deposits are characterised by coarse-grained gravel, deposited by debris flows that document
continuous discharge. Slump and slide deposits are related to steep depositional slopes. Themid-fan contains basinward fining and
thinning deposits of quasi-steady and surge-type high- and low-density turbidity currents, indicating more ice-distal and periodic
deposition. The outer-fan deposits mainly consist of surge-type low-density turbidites and glacial debris dumped by icebergs.
The forcing parameters governing the development of depositional sequences in both delta and fan settings were lake-level
fluctuations, sediment yield rates and physiography. The depositional sequences were deposited on a time scale of seventh- and
eighth-order high-frequency cycles (101–102 years). In this short time span, lake-level fluctuations were on the order of 120 m;
therefore, accommodation space was largely controlled by lake level and subsidence can be ignored.
D 2004 Elsevier B.V. All rights reserved.
Keywords: Pleistocene; Glaciolacustrine deposits; Subaqueous ice-contact fan; Gilbert-type deltas; Sequence stratigraphy; Ice scour
0037-0738/$ - see front matter D 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.sedgeo.2003.11.010
* Corresponding author.
E-mail address: [email protected] (J. Winsemann).
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251224
1. Introduction
Glaciolacustrine ice-margin deposits are important
and well-studied palaeogeographic and palaeoclimatic
archives and record the history and dynamics of
glacier termini in lacustrine basins (Ashley et al.,
1985; Eyles and Clark, 1988; Fyfe, 1990; Mastalerz,
1990; Postma, 1990; Brodzikowski and Van Loon,
1991; Ashley, 1995; Martini and Brookfield, 1995;
Lemons and Chan, 1999). Glaciolacustrine ice-contact
systems are rather complex depositional settings and
only a few studies include detailed analysis of high-
resolution facies architecture (e.g. Clemmensen and
Houmark-Nielsen, 1981; Martini, 1990; Mastalerz,
1990; Martini and Brookfield, 1995; Sadolin et al.,
1997).
Early Saalian glacial lake deposits are widespread
in northern Germany and have been deposited in
glacial lakes at the southern margin of the Scandina-
vian ice shield. The ice margin depositional systems
Fig. 1. Location map of the study area in NW Germany and a palaeogeogra
grained delta and subaqueous fan systems.
are characterised by coarse-grained deltas or subaque-
ous fans, which are formed by stacked transgressive–
regressive sequences. Glacial Lake Rinteln, first
named by Spethmann (1908), is located south of the
Weser Chains in northwest Germany (Fig. 1). Various
coarse-grained deltas and subaqueous fans were built
out into this lake. Deltas were fed by proglacial
streams discharging from the ice margin into the lake.
Glaciofluvial detritus carried to the lake via tunnels
near or at the base of the ice formed subaqueous fan
deposits well below the surface of the lake (Winse-
mann and Asprion, 2001; Winsemann et al., 2003).
During its initial stage, glacial Lake Rinteln stood at c.
55 m a.s.l. The lake level rose some 120 m to form a
high water surface at c. 175 m a.s.l (Fig. 2). The lake-
level rise was very fast and probably took place within
a few tens to a hundred years, inferred from varve
deposits in the basin centre. The reconstructed lake-
level curve shows minor lake-level falls, which are
interpreted by seasonal variations of water discharge
phic reconstruction of the glacial Lake Rinteln and associated coarse-
Fig. 2. Reconstructed lake level curve of glacial Lake Rinteln
(modified after Jarek, 1999; Winsemann and Asprion, 2001).
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 225
or drainage of the lake by the opening of outlets
(Jarek, 1999; Winsemann and Asprion, 2001).
This paper presents a detailed analysis of high-
resolution facies architecture of glaciolacustrine ice-
margin deposits of the glacial Lake Rinteln. These
subaqueous ice-margin deposits are well exposed in
sand and gravel pits and have previously been de-
scribed by several authors who generally assumed a
subaerial formation (Naumann, 1922, 1927; Grupe,
1925, 1930; Naumann and Burre, 1927; Stach, 1930;
Grupe et al., 1933; Luttig, 1954, 1960; Attig, 1965;
Wortmann, 1968; Miotke, 1971; Seraphim, 1972,
1973; Hesemann, 1975; Rausch, 1977; Merkt, 1978;
Deutloff et al., 1982; Rohm, 1985; Wortmann and
Wortmann, 1987; Rakowski, 1990; Wellmann, 1990,
1998; Groetzner, 1995; Deters, 1999). The origin and
significance of these deposits are discussed and relat-
ed to glacier termini dynamics and associated calving
events.
2. Sequence stratigraphy in glacially influenced
basins
Sequence stratigraphy is a well-established tool for
correlating sedimentary successions and has been
widely used in marine and lacustrine basins (Posa-
mentier and Vail, 1988; Van Wagoner et al., 1988,
1990; Posamentier et al., 1992; Lemons and Chan,
1999). The Emme delta and Coppenbrugge subaque-
ous fans were deposited on a time scale of seventh- and
eighth-order high-frequency cycles (101–102 years).
In this short time span, lake-level fluctuations were on
the order of 120 m; therefore, accommodation (space
made available for potential sediment accumulation;
cf. Jervey, 1988) was largely controlled by lake level
and subsidence can be ignored.
Only a few studies have been carried out using
sequence stratigraphy in glaciolacustrine basins (e.g.
Martini and Brookfield, 1995; Brookfield and Martini,
1999). In glacial lakes, glacier advance usually corre-
lates with lake-level changes and accommodation
space, water level and sediment injection points can
vary independently due to opposing and delayed
effects of glacial isostacy, glacial eustacy and glacial
advance and retreat (Martini and Brookfield, 1995;
Brookfield and Martini, 1999). Problems in applying
the sequence stratigraphic concepts on glacial systems
have been discussed in detail by Brookfield and
Martini (1999). Accommodation space and sediment
injection points in glacial basins are controlled not
only by relative water level, but also by the position of
the front of the glacier. During high water levels, the
glacier injection point may be underwater at the base
of the slope. During low water levels, the injection
point of the glacier may be on land. Since the lake level
is controlled by the position of drainage outlets, water
levels may change dramatically, abruptly and indepen-
dently of the glacial input point. The basin can empty
or fill with water rapidly, with only slight changes in
glacier position. In this case, accommodation space
has no relation to the glacier injection point.
In ‘‘lake-level systems’’ (cf. Brookfield andMartini,
1999), deposition is controlled by water level and
sediment supply from streams in the same way as lake
level controls deposition in conventional sequence
stratigraphy since the sediment input point is a shore-
line. Thus, within one lake basin, sequence stratigraphy
needs little modification, although water-level changes
may be more abrupt and of greater magnitude. In the
‘‘glacier input-point system’’ (cf. Brookfield and Mar-
tini, 1999), deposition is controlled by the sediment
input point at or near the end of the glacier. If the glacier
terminates on land, then the sequences are basically
controlled by lake-level systems. But if the glacier
terminates underwater, then the position of the sedi-
ment input point can fluctuate independently of lake
level. In the Exxon model, a relatively rising water
level corresponds to maximum flooding surfaces cul-
minating in highstand systems tracts, and relatively
dropping water levels correspond to unconformities
culminating in lowstand systems tracts. But rising lake
levels often correspond with glacial advances into a
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251226
basin, as the glacier isostatically depresses the land and
blocks drainage outlets. This causes a shift in the locus
of proglacial sedimentation to deeper waters and cor-
responds to the lowstand fans of the Exxon model.
Thus, lowstand systems tracts for the glacier input point
system correlate with highstand systems tracts for
deltas of the water-level system and there, input points
fluctuate independently. It is thus essential to keep
systems controlled by relative water levels and glacier
input points separate.
Where glaciers terminate on land, standard Exxon
sequence stratigraphy can easily be applied to adja-
cent lakes. In such cases, the sediment injection point
in the basin is directly related to water level. The basal
sequence boundary of the lake-level system forms as
lake level drops during glacier retreat, when outlets
are opened. Unblocking these outlets may cause
catastrophic drainage and almost instantaneous and
very large irregular drops in lake level. Thus, each
lake-level sequence will probably start and end with
very marked erosional surfaces and incised valleys of
type 1 sequence boundaries (Posamentier and Vail,
1988). The lowstand systems tract of the lake-level
system develops during and after the drop in lake
level, and in some places, deep incised valleys may be
cut through the delta plain and lowstand fans may
develop at the end of these valleys. The transgressive
systems tract marks a rise in relative water level due to
glacier advance causing blocking of drainage outlets.
