3 Coastal and Shallow Sea Sediments
3.5 Sediments of
Marine Delta Complexes
3.5.1 Introduction
3.5.2 Types ofMarine Deltas
Prograding Fan Deltas
Larger Marine Deltas (Overview)
3.5.3 Sedimentary Processes and Facies ofVarious
Delta Types
Fluvial-Dominated and Lobate Deltas
Wave-Dominated Deltas
Tide-Dominated Deltas
3.5.4 Constructional and Destructional Delta Phases
Facies Architecture ofLobate Deltas
Facies Architecture ofBirdfoot Deltas
Prograding and Switching ofDelta Lobes
The Scale ofMarine Deltas and Depositional
Cycles
3.5.5 Response ofMarine Deltas to Sea-Level Changes
3.5.6 Summary (Marine Deltas)
3.5.1 Introduction
Modem, large marine deltas commonly represent
complex depositional systems, in contrast to the relatively simple lake deltas (cf. Sect. 2.5). Marine deltas
are composed of sediments of greatly differing characteristics and environments (Fig. 3.3Ic). Their facies range from fluvial plains over shallow lakes,
lagoons, tidal flats, estuaries, beach and shorefaces,
to subaqueous delta fronts, delta platforms, and
prodelta slopes. In addition, the offshore shelf may
be affected significantly by deltaic sedimentation.
Many deep-sea fans are associated with large marine
deltas shedding huge volumes of terrestrial material
into the sea. For these reasons, the depositional environments of marine deltas are discussed here with
reference to the less complex subenvironments described earlier (cf. Sects. 3.1 and 3.2).
In spite of the variety in depositional environments, the different facies types of lateral or vertical
deltaic sequences represent a characteristic, diagnostically significant fades association.
The following brief summary is based on special publications and books on marine deltas (e.g., Allen 1965; Morgan
and Shaver 1970; Wright and Coleman 1973; Galloway
and Hobday 1983; Fraser 1989; Bhattacharya and Walker
1992; Chough and Orton 1995; Oti and Po~tma 1995;
Reading and Collinson 1996, and others). ThIS summary
cannot cover all variations and details observed in recent
and ancient case studies. The response of marine deltas is
also briefly discussed in Sect. 7.4.
3.5.2 Types of Marine Deltas
Prograding Fan Deltas
Marine deltas develop where rivers enter the sea and
cause a seaward prograding of the coastline due to
their high sediment load. In the case of a narrow
coastal plain in front of a high mountain range
drained by small and middle-sized rivers, such a
progradation can take place rather uniformly along a
wide coast-parallel zone and generate aseries of coalescing fan deltas (Fig. 3.31a). Coarse material
transported during river floods reaches the coast and
may form comparatively wave-resistant blocky and
gravelly beach ridges. Lagoonal muds can accumulate behind such ridges. The foreshore is characterized by sorted gravel and sand; the shoreface profile
tends to be relatively steep and may show indications
of delta foresets similar to those of lake deltas (Sect.
2.5). Oversteepend prodelta slopes cause gravity
flows (see, e.g., Collela and Prior 1990; Postma
1990). Most of the sand transported into shallow water depth, however, is reworked repeatedly by storm
waves and currents and therefore loses its primary
deltaic sedimentary structures.
Long-terrn, this scenario tends to generate a
prograding coastal plain, delta front, and submarine
fan delta body of limited thickness which is followed
seaward by predominantly siliciclastic shallow-marine sediments (cf. Fig. 2.13)
Larger Marine Deltas (Overview)
The greater and more typical marine deltas are built
by rivers which drain large areas and reach the sea
after a long passage through alluvial plains. Their
sediment load is therefore finer grained and consists
predominantly of silt and clay with minor proportions
of sand. Gravel is often absent or transported only in
very small quantities. The shape of these deltas is
mainly controlled by the rate of sediment input and
the hydraulic regime of the sediment-receiving basin.
