Patrice Imbert¹, John Wu¹

(1) TotalFinaElf Exploration and Production USA, Houston, TX

ABSTRACT: Seismic Scale Sediment Waves in the Pliocene of the Gulf of Mexico: Examples and Implications for Exploration

Experience gathered by TFE on several examples worldwide indicates that seismic-scale sediment waves are a common ingredient of deep-water systems. They develop with geometries similar to climbing ripples, but at seismic scale and with upcurrent migration. The downcurrent side of the waves undergoes low sedimentation.

Sediment waves show well only on sections crossing them perpendicular to their strike, and oblique sections show complex morphologies easily mistaken for mass transport complexes. They also tend to mimic sets of low angle normal faults, even with optimal profile orientation. Recognition criteria for sediment waves vs. normal faults include very low angle of "fault plane", lack of continuity of the "plane", occurrence in specific settings (levees at the outer bends of turbidite channels, toe of slope).

The morphology of sediment waves varies from vertically aggrading to strongly migrating upslope, with downslope deposition below seismic resolution. This variability can be characterized by the angle of climb of the sediment wave and reflects the respective importance of actual sediment wave buildup (upslope migration) and drape during inactive phases. As a result, the angle of climb is interpreted to directly reflect the sand/mud ratio of the sediment wave.

The lee side of some strongly migrating sediment waves is sometimes underlined by a seismic reflection, highlighting the lithological contrast between the sandier stoss side and the muddier lee side. Although not a first choice target for exploration (multilayered, thin-bedded reservoir if any), sediment waves are common enough to be worth including in our lists of deep-water depositional elements

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado