The Importance of Mud Deposition in Generating Realistic Stratigraphic Models

Boyan Vakarelov
UT Dallas, Richardson, TX

Mud deposition on shelf settings is the product of a complex array of processes, such as buoyant and hyperpycnal plume transport, wind-induced surface current transport, fluid mud transport, wave and tide reworking, and geostrophic circulation. The combined effect of these processes is commonly the formation of clinoforming mud deposits positioned away from shorefaces, with distinct topset (sediment bypass area), foreset and bottomset portions. Progradation in low-accommodation settings can result in significant decoupling between the shoreface (highest rates of sand accumulation), and the foreset region of a mud belt (highest rate of mud accumulation), separated by a sediment bypass area. A mud belt prograding ahead of a shoreline will (1) infill accommodation in the offshore portion of the basin, (2) limit the thickness of the prograding shoreface to the depth of its topset area, and (3) prevent the delivery of appreciable quantities of sand-sized particles to significant water depths. Progradation of a shoreface – mud belt system into deeper water will result in slowing down of the rate of mud belt progradation, but an unchanged rate of shoreline progradation. This will result in the shoreface “catching-up” to the mud belt foreset and the formation of a single joint clinoform, followed by lowering of the rate of shoreline progradation, increased sand delivery to greater water depths, and thickening of the sand-dominated portion of the clinoform package. The presented model attempts to incorporate known complexities of shelf mud deposition and is tested against ancient examples.