Grain properties

Abstract

Sediment grains range in size from minute specks of windblown dust to gigantic boulders (Table 4.1). Note that size is usually expressed as a linear dimension. No further difficulty would arise if all grains approximated to spheres, but unfortunately this is not the case. There are a number of alternative linear measures of grain size which take grain shape into account (Table 4.2), one of the most useful being the volume diameter, defined as the diameter of a sphere having the same volume as the grain in question. In the following account, grains will be treated as spheres or spheroids for the sake of simplicity and space. However, the reader should remember that many grains, particularly fragmented bioclastic debris, present grave problems in rational particle size analysis because of their shapes.