1.3 APPLIED SEDIMENTOLOGY
7
Turning inland, studies of modern fluvial processes have many important applications. The work of the U.S. Army Corps of Engineers in attempting to prevent the
Mississippi from meandering is an example. Studies of fluvial channel stability, flood
frequency, and flood control are an integral part of any land utilization plan or town development scheme.
Engineering geology is another field in which sedimentology may be applied. In this
case, however, most of the applications are concerned with the physical properties of
sediments once they have been deposited and their response to drainage, or to the
stresses of foundations for dams, motorways, or large buildings. These topics fall under
the disciplines of soil mechanics and rock mechanics.
Thus before proceeding to examine the applications of sedimentology to the study of
ancient sedimentary rocks, the previous section demonstrates some of its many applications in environmental problems concerning recent sediments and sedimentary processes (Murck et al., 1996; Evans, 1997). Most applications of sedimentology to ancient
sedimentary rocks are concerned with the extraction of raw materials. These fall into
two main groups: the extraction of certain strata of sediment, and the extraction of fluids
from pores, leaving the strata intact.
Many different kinds of sedimentary rock are of economic value. These include recent unconsolidated sands and gravels that are useful in the construction industry. Their
effective and economic exploitation requires accurate definition of their physical properties such as size, shape, and sorting, as well as the volume and geometry of individual
bodies of potentially valuable sediment. Thus in the extraction of river gravels it is necessary to map the distribution of the body to be worked, be it a paleochannel or an old
terrace, and to locate any ox-bow lake clay plugs that may diminish the calculated reserves of the whole deposit.
Similarly, consolidated sandstones have many uses as aggregate and building stones.
Clays have diverse applications and according to their composition can be used for
bricks, pottery, drilling mud, and so forth. Limestones are important in the manufacture
of cement and fertilizer and as a flux in the smelting of iron. The use of all these sedimentary rocks involves two basic problems. The first is to determine whether or not the
rock conforms to the physical and chemical specifications required for a particular purpose. This involves petrography and geochemistry. The second problem is to predict
the geometry and hence calculate the bulk reserves of the economic rock body. This involves sedimentology and stratigraphy. Here geology mingles with problems of quarrying, engineering, and transportation. Geology is nevertheless of extreme importance.
It is no use building a brand new cement works next to a limestone crag if, when quarrying commences, it is discovered that the limestone is not a continuous formation, but
a reef of local extent.
Coal is another sedimentary rock of importance to the energy budget of most industrial countries. Coal technology is itself a major field of study. Like the other economic
sedimentary rocks, coal mining hinges on two basic geological problems: quality and
quantity. The quality of the coal is determined by specialized petrographic and chemical techniques. The quantitative aspects of coal mining involve both problems of structural geology and mining engineering as well as careful facies analysis. Classic examples
of ancient coal-bearing deltaic rocks have been documented in the literature (e.g.,
the Circulars of the Illinois State Geological Survey). These studies have been made
possible by a combination of closely spaced core holes and data from modern deltaic
7
Turning inland, studies of modern fluvial processes have many important applications. The work of the U.S. Army Corps of Engineers in attempting to prevent the
Mississippi from meandering is an example. Studies of fluvial channel stability, flood
frequency, and flood control are an integral part of any land utilization plan or town development scheme.
Engineering geology is another field in which sedimentology may be applied. In this
case, however, most of the applications are concerned with the physical properties of
sediments once they have been deposited and their response to drainage, or to the
stresses of foundations for dams, motorways, or large buildings. These topics fall under
the disciplines of soil mechanics and rock mechanics.
Thus before proceeding to examine the applications of sedimentology to the study of
ancient sedimentary rocks, the previous section demonstrates some of its many applications in environmental problems concerning recent sediments and sedimentary processes (Murck et al., 1996; Evans, 1997). Most applications of sedimentology to ancient
sedimentary rocks are concerned with the extraction of raw materials. These fall into
two main groups: the extraction of certain strata of sediment, and the extraction of fluids
from pores, leaving the strata intact.
Many different kinds of sedimentary rock are of economic value. These include recent unconsolidated sands and gravels that are useful in the construction industry. Their
effective and economic exploitation requires accurate definition of their physical properties such as size, shape, and sorting, as well as the volume and geometry of individual
bodies of potentially valuable sediment. Thus in the extraction of river gravels it is necessary to map the distribution of the body to be worked, be it a paleochannel or an old
terrace, and to locate any ox-bow lake clay plugs that may diminish the calculated reserves of the whole deposit.
Similarly, consolidated sandstones have many uses as aggregate and building stones.
Clays have diverse applications and according to their composition can be used for
bricks, pottery, drilling mud, and so forth. Limestones are important in the manufacture
of cement and fertilizer and as a flux in the smelting of iron. The use of all these sedimentary rocks involves two basic problems. The first is to determine whether or not the
rock conforms to the physical and chemical specifications required for a particular purpose. This involves petrography and geochemistry. The second problem is to predict
the geometry and hence calculate the bulk reserves of the economic rock body. This involves sedimentology and stratigraphy. Here geology mingles with problems of quarrying, engineering, and transportation. Geology is nevertheless of extreme importance.
It is no use building a brand new cement works next to a limestone crag if, when quarrying commences, it is discovered that the limestone is not a continuous formation, but
a reef of local extent.
Coal is another sedimentary rock of importance to the energy budget of most industrial countries. Coal technology is itself a major field of study. Like the other economic
sedimentary rocks, coal mining hinges on two basic geological problems: quality and
quantity. The quality of the coal is determined by specialized petrographic and chemical techniques. The quantitative aspects of coal mining involve both problems of structural geology and mining engineering as well as careful facies analysis. Classic examples
of ancient coal-bearing deltaic rocks have been documented in the literature (e.g.,
the Circulars of the Illinois State Geological Survey). These studies have been made
possible by a combination of closely spaced core holes and data from modern deltaic