Stylolites in limestones: Barriers to fluid flow?

Michael J Heap,Thierry Reuschlé,Patrick Baud,Philip G Meredith

doi:10.1130/g34900.1

Michael J Heap, Thierry Reuschlé + Show 2 more

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https://doi.org/10.1130/g34900.1

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Abstract

Stylolites—products of intergranular pressure-solution—are laterally extensive, planar features. They are a common strain localization feature in sedimentary rocks. Their potential impact on regional fluid flow has interested geoscientists for almost a century. Prevalent views are that they act as permeability barriers, although laboratory studies are extremely rare. Here we report on a systematic laboratory study of the influence of stylolites on permeability in limestone. Our data demonstrate that, contrary to conventional wisdom, the studied stylolites do not act as barriers to fluid flow. In detail, when a stylolite occurs perpendicular to the direction of flow, the permeability simply follows the same power law permeability-porosity trend as the stylolite-free material. We show, using a combination of high-resolution (4 µm) X-ray computed tomography, optical microscopy, and chemical analyses, that the stylolites of this study are not only perforated layers constructed from numerous discontinuous pressure solution seams, but comprise minerals of similar or lower density to the host rock. The stylolites are not continuous high-density layers. Our data affirm that stylolites may not impact regional fluid flow as much as previously anticipated.

Highlights

IntroductionStylolites are complex column-and-socket interdigitation features that form as a result of intergranular pressure solution (e.g., Nenna and Aydin, 2011; Croizé et al, 2013)
Stylolites are complex column-and-socket interdigitation features that form as a result of intergranular pressure solution (e.g., Nenna and Aydin, 2011; Croizé et al, 2013). They are a common product of strain localization in sedimentary rocks and can form laterally extensive, planar drapes. Knowledge of their impact on regional fluid flow is an important consideration in many facets of geoscience
While recent laboratory investigations have shown that compaction bands significantly decrease the permeability of sedimentary rock, complementary laboratory data on the impact of stylolites are extremely rare

Summary

Introduction

Stylolites are complex column-and-socket interdigitation features that form as a result of intergranular pressure solution (e.g., Nenna and Aydin, 2011; Croizé et al, 2013) They are a common product of strain localization in sedimentary rocks and can form laterally extensive, planar drapes (some stylolites are known to reach lengths of almost 1 km; Safaricz and Davison, 2005). Several studies have observed that, during the formation of a stylolite, enhanced porosity zones can develop along the flanks and at the tip of the stylolite (Carozzi and von Bergen, 1987; Dawson, 1988; Raynaud and CarrioSchaffhauser, 1992; Van Geet et al, 2000; Gingras et al, 2002; Harris, 2006). We present a systematic laboratory study on the porosity and permeability of limestones containing stylolites

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