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Among tidally influenced sedimentary environments, tide-dominated deltas are perhaps the most variable and difficult to characterize. This variability is due in part to the major role that fluvial systems play in defining their delta, with rivers differing widely in discharge, sediment load, seasonality, and grain size. Tide-dominated deltas also tend to be large systems that can extend hundreds of kilometers across and along the continental margin. The associated sediment transport regimes are typically high energy, but they vary considerably at the scale of tidal cycles and seasonal river discharge. As a consequence of varying transport energy, the sedimentary successions formed in tide-dominated deltaic settings tend to be heterolithic, with interbedded sands, silts, and clays and both fining- and coarsening-upward facies associations. The deltaic nature of tide-dominated deltas that distinguishes them from other tidally influenced settings is defined by the cross- or along-shelf progradation of a clinoform, or 'S' shaped, sedimentary deposit. Under the influence of strong bed shear in tidally dominated margins, this prograding clinoform is often separated into two distinct units, one associated with the subaerial deltaplain and one with an offshore subaqueous delta. Onshore, the large, fertile deltaplains built by many modern tide-dominated deltas, especially in South and East Asia, are heavily populated and sustain large economies, making them global important settings. However, the reduction of fluvial inputs by damming and water extraction, as well as intense agricultural, urban, and industrial land uses, threaten the stability and sustainability of these environments. © 2012 Springer Science+Business Media B.V. All rights reserved.
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R.A. Davis, Jr. and R.W. Dalrymple (eds.), Principles of Tidal Sedimentology,
DOI 10.1007/978-94-007-0123-6_7, © Springer Science+Business Media B.V. 2012
7.1 Introduction
River deltas are variably defi ned by their geography,
morphology, or stratigraphy, but are most generally
considered to be a sedimentary deposit formed by a
river at its mouth. Here, to distinguish deltas from riv-
ermouth estuaries that also receive fl uvial sediment
S. L. Goodbred, Jr. (*)
Department of Earth and Environmental Sciences ,
Vanderbilt University , Nashville , TN 37240 , USA
Y. Saito
Geological Survey of Japan , AIST, Central 7 , Higashi 1-1-1 ,
Tsukuba 305-8567 , Japan
Among tidally infl uenced sedimentary environments, tide-dominated deltas are
perhaps the most variable and diffi cult to characterize. This variability is due in
part to the major role that fl uvial systems play in defi ning their delta, with rivers
differing widely in discharge, sediment load, seasonality, and grain size. Tide-
dominated deltas also tend to be large systems that can extend hundreds of kilo-
meters across and along the continental margin. The associated sediment transport
regimes are typically high energy, but they vary considerably at the scale of tidal
cycles and seasonal river discharge. As a consequence of varying transport energy,
the sedimentary successions formed in tide-dominated deltaic settings tend to be
heterolithic, with interbedded sands, silts, and clays and both fi ning- and coarsen-
ing-upward facies associations. The deltaic nature of tide-dominated deltas that
distinguishes them from other tidally infl uenced settings is defi ned by the cross- or
along-shelf progradation of a clinoform, or ‘S’ shaped, sedimentary deposit. Under
the infl uence of strong bed shear in tidally dominated margins, this prograding
clinoform is often separated into two distinct units, one associated with the suba-
erial deltaplain and one with an offshore subaqueous delta. Onshore, the large,
fertile deltaplains built by many modern tide-dominated deltas, especially in South
and East Asia, are heavily populated and sustain large economies, making them
global important settings. However, the reduction of fl uvial inputs by damming
and water extraction, as well as intense agricultural, urban, and industrial land
uses, threaten the stability and sustainability of these environments.
Tide-Dominated Deltas
Steven L. Goodbred, Jr. and Yoshiki Saito
130 S.L. Goodbred, Jr. and Y. Saito
input (see tide-dominated estuaries chapter), river del-
tas must receive adequate sediment from the river to
build a clinothem, which is a sedimentary deposit having
characteristic topset-foreset-bottomset morphology,
often in a sigmoidal or ‘S’ shape. In this way river-fed
coastal systems may be depositional, but they are not
deltaic if lacking a defi nable clinoform morphology
and progradational features. The surfaces defi ning
many deltaic clinothems are very low-gradient (<3°)
for fi ne-grained deltas and may be diffi cult to recog-
nize in core or outcrop, so other criteria discussed in
this chapter may be important in recognizing deltaic
settings from such data. In simplest terms, it is expected
that large volumes of heterolithic mud will be found
offshore of deltaic rivermouths, which should be a dis-
tinguishing character from most other river-infl uenced
settings. Inherent in this defi nition, deltaic systems
will be controlled at a fi rst order by river discharge and
uvial sediment load and secondarily to the rate of
reworking by marine processes, primarily waves, tides,
and coastal currents.
Although modern and ancient deltas may share a
general clinoform morphology, examples from around
the world show considerable variability in their sur-
face geomorphology, lithology, process, and response
to external forcing. To account for some of this vari-
ability, deltas are commonly classifi ed by the domi-
nant process controlling sediment dispersal, and hence
surface geomorphology (Galloway 1975 ) . The end-
members in this ternary classifi cation scheme are
river-, wave- and tide-dominated delta systems, with
many examples exhibiting intermediate characteristics
that can be classifi ed as mixed-energy (Figs. 7.1 and 7.2 ).
Large deltas may also comprise a composite system,
where different portions of the delta are morphologi-
cally distinct and controlled differently by fl uvial, wave,
or tidal processes (Bhattacharya and Giosan 2003 ) .
More recent variations of this scheme have in addition
considered grain size (Orton and Reading 1993 ) , sedi-
ment supply, and sea level (Boyd et al. 1992 ) , although
the original Galloway classifi cation arguably remains
the most useful for large river deltas.
7.2 Background
7.2.1 Past Research
Although the study of river deltas was active during
the fi rst half of the twentieth century (e.g. Russell and
Russell 1939 ) , comparatively little research was done on
tidally dominated systems, due in part perhaps to
their large size, remote locations, and challenging
navigation. In the 1970s when delta classifi cation
models were fi rst emerging (e.g. Wright and Coleman
1971 ; Galloway 1975 ) , the only “tide-dominated”
end-members that had been studied in any detail
were the very small Klang-Langat delta of Malaysia
Fig. 7.1 Map of the world’s major river delta systems, with those forming tide-dominated deltas indicated ( bold type; fi lled circle )
(Modifi ed after Hori and Saito
2007 )
1317 Tide-Dominated Deltas
( Coleman et al. 1970 ) and the Yalu and Ord rivers of
Korea and Australia, respectively (Coleman and Wright
1978 ) . None of these systems are discussed at length
in this chapter as they are best reclassifi ed as tide-
infl uenced deltas (Klang-Langat) or as tidal estuaries
(Yalu and Ord; see Chap. 5 ). In the 1980s the Amazon
and Changjiang (i.e. Yangtze) were the fi rst large tide-
infl uenced deltas to be studied in detail through large,
comprehensive, and multidisciplinary investigations.
The Amazon project, called AMASEDS, collected
observational data simultaneously at the seabed and
water column over different phases of the river hydro-
graph and tidal conditions, demonstrating the tremen-
dous benefi ts of such an integrated approach (Nittrouer
and DeMaster 1986 ) . Combined with sediment coring and
seismic-refl ection surveys, AMASEDS defi ned the mod-
ern approach for studying complex, river-fed continental
margin systems. A similar comprehensive study was done
for the Changjiang in Asia (Milliman and Jin 1985 ) .
However research of tide-dominated deltas remained lim-
ited as most studies were of river- or wave-dominated
examples (e.g. Mississippi, Nile, Ebro, Rhine).
Middleton ( 1991 ) pointed out that a majority of
very large rivers in terms of sediment load discharge
along meso- to macrotidal coasts, forming tide-dominated
or tide-infl uenced deltas (Fig. 7.1 ). In response,
research was initiated in several tidally affected
deltas, with the Fly river being among the fi rst major
tide-dominated deltas to be studied in detail (Harris
et al. 1996 ; Wolanski et al. 1995 ) . Since that time the
rate of investigation has accelerated and today most
major tide-dominated delta systems have received some
formal investigation. Most studies have employed
stratigraphic or seismic-refl ection approaches, but
observational and hydrodynamic data remain rare for
many systems. Among several coordinated research
programs, recent efforts have focused on the Changjiang,
Mekong, and other nearby Asian deltas (e.g. Hori et al.
2001 ; Ta et al. 2005 ) , and the Gulf of Papua ‘contin-
uum’ that includes the tide-dominated Fly and Kikori
deltas (e.g., Ogston et al. 2008 ; Walsh et al. 2004 ) . The
Ganges-Brahmaputra has been reasonably well studied
by individual working groups (Goodbred and Kuehl
2000 ; Kuehl et al. 2005 ; Michels et al. 1998 ) , and to a
lesser extent the Indus (Giosan et al. 2006 ) and Colorado
(Carriquiry and Sanchez 1999 ; Thompson 1968 )
deltas. The Ayeyarwady (i.e., Irrawaddy) and Tigris-
Euphrates deltas, however, remain notable exceptions
with very little published research.
Other more general studies have advanced our
understanding of continental margin systems with
great implications for tide-dominated deltas, including
developments in shelf hydrodynamics and sediment
transport (Wright and Friedrichs 2006 ) , and the
Fig. 7.2 ( a ) Major river deltas classifi ed by the relative infl u-
ence of river, wave, and tidal processes (After Galloway
1975 ) .
( b ) Mean wave height versus mean tidal range for major large
river deltas. The areas are grouped into fi ve morphological
classes after the classifi cation of Davis and Hayes (
1984 )
(Modifi ed after Hori et al.
2002a )
132 S.L. Goodbred, Jr. and Y. Saito
quantitative modeling of delta evolution, stratigraphy
(Fagherazzi and Overeem 2007 ) , and clinothem devel-
opment (Swenson et al. 2005 ; Slingerland et al. 2008 ) .