Condensed fine-grained sediments may abruptly over-
lie the lowstand wedges and fill any valleys incised
during lowstand. Diamict slumps, stream or shoreline
sands may mark the transgression in incised valleys
passing upwards into increasingly distal rhythmites.
The highstand systems tract corresponds with the
maximum height of the lake. During this equilibrium
phase in glacier development, sediment supplied from
glaciers may build out deltas in places, separated by
areas dominated by continued condensed sedimenta-
tion with ice-rafted debris.
Where glaciers terminate underwater, sediment in-
put points can fluctuate independently of lake level.
Sediment may be supplied in by subglacial, englacial
or supraglacial meltwater flows at the ice front and by
rainout from a floating glacier. According to Brook-
field and Martini (1999), the sequence boundaries and
systems tracts for this glacier input-point systems
equate entirely with the lake-level highstand. Keeping
the lake level at highstand, input points of the glacier
system vary according to the position and nature of the
ice front. As a glacier retreats out of the basin, a series
of retreating fining-upwards subaqueous fans forms.
The resulting fining-upwards section would normally
be interpreted as a transgressive systems tract caused
by rising relative water levels. The sequence boundary
of this input-point sequence is the ice-scoured uncon-
formity, and its top (which looks like the maximum
flooding surface) is simply the sediment-starved area
furthest from the ice-front. When the glacier readvan-
ces into the basin, it may deposit a coarsening-upwards
subaqueous outwash section capped by an erosion
surface. Sequence boundaries of lake-level systems
therefore may correlate with glacial retreat deposits in
glacier input-point systems, and sequence boundaries
of the glacier input system may correlate with trans-
gressive systems tracts of the lake-level system. Fur-
thermore, local fluctuating ice fronts through ice-front
calving may produce successive subaqueous fans,
overlain by thin mud drapes, which could be misinter-
preted as a glacier retreat by a rising lake level. Only
where the lake level drops below the glacier injection
point, the formed erosional surfaces (sequence bound-
ary) can be correlated with sequence boundaries of the
lake-level system.
3. Emme delta
The Emme delta complex is about 2 km long, 1.5
km wide and 70 m thick and overlies glaciolacus-
trine mud or Jurassic basement rocks, forming a
steep dipping ramp surface. The delta deposits are
exposed in various gravel pits (Fig. 3), at an altitude
of 95–165 m, which allow a detailed reconstruction
of the facies architecture. The tripartite structure of
the exposed sedimentary successions with well-de-
veloped bottomsets, foresets and topsets indicates
Gilbert-type deltas (Fig. 4). A description and inter-
pretation of lithofacies is given in Table 1. The
terminology for gravel characteristics is after Walker
(1975). The fabric notation uses symbols a and b for
the clast long axes, with indices (t) and (p) denoting
axis orientation transverse or parallel to flow direc-
tion, and index (i) denoting axis imbrication. The
notation of turbidites, Tabcd, refers to the Bouma
divisions (cf. Bouma, 1962).
Fig. 3. Location map of the open-pit outcrops of the Emme delta
complex; the topographic contour values are in metres.
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 227
3.1. Facies associations
3.1.1. Bottomsets
The bottomsets consist of 1–2.5 m thick planar
parallel-stratified granule to medium-grained sand
(F11) that pass updip into steeply inclined gravelly
foreset beds (Fig. 4C). The planar parallel-stratified
sand is interpreted to result from surge-type turbulent
low-density gravity flows (Tb), triggered by the
release of limited sediment volumes by discrete fail-
ures of the delta’s upper slope and/or brink zone. The
finer-grained, low-density parts of these currents have
apparently bypassed the delta slope and deposited
their load in the delta toe and prodelta zone. The
occurrence of scattered pebbles at the bed boundaries
is interpreted to result from coeval debris fall process-
es (Nemec et al., 1999). In the toe part of the delta
foreset, the planar parallel-stratified sand forms
mound-shaped successions, whose convex-upward
tops suggest a series of depositional lobes, similar to
those described by Postma and Cruickshank (1988)
and Nemec et al. (1999), which apparently coalesced
with one another into an aggradational ramp (Fig.
4C). The multiple delta toe and lobes suggest that the
delta was advancing by the alternating episodes of
slope-base aggradation and progradation. The toe of
the delta slope aggraded in response to the slope
steepening, causing intense sediment sloughing by
means of chutes and occasional large-scale failures
(Nemec et al., 1999).
3.1.2. Foresets
The foresets mainly consist of 5–15 m thick steeply
dipping medium- to thick-bedded matrix- and clast-
supported gravel (F7, F8), often showing an a(p) a(i)
steep-clast fabric, dipping in an upslope direction (Fig.
4F). The absence of current-produced structures and
the occurrence of steep-clast fabric suggest a steep
slope with gravity-driven sediment transport (Postma
and Cruickshank, 1988; Martini, 1990; Massari and
Parea, 1990; Nemec, 1990). The vast majority of beds
have a coarse-grained sandy matrix nearly avoid of
mud, and these debris flows were probably cohension-
less (Nemec and Steel, 1984), controlled mainly by the
sediment’s frictional strength, which would explain
their low mobility and preferential deposition on the
delta’s upper to middle slope (Nemec et al., 1999). In
dip-parallel sections, the debris-flow beds are exten-
sive and fairly tabular. Floating outsized clasts are
common and beds are often inversely graded, indicat-
ing a loss of the largest clasts from the lower, faster-
shearing and rheologically weakest part of the debris
flow (Naylor, 1980). Many beds show upslope-dip-
ping internal shears, listric or sigmoidal in shape,
marked by pebble stringers or sandy bands nearly
avoid of gravel (Fig. 4F). These features are thought
to be syndepositional thrusts. The occurrence of an
a(p) or a(i) clast fabric is attributed to laminar shear
(Nemec, 1990). Subordinate, thin- to medium-bedded
pebbly sand beds occur, which are massive or inverse-
ly graded (F9) or show normal grading or planar
parallel stratification (F10), interpreted to have been
deposited by sandy debris flows or surge-type low-
density turbidity flows, respectively (cf. Shanmugam,
2000; Nemec et al., 1999).
Sediment was supplied to the delta front by braided
glaciofluvial streams. Material that bypassed the braid
plain avalanched downslope as debris flows and
stopped by freezing when the slope diminished. The
occurrence of debris flows corresponds with the
combination of high-bedload events of fluvial dis-
charge to the delta front (Nemec, 1990; Prior and
Bornhold, 1990) or slope instability events triggered
Fig. 4. Architectural elements of the Emme delta complex. Lithofacies types (F1–11) refer to Table 1. (A) Delta foreset, unconformably overlain
by a channelised topset, Fell open pit. Note gravel lag at the base of the channel. (B) Close-up view of (A), showing large-scale trough cross-
bedding of topset channel fill (F1). (C) Coarse-grained sandy bottomset (F11), overlain by steeply dipping gravelly foreset beds (F8). The
foreset beds are dipping southwestwards and the delta toe rises in that direction, indicating aggradation of the bottomset zone during delta-front
progradation. The mound-shaped geometries of bottomset successions (arrows) suggest a series of coalescing depositional lobes; Prange open
pit. (D) Sheetlike topset facies (F5), consisting of sand, silt and mud alternations with ripple cross-lamination, Prange open pit. (E) Steeply
dipping matrix-supported gravel and pebbly sand, Fell open pit (F7). (F) Steep-clast fabric within foreset bed, indicating laminar shear during or
immediately after the flow’s stop (F8), Fell open pit.
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251228
Table 1
Lithofacies classification and architectural elements, Emme delta
Lithofacies and sedimentary structures Geometry Interpretation
Topsets
Channel deposits
F1 Pebbly sand with large-scale
trough-cross-bedding. Bed
thickness up to 2 m.
