Content uploaded by David Mark Hodgson
Author content
All content in this area was uploaded by David Mark Hodgson on Jul 22, 2014
Content may be subject to copyright.
Denudation of the continental shelf between Britain and France at the
glacial–interglacial timescale
Claire L. Mellett
a,
⁎, David M. Hodgson
c,1
, Andrew J. Plater
a
, Barbara Mauz
a
, Ian Selby
b
, Andreas Lang
a
a
School of Environmental Sciences, University of Liverpool, Liverpool, L69 7ZT, UK
b
The Crown Estate, 16 Burlington Place, London, W1S 2XH, UK
c
School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
abstractarticle info
Article history:
Received 12 March 2012
Received in revised form 28 February 2013
Accepted 29 March 2013
Available online 8 April 2013
Keywords:
Drowned landscapes
English Channel
Sea level
Straits of Dover
Continental shelf stratigraphy
Quaternary
The erosional morphology preserved at the sea bed in the eastern English Channel dominantly records denu-
dation of the continental shelf by fluvial processes over multiple glacial–interglacial sea-level cycles rather
than by catastrophic flooding through the Straits of Dover during the mid-Quaternary. Here, through the
integration of multibeam bathymetry and shallow sub-bottom 2D seismic reflection profiles calibrated
with vibrocore records, the first stratigraphic model of erosion and deposition on the eastern English Channel
continental shelf is presented. Published Optical Stimulated Luminescence (OSL) and
14
C ages were used
to chronometrically constrain the stratigraphy and allow correlation of the continental shelf record with
major climatic/sea-level periods. Five major erosion surfaces overlain by discrete sediment packages have
been identified. The continental shelf in the eastern English Channel preserves a record of processes operat-
ing from Marine Isotope Stage (MIS) 6 to MIS 1. Planar and channelised erosion surfaces were formed by flu-
vial incision during lowstands or relative sea-level fall. The depth and lateral extent of incision was partly
conditioned by underlying geology (rock type and tectonic structure), climatic conditions and changes in
water and sediment discharge coupled to ice sheet dynamics and the drainage configuration of major rivers
in Northwest Europe. Evidence for major erosion during or prior to MIS 6 is preserved. Fluvial sediments of
MIS 2 age were identified within the Northern Palaeovalley, providing insights into the scale of erosion by
normal fluvial regimes. Seismic and sedimentary facies indicate that deposition predominantly occurred
during transgression when accommodation was created in palaeovalleys to allow discrete sediment bodies
to form. Sediment reworking over multiple sea-level cycles (Saalian–Eemian–early Weichselian) by fluvial,
coastal and marine processes created a multi-lateral, multi-storey succession of palaeovalley-fills that are
preserved as a strath terrace. The data presented here reveal a composite erosional and depositional record
that has undergone a high degree of reworking over multiple sea-level cycles leading to the preferential
preservation of sediments associated with the most recent glacial–interglacial period.
© 2013 Elsevier B.V. All rights reserved.
1. Introduction
Significant changes in relative sea level repeatedly submerge and
expose shallow continental shelves making them susceptible to ero-
sion, reworking and deposition, by sedimentary processes operating
in terrestrial, marine, and transitional environments. Consequently,
the preservation of ancient landscapes on the sea bed of the continen-
tal shelf provides archives of palaeoenvironmental change (Fedje and
Josenhans, 2000; Fitch et al., 2005; Gaffney et al., 2007; Kelley et al.,
2010; Hijma et al., 2012), commonly from time periods poorly repre-
sented on land (Mellettetal.,2012a). These drowned landscapes are
ideal for examining the interactions between sedimentary processes
over glacial–interglacial sea-level cycles, and the factors that determine
the imprint they leave (both erosional and depositional) on the conti-
nental shelf. The number of detailed case studies is growing rapidly
due to recent advances in submarine technologies and the increasing
availability of commercially acquired data, thus greatly improving our
understanding of submarine landscape evolution. These advances are
providing crucial evidence for assessing the impacts of future sea-level
rise on coastal economies and ecosystems.
The continental shelf between Britain and France has received atten-
tion in the literature for many years (see Gibbard and Lautridou, 2003;
Preece, 1995 for reviews, and Dingwall, 1975; Kellaway et al., 1975;
Roep et al., 1975; Smith, 1985; Gibbard et al., 1988; Smith, 1989;
Gibbard, 2007; Gupta et al., 2007; Toucanne et al., 2009a)becauseofits
potential to preserve a record of the timing and mechanism that led to
the isolation of Britain, as a geographical island, from the European con-
tinent during the mid-Quaternary. Despite ongoing debates regarding
the timing of erosion (Meijer and Preece, 1995; van Vliet-Lanoë et al.,
Geomorphology 203 (2013) 79–96
⁎Corresponding author. Tel.: +44 151 795 0126.
URL: mellettc@liverpool.ac.uk (C.L. Mellett).
1
Present address: School of Environmental Sciences, University of Liverpool, Liver-
pool, L69 7ZT, UK.
0169-555X/$ –see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.geomorph.2013.03.030
Contents lists available at ScienceDirect
Geomorphology
journal homepage: www.elsevier.com/locate/geomorph
2000; Busschers et al., 2008; Hijma et al., 2012), the most recent evidence
supports a Marine Isotope Stage (MIS) 12 age, at least for the initial
breach (Toucanne et al., 2009a), with an English Channel–North Sea ma-
rine connection during highstand, at some point between MIS 12 to MIS 6
(Meijer and Cleveringa, 2009). The resulting palaeogeographical configu-
ration of Britain and Northwest Europe has implications for the migration
of floraandfauna(Preece, 1995; Meijer and Cleveringa, 2009) including
hominids (Stringer, 2006; Hijma et al., 2012) throughout the Pleistocene.
Additionally, reorganisation of drainage basins and funnelling of fresh-
water discharge through the English Channel during cold stages as a con-
sequence of breaching of the Straits of Dover (Gibbard et al., 1988;
Bridgland et al., 1993; Bridgland and D'Olier, 1995; Gibbard, 1995;
Busschers et al., 2007, 2008), may have contributed to destabilisation of
the Atlantic thermohaline circulation (Menot et al., 2006; Gibbard,
2007; Toucanne et al., 2009b, 2010).
A number of mechanisms have been proposed to explain breaching
at the Straits of Dover including gradual erosion as a result of fluvial
downcutting (Dingwall, 1975; Gibbard et al., 1988; Busschers et al.,
2008) and catastrophic flooding (Smith, 1985; Gibbard, 2007; Gupta
et al., 2007). The bedrock morphology of the continental shelf in the
eastern English Channel, particularly the erosional bedrock bedforms
preserved in the Northern Palaeovalley, have been interpreted as the
productofhighmagnitudeflows linked to erosion at the Straits of
Dover by megaflood events (Gupta et al., 2007). However, this interpre-
tation was based on bathymetric data of the sea bed only, and did not
consider the sedimentary record preserved in the subsurface stratigra-
phy. Distinguishing catastrophic events from ‘normal’sedimentary pro-
cesses requires an understanding of how fluvial and marine processes,
over multiple sea-level cycles, interact to create the morphological
and sedimentary history of the continental shelf.
Here, the first detailed chronometrically constrained stratigraphic
record of palaeoenvironmental change on the eastern English Channel
continental shelf is presented. The erosional and depositional record
is established through the integration of multi-beam bathymetric
data with subsurface geophysical and vibrocore data. Tying sedimen-
tary and morphological data to available chronometry (Wessex
Archaeology, 2008; Mellett et al., 2012b) permits reconstructions
of palaeogeographic- and drainage configurations. Catastrophic flood
events are discussed in the light of new insights into the timing and
nature of erosion and deposition on the continental shelf.
2. Geographical and geological setting
The English Channel, or La Manche, is a narrow seaway that during
sea-level highstands separates the terrestrial environmentsof southern
Britain and northern France. The narrowest and shallowest tract is at
the Straits of Dover in the East, and the widest and deepest tract is
between Cornwall and Brittany in the West. The continental shelf sub-
merged beneath the English Channel forms a gently sloping platform
(ca. 0.01°) that extends 600 km westwards from the Straits of Dover
towards the continental shelf edge break in water depths of −200 m
Ordnance Datum (OD) (Pantin and Evans, 1984). In the north-east,
this slope is dissected by a complicated network of palaeovalleys that
locally form offshore extensions of contemporary rivers such as the
Seine, Somme and Solent (Lericolais, 1997; Velegrakis et al., 1999;
Bridgland, 2002; Antoine et al., 2003; Lericolais et al., 2003; Tessier et
al., 2010)(Fig. 1). These palaeovalleys are tributaries of a major axial
fluvial system (Channel River/Fleuve Manche) that channelled dis-
charge from the Thames and Rhine–Meuse rivers (Gibbard et al.,
1988; Lericolais, 1997) along with meltwater from Northwest European
Ice Masses (Toucanne et al., 2009b, 2010) during late Quaternary
sea-level lowstands (Fig. 1). Large palaeovalleys of the Channel River
that are not linked to present day onshore drainage networks include
the Lobourg Channel in the Straits of Dover, the Northern Palaeovalley
in the eastern English Channel and the Median Palaeovalley in the cen-
tral Channel basin (Fig. 1). The course of the Channel River to the shelf
edge break is interrupted by the Hurd Deep, a NE–SW trending linear
depression of Neogene tectonic origin that acted as a sediment sink
when the shelf was exposed during sea-level lowstands (Lericolais
et al., 1996).
The area referred to in this paper as the eastern English Channel
represents ca. 5000 km
2
of the sea bed offshore of the south-east
coast of Britain (Fig. 1). The extent of this study area is delimited by
the availability of geophysical data (Fig. 2). Sea bed morphology
reveals a number of E–WtoNE–SW trending confined bathymetric
lows, one of which includes the Northern Palaeovalley. This morphol-
ogy is the sea bed expression of a network of palaeovalleys that
physically connect the Lobourg Channel to the Northern Palaeovalley
and the Median Palaeovalley (Fig. 1).
The geology of the eastern English Channel is dominated by Creta-
ceous strata of the Weald–Artois anticline and Cenozoic deposits of the
Hampshire–Dieppe Basin (Hamblin et al., 1992). A general WSW–ENE
alignment of fold and fault structures is apparent. The eastern English
Channel as a geological province has remained relatively stable since up-
lift of the Weald–Artois anticline and sedimentation in the Hampshire–
Dieppe Basin in response to a late Alpine compressional phase during
the Miocene (Anderton, 2000). Thus, Pliocene and Pleistocene evolution
can mostly be attributed to fluvial response to long-term tectonics with
higher frequency relative sea-level changes (Lagarde et al., 2003; Le Roy
et al., 2011). Gradual uplift of the English Channel during the Quaternary
is recorded in fluvial terrace staircases of major rivers draining southern
Britain and northern France (Antoine et al., 2000; Briant et al., 2006;
Westaway et al., 2006; Antoine et al., 2007) and raised beaches of the
south coast of Britain (Preece et al., 1990; Bates et al., 2003; Westaway
et al., 2006; Bates et al., 2010). It is likely that uplift and subsidence in re-
sponse to glacio-isostasy over glacial–interglacial cycles (Lambeck,
1997; Shennan et al., 2000; Waller and Long, 2003; Busschers et al.,
2008)alsoinfluenced development of the eastern English Channel.
In the eastern English Channel study area up to 70% of the sea bed is
characterised as bedrock exposed at the sea bed or bedrock covered by a
thin (b1 m) veneer of sediment (James et al., 2011). Significant thick-
nesses (up to 30 m) of sediment are limited to infilled portions of
palaeovalleys and a small number of constructional bedforms (Hamblin
et al., 1992). Sediments are predominately siliciclastic, comprising sand
and gravel. Fine grained and organic-rich sediments are rare and limited
to drowned palaeovalleys (Bellamy, 1995; Velegrakis et al., 1999; Gupta
et al., 2004) or back barrier-settings (Mellett et al., 2012a), proximal to
the present-day coastline.
