--> Abstract: Extreme Overthrusting and Extension Above Allochthonous Salt Sheets Emplaced During Experimental Progradation, by M. P. A. Jackson and B. C. Vendeville; #90987 (1993).

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JACKSON, MARTIN P. A., and B. C. VENDEVILLE, Bureau of Economic Geology, The University of Texas at Austin, Austin, TX

ABSTRACT: Extreme Overthrusting and Extension Above Allochthonous Salt Sheets Emplaced During Experimental Progradation

Scaled physical models and restorations of their cross sections were

used to investigate the breakout of salt sheets emplaced during progradation. Synkinematic sediments (brittle dry sand deposited during deformation) prograded across a "salt" basin (viscous silicone) that pinched out seaward. "Salt" was expelled seaward from beneath the prograding wedge into the core of a box fold of prekinematic strata. Fore- and back-grabens formed along the hinges of the box fold. Pressurized by the prograding overburden, a diapiric wall emerged through the structurally thinned back-graben. Extrusions from the fore-graben flowed down the fore-limb and spread radially like piedmont glaciers over the abyssal plain, coalescing laterally to form a lobate canopy. "Salt" extrusion inverted the fore-limb of the original box fold below the flow. The roof of the box fold wa detached by arcuate slumps and ruptured into extensional rafts. The roof fragments were carried as overtlirusts on the back of the spreading "salt" over the inverted limb of the isocline, locally producing triple stratigraphic repetition and buckling at the leading fringe of the extrusion. Younger deposits blanketing the coalesced extrusive flows also broke up extensionally, exposing polygonal windows of underlying "salt." Younger extrusions flowed seaward as second- and third-tier extrusions over the first flows. "Salt" evacuation from the original box fold left a tertiary fault weld behind the "salt" sheet.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.