One continuing challenge, though, is the diffi culty in
numerically modeling tidal sediment transport due to
complications of the bidirectional fl ow, thus limiting
our ability to assess impacts of environmental changes
such as discharge variations, sediment loading, and
sea-level change. Although effective modeling of tidal
sediment transport remains elusive, progress is being
made in understanding hydrodynamics of the complex
network of tidal channels (Fagherazzi 2008 ) and com-
pound clinoform morphology (Swenson et al. 2005 ;
Wright and Friedrichs 2006 ) that characterize tide-
dominated delta systems. These topics are discussed in
detail later in this chapter.
7.2.2 Modern Examples
In this chapter we focus primarily on tide-dominated
deltas, including examples of the Colorado, Fly,
Ganges-Brahmaputra, Indus, Irrawaddy, and
Changjiang, with some discussion of tide-infl uenced
deltas such as the Amazon, Mahakam, and Mekong.
Overall these systems are best characterized by their
wide river mouths that have a pronounced upstream
taper and well-developed channel bars and islands. All
examples are subject to mesotidal to macrotidal condi-
tions with spring tidal ranges typically ³ 3 m. Because
of this continual exposure to tidal exchange and sedi-
ment transport, tide-dominated deltas along open shore-
lines are typically fed by large rivers that discharge
high sediment loads, although smaller rivers may form
deltas in more embayed settings (e.g. Gironde River,
France). Indeed, 10 of the river deltas listed above
(excluding the Mahakam) rank among the world’s top
25 rivers in terms of their fl uvial sediment discharge
(Milliman and Meade 1983 ; Milliman and Syvitski
1992 ) . Rankings for the Colorado, Tigris-Euphrates,
and Indus rivers are based on historical estimates prior
to major damming and sediment trapping.
Most tide-dominated deltas today are located in tec-
tonically active, low-latitude regions, including South
Asia, East Asia, and Oceania (Fig. 7.1 ). Many factors
relevant to the development of tide-dominated delta
systems are common to these areas. First, amplifi ca-
tion of the M2 tidal component in high tidal-range
areas is supported by broad, relatively shallow
continental shelves and seas that are well connected to
the open ocean, and in many instances taper in width
toward their apex. Prominent examples include the
Arabian Sea (Indus), Bay of Bengal (Ganges-
Brahmaputra), Andaman Sea (Ayeyarwady), Gulf of
Papua (Fly), and East China Sea (Changjiang). A sec-
ond factor common to most tide-dominated deltas, and
many deltas in general, is that they drain high-stand-
ing, tectonically active mountains. Such active orogens
yield the abundant sediment required for deltas to form
in high-energy coastal basins. In particular the
Himalayan-Tibetan uplift and Indonesian archipelago
sustain among the world’s highest sediment yields
(Milliman and Syvitski 1992 ) .
7.2.3 Humans and Deltas
Many tide-dominated deltas are among the world’s
largest in areal extent (Woodroffe et al. 2006 ) , and the
immense, agriculturally rich, lowland delta plains that
have formed at the mouths of the Ganges-Brahmaputra,
Indus, Ayeyarwady, Mekong, and Changjiang rivers
support nearly 200 million people. These populations,
like those in all deltas, are at risk from fl ooding, tropi-
cal cyclones, sea-level rise and related environmental
hazards. Unfortunately, our current understanding of
the process-response (morphodynamic) relationships
in tide-dominated deltas is inadequate to assess the
likely outcome of various environmental-change sce-
narios. Much may be learned by further investigation
of the several tide-dominated deltas that have already
been severely degraded due to river damming, water
extraction, and reduced sediment discharge, notably
the Indus, Colorado, and Tigris-Euphrates (Syvitski
et al. 2009 ) . Despite risk and uncertainty, major dams
continue to be constructed on rivers that feed high-
energy, tide-dominated delta systems, such as the
Three Gorges Dam on the Changjiang and the Xiaowan
Dam on the Mekong (Yang et al. 2006 ; Kummu et al.
2010 ) . Not all tide-dominated deltas are strongly
human-impacted, however, with the Amazon, Copper,
and Fly river systems draining relatively natural catch-
ments and having sparsely populated delta plains.
Similarly, the Ganges-Brahmaputra and Ayeyarwady
rivers remain undammed despite their heavily popu-
lated catchments, and so their large water discharge
and sediment loads sustain stable, if still locally
dynamic, delta systems.
1337 Tide-Dominated Deltas
7.3 Hydrodynamics
Tide-dominated deltas have complex hydrodynamics
that are strongly infl uenced by river discharge, tidal
exchange, and other marine processes such as waves
and storms (Fig. 7.3 ). Each of these controls varies
considerably with time (e.g., fortnightly, seasonal,
episodic) and location (e.g. active rivermouth, ‘inactive’
delta plain, subaqueous delta). By defi nition, tides are
perhaps the overarching control on tide-dominated
delta systems, but the fact that these are prograding
deltas and not transgressing tidal estuaries also
refl ects the tremendous infl uence of large fl uvial
systems feeding them. In addition, large riverine
Fig. 7.3 Major physiographic and morphologic features of
tide-dominated delta systems shown in ( a ) cross-section and
( b ) planform. Note the well developed subaerial and subaque-
ous portions of the delta, each represented by a prograding
clinoform. The rivermouth is also characterized by channel-
mouth bars that build just seaward of the shoreline, and in many
cases become emergent and amalgamate into large channel-
mouth islands (Modifi ed from Hori and Saito
2007 )
134 S.L. Goodbred, Jr. and Y. Saito
sediment fl uxes and persistent tidal energy sustain
high suspended-sediment concentrations offshore,
where these particulates are subject to widespread dis-
persal by coastal and ocean currents that are normally
too slow for entraining sediments without the addition
of a tidal-velocity component (Fig. 7.4 ). Overall,
though, tide-dominated deltas bear the mark of not
only strong tidal infl uence, but also fl uvial and marine
processes that play critical roles in defi ning the charac-
ter and behavior of these complex margin systems.
Fig. 7.4 MODIS satellite images of two major tide-dominated
delta systems, ( a ) the Changjiang river delta taken near the end
of the fl ood season on 25 October 2000 and ( b ) the Ganges-
Brahmaputra river delta taken late in the dry season on 19 March
2002. Major geographic and physiographic features of the delta
and surrounding areas are labeled. Both images show high
suspended sediment concentrations that extend 50–100 km off-
shore and hundreds of kilometers alongshore, largely due to
suspension by tidal currents (Images from NASA MODIS, )
1357 Tide-Dominated Deltas
7.3.1 Tidal Processes Tidal Amplifi cation
At the offshore limits of the delta system, the incom-
ing ocean tide fi rst interacts with the clinoform delta-
front, where water depths shoal from 20 to 90 m at
the bottomsets to 5–30 m at the topset-foreset roll-
over point, a distance typically of a few tens of kilo-
meters for megadeltas to a few kilometers for smaller
deltas (Fig. 7.3 ; Storms et al. 2005 ) . Tidal currents
accelerate across this zone from <20 cm/s on the
open shelf to 30–80 cm/s on the outer delta-front
platform (ie., topsets), still tens of kilometers off-
shore. This acceleration across the prograding delta-
front represents an important morphodynamic
feedback that in large part is responsible for forming
the compound clinoform that is typical of most tide-
dominated delta systems. In this case strong bed
shear on the inner shelf (i.e., delta platform) defi nes
a zone of limited deposition that separates the pro-
grading subaqueous and subaerial clinoforms
(Fig. 7.3a ; see also Sect. ).
After crossing the delta-front platform (i.e. topsets)
the progressive tide wave becomes channelized as it
propagates upstream of the shoreline, inducing a sec-
ond phase of energy focusing that accelerates tidal cur-
rents to velocities of 50 to >100 cm/s. This acceleration
continues for a signifi cant distance upstream (10s of
km) due to tidal amplifi cation. Although tidal energy is
lost to friction, the local tidal power is actually ampli-
ed by the decreasing cross-sectional area of the nar-
rowing channels. This is called a hypersynchronous
channel system, whereby tidal height and current
velocities increase steadily upstream before declining
to zero as tidal energy becomes increasingly attenu-
ated by frictional forces.
Due to this positive feedback of tidal amplifi cation
across the shallow prograding delta-front and tapering
delta-plain channels, tides actually infl uence a much
larger reach of the continental margin than they would
in the absence of the delta. In larger tide-dominated
deltas, this enhanced tidal infl uence may extend
100–200 km across the margin (Fig. 7.5 ). In general
tidal-bed shear in this broad reach is suffi cient to
impart a strong infl uence on sediment transport and
deposition, although preservation of tidal signatures in
the sedimentary record is less certain (see 7.4.2 ). Tidal Asymmetry
An important consequence of hypersynchronous tidal
amplifi cation is the development of an asymmetry in
the ebb and fl ood limbs of the tidal wave. In this case
the wave crest (high tide) propagates faster than the
wave trough (low tide), causing the fl ood period (low
to high tide) to shorten and ebb period (high to low
tide) to lengthen. This time asymmetry requires higher
current velocities for the fl ooding tide to accommodate
the tidal prism, and is described as being a fl ood-dom-
inant tidal system.
Given that the rate of sediment transport ( y )
increases as a power function ( b ) of current velocity
( x ), where y = ax b
with b = 1.6–2.0, most fl ood-dominant
tidal systems result in a net onshore-directed trans-
port of sediment, an effect called “tidal pumping”
(Postma 1967 ) . This effect may have fundamental
implications for the morphology and behavior of
tide-dominated delta systems (see Sect. 7.4.1 ), but its
nfl uence likely varies spatially and temporally with
such factors as river discharge. For example, where
river discharge is high the net fl ow and sediment trans-
port patterns may be signifi cantly altered or even
reversed from the tidal signature alone. In general low
river discharge allows a net upstream (landward) trans-
port of sediment (e.g., during the dry season), whereas
high discharge weakens this tidal-pumping effect and
forces net offshore transport. These natural patterns
in tidal pumping and sediment transport may be
considerably altered on rivers with large dams used to
artifi cially control water discharge (Wolanski and
Spagnol 2000 ) .