Lenticular
(5–10 m thick and
up to 70 m wide)
Bedload deposition of braided streams
F2 Medium-bedded medium- to
coarse-grained sand with
planar parallel stratification
Lenticular, up to
1.5 m thick
Bedload deposition of braided streams
F3 Clast-supported gravel with
large-scale trough cross-bedding
Lenticular, up to
0.5 m thick
Bedload deposition of braided streams
F4 Clast-supported gravel with
blocks up to 1.3 m across
Lenticular (0.5–1.5 m
thick and 70 m wide)
Gravel lag at channel floor
F5 Alternations of thin- to
medium-bedded fine- to medium-
grained sand, silt and mud with
plan parallel lamination, ripple
cross-lamination, wave-ripple
cross-lamination and dropstones
Lenticular (up to 3 m
thick and 60 m wide)
Low-energy unidirectional and oscillatory flows
with coeval dumping of ice-rafted debris.
Glaciolacustrine sedimentation in incised valley.
Interchannel deposits
F6 Thin- to medium-bedded (1–20 cm)
alternations of fine- to medium-grained
sand, silt, mud and clay with plan
parallel stratification, ripple cross-
lamination and plan-parallel lamination
Sheetlike (0.5–1 m thick,
up to 30 m wide)
Unconfined low- to high-energy
flows on delta plain
Foresets
F7 Matrix-supported gravel with normal
or inverse grading. The matrix consists
of middle- to coarse-grained sand.
Outsized clasts up to 50 cm across.
Bed thickness between 10 and 40 cm;
sharp bed contacts. Long axes of large
clasts are often oriented parallel to dip
and may show an a(p) a(i) fabric.
Wedge (5–15 m, up to
150 m long). High-angle
bedding (10–30j)
Deposition from debris flows; the steep-clast
fabric indicates laminar shear during or
immediately after the flow’s stop (Nemec, 1990)
F8 Clast-supported gravel with
normal or inverse grading. Sharp bed
contacts. Clasts up to 50 cm in diameter.
The matrix consists of middle- to
coarse-grained sand. Bed thickness
between 10 and 60 cm. Clasts often show
a steeply imbricate fabric with the a-axes
dipping in an upslope direction. Long
axes are mainly oriented parallel to dip.
Wedge (5–15 m thick,
up to 50 m long).
High-angle bedding
(10–30j)
Deposition from debris flows; the steep-clast
fabric indicates laminar shear during or
immediately after the flow’s stop (Nemec, 1990)
(continued on next page)
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 229
Lithofacies and sedimentary structures Geometry Interpretation
F9 Massive or inversely graded pebbly sand.
Bed thickness between 2 and 20 cm.
Long axes of large clasts are often
oriented parallel to dip and may show
an a(p) a(i) fabric.
Wedge (5 m thick,
up to 50 m long).
High-angle bedding
(10–20j)
Deposition from sandy debris flows
(Shanmugam, 2000)
F10 Normally graded or planar
parallel-stratified
pebbly sand. Bed thickness
between 2 and 20 cm.
Wedge (5 m thick, up
to 50 m long).
High-angle
bedding (10–20j)
Deposition from surge-type turbidity flows
(Shanmugam, 2000; Lowe, 1982)
Bottomsets
F11 Planar parallel-stratified fine- to
coarse-grained sand with scattered
pebbles. Bed thickness
between 2 and 10 cm.
Mound (0.5 m thick,
up to 5 m wide).
Horizontal to low-angle
bedding (0–3j).
Deposition from surge-type low-density
turbidity flows and coeval debris fall
(cf. Nemec et al., 1999). Mounds are interpreted
as individual depositional lobes.
Table 1 (continued)
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251230
by the shear of overriding flows or by gravity (Nemec
et al., 1999; Plink-Bjorklund and Ronnert, 1999). The
finer-grained sandy material moved to the basin floor
where it was deposited from turbidity flows.
3.1.3. Topsets
The gravelly foresets are overlain by 0.5–2 m
thick subhorizontal sheet-like sand, silt, mud alter-
nations and/or channelised sand and gravel (Fig. 4A,
B and D). The sheet-like strata show ripple cross-
lamination and planar parallel lamination/stratifica-
tion (F6), interpreted to result from unconfined low-
and high-energy flows on the delta plain. Channel-
fill deposits (F1–F5) are 5–15 m thick and up to 70
m wide and mainly consist of large-scale trough
cross-bedded and planar parallel-stratified pebbly
sand, indicative of 3-D dunes and upper flow-regime
deposits of braided glaciofluvial channels. Subordi-
nate thin- to medium-bedded sand, silt, mud alter-
nations with ripple cross-lamination, planar parallel
lamination and wave-ripple cross-lamination occur,
interpreted to result from low-energy unidirectional
and oscillatory flows. Within these fine-grained
channel deposits, occasionally, dropstones can be
observed.
3.2. Open-pit Fell section
The basal succession of the Emme delta complex is
exposed in the open-pit Fell (Fig. 3) at an altitude of c.
108–124 m (Fig. 5A and B). The lower foreset is up to
15 m thick and can be traced laterally for about 150 m.
Individual foreset beds are 10–60 cm thick and
remarkably constant in thickness along dip. The beds
consist of matrix- or clast-supported sandy gravel,
which are massive or show inverse or normal grading
(F7, F8). Outsized clasts often show an upslope
dipping steep-clast fabric, interpreted to result from
laminar shear (Nemec, 1990). Bed contacts are usually
sharp. The foreset beds steeply dip (18–30j) into
westerly directions. This foreset is unconformably
overlain by a c. 7-m-thick foreset, dipping (10j–20j) into southerly directions. Foreset beds are 2–20
cm thick and mainly consist of massive pebbly sand
(F9) with outsized clasts, oriented parallel to dip.
Occasionally, normally or inversely graded pebbly
sand beds can be observed. Subordinate thin- to
medium-bedded intercalations of planar parallel-strat-
ified medium- to coarse-grained sand can be observed
(F10), interpreted to have been deposited from low-
density turbidity flows (Tb).
Both foresets are unconformably overlain by a
channel-fill, 5 m thick and c. 70 m wide. The basal
channel-fill consists of a 1-m-thick clast-supported
gravel lag (F4), which passes upward into pebbly
sand with large-scale trough cross-bedding (F1). The
succession is interpreted to be a glaciofluvial channel-
fill. The erosive gravel lag is apparently a channel-
floor deposit, whereas the overlying cosets of trough
cross-strata represent 3-D dunes. The channel-fill
deposits are overlain by a c. 5-m-thick gravelly foreset
(F7, F8) dipping (10j–25j) towards the southwest.
Fig. 5. (A) Sketch of the open-pit outcrop Fell with location of the measured section. (B) Measured section of the open-pit outcrop Fell. For
legend, see Fig. 6.
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 231
Fig. 6. Sketch of the open-pit outcrop Prange with location of measured sections.
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251232
3.3. Open-pit Prange section
The upper part of the delta complex is exposed in
the open-pit Prange (Fig. 3) at an altitude of 138–158
m. At the base of the open pit, 2.5-m-thick sandy
bottomsets are exposed, which pass updip into coarse-
grained gravelly foreset beds (Fig. 6). The foreset
beds are steeply dipping (25j–30j) southwestwards
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 233
and the delta toe rises in that direction (Fig. 4C),
indicating aggradation of the bottomset zone during
delta-front progradation. The mound-shaped geome-
Fig. 7. (A) Sketch of the open-pit outcrop Im Teufelsbad with location of th
Teufelsbad. For legend see Fig. 6.
tries of bottomset successions suggest a series of
coalescing depositional lobes, forming an aggrada-
tional ramp. Foreset beds consist of matrix- or clast-
e measured section. (B) Measured section of the open-pit outcrop Im
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251234
supported gravel (F7, F8, Table 1), frequently show-
ing inverse or normal grading and an upslope dipping
a(p) a(i) steep-clast fabric. The gravelly foreset is up
to 8 m thick and deeply incised by a c. 10-m deep and
60-m-wide channel, interpreted to represent an incised
valley. The basal part of this incised valley-fill con-
sists of c. 5-m-thick mud, silt and sand alternations
with wave-ripple cross-lamination, planar-ripple
cross-lamination and dropstones (F5). These fine-
grained glaciolacustrine valley-fill deposits are ero-
sively overlain by large-scale trough cross-stratified
and planar parallel-stratified sand and pebbly sand
(F1, F2), interpreted as glaciofluvial bedload deposits
with numerous phases of erosion and reactivation.
Laterally, these channelised sand and pebbly sand
pass into sheet-like topset deposits (Figs. 4D and 6).
