A sediment is, by definition, a collection of particles, loose or indurated. Any sedimentological study commences with a description of the physical properties of the deposit
in question. This may be no more than the terse description "sandstones" if the study
concerns regional tectonic problems. On the other hand, it may consist of a multipage
report if the study is concerned with the physical properties of a small volume of a sedimentary unit such as a petroleum reservoir. Remember that the analysis of the physical properties of a sedimentary rock should be adapted to suit the objectives of the project as a whole.
The study of the physical properties of sediments is an extensive field of analysis in
its own right, and is of wide concern not only to geologists. In its broadest sense of particle size analysis, it is of importance to the managers of sewage farms, manufacturers
of leadshot and plastic beads and to egg graders. Enthusiasts for this field of study are
directed to Tucker (1988) and Lewis and McConchie (1994).
The following account is a summary of this topic that attempts only to give sufficient
background knowledge needed for the study of sedimentary rocks in their broader setting. This is in two parts. The first describes individual particles and sediment aggregates;
the second describes the properties of p o r e s - the voids between sediment particles.
3.1 PHYSICAL PROPERTIES OF PARTICLES
3.1.1 Surface Texture of Particles
The surface texture of sediment particles has often been studied, and attempts have
been made to relate texture to depositional process. In the case of pebbles, macroscopic
striations are generally accepted as evidence of glacial action. Pebbles in arid eolian environments sometimes show a shiny surface, termed "desert varnish." This is conventionally attributed to capillary fluid movement within the pebbles and evaporation of
the silica residue on the pebble surface. The folklore of geology records that windblown
sand grains have opaque frosted surfaces, while water-laid sands have clear translucent
surfaces. Kuenen and Perdok (1962) attributed frosting not to the abrasive action of
wind and water but to alternate solution and precipitation under subaerial conditions.
Electron microscopic studies show that there are several types of surface texture on
sand grains produced by glacial, eolian, and aqueous processes (Krinsley, 1998). The
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in question. This may be no more than the terse description "sandstones" if the study
concerns regional tectonic problems. On the other hand, it may consist of a multipage
report if the study is concerned with the physical properties of a small volume of a sedimentary unit such as a petroleum reservoir. Remember that the analysis of the physical properties of a sedimentary rock should be adapted to suit the objectives of the project as a whole.
The study of the physical properties of sediments is an extensive field of analysis in
its own right, and is of wide concern not only to geologists. In its broadest sense of particle size analysis, it is of importance to the managers of sewage farms, manufacturers
of leadshot and plastic beads and to egg graders. Enthusiasts for this field of study are
directed to Tucker (1988) and Lewis and McConchie (1994).
The following account is a summary of this topic that attempts only to give sufficient
background knowledge needed for the study of sedimentary rocks in their broader setting. This is in two parts. The first describes individual particles and sediment aggregates;
the second describes the properties of p o r e s - the voids between sediment particles.
3.1 PHYSICAL PROPERTIES OF PARTICLES
3.1.1 Surface Texture of Particles
The surface texture of sediment particles has often been studied, and attempts have
been made to relate texture to depositional process. In the case of pebbles, macroscopic
striations are generally accepted as evidence of glacial action. Pebbles in arid eolian environments sometimes show a shiny surface, termed "desert varnish." This is conventionally attributed to capillary fluid movement within the pebbles and evaporation of
the silica residue on the pebble surface. The folklore of geology records that windblown
sand grains have opaque frosted surfaces, while water-laid sands have clear translucent
surfaces. Kuenen and Perdok (1962) attributed frosting not to the abrasive action of
wind and water but to alternate solution and precipitation under subaerial conditions.
Electron microscopic studies show that there are several types of surface texture on
sand grains produced by glacial, eolian, and aqueous processes (Krinsley, 1998). The
41