The genesis of polygonal fault systems: a review

Polygonal fault systems are widely developed in fine-grained sedimentary successions and have been recognized in over 50 basins worldwide. They are normal faults with modest throw values (typically 10-100 m), organized with a characteristic plan form pattern that is crudely polygonal, but with considerable variation in specific planform patterns. They have been attributed to four genetic mechanisms: gravity collapse, density inversion, syneresis and compactional loading. Their strain characteristics allow them to be distinguished from tectonic normal faults. The strengths and weaknesses of the four genetic mechanisms are considered in the light of these strain characteristics. It is argued that syneresis offers the likeliest mode of genesis and best explains the local and global features of these extraordinary structures. The detailed physical mechanism driving syneresis remains poorly understood.