Controls on Relay Ramp Genesis, Evolution and Breaching: An Analysis Using Both Field Studies and High Resolution 3-D Seismic Data

D. M. Dutton
Imperial College, TH Huxley School, London, UK

Relay ramps are ephemeral features that develop during the evolution of fault systems. Breakdown of ramps by breaching is part of the process through which fault arrays grow by linkage of overlapping segments. However, a better understanding of the variables that control ramp breaching is needed before any quantitative predictions can be made as to whether or when a ramp in the subsurface is/was breached.

This is a multidiscipline project examining the controls on relay ramp breaching across a wide range of scales from small-scale field examples to large-scale normal fault systems imaged on 3-D seismic data and present in the field in Utah. Large-scale relay ramps are well developed in the Canyonlands Grabens in SE Utah and along the Hurricane Fault in SW Utah. Comparable scale features are well imaged on 3-D seismic data sets from the Lower Congo Basin, offshore Angola and from the Abidjan margin, Cote d’Ivoire.

Detailed seismic analysis of both the postrift salt related fault arrays from offshore Angola and the Cote d’Ivoire synrift basement controlled fault systems has been coupled with 3-D restorations of the structures through time. This has allowed the evolution of a number of relay ramp structures to be catalogued. Analysis of these structures has been enhanced through use of 3-D visualization and displacement mapping software.

AAPG Search and Discovery Article #90902©2001 AAPG Foundation Grants-in-Aid