10
observations that we would regard as being sedimentological in nature, his primary concern was
with establishing the working methods of historical
geology, and it would not be correct to regard him as
a founder of sedimentology. It is now suggested by
historians of geology that Lyell overemphasized the
importance of slow, steady processes in his attempts
to discredit biblical ideas. Catastrophism, that is to
say, the rare occurrence of catastrophic events, including violent floods, may in fact be very important
processes in building the stratigraphic record (Ager
1993).
The next importal).t figure in the study of fluvial
sediments is Sorby, whose earliest contribution on
this topic constitutes the first paper on paleocurrent
analysis (Sorby 1852; available, along with other papers by this great innovator, in a c O llection edited by
Summerson 1976). The principles were stated as follows:
" ... By observing the direction of these ripple marks the
line in which the current moved may be known ... [when
ripple drift or false bedding] is observed in progress in
modern sand drifts ... it will be perceived that the line of the
dip of the talus [foreset] is not constantly in the true
direction of the current on account of the fo rmation of
complicated deltoid deposits, in which the line of the dip of
their sloping termination varies very considerably on each
side of that of the current. Its mean direction, however,
coincides with it; and hence, if a number of properly placed
observations be made, their mean gives a result very
closely agreeing with the true line of the current."
Sorby first studied paleocurrent patterns in the
Carboniferous coal measures near Edinburgh. He
classified the sandstones into four types: level bedded, ripple laminated (single ripple train), ripple
drifted, and drift bedded (large-scale cross-bedding)
and referred to them using the first known set of
facies symbols. He recognized that structure size is
·partly dependent on flow velocity.
In a paper published only 7 years later, Sorby
(1859) was able to boast "I must now have, in my
notebooks, not less th 3. n twenty thousand recorded
observations" of paleocurrent directions, a record
that few have equaled. Most were never published.
He went on to say "In various papers ... I have explained many of my deductions, and I have shown
that many peculiarities of physical geography at
former epochs may be learned from a knowledge of
the directions of the currents in various localities".
He lamented that others had not taken up his methods of facies and paleocurrent analysis, and could
not know that such methods would not be widely
used again until the 1950s, over 90 years later.
Sorby, in his 1859 paper, also made the first tentative attempts at understanding bedform hydraulics.
Historical Background
He stated « ... when strata are deposited under the
influence of a current, the character of the resulting
structure must depend on the depth of the water, the
velocity of the current, the nature of the deposits and
the rate of deposition". He thought that it should be
possible to deduce the rate of deposition of rippledrift cross-bedding from lamina thickness which
'(indicates the excess of material deposited on the
sheltered side of ripples over that washed up again
from the exposed side, during the time required for
each ripple to advance a distance equal to its own
length", and he carried out hydraulic experiments in
a stream passing through the grounds of his house
(see Sect. 2.3.5).
Sorbis contributions to the study of sedimentary
structures appear to have remained unappreciated
and largely unknown until exhumed by Pettijohn
(1962) and reinterpreted by Allen (1963b). They are
barely mentioned in Higham's (1963) biography,
and Sorby has generally been much better known for
his work in establishing the use of the microscope in
petrographic studies and in metallurgy. However,
Sorbis accumulation of much data that never be�
came published is, regrettably, a familiar tendency
amongst present-day geologists.
Several advances in the study of sedimentary
structures were made by other naturalists in this
period. For example, jamieson (1860) first recognized clast imbrication, while studying fluvioglacial
gravels in Scotland, and Reade (1884) described examples of ripple lamination in British fluvioglacial
deposits. Gilbert (1884, 1899) described large-scale
symmetrical ripples from some of the Paleozoic marine sandstones of New York State and stated (1899)
"previous to 1882) ideas as to the origin of watermade sand-ripples were crude and unsatisfactory",
but quoted several papers that had appeared since
that date that had improved theoretical knowledge.
He procee!=led to supply an explanation of oscillation
ripples and current ripPles which, for the latter, included Darwin's (1883) discovery of the separation
eddy which forms over ripple crests. "An eddy or
vortex is created in the lee of the prominence, and
the return current of this vortex checks travelling
particles, causing a growth of the prominence on its
downstream side" (Fig. 2.5). Gilbert (1899) provided
a classification of ripple-drift cross-bedding (Fig.
2.6) which was, in effect, only replaced in the early
1960s.
The first investigations into the nature and quantity of sediment carried by rivers were those of
Everest (1832), who measured the suspended load of
the River Ganges under a variety of flow conditions.
