A surface or contact, usually in carbonate rocks, that is marked by an irregular and interlocking penetration of the two sides: the columns, pits, and teethlike projections on one side fit into their counterparts on the other. As usually seen in cross section, it 3155 resembles a suture or the tracing of a stylus. The seam is characterized by a concentration of insoluble constituents of the rock; e.g., clay, carbon or iron oxides, and is commonly parallel to the bedding. Etymol: Greek stylos, pillar, + lithos, stone.