7.3.2 Fluvial and ‘Estuarine’ Processes
The evolution of tidal hydrodynamics at the coast is not
only infl uenced by seabed and shoreline morphology
but also by interactions with freshwater discharge. In
the case of most tide-dominated deltas, the interaction
of large river-water fl uxes and meso- to macro-tidal
regimes tend to generate strong horizontal shear, tur-
bulent eddies, and vigorous vertical mixing. Such
dynamic fl ows are generally adequate to preclude
density stratifi cation and result in a well-mixed estuary
at the delta rivermouth. Therefore buoyancy-driven
gravitational circulation is not as significant in
136 S.L. Goodbred, Jr. and Y. Saito
tide-dominated deltas as it is at many less energetic
river mouths. As with any complex natural system,
though, partially mixed stratifi cation and weak estuarine
circulation may develop locally within tide-dominated
deltas given spatiotemporal differences in tidal energy
(spring vs. neap) and river discharge (seasonality and
ow splitting amongst the distributary channels). Sediment Transport Convergence
Although stratifi cation is not generally important in
tide-dominated delta systems, river discharge plays at
least two other key roles in defi ning system-scale
hydrodynamics. First, the fl ux of freshwater from the
river relative to the incoming tidal prism determines
the position of sediment transport convergence within
the rivermouth or on the shelf. Sediment convergence
occurs where sediments are trapped by outfl owing river
discharge and onshore tidal transport, causing a high
concentration of suspended sediment, often referred to
as the turbidity maximum, and high deposition rates on
the underlying seabed. In general, high river discharge
relative to the tidal prism forces the location of this
sediment convergence further seaward and defi nes an
important location of dynamic-scale sediment accretion
Fig. 7.5 Physiographic maps of four major tide-dominated
delta systems, including the ( a ) Changjiang, ( b ) Fly, ( c ) Amazon,
and ( d ) Ganges-Brahmaputra. Note the variable scale but similar
funnel-shaped morphology of the rivermouths, each with char-
acteristic channel-margin bars that are many tens of kilometers
long. Each delta system is also characterized by a large muddy
clinothem deposit that is forming off the rivermouth, at a similar
length-scale of many tens of kilometers offshore (Compiled
after Hori et al.
2002a ; Harris et al. 2004 ; Nittrouer et al. 1986 ;
Goodbred and Kuehl
2000 )
1377 Tide-Dominated Deltas
(i.e., where sediments may be stored for short time
periods, less than a year, and subject to later rework-
ing). In contrast to tide-dominated estuaries where the
ux convergence of suspended sediment tends to be
located near the apex of the rivermouth embayment,
the convergence in tide-dominated deltas is typically
near the mouth of the embayment or slightly seaward
(e.g. Fly, Ganges-Brahmaputra, Changjiang; Dalrymple
and Choi 2007 ) . The convergence may shift many
kilometers upstream during the low-discharge dry sea-
son (Wolanski et al. 1996 ) , but, with the majority of
sediment delivered during high river fl ow, the wet-season
transport regime is more important to delta evolution.
In an extreme case the Amazon River, with more dis-
charge than any other river on Earth, actually forces its
tide-river fl ux convergence 60–90 km offshore onto
the middle continental shelf where most sediment
accumulates in the subaqueous clinothem (Kuehl et al.
1986 ; Nittrouer et al. 1986 ) . Although depositional
patterns here are strongly tide infl uenced, no saltwater
enters the Amazon rivermouth at any time of the year
despite a spring tidal range of ~7 m. Finally, it is
important to note that the location of fl ux convergence
for coarser-grained bedload may lie considerably
landward of that for suspended load (Montaño and
Carbajal 2008 ) . Residual Flow
The second important interaction of river discharge
with tidal hydrodynamics is that river fl ow, at least sea-
sonally, dominates the residual fl ow in tide-dominated
deltas. Residual fl ow is the resultant current vector
(i.e., ‘net drift’) that emerges from averaging all fl ow
components (tidal, fl uvial, and marine) over a period
of weeks to a year. Residual fl ow can be diffi cult to
determine from short-term instrumental deployments
because of the dominance of non-steady synoptic-scale
forces (e.g., waves, storms, fl ood discharge), and thus
results may differ depending on the time-scale over
which observations or calculations are made.
Ultimately, though, it is the asymmetry in tidal cur-
rents and the unidirectional fl ow of river discharge that
tend to generate residual fl ows and dominate the net
uid transport in tide-dominated delta systems (Barua
et al. 1994 ) .
Because residual fl ow is a purely fl uid transport
phenomenon, its role in sediment transport will vary
depending on the timing, magnitude, and duration that
sediments are suspended in the water column. Thus,
along lower-energy margins where suspended sedi-
ment concentrations are comparatively low and much
of the sediment is relatively coarse (i.e., sand-sized)
bedload, time-averaged residual fl ows may not be
important to overall morphologic development. However,
on high-energy, tide-dominated deltaic margins where
suspended-sediment concentrations are consistently
high, the weak but persistent residual fl ows may
account for much of the long-term net sediment trans-
port and resulting morphological evolution of the
rivermouth delta and adjacent tidal delta plain.
7.3.3 Marine Processes
The large rivers that feed most modern tide-dominated
deltas export much of their sediment load to the shelf,
where it is subject to a suite of marine processes – tides,
waves, storms, geostrophic currents – that ultimately
defi ne the morphology and development of the sub-
aqueous portion of the delta (Walsh and Nittrouer
2009 ) . Often the greatest effect of these processes on
sediment dispersal and development of the subaqueous
delta occurs when they are coincident with high river
discharge. Complex, non-linear interactions that
emerge during high-energy stochastic events (e.g.,
storms, fl oods) may account for large-scale transport
and redistribution of fi ne-grained sediment to all por-
tions of the delta, but has been demonstrated to be
especially important to offshore transport (e.g. Ogston
et al. 2000 ) . In this case the importance of such off-
shore mud transport has long been recognized (Swift
et al. 1972 ) from the widespread occurrence of accret-
ing mud wedges on the shelf, but the mechanisms of
such transport remained uncertain and controversial
until recently (Hill et al. 2007 ). In the past two decades
direct instrumental observations have revealed the reg-
ular occurrence of gravity-driven cross-shelf transport
occurring off the mouths of most of the world’s major
rivers (Wright and Friedrichs 2006 ) . This transport
phenomenon, which is generated by the interaction of
uvial and marine processes, shares many of the same
conditions shown to be necessary for the development
of a subaqueous muddy clinothem (Swenson et al.
2005 ) , and probably defi nes much of the shelf mor-
phology found offshore of large rivers in high-energy
138 S.L. Goodbred, Jr. and Y. Saito Gravity-Driven Sediment Transport
Widespread occurrence of mud deposits and active
mud accretion on the middle of continental shelves
has long drawn speculation as to the mechanisms
responsible for their emplacement (Swift et al. 1972 ) .
General observations of focused, rapid accumulation
imply an association of these deposits with sediment-
laden density currents, which are near-bottom fl uid
ows that are denser than the overlying water column
because of a high concentration of suspended sedi-
ment. Turbidity currents are an example of gravity-
driven transport, but the gradient of the shelf is typically
too low to sustain the high fl ow velocities needed to
maintain continuous sediment suspension and the
downslope propagation of such gravity fl ows. Not only
are shelf gradients low, but very few rivers discharge
sediment plumes that are hyperpycnal (i.e., denser than
the ambient coastal seawater), and this is especially
true of the larger, relatively dilute rivers offshore of
which shelf mud deposits are most prevalent.
In the past two decades, though, repeated synoptic-
scale observations of seabed and water column dynam-
ics during storms and high-discharge fl ood events have
demonstrated that gravity-driven near-bed density
ows are a common mode of cross-shelf mud transport
(Wright and Friedrichs 2006 ) . The controlling pro-
cesses and boundary conditions can vary widely, but
the fundamental requirements are hyperpycnal near-
bed sediment concentrations and a mechanism for
maintaining sediment suspension on the low-gradient
shelf, typically accomplished by waves and/or tidal
currents. These specialized requirements are most typ-
ically met when rivers are discharging peak sediment
loads onto an energetic shelf, which arguably occurs
with the greatest regularity along tide-dominated del-
taic margins (Harris et al. 2004 ) . It is uncertain whether
this assertion is true because gravity-driven transport is
recognized in many margin systems, but it can be said
that gravity-driven transport has been documented in
all tide-dominated deltas with adequate observations
(Wright and Friedrichs 2006 ) . Compound Clinoform Development
As gravity-driven transport is generally associated
with high-discharge and high-energy conditions, so
too is the development of a compound-clinoform
morphology in delta systems (Fig. 7.3 ; Swenson et al.
2005 ) . The concept of compound clinoforms emerged
from investigations of tide-dominated and tide-
infl uenced deltas in the 1980s (e.g. Amazon, Huanghe),
when it became clear that these systems supported
actively accreting subaqueous deltas that are located
substantial distances offshore of, and separate from,
their better recognized subaerial landforms (Fig. 7.5 ;
Nittrouer et al. 1986 ; Prior et al. 1986 ) . The presence
of well-developed subaqueous deltas has also
been documented for the tide-dominated Ganges-
Brahmaputra, Indus, and Changjiang river deltas
(Chen et al. 2000 ; Kuehl et al. 1997 ; Giosan et al.
2006 ) . In these systems the subaerial clinoform
includes primarily the lower delta plain and advancing
shoreline that form at the convergence of onshore-
directed marine processes and river discharge,
whereas the subaqueous clinoform develops at the
boundary between shallow-water and deep-water
processes (i.e., wave-tide-current transport vs. gravity-
driven transport; Swenson et al. 2005 ) .
7.3.4 Sediment Budgets
Tide-dominated deltas are commonly large sediment
dispersal systems controlled both by high-energy
coastal processes and high-discharge rivers. Their sed-
iment load is widely dispersed with active deltaic sedi-
mentation occurring tens to hundreds of kilometers
across and along the continental margin. Therefore,
developing sediment budgets for these systems is
inherently useful in understanding how they respond
to external forcings (e.g., climate, sea level) and how
their fl uvial, coastal, and marine reaches interact.
