LE CALVEZ, JOEL H.1 and BRUNO C. VENDEVILLE2
1Department of Geological Sciences, The University of Texas at Austin, Austin, TX
2Bureau of Economic Geology, The University of Texas at Austin, Austin, TX
Abstract: X-Ray Tomographic Analysis Of A Physical Experiment Of Salt Tongue Remobilization During Sedimentation
We present results of a physical experiment simulating remobilization and spreading of an allochthonous salt tongue during deposition of suprasalt sediments. After conducting the experiment in a laboratory, we analyzed the model's 3-D geometry using X-ray-computed tomography. The model comprised dry sand, representing nonevaporitic sediments that deform by folding or faulting and a silicone polymer, representing viscous rock salt.
The initial model's geometry was that of a funnel-shaped salt body (silicone) encased in comparatively more rigid sediments (sand). The top of the silicone had been originally horizontal and level with the encasing sediments. Deformation started as successive sediment wedges prograded seaward across the salt tongue. We then placed the deformed model in a CAT scan, which produced more than 1200 vertical sections and horizontal slices, each 0.5 mm apart, covering the entire model volume.
Tomography results indicate that the model first deformed by differential loading and early seaward extension. Early extensional faulting allowed diapirs to rise reactively below faulted grabens. Seaward extension and reactive diapirism stopped early and the model subsequently deformed by differential loading only. The prograding sediments accumulated in a single circular depocenter, having a concave-upward base. The depocenter subsided en masse, displacing the underlying salt and expelling it seaward, where the overburden wedge tapered. Salt rose distally and eventually spread seaward. Faulting was restricted to one or two faults bounding the proximal edge of the depocenter and accommodating its vertical subsidence.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas