ABSTRACT: Paleotectonic Restoration and Simulation Modeling Applicable to the Louisiana Offshore

WHITTLE, GREG, and CHRISTOPHER G. ST. C. KENDALL, Department of Geological Sciences, University of South Carolina, Columbia, SC, MICHAEL A. FOGERTY, Exploration Systems, Inc., New Orleans, LA, and ALLEN LOWRIE, Consultant, Picayune, MS

Sophisticated computer-based models are available to recapitulate sequences found along a cross-section. Here, results from paleotectonic restoration and simulation modeling have been obtained for a dip seismic section along the western Louisiana offshore. The section contains fourth-order (Milankovitch) sealevel cycles within Exxon/Vail third-order cycles. Propagation has exceeded subsidence multifold in the past 6.7 m.y., and by two-fold back to at least 22 m.y. Lowstands were times of sediment bypass along the outer shelf with shelf deposition during highstands. Salt-sediment interaction is isostatic, the adjustments occurring principally during lowstands.

Paleotectonic restoration modeling is a restoration procedure that uses dated reflectors with which to derive sequences. These sequences are backstripped through time with the remaining sequences geometrically adjusted to reflect original deposition by retaining the cross section area of each sequence. The result is a series of cross-sections representing geology at times of the various dated horizons. The modeling mechanics are the dynamics of regional tectonics applied to the measured sequences.

Simulated stratigraphy is inverse modeling, operated on an interactive computer program (SEDPAK), which erects models of sedimentary geometries by infilling a two-dimensional basin from both sides with clastic and/or carbonate sediments. Data inputs include initial basin configuration, local tectonics, sealevel curves, and amount and source of sediment as a function of water depth.

Both modelings allow for a quantification of the various geologic processes interpreted. These modeling procedures are over different time spans and are complimentary, as with a paleotectonic restored section, yielding an initial basin configuration for subsequent simulation modeling.

AAPG Search and Discovery Article #91014©1992 AAPG GCAGS and GC-SEPM Meeting, Jackson, Mississippi, October 21-23, 1992 (2009)