One of the fi rst budgets developed for a tide-dominated
delta was in the Fly River system, where Harris et al.
( 1993 ) could only account for about half (55 ± 20%)
of the annual sediment load of ~85 × 10
6 metric
tons within the tide-dominated portion of the delta
(note: load estimate prior to construction of the Ok
Tedi mine). Of the sediment that could be located,
roughly equal volumes were apportioned to the lower
delta plain (i.e., subaerial clinothem) and deltafront/
prodelta system (i.e., subaqueous clinothem).
Subsequent work has shown that most of the ‘missing’
fraction is split between deposition on the Fly’s vast
lowland river fl oodplain (Swanson et al. 2008 ) and the
actively growing alongshelf clinothem (Slingerland
et al. 2008 ) . A similar distribution of sediment was
1397 Tide-Dominated Deltas
determined for the Ganges-Brahmaputra river delta,
where both modern and Holocene budgets show
that ~40% of the annual load is trapped within the pro-
grading subaerial and subaqueous clinothems of the
tide-dominated portion of the delta. The remaining
60% is distributed about evenly to the fl uvial deltaplain
through overbank sedimentation and to the Swatch of
No Ground canyon that feeds the deep-sea Bengal Fan
(Goodbred and Kuehl 1999 ) .
Liu et al. ( 2009 ) recently developed budget approx-
imations for several tide-dominated or tide-infl uenced
deltas, showing that 30–40% of the sediment load for
the Huanghe (Yellow), Mekong, and Changjiang rivers
escape the deltaic depocenters located in the vicinity
of the river mouth, similar to the portion observed for
the Fly and Ganges-Brahmaputra dispersal systems. In
the case of these East Asian examples, though, sedi-
ments are advected distances of up to 500–800 km
before being deposited as an alongshelf clinothem at
inner- to mid-shelf water depths. Prior to these recent
studies, it was thought that only the Amazon dispersal
system supported such long-distance alongshelf-export
of sediment from its river delta (Allison et al. 2000 ) .
Aside from their distance, though, these remote cli-
nothems share nearly all characteristics of a prodelta
mud wedge, raising the question of whether they
should be considered part of the delta system.
Regardless of their classifi cation, these fi ndings
emphasize that tide-dominated deltas are only part
of a larger source-to-sink continuum of interacting
continental-margin components (e.g., Goodbred 2003 ) .
7.4 Sedimentary Environments
The sedimentary environments of tide-dominated delta
systems can be largely divided into those associated
with the ‘subaerial’ and ‘subaqueous’ portions of the
compound clinoform (Figs. 7.3 and 7.5 ). The subaerial
delta can be further subdivided into a ‘lower delta
plain’ that is infl uenced by tides and other marine pro-
cesses and an ‘upper delta plain’ that is above the tidal
infl uence and dominated by fl uvial processes. Offshore
the subaqueous delta has often been subdivided into the
‘delta front’ and ‘prodelta’, but here we subdivide
the clinothem into the ‘delta-front platform’ (or sub-
tidal delta plain), the ‘delta-front slope’, and ‘prodelta’
based on both morphology and sediment facies
(Fig. 7.3a ). In river-dominated delta systems the
subaerial delta, together with the delta-front platform,
comprises the topsets of a single deltaic clinoform,
with wave-dominated systems often having a defi nable
but closely spaced double clinoform. In the case of
most tide-dominated deltas though, these environ-
ments are separated by a broad high-shear zone of
limited sediment accumulation that separates the pro-
grading subaerial and subaqueous clinoforms of the
compound delta system (Nittrouer et al. 1986 ; Swenson
et al. 2005 ) . Beyond the rollover point (i.e. topset-
foreset transition) the ‘foreset’ and ‘bottomset’ regions
of the clinoform correspond to the delta-front slope
and prodelta, respectively. Another feature of tide-
dominated deltas is that this zonation is irregular along
the coast with multiple, wide distributary channels and
islands occurring within a funnel-shaped embayment
(Fig. 7.5 ), as compared with wave-dominated deltas
where environmental zonation is roughly parallel to
the shoreline.
7.4.1 Subaerial Delta
As noted by Middleton ( 1991 ) many of the largest riv-
ers discharging to tide-dominated coasts have a princi-
pally fi ne-grained sediment load that forms a
mud-dominated delta system. The shoreline of such
deltas is often fringed by expansive tidal fl ats, marshes,
and/or mangroves threaded by tidal channels (see
Chaps. 8 – 10 ). These tidally-dominated environments
are characteristic of the intertidal to shallow subtidal
zone, particularly at the rivermouth and along adjacent
coasts, and may include salt marshes, mangroves,
muddy tidal fl ats, tidal channels, and channel-mouth
bars. In tropical to subtropical tide-dominated deltas
the subaerial deltaplain comprises broad mangrove-
colonized plains that extend from the limits of salt
intrusion downward to the upper half of the intertidal
zone, where they merge with wide intertidal mud and
sand fl ats in the lower intertidal zone.
This transition between subtidal and supratidal
environments is the principal zone of subaerial delta
progradation and is largely defi ned by the develop-
ment of channel-mouth bars within and just seaward
of the active river mouth (Allison 1998 ) . These bars
are generally large (10
2 –10 4 m) elongate features that
extend from shallow subtidal to supratidal elevations,
140 S.L. Goodbred, Jr. and Y. Saito
forming within or along the active distributaries of
the rivermouth estuary and comprising muddy, sandy,
to heterolithic sediments (Fig. 7.5 ; Chen et al. 1982 ;
Dalrymple 2010 ) . For rivers discharging large sedi-
ment loads, such tidal ridges accrete vertically and
horizontally, and ultimately merge to form shallow,
intertidal fl ats. These ats eventually become emer-
gent and vegetated to form new delta-plain environ-
ments. In this way the growth of tidal ridges marks the
incipient stage of delta-plain progradation and is a
defi ning process in tide-dominated deltas (Allison
et al. 2003 ) .
The sedimentary facies that characterize the tide-
infl uenced distributaries comprise laminated to thinly
bedded sand-mud alternations with tidal signatures,
although these are not always well preserved or statis-
tically defi nable (Dalrymple et al. 2003 ) . Due to the
saltwater intrusion into distributary and tidal channels,
marine to brackish fauna (e.g. molluscs, foraminifera
and ostracods) can be found >100 km upstream of the
shoreline. Foraminifera transported by fl ood tides are
recognized even further upstream, presumably trans-
ported during low river discharge and high astronomi-
cal tidal conditions. However, such patterns are
expected to be temporally and spatially variable in
complex delta systems, where differences in discharge
among active and abandoned distributary may strongly
affect onshore transport distances for marine-derived
Along the distributary channel margins, inclined
sand-mud alternations are reported from channel slope
to tidal fl ats, which are termed inclined heterolithic
stratifi cation (IHS) (Choi et al. 2004 ) . Rhythmic climbing-
ripple cross-lamination and neap-spring cycles may
also be associated with IHS (Choi 2009 ) . These
distributary-channel deposits contain well-sorted fi ne
silt to clay, often derived from near-bed fl uid muds
(e.g. Fly River; Ichaso and Dalrymple 2009 ) . These
sediments with high accumulation rate and large sedi-
ment supply can provide indirect evidence of river del-
tas in the rock record, although they do not necessarily
distinguish them from tide-dominated estuaries unless
other indicators, such as a progradational stacking of
facies, can also be recognized.
Muddy tidal fl ats are one of the most important
components of tide-dominated deltas. The typical sed-
iment facies of this environment comprises sand-mud
alternations with fl aser, lenticular and wavy lamina-
tions or bedding, especially close to the river mouth
where sedimentation rates are high and bedding is well
preserved (Reineck and Singh 1980 ). Bidirectional
features of sand-layer stacking and cross-laminations,
and mud-drapes or double mud-drapes, indicate tidally
infl uenced deposition. These sand-mud layers are basi-
cally controlled by cycles of fl ood-slack-ebb-slack
tidal currents, where slack periods produce the draping
muds and fl ood and ebb currents form planar to ripple-
laminated sand layers. However, neap-spring tidal
cycles are not often recorded in the laminations
(Dalrymple and Makino 1989 ) , as much of the record
is destroyed by bioturbation, waves, storms, and other
events (Fan and Li 2002 ; Fan et al. 2004, 2006 ) . From
the subtidal to intertidal zones, these sediment facies
typically show an upward-fi ning and thinning succes-
sion. The thicker and coarser layers in the lower inter-
tidal zone result from more mud settling from the water
column at slack tide and stronger currents during fl ood
and ebb for sand transport. The migration of tidal chan-
nels and creeks across tidal fl ats may also generate a
typically fi ning-upward and thinning-upward succes-
sion (e.g., Gulf of Papua, Walsh and Nittrouer 2004 ) .
Toward the top of the succession in the upper intertidal
zone, plant rootlets and peat/peaty sediments become
common and refl ect transition to a vegetated delta-
plain facies with subaerial soil formation (Allison et al.
2003 ) . In tropical to subtropical areas woody man-
groves dominate these environments, with tree roots,
leaves, and other plant fragments forming peats and
organic-rich sediments.
Alternating sand-mud layers also commonly occur
within subtidal shoals that form on the delta-front
platform and likely represent the incipient phase of
channel-mouth bar formation. In the Amazon and
Ganges-Brahmaputra deltas these deposits are inter-
bedded or interlaminated sand and mud that are formed
under the strong infl uence of tides, especially the
neap–spring cycle (Jaeger and Nittrouer 1995 ; Michels
et al. 1998 ) . The daily tidal exchange is not typically
recorded, though, either not being formed or not pre-
served. The sand layers within the delta-front platform
develop through erosion and bedload transport during
spring tides, whereas muddy layers are produced under
relatively low-energy conditions during neap tides. In
case of the Gulf of Papua shelf of the Fly and Kikori
deltas, the delta-front platform (topset) shows massive
mud with laminated sandy mud, interbedded mud and
sand, and bioturbated sandy mud (Dalrymple et al.
