Print this pageAbstract: Estimating Pore and Cement Volumes of Carbonate Rocks in Thin Section
Many point-count estimates of pore, grain, and cement volumes of carbonate rocks from thin sections are inaccurate (often by more than 100%), although they may be surprisingly precise (reproducibility ±3%). Errors are produced by (1) inclusion of submicroscopic pore space within solid volume and (2) edge effects caused by grain curvature within a 30-µ thick thin section. Submicroscopic porosity may be measured by various physical tests or may be estimated visually from scanning electron micrographs. Edge error takes the form of an envelope around grains and increases with decreasing grain size and sorting, increasing grain irregularity, and tighter grain packing. Cements are greatly involved in edge error because of their position at grain peripheries and their enerally small grain size. Edge error is minimized by methods which reduce the thickness of the sample viewed during point counting. Methods which effectively reduce thickness include use of ultrathin thin sections or acetate peels, point counting in reflected light, or careful focusing and counting on the upper surface of the thin section.
AAPG Search and Discovery Article #90964©1978 AAPG Rocky Mountain Section Meeting, Salt Lake City, Utah