Chapter 11
Te ctollk Co11tro� of Fh.nviai Sedimelltatioll
11.1 introduction
The .major external, or allogenic, controls on fluvial
sedimentation are tectonics and climate. This chapter considers tectonic controls; climatic controls are
discussed in Chap. 12. Base-level changes, driven
either by tectonism or eustasy, are of great importance in controlling fluvial style and sedimentation
rates in the lower reaches of rivers, through the
control base level exerts on regional slope and sedimentary accommodation space. The role of eustasy
in controlling stratigraphic processes remains controversial and is described in Chap. 13,. where the
main theoretical discussion of sequence stratigraphy
is presented. In this chapter changes in base level are
considered as relative changes, and their effects on
stratigraphic processes in the fl uvial environment
are considered without entering into the tectonismversus-eustasy debate.
There is a vast literature on the tectonic control of
sedimentation (Sect. 11.2). In this chapter it is considered under the following subheadings. In Sect.
11.2.1, the local effects of intrabasin fault and fold
movement are considered, including the effects of
rejuvenating fluvial systems and the diversion of
drainages. Relative changes in base level are discussed in Sect. 11.2.2. Regional, basin-scale effects
are discussed in Sect. 11.3, including the differing
responses of depositional systems to the major types
of tectonism. Particular attention is paid to the styles
of nonmarine sedimentation that occur in extensional basins and fo reland basins. Recent quantitative models for sediment dispersal are evaluated.
Nonmarine sedimentation is then discussed within
the context of plate tectonics (Sect. 1!.4), and, finally, some generalizations regarding the tectonic
control of regional fa cies and dispersal patterns are
given (Sect. 11.5).
11.2 Tectonic Control of Ail uvial Stratigraphy
It has been realized since ancient times that the
deposition of coarse-grained sediment in rivers is
related to the presence of elevated source areas. As
noted in Sect. 2.2.1, a dear link between the grain size
of gravels and proximity to a mountainous source
area was suggested by Playfair (1802). It has been a
standard interpretation, at least since the work of
Barrell (1917), that beds of coarse clastic deposits
close to a basin margin indicate tectonic rejuvenation of that margin.
The links between tectonic movement and
coarse-clastic sedimentation have recently been reexamined by jordan et al. (1988), Heller et al. (1988),
and Blair and Bilodeau (1988). These researchers
have challenged the conventional idea that wedges of
coarse sediment are syntectonic in origin, presenting several lines of argument to suggest that in many
cases the most widespread coarse units form afte. r
tectonism has ceased. The actual link between sedimentation and tectonics is not questioned; it is not
doubted that rejuvenated relief is required to generate and transport coarse debris in large quantities.
What is questioned is the detailed timing of the
various events, relating to the speed of basinal and
depositional response to uplift and subsidence. This
topic is examined in Sect. 11.3. Here the discussion is
limited to a presentation of the immediate evidence
for tectonic influence in nonmarine basins - the
effects of changes in slope on grain size and dispersal
patterns. There are two main kinds of effects to
be described: the effects of fault pulses at basin
margins, and the growth of faults and folds within
basins. Many data on these topics from the 1960s and
1970s were summarized by Miall (1978d) and
Heward (1978a), and numerous case studies have
been published since these papers appeared. A re-
Te ctollk Co11tro� of Fh.nviai Sedimelltatioll
11.1 introduction
The .major external, or allogenic, controls on fluvial
sedimentation are tectonics and climate. This chapter considers tectonic controls; climatic controls are
discussed in Chap. 12. Base-level changes, driven
either by tectonism or eustasy, are of great importance in controlling fluvial style and sedimentation
rates in the lower reaches of rivers, through the
control base level exerts on regional slope and sedimentary accommodation space. The role of eustasy
in controlling stratigraphic processes remains controversial and is described in Chap. 13,. where the
main theoretical discussion of sequence stratigraphy
is presented. In this chapter changes in base level are
considered as relative changes, and their effects on
stratigraphic processes in the fl uvial environment
are considered without entering into the tectonismversus-eustasy debate.
There is a vast literature on the tectonic control of
sedimentation (Sect. 11.2). In this chapter it is considered under the following subheadings. In Sect.
11.2.1, the local effects of intrabasin fault and fold
movement are considered, including the effects of
rejuvenating fluvial systems and the diversion of
drainages. Relative changes in base level are discussed in Sect. 11.2.2. Regional, basin-scale effects
are discussed in Sect. 11.3, including the differing
responses of depositional systems to the major types
of tectonism. Particular attention is paid to the styles
of nonmarine sedimentation that occur in extensional basins and fo reland basins. Recent quantitative models for sediment dispersal are evaluated.
Nonmarine sedimentation is then discussed within
the context of plate tectonics (Sect. 1!.4), and, finally, some generalizations regarding the tectonic
control of regional fa cies and dispersal patterns are
given (Sect. 11.5).
11.2 Tectonic Control of Ail uvial Stratigraphy
It has been realized since ancient times that the
deposition of coarse-grained sediment in rivers is
related to the presence of elevated source areas. As
noted in Sect. 2.2.1, a dear link between the grain size
of gravels and proximity to a mountainous source
area was suggested by Playfair (1802). It has been a
standard interpretation, at least since the work of
Barrell (1917), that beds of coarse clastic deposits
close to a basin margin indicate tectonic rejuvenation of that margin.
The links between tectonic movement and
coarse-clastic sedimentation have recently been reexamined by jordan et al. (1988), Heller et al. (1988),
and Blair and Bilodeau (1988). These researchers
have challenged the conventional idea that wedges of
coarse sediment are syntectonic in origin, presenting several lines of argument to suggest that in many
cases the most widespread coarse units form afte. r
tectonism has ceased. The actual link between sedimentation and tectonics is not questioned; it is not
doubted that rejuvenated relief is required to generate and transport coarse debris in large quantities.
What is questioned is the detailed timing of the
various events, relating to the speed of basinal and
depositional response to uplift and subsidence. This
topic is examined in Sect. 11.3. Here the discussion is
limited to a presentation of the immediate evidence
for tectonic influence in nonmarine basins - the
effects of changes in slope on grain size and dispersal
patterns. There are two main kinds of effects to
be described: the effects of fault pulses at basin
margins, and the growth of faults and folds within
basins. Many data on these topics from the 1960s and
1970s were summarized by Miall (1978d) and
Heward (1978a), and numerous case studies have
been published since these papers appeared. A re-