Salt Sutures in Single- and Multi-Tiered Allochthons, Green Canyon and Walker Ridge Areas, Deepwater Gulf of Mexico, U.S.A.

Liro, Louis, RepsolYPF, The Woodlands, TX

Single-tiered allochthons originate from Mesozoic salt layers. Such allochthons define the present-day Sigsbee Escarpment in Walker Ridge and Keathley Canyon. Triangular notches along the base of the allochthonous salt are observed. The notches are located between salt feeder regions, and are interpreted to represent early, lateral sutures with little associated sediment deformation. Perimeter sutures are located between the leading edge of the allochthon and its impingement with an adjacent allochthon. These sutures are pro­nounced where the leading edge of one allochthon impinges upon the feeder region of the second allochthon.

Multi-tiered allochthons emanate from precursors at deeper levels. Across the study area, a consistent weld level at approximately 8 km depth suggests a pre-Miocene, exten­sive allochthon likely similar to the relatively undisturbed Miocene allochthon observed to the south. The multi-tiered allochthons have rugose tops, resulting in a poor subsalt image. They also display internal reflectors and complex suturing.

Extensive lateral sutures are observed both in single-tiered and multi-tiered salt regions. Lateral sutures in single-tiered allochthons are associated with feeder regions and parallel or diverge slightly from the base allochthon seismic event. These sutures are located in the lower third of the salt body, suggesting an early origin. In multi-tiered allochthons, the lat­eral sutures are observed at any height within the allochthon, and display less affinity to ver­tical salt sourcing regions. This relationship suggests that in the multi-tiered regions, “crowding” of allochthons, due to higher salt flux and secondary allochthon development, results in “pancaking” of salt allochthons, rather than lateral amalgamation.