2003 ; Walsh et al. 2004 ) . Some of these thick mud sets
1417 Tide-Dominated Deltas
on the delta-front slope are likely formed by wave-
supported hyperpycnal fl ows during storm events
(Kudrass et al. 1998 ) and may be correlative with local
wave-scoured erosion surfaces on the delta-front
Where wave infl uence is high at the shoreline, sedi-
ment facies in the intertidal zone change signifi cantly
with the development of sandy beaches and longshore
bars. The Mekong and Red river deltas of Vietnam
both have beach ridges with aeolian dunes and fore-
shore with longshore bars in an intertidal zone in parts
of the delta (Thompson 1968 ; Ta et al. 2005 ; Tanabe
et al. 2006 ; Tamura et al. 2010 ) . Portions of these del-
tas are also tide-dominated and characterized by man-
groves and tidal channels. Where changes in river,
wave, and tidal infl uence vary through time, reductions
in sediment supply to muddy tidal fl ats can induce ero-
sion and the downdrift formation of sand/shell-mound
along the shoreline, called ‘cheniers’. Such episodic
changes locally form a series of cheniers on the prograd-
ing delta plain (Fig. 7.5a ; e.g., Changjiang, Mekong).
7.4.2 Subaqueous Delta
Seaward of the muddy subaerial delta and inner delta-
front platform, sediments typically coarsen again on
the outer delta-front platform toward the rollover point
(e.g., Changjiang, Gulf of Papua, Mekong; Hori et al.
2001 ; Ta et al. 2005 ) . This situation is common for
deltas with a relatively shallow rollover where abrupt
shoaling across the delta-front slope exposes the
Delta-front Platform
A. Subtidal shelf facies association B. Migrating intertidal/subtidal
bedform facies association
C. Tidal channel facies
D. Incised channel facies
-Low energy subtidal shelf, intermittent coarse
sediment supply
CSFSMS Grainsize
C SFSMS Grainsize
C SFSMS Grainsize
Sheet sands
Wave ravinement
channel fill
Erosion base
Erosion into
rhizolith clay
Rhizolith clay
Rootlet horizon, evidence
of exposure/near surface
exposure of sediment
Erosion surface
Fluidised sands into muds
Sheet sands
Channelised sands with
bidirectional current ripples
Channelised sands with
unidirectional climbing
current ripples
Extensive sands which fine
to silts and clays
Loading of sands into clay
- Intertidal/subtidal sand rich shelf - Supratidal/intertidal channels - Intertidal/subtidal shelf with high energy
channelised influx and intermittent surface
Channel-mouth Bar Deltaplain Tidal
Rivermouth Distributary
Fig. 7.6 Sketch logs of major facies associations identifi ed
from a 500-m thick Miocene-age sequence of the tide-dominated
Ganges-Brahmaputra river delta. These facies associations
comprise juxtaposed deltaic environments (see Fig.
7.3 ) that
can be found within 50 km of one another in the modern
Ganges-Brahmaputra delta system (see Figs.
7.4 b and 7.5d ).
Note that neither the fl uvially dominated upper delta plain nor
the marine-dominated delta-front slope or prodelta are repre-
sented in this thick deltaic section, suggesting limited transgres-
sion/regression during this time (After Davies et al.
2003 )
142 S.L. Goodbred, Jr. and Y. Saito
outer platform to high wave energy and tidal-current
acceleration (Figs. 7.5 and 7.6 ). Structures on this
outer portion of the delta-front platform include fi ne to
medium-scale bedding with wave ripples, hummocky
and trough cross-stratifi cation and frequent sharp-
based erosional contacts formed by storm-wave scour.
Subaqueous dunes are also occasionally reported from
this zone of the delta-front platform (Gagliano and
McIntire 1968 ; Kuehl et al. 1997 ) . Overall tidal signa-
tures are not well developed in these deposits despite
the strong cross-shelf tidal currents, because of gener-
ally lower sedimentation rates and frequent bed resus-
pension by waves.
At water depths below fair-weather wave base
(~5–30 m), sedimentary facies of the delta-front slope
are characterized by a coarsening-upward succession
of alternating sand and mud deposits (e.g., Changjiang,
Mekong, Ganges-Brahmaputra) or laminated to biotur-
bated muds (e.g., Gulf of Papua, Amazon). Individual
bedding units often comprise graded (upward fi ning)
and fi nely laminated sand–silt layers with sharp basal
contacts, such as in the Ganges-Brahmaputra (Michels
et al. 1998 ) and Changjiang deltas. Ripples are also
found on the seabed of the delta front of the Changjiang
(Chen and Yang 1993 ) . However, clear tidal signatures
are not always present in the delta-front slope sedi-
ments of tide-dominated deltas, because tidal currents
are not usually well-developed this far offshore.
Similarly, prodelta sediments even further offshore are
often highly bioturbated and intercalated with silt
stringers and thin shell beds. The shell beds result pri-
marily from storms, which may also transport coarser-
grained sediments to the prodelta. In contrast to the
prevalent tide-dominated facies formed in the delta-
plain distributaries and the adjacent intertidal to sub-
tidal delta-front platform, the delta-front slope to
prodelta environments are mostly infl uenced by waves,
ocean currents, and storms.
7.4.3 Facies Associations
Because many factors can infl uence the formation of
stratigraphic sequences over 10
3 –10 5 years, it is also
useful to consider mesoscale facies associations that
characterize the various subenvironments of tide-
dominated deltas (Fig. 7.6 ; Gani and Bhattacharya
2007 ; Heap et al. 2004 ) . A facies association is a group
of sedimentary facies that are typically found together
and defi ne a particular environment, but also allow for
local variability in lithology, structure, and stratal
relationships. In deltaic settings where accretion rates
are relatively high, facies associations record delta pro-
gradation and lobe development that typically occurs at
timescales of 10
1 –10 3 years . For tide-dominated deltas
the most frequently described facies association is that
of the lower delta plain, which captures the advancing
deltaic shoreline and subtidal to supratidal transition
(Allison et al. 2003 ; Harris et al. 1993 ; Hori et al. 2002a, b ;
Ta et al. 2002 ; Dalrymple et al. 2003 ) . As described
from numerous delta-plain systems, the facies association
comprises an 8–10 m thick, fi ning upward succession
starting with sandy, cross-stratifi ed subtidal shoals,
which grade into heterolithic intertidal mud-sand cou-
plets and are capped by a rooted mud-dominated
supratidal soil (Fig. 7.7 ).
Other facies associations that have been described
for tide-dominated deltas include tidal bars, tidal gul-
lies and channels, incised distributary channels, and
the subtidal shelf (Fig. 7.7 ; Davies et al. 2003 ;
McCrimmon and Arnott 2009 ; Tänavsuu-Milkeviciene
and Plink-Björklund 2009 ) . The tidal-bar facies asso-
ciation is variably described as a fi ning-up or coars-
ening-up succession of cross-stratifi ed sand with
bidirectional fl ow indicators and inclined planes that
is very similar to, if not the same as, the portion of
the delta-plain facies association (Fig. 7.6b ). The
difference between the upward-fi ning and upward-
coarsening descriptions is likely related to their
proximity to the active distributary mouth, the fi ning-
up example being more proximal to the rivermouth
and receiving abundant sediment to make a rapid
transition from subtidal to vegetated intertidal
setting, whereas the coarsening-up succession may
be a more wave-tide dominated downdrift littoral
deposit. The tidal gullies and distributary channels are
regularly described as fi ning-up , current-rippled to
planar-bedded deposits with a sharp, often incised,
lower contact. However, the most characteristic features
of these facies associations is the regular occurrence
of mud clasts that refl ect the local reworking of shal-
low intertidal and supratidal delta-plain deposits as
channels migrate, avulse, and incise (Fig. 7.6c ;
Dalrymple et al. 2003 ; Davies et al. 2003 ; Tänavsuu-
Milkeviciene and Plink-Björklund 2009 ) . On aver-
age, though, tidal channels are relatively laterally
stable (e.g. Fagherazzi 2008 ) and so the muddy delta-
plain deposits that cap tidal-channel sands are
commonly preserved in the upper stratigraphy of the
subaerial delta clinothem.
1437 Tide-Dominated Deltas
Offshore facies associations are less frequently
described for tide-dominated deltas, in part because of
sampling constraints in modern examples, but also
because tidal signatures become increasingly weak
offshore and may not be recognized in the rock record.
This potential bias may explain early confusion with
interpreting the Sego sandstones (Book Cliffs, USA),
which are incised into marine shales and thus described
Fig. 7.7 Stratigraphic succession models for three major
tide-dominated delta systems, ( a ) the Ganges-Brahmaputra,
( b ) the Mekong, and ( c ) the Changjiang. Each model includes
the lower coarsening-up subaqueous clinothem overlain by the
upper, generally fi ning-up, subaerial clinothem. The Mekong
example also shows an alternate coarsening-up model that is
characteristic of more wave-infl uenced portions of the delta
where beach ridges are well developed at the shoreface
(Modifi ed after Kuehl et al.
2005 ; Ta et al. 2002 ; Hori et al.
2002a , respectively)
144 S.L. Goodbred, Jr. and Y. Saito
as various types of forced regression deposits in a
tidally infl uenced setting (Van Wagoner et al. 1991 ;
Yoshida et al. 1996 ) . Willis and Gabel ( 2001, 2003 )
have since argued that the Sego Sandstone actually
represent the tidal channels and inner shelf sand sheet
of a tide-dominated delta system, which incised into its
own muddy delta-front platform and prodelta deposits
during progradation. Such a mud-incised succession of
progradating tidal channel deposits has also been
described from the Miocene-age record of the Ganges-
Brahmaputra delta (Fig. 7.6d ; Davies et al. 2003 ) .
