Stylolite

A stylolite is an irregular fracture in limestone and other sedimentary rocks. Styolites result from compaction and dissolution during diagenesis and may be enlarged by subsequent groundwater flow. Sylolites appear as jagged discontinuities in outcrops and hand samples and are often lined with insoluble clays and iron oxides.

A stylolite is an irregular discontinuity, common in limestone and other sedimentary rocks. Styolites result from compaction and dissolution during diagenesis and may be enlarged by subsequent groundwater flow. Sylolites appear as jagged discontinuities at the scale of outcrops, hand specimen, and thin section and are often decorated with insoluble/less soluble clays, opaques, or dark organic matter.

The term stylolite is derived from the Greek for pillar, stylo. Compare the French 'stylo' for pencil, and 'stylite' for 'pillar saint', an ascetic deliberately living standing on top of a pillar.

A stylolite is not a fracture. Proof exists in the form of eg. fossiliferous limestones where fossils are crosscut by a stylolite and only one half still exists; the other half has been dissolved away. Rye & Bradbury (1988) investigated ^13/12C and ^18/16O stable isotope systematics in limestone on either side of a stylolity plane and found differences confirming different degrees of fluid-rock interaction.

References

Rye, DM, and Bradbury, HJ (1988): Fluid flow in the crust: an example from a Pyrenean thrust ramp. American Journal of Science (288): 197-235.

• Schlumberger Oilfield Glossary
• S. Sinha-Roy, Kinetics of differentiated stylolite formation, Current Science, V. 82, No. 8, 25 April 2002