24
following Walther's (1893-1894) teachings, which
belies Grabau's pessimistic statement published 5
years later (quoted above). The paper had a profound impact on the development of sedimentology.
As regards fluvial sedimentation Barrell stated (in
part):
"In rivers where sands are being deposited the channel
is subject to meandering. It cuts laterally into the banks
and scours dovm into older floodplain deposits. The sands
of the abandoned channels cut across the bedding of
the floodplain deposits on the convex sides of the meanders and on the concave side are interlaminated with
them.n
This last statement is, of course, i:q.correct. Barrell
continued:
"The river works across the floodplain and buries channel
structures widely in the fluviatile deposits. The river bars
work regularly do-wnstream, being continually cut out
above and deposited below ... Gravel tends to be concen�
trated along such channel bottoms. Lateral discontinuity
of the sandstone lenses is also a feature, the ancient chan�
nel deposits forming a meshwork."
Barrell was also aware of another style of fluvial
sedimentation:
"Effects of sheet-flood deposition: Many aggrading
streams overloaded with sand exhibit at low stage shallow
braided channels within the main channel. At higher water
the main channel may likewise form a braided system,
and at highest water the whole floodplain may be covered
by a shallow moving water body ... It is such conditions
which seem to be required t9 produce the great depths
of regularly bedded and widely extended sandstones
which mark certain continental deposits ... They succeed
each other without inter-lamination of clays and commonly show neither structure nor fossils. False bedding
oblique to the even · regular bedding is occasionally
observed, but the homogeneous material conceals its
frequent presence. Ripple and current marks, however, are
rare or absent."
A more recent descdption of this type of sheetflood deposition in Bijou Creek, Colorado, by McKee
et al. (1967), formed the basis for one of the facies
models of (Miall l977).
Detailed criteria such as those described by
Barrell (1912) were used by Grabau (1913b) and
Barrell (1913, 1914) in their lengthy descriptions of
the Paleozoic deltas of the Appalachians. The alternation of sandstone and shale units in these deposits
was noted, and Barrell (1913, p. 458) stated of the
alternations in the Catskill Formation:
"A gray or olive sandstone member is commonly sharply
delimited at bottom, but at the top grades first into maroon
argillaceous sandstone, ·and this in turn into r.ed sandy
shale."
Historical Background
Elsewhere Barrell (1913, p. 466) attributed the
alternation of fine and coarse units to "the lateral
shifting of distributaries, the red shales representing
flood plain areas temporarily removed from the
presence of currents". Here, then, is the first inkling
of the fining-upward cycle and its origin, although
Barrell was not aware of the general significance of
this observed sequence. This seems to have first occurred to Dixon (1921, p. 32) in his studies of the
South Wales coalfield:
"The relations of each sandstoneMband (b) to the marls
(c and a) above and below are, typically, as follows:
(c) Red marls; passing down into
(b) Flaggy sandstones, the upper red, the lower green; at
the base of the whole band one or more conglomeratic
cornstone; eroding
(a) Marl, green immediately below (b) to a depth which
varies between a mere skin and several fe et, but, in
each case, is fa irly uniform; often a purple band below;
lower still the marl is red and passes down into anM
other sandstone band, which repeats the features of
(b).
This sequence is repeated interminably and in all parts of
the series."
Other contributions made at this time include a
study of the fine banding in Tertiary fluvial sediments in Burma by Stamp (1925), who attributed it
to the effects of seasonal floods, and a study of the
origins and transportation processes of gravel, including fluvial gravel, by Barrell (1925).
A good summary of the state of knowledge of
fluvial sedimentology is included in Twenhofel's
(1932) great treatise. Alluvial-fan, valley-flat, and
fluviodeltaic environments are distinguished, and
the general facies descriptions are much as we would
use today, except Twenhofel thought that "channel
deposits are entirely ephemeral" and that the distribution of the various lithologies is "extremely erratic''.
The next important contributions were those of
Happ et al. (1940) and Fisk (1944, 1947). Based on
their work in modern rivers, Happ et al. divided
fluvial sediments into six types: channel fills, vertical-accretion deposits, floodplain splays, colluvial
deposits (hill wash), lateral-accretion deposits, and
channel lag deposits. They thought that "the last two
types are of little importance under pre-modern
conditions". Good descriptions of the facies were
given, and four facies associations were proposed:
normal floodplain or valley-flat, alluvial-fan, valleyplug, and delta. Their description of the valley-flat
association includes the first block diagram of a
fluvial facies model (Fig. 2.11) which clearly shows
following Walther's (1893-1894) teachings, which
belies Grabau's pessimistic statement published 5
years later (quoted above). The paper had a profound impact on the development of sedimentology.