3. Methods
3.1. Bathymetric data collection and processing
To determine the depth to sea bed relative to Ordnance Datum
(OD), i.e. the British reference altitude of mean sea level at Newlyn,
a range of bathymetric data sources were used, depending on the
resolution required. Single-beam and multi-beam echo soundings
were collected simultaneously with seismic reflection data (see
Section 3.2 and Fig. 2 for survey track lines). The bathymetric data
are used to calibrate sea bed response from seismic reflection profiles
to OD. SeaZone Solutions Ltd. digital bathymetry and digital charted
bathymetry were obtained and interpolated using a standard kriging
algorithm in ArcGIS into a 120 m cell size grid. This allowed the
morphology of the sea bed to be assessed and provided a local surface
to which all other interpolations could be tied. The Olex global ba-
thymetry database (www.olex.no) was used to characterise regional
bathymetry outside the study area (Fig. 1). These data were collected
using standard single-beam echo sounders and GPSs. Data coverage
in the English Channel is exceptional producing a high resolution
chart (between 20 m and 200 m track spacing) of the sea bed. Posi-
tioning accuracy is generally b10 m and vertical resolution in water
depths of b100 m is 0.1 m (Bradwell et al., 2008).
80 C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
3.2. Seismic data acquisition and interpretation
Shallow sub-bottom, 2D seismic reflection data were collected over
20 years of prospecting surveys by the Resource Management Associa-
tion (RMA, comprising CEMEX UK Marine Ltd., Hanson Aggregates Ma-
rine Ltd. and Tarmac Marine Dredging Ltd.), and made available for this
study. These seismic data were collected using surface-towed Boomer
sources typically operating at frequencies between 0.5 and 5 kHz that
penetrate and resolve unconsolidated sediments to ca. 50 m below
the sea bed. These data were collated with 2D seismic reflection data
collected as part of the Eastern English Channel Marine Habitat Map
Project (James et al., 2007). Additional shallow sub-bottom seismic
Fig. 1. Sea bed bathymetry of the English Channel continental shelf. Inset map shows merged bathymetric and topographic data for Northwest Europe (Bathymetry: The GEBCO_08
Grid, version 20091120, http://www.gebco.net. Digital elevation data: SRTM (Jarvis et al., 2008) available from http://srtm.csi.cgiar.org). Bathymetry source for the main map is
Olex, used with permission of Olex AS. Depths are relative to UK mean sea-level (OD). Arrows indicate major drainage configurations and numbers identify offshore extensions
of large European rivers and main palaeovalleys/topographic features: (1) Lobourg Channel, (2) South Basserelle (SB) Palaeovalley, (3) Northern Palaeovalley, (4) Palaeo-Solent,
(5) Median Palaeovalley (Antoine et al., 2003), (6) Palaeo-Seine, (7) Hurd Deep. Coordinate system WGS84 UTM Zn 31 N.
Fig. 2. Offshore seismic and vibrocore data. Bathymetric data were extracted from the Olex database, used with permission of Olex AS. Enlarged inset maps show the location of
seismic profiles presented in Figs. 4–6, and the positioning of vibrocores referred to in Figs. 10 and 11, and Table 3. Map coordinates WGS84 UTM Zn 31 N.
81C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
reflection data (Boomer 1–4 kHz) were collected as part of this study to
permit integration and correlation between individual surveys and im-
prove spatial resolution where data coverage was sparse. Through the
integration of all datasets a total of 6000-line km of seismic reflection
data were used to assess the nature, extent and thickness of sediments
preserved in the eastern English Channel. The locations of all survey
data are presented on Fig. 2.
Interpretation of seismic reflection profiles is based on Mitchum
et al. (1977). Characterisation of seismic facies and seismic stratigra-
phy was carried out according to the criteria presented in Fig. 3.A
summary of all seismic facies is presented in Table 1 and shown to-
gether with interpreted seismic lines in Figs. 4–6. In unconsolidated
sediments, an acoustic velocity of 1700 ms
−1
was used to convert
two way travel time (TWTT) to depth in metres.
3.3. Identification of erosion surfaces
To determine the morphology of the unconformity separating
bedrock from overlying unconsolidated sediments, an isopach of
sediment thickness, determined from individual seismic lines and in-
terpolated into a 3D grid using ArcGIS (Fig. 7b), was subtracted from
sea bed bathymetry (Fig. 7a) to produce a map showing bedrock ele-
vation relative to OD (Fig. 7c). Spatial limitations of available seismic
data meant this could only be carried out within a limited area re-
ferred to herein as the interpolated grid. Identification of discrete ero-
sion surfaces within the interpolated grid was achieved by producing
a frequency histogram of bedrock elevations and distinguishing
between multiple populations by qualitatively identifying peaks in
the distribution (Fig. 8a). To test the geomorphological significance
of discrete populations associated with each peak, 2D profiles of
bedrock elevation were evaluated to ensure that breaks in slope iden-
tified in the frequency histogram were true breaks in elevation
separating individual erosion surfaces (Fig. 8b). Key morphological
features within each erosion surface (e.g. river channels, platforms,
breaks in slope and bedrock bedforms) were visually identified
(Figs. 8b and 9). James et al. (2011) identify areas where bedrock is
exposed at sea bed (Fig. 8c), which was used to provide additional
information on the morphology of the bedrock unconformity outside
the interpolated grid.
3.4. Vibrocoring and sedimentary facies
A database containing over 300 vibrocores tied to seismic reflec-
tion profiles was made available by the RMA. This database included
core descriptions logged in accordance with BS5930 (1981), core
photographs and the results of particle size distribution analysis
carried out at the discretion of the RMA within each core. All cores
were recovered with a high-powered vibrocorer (6 m maximum
penetration) over a series of individual surveys that corresponded
with the collection of seismic reflection data. Sub-samples of these
cores were selected to allow higher resolution sedimentary facies de-
scriptions and sampling for lithological and chronometric analyses.
An additional 11 vibrocores were collected during March 2010 to sup-
plement the core database, to calibrate seismic facies with sedimenta-
ry facies, and to obtain samples for chronometric analysis (Mellett
et al., 2012b). The locations of vibrocores are indicated on Fig. 2.
Data obtained from the core database and vibrocore samples form
the basis for lithostratigraphic analysis and characterisation of sedi-
mentary facies. A summary of all sedimentary facies is presented in
Table 2 and representative core photographs are shown in Figs. 10
and 11.
3.5. Chronometric data
A total of 9 optical stimulated luminescence (OSL) ages were obtained
using sand-sized quartz extracted from a selection of vibrocores, full
methodological details and results are published in Mellett et al.
(2012b). This chronological information was supplemented by published
OSL and radiocarbon (
14
C) ages from sediments deposited in the South
Basserelle (SB) Palaeovalley (Fig. 6b) (Wessex Archaeology, 2008). A
summary of all ages including information pertaining to the accuracy of
published ages is presented in Table 3.
4. Results
Peak analysis of the frequency distribution of bedrock elevations
revealed four major erosion surfaces referred to as T2, T3, T4 and
maximum (deepest) erosion (ME) surface (−67 m OD) (Fig. 8a).
An additional erosion surface (T1) is characterised according to sea
bed elevations outside of the interpolated grid where bedrock is ex-
posed at sea bed (Fig. 8c). A framework for establishing the relative
stratigraphy of erosion surfaces assumes denudation through time
in an area of overall tectonic uplift (Davis, 1899). This implies surface
T1 is the oldest surface at the highest elevations and ME is the youn-
gest base level of the most recent erosional regime prior to submer-
gence of the continental shelf by post-glacial sea-level rise. Erosion
surfaces and depositional facies are discussed in chronological order
from oldest to youngest.
Fig. 3. Guide to the interpretation of seismic reflection data based on Mitchum et al. (1977).
82 C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
4.1. Bedrock erosion
Erosion surface T1 lies outside of the interpolated grid and occupies
elevations between 0 m and −30 m OD (Fig. 8c). The erosion surface
dips at 0.1° towards the south and gently westward (0.02°) towards
the continental shelf break (Fig. 8c).
Erosion surface T2 lies within the interpolated grid at elevations
between −30 m OD and −38 m OD. Outside of the interpolated
grid, bedrock is exposed at sea bed at these elevations implying sur-
face T2 is present to the NE of the interpolated grid where it appears
as a planar topographic platform (Fig. 8c).
Surface T3 is the most widespread surface within the interpolated
grid and it displays a strong degree of continuity at elevations between
−38 m and −47 m. As a whole it is characterised by a relatively planar
gently dipping (ca. 0.05° westwards) continuous platform (Fig. 8c). Cut
into this surface is a network of cross-cutting bedrock channels with
planform geometries ranging from low sinuosity linear channels to a
meander cut-off indicative of higher degrees of sinuosity (Fig. 9). Sur-
face T3 only occurs on strata of the Hampshire–Dieppe Basin. The low
angle but well defined slope (0.5° to 3.0°) that separates this surface
from surfaces T1 and T2 has been defined as the margin of the Northern
Palaeovalley (Smith, 1985, 1989; Hamblin et al., 1992; Antoine et al.,
2003; Gupta et al., 2007).
Surface T4 occupies elevations between −47 m and −58 m, and
in the NE forms the base of WSW–ENE trending, sub-parallel, chan-
nels (on average 15 km length and 1.5 km width) that subdivide sur-
face T3 into elongate bedrock islands (Fig. 9b). To the SW, surface T4
broadens into a 20 km-wide depression (Fig. 9) that is part of a large
SW–NE trending palaeovalley that extends westwards towards the
Hurd Deep (Fig. 1).
The base of the maximum erosion (ME) surface is planar at −67 m
OD. It is incised into surface T4 and creates a confined channel (the SB
Palaeovalley Fig. 9a) that widens towards the west to form the base
of the Northern Palaeovalley (Fig. 9a). The SB Palaeovalley follows
structural folds in the bedrock geology, incising into and running
parallel with London Clay at its contact with underlying chalk until it
reaches Eocene-aged stratigraphy exposed in the base of the Northern
Palaeovalley. Within the Northern Palaeovalley, isolated remnants of
T4 form a collection of streamlined mid-channel bedrock islands
(Fig. 9a).
4.2. Depositional facies and environments
4.2.1. Deposits on surfaces T1 and T2
Bedrock is exposed at the sea bed across large areas of surface T1
(Fig. 8c). The thickest sediment cover is observed in the northeast
Table 1
Seismic facies characteristics. Refer to Fig. 3 for a guide to the interpretation of reflector configurations and facies geometries.
Seismic facies Internal geometry Frequency Amplitude Continuity Reflector configuration Reflector termination
sf
1
Sheet Medium to high High Continuous Parallel to low angle parallel oblique Onlap
sf
2
Channel Medium to low High Continuous Parallel draped Concordance
sf
3
Channel or lens medium High Continuous to discontinuous Sub-parallel Onlap
sf
4
Channel or lens Medium to low Medium to high Continuous to discontinuous Oblique to sigmoid Downlap and truncation
sf
5
Lens Medium Medium to high Continuous Parallel oblique Downlap and truncation
sf
6
Channel Medium to high medium Discontinuous Oblique to hummocky Downlap and truncation
sf
7
Channel Medium Medium to low Discontinuous Hummocky to chaotic –
sf
8
Channel Medium to low Low Discontinuous Undifferentiated –
sf
9
Mound Medium Medium to high Discontinuous Oblique to sigmoid Downlap and truncation
sf
10
Drape Reflectors below resolution of unit
Fig. 4. Seismic reflection profile and interpreted panels illustrating seismic facies character and association for deposits overlying surface T3. The location of profiles C–C' and D–D' are
highlighted on Fig. 2. A sedimentary log of VC52b is shown in Fig. 11.
