Abstract: Controls on the Syn-Rift Degradation of Normal Fault Scarps

McLEOD, AILEEN E.

Steep normal fault scarps are commonly gravitationally unstable slopes and thus prone to failure. This will frequently occur in response to sudden, rapid tectonic shocks as the fault propagates and can result in significant structural degradation and sedimentological reworking of the footwall. Recent research in the northern North Sea has highlighted the importance of mass wastage processes in determining the limits to structural traps containing tilted reservoirs. Complexes of degraded pre-rift sediments mounted on the fault scarp have been documented from several mature fields including the largest, Brent, where one third of remaining reserves are estimated to remain trapped within the degradation complex. However, despite the importance of the products of footwall degradation as subtle traps, both in the footwall and hangingwall, little is understood about their external form, internal geometry and genesis.

This project was established to describe and quantify the controls on the process of fault scarp degradation by undertaking detailed field analysis of sedimentation around ancient normal fault populations in the Mesozoic of NE Greenland and Oligo-Miocene outcrops of the Suez Rift. In both these areas excellent exposure allows documentation of the degradation products by mapping and, thus, the opportunity to investigate the controls that footwall Ethology and rheology, fault evolution and palaeoenvironment had on the lateral disaggregation of sediment. By integrating the results with analogous sub-surface work in the North Sea the ultimate goal of this research is to attain an understanding of the controls and evolutionary development of fault scarp degradation complexes which can then be applied as a predictive model for hydrocarbon exploration and recovery from these subtle structural and stratigraphic traps. 

AAPG Search and Discovery Article #90940©1997 AAPG Foundation Grants-in-Aid