--> ABSTRACT: Deformation Produced by Subsait Normal Fauitlng: An Experimental Study with Implications for Seismic Interpretation, by J. Sybil Callaway and Martha Oliver Withjack; #91019 (1996)

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Deformation Produced by Subsait Normal Fauitlng: An Experimental Study with Implications for Seismic Interpretation

J. Sybil Callaway and Martha Oliver Withjack

We have conducted a series of scaled physical models to study the deformation produced by subsalt normal faulting. ln the models, a constant-thickness layer of silicone putty represents a salt sheet, and a layer of homogenous dry sand or wet clay represents the sedimentary cover. Movement on a precut, 45°-dipping surface below the silicone putty simulates subsalt normal faulting. We have tested the sensitivity of the modeling results by varying the thickness of the putty layer, the thickness of the sand/clay cover, the magnitude of the fault displacement, the rate of fault displacement, and deposition during deformation.

Our modeling results imply that a broad forced fold forms above an active subsalt normal fault. The width of the monoclinal limb increases as the salt thickness increases and if nominal deposition occurs during deformation. The dip of the limb increases as the magnitude of the fault displacement increases, as the salt thickness decreases, and if deposition occurs during deformation. Our modeling results also imply that normal faults can form in the sedimentary cover above the salt sheet during subsalt normal faulting. These normal faults commonly form near the footwall hinge of the monocline and are offset and detached from the underlying subsalt normal fault. They are more likely to develop if the salt sheet is thin, if the sedimentary cover is thick, if the fault displacement is large, and if deposition occurs during deformation.

The experimental results suggest that the structural geometries of suprasalt folds and faults provide information about subsalt faulting. Seismic examples from Norway, Alaska, and the Gulf of Mexico support these conclusions.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California