Active Salt Tectonics and Its Effect on the Internal Architecture and Connectivity Between Minibasins Near the Sigsbee Escarpment, Gulf of Mexico

Montoya, Patricia¹, Michael R. Hudec² (1) Anadarko, The Woodlands, TX (2) Bureau of Economic Geology, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX

Three key factors controlled the evolution and distribution of sediment-transport systems in lower slope minibasins: the rise of interbasin salt massifs (caused either by shortening or minibasin subsidence), variations in sedimentation rate, and the construction of leveed-channel systems. These factors were combined to create a new dynamic-salt fill-and-spill model. This model differs from published upper-slope models in that it not only considers variations in sedimentation rate, but also includes the effects of mobile salt surrounding the minibasins. The model also examines multidirectional connections between proximal and distal minibasins. This presents four connection styles between nearby minibasins. These four styles of connections are: 1. No connection, in which sediments are not transported between adjacent minibasins. 2. Wide connection, in which suspended fine-grained flows spill over the downdip edge proximal minibasins as run-out clouds through wide source areas. 3. Narrow connection, in which flows are transported from a proximal to distal minibasins through narrow zones by channel systems. 4. Bypass connection, in which high-energy flows erode across chains of minibasins. In the study area, the analysis showed that minibasin sedimentation was strongly cyclical, with periods of low sedimentation associated with drapes above each interpreted sequence boundary. As a result, cycles in connection style were also identified, with drape intervals largely shutting down channels systems. Drape intervals were therefore associated with minibasin isolation while connectivity was typically reestablished later within each sequence.