Source-to-Sink Sediment Movements in Structurally Complex Setting: The Role of Gateway Basins

Lesli J. Wood
University of Texas at Austin, Austin, TX

Regional movement of sediments in both subaerial and submarine settings is strongly influenced by the tectonic regime, the orientation of the slope and type and nature of structures. Understanding what controls the ability of a sediment system to move between established pathways or open new pathways is critical to assessing the prospectivity of frontier basins.

Several margins around the world have been studied using 3D seismic mega-data sets, and regional topography and bathymetry to assess the nature of sediment sinks and barriers, and those preferred pathways and gateways by which deposits move across structurally complex regions. In transpressive terrains, such as Trinidad gateways are provided by transfer zones between transpressive uplifts. Sediments move down intra-anticlinal chutes until encountering such gateways transfer zones whose existence is critical to successful movement of sediment across the region. In compressional terrains, such as accretionary prisms, trellis drainages of sediment parallel thrusts until drainages encounter gateways formed by the dissipation of throw across thrusts. Diapiric terrains, such as the Gulf of Mexico salt canopy form tortuous drainage of sediments basinward. There gateways, formed by salt sheet discontinuities located at the edge of the Sigsbee Escarpment, provide escape for sediments from the canopy to the escarpment front.. These gateways may in some way be associated with long-dormant Mesozoic-age tranform faulting. Since many gateways appear to be controlled by long lived structural discontinuities, identifying the type and location of gateways may have implications for long periods of geologic time regarding the nature of frontier basin sedimentation and provide a means to reduce uncertainty in frontier exploration.