Humphreys and Abbot (1861), working for the US
observations that we would regard as being sedimentological in nature, his primary concern was
with establishing the working methods of historical
geology, and it would not be correct to regard him as
a founder of sedimentology. It is now suggested by
historians of geology that Lyell overemphasized the
importance of slow, steady processes in his attempts
to discredit biblical ideas. Catastrophism, that is to
say, the rare occurrence of catastrophic events, including violent floods, may in fact be very important
processes in building the stratigraphic record (Ager
1993).
The next importal).t figure in the study of fluvial
sediments is Sorby, whose earliest contribution on
this topic constitutes the first paper on paleocurrent
analysis (Sorby 1852; available, along with other papers by this great innovator, in a c O llection edited by
Summerson 1976). The principles were stated as follows:
" ... By observing the direction of these ripple marks the
line in which the current moved may be known ... [when
ripple drift or false bedding] is observed in progress in
modern sand drifts ... it will be perceived that the line of the
dip of the talus [foreset] is not constantly in the true
direction of the current on account of the fo rmation of
complicated deltoid deposits, in which the line of the dip of
their sloping termination varies very considerably on each
side of that of the current. Its mean direction, however,
coincides with it; and hence, if a number of properly placed
observations be made, their mean gives a result very
closely agreeing with the true line of the current."
Sorby first studied paleocurrent patterns in the
Carboniferous coal measures near Edinburgh. He
classified the sandstones into four types: level bedded, ripple laminated (single ripple train), ripple
drifted, and drift bedded (large-scale cross-bedding)
and referred to them using the first known set of
facies symbols. He recognized that structure size is
·partly dependent on flow velocity.
In a paper published only 7 years later, Sorby
(1859) was able to boast "I must now have, in my
notebooks, not less th 3. n twenty thousand recorded
observations" of paleocurrent directions, a record
that few have equaled. Most were never published.
He went on to say "In various papers ... I have explained many of my deductions, and I have shown
that many peculiarities of physical geography at
former epochs may be learned from a knowledge of
the directions of the currents in various localities".
He lamented that others had not taken up his methods of facies and paleocurrent analysis, and could
not know that such methods would not be widely
used again until the 1950s, over 90 years later.
Sorby, in his 1859 paper, also made the first tentative attempts at understanding bedform hydraulics.
Historical Background
He stated « ... when strata are deposited under the
influence of a current, the character of the resulting
structure must depend on the depth of the water, the
velocity of the current, the nature of the deposits and
the rate of deposition". He thought that it should be
possible to deduce the rate of deposition of rippledrift cross-bedding from lamina thickness which
'(indicates the excess of material deposited on the
sheltered side of ripples over that washed up again
from the exposed side, during the time required for
each ripple to advance a distance equal to its own
length", and he carried out hydraulic experiments in
a stream passing through the grounds of his house
(see Sect. 2.3.5).
Sorbis contributions to the study of sedimentary
structures appear to have remained unappreciated
and largely unknown until exhumed by Pettijohn
(1962) and reinterpreted by Allen (1963b). They are
barely mentioned in Higham's (1963) biography,
and Sorby has generally been much better known for
his work in establishing the use of the microscope in
petrographic studies and in metallurgy. However,
Sorbis accumulation of much data that never be�
came published is, regrettably, a familiar tendency
amongst present-day geologists.
Several advances in the study of sedimentary
structures were made by other naturalists in this
period. For example, jamieson (1860) first recognized clast imbrication, while studying fluvioglacial
gravels in Scotland, and Reade (1884) described examples of ripple lamination in British fluvioglacial
deposits. Gilbert (1884, 1899) described large-scale
symmetrical ripples from some of the Paleozoic marine sandstones of New York State and stated (1899)
"previous to 1882) ideas as to the origin of watermade sand-ripples were crude and unsatisfactory",
but quoted several papers that had appeared since
that date that had improved theoretical knowledge.
He procee!=led to supply an explanation of oscillation
ripples and current ripPles which, for the latter, included Darwin's (1883) discovery of the separation
eddy which forms over ripple crests. "An eddy or
vortex is created in the lee of the prominence, and
the return current of this vortex checks travelling
particles, causing a growth of the prominence on its
downstream side" (Fig. 2.5). Gilbert (1899) provided
a classification of ripple-drift cross-bedding (Fig.
2.6) which was, in effect, only replaced in the early
1960s.
The first investigations into the nature and quantity of sediment carried by rivers were those of
Everest (1832), who measured the suspended load of
the River Ganges under a variety of flow conditions.
Humphreys and Abbot (1861), working for the US