The dynamics of marine deposition still hold many mysteries because the processes are immediately responsive to changes in sea level and sediment flux.
Understanding the sediment pathways and the dynamics of sand transport and deposition are key to finding new clastic reservoirs for oil and gas.
The challenge of understanding sediment deposition from the continental shelf into the deeper basin inspired the recent "Shelf Margin Deltas and Linked Down Slope Petroleum Systems," symposium at the 23rd GCSSEPM Foundation Conference in Houston. Organized annually by the Gulf Coast Section of the Society of Economic Paleontologists and Mineralogists, the meeting focused on questions of immediate concern to petroleum explorers. The conference examined deltaic depositional systems from around the world, but most talks dealt with studies in the exploration trends of the northern Gulf of Mexico.
Several themes were considered, including:
• Sediment supply - Studies show that climate change has only a minor effect on sediment yield. Yield is tied to the tectonic system and topographic/bathymetric relief
• Sediment transport is still a question with two major models proposed: "vacuum cleaner" and "conveyor belt" movement of material. This difference is best seen at lowstand sea levels
• The location of a sequence boundary significantly alters the expectation of sediment supply for a given shelf margin delta. Lowstand systems are thought to hold more sand
• In basins with active salt, the interaction between ponded and perched sediment helps the interpreter understand the dynamic of loading versus accommodation in complex terrains.
These topics were explored throughout the three-day event. The focus of exploration is shifting, moving down the continental slope and onto the abyssal plain. It is also moving into deeper and older sediments, where the rock systems are less well known. By closely examining younger shelf-margin delta systems, sedimentation and its interaction with other forces can be discerned.