ABSTRACT

Three different sizes of downwarps and posiments (positive elements) are recognized in the North Louisiana (Salt Dome) basin. The Bistineau bridge separates the Minden trough from the Winnfield trough. Second-order ridges and synclines connect third-order arches and sub-basins. The structural features are strong and closed on the north and open to the south, differences which are probably related to salt deposition and subsequent movements. Isopachous studies of electric log data confirm that marked reductions in rates of basin deformation occurred at the end of the Jurassic, the Lower Cretaceous, and the Eocene; but all structures, including salt domes, showed individual variations from the norm. Rim synclines are arranged concentrically inward and upward around 19 salt domes. Salt movement occurred in four stages: horizontal flow into pillows (Jurassic), active flow into stocks (Lower Cretaceous), cylindrical-vertical rise, and stagnation. A "vermiform" hypothesis involving "turtle-structures" suggests present "highs" were original salt-withdrawal basins, and the original bedded salt may have been only 1500-2000 feet (500-600 m) thick as partially confirmed by volumetric calculations. Although post-Eocene strata are missing, salt movement during that time is inferred to be inconsequential.