3.4. Open-pit Im Teufelsbad section
The uppermost part of the Emme delta complex is
exposed in the open-pit Im Teufelsbad at an altitude of
c. 150–160 m (Fig. 3). The open pit has already been
refilled and exposures are poor. The sedimentary
succession starts with a 3-m-thick gravelly foreset,
which is bounded by an upper erosional surface (Fig.
7A and B). Foreset beds are 10–50 cm thick and
consist of matrix- or clast-supported gravel, steeply
dipping (15–25j) into southerly directions. Normal or
inverse grading is commonly developed and larger
Fig. 8. Stackening pattern and sequence stratigraph
clasts often show an a(p) a(i) steep-clast fabric,
dipping in an upslope direction (F7, F8). The upper
erosional surface is overlain by a 0.5–1.5 m thick
clast-supported gravel-lag, which passes upwards into
1.5-m-thick coarse- to medium-grained sand with
planar parallel stratification (Fig. 7B). The erosive
gravel lag is interpreted to represent a channel-floor
deposit, whereas the overlying planar parallel-strati-
fied sand is interpreted as a glaciofluvial bedload
deposit. These deposits are overlain by 6-m-thick
matrix-supported disorganized sandy gravel of a
young subaerial debris flow. Locally, at the base of
this unit, a 0.2–1 m thick boulder lag can be ob-
served, which is traceable for about 10 m (Fig. 7A).
3.5. Large-scale stackening pattern and depositional
sequences
The Emme delta complex consists of six vertically
stacked Gilbert-type deltas, which are interpreted to
represent eighth-order high-frequency depositional
sequences (Fig. 8). Sequence boundaries are indicated
by erosional unconformities, produced by stream
entrenchment during lake-level falls. The incised
channels and valleys were filled with lake and glacio-
fluvial deposits during the subsequent transgression.
The fluvial incision resulted in steep unstable slopes
along the channel-margins, and a series of slides and
slumps has occurred along these slopes and could be
ic interpretation of the Emme delta complex.
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 235
observed during excavation. A minimum number for
the lake-level fall is obtained from the erosion depth
of the glaciofluvial channels, which must be near or
above lake level landward of the shoreline (Postma,
1995). The main delta progradation occurred during
lake-level highstands, when high meltwater and sed-
iment discharge occurred during the summer.
The large-scale stacking pattern of the Emme delta
complex indicates an overall lake-level rise, interrup-
ted by minor short-term lake-level falls and closely
resembles the Rf type of Postma (1995). A similar Rf
lake-level control on delta architecture and facies has
been described by Fernandez et al. (1993). Opening of
outlets probably led to short-term lake-level falls, a
forced regression and the formation of subaerially
exposed sequence boundaries and the erosion of the
highstand systems tract (cf. Posamentier and Vail,
1988; Van Wagoner et al., 1988, 1990; Posamentier
Fig. 9. Location map of the open-pit outcrops of the Coppenbrugg
et al., 1992). The delta was finally abandoned due to
the northward retreat of the ice front.
4. Coppenbrugge subaqueous fan
The Coppenbrugge fan complex is situated on the
eastern margin of glacial Lake Rinteln and is about 10
km long and up to 10 km wide (Fig. 9). The fan
sediments form approximately NW–SE striking sed-
iment ridges and are exposed in various gravel pits
(Fig. 9), at an altitude of 90–170 m. They overlie
glaciolacustrine mud and a diamicton, interpreted to
represent a basal till (Deters, 1999) and lack any
subaerial glaciofluvial or distributary delta-plain com-
ponents. Clasts consist mainly of resedimented fluvial
material (95%), previously deposited by the River
Leine and River Weser or originated from the adjacent
e fan complex; the topographic contour values are in metres.
Table 2
Classification of facies associations, Coppenbrugge subaqueous fan
Facies association Geometry Interpretation of depositional processes
FA1 Massive clast-supported gravel (60–95%) with
bed thickness between 10 and 40 cm. The
matrix consists of fine- to coarse-grained
sand and bed contacts are mainly sharp;
occasionally, erosive bed contacts occur.
Larger clasts can be oriented parallel to dip
and show a steeply imbricate clast fabric with
the a-axes dipping in upslope direction.
Intercalations of thin- to medium-bedded
inversely or normally graded gravel, massive
or normally graded pebbly sand and massive
or plan parallel-stratified sand amount to 5–30%.
Wedge (3–7 m thick,
up to 50 m long).
High-angle bedding
(16–34j). Lenticularin chutes and channels.
The massive clast-supported gravel and pebbly
sand with sharp bed contacts indicate deposition
from noncohesive debris flows (Shanmugam, 2000);
the steep-clast fabric indicates laminar shear during
or immediately after the flow’s stop (Nemec, 1990).
The normally graded gravel, pebbly sand and
stratified sand are interpreted to result from
surge-type high- and low-density turbidity flows
(Bouma, 1962; Lowe, 1982; Nemec et al.,
1999; Plink-Bjorklund and Ronnert, 1999).
Usually found in the proximal upper fan and both
feeder and distributary channels.
FA2 Thin- to thick-bedded clast-supported massive
or inversely graded gravel (40%), alternating with
thin- to thick-bedded massive, normally or
inversely graded pebbly sand (33%), massive,
normally graded, planar parallel-stratified, ripple
cross-laminated sand (20%) or large-scale trough
cross-bedded coarse-grained sand (7%). Subordinate
thin beds of massive silt or silty sand (1%) occur.
Wedge (3–5 m thick,
up to 50 m long).
Low- to high-angle
bedding (5–25j).Lenticular in
chutes and channels.
The massive or inversely graded gravel and pebbly
sand with sharp bed contacts indicate deposition from
noncohesive debris flows (Nemec, 1990; Shanmugam,
2000). The normally graded gravel, pebbly sand and
stratified sand are interpreted to result from surge-type
high-density turbidity flows (Lowe, 1982; Nemec et al.,
1999; Plink-Bjorklund and Ronnert, 1999). The
intercalated thin- to thick-bedded sand, silt and
mud alternation with normal grading, planar
parallel-stratification, climbing-ripple cross-lamination
and planar parallel lamination are interpreted to result
from surge-type low-density turbidity flows (Ta–d).
Large-scale trough cross-bedding indicates the downslope
migration of dunes driven by quasi-steady low-density
turbidity flows (Nemec et al., 1999; Lowe, 1982; Mulder
and Alexander, 2001). Usually found in the distal upper
fan and both feeder and distributary channels.
FA3 Alternations of thin- to medium-bedded massive,
normally, inversely graded or planar parallel-
stratified pebbly sand (10–25%), thin- to
medium-bedded large-scale trough cross-bedded
medium- to coarse-grained sand (0–15%), very
thin- to thick-bedded massive, normally graded,
planar parallel-stratified and ripple cross-laminated
fine- to coarse-grained sand (20–80%) and
massive or normally graded gravel with erosive bed
contacts (10%). Subordinate thin beds of massive or
horizontally laminated silt and mud occur (1–3%).
Wedge (2.5–6 m thick,
up to 200 m long).
High- to low-angle
bedding (3–19j).Lenticular in channels.
The graded-stratified gravel and pebbly sand are
interpreted to have been deposited from surge-type
high-density turbidity flows (Lowe, 1982; Nemec et al.,
1999; Plink-Bjorklund and Ronnert, 1999). The
intercalated thin- to thick-bedded sand, silt
and mud alternation with grading, planar parallel
stratification, climbing-ripple cross-lamination and
planar parallel lamination are interpreted to result
from surge-type low-density turbidity flows (Ta–d).
Usually found in the proximal mid fan and both
feeder and distributary channels.
FA4 Medium- to very thick-bedded fine- to coarse-
grained sand with scattered pebbles. Beds are
massive (10–50%), or show planar parallel
stratification (30%), ripple-trough cross-lamination
(10–25%), climbing-ripple cross-lamination
(0–40%) or large-scale trough cross-bedding
(5%). Very thin-bedded silt and mud beds
occasionally can be observed at the top of
climbing-ripple cross-laminated beds (1–2%).
These beds often show a fining-upward where
Wedge (2–6 m thick,
up to 80 m long).
Low-angle bedding
(3–9j). Lenticularin channels.
