A Deterministic Evaluation of eismic Fidelity using Velocity Modeling ...

typical of the shelf margin. Because of the strong extensional component of the faults and
the movement of salt, the geometry as described by Nelson, 1991 (Figure 10) indicates
that during Hackberry deposition Vinton Dome continued to form as an active diapir.
Active diapirism could have resulted from the prograding margin pushing salt basinward
initiating faulting. As the fault developed in response to salt movement, the salt pushed
upward into the zone of weakness.
Finally, the eighth and last event was the deposition of the remaining Frio and the early
Anahuac (Paine, 1968). Upper Frio represents a regressive phase and lowering of sea
level as is evident from the numerous sand sequences found in the upper Frio (Figure 23).
Mapping of two of these sand units on 3-D PSTM (Figure 24) data indicate that a
transition from active to passive diapirism as described by Nelson (1991), Figures 10 and
11 began by the upper Frio. Anahuac sedimentation represents a late Oligocene
transgression when the shelf margin was probably mud dominated (Figure 25) (Winker,
1982). Structural interpretation of 3-D PSTM surface seismic data (Figure 26) indicate
that diapirism continued to be passive at the end of Anahuac deposition based on the
interpretation of radial faulting and the lack of a major growth fault using Nelson’s model
Figure 11.
Miocene deposition shifted to a deltaic environment and back to a broad sandy strand
plain (Figure 27) (Galloway et al., 2000). The early Miocene shelf-margin depocenter
located in southwestern Louisiana remained active through the Quaternary and
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