ABSTRACT

The purpose of the investigation was to determine the precision of linear and areal measurements in estimating the size (volume) of individual sedimentary particles.

The volume of 60 pebbles was determined, and, for each pebble, the area and the long and intermediate axes were measured on planes comparable to those obtained by (1) projecting images of loose grains, (2) sectioning randomly oriented grains, and (3) sectioning grains oriented as they may occur in thin section. The degree of correspondence of these various planar measurements to the volume measurements was determined by regression analysis.

Results of the analysis indicate that the best estimator of the size of a loose grain is the projected area of the grain. The measurement commonly made on particles in thin section, the apparent long axis, was found to be an extremely poor estimator of grain size, but it is not significantly less precise than any other measurement that can be easily made on sectioned grains.