The thick fining-upward beds with planar parallel
stratification, large-scale trough cross-stratification
and ripple cross-lamination are interpreted to have
been deposited from pulsating quasi-steady low-density
turbidity flows (Mulder and Alexander, 2001). The
scattered pebbles are interpreted as coeval debris
fall from the steep upper fan slope (cf. Nemec et al.,
1999). Intercalated thin- to medium-bedded sand, silt
and mud alternation with planar parallel
stratification, climbing-ripple cross-lamination and
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251236
Facies association Geometry Interpretation of depositional processes
a lamination with eroded ripple stoss sides
commonly passes upwards into lamination with
preserved stoss sides and into draping
lamination. Bed contacts are usually sharp.
planar parallel lamination is interpreted to result
from surge-type low-density turbidity flows (Ta–d).
Usually found in the distal mid fan and both
feeder and distributary channels.
FA5 Alternations of thin- to medium-bedded
fine-grained sand, silt and mud. The
fine-grained sand beds are massive (25%),
planar parallel-laminated (50%)
or show climbing-ripple cross-lamination
(15%). Silt and mud beds are massive
or show planar parallel-lamination (10%).
Bed contacts are usually sharp.
Dropstones can frequently be observed
and are often concentrated in mud layers.
Blanket, 0.5–2 m
thick. Lenticular
in channels.
The thin- to medium bedded sand, silt and mud
alternation with plan parallel stratification,
climbing-ripple cross-lamination and plan parallel
lamination is interpreted to result from surge-type
low-density turbidity flows (Ta–d). The frequent
occurrence of dropstones indicates dumping of ice-rafted
debris from icebergs (Lønne, 1995). Found in the outer
fan and feeder channels.
Table 2 (continued)
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 237
Mesozoic bedrock (Rausch, 1977; Rohde, 1994;
Deters, 1999). Frequent occurrences of ice-rafted de-
bris and compressive deformational structures point to
an ice-contact fan setting (Deters, 1999; Winsemann et
al., 2003). A description and interpretation of facies
associations is given in Table 2. The terminology for
gravel characteristics is after Walker (1975) and the
notation of turbidites, Tabcd, refers to the Bouma
divisions (cf. Bouma, 1962).
Fig. 10. Facies associations of the Coppe
4.1. Facies associations
4.1.1. Upper-fan facies associations (FA1 and FA2)
The proximal upper-fan deposits consist of 3–7 m
thick steeply dipping (16–34j) medium- to thick-
bedded clast-supported gravel (Fig. 10). The matrix is
sandy and bed contacts are mainly sharp. Larger clasts
can be oriented parallel to dip and a steeply imbricate
clast fabric with the a-axes dipping in upslope direction
nbrugge subaqueous fan complex.
Fig. 11. Facies associations of the Coppenbrugge subaqueous fan complex. (A) Steeply dipping gravel of the proximal upper fan (FA1),
unconformably overlain by outer- to mid fan-facies (FA5, FA4), Heerburg open pit. (B) Channelised thick- to medium-bedded sand and gravel
of the distal upper fan (FA2), Heerburg open pit. (C) Ripple cross-laminated sand of the distal mid fan (FA4), Steinbrink open pit. (D) Thin- to
medium-bedded sand, silt and mud of the outer-fan facies association (FA5), channel fill, Heerburg open pit. (E) Alternation of normally graded
gravel, massive and planar parallel-stratified pebbly sand, proximal mid-fan (FA3), Steinbrink open pit. (F) Climbing-ripple cross-lamination
and large-scale trough cross-bedding in sandy distal mid-fan deposits (FA4), Heerburg open pit.
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251238
is occasionally observed. Massive beds and sharp bed
contacts indicate deposition from noncohesive debris
flows (Nemec and Steel, 1984; Nemec, 1990; Shanmu-
gam, 2000). The scarcity of normal grading at the bed
tops suggests relatively slow, low-mobility debris
flows, with negligible shear and no turbulent churning
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 239
at the upper interface (Hampton, 1972; Nemec et al.,
1999). Intercalations of thin- to medium-bedded in-
versely or normally graded gravel, pebbly sand or
planar parallel-stratified sand amount to 5–30% and
increase towards the distal upper fan zone (FA2; Figs.
10, 11A and B). These deposits are interpreted to result
from surge-type high- and low-density turbidity flows
(Lowe, 1982; Mulder and Alexander, 2001). Occasion-
ally, large-scale trough cross-bedding can be observed,
indicating the downslope migration of dunes driven by
quasi-steady low-density turbidity flows (Cheel and
Rust, 1982; Nemec et al., 1999). Local chaotic bedding
indicates slumps caused by fan slope collapse probably
due to the alternating periods of fan-head aggradation
and high meltwater discharges (Postma, 1984, 1990;
Nemec, 1990; Ashley, 1995; Lønne, 1997; Plink-Bjor-
klund and Ronnert, 1999). Shallow chutes, filled with
massive or normally graded gravel or pebbly sand, can
frequently be observed and are 3–5 m wide and up to
0.3m deep, probably reflecting cut and fill processes on
the fan surface. Typical for the upper-fan environment
is the occurrence of large U-shaped feeder channels, up
to 25 m wide and 6 m deep. These feeder channels are
filled with coarse-grained gravelly deposits (FA1, FA2)
as well as finer-grained sandy and muddy deposits
(FA3–FA5, Figs. 10 and 11D).
4.1.2. Mid-fan facies associations (FA3 and FA4)
The proximal mid fan deposits (Figs. 10 and 11E)
consist of 2–6 m thick alternations of subhorizontal to
moderately dipping (3–19j) thin- to medium-bedded
massive, normally, inversely graded or planar parallel-
stratified pebbly sand, thin- to medium-bedded large-
scale trough cross-bedded sand and very thin- to
thick-bedded massive, normally graded, planar paral-
lel-stratified and ripple cross-laminated sand. Interca-
lations of massive or normally graded gravel with
erosive bed contacts can occasionally be observed.
Subordinate thin beds of massive or horizontally
laminated silt and mud occur. The proximal mid fan
slope is characterised by distributary channels, up to
20 m wide and 2.5 m deep, filled with graded or
stratified gravel, sand and silt. The graded-stratified
gravel and pebbly sand beds are interpreted to have
been deposited from surge-type high-density flows
(Lowe, 1982; Mulder and Alexander, 2001), whereas
the intercalated thin- to thick-bedded sand, silt and
mud alternation with grading, planar parallel stratifi-
cation, climbing-ripple cross-lamination and planar
parallel lamination are interpreted to result from
surge-type low-density turbidity flows (Ta–d). Fur-
ther downslope, the deposits grade into low-angle
dipping (3j–9j) fine- to coarse-grained sand beds
with scattered pebble, showing planar parallel strati-
fication and/or ripple cross-lamination. Typical are
thick beds with climbing-ripple cross-lamination often
showing a fining-upward where a lamination with
eroded ripple stoss sides commonly passes upwards
into lamination with preserved stoss sides and into
draping lamination (Figs. 10, 11C and F). The thick
beds with planar parallel stratification, trough cross-
stratification and ripple cross-lamination are inter-
preted to have been deposited from quasi-steady
low-density turbidity flows (Nemec et al., 1999;
Mulder and Alexander, 2001). High-suspension fall-
out rates are indicated by climbing-ripple cross-lam-
ination and graded or massive sand and silt beds. The
ripple cross-lamination shows evidence of a fluctuat-
ing and periodically waning flow, indicated by an
increase in the vertical aggradation rate of migrating
current ripples. The draping lamination indicates rip-
ples whose migration nearly ceases and vertical ac-
cretion prevailed (Ashley, 1995). The multiple
sequences of fining-upward beds reflect pulsating
quasi-steady underflows (cf. Mulder and Alexander,
2001), although the meltwater outflow was probably
semicontinuous. The pulsatory sediment discharges
may therefore be attributed to an autocyclic process of
fan-head aggradation and erosion or upper fan-slope
collapses (cf. Nemec et al., 1999). The scattered
pebbles are interpreted as coeval debris fall from the
steep upper fan slope.
4.1.3. Outer-fan facies association (FA5)
The outer-fan deposits are up to 4 m thick and
consist of thin- to medium-bedded fine-grained sand,
silt and mud (Figs. 10 and 11D), reflecting the decrease
of flow power with distance from subglacial tunnel
outlets. The fine-grained sand beds are massive (25%),
planar parallel-laminated (50%) or show climbing-
ripple cross-lamination (15%). Silt, mud and clay beds
are massive or show planar parallel lamination (10%).