83C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
around Hastings Bank and Rye Bay (Fig. 8c). Depositional architecture
and geomorphic change in the Hastings Bank area are addressed in
Mellett et al. (2012a). In summary, a seaward-thickening wedge has
been identified comprising sand overlain by coarse grained gravel
ridges that are breached by finer grained silty deposits. The entire
succession has been interpreted as a submerged barrier complex of
Holocene age. Other deposits in the Rye Bay have been characterised
as a seaward prograding shelf sand body with a minor coarse clastic
component (Dix et al., 1998). Elsewhere on surface T1, sediment is
confined to the fills of palaeovalleys that drained the southern British
uplands (Bellamy, 1995; Gupta et al., 2004).
Deposition on surface T2 is limited to sandy sediment waves and
banks (Fig. 7a). These relict sediment banks are inactive under the
present-day hydrodynamic regime (Anthony, 2002) but probably repre-
sent deposition during the mid- to late Holocene sea-level rise when
tidal currents were influential at these depths (Uehara et al., 2006).
4.2.2. Deposits on surface T3
Surface T3 is the most extensive surface in the eastern English
Channel making a simple classification of associated deposits difficult.
The most volumetrically significant sedimentary deposits of the east-
ern English Channel are associated with this surface and form a sheet
of sediment that thins to bedrock in the west and is truncated by
erosion surfaces T4 and ME in the north and west (Fig. 7b). Deposits
overlying T3 have a composite and complicated seismic signature
comprising multiple discontinuous erosion surfaces overlain by
oblique to chaotic reflector patterns (Fig. 4). This seismic facies asso-
ciation is interpreted to represent a multi-storey and multi-lateral
amalgamated channel belt (Miall, 2006)(Fig. 3). The channel belt
extends 30 km to the west and 20 km to the north within the area
delimited as the interpolated grid and is on average less than 6 m
thick (Fig. 7b). Channel incision is either directly into bedrock or
through alluviumuntil the bedrock is reached. The characteristic seismic
stratigraphy and depositional architecture of individual palaeovalleys
within the channel belt are shown in Fig. 4, and full descriptions of
seismic and sedimentary facies are given in Tables 1 and 2.
Identifying single channels can be achieved on N–S trending
seismic profiles where channels are intersected at 90° to their longi-
tudinal profile and can be traced downslope across seismic profiles
(Fig. 4). Channel margins cut into alluvium with channel thalweg ero-
sion into bedrock. Asymmetric cross-sections of the channel bodies
combined with oblique to sigmoid reflector patterns (sf
4
) at the chan-
nel margins indicate some degree of sinuosity, which is also reflected
in the morphology of surface T3 (Fig. 9). Assuming channels are
intersected perpendicular to flow direction, individual channels are
on average between 0.5 and 1.5 km wide.
Fig. 5. Seismic reflection profile and interpreted panels illustrating seismic facies character and association for deposits overlying surface T4 and ME. (a) Cross-profile showing
bathymetry of the sea bed and the location of deposits overlying surfaces T4 and ME. (b) Seismic reflection profile and interpreted panels illustrating seismic facies character
and association for deposits overlying surface ME. The location of profile E–E' is highlighted on Fig. 2. (c) Seismic reflection profile and interpreted panels illustrating seismic facies
character and association for deposits overlying surface T4. The location of profile F–F' is highlighted on Fig. 2. A sedimentary log of vibrocore L1a is presented in Fig. 11.
84 C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
Sedimentary infill is complicated, with a number of smaller
cut-and-fill cycles confined within the composite channel geometry.
Oblique downlapping seismic reflectors (Sf
4
) are limited to the steepest
margin of the channels suggesting deposition is driven by lateral- and
downstream-accretion of bar complexes (Fig. 4). Discontinuous, hum-
mocky to chaotic reflectors of Sf
7
(Table 1) indicative of contrasting
lithologies are present at the base of the channel implying that deposition
occurred under a variable process regime. Sub-parallel reflectors of Sf
3
(Table 1) representing lateral continuity in lithology, correspond to the
latest stages of sedimentary infill and indicate aggradation under a
more consistent energy regime.
Precise calibration of sedimentary facies with seismic facies is
problematic due to the resolution of both seismic and core records
that are biased towards superficial strata and thus the later stages of
channel infill. Typically, coresreveal gravels supported by a sand matrix
(Gm) interbedded with fine grained well-sorted, laminated sands (Sfw)
(Table 2 and Fig. 10). Coarse-grained, flint-rich gravels are most likely
the product of local bedrock erosion and later transport by fluvial pro-
cesses within the channel belt complex. The abundance of shallow ma-
rine foraminifera (predominantly Elphidium sp. and Ammonia sp.) in
Sfw indicates deposition in a shoreface setting and these sedimentary
facies are considered the product of flooded valley infilling during
sea-level rise. The intercalation of fluvial and shallow marine environ-
ments is reflected in the amount of reworked thick-walled shells within
the coarse grained deposits. Distinguishing between marine reworked
fluvial deposits and fluvial reworked marine deposits is challenging
but implies deposition occurred in an environment where the position
of the shoreline fluctuated in response to sea-level oscillations. In
summary, deposits overlying surface T3 are interpreted as a composite
sheet of sand and gravel that represent widespread interfingering and
reworking by marine and fluvial processes.
Thinning of deposits overlying surface T3 to the west is attributed
to an erosional event as seen from the truncation of seismic reflectors
and deposition of sf
1
(Table 1 and Fig. 4) which is evident on seismic
profiles throughout the eastern English Channel. The erosion surface
at the base of Sf
1
is interpreted to represent wave ravinement during
transgression due to its spatial extent and the planar nature of the
lower bounding surface. Parallel onlapping seismic reflectors and
the uniform thickness of sedimentary facies Smw and Cm (Table 2
and Fig. 10) suggest deposition subsequently occurred in a marine
environment.
One of the most striking features of the channel belt deposits is var-
iations in colour within sedimentary facies Gm (Table 2 and Fig. 10). The
gravels are clearly heavily weathered and show evidence, based on
their colour, of different degrees of secondary iron oxide development
(Hurst, 1977). This would suggest that subsequent to deposition, chan-
nel belt sediments were sub-aerially exposed for a sufficient period to
develop a red to dark brown coloured soil prior to erosion by wave
ravinement.
4.2.3. Deposits on surfaces T4 and ME
Sediments associated with surface T4 occur in isolated patches
and are usually smaller than the spatial resolution of the available
data. Seismic Line L1 reveals a thin (b5 m) remnant deposit at the
base of a slope (1°) separating surface T4 from surface T3 (Fig. 5a).
This small lens of sediment appears to occupy a minor depression with-
in surface T4 and oblique downlapping reflectors (sf
4
) indicate down-
slope progradation (Fig. 5c). Full recovery of vibrocore L1a revealed a
very poorly sorted and poorly stratified succession of sandy mud,
muddy sand and muddy gravel (Fig. 11). The gravel component com-
prises fine- to cobble-sized clasts of angular flint and chalk. Coarse
grained beds are interbedded with finer grained beds dominated by a
Fig. 6. Seismic reflection profile and interpreted panels illustrating seismic facies character and association for deposits overlying surface T3 and ME. (a) Bathymetry in the eastern
English Channel showing the morphology of the SB Palaeovalley at its confluent with the Northern Palaeovalley (Bathymetry © British Crown and SeaZone Solutions Limited. All
rights reserved. Product license No. 112010.009). Bathymetry is shaded according to the scale given in Fig. 7a. Locations of cross-profiles G–G' and H–H' are shown as white lines.
(b) Schematic representation showing the stratigraphy and depositional context of sediments preserved within the SB Palaeovalley adapted from Wessex Archaeology (2008). Sed-
imentary facies are provided in italics. Age data obtained from samples representing each stratigraphic unit are presented. Full details of these ages are given in Table 3. OSL ages are
given in ka and
14
C ages in cal. BC.For marine marginal sediments, a single samplewas extracted for OSLand
14
C was carriedout on shell materialcontained withinthat sample. (c)Seismic
reflection profile and interpreted panel illustrating seismic facies character and association for deposits overlying surface T3 and ME.
85C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
Fig. 7. Interpolationof the unconformity separatingunconsolidated sediment from bedrock in the eastern EnglishChannel.(a) Sea bed bathymetryof the easternEnglish Channel studyarea
(© British Crown andSeaZone Solutions Limited. Allrights reserved. Product license No. 112010.009), overlying Olexshaded relief data, used with the permissionof Olex AS. (b) Isopach of
sediment thickness overlying Olex shadedrelief data, used with permission of Olex AS. Solid black linedelimits eastern English Channel study area. Dashed black line delimits interpolated
grid. (c)Depth to bedrock shown withininterpolatedgrid delimitedby dashed black line,overlying Olexshaded relief data, used withpermission of Olex AS. Map coordinates WGS84 UTM
Zn 31 N.
86 C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
clay component. At the base of the core, highly weathered chalk
confirmed that bedrock was reached. This deposit is interpreted as a
mass wasting deposit at the base of a slope formed under cold climate
conditions (periglacial colluvium; termed ‘Head’regionally).
Preservation of sediments associated with the maximum erosion
surface is rare and limited to a single palaeovalley fill (SB palaeovalley,
Fig. 9a), as well as isolated deposits within the Northern Palaeovalley.
The extent of these deposits is highlighted in Fig. 7b and the seismic
stratigraphy presented in Figs. 5 and 6.
Sediments within the Northern Palaeovalley are limited to the
margins of the main channel (Fig. 5a). The characteristic geometry,
seismic stratigraphy and lithology of these deposits are shown on
Figs. 5b and 11. Sediments partially fill the channel, are thickest at
the channel margins, and thin towards the centre of the channel
and outer channel banks. Seismic reflector patterns (sf
4
) indicate
accretion towards the channel thalweg. Recovery of vibrocores was
low due to the coarse clastic nature of sediments. Maximum recovery
was achieved with N4c and N4d (Fig. 11) revealing matrix-supported
gravel (Gm) interbedded with laminated silty fine sand (Sfp). Both
the geometry of seismic facies and lithology of sediments imply depo-
sition of a point bar within a bedrock fluvial channel. In the example
shown in Fig. 5b at least three phases of accretion can be identified by
separation of inclined reflectors by high amplitude reflectors. Within
the channel thalweg, a bounding surface delimits the extent of accre-
tion and slightly inclined to parallel onlapping reflectors mark a
change in sedimentary regime (sf
2
,sf
3
and sf
5
) with deposition of
finer grained, less variable sediments.
The SB palaeovalley has a clear bathymetric and seismic expression
and can be traced for 45 km in the eastern English Channel (Fig. 6a).
Analysis of sub-bottom seismic profiles revealed a bedrock-confined
Fig. 8. Distinction of bedrockerosion surfaces in theeastern English Channel.(a) Frequency distribution of bedrock elevations showingsubdivision of erosionsurfaces. (b) Cross-sections
showing depthto bedrock. Locations of profiles given in Fig.8c. Elevation of erosion surfacesshaded according to the scale in Fig. 8c.Black arrows indicate breaks in slopethat distinguish
differenterosion surfaces. (c)Depth to bedrock shown within interpolated grid, shaded to highlightmajor erosion surfacesidentified in Fig. 8a. Outside the interpolated grid,the depth to
sea bed is given (© BritishCrown and SeaZone Solutions Limited. All rightsreserved. Productlicense No. 112010.009). Areaswhere bedrock is exposed at the seabed are taken from James
et al. (2011). Map coordinates WGS84 UTM Zn 31 N.
Fig. 9. Morphology of the sea bed and bedrock erosion surface. (a) Sea bed bathymetry highlighting key morphological features (© British Crown and SeaZone Solutions Limited. All
rights reserved. Product license No. 112010.009). (b) Bedrock geology (Geological Map Data © NERC 2012) overlain by an interpolated surface showing the depth to bedrock.