7.5 Stratigraphy
7.5.1 Stratigraphic Successions
Deltas are defi ned as discrete shoreline deposits formed
where rivers supply sediment more rapidly than can be
redistributed by basinal processes (Elliott 1986 ) ; thus
shoreline advance is essential for distinguishing them
from estuaries, which also occur at river mouths but are
transgressive depositional systems. As defi ned, deltas
are regressive prograding to aggrading systems (Boyd
et al. 1992 ; Dalrymple et al. 1992 ) . Therefore deltaic
successions will overall shallow upward, ideally includ-
ing facies associations from prodelta, delta-front slope,
delta-front platform, and delta-plain environments, in
ascending order (Fig. 7.7 ; Dreyer et al. 2005 ) .
In tide-dominated deltas that support a compound
clinothem with prograding subaerial and subaqueous
deltaic units, the idealized stratigraphic succession can
be subdivided into two major intervals (Fig. 7.7 ). The
lower portion shows an upward-coarsening facies suc-
cession from the prodelta to delta-front slope and outer
platform deposits that is marked at its top by sharp-
based wave and current scours. This lower interval is
overlain by an upward-fi ning succession of prograding
deposits from the inner delta-front platform and shoal-
ing to subaerial delta-plain facies. The upper interval is
most typically represented by the delta-plain facies
association (see Sect. 7.4.1 ), but may also include local
sub-environments such as tidal channel bars or estua-
rine distributary associations. Within the overall deltaic
succession, the coarsest and most well-sorted deposits
typically occur in the boundary zone between the
delta-front platform and slope, and secondarily in the
prograding, distributary-mouth channel bars (Coleman
1981 ; Hori et al. 2001, 2002b ; Dalrymple et al. 2003 ;
Tänavsuu-Milkeviciene and Plink-Björklund 2009 ) .
With only modest variation this general succession of
an upward-coarsening subaqueous-delta unit overlain
by an upward fi ning subaerial-delta unit has been
documented in many of the world’s modern tide-
dominated delta systems, including the Ganges-
Brahmaputra (Allison et al. 2003 ) , Mekong (Ta et al.
2002 ) , Changjiang (Hori et al. 2001 ) , and Fly (Harris
et al. 1993 ; Dalrymple et al. 2003 ) . Such similarity
suggests that this stratigraphic succession may be a
useful tool in distinguishing tide-dominated deltas in
the rock record (Willis 2005 ) . Local variation in the
tide-dominated delta succession has been recognized
in the Mekong system, which has become increasingly
wave infl uenced in the late Holocene and shows an
upward-coarsening succession ending in wave-swept
foreshore to aeolian beach-ridge deposits (cf. Fig. 7.6b ,
lower profi le; Ta et al. 2002 ) . In the Mahakam delta,
alongshore heterogeneity in stratigraphic successions
arises from the greater fl uvial infl uence relative to tidal
reworking (Gastaldo et al. 1995 ) .
7.5.2 Delta Progradation
The rate of delta progradation can strongly infl uence
the delta facies succession. As the subaerial delta pro-
grades basinward, the tidal distributary channels can
incise up to 20 m into the delta-front platform deposits,
and a relative rise of sea level (e.g., commonly through
subsidence) is important in order to preserve topset
deposits of the outer delta-front platform. The Ganges-
Brahmaputra and Mahakam deltas are examples of
such progradational and aggradational deltas that dis-
play a largely continuous and conformable Holocene
succession from prodelta to delta-plain facies
(Goodbred et al. 2003 ; Storms et al. 2005 ) . If distribu-
tary channels are stable relative to delta progradation,
a delta succession will form as described above.
However, if the lateral migration of distributaries is
fast relative to delta progradation, then much of the
delta-front facies will be replaced by distributary-
channel fi ll, which is thought to occur in the Fly river
delta (Dalrymple et al. 2003 ) .
7.5.3 Role of Sea-Level Change
Sea-level change can also force environmental changes
that may appear similar to delta progradation in the
stratigraphic record. During periods of sea-level fall
1457 Tide-Dominated Deltas
there is a forced regression of the shoreline that drives
delta progradation and potentially downward incision.
If the drop in sea level is relatively fast compared to
the rate of delta progradation, then the succession
should shift toward a more fl uvially dominated stratig-
raphy with decreasing marine and tidal infl uence
(Bhattacharya 2006 ) . However, with further sea-level
fall and a narrowing of the shelf, tidal range will ulti-
mately drop and tidal energy will decrease consider-
ably relative to a growing wave infl uence. It might
therefore be inferred that tide-dominated deltas are
more generally highstand features, as adequate tidal
energy is less well developed during lowstands due to
narrow shelf widths. Indeed meso- to macrotidal con-
ditions in the modern are associated exclusively with
broad shelves or large drowned valleys and embay-
ments. Regional morphology of the continental margin
(e.g. rift settings, epicontinental seas) could maintain
tidal amplifi cation even during lowstand, though, in
such settings as the Cretaceous Western Interior
Seaway (Bhattacharya and Willis 2001 ) and the Gulf
of California.
Sea-level rise following a lowstand leads to the
transgression and marine inundation of incised valleys
formed during the previous fall of sea level. Riverine
sediments are effectively trapped in these valleys to
form fl uvial and coastal plains, resulting in sediment
starvation on the adjacent shelf and the formation of a
ravinement surface and condensed section (Hori et al.
2004 ; Goodbred and Kuehl 2000 ) . Continued sea-level
rise and transgression of the shelf and valleys will
tend to favor tidal amplifi cation and the development
of tide-infl uenced or tide-dominated environments
(Uehara et al. 2002 ; Uehara and Saito 2003 ) , although
such responses are also dependent on shelf and shore-
line physiography. If sediment supply is suffi cient rela-
tive to the rate of sea-level rise, though, then these
transgressive estuarine settings will evolve into deltas
with an associated change in shoreline trajectory from
landward to seaward. When constrained within the
incised valleys, such highstand deltaic successions
typically overlie transgressive estuarine sediments
along the maximum fl ooding surface (Hori et al. 2002a, b ;
Tanabe et al. 2006 ) . Where deltas have infi lled their
lowstand valley, channel avulsion and migration to
interfl uve areas will lead to delta-lobe formation
directly on the lowstand exposure surface and sequence
boundary (Goodbred and Kuehl 2000 ; Ta et al. 2005 ) .
In some cases, such as the Mekong and Red river
deltas, tidal dominance may wane as the delta progrades
into the estuarine embayment and coastal morphology
shifts from concave to convex, making the system
more wave-dominated as the delta lobe faces more
open ocean (Ta et al. 2005 ; Tanabe et al. 2006 ) .
7.6 Summary
Tide-dominated deltas are an end member of the
river-wave-tide ternary delta classifi cation and have
been studied in earnest only since the 1970s. Several
comprehensive research programs during the 1980s
and 1990s developed a sound knowledgebase on the
hydrodynamics, sediment transport and marine pro-
cesses, and strata formation in tide-dominated deltaic
settings. More recent research on modern deltas, par-
ticularly studies involving the drilling of cores and
the collection of observational data, have accelerated
our understanding of the specifi c sedimentary envi-
ronments, processes, and stratigraphic successions
found within and around tide-dominated deltaic
Today most modern tide-dominated deltas are build-
ing seaward through modestly prograding deltaplains
and more rapidly prograding muddy subaqueous cli-
nothems. The sedimentary facies within these settings
are typically, perhaps characteristically, heterolithic
and often mud-dominated (e.g. Changjiang, Fly),
although some systems may have an appreciable sand
component (e.g. Ganges-Brahmaputra). In contrast,
most sections of the rock record that have been inter-
preted as tide-dominated deltas comprise sand-domi-
nated, or alternating sand-mud, sedimentary facies.
This apparent bias toward coarse-grained ancient
examples may arise from the diffi culty of distinguish-
ing deltaic successions from other mud-dominated
sedimentary facies, many of which may lack clear
indicators of fl uvial origin due to the strong overprint
of tidal processes. The broad distances across which
many modern tide-dominated deltas develop also pres-
ent a challenge at the outcrop scale, and differences in
uvial sediment input (e.g., coarse vs. fi ne) may further
limit the recognition of unique facies characteristics.
In terms of human impacts, more than 200 million
people live in tide-dominated delta systems today,
ranking them among the world’s most economically
and culturally important environments. In many systems
the mangroves, salt marshes, and tidal fl ats typical of
tide-dominated delta systems are threatened by human
activities. Several modern deltas are already severely
146 S.L. Goodbred, Jr. and Y. Saito
degraded due to decreases in sediment and freshwater
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tions and activities have been implemented along the
Yangtze river system, with anticipated negative
impacts; damming and water consumption remain
likely threats to the heavily populated Ganges-
Brahmaputra and Ayeyarwady basins as well.
Regardless, sustainable ways to conserve and use these
environments will be a continuing challenge.
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... Even a casual reading of publications on the Tilje and Cook formations shows a surprising similarity of facies, suggesting that the northern and southern regions shared some common tide-dominated or tideinfluenced depositional systems within the Early Jurassic Seaway. The common thread is that they were both part of the same epicontinental seaway (Doré 1991), a basin setting that typically favours and amplifies tidal currents, and despite its long extension (hundreds of kilometres), had some tendency to suppress wave action (see also Goodbred and Saito 2012). The intriguing question is whether these two time-equivalent formations were in spatial continuity with each other along offshore Norway or comprise separate units with a similar basin setting that gave them both a strong tidal character. ...
... The shallow water depths of epicontinental shelves or seaways, as well as the tectonic partitioning of such seaways, typically suppresses wave activity and enhances tidal currents. It should also be noted that tidal currents can weaken with a narrowing of the shelf width, or if the coastal morphology changes from concave to convex (Goodbred and Saito 2012). ...
... Tide-dominated deltas have a set of distinguishing features on the scale of facies, facies successions and at the basin scale. Many of the modern examples are found in tropical areas with a wet climate and often associated with active uplift tectonism, resulting in abundant sediment yield in the mountain catchments allowing deltas to form along continental shelves (Goodbred and Saito 2012). Modern tidedominated deltas are commonly larger in size than other types of deltas because of their protruding subaqueous portion (Fig. 3), and they often have high sediment discharges bringing large volumes of very fine-grained sandstones and muddy sediment onto moderately wide shelves (Middleton 1991). ...