Bed contacts are usually sharp. Dropstones can fre-
quently be observed and are often concentrated in mud
or clay layers. The thin- to medium-bedded sand, silt
and mud alternations are interpreted to result from
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251240
surge-type low-density turbidity flows (Ta–d). Mas-
sive beds and climbing-ripple cross-lamination indicate
high suspension fallout rates. The frequent occurrence
of dropstones indicates dumping of ice-rafted debris
from icebergs. Outer-fan deposits are mainly recorded
from channels or form blankets on more proximal fan
deposits.
4.2. The open-pit Otto section
The basal part of the Coppenbrugge fan complex is
exposed in the open-pit Otto (Fig. 9). Large parts of the
open pit have already been refilled and only a few
outcrop walls are still available for observation. The
fan deposits are exposed at an altitude of c. 84–100 m
and overlie glaciolacustrine mud and Mesozoic base-
ment rocks (Naumann, 1922; Deters, 1999). The
sedimentary succession is strongly deformed and part-
ly overlain by a basal till. The deformation is charac-
terised by large-scale folds and thrusts, steeply dipping
into easterly directions. The exposed facies includes
upper-fan coarse-grained gravels and mid-fan sands,
steeply dipping (16–30j) into southerly to southwest-
erly directions and interpreted to represent individual
foresets of small prograding fan lobes. Exposed fore-
sets are about 2–3 m thick and consist of thin- to
medium-bedded (5–25 cm) massive, matrix- or clast-
supported gravel. The sandy mid-fan deposits consist
of thin- to medium-bedded coarse- to medium-grained
sand or pebbly sand. Pebbly sand beds are massive or
show large-scale trough cross-bedding, whereas sandy
beds show planar-ripple cross-lamination or climbing-
ripple cross-lamination. Bed contacts are usually
sharp. Intercalated channels (chutes) are up to 1 m
deep and several meters wide and filled with normally
graded gravel and/or normally graded pebbly sand.
4.3. The open-pit HBT section
The sedimentary succession of the open-pit HBT,
exposed at an altitude of c. 147–165 m, overlies a
basal diamicton (Deters, 1999). As the open-pit Otto,
the HBT open pit has already been partly refilled and
only a few outcrop walls are available for observation.
The basal sedimentary succession consists of coarse-
grained channelised gravelly foresets, dipping (14–
20j) into northeasterly and southeasterly directions.
Individual foreset beds are 10–40 cm thick and consist
of massive clast-supported gravels with a coarse-
grained sandy matrix. Subordinate inversely and nor-
mally graded gravel beds occur. The coarse-grained
gravelly foresets are unconformably overlain by sandy
low-angle foresets, dipping (3–11j) into northwester-
ly directions. Beds are 5–70 cm thick and consist of
sand and pebbly sand, which are massive or show
climbing-ripple cross-lamination. Climbing-ripple
sequences often show fining-upward beds with eroded
stoss sides at the base and preserved stoss sides at the
upper parts of the beds. The major erosional surface is
only partly exposed. In one outcrop wall, c. 1 m above
this unconformity (c. 152-m altitude), wave-rippled
sand could be observed, indicating very shallow water
depths.
4.4. The open-pit Heerburg section
The sedimentary succession of the open-pit Heer-
burg is exposed at an altitude of c. 143–165 m and
overlies a basal diamicton, interpreted to represent a
basal till (Deters, 1999). The basal succession consists
of coarse-grained foresets, bounded by an erosional
upper surface. The foreset beds are 10–40 cm thick
and mainly consist of massive clast-supported gravel
with a coarse sandy matrix. The foreset beds are
steeply dipping (20–30j) into northwesterly and
southwesterly directions. The truncated gravelly fore-
sets are overlain by sandy mid-fan deposits (Figs. 11
and 12) whose deposition commenced with the infill-
ing of large channels incised into the underlying fan
body. These palaeochannels are up to 6 m deep and 25
m wide and exposed at an altitude of c. 148–154 m.
The basal channel-fill consists of thin- to medium-
bedded sand, which are massive, normally graded
and/or show planar parallel stratification and ripple
cross-lamination. Bed contacts are usually sharp.
Alternations of very thin-bedded clay, mud and silt
with thin- to medium-bedded sand occur upward in
the channel-fill succession. The fine-grained sand
beds are massive or normally graded. The silt, mud
and clay layers are massive and show sharp undula-
tory contacts. Dropstones are common and scattered
or accumulated in mud or clay layers. The sandy
channel-fill deposits are overlain by alternating thin-
to medium-bedded sand and gravel. The sand beds are
massive or normally graded and often pass upwards
into planar parallel-stratified and/or ripple cross-lam-
Fig. 12. Correlation panel of measured logs showing the facies stratigraphy in the Heerburg open-pit section.
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 241
inated sand. Gravel beds are matrix- or clast-sup-
ported and most often normally graded. Bed contacts
are sharp.
The erosional unconformity in the interchannel
areas is overlain by alternating beds of sand, silt
mud and clay, passing upwards into thick sand beds
with climbing-ripple cross-lamination, commonly
with an upward increasing stoss-side preservation. In
these sandy interchannel deposits, a localized erosion-
al structure, up to 1.5 m deep and 0.8–1.5 m wide, has
been recognized and attributed to iceberg ploughing
(Winsemann et al., 2003). Repeated observations of
the open-pit exposure during excavation revealed that
the scour structure is laterally continuous, extending
approximately 20 m in an east–west direction. The
scour has a concave-upward lower surface that trun-
cates the underlying deposits. The upper bounding
surface is formed by a subhorizontal erosional surface.
The steep-sided scour occurs in deformed sedi-
ments, and on both sides, downbending of marginal
strata into the central trough can be observed (Fig.
13). In the frontal (eastern) part of the scour, a wedge-
shaped deformation zone could be observed (Fig.
13C), which is interpreted to represent a relic of the
frontal ridge (berm). A detailed description and dis-
cussion of the ice scour formation is given in Winse-
mann et al. (2003). This scour feature is overlain
unconformably by c. 15 m of mid-fan deposits,
Fig. 13. Photographs of the iceberg scour recognized in the Heerburg open pit. The iceberg scour is laterally continuous, extending approx. 20 m
in an east–west direction. Flow direction of the iceberg was from west to east. (A) Frontal zone of the iceberg scour. The scour occurs in
deformed mid-fan sediments. (B) Close-up view of (A), showing the central trough and deformed marginal sediments. The zone of the central
trough is characterised by a pronounced downbending of overlying strata. These downbent strata are cut by vertical dewatering structures. (C)
Close-up view of (A), showing a wedge-shaped deformation zone at the right-hand side of the central trough, interpreted to represent a relic of
the frontal ridge (berm) of the iceberg scour. (D) Rear zone of the iceberg scour, approx. 15 m to the west of (A). The scour infill consists of
downbent marginal strata and turbated sandy mid-fan deposits.
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251242
consisting in the lower part of thinly to thickly bedded
cross-stratified sand and ripple cross-laminated silt.
Extensional faulting was active above the central
trough during deposition of these ‘‘post-iceberg-scour
strata,’’ as indicated by growth faults.
Normally or inversely graded gravel lenses occur
in the upper part, alternating with beds of pebbly
sand and sand, which are massive or normally gra-
ded or show planar parallel stratification and ripple
cross-lamination. Bed contacts are mainly sharp,
planar or undulatory, and dropstone horizons are
common. Channels in this part of the section are
10 m wide and up to 1.5 m deep, filled with thin
beds of massive or normally graded sand and pebbly
sand that pass upwards into fine-grained sand and
silt with horizontal or undulatory lamination. Bed
contacts are sharp, often erosive, and dewatering
structures are common.
4.5. The open-pit Steinbrink section
Deposits of the Steinbrink open pit are exposed at
an altitude of c. 150–162.5 m (Fig. 14) and overlie
glaciolacustrine mud and a diamicton, interpreted to
represent a basal till (Deters, 1999). Well data show
that in the western part of the open pit, sand predom-
inates the sedimentary succession, whereas the eastern
part is dominated by coarse gravel facies. This bipar-
tite division corresponds with opposite flow directions
measured in sandy and gravelly foresets.
Fig. 14. Correlation panel of measured logs showing the facies stratigraphy in the Steinbrink open-pit section.