Dashed black line delimits the extent of the interpolated grid. Map coordinates WGS84 UTM Zn 31 N.
87C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
single channel incised into deposits associated with T3 and infilled with
up to 25 m of sediments (Fig. 6c). At the base of the channel is a thin
(b1 m) drape of sediment (sf
10
) that is succeeded by multi-storey
stacking of sf
6
(Table 1 and Fig. 6c). A vibrocore survey by Wessex
Archaeology (2008) uncovered the lithology of deposits associated
with each seismic facies, which is summarised in Table 3 and Fig. 6c.
When tied to seismic facies, the sedimentary facies demonstrate a tran-
sition from coarse grained gravel (Gm) at the base of the channel to
laminated sands (Sfp) within the lower channel-fill with increasingly
shell rich sands towards the surface (Sh and Smw) (Table 2 and
Fig. 6b). The association of seismic facies and sedimentary facies are
interpreted to represent deposition of a coarse-grained basal lag subse-
quent to channel incision followed by deposition of estuarine and shal-
low marine sediments in response to sea-level transgression (Fig. 6c).
4.3. Stratigraphy and chronology
Erosion surfaces are cut into bedrock and overlain by shallow ma-
rine, coastal and fluvial deposits. Published OSL and
14
C ages in the
range of 176.6 ± 20 ka to 5.3 ± 0.5 ka (Table 3) provide a chrono-
logical constraint to deposition on the continental shelf over at least
two glacial–interglacial cycles (Wessex Archaeology, 2008; Mellett
et al., 2012b). OSL and
14
C ages obtained by Wessex Archaeology
(2008) are inconsistent within the same core, at the same depth,
with a
14
C age (9160–8350 Cal. BC) underestimating an OSL age
(14.16 ± 1.1 ka) by approximately 3 ka (~20%).
According to the chronometric data, sediments within the channel
belt overlying surface T3 were deposited during marine oxygen iso-
tope stage MIS 6 and the late stages of MIS 5 (Fig. 12). Exposure of
surface T4 and deposition of sediments associated with surface ME
occurred during MIS 2. This places formation of surface T4 at some
point between the late sub-stages of MIS 5 and MIS 2. Partial infilling
of surface ME and deposition of coastal sediments on surface T1
correlate to MIS 1 (Mellett et al., 2012b).
4.4. Formation of erosion surfaces
The similar morphologies of surfaces T1 and T2 (see Section 4.1)
may suggest that they were formed by similar processes. Widespread
erosion and formation of seaward-dipping planar surfaces can occur
during sea-level transgression (Bradley and Griggs, 1976). Initial
formation of surface T1 has been linked to marine planation during
Neogene transgressions when the English Channel basin first became
a marine embayment (Lautridou et al., 1986; Gibbard et al., 1988;
Curry, 1989; Stride, 1990; Hamblin et al., 1992). The stepped margin
separating surface T1 from all other surfaces has been interpreted
as a submerged cliff line that formed during Neogene sea-level
stillstands (Kellaway et al., 1975; Hamblin et al., 1992). The data
presented here support such a model.
Using formation of T1 as a basis, surface T2 can also be considered
the product marine planation, but during a later phase of marine
transgression. Erosion of this surface would have occurred prior to
opening of the Straits of Dover, dated to MIS 12 (Toucanne et al.,
2009a). Surface T2 is drained by a dendritic channel network. Given
the limited size of these channels it is unlikely that they acted as a
conduit for drainage during breaching of the Straits of Dover and
probably reflect more localised incision in response to regression.
Sediments currently preserved on surfaces T1 and T2 originate from
palaeovalley infill and shoreline retreat during the Holocene trans-
gression (Table 3). Therefore, a significant hiatus between erosion
and deposition is apparent.
Seismic profiles indicate that surface T3 formed through fluvial
erosion by individual channels within a channel belt complex that
combined to create a bedrock strath surface. Individual channels
show evidence of lateral and downstream mobility that together
with transport of a coarse-grained bedload, represented by a basal
lag, is responsible for incision and valley widening during cold stages
(Lewin and Gibbard, 2010). A single OSL age of 176.6 ± 20 ka
(Table 3) from fluvial deposits overlying surface T3 suggests that, at
least locally, incision occurred during or prior to the early parts of
MIS 6. However, individual palaeovalleys are infilled with transgres-
sive deposits dating to the early sub-stages of MIS 5, which have
Table 2
Classification and interpretation of sedimentary facies according to lithological
composition.
Sedimentary
facies
Description Depositional
environment/process
Gm Very poorly sorted matrix supported sandy
gravel. Gravel typically comprises
sub-angular to sub-rounded flint clasts.
Matrix is medium to coarse sand.
Fluvial
Gfu Well sorted clast supported coarse gravel up
to cobble size. Gravel is largely flint and
sub-rounded
Coastal (nearshore)
Sfp Fine to medium sand with frequent
laminations of silty clay. Laminations are
generally fine but can be up to 1 cm in
thickness. Clay is occasionally organic rich.
Alluvial or tidally
influenced
Sh Poorly sorted slightly gravelly fine to medium
sand with frequent outsized gravel clasts.
Gravel component is sub-angular to
sub-rounded, fine to medium size and of
various lithologies. Frequent shell fragments
throughout.
Shallow marine to
coastal (nearshore)
Smw Generally well sorted occasionally
moderately sorted slightly gravelly medium
to coarse calcareous sand. Shells, both whole
and fragmented are frequent. Occasional
organic mottles and inclusions of granule size
coal.
Coastal–shallow
marine
Sfw Very well sorted laminated fine to medium
size quartz sand. Occasional inclusions of coal
of granule size.
Shallow marine
(shoreface)
Cd Very poorly sorted silty sandy gravelly clay.
Gravel is largely chalk and flint. Deposit is
stiff and varies considerably in composition.
Periglacial slope
Cm Very poorly sorted matrix supported gravel.
Matrix is clayey sandy silt with frequent shell
fragments throughout. Gravel is angular to
sub-rounded, fine to medium size.
Wave/tide
reworking
Br Bedrock, often highly weathered. –
Fig. 10. Photographs showing the composition of sedimentary facies in two vibrocores
taken from the locations shown in Fig. 2. Each core comprises two sections that are 1 m
in length.
88 C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
subsequently been partially eroded and reworked by renewed phases
of fluvial incision. Therefore, erosion of surface T3 cannot be linked to
a single climatic event. Whilst surface T3 demonstrates characteristics
of a strath surface, the variable lithological composition of sediments
within the channel belt complex and the degree of variability
recorded in seismic profiles suggests that composite erosion was
achieved through repeated phases of incision in response to fluctuat-
ing sea levels, rather than channel avulsion across a broad fluvial
plain.
Sediments preserved on surface T4 show that after incision the
area was sub-aerially exposed and subjected to periglacial conditions
during MIS 2. A hiatus between incision and deposition is inferred as
localised weathering of bedrock alone cannot explain the formation
of surface T4. Subsequent modification by surface ME precludes con-
fident interpretation of the erosion mechanisms. Surface T4 may have
encompassed the area now occupied by the Northern Palaeovalley, as
remnants of this surface are preserved at the valley margins. Incision
of parallel-aligned, linear grooves (low sinuosity channels in Fig. 9)
Fig. 11. Sedimentary logs and core photographs showing stratigraphy and lithologicalcomposition of sedimentary facies discussed in Table 2. Locations of vibrocores are highlighted in
Fig. 2 and correlated to seismic lines in Figs. 4 and 5. The location of OSL samples and resulting ages (Mellett et al., 2012b) are given.
89C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
show a morphological resemblance to bedrock furrows described in
Richardson and Carling (2005). These features are typically attributed
to fluvial erosion but they can also occur in tidal environments where
bedrock is sufficiently erodible (Carling et al., 2009). In the eastern
English Channel, these furrows/low sinuosity channels are confined
to the relatively softer bedrock of the Hampshire–Dieppe Basin
suggesting that underlying lithology has some control over their for-
mation (Fig. 9b). Based on the available data, distinguishing between
fluvial or tidal erosion is not possible. Elsewhere, surface T4 forms the
base of a broad palaeovalley that is confluent with the Median
Palaeovalley in the central English Channel (Fig. 1) and indicates
that at least part of surface T4 formed through fluvial incision. Erosion
of this surface occurred at some time during MIS 4–3 when the conti-
nental shelf was sub-aerially exposed (Fig. 12).
Planform and cross-sectional geometries of surface ME in the SB
Palaeovalley suggest that incision was driven by downcutting of a
bedrock-confined fluvial channel. Assuming deposition of a basal lag
on top of surface ME is a product of the processes driving erosion,
an OSL age from this deposit provides a chronometric constraint for
incision at ca. 21 ka (Table 3).
A change in morphology between the SB Palaeovalley and the
Northern Palaeovalley (Fig. 9a) indicates a change in erosive regime.
Bedrock morphology of the Northern Palaeovalley has been interpreted
as the product of high magnitude flow regimes linked to catastrophic
Table 3
Age data. Locations of cores, with the exception of those recovered by Wessex Archaeology (2008), are shown in Fig. 2. Refer to cited literature for full methodological details. Un-
certainty on OSL ages is given at 1-σlevel and for
14
C ages, at 2σlevel. MAM-3—minimum age model with 3 parameters.
Erosion
surface
Location Depositional environment Core Depth
(m OD)
Dating
method
Age Reference Reliability
T1 Hastings Bank Coastal (washover fan) VC37a −16.81 OSL 5.3 ± 0.5 ka Mellett et al. (2012a, 2012b) Incomplete bleaching, MAM-3
applied
Shallow marine VC28 −19.11 OSL 7.8 ± 0.2 ka Well bleached
Shallow marine VCL3b −13.70 OSL 8.4 ± 0.2 ka Well bleached
Coastal (nearshore beach) VC37b −24.02 OSL 8.0 ± 0.6 Incomplete bleaching, MAM-3
applied
T3 Channel belt complex Shallow marine VC52b −48.80 OSL 107.8 ± 5.2 ka Mellett et al. (2012a)
Wessex Archaeology (2008)
Well bleached
SB palaeovalley
(alluvial terrace)
Marine marginal VC7 −41.56 OSL 83.2 ± 6.6 ka No information published
Fluvial (palaeosol) −42.88 OSL 176.6 ± 20 ka
T4 Northern Palaeovalley
margin
Periglacial (head deposit) VCL1a −53.10 OSL 17.9 ± 0.7 ka Mellett et al. (2012b) Potential post-depositional
mixing and variable dose rate
ME Northern Palaeovalley Fluvial (point bar) N4c −53.20 OSL 15.8 ± 0.9 ka Mellett et al. (2012b) Well bleached
Fluvial (point bar) N4d −53.40 OSL 16.8 ± 0.7 ka
Fluvial (point bar) N4d −52.70 OSL 17.1 ± 0.8 ka
SB Palaeovalley Shallow marine VC1 −47.90 C
14
(shell) 7320–6860 cal. BC Wessex Archaeology (2008) Marine reservo ir effect
Marine marginal VC1 −48.03 OSL 11.9 ± 0.9 ka No information published
VC1 −48.86 C
14
(shell) 9160–8150 cal. BC Marine reservoir effect
Marine marginal
(estuarine to freshwater)
VC3 −55.12 OSL 14.2 ± 1.1 ka No information published
VC3 −55.13 C
14
(shell) 9160–8350 cal. BC Marine reservoir effect
Alluvial or tidally influenced VC3 −55.58 OSL 15.1 ± 1.2 ka No information published
Fluvial (basal lag) VC5 −49.34 OSL 21.2 ± 1.5 ka No information published
Fig. 12. Erosional and depositional records preserved on the eastern English Channel continental shelf presented alongside the marine isotope record (Lisiecki and Raymo, 2005)
and a composite global sea-level curve (Waelbroeck et al., 2002) during the mid- to late Quaternary. Chronostratigraphic subdivisio n is based on Cohen and Gibbard (2011). Timing
of the Last Glacial Maximum (LGM) after Clark et al. (2009). Elevations of erosion surfaces shown on the sea-level curve with present-day sea-level highlighted by a thick dashed
line. Interpretations of sedimentary regimes during each stage are based on the data presented in Section 4.
