Abstract

Three varieties of limestone are distinguished: (1) microcrystalline or granular, more than 50 percent of the rock granular; (2) crystalline, composed mainly of sutured anhedra; (3) fragmental, consists chiefly of calcite fragments, quartz grains, and organic remains. Limestones especially susceptible to metasomatic replacement include the medium-bedded crystalline and fragmental varieties. Thin sections and photomicrographs show that diagenesis of various constituents follows a definite sequence: (1) for carbonates, aragonite or calcite to calcite to dolomite; (2) for silica, opal to chalcedony to quartz. Metasomatic materials are derived in part from associated sediments and in part from the host rocks.

You do not currently have access to this article.