Full-text available
The Lower Jurassic Cook Formation reservoir is a hydrocarbon-prolific unit that produces from several fields in the northern North Sea. For 40 years this formation has been interpreted as a westward-prograding deltaic unit sourced from Norway. Despite numerous discoveries, exploration targeting this unit has been hampered by well failures with lack of reservoir sand, discouraging companies from further exploration of this play. During a current re-evaluation of the process sedimentology of the Norwegian offshore basins, the Cook Formation is now interpreted as the middle to distal reaches of a very large, north-to-south-oriented delta system, variably confined within the Early Jurassic Seaway running from the Norwegian Sea into the northern North Sea. The Cook Formation is a subaqueous delta built southward during regression, whereas several internal transgressive phases produced sands that were reworked as north–south-oriented, shelf tidal ridges. The tidal ridges of the Cook Formation constitute some of the best reservoirs and are elongated with stacked, well-sorted, cross-bedded sandstone sets with mudstone drapes. Both the elongate tidal sand-ridges and intervening mudstone-rich, inter-ridge zones are proven by numerous well observations and illustrated by seismic amplitudes. In contrast to earlier eastern derivation models, these new results for the depositional system of the Cook Formation better explain the Cook well successes and failures in the northern North Sea. This work also strongly suggests that the tide-dominated subaqueous delta to transgressive-ridge system of the Cook Formation is spatially linked with the time-equivalent shorelines, subaerial tidal deltas and estuaries of the Tilje Formation in the Haltenbanken region to the north. The Tilje Formation deltas built into the Early Jurassic Seaway due to rift-initiation and rift-shoulder uplift, drained southwards and spilled eventually into the northern North Sea, becoming the entirely subaqueous Cook Formation. The relatively narrow seaway enhanced the tidal currents and suppressed wave activity, resulting in Cook subaqueous delta lobes and ridges without any delta-top facies. Overall, this elongate and extensive, Pliensbachian deltaic to estuarine system of the Early Jurassic Seaway off Norway competes in scale with some of Earth's largest present-day deltas.
... (direct linkage or canyon capture), surface mud plumes (hypopycnal flow), dilute-suspension bottom-boundary-layer dispersal sometimes enhanced by waves or tide-driven currents, and sediment gravity flows (hyperpycnal underflows and fluid-mud flows). Wave and tidal processes on the other hand, constantly rework the shoreline and shelf sediments supplied by the river, and morphological changes can be observed in a century (Dominguez 1996;Goodbred and Saito 2012;Anthony 2015;Rossi et al. 2016). ...
... The model presented herein is valid for the bypass zone where neither deposition nor erosion occurs. Adapted from Walsh and Nittrouer (2009) (Goodbred and Saito 2012). If there are only weak waves on the shelf, it is the enhanced tidal currents on the thicker subaqueous delta and its highenergy upper surface that build the delta towards the shelf-slope transition zone, supplementing river flow. ...
The processes that transport sediment from the coastline to the shelf edge are key components of the sedimentary source-to-sink system, determining basin-margin building, deepwater deposition, organic-material accumulation, and the long-term carbon cycle. Research on shelf sediment transport has been aided recently by advances in modeling and marine technology. In this study we provide a much needed review of up-to-date findings on how sediment moves from the outer shelf onto the upper slope, and we summarize four dominant shelf-to-slope drivers: 1) river currents, 2) reworking storm waves and longshore currents, 3) strong tidal currents supplementing river outflow, and 4) small-scale to very large-scale gravity collapse of the shelf-edge area.
... Conversely, waves tend to redistribute sediments near river mouths 95 by alongshore and cross-shore fluxes caused by spatial gradients in wave breaking 96 (Komar, 1973). This process flattens shorelines and can seal of river mouths (Jerolmack 97 (Dalrymple et al., 1992;Goodbred & Saito, 2012;Valle-Levinson, 2010). Delta 100 morphologies also exist where there is a mix of fluvial and marine fluxes (e.g., Sinu). ...
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Waves, rivers, and tides play a leading role in shaping delta morphology. Recent studies have enabled predictions of their relative influence for deltas globally, but methods and associated uncertainties have remained poorly described. Here we aim to address that gap and assess the quality of delta morphology predictions compared to observations for 31 deltas globally. We expand on seminal works that quantified the Galloway ternary diagram from the balance between river, wave, and tidal sediment fluxes. Our data includes uncertainties for delta shoreline protrusion angles set by wave influence (14.1°±12° predicted vs. 20.8°±16.1° observed), channel widening, set by tidal influence (53.5±170.8 predicted vs. 6.5±11.5 observed), and number of distributary channels, set by river influence (55.9±127.5 predicted vs. 21.4±43.0 observed). Within the ternary diagram for delta morphology, we find an average error of 8% (±11%, 1 standard deviation), linked to uncertainties in wave and tide sediment fluxes. Relative uncertainties are greatest for mixed-process deltas (e.g., Sinu, error of 49%) and tend to decrease for end-member morphologies where either one of wave, tide, or river sediment fluxes dominates (e.g., Fly, error of 0.2%). Large sources of prediction uncertainties are (1) delta morphology data, e.g., delta slopes that modulate tidal fluxes, (2) data on river sediment flux distribution between individual delta river mouths, and (3) theoretical basis behind fluvial and tidal dominance. Future work could help address these three sources and improve predictions of delta morphology.
... Headless channels are ubiquitous on tide-dominated deltas in the field and are self-formed or relict abandoned distributaries maintained via bi-directional tidal flow and landward-decreasing shear stresses (Fagherazzi, 2008;Hood, 2010). These deltas also have large subaqueous platforms that extend seaward from the shoreline, consistent with field deltas subjected to significant tidal influence (Goodbred & Saito, 2012;Rossi et al., 2016). Rough shorelines are common features of tide-dominated deltas in the field such as the Orinoco delta ( Figure 2b) (Galloway, 1975;Geleynse et al., 2011;Rossi et al., 2016), and in our simulations roughness results from a combination of headless tidal channels and distributary channels perturbing the shoreline as protrusions and indentations. ...
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Plain Language Summary River deltas are ecologically and economically important, and each delta is unique in terms of its environmental conditions and overall form. We test a 50‐year‐old hypothesis that qualitatively relates the overall form of a delta (in terms of its shoreline and channel network) to the balance between river and marine influence. We develop a suite of simulated river deltas using a physics‐based numerical model. We quantitatively describe the overall form for each of the simulated deltas and for a globally‐distributed set of real‐world deltas. The simulations and global deltas indeed exhibit relationships between their overall form and the balance of river and marine influence. Deltas with little to no marine influence have abundant channel mouths and rough shorelines. Tides act to roughen the shoreline but do not affect the number of distributary channel mouths. Waves tend to smooth the shoreline and reduce the number of distributary channel mouths. Waves may also lead to the formation of barrier islands and sand spits, though these features do not necessarily indicate wave “dominance.” These results confirm the hypothesis from the 1970's while adding important information about the morphological transitions between different end‐member “type” deltas.
... The Yangtze River Delta is a typical tide-dominated river delta (Figure 1; Goodbred and Saito, 2012) and there have Niu et al., 2021). (B) Locations of cores KZ01-A and KZ02 in the present-day North Channel and the turbidity maximum zone (TMZ; after Shen and Pan, 2001). ...
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Muddy sediments are the most prominent constituents of sedimentary successions in tide-dominated river deltas and have highly complex depositional mechanisms. In this study, we performed fine-grained (4–11 μm) quartz optically stimulated luminescence (OSL) dating on two sediment cores collected at a shipwreck site in the turbidity maximum zone (TMZ) of the modern Yangtze River mouth, China, which were compared with previously published dating results including 45–63 um quartz OSL dating, radionuclide dating, porcelain artifacts recovered from the wreck, macro-plastics, and the morphological history recorded in marine charts. We investigate the luminescence characteristics of muddy sediments trapped in the TMZ and discuss the implications of OSL ages in understanding depositional mechanisms in tide-dominated river mouths. The results indicate that most OSL ages of muddy sediments in the delta front setting are overestimated compared with other dating methods. We suggest that OSL age overestimation reflects the trapping of sediments from offshore in the TMZ imported by saltwater intrusions and storm events. The offshore inputs contain high percentages of residual luminescence and are also subjected to incomplete bleaching due to turbid water conditions and near-bed dispersal in the salt-wedge river mouth. We thus suggest that the reduced bleaching efficiency of muddy sediments in delta front settings needs to be accounted for in understanding sedimentary processes and distinguishing between different sedimentary facies in tide-dominated river mouths. Furthermore, we propose that differences in quartz OSL ages of fine- and medium-grained fractions may arise in response to extreme events.
Accurate source rock characterizations via geochemical and optical methods require advanced knowledge of the processes of their formation and the factors that control their development. The current chapter starts by addressing the fundamentals of sedimentary organic matter’s origin and chemical compositions and how they interact with the atmosphere, lithosphere, and hydrosphere through comprehensive elucidations of the biogeochemical cycles of carbon, nitrogen, sulfur, and phosphorus. Then, it discusses the deposition and transportation of organic matter in different habitats and the physical and chemical factors that affect its preservations. The third part of the chapter provides insights into the kerogen formation pathways, classifications, and alteration processes. Finally, the chapter introduces the common terrestrial and marine source rock depositional environments and the processes that control the organic productivity and source rock development richness and quality. The knowledge in this chapter represents a reliable base for accurate source rocks and petroleum data interpretations. Furthermore, it can assist in explaining the changes in organofacies and thermal maturity, identifying sweet spots in unconventional resources, types of generated hydrocarbons (sweet versus sour oils), and maturing basin modeling calibrations.
Deltas are depositional landforms that are distinguished by a shoreline protrusion formed where rivers enter a standing body of water and their sediments are more or less redistributed by marine processes. This chapter describes the global distribution, classification, morphology, sedimentary processes, and evolution of deltas by referring to modern and Holocene examples. The application of various dating techniques has made it possible to determine the accumulation rates of deltaic sediments and their morphodynamic evolution on different timescales. This chapter concludes by touching on the effects of relative sea-level rise and anthropogenic decreases of sediment discharge on the vulnerability and sustainability of deltas.
