--> Abstract: Controls on the Degradation of Normal Fault Scarps: Examples from the northern North Sea and NE Greenland, by A. E. McLeod; #90937 (1998).

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Abstract: Controls on the Degradation of Normal Fault Scarps: Examples from the northern North Sea and NE Greenland

MCLEOD, AILEEN E., The University of Edinburgh, Edinburgh, Scotland, UK ([email protected])

The steep footwall scarps of normal faults are gravitationally unstable geomorphological features, and thus liable to slope denundation resulting in scarp shallowing and retreat. Hillslope failure processes, a mechanical continuum from surface creep to turbulent flow, are complex and can be described by the interaction of numerous parameters, principally the physical environment, rheology of the footwall geology and time. Despite the prevalence of mass wastage processes in modern extensional regimes, the occurrence and genesis of ancient degraded fault scarps are poorly documented and understood.

This study investigates the geometry of ancient normal fault scarps and the character of the complexes of sediment degraded from the scarp, and now deposited on the footwall and in the proximal hangingwall. Analysis of subsurface data across the Mesozoic fault blocks in the northern North Sea has demonstrated the denuded nature of many of the normal fault scarps. These are compared with tectonically analogous, but environmentally and geologically distinct, Cretaceous fault blocks exposed in the Wollaston Foreland region of NE Greenland.

The 4-dimensional genetic models produced to describe the evolution of each unique fault scarp allow the relative influence, and hence importance, of the parameters controlling degradation to be defined. Three primary controls on degradation mechanism and slope topography are described: 1) The temporal evolution, both structurally and sedimentologically, of the system, 2) The maximum slope angle that can be sustained by the scarp, a function of rheology, and, 3) Whether the scarp is submarine or subaerial. These results are interpolated to produce a predictive model for the architecture, and hence reservoir potential, of fault scarp degradation complexes in different geological and physiographic conditions.