J.Winsem
annet
al./Sedimentary
Geology165(2004)223–251
243
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251244
The exposed part of the eastward dipping sandy
mid-fan foreset can be traced laterally for about 40 m
and is up to 7 m thick. Foreset beds are 10–50 cm
thick and consist of coarse- to medium-grained sand
and pebbly sand. Beds are often fining-upwards and
show planar parallel stratification, large-scale cross-
stratification or ripple-trough cross-lamination and
planar-ripple cross-lamination, passing upwards into
climbing-ripple cross-lamination. Within the foreset
beds, small-scale channels, 1–1.5 m deep and up to
10 m wide, occur, which are filled with normally
graded gravel, pebbly sand and sand. Dip angles of
the sandy foreset are between 5j and 28j.The up to 7-m-thick upper-fan gravelly foreset
beds are steeply dipping (14–33j) into westerly
directions and consist of clast- and matrix-supported
gravel. Beds are 10–30 cm thick and contacts are
sharp. Both foresets are truncated by a major uncon-
formity, exposed at an altitude of c. 151–156 m and
partly evolved as a large U-shaped channel, up to 5 m
deep and about 25 m wide (Fig. 14). The basal
channel-fill consists of c. 2-m thin- to medium-bedded
sand, silt and sandy mud with inverse grading or
planar parallel lamination. These fine-grained chan-
nel-fill sediments are overlain by massive matrix- and
clast-supported gravels and massive pebbly sand.
The channel-fill and the truncated sandy and grav-
elly foresets are overlain by a c. 5-m-thick gravelly
foreset, steeply dipping (30j) into westerly directions.
This foreset again is incised by a channel, up to 2.5 m
deep and 25 m wide, and filled with thin- to medium-
bedded sands, showing climbing ripple cross-lamina-
tion, planar ripple cross-lamination, trough cross rip-
ple-lamination and thin- to medium-bedded massive
or planar parallel-stratified coarse sand and pebbly
sand. Bed often shows fining-upward trends and bed
contacts are sharp, erosive or gradual.
To determine the stratigraphic relation between the
oppositely dipping sandy and gravelly foresets, sev-
Fig. 15. (A) Georadar line from the open-pit Steinbrink at 150-m altitude.
the sandy foresets exposed in the western part of the open pit (Fan A). This
as a channel, which has been laterally filled by west- and eastward dippin
higher signal attenuation (1) limits further penetration. This sudden termin
attenuating finer-grained silt and mud, which underlie the fan deposits.
approximately 20 m northwards of georadar line A. The radar line shows
dipping reflectors (3) in the east (Fan B), which are correlated with the sa
Both foresets are incised by a channel (4), which has been laterally filled
channel towards the north. Penetration depth is c. 7 m (130 ns).
eral georadar lines were measured in the open pit at
different levels (150- and 157-m altitude). These
georadar lines have been measured in February and
October 2002, respectively. Georadar line A (Fig.
15A) was measured at 150-m altitude in February
2002. The GPR device used was a GSSI SIR-10B
with different antennae. The best penetration was
obtained using an 80-MHz bistatic antenna. The
dipoles have been separated by 1.8 m, and a trace
distance of 0.3 m was applied. A horizontal stacking
of 64 traces was applied in the field, and thus no
further processing was needed for enhancing the data
quality. The weather conditions have been dry; how-
ever, it was the first day after a period of heavy
rainfall.
The radar line shows eastward dipping reflectors
(2), ending at a depth of 200 ns (Fig. 15A). These
reflectors are correlated with the sandy foreset, ex-
posed in the western part of the open pit (Fan A). The
sandy foreset is bounded by an upper erosional
surface (4), partly evolved as a channel, which has
been laterally filled by west- and eastward dipping
strata (5). At the base of the georadar line, a layer
with a higher signal attenuation (1) limits further
penetration. This sudden termination of penetration
depth at c. 210 ns (c. 7 m) is attributed to finer-
grained silt and mud or diamicton beds, which un-
derlie the fan deposits.
Georadar line B (Fig. 15B) wasmeasured in October
2002 at 157-m altitude, approximately 20 m north-
wards of georadar line A. The best penetration was
obtained using a 100-MHz, bistatic antenna in a con-
tinuous mode. The radar data have been bandpass-
filtered with a butterworth filter to increase the data
quality. Penetration depth was limited by a high
groundwater level and there is no information below
130 ns (c. 7 m).
The radar line shows eastward-dipping reflectors
(1) in the west (Fan A) and westward-dipping reflec-
The radar line shows eastward dipping reflectors (2), correlated with
foreset is bounded by an upper erosional surface (4), partly evolved
g strata (5, Fan B). At the base of the georadar line, a layer with a
ation of penetration depth at c. 210 ns (c. 7 m) is attributed to higher
(B) Georadar line from the open-pit Steinbrink at 157-m altitude,
eastward dipping reflectors (2) in the west (Fan A) and westward
ndy and gravelly foresets exposed at the lower level of the open pit.
(5) by westward and eastward dipping strata. Note shallowing of
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 245
tors (3) in the east (Fan B), which are correlated with
the sandy and gravelly foresets exposed at the lower
level of the open pit. Both foresets are incised by a
channel (4), which has been laterally filled (5) by
westward- and eastward-dipping strata and is shallow-
ing towards the north.
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251246
4.6. Large-scale stackening pattern and depositional
sequences
The Coppenbrugge subaqueous fan complex con-
sists of laterally and vertically stacked small-scale
fan bodies, which are exposed in topographic heights
between c. 90–170 m. Palaeoflow directions are
highly variable and individual fan bodies are up to
10 m thick and several tens to hundreds of meters
across, lacking any subaerial, glaciofluvial or distrib-
utary delta-plain components. The small-scale fans
typically consist of coarse gravel in the proximal
core part, showing large-scale foreset bedding (cli-
Fig. 16. Stackening pattern and sequence stratigraphic interpr
nothems). The coarse gravel grades distally into
better-sorted, finer-grained sandy facies. Various
types of grading, cross-bedding and cross-lamination
are present, recording the downflow of both surge-
type and quasi-steady turbidity flows. Proximal to
distal fining reflects the drop-off of flow velocities
with distance from the tunnel mouth. Towards the
fan margin, high-suspension sedimentation rates pro-
duce climbing ripple-drift and graded or massive
sands and silts. Ball and pillow and flame structures
are common, owing to dewatering.
Within the subaqueous fan complex, three geneti-
cally distinct clastic units can be defined from facies-
etation of the Coppenbrugge subaqueous fan complex.
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 247
architectural analysis, which are separated by major
unconformities.
(1) A lower unit, which records proximal deposition on
a subaqueous fan during glacier advance. This unit,
exposed in the Otto open pit at altitudes between 84
and 100 m, is characterised by steeply dipping
coarse-grained foresets, dipping away from the
former ice margin. The fan deposits overlie
glaciolacustrine mud and are strongly deformed
by synsedimentary glacial tectonics. These deposits
mark the maximum ice-front position at the eastern
margin of glacial Lake Rinteln. Flow directions are
mainly from the northeast. The basal sequence
boundary is indicated by the abrupt onset of coarse-
grained fan deposition on fine-grained glaciolacus-
trine mud. The upper sequence boundary is
indicated by a basal till, which unconformably
overlies the fan deposits (Fig. 16).
(2) A medial unit, which records proximal deposition
on a subaqueous fan during glacier stillstand, after
the glacier and its injection points had retreated
towards a more upslope position. This medial unit
overlies a basal till and is exposed in the open-pits
HBT, Heerburg and Steinbrink at altitudes be-
tween c. 143 and 154 m. This medial unit is
characterised by steep coarse-grained foresets,
dipping away from the former ice margin and
showing only minor synsedimentary glaciotecton-
ic deformation. Flow directions are mainly
recorded from the west and southwest, and the
steeply dipping foresets are bounded by an upper
unconformity (Fig. 16), which is associated with
the formation of deep U-shaped channels, inter-
preted to represent a type-1 sequence boundary,
which resulted from a major lake-level fall.
Evidence for a lake-level fall is given by the
occurrence of wave ripple-cross-lamination, ob-
served in the open-pit HBT on top of the
unconformity at an altitude of c. 152 m. The
basal sequence boundary is indicated by the basal
till.
(3) An upper unit, which unconformably overlies the
coarse-grained foresets of the medial lower unit.