90 C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
flooding through the Straits of Dover (Smith, 1985; Gupta et al., 2007).
In part this morphology is constructional resulting from deposition of
sediments from a laterally migrating point bar along the margin of the
Northern Palaeovalley (Fig. 5b). Fluvial regimes operated between
17 ka and 15.8 ka according to the deposits correlated to the oldest
seismic facies (Table 3). Here, formation of the erosion surface is driven
by fluvial processes as seismic reflectors are concordant with the under-
lying erosion surface (Fig. 5b).
The time relationship between the formation of mid-channel bed-
rock bars (Fig. 9a) and deposition of laterally migrating point bars in
the Northern Palaeovalley (Fig. 5b) is unknown. The mid-channel
bedrock bars may be a remnant of antecedent fluvial regimes or of
megaflood processes (Gupta et al., 2007) prior to occupation of the
Northern Palaeovalley by a mobile channel during MIS 2. Alternative-
ly, erosion of the mid-channel bars may have occurred at the same
time as deposition at the valley margins. Large meltwater-fed,
cold-climate gravel-bed rivers can exhibit a full range of fluvial styles
within the same channel reach (Vandenberghe, 2001) and alluvial
point bars and bedrock mid-channel bars can be created simulta-
neously, especially in areas where bedrock is exposed and susceptible
to periglacial weathering.
Secondary drainage networks of considerably smaller magnitude are
located on the bedrock bar surfaces within the Northern Palaeovalley
(Gupta et al., 2007), which have been interpreted as representing
periods of ‘normal fluvial processes’. According to the data presented
here, the secondary drainage networks identified by Gupta et al. (2007)
are considerably undersized in comparison. These secondary drainage
networks show a similar morphology to cross-bar channels commonly
observed in gravel-bed braided rivers (Bridge and Lunt, 2006). Therefore
an alternative hypothesis may suggest that these superimposed minor
drainage networks are the result of cross-bar bedrock scour during pe-
riods of high flow.
Separation of seismic facies by an erosional surface within sediments
preserved at the margin of the Northern Palaeovalley (Fig. 5b) marks a
change in sedimentary regime after ca. 16 ka that is probably related to
reworking by tides during Holocene sea-level rise. This shows the erosive
power of tides propagating through and confined within the Northern
Palaeovalley, as they can produce erosional bedforms characteristic of
high magnitude flows, particularly in less resistant lithologies (Carling
et al., 2009). Whilst it is not possible to fully resolve the nature of process-
es responsible for formation of the Northern Palaeovalley, it is apparent
that incision is at least partly controlled by fluvial processes operating
during MIS 2 and erosion by coastal and shallow marine processes during
Holocene transgression.
A summary of the sedimentary processes driving evolution of the
continental shelf evolution from MIS 6 to MIS 1, as interpreted from
erosional and depositional evidence preserved in the eastern English
Channel, is presented in Fig. 12.
5. Discussion
Seismic stratigraphic, sedimentological and chronometric data
from the eastern English Channel reveal that sculpting of the conti-
nental shelf occurred during multiple erosional phases resulting in
the formation of a major composite erosion surface. Preservation of
sediment on this bedrock erosion surface is typically confined to
palaeovalleys or relict coastal landscapes. The data presented in this
paper provide a framework to reconstruct the Middle to Late Pleisto-
cene palaeogeographic configuration in the eastern English Channel
(Fig. 13). Reconstructions are subdivided into time periods that corre-
late to the marine isotope record and Northwest European chrono-
stratigraphic stages (Cohen and Gibbard, 2011). With the exception
of the Holocene (MIS 1), interglacial periods are not discussed as no
sedimentary records corresponding to these time periods were
encountered in the eastern English Channel. This may have been
due to the distribution of cores, where a bias towards coarser grained
sediments was incorporated into the selection of sites. However, on
non-subsiding continental shelves, interglacials are periods of relative
sedimentary quiescence when compared to glacial stages, thus hav-
ing less persistence in the sedimentary record (Hjelstuen et al.,
2012). Further, there is a greater chance of reworking as successive
erosion phases modify the morphological and sedimentary evidence
of previous periods, and as a consequence the most recent phase
of erosion and deposition is best preserved. The degree to which
climate, relative sea level, sediment supply and discharge have
influenced the timing and nature of shelf erosion and deposition is
addressed by linking the submerged palaeovalleys of the eastern
English Channel with pre-existing fluvial archives and sedimentary
records at the shelf margin. Here we illustrate that knowledge of
the timing and duration of processes operating at the basin-wide
scale, and the persistence of landscapes thus created (cf. Brunsden,
1993), is essential to understand continental shelf evolution and
distinguish between ‘normal’and ‘catastrophic’processes.
5.1. Palaeogeography and drainage configuration
5.1.1. Saalian Drenthe (MIS 6)
Locally, fluvial incision of surface T3 corresponds to a period of cli-
matic deterioration associated with the extensive Saalian (Drenthe
substage) glaciation in Northwest Europe during MIS 6 (Graham
et al., 2011). A significant base level fall of 120 m (Waelbroeck et
al., 2002) would have steepened the fluvial profile and led to incision.
Coalescence of the British and Fennoscandian ice sheets in the central
North Sea Basin forced the Thames and Scheldt fluvial systems south-
wards towards the Straits of Dover (Bridgland et al., 1993; Bridgland
and D'Olier, 1995; Gibbard, 1995; Bridgland and Gibbard, 1997). Inci-
sion at the Straits of Dover produced a lowered local base level which
is reflected by widespread erosion in the Netherlands and southern
North Sea (Busschers et al., 2008; Hijma and Cohen, 2011). This inci-
sion may have been driven or reinforced by potential ‘catastrophic’
discharge from a proglacial lake in the southern North Sea (Murton
and Murton, 2012). However, the imprint such discharges leave on
the landscape is difficult to determine and may be buffered by
‘normal’background levels that are influenced by the dynamics of
major NW European ice sheets and a very large catchment size. It is
expected that effective drainage capture by the eastern English Chan-
nel of the Thames and Rhine–Meuse fluvial systems through the
Straits of Dover would have increased sediment and water discharge
above the capacity of existing rivers (Somme, Canche and Authie) and
encouraged incision through the creation of new channel networks.
Sediment supply would have been maintained by erosion of Mesozoic
and Cenozoic strata, particularly Cretaceous chalk at the Straits of
Dover, producing an abundant supply of flint for bedload transport
within the palaeovalley network. During this time the fluvial regime
would have been moderated by weathering and weakening of the
underlying bedrock (Murton and Lautridou, 2003) and sediment
flux derived from hillslopes (Murton and Belshaw, 2011), both condi-
tioned by periglacial processes.
Seismic and bathymetric data show that the resulting palaeovalley
network adopted a general E–W drainage configuration confluent
with the Median Palaeovalley and Palaeo-Seine in the central English
Channel (Lericolais et al., 2003)(Fig. 13a). The morphology preceding
this erosion phase is unknown because parts of surface T3 form the
oldest fluvial terrace preserved in the eastern English Channel. Inci-
sion may have extended northwards to the area that is now the
Northern Palaeovalley and was potentially constrained by the mor-
phology of surfaces T1 and T2. However, subsequent erosion of the re-
cord makes it difficult to confirm this. It is apparent that flow was
confined to a single channel (Lobourg Channel, Fig. 1) in the relative
uplands of the Weald–Artois anticline and became more distributive
within the Hampshire–Dieppe Basin. This drainage configuration may
simply have been the product of preceding morphology. However,
91C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
there is potential for vertical incision and formation of the Lobourg
Channel tohave been enhanced by uplift and tilting of the Weald–Artois
anticline in response to glacio-isostatic uplift in front of ice sheet
margins (Busschers et al., 2008).
A single OSL age is available to constrain the incision to a period of
increased ‘Channel River’activity where peak discharges occurred at
ca. 155 ka (Toucanne et al., 2009b). During this time discharge was
primarily attributed to meltwater flux during ice sheet retreat
between the Drenthe and Warthe advances of the Saalian glacial
(Toucanne et al., 2009b), although Meinsen et al. (2011) suggested
that catastrophic discharge from proglacial lakes in Northwest Europe
may have flowed through the English Channel during this time.
5.1.2. Early Weichselian glacial (MIS 5d–5a)
Relative sea-level fall during the transition from the Eemian (MIS 5e)
to early Weichselian was not linear and globally sea-level fluctuated
between a minimum of −30 m and a maximum of −80 m during
MIS 5d–5a (Waelbroeck et al., 2002). This meant that for a long period
(at least 55 ka) the eastern English Channel was a marginal marine en-
vironment where the interactions between fluvial and marineprocesses
were controlled by multiple minor sea-level oscillations (Fig. 12). Fluvial
systems during the initial sea-level fall of MIS 5d extended offshore onto
the continental shelf. Most likely they reoccupied and modified valley
networks formed during previous lowstands, and in many places,
eroded sediments preserved within the palaeovalleys. As base-level
continued to fall, incision of the underlying bedrock (surface T3) was
initiated. During this time the palaeovalleys were most likely a conduit
for sediment throughput and deposition appears to have been restricted
to basal lags. Locally, lateral and downstream channel accretion has
helped to preserve some sediments associated with earlier phases of
deposition.
Minor transgressions punctuate the overall falling trajectory of sea
level during the early glacial (Waelbroeck et al., 2002). At elevations
where these transgressions flood palaeovalleys, there is the potential
for deposition of coastal and shallow marine sediments as accommo-
dation is created and shorelines step landward. Sediment supply may
have been maintained through reworking of pre-existing deposits in
a coastal plain setting as the interface between fluvial and marine
processes shifted in response to changes in sea level (Fig. 13b). Phases
of sediment reworking, incision and deposition as discussed above
Fig. 13. Palaeogeography and drainage configurations in the eastern English channel during; (a) MIS 6; (b) MIS 5d–5a; (c) MIS 4–3, and: (d) MIS 2. Black arrows show the direction
of drainage and the thickness is proportional to discharge with thicker lines indicating higher discharges. The extent of the MIS 6 proglacial lake is based on Busschers et al. (2008)
and Murton and Murton (2012). The position of the Rhine–Meuse (1) is taken from Busschers et al. (2008) and the position of the Thames (2) from Bridgland and D'Olier (1995). Ice
margins are taken from Ehlers and Gibbard (2004). Shoreline locations are based on glo bal relative sea-level history (Waelbroeck et al., 2002) and the bathymetry of the continental
shelf.
92 C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
are expected to have operated over each stadial to inter-stadial
sea-level cycle resulting in formation of a composite sheet of sedi-
ment and partial erosion of surface T3. There are no other deposits
of the extent and thickness of the early Weichselian deposits pre-
served in the eastern English Channel. This reflects the uniqueness
of the sea-level and climate history at these elevations during this
period.
5.1.3. Weichselian Pleniglacial (MIS 4–3)
Initial climatic deterioration and associated sea-level fall during late
MIS 4 and MIS 3 led to sub-aerial exposure of the continental shelf in
the eastern English Channel. Sediments deposited on surface T3 during
MIS 6 to early sub-stages of MIS 5 were spared from significant physical
reworking but subjected to chemical weathering, evident from the de-
velopment of secondary iron, particularly in coarser grained sediments.
