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Geological Society, London, Special Publications; 2003; v. 216; p. 245-261;
DOI: 10.1144/GSL.SP.2003.216.01.16
© 2003 Geological Society of London

Polygonal Faults and Sediment Mobilization

The geometry, growth and linkage of faults within a polygonal fault system from South Australia

A. Nicol1,2, J.J. Walsh1, J. Watterson3, P.A.R. Nell4 & P. Bretan4

1 Fault Analysis Group, Department of Geology, University College, Dublin L69 3GP, UK fault{at}fag.ucd.ie
2 Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand
3 Fault Analysis Group, Liverpool University Marine Laboratory, Port Erin, Isle of Man IM9 6JA, British Isles
4 Badley Earth Sciences Ltd, North Beck Lane, Hundleby, Spilsby, Lincolnshire PE23 5NB, UK

Quantitative analysis of faults within a South Australian polygonal fault system, interpreted from a 3-D onshore seismic survey, provides a basis for establishing their growth and linkage histories. The geometric characteristics of faults are consistent with an origin arising from the gravitational instability of an underlying low-density, overpressured, mobile layer. Fault size populations have scale-bound, non-power-law properties reflecting the thicknesses of the faulted and mobile layers and the strongly connected nature of the system. The spatial distributions of faults reflect the localization of conjugate faults at the top of the mobile layer and the scale of fault-bounded polygons. Displacement variations on faults show marked decreases at or adjacent to the top of the mobile layer and attest to its active role in faulting. The wide range of fault strike directions provides numerous fault intersections with high intersection angles (≥ 60°) forming triple-junctions at which fault linkage and capture occurred. Fault linkage and capture is attributed to a simple model in which continued movement on faults which share a mutual footwall is favoured and hanging wall faults are deactivated. The model involves thickening of the mobile layer within the footwalls of faults and thinning and eventual grounding of the overlying sequence, within their hanging walls.





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Petroleum Geoscience, 2008; 14: 389 - 397.
[Abstract] [Full Text] [PDF]