Intraslope Basin Evolution, Northwest Gulf of Mexico

Will M. Satterfield, E. W. Behrens

A succession of three stages in the cyclical development of sand-rich intraslope basins is suggested from piston core data in the northwest Gulf of Mexico. The initiation stage is identified by a sedimentary assemblage of mud pebble conglomerates and plastically deformed sediments. These sediments reflect initiation of vertical movement of basin margins. The sediment-loaded mobilization of the salt/shale diapirs produces oversteepening and failure of the margin sediments. The affected sediments commonly form slumps, and grade upward into debris flows as the intensity and rate of deformation increases.

Deposits of the initiation stage are followed by the thin silt laminites to massive graded sands of the active stage. Subsidence and uplift rates become stable and lead to the development of a constant sediment source. Fan-like basin filling and loading marks the active stage in intraslope basin evolution. The basin has reached a period of dominantly turbidite deposition which suggests a dependable sediment source and the formation of sheet-like unchannelized flows within the slowly subsiding basin.

Capping the sequence are the bioturbated muds and scattered foram silts of the dormancy stage. The dormancy stage marks the change to hemipelagic deposition in the basin. The previously dominant clastic source has been cut off to either channel blockage, upslope channel or shelf-edge deltaic avulsion, or a relative rise in sea level. The above three stages commonly occur consecutively. However, it is possible to have a missing stage, repetition of stages, or other complications.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.