Chapter 1
�litro
Fluvial deposits represent the preserved record of
one of the major nonmarine environments. They
accumulate in large and small mountain-girt valleys,
in the broad valleys of trunk rivers, in the wedges of
alluvial fans fl anking areas of uplift, in the outwash
plains fronting melting glaciers, and in coastal
plains. The composition of fluvial detritus depends
on the geology of the source areas from which the
sediment was derived, and the climatic influences to
which the detritus was subjected before final burial.
The nature of the fluvial assemblage� its lithofacies
composition, vertical stratigraphic record and architecture - reflects an interplay of many processes,
from the wandering of individual channels across a
floodplain, to the long-term effects of uplift and
subsidence. Fluvial deposits are a sensitive indicator
of tectonic processes, and also carry subtle signatures of the climate at the time of deposition. They
are the hosts for many petroleum and mineral deposits. This book is about all these subjects.
Why such a book now? The study of fluvial deposits has a lengthy history, as documented in some
detail in Chap. 2. Up until the early 1960s such study
constituted part of the broader study of ('stratigraphy". During the 1960s and 1970s, the new subdiscipline cailed <
our ideas about fades and intrabasinal, autogenic
depositional processes, leading to the concept of the
process-response model and to generation of suites
of facies models. Since the early 1980s, sedimentology itself has undergone something of a revolution,
and the term ('basin analysis" is a more accurate
description of what many sedimentary geologists
now do. Duting this most recent phase, a renewed
interest in extrabasinal (allogenic) processes has led
to the realization that fluvial basin architecture is
much more complicated than just a record of the
meandering and switching of river channels. Stimulated primarily by developments in the interpretation of regional seismiC-reflection data, geologists
are learning to appreciate the importance of regional
and global controls on basin architecture. The sedimentological effects of orogenic uplift, of basin subsidence, and of base-level change brought about by
these processes, and by eustasy, are profound and
pervasive. They influenCe the entire architecture of a
fluvial succession, ranglng from such small-scale
characteristics as the vertical facies sequence in a
drill core, to the large-scale stratigraphy of a basinfill complex. In this sense, fluvial sedimentology has
now been incorporated into the larger field of sequence stratigraphy, which has revolutionized sedi.mentology and basin analysis s�nce the 1980s.
At the same time, two other areas of research have
contributed significantly to the development of the
science. Firstly, observational and experimental geomorphology have added much to our understanding
of sedimentological processes. In recent years, many
geomorphological Studies have been stimulated by
the needs of geologists to better understand the rock
record. In particular, much geomorphic work has
been carried out in order to explore the effects of
geological processes, such as tectonism, acting over
geologically significant lengths of time. Experimental geomorphology, simulating natural processes in
laboratory flumes, has provided many valuable insights, for example, into the effects of changing the
sediment load, or the regional slope, or the base level
of a fluvial system. At the time of writing this book,
interaction between sequence stratigraphers and
geomorphologists was begl. nning to recognize the
considerable complexity of the relationship between
climate change, base-level change, and the fluvial
response, and a renewed interest was developing in
the incised valleys and terrace deposits of rivers
formed during the Late Cenozoic cycle of glacial and
interglacial phases.
Secondly, numerical models of geological processes are providing a powerful means of quantitatively testing complex, multivariate processes. The
effects of base-level change and tectonism on basin
stratigraphy have now been modeled by many
�litro
Fluvial deposits represent the preserved record of
one of the major nonmarine environments. They
accumulate in large and small mountain-girt valleys,
in the broad valleys of trunk rivers, in the wedges of
alluvial fans fl anking areas of uplift, in the outwash
plains fronting melting glaciers, and in coastal
plains. The composition of fluvial detritus depends
on the geology of the source areas from which the
sediment was derived, and the climatic influences to
which the detritus was subjected before final burial.
The nature of the fluvial assemblage� its lithofacies
composition, vertical stratigraphic record and architecture - reflects an interplay of many processes,
from the wandering of individual channels across a
floodplain, to the long-term effects of uplift and
subsidence. Fluvial deposits are a sensitive indicator
of tectonic processes, and also carry subtle signatures of the climate at the time of deposition. They
are the hosts for many petroleum and mineral deposits. This book is about all these subjects.
Why such a book now? The study of fluvial deposits has a lengthy history, as documented in some
detail in Chap. 2. Up until the early 1960s such study
constituted part of the broader study of ('stratigraphy". During the 1960s and 1970s, the new subdiscipline cailed <
our ideas about fades and intrabasinal, autogenic
depositional processes, leading to the concept of the
process-response model and to generation of suites
of facies models. Since the early 1980s, sedimentology itself has undergone something of a revolution,
and the term ('basin analysis" is a more accurate
description of what many sedimentary geologists
now do. Duting this most recent phase, a renewed
interest in extrabasinal (allogenic) processes has led
to the realization that fluvial basin architecture is
much more complicated than just a record of the
meandering and switching of river channels. Stimulated primarily by developments in the interpretation of regional seismiC-reflection data, geologists
are learning to appreciate the importance of regional
and global controls on basin architecture. The sedimentological effects of orogenic uplift, of basin subsidence, and of base-level change brought about by
these processes, and by eustasy, are profound and
pervasive. They influenCe the entire architecture of a
fluvial succession, ranglng from such small-scale
characteristics as the vertical facies sequence in a
drill core, to the large-scale stratigraphy of a basinfill complex. In this sense, fluvial sedimentology has
now been incorporated into the larger field of sequence stratigraphy, which has revolutionized sedi.mentology and basin analysis s�nce the 1980s.
At the same time, two other areas of research have
contributed significantly to the development of the
science. Firstly, observational and experimental geomorphology have added much to our understanding
of sedimentological processes. In recent years, many
geomorphological Studies have been stimulated by
the needs of geologists to better understand the rock
record. In particular, much geomorphic work has
been carried out in order to explore the effects of
geological processes, such as tectonism, acting over
geologically significant lengths of time. Experimental geomorphology, simulating natural processes in
laboratory flumes, has provided many valuable insights, for example, into the effects of changing the
sediment load, or the regional slope, or the base level
of a fluvial system. At the time of writing this book,
interaction between sequence stratigraphers and
geomorphologists was begl. nning to recognize the
considerable complexity of the relationship between
climate change, base-level change, and the fluvial
response, and a renewed interest was developing in
the incised valleys and terrace deposits of rivers
formed during the Late Cenozoic cycle of glacial and
interglacial phases.
Secondly, numerical models of geological processes are providing a powerful means of quantitatively testing complex, multivariate processes. The
effects of base-level change and tectonism on basin
stratigraphy have now been modeled by many