These fine-grained deposits consist of outer- to
mid-fan sediments, dipping towards the former ice
margin and thus representing an ice margin retreat
(Lønne, 1995, 2001). As the glacier retreated, the
deposition gradually switched from the fan’s
frontal slope to its ice-proximal backslope. Flow
directions, obtained from the climbing-ripple
sequences, show clear transport direction towards
the west, climbing up the older foreset slope
(open-pit Heerburg section). The rapid retreat of
the glacier resulted in calving and an abrupt cutoff
of the sediment flux to the fan. Evidence of
iceberg grounding and reworking is given by a
prominent ice scour mark, cut into mid-fan
deposits of the Heerburg section. The upper unit
shows an overall upward coarsening, indicating
the progradation of the new fan system.
5. Discussion
The Emme delta and Coppenbrugge subaqueous
fan are formed by stacked transgressive–regressive
sequences, indicating lake-level fluctuations. The
Emme delta complex, formed at the northern margin
of glacial Lake Rinteln, is thought to reflect a rela-
tively stable position of the ice margin in front of the
Weser Chains mountain ridges. The onset of delta
progradation probably represents a halt in ice advance
and a related high sediment supply period (cf. Lønne,
1995, 2001; Plink-Bjorklund and Ronnert, 1999). The
sedimentary facies and depositional architecture re-
semble those of nonglacial Gilbert-type deltas, except
for the deposition of glacial debris. Gravelly foreset
beds suggest a steep slope with gravity-driven flows.
Material that bypassed the braid plain avalanched
downslope as debris flow and stopped by freezing
when the slope diminished. The finer-grained sandy
material moved to the basin floor where it was
deposited from surge-type turbidity flows. The delta
stacking patterns indicate a long-term transgression,
interrupted by minor short-term lake-level falls and
closely resemble the Rf type (an overall rise with
superimposed falls) of Postma (1995). A similar Rf
lake-level control on delta architecture and facies has
been described by Fernandez et al. (1993). The main
delta progradation is recorded from the highstand
systems tract, when high meltwater and sediment
discharge occurred during the melt season. A forced
regression during opening of outlets led to the forma-
tion of subaerially exposed sequence boundaries and
the erosion of the highstand systems tract. The deeply
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251248
incised channels were filled with lake and glacioflu-
vial deposits during the subsequent transgression.
In contrast, the Coppenbrugge subaqueous fan was
associated with a retreating ice margin, indicated by the
shift of depocentres to more upslope positions. The
maximum ice advance is recorded from the open-pit
Otto, where the subaqueous fan deposits directly over-
lie glaciolacustrine mud. The sediments are strongly
deformed, thus indicating an advancing ice margin
(Lønne, 1995; Lønne and Syvitski, 1997). As the
glacier advanced into the lake basin, a conformable
coarsening-upwards sequence from lake sediments to
subaqueous outwash occurred, culminating in an ero-
sional sequence boundary and the deposition of a basal
till on top of the fan sediments. A subsequent glacier
retreat is recorded from the abrupt backstepping of fan
bodies, exposed in the open-pits HBT, Heerburg and
Steinbring at topographic heights between 143 and 170
m. These fan deposits overlie the basal till and form the
stratigraphic upper part of the Coppenbrugge fan com-
plex. The deposits only show minor synsedimentary
deformation structures and therefore probably mark
stillstand positions of the ice margin (cf. Lønne, 1995).
A prominent unconformity, exposed in topographic
heights between c. 145 and 156 m, is observable in
the open-pit outcrops HBT, Heerburg and Steinbrink.
This unconformity is associated with a major change in
palaeoflow directions. Below the unconformity,
palaeoflow directions are mainly from westerly and
southwesterly directions, whereas above the unconfor-
mity, palaeoflow directions are mainly from the east.
The formation of this unconformity is attributed to a
major lake-level fall, which probably led to a partial
subaerial exposure of the fan surface. Evidence for a
major drop in lake level is given by the occurrence of
wave-ripple cross-lamination on top of the unconfor-
mity, found in the HBT open pit at an altitude of c. 152
m. Therefore, it seems possible that this prominent
unconformity corresponds to the incised valley recog-
nized in the Emme delta at altitudes of c. 140–150 m
(Fig. 6). A subsequent lake-level rise is deduced from
the deposition of outer- to mid-fan deposits above the
unconformity, observable in the open-pits Heerburg
and HBT. In this section, an iceberg scour is recog-
nized, which is comparable in width and depth to
analogous features reported from modern and Pleisto-
cene ice scours and would require a water depth of at
least c. 10–20m above the fan surface (cf.Woodworth-
Lynas, 1996; Eden and Eyles, 2001). The trend of the
scour runs roughly west–east and a flow direction from
west to east is inferred from the formation of a frontal
ridge (berm). This flow direction is opposite to themain
flow directions measured in the upper sequence in the
open-pit outcrop Heerburg.
The deposition of the Coppenbrugge subaqueous
fan does not correlate with the maximum lake-level
highstand of glacial Lake Rinteln. Most probably, a
coeval ice advance from the western basin margin
successively closed lake outlets and led to the ob-
served overall lake-level rise. Possible lake outlets at
the southwestern margin of glacial Lake Rinteln lie at
altitudes between 49 and 207 m and increase in
altitude towards the east (Thome, 2001) and correlate
remarkably well with the topographic heights of
foreset–topset transitions of the Emme delta.
The ice front at the eastern lake margin, affected by
this lake-level rise, was thus probably very unstable,
subject to periodic calving, short-term oscillations and
possibly surges. These conditions can be expected to
have generated floating icebergs and caused switching
of meltwater outlets and variation in sediment dis-
charge (Boulton, 1986, 1990; Powell, 1990; Lønne,
1995; Plink-Bjorklund and Ronnert, 1999).
6. Conclusion
The forcing parameters governing the development
of depositional sequences were lake-level fluctuations,
sediment yield rates and physiography. Compared to
the changing lake level, which was on the order of 120
m, subsidence of the basin was insignificant.
Depositional processes reflect the character of sed-
iment supply and distance from the ice margin. The
sedimentary facies and depositional architecture of ice-
contact deltas resemble those of nonglacial Gilbert-
type deltas, except for the deposition of glacial debris.
Gravelly foreset beds suggest a steep slope with grav-
ity-driven flows. Material that bypassed the braid plain
avalanched downslope as debris flow and stopped by
freezing when the slope diminished. The finer-grained
sandy material moved to the basin floor where it was
deposited from surge-type turbidity flows. The main
delta progradation is recorded from the highstand
systems tract, when high meltwater and sediment
discharge occurred during the melt season. A forced
J. Winsemann et al. / Sedimentary Geology 165 (2004) 223–251 249
regression during opening of outlets led to the forma-
tion of subaerially exposed sequence boundaries and
the erosion of the highstand systems tract. The deeply
incised channels were filled with lake and glaciofluvial
deposits during the subsequent transgression.
A subaqueous fan complex formed where detritus
were carried to the lake via tunnels near or at the base
of an ice cliff. The Coppenbrugge fan complex was
constructed by the coalescence of several fan bodies,
which are recognizable as backstepping, southwest-
trending parallel morphologic sediment ridges. The
fan-stacking pattern and bulk geometry were deter-
mined by the ice-front fluctuations, the shifting of
meltwater outlets and the short-term lake-level fluc-
tuations. Individual fan bodies are up to 10 m thick
and several tens to hundreds of meters across, lacking
any subaerial, glaciofluvial or distributary delta-plain
components. Upper-fan deposits are characterised by
coarse-grained ice-proximal gravel, deposited by de-
bris flows that document continuous discharge. Slump
and slide deposits are related to steep depositional
slopes. The mid-fan contains basinward fining and
thinning deposits of quasi-steady and surge-type high-
and low-density turbidity currents, indicating more
ice-distal and periodic deposition. The outer-fan
deposits mainly consist of surge-type low-density
turbidites and glacial debris dumped by icebergs.
The formation of a prominent unconformity, associ-
ated with deeply incised channels, is attributed to a
major lake-level fall.
Acknowledgements
We would like to thank H.-B. Deters, P. Groetzner,
K. Skupin, P. Rohde, E. Speetzen, W. Thiem, K.
Thome, C. Vandre and P. Victor for discussions. A.
van Loon and two anonymous reviewers are thanked
for their critical comments, which helped to improve
the manuscript.
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