TY - JOUR TI - Experimental modeling of focused shortening DO - https://doi.org/doi:10.7282/T3N58MF1 PY - 2010 AB - This thesis presents four series of sand and clay analogue models of compressional deformation: no erosion and sedimentation (S1), erosion (S2), sedimentation (S3s and S3c), and no erosion and sedimentation with an indentor (S4). All models produce a single fault zone, except S4 which produced multiple fault zones. The models show that erosion and sedimentation influence the major fault and fold geometries, fault displacement, ramp-dip angles, and the width of the deformation zones. The major faults in the models with low or no sedimentation (S1) and erosion (S2) have a flat-ramp-flat geometry. Erosion produces the narrowest deformation zone. In contrast, the sand model with sedimentation (S3s) has the widest deformation zone and the steepest ramp-dip angle; it lacks the upper flat section of the main thrust fault. Clay and sand models have similar large-scale deformation patterns. The models produce a series of backthrusts and an upward-widening main reverse fault zone. Steeply dipping to overturned beds and branching faults are present within the main fault zones. The clay models have narrower fault zones, more faults with smaller displacements, more blind faults, more folding, and steeper backthrusts than the sand model. Calculations for the sand and clay models show that the backthrusts and main thrust account for only 45-50% of the imposed shortening. S4 provides insight on the patterns of secondary faulting that develop on the anticlines above the main thrust faults. Normal faults form parallel to the hinge line on the crest of the anticlines and perpendicular to the hinge line at the plunging ends of the anticlines where two offset anticlines propagated and merged together. Seismic data from areas of reverse/thrust faulting (e.g., offshore Nigeria) commonly contain no-record zones corresponding to the main reverse fault zone in the experimental models. The experimental models provide insight into the complex structures within these fault zones: steeply dipping to overturned beds and multiple branching faults. KW - Geological Sciences KW - Erosion KW - Sedimentation and deposition KW - Surfaces, Deformation of KW - Fault zones LA - eng ER -