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Abstract: Oligocene-Miocene Shallow Marine Carbonates in Offshore Tunisia: A Sequence Stratigraphic Case Study of an Integrated Data Set

Anne M. Schwab

The Ketatna-Salammbo series of Offshore Tunisia contains shallow water marine carbonates that interfinger with shales. The aim of this study was to determine a depositional model for this series based on an integrated data set. The study used a seismic stratigraphic interpretation together with the well logs and limited biostratigraphy to construct a stratigraphic model, comprising sequence stratigraphy and lithology. A synthetic seismic line was generated from this model which was then compared with the original seismic. This synthetic seismic line shows a good match with the real data which validates the stratigraphic model and also shows that the seismic reflections correspond to time lines associated with major base level accommodation cycle changes.

The seismic stratigraphic analysis of the 3D data defined major surfaces of onlap and downlap. The well log stacking patterns defined 4 major progradation/retrogradation systems (base level fall/rise accommodation cycles). Limited foraminifera biostratigraphy control tied to most of the major seismic reflections which hounded the base level accommodation cycles.

A stratigraphic model was constructed and geophysical properties were assigned to the model. Velocities were taken directly from the log control, while the densities were calculated from Gardner's Equation.

The good fit of the synthetic seismic line to the real seismic data shows that the stratigraphic model proposed for this shallow carbonate platform is a viable one. The integrated data set shows that the major base level accommodation cycle changes follow major seismic reflections.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France