Localized strata-bound domino faulting offshore Espírito Santo Basin (southeastern Brazil): The case for sudden release of fluid in salt-withdrawal basins

Abstract

Hydraulic-driven faults and fractures are important subsurface fluid-flow pathways, yet their seismic expressions are poorly documented. This paper uses high-quality three-dimensional seismic data to investigate curved, strata-bound domino-style faults above which a pockmark field is observed and interpreted to be associated with their formation. The faulted interval covers an area of 24 km2 and is ∼100 m thick. Faults show a concentric pattern with an average spacing of 120 m, whereas their throws approach 10 ms two-way time. Strata-bound domino faults were formed because of overpressure buildup and release in a mud-dominated succession, with their geometry responding to the local dip of the salt-withdrawal basin in which they occur. Further overpressure buildup resulted primarily from fluid migration through underlying crestal faults and secondarily through capillary permeability within permeable strata. Apart from the strata-bound domino faults and associated pockmark fields, other randomly distributed pockmarks indicate episodic fluid flow in the study area. Random pockmarks were likely formed during rapid burial of continental slope strata, resulting in the elevation of fluid pressure in underlying soft sediment. This paper concludes that strata-bound domino faults are a typical feature of fluid flow on salt-rich continental margins, such as southeastern Brazil, the Gulf of Mexico, and the western African continental margin. During their formation, strata-bound domino faults form significant conduits for migrating fluid into soft, porous strata, away from regional and local structural traps.