Stylolites

Top: Stylolite in Carboniferous limestones from south Wales, United Kingdom. These stylolites formed from vertical compression which also formed the cross-cutting vertical veins. Photo credit: Rob Knipe. Image from website: http://earth.leeds.ac.uk/learnstructure/index.htm

Bottom: Photograph of thin section of calcite vein containing a stylolite. Compression direction is indicated by the arrows. Image from website: http://www.earth.monash.edu.au/Teaching/mscourse/index.html