During this time, ice sheets were expanding from Northern Scotland and
Scandinavia (Ehlers and Gibbard, 2004) and the Thames and Rhine–
Meuse fluvial systems occupiedpreceding channel networks andflowed
south through the Straits of Dover into the eastern English Channel
(Bridgland et al., 1993; Bridgland and D'Olier, 1995; Busschers et al.,
2007). Sediment flux, as a proxy for discharge, through the ‘Channel
River’to the continental shelf margin was significantly less than during
MIS 6 or MIS 2 (Toucanne et al., 2009b). Despite this, the eastern English
Channel records an episode of substantial fluvial incision, suggesting
discharge was high enough to enable erosion.
Extension of the Lobourg Channel into the eastern English Chan-
nel partially eroded sediments associated with earlier phases of
palaeogeographic development (MIS 6–MIS 5) (Fig. 13c). Incision
in the area of the Northern Palaeovalley occurred, potentially taking ad-
vantage of existing drainage configurations forged during previous
sea-level lowstands. Valleys appear to have adopted a general E–Wto
NE–SW trend extending westwards to the continental shelf margin
(Fig. 13c). The exact timing and nature of processes driving incision is
unknown. Upstream, the Rhine–Meuse system records a phase of
extensive reworking and lateral erosion during MIS 4 followed by a
phase of aggradation during MIS 3 (Busschers et al., 2007). However,
linking the timing of incision in the English Channel to the behaviour
of the Rhine–Meuse system is problematic due to different time delays
in the response to external controls along the catchment profile.
5.1.4. Weichselian–Last Glacial Maximum (MIS 2)
Chronometric data for the SB Palaeovalley and Northern Palaeovalley
places bedrock incision by fluvial processes in the period of maximum
sea-level lowstand (−120 m) at the Last Glacial Maximum (LGM) be-
tween 26.5 ka and 19 ka (Clark et al., 2009). During this time drainage
beyond the Straits of Dover appears to have adopted a westerly direction
following a structural fold (SB Palaeovalley) after emerging from the
Lobourg Channel (Fig. 13d). The morphology of erosion surface ME sug-
gests dominant flow then returned to a SW direction within the North-
ern Palaeovalley to become confluent with the Median Palaeovalley and
Palaeo-Seine within the central English Channel (Fig. 1).
Given the relative timing during a sea-level lowstand period, the
deep fluvial incision is interpreted to have been driven by steepening
of the fluvial profile to a base-level that was maintained for a period
of time sufficient to enable knickpoint retreat to extend 500 km
upstream. Assuming that the knickpoint started at a lowstand shore-
line where a noticeable change in the shelf gradient was exposed
(0.00008 to 0.0002 at −70 m OD), the rate of knickpoint retreat dur-
ing the last glacial would be ca. 20 km/ka according to the duration of
time that sea level was below this break in slope (Siddall et al., 2003),
and the distance between the retreating shoreline and the knickpoint.
The timing of incision and corresponding deposition within the North-
ern Palaeovalley correlates with a period of enhanced discharge through
the English Channel that appears to be coupled to the collapse of
the British and Fennoscandian ice sheets between 20 ka and 17 ka
(e.g. Toucanne et al., 2010). Whilst it is expected that incision would
principally be driven by relative sea-level fall, the depth of incision
may have been enhanced or modified by sediment-laden waters at the
onset of ice sheet collapse, the routing pattern guided by lithological
changes and tectonic structures in the bedrock geology, and the rate of
knickpoint retreat according to shelf topography. In addition, significant
weakening of exposed bedrock at this time (surface T4) produced a
basement susceptible to erosion.
Age-data place deposition within the Northern Palaeovalley
between ca. 17 ka and 16 ka. In the Rhine–Meuse system, this time
period is characterised by downstream sediment transport and
reworking of older deposits (Busschers et al., 2007). Mineralogical
analyses of sediments preserved within the Northern Palaeovalley
indicate a partial Rhine origin (Busschers, pers. comm.). This would
suggest that sediment routing from source to sink is not one of
continuous throughput and bypass. The data presented here reveal
that palaeovalleys on the continental shelf in the eastern English
Channel act as transient or minor sediment sinks. However, a more
highly resolved chronology is required to understand response and
lag times along the catchment profile.
5.1.5. Holocene (MIS 1)
In the eastern English Channel part of the palaeovalley network
created during MIS 2 is infilled with deposits typically associated
with a transgressive system tract (Miall, 2006). The sedimentary
succession is comparable to palaeovalley fills preserved elsewhere
in the English Channel during the Holocene sea-level transgression
(Bellamy, 1995; Velegrakis et al., 1999; Gupta et al., 2004; Tessier
et al., 2010). Deposition during relative sea-level rise is principally
driven by the interaction between the creation of accommodation
and sediment supply (Posamentier and Allen, 1999).
The SB Palaeovalley becomes confluent with the Northern
Palaeovalley in the eastern English Channel. Whilst the SB Palaeovalley
is completely filled, the Northern Palaeovalley is underfilled. This could
be attributed to differences in valley morphology, where the Northern
Palaeovalley has a greater cross-sectional area. Under these conditions
an additional sediment source would be required to ensure the
complete filling of the Northern Palaeovalley. However, the degree to
which the Northern Palaeovalley was initially filled during early trans-
gression is difficult to constrain, as due to the valley morphology there
is significant potential for coastal and shallow marine processes during
Holocene sea-level rise to rework any pre-existing valley infill. A
bedload segregation zone in the Northern Palaeovalley around a tidal
amphidromic point in the vicinity of the Isle of Wight triggered the
transport of sediment towards the Straits of Dover (Anthony, 2002)
and may have promoted excavation of the (partially filled) Northern
Palaeovalley. The ability for tidal processes to entrain and erode
would strongly depend on the sea bed morphology and grain size of
the palaeovalley fill at different relative sea levels. Changes in the tidal
regime in relation to reconnection of the North Atlantic with North
Sea waters through the Straits of Dover at 8 ka (Scourse and Austin,
1995; Shennan et al., 2000) would complicate the matter further.
Deposits associated with sea-level transgression are not limited
to palaeovalley fills (Mellett et al., 2012a). Coastal environments
migrate landward in response to rising sea levels and, under certain
circumstances, can be preserved. Reworking of finer sandy sediments
into bedforms (sediment waves) and modification of sea bed mor-
phology by tidal currents during the later stages of the Holocene is
expected (Anthony, 2002; Cazenave, 2007).
5.2. Catastrophic flooding in the English Channel
It has been proposed that one or more catastrophic flood events
where responsible for producing the erosive morphology of the
Northern Palaeovalley in the English Channel (Smith, 1985; Gupta
et al., 2007). The timing of this flood, or floods, has been linked to
glacial-maxima during MIS 12 (Toucanne et al., 2009a) and/or MIS 6
93C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
(Meijer and Preece, 1995), and largely depends on the drainage of a
proglacial lake in the southern North Sea Basin (Gibbard et al., 1988).
The depositional record in the eastern English Channel is biased to-
wards the most recent glacial–interglacial cycle and the sediments pre-
served are associated with relict coastlines and palaeovalley fills. No
evidence was uncovered of constructional bedforms typically associat-
ed with catastrophic floods (e.g. Carling et al., 2009). However, the
data presented here demonstrates that continental shelves are highly
susceptible to reworking at the glacial–interglacial timescale. Therefore,
if flood events did occur during MIS 12 and/or MIS 6, the sedimentary
record of these events is likely to have been destroyed.
The erosional record in the eastern English Channel is composite
and the morphology prior to MIS 6, particularly in the Northern
Palaeovalley, cannot be constrained. There is evidence to suggest
that ‘normal’fluvial processes were at least partly responsible for
shaping the Northern Palaeovalley during MIS 2, thus contradicting
the conclusion by Gupta et al. (2007) that the morphology is the
product of two discrete flood events. There is a possibility that
the Northern Palaeovalley was sculpted by ‘catastrophic’floods and
then later reoccupied and modified by a fluvial system. However, to
preserve the antecedent flood morphology would require the fluvial
regime operating during subsequent sea-level lowstands to have lim-
ited erosive capabilities, which contradicts present models of fluvial
behaviour in response to climate and sea-level change (Blum and
Törnqvist, 2000; Vandenberghe, 2008; Gibbard and Lewin, 2009). As
an alternative hypothesis it is suggested that multiphase fluvial pro-
cesses operating over a long period of time (at least 200 ka) sculpted
the eastern English Channel continental shelf, creating a landscape
that has a comparable morphological character to one produced in-
stantaneously by a catastrophic event, e.g. the Channeled Scablands
(Bretz, 1969).
6. Conclusions
The landscape preserved on the present-day sea bed of the eastern En-
glish Channel is a record of the sedimentary processes that operated over
glacial–interglacial sea-level cycles from MIS 6 to MIS 1. The mid- to late
Quaternary landscape is a palimpsest of composite erosion surfaces
formed through multiple phases of fluvial incision and a fragmentary
and highly reworked depositional record that is biased towards sedimen-
tary processes operating in shallow marine and coastal environments.
The extensive volumes of coarse clastic sediments that are uncharacteris-
tic for the erosional landscape of the English Channel continental shelf,
and an essential aggregate resource, formed over multiple sea-level cycles
as a multi-lateral, multi-storey succession of palaeovalley fills.
Fluvial incision occurs during relative sea-level fall or lowstand
and correlates with periods of cold climatic conditions where bedrock
is weakened by periglacial weathering. In part, fluvial incision may be
coupled to ice sheet dynamics and ice front palaeogeography with
increased discharges during phases of retreat. Palaeovalleys then infill
as accommodation is created during sea-level transgression and
sediment is supplied through bedrock and regolith erosion, and
maintained through continuous recycling of terrestrial deposits over
glacial–interglacial sea-level cycles. Evidence of sea-level highstands
in the form of deposits during interglacial periods appears not to be
preserved on the continental shelf. Further, the stratigraphic record
is incomplete and sediments, as well as erosion surfaces, associated
with each sea-level stage are only partially preserved. Over successive
relative sea-level cycles the morphological and sedimentological
expressions of sedimentary processes become superimposed and en-
vironmental information from the most recent glacial to inter-glacial
cycle is preferentially preserved.
In the eastern English Channel there are no unequivocal erosional
or sedimentological records of the processes operating during MIS 12
preserved. Understanding palaeogeographic development during this
time, particularly in relation to the mechanisms driving breaching of
the Weald–Artois anticline at the Straits of Dover, is problematic
due to later bedrock erosion and multi-phase recycling of sediments.
Evidence is preserved to support major erosion during MIS 6. Howev-
er, sedimentary processes during this time alone cannot account for
the morphology of the Northern Palaeovalley as it was at least partly
re-sculpted by fluvial processes during MIS 2. Events of catastrophic
magnitude are not necessarily responsible for formation of the
palaeovalley network preserved in the eastern English Channel and
it is much more likely that the landforms were created by processes
of non-catastrophic magnitude operating over long (10
4
yr) periods
of time.
Acknowledgments
This research resulted from a NERC-CASE award (NE/F013388/1)
in partnership with Hanson Aggregates Marine Ltd. The Resource
Management Association (Hanson Aggregates Marine Ltd., Tarmac
Marine Dredging Ltd. and Cemex UK Marine) is thanked for its contri-
bution of seismic data and cores. Ceri Jamesof the British Geological So-
ciety facilitated the attainment of geophysical data from projects funded
through the Marine Aggregate Levy Sustainability Fund. Dr. Justin Dix is
thanked for guidance processing and interpreting geophysical data. Dr.
Andrew Bellamy, Tarmac Marine Dredging Ltd., provided support and
guidance throughout this research. Robert Langman, Marine Space Ltd.,
is thanked for his assistance with marine surveys and data handling.
Dr. Richard Chiverrell and Prof. James Scourse are thanked for their com-
ments on the manuscript. The Olex AS global bathymetry dataset was
partly funded through the British Society for Geomorphology. The
authors would also like to thank an anonymous reviewer, Dr. Freek
Busschers and Dr. Francisco Lobo (editor) for their constructive com-
ments that helped improve the manuscript.
