130
5.6 Associated Facies
Fluvial deposits are commonly inti�ately interbedded with the deposits of other environments, notably
lakes, eolian deserts, estuaries, glaciated environments, and volcanic environments. It is not the purpose of this book to describe such environments or
their deposits in detail. The following are some brief
notes on these deposits, and some additional reference is made to some of the related environments in
Sect. 12.9, which is a discussion of the climatic information that can be gleaned from such deposits.
In arid fluvial settings, windblown sediment is
common, consisting of individual ventifacts, isolated eolian dunes, or discrete laminae or beds of
eolian dust (loess) or sand. Good descriptions of
interbedded fluvial and eolian strata were provided
by Langford (1989) and Langford and Chan (1989),
to which additional reference is made, with a brief
description of other examples, in Sect. 12.9.4.
Fluvial floodplains commonly contain ponds,
and the distinction between ponds and lakes may
become somewhat arbitrary. Many fluvial systems
also drain into and out of lakes. Fluvial and lake
sediments are therefore intimately interbedded in
many settings. Fluvial crevasse splays may be difficult to distinguish from lacustrine deltas. Associated
lake sediments may include oil shales, palustrine
Lithofacies
limestones (Sect. 12.9.5), and shales containing
lacustrine faunas, such as pelecypods, ostracods, or
fish (e.g., Gersib and McCabe 1981).
Estuarine environments may contain fluvial and
tidal deposits in close association (Zaitlin et al.
1994). Tidal influence may be indicated by the presence of typical tidal sedimentary structures, such as
tidal rhythmites, flaser bedding, and inclined
heterolithic stratification (Thomas et al. 1987; Figs.
2.38, 13.18) in otherwise typical fluvial successions
(e.g., Shanley et al. 1992). The fl uvial-tidal relationship is a common one where coastlines undergo
repeated changes in base level, and has therefore
received considerable attention from sequence
stratigraphers (Sect. 13.3.3).
In glacial environments, flu vial sediments occur
on outwash plains (sandurs) in front of conti11ental
glaciers and ice sheets. There is, therefore, a common association with till and moraine deposits, and
the deposits of glacial lakes (Eyles et al. 1983; Miall
1983b; Byles and Eyles 1992).
Fluvial sedimentation is also an important component of the volcanic environment. The rapid production of abundant volcanic debris and the violent
rainfall that commonly accompanies volcanic eruptions typically leads to catastrophic debris-flow activity (e.g., Vessell and Davies 1981; Lajoie and Stix
1992}. The sedimentary apron around volcanos may
be interbedded with lava flows.
5.6 Associated Facies
Fluvial deposits are commonly inti�ately interbedded with the deposits of other environments, notably
lakes, eolian deserts, estuaries, glaciated environments, and volcanic environments. It is not the purpose of this book to describe such environments or
their deposits in detail. The following are some brief
notes on these deposits, and some additional reference is made to some of the related environments in
Sect. 12.9, which is a discussion of the climatic information that can be gleaned from such deposits.
In arid fluvial settings, windblown sediment is
common, consisting of individual ventifacts, isolated eolian dunes, or discrete laminae or beds of
eolian dust (loess) or sand. Good descriptions of
interbedded fluvial and eolian strata were provided
by Langford (1989) and Langford and Chan (1989),
to which additional reference is made, with a brief
description of other examples, in Sect. 12.9.4.
Fluvial floodplains commonly contain ponds,
and the distinction between ponds and lakes may
become somewhat arbitrary. Many fluvial systems
also drain into and out of lakes. Fluvial and lake
sediments are therefore intimately interbedded in
many settings. Fluvial crevasse splays may be difficult to distinguish from lacustrine deltas. Associated
lake sediments may include oil shales, palustrine
Lithofacies
limestones (Sect. 12.9.5), and shales containing
lacustrine faunas, such as pelecypods, ostracods, or
fish (e.g., Gersib and McCabe 1981).
Estuarine environments may contain fluvial and
tidal deposits in close association (Zaitlin et al.
1994). Tidal influence may be indicated by the presence of typical tidal sedimentary structures, such as
tidal rhythmites, flaser bedding, and inclined
heterolithic stratification (Thomas et al. 1987; Figs.
2.38, 13.18) in otherwise typical fluvial successions
(e.g., Shanley et al. 1992). The fl uvial-tidal relationship is a common one where coastlines undergo
repeated changes in base level, and has therefore
received considerable attention from sequence
stratigraphers (Sect. 13.3.3).
In glacial environments, flu vial sediments occur
on outwash plains (sandurs) in front of conti11ental
glaciers and ice sheets. There is, therefore, a common association with till and moraine deposits, and
the deposits of glacial lakes (Eyles et al. 1983; Miall
1983b; Byles and Eyles 1992).
Fluvial sedimentation is also an important component of the volcanic environment. The rapid production of abundant volcanic debris and the violent
rainfall that commonly accompanies volcanic eruptions typically leads to catastrophic debris-flow activity (e.g., Vessell and Davies 1981; Lajoie and Stix
1992}. The sedimentary apron around volcanos may
be interbedded with lava flows.