As regards fluvial sedimentation Barrell stated (in
part):
"In rivers where sands are being deposited the channel
is subject to meandering. It cuts laterally into the banks
and scours dovm into older floodplain deposits. The sands
of the abandoned channels cut across the bedding of
the floodplain deposits on the convex sides of the meanders and on the concave side are interlaminated with
them.n
This last statement is, of course, i:q.correct. Barrell
continued:
"The river works across the floodplain and buries channel
structures widely in the fluviatile deposits. The river bars
work regularly do-wnstream, being continually cut out
above and deposited below ... Gravel tends to be concen�
trated along such channel bottoms. Lateral discontinuity
of the sandstone lenses is also a feature, the ancient chan�
nel deposits forming a meshwork."
Barrell was also aware of another style of fluvial
sedimentation:
"Effects of sheet-flood deposition: Many aggrading
streams overloaded with sand exhibit at low stage shallow
braided channels within the main channel. At higher water
the main channel may likewise form a braided system,
and at highest water the whole floodplain may be covered
by a shallow moving water body ... It is such conditions
which seem to be required t9 produce the great depths
of regularly bedded and widely extended sandstones
which mark certain continental deposits ... They succeed
each other without inter-lamination of clays and commonly show neither structure nor fossils. False bedding
oblique to the even · regular bedding is occasionally
observed, but the homogeneous material conceals its
frequent presence. Ripple and current marks, however, are
rare or absent."
A more recent descdption of this type of sheetflood deposition in Bijou Creek, Colorado, by McKee
et al. (1967), formed the basis for one of the facies
models of (Miall l977).
Detailed criteria such as those described by
Barrell (1912) were used by Grabau (1913b) and
Barrell (1913, 1914) in their lengthy descriptions of
the Paleozoic deltas of the Appalachians. The alternation of sandstone and shale units in these deposits
was noted, and Barrell (1913, p. 458) stated of the
alternations in the Catskill Formation:
"A gray or olive sandstone member is commonly sharply
delimited at bottom, but at the top grades first into maroon
argillaceous sandstone, ·and this in turn into r.ed sandy
shale."
Historical Background
Elsewhere Barrell (1913, p. 466) attributed the
alternation of fine and coarse units to "the lateral
shifting of distributaries, the red shales representing
flood plain areas temporarily removed from the
presence of currents". Here, then, is the first inkling
of the fining-upward cycle and its origin, although
Barrell was not aware of the general significance of
this observed sequence. This seems to have first occurred to Dixon (1921, p. 32) in his studies of the
South Wales coalfield:
"The relations of each sandstoneMband (b) to the marls
(c and a) above and below are, typically, as follows:
(c) Red marls; passing down into
(b) Flaggy sandstones, the upper red, the lower green; at
the base of the whole band one or more conglomeratic
cornstone; eroding
(a) Marl, green immediately below (b) to a depth which
varies between a mere skin and several fe et, but, in
each case, is fa irly uniform; often a purple band below;
lower still the marl is red and passes down into anM
other sandstone band, which repeats the features of
(b).
This sequence is repeated interminably and in all parts of
the series."
Other contributions made at this time include a
study of the fine banding in Tertiary fluvial sediments in Burma by Stamp (1925), who attributed it
to the effects of seasonal floods, and a study of the
origins and transportation processes of gravel, including fluvial gravel, by Barrell (1925).
A good summary of the state of knowledge of
fluvial sedimentology is included in Twenhofel's
(1932) great treatise. Alluvial-fan, valley-flat, and
fluviodeltaic environments are distinguished, and
the general facies descriptions are much as we would
use today, except Twenhofel thought that "channel
deposits are entirely ephemeral" and that the distribution of the various lithologies is "extremely erratic''.
The next important contributions were those of
Happ et al. (1940) and Fisk (1944, 1947). Based on
their work in modern rivers, Happ et al. divided
fluvial sediments into six types: channel fills, vertical-accretion deposits, floodplain splays, colluvial
deposits (hill wash), lateral-accretion deposits, and
channel lag deposits. They thought that "the last two
types are of little importance under pre-modern
conditions". Good descriptions of the facies were
given, and four facies associations were proposed:
normal floodplain or valley-flat, alluvial-fan, valleyplug, and delta. Their description of the valley-flat
association includes the first block diagram of a
fluvial facies model (Fig. 2.11) which clearly shows