References
Anderton, R., 2000. Tertiary events: the North Atlantic plume and Alpine pulses. In:
Woodcock, N.H., Strachan, R.A. (Eds.), Geological history of Britain and Ireland.
Blackwell Science, Oxford, pp. 374–391.
Anthony, E.J., 2002. Long-term marine bedload segregation, and sandy versus gravelly
Holocene shorelines in the eastern English Channel. Marine Geology 187, 221–234.
Antoine, P., Lautridou, J.P., Laurent, M., 2000. Long-term fluvial archives in NW France:
response of the Seine and Somme rivers to tectonic movements, climatic variations
and sea-level changes. Geomorphology 33, 183–207.
Antoine, P., Coutard, J.-P., Gibbard, P., Hallegouet, B., Lautridou, J.-P., Ozouf, J.-C., 2003.
The Pleistocene rivers of the English Channel region. Journal of Quaternary Science
18, 227–243.
Antoine, P., Limondin Lozouet, N., Chaussé, C., Lautridou, J.-P., Pastre, J.-F., Auguste, P.,
Bahain, J.-J., Falguères, C., Galehb, B., 2007. Pleistocene fluvial terraces from north-
ern France (Seine, Yonne, Somme): synthesis, and new results from interglacial
deposits. Quaternary Science Reviews 26, 2701–2723.
Bates, M.R., Keen, D.H., Lautridou, J.-P., 2003. Pleistocene marine and periglacial
deposits of the English Channel. Journal of Quaternary Science 18, 319–337.
Bates, M.R., Briant, R.M., Rhodes, E.J., Schwenninger, J.-L., Whittaker, J.E., 2010. A new
chronological framework for Middle and Upper Pleistocene landscape evolution
in the Sussex/Hampshire coastal corridor, UK. Proceedings of the Geologists' Asso-
ciation 121, 369–392.
Bellamy, A.G., 1995. Extension of the British landmass: evidence from shelf sediment
bodies in the English Channel. In: Preece, R.C. (Ed.), Island Britain: A Quaternary
PerspectiveGeological Society, London, Special Publications 96, 47–62.
Blum, M.D., Törnqvist, T.E., 2000. Fluvial responses to climate and sea-level change: a
review and look forward. Sedimentology 47, 2–48.
Bradley, W.C., Griggs, G.B., 1976. Form, genesis, and deformation of central California
wave-cut platforms. Geological Society of America Bulletin 87, 433–449.
Bradwell, T., Stoker, M.S., Golledge, N.R., Wilson, C.K., Merritt, J.W., Long, D., Everest,
J.D., Hestvik, O.B., Stevenson, A.G., Hubbard, A.L., Finlayson, A.G., Mathers, H.E.,
2008. The northern sector of the last British Ice Sheet: maximum extent and
demise. Earth-Science Reviews 88, 207–226.
Bretz, J.H.,1969. The Lake Missoulafloods and the channeled scabland.Journal of Geology
77, 505–543.
Briant, R.M., Bates, M.R., Schwenninger, J.-L., Wenban-Smith, F., 2006. An optically
stimulated luminescence dated Middle to Late Pleistocene fluvial sequence from
the western Solent Basin, southern England. Journal of Quaternary Science 21,
507–523.
Bridge, J.S., Lunt, I.A., 2006. Depositional models of braided rivers. In: Sambrook Smith,
G.H., Best, J.L., Bristow, C.S., Petts, G.E. (Eds.), Braided Rivers: Process, Deposits,
Ecology and Management. Blackwell Publishing, Oxford, UK, pp. 11–50.
94 C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
Bridgland, D.R., 2002. Fluvial deposition on periodically emergent shelves in the
Quaternary: example records from the shelf around Britain. Quaternary Interna-
tional 92, 25–34.
Bridgland, D.R., D'Olier, B., 1995. The Pleistocene evolution of the Thames and Rhine
drainage systems in the southern North Sea basin. In: Preece, R.C. (Ed.), Island
Britain: a Quaternary perspectiveGeological Society, London, Special Publications
96, 27–45.
Bridgland, D.R., Gibbard, P.L. , 1997. Quaternary river diversions in the London Basin
and the eastern English Channel. Geographie Physique et Quaternaire 51,
337–346.
Bridgland, D.R., D'Olier, B., Gibbard, P.L., Roe, H.M., 1993. Correlation of Thames terrace
deposits between the Lower Thames, eastern Essex and the submerged offshore
continuation of the Thames–Medway Valley. Proceedings of the Geologists' Associ-
ation 104, 51–57.
Brunsden, D., 1993. The persistence of landforms. Zeitschrift für Geomorphologie
Supplementband 93, 13–28.
Busschers, F.S., Kasse, C., van Balen, R.T., Vandenberghe, J., Cohen, K.M., Weerts, H.J.T.,
Wallinga, J., Johns, C., Cleveringa, P., Bunnik, F.P.M., 2007. Late Pleistocene evolu-
tion of the Rhine–Meuse system in the southern North Sea basin: imprints of
climate change, sea-level oscillation and glacio-isostacy. Quaternary Science
Reviews 26, 3216–3248.
Busschers, F.S., Van Balen, R.T., Cohen, K.M., Kasse, C., Weerts, H.J.T., Wallinga, J.,
Bunnik, F.P.M., 2008. Response of the Rhine–Meuse fluvial system to Saalian ice-
sheet dynamics. Boreas 37, 377–398.
Carling, P.A., Herget, J., Lanz, J.K., Richardson, K., Pacifici, A., 2009. Channel-scale
erosional bedforms in bedrock and in loose granular material: process and implica-
tions. In: Burr, D.M., Carling, P.A., Baker, V.R. (Eds.), Megaflooding on Earth and
Mars. Cambridge University Press, Cambridge, pp. 13–32.
Cazenave, P.W., 2007. High-resolution bedform analysis at Hastings Shingle Bank. (MSc
Thesis) School of Ocean and Earth Science.University of Southampton.
Clark, P.U., Dyke, A.S., Shakun, J.D., Carlson, A.E., Clark, J., Wohlfarth, B., Mitrovica, J.X.,
Hostetler, S.W., McCabe, A.M., 2009. The Last Glacial Maximum. Science 325,
710–714.
Cohen, K.M., Gibbard, P.L., 2011. Global chronostratigraphical correlation table for the last
2.7 million years v. 2011. Subcommission on Quaternary Stratigraphy.International
Commission on Stratigraphy, Cambridge, England (http://www.quaternary.
stratigraphy.org.uk/charts/).
Curry, D., 1989. The rock floor of the English Channel and its significance for the inter-
pretation of marine unconformities. Proceedings of the Geologists' Association 100,
339–352.
Davis, W.M., 1899. The geographical cycle. The Geographical Journal 14, 481–504.
Dingwall, R.G., 1975. Sub-bottom infilled channels in an area of the eastern English
Channel. Philosophical Transactions of the Royal Society of London. Series A: Math-
ematical and Physical Sciences 279, 233–241.
Dix, J.K., Long, A.J., Cooke, R., 1998. The evolution of Rye Bay and Dungeness Foreland:
new evidence from the offshore seismic record. In: Eddison, J., Gardiner, M., Long,
A.J. (Eds.), Romney Marsh: Environmental Change and Human Occupation in a
Coastal Lowland. : Monograph, 46. Oxford University Committee for Archaeology,
Oxford, pp. 3–12.
Ehlers, J., Gibbard, P.L., 2004. Quaternary glaciations: extent and chronology. Develop-
ments in Quaternary Science, 2. Elsevier, Amsterdam.
Fedje, D.W., Josenhans, H., 2000. Drowned forests and archaeology on the continental
shelf of British Columbia, Canada. Geology 28, 99–102.
Fitch, S., Thomson, K., Gaffney, V., 2005. Late Pleistocene and Holocene depositional
systems and the palaeogeography of the Dogger Bank, North Sea. Quaternary
Research 64, 185–196.
Gaffney, V., Thomson, K., Fitch, S. (Eds.), 2007. Mapping Doggerland. The Mesolithic
Landscapes of the Southern North Sea. Archaeopress, Oxford (131 pp.).
Gibbard, P.L., 1995. The formation of the Strait of Dover. In: Preece, R.C. (Ed.), Island
Britain: A Quaternary PerspectiveGeological Society, London, Special Publications
96, 15–26.
Gibbard, P., 2007. Palaeogeography: Europe cut adrift. Nature 448, 259–260.
Gibbard, P.L., Lautridou, J.P., 2003. The Quaternary history of the English Channel: an
introduction. Journal of Quaternary Science 18, 195–199.
Gibbard, P.L., Lewin, J., 2009. River incision and terrace formation in the Late Cenozoic
of Europe. Tectonophysics 474, 41–55.
Gibbard, P.L., Rose, J., Bridgland, D.R., 1988. The history of the great Northwest Europe-
an rivers during the past three million years. Philosophical Transactions of the
Royal Society of London. Series B, Biological Sciences 318, 559–602.
Graham, A.G.C., Stoker, M.S., Lonergan, L., Bradwell, T., Stewart, M.A., 2011. The Pleisto-
cene glaciation of the North Sea basin. In: Elhers, J., Gibbard, P.L. (Eds.), Quaternary
Glaciations —Extent and Chronology. A Closer Look. : Developments in Quaternary
Science. Amsterdam, Elsevier, pp. 261–278.
Gupta, S., Collier, J.S., Palmer-Felgate, A., Julie, D., Bushe, K., Humber, S., 2004.
Submerged Palaeo-Arun River: reconstruction of prehistoric landscapes and evalu-
ation of archaeological resource potential (Integrated Projects 1 and 2). Final
Report for English Heritage. Seafloor Image & Processes Group, Department of
Earth Science & Engineering, Imperial College, London.
Gupta, S., Collier, J.S., Palmer-Felgate, A., Potter, G., 2007. Catastrophic flooding origin of
shelf valley systems in the English Channel. Nature 448, 342–345.
Hamblin, R.J.O., Crosby, A., Balson, P.S., Jones, S.M., Chadwick, R.A., Penn, I.E., Arthur,
M.J., 1992. United Kingdom Offshore Regional Report: The Geology of the English
Channel. HMSO for the British Geological Survey, London (106 pp.).
Hijma, M.P., Cohen, K.M., 2011. Holocene transgression of the Rhine river mouth area,
The Netherlands/Southern North Sea: palaeogeography and sequence stratigraphy.
Sedimentology 58, 1453–1485.
Hijma, M.P., Cohen, K.M., Roebroeks, W., Westerhoff, W.E., Busschers, F.S., 2012. Pleis-
tocene Rhine–Thames landscapes: geological background for hominin occupation
of the southern North Sea region. Journal of Quaternary Science 27, 17–39.
Hjelstuen, B.O., Nygård, A., Sejrup, H.P., Halflidason, H., 2012. Quaternary denuda-
tion of southern Fennoscandia —evidence from the marine realm. Boreas 41,
379–390.
Hurst, V.J., 1977. Visual estimation of iron in saprolite. Geological Society of America
Bulletin 88, 174–176.
James, J.W.C., Coggan, R.A., Blyth-Skyrme, V.J., Morando, A., Birchenough, S.N.R., Bee, E.,
Limpenny, D.S., Verling, E., Vanstaan, K., Pearce, B., Johnston, C.M., Rocks, K.F.,
Philpott, S.L., Rees, H.L., 2007. The eastern English Channel Marine habitat map.
Science Series Technical Report, Cefas, Lowestoft (191 pp.).
James, J.W.C., Pearce, B., Coggan, R.A., Leivers, M., Clark, R.W.E., Plim, J.F., Hill, J.M.,
Arnott, S.H.L., Bateson, L., De-Bugh Thomas, A., Baggaley, P.A., 2011. The MALSF
synthesis study in the central and eastern English Channel. British Geological
Survey Open report OR/11/01 (249 pp.).
