This chapter begins by describing the concepts of sedimentary environments, sedimentary facies, and sedimentary models. These concepts linked together provide the depositional systems approach to understanding the origins of sedimentary rocks. In this
method the ancient depositional environment (process) of a sedimentary rock (the
product) is deduced by comparison with modern depositional environments. The main
part of the chapter provides a concise review of the various depositional systems in terms
of their environments (process), facies (product), and economic importance. The chapter concludes by describing the spatial organization of sedimentary rocks, in terms of
sequences and cyclicity.
6.1 SEDIMENTARY ENVIRONMENTS
6.1.1 Environments Defined
The modern earth's surface is the geologist's laboratory. Here can be studied the processes that generate sediments and their resultant deposits. By applying the principle
of uniformitarianism ("the key to the past is in the present"), it is possible to deduce the
origin of ancient sedimentary rocks. For this reason many geologists, and scientists of
other disciplines, have studied modern sedimentary processes and products intensively.
The surface of the earth can be classified by geomorphologists into distinctive physiographic units, such as mountain ranges, sand deserts, and deltas. Similarly, oceanographers define morphologic types of sea floors, such as continental shelves, submarine
fans, and abyssal plains. The most cursory of such studies shows that the number of
physiographic types is finite. For example, lakes and deltas occur on most of the continents; submarine fans and coral reefs are spread wide across the oceans. From this observation it follows that the surface of the earth may be classified into different sedimentary realms or environments. A sedimentary environment has been defined as a "part
of the earth's surface which is physically, chemically and biologically distinct from adjacent areas" (Selley, 1970, p. 1). As already pointed out, sand deserts, deltas, and submarine fans are examples of these different sedimentary environments.
The physical parameters of a sedimentary environment include the velocity, direction,
and variation of wind, waves, and flowing water; they include the climate and weather
of the environment in all their subtle variations of temperature, rainfall, snowfall, and
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method the ancient depositional environment (process) of a sedimentary rock (the
product) is deduced by comparison with modern depositional environments. The main
part of the chapter provides a concise review of the various depositional systems in terms
of their environments (process), facies (product), and economic importance. The chapter concludes by describing the spatial organization of sedimentary rocks, in terms of
sequences and cyclicity.
6.1 SEDIMENTARY ENVIRONMENTS
6.1.1 Environments Defined
The modern earth's surface is the geologist's laboratory. Here can be studied the processes that generate sediments and their resultant deposits. By applying the principle
of uniformitarianism ("the key to the past is in the present"), it is possible to deduce the
origin of ancient sedimentary rocks. For this reason many geologists, and scientists of
other disciplines, have studied modern sedimentary processes and products intensively.
The surface of the earth can be classified by geomorphologists into distinctive physiographic units, such as mountain ranges, sand deserts, and deltas. Similarly, oceanographers define morphologic types of sea floors, such as continental shelves, submarine
fans, and abyssal plains. The most cursory of such studies shows that the number of
physiographic types is finite. For example, lakes and deltas occur on most of the continents; submarine fans and coral reefs are spread wide across the oceans. From this observation it follows that the surface of the earth may be classified into different sedimentary realms or environments. A sedimentary environment has been defined as a "part
of the earth's surface which is physically, chemically and biologically distinct from adjacent areas" (Selley, 1970, p. 1). As already pointed out, sand deserts, deltas, and submarine fans are examples of these different sedimentary environments.
The physical parameters of a sedimentary environment include the velocity, direction,
and variation of wind, waves, and flowing water; they include the climate and weather
of the environment in all their subtle variations of temperature, rainfall, snowfall, and
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