The sutures are mainly produced in relatively pure carbonate rocks, and sometimes appear in quartz sandstone, salt rock, and siliceous rock, which refers to the two adjacent rock layers or two adjacent parts of the same rock layer Zigzag seams connected together. It is actually a reflection of the stitched surface on the cross section. The rocks on both sides of this line are mostly irregular canine teeth staggered or connected with each other. Sutures often enrich insoluble residues of this type of rock, such as clay, organic matter, sand, etc.