Jarvis, A., Reuter, H.I., Nelson, A., Guevara, E., 2008. Hole-filled Seamless SRTM Data V4.
International Centre for Tropical Agriculture (CIAT) (available from http://srtm.csi.
cgiar.org).
Kellaway, G.A., Redding, J.H., Shephard-Thorn, E.R., Destombes, J.-P., Lamb, H.H., Smith,
A.J., Cooper, L.H.N., Turner, C., 1975. The Quaternary history of the English Channel.
Philosophical Transactions of the Royal Society of London. Series A: Mathematical
and Physical Sciences 279, 189–218.
Kelley, J.T., Belknap, D.F., Claesson, S., 2010. Drowned coastal deposits with associated
archaeological remains from a sea-level “slowstand”: Northwestern Gulf of Maine,
USA. Geology 38, 695–698.
Lagarde, J.L., Amorese, D., Font, M., Laville, E., Dugué, O., 2003. The structural evolution
of the English Channel area. Journal of Quaternary Science 18, 201–213.
Lambeck, K., 1997. Sea-level change along the French Atlantic and Channel coasts since
the time of the Last Glacial Maximum. Palaeogeography, Palaeoclimatology,
Palaeoecology 129, 1–22.
Lautridou, J.P., Monnier, J.L., Morzadec, M.T., Somme, J., Tuffreau, A., 1986. The Pleisto-
cene of Northern France. Quaternary Science Reviews 5, 387–393.
Le Roy, P.L., Gracia-Garay, C., Guennoc, P., Bourillet, J.F., Reynaud, J.Y., Thinon, I.,
Kervevan, P., Paquet, F., Menier, D., Bulois, C., 2011. Cenozoic tectonics of the West-
ern Approaches Channel basins and its control of local drainage systems. Bulletin
de la Societe Geologique de France 182, 451–464.
Lericolais, G., 1997. Evolution plio-quaternaire du fleuve Manche: Stratigraphie et
Géomorphologie d'une plateforme continentale en régime périglaciaire. (Thèse
de) Géologie Marine, Univ., Bordeaux 1.
Lericolais, G., Guennoc, P., Auffret, J.-P., Bourillet, J.-F., Berne, S., 1996. Detailed survey of
the western end of the Hurd Deep (English Channel): new facts for a tectonic
origin. Geological Society, London, Special Publications 117, 203–215.
Lericolais, G., Auffret, J.-P., Bourillet, J.-F., 2003. The Quaternary Channel River: seismic
stratigraphy of its palaeo-valleys and deeps. Journal of Quaternary Science 18,
245–260.
Lewin, J., Gibbard, P.L., 2010. Quaternary river terraces in England: forms, sediments
and processes. Geomorphology 120, 293–311.
Lisiecki, L.E., Raymo, M.E., 2005. A Pliocene–Pleistocene stack of 57 globally distributed
benthic δ
18
O records. Paleoceanography 20, PA1003.
Meijer, T., Cleveringa, P., 2009. Aminostratigraphy of Middle and Late Pleistocene
deposits in The Netherlands and the southern part of the North Sea Basin. Global
and Planetary Change 68, 326–345.
Meijer, T., Preece, R.C., 1995. Malacological evidence relating to the insularity of the
British Isles during the Quaternary. In: Preece, R.C. (Ed.), Island Britain: A Quater-
nary PerspectiveGeological Society, London, Special Publications 96, 89–110.
Meinsen, J., Winsemann, J., Weitkamp, A., Landmeyer, N., Lenz, A., Dölling, M., 2011. Mid-
dle Pleistocene (Saalian) lake outburst floods in the Münsterland Embayment (NW
Germany): impacts and magnitudes. Quaternary Science Reviews 30, 2597–2625.
Mellett, C.L., Hodgson, D.M., Mauz, B., Lang, A., Selby, I., Plater, A.J., 2012a. Preservation
of a drowned gravel barrier complex: a landscape evolution study from the north-
eastern English Channel. Marine Geology 315–318, 115–131.
Mellett, C.L., Mauz, B., Hodgson, D.M., Plater, A.J., Lang, A., 2012b. Optical dating of
drowned landscapes: a case study from the English Channel. Quaternary Geochro-
nology 10, 201–208.
Menot, G., Bard, E., Rostek, F., Weijers, J.W.H., Hopmans, E.C., Schouten, S., Damste,
J.S.S., 2006. Early reactivation of European rivers during the last deglaciation.
Science 313, 1623–1625.
Miall, A.D., 2006. The Geology of Fluvial Deposits: Sedimentary Facies, Basin Analysis
and Petroleum Geology. Springer, New York (582 pp.).
Mitchum, J.R., Vail, P.R., Sangree, J.B., 1977. Stratigraphic interpretation of seismic reflec-
tion pattern in depositional sequences. In: Payton, C.E. (Ed.), Seismic Stratigraphy—
Applications to Hydrocarbon ExplorationAAPG Memoirs 26, 117–134.
Murton, J.B., Belshaw, R.K., 2011. A conceptual model of valley incision, planation and
terrace formation during cold and arid permafrost conditions of Pleistocene south-
ern England. Quaternary Research 75, 385–394.
Murton, J.B., Lautridou, J.-P., 2003. Recent advances in the understanding of Quaternary
periglacial features of the English Channel coastlands. Journal of Quaternary
Science 18, 301–307.
Murton, D.K., Murton, J.B., 2012. Middle and Late Pleistocene glacial lakes of lowland
Britain and the southern North Sea Basin. Quaternary International 280, 115–142.
Pantin, H.M., Evans, C.D.R., 1984. The Quaternary history of the central and southwestern
Celtic Sea. Marine Geology 57, 259–293.
Posamentier, H.W., Allen, G.P., 1999. Siliciclastic Sequence Stratigraphy —Concepts and
Applications. Concepts in Sedimentology and Palaeontology, No. 7. Society for
Sedimentary Geology, Tulsa (204 pp.).
95C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
Preece, R.C. (Ed.), 1995. Island Britain : a Quaternary perspectiveGeological Society,
London, Special Publications 96 (274 pp.).
Preece, R.C., Scourse, J.D., Houghton, S.D., Knudsen, K.L., Penney, D.N., 1990. The Pleis-
tocene sea-level and neotectonic history of the eastern Solent, Southern England.
Philosophical Transactions of the Royal Society of London. Series B, Biological
Sciences 328, 425–477.
Richardson, K., Carling, P., 2005. A typology of sculpted forms in open bedrock
channels. Geological Society of America Special Paper 392 (108 pp.).
Roep, T.B., Holst, H., Vissers, R.L.M., Pagnier, H., Postma, D., 1975. Deposits of
southward-flowing, pleistocene rivers in the channel region, near Wissant, NW
France. Palaeogeography, Palaeoclimatology, Palaeoecology 17, 289–308.
Scourse, J.D., Austin, R.M., 1995. Palaeotidal modelling of continental shelves: marine im-
plications of a land-bridge in the Strait of Dover during the Holocene and Middle
Pleistocene. In: Preece, R.C. (Ed.), Island Britain: A Quaternary PerspectiveGeological
Society, London, Special Publications 96, 75–88.
Shennan, I., Lambeck, K., Flather, R., Horton, B., McArthur, J., Innes, J., Lloyd, J., Rutherford,
M., Wingfield, R., 2000. Modelling western North Sea palaeogeographies and tidal
changes during the Holocene. Geological Society, London, Special Publications 166,
299–319.
Siddall, M., Rohling, E.J., Almogi-Labin, A., Hemleben, C., Meischner, D., Schmelzer, I.,
Smeed, D.A., 2003. Sea-level fluctuations during the last glacial cycle. Nature 423,
853–858.
Smith, A.J., 1985. A catastrophic origin for the palaeovalley system of the eastern
English Channel. Marine Geology 64, 65–75.
Smith, A.J., 1989. The English Channel —by geological design or catastrophic accident?
Proceedings of the Geologists' Association 100, 325–337.
Stride, A.H., 1990. Growth and burial of the English Channel unconformity. Proceedings
of the Geologists' Association 101, 335–340.
Stringer, C.B., 2006. Homo Britannicus: The Incredible Story of Human life in Britain.
Allen Lane, London (319 pp.).
Tessier, B., Delsinne, N., Sorrel, P., 2010. Holocene sedimentary infilling of a tide-
dominated estuarine mouth. The example of the macrotidal Seine estuary (NW
France). Bulletin de la Societe Geologique de France 181, 87–98.
Toucanne, S., Zaragosi, S., Bourillet, J.F., Gibbard, P.L., Eynaud, F., Giraudeau, J., Turon,
J.L., Cremer, M., Cortijo, E., Martinez, P., Rossignol, L., 2009a. A 1.2 Ma record of gla-
ciation and fluvial discharge from the West European Atlantic margin. Quaternary
Science Reviews 28, 2974–2981.
Toucanne, S., Zaragosi, S., Bourillet, J.F., Cremer, M., Eynaud, F., Van Vliet-Lanoë, B.,
Penaud, A., Fontanier, C., Turon, J.L., Cortijo, E., Gibbard, P.L., 2009b. Timing of mas-
sive ‘Fleuve Manche’discharges over the last 350 kyr: insights into the European
ice-sheet oscillations and the European drainage network from MIS 10 to 2.
Quaternary Science Reviews 28, 1238–1256.
Toucanne, S., Zaragosi, S., Bourillet, J.-F., Marieu, V., Cremer, M., Kageyama, M., Van
Vliet-Lanoë, B., Eynaud, F., Turon, J.-L., Gibbard, P.L., 2010. The first estimation of
Fleuve Manche palaeoriver discharge during the last deglaciation: evidence for
Fennoscandian ice sheet meltwater flow in the English Channel ca 20–18 ka ago.
Earth and Planetary Science Letters 290, 459–473.
Uehara, K., Scourse, J.D., Horsburgh, K.J., Lambeck, K., Purcell, A.P., 2006. Tidal evolution
of northwest European shelf seas from the Last Glacial Maximum to the present.
Journal of Geophysical Research 111, C09025.
Van Vliet-Lanoë, B., Laurent, M., Bahain, J.L., Balescu, S., Falguères, C., Field, M.,
Hallégouët, B., Keen, D.H., 2000. Middle Pleistocene raised beach anomalies in
the English Channel: regional and global stratigraphic implications. Journal of
Geodynamics 29, 15–41.
Vandenberghe, J., 2001. A typology of Pleistocene cold-based rivers. Quaternary Inter-
national 79, 111–121.
Vandenberghe, J., 2008. The fluvial cycle at cold–warm–cold transitions in lowland
regions: a refinement of theory. Geomorphology 98, 275–284.
Velegrakis, A.F., Dix, J.K., Collins, M.B., 1999. Late Quaternary evolution of the upper
reaches of the Solent River, Southern England, based upon marine geophysical
evidence. Journal of the Geological Society 156, 73–87.
Waelbroeck, C., Labeyrie, L., Michel, E., Duplessy, J.C., McManus, J.F., Lambeck, K.,
Balbon, E., Labracherie, M., 2002. Sea–level and deep water temperature changes
derived from benthic foraminifera isotopic records. Quaternary Science Reviews
21, 295–305.
Waller, M.P., Long, A.J., 2003. Holocene coastal evolution and sea-level change
on the southern coast of England: a review. Journal of Quaternary Science 18,
351–359.
Wessex Archaeology, 2008. Sea bed prehistory: gauging the effects of marine aggregate
dredging. Volume V, eastern English Channel. Final Report for En glish Heritage.Wessex
Archaeology, Salisbury (48 pp.).
Westaway, R., Bridgland, D., White, M., 2006. The Quaternary uplift history of central
southern England: evidence from the terraces of the Solent River system and
nearby raised beaches. Quaternary Science Reviews 25, 2212–2250.
96 C.L. Mellett et al. / Geomorphology 203 (2013) 79–96