During the Albian age, siliciclastic input in the Arabian carbonate-dominated shelf formed important petroleum system elements. Hence, the Albian Burgan-Kazhdumi succession hosts world-class sandstone reservoirs in some Middle East oil fields. Moreover, stratigraphic traps are possible due to changes in facies and structural dips. Accordingly, we used process-based forward stratigraphy modeling as a powerful tool to predict Burgan-Kazhdumi units and de-risking new exploration prospects. A 3D stratigraphic model was constructed in this study for the first time by integrating multi-disciplines and multi-scales of seismic and well data from several countries. The model (324 km × 264 km, 4 km × 4 km grid size) encompasses NW of the Persian Gulf, Kuwait, south Iraq and SW of Iran and is vertically divided into three units based on Albian regional third-order sequences. Results indicated that the lower unit, unit-1, contains onlapping aggradational-retrogradational stacking compounds, high sand bodies thickness and distribution as well as good reservoir quality. This unit was deposited on a tide-dominated delta system. Gradually, with rising sea level, progradational fine-grain marine sedimentation dominated in units 2 and 3. Hence, intra-formational seal facies formed in the proximal and organic-rich facies in the distal intra-shelf areas. The gentle topography of the basin floor seems responsible for the lack of turbidity lobes. The sand bodies of up-dip arches such as Khafji-Norooz and Kharg-Mish highs and pinched out in fine-grained facies provide a significant potential for stratigraphic traps. The model sensitivity analysis showed eustasy, and water-driven diffusion coefficient (Kw) has the most critical impact on the clastic sedimentation of unit-1 and unit-3. Furthermore, tectonic events have the most significant sedimentation effect in unit-2 sedimentation. The findings of this study can help for better understanding of a more precise regional sequence stratigraphic and stratigraphic architecture of the Albian succession of the study area. This study also helps identify elements of petroleum plays as well as stratigraphic trap potential between mixed siliciclastic-carbonate depositional systems.
Recent work has focused on erecting new Seilacherian ichnofacies for depositional environments subject to recurring temporal and spatial variations in physico-chemical stress. In marine deltaic settings, these correspond to the Phycosiphon Ichnofacies for mudstone-dominated prodeltaic deposits and the Rosselia Ichnofacies for sandstone-dominated delta-front successions. The archetypal expressions of these ichnofacies, however, are founded on mixed process (wave- and river-influenced) systems, because the juxtaposition of ambient marine conditions during periods of prolonged wave energy with rapid deposition and physico-chemically stressed conditions during heightened fluvial discharge best expresses the deltaic signal. As deltaic settings shift towards end-member processes (e.g. river domination, wave domination and tide domination), or towards mixed-process conditions other than river and wave influence, the resulting ichnological suites and bioturbation fabrics depart from the recently published archetypes. Using selected studies of marine deltaic deposits, predictable departures from the archetypes can be recognized on the basis of these changing processes and their associated physico-chemical stresses. River-dominated delta deposits and tide-dominated delta successions display the greatest deviation from the published archetypes. River-dominated examples show elevated deposition rates, periods of salinity reduction, slumping and dewatering, elevated water turbidity, flood-induced sediment gravity flows and hypopycnal-generated fluid mud. As a result, river-dominated successions are largely devoid of bioturbation. Evidence of marine conditions is commonly restricted to isolated occurrences of dwelling structures such as Arenicolites , Ophiomorpha or Rosselia in sandstone, and Chondrites , Phycosiphon or Zoophycos in mudstone beds, particularly in prodeltaic intervals. Tide-dominated deltaic successions are markedly heterolithic and typified by highly mobile substrates manifested by incrementally migrating asymmetric bedforms and abundant fluid mud. Such settings are also prone to marked changes in salinity and shifts in the position of the turbidity maximum zone. Successions typically show low intensities of bioturbation and sporadically distributed burrows, as well as deposit-feeding structures, deeply penetrating dwelling structures or fugichnia. Many trace fossil suites consist entirely of facies-crossing elements, making assignment to an ichnofacies impossible. Storm flood-dominated deltaic successions are characterized by tempestites that are typically interstratified with river flood-induced sediment-gravity flow deposits and/or mantled by largely unburrowed mudstone drapes derived from hypopycnal plumes associated with river floods. Where these storm flood cycles are interstratified with ambient fairweather beds, assignment to the archetypal deltaic ichnofacies is straightforward. However, as storm beds become increasingly erosionally amalgamated, the preservation potential of the fairweather beds is reduced and the resulting trace fossil suites are biased towards those recording opportunistic colonization of the event beds. The presence of mudstone layers with low bioturbation intensity (BI) containing small numbers of ichnogenera positively correlated with marine conditions (e.g. Chondrites , Phycosiphon and/or Zoophycos ) may be the only evidence that the suites should be assigned to one of the deltaic ichnofacies. Wave-dominated deltas lacking significant storm influence are typically challenging to differentiate from their archetypal strandplain shoreface counterparts and, correspondingly, the resulting trace fossil suites are broadly comparable to the archetypal Cruziana and Skolithos ichnofacies. Most of the preserved record of wave-dominated delta successions is related to fairweather ambient conditions, and so facies typically show high BI values and uniformly distributed bioturbation. Key to recognizing that the suites should be assigned to one of the deltaic ichnofacies is the presence of rare river-generated mudstone and sandstone beds that display evidence of physico-chemical stress and/or the paucity of domichnia typical of suspension-feeding organisms. In most delta types, the prodeltaic facies are most readily discerned to contain trace fossil suites of the Phycosiphon Ichnofacies, owing to the higher preservation potential of all depositional processes, including marine fairweather beds, river-supplied hyperpycnites and other sediment gravity flow deposits, tempestites and fluid mud derived from river flood-related hypopycnal plumes. Assignment of trace fossil suites to the Rosselia Ichnofacies requires some record of the fairweather conditions, which are generally diminished in river-, tide- and storm-dominated successions. The dominance of structures positively correlated to deposit-feeding ethologies at the expense of those attributed to suspension-feeding strategies may point to elevated water turbidity and assignment of the suite to the Rosselia Ichnofacies. However, in many cases, the ichnological suites of delta fronts are so depauperate that assignment to an ichnofacies is problematic and should be avoided.
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In western Manipur, India, a ~765 m thick dominantly fine-grained succession of the Late Eocene–Early Oligocene Laisong Formation, constituted of siltstone-silty-shale heterolithic units at its lower part and thickly bedded sandstones in the upper part, allowed documentation of subaqueous part of a tidal delta. The abundant incidence of features including lenticular, wavy bedding, starved ripple trains, syn-sedimentary deformation, reactivation and erosional surfaces, double-mud drapes, tangential bottom set contact, rip-up mud clasts bear tell-tale evidence in favour of tidal modulations. Furthermore, a prominent thickening- and coarsening-up progradational facies stacking motif is correlated as signature for tide-dominated delta. From process-based facies and facies succession analysis, five different sub-aqueous environments of delta were delineated which include prodelta, terminal distributary channel, distal delta front, proximal delta front sheet and proximal delta front lobe in order of stratigraphic superposition. The river-fed sediments were extensively reworked by accentuated tidal currents in an embayed coastline, developed along a narrow, elongated ocean basin bordered by the Indian plate on its west and Burmese micro-plate in the east. A local-scale subsidence and sea-level rise is inferred as trigger for the Laisong tidal delta development in the backdrop of its Late Eocene–Early Oligocene time frame that otherwise witnessed large-scale growth of east Antarctic ice sheet and regional scale fall in sea-level.
Barren mud and salt flats occur on the seaward margin of the Colorado River delta, in the northwestern Gulf of California, flanking the lower 50 km of the Colorado River course, and extend southward from the river mouth for 60 km along the coastal plain of Baja, California (Fig. 7-1). The sedimentology and geologic history of this southern extension were studied in some detail by Thompson (1968), and the results show that intertidal and shallow subtidal sediments here differ markedly from those of other extensive tidal flats described in the literature (for example, Straaten, 1954; Evans, 1965; Reineck, 1967).
This volume is a compilation of 14 papers dealing with the Changjiang and East China Sea. Thirteen of them were presented at the Hangzhou meeting, but all have been modified extensively based on discussions and data exchanges during and after the meeting. Together these papers present an integrated picture of the Changjiang and the environmental regime of the adjacent East China Sea. They are abstracted separately.-from Authors
The river mouth bar at the Chang Jiang Estuary has depths of less than 10 m over a broad area that extends across the entire estuary and out over the inner continental shelf. Flood and ebb channels are usually separate, with shallower areas between them. Over the past 100 years the 5 m contour has progressed seaward 5–12 km and the 10 m contour up to 14 km seaward (opposite the South Channel). The Heng Sha has migrated 5 km upstream and been brought under cultivation during that period, although there has been little change at the central core of the bar. Only about a 2 m change in channel depth (from 5 m to 7 m) has occurred. The bar is a part of and rests upon the Chang Jiang delta and cores bored into the bar reveal the longer-term history of the delta. Changing sediment characteristics and flux in the estuary have been recorded, as well as the changing form of the delta itself.
This field guide documents the sequence stratigraphy and lithofacies of some of the best exposed Late Cretaceous strata of the Western Interior Seaway in north America. The field guide is organized into two segments. The first examines the sequence stratigraphy of spectacular Campanian outcrops, which form part of the Book Cliffs in western Colorado and eastern Utah. The guide continues in northwestern New Mexico, with the second segment investigating Turonian and Coniacian strata in the western outcrop belt of the San Juan Basin. A detailed road log, description and sequence-stratigraphic interpretation of the rocks is provided at each field-stop locality. After each day's road log, an accompanying paper is presented, designed to provide a sequence-stratigraphic overview of the rocks examined during the day, drawing on additional outcrop and subsurface observations. -from Authors