3.5 Sediments of
Marine Delta Complexes
3.5.1 Introduction
3.5.2 Types ofMarine Deltas
Prograding Fan Deltas
Larger Marine Deltas (Overview)
3.5.3 Sedimentary Processes and Facies ofVarious
Delta Types
Fluvial-Dominated and Lobate Deltas
Wave-Dominated Deltas
Tide-Dominated Deltas
3.5.4 Constructional and Destructional Delta Phases
Facies Architecture ofLobate Deltas
Facies Architecture ofBirdfoot Deltas
Prograding and Switching ofDelta Lobes
The Scale ofMarine Deltas and Depositional
Cycles
3.5.5 Response ofMarine Deltas to Sea-Level Changes
3.5.6 Summary (Marine Deltas)
3.5.1 Introduction
Modem, large marine deltas commonly represent
complex depositional systems, in contrast to the relatively simple lake deltas (cf. Sect. 2.5). Marine deltas
are composed of sediments of greatly differing characteristics and environments (Fig. 3.3Ic). Their facies range from fluvial plains over shallow lakes,
lagoons, tidal flats, estuaries, beach and shorefaces,
to subaqueous delta fronts, delta platforms, and
prodelta slopes. In addition, the offshore shelf may
be affected significantly by deltaic sedimentation.
Many deep-sea fans are associated with large marine
deltas shedding huge volumes of terrestrial material
into the sea. For these reasons, the depositional environments of marine deltas are discussed here with
reference to the less complex subenvironments described earlier (cf. Sects. 3.1 and 3.2).
In spite of the variety in depositional environments, the different facies types of lateral or vertical
deltaic sequences represent a characteristic, diagnostically significant fades association.
The following brief summary is based on special publications and books on marine deltas (e.g., Allen 1965; Morgan
and Shaver 1970; Wright and Coleman 1973; Galloway
and Hobday 1983; Fraser 1989; Bhattacharya and Walker
1992; Chough and Orton 1995; Oti and Po~tma 1995;
Reading and Collinson 1996, and others). ThIS summary
cannot cover all variations and details observed in recent
and ancient case studies. The response of marine deltas is
also briefly discussed in Sect. 7.4.
3.5.2 Types of Marine Deltas
Prograding Fan Deltas
Marine deltas develop where rivers enter the sea and
cause a seaward prograding of the coastline due to
their high sediment load. In the case of a narrow
coastal plain in front of a high mountain range
drained by small and middle-sized rivers, such a
progradation can take place rather uniformly along a
wide coast-parallel zone and generate aseries of coalescing fan deltas (Fig. 3.31a). Coarse material
transported during river floods reaches the coast and
may form comparatively wave-resistant blocky and
gravelly beach ridges. Lagoonal muds can accumulate behind such ridges. The foreshore is characterized by sorted gravel and sand; the shoreface profile
tends to be relatively steep and may show indications
of delta foresets similar to those of lake deltas (Sect.
2.5). Oversteepend prodelta slopes cause gravity
flows (see, e.g., Collela and Prior 1990; Postma
1990). Most of the sand transported into shallow water depth, however, is reworked repeatedly by storm
waves and currents and therefore loses its primary
deltaic sedimentary structures.
Long-terrn, this scenario tends to generate a
prograding coastal plain, delta front, and submarine
fan delta body of limited thickness which is followed
seaward by predominantly siliciclastic shallow-marine sediments (cf. Fig. 2.13)
Larger Marine Deltas (Overview)
The greater and more typical marine deltas are built
by rivers which drain large areas and reach the sea
after a long passage through alluvial plains. Their
sediment load is therefore finer grained and consists
predominantly of silt and clay with minor proportions
of sand. Gravel is often absent or transported only in
very small quantities. The shape of these deltas is
mainly controlled by the rate of sediment input and
the hydraulic regime of the sediment-receiving basin.