| Many rift basins (e.g., the Jeanne d'Arc rift basin, the North Sea, the East African rift system) have undergone multiple episodes of extension with differing extension directions. Commonly, pre-existing faults formed during an earlier extensional episode act as zones of weakness, influencing subsequent deformation and affecting the development of these provinces. This thesis uses scaled experimental (analog) models to study the effect of a pre-existing fault fabric on fault development during extension. Specifically, I investigate how the orientation of a pre-existing fault fabric and the properties of a pre-existing fault fabric (including burial of the fabric) influence deformation during extension. The experiments show that the normal faults that develop during an initial extensional phase influence normal-fault development during subsequent extension. The orientation of pre-existing normal faults, relative to the second-phase extension direction, controls the reactivation of pre-existing normal faults during the second phase the sense of slip on reactivated faults and the attitude, number, and length of new normal faults. The magnitude of first-phase extension (which controls the number, size, and density of first-phase faults) influences the dominance of a particular fault population, in addition to the attitude and length of new normal faults. If a pristine cover is present, pre-existing faults affect the size, length, and location of new normal faults but not new fault orientations. All of the models indicate that fault orientations and populations in areas with a complex deformational history (observed either in map view or cross section) may not reflect the number, direction, and relative magnitude of each extensional episode. Variations in fault geometries, interactions, and fault reactivations in the models are similar to those observed in the Jeanne d'Arc basin, offshore Newfoundland the Suez rift the northern North Sea and the Pattani basin, Thailand. |
