A Mechanism for Development of Stylolites

Abstract

A sequence of processes is offered by which a rock that is initially almost homogeneous could become stylolitic. The host rock is assumed to contain initially a not-quite-uniform distribution of clay particles that have two properties: when dispersed, they are sites where dissolution of host rock is enhanced, but when concentrated and compacted they can form a low-permeability obstacle to migrating fluids. Initially, compression is isotropic; then extra compression is imposed along some single direction. The first property of the clay causes initial small fluctuations in clay abundance to be self-accentuating, and also leads to development of contrasted layers normal to the extra compression. Flow of solvent parallel to these layers ultimately bifurcates because of the clay's second property. Thereafter, to an increasing extent, flow of solvent takes advantage of those portions of the clay-rich seam that form the sides of stylolitic columns and are not compressed by the extra compression.