The propagation and growth of polygonal fault systems

• Main Author: King, J
• Other Authors: Cartwright, J, Levell, B
• Format: Thesis
• Language: English
• Published: 2021
• Subjects: Geology; Structural; Numerical Modelling; Structural Geology; Norwegian Sea
• Online Access: https://ora.ox.ac.uk/objects/uuid:fd75ae7c-2d95-4c2f-8ca8-f46a3c2d96d3

Polygonal fault systems (PFSs) are laterally-pinned arrays of multi-directional nontectonic normal faults that develop in fine-grained sedimentary sequences. PFSs have been documented in over 150 basins globally, since they were first reported in early three-dimensional seismic reflection datasets in the late 1980’s. The structural characteristics of PFSs are well documented, yet despite over three decades of research and wide debate within the published literature, the processes that govern the growth of polygonal faults are poorly understood. This thesis investigates the propagation and growth of polygonal fault systems through spatial, temporal, and kinematic analysis of surface-breaching polygonal faults in the Vøring Basin, Norwegian Sea, and numerical modelling simulations. This thesis documents the first recorded throw rates from a PFS globally. These ultra-slow rates range between 1.4-10.9 m/m.y. and mark the lower limit of a continuous spectrum of extensional fault displacement rates, that are as much as three orders of magnitude slower than those of the fastest-growing tectonic faults. This thesis also establishes, through numerical modelling, that the growth of polygonal faults can be explained solely by gravity-driven differential compaction of unconsolidated fine-grained sediments at residual friction angles less than ~9°. These findings elucidate our understanding of the growth